Behavioural and biochemical investigations of the influence of altered gravity on the CNS of aquatic vertebrates during ontogeny.

Quantitative data are presented on the influences of hyper-gravity (3 +/- 1g) and of simulated weightlessness (approximately 0g) during early ontogeny of cichlid fish (Oreochromis mossambicus) and clawed toad (Xenopus laevis, Daudin) demonstrating changes in the swimming behaviour and the brain energy and plasma membrane metabolism. After return to 1g conditions, hyper-g reared fish and toads express the well known "loop-swimming" behaviour. By means of a computer based video analyzing system different types of swimming movements and velocities were quantitatively determined. Analyses of the brain energy and plasma-membrane metabolism of hyper-g fish larvae demonstrated an increase in energy availability (glucose 6Pi dehydrogenase, G-6P-DH), a decrease of cellular energy transformation (creatine kinase activity, CK) but no changes in energy consumptive processes (e.g. ATPases) and cytochrome oxidase activity (Cyt.-Ox). In contrast hypo-g fish larvae showed a slight increase in brain CK activity. In addition, unlike 1g controls, hyper-g fish larvae showed pronounced variations in the composition (=polarity) of sialoglycosphingolipids (=gangliosides), typical constituents of the nerve cell membranes, and a slight increase in the activity of sialidase, the enzyme responsible for ganglioside degradation.     

Effects of altered gravity on the swimming behaviour of fish.

Humans taking part in parabolic aircraft flights (PAFs) may suffer from space motion sickness-phenomena (SMS, a kinetosis). It has been argued that SMS during PAFs might not be based on microgravity alone but rather on changing accelerations from 0 g to 2 g. We test here the hypothesis that PAF-induced kinetosis is based on asymmetric statoliths (i.e., differently weighed statoliths on the right and the left side of the head), with asymmetric inputs to the brain being disclosed at microgravity. Since fish frequently reveal kinetotic behaviour during PAFs (especially so-called spinning movements and looping responses), we investigated (1) whether or not kinetotically swimming fish at microgravity would have a pronounced inner ear otolith asymmetry and (2) whether or not slow translational and continuously changing linear (vertical) acceleration on ground induced kinetosis. These latter accelerations were applied using a specially developed parabel-animal-container (PAC) to stimulate the cupular organs. The results suggest that the fish tested on ground can counter changing accelerations successfully without revealing kinetotic swimming patterns. Kinetosis could only be induced by PAFs. This finding suggests that it is indeed microgravity rather than changing accelerations, which induces kinetosis. Moreover, we demonstrate that fish swimming kinetotically during PAFs correlates with a higher otolith asymmetry in comparison to normally behaving animals in PAFs.     

Synaptic plasticity and gravity: ultrastructural, biochemical and physico-chemical fundamentals.

On the basis of quantitative disturbances of the swimming behaviour of aquatic vertebrates ("loop-swimming" in fish and frog larvae) following long-term hyper-g-exposure the question was raised whether or not and to what extent changes in the gravitational vector might influence the CNS at the cellular level. Therefore, by means of histological, histochemical and biochemical analyses the effect of 2-4 x g for 9 days on the gross morphology of the fish brain, and on different neuronal enzymes was investigated. In order to enable a more precise analysis in future-microgravity-experiments of any gravity-related effects on the neuronal synapses within the gravity-perceptive integration centers differentiated electron-microscopical and electronspectroscopical techniques have been developed to accomplish an ultrastructural localization of calcium, a high-affinity Ca2(+)-ATPase, creatine kinase and cytochrome oxidase. In hyper-g animals vs. 1-g controls, a reduction of total brain volume (15%), a decrease in creatine kinase activity (20%), a local increase in cytochrome oxidase activity, but no differences in Ca2+/Mg(2+)-ATPase activities were observed. Ultrastructural peculiarities of synaptic contact formation in gravity-related integration centers (Nucleus magnocellularis) were found. These results are discussed on the basis of a direct effect of hyper-gravity not only on the gravity-sensitive neuronal integration centers but possibly also on the physico-chemical properties of the lipid bilayer of neuronal membranes in general.     

Fish otolith growth in 1g and 3g depends on the gravity vector.

Size and asymmetry (size difference between the left and the right side) as well as calcium (Ca) content of inner ear otoliths of larval cichlid fish Oreochromis mossambicus were determined after a long-term stay at hypergravity conditions (3g; centrifuge). Both utricular and saccular otoliths (lapilli and sagittae, respectively) were significantly smaller after hyper-g exposure as compared to parallely raised 1g-control specimens and the absolute amount of otolith-Ca was diminished. The asymmetry of sagittae was significantly increased in the experimental animals, whereas the respective asymmetry concerning lapilli was markedly decreased. In the course of another experiment larvae were raised in aquarium hatch baskets, from which one was placed directly above aeration equipment which resulted in random water circulation shifting the fish around ("shifted" specimens). The lapillar asymmetry of the "stationary" specimens showed a highly significant increase during early development when larvae were forced to lay on their sides due to their prominent yolk-sacs. In later developmental stages, when they began to swim freely, a dramatic decrease in lapillar asymmetry was apparent. Taken together with own previous findings according to which otolith growth stops after vestibular nerve transaction, the results presented here suggest that the growth and the development of bilateral asymmetry of otoliths is guided by the environmental gravity vector, obviously involving a feedback loop between the brain and the inner ear.     

Readaptation of fish to 1g after long-term microgravity: behavioural results from the STS 89 mission.

The swimming behaviour of adult and neonate swordtail fish Xiphophorus helleri was qualitatively analysed from video recordings taken throughout the STS 89 spaceshuttle mission from launch to landing and thereafter. After the flight, the swimming behaviour of neonate samples was quantitatively assessed in the course of the readaptation to 1g earth gravity at days 0, 1 and 4 after recovery. Regarding the swimming behaviour during the mission, the adult fish swam thigmotactically (i.e., responding to tactile stimuli) along the walls of their aquarium, but like the neonates, they did not show any aberrant behavioural patterns. This indicates that they could easily adapt themselves to microgravity. On mission day 9, however, looping responses (most probably initiated by mechanical disturbances) occurred indicating a continuously performed "C-start" escape response (the respective body bend looks like the letter "C"). Immediately after landing (observed in videos recorded onboard the space shuttle), the adults performed a head-up swimming beating heavily with the caudal and pectoral fins; this aberrant behaviour gradually decreased during the first hours after recovery.     

非对称液压缸对称性控制

阀控非对称缸两个运动方向上系统的开环增益及某些参数的不同,使得两个方向上的动态特性不对称,这种本质上的非线性和非对称性给系统控制带来困难.PБ-211机器人后3个关节是对称阀控制非对称液压缸伺服系统,为了使机器人运行平稳和提高控制精度,在控制中必须加以适当补偿.在分析非对称液压缸工作原理基础上,考虑液压缸伸出和缩回性能不同,提出了模型参考变增益自适应控制算法对非对称液压缸进行补偿.该算法包括单神经元自适应PID控制、模型参考自适应控制和输出增益的自动调节3个部分.仿真分析和实验表明该算法可以基本实现非对称液压缸的对称性控制,较普通PID控制算法具有明显优势.      

A drop-tower experiment to determine the threshold of gravity for inducing motion sickness in fish.

It has been repeatedly shown earlier that some fish of a given batch reveal motion sickness (a kinetosis) at the transition from 1 g to microgravity. In the course of parabolic aircraft flight experiments, it has been demonstrated that kinetosis susceptibility is correlated with asymmetric inner ear otoliths (i.e., differently weighed statoliths on the right and the left side of the head) or with genetically predispositioned malformed cells within the sensory epithelia of the inner ear. Hitherto, the threshold of gravity perception for inducing kinetotic behavior as well as the relative importance of asymmetric otoliths versus malformed epithelia for kinetosis susceptibility has yet not been determined. The following experiment using the ZARM drop-tower facility in Bremen, Germany, is proposed to be carried out in order to answer the aforementioned questions. Larval cichlid fish (Oreochromis mossambicus) will be kept in a camcorder-equipped centrifuge during the microgravity phases of the drops and thus receive various gravity environments ranging from 0.1 to 0.9 g. Videographed controls will be housed outside of the centrifuge receiving 0 g. Based on the video-recordings, animals will be grouped into kinetotically and normally swimming samples. Subsequently, otoliths will be dissected and their size and asymmetry will be measured. Further investigations will focus on the numerical quantification of inner ear supporting and sensory cells as well as on the quantification of inner ear carbonic anhydrase reactivity. A correlation between: (1) the results to be obtained concerning the g-loads inducing kinetosis and (2) the corresponding otolith asymmetry/morphology of sensory epithelia/carbonic anhydrase reactivity will further contribute to the understanding of the origin of kinetosis susceptibility. Besides an outline of the proposed principal experiments, the present study reports on a first series of drop-tower tests, which were undertaken to elucidate the feasibility of the proposal (especially concerning the question, if some 4.7 s of microgravity are sufficient to induce kinetotic behavior in larval fish).     

前体非对称涡Re效应初探及其风洞模拟技术

对不同长细比(11和6.15)的细长旋成体模型在低速风洞中完成了亚临界和 临界雷诺数(Re)的测压实验研究.结果表明,只要后体尾部截断至离二涡区足够远,就不会影响由前体二涡主控的多涡系结构,并且头部扰动与非对称涡响应之间的相关关系也保持不变,这为在常规低速风洞中通过增大旋成体直径、减小长细比来扩大Re实验范围提供了实验依据.基于此技术,临界Re下低速实验结果表明细长旋成体在层流和转捩分离区的截面压力分布有明显的区别,导致在临界Re内的侧向力较亚临界显著减小,而且头部扰动对背涡流动的主控作用明显减弱,单孔位微吹气扰动主动控制技术不再适用.      

Influence of hypergravity on fish inner ear otoliths: II. Incorporation of calcium and kinetotic behaviour.

Larval siblings of cichlid fish (Oreochromis mossambicus) were subjected to hypergravity (hg; 3 g, 14 days) during development. Following the transfer to 1 g (i.e., stopping the centrifuge) they were separated into normally and kinetotically swimming individuals (the latter performed spinning movements). During hg, the animals were maintained in aquarium water containing alizarin-complexone (AC), a fluorescent calcium tracer. Densitometric measurements of AC uptake into inner ear otoliths (optical density of AC/micrometers2) revealed that the kinetotic individuals had incorporated significantly more AC/calcium than the normally behaving fish. Since the amount of otolithic calcium can be taken as an approximation for otolith weight, the present results indicate that the otoliths of kinetotically swimming samples were heavier than those of the normally behaving larvae, thus exhibiting a higher absolute weight asymmetry of the otoliths between the right vs. the left side of the body. This supports an earlier concept according to which otolith (or statolith) asymmetry is the cause for kinetoses such as human static space sickness.     

海上夜间飞行的实时仿真

自然场景仿真是虚拟现实技术的重要部分,夜间海上飞行时,星空、月亮以及海面的倒影是独具特色的自然场景.为营造沉浸感强的夜海飞行虚拟现实系统,用粒子系统实现了星空的模拟,将星体动态闪烁现象演化为粒子生命的概念,并按照主导算法加扰动的思想实现星空随机性模拟;用特殊纹理融合算法模拟月亮及星月在海面的镜像,特殊纹理经过制作、着色和融合3个过程,并根据夜空景像在海面倒影的亮度衰减规律确定融合因子,将纹理和背景按照融合因子进行深度融合;最终实现了较逼真的夜海飞行虚拟现实系统.      

基于轮询的高级在轨系统多路复用包时延分析

目前的高级在轨系统(AOS,Advanced Orbiting Systems)多路复用研究主要以仿真为主,很少有文献给出专门的理论分析.针对基于轮询的AOS多路复用包时延进行研究,通过采用排队论中非空竭限量服务的休假排队系统建立模型,并采用循环再生法进行分析,得到了多路复用包时延计算公式,并给出包时延的下限值.仿真结果表明,在包到达率取值分别为1,2,3包/s,在各种不同的下行速率(范围240~330 bit/s)之下,包时延的仿真值曲线均高于理论下限值曲线,从而论证了理论推导的正确性.研究结果可以为工程设计提供一定的参考作用.     

扰动形状对钝头体非对称流动的影响

通过在钝头体头部施加人工扰动块可以得到确定的大攻角下的非对称背涡结构。为了研究扰动块形状对非对称背涡结构的影响,本文在攻角50°、雷诺数Re_D=1.54×105的条件下,利用数值模拟对周向角90°、子午角10°的扰动位置的半球形、D型及方形3种扰动块形状分别进行了研究。研究发现在同一扰动位置,半球形扰动主控下的背涡结构为右涡型,而D型扰动和方形扰动主控下的背涡结构呈现左涡型,且方形扰动主控下的背涡结构的非对称性弱于其他2种扰动主控的非对称背涡。通过分析发现扰动块所引起的微流动直接影响钝头体非对称背涡结构。因此为了更精准地通过施加人工扰动得到确定的非对称背涡结构,应尽量选择形状简单、表面平滑过渡的扰动块形状。      

Vestibular and visual contribution to fish behavior under microgravity.

Vestibular and visual information are two major factors fish use for controlling their posture under 1 G conditions. Parabolic flight experiments were carried out to observe the fish behavior under microgravity for several different strains of Medaka fish (Oryzias latipes). There existed a clear strain-difference in the behavioral response of the fish under microgravity: Some strains looped, while other strains did not loop at all. However, even the latter strains looped under microgravity conditions when kept in complete darkness, suggesting the contribution of visual information to the posture control under microgravity. In the laboratory, eyesight (visual acuity) was checked for each strain, using a rotating striped-drum apparatus. The results also showed a strain-difference, which gave a clue to the different degree of adaptability to microgravity among different strains. Beside loopings, some fish exhibited rolling movement around their body axis. Tracing each fish during and between parabolas, it was shown that to which side each fish rolls was determined specifically to each individual fish, and not to each strain. Thus, rolling direction is not genetically determined. This may support the otolith asymmetry hypothesis. Fish of a mutant strain (ha strain, having homozygous recessive of one gene ha) have some malfunction in otolith-vestibular system, and their behavior showed they are not dependent on gravity. Morphological abnormalities of their ear vesicles during the embryonic and baby stages were noted. Their eyesight and dorsal light responses were also studied. Progress in the project of establishing a new strain which has good eyesight and, at the same time, being deficient in otolith-vestibular system was reported. Crosses between the strain of good eyesight and ha strain were made, and to some extent, F2 fish have already shown such characteristics suited for living under microgravity conditions.     

推力矢量防空导弹伺服弹性的抑制

大长径比,低弹性频率的推力矢量控制导弹,由于其喷管摆动形成的惯性力对弹性模态产生激振,使弹体控制中存在伺服弹性问题.为了解决该问题,对摆动喷管控制下的弹性弹体模型进行了分析,针对弹性模态对控制系统的影响途径,提出了双传感器布局及测量信号预综合的方法.在此基础上,基于Steiglitz-McBride系统辨识方法,设计一种自适应噪声抑制滤波器对测得信号中的弹性分量进行处理,取得导弹刚体运动的有用信号.仿真证明该方法有效提高了控制系统对弹体弹性特征变化的适应性.双传感器的使用也增加了测量及滤波系统的可靠性.     

Effect of hypergravity on carboanhydrase reactivity in inner ear ionocytes of developing cichlid fish.

It has been shown earlier that hypergravity slows down inner ear otolith growth in developing fish. Otolith growth in terms of mineralization mainly depends on the enzyme carboanhydrase (CA), which is responsible for the provision of the pH-value necessary for calcium carbonate deposition. Larval siblings of cichlid fish (Oreochromis mossambicus) were subjected to hypergravity (3 g, hg; 6 h) during development and separated into normally and kinetotically swimming individuals following the transfer to 1 g (i.e., stopping the centrifuge; kinetotically behaving fish performed spinning movements). Subsequently, CA was histochemically demonstrated in inner ear ionocytes (cells involved in the endolymphatic ion exchange) and enzyme reactivity was determined densitometrically. It was found that both the total macular CA-reactivity as well as the difference in reactivities between the left and the right maculae (asymmetry) were significantly lower (1) in experimental animals as compared to the 1 g controls and (2) in normally swimming hg-animals as compared to the kinetotically behaving hg-fish. The results are in complete agreement with earlier studies, according to which hypergravity induces a decrease of otolith growth and the otolithic calcium incorporation (visualized using the calcium-tracer alizarin complexone) of kinetotically swimming hg-fish was higher as compared to normally behaving hyper-g animals. The present study thus strongly supports the concept that a regulatory mechanism, which adjusts otolith size and asymmetry as well as otolithic calcium carbonate incorporation towards the gravity vector, acts via activation/deactivation of macular CA.     

卫星光学敏感器视场有效性分析工具设计

为了提高分析的效率和准确性,基于SolidW orks平台开发了一个卫星光学敏感器视场有效性分析工具.该工具用于分析敏感器在卫星任务期间是否会因为视场问题而失效,以及何时失效.敏感器有效性分析所涉及的问题有:有效性判断的3个层次——敏感器系统、敏感器组和单敏感器的有效性判断;遮挡问题——敏感器会受到卫星部件或目标的遮挡;反光问题——敏感器会受到行星反光和卫星部件反光的干扰;运动问题——包括目标、卫星本体、卫星部件和敏感器的运动.给出了解决以上问题的软件设计方案.介绍了有效性分析功能的实现原理.给出了分析过程的5个步骤:定义时间,定义目标,定义部件运动,定义敏感器和执行分析.最后给出了一个实例演示,验证了该工具的功能.     

Swimming behaviour and calcium incorporation into inner ear otoliths of fish after vestibular nerve transection.

Previous investigations on neonate swordtail fish (Xiphophorus helleri) revealed that otolithic calcium incorporation (visualized using the calcium tracer alizarin complexone) and thus otolith growth had ceased after nerve transection, supporting a hypothesis according to which the gravity-dependent otolith growth is regulated neuronally. Subsequent investigations on larval cichlid fish (Oreochromis mossambicus) yielded contrasting results, repeatedly depending on the particular batch of cichlids investigated. Like most neonate swordtails, Type I cichlids revealed a stop of calcium incorporation after unilateral vestibular nerve transection. Their behaviour after transection was normal, and the otolithic calcium incorporation in controls of the same batch was symmetric. In Type II cichlids, however, vestibular nerve transection had no effect on otolithic calcium incorporation. They behaved kinetotically after transection (this kind of kinetosis was qualitatively similar to the swimming behaviour exhibited by larval cichlids during microgravity in the course of parabolic aircraft flights). The otolithic calcium incorporation in control animals was asymmetric. These results show that the effects of vestibular nerve transection as well as the efficacy of the mechanism, which regulates otolith growth/otolithic calcium incorporation, are--depending on the particular batch of animals--genetically predispositioned. In conclusion, the regulation of otolithic calcium incorporation is guided neuronally, in part via the vestibular nerve and, in part, via a further pathway, which remains to be addressed in the course of future investigations.     

高精度连续时频信号产生和控制系统的分析

具体分析了NTSC和LORAN-C的两套时频基准系统。结果表明,NTSC时频基准系统可以产生高精度的时间频率信号,但是没有主标备份,不利于连续性的保持;而LORAN-C的时频基准系统产生控制高精度时频信号,同时主标发生故障时自动切换到副标,不停止信号的输出,而且切换主标时不会发生信号瞬间中断或相位突变,这些又保证了信号的瞬间连续性。它可广泛应用于守时、授时及导航系统中。     

Experimental analysis of the breakage of a liquid bridge under microgravity conditions

The experimental results obtained in experiment “STACO” made on board the Spacelab D-2 are re-visited, with image-analysis tools not then available. The configuration consisted of a liquid bridge between two solid supporting discs. An expected breakage occurred during the experiment. The recorded images are analysed and the measured behaviour compared with the results of a three dimensional model of the liquid dynamics, obtaining a much better fit than with linear models.