Lamellipodium-driven tissue reshaping: a parametric study

We recently showed that lamellipodia are able to generate forces of the right type to drive convergent extension (CE), an important class of tissue reshaping, in early stage embryos. The purpose of the present work is to quantify the mechanics of this process using parametric analyses. We use finite elements to implement a gamma-mu model in which a net interfacial tension gamma acts along each cell boundary and the cytoplasm exhibits an effective viscosity mu. The stress-strain characteristics of a rectangular patch of model tissue are investigated in terms of the rate r at which lamellipodia form and the relative strength q of their contractions. In tissues that are not constrained in-plane by adjacent tissues, the rate of tissue reshaping is proportional to r the rate of lamellipodium formation and its dependence on q is nonlinear and, near its expected value of 2 highly sensitive to q. Cell elongation, a central characteristic of CE, and stress is found to vary linearly with e the degree of kinematic restraint. Relevant "mechanical pathways" are also identified.     

Performance prediction of deep learning applications training in GPU as a service systems

Cluster Computing - Data analysts predict that the GPU as a service (GPUaaS) market will grow to support 3D models, animated video processing, gaming, and deep learning model training. The main...     

Uncomfortable prescribing decisions: a critical incident study.

OBJECTIVE--To explore the discomfort experienced by general practitioners in relation to decisions about whether or not to prescribe. DESIGN--Focused interviews of general practitioners about prescribing decisions that made them uncomfortable. Analysis based on the critical incident technique. SETTING--One family practitioner committee area in the north of England. RESPONDENTS--69 principals and five trainee general practitioners. MAIN OUTCOME MEASURES--Drugs and clinical problems associated with prescribing discomfort. Reasons given by doctors for making the prescribing decisions they did and reasons for feeling uncomfortable. RESULTS--Antibiotics, tranquillisers, hypnotics, and symptomatic remedies were most often associated with discomfort, but any prescribable item could be associated with discomfort. Respiratory diseases, musculoskeletal problems, and anxiety were most often associated with discomfort, but again any condition could be associated. The main reasons given for the decisions made were patient expectation, clinical appropriateness, factors related to the doctor-patient relationship, and precedents. The main reasons given for feeling uncomfortable were concern about drug toxicity, failure to live up to the general practitioner''s own expectations, concern about the appropriateness of treatment, and ignorance or uncertainty. CONCLUSIONS--Many considerations, including medical, social, and logistic ones, influence the decision to prescribe in general practice. The final action taken depends on a complex interaction of these disparate influences.     

Museum learning: a study of motivation and learning achievement

According to Reinmann-Rothmeier and Mandl (2001), learning environments should provide an ideal balance between constructivist and instructive elements. Most interesting for constructivist learning processes is the combination of the cognitive and the motivational domain. In an empirical study with 207 fifth-graders of the highest stratification level, we evaluated three different approaches to the learning process based on a visit to the Natural History Museum in Berlin: the three approaches were principally characterised by closed, open and mixed tasks. One objective of our study was to as-sess learning achieved through the visit and the effect of different treatments. Another goal was to evaluate the motivation of the three treatment groups. We conducted a pre/post-test study with follow-up measurement. The test instruments consisted of 26 open and closed questions in the cognitive domain and a further 12 items (subdivided into four subsections) for measuring motivation according to self-determination theory. In contrast to our hypotheses based on constructivist theories, open tasks were less successful for gaining knowledge and less intrinsically motivating.     

Individual food-hoarding decisions in a nonterritorial coal tit population: the role of social context

Among the Paridae, food hoarding is thought to be strongly associated with the exclusive use of territories by winter groups, although it has also been described in populations with loose social systems. However, detailed data on such populations are scarce. To identify the mechanisms underlying individual storing decisions, I studied hoarding behaviour in a nonterritorial, high-density coal tit, Parus ater, population in a subalpine forest. The presence of close neighbours (within 5 m) had the strongest, negative influence on caching probability, whereas more distant neighbours foraging in the same flock did not affect the probability of caching. Adults concentrated their stores in the centre of their home ranges. Caching location, but not caching intensity, was affected by the time of day. Coal tits took longer, and travelled further, to cache food in the inner parts of trees than in the outer parts. Resident adults stored in inner, safer caching locations more often than juvenile residents and transients. Differences in hoarding effort according to the storing substrate, and the daily storing location pattern of juvenile residents and transients, suggest that stores have a different use depending on where they are located. Therefore, my results show that hoarding is compatible with a nonterritorial, nonbreeding social system; hoarding could thus have originated in an ancient, nonterritorial, but sedentary, tit species. Copyright 2000 The Association for the Study of Animal Behaviour.     

Amplification of mutator cells in a population as a result of horizontal transfer

Mutator cells that lack the mismatch repair system (MMR(-)) occur at rates of 10(-5) or less in laboratory populations started from wild-type cells. We show that after selection for recombinants in an interspecies mating between Salmonella enterica serovar Typhimurium and Escherichia coli, the percentage of MMR(-) cells rises to several percent of the recombinant population, and after a second successive mating and selection, greater than 95% of the recombinants are MMR(-). Coupling a single cross and selection with either mutagenesis or selection for spontaneous mutants also results in a dramatic increase in MMR(-) cells. We discuss how horizontal transfer can result in mutator strains during adaptive evolution.     

Identification of learning mechanisms in a wild meerkat population

Vigorous debates as to the evolutionary origins of culture remain unresolved due to an absence of methods for identifying learning mechanisms in natural populations. While laboratory experiments on captive animals have revealed evidence for a number of mechanisms, these may not necessarily reflect the processes typically operating in nature. We developed a novel method that allows social and asocial learning mechanisms to be determined in animal groups from the patterns of interaction with, and solving of, a task. We deployed it to analyse learning in groups of wild meerkats (Suricata suricatta) presented with a novel foraging apparatus. We identify nine separate learning processes underlying the meerkats' foraging behaviour, in each case precisely quantifying their strength and duration, including local enhancement, emulation, and a hitherto unrecognized form of social learning, which we term 'observational perseverance'. Our analysis suggests a key factor underlying the stability of behavioural traditions is a high ratio of specific to generalized social learning effects. The approach has widespread potential as an ecologically valid tool to investigate learning mechanisms in natural groups of animals, including humans.     

Reinforcement learning with internal expectation in the random neural networks for cascaded decisions

The reinforcement learning scheme proposed in Halici (J. Biosystems 40 (1997) 83) for the random neural network (RNN) (Neural Computation 1 (1989) 502) is based on reward and performs well for stationary environments. However, when the environment is not stationary it suffers from getting stuck to the previously learned action and extinction is not possible. To overcome the problem, the reinforcement scheme is extended in Halici (Eur. J. Oper. Res., 126(2000) 288) by introducing a new weight update rule (E-rule) which takes into consideration the internal expectation of reinforcement. Although the E-rule is proposed for the RNN, it can be used for training learning automata or other intelligent systems based on reinforcement learning. This paper looks into the behavior of the learning scheme with internal expectation for the environments where the reinforcement is obtained after a sequence of cascaded decisions. The simulation results have shown that the RNN learns well and extinction is possible even for the cases with several decision steps and with hundreds of possible decision paths.     

Correction: genetic algorithm learning as a robust approach to RNA editing site site prediction

After the publication of [1], we were alerted to an error in our data. The error was an one-off miscalculation in the extraction of position information for our set of true negatives. Our data set should have used randomly selected non-edited cytosines (C) as true negatives, but the data generation phase resulted in a set of nucleotides that were each one nucleotide downstream of known, unedited cytosines. The consequences of this error are reflected in changes to our results, although the general conclusions presented in our original publication remain largely unchanged.     

The Pahira: a population genetical study

The Pahira is a small, primitive population of 1353 individuals inhabiting the hills and forests of the Ajodhya and the Dalma hill ranges in eastern India. Demographic, ABO blood groups, P.T.C. tasteblindness and anthropometric data are presented. The purpose of the present study is: to describe the biological characteristics of the population; to review the data from the point of view of the possible occurrence of maritally isolated, genetically different subpopulations within the population; to assess the possible causes of such differences, and to discuss the implications of such subpopulations and to examine the common assumption that allele frequencies throughout a population (i.e., among its several subpopulations) are homogeneous. It is shown that the Pahiras are divided into three subpopulations; that the subpopulations are different with respect to blood groups, tasteblindness and anhropometric measurements; that some of the variations show a clinal trend; that N.P. and S.P.I. are closer to each other than either of them to S.P.II; that such a breeding structure and genetic composition may have important evolutionary implications; that such a breeding structure emphasizes the importance of demographic information in population genetics; and, that our common assumption that allele frequencies throughout a population are homogeneous may not be valid.     

Surnames in Texas: a population study through isonymy

To study the isonymy structure of Texas, we analyzed the surname distributions of 3.6 million telephone users registered for the year 1996 in 232 towns distributed in the 7 regions of the state. The number of different surnames was 235,740. Matrices of isonymy distances between towns and between geographic regions were constructed and tested for correlation with geographic distance. We found that isonymy distances between the seven regions showed borderline or no correlation with geographic distance, with r = 0.089 +/- 0.232, r = 0.492 +/- 0.232, and r = 0.337 +/- 0.232 for Lasker's, Euclidean, and Nei's distances, respectively. Isonymy distances between towns were significantly correlated with geographic distance, with r = 0.249 +/- 0.006 for Lasker's distance, r = 0.338 +/- 0.006 for the Euclidean distance, and r = 0.418 +/- 0.006 for Nei's distance. Two dendrograms, one for the 7 regions and one for the 232 towns, were built from the matrices of Nei's distances. The dendrogram for regions indicates that a main surname differentiation exists between the East and West areas of Texas, with West Texas being predominantly Hispanic and East Texas being predominantly English-speaking. The dendrogram for the towns confirms in detail the differences identified by the matrix of distances between regions. Random inbreeding calculated from isonymy, F(ST), was highest in the west and in the south of the state. It was lowest in the area of Austin and Houston. Average Fisher's alpha for towns was 734, for regions it was 1,047, and for Texas as a whole it was 1,230. The geographic distribution of alpha in the state shows distinctly lower values in the traditionally Hispanic west and higher values in the east and on the Gulf of Mexico.     

Surnames in Argentina: a population study through isonymy

In order to study the isonymic structure of Argentina, the surname distributions of 22.6 million electors registered for the year 2001 were analyzed in the 24 districts (distritos) and 541 municipalities (municipios) of the country. The number of different surnames found was 414,441. Matrices of isonymic distances between districts were constructed and tested for correlation with the geographic distance between the capital towns of the districts. We found that, for the whole of Argentina, Euclidean distance was correlated with the log of geographic distance (r=0.480+/- 0.067). A dendrogram of the 24 regions was built from the matrix of Euclidean distances, using the UPGMA method. The clusters identified by the dendrogram are coincident with conterminous geographical regions of the country. Random inbreeding calculated from isonymy, F(ST), was highest in La Rioja, Corrientes, and Santiago del Estero. It was lowest in the area of Buenos Aires and in the north-central region of Santa Fé. Average Fisher's alpha for municipalities was 358; for districts, it was 422; and for Argentina as a unit, it was 602. The geographical distribution of alpha in 541 municipalities, high in the east and lower in the west of the country, is compatible with the settlement in the 20th century of subsequent waves of immigrants moving from the North Atlantic coast toward the foot of the Andes and toward the south. The present structure of Argentina indicates that migration dominates over drift.     

Density-based load estimation using two-dimensional finite element models: a parametric study

A parametric investigation was conducted to determine the effects on the load estimation method of varying: (1) the thickness of back-plates used in the two-dimensional finite element models of long bones, (2) the number of columns of nodes in the outer medial and lateral sections of the diaphysis to which the back-plate multipoint constraints are applied and (3) the region of bone used in the optimization procedure of the density-based load estimation technique. The study is performed using two-dimensional finite element models of the proximal femora of a chimpanzee, gorilla, lion and grizzly bear. It is shown that the density-based load estimation can be made more efficient and accurate by restricting the stimulus optimization region to the metaphysis/epiphysis. In addition, a simple method, based on the variation of diaphyseal cortical thickness, is developed for assigning the thickness to the back-plate. It is also shown that the number of columns of nodes used as multipoint constraints does not have a significant effect on the method.     

Density-based load estimation using two-dimensional finite element models: a parametric study

A parametric investigation was conducted to determine the effects on the load estimation method of varying: (1) the thickness of back-plates used in the two-dimensional finite element models of long bones, (2) the number of columns of nodes in the outer medial and lateral sections of the diaphysis to which the back-plate multipoint constraints are applied and (3) the region of bone used in the optimization procedure of the density-based load estimation technique. The study is performed using two-dimensional finite element models of the proximal femora of a chimpanzee, gorilla, lion and grizzly bear. It is shown that the density-based load estimation can be made more efficient and accurate by restricting the stimulus optimization region to the metaphysis/epiphysis. In addition, a simple method, based on the variation of diaphyseal cortical thickness, is developed for assigning the thickness to the back-plate. It is also shown that the number of columns of nodes used as multipoint constraints does not have a significant effect on the method.     

Misunderstandings in prescribing decisions in general practice: qualitative study

ObjectivesTo identify and describe misunderstandings between patients and doctors associated with prescribing decisions in general practice.DesignQualitative study.Setting20 general practices in the West Midlands and south east England.Participants20 general practitioners and 35 consulting patients.Results14 categories of misunderstanding were identified relating to patient information unknown to the doctor, doctor information unknown to the patient, conflicting information, disagreement about attribution of side effects, failure of communication about doctor''s decision, and relationship factors. All the misunderstandings were associated with lack of patients'' participation in the consultation in terms of the voicing of expectations and preferences or the voicing of responses to doctors'' decisions and actions. They were all associated with potential or actual adverse outcomes such as non-adherence to treatment. Many were based on inaccurate guesses and assumptions. In particular doctors seemed unaware of the relevance of patients'' ideas about medicines for successful prescribing.ConclusionsPatients'' participation in the consultation and the adverse consequences of lack of participation are important. The authors are developing an educational intervention that builds on these findings.     

Complexity is costly: a meta‐analysis of parametric and non‐parametric methods for short‐term population forecasting

Short‐term forecasts based on time series of counts or survey data are widely used in population biology to provide advice concerning the management, harvest and conservation of natural populations. A common approach to produce these forecasts uses time‐series models, of different types, fit to time series of counts. Similar time‐series models are used in many other disciplines, however relative to the data available in these other disciplines, population data are often unusually short and noisy and models that perform well for data from other disciplines may not be appropriate for population data. In order to study the performance of time‐series forecasting models for natural animal population data, we assembled 2379 time series of vertebrate population indices from actual surveys. Our data were comprised of three vastly different types: highly variable (marine fish productivity), strongly cyclic (adult salmon counts), and small variance but long‐memory (bird and mammal counts). We tested the predictive performance of 49 different forecasting models grouped into three broad classes: autoregressive time‐series models, non‐linear regression‐type models and non‐parametric time‐series models. Low‐dimensional parametric autoregressive models gave the most accurate forecasts across a wide range of taxa; the most accurate model was one that simply treated the most recent observation as the forecast. More complex parametric and non‐parametric models performed worse, except when applied to highly cyclic species. Across taxa, certain life history characteristics were correlated with lower forecast error; specifically, we found that better forecasts were correlated with attributes of slow growing species: large maximum age and size for fishes and high trophic level for birds. Synthesis Evaluating the data support for multiple plausible models has been an integral focus of many ecological analyses. However, the most commonly used tools to quantify support have weighted models’ hindcasting and forecasting abilities. For many applications, predicting the past may be of little interest. Concentrating only on the future predictive performance of time series models, we performed a forecasting competition among many different kinds of statistical models, applying each to many different kinds of vertebrate time series of population abundance. Low‐dimensional (simple) models performed well overall, but more complex models did slightly better when applied to time series of cyclic species (e.g. salmon).     

Congenital hip disease in a Cree-Ojibwa population: a retrospective study.

Retrospective study of data from annual surveys and hospital records over 23 years confirmed the 1950 report of a high prevalence of congenital hip disease (CHD) in the Cree-Ojibwa population of Island Lake, Man. Annual ascertainment rates ranged from 35 to 600 cases per 1000 live births; 5-year rates for dislocation or subluxation were the highest reported for any population. The minimally declining rates of CHD may reflect upgrading in criteria for hip abnormality as well as decreasing isolation and increasing outbreeding of the population. The preponderance of females (female:male ratio, 1.90:1) was low compared with that found in other studies. For all diagnoses bilateral hip involvement exceeded unilateral in frequency; laterality differences were not significant when the sexes were studied separately. Function in everyday activities was impaired little.     

Pulmonary function of a firemen-diver population: a longitudinal study

Non smoking, male professional firemen-divers (n = 20) underwent two pulmonary function tests (PFT) separated by 8–9 years. Measured data were compared to European Coal Steel Community recommended reference values to permit cross-sectional and then longitudinal studies. Higher vital capacity (VC) and forced expiratory volume in 1 s (FEV₁; bothP<0.001), and lower residual volume (P<0.01) were observed in both PFT. Longitudinal analysis showed a smaller VC reduction than FEV₁ reduction, leading to a FEV₁/VC percentage decrease with time. Maximal mid expiratory flow (MMEF) and MMEF/VC changes during this 9-year period showed an unusually pronounced decrease, suggesting possible chronic effects of diving on small airways. Thus, it is suggested from our observations that a hyperbaric stimulus compensates in part for the effects of aging on VC and that obstructive disease could occur in subjects with long diving experience.