High mobility two-dimensional electron system on hydrogen-passivated silicon(111) surfaces

We have fabricated and characterized a field-effect transistor in which an electric field is applied through an encapsulated vacuum cavity and induces a two-dimensional electron system on a hydrogen-passivated Si(111) surface. This vacuum cavity preserves the ambient sensitive surface and is created via room temperature contact bonding of two Si substrates. Hall measurements are made on the H-Si(111) surface prepared in aqueous ammonium fluoride solution. We obtain electron densities up to $6.5 \times 10^{11}$ cm$^{-2}$ and peak mobilities of $\sim 8000$ cm$^{2}$/V s at 4.2 K.Comment: to appear in Applied Physics Letter

Parametric study of cavity length and mirror reflectivity in ultralow threshold quantum well InGaAs/AlGaAs lasers

Record low CW threshold currents of 16 μA at-room temperature and 21 μA at cryogenic temperature have been demonstrated in buried heterostructure strained layer, single quantum well InGaAs/AlGaAs lasers with a short cavity length and high reflectivity coatings

Very High Modulation Efficiency of Ultralow Threshold Current Single Quantum Well InGaAs Lasers

A record high current modulation efficiency of 5 GHz/[sqrt](mA) has been demonstrated in an ultralow threshold strained layer single quantum well InGaAs laser

Consumers and Their Celebrity Brands: How Personal Narratives Set the Stage for Attachment

This research demonstrates how consumer attachment to celebrity brands is driven by perceived narratives about the celebrity’s persona, which triggers communal (i.e., altruistic) relationship norms. The research investigates the differential role of narratives about celebrities’ personal vs. professional lives in creating attachment, and identifies and tests moderating effects of narrative characteristics including perceived source of fame, valence and authenticity. Design/methodology/approach – Three online experiments tested the proposed direct, mediating, and moderating relationships. Data was analyzed using mediation analysis and multiple ANOVAs. Findings – Results suggest relationship norms that are more altruistic in nature fully mediate the relationship between narrative type and brand attachment. Additionally, personal narratives produce stronger attachment than professional narratives; the celebrity’s source of fame moderates narrative type and attachment; and on-brand narratives elicit higher attachment than off-brand narratives, even when these narratives are negative. Practical implications – We offer recommendations for how marketers can shape celebrity brand narratives to build stronger consumer attachment. Notably, personal (vs. professional) narratives are critical in building attachment, especially for celebrity brands that are perceived to have achieved their fame. Both positive and negative personal narratives can strengthen attachment for achieved celebrity brands, but only if they are on-brand with consumer expectations. Originality/value – This research is an introductory examination of the fundamental theoretical process by which celebrity brand relationships develop from brand persona narratives, and how characteristics of those narratives influence consumer-brand attachment

Integer quantum Hall effect on a six valley hydrogen-passivated silicon (111) surface

We report magneto-transport studies of a two-dimensional electron system formed in an inversion layer at the interface between a hydrogen-passivated Si(111) surface and vacuum. Measurements in the integer quantum Hall regime demonstrate the expected sixfold valley degeneracy for these surfaces is broken, resulting in an unequal occupation of the six valleys and anisotropy in the resistance. We hypothesize the misorientation of Si surface breaks the valley states into three unequally spaced pairs, but the observation of odd filling factors, is difficult to reconcile with non-interacting electron theory.Comment: 4 pages, 4 figures, to appear in Physical Review Letter

Control of rat glomerular epithelial cell growth in vitro

Control of rat glomerular epithelial cell growth in vitro. The interaction of cultured rat GEC1 with several growth factors was explored in order to obtain a better understanding of in vivo factors which might stimulate GEC proliferation. GEC proliferated in response to EGF but not IGF-1, MSA or PDGF. Specific, saturable receptors for EGF were detected in saturation and competition binding studies utilizing 125I-EGF with an approximate Kd of 1.7nM and 86,000 binding sites per cell. TGF-β inhibited GEC growth in a time and dose dependent manner with a brief early exposure resulting in prolonged growth inhibition which was not reversible by EGF. Exposure to TGF-β sufficient to maximally inhibit growth had no effect on EGF binding to GEC. More prolonged exposure to TGF-β, however, did result in an increase in the apparent number of EGF receptors on GEC but no change in Kd. These studies suggest that EGF and TGF-β released by inflammatory cells or platelets during the course of glomerular injury may play a role in modulating glomerular cell proliferation

Submilliamp threshold InGaAs-GaAs strained layer quantum-well laser

Strained-layer InGaAs-GaAs single-quantum-well buried-heterostructure lasers were fabricated by a hybrid beam epitaxy and liquid-phase epitaxy technique. Very low threshold currents, 2.4 mA for an uncoated laser (L=425 μm) and 0.75 mA for a coated laser (R~0.9, L=198 μm), were obtained. A 3-dB modulation bandwidth of 7.6 GHz was demonstrated at low bias current (14 mA). Procedures for material preparation and device fabrication are introduced

8-PSK Signaling over non-linear satellite channels

Space agencies are under pressure to utilize better bandwidth-efficient communication methods due to the actual allocated frequency bands becoming more congested. Also budget reductions is another problem that the space agencies must deal with. This budget constraint results in simpler spacecraft carrying less communication capabilities and also the reduction in staff to capture data in the earth stations. It is then imperative that the most bandwidth efficient communication methods be utilized. This thesis presents a study of 8-ary Phase Shift Keying (8PSK) modulation with respect to bandwidth, power efficiency, spurious emissions and interference susceptibility over a non-linear satellite channel

Sequestration of G3BP coupled with efficient translation inhibits stress granules in Semliki Forest virus infection

Dynamic, mRNA-containing stress granules (SGs) form in the cytoplasm of cells under environmental stresses, including viral infection. Many viruses appear to employ mechanisms to disrupt the formation of SGs on their mRNAs, suggesting that they represent a cellular defense against infection. Here, we report that early in Semliki Forest virus infection, the C-terminal domain of the viral nonstructural protein 3 (nsP3) forms a complex with Ras-GAP SH3-domain–binding protein (G3BP) and sequesters it into viral RNA replication complexes in a manner that inhibits the formation of SGs on viral mRNAs. A viral mutant carrying a C-terminal truncation of nsP3 induces more persistent SGs and is attenuated for propagation in cell culture. Of importance, we also show that the efficient translation of viral mRNAs containing a translation enhancer sequence also contributes to the disassembly of SGs in infected cells. Furthermore, we show that the nsP3/G3BP interaction also blocks SGs induced by other stresses than virus infection. This is one of few described viral mechanisms for SG disruption and underlines the role of SGs in antiviral defense

Development of a Constant -Stress Creep Testing Equipment

ABSTRACT The design and development of constant stress creep testing equipment has been undertaken in this work. It was discovered that the cost of purchasing laboratory testing equipment is huge due to the present foreign exchange rate in Nigeria, thereby depriving most of laboratories of this necessary equipment. This accounts for one of the reasons why many science and engineering graduates go through tertiary institutions without having adequate practical experience of some of these equipment which are either non functional or not available in most cases. The developed constant stress creep testing equipment is one of such equipment required in a materials testing laboratory. The materials used for the equipment development were locally sourced, therefore expected to be easily assessable and affordable as well as preserve foreign exchange. As of July, 2010, a unit cost less than N 250,000 Nigerian (approximately $1,700 U.S.)