Boosting the feasibility pump

The feasibility pump (FP) has proved to be an effective method for finding feasible solutions to mixed integer programming problems. FP iterates between a rounding procedure and a projection procedure, which together provide a sequence of points alternating between LP feasible but fractional solutions, and integer but LP infeasible solutions. The process attempts to minimize the distance between consecutive iterates, producing an integer feasible solution when closing the distance between them. We investigate the benefits of enhancing the rounding procedure with a clever integer line search that efficiently explores a large set of integer points. An extensive computational study on benchmark instances demonstrates the efficacy of the proposed approach.     

Polar modes with elastic restoring forces, “bose condensation” and the possibility of a metastable “ferroelectric” state

The system consists of an electric polarisation field coupled on the one hand to an elastic field and on the other to a thermal reservoir. When the polarisation modes are pumped, Bose condensation in the lowest mode occurs, for energy inflow above a certain critical amount. It is shown that elastic forces, called into play to stabilise the excitation of the polar modes, lowers the threshold for Bose condensation. With further increase in the pumping rate the possibility exists for the softening of the polarisation oscillations leading, in the presence of quartic self-interaction of the polarisation field (inserted for stability), to a metastable ferroelectric state. The work represents an attempt to develop a microscopic approach to the Fröhlich model for the dynamics of macromolecules (such as proteins and enzymes) of biological significance.     

Perturbation theory for a bound piezoelectric polaron

We calculate the change in energy of an electron bound to a Coloumb center, due to the piezoelectric interaction with acoustic phonons, to second-order in the interaction. We show that the recent calculation by Bajaj et al., while correct to order β², is incorrect to order β⁴. β is the strength of the Coloumb potential. The coefficient of the β⁴ term is shown to be divergent.     

Laser Raman spectroscopic investigations of biodegradable vehicle of active agents eluting LVM 316 stainless steel cardiovascular stents for in vivo degradation characteristics

Laser Raman spectroscopy is an effective tool for the study of biodegradable polymers, which play a vital role in the new developments in coronary implants such as stents. There is much excitement around the potential capabilities of synthetic biodegradable polymers and the effect they will have on the design and function of implanted devices. In the present investigation, heparin‐conjugated biodegradable copolymers were evaluated for their durability as drug‐eluting stent coatings. Laser Raman spectroscopic studies were carried out and spectra recorded and analyzed of explanted stents coated with different amounts of polymer alone, showing the existence of different levels at different quantities of polymer. The polymer was detected on every stent analyzed. On the stents coated with a thick layer of polymer, a firm layer of polymer still existed on the stent. In contrast, this layer was degraded and spread around on the stents coated with only a thin layer of the polymer. This indicates that the polymers used in the stents in the present investigation exhibit acceptable biodegradability. Such polymers can be used as efficient drug carriers, as these materials show good degradation after the stipulated period. Copyright © 2009 John Wiley & Sons, Ltd.     

掺铜KNSBN光折变晶体的光致吸收特性

掺铜KNSBN(钾钠铌酸锶钡)光折变晶体具有光致吸收(LIA)特性.实验表明,泵浦光的光强越强,波长越短,LIA系数就越大,探测光为e偏振态时的LIA系数是o光时的1.2倍.这种现象将被用来提高光场的空间或时间均匀性.     

距离选通成像系统分辨率模拟测试装置

距离选通成像系统采用脉冲激光主动照明与ICCD选通技术相结合. 为了在室内模拟测试一定大气条件下距离选通成像系统的分辨率,设计了一套模拟测试装置. 采用两个模拟光源,分别模拟信号光和后向散射光. 结合大气距离选通成像系统后向散射光和信号光模型的研究结果,采用阴极面等效辐射照度法,给出了模拟光源功率的计算方法和功率范围的确定方法,以S-20光电阴极的像增强器与CCD耦合为例,计算了模拟光源功率.