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排序方式: 共有751条查询结果,搜索用时 15 毫秒
91.
Makanya AN Stauffer D Ribatti D Burri PH Djonov V 《Microscopy research and technique》2005,66(6):275-288
Embryonic development is associated with extensive vascular growth and remodeling. We used immunohistochemical, light and electron microscopical techniques, as well as vascular casting methods to study the developing chick embryo kidney with special attention to the interplay between sprouting and intussusceptive vascular growth modes. During inauguration at embryonic day 5 (E5), the early mesonephros was characterised by extensive microvascular sprouting. By E7, the vascular growth mode switched to intussusception, which contributed to rapid kidney vasculature growth up to E11, when the first obvious signs of vascular degeneration were evident. The metanephros underwent similar phases of vascular development inaugurating at E8 with numerous capillary sprouts and changing at E13 to intussusceptive growth, which was responsible for vascular amplification and remodeling. A phenomenal finding was that future renal lobules arose as large glomerular tufts, supplied by large vessels, which were split into smaller intralobular feeding and draining vessels with subsequent formation of solitary glomeruli. This glomerular duplication was achieved by intussusception, i.e., by formation of pillars in rows and their successive merging to delineate the vascular entities. Ultimately, the maturation of the vasculature was achieved by intussusceptive pruning and branching remodeling. An interesting finding was that strong VEGF expression was associated with the sprouting phase of angiogenesis while bFGF was upregulated during the phase of intussusceptive microvascular growth. We conclude that microvascular growth and remodeling in avian kidney follows an adroitly crafted pattern, which entails a precise spaciotemporal interplay between sprouting and intussusceptive angiogenic growth modes supported partly by VEGF and bFGF. 相似文献
92.
Poul Valentin Jensen 《Zeitschrift für Jagdwissenschaft》1956,4(4):164-167
Zusammenfassung Erstmalig finden Untersuchungen des Panseninhaltes dänischen Rotwildes statt. Das Rotwild stammt aus den Gebieten von Oksböl und Rold Skov.Die speziel für die Untersuchung entwickelte Methode wird erläuterts und zur Diskussion gestellt. Das Untersuchungsmaterial gewinnt man aus den Pansen frisch erlegten Wildes.Die vorkommenden Nahrungsstoffe, in vorläufig 70 untersuchten Pansen, sind nach der Zugehörigkeit zu den folgenden acht Gruppen aufgegliedert: Rinde, Triebe, Gräser und grasähnliche Pflanzen, Kräuter, Farne, Pilze, Flechten und Moose (außerdem Feldfrüchte). Die botanischen Arten werden nach prozentualen Anteilen angegeben.Die Untersuchungen sind noch nicht abgeschlossen, deshalb sind keine Ergebnisse zusammengestellt und auch keine Folgerungen gezogen.
Summary For the first time the contents of the rumen of the Danish red-deer is examined. The red-deer come from the areas of Oksböl and Rold Skov.The method developed especially for this investigation is explained and made subject to discussion. The material investigatet has been taken from the rumens of freshly shot deer.The nontritions matter which occurred in the 70 rumens investigated op to now, has been arranged in the following 8 groups: bark, browse, grasses and grasslike plants, herbs, ferns, mushrooms, lichens, and mosses (besides field fruit). The botanical species are stated according to percentages.The investigation is not yet finished, and therefore no results have been classified and no conclusions have been drawn.
Résumé Pour la première fois sont entamés des recherches sur le contenu des panses de cerfs et chevreuils en Danmark. Ces cerfs et chevreuils sont de la région d'Oksböl et de Rold Skov.La méthode développée spécialement pour ces recherches est démontrée et mise à la discussion. Le matériel pour l'examen est gagné sur les panses des bêtes récemment tués. Sur 70 panses examinées jusqu'ici la présence des élements nutritifs est mentionnée conformement à leur appartenance aux huits groupes suivantes: écorce, jets, graminées, plantes graminiforme, herbes, filicinées, champignons, lichens et mousses (en plus fruits de champ). Les espèces botaniques sont énumérées suivant le pourcentage de leur quote-part.Les recherches n'étant pas encore terminés on n'en a ni rassemblé des résultats ni tiré des déductions.相似文献
93.
Jean-Michel Lucas Philippe Berticat Bernard Chabert Jean-Pierre Soulier Louis Gavet Noëlle Valentin 《大分子材料与工程》1977,65(1):103-120
Sizing is generally employed to protect yarns when submitted to mechanical stress during weaving. Two commercial acrylic copolymers used for sizing of polyester yarns are studied: an acrylonitril-acrylic acid copolymer (A) as a bad sizing product and an acrylonitril-acrylic acid-ethyl acrylate copolymer (B) as a good one. A relationship has been established between physico-chemical parameters and sizing efficiency. Interactions between polyester yarn and size (and samples used as models) are studied both in solution and in dry state. It must be pointed out that the action of water is basically due to its plasticizing properties. The presence of ethyl acrylate favorizes the polyester yarn impregnation with size B in aqueous solution. Adhesion in the dry state is mainly caused by acrylic acid. Finally the action of neutralizing agents and imbeding oils is discussed. 相似文献
94.
Reaktionen während des Anlaufs. Brennfleckentkohlung während des linearen Abfalls. Schematische Temperaturprofile durch den Reaktionsraum. Modellvorstellungen zu den Vorgängen im Blasstrahl. Badentkohlung während des Auslaufs. 相似文献
95.
B Carcy E Precigout A Valentin A Gorenflot J Schrevel 《Canadian Metallurgical Quarterly》1995,63(3):811-817
The supernatants of in vitro cultures of Babesia divergens Rouen 1987 in human erythrocytes, obtained by using a semidefined medium based on human high-density lipoproteins, were fractionated by gel filtration chromatography into four fractions, F1 to F4. The crude supernatant as well as each fraction adjuvanted with Quil-A protected gerbils from mortality due to a homologous infectious challenge. Analysis of the humoral response of the 10 protected gerbils with fraction F4, containing major proteins with molecular masses lower than 50 kDa, showed that a few antigens (from 50 to 17 kDa) could be important candidates for an improved vaccine against B. divergens babesiosis. As an immunodominant response was directed against the 37-kDa antigen (Bd37) in two different B. divergens strains tested, a polyclonal antibody directed against Bd37 was produced in a rabbit. In an immunofluorescence assay, the anti-Bd37 antiserum strongly labelled small internal vesicles of the merozoites and the cell surface was diffusely labelled after fixation, whereas on live merozoites, this labelling was not observed. [3H]glucosamine-radiolabelling experiments demonstrate that Bd37 is a glycoprotein. The Bd37 protein can also be labelled with [14C]palmitate but not with [3H]myristic acid. In Triton X-114 temperature phase partitioning of B. divergens-infected erythrocyte extracts, Bd37 was exclusively found into the detergent phase, indicating that the palmitoylated Bd37 protein was in the membrane fraction. In the in vitro supernatant, the glycoprotein Bd37 was found in a nonpalmitoylated form, indicating excretion and/or release of the glycoprotein from the merozoite. 相似文献
96.
Hans Berns Sergej Nikolaijevitsch Bugajchuk Vladimir Andrejevitsch Duz Rüdiger Ehrhardt Valentin Gennadijevitsch Gavriljuk Yuri Nikolaljevitsch Petrov Igor Arkabijevitsch Yakubzov 《国际钢铁研究》1994,65(10):444-450
Hardness measurements, dilatometry, internal friction measurements, Mössbauer spectroscopy and transmission electron microscopy are utilized in order to study the effect of tempering on the microstructure of a stainless martensitic steel containing 15% Cr, 1% Mo and 0.6% N. A similar carbon steel containing 15% Cr, 1% Mo and 0.6% C is used for comparison. Tempering of alloy Fe-15Cr-1Mo-0.6N in the low temperature range of 353-473 K leads to formation of hexagonal ?-nitride (Fe,Cr)2N, which is followed by precipitation of the orthorombic ?-nitride (Fe,Cr)2N at temperatures of 573-773 K. The hexagonal nitride Cr2N is precipitated at 923 K and preferably formed at grain boundaries. The alloy Fe-15Cr-1Mo-0.6C shows the expected tempering behaviour. ?-carbide (Fe,Cr)2C and cementite (Fe,Cr)3C are precipitated during low temperature ageing, followed by the formation of Cr7C3 carbides after the temperature has risen to 873 K. With a similar interstitial content the amount of retained austenite in the nitrogen martensite is nearly twice as high as in the carbon one. Furthermore, the thermal stability of the retained austenite of the nitrogen alloy is substantially higher than that of the carbon steel. 相似文献
97.
Suman Pokhrel Cristian E. Simion Valentin S. Teodorescu Nicolae Barsan Udo Weimar 《Advanced functional materials》2009,19(11):1767-1774
Widely applicable nonaqueous solution routes have been employed for the syntheses of crystalline nanostructured tungsten oxide particles from a tungsten hexachloride precursor. Here, a systematic study on the crystallization and assembly behavior of tungsten oxide products made by using the bioligand deferoxamine mesylate (DFOM) (product I ), the two chelating ligands hexadecyltrimethylammoniumbromide (CTAB) ( II ) and poly(alkylene oxide) block copolymer (Pluronic P123) ( III ) is presented. The mechanistic pathways for the material synthesis are also discussed in detail. The tungsten oxide nanomaterials and reaction solutions are characterized by Fourier transform IR, 1H, and 13C NMR spectroscopies, powder X‐ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high‐resolution TEM, and selected‐area electron diffraction. The indexing of the line pattern suggests WO3 is in its monoclinic structure with a = 0.7297 nm, b = 0.7539 nm, c = 0.7688 nm, and β‐i; = 90.91 °. The nanoparticles formed have various architectures, such as chromosomal shapes (product I ) and slates ( II ), which are quite different from the mesoporous one ( III ) that has internal pores or mesopores ranging from 5 to 15 nm. The nanoparticles obtained from all the synthetic procedures are in the range of 40–60 nm. The investigation of the gas‐sensing properties of these materials indicate that all the sensors have good baseline stability and the sensors fabricated from material III present very different response kinetics and different CO detection properties. The possibility of adjusting the morphology and by that tuning the gas‐sensing properties makes the preparation strategies used interesting candidates for fabricating gas‐sensing materials. 相似文献
98.
Valentina Matveeva Alexey Bykov Valentin Doluda Mikhail Sulman Narendra Kumar Stanislaw Dzwigaj Eric Marceau Leonid Kustov Olga Tkachenko Esther Sulman 《Topics in Catalysis》2009,52(4):387-393
In the present work, nanocatalysts prepared on inorganic supports (zeolites) were investigated in d-glucose oxidation and compared to systems supported on polymer (hypercrosslinked polystyrene (HPS)) previously described.
Catalytic activities and selectivities were measured under various reaction conditions. The selectivity of d-glucose oxidation and activity of both Pd-containing zeolites and HPS-Ru were similar (99.7% and TOF 0.013–0.014 mol/(mol Me s)).
Physicochemical analysis X-ray photoelectron spectroscopy, liquid nitrogen physisorption, diffuse reflectance infrared Fourier
transform spectroscopy of adsorbed CO for metal sites evaluation, CD3CN for acid sites evaluation showed that Pd species were in oxidic form, while Ru species were in oxidic and reduced form.
The catalytic activity decreased when acidic sites were present in Pd-containing zeolites. 相似文献
99.
Sergey Y. Nechaev Alexei V. Lutay Valentin V. Vlassov Marina A. Zenkova 《International journal of molecular sciences》2009,10(4):1788-1807
RNA non-enzymatic recombination reactions are of great interest within the hypothesis of the “RNA world”, which argues that at some stage of prebiotic life development proteins were not yet engaged in biochemical reactions and RNA carried out both the information storage task and the full range of catalytic roles necessary in primitive self-replicating systems. Here we report on the study of recombination reaction occuring between two 96 nucleotides (nts) fragments of RNAs under physiological conditions and governed by a short oligodeoxyribonucleotide template, partially complementary to sequences within each of the RNAs. Analysis of recombination products shows that ligation is predominantly template-directed, and occurs within the complementary complex with the template in “butt-to-butt” manner, in 1- or 3- nts bulges or in 2–3 nts internal loops. Minor recombination products formed in the template-independent manner are detected as well. 相似文献
100.