The hard scale in the exclusive rho-meson production in diffractive DIS

We re-examine the issue of the pQCD factorization scale in the exclusive rho production in diffractive DIS from the k_t-factorization point of view. We find that this scale differs significantly from, and possesses much flatter Q^2 behavior than widely used value (Q^2 + m_\rho^2)/4. With these results in mind, we discuss the Q^2 shape of the rho meson production cross section. We introduce rescaled cross sections, which might provide further insight into the dynamics of rho production. We also comment on the recent ZEUS observation of energy-independent ratio sigma(gamma* p --> rho p) / sigma_{tot}(gamma*p).Comment: 14 pages, 7 eps figure

Hysteresis Switching Loops in Ag-manganite memristive interfaces

Multilevel resistance states in silver-manganite interfaces are studied both experimentally and through a realistic model that includes as a main ingredient the oxygen vacancies diffusion under applied electric fields. The switching threshold and amplitude studied through Hysteresis Switching Loops are found to depend critically on the initial state. The associated vacancy profiles further unveil the prominent role of the effective electric field acting at the interfaces. While experimental results validate main assumptions of the model, the simulations allow to disentangle the microscopic mechanisms behind the resistive switching in metal-transition metal oxide interfaces.Comment: 14 pages, 3 figures, to be published in Jour. of Appl. Phy

C019 Protéine C activ ée et glucocorticoïdes sont synergiques dans le choc septique expérimental

IntroductionLa Protéine C Activée (PCa) et les glucocorticoïdes sont recommandés dans le traitement du choc septique. Le but de notre étude est de comparer dans deux modèles de choc expérimentaux les effets de la dexaméthasone (glucocorticoïde de référence chez le rat) (Dexa) et de la PCa, seuls ou en association.Matériels et MéthodesDeux modèles de choc chez le rat Wistar : LPS sédaté (10mg/kg) ou CLP chroniquement perfusé + antibiothérapie plus expansion volémique continue (10ml/kg/h) 4 heures après la chirurgie.Traitements et groupes : Sham LPS ou CLP, Dexa [(1mg/kg IV bolus (LPS) ou 2mg/kg/24h IV continue (CLP)], PCa : Xigris, 33 μg/kg/h, PCa + D exa (PCaD)Mesures : PAM, Fc, débit aortique, laser-doppler et PO2 musculaire, lactates, vasoréactivité à la noradrénaline, TNF, NOx et prélèvements tissulaires pour études des voies de signalisation (MAPk, ERK1/2, iNOS, eNOS, glucocorticoïde receptor, ..).Résultats+/- = p<0.05vs LPS/CLP ++/-- = p<0.05vs autres groupesDans le groupe LPS, le débit et la PO2 musculaire sont améliorés par PCa+Dexa. La vasoréactivité diminuée par le sepsis est améliorée par tous les traitements sans différence entre les groupes.ConclusionDans les deux modèles, la combinaison PCa+Dexa est associé à une amélioration marquée des paramètres hémodynamiques et de perfusion tissulaire, une baisse importante des lactates ainsi qu’une amélioration de la survie. L’étude des voies de signalisation à venir devrait nous permettre de mieux préciser les mécanismes en cause

Patient Perceptions of In Vivo Versus Virtual Reality Exposures for the Treatment of Anxiety Disorders: Cross-Sectional Survey Study

BACKGROUND Psychotherapy, and particularly exposure therapy, has been proven to be an effective treatment for many anxiety disorders, including social and specific phobias, as well as posttraumatic stress disorders. Currently, exposures are underused and mostly delivered in vivo. Virtual reality exposure therapy (VRET) offers a more flexible delivery mechanism that has the potential to address some of the implementation barriers of in vivo exposures while retaining effectiveness. Yet, there is little evidence on how patients perceive different exposure therapy methods. OBJECTIVE This study aims to explore the perceptions of individuals with anxiety disorders toward in vivo and VRET. Our findings can inform therapists about the degree of patient interest in both methods while exploring the demand for VRET as an alternative and novel treatment approach. METHODS Web-based survey assessing the (1) interest in, (2) willingness to use, (3) comfort with, (4) enthusiasm toward, and (5) perceived effectiveness of exposure therapy when delivered in vivo and through VR. Participants included individuals with specific phobia, social phobia, posttraumatic stress disorder, or acute stress disorder or reaction. Participants were presented with educational videos about in vivo and VRET and asked to provide their perceptions quantitatively and qualitatively through a rated scale and free-text responses. RESULTS In total, 184 surveys were completed and analyzed, in which 82% (n=151) of participants reported being willing to receive in vivo exposures and 90.2% (n=166) reported willingness to receive VRET. Participants reported higher interest in, comfort with, enthusiasm toward, and perceived effectiveness of VRET compared to in vivo. Most reported in vivo concerns were linked to (1) increased anxiety, (2) feelings of embarrassment or shame, and (3) exacerbation of current condition. Most reported VRET concerns were linked to (1) risk of side effects including increased anxiety, (2) efficacy uncertainty, and (3) health insurance coverage. The most frequently mentioned VRET benefits include (1) privacy, (2) safety, (3) the ability to control exposures, (4) comfort, (5) the absence of real-life consequences, (6) effectiveness, and (7) customizability to a wider variety of exposures. CONCLUSIONS On average, our participants expressed positive perceptions toward exposure therapy, with slightly more positive perceptions of VRET over in vivo exposures. Despite valid personal concerns and some misconceptions, our findings emphasize that VRET provides an opportunity to get much-needed therapy to patients in ways that are more acceptable and less concerning

Does Giant Magnetoresistance Survive in Presence of Superconducting Contact?

The giant magnetoresistance (GMR) of ferromagnetic bilayers with a superconducting contact (F1/F2/S) is calculated in ballistic and diffusive regimes. As in spin-valve, it is assumed that the magnetization in the two ferromagnetic layers F1 and F2 can be changed from parallel to antiparallel. It is shown that the GMR defined as the change of conductance between the two magnetic configurations is an oscillatory function of the thickness of F2 layer and tends to an asymptotic positive value at large thickness. This is due to the formation of quantum well states in F2 induced by Andreev reflection at the F2/S interface and reflection at F1/F2 interface in antiparallel configuration. In the diffusive regime, if only spin-dependent scattering rates in the magnetic layers are considered (no difference in Fermi wave-vectors between spin up and down electrons) then the GMR is supressed due to the mixing of spin up and down electron-hole channels by Andreev reflection.Comment: 7 pages, 4 figures, submitted to Phys.Rev.Let

Universal features of electron-phonon interactions in atomic wires

The effect of electron-phonon interactions in the conductance through metallic atomic wires is theoretically analyzed. The proposed model allows to consider an atomic size region electrically and mechanically coupled to bulk electrodes. We show that under rather general conditions the features due to electron-phonon coupling are described by universal functions of the system transmission coefficients. It is predicted that the reduction of the conductance due to electron-phonon coupling which is observed close to perfect transmission should evolve into an enhancement at low transmission. This crossover can be understood in a transparent way as arising from the competition between elastic and inelastic processes.Comment: 5 pages, 5 figure

Vascular hyporesponsiveness to vasopressors in septic shock: from bench to bedside

PurposeTo delineate some of the characteristics of septic vascular hypotension, to assess the most commonly cited and reported underlying mechanisms of vascular hyporesponsiveness to vasoconstrictors in sepsis, and to briefly outline current therapeutic strategies and possible future approaches. Methods Source data were obtained from a PubMed search of the medical literature with the following MeSH terms: Muscle, smooth, vascular/physiopathology; hypotension/etiology; shock/physiopathology; vasodilation/physiology; shock/therapy; vasoconstrictor agents. Results Nitric oxide (NO) and peroxynitrite are crucial components implicated in vasoplegia and vascular hyporeactivity. Vascular ATP-sensitive and calcium-activated potassium channels are activated during shock and participate in hypotension. In addition, shock state is characterized by inappropriately low plasma glucocorticoid and vasopressin concentrations, a dysfunction and desensitization of alpha-receptors, and an inactivation of catecholamines by oxidation. Numerous other mechanisms have been individualized in animal models, the great majority of which involve NO: MEK1/2–ERK1/2 pathway, H2S, hyperglycemia, and cytoskeleton dysregulation associated with decreased actin expression. Conclusions Many therapeutic approaches have proven their efficiency in animal models, especially therapies directed against one particular compound, but have otherwise failed when used in human shock. Nevertheless, high doses of catecholamines, vasopressin and terlipressin, hydrocortisone, activated protein C, and non-specific shock treatment have demonstrated a partial efficiency in reversing sepsis-induced hypotension

Volatility clustering and scaling for financial time series due to attractor bubbling

A microscopic model of financial markets is considered, consisting of many interacting agents (spins) with global coupling and discrete-time thermal bath dynamics, similar to random Ising systems. The interactions between agents change randomly in time. In the thermodynamic limit the obtained time series of price returns show chaotic bursts resulting from the emergence of attractor bubbling or on-off intermittency, resembling the empirical financial time series with volatility clustering. For a proper choice of the model parameters the probability distributions of returns exhibit power-law tails with scaling exponents close to the empirical ones.Comment: For related publications see http://www.helbing.or

Na2IrO3 as a spin-orbit-assisted antiferromagnetic insulator with a 340 meV gap

We study Na2IrO3 by ARPES, optics, and band structure calculations in the local-density approximation (LDA). The weak dispersion of the Ir 5d-t2g manifold highlights the importance of structural distortions and spin-orbit coupling (SO) in driving the system closer to a Mott transition. We detect an insulating gap {\Delta}_gap = 340 meV which, at variance with a Slater-type description, is already open at 300 K and does not show significant temperature dependence even across T_N ~ 15 K. An LDA analysis with the inclusion of SO and Coulomb repulsion U reveals that, while the prodromes of an underlying insulating state are already found in LDA+SO, the correct gap magnitude can only be reproduced by LDA+SO+U, with U = 3 eV. This establishes Na2IrO3 as a novel type of Mott-like correlated insulator in which Coulomb and relativistic effects have to be treated on an equal footing.Comment: Accepted in Physical Review Letters. Auxiliary and related material can be found at: http://www.phas.ubc.ca/~quantmat/ARPES/PUBLICATIONS/articles.htm