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排序方式: 共有291条查询结果,搜索用时 296 毫秒
151.
P. VingerhoetsK.T. Flanagan J. BillowesM.L. Bissell K. BlaumB. Cheal M. De RydtD.H. Forest Ch. GeppertM. Honma M. KowalskaJ. Krämer K. KreimA. Krieger R. NeugartG. Neyens W. Nörtershäuser J. PapugaT.J. Procter M.M. RajabaliR. Sánchez H.H. StrokeD.T. Yordanov 《Physics letters. [Part B]》2011,703(1):34-39
152.
Warren RM Pointon L Caines R Hayes C Thompson D Leach MO;UK MRI breast screening study 《Magnetic resonance imaging》2002,20(7):557-565
Breast screening acceptability is dependent on sensitivity and recall rate. We aimed to establish the recall rate for MRI and mammography, separately and together, when screening a cohort of women at high genetic risk. Women aged 35-49 years in the MARIBS study form the cohort. We analysed the recall rate, the number of extra tests and their effectiveness. Wilcoxon Rank test was used to estimate the effect of age and logistic regression with robust variance the effect of mammographic density on recall rates. The first 726 screening studies took place in 415 women. Following 86 of these recall occurred, comprising 140 additional investigations. 28 of the cases were resolved without further MRI, and 18 women had more than 2 additional tests. Neither age nor mammographic density was associated with recall. MRI had a recall of rate of 10.19%, and mammography 4.00%. The two techniques largely recalled different cases and 10 cases only (11.62% of those recalled) were abnormal by both tests. The two together had a recall rate of 11.85%. Recall rates varied widely between centres of the study. Breast MRI in asymptomatic high-risk women age 35-49 years largely recalls different women from mammography. The combined figure of approximately 12% may be acceptable for screening and will be useful for planning similar studies. 相似文献
153.
We show that the isomorphism problem is solvable in the class of central extensions of word-hyperbolic groups,and that the isomorphism problem for biautomatic groups reduces to that for biautomatic groups with finite centre.We describe an algorithm that,given an arbitrary finite presentation of an automatic group Γ,will construct explicit finite models for the skeleta of K(Γ,1) and hence compute the integral homology and cohomology of Γ. 相似文献
154.
Dr. James D. Firth Dr. L. Anders Hammarback Thomas J. Burden Jonathan B. Eastwood Dr. James R. Donald Dr. Chris S. Horbaczewskyj Matthew T. McRobie Adam Tramaseur Dr. Ian P. Clark Prof. Michael Towrie Dr. Alan Robinson Dr. Jean-Philippe Krieger Dr. Jason M. Lynam Prof. Dr. Ian J. S. Fairlamb 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(12):3979-3985
Manganese-mediated borylation of aryl/heteroaryl diazonium salts emerges as a general and versatile synthetic methodology for the synthesis of the corresponding boronate esters. The reaction proved an ideal testing ground for delineating the Mn species responsible for the photochemical reaction processes, that is, involving either Mn radical or Mn cationic species, which is dependent on the presence of a suitably strong oxidant. Our findings are important for a plethora of processes employing Mn-containing carbonyl species as initiators and/or catalysts, which have considerable potential in synthetic applications. 相似文献
155.
Gui-Qiang G.Chen School of Mathematical Sciences Fudan University Shanghai China Mathematical Institute University of Oxford - St Giles Oxford OX LB UK 《数学物理学报(B辑英文版)》2010,30(2):391-427
We are concerned with the derivation and analysis of one-dimensional hyperbolic systems of conservation laws modelling fluid flows such as the blood flow through compliant axisymmetric vessels.Early models derived are nonconservative and/or nonhomogeneous with measure source terms,which are endowed with infinitely many Riemann solutions for some Riemann data.In this paper,we derive a one-dimensional hyperbolic system that is conservative and homogeneous.Moreover,there exists a unique global Riemann solution for the Riemann problem for two vessels with arbitrarily large Riemann data,under a natural stability entropy criterion.The Riemann solutions may consist of four waves for some cases.The system can also be written as a 3×3 system for which strict hyperbolicity fails and the standing waves can be regarded as the contact discontinuities corresponding to the second family with zero eigenvalue. 相似文献
156.
157.
R. M. Shelby R. M. Macfarlane D. P. Burum J. Friedrich D. Haarer W. E. Moerner F. M. Schellenberg G. C. Bjorklund A. R. Chraplyvy A. J. Sievers R. H. Silsbee F. Frenkel J. Häger W. Krieger H. Walther G. Ertl J. Segner W. Vielhaber R. B. Gerassimov S. M. Metev S. K. Savtchenko G. A. Kotov V. P. Veiko J. F. Figueira S. J. Thomas D. Bäuerle G. Leyendecker P. Geittner H. Lydtin 《Applied physics. B, Lasers and optics》1982,28(2-3):262-268
158.
Self-induced transparency on the neon transition 2s
2(J=1)–2p
4(J=2) is studied both experimentally by investigating the propagation of 3-nsec laser pulses at 1.15 µm in an absorber discharge and theoretically by a numerical integration of Bloch's equations and the wave equation.—The application of linearly and circularly polarized light corresponds to the interaction with a quasi-nondegenerate and degenerate transition, respectively. Pulse shapes, delays, and transmittancevs. input peak intensity are found in quantitative agreement with the calculated data. While with linear light polarization all SIT characteristics clearly appear, with circular polarization the pulse break-up and the oscillation of transmittance due to optical nutations are washed out.—The homogeneous linewidth derived from pulse delay data agrees with the value from conventional measurements. The results prove SIT useful as a quantitative spectroscopic method. 相似文献
159.
160.