X-ray photoelectron spectroscopy studies of non-stoichiometric superconducting NbB2+x

Polycrystalline samples of NbB2+x with nominal composition (B/Nb) = 2.0, 2.1, 2.2, 2.3, 2.4 and 2.5 were studied by X-ray photoelectron spectroscopy (XPS). The spectra revealed Nb and B oxides on the surface of the samples, mainly B2O3 and Nb2O5. After Ar ion etching the intensity of Nb and B oxides decreased. The Nb 3d5/2 and B 1s core levels associated with the chemical states (B/Nb) were identified and they do not change with etching time. The Binding Energy of the Nb 3d5/2 and B 1s core levels increase as boron content increases, suggesting a positive chemical shift in the core levels. On the other hand, analysis of Valence Band spectra showed that the contribution of the Nb 4d states slightly decreased while the contribution of the B 2p(pi) states increased as the boron content increased. As a consequence, the electronic and superconducting properties were substantially modified, in good agreement with band-structure calculations.Comment: 10 pages, 7 figures, 1 tabl

Veteran Wellness and Reintegration: Factors Contributing to Their Success in the Community

The purpose of the following study is to determine if there is a relationship between veteran wellness based on gender, discharge status, theatre of operations, substance use disorder, veteran self-efficacy, community reintegration post discharge, stigma and veteran physical and psychosocial factors. Military veteran wellness has been the focal point of service providers for ensuring post-discharge veterans\u27 success. During the last decade there has been an increase in military veterans reintegrating into society with chronic ailments and undiagnosed conditions. The study examined 85 Texas veterans: (a) the relationship between veterans\u27 substance abuse and their perception of stigma, (b) the relationship between veteran self-efficacy and veteran personal wellness, (c) the impact of psychological factors of veteran wellness on veterans\u27 reintegration into the community post discharge from the armed services, and (d) the specific demographic factors of veterans on their reintegration into the community. Results indicated veteran wellness was highly correlated with specific veteran demographic factors, and stigma. Implications of the study and recommendations for future research are included in the study to better identify factors that can improve veteran well-being

Correlation between the transition temperature and the superfluid density in BCS superconductor NbB_2+x

The results of the muon-spin rotation experiments on BCS superconductors NbB_2+x (x = 0.2, 0.34) are reported. Both samples, studied in the present work, exhibit rather broad transitions to the superconducting state, suggesting a distribution of the volume fractions with different transition temperatures (T_c)'s. By taking these distributions into account, the dependence of the inverse squared zero-temperature magnetic penetration depth (\lambda_0^{-2}) on T_c was reconstructed for temperatures in the range 1.5K<T_c<8.0K. \lambda_0^{-2} was found to obey the power law dependence \lambda_0^{-2}\propto T_c^{3.1(1)} which appears to be common for some families of BCS superconductors as, {\it e.g.}, Al doped MgB_2 and high-temperature cuprate superconductors as underdoped YBa_2Cu_3O_{7-\delta}.Comment: 9 pages, 7 figures. Accepted for publication in Phys. Rev.

The impact of new technologies over the city “explosion”.

It has been argued that new information and communications technologies (ICT) have been fundamental for urban expansion. Also, from the late sixties until the end of the past millennium, the “dead of the city” had been heralded .Throughout this theoretical paper, we review literature concerning the impact that new technologies have had over the metropolization process, debunking some premises and exemplifying the spatial transformations. The first part analyses the dispersion /concentration potential inherent to ICT. The second part highlights the importance and legitimacy of face -to - face relationships that allow urban agglomerations to be in force. Finally, we enlist new research lines that relates ICT with cities

Cosmological parameter inference with Bayesian statistics

Bayesian statistics and Markov Chain Monte Carlo (MCMC) algorithms have found their place in the field of Cosmology. They have become important mathematical and numerical tools, especially in parameter estimation and model comparison. In this paper, we review some fundamental concepts to understand Bayesian statistics and then introduce MCMC algorithms and samplers that allow us to perform the parameter inference procedure. We also introduce a general description of the standard cosmological model, known as the $\Lambda$CDM model, along with several alternatives, and current datasets coming from astrophysical and cosmological observations. Finally, with the tools acquired, we use an MCMC algorithm implemented in python to test several cosmological models and find out the combination of parameters that best describes the Universe.Comment: 30 pages, 17 figures, 5 tables; accepted for publication in Universe; references adde