Effects of kinetics of adsorption and coalescence on continuous foam concentration of proteins: Comparison of experimental results with model predictions

Protein enrichment and recovery were measured in a continuous foam concentration column for bovine serum albumin (BSA) for different pool heights, foam heights, superficial gas velocities, bubble sizes, feed flow rates, pH, and ionic strengths. Protein enrichment was found to decrease with an increase in pool height for low pool heights, reach a minimum at an intermediate pool height, and subsequently increase with pool height for sufficiently large pool heights eventually approaching an asymptotic value. Such a behavior was due to the combined effects of kinetics of adsorption of protein and coalescence. The increase in protein enrichment with pool height was due to the predominant effect of kinetics of adsorption of protein, whereas the opposite behavior at low pool heights was due to the predominant effect of coalescence in the foam. Protein enrichment was found to be higher for smaller feed concentrations, smaller gas velocities, larger bubble sizes, and larger foam heights. Enrichment at pH values different from the isoelectric point was found to be higher because of more coalescence. A model for foam concentration of proteins was employed to predict enrichment and recovery. The model predictions agreed well with the experimental data. (c) 1996 John Wiley & Sons, Inc.     

A simplified model of hydrodynamics in airlift loop reactors

As a function of the gas throughput the following parameters were measured in an external loop reactor with a riser diameter of 0.6 m and a gassed liquid height of 8.6 m: integral and local values of gas hold-up; liquid velocities; mixing times and axial dispersion coefficients of the liquid phase. The height of the reactor could be altered by reconstruction. Measurements were also carried out with lower heights than 8.6 m. Besides pure water, aqueous solutions of coalescing, non-coalescing and viscosity-increasing substances were used as model systems. With the results a general relationship between superficial gas velocity, gas hold-up and liquid velocity was established. This hydrodynamic model uses the relative velocity between gas and liquid phase as the fundamental parameter. The generally valid model consists of one term for the homogeneous and of two additional terms for the heterogeneous flow regime.     

Atomic force microscopy of DNA in aqueous solutions.

DNA on mica can be imaged in the atomic force microscope (AFM) in water or in some buffers if the sample has first been dehydrated thoroughly with propanol or by baking in vacuum and if the sample is imaged with a tip that has been deposited in the scanning electron microscope (SEM). Without adequate dehydration or with an unmodified tip, the DNA is scraped off the substrate by AFM-imaging in aqueous solutions. The measured heights and widths of DNA are larger in aqueous solutions than in propanol. The measured lengths of DNA molecules are the same in propanol and in aqueous solutions and correspond to the base spacing for B-DNA, the hydrated form of DNA; when the DNA is again imaged in propanol after buffer, however, it shortens to the length expected for dehydrated A-DNA. Other results include the imaging of E. coli RNA polymerase bound to DNA in a propanol-water mixture and the observation that washing samples in the AFM is an effective way of disaggregating salt-DNA complexes. The ability to image DNA in aqueous solutions has potential applications for observing processes involving DNA in the AFM.     

Footprints,Trackways, and Hip Heights of Bipedal Dinosaurs—Testing Hip Height Predictions with Computer Models

Three-dimensional, dynamic, computer models of the pelvis and hind limbs of theropods and ornithopods are used to produce synthetic trackways using a range of gait angles and degrees of limb joint flexion. The hip heights of the modeled stances are compared with the predictions of hip heights computed with various formulae that incorporate parameters measured from footprints and trackways. The tested formulae include: 4*footprint-length and other morphometric methods where the coefficients vary according to the size and taxonomic group of the inferred trackmaker, allometric methods with size and taxon specific coefficients and exponents, and pace-length divided by 0.6. The best fit (least difference) between model and predicted hip heights is achieved with the simple 4*footprint-length formula. The pace-length formula also works well, but only for a very narrow gait range. With one exception, a small theropod, the variable morphometric and allometric formulae consistently overestimate the hip heights in all case. For large theropods and ornithopods the overestimates can be up to 84% in extreme cases. There was also a trend for the magnitudes of overestimation to increase with increasing size of the trackmaker. The overestimates of hip height using these methods results in underestimation of the computed velocities attributed to the dinosaurs that made the trackways.     

Maxwell’s Mixing Equation Revisited: Characteristic Impedance Equations for Ellipsoidal Cells

We derived a series of, to our knowledge, new analytic expressions for the characteristic features of the impedance spectra of suspensions of homogeneous and single-shell spherical, spheroidal, and ellipsoidal objects, e.g., biological cells of the general ellipsoidal shape. In the derivation, we combined the Maxwell-Wagner mixing equation with our expression for the Clausius-Mossotti factor that had been originally derived to describe AC-electrokinetic effects such as dielectrophoresis, electrorotation, and electroorientation. The influential radius model was employed because it allows for a separation of the geometric and electric problems. For shelled objects, a special axial longitudinal element approach leads to a resistor-capacitor model, which can be used to simplify the mixing equation. Characteristic equations were derived for the plateau levels, peak heights, and characteristic frequencies of the impedance as well as the complex specific conductivities and permittivities of suspensions of axially and randomly oriented homogeneous and single-shell ellipsoidal objects. For membrane-covered spherical objects, most of the limiting cases are identical to—or improved with respect to—the known solutions given by researchers in the field. The characteristic equations were found to be quite precise (largest deviations typically <5% with respect to the full model) when tested with parameters relevant to biological cells. They can be used for the differentiation of orientation and the electric properties of cell suspensions or in the analysis of single cells in microfluidic systems.     

Parameter optimization model of learning in stepping motion

In this study we combine the representation of motion by a finite number of hardwired functions with parameter optimization to model learning during a stepping motion. Representation of experimental kinematic data by a finite number of predetermined functions and undetermined coefficients was analyzed. Least squares approximation was used to represent experimental data of stepping motions over obstacles of different heights. Functional relationships between coefficients and obstacles heights were also obtained. Learning of stepping over an obstacle was then formulated as a finite dimensional optimization problem. The pattern of foot path, and joint angles trajectories obtained by this learning model, were then compared to the experimental data. The results of the data fitting analysis and of the optimization process as a model for motion learning, indicate that motion can be adequately represented by a set of hardwired functions, and a finite number of task dependent coefficients.     

Robust protein quantitation in chromatographic fractions using MALDI-MS of tryptic peptides

A method is introduced to evaluate protein concentrations using the height sum of all MALDI-MS peaks that unambiguously match theoretic tryptic peptide masses of the protein sought after. The method uses native chromatographic protein fractionation prior to digestion but does not require any depletion, labeling, derivatization, or preparation of a compound similar to the analyte. All peak heights of tryptic peptides are normalized with the peak height of a unique standard peptide added to the MALDI-MS samples. The sum of normalized peak heights, S(n), or the normalized mean peak height, M(n), reflects the concentration of the respective protein. For fractions containing various proteins, S(n) and M(n) can be used to compare concentrations of a protein between different fractions. For fractions with one predominating protein, they can be used to estimate concentration ratios between fractions, or to quantify the fractional protein concentration after calibration with pure protein solutions. Initial native fractionation retains the possibility to apply all conventional analytic procedures. Moreover, it renders the method relatively robust to MS mass accuracy. The method was validated with albumin, transferrin, alpha1-antitrypsin, and immunoglobulin G within highly complex chromatographic fractions of pathological and normal sera, which contained the respective intact native protein in dominating as well as minor concentrations. The correlation found between S(n) and the protein concentration as determined with ELISA showed that the method can be applied to select markers for distinguishing between normal and pathological serum samples.     

Homemakers and heights. Intra-household resource allocation and male stature in the Netherlands, 1860–1930

In this article we test the hypothesis that the secular increase in heights in the course of the second half of the nineteenth century was associated with the rise of the breadwinner-homemaker household. In these ‘modern’ households, women raised the living standards (quality and quantity of food, hygiene and care) for all members, especially the children. We model the assumed contributions to the family budget by age and gender of household members, and find that a strong imbalance between consumers and producers in the household put severe strains on effective resource allocation, leading to lower net nutrition and lower young adult heights. We suggest a carefully calibrated consumer/producer ratio as an indicator to capture these effects. The ratio is not meant to replace others, and we show that sibling rank order as well as gender preferences also played a role in intra-household resource allocation. For our research, we have used a database with reconstructed life histories (including co-residence) of 3003 Dutch army recruits. Our results indicate that the consumer/producer ratio as experienced by recruits in their early life indeed had a strong impact (-1,8 cm) on their heights. However, this effect differed by social class, which can be explained by differences in acceptance of the income pooling model.     

A Computational Methodology to Screen Activities of Enzyme Variants

We present a fast computational method to efficiently screen enzyme activity. In the presented method, the effect of mutations on the barrier height of an enzyme-catalysed reaction can be computed within 24 hours on roughly 10 processors. The methodology is based on the PM6 and MOZYME methods as implemented in MOPAC2009, and is tested on the first step of the amide hydrolysis reaction catalyzed by the Candida Antarctica lipase B (CalB) enzyme. The barrier heights are estimated using adiabatic mapping and shown to give barrier heights to within 3 kcal/mol of B3LYP/6-31G(d)//RHF/3-21G results for a small model system. Relatively strict convergence criteria (0.5 kcal/(molÅ)), long NDDO cutoff distances within the MOZYME method (15 Å) and single point evaluations using conventional PM6 are needed for reliable results. The generation of mutant structures and subsequent setup of the semiempirical calculations are automated so that the effect on barrier heights can be estimated for hundreds of mutants in a matter of weeks using high performance computing.     

Ewens' sampling formula and related formulae: combinatorial proofs, extensions to variable population size and applications to ages of alleles

Ewens' sampling formula, the probability distribution of a configuration of alleles in a sample of genes under the infinitely-many-alleles model of mutation, is proved by a direct combinatorial argument. The distribution is extended to a model where the population size may vary back in time. The distribution of age-ordered frequencies in the population is also derived in the model, extending the GEM distribution of age-ordered frequencies in a model with a constant-sized population. The genealogy of a rare allele is studied using a combinatorial approach. A connection is explored between the distribution of age-ordered frequencies and ladder indices and heights in a sequence of random variables. In a sample of n genes the connection is with ladder heights and indices in a sequence of draws from an urn containing balls labelled 1,2,...,n; and in the population the connection is with ladder heights and indices in a sequence of independent uniform random variables.     

Countermovement strategy changes with vertical jump height to accommodate feasible force constraints

In this study, we developed a curve-fit model of countermovement dynamics and examined whether the characteristics of a countermovement jump can be quantified using the model parameter and its scaling; we expected that the model-based analysis would facilitate an understanding of the basic mechanisms of force reduction and propulsion with a simplified framework of the center of mass (CoM) mechanics. Ten healthy young subjects jumped straight up to five different levels ranging from approximately 10% to 35% of their body heights. The kinematic and kinetic data on the CoM were measured using a force plate system synchronized with motion capture cameras. All subjects generated larger vertical forces compared with their body weights from the countermovement and sufficiently lowered their CoM position to support the work performed by push-off as the vertical elevations became more challenging. The model simulation reasonably reproduced the trajectories of vertical force during the countermovement, and the model parameters were replaced by linear and polynomial regression functions in terms of the vertical jump height. Gradual scaling trends of the individual model parameters were observed as a function of the vertical jump height with different degrees of scaling, depending on the subject. The results imply that the subjects may be aware of the jumping dynamics when subjected to various vertical jump heights and may select their countermovement strategies to effectively accommodate biomechanical constraints, i.e., limited force generation for the standing vertical jump.     

The Indian Enigma revisited

This paper re-enters the contested discussion surrounding the Indian Enigma, the high prevalence of chronic undernutrition in India relative to sub-Saharan Africa. Jayachandran & Pande (JP) argue that the key to the Indian Enigma lies in the worse treatment of higher birth order children, particularly girls. Analyzing new data, and taking into account issues relating to robustness to model specification, weighting and existing critiques of JP., we find: (1) Parameter estimates are sensitive to sampling design and model specification; (2) The gap between the heights of pre-school African and Indian children is closing; (3) The gap does not appear to be driven by differential associations by birth order and child sex; (4) The remaining gap is associated with differences in maternal heights. If Indian women had the heights of their African counterparts, pre-school Indian children would be taller than pre-school African children; and (5) Once we account for survey design, sibling size and maternal height, the coefficient associated with being an Indian girl is no longer statistically significant.     

How Short is Too Short According to Parents of Primary Care Patients

ObjectiveHeight is a physical trait on a continuum. The threshold between normal and abnormal is arbitrarily set but can potentially influence medical decision-making. We sought to examine parents’ perceptions of adult heights and associated demographic factors.MethodsParents of pediatric primary care patients of various heights completed a one-time survey. Parents answered the question “How short is too short?” for adult males and females. The results were summarized as median [interquartile range]. Factors significantly associated with height threshold by simple linear regression were included in a multivariable mixed effects analysis of covariance model.ResultsA total of 1,820 surveys were completed (83% response rate, 1,587 females, 231 males). The median threshold height deemed too short for adult females was 56 inches [48, 59] among male respondents and 57 inches [50, 60] among females (P < .05). The median threshold height for adult males was 61 inches among males [60, 64] and females [59, 66] (P < .05). The median of male minus female heights per respondent (delta heights) was 5 [2, 7] inches. Factors found to be significant main effects in a parsimonious model were sex of the adult considered, height of respondent, sex of respondent, respondent race, primary care practice, income, and having concerns about their child’s height.ConclusionTaller acceptable height thresholds were perceived by respondents who were taller, wealthier, white, female, from nonurban practices, or who had a personal concern about their child’s height. Male heights were expected to be taller than female heights. Such traits may influence who is concerned and more likely to seek medical treatment for their children. (Endocr Pract. 2014;20: 1113-1121)     

急性轻中度缺氧EEG信号的复杂度研究

建立了一个急性高空缺氧实验模型,记录了四种不同高度条件下从缺氧前(正常呼吸)到缺氧后30分钟时的EEG,分析了其复杂度。发现缺氧引起复杂度明显变化,随时间和高度增加,一定程度缺氧可使EEG复杂度低于正常。表明EEG复杂度对脑缺氧较为敏感,可用于缺氧程度进行评估,有望成为临床诊断的一个指标。     

Statistical Analysis of Spatial Point Processes: A Soft-Core Model and Cross-Correlations of Marks

This paper suggests correlation characteristics for marked point processes with two marks for each point and describes statistical methods for their estimation. Its use is demonstrated by means of an example, where the points are locations of pine saplings, and the marks are their heights and ages. Furthermore, a soft-core point process model is presented. It is shown that a pattern of sites of beadlet anemones on a rock has a pair-correlation function and intensity which can be very well approximated by the model.     

MULTIPLE EQUILIBRIA AND MAINTENANCE OF ADDITIVE GENETIC VARIANCE IN A MODEL OF PLEIOTROPY

We describe a multilocus model that incorporates pleiotropic stabilizing selection on a large number of characters. We find many different stable equilibria with different levels of polymorphism and additive genetic variability. The results lend support to Wright's concept of a complex adaptive surface with many peaks of different heights. The model assumes that alleles contribute additively to the characters. We analyze the multilocus model by first considering a two-locus model. The two-locus model depends critically on having loci of different effect and on having the optimum phenotype not be that of a completely heterozygous individual. The effects of different loci need to differ only by less than a factor of two. For the multilocus, multicharacter model, we assume that completely heterozygous individuals do not have the optimum phenotype. By restricting attention to a two-allele model, we also assume that there are no alleles that can affect all characters in all possible combinations of directions.     

Heterostyly: speciation within a species

Almost all organisms in nature show nonrandom mating to different degrees. Two extreme results of nonrandom mating are speciation and sexual differentiation. Heterostyly is a form of sexual differentiation considered to have evolved to resolve conflicts between male and female functions of hermaphrodite flowers. Our study examines necessary and sufficient conditions for establishment of heterostyly using a configuration individual-based model. Previous models assume invasion of a mutant phenotype into a population with monomorphic wild phenotype. In contrast, our model demonstrates that heterostyly can be established from a population with continuous phenotypic variation, a proposition that requires simpler assumptions than the previous hypotheses. Results of our simulation show that genetic linkage between stigma and anther heights is essential for establishment of heterostyly. Dominance effects on the genes for stamen or stigma heights are not necessary, but they promote evolution of heterostyly. Probability of evolution of heterostyly also depends on the functional relationship between stigma–anther distance and strength of sexual interference, and the distance and probability of pollen deposition success. Parallelity and difference between speciation and sexual differentiation are also discussed.     

Biomechanical analysis of foot with different foot arch heights: a finite element analysis

Clinically, different foot arch heights are associated with different tissue injuries to the foot. To investigate the possible factors contributing to the difference in foot arch heights, previous studies have mostly measured foot pressure in either low-arched or high-arched feet. However, little information exists on stress variation inside the foot with different arch heights. Therefore, this study aimed to implement the finite element (FE) method to analyse the influence of different foot arches. This study established a 3D foot FE model using software ANSYS 11.0. After validating the FE model, this study created low-arched, high-arched and normal-arched foot FE models. The FE analysis found that both the stress and strain on the plantar fascia and metatarsal were higher in the high-arched foot, whereas the stress and strain on the calcaneous, navicular and cuboid were higher in low-arched foot. Additionally, forefoot pressure was increased with an increase in arch height.     

Biomechanical analysis of foot with different foot arch heights: a finite element analysis

Clinically, different foot arch heights are associated with different tissue injuries to the foot. To investigate the possible factors contributing to the difference in foot arch heights, previous studies have mostly measured foot pressure in either low-arched or high-arched feet. However, little information exists on stress variation inside the foot with different arch heights. Therefore, this study aimed to implement the finite element (FE) method to analyse the influence of different foot arches. This study established a 3D foot FE model using software ANSYS 11.0. After validating the FE model, this study created low-arched, high-arched and normal-arched foot FE models. The FE analysis found that both the stress and strain on the plantar fascia and metatarsal were higher in the high-arched foot, whereas the stress and strain on the calcaneous, navicular and cuboid were higher in low-arched foot. Additionally, forefoot pressure was increased with an increase in arch height.