Effect of the number of quantum wells in the active region on the linearity of the light-current characteristic of a semiconductor laser

The light-current characteristic of a semiconductor laser with multiple quantum wells (QWs) is calculated, with the delayed capture of charge carriers from the waveguide region into the wells taken into account. It is shown that increasing the number of QWs is a more effective way to improve the power characteristics of a laser, compared with an increase in the velocity of carrier capture into each of the wells. For example, using two QWs as the active region leads to a substantial increase in the internal quantum efficiency of stimulated emission and to a significantly better linearity of the light-current characteristic of the laser, compared with a single-well structure. At the same time, using three or more QWs only slightly improves the power characteristics of the laser, compared with the double-well structure. Thus, a double-well structure is the optimal as regards high output power and simplicity of growth.     

A singular integral equation for the current density of a conformal microstrip dipole on a dielectric cylinder

Technical Physics Letters - The problem of current-density distribution over the surface of a microstrip dipole antenna conformally arranged on a dielectric cylinder is reduced to a singular...     

Sorption removal of Fe(CN)6 3− ion impurities from water and evaluation of water quality by the biotesting method

The sorption removal of Fe(CN)₆ ^3? ion impurities from water was investigated. A specially synthesized magnesium-aluminum double hydroxide with the hydrotalcite-type structure was used as a sorbent. The biotesting method used for various test objects proved the efficiency of sorption removal of Fe(CN)₆ ^3? from water.     

Producing Polydicyclopentadiene from Lower-Grade Dicyclopentadiene

Russian Engineering Research - Polymer samples based on polydicyclopentadiene produced from Russian dicyclopentadiene are investigated by thermogravimetric analysis and differential scanning...     

Solution of reverse kinetic problem for oscillatory reactions

Based on the example of stationary chemical oscillations, that proceed according to Gray-Scott mechanism, it has been shown that the representation of experimental data as amplitude-period pairs enables one to form a target function of the minimal squares method, which is unimodal in a fairly large neighborhood of the solution, and obtain unambiguous estimations of the parameters of the kinetic model. In particular, for this purpose, experimental data should simultaneously involve the measurements of amplitudes and periods of concentration oscillations. When these data of the kinetic experiment are represented in the conventional form of concentration-time pairs, a set of extraneous local minima and, accordingly, a set of solutions appear. The periods of oscillations of these extraneous solutions are often in integer relationships with the period of the required solution.     

Investigating the Kinetics of the Process of Adsorption of Phosphate Starch on Cellulose

The kinetic dependencies have been investigated of the adsorption process of phosphate starch on cotton cellulose and on unbleached sulphate cellulose of softwood at temperatures of 0°, 20°, 40° and 60°C. It has been found that the kinetics of adsorption can be described by means of the Elovich-Tyomkin exponential kinetic equation. The values of the activation energy obtained for the two types of cellulose are of the order of 5-9 kJ/mol, and do not depend on the quantity of the phosphate starch adsorbed.     

Parathyroid hormone regulates the expression of the nuclear mitotic apparatus protein in the osteoblast-like cells, ROS 17/2.8

This study assessed the prevalence of tobacco and alcohol use in top-grossing American films from 1985 to 1995. The top ten money-making films for 1985 to 1995 were viewed to identify the prevalence of alcohol and tobacco use overall and by lead characters. While the use of tobacco and alcohol was stable across the study period, use of these substances was common. Most films (98%) had references that supported tobacco use and 96% had references that supported alcohol use. Discouraging the use of these substances was uncommon. Only one third of films had any references that discouraged the use of tobacco or alcohol (38% and 37%, respectively). At least one lead character used tobacco or alcohol in 46% and 79% of the films, respectively. The hazards of smoking and drinking are not reflected in the behaviors of film characters who are potential role models for youth facing the decision to smoke or drink.     

Ankle, knee, and hip moments during standing with and without joint contractures: simulation study for functional electrical stimulation

Joint contractures have been one of the contraindications for use of functional electrical stimulation for standing in paraplegic patients. A simulation study using a three-segment link mechanical model of the human body was performed to calculate the muscle moments at the ankles, knees, and hips during standing with and without having joint contractures. The knee and hip angles were varied in 5 degrees increments, whereas the ankle angles were varied in 1 degree increments. It was assumed that energy efficient posture was obtained with the least sum of the squared moments of the ankles, knees, and hips joints by the muscles. Ankles at 5 degrees of dorsiflexion, knees at 0 degrees, and hips at 15 degrees of extension resulted in the most energy efficient posture without joint contractures. The muscle moments increased with the increase in angle of contractures. The joint contractures at ankle angles > or = 6 degrees of plantar flexion, knee angles > or = 20 degrees of flexion, and/or hip angles > or = 20 degrees of flexion produce a potentially unstable posture. These findings suggest that some degree of joint contractures can be tolerated in paraplegic patients using functional electrical stimulation for standing.