Bayesian experimental design for nonlinear mixed-effects models with application to HIV dynamics

Bayesian experimental design is investigated for Bayesian analysis of nonlinear mixed-effects models. Existence of the posterior risk for parameter estimation is shown. When the same prior distribution is used for both design and inference, existence of the preposterior risk for design is also proven. If the prior distribution used in design is different from that used for inference, sufficient conditions are established for existence of the preposterior risk for design. A case study of design for an experiment in population HIV dynamics is provided.     

草基-鱼塘生态系统的能量转化与养分循环研究

应用模拟试验的方法,研究了“草基-鱼塘”系统中的能量转化与养分循环.结果表明,该系统中饲草对太阳能的利用率为0.83%,鱼对饲料能的转化率为7.3%.与以粮食作为鱼饲料比较,单位面积草地的产鱼当量是粮食作物的1.6倍.鱼对饲料N、P、K的转化率分别为16.8%、32.3%和2.0%.塘泥沉积的N、P分别占饲料的23.4%和56.1%;猪对饲料N、P、K的转化率分别为20.5%、33.7%和4.6%,猪粪尿回收饲料N为36.4%、P为63.8%、K为39.4%.猪-草-鱼结合的基塘系统其能量和养分转化效率均高于单一的养鱼系统.     

Age Determination of Bovine Foetuses

The need for methods for age determination of foetuses is defined. X-ray examination of the foetal head is recommended as the surest basis for age determination. Calculations are made concerning the correlation between cranial length and foetal age, and the methods used for measurements are described in detail. Measurements of the metacarpus and metatarsus may also be used, but they give a poorer correlation. A formula is worked out for age determination based on cranial measurements. On x-ray photographs, tooth development is seen to occur in an obvious sequence. This is described. However, the interpretation of these observations is subjective and requires control material for comparison. The same is true for the sequence of ossification of the skeleton, which in foetuses < 120 days gives the surest basis for evaluation. Here, too, a wide range of control material for comparison is necessary. The sequence in the appearance of body hair — development and eruption — is noted, as far as the head is concerned. This alone gives an insecure basis for evaluation. By using the 4 systems of parameters mentioned, the age of a foetus can be determined within an error of ± 4—5 days.     

草基—鱼塘生态系统的能量转化与养分循环研究

应用模拟试验的方法,研究了“草基-鱼塘”系统中的能量转化与养分循环．结果 表明,该系统中饲草对太阳能的利用率为 ０． ８３％,鱼对饲料能的转化率为 ７． ３％．与以粮 食作为鱼饲料比较,单位面积草地的产鱼当量是粮食作物的１．６倍．鱼对饲料Ｎ、Ｐ、Ｋ的 转化率分别为１６．８％、３２．３％和２．０％．塘泥沉积的Ｎ、Ｐ分别占饲料的２３．４％和５６．１％; 猪对饲料 Ｎ、 Ｐ、 Ｋ的转化率分别为 ２０． ５％、 ３３． ７％和 ４． ６％,猪粪尿回收饲料 Ｎ为 ３６． ４％、 Ｐ为 ６３． ８％、 Ｋ为 ３９． ４％．猪-草-鱼结合的基塘系统其能量和养分转化效率均高于单一的 养鱼系统．     

湖南土家族的体质特征

以20至69岁的湖南土家族人为观察测量对象,根据1392人(男896,女496)的身高,1038人(男668,女370)的头部测量,364人(男235,女129)的五官测量和观察结果,分析该民族的体质特征,并与国内其他民族相比较。     

SIR-SVS epidemic models with continuous and impulsive vaccination strategies

Vaccination is important for the control of some infectious diseases. This paper considers two SIR-SVS epidemic models with vaccination, where it is assumed that the vaccination for the newborns is continuous in the two models, and that the vaccination for the susceptible individuals is continuous and impulsive, respectively. The basic reproduction numbers of two models, determining whether the disease dies out or persists eventually, are all obtained. For the model with continuous vaccination for the susceptibles, the global stability is proved by using the Lyapunov function. Especially for the endemic equilibrium, to prove the negative definiteness of the derivative of the Lyapunov function for all the feasible values of parameters, it is expressed in three different forms for all the feasible values of parameters. For the model with pulse vaccination for the susceptibles, the global stability of the disease free periodic solution is proved by the comparison theorem of impulsive differential equations. At last, the effect of vaccination strategies on the control of the disease transmission is discussed, and two types of vaccination strategies for the susceptible individuals are also compared.     

Seasonal population dynamics of ticks,and its influence on infection transmission: A semi-discrete approach

In this paper, a simple semi-discrete (ticks’ feeding is assumed to occur only during the summers of each year) model for tick population dynamics is presented. Conditions for existence, uniqueness, and stability of a positive equilibrium are found; the system is then studied numerically using parameter estimates calibrated for the tick Ixodes ricinus in Trentino, Italy, and the sensitivity to parameters is examined. Then, this model is extended to consider a tick-transmitted infection of one species of hosts, while other hosts are incompetent to the infection. Assuming, for simplicity, that the infection is not affecting the total number either of hosts or ticks, a threshold condition for infection persistence is obtained. The dependence of the equilibrium infection prevalence on parameters is studied numerically; in particular, we considered how infection prevalence depends on host densities. This analysis reveals that a ‘dilution effect’ occurs both for competent and for incompetent hosts; this means that, besides a lower threshold for host densities for infection to persist, there exists also an upper threshold: if host densities were higher than the upper threshold, the infection would go to extinction. Numerically, it is found that, for realistic parameter values, the upper threshold is not much higher than observed densities.     

A component of C. elegans meiotic chromosome axes at the interface of homolog alignment, synapsis, nuclear reorganization, and recombination

A universal feature of meiotic prophase is the pairing of homologous chromosomes, a fundamental prerequisite for the successful completion of all subsequent meiotic events. HIM-3 is a Caenorhabditis elegans meiosis-specific non-cohesin component of chromosome axes that is required for synapsis. Our characterization of new him-3 alleles reveals previously unknown functions for the protein. HIM-3 is required for the establishment of initial contacts between homologs, for the nuclear reorganization characteristic of early meiotic prophase, and for the coordination of these events with synaptonemal complex (SC) assembly. Despite the absence of homolog alignment, we find that recombination is initiated efficiently, indicating that initial pairing is not a prerequisite for early steps of the recombination pathway. Surprisingly, RAD-51-marked recombination intermediates disappear with apparent wild-type kinetics in him-3 null mutants in which homologs are spatially unavailable for recombination, raising the possibility that HIM-3's presence at chromosome axes inhibits the use of sister chromatids as templates for repair. We propose that HIM-3 is a molecular link between multiple landmark events of meiotic prophase; it is critical for establishing chromosome identity by configuring homologs to facilitate their recognition while simultaneously imposing structural constraints that later promote the formation of the crossover essential for proper segregation.     

The effect of glutamine concentration on the activity of carbamoyl-phosphate synthase II and on the incorporation of [3H]thymidine into DNA in rat mesenteric lymphocytes stimulated by phytohaemagglutinin.

The maximum catalytic activities of carbamoyl-phosphate synthase II, a limiting enzyme for pyrimidine nucleotide synthesis, are very much less than those of glutaminase, a limiting enzyme for glutamine utilization, in lymphocytes and macrophages; and the flux through the pathway for pyrimidine formation de novo is only about 0.4% of the rate of glutamine utilization by lymphocytes. The Km of synthase II for glutamine is about 16 microM and the concentration of glutamine necessary to stimulate lymphocyte proliferation half-maximally is about 21 microM. This agreement suggests that the importance of glutamine for these cells is provision of nitrogen for biosynthesis of pyrimidine nucleotides (and probably purine nucleotides). However, the glutamine concentration necessary for half-maximal stimulation of glutamine utilization (glutaminolysis) by the lymphocytes is 2.5 mM. The fact that the rate of glutamine utilization by lymphocytes is markedly in excess of the rate of the pathway for pyrimidine nucleotide synthesis de novo and that the Km and 'half-maximal concentration' values are so different, suggests that the glutaminolytic pathway is independent of the use of glutamine nitrogen for pyrimidine synthesis.     

An extension of the proportional-hazards model for grouped data

A family of transformations for probabilities is considered for the analysis of grouped survival data. Additive and multiplicative models for the hazard function are compared. A method is suggested for estimating the scale on which an additive representation of the hazard, in terms of explanatory variables, is appropriate. Computations are performed using GLIM. A test for departures from the grouped proportional-hazards model is introduced. An example is analyzed by the methods put forward.     

Likelihood of a particular order of genetic markers and the construction of genetic maps

We model the recombination process of fungal systems via chromatid exchange in meiosis, which accounts for any type of bivalent configuration in a genetic interval in any specified order of genetic markers, for both random spore and tetrad data. First, a probability model framework is developed for two genes and then generalized for an arbitrary number of genes. Maximum likelihood estimators (MLEs) for both random and tetrad data are developed. It is shown that the MLE of recombination for tetrad data is uniformly more efficient over that from random spore data by a factor of at least 4 usually. The MLE for the generalized probability framework is computed using the expectation-maximization (EM) algorithm. Pearson's chi-squared statistic is computed as a measure of goodness of fit using a product-multinomial setup. We implement our model with genetic marker data on the whole genome of Neurospora crassa. Simulated annealing is used to search for the best order of genetic markers for each chromosome, and the goodness of fit value is evaluated for model assumptions. Inferred map orders are corroborated by genomic sequence, with the exception of linkage groups I, II, and V.     

Thresholds of bifurcation of the degree of circular polarization of the bremsstrahlung-generated pump field harmonics in plasma

It is established that, for a Maxwellian plasma in a monochromatic pump field, the phenomenon of bifurcation of the degree of circular polarization of the field harmonics is of a universal nature. A general equation determining the thresholds for this phenomenon for arbitrary harmonics is derived, and a set of its solutions is presented for illustrative purposes.     

Statistical Testing for Seasonality in Data with Multiple Peaks and Troughs

EDWARDS'S test for seasonality is extended to multiple peaks and troughs. It is shown how the extended statistic may be adjusted for the population at risk and for unequal lengths of time intervals in the cycle of seasons. A simulation study shows that the extended test statistic is, for sample sizes N ≧ 100, very specific in detecting the number of peaks and troughs for which it is intended. The associated method of parameter estimation is also assessed; for N ≦ 100, the amplitude of a possibly adequate simple harmonic model is estimated well, but the initial value of the phase angle is not. Estimated percentage points for the extended test statistic are tabulated, and some recommendations are offered regarding usage of this method.     

METHODS FOR FASTER PARSIMONY ANALYSIS

Abstract — Several algorithms to speed up branch swapping searches for most parsimonious trees are described. The method for indirect tree length calculation when moving a clipped clade, based on final states for the divided tree, is expanded to take into account polymorphic characters, and to include the possibility of rejecting several locations as suboptimal by checking just one node. Three different algorithms for faster estimation of final state assignments for the divided tree based on calculations for the whole tree are presented. The first of these is approximate; it uses information from the final state sets for the whole tree. The second is exact, but it is slower than the first, and requires more memory; it is based on the union of the state sets of the descendants for each node. The third is also exact; it requires more memory and programming effort than the other two but it is faster, it is based on final and preliminary state sets for the whole tree ("incremental two-pass optimization"). Efficient ways to derive state assignments for collapsing trees, based on final states for the divided tree, are described. The recently proposed method of "incremental optimization" is discussed. It is likely that searches using that method will be no faster than searches using indirect calculation as originally described, and will be quite slower than the modified indirect calculation described here. Searches using that method will probably be significantly slowed down when zero-length branches are to be collapsed, since shortcuts for faster collapsing are not directly applicable.     

New principles and criteria in assessing pathogenic and opportunistic microorganisms

Using the ecological and natural-science approaches, the authors have come to the conclusion that microorganisms, pathogenic for humans (animals), are their parasites for whom the disease of their biological host is the necessary condition of their existence as a biological species. And accordingly, microorganisms, opportunistic in humans (animals) are their parasites and commensals, as well as saprophytes, for whom the disease of their host is not the necessary condition of their existence in nature. The biological host is a symbion necessary for the existence of pathogenic and most opportunistic microorganisms, but for a pathogenic microorganism the disease of the host is the result of symbiotic relationships, while for an opportunistic microorganism the disease of the host is the consequence of disturbances in symbiotic relationships. Such view of pathogenicity is important for creating a scientifically grounded theory of the liquidation of human infectious diseases.     

维吾尔族的体质特征研究

１９９１年５月,对新疆伊梨维吾尔族５２９人（男２７１,女２５８）进行了活体观察和测量。观察２９项,测量９２项。维吾尔族的主要特征是：黑直发,黑褐色眼,眉毛较浓密,大都有上眼脸皱褶,鼻根中等偏高,大多为直形鼻,鼻尖向前,鼻基部下垂,大多有达尔文结节,耳垢湿型。头面部指数分型,属于特短头型,阔头型和高头型。身材中等偏高,平均身高男１６８．６毫米,女１５７８．８毫米。     

演化极端结合分支分类方法

从生物演化的逆方向考虑,提出一种聚合的分支分类运算方法,称为演化极端结合分支分类法。文章阐明其设计思路、演算步骤,并以实例具体说明其演算过程。最后以演化长度系数、合理解与合理方法等概念,对演化极端结合法进行评价。     

Amalgam is a ligand for the transmembrane receptor neurotactin and is required for neurotactin-mediated cell adhesion and axon fasciculation in Drosophila

Neurotactin (NRT), a member of the cholinesterase-homologous protein family, is a heterophilic cell adhesion molecule that is required for proper axon guidance during Drosophila development. In this study, we identify amalgam (AMA), a member of the immunoglobulin superfamily, as a ligand for the NRT receptor. Using transfected Schneider 2 cells and embryonic primary cultures, we demonstrate that AMA is a secreted protein. Furthermore, AMA is necessary for NRT-expressing cells both to aggregate with themselves and to associate with embryonic primary culture cells. Aggregation assays performed with truncated NRT molecules reveal that the integrity of the cholinesterase-like extracellular domain was not required either for AMA binding or for adhesion, with only amino acids 347-482 of the extracellular domain being necessary for both activities. Moreover, the NRT cytoplasmic domain is required for NRT-mediated adhesion, although not for AMA binding. Using an ama-deficient stock, we find that ama function is not essential for viability. Pupae deficient for ama do exhibit defasciculation defects of the ocellar nerves similar to those found in nrt mutants.     

Does bone mineralization reflect economic conditions? An examination using a national US sample

BACKGROUND: Bone density is the most important determinant of osteoporotic fractures, which lead to significant morbidity, disability and mortality for older persons, particularly women. Sensitive periods for bone mineralization in infancy, childhood and adolescence overlap with those for height attainment. After peak density is reached in early adulthood, there is age-related decline. We ask whether bone density, as height, reflects economic conditions. SUBJECTS AND METHODS: Using the third National Health and Nutrition Examination Survey, a probability sample of the US population which over-sampled Blacks and Mexican Americans, we examine the associations between adult bone mineral content (BMC) adjusted for bone and body size and three economic indicators: education, height and the poverty income ratio (PIR). We compare four groups: US-born Whites, Blacks and Mexican Americans and Mexican-born Mexican Americans. RESULTS: Education is positively associated with BMC only for White women, although there are similar, non-significant associations for Black women and White and Black men. For women, BMC is more strongly associated with height for Mexican Americans, especially the Mexican-born, than for Whites. For men, the only significant association is a negative one with education for men born in Mexico. PIR is not significantly associated with BMC, although there is pattern of lower income being associated with lower BMC for Whites and Blacks and higher BMC for Mexican Americans. CONCLUSION: Bone density does not reflect economic conditions as strongly or consistently as does physical stature. However, for women there is evidence that lower economic status in childhood or adolescence is associated with lower bone density.     

The transmembrane nucleoporin NDC1 is required for targeting of ALADIN to nuclear pore complexes

NDC1 is a transmembrane nucleoporin that is required for NPC assembly and nucleocytoplasmic transport. We show here that NDC1 directly interacts with the nucleoporin ALADIN, mutations of which are responsible for triple-A syndrome, and that this interaction is required for targeting of ALADIN to nuclear pore complexes (NPCs). Furthermore, we show that NDC1 is required for selective nuclear import. Our findings suggest that NDC1-mediated localization of ALADIN to NPCs is essential for selective nuclear protein import, and that abrogation of the interaction between ALADIN and NDC1 may be important for the development of triple-A syndrome.