Spatially explicit estimates of length and biomass of Clupea harengus (Norwegian spring spawning herring) from acoustic and trawl surveys in the North-East Atlantic in May 2011

Acoustic estimates of herring and blue whiting abundance were obtained during the surveys using the Simrad ER60 scientific echosounder. The allocation of NASC-values to herring, blue whiting and other acoustic targets were based on the composition of the trawl catches and the appearance of echo recordings. To estimate the abundance, the allocated NASC -values were averaged for ICES-squares (0.5° latitude by 1° longitude). For each statistical square, the unit area density of fish (rA) in number per square nautical mile (N*nm-2) was calculated using standard equations (Foote et al., 1987; Toresen et al., 1998). To estimate the total abundance of fish, the unit area abundance for each statistical square was multiplied by the number of square nautical miles in each statistical square and then summed for all the statistical squares within defined subareas and over the total area. Biomass estimation was calculated by multiplying abundance in numbers by the average weight of the fish in each statistical square then summing all squares within defined subareas and over the total area. The Norwegian BEAM soft-ware (Totland and Godø 2001) was used to make estimates of total biomass.

Spatially explicit estimates of length and biomass of Clupea harengus (Norwegian spring spawning herring) from acoustic and trawl surveys in the North-East Atlantic in May 2007

Acoustic estimates of herring and blue whiting abundance were obtained during the surveys using the Simrad ER60 scientific echosounder. The allocation of NASC-values to herring, blue whiting and other acoustic targets were based on the composition of the trawl catches and the appearance of echo recordings. To estimate the abundance, the allocated NASC -values were averaged for ICES-squares (0.5° latitude by 1° longitude). For each statistical square, the unit area density of fish (rA) in number per square nautical mile (N*nm-2) was calculated using standard equations (Foote et al., 1987; Toresen et al., 1998). To estimate the total abundance of fish, the unit area abundance for each statistical square was multiplied by the number of square nautical miles in each statistical square and then summed for all the statistical squares within defined subareas and over the total area. Biomass estimation was calculated by multiplying abundance in numbers by the average weight of the fish in each statistical square then summing all squares within defined subareas and over the total area. The Norwegian BEAM soft-ware (Totland and Godø 2001) was used to make estimates of total biomass.

Si and SixGe1-x NWs studied by Raman spectroscopy

Group IV nanostructures have attracted a great deal of attention because of their potential applications in optoelectronics and nanodevices. Raman spectroscopy has been extensively used to characterize nanostructures since it provides non destructive information about their size, by the adequate modeling of the phonon confinement effect. The Raman spectrum is also sensitive to other factors, as stress and temperature, which can mix with the size effects borrowing the interpretation of the Raman spectrum. We present herein an analysis of the Raman spectra obtained for Si and SiGe nanowires; the influence of the excitation conditions and the heat dissipation media are discussed in order to optimize the experimental conditions for reliable spectra acquisition and interpretation.

Conformación de Superficies Reflectoras de Sistemas Dobles de Tipo Offset con Alimentadores descritos en Campo Próximo

This work discusses an iterative procedure of shaping offset dual-reflector antennas based on geometrical optics considering both far-field and near-field measurements of amplitude and phase from the feed horn. The surfaces synthesized will transform a known radiation field of a feed to a desired aperture distribution. This technique is applied for both circular and elliptical apertures and has the advantage to simplify the problem compared with existing techniques based on solving nonlinear differential equations. A MATLAB tool has been developed to implement the shaping algorithms. This procedure is applied for the design of a 1.1 m high-gain antenna for the ESA’s Solar Orbiter spacecraft. This antenna operating at X-band will manage high data rate and high efficiency communications with Earth stations.

Size, strain, and band offset engineering in GaAs(Sb)(N)-capped InAs quantum dots for 1.3 - 1.55 µm LEDs and LDs

The optical and structural properties of InAs/GaAs quantum dots (QD) are strongly modified through the use of a thin (~ 5 nm) GaAsSb(N) capping layer. In the case of GaAsSb-capped QDs, cross-sectional scanning tunnelling microscopy measurements show that the QD height can be controllably tuned through the Sb content up to ~ 14 % Sb. The increased QD height (together with the reduced strain) gives rise to a strong red shift and a large enhancement of the photoluminescence (PL) characteristics. This is due to improved carrier confinement and reduced sensitivity of the excitonic bandgap to QD size fluctuations within the ensemble. Moreover, the PL degradation with temperature is strongly reduced in the presence of Sb. Despite this, emission in the 1.5 !lm region with these structures is only achieved for high Sb contents and a type-II band alignment that degrades the PL. Adding small amounts of N to the GaAsSb capping layer allows to progressively reduce the QD-barrier conduction band offset. This different strategy to red shift the PL allows reaching 1.5 !lm with moderate Sb contents, keeping therefore a type-I alignment. Nevertheless, the PL emission is progressively degraded when the N content in the capping layer is increased

Control en modo corriente y tensión eficaz con lazo de offset para inversor monofásico embarcado en aviones adecuado para funcionamiento en paralelo y conexión trifásica

La incorporación de un lazo de tensión eficaz de (RMS) es una posibilidad atractiva para el control de inversores de potencia de una manera sencilla. Si se combina con un control en modo corriente usando una sonda de efecto Hall, el ruido de modo común de la etapa de potencia transmitido al control puede ser reducido, mejorando la distorsión armónica total (THD) y manteniendo la posibilidad de operación en paralelo. Además, al estar el control de tensión definido sobre baja frecuencia (DC), obtener una gran ganancia a la frecuencia de interés (0Hz) es sencilla con control basado en PI, lo cual garantiza una onda de tensión de salida a 400Hz sin error, a costa de un peor desempeño ante transitorios y ante cargas no lineales. Sin embargo, la implementación de una estrategia de control de esta naturaleza puede provocar la aparición de offset en la salida. Por otra parte, el esquema oculta la información de la fase de la onda de tensión de salida, necesaria para sincronizar tres módulos monofásicos en un montaje trifásico. En este artículo el diseño e implementación del sistema completo es abordado, resolviendo los inconvenientes mencionados mediante un tercer lazo analógico de control para el offset y un algoritmo de sincronización implementado en una FPGA.

Current Mode with RMS Voltage and Offset Control Loops for a Single-Phase Aircraft Inverter Suitable for Parallel and 3-Phase Operation Modes

Rms voltage regulation may be an attractive possibility for controlling power inverters. Combined with a Hall Effect sensor for current control, it keeps its parallel operation capability while increasing its noise immunity, which may lead to a reduction of the Total Harmonic Distortion (THD). Besides, as voltage regulation is designed in DC, a simple PI regulator can provide accurate voltage tracking. Nevertheless, this approach does not lack drawbacks. Its narrow voltage bandwidth makes transients last longer and it increases the voltage THD when feeding non-linear loads, such as rectifying stages. On the other hand, the implementation can fall into offset voltage error. Furthermore, the information of the output voltage phase is hidden for the control as well, making the synchronization of a 3-phase setup not trivial. This paper explains the concept, design and implementation of the whole control scheme, in an on board inverter able to run in parallel and within a 3-phase setup. Special attention is paid to solve the problems foreseen at implementation level: a third analog loop accounts for the offset level is added and a digital algorithm guarantees 3-phase voltage synchronization.

Raman spectrum of group IV nanowires: influence of temperature

Group IV semiconductor nanowires are characterized by Raman spectroscopy. The results are analyzed in terms of the heating induced by the laser beam on the nanowires. By solving the heat transport equation one can simulate the temperature reached by the NWs under the exposure to a laser beam. The results are illustrated with Si and Si1-xGex nanowires. Both bundles of nanowires and individual nanowires are studied. The main experimental conditions contributing to the nanowire heating are discussed

Neutron spectrometry using artificial neural networks for a bonner sphere spectrometer with 3He detector

Neutron spectra unfolding and dose equivalent calculation are complicated tasks in radiation protection, are highly dependent of the neutron energy, and a precise knowledge on neutron spectrometry is essential for all dosimetry-related studies as well as many nuclear physics experiments. In previous works have been reported neutron spectrometry and dosimetry results, by using the ANN technology as alternative solution, starting from the count rates of a Bonner spheres system with a LiI(Eu) thermal neutrons detector, 7 polyethylene spheres and the UTA4 response matrix with 31 energy bins. In this work, an ANN was designed and optimized by using the RDANN methodology for the Bonner spheres system used at CIEMAT Spain, which is composed of a He neutron detector, 12 moderator spheres and a response matrix for 72 energy bins. For the ANN design process a neutrons spectra catalogue compiled by the IAEA was used. From this compilation, the neutrons spectra were converted from lethargy to energy spectra. Then, the resulting energy ?uence spectra were re-binned by using the MCNP code to the corresponding energy bins of the He response matrix before mentioned. With the response matrix and the re-binned spectra the counts rate of the Bonner spheres system were calculated and the resulting re-binned neutrons spectra and calculated counts rate were used as the ANN training data set.

Raman and infrared spectra of dimethyl ether 13C-isotopologue (CH3O13CH3) from a CCSD(T) potential energy surface

So far, no experimental data of the infrared and Raman spectra of 13C isotopologue of dimethyl ether are available. With the aim of providing some clues of its low-lying vibrational bands and with the hope of contributing in a next spectral analysis, a number of vibrational transition frequencies below 300 cm−1 of the infrared spectrum and around 400 cm−1 of the Raman spectrum have been predicted and their assignments were proposed. Calculations were carried out through an ab initio three dimensional potential energy surface based on a previously reported one for the most abundant dimethyl ether isotopologue (M. Villa et al., J. Phys. Chem. A 115 (2011) 13573). The potential function was vibrationally corrected and computed with a highly correlated CCSD(T) method involving the COC bending angle and the two large amplitude CH3 internal rotation degrees of freedom. Also, the Hamiltonian parameters could represent a support for the spectral characterization of this species. Although the computed vibrational term values are expected to be very accurate, an empirical adjustment of the Hamiltonian has been performed with the purpose of anticipating some workable corrections to any possible divergence of the vibrational frequencies. Also, the symmetry breaking derived from the isotopic substitution of 13C in the dimethyl ether was taken into account when the symmetrization procedure was applied.

Interaction between a laser beam and semiconductor nanowires: application to the raman spectrum of Si nanowires

One presents in this work the study of the interaction between a focused laser beam and Si nanowires (NWs). The NWs heating induced by the laser beam is studied by solving the heat transfer equation by finite element methods (fem). This analysis permits to establish the temperature distribution inside the NW when it is excited by the laser beam. The overheating is dependent on the dimensions of the NW, both the diameter and the length. When performing optical characterization of the NWs using focused laser beams, one has to consider the temperature increase introduced by the laser beam. An important issue concerns the fact that the NWs diameter has subwavelength dimensions, and is also smaller than the focused laser beam. The analysis of the thermal behaviour of the NWs under the excitation with the laser beam permits the interpretation of the Raman spectra of Si NWs, where it is demonstrated that temperature induced by the laser beam play a major role in shaping the Raman spectrum of Si NWs

A model of the spatially dependent mechanical properties of the axon during its growth

Neuronal growth is a complex process involving many intra- and extracellular mechanisms which are collaborating conjointly to participate to the development of the nervous system. More particularly, the early neocortical development involves the creation of a multilayered structure constituted by neuronal growth (driven by axonal or dendritic guidance cues) as well as cell migration. The underlying mechanisms of such structural lamination not only implies important biochemical changes at the intracellular level through axonal microtubule (de)polymerization and growth cone advance, but also through the directly dependent stress/stretch coupling mechanisms driving them. Efforts have recently focused on modeling approaches aimed at accounting for the effect of mechanical tension or compression on the axonal growth and subsequent soma migration. However, the reciprocal influence of the biochemical structural evolution on the mechanical properties has been mostly disregarded. We thus propose a new model aimed at providing the spatially dependent mechanical properties of the axon during its growth. Our in-house finite difference solver Neurite is used to describe the guanosine triphosphate (GTP) transport through the axon, its dephosphorylation in guanosine diphosphate (GDP), and thus the microtubules polymerization. The model is calibrated against experimental results and the tensile and bending mechanical stiffnesses are ultimately inferred from the spatially dependent microtubule occupancy. Such additional information is believed to be of drastic relevance in the growth cone vicinity, where biomechanical mechanisms are driving axonal growth and pathfinding. More specifically, the confirmation of a lower stiffness in the distal axon ultimately participates in explaining the controversy associated to the tensile role of the growth cone.

Interaction of spatially overlapping standing electromagnetic solitons in plasmas

Numerical investigations on mutual interactions between two spatially overlapping standing electromagnetic solitons in a cold unmagnetized plasma are reported. It is found that an initial state comprising of two overlapping standing solitons evolves into different end states, depending on the amplitudes of the two solitons and the phase difference between them. For small amplitude solitons with zero phase difference, we observe the formation of an oscillating bound state whose period depends on their initial separation. These results suggest the existence of a bound state made of two solitons in the relativistic cold plasma fluid model.

Interaction between a laser beam and semiconductor nanowires: application to the raman spectrum of Si nanowires

One presents in this work the study of the interaction between a focused laser beam and Si nanowires (NWs). The NWs heating induced by the laser beam is studied by solving the heat transfer equation by finite element methods (FEM). This analysis permits to establish the temperature distribution inside the NW when it is excited by the laser beam. The overheating is dependent on the dimensions of the NW, both the diameter and the length. When performing optical characterisation of NWs using focused laser beams, one has to consider the temperature increase introduced by the laser beam. An important issue concerns the fact that the NW's diameter has subwavelength dimensions, and is also smaller than the focused laser beam. The analysis of the thermal behaviour of the NWs under the excitation with the laser beam permits the interpretation of the Raman spectrum of Si NWs. It is demonstrated that the temperature increase induced by the laser beam plays a major role in shaping the Raman spectrum of Si NWs.