Chronic obstructive pulmonary disease (COPD) and asthma are considered as the two most widespread obstructive lung diseases, whereas they affect more than 500 million people worldwide. Unfortunately, the requirement for detailed geometric models of the lungs in combination with the increased computational resources needed for the simulation of the breathing did not allow great progress to be made in the past for the better understanding of inflammatory diseases of the airways through detailed modelling approaches. In this context, computational fluid dynamics (CFD) simulations accompanied by fluid particle tracing (FPT) analysis of the inhaled ambient particles are deemed critical for lung function assessment. Also they enable the understanding of particle depositions on the airways of patients, since these accumulations may affect or lead to inflammations. In this direction, the current study conducts an initial investigation for the better comprehension of particle deposition within the lungs. More specifically, accurate models of the airways obstructions that relate to pulmonary disease are developed and a thorough assessment of the airflow behavior together with identification of the effects of inhaled particle properties, such as size and density, is conducted. Our approach presents a first step towards an effective personalization of pulmonary treatment in regards to the geometric characteristics of the lungs and the in depth understanding of airflows within the airways.A geometry processing technique involving contraction algorithms is established and used to employ the different respiratory arrangements associated with lung related diseases that exhibit airways obstructions. Apart from the normal lung case, two categories of obstructed cases are examined, i.e. models with obstructions in both lungs and models with narrowings in the right lung only. Precise assumptions regarding airflow and deposition fraction (DF) over various sections of the lungs are drawn by simulating these distinct incidents through the finite volume method (FVM) and particularly the CFD and FPT algorithms. Moreover, a detailed parametric analysis clarifies the effects of the particles size and density in terms of regional deposition upon several parts of the pulmonary system. In this manner, the deposition pattern of various substances can be assessed.3 to 2000 Kg/m3, the DF is enhanced on every generation and for all cases investigated herein. The results obtained by our simulations provide an accurate and quantitative estimation of all important parameters involved in lung modeling.For the specific case of the unobstructed lung model most particles are detected on the right lung , a fact that is also true when obstructions arise symmetrically in both lungs . In contrast, when narrowings are developed on the right lung only, most particles are pushed on the left section  indicating that inhaled medication is generally deposited away from the areas of inflammation. This observation is useful when designing medical treatment of lung diseases. Furthermore, particles with diameters from 1 μm to 10 μm are shown to be mainly deposited on the lower airways, whereas particles with diameters of 20 μm and 30 μm are mostly accumulated in the upper airways. As a result, the current analysis indicates increased DF levels in the upper airways when the particle diameter is enlarged. Additionally, when the particles density increases from 1000 Kg/mThe treatment of respiratory diseases with inhaled medical substances can be advanced by the clinical use of accurate CFD and FPT simulations and specifically by evaluating the deposition of inhaled particles in a regional oriented perspective in regards to different particle sizes and particle densities. Since a drug with specific characteristics (i.e. particle size and density) exhibits maximum deposition on particular lung areas, the current study provides initial indications to a qualified physician for proper selection of medication. Chronic obstructive pulmonary disease (COPD) and asthma are deemed as the two most frequent life-long inflammatory maladies of the respiratory system affecting over 500 million people worldwide. Since the assessment of their severity is of paramount importance, several clinical tools established by ICT infrastructure , 2 have Moreover, a method that utilizes multidetector computer tomography (MDCT) volumetric data sets, obtained at diverse inflation levels, in order to assemble a multiscale breathing lung model has been introduced in . AdditioThe dose evaluation of ambient particles transported from a subway microenvironment into the human respiratory tract, as well as the significance of individual exposure to them, have been described by , so thatThe objective of this work is to develop precise models of the airways narrowings that correlate to respiratory maladies. Moreover, we provide an extensive assessment of the airflow features together with clarification of the inhaled particle attributes as a next step towards attaining effective personalized treatment with properly tailored substances. To pursue these goals, a geometry processing methodology is established and employed for the formation of various important models of the pulmonary system. The proposed sequence mitigates several effects that degrade the quality of the surface models, thus facilitating the required simulations. Apart from the normal lung case, two obstructed cases are examined, i.e. a model with obstructions in both lungs and a model with obstructions in the right lung only. The partially obstructed model is evaluated only for the right lung to assess the effects of obstructions in the asymmetric behavior of the normal model, since most particles are deposited in the right section as shown by our initial investigations. These distinct cases are examined through the finite volume method (FVM) and specifically the CFD and FPT algorithms which allow accurate deductions about airflow and deposition fraction (DF) upon numerous parts of the lungs. In addition, a thorough parametric analysis is conducted to identify the effects of particle size and density on their deposition efficacy upon various sections of the pulmonary system. In this way, the behavior of various substances with diverse dosages can be assessed in terms of the deposition pattern that they exhibit. The data obtained demonstrate potential employment in personalized medical remedy of lung diseases by providing regional-oriented deposition information.Geometry processing sequences are established to allow the simulation of the effects of obstructions in the 3D lung topology. This approach enables the investigation of the impact of any narrowings on the airflow into the lung, by employing a CFD simulation. The proposed sequences are implemented directly on an already available 3D model of the lung , obtainen vertices can be denoted by two distinct sets V) that represent the geometry information and the indexed faces (F) of the mesh. Each vertex can be represented as a point vi =  ∀  i = 1, …n and each centroid of a face as E) can be directly derived from V and F, which correspond to the connectivity information. If we denote with v the vertices of a mesh, then each face can be represented by its centroid point mi, and its outward unit normal:fi and Our geometry approach is focused on polygon models whose surface is represented using triangles. Each triangle mesh i-th row and j-th column of a matrix A is represented by Ai, j)( and Aj)T denotes transposition.In this section we use the following notation: Lower- and upper-case boldface letters are used to represent column vectors and matrices, respectively; calligraphic letters are used to denote sets. The entry in the V, the set of edges E and the faces F. The 1D representation of the lung is extracted by applying skeletonization  denotes a smoothness parameter.The hard clustering yields the final segmentation of the input mesh and results from minimizing an energy function combining the aforementioned probability matrix and geometric surface features. The energy function minimized using alpha-expansion graph cut algorithm  is definrt of the sum of the SDF values before the narrowing procedure to the sum of the SDF values after the narrowing procedure is associated to a metric of the narrowing percentage of the airwayrt is the narrowing ratio after iteration t, i after iteration t, i and N is the number of processed faces.The SDF values assigned to each face correspond to the local diameter of the shape. Hence, by summing up the SDF values of the faces of the processed segment of the mesh we extract a representative value for the local mean diameter of the processed part. The ratio t, the user-defined weight ω, the desired narrowing ratio r and the accepted narrowing ratio error e.WL and WH in the following manner:Initialize Taking into account the aforesaid geometry processing schemes we employ the following algorithm to simulate bronchoconstriction given the desired number of iterations I is a unitary matrix, k a double constant set to 10−3 and A the average face area of the model.2.V′.Solve (2) for 3.WL and WH so thatUpdate where 4.L.Recompute 5.rt.Compute narrowing ratio 6.rt > r + e.Repeat steps 2 to 5 where t represents the iteration index.r = 0.5, e = 0.05, t = 8 and ω = 0.8. The area under study is segmented for more efficient processing and mesh contraction is performed. Figure th, and 5th generation, whereas Fig. rd generation before and after the narrowing process. These cases exhibit a narrowing ratio of 50%.For the current investigation, we set The application of different levels of deformation across the airways as a function of distance is proposed in order to enhance the mesh contraction procedure and to simulate the surface abnormalities during bronchoconstriction. Therefore, as the authors in  propose,WV is a diagonal weighting matrix. For WV we can use a custom function:where d is the geodesic distance of a point of the mesh from an anchor point.where A sinusoidal function is utilized in this study for demonstration purposes only. The user can define the function on a case-by-case basis. Therefore, a weighting parameter is set for each vertex equal to:ω is the user defined parameter.where Discontinuities and edge effects may appear considering that the processed part is reconnected with the rest of the mesh. To deal with this issue, we employ surface smoothing methods such as Taubin smoothing  or bilatThe bilateral technique estimates the new normals that can be used for vertex updating according to:D is a diagonal matrix, ζ is an integer that represents a denoising factor andwhere mi ∀ i = 1, ⋯, nf the weights of is the weighted bilateral adjacency matrix. Eq.  shows thCa is the binary adjacency matrix constructed using the k-nearest neighbors method. Finally, the vertices in each iteration t are updated according to:where a, b> represents the inner product of a and b, (t) represents iteration number and Ψi represents the set of the face vertices which are connected with vi. Equations  an ana, b> quations  are execVarious methods, such as surface reconstruction, surface remeshing, triangulation, and decimation are employed for cleaning-up the lung geometry, in order to enable smoothness and accelerate the upcoming techniques of volume meshing and solving. A smoothing process is considered compulsory to minimize any adverse effects on the study results, since the CFD analysis could be affected by additional edge effects created by the deformation of the airway geometry. Furthermore, our analysis will not be disturbed much by the structural modeling procedures, since the airflow into the lungs is essentially resolved by the topology of the generations’ geometry rather than the surface arrangement of the airways.An open source platform associated to CFD and FPT analyses, called OpenFoam , is effi−4 s is employed in order to allow numerical stability. The Courant number, the air velocity, and the mesh discretization, as designated in the CFD theoretical formulations, determine the value of the aforementioned time step. In this manner, stability and convergence of the simulations are ensured. A hypothesis of a total pressure drop of −15 Pa is taken into account throughout the simulations of inspiratory states. An additional evaluation of the inhaled particles attributes is allowed by the airflow velocity and pressure, which are assessed over the computational domain.The lung’s activity can be computationally evaluated by employing various models, such as Reynolds-averaged Navier-Stokes (RANS) or Reynolds-averaged simulation (RAS), direct numerical simulation (DNS) and large eddy simulation (LES). Amid them, the RAS model exhibits acceptable levels of accuracy along with the minimum computational cost . In thisThe motion of particles in fluids is examined by utilizing a Lagrangian approach that solves a set of ordinary differential equations along their trails. The modification of the particle location as well as the components of the particle velocity are extracted by the fluid particle tracing procedure. The associated forces applied on the particle need to be considered. Consequently, the differential equations for determining the particle location and velocity are specified by Newtonian second law, if spherical particles are taken into account:ρP is the density of a particle and dP is the diameter of a particle), Fi represents the relevant forces applied on the particle, uP is the linear velocity of a particle, ωP is the angular velocity of a particle and T is the torque applied on a rotating particle due to the viscous interaction with the fluid.where C is introduced to be multiplied with the force, in order to adopt an extension to higher Reynolds numbers. This coefficient C is based on empirical correlations obtained from direct numerical simulations or experiments. Moreover, the drag force dictates the particle’s motion in most fluid-particle systems. A drag coefficient CD is introduced as an extension to higher particle Reynolds number, whereas it is defined fromAnalytical solutions are offered for the distinct forces taken into account (Stokes flow) for small Reynolds numbers. A coefficient uF is the linear velocity of a fluid, and where The ratio of inertial force to friction force specifies the particle Reynolds number as:ρF is the density of the fluid and μF is the dynamic viscosity of the fluid. The aforesaid methodology is intended to allow the evaluation of the particle deposition into the respiratory system. In addition, it is envisaged as the first step for the detailed analysis of drug delivery efficiency, whereas it enables conclusions related to the selection of medication (size and concentration of particles).where 3, whereas their diameter is set to 10 μm, taking into account that typical coarse ambient particles (PM10) are 2.5 μm to 10 μm in diameter. Moreover, the flowrate of air at the normal lung model is 12.6 L/min, which allows particles with a diameter of 10 μm to be transported into the central generations. The inlet boundary of the computational domain is considered the input of the system, since a total of 54,000 particles are injected through it.The transfer of inhaled particles through the pulmonary system, along with the deposition fraction over several areas of interest, are investigated by a transient FPT analysis. In particular, the steady state field of airflow velocity obtained by the CFD simulation is employed to estimate the position and velocity of the particles, because of the one-way coupling between the flow field and the particles that is taken into consideration. Our simulations involve the density of the particles that is selected to be 1000.0 kg/mThe initial velocity of the particles as well as the inlet velocity of air for the CFD simulations are deemed the same. For the normal lung model, the inlet velocity of air is 1.475 m/s, which corresponds to a flowrate of 12.6 L/min. In addition, the substance of the particles is injected during an injection period of 0.75 msec by a flowrate of 199.2 mL/min to allow accurate identification of the deposition patterns. An effective simulation of the particle’s entrapment on the wall’s surface is accomplished by a stick boundary condition which is employed on the wall of the lung topology as well as on the outlets. The icoUncoupledKinematicParcelFoam solver, which is part of the OpenFoam platform, is utilized to conduct a transient analysis. In this method the flow affects the particles but the particles don’t affect the flow, since it presumes that the particles’ effects on turbulence are negligible. Consequently, an estimation of the position of the particles on the pulmonary airways is attained.Various lung models related to diverse levels of narrowings have been generated using the method previously designated. More specifically and in addition to the unobstructed lung model, a group of obstructed models have been created. Each model is characterized by the lung generation after which narrowings with a structure similar to that of a bottleneck are introduced. Furthermore, an asymmetric case where obstructions are introduced only in the right lung after the second generation is examined. An in-house established software, based on the aforesaid geometry processing sequences, have been effectively utilized for the development of these models. A CFD analysis is conducted for each model, while the output velocity fields are exploited for the corresponding FPT investigations. As a next step, the calculation of the particles deposition is attained for every segment of the lung’s model. In this context, deposition fractions are obtained for each generation of the pulmonary system, besides the left/right sections.A total pressure drop of −15 Pa is presumed in all cases as certified by past studies of airflow into the human respiratory system , 22, thuFor each lung model examined in the previous paragraph, a transient analysis of the particles characteristics is performed. A total duration of 2.16 s is considered in order to simulate the whole inhalation procedure. Three snapshots of the particles transfer into the domain of the normal lung are depicted in Fig. Moreover, particle DF is acquired for various generations as well as for distinct lung sections. By examining Fig. As a next step and as presented in Fig. d = 1 μm, d = 10 μm and d = 20 μm. These results make evident the importance of particle sizes on their distribution between the upper and lower airways, showing a great increase of DF on the upper airways when the size of the particle is increased.A parametric analysis of the particles characteristics is performed by means of several simulations for each lung model examined in the previous paragraph, where a 10 μm particles diameter was considered. In this context, the impact of the particles diameter on particle DF is assessed in conjunction with the effects of the particle density variations. For each case, particle DF is acquired for several generations as well as for distinct lung sections. Figure More specifically, Fig. d = 20 μm. This notice should be considered in combination with the fact that the majority of particles in this case are already deposited before they reach the lower airways, as illustrated in Fig. d increases, DF is enhanced even though it shows a local minimum.By inspecting the diagrams of Fig. 3 to 2000 Kg/m3, as depicted in Figs. ρ is increased, as depicted in Fig. ρ is augmented. These results can be used as an initial step for future detailed analysis by medical researchers for the in depth understanding of medication effectiveness in regards to the particle densities.Finally, an additional analysis is performed regarding the variation of the particles density between 1000 Kg/mIn the present study several detailed models of the airways obstructions associated with pulmonary diseases have been developed utilizing a custom geometry processing sequence, whereas the breathing process of airborne particles has been assessed numerically via CFD and FPT algorithms. Apart from the evaluation of the airflow behavior, the study focused on the properties of inhaled particles as an effective assessment tool for the optimization of treatment with the appropriate substances and densities. Two obstructed groups of models were examined, i.e. models with obstructions in both lungs and a model with obstructions in the right lung only. Moreover, a detailed parametric analysis identified the effects of the particles size and density on the substances deposition in the upper airways as well as the five first generations of the lower airways.The results of the study confirmed the effects of obstructions in breathing capability of patients, as well as the discrepancy between the left and right lung in terms of airflow and particles deposition. Several DF assessments clarified that most particles are guided on the one lung, when narrowings are detected on the other side only and thus, any medication is shown to be directed away from the problematic blocked area. These results form the basis for further clinical investigations in regards to the personalized effectiveness of inhaled medication associated to specific lung characteristics of patients. The vision of the current work is to form the basis for a clinical methodology that will allow the in depth analysis of personalized lung models, so that medical personnel could select and provide appropriate medication (particle size and density) by quantifying the particle deposition capability on different parts of the patient’s lungs. This feature envisages a very important and innovative aspect to the personalization treatment of lung diseases by maximizing the efficiency of the inhaled medication on a regional perspective.Even though the derived lung models provide information about the first five generations, adequate deductions have been drawn that could be extended in the future with more thorough analysis of more detailed lung models including higher airway generations. Such an extension of the models to higher generations of the lungs may provide further details and accuracy and could also reveal medication deposition phenomena that are inaccessible in the current investigation. In this context, an extended study for a large number of patients may allow the necessary quantification of inhaled medication into the lungs, which is required for extended personalized treatment.Apart from the extension of the simulation scenarios to a wider spectrum of models and obstruction cases, future directions of the current study will include the investigation of outcomes in the clinical setting and with the involvement of patients. This approach aspires to verify the effects that the lung geometry may have on the actual effectiveness of inhaled medication and how the current results can be translated into useful and clinically significant methodologies for the optimization of management of respiratory diseases.The utilization of contraction algorithms to clarify the diverse conditions of lung obstructions has been presented in this paper. In addition, an effective assessment of the consequences of inhaled particles in a regional oriented perspective has been performed by accurate CFD and FPT simulations. For the case of obstructions in both lungs most particles are driven upon the narrow regions when symmetrical narrowings appear. Moreover, partial medication transport is accomplished when only one lung is obstructed showing a decreased deposition of particles in the areas of inflammation. An additional parametric analysis regarding the variation of particles size and density allowed the better interpretation of particle deposition within the pulmonary system. It has been shown that the specific characteristics of particles (particle size and density) significantly affect the point of the respiratory system that they are deposited. More specifically, larger particles of higher density are shown to be affecting mainly the upper airways, whereas substances of lower particle size and density are deposited mainly on the higher generations of the airways. These observations could be valuable when treating lung maladies with inhaled medical substances and are aiming to form the basis for the clinical investigation and testing of innovative personalized treatment approaches that take into account the size and density of particles of inhaled medications.


The adjoint method shows an efficient way to incorporate inverse dynamics to engineering multibody applications, as, e.g., parameter identification. In case of the identification of parameters in oscillating multibody systems, a combination of Fourier analysis and the adjoint method is an obvious and promising approach. The present paper shows the adjoint method including adjoint Fourier coefficients for the parameter identification of the amplitude response of oscillations. Two examples show the potential and efficiency of the proposed method in multibody dynamics. Applications of the adjoint method to solve a variety of optimization problems in engineering sciences are widespread. Much attention to this approach has been paid recently in the context of multibody systems  in thMoreover, from the experiment point of view, the frequency domain plays a key role when analyzing complex multibody systems. Very often only frequency ranges can be investigated in detail. Too low frequencies may not be measured, e.g., with acceleration sensors, and too high frequencies are mainly caused by measuring noise. Identification in the time domain would lead to some kind of best-fit solution. Hence, the goal of the identification is in general to fit a special frequency range. In , a systeThe latter mentioned works emphasize the importance of the spectral analysis of the system in order to understand the behavior of the system and consequently be capable of efficient parameter identification. The present paper shows a method for parameter identification in complex multibody systems in the frequency domain. A combination of the adjoint method and classical Fourier analysis for the identification of the amplitude response is presented herein as a novel approach and is applied to engineering problems.Let us consider the system equations of motion in first order formFollowing the basic idea presented in Nachbagauer et al. , the adjmentclass2pt{minim if Eqs.  are satimentclass2pt{minimSecond, the terms including ) in Eq. . Finallymentclass2pt{minimIn most cases, multibody systems are described by a system of differential algebraic equations (DAE)Using the additional variables The differential equations for the Fourier coefficients can be formulated analogously to Eqs.  and 7)  7) by18n in Eq.  is minimn in Eq.  and by tIt has to be mentioned here that the symmetry of the mass matrix  If Eqs.  are satiIn order to present the performance of the identification method, we study a system of pendula connected to a cart performing a one-dimensional motion. As it can be seen in Fig. The desired spectrum needed for the computation of the cost function J in Eq.  is genermentclass2pt{minimThe actual parameter identification is initiated with the parameters In order to demonstrate the difference from identification performed in the time domain, in Fig. By using a quasi-Newton method like the BFGS algorithm for finding a minimum of t of Eq. , the solIn this section the presented method is applied to a model of a four-cylinder engine, shown in Fig. The torsional vibration modes of the crankshaft are crucial for the parameter identification process. Therefore, six lumped masses resulting in six degrees of freedom see Fig.  are intrFor describing the in-plane motion of an engine’s connecting rod (conrod) three degrees of freedom are introduced. According to Fig. In the used model, each piston features only one translational degree of freedom. The mass of each piston is denoted as The primary side of the dual mass flywheel (DMF) is mounted on the right end of the crankshaft see Fig. . Hence, The torsional vibration damper (TVD) is installed for reducing the internal torsional vibrations of the crankshaft. Within the case of the TVD, a flywheel ring is gliding in a viscous fluid. Usually, the mathematical model of the TVD is approximated by Maxwell elements. In this contribution, two Maxwell elements and one parallel spring are used. In Fig. The pulley wheel used for driving additional aggregates introduces another degree of freedom (The cylinder pressure is given by a two-dimensional map depending on the rotational speed and the crankshaft angle. The pressure is applied on each piston in accordance with the firing order.In order to simulate the run-up performed on the real test bench, the rotational speed of the secondary side of the DMF is increased up to the final rotational speed. The ramp used for the simulation is given in Fig. In this section the identification of four parameters  to Eqs. , the difIn Fig. In Fig. mentclasspt{minimaIn Fig. The present paper shows a new method for parameter identification using the amplitude response of oscillations in multibody system dynamics. The proposed method combines the classical Fourier analysis with the adjoint sensitivity analysis for the gradient computation in an optimization problem. Using the spectrum of a system output helps in understanding the behavior of a system whereas the interpretation of the time domain data is not always promising because of excessive time ranges, noisy signals, or systematic errors.The method is applied to a nonlinear cart–pendulum system. In order to demonstrate that the method copes with system uncertainties in the example, one parameter, which is not part of the identification, is set to a value different from the one used for generating the measurement. Therefore, the desired spectrum cannot be obtained to its full extent, but only in the given frequency range. In the time domain this would lead to an optimization problem that is not well-posed.Further, an identification is performed using the model of a four-cylinder engine. Here, the robustness of the method and also the capability to deal with larger systems are pointed out.


Cool water packs are a useful alternative to ice packs for preventing unintentional freezing of vaccines during outreach in some situations. Current guidelines recommend the use of a separate refrigerator for cooling water packs from ambient temperatures to prevent possible heat degradation of adjacent vaccine vials. To investigate whether this additional equipment is necessary, we measured the temperatures that vaccine vials were exposed to when warm water packs were placed next to vials in a refrigerator. We then calculated the effect of repeated vial exposure to those temperatures on vaccine vial monitor status to estimate the impact to the vaccine. Vials were tested in a variety of configurations, varying the number and locations of vials and water packs in the refrigerator. The calculated average percentage life lost during a month of repeated warming ranged from 20.0% to 30.3% for a category 2 (least stable) vaccine vial monitor and from 3.8% to 6.0% for a category 7 (moderate stability) vaccine vial monitor, compared to 17.0% for category 2 vaccine vial monitors and 3.1% for category 7 vaccine vial monitors at a constant 5 °C. The number of vials, number of water packs, and locations of each impacted vial warming and therefore percentage life lost, but the vaccine vial monitor category had a higher impact on the average percentage life lost than any of the other parameters. The results suggest that damage to vaccines from repeated warming over the course of a month is not certain and that cooling water packs in a refrigerator where vaccines are being stored may be a useful practice if safe procedures are established. Studies from 2006 to 2015 reported that 19% of vaccine shipments in lower-income countries and 38% in higher-income countries were exposed to temperatures below recommended values The impact of heat exposure on potency is unique to each vaccine and manufacturer. A tool that can be used to generalize this impact is the vaccine vial monitor (VVM), a heat-sensitive label required on WHO prequalified vaccines. Similar methods have been used in previous studies a is the activation energy, R is the gas constant, A is a constant, and T is the temperature in kelvin VVMs consist of a reference circle with a color-changing indicator dot inside. The lifetime can be defined as the time it takes for the optical density (OD) of the indicator dot to match the OD of the reference circle (referred to as the endpoint by WHO). This lifetime is temperature dependent, and there is a known relationship between temperature and lifetime for each VVM category based on the Arrhenius equation, y of VVM . Each WHThe goal of our study was to understand the impact on vaccine life of cooling warm water packs in a refrigerator used to store vaccines by using VVM life as a proxy for vaccine life and the Arrhenius equation for calculation of VVM life. This would give us information on the value of having a dedicated refrigerator for cooling water packs.2The overall design of testing was to place water packs at 43 °C into a refrigerator with vaccine vials at 2–8 °C and measure the temperatures of the vials over time to generate warming curves. These curves were subsequently analyzed using calculated time-temperature curves for each category of VVM to estimate the impact of cyclic warming on vaccine life.To prepare for testing, 10-mL vials were filled with water and some were instrumented with thermocouples . Before the start of each test, the selected number of vials was arranged in a PQS-prequalified refrigerator  to cool. PQS-prequalified water packs  instrumented with thermocouples were conditioned to 43 °C, the “hot zone” temperature for prequalifying cold chain equipment Temperature collection at a rate of two samples/minute  began immediately following placement of the water packs in the refrigerator and continued until the vials and water packs reached at least 5 °C. Warming curves were plotted and then trimmed to include only the values from the first measurement to the last one where the vial temperature exceeded 5 °C. In this way, excursion curves were generated so that a low refrigerator set point or a long test would not artificially deflate the impact of warming. A threshold of 5 °C was chosen as it is the middle of the cold chain temperature range and is a standard testing point for VVMs Once warming curves were trimmed, an intermediate step was necessary to use VVMs to generalize the thermal impact of warming to vaccines in each category of VVM. To apply the time-temperature curves for VVMs to the measured data, it was necessary to calculate those curves from the published lifetime-temperature points. In the Arrhenius equation, perature . Since tThe known Arrhenius equation for each VVM must then be applied to the warming curves to estimate the impact of warming. To do this, the percentage life lost for each data point is calculated by finding the daily life lost at that temperature from the Arrhenius equation and then calculating the life lost in 30 s at that temperature. The total life lost due to warming is the sum of the values for life lost at each 30-s data point. This process is demonstrated in It is likely that vaccines would be exposed to excursions from 5 °C more than once from placement of warm water packs, but only at the last stage before use. This would be at the final health post or clinic, where cool water packs would be recooled in the vaccine refrigerator. Thus, our aim was to understand the impact of one month of repeated, daily cycling of water packs on vaccine lifetime. Because VVMs (and vaccines) continue to decay even within the cold chain, this would not be only the life lost during one excursion multiplied by 30, but rather would be life lost over 30 daily cycles, each consisting of one excursion from 5 °C plus the remainder of the day at 5 °C. This could be reported as the percentage life lost during this daily cycling, or as the amount of time the vaccines would have to be kept at a constant 5 °C for the repeated excursions to cause the VVM on the vial to reach endpoint before the end of the month. A month has been simplified here to 30 days.3Average and maximum values for life lost during 30 days of cyclic warming in eight different test cases are shown in These results demonstrate that while vials in all test setups were exposed to temperatures above 5 °C, 30 days of cyclic warming would not inevitably cause early conversion to endpoint for any category of VVM. The life lost during a month for all four categories of VVM using the worst-case vial temperature curve, from setup 8, is shown in We investigated several factors that could influence the level of warming a vial would be exposed to, including the number of water packs cooling at a time, the arrangement and spacing of a fixed number of vials in the refrigerator, and the total number of vaccine vials in the refrigerator. From setup 1 to setup 2, the water pack load was increased from four to eight water packs, enough to fill one or two vaccine carriers. The average percentage life lost for the most sensitive category—VVM2—over a month increased 2.92%—from 19.98% to 22.90%—due to the increase in water pack load, and the maximum for any measured vial increased 7.33%. To investigate the impact of vial arrangement, ten vials were tested in identical arrangements on the floor and on a shelf in the refrigerator in setup 3 and setup 4. The average life lost increased 10.59% and the maximum increased 9.66% due to moving the vials from the floor to the shelf.The spacing of vials was tested by arranging ten vials close together in setup 4, then distributing them more loosely in setups 6 and 7. Results for the VVM2 category were similar for these tests, the largest difference among the three being a decrease of 3.62% in the average life lost from setup 4 to setup 7. However, there was an increase of 0.61% in the maximum life lost between the same tests despite the decrease in the average life lost, indicating that a larger spatial distribution leads to a wider range of life lost, due to varying proximity to the water packs . In setuTo investigate the impact of vial load on vial warming, tests were run with 1 or 10 vials on a shelf in setups 5 and 4, respectively, and with 20 and 168 vials on the refrigerator floor in setups 2 and 8, respectively. The average calculated life lost across 10 vials for VVM2 in setup 4 was 4.16% lower than that for the single vial in setup 5, and the maximum single vial life lost in setup 4 was 3.81% lower than that for the single vial in setup 5 .Comparing 20 vials in setup 2 and 168 vials in setup 8, the average VVM2 percentage life lost across 30 days increased 3.15% from setup 2 to setup 8, but the maximum increased 9.72%, indicating that there was again higher variability in the larger vial load. This is evident when comparing the vial arrangements layer to layer: the average VVM2 percentage life lost decreased 1.51% from setup 2 to setup 8 when comparing only the bottom layer of vials on the refrigerator floor. The percentage life lost for the second layer decreased 0.25%. Only the top two layers of the setup 8 vial arrangement contributed to the overall increase in life lost from setup 2 to setup 8. This stratification across layers, as well as the temperature gradient due to proximity to the water packs seen in setup 7, demonstrates that location in the refrigerator has a higher impact on VVM life lost than the number of vials, though the number and location of vials in the refrigerator are dependent. However, as it might be expected, VVM category was shown to have a greater effect on VVM life than any of the other factors investigated here.Some limitations of this study were that testing was only carried out in one refrigerator and that many tests were carried out with lower vial loads than would likely be found in a vaccine refrigerator in a low-resource setting. Other factors that would be valuable to study include the volume of vaccine in the vials, the impact of refrigerator air flows, and the impact of warming in different types of refrigerators. In addition, there is a lack of data on the impact of thermal cycling on the relationship between vaccine potency and VVM behavior within this temperature range. Another caution is that if the vaccines had not returned to equilibrium before cooled water packs were exchanged for additional warm ones, the thermal impact could intensify and it might take fewer cycles before the VVMs on the vaccines reached endpoint. One further concern regarding the use of VVMs as a proxy for vaccine life is the correlation between VVM decay and vaccine decay. VVMs do not provide direct information on stability 4Our study suggests that serious damage to vaccines cannot be assumed from a single excursion event or from repeated exposure to warm water packs in the same refrigerator over the course of a month. Several factors result in loss of VVM life due to warming, but the inherent heat stability represented by the different categories of VVMs was found to be most important; i.e., vaccines in vials with a VVM2 are most likely to be damaged from cyclic warming. The other important factor was location in the refrigerator, with the phase-change material-lined floor and walls of the testing refrigerator better at resisting warming of vials. In many situations, the practice of placing warm water packs in a vaccine refrigerator would not cause any serious loss of vaccines beyond that occurring at cold chain temperatures over time. Further research is necessary to define safe ratios of and distances between vaccine vials and warm water packs in varying refrigerators. If the decrease in cool life due to using cool water-packs is acceptable, and if there is extra space available in vaccine refrigerators, cooling water packs in a refrigerator with vaccines may be a beneficial practice in cold chain management. By using space in already installed and available equipment, this practice could reduce loss of vaccines due to freezing without additional cost. The data presented here and the process outlined for evaluating the effects of the practice are useful tools to support cold chain management and regulatory entities in making these decisions.


This paper describes in detail the new circuit, summarizes the enclosure construction, and presents data on the performance of the system.We describe the design of a new temperature-regulation circuit, which is used as an outer oven controller for new standard cell enclosures, with the emphasis on improving the reliability of the temperature control. A redundant protection circuit is used to prevent loss of temperature control caused by component failures in the controller. The temperature control of the outer oven of the enclosure is better than 0.4 mK per °C change in ambient temperature. When used with the additional inner controller the sensitivity of the cell temperature to the ambient temperature is improved to 20  If saturated standard cells are to be used as a high precision voltage reference, they must be kept in a constant temperature-regulated oil bath or air enclosure because of their large temperature coefficient of EMF. The requirements for such an enclosure are good temperature stability and high reliability of the temperature control circuit. The importance of the reliability requirement is often overlooked. If the enclosure (and cell) temperature changes significantly , the chemical equilibrium within the cell is disturbed and after control is re-established it may still take several weeks or months for the cell EMFs to recover to their original values. Sometimes an unpredictable permanent change in the cell EMFs can also occur. Recently, two new standard cell enclosures have been constructed with the emphasis on reliability of the temperature control circuitry. The new enclosures are similar to two older standard cell enclosures, previously constructed at NBS in 1974, but the controller circuitry has been redesigned to be more reliable and to replace obsolete components [The mechanical construction details of the new enclosures are the same as for the previous enclosures, i.e., they consist of four concentric aluminum cylinders separated by formed polystyrene insulation with two of the four cylinders controlled by an outer oven controller and an inner oven controller. As in the original design, the outer cylinder is unheated and thermally lags the enclosure from ambient temperature changes. The next two cylinders are the outer heater and inner heater, respectively, with the last cylinder being a temperature lagged cell compartment to further reduce any temperature gradients. However, the original controller circuitry has been changed completely. A simple control circuit using a platinum resistance thermometer with chopped-dc excitation and phase sensitive detection developed by Cutkosky and Davis is used as the inner oven controller . The outThe enclosure is designed for an inner oven temperature of 30°C with the outer oven sėt to 29.9 °C. Thus, the outer oven provides most of the power, 4 W with an ambient temperature of 23°C, while the inner oven typically supplies 75 mW with a maximum output capacity of 300 mW. Because of the limited power capacity of the inner oven (and the correspondingly limited temperature increase), guaranteeing the integrity of the outer oven is sufficient to prevent extreme changes in the inner oven temperature even in the event of an inner oven failure.The main controller and backup controller for the outer oven are nearly identical control circuits using independent thermistor sensors in Wheatstone bridges and high-gain dc amplifiers to provide proportional temperature control see . Power tThe arbitration circuit consists of four voltage comparators, a transistor and a sensitivity relay. This circuit determines which controller is operating correctly and switches the proper controller output to the outer oven heater. Each controller output is compared to a high and low limit using two comparators. The high and low limits are set to ± 10 V for the main controller and ± 5 V for the backup controller. The outputs of the controllers exceed either of the limits only if a controller has failed or the enclosure is warming up from ambient temperature. Under normal conditions when the controller outputs are within the limits, the output voltages of the four comparators CP1–CP4 are high see . The fouIf the main controller were to fail due to a faulty component and supply no power to the heater while the backup controller continued operating properly, the output of comparator CP2 would go low and diode D2 would turn on. As the temperature of the enclosure drifted down eventually CP3 would go low turning on diode D3, forcing potentials a and b low, and causing the relay to operate. A similar sequence occurs if the main controller were to fail and supply full power to the heater. The logic requires that both controllers indicate that the enclosure temperature is out of control and to disagree as to the direction (high or low) before switching to the backup controller. This permits the enclosure to warm from room temperature without switching to the backup controller. Once the backup controller has gained control the second set of contacts on the relay provide a self-locking arrangement to keep the relay energized. The control can be returned to the main controller only by opening switch S1 manually. A failure of the backup controller has no effect on the operation of the circuit as long as the main controller operates normally. Diodes D1–D6 are light emitting diodes mounted on the front panel of the controller to indicate the status of the outer oven temperature control. One of the advantages of this design is that a failure of the backup controller can be discovered immediately by observing the light emitting diodes, even if it is not the active controller.5 and 2.17×104, respectively. The gain of the main controller was empirically determined for good regulation and rapid recovery from ambient temperature changes. The gain of the backup controller was deliberately set lower to avoid a conflict between the controllers due to their temperature set points drifting apart. It should be noted that for proper operation the control temperatures (set points) of the main controller and backup controller must be carefully adjusted to the same value. This was accomplished when the enclosures were first put under test by adjusting the trim resistor on the backup controller, which parallels an arm of the bridge, to equalize the outputs of the controllers. Under normal operating conditions a change in the set point of the main controller of 5 m °C (due to a drifting resistor in the bridge for example) would cause a negligible change in the amplifier output to the heater, while the voltage output of the backup controller would change 1V. With the currently set limits of the comparators the two controller set points can drift apart as much as 0.025 °C (and this is considered to be an unlikely occurence) before a failure is indicated.The main and backup controllers differ only with respect to the total circuit gain, with gains of 2.17×10μK. Since the enclosure is a system with large thermal inertia, the time constant of the controller feedback must match it. The inner oven is held at a temperature of 30°C, approximately 0.1 °C higher than the surrounding outer oven. The heater voltage is indicated on a meter mounted on the front of the controller and the outer oven temperature is adjusted so the inner oven output voltage is at mid-scale (≈75 mW which corresponds to a 0.1 °C temperature rise). A platinum resistance thermometer (110 Ω @ 30°C) was chosen as the sensor because of its excellent long-term stability, although its temperature coefficient is much smaller than that of the thermistor and the output of the bridge is only 63.3 nV/mK. In order to avoid the effects of dc voltage offsets and drifts in a dc amplifier circuit, a circuit consisting of a chopped dc amplifier and a phase sensitive detector was chosen . Its outμK for ambient temperature changes of 1 °C. The maximum temperature excursion over a period of more than fifty days was found to be less than 1 mK.In order to test the stability of temperature control of the enclosures with a changing ambient temperature, the enclosures were placed in a temperature-controlled chamber and the temperature was changed in the sequence 24°C, 28°C, 24°C, 20°C, 24°C. The enclosures were held at each temperature for one or two days. The outer oven temperature was monitored by measuring the output of the backup controller. A plot of the outer oven temperature change with ambient temperature for one of the enclosures is shown in μW dissipated in each thermistor. The output is measured directly by a nanovoltmeter or a high-resolution DVM. For the following measurements a DVM was used that had a short term measurement noise of 0.02 μV, which corresponds to 5 μK. As shown in μK for ambient temperature changes of 1 °C.The temperature of the cell compartment of the enclosure is monitored by two thermistors mounted in a hole in the bottom of the compartment. The thermistors (10 kΩ @ 25°C) are connected in opposite arms of a Wheatstone bridge with two low-temperature-coefficient resistors (10 kΩ) in the other arms. The low-temperature-coefficient resistors are contained within the outer oven to further improve their stability. The bridge is powered from the regulated power supply of the inner oven. The output of the bridge is 4.155 mV / °C with only 1.37 We have demonstrated that with a small amount of additional circuitry a substantial improvement can be made in the reliability of a temperature controller. With this design, a failure of anyone component will not cause a significant aberration to the cell temperature and a failure can be detected immediately so that corrective action can be taken. In addition, the circuitry has been simplified over the original design, thus greatly reducing the possibility of a failure. Despite the simplicity of the outer oven controller it can be used alone to obtain temperature control with a stability of 1 mK or, as shown here, it can be used with an additional inner controller to provide even better stability.


The aim of this study was to show the preferences of terminal values of personal and social character and the level of religious experience: God’s presence and God’s absence, as well as to examine the relationship between the two variables in the groups of seminary students of philosophy and students of physics. The following methods were applied in the study: Rokeach Value Survey and Głaz’s Scale of Religious Experience. The study was conducted amongst university students in Kraków (Poland). The results of 100 correctly completed sets of questionnaires were analysed. The results analysis proves that seminary students of philosophy have a higher level of religious experience: God’s presence and God’s absence than students of physics. Seminary students of philosophy most preferred terminal values in personal and in social character. In the group of seminary students of philosophy, from amongst the four most preferred terminal values, two have a significant relation with the experience of God’s presence and God’s absence, whereas in the group of students of physics only one of them has a significant relation with the experience of God’s absence. Research studies show that values have significant relations with the religious experience and perform an important regulatory function in the process of development of a human being’s religious life  called instrumentalvalues, which have a moral and competence dimension. According to Rokeach, values have a beyond situational character and provide standards for the choice of behaviour as well as for the assessment of one’s own behaviour and that of other people. Rokeach believes that all people, regardless of time and place, respect the same values, although to a different extent. The system in which particular terminal and instrumental values function is characterised by a specific organisation . Sacrum influences a human being in two ways—it fills them with awe and fear (mysteriumtremendum), and simultaneously attracts and encompasses them (mysteriumfascinans). On the one hand, sacrum arouses fear in a person, anxiety, sometimes fright, and, on the other hand, it is appealing and arouses fascination. Religious experience is often accompanied by tension and one’s inner conflicts. It is because it is ambivalent in itself. A human being, when establishing contact with sacrum, experiences an ambiguous feeling: he sees his imperfection and sinfulness, and, at the same time, he desires meeting which is sacred. Obviously, these are by no means purely emotional states due to the fact that they engage the whole personality. Other scientists show that in origin it has no religious reference. For instance, it is thought that religious experience may be sourced by psychedelic drugs , meaning something that happens to man, such as a meeting with another person. Religious experience is a process taking place in the context of a specific religious tradition. Therefore, it is considered as part of two dimensions of human life: the community dimension and individual dimension , the subject of religion (a human being), and a religious relation personal in character Głaz . What deTwo kinds of lifestyle are encountered in our culture: clerical and secular (lay). The clerical lifestyle is directed at self-realisation with respect to God and another person, whereas the secular one is directed at self-realisation with regard to another person and the surroundings. The former suggests that a human being’s care about their own development, experiencing happiness, and solitude takes place in an institutional religious group where a person finds fulfilment individually and socially. The development includes following Christ’s footsteps and rejecting certain values (marriage—in the Roman-Catholic Church) Thoppil . The latWhen choosing lifestyle and a university faculty, a person is guided by various criteria. One of them is the content of the curriculum for a given faculty. Another criterion is, for instance, being there for others and with others. It encompasses any kind of service manifesting itself in engaging for the sake of others. There are also more practical criteria, namely prospects of a good job or being popular in a given social circle. Motivations of this kind of choice can to a greater or lesser extent contribute to realisation of a person’s talents, choosing the right values, and to integrate development of his or her personality and religious life . The study was scheduled for after academic classes. All the participants had been personally instructed how to complete the questionnaires. Over a dozen of sets of questionnaires were only partly completed, and consequently, they were excluded from the analysis. The results of 100 correctly completed sets of questionnaires (50 by seminary students of philosophy and 50 by students of physics) were then analysed.In order to obtain empirical material with the help of which the research problem can be solved, a study was conducted in Kraków in 2012 amongst university students. The group of students of physics consisted of young people at a state university (Jagiellonian University). The group of seminary students, though, consisted of clerics at a private university (Academy Ignatianum). All participants were Polish born. All the students declared belonging to the Roman-Catholic Church and have had religious experience of God’s presence and God’s absence. The age of the participants ranged between 21 and 27  between the Scale of Religious Experience and Prężyna’s Scale of Religious Attitude is .63.The scale has three sub-scales. The first one describes the intensity of the experience of God in general (OB); Cronbach’s alpha coefficient of internal consistency is .92. The second scale serves to measure the intensity of the experience of God’s presence (OB), with Cronbach’s alpha coefficient of internal consistency at .94. The third scale describes the intensity of the experience of God’s absence (NB). Cronbach’s alpha coefficient of internal consistency is also high and stands at .91 Głaz . In the N = 250) and obtained for terminal values coefficients ranging from .51 to .88. The scale was adapted to the Polish conditions by Brzozowski  and standard deviations (SD). In order to define a statistically significant relation between terminal values of personal and social character, and religious experience: God’s presence and God’s absence, the analysis of multiple stepwise regression was applied. Therefore, a decision was made to extract independent variables in order to see which and to what extent explain the variance of religious experience: God’s presence and His absence within the respective groups of the studied subjects.The analysis of variance (ANOVA) was applied. The results analysis was carried out on the basis of mean values  and a higher level of experience of God’s absence (NB) than males studying physics .The results obtained in the Scale of Religious Experience (SRE) Table  indicateFor the interpretation of the preferences of terminal values, the top four values with the highest ranks were considered. The results obtained in the Rokeach Value Survey (RVS) Table  concerniR = 0.33), and together all the values explain 38 % of the variance of that experience (OB) (R = 0.61). The goodness of fit of the obtained stepwise regression equation defines the test value F = 5.49; p < 0.01. In the group of males studying physics, one terminal value counts—equality, which explains 12 % of the variance of the experience of God’s presence (OB) (R = 0.34). The goodness of fit of the obtained stepwise regression equation defines the test value F = 4.22; p < 0.01.Five different terminal values have a significant relation with religious experience of God’s presence (OB) Table . In the R = 0.32), and all of the terminal values, in turn, explain 39 % of the variance of that experience (NB) (R = 0.62). The goodness of fit of the obtained stepwise regression equation defines the test value F = 5.69; p < 0.01. In the group of students of physics, two terminal values count: an exciting life and wisdom. The first value—an exciting life—explains 20 % of the variance of experience of God’s absence (NB) (R = 0.45), whereas both of them explain 22 % of the variance of experience of God’s absence (NB) (R = 0.47). The goodness of fit of the obtained stepwise regression equation defines the test value F = 4.02; p < 0.05.Five different terminal values have a significant relation with experience of God’s absence (NB) Table . In the This paper presents the author’s attempt to show the relations between terminal values in personal and in social character and religious experience: God’s presence and God’s absence in the lives of seminary students of philosophy and students of physics. For the interpretation of the preferences of terminal values, the top four values with the highest ranks were taken into consideration for the analysis. The verification of the study hypotheses and the analysis of the study problem are as follows.The first part of the hypothesis, which suggests that there is a difference in the level of religious experience: God’s presence and God’s absence between seminary students of philosophy and students of physics, was fully confirmed. Seminary students of philosophy are accompanied by a higher level of experience of God’s presence and His absence than students of physics. According to the literature and some researchers’ suggestions Głaz , this reThe hypothesis which suggests that the most preferred terminal values significantly contribute to the occurence of religious experience of God’s presence and God’s absence was confirmed only to a certain extent in the group of seminary students of philosophy as well as in the group of students of physics. In the group of seminary students of philosophy out of the four most preferred terminal values in personal character, salvation and wisdom are significantly related to experience of God’s presence, and, as far as religious experience of God’s absence is concerned, so are the terminal values—salvation and personal freedom. These values are in personal character. However, in the group of students of physics none of the four most preferred by them values has a significant relation with experience of God’s presence, and only one value respected by them, in personal character—wisdom—is significantly related to experience of God’s absence. In this case, Rokeach’s theory was confirmed only to a certain extent.According to Rokeach’s  theory, It was expected, in accordance with the vocation and lifestyle of seminary students preparing for priesthood, that seminary students of philosophy are accompanied by a higher level of experience of God’s presence and His absence than students of physics. Some research findings (Zarzycka and Maslowski A greater number of terminal values were expected to have a significant contribution to the occurence of religious experience: God’s presence and His absence in the group of students of physics, which was not confirmed. It would suggest that students of physics reveal lack of internalisation of terminal values. According to Rokeach’s  theory, In the group of seminary students of philosophy, the contribution of terminal values in the process of explaining the variance of experience of God’s presence ranges from 11 to 38 % and God’s absence from 10 to 39 %. In the group of students of physics, though, the contribution of terminal values in the process of explaining the variance of experience of God’s presence is 12 % and God’s absence from 20 to 22 %. It suggests that in this case terminal values, which define the students’ aspirations and goals and present a certain system of reference which allows young people to assess reality and direct their lives, a few times more strongly imply and strengthen experience of God’s presence and His absence in the lives of seminary students of philosophy than in the lives of students of physics.Religious experience of God’s absence—and even more God’s presence—as an important element of young people’s religiosity, which enhance getting to know more oneself and the surroundings, is strongly conditioned by the regulatory function performed by terminal values in personal character, which means the ones which refer to university students’ process of personal development; a considerably less important role is played by terminal values of pro-social dimension, meaning the ones which demark correct interpersonal relations.The analysis of the problem indicates that there exists a significant correlation between terminal values of personal and social character and religious experience: God’s presence and God’s absence. In spite of their correlations, each of these dimensions is autonomous in terms of its cognitive, behavioural, emotional, and evaluative aspects. Each of these decides about self-realisation of a person and about the way of living one’s own life. The choice of a lifestyle and the related university faculty creates conditions for gaining knowledge, and the realised system of values determines the cognitive network of seminary students of philosophy and students of physics; it activates and outlines standards of their behaviour, as well as performs an important function of the criteria determining their line of thinking and acting. Religious experience: God’s presence and God’s absence encourages students to deeper reflection and examination of their reality and the surroundings.A current problem is emerging, namely that of academic youth in Poland departing from the dimension of institutional religiosity in favour of the aspects of religious experiences (Zarzycka and Masłowski


The light scattering photometer recently described in this journal by McIntyre and Doderer has been examined to determine its ability to measure the absolute scattering of liquids. The absolute scattering of polymer solutions was determined from transmission measurements and from two different transverse measurements. The experimental results are in good agreement. The variables of the photometric system were also analyzed and experimentally studied to determine its ability to measure absolute scattering of liquids under different geometrical arrangements. For the determination of the molecular weight of a solute by light scattering, the proportion of incident light that is dissipated as molecular scattering must be measured. This scattered light may be determined in either of two ways. First, the amount of light scattered at a given angle with respect to the incident beam of light may be experimentally determined when a given volume of illuminated solution is seen by a detector that has a well-defined angular acceptance. This method obviously requires that either a great number of dimensional details and optical constants be known or a comparison standard be available. Second, the amount of light scattered over all angles may be determined. The total scattered light may be determined by using an integrating sphere or by measuring the loss of light that occurs in the passage of a light beam through a given path of solution. The latter method of measuring total scattering requires that very precise transmission measurements be made, that extreme care be employed to eliminate secondary scattering in the experimental setup, and that materials be chosen that remove energy from the light beam only by molecular scattering and not by absorption or fluorescence. A molecular theory of light scattering is needed to relate the first experimental method, which measures the light scattered from a solution at a given angle, to the second method, which measures the total amount of light scattered at all angles.2θ) when the incident light is unpolarized and θ is the angle measured from the direction of the incident beam to the direction of observation. The radiant intensity of scattered light, θJ, in the direction θ, from a volume, V, that is illuminated by an incident beam of irradiance H0, can be described by a parameter called Rayleigh’s ratio, θR, as shown in The theories of Rayleigh , 2,1 whidl, of solution can be calculated and is known as the turbidity, τ. It is usually expressed in the integrated form shown in 2θ) applies, the integration of the scattering over all angles yields a simple relation between Rayleigh’s ratio and the turbidity as shown in If now the scattering is summed up over all angles, the fractional decrease in the flux of the incident light for a small length, By measuring both Rayleigh’s ratio at 90° and turbidity of a solution of isotropic particles, a light scattering photometer can be tested for self-consistency solely on the basis of optical determinations.The work of Carr and Zimm  on the aIn addition to the direct optical methods of checking the consistency of a light scattering photometer, there are also indirect ways which use molecular theories to relate either the scattering of pure liquids to Avogadro’s number, or the scattering of solutions to the known molecular weight of the solute. Both of these indirect measurements have been carried out with this photometer although the results are not given at this time because greater care must be given to the preparation of “pure” liquids. A comparison of the molecular weights of polystyrene fractions determined by equilibrium ultracentrifugation and by light scattering will be published later.A, solid angle dΩ, and the angle α between the normal to the surface and the direction of irradiation:Pradiant flux, J=dP/dΩ, flux per unit solid angle.radiant intensity, N=dJ/dA cos α, intensity of the area dA projected perpendicularly to the direction θ.radiance, H=dP/dA2, flux incident on the small area dA2.irradiance, W=dP/dA1, flux from the element of the surface dA1.radiant emittance, If a source of radiant energy is designated 1, and a point in space from which the flux is measured is designated 2, then the following photometric quantities may be defined in terms of the area H0. All other quantities without subscripts refer to the secondary source. Unfortunately two secondary sources need to be considered, a diffuser and a scattering solution, and accepted convention makes it necessary to talk about the directions from the source to the detector in different ways. For a plane diffuser the angle θ is measured from the normal to the surface of the diffuser. For a scattering solution the angle θ is measured from the forward direction of the beam.The incident irradiance from the lamp to a secondary source is referred to as Diffusing plates of magnesium oxide or magnesium carbonate are used frequently as attenuators in light scattering calibrations to provide a known fraction of the incident radiant flux. Since only the total diffuse reflectance has been determined for these diffusers, it is necessary to know that the particular diffuser used in the light scattering experiments redistributes the flux so that the radiance is equal in all directions. If this is true, it follows that the radiant intensity from the diffuser obeys Lambert’s law  that are separated by a distance q, and the radiant source is located in the plane of one of the apertures S1 and has a radiance θN in the direction of θ. The source is uniform over S1 so that the radiance is constant over the area. The solid angle, dΩ, from which the radiant flux is received at the second aperture is small enough so that the variation of the irradiance from the scattered light can be considered to be an average value equal to that at θ. Then the increment of radiant flux, dP, coming to the area dS2 on aperture S2, at a distance ρ from a small area dS1 on aperture S1, may be integrated to determine the total flux incident on S2.If a lens is used, the stops either in image space or object space can be analyzed. Consider the system shown in These equations lead to elliptic integrals and numerical integration for any stop system, circular or rectangular. However, an approximation may be easily made in circular coordinates that will be valid for circular stop systems. If the aperture stop in the optical system is small compared to the interstop distance and the field stop, then the above expression may be integrated and expanded in powers of the ratio of field stop radius to interstop distance as shown in S1S2/q2) J90 to measure the flux would indicate an error less than 1 percent from the true value.For the setup used in these experiments, the approximation in R90 can be evaluated from H0. A special case of this general photometric analysis is the telecentric optical system. The irradiance from the source is accepted in such a way that the principal ray always passes through the principal point of the lens because the aperture stop is centered at this position. If the focal length of the lens is f, then the magnification, m, of the system according to Newton’s formula is f/q, so that the viewed area will be S1(m)2. In this case the flux can be represented as shown in Only the aperture stop and focal length must be known to determine the radiant intensity in such an optical system.S2. The angular acceptance of the system increases in the same proportion that the area of the source is decreased by the aperture stop provided that the movement of the surface is much less than the interstop distance.A scattering solution, however, occupies volume and may not be exactly centered in the plane of one of the stops. In this case the scattering surface can be considered to be moved toward or away from stop The total volume contributing to the scattering is not that defined by a principal ray but rather the volume that is defined by a pencil of rays over the entire aperture stop. If the ray that passes through the center of the aperture stop also passes through the focal plane, there is no volume correction because the zones in the field of view for which only a portion of the aperture is filled are equally compensated by those portions of the field that pass symmetrically on the other side of the aperture stop. If, on the other hand, the ray through the center of the aperture stop is not also the ray through the focal point, the scattering volume will be that defined by the rays through the center of the aperture stop.n. They found that in all cases where the image of the field stop did not exceed the dimensions of the radiant source, the angular acceptance would be proportional to n2. Their calculation was based upon an optical system that had the same dimensional restrictions as ours, but had the additional implicit restriction that the stops be much smaller in a linear dimension than the interstop distance.Hermans and Levinson  have detD line is 1.516, and the calculated indexes for 436 mμ and 546 mμ are 1.524 and 1.517, respectively. The 90° light scattering measurements are thus decreased by factors of 0.915 and 0.913, respectively. For a Pyrex cell the reflectance is computed to increase by about a percent to 0.927 at 546 mμ if the refractive index of the Pyrex is 1.474.The Fresnel formula for computing reflection at normal incidence allows a correction to be made easily for reflections from the glass-air interfaces in these experiments. The correction needs to be made only when the direct beam is being measured through a square cell. In this case, the additional scattering due to reflection of the scattered beam from the back surface of the cell and the reflection of the incident beam where it leaves the cell is subtracted from the 90° measurement of scattering. When the incident beam irradiance is measured without the cell in place, the loss of light in entering the cell and leaving the cell is just compensated by the back reflections discussed above. The Fresnel reflections from the liquids to the glass, when they are not isorefractive, are usually no more than 0.2 percent. For soft glass cells, the refractive index for the sodium Several different types of light scattering cells were used. Two of them were 44 mm semi-octagonal cells. One cell was coated with a black absorbing paint on the back; the other was uncoated. Two other cells had cross sections 37 mm square. One was made of Pyrex glass; the other of lime glass. A fifth rectangular cell was used that could be tightly sealed. A seventh cell was a specially constructed cell made of Pyrex glass, measuring 55 × 10 × 10 mm, and had extreme close tolerances on angles and high clarity in the fused joints. A sixth cell was a Rayleigh horn which had 1-in. fused Pyrex circular entrance and exit windows and a total volume of 200 ml.The polystyrene samples used in these measurements were fractions that had been prepared for work on molecular weight determinations. The fraction used for the comparison of transverse scattering and transmission measurement had a molecular weight of 390,000. The fraction used for studies of the variables involved in low-level light scattering from solutions had a molecular weight of 150,000. Another fraction of 50,000 molecular weight was also studied. The strongly scattering solutions of colloidal silica were selected samples of Ludox.Reagent-grade cyclohexane was used. After a fractional distillation from a glass helix-packed column it had a refractive index All solutions of polystyrene in cyclohexane were handled in a large heated box.Magnesium oxide diffusers were prepared in two ways. Magnesium oxide was obtained on an aluminum plaque 2 in. in diameter by burning magnesium turnings . On seveMagnesium carbonate diffusers were surfaced by drawing a straight edge over the surface of magnesia blocks. In addition, a piece of white Vitrolite  was usedμ incident at 45°.α which corresponds to the relative irradiance from a Lambertian diffuser. Column 5 lists the polarization ratio for the smoked oxide that is, the ratio of horizontally to vertically polarized scattered light. In view of the relatively good agreement of cols. 2 and 3 with col. 4, the diffusers were considered to obey Lambert’s law to a satisfactory degree.The divergence of the incident beam was less than 0.1° in all directions and the angular acceptance of the receiver was 2.5°. Column 4 lists the function cos μ incident upon them at 45°. The angular acceptance of the receiver was again 2.5°, and the field of view was 6×11 mm at all times. In this setup, measurements beyond 80° must be excluded since the projected area of the receiver field of view becomes larger than the width of the beam. The values have also been obtained for 436 mμ and are similar. Magnesium carbonate was studied in the same manner and the results are shown in Diffusers are illuminated by a relatively large beam, usually of the order of 10 mm in width, when they are used in light scattering calibration. 3 as well as for Vitrolite and MgO under conditions of 45° incidence and normal viewing when using freshly smoked MgO and freshly scraped MgCO3. In order to obtain more information about possible variations of these diffusers, a pressed MgO and a smoked MgO were compared directly with the Vitrolite. The reflectance ratios at 546 mμ and 436 mμ, respectively, were 0.855 and 0.840 for the pressed sample, and 0.854 and 0.840 for the smoked.3 diffuser which was used to obtain a constant luminance over a larger angular range. Both samples were measured for total reflectance relative to freshly smoked MgO and found to be within 1 percent in the green portion of the spectrum but different by about 5 percent in the blue. A similar slight decrease in the total reflectance at 436 mμ of the magnesia blocks was found later. The magnesium oxide did not show any appreciable reflectance changes with time.Columns (5) and (6) of H0 was determined by reference to neutral filters calibrated at the same time. The reflectances of Vitrolite, which does not have a fragile surface and can be assumed to have a greater permanence, were also determined at the same time. The measured Vitrolite reflectances were repeatable within 1.3 percent in the green and 0.8 percent in the blue over the course of several months. The MgO over the same period varied by 1.6 percent in the green and 1.3 percent in the blue. The reflection factor of the MgO diffuser was determined to be 0.967 in the green and 0.888 in the blue.The total reflectance of the magnesium oxide diffuser was determined several times under the same viewing conditions and also, as will be discussed later, several times under different viewing conditions. The total reflectance was determined from Transmission measurements were made by using 5 cm or 10 cm Beckman cells. The transmission cell holder was built with a jacket so that water from a constant-temperature bath could circulate to keep constant temperatures in the cell at temperatures not too far from ambient temperature. The blackened thermostat was slightly longer than the cell to minimize the effect of ambient air on the cell ends. The experimental setup was very adaptable, and in view of Heller and Tabibian’s work  it was dμ for different dilutions of a high turbidity (0.123 cm−1) Ludox solution in a 10 cm cell using a 2 mm beam of 0.07° divergence and a receiver allowing use of different fields of view and angular acceptance. With a 5.5×9.9 mm field of view and angular acceptances of both 0.5° and 4° the measured turbidity increased less than 2 percent. With a 2 mm diameter circular field of view and the same angular acceptances there was no change in the transmission measurements within experimental error.Measurements were made at 546 mJ0 and J are the radiant intensities of the incident and transmitted beams, respectively, after subtraction of any solvent absorption blank, and l is the solution path length in cm. The turbidity can be related to the transversely scattered light by The small amount of secondary scattering is unquestionably due to the very small size and angular divergence of the light beam used in these transmission measurements. The turbidity was obtained from transmission measurements using a 4 mm diameter circular field of view. D2) to the phototube signal, G, should be a constant. D2/G obtained with two solutions of vastly different scattering intensities (polystyrene and Ludox) and also from a magnesium oxide diffuser. The low-molecular weight polystyrene fraction in cyclohexane had a turbidity of approximately 0.008 cm−1 while the Ludox solution had a turbidity of approximately 0.07 cm−1. Since a wide variety of stop arrangements were available in the instrument, several experiments were conducted to test the applicability of The effect of the divergence of the incident beam on the scattering measurement from these weakly scattering solutions is shown to be quite small, though not negligible, in μ the ratio of the scattered flux intensities when using these two beam widths was 2.93 while the ratio calculated on the basis of the measured widths was 2.95.The analysis of this optical system indicated that the volume of scattering should be calculable from the field stop image and the width of the incident beam. To see if edge effects were actually important, a comparison was made on the above polystyrene solution with a 3 mm and also a 9 mm incident beam whose dimensions had been measured earlier . At 546 Another conclusion of the previous photometric discussion is that the position of the field stop image with respect to the exact center of the secondary scattering source should not be critical in defining the scattering volume. The effects of the volume correction were also examined to determine if the edge effects in the volume had really been eliminated by assuming that the principal ray in this telecentric system did define the volume that was to be considered in Rayleigh’s ratio. For this purpose several field stops were used to measure the scattering from the same solution irradiated by the same beam. The ratio of scattered to incident radiation was then determined. The scattering is almost constant. Since the results appear random, and since the incident beam is known to be uniform over its area , it appeμ and 436 mμ light. The projected incident beam was 10 mm wide; it had an angular divergence of 0.5° in the horizontal direction and 1° in the vertical direction. The receiver accepted a 2.5° half angle and viewed an area 6×11 mm. The benzene was thermostatted at 25° C. The scattering from the Rayleigh horns were corrected for the loss of the back reflections by increasing the scattering ratio for the Fresnel reflections at two Pyrex surfaces. The ratio for the semioctagonal cell that had been coated on its back surface with an absorbing paint was increased by the lime-glass correction for one reflection surface. The data given are for the ratio of the scattered beam signal to the incident beam signal. These different cells do not give as widely different values of absolute scattering as might have been assumed; however, the depolarization values vary considerably. In the case of carbon tetrachloride successive purification was necessary to reduce the depolarization apparently due to some fluorescing impurity.Another possible source of error in transverse measurements arises from a cell construction that allows stray light to interfere with low-level scattering measurements. An attempt was made to determine if cell construction had very much effect upon the determination of scattering from pure solvents like benzene and cyclohexane. Extraneous scattering from the cell walls should be most noticeable at these low levels of scattering. Although there is no easy way to explore the errors in cell design systematically, several quite different cells were examined with the same solvent to observe any large changes in scattering values. Experiments were made on solutions of polystyrene to determine Rayleigh’s ratio by transmission measurements as well as by two different transverse scattering measurements. The transverse measurements involved the use of The solutions were cleaned by filtration through ultrafine filters and were measured in a semioctagonal cell so that the high-angle dissymmetry of scattering was always easy to establish. In some cases the solutions were first used in the semioctagonal cells, then put into the transmission cell, and again introduced into the semi-octagonal cell to see if time and repeated handling perceptibly changed any of the scattering values. The values of the scattering always stayed the same within 0.5 percent. The results are listed in A stock solution of Ludox about two years old was examined in order to check the consistency of the transmission turbidity and transverse scattering from water media at very high turbidities. It was realized that, in view of Goring’s work , such coR90 and τ was similar to that described earlier for the polystyrene solutions. The ratio (16π/3) R90/τ was plotted against concentration to give a curve which on extrapolation to zero concentration gave a value of 0.98 for light at 436 mμ and 0.97 at 546 mμ. Theoretically the intercept should be 1.000. The reason for this difference was not investigated further but could be due to a small amount of absorption by the solute. The slopes of the curves do give some measure of the amount of secondary scattering which, as is to be expected, is smaller for the 546 mμ light than the 436 mμ.Since many people have used this particular technique to calibrate their photometers, it was of interest to us to find out how routine use of this method would agree with our other determinations of scattering. The experimental measurement of μ and 546 mμ, respectively, to 0.008 and 0.008 at 0.5 percent.The increased secondary scattering at higher concentrations also causes the depolarization ratios to change from 0.033 and 0.012 for a 4 percent solution at 436 mμ wavelength light are consistent and make these transverse scattering measurements extremely reliable. However, a disturbing fact arises for the results at 436 mμ because the direct-beam measurements and diffuser measurements agree within a few percent even though the experimental determination of the absolute reflectance of the magnesium oxide is 0.88 rather than the literature value of 0.96 which was used to calculate R90.The data in The agreement of the transmission turbidities and the transverse scattering are within ±1.5 percent in all but one case. However, this particular run must have been in error since the results of the direct transverse measurement and the diffuser transverse measurement are also different. In both green and blue light, the agreement of the turbidities is equally good. It must be emphasized at this point that only impurities in the polymer sample could have an effect on the transmission since the solution transmission was always referred to the solvent. The transverse scattering measurements which were made in semioctagonal cells are correct, even if the sample absorbs light, because the incident beam is measured after passage through the cell. The additional results with lower molecular weight samples indicate that even at very low turbidities, where the transmission results are subject to great errors, the two methods of transverse scattering agree. It should also be pointed out, as the data in The results of the Ludox experiments indicate that any calibration with such a highly scattering substance is bound to be difficult because of secondary scattering most pronounced in blue light. However, the agreement of the Ludox results with the polystyrene calibrations indicates that the refractive index correction for the square cell is correct for the small refractive index range 1.33 to 1.42.As the data in 3. The experimental value for the particular sample of Vitrolite agreed with that determined with an integrating sphere. Furthermore the agreement with Lambert’s law was satisfactory in all of the samples used. It should be noted that making a MgO diffuser by packing MgO powder in a plaque did not at first yield good results, but gradually a technique was developed in which a Lambertian diffuser could be prepared at will.The results indicate that the freshly prepared diffusers agree very well in relation to each other and with respect to the relative literature values for MgO and MgCOThe very good agreement mentioned earlier when comparing two different beam widths indicates that the calculations which predict no volume effects in scattering when using this type of receiver are correct. Similarly, the data in μ in the semi-octagonal cell illustrates some of the dangers and problems in making low-level measurements. It also points out the value of making additional measurements of depolarization and fluorescence, especially at 436 mμ. At first, the apparent discrepancy in cells was difficult to understand. After many days of retesting and rinsing, it was discovered that this cell had been cleaned at one time with a detergent that had a strongly fluorescing material. Only after a lengthy treatment with strong acid did the scattering in this cell revert to the lower values obtained with the other cells. The values obtained at 546 mμ were at all times normal.The results with pure solvents in different types of cells is highly encouraging because it suggests that even at low turbidities the cells are not contributing stray light. The data in The transmission values are very reproducible. The same values have been measured whatever variety of experimental arrangements has been used. At one time a diffuser was even inserted before the phototube to make certain that any possible geometrical changes in the positioning of the small beam used for transmission measurements were not producing erroneous results by allowing light to strike the photosensitive surface at different places. The results were the same with or without the diffuser.A light-scattering photometer has been examined by two independent optical means, that is, by transmission and transverse scattering measurements, and the results shown to be in agreement. The results of this study indicate that the instrument is capable of a diversity of different arrangements which give reliable results. It should allow a more extensive investigation of the theory and practice of light scattering. The extension of these measurements to molecular weight determinations and other absolute liquid scattering should be a straightforward experimental procedure when clarification techniques become more reproducible.


In this paper, the authors present a new methodology to study the viscoelastic behaviour of the human finger. The methodology is based on experimental research consisting of a finger’s indentation with a small steel cylindrical object for various indentation speeds. The tests were realized on a CETR UMT-2 Tribometer for indentation speed between 0.02 mm/s and 4 mm/s with a normal load of up to 22 N. Using the force–deformation diagrams recorded at the smallest indentation speed determined the elastic modulus of the human finger according to an adapted Hertzian model. By considering the increasing of the indentation force with indentation speed, the viscous component of the human finger was evidenced. The power dissipated in the finger tissue as a result of the prehension process has been obtained as a function of indentation speed and indentation depth. In addition, a general equation for the prehension force as a function of indentation speed and indentation depth has been obtained. The results of this study will be relevant for selection of the specific elastomers used in biomimetic hands. The prehension of the small objects realized by a biomimetic hand is dependent on the mechanical behavior of the elastomers that cover the solid structures of the artificial fingers . Both thp is contact pressure and the exponent α have values between 0.15 and 0.96 in the dry finger/glass contacts. Derler and Rotaru  in the finger’s tissue as a function of depth of indentation Pe(δ) [mW] can be obtained:From Equation (6), the power dissipated in the finger’s tissue caused by the “elastic hysteresis” Equation (12) is a general one including both elastic deformation and damping effect caused by the speed and can be used in the limits imposed in the experiments, while Equation (13) is a particular case when the damping effect can be neglected at a very low indentation speed.δ and indentation speed v in the general Equation (12) for variation of the power loss suggest to us that a simple Kelvin–Voigt viscoelastic model is difficult to adopt for our indentation procedure.The presence of the indentation depth δ and indentation speed v was obtained by curve fitting the force-deformation curves from A complex equation for the indentation force as a function both the indentation depth F1(v) and F2(v) are obtained by curve fitting the numerical values for indentation speeds between 0.02 mm/s and 4 mm/s.Thus, every force-deformation curve can be approximated by exponential functions having the following general form: F1(v) and F2(v), respectively. The blue points represent the numerical values for various indentation speeds and the red curves are the analytical model.In F1(v) and F2(v) have been obtained:The following equations for F is obtained in N.It must be highlighted that if Equation (14) has a general form, Equations (15) and (16) include numerical values obtained as a result of the experiments on a middle finger of young people where indentation speed is given in mm/s and the indentation force The general equation for the indentation force between a small steel cylinder and a human finger given by Equation (14) suggests the complexity of the dependence between the prehension force and the two parameters: depth of indentation and indentation speed.The two Equations (12) and (14) can be considered as starting points for new experiments by considering the prehension of the other small objects by the human fingers. Based on these results, the authors intend to extend the similar research applied to some classes of the elastomers used in the construction of the biomimetic hands.The authors determined the Young’s modulus for a middle human finger by using the indentation of the finger with a small steel cylinder at a very low indentation speed to avoid the dissipative processes in the finger’s tissue. The Hertz contact model has been used and it has been obtained a linear dependence between the Young’s modulus of the human finger and indentation force, for a maximum indentation depth of 4 mm. Values for Young’s modulus between 0.027 MPa and 0.16 MPa have been obtained. In addition, a general equation between indentation force and elastic deformation of the finger has been obtained (Equation (6)).To determine the influence of the indentation speed on the viscoelastic behavior of the finger’s tissue, the authors performed indentations between steel cylinder and human middle finger for a lot of indentation speeds between 0.02 mm/s and 4 mm/s. By increasing of the indentation speed, an important increase of the indentation forces has been obtained. Thus, the increase of the damping effect in the human finger’s tissue was made evident by increasing of the indentation speed.To make the dissipative effect in the finger’s tissue evident as a result of increasing of the indentation speed, the authors determined the total power dissipated during the indentation process for every indentation speed. When the indentation speed increased between 0.02 mm/s and 4 mm/s, the total power dissipated in the finger’s tissue increased from 0.032 mW to 12 mW, respectively.Based on the experimental values and by curve fitting the experimental results, the authors obtained a general equation for power dissipated in the finger’s tissue as a function of indentation depth and indentation speed (Equation (12)). The power dissipated in the finger’s tissue by using the contact between steel cylinder and human finger can be expressed as a product between a function depending on the indentation depth and a function depending only on the indentation speed.δ and indentation speed v was obtained by curve fitting the force–deformation curves obtained by experiments.It was demonstrated that it is difficult to adopt a simple Kelvin–Voigt viscoelastic model for the indentation procedure. A complex equation for the indentation force as a function of both indentation depth The authors consider that the results highlight the importance of the indentation speed in the description of the viscoelastic behavior of the finger’s tissue. These kinds of tests and consequent results are not found in the literature.