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1.
The collection and handling of colony resources such as food, water, and nest construction material is often divided into subtasks in which the material is passed from one worker to another. This is known as task partitioning. When material is transferred directly from one individual to another, queueing delays frequently occur because individuals must sometimes wait for a transfer partner. A stochastic simulation model was written to study the effect of colony size on these delays. Queueing delay decreases roughly exponentially with colony size because stochastic fluctuations in the arrival of individuals are lower in larger colonies. These results support empirical studies of Polybia occidentalis and other theoretical studies of honeybees. The effect of the relative number of individuals in the two subtask groups was also studied. There is a unique optimal ratio of the number of workers associated with each of the subtasks that simultaneously minimizes mean queueing delay and maximizes colony nectar-processing rate. Deviations from this optimal ratio, for example, as a result of forager mortality or changes in nectar productivity that affect foraging trip duration, increase mean queueing delays greatly, especially in smaller colonies. 相似文献
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Background
When switching from one task to a new one, reaction times are prolonged. This phenomenon is called switch cost (SC). Researchers have recently used several kinds of task-switching paradigms to uncover neural mechanisms underlying the SC. Task-set reconfiguration and passive dissipation of a previously relevant task-set have been reported to contribute to the cost of task switching.Methodology/Principal Findings
An unpredictable cued task-switching paradigm was used, during which subjects were instructed to switch between a color and an orientation discrimination task. Electroencephalography (EEG) and behavioral measures were recorded in 14 subjects. Response-stimulus interval (RSI) and cue-stimulus interval (CSI) were manipulated with short and long intervals, respectively. Switch trials delayed reaction times (RTs) and increased error rates compared with repeat trials. The SC of RTs was smaller in the long CSI condition. For cue-locked waveforms, switch trials generated a larger parietal positive event-related potential (ERP), and a larger slow parietal positivity compared with repeat trials in the short and long CSI condition. Neural SC of cue-related ERP positivity was smaller in the long RSI condition. For stimulus-locked waveforms, a larger switch-related central negative ERP component was observed, and the neural SC of the ERP negativity was smaller in the long CSI. Results of standardized low resolution electromagnetic tomography (sLORETA) for both ERP positivity and negativity showed that switch trials evoked larger activation than repeat trials in dorsolateral prefrontal cortex (DLPFC) and posterior parietal cortex (PPC).Conclusions/Significance
The results provide evidence that both RSI and CSI modulate the neural activities in the process of task-switching, but that these have a differential role during task-set reconfiguration and passive dissipation of a previously relevant task-set. 相似文献3.
A Shoot:Root Partitioning Model 总被引:14,自引:0,他引:14
A model for partitioning newly-synthesized structural dry matterbetween shoot and root is developed. It is based on a postulatedpartitioning function, which depends upon the relative levelsof carbon and nitrogen substrates, with parameters determiningthe control point and also the degree of control. The modelis used to investigate the relationships between plant specificgrowth rate, shoot:root ratio, and the specific activities ofshoot and root (which depend upon environment), during steady-stateexponential growth; the transient behaviour of the model isalso explored and oscillations in these quantities are obtained. Shoot:root ratio, specific growth rate, mathematical model, partition of assimilates 相似文献
4.
The collection and handling of colony resources such as food, water, and nest-construction material is often divided into subtasks in which the material is passed from one worker to another. This is known as task partitioning. If tasks are partitioned with direct transfer of material between foragers and receivers, queueing delays can occur as individuals search or wait for a transfer partner. Changes in environmental conditions and relative number of foragers and receivers affect these delays as well as colony ergonomic efficiency. These delays are used in recruitment in both honeybees and Polybia wasps. This study investigates the distribution of queueing delays and the information content and quality of those delays using a stochastic-simulation model. Information quality increases with colony size. When the relative proportions of foragers and receivers are suboptimal, the group in excess has better information. Individuals can increase information quality of delays by two mechanisms: averaging over consecutive trips and averaging over multiple transfers within a trip where direct transfer occurs. We suggest that multiple transfer occurs in the honeybee in order to improve information quality. 相似文献
5.
The ability to switch between tasks is critical for animals to behave according to context. Although the association between the prefrontal cortex and task switching has been well documented, the ultimate modulation of sensory–motor associations has yet to be determined. Here, we modeled the results of a previous study showing that task switching can be accomplished by communication from distinct populations of sensory neurons. We proposed a leaky-integrator model where relevant and irrelevant information were stored separately in two integrators and task switching was achieved by leaking information from the irrelevant integrator. The model successfully explained both the behavioral and neuronal data. Additionally, the leaky-integrator model showed better performance than an alternative model, where irrelevant information was discarded by decreasing the weight on irrelevant information, when animals initially failed to commit to a task. Overall, we propose that flexible switching is, in part, achieved by actively controlling the amount of leak of relevant and irrelevant information. 相似文献
6.
研究了与生物资源管理相关的食饵具脉冲扰动与成年捕食者具连续收获的阶段结构时滞捕食-食饵模型.利用离散动力系统的频闪映射和脉冲时滞微分方程理论,得到了捕食者灭绝周期解的全局吸引和系统持久的充分条件,也证明了系统的所有解的一致完全有界.结论为现实的可再生生物资源管理提供了可靠的策略依据. 相似文献
7.
A Model to Describe the Partitioning of Photosynthate during Vegetative Plant Growth 总被引:7,自引:0,他引:7
An approach is described to the problem of modelling quantitativelythe partitioning of photosynthate during vegetative plant growth.Two plant processes are important in the scheme: the first ofthese is the utilization of substrate for growth and how thisutilization depends upon substrate concentration, the secondconcerns the transport of substrate between different plantparts and how this depends upon the substrate concentrationsin the plant parts. In both cases simple phenomenological relationshave been assumed which seem to be in reasonable accord withexperimental data and with more basic theoretical considerations.The model is able to describe some of the features of steady-statevegetative plant growth in a natural manner. The limitationsof the present formulation are considered, and the implicationsof this type of approach for whole-plant models are discussed. 相似文献
8.
A Model of Shoot: Root Partitioning with Optimal Growth 总被引:6,自引:3,他引:6
A shoot: root partitioning model is presented, which is a developmentof previous approaches in the area. The model incorporates asa physiologically reasonable apparent goal forthe plant, the assumption that the partitioning of growth betweenthe shoot and root maximizes the plant specific growth ratein balanced exponential growth. The analysis is concerned principallywith plant growth being a function of carbon and nitrogen only,although it is indicated how other nutrients, or growth factors,may be incorporated. Plant growth is driven by the environmentalconditions, and partitioning is defined entirely in terms ofthe shoot: root ratio and carbon and nitrogen status of theplant. In its basic form the model requires the definition ofa single plant growth parameter, along with the shoot and rootspecific activities and structural composition. Shoot: root partitioning, specific growth rate, vegetative phase 相似文献
9.
A Model to Investigate the Effect of Evaporative Cooling on the Pattern of Evaporation in Sub-stomatal Cavities 总被引:2,自引:1,他引:1
A model has been developed to investigate the pattern of waterevaporation from sub-stomatal cavities. In this model equationsfor the flux of matter are coupled to equations for the fluxof heat. Failure to couple heat and mass transfer processesin previous models may have led to erroneous conclusions regardingthe pattern of evaporation in sub-stomatal cavities. Our model predicts that the coolest surfaces are likely to be0.10.4 °C cooler than the warmest surfaces. Evaporativecooling does alter the pattern of evaporation in sub-stomatalcavities, yet 63 to 80 per cent of all evaporation still occursfrom a peristomatal region occupying about 4 per cent of thetotal sub-stomatal surface area. stomata, sub-stomatal cavities, transpiration, peristomatal evaporation, evaporative cooling 相似文献
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A Model of the Partitioning of New Above-ground Dry Matter 总被引:1,自引:0,他引:1
A model for the partitioning of new above-ground dry matterof a vegetative dicotyledonous plant is developed. It assumestwo distinct functional components of the stem tissues. One,the primary stem tissue, includes physiologically active tissuessuch as xylem, phloem and meristematic tissues, and the other,secondary stem tissue, includes the main mechanical structures.The model is used to examine the partitioning of dry matterbetween leaf and stem tissues, and its behavour is comparedwith experimental observations. Partitioning, leaf, stem, secondary stem tissues 相似文献
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A Transport-resistance Model of Forest Growth and Partitioning 总被引:8,自引:0,他引:8
The transport-resistance approach to dry-matter partitioningis used to construct a model of forest growth The model is atthe stand level for a monoculture of identical trees of thesame age There are five major organ compartments in the modelfoliage, branches, stem, coarse roots, and fine roots and mycorrhizasThe matter in each compartment is further subdivided into menstem,structure, carbon substrate, and nitrogen substrate The modelis driven by daily radiation including day length, ambient CO2concentration, and daily means of air and soil temperature Thefine roots are provided with constant values of soil mineralnitrogen pools (ammonium and nitrate) from which uptake occursGrowth over about 100 years is simulated for various environmentalconditions and soil mineral nitrogen levels, thinning is alsosimulated Natural tree death occurs within the model Particularattention is paid to dry matter partitioning patterns, and tothe dry matter per stem when death occurs The model is robustand responsive, and provides a framework for further developmentand application to many ecological and environmental scenarios,as well as to some forest management problems Model, forest, growth, partitioning 相似文献
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研究了不连续的抗生素输入以及时滞效应对栖生的两菌群的影响,获得了菌群灭绝和持续生存的条件.结果表明抗生素的不连续输入对系统的动力学行为带来很大影响,而抗生素的时滞作用是无害的. 相似文献
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本文提出并分析了两个关于人体T-细胞淋巴回归Ⅰ型病毒(HTL V-I)感染并带有坏死白血病细胞(ATL)进程的数学模型,一个常微分方程模型,一个离散时滞模型.首先对常微分方程模型进行了分析,运用相应的特征方程得到一个阈值Ro(CD4+ T-细胞的基本再生数).当R0≤1时,仅有未染病平衡态存在,并且给出了其稳定性;当R0>1时,有一个染病稳定态存在,并且此时它是稳定的.然后,我们在常微分方程模型中引入了一个离散时滞,通过对时滞模型的超越特征方程的分析,导出了与常微分方程模型中同样的稳定性条件,即时滞模型平衡态的稳定性与时滞的具体值无关. 相似文献
18.
We consider a two-patch model for a single species with dispersal and time delay. For some explicit range of dispersal rates, we show that there exists a critical value τ c for the time delay τ such that the unique positive equilibrium of the system is locally asymptotically stable for τ∈[0,τ c ) and unstable for τ>τ c . 相似文献
19.
研究了一类具有分布时滞的扩散种群模型行波解的存在性,证明了当平均时滞充分小时,方程具有连接两个平衡点的单调行波解. 相似文献
20.
文章研究的是一个具有时滞的媒介传播流行病模型.假定长期的发病率是双线性大规模行动的方式,确定了疾病是否流行的阈值R_0.当R_0≤1时,得到无病平衡点是全局稳定的,即疾病消失;当R_0〉1时,得到地方病平衡点.在具有时滞的微分模型中,时滞与载体转变成传染源的孵化期有关。我们研究了时滞对平衡点稳定性的影响,研究表明,在从寄生源到载体的传播过程中,时滞可以破坏动力系统并且得到了Hopt分支的周期解. 相似文献