Aproximaci?n a la estimaci?n espacial de sequ?as meteorol?gicas en la cuenca hidrogr?fica del rio Coello, Colombia

15 p. Recurso Electr?nicoLa evaluaci?on espacio temporal para la caracterizaci?on de las sequ??as meteorol?ogicas se bas?o en datos de precipitaci ?on mensual acumulada entre 1996-2005 de 20 estaciones meteorol?ogicas distribuidas en la cuenca hidrogr?afica del r??o Coello. Se realiz?o un preprocesamiento a los datos de precipitaci?on con pruebas de consistencia de datos para corregir y eliminar datos sobre o sub estimados. Para estimar los datos faltantes de precipitaci?on se comparan tres m?etodos geoestad??sticos de interpolaci ?on, derivados de Kriging, asociados con variables secundarias como el Kriging Ordinario, CoKrigin Ordinario asocidadas a las variables secundarias de un Modelo de Elevaci?on Digital y datos de precipitaci?on satelital TRMM. Para seleccionar el m?etodo geoestad??stico se compar?o el ajuste de cada interpolaci?on con respecto a tres estaciones de referencia a trav?es de tres pruebas de calidad, las cuales fueron Ra??z del Error Cuadr?atico Medio (RMSE), Criterio de Informaci?on de Akaike (AIC) y Criterio de Informaci?on Bayesiano (BIC). En esta investigaci?on dos de tres pruebas favorecen al CoKriging Ordinario usando como variable secundaria la Altitud (CoK+DEM). Con la serie interpolada de precipitaci?on se evaluaron y caracterizaron las sequ??as por medio del ?Indice de Precipitaci?on Estandarizado (SPI) a escala mensual y trimestral, calculando los par?ametros de severidad, duraci?on, intensidad y frecuencia de las sequ??as. Por medio de mapas se delimitaron las regiones en donde se presentan los valores negativos de SPI. En el an?alisis espacio temporal los meses de Enero, Febrero, Julio y Agosto son los m?as secos del a?no. En el a?no 1997 se present?o la sequ??a meteorol?ogica de mayores afectaciones en la cuenca del r??o Coello generalmente concentrados en la parte media y baja de la cuenca, con una intensidad maxima de -2,57 de SPI. Palabras Clave: Sequ??a meteorol?ogica; m?etodos de interpolaci?on geoestad??sticos; ?Indice de Precipitaci?on Estandarizado (SPI); par?ametros de sequ??as; cuenca hidrogr?afica del r??o Coello.The space-temporal evaluation to characterize meteorological droughts was based on data accumulated monthly precipitation between 1996-2005 from 20 meteorological stations distributed in the Coello River basin. Data precipitation was performed preprocessing with data consistency tests to correct and delete data over- or under estimated. To estimate missing precipitation data are compared three geostatistical interpolation methods derived from Kriging, associated with secondary variables such as the Ordinary Kriging, CoKrigin Ordinary associated with secondary variables of a Digital Elevation Model and data satellite TRMM. To select the statistical method the setting of each interpolation was compared with respect to three reference stations through three quality tests, which were Root Mean Square Error (RMSE), Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). In this investigation two of three tests favor the Ordinary CoKriging using as a secondary variable Altitude (COK+DEM). With the interpolated series of precipitation were evaluated and characterized by drought Standardized Precipitation Index (SPI) at monthly and quarterly scale, calculating the parameters of severity, duration, intensity and frequency of droughts. By mapping are delimited the regions where occur the more negative values of SPI. In analyzing spacetemporal the months of January, February, July and August are the driest of the year. In 1997 the meteorological drought greatest damage occurs in the Coello River basin generally concentrated in the middle and lower part of the basin, with a maximum intensity of SPI -2,57. Keywords: Meteorological drought; geostatistical interpolation methods; Standardized Precipitation Index (SPI); parameters droughts; Coello River Basin

The ground state of a spin-1/2 neutral particle with anomalous magnetic moment in a Aharonov-Casher configuration

We determine the (bound) ground state of a spin 1/2 chargless particle with anomalous magnetic moment in certain Aharonov-Casher configurations. We recast the description of the system in a supersymmetric form. Then the basic physical requirements for unbroken supersymmetry are established. We comment on the possibility of neutron trapping in these systems

Stability analysis of bicycles by means of analytical models with increasing complexity

The basic Whipple-Carvallo bicycle model for the study of stability takes into account only geometric and mass properties. Analytical bicycle models of increasing complexity are now available, they consider frame compliance, tire properties, and rider posture. From the point of view of the designer, it is important to know if geometric and mass properties affect the stability of an actual bicycle as they affect the stability of a simple bicycle model. This paper addresses this problem in a numeric way by evaluating stability indices from the real parts of the eigenvalues of the bicycle's modes (i.e., weave, capsize, wobble) in a range of forward speeds typical of city bicycles. The sensitivity indices and correlation coefficients between the main geometric and mass properties of the bicycle and the stability indices are calculated by means of bicycle models of increasing complexity. Results show that the simpler models correctly predict the effect of most of geometric and mass properties on the stability of the single modes of the bicycle. Nevertheless, when the global stability indices of the bicycle are considered, often the simpler models fail their prediction. This phenomenon takes place because with the basic model some design parameters have opposite effects on the stability of weave and capsize, but, when tire sliding is included, the capsize mode is always stable and low speed stability is chiefly determined by weave stability

Decoherence assisting a measurement-driven quantum evolution process

We study the problem of driving an unknown initial mixed quantum state onto a known pure state without using unitary transformations. This can be achieved, in an efficient manner, with the help of sequential measurements on at least two unbiased bases. However here we found that, when the system is affected by a decoherence mechanism, only one observable is required in order to achieve the same goal. In this way the decoherence can assist the process. We show that, depending on the sort of decoherence, the process can converge faster or slower than the method implemented by means of two complementary observables.Comment: Four pages, three figures included ([email protected]

Turbulence Hierarchy in a Random Fibre Laser

Turbulence is a challenging feature common to a wide range of complex phenomena. Random fibre lasers are a special class of lasers in which the feedback arises from multiple scattering in a one-dimensional disordered cavity-less medium. Here, we report on statistical signatures of turbulence in the distribution of intensity fluctuations in a continuous-wave-pumped erbium-based random fibre laser, with random Bragg grating scatterers. The distribution of intensity fluctuations in an extensive data set exhibits three qualitatively distinct behaviours: a Gaussian regime below threshold, a mixture of two distributions with exponentially decaying tails near the threshold, and a mixture of distributions with stretched-exponential tails above threshold. All distributions are well described by a hierarchical stochastic model that incorporates Kolmogorov's theory of turbulence, which includes energy cascade and the intermittence phenomenon. Our findings have implications for explaining the remarkably challenging turbulent behaviour in photonics, using a random fibre laser as the experimental platform.Comment: 9 pages, 5 figure

Stability of exomoons around the Kepler transiting circumbinary planets

The Kepler mission has detected a number of transiting circumbinary planets (CBPs). Although currently not detected, exomoons could be orbiting some of these CBPs, and they might be suitable for harboring life. A necessary condition for the existence of such exomoons is their long-term dynamical stability. Here, we investigate the stability of exomoons around the Kepler CBPs using numerical $N$-body integrations. We determine regions of stability and obtain stability maps in the (a_m,i_pm) plane, where a_m is the initial exolunar semimajor axis with respect to the CBP, and i_pm is the initial inclination of the orbit of the exomoon around the planet with respect to the orbit of the planet around the stellar binary. Ignoring any dependence on i_pm, for most Kepler CBPs the stability regions are well described by the location of the 1:1 mean motion commensurability of the binary orbit with the orbit of the moon around the CBP. This is related to a destabilizing effect of the binary compared to the case if the binary were replaced by a single body, and which is borne out by corresponding 3-body integrations. For high inclinations, the evolution is dominated by Lidov-Kozai oscillations, which can bring moons in dynamically stable orbits to close proximity within the CBP, triggering strong interactions such as tidal evolution, tidal disruption, or direct collisions. This suggests that there is a dearth of highly-inclined exomoons around the Kepler CBPs, whereas coplanar exomoons are dynamically allowed.Comment: Accepted for publication by MNRAS. 12 pages, 7 figure

Corrigendum: Positive and Negative Symptoms in Schizophrenia Relate to Distinct Oscillatory Signatures of Sensory Gating

Oscillatory activity in neural populations and temporal synchronization within these populations are important mechanisms contributing to perception and cognition. In schizophrenia, perception and cognition are impaired. Aberrant gating of irrelevant sensory information, which has been related to altered oscillatory neural activity, presumably contributes to these impairments. However, the link between schizophrenia symptoms and sensory gating deficits, as reflected in oscillatory activity, is not clear. In this electroencephalography study, we used a paired-stimulus paradigm to investigate frequency-resolved oscillatory activity in 22 schizophrenia patients and 22 healthy controls. We found sensory gating deficits in patients compared to controls, as reflected in reduced gamma-band power and alpha-band phase synchrony difference between the first and the second auditory stimulus. We correlated these markers of neural activity with a five-factor model of the Positive and Negative Syndrome Scale. Gamma-band power sensory gating was positively correlated with positive symptoms. Moreover, alpha-band phase synchrony sensory gating was negatively correlated with negative symptoms. A cluster analysis revealed three schizophrenia phenotypes, characterized by (i) aberrant gamma-band power and high positive symptoms, (ii) aberrant alpha-band phase synchrony, low positive, and low negative symptom scores or (iii) by intact sensory gating and high negative symptoms.Our study demonstrates that aberrant neural synchronization, as reflected in gamma-band power and alpha-band phase synchrony, relates to the schizophrenia psychopathology. Different schizophrenia phenotypes express distinct levels of positive and negative symptoms as well as varying degrees of aberrant oscillatory neural activity. Identifying the individual phenotype might improve therapeutic interventions