Non-peptidic HIV protease inhibitors: C2-symmetry-based design of bis-sulfonamide dihydropyrones

Potent, non-peptidic, dihydropyrone sulfonamide HIV protease inhibitors have been previously described. Crystallographic analysis of dihydropyrone sulfonamide inhibitor/HIV protease complexes suggested incorporation of a second, C2 symmetry-related sulfonamide group. Selected bis-sulfonamide dihydropyrone analogues display high HIV protease inhibitory activity.     

Space-variant optical interconnection through the use of computer-generated holograms

A space-variant optical interconnection through the use of computer-generated holograms is proposed, and specific configurations to increase the number of parallel channels are analyzed. To this end, the well-known method based on a matrix composed of subholograms is applied. The field diffracted by each channel (assumed to be square apertures) is calculated through the angular-spectrum technique, and the resulting fields are suitably superimposed to obtain a hologram matrix with a reduced bandwidth. Results show that a compact transmissive planar configuration can be handled; in particular, the small interconnect distance between the array planes and the hologram yields a limited system volume.     

Nuclear data sensitivity,uncertainty and target accuracy assessment for future nuclear systems

A sensitivity and uncertainty study has been performed to evaluate the impact of neutron cross-section uncertainty on the most significant integral parameters related to the core and fuel cycle. This work is a contribution to the feasibility assessment of innovative reactor and fuel cycle systems, proposed within the Generation IV initiative. Results of an extensive analysis indicate the most relevant parameters and show any potential significant problems arising from the quality of existing nuclear data, in the assessment of the systems considered. In order to perform these studies, uncertainty covariance data have been produced, mostly based on selected, high accuracy integral experiments. A target accuracy assessment has been also performed in order to evaluate nuclear data improvement requirements. The results of the assessment allows to give guidelines in order to define the most appropriate and effective strategy for data uncertainty reduction.     

Searching for the center: Spatial cognition in the domestic chick (Gallus gallus).

Chicks learned to find food hidden under sawdust by ground-scratching in the central position of the floor of a closed arena. When tested in an arena of identical shape but a larger area, chicks searched at 2 different locations, one corresponding to the correct distance (i.e., center) in the smaller (training) arena and the other to the actual center of the test arena. When tested in an arena of the same shape but a smaller area, chicks searched in the center of it. These results suggest that chicks are able to encode information on the absolute and relative distance of the food from the walls of the arena. After training in the presence of a landmark located at the center of the arena, animals searched at the center even after the removal of the landmark. Marked changes in the height of the walls of the arena produced some displacement in searching behavior, suggesting that chicks used the angular size of the walls to estimate distances. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tuning light emission of PbS nanocrystals from infrared to visible range by cation exchange

Colloidal semiconductor nanocrystals, with intense and sharp-line emission between red and near-infrared spectral regions, are of great interest for optoelectronic and bio-imaging applications. The growth of an inorganic passivation layer on nanocrystal surfaces is a common strategy to improve their chemical and optical stability and their photoluminescence quantum yield. In particular, cation exchange is a suitable approach for shell growth at the expense of the nanocrystal core size. Here, the cation exchange process is used to promote the formation of a CdS passivation layer on the surface of very small PbS nanocrystals (2.3 nm in diameter), blue shifting their optical spectra and yielding luminescent and stable nanostructures emitting in the range of 700–850 nm. Structural, morphological and compositional investigation confirms the nanocrystal size contraction after the cation-exchange process, while the PbS rock-salt crystalline phase is retained. Absorption and photoluminescence spectroscopy demonstrate the growth of a passivation layer with a decrease of the PbS core size, as inferred by the blue-shift of the excitonic peaks. The surface passivation strongly increases the photoluminescence intensity and the excited state lifetime. In addition, the nanocrystals reveal increased stability against oxidation over time. Thanks to their absorption and emission spectral range and the slow recombination dynamics, such highly luminescent nano-objects can find interesting applications in sensitized photovoltaic cells and light-emitting devices.     

TiO(2) nanorods/PMMA copolymer-based nanocomposites: highly homogeneous linear and nonlinear optical material

Original nanocomposites have been obtained by direct incorporation of pre-synthesized oleic acid capped TiO(2) nanorods into properly functionalized poly(methyl methacrylate) copolymers, carrying carboxylic acid groups on the repeating polymer unit. The presence of carboxylic groups on the alkyl chain of the host functionalized copolymer allows an highly homogeneous dispersion of the nanorods in the organic matrix. The prepared TiO(2)/PMMA-co-MA nanocomposites show high optical transparency in the visible region, even at high TiO(2) nanorod content, and tunable linear refractive index depending on the nanoparticle concentration. Finally measurements of nonlinear optical properties of TiO(2) polymer nanocomposites demonstrate a negligible two-photon absorption and a negative value of nonlinear refractive index, highlighting the potential of the nanocomposite for efficient optical devices operating in the visible region.     

Mechanical properties of human saphenous veins from normotensive and hypertensive patients

The three-dimensional structure of a synthetic peptide corresponding to the putative transmembrane segment M3 (amino acid residues 277-301) of the alpha subunit of the nicotinic acetylcholine receptor from Torpedo californica has been studied by means of two-dimensional 1H-NMR spectroscopy in a chloroform/methanol (1:1) mixture containing 0.1 M LiClO4. Complete resonance assignment has been performed using double-quantum-filtered COSY (DQF-COSY), TOCSY and NOESY spectra. The spatial structure has been calculated using the Diana program on the basis of integrated intensities of NOESY spectra. HN-C(alpha)H and HC(alpha)-C(beta)H spin-spin coupling constants. Residues 279-297 of M3 form a right-handed helix (root mean square deviation is 0.032 nm for backbone atoms and 0.088 nm for all heavy atoms). The conformations of the 17 side chains have been unambiguously determined. The obtained structure is in accord with the photolabeling pattern of the membrane nicotinic acetylcholine receptor (nAChR) which suggests alpha-helical structure of M3 in the labeled portion [Blanton, M. P. & Cohen, J. B. (1994) Biochemistry 33, 2859-2872].     

Evaluation and characterization of micronuclei in early spermatids of mice exposed to 1,3-butadiene

The 18S rRNA gene (Rns) phylogeny of Acanthamoeba is being investigated as a basis for improvements in the nomenclature and taxonomy of the genus. We previously analyzed Rns sequences from 18 isolates from morphological groups 2 and 3 and found that they fell into four distinct evolutionary lineages we called sequence types T1-T4. Here, we analyzed sequences from 53 isolates representing 16 species and including 35 new strains. Eight additional lineages (sequence types T5-T12) were identified. Four of the 12 sequence types included strains from more than one nominal species. Thus, sequence types could be equated with species in some cases or with complexes of closely related species in others. The largest complex, sequence type T4, which contained six closely related nominal species, included 24 of 25 keratitis isolates. Rns sequence variation was insufficient for full phylogenetic resolution of branching orders within this complex, but the mixing of species observed at terminal nodes confirmed that traditional classification of isolates has been inconsistent. One solution to this problem would be to equate sequence types and single species. Alternatively, additional molecular information will be required to reliably differentiate species within the complexes. Three sequence types of morphological group 1 species represented the earliest divergence in the history of the genus and, based on their genetic distinctiveness, are candidates for reclassification as one or more novel genera.     

Flavonol and chalcone ester glycosides from Bidens andicola

OBJECTIVES: To examine the effect of black race and acute (negative life events) and chronic (lack of social support) psychological stress on the risk of herpes zoster in late life. DESIGN: A population-based, prospective cohort study. SETTING: Central North Carolina. PARTICIPANTS: Duke Established Populations for Epidemiological Studies of the Elderly, a stratified probability sample of community-dwelling persons more than 65 years of age. MEASUREMENTS: Interviewers administered a comprehensive health survey to the participants in 1986-1987 (P1, n = 4162), 1989-1990 (P2, n = 3336), and 1992-1994 (P3, n = 2568). Incident cases of zoster between P1 and P2 and P2 and P3 served as the dependent variable. Hypothesis-testing variables included race, negative life events, and five measures of social support. Control variables included age, sex, education, cancer, chronic diseases, basic ADLs, instrumental ADLs, depression, self-rated health, hospitalization, and cigarette smoking. Statistical analyses employed chi-square tests and proportional hazards model. RESULTS: At baseline, the sample had a mean age of 73.6 years and was 55% black, 45% white, and 65% female. There were 65 cases of zoster between P1 and P2 and 102 cases of zoster between P2 and P3. From P1 to P2, 1.4% of blacks and 3.4% of whites developed zoster (P < .001). From P2 to P3, 2.9% of blacks and 7.5% of whites developed zoster (P < .001). After controlling for the above variables, blacks were significantly less likely to develop zoster (adjusted risk ratio = 0.35; 95% confidence interval (CI), 0.24-0.51; P < .001). Negative life events increased the risk of zoster, but the result was borderline for statistical significance (adjusted RR = 1.38, 95% CI 0.96-1.97; P = .078). No measures of social support were significantly associated with zoster. CONCLUSION: Black race decreased the risk of zoster in late life significantly. Measures of stress were not significantly related to zoster, but study limitations preclude definitive conclusions. Future research should focus on these factors in larger samples and different populations.