排序方式: 共有13条查询结果,搜索用时 15 毫秒
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Sanford TW Allshouse GO Marder BM Nash TJ Mock RC Spielman RB Seamen JF McGurn JS Jobe D Gilliland TL Vargas M Struve KW Stygar WA Douglas MR Matzen MK Hammer JH De Groot JS Eddleman JL Peterson DL Mosher D Whitney KG Thornhill JW Pulsifer PE Apruzese JP Maron Y 《Physical review letters》1996,77(25):5063-5066
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An integral equation formulation for buoyancy-driven convection problems is developed and illustrated. Buoyancy-driven convection in a bounded cylindrical geometry with a free surface is studied for a range of aspect ratios and Nusselt numbers. The critical Rayleigh number, the nature of the cellular motion, and the heat transfer enhancement are computed using linear theory. Green's functions are used to convert the linear problem into linear Fredholm integral equations. Theorems are proved which establish the properties of the eigenvalues and eigenfunctions of the linear integral operator which appears in these equations. 相似文献
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Ellis DE Terra J Warschkow O Jiang M González GB Okasinski JS Bedzyk MJ Rossi AM Eon JG 《Physical chemistry chemical physics : PCCP》2006,8(8):967-976
Characterization of lead substitution for calcium in hydroxyapatite (CaHA) is carried out, using experimental techniques and Density Functional theoretical (DFT) analyses. Theoretical modeling is used to obtain information of the Pb chemical environment for occupancy at either Ca(I) or Ca(II) sites of CaHA. Effects of the larger ionic radius of Pb(+2) compared to Ca(+2) are apparent in embedded cluster calculations of local chemical bonding properties. DFT periodic planewave pseudopotential studies are used to provide first-principles predictions of local structural relaxation and site preference for Pb(x)Ca(10-x)HA over the composition range x< or = 6. General characteristics of the polycrystalline material are verified by X-ray diffraction and FTIR analysis, showing the presence of a single phase of CaHA structure. A short range structure around lead is proposed in order to interpret the Pb L-edge EXAFS spectrum of the solid solution Ca(6.6)Pb(3.4)HA. In this concentration we observe that lead mainly occupies Ca(II) sites; the EXAFS fit slightly favors Pb clustering, while theory indicates the importance of Pb-Pb avoidance on site (II). 相似文献
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Fernández P Durand JS Pérez-Conde C Paniagua G 《Analytical and bioanalytical chemistry》2003,375(8):1020-1023
This paper reports a new flow-through fluoroimmunosensor, the function of which is based on antibodies immobilized on an inmunoreactor of controlled-pore glass (CPG), for determination of digoxin, used in the treatment of congestive heart failure and artery disease. The immunosensor has a detection limit of 1.20 microg L(-1) and provides high reproducibility (RSD=4.5% for a concentration of 0.0025 mg L(-1), and RSD=6.7% for 0.01 mg L(-1)). The optimum working concentration range was found to be 1.2 x 10(-3)-4.0 x 10(-2) mg L(-1). The lifetime of the immunosensor was about 50 immunoassays; if stored unused its lifetime can be extended to three months. A sample speed of about 10-12 samples per hour can be attained. Possible interference from substances with structures similar to digoxin (morphine, heroin, tebaine, codeine, pentazocine and narcotine) was investigated. No cross-reactivity was seen at the highest digoxin: interferent ratio studied (1:100). The proposed fluoroimmunosensor was successfully used to determine digoxin concentrations in human serum samples. 相似文献
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Jun-Sang Park John Okasinski Kamalika Chatterjee Yiren Chen Jonathan Almer 《Synchrotron Radiation News》2017,30(3):9-16
Engineering materials are typically made from transition metals and exist in polycrystalline form. The ability to characterize this class of materials, both ex situ and in situ, is particularly important as the demand for efficient, environment-friendly machines rises and the need to understand the material response at a smaller length scale increases. In the past decade, the use of high-energy synchrotron X-rays to characterize bulk engineering materials has increased significantly, with several high-energy beamlines and new characterization techniques coming online around the world. 相似文献
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A series of thieno[2,3-c]pyridine antagonists of cell adhesion molecule (CAM) expression, such as A-205804 (1) and A-249377 (2), selectively suppressed the induced expression of E-selectin and ICAM-1 over VCAM-1. In an effort to explore the biological mechanism of action of these inhibitors, we synthesized (125)I- and (3)H-labeled thieno[2,3-c]pyridines 5 and 6. An isolated diazonium tetrafluoroborate salt efficiently trapped Na(125)I on very small scale (7.5 microg of Na(125)I), providing the corresponding (125)I-labeled thieno[2,3-c]pyridine in modest yield. Preliminary mechanistic investigations using these radiolabeled compounds revealed that, upon incubation with human umbilical vein endothelial cells (HUVECs), these inhibitors of CAM expression translocated to the cell nucleus and were noncovalently associated with macromolecules of molecular weight greater than 650 kDa. 相似文献
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Mezger M Schöder S Reichert H Schröder H Okasinski J Honkimäki V Ralston J Bilgram J Roth R Dosch H 《The Journal of chemical physics》2008,128(24):244705
We present a high energy x-ray reflectivity study of the density profiles of water and ice at hydrophobic and hydrophilic substrates. At the hydrophobic water/octadecyl-trichlorosilane (water-OTS) interface, we find clear evidence for a thin density depletion layer with an integrated density deficit corresponding to approximately 40% of a monolayer of water molecules. We discuss the experimental results in terms of a simple model of hydrophobic/hydrophilic solid-liquid interfaces. Our results also exclude the presence of nanobubbles. A detailed study of possible radiation damage induced by the intense x-ray beam at the dry OTS surface and at the ice-OTS, as well as at water-OTS interfaces, discloses that noticeable damage is only induced at the water-OTS interface, and thus points to the dominant role of highly mobile radicals formed in bulk water close to the interface. 相似文献
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