576 research outputs found
Biometrics of the Posterior Communicating Artery and the Posterior Cerebral Artery in its Precommunicating Segment (P1) of the Arterial Circle of Brain (Willis)
Indexación: ScieloEl conocimiento anatómico y clínico preciso del círculo arterial del cerebro, se hace cada vez más necesario, por la compleja relación neural que presentan las diversas arterias que entran en su formación y además por su gran variabilidad.
Utilizamos 36 encéfalos humanos frescos, provenientes de especímenes autopsiados adultos, cuyos datos bioantropológicos fueron previamente registrados. El calibre de las aa. comunicantes posteriores fue, en promedio, de 1,08 mm (DE 0,45 ) en ambos lados y su longitud de 17,51 mm( DE 7,9) en el lado derecho y de 16,9 mm (DE 8,0 ) en el lado izquierdo. La ACP en el segmento P1 presentó un calibre de 2,56 mm (DE 077) en el lado derecho y de 2,32 mm (DE 0,64) en el lado izquierdo. La longitud de
estas arterias correspondió a 9,43 mm (DE 8,92) en el lado derecho y de 8,82 mm (DE 7,33 ) en el lado izquierdo.
Las dimensiones observadas demuestran variabilidad que consideramos interesante de considerar en la anatomía quirúrgica.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-95022006000500015&lang=p
Biometrical Analysis of the Anterior Communicating Artery and the Anterior Cerebral Artery in the Precommunicating Segment of the Cerebral Arterial Circle
Indexación: ScieloLa conformación del círculo arterial cerebral tiene relevancia en la clínica neuroquirúrgica por la relación compleja que presentan las arterias que lo originan y su gran variabilidad. Debido a la alta frecuencia con que se observan aneurismas en las arteria comunicante anterior y en el segmento precomunicante (A1) de la arteria cerebral anterior se efectuó un análisis biométrico de ellas.
El trabajo se realizó en 36 cerebros frescos procedentes de especímenes cuyos datos bioantropológicos estaban registrados. El calibre de la arteria comunicante anterior fue de 1.68 mm y la longitud, en promedio, de 2.50 mm. En el lado derecho el segmento A1 de la arteria cerebral anterior tenía una longitud de 12.91mm y un calibre de 2.39 mm. En el lado izquierdo, la longitud de este segmento fue de 12.77 mm y presentó un calibre de 2.46mm. En un 29% de las muestras analizadas, se presentaron arterias comunicantes dobles, con una longitud de 2.92 mm y un calibre de 0.95 mm.
Se observó variabilidad en los componentes que constituyen el círculo arterial cerebral, cuando se consideran variables como lado, sexo e índice cefálico.
PALABRAS CLAVE: Arteria comunicante anterior; Arteria cerebral anterior; Círculo arterial del cerebro; Índice cefálico.SUMMARY: The conformation of the cerebral arterial circle has relevance in the clinical neurosurgery for the complex relate that present the arteries that originate it and its great variability. Due to the high frequency with that aneurysms are observed in the anterior communicant artery and the anterior cerebral artery in the precommunicating segment (A1), we have decided to make an analysis biometrical in them.
The work had done in 36 available fresh brains in the laboratories and they come from specimens whose data bioanthropological were registered. The caliber of the anterior communicating artery corresponds to 1.68 mm and the longitude to 2.50 mm. The segment A1 of the anterior cerebral artery it corresponds to a longitude of 12.91mm and it presents a caliber of 2.39 mm in the right side. In the left side the longitude of this segment is of 12.77 mm and it presents a caliber of 2.46. In 29% of the analyzed samples, they register double communicating arteries, with a longitude of 2.92 mm and a caliber of 0.95 mm. Variability of the components is observed that they constitute the cerebral arterial circle when is considered: side, sex and cephalic index
KEY WORDS: Anterior communicating artery; Anterior cerebral artery; Cerebral arterial circle; Cephalix index
Reuse of Zeolite By-Products Derived from Petroleum Refining for Sustainable Roads
The reduction in consumption of natural resources (fuel, gas, etc.) and contaminant emissions (CO2, CO, NOx, etc.) during the
production of asphalt mixtures has become one of the main challenges in road engineering. Warm mix asphalts (WMAs) have
been developed in order to achieve this objective while ensuring the mechanical performance and durability of traditional hot mix
asphalts (HMAs). However, these materials are commonly manufactured using additives or products whose production could
reduce both their environmental benefits and cost effectiveness. /is paper presents a research study that aims to analyse the reuse
of zeolite wastes derived from petroleum refining in the production of warm mix asphalts. For this purpose, two different types of
zeolite wastes were analysed as additives for the manufacture of two warm mix asphalts, whose mechanical performance was
compared with conventional WMA and hot mix asphalt. /e results indicate that zeolite wastes with a lower particles size
presented higher capacity to absorb water, while its dosage at 0.3% allows for producing warm mix asphalts at temperatures
around 145°C, with comparable workability and densification to conventional HMA at 165°C without reducing its bearing
capacity, fatigue life, and resistance to water action and plastic deformation.“Soluciones de
Pavimentación Ecológicamente Sostenibles: Ecoasfaltos”
funded by the Ministry of Economy and Knowledge of
Andalusia and the Ministry of Economy and Competitiveness
of Spain in the framework of CTA (Corporación
Tecnológica de Andalucía)
Satellite potentials for hypergeometric Natanzon potentials
As a result of the so(2,1) of the hypergeometric Natanzon potential a set of
potentials related to the given one is determined. The set arises as a result
of the action of the so(2,1) generators.Comment: 9 page
Connection Between Type A and E Factorizations and Construction of Satellite Algebras
Recently, we introduced a new class of symmetry algebras, called satellite
algebras, which connect with one another wavefunctions belonging to different
potentials of a given family, and corresponding to different energy
eigenvalues. Here the role of the factorization method in the construction of
such algebras is investigated. A general procedure for determining an so(2,2)
or so(2,1) satellite algebra for all the Hamiltonians that admit a type E
factorization is proposed. Such a procedure is based on the known relationship
between type A and E factorizations, combined with an algebraization similar to
that used in the construction of potential algebras. It is illustrated with the
examples of the generalized Morse potential, the Rosen-Morse potential, the
Kepler problem in a space of constant negative curvature, and, in each case,
the conserved quantity is identified. It should be stressed that the method
proposed is fairly general since the other factorization types may be
considered as limiting cases of type A or E factorizations.Comment: 20 pages, LaTeX, no figure, to be published in J. Phys.
Deformations of the Boson Representation and its Subalgebras
The boson representation of the sp(4,R) algebra and two distinct deformations
of it, are considered, as well as the compact and noncompact subalgebras of
each. The initial as well as the deformed representations act in the same Fock
space.
One of the deformed representation is based on the standard q-deformation of
the boson creation and annihilation operators. The subalgebras of sp(4,R)
(compact u(2) and three representations of the noncompact u(1,1) are also
deformed and are contained in this deformed algebra. They are reducible in the
action spaces of sp(4,R) and decompose into irreducible representations.
The other deformed representation, is realized by means of a transformation
of the q-deformed bosons into q-tensors (spinor-like) with respect to the
standard deformed su(2). All of its generators are deformed and have
expressions in terms of tensor products of spinor-like operators. In this case,
an other deformation of su(2) appears in a natural way as a subalgebra and can
be interpreted as a deformation of the angular momentum algebra so(3). Its
representation is reducible and decomposes into irreducible ones that yields a
complete description of the same
Ab initio optical properties of Si(100)
We compute the linear optical properties of different reconstructions of the
clean and hydrogenated Si(100) surface within DFT-LDA, using norm-conserving
pseudopotentials. The equilibrium atomic geometries of the surfaces, determined
from self-consistent total energy calculations within the Car-Parrinello
scheme, strongly influence Reflectance Anisotropy Spectra (RAS), showing
differences between the p(2x2) and c(4x2)reconstructions. The Differential
Reflectivity spectrum for the c(4x2) reconstruction shows a positive peak at
energies < 1 eV, in agreement with experimental results.Comment: fig. 2 correcte
Computational Stem Cell Biology: Open Questions and Guiding Principles
Computational biology is enabling an explosive growth in our understanding of stem cells and our ability to use them for disease modeling, regenerative medicine, and drug discovery. We discuss four topics that exemplify applications of computation to stem cell biology: cell typing, lineage tracing, trajectory inference, and regulatory networks. We use these examples to articulate principles that have guided computational biology broadly and call for renewed attention to these principles as computation becomes increasingly important in stem cell biology. We also discuss important challenges for this field with the hope that it will inspire more to join this exciting area
Short-range oscillators in power-series picture
A class of short-range potentials on the line is considered as an
asymptotically vanishing phenomenological alternative to the popular confining
polynomials. We propose a method which parallels the analytic Hill-Taylor
description of anharmonic oscillators and represents all our Jost solutions
non-numerically, in terms of certain infinite hypergeometric-like series. In
this way the well known solvable Rosen-Morse and scarf models are generalized.Comment: 23 pages, latex, submitted to J. Phys. A: Math. Ge
Efficient Identification of Critical Residues Based Only on Protein Structure by Network Analysis
Despite the increasing number of published protein structures, and the fact that each protein's function relies on its three-dimensional structure, there is limited access to automatic programs used for the identification of critical residues from the protein structure, compared with those based on protein sequence. Here we present a new algorithm based on network analysis applied exclusively on protein structures to identify critical residues. Our results show that this method identifies critical residues for protein function with high reliability and improves automatic sequence-based approaches and previous network-based approaches. The reliability of the method depends on the conformational diversity screened for the protein of interest. We have designed a web site to give access to this software at http://bis.ifc.unam.mx/jamming/. In summary, a new method is presented that relates critical residues for protein function with the most traversed residues in networks derived from protein structures. A unique feature of the method is the inclusion of the conformational diversity of proteins in the prediction, thus reproducing a basic feature of the structure/function relationship of proteins
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