Polymorphism in Gag Gene Cleavage Sites of HIV-1 Non-B Subtype and Virological Outcome of a First-Line Lopinavir/Ritonavir Single Drug Regimen

Virological failure on a boosted-protease inhibitor (PI/r) first-line triple combination is usually not associated with the detection of resistance mutations in the protease gene. Thus, other resistance pathways are being investigated. First-line PI/r monotherapy is the best model to investigate in vivo if the presence of mutations in the cleavage sites (CS) of gag gene prior to any antiretroviral treatment might influence PI/r efficacy. 83 patients were assigned to initiate antiretroviral treatment with first-line lopinavir/r monotherapy in the randomised Monark trial. We compared baseline sequence of gag CS between patients harbouring B or non-B HIV-1 subtype, and between those who achieved viral suppression and those who experienced virological failure while on LPV/r monotherapy up to Week 96. Baseline sequence of gag CS was available for 82/83 isolates; 81/82 carried at least one substitution in gag CS compared to HXB2 sequence. At baseline, non-B subtype isolates were significantly more likely to harbour mutations in gag CS than B subtype isolates (p<0.0001). Twenty-three patients experienced virological failure while on lopinavir/r monotherapy. The presence of more than two substitutions in p2/NC site at baseline significantly predicted virological failure (p = 0.0479), non-B subtype isolates being more likely to harbour more than two substitutions in this specific site. In conclusion, gag cleavage site was highly polymorphic in antiretroviral-naive patients harbouring a non-B HIV-1 strain. We show that pre-therapy mutations in gag cleavage site sequence were significantly associated with the virological outcome of a first-line LPV/r single drug regimen in the Monark trial

Lithium boro-hydride LiBH₄ : I. Crystal structure

The crystal structure of LiBH4 has been studied by synchrotron X-ray powder diffraction at room temperature and at 408 K. At room temperature it has orthorhombic symmetry [space group Pnma, a=7.17858(4), b=4.43686(2), c=6.80321(4) Å]. The tetrahedral (BH4)− anions (point symmetry m) are aligned along two orthogonal directions and are strongly distorted with respect to bond lengths [B–H=1.04(2)–1.28(1) Å] and bond angles [H–B–H=85.1(9)°–120.1(9)°]. As the temperature is increased the structure undergoes a first-order transition and becomes hexagonal (space group P63mc, a=4.27631(5), c=6.94844(8) Å at T=408 K). The (BH4)− tetrahedra align along c, become more symmetric [point symmetry 3m, B–H=1.27(2)–1.29(2) Å, H–B–H=106.4(2)°–112.4(9)°] and show displacement amplitudes that are consistent with dynamical disorder about their trigonal axi

High-throughput synthesis and characterization of Eu doped Ba_xSr_2–xSiO₄ thin film phosphors’

High-throughput techniques have been employed for the synthesis and characterization of thin film phosphors of Eu-doped Ba xSr2- xSiO4. Direct synthesis from evaporation of the constituent elements under a flux of atomic oxygen on a sapphire substrate at 850 °C was used to directly produce thin film libraries (415 nm thickness) of the crystalline orthosilicate phase with the desired compositional variation (0.24 &gt; x &gt; 1.86). The orthosilicate phase could be synthesized as a pure, or predominantly pure, phase. Annealing the as synthesized library in a reducing atmosphere resulted in the reduction of the Eu while retaining the orthosilicate phase, and resulted in a materials thin film library where fluorescence excited by blue light (450 nm) was observable by the naked eye. Parallel screening of the fluorescence from the combinatorial libraries of Eu doped Ba xSr2- xSiO4 has been implemented by imaging the fluorescent radiation over the library using a monochrome digital camera using a series of color filters. Informatics tools have been developed to allow the 1931 CIE color coordinates and the relative quantum efficiencies of the materials library to be rapidly assessed and mapped against composition, crystal structure and phase purity. The range of compositions gave values of CIE x between 0.17 and 0.52 and CIE y between 0.48 and 0.69 with relative efficiencies in the range 2.0 × 10-4-7.6 × 10-4. Good agreement was obtained between the thin film phosphors and the fluorescence characteristics of a number of corresponding bulk phosphor powders. The thermal quenching of fluorescence in the thin film libraries was also measured in the temperature range 25-130 °C: The phase purity of the thin film was found to significantly influence both the relative quantum efficiency and the thermal quenching of the fluorescence

Al3Sc thin films for advanced interconnect applications

AlxSc1-x thin films have been studied with compositions around Al3Sc (x = 0.75) for potential interconnect metallization applications. As-deposited 25 nm thick films were x-ray amorphous but crystallized at 190 degrees C, followed by recrystallization at 440 degrees C. After annealing at 500 degrees C, 24 nm thick stoichiometric Al3Sc showed a resistivity of 12.6 mu Scm, limited by a combination of grain boundary and point defect (disorder) scattering. Together with ab initio calculations that found a mean free path of the charge carriers of 7 nm for stoichiometric Al3Sc, these results indicate that Al3Sc bears promise for future interconnect metallization schemes. Challenges remain in minimizing the formation of secondary phases as well as in the control of the non-stoichiometric surface oxidation and interfacial reactions with underlying dielectrics