The AdS/CFT correspondence in two dimensions

We review recent progress in understanding the anti-de Sitter/conformal field theory correspondence in the context of two-dimensional dilaton gravity theory.Comment: Contribution to the Proceedings of the Euroconference on "Brane New World and Noncommutative Geometry", Turin, October 200

Creditor Control Rights and Board Independence

We find that the number of independent directors on corporate boards increases by approximately 24% following financial covenant violations in credit agreements. Most of these new directors have links to creditors. Firms that appoint new directors after violations are more likely to issue new equity, and to decrease payout, operational risk and CEO cash compensation than firms without such appointments. We conclude that a firm’s board composition, governance, and policies are shaped by current and past credit agreements

Structural properties of fluids interacting via piece-wise constant potentials with a hard core

The structural properties of fluids whose molecules interact via potentials with a hard core plus two piece-wise constant sections of different widths and heights are presented. These follow from the more general development previously introduced for potentials with a hard core plus $n$ piece-wise constant sections [Condens. Matter Phys. {\bf 15}, 23602 (2012)] in which use was made of a semi-analytic rational-function approximation method. The results of illustrative cases comprising eight different combinations of wells and shoulders are compared both with simulation data and with those that follow from the numerical solution of the Percus-Yevick and hypernetted-chain integral equations. It is found that the rational-function approximation generally predicts a more accurate radial distribution function than the Percus-Yevick theory and is comparable or even superior to the hypernetted-chain theory. This superiority over both integral equation theories is lost, however, at high densities, especially as the widths of the wells and/or the barriers increase.Comment: 10 pages, 11 figures; v2: Old Fig. 1 removed, new text on the correlation length, 7 new references added, plus other minor change

Instability of the R^3\times S^1 vacuum in low-energy effective string theory

We present and discuss an euclidean solution of the low-energy effective string action that can be interpreded as a semiclassical decay process of the ground state of the theory.Comment: 9 pages, plain-tex file, 2 figures available upon reques

Gender Differences in Acute Ischemic Stroke Treatment

Introduction: In order to personalize stroke treatment, it is important to know if there are differences between genders in clinical features, acute phase treatment and outcomes. Material and Methods: Longitudinal retrospective study that included patients with ischemic stroke, admitted in a stroke unit during a 30 months period and treated with throm bectomy with or without thrombolysis. The objective was to assess gender differences. Results: Of 594 patients included, 50% were women. At admission, women had higher median age (78 vs 73 years), higher modified Rankin Score (mRS) and higher median Na tional Institutes of Health Stroke Scale (NIHSS). No gender differences were found in treatment type, median time be tween symptoms onset and computed tomography, between computed tomography and thrombolysis and with respect to revascularization success. Disability expressed by mRS and mortality at 3 months were similar between genders. More women had atrial fibrillation (AF) (51% vs 35%), nevertheless, less women with known AF were receiving anticoagulant ther apy before the event, compared to men (38% vs 52%). Discussion: Even if women were older and had worse pre morbid functional status, no gender differences were evident with regard to acute phase treatment efficacy and medium term outcomes. Conclusion: In women, age should not limit acute phase treatment of stroke and decisions should be individualizedIntrodução: Na abordagem personalizada do acidente vascular cerebral (AVC) é importante definir se existem diferenças de género relativamente às caraterísticas clínicas, tratamento de fase aguda e resultados. Material e Métodos: Estudo longitudinal retrospetivo que incluiu doentes com AVC isquémico admitidos na Unidade Cerebro Vascular, durante 30 meses, tratados com trombectomia com ou sem trombólise prévia, com o objetivo de avaliar diferenças de género. Resultados: De 594 doentes, 50% eram mulheres apresentando, à admissão, idade mediana maior (78 vs 73 anos), maior pontuação na escala modificada de Rankin (mRS) e na National Institutes of Health Stroke Scale (NIHSS). Não houve diferenças no tipo de tratamento, no tempo mediano entre o início dos sintomas e tomografia computadorizada (TC), entre o tempo TC-trombólise ou na eficácia da revascularização. A disabilidade expressa pelo valor de mRS e a mortalidade aos 3 meses foram sobreponíveis entre géneros. Mais mulheres sofriam de fibrilhação auricular (FA) (51% vs 35%), no entanto menos mulheres com FA conhecida recebiam terapêutica anticoagulante antes do evento, comparativamente aos homens (38% vs 52%). Discussão: Apesar das mulheres apresentarem idade mais elevada e maior grau de dependência, não existiram diferenças de género na eficácia do tratamento de fase aguda nem nos resultados a médio prazo. Conclusão: No género feminino, a idade não deve constituir uma limitação à realização de terapêutica de fase aguda do AVC.info:eu-repo/semantics/publishedVersio

Structural, vibrational and electronic properties of SnMBO4 (M = Al, Ga): A predictive hybrid DFT study

We propose two new members of the mullite-type family, SnAlBO4 and SnGaBO4, and carry out an in-depth study of their crystal properties using the hybrid method PW1PW. Both are isostructural to PbMBO4 (M = Fe, Mn, Al, Ga), which show axial negative linear compressibility (ANLC), among other interesting features. We find that, although Sn2+ is susceptible of being oxidized by oxygen, a suitable range of experimental parameters exists in which the compounds could be synthesized. We observe absence of ANLC below 20 GPa and explain it by the small space occupied by the lone electron pairs, as indicated by the small length of the corresponding Liebau Density Vectors. In agreement with this fact, the structures present a low number of negative mode-Grüneisen parameters, which may also suggest lack of negative thermal expansion. The electronic properties show a remarkable anisotropic behaviour, with a strong dependence of the absorption spectra on light polarization direction

Prediction of stable walking for a toy that cannot stand

Previous experiments [M. J. Coleman and A. Ruina, Phys. Rev. Lett. 80, 3658 (1998)] showed that a gravity-powered toy with no control and which has no statically stable near-standing configurations can walk stably. We show here that a simple rigid-body statically-unstable mathematical model based loosely on the physical toy can predict stable limit-cycle walking motions. These calculations add to the repertoire of rigid-body mechanism behaviors as well as further implicating passive-dynamics as a possible contributor to stability of animal motions.Comment: Note: only corrections so far have been fixing typo's in these comments. 3 pages, 2 eps figures, uses epsf.tex, revtex.sty, amsfonts.sty, aps.sty, aps10.sty, prabib.sty; Accepted for publication in Phys. Rev. E. 4/9/2001 ; information about Andy Ruina's lab (including Coleman's, Garcia's and Ruina's other publications and associated video clips) can be found at: http://www.tam.cornell.edu/~ruina/hplab/index.html and more about Georg Bock's Simulation Group with whom Katja Mombaur is affiliated can be found at http://www.iwr.uni-heidelberg.de/~agboc

Dynamical model for Pion - Nucleon Bremsstrahlung

A dynamical model based on effective Lagrangians is proposed to describe the bremsstrahlung reaction $\pi N \to \pi N \gamma$ at low energies. The $\Delta(1232)$ degrees of freedom are incorporated in a way consistent with both, electromagnetic gauge invariance and invariance under contact transformations. The model also includes the initial and final state rescattering of hadrons via a T-matrix with off-shell effects. The $\pi N \gamma$ differential cross sections are calculated using three different T-matrix models and the results are compared with the soft photon approximation, and with experimental data. The aim of this analysis is to test the off-shell behavior of the different T-matrices under consideration.Comment: 16 pages, latex, 6 eps figures. Accepted for publication in Physical Review

2D Extremal Black Holes as Solitons

We discuss the relationship between two-dimensional (2D) dilaton gravity models and sine-Gordon-like field theories. We show that there is a one-to-one correspondence between the solutions of 2D dilaton gravity and the solutions of a (two fields) generalization of the sine-Gordon model. In particular, we find a connection between the soliton solutions of the generalized sine-Gordon model and extremal black hole solutions of 2D dilaton gravity. As a by-product of our calculations we find a easy way to generate cosmological solutions of 2D dilaton gravity.Comment: 12 pages, LaTex, no figures, typos correcte