X-ray holograms at improved resolution: a study of zymogen granules

X-ray holography offers the possibility of three-dimensional microscopy with resolution higher than that of the light microscope and with contrast based on x-ray edges. In principle, the method is especially advantageous for biological samples if x-rays in the wavelength region between the carbon and oxygen K edges are used. However, until now the achieved resolution has not exceeded that of the light microscope because of the poor coherence properties of the x-ray sources and the low resolution of the detectors that were available. With a recently developed x-ray source based on an undulator on an electron storage ring, and high resolution x-ray resist, a hologram has been recorded at about 400-angstrom resolution. The experiment utilized x-rays with wavelengths of 24.7 angstroms and required a 1-hour exposure of the pancreatic zymogen granules under study.     

Erratum

In the abstract of the Report ;;Three-dimensional readout of flash x-ray images of living sperm in water by atomic-force microscopy' by T. Tomie et al. (3 May, p. 691), the word ;;subpicosecond' should have been ;;subnanosecond.'     

Microanalysis of individual mitochondrial granules with diameters less than 1000 angstroms

A scanning electron microscope was converted to an electron microprobe with high spatial resolution by the addition of a transmitted electron detector and a solid-state x-ray detector. Spectra obtained from mitochondrial granules of chondrocytes in situ confirm the suspected presence of calcium and phosphorus. Contamination during analysis can lead to false indications of silicon in living tissue.     

Electrical responses of eggs to acrosomal protein similar to those induced by sperm

The earliest known response of eggs to sperm in many species is a change in egg membrane potential. However, for no species is it known what components of the sperm cause the opening of the egg plasma membrane channels. Protein isolated from sperm acrosomal granules of the marine worm Urechis caused electrical responses in oocytes with the same form, amplitude, and ion dependence as the fertilization potentials induced by living sperm. Sperm initiated fertilization potentials in oocytes when sperm-oocyte fusion, but not binding, was inhibited by clamping oocyte membrane potentials to positive values. Acrosomal protein also initiated electrical responses in clamped oocytes. These results support the hypothesis that it is the sperm acrosomal protein that opens ion channels in the oocyte membrane.     

灾民生活史:基于中西社会的初步考察

灾民生活是灾荒史考察的重要内容,在中西方历史灾荒比较研究的基础上,本文将研究灾民生活的诸多方面,比较研究了中西方农民生活的一般景象、灾荒发生后灾民生活的巨大差异以及特殊灾害时期灾民的生活行为。结果表明,中国古代完备的荒政制度在救荒济民的过程中发挥了良好的救灾效果,大灾之后并非一定大荒;欧洲国家缺乏有效的国家政策救济灾民,重大灾害发生后灾情极为严重。     

Abductin: a rubber-like protein from the internal triangular hinge ligament of pecten

The rubber-like internal triangular hinge ligament from Pecten was studied by light and electron microscopy, x-ray diffraction, and chemical analysis. The ligament is composed of an amorphous protein, abductin. In physical properties abductin is similar to elastin and resilin but distinct by amino acid analysis. It is characterized by high concentrations of glycine and methionine.     

Synthesis of polycrystalline chalcopyrite semiconductors by microwave irradiation

Polycrystalline samples of the chalcopyrites CulnS(2), CulnSe(2), and CulnSSe were Prepared from stoichiometric mixtures of the pure elements by microwave irradiation. The reactions were performed in sealed quartz tubes in as few as 3 minutes. The products were analyzed by x-ray diffraction, scanning electron microscopy, energy dispersive x-ray analysis, and x-ray photoelectron spectroscopy. The surface morphology and shape of the particles produced by this method suggest that the products are formed from liquid melts. This method could be applied to the production of bulk chalcopyrite as sources for thin film growth.     

Interstratified clays as fundamental particles

Materials representing common interstratified clay minerals are shown to be composed of aggregates of fundamental particles. Transmission electron microscopy and x-ray diffraction demonstrate that the x-ray diffraction characteristics of a wide range of interstratification can be modeled experimentally by utilizing materials containing only three types of particles. The data have been incorporated into a new model that regards interstratified clay minerals as populations of fundamental particles whose x-ray diffraction patterns result from interparticle diffraction.     

草鱼肠道抗菌肽对细菌形态结构的影响及理化性质研究

通过扫描电子显微镜观察草鱼肠道抗菌肽处理后的大肠杆菌、金色葡萄球菌、嗜水气单胞菌的形态结构的变化.结果显示,经过抗菌肽处理后的细菌形态发生变化,菌体严重变形,表面变得粗糙,出现皱褶,胞膜破裂.对草鱼肠道抗菌肽的理化性质的研究结果显示,草鱼肠道抗菌肽具有很好的热稳定性,耐胰蛋白酶特性.     

中间球海胆精子超低温冷冻损伤的研究

应用透射电镜技术研究了超低温冷冻保存对中间球海胆Strongylocentrotus intermedius精子超微结构的影响。结果表明：不加抗冻剂的情况下,精子线粒体和顶体结构不完整,质膜、鞭毛破损。加入保护剂后,多数精子结构完好,部分精子细胞器受损,表现为质膜褶皱或膨胀举起,与核膜的间隙明显增大;顶体肿胀、破裂或脱落;线粒体嵴间隙增大,内部出现空泡,甚至线粒体内膜破损,内嵴减少,呈弥散状;鞭毛被膜肿胀,呈波浪状,＂9＋2＂型结构模糊;细胞核结构没有明显变化。应用单细胞凝胶电泳技术研究了精子冷冻保存前后DNA的损伤。结果表明,不加抗冻剂的冷冻组及添加抗冻剂的试验组精子DNA损伤情况与鲜精相比均无显著差异（P〉0.05）,冷冻对精子结构的损伤是造成精子活力及受精率下降的主要原因。     

Three-dimensional orientation mapping in the transmission electron microscope

Over the past decade, efforts have been made to develop nondestructive techniques for three-dimensional (3D) grain-orientation mapping in crystalline materials. 3D x-ray diffraction microscopy and differential-aperture x-ray microscopy can now be used to generate 3D orientation maps with a spatial resolution of 200 nanometers (nm). We describe here a nondestructive technique that enables 3D orientation mapping in the transmission electron microscope of mono- and multiphase nanocrystalline materials with a spatial resolution reaching 1 nm. We demonstrate the technique by an experimental study of a nanocrystalline aluminum sample and use simulations to validate the principles involved.     

萜类化合物的生理生态功能及经济价值

从增强植物抗病能力、帮助植物抵御天敌、维系植物与其他生物类群的互惠关系以及化感作用等方面综述了萜类化合物维系植物自身生存和发展的生理生态功能。同时，从作为药物的有效成分以及在工业和农业上的利用等方面，综述了萜类化合物对人类的经济价值。     

体外成熟猪卵母细胞的体外受精研究

实验采用体外成熟的猪卵巢卵母细胞，将鲜精以前培养结合咖非因法获能后进行ＩＶＦ实验．体外成熟卵ＩＶＦ后的卵裂率为２４．７％～３８．４％，与目前文献报道的近似；授精时精子浓度为２×１０５／ｍＬ，１×１０６／ｍＬ和５×１０６／ｍＬ体外受精后的卵裂率分别为４０．８％（８２／２０１）．４５％（８５／１８９）和３０．５％（５０／１６４）．前二者无显著差异，但都与最后一组差异显著．我们认为，在本实验条件下，体外受精时适当的精子浓度要比目前常用的１×１０６／ｍＬ低．我们将肝素结合咖啡因的精子在能方法与前培养结合咖啡因法进行了比较，卵裂率分别为１０．７％（９／８４）和４０％（３２／８０），前者虽然在牛体受精实验中很成功．但在猪效果差．将体外成熟体外受精卵移入同步的受体猪输卵管后．有一头母猪成功地产下了５只“试管猪’，存活３只．     

大白公猪精浆外泌体miRNA表征鉴定及功能分析

【目的】精浆外泌体(Seminal plasma exosome,spEX)在精子成熟、凋亡、受精中起着至关重要的作用。本文旨在探究种公猪spEX miRNA表达及miRNA在精子成熟及功能维持过程中的潜在调控作用。【方法】提取大白公猪spEX并进行电镜分析、粒径分析、标志性蛋白表达分析和miRNA高通量测序。【结果】成功分离出spEX，利用miRNA测序共鉴定出329个spEX miRNA。对高表达miRNA进行靶基因预测和功能富集分析，结果表明spEX miRNA在射精、P53信号通路、前列腺癌、细胞对DNA损伤刺激的反应、负调控凋亡过程、顶体膜结合、受精等通路中均发挥了潜在调控作用。【结论】本研究为spEX miRNA在调控精子活力和精子受精作用方面提供基础数据，并为精液保存调控机制的研究提供参考。     

辽宁省完善扶贫开发与农村低保制度衔接机制实施研究

阐述了扶贫开发与农村最低生活保障制度的功能定位及其在辽宁省的实施状况,提出完善辽宁省扶贫开发与农村最低生活保障制度有效衔接的建议:建立贫困人口识别机制,科学界定"两项制度"的工作对象;善用"两项制度"的专项资金,提高资金使用效益;稳步推进农村最低生活保障,确立"发展型"扶贫开发工作机制;加强配套性制度建设,为"两项制度"有效衔接创造良好条件。     

High cristobalite and high tridymite in a middle eocene deep-sea chert

The high-temperature forms of cristobalite and tridymite have been found occurring in a Middle Eocene, radiolarian-rich claystone. Evidence indicates that these crystals formed at low temperature and were chemical precipitates. Scanning electron microscopy, energy-dispersive x-ray analysis (microprobe), and x-ray diffraction provided the data upon which the determinative mineralogy was based.     

A Spatially Resolved X-ray Image of a Star Like the Sun

Observations made with the x-ray satellite ROSAT (Roentgen Satellite) have produced the first spatially resolved x-ray image of a corona around a star like our sun. The star is the secondary in the eclipsing binary system alpha Coronae Borealis (CrB), which consists of one star of spectral type A0V and one of type G5V. The x-ray light curve of alpha CrB shows a total x-ray eclipse during secondary optical minimum, with the G star behind the A star. The totality of the eclipse demonstrates that the A-type component in alpha CrB is x-ray dark and that the x-ray flux arises exclusively from the later-type companion. The x-ray eclipse ingress and egress are highly asymmetric compared with the optical eclipse, indicating a highly asymmetric x-ray intensity distribution on the surface of the G star. From a detailed modeling of the ingress and egress of the x-ray light curve, an eclipse map of the G star was constructed by a method based on an optimization by simulated annealing.     

包世臣在江苏的救荒活动及其思想

作为鸦片战争前后杰出的经世思想家,包世臣身处清朝国力渐弱、荒政渐衰之际,高度关怀民生疾苦。在江苏扬州和江宁,他主动参与救荒活动,积极出谋划策,赈济灾民。他批判荒政黑幕,切中时弊,并紧密结合具体需要,提出一些建设性的措施,如及早备荒、安辑流民、以工代赈、劝捐救荒等。对于灾民,他抱着深切的同情,忧其所忧,乐其所乐,并表现出...     

TEMPO氧化法制备氧化纤维素纳米纤维

以漂白针叶木浆为纤维原料,在2,2,6,6-四甲基哌啶氧自由基(TEMPO)-NaClO-NaBr的氧化体系下制备得到氧化纤维素纳米纤维.采用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、红外光谱(FT-IR)、X-射线衍射仪(XRD)、热重分析仪(TG)等手段对氧化纤维素进行表征,并测定氧化纤维素羧基质量摩尔浓...     

Smectic liquid crystal monolayers on graphite observed by scanning tunneling microscopy

By means of scanning tunneling microscopy, it is observed that molecules of the form n-alkylcyanobiphenyl, where n = 8 to 12, form two-dimensional crystalline domains when adsorbed onto graphite. The layer spacings measured by tunneling microscopy are 20% larger than those measured previously on bulk material by x-ray diffraction. The structure of the adsorbed molecules is quite different from that of the bulk.