Quantum Phase Transition in Pr2CuO4 to Collinear Spin State in Inclined Magnetic Field: A Neutron Diffraction Observation

In the external field slightly inclined to the $x$- or y-axis of the frustrated tetragonal atiferromagnet Pr2CuO4, a transition is discovered from the phase with orthogonal antiferromagnetic spin subsystems along [1,0,0] and [0,1,0] to the phase with the collinear spins. This phase is shown to be due to the pseudodipolar interaction, and transforms into the spin-flop phase S perp H asymptotically at very high field. The discovered phase transition holds at T=0 and is a quantum one, with the transition field being the critical point and the angle between two subsystems being the order parameter

A New Scenario on the Metal-Insulator Transition in VO2

The metal-insulator transition in VO2 was investigated using the three-band Hubbard model, in which the degeneracy of the 3d orbitals, the on-site Coulomb and exchange interactions, and the effects of lattice distortion were considered. A new scenario on the phase transition is proposed, where the increase in energy level separation among the t_2g orbitals caused by the lattice distortion triggers an abrupt change in the electronic configuration in doubly occupied sites from an S=1 Hund's coupling state to a spin S=0 state with much larger energy, and this strongly suppresses the charge fluctuation. Although the material is expected to be a Mott-Hubbard insulator in the insulating phase, the metal-to-insulator transition is not caused by an increase in relative strength of the Coulomb interaction against the electron hopping as in the usual Mott transition, but by the level splitting among the t_2g orbitals against the on-site exchange interaction. The metal-insulator transition in Ti2O3 can also be explained by the same scenario. Such a large change in the 3d orbital occupation at the phase transition can be detected by linear dichroic V 2p x-ray absorption measurements.Comment: 5 pages, 5 figures, to be published in J. Phys. Soc. Jpn. Vol. 72 No. 1

Depressed mood in a cohort of elderly medical inpatients: Prevalence, clinical correlates and recognition rate

The objectives of this prospective cohort study were to 1) determine the prevalence of depressed mood, 2) identify the characteristics associated with it, and 3) evaluate the recognition rate of depressed mood by clinicians. The study population was a cohort of 401 elderly patients, aged 75 years and older, admitted to the internal medicine service of a tertiary care academic medical center in Western Switzerland over six months. We excluded patients with severe cognitive impairment, terminal disease or those living in a nursing home. Data on demographics, medical, physical, social and mental status were collected upon admission. Presence of depressed mood was defined as a score ≥ 6 on the Geriatric Depression Scale (GDS), short form (15-item). An independent re-viewer performed a discharge summary abstraction to assess recognition rate. Subjects' mean age was 82.4 years, 60.9% were women. Overall, 90 patients (22.4%) had an abnormal GDS score (≥6). Compared to those without a depressed mood, these subjects were (all p<0.05) older (83.5 vs 82.0 years), more frequently living alone (66.7 vs 55.0%), dependent in both basic activities of daily living (BADL) and instrumental ADL (48.9 vs 36.0%, and 91.1 vs 84.9%, respectively), and cognitively impaired (47.8 vs 27.7% with MMSE score<24). In addition, they had more comorbidities (Charlson index 1.6 vs 1.2). In multivariate analysis, an independent association remains for subjects living alone (OR 1.8, 95%CI 1.1-3.0), with cognitive impairment (OR 1.9, 95%CI 1.1-3.2), and comorbidities (OR 1.3 per point, 95%CI 1.1-1.5). Detection rate during the index hospitalization was only 16.7% (15/90). In conclusion, depressed mood was frequent but rarely detected in this population. These findings emphasize the need to improve screening efforts, and to develop additional strategies such as using a pre-screening question to enhance clinical recognitio

Resonant inelastic x-ray scattering probes the electron-phonon coupling in the spin-liquid kappa-(BEDT-TTF)2Cu2(CN)3

Resonant inelastic x-ray scattering at the N K edge reveals clearly resolved harmonics of the anion plane vibrations in the kappa-(BEDT-TTF)2Cu2(CN)3 spin-liquid insulator. Tuning the incoming light energy at the K edge of two distinct N sites permits to excite different sets of phonon modes. Cyanide CN stretching mode is selected at the edge of the ordered N sites which are more strongly connected to the BEDT-TTF molecules, while positionally disordered N sites show multi-mode excitation. Combining measurements with calculations on an anion plane cluster permits to estimate the sitedependent electron-phonon coupling of the modes related to nitrogen excitation

Competing phases in the high field phase diagram of (TMTSF)2_2ClO4_4

A model is presented for the high field phase diagram of (TMTSF)$_2$ClO$_4$, taking into account the anion ordering, which splits the Fermi surface in two bands. For strong enough field, the largest metal-SDW critical temperature corresponds to the N=0 phase, which originates from two intraband nesting processes. At lower temperature, the competition between these processes puts at disadvantage the N=0 phase vs. the N=1 phase, which is due to interband nesting. A first order transition takes then place from the N=0 to N=1 phase. We ascribe to this effect the experimentally observed phase diagrams.Comment: 5 pages, 3 figures (to appear in Phys. Rev. Lett.

Environmental health risks perceptions: results from cross-sectional surveys in Southeastern France

International audienceBackground: Arsenic is a toxic metalloid element frequently found in the environment. Chronic arsenic exposure is a critical public health issue in many countries since the identification of arsenic and its compounds as human carcinogens by the World Health Organization. After absorption, inorganic arsenic (iAs) is mainly methylated into monomethylated and dimethylated compounds (MMA, DMA), which are then excreted through the kidney together with unmethylated iAs. Whether the methylation process is to detoxify or potentiate arsenic toxicity, however, remains an ongoing debate. The purpose of this systematic review was to conduct a comprehensive meta-analysis to estimate the association between arsenic exposure and urothelial cancer. Methods: 10 observational studies met the inclusion criteria and were included in the systematic review. IAs%, MMA% and DMA% were extracted from each paper. Weighted Mean Differences with 95% confidence intervals were defined according to Cases minus Controls. Pooled risk estimates from individual studies were assessed using random effects models. Meta-regression analysis was performed to estimate the extent of urothelial cancer risk as a function of iAs%, MMA% and DMA%. Results: Results showed as patients with urothelial cancer presented higher level of urinary iAs% (WMD 2.70, 95%CI 0.64-4.76), MMA% (WMD 2.81, 95%CI 1.43-4.20) and DMA% (WMD-3.44, 95%CI-6.57-0.30). Conclusions: These findings suggest that higher level of iAs% and MMA% and lower level of DMA% were associated with an increased risk of urothelial cancer. Additional population based studies are needed to understand the role of arsenic in cancer development. Understanding the meaning of arsenic metabolism could improve the risk assessment of arsenic toxicity and provide a potential tool for disease prediction and prevention. Key messages: Higher level of iAs%, MMA% and DMA% were associated with an increased risk of urothelial cancer. Understanding the meaning of arsenic metabolism could improve the risk assessment of arsenic toxicity. Background: Heatwaves can lead to increased mortality. Portugal has a Heat-Health Warning System (HHWS) in place (ÍCARO system). Researchers at the Instituto Ricardo Jorge send a daily report with heat-related mortality forecasts to key stakeholders (e.g. Heat-Health Action Plans (HHAP) staff). HHAP practitioners issue warnings and implement measures to prevent heatwaves-related mortality. ICARO is amongst the recommended data sources to assess risk and issue warnings but its use and understanding is unknown. Therefore, we aimed to assess ÍCARO's use and understanding by key HHAP practitioners. Methods: We conducted semi-structured interviews with national and regional HHAP practitioners. Interviews were recorded, transcribed, and analysed using thematic content analysis. Intercoder reliability was applied to a sample of segments from 5 of 6 interviews. Results: We conducted 6 interviews with 9 professionals (mean time 52 minutes). We identified 4 categories: Report's content and presentation, Report's reception and communication, ÍCARO and risk assessment, Other issues. Practitioners use ÍCARO and perceived it as very relevant tool. However, they mentioned several questions on its interpretation. Practitioners also felt their questions were not fully answered, given researchers' use of statistical terms. Finally, practitioners referred the need to assess risk at the local level, information not currently provided. We also identified the need for improved communication and report's clarity. Conclusions: Our study stresses the need for an integrated collaboration between experts within HHWS and HHAP. Despite ICARO's understanding being challenging, practitioners consider it a relevant tool. Researchers should use less statistical language and clarify ÍCARO interpretation. Practitioners' needs should be considered when developing or revising tools. We are currently implementing some of these recommendations in an attempt to close the gap between researchers and practitioners

Field-induced spin density wave in (TMTSF)2_2NO3_3

Interlayer magnetoresistance of the Bechgaard salt (TMTSF)$_2$NO$_3$ is investigated up to 50 teslas under pressures of a few kilobars. This compound, the Fermi surface of which is quasi two-dimensional at low temperature, is a semi metal under pressure. Nevertheless, a field-induced spin density wave is evidenced at 8.5 kbar above $\sim$ 20 T. This state is characterized by a drastically different spectrum of the quantum oscillations compared to the low pressure spin density wave state.Comment: to be published in Phys. Rev. B 71 (2005

Contributions of spontaneous phase slippage to linear and non-linear conduction near the Peierls transition in thin samples of o-TaS_3

In the Peierls state very thin samples of TaS_3 (cross-section area \sim 10^{-3} mkm^2) are found to demonstrate smearing of the I-V curves near the threshold field. With approaching the Peierls transition temperature, T_P, the smearing evolves into smooth growth of conductance from zero voltage interpreted by us as the contribution of fluctuations to the non--linear conductance. We identify independently the fluctuation contribution to the linear conductance near T_P. Both linear and non-linear contributions depend on temperature with close activation energies \sim (2 - 4) x 10^3 K and apparently reveal the same process. We reject creep of the {\it continuous} charge-density waves (CDWs) as the origin of this effect and show that it is spontaneous phase slippage that results in creep of the CDW. A model is proposed accounting for both the linear and non-linear parts of the fluctuation conduction up to T_P.Comment: 6 pages, 5 Postscript figure, RevTeX, accepted for publication in PR