Nonlinear c-axis transport in Bi_2Sr_2CaCu_2O_(8+d) from two-barrier tunneling

Motivated by the peculiar features observed through intrinsic tunneling spectroscopy of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ mesas in the normal state, we have extended the normal state two-barrier model for the c-axis transport [M. Giura et al., Phys. Rev. B {\bf 68}, 134505 (2003)] to the analysis of $dI/dV$ curves. We have found that the purely normal-state model reproduces all the following experimental features: (a) the parabolic $V$-dependence of $dI/dV$ in the high-$T$ region (above the conventional pseudogap temperature), (b) the emergence and the nearly voltage-independent position of the "humps" from this parabolic behavior lowering the temperature, and (c) the crossing of the absolute $dI/dV$ curves at a characteristic voltage $V^\times$. Our findings indicate that conventional tunneling can be at the origin of most of the uncommon features of the c axis transport in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$. We have compared our calculations to experimental data taken in severely underdoped and slightly underdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ small mesas. We have found good agreement between the data and the calculations, without any shift of the calculated dI/dV on the vertical scale. In particular, in the normal state (above $T^\ast$) simple tunneling reproduces the experimental dI/dV quantitatively. Below $T^\ast$ quantitative discrepancies are limited to a simple rescaling of the voltage in the theoretical curves by a factor $\sim$2. The need for such modifications remains an open question, that might be connected to a change of the charge of a fraction of the carriers across the pseudogap opening.Comment: 7 pages, 5 figure

Reparametrization invariance of B decay amplitudes and implications for new physics searches in B decays

When studying B decays within the Standard Model, it is customary to use the unitarity of the CKM matrix in order to write the decay amplitudes in terms of only two of the three weak phases which appear in the various diagrams. Occasionally, it is mentioned that those two weak phases can be used in order to describe any decay amplitude, even beyond the Standard Model. Here we point out that, when describing a generic decay amplitude, the two weak phases can be chosen completely at will, and we study the behavior of the decay amplitudes under changes in the two weak phases chosen as a basis. Of course, physical observables cannot depend on such reparametrizations. This has an impact in discussions of the SM and in attempts to parametrize new physics effects in the decay amplitudes. We illustrate these issues by looking at B --> psi K_S and the isospin analysis in B --> pi pi.Comment: 16 pages, RevTe

Household water security through stored rainwater and consumer acceptability: a case study of the Anuradhapura District

Rainwater harvesting has increased in popularity in Sri Lanka over the past two decades due to the number of water supply projects funded by the government and non-governmental organizations (NGOs). The stored rainwater can provide accessible, reliable, timely and adequate supplies of water to households but there are uncertainties as to safety, in terms of water quality, and consumer acceptability. A study was, therefore, conducted in the Anuradhapura District, in the dry zone, to assess consumer acceptability of stored rainwater for household purposes and to conduct rainwater quality tests in a laboratory. The majority of households in Anuradhapura meet their drinking water requirements from protected wells (59.6 %). Prior to the project, people greatly preferred open wells as a source of domestic water, followed by tubewells, because they believed that water in open wells is of good quality and drinkable. However, stored rainwater has become the priority source now, especially through roof rainwater harvesting (RRWH), which is used during the dry periods. The study revealed that more than 85 % of households use stored rainwater for drinking although some have concerns over the quality and only drink it after boiling. The easy accessibility of water and the assurance by the project team that it is of good quality are the main reasons that people are willing to drink it. The acceptability of stored rainwater for consumption was very high in water-scarce areas and with the increasing distance to the nearest and alternative sources of good-quality water. Of those who felt that they had adequate water, 84 % of the sample households found it adequate in the wet season but only 21 % in the dry season. Water quality analysis revealed that the chemical and physical quality of stored rainwater is within the acceptable range with respect to Sri Lankan Standards, SLS: 614, for potable water quality (SLIS 1983). Other domestic water sources exceeded standards for electrical conductivity, total alkalinity, hardness, ammonium nitrogen, fluorides and total iron. However, stored rainwater was of lower biological quality than other domestic water sources.Length: pp.87-97Domestic waterWater securityWater harvestingWater qualityRural areasCase studies

Algebroid Yang-Mills Theories

A framework for constructing new kinds of gauge theories is suggested. Essentially it consists in replacing Lie algebras by Lie or Courant algebroids. Besides presenting novel topological theories defined in arbitrary spacetime dimensions, we show that equipping Lie algebroids E with a fiber metric having sufficiently many E-Killing vectors leads to an astonishingly mild deformation of ordinary Yang-Mills theories: Additional fields turn out to carry no propagating modes. Instead they serve as moduli parameters gluing together in part different Yang-Mills theories. This leads to a symmetry enhancement at critical points of these fields, as is also typical for String effective field theories.Comment: 4 pages; v3: Minor rewording of v1, version to appear in Phys. Rev. Let

Mamíferos encontrados ao Sul do Estado do Acre, Brasil.

Entre os anos de 2004 e 2008, sete inventários de mamíferos foram realizados em quatro áreas sob manejo florestal madeireiro e não madeireiro localizadas ao sul do Estado do Acre. A partir de transectos lineares instalados nas áreas, foi possível identificar 32 espécies pertencentes às ordens Artiodactyla, Perissodactyla, Carnivora, Primates, Rodentia e Xenarthra, que incluíram as espécies ameaçadas de extinção, de distribuição geográfica restrita ou pouco conhecidas. Entre os animais observados destaca-se a predominância dos primatas nas quatro áreas estudadas. Nesse caso, especula-se sobre a possibilidade desse grupo taxonômico ser utilizado como bioindicador da qualidade ambiental das áreas de manejo florestal no Estado do Acre.bitstream/item/77684/1/boletim-de-pesquisa-48.pd

Adoption of Software-as-a-Service (SaaS) Applications in E-learning: Perception of the Management Undergraduates in a Selected State University of Sri Lanka

Software-as-a-Service applications immensely impact the success of e-learning with their ability of cost saving, scalability, and better collaboration. Identifying the factors influencing Software-as-a-Service applications’ adoption and their impact on the adoption of e-learning by management undergraduates in Sri Lanka became the main objectives for this research. 116 responses obtained were analyzed adopting Partial Least Squares-Structural Equation Modelling in SmartPLS. Findings revealed that behavioral intention to adopt such software together with facilitating conditions has a significant impact on the SaaS applications’ adoption by undergraduates in e-learning and factors such as performance expectancy, effort expectancy, and trust determine the intention towards adoption. This research is a value addition to the theoretical arena where studies are lacking regarding SaaS technology, specifically in the context of e-learning. Universities can focus on significant factors determined in this research when promoting the adoption of SaaS applications as an innovative tool to enhance the quality of education. Keywords: Software-as-a-Service; e-learning; UTAUT model; Partial Least Squares-Structural Equation Modellin

Testing for Budget Constraint Effects in a National Advisory Referendum Survey on the Kyoto Protocol

In contrast to providing standard reminders about remembering household budgets, does asking survey respondents about their discretionary income and its use affect their voting responses in a national advisory referendum survey? We explore this question using U.S. household data from a unique set of multi-mode random samples (telephone and Internet surveys), and an advisory referendum concerning the Kyoto Protocol. The contingent valuation method is applied to estimate household willingness to pay (WTP) for a split-sample treatment: respondents who only received a standard reminder of household budgets (control group) versus respondents who received two mental accounting-type questions on discretionary income and its uses (treatment group). Results indicate that the treatment significantly influences voting responses and lowers estimated household WTP.budget constraint, contingent valuation, Kyoto Protocol, mental accounts, referendum, Environmental Economics and Policy,