The implications of resonant x-ray scattering data on the physics of the insulating phase of V_2O_3

We have performed a quantitative analysis of recent resonant x-ray scattering experiments carried out in the antiferromagnetic phase of V_2O_3 by means of numerical ab-initio simulations. In order to treat magnetic effects, we have developed a method based on multiple scattering theory (MST) and a relativistic extension of the Schr\"{o}dinger Equation, thereby working with the usual non relativistic set of quantum numbers $l,m,\sigma$ for angular and spin momenta. Electric dipole-dipole (E1-E1), dipole-quadrupole (E1-E2) and quadrupole-quadrupole (E2-E2) transition were considered altogether. We obtain satisfactory agreement with experiments, both in energy and azimuthal scans. All the main features of the V K edge Bragg-forbidden reflections with $h+k+l=$odd can be interpreted in terms of the antiferromagnetic ordering only, {\it ie}, they are of magnetic origin. In particular the ab-initio simulation of the energy scan around the (1,1,1)-monoclinic reflection excludes the possibility of any symmetry reduction due to a time-reversal breaking induced by orbital ordering.Comment: 11 pages, 6 figure

Spin-1 effective Hamiltonian with three degenerate orbitals: An application to the case of V_2O_3

Motivated by recent neutron and x-ray observations in V_2O_3, we derive the effective Hamiltonian in the strong coupling limit of an Hubbard model with three degenerate t_{2g} states containing two electrons coupled to spin S = 1, and use it to re-examine the low-temperature ground-state properties of this compound. An axial trigonal distortion of the cubic states is also taken into account. Since there are no assumptions about the symmetry properties of the hopping integrals involved, the resulting spin-orbital Hamiltonian can be generally applied to any crystallographic configuration of the transition metal ion giving rise to degenerate t_{2g} orbitals. Specializing to the case of V_2O_3 we consider the antiferromagnetic insulating phase. We find two variational regimes, depending on the relative size of the correlation energy of the vertical pairs and the in-plane interaction energy. The former favors the formation of stable molecules throughout the crystal, while the latter tends to break this correlated state. We determine in both cases the minimizing orbital solutions for various spin configurations, and draw the corresponding phase diagrams. We find that none of the symmetry-breaking stable phases with the real spin structure presents an orbital ordering compatible with the magnetic space group indicated by very recent observations of non-reciprocal x-ray gyrotropy in V_2O_3. We do however find a compatible solution with very small excitation energy in two distinct regions of the phase space, which might turn into the true ground state of V_2O_3 due to the favorable coupling with the lattice. We illustrate merits and drawbacks of the various solutions and discuss them in relation to the present experimental evidence.Comment: 36 pages, 19 figure

Variational study of the antiferromagnetic insulating phase of V2O3 based on Nth order Muffin-Tin-Orbitals

Motivated by recent results of $N$th order muffin-tin orbital (NMTO) implementation of the density functional theory (DFT), we re-examine low-temperature ground-state properties of the anti-ferromagnetic insulating phase of vanadium sesquioxide V$_2$O$_3$. The hopping matrix elements obtained by the NMTO-downfolding procedure differ significantly from those previously obtained in electronic structure calculations and imply that the in-plane hopping integrals are as important as the out-of-plane ones. We use the NMTO hopping matrix elements as input and perform a variational study of the ground state. We show that the formation of stable molecules throughout the crystal is not favorable in this case and that the experimentally observed magnetic structure can still be obtained in the atomic variational regime. However the resulting ground state (two $t_{2g}$ electrons occupying the degenerate $e_g$ doublet) is in contrast with many well established experimental observations. We discuss the implications of this finding in the light of the non-local electronic correlations certainly present in this compound.Comment: 7 pages, 2 figure

Should the General Practitioner Consider Mesotherapy (Intradermal Therapy) to Manage Localized Pain?

Wide variations in the types of pain and response to analgesic pharmacotherapy mean that a variety of treatment strategies are needed. One approach is mesotherapy (intradermal therapy). This consists of microinjections into the skin and is ideally suited to the management of localized pain. Advantages include increasing the duration of drug activity, reduced risk of adverse events and interactions, and possible synergy with other therapies. Mesotherapy provides general practitioners with another tool for the treatment of local pain. However, it is important to provide patients with full details of the pros and cons of this approach and obtain informed patient consent

Correlated Component Analysis for diffuse component separation with error estimation on simulated Planck polarization data

We present a data analysis pipeline for CMB polarization experiments, running from multi-frequency maps to the power spectra. We focus mainly on component separation and, for the first time, we work out the covariance matrix accounting for errors associated to the separation itself. This allows us to propagate such errors and evaluate their contributions to the uncertainties on the final products.The pipeline is optimized for intermediate and small scales, but could be easily extended to lower multipoles. We exploit realistic simulations of the sky, tailored for the Planck mission. The component separation is achieved by exploiting the Correlated Component Analysis in the harmonic domain, that we demonstrate to be superior to the real-space application (Bonaldi et al. 2006). We present two techniques to estimate the uncertainties on the spectral parameters of the separated components. The component separation errors are then propagated by means of Monte Carlo simulations to obtain the corresponding contributions to uncertainties on the component maps and on the CMB power spectra. For the Planck polarization case they are found to be subdominant compared to noise.Comment: 17 pages, accepted in MNRA

The challenge of perioperative pain management in opioid-tolerant patients

The increasing number of opioid users among chronic pain patients, and opioid abusers among the general population, makes perioperative pain management challenging for health care professionals. Anesthesiologists, surgeons, and nurses should be familiar with some pharmacological phenomena which are typical of opioid users and abusers, such as tolerance, physical dependence, hyperalgesia, and addiction. Inadequate pain management is very common in these patients, due to common prejudices and fears. The target of preoperative evaluation is to identify comorbidities and risk factors and recognize signs and symptoms of opioid abuse and opioid withdrawal. Clinicians are encouraged to plan perioperative pain medications and to refer these patients to psychiatrists and addiction specialists for their evaluation. The aim of this review was to give practical suggestions for perioperative management of surgical opioid-tolerant patients, together with schemes of opioid conversion for chronic pain patients assuming oral or transdermal opioids, and patients under maintenance programs with methadone, buprenorphine, or naltrexone

"Post-Nollan" land use planning : how communities are coping with the recent Supreme Court decision

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1988.Includes bibliographical references.by Nancy Schuster Natoli.M.C.P

Thermal Approaches to Interpret Laser Damage Experiments

International audienc

Elevated aggression is associated with uncertainty in a network of dog dominance interactions

This is the author accepted manuscript. The final version is available from The Royal Society via the DOI in this record.Dominance hierarchies are widespread in animal societies and reduce the costs of within group conflict over resources and reproduction. Variation in stability across a social hierarchy may result in asymmetries in the benefits obtained from hierarchy formation. However, variation in the stability and behavioural costs of dominance interactions with rank remain poorly understood. Previous theoretical models have predicted that the intensity of dominance interactions and aggression should increase with rank, but these models typically assume high reproductive skew, and so their generality remains untested. Here we show in a pack of free-living dogs with a sex-age graded hierarchy that the central region of the hierarchy was dominated by more unstable social relationships and associated with elevated aggression. Our results reveal unavoidable costs of ascending a dominance hierarchy, run contrary to theoretical predictions for the relationship between aggression and social rank in high skew societies, and widen our understanding of how heterogeneous benefits of hierarchy formation arise in animal societies.Natural Environment Research Council (NERC

Low genetic diversity after a bottleneck in a population of a critically endangered migratory marine turtle species

Hawksbill turtles (Eretmochelys imbricata), which are distributed throughout the world's oceans, have undergone drastic declines across their range, largely due to anthropogenic factors. Assessing sizes, genetic variability and structure of their populations at global and regional levels is critical to the development of conservation management strategies. Here, nuclear and mitochondrial markers were used to analyse patterns of parentage and population structure in hawksbill turtles in United Arab Emirates (UAE) waters, utilizing samples from two life stages (hatchlings and juveniles), and to compare the UAE population with neighboring populations. Weak genetic differentiation was detected between juveniles and hatchlings and between the nesting sites of Dubai and Sir Bu Nair. Parentage analysis suggested that only 53 females and 74–80 males contributed to the hatchlings from 67 nests across three nesting sites in UAE (Dubai, Sir Bu Nair, Abu Dhabi). No females were identified as nesting in more than one location. In Dubai and Abu Dhabi, single paternity was the norm (75%), whereas on Sir Bu Nair, multiple paternity was detected in the majority of nests (67%). Polygyny was also frequently detected on Sir Bu Nair (15% of the overall number of males), but not in the other nesting sites. Comparison of the UAE population with published data from other populations suggests that population structure exists both within the Gulf and between the Gulf and Indian Ocean populations, and that the UAE population has lower genetic variability than the Seychelles population. Finally, the data suggest that the UAE population, and the Gulf population overall, experienced a bottleneck/founder event. The observed overall low genetic variability, evidence of population structure in the Gulf, and strong differentiation between the Gulf and the Indian Ocean populations, raises concerns about the sustainability of this species in this near-enclosed basin. These results highlight the need for regional collaboration in the development of management measures for the long-term conservation of this Critically Endangered specie