Spin-transfer-driven nano-oscillators are equivalent to parametric resonators

The equivalence between different physical systems permits us to transfer knowledge between them and to characterize the universal nature of their dynamics. We demonstrate that a nanopillar driven by a spin-transfer torque is equivalent to a rotating magnetic plate, which permits us to consider the nanopillar as a macroscopic system under a time-modulated injection of energy, that is, a simple parametric resonator. This equivalence allows us to characterize the phases diagram and to predict magnetic states and dynamical behaviors, such as solitons, stationary textures, and oscillatory localized states, among others. Numerical simulations confirm these predictions.Comment: 8 pages, 7 figure

To be or not to be in monetary union: A synthesis

Monetary union can benefit countries suffering from policy credibility problems if it eliminates the inflation bias and also allows for more efficient management of certain shocks. But it also carries costs as some stabilization may be feasible even in the absence of credibility, and this may be more than what an individual country can hope for in a monetary union. In this paper, we combine the stabilization and credibility branches of the currency union literature and construct a simple welfare criterion that can be used to evaluate alternative monetary arrangements. We produce examples where monetary union may be welfare improving even for low-modest levels of inflation bias (2-3%) as long as business cycles are not too a-synchronized across countries.Currency union, credibility, stabilization, inflation bias.

Consommation d'alcool, syndrome métabolique et diabète dans une population à consommation moyenne d'alcool élevée

ButsDans la littérature actuelle, peu d'études existent sur la relation entre la consommation d'alcool et le syndrome métabolique. Les quelques données disponibles sont contradictoires et très limitées chez les buveurs à haut risque. Quant au diabète, une association est connue entre la consommation à bas risque d'alcool et une prévalence diminuée de la maladie. Là encore, les données sur la consommation à haut risque sont très limitées. Par conséquent, notre but était d'étudier la relation entre la consommation d'alcool, le syndrome métabolique et le diabète dans la cohorte lausannoise (CoLaus), où la consommation moyenne d'alcool est nettement plus élevée que dans la plupart des études disponibles, notamment celles des États-Unis.MéthodesNous avons analysé les données de 6172 hommes et femmes, âgés de 35 à 75 ans. La consommation d'alcool a été catégorisée en 0,1-6, 7-13, 14-20, 21-27, 28-34 et >35 boissons par semaine ou comme non-buveurs (0), buveurs à bas risque (1-13), à risque moyen à élevé (14-34) et à très haut risque (>35). Nous avons confirmé la consommation d'alcool par la y- glutamyl transferase et la transferrine déficiente en hydrates de carbone (CDT). Après l'analyse des caractéristiques des groupes de consommateurs, nous avons utilisé des régressions multivariées pour évaluer la relation entre la consommation d'alcool, la prévalence du syndrome métabolique et du diabète ainsi que la résistance à l'insuline, déterminée par le modèle d'homéostasie de la résistance à l'insuline (HOMA-IR). Dans le modèle d'ajustement, nous avons inclus l'âge, le genre, le status tabagique, l'activité physique et le niveau de formation. Nous avons aussi comparé la relation du type d'alcool (vin, bière et spiritueux) avec le syndrome métabolique, le diabète et le HOMA-IR en testant l'hypothèse d'égalité de leurs coefficients de régression, après ajustement.RésultatsParmi les participants, 73% buvaient de l'alcool, 16% étant buveurs à risque moyen à élevé et 2% à risque très élevé. En analyse multivariée, la prévalence du syndrome métabolique et du diabète ainsi que le HOMA-IR moyen diminuaient avec la consommation d'alcool à bas risque et augmentaient avec la consommation à très haut risque, montrant une relation en U. La prévalence ajustée du syndrome métabolique était de 24% chez les non-buveurs, 19% chez les buveurs à bas risque (p<0.001 vs. non-buveurs), 20% chez ceux à risque moyen à élevé et 29% chez ceux à très haut risque (p=0.005 vs. bas risque). La prévalence ajustée du diabète était de 6.0% chez les non-buveurs, 3.6% chez les buveurs à bas risque (p<0.001 vs. non-buveurs), 3.8% chez ceux à risque moyen à élevé et 6.7% chez ceux à très haut risque (p=0.046 vs. bas risque). Le HOMA-IR moyen ajusté était de 2.47 chez les non-buveurs, 2.14 chez ceux à bas risque (pcO.OOl vs. non-buveurs), 2.27 chez ceux à risque moyen à élevé et 2.53 chez ceux à très haut risque (p=0.04 vs. bas risque). Ces relations ne différaient pas selon les types de boissons.ConclusionsLa prévalence du syndrome métabolique, du diabète et le HOMA-IR baissent pour les faibles consommations d'alcool, mais augmentent à nouveau avec les plus fortes consommations, sans différence entre les types de boissons

The future of monetary policy Summary of the conference held in Rome on 30 September and 1 October 2010.

The recent economic and financial crisis does not call for a change in monetary policy strategy, but rather better integration of financial conditions and financial-crisis risks in the implementation of this strategy: this appears to be the main conclusion of a conference organised by the Banque de France, the Banca d’Italia and the Einaudi Institute.asset price bubbles, financial crisis, interbank market, macroprudential policy, monetary policy.

X-ray AGN in the XMM-LSS galaxy clusters: no evidence of AGN suppression

We present a study of the overdensity of X-ray selected AGN in 33 galaxy clusters in the XMM-LSS field, up to redhift z=1.05. Previous studies have shown that the presence of X-ray selected AGN in rich galaxy clusters is suppressed. In the current study we investigate the occurrence of X-ray selected AGN in low and moderate X-ray luminosity galaxy clusters. Due to the wide contiguous XMM-LSS survey area we are able to extend the study to the cluster outskirts. We therefore determine the projected overdensity of X-ray point-like sources out to 6r_{500} radius. To provide robust statistical results we also use a stacking analysis of the cluster projected overdensities. We investigate whether the observed X-ray overdensities are to be expected by estimating also the corresponding optical galaxy overdensities. We find a positive X-ray projected overdensity at the first radial bin, which is however of the same amplitude as that of optical galaxies. Therefore, no suppression of X-ray AGN activity with respect to the field is found, implying that the mechanisms responsible for the suppression are not so effective in lower density environments. After a drop to roughly the background level between 2 and 3r_{500}, the X-ray overdensity exhibits a rise at larger radii, significantly larger than the corresponding optical overdensity. Finally, using redshift information of all optical counterparts, we derive the spatial overdensity profile of the clusters. We find that the agreement between X-ray and optical overdensities in the first radial bin is also suggested in the 3-dimensional analysis. However, we argue that the X-ray overdensity "bump" at larger radial distance is probably a result of flux boosting by gravitational lensing of background QSOs. For high redshift clusters an enhancement of X-ray AGN activity in their outskirts is still possible.Comment: 16 pages. Accepted for publication in A&

Le futur de la politique monétaire : synthèse de la conférence tenue à Rome le 30 septembre et le 1er octobre 2010.

La récente crise économique et fi nancière appelle non pas une modification de la stratégie de politique monétaire, mais une meilleure prise en compte des conditions financières et du risque de crise fi nancière dans la mise en oeuvre de cette stratégie : telle semble être la principale conclusion d’un colloque organisé par la Banque de France, la Banque d’Italie et l’institut Einaudi.Bulles de prix d’actif, crise financière, marché interbancaire, politique macroprudentielle, politique monétaire.

Adult native septic arthritis: a review of 10 years of experience and lessons for empirical antibiotic therapy.

Objectives To review the epidemiology of native septic arthritis to establish local guidelines for empirical antibiotic therapy as part of an antibiotic stewardship programme. Methods We conducted a 10 year retrospective study based on positive synovial fluid cultures and discharge diagnosis of septic arthritis in adult patients. Microbiology results and medical records were reviewed. Results Between 1999 and 2008, we identified 233 episodes of septic arthritis. The predominant causative pathogens were methicillin-susceptible Staphylococcus aureus (MSSA) and streptococci (respectively, 44.6% and 14.2% of cases). Only 11 cases (4.7%) of methicillin-resistant S. aureus (MRSA) arthritis were diagnosed, among which 5 (45.5%) occurred in known carriers. For large-joint infections, amoxicillin/clavulanate or cefuroxime would have been appropriate in 84.5% of cases. MRSA and Mycobacterium tuberculosis would have been the most frequent pathogens that would not have been covered. In contrast, amoxicillin/clavulanate would have been appropriate for only 75.3% of small-joint infections (82.6% if diabetics are excluded). MRSA and Pseudomonas aeruginosa would have been the main pathogens not covered. Piperacillin/tazobactam would have been appropriate in 93.8% of cases (P < 0.01 versus amoxicillin/clavulanate). This statistically significant advantage is lost after exclusion of diabetics (P = 0.19). Conclusions Amoxicillin/clavulanate or cefuroxime would be adequate for empirical coverage of large-joint septic arthritis in our area. A broad-spectrum antibiotic would be significantly superior for small-joint infections in diabetics. Systematic coverage of MRSA is not justified, but should be considered for known carriers. These recommendations are applicable to our local setting. They might also apply to hospitals sharing the same epidemiology

Impact of Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry on the Clinical Management of Patients With Gram-negative Bacteremia: A Prospective Observational Study.

Background. Early identification of pathogens from blood cultures using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry may optimize the choice of empirical antibiotic therapy in the setting of bloodstream infections. We aimed to assess the impact of this new technology on the use of antibiotic treatment in patients with gram-negative bacteremia. Methods. We conducted a prospective observational study from January to December 2010 to evaluate the sequential and separate impacts of Gram stain reporting and MALDI-TOF bacterial identification performed on blood culture pellets in patients with gram-negative bacteremia. The primary outcome was the impact of MALDI-TOF on empirical antibiotic choice. Results. Among 202 episodes of gram-negative bacteremia, Gram stain reporting had an impact in 42 cases (20.8%). MALDI-TOF identification led to a modification of empirical therapy in 71 of all 202 cases (35.1%), and in 16 of 27 cases (59.3%) of monomicrobial bacteremia caused by AmpC-producing Enterobacteriaceae. The most frequently observed impact was an early appropriate broadening of the antibiotic spectrum in 31 of 71 cases (43.7%). In total, 143 of 165 episodes (86.7%) of monomicrobial bacteremia were correctly identified at genus level by MALDI-TOF. Conclusions. In a low prevalence area for extended spectrum betalactamases (ESBL) and multiresistant gram-negative bacteria, MALDI-TOF performed on blood culture pellets had an impact on the clinical management of 35.1% of all gram-negative bacteremia cases, demonstrating a greater impact than Gram stain reporting. Thus, MALDI-TOF could become a vital second step beside Gram stain in guiding the empirical treatment of patients with bloodstream infection

Admissions of patients with alcohol intoxication in the Emergency Department: a growing phenomenon.

QUESTION UNDER STUDY: To investigate the change over time in the number of ED admissions with positive blood alcohol concentration (BAC) and to evaluate predictors of BAC level. METHODS: We conducted a single site retrospective study at the ED of a tertiary referral hospital (western part of Switzerland) and obtained all the BAC performed from 2002 to 2011. We determined the proportion of ED admissions with positive BAC (number of positive BAC/number of admissions). Regression models assessed trends in the proportion of admissions with positive BAC and the predictors of BAC level among patients with positive BAC. RESULTS: A total of 319,489 admissions were recorded and 20,021 BAC tests were performed, of which 14,359 were positive, divided 34.5% female and 65.5% male. The mean (SD) age was 41.7(16.8), and the mean BAC was 2.12(1.04) permille (g of ethanol/liter of blood). An increase in the number of positive BAC was observed, from 756 in 2002 to 1,819 in 2011. The total number of admissions also increased but less: 1.2 versus 2.4 times more admissions with positive BAC. Being male was independently associated with a higher (+0.19 permille) BAC, as was each passing year (+0.03). A significant quadratic association with age indicated a maximum BAC at age 53. CONCLUSION: We observed an increase in the percentage of admissions with positive BAC that was not limited to younger individuals. Given the potential consequences of alcohol intoxication, and the large burden imposed on ED teams, communities should be encouraged to take measures aimed at reducing alcohol intoxication