Prey localization by surface wave ray-tracing: Fish track bugs like oceanographers track storms

Summary Surface-feeding fish accurately determine direction and distance to the center of a concentric wave stimulus, even if only a single, short lasting wave train is presented^1,2. It has been suggested that one cue used by these fish to localize the wave center is the distance dependent frequency modulation of the initial part of a wave stimulus^3,4. Here we show how the distance information contained in the fractional frequency change of a capillary wave group can be decoded. We suggest that wave source localization in surface-feeding fish in part is based on a principal similar to that used by oceanographers to track storms by the frequency change of forerunners of swell.     

双块式无砟轨道温度场试验研究和数值分析

为较准确掌握无砟轨道温度场的分布规律,建立无砟轨道温度与环境温度的对应关系,为温度应力的计算和无砟轨道设计提供基础参数,本文测试了双块式无砟轨道不同部件、不同位置的温度和环境温度变化情况,建立有限元模型对无砟轨道温度场进行了数值模拟和对比.实测数据及数值模拟的结果均表明:道床板温度随外界气温呈以日为周期的周期性变化,秋季平均每天的升温时间约为8 h,降温约16 h;由于热交换条件的差异,距轨道表面越远,轨道温度受环境气温的影响越小,道床板角部的温度变化幅度大于中部,支撑层与基床表层的温度变化幅度很小;道床板内存在较大的温度梯度,随着距表面距离的增大,温度梯度逐渐减小,至支撑层时温度梯度可忽略不计;采用有限元模拟的方法获取无砟轨道温度随气温变化规律是可行的.     

Threshold and directional sensitivity of air-current-sensitive giant interneurons of a cricket

Summary Some of the directional characteristics of air-current-sensitive giant interneurons (GIs) of a cricket were investigated by using an exactly defined unidirectional air-current stimulus. In each GI, the velocity thresholds for the stimulating air-current in two different directions were measured, using various time-courses of the velocity change (frequency). Each GI showed identical velocity threshold curves, depending on the stimulus direction.     

一种基于微带天线的应变测量技术

结构在长期使用中常常会产生裂纹，裂纹萌生时的尺寸一般很小，不容易被发现；当裂纹被发现时，往往已经扩展，甚至接近临界尺寸，危及结构安全．由于裂纹主要产生在结构的应变集中处，所以对“关键区域”的应变进行监测可以作为裂纹萌生的表征．传统的应变测量技术很难满足长时间、低成本、快速检测等要求．为克服传统应变传感器的缺点，本文对基于微带天线的应变测量技术进行了可行性探究．微带天线的中心频率与自身尺寸有关：当其变形时，中心频率也会发生相应的偏移．因此，可利用微带天线中心频率的变化来表征应变．本文设计和制作了四种不同尺寸的微带天线，以探兖基于微带天线的应变测量技术，同时研究其影响因素．将天线黏附在悬臂梁上，并在悬臂梁自由端处施加载荷，进行应变测量实验．通过矢量网络分析仪得到回波损耗S-一曲线，并获得应变与微带天线频率偏移的关系．分析结果显示，应变与中心频率偏移之间存在近似线性关系，可利用微带天线测量应变．     

Bestimmung der optimalen Reizparameter bei Reizung des aszendierenden retikulären Systems

Summary For the initiation of an arousal reaction, the stimulation of the reticular activating system by square waves of frequencies varying from 50 to 400 c/s was studied. To evaluate the stimulation efficiency, the initial frequency of the rhinencephalic arousal reaction was used. The optimal stimulus frequency depends on the duration of the pulses. The optimal frequency was found to be 200 c/s at a pulse duration of 0.5 ms and 100 c/s at a pulse duration of 1.5 ms.     

Über die Funktion der Lorenzinischen Ampullen der Selachier

Summary The afferent impulses from the ampullae ofLorenzini ofScyllium show, both in the intact animal and in the isolated preparation, a steady discharge at constant temperature with a frequency reaching a maximum at an average of 20° and decreasing continuously at higher and lower temperatures. The discharge stops between 5° and 30° on the average. Rapid cooling causes a temporary rise in frequency, while rapid warming causes a temporary drop in frequency. While the ampullae are not sensitive to a mechanical stimulus, they react definitely to a change in temperature of 0.05°C. The ampullae thus behave like the cold receptors of the homoiotherms.     

A duration-dependent negative potential in the cichlid electroretinogram.

A negative potential can be evoked in the local electroretinogram of the cichlid fish Cichlasoma octofasciatum by light stimuli of duration longer than 70 msec. This response superficially resembles the proximal negative response, but differs in some waveform components and dependence upon stimulus configuration and duration.     

基于模型突变检测的管道泄漏检测定位方法

为了改进负压波法在管道微弱泄漏的检测和定位中的效果,提出了基于模型突变检测的特征提取和泄漏定位算法。首先运用广义似然比检测理论,建立压力信号变化的统计检验模型,计算广义似然比比率r和下降幅度d作为压力信号突变发生的敏感特征,并通过求得的压力变化时间点进行泄漏定位。针对缓慢泄漏时压力信号变化的特点,提出了相应的改进模型,更精确的求出缓慢泄漏压力信号的下降拐点。实验证明,参数r和d对不同变化类型的压力信号有较好的区分度,利用管道内压力和流量信号的特征值作为神经网络的特征向量可以实现管道的微弱泄漏识别,且基于改进模型的定位算法在缓慢泄漏定位中有较好的定位结果和稳定度。     

高速铁路无砟轨道不平顺谱

研究提出了我国高速铁路无砟轨道不平顺谱的计算方法、轨道不平顺谱拟合公式及轨道不平顺谱图.为提高轨道不平顺谱的计算精度,研究提出了基于线性插值和小波分析方法的轨道不平顺检测数据异常值和趋势向剔除算法.同时通过不同窗函数长度、不同窗函数和不同谱估计方法的轨道不平顺谱计算对比分析,确定了轨道不平顺谱的计算方法.利用高速综合检测列车检测数据计算确定了高速铁路无砟轨道不平顺谱及其拟合公式,并引入倍频能量表反映高速铁路无砟轨道周期结构的影响.由轨道不平顺谱拟合公式与倍频能量表共同构成的高速铁路无砟轨道不平顺谱,为高速铁路设计、评估和养护维修等提供了依据.     

超高频RFID物联网前端感知系统的设计

介绍了一种基于超高频RFID的物联网前端感知系统的设计和实现,以及主要模块的功能,然后分别从硬件结构,工作流程和软件设计三个方面进行了详细阐述.本系统的工作频率在860～960 MHz可调节,能支持EPC Gen2和ISO/IEC 18000-6B/6C标准.它的射频前端是以射频芯片AS3992为核心,使用内部集成的功放,外加一系列外围电路实现.其优点是体积小、重量轻、集成度高和功耗低.实验结果表明,该系统的读写距离能达到2.5m,能够满足实际应用的需要.     

Vergleichende Untersuchungen über die angeborene Grössenunterscheidung beiTilapia nilotica undHemihaplochromis multicolor (Pisces; Cichlidae)

Summary Female mouth-brooding Cichlid fishes pick up the young fry again when disturbed. The young, for their part, collect about the head of the mother fish and, contacting it, try to enter the mouth cavity. This contact behaviour is based upon an inborn readiness to react on the visual stimulus offered by the mother. Mother fishes inTilapia nilotica are much larger than those ofHemihaplochromis multicolor. By comparative experimental studies with models of various size (black balls of different diameters) it is shown that the young of the 2 species strictly prefer different sizes of the model, corresponding with the different sizes of the parent fishes.

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Herrn Prof.H. M. Peters zum 60. Geburtstag gewidmet.     

Transgenesis in fish

Gene transfer into fish embryo is being performed in several species (trout, salmon, carps, tilapia, medaka, goldfish, zebrafish, loach, catfish, etc.). In most cases, pronuclei are not visible and microinjection must be done into the cytoplasm of early embryos. Several million copies of the gene are generally injected. In medaka, transgenesis was attempted by injection of the foreign gene into the nucleus of oocyte. Several reports indicate that the injected DNA was rapidly replicated in the early phase of embryo development, regardless of the origin and the sequence of the foreign DNA. The survival of the injected embryos was reasonably good and a large number reached maturity. The proportion of transgenic animals ranged from 1 to 50% or more, according to species and to experimentators. The reasons for this discrepancy have not been elucidated. In all species, the transgenic animals were mosaic. The copy number of the foreign DNA was different in the various tissues of an animal and a proportion lower than 50% of F1 offsprings received the gene from their parents. This suggests that the foreign DNA was integrated into the fish genome at the two cells stage or later. An examination of the integrated DNA in different cell types of an animal revealed that integration occurred mainly during early development. The transgene was found essentially unrearranged in the fish genome of the founders and offsprings. The transgenes were therefore stably transmitted to progeny in a Mendelian fashion. Southern blot analysis revealed the presence of possible junction fragments and also of minor bands which may result from a rearrangement of the injected DNA. In all species, the integrated DNA appeared mainly as random end-to-end concatemers. In adult trout blood cells, a small proportion of the foreign DNA was maintained in the form of non-integrated concatemers, as judged by the existence of end fragments. The transgenes were generally only poorly expressed. The majority of the injected gene constructs contained essentially mammalian or higher vertebrates sequences. The comparison of the expression efficiency of these constructs in transfected fish and mammalian cells indicates that some of the mammalian DNA sequences are most efficiently understood by the fish cell machinery. Chloramphenicol acetyl transferase gene under the control of promoters from Rous sarcoma virus, and human cytomegalovirus, was expressed in several tissues of transgenic fish. Chicken -crystallin gene was expressed in several tissues of transgenic fish. Rainbow trout growth hormone cDNA driven by the Rous sarcoma virus promoter was expressed in transgenic carps leading to a faster growth of these animals. The antifreeze protein gene from flounder was expressed in transgenic salmon. These data indicate that transgenesis in fish is relatively easy but that fish gene sequences must be preferably used to obtain a good expression of the transgenes. Fish is a good biological model, specially for developmental studies and it is an increasing part of human food. For these reasons, transgenesis in fish is most likely to be more and more practised in the coming years.     

Medial forebrain bundle projections to the nucleus of the diagonal band of Broca.

The electrophysiological characteristics of the medical forebrain bundle (MFB) projections to the nucleus of the diagonal band of Broca (nDBB) were studied in acutely prepared cats. MFB stimulation evoked field potentials which consisted of a large negative wave followed by a shallow positivity. Extracellular unitary discharges appeared out of the negativity. In addition, intracellularly recorded EPSPs showed no significant shift in the latency to onset with changes in stimulus intensity. These observations indicate that at least some of the MFB projections to the nDBB are excitatory with respect to their target cells.     

Correlation between inhibition of stimulatory membrane repolarization and positive inotropic response caused by ouabain in rat heart]

During a stimulus train, the diastolic membrane potential of rat atria exhibits a depolarization phase followed by a slower repolarization phase which has been attributed to the activation of an electrogenic sodium pump (ATPase Na+, K+). This pump seems to be all the more active as stimulation frequency is higher. The parallel evolution of the sodium pump inhibition and a positive inotropic effect in response to ouabain perfusion, suggests that the enzymatic inhibition is directly involved in the development of the cardiotonic effect of digitalis.     

Pressure acclimation of the eel and liver membrane composition

Homeoviscous adaptation of membrane fluidity is known to exist in fish living at great depths. Is this adaptation also present in fish living near the surface but experimentally acclimated to high pressure? The composition of mitochondria-rich fractions extracted from the livers of eels acclimated for 15 days at 101 ATA was determined. The results show that pressure induced a significant increase (+100%) of total phospholipids (PL) and cholesterol without a change in their ratio. The increase of PL content was accompanied by a decrease in phosphatidylcholine in favour of phosphatidyl ethanolamine which, due to its preference for the H₁₁ form, is able to compensate for the loss in fluidity induced by pressure.     

基于DDS技术的多路高精度信号源设计

本系统以DSP2812和CPLD相结合,采用DDS（DDFS,直接频率数字频率合成）技术设计的多路高精度信号源,它可以根据用户设定的电流、电压参数,实现12路模拟量的输出.其模拟量的基本波形为：正弦波、三角波、方波和用户自定义的波形,同时可根据需要实现20次以内任意次谐波的迭加.     

Facilitation of avoidance conditioning by reticular stimulation in the cat]

Learning is facilitated in Cats by posttrial reticular stimulation. It has been pointed out that this stimulation has no immediate anterograde effect and does not evoke any change in the cortical, motor or autonomic functions during its delivery. Moreover this stimulation has no effect on the time course of cortical and autonomic responses to the conditioned stimulus. Therefore, these results suggest that reticular stimulation has a specific action on memory consolidation or information processing.     

Leibnizian relationalism for general relativistic physics

An ontology of Leibnizian relationalism, consisting in distance relations among sparse matter points and their change only, is well recognized as a serious option in the context of classical mechanics. In this paper, we investigate how this ontology fares when it comes to general relativistic physics. Using a Humean strategy, we regard the gravitational field as a means to represent the overall change in the distance relations among point particles in a way that achieves the best combination of being simple and being informative.     

Reaction time of the topminnowAplocheilus lineatus to surface waves determined by video- and electromyogram recordings

Summary Evoked muscle potentials during a localizing response for a wave center occur inAplocheilus lineatus 30±1.5 msec ( ) earlier than the simultaneously monitored body movements. Considering this time, only the first 8–10 wave cycles of a total wave signal are utilized to identify and localize a wave source.This study was supported by the Deutsche Forschungsgemeinschaft.     

Effects of pressure on oxygen consumption in cottid fish from Lake Baikal

Summary Rates of oxygen consumption in shallow dwelling cottid fish from Lake Baikal were unaffected by a change in pressure from 11 to 51 ata. The metabolic rate of deep cottids decreased by 72% when the pressure was decreased by 50% from that corresponding to habitat depth. Recovery from decreased pressures was incomplete in deep fish, suggesting that measurements of in deep dwelling fish in the literature may underestimate actual rates.Acknowledgments. Thanks are due to the US and USSR Academies of Sciences and the crew of the Titov. Support was provided by grants from The National Geographic Society, The George Baker Trust, The Max and Victoria Dreyfus Foundation, and The Griffis Foundation, Inc.