ALBERT

Description: We present a technique to fit the stellar components of the Galaxy by comparing Hess Diagrams (HDs) generated from trilegal models to real data. We apply this technique, which we call mwfitting, to photometric data from the first 3 yr of the Dark Energy Survey (DES). After removing regions containing known resolved stellar systems such as globular clusters, dwarf galaxies, nearby galaxies, the Large Magellanic Cloud, and the Sagittarius Stream, our main sample spans a total area of ∼2300 deg2. We further explore a smaller subset (∼1300 deg2) that excludes all regions with known stellar streams and stellar overdensities. Validation tests on synthetic data possessing similar properties to the DES data show that the method is able to recover input parameters with a precision better than 3 per cent. We fit the DES data with an exponential thick disc model and an oblate double power-law halo model. We find that the best-fitting thick disc model has radial and vertical scale heights of 2.67 ± 0.09 kpc and 925 ± 40 pc, respectively. The stellar halo is fit with a broken power-law density profile with an oblateness of 0.75 ± 0.01, an inner index of 1.82 ± 0.08, an outer index of 4.14 ± 0.05, and a break at 18.52 ± 0.27 kpc from the Galactic centre. Several previously discovered stellar overdensities are recovered in the residual stellar density map, showing the reliability of mwfitting in determining the Galactic components. Simulations made with the best-fitting parameters are a promising way to predict Milky Way star counts for surveys such as the LSST and Euclid.

Description: We review some approaches to macroscopic irreversibility from reversible microscopic dynamics, introducing the contribution of time dependent perturbations within the framework of recent developments in non-equilibrium statistical physics. We show that situations commonly assumed to violate the time reversal symmetry (presence of magnetic fields, rotating reference frames, and some time dependent perturbations) in reality do not violate this symmetry, and can be treated with standard theories and within standard experimental protocols.

Description: This article empirically investigates the impact of trade barriers on the world wine trade focusing on trade costs impeding exports, including transport, tariffs, technical barriers and sanitary and phytosanitary (SPS) standards. A gravity model is estimated using data from the main importing and exporting countries for the years 1997–2010. The Poison pseudo-maximum likelihood estimator accounts for heteroskedasticity and the presence of zero trade flows. Our results identify which regulations can adversely affect trade providing useful information to policy-makers involved in negotiations on trade frictions. While SPS measures do not seem to obstruct exports, technical barriers have a varying impact on trade. A decreasing trend for tariffs has largely been compensated by more stringent technical barriers. The overall result is that frictions in the world wine trade have not changed during the past 15 years.

Description: Trans-lesion synthesis polymerases, like DNA Polymerase- (Pol-), are essential for cell survival. Pol- bypasses ultraviolet-induced DNA damages via a two-metal-ion mechanism that assures DNA strand elongation, with formation of the leaving group pyrophosphate (PPi). Recent structural and kinetics studies have shown that Pol- function depends on the highly flexible and conserved Arg61 and, intriguingly, on a transient third ion resolved at the catalytic site, as lately observed in other nucleic acid-processing metalloenzymes. How these conserved structural features facilitate DNA replication, however, is still poorly understood. Through extended molecular dynamics and free energy simulations, we unravel a highly cooperative and dynamic mechanism for DNA elongation and repair, which is here described by an equilibrium ensemble of structures that connect the reactants to the products in Pol- catalysis. We reveal that specific conformations of Arg61 help facilitate the recruitment of the incoming base and favor the proper formation of a pre-reactive complex in Pol- for efficient DNA editing. Also, we show that a third transient metal ion, which acts concertedly with Arg61, serves as an exit shuttle for the leaving PPi. Finally, we discuss how this effective and cooperative mechanism for DNA repair may be shared by other DNA-repairing polymerases.

Description: Turbulence in the weakly collisional intracluster medium (ICM) of galaxies is able to generate strong thermal velocity anisotropies in the ions (with respect to the local magnetic field direction), if the magnetic moment of the particles is conserved in the absence of Coulomb collisions. In this scenario, the anisotropic pressure magnetohydrodynamic (AMHD) turbulence shows a very different statistical behaviour from the standard MHD one and is unable to amplify seed magnetic fields. This is in contrast to previous cosmological MHD simulations that are successful in explaining the observed magnetic fields in the ICM. On the other hand, temperature anisotropies can also drive plasma instabilities that can relax the anisotropy. This work aims to compare the relaxation rate with the growth rate of the anisotropies driven by the turbulence. We employ quasi-linear theory to estimate the ion scattering rate resulting from the parallel firehose, mirror and ion-cyclotron instabilities, for a set of plasma parameters resulting from AMHD simulations of the turbulent ICM. We show that the ICM turbulence can sustain only anisotropy levels very close to the instability thresholds. We argue that the AMHD model that bounds the anisotropies at the marginal stability levels can describe the Alfvénic turbulence cascade in the ICM.

Description: Observations of the intracluster medium (ICM) in galaxy clusters suggest for the presence of turbulence and the magnetic fields’ existence has been proved through observations of Faraday Rotation (FR) and synchrotron emission. The ICM is also known to be filled by a rarefied weakly collisional plasma. In this work, we study the possible signatures left on FR maps by collisionless instabilities. For this purpose, we use a numerical approach to investigate the dynamics of the turbulence in collisionless plasmas based on an magnetohydrodynamical (MHD) formalism taking into account different levels of pressure anisotropy. We consider models covering the sub/super-Alfvénic and trans/supersonic regimes, one of them representing the fiducial conditions corresponding to the ICM. From the simulated models, we compute FR maps and analyse several statistical indicators in order to characterize the magnetic field structure and compare the results obtained with the collisionless model to those obtained using standard collisional MHD framework. We find that important imprints of the pressure anisotropy prevails in the magnetic field and also manifest in the associated FR maps which evidence smaller correlation lengths in the collisionless MHD case. These points are remarkably noticeable for the case mimicking the conditions prevailing in ICM. Nevertheless, in this study we have neglected the decrease of pressure anisotropy due to the feedback of the instabilities that naturally arise in collisionless plasmas at small scales. This decrease may not affect the statistical imprint differences described above, but should be examined elsewhere.

Description: A significant proportion of disease-causing mutations affect precursor-mRNA splicing, inducing skipping of the exon from the mature transcript. Using F9 exon 5, CFTR exon 12 and SMN2 exon 7 models, we characterized natural mutations associated to exon skipping in Haemophilia B, cystic fibrosis and spinal muscular atrophy (SMA), respectively, and the therapeutic splicing rescue by using U1 small nuclear RNA (snRNA). In minigene expression systems, loading of U1 snRNA by complementarity to the normal or mutated donor splice sites (5'ss) corrected the exon skipping caused by mutations at the polypyrimidine tract of the acceptor splice site, at the consensus 5'ss or at exonic regulatory elements. To improve specificity and reduce potential off-target effects, we developed U1 snRNA variants targeting non-conserved intronic sequences downstream of the 5'ss. For each gene system, we identified an exon-specific U1 snRNA (ExSpeU1) able to rescue splicing impaired by the different types of mutations. Through splicing-competent cDNA constructs, we demonstrated that the ExSpeU1-mediated splicing correction of several F9 mutations results in complete restoration of secreted functional factor IX levels. Furthermore, two ExSpeU1s for SMA improved SMN exon 7 splicing in the chromosomal context of normal cells. We propose ExSpeU1s as a novel therapeutic strategy to correct, in several human disorders, different types of splicing mutations associated with defective exon definition.

Description: SUMMARY Viscoplasticity has been considered to be a dominant element in causing the nucleation of shear instability leading to lithospheric weakening. Here, we propose that a simple contrast in shear moduli may be sufficient for explaining the fast timescale asymmetric shear instability in a bimaterial setting. Not much attention has been paid to heterogeneous elasticity in geodynamical modelling because it is dominant only for short timescales. Up to now, no studies have been made on asymmetric shear instability induced by elastic modulus contrast. Thermal–mechanical numerical simulations based on high-resolution (from 0.4 km × 0.4 km to 0.2 km × 0.4 km meshes) finite-element methods were performed to understand the effects of shear modulus contrast on inducing asymmetric instabilities. Strain-rate and stress-dependent rheology are used with a wide range of activation energy 0–850 kJ mol –1 for all models. Numerical results with enough shear modulus contrast show asymmetric shear instability, which is generated around the interface and then propagates across the interface. Two parts of the lithosphere with different shear moduli (stiff for higher and soft for lower shear modulus lithospheres), which are simply connected to each other without a pre-defined weak zone, were compressed at a constant rate of 2 cm yr –1 . Having different shear modulus is justified by chemical heterogeneity of geological minerals and their pressure–temperature dependence. To explore the dynamical effects generated by the contrast in the elastic modulus, the shear modulus of the soft lithosphere is fixed at 32 GPa, whereas that of stiff lithosphere is increased systematically from 32 up to 640 GPa. We also examined the role of activation energy (0–850 kJ mol –1 ) on the geometrical pattern and the initiation time of asymmetric shear localization. The shear modulus contrast has to be close to two for triggering asymmetric shear instability and is found to be by far a more important controlling factor in causing shear instability than activation energy of the creep law. The instability develops rapidly between 250 000 and 500 000 yr after deformation begins, and thermal weakening in the shear zone is greater, when a stronger shear modulus contrast is prescribed. Our work suggests that initiation of lithosphere-scale asymmetric instability would be faster than previous considerations. Our finding stresses that naturally occurring shear modulus contrast has also important impact on many geological problems related to bimaterial instability.

Description: Strong downstream magnetic fields of the order of ~1 G, with large correlation lengths, are believed to cause the large synchrotron emission at the afterglow phase of gamma-ray bursts (GRBs). Despite the recent theoretical efforts, models have failed to fully explain the amplification of the magnetic field, particularly in a matter-dominated scenario. We revisit the problem by considering the synchrotron emission to occur at the expanding shock front of a weakly magnetized relativistic jet over a magnetized surrounding medium. Analytical estimates and a number of high-resolution 2D relativistic magnetohydrodynamical (RMHD) simulations are provided. Jet opening angles of  = 0°–20°, and ambient to jet density ratios of 10 –4 –10 2 were considered. We found that most of the amplification is due to compression of the ambient magnetic field at the contact discontinuity between the reverse and forward shocks at the jet head, with substantial pile-up of the magnetic field lines as the jet propagates sweeping the ambient field lines. The pile-up is maximum for -〉 0, decreasing with , but larger than in the spherical blast problem. Values obtained for certain models are able to explain the observed intensities. The maximum correlation lengths found for such strong fields is of l corr  ≤ 10 14  cm, 2–6 orders of magnitude larger than the found in previous works.