不同栖息地破坏格局下具捕食偏爱似然竞争结局的模拟分析

使用元胞自动机模型,对具有捕食偏爱、不同栖息地破坏比例和不同空间破坏格局条件下的捕食-食饵系统中各物种的变化动态进行了模拟分析。在捕食者和两猎物物种共存时:栖息地破坏比例、栖息地破坏的聚集度对猎物物种间强弱关系产生相反的作用,若增加栖息地破坏比例不利于某一猎物生存,则提高聚集度对其有利;适当提高适宜栖息地的聚集度,对所有物种都有利,若聚集度过高,效果相当于减少了栖息地的破坏比例,可能对某些猎物物种不利,但对整体系统有利;被破坏栖息地的聚集度发生变化时,捕食者的反应更敏感;在一定条件下,增强弱势种群的捕食偏爱会有助于其生存。     

不同规模餐馆食物浪费及其氮足迹——以北京市为例

餐饮食物浪费的普遍性和严重性已得到了社会各界的关注。通过实证研究的方法对餐饮消费中食物浪费问题进行了研究,并从食物全供应链的视角,对比分析了不同规模餐馆食物浪费的氮足迹及其环境影响。研究表明:北京市餐饮食物浪费人均浪费量为74.39g/人次,其含氮量为1.24g/人次,约占总浪费量的2%。北京市餐饮食物浪费所引起总的氮排放量为16.37 g/人次,其中有1.24g/人次的氮排放来自于食物的直接浪费,其余15.13g/人次氮排放来自于食物生产过程。北京市餐饮食物浪费的氮足迹为0.22g N/g,即每浪费1g的食物,就会有0.22 g的氮排放到环境中。对比不同规模餐馆的食物浪费情况可知,大型餐馆的人均浪费量最高,有99.38g/人次,其氮排放量也相应最大,为22.53g/人次;中型餐馆和小型餐馆的食物浪费人均量及N排放量依次减少,而快餐的最低,仅为北京市整体平均水平的1/3。     

The perception of visual images encoded in musical form: a study in cross-modality information transfer

This study demonstrates the ability of blind (previously sighted) and blindfolded (sighted) subjects in reconstructing and identifying a number of visual targets transformed into equivalent musical representations. Visual images are deconstructed through a process which selectively segregates different features of the image into separate packages. These are then encoded in sound and presented as a polyphonic musical melody which resembles a Baroque fugue with many voices, allowing subjects to analyse the component voices selectively in combination, or separately in sequence, in a manner which allows a subject to patch together and bind the different features of the object mentally into a mental percept of a single recognizable entity. The visual targets used in this study included a variety of geometrical figures, simple high-contrast line drawings of man-made objects, natural and urban scenes, etc., translated into sound and presented to the subject in polyphonic musical form.     

Processes generating macroevolutionary patterns of morphological variation in birds: a simulation study

Multivariate patterns of morphological variation in birds are analysed. In general, there are strong allometric patterns among characters such that most of the variation is confined to a major “size” axis. To analyse the possible evolutionary processes behind this pattern I employed a computer simulation of cladogenesis and anagenesis based on a genetic and a random walk model (drift). All runs started with one species and speciation occurred to generate 100 species. Three levels of correlations were allowed. The results from the simulations were compared with the pattern of variation in finches (Fringillidae). The simulations showed two things. First, the univariate drift model was inappropriate in terms of the level of variation; the observed level was lower than expected by drift. Univariate drift was also unable to create tight correlations among characters as observed in several taxa. Second, to create the pattern observed, either relatively strong genetic correlations (r_g ≈ 0.5), or alternatively strong correlated selection, was needed. This suggests that morphological change in birds in general consists of changes in growth such that species become larger or smaller than their ancestors but retain their ancestral shape. The results stress the importance of stabilising selection in shaping the macroevolutionary patterns of morphological variation in birds.     

Differential patterns of food appreciation during consumption of a simple food in congenitally anosmic individuals: an explorative study

Food is evaluated for various attributes. One of the key food evaluation domains is hedonicity. As food is consumed, its hedonic valence decreases (due to prolonged sensory stimulation) and hedonic habituation results. The aim of the present study was to investigate changes in food pleasantness ratings during consumption of a simple food by individuals without olfactory experience with food as compared to normosmics. 15 congenital anosmics and 15 normosmic controls were each presented with ten 10 g banana slices. Each was visually inspected, then smelled and chewed for ten seconds and subsequently rated for hedonicity on a 21-point scale. There was a significant difference in pleasantness ratings between congenital anosmics and controls (F(1, 26) = 6.71, p = .02) with the anosmics exhibiting higher ratings than the controls, a significant main repeated-measures effect on the ratings (F(1.85, 48) = 12.15, p<.001), which showed a decreasing trend over the course of consumption, as well as a significant portion*group interaction (F(1.85, 48) = 3.54, p = .04), with the anosmic participants experiencing a less pronounced decline. The results of the present explorative study suggest that over the course of consumption of a simple food, congenitally anosmic individuals experience differential patterns of appreciation of food as compared to normosmics. In this particular case, the decrease of hedonic valence was less pronounced in congenital anosmics.     

不同施肥条件下玉米田土壤养分淋溶规律的原位研究

利用排水采集器法结合田间原位试验,研究了夏玉米不同施肥处理对棕壤土养分淋失的影响.结果表明:在夏玉米生长期内,影响玉米田土壤水分淋溶的主要因素是大量降雨和灌溉,夏玉米生长前期的土壤淋溶水量较大,但随夏玉米生育进程的推进而递减,各处理差异也逐渐减小;与施氮肥处理相比,秸秆还田配施氮肥处理可加剧土壤水淋溶.在夏玉米生长期内,施肥处理的土壤淋溶水硝态氮浓度均呈"双峰"曲线变化趋势,而铵态氮浓度则呈先升后降的变化趋势.玉米田土壤氮素淋失以硝态氮形式为主,其累计淋失量为12.90～46.53 kg·hm-2,铵态氮的累计淋仅为1.66～5.11 kg·hm-2,两种形态氮的淋失量都随施氮量的增加而升高.秸秆还田配施氮肥处理的氮素淋失率比单施氮肥处理高6.53%～13.07%,低氮处理的氮素淋失率比高氮处理高3.66%～10.10%;玉米田土壤速效磷的累计淋失量较小,仅为0.148～0.235 kg·hm-2,而速效钾的累计淋失量较大,为7.08～13.00 kg·hm-2.在夏玉米生长后期,秸秆还田配施氮肥处理使土壤速效磷淋失量升高,并可加剧土壤速效钾的淋失,而单施氮肥处理作用不明显.     

Spatial genetic patterns generated by two admixing genetic lineages: a simulation study

Two formerly geographically separated lineages of the zebra mussel Dreissena polymorpha had been given the opportunity to mix extensively across the newly built German Main–Danube canal. We had monitored this admixture of mussel lineages and had described spatial patterns in different genetic measures [Müller et al. 2001 (Heredity, 86: 103); 2002 (Proc. R. Soc. Lond., 269: 1139)]. Here, we present an individual-based model to assess the potential of spatial genetic patterns of detecting and quantifying admixture of mussel lineages. Genetic measures studied are (1) allele frequencies, (2) deviations from Hardy–Weinberg expectations of loci (deficit of heterozygotes, HWD) and (3) linkage disequilibria between unlinked loci (LD). For allele frequencies, we observed a cline over the zone of admixture in all simulations of mixing mussel lineages suggesting that these are appropriate for verification of their mixture. The point of the first contact between lineages was always detectable from their intermediate allele frequencies. LD and HWD were only spatially informative for diagnostic loci or loci with very strong differences in allele frequencies of lineages. For such loci, the probability of disequilibria was highest where lineages had met and decreased towards both sources of lineages Main and Danube. The overall probability of detecting any disequilibrium was higher for LD than for HWD and increased with an increasing rate of genetic interchange. Our simulation results are corroborated by our zebra mussel data and studies from literature. They are applicable to any case of two known linearly mixing genetic lineages.     

Adult-infant food transfer in common marmosets: an experimental study

Infant marmosets and tamarins obtain solid food items from adults during and after the time of weaning. In addition to providing nutrients, food transfers may provide infants with the opportunity to learn about diet. The aim of this study was to investigate patterns of begging and food transfer in captive groups of common marmosets during tests with 1) palatable novel food, 2) unpalatable novel food, and 3) familiar food. Infants may gain an opportunity to learn about diet breadth by preferentially begging for novel rather than familiar items, while adults may facilitate infant learning by differing in their willingness to transfer food depending upon the food's novelty or palatability. In this study, infants exhibited more interest and begging with novel food items than with familiar ones. However, food transfers were not more likely to occur with novel foods than with familiar ones, and in fact adults were more likely to refuse infant begging attempts with novel foods. The palatability of the food also did not influence the rates of refusal and transfer: adults transferred palatable and unpalatable novel foods with similar frequencies. These results suggest that infant marmosets gain an opportunity to learn about diet breadth by begging for novel foods, but adults do not preferentially transfer novel or palatable food items.     

The temporal patterns of food intake and allelomimetic feeding by pigs of different ages

The feeding behaviour of 4 castrated boars was studied over 24 hours using a photoelectric cell and continuous recorder at 4 body-weight stages, viz. 20, 40, 60 and 80 kg. Two of the pigs were on continuous light, and 2 were on 8.5 h light and 15.5 h of darkness. The 2 pigs in each treatment were in adjacent stalls but well separated from the other pair and other pigs. There were no differences in total food consumption between the animals in the 2 treatments. Eating speed also did not differ between treatments; neither did it differ between body-weight stages when adjusted for body weight. The percentage of the total time devoted to feeding differed between body-weight stages but not between treatments. However, over the first 8-h period of the day, the pigs on the short day-length spent more time feeding, but body weight did not affect this measure. Meal intervals were determined by a logarithm survivorship curve analysis, and it was found that pigs on the long day-length had significantly more meals than the others. Body weight also affected the number of meals, with the youngest taking most. Furthermore, both pairs showed a significant degree of synchronized feeding.     

Scheduling of FMSs with information delays: A simulation study

Practitioners and academicians throughout the world recognize the crucial role played by flexibility within manufacturing organizations, especially those engaged in small batch manufacture. However, although the concept of flexibility has begun to attract increased attention, its interaction with information integration and automation has not captured due attention. For example, it almost always has been assumed that a real-time control mechanism is available for exploiting routing flexibility on the shop floor. While this may be true for FMSs, it generally is not so for the vast majority of conventional manufacturing systems with varying levels of information integration and automation. The lack of a fully integrated and automated control mechanism within such semi-automated flexible manufacturing systems (SAFMSs) would eventually cause delays in the availability of shop status information. In this paper, we study the impact that defined modes of information delay have on the performance of a hypothetical SAFMS through detailed simulation experiments. Given that the level of routing flexibility is a controllable design parameter, our interest is in determining the impact that information delays have on decisions pertaining to the selection of appropriate levels of routing flexibility. To highlight the impact of information delays within the SAFMS, the Taguchi experimental design procedure is adopted as a performance evaluation and analysis vehicle, using makespan as a measure of performance. Simulation results indicate the presence of a system specific tolerance limit, operation below which minimizes performance loss.     

Dynamic simulation and steady-state analysis of a bentho-pelagic coupled ecosystem under different simulation scenarios

Trophic dynamic studies of aquatic ecosystem are usually based on either dynamic or state-state models of energy and material transfer, comprising of a few functional tropic levels such as phytoplankton, primary consumers and secondary consumers. However, though benthic components (and production) are important parts of an aquatic ecosystem, they are often omitted from such approaches.Considering this inadequacy of previous simulation approaches, the aim of the present study, is to investigate the effect of benthic components on overall system dynamics. The objectives of this study are (a) to develop and study a dynamic model for Kakinada bay to understand how benthic components interact with others under a fixed set of conditions, and to find the sensitive parameters for such a benthic-pelagic coupled system (b) to study the effects of different biomasses of benthic components via scenario analysis and (c) to identify the different equilibrium states that a benthic-pelagic coupled system such as Kakinada Bay may reach.On running the simulation for a period of 5000 days (∼10+ years), the system was not seen to reach any equilibrium state; however, all state variables considered in the model were seen to coexist even at the end of this period. While zooplankton was found to be the most sensitive state variable, parameters directly associated with benthic components were indicated to be the most sensitive. Microphytobenthos was negatively correlated with phytoplankton which was corroborated by results of the perturbation scenario analyses as well. Only one equilibrium state – microphytobenthos dominated steady state was found for Kakinada Bay system when certain parameters were slightly changed.     

Stress transfer properties of different commercial dental implants: a finite element study

Dental implantology has high success rates, and a suitable estimation of how stresses are transferred to the surrounding bone sheds insight into the correct design of implant features. In this study, we estimate stress transfer properties of four commercial implants (GMI, Lifecore, Intri and Avinent) that differ significantly in macroscopic geometry. Detailed three-dimensional finite element models were adopted to analyse the behaviour of the bone-implant system depending on the geometry of the implant (two different diameters) and the bone-implant interface condition. Occlusal static forces were applied and their effects on the bone, implant and bone-implant interface were evaluated. Large diameters avoided overload-induced bone resorption. Higher stresses were obtained with a debonded bone-implant interface. Relative micromotions at the bone-implant interface were within the limits required to achieve a good osseointegration. We anticipate that the methodology proposed may be a useful tool for a quantitative and qualitative comparison between different commercial dental implants.     

Non-enzymatic transfer of sequence information under plausible prebiotic conditions

We simulated in our laboratory a prebiotic environment where dry and wet periods were cycled. Under anhydrous conditions, lipid molecules present in the medium could form fluid lamellar matrices and work as organizing agents for the condensation of nucleic acid monomers into polymers. We exposed a mixture of 2′-deoxyribonucleoside 5′-monophosphates and a ssDNA oligomer template to this dry environment at 90 °C under a continuous gentle stream of CO₂ and we followed it with rehydration periods. After five dry/wet cycles we were able to detect the presence of a product that was complementary to the template. The reaction had a 0.5% yield with respect to the template, as measured by staining with the Pico Green^® fluorescent probe. Absent initial template, the product of the reaction remained below the detection limit. In order to characterize the fidelity of replication, the synthesized strand was ligated to adapters, amplified by PCR, and sequenced. The alignment of the sequenced DNA to the expected complementary sequence revealed that the misincorporation rate was 9.9%. We present these results as a proof of concept for the possibility of having non-enzymatic transfer of sequence information in a prebiotically plausible environment.     

Activity patterns in Glossina longipennis : a field study using different sampling methods

Abstract .Studies on the daily activity of Glossina longipennis at Galana Ranch using a black odour-baited electrocuting target confirmed its crepuscular activity profile. Activity started at 05.00–05.30 hours and peaked at 06.00–06.30 hours, stopped by 09.00 hours, then started again at 17.00–17.30 hours with a peak at 18.30–19.00 hours, ceasing by 19.30 hours. Females made up 60% of the overall catch, and tended to arrive later than males. Other stationary sampling methods (trap, stationary ox) gave similar results. With the stationary methods, very few flies were caught outside the periods of peak activity (only 1.5% of the total between 09.00 and 17.00 hours); the ox was the only stationary bait to catch any flies between 10.00 and 16.00 hours. More flies were caught throughout the day at mobile baits (8.3% of the male and 2.3% of the female catch was taken between 09.00 and 17.00 hours). Mobile baits caught considerably more males than females (females were 17% of the catch). These males had on average higher fat and haematin reserves. Similar nutritional differences were not observed for females. There were fewer older females (ovarian category 3 or more) in mobile compared to stationary baits, and a lower proportion of the youngest males (wing fray category 1) at natural compared with artificial baits.     

The evolutionary genetics of adaptation: a simulation study

It is now clear that the genetic basis of adaptation does not resemble that assumed by the infinitesimal model. Instead, adaptation often involves a modest number of factors of large effect and a greater number of factors of smaller effect. After reviewing relevant experimental studies, I consider recent theoretical attempts to predict the genetic architecture of adaptation from first principles. In particular, I review the history of work on Fisher's geometric model of adaptation, including recent studies which suggest that adaptation should be characterized by exponential distributions of gene effects. I also present the results of new simulation studies that test the robustness of this finding. I explore the effects of changes in the distribution of mutational effects (absolute versus relative) as well as in the nature of the character studied (total phenotypic effect versus single characters). The results show that adaptation towards a fixed optimum is generally characterized by an exponential effects trend.     

Quantum-classical simulation methods for hydrogen transfer in enzymes: a case study of dihydrofolate reductase

A variety of theoretical approaches have been used to investigate hydrogen transfer in enzymatic reactions. The free energy barriers for hydrogen transfer in enzymes have been calculated using classical molecular dynamics simulations in conjunction with quantum mechanical/molecular mechanical and empirical valence bond potentials. Nuclear quantum effects have been included with several different approaches. Applications of these approaches to hydride transfer in dihydrofolate reductase are consistent with experimental measurements and provide significant insight into the protein conformational changes that facilitate the hydride transfer reaction.     

The role of hydrogen bonds in an aqueous solution of acetylsalicylic acid: a molecular dynamics simulation study

This work focuses on the role of the dynamic hydrogen bonds (HB) formed in an aqueous solution of aspirin using molecular dynamics simulation. The statistics reveal the existence of internal HB that inhibit the rotational movements of the acetyl and the carboxylic acid groups, forcing the molecule to adopt a closed conformer structure in water, and playing an important role in stabilizing this conformation.     

Oxytocin and cooperation under conditions of uncertainty: The modulating role of incentives and social information

The neuropeptide Oxytocin (OT) has been implicated in many aspects of mammalian social behavior. This study investigates how OT interacts with two well-studied determinants of cooperative behavior: incentives and social information. Participants received OT or a placebo and played two economic games: a Coordination Game (with strong incentives to cooperate) and a Prisoner's Dilemma (with weak cooperative incentives). OT enhanced cooperation only when social information was present, and this effect was significantly more pronounced in the Coordination Game. When social information was lacking, OT surprisingly decreased cooperation. Consistent with the well-established role of OT in trust-building and in social cognition, social information appears to be crucial for OT to boost cooperative expectations in an interdependent social interaction that provides incentives to cooperate. When these cues are absent, OT appears to instead elicit a risk-averse strategy.     

The efficiency of adaptive search tactics for different prey distribution patterns: a simulation model based on the behaviour of juvenile plaice

Juvenile plaice Pleuronectes platessa are particularly useful for studying forager search behaviour because their search paths are essentially two dimensional, and punctuated by natural stops. Their prey occur in a range of natural distributions from highly aggregated to over‐dispersed. Juvenile plaice use area‐restricted search near aggregated prey and extensive search, consisting of longer moves and fewer turns, between aggregations and when searching for dispersed prey. They search for less conspicuous prey items mainly in the pauses between movements. This saltatory search behaviour contrasts with the continuous search that is usually assumed in search models. A simulation model of saltatory search behaviour showed that a strategy combining extensive and intensive search allows the efficient exploitation of a range of natural prey distribution patterns, and that it is particularly effective when the search behaviour is controlled by perceived prey density. This allows the predator to respond to the localized aggregations which often occur in nature. The selective use of intensive search was more efficient than the continuous use of extensive search even in prey distribution patterns that were statistically over‐dispersed.