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991.
992.
S M Houten W Kuis M Duran T J de Koning A van Royen-Kerkhof G J Romeijn J Frenkel L Dorland M M de Barse W A Huijbers G T Rijkers H R Waterham R J Wanders B T Poll-The 《Nature genetics》1999,22(2):175-177
Hyperimmunoglobulinaemia D and periodic fever syndrome (HIDS; MIM 260920) is an autosomal recessive disorder characterized by recurrent episodes of fever associated with lymphadenopathy, arthralgia, gastrointestinal dismay and skin rash. Diagnostic hallmark of HIDS is a constitutively elevated level of serum immunoglobulin D (IgD), although patients have been reported with normal IgD levels. To determine the underlying defect in HIDS, we analysed urine of several patients and discovered increased concentrations of mevalonic acid during severe episodes of fever, but not between crises. Subsequent analysis of cells from four unrelated HIDS patients revealed reduced activities of mevalonate kinase (MK; encoded by the gene MVK), a key enzyme of isoprenoid biosynthesis. Sequence analysis of MVK cDNA from the patients identified three different mutations, one of which was common to all patients. Expression of the mutant cDNAs in Escherichia coli showed that all three mutations affect the activity of the encoded proteins. Moreover, immunoblot analysis demonstrated a deficiency of MK protein in patient fibroblasts, indicating a protein-destabilizing effect of the mutations. 相似文献
993.
994.
Localization of nitrogen fixation in Anabaena 总被引:10,自引:0,他引:10
995.
Summary Islet cell suspensions were prepared from neonatal rat pancreatic islets. While mechanical disintegration results in a higher yield, cells prepared by trypsin treatment appear to be better preserved. Trypsin treatment of pancreatic islets during the cell preparation procedure does not influence the stimulation by glucose of (pro)insulin biosynthesis in freshly isolated cells.Investigations were carried out as a part of the HFR Diabetes mellitus and Fettstoffwechselstörungen supported by the Ministry of Health of the GDR. 相似文献
996.
C. van Eykelenburg 《Cellular and molecular life sciences : CMLS》1979,35(8):1127-1128
Summary An apparatus is described for culturing micro-algae in a discontinuous temperature gradient and a continuous light intensity gradient. The apparatus provides 100 different combinations of these abiotic factors at 1 time. The crossgradient culture apparatus is called ecobox. 相似文献
997.
Michael P. Clements Philip Hans Franses Jeremy Smith Dick van Dijk 《Journal of forecasting》2003,22(5):359-375
We compare linear autoregressive (AR) models and self‐exciting threshold autoregressive (SETAR) models in terms of their point forecast performance, and their ability to characterize the uncertainty surrounding those forecasts, i.e. interval or density forecasts. A two‐regime SETAR process is used as the data‐generating process in an extensive set of Monte Carlo simulations, and we consider the discriminatory power of recently developed methods of forecast evaluation for different degrees of non‐linearity. We find that the interval and density evaluation methods are unlikely to show the linear model to be deficient on samples of the size typical for macroeconomic data. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
998.
南苏鲁超高压榴辉岩中罕见的原生高密度盐水溶液包裹体 总被引:5,自引:3,他引:5
在南苏鲁超高压变质带发现了原生高密度流体包裹体. 这种包裹体在超高压榴辉岩的石榴石中呈孤立和小群分布, 冷冻法确定包裹体的低共熔温度≤–52℃, 在重复冷冻-升温的特定阶段, 液相包裹体中出现气泡, 测得液-气均一温度≤–12.5℃, 由此得到流体成分属CaCl2-NaCl-H2O体系, 流体密度为1.27 g/cm3, 在相当于榴辉岩相峰期温度下的压力约为2.4 GPa, 接近超高压变质条件. 这类包裹体在榴辉岩的折返过程中与寄主矿物发生反应, 形成含水硅酸盐矿物, 并使其密度降低, 转变成气液多相包裹体. 相似文献
999.
In this article we propose a framework which can assist analysts in their reflection on the requirements for a participatory
modelling exercise in natural resource management. Firstly, we distinguish different types of formal models which may be developed,
ranging from models that focus on (bio)physical mechanisms to models which also include the actors involved in the utilisation
of the resource and the social mechanisms that co-determine actor behaviour. Secondly, we consider what different modes of
stakeholder participation entail for model construction and use. Finally, we propose six different purposes for a modelling
exercise (clarify arguments and values, research and analyse, design and recommend, provide strategic advice, mediate, and
democratise), and highlight conditions that affect the appropriateness of stakeholder participation for each purpose. The
framework does not provide a straightforward recipe for the selection of participatory modelling methods, but we expect that
the systematic reflection it affords will help analysts to make appropriate choices while designing a modelling exercise. 相似文献
1000.
Summary A survey of recent work on the theories of the peculiar mechanical behaviour of substances with rubber-like properties is given. All the theories are based on the assumption that these substances (including rubber itself) are composed of very long, flexible chainmolecules. Any segment of a chain is linked to two neighbouring segments by bonds similar to those which are present in typical solids and to all other neighbours by linkages like the bonds prevailing between the particles of liquids. The chain molecules are intermingled so as to form a kind of a felt.This state of aggregation is intermediate between the solid and the liquid; it is called the rubber-like state (état gommoïdal). Elasticity, viscosity and plastic flow as well as the influence of crystallization, vulcanization and degradation are discussed in terms of this theory. 相似文献