The Stationary Phase Method for a Wave Packet in a Semiconductor Layered System. The applicability of the method

Using the formal analysis made by Bohm in his book, {\em "Quantum theory"}, Dover Publications Inc. New York (1979), to calculate approximately the phase time for a transmitted and the reflected wave packets through a potential barrier, we calculate the phase time for a semiconductor system formed by different mesoscopic layers. The transmitted and the reflected wave packets are analyzed and the applicability of this procedure, based on the stationary phase of a wave packet, is considered in different conditions. For the applicability of the stationary phase method an expression is obtained in the case of the transmitted wave depending only on the derivatives of the phase, up to third order. This condition indicates whether the parameters of the system allow to define the wave packet by its leading term. The case of a multiple barrier systems is shown as an illustration of the results. This formalism includes the use of the Transfer Matrix to describe the central stratum, whether it is formed by one layer (the single barrier case), or two barriers and an inner well (the DBRT system), but one can assume that this stratum can be comprise of any number or any kind of semiconductor layers.Comment: 15 pages, 4 figures although figure 4 has 5 graph

Setting up a large set of protein-ligand PDB complexes for the development and validation of knowledge-based docking algorithms

<p>Abstract</p> <p>Background</p> <p>The number of algorithms available to predict ligand-protein interactions is large and ever-increasing. The number of test cases used to validate these methods is usually small and problem dependent. Recently, several databases have been released for further understanding of protein-ligand interactions, having the Protein Data Bank as backend support. Nevertheless, it appears to be difficult to test docking methods on a large variety of complexes. In this paper we report the development of a new database of protein-ligand complexes tailored for testing of docking algorithms.</p> <p>Methods</p> <p>Using a new definition of molecular contact, small ligands contained in the 2005 PDB edition were identified and processed. The database was enriched in molecular properties. In particular, an automated typing of ligand atoms was performed. A filtering procedure was applied to select a non-redundant dataset of complexes. Data mining was performed to obtain information on the frequencies of different types of atomic contacts. Docking simulations were run with the program DOCK.</p> <p>Results</p> <p>We compiled a large database of small ligand-protein complexes, enriched with different calculated properties, that currently contains more than 6000 non-redundant structures. As an example to demonstrate the value of the new database, we derived a new set of chemical matching rules to be used in the context of the program DOCK, based on contact frequencies between ligand atoms and points representing the protein surface, and proved their enhanced efficiency with respect to the default set of rules included in that program.</p> <p>Conclusion</p> <p>The new database constitutes a valuable resource for the development of knowledge-based docking algorithms and for testing docking programs on large sets of protein-ligand complexes. The new chemical matching rules proposed in this work significantly increase the success rate in DOCKing simulations. The database developed in this work is available at <url>http://cimlcsext.cim.sld.cu:8080/screeningbrowser/</url>.</p

Roturas tendinosas y musculares en el hombro del deportista

El complejo articular del hombro está sometido a solicitaciones mecánicas en la mayoría de las modalidades deportivas; así el 10-15% de los traumatismos sufridos por los atletas afectan a esta articulación (1). La "patología reina" del hombro del deportista es la inestabilidad, por su frecuencia, importantes implicaciones funcionales y tratamiento problemático. Por el contrario, las roturas musculares y tendinosas del hombro son lesiones poco frecuentes en el deportista pero no por ello irrelevantes, pues pueden provocar una gran incapacidad para seguir desempeñando el mismo deporte y al mismo nivel de competición si no se hace un tratamiento correcto, a pesar del cual a veces los resultados no son satisfactorios. Es decir, pueden representar el "principio del fin" de la actividad deportiva. Tibone y cols. (2) en un estudio realizado sobre tratamiento quirúrgico de roturas del manguito de los rotadores en atletas, encuentran que sólo el 32% de los jugadores de baseball profesionales tratados por ellos volvían a jugar en la liga profesional americana después de su lesión

Traumatic Dental Injuries: Clinical Case Presentation and a 10-Year Epidemiological Investigation in an Italian Dental Emergency Service

Traumatic dental injuries (TDIs) are very common in the world population, and international literature reports several studies which helped in the definition of international guidelines. The aim of this study is to present two clinical cases of TDI and to investigate epidemiological and etiological aspects of TDIs in patients treated in Modena, Italy, between January 2010 and December 2020. The presented case reports are two explicative clinical cases of successful TDI management with a long-Term follow-up. The epidemiological analysis was performed on patients who visited the Dental Emergency Service of the Dentistry and Oral-Maxillo-Facial Surgery Unit of Modena (Italy) over a period of 10 years. Data relating to age, gender, type of trauma, and place of accident were collected. Five-hundred-sixty-five TDIs that occurred to patients from 1 to 68 years old were reported, with a total of 860 injured teeth. The peak age at which TDIs are most represented varies between 2 and 3 years old, and they occurred frequently from 1 up to 7 years old. 57.5% were male, while 42.5% were female. The most common trauma resulted to be the uncomplicated crown fracture (20%), immediately followed by lateral luxation (19%), intrusive luxation (18%), avulsion (17%), and complicated crown fracture (15%). TDIs occurred at home in 44% of cases. The need for more prevention training must be highlighted, due to the fact that many TDIs occur at home and in a preschool age