A laboratory-based experiment procedure of reception plate method for structure-borne soundsource characterisation is reported in this paper. The method uses the assumption that the inputpower from the source installed on the plate is equal to the power dissipated by the plate. In thisexperiment, rectangular plates having high and low mobility relative to that of the source wereused as the reception plates and a small electric fan motor was acting as the structure-bornesource. The data representing the source characteristics, namely, the free velocity and the sourcemobility, were obtained and compared with those from direct measurement. Assumptions andconstraints employing this method are discussed. The structure-borne sound is still a challenging problem in engineering especially in buildings where machineries such as fans, compressors, hydraulic equipment, electrical motors, heating pumps, washing machines, and air conditioning system can produce a considerable amount of vibration . The traThe symptom before the structural damage due to the effect of vibration is sometimes not visible. With the information of the vibration level strength of the structure-borne sound source, a preliminary control measure can be planned. This is where characterisation of the source becomes important . UnfortuFor structure-borne source characterisation, the reception plate method as a laboratory measurement test has been proposed , 5. The In this paper, the reception plate method is again addressed and discussed. The methodology is similar to that in  where heZS freely suspended and vibrates with velocity vf as shown in FB by the source is called the “blocked force”. From definitionYS = ZS−1 is the mobility of the source.Consider a vibrating source with impedance ZR as shown in v. The blocked force at the contact point is now the sum of the force from the source FS and that applied to the receiver FR [Consider now the source is rigidly connected to a receiver structure with impedance iver FR . The bloF* is the complex conjugate of F.Equation  can be rN contact points, the formulation can be represented in terms of vectors and matrices given byFR and v are column vectors of size N × 1 and the impedance Z is a N × N matrix. The superscript H denotes the conjugate transpose. By substituting (Assuming that the source is now attached to the receiver through tituting  into 5)N contactituting ,,8), the given byY=[Y11Y12mR is the total mass of the plate, ηR is the total damping loss factor of the plate, ω is the operating frequency, and 〈vR2〉 is the spatial average of mean-squared velocity.The reception plate method is a technique where a vibrating source under normal operating condition is connected to a flat plate structure. The total structure-borne power of the source is equal to the power generated on the plate given as (13)PinTYS| ≪ |YR|, employing the effective mobility in ,,YS| ≪ |ility in  can therlity in ∑iN|int giveηRωmR〈vR2plate in .This section presents the reception plate measurement conducted with high and low mobility plates. A small table electric fan motor was used as a structure-borne source mounted rigidly on four contact points and operated at normal speed condition.The high mobility plate in the experiment used an aluminium plate having thickness of 1 mm and dimensions of 1.4 × 0.8 m. The plate was clamped with a steel frame and mounted on four rigid stands. Point mobilities were taken at four contact points (where the source was to be attached) using Kistler impact hammer Type 9722A500 and Kistler accelerometer Type 2021514. Mobilities at the motor feet were also taken. vR2〉 of the plate was measured. The result can be seen in The motor was then attached on the plate positioned close, but off-centered on the plate to generate optimum modes of vibration. The arrangement can be seen in Yp is the point mobility and 〈|Yt|2〉 is the spatially average squared transfer mobilities. Five measurement locations out of ten points for measuring the spatially average squared velocity were chosen for the measurement of input and transfer mobilities. The result of the measured damping loss factor is plotted in One more parameter to be measured before obtaining the free velocity from the reception plate method is the damping loss factor of the plate (see ). The daiN|vfi|2 of the motor can be obtained and presented in By using , the estFor the low mobility reception plate, a 2.5 cm thick steel plate was used with dimensionts of 1.24 × 0.61 m as seen in Note that in  the inpuEquation  also assThe spatially average of mean-squared velocity of the plate is shown in The measured damping loss factor in Finally, the results for the estimation of the effective source mobility are presented in Characterisation of a structure-borne source of a table fan motor using the reception plate method has been done successfully. Good agreement of the estimated free velocity and mobility of the source has been achieved from mid to high frequency. However, the use of a low mobility plate to estimate the source mobility is found to be cumbersome as it has low modal density, which is contrary to the condition required by the reception plate power. Careful measurement of the vibration velocity is therefore important to consider the modal behaviour of the plate especially at the area close the excitation point. For the future work, instead of the mean-average result, possible range of the data results of the free velocity and mobility from the measured structure-borne source in terms of its statistical variation across the frequency is also of interest to account the uncertainty coming from source and the receiver.


Previous experiments suggested the possibility of a short-term sound stimulus-evoked and transient increase in DPOAE amplitudes. This phenomenon is possibly due to the complexity of the outer hair cells and their efferent control system and the different time scales of regulatory processes. A total of 100 healthy subjects ranging from 18 to 40 years of age with normal hearing and normal DPOAE values in the range of 781–4000 Hz were recruited in the study. Diagnostic DPOAE measurements were performed after short-term sound exposure. We proposed a 10 sec, 50 dB sound impulse as the most effective stimulus for clinical practice between 40 and 60 sec poststimulus time to detect the aforementioned transient DPOAE increase. We developed a procedure for detection of this transient increase in DPOAE by the application of a short-term sound exposure. The phenomenon was consistent and well detectable. Based on our findings, a new aspect of cochlear adaptation can be established that might be introduced as a routine clinical diagnostic tool. A mathematical model was provided that summarizes various factors that determine electromotility of OHCs and serves as a possible clinical application using this phenomenon for the prediction of individual noise susceptibility. The outer hair cells play a crucial role in the mammalian cochlea. These cells are part of a complex system that is necessary to detect low intensity sounds as well as to provide a self-defense against high intensity sounds . In the 2+]i and is also linked to the metabolic modification of cytoskeletal structure i levels in OHCs that is secondary to the sustained effect of efferent neurotransmitters i concentration. This increase shifts the phosphorylation-dephosphorylation balance of cytoskeletal proteins. The protein deformation results in decreased lateral wall stiffness. This decrease is exponential in time [a is the difference of the maximal otoacoustic emission and the baseline value; b is the time constant of the effect of efferent neurotransmitters; c is the maximum decrease of otoacoustic emission due to an increase in cell stiffness in response to slow motility; d is the time constant of the mechanical cell response; t is time; t0 is the half-life of the slow motility; and e is the base of the natural logarithm.We provide the following explanation for the mechanism of these changes. Efferent neurotransmitters increase the intracellular [Ca in time . The slo in time . ConsequAccording to the fact that increase in intrinsic regulatory stiffness, lateral wall stiffness, and electromotility are all linearly related to the otoacoustic emission, their time courses are also characterized by similar functions. in vitro experiments [Borkó et al. found that cell responses to a mechanical stimulus develops and decays with similar characteristics. We assumed that the efferent neurotransmitter-induced changes in lateral wall stiffness behave similarly. The time course of DPOAE intensity changes due to appropriate sound stimulation that can be predicted by the mathematical model , which weriments . The modThe magnitude and frequency of OAE increase show individual differences and depends on the intensity of the sound stimulus  and 2. TThe time-related peak ΔDPOAE (30–60 sec) and decay (3–5 min) are determined by two regulatory mechanisms: (1) intrinsic lateral wall stiffness increase and (2) neurotransmitter-controlled stiffness of OHCs. These two processes start simultaneously, but the intrinsic mechanism works slower. The OHC lateral wall stiffness-reducing effect of neurotransmitters occurs faster (~10 sec) and lasts longer (at least 2 min) than the cell stiffness changes due to a sound stimulus (~50 sec) . in vitro and present in vivo observations require further morphologic and immunohistologic examinations in the future in order to confirm or to confute this hypothesis.A possible explanation for the existence of characteristic frequency is the tonotopic distribution of ACh and GABA receptors that corresponds to the tonotopic location of OHCs in the cochlea , 29–31. Kim, team of Kössl reported that the time interval of slow adaptation is exerted between 1.5 and 10 seconds [In summary, the adaptation process of DPOAE is composed of three well-differentiated phases: an early, a transient, and a late phase. The early phase is composed of two episodes: the previously described fast and slow adaptation . The tim seconds –16. The in vivo measurement of the electromotility of OHCs. Our results suggest that clinical examinations are supposed to perform by the application of a 10 sec-long 50 dB pure tone sound stimulus. The ideal time interval for detecting DPOAE increase is between 40 and 60 sec after the stimulus. This method is well reproducible, reliable, and cheap and provides a “window” on the cochlear amplifier. Its standardization and clinical introduction might contribute to the evaluation of individual noise susceptibility. As a potential clinical test it can exhibit the functional cooperation between the MOC system and the organ of Corti.In conclusion, analysis of DPOAE intensity-time function after a single sound stimulus makes it possible to extract the two simultaneous regulatory mechanisms. This method has sufficient sensitivity and specificity for the


This explains why most colon cancers are initiated by APC mutation. The results could have implications for preventing or retarding the onset of colon cancer in people with inherited or acquired mutation of one APC allele. Experimental validation of the hypothesis as well as investigation into the molecular mechanisms of this effect may therefore be worth undertaking.Mutations in the adenomatous polyposis coli (APC) gene are found in most colorectal cancers. They cause constitutive activation of proliferative pathways when both alleles of the gene are mutated. However studies on individuals with familial adenomatous polyposis (FAP) have shown that a single mutated APC allele can also create changes in the precancerous colon crypt, like increased number of stem cells, increased crypt fission, greater variability of DNA methylation patterns, and higher somatic mutation rates. In this paper, using a computational model of colon crypt dynamics, we evolve and investigate a hypothesis on the effect of heterozygous APC mutation that explains these different observations. Based on previous reports and the results from the computational model we propose the hypothesis that heterozygous APC mutation has the effect of increasing the chances for a stem cell to divide symmetrically, producing two stem cell daughters. We incorporate this hypothesis into the model and perform simulation experiments to investigate the consequences of the hypothesis. Simulations show that this hypothesis links together the changes in FAP crypts observed in previous studies. The simulations also show that an APC Intestinal epithelium is a rapidly renewing tissue which renews itself every 4–6 days by a coordinated series of cell proliferation, migration and differentiation events Colorectal cancer arises as the cumulative effect of multiple mutations that enable the epithelial cell to escape all the controls that keep it from uncontrolled proliferation. Since in the colon mucosa, no cell other than the stem cells can survive more than a week, stem cells are the most reasonable candidates for the accumulation of multiple mutations. The initial genetic change in most colorectal adenomas is thought to be mutations in the tumor suppressor gene APC APC is a crucial member of the Wnt/β-catenin signaling pathway, which is an important determinant of cell proliferation, differentiation and apoptosis. APC also regulates cytoskeletal proteins including F-actin and microtubules, thus allowing it to regulate adhesion, migration and mitosis Two types of division are possible for stem cells. In “asymmetric division” each stem cell generates exactly one stem cell and one semi differentiated (transit amplifying) cell at each division. The differentiated daughter cell leaves the niche to migrate up the crypt while the mother stem cell remains in the niche. In asymmetrical division, since the stem cells always replace themselves, their lineages never become extinct.Stem cells can also divide “symmetrically”, producing either two semi differentiated daughters that leave the niche or two stem cell daughters that remain in the niche. Stem cells have the ability to switch between asymmetric and symmetric modes of division. The balance between these two modes of division is defective in some disease states Analysis of the variability of methylation patterns that arise in a crypt during aging provide evidence Niche succession is a consequence of symmetric stem cell division. With symmetric division, stem cell lineages become extinct whenever both daughters differentiate and leave the niche. To maintain a constant niche stem cell number, this extinction is balanced by expansion of another lineage by symmetric division in which both daughters remain as stem cells. This random stem cell loss with replacement can eventually lead to the extinction of all lineages except one, or “niche succession”. The intra-crypt variability of methylation tags is indicative of the period of niche succession, greater variability showing slower niche succession Methylation patterns in normal appearing FAP crypts show greater diversity than non FAP crypts indicating slower niche succession cycles in FAP crypts. This slowing down can be explained as due to an increase in stem cell population. FAP crypts also exhibit a shift in the distribution of proliferative cells along the crypt axis and this also has been linked to an increase in stem cell number In this paper we start with question, “What is the effect that a heterozygous APC mutation has on the behavior of an intestinal epithelial cell that can result in the changes observed in the precancerous FAP crypts?” The methodology we follow is that through computational experiments using an Agent Based model The computer program that implements the model is developed using an ABM Framework developed in our group. The framework provides methods for defining agents and the rules that govern the actions they perform. A time loop is executed in which every agent and its environment is examined to see if the conditions for any action and consequent change of any attribute are fulfilled. The changes for all agents are effected together at the end of the time loop and the new time step starts with the changed conditions.The framework is developed on VC.net platform.The normal crypt model is adapted from the model developed by Potten and Loeffler in 1987 “State” ,“Position”  co-ordinates on the grid),“Time in State”(time spent in a particular state),“Age” (time that has passed since birth),“Number of Divisions” (number of times it has passed through mitosis),“Stemness” (which defines the stage of differentiation/determination of the cell) and“Ancestor” .The basic model has nine parameters namelyNumber of columns - NNumber of rows - M0Initial number of stem cells - Ns,Cell Cycle Time for Stem cells - TCt,Cell Cycle Time for Transit cells - TCsTime in G1 state by Stem cells - TG1tTime in G1 state by Transit cells - TG1The maximum number of divisions before terminal differentiation - Num_div_maxTime step - Δt0 stem cells are placed in the niche. All of them are initially assumed to be in G1 state but with different, randomly assigned values for the time that they have spent in that state. Therefore their division as well as the division of further generations is not synchronous. Time is incremented in steps of Δt.The bottom row of the grid is considered as the stem cell niche. Initially NIf State is ”Quiescent” and Stemness>0 state is changed to “G1”. Time in State is set to 0If state is “G1” and Time in State<TG1, Time in State is incremented by ΔtIf state is “G1” and Time in state > =  TG1 State is changed to “S+G2” and Time in State is set to 0If state is “S+G2” and Time in State< Cell cycle time –TG1, Time in State is incremented by ΔtIf state is “S+G2” and Time in state > =  Cell cycle time-TG1. State is changed to “Mitosis” and Time in State is set to 0If State is “Mitosis” Create and Insert daughter cell and set State of both to “Quiescent”It is possible for more than one cell to occupy a grid space; however daughter cells are preferably inserted into empty neighboring grid. If there is no empty neighbor, it is possible to insert it into an occupied neighbor also. The priorities for choosing the insertion position in the descending order are given belowEmpty north neighborEmpty east or west neighbor ( random choice between them if both are empty)Empty south neighborOccupied north , east or west neighbor (random choice)Stem cell daughters are inserted always only into east or west neighbor to ensure that stem cells do not leave the nicheWith each division the progenies get more differentiated and become less stem-cell-like. Therefore the “Stemness” value decreases from 1 to 0 as the stem cells divide to form semi-differentiated progenitor cells (transit amplifying cells) that divide several times before becoming terminally differentiated cells that cannot divide any more. The maximum number of divisions a progenitor cell can undergo before full differentiation is fixed by an input parameter “Num_div_max”. The decrease in stemness per division is given by 1/ Num_div_max. After terminal differentiation the cells remain in state “Quiescent”.When new cells are born at the bottom, older cells get pushed up due to mitotic pressure. The model implements this through the rule that whenever more than one cell occupies the same grid space, the oldest cells are made to move up and push the whole column of cells above it by one grid space.Stem cells never move out of the niche.Cells that reach the top row of the matrix are removed from the simulation to simulate cell shedding.variations of the observables that we get out of the simulations are representative of the trends of behavior of these observables in the crypt. Since our interest is to evaluate the changes that APC mutation would make on the crypt it is sufficient to obtain the trends of behavior rather than the absolute values. The values pertaining to cell division behavior are taken from References The input parameters used in the simulations are shown in In the basic crypt model, stem cell division is considered to be purely asymmetric, each division resulting in one stem cell that remains in the niche and one differentiated cell which is capable of leaving the niche. We include the possibility of symmetric division as follows:s)”“symmetric division probability ” decides whether the progeny will be two differentiated cells or two stem cells.A parameter s and Pd as:The probabilities that a cell division leads to 0, 1 or 2 stem cells are related to P0 must be equal to P2 and therefore the differentiation probability Pd should be 0.5. However in practice we found that setting the differentiation probability to 0.5 was not sufficient to maintain the stem cell number in our stochastic simulations. To ensure stability of the stochastic numerical computations we introduce a correction factor to the differentiation probability that corrects for deviations of the actual stem cell number Ns from the original stem cell number N0.For normal crypts the stem cell number needs to be maintained constant which is possible only if there are equal chances for both types of symmetric division. This implies that Ps/N0 ) ensures that when the number of stem cells goes above N0 the differentiation probability increases above 0.5 producing more differentiated cells than stem cells and vice versa.The correction factor  of Section 2.2) maintains the number of stem cells mostly in the 8–13 range with an average value of 10. The time taken for all the stem cells to become descendants of one of the initial stem cells is the niche succession period. Niche succession results in all the non-stem cells in the crypt also becoming descendants of the dominant stem cell lineage that succeeds in capturing the niche.There is an apparent contradiction between the results of Methylation pattern analysis shows that niche succession period increases in APC mutated (FAP) crypts However it has been reported We attempt to resolve this contradiction by hypothesizing that APC mutation not only increases symmetric division, but also biases the division in favor of producing stem cell progeny. In the normal crypt it is assumed that there are equal chances for differentiated progeny and stem cell progeny in symmetric division. If, in addition to increasing symmetric division, the APC mutation biases the symmetric division in favor of stem cell progeny, the stem cell number would increase and it is likely that the larger number of stem cells would result in increasing the niche succession period.s/N0<0.5 are restricted to zero and values greater than one corresponding to Ns/N0 >1.5 are restricted to one. With no bias (B = 1) the probability of producing two stem cells P2 and the probability of producing no stem cells P0 are in the same range. The ranges of values possible for P0 and P2 for different bias factors are shown in 2 to have values greater than P0 . For example for Ps = .2 and B = 0.6, the biased differentiation probability can vary between 0 and 0.6 and P0 can vary between 0 and 0.12 and P2 can vary between 0.08 and 0.2. P0 and P2 have an overlapping range (.08 to 0.12 ) outside of which P2 takes values higher than P0. When the biasing factor is less than 0.5 P2 remains constantly larger than P0.The maintenance of stem cell number must be having an environmental control mechanism that gives global signals as to whether stem cell number needs to be increased or decreased. APC mutation may not have an impact on this environmental control while the response of the cell to the environmental control may be affected by the mutation. The corrected differentiation probability (Equation 4) that attempts to keep the stem cell number constant can be considered as a computational representation of the environmental control. The effect of APC mutation in biasing the division in favor of stem cell progeny is then represented by reducing the corrected differentiation probability by multiplying it by a biasing factor less than 1. The corrected differentiation probability calculated by Equation 4 can take values in the range 0 to 1 depending on the number of stem cells at any point of time. Values of differentiation probability less than zero corresponding to N0 and P2 are in the same range the number of stem cells is maintained within a range 8–13 with an average value of 10  protects the cell from accumulation of mutations The observation that most sporadic colon cancers are initiated by APC mutation suggests that the first APC mutation has a better chance than any other mutation for getting fixed in the crypt by niche succession. We show below that if the effect of heterozygous APC mutation is only to increase symmetric division, an APC mutated stem cell lineage has a higher chance of getting extinct. On the other hand if the effect of the mutation is not only to increase symmetric division, but also to bias it in favor of stem cell progeny, we show below that the mutation has a high probability of getting fixed in the crypt.We performed simulations where 9 out of the 10 stem cells were considered normal (control) cells, and one stem cell was assumed to have a mutation that makes its symmetric division probability twice the control probability and a differentiation probability that is biased to different degrees in favor of producing stem cell progeny. The control symmetric division probability is assumed to be 0.1. The results are shown in Interestingly, when it was assumed that the effect of the mutation is to increase the rate of division by a factor of 2 the mutated cell lineage was lost in all the simulations because the increased number of divisions only increases the chances of its extinction. Therefore a proliferative advantage actually seems to work against the survival of the stem cell lineage. It is thus likely that if our hypothesis is true, a sporadic heterozygous APC mutation gets fixed in the crypt before the acquisition of proliferative mutations. This fits very well with the observation that most sporadic colorectal cancers are initiated by APC mutation even though there are other mutations like in KRAS or β-Catenin that could as well enhance cell proliferation.In FAP colons the onset of cancer is faster than what could be expected if the pre-existing APC mutation implies only that the cells need one mutation less in order to initiate cancer An interesting computational study by Pepper etal biased symmetric division, is able to explain the increase of somatic mutation rates in FAP crypts.We see that increased symmetric division by itself does not has a significant effect on the time taken for the second mutation. When the symmetric division is biased in favor of stem cell progeny the time for appearance of the second mutation is reduced. Thus the hypothesis that heterozygous APC mutation results in In summary, the hypothesis that heterozygous APC mutation increases symmetric division of stem cells as well as biases the division in favor of stem cell progeny, results in the following effects:FAP crypts have increased stem cell numbers and increased niche succession period.Sporadic APC mutation has a high probability of getting fixed in the crypt by niche succession. On the other hand a mutation that increases proliferation rate increases the chance of extinction of the stem cell lineage.Somatic mutation rates are increased in cells which have APC mutation.Thus through getting dominance in the crypt, through increase of stem cell number and consequent crypt fission, and increased chances of replication errors, heterozygous APC mutation sets the stage for colorectal cancer. If the molecular mechanism by which the mutant APC effects the increase of biased symmetric division can be experimentally deciphered it can lead to drugs that could prevent the progression to cancer in people who have inherited or acquired a mutation in one of their APC alleles.


ZnO nanowire nucleation mechanism and initial stages of nanowire growth using the carbothermal reduction technique are studied confirming the involvement of the catalyst at the tip in the growth process. Role of the Au catalyst is further confirmed when the tapering observed in the nanowires can be explained by the change in the shape of the catalyst causing a variation of the contact area at the liquid–solid interface of the nanowires. The rate of decrease in nanowire diameter with length on the average is found to be 0.36 nm/s and this rate is larger near the base. Variation in the ZnO nanowire diameter with length is further explained on the basis of the rate at which Zn atoms are supplied as well as the droplet stability at the high flow rates and temperature. Further, saw-tooth faceting is noticed in tapered nanowires, and the formation is analyzed crystallographically. Interest in nanowires continues to grow fueled by applications in electronics, optoelectronics, sensors, piezoelectric and thermoelectric devices, and energy storage . In spitThe source consists of zinc oxide (ZnO) metal basis of 99.999% purity mixed with graphite in a weight ratio of 1:1 to carry out a carbothermal reduction process. A 1" diameter quartz tube was inserted inside an isothermal furnace, and the source mixture was kept in a quartz boat inside this tubular reactor. Gold colloids were used as the catalyst for different experiments. The substrate with the Au catalyst was placed downstream from the quartz boat located at the center of the heating zone. One end of the quartz tube was connected to a mass flow controller, which controls the flow rate of the carrier gas, argon, and the other end was connected to the exhaust. Nanowires were grown within a temperature window of 900–980°C, whereas the carrier gas flow rate was varied between 100–160 sccm.Fifty nanometres Au colloids  were used as the starting catalyst. The c-sapphire substrate was treated with poly-L-Lysine before dropcasting the Au colloidal solution. The substrate was then spun at 2000 rpm for 1.5–2 min ensuring a random dispersion of the gold particles. The flow rate of Ar carrying the Zn vapor was maintained at 100 sccm and turned on only for the duration of growth after the temperature was allowed to stabilize at 900°C. At the synthesis temperature, carbothermal reduction of the ZnO powder yields Zn vapor according to the following reactions:t = 90 ± 10 s. In the initial stages of temperature ramping, the substrate becomes covered with Au islands, which become the preferential sites for Zn incorporation. The Zn atoms can either condense from the vapor phase or be transferred from adjacent regions of the substrate. Then, they rapidly diffuse into the Au clusters forming the Au–Zn clusters. The Zn concentration in these particles increases with time, until a solid crystal nucleates out of the alloy droplet due to supersaturation in the droplet. SEM-EDX was performed in order to investigate the islands seen in Figure t = 90 ± 10 s. The EDS measurement was performed on points A and B of the island in Figure Figure t = 90 ± 10 and 120 ± 10 s, respectively. Thermodynamically, Gibbs free energy minimization is the criterion to be satisfied for the formation of the nucleus. After the nucleus is formed, ZnO nanowires start to form, as shown in Figure t = 18 ± 1 min and 20 ± 0.5 min, respectively, with the catalyst at the tip which acts as the sink for the Zn atoms and generates a concentration gradient along the catalyst particle. However, the Zn–Au alloy droplet on which the nuclei forms remains on the substrate. The nanowire formation can be described by the following reactionFormation of a crystal nucleus from the liquid Zn–Au metal droplet  for needle-like nanowires here is estimated as 0.36 nm/s and plotted in Figure α with length is large close to the base of the nanowire and decreases gradually. Thus, one reason for the decrease in nanowire diameter with length, i.e. tapering, is the reduction in the size of the catalyst at the tip as growth progresses.which means that the droplet approaches a larger solid angle of spherical section. Here, β of the liquid droplet at the nanowire tip found surprisingly that tapered nanowire growth (∂ > 0) is more likely for a wide range of contact angles β compared to nanowires with uniform diameters.Nanowires of two different morphologies are recalled here: in one case, we have the tapering just restricted to the base, as seen in Figure c-axis, whereas the tapered wire along the The tapering of the nanowires can also be explained on the basis of the stability and shape of the Au catalyst at the tip of the nanowires. Nanowires with uniform diameters, seen in Figures H is about 4 nm. Incidentally, such faceting is observed only in tapered nanowires and not in straight ones as seen in Figure Oversupply of source vapor as well as interplay of surface energies of the wire and liquid droplet was also reported to cause the droplet to be unstable, leading to oscillations in resulting Si NW structures . This isFigure The tapered wire in Figure 2- and Zn2+ planes parallel to the surface. If the resulting dipole moment perpendicular to the surface is nonzero, stabilization of such a surface is accomplished by a rearrangement of surface charges or by introducing compensating charges into the outermost surface planes [β (Figure One mechanism that could lead to such faceting is surface reconstruction due to charge stabilization in polar compounds. ZnO crystal is formed by alternating stacks of oppositely charged Oe planes . This coe planes  combinede planes  suggest e planes .However,e planes . The allβ Figure  decreaseβ of the catalyst droplet at the nanowire tip causing a change in the contact area R at liquid–solid interface. The growth rate of the needle-like nanowires is found to be 3.9 nm/s and the tapering rate is established to be 0.36 nm/s on the average. Finally, the rate of addition of Zn atoms is found to control the tapering where the tapering limited to the nanowire base gives way to a continuous taper along the nanowire length at higher deposition rates. The tapered wires are also found to have unstable droplets at their tips, which are believed to be a cause of tapering.In this investigation, using the carbothermal reduction technique, ZnO nanowires are found to grow from nuclei on the molten Au–Zn clusters. A tapering of diameter along the axis is observed with the largest diameter at the base. This may be due to the change in the contact angle


Near-infrared spectroscopy (NIRS) is susceptible to signal artifacts caused by relative motion between NIRS optical fibers and the scalp. These artifacts can be very damaging to the utility of functional NIRS, particularly in challenging subject groups where motion can be unavoidable. A number of approaches to the removal of motion artifacts from NIRS data have been suggested. In this paper we systematically compare the utility of a variety of published NIRS motion correction techniques using a simulated functional activation signal added to 20 real NIRS datasets which contain motion artifacts. Principle component analysis, spline interpolation, wavelet analysis, and Kalman filtering approaches are compared to one another and to standard approaches using the accuracy of the recovered, simulated hemodynamic response function (HRF). Each of the four motion correction techniques we tested yields a significant reduction in the mean-squared error (MSE) and significant increase in the contrast-to-noise ratio (CNR) of the recovered HRF when compared to no correction and compared to a process of rejecting motion-contaminated trials. Spline interpolation produces the largest average reduction in MSE (55%) while wavelet analysis produces the highest average increase in CNR (39%). On the basis of this analysis, we recommend the routine application of motion correction techniques  to minimize the impact of motion artifacts on functional NIRS data. Near-infrared spectroscopy (NIRS) is a burgeoning neuro-investigatory technique that uses measures of the intensity of diffusely scattered near-infrared light to calculate changes in oxyhemoglobin concentration (HbO) and deoxy-hemoglobin concentration (HbR) in cortical tissues  and those that do not.The first category encompasses a variety of approaches which require an input signal that is highly correlated with the NIRS motion artifacts but not with the NIRS functional response. Such an input signal can be obtained via an external measure of motion  and the number of components that are removed (r). Note that the number of NIRS measurements is twice the number of channels as we define them: each channel consists of measurements at two different wavelengths, in our case therefore, N = 16. The optimum value of the parameter r will clearly depend on the total number of components (N) and on how many of those components constitute artifact, which will change from dataset to dataset.where Ar is to normalize the diagonal elements of the matrix Ω by their sum to produce the vector nth element of nth component. By fixing the proportion of data variance that is to be removed (referred to from herein as σ_PCA), the number of components to remove (r) can be defined by finding the lowest value of r for which:A simple way to approach the selection of hmrMotionArtifact from HOMER2) each of those periods is modeled one by one, throughout each NIRS time-course using the MATLAB™ cubic spline interpolation function csaps. Each period of modeled data is then subtracted from that period of the original data. In order to produce a continuous signal all the data points after the start of the corrected motion segment after shifted by a constant value. This value is defined as the difference between the mean of the signal at the start of the corrected motion period and the mean of the signal prior to the corrected motion period. The durations over which these means are calculated must be variable, as the length of motion artifacts and the length of the data prior to each motion artifact is also variable. These durations were defined using the framework set out in Scholkmann et al.  and suggest that a value corresponding to p_Spline = 0.99 is reliably effective in the removal of motion artifacts.The spline interpolation depends on the interpolation parameter n et al.  define ty(t), is transformed into the wavelet domain using the general discrete wavelet transformation:We employed the discrete wavelet analysis and filtering approach described by Molavi and Dumont . While ajk(t) and ψjk(t) are the scaling and wavelet functions and jkω are the approximation and detail coefficients respectively. Indices j and k are the wavelet dilation and translation parameters with j0 the coarsest decomposition. After decomposition, the model assumes that the NIRS signal consists of meaningful physiological signals f(t) plus artifact terms e(t) such that y(t) = f(t) + e(t) and assumes the wavelet coefficients (ωjk) exhibit a Gaussian probability distribution. Because the physiological hemodynamic signal is generally smooth compared to motion artifact, the distribution of the wavelet coefficients that represent the physiological components of the NIRS signal will be centered around zero and have a low variance, whereas those corresponding to motion artifact will appear as outliers in the probability distribution. In order to remove these motion artifact coefficients before performing the inverse wavelet transformation to reconstruct the NIRS time-course, we apply a probability threshold to remove outlying wavelet coefficients. For a given wavelet coefficient ωjk, if the probability of observing values greater than ωjk is less than a threshold value α_Wav, then we assume that the coefficient corresponds to motion artifact and it is set to zero. The probability threshold α_Wav is a tunable parameter and a correct choice of its value is essential to the performance of wavelet analysis in the removal of motion artifacts from NIRS data. This analysis employed the Wavelab 850 toolbox for MATLAB™Here, ϕx at time = k, based on the state at time = k−1 such that:The approach described by Izzetoglu et al.  was the A is the transition model (which uses knowledge of the prior state to predict the current state) and γk is the system noise. This prediction is then compared to the actual measured state at time = k, kz, which is modeled as a function of the true state x:where H is the observation model that maps the true state-space into the measurement space and δk is the measurement noise. The second step is to use the prediction kx, the measurement kz, and their error covariances to produce an updated estimate of the true state, which is determined by the Kalman gain. The resulting optimal estimator is then fed back in to the prediction step as the prior state and the process is repeated to find the optimal estimator of the (k+1)th state. For more details see Grewal and Andrews . A timing vector, which provides 25 trial onset positions spaced randomly throughout the 10 min dataset but with a minimum separation of 20 s was then constructed. This vector mimics the experimental design of a typical functional NIRS experiment, with each onset position corresponding to the beginning of a functional task. A simulated HRF was then designed that consisted of a gamma function with a time-to-peak of 7 s, a duration of 20 s and an amplitude defined so as to produce a 15 μM increase in HbO concentration and a 5 μM decrease in HbR concentration [these figures include a partial volume correction factor of 50  was applied such that if a stimulus trial coincided with a defined period of motion, then that stimulus was rejected. The remaining stimuli periods were then block-averaged in order to recover the mean HRF.Once the simulated functional dataset had been completed, it was then passed through six different processing streams. The first was the recovery of the HRF without motion correction or the rejection of trials. The data was band-pass filtered (a third order Butterworth filter between 0.01 and 0.5 Hz) to remove low-frequency drift and cardiac oscillations before being converted into HbO and HbR using the modified Beer–Lambert law  between the recovered and true HRF and finally the CNR of the recovered HRF. The CNR was calculated by taking the mean of the 2 s of recovered HRF data centered at the true HRF peak time (7 s after onset) and dividing by the standard deviation of the 5 s of data prior to onset. These three metrics allow a direct comparison of the accuracy of the HRFs recovered via standard NIRS processing approaches and via each motion correction method. All metrics are calculated on the basis of the recovered HbO signal only for computational simplicity.The result of the simulation process described above was 300 HRFs (20 datasets × 3 channels × 5 repetitions) for each of the six processing streams . Three metrics were then calculated for each processing stream. These consisted of the MSE between each recovered HRF and the true (simulated) HRF, the Pearson’s correlation coefficient (_PCA), the interpolation parameter (p_Spline) and the probability threshold (α_Wav) respectively and are described above. In order to optimize the performance of each of these methods, it was first necessary to perform a sensitivity analysis for each of these three techniques. The simulation described above was repeated, in full, for a variety of values for each input parameter. Guided by the values of these parameters applied in previous publications, σ_PCA was varied from 50 to 99.9%, p_Spline was varied from 0 to 1, and α_Wav was varied from 0.01 to 0.8.Several of the motion correction techniques applied here require the selection of an input parameter that can significantly affect the performance of the technique. For PCA, spline, and wavelet approaches, these parameters are the percentage variance to remove (σy-axis) vs. no correction (x-axis). In 62% of cases, trial rejection actually increases the MSE. However in this simulation the difference between the MSE for the trial rejection and no correction approaches is not significant in a two-tailed paired t-test (p = 0.18).As described above, the two standard approaches to motion artifacts in functional NIRS data are to perform no correction, or to simply reject those trials which coincide with motion and not include them in the calculation of the mean HRF. Which of these two approaches produces the best recovered HRF will clearly depend on the nature and extent of the motion artifacts in each dataset and the number of stimulus trials. In our simulation the number of trials rejected (out of a possible 25) varied from 7 to 23 and averaged 13.9 across the 20 NIRS datasets and 5 repetitions. Figure _PCA, p_Spline, and α_Wav allowed us to determine the values that minimized MSE and maximized R2 and CNR. In all three cases, a single value of each parameter produced the best result for all three metrics. These were σ_PCA = 97%, p_Spline = 0.99, and α_Wav = 0.1. The optimized parameter value for wavelet analysis, α_Wav = 0.1, is close to the figure of 0.15 calculated by Molavi and Dumont . Note that the decrease is also significant for all four techniques when compared to the trial rejection approach. All four techniques produce an increase in MSE in a subset of cases . All four techniques also show a trend which indicates that motion correction is much more likely to have a detrimental effect if the initial (no correction) HRF has a low MSE, i.e., if the HRF is already very accurate. This is particularly clear for wavelet analysis, where an increase in MSE is common if the uncorrected value was below 10 μM2, while a decrease in MSE is assured if wavelet analysis is applied when the uncorrected MSE is greater than 20 μM2.Figure p < 0.01, one-tailed t-test). This is also the case when compared to the trial rejection approach. The distributions shown in Figures Figure R2 and CNR respectively.Figure R2, but while the increase produced by PCA, spline, and wavelet approaches are highly significant (p < 0.01) the change due to Kalman filtering is not significant (p > 0.05). All four methods also produced a significant increase in CNR, with wavelet filtering yielding the highest median CNR at 10.9 compared to 6.9 for no correction. The pair-wise percentage change in CNR (not shown) was also greatest for wavelet analysis, which produced a median increase of 39%.In general, PCA, spline, and wavelet techniques all perform well, Kalman filtering less so. PCA, spline, and wavelet approaches produce a median decrease in MSE of 38, 55, and 50% respectively, compared to no correction. Kalman filtering produces a decrease of only 21%. All four methods produce an increase in Although many approaches to the correction or minimization of motion artifacts in NIRS data have been put forward , reduces MSE in 80% of cases Figure  and prod2 Figure  while wa2 Figure . AlthougThe results of Figures The fact that wavelet analysis exhibits a clear relationship between the uncorrected MSE and the improvement it can provide may give it an advantage over spline interpolation, where such a pattern is less clear. It may be possible to define a threshold (based on the proportion of data that is affected by motion artifact or the uncorrected CNR) that will determine whether the application of wavelet analysis is suitable and therefore avoid cases where wavelet analysis will be detrimental._PCA to only those periods may produce better results that applying PCA to the entire dataset, particularly in cases where motion is not particularly prevalent and therefore accounts for a lesser proportion of the variance of the entire dataset. Another obvious advance would be to employ trial rejection in conjunction with a given motion correction technique. It would be trivial to apply hmrMotionArtifact to identify motion artifacts still present in the corrected NIRS data and remove any stimulus trials that remain contaminated. One can also conceive of a recursive technique whereby motion correction is performed repeatedly until no motion artifacts are detected.Although we have attempted to apply these pre-published motion correction techniques in the manner described by their respective authors, there are a number of ways in which these techniques could potentially be improved without the need for additional external inputs or for alteration of an experimental paradigm. One obvious example is to target the PCA and Kalman approaches so as to only examine periods of data that are pre-determined as motion. Wavelet analysis takes advantage of the abnormal spatial and temporal characteristics of motion artifacts in the wavelet domain to identify and remove them. Spline interpolation requires knowledge of the location of motion artifacts throughout the dataset, and interpolation is only performed for those periods. However, PCA and Kalman filtering are applied to the entire NIRS time-course, including periods where we do not believe there is motion artifact. These algorithms could easy be altered so as to only be applied during periods of identified motion artifact. The variance of the NIRS signal that is due to motion artifact during periods identified as motion artifact will obviously be very large. Applying PCA with a high value of σAs described in the introduction, we set out to test only those motion correction techniques that can be applied after NIRS data acquisition, without altering the experimental design and without the need for additional external inputs. While we believe this is the most relevant approach to motion correction for the majority of NIRS applications at present, this may in fact change.The use of short separation NIRS channels (which we would define as channels with a source-detector separation of less than 10 mm in adults) has been shown to be extremely beneficial to functional NIRS studies because they provide an explicit measure of NIRS signal components originating from superficial  tissues (Saager and Berger, R2, and CNR. The spline technique proposed by Scholkmann et al. (R2, while wavelet analysis described by Molavi and Dumont (Overall, the analysis of the impact of post-processing motion correction techniques on functional NIRS data described here allows us to conclude that motion correction techniques can and should be used to improve the accuracy of the recovered HRF in functional NIRS studies that are affected by motion artifacts, especially in cases where motion artifacts are prevalent. Our results show that, on average across 20 datasets and multiple repetitions, PCA, spline interpolation, and wavelet techniques all produced significant improvements in MSE, n et al.  producedd Dumont  producedThe authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


A coarse-grained model is used to study the mechanical response of 35 virus capsids of symmetries T = 1, T = 2, T = 3, pseudo T = 3, T = 4, and T = 7. The model is based on the native structure of the proteins that constitute the capsids and is described in terms of the C Simple globular viruses protect their strands of RNA or DNA with remarkable self-assembled proteinic shells known as capsids. The chemical and thermal stability of capsids has been studied for decades, but their mechanical properties are only beginning to be determined using nanoindentation The capsids of simple globular viruses are typically of icosahedral symmetry and they are assembled from one or several kinds of proteins. The proteins cluster into Capsids are thought to be sturdy mechanically The nanoindentation technique typically involves anchoring a capsid on a substrate and then pushing on it with the tip of an atomic force microscope Here, we extend our previous theoretical studies The model we use has been developed and tested in the context of single protein manipulation Another striking prediction of the coarse-grained model is a large difference in the mechanical properties of CCMV and CPMV even though they have similar In the following section we describe the model used for the simulations. We then present results for CCMV to illustrate the role of temperature and a finite radius, We start by presenting the pertinent aspects of the model. The molecular dynamics The interaction for the native contact between atoms Simulations are performed at a constant temperature using a Langevin thermostat To model nanoindentation the capsid is placed between two repulsive plates. The interaction with flat plates is described by a repulsive potential that scales as In the initial state, the plates are far enough apart that they do not interact with the capsid. The plates are then brought together by increasing the speed of both plates symmetrically to a value We now illustrate the type and magnitude of changes produced by temperature and In the top left panel there are three trajectories The onset of irreversibility in our simulations of CCMV at Several aspects of the results show that the bond rupture at For all nonzero temperatures shown, we find a sharp drop in We now consider the influence of tip curvature on capsid response. The lower left panel of As mentioned in the Introduction, nanoindentation measurements have also been made for MVM, NV, HBV, and HK97. The traces for MVM and NV are relatively simple. At A series of peaks is superimposed on a steadily increasing force in the case of HBV. This complicates the determination of Finally, in the case of HK97, there is a weakly articulated force peak followed by a plateau. The plateau ends with a drop for Experimental values of We now present the For some capsids, dotted lines show results for a tip with radius of curvature  is HK97  where  dIn most cases, the The structure in We now ask: what do the values of Another important factor might be the structural classification. The pseudo T = 3 capsids tend to be strongest. The weakest are T = 2, T = 7 and some of the T = 3 capsids. T = 4 capsids span the full range of strength, while T = 1 and T = 3 span intermediate values. These observations indicate that there is some correlation to structure, but not a strong one.In our previous study of CCMV and CPMV we noted that while most of their geometrical properties were very similar they had very different average coordination numbers To explore the effect of coordination number, the results for To try to separate the effect of capsid dimensions from the local modulus describing the mechanical properties within the shell, we follow a dimensional analysis motivated by the elastic shell models of Gibbons and Klug that characterizes the local response in the shell  and 2.Studies of randomly linked systems have also found a power law relation between modulus and the excess coordination. Square and Kagome lattices are marginally stable when only nearest-neighbors interact. Their shear modulus grows as the square of the number of next-nearest-neighbor bonds It should be noted that the coordination number for a given capsid is sensitive to the details of the determination of the contact map. Changing the details would alter the number of native contacts and thus A coarse-grained molecular model was used to study the mechanical response of 35 virus capsids. The full force-separation curves have a variety of shapes, but in general share two common features. In particular, there is a linear elastic response characterized by a spring constant The elastic response and onset of irreversibility have also been considered by Arkhipov et al. For the capsids studied in this paper, the values of Experimental values of The variability in elastic properties of virus capsids has also been observed by Tama and Brooks The studies presented here have focused on the experimentally accessible macroscopic response of capsids. Future studies should assess the variability in local response within capsids. Variations in local deformation may be correlated with changes in local coordination number and/or with the boundaries of proteins as in our earlier simulations and recent experiments on MVM


Electrohydrodynamic patterning of arbitrary patterns is achieved by optimizing the critical parameters (applied voltage and spacer height). The applied voltage has a great influence on the fidelity of L-shaped line structures with different sizes. The L-shaped line structures with high fidelity are obtained by using the moderate applied voltage. The spacer height has a great influence on the fidelity of square structures with different sizes. The square structures with high fidelity are obtained by using the low height spacer. The multi-field coupling transient finite element simulation demonstrates that the lack of polymer owing to the high height spacer leads to the formation of defects. Polymer patterning has a wide range of applications in optoelectronics, biotechnology, novel sensors, actuators, and so on –3. Electλ derived by the linear stability theory. λ is qualitatively determined by the surface tension of polymer, the polymer viscosity, and the electrostatic pressure [The shape of structures formed in EHD patterning depends on the topography of template. The flat template produces the self-assembled pillars with hexagonal arrangement , 12, 13.pressure , 11. Thepressure , 15. Schpressure , 16. Zhupressure .The structures produced by the topographic template attract more attention from researcher , 18–20. μm line width [There is still lack of the research about EHD technique using template with arbitrary structures. Only a few researchers have paid attention to this field. Chou et al. created the structures with the pattern of the word “PRINCETON” with 3 ne width . Harkemane width . He repoIn this paper, we presented the fabrication of the structures with different patterns and sizes on one sample and studied the influence of the critical parameters (the applied voltage and the spacer height) on the replication fidelity. The template patterns used in this paper can be divided into two categories: the patterns with aspect ratio of much larger than one such as the line patterns and the patterns with aspect ratio close to one such as square patterns. The two categories of patterns can basically cover most of the patterns in micro-/nanomanufacturing.We show that the applied voltage has a great influence on the fidelity of structures of L-shaped line patterns with different size, and the spacer height has a great influence on the fidelity of structures of square patterns with different size. The multifield coupling simulation for the EHD patterning process is carried out.∙s. Its relative permittivity was 4.5 measured by a dielectric constant meter . The solvent Ormothin  was added to dilute Ormostamp. We mixed Ormostamp and Ormothin at mass ratio of 0.1 using a magnetic stirrer for 24 hours. The dynamic viscosity of mix with a mass ratio of 0.1 was 0.007 Pa∙s measured by a viscometer  with an adapter for low viscosity materials . The mix was spin-coated on a transparent substrate at 3000 rpm for 30 s. The film thickness was 400 nm measured by an ellipsometer . The air gap between the polymer film and the template patterns was controlled by an insulated spacer made of silicon dioxide. A press with 20 MPa was used to hold the gap distance unchanged. The voltage applied between template and substrate ranged from 20 V to 100 V. The spacer height of template ranged from 3 μm to 4 μm. The forming process of EHD patterning maintained 20 minutes. The structures were cured via UV light through the transparent substrate for 60 seconds.μm, 3 μm, 4 μm, and 5 μm. (b) The array of square patterns: a single group of square patterns has eight square patterns. Their side lengths are 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, and 40 μm.There are two types of template patterns used in this paper. (a) The array of L-shaped line patterns: a single pattern has four L-shaped line lines. Their line widths are 2 μm line width formed in E is a scalar variable denoting the electric intensity, ε0 is the permittivity of vacuum, εr is the relative permittivity of the polymer, and Theoretical of the EHD patterning is established to obtain the better understanding of the effects of the applied voltage on the replication fidelity. The driving force in EHD patterning deduces from the Maxwell stress tensor which represents the electric stress in the polymer film imposed by the electric field. The Maxwell tensor is expressed as follows :(1)T⃡=εx-y plane and the evolution process of EHD patterning are influenced by z component of the electric field which is in normal direction of polymer film. The driving force in EHD patterning can be transformed to the electrostatic pressure determined by z component of the electric field:Ez is a scalar variable denoting z component of the electric field on the surface of the polymer film and εp is the permittivity of polymer film.We assume that the polymer film located in ρ is the mass density of polymer, v is the velocity of polymer, p0 is atmosphere pressure, ps is the pressure generated by surface tension, μ is the viscosity coefficient of polymer, and f is the volume driving force. f could be neglected because their value is too small. p0 and ps remain unchanged in the polymer film. Therefore, pe determines the evolution process of EHD patterning. Additionally, the flow velocity of the polymer in x-y plane can be obtained by simplifying  to analyze the electric field distribution on the surface of polymer film in the initial phase of EHD patterning. The applied voltage in simulation is set to 50 V. p to the difference between the electrostatic pressure under the line patterns with different line widths and the electrostatic pressure under the template cavity in right side of these patterns:Ep is a scalar variable denoting z component of the electric field on the surface of the polymer film under the line patterns and El is a scalar variable denoting z component of the electric field on the surface of the polymer film under the template cavity in right side of these patterns.The electric field in A direction is strongly modulated by the lines. We set Δp of the template patterns with different line width increases under higher voltage. The experimental result in p mainly determines the replication fidelity in cross section of the template patterns. The homogeneous electric field in B direction induced the separated periodic structures according to the linear stability analysis theory. The stronger electric field is more conductive to the formation of the separated structures. λ the period of the separated structures with different applied voltage. The period of the separated structures gets larger with the reduction of applied voltage. The separated structures with large size tend to coalesce into an integral structure. The formation of separated structures with small size is generated by larger applied voltage. The template patterns with broader line width generate the accumulation of the polymer film in A direction more easily. Δμm and 35 μm side lengths in μm side lengths become larger in ϕ. ϕ is a basic phase function of position vector describing the types of substance. The range of ϕ is from 0 to 1 in phase field. 0 represents the polymer, and 1 represents the air in our model. 0.5 represents the interface between the two substances. We analyze the experiment with the lowest spacer (3.0 μm) and the experiment with the highest spacer (4.0 μm).We carry out the multifield coupling simulation for the EHD patterning process of the array of square patterns with different size. The geometric model of the simulation is set to be a two-dimensional cross-section model through the center of the square patterns. The simulation uses a uniform phase field model including three control equations: Gauss equation for electrical field, Navier-Stokes equation for flow field, and Cahn-Hilliard equation for phase field. The phase field model uses a boundary layer to replace the liquid-gas interface. There is no strict distinction between the polymer and air which are treated as a total fluid in the simulation process. The change of the gas-liquid interface is obtained by tracking the phase function μm spacer. The blue region is the polymer; the red region is the air. The white protrusion is the cross section of template. We enlarge the shape of interface at the template patterns with 40 μm and the template patterns with 5 μm to contrast the size effect on EHD patterning. The polymer always flows upward to the template patterns and forms the structures with high fidelity. μm spacer. In condition that the spacer height is increased, the polymer under the template patterns with small size could still merge to form the structures with high fidelity. However, the higher spacer generates a greater impact on the polymer under the template patterns with large size. The replication for the template patterns with large size needs more polymer than that for the template patterns with small size. The lack of polymer results in the fact that the separated pillars could not merge to the structures with high fidelity.p. We could obtain the structures of line patterns with high fidelity by using the moderate applied voltage. The optimization of spacer height can improve the replication fidelity of the structures with square patterns having different size. The high fidelity structures could be obtained under the low height spacer. The work in this paper has important implications for the capability and versatility of EHD patterning of ultraviolet cured polymer film.We demonstrate that the optimization of applied voltage can improve the replication fidelity of the structures with line patterns having different size. The constant voltage is applied on the patterned template to generate the spatially modulated electric field, and the flow behavior of the polymer film in experiment is significantly influenced by Δ


The NCBI Taxonomy underpins many bioinformatics and phyloinformatics databases, but by itself provides limited information on the taxa it contains. One readily available source of information on many taxa is Wikipedia. This paper describes iPhylo Linkout, a Semantic wiki that maps taxa in NCBI's taxonomy database onto corresponding pages in Wikipedia. Storing the mapping in a wiki makes it easy to edit, correct, or otherwise annotate the links between NCBI and Wikipedia. The mapping currently comprises some 53,000 taxa, and is available at http://iphylo.org/linkout. The links between NCBI and Wikipedia are also made available to NCBI users through the NCBI LinkOut service. One of the great challenges of phyloinformatics is linking together information on phylogenies, taxa, genomes, specimens, and publications Stein The NCBI taxonomy database provides the taxonomy underlying GenBank RNA Biology now requires authors of articles on RNA families to create a corresponding article in Wikipedia In the ten years since its launch Given the centrality of the NCBI taxonomy database within bioinformatics There are several ways we could link two databases together. One is to create reciprocal links in both databases, that is, the NCBI page for a taxon would contain a link to the Wikipedia page, and visa versa. Although having the original databases manage the links has obvious advantages, there may be reasons for devolving this task to a third party. Maintaining and updating links requires work, and those managing the database may not have sufficient resources to provide this service. They may also feel that the links are beyond the intended scope of the database.Having the links stored in a third party database (the "knuckle") enables the links to be edited and annotated. If the rationale for a particular link requires explanation , or if either of the source databases contain errors , these can be flagged in the knuckle database. This enables annotations on databases in cases where those managing the data may be reluctant to let users modify the primary data A further reason for an intermediate service is to provide programmatic access to the mapping. NCBI provides utilities to retrieve LinkOut resources http://en.wikipedia.org/wiki/Template:Taxobox). The Taxobox template records basic facts about the taxon, such as its name, taxonomic classification, and optional details of synonymy, authorship, geographic range, and an image of one or more members of the taxon. Below is an example from the page for the Giant freshwater stingray http://en.wikipedia.org/wiki/Giant_freshwater_stingray:The mapping between NCBI was initially based upon the 18 June 2009 SQL dump of Wikipedia and a dump of the NCBI taxonomy database obtained on 29 September 2009. The NCBI taxonomy database is provided as a series of delimited text files, which can be readily loaded into a MySQL database. Taxon pages were extracted from Wikipedia by loading the Wikipedia SQL dump into a MySQL database and searching for pages that included the Taxobox template  and Rondeletia (a genus of fish and a genus of plant). To minimise these errors the GenBank "division_id" in NCBI and the "regnum" value in the Wikipedia Taxobox was used to distinguish between plants and animal names.The initial mapping was constructed by extracting the scientific name of the taxon that was the topic of each Wikipedia page, then finding a match for this in the NCBI taxonomy database. If NCBI and Wikipedia use the same name for the same taxon then in most cases the mapping is straightforward, we simply link the two records. However, because plant and animal names are governed by separate codes of nomenclature the same name may be used for a plant and an animal, such as Rana includes several subgenera, including Rana (Rana). NCBI uses just the subgenus name for the subgeneric nodes, hence tax_ids 8399 and 121175 both bear the name "Rana".Duplication of names can also result from the way NCBI assigns names to nodes in its taxonomical hierarchy. For example, the genus Both the NCBI taxonomy and Wikipedia have support for synonyms, that is, different names for the same taxon. In the NCBI database there may be multiple names that have the same tax_id, but only one will be regarded as the accepted scientific name. In Wikipedia a synonym may have its own page in the form of a "redirect" page which automatically sends the user to the page with the name that Wikipedia regards as the accepted name.Chalinolobus poensis in the NCBI taxonomy, but there is no corresponding page in Wikipedia that has Chalinolobus poensis as the accepted name. However, there is a Wikipedia page for Chalinolobus poensis, which is a redirect to the page for the Abo bat (for which Wikipedia gives the accepted name as Glauconycteris poensis). This is an example of a type ➁ mapping in Fig. 1, where the link from NCBI to Wikipedia is made via a Wikipedia redirect page. In the case of the Abo bat, NCBI lists Glauconycteris poensis as a synonym, so we could also discover this link via a type ➂ mapping (NCBI synonym to Wikipedia page). The last type of mapping, ➃, is where NCBI and Wikipedia disagree on the accepted name for a taxon, but a synonym in NCBI corresponds to a redirect page in Wikipedia.If both NCBI and Wikipedia agree on the name of a taxon then the mapping is straightforward and is indicated by ➀ in Fig. 1. In other cases we may have to use synonyms to link the two databases. For example, at the time of writing the Abo bat has the accepted name Orycteropus afer) to illustrate this, where the Wikipedia pages for Tubulidentata, Orycteropodidae, Orycteropus, and Orycteropus afer were one and the same page, because there is only a single extant species of Orycteropusafer, and it is the sole extant member of the family Orycteropodidae, and the order Tubulidentata. It is only when we add fossil aardvarks that we can create unique content for these other taxonomic ranks (and such pages have since been added to Wikipedia). However, there are still cases where more than one NCBI taxon will map to the same Wikipedia page . In iPhylo Linkout only the lowest taxonomic rank is mapped .Gregg http://iphylo.org/linkout. This makes it easy to edit, add to, or annotate the mapping. The wiki software used is the Semantic Mediawiki extension The mapping between NCBI and Wikipedia is stored in a wiki at Morus is a genus of plant and a genus of bird) the wiki page is a disambiguation page which lists the different "Ncbi:tax_id" pages with the same name.The iPhylo Linkout wiki was populated using the Mediawiki API. Batch scripts read the NCBI taxonomy data dump, and called the Mediawiki API to create a wiki page for each NCBI tax_id, the page name being the prefix "Ncbi:" followed by the tax_id. This naming convention makes it easy to refer to any NCBI taxon by simply appending the tax_id to http://iphylo.org/link out/Ncbi:. To enable easy retrieval of pages by taxon name, pages were also created for each taxon name in the NCBI taxonomy. These pages automatically redirect the user to the corresponding "Ncbi:tax_id" page. In cases where the same name may refer to more than one taxon  is shown below :The code for a wiki page from the mapping , and the name of the image file (if any). The Wikipedia page id is stored as the name of a Wikipedia page may change over time, whereas the page id is stable  .http://iphylo.org/linkout/Citation:4306. These citation pages were then included in the wiki page for the corresponding tax_id(s) using Mediawiki's transclusion mechanism (see http://iphylo.org/linkout/Ncbi:77658 for an example). This has the advantage that any edits made to the citation page  are automatically reflected in all the taxon pages that include that citation.In addition to information about taxa, the NCBI taxonomy database dump contains bibliographic information in a file called citations.dmp. Each record in this file has a unique identifier (the "cit_id") and is linked to one or more tax_ids. Many, but not all, of these bibliographic records include PubMed identifiers (PMID). Records that lacked PMIDs were parsed and the bioGUID OpenURL service Semantic Mediawiki supports exporting individual pages in RDF . There are numerous vocabularies that could be used to express information in RDF, iPhylo Linkout uses the most general vocabulary wherever possible. Following Uniprot An advantage of providing RDF is that users wanting to retrieve details about the mapping between a NCBI taxon and Wikipedia can do so using standard tools for XML parsing, rather than attempt to parse the Mediawiki template.An limitation of having the mapping stored in a third party database is that users of NCBI and Wikipedia may be unaware of the existence of that third database. Ideally the mapping could be included in both "node" databases so that users can easily go from one database to another. NCBI LinkOut Integrating the mapping into Wikipedia has proved less straightforward. Ideally the NCBI tax_id would be stored in the Wikipedia page in a place where it would be easy to add or edit using an automated tool such as a Wikipedia "bot". The Taxobox template would be a good choice as every Wikipedia page for a taxon includes this template. However, a proposal to add NCBI tax_ids to this template generated enough resistance to prevent it being adopted Because the mapping is implemented as a wiki it is possible to edit an individual NCBI-Wikipedia mapping. Although the user has the option of editing the underlying text of the wiki page, this requires some knowledge of the rather arcane syntax of Mediawiki templates. To make editing easier iPhylo Linkout makes use of the forms feature of Semantic Mediawiki, so that if the user clicks on the "Edit with form" tab they are presented with a simple form to edit . Both NCBI and Wikipedia are continually growing with the sequencing of new taxa and the addition of new articles, respectively. Although the original mapping between NCBI and Wikipedia was based on data from 2009, it has been actively updated manually, or by running local scripts (for example to add large numbers of newly added NCBI tax_ids). An obvious enhancement would be to automate this process. If both the NCBI taxonomy database and Wikipedia both provided services listing recently added or modified taxa, then iPhylo Linkout could consume these and update the mapping automatically. At present neither the NCBI Taxonomy nor Wikipedia explicitly provides such services, although one could be constructed for the NCBI database using their EUtils tools Although the focus of iPhylo Linkout has been mapping NCBI tax_ids to Wikipedia pages, it could easily be extended to include other identifiers of interest, such as links to the original taxonomic literature. The approach of using a wiki to manage the mapping between identifiers could also be used outside the specific case here of mapping a taxonomic database to Wikipedia pages.http://iphylo.org/linkout and can be edited by anyone who creates an account. The contents of the mapping are in the public domain.The iPhylo Linkout wiki is available at Some of the ideas discussed here were developed on my blog This work was funded by the University of Glasgow.The author has declared that no competing interests exist.


Wing flapping is one of the most widespread propulsion methods found in nature; however, the current understanding of the aerodynamics in bird wakes is incomplete. The role of the unsteady motion in the flow and its contribution to the aerodynamics is still an open question. In the current study, the wake of a freely flying European starling has been investigated using long-duration high-speed Particle Image Velocimetry (PIV) in the near wake. Kinematic analysis of the wings and body of the bird has been performed using additional high-speed cameras that recorded the bird movement simultaneously with the PIV measurements. The wake evolution of four complete wingbeats has been characterized through reconstruction of the time-resolved data, and the aerodynamics in the wake have been analyzed in terms of the streamwise forces acting on the bird. The profile drag from classical aerodynamics was found to be positive during most of the wingbeat cycle, yet kinematic images show that the bird does not decelerate. It is shown that unsteady aerodynamics are necessary to satisfy the drag/thrust balance by approximating the unsteady drag term. These findings may shed light on the flight efficiency of birds by providing a partial answer to how they minimize drag during flapping flight. Flapping flight is one of the most complex yet widespread propulsion methods found in nature. Although aeronautical technology has advanced remarkably over the past century, flying animals still demonstrate higher efficiency Among the first few attempts to describe unsteady aerodynamics According to quasi-steady-state aerodynamic theory, slow-flying vertebrates  should not be able to generate enough lift to remain aloft Corvus monedula) wake and indicated that approximately half of the required momentum for weight support was present for jackdaw flight. As a consequence, the ‘wake momentum paradox’ arose. It was concluded that the discrepancy could be a result of unidentified complexities in the wake structure; i.e., Rayner’s model was too idealized. Spedding Falco tinnunculus) flight at moderate (∞U = 7 m/s) speeds and observed a distinctly different wake topology. He found that, instead of discrete loops separated by aerodynamically inactive upstrokes, two continuous undulating vortex tubes exist in the wake; i.e., the upstrokes were also aerodynamically active. The measured circulation of the shed vortices was similar during the downstroke and upstroke and it was adequate for supporting the weight of the bird. In addition to the lift force it was found that generating net thrust occurred through varying the wing geometry – not through varying the circulation – implying that the wing motion is important.The complex unsteady features of flapping flight introduce challenges to any realistic aerodynamic analysis. One of the first attempts to incorporate realistic wake structure in an aerodynamic model of bird flight was by Rayner Luscinia luscinia). They concluded that the structure of the wake downstream, far from the body (roughly 17 chord lengths), varies gradually from an approximately elliptical vortex wake to a continuous trailing vortex wake. Therefore, the wake is comprised neither of a series of elliptical vortex loops, nor a pair of continuous trailing vortices, but is a combination of both. Eventually, the ‘wake momentum paradox’ was addressed, within the bounds of experimental uncertainty, through the high spatial resolution available in PIV as well as a detailed accounting procedure for the calculation of circulation in the wake The concept of different wake topologies prompted analyses of vortex gaits Erithacus rubecula) and found that they resemble the thrush nightingale wake Glossophaga soricina), Johansson et al. The vorticity structure in the wake of a flying bird, similar to the distribution of vorticity in any wake, is dependent on the boundary conditions. Consequently, the kinematics of the wings have been investigated in the literature with the goal of either using the wing motion to predict forces or associating the wake topology with the motion of the wings. Two wingbeat kinematics of a thrush nightingale The contribution of unsteady aerodynamics to force calculations on flying birds, which results mainly from the wing’s motion, has not been addressed rigorously in the past Currently, many of the aerodynamic models for birds are based on fixed wings in steady flow 2, preceded by a 2.5∶1 contraction. The width, height and length of the test section are 1.5 m, 1 m, and 2 m, respectively. It is enclosed in a hypobaric chamber allowing for testing at high altitude conditions by controlling pressure, temperature and humidity in the test section. An open jet exists between the downstream end of the test section and the diffuser for the purpose of introducing the live bird into the wind tunnel during the experiments. The turbulence intensity is lower than 0.3% at the location where the measurements were taken. A fine net was placed at the upstream end of the test section to prevent the bird from entering the contraction, which was not observed to alter the turbulence significantly. The flight conditions were at atmospheric pressure, a temperature of 15°C, and relative humidity of 80%.The experiments were performed in the closed-loop hypobaric climatic wind tunnel at the Advanced Facility for Avian Research (AFAR) at the University of Western Ontario. The octagonal test section of the wind tunnel has a cross-sectional area of 1.2 mc, of 6 cm, a maximum wingspan of b = 38.2 cm (bsemi = 19.1 cm) and an aspect ratio (wingspan squared divided by the wings’ lifting area), AR, of 6.4. A typical cruising speed of U∞ = 12 m/s was chosen for the experiments based on the comfort of the starling and its ability to fly for prolonged periods of time during the testing. The wingbeat frequency, f , was 13.3 Hz on average, and the average peak-to-peak wingtip vertical amplitude, A, was 28 cm. These quantities correspond to a chord-based Reynolds number of 4.8·104, a Strouhal number, St = Af/U∞ = 0.30, and a reduced frequency, k = πfc/U∞ = 0.20. At the time the experiments were performed the bird had a mass of 78 g and a lateral body width of 4 cm.The wake measurements  were designed to protect the bird’s vision as well as to reduce the potential of the light sheet frightening the bird. After an accommodation period of 20 minutes in a cage, the bird would fly normally in the wind tunnel while wearing the goggles. In addition, for preventing direct contact between the bird and the light sheet, a collection of optoisolators operated by six infrared transceivers were integrated into the PIV system. The function of the optoisolators was to trigger the laser only when the bird was in a desired position upstream of the PIV field of view thus ensuring that the bird was in a position where it was not in danger of being hit by the laser. All animal care and procedures were approved by the University of Western Ontario Animal Use Sub-Committee . Further details pertaining to the experiments can be found in Kirchhefer et al. 2 at a rate of 1000 Hz. The PIV system is capable of acquiring image pairs at 500 Hz using the two cameras for 20 minutes continuously. In the current experiments, one camera was used to record the bird kinematics during the wingbeat and the other was used for PIV measurements in the wake. The PIV camera’s field of view was approximately 12×12 cm2 in size, or 2c by 2c. Vector fields were computed by OpenPIV 2 interrogation windows with 50% overlap, giving a spatial resolution of 32 vectors per chord. In the current experiments, 4,600 vector maps were recorded, and out of this dataset 650 vector maps contained features of the near wake behind the starling’s wing. The PIV data were measured 4 wing chord lengths (∼0.24 m) behind the right wing, so it took 20 ms for events generated at the wing to enter the PIV field of view. The wake was sampled in the parasagittal plane (9×9 cm2) at 2 ms intervals (500 Hz), so that both the downstroke and upstroke phases were temporally resolved.Flow measurements were taken using the long-duration time-resolved PIV system developed by Taylor et al. c by 9c. The streamwise and vertical positions of the bird were recorded simultaneously with the flow field measurements. The field of view in these recordings had an area of 9An error analysis based on the root sum of squares method has been applied to the velocity data and the wing kinematics. The errors were estimated as: 2.5% for the instantaneous velocity values, 12% for the instantaneous vorticity and 3% for the drag values A number of wake velocity maps were sampled where the starling was flying in a steady flapping mode without performing any maneuvers. The data discussed herein was selected from a broad acquisition batch where the bird was flying continuously for a few seconds  yields:φ on the downstroke and - φ on the upstroke φ = 26°) occurs for wingbeat 4 and that the value is larger than the stalling angle of conventional fixed wing aircraft of approximately 15° bsemi where the chord length is greatest. This enables us to use the pitch of the wing (∼13°) and the wing’s tangential velocity to approximate the angle of attack, α. The instantaneous angle of attack is found to be approximately 15°.For a bird flapping its wings up and down in the vertical plane and keeping the wing chord horizontal all the time e.g., , the winIn the previous section the wing kinematics were quantified for each of the four complete wingbeats. In this section the wake is characterized in terms of aerodynamic forces and vorticity content. The vorticity in the wake is computed directly from the PIV data using a least squares differentiation scheme It is observed that the peak normalized vorticity of the starling is 4.1 in the present study , which ith successive PIV images is calculated as Uc⋅Δt⋅n. The convection velocity, Uc, is the velocity at which the characteristics of the wake collectively travel downstream. In the present study, wake composites have been generated using the free-stream velocity (U∞) as a convection velocity. The generation of a wake composite provides a useful visualization tool for observation of the wake dynamics over the time series of a wing beat cycle. What appears as “downstream” in the wake composite happens earlier, while what appears “upstream” in the composite happens later meaning that the generation of the wake composite invokes Taylor’s hypothesis in which the characteristics of the flow are a frozen spatial pattern convected through the field of view.During flapping flight bird wings change position causing the momentum and circulation in the wake to vary. In many simplified models the wake changes in a periodic manner where the downstroke and upstroke phases have different signatures A–D) patterns and two different positively-signed (E and F) patterns. It can be seen that the different patterns of vorticity move downstream during the time difference between the consecutive images (2 msec).zω, varying from −650 to 650 sec−1. In addition, the spatially averaged velocity has been subtracted from each frame, so the velocity vectors displayed are fluctuations.The wake features are presented through fluctuating velocity and vorticity fields as depicted in Using the floor-mounted camera, the wake patterns presented in The most immediate observation from the wake reconstructions in ∂u/∂y). However, it is known that vorticity alone does not indicate the presence of a vortex In the available literature, there has been considerable focus on the vortex topology in bird wakes ABCDEFGHIA) with its width in the z direction being unity. Inside the control volume, the integral form of the momentum equation is ρ is the density (constant), p is the pressure and R′ is the resultant aerodynamic force per unit span exerted on the body by the normal and shear stresses acting at the body surface. Note that the viscous terms have been ignored as they scale with Re−1. The integrals are taken over the control volume, V, enclosed by the surface, S. Using the x-component of Eq. (4), the aerodynamic drag per unit span, D′, isConsider a two-dimensional section of the bird wing in an incompressible flow as sketched in D′ is defined as drag and a negative one as thrust. For simplicity the resultant force, D′, is referred to as drag per unit span where negative drag per unit span refers to thrust. For S, estimated sufficiently far from the body where the pressure is assumed constant, and equal to the undisturbed free-stream pressure p∞, Eq. (5) becomes:A positive value of dS is perpendicular to the control surface. Thus, for streamlines ED, FG and BAI the multiplication BC and HI are adjacent to each other, so their contribution to the second term in Eq. (6) cancels each other. As a result, the second term in Eq. (6) consists of contributions only from sections EF and DG ,Using the integral form of the continuity equation and multiplying by h is the wake vertical extent of the PIV velocity field. The so-called ‘unsteady drag’ per unit span can be derived using the first term in Eq. (9) and expressed asx-positions for each velocity field map. Subsequently, these profiles within one PIV vector map were spatially averaged into one profile describing the velocity deficit (steady drag per unit span) similar to the procedure described in It should be noted that the full area integral  cannot be directly computed as it appears in Eq. (9) since only a portion of the control surface enveloping the bird wing is measured in the current experiments e.g., . However∂u/∂t = 0 everywhere in the chosen control volume. While this assumption is reasonable in the wake of a section model mounted in a wind tunnel, it seems unlikely that this condition is satisfied in the wake of a freely flying bird. However, experimental measurements of the entire control volume remain prohibitive and many studies have approximated the drag force through the profile drag In classical aerodynamics, the profile drag (Eq. (10)) inherently assumes that The profile drag developed over the wing is manifested through the wake velocity profile. In the case of flapping wings , the velocity field changes spatially and temporally. Since the bird is flying freely, and the kinematic images  demonstr∂u/∂t term. Considering the control volume drawn in ∂u/∂t = 0 everywhere in the flow upstream of the wing since the wind tunnel is operating at a constant wind speed. Conversely, ∂u/∂t is not expected to be zero around the wings and especially in the wake. It is expected that ∂u/∂t is greater than zero in the wake during the downstroke since work  is an input to the wake ∂u/∂t. The unsteady drag results presented in ∂u/∂t is smaller than zero as expected during the downstroke as the bird generates lift and propels itself forward ∂u/∂t appears to be positive; however, once the steady drag reach a maximum value halfway through the upstroke ) it is expected that the compensating force for the profile drag is the volume integral containing the upstroke , the uns∂u/∂t cannot be neglected. Furthermore, the flow mechanisms underlying the present measurements of ∂u/∂t are expected to correlate to the bird’s use of unsteady aerodynamics and improved efficiency.It should be noted that performing PIV measurements around freely flying birds limits the capability of capturing the entire span of the wing; therefore, our estimates are based on a sectional measurement. However, the current dataset offers much lower uncertainty of the streamwise velocity compared to attempts to capture the entire volume using the Trefftz plane Many studies that investigate flying animals utilize quasi-steady models to analyze the flapping mechanism In this study, a long-duration time-resolved PIV system was used to obtain accurate, time-resolved measurements of the streamwise velocity in the wake of a freely flying European starling flying in flapping flight at the AFAR hypobaric wind tunnel. The system is capable of capturing images for 20 min continuously in order to characterize unsteady phenomena within a given flow field. A total of 4,600 vector maps were analyzed in the current study, and four wingbeat cycles were identified within this data set. The identification was performed by using an additional high-speed camera that recorded flight kinematics and was synchronized with the PIV. The kinematic analysis showed that during the four wingbeats used to analyze the wake, the bird did not accelerate or decelerate significantly in the streamwise direction.The wake topology of the starling was characterized using a wake reconstruction based on patterns from the instantaneous vorticity fields where the measurement plane of the velocity was close to the wing root of the bird. The resolution of the data were insufficient to determine if spanwise vortices were present in the near wake or if the observed vorticity was due to the shear created by the flow over the bird’s wings and body. Thus, any connecting spanwise vortices that exist at this stage of the wake development should be relatively small.∂u/∂t is zero everywhere or integrates to zero instantaneously, yet this does not necessarily correspond to the case for flapping flight. As with previous studies, the integration of the velocity profiles over the measurement plane admittedly misses the remaining span of the wake, yet clear trends have been observed. It was found that the profile drag term was almost always positive; however, the bird was not observed to noticeably decelerate. Thus, there should be a compensating force to this classical drag term. It was observed that ∂u/∂t is generally negative during the downstroke from the current dataset; however, the results also show that during the upstroke ∂u/∂t is generally positive. The approximation of the unsteady term suggests that unsteady aerodynamics may provide some thrust in the overall streamwise force balance.The time variation of the profile drag per unit span from classical aerodynamics over each of the four different wingbeat cycles was approximated using the PIV data. Inherent in the calculation of profile drag is the assumption that The role of the unsteady portion of the flow on the flight efficiency of birds is yet to be determined and still remains an open question. Yet, the current results shed light on the role of the unsteadiness during flight and its impact on drag/thrust. In addition, future studies are required to assess how the spanwise variations of these forces affect the balance between drag and thrust.