Pairs-Production of Higgs in Association with Bottom Quarks Pairs at e+e−e^+e^- Colliders

In a previous paper, we studied the Higgs pair production in the standard model with the reaction $e^{+}e^{-}\to t \bar t HH$. Based on this, we study the Higgs pair production via $e^{+}e^{-}\to b \bar b HH$. We evaluate the total cross section of $b\bar bHH$ and calculate the number total of events considering the complete set of Feynman diagrams at tree-level, and compare this process with the process $e^{+}e^{-}\to t \bar t HH$. The numerical computation is done for the energy which is expected to be available at a possible Next Linear $e^{+}e^{-}$ Collider with a center-of-mass energy $800, 1000, 1600$ $GeV$ and luminosity 1000 $fb^{-1}$.Comment: 12 pages, 6 figure

A time-reversal suboptimal detector for underwater acoustic barriers

This paper proposes an experimental setup composed of two interconnected vertical arrays: one transmit only array (TOA) and a receive only array (ROA). It is shown that using the time reversal principle, where the ocean is used as a spatial matched filter, signal energy can be simultaneously focused on each ROA hydrophone and thus obtain the detector output by simple summation of the received energy over the array. This setup effectively configures a multistatic system with several transmitters and several receivers coherently processed both in time and space. Simulations using a ray trace propagation model combined with a naive scattering formulation show that the obtained empirical detection probability is close to the theoretical optimal bound derived assuming space - time white Gaussian noise. This system was tested in a sea trial that took place during September 2007 in the Hopav°agen Bay near Trondheim, Norway. The actual setup was composed of a 2 sources TOA on a shallow area of 8 m depth near the shore and a 16 receivers ROA approximately 100 m apart in a 8 to 25 m depth range dependent duct. The transmitted signals were 200 ms duration LFMs with 3 kHz bandwidths in two frequency bands centered on 5 and 10 kHz. The results obtained in realistic conditions show that a 1.7 m2 hard plate could be detected when placed across the barrier. Several results are presented and compared with the theoretical values. Although the system can be significantely improved, in particular by using more populated source and receiving arrays, it is believed that these results can be reproduced at sea in harbor like conditions

Evidence for Multiple Phase Transitions in La_1-xCa_xCoO_3

We report thermal-expansion and specific-heat data of the series La_1-xCa_xCoO_3 for 0 <= x <= 0.3. For x = 0 the thermal-expansion coefficient alpha(T) features a pronounced maximum around T = 50 K caused by a temperature-dependent spin-state transition from a low-spin state (S=0) at low temperatures towards a higher spin state of the Co^3+ ions. The partial substitution of the La^3+ ions by divalent Ca^2+ ions causes drastic changes in the macroscopic properties of LaCoO_3. Around x ~ 0.125 the large maximum in alpha(T) has completely vanished. With further increasing x three different anomalies develop

Reconstruction of the second layer of Ag on Pt(111)

The reconstruction of an Ag monolayer on Ag/Pt(111) is analyzed theoretically, employing a vertically extended Frenkel-Kontorova model whose parameters are derived from density functional theory. Energy minimization is carried out using simulated quantum annealing techniques. Our results are compatible with the STM experiments, where a striped pattern is initially found which transforms into a triangular reconstruction upon annealing. In our model we recognize the first structure as a metastable state, while the second one is the true energy minimum

PyMes: las grandes organizaciones del mañana, ¿ISO la solución del hoy?.

Resumen: En este articulo abordaremos el tema de la importancia que es para las empresas desarrollarse a la par de sus competidores, así como de las posibles exigencias de sus clientes, buscando las mejores herramientas de acuerdo a sus posibilidades financieras, enfocando este análisis a las PyMes (Pequeñas y Medianas Empresas). Esto se debe a que las empresas que buscan crecer dependen del compromiso de sus empleados, así como del desarrollo de sus procesos buscando su disminuir la variación. Este artículo enunciará las opciones de crecimiento de las Pymes, al buscar la certificación, estandarización y la implementación de sus procesos, con la ayuda de normas de estandarización, como la ISO 9000. Todo esto tomando en cuenta el compromiso total de su personal en todos los niveles, dado que no existir tal compromiso, para la organización solo será tomado tal proceso como un gasto innecesario y no como una inversión de crecimiento de la misma

Range-dependent regularization of travel-time tomography based on theoretical modes

Travel time inversion is a fundamental method of Ocean Acoustic Tomography, for the estimation of perturbations in sound speed. By discretizing the watercolumn into a system of layers, the method allows to introduce a system of linear equations, relating a known vector of perturbations in travel time, to an unknown vector of perturbations in sound speed, through the so-called \observation matrix". Inverting the system allows to determine a solution, which estimates the perturbation in sound speed in each layer of the watercolumn. However, in most problems of practical interest, the number of unknowns (i.e. the perturbations in sound speed) is larger that the number of equations (which correspond to the number of delays in travel time), which implies that inverting the system of linear equations can be viewed as an ill-posed problem. The discussion presented in this paper illustrates an approach to the problem of inversion, which is based on the usage of theoretical modes. Further, it is shown that for a range-dependent perturbation in sound speed, which corresponds to a superposition of plane waves, the inversion problem can be regularized (i.e. the system of linear equations can be rewritten in order to deal with more equations than unknowns) by estimating only the amplitudes and phases of the linear waves. Particular examples are given for simulated and real data