Analysis of low temperature trapping and recombination in II-VI compounds using photodielectric techniques

Using photodielectric effect to detect densities of free and trapped carriers in II-VI compounds at cryogenic temperature

Ponticulin is the major high affinity link between the plasma membrane and the cortical actin network in Dictyostelium

Interactions between the plasma membrane and underlying actin-based cortex have been implicated in membrane organization and stability, the control of cell shape, and various motile processes. To ascertain the function of high affinity actin-membrane associations, we have disrupted by homologous recombination the gene encoding ponticulin, the major high affinity actin-membrane link in Dictyostelium discoideum amoebae. Cells lacking detectable amounts of ponticulin message and protein also are deficient in high affinity actin-membrane binding by several criteria. First, only 10-13% as much endogenous actin cosediments through sucrose and crude plasma membranes from ponticulin-minus cells, as compared with membranes from the parental strain. Second, purified plasma membranes exhibit little or no binding or nucleation of exogenous actin in vitro. Finally, only 10-30% as much endogenous actin partitions with plasma membranes from ponticulin-minus cells after these cells are mechanically unroofed with polylysine-coated coverslips. The loss of the cell\u27s major actin-binding membrane protein appears to be surprisingly benign under laboratory conditions. Ponticulin-minus cells grow normally in axenic culture and pinocytose FITC-dextran at the same rate as do parental cells. The rate of phagocytosis of particles by ponticulin-minus cells in growth media also is unaffected. By contrast, after initiation of development, cells lacking ponticulin aggregate faster than the parental cells. Subsequent morphogenesis proceeds asynchronously, but viable spores can form. These results indicate that ponticulin is not required for cellular translocation, but apparently plays a role in cell patterning during development

Identification of Transit Service Gaps through Accessibility and Social Vulnerability Mapping in Miami-Dade County

Inadequate provision of public transportation services can lead to mobility-related social exclusion for disadvantaged population groups (e.g., lower-income families, the elderly), and limited accessibility to jobs, healthy food, and recreational as well as social activities. The aim of this study is to identify areas in Miami-Dade County, Florida, where disadvantaged populations lack transit-based access to these opportunities, and where transit service improvement could benefit these groups especially. This involves developing a transit-based accessibility index which uses timetable data from three public transit agencies. It also entails devising a vulnerability index based on a combination of socioeconomic variables to identify disadvantaged population groups with regards to mobility. Both indices can be combined into a service provision score which quantifies the presence of populations in need of transit service improvements. Results show that the combination of the different index maps and the application of Hotspot analysis can help to identify areas requiring transit service improvement in order to achieve accessibility equity. The analysis and interpretation of accessibility maps and selected demographic layers, such as percentage of households without vehicle, facilitates the identification of areas with above-average rates of users who rely on public transportation

Soil and Water Loss from Conservation Tillage Systems

A rainfall simulator was used to evaluate the effects of six different tillage practices on soil and water losses from continuous corn for three soils in Iowa. Soil loss decreased as tillage decreased. Percent of soil covered by corn residue explained between 78 and 89 percent of the variance in erosion among tillage systems. The effect of non-uniformly distributed corn residue on controlling erosion was greater than expected based on a published mulch factor. Runoff amounts decreased as residue cover increased for two of the three soils studied. No critical slope length limits were found for the tillage practices, soils, slopes, and slope lengths studied except for till-planting on the Ida soil. As sediment concentrations increased, mean sediment size increased for one soil, decreased for a second soil, and was unrelated to sediment concentration for the third soil