Effect of intraband carrier relaxation on the threshold characteristics of quantum well lasers

The effect of intraband carrier relaxation on the threshold characteristics of InGaAsP quantum well (QW) lasers is studied. The dependence of the intraband hole-hole relaxation time τ _int on temperature and carrier density is analyzed. It is shown that taking into account the finiteness of τ _int and its dependence on temperature and carrier density strongly affects the gain and the threshold current density of QW lasers.     

A kinetic method for HO2*/O2*- determination in advanced oxidation processes

A new kinetic method is developed for the determination of hydroperoxyl radical (HO(2)(*))/superoxide radical (O(2)(*)(-)) in aqueous solution, and the calibration using a kinetic half-life technique is also established for determining the concentration of HO(2)(*)/O(2)(*)(-) as produced in the UV/H(2)O(2) process. This new method is based on the reduction of Fe(3+)-EDTA into Fe(2+)-EDTA by HO(2)(*)/O(2)(*)(-) and the well-known Fenton-like reaction of H(2)O(2) and Fe(2+)-EDTA to yield the hydroxyl radicals (OH(*)). Benzoic acid scavenges the OH radicals to produce hydroxybenzoic acids, which are analyzed by fluorescence detection (lambda(ex) = 320 nm; lambda(em) = 400 nm). The limit of detection for the new method depends on the pH values, and it is determined as 3.22 x 10(-)(11) M with signal-to-noise ratio of 2 at pH 5. In addition, the present technique has the advantage of using inexpensive and easily available nonenzymatic reagents that do not require the specific instrument and chemicals and of being insensitive to the moderate concentration of possible interferences often found in aqueous phase.     

Microfluidic Synthesis of pH‐Sensitive Multicompartmental Microparticles for Multimodulated Drug Release

Stimuli‐responsive carriers releasing multiple drugs have been researched for synergistic combinatorial cancer treatment with reduced side‐effects. However, previously used drug carriers have limitations in encapsulating multiple drug components in a single carrier and releasing each drug independently. In this work, pH‐sensitive, multimodulated, anisotropic drug carrier particles are synthesized using an acid‐cleavable polymer and stop‐flow lithography. The particles exhibit a faster drug release rate at the acidic pH of tumors than at physiological pH, demonstrating their potential for tumor‐selective drug release. The drug release rate of the particles can be adjusted by controlling the monomer composition. To accomplish multimodulated drug release, multicompartmental particles are synthesized. The drug release profile of each compartment is programmed by tailoring the monomer composition. These pH‐sensitive, multicompartmental particles are promising drug carriers enabling tumor‐selective and multimodulated release of multiple drugs for synergistic combination cancer therapy.     

The effect of skin penetration enhancers on the transdermal delivery of pyridostigmine bromide

In vitro skin penetration studies of pyridostigmine bromide through human cadaver skin were conducted using a diffusion cell with constant hydrodynamic conditions. The results indicate that the drug penetrates poorly through human cadaver skin. However, skin penetration enhancers such as sodium oleate, sodium lauryl sulfate, n-decyl methyl sulfoxide, and N,N-dimethyldodecylamine-N-oxide substantially enhanced the permeability coefficient of the drug through human cadaver skin. The penetration enhancement of pyridostigmine bromide could be due to increased partitioning of the drug in the skin or due to the decreased tortuosity of the porous pathway in the stratum corneum.     

Liquid nucleating additives for improving thermal insulating properties and mechanical strength of polyisocyanurate foams

The effects of liquid-type nucleating silane additives on the cell structure, mechanical strength, and thermal insulating properties of the polyisocyanurate (PIR) foams have been studied. The PIR foams synthesized with hexamethyldisilazane (HMDS) as a silane additive showed the smaller average cell size and lower thermal conductivity than those of the PIR foams prepared with the hexamethyldisiloxane, dimethoxydimethylsilane, and hexadecyltrimethoxysilane. When HMDS was added, average cell size of the PIR foam was becoming smaller due to lower surface tension of the polyol solution, thereby the nucleation rate and number of bubbles produced were increased and then the cell size becomes smaller. The additives likely act as nucleating agents during the formation of PIR foams. The smaller cell size appears to be one of the major reasons for the improvement of thermal insulation properties and mechanical properties of the PIR foams. From the results of cell size, thermal conductivity, and mechanical strength of the PIR foams, it is suggested that the HMDS may be the efficient liquid-type additive for the reduction of cell size and improvement of the thermal insulation property of the PIR foams.     

Study of the compatibility of phenyltrinitroxylenethane (Phenylxylilethane) with structural materials

The influence of structural materials on the basic electrophysical characteristics (relative permittivity, loss tangent, volume electric resistivity, and electric strength) of phenylxylilethane is considered in this paper.