Central Place Foraging in Nonpatchy Habitats

This paper deal with a model of optimal foraging in a habitat with arbitrary food distribution. It takes into account an arbitrary risk cost related to the distance to the animal's nest. Food acquisition and risk cost are accounted for in common units of fitness. The resulting problem is solved in the context of Calculus of Variations. The optimal duration of absence from the nest and the optimal spatial allocation of foraging time are obtained: the optimal strategy leads to separate the habitat into a region to exploit and a region to ignore. The definition of these two distinct regions depends on the relative importance of risk and food availability. With realistic risk costs, the resulting strategy indicates a highly selective behaviour when far from the nest, as observed in field studies. The model is also extended to take account of the need of returning to the nest to guard it or to feed the young.     

A mathematical framework for optimal foraging of herbivores

The aim of this paper is to study a model of optimal foraging of herbivores (with special reference to ungulates) assuming that food distribution is arbitrary. Usually the analysis of foraging of herbivores in the framework of optimal foraging theory is based on the assumption of a patchy food distribution. We relax this assumption and we construct more realistic models. The main constraint of our model is the total amount of food which the animal may eat and the currency is the total foraging time. We represent total foraging time as a variational expression depending on food eaten and the length of the path. We prove that there exists a threshold for food acquisition. More explicitly, it exists a positive real number such that, at any point x of the path, the animal either eats till the density of food is decreased to the value or, if the density of food at x is less than , there it does not eat. We discuss the results and emphasize some biologically important relationships among model parameters and variables. Finally, we try to give a sound biological interpretation of our results.     

Using image and curve registration for measuring the goodness of fit of spatial and temporal predictions

Conventional measures of model fit for indexed data (e.g., time series or spatial data) summarize errors in y, for instance by integrating (or summing) the squared difference between predicted and measured values over a range of x. We propose an approach which recognizes that errors can occur in the x-direction as well. Instead of just measuring the difference between the predictions and observations at each site (or time), we first "deform" the predictions, stretching or compressing along the x-direction or directions, so as to improve the agreement between the observations and the deformed predictions. Error is then summarized by (a) the amount of deformation in x, and (b) the remaining difference in y between the data and the deformed predictions (i.e., the residual error in y after the deformation). A parameter, lambda, controls the tradeoff between (a) and (b), so that as lambda-->infinity no deformation is allowed, whereas for lambda=0 the deformation minimizes the errors in y. In some applications, the deformation itself is of interest because it characterizes the (temporal or spatial) structure of the errors. The optimal deformation can be computed by solving a system of nonlinear partial differential equations, or, for a unidimensional index, by using a dynamic programming algorithm. We illustrate the procedure with examples from nonlinear time series and fluid dynamics.     

Can marine protected areas enhance both economic and biological situations?

This paper investigates impacts of the creation of Marine Protected Areas (MPAs), in both economic and biological perspectives. The economic indicator is defined as the sum of discounted benefits derived from exploitation of the resource in the fishery sector, assumed to be optimally managed. The biological indicator is taken as the stock density of the resource. The basic fishery model (C.W. Clark, Mathematical Bioeconomics: The Optimal Management of Renewable Resources, second ed., John Wiley and Sons, New York, 1990) will serve as a convenient benchmark in comparing results with those that are derived from a model of two patchy populations (cf. R. Hannesson, Marine reserves: what would they accomplish, Mar. Resour. Econ. 13 (1998) 159). In the latter, a crucial characteristic is the migration coefficient with describes biological linkages between protected and unprotected areas. A set of situations where both economic and biological criteria are enhanced, after introducing a MPA, is presented. These results are obtained with the help of numerical simulations.     

天然牛黄对MODS大鼠保护作用的实验研究

目的:肠道内的消化酶在MODS发生发展过程中起着关键的作用,有研究发现非结合型胆红素可以灭活胰蛋白酶和糜蛋白酶.基于非结合型胆红素对消化酶的灭活作用,本研究主要探讨非结合型胆红素含量丰富的天然牛黄对多器宫功能障碍综合症大鼠的保护作用.方法:通过腹腔注射无菌石蜡酵母多糖混悬液的方法制作MODS大鼠模型.观察天然牛黄对MODS大鼠的生理状态,生命体征,血气分析,多指标系列生化检测,二胺氧化酶水平,以及心肺肝肾重要脏器病理组织学检查的变化及影响.结果:天然牛黄治疗纽大鼠生命体征,血气分析结果,生化指标,血清DAO水平与MODS模型纽比较,体温、心率、呼吸检测结果显著降低;pH、PaO2、SO2、AB、BE值升高,PaCO2值降低;LDH、ALT、Cr值减少;DAO水平降低,均有显著差异(P＜0.05),且心肺肝肾等组织病理变化也有明显改善.结论:天然牛黄能明显恢复石蜡酵母多糖混悬液造模方法引起的MODS大鼠生理状态,生命体征,能有效改善MODS大鼠脏器功能及病理形态,对MODS大鼠具有脏器保护作用.其机制可能是非结合型胆红素灭活消化酶所致,待进一步研究.     

The most likely voltage path and large deviations approximations for integrate-and-fire neurons

We develop theory and numerical methods for computing the most likely subthreshold voltage path of a noisy integrate-and-fire (IF) neuron, given observations of the neuron’s superthreshold spiking activity. This optimal voltage path satisfies a second-order ordinary differential (Euler-Lagrange) equation which may be solved analytically in a number of special cases, and which may be solved numerically in general via a simple “shooting” algorithm. Our results are applicable for both linear and nonlinear subthreshold dynamics, and in certain cases may be extended to correlated subthreshold noise sources. We also show how this optimal voltage may be used to obtain approximations to (1) the likelihood that an IF cell with a given set of parameters was responsible for the observed spike train; and (2) the instantaneous firing rate and interspike interval distribution of a given noisy IF cell. The latter probability approximations are based on the classical Freidlin-Wentzell theory of large deviations principles for stochastic differential equations. We close by comparing this most likely voltage path to the true observed subthreshold voltage trace in a case when intracellular voltage recordings are available in vitro. Action Editor: Peter Latham     

微创经皮肾穿刺碎石术（MPCNL）治疗上尿路结石的临床分析

目的：探讨微创经皮肾穿刺碎石术（MPCNL）用于治疗尿路结石的临床效果。方法：选取120例单侧上尿路结石病患者,随机分为两组,每组60人。一组应用微创经皮肾穿刺碎石术（MPCNL）进行一期单通道上尿路取石,另一组采用开放手术治疗。比较并分析两组患者的临床疗效。结果：应用MPCNL治疗的60名患者中,结石清除的有55名,清除率为91．17％,手术时间平均为77分钟,住院时间平均为5-3天。术中平均出血100mL,术后发生大出血者一例,经输血后好转,术后发热者38例,发热比例为63-3％,尿液转清时间平均为2．5天。应用开放式手术的60名患者中,结石清除的有39例,清除率为65．0％,平均手术之间为112分钟,住院时间平均为18．1天,术中平均出血380mL,术后发生大出血者9例,经输血后好转,术后发热者43例,发热比例为71．2％,尿液转清时间平均为8．6天。结论：MPCNL方法治疗上尿路结石的效果明显比开放式手术好,具有清除率高、手术时间短、术后并发症少、术后感染少以及患者恢复快的优点。     

Yugoslav Mesolithic dental reduction

Yugoslav Mesolithic dentition exhibits maximum mesiodistal reduction compared with contemporary European and North African groups. This reduction is not explained entirely by attrition, and may be seen as a continuation of the European Upper Paleolithic trend. Buccolingual dimension does not reduce as much. In fact, this dimension in premolars and molars is larger than in other groups. This observation also occurs in Natufians, who were grain collectors, hunters, and gatherers. The Yugoslav Mesolithic group was collecting and domesticating Cerelia as well as fishing and hunting. Linear enamel hypoplasias (LEH) indicate childhood stress through the fifth year, which corroborates previously reported incidence of rickets in this group. The central maxillary incisors and canines manifest higher degrees of LEH, but the appearance on the second molars suggest a more severe physiological disruption. Sex differences in distributions of alveolar resorption and calculus suggest differences in diet or nutritional stress. Previous reports indicate that females had higher incidence of osteomalacia. If so, female nutritional stress may explain the extreme mesiodistal reduction and minimal sexual dimorphism in this group.