Transport in random quantum dot superlattices

We present a novel model to calculate single-electron states in random quantum dot superlattices made of wide-gap semiconductors. The source of disorder comes from the random arrangement of the quantum dots (configurational disorder) as well as spatial inhomogeneities of their shape (morphological disorder). Both types of disorder break translational symmetry and prevent the formation of minibands, as occurs in regimented arrays of quantum dots. The model correctly describes channel mixing and broadening of allowed energy bands due to elastic scattering by disorder

Experimental evidence of delocalized states in random dimer superlattices

We study the electronic properties of GaAs-AlGaAs superlattices with intentional correlated disorder by means of photoluminescence and vertical dc resistance. The results are compared to those obtained in ordered and uncorrelated disordered superlattices. We report the first experimental evidence that spatial correlations inhibit localization of states in disordered low-dimensional systems, as our previous theoretical calculations suggested, in contrast to the earlier belief that all eigenstates are localized.Comment: 4 pages, 5 figures. Physical Review Letters (in press

High temperature creep of 20 vol.% SiC-HfB2 UHTCs up to 2000 °C

High temperature compressive creep of SiC-HfB2 UHTCs up to 2000 °C has been studied. Microstructural analysis after deformation reveals formation of new phases in the Hf-B-Si and Hf-B-Si-C systems, which are responsible for the poor creep resistance. RE oxide additions have a negative effect reducing the creep resistance of SiC-HfB2 UHTCs. A simplistic analysis for the required creep resistance is described, indicating that only SiC-HfB2 UHTCs could withstand re-entry conditions for 5 min in a single use. However, RE oxide addition to SiC-HfB2 UHTCs does not provide the required creep resistance for them to be candidate materials for hypersonic applications

Correlation and regression analysis between residual gradation and uncorrected visual acuity one year after refractive surgery with LASIK, FS-LASIK, PRK, PRK Xtra techniques and the implantation of ICL® posterior chamber phakic lens in myopic correction

Purpose To analyze the influence of the final spherical equivalent (SE) in LogMAR uncorrected distance visual acuity (UDVA) one year after refractive surgery. We analysed refractive results, their predictability and efficacy, and the safety results of the different methods as secondary outcomes. Setting Refractive Surgery Unit of the Institut Català de Retina (ICR) in Barcelona, Spain. Design Retrospective, analytical observational study. Methods Retrospective and observational study of 654 eyes of 327 patients who underwent refractive surgery to treat their myopia or myopic astigmatism using LASIK, FS-LASIK, PRK, PRK Xtra or ICL-type lens implantation surgery were included. Results The correlation between the SE in absolute value was statistically significant in all techniques utilized, reaching higher values in the FS-LASIK and LASIK techniques, 0.774 and0.706 respectively, and lesser values in PRK (0.480) and PRK Xtra (0.482). A significant adjustment via a univariate linear regression model could be implemented in all techniques, albeit the R2 coefficient of determination values were higher than those for the FS-LASIK (0.599) and LASIK (0.494) techniques. Conclusions There is a positive correlation between post-surgical SE value and post-operative LogMAR UDVA. These regression models can be adjusted to predict the final UDVA according to the final SE. The techniques that are most influenced by the final SE in terms of their visual results are FS-LASIK and LASIK

Characterization of Escherichia coli Carrying mcr-1-Plasmids Recovered From Food Animals From Argentina

In this study, we found mcr-1.1 and mcr-1.5 genes carried by IncI2 plasmids in a subset of Escherichia coli isolates recovered from commercial broiler farms in Argentina. The comparative analysis of the sequences of these plasmids with those described in human clinical isolates suggests that this replicon-type is one of the main mcr-disseminator sources in Argentina

On the Stability of Quasi-Equilibrium Self-Gravitating Configurations in a Tidal Field

The possibility that quasi-equilibrium self-gravitating galaxy-like configurations exist in a tidal field is analyzed in this paper. More specifically, we address the question of how to predict initial configurations modeling galaxies that are able to survive environmental effects in a dense environment for a Hubble time or so, provided thay dynamical friction is neglected. The initial quasi-equilibrium configurations have been built up taking into account the external tidal field produced by the halo. It modifies the escape velocity field of the configuration, compared with isolated configurations. The survival of the configurations as they orbit inside the halos has been studied through N-body simulations. As a general result, it has been found out that the bulk of the models is conserved along 12.5 Gyears of evolution, and that the low rates of mass losses they experience are consistent with those expected when the adiabatic protection hypothesis is at work. So, solutions for galaxy configurations in tidal quasi-equilibrium have been found, showing that tidal stripping in quiescent phases does not seem to be very important, unless that the density of the galaxy environment at its formation had been much lower than that of the galaxy environment at the point of its orbit where the tidal perturbation is maximum. (Abridged)Comment: 36 pages, 7 postscript figures, to be published in Ap

Electromagnetic vertex function of the pion at T > 0

The matrix element of the electromagnetic current between pion states is calculated in quenched lattice QCD at a temperature of $T = 0.93 T_c$. The nonperturbatively improved Sheikholeslami-Wohlert action is used together with the corresponding ${\cal O}(a)$ improved vector current. The electromagnetic vertex function is extracted for pion masses down to $360 {\rm MeV}$ and momentum transfers $Q^2 \le 2.7 {\rm GeV}^2$.Comment: 17 pages, 8 figure

Breast Cancer Mortality in Older and Younger Patients in California

BACKGROUND: Breast cancer in younger patients is reported to be more aggressive and associated with lower survival; however, factors associated with age-specific mortality differences have not been adequately assessed. METHODS: We used data from the population-based California Cancer Registry for 38,509 younger (18-49 years) and 121,573 older (50 years and older) women diagnosed with stage I to III breast cancer, 2005-2014. Multivariable Cox regression models were used to estimate breast cancer-specific mortality rate ratios (MRR) and 95% confidence intervals (CI), stratified by tumor subtype, guideline treatment, and care at an NCI-designated cancer center (NCICC). RESULTS: Older breast cancer patients at diagnosis experienced 17% higher disease-specific mortality than younger patients, after multivariable adjustment (MRR = 1.17; 95% CI, 1.11-1.23). Higher MRRs (95% CI) were observed for older versus younger patients with hormone receptor (HR)(+)/HER2(-) (1.24; 1.14-1.35) and HR(+)/HER2(+) (1.38; 1.17-1.62), but not for HR(-)/HER2(+) (HR = 0.94; 0.79-1.12) nor triple-negative breast cancers (1.01; 0.92-1.11). The higher mortality in older versus younger patients was diminished among patients who received guideline-concordant treatment (MRR = 1.06; 95% CI, 0.99-1.14) and reversed among those seen at an NCICC (MRR = 0.86; 95% CI, 0.73-1.01). CONCLUSIONS: Although younger women tend to be diagnosed with more aggressive breast cancers, adjusting for these aggressive features results in older patients having higher mortality than younger patients, with variations by age, tumor subtype, receipt of guideline treatment, and being cared for at an NCICC. IMPACT: Higher breast cancer mortality in older compared with younger women could partly be addressed by ensuring optimal treatment and comprehensive patient-centered care