4,502 research outputs found
Energy consumption, income and CO2 emissions in Latin America
I describe and compare the environment policies of European Union and of 12 Latin Americans economies. For this, I use common statistical methods, such as non-parametric tests, convergence analysis (Beta and Sigma) and panel data, in order to verify the hypothesis that emissions and energy use in Latin America has been increasing since the mid-20th century. The statistical tests used confirm the proposed hypothesis. I also rely upon the Environmental Kuznets Curve- whereby economies that are at the growth stage are more focused on achieving the latter than they are on environmental concerns and those which have already achieved growth focus more on environmental concerns-to take an alternative approach by introducing the role of economic growth in the evolution of energy consumption and emissions. This chapter reaches the conclusion that energy consumption and pollutant emissions in LA, in per capita terms, are converging. This suggests that the initial levels of the variables help to explain why some countries have increased emissions (in this case, energy consumption) to a greater extent than other economies in the region. Evidence of convergence is also found, as well as a monotonic relationship between the level of pollution and the level of development (consistent with the Environmental Kuznets Curve).Energy Consumption, emissions, Latin America, Convergence
Ekpyrotic universes in Ho\v{r}ava-Lifshitz gravity
The Ekpyrotic scenario is studied in the context of some extensions of
Ho\v{r}ava-Lifshitz gravity. Some particular solutions that lead to cyclic
Hubble parameters are analyzed, where the corresponding gravitational actions
are reconstructed by using several techniques and auxiliary fields. Its
comparison with standard gravity is performed. In addition, the
so-called Little Rip, a stage of the universe evolution when some bounded
systems may be dissolute, is also studied in this frame of theories.Comment: 12 pages. Version to be published in PR
Quasi-exact solvability beyond the SL(2) algebraization
We present evidence to suggest that the study of one dimensional
quasi-exactly solvable (QES) models in quantum mechanics should be extended
beyond the usual \sla(2) approach. The motivation is twofold: We first show
that certain quasi-exactly solvable potentials constructed with the \sla(2)
Lie algebraic method allow for a new larger portion of the spectrum to be
obtained algebraically. This is done via another algebraization in which the
algebraic hamiltonian cannot be expressed as a polynomial in the generators of
\sla(2). We then show an example of a new quasi-exactly solvable potential
which cannot be obtained within the Lie-algebraic approach.Comment: Submitted to the proceedings of the 2005 Dubna workshop on
superintegrabilit
Formation of X-ray emitting stationary shocks in magnetized protostellar jets
X-ray observations of protostellar jets show evidence of strong shocks
heating the plasma up to temperatures of a few million degrees. In some cases,
the shocked features appear to be stationary. They are interpreted as shock
diamonds. We aim at investigating the physics that guides the formation of
X-ray emitting stationary shocks in protostellar jets, the role of the magnetic
field in determining the location, stability, and detectability in X-rays of
these shocks, and the physical properties of the shocked plasma. We performed a
set of 2.5-dimensional magnetohydrodynamic numerical simulations modelling
supersonic jets ramming into a magnetized medium and explored different
configurations of the magnetic field. The model takes into account the most
relevant physical effects, namely thermal conduction and radiative losses. We
compared the model results with observations, via the emission measure and the
X-ray luminosity synthesized from the simulations. Our model explains the
formation of X-ray emitting stationary shocks in a natural way. The magnetic
field collimates the plasma at the base of the jet and forms there a magnetic
nozzle. After an initial transient, the nozzle leads to the formation of a
shock diamond at its exit which is stationary over the time covered by the
simulations (~ 40 - 60 yr; comparable with time scales of the observations).
The shock generates a point-like X-ray source located close to the base of the
jet with luminosity comparable with that inferred from X-ray observations of
protostellar jets. For the range of parameters explored, the evolution of the
post-shock plasma is dominated by the radiative cooling, whereas the thermal
conduction slightly affects the structure of the shock.Comment: Accepted for publication in Astronomy and Astrophysic
Mapping lung squamous cell carcinoma pathogenesis through in vitro and in vivo models
Lung cancer is the main cause of cancer death worldwide, with lung squamous cell carcinoma (LUSC) being the second most frequent subtype. Preclinical LUSC models recapitulating human disease pathogenesis are key for the development of early intervention approaches and improved therapies. Here, we review advances and challenges in the generation of LUSC models, from 2D and 3D cultures, to murine models. We discuss how molecular profiling of premalignant lesions and invasive LUSC has contributed to the refinement of in vitro and in vivo models, and in turn, how these systems have increased our understanding of LUSC biology and therapeutic vulnerabilities
El modelo de Ausubel en la didáctica de la física : una aproximanción experimental al proceso de E/A de contenidos que presentan constructos poco elaborados por los aprendices
This paper shows the results of a research on physics education about «Magnetism» in secondary school. We investigate a constructivist approach to instructional design based upon Ausubel's model in the treatment of subjects on which pupils have poor conceptual representations and alternative frameworks. The first results with respect to inmediate and lasting learning, are shown
A conjecture on Exceptional Orthogonal Polynomials
Exceptional orthogonal polynomial systems (X-OPS) arise as eigenfunctions of
Sturm-Liouville problems and generalize in this sense the classical families of
Hermite, Laguerre and Jacobi. They also generalize the family of CPRS
orthogonal polynomials. We formulate the following conjecture: every
exceptional orthogonal polynomial system is related to a classical system by a
Darboux-Crum transformation. We give a proof of this conjecture for codimension
2 exceptional orthogonal polynomials (X2-OPs). As a by-product of this
analysis, we prove a Bochner-type theorem classifying all possible X2-OPS. The
classification includes all cases known to date plus some new examples of
X2-Laguerre and X2-Jacobi polynomials
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