Bound - states for truncated Coulomb potentials

The pseudoperturbative shifted - $l$ expansion technique PSLET is generalized for states with arbitrary number of nodal zeros. Bound- states energy eigenvalues for two truncated coulombic potentials are calculated using PSLET. In contrast with shifted large-N expansion technique, PSLET results compare excellently with those from direct numerical integration.Comment: TEX file, 22 pages. To appear in J. Phys. A: Math. & Ge

Comment on "Position-dependent effective mass Dirac equations with PT- symmetric and non - PT- symmetric potentials" [J. Phys. A: Math. Gen. 39 (2006) 11877--11887]

Jia and Dutra (J. Phys. A: Math. Gen. 39 (2006) 11877) have considered the one-dimensional non-Hermitian complexified potentials with real spectra in the context of position-dependent mass in Dirac equation. In their second example, a smooth step shape mass distribution is considered and a non-Hermitian non - PT- symmetric Lorentz vector potential is obtained. They have mapped this problem into an exactly solvable Rosen-Morse Schrodinger model and claimed that the energy spectrum is real. The energy spectrum they have reported is pure imaginary or at best forms an empty set. Their claim on the reality of the energy spectrum is fragile, therefore.Comment: 3 pages, 1 figure. To appear in J. Phys.

Classical and quantum quasi-free position dependent mass; P\"oschl-Teller and ordering-ambiguity

We argue that the classical and quantum mechanical correspondence may play a basic role in the fixation of the ordering-ambiguity parameters. We use quasi-free position-dependent masses in the classical and quantum frameworks. The effective P\"oschl-Teller model is used as a manifested reference potential to elaborate on the reliability of the ordering-ambiguity parameters available in the literature.Comment: 10 page

Position-dependent-mass; Cylindrical coordinates, separability, exact solvability, and PT-symmetry

The kinetic energy operator with position-dependent-mass in cylindrical coordinates is obtained. The separability of the corresponding Schr\"odinger equation is discussed within radial cylindrical mass settings. Azimuthal symmetry is assumed and spectral signatures of various z-dependent interaction potentials (Hermitian and non-Hermitian PT-symmetric) are reported.Comment: 16 page

Non-Hermitian von Roos Hamiltonian's η\eta-weak-pseudo-Hermiticity, isospectrality and exact solvability

A complexified von Roos Hamiltonian is considered and a Hermitian first-order intertwining differential operator is used to obtain the related position dependent mass $\eta$-weak-pseudo-Hermitian Hamiltonians. Using a Liouvillean-type change of variables, the $\eta$-weak-pseudo-Hermitian von Roos Hamiltonians H(x) are mapped into the traditional Schrodinger Hamiltonian form H(q), where exact isospectral correspondence between H(x) and H(q) is obtained. Under a user-friendly position dependent mass settings, it is observed that for each exactly-solvable $\eta$-weak-pseudo-Hermitian reference-Hamiltonian H(q)there is a set of exactly-solvable $\eta$-weak-pseudo-Hermitian isospectral target-Hamiltonians H(x). A non-Hermitian PT-symmetric Scarf II and a non-Hermitian periodic-type PT-symmetric Samsonov-Roy potentials are used as reference models and the corresponding $\eta$-weak-pseudo-Hermitian isospectral target-Hamiltonians are obtained.Comment: 11 pages, no figures

Microbial carbon use efficiency predicted from genome-scale metabolic models

Respiration by soil bacteria and fungi is one of the largest fluxes of carbon (C) from the land surface. Although this flux is a direct product of microbial metabolism, controls over metabolism and their responses to global change are a major uncertainty in the global C cycle. Here, we explore an in silico approach to predict bacterial C-use efficiency (CUE) for over 200 species using genome-specific constraint-based metabolic modeling. We find that potential CUE averages 0.62 ± 0.17 with a range of 0.22 to 0.98 across taxa and phylogenetic structuring at the subphylum levels. Potential CUE is negatively correlated with genome size, while taxa with larger genomes are able to access a wider variety of C substrates. Incorporating the range of CUE values reported here into a next-generation model of soil biogeochemistry suggests that these differences in physiology across microbial taxa can feed back on soil-C cycling.Published versio

A Forward Looking Version of the MIT Emissions Prediction and Policy Analysis (EPPA) Model

Abstract and PDF report are also available on the MIT Joint Program on the Science and Policy of Global Change website (http://globalchange.mit.edu/).This paper documents a forward looking multi-regional general equilibrium model developed from the latest version of the recursive-dynamic MIT Emissions Prediction and Policy Analysis (EPPA) model. The model represents full inter-temporal optimization (perfect foresight), which makes it possible to better address economic and policy issues such as borrowing and banking of GHG allowances, efficiency implications of environmental tax recycling, endogenous depletion of fossil resources, international capital flows, and optimal emissions abatement paths among others. It was designed with the flexibility to represent different aggregations of countries and regions, different horizon lengths, as well as the ability to accommodate different assumptions about the economy, in terms of economic growth, foreign trade closure, labor leisure choice, taxes on primary factors, vintaging of capital and data calibration. The forward-looking dynamic model provides a complementary tool for policy analyses, to assess the robustness of results from the recursive EPPA model, and to illustrate important differences in results that are driven by the perfect foresight behavior. We present some applications of the model that include the reference case and its comparison with the recursive EPPA version, as well as some greenhouse gas mitigation cases where we explore economic impacts with and without inter-temporal trade of permits.This research was supported by the U.S Department of Energy, U.S. Environmental Protection Agency, U.S. National Science Foundation, U.S. National Aeronautics and Space Administration, U.S. National Oceanographic and Atmospheric Administration; and the Industry and Foundation Sponsors of the MIT Joint Program on the Science and Policy of Global Change: Alstom Power (USA), American Electric Power (USA), A.P. Møller-Maersk (Denmark), Cargill (USA), Chevron Corporation (USA), CONCAWE & EUROPIA (EU), DaimlerChrysler AG (USA), Duke Energy (USA), Electric Power Research Institute (USA), Electricité de France, Enel (Italy), Eni (Italy), Exelon Power (USA), ExxonMobil Corporation (USA), Ford Motor Company (USA), General Motors (USA), Iberdrola Generacion (Spain), J-Power (Japan), Merril Lynch (USA), Murphy Oil Corporation (USA), Norway Ministry of Petroleum and Energy, Oglethorpe Power Corporation (USA), RWE Power (Germany), Schlumberger (USA),Shell Petroleum (Netherlands/UK), Southern Company (USA), StatoilHydro (Norway), Tennessee Valley Authority (USA), Tokyo Electric Power Company (Japan), Total (France), G. Unger Vetlesen Foundation (USA)

How rare is isolated rheumatic tricuspid valve disease?

The incidence of rheumatic fever (RF) has markedly decreased in Europe since the beginning of the 20th century due to improved living conditions, early antibiotic therapy in streptococcal pharyngitis, and changes in serotypes of circulating streptococci. Isolated outbreaks of RF are still found in various parts of the world and the disease has changed its presentation with milder joint symptoms and subclinical carditis that make the correct diagnosis more difficult. Patients can present many years later with severe valve disease and significant disability. This article presents a case of isolated rheumatic tricuspid valve disease that presented with signs and symptoms of right heart failure and severe valve damage. Isolated involvement of the tricuspid valve is rarely found in rheumatic fever and a thorough differential diagnosis is needed