A Look at Sovereign Credit Ratings and Their Determinants Throughout the Financial Crisis

The determinants of sovereign credit rating are becoming increasingly more important as many rating agencies have been more active in adjusting their ratings. Our paper analyzed the determinants based on Standard & Poor’s sovereign credit ratings, for the period 1995-2009. Using a linear regression framework, we examined several variables under the political, economic, external, fiscal and monetary categories. The relationship between each determinant was analyzed by isolating each credit rating, and by further employing transformation on specific variables. The results indicate a good performance of the estimated model with a high level of fit. GDP per capita, inflation, default history and advanced economic regions have a significant impact on a country’s credit rating

PPARs and the Cardiovascular System

Abstract Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone-receptor superfamily. Originally cloned in 1990, PPARs were found to be mediators of pharmacologic agents that induce hepatocyte peroxisome proliferation. PPARs also are expressed in cells of the cardiovascular system. PPARγ appears to be highly expressed during atherosclerotic lesion formation, suggesting that increased PPARγ expression may be a vascular compensatory response. Also, ligand-activated PPARγ decreases the inflammatory response in cardiovascular cells, particularly in endothelial cells. PPARα, similar to PPARγ, also has pleiotropic effects in the cardiovascular system, including antiinflammatory and antiatherosclerotic properties. PPARα activation inhibits vascular smooth muscle proinflammatory responses, attenuating the development of atherosclerosis. However, PPARδ overexpression may lead to elevated macrophage inflammation and atherosclerosis. Conversely, PPARδ ligands are shown to attenuate the pathogenesis of atherosclerosis by improving endothelial cell proliferation and survival while decreasing endothelial cell inflammation and vascular smooth muscle cell proliferation. Furthermore, the administration of PPAR ligands in the form of TZDs and fibrates has been disappointing in terms of markedly reducing cardiovascular events in the clinical setting. Therefore, a better understanding of PPAR-dependent and -independent signaling will provide the foundation for future research on the role of PPARs in human cardiovascular biology. Antioxid. Redox Signal. 11, 1415-1452.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78115/1/ars.2008.2280.pd

Carpet cloaking on a dielectric half-space

Carpet cloaking is proposed to hide an object on a dielectric half-space from electromagnetic (EM) detection. A two-dimensional conformal transformation specified by an analytic function is utilized for the design. Only one nonsingular material parameter distribution suffices for the characterization. The cloaking cover situates on the dielectric half-space, and consists of a lossless upper part for EM wave redirection and an absorbing bottom layer for inducing correct reflection coefficient and absorbing transmission. Numerical simulations with Gaussian beam incidence are performed for verification.Comment: 6 pages, 3 figure

Bulk and brane gauge propagator on 5d AdS black hole

The bulk gauge fields on 5d AdS black hole are discussed. We construct the bulk (and the corresponding brane) gauge propagator when black hole has large radius. The properties of gauge and ghost propagators are studied in both, minkowski or euclidean signature. In euclidean formulation the propagator structure corresponds to the one of theory at finite temperature (which depends on coordinates). The decoupling of KK modes and localization of gauge fields on flat brane is demonstrated. We show that with such a bulk there is no natural solution of hierarchy problem.Comment: LaTeX 14 pages, shortened version, to be published in PL

String Cosmology: A Review

The second string revolution, which begin around 1995, has led to a drastic alteration in our perception of the universe, perhaps even more so then did the first string revolution of 1984. That is, extending 10-dimensional string theory to 11-dimensional M-theory has had more profound implications than did the original extension of 4-dimensional quantum mechanics and relativity to 10-dimensional string theory. After a brief review of M-theory, I discuss some implications of large extra dimensions. I then consider astronomical evidence for, and constraints on, large compactified dimensions. I conclude with a possible resolution to the apparent inconsistency between the MSSM scale and string scale in the weak coupling limit. Talk presented at COSPAR '02, Houston, Texas, October 2002.Comment: 10 pages. Standard Latex. Changes to match retitled published versio

Experimental procedures for precision measurements of the Casimir force with an Atomic Force Microscope

Experimental methods and procedures required for precision measurements of the Casimir force are presented. In particular, the best practices for obtaining stable cantilevers, calibration of the cantilever, correction of thermal and mechanical drift, measuring the contact separation, sphere radius and the roughness are discussed.Comment: 14 pages, 7 figure

Structural Characteristics of Polycyclic Aromatic Hydrocarbon Isomers in Coal Tars and Combustion Products

4 Isomeric polycyclic aromatic hydrocarbons (PAH) with two to six rings in coal-derived products and in a carbon black were separated, identified, and quantified by using capillary column gas chromatography and gas chromatography-mass spectrometry. A newly synthesized smectic liquid-crystalline polysiloxane and a conventional polymethylsiloxane were utilized as stationary phases. Many previously difficult to separate isomeric PAH (i.e., methylphenanthrenes/methylanthracenes, triphenylene/ chrysene, methylchrysenes, benzofluoranthenes, and pentaphene/benzo[b]chrysene) were identified. The relative abundances of the PAH in these samples were compared and correlated to the reaction conditions during their production. The relationship between abundance and structure for the identified PAH was also discussed. Introduction Coal-derived products and thermally cracked petroleum oils are highly aromatic in nature and contain polycyclic aromatic hydrocarbons (PAH) as major components. Although average descriptive parameters are usually obtained for such materials (i.e., distillation curve, molecular weight range, aromaticity, etc.), it is oftentimes very important to obtain detailed compositional and structural information. Many of the PAH are toxic and/or mutagenic in various biological test systems. The toxicities of various PAH are related to specific structures and positions of ring substitution. The methylphenanthrene and methylchrysene isomers are typical examples. The 1-and 9-methylphenanthrenes are mutagenic, while the other isomers are inactive ( I ) , and 5-methylchrysene is one of the strongest carcinogens, while the other isomers are only moderately carcinogenic (2). Isomeric parent PAH may differ markedly in their activities; benzo[a]pyrene has significantly greater carcinogenicity than benzo[e]pyrene, the relative carcinogenicity varies within the series of dibenzanthracenes, and benzo[g]chrysene appears to be more active than benzo[c]chrysene A number of components of the process oils play important roles in the upgrading processes. Hydrogenated compounds such as tetralin are hydrogen donor solvents for coal liquefaction (5). Cracked gas oils containing highly aromatic compounds are often composed of discontinuous fractions in discrete boiling point ranges. For example

Modifying the Casimir force between indium tin oxide film and Au sphere

We present complete results of the experiment on measuring the Casimir force between an Au-coated sphere and an untreated or, alternatively, UV-treated indium tin oxide film deposited on a quartz substrate. Measurements were performed using an atomic force microscope in a high vacuum chamber. The measurement system was calibrated electrostatically. Special analysis of the systematic deviations is performed, and respective corrections in the calibration parameters are introduced. The corrected parameters are free from anomalies discussed in the literature. The experimental data for the Casimir force from two measurement sets for both untreated and UV-treated samples are presented. The experimental errors are determined at a 95% confidence level. It is demonstrated that the UV treatment of an I TO plate results in a significant decrease in the magnitude of the Casimir force (from 21% to 35% depending on separation). However, ellipsometry measurements of the imaginary parts of dielectric permittivities of the untreated and UV-treated samples did not reveal any significant differences. The experimental data are compared with computations in the framework of the Lifshitz theory. It is found that the data for the untreated sample are in a very good agreement with theoretical results taking into account the free charge carriers in an ITO film. For the UV-treated sample the data exclude the theoretical results obtained with account of free charge carriers. These data are in a very good agreement with computations disregarding the contribution of free carriers. According to the explanation provided, this is caused by the phase transition of the ITO film from metallic to dielectric state caused by the UV treatment. Possible applications of the discovered phenomenon in nanotechnology are discussed.Comment: 30 pages, 19 figures, 1 tabl

Hydrodynamic limit for a zero-range process in the Sierpinski gasket

We prove that the hydrodynamic limit of a zero-range process evolving in graphs approximating the Sierpinski gasket is given by a nonlinear heat equation. We also prove existence and uniqueness of the hydrodynamic equation by considering a finite-difference scheme.Comment: 24 pages, 1 figur

Measurement of the gradient of the Casimir force between a nonmagnetic sphere and a magnetic plate

We measured the gradient of the Casimir force between an Au sphere and a plate made of ferromagnetic metal (Ni). It is demonstrated that the magnetic properties influence the force magnitude. This opens prospective opportunities for the control of the Casimir force in nanotechnology and for obtaining Casimir repulsion by using ferromagnetic dielectrics.Comment: 15 pages, 4 figures, to appear in Phys. Rev.