Small polyhedral superparamagnetic iron oxide (SPIO) nanoparticles (<10 nm) coated with a thin layer of silica were prepared (SPIO@SiO2 and SPIO@SiO2‐NH2). Surface modification of the small polyhedral silica‐coated SPIO nanoparticles with amines led to substantially higher mesenchymal stem cell (MSC) labelling efficiency without the use of additional transfecting agents. Therefore, amine surface‐modified nanoparticles (SPIO@ SiO2‐NH2) appeared to be the preferred candidate for MSC labelling. In vitro studies demonstrated that controlled labelling of SPIO@SiO2 and SPIO@SiO2‐NH2 did not cause MSC death or proliferation inhibition. MSCs labelled with SPIO@SiO2‐NH2 nanoparticles retained differentiation potential and showed osteogenic, adipogenic and chondrogenic differentiations. The noncytotoxic polyhedral SPIO@SiO2‐NH2 nanoparticle‐labelled MSCs were successfully implanted in rabbit brain and erector spinae muscle, and demonstrated long‐lasting, durable MRI labelling efficacy after 8–12 weeks. 相似文献
Spotting clots : Vascularly constrained colloidal gold nanobeacons (GNBs; see picture) can be used as exogenous photoacoustic contrast agents for the targeted detection of fibrin, a major biochemical feature of thrombus. Fibrin‐targeted GNBs provide a more than tenfold signal enhancement in photoacoustic tomography in the near‐IR wavelength window, indicating their potential for diagnostic imaging.
Based on linearized equations of the theory of elastic stability of straight composite bars with a low shear rigidity, which
are constructed using the consistent geometrically nonlinear equations of elasticity theory for small deformations and arbitrary
displacements and a kinematic model of Timoshenko type, exact analytical solutions of nonclassical stability problems are
obtained for a bar subjected to axial compression and torsion for various modes of end fixation. It is shown that the problem
of direct determination of the critical parameter of the compressive load at a given torque parameter leads to transcendental
characteristic equations that are solvable only if bar ends have cylindrical hinges. At the same time, we succeeded in obtaining
solutions to these equations in terms of wave formation parameters of the bar; these parameters, in turn, enabled us to find
the parameter of the critical load at any boundary conditions. Also, an algorithm for numerical solution of the problems stated
is proposed, which is based on reducing the problems to systems of integroalgebraic equations with Volterra-type operators
and on solving these equations by the method of mechanical quadratures (finite sums). It is demonstrated that such numerical
solutions exist only for certain ranges of parameters of the bar and of the parameter of torque. In the general case, they
can not be obtained by the numerical method used. It is also shown that the well-known solutions of the stability problem
for a bar subjected to torsion or to compression with torsion are in correct.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 45, No. 2, pp. 167–200, March–April, 2009. 相似文献
Advances in nanotechnology enable scientists for the first time to study biological processes on a nanoscale molecule-by-molecule
basis. They also raise challenges and opportunities for statisticians and applied probabilists. To exemplify the stochastic
inference and modeling problems in the field, this paper discusses a few selected cases, ranging from likelihood inference,
Bayesian data augmentation, and semi- and non-parametric inference of nanometric biochemical systems to the utilization of
stochastic integro-differential equations and stochastic networks to model single-molecule biophysical processes. We discuss
the statistical and probabilistic issues as well as the biophysical motivation and physical meaning behind the problems, emphasizing
the analysis and modeling of real experimental data.
This work was supported by the United States National Science Fundation Career Award (Grant No. DMS-0449204) 相似文献
Computer models are artifacts that facilitate conducting computational experiments. In that sense they are laboratory equipment.
The utility of a piece of laboratory equipment comes from the range of useful experiments it supports. However, general purpose
models are in general much more costly to create and maintain. Consequently, issues regarding the design of computer models
are best understood as pragmatic questions regarding the costs and utility of alternative designs.
Supercritical CO2-based fluid is not only being considered as environmentally benign medium for photoresist (PR) removal in electronic device manufacture, but also capable of challenging feature dimensions. Despite many attractive properties, clear supercritical CO2 has little solvating power for PR. Here, two acetate modifiers were selective to add in the CO2 and evaluated individual contribution to the overall stripping rate by factorial experiment design, which included four other factors with four level ranges for each one and concluded the best 90% extraction efficiency would be obtained under the optimized parameters: 2.5 min static time, 35 min dynamic time, 1.25 ml ethylacetate spiked, 125 °C oven temperature and 480 atm CO2 pressure. As analyzing the variances of these contributors to this system, it disclosed that dynamics controlled the stripping mechanism before near 35 min purging but thermodynamics took over after then; and that increasing pressure was more competent for removing PR than increasing temperature. All supercritical extracts were from two commercial PR coated on two substrates and analyzed by UV absorption spectrometry. Removing PR coated on silicon oxide layer was easier than that on Al-Cu alloy one. 相似文献