A phase I, randomized study of combined IL-2 and therapeutic immunisation with antiretroviral therapy

Background  

Fully functional HIV-1-specific CD8 and CD4 effector T-cell responses are vital to the containment of viral activity and disease progression. These responses are lacking in HIV-1-infected patients with progressive disease. We attempted to augment fully functional HIV-1-specific CD8 and CD4 effector T-cell responses in patients with advanced chronic HIV-1 infection.     

Band structure and electron-phonon interaction in lead

A self-consistent semi-relativistic APW method has been employed to calculate from first principles the band structure and the electronic density of states of Pb. Our results were used to obtain the electron-phonon interaction and the superconducting transition temperature of lead.     

High accuracy calculations of the optical gap and absorption spectrum of oxygen contaminated Si nanocrystals

We report accurate high level calculations of the optical gap and absorption spectrum of small Si nanocrystals, with hydrogen and oxygen at the surface. Our calculations have been performed in the framework of time dependent density functional theory (TDDFT) using the hybrid nonlocal exchange and correlation functional of Becke and Lee, Yang and Parr (B3LYP). The accuracy of these calculations has been verified by the high level multi-reference second order perturbation theory. The effect of oxygen contamination is studied by considering several different bonding configurations of the surface oxygen atoms. We show that for nanocrystals of sizes smaller than 20 angstroms, the widening of the gap due to quantum confinement facilitates the stabilization of Si[double bond, length as m-dash]O double bonds. For this type of bonding, the oxygen related states determine the value of the optical gap and make it significantly lower compared to the corresponding gap of oxygen-free nanocrystals. For diameters larger than 20 angstroms, the double bonds delocalize inside the valence band. We find that for small amounts of oxygen, the size of the optical gap depends strongly on their relative distribution and bonding type, while it is practically insensitive to the exact number of oxygen atoms.     

High-stability hydrogenated silicon-carbon clusters: a full study of Si2C2H2 in comparison to Si2C2, C2B2H4, and other similar species

The structural and electronic characteristics of the Si2C2H2 and Si2C2 clusters are studied by ab initio calculations based on coupled cluster and density functional theory using the hybrid B3LYP functional. In addition, similar species, such as SiC2H2 and Si3C2H2, are also studied for comparison. It is illustrated that the lowest energy structures of all three hydrogenated clusters, which have the general form Si(n)(CH)2, n = 1, 2, 3, are fully analogous to the structures of the corresponding organometallic isovalent carboranes. The most stable structure of Si2C2H2 is obtained by attaching two hydrogens onto the carbon atoms of a higher energy (+1.5 eV) planar trapezoidal structure of Si2C2, followed by geometry optimization which leads to puckering of the planar structure. Furthermore, it is demonstrated that Si2C2H2 and the other two "similar" hydrogenated clusters are much more stable than the corresponding bare nonhydrogenated clusters. Comparison of Si2C2H2 and C2B2H4 shows that their structural and bonding similarity includes also nuclear rearrangement similarity. The two species are isomerizable with an energy difference between their lowest energy puckered 1,2- and 1,3-isomers of about +/-0.3 eV. It is suggested that SiC2H2, Si2C2H2, and Si3C2H2 are special cases of a larger class of stable clusters. It is speculated on the basis of the calculated infrared spectrum that Si2C2H2 and perhaps other members of this class of clusters could be found in appreciable abundance in interstellar space.     

Stabilization of flat aromatic Si6 rings analogous to benzene: ab initio theoretical prediction

It is shown by ab initio calculations, based on density functional (DFT/B3LYP), and high level coupled-cluster [CCSD(T)] and quadratic CI [QCISD(T)] methods, that flat aromatic silicon structures analogous to benzene (C6H6) can be stabilized in the presence of lithium. The resulting planar Si6Li6 structure is both stable and aromatic, sharing many key characteristics with benzene. To facilitate possible synthesis and characterization of these species, routes of formation with high exothermicity are suggested and several spectral properties (including optical absorption, infrared, and Raman) are calculated.     

Properties of hydrogen terminated silicon nanocrystals via a transferable tight-binding Hamiltonian,based on ab-initio results

Tight-binding transferable parameters are created to reproduce ab initio energies of hydrogen-terminated Si-nanocrystals in order to extend the study of electronic and 0th order optical properties, through the HOMO–LUMO energy gap, to other larger or less symmetric silicon nanocrystals. For practical reasons the study is restricted to clusters where each Si atom has either three or no H neighbors. Results obtained so far are promising for future improvements and extensions to other systems.