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Showing papers in "Revista Mexicana De Fisica in 2007"


Journal Article
TL;DR: In this paper, optical properties of unsupported or powdered nanostructures are frequently determined through UV-Vis absorption spectroscopy of their dispersed solutio-graphs.
Abstract: Resumen en: Optical properties of un-supported or powdered nanostructures are frequently determined through UV-Vis absorption spectroscopy of their dispersed solutio...

676 citations


Journal Article
TL;DR: In this paper, the bioheat transfer equation is solved for a simplified model of a female breast and a cancerous tumor to quantify the minimum size of a tumor or the maximum depth of a certain sized tumor that a modern state-of-the-art infrared imaging system can detect.
Abstract: It is well known that differences in energy consumption exist for normal and cancerous tissue. These differences lead to small but detectable local temperature changes, which is why infrared imaging has been used in the detection of different types of cancer; however, the early instrumentation was not sensitive enough to detect the subtle changes in temperature needed to accurately diagnose and monitor the disease. In recent years the sensitivity of infrared instruments has greatly improved. In this paper the bioheat transfer equation is solved for a simplified model of a female breast and a cancerous tumor in order to quantify the minimum size of a tumor or the maximum depth of a certain sized tumor that a modern state-of-the-art infrared imaging system can detect. Finite Element simulations showed that current state-of-the-art imagers are capable of detecting 3 cm tumors located deeper than 7 cm from the skin surface, and tumors smaller than 0.5 cm can be detected if they are located close to the surface of the skin.

68 citations


Journal Article
TL;DR: In this paper, an estudio de la evolucion de las caracteristicas de los espectros de FTIR and the respuesta of fotoluminiscencia (PL) in peliculas de silicio poroso (PSL) oxidadas quimicamente and envejecidas in condiciones controladas was presented.
Abstract: Se presenta un estudio de la evolucion de las caracteristicas de los espectros de FTIR y la respuesta de fotoluminiscencia (PL) en peliculas de silicio poroso (PSL) oxidadas quimicamente y envejecidas en condiciones controladas. Las PSL se obtuvieron por el metodo electroquimico para obtener buena uniformidad en grandes areas. Las mediciones de FTIR en las PSL recien preparadas manifiestan bandas de siliciohidrogeno asociadas con la terminacion en hidrogeno de superficie de silicio poroso justo despues del proceso de porificacion. Al oxidar las peliculas, los distintos modos de vibracion se modifican. Esos modos de vibracion se relacionan con los defectos en el oxido de silicio que recubre la superficie del silicio poroso. Los espectros de PL en muestras recien preparadas presentan un maximo en ~700 nm. El espectro de PL en las PSL oxidadas quimicamente y luego envejecidas, en condicion de vapor de agua saturado, se modifica fuertemente con respecto a las muestras recien obtenidas. Estas variaciones estan asociadas con los cambios en la estructura de las PSL inducidos por los procesos de oxidacion. Los datos de FTIR y el comportamiento de la senal de PL nos permiten relacionar estas senales con los efectos de cuantizacion por pequenas dimensiones e indicar que las transiciones a altas energias las produce algun centro de defecto en la pelicula de oxido de silicio que se forma en su superficie. Las caracteristicas de las PSL reportadas en este trabajo son perfectamente reproducibles en las condiciones que se utilizaron para prepararlas; por ello, las peliculas pueden usarse en distintas aplicaciones.

54 citations


Journal ArticleDOI
TL;DR: The paper as mentioned in this paper presented by one of the authors (S.P.) at the first International Symposium on Nuclear Physics in Cocoyoc, Mexico, from 7-10 January 2008.
Abstract: 5 pags., 3 figs., 1 tab. -- PACS: 21.60.–n, 03.75.Ss, 02.30.Ik; 74.20.Fg . -- This report was presented by one of the authors (S.P.) at the XXXIst International Symposium on Nuclear Physics in Cocoyoc, Mexico, from 7-10 January 2008.

25 citations


Journal Article
TL;DR: In this paper, a conjunto residual obtenido of the data medidos in 20 estaciones for concentracion of ozono for a periodo de 21 dias in the Ciudad de Mexico.
Abstract: Las tecnicas de interpolacion espacial, peso inverso con la distancia (IDW) y Kriging, son las mas comunmente usadas para la estimacion de niveles de contaminante en regiones que tienen un limitado numero de estaciones de monitoreo. Los valores del pico de contaminacion por ozono, medidos en la atmosfera de la region de la Ciudad de Mexico, se consideran como un conjunto de datos muestreados cuya media no es estacionaria. Con el fin de estudiar el efecto de una media no estacionaria sobre el desempeno de los metodos de interpolacion IDW Y KRiging, se transforma el conjunto de datos al remover de cada uno de ellos el valor de su tendencia. El conjunto residual obtenido se considera como un conjunto de variables aleatorias estacionarias. Para este caso se considera inicialmente el conjunto residual obtenido de los datos medidos en las 20 estaciones para concentracion de ozono a las 15 horas por un periodo de 21 dias del mes de diciembre del 2001. Este conjunto de 420 datos constituye el conjunto de entrenamiento. Para determinar el valor de los parametros que definen los pesos en cada uno de los metodos IDW y Kriging que se analizan en este trabajo, se considera un metodo de validacion cruzada mediante el cual se suponen para los parametros valores iniciales, que se van ajustando iterativamente hasta obtener el valor que produce el minimo error cuadratico medio entre los datos medidos y los estimados en cada una de las estaciones, Para lo cual hacemos uso de los datos que constituyen el conjunto de entrenamiento. Una vez determinados, por el procedimiento anterior, los valores de los parametros que definen los pesos de cada uno de los metodos IDW o Kriging, se usan estos metodos para hacer estimaciones de los valores de las concentraciones de ozono, a las 15 horas en las estaciones para los 10 dias de diciembre de 2001 no considerados en el conjunto de entrenamiento. El error cuadratico medio entre datos medidos y estimados es calculado para este conjunto de prueba y se muestra en porcentaje en la tabla I. Estos valores y el parametro de generalizacion G pueden ser usados para medir el desempeno y habilidad de los modelos para predecir y reproducir el pico de ozono tanto para los residuales como para los datos originalmente muestreados sin ninguna transformacion. Se muestran graficas de dispersion de los datos de prueba para cada metodo de interpolacion. Se da una interpretacion de los niveles de contaminacion de ozono obtenidos para Diciembre 21 de 2001 a las 15 horas usando el campo de vientos preexistente en la region, a las 14:00 horas del mismo dia

22 citations


Journal Article
TL;DR: In this article, an explanation of the basic phenomena is presented, together with possible uses of the emission of X-rays by the impact of the heavy ions, as an extension of the traditional method Particle Induced X-ray Emission (PIXE).
Abstract: The emission of X-rays after the excitation with photons, electrons, or light ions (such as protons or deuterons), has been extensively studied. However, when heavier ions are used as primary radiation to induce this effect, other phenomena appear that are not present in the other cases. They include, for example, the formation of short-lived molecules, the capture of electrons from the target atom by the incoming ion, and a strong increase in the multiple ionization of the target atom. Usually, the ionization cross sections are higher as compared to those of photons, electrons, or protons. Furthermore, when thick targets are irradiated with heavy ions, there is a larger probability to create defects in the material, and also a higher stopping power in the target material. All these differences make the study of the X-ray production by heavy ions a problem not fully understood, and far from being applied in an extensive manner to the characterization of materials. In this work, an explanation of the basic phenomena is presented, together with possible uses of the emission of X-rays by the impact of the heavy ions, as an extension of the traditional method Particle Induced X-ray Emission (PIXE).

19 citations


Journal Article
Oscar Rosas-Ortiz1
TL;DR: In this paper, Gamow solutions are used to transform self-adjoint energy operators by means of factorization (supersymmetric) techniques, and the transformed non-hermitian Ope...
Abstract: Gamow solutions are used to transform self–adjoint energy operators by means of factorization (supersymmetric) techniques. The transformed non–hermitian ope...

19 citations


Journal Article
TL;DR: In this article, the Si/Mo multilayer by alternate deposition with a multi-gun rf/dc magnetron sputtering system was presented, and the current collector was Cu foil.
Abstract: Resumen en: We have prepared the Si/Mo multilayer by alternate deposition with a multi-gun rf/dc magnetron sputtering system. A current collector was Cu foil that h...

17 citations


Journal Article
TL;DR: In this article, a geometric analysis of the screens used for testing convex optical surfaces is presented, and some properties of the transformation between the image plane and the screen plane such as symmetry and magnification are presented for the case when the reflecting surface is a sphere.
Abstract: A geometric analysis of the screens used for testing convex optical surfaces is presented. Some properties of the transformation between the image plane and the screen plane, such as symmetry and magnification, are presented for the case when the reflecting surface is a sphere. Due to the intrinsic variations in the magnification, the geometric relationship between the image and the object shows some unexpected behavior. Two cases are analyzed in detail: i) a set of concentric circles centered on the origin of coordinates of the image plane with a set of radial straight lines; and ii) a square grid and a square array of circles of the same size

16 citations


Journal Article
TL;DR: In this article, the physical and chemical characterization of inorganic atmospheric particle samples collected on TSP and PM10 filters from January 2003 through December 20, 2003 was studied, and the results showed that inorganic particle samples were collected on both TSP filters and PM 10 filters.
Abstract: Resumen en: Physical and chemical characterization of inorganic atmospheric particle samples collected on TSP and PM10 filters from January 2003 through December 20...

16 citations


Journal Article
TL;DR: In this article, a new approach is suggested to explain the Peltier effect, based on the idea of the occurrence of induced thermal diffusion fluxes in any non-uniform medium through which a d.c. electric current flows, in particular in a structure composed of two different uniform semiconductors.
Abstract: A new approach is suggested to explain the Peltier effect. This approach is based on the idea of the occurrence of induced thermal diffusion fluxes in any non-uniform medium through which a d.c. electric current flows, in particular in a structure composed of two different uniform semiconductors. These induced thermal diffusion fluxes arise to compensate for the change in thermal fluxes carried out by an electric current (drift thermal fluxes) during their driving through the junction in accordance with the general Le Chprinciple. The occurrence of these thermal diffusion fluxes leads to temperature non-uniformity in the structure and, as a result, to the junction's cooling or heating. The general heat balance equations are obtained. It is shown that only two sources of heat exist: the Joule source of heat, and the Thomson source of heat. They have commensurable magnitudes in the problem considered. There is no Peltier's source of heating or cooling present. The new equation for the Thomson heat is obtained and its physical interpretation is made. New boundary conditions for the heat balance equation are derived. The analysis of these boundary conditions shows that the Peltier sources of heat are also absent at the junctions. It is shown that, in the general case, the thermoelectric cooling represents the superposition of two effects, the isothermal Peltier effect and the adiabatic Peltier effect. Both essentially depend on the junction surface thermal conductivity. The isothermal Peltier effect disappears in the limiting case of a very small surface thermal conductivity while the adiabatic Peltier effect disappears in the limiting case of a very large surface thermal conductivity. The dependence of thermoelectric cooling on the geometrical dimensions of the structure is discussed. It is shown that the thermoelectric cooling (heating) is a thermodynamically reversible process in the linear approximation of the electric current

Journal Article
TL;DR: Mostramos que un oscilador armonico sujeto a un cambio repentino de masa produce estados comprimidos Nuestro formalismo requiere una transformacion ad hoc de la ecuacion diferencial original and es aplicable tambien for variaciones of masa rapidas, no solo instantaneas.
Abstract: Mostramos que un oscilador armonico sujeto a un cambio repentino de masa produce estados comprimidos Nuestro estudio esta basado en una solucion analitica aproximada para el oscilador armonico dependiente del tiempo El tratamiento continuo que estudiamos difiere de estudios anteriores en los cuales se igualan las soluciones en la discontinuidad Nuestro formalismo requiere una transformacion ad hoc de la ecuacion diferencial original y es aplicable tambien para variaciones de masa rapidas, no solo instantaneas

Journal Article
TL;DR: In this paper, a brief introduction to spin-weighted spherical harmonics is given, and some applications of these functions in the solution by separation of variabels are discussed.
Abstract: Resumen en: A brief introduction to the spin-weighted spherical harmonics is given, and some applications of these functions in the solution by separation of variab...

Journal Article
TL;DR: In this article, compositional, structural and optical properties of silicon rich oxide (SRO) films containing different silicon excess were investigated using X ray photoelectron spectroscopy (XPS), Raman Spectroscopy, energy filtered transmission electron microscopy (EFTEM) and photoluminescence (PL).
Abstract: Compositional, structural and optical properties of silicon rich oxide (SRO) films containing different silicon excess were investigated using X ray photoelectron spectroscopy (XPS), Raman spectroscopy, energy filtered transmission electron microscopy (EFTEM) and photoluminescence (PL). The XPS-Si2p peaks fitting showed the presence of Si - Si 4 tetrahedra only for the SRO film with the highest silicon excess. Raman spectroscopy revealed amorphous phase silicon in the SRO films with lowest silicon excess; when it was increased, a sharp peak at around 517 cm -1 appeared, which corresponds to crystalline silicon. Si-nanoclusters were slightly observed by EFTEM in the SRO film with the lowest silicon content. They became more evident when the silicon excess was increased, in agreement to Raman spectra. A strong PL was observed in the SRO films with low silicon excess. However, in SRO films with the highest silicon excess, where the silicon agglomeration is greater, the PL practically disappeared. According to these results, we have analysed the dependence of photoluminescence on the composition and structure of the SRO films.

Journal Article
TL;DR: In this paper, the effects of temperature and DC magnetic field on the modulated non-resonant microwave power absorption measurements at 8.8-9.8 GHz, in po...
Abstract: Resumen en: We report on the effects of temperature and DC magnetic field on the modulated non-resonant microwave power absorption measurements at 8.8-9.8 GHz, in po...

Journal Article
TL;DR: In this article, a caracterización of rocas fuentes de the radiactividad in el valle de Chihuahua was presented. But, as part of un proyecto cientifico sobre actividad alfa en agua subterranea de consumo humano in la ciudad de Chahuas, se ha desarrollado the caracteríncia de las rocas.
Abstract: Como parte de un proyecto cientifico sobre actividad alfa en agua subterranea de consumo humano en la ciudad de Chihuahua, se ha desarrollado la caracterizacion de las rocas fuentes de la radiactividad en el valle de Chihuahua. Se determino tambien la actividad de muestras de agua subterranea y de sedimentos. La actividad de los isotopos de las series radiactivas en las rocas se obtuvo usando espectroscopia gamma de alta resolucion. Algunos valores representativos son 50 Bq/kg para el valor medio de la actividad del Bi-214 y 121.5 Bq/kg para el valor mas alto al oeste de la ciudad. La actividad de los sedimentos extraidos durante la perforacion de pozos para agua potable, se determino usando un detector de NaI(Tl). En la formacion montanosa de San Marcos se localizo un deposito de uranio no publicado. Sus afloramientos se encuentran dentro de la cuenca del valle Chihuahua-Sacramento y se realizo la caracterizacion de su radiactividad. Se determinaron actividades por espectrometria alfa de agua, plantas, sedimentos y peces extraidos en emplazamientos cercanos a los afloramientos de minerales de uranio. La actividad del agua en la presa de san Marcos llego a 7.7 Bq/L. La actividad de pescados de la misma presa alcanza 0.99 Bq/kg. Se obtuvieron conclusiones sobre la contaminacion del agua subterranea al norte de la ciudad de Chihuahua.

Journal Article
TL;DR: The brane-world picture of the universe, as inspired by string theory, opens up new vistas in cosmology as discussed by the authors, and the hope is that these new ingredients will shed light on the major puzzles associated with the standard cosmological model.
Abstract: If string theory is on the right track as a description of nature, then our observable universe may be a 3-dimensional membrane surface in a higher-dimensional spacetime. The brane-world picture of the universe, as inspired by string theory, opens up new vistas in cosmology. The extra polarizations of the higher-dimensional graviton, and the additional fields arising from the extra dimensions, bring new features that may leave detectable signatures. Moreover, the hope is that these new ingredients will shed light on the major puzzles associated with the standard cosmological model – in particular, the problem of explaining inflation and the dark energy problem

Journal Article
N Fernández-García1
TL;DR: In this paper, Scattering states in the continuum are used as Darboux transformation functions to deform square barrier potentials, and the results include complex as well as complex structures.
Abstract: Resumen en: Scattering states in the continuum are used as Darboux transformation functions to deform square barrier potentials. The results include complex as well...

Journal Article
TL;DR: In this paper, the effects of hydrostatic pressure over the ground state binding energy of light hole excitons confined in GaAs i Ga1ixAlxAs spherical quantum dots were studied.
Abstract: We study the effects of hydrostatic pressure over the ground state binding energy of light hole excitons confined in GaAs i Ga1ixAlxAs spherical quantum dots. We applied the variational method using 1s-hydrogenic wavefunctions, in the framework of the effective mass approximation. We computed the exciton binding energy as a function of the dot radius, Al concentrations and pressures. Our results show that (i) the hydrostatic pressure increases the binding energy, for all quantum dot radii; (ii) the binding energy is an increasing function of the Al concentration, for fixed radius and pressure, especially for a smaller dot; (iii) the binding energy follows approximately a linear dependence with the pressure, for fixed radius and Al concentration.

Journal Article
TL;DR: In this paper, the authors present the result of the simulation numerica por medio de la tecnica de discretizacion of the volumenes finitos of the flujo tridimensional in un ducto rectangular with un escalon al frente.
Abstract: En este trabajo se presentan los resultados de la simulacion numerica por medio de la tecnica de discretizacion de los volumenes finitos de las estructuras de flujo tridimensional en un ducto rectangular con un escalon al frente. Se emplea el algoritmo SIMPLE para asociar la distribucion de presion y el campo de velocidad dentro del dominio computacional. El ducto que se propone es de forma rectangular y encierra un escalon, de tal forma que la relacion de expansion y la relacion de aspecto son iguales a dos y cuatro respectivamente. La longitud total del canal en la direccion principal del flujo es igual a 60 veces la altura del escalon, mientras que la orilla del escalon se localiza a una distancia igual a 20 veces la altura del mismo corriente abajo de la entrada del canal. A la entrada se considera que el flujo es tridimensional y completamente desarrollado. Resultados de la linea de reacomodo, linea de separacion, asi como perfiles de velocidad a diferentes planos dentro del ducto se presentan para diferentes parametros de Reynolds.

Journal Article
TL;DR: In this paper, a novel and simple physical method for obtaining ZnO nanocrystals using the pressure cycle method and the membrane diamond anvil cell up to 13 GPa at 500 K was presented.
Abstract: We present here a novel and simple physical method for obtaining ZnO nanocrystals using the pressure cycle method and the membrane diamond anvil cell (MDAC) up to 13 GPa at 500 K. The recovered nanocrystals in the wurtzite phase (w‐ZnO) were characterized by high resolution Raman scattering and XRD studies. Single crystal of the w‐ZnO was used in this work. The high‐pressure cell was a membrane DAC specifically designed for high‐temperature studies. The Raman spectra of high quality ZnO single crystal and nanocrystals were compared, and we observed both the softening and the asymmetric broadening of Raman peaks, which are in good agreement with the effect of relaxation of the q‐vector selection rule due to quantum size confinement effect. The experimental results confirms the existence of ZnO nanocrystals in the wurtzite phase with a diameter of the order of 17 nm.

Journal Article
TL;DR: In this paper, a dielectric material that contains Si nanoparticles, thus showing novel physical characteristics which permits its use in optoelectric materials, is described and compared to Silicon Rich Oxide (SRO).
Abstract: Resumen en: Silicon Rich Oxide (SRO) is a dielectric material that contains Si nanoparticles, thus showing novel physical characteristics which permitsits use in opt

Journal Article
TL;DR: A horno al vacio based on a tubo cilindrico de cuarzo for difundir two or mas capas delgadas metalicas for formar una aleacion was presented in this paper, where the horno trabaja in un ambiente inerte de argon (Ar) and una temperatura controlada a traves of una plancha interior de ceramica.
Abstract: En este trabajo se discute la fabricacion de un horno al vacio basado en un tubo cilindrico de cuarzo para difundir dos o mas capas delgadas metalicas para formar una aleacion. El horno trabaja en un ambiente inerte de argon (Ar) y una temperatura controlada a traves de una plancha interior de ceramica y un sistema de control PID basado en un software desarrollado en LabView 7.0. El area de calentamiento de 10 × 5 cm 2 puede elevar la temperatura hasta 600oC debido a sus tapas circulares que cuentan con un sistema de enfriamiento de agua. El horno es calentado y controlado con una fuente de corriente directa y utiliza un termopar tipo K para monitorear la temperatura con una resolucion de ±0.1oC. Se detallan pruebas realizadas en el horno para obtener la aleaciones nanoestructuradas de AuCu.

Journal Article
TL;DR: In this paper, the deformation quantization of any Grassmann free field, or fermionic free field in particular, the Dirac free field is discussed and a Stratonovich-Weyl quantizer, Moyal product and Wigner functionals are obtained by deforming suitable Fermi oscillator variables.
Abstract: The deformation quantization of any Grassmann free field, or fermionic free field, in particular, the Dirac free field is discussed. Stratonovich-Weyl quantizer, Moyal product and Wigner functionals are obtained for this field by deforming suitable Fermi oscillator variables. In addition the propagator of the Dirac field is computed in this context.

Journal Article
TL;DR: In this article, it was shown that the four-dimensional spherical harmonics separable in Euler angles correspond to solutions of the time-independent Schrodinger equation that are separability in parabolic coordinates.
Abstract: Using the fact that the Schrodinger equation for the stationary states of the hydrogen atom is equivalent to an integral equation on the unit sphere in a four-dimensional space, the eigenvalues, the eigenfunctions, and a dynamical symmetry group for this problem are obtained from the four-dimensional spherical harmonics and the group of rotations on the sphere. It is shown that the four-dimensional spherical harmonics separable in Euler angles correspond to solutions of the time-independent Schrodinger equation that are separable in parabolic coordinates

Journal Article
TL;DR: In this article, a nanocomposite hybrid material based on previously oxidized carbon nanofibers (fCNFs) and polyoxometalates (POM) was proposed.
Abstract: Resumen en: We prepared nanocomposite hybrid materials based on previously oxidized carbon nanofibers (fCNFs) and polyoxometalates (POM). We analyzed fCNFs by XRD an...

Journal Article
TL;DR: In this article, an overview of a methodology based on the Numerical Laplace Transform (NLT) and applied to the analysis of electromagnetic transient phenomena in power systems is presented.
Abstract: This work presents an overview of a methodology based on the Numerical Laplace Transform (NLT) and applied to the analysis of electromagnetic transient phenomena in power systems. The basic development of the method is described, with its main qualitative advantages as compared to conventional time domain methods, such as the method of characteristics and professional programs for transient simulation such as EMTDC and ATP/EMTP. Current practices for reducing errors derived from the truncation and discretization of the analytical equations are also discussed. Finally, some important results obtained recently with this tool are shown. Comparisons with time domain methods reveal a high accuracy of the Numerical Laplace Transform in several studies.

Journal Article
TL;DR: This research presents new challenges that are difficult to handle using by currently adopted encryption schemes (RSA-Rivest-Shamir-Ade...
Abstract: La seguridad en sistemas de comunicacion de multimedia (texto, audio, imagen y video) representa un reto dificil de alcanzar para los actuales estandares de cifrado (RSA-Rivest-Shamir-Adelman, AES-Advanced Encryption Standard e IDEA-International Data Encryption algorithm) [28]. Se requiere el procesamiento de grandes cantidades de informacion a velocidades que fluctuan entre los Kilobits/seg (Kbs) hasta los Megabits/seg (Mbs). Enfocados en este problema se propone un sistema de cifrado seguro y eficiente basado en un arreglo de mapas logisticos independientemente iterados junto con un sistema de retroalimentacion espacio-temporal usado como proceso de difusion de la informacion. Adicionalmente se hace uso de tres niveles de perturbacion para modificar el estado actual del sistema e incrementar asi su robustez contra ataques de oponentes; una perturbacion es a nivel de la llave del sistema y dos adicionales a nivel de los mapas caoticos. El analisis de resultados muestra excelentes propiedades estadisticas del sistema propuesto, sensibilidad a las condiciones iniciales y la mas alta velocidad de ejecucion reportada en la literatura para llevar a cabo comunicaciones de multimedia en tiempo real.

Journal Article
TL;DR: In this article, the ergodic/non-ergodic transition in monodisperse colloidal suspensions is determined by an equation for the long-time asymptotic value γ of the mean squared displacement of the colloidal particles, whose finite real solutions signal the nonergodic state.
Abstract: This letter presents a remarkably simple approach to the first-principles determination of the ergodic/non-ergodic transition in monodisperse colloidal suspensions. It consists of an equation for the long-time asymptotic value γ of the mean squared displacement of the colloidal particles, whose finite real solutions signal the non-ergodic state, and determines the non-ergodic parameter f(k). We illustrate its concrete application to three simple model colloidal systems, namely, hard-spheres, hard-spheres plus repulsive (screened Coulomb) Yukawa interaction, and hard-sphere plus attractive Yukawa tail. The results indicate that this is quite a competitive theory, similar in spirit to, but conceptually independent from, the well-known mode coupling theory.

Journal Article
TL;DR: In this paper, the interaction and stabilization energies of the Watson-Crick H-bonded base pairs Guanine-Cytosine and Adenine-Thymine at the GGA level of DFT using the SIESTA method were calculated.
Abstract: In this work we calculate interaction and stabilization energies of the the Watson-Crick H-bonded base pairs Guanine-Cytosine and Adenine-Thymine at the GGA level of DFT using the SIESTA method. Structural optimizations are performed by conjugate gradients without geometrical constraints, allowing both nonzero propeller twist angle between nucleobases and pyramidalization of amino groups. Comparison of the obtained geometries with results from the best ones reported in literature (correlated MP2 level) shows differences of the order of 1% in the intramolecular base distances. On the other hand, proportion between stabilization energies under pair formation is found to have approximately the same value as the reported results, while absolute stabilizations energies are different than the reported ones.