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1.
Zusammenfassung Der Verfasser nimmt an, dass durch Konglutination von Spermien mit Embryonen vonTriton cristatus verschiedener Entwicklungsstadien morphogenetische Wirkstoffe entstehen, die je nach Stadium des verwendeten Embryos ganz verschiedene, aber spezifische Wirkungen haben. Es werden die wichtigsten morphogenetischen Prozesse wie Furchung, Morulabildung, Gastrulation und Neurulation selektiv beeinflusst. Diese Wirkstoffe, welche auch in der Normalentwicklung nacheinander entstehen und jedesmal die betreffende Entwicklungsphase einleiten sollen, werden als «Ontogenine» bezeichnet.  相似文献   

2.
Summary The transmitter substance released by nigro-thalamic fibres is proposed to be -aminobutyric acid, since picrotoxin blocked nigra-evoked monosynaptic inhibition of thalamic neurons.Supported by grants Nos 212009 and 311410 from Ministry of Education of Japan.The authors wish to thank Dr Marjorie Anderson, University of Washington, Seattle, for improving the English.  相似文献   

3.
采用羟甲基化技术对碱木质素进行活化,对比了羟甲基化前后未质素改性酚醛树脂胶的粘结强度、残留甲醛、贮存稳定性和热稳定性等性能,为木质素的高值应用探讨新的途径.试验结果表明在木质素对笨酚的替代率低于30%务件下,以分离提纯后的木质素可直接应用于酚醛树脂胶粘剂的改性;而当替代率大于50%后,木质素的羟甲基化展示对木质素改性酚醛树脂的胶结强度、热稳定性具有良好的促进作用.但木质素的羟甲基化作用同时也导致木质素改性酚醛树脂中残留甲醛含量增加,进而导致制备的胶粘荆的贮存稳定性降低,可以通过改变合成过程中甲醛和碱的用量来达到降低酚醛树脂中残留甲醛含量.  相似文献   

4.
近年来新西兰政府大力调整其科技政策,在建设知识社会的蓝图下,建构了科技投资的基本框架,凸显了知识、经济、环境、社会四大目标,另外通过对投资决策、运行和监督的改革,使政府科技投资的机制更为科学有效,本文还给出了新西兰政府近年来科技投资的分配比例状况,阐明了其投资的重点领域。  相似文献   

5.
Zusammenfassung Die spezifische Oberfläche von BaSO4-Niederschlägen wurde bestimmt durch Messung des Austausches von Oberflächen-Ba-Ionen mit-radioaktiven Ba131-Ionen (spezifische Aktivität etwa 1 mc/g) einer gesättigten BaSO4-Lösung. Die spezifische Oberfläche war 5150 cm2/g.Dann wurden die Adsorptionsisothermen von Farbstoffen (Kristallviolett, Methylenblau und Pikrinsäure) an der Oberfläche von BaSO4-Teilchen bestimmt. Unter der Annahme, dass jedes Farbstoffmolekül im adsorbierten Zustand eine Oberfläche von 100 A2 einnimmt, ergab sich ein maximaler Besetzungsgrad von 22–30%.  相似文献   

6.
Summary The carotenoid crocetin was found to be taken up by normal rat muscle cells grown in vitro, and was found in the ribosomal-microsomal fraction, supporting the hypothesis that crocetin affects cell division enzymatic processes.  相似文献   

7.
Zusammenfassung Experimentell hergestellte, virusähnliche Partikel, bestehend aus einem Kern von genetischem Material und einer Proteinhülle, werden in Analogie zu einer Virusinfektion in Zellen eingeschleust.  相似文献   

8.
We outline a framework for analyzing episodes from the history of science in which the application of mathematics plays a constitutive role in the conceptual development of empirical sciences. Our starting point is the inferential conception of the application of mathematics, recently advanced by Bueno and Colyvan (2011). We identify and discuss some systematic problems of this approach. We propose refinements of the inferential conception based on theoretical considerations and on the basis of a historical case study. We demonstrate the usefulness of the refined, dynamical inferential conception using the well-researched example of the genesis of general relativity. Specifically, we look at the collaboration of the physicist Einstein and the mathematician Grossmann in the years 1912–1913, which resulted in the jointly published “Outline of a Generalized Theory of Relativity and a Theory of Gravitation,” a precursor theory of the final theory of general relativity. In this episode, independently developed mathematical theories, the theory of differential invariants and the absolute differential calculus, were applied in the process of finding a relativistic theory of gravitation. The dynamical inferential conception not only provides a natural framework to describe and analyze this episode, but it also generates new questions and insights. We comment on the mathematical tradition on which Grossmann drew, and on his own contributions to mathematical theorizing. The dynamical inferential conception allows us to identify both the role of heuristics and of mathematical resources as well as the systematic role of problems and mistakes in the reconstruction of episodes of conceptual innovation and theory change.  相似文献   

9.
Four new hexapeptide analogues of C-terminal Substance P fragment with increased solubility in aqueous solutions are described. The peptides contain histidine in positions 6, 8, 9 and 10, respectively. The effect of the structural changes on the hypotensive activity and antigenic properties of analogues was compared. It was found that substitution of amino acid residues in various positions in the C-terminal hexapeptide of Substance P resulted in different effects on the hypotensive and antigenic properties, respectively. Only the [His6] SP6-11 analogue had an unchanged antigenic structure when compared with the C-terminal region of Substance P, but it showed an almost total loss of hypotensive activity. The [His9] SP6-11 analogue retained 50% of the hypotensive activity of the C-terminal hexapeptide but showed a markedly reduced expression of the antigenic epitope localized in this region of Substance P.  相似文献   

10.
Summary The levels of light adaptation at which the retinas of 4 species of microchiropteran bats became unable to generate electroretinograms were progressively ordered. The order correlated well with light preferences based on activity patterns of the 4 species. These results suggest that the ability of the retina to function in ambient light may govern some natural behaviors of these bats.This work was supported in part by grant No. EY 01228 from the U.S.P.H.S. and was facilitated by equipment provided by Bob Hope Fight for Sight Award No. G522 and a grant from Research to Prevent Blindness, Inc. Portions of this work were presented at the Fifth International Bat Research Conference, Albuquerque, New Mexico, USA, August, 1978.  相似文献   

11.
Zusammenfassung Die marklosen Nerven-Einzelfasern vonCarcinus maenas wurden mit monochromatischem Ultraviolett bestrahlt. Zuerst tritt bei Bestrahlung ein langsamer Abfall der Reizschwelle, dann ein rascher Abfall, gefolgt von einem steilen Anstieg auf. Der Abfall rührt von einer Depolarisation her, deren Zunahme dann zu Unerregbarkeit führt. Durch Verbesserung der Ableitungstechnik konnten die elektrischen Veränderungen lokalisiert an der bestrahlten Stelle gemessen werden. Anstieg der Reizschwelle, Abfall der Steilheit und Abfall der Höhe des Spitzenpotentials wurden auch bei diesen marklosen Fasern beobachtet, aber nicht so ausgeprägt wie bei der Bestrahlung markhaltiger Fasern.

This work was carried out during the tenure of a Postdoctoral fellowship from the United States Public Health Service.  相似文献   

12.
Summary Four new hexapeptide analogues of C-terminal Substance P fragment with increased solubility in aqueous solutions are described. The peptides contain histidine in positions 6, 8, 9 and 10, respectively. The effect of the structural changes on the hypotensive activity and antigenic properties of analogues was compared. It was found that substitution of amino acid residues in various positions in the C-terminal hexapeptide of Substance P resulted in different effects on the hypotensive and antigenic properties, respectively. Only the [His6] SP6-11 analogue had an unchanged antigenic structure when compared with the C-terminal region of Substance P, but it showed an almost total loss of hypotensive activity. The [His9] SP6-11 analogue retained 50% of the hypotensive activity of the C-terminal hexapeptide but showed a markedly reduced expression of the antigenic epitope localized in this region of Substance P.  相似文献   

13.
Our results on the number of nuclei, pycnoses, karyorrhexis and mitoses in protected irradiated mice demonstrate that mixtures of chemical protectors largely diminish the lesions produced in the stem cells of the duodenum of mice irradiated with 2000 R of X-rays, but a delay of about 30 days is nevertheless needed to allow complete recovery of the duodenal mucosa.
Résumé Nos résultats sur le nombre de noyaux, de pycnoses, de caryorrexis et de mitoses, chez les souris protégées et irradiées, montrent que des associations de substances radioprotectrices diminuent fortement les lésions produites dans les cellules souches du duodénum de souris irradiées avec une dose de 2000 R de rayons X; un délai d'au moins 30 jours est néanmoins nécessaire avant que la muqueuse duodénale ait retrouvé un aspect entièrement normal.


This work was supported in part by research contract A.I.E.A. No. 347/RB and by grants from the Fonds de la Recherche scientifique fondamentale collective.  相似文献   

14.
介绍了一种基于超高频RFID的物联网前端感知系统的设计和实现,以及主要模块的功能,然后分别从硬件结构,工作流程和软件设计三个方面进行了详细阐述.本系统的工作频率在860~960 MHz可调节,能支持EPC Gen2和ISO/IEC 18000-6B/6C标准.它的射频前端是以射频芯片AS3992为核心,使用内部集成的功放,外加一系列外围电路实现.其优点是体积小、重量轻、集成度高和功耗低.实验结果表明,该系统的读写距离能达到2.5m,能够满足实际应用的需要.  相似文献   

15.
Zusammenfassung Mittels Chromatographie auf Calciumphosphat-DEAE-Cellulose lassen sich aus Hämolysat von Menschenerythrocyten zwei Fraktionen gereinigter Katalase darstellen. Im Gegensatz zu den Fraktionen aus normalen und homozygot akatalatischen Zellen zeigen die aus Blut heterozygoter Defektträger isolierten Katalasefraktionen ein elektrophoretisch verschiedenes Verhalten. Die Beweglichkeit der rascher wandernden Fraktion entspricht jener des normalen Enzyms, während die langsamer wandernde Fraktion sich gleich verhält wie das aus Akatalasieerythrocyten isolierte Enzym. Daraus folgt, dass zwischen Katalase in normalen und Akatalasiezellen trotz nachgewiesener Antigenidentität gewisse Strukturunterschiede zu bestehen scheinen.  相似文献   

16.
Zusammenfassung Feststellung, dass die Antigen-Determinanten meistens mit Purin-Mononukleotiden (AMP und GMP) verbunden sind, was auf eine charakteristische und spezifische Eigenschaft der Antigen-«processing»-Zelle zurückgeführt wird.  相似文献   

17.
Riassunto Nel quadro di una serie di ricerche tendenti a determinare le età relative delle rocce granitiche dell'arcipelago toscano e della Toscana continentale, è stata studiata con il metodo degli aloni pleocroici la quarzomonzonite di Porto Azzurro (isola d'Elba).In base ai risultati ottenuti, riportati nel grafico, si può asserire che non vi è apprezzabile differenza di età tra la roccia studiata e la vicina granodiorite del Monte Capanne.  相似文献   

18.
According to the historian and sociologist of science Terry Shinn, the creator of the concept of ‘research technologies’: “Research technologies may sometimes generate promising packets of instrumentation for yet undefined ends. They may offer technological answers to questions that have hardly been raised. Research technologists׳s instruments are then generic in the sense that they are base-line apparatus which can subsequently be transformed by experimenters into products tailored to specific economic ends or adapted by experimenters to further cognitive ends in academic research.”1 Genericity thus manifests one of three fundamental characteristics of research technologies. At the same time, however, each research technology emerges out of the specific disciplinary context in which it is initially developed with entirely concrete aims. Consequently, genericity does not exist from the outset but first has to form, along a path that remains to be clarified. It is produced or constructed by the actors on two levels: as an instrument in the laboratory and as a way of speaking at the representational level. This issue yields the structure of this paper. Three options for the transition of a specific technique into a generic research technology are compared. One of them proves to be the most frequent pattern of this dynamic. This is explored further, taking as paradigmatic examples ‘computed tomography’ (CT), ‘nuclear magnetic resonance׳ (NMR) and its application known as ‘magnetic resonance imaging’ (MRI), together with several additional examples.  相似文献   

19.
Summary The present report deals with the effect of excessive ingestion of fluoride on glycosaminoglycan (GAG). Increase in fluoride deposition in bone, and in circulating levels of fluoride in serum, are also reported. Among the 3 constituents of GAG investigated; hexosamine, uronic acid and sulphate, the content remained unaltered except for sulphate.Acknowledgment. The authors wish to acknowledge the Department of Science and Technology (DST), Government of India, for the financial aid. One of us (M.J.) acknowledges the receipt of a Junior Research Fellowship from DST, during the tenure of which the investigations were carried out.  相似文献   

20.
Biotin administration to old rats (28 months) causes in the blood an increase of ATP, glucose, triglycerides, alkaline phosphatase and a decrease of cholesterol and acid phosphatase; in the liver DNA and electrostatic interactions between DNA and histones are increased. Such parameters come within the values shown by adult rats.  相似文献   

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