Silicon-based semiconductor heterostructures: column IV bandgapengineering

The use of strained layer epitaxy to grow high-quality Ge_x Si_1-x/Si heterostructures and their application to a wide range of heterostructure devices are addressed. The author reviews the mechanisms of strained layer growth, the bandstructure of the resulting material, and its use in test devices, including superlattice avalanche photodiodes for fiber optic communication, intrasubband optical detectors and arrays operating in the 10-15 μm wavelength range, mobility enhanced modulation-doped transistors, heterojunction bipolar transistors with cutoff frequencies of 75 GHz, and negative resistance devices based on resonant tunneling and real-space carrier transfer     

Stability analysis and guaranteed domain of attraction for a class of hybrid systems: an LMI approach

This paper presents sufficient conditions for the regional stability problem for switched piecewise affine systems, a special class of Hybrid Systems. This class of systems are described by an affine differential equation of the type x˙=A(δ)x+b(δ), where x denotes the continuous state vector and δ is a vector of logical variables that modifies the local model of the system in accordance with the continuous dynamics. Using a Lyapunov function of the type v(x)=x′P(x)x, we present LMI conditions that, when feasible, guarantee local stability of the origin of the switched system. Examples of switched affine systems are used to illustrate the results. Copyright © 2003 John Wiley & Sons, Ltd.     

Disaster Warnings in Your Pocket: How Audiences Interpret Mobile Alerts for an Unfamiliar Hazard

This study investigates how people interpret Wireless Emergency Alerts (WEAs) and Twitter‐length messages (‘tweets’) delivered over mobile devices for an unfamiliar hazard. Specifically, through four (N = 31) focus groups and 31 think‐out‐loud interviews, participants’ understanding of, belief in and personalisation of WEAs and tweets were assessed for a mock improvised nuclear device detonation in a major U.S. metropolitan area. While participants offered a wide variety of interpretations, WEAs and tweets were often deemed confusing, difficult to believe and impersonal. Participants also consistently found WEAs and tweets to be fear inducing and uninformative. The findings compel improvements in the way that WEAs and tweets are currently written, as well as indicate future directions for applied risk and crisis communication theory development.     

Melting curve of o-terphenyl

Melting of high purity o-terphenyl was investigated in the range 0–500 MPa by differential thermal analysis. The sample was purified by repeated recrystallization from methanol, followed by vacuum sublimation. This material was approximately 99.995% pure, and the results suggest that sample purity was maintained to within the experimental uncertainty. The sample was loaded into a high pressure cell with a teflon/nylon composite pressure transmitting diaphragm. A differential thermocouple and a calibrated temperature measuring thermocouple were in direct contact with the sample. The data are best fitted by a quadratic melting equation: t _m = 56.0 + 0.357 P – 0.000129 P ², where t _m is in C and P is in MPa. The intercept and initial slope agree well with existing ambient pressure melting data.National Bureau of Standards-National Research Council Postdoctoral Research Associate, 1979–80.     

Labeling of cycling corneal endothelial cells during healing with a monoclonal antibody to the Ki67 antigen (MIB-1)

PURPOSE: To assess the efficacy of labeling actively cycling corneal endothelial cells by using a monoclonal antibody to the Ki67 antigen (MIB-1) and to determine what changes in f-actin and ZO-1 organization are associated with entry into the cell cycle during wound healing under different culture conditions. METHODS: Three corneal buttons (6 mm diameter) were punched from each cornea of 15 cats. After a mechanical scrape injury (2 mm diameter) was made, buttons were cultured for 24, 48, or 72 h in serum-free media (SFM), SFM plus 10% fetal calf serum, or SFM plus basic fibroblast growth factor (bFGF). Buttons were single and double labeled by using phalloidin, anti-ZO-1, and MIB-1. Counts of Ki67-positive cells were used to determine the number of actively cycling endothelial cells. RESULTS: After culture in SFM, wounds healed by cell spreading with maintenance of normal apical f-actin and ZO-1 organization; Ki67-positive cells were detected near the leading edge in some areas. A significant increase in the number of cycling cells was measured after 48 h of culture in bFGF as compared with SFM (p<0.05); serum increased the number of cycling cells more than both SFM and bFGF (p<0.05). In all cases, positive MIB-1 staining was not observed until 48 h after injury, was limited to cells actively spreading over the wound area, and was diminished after wound closure (72 h). Double labeling demonstrated that endothelial cells exhibited a fibroblastic phenotype in some central areas of cell proliferation after culture in serum or bFGF, but, in general, apical cell border-associated f-actin and ZO-1 organization was partially maintained in most Ki67-positive cells. CONCLUSION: The data suggest that spreading corneal endothelial cells are capable of proliferating and can respond to growth factors, but that dedifferentiation or fibroblastic transformation is not required before entry into the cell cycle. Overall, the MIB-1 antibody appears to be ideally suited to the study of corneal endothelial proliferation during wound healing.     

Effect of Salt and Ethanol Addition on Zein–Starch Dough and Bread Quality

Development of viscoelastic doughs from non‐wheat proteins allows for a wider range of gluten‐free products. Little work has been completed to describe mechanisms of zein functionality in food systems. To identify factors responsible for dough development in zein–starch mixtures and their influence on zein bread quality, a mixture of 20% zein–80% maize starch was mixed with water and various reagents. Salts, NaSCN, NaCl, and Na₂SO₄ were evaluated at concentrations from 0 to 2M for their influence on the properties of zein–starch dough systems. NaSCN at low concentrations produced softer dough. Ethanol treatments produced softer more workable dough in the absence of salts. Increasing concentrations of NaCl and Na₂SO₄ resulted in coalescing of the proteins and no dough formation. The addition of β‐ME had minimal softening effects on zein–starch dough. Specific volumes of zein–starch bread increased with decreasing NaCl addition in bread formulations. Likewise, including 5% ethanol (v/v) in the bread formula increased bread quality.