Selective area growth and characterization of AlGaN/GaNheterojunction bipolar transistors by metalorganic chemical vapordeposition

The selective area growth (SAG) and properties of AlGaN/GaN heterojunction bipolar transistors (HBTs) grown by low-pressure metalorganic chemical vapor deposition (MOCVD) are described and analyzed. Transistors based on group III-nitride material are attractive for high-power and high-temperature applications. Much work has been focused on improving p-type material, as well as heterojunction interfaces. However, there have been very few reports on HBTs operating at room temperature, At this time, current gains for nitride-based HBTs have been limited to ~10. Selective area regrowth was applied to the growth of AlGaN/GaN HBTs to analyze its potential advantages as compared to more traditional growth techniques in order to realize improved electrical performance of the devices     

Evaluation of left visuospatial neglect: Norms and discrimination power of two tests.

Conducted 2 cancellation tests, Albert's Test and the Bells Test, which are both used for the evaluation of unilateral visuospatial neglect, with 40 neurologically normal adults and 47 right cerebrovascular accident patients (aged 32–87 yrs), 4–22 wks after stroke. Norms are proposed for both tests. Results show that the Bells Test has greater discrimination power than Albert's Test. In both tasks, a left-to-right gradient of neglect is found in Ss who show neglect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Planar AlGaAs/GaAs HBT fabricated by MOCVD overgrowth with a grownbase

A planar heterojunction bipolar transistor (HBT) with an AlGaAs emitter layer epitaxially grown onto a selectively defined grown base layer, where the base is grown with the collector as part of the original epi, is discussed. The transistors fabricated with this process exhibit good gain and output characteristics. Transistors with 7×7 μm² emitters have exhibited a DC current gain of 10 to 1000 for base doping from 1×10¹⁹ to 8×10¹⁷ cm³, respectively, and Early voltages ⩾100 V. The propagation delay of 19-stage ring oscillators was 87 ps/gate. The transistor-fabrication process was designed to be manufacturable, and the planar nature of the transistor surface should permit large-scale integration with good yields     

Over- and undercontrolled clinic referral problems of Jamaican and American children and adolescents: The culture general and the culture specific.

Child behavior problems and corresponding clinic referral patterns may be significantly influenced by cultural factors. Prevailing values and childrearing practices within a culture may discourage development of some child problems while fostering others. We explored this possibility, focusing on clinic referral problems of two different societies: (a) Jamaica, where the Afro-British culture discourages child aggression and other undercontrolled behavior and possibly fosters inhibition and other overcontrolled behavior, and (b) the United States, where undercontrolled child behavior is seemingly more generally accepted. We coded clinic-referred problems listed by parents of Jamaican and American youngsters (N?=?720). Cross-cultural differences were striking: Overcontrolled problems were noted more often for Jamaican than American youngsters, whereas the converse was true for uncontrolled problems. These and other findings suggest that factors such as culture and sex may be linked to substantial differences in the problems for which youngsters of different countries are treated in clinics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bulk properties of pressure-induced superconductivity in EuMo6S8

Characteristics of superconductivity induced by pressureP in EuMo₆S₈ have been investigated by dc magnetization and heat capacity measurements under nearly hydrostatic pressure. No Meissner effect was detected at the superconducting transition, in agreement with previous results, but a discontinuity in the heat capacity data demonstrates the bulk nature of the superconducting state forP≳ 13 kbar. An analysis of the heat capacity data yields a value for this discontinuity comparable to that expected from the BCS theory. In addition, heat capacity measurement forP=11 kbar reveal a feature arising from the structural transition responsible for the absence of superconductivity whenP<13 kbar in EuMo₆S₈.     

External stimulus‐responsive interfaces in polymer nanocomposites

Materials that can switch from stiff to soft or from brittle to tough by slightly changing the temperature, pH, electric, or magnetic fields of their environments, can have a pronounced impact on many applications, including sensors, biomedical materials for less invasive surgeries, and packaging materials. In this work, temperature‐sensitive poly(N‐isopropyl acrylamide) grafts and low molar mass polyethylene glycol were incorporated in the interfacial region between clay nanoparticles and a bacteria‐derived polyhydroxybutyrate matrix to determine if the application of an external stimulus, such as small changes in temperature, could increase the toughness of the nanocomposites. The obtained materials were characterized by using thermal analysis, infrared spectroscopy, dynamic light scattering and dynamic mechanical tests. Mechanical properties were also evaluated at different temperatures and showed that small changes in temperature, such as from 25°C to 40°C, led to a pronounced increase in strain at break of the nanocomposites containing the modified interface. The external stimulus associated with the increase in temperature from 25°C to 40°C can reduce the interfacial interactions between clay and polymer matrix and create a highly plasticized polymer layer between the components of the nanocomposite, which favored the sliding of the interface and ultimately led to high values of elongation. POLYM. COMPOS., 37:1342–1349, 2016. © 2014 Society of Plastics Engineers     

Flexible Nanosomes (SECosomes) Enable Efficient siRNA Delivery in Cultured Primary Skin Cells and in the Viable Epidermis of Ex Vivo Human Skin

The extent to which nanoscale‐engineered systems cross intact human skin and can exert pharmacological effects in viable epidermis is controversial. This research seeks to develop a new lipid‐based nanosome that enables the effective delivery of siRNA into human skin. The major finding is that an ultraflexible siRNA‐containing nanosome—prepared using DOTAP, cholesterol, sodium cholate, and 30% ethanol—penetrates into the epidermis of freshly excised intact human skin and is able to enter into the keratinocytes. The nanosomes, called surfactant‐ethanol‐cholesterol‐osomes (SECosomes), show excellent size, surface charge, morphology, deformability, transfection efficiency, stability, and skin penetration capacity after complexation with siRNA. Importantly, these nanosomes have ideal characteristics for siRNA encapsulation, in that the siRNA is stable for at least 4 weeks, they enable highly efficient transfection of in vitro cultured cells, and are shown to transport siRNA delivery through intact human skin where changes in the keratinocyte cell state are demonstrated. It is concluded that increasing flexibility in nanosomes greatly enhances their ability to cross the intact human epidermal membrane and to unload their payload into targeted epidermal cells.