X-ray rocking curve study of Si-implanted GaAs, Si, and Ge

Crystalline properties of Si-implanted GaAs, Si, and Ge have been studied by Bragg case double-crystal x-ray diffraction. Sharp qualitative and quantitative differences were found between the damage in GaAs on one hand and Si and Ge on the other. In Si and Ge the number of defects and the strain increase linearly with dose up to the amorphous threshold. In GaAs the increase in these quantities is neither linear nor monotonic with dose. At a moderate damage level the GaAs crystal undergoes a transition from elastic to plastic behavior. This transition is accompanied by the creation of extended defects, which are not detected in Si or Ge

Development of the health and economic consequences of smoking interactive model

Objective-To describe the health and economic consequences of smoking model, a user friendly, web based tool, designed to estimate the health and economic outcomes associated with smoking and the benefits of smoking cessation. Results-An overview of the development of the model equations and user interface is given, and data from the UK are presented as an example of the model outputs. These results show that a typical smoking cessation strategy costs approximately pound 1200 per life year saved and pound 22 000 per death averted. Conclusions-The model successfully captures the complexity required to model smoking behaviour and associated mortality, morbidity, and health care costs. Furthermore, the interface provides the results in a simple and flexible way so as to be useful to a variety of audiences and to simulate a variety of smoking cessation methods

Teaching E-Business with Limited Resources

This case study is an initial attempt to assist colleagues at resource-limited colleges to efficiently design and conduct new e-business courses. This detailed case study of the results is intended to assist others at similar schools in creating e-business offerings which result in similarly high levels of student satisfaction, cognitive learning and affective outcomes. E-business is a rapidly evolving and confused area. As a result, a major challenge to instructors is how to support students in learning how to learn rather than to master an established body of information. No one at the present time is, or really can be, an “expert” at e-business. Which means that, particularly at smaller schools, the real challenge is to determine how existing faculty with no formal background in the e-business area can leverage their pedagogical skills to successfully offer new courses in on topics such as electronic commerce (EC) and electronic marketing (EM). To facilitate that process, the following case analyzes in some detail the experience of designing and offering two new graduate business courses at a small (6,000+) state college in the United States. A few, very preliminary, conclusions and recommendations can be made but each should be carefully assessed within the context of other institutions and situations

Nonlinear strain effects in ion-implanted GaAs

The nonlinear production of strain in (100) GaAs by room-temperature ion implantation has been studied. Ions of Ne, Si, and Te were used, with energies of 300, 300, and 500 keV, respectively. Doses ranged up to those required for amorphization. Strains were monitored by x-ray double-crystal diffractometry. Rocking curves were recorded about the (400) Bragg condition and detailed depth profiles of strain perpendicular to the sample surface, epsilon[perpendicular](x), found by fitting the rocking curves with a kinematic model. These were compared with calculated profiles of the density of energy deposited in nuclear interactions, rhoE(x). Rocking curves were also recorded about the (422) Bragg condition for selected samples, to monitor strain in the directionparallel with their surfaces. At low doses, epsilon[perpendicular](x) is a linear function of rhoE(x). At doses sufficient to create strains exceeding about 0.3%, strong nonlinearities are evident and strain profiles depart significantly from the rhoE(x) curves. For the Ne and Si implantations, the profiles tend to saturate at 0.4%–0.5% over a depth of ~4000 Å. At higher doses a narrow (~2000 Å), sharply peaked region develops, with strains up to 1.5%. At still higher doses this region becomes amorphous. The Te-implanted samples do not experience appreciable saturation; rather a sharply peaked profile develops, and grows with dose to amorphicity. Curves of epsilon[perpendicular] vs rhoE were extracted by comparison of epsilon[perpendicular](x) and rhoE(x) profiles. These demonstrated that for each ion species epsilon[perpendicular] is a unique function of rhoE at all depths. Although this function has the same general form for all three implantations, the curves differ from species to species. Above epsilon[perpendicular]=0.3%, epsilon[perpendicular] increases sublinearly with rhoE for all three implanted ions. For Ne and Si, epsilon[perpendicular] becomes almost constant at 0.4%, beginning at rhoE~0.15 eV/Å^3. The strain epsilon[perpendicular] starts increasing again with rhoE at about 0.7 eV/Å^3 for Ne and 0.3 eV/Å^3 for Si, until the GaAs goes amorphous. The curve for Te shows only a slight inflection at epsilon[perpendicular]~0.3%, continuing to increase with rhoE to amorphicity. Parallel strains in the Si-implanted samples were not more than 0.02% at all values of rhoE

Production of Hydrogen Sulphide by Members of the Colon Group of Bacteria

Not a little work has been done in the past few years in investigating the sulphur metabolism of the colon group of bacteria. So far no very definite conclusions seem to have been arrived at, and the results are rather conflicting. Myers (1920) suggests that hydrogen sulphide production in the intestinal tract is due to proteolytic organisms. He attempted to use hydrogen sulphide production for water analysis, but concludes: There is no constant relationship between the number of colon bacilli present from different animals and the amount of H2S produced. Other workers have believed the production of hydrogen sulphide in the intestinal tract to be due to the action of B. coli on traces of systine present. B coli is not generally considered a producer of this gas from peptone. Sasaki and Otuska (1912), Berger (1914), and Tanner (1917) report B. coli as giving hydrogen sulphide from cystine