偏铌酸铅压电陶瓷材料老化问题的探讨

对偏铌酸铅压电陶瓷的老化性能作了一些探讨 ,实验表明 ,掺杂改性后的偏铌酸铅显微结构发生了变化 ,晶界处有杂质分凝使得该材料老化性能好。

Influence of Copper Stress on Ultra-structure of Wheat Seedlings

Transmission Electron Microscope (TEM) Technology was used to investigate the effect of 25,100 and 200 mg/kg copper on ultra-structure of root tip and leaf blade of wheat. Result showed that serious damage was found with Copper of 25,100 and 200 mg/kg. Plasmolysis,concentrated cytoplasm,chloroplast inflation,lamellar structure disturbance,capsule disappearance and disintegration,mitochondria structures ambiguity and vacuolization were all symptoms under Cu stress. There were positive correlation between concentration of coper stress and the degree of injury,and the degree of injury of copper were different in different organelles. Mitochondria were the most sensitive organelles,and there was patient difference in the same organelles of different parts.

Influence of electromagnetic stirring on microstructure of AZ91-0.8%Ce magnesium alloy

Effect of electromagnetic stirring on microstructure of AZ91-0.8%Ce magnesium alloy was investigated. The results show that electromagnetic stirring causes a change of morphology of α-Mg phase from coarse dendrites to fine rosette-like or spherical shape. Grain size is significantly refined within the range of input voltage 75?125 V, moreover, the optimum input voltage corresponded to the minimum value (64 μm) of grain size is 125 V. Compared to the non-stirred condition, the amount of β-Mg17Al12 precipitate under the stirred condition obviously increases. The grain refinement of AZ91-0.8%Ce alloy is mainly attributed to multiplication of existing grains in the melt caused by forced fluid flow under electromagnetic stirring condition. Addition of 0.8% Ce results in the formation of ‘necking’ at secondary dendrite arm roots of α-Mg crystals, and consequently, it is helpful to increase the number of heterogeneous nucleation.

Ultrastructure of Kupffer cells and hepatocytes in the Dubin-Johnson syndrome:A case report

Ultrastructure of Kupffer cells and hepatocytes in liver bioptate was evaluated in a 17-year-old boy with Dubin -Johnson syndrome （D.1S）. The liver tissue obtained by needle biopsy was fixed in glutaraldehyde and paraformaldehyde and routinely processed for electron microscopic analysis. The ultrastructural examinations of liver bioptate revealed the accumulation of membranebound, electron-dense lysosomal granules within the cytoplasm of hepatocytes, characteristic of D.1S. They were located mainly in the vicinity of the biliary pole, and preferentially in the centrilobular region that corresponded to the pigment deposits seen under light microscope. The presence of the granules was accompanied by dilated elements of the granular endoplasmic reticulum and paracrystalline mitochondrial inclusions as well as dilation of the bile canaliculi. The changes in hepatocytes coexisted with marked stimulation and enhanced phagocytic activity of Kupffer cells. This was manifested in the accumulation of pigment deposits within their cytoplasm that corresponded to those observed in hepatocytes. Hyperactive pericentral Kupffer cells which are involved in the response to pigmentary material originating from disintegrated hepatocytes may play an essential role in the development of DJS.

Influence of minor Sc additions on grain refinement and microstructure characteristics of a high Zn-containing Al-Zn-Mg-Cu-Zr alloy

In the present work, scandium elements with a series of contents(0.06 wt.%, 0.10 wt.%, 0.14 wt.%,0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cast microstructure characteristics including grains and phases were thoroughly investigated. The results indicated that fine grain boundaries existed in these alloys and fine MgZn2phases discontinuously distributed on them. Besides,AlZnMgCu eutectic phases and Sc, Zr-containing phases with flocculent morphology were observed. As scandium contents vary from 0.06 wt.% to 0.17 wt.%, the average grain size continuously decreased and its equiaxial characteristics were strengthened. Meanwhile, the content of AlZnMgCu eutectic phase showed a decrease trend. When scandium contents were 0.20 wt.% and 0.25 wt.%, no further enhancement on grain refinement was observed, so as to the reduction of AlZnMgCu eutectic phase content. Besides, Sc, Zr-containing phases with blocky morphology were observed and the alloy with a scandium content of 0.25 wt.% possessed a larger amount of blocky Sc, Zr-containing phase than the alloy with a scandium content of 0.20 wt.%. Grain refinement and reduction of AlZnMgCu eutectic phase content associated with scandium addition were discussed.

Analysis of the Microstructure and Permeability of the Laminates with Different Fiber Volume Fraction

Microstructures of laminates produced by epoxy/carbon fibers with different fiber volume fraction were studied by analyzing the composite cross-sections.The main result of the compaction of reinforcement is the flatting of bundle shape,the reducing of gap and the embedment of bundles among each layer.The void content outside the bundle decreased sharply during the compaction until it is less than that inside the bundle when the fiber volume fraction is over 60%.The resin flow velocity in the fiber tow is 102-104 times greater than the flow velocity out the fiber tow no matter the capillary pressure is taken into account or not.

Feasibility studies on cleaning of high sulfur coals by using ionic liquids

Coal has been used as an energy resource around the world, primarily for the generation of electricity. The cleaning of coal by removing its unwanted sulfur and mineral matter components is utmost essential before their gainful utilizations. The ionic liquids （ILs） are considered as non-toxic solvents for using in different industrial processes. The effect of two ILs namely, 1-n-butyl, 3-methylimidazolium tetrafluoro borate （ILl） and 1-n-butyl, 3-methylimidazolium chloride （IL2） in oxidative de-sulfurization and de-ashing of two industrially important high sulfur coal samples from Meghalaya （India） is discussed in this paper. The maximum removal of total sulfur, pyritic sulfur, sulfate sulfur and organic sulfur are observed to be 37.36 %, 62.50 %, 83.33 % and 31.63 % respectively during this oxidative process. The quantitative diffuse reflectance Fourier transform-infrared spectroscopy analysis supports the formation of sulfoxides （S--O） and sulfones （-SO2） and their subsequent removal during the oxidation of the coals in presence of ILs. The X-ray fluorescence combined with near edge X-ray absorption fine structure and scanning electron microscopic studies reveal the removal of mineral matters （ash yields） from the coal samples. The thermogravimetric analysis of the raw and clean coals indicates their high combustion efficiencies and suitability for using in thermal plants. The method is partially green and the ILs could be recovered and reused in the process.

Ultrastructure Developments During Spermiogenesis in Polydora ciliata(Annelida: Spionidae),a Parasite of Mollusca

Spionid worms of Polydora ciliata inhabit the shells of many commercially important bivalves and cause disease in molluscan aquaculture. Their sperm structure is closely related to their fertilization method. To give an insight into the sperm structure and spermatogenesis, ultrastructure details of the subcellular components of germ cells during spermiogenesis of Polydora ciliata are detected by transmission electron microscopy(TEM). In P. ciliata, during spermiogenesis, chromatin is regularly arranged as dense fibrils and becomes more condensed when the nucleus elongates. Microtubules do not surround the nucleus during its elongation. The Golgi phase is characterized by the formation of proacrosomal granules within the Golgi apparatus. The proacrosomal granules fuse to form a single, spherical acrosomal vesicle that migrates to the anterior pole of the cell. At the time of nuclear condensation, mitochondria become reduced in number but increased in size, causing deep indentation at the base of the nucleus. The mid-piece has a few mitochondria. The cap phase includes the spreading of the acrosomal granule over the surface of the nucleus of the differentiating spermatid. The acrosomal phase of spermiogenesis is typically associated with changes in the shape of the nucleus, acrosome and tail. The relationship of sperm ultrastructure to spermiogenesis in spionidae species was discussed.

Effects of spaceflight and simulated microgravity on cell sub-microstructure and antioxidant enzyme activity in tomato

Controlled ecological life support systems provide food, air, water, and other basic living resources for crew members on long-duration spaceflight missions. Plants are an important basic requirement of these systems and their biological characteristics in space have very high research value. Based on experiments of spaceflight in Shenzhou 8 spacecraft and simulating microgravity effects on three-dimensional （3-D） clinostat, the biological characteristics of tomato＇s leaf cell sub-microstructure and antioxidant enzyme activities were studied and compared in this work. Results showed that leaf cell sub-microstructure of the tomato samples experiencing spaceflight had more changes than effects, and both peroxidase （POD） and superoxide dismutase （SOD） that of the samples processed by simulated microgravity activities increase obviously in both the environments.

Actin,more than just a housekeeping protein at the scene of fertilization

Since the first demonstration of sperm entry into the fertilized eggs of Mediterranean sea urchin Paracentrotus lividus by Hertwig(1876),enormous progress and insights have been made on this topic.However,the precise molecular mechanisms underlying fertilization are largely unknown.The two most dramatic changes taking place in the zygote immediately after fertilization are:(i) a sharp increase of intracellular Ca2+ that initiates at the sperm interaction site and traverses the egg cytoplasm as a wave,and(ii) the concomitant dynamic rearrangement of the actin cytoskeleton.Traditionally,this has been studied most extensively in the sea urchin eggs,but another echinoderm,starfish,whose eggs are much bigger and transparent,has facilitated experimental approaches using microinjection and fluorescent imaging methodologies.Thus in starfish,it has been shown that the sperm-induced Ca2+ increase in the fertilized egg can be recapitulated by several Ca2+ -evoking second messengers,namely inositol 1,4,5-trisphosphate(InsP3) ,cyclic ADP-ribose(cADPr) and nicotinic acid adenine dinucleotide phosphate(NAADP) ,which may play distinct roles in the generation and propagation of the Ca2+ waves.Interestingly,it has also been found that the dynamic rearrangement of the actin cytoskeleton in the fertilized eggs plays pivotal roles in guiding monospermic sperm entry and in the fine modulation of the intracellular Ca2+ signaling.As it is well known that Ca2+ regulates the structure of the actin cytoskeleton,our finding that Ca2+ signaling can be reciprocally affected by the state of the actin cytoskeleton raises an intriguing possibility that actin and Ca2+ signaling may form a'positive feedback loop'that accelerates the downstream events of fertilization.Perturbation of the cortical actin networks also inhibits cortical granules exocytosis.Polymerizing actin bundles also compose the'acrosome process,'a tubular structure protruding from the head of fertilizing sperm. Hence,actin,which is one of the most strictly conserved proteins in eukaryotes,modulates almost all major aspects of fertilization.

The cytotoxicity of oxidized multi-walled carbon nanotubes on macrophages

Carbon nanotubes(CNTs) have been developed for medical and biotechnological applications in the past decades. Their widespread applications make it important to understand their potential hazards to human and the environment. In this study, the possible toxicological effects of the oxidized multi-walled carbon nanotubes(O-MWCNTs) were assessed on RAW 264.7 macrophages in vitro. Several toxicological endpoints, such as cell viability, the release of LDH and IL-8, GSH/GSSG ratio, intracellular calcium concentration and ultrastructural changes in cell morphology, were carried out. The results showed that O-MWCNTs had very limited effects on oxidative stress, cellular toxicity and apoptosis. Transmission electron microscope clearly demonstrates RAW 264.7 macrophages engulfed plenty of O-MWCNTs, and some of them resided in the cytoplasm, while the morphology was not altered by O-MWCNTs. As the control, the pristine MWCNTs(p-MWCNTs) show higher cytotoxicity than O-MWCNTs, damaging cell viability and inducing cell apoptosis. All these toxicological data are of benefit to more wide applications of O-MWCNTs in the future.