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We use small angle X-ray scattering (SAXS) to characterise a class of star diblock polymers with a nanogel core on which the outer block arms are comprised of random copolymers of temperature sensitive PEGMA with pH sensitive basic (PDMAEMA) and acidic (PMAA) monomers. The acquired SAXS data show that many of the nanogel star polymers undergo a sharp structural transition over a narrow range of pH, but with unexpectedly large shifts in the apparent pKa with respect to that of the acidic or basic monomer unit, the linear polymer form or even an alternate star polymer with a tightly cross-linked core chemistry. We have demonstrated a distinct and quantifiable structural response for the nanogel star copolymers by altering the core or by pairing the monomers PDMAEMA–PEGMA and PMAA–PEGMA to achieve structural transitions that have typically been observed in stars through changes in arm length and number.

Limited information exists about African American parents' substance use and attitudes, independent of how they relate to their children. This study examined whether the behaviors and attitudes of a sample of African American parents differed from the general population of adults. Results indicated their attitudes were relatively more conservative, and that alcohol and illicit drug use were lower. Cigarette and marijuana use were comparable. Correlations between attitudes and behaviors were found. Findings suggest that increased educational efforts are needed among parents, especially about cigarettes, marijuana, and the negative impact these attitudes and behaviors may have on their children. [ABSTRACT FROM AUTHOR]

The article undertakes growth of electroluminescent devices based on strain-compensated InxGa1--xAs/ InyAl1--yAs. The very high conduction band offset of the strained material allows the design of such devices with very short emission wavelength. Device design and material characterisation for 2μm emission has been undertaken. An analysis of the direct current amplitude modulation response of the strained structure has also been performed. Strong room temperature emission with peaks around 1.55 μm dependent upon driving current has been observed under continuous wave reverse operational bias. Experimentally measured current-voltage characteristics in forward bias have been found to be in good agreement with theoretical predictions.

Organophosphorus sprays applied to crops of potatoes in eastern England in 1969-73 inclusive controlled aphid numbers and increased yield by at least 10 per cent when populations of aphids reached 500 or more per 100 leaves on untreated plants. They also tended to reduce the severity of potato blight at sites heavily infected before mid-September. Fungicide sprays (mostly mancozeb or maneb) were extremely successful in controlling blight on the foliage and increased yield of ware tubers by 12-24 per cent at sites where blight became severe, the larger increase occurring when, blight became severe by the end of August. Blight sprays also appeared to increase the number of aphids present in mid and late July on plots receiving aphicides. [ABSTRACT FROM AUTHOR]