Passivation of high temperature superconductors

The surface of high temperature superconductors such as YBa2Cu3O(7-x) are passivated by reacting the native Y, Ba and Cu metal ions with an anion such as sulfate or oxalate to form a surface film that is impervious to water and has a solubility in water of no more than 10(exp -3) M. The passivating treatment is preferably conducted by immersing the surface in dilute aqueous acid solution since more soluble species dissolve into the solution. The treatment does not degrade the superconducting properties of the bulk material

Right-handed lepton mixings at the LHC

We study how the elements of the leptonic right-handed mixing matrix can be determined at the LHC in the minimal Left-Right symmetric extension of the standard model. We do it by explicitly relating them with physical quantities of the Keung-Senjanovi\'c process and the lepton number violating decays of the right doubly charged scalar. We also point out that the left and right doubly charged scalars can be distinguished at the LHC, without measuring the polarization of the final state leptons coming from their decays.Comment: 12 pages, 6 figures, discussion in section III expanded and sharpened, one appendix added, updated reference

Long wavelength infrared detector

Long wavelength infrared detection is achieved by a detector made with layers of quantum well material bounded on each side by barrier material to form paired quantum wells, each quantum well having a single energy level. The width and depth of the paired quantum wells, and the spacing therebetween, are selected to split the single energy level with an upper energy level near the top of the energy wells. The spacing is selected for splitting the single energy level into two energy levels with a difference between levels sufficiently small for detection of infrared radiation of a desired wavelength

Melanosuchus, M. niger

Number of Pages: 4Integrative BiologyGeological Science

Post-disaster: an opportunity to address sustainable reconstruction, based on the 2010 Chile earthquake

On Friday 27th February 2010 at 3:40 am, a terrible earthquake measuring 8.8 on the Richter scale rocked the central territory of Chile. Hours later a terrible Tsunami hit a large part of its coastal region. This event spanned a longitude of 630 km causing damages in at least six regions of the country which concentrate 75% of national population. Besides the destruction and all the panic, the quake caused an instantaneous black out for more than four days. As a result of this black out, cities suffered severe difficulties related to provisions, communication and safety, to name a few. This situation demonstrated the vulnerability of Chile electrical grid and the people’s dependence of energy. According to data from National Reconstruction Plan (2010) the number of damaged houses reached 370,051 generating enormous work in rebuilding not only houses, but entire communities and town, each of which had particular way of life. It is important to mention the destruction of many major historic centers with low density residential communities that had taken dozens of years to consolidate their cultural wealth (Letelier, 2010). That cultural richness is characterized by the diversity in its population, including people of various social classes having accesses the same services and facilities. Also, this proximity to services produced a low dependence on automobiles, keeping walking as a basic system of transportation. As these current events imply a lot of work, questions are raised about what kind of cities can be rebuilt or what kind of neighborhoods can be developed

Effects of aerogel-like disorder on the critical behavior of O(m)-vector models. Recent simulations and experimental evidences

We review some results on the effect of a specific type of quenched disorder on well known O(m)-vector models in three dimension. Evidences of changes of criticality in both systems, when confined in aerogel pores, are briefly referenced. The 3DXY model (m=2) represents the universality class to which the \lambda-transition of bulk superfluid $^4$He belongs. Experiments report changes of critical exponents for this transition, when superfluid $^4$He is confined in aerogels. Numerical results of the 3DXY model, confined in aerogel-like structures, are in agreement with experiments. Both results seem to contradict Harris criterion: being the specific heat exponent negative for the pure system, changes must be explained in terms of the extended criterion due to Weinrib and Halperin, which requires disorder to be long-range correlated (LRC) at all scales. Aerogels are fractal through some decades only, and present crossovers to homogeneous regimes at finite scales, so the violation to Harris criterion persists. The apparent violation has been explained in terms of hidden LRC subsets within aerogels $[$Phys. Rev. Lett., 2003, {\bf 90}, 170602$]$. On the other hand, experiments on the liquid-vapor (LV) transition of $^4$He and N$_2$ confined in aerogels, also showed changes in critical-point exponents. Being the LV critical-point in the O(1) universality class, criticality may be affected by both, short-range correlated (SRC) and LRC subsets ofdisorder. Simulations of the 3DIS in DLCA aerogels can corroborate experimental results. Experiments and simulations both suggest a shift in critical exponents to values closer to the SRC instead of those of the LRC fixed point.Comment: 14 pages, 7 figures. Contribution to the "Mochima theoretical physics spring school". Joint CEA-IVIC-SFP workshop on Foundations of Statistical and Mesoscopic Physics. Venezuela. 200