树干径流过程的计算机模拟

本文应用系统分析方法,将树干径流过程这一连续系统离散化,编制程序,以计算机直接模拟过程行为,绕过了解微分方程之烦恼,并取得了满意的结果。此举对扩展系统分析概念,研究连续系统颇有意义。     

Growth and refuge location in continuous,modular organisms: experimental and computer simulation studies

Summary Guilds of crustose bryozoans exhibited a range of growth outlines, varying from circular to elongate, and the stones on which they grew contained a range of refuge types, varying in size from a few mm² to a few hundred cm². These refuges, if encountered by the growing colonies of competitively subordinate species such as Electra pilosa L., enabled the latter to avoid competitive exclusion due to overgrowth mortality. Computer simulations suggested that, although modular organisms which are elongate are, in general, more likely to encounter spatial refuges than those with a different shape through vegetative growth, shape is less important than the size of the organisms themselves or the size and density of the spatial refuges. Moreover significant interactions between these 4 variables showed that they should be considered together and not in isolation from one another. Examples are given of variable growth forms in continuous, modular organisms from different taxa, including plants, and the importance of these predictive studies to refuge location by modular organisms is discussed.     

Physical growth of St. Lawrence Island Eskimos: Body size,proportion, and composition

Growth patterns of body size, proportion, and composition were analyzed in 57 male and 56 female Eskimos from St. Lawrence Island in the Bering Sea, ranging in age from 1.23 through 19.82 years. Age-groups means for whites and blacks of the U.S. Health Examination Survey served as reference data. Relative to HES data, the Eskimo sample were shorter with lower values for leg length, while there were no differences from the reference values for sitting height. The Eskimos also had higher values of Quetelet's Index, the sitting height/height ratio, and the upper arm muscle circumference, while there were no differences in body weight or triceps skinfold thickness. Differences from the reference data were more pronounced in males than in females. The growth patterns for size and body proportion are in conformity with known relationships between morphology and climate.     

Contact pressure models for spiral phyllotaxis and their computer simulation

We present a simple, biologically motivated model for the creation of phyllotactical patterns in capitula and their computer simulation. An in-depth investigation of Ridley's contact pressure model is performed and a refinement of contact pressure between primordia on the basis of local centroidal Voronoi relaxation is presented. Using this method in combination with Hofmeisters rule for placing new primordia creates stable patterns with Fibonacci spirals of high degree for a large range of initial conditions.     

The St. Lawrence Island Eskimos: genetic variation and genetic distance

The Eskimos of St. Lawrence Island have been typed for genetic variation at 44 discrete genetic loci. Three private polymorphisms, at the 2,3-diphosphoglycerate mutase, peptidase B, and purine nucleoside phosphorylase loci, have been observed, which may be useful in future studies of genetic relationships between Eskimos and other circumpolar populations. Genetic distance analysis reveals a close relationship between the St. Lawrence Island Eskimos and other Eskimo populations and that the Eskimo populations form a distinct cluster from Amerindian populations. The St. Lawrence Island Eskimos appear to be more similar to Asiatic Eskimos than to other groups. Caucasian admixture in this population is estimated to be between 2 and 7%.     

Supraorbital ridge and masticatory apparatus II: Humans (Eskimos)

Thirteen adult male skulls of St. Lawrence Island Eskimos were studied to determine the factor or factors responsible for the development of the supraorbital ridges. Results showed that the determining factor is the ratio of the power arm to the load arm of the mandible. The smaller this ratio, the greater the traction force exerted by the anterior temporalis muscle and the greater the supraorbital ridge. Pearson’s correlation coefficient shows two positive correlations, i.e. between the anterior temporalis muscle and the ridge and between the ridge/sinus and the anterior/whole temporalis muscle. Conversely, there is a negative correlation between the power/load arm and the muscle ratio as well as between the power/load arm ratio and the ridge/sinus ratio.     

Global Kinetic Explorer: A new computer program for dynamic simulation and fitting of kinetic data

We describe a new dynamic kinetic simulation program that allows multiple data sets to be fit simultaneously to a single model based on numerical integration of the rate equations describing the reaction mechanism. Unlike other programs that allow fitting based on numerical integration of rate equations, in the dynamic simulation rate constants, output factors, and starting concentrations of reactants can be scrolled while observing the change in the shape of the simulated reaction curves. Fast dynamic simulation facilitates the exploration of initial parameters that serve as the starting point for nonlinear regression in fitting data and facilitates exploration of the relationships between individual constants and observable reactions. The exploration of parameter space by dynamic simulation provides a powerful tool for learning kinetics and for evaluating the extent to which parameters are constrained by the data. This feature is critical to avoid overly complex models that are not supported by the data.     

Analysis and computer simulation of accretion patterns in bacterial cultures

Patterned growth of bacteria created by interactions between the cells and moving gradients of nutrients and chemical buffers is observed frequently in laboratory experiments on agar pour plates. This has been investigated by several microbiologists and mathematicians usually focusing on some hysteretic mechanism, such as dependence of cell uptake kinetics on pH. We show here that a simpler mechanism, one based on cell torpor, can explain patterned growth. In particular, we suppose that the cell population comprises two subpopulations —one actively growing and the other inactive. Cells can switch between the two populations depending on the quality of their environment (nutrient availability, pH, etc.) We formulate here a model of this system, derive and analyze numerical schemes for solving it, and present several computer simulations of the system that illustrate various patterns formed. These compare favorably with observed experiments.     

Distribution of albumin variants Naskapi amd Mexico among Aleuts, Frobisher Bay Eskimos, and Micmac, Naskapi, Mohawk, Omaha, and Apache Indians

In order to help define the boundaries of the distribution of the albumin variants Naskapi and Mexico which are polymorphic among several American Indian groups, we examined sera from Micmac, Mohawk, Northwest River Naskapi, Omaha and Apache Indians, and from Aleuts and Eskimos. Sera from a total of 1,524 individuals were examined. Using a cellulose acetate membrane electrophoretic system with Tris-Citric acid at pH 5.4 we were able to distinguish normal albumin and both variants in the same run. Naskapi and Mexico variants were absent from Aleut, Eskimo, Micmac, Mohawk and Omaha samples. The albumin Naskapi variant was present in an allele frequency of 0.03 in the Naskapi Indian sample. Albumin variants Naskapi and Mexico were found in the Apache sample at frequencies of 0.016 and 0.037, respectively. This report supersedes that previously published by Schell and Agarwal ('76). Generally, within an area there is a correspondence between changes in the frequency of albumin variants and changes in the ethnic background and history of the area's populations. At the same time, when viewing widely separated areas, relationships between distant groups based on linguistic and cultural similarities are paralleled on a biologic level by the distribution of normal albumin and variant albumins.     

Evaluation of marker-assisted selection through computer simulation

Computer simulation was used to evaluate responses to marker-assisted selection (MAS) and to compare MAS responses with those typical of phenotypic recurrent selection (PRS) in an allogamous annual crop species such as maize (Zea mays L.). Relative to PRS, MAS produced rapid responses early in the selection process; however, the rate of these responses diminished greatly within three to five cycles. The gains from MAS ranged from 44.7 to 99.5% of the maximum potential, depending on the genetic model considered. Linkage distance between markers and quantitative trait loci (QTLs) was the factor which most limited the responses from MAS. When averaged across all models considered, flanking QTLs within two marker loci produced 38% more gain than did selection based on single markers if markers were loosely-linked to a QTL (20% recombination). Flanking markers were much less advantageous when markers were closely-linked to a QTL (5% recombination), producing an advantage over single markers of only 11%. Markers were most effective in fully exploiting the genetic potential when fewer QTLs controlled the trait. Large QTL numbers exacerbated the problem of marker-QTL recombination by requiring more generations for fixation. In annual crop species, MAS may offer a primary advantage of enabling two selection cycles per year versus the 2 years per cycle required by most PRS schemes for the evaluation of testcross progeny. MAS thus appears to allow very rapid gains for the first 2–3 years of recurrent selection, after which time conventional methods might replace MAS to achieve further responses.Publication number 19, 330 of the Minnesota Agricultural Experiment Station     

Ovarian hydrobursitis in female camels (Camelus dromedarius): clinical findings, histopathology and fertility after unilateral surgical ablation

This study was undertaken to verify the clinical signs, incidence, location, etiology and pathology of ovarian hydrobursitis in infertile female camels and estimate the fertility after unilateral surgical ablation. Genital organs (n = 124) were examined in camels slaughtered at Makkah abattoir during Hajj of 2009. Infertile female camels (n = 142) presented for management to the Veterinary Teaching Hospital, Qassim University, Saudi Arabia, were clinically examined and ultrasound-scanned for the diagnosis of genital abnormalities. Twenty eight camels diagnosed with ovarian hydrobursitis were further investigated for the effect of unilateral surgical ablation on breeding outcomes. Surgical ablation was carried on 14 cases (treated group), the remaining 14 cases were followed as controls (control group). Both groups were observed for breeding results: 90 days non-return rate (90d NRR) and calving rate (CR). Removed bursae were sent to the laboratory for histopathological investigation. Results showed that the incidence of ovarian hydrobursitis was 6.5% in slaughtered camels and 33.8% in infertile females. Camels with hydrobursitis were concurrently affected with pyometra, uterine and vaginal adhesions or purulent endometritis. Histopathology reported degeneration and hyperplasia of the lining epithelium, mononuclear cells infiltration, focal aggregation of inflammatory cells, cystic dilatation of multi-acinal structures, tiny hemorrhages, and presence of hemosiderin-laden macrophages. The 90d NRR and CR of the surgically-treated cases were 64.3% and 50%, respectively. None of the untreated cases conceived. These results confirmed that ovarian hydrobursitis causes infertility in dromedary female camels and is associated with inflammatory genital conditions and surgical ablation in unilaterally affected animals presents a potential treatment.     

On investigating the statistical properties of the populous path algorithm by computer simulation

Summary Goodman et al.'s (1974) populous path algorithm for estimating hidden mutational change in protein evolution is designed to be used as an adjunct to the maximum parsimony method. When the algorithm is so used, the augmented maximum parsimony distances, far from being overestimates, are underestimates of the actual number of nucleotide substitutions which occur in Tateno and Nei's (1978) computer simulation by the Poisson process model, even when the simulation is carried out at two and a half times the sequence density. Although underestimates, our evidence shows that they are nevertheless more accurate than estimates obtained by a Poisson correction. In the maximum parsimony reconstruction, there is a bias towards overrepresenting the number of shared nucleotide identities between adjacent ancestral and descendant nodal sequences with the bias being stronger in those portions of the evolutionary tree sparser in sequence data. Because of this particular property of maximum parsimony reconstructed sequences, the conclusions of Tateno and Nei concerning the statistical properties of the populous path algorithm are invalid. We conclude that estimates of protein evolutionary rates by the maximum parsimony - populous path approach will become more accurate rather than less as larger numbers of closely related species are included in the analysis.     

Different types of rectification at electrical synapses made by a single crayfish neurone investigated experimentally and by computer simulation

Summary The rectification properties of electrical synapses made by the segmental giant (SG) neurone of crayfish (Pacifastacus leniusculus) were investigated. The SG acts as an interneurone, transmitting information from the giant command fibres (GFs) to the abdominal fast flexor (FF) motoneurones. The GF-SG (input) synapses are inwardly-rectifying electrical synapses, while the SG-FF (output) synapses are outwardly rectifying electrical synapses. This implies that a single neurone can make gap junction hemichannels with different rectification properties.The coupling coefficient of these synapses is dependent upon transjunctional potential. There is a standing gradient in resting potential between the GFs, SG and FFs, with the GFs the most hyperpolarized, and the FFs the most depolarized. The gradient thus biases each synapse into the low-conductance state under resting conditions.There is functional double rectification between the bilateral pairs of SGs within a single segment, such that depolarizing membrane potential changes of either SG pass to the other SG with less attenuation than do hyperpolarizing potential changes. Computer simulation suggests that this may result from coupling through the intermediary FF neurones.Abbreviations l left - r right - FF fast flexor motoneurone - GF giant fibre - LG lateral giant interneurone - MG medial giant interneurone - MoG motor giant motoneurone - R root, e.g. 1R1 is the first root on the left side - SG Segmental giant neurone     

Genetic selection in presence of pathogens such as the lymphoid leukosis virus: computer simulation

Summary A computer model was developed to simulate the population dynamics involved when selection is for a trait influenced by the presence of a pathogen in addition to quantitative genetic factors. The lymphoid leukosis virus is such a pathogen, when selection is for egg production in chickens. It is transmitted congenitally from dam to offspring and horizontally from one individual to another. For these simulations, individual selection for high performance in the trait influenced by the pathogen was more effective than family selection for removing infected individuals from populations. The resulting reduction in the incidence of infected individuals in following generations made the overall response to individual selection greater than for family selection. However, the virus would remain in most populations due to horizontal transmission to individuals which later transmit the virus to their offspring. These horizontally infected individuals would not be eliminated in the selection process because their egg production was assumed to be less reduced than that of congenitally infected birds. These simulation results seem to mimic certain experimental results which heretofore have been difficult to explain since they were not consistent with quantitative genetic theoretical expectations from selection.Journal Paper No. 9028 of the Purdue Agricultural Experiment StationAnimal Research Centre Contribution No. 1145     

A study of hominin dispersal out of Africa using computer simulations

A study of hominin dispersal out of Africa using computer simulations is presented. Attention is focused on the joint probability of the colonization of Western Europe later than 1 Ma and that of Eastern Asia prior to 1.6 or 1.8 Ma, as current archaeological estimates suggest. We found that the determinant factor to hominin dispersal is the mode of hominin movement. If the movement of all populations is uniform and their number great enough, greater than 300 in our models, then such movement favors the colonization of Eastern Asia and Western Europe at more or less the same time. On the other hand, the colonization acquires prominent probabilistic features if the number of populations migrating is small enough, smaller than 10 in our models, or when all hominin populations may move but there are only a few with much higher mobility. In this case, the joint probability for the earliest dispersals of hominins in Western Europe after 1 Ma and Eastern Asia prior to 1.6 Ma ranges from 0.02 to 0.05. The single probability of colonization of Western Europe after 1 Ma is very high, about 0.5 for the majority of the colonization routes, whereas the corresponding probability of the colonization of Eastern Asia prior to 1.6 Ma is ten times lower, about 0.05. The least probable event is the earliest colonization of Java prior to 1.6 Ma, to which our simulation attributes a probability of ca 0.01. Deserts, mountains, and mountain ranges may delay the arrival at a certain location; nevertheless, their effect on the joint probability is very small.     

Aneuploidy in rabbit males: semen traits and fertility

Chromosomal analyses were performed from peripheral blood samples from 20 adult rabbit males from Line R. This line has been selected for growth rate after weaning through 25 generations. Seminal characteristics and reproductive outcomes from these males were also examined. The chromosomal analysis results showed that one male had an aneuploidy rate of 16% (male A). The aneuploidies found represented both hypo- and hyper- haploidy. Differences between the male A and the contemporary males (males N), in fertility at 12 days post-insemination (44% vs. 66%) and at birth (31% vs. 59%) were observed. The male A also showed a high percentage of pregnancy losses (29% vs. 12%). For seminal characteristics, the percentage of abnormal spermatozoa was statistically different (P < 0.05) between male A and males N (34 ± 4 vs. 18 ± 2), and concentration differed significantly between males, showing the male A reduced fewer spermatozoa than males N (67 ± 23 vs. 172 ± 10, x106/ml). Motility and kinematic parameters revealed no differences between males. Differences between male reproductive performance found in this study could be explained by the effect of aneuploidy on spermatogenesis and its deleterious effect on male reproduction.     

Tyrosinase positive oculocutaneous albinism among the Zuni and the Brandywine triracial isolate: biochemical and clinical characteristics and fertility

Zuni albinos develop increased pigmentation in hair and eyes, and decreased nystagmus and photophobia with age. Hair bulbs cultured in l-tyrosine produced pigment. Ultrastructure of melanocytes demonstrated a predominance of Stage II and early Stage III premelanosomes that readily converted to mature Stage IV melanosomes after incubation in 1-tyrosine. Eleven obligate heterozygotes failed to demonstrate diaphanous irides. Data on the fertility of Zuni and Brandywine male albinos did not indicate that they had more offspring than pigmented males. As the physical features of this form of albinism overlap those of many normal Caucasians, it is probably not a particularly deleterious trait with high selective value under the recent conditions of Zuni life.     

Sleep problems and computer use during work and leisure: Cross-sectional study among 7800 adults

Previous studies linked heavy computer use to disturbed sleep. This study investigates the association between computer use during work and leisure and sleep problems in working adults. From the 2010 round of the Danish Work Environment Cohort Study, currently employed wage earners on daytime schedule (N?=?7883) replied to the Bergen insomnia scale and questions on weekly duration of computer use. Results showed that sleep problems for three or more days per week (average of six questions) were experienced by 14.9% of the respondents. Logistic regression analyses, controlled for gender, age, physical and psychosocial work factors, lifestyle, chronic disease and mental health showed that computer use during leisure for 30 or more hours per week (reference 0–10 hours per week) was associated with increased odds of sleep problems (OR 1.83 [95% CI 1.06–3.17]). Computer use during work and shorter duration of computer use during leisure were not associated with sleep problems. In conclusion, excessive computer use during leisure – but not work – is associated with sleep problems in adults working on daytime schedule.     

Reaction kinetics and mechanisms of penicillin amidase: A comparative study by computer simulation

Based on experimental results, two different kinetic models and reaction mechanisms of penicillin amidase (penicillin amidohydrolase EC 3.5.1.11) have been studied and analysed. The enzyme from Escherichia coli shows an ordered uni-bi reaction mechanism while the enzyme from Bacillus megaterium shows kinetics of double inhibition by the reaction products. The difference in the reaction mechanism is elucidated by two possible mechanistic models on a theoretical basis. Also suggested is the analytical method by which two different reaction mechanisms can be tested and confirmed.