Absorption and Direct Processes in Chaotic Wave Scattering

Recent results on the scattering of waves by chaotic systems with losses and direct processes are discussed. We start by showing the results without direct processes nor absorption. We then discuss systems with direct processes and lossy systems separately. Finally the discussion of systems with both direct processes and loses is given. We will see how the regimes of strong and weak absorption are modified by the presence of the direct processes.Comment: 8 pages, 4 figures, Condensed Matter Physics (IV Mexican Meeting on Mathematical and Experimental Physics), Edited by M. Martinez-Mares and J. A. Moreno-Raz

Electromagnetic prompt response in an elastic wave cavity

A rapid, or prompt response, of an electromagnetic nature, is found in an elastic wave scattering experiment. The experiment is performed with torsional elastic waves in a quasi-one-dimensional cavity with one port, formed by a notch grooved at a certain distance from the free end of a beam. The stationary patterns are diminished using a passive vibration isolation system at the other end of the beam. The measurement of the resonances is performed with non-contact electromagnetic-acoustic transducers outside the cavity. In the Argand plane, each resonance describes a circle over a base impedance curve which comes from the electromagnetic components of the equipment. A model, based on a variation of Poisson's kernel is developed. Excellent agreement between theory and experiment is obtained.Comment: 4 pages, 5 figure

Scattering of Elastic Waves in a Quasi-one-dimensional Cavity: Theory and Experiment

We study the scattering of torsional waves through a quasi-one-dimensional cavity both, from the experimental and theoretical points of view. The experiment consists of an elastic rod with square cross section. In order to form a cavity, a notch at a certain distance of one end of the rod was grooved. To absorb the waves, at the other side of the rod, a wedge, covered by an absorbing foam, was machined. In the theoretical description, the scattering matrix S of the torsional waves was obtained. The distribution of S is given by Poisson's kernel. The theoretical predictions show an excellent agreement with the experimental results. This experiment corresponds, in quantum mechanics, to the scattering by a delta potential, in one dimension, located at a certain distance from an impenetrable wall

Experimental determination of the absorption strength in absorbing chaotic cavities

Due to the experimental necessity we present a formula to determine the absorption strength by power losses inside a chaotic system (cavities, graphs, acoustic resonators, etc) when the antenna coupling, always present in experimental measurements, is taken into account. This is done by calculating the average of the absorption coefficient as a function of the absorption strength and the coupling of the antenna to the system, in the one channel case.Comment: 6 pages, 3 figures, Submitted to Phys. Rev.

Distribution of the S-matrix in chaotic microwave cavities with direct processes and absorption

We quantify the presence of direct processes in the S-matrix of chaotic microwave cavities with absorption in the one-channel case. To this end the full distribution P_S(S) of the S-matrix, i.e. S=\sqrt{R}e^{i\theta}, is studied in cavities with time-reversal symmetry for different antenna coupling strengths T_a or direct processes. The experimental results are compared with random-matrix calculations and with numerical simulations based on the Heidelberg approach including absorption. The theoretical result is a generalization of the Poisson kernel. The experimental and the numerical distributions are in excellent agreement with random-matrix predictions for all cases.Comment: 4 pages, 4 figure

Chaotic scattering with direct processes: A generalization of Poisson's kernel for non-unitary scattering matrices

The problem of chaotic scattering in presence of direct processes or prompt responses is mapped via a transformation to the case of scattering in absence of such processes for non-unitary scattering matrices, \tilde S. In the absence of prompt responses, \tilde S is uniformly distributed according to its invariant measure in the space of \tilde S matrices with zero average, < \tilde S > =0. In the presence of direct processes, the distribution of \tilde S is non-uniform and it is characterized by the average (\neq 0). In contrast to the case of unitary matrices S, where the invariant measures of S for chaotic scattering with and without direct processes are related through the well known Poisson kernel, here we show that for non-unitary scattering matrices the invariant measures are related by the Poisson kernel squared. Our results are relevant to situations where flux conservation is not satisfied. For example, transport experiments in chaotic systems, where gains or losses are present, like microwave chaotic cavities or graphs, and acoustic or elastic resonators.Comment: Added two appendices and references. Corrected typo

Lesiones traumáticas de la columna vertebral en niños

—Se ha realizado un estudio retrospectivo de los casos de traumatismo raquídeo atendidos en urgencias de nuestro centro desde 1987 hasta 1995. Del total de 159.202 niños atendidos en dicho período, el 1,8% sufría algún tipo de patología traumática de la columna, de los cuales requirieron ingreso 45 casos. Se analizan la distribución por edad, los factores etiológicos y la localización de la lesión. En 4 casos existió afectación neurológica, 2 de ellos con paraplejía completa. Los traumatismos del raquis en el niño son lesiones poco frecuentes, siendo aún más rara la afectación neurológica. fin nuestra serie el grupo más afectado fueron varones de 8 a 13 años de edad. El tratamiento conservador generalmente da resultados satisfactorios, recurriendo a la cirugía sólo en casos de severa inestabilidad o compromiso neurológico.We report the results of a restrospective study of cases with spinal trauma in children treated in our institution from 1987 until 1995. From 159,202 children under fourteen, only in 1.8% spinal traumatism was present being necessary hospitalization in 45 cases. We analized age distribution, etiologic factors, and level of the lesion. In four patients a neurologic deficit was present, two of them had complete paraplegia. Pediatric spinal trauma is a rare lesion, and associated neurologic deficit is still less common. In our scries, the most affected group was boys, from 8 to 13. Usually conservative treatment provides satisfactory results. Surgery is required only when severe unstability or neurologic deficit are present

Antimicrobial Susceptibility and Characterization of Resistance Mechanisms of Corynebacterium urealyticum Clinical Isolates

Corynebacterium urealyticum is a non-diphtherial urease-producing clinically relevant corynebacterial, most frequently involved in urinary tract infections. Most of the C. urealyticum clinical isolates are frequently resistant to several antibiotics. We investigated the susceptibility of 40 C. urealyticum isolated in our institution during the period 2005-2017 to eight compounds representative of the main clinically relevant classes of antimicrobial agents. Antimicrobial susceptibility was determined by the Epsilometer test. Resistance genes were searched by PCR. All strains were susceptible to vancomycin whereas linezolid and rifampicin also showed good activity (MICs90 = 1 and 0.4 mg/L, respectively). Almost all isolates (39/40, 97.5%) were multidrug resistant. The highest resistance rate was observed for ampicillin (100%), followed by erythromycin (95%) and levofloxacin (95%). Ampicillin resistance was associated with the presence of the blaA gene, encoding a class A ?-lactamase. The two rifampicin-resistant strains showed point mutations driving amino acid replacements in conserved residues of RNA polymerase subunit ? (RpoB). Tetracycline resistance was due to an efflux-mediated mechanism. Thirty-nine PFGE patterns were identified among the 40 C. urealyticum, indicating that they were not clonally related, but producing sporadic infections. These findings raise the need of maintaining surveillance strategies among this multidrug resistant pathogen.This research was funded by Plan Nacional de I+D+i 2013-2016 and Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Ciencia, Innovación y Universidades, Spanish Network for Research in Infectious Diseases (REIPI) D16/0016/0007 and RD16/0016/0008), and co-financed by European Development Regional Fund “A way to achieve Europe”, Operative program Intelligent Growth 2014-2020

Cultivo intensivo tradicional de nopal verdura (<i>Opuntia ficus-indica</i> L.) en ámbitos urbanos delegación Milpa Alta al oriente de la ciudad de México

La Ciudad de México tiene una altitud promedio de 2.200 metros, un clima templado, con temperaturas de 18 º C a 24 º C y precipitación anual que varía de 700 a 1.400 mm. La Zona Metropolitana de la Ciudad de México (ZMCM) cubre un área de 7.860 kilometros2. Esta área incluye al Distrito Federal y 54 municipios, que en conjunto tienen una población de 24 millones. A pesar del constante crecimiento actividades agrícolas persisten dentro de sus límites. Al oriente de la ciudad se localiza la delegación Milpa Alta misma que se caracteriza por sus zona de terrazas. Existen cultivos como maíz, avena, veza pero sobresale el cultivo de nopal (Opuntia ficus indica L) con 7500 ha. El cultivo de nopal se caracteriza por su producción durante todo el año y existen estimaciones que puede llegar a producir 50 tonaño por parcela. Se aplicaron 40 cuestionarios con la finalidad de conocer el entorno productivo del cultivo de nopal. Existen 3 tres tamaños de parcela en cual se realiza el cultivo de nopal yunta chica, mediana y grande. Existen tres temporadas de producción que van acorde al año y muy ligadas a la comercialización. Producción alta (febrero a mayo) y bajo precio, producción mediana (junio a octubre) y producción baja (noviembre a enero) alto precio. El tiempo de vida útil de una nopalera es de 20 a 25 años. No existe época de siembra de la nopalera y un cultivo tradicional es de 30 cm entre nopal con un pasillo de 1.0 metros. Su principal fuente de fertilización es el estiércol de ganado lechero. Enfermedades principales del cultivo de nopal son los hongos, bacterias e insectos mismos que dependen de la época del año. El nopal es un cultivo que se a desarrollado mediante el ensayo error de los productores y es actividad que tiene amplia aceptación desde el punto de vista cultural en cualquier parte del país.Eje B1 Sistemas de producción de base agroecológica (Relatos de experiencias)Facultad de Ciencias Agrarias y Forestale