Electrical characteristics of core-shell p-n GaAs nanowire structures with Te as the n-dopant.

GaAs nanowire (NW)-based p-n photovoltaic devices, with two distinct p and n spatial distributions and where Te was the n-dopant, have been studied by impedance spectroscopy in the 10(3)-10(7) Hz frequency range and the - 1.5-1.5 V bias range. For a large n-core/p-shell overlap region within NWs in a coaxial geometry, the p-n junction properties (DC rectification and p-n depletion capacitance) are found to prevail. The impedance data at low bias for both NW devices show large frequency dispersions with relaxation frequencies that are compatible with carrier re-emission times from traps due to GaAs surface states. An increasing conductance with increasing frequency for low bias is observed, suggesting hopping transport through localized states. For large bias the conductance increases exponentially with bias and is frequency independent, indicating conduction through extended states in this regime.

Sexually transmitted diseases in a family planning and an antenatal clinic in Peru: limitations of current practices and analysis of the use of potential markers, pH testing, and Whiff testing.

BACKGROUND: Little data exist on sexually transmitted diseases (STDs), including HIV, in family planning and antenatal clinics in Peru. GOAL: To evaluate (1) the prevalence of infection, (2) associated factors, (3) current clinical practices, and (4) the sensitivity of whiff and pH testing for STDs. STUDY DESIGN: A study of 363 women from an antenatal (n = 259) and a family planning (n = 104) clinic in central Lima, Peru that included oral histories and physical examinations. Samples were collected for laboratory diagnosis of common STDs, including HIV. RESULTS: Overall, 10.8% of antenatal clinic patients and 15.4% of family planning clinic patients had an STD, but no HIV infection was found. The diagnostic sensitivity of health providers was low, especially for cervical infections (sensitivity, 0%). In addition, few factors were associated with cervical infections or trichomoniasis. In the family planning clinic, pH testing was 100% sensitive for trichomoniasis and bacterial vaginosis. In both clinics, whiff testing was 84% sensitive and 47% specific for trichomoniasis and 88% sensitive and 53% specific for bacterial vaginosis. CONCLUSION: The burden of STDs was high and the sensitivity of current diagnostic practices was low. These results point to the need for simple diagnostic tools. Whiff and pH testing was found potentially useful for the diagnosis of vaginal infections. These simple tests should be implemented as screening tools.