Neutron/proton ratio of nucleon emissions as a probe of neutron skin

The dependence between neutron-to-proton yield ratio ($R_{np}$) and neutron skin thickness ($\delta_{np}$) in neutron-rich projectile induced reactions is investigated within the framework of the Isospin-Dependent Quantum Molecular Dynamics (IQMD) model. The density distribution of the Droplet model is embedded in the initialization of the neutron and proton densities in the present IQMD model. By adjusting the diffuseness parameter of neutron density in the Droplet model for the projectile, the relationship between the neutron skin thickness and the corresponding $R_{np}$ in the collisions is obtained. The results show strong linear correlation between $R_{np}$ and $\delta_{np}$ for neutron-rich Ca and Ni isotopes. It is suggested that $R_{np}$ may be used as an experimental observable to extract $\delta_{np}$ for neutron-rich nuclei, which is very significant to the study of the nuclear structure of exotic nuclei and the equation of state (EOS) of asymmetric nuclear matter.Comment: 7 pages, 5 figures; accepted by Phys. Lett.

Structure and Thermodynamical Properties of Zirconium hydrides from first-principle

Zirconium alloys are used as nuclear fuel cladding material due to their mechanical and corrosion resistant properties together with their favorable cross-section for neutron scattering. At running conditions, however, there will be an increase of hydrogen in the vicinity of the cladding surface at the water side of the fuel. The hydrogen will diffuse into the cladding material and at certain conditions, such as lower temperatures and external load, hydrides will precipitate out in the material and cause well known embrittlement, blistering and other unwanted effects. Using phase-field methods it is now possible to model precipitation build-up in metals, for example as a function of hydrogen concentration, temperature and external load, but the technique relies on input of parameters, such as the formation energy of the hydrides and matrix. To that end, we have computed, using the density functional theory (DFT) code GPAW, the latent heat of fusion as well as solved the crystal structure for three zirconium hydride polymorphs: \delta-ZrH1.6, \gamma-ZrH, and \epsilon-ZrH2.Comment: 9 pages, 9 figures, 15th Int. Conf. Environmental Degradation of Materials in Nuclear Power Systems-water reactors Uses graficx, subfigure, threeparttable (2012

Finite Volume Effect of Nucleons and the Formation of the Quark-Gluon Plasma

We study a thermodynamically consistent implementation of the nucleon volume in the mean field theory, and find that this volume has large consequences on the properties of hadronic matter under extreme conditions such as in astrophysical objects and high energy heavy-ion collisions. It is shown that we can reproduce the critical temperature $T_{c}\simeq 200$ MeV predicted by lattice QCD calculations for the phase transition from hadronic matter to quark-gluon plasma, by using parameters which are adjusted to fit all empirical data for normal nuclear matter.Comment: 11 Latex pages, 4 figures upon reques

Effects of isospin and momentum dependent interactions on thermal properties of asymmetric nuclear matter

Thermal properties of asymmetric nuclear matter are studied within a self-consistent thermal model using an isospin and momentum dependent interaction (MDI) constrained by the isospin diffusion data in heavy-ion collisions, a momentum-independent interaction (MID), and an isoscalar momentum-dependent interaction (eMDYI). In particular, we study the temperature dependence of the isospin-dependent bulk and single-particle properties, the mechanical and chemical instabilities, and liquid-gas phase transition in hot asymmetric nuclear matter. Our results indicate that the temperature dependence of the equation of state and the symmetry energy are not so sensitive to the momentum dependence of the interaction. The symmetry energy at fixed density is found to generally decrease with temperature and for the MDI interaction the decrement is essentially due to the potential part. It is further shown that only the low momentum part of the single-particle potential and the nucleon effective mass increases significantly with temperature for the momentum-dependent interactions. For the MDI interaction, the low momentum part of the symmetry potential is significantly reduced with increasing temperature. For the mechanical and chemical instabilities as well as the liquid-gas phase transition in hot asymmetric nuclear matter, our results indicate that the boundary of these instabilities and the phase-coexistence region generally shrink with increasing temperature and is sensitive to the density dependence of the symmetry energy and the isospin and momentum dependence of the nuclear interaction, especially at higher temperatures.Comment: 21 pages, 29 figure

Investigation of Corrosion Mechanism of Ribbed Mild Steel Bars Coated with Magnesium Potassium Phosphate Cement Paste

This Study Investigated the Anti-Corrosion Performance of Magnesium Potassium Phosphate Cement (MKPC) Paste Applied to the Surface of Ribbed Mild Steel Bars – Which Was Exposed to Simulated Accelerated Corrosive Environment. Four Electrochemical Approaches Were Used Including Open-Circuit Potential (OCP), Electrochemical Impedance Spectroscope (EIS), Polarization Resistance (PR) and Potentiodynamic Polarization (PDP) over a Period of 5376 H (224 Days). Moreover, Visual Inspection, Optical Microscope, and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) Were Used to Assess the Extent of Corrosion on the Samples. to Understand the Mechanism of Corrosion Protection of the Coating System, X-Ray Photoelectron Spectroscopy (XPS) Was Employed to Characterize the Chemical Groups on the Surface of Mild Steel, and the Chemical Changes in the Coating Layer Were Characterized using Thermogravimetric/differential Thermal Analysis (TG/DTA) and X-Ray Diffraction (XRD). the MKPC Paste Coated Bars Were Compared with Not Only Uncoated Bars, But Also Bars Coated with Ordinary Portland Cement (OPC) that is Known to Passivate Steel Due to its High Alkalinity. Results Indicated that MKPC Paste Coating Layer Could Effectively Protect the Ribbed Mild Steel Bars, and its Protectiveness Significantly Surpassed that of OPC. Both the De-Passivation Effects of Chloride Ions and Carbonation of the OPC Resulted in Relatively Severe Corrosion of the OPC Coated Bars during the Long Exposure Duration; While the Anti-Corrosion Merit of the MKPC Paste Coating Layer Could Be Attribute to a Double-Protection System– the Dense Microstructure of MKPC and the Formation of an Iron (III) Phosphate Passivation Layer between the Substrate Steel and the MKPC Paste Coating Layer

Short tandem repeat sequences in the Mycoplasma genitalium genome and their use in a multilocus genotyping system

<p>Abstract</p> <p>Background</p> <p>Several methods have been reported for strain typing of <it>Mycoplasma genitalium</it>. The value of these methods has never been comparatively assessed. The aims of this study were: 1) to identify new potential genetic markers based on an analysis of short tandem repeat (STR) sequences in the published <it>M. genitalium </it>genome sequence; 2) to apply previously and newly identified markers to a panel of clinical strains in order to determine the optimal combination for an efficient multi-locus genotyping system; 3) to further confirm sexual transmission of <it>M. genitalium </it>using the newly developed system.</p> <p>Results</p> <p>We performed a comprehensive analysis of STRs in the genome of the <it>M. genitalium </it>type strain G37 and identified 18 loci containing STRs. In addition to one previously studied locus, MG309, we chose two others, MG307 and MG338, for further study. Based on an analysis of 74 unrelated patient specimens from New Orleans and Scandinavia, the discriminatory indices (DIs) for these three markers were 0.9153, 0.7381 and 0.8730, respectively. Two other previously described markers, including single nucleotide polymorphisms (SNPs) in the rRNA genes (rRNA-SNPs) and SNPs in the MG191 gene (MG191-SNPs) were found to have DIs of 0.5820 and 0.9392, respectively. A combination of MG309-STRs and MG191-SNPs yielded almost perfect discrimination (DI = 0.9894). An additional finding was that the rRNA-SNPs distribution pattern differed significantly between Scandinavia and New Orleans. Finally we applied multi-locus typing to further confirm sexual transmission using specimens from 74 unrelated patients and 31 concurrently infected couples. Analysis of multi-locus genotype profiles using the five variable loci described above revealed 27 of the couples had concordant genotype profiles compared to only four examples of concordance among the 74 unrelated randomly selected patients.</p> <p>Conclusion</p> <p>We propose that a combination of the MG309-STRs and MG191-SNPs is efficient for general epidemiological studies and addition of MG307-STRs and MG338-STRs is potentially useful for sexual network studies of <it>M. genitalium </it>infection. The multi-locus typing analysis of 74 unrelated <it>M. genitalium</it>-infected individuals and 31 infected couples adds to the evidence that <it>M. genitalium </it>is sexually transmitted.</p

Efficient processing of raster and vector data

[Abstract] In this work, we propose a framework to store and manage spatial data, which includes new efficient algorithms to perform operations accepting as input a raster dataset and a vector dataset. More concretely, we present algorithms for solving a spatial join between a raster and a vector dataset imposing a restriction on the values of the cells of the raster; and an algorithm for retrieving K objects of a vector dataset that overlap cells of a raster dataset, such that the K objects are those overlapping the highest (or lowest) cell values among all objects. The raster data is stored using a compact data structure, which can directly manipulate compressed data without the need for prior decompression. This leads to better running times and lower memory consumption. In our experimental evaluation comparing our solution to other baselines, we obtain the best space/time trade-offs.Ministerio de Ciencia, Innovación y Universidades; TIN2016-78011-C4-1-RMinisterio de Ciencia, Innovación y Universidades; TIN2016-77158 C4-3-RMinisterio de Ciencia, Innovación y Universidades; RTC-2017-5908-7Xunta de Galicia; ED431C 2017/58Xunta de Galicia; ED431G/01Xunta de Galicia; IN852A 2018/14University of Bío-Bío; 192119 2/RUniversity of Bío-Bío; 195119 GI/V

Corner contributions to holographic entanglement entropy

The entanglement entropy of three-dimensional conformal field theories contains a universal contribution coming from corners in the entangling surface. We study these contributions in a holographic framework and, in particular, we consider the effects of higher curvature interactions in the bulk gravity theory. We find that for all of our holographic models, the corner contribution is only modified by an overall factor but the functional dependence on the opening angle is not modified by the new gravitational interactions. We also compare the dependence of the corner term on the new gravitational couplings to that for a number of other physical quantities, and we show that the ratio of the corner contribution over the central charge appearing in the two-point function of the stress tensor is a universal function for all of the holographic theories studied here. Comparing this holographic result to the analogous functions for free CFT's, we find fairly good agreement across the full range of the opening angle. However, there is a precise match in the limit where the entangling surface becomes smooth, i.e., the angle approaches $\pi$, and we conjecture the corresponding ratio is a universal constant for all three-dimensional conformal field theories. In this paper, we expand on the holographic calculations in our previous letter arXiv:1505.04804, where this conjecture was first introduced.Comment: 62 pages, 6 figures, 1 table; v2: minor modifications to match published version, typos fixe