In bulk form 2, as well as a change in the magnetic state from a paramagnetic to an antiferromagnetic state. 4.Vanadium sesquioxide  peak of the a and c lattice parameters relax reaching almost bulk values for the 620 a lattice parameter is larger than in the c lattice parameter. In Fig. 10.Figure entclass1pt{minimaentclass1pt{minimaAtomic force microscopy scans recorded for films deposited within the high quality epitaxy temperature window display low roughness surfaces exhibiting atomic terracing, see Fig. 8 as well as the local strain in the films10. The ratio between the vertical and lateral lattice parameters has been discussed as a governing factor in modifying the transition temperature5 both for overall thin film properties as well as under local stress induced using contact probe pressure29.As the structural phase transition and MIT in The properties of Figure 11. Figure As has been shown in this paper, the deposition settings strongly affect the structural as well as electrical properties of Comparing the results of resistance measurements for films deposited at higher power to films deposited at lower power but with a smaller In this study we focus our attention on the effect of the growth settings on the structural and electrical properties of c lattice parameter as a function of the a lattice parameter for all of the films. It can be seen that there is a clear trend in the distribution of the lattice parameters. The unit cell expands preferentially with regards to the a lattice parameter at lower temperatures. From the results presented in the graph, the dominant factor in affecting the observed lattice parameters is the growth temperature while the oxygen flow rates affects the parameters to a lesser extent and preferentially the a lattice parameter. This result is further illustrated in Fig. c/a ratio and unit cell volume as a function of growth temperature. Films grown at a higher temperature show a c/a corresponding closer to the bulk value with increasing growth temperature while films grown at lower temperatures reveal a lower c/a ratio. For the temperature series, films grown at the higher temperatures had larger a and smaller c lattice parameters than films grown at the lower temperatures with the highest temperature reaching bulk values in both the a and c lattice parameters. Although the point of origin for these values is shifted, this expansion of the a lattice parameter and compression of the c lattice parameter is in agreement with the thermal expansion of a lattice parameter has been observed to increase while the c lattice parameter has been shown to decrease with increasing temperature up to 31.Figure a lattice parameter while having much less impact on the c lattice parameter , X-ray reflectivity (XRR) and reciprocal space mapping (RSM) measurements using a Panalytical X’Pert Pro diffractometer at room temperature.For the X-ray measurements there were 2 different optic setups. Firstly for the 230. The thickness of the films investigated in this study was between 55 and 65 nm. X-ray diffraction measurement and reciprocal space mapping were utilized to determine the internal crystallographic parameters, such as the in-plane and out-of-plane lattice parameters, lateral correlation length and mosaicity of the films.From the XRR measurements the thickness and density of the films were determined by fitting using the X’Pert Reflectivity program. For all the films the density was close to bulk value, being in the range 4.95–5.02 g/cmThe surface morphology of the films was investigated by atomic force microscopy using a Park XE-100 instrument in both contact as well as non-contact mode.The resistance of the films was recorded using a mini cryogen free system from Cryogenic Uk ltd. Measurements were performed with a 2 point setup using a Keithley 2400 sourcemeter connected to a Keithley 7001 switch system with a 7012-S 4 To connect leads to the sample, contacts were e-beam evaporated onto the edges of the films using a shadow mask. These contacts consisted of 5 nm of chromium followed by 100 nm of gold. Wires from the system were attached to the contacts using conductive silver paint. Each sample was scanned decreasing the temperature from 300 to 10 K followed by a second scan increasing the temperature from 10 K up to 300 K. Both temperature scans were performed at a scan rate of 0.8 K/min.


We present a novel velocity based up-winding scheme for the node control volume finite element (NCVFE) method. The NCVFE method solves for the pressure at the vertices of elements and a control volume mesh is constructed around them; where the advection of fluids is modelled. Therefore, each element shares several control volumes, and traditionally the fluid saturations used in calculating the mobilities over each element  −  hence updating pressure  −  are arithmetically weighted. In this paper, we use the velocity vector to allocate the upstream direction of the fluid flow in each element and use the upstream fluid saturation in calculating the mobility needed for the pressure equation. We test his novel approach using triangle and tetrahedron elements, and we show that it produces more accurate fluid saturation profiles than the traditional approach. The method can easily be implemented in current NCVFE simulators. The method is similar to the donor cell up-wending scheme applied in the finite volume method2. Sammon3 and Brenier and Jaffre4 showed that the method is consistent, convergent and well-defined . Higher order schemes of the method were also applied6.Upstream mobility calculation in modelling multi-phase flow in porous media is widely accepted and considered stable and accurate. This approach uses fluid phase information from the upstream cell/grid for the calculation of fluxes when modelling the transport of fluids to solve fluid dynamic problems. Aziz and Settari7 and even in pore-scale modelling of heterogeneous porous media8. Moreover, the hydrology community relies on similar numerical models to simulate groundwater movement, contaminants transport in aquifers chemical reactions between minerals10. The numerical method used to solve these equations is the core of reservoir simulation. Such methods discretize the equations from partial differential form to algebraic equations in space and time. Two popular categories for numerical discretization of flow problems amongst the reservoir community are the finite volume method (FVM) and finite element method (FEM), where the latter is divided into three approaches: sadfss. FVM is a simple and common numerical method in the computational flow dynamics community. It is used discretize the reservoir fluid flow equations and is well adapted for conservation laws. However, its geometrical flexibility is limited since it is dependent on the level of orthogonality between the cells11. This is considered a large handicap as it makes it very difficult to model the complex geometry of hydrocarbon reservoirs and requires very fine meshes to obtain reasonable results which is computationally very expensive12.The equations governing multi-phase fluid flow in subsurface porous media are of mixed characteristics. The pressure equation is elliptic and the transport equations of fluids are hyperbolic. These governing equations have been implemented in various studies to predict fluid flow in naturally fractured reservoirs13. To solve for complex reservoir engineering problems, many advances have been made over the past 50 years, which can be categorized into three main approaches. In the Coupled upwind-weighted finite element method (CUFE) approach, we solve for the fully coupled flow equations, saturation and pressure equations with up-streamed mobility values16. The interfaces between neighboring elements do not necessarily have to be to be orthogonal12 and and the accuracy of the method is mesh dependent20. Moreover, Newton’s method is needed to solve for the coupled equations which increase the computational cost deeming it as a drawback21.In FEM, the domian is divided into a set of elements that communicate through interpolation function. The governing equations are written in integral formulation and forms a system of local algebraic equations written in matrix form. This matrix is solved to obtain the pressure value at the nodes which can be located at the vertices, centroid, or interfaces of the elements. FEM represent the domain using various shapes of elements: line, triangle, tetrahedron, prism, hexahedron and others. This large library of elements gives the method the ability and the strength to model domains with large complexity including discrete fracture models22. In NCVFE, we we use the Galerkin finite element method to solve for the pressure on the element’s vertices, while the saturation is solved explicitly on the control volumes. After that, the the phase velocities are computed using Darcy’s law and the pressures. Finally, the continuity equation is used to calculate the advection and transport of fluid on the node control volumes25.In the Node control volume finite element method (NCVFE) approach, the saturation and pressure equations are decoupled while imposing a secondary mesh around the finite element nodes (vertices). This method was first introduced to the computational flow dynamics community by21. Moreover, adaptive mesh in space and time can be used easily in NCVFE, as proposed by11, and the use of discrete fracture models (DFM) in 2D and 3D meshes27. However, a main drawback of NCVFE is the fact that the control volume mesh is constructed around the nodes and the material properties are assigned on elements. This entails that there is a loss of physical accuracy and artificial fluid smearing when modelling multi-phase flow in highly heterogeneous and fractured reservoirs.The NCVFE can be used to model complex structures while yielding better simulation results than CUFE methods. However, the capillary pressure can only vary in a continuous fashion for the method to be accurate32. In this methods, two or more primary variables are solved where in fluid flow problems, the MFE method solves the pressure and the velocity fields simultaneously. The continuity of fluxes across the elements’ interfaces is guaranteed by vectorial interpolation functions, i.e. Raviart-Thomas33. The fluxes are solved on the element interfaces and the pressure is solved on the centroid of element in a fully implicit scheme similar to34. The main difference between MFE and NCVFE methodsis that MFE approximates flow variables more accurately and realistically than NCVFE in small highly heterogeneous permeability cases35.In order to overcome this drawback of artificial smearing, continuous fluxes across element interfaces need to be assured. This concept is applied in the mixed finite element (MFE) method36, see Fig. et al.37. Higher order schemes for the mobility calculation between the control volumes have also been applied39.In our work, we utilize node control volume finite element (NCVFE) method. As mentioned earlier, the elliptic and hyperbolic equations are decoupled, and they are solved on two different meshes. The former is solved using the Galerkin method on a finite element mesh and the latter using the finite volume method on the node control volume meshThe objective of this paper is to present and investigate a new mathematical formulation for mobility upstreaming over mesh elements in a reservoir simulation. The method entails a velocity vector that starts from the element’s interface and is piece-wise constant in first order elements. The vector is used to approximate the upstream saturation in the given element. This results showed accurate saturation profiles when compared to the traditional arithmetic weighting method,even in multiphase flow scenarios. Furthermore, the UMC method can be easily implemented in current NCVFE based simulators. The paper is organized as follows. In Sections 2 and 3, the governing equations and the Node Control Volume Finite Element method are introduced. In Section 4, the upstream mobility calculation for NCVFE is described, and in Section 5, numerical tests are presented. Finally, conclusions are given in Section 5.40. We assume a slightly compressible rock. The mass balance for the fluid phase α is, We consider two-phase immiscible fluid flow of water and oil in heterogeneous porous media described by the continuity equation and Darcy’s lawS is the saturation of the phase, ϕ is the porosity of the rock, ρ is the density of the phase, q is the source-sink rate of the phase, v is the Darcy velocity for phase, and t is time. We also assume capillarity and gravity forces are negligible. The Darcy phase velocity is, P is the phase pressure, K is the absolute rock permeability, and λ is the phase mobility, kr is the relative permeability of phase and μ is fluid viscosity of phase. The fluid viscosity is constant and usually different for each phase. The relative permeability is saturation dependent, and in this paper we use Corey-type41 functions, No and Nw are history matching parameters, Swo is the normalized water saturation, Sor is residual oil saturation.25.In our simulation, we assume a closed system with know boundary conditions, and flowing source/sink terms represented by wells. For the cases when incompressible fluids are assumed, we can write a pressure equation that is independent of the water saturation of the systemCr is rock compressibility, qt is the total source-sink rate of both phases and v is the total velocity, λt is the total mobility given by, The pressure equation is, We then calculate the velocity of the phase using Darcy’s law. Equation  and the 39 Then, the advection of fluid between the node control volumes is calculated using the finite volume method. In this paper, we do not detail the discretization procedures of the governing equations and the construction of the secondary control volume mesh, as they are thoroughly discussed by Abushaikha et al.37. We rather present the final form of the pressure equation: In the NCFVE method, a multi-phase flow problem is solved in two steps. First, the primary variable, pressure, is calculated using the finite element method; in this paper we use the well-established Galerkin methodThere are five finite element matrices that need to be defined for each element based on the recovery mechanisms in the pressure equation:Conductance matrix [M].Capillarity matrix [CP].Gravity matrix [G].Capacitance matrix [C].Source/sink terms (force vector) [F]. We use implicit pressure and explicit saturation (IMPES) so Eq.  linear solver with final residual of 1.0 × 10−942.) so Eq.  becomes:n) and apply the divergence theorem and the forward Euler discretization in time to get: CV is the pore volume Vn)( depending on the type of node control volume mesh (it is pressure dependent: updated each time step using equation n), and the fluxn),j( is the flux of face j in node control volume (n) and calculated by, N is the are normal vector.After the pressure is calculated, we integrate the transport equation over the node control volume , Sk is the water saturation at location K for element, and Ak is given by, Ak is the component of the distance vector projected onto the velocity vector, if this dot product is positive (no obtuse angle) its saturation is accounted for, otherwise it is not, vel is the element velocity and ak the distance vector from location k (node or centroid of interface) to element centroid, see Fig. where entclass1pt{minimaThe algorithm below shows the implementation steps for NCVFE numerically.−10Pa−1. We assume the medium is fully saturated with oil and the porosity and permeability are 0.2 and 100 mD respectively, unless otherwise stated.In this section we test the UMC in the NCVFE method for various cases. In all the tests, water and oil viscosities are 0.4 and 2.5 mPa.s respectively and the rock compressibility equals 4.0 × 1026. The domain is represented by a plane with dimensions of 1 m  ×  Element Length to test the triangle elements and by a rectangular tube with dimensions of 1 m  ×  Element Length  ×  Element Length for the tetrahedron elements. Figure To validate the new upstream mobility calculation for the NCVFE method, we use the one dimensional analytical solution of the Buckley-Leverett problem, where gravity and capillarity are negligibleet al.39 and Hoteit and Firoozabadi44 applied the Buckley-Leverett problem for various numerical methods. They observed low convergence rates for the Buckley-Leverett problem regardless of the numerical method used, as we saw here, because of this sharp separation between the two fluids.To measure the difference between the two methods, we calculate the error L2 norm for the saturation profiles for various element lengths . Figure In this test, we validated and tested the convergence of the traditional approach and the new method for triangle and tetrahedron elements. We saw the traditional approach not producing very accurate saturation profiles because the fluid mobility needed for the pressure calculation is computed using the arithmetic weighting of the encompassed control volumes saturations. On the other hand, the UMC method employs the velocity vector to allocate the upstream saturation therefor producing more accurate saturation profiles. Next, we test the method for multi-dimensional domains.The five-spot is a simple case of a water flooding scenario in a homogeneous domain. Water is injected at constant rate in the top left and lower right corners, while oil (including water after breakthrough) is extracted at the same constant rate in the lower left and upper right corners. The domain is represented by a plane with dimensions of 1 m  ×  1 m to test the triangle elements and by a cube with dimensions of 1 m  ×  1 m  ×  Element Length for the tetrahedron elements see Fig. . In thisqt = qw + qo, qw and qo equal the water and oil production flow rates. Figure  Figures Next, we test the UMC method in more heterogeneous domains represented by highly conductive zones (fractures).45 The area is meshed in 2-D using triangular elements with a central water injector that pushes the oil into the four producers located at the corners as shown in Fig. In this last test, a heterogeneous petro-physical model of Coats Engineering upscaled model of SPE10 layer 10The water cut for the producers is plotted in Fig. This velocity up-winding scheme is very crucial when up-scaling techniques are implemented. A solid understanding of the flow functions governing fluid flow in fractured reservoirs provides the necessary foundation for up-scaling laboratory results to the field scale using numerical simulators. Scaling groups are mainly used to increase computational efficiency of simulators by several orders of magnitudes. However, truncation error in up-scaling is inevitable, and the up-winding of the velocity using UMC can contribute to improving the saturation calculation.In this work, we have presented a novel approach for up-streaming mobility calculation in NCVFE simulators for triangular (2-D) and tetrahedral (3-D) domains. Based on our results, we were able to show that our method produces more accurate fluid saturation profiles compared to the traditional (arithmetic) approach. The utilization of the velocity vector to determine the appropriate saturation for upstreaming is more accurate than the arithmetic weighting of the saturations in the control volumes. Upon injection of water in a simulation case, the water front was less smeared when UMC is used for different mesh resolutions and the breakthrough of water is delayed. Moreover, the UMC approach can show good accuracy when the method is used for up-scaled models, up-scaling is an essential approach when the aim is to reduce simulation time and cost, and UMC allows for better prediction of the movement of the water front in such scenarios.This novel approach can be easily implemented in current reservoirs simulators and has a wide range of applicability to various fields of hydrocarbon recovery, ground water movement and contaminant transport.We explicitly define the five finite element matrices of the pressure equation Me)(] is the force vector, [N and their derivatives are defined for a triangle and tetrahedron as follows (see Fig. The interpolation function see Fig. .Figure 1TrianglesTetrahedrons


Background and Objectives: Patients with Down syndrome have many orthopedic problems including flat foot. Insertion of an insole for a flat foot provides support to the medial longitudinal arch; thus, insole therapy is often used to treat a flat foot. However, the influence of an insole insertion on the knee joint kinematics for a patient with Down syndrome is unknown. This study aimed to elucidate the influence of an insole for a flat foot on the knee kinematics during gait for a patient with Down syndrome. Materials and Methods: The subject was a 22-year-old male with Down syndrome who had a flat foot. The knee joint angle during the gait was measured using a 3D motion capture system that consisted of eight infrared cameras. Results: The gait analysis demonstrated a reduction in the knee flexion angle during double knee action. The knee valgus and tibial internal rotation angles also decreased during the loading response phase while wearing shoes that contained the insole. Conclusions: As the angle of the knee joint decreased during the gait, it was considered that the stability of the knee joint improved by inserting the insole. In particular, there was a large difference in the tibial internal rotation angle when the insole was inserted. It is thus hypothesized that the insole contributes to the rotational stability of the knee joint. This study suggests that knee stability may improve and that gait becomes more stable when a Down syndrome patient with a flat foot wears an insole. A large number of patients with Down syndrome have problems associated with their musculoskeletal system and joints. Foot and ankle deformities are particularly recognized as common orthopedic problems in patients with Down syndrome. Flat foot is also a common orthopedic complaint for patients with Down syndrome . A previPrevious studies have also recommended that patients with Down syndrome should use an insole . In addiA 22-year-old male  patient with Down syndrome participated in this study. He was diagnosed with bilateral flat foot two years ago, and the calcaneal angle was 13.9° for his right barefoot and 15.1° for his left barefoot. The normal range of the calcaneal pitch is reported to be 18 to 20° in the literature [th of the thigh segment coordinate axis to the rotation matrix R(t)sh of the shank segment coordinate axis, was calculated from the following equation to obtain the knee joint angle.The gait analysis was performed under two conditions: insole-inserted shoes and non-inserted shoes. The knee joint angle data of the dominant lower extremity was measured for the gait analysis. Kinematic data during gait was acquired using a motion capture system , which consisted of eight infrared reflective cameras with a sampling rate of 100 Hz. Thirty-five 14 mm infrared reflective markers were placed on the patient’s lower extremities  and the The knee joint angle was calculated using MATLAB R2016b . The obtained knee joint angle was normalized while considering one gait cycle as heel contact to heel contact for the ipsilateral lower extremity. The knee joint data for three gait cycles were averaged and compared for the conditions with and without the insole. The patient was instructed to walk at his usual preferred speed. The measurements were performed for the patient walking without the insole first, followed by walking with the insole. This study was approved by the ethics committee of the Ibaraki Prefectural University of Health Sciences on October 10, 2017 , and written informed consent was obtained from the subject and his family.The mean angles of the dominant knee joint were calculated from three gait trials and are plotted in The mean angle and standard deviation of knee joint flexion was 26.53 ± 1.95° with the insole and 31.73 ± 3.45° without the insole. The knee flexion angle decreased when the patient wore shoes with the insole in comparison to wearing shoes without the insole. The knee flexion angle during the double knee action decreased. The maximum knee flexion angles for the first peak during double knee action with and without the insole were 23.60° and 29.03°, respectively. The maximum knee flexion angles for the second peak during double knee action with and without the insole were 62.75° and 67.27°, respectively.The mean angle and standard deviation of knee joint varus was −0.69 ± 0.45° with the insole and −2.52 ± 0.36° without the insole. The knee valgus angle decreased when the patient wore the shoes with the insole. During the loading response phase, the maximum valgus angle difference was observed between the shoes with the insole (3.21°) and the shoes without the insole (7.55°).The mean angle and standard deviation of tibial external rotation was 3.78 ± 0.90° with the insole and −2.77 ± 1.41° without the insole. The maximum tibial internal rotation angle for the shoes without the insole (3.65°) was larger than for the shoes with an insole (12.39°) by 60% for a gait cycle that corresponded to the terminal stance phase to the initial swing phase. The gait cycle durations under with insole and without insole conditions were 1.12 ± 0.01 s and 1.27 ± 0.05 s, respectively.In this study, the knee joint flexion angle decreased when an insole was inserted. This result was observed during double knee action. Double knee action is defined as a biphasic knee joint flexion–extension pattern during a gait cycle , which fThe tibial internal rotation angle during the gait decreased by inserting the insole; however, the external tibial rotation angle increased. The rotational stability of the knee joint increased since the movement range of the tibial rotation angle was reduced. The increased rotational stability was caused by the effect of the insole on reducing the pronation of the foot. An increase in knee rotational stability is important for joint protection and may prevent osteoarthritis in the long term.Conversely, the knee joint valgus angle during the gait decreased by inserting the insole. The valgus angle of the knee joint decreased by inserting the insole, which supports the medial longitudinal arch of the foot. This result supported the original hypothesis. In terms of the results for this case study, individual differences are considered to have an influence.In a previous study that verified the insertion effect of a biplanar insole, it has been reported that the ankle joint eversion angle decreased significantly . HoweverWith regard to other gait parameters, the gait cycle duration was higher with the insole than that without the insole. Notably, the patient walks with the insole in his daily life, which may have caused the effect of habituation in the gait pattern.This study has some limitations. The main limitation of this research is that this investigation was performed for a single patient. It is difficult to apply the results obtained in this study to all patients with Down syndrome. We analyzed the dominant lower extremity in order to unify the lower extremities measured, assuming that we would have data of a larger sample size in the future. The foot deformation varies from patient to patient, and accordingly, the insole should be customized to the individual’s foot shape. Further research is warranted to verify the effects of different classes of foot deformations and insole shapes. Long-term follow-up is also necessary to verify whether insole insertion is effective in preventing osteoarthritis.This study investigated the effect of insole insertion on knee joint kinematics for a patient with Down syndrome that has a flat foot. By decreasing the angle of the knee joint during the gait, the stability of the knee joint improved upon insertion of the insole. In particular, there was a large difference in the tibial internal rotation angle when the insole was inserted in comparison to the case without the insole. It is hypothesized that the insole contributes to the rotational stability of the knee joint. As the knee stability improves, the gait becomes more stable for a patient with Down syndrome that has a flat foot while wearing the insoles. Further examinations of more patients with Down syndrome that have a flat foot are needed to fully establish the effect of insole insertion.


The spectroscopic analysis of the archaeological textiles by SERS reveals the presence of bands attributed to carminic acid and nucleobases, mainly adenine and guanine. The identification of these biomolecules was also verified in raw cochineal extract and in cochineal dyed replica wool fibers fabricated by us following ancient receipts. The effect of Al on the complexation of carminic acid and other biomolecules was also tested in order to understand the changes induced by the metal interaction on the colorant structure. This study revealed that Al can also complex biomolecules existing in the cochineal extract. In particular, guanine residue seems to interact strongly with the metal, since SERS bands of this residue are enhanced. Furthermore, a theoretical analysis on the interaction of carminic acid and a silver surface was also performed in order to better understand the interaction mechanism between carminic acid and a metal surface that leads to the final SERS spectrum. The results of the present work will be very useful in the identification of different molecules and metal complexes that may be forming part of the cochineal colorant found in archaeological materials.SERS spectroscopy is successfully employed in this work to reveal different components integrating the cochineal colorant employed for dying archaeological textile samples from the Arica Region in North Chile. This analysis was done by  Dactylopidae cocus), which can be found in the tuna cactus (Opuntia spp.). Carminic acid  is the most abundant colorant component of Cochineal colorant, and represents the 15–20% of the total insect weight1. Cochineal trade gave rise to one of the main historical markets between America and Europe until the synthesis of new red dyes in the XIXth century1. In fact, it was employed to dye textiles in the antiquity. The potential presence of many other biological constituents of the insect body in the carmine colorant difficult its detection in archaeological materials. In general, cochineal fabrication implies a process of purification by alkaline treatment which renders a great variability in the composition. This extract is generally named as cochineal extract. Moreover, this variability is further increase because of the different origin of the harvested insects2. An important step in the use of cochineal dyes is the use of metals, usually Al, leading to the formation of Al lakes that also favor the immobilization of carminic acid on textile fibers. In general Carmine refers to a metal coordination complex or lake involving aluminum and carminic acid. This colorant is produced directly from the cochineal extract without a further purification2. Therefore, carmine is usually a very complex material integrated by a large list of different colorants and other biological molecules as well as fragments of the insect body, waxy exudates and residue from the environment, although carminic acid is the main component of this mixture. In fact, chromatographic methods have revealed the presence of other minor colorants in the cochineal extract, such as kermesic and flavokermesic acids, as well as other unidentified compounds3. All these molecules can also form a complex with the metal used in the fabrication of the carmine lake. The presence of cochineal and/or carmine in textile archaeological materials is very frequent in samples found in the American continent5. In fact, the detection of this colorant in many ancient American textiles was reported in recent works9.Cochineal is one of the most important red colorants used for dying textiles. Specifically, the Mexican Cochineal refers to the crude material obtained from the dried bodies of the plant parasitic hemipterous insect of the same name . However, the analysis derived from this technique is not univocal because it provides broad bands that are difficult to assign13.Analytical methods based on chromatography15. However, the intrinsic low intensity Raman scattering and the large fluorescence emission usually induced by biomolecules, avoids, in the majority of cases, the analysis of organic dyes. To overcome this issue, the use of metal nanoparticles, mainly made of gold and silver, increases the Raman cross section of molecules thanks to the SERS (Surface-Enhanced Raman Scattering)16. SERS has been successfully employed in the identification of natural colorants, including cochineal and other red related lakes, in archaeological materials in general20 and in textile fibers in particular22. Metal nanoparticles have also the advantage of inducing fluorescence quenching. Another advantage of SERS is that it allows the analysis of colorants without extraction of the pigment from the fibers textile in methods implying the deposition of metal nanoparticles on the fiber23 or by in-situ photoreduction of Ag+24.Raman spectroscopy has been largely employed in the analysis of colorants in art and archaeological materials25; (c) the different structures adopted by carminic acid in the mixture by the possible ionization of the carboxylate and phenol groups25; (d) the metal complexation that also leads to a wide spectrum of vibrational bands in cochineal extracts; and (e) the intrinsic heterogeneity of cochineal colorants that are accompanied by a large list of organic material and biomolecules from the insect body. Therefore, it is difficult the elaboration of a complete carminic acid and cochineal Raman database that could be used for the colorant identification.The spectroscopic analysis of cochineal is advantageous but it poses significant challenges: (a) the rather weak interaction of carminic acid with metal interfaces, a required process for SERS intensification; (b) the residual fluorescence that can still be detected in samples containing cochineal26. In addition, the metal complexation of carminic acid in lakes was not studied in depth. In this context, SERS spectroscopy can be proposed as a very sensitive technique that can afford more insight on the analysis of the complex archaeological samples where carminic acid is present.The problem of the heterogeneity in cochineal dyestuff was not addressed conveniently so far. Spectroscopic and chromatographic analysis of textile extracts or cochineal extracts where not able to identify unknown bands that could be originated from biological components of the insect bodyin-situ analysis was also completed with a spectral investigation of carminic acid and D-glucose, as well as a theoretical study on the interaction with metal surfaces in order to improve the band assignment of these materials.For all the above reasons, the main goals of the present work were (a) the identification of biomolecules in cochineal dyed textile fibers and (b) the analysis of the effect of Al as mordant in the immobilization of the colorant as well as other biomolecules naturally occurring in archaeological materials onto the wool fiber. To accomplish these tasks, a spectral Raman and SERS analysis was done in historical textile samples and replica dyed wool fibers. These replica samples were prepared by employing the same procedures used in the past and using wool threads directly dyed with commercial carminic acid and the cochineal extracted by us from commercial insects. The spectral For the best of our knowledge, this is the first time that Raman is employed in the analysis of biological molecules potentially existing in cochineal dyestuff and that the effect of Al complexation on cochineal is tested by Raman and SERS. Furthermore, the use of star-shaped silver nanoparticles (AgNPs), following the nanofabrication developed at our laboratory, was able to induce strong enhancement the SERS sensitivity leading to more successful results. The information reported in the present analysis will be helpful for specialists that can infer about the dying techniques used by ancient cultures, mainly in Central and Southern America where red colorants were frequently employed.2(SO4)3  were purchased from Sigma-Aldrich and used as received. Calf thymus DNA (ct-DNA) and poly(dG-dC).poly(dC-dG) (pGC.pCG) were purchased from Sigma Aldrich. D-glucose (Glu) powder was purchased from ThermoFisher and used as received. Dried and grinded cochineal insects employed in the dyeing wool-cochineal process were purchased from Telasybastidores . The stock solutions were prepared in ultrapure water . Commercial white wool was purchased from a textile shop in Madrid, and it was used for the dying process without any treatment and used as received. Silver nitrate, trisodium citrate and absolute ethanol were purchased from Merck, while hydroxylamine hydrochloride and hydroxylamine solution (50% w/w in water) were purchased from Sigma Aldrich. The thin sheet of gold was specially prepared in the facilities at the Faculty of Physical and Mathematical Science (University of Chile) in order to perform the Raman measurements of carminic acid and Glu. Archaeological samples correspond to the Formative Period of the Arica Culture and were provided by the Museo Chileno de Arte Precolombino in Santiago de Chile.Carminic acid and Al27. According to this method, three dried cochineal insects  were placed into the agate mortar and grind treated until obtaining a fine powder. Then, this powder was deposited in a flask with 5 mL of ultrapure water. The solution was stirred and heated to 90 °C and after that, a piece of 1 cm of length of commercial white wool was added. The solution was stirred during 30 min without heat. After this dying procedure, the resulting red wool was washed with ultrapure water and dried for 12 h. A second piece of white wool was dyed with the same methodology, with the difference that 100 mg of Al2(SO4)3 was added before soaking the white wool in the cochineal solution following previously reported recipes29. Both pieces were used in dry conditions before adding a drop of star-shaped NPs suspension for the SERS experiments. Both samples displayed a final pH of 5.2.Textile fibers dying was accomplished by following the protocol published by Maier et al.+ with neutral hydroxylamine and sodium citrate in two steps, according to the method reported previously by us30. First, 500 μL of NaOH 5 × 10–2 M was mixed with 500 μL of hydroxylamine 6.02 × 10–2 M. Then, 9 mL of AgNO3 1 × 10–3 M was added dropwise to the solution. The resulting solution was stirred during 5 min. Finally, 100 μL of 4.13 × 10–3 M trisodium citrate was added. This suspension was stirred for 15 min. Spherical citrate AgNPs were prepared according to the Lee and Meisel chemical reduction method31.Silver nanostars (AgNS) were prepared by reduction of Ag–3 M) on an Au thin surface. The gold surface was prepared by deposited Au film in Argon plasma on glass substrate by sputtering method. A laser at 785 nm laser line was employed as excitation with a final power at the sample of 1mW. Final spectra were the result of 5 accumulations registered with an integration time of 20 s and a spectral resolution set at 4 cm−1.The Raman spectra of carminic acid and Glu were obtained by depositing an aliquot of the carminic acid solution , thus removing the supernatant until concentration in 10% of the initial volume. Each piece of wool was deposited inside the well of a microscope slide. After deposition of the concentrated AgNS suspension, the water solvent was evaporated at room temperature without heating. Spectra were registered three hours later on different points of the sample. Under these conditions high spectral reproducibility batch to batch was obtained for each sample.−1 band of a Si wafer and a 50 × objective. Its resolution was set to 4 cm−1. Spectral recording conditions and the choice of the laser line used were selected in order to avoid sample degradation. In this sense, the 633 nm laser line was used in the SERS analysis of the wool and the red dyed wool, while the line at 785 nm was employed for the solid samples in order to avoid the fluorescence emission. The 514 nm line was employed to measure the SERS of nucleic acids. SERS spectra were recorded by averaging 5 scans using an integration time of 20 s and a spectral resolution at 4 cm−1.A micro-Raman system  equipped with the 785, 633 and 514 nm laser lines, a Leica microscope and an electrically cooled charge couple device (CCD) detector was used to register the Raman and SERS spectra. The laser power on the Ag colloidal coated samples was ca 2 mW. The instrument was calibrated using the 520 cmUV–vis absorption spectra of AgNS and AgNPs were recorded from on a Shimadzu 3600 spectrometer by using quartz cells, 1 cm optical path. Samples were diluted 30% in MilliQ water (volume/volume). The UV–visible spectrum of AgNS shows two maxima at 384 and 418 nm, while a large extinction with a broad tail towards the red-near infrared is seen at higher wavelength which is due to the presence of AgNS with different morphologies.TEM images were obtained with an Inspect S50  scanning electron microscope. The analysis was performed with 20 kV as High Voltage. Extinction spectra of colloids were recorded on a Shimadzu 3600 spectrometer  equipped with a PMT for light detection in the UV–visible range and an InGaAs detector for the NIR was employed to obtain the plasmon extinction spectra. Samples were placed in quartz cells of 1 cm optical path, after dilution to 30% in MilliQ water (v/v).32. The silver metal surface model, Fig. 33 and the HyperChem software  was used for the calculations. To optimize the carminic acid-Ag geometry we have employed molecular mechanics at the OPLS level by maintaining fixed the Ag layer geometry.The carminic acid geometry was optimized by using the B3LYP/6-31 g calculation level in Gaussian 09 software) and on a rough gold surface  in order to reduce the intrinsic fluorescence emission and improve the Raman signal. The analysis of spectra reveals the appearance of bands with an intensity variation depending on the sample preparation (glass or Au surface). Raman of carminic acid in solid state presents the characteristic Raman bands of the protonated molecular form. In general, the most intense bands of the spectrum correspond to the aromatic anthraquinone moiety, undergoing the highest intensification in Raman. For instance, the bands at 1233 and 1471 cm−1 which are assigned to ring νCC stretching coupled to in plane deformations (δ) modes of the CH3 and COH fragments. The broad and medium bands at 453 and 554 cm−1 corresponds to a skeletal mode, while the other broad bands at 1306 and 1590 cm−1 are assigned to coupled vibrations of the νCC and δCOH modes25.The Raman spectrum of carminic acid in solid state was obtained by depositing a solution of this compound on glass Fig. c and on ace Fig. d in orde−1 range, as well as the bands at 852, 642 and 401 cm−1. The position and broadness of these bands suggest that they are due to the glucose residue of carminic acid. In order to confirm this, we have also registered the Raman of glucose on Au film  and adenine (A) due to the great similarity with the Raman spectra of these bases36. In addition, other bands of these nucleic bases can also be identified in the 1300–1500 cm−1 region, while other less intense ring breathing bands are observed at 770 and 800 cm−1 corresponding to the nucleobases thymine (T) and cytosine (C)38. Similar spectra were also obtained from the analysis of many other textile materials from the Arica area in North Chile (results not shown). Moreover, bands appearing at similar wavenumber values were also identified in archaeological textiles dyed with cochineal that were original from Peru7.In particular, the SERS spectra were obtained from the yellow-orange and brown points Fig. b and 2c.40, although a weak G signal is also observed at 660 cm−1. The bands corresponding to G are better observed in the SERS spectrum of the pGC.pCG polymer 3 as mordant ; tryptophan ; tyrosine ; cysteine , as well as bands corresponding to the polypeptide keratin backbone amide III and amide I at 1280 and 1666 cm−1, respectively.The extracted cochineal colorant was then employed to dye commercial wool fibers in the fabrication of textile replicas. Figure ber Fig. h and by ant Fig. g. The laant Fig. j and i. −1, but also many of the ring breathing bands of nucleobases observed in the 800–600 cm−1 region, which are also observed in the SERS analysis of historical textiles . This selective interaction of G with Al has been also recently described in the literature, involving a strong charge-transfer between Al to the C=O and the N7 atom of the G purine residue53.The use of Al as mordant leads to a deep modification of the SERS of the resulting fiber, the presence of this metal induces a selective enhancement of the 660 cmdue Fig. g, while ing Fig. e. This i25. As a consequence of this strong interaction, a large shift of the 1290 cm−1 characteristic band of carminic to 1322 cm−1 is observed. The latter shift is very important in the identification of the presence of mordants in historical textiles, as similar effects can be observed in the analysis of many historical cochineal-dyed fibers. This is the case of the SERS of the historical textile fiber shown in Fig. 7. The 1290 cm−1 band is attributed to the C–OH deformations coupled to ring stretching vibrations in the anthraquinone ring I25 (Fig. Al is then interacting very strongly with the carminic acid and thanks to this mordant interaction improves the fixation of the colorant to the wool fiber through the keto and phenol groups of the anthraquinone rings Fig. d, as als54. Therefore, more investigation on the effect of the metal and the presence of biomolecules should be done in order to better interpret the resulting SERS spectra and correlate them to the analyzed archaeological samples.However, the analysis of archaeological textiles still reveals a large variability regarding the bands intensity of G and A nucleobases, as well as other biomolecule characteristic bands depending on the color of the studied area. This is the case of the belt-bag analyzed in the present work, where different spectra were measured in the red, brown, yellow and orange areas Fig. a showingin-situ experiments that does not imply the colorant extraction. The regular Raman study of carminic acid indicates that the spectrum is dominated by the anthraquinone moiety signals, although Raman signals from the glucose residue have been obtained and identified when carminic acid is deposited on a gold thin layer. The interaction with metal surfaces leads to the relative intensity increasing of the glucose residue bands which is evidenced from the SERS spectrum of carminic acid and the theoretical representation of the dye-surface interaction. The SERS analysis of archaeological red dyed textiles demonstrated the existence of carminic acid, but also other biomolecules, mainly nucleic acids, in real archaeological textiles. The presence of nucleic acids in these samples was deduced from the appearance of nucleobase bands that can be mainly attributed to adenine and guanine, also detected in the raw cochineal colorant. This was further confirmed by obtaining cochineal dyed textile wool fibers according to ancient receipts. The effect of Al in mordant carminic acid leads to a significant structural change in the Raman spectrum of carminic acid involving the keto group as well as the adjacent C–OH groups. The complexation of Al also leads to specific interactions of the nucleobases with the wool in the fiber. In fact, guanine bands are further enhanced in SERS spectra because of the strong interaction established between Al and the purine residue through the C=O or pyrimidine ring and the N7 of imidazole ring. The results of the present work will be very useful in the identification of different molecules and metal complexes that may be forming part of the cochineal colorant found in archaeological materials.SERS spectroscopy has been successfully employed for the multiplexing identification of the different components integrating the cochineal colorant. This analysis was performed on the cochineal dyed archaeological textile samples and replicas using


This research presents the behavior of dombeya buettneri fiber/graphite hybrid composites which was studied to harness a favorable balance between the inherent advantages and disadvantages of natural and synthetic reinforcements. The fibers after extraction were chemically treated for surface modification. The composite was developed using compression molding process by randomly dispersing the reinforcements in the polypropylene matrix in predetermined proportions. The developed samples were tested to ascertain the response of the materials to the selected properties. Experimental results showed that hybrid composite sample C which is a blend of 12 wt% dombeya buettneri fiber (DBF) and 8 wt% graphite particle (GP) gave enhanced results in many of the properties which includes; hardness, impact, thermal insulation and abrasion resistance properties. Also, the hybrid composites sample denoted as sample E which is the blend of 6 wt% DBF and 14 wt% GP produce higher enhancement in the flexural properties and Young’s Modulus of Elasticity than other samples. Composite sample reinforced with dombeya buettneri fiber as single reinforced composites performed more in ultimate tensile strength compared to other samples while graphite particle reinforced sample emerges as the best in thermal conductivity. Diffusion of water into the composites also obeys Fick’s law where sample C was seen to be the best among the composites. It was therefore, discovered that the synergy between the two reinforcements has encouraged the improvement of polypropylene (PP) properties in a unique mode. The characteristics properties such as good dimensional stability, ease of design, corrosion resistance, good mechanical strength and lighter weight makes these set of materials desirable over the traditional materials3. They have been successfully utilized in the development of composite materials with good property when compared with synthetic fibers4. In composite formation, the physical and chemical identities of the fibers and matrix are retained, while the composite formed, possess a blend of properties not attainable by each constituents. It has been established that in fiber reinforced polymer composite, fibers are the main load-carrying members. Notable characteristics of the matrix material are; to transfer stresses between the fibers, serves as a barrier against an extreme environment, and to shield the fiber exterior against mechanical abrasion6. Plant fibers have better specific properties, i.e. the ratio of mechanical properties per mass, which makes them good candidates for lighter materials. As renewable and recyclable materials, they are environmentally friendly7. Suddell and Evans8, reported on the categories of natural fibers with their unique properties for consideration in the development of fiber based composites. Few of the natural fibers include coir, cotton, wood, ramie, coconut leaves, jute, sisal, hemp etc. Their choice as candidate reinforcement material is informed by the potential area of application among other criteria. Natural fiber such as hemp, kenaf and flax have been successfully utilized in the design of polymer based composites. This is due to their excellent functional properties with their positive economic implication8.The choice of natural reinforcement materials in the design of polymeric based composites has gained significant attention from researchers9. PP finds its application in many house wares, packaging for user products, appliances, bottles, special devices like living hinges, automotive industry, textiles and heater ducts where high heat deflection is required9. Essential properties possessed by PP include good transmissivity, elasticity, toughness property, fatigue resistance and good chemical resistance10.Polypropylene (PP) is a known thermoplastic “addition polymer” derived from the combination of propylene monomers. It is reported to be one of the most widely used plastics in the world and is ranked third in usage after polythene12. Detailed information on the fiber properties is lacking as it has only been used extensively in the field of medical sciences but not for materials development or engineering application as in the case of this present work. In traditional medicine, it finds a unique impart, the leaf has been used in the treatment of gastrointestinal problems confirmed in experiments with rats12. In DR Congo for instance, they are made as cords to support basket on the back for carrying loads. Hence, the choice of DBF as lignocellulosic reinforcement in polymer composites becomes more appealing due to their inherent strength12.Dombeya buettneri fiber (DBF) is a readily available plant fiber grown in Madagascar and some other African countries like Nigeria. The stem releases a very sticky fluid when cut which exude gums and resins. The stem bark is very fibrous from where fiber can be extracted manually to make rope, nets and fishing apparatus13. It is an allotrope of carbon with high thermal conductivity property. Literature has it that at ambient temperature and pressure, carbon often exhibits a lowest energy state14. However, at higher temperature  carbon and graphite display a good strength and stiffness properties. Composites developed from carbon fiber are mostly used in space, aeronautical, bio-medical, and industrial application. Currently, they are mostly used in commercial and defense areas15 with the availability of inorganic fillers. Previous works from researchers have established the use of hybrid reinforcements for composite development19, however, dombeya buettneri fiber and graphite has not been used. The current work examines the influence of dombeya buettneri fiber and graphite particles on polypropylene. Part of the novelty of the research was the synergy between newly applied vegetable fiber and an established synthetic particle. This was done to extend the frontiers of knowledge in the use of natural fiber and the areas of applications23. These reinforcements were selected so as to explore their effect on polypropylene matrix, which is widely used among the thermoplastic material.Graphite is one of the softest metals that is carbon in its stable form. It has good thermal and electrical conductivity and makes a good lubricant. Graphite powder is soft but does not have elastic or stretching properties. Graphite exhibiting an anisotropic nature within the in-plane and out-of-plane of its atoms with higher elastic modulus parallel to the plane as well as compared to the perpendicularThe chemicals; dioctyl phthalate (DOP), zinc stearate and sodium hydroxide were procured from allied stores in Edo State, Nigeria while the homopolymer polypropylene (PP) shown in Plate One of the prime materials used for this research was dombeya buettneri fiber. The fiber was extracted by removing the bark from the stem, followed by manually separation of the strands and sun dried for 5 days. The fiber was treated by immersion in a solution of 1 M NaOH at 50 °C for 4 h in a shaker water bath. The treated fiber was washed with tap water and rinse with distilled water till neutral status was ensured after confirmation by litmus paper. The treated fiber was sun dried for 5 days during the dry season until the moisture content is removed.The composite was developed using compression molding process by randomly dispersing the dombeya buettneri fiber and graphite particle in the polypropylene matrix in predetermined proportions. The working condition for the production of the hybrid composite was 170 °C for 7 min at 5 bar. Compounding of samples was carried out to ensure an even distribution of the reinforcement in the matrix and a proper blend, followed by reproduction of the sample but with the addition of plasticizer and stabilizer using the same working parameters. The ratio of dioctyl phthalate to zinc stearate that was used as plasticizer and stabilizer respectively was 2:1. The fiber after compounding was cut to short fiber lengths of average size 6–8 mm during grinding. The composite composition was presented in Table Total weight of the materials that filled the mould was 173 g.24 standard on a universal testing machine Instron series 3,369 model. The specimens with dimensions 90 × 10 × 5 mm dumb-bell shape were used. The test was conducted at a crosshead speed of 5 mm/min using 10 kg load cell. To ensure precision and reliability of tensile test results, three repeatability tests were performed for each of the developed samples.The tensile tests were conducted according to ASTM D3039/D3039M-1725 standard. A sample cut into 150 × 50 × 5 mm was placed in grip of the machine and was stretch at a test speed of 5 mm/min over a span of 65.00 mm. Three samples were tested for each composition and the average value was used as the representative values.Three points bending test was used to evaluate the flexural property of the samples. Universal testing machine series 3,369 model was used to carry out the flexural test in accordance to ASTM D790-0326 a standardized test method for determining the Izod Pendulum impact resistance of plastics. The test was carried out using a Hounsfield balanced impact testing machine, serial number 3915, model number h10-3. Impact test dimension of 64 × 11 × 3 mm was notched at the center. Samples were placed horizontally on the machine, maintaining a distance of 60 mm between lines of supports. The test samples were placed in a cantilever position, clamped upright with a V- notch at the level of the top of the clamp. The machine pendulum hit the test piece and was allowed to fall freely to a fixed height.The notched Izod impact test was conducted in accordance with ASTM D 256-1027. The samples were placed on the flat surface of the tester stand and indented. Four values were obtained by indenting the samples in four different places and the average value was used for analysis.Hardness test was conducted on the specimen using a Shore D hardness tester in accordance with ASTM D2240-0028, a standardized test method for resistance of transparent plastics to surface abrasion. Prior to the test, the initial weight of the sample was measured. Each sample was mounted on the Taber abrasive tester operated at 150 rpm for 10 min, and then the weight post abrasion testing was taken. A mould of 100 mm diameter × 4 mm thickness was used to produce the wear samples. The wear index was determined from Eq.  is weight gain per hour, Water absorption tests were carried out in accordance with ASTM D5229M-1223. In the hybrid composites, the UTS tend to decrease as the DBF reduces from sample A to F. The observed trend can also occur due to improper transfer of load from the matrix to the reinforcement resulting from improper interfacial adhesion at the reinforcement/matrix phase or when the ratio of the two constituents are inappropriate; consequently, weak interface will occur. In this hybrid system, the interfacial phase seems more complex due to the origin and shape of the reinforcements which are synthetic/natural and particulate/fiber, respectively. From the results obtained for single and hybrid reinforced composites, it shows that, the presence of graphene particulate in high proportion tends to decrease the UTS compared to dombeya buettneri fiber. This may be due to inadequate wettability of the particles owing to higher filler loading that resulted in poor fiber-particle–matrix adhesion and, thus, decreased tensile strength. The decrease in the tensile strength as the graphite particles increased beyond hybrid composite sample A can be due to the interference of DBF and GP in the mobility or deformability of the matrix. While the improved tensile property of the hybrid reinforced composite may be attributed to the fair distribution of the DB fiber in the polypropylene matrix resulting in strong DBF-GP-PP matrix interaction. Similar results have been reported by previous researchers34.Figure 35 reported from their results that, the enhancement of tensile modulus is not dependent on the particle size but on particle loading. Also, stated was that the occurrence of improved stiffness with corresponding increase in filler loading in particulate-filled polymer composites has been attributed to the fact that most inorganic fillers exhibit rigidity that is significantly higher than that of the polymer matrix. These observations are in agreement with the investigation of Fu et al.36 where they studied the effect of particle size on the tensile modulus of particulate–polymer composites37. Therefore, as the filler loading increases, the degree of obstruction increases, this in turn increased the stiffness. This is also in agreement with the findings of Fardausy et al.38 that the tensile modulus of the fabricated composites increases with increase of filler addition. The results obtained in this study attributed that the fillers had created some reinforcing effect and had been responsible for the increase in Young’s modulus34. It can be deduced that the samples that has high modulus of elasticity has better stiffness property compared to others and this is due to the presence of the higher proportion of graphite particles13. In this research, about 5% enhancement was achieved.Figure 14. This implies that the composition of sample F gave the best propensity for high strain before failure.Figure Figure Figure 39 that fibers play an important role in the impact strength; they resist the crack propagation and act as a load transfer medium. Similar findings were reported by other researchers40. The maximum impact energy obtained in this research was 20.28 J with hybrid composite sample C which connotes about 32% enhancement in this property. Considering the impact property of the single reinforced composites, it was observed that the addition of GP in the matrix led to improved impact energy of the composites. However, the improvement was more appreciable with the addition of DB fiber.The effect of different proportion of reinforcement content on the impact energy of the developed composites and the control sample was shown in Fig. 41.Surface hardness of the composites is one of the most important factors that directly have effect on the wear resistance of the composites. From Fig. Figure 42. A material with higher thermal conductivity implies that it is more conductive and lesser value implies a good insulating property of the material. Thermally conductive polymer composites are typically developed by introducing fillers of high thermal conductivity, such as lightweight carbonic materials45. It was observed in Fig. 46, that polymer/graphite composites exhibited a high thermal conductivity and an electrical conductivity at a fairly low concentration, amongst other fillers, graphite features unique properties such as a high thermal and electrical conductivity, a low coefficient of thermal expansion, a high thermal shock resistance, improved stiffness and an increased strength. From the results, it was noticed that the thermal conductivity varies with the reinforcement content. It was discovered from the mechanical properties results that the reinforcement materials toughens the matrix and, hence, prevent the composites from conducting the thermal energy as more barriers are developed in transporting from one side of the sample to the other47. The moderate thermal conductivity value of the hybrid composites was a proved that there is a synergetic effect of GP and DB fiber on the compositions. When the single reinforced composites are compared, the DB fiber reinforced composite and GP reinforced composite has values of 0.085 W/mk and 0.149 W/mk, respectively. This signifies that DB fiber is more insulating than the GP. From the result, it was observed that the blend of 12 wt% of DB fiber and 8 wt% of GP gave the optimum result of 0.058 W/mk which amount to about 105% enhancement from sample C as the best insulating materials. Conversely, GP reinforced composite was the best in terms of conductivity with about 25% improvement when compare with the control sample (0.119 W/mk).Thermal conductivity is a measure of the rate of heat flow through one-unit thickness of a material subject to a temperature gradientFigure 49. The first thing to do in order to understanding water diffusion is to examine diffusion path and relaxation conditions as given by Fick’s law49. Though, this is challenging because of the complexity of polymer structure and compositions, and the difficulty in evaluating the details of molecular-level for such a small sample50. The second assumption of ideal Fick’s diffusion is that the polymer variation caused by water diffusion can be negligible, which is absolutely not acceptable for most experiments. According to the relative rate of polymer relaxation compared to that of water diffusion, three types of water diffusion are possible as stated by Frisch51. These three types were seen in the results presented in Fig. According to Fick’s law (J) which measures the amount of substance that will flow through a unit area during a unit time interval, diffusion of water in polymer also occurred in such mode. Water is a transmission medium for oxygen and ions, hence, diffusion of water in polymers is an important mechanism to be understood49.The diffusion rate from 0 to 48 h agreed with Case I  where polymer relaxation is much faster than water diffusion, and the diffusion is followed by an instantaneous response of the system, resulting in Fick’s behavior. The instantaneous response of the system requires large flexibility of the polymer chains in the system, that is, the polymer is in a rubbery state. In this case, diffusion is controlled by the diffusion coefficient53.The diffusion rate from 48 to 144 h agreed with both Case II (n = 1) and Super Case II . Under these conditions, the rate of diffusion is much faster than that of relaxation initially which marks the innermost limit of water diffusion, and it is the boundary between the (stressed equilibrium) swollen gel and the glassy core of polymers. At this moment, the swelling of polymers occurs. This was followed by rate of diffusion that is equal to that of relaxation  where evolution, under certain circumstances, of Super Case II transforming from Case II makes it somewhat uncertainThe final stage from 144 to 168 h in these results revealed that, the diffusion or absorption of water become constant or fixed and it is referred to as saturation point.The total moisture uptake of the control sample after 168 h was 0.05% while the sample with least moisture absorption among the composites was from single reinforced composite GP was with a value of about 0.61%. DBF reinforced composites was the sample with the highest moisture absorption of about 1.30%. This was followed by sample A being the blend of 18 wt% of DBF and 2 wt% of GP with a value of about 1.23%. These results showed that the DB fiber has high affinity for water than GP as confirmed in hybrid composite sample F (a blend 3 wt% DB fiber and 17 wt% GP) having total moisture uptake of 0.87%. For the hybrid composites, the water absorption tends to decrease with increase in the GP content with the exception of hybrid composite sample D. Hybrid composite sample C (a blend 12 wt% DB fiber and 8 wt% GP) has the lowest water up take amidst the hybrid composite developed which is 0.83%. This composition and the feat can be due to the interplay of DB fiber and GP being at equilibrium to effectively reinforce the polypropylene matrix. Considering the single reinforced composite, GP has a higher resistance to moisture absorption than DB fiber. Thus, it was noticed that GP was hydrophobic while the DBF was hydrophilic in nature. However, the synergetic influence of these reinforcements aids a better material for structural applications with respect to water intake.54. The chemical treatments reduce the level of surface roughness compared to the untreated DB fiber. Alkali treatment has been discovered to be responsible for the removal of some hemicelluloses, lignin, glue and other extractives in fiber bundles which yields higher percentage of α- and cellulose in natural fibers23.The surface morphology of the fibers as observed from the SEM in Plate Plate Chemical treatment was noticed to reduce the roughness of the untreated DB fiber surface, thereby, making the surface more suitable for good fiber-matrix interaction due to de-lignification of the surface. The hybrid composites emerged as the best material in most of the properties examined except ultimate tensile strength, water absorption and thermal conductivity compared to other samples. Sample denoted as C which is the blend of 12 wt% DB fiber and 8 wt% GP has the optimum properties from all the samples being 31%, 32%, 105% and 150% enhancement in hardness, impact, thermal and wear properties, respectively followed by sample denoted as E which is the blend of 3 wt% DB fiber and 17 wt% GP with best results from flexural properties and Young’s modulus. With the good wear resistance and thermal insulating properties of the hybrid composite samples, it can find application in automobile industries for interior application like door panel and can also be used as protection for pipelines vessels. Diffusion of water into the composites also obeys Fick’s law where sample C was seen to be the best among the composites.


COVID-19 is a respiratory disease caused by a coronavirus, designated SARS-CoV-2, which is responsible for a global pandemic in 2020. Public interest in this disease has led to the publication of thousands of articles in the medical literature in a very short timeframe. It is imperative that medical research into COVID-19 is conducted quickly and safely, and that due reference is given to the ethical considerations enshrined in the ICH GCP guidelines, according to the Declaration of Helsinki.th 2020. The search criteria proposed for the review are based upon what would be a reasonable search conducted by a lay member of the public with access to PubMed.gov. Institutional Research Ethics Committees (RECs) face significant challenges in providing thorough and timely ethical review during the COVID-19 pandemic. It is proposed to publish the findings of this rapid review along with a summary of an institutional REC response to the challenges of reviewing and approving clinical research proposals in the time of a pandemic. In order to review the reporting of ethical considerations in these papers, we hereby propose a protocol for a systematic review of COVID-19 papers up to April 14 Since then SARS-CoV-2 has spread across the globe and is the agent responsible for a viral pneumonitis called COVID-192. Its virulence, the rapidity of its spread and the lack of either a vaccine or a treatment have led to the adoption of unprecedented public health measures worldwide3; and to high levels of interest and anxiety in the general population4.In December 2019 the first reports of a novel coronavirus, now designated SARS-CoV-2, emerged from China5. The COVID-19 related publications range from commentary and case reports to epidemiological studies and clinical trials. It is the policy of many journals during the pandemic to offer rapid review in order to make reports and research on COVID-19 available quickly6. However, London and Kimmelman have expressed concern that scientific and methodological research standards will fall in the urgency to produce results7. Similarly, the authors have observed considerable variability in the reported ethical review of the studies published and seek to conduct a systematic review of this question – how well are ethical disclosures ethical disclosures reported in the COVID-19 literature? Spector-Bagdady et al pointed out that clinicians and medical centres are faced with difficult decisions regarding which trials to participate in and are faced with challenges with implementing both an ethical and efficient recruitment method for COVID-19 trials8. Tansey and colleagues also highlighted the importance of having a framework in place for ethical review in an emergency situations9. Along with the results of this Rapid Review, a description will be provided of the response of an Irish Ethics Committee to the challenges presented by the COVID-19 pandemic. The Standard Operating Procedures of this Ethics Committee will be presented, along with how these were adapted to ensure thorough and timely ethical review during the COVID-19 pandemic.The international medical and scientific research community has responded to the COVID-19 pandemic by generating a huge amount of literature to which the general public has access11. The protocol is not eligible for registration on the PROSPERO database, as the question of interest relates to reporting and methodology rather than to a clinical outcome for participants.The protocol is designed in line with the PRISMA-P checklist for systematic review12 will be used. These include an assessment of the standards agreed by the International Committee of Medical Journal Editors13 following the Declaration of Helsinki14; the report of consent obtained for the study and the report of ethical review of the study.The ethical standards of interest described by Yank and Rennieth 2020.The search parameters are: Pubmed search of the term “COVID-19” with the filters of Free full text and English language publication – the rationale for this search is that it would be reasonable for a lay member of the public to conduct such a search. No start date is applied and the finish date of the search is April 14The bibliography of the search will be saved and the assessors will use an Excel spreadsheet to record excluded and included studies, using the reference number from the search bibliography. Papers may be included if they are defined by an assessor as a case report, case series, observational study or clinical trial. Papers will be excluded if they are classified as a commentary, editorial, review, guideline, non-clinical report, cell-based study, animal study, epidemiologic study or report of a mathematical model. Two reviewers will conduct the initial assessment . The reviewers will confer where there is any uncertainty.Two independent reviewers will conduct a bias assessment. Each independent reviewer will assess 10 studies each for each initial assessor, identified randomly from the search bibliography . A threshold of 20% discrepancy between initial and independent assessors has been set to determine whether a further methodological revision is required. A further five records each will be reviewed following this initial method assessment.For case studies and case series, the assessor will record: the first three authors; journal; study title; whether written consent reported; if not written consent whether oral consent reported or whether not available (i.e. patient deceased); whether written consent to publish provided to journal; the wording of consent; the nature of identifiers reported ; whether the article included a statement of compliance with International Conference on Harmonisation (ICH) good clinical practice (GCP)/Declaration of Helsinki standards.For observational studies and clinical trials, the assessor will record: the first three authors; journal; study title; whether written consent reported; the wording of consent; if not written consent whether oral consent reported; review by research ethics committee; whether that committee is identifiable on line; whether the article included a statement of compliance with ICH GCP/Declaration of Helsinki standards and in the case of a clinical trial, whether the trial was registered.The outcome is the proportion of papers where informed consent to publish (in case studies and series) and for inclusion in a clinical research study as well as publication  was recorded. An assessment of the role of ethics committees will be included; specifically, whether ethics committee approval was sought and whether requirement for consent was waived by said committee and whether there is a geographical or publication pattern associated with the reported role of the ethics committee.This is a methodologic review; therefore, bias in interpretation of results is not relevant to this study. The proposed assessment of the ethics reporting standard categorized by journal may identify a publication bias.A quantitative summary of numbers of studies identified, and their classification by assessor, will be provided. A further summary of consent reported and the nature of that consent will be prepared. The proportion of studies reporting ethical review and including a statement of compliance with ethical guidelines for conduct of clinical research studies , will be included. A qualitative description of the measures to preserve anonymity of the participants will be made.This study will not be clinical in nature and does not meet the requirement for a research ethics committee review. In view of the nature of the study and the impact of ethical conduct of research on public confidence in research, it is proposed to share the final draft of the study manuscript with two lay volunteers for a lay perspective on the findings prior to submission for publication. The protocol will be made available for the public on the UCD COVID-19 website.The search bibliography and finalized Excel spreadsheets will be included as supplementary documents with the final publication. As a publication relating to COVID-19, it is anticipated that this will be open access. Should this not be the case the authors will make these files available on request to the corresponding author.The purpose of conducting this review is to describe the existing publication status for ethical declarations in COVID-19 clinical research and discuss the potential impact on public trust in clinical research. It is proposed to include the findings with a description of how n Irish Research Ethics Committee conducted ethical assessment both expeditiously and safely in a time of pandemic; in order to maintain ethical standards, maximize public access to participation in clinical trials and research, and maintain public confidence in future research studies and their findings.No data are associated with this article.https://doi.org/10.6084/m9.figshare.12249224.v111.Figshare: PRISMA-P checklist for ‘Protocol for systematic review of ethical declarations made in clinical publications concerning COVID-19’.Creative Commons Attribution 4.0 International license (CC-BY 4.0).The completed PRISMA-P checklist is available under the terms of the I am satisfied with the changes; it can be indexedIs the study design appropriate for the research question?YesIs the rationale for, and objectives of, the study clearly described?YesAre sufficient details of the methods provided to allow replication by others?YesAre the datasets clearly presented in a useable and accessible format?Not applicableReviewer Expertise:Bioethics and law of human subjects research.I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. Thank you to the team for updating the protocol and providing Version 2. I wish you all the very best with this review.Is the study design appropriate for the research question?YesIs the rationale for, and objectives of, the study clearly described?PartlyAre sufficient details of the methods provided to allow replication by others?PartlyAre the datasets clearly presented in a useable and accessible format?Not applicableReviewer Expertise:Qualitative research, trial methodology, evidence synthesis .I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. This can be a useful study. I look forward to reading it upon completion. The study could be improved by addressing several issues described below:Introduction The following literature should be engaged/cited:1; Spector-Bagdadyet al. (2020)2; Tansey et al. (2010)3. London and Kimmelman (2020)Abstract The abstract states that the study will publish a summary of the ethics committee responses to challenges of reviewing and approving protocols during a pandemic, but the protocol does not have a way of identifying what those challenges are or what committee responses to the pandemic situation have been. Some committees may always have been lax; the pandemic situation may not be more lax than their baseline. Protocol Protocol Design and Registration:  Please consider adopting completely Yank's categories for describing informed consent. Or, alternatively, explain: a) why you are not doing so and b) how readers should compare Yank's outcomes to yours. Comparison could be an important step in understanding pandemic constraints/responses if you make a greater effort to make your study comparable to Yank's. "Search Record and Outcome Management" For case studies and case series, the "wording of consent" will be recorded. It will not be recorded for observational studies and clinical trials. Why not?Conclusions One of the stated purposes of the study is to describe the potential impact on public trust in clinical research. What are you going to ask lay people at the end of the study that will help determine that impact? Do you have enough lay people to say much? Is this really a second phase of the study? The conclusion states that a "description of how ethical assessment can be expedited safely in a time of pandemic...." will be included. The proposed study will not support any conclusions about whether the way things were done in the COVID 19 studies was expeditious or safe, or whether public access to participation was maximized. It will support conclusions about whether certain ethical standards were maintained (particularly if Yank's outcomes are used as a touchpoint); and it may (if the lay role is made more rigorous) support conclusions about public confidence.Is the study design appropriate for the research question?YesIs the rationale for, and objectives of, the study clearly described?YesAre sufficient details of the methods provided to allow replication by others?YesAre the datasets clearly presented in a useable and accessible format?Not applicableReviewer Expertise:Bioethics and law of human subjects research.I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Thank you Bethany for your time in reviewing our protocol. We appreciate all of your comments and suggested changes. We have addressed each of the points you have raised and amended the protocol accordingly. Thank you for highlighting these publications. We have added them to the Introduction section. The final publication will include a description of the Standard Operating Procedures of a REC which will demonstrate the rigour of their review pre-COVID 19. The publication will also identify how they adapted their operational procedures to ensure timely and thorough ethical review during the COVID-19 pandemic. The Introduction and Conclusion have been amended to explain this.The outcomes described by Yank and Rennie will be used. The wording in the ‘Protocol design and registration’ section has been amended to clarify this. The ‘wording of consent’ will be recorded for observational and clinical trials, so this sentence was amended accordingly. The purpose of the review is to determine to what extent COVID-19 publications report ethical declarations, given that the lack of these declarations may damage public trust in research. We have amended the wording of this section slightly to clarify this. The purpose of requesting two lay persons to review the manuscript was to incorporate their opinions, as well as the viewpoints of clinical researchers on the findings of this review. A larger exploration of lay opinions on COVID-19 research would indeed be valuable and interesting but it is unfortunately not within the scope of this research.This wording referred to the description of the Standard Operating Procedures of an Irish Research Ethics Committee in pre-COVID 19 (please see amended text in the Introduction), which will be included in the publication. Along with this description, an account will be given of how this Ethics Committee adapted their practices to ensure timely and thorough ethical review despite the challenges presented by the COVID-19 pandemic. We have amended the wording of the Conclusion to clarify this.Many thanks again Bethany. I want to start by congratulating the team on their proposal. This is an important study and I was delighted to have the opportunity to offer some thoughts and comments.  Some points of feedback and comments:The Title of the Study: I suggest that the title needs to be reviewed. At present it does not indicate clearly to a reader that “ethical declarations” relate only to the reporting of informed consent and ethics committee approval. The teams definition of ‘Clinical publications’ also needs to be explicit in the title and the ‘type’ of studies to be included needs to remain consistent throughout the protocol. Abstract: The last point in the abstract is not clear. What is meant by publishing the findings of this review “with” a summary of the IREC response to the challenges of reviewing and approving clinical research proposals in the time of pandemic? If the review authors intend to use the IREC response as a step in their interrogation of the findings this needs to be clear. Introduction: The review authors draw attention to the Torres-Salinas paper presenting “a global vision of the daily growth of scientific production on Covid-19 in various databases”. I was able to access only an English translation of the abstract of this paper, therefore, how it links to the amount of literature the general public can access, remains unclear.  The question identified at the end of this section  is broader than the focus of the review as documented in other places  this needs to be realigned. Protocol: Some rational needs to be provided as to why the review authors state that it is “reasonable for a lay member of the public to conduct such a search”. Is there evidence to suggest that the use of Pubmed (and Pubmed only) is appropriate? Have the different variations of the terms of COVID-19 been considered and how will the search account for this? Will this review include pre-prints and what considerations have been given to the time frame between the availability of a publication and its indexing in Pubmed? Search record and outcome management: Where does qualitative research fit within the inclusion / exclusion criteria?Analysis: It is not clear what is meant by “a qualitative assessment”, this needs to be clarified. The analysis section notes that a qualitative description of the measures to preserve anonymity – however no reference is made to extracting data relating specifically to anonymity. Ethical review and lay opinion: Including a lay perspective in the review is welcome, however, the role of the 2 lay volunteers is not clear. Will the volunteers be asked offer their opinions in relation to the accuracy of the review, the rigour of your methods or the readability of the paper? Conclusions: The claims noted in this section need to be revisited. The purpose of this review noted on line 2 of this section denotes that the review will focus on “ethical standards in COVID-19 clinical trials” – this is not in keeping with the rest of the protocol. Nor does the protocol indicate how this review can highlight issues in relation to public trust. It is not clear how the review will provide a description of how ethical assessment can be expedited safely in a time of pandemic. Nor is it clear how the findings of this review will support the assumption that reporting ethical approval equates to maintaining ethical standards. The link between reporting the findings of this review and the “ … public’s confidence in future research and their findings” also needs to be reconsidered.Is the study design appropriate for the research question?YesIs the rationale for, and objectives of, the study clearly described?PartlyAre sufficient details of the methods provided to allow replication by others?PartlyAre the datasets clearly presented in a useable and accessible format?Not applicableReviewer Expertise:Qualitative research, trial methodology, evidence synthesis .I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Thank you Linda for your time in reviewing our protocol. We appreciate all of your comments and suggested changes. We have addressed each of the points you have raised and amended the protocol accordingly.Ethical Considerations for safeguarding human participants in pandemic research: a rapid review protocol Title was amended to reflect the reviewer’s comment and also because the authors feel that the review more accurately fits the Rapid Review methodology. Title now reads: The wording of ‘clinical publications’ has been amended throughout to clarify and ensure consistency. A description of the response of an Irish Ethics Committee to the challenges presented by the COVID-19 pandemic will be provided in the Discussion section of the Rapid Review to complement the Rapid Review findings. Operational and logistical challenges in providing thorough and timely ethical review during the COVID-19 pandemic will be discussed. The Introduction and Conclusion were amended to clarify this.The Torres-Sallinas reference was removed and a reference to an announcement on the PubMed website that over 50 publishers have made COVID-19 publications accessible was added.The sentence at the end of the Introduction  was amended to clarify scope of this review.https://www.ncbi.nlm.nih.gov/pmc/about/covid-19/ so the rationale was that this platform would make these publications accessible to members of the public. A reference to this webpage has been added to the protocol (see above point). PubMed facilitated over 50 publishers in providing access to full-text publications relating to COVID-19:  The purpose of this rapid review was to assess how well a representative sample of human research on COVID-19 adhered to ethical guidelines such as informed consent, REC review etc, rather than to perform an exhaustive search of all COVID-19 publications. For this reason, a single but comprehensive database was selected, which provides full-text access to lay people. Due to the fact that pre-prints have not undergone peer review, they will not be included in this review, as the intent is to assess peer reviewed articles. However, ‘Epub ahead of print’ articles will be included, as they have undergone peer review.A search for ‘COVID-19’ in PubMed yields the following terms: "COVID-19"[All Fields] OR "severe acute respiratory syndrome coronavirus 2"[All Fields] OR "severe acute respiratory syndrome coronavirus 2"[All Fields] OR "2019-nCoV"[All Fields] OR "SARS-CoV-2"[All Fields] OR (("Wuhan"[All Fields] AND ("coronavirus"[MeSH Terms] OR "coronavirus"[All Fields])) AND 2020[All Fields]). It was therefore felt that that the term ‘COVID-19’ would provide us with a broadly representative sample of COVID-19 research publications.No filters will be applied other than ‘Free Full Text’ and ‘English Language’ so qualitative studies will be included. A initial search indicated that the qualitative COVID-19 studies were   observational in nature, so they will be included in this category. A review of whether publications record if REC approval was sought and whether the requirement for consent was waived by the REC will be conducted. If the information is available, a review will be conducted of the geographical or publication patterns also. We have removed the word ‘qualitative’.Under ‘Search Record and Outcome Management’, one of the items that will be recorded is ‘nature of identifiers’. We have added ‘’ to clarify the meaning of this.The purpose of requesting two lay persons to review the manuscript was to incorporate their opinions, as well as the viewpoints of clinical researchers on the findings of this review. We have amended this sentence to clarify.The final publication will include a description of the Standard Operating Procedures of a REC which will demonstrate the rigour of their review pre-COVID 19. The publication will also identify how they adapted their operational procedures to ensure timely and thorough ethical review during the COVID-19 pandemic. The Conclusion has been re-worded to address this comment. Many thanks again Linda.


Early transmissibility assessment of the N501Y mutant strains of SARS-CoV-2 in the United Kingdom, October to November 2020’ by K. Leung et al. published on 7 January 2021, the term ‘clade GR’ as per the GISAID Initiative on common clade nomenclature system was added to complete the different assignments of the newly detected SARS-CoV-2 variant at the time of publication. It was further specified that the sequences were retrieved from the GISAID Initiative’s EpiCoV database. The acknowledgement was replaced by ‘We gratefully acknowledge the following authors from the originating laboratories responsible for obtaining the specimens, as well as the submitting laboratories where the genome data were generated and shared via GISAID, on which this research is based. ’ to match the wording in the Supplementary material.In the article ‘The table with sequence contributors in the Supplementary Table S2 was replaced by a table with more comprehensive information about submitters by authors.These additions were made on 21 January 2021.