spl(2,1) dynamical supersymmetry and suppression of ferromagnetism in flat band double-exchange models

The low energy spectrum of the ferromagnetic Kondo lattice model on a N-site complete graph extended with on-site repulsion is obtained from the underlying spl(2,1) algebra properties in the strong coupling limit. The ferromagnetic ground state is realized for 1 and N+1 electrons only. We identify the large density of states to be responsible for the suppression of the ferromagnetic state and argue that a similar situation is encountered in the Kagome, pyrochlore, and other lattices with flat bands in their one-particle density of states.Comment: 7 pages, 1 figur

Equine leukoencephalomalacia (ELEM) due to fumonisins B1 and B2 in Argentina

In August 2007 an outbreak of neurological disease and sudden death in Arabian horses occurred in a farm located in Coronel Rosales County, Buenos Aires Province, Argentina. The animals were on a pasture of native grasses and supplemented ad libitum with corn kernels and wheat bran. Three horses were observed having acute neurologic signs including blindness, four leg ataxia, hyperexcitability, aimless walking and circling, followed by death in two of them. Four other horses were found dead overnight without a history of neurologic signs. The morbidity, mortality and lethality rates were 11.6%, 10% and 85.7%, respectively. Grossly, the brain showed focal areas of hemorrhage, brown-yellow discoloration and softening of the sub-cortical white matter. The microscopic brain lesions consisted of extensive areas of malacia within the white matter of the cerebral hemispheres, brainstem and cerebellum, characterized by rarefaction of the white matter with cavitations filled with proteinaceous edema, multifocal hemorrhages and mild infiltration by neutrophils, and rare eosinophils. Swollen glial cells with abundant eosinophilic cytoplasm, distinct cell borders, intracytoplasmic deeply eosinophilic globules and eccentric, hyperchromatic, occasionally pyknotic nucleus were present throughout the areas of rarefaction hemorrhage, edema and necrosis. The feed supplements contained 12,490µg/kg of fumonisin B1 and 5,251µg/ kg of fumonisin B2. This is the first reported outbreak of ELEM associated with consumption of feed supplements containing high concentrations of fumonisins in Argentina

Thermodynamics of the rupture in a Morse lattice

The rupture of a Morse lattice is considered in the present paper. The critical rupture force Fcr is found to decrease with the number of particles N as Fcr ~ 1/$\sqrt{N}$. The partition function is obtained for two states of the lattice – with all equal bond lengths and one broken bond. In the first case an accurate expressions for thermodynamic parameters are obtained, and thermodynamic expressions are derived in the harmonic approximation in the latter case. The analytical predictions are confirmed by extensive MD simulations. Cis-trans isomerization is considered as an example. Volume fractions of trans- and cis-isomers versus number of monomer units N are found depending on the torsion stiffnesses

Nevirapine Use Is Associated with Higher Bone Mineral Density in HIV-1 Positive Subjects on Long-Term Antiretroviral Therapy

International audienceWe assessed bone mineral density (BMD) in a cohort of human immunodeficiency virus (HIV)-positive patients after a median of 11 years of combination antiretroviral therapy (cART) and evaluated the respective role of HIV infection and antiretroviral drugs (ARVs). A cross-sectional study of 162 participants (131 male) from the ANRS-C08 cohort was performed with bone dual-energy X-ray absorptiometry (DXA) scans and renal assessment. The window of exposure to ARVs was defined as an exposure of more than six cumulative months during the last 3 years before the DXA evaluation to account for a cumulative exposure that could affect bone remodeling. The association with low BMD (Z-score < -2) was assessed by a multiple logistic regression model. The study population was 50 years (median), hepatitis C virus (HCV) (18%), and hepatitis B virus (HBV) (8%) coinfection with HIV-RNA <50 c/mL in 89%, median CD4 of 619/mm3. Prevalence of low BMD was 18% in males and 6% in females. The factors associated with a Z-score < -2 in males were uric acid renal loss [adjusted odds ratio (aOR): 6.1; 95% confidence interval (CI): 1.2-31.5; p = .03], HCV coinfection (aOR: 4.0; 95% CI: 1.3-12.2; p = .02), and less frequent window of exposure to nevirapine (NVP) (aOR: 0.1; 95% CI: 0.02-0.6; p = .01). For the full study sample, there was a strong positive association between duration of exposure to NVP and lumbar spine Z-score (p = .004). HIV-positive patients exposed to long-term cART have a high incidence of low BMD. Tenofovir disoproxil fumarate and ritonavir-boosted protease inhibitors did not seem to be associated with increased risk of low BMD, whereas NVP exposure appeared to have an independent positive association