The Luminous Convolution Model as an alternative to dark matter in spiral galaxies

The Luminous Convolution Model (LCM) demonstrates that it is possible to predict the rotation curves of spiral galaxies directly from estimates of the luminous matter. We consider two frame-dependent effects on the light observed from other galaxies: relative velocity and relative curvature. With one free parameter, we predict the rotation curves of twenty-three (23) galaxies represented in forty-two (42) data sets. Relative curvature effects rely upon knowledge of both the gravitational potential from luminous mass of the emitting galaxy and the receiving galaxy, and so each emitter galaxy is compared to four (4) different Milky Way luminous mass models. On average in this sample, the LCM is more successful than either dark matter or modified gravity models in fitting the observed rotation curve data. Implications of LCM constraints on populations synthesis modeling are discussed in this paper. This paper substantially expands the results in arXiv:1309.7370.Comment: Implications of LCM constraints on populations synthesis modeling are discussed in this paper. This paper substantially expands the results in arxiv:1309.737

Effect of strontium and cooling rate upon eutectic temperatures of A319 aluminum alloy

DTA analysis was used to investigate the solidification reactions of alloy A319 with either 12 or 136 ppm of Sr added. Strontium does not affect primary solidification of (Al) dendrites but modifies the kinetics of the (Al)–Si eutectic. The effects of Sr level and of cooling rate on the characteristic temperatures for the (Al)–Si and other eutectic reactions are described

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

Evaluación briológica de los efectos de la contaminación atmosférica en la Ciudad de México

The Index of Atmospheric Purity (IAP) was used to make a preliminary evaluation of epiphytic moss response to atmospheric pollution in the urban area of Mexico City. Areal analysis indicates that there is a significant negative correlation (p < 0.5) between IAP values and SO2, NO2, NOx, Pb and temperature values of -0.45, -0.90, -0.80, -0.80, -0.90. Significant positive correlation (p < 0.05) between IAP values and O3, rainfall and relative atmospheric humidity with values of 0.70, 0.80, 0.90. Increase in atmospheric pollutants in Mexico City have promoted a gradual decrease in frequency and cover of epiphytic mosses even though some ecological factors may show the oposite effect.Se hace una evaluación preliminar de la respuesta de los musgos epífitos a la contaminación atmosférica usando el Indice de Pureza Atmosférica (IPA) en el área urbana de la Ciudad de México. El análisis por zonas indica que hay una relación inversa y significativa (p < 0.5) entre el IPA y SO2, NO2, NOx, Pb y la temperatura con valores de -0.45, -0.90, -0.80, -0.80, -0.90. También se encontró una relación directa y significativa (p < 0.05) entre el IPA y el O3, la precipitación pluvial y la humedad relativa con valores de 0.70, 0.80, 0.90. Los incrementos en los niveles de algunos contaminantes atmosféricos en la Ciudad de México han promovido la disminución gradual en la frecuencia de aparición y cobertura de musgos epífitos, aunque algunas variables ambientales pueden tener el efecto opuesto

Discussion on the article “Numerical evaluation of the flange thickness effect on the contact stress and prying action in T-Stub steel connection” by L.M. Bezerra, C.S. de Freitas, W.T. Matias and J.E. Carmona

En el presente documento se propone una discusión sobre el artículo «Evaluación numérica del efecto del espesor de la placa de contacto en la acción de palanca en conexión de acero tipo T» de L.M. Bezerra, C.S. de Freitas, W.T. Matias y J.E. Carmona. El principal punto que hay que tratar es la definición de los modelos T-equivalente (T-stub). También se han revisado las referencias bibliográficas existentes hasta el momento, así como el procedimiento seguido para el modelado de los componentes.A discussion is proposed on the paper “Evaluación numérica del efecto del espesor de la placa de contacto en la acción de palanca en conexión de acero tipo T” by L.M. Bezerra, C.S. de Freitas, W.T. Matias and J.E. Carmona. The topics to be discussed are the definition of the T-stub model, the bibliographic references used in the work and the finite element analysis assumptions adopted in the modeling of the components.Peer Reviewe

Multiphoton Ionization of Uracil at 355 nm

We present the experimental results from ionization and dissociation by multiphoton absorption (MPI) of uracil and a mixture of uracil with Ar using a Reflectron time of flight spectrometer along with radiation from 355 nm at pulsed Nd:YAG laser . We focus on the light ions production. The MPI mass spectra show that the presence and intensity of the resulting ions depend on the density power of the laser. The resulting ions in the mass spectra are identified and found similar behavior in the case of H+ and C+ as when multiple charged ions are used. Different results were found in contrast with those, recently reported, when electrons or photons of other wavelength were used. The number of 355nm absorbed photons was calculated accordingly to Keldysh theory and similar results were fond using pure uracil or uracil-Ar mixture. Our results are compared with those obtained in other laboratories under different experimental conditions, some of them show only partial agreement and differences are discussed