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InGaAlP/InGaP visible laser diodes emitting in the 600 nm range are considered to be promising optical sources for use in optical information systems such as high density optical disks, laser beam printers, and bar-code readers.1 One of the important problems to be solved for practical use is high threshold current of this system. Among many methods, high doping in the clad layer and compressive strain in the active layer2 are considered the most effective ones to reduce a threshold current. This study demonstrates that a very low threshold current can be obtained for simple one step epitaxial structure by applying these two effects.

Using stored energy considerations an operationally well defined general expression is derived for the capacitance of a p–n Junction. The separation of this capacitance into space charge and diffusion parts is carried out in a functional rather than a regional manner, based on the distinction between the time dependences of dielectric relaxation and carrier recombination. Par l'emploi des reflexions d'energie emmagasinee on tire une expression bien definie operationnelle pour la capacite d'une jonction p–n. Ensuite on partage cette capacite entre une partie de la charge d'espace et une partie de la diffusion dans une maniere fonctionelle plutǒt que regionale. La base de ce partage est le difference entre la dependance temporelle de la remise dielectrique et celle de la recombinaison des porteurs.

In this study, the propagation of electromagnetic waves in one-dimensional plasma photonic crystals (PPCs), namely, superlattice structures consisting alternately of a homogeneous unmagnetized plasma and dielectric material, is simulated numerically using the finite-difference time-domain (FDTD) algorithm. A perfectly matched layer (PML) absorbing technique is used in this simulation. The reflection and transmission coefficients of electromagnetic (EM) waves through PPCs are calculated. The characteristics of the photonic band gap (PBG) are discussed in terms of plasma density, dielectric constant ratios, number of periods, and introduced layer defect. These may provide some useful information for designing plasma photonic crystal devices.

In this paper, the second-order and fourth-order relativistic chromatic variational functions for all kinds of relativistic chromatic aberrations of a combined electrostatic-magnetostatic focusing-deflection system have been derived in detail. Here, the relativistic chromatic aberrations produced by the variations of accelerating voltage, currents of magnetostatic round lenses, voltages of electrostatic round lenses and excitations of deflector multipoles are considered.

By using chemical analyses, as well as laboratory and field behavioral tests, we tested the hypothesis that rove beetles of the myrmecophilous genus Pella use alarm pheromone compounds to avert attacks by their host ant Lasius fuliginosus. The secretions of Pellafunestus and P. humeralis contain quinones and different aliphatic compounds, mainly undecane and 6-methyl-5-hepten-2-one (sulcatone). The latter two chemicals are also found in L. fuliginosus pheromone glands. Behavioral tests confirmed that undecane serves as an "aggressive alarm"-inducing pheromone in L. fuliginosus, whereas sulcatone most likely is a "panic-alarm"-inducing pheromone. The main tergal-secretion compounds, various quinones and undecane, individually and in mixtures induced aggression in L. fuliginosus workers. When sulcatone was added to these compounds, the space around the odor source was avoided and a reduced number of aggressive acts observed, suggesting that sulcatone blocks the aggression-inducing effect of undecane and the quinones. These results support the hypothesis that Pella beetles mimic alarm pheromones of their hosts. This is a rare example of chemical mimicry in myrmecophilous insects in which chemicals other than cuticular hydrocarbons are used.

Risks associated with technologies such as those used in hazardous waste manage ment have the potential to impact a broad array ofcommunity social structures and associated dimensions of social well-being that derive from local conditions and events. This analysis examines survey data collected in a community area closest to several operating hazardous waste management facilities to assess the relationships between various aspects of technological risk and a measure of collective morale in the local community. Results indicate that collective morale is substantially influenced by perceived community stigmatization associated with waste facility siting and operation. Other dimensions of technological risk identified as exerting an influence on collective morale include levels of confidence in waste facility technologies, levels of concern about the potential for environmental contamination, and levels of trust in organizational authorities. Overall, the results suggest that social responses to technologica...

The perturbation of the Ba atom by radiation from a color center laser in the range between 8400 and 8700 cm−1 is experimentally studied. The study was performed by the method of resonance ionization spectroscopy by simultaneously irradiating a beam of Ba atoms by a color center laser and a dye laser at 17735 cm−1. The dynamic polarizabilities of the 5d6p1F03 and 6p2 1D2 levels are measured.