Dynamical Aspects of Generalized Palatini Theories of Gravity

We study the field equations of modified theories of gravity in which the lagrangian is a general function of the Ricci scalar and Ricci-squared terms in Palatini formalism. We show that the independent connection can be expressed as the Levi-Civita connection of an auxiliary metric which, in particular cases of interest, is related with the physical metric by means of a disformal transformation. This relation between physical and auxiliary metric boils down to a conformal transformation in the case of f(R) theories. We also show with explicit models that the inclusion of Ricci squared terms in the action can impose upper bounds on the accessible values of pressure and density, which might have important consequences for the early time cosmology and black hole formation scenarios. Our results indicate that the phenomenology of f(R_{ab}R^{ab}) theories is much richer than that of f(R) and f(R_{ab}R^{ab}) theories and that they also share some similarities with Bekenstein's relativistic theory of MOND.Comment: 8 pages, no figure

DYNAMIC STUDY OF FOOTWEAR MATERIALS SIMULATING REAL LOADS

The study of footwear materials has been traditionally based on the determination of the stiffness and the use of the shore A level or in the shock absorbing capacity. In most of the papers ody one of those parameters is determined in spite of the relation between them is not clear; a quite soft material doesn't have necessary to be shock absorbing and a shock absorbing material can be quite rigid. Besides the study of footwear materials has to face two main problem. The first one is that most of the materials used in footwear under the loads occurring in the sport movements, specially in running or jumping, are no more linear because of the high level of the forces developed in those movements. This means that the rigidity of the material depends on the load and increases with load. The second problem is owed to the viscoelastic behaviour of most of those materials. The rigidity of a viscoelastic material increases as the frequency increases. For these reasons the study of footwear materials must be done by simulating the forces occurring in the movements developed in the sport the footwear is conceived for. This paper presents a new methodology of study of footwear materials bawd on the determination of the loads applied and its simulation by means of a dynamic testing machine. Both the rigidity and the shock absorbing capacity of the materials are investigated a a function of frequency. This method permits lo know not only the behaviour of the material in real situations but also which frequencies are the ones preferably absorbed. This is specially interesting because of the general estimation that high frequencies are related with injuries located in the articular cartilage. Some materials used in running shoes are studied and both the influence of thickness and composition aw investigated. The results presented are compared with the previously published obtained when the loads applied are perfect sinus waves. The results show that while the rigidity always increases with frequency with a rate depending on the material, the shock absorbing capacity variation with frequency depends on the material. The shock absorbing capacity of the material a a function of thickness results show that as the thickness increases the shock absorbing capacity increases too. For the rigidity the influence of the thickness in the bottoming out of the material is clearly showed. The thickness analysis also shorn that it is possible to obtain a optimum thickness determined when a thicker material doesn't means a significant increase in shock absorbing capacity and a lowering of rigidity

El presente de la cirugía artroscópica. ¿Dónde está el límite?

La cirugía artroscópica ha supuesto un importante avance en las técnicas terapéuticas y diagnósti - cas dentro del campo de la cirugía ortopédica, convirtiéndose en estas dos últimas décadas en uno de los grandes pilares de la cirugía mínimamente invasiva de grandes y pequeñas articulaciones, permitiendo la realización de técnicas quirúrgicas que hace unos años hubiese sido impensable. El objetivo de este trabajo es analizar las indicaciones y técnicas quirúrgicas artroscópicas que actualmente realizamos en nuestro equipo basándonos en niveles de evidencia científica y una valoración del futuro de la cirugía artroscópica.Arthroscopic surgery has involved a great advance in diagnostic and therapeutic techniques within orthopedic surgery field. For twenty years now, it has become as one of the great pillars of minimally invasive surgery of large and small joints, allowing the realization of surgical techniques that a few years ago would be unthinkable. Aim of this study is to analyze currently indications and arthroscopic surgical techniques performed in our work team based on levels of scientific evidence and the assessment of arthroscopic surgery in the future

Fracturas diafisarias de húmero : enclavijamiento intramedular con agujas de Hackethal por vía epicondílea lateral

Presentamos un estudio de 58 pacientes con fracturas diafisarias de húmero tratados mediante enclavijamiento intramedular con agujas de Hackethal por la vía epicondílea lateral. Se analizan las indicaciones quirúrgicas y la técnica empleada y se valoran los resultados finales tanto clínica como radiológicamente, obteniendo buenos resultados en el 85% de los casos y malos en el 15%. La causa principal de estos malos resultados fue la aparición de pseudoartrosis, relacionándose ésta con diástasis del foco de fractura después de la reducción y la existencia de fuerzas distractoras y rotacionales en los métodos de inmovilización postquirúrgica.This study was based on 58 patients with diaphyseal fractures of the humerus, treated by Hackethal fascicular intramedullary pinning inserted at the lateral humeral epicondyle. We analysed the indications for the operation using the modified Hackethal technique. We evaluated the final clinical and radiological results, obtaining 85% good results and 15% poor results. The main cause for these poor results was the appearance of no-union due to diastasis of the fracture focus after reduction and the presence of traction and rotational forces in the postoperative inmobilization methods

Fractura bilateral de epitroclea: a propósito de 1 caso

Presentamos 1 caso infrecuente de fractura bilateral de epitroclea en un paciente varón de 15 años, tratado mediante osteosíntesis con agujas de Kirschner más transposición anterior de ambos nervios cubitales.We present an unfrequent case of bilateral fracture of the medial epicondyle, in a 15-year-old boy that was treated with Kirschner wires and anterior transposition of the ulnar nerve

Static quantum corrections to the Schwarzschild spacetime

We study static quantum corrections of the Schwarzschild metric in the Boulware vacuum state. Due to the absence of a complete analytic expression for the full semiclassical Einstein equations we approach the problem by considering the s-wave approximation and solve numerically the associated backreaction equations. The solution, including quantum effects due to pure vacuum polarization, is similar to the classical Schwarzschild solution up to the vicinity of the classical horizon. However, the radial function has a minimum at a time-like surface close to the location of the classical event horizon. There the g_{00} component of the metric reaches a very small but non-zero value. The analysis unravels how a curvature singularity emerges beyond this bouncing point. We briefly discuss the physical consequences of these results by extrapolating them to a dynamical collapsing scenario.Comment: 10 pages; Talk given at QG05, Cala Gonone (Italy), September 200

Estudio biomecánico in vivo del grupo muscular flexor del codo en condiciones basales y su respuesta a la fatiga.

El objetivo del presente trabajo es establecer una aproximación al patrón de referencia habitual de la biomecánica del bíceps braquial y su respuesta a la fatiga. Sobre 37 voluntarios varones sanos se determinó una capacidad de contracción voluntaria máxima de flexión del codo de 266,8 ± 58,7N en el brazo dominante y de 258,2 ± 59,4N en el no dominante, que descendió a 211,5 ± 53N y 205,3 ± 56,5N respectivamente al someter a los voluntarios al test de fatiga (p<0,001 en ambos). El tiempo de fatiga se objetivó en 160,7 ± 72,8 s en el brazo dominante y en 156,7 ± 68,7 s en el no dominante. La supinación voluntaria máxima disminuyó de 208,7 ± 54N y 207 ± 54,8N hasta 194,1 ± 66,6N y 192,8 ± 66N respectivamente en el estudio postfatiga (p<0,001 en ambas). No se apreciaron diferencias significativas en el estudio de subgrupos por edades

The 5' Untranslated Region of the EFG1 Transcript Promotes Its Translation To Regulate Hyphal Morphogenesis in Candida albicans

Extensive 5' untranslated regions (UTR) are a hallmark of transcripts determining hyphal morphogenesis in Candida albicans The major transcripts of the EFG1 gene, which are responsible for cellular morphogenesis and metabolism, contain a 5' UTR of up to 1,170 nucleotides (nt). Deletion analyses of the 5' UTR revealed a 218-nt sequence that is required for production of the Efg1 protein and its functions in filamentation, without lowering the level and integrity of the EFG1 transcript. Polysomal analyses revealed that the 218-nt 5' UTR sequence is required for efficient translation of the Efg1 protein. Replacement of the EFG1 open reading frame (ORF) by the heterologous reporter gene CaCBGluc confirmed the positive regulatory importance of the identified 5' UTR sequence. In contrast to other reported transcripts containing extensive 5' UTR sequences, these results indicate the positive translational function of the 5' UTR sequence in the EFG1 transcript, which is observed in the context of the native EFG1 promoter. It is proposed that the 5' UTR recruits regulatory factors, possibly during emergence of the native transcript, which aid in translation of the EFG1 transcript. IMPORTANCE Many of the virulence traits that make Candida albicans an important human fungal pathogen are regulated on a transcriptional level. Here, we report an important regulatory contribution of translation, which is exerted by the extensive 5' untranslated regulatory sequence (5' UTR) of the transcript for the protein Efg1, which determines growth, metabolism, and filamentation in the fungus. The presence of the 5' UTR is required for efficient translation of Efg1, to promote filamentation. Because transcripts for many relevant regulators contain extensive 5' UTR sequences, it appears that the virulence of C. albicans depends on the combination of transcriptional and translational regulatory mechanisms

Estudio biomecánico del proceso de consolidación de fracturas con sistemas de fijación externa rígidos y elásticos

El objetivo básico de este trabajo es discernir las diferencias existentes entre los sistemas de fijación externa rígidos y elásticos aplicados al tratamiento de fracturas óseas. El abordaje de este problema se ha cubierto en varias etapas, la primera de ellas ha consistido en el diseño de un fijador externo que permitiera un comportamiento rígido y con posibilidad de transformación en elástico, utilizable en tibias de conejo adulto. A continuación se ha realizado un estudio teórico de dicho fijador mediante el método de los elementos finitos (MEF) y, finalmente, un estudio en animales de experimentación en tres campos: biomecánico, morfológico y monitorización "in vivo" del callo de fractura. El estudio teórico realizado en ambos sistemas de fijación ha mostrado que, con independencia del método de inmovilización utilizado (rígido o elástico), las cargas soportadas por el callo de fractura dependen básicamente de las características elásticas de este elemento. Los ensayos de rotura a tracción practicados en los distintos especímenes no han mostrado diferencias estadísticamente significativas según el método de fijación utilizado. De igual forma las imágenes histológicas de los distintos callos dependen exclusivamente del tiempo de consolidación transcurrido y no del sistema de fijación empleado. Los resultados teóricos están refrendados por la monitorización "in vivo" realizada mediante el captador de fuerzas. La evaluación de los registros obtenidos muestra como en el período comprendido entre la 2ª y 3ª semana de evolución postoperatoria acontece un aumento rápido y muy importante de la rigidez del callo, prevista por el estudio teórico. La interpretación global de los resultados, tanto teóricos como experimentales, plantea la necesidad de una rigidez del sistema de fijación externa en las etapas iniciales de la consolidación que garantice una protección mecánica del callo en dicho momento. El comportamiento de este sistema «rígido» es prácticamente idéntico al presentado por los sistemas «elásticos», cuando el callo adquiere unas características elásticas que permitan asumir su entrada en carga. Esto sucede transcurrido un 20% del tiempo de consolidación total de la fractura.To study the differences between rigid and elastic external fixation, the authors have designed an external fixator, used at the tibia of the rabbit, which allows a rigid behaviour and with the possibility of transformation in an elastic system. They have carried out a theoretical study of the fixator by 'finite elements' method and an experimental study, biomechanical, morfological and 'in vivo' monitoritation of the callus of fracture. The theoretical study showed that the weights supported by the fracture's callus depended on their elastic characteristics and not on the immobilization method used (rigid or elastic). At the fracture callus of the rabbit tibias there wer e no differences of resistance to the traction with either methods (rigid or elastic). There wer e also no histological differences in the evolution of the callus. The "in vivo" monitoritation through force measuranient show ed a rapid increase in the rigidity of the callus between the second and third week. The overall interpretation of the results, both theoretical and experimental, established the necessity of rigidity of the system of external fixation in the initial estages of consolidation that garantices a mechanical protection of the callus in that moment. The behaviour of this "rigid" system is praticaly identical to that presented by "elastic" systems, when the callus acquires some elastic characteristics that permits it to support weights. This occurs when more than 20 % of the total consolidation time of the fracture has passed

Nucleon axial and pseudoscalar form factors from the covariant Faddeev equation

We compute the axial and pseudoscalar form factors of the nucleon in the Dyson-Schwinger approach. To this end, we solve a covariant three-body Faddeev equation for the nucleon wave function and determine the matrix elements of the axialvector and pseudoscalar isotriplet currents. Our only input is a well-established and phenomenologically successful ansatz for the nonperturbative quark-gluon interaction. As a consequence of the axial Ward-Takahashi identity that is respected at the quark level, the Goldberger-Treiman relation is reproduced for all current-quark masses. We discuss the timelike pole structure of the quark-antiquark vertices that enters the nucleon matrix elements and determines the momentum dependence of the form factors. Our result for the axial charge underestimates the experimental value by 20-25% which might be a signal of missing pion-cloud contributions. The axial and pseudoscalar form factors agree with phenomenological and lattice data in the momentum range above Q^2 ~ 1...2 GeV^2.Comment: 17 pages, 7 figures, 1 tabl