Superconductivity and antiferromagnetism in a hard-core boson spin-1 model in two dimensions

A model of hard-core bosons and spin-1 sites with single-ion anisotropy is proposed to approximately describe hole pairs moving in a background of singlets and triplets with the aim of exploring the relationship between superconductivity and antiferromagnetism. The properties of this model at zero temperature were investigated using quantum Monte Carlo techniques. The most important feature found is the suppression of superconductivity, as long range coherence of preformed pairs, due to the presence of both antiferromagnetism and $S^z=\pm 1$ excitations. Indications of charge ordered and other phases are also discussed.Comment: One figure, one reference, adde

Stripes and holes in a two-dimensional model of spinless fermions and hardcore bosons

We consider a Hubbard-like model of strongly-interacting spinless fermions and hardcore bosons on a square lattice, such that nearest neighbor occupation is forbidden. Stripes (lines of holes across the lattice forming antiphase walls between ordered domains) are a favorable way to dope this system below half-filling. The problem of a single stripe can be mapped to a spin-1/2 chain, which allows understanding of its elementary excitations and calculation of the stripe's effective mass for transverse vibrations. Using Lanczos exact diagonalization, we investigate the excitation gap and dispersion of a hole on a stripe, and the interaction of two holes. We also study the interaction of two, three, and four stripes, finding that they repel, and the interaction energy decays with stripe separation as if they are hardcore particles moving in one (transverse) direction. To determine the stability of an array of stripes against phase separation into particle-rich phase and hole-rich liquid, we evaluate the liquid's equation of state, finding the stripe-array is not stable for bosons but is possibly stable for fermions.Comment: 24 pages, 18 figure

Nuclear Interactions of 400 GeV Protons in Emulsion

We report on 400 GeV proton-emulsion nucleus reactions and compare the results to hadron-nucleus reactions at smaller energies. In particular we present results on the emission of fast target protons (essentially grey track particles) and on their correlation with the number of collisions inside the nucleus, ν, with the number of charged evaporated particles (essentially black track particles) and with the number of pions produced (essentially shower particles). We observe that the main features of the 200¿400 GeV data are very similar. However, we find that the mean shower-particle multiplicity at 400 GeV is essentially higher than expected from the simple independent particle model prediction 〈ns〉 = 〈nch〉[1 + 0.5(〈ν〉 − 1)]. The shower particle multiplicities do not seem to follow a target mass dependence of the form 〈ns〉 = 〈nch〉 Aα with α = 0.14 or α = 0.19 as has been suggested in the literature. The pseudo-rapidity distribution shows limiting target and projectile fragmentation. The shower-particle multiplicity in the ¿central region¿ increases linearity with 〈ν〉 but faster than 0.5〈ν〉 times the corresponding multiplicity in pp reactions

Child sexual abuse as a risk factor for dating victimization in adolescent girls and young adult women in France

International audienc

Vertical and horizontal concentration profiles from a tracer experiment in a heterogeneous urban area

International audienc

Whole chromosome aneuploidy in the brain of Bub1bH/H and Ercc1-/Δ7 mice

High levels of aneuploidy have been observed in disease-free tissues, including post-mitotic tissues such as the brain. Using a quantitative interphase-fluorescence in situ hybridization approach, we previously reported a chromosome-specific, age-related increase in aneuploidy in the mouse cerebral cortex. Increased aneuploidy has been associated with defects in DNA repair and the spindle assembly checkpoint, which in turn can lead to premature aging. Here, we quantified the frequency of aneuploidy of three autosomes in the cerebral cortex and cerebellum of adult and developing brain of Bub1b(H/H) mice, which have a faulty mitotic checkpoint, and Ercc1(-/Δ7) mice, defective in nucleotide excision repair and inter-strand cross-link repair. Surprisingly, the level of aneuploidy in the brain of these murine models of accelerated aging remains as low as in the young adult brains from control animals, i.e. <1% in the cerebral cortex and ∼0.1% in the cerebellum. Therefore, based on aneuploidy, these adult mice with reduced life span and accelerated progeroid features are indistinguishable from age-matched, normal controls. Yet, during embryonic development, we found that Bub1b(H/H), but not Ercc1(-/Δ7) mice, have a significantly higher frequency of aneuploid nuclei relative to wild-type controls in the cerebral cortex, reaching a frequency as high as 40.3% for each chromosome tested. Aneuploid cells in these mutant mice are likely eliminated early in development through apoptosis and/or immune-mediated clearance mechanisms, which would explain the low levels of aneuploidy during adulthood in the cerebral cortex of Bub1b(H/H) mice. These results shed light on the mechanisms of removal of aneuploidy cells in vivo

PilT mutations lead to simultaneous defects in competence for natural transformation and twitching motility in piliated Neisseria gonorrhoeae

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73932/1/j.1365-2958.1998.00935.x.pd