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Electron Microscopes (electron + microscopes)
Kinds of Electron Microscopes Selected AbstractsNear Field Emission SEMIMAGING & MICROSCOPY (ELECTRONIC), Issue 1 2009Localised Electron Excitation Imaging via SPM Recent developments in electron optics enable "extreme" high-resolution Scanning Electron Microscopes (SEM)s to attain subnanometer resolution using landing energies as low as 200 eV, which is essential to prevent damaging of the investigated object and minimise the interaction volume. We have also implemented low beam energies in a simplified SEM where the electron source, remote in standard SEMs, is brought within tens of nanometers to the object. This microscope, which we call the "near field emission scanning electron microscope" (NFESEM), is capable of imaging conducting surfaces with nanometer resolution using beam energies less than 60eV. [source] Light and scanning microscopic studies of integument differentiation in the grass snake Natrix natrix L. (Lepidosauria, Serpentes) during embryogenesisACTA ZOOLOGICA, Issue 1 2009Elwira Swad Abstract We analysed the differentiation of body cover in the grass snake (Natrix natrix L.) over the full length of the embryo's body at each developmental stage. Based on investigations using both light and scanning electron microscopes, we divided the embryonic development of the grass snake integument into four phases. The shape of the epidermal cells changes first on the caudal and ventral parts of the embryo, then gradually towards the rostral and dorsal areas. In stage V on the ventral side of the embryo the gastrosteges are formed from single primordia, but on the dorsal side the epidermis forms the scale primordia in stage VII. This indicates that scalation begins on the ventral body surface, and spreads dorsally. The appearance of melanocytes between the cells of the stratum germinativum in stage VII coincides with changes in embryo colouration. The first dermal melanocytes were detected in stage XI so in this stage the definitive skin pattern is formed. In the same stage the epidermis forms the first embryonic shedding complex and the periderm layer begins to detach in small, individual flakes. This process coincides with rapid growth of the embryos. [source] Difference in organization of corticostriatal and thalamostriatal synapses between patch and matrix compartments of rat neostriatumEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2006Fumino Fujiyama Abstract The neostriatum, which possesses a mosaic organization consisting of patch and matrix compartments, receives glutamatergic excitatory afferents from the cerebral cortex and thalamus. Differences in the synaptic organization of these striatopetal afferents between the patch and matrix compartments were examined in the rat using confocal laser scanning and electron microscopes. Thalamostriatal terminals immunopositive for vesicular glutamate transporter (VGluT) 2 were less dense in the patch than in the matrix compartment, although the density of VGluT1-immunopositive corticostriatal terminals was almost evenly distributed in both the compartments. Quantitative analysis of ultrastructural images revealed that 84% of VGluT2-positive synapses in the patch compartment were formed with dendritic spines, whereas 70% in the matrix compartment were made with dendritic shafts. By contrast, VGluT1-positive terminals display a similar preference for specific synaptic targets in both compartments: about 80% made synapses with dendritic spines. In addition, VGluT2-positive axospinous synapses in the patch compartment were larger than the VGluT1-positive axospinous synapses in both compartments. As axospinous synapses are generally found in neuronal connections showing high synaptic plasticity, the present findings suggest that the thalamostriatal connection requires higher synaptic plasticity in the patch compartment than in the matrix compartment. [source] REMOVAL OF LIPID FROM SURFACES OF ROASTED PEANUTS BY SONICATION AS ASSESSED BY FLUORESCENCE AND SCANNING ELECTRON MICROSCOPYJOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2010PETER WAMBURA ABSTRACT Peanut oil migrates to the outer surface during roasting, where it comes into contact with oxygen, leading to the oxidation reactions. Because of its cleaning effect, power ultrasound (sonication) was used for removing surface lipid of roasted peanuts. Georgia green runner-type peanuts were roasted at 178C for 15 min. Roasted peanuts were subjected to lipid extraction in n-hexane by sonication. Fluorescent and electron scanning micrographs revealed that the surface of sonicated peanuts was free of oil stains, as opposed to that of freshly roasted peanuts. These results showed that power ultrasound could remove the lipids from peanut surfaces very effectively. Details of microstructure of sonicated peanuts as was observed using scanning electron microscope reveal that 10 min sonication was sufficient to extract most of the lipids on the roasted peanut surfaces. Fluorescence and scanning electron microscopy are useful in peanut analysis because they can detect lipids in low concentration. PRACTICAL APPLICATIONS There is increasing interest of quick procedures to examine the surfaces of roasted peanut samples after undergoing treatments, such as removal of lipids. This research demonstrated the significant use of fluorescent and scanning electron microscopes to quickly study the extent of lipid removal from the surface of roasted peanuts after power ultrasound treatment (sonication). [source] Influences of milk components on biofilm formation of Cronobacter spp. (Enterobacter sakazakii)LETTERS IN APPLIED MICROBIOLOGY, Issue 6 2009G.I. Dancer Abstract Aim:, To determine the critical component(s) of skim milk for biofilm formation of Cronobacter species. Methods and Results:, Biofilm forming ability of 72 Cronobacter strains in skim milk preparation was assayed by crystal violet staining. The results revealed that whey protein and casein are more important determinants of skim milk for biofilm formation than lactose, although there was a wide variation in biofilm forming ability. Biofilm structure and capsular material of six strains exhibiting different biofilm forming ability was investigated via electron microscopes. Scanning electron microscopy showed visually that while the strong biofilm formers (E27B, FSM 30 and 2·82) resulted in almost complete coagulation of skim milk, the weak biofilm formers (55, FSM 290 and 2·84) caused less coagulation. No capsule was clearly delineated in transmission electron micrographs of either strong or weak biofilm formers. Conclusion:, These results indicate that, for biofilm formation of Cronobacter species in skim milk, nitrogen source is probably a more important determinant than carbohydrate, and that strong biofilm formers are responsible for substantial coagulation of skim milk. Significance and Impact of the Study:, This study provides information for better understanding of the underlying mechanisms by which Cronobacter species form biofilm in infant formula milk. [source] Recanalization of the Collecting Lymphatics in Rabbit Hind LegMICROCIRCULATION, Issue 5 2006FUMITAKA IKOMI ABSTRACT Objective: This study was designed to examine whether mature collecting lymphatics can regenerate in the adult tissue or not. Materials and Methods: The X-ray lymphograms were used to detect network of the collecting lymphatics in rabbit hind leg. Regeneration of the lymphatics was observed after surgical removal of the popliteal lymph node or a part of the popliteal afferent lymphatic. Structure and mechanical properties of the lymphatics were also examined by light and electron microscopes and in vitro functional experiments. Results: One week after removal of the lymph node, only an afferent lymphatic and a deposit of the contrast medium at the popliteal region were observed. Four weeks after the removal, the connection of the afferent and efferent lymphatics at the popliteal region, and collateral lymphatics were present in the leg. Further, 4 weeks after 1-mm excisions of a part of the lymphatic, recanalization was observed between the central and peripheral cut ends of the lymphatic but not after 3- and 10-mm excisions. Endothelial cells and smooth muscle cells could be observed by electron microscope, and contractile proteins, and alpha-smooth muscle actin SM1 and SM2 were immunofluorescently detected in both intact and the regenerated lymphatic walls. In both lymphatics, norepinephrine and acetylcholine induced dose-dependent constriction and dilation of the vessels, respectively. Conclusion: The present study demonstrated that mature collecting lymphatics are able to regenerate in the adult tissues. [source] The Hall,Petch law investigated by means of in situ straining experiments in lamellar TiAl and deformed AlMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2009Daniel Caillard Abstract Dislocation-boundary interactions are studied in TiAl and Al by means of in situ straining experiments in transmission electron microscopes (TEM). The results in TiAl allow us to measure the strength of domain boundaries against the motion of ordinary dislocations and twins. The results in Al are used to analyze the interaction between dislocations and cell walls. Parameters involved in the Hall-Petch law are then deduced from these observations. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc. [source] Comparative observations on the cyst shells of seven Artemia strains from ChinaMICROSCOPY RESEARCH AND TECHNIQUE, Issue 8 2007Sufeng Wang Abstract The quiescent Artemia cysts of seven geographical origins in China were examined with scanning and transmission electron microscopes. SEM observations on cysts of these Artemia strains showed that the surface topography of cyst shells could be categorized into 6 types: complete smooth surface; smooth surface with sparsely distributed glabrate humps; surface with densely arranged wart-like humps that are composed of packed minute tubercles; rugged surface, with densely arranged tubercles not piling up to form larger humps; shallow-pocked surface; and surface with numerous and densely spaced pore-like fossulae. Some of the patterns were strain specific [e.g., cysts from Ga Hai (GH) are characterized by having a surface with wart-like ornaments that are composed of packed minute tubercles, rugged surface is only found in Chengkou (CK) cysts], and apparent intrastrain variation of cyst surface topography was found in Xizang (XZ), Jingyu Hu, and Xie Chi (SIN) strains. TEM studies on the ultrastructure of cyst shells revealed an apparent divergence in the structure of outer cuticular membrane (OCM) among Artemia strains. In CK, Aqqikkol Hu (AQK), SIN, and GH strains, it is a normal, asymmetrical, and multi-layered structure similar to those described in previous works. In XZ, JYH, and Lagkor Co (LGC) strains, however, the OCM is not obviously multi-layered and the borderlines between OCM and adjacent layers seem indistinct. The present results suggest that the diversity of the surface topography of Artemia cysts may be an available tool for identifying certain Artemia strains as well as for tracking the origins of some Artemia cysts, and the hypoplastic OCM may be a characteristic of the species A. tibetiana. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source] Ultrastructure of the Male Reproductive System of Cotesia vestalis (Hymenoptera: Braconidae) with Preliminary Characterization of the SecretionsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 7 2007Fang Huang Abstract The morphology and ultrastructure of testes and accessory glands along with the characterization of their secretions were investigated for a braconid species Cotesia vestalis (Hymenoptera: Braconidae) using light and electron microscopes. The male internal reproductive system of this species is distinguished by a pair of testes, one vas deferens, and a pair of male accessory glands. The testes are separate, and the accessory glands are oval and not fused. It was observed that the secretory cells of testes have characteristic smooth and rough endoplasmic reticulum, and that the cytoplasm is filled with an array of granule droplets usually of two to three types. The secretory cells in the case of accessory glands are typified by the presence of microvilli on their apical cell surfaces and numerous mitochondria in their cytoplasm. SDS-PAGE profile when performed depicted a similarity in most bands of the secretions from both testes and accessory glands, except for four proteins of which two were present only in testes, while the other two only appeared in accessory glands. Their molecular weights were 117 and 55 kDa for testes and 196 and 30 kDa for accessory glands, respectively. This study gives new insights into the intriguing features of male internal reproductive system and it especially constitutes the first report of its kind about the secretion properties of these organs in C. vestalis. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source] The assessment of microscopic charging effects induced by focused electron and ion beam irradiation of dielectricsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2007Marion A. Stevens-Kalceff Abstract Energetic beams of electrons and ions are widely used to probe the microscopic properties of materials. Irradiation with charged beams in scanning electron microscopes (SEM) and focused ion beam (FIB) systems may result in the trapping of charge at irradiation induced or pre-existing defects within the implanted microvolume of the dielectric material. The significant perturbing influence on dielectric materials of both electron and (Ga+) ion beam irradiation is assessed using scanning probe microscopy (SPM) techniques. Kelvin Probe Microscopy (KPM) is an advanced SPM technique in which long-range Coulomb forces between a conductive atomic force probe and the silicon dioxide specimen enable the potential at the specimen surface to be characterized with high spatial resolution. KPM reveals characteristic significant localized potentials in both electron and ion implanted dielectrics. The potentials are observed despite charge mitigation strategies including prior coating of the dielectric specimen with a layer of thin grounded conductive material. Both electron- and ion-induced charging effects are influenced by a delicate balance of a number of different dynamic processes including charge-trapping and secondary electron emission. In the case of ion beam induced charging, the additional influence of ion implantation and nonstoichiometric sputtering from compounds is also important. The presence of a localized potential will result in the electromigration of mobile charged defect species within the irradiated volume of the dielectric specimen. This electromigration may result in local modification of the chemical composition of the irradiated dielectric. The implications of charging induced effects must be considered during the microanalysis and processing of dielectric materials using electron and ion beam techniques. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source] Seal bond characterization of laminated plastic food cups by scanning electron and optic microscopesPACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2004Zehra Ayhan Abstract Heat seals of laminated semi-rigid food cups were evaluated to characterize the seal bond. Laminated lidding material was sealed at temperatures of 160,180°C to thermoformed cups. Various seal regions of the cups with different ultrasonic signal strengths (%) were sectioned at the rim and examined using optical and scanning electron microscopes (SEM). Ultrasonic signals were able to pinpoint seal defects; however, the magnitude of the signals did not relate to the actual seal condition or seal quality affected by the sealing process. This was attributed to the very short seal width and non-parallel surface of the heat seal, which possibly resulted in signal loss by reflection and scattering from the seal surface. C-scan of ultrasound, SEM and optical microscopic images provided the information that the heat-sealing process was unstable, due to insufficient and non-uniform heat-seal temperature or pressure, misalignment of the sealing jaws or non-parallel sealing or cutting unit configuration. Copyright © 2004 John Wiley & Sons, Ltd. [source] Systematics of Chaetocerotaceae (Bacillariophyceae).PHYCOLOGICAL RESEARCH, Issue 2 2003SUMMARY In order to construct a model of evolutionary relationships within the diatom family Chaetocerotaceae, 37 species of Chaetoceros Ehrenberg, representing all subgenera and 21 of 22 subgeneric sections of the genus, plus three Bacteriastrum Shadbolt species, representing both of its subgeneric sections, were subjected to cladistic analysis. One species each of Eucampia Ehrenberg, Cerataulina Peragallo, Hemiau-lus Ehrenberg, Attheya West and Gonioceros H. & M. Peragallo were used as outgroups. A matrix of 65 binary and multistate morphological characters was constructed, with data being gathered from original observation of material in the light and electron microscopes, and from the published literature. The analysis yielded 36 most-parsimonious cladograms of 316 steps; incongruence between trees is largely restricted to some taxa representing undersampled sections of Chaetoceros subg. Hyalochaete. The robustness of this hypothesis was examined in several ways. To assess the effect of character weighting, the bootstrap was used to randomly weight characters. The parsimony criterion was relaxed via a decay index, and finally, the tree length was compared to that of trees randomly generated from the data matrix. The majority of investigated species of Chaetoceros subg. Phaeoceros, Chaetoceros subg. Hyalochaete and Bacteriastrum appear to belong to a continuous grade, rather than comprising individual clades. Chaetoceros is paraphyletic. Thus, the traditional classification does not accurately reflect the hypothesized phylogenetic relationships of this family. [source] The recently established diatom Coscinodiscus wailesii (Coscinodiscales, Bacillariophyta) in Brazilian waters.PHYCOLOGICAL RESEARCH, Issue 2 2001I: Remarks on morphology, distribution SUMMARY Coscinodiscus wailesii Gran et Angst is a large centric diatom (280,500 ,m diameter) from marine phytoplankton, characterized by a cylindrical frustule with flat valvar surface, two marginal rings of rimoportulae on the mantle, and two macrorimoportulae. Cells from cultured and natural populations collected in Paranaguá Bay, Paraná, southern Brazil were observed under light and scanning electron microscopes to verify the populations' correct identity and morphology. In both populations, a typical central rosette or a hyaline area was found in the valvar center. The species' distribution in Brazilian waters was revised, and a discussion on possible vectors of transport was made. Blooms of the species occur sporadically in the coast of Paraná, seeming to affect the local trophic chain. [source] Comparative micromorphology of nectariferous and nectarless labellar spurs in selected clades of subtribe Orchidinae (Orchidaceae)BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009ALEXANDRA K. BELL Floral nectar spurs are widely considered to influence pollinator behaviour in orchids. Spurs of 21 orchid species selected from within four molecularly circumscribed clades of subtribe Orchidinae (based on Platanthera s.l., Gymnadenia,Dactylorhiza s.l., Anacamptis s.l., Orchis s.s.) were examined under light and scanning electron microscopes in order to estimate correlations between nectar production (categorized as absent, trace, reservoir), interior epidermal papillae (categorized as absent, short, medium, long) and epidermal cell striations (categorized as apparently absent, weak, moderate, strong). Closely related congeneric species scored similarly, but more divergent species showed less evidence of phylogenetic constraints. Nectar secretion was negatively correlated with striations and positively correlated with papillae, which were especially frequent and large in species producing substantial reservoirs of nectar. We speculate that the primary function of the papillae is conserving energy through nectar resorption and explain the presence of large papillae in a minority of deceit-pollinated species by arguing that the papillae improve pollination because they are a tactile expectation of pollinating insects. In contrast, the prominence of striations may be a ,spandrel', simply reflecting the thickness of the overlying cuticle. Developmentally, the spur is an invagination of the labellum; it is primarily vascularized by a single ,U'-shaped primary strand, with smaller strands present in some species. Several suggestions are made for developing further, more targeted research programmes. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160, 369,387 [source] Vanadyl sulfate protects against streptozotocin-induced morphological and biochemical changes in rat aortaCELL BIOCHEMISTRY AND FUNCTION, Issue 6 2007Kadriye Akgün-Dar Abstract The aim of this study was to investigate the protective effects of vanadyl sulfate on aorta tissue of normal and streptozotocin (STZ)-induced diabetic rats, morphologically and biochemically. The animals were made diabetic by an intraperitoneal injection of streptozotocin (65,mg/kg) and vanadyl sulfate (100,mg/kg) that was given every day for 60 days by gavage technique to rats. Under the light and transmission electron microscopes, hypertrophy of the vessel wall, focal disruption in the elastic lamellae, an increase in thickness of total aortic wall, tunica intima, subendothelial space and adventitial layer, and a disorganization in smooth muscular cells of the tunica media were observed in diabetic animals. The aorta lipid peroxidation (LPO) levels were significantly increased and the aorta glutathione (GSH) levels were significantly reduced in STZ diabetic rats. In diabetic rats administered vanadyl sulfate for 60 days, aorta LPO levels significantly decreased and the aorta GSH level significantly increased. In conclusion, in vivo treatment with vanadyl sulfate of diabetic rats prevented the morphological and biochemical changes observed in thoracic aorta of diabetic animals. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||