内外螺旋管道机器人性能分析和结构参数优化

数值比较了内外螺旋机器人、单节外螺旋机器人和双节外螺旋机器人的轴向推进力、管道壁所受最大压力、液体对机器人的承载力和液体对机器人周向阻力矩与其外壳转速的关系,分析了内螺旋转速和外螺旋转速的变化对机器人轴向推进力的影响以及机器人外螺旋槽结构参数(槽口宽a2、 槽底宽b2、倾角α2、螺旋槽槽深h2、螺纹升角Φ2和螺纹线数n2）对机器人轴向推进力的影响, 并运用正交试验优化方法优化了外螺旋槽结构参数组合。结果表明：内外螺旋机器人单位有效体积的推进力和液体对其的承载力最大;外螺旋参数的变化对机器人性能的影响远大于内螺旋参数的变化对机器人性能的影响;机器人外螺旋槽结构参数和机器人轴向推进力成非线性关系。在管道直径和机器人内外径确定的条件下,一组最优的外螺旋槽结构参数组合为：a2=1.25mm,b2=0.75mm,α2=70°,h2=0.8mm,Φ2=30°,n2=10。     

Microscopy of sclerotinites in the coal beds of the central part of the Appalachian coal field,U.S.A

Rodlets from fusain and carbominerite bands or lenses in bituminous coal beds of the central part of the Appalachian coal field in the eastern United States were studied in three dimensions using both light microscopy and scanning-electron microscopy (SEM). Infrared studies and chemical analyses complemented reflectance measurements. The rodlets are found strati-graphically from the Pocahontas no. 3 coal bed (Pocahontas Formation, Lower Pennsylvanian or Namurian B & C) to the Washington coal bed (Washington Formation, Lower Permian). The most common rodlets are noncellular, range in diameter from 60 to 440 μm, and, when polished, have the relief and high reflectances typical of the inertinite maceral group. They have characteristic notches, ovoid shapes, distinctive fracture patterns, dense (oxidized) rims, vesicles, cavities and canals, some of which contain minerals (tentatively identified by SEM semiquantitative X-ray and infrared analyses). Some rodlets show a cellular cast on their longitudinal surfaces. Due to different exposures in variously-oriented polished sections, this type of rodlet is classified as sclerotinite of the inertinite maceral group. Comparison of the sclerotinites from the central part of the Appalachian coal field with the fusinitized resin rodlets from coal and coal balls of the Illinois basin (Kosanke & Harrison, 1957) and with the ‘sclerotioids’ of the St Rose no. 5 coal of Nova Scotia indicates that they represent the same bodies. All are interpreted to be rodlets of resinous origin belonging to one or more of the genera of medullosan seed ferns of Carboniferous and Permian age. We suggest using the existing terms ‘resino-sclerotinite’ and ‘fungo-sclerotinite’ for two distinct maceral varieties of the inertinite maceral group because of their distinguishing properties and their different paleobotanical origins. Two types of cellular rodlets, woody splinters and sclerenchyma strands, are also documented in this study because of their close association with the resino-sclerotinites of the central part of the Appalachian coal field.     

New insights into the morphology of Trypanosoma cruzi reservosome

Reservosomes are late endosomes present only in members of the Schizotrypanum subgenus of the Trypanosoma genus and are defined as the site of storage of endocytosed macromolecules and lysosomal enzymes. They have been extensively described in Trypanosoma cruzi epimastigote: are bounded by a membrane unit, present an electron-dense protein matrix with electron-lucent lipid inclusions, being devoid of inner membranes. Here we performed a detailed ultrastructural analysis of these organelles using a variety of electron microscopy techniques, including ultrathin sectioning, uranyl acetate stained preparations, and freeze fracture, either in intact epimastigotes or in isolated reservosomes. New informations were obtained. First, both isolated and in situ reservosomes presented small profiles of inner membranes that are morphologically similar to the membrane surrounding the organelle. In uranyl acetate stained preparations, internal membrane profiles turned out to be longer than they appeared in ultrathin section images and traversed the organelle diameter. Internal vesicles were also found. Second, endocytosed cargo are not associated with internal vesicles and reach reservosomes on board of vesicles that fuse with the boundary membrane, delivering cargo directly into reservosome lumen. Third, electron-lucent bodies with saturated lipid core surrounded by a membrane monolayer and with unusual rectangular shape were also observed. Fourth, it was possible to demonstrate the presence of intramembranous particles on the E face of both internal vesicles and the surrounding membrane. Collectively, these results indicate that reservosomes have a complex internal structure, which may correlate with their multiple functions.     

Tales of tethers and tentacles: golgins in plants

As plant Golgi bodies move through the cell along the actin cytoskeleton, they face the need to maintain their polarized stack structure whilst receiving, processing and distributing protein cargo destined for secretion. Structural proteins, or Golgi matrix proteins, help to hold cisternae together and tethering factors direct cargo carriers to the correct target membranes. This review focuses on golgins, a protein family containing long coiled-coil regions, summarizes their known functions in animal cells and highlights recent findings about plant golgins and their putative roles in the plant secretory pathway.     

Functional morphology of the secretory pathway organelles in yeast

The glycoprotein secretory pathway of yeast serves mainly for cell surface growth and cell division. It involves a centrifugal transport of transit macromolecules among organelles, whose membranes contain resident proteins needed for driving the transport. These resident membrane proteins return by retrograde vesicular transport. Apart from this, the pathway involves endocytosis. The model yeast Saccharomyces cerevisiae and vertebrate cells were found to contain very similar gene products regulating the molecular mechanism of glycoprotein transport, and the cellular mechanism of their secretion pathways was therefore also presumed to be identical. Biochemists have postulated that, in S. cerevisiae, the translocation of peptides through the endoplasmic reticulum membranes into the lumen of ER cisternae and the core glycosylation is followed by a vector-mediated transport into the functional cascade of the Golgi system cisternae and between them. This is the site of maturation and sorting of glycoproteins, before the ultimate transport by other vectors involving either secretion from the cells (exocytosis across the plasmalemma into the cell wall) or transport into the lysosome-like vacuole via a prevacuolar compartment, which serves at the same time as a primary endosome. The established cellular model of secretion deals with budding yeast; interphase yeast cells, in which the secretion is limited and which predominate in exponential cultures, have not been taken into consideration. The quality of organelle imaging in S. cerevisiae ultra-thin sections depends on the fixation technique used and on specimen contrasting by metals. The results achieved by combinations of different techniques differ mostly in the imaging of bilayers of membrane interfaces and the transparence of the matrix phase. Fixation procedures are decisive for the results of topochemical localisations of cellular antigenic components or enzyme activities, which form the basis of the following survey of functional morphology of organelles involved in the yeast secretory pathway. The existing results of these studies do not confirm all aspects of the vertebrate model of the Golgi apparatus proposed by molecular geneticists to hold for S. cerevisiae, and alternative models of the cellular mechanism of secretion in this yeast are, therefore, also discussed.     

Localization of Ca2+ -stores and tissue compartments with a Ca2+ -binding capacity in the organ of Corti of the guinea-pig by electron energy-loss spectroscopy

The addition of 10 mM CaCl₂ to glutaraldehyde fixative leads to the formation of small electron-dense deposits in the organ of Corti of the guinea-pig. These precipitates are mainly attached to cell membranes in contact with different extracellular lymphatic fluids. A higher number of precipitates is localized in the acellular parts of tectorial and basilar membrane. Electron energy-loss spectroscopy (EELS) was used to determine the elemental composition of the deposits formed. The spectra showed a prominent signal at the Ca²⁺ L_2,3 ionization edge. Oxygen could also be detected in all the precipitates analysed. EELS analysis of mitochondria of the inner and outer hair cells after conventional fixation (glutaraldehyde followed by post-fixation in OsO₄) revealed a small but significant calcium signal.     

Apoptogenic effect of the lipophilic <i>o</i>-naphthoquinone CG 10-248 on rat hepatocytes: light and electron microscopy studies

CG 10-248 (3,4-dihydro-2,2-dimethyl-9-chloro-2H-naphtho[1,2b]pyran- 5,6-dione; CG-NQ), a β-lapachone analogue, modified the ultrastructure of rat hepatocytes, as demonstrated by light and electron microscopy. After 4 h incubation with 100 µM CG-NQ, the following effects were observed: (a) nuclear chromatin condensation; (b) chromatin fragmentation; (c) displacement of mitochondria, concentrated around the nucleus; (d) disruption or expansion of mitochondrial outer or inner membranes, respectively; (e) displacement and alteration of endoplasmic reticulum (rough and smooth); (f) decrease of microvilli; (g) blebbing of plasma membrane and production of apoptotic bodies formed by folding of plasma membrane fragments around mitochondria or peroxysomes; and (h) production of hydrogen peroxide. Expression of such effects varied according to hepatocyte samples and taken together strongly support an apoptotic action of CG-NQ dependent on “reactive oxygen species”.     

Mineralization patterns in elasmobranch fish

This article reviews current findings on the organic matrix and the mineralization patterns in elasmobranchs, including an analysis of the role of the dental epithelial cells and the odontoblasts during odontogenesis. Our electron micrographs demonstrated that tubular vesicles limited by a unit membrane occupied the bulk of the elasmobranch enameloid matrix during the stage of enameloid matrix formation. It is likely that the tubular vesicles originated from the odontoblast processes. Two types of electron-dense fibrils, with cross-striations at intervals of approximately either 17 nm or 55 nm, respectively, were detected in the enameloid matrix. These data suggest that odontoblasts were strongly involved in enameloid matrix formation and in initial enameloid mineralization. Two types of odontoblasts, dark and light cells, were recognized during the stage of dentinogenesis. The light cells contained numerous mitochondria, intermediate filaments, and microtubules that extended their processes into the dentin. The dark cells possessed a well-developed Golgi apparatus and many cisternae in the rough endoplasmic reticulum, which suggests that the dark cells are involved in the formation of dentin. The inner dental epithelial (IDE) cells exhibited a well-developed Golgi apparatus, many mitochondria, cisternae of smooth endoplasmic reticulum, vesicles, vacuoles, and granules during the mineralization and maturation stages. During the stages of mineralization and early maturation, ACPase-positive granules were visible in the IDE cells and ALPase and Ca-ATPase activities were found at the lateral and proximal cell membrane of the IDE cells, suggesting that the IDE cells are involved in the removal of enameloid organic matrix and in the process of mineralization during later stages of enameloid formation. Our data indicate that elasmobranch enameloid is distinct from teleost enameloid, based on its organic content, on the mechanisms of its mineralization, and on the role of IDE cells concerning enameloid formation.     

Relationship between structure and function in distal tubule and collecting duct

The relationship between structure and function in the distal tubule and collecting duct has been studied with morphologic and physiologic techniques, including morphometric analysis, to identify functionally distinct cell populations. The distal tubule, including the thick ascending limb (TAL) and the distal convoluted tubule (DCT), is involved in active reabsorption of sodium chloride. It is characterized by extensive invaginations of the basolateral plasma membrane, numerous mitochondria, and high Na-K-ATPase activity, features characteristic for an epithelium involved in active transport. Between the distal tubule and the collecting duct is a transition region, the connecting segment or the connecting tubule (CNT), which exhibits species differences with respect to both structure and function. The collecting duct includes the cortical (CCD), the outer medullary (OMCD), and the inner medullary (IMCD) collecting ducts. Principal cells are present throughout the collecting duct, whereas intercalated cells are located mainly in the CCD and OMCD. Morphometric analysis combined with micropuncture and microperfusion studies has provided evidence that the CNT and principal cells are responsible for potassium secretion in the connecting segment and the CCD. The OMCD is a main site of hydrogen ion secretion, and morphometric studies have provided evidence that the intercalated cells in this segment secrete hydrogen ion at least in the rat. Two configurations of intercalated cells exist in the CCD—a type A and a type B. The A cells are similar in ultrastructure to the intercalated cells in the OMCD and are believed to be involved in hydrogen ion secretion. The function of the B cells remains to be established. The inner two-thirds of the IMCD corresponds to the papillary collecting duct, which has a high permeability to urea. The relationship between structure and function in the IMCD has not been studied in detail. This review emphasizes the role of morphometric analysis in establishing the relationship between structure and function in the distal nephron.     

螺旋槽端面密封脱开转速的理论及试验

提出螺旋槽端面密封脱开转速的理论分析模型,并建立适合于密封端面脱开后的内外双槽结构的非接触式端面密封数学模型。理论研究一种外螺旋槽和内人字槽组合的双螺旋槽端面密封的临界脱开转速,同时讨论该类非接触端面密封开启力、流量、摩擦力矩等随转速和密封间隙的变化规律。试验得到了直径100 mm、槽深3 μm的组合螺旋槽(外螺旋槽和内人字槽组合)端面密封在水介质(27 ℃)工况下的临界脱开转速,并将其与理论结果进行对比研究。研究结果表明,当密封转速超过约9 kr/min后,密封处在非接触状态,此时的密封泄漏量仅为1.2 mL/s。试验得到的端面密封脱开转速与理论结果一致(误差小于10%),从而有效地证实了端面脱开转速可作为对密封端面接触与否的判定依据。当密封转速高于脱开转速后,密封处在非接触状态,其工作寿命较长,泄漏量较小,这对于可重复使用火箭发动机涡轮泵端面密封的研制具有重要理论和试验参考价值。     

Thin frozen-dried cryosections and biological X-ray microanalysis

The application of X-ray microanalysis to problems of cell physiology required the development of methods to retain diffusible substances within the subcellular compartments that they occupied in vivo. Several groups have developed methods of rapidly freezing small samples in ways that minimize mechanical traumae and ice crystal formation. This provides a narrow zone from which cryosections, believed to be representative of the in vivo distribution of electrolytes, can be cut. The production of thin (less than 0·5 μm) cryosections that are apparently free of diffusion can be routinely performed when temperature parameters are kept below 173 K. Efficient cryosectioning requires several modifications to commercially available machines, in order to improve the ease and reliability with which various manipulations can be carried out. Initial attempts to localize calcium at the subcellular level were disturbed by the use of mechanically damaged specimens and by insufficiently cold conditions in the cryochamber. Such sections indicated that mitochondria were calcium-rich organelles. When tissue freezing and cryosectioning were performed under optimized conditions, mitochondrial calcium was so low as to be quantifiable only with difficulty. Available microanalytical results show that ER-rich cytoplasm and terminal cisternae of the sarcoplasmic reticulum seem to contain higher levels of calcium than mitochondria. Nuclei and secretory granules also contain more calcium than mitochondria.     

Venom apparatus of the endoparasitoid wasp Opius caricivorae Fischer (Hymenoptera: Braconidae): morphology and ultrastructure

The morphology and ultrastructure of the venom apparatus of the endoparasitoid wasp, Opius caricivorae Fischer (Hymenoptera: Braconidae), were observed using light and electron microscopes. The venom apparatus consists of one venom reservoir and several gland filaments. The gland filaments join together at the end of the reservoir and consist of an outer single layer of secretory cells, a layer of degenerated epidermal cells, and an inner intima that encloses the lumen. The secretory cells are organelle rich, with abundant rough endoplasmic reticulum, mitochondria, and vacuole, in which vesicular organelles secrete the components of venom. The reservoir consists of a muscular sheath, secretory cells, and squamous cells. The intima has an unevenly thickened chitinous coat. The vesicular organelles of the reservoir secretory cells differ from those of the gland filament: the microvilli being much longer and radiating in all directions. The venom reservoir not only serves to store but also secretes the venom. Virus-like particles were discovered in the secretory cells of the gland filaments. The structural features of venom apparatus of this species are discussed in a biological context.     

Rodlet cells development in the intestine of sea bass (Dicentrarchus labrax)

The enigmatic rodlet cells (RCs) are characterized by conspicuous inclusions named “rodlets”. They were discovered over 100 years ago and were considered as parasites but shortly afterward interpreted as endogenous cells. The RCs have been described in different tissues of marine and freshwater teleosts, but their origin and function remain unknown. This work was designed to an ultrastructural study on RCs development and distribution in intestinal epithelium of Dicentrarchus labrax. Three different stages of RCs development from early precursor cells to mature phase were observed, as well as a migration and finally an extrusion of their contents. In this study, the immature cells were found near the basal epithelium membrane. They were mainly identified by a rough endoplasmic reticulum with dilated cisternae, by developing rodlets and a thin fibrillar coat. The maturing RCs, localized in the middle zone of the epithelium, appeared to be undergoing a reorganization of the cell organelles. The mature RCs, placed near the free surface, showed a thick subplasmalemmar fibrillar coat. Most of the organelles were aggregated at the cell apex with a basally located nucleus. A cellular polarity was more evident. One of the most conspicuous features was the occurrence of mature rodlets club‐sac in shape orientated toward the cell apex. Adhesive junctions between surface epithelial cells and RCs, while discharging their contents, were seen. We have connected morphological figures and distribution to different stages of development in RCs, supporting the hypothesis of their secretory function. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Organelle interactions and possible degradation pathways visualized in high-pressure frozen algal cells

Organelle interactions, although essential for both anabolic and catabolic pathways in plant cells have not been examined in detail so far. In the present study the structure of different organelle–organelle, organelle–vesicle and organelle–membrane interactions were investigated in growing and nongrowing cells of the green alga Micrasterias denticulata by use of high pressure freeze fixation and energy filtering transmission electron microscopy. It became clear that contacts between mitochondria always occur by formation of a cone-shaped protuberance of one of the mitochondria which penetrates into its fusion partner. In the same way, structural interactions between mitochondria and mucilage vesicles and between microbodies and mucilage vesicles are achieved. Lytic compartments contact mitochondria or mucilage vesicles again by forming protuberances and by extending their contents into the respective compartment. Detached portions of mitochondria are found inside lytic compartments as a consequence of such interactions. Mitochondria found in contact with the plasma membrane reveal structural disintegration. Our study shows that interactions of organelles and vesicles are frequent events in Micrasterias cells of different ages. The interactive contacts between lytic compartments and organelles or vesicles suggest a degradation pathway different from autophagy processes described in the literature. Both the interactions between vesicles and organelles and the degradation pathways occur independently from cytoskeleton function as demonstrated by use of cytochalasin D and the microtubule inhibitor amiprophos-methyl.     

Fine structure of the male accessory glands of Triatoma rubrofasciata (De Geer, 1773) (Hemiptera, Triatominae)

Male of Triatoma rubrofasciata has four elongated sac-like reproductive mesodermic accessory glands, lined by an inner single layer of secretory cells, with basal plasma membrane infolds and short apical microvilli, and externally enveloped by a thin visceral muscle layer. The secretory cells have a well-developed rough endoplasmic reticulum, Golgi complex, mitochondria, and secretory granules. In one day old adult the gland cells are poorly developed, presenting small, electron-transparent secretory granules scattered among the rough endoplasmatic reticulum, whereas in three days old adult these cells have the cisternae of the rough endoplasmatic reticulum varing size degree, filled with granular electrondense content. In five days old males the secretory granules increase in diameter, being released to the gland lumen. Therefore, there is an increase of the secretory activity according to male maturation.     

Cellular location of thymus-leukemia (TL) antigen as shown by immuno-cryoultramicrotomy

Thymus-leukemia (TL) antigen is a class I molecule of the major histocompatibility complex that is expressed on the surface of mouse cortical thymocytes. Though not expected, it has been reported that TL antigen can be found on isolated mitochondria of TL⁺ cells. We used immuno-cryoultramicrotomy to look for TL on mitochondria in situ, thereby avoiding the plasma membrane contamination that occurs when isolating organelles. Establishing optimal fixation conditions was crucial, as mitochondrial structure was not preserved by the low concentrations of fixative needed for detection of antibody labeling. The plasma membranes of tissue culture and thymus cells were labeled well with anti-TL antibody and protein A-gold conjugate, while mitochondria within the cells were not labeled. Isolation of mitochondria on a one-step Ficoll gradient resulted in a purer organelle preparation than did isolation of mitochondria by centrifugation alone. Generally, mitochondria within this purer preparation were not labeled. Our data show that under conditions where contamination by plasma membrane is not a major concern, TL antigen cannot be detected on mitochondria.     

Atomic force microscopy imaging and 3-D reconstructions of serial thin sections of a single cell and its interior structures

The thin sectioning has been widely applied in electron microscopy (EM), and successfully used for an in situ observation of inner ultrastructure of cells. This powerful technique has recently been extended to the research field of atomic force microscopy (AFM). However, there have been no reports describing AFM imaging of serial thin sections and three-dimensional (3-D) reconstruction of cells and their inner structures. In the present study, we used AFM to scan serial thin sections approximately 60 nm thick of a mouse embryonic stem (ES) cell, and to observe the in situ inner ultrastructure including cell membrane, cytoplasm, mitochondria, nucleus membrane, and linear chromatin. The high-magnification AFM imaging of single mitochondria clearly demonstrated the outer membrane, inner boundary membrane and cristal membrane of mitochondria in the cellular compartment. Importantly, AFM imaging on six serial thin sections of a single mouse ES cell showed that mitochondria underwent sequential changes in the number, morphology and distribution. These nanoscale images allowed us to perform 3-D surface reconstruction of interested interior structures in cells. Based on the serial in situ images, 3-D models of morphological characteristics, numbers and distributions of interior structures of the single ES cells were validated and reconstructed. Our results suggest that the combined AFM and serial-thin-section technique is useful for the nanoscale imaging and 3-D reconstruction of single cells and their inner structures. This technique may facilitate studies of proliferating and differentiating stages of stem cells or somatic cells at a nanoscale.     

螺旋槽机械密封瞬态启动过程润滑特性

建立了螺旋槽机械密封瞬态启动过程润滑特性的计算模型,耦合求解了含流量因子、接触因子及质量守恒空化边界的雷诺方程、弹塑性粗糙峰接触方程及动力学方程,比较了不同运行工况及结构参数的润滑状态转变过程。结果表明：增速阶段流体承载力与液膜厚度不断增大,粗糙峰承载力逐渐减小至消失;相比较于流体动压润滑状态,混合摩擦状态的液膜刚度较大且振荡幅值明显,在到达脱开转速时刻有较大的轴向速度突变。受挤压效应影响,较小的启动加速度可以在低转速下进入流体润滑状态,较高的外压和较低的内压均有利于润滑状态的转变。随槽数的增加,脱开转速呈先增大后减小趋势,螺旋角与槽深的减小或槽坝比的增大均对润滑状态转变能力起促进作用。     

气穴现象对动静压浮环径向轴承压力场的影响研究

由Navier-Stokes方程得出计入惯性项的变密度、变粘度的深浅腔动静压浮环径向轴承的内、外油膜无量纲非定常Reynolds方程,给出深腔压力边界条件和流量边界条件,对不同偏心率下不同含气率的内、外油膜压力场进行了分析。计算表明,深腔气穴使动静压浮环径向轴承的内、外油膜的压力峰值下降,在小偏心率下影响较为明显,对内油膜压力峰值的影响大于外油膜。     

Stroboscopic two-dimensional ultrasonic velocity profiling for measuring flow transition in Taylor Couette systems

Flow characterization in a Taylor Couette system was made by investigating the radial velocity component with Ultrasonic Doppler Velocimetry based flow mapping. With the technique presented in this work, it is possible to measure the radial velocity components for variable axial position in a Couette cell within Taylor vortex flow (TVF), wavy vortex flow (WVF), modulated vortex flow (MVF) as well as spiral vortex domains in a conical shaped gap. The resulting maps for the different flow states show the location of vortices in the annular gap between the inner and outer cylinder. Cylindrical and conical concentrically rotating inner bodies were applied and respective flow patterns were analyzed. The method uses a stroboscopic triggering to synchronize flow measurements and rotational motion. The oscillation frequency f of unsteady motion in WVF, MVF, and spirals can be obtained from the power spectrum of velocity. The UVP transducer was preferably positioned in radial direction, perpendicular to the surface of the inner rotating body for measuring the radial velocity component. At the same time, the transducer was moved with constant velocity vertically along the outer cylinder height.