Effect of barrier height on the uneven carrier distribution inasymmetric multiple-quantum-well InGaAsP lasers

Four asymmetric multiple-quantum-well (AMQW) laser structures have been grown and tested. The structures demonstrate that carriers are not evenly distributed across the active region of a MQW laser. Wells at the p-side of the active region are preferentially pumped indicating there are more carriers at the p-side of the active region than at the n-side. The structures also demonstrate that decreasing the height of the barriers reduces this effect and results in a more even carrier distribution. Thus, well position and barrier height are shown to be important design parameters for AMQW and conventional MQW lasers     

Looking across communicative genres: a call for inclusive indicators of interdisciplinarity

Disciplines vary in the types of communicative genres they use to disseminate knowledge and citing patterns used within these genres. However, citation analyses have predominately relied on the references and citations of one type of communicative genre. It is argued that this is particularly problematic for studies of interdisciplinarity, where analyses bias the disciplines that communicate using the genre under investigation. This may lead to inaccurate or incomplete results in terms of fully understanding the interrelationships between disciplines. This study analyzes a set of 15,870 references from 97 LIS dissertations, in order to demonstrate the difference in discipline and author rankings, based on the genre under investigation. This work encourages future work that takes into account multiple citing and cited works, especially where indicators of interdisciplinarity are used for the allocation of resources or ranking of scholars.     

Effects of fluoropolymer addition to an epoxy on scratch depth and recovery

Samples were prepared by addition of a fluorinated poly(aryl ether ketone) (12F-PEK) to a commercial epoxy resin and curing at either 24 °C or 70 °C. The concentrations of fluoropolymer in the samples were 0, 5, 10, 20, 30, 40, and 50%. Phase inversion facilitates the formation of more and more smooth surfaces for scratch testing with increasing fluoropolymer concentration. A progressively increasing load from 0.03 N to 12 N was administered with a diamond tip to the surfaces of the samples; depths were determined within ±7.5 nm. The original scratch depth is a function of the fluoropolymer concentration. Scratch recovery (healing) reaches values up to 95%. Plots of the residual depth versus concentration of the fluoropolymer at 4, 6, 8, and 10 N reveal minima for all forces and both temperatures. Addition of only 5% or 10% 12F-PEK improves the scratch recovery significantly. The results are explained by changes of material morphology with the fluoropolymer concentration. Electronic Publication     

A novel TiO2/PVC layer for use in a photoelectrochemical cell

Titanium dioxide (TiO₂) has been widely used with UV light to degrade organic waste contaminants. Immobilised layers of TiO₂ on electrode surfaces have shown enhanced activity when appropriate potentials have been applied. In this work, it is shown that a novel immobilised layer of TiO₂ on an electrode, a TiO₂/poly(vinylchloride) composite cast from THF, mineralises acetone or starch when exposed to a xenon arc light only if the electrode is connected to a Pt electrode where concomitant reduction of oxygen occurs. When an isolated electrode with an immobilised TiO₂ layer is exposed to UV light in a solution of starch or acetone, no decrease in acetone or starch concentration is observed.     

Permeation and diffusion of environmental pollutants through flexible polymers

Permeation and diffusion characteristics of high density polyethylene (HDPE), elasticized polyolefin, and polychloroprene membranes have been determined for various organic pollutants at 22 and 50°C. A standard ASTM permeation cell method was used to measure the permeation rate while an immersion/weight gain method was used to obtain the diffusion coefficient. Thickness-dependent permeation rates were determined for HDPE membranes. An equimolar mixture of various permeants was also used to see the possibility of synergistic effects by combination of permeants. The experimental results are discussed in relation to the suitability of HDPE membranes in severe environments.     

Imaging of stresses in GaAs diode lasers usingpolarization-resolved photoluminescence

Images of stress distributions in GaAs-based diode lasers have been obtained using scanned polarization-resolved photoluminescence. A stress resolution of about 10⁷ dyn/cm² and a spatial resolution of about 1 μm have been obtained. The experimental technique is described, and measured stress distributions due to ridge structures, metallization, applied force, and bonding are presented     

Front/back tracking InGaAsP diode laser transmitter modules

Variations in the detected power for movement of a single-mode and a multimode fiber in front of various 1.3-μm InGaAsP diode lasers are measured and compared to the signal obtained from the back-facet monitor. A model to explain the nonlinear relationship between the detected front and back-facet powers is given. This work has application in the design and understanding of stable light sources, biasing of transmitter modules, the fiber attach process, and the interpretation of tests which check the integrity of the fiber attachment     

The Relationship of Glass Transition Temperature to Adhesive Strength

The effects of glass transition temperature (T_g) on mechanical properties have been further demonstrated by the observation of adirect relationship between the T_g of an epoxy adhesive and its lap shear bond strength to metal at elevated test temperatures. An additive (coupling agent) which lowers the T_g from a point near or above the test temperature to below it causes a subsequent decrease in the strength of the system and generally increased cohesive failure. Therefore effects on the T_g of the adhesive are more important than on interfacial properties. The end result is that differential thermal analysis (DTA) can be utilized as a effective screening method for adhesives and additives, and can be a good indicator of maximum use temperature. From these data T_g can also be used to estimate adhesive strength at a given use temperature.     

The role of the data manager in clinical cancer research. An opportunity for nurses

A clinical trial is a research study conducted in humans and designed to answer specific questions using scientifically controlled methods. These trials require considerable effort to assure that the data obtained are reliable, reproducible, and readily available. Data managers play a key role in this research effort. A nurse with a clinical background, computer knowledge, and some experience in the research environment is well suited for the role of data manager. The data manager performs a variety of tasks in this position that will enhance the quality of the data gathered in a research study. These responsibilities include designing forms, monitoring protocol accrual, abstracting data, entering data onto protocol-specific forms and/or specifically designed computerized data-entry screens, assuring the quality and the integrity of the data, and providing investigators with interim and summary reports. In addition, the data manager can be responsible for the management of a computerized clinical data base system, including the training of users and the designing of basic reports for the investigators. A nurse, functioning as a data manager, who understands research methodology, is detail oriented, and is well organized, could be a valuable asset to the clinical trials team in the successful management of any clinical study.     

Sequences of the coat protein gene of five peanut stripe virus (PStV) strains from Thailand and their evolutionary relationship with other bean common mosaic virus sequences

The coat protein gene and part of the 3' non-coding region of five strains of peanut stripe virus (PStV) from Thailand have been cloned and sequenced. Phylogenetic comparisons of these strains, known as T1, T3, T5, T6 and T7, and related sequences showed that these strains are indeed strains of PStV. Further, PStV strains appear to be related to each other according to their geographic origin. That is, the Thai strains are more closely related to each other than they are to strains from the USA or Indonesia, despite the variety of symptoms caused by these strains and the overlap of symptom types between the strains from different locations. Like other PStV strains, PStV-Thai can be considered strains of bean common mosaic virus (BCMV) but can be distinguished from bean-infecting strains of BCMV and blackeye cowpea mosaic virus (B1CMV) through sequence and host range. No evidence was found that PStV-Thai strains, unlike PStV-Ib, are recombinants of PStV and B1CMV, although the T3 strain may be a recombinant of different PStV sequences. Phylogenetic analyses of viruses of the BCMV group suggest that acquisition of the ability to infect peanut may have occurred only once.