Structure and dynamics of the fullerene polymer Li4 C60 studied with neutron scattering

The two-dimensional polymer structure and lattice dynamics of the superionic conductor Li4 C60 are investigated by neutron diffraction and spectroscopy. The peculiar bonding architecture of this compound is definitely confirmed through the precise localisation of the carbon atoms involved in the intermolecular bonds. The spectral features of this phase are revealed through ab-initio lattice dynamics calculations and inelastic neutron scattering experiments. The neutron observables are found to be in very good agreement with the simulations which predict a partial charge transfer from the Li atoms to the C60 cage. The absence of a well defined band associated to one category of the Li atoms in the experimental spectrum suggests that this species is not ordered even at the lowest temperatures. The calculations predict an unstable Li sublattice at a temperature of 200 K, that we relate to the large ionic diffusivity of this system. This specificity is discussed in terms of coupling between the low frequency optic modes of the Li ions to the soft structure of the polymer.Comment: 29 pages, 13 Figure

Converging Strategies in Expression of Human Complex Retroviruses

The discovery of human retroviruses in the early 1980s revealed the existence of viral-encoded non-structural genes that were not evident in previously described animal retroviruses. Based on the absence or presence of these additional genes retroviruses were classified as ‘simple’ and ‘complex’, respectively. Expression of most of these extra genes is achieved through the generation of alternatively spliced mRNAs. The present review summarizes the genetic organization and expression strategies of human complex retroviruses and highlights the converging mechanisms controlling their life cycles

Polysaccharide antigen-glycolipid conjugate vaccines

The present invention relates to the field of synthesizing and biologically evaluating of a novel class of carbohydratebased vaccines. The new vaccines consist of a multi- modular structure which allows applying the vaccine to a whole variety of pathogenes. This method allows preparing vaccines against all pathogens expressing immunogenic carbohydrate antigens. As conjugation of antigenic carbohydrates to proteins is not required the conjugate vaccine is particularly heat stable. No refrigeration is required, a major drawback of protein-based vaccines

Beam related thermal losses on the cryogenic and vacuum systems of LEP

The LEP Collider was operated in 1997 with 60 superconducting four-cavity accelerating modules (about 2600 MV available) installed at the four interaction points. During operation for physics it was o bserved that the dissipated heat in the superconducting cavities is not only a function of the acceleration gradient but it also depends on beam characteristics: number of bunches, bunch length and cu rrent per bunch. These beam effects were not foreseen in the original heat budget of the LEP refrigerators. Three days of LEP Machine Development were dedicated in August 97 to clarifying the correlat ion of the losses with the beam characteristics. The beam dependent heat load of the cryogenic system for the superconducting cavities is described. The dependence on various beam parameters is presen ted and scaling laws are given. A possible explanation will be presented and the consequence for LEP operation will be discussed

On the temperature behavior of shunt-leakage currents in Cu(In,Ga)Se2 solar cells: The role of grain boundaries and rear Schottky contact

By comparing simulated and measured dark current-voltage (I-V) characteristics of CIGS cells at different temperatures, we investigate the temperature behavior of the shunt leakage current, and find that it can be explained by large donor trap concentrations at grain boundaries (GBs), and by a Schottky barrier at the backside contact where the GBs meets the anode metallization. We studied the I-V characteristics in the temperature range 280 K - 160 K achieving good fits of the measured I-V curves, especially for reverse bias and low forward bias, where the shunt leakage current dominates. The most important parameters determining the shunt leakage current value and its temperature dependence are the peak energy and density of the GB donor distribution, which control the inversion of GBs and the pinning of Fermi level at the anode/GB contact

Post-transcriptional regulation of HTLV gene expression: Rex to the rescue

Human T-lymphotropic virus type 1 (HTLV-1) and other members of the Deltaretrovirus genus code for a regulatory protein named Rex that binds to the Rex-responsive element present on viral mRNAs. Rex rescues viral mRNAs from complete splicing or degradation and guides them to the cytoplasm for translation. The activity of Rex is essential for expression of viral transcripts coding for the virion components and thus represents a potential target for virus eradication. We present an overview of the functional properties of the HTLV-1 and HTLV-2 Rex proteins (Rex-1 and Rex-2), outline mechanisms controlling Rex function, and discuss similarities and differences in the sequences of Rex coded by HTLV-1, -2, -3, and -4 that may influence their molecular anatomy and functional properties