非接触式间隙密封旋转接头动力学建模与分析

目的研究非接触式间隙密封旋转接头的动力学特性。方法针对一种典型的间隙密封旋转接头,建立考虑非线性油膜力、转子旋转运动和浮环振动等因素的系统动力学方程,采用数值仿真分析油膜间隙、转速、密封圈刚度等对转子和浮环运动的影响。结果间隙越大,转子运动幅值越大,转子与浮环的相对运动位移也越大;随着转速的升高,转子和浮环运动幅值先增大后减小;随着密封圈刚度的增大,转子和浮环的运动幅值先增大后减小。结论建立的动力学模型可用于分析非接触式间隙密封旋转接头的动力学特性,为旋转接头设计提供了理论方法。     

Prenatal investigation of a 45,X/46,X,r(?) karyotype in amniocytes using fluorescence in situ hybridization with an X-centromeric probe

The karyotype of cultured amniotic fluid cells obtained on the indication of advanced maternal age was shown to be a mosaic 45,X/46,X,r(?). The small size and banding pattern made it difficult to determine whether the ring was derived from and X or a Y chromosome, or even from an autosome. By using an X-centromeric probe and fluorescence in situ hybridization (FISH), we demonstrated the ring to have an X centromere. Thus, a more complete genetic counselling was possible. This confirms the usefulness of FISH in identifying and characterizing this and other chromosome rearrangements in prenatal diagnosis.     

Habitat patch size and isolation as predictors of occupancy and number of argyrodine spider kleptoparasites in Nephila webs

How fully a suitable habitat patch is utilized by organisms depends crucially on patch size and isolation. Testing this interplay is made difficult in many systems by the arbitrariness of defining a "habitat patch", measuring its boarders, and relatively low detection probability of the inhabitants. Spider webs as habitat patches for obligate web kleptoparasites are free from these problems. Each individual web is a highly discrete and readily measured habitat patch, and the detection probability of argyrodine spider kleptoparasites is very nearly 1. Hence, spider webs emerge as simple systems for ecological models such as patch occupancy and metapopulation biology. Recently, I showed that the distribution of kleptoparasites among host webs relates both to web (patch) size as well as patch connectivity. Here, I test the relative importance of patch size versus isolation in explaining patch occupancy and abundance of inhabitants. I find that (1) web size is the better predictor of patch occupancy and abundance. (2) Web size is overall positively correlated with abundance, but predicts it most precisely among interconnected webs and not at all among the most isolated webs. Hence, patch occupancy and inhabitant abundance is explained by a rather complex interplay between patch size and isolation.     

A new giant pterosaur with a robust skull from the latest cretaceous of Romania

A new giant pterosaur, Hatzegopteryx thambema, nov.gen., nov.sp., from the Maastrichtian Densu?-Ciula Formation of Romania is remarkable for its very large size (estimated wing span > or = 12 m) and for the robustness of its large skull, which may have been nearly 3 m long. The stout skull bones contrast with the usually thin and slender skull elements of other pterosaurs, and raise the question of how the weight of the skull was reduced in order to make flight possible. The answer probably lies in the very peculiar internal structure of the bones, which consists of a dense network of very thin trabeculae enclosing small alveoli. This structure is reminiscent of expanded polystyrene and, like it, probably combined strength with lightness.     

中国3个AERONET站点气溶胶微物理特性分析及比较

选取中国地区区域代表性较强且观测时间序列较长的3个AERONET站点(SACOL、香河和太湖),分析了其气溶胶微物理参数特征. 香河和太湖多年平均气溶胶光学厚度(AOD)分别为0.67±0.66和0.72±0.44,是SACOL AOD平均值(0.38±0.27)的近2倍,且AOD变化范围较大. SACOL春冬季AOD较大,夏秋季AOD较小;而香河和太湖夏春季较大,秋冬季较小.结合尺度分布、体积浓度等参数特征说明沙尘是SACOL春季最主要的气溶胶类型,香河春季受沙尘的影响也较严重,而太湖受沙尘影响的频率较香河要小的多;香河和太湖AOD最大值出现月份与细模态粒子体积浓度最大值出现月份一致,是由于细模态粒子的消光效率是粗模态粒子的3~4倍.细模态体积比(Vf/Vt)的年变化趋势与?ngstr?m波长指数(?)的年变化趋势相似,Vf/Vt和?均可以用来分析粒子尺度大小的年变化特征.但?1.7时,Vf/Vt大于0.6,以细模态粒子为主;而0.75相似文献   

基于温度循环失效机理的铝制金属密封圈疲劳寿命仿真

目的 解决真空法兰密封中的金属密封圈寿命难以预测的问题.方法 基于金属密封圈的失效机理,提出一种疲劳仿真方法 ,对金属密封圈的使用寿命进行有效预测.通过有限元仿真方法 对金属密封圈安装过程及其使用过程进行仿真模拟,得到金属密封圈使用过程的应力分布,然后结合Conffin-Manson疲劳模型,对金属密封圈的使用寿命进行...     

A case of ring chromosome 22 with deletion of the 22q13.3 region associated with agenesis of the corpus callosum,fornix and septum pellucidum

We report a 16-week-gestation foetus obtained by voluntary abortion after prenatal diagnosis, in which a ring chromosome 22 was observed with deletion of the 22q13.3 region. A prenatal study of the amniotic fluid by standard chromosome technique with G bands and FISH (fluorescence in situ hybridisation) was performed. After the abortion, the anatomopathological study of the obtained foetus was carried out. Morphological and histological analysis of the foetus did not reveal severe physical abnormalities, although alterations of the nervous system were observed consisting of corpus callosum, fornix and septum pellucidum agenesia. It could be that the genes in this region that were involved in the development of the central nervous system were responsible for the alterations found in the morphological study. The wide range of manifestations observed in patients with this cytogenetic alteration is probably due to size differences in the deleted region. Copyright © 2004 John Wiley & Sons, Ltd.     

黄海表层沉积物中总磷的地球化学特征

对黄海陆架区的 7条测线的表层沉积物样品进行了总磷 (TP)的分析测定 ,阐述了调查海区TP的平面分布特征 ,通过分析水动力条件、粒度及磷的自生作用等因素 ,探讨了TP聚集区和分散区的成因 ,发现沉积物的粒径与TP含量的相关性较差 ,与其他区域P的丰度进行比较后 ,认为黄海表层沉积物中P为非陆源性的 ,并处于“弱贫化”状态。     

20世纪初以来沂蒙山区森林植被动态及其对气候变化的响应——基于遥感和树轮的研究

遥感能够直接反映植被生长信息,但目前观测时间较短;树轮资料可以弥补遥感手段的不足,但往往缺乏与植被生长状况（如植被生产力）的直接关联。已有研究往往计算不同植被指数指标和树轮指数的相关性,并基于此来重建长时间尺度的植被动态信息。但基于相关性所选取的指标在不同地区存在较大差异,不利于空间对比研究。以沂蒙山区为研究区,选取能够有效表征植被年初级生产力的生长季NDVI累积值指标,利用Bootstrap法建立了其与树轮宽度的关系,重建了20世纪初期以来植被动态时间序列,并分析了变化特征及其与气候变化的关系。结果表明：沂山地区生长季NDVI累积值的多年平均值为7.36,低于蒙山和塔山地区;蒙山地区植被状况呈现好转趋势,特别是20世纪90年代之后植被好转趋势更加明显,而塔山和沂山地区植被无显著变化。小波分析结果表明研究区植被动态存在较显著的2 a、4 a或8 a尺度的周期变化,与生长季帕尔默干旱指数及平均温度的周期变化相一致,但干旱指数与植被动态具有更高的相关性。本研究综合运用树轮与遥感技术发展了长时间尺度植被动态时间序列重建方法,有助于更好地理解植被动态及其对气候变化的响应。     

藻-菌颗粒污泥胞外聚合物及其表面特性研究

藻-菌颗粒污泥具有能耗低、温室气体排放量少等优点,近年来在污水处理领域受到关注.胞外聚合物(EPS)在保护微生物免受恶劣环境影响及促进细胞聚集方面发挥重要作用,而关于藻-菌颗粒EPS及其表面特性鲜有报道.选取了粒径范围在0.36~0.71、1~1.25、1.6~2.0 mm的3组藻-菌颗粒,分析了其EPS中多糖和蛋白质的含量,并进一步地对其组成差别以及官能团特征进行探究,探讨了EPS提取前后藻-菌聚集体表面电荷的变化.结果表明,随着粒径的增大,藻-菌颗粒污泥EPS中多糖和蛋白质的含量均有增加,而蛋白质与多糖的比值减小.不同粒径的藻-菌颗粒污泥EPS中芳香蛋白与酪氨酸类物质的含量明显增加,腐殖酸类物质含量亦呈总体增加趋势,与胞外蛋白相比,胞外多糖特征峰的波峰强度增加较明显.进一步分析表明,粒径较大的颗粒可能更能抵御外界环境因素的变化,以维持颗粒性能.以上结果表明,粘性和亲水性的多糖、芳香蛋白和酪氨酸类物质可能更有利于藻-菌颗粒的微生物细胞聚集.本文的研究结果进一步地拓展了对藻-菌颗粒污泥的认识,并为其进一步的工程应用提供基础.     

Species-dependent effects of the phenolic herbicide ioxynil with potential thyroid hormone disrupting activity: modulation of its cellular uptake and activity by interaction with serum thyroid hormone-binding proteins

Ioxynil, a phenolic herbicide, is known to exert thyroid hormone (TH) disrupting activity by interfering with TH-binding to plasma proteins and a step of the cellular TH-signaling pathway in restricted animal species. However, comparative studies are still lacking on the TH disruption.We investigated the interaction of [¹²⁵I]ioxynil with serum proteins from rainbow trout, bullfrog, chicken, pig, rat, and mouse, using native polyacrylamide gel electrophoresis. Candidate ioxynil-binding proteins, which included lipoproteins, albumin and transthyretin (TTR), differed among the vertebrates tested. Rainbow trout and bullfrog tadpole serum had the lowest binding activity for ioxynil, whereas the eutherian serum had the highest binding activity. The cellular uptake of, and response to, ioxynil were suppressed by rat serum greater than by tadpole serum. The cellular uptake of [¹²⁵I]ioxynil competed strongly with phenols with a single ring, but not with THs. Our results suggested that ioxynil interferes with TH homeostasis in plasma and with a step of cellular TH-signaling pathway other than TH-uptake system, in a species-specific manner.     

Kernfusion und das Energieproblem

The present understanding of the physics and technology problems of confining a hot plasma ring by magnetic fields and of heating it to such temperatures that thermonuclear fusions between deuterium and tritium nuclei provide the energy required to maintain this temperature seems to allow to predict the possibility of a self-sustaining thermonuclear reactor. Imbedding this chance into world energy scenarios for the next fifty years, it is shown that fusion reactors of a type of which each may supply about ten slow fission reactors with fissionable material may play a critical rôle by drastically reducing the number of required fast fission breeder reactors.     

径轴向辗环机优化轧制规程的计算机辅助设计

此文介绍了利用数字计算机进行矩形截面环轧制的优化规程设计方法,优化是基于轧制过程的物理模型,考虑了各种轧制约束条件,结果符合实际生产情况,并且可使轧机容量得到充分利用,大大缩短轧制所需时间,节约材料与能源消耗。     

Design of Profile Ring Rolling by Backward Simulation Using Upper Bound Element Technique (UBET)

The upper bound element technique (UBET) is used to determine the optimum intermediate shape for profile ring rolling using backward simulation. The lowest energy rate is the key issue in achieving the optimal intermediate shape as well as the backward simulation of the process. The plastic flow of material in ring rolling is assumed to be a sequence of successive closed-die forging processes. The ring is divided into features, which provide an approximated profile consisting of a number of rectangular elements. The simulation of the profile ring rolling was tested with different profiles of rolls, and two such cases are presented here. The present method was validated using an experimental radial ring rolling mill designed and fabricated in the Dept. of Mechanical Engineering at Ohio University for the investigation of both cold and hot ring rolling processes. As the results show, this technique is capable of solving the backward simulation of profile ring rolling problems in a much shorter time compared to the finite element method (FEM), which cannot easily simulate profile ring rolling. Moreover, as an engineering tool, this approach can be applied effectively to the profile ring rolling process and can serve as a useful tool in industrial applications.     

厦门近海表层沉积物结构特征及物源初探

为研究厦门近海海域表层沉积物的结构特征、组成及来源,于2010年7月采集厦门湾表层沉积物,综合粒径分析、X射线衍射、扫描电镜等方法对沉积物进行表征。粒径分析的结果表明,沉积物的主体粒径在80μm附近,且有明显的次粒级峰,并以粗颗粒的主体粒级峰占有优势。研究的沉积物类型主要有三种,砂质粉砂、粉砂质砂和砂-粉砂,其中砂质粉砂是分布最广泛的沉积物类型区域沉积物,其含量达90%以上;而粘土含量以背景点鸡屿岛为最高,达到11.97%。X射线衍射分析表明,沉积物中优势轻矿物为石英、高岭石,部分区域含有石墨及一些零星分布的伊利石、海绿石和斜绿泥石。这些矿物组成显示了厦门湾海域表层沉积物具有较好的亲陆性,同时,其组成也受到了涨潮流的较大影响。沉积物形貌形态的研究发现,厦门湾沉积物组分较为复杂,其中含有多种藻类及其碎片(主要为硅藻)、矿物颗粒(高岭石)及未知名碎片;形状主要有孔状结构、层叠状结构、长条片状和不规则的六边形块状等。     

空气环境飘尘测定中的若干问题

空气环境超微飘尘颗粒，不能用一般光学方法测定，必须用X射线小角散射测定，在这种测定中，都认为测量角度越低就越准确，本文指出太低角区的散射光是由于颗粒间的干涉造成的，若不设法消除，会使测定结果偏大，甚至是错误的，同时由于不同粒度的颗粒会散射到不同的角区，所以又想用这个方法去测粒度的分布，这种做法会产生错误的结果，所以测定时应特别注意。     

含钛高炉渣光催化降解糠醛废水

利用含钛高炉渣作为光催化材料光催化降解糠醛废水,采用静态试验的方法研究了粉末含钛高炉渣光催化降解糠醛废水的部分影响因素。在糠醛废水溶液浓度一定的条件下,存在一个最佳投放量为0.7g,降解率为63%,并且催化剂粒径越小催化效果越好,粒径为2μm时,降解率为36%。废水温度30℃时,处理效率最高,达到22%。在酸性条件下,催化剂催化效果稳定。因此含钛高炉渣作为光催化材料对糠醛废水有降解作用。     

基于三角网格的电磁数据的内插和可视化方法

研究了从采集的离散点场强生成整个平面区域的场强的插值方法,及生成的场强数据可视化的颜色映射方法.采用基于三角网格的内插技术,先对二维离散点构造三角网格;假定每个三角形的顶点场强、坐标构成一平面空间,三角形内部的未采集点场强可以由顶点决定的场强平面方程插值求得.给出了插值结果可视化的四段制颜色映射解决方案,与目前国际上主流电磁软件颜色映射方式一致.     

Olfactory learning and memory in the bumblebee Bombus occidentalis

In many respects, the behavior of bumblebees is similar to that of the closely related honeybees, a long-standing model system for learning and memory research. Living in smaller and less regulated colonies, bumblebees are physiologically more robust and thus have advantages in particular for indoor experiments. Here, we report results on Pavlovian odor conditioning of bumblebees using the proboscis extension reflex (PER) that has been successfully used in honeybee learning research. We examine the effect of age, body size, and experience on learning and memory performance. We find that age does not affect learning and memory ability, while body size positively correlates with memory performance. Foraging experience seems not to be necessary for learning to occur, but it may contribute to learning performance as bumblebees with more foraging experience on average were better learners. The PER represents a reliable tool for learning and memory research in bumblebees and allows examining interspecific similarities and differences of honeybee and bumblebee behavior, which we discuss in the context of social organization.     

Pilot study for the neonatal screening of fragile X syndrome

An Erratum has been published for this article in Prenatal Diagnosis 23 (9), 2003, 771. Fragile X syndrome (SFX) is the commonest form of inherited mental retardation. Due to the highly variable phenotype clinical diagnosis is complicated. In nearly all cases, the disorder is caused by expansion of a CGG-repeat in the 5′-untranslated region of the FMR1 (fragile X mental retardation-1) gene. We have evaluated the feasibility, efficiency and costs of two methodologies in order to develop a simple test to screen large populations: PCR and fragile X mental retardation-1 protein (FMRP) immunodetection. We studied 100 newborn males using PCR and immunodetection (26.91 Euro). All but one amplified the CGG repeat of the FMR1 gene within the normal size range. The sample that failed to amplify showed only 28% of FMRP expression by immunodetection study; both results indicated an affected male. A further 100 males were studied only by polymerase chain reaction (PCR) (7.8 Euro); all of them amplified within the normal size range. Both methodologies, PCR and immunodetection, are feasible for screening large populations, PCR being the most suitable, economical and less time-consuming. However, it is advisable to keep slides for immunodetection when PCR fails or the external control shows no amplification. Early detection of SFX-affected individuals would represent a great benefit for their maximum social integration, due to appropriate treatment and early stimulation and would permit a cascade screening in their pedigree. Copyright © 2002 John Wiley & Sons, Ltd.