Interactions in a mixed bacterial population growing on methane in continuous culture

The growth of a mixed methane-utilizing culture in a continuous flow fermenter has been studied under both methane and oxygen limitation. Small additions of methanol have been shown to inhibit the methane-utilizing moiety in the culture and it has been shown that the Hyphomicrobium sp. in the mixed culture removes any inhibitory methanol. The interaction between the methane-utilizing Pseudomonas sp., and the Hyphomicrobium sp. has been explained and a model of the continuous mixed culture under oxygen limitation has been formulated. Qualitative predictions of transient phenomena by the model have been verified experimentally.     

Study on dynamic characteristics’ change of hippocampal neuron reduced models caused by the Alzheimer’s disease

In the paper, based on the electrophysiological experimental data, the Hippocampal neuron reduced model under the pathology condition of Alzheimer’s disease (AD) has been built by modifying parameters’ values. The reduced neuron model’s dynamic characteristics under effect of AD are comparatively studied. Under direct current stimulation, compared with the normal neuron model, the AD neuron model’s dynamic characteristics have obviously been changed. The neuron model under the AD condition undergoes supercritical Andronov–Hopf bifurcation from the rest state to the continuous discharge state. It is different from the neuron model under the normal condition, which undergoes saddle-node bifurcation. So, the neuron model changes into a resonator with monostable state from an integrator with bistable state under AD’s action. The research reveals the neuron model’s dynamic characteristics’ changing under effect of AD, and provides some theoretic basis for AD research by neurodynamics theory.     

一类含间隙分布时滞的种群增长模型的稳定性

本文首先利用间隙分布时滞函数来建立更为符合实际的种群增长模型,然后运用两种不同的方法,对其平衡位置的局部稳定性进行了全面的讨论,得出了局部渐近稳定的充分必要条件,在参数平面上划分出了稳定和不稳地的区域。     

The role of the carboxamide group in nicotinamide adenine dinucleotide in relation to hydride transfer: the reduced form of the dinucleotide as remedy in the modulation of neurotransmission

The stereochemical significance of the carboxamide group in combination with the ring nitrogen in NADH-NAD+ conversions has been demonstrated. This has been shown in model systems as well as under enzymatic conditions. The role of the carboxamide group in selective regiospecific interactions has been discussed for neurodegenerative diseases.     

Applications of Decision Support System: A Case Study of Solanaceous Vegetables

Crop simulation models constitute the major proportion in decision support systems. A large number of crop models have been developed for potato and few for tomato and peppers. In the literature, thirty three crop models have been reported to simulate potato, nine for tomato and six for peppers. Some of these models dealt with the climate change scenario and others with the crop management practices such as sowing time, irrigation, nitrogen, and insect-pests management. The most evaluated and applied models for potato include; SUBSTOR, and LINTUL-Potato, whereas CROPGRO-tomato model is the most tested and applied for tomato. The AQUACROP is the most widely used model to simulate the water dynamics. The CROPGRO model has been tested for elevated temperatures and CO₂ under greenhouse conditions for tomato. In tomato and peppers, almost similar models have been applied for field conditions as well as under greenhouse environments with some modifications. Nitrogen dynamics has been widely tested by employing the EU-Rotate-N model for tomato and peppers. Simulation studies dealing with changing climate conditions are rare in potato and are not found for tomato and peppers. To modify potato, tomato and peppers models for climate impact studies, it is required that they are (a) calibrated and evaluated with new cultivars under various agro-environmental conditions and (b) assessed under varying field conditions under changing climates and crop management practices, including temperature increases, water and nutrient management and their interactions. These comprehensive model studies and modifications need a collaborative international effort and a multi-year, large scale field research studies on potato, tomato and peppers.     

A General Class of Ratio‐Type Estimators Under Super‐Population Model

The problem of constructing classes of estimators for population mean has been widely discussed by various authors under design approach in sample surveys. An attempt by Upadhyaya , Singh , and Vos (1985) has been made to combine the usual mean and ratio estimator with suitable weights in order to define a general class of estimators. This paper is an attempt to study properties of the same estimator under super‐population model. Optimum weights have also been proposed. Results have been supported with some numerical examples.     

THE ROLE OF THE CARBOXAMIDE GROUP IN NICOTINAMIDE ADENINE DINUCLEOTIDE IN RELATION TO HYDRIDE TRANSFER: THE REDUCED FORM OF THE DINUCLEOTIDE AS REMEDY IN THE MODULATION OF NEUROTRANSMISSION

The stereochemical significance of the carboxamide group in combination with the ring nitrogen in NADH-NAD⁺ conversions has been demonstrated. This has been shown in model systems as well as under enzymatic conditions. The role of the carboxamide group in selective regiospecific interactions has been discused for neurodegenerative diseases.     

New coarse-grained DNA model

A new coarse-grained model of the DNA molecule has been proposed, which was elaborated on the basis of its all-atomic model analysis. The model has been shown to rather well reproduce the DNA structure under low and room temperatures. The Young's and torsion moduli calculated using the coarse-grained model are in close agreement with experimental data and the theoretical results of other authors. The model can be used for DNA fragments of several hundreds base pairs for rather long time scales (of the order of micros) and for simulating their interactions with other structures.     

Score test for missing at random or not under logistic missingness models

Missing data are frequently encountered in various disciplines and can be divided into three categories: missing completely at random (MCAR), missing at random (MAR), and missing not at random (MNAR). Valid statistical approaches to missing data depend crucially on correct identification of the underlying missingness mechanism. Although the problem of testing whether this mechanism is MCAR or MAR has been extensively studied, there has been very little research on testing MAR versus MNAR. A critical challenge that is faced when dealing with this problem is the issue of model identification under MNAR. In this paper, under a logistic model for the missing probability, we develop two score tests for the problem of whether the missingness mechanism is MAR or MNAR under a parametric model and a semiparametric location model on the regression function. The implementation of the score tests circumvents the identification issue as it requires only parameter estimation under the null MAR assumption. Our simulations and analysis of human immunodeficiency virus data show that the score tests have well-controlled type I errors and desirable powers.     

Evolutionary significance of the presence in mobile genetic elements of regulatory sites reacting to the environment. Regulatory site as a trigger

A mathematical model of the Markov's process type describing the duplicative transposition of mobile genetic elements (MGE) has been developed. The possible role of MGE containing regulatory sites activated under unfavourable conditions has been considered. An analysis of the model has shown that there may be such regimes of environmental changes (sharp but random changes of the environment parameters) when sufficiently reliable survival of population is dependent on such MGE.     

Branching process with emigration--a genetic model.

Solution of a genetic improvement problem under the model of assortative mating is proposed. This has been achieved through the technique applied to a branching process incorporating a generation-dependent emigration component. The model explains a population subject to culling against genes governing undesirable characters and this work has been tried for a diploid population with two alleles at a single locus, which may be extended to the multilocus case.     

New coarse-grained DNA model

A new coarse-grained model of the DNA molecule has been proposed, which was elaborated on the basis of its all-atomic model analysis. The model has been shown to rather well reproduce the DNA structure under low and room temperatures. The Young’s and torsion moduli calculated using the coarse-grained model are in close agreement with experimental data and the theoretical results of other authors. The model can be used for DNA fragments of several hundreds base pairs for rather long time scales (of the order of μs) and for simulating their interactions with other structures.     

Analysis of the Fixation of Discrete Genetic Structures by Means of an Integral Model of Evolution in a Mendelian One-Locus Population of Diploid Organisms

An integral model of the evolution of a Mendelian one-locus population of diploid organisms with continual allele diversity developing under density-limiting conditions or without density limitation has been proposed and analyzed. The model was used to study the mechanism of the appearance of discrete genetic structures, i.e., the fixation of a limited number of alleles. Local resistance of the resultant genetic distributions to homogeneous equiprobable mutations has been demonstrated.     

Mechanical buckling of artery under pulsatile pressure

Tortuosity that often occurs in carotid and other arteries has been shown to be associated with high blood pressure, atherosclerosis, and other diseases. However the mechanisms of tortuosity development are not clear. Our previous studies have suggested that arteries buckling could be a possible mechanism for the initiation of tortuous shape but artery buckling under pulsatile flow condition has not been fully studied. The objectives of this study were to determine the artery critical buckling pressure under pulsatile pressure both experimentally and theoretically, and to elucidate the relationship of critical pressures under pulsatile flow, steady flow, and static pressure. We first tested the buckling pressures of porcine carotid arteries under these loading conditions, and then proposed a nonlinear elastic artery model to examine the buckling pressures under pulsatile pressure conditions. Experimental results showed that under pulsatile pressure arteries buckled when the peak pressures were approximately equal to the critical buckling pressures under static pressure. This was also confirmed by model simulations at low pulse frequencies. Our results provide an effective tool to predict artery buckling pressure under pulsatile pressure.     

Analysis of the fixation of discrete genetic structures by means of an integral model of evolution in a Mendelian one-locus population of diploid organisms

An integral model of the evolution of a Mendelian one-locus population of diploid organisms with continual allele diversity developing under density-limiting conditions or without density limitation has been proposed and analyzed. The model was used to study the mechanism of the appearance of discrete genetic structures, i.e., the fixation of a limited number of alleles. Local resistance of the resultant genetic distributions to homogeneous equiprobable mutations has been demonstrated.     

Kinetic modeling of ATP synthesis by ATP synthase and its mechanistic implications

Based on the torsional mechanism of ATP synthesis by ATP synthase, a kinetic scheme has been developed in this work. The scheme considers adenine nucleotide transport, binding of substrates ADP and P(i), unbinding of product ATP, and ATP synthesis. This kinetic scheme has been analyzed mathematically, and a kinetic model has been obtained to explain the experimentally observed hyperbolic Michaellian dependence of the rate of ATP synthesis on the ADP concentration by ATP synthase under physiological steady-state operating conditions. The principal results of the kinetic model have been compared with the experimental data and an estimate of the enzymological kinetic parameters V(max), K(M), and K(I) has been determined. Mechanistic implications arising from further analysis of the kinetic model have been discussed. These biological implications provide deep insight into the sequence of events leading to ATP synthesis.     

长白落叶松幼苗在受控条件下干物质积累的模拟

本文通过建立长白落叶松(Larix olgensis)幼苗在受控环境条件下的净光合速率与温度和CO2 等因子之间的关系,模拟了在受控条件下长白落叶松幼苗的日净光合速率进程与生长季中日干物质积累过程,并预测了在温度与CO2 浓度改变后干物质积累的变化。     

Mathematical modelling of the effect of sole elasticity distribution on pronation.

A coronal plane model of a distributed elastic sole has been proposed and analyzed with respect to the effects of different medial-lateral elasticity distribution on pronation under quasi-static conditions. The distributed model consists of an array of linear vertical line springs. Under minimum energy assumption, the behavior of the top surface of the interface under resultant force and moment loading was shown to be equivalent to that of a rigid-body mechanism under the same loading. The model was then combined with a rigid-link model of the lower limb. Expressions that describe the relationship of the interface aggregate parameters with pronation and the center of pressure were obtained. These expressions were confirmed by an experiment in which the elastic distribution in the interface was systematically varied and the pronation angle and the center of pressure measured. The model has the potential of being a useful analytical tool in the design of elastic soles in running shoes.     

Terrestrial carbon storage resulting from CO2 and nitrogen fertilization in temperate grasslands

Abstract. A temperate grassland model has been used to simulate carbon sequestration under various environmental conditions. The results suggest that the CO₂ and nitrogen fertilization that has occurred may contribute appreciably to the so-called missing carbon sink, which it has been suggested must exist to balance the global carbon budget.