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排序方式: 共有262条查询结果,搜索用时 15 毫秒
1.
Scientometrics - Using a selection of general science journals, general medical journals and specialized medical journals, this paper analyses four indicators of epistemic community formation:... 相似文献
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We present an Extended Quadratic Frobenius Primality Test (EQFT), which is related to the Miller-Rabin test and to several
other known probabilistic tests. EQFT takes time equivalent to about two or three Miller-Rabin tests, but has a much smaller
error probability, namely 256/331776t for t iterations of the test in the worst case. We also give bounds on the average-case behaviour of the test: consider
the algorithm that repeatedly chooses random odd k bit numbers, subjects them to t iterations of our test and outputs the
first one found that passes all tests. We obtain numeric upper bounds for the error probability of this algorithm as well
as a general closed expression bounding the error. For instance, it is at most 2-155 for k = 500, t = 2. Compared with earlier similar results for the Miller-Rabin test, the results indicate that our test in
the average case has the effect of nine Miller-Rabin tests. We also give bounds for the error in case a prime is sought by
incremental search from a random starting point. 相似文献
4.
Sten Kaiser 《International Journal of Fracture》1985,29(2):85-99
The stability of a cracked, nonlinear component connected to an elastic structure and subjected to an arbitrary number of
controlled loads or displacements, is discussed. First this is done with a general instability criterion expressed in terms
of loads and displacements of the cracked part. Then general expressions for the tearing modulus are given for different loading
situations. Finally the given equations are applied to SEN specimens under bending and tension.
Résumé On discute de la stabilité d'un composant fissuré et non linéaire assemblé à une structure élastique et soumis à un monbre quelconque de charges ou de déplacements, appliqués dans des conditions connues. Ceci est réalisé en faisant appel, en premier lieu, à un critère général d'instabilité exprimé en termes the sollicitation et de déplacement de la portion fissurée. Ensuite, on fournit des expressions générales pour le module d'arrachement, correspondant à diverses situations de mise en charge. Enfin, les équations obtenues sont appliquées à des éprouvettes à entaille latérale simple soumises à flexion et traction.相似文献
5.
Katarzyna Jasieniecka-Gazarkiewicz Kamil Demski Satinder K. Gidda Sylwia Kliska Janusz Niedojado Ida Lager Anders S. Carlsson Elena A. Minina Robert T. Mullen Peter V. Bozhkov Sten Stymne Antoni Bana 《International journal of molecular sciences》2021,22(6)
Arabidopsis thaliana possesses two acyl-CoA:lysophosphatidylethanolamine acyltransferases, LPEAT1 and LPEAT2, which are encoded by At1g80950 and At2g45670 genes, respectively. Both single lpeat2 mutant and double lpeat1 lpeat2 mutant plants exhibit a variety of conspicuous phenotypes, including dwarfed growth. Confocal microscopic analysis of tobacco suspension-cultured cells transiently transformed with green fluorescent protein-tagged versions of LPEAT1 or LPEAT2 revealed that LPEAT1 is localized to the endoplasmic reticulum (ER), whereas LPEAT2 is localized to both Golgi and late endosomes. Considering that the primary product of the reaction catalyzed by LPEATs is phosphatidylethanolamine, which is known to be covalently conjugated with autophagy-related protein ATG8 during a key step of the formation of autophagosomes, we investigated the requirements for LPEATs to engage in autophagic activity in Arabidopsis. Knocking out of either or both LPEAT genes led to enhanced accumulation of the autophagic adaptor protein NBR1 and decreased levels of both ATG8a mRNA and total ATG8 protein. Moreover, we detected significantly fewer membrane objects in the vacuoles of lpeat1 lpeat2 double mutant mesophyll cells than in vacuoles of control plants. However, contrary to what has been reported on autophagy deficient plants, the lpeat mutants displayed a prolonged life span compared to wild type, including delayed senescence. 相似文献
6.
Microsomes of developing soya bean cotyledons transfer oleate from oleoyl-CoA to phosphatidylcholine (PC) by two different
mechanisms: one in which oleate transfer is accompanied by the release of free CoA and another which results in the exchange
of oleate from oleoyl-CoA for unsaturated 18-carbon fatty acids of PC. The acyl exchange can be demonstrated only when bovine
serum albumin is present in the incubation medium. ATP-dependent acyl-CoA synthetase is not involved in the exchange process,
which apparently does not require any cofactors. In light of this exchange process, the oleate desaturase system was reinvestigated
in order to determine what the actual substrate for this system is. Upon incubation of microsomes with high concentrations
of [14C] oleoyl-CoA, bovine serum albumin and NADH, it could be conclusively demonstrated that most oleic acid is desaturated while
part of the PC molecule. The amounts of [14C] linoleoyl-CoA formed could be explained entirely by the acyl exchange. The physiological significance of the acyl exchange
system is discussed. A new method for separation of acyl-CoA from other lipids and free CoA using reversed phase column chromatography
also is described. 相似文献
7.
Maureen Bafor Allan Keith Stobart Sten Stymne 《Journal of the American Oil Chemists' Society》1990,67(4):217-225
Microsomal membrane preparations from the developing seeds of safflower (Carthamus tinctorius, var. Gila) and turnip-rape (Brassica campestris, var. Bele) catalyzed the assembly of triacylglycerols (triglycerides) from sn-glycerol 3-phosphate and acyl-CoA. The membrane
preparations were used to assess the acyl specificity properties of the initial acylating enzymes—glycerol 3-phosphate acyltransferase
(GPAT) and 1-acylglycerol 3-phosphate acyltransferase (lysophosphatidic acid acyltransferase, LPAAT)—that are responsible
for the fatty acids at positions sn-1 and sn-2 of the sn-triacylglycerol, respectively. In spectrophotometric assays it was
possible to evaluate, to some extent, how these enzymes will utilize unusual and foreign fatty acids that are not normally
found in these particular plant species. The acylating enzymes from both plants used, to varying extents, a comprehensive
range of acyl-CoA donor species and some kinetic properties of the substrates involved are presented. The enzymes from safflower,
however, were generally the more selective, whereas the turnip-rape was less particular and could utilize a range of acyl
substrates. The enzymes from both plants hardly utilized erucate (C22∶1), and the significance of this is discussed in terms
of mechanisms which have evolved in order to exclude certain, perhaps detrimental, fatty acids from structural membrane lipids
and dedicate them to storage lipid assembly.
The ability of the microsomal preparations, from the developing seeds of both plants, to synthesize cocoabutter type fats
was investigated. Microsomal membranes were incubated with glycerol 3-phosphate and equimolar amounts of palmitate, oleate
and stearate. Safflower preparations catalyzed the construction of sn-triacylglycerol with largely palmitate, oleate and stearate
in positions sn-1, 2 and 3, respectively. The selectivity for acyl species in rape was less pronounced, however, substantial
saturated-unsaturated-saturated oils were still produced. The results are discussed in terms of the acyl selectivity properties
of the glycerol acylating enzymes. It is evident that given the correct composition of fatty acids, the plant can produce
cocoabutter or other exotic fats. 相似文献
8.
Björn Sten Mark Kretzschmar Paul Bergelt Daniel Göhler Fabian Firmbach Ronny Köcher Andreas Heft 《Aerosol science and technology》2020,54(10):1124-1134
Abstract For the purpose of silica surface layer modulation, a pneumatic-controlled two-substance atomizer with inertia-based coarse droplet separation was operated at different system pressures for tetraethyl orthosilicate precursor aerosol supply during combustion chemical vapor deposition. A comprehensive testing study was performed to characterize the atomizer’s performance characteristics, initial precursor aerosols at the atomizer’s outlet, transformed aerosols before combustion, combustion aerosols and formed layers. Laser diffraction spectrometry, differential electrical mobility analyses and condensation particle counting were used for aerosol characterization with regard to particle size and particle production quantities. Layers were characterized by scanning electron microscopy, atomic force microscopy, spectral ellipsometry, water contact angle measurements and light transmission concerning geometric properties (thickness, surface structure and roughness) and physical behaviors (i.e., optical behaviors, hydrophobicity). Results show a quasi-linear relationship of the ejection mass flow of the pneumatic-controlled atomizer and geometric layer properties which again show a direct relationship to the physical properties. No correlation was found between the aerosols before combustion and the combustion aerosols since the majority of combustion aerosol particles are synthesized solely from the gas phase based on evaporated precursor material. Copyright © 2020 American Association for Aerosol Research 相似文献
9.
10.
Bernt M. kesson John Bagterp Jrgensen Niels Kjlstad Poulsen Sten Bay Jrgensen 《Journal of Process Control》2008,18(7-8):769-779
This paper discusses a method for estimating noise covariances from process data. In linear stochastic state-space representations the true noise covariances are generally unknown in practical applications. Using estimated covariances a Kalman filter can be tuned in order to increase the accuracy of the state estimates. There is a linear relationship between covariances and autocovariance. Therefore, the covariance estimation problem can be stated as a least-squares problem, which can be solved as a symmetric semidefinite least-squares problem. This problem is convex and can be solved efficiently by interior-point methods. A numerical algorithm for solving the symmetric is able to handle systems with mutually correlated process noise and measurement noise. 相似文献