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High-redshift quasars are unique probes of the evolution of supermassive black holes and the intergalactic medium at the end of the epoch of reionization. We present the optical spectra of eight new z ~ 6 quasars selected from the Panoramic Survey Telescope & Rapid Response System 1 (Pan-STARRS1). Details of the selection strategy can be found in Bañados et al. (2014). With this work we increase the number of known quasars at z < 5.7 by more than 10%. The quasars discovered here span a large range of luminosities (19.6 ≤ zP1 ≤ 21.2) and are remarkably heterogeneous in their spectral features: half of them show bright emission lines whereas the other half show weak or no Lyα emission line. We find a larger fraction of weak–line emission quasars than in lower redshift studies, although still based on low number statistics, this may imply that the quasar population could be more diverse than previously thought.
We have studied the influence of ultra-thin interfacial Fe layers on the structural and magnetoresistance properties of CO/Cu Multilayers. Our results show that the giant magnetoresistance arises from spin dependent scattering at the CO/Cu interfaces and in the bulk of Co, the interfacial contribution being predominant. We also demonstrate that the close-packed crystallographic structure of Co and Cu is very sensitive to the insertion of interfacial bec Fe layers: for small thicknesses, Co as well as Cu adopt a metastable bec structure.
A study has been made of the magnetic properties of epitaxial 6 Monolayer (ML) fcc-Fe films on Cu (100) with various thicknesses of epitaxial Cu deposited on top of the Fe. It was found that the magnetic properties undergo striking changes as a function of the Cu thickness. The easy axis of magnetization goes from being in-plane for the bare Fe to perpendicular upon the deposition of 1 ML Cu. Concurrently there is a dramatic decrease in the Kerr signal intensity at saturation. Upon depositing a second ML of Cu the Kerr signal intensity more than doubles, and the easy axis remains perpendicular. For Cu overlayers of 3 ML to 10 ML the Kerr signal intensity at saturation gradually diminishes to below the level of detectability, as if the Fe were nonmagnetic. A superlattice consisting of 60 ML Cu/ (6 ML 57Fe/10 ML Cu)×5/Cu (100) was fabricated and studied at room temperature by conversion electron Mòssbauer spectroscopy. The results confirmed that the Fe is indeed nonmagnetic. The four inner Fe layers of the 6 ML film have the same isomer shift as bulk fcc-Fe in precipitates in Cu, and the two boundary Fe layers exhibit an asymmetric quadrupole doublet.
Leishmania spp. are sandfly-transmitted protozoa parasites that cause a spectrum of diseases in humans. Many enzymes involved in Leishmania central carbon metabolism differ from their equivalents in the mammalian host and are potential drug targets. In this review we summarize recent advances in our understanding of Leishmania central carbon metabolism, focusing on pathways of carbon utilization that are required for growth and pathogenesis in the mammalian host. While Leishmania central carbon metabolism shares many features in common with other pathogenic trypanosomatids, significant differences are also apparent. Leishmania parasites are also unusual in constitutively expressing most core metabolic pathways throughout their life cycle, a feature that may allow these parasites to exploit a range of different carbon sources (primarily sugars and amino acids) rapidly in both the insect vector and vertebrate host. Indeed, recent gene deletion studies suggest that mammal-infective stages are dependent on multiple carbon sources in vivo. The application of metabolomic approaches, outlined here, are likely to be important in defining aspects of central carbon metabolism that are essential at different stages of mammalian host infection.
Oligodendrogliomas respond to nitrosourea-based chemotherapy and are induced in rats following transplacental exposure to ethylnitrosourea, observations suggesting that neoplastic and normal cells of the oligodendrocyte lineage are “sensitive” to nitrosoureas. Nitrosoureas alkylate DNA at O6-guanine with repair mediated by O6-methyIguanine-DNA methyltransferase (MGMT). The cytotoxic and carcinogenic properties of the nitrosoureas appear related to MGMT activity.
To explore why oligodendrogliomas respond to chemotherapy, we measured MGMT activity in five chemosensitive human oligodendrogliomas and in rat oligodendrocyte lineage cells. We also measured MGMT activity in rat astrocytes and compared the cytotoxic effects of carmustine (BCNU) on oligodendrocyte lineage cells and astrocytes.
Low levels of MGMT activity were found in five of five human oligodendrogliomas. Cultures of neonatal rat glia enriched for oligodendrocyte lineage cells also had low levels of MGMT activity, approximately one-third that found in astrocytes (p < 0.02), and oligodendrocyte lineage cells were more sensitive to BCNU than astrocytes.
Low MGMT activity may contribute to the chemosensitivity of some human oligodendrogliomas and rat oligodendrocyte lineage cells also have low levels. If drug resistance mechanisms in tumors reflect the biochemical properties of their cells of origin, then normal glia may serve as a laboratory substitute for human glioma.
La masse de la colonne vertébrale lombaire ainsi que la masse osseuse totale ont été déterminées chez 119 hommes et femmes âgés en bonne santé par la technique d'absorptiométrie bi-photonique. Le taux de perte du contenu minéral de la colonne vertébrale lombaire est le même chez l'homme âgé et chez la femme âgée, et n'est, sans doute, pas différent du taux accepté pour les jeunes adultes. Chez les femmes âgées, nous avons mesuré une perte annuelle significative de 24 g du contenu minéral osseux du squelette. Le plus important indice de prédiction de la masse osseuse est le poids de la personne. Des variables représentant la santé physique ou la force, seule la force du bras contribue à la variation de la masse osseuse, étant responsable de 4 pour cent de la variation dans la densité du minéral osseux de la colonne vertébrale lombaire de la femme.
Much attention has been devoted to the classification of the behaviour disorders of childhood, and various authors have identified what they consider to be clinically homogeneous groups. The alternative to a clinical approach to classification is a multivariate approach in an attempt to identify more scientifically the main dimensions underlying the wide range of behaviour disorders that occur in children. A model for a multivariate classification was pioneered by Hewitt and Jenkins (1946), who delineated three behaviour syndromes:
(b)unsocialized aggressive behaviour;
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