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排序方式: 共有335条查询结果,搜索用时 9 毫秒
81.
Meike L. Schipper Gopal Iyer Ai Leen Koh Zhen Cheng Yuval Ebenstein Assaf Aharoni Shay Keren Laurent A. Bentolila Jianquing Li Jianghong Rao Xiaoyuan Chen Uri Banin Anna M. Wu Robert Sinclair Shimon Weiss Sanjiv S. Gambhir 《Small (Weinheim an der Bergstrasse, Germany)》2009,5(1):126-134
This study evaluates the influence of particle size, PEGylation, and surface coating on the quantitative biodistribution of near‐infrared‐emitting quantum dots (QDs) in mice. Polymer‐ or peptide‐coated 64Cu‐labeled QDs 2 or 12 nm in diameter, with or without polyethylene glycol (PEG) of molecular weight 2000, are studied by serial micropositron emission tomography imaging and region‐of‐interest analysis, as well as transmission electron microscopy and inductively coupled plasma mass spectrometry. PEGylation and peptide coating slow QD uptake into the organs of the reticuloendothelial system (RES), liver and spleen, by a factor of 6–9 and 2–3, respectively. Small particles are in part renally excreted. Peptide‐coated particles are cleared from liver faster than physical decay alone would suggest. Renal excretion of small QDs and slowing of RES clearance by PEGylation or peptide surface coating are encouraging steps toward the use of modified QDs for imaging living subjects. 相似文献
82.
Marc Termote H. St. Seidenfus Ruth Shen Dale R. Schmeichel R. Keith Semple Lay James Gibson Ryszard Domanski Michael F. Sheehan Josephine Olu Abiodun A. M. Fuller Turgut Var Diane J. Martz Douglas M. Brown Peter Cowan James L. Mulvihill Tom Rijerkerk Konrad Dramowicz Roger F. Riefler C. J. Robertson Bernard Malamud Rudolf Andorka James L. LeBeau J. C. Stabler Wilbur R. Maki Jan S. Kowalski Nigel Thrift Richard W. Lichty Dr. Andre Simmons Raimund K. Herz Donald Jones Kurt Puchinger J. Barry Riddell R. Ross MacKay Noel D. Uri Peter Boothroyd John F. Jakubs Peter M. Schulze P. N. Mathur 《The Annals of Regional Science》1985,19(2):100-157
83.
84.
Paul E. Barbone Carlos E. Rivas Isaac Harari Uri Albocher Assad A. Oberai Yixiao Zhang 《International journal for numerical methods in engineering》2010,81(13):1713-1736
We describe a novel variational formulation of inverse elasticity problems given interior data. The class of problems considered is rather general and includes, as special cases, plane deformations, compressibility and incompressiblity in isotropic materials, 3D deformations, and anisotropy. The strong form of this problem is governed by equations of pure advective transport. The variational formulation is based on a generalization of the adjoint‐weighted variational equation (AWE) formulation, originally developed for flow of a passive scalar. We describe how to apply AWE to various cases, and prove several properties. We prove that the Galerkin discretization of the AWE formulation leads to a stable, convergent numerical method, and prove optimal rates of convergence. The numerical examples demonstrate optimal convergence of the method with mesh refinement for multiple unknown material parameters, graceful performance in the presence of noise, and robust behavior of the method when the target solution is C∞, C0, or discontinuous. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
85.
Rafael Wertheim Uri Ben-Hanan Steffen Ihlenfeldt Andrea Stoll Frank Treppe Markus Wabner 《CIRP Annals》2012,61(1):75-78
Drilling a stack made of fiber-reinforced plastic and metal layers is investigated and presented in this paper. Improvement of performance can be achieved if the process parameters will be adapted to the various drilled materials and drill position. Therefore, the true position of the drill should be precisely known. An algorithm for real time monitoring of drill position is suggested. Drill position is defined by analyzing acoustic emission signals from a sensor located near the drilling point. During drilling of CFRP and Al-stacks, it could be proved that material changeover can be identified ahead of time, especially when using stepped drills. 相似文献
86.
The effect of the shape of nanocrystal sensitizers in photoelectrochemical cells is reported. CdSe quantum rods of different dimensions were effectively deposited rapidly by electrophoresis onto mesoporous TiO(2) electrodes and compared with quantum dots. Photovoltaic efficiency values of up to 2.7% were measured for the QRSSC, notably high values for TiO(2) solar cells with ex situ synthesized nanoparticle sensitizers. The quantum rod-based solar cells exhibit a red shift of the electron injection onset and charge recombination is significantly suppressed compared to dot sensitizers. The improved photoelectrochemical characteristics of the quantum rods over the dots as sensitizers is assigned to the elongated shape, allowing the build-up of a dipole moment along the rod that leads to a downward shift of the TiO(2) energy bands relative to the quantum rods, leading to improved charge injection. 相似文献
87.
Edyta Burda Marina Kraußer Gabriele Fischer Werner Hummel Frieder Müller‐Uri Wolfgang Kreis Harald Grger 《Advanced Synthesis \u0026amp; Catalysis》2009,351(17):2787-2790
It was found that Δ4,5‐steroid 5β‐reductases are capable of reducing also small molecules bearing an activated CC double bond such as monocyclic enones and acyclic enoate esters. As preferred Δ4,5‐steroid 5β‐reductase (5β‐StR) for this purpose, 5β‐StR from Arabidopsis thaliana was used. In part, enzyme activities are even higher than that for progesterone. Successful preliminary biotransformations with enzymatic in situ cofactor recycling were also carried out. When using the prochiral compound isophorone as a substrate, a high enantioselective reaction course (>99% ee) was observed. 相似文献
88.
Amylose molecular inclusion complexes, or V-amylose, have been studied as a possible nano-sized delivery system for unsaturated fatty acids. This study aimed to study three different structural levels of V-amylose produced via an acidification method. Molecular attributes were studied using XRD, DSC and 13C CP/MAS NMR, nanostructures using SAXS and AFM, and the microscopic level by SEM and AFM. 13C labeled fatty acids revealed head groups were entrapped in both COO- and COOH forms. SAXS data, showed that conjugated linoleic acid yield particles with the highest values for parameters like average crystalline lamellar thickness (φ = 0.46) and characteristic particle dimension (Rg = 1011). AFM revealed surface roughness increases from 7.72 ± 4.34 nm to 11.54 ± 6.05 nm during the formation of V-amylose. The insights described contribute to the understanding of V-amylose structure and help establish a model for V-amylose structure which may prospectively be used in the fabrication of a novel delivery system. 相似文献
89.
Modeling electronic tunneling through molecular bridges is desired in order to understand the mechanism of long-range electron transfer reactions in nature, as well as for the design of novel molecular electronics devices. Particularly interesting is the effect of the nuclear motion at the molecular bridge on the electron transfer mechanism and rate. In this work we study the effect of electronic nuclear coupling at the molecular bridge on a unidirectional electronic tunneling process from an electron donor into a dissipative acceptor, as may appear in controlled electron transfer reactions at biological membranes, or in heterogeneous electron transfer reactions. The model includes a collection of harmonic bath modes coupled to the dissipative acceptor site and a single mode at the molecular bridge. The parameters of the dissipative bath are tuned such that the electronic population decays from the donor to the acceptor. This process is simulated using a time-dependent nonlinear Langevin-Schroedinger equation, based on a mean-field approximation for the electronic-nuclear coupling at the acceptor site and a numerically exact treatment of the electronic-nuclear coupling at the molecular bridge. The simulations at zero temperature and weak electronic-nuclear coupling demonstrate that electronic tunneling is promoted by coupling to the nuclear mode at the bridge. This result is consistent with our previous studies of electronic tunneling oscillations in a symmetric donor-bridge-acceptor complex, and it emphasizes the importance of electronic nuclear coupling in analyzing long-range electron transfer processes through molecular bridges or wires. 相似文献
90.