微胞结构纯铁/铁氧体复合材料制备及性能研究

文章通过放电等离子烧结技术(Spark Plasma Sintering,简称SPS),烧结由化学沉淀法制备的Zn0.5Ni0.5Fe2O4包覆的纯Fe微米级颗粒,实验结果表明:经化学包覆后烧结的块体复合材料较纯铁矫顽力明显降低具有优异软磁性能。

SPS烧结TiO_2/Al_(90)Mn_9Ce_1微胞陶瓷金属基块体复合材料

用表面包覆8wt％TiO2纳米粉末的微米Al90Mn9Ce1合金复合粉末，制备了高致密的闭合微胞陶瓷结构，内充金属合金的块体复合材料，烧结温度仅为520℃，烧结后的致密度达到98．2％。SEM观察结果显示，该材料的陶瓷胞壁厚度约为1．0～2．0μm，胞体尺寸约为15～40μm，经10％HCl深腐蚀后，留下完整的微胞状陶瓷骨架。根据实验结果，对SPS烧结微-纳米混合粉体的瞬时界面烧结机理进行探讨。

微胞陶瓷/金属块体复合材料

用放电等离子烧结（spark plasma sintering，SPS）方法，烧结表面包覆纳米Al2O3的球形Al90Mn9Ce1合金复合粉末，制备了一种高致密微胞陶瓷／金属块体复合材料，烧结温度只有520℃．该材料由蜂窝状封闭Al2O3陶瓷胞壁和Al90Mn9Ce1合金胞体组成，胞体尺寸约为20-40gm，胞壁壁厚1-2μm．材料抗压强度达到514MPa，压延塑性约0．65％．这种特殊结构预示可能具有极好的耐腐蚀性能及耐热性能．这种微胞结构Al90Mn9Ce1，Al2O3复合材料的成功制备，为新型陶瓷／金属复合材料的设计提供了新思路．

Ultrastructure of the Multicellular Nodules in Hypericum perforatum Leaves

With the development of the multicellular nodules in the leaves of Hypericum per plastids increased both in number and volume, and some plastids degenerated and were surrounded by dark tubular elements and vesicles. Some vesicles fused with vacuoles and secreted substances into vacuoles. There are many multivesicles, multimembrane structures and osmiophilic droplets in vacuoles of nodule cells. Meanwhile, dictyosome secreted vesicles into the vacuoles. However, there is a large central vacuole completely filled with secretory materials (hypericin) in matured multicellular nodules. This suggests that the osmiophilic droplets may be a precursor of hypericin originated from the degenerated plastids. There were abundant endoplasmic reticulums and dictyosomes between the plastids and osmiophilic droplets, suggesting that they may be involved in the synthesis and/or transport of the precursor of hypericin.

Nerve Terminal Types of Sinus Gland and Neurosecretory Cell Types of X-organ in Crab Eriocheir sinensis

The ultrastructure of the X organ sinus gland complex in sexually immature Chinese mitten crab Eriocheir sinensis was examined under the electron microscope. The sinus gland (SG) is composed primarily of nerve terminals and glial cells. The terminal contains a great number of membrane bound granules, mitochondria, rough endoplasmic reticulum and electron lucent vesicles. The profiles of the terminals are sometimes exhibited finger like projections. The X organ (XO) locates at the ventral surface of the medulla terminalis ganglion in the eyestalk, oppositing to SG. According to the features of granule size, shape, electron density and cytoplasm, 6 types of terminals in SG and 7 types of neurosecretory (NS) cells in XO were identified. The release process by exocytosis of the granules in SG was observed and a tentative comparison was made for the granules between different types of terminals and NS cells. It seemed that they had a good correspondence since no change in electron density and just a slight increase of sizes was shown.

Seasonal Changes in the Ultrastructure of the Vascular Cambium in Shoots of Populus tomentosa

Wood is the product of cambial activity in trees, and the seasonal activity style of cambium directly influences wood biomass production, structures and properties. The seasonal changes in the ultrastructure of the vascular cambium activity of Populus tonientosa Carr. planted in Beijing area were examined in shoot tissues collected during 15 months by means of transmission electron microscopy. Before xylem mother cells reactivated completely, the dividing fusiform cells in cambium and new phloem cells had appeared at the same time. The initiation of cambial activity may be related to the bud sprouting and the young leaf growth in shoots. More details about the ultrastructural changes of cambial cells at the onset of cambial activity have been gained. When the large vacuole in active cambial cells divided into smaller ones during the dormant phase, proteinaceous material that disappeared in active cambial cells refilled many of these small vactioles. In addition, lipid droplets and starch granules had the same cycles as proteinaceous material. The plasmalemma invaginations of fusiform cells were observed not only in active phase but also in dormancy. The endomembrane system consisting of nuclear membrane, endoplasmic reticulum (ER), dictyosomes and their secretory vesicles, changed in form and distribution at different phases during a cycle and performed important roles at the onset of active cambium and during the wall formation process of secondary xylem cells. The tangential walls remained relatively thin throughout the year but the radial walls thickened markedly when the cambium was dormant. During the transition from dormancy to activity, a partial autolysis occurred in the radial walls of the cambial cells, especially at the cell wall junctions. A notable feature of the cells at the onset of cambial activity was the thinning of the radial walls.

THE SECRETORY STIGMAS IN POPULUS: DEVELOPMENT, CYTOCHEMISTRY, ULTRASTRUCTURE AND THEIR RELATION TO INTERSECTIONAL INCOMPATIBILITY *

The stigmas of five species, Populus euphratica Oliv., P. alba L., P. simonii Carr., P. lasiocarpa Oliv. and P. nigra L. have been studied. Scanning electron microscopy re veals that exudates are present in the intercellular spaces, in the clefts between the multicel lular papillae and on the receptive surface. Release and movement of exudates can be visual ized when the fresh stigmas are stained with sudan Ⅲ and auramine O. Paraffin and semi thin resin sections of stigmas after glutaraldehyde osmium fixation evidence the lipidic nature of the exudates. Transmission electron microscopy reveals the glandular features of the stigmatic papillae cells, such as abundance of rough and smooth endoplasmic reticulum, polyribosomes, and well developed dictyosomes with secretory vesicles. Pellicle and epicuticular lamellate layers which have been considered as typical features of the dry type stigmas are also present in the species where stigmas appear extremely wet. It is concluded that stigmas in all of the five species are secretory at the receptive stage. Well developed generative and sperm cells were observed in the pollen tubes penetrating through the deep layers of the stigmatic tissue in the reciprocal crosses between P. euphratica and P. simonii, which indicated that there is no significant barrier in the stigma.

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.

Ultrastructural Studies on the Development of Oil Cells in Litsea pungens

The developmental process of oil cells in the shoot of Litsea pungens Hemsl. has been studied with transmission electron microscopy. According to the development of the three layers of cell wall, the developmental process could be divided into 4 stages. In stage 1, the cell wall consisted only of a primary (the outmost) cellulose layer, which might further be divided into two substages, the oil cell initial, and the vacuolizing oil cell. During this stage, there were some small electron translucent vesicles and dark osmiophilic droplets of variant sizes in the different-shaped plastids. It was observed that some dark and gray osmiophilic materials coalesced to vacuoles in the cytoplasm. In stage 2, a lamellated suberin layer accumulated inside the primary cellulose layer. In stage 3, a thicker and looser inner cellulose wall layer was formed gradually inside the suberin layer. Some dark osmiophilic droplets have been observed in this loose inner cellulose wall layer. The plasmodesmata were blocked up and became a special structure. Then, the big vacuole, which is the oil sac, was full of osmiophilic oil. In stage 4, the oil cell became matured and the cytoplasm disintegrated. The oil sac enveloped from plasmalemma was attached to the cupule, which was formed by the protuberance of the inner cellulose wall layer into the lumen. After the maturity of oil cell, the ground cytoplasm began to disintegrate and became electron opaque or exhibited in a disordered state, and the osmiophilic oil appeared light gray.

ULTRASTRUCTURE OF THE VEGETATIVE CELLS OF NOSTOC FLAGELLIFORME PREPARED WITH HIGH PRESSURE FREEZING AND FREEZE SUBSTITUTION TECHNIQUE

The ultrastructure of the vegetative cells of Nostoc flagelliforme Born. et Flah. was investigated with high pressure freezing and freeze substitution technique and compared with the results obtained by using conventional preparation methods. During the processes of chemical fixation, dehydration and embedding, the cell structures might be more artificially modified than that obtained from high pressure freezing and freeze substitution. With the present method, the sheath of N. flagelliforme could be well penetrated and no extra big space could exist between the cell and the sheath. The cell protoplasm rarely shrinked. Some fine structures of cell inclusions and unit membranes became visualized. Many bacteria were harbored in the sheath. In addition, the presence of big vacuoles in the cell of N. flagelliforme as well as the presence of bacteria in the sheath shown in the present preparation for cyanobacteria has not been described so far in the literature.

Cytochemical localization of ATPase and sub-cellular variation in mesophyll cell of Cyclocarya paliurus seedlings under iso-osmotic stress and calcium regulation

The ultrastructural distribution and active location of ATPase and the ultrastructural variations were investigated in mesophyll cells of Cyclocarya paliurus seedlings after iso-osmotic salt/water treatments in combination with calcium regulation. C. paliurus seed- lings were treated with five groups （control, 85 mM NaCl, 85 mM NaCl＋ 12 mM Ca（NO3）2, PEG iso-osmotic to 85 mM NaCl and PEG iso-osmotic to 85 mM NaCl＋12 mM Ca（NO））2） in a hydroponic system in a phytotron. Results show that under normal growth conditions the ATPase activity was low and the enzyme was primarily located on the nucleus. After 12 days of iso-osmotic salt/water treatments, ATPase activity on the tonoptast increased. Osmiophilic globules for iso-osmotic water treatment were greater than that for iso-osmotie salt treatments. The ATPase activity increased and was mostly transferred onto the nucleus for calcium regulation treatment under iso- osmotic salt/water stresses, and the osmiophilic globules significantly decreased under iso-osmotic water stress with calcium regulation. The ATPase located on the nucleus indicated that the degree of salt/drought damage that seedlings suffered was slighter, while the amount of the enzyme located on the tonoplast showed that the degree of salt/drought damage there was more serious. After 4 and 20 days of iso- osmotic treatments, the injury suffered by the leaf ultrastructures of C. paliurus seedlings for iso-osmotic treatment with calcium regula- tion was lower than those without calcium regulation, especially for the iso-osmotic water treatments. Preliminary analysis suggests that the iniury suffered by C. paliurus seedlings was lower for iso-osmotic salt treatments than for iso-osmotic water treatments, while the effect of calcium regulation under iso-osmotic water stress was greater than that of the iso-osmotic salt stress.

Ultrastructural Changes of Vegetative Cells in Amaryllis Pollen during Its Germination

Structural and organizational changes of the vegetative cell in Amaryllis vittata Ait. during such dynamic processes of pollen as hydration, activation and germination have been examined with electron microscopy. The mature pollen grain is composed of such organelles as plastids, mitochondria,endoplasmic reticulum, dictyosomes and lipid bodies which are in their resting state. Microfilaments appear as aggregates. After pollen activation, however,the organelles undergo great changes in number and shape: the lamellae of plastids and the cristae of mitochondria increase conspicuously in number, the cisternae of the endoplasmic reticulum become narrower; the dictyosomes produce vesicles actively the lipid bodies become degraded and the microfilament aggregates disperse. Cortical microtubules and spiny vesicles appear in the cytoplasm after germination of the pollen tube. No apparent structural changes of the organelles were noticed any longer during this period and microfilaments are distributed throughout the entire pollen tube as a three-dimensional network.

Lipopolysaccharide-induced cerebral inflammatory damage and the therapeutic effect of platelet activating factor receptor antoganist

Objective To investigate lipopolysaccharide （LPS） induced acute cerebral inflammatory damage and the therapeutic effect of ginkgolide B （BN52021）. Methods Thirty Sprague-Dawley rats were randomly divided into 3 groups （n = 10 for each group）： Control group, Model group and Treatment group （treated with BN52021）. LPS were injected into the fourth ventricle of rat to make a neuroinflammatory murine model. Morris water maze was used to detect the learning and memory ability of rats; changes of synapse number and subcellular ultrastructures were observed under a transmission electron microscope; OX-42 positive microglia in the brain was detected by immunohistochemical method. Results The average escape latency in the Treatment group were significantly shortened than that in the Model group; and the percentage of swimming distance traveled in platform quadrant accounting for total distance increased markedly. The rough endoplasmic reticulum and polyribosomes in the Treatment group were more than that in the Model group, but the number of synapses seemed to have no obvious change. The number of OX-42 positive microglia in the Treatment group decreased markedly than that in the Model group, and the grey density of OX-42-positive cells increased significantly. Conclusion LPS can induce inflammatory damages to the brain, but the damage could be antagonized by BN52021. Platelet activating factor receptor antagonist may offer an effective therapy for neurodegeneration diseases.

Ultrastructure Features of Sperm Cell in Amaryllis vittata

Ultrastructure of sperm cells in pollen tube of Amaryllis vittata Ait. has been investigated in details by electron microscopy ,with particular emphasis on the organization and distribution of microtubules.The two newly formed sperm cells are arranged in tandem and sometimes in transverse at the right angle to the long axis of the pollen tube.Thevegetative nucleus is ahead and closely associated with the two sperm cells in all examined pollen tubes. The microtubules are distributed in the region between the common cell wall and the proximity of the sperm nucleus,they are singles and dispersed with mainly orientation of longitudinal and oblique,forming a loose bucket-like structure as a whole.In late stage of development,all of the microtubule array longitudinally and enclose the sperm nucleus.This configuration is very similar to the basket-like structure of microtubule in the generative cell. These results show that the organization and distribution of microtubules in the sperm cells are dynamic during cell development.

Ultrastructure of Single Cells, Callus-like and Monospore-like Cells in Porphyra yezoensis Ueda on Semi-solid Culture Medium

It had been demonstrated that individual cells or protoplasts isolated fromPorphyrathallus by enzyme could develop into normal leafy thalli in the same way as monospores, and that isolated cells develop in different way in liquid and on semi-solid media. The authors observed the ultrastructure of isolated vegetative cells cultured on semi-solid media and compared them with those of monospores and isolated cells cultured in liquid media. The results showed that subcellular structures were quite different among cells in different conditions. In their development, isolated cells on semi-solid media did not show the characteristic subcellular feature of monospore formation, such as production of fibrous vesicles. Callus-like cells formed on semi-solid media underwent a distinctive modification in cellular organization. They developed characteristic cell inclusions and a special 2-layer cell covering. Golgi bodies, ER, starch grains, mitochondria. Vacuoles were not commonly found in them.

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.

Ultrastructural changes in hepatocytes after taurinetreatment in CCl_4 induced liver injury

AIM: To search the organelle based changes in hepatocytes after taurine treatment in experimental liver fi brosis induced by CCl_4 administration. METHODS: Thirty rats were divided into two groups. Group 1 (n = 15) was injected with CCl_4 plus taurine and Group 2 (n = 15) with CCl_4 plus saline for 12 wk. At the end of 12th wk, mitochondria, rough and smooth endoplasmic reticulum, and nuclei of hepatocytes were evaluated using a scoring system. The results were compared with histopathological f indings, as well. RESULTS: Taurine treatment reduced fi brosis scores signifi cantly as compared to placebo. Organelle injury scores decreased signifi cantly with taurine treatment. Ultrastructural and histopathological scores in both groups were in strong correlation (r = 0.931 for CCl_4 plus taurine and r = 0.899 for CCl_4 plus saline group). CONCLUSION: Organelle based transmission electron microscopy fi ndings can reflect successfully histological results as well as tissue healing in hepatocytes from hepatotoxin-induced liver fi brosis.

Siderophores from Marine Microorganisms and Their Applications

In view of the fact that siderophores from microorganisms in different environments have received much attention in recent years because of their potential applications and diverse physiological functions, this review deals with side rophore producing marine microorganisms and the detection, chemical structure and potential applications of siderophores.

EXPERIMENTAL STUDY OF RIGHT VENTRICULAR ASSIST IN ACUTE RIGHT VENTRICULAR FAILING

The efficacy of right atrial-pulmonary artery (RA-PA) bypass during acute right ventricular failure (RVF) produced by pulmonary artery constriction in dogs was examined in this study Control group (n=7) was supported with conventional volume loading and inotropic therapy. In the experimental animals (n=8) , RA-PA bypass was initiated 5 min. after the onset of severe RVF. Three control animals died from refractory ventricular fibrillation within one hour of RVF. No animals in the experimental group died within two hours of RA-PA bypass , but the histological study of the lungs in these animals demonstrated peribronchial , perivascular and intraalveolar hemorrhage. Light microscopic and electron microscopic examination of the myocardial specimens of the right ventricular free wall displayed the myocardial structures and ultrastructures were maintained effectively with RA-PA bypass while irreversible myocardial injuries occurred in the control animals after two hours of RVF with conventional therapy. During the 2 hours of RA-PA bypass, the hemodynamic indices were also maintained better when compared to the control animals. It may be concluded , a roller pump right ventricular assist device effectively unloads the acute failing right ventricle, maintains systemic cardiac output , and significantly reverses the myocardial ischemia during right ventricular failure, but RA-PA bypass may induce pulmonary hypertension due to increased pulmonary vascular resistance secondary to pulmonary edema and interstitial hemorrhage.

A Tri-Port MIMO Antenna Designed for Micro/Pico Cell Applications with Self-Decoupled Structure

A tri-port MIMO antenna designed for Micro/Pico-Cell application is proposed.It is based on printed elements with X-shaped arms,which are oriented to 0°,120° and240° in the azimuth plane.The arms of these elements are connected,with which a selfdecoupled structure is formed.The mutual coupling between adjacent elements is below-15 dB.Meanwhile,it size is compact and bidirectional radiation patterns with around 4dBi Gain and 92° 3dB beam width is achieved,which can provide good pattern diversity and full azimuth coverage in real applications.