Optoelectronics in satellite designs

Design of artificial satellites for communication, remote sensing and scientific investigations follows, at present, a fixed pattern based on existing and proven technologies and the requirements of payload or experiment within the constraints of weight, volume and power available. The advances in optoelectronic components and systems have opened up a new dimension in designing satellites of the future, incorporating new technologies. This paper deals with general satellite design concepts based on optoelectronic systems wherever applicable.     

Micro-Raman spectroscopy study of the process of microindentation in polymers

The residual deformation produced by Vickers microindentations in poly(3,3-dimethyl oxetane) (PDMO) was analysed by Raman microspectroscopy. Microstructural variations were observed as the Raman spectra were recorded at different positions along and out of the microindentation. A gradual distribution of the monoclinic and orthorhombic structures arises as the spectra were scanned from the centre to the edge of the impression area. This crystalline variation in PDMO, which reflects the degree of stress present on the surface of the sample, was utilized to obtain information on the distribution of pressure in and around the microindentation. In addition to the clear variation of pressure inside the permanently deformed region, no crystalline transformation was noted out of the impression area. Similar features were observed when the Raman spectra were recorded along one of the diagonals of the indentation.     

A mathematical model for the prediction of temperature in a dry snow layer

A mathematical model for predicting the temperature in a homogeneous layer of dry snow is presented. The model, which is physically based, is capable of predicting diurnal temperature behaviour at the snow surface and at any depth within a snow layer given the variation in a limited set of meteorological parameters over that period. A sensitivity analysis is performed to determine the important parameters in the prediction of snow surface temperatures. These are found to be consistent with simple physical reasoning.     

A transgenic T cell receptor restores thymocyte differentiation in interleukin-7 receptor alpha chain-deficient mice

Traffic accidents are a well-known public health problem worldwide. In Mexico research into risk factors for motor involving vehicles accidents and their consequences has recently been taken into account. The relevant literature does not normally describe the methodological aspects involved in the collection of primary data, since most studies have used secondary data the good quality and validity of which are assumed. The paper presented seeks to discuss and share with researchers in this field, some of the methodological aspects to be considered in the attempt to recreate the scene of the accident and obtain information approximating to reality. The measurements in situ of, such traffic accident variables as injury, use of seat belt, speed and alcohol intake are discussed.     

Persistent caching: an implementation technique for complex objectswith object identity

Many recent complex object database systems support the concepts of object identity and object identifier. Following an object identifier to access the referenced object is called navigation operation and is an essential operation in dealing with complex objects. Navigation operation is a difficult operation to implement efficiently since every navigation operation inherently causes one disk access operation. A scheme to notably accelerate the navigation operation among a sea of complex objects, by increasing the effective number of objects in one disk page is proposed. The main concept of the presented technique is threefold. The first idea is to store a cached value within a complex object that is referencing another complex object. The second is that when the referenced object is to be updated the update propagation is delayed until the time when the cached value is referenced. The third is to utilize a hashed table on main memory to efficiently validate the consistency between the cached values and the original values     

Cars, phones, and Tamagotchi tribes

As if life isn't already crowded enough with obligations, “Tamagotchis” (virtual pets) would seem to be at odds with the Information Age, but cars, phones and TV-like appliances will become more like Tamagotchis as the friction-free economy once again expresses itself in tribalism. My premise is simple: the friction-free economy rewards retro-cultures that yearn to return to agrarian tribalism. Selling hi-tech products in this new economy becomes ritual, and the greater the ritual, the greater the financial rewards. Some may use different names-database marketing, targeting or niche marketing-but the key to expanding the computer industry will be to build a tribe around your brand and flaunt it. Successful product design and sales will increasingly require targeting products, services and ideas to various tribes. An idea long understood in the entertainment and services industry, this is only now becoming a computer industry mantra. The question is, how will this impact the design of future computer products? Study the Tamagotchi and other Christmas season best-sellers to find out     

High-power 980-nm AlGaAs/InGaAs strained quantum-well laser grown by OMVPE

High-power lattice-strained AlGaAs/InGaAs graded index separate-confinement heterostructure (GRINSCH) quantum-well lasers emitting at a 980-nm wavelength have been grown by organometallic vapor phase epitaxy (OMVPE) and fabricated with a self-aligned ridge-waveguide structure. Using a 3- mu m-wide and 750- mu m-long AR-HR coated laser, 30 mV of optical power was coupled into optical fibers with 28.6% efficiency. A dominating single-lobe far-field radiation pattern was obtained from a wedge-shaped ridge-waveguide laser for output power as high as 240 mW with a maximum output power of 310 mW.<>     

Future developments in cosmetic formulations

In recent years, there have been a great deal of interest in applications of microemulsions, liposomes (vesicles) and multiple emulsions in cosmetic formulations. These systems will provide the cosmetic industry with new types of formulations which are easier to apply, better functional benefit and potentially safer formulations. Microemulsions are thermodynamically stable systems and hence shelf life is no problem. Many cosmetic ingredients can be adequately solubilized in the swollen micelles of the microemulsions. Such solubilized systems may enhance transport and diffusion through various barriers, eg., the skin, thus enhancing the efficacy of the formulations. However, microemulsions may cause skin irritation by disrupting the liquid crystalline structure of the stratum corneum. This problem may be overcome by formulating microemulsions, which on evaporation produce lamellar liquid crystalline structures. The problem of skin irritation is certainly reduced or eliminated using liposomes or vesicles, which offer an alternative to microemulsions. The principles for formation and stabilization of vesicles are discussed in this paper and research work is needed to produce nanocapsules from liposomes, using polymerizable surfactants. Multiple emulsions of the water/oil/water (w/o/w) or oil/water/oil (o/w/o) types are also valuable systems for formulating cosmetics. In the first place, they offer a means of sustained release of the various ingredients. Secondly, they allow one to separate the various ingredients in the formulation, thus preventing their possible interaction. The basic principles required for preparation of stable multiple emulsions are summarised. Developments of polymeric surfactants led to the formulation of stable multiple emulsions. An example of a recently formulated stable w/o/w multiple emulsion is given in this paper The stability of the system was investigated using optical microscopy. Creaming occurred on storage, particularly at high temperature (40°C) and this was significantly reduced by addition of Kelzan (a polysaccharide with high molecular weight). The final formulation was studied rheological techniques.