Noether's theorem and gauge transformations. Application to the bosonic string and CP(2,n-1) model

New results on the theory of constrained systems are applied to characterize the generators of Noethers symmetry transformations. As a byproduct, an algorithm to construct gauge transformations in Hamiltonian formalism is derived. This is illustrated with two relevant examples.

Regio- and stereoselective microwave-assisted synthesis of 5-alkyl-4-alkenyl-4-phenyl-1,3-oxazolidin-2-ones

Chiral symmetrical alk-2-yne-1,4-diols have been stereoselectively transformed into 5-alkyl-4-alkenyl-4-phenyl-1,3-oxazolidin- 2-ones, which are precursors of quaternary α-amino β-hydroxy acids. The key step was the cyclization of the bis(tosylcarbamates) of 2- phenylalk-2-yne-1,4-diols, easily obtained from the starting chiral diols. These cyclizations were accomplished with complete regioselectivity and up to 92:8 dr in the presence of catalytic amounts of Ni(0) or Pd (II) derivatives under microwave heating.

La decisión de endeudamiento y los factores de mayor relevancia. Una aplicación empírica en la empresa industrial española

El presente trabajo aborda el estudio de los factores determinantes del endeudamiento empresarial para contrastar empíricamente la hipótesis del Pecking Order. El endeudamiento empresarial se mide junto a su madurez y para los diferentes tamaños empresariales dada la importancia de diferenciar sus posibles efectos contrapuestos o compensados. Los modelos utilizados para el contraste de hipótesis se han estimado con una muestra de 1.320 empresas manufactureras españolas proporcionada por la Encuesta sobre Estrategias Empresariales (ESEE), para el período 1993-2001. El análisis empírico aplica un modelo multivariante de regresión logística que permite concluir que la teoría del Pecking Order es la de mejor cumplimiento, además de constatarse que las empresas de menor tamaño tienen mayores dificultades de acceso a la financiación con deuda a largo plazo.

Supremacía del derecho federal sobre el Common Law en materia de requisitos de seguridad y eficacia terapéutica de productos sanitarios. Comentario a Riegel v. Medtronic, Inc. [552 U.S.__ (2008); February 20, 2008]

En Riegel v. Medtronic Inc. (552 U.S.__2008; February 20, 2008), el Sr. Riegel tuvo que ser sometido a un by-pass como consecuencia de la rotura del catéter, fabricado por Medtronic, con el que su médico le practicaba una angioplastia. A pesar de que el catéter había obtenido la autorización de comercialización de la FDA y cumplía los requisitos de seguridad previstos por el sistema regulatorio federal, el Sr. Riegel y su mujer interpusieron una acción de daños contra Medtronic –y no contra el médico- conforme a las reglas de responsabilidad civil objetiva y por negligencia del Common Law neoyorquino. Sin embargo, el Tribunal Supremo federal de los EE.UU., en ponencia del Magistrado Antonin Gregory Scalia, votó, por mayoría de ocho magistrados, rechazar el recurso de la Sra. Riegel y confirmar la sentencia de segunda instancia, desestimatoria de la demanda, porque consideró que la regla de primacía del derecho regulatorio federal sobre seguridad de productos sanitarios [Medical Device Amendments de 1976, 21 U.S.C. Artículo 360k(a)] excluye la aplicabilidad no sólo del derecho regulatorio estatal sobre seguridad de productos sanitarios, sino también del Common Law sobre responsabilidad civil del fabricante.

Klammt's elastic open activator: Ricketts' cephalometrics results

The purpose of this study is to investigate the orthodontic and orthopaedic real effects of the Klammt's Elastic Open Activator (EOA) in 25 Class II Division 1 patients in growing period. We wanted to determine statistically the cephalometrics changes produced in the patients, comparing the lateral cranium teleradiographies we took for the diagnosis with the ones we took at the end of treatment. At the end of this study we confirm that by using the EOA we obtained the desired effects, especially reducing the molar relation 2.53 mm and the overjet 2.56 mm. The EOA corrected the inclination and protrusion of incisors, although we cannot avoid the use of fixed appliances to round off. The reduction of 2.48 mm of facial convexity stands out as the most important skeletal effect; the facial depth angle increases 0.8 degree, and the maxillary depth decreases 1.16 degrees. The length of the mandibular corpus also increases 6.7 mm, although this change is mainly due to the growth of the patient. The changes in the aesthetic profile do not stand out

Long-term X-ray variability of the microquasar system LS5039/RX J1826.2-1450

We report on the results of the spectral and timing analysis of a BeppoSAX observation of the microquasar system LS 5039/RX J1826.2-1450. The source was found in a low-flux state with Fx(1-10 keV)= 4.7 x 10^{-12} erg cm^{-2} s^{-1}, which represents almost one order of magnitude lower than a previous RXTE observation 2.5 years before. The 0.1--10 keV spectrum is described by an absorbed power-law continuum with photon-number spectral index Gamma=1.8+-0.2 and hydrogen column density of NH=1.0^{+0.4}_{-0.3} x 10^{22} cm^{-2}. According to the orbital parameters of the system the BeppoSAX observation covers the time of an X-ray eclipse should one occur. However, the 1.6-10 keV light curve does not show evidence for such an event, which allows us to give an upper limit to the inclination of the system. The low X-ray flux detected during this observation is interpreted as a decrease in the mass accretion rate onto the compact object due to a decrease in the mass-loss rate from the primary.