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We consider spin transport in a two-component ultracold Fermi gas with attractive interspecies interactions close to the BCS pairing transition. In particular, we consider the spin-transport relaxation rate and the spin-diffusion constant. Upon approaching the transition, the scattering amplitude is enhanced by pairing fluctuations. However, as the system approaches the transition, the spectral weight for excitations close to the Fermi level is decreased by the formation of a pseudogap. To study the consequence of these two competing effects, we determine the spin-transport relaxation rate and the spin-diffusion constant using both a Boltzmann approach and a diagrammatic approach. The former ignores pseudogap physics and finite lifetime effects. In the latter, we incorporate the full pseudogap physics and lifetime effects, but we ignore vertex corrections, so that we effectively calculate single-particle relaxation rates instead of transport relaxation rates. We find that there is qualitative agreement between these two approaches, although the results for the transport coefficients differ quantitatively. [ABSTRACT FROM AUTHOR]

The viral genomic RNA (vRNA) of human respiratory syncytial virus is a nonsegmented negative strand that is not infectious alone. To develop methods for complementing synthetic vRNA with viral proteins, a cDNA was constructed to encode a vRNA in which all of the viral protein-coding sequences were removed and replaced with a negative-sense copy of the bacterial chloramphenicol acetyltransferase gene. Upon transfection into respiratory syncytial virus-infected cells, the synthetic vRNA was "rescued" such that it was amplified, expressed, and packaged into infectious virions. A heterologous paramyxovirus, parainfluenza virus 3, was inactive in rescue. Further internal deletions mapped the cis-acting viral sequences required for rescue to two segments totaling 105 nucleotides (nt) derived from the two vRNA ends. Rescue was unaffected by replacement of the 44-nt 3'-terminal leader region with a 50-nt sequence that is complementary to the 5' terminus and represents the 3' end of the positive-sense replicative intermediate RNA. This 5'-end complement was related to the parental leader region only near the 3' terminus (91% or 73% identical for the first 11 or 22 nt, respectively). The addition of 11 heterologous nt to the 3' end of the parental leader region ablated rescue, suggesting that the 3'-proximal conserved domain is required and cannot function from an internal site. However, deletion of the 3'-terminal 3 nt, or a double transition at positions 4 and 5, had no effect on rescue. Thus, the 3'-terminal 5 nt, although conserved between 3' ends of the negative- and positive-sense RNAs, do not appear to be essential.

Vectors expressing the first 58 amino acids of the hepatitis C virus (HCV) nucleocapsid alone or as a fusion protein with the middle (pre-S2 and S) or major (S) surface antigens of hepatitis B virus (HBV) were constructed. Intramuscular immunization of BALB/c mice with the chimeric constructs in the form of naked DNA elicited humoral responses to antigens from both viruses within 2 to 6 weeks postinjection. No anti-HCV responses were obtained in mice immunized with the vector expressing the HCV sequence in the nonfusion context. Sera from chimera-injected mice specifically recognized both HCV capsid and HBV surface antigens in enzyme-linked immunosorbent assay and immunoblot testing. Anti-HCV serum titers formed plateaus of approximately 1:3,000; these remained stable until the end of the study (18 weeks postinfection). Anti-HBV immune responses were found to be lower in the chimera-injected animals (< 200 mIU/ml) than in those immunized with the native HBV vector (> 2,000 mIU/ml). This is the first report of the use of DNA-based immunization for the generation of immune responses to an HCV protein. In addition, these findings show that it is possible to elicit responses to viral epitopes from two distinct viruses via DNA immunization with chimeric vectors.

We consider dynamic, i.e., frequency-dependent, correlations in noncondensed ultracold atomic Bose gases. In particular, we consider the single-particle correlation function and its power spectrum. We compute this power spectrum for a one-component Bose gas, and we show how it depends on the interatomic interactions that lead to a finite single-particle relaxation time. As another example, we consider the power spectrum of spin-current fluctuations for a two-component Bose gas and show how it is determined by the spin-transport relaxation time. [ABSTRACT FROM AUTHOR]