Predistorsión Digital mediante Señales Enventanadas Tipo Chirp para la Linealización de Amplificadores de Potencia

Digital PreDistortion (DPD) is a well-known method to reduce nonlinear distortion in power amplifiers (PA). In a LTE uplink transmission, the modulation schemes are adaptive. Thus, the DPD function will have to be re-calibrated once the modulation changes. This fact increases the DPD computational cost and the required memory. If the DPD is not re-trained its linearity performance will decrease. This effect can be reduced using a suitable training signal. We propose several novel non-stationary calibration signals based on a windowed-chirp waveform. The envelope of these sequences is bounded by different windows used in signal processing such as Bartlett, Blackman, Hamming or Welch. Bartlett and Blackman windows generate calibration sequences with higher peak to average power ratio values than Welch. Welch envelope creates a signal with a more uniform probability density function (pdf) than the Hamming-window, whose pdf is similar to a Rayleigh distribution. The linearization strategy is based on capturing the described sequences at the PA input and output to extract the predistortion parameters. Once the predistorter functions are computed, we apply them on various LTE-transmissions and perform linearity measurements in terms of the adjacent channel leakage ratio to compare with the standard requirements. In all cases the maximum nonlinear distortion reduction is accomplished with the Chirp-Bartlett sequence (up to 37dBc when transmitting a QPSK-LTE-signal). Thus, good DPD performance is achieved when using the proposed Bartlett-Chirp in the DPD-training-stage. This avoids generating specific DPDs for each modulation scheme, saving computational cost, required memory, and increasing the system efficiency

Expression of B-nerve growth factor in rabbit male tract and seminal plasma

Nerve growth factor (NGF) has been recently identified as an ovulation inductor factor (OIF) in the seminal plasma (SP) (Ratto et al. PNAS 2012; 109:15042-7). The presence of OIF in rabbit has been suggested but this protein has not yet been identified. Our aim was to study the mRNA expression in the rabbit male reproductive tract and to identify the protein β-NGF in the SP

Breathers in a system with helicity and dipole interaction

Recent papers that have studied variants of the Peyrard-Bishop model for DNA, have taken into account the long range interaction due to the dipole moments of the hydrogen bonds between base pairs. In these models the helicity of the double strand is not considered. In this particular paper we have performed an analysis of the influence of the helicity on the properties of static and moving breathers in a Klein--Gordon chain with dipole-dipole interaction. It has been found that the helicity enlarges the range of existence and stability of static breathers, although this effect is small for a typical helical structure of DNA. However the effect of the orientation of the dipole moments is considerably higher with transcendental consequences for the existence of mobile breathers.Comment: 4pages, 5 eps figure

Uso de las etapas de Tanner para estimar la edad cronológica en presuntos casos de pornografía infantil: revisión sistemática

En las dos últimas décadas se ha producido un crecimiento exponencial de la distribución y disponibilidad de material pornográfico infantil en Internet y las redes sociales. La comunidad médica está involucrada con la asistencia a las autoridades investigadoras en relación con la estimación de la edad y la madurez sexual de las presuntas víctimas. Objetivo: Determinar la eficacia del uso de las etapas de Tanner como método para estimar la edad cronológica en presuntos casos de pornografía infantil basada en la evidencia publicada. Material y Método: Estudio de revisión sistemática en las bases de datos PubMed y Scopus siguiendo directrices PRISMA. Se identificaron los artículos que describen el resultado del uso de las etapas de Tanner para estimar la edad cronológica en presuntos casos de pornografía infantil. Para el cribado se consideraron los escritos en inglés o español publicados desde el 1 de enero de 2000 hasta el 30 de abril de 2020. De los artículos finalmente incluidos se extrajeron los siguientes datos: tipo de estudio; material y métodos utilizados; ítems de Tanner examinados; características de los evaluadores; resultados; edad cronológica estimada versus la edad real; variaciones dependientes del observador (sesgo); conclusiones. Resultados: Se incluyeron siete estudios. Tres eran revisiones de la literatura y cuatro estudios de casos con testimonio de expertos y sesgo de los observadores. Este método es ineficaz cuando la presunta víctima, para ambos sexos, muestra una maduración sexual en las etapas 3-5 de Tanner. En las etapas 1-2 puede ser útil para testificar que la víctima es menor de 18 años, pero no para determinar su edad cronológica. Conclusión: La evidencia científica desaconseja el uso de las etapas de Tanner para estimar la edad cronológica de la víctima a partir de imágenes en supuestos casos de pornografía infantil. Los pediatras, y otros profesionales de la medicina, deben evitar emitir un testimonio que no tenga una base científica. The last two decades have seen an exponential growth in the distribution and availability of child pornographic material on the Internet and social networks. The medical community is involved in assisting the investigating authorities in relation to estimating the age and sexual maturity of the alleged victims. Objective: To determine the efficacy of using Tanner stages as a method for estimating chronological age in alleged child pornography cases based on published evidence. Material and Method: Systematic review study in PubMed and Scopus databases following PRISMA guideli-nes. Articles describing the outcome of using Tanner stages to estimate chronological age in alleged child pornography cases were identified. For screening, those written in English or Spanish published from January 1, 2000, to April 30, 2020, were considered. The following data were extracted from the articles included: type of study; material and methods used; Tanner items examined; evaluators’ characteristics; results; estimated chronological age versus real age; observer-dependent variations (bias); and conclusions. Results: Seven studies were included. Three were literature reviews and four were case studies with expert testimony and observer bias. This method is ineffective when the alleged victim, in both sexes, shows sexual maturation in Tanner stages 3-5. In stages 1-2, it may be useful to state that the victim is under 18 years old, but not to determine their chronological age. Conclusion: Scientific evidence discourages the use of Tanner stages to estimate the chronological age of the victim from images in alleged child pornography cases. Pediatricians, and other medical professionals, should avoid making a testimony that is not scientifically based. © 2021, Sociedad Chilena de Pediatria. All rights reserved

Characterization of modular deposits for urban drainage networks using CFD techniques

[EN] The growing urban development of population centers in much of the world joined with the significant effects of climate change are causing an increasingly important and recurring increase of the damage caused by flooding. Much of the drainage networks of cities were designed for precipitation characteristics and return periods that have proved to be insufficient with the lapse of time. Therefore, solutions need to be addressed both to reduce runoff generated flows as to control circulating ones through the rainwater drainage networks. All these flow control rain technologies are commonly known as SUDS (Sustainable Urban Drainage), term that encompasses a multitude of solutions to control runoff although many of them require significant costs that make them practically unviable. Therefore, not only should focus on reducing runoff input to the network but also in the flow control techniques development. The idea is to design strategies to reduce flow rain peaks and maximize the capacity of existing networks. The use of detention and storm tanks for flood control is a solution increasingly used as an alternative one to control increased rainfall caused by climate change [1]. Nature and execution of storm tanks can be very diverse, from conventional way based on concrete structures to the most innovative ones in which modular structures are employed to improve the construction speed if many modular units are required at the same time that minimizing urban supply disruption is achieved. Currently, a wide range of modular structures exists on the market with both, different geometries and sizes. In this study the Aquacell brand supplied by Mexichem-PAVCO in Colombia shown in Fig. 1 has been chosen for the development of this study.S849218

Maximally-localized Wannier functions for entangled energy bands

We present a method for obtaining well-localized Wannier-like functions (WFs) for energy bands that are attached to or mixed with other bands. The present scheme removes the limitation of the usual maximally-localized WFs method (N. Marzari and D. Vanderbilt, Phys. Rev. B 56, 12847 (1997)) that the bands of interest should form an isolated group, separated by gaps from higher and lower bands everywhere in the Brillouin zone. An energy window encompassing N bands of interest is specified by the user, and the algorithm then proceeds to disentangle these from the remaining bands inside the window by filtering out an optimally connected N-dimensional subspace. This is achieved by minimizing a functional that measures the subspace dispersion across the Brillouin zone. The maximally-localized WFs for the optimal subspace are then obtained via the algorithm of Marzari and Vanderbilt. The method, which functions as a postprocessing step using the output of conventional electronic-structure codes, is applied to the s and d bands of copper, and to the valence and low-lying conduction bands of silicon. For the low-lying nearly-free-electron bands of copper we find WFs which are centered at the tetrahedral interstitial sites, suggesting an alternative tight-binding parametrization.Comment: 13 pages, with 9 postscript figures embedded. Uses REVTEX and epsf macro

On-Surface Driven Formal Michael Addition Produces m-Polyaniline Oligomers on Pt(111)

On-surface synthesis is emerging as a highly rational bottom-up methodology for the synthesis of molecular structures that are unattainable or complex to obtain by wet chemistry. Here, oligomers of meta-polyaniline, a known ferromagnetic polymer, were synthesized from para-aminophenol building-blocks via an unexpected and highly specific on-surface formal 1, 4 Michael-type addition at the meta position, driven by the reduction of the aminophenol molecule. We rationalize this dehydrogenation and coupling reaction mechanism with a combination of in situ scanning tunneling and non-contact atomic force microscopies, high-resolution synchrotron-based X-ray photoemission spectroscopy and first-principles calculations. This study demonstrates the capability of surfaces to selectively modify local molecular conditions to redirect well-established synthetic routes, such as Michael coupling, towards the rational synthesis of new covalent nanostructures

On the energy functional on Finsler manifolds and applications to stationary spacetimes

In this paper we first study some global properties of the energy functional on a non-reversible Finsler manifold. In particular we present a fully detailed proof of the Palais--Smale condition under the completeness of the Finsler metric. Moreover we define a Finsler metric of Randers type, which we call Fermat metric, associated to a conformally standard stationary spacetime. We shall study the influence of the Fermat metric on the causal properties of the spacetime, mainly the global hyperbolicity. Moreover we study the relations between the energy functional of the Fermat metric and the Fermat principle for the light rays in the spacetime. This allows us to obtain existence and multiplicity results for light rays, using the Finsler theory. Finally the case of timelike geodesics with fixed energy is considered.Comment: 23 pages, AMSLaTeX. v4 matches the published versio

Systematic Study of Electron Localization in an Amorphous Semiconductor

We investigate the electronic structure of gap and band tail states in amorphous silicon. Starting with two 216-atom models of amorphous silicon with defect concentration close to the experiments, we systematically study the dependence of electron localization on basis set, density functional and spin polarization using the first principles density functional code Siesta. We briefly compare three different schemes for characterizing localization: information entropy, inverse participation ratio and spatial variance. Our results show that to accurately describe defect structures within self consistent density functional theory, a rich basis set is necessary. Our study revealed that the localization of the wave function associated with the defect states decreases with larger basis sets and there is some enhancement of localization from GGA relative to LDA. Spin localization results obtained via LSDA calculations, are in reasonable agreement with experiment and with previous LSDA calculations on a-Si:H models.Comment: 16 pages, 11 Postscript figures, To appear in Phys. Rev.

Energy funneling in a bent chain of Morse oscillators with long-range coupling

A bent chain of coupled Morse oscillators with long-range dispersive interaction is considered. Moving localized excitations may be trapped in the bending region. Thus chain geometry acts like an impurity. An energy funneling effect is observed in the case of random initial conditions.Comment: 6 pages, 12 figures. Submitted to Physical Review E, Oct. 13, 200