Quantum Opacity, the RHIC HBT Puzzle, and the Chiral Phase Transition

We present a relativistic quantum mechanical treatment of opacity and refractive effects that allows reproduction of observables measured in two-pion (HBT) interferometry and pion spectra at RHIC. The inferred emission duration is substantial. The results are consistent with the emission of pions from a system that has a restored chiral symmetry.Comment: 4 pages, 2 figures. This version mentions shows the STAR 200 GeV data, and includes some technical improvements. The agreement with experiment is improved slightly, and the parameters of the model are changed slightl

Maternity waiting home as a potential intervention for reducing the maternal mortality ratio in El Salvador: an observational case study

Abstract Background El Salvador is recognized as a country that has effectively reduced its Maternal Mortality Ratio (MMR). While health indicators, such as total fertility rate, adolescent fertility rate, skilled birth attendance, and health expenditures, have improved in El Salvador, this improvement was unremarkable compared to advancements in other developing countries. How El Salvador could achieve an outstanding decrease in MMR despite unexceptional improvements in health and non-health indicators is a question that deserves deep research. We used quantitative methods and an observational case study to show that El Salvador could reduce its MMR more than expected by instituting health policies that not only aimed to reduce the (adolescent) fertility rate, but also provide safe birthing conditions and medical services to pregnant women through maternity waiting homes. Methods We ran pooled ordinary least squares regression and panel regression with fixed effects using MMR as the dependent variable and health and non-health factors as the independent variables. We conducted residual analysis, calculated the predicted value of MMR, and compared it with the observed value in El Salvador. To explain the change in MMR in El Salvador, we carried out an observational case study of maternity waiting homes in that country. Results El Salvador could reduce MMR by improving health factors such as fertility rate skilled birth attendance and non-health factors, such as gross domestic product (GDP) per capita and female empowerment. However, even while considering these factors, the MMR of El Salvador decreased by more than expected. We confirmed this by analyzing the residuals of the regression model. This improvement in MMR, which is larger than expected from the regression results, can be attributed partly to government measures such as maternity waiting homes. Conclusions The reason for the unexplained reduction in El Salvadors MMR seems to be attributed in part to health policies that not only aim to reduce the fertility rate but also to provide safe birthing conditions and medical services to pregnant women through maternity waiting homes

Singularity Structures in Coulomb-Type Potentials in Two Body Dirac Equations of Constraint Dynamics

Two Body Dirac Equations (TBDE) of Dirac's relativistic constraint dynamics have been successfully applied to obtain a covariant nonperturbative description of QED and QCD bound states. Coulomb-type potentials in these applications lead naively in other approaches to singular relativistic corrections at short distances that require the introduction of either perturbative treatments or smoothing parameters. We examine the corresponding singular structures in the effective potentials of the relativistic Schroedinger equation obtained from the Pauli reduction of the TBDE. We find that the relativistic Schroedinger equation lead in fact to well-behaved wave function solutions when the full potential and couplings of the system are taken into account. The most unusual case is the coupled triplet system with S=1 and L={(J-1),(J+1)}. Without the inclusion of the tensor coupling, the effective S-state potential would become attractively singular. We show how including the tensor coupling is essential in order that the wave functions be well-behaved at short distances. For example, the S-state wave function becomes simply proportional to the D-state wave function and dips sharply to zero at the origin, unlike the usual S-state wave functions. Furthermore, this behavior is similar in both QED and QCD, independent of the asymptotic freedom behavior of the assumed QCD vector potential. Light- and heavy-quark meson states can be described well by using a simplified linear-plus-Coulomb-type QCD potential apportioned appropriately between world scalar and vector potentials. We use this potential to exhibit explicitly the origin of the large pi-rho splitting and effective chiral symmetry breaking. The TBDE formalism developed here may be used to study quarkonia in quark-gluon plasma environments.Comment: 23 pages, 4 figure

Fatty Acid-Induced Lipotoxicity in Pancreatic Beta-Cells During Development of Type 2 Diabetes

Type 2 diabetes is caused by chronic insulin resistance and progressive decline in beta-cell function. Optimal beta-cell function and mass is essential for glucose homeostasis and beta-cell impairment leads to the development of diabetes. Elevated levels of circulating fatty acids (FAs) and disturbances in lipid metabolism regulation are associated with obesity, and they are major factors influencing the increase in the incidence of type 2 diabetes. Chronic free FA (FFA) treatment induces insulin resistance and beta-cell dysfunction; therefore, reduction of elevated plasma FFA levels might be an important therapeutic target in obesity and type 2 diabetes. Lipid signals via receptors, and intracellular mechanisms are involved in FFA-induced apoptosis. In this paper, we discuss lipid actions in beta cells, including effects on metabolic pathways and stress responses, to help further understand the molecular mechanisms of lipotoxicity-induced type 2 diabetes

In-rich InGaN/GaN quantum wells grown by metal-organic chemical vapor deposition

Growth mechanism of In-rich InGaN/GaN quantum wells (QWs) was investigated. First, we examined the initial stage of InN growth on GaN template considering strain-relieving mechanisms such as defect generation, islanding, and alloy formation at 730 degrees C. It was found that, instead of formation of InN layer, defective In-rich InGaN layer with thickness fluctuations was formed to relieve large lattice mismatch over 10% between InN and GaN. By introducing growth interruption (GI) before GaN capping at the same temperature, however, atomically flat InGaN/GaN interfaces were observed, and the quality of In-rich InGaN layer was greatly improved. We found that decomposition and mass transport processes during GI in InGaN layer are responsible for this phenomenon. There exists severe decomposition in InGaN layer during GI, and a 1-nm-thick InGaN layer remained after GI due to stronger bond strength near the InGaN/GaN interface. It was observed that the mass transport processes actively occurred during GI in InGaN layer above 730 degrees C so that defect annihilation in InGaN layer was greatly enhanced. Finally, based on these experimental results, we propose the growth mechanism of In-rich InGaN/GaN QWs using GI.open9

Relativistic Generalization of the Gamow Factor for Fermion Pair Production or Annihilation

In the production or annihilation of a pair of fermions, the initial-state or final-state interactions often lead to significant effects on the reaction cross sections. For Coulomb-type interactions, the Gamow factor has been traditionally used to take into account these effects. However the Gamow factor needs to be modified when the magnitude of the coupling constant or the relative velocity of two particles increases. We obtain the relativistic generalization of the Gamow factor in terms of the overlap of the Feynman amplitude with the relativistic wave function of two fermions with an attractive Coulomb-type interaction. An explicit form of the corrective factor is presented for the spin-singlet S-wave state. While the corrective factor approaches the Gamow factor in the non-relativistic limit, we found that the Gamow factor significantly over-estimates the effects when the coupling constant or the velocity is large.Comment: 16 pages, 4 figures in LaTe

Relativistic Modification of the Gamow Factor

In processes involving Coulomb-type initial- and final-state interactions, the Gamow factor has been traditionally used to take into account these additional interactions. The Gamow factor needs to be modified when the magnitude of the effective coupling constant increases or when the velocity increases. For the production of a pair of particles under their mutual Coulomb-type interaction, we obtain the modification of the Gamow factor in terms of the overlap of the Feynman amplitude with the relativistic wave function of the two particles. As a first example, we study the modification of the Gamow factor for the production of two bosons. The modification is substantial when the coupling constant is large.Comment: 13 pages, in LaTe

Optical and microstructural studies of atomically flat ultrathin In-rich InGaN/GaN multiple quantum wells

Optical and microstructural properties of atomically flat ultrathin In-rich (UTIR) InGaN/GaN multiple quantum well were investigated by means of photoluminescence (PL), time-resolved PL (TRPL), and cathodoluminescence (CL) experiments. The sample exhibits efficient trapping of the photoexcited carriers into quantum wells (QWs) and the effect of internal electric field in the QWs was found negligible by excitation power-dependent PL and TRPL. These phenomena were attributed to the nature of UTIR InGaN QWs, indicating the potential of this system for application in optoelectronic devices. Variation of TRPL lifetime across the PL band and spatially resolved monochromatic CL mapping images strongly suggest that there is micrometer-scale inhomogeneity in effective band gap in UTIR InGaN/GaN QWs, which is originated from two types of localized areas.open141