Nuclear forces from chiral Lagrangians using the method of unitary transformation I: Formalism

We construct the two- and three-nucleon potential based on the most general chiral effective pion-nucleon Lagrangian using the method of unitary transformations. For that, we develop a power counting scheme consistent with this projection formalism. In contrast to previous results obtained in old-fashioned time-ordered perturbation theory, the method employed leads to energy-independent potentials. We discuss in detail the similarities and differences to the existing chiral nucleon-nucleon potentials. We also show that to leading order in the power counting, the three-nucleon forces vanish lending credit to the result obtained by Weinberg using old-fashioned time-ordered perturbation theory.Comment: 27 pp, LaTeX file, 8 figures (uses epsf

Spatial and temporal variability of CO2 emisions in soils under conventional tillage and no-till farming

Agricultural soils can act as a carbon sink depending on the soil management practices employed. As a result of this functional duality, soil management systems are present in international documents relating to climate change mitigation. Agricultural practices are responsible for 14% of total greenhouse gas emissions (GHG’s) (MMA, 2009)(1). Conservation agriculture (CA) is one of the most effective agricultural systems for reducing CO2 emissions, as it increases the sequestration of atmospheric carbon in the soil. In order to assess the performance of CA in terms of CO2 emissions, a field trial was conducted comparing soil derived CO2 fluxes under No-till (NT) farming and under conventional tillage. Three pilot farms were selected in the cereal-growing area of southern Spain, located in Las Cabezas de San Juan (Seville), Carmona (Seville) and Cordoba. Each pilot farm comprises six experimental plots with an approximate area of five hectares; three of the six plots implement CA practices, while the other three use conventional tillage techniques. The subdivision of each tillage system into 3 plots allowed the simultaneous cropping of the three crops of the wheat-sunflower-legume rotation each year. Results showed that carbon dioxide emissions were 31 to 91% higher in tilled soils than in untilled soils, and that there was a great seasonal variability of CO2 emissions, as weather conditions also differed considerably for the different sampling periods. In all cases, the CO2 fluxes emitted into the atmosphere were always higher when soil was subject to conventional tillage

Regularized Green's Function for the Inverse Square Potential

A Green's function approach is presented for the D-dimensional inverse square potential in quantum mechanics. This approach is implemented by the introduction of hyperspherical coordinates and the use of a real-space regulator in the regularized version of the model. The application of Sturm-Liouville theory yields a closed expression for the radial energy Green's function. Finally, the equivalence with a recent path-integral treatment of the same problem is explicitly shown.Comment: 10 pages. The final section was expande

El seguro de accidentes personales en Colombia y su visión jurisprudencial.

Un recorrido a través de 25 años de jurisprudencia colombiana, permite al autor exponer y comentar la posición de la jurisprudencia nacional en torno a la definición de accidente y la distribución de la carga probatoria en las pólizas de seguro de riesgos accidentales. Se destaca este artículo por poner de presente el contraste existente entre el derecho colombiano y el de los países europeos en lo referido a la definición del riesgo en este tipo de pólizas, con base en requerimientos de intencionalidad por parte del tercero que con su intervención da lugar al siniestro

Four-nucleon force in chiral effective field theory

We derive the leading contribution to the four-nucleon force within the framework of chiral effective field theory. It is governed by the exchange of pions and the lowest-order nucleon-nucleon contact interaction and includes effects due to the nonlinear pion-nucleon couplings and the pion self interactions constrained by the chiral symmetry of QCD. The resulting four-nucleon force does not contain any unknown parameters and can be tested in few- and many-nucleon studies.Comment: 4 pages, 4 figure

Distributional extensions of Carollia castanea and Micronycteris minuta from Guatemala, Central America

Field expeditions in 2011 that inventoried the terrestrial vertebrate fauna of two wildlife protected areas in the tropical Caribbean of Guatemala have produced the first confirmed records of two bats for the country: the white-bellied big-eared bat, Micronycteris (Schizonycteris) minuta (Gervais 1856) and the Chesnut short-tailed bat Carollia castanea H. Allen, 1890, both of neotropical distribution and with their current northern limit at Lancetilla, Honduras. The record of M. minuta at Sierra de Caral, Guatemala extends the range of this species 137 km to the west, and the record of C. castanea at Cerro San Gil extends its range 147 km to the west

The Dark Side of Goal Setting: The Role of Goals in Motivating Unethical Decision Making

A substantial literature has demonstrated that goal setting improves task performance (Locke & Latham, 1990). In this article we explore the proposition that challenging goals motivate not only constructive behavior, but also unethical behavior such as lying and cheating. We conducted eight scenario studies and an anagram experiment, and find support for our thesis. Respondents rated individuals with unmet goals as significantly more likely to engage in unethical behavior than similar individuals attempting to do their best or with met goals. Similarly, participants in the goal conditions in our experiment were significantly more likely to misrepresent their productivity in an anagram task than were participants in the do your best condition. This relationship was particularly strong when people had reward rather than mere goals, and when people were just short of reaching the goal. We explain our results in terms of the reference point adoption process consistent with Prospect Theory (Kahneman & Tversky, 1979), and identify specific contributions to goal setting theory and management practice