降雨噪声对菲菊头蝠出飞行为的影响

降雨噪声属于常见的自然噪声,由雨滴撞击物体表面产生。目前,有关降雨噪声对动物的潜在影响被普遍忽视。回声定位蝙蝠主要利用声信号在黑暗环境导航空间、探测猎物及社群交流,是开展降雨噪声影响研究的理想类群。本研究选择菲菊头蝠 (Rhinolophus pusillus)作为研究对象,检验降雨噪声是否影响蝙蝠出飞行为。我们在集群栖息地外,播放强降雨噪声、空白对照和种内回声定位声波,开展野外回放实验。利用单因素方差分析及其事后检验,评价菲菊头蝠对不同回放刺激的反应差异。研究发现,相比空白对照,强降雨噪声导致菲菊头蝠的通勤数量百分比平均降低2.82倍,回声定位脉冲数量平均减少4.86倍,集群出飞时间延长3.75 min。相比空白对照,同种回声定位声波对菲菊头蝠出飞行为的影响并不显著。研究结果证实强降雨噪声抑制菲菊头蝠的出飞行为。本研究表明,降雨引起 的噪声干扰可能是导致蝙蝠躲避降雨的重要因素,为野生蝙蝠物种保育与管理提供启示。     

The use of noise equivalent count rate and the NEMA phantom for PET image quality evaluation

PET image quality is directly associated with two important parameters among others: count-rate performance and image signal-to-noise ratio (SNR). The framework of noise equivalent count rate (NECR) was developed back in the 1990s and has been widely used since then to evaluate count-rate performance for PET systems. The concept of NECR is not entirely straightforward, however, and among the issues requiring clarification are its original definition, its relationship to image quality, and its consistency among different derivation methods. In particular, we try to answer whether a higher NECR measurement using a standard NEMA phantom actually corresponds to better imaging performance. The paper includes the following topics: 1) revisiting the original analytical model for NECR derivation; 2) validating three methods for NECR calculation based on the NEMA phantom/standard; and 3) studying the spatial dependence of NECR and quantitative relationship between NECR and image SNR.     

A stochastic model for the detection of coherent motion

A computational model is presented for the detection of coherent motion based on template matching and hidden Markov models. The premise of this approach is that the growth in detection sensitivity is greater for coherent motion of structured forms than for random coherent motion. In this preliminary study, a recent experiment was simulated with the model and the results are shown to be in agreement with the above premise. This model can be extended to be part of a more complex and elaborate computational visual system.     

Detection of simple radially symmetric targets: further evidence for the matched filter processing scheme in human pattern detection

The detection of small radially symmetric targets was studied using a subthreshold summation paradigm. Small disc and disc-like patterns with diameters up to 0.6^∘ were used for superposition on Bessel functions of zero order, subthreshold contrast and various spatial frequencies. Contrast interrelation functions prove linear over the whole range of contrasts used for the Bessel functions while their slopes show systematic variation with spatial frequency. An extrapolation of sensitivity from the slopes reveals that sensitivity can be predicted by a simple model assuming detection to be mediated by a transfer function made up as a cascade of an even bandpass function and the disc pattern spectrum, as has been found previously using one dimensional luminance distributions. Problems concerning the formation of pattern-specific radial symmetric filters are discussed. Received: 31 January 2000 / Accepted in revised form: 16 June 2000     

Attomole detection of in vivo protein targets of benzene in mice: evidence for a highly reactive metabolite

Modified proteins were detected in liver and bone marrow of mice following treatment with [(14)C]benzene. Stained sections were excised from one-dimensional and two-dimensional gels and converted to graphite to enable (14)C/(13)C ratios to be measured by accelerator mass spectrometry. Protein adducts of benzene or its metabolites were indicated by elevated levels of (14)C. A number of proteins were identified by in-gel proteolysis and conventional mass spectrometric methods with the low molecular weight proteins identified including hemoglobin and several histones. The incorporation of (14)C was largely proportional to the density of gel staining, giving little evidence that these proteins were specific targets for selective labeling. This was also true for individual histones subfractionated with Triton-acid-urea gels. A representative histone, H4, was isolated and digested with endopeptidase Asp-N, and the resulting peptides were separated by high performance liquid chromatography. (14)C levels in collected fractions were determined, and the peptides were identified by conventional mass spectrometry. The modifications were distributed throughout the protein, and no particular amino acids or groups of amino acids were identified as selective targets. Thus chemical attack by one or more benzene metabolites upon histones was identified and confirmed, but the resulting modifications appeared to be largely nonspecific. This implies high reactivity toward proteins, enabling such attack to occur at multiple sites within multiple targets. It is not known to what extent, if any, the modification of the core histones may contribute to the carcinogenicity of benzene.     

Adult tissue angiogenesis: evidence for negative regulation by estrogen in the uterus.

Increased uterine vascular permeability and angiogenesis are two major events of embryo implantation and placentation during pregnancy. These latter processes require coordinated, uterine-specific interactions between progesterone (P4) and estrogen (E) signaling. Although roles of these steroids have long been suspected, definitive functions of E and/or P4 in uterine angiogenesis still remain elusive. We have therefore exploited the availability of reporter and mutant mice to explore the regulation of angiogenesis in response to steroid hormonal changes in vivo. We present here molecular, genetic, physiological, and pharmacological evidence that E and P4 have different effects in vivo: E promotes uterine vascular permeability but profoundly inhibits angiogenesis, whereas P4 stimulates angiogenesis with little effect on vascular permeability. These effects of E and P4 are mediated by differential spatiotemporal expression of proangiogenic factors in the uterus.     

The use of noise information for detection of temporomandibular disorder

A new method for detection of temporomandibular disorder based on singular spectrum analysis is presented. In this method the motion data of markers placed on the points of special interest on the faces of several subjects is extracted and analysed. The individuals are classified into a group of healthy subjects and a group of those with temporomandibular disorder by extracting the signal components of the original time series and separating the noise using the proposed technique. The results for both simulated and real data verify the effectiveness of the proposed algorithm.     

Correction of negative buoyancy in the phantom larva, Chaoborus americanus

Fourth instar larvae of Chaoborus americanus correct a condition of negative buoyancy by increasing the amount of gas held by two pairs of tracheal sacs. Mass spectrometric analysis of sac gas during the period following the addition of weights to larvae, reveal that the added gas is derived from the dissolved gases present in the surrounding medium and that it enters by physical means. The response is characterized by a transient decrease in the rigidity of the sac wall. Electron and light microscopy reveal that muscular tissue and motor terminals are associated with the sac wall and that a resilin-like protein may be present. These results suggest that the increase in the amount of gas held by the sacs is a secondary effect of an initial expansion of the sac wall itself and that the cuticular lining of the sacs is an active participant in the adjustment process.     

Detection of negative buoyancy in the phantom larva, Chaoborus americanus

Fourth instar larvae of Chaoborus americanus regain neutral buoyancy after receiving weights or under added hydrostatic pressure by increasing the size of gas-filled tracheal sacs. The rate and degree of the response are directly related to the velocity of vertically flowing current experienced by the larva. Weighted larvae showing the more rapid sinking rates also show the more rapid adjustment rates. The usual response disappears when weighted larvae are suspended but reappears when water is caused to flow upwards past the stationary larva. The degree of sac expansion under any increment in hydrostatic pressure may be reduced by decreasing larval sinking rates with polyethylene floats. These results support the hypothesis of previous workers that water currents initiate the process of buoyancy adjustment.     

A model for the detection of moving targets in visual clutter inspired by insect physiology

We present a computational model for target discrimination based on intracellular recordings from neurons in the fly visual system. Determining how insects detect and track small moving features, often against cluttered moving backgrounds, is an intriguing challenge, both from a physiological and a computational perspective. Previous research has characterized higher-order neurons within the fly brain, known as 'small target motion detectors' (STMD), that respond robustly to moving features, even when the velocity of the target is matched to the background (i.e. with no relative motion cues). We recorded from intermediate-order neurons in the fly visual system that are well suited as a component along the target detection pathway. This full-wave rectifying, transient cell (RTC) reveals independent adaptation to luminance changes of opposite signs (suggesting separate ON and OFF channels) and fast adaptive temporal mechanisms, similar to other cell types previously described. From this physiological data we have created a numerical model for target discrimination. This model includes nonlinear filtering based on the fly optics, the photoreceptors, the 1(st) order interneurons (Large Monopolar Cells), and the newly derived parameters for the RTC. We show that our RTC-based target detection model is well matched to properties described for the STMDs, such as contrast sensitivity, height tuning and velocity tuning. The model output shows that the spatiotemporal profile of small targets is sufficiently rare within natural scene imagery to allow our highly nonlinear 'matched filter' to successfully detect most targets from the background. Importantly, this model can explain this type of feature discrimination without the need for relative motion cues.     

The decline in fitness with inbreeding: evidence for negative dominance‐by‐dominance epistasis in Drosophila melanogaster

Genetic interactions can play an important role in the evolution of reproductive strategies. In particular, negative dominance‐by‐dominance epistasis for fitness can theoretically favour sex and recombination. This form of epistasis can be detected statistically because it generates nonlinearity in the relationship between fitness and inbreeding coefficient. Measures of fitness in progressively inbred lines tend to show limited evidence for epistasis. However, tests of this kind can be biased against detecting an accelerating decline due to line losses at higher inbreeding levels. We tested for dominance‐by‐dominance epistasis in Drosophila melanogaster by examining viability at five inbreeding levels that were generated simultaneously, avoiding the bias against detecting nonlinearity that has affected previous studies. We find an accelerating rate of fitness decline with inbreeding, indicating that dominance‐by‐dominance epistasis is negative on average, which should favour sex and recombination.     

Population genetic structure of serotine bats (Eptesicus serotinus) across Europe and implications for the potential spread of bat rabies (European bat lyssavirus EBLV-1)

Understanding of the movements of species at multiple scales is essential to appreciate patterns of population connectivity and in some cases, the potential for pathogen transmission. The serotine bat (Eptesicus serotinus) is a common and widely distributed species in Europe where it frequently harbours European bat lyssavirus type 1 (EBLV-1), a virus causing rabies and transmissible to humans. In the United Kingdom, it is rare, with a distribution restricted to south of the country and so far the virus has never been found there. We investigated the genetic structure and gene flow of E. serotinus across the England and continental Europe. Greater genetic structuring was found in England compared with continental Europe. Nuclear data suggest a single population on the continent, although further work with more intensive sampling is required to confirm this, while mitochondrial sequences indicate an east–west substructure. In contrast, three distinct populations were found in England using microsatellite markers, and mitochondrial diversity was very low. Evidence of nuclear admixture indicated strong male-mediated gene flow among populations. Differences in connectivity could contribute to the high viral prevalence on the continent in contrast with the United Kingdom. Although the English Channel was previously thought to restrict gene flow, our data indicate relatively frequent movement from the continent to England highlighting the potential for movement of EBLV-1 into the United Kingdom.     

Biochemical evidence for multiple dimeric states of the Sinorhizobium meliloti DctD receiver domain

X-ray crystal structures suggest very different dimeric states for the inactive and active forms of the two-component receiver domain of Sinorhizobium meliloti DctD, a sigma(54)-dependent AAA+ ATPase. Moreover, the receiver domain in crystals grown from unphosphorylated protein is refractory to phosphorylation whereas solution protein is fully phosphorylatable, and equilibrium analytical ultracentrifugation data are consistent with solution dimers for both phosphorylated and unphosphorylated forms of the protein. Here we report biochemical data consistent with the presence of multiple dimeric conformations in the inactive and active states, and evidence for significant change in the dimeric state upon activation by phosphorylation or binding of Mg(2+) and BeF(3)(-).     

On the detection of signals in non-white noise

We have studied the detection, by human observers, of suprathreshold bandlimited signals embedded at various locations in non-white, Gaussian filtered noise. Detection models based upon the direct cross-correlation between the signal and the noise image (matched filtering) cannot account for the results of our experiments. Our findings point instead at a detection process occurring at the level of signal decomposition, and jointly determined by: (a) the differential outputs of discrete, bandlimited spatial analyzers selectively responsive to different components of the signal; and (b) variable detection rules adaptively related to such outputs and to the type of signal information available to the observer.     

Use of vision in prey detection by brown long-eared bats, Plecotus auritus

We investigated the ability of brown long-eared bats to make use of visual cues when searching for food. By using petri dishes containing mealworms that were subjected to different levels of illumination, we presented four bats with different sensory cues: visual, sonar and a combination of these. The bats preferred situations where both sonar cues and visual cues were available, and the visual information was more important than the sonar cues. The bats did, however, emit echolocation calls throughout the experiments. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.