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61.
Werner Kuhn 《Cellular and molecular life sciences : CMLS》1947,3(8):315-318
Summary Some arguments put forward byG. Bier in a recent article in order to supportH. Staudinger's assumption that chain molecules in solution should behave like straight rigid rods are examined. It is shown that the assumptions made byG. Bier are largely arbitrary. The main argument is the assumption that the C-C-bond in long chain molecules should not show any rotation. As far as this point is concerned, attention is drawn to some recent publications showing that the viscosity of shape of chain molecules can be determined by experiment (specific viscosity and double refraction of flow at high velocity gradients). According to these determinations the time necessary for a complete change of shape, using partially free rotation, is of the order of 10–5–10–3 seconds for molecules like nitrocellulose or polystyrene up to degrees of polymerization of several thousands and for viscosities of the solvent of the order of 10–2 poises. 相似文献
62.
G T Werner 《Experientia》1979,35(11):1514-1515
Pretreatment with BCG yielded a high degree of protection against experimental vaccinia virus infections in mice. Corynebacterium parvum and Aristolochia acid were less protective; other immunostimulants were ineffective. 相似文献
63.
Early consolidation in human primary motor cortex. 总被引:26,自引:0,他引:26
Wolf Muellbacher Ulf Ziemann Joerg Wissel Nguyet Dang Markus Kofler Stefano Facchini Babak Boroojerdi Werner Poewe Mark Hallett 《Nature》2002,415(6872):640-644
Behavioural studies indicate that a newly acquired motor skill is rapidly consolidated from an initially unstable state to a more stable state, whereas neuroimaging studies demonstrate that the brain engages new regions for performance of the task as a result of this consolidation. However, it is not known where a new skill is retained and processed before it is firmly consolidated. Some early aspects of motor skill acquisition involve the primary motor cortex (M1), but the nature of that involvement is unclear. We tested the possibility that the human M1 is essential to early motor consolidation. We monitored changes in elementary motor behaviour while subjects practised fast finger movements that rapidly improved in movement acceleration and muscle force generation. Here we show that low-frequency, repetitive transcranial magnetic stimulation of M1 but not other brain areas specifically disrupted the retention of the behavioural improvement, but did not affect basal motor behaviour, task performance, motor learning by subsequent practice, or recall of the newly acquired motor skill. These findings indicate that the human M1 is specifically engaged during the early stage of motor consolidation. 相似文献
64.
Werner Schuhmann 《Systemic Practice and Action Research》1990,3(3):265-287
This paper describes a framework for information systems development, based on the Viable System Model, currently used within the Film Division of Hoechst AG. 相似文献
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G. de Stevens L. H. Werner W. E. Barrett J. J. Chart A. H. Renzi 《Cellular and molecular life sciences : CMLS》1960,16(3):113-114
Zusammenfassung In der Reihe der Dihydro-benzothiadiazine wurde mit Hydrotrichlorthiazid (III) ein neues, ausserordentlich stark wirksames Diuretikum gefunden. Herstellung und pharmakologische Evaluation werden kurz beschrieben. Im Vergleich zu Hydrochlorthiazid (I) ist III beim Hundper os bis zu 20mal stärker diuretisch wirksam. 相似文献
68.
Transport and membrane integration of polypeptides is carried out by specific protein complexes in the membranes of all living cells. The Sec transport path provides an essential and ubiquitous route for protein translocation. In the bacterial cytoplasmic membrane, the channel is formed by oligomers of a heterotrimeric membrane protein complex consisting of subunits SecY, SecE and SecG. In the endoplasmic reticulum membrane, the channel is formed from the related Sec61 complex. Here we report the structure of the Escherichia coli SecYEG assembly at an in-plane resolution of 8 A. The three-dimensional map, calculated from two-dimensional SecYEG crystals, reveals a sandwich of two membranes interacting through the extensive cytoplasmic domains. Each membrane is composed of dimers of SecYEG. The monomeric complex contains 15 transmembrane helices. In the centre of the dimer we observe a 16 x 25 A cavity closed on the periplasmic side by two highly tilted transmembrane helices. This may represent the closed state of the protein-conducting channel. 相似文献
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Estimating the Cluster Tree of a Density by Analyzing the Minimal Spanning Tree of a Sample 总被引:2,自引:0,他引:2
Werner Stuetzle 《Journal of Classification》2003,20(1):025-047
runt pruning , a new clustering method that attempts to
find modes of a density by analyzing the minimal spanning tree of a sample.
The method exploits the connection between the minimal spanning tree and
nearest neighbor density (e.g. normal mixture) or about the geometric shapes
of the clusters, and is computationally feasible for large data sets. 相似文献