Synthesis and size-dependent properties of zinc-blende semiconductor quantum rods

Dimensionality and size are two factors that govern the properties of semiconductor nanostructures. In nanocrystals, dimensionality is manifested by the control of shape, which presents a key challenge for synthesis. So far, the growth of rod-shaped nanocrystals using a surfactant-controlled growth mode, has been limited to semiconductors with wurtzite crystal structures, such as CdSe (ref. 3). Here, we report on a general method for the growth of soluble nanorods applied to semiconductors with the zinc-blende cubic lattice structure. InAs quantum rods with controlled lengths and diameters were synthesized using the solution-liquid-solid mechanism with gold nanocrystals as catalysts. This provides an unexpected link between two successful strategies for growing high-quality nanomaterials, the vapour-liquid-solid approach for growing nanowires, and the colloidal approach for synthesizing soluble nanocrystals. The rods exhibit both length- and shape-dependent optical properties, manifested in a red-shift of the bandgap with increased length, and in the observation of polarized emission covering the near-infrared spectral range relevant for telecommunications devices.     

Catalyst Sintering and Reactor Design

The subject of sintering (sometimes termed coarsening) has received considerable attention since the late 1960s, and a review [1] appeared in this journal in 1975. Significant progress has been made since then, in particular, with regard to the mechanisms and kinetics of sintering and measurement techniques. With these advances it is now possible to utilize the understanding gained for the design of reactors undergoing catalyst sintering. In fact, a few attempts have already been made.     

Navigating personal and relational concerns: The quest for equilibrium.

The authors' personal-relational equilibrium model suggests that people come to seek equilibrium in their dedication to personal and relational concerns in that these 2 important needs cannot always be gratified simultaneously. The authors proposed that the experience of personal-relational disequilibrium motivates attempts to restore equilibrium and that achieving equilibrium promotes life satisfaction. Four studies revealed good support for the model. In Study 1, a manipulation of anticipated future disequilibrium (vs. equilibrium) as a result of overdedication to either the personal or relational domain caused reduced motivation to address concerns in that domain and increased motivation toward the complementary domain. In Study 2, narratives describing disequilibrium experiences (vs. equilibrium experiences) exhibited increased motivation to restore equilibrium and reduced life satisfaction. In Study 3, diary reports of everyday disequilibrium were associated with increased same-day motivation to restore equilibrium, reduced same-day life satisfaction, and increased next-day dedication of effort to the complementary domain. In Study 4, experiences of disequilibrium predicted reduced well-being 6 months later. Collectively, these findings extend knowledge of how people regulate themselves toward equilibrium in pursuing 2 fundamental human concerns. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Report of an IEEE Task Force?An IEEE Opinion on Research Needs for Biomedical Engineerng Systems

MORE than 200 years ago, our forefathers made note of man's inalienable rights to life, liberty, and the pursuit of happiness. To the engineering community (applied science in the service of man), these may be coincident with applications to medicine and biology (biomedical engineering), defense, and entertainment. Biomedical engineering research has the distinction, among these three missions, of not only contributing to the quality of human life through the industrial economy but also to life itself?the most fundamental concern of all people. It is through biomedical engineering research that we have been able to learn much concerning the functioning of living systems, and it is through such knowledge that we have been able to develop improved clinical diagnosis, monitoring, and treatment, including life-sustaining devices and aids to the handicapped. Each step represents an improvement in the quality of life, and each step forms the foundation upon which to gain new knowledge to improve upon earlier developments.     

In vivo degradation of semi-rigid polymeric films made of alginate and polyethylene glycol

Alginate-based biomaterials can form naturally derived polymeric hydrogels with sufficient structural integrity to readily be used in many clinical applications. However, ionically cross-linked alginate gels do not always possess structural properties suitable for application as erodable polymeric films for controlled release of drugs and growth factors. In this study, semi-rigid polymeric films were constructed of sodium alginate and polyethylene glycol (PEG) by means of a rehydration cross-linking technique. The films were assembled by dehydrating a solution of alginate and PEG and cross-linking the alginate during its rehydration with a solution of calcium chloride. The product is a highly dense polymeric network that prevents in vivo cellular infiltration and disassembles primarily by surface erosion. By implanting the PEG-alginate films into the subcutis of rats, the mechanism of polymer degradation was demonstrated to occur via inflammation-mediated erosion of the material rather than by means of cellular infiltration. There were extensive areas of foamy macrophages at the site of the implant, indicating a likely mechanism of removal and disposal of the disassembled PEG and alginate polymer. The eroded fragments of the film that remained after six weeks did not exhibit signs of a cellular infiltrate but rather stayed intact, appearing as small, dense fragments of polymer. Our observations that nearly all the PEG-alginate material was cleared from the implantation site by the sixth postoperative week highlight the potential exploitation of these films as bioresorbable wound dressings with prospective utilization as a drug delivery device. Moreover, the employment of polymeric films made of functionalized PEG, which enables covalent attachment of biological molecules, potentiates their use for growth factor delivery applications.     

Replication Route Synthesis of Mesoporous Titanium–Cobalt Oxides and Their Photocatalytic Activity in the Degradation of Methyl Orange

Mesoporous Ti–Co oxides were synthesized via a replication route, using a 3-D wormlike mesoporous silica as template and tetra-tert-butyl orthotitanate (TBOT) and Co(NO₃)₂ as source materials. The prepared materials were characterized by X-ray diffraction (XRD), N₂-physisorption, TEM, EDS, and UV/Vis-DRS and found to possess a spherical morphology and a 3-D wormhole-like mesoporous structure, with the average pore size between 4.5 and 16.0 nm. The pore walls consisted mainly of a cobalt-incorporated anatase phase. The Co³⁺ ions were generated in the replicated mesoporous Co–Ti oxides, via the transfer of electrons from Co²⁺ to Ti⁴⁺ ions. The formation of cobalt-incorporated anatase phase and Co³⁺ ions were both favored by larger Co/Ti atomic ratios and by relatively low calcination temperatures. The specific surface area decreased and the mesopore sizes increased, with increasing Co/Ti atomic ratio or calcination temperature. The average crystal size of the anatase phase decreased with increasing Co/Ti atomic ratio but increased with increasing calcination temperature. The photocatalytic activity of the replicated mesoporous Co–Ti oxides in the degradation of methyl orange dye was investigated. It was observed that the photocatalytic activity increased with increasing Co/Ti atomic ratio and exhibited a maximum with increasing calcination temperature. With the exception of those prepared at too high calcination temperatures, the replicated mesoporous Co–Ti oxides were much more active than the pure titania. It is concluded that, in addition to a higher diffusion, the cobalt-containing anatase, as the active phase, and the Co³⁺ ions, as the active sites, are responsible for the high photocatalytic activity of the replicated mesoporous Co–Ti oxide.     

烷基羧酸钠与β—环糊精包结物稳定常数的测定

用表面张力法研究了基羟酸钠与β－环状糊精形成的包结物。实验结果表明表面张力法可以作为一种行之有效的方法确定表面活性剂与β－ＣＤ形成包结物的稳定常数，发现在表面活性剂浓不变时，增加β－ＣＤ的浓度溶液的表面张力上升，并达到纯水的表面张力值。