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排序方式: 共有221条查询结果,搜索用时 15 毫秒
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Alexey A. Shadrin PhD Sören Mucha PhD David Ellinghaus PhD Mary B. Makarious BSc Cornelis Blauwendraat PhD Ashwin A.K. Sreelatha MSc Antonio Heras-Garvin PhD Jinhui Ding PhD Monia Hammer PhD Alexandra Foubert-Samier MD Wassilios G. Meissner MD Olivier Rascol PhD Anne Pavy-Le Traon MD Oleksandr Frei PhD Kevin S. O'Connell PhD Shahram Bahrami PhD Stefan Schreiber MD Wolfgang Lieb MD Martina Müller-Nurasyid PhD Ulf Schminke MD Georg Homuth PhD Carsten O. Schmidt PhD Markus M. Nöthen MD Per Hoffmann PhD Christian Gieger PhD Gregor Wenning MD for the European Multiple System Atrophy Study Group J. Raphael Gibbs PhD Andre Franke PhD John Hardy PhD Nadia Stefanova PhD Thomas Gasser MD Andrew Singleton PhD Henry Houlden MD Sonja W. Scholz MD Ole A. Andreassen PhD Manu Sharma PhD 《Movement disorders》2021,36(2):449-459
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We consider optimal design problems for dose-finding studies with censored Weibull time-to-event outcomes. Locally D-optimal designs are investigated for a quadratic dose–response model for log-transformed data subject to right censoring. Two-stage adaptive D-optimal designs using maximum likelihood estimation (MLE) model updating are explored through simulation for a range of different dose–response scenarios and different amounts of censoring in the model. The adaptive optimal designs are found to be nearly as efficient as the locally D-optimal designs. A popular equal allocation design can be highly inefficient when the amount of censored data is high and when the Weibull model hazard is increasing. The issues of sample size planning/early stopping for an adaptive trial are investigated as well. The adaptive D-optimal design with early stopping can potentially reduce study size while achieving similar estimation precision as the fixed allocation design. 相似文献
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Schnake Klaus John Pumberger Matthias Rappert Denis Götz Achim Zolotoverkh Oleksandr Waligora Rita Scheyerer Max Joseph 《European spine journal》2022,31(5):1331-1331
European Spine Journal - 相似文献
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Oleksandr Shtyka Waldemar Maniukiewicz Radoslaw Ciesielski Adam Kedziora Viktar Shatsila Tomasz Sieraski Tomasz Maniecki 《Materials》2021,14(12)
In the present work, for the first time, the possibility of formation of CrAl2O4 was shown from the equimolar mixture of co-precipitated Al2O3 and Cr2O3 oxides under a reductive environment. The crystallographic properties of the formed compound were calculated using the DICVOL procedure. It was determined that it has a cubic crystal structure with space group Fd-3m and a unit cell parameter equal to 8.22(3) Å. The formed CrAl2O4 is not stable under ambient conditions and easily undergoes oxidation to α-Al2O3 and α-Cr2O3. The overall sequence of the phase transformations of co-precipitated oxides leading to the formation of spinel structure is proposed. 相似文献
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Bogdan Antoszewski Oksana P. Gaponova Viacheslav B. Tarelnyk Oleksandr M. Myslyvchenko Piotr Kurp Tetyana I. Zhylenko Ievgen Konoplianchenko 《Materials》2021,14(4)
In this paper, the possibility of applying the electrospark alloying (ESA) method to obtain boron-containing coatings characterised by increased hardness and wear resistance is considered. A new method for producing such coatings is proposed. The method consists in applying grease containing aluminium powder and amorphous boron to the surface to be treated and subsequently processing the obtained surface using the ESA method by a graphite electrode. The microstructural analysis of the Al-C-B coatings on steel C40 showed that the surface layer consists of several zones, the number and parameters of which are determined by the energy conditions of the ESA process. Durametric studies showed that with an increase in the discharge energy influence, the microhardness values of both the upper strengthened layer and the diffusion zone increased to Wp = 0.13 J, Hµ = 6487 MPa, and Wp = 4.9 J, Hµ = 12350 MPa, respectively. The results of X-ray diffraction analysis indicate that at the discharge energies of 0.13 and 0.55 J, the phase composition of the coating is represented by solid solutions of body-centred cubic lattice (BCC) and face-centred cubic lattice (FCC). The coatings obtained at Wp = 4.9 J were characterised by the presence of intermetallics Fe4Al13 and borocementite Fe3 (CB) in addition to the solid solutions. The X-ray spectral analysis of the obtained coatings indicated that during the electrospark alloying process, the surface layers were saturated with aluminium, boron, and carbon. With increasing discharge energy, the diffusion zone increases; during the ESA process with the use of the discharge energy of 0.13 J for steel C40, the diffusion zone is 10–15 μm. When replacing a substrate made of steel C40 with the same one material but of steel C22, an increase in the thickness of the surface layer accompanied by a slight decrease in microhardness is observed as a result of processing with the use of the ESA method. There were simulated phase portraits of the Al-C-B coatings. It is shown that near the stationary points in the phase portraits, one can see either a slowing down of the evolution or a spiral twisting of the diffusion-process particle. 相似文献
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Ligand binding and protein dynamics in neuroglobin 总被引:23,自引:0,他引:23
Kriegl JM Bhattacharyya AJ Nienhaus K Deng P Minkow O Nienhaus GU 《Proceedings of the National Academy of Sciences of the United States of America》2002,99(12):7992-7997
Neuroglobin (Ngb) is a recently discovered protein in vertebrate brain tissue that belongs to the globin family of proteins. It has been implicated in the neuronal response to hypoxia or ischemia, although its physiological role has been hitherto unknown. Ngb is hexacoordinate in the ferrous deoxy form under physiological conditions. To bind exogenous ligands like O(2) and CO, the His E7 endogenous ligand is displaced from the sixth coordination. By using infrared spectroscopy and nanosecond time-resolved visible spectroscopy, we have investigated the ligand-binding reaction over a wide temperature range (3-353 K). Multiple, intrinsically heterogeneous distal heme pocket conformations exist in NgbCO. Photolysis at cryogenic temperatures creates a five-coordinate deoxy species with very low geminate-rebinding barriers. The photodissociated CO is observed to migrate within the distal heme pocket even at 20 K. Flash photolysis near physiological temperature (275-353 K) exhibits four sequential kinetic features: (i) geminate rebinding (t < 1 micros); (ii) extremely fast bimolecular exogenous ligand binding (10 micros < t < 1 ms) with a nontrivial temperature dependence; (iii) endogenous ligand binding (100 micros < t < 10 ms), which can be studied by using flash photolysis on deoxy Ngb; and (iv) displacement of the endogenous by the exogenous ligand (10 ms < t < 10 ks). All four processes are markedly nonexponential, suggesting that Ngb fluctuates among different conformations on surprisingly long time scales. 相似文献