Spin, charge and orbital ordering in ferrimagnetic insulator YBaMn2_2O5_5

The oxygen-deficient (double) perovskite YBaMn$_2$O$_5$, containing corner-linked MnO$_5$ square pyramids, is found to exhibit ferrimagnetic ordering in its ground state. In the present work we report generalized-gradient-corrected, relativistic first-principles full-potential density-functional calculations performed on YBaMn$_2$O$_5$ in the nonmagnetic, ferromagnetic and ferrimagnetic states. The charge, orbital and spin orderings are explained with site-, angular momentum- and orbital-projected density of states, charge-density plots, electronic structure and total energy studies. YBaMn$_2$O$_5$ is found to stabilize in a G-type ferrimagnetic state in accordance with experimental results. The experimentally observed insulating behavior appears only when we include ferrimagnetic ordering in our calculation. We observed significant optical anisotropy in this material originating from the combined effect of ferrimagnetic ordering and crystal field splitting. In order to gain knowledge about the presence of different valence states for Mn in YBaMn$_2$O$_5$ we have calculated $K$-edge x-ray absorption near-edge spectra for the Mn and O atoms. The presence of the different valence states for Mn is clearly established from the x-ray absorption near-edge spectra, hyperfine field parameters and the magnetic properties study. Among the experimentally proposed structures, the recently reported description based on $P$4/$nmm$ is found to represent the stable structure

Diabetes prevention in the non-obese diabetic mouse

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Prevalence of serological markers for hepatitis-B in patients with insulin-dependent diabetes

The prevalence of serological markers for hepatitis-B infection was investigated in patients affected by insulin-dependent diabetes (IDDM) living in different Italian regions and in the London area of the UK. Thirty five percent of Italian and 13% of British patients showed positive markers for hepatitis-B infection but none was found to be HBsAg carrier positive. When these results are compared with data observed in control populations in both countries, these findings suggest a higher prevalence of hepatitis-B infection in patients with IDDM. However, the negativity for HbsAg indicates that diabetic patients infected by the hepatitis-B virus have an effective capacity for clearance of HBsAg