On the Sobolev stability threshold for the 2D MHD equations with horizontal magnetic dissipation

In this article we consider the stability threshold of the 2D magnetohydrodynamics (MHD) equations near a combination of Couette flow and large constant magnetic field. We study the partial dissipation regime with full viscous and only horizontal magnetic dissipation. In particular, we show that this regime behaves qualitatively differently than both the fully dissipative and the non-resistive setting

On echoes in magnetohydrodynamics with magnetic dissipation

We study the long time asymptotic behavior of the inviscid magnetohydrodynamic equations with magnetic dissipation near a combination of Couette flow and a constant magnetic field. Here we show that there exist nearby explicit global in time low frequency solutions, which we call waves. Moreover, the linearized problem around these waves exhibits resonances under high frequency perturbations, called echoes, which result in norm inflation Gevrey regularity and infinite time blow-up in Sobolev regularity

On the Sobolev Stability Threshold for the 2D MHD Equations with Horizontal Magnetic Dissipation

In this article we consider the stability threshold of the 2D magnetohydrodynamics (MHD) equations near a combination of Couette flow and large constant magnetic field. We study the partial dissipation regime with full viscous and only horizontal magnetic dissipation. In particular, we show that this regime behaves qualitatively differently than both the fully dissipative and the non-resistive setting.Comment: 31 pages; comments welcom

Geometry and dimensions of the pulmonary artery bifurcation in children and adolescents: assessment in vivo by contrast-enhanced MR-angiography

We sought to establish normal values for the diameters of the main (MPA), right (RPA), and left (LPA) pulmonary arteries and for the angles describing the geometry of the pulmonary artery bifurcation in children by using contrast-enhanced magnetic resonance angiography (CE-MRA). CE-MRA was performed in 69 children without cardiovascular disease. The median age was 10±4.9years (range 2-20), weight 37.4±18.5kg (10-82), body surface area (BSA) 1.18±0.4m2 (0.48-2.07). The pulmonary artery diameters and angles were measured at standardized sites and projections. Regression analysis of diameters and angles in relation to BSA demonstrated linear relationship between the cross-sectional diameters of the pulmonary arteries and the square root of BSA (BSA0.5). Normalized mean diameters were for the MPA 17.6±5.1mm/m2, origin of RPA 13.1±2.9mm/m2, origin of LPA 14.2±2.9mm/m2. The MPA showed a mean antero-posterior inclination of 33°±8° and a lateral leftward angulation of 18°±5°. The mean angle of the bifurcation was 99.5°±10.3°. Both side branches showed a supero-inferior course of the proximal segments, steeper for the RPA (7.7°±6.5°) than for the LPA (2.1°±7.8°). Normative curves in relation to BSA are presented for all measurements. This study provides normative values by CE-MRA for the main pulmonary artery and its side branches in children during somatic growth. These data can be used for identifying pulmonary arteries anomalies in children, and evaluate the need and the modality for treatmen

The zCOSMOS 10k-Bright Spectroscopic Sample

We present spectroscopic redshifts of a large sample of galaxies with I_(AB) < 22.5 in the COSMOS field, measured from spectra of 10,644 objects that have been obtained in the first two years of observations in the zCOSMOS-bright redshift survey. These include a statistically complete subset of 10,109 objects. The average accuracy of individual redshifts is 110 km s^(–1), independent of redshift. The reliability of individual redshifts is described by a Confidence Class that has been empirically calibrated through repeat spectroscopic observations of over 600 galaxies. There is very good agreement between spectroscopic and photometric redshifts for the most secure Confidence Classes. For the less secure Confidence Classes, there is a good correspondence between the fraction of objects with a consistent photometric redshift and the spectroscopic repeatability, suggesting that the photometric redshifts can be used to indicate which of the less secure spectroscopic redshifts are likely right and which are probably wrong, and to give an indication of the nature of objects for which we failed to determine a redshift. Using this approach, we can construct a spectroscopic sample that is 99% reliable and which is 88% complete in the sample as a whole, and 95% complete in the redshift range 0.5 < z < 0.8. The luminosity and mass completeness levels of the zCOSMOS-bright sample of galaxies is also discussed

Epidemiological characteristics and predictors of late presentation of HIV infection in Barcelona (Spain) during the period 2001-2009

<p>Abstract</p> <p>Background</p> <p>Early diagnosis of HIV infection can prevent morbidity and mortality as well as reduce HIV transmission. The aim of the present study was to assess prevalence, describe trends and identify factors associated with late presentation of HIV infection in Barcelona (Spain) during the period 2001-09.</p> <p>Methods</p> <p>Demographic and epidemiological characteristics of cases reported to the Barcelona HIV surveillance system were analysed. Late presentation was defined for individuals with a CD4 count below 350 cells/ml upon HIV diagnosis or diagnosis of AIDS within 3 months of HIV diagnosis. Multivariate logistic regression were used to identify predictors of late presentation.</p> <p>Results</p> <p>Of the 2,938 newly diagnosed HIV-infected individuals, 2,507 (85,3%) had either a CD4 cell count or an AIDS diagnosis available. A total of 1,139 (55.6%) of the 2,507 studied cases over these nine years were late presenters varying from 48% among men who have sex with men to 70% among heterosexual men. The proportion of late presentation was 62.7% in 2001-2003, 51.9% in 2004-2005, 52.6% in 2006-2007 and 52.1% in 2008-2009. A decrease over time only was observed between 2001-2003 and 2004-2005 (p = 0.001) but remained constant thereafter (p = 0.9). Independent risk factors for late presentation were older age at diagnosis (p < 0.0001), use of injected drugs by men (p < 0.0001), being a heterosexual men (p < 0.0001), and being born in South America (p < 0.0001) or sub-Saharan Africa (p = 0.002).</p> <p>Conclusion</p> <p>Late presentation of HIV is still too frequent in all transmission groups in spite of a strong commitment with HIV prevention in our city. It is necessary to develop interventions that increase HIV testing and facilitate earlier entry into HIV care.</p

Epidemiology of infections by HIV, Syphilis, Gonorrhea and Lymphogranuloma Venereum in Barcelona City: a population-based incidence study

Background The aim of this study was to determine the evolution of HIV infection, gonorrhea, syphilis and lymphogranuloma venereum (LGV), and their epidemiological characteristics in Barcelona city. Methods Population-based incidence study of all newly occurring diagnoses of HIV infection, syphilis, gonorrhea and LGV detected in Barcelona between January 2007 and December 2011. A descriptive analysis was performed. The annual incidence rates per 100,000 inhabitants were calculated by sex, sexual conduct and educational level. To estimate global sex-specific rates we used the Barcelona city census; for the calculation of rates by sexual conduct and educational level we used estimates of the Barcelona Health Interview Survey. Trends were analysed using the chi-squared test for linear trend. Results HIV. 66.8 % of the HIV cases were men who had sex with men (MSM). The incidence rates in MSM over the study period were from 692.67/100,000 to 909.88/100,000 inh. Syphilis. 74.2 % of the syphilis cases were MSM. The incidence rates in MSM were from 224.9/100,000 to 891.97/100,000 inh. and the MSM with a university education ranged from 196.3/100,000 to 1020.8/100,000. Gonorrhea. 45.5 % of the gonorrhea cases were MSM. The incidence rates in MSM were from 164.24/100,000 to 404.79/100,000 inh. and the MSM with university education ranged from 176.7/100,000 to 530.1/100,000 inh.. Lymphogranuloma venereum (LGV). 95.3 % of the LGV cases are MSM. The incidence rates in MSM were from 24.99/100,000 to 282.99/100,000 inh. and the MSM with university education ranged from 9.3/100,000 to 265/100,000 inh. Conclusion An increase in cases of STI was observed. These STI mainly affected MSM with a university education. Continuing to monitor changes in the epidemiology of STI, and identifying the most affected groups should permit redesigning preventive programs, with the goal of finding the most efficient way to reach these population groups

Mass and environment as drivers of galaxy evolution in SDSS and zCOSMOS and the origin of the Schechter function

We explore the inter-relationships between mass, star-formation rate and environment in the SDSS, zCOSMOS and other surveys. The differential effects of mass and environment are completely separable to z ~ 1, indicating that two distinct processes are operating, "mass-quenching" and "environment-quenching". Environment-quenching, at fixed over-density, evidently does not change with epoch to z ~ 1, suggesting that it occurs as large-scale structure develops in the Universe. The observed constancy of the mass-function shape for star-forming galaxies, demands that the mass-quenching of galaxies around and above M*, must be proportional to their star-formation rates at all z < 2. We postulate that this simple mass-quenching law also holds over a much broader range of stellar mass and epoch. These two simple quenching processes, plus some additional quenching due to merging, then naturally produce (a) a quasi-static Schechter mass function for star-forming galaxies with a value of M* that is set by the proportionality between the star-formation and mass-quenching rates, (b) a double Schechter function for passive galaxies with two components: the dominant one is produced by mass-quenching and has exactly the same M* as the star-forming galaxies but an alpha shallower by +1, while the other is produced by environment effects and has the same M* and alpha as the star-forming galaxies, and is larger in high density environments. Subsequent merging of quenched galaxies modifies these predictions somewhat in the denser environments, slightly increasing M* and making alpha more negative. All of these detailed quantitative relationships between the Schechter parameters are indeed seen in the SDSS, lending strong support to our simple empirically-based model. The model naturally produces for passive galaxies the "anti-hierarchical" run of mean ages and alpha-element abundances with mass.Comment: 66 pages, 19 figures, 1 movie, accepted for publication in ApJ. The movie is also available at http://www.exp-astro.phys.ethz.ch/zCOSMOS/MF_simulation_d1_d4.mo