Anisotropy in the orbital susceptibilities of hcp metals

Calculations of the magnetic susceptibility of the hcp transition metals Sc and Zr are carried out. The major contributions to the susceptibility are found to be the Van Vleck orbital and Pauli spin terms. Other smaller yet significant contributions are the Landau-Peierls and core diamagnetic terms. Particular attention is given the Van Vleck contribution in order to advance the understanding of orbital paramagnetism in transition metals;The required energy bands and wavefunctions are determined^from the augmented plane wave (APW) method, and the Kubo-^Obata formula (1) is used to obtain a value for the Van Vleck orbital^susceptibility. Estimates of the spin and diamagnetic terms are made^and the sum of the various contributions is computed to obtain the^bulk susceptibility. Our calculations yielded the values (chi)(,(PARLL)) = 362 x^10(\u27-6) emu/mole and (chi)(,(PERP)) = 384 x 10(\u27-6) emu/mole for the susceptibility^of Sc and the values (chi)(,(PARLL)) = 159 x 10(\u27-6) emu/mole and (chi)(,(PERP)) = 164 x^10(\u27-6) emu/mole for the susceptibility of Zr. These calculated resultsfor Sc and Zr are then compared to the measurements of Speddingand Croat (2) and Collings and Ho (3), respectively. The calculatedand measured values of the susceptibility in Sc are found to agreequite well with one another. On the other hand, for Zr we find amarked disagreement between the calculated and measuredsusceptibilities. Attempts are made to understand this disagreement;and suggestions are made for additional calculations to expedite the solution of this and related problems; *DOE Report IS-T-1050. This work was performed under Contract No. W-7405-eng-82 with the U.S. Department of Energy.(1) R. Kubo and Y. Obata, J. Phys. Soc. Japan 11, 547 (1956).(2) F. H. Spedding and J. J. Croat, J. Chem. Phys. 58, 5514 (1973).(3) E. W. Collings and J. C. Ho, Phys. Rev. B 4, 349 (1971)

The major genetic determinants of HIV-1 control affect HLA class I peptide presentation.

Infectious and inflammatory diseases have repeatedly shown strong genetic associations within the major histocompatibility complex (MHC); however, the basis for these associations remains elusive. To define host genetic effects on the outcome of a chronic viral infection, we performed genome-wide association analysis in a multiethnic cohort of HIV-1 controllers and progressors, and we analyzed the effects of individual amino acids within the classical human leukocyte antigen (HLA) proteins. We identified >300 genome-wide significant single-nucleotide polymorphisms (SNPs) within the MHC and none elsewhere. Specific amino acids in the HLA-B peptide binding groove, as well as an independent HLA-C effect, explain the SNP associations and reconcile both protective and risk HLA alleles. These results implicate the nature of the HLA-viral peptide interaction as the major factor modulating durable control of HIV infection