Neutron Scattering Study of Crystal Field Energy Levels and Field Dependence of the Magnetic Order in Superconducting HoNi2B2C

Elastic and inelastic neutron scattering measurements have been carried out to investigate the magnetic properties of superconducting (Tc~8K) HoNi2B2C. The inelastic measurements reveal that the lowest two crystal field transitions out of the ground state occurat 11.28(3) and 16.00(2) meV, while the transition of 4.70(9) meV between these two levels is observed at elevated temperatures. The temperature dependence of the intensities of these transitions is consistent with both the ground state and these higher levels being magnetic doublets. The system becomes magnetically long range ordered below 8K, and since this ordering energy kTN ~ 0.69meV << 11.28meV the magnetic properties in the ordered phase are dominated by the ground-state spin dynamics only. The low temperature structure, which coexists with superconductivity, consists of ferromagnetic sheets of Ho{3+ moments in the a-b plane, with the sheets coupled antiferromagnetically along the c-axis. The magnetic state that initially forms on cooling, however, is dominated by an incommensurate spiral antiferromagnetic state along the c-axis, with wave vector qc ~0.054 A-1, in which these ferromagnetic sheets are canted from their low temperature antiparallel configuration by ~17 deg. The intensity for this spiral state reaches a maximum near the reentrant superconducting transition at ~5K; the spiral state then collapses at lower temperature in favor of the commensurate antiferromagnetic state. We have investigated the field dependence of the magnetic order at and above this reentrant superconducting transition. Initially the field rotates the powder particles to align the a-b plane along the field direction, demonstrating that the moments strongly prefer to lie within this plane due to the crystal field anisotropy. Upon subsequently increasing the field atComment: RevTex, 7 pages, 11 figures (available upon request); Physica

Modification of forests by people means only 40% of remaining forests have high ecosystem integrity

Many global environmental agendas, including halting biodiversity loss, reversing land degradation, and limiting climate change, depend upon retaining forests with high ecological integrity, yet the scale and degree of forest modification remain poorly quantified and mapped. By integrating data on observed and inferred human pressures and an index of lost connectivity, we generate a globally consistent, continuous index of forest condition as determined by the degree of anthropogenic modification. Globally, only 17.4 million km2 of forest (40.5%) has high landscape-level integrity (mostly found in Canada, Russia, the Amazon, Central Africa, and New Guinea) and only 27% of this area is found in nationally designated protected areas. Of the forest inside protected areas, only 56% has high landscape-level integrity. Ambitious policies that prioritize the retention of forest integrity, especially in the most intact areas, are now urgently needed alongside current efforts aimed at halting deforestation and restoring the integrity of forests globally

The metabolism and toxicology of strontium-90 in the rat : rationale, experimental procedures, pilot experiments /

"Contract W-7401-eng-49 between the U.S. Atomic Energy Commission and the University of Rochester, administered by the Department of Radiation Biology of the School of Medicine and Dentistry.""Date completed: 9/1/59 ; Date of Issue: 9/23/59.""UR-424 ; Biology and Medicine ; TID-4500, (14th Ed.)."Includes bibliographical references (page 12).Mode of access: Internet

The Style Consistency of Hedge Funds

"This study examines the style classification and the style consistency of hedge funds using a new proprietary database over the period May 1989 to April 1999. First, a hard clustering procedure is applied to classify hedge funds into homogeneous groups. It is shown that the methodology is robust and can be used to build stable hedge funds indexes. The method performs equally well as the principal component analysis in explaining in- and out-of-sample cross-sectional hedge funds' returns. Second, we extend hard to fuzzy cluster memberships, relaxing the full assignment of the funds to individual clusters. We apply the fuzzy clustering methodology to estimate hedge funds' probabilistic exposure to various styles. We introduce three consistency indicators to quantify the hedge fund managers' style opportunism levels. We finally document that there is no evidence that style consistency leads to superior hedge funds' performance." Copyright 2007 The Authors Journal compilation (c) 2007 Blackwell Publishing Ltd.