Efficient Spectral Domain MoM for the Design of Circularly Polarized Reflectarray Antennas Made of Split Rings

The method of moments (MoM) in the spectral domain is used for the analysis of the scattering of a plane wave by a multilayered periodic structure containing conducting concentric split rings in the unit cell. Basis functions accounting for edge singularities are used in the approximation of the current density on the split rings, which makes it possible a fast convergence of MoM with respect to the number of basis functions. Since the 2-D Fourier transforms of the basis functions cannot be obtained in closed-form, judicious tricks (controlled truncation of infinite summations, interpolations, etc.) are used for the efficient numerical determination of these Fourier transforms. The implemented spectral domain MoM software has been used in the design of a circularly polarized reflectarray antenna based on split rings under the local periodicity condition. The antenna has been analyzed with our spectral domain MoM software, with CST and with HFSS, and good agreement has been found among all sets of results. Our software has proven to be around 27 times faster than CST and HFSS

Channel adjustments to a succession of water pulses in gravel bed rivers

Gravel bed rivers commonly exhibit a coarse surface armor resulting from a complex history of interactions between flow and sediment supply. The evolution of the surface texture under single storm events or under steady flow conditions has been studied by a number of researchers. However, the role of successive floods on the surface texture evolution is still poorly understood. An experimental campaign in an 18 m-long 1 m-wide flume has been designed to study these issues. Eight consecutive runs, each one consisting of a low-flow period of variable duration followed by a sudden flood (water pulse) lasting 1.5 h, have been conducted. The total duration of the experiment was 46 h. The initial bed surface was created during a 280 h-long experiment focused on the influence of episodic sediment supply on channel adjustments. Our experiments represent a realistic armored and structured beds found in mountain gravel bed rivers. The armor surface texture persists over the duration of the experiment. The experiment exhibits downstream fining of the bed-surface texture. It was found that sorting processes were affected by the duration of low-flow between flood pulses. Since bed load transport is influenced by sediment sorting, the evolution of bed load transport is impacted by the frequency of the water pulses: short interpulse durations reduce the time over which fine material (transported as bed load) can be winnowed. This, in turn, contributes to declining reduction of the bed load transport over time while the sediment storage increases.Peer ReviewedPostprint (author's final draft

Influence of the sediment supply texture on morphological adjustments in gravel-bed rivers

The role played by the texture of the sediment supply on channel bed adjustments in gravel-bed rivers is poorly understood. To address this issue, an experimental campaign has been designed. Flume experiments lasting 96 h in a 9 m long, 0.60 m wide have been performed with different sand-gravel mixtures as feed textures. The response of the surface texture has been found to be highly dependent on the grain size distribution of the feed. When the feed texture included gravel, the finest fractions of the sediment supply infiltrate beneath the surface. Conversely, sand remains on the surface when the feed texture lacks gravel. This different textural response becomes obscured when water discharge increases. Further, the sediment transport rate approaches the feed rate differently depending on the content of gravel in the feed texture. When a small proportion of gravel is part of the feed texture, bed load transport rate asymptotically approaches the feed rate. However, when a significant fraction of gravel is part of the feed grain size distribution, bed load transport rate approaches the feed rate by following an oscillatory path. These findings have been verified in terms of a one-dimensional numerical model. This modeling reveals that the higher the differences in mobility among the grain sizes contained in the feed texture, the more evident is the nonasymptotic transient trend toward equilibrium.Peer ReviewedPostprint (published version

AN ALGORITHM FOR CONSTRUCTING CERTAIN DIFFERENTIAL OPERATORS IN POSITIVE CHARACTERISTIC

Given a non-zero polynomial f in a polynomial ring R with coefficients in a finite field of prime characteristic p, we present an algorithm to compute a differential operator delta which raises 1/f to its pth power. For some specific families of polynomials, we also study the level of such a differential operator delta, i.e., the least integer e such that delta is R-pe -linear. In particular, we obtain a characterization of supersingular elliptic curves in terms of the level of the associated differential operator

New system and methodology for avoiding calibers in ceramic tile production

MACER, S.L, in collaboration with the Institute of Ceramic Technology, has developed a comprehensive control system of the pressing operation called CALIBREUNICO® which keeps constant in time the bulk density of all the ceramic pieces shaped in an industrial press. The CALIBREUNICO® system consists of two subsystems that permit one hand, balance the variations in moisture spray-dried powder by the continuous regulation in real time of the pressure moulding and, secondly, regulate the load individually in each of the holes of the press with de purpose of equalling the bulk density of all pieces obtained in the same press cycle. CALIBREUNICO®, ensuring the constancy of bulk density of all pieces processed, guarantees a single piece size and the minimization of the production problems associated with variability in bulk density of the pieces.MACER, S.L., en colaboración con el Instituto de Tecnología Cerámica, ha desarrollado un sistema de control integral de la operación de prensado denominado CALIBREUNICO® que permite mantener constante en el tiempo la densidad aparente de todas las piezas cerámicas conformadas en una prensa industrial. El sistema CALIBREUNICO® está constituido por dos subsistemas complementarios que permiten, por un lado, compensar las variaciones de humedad del polvo atomizado mediante la regulación continua y en tiempo real de la presión de prensado y, por otro lado, regular la carga individualizada en cada uno de los alvéolos de la prensa con el fin de igualar la densidad aparente de todas las piezas obtenidas en un mismo ciclo de prensado. CALIBREUNICO®, al asegurar la constancia de la densidad aparente de todas las piezas procesadas, garantiza un único tamaño de pieza y la minimización de los problemas de producción asociados a la variabilidad de la densidad aparente de los soportes

Nuevo sistema para la medida y control de la presión máxima de prensado en los alvéolos del molde: ISOPRESS®

The organization MACER, in collaboration with the Institute of Ceramic Technology, has developed the system ISOPRESS®, an integrated control device that permits to equal automatically the maximum pressure applied on the powder contained in each of the holes of the mould. This system consists of a set of pressure transducers which are located in the isostatic punches of the mould itself. With them it is possible to register in real-time the evolution of the measured pressure of the oil contained in the compensation chamber of each punch. All the transducers are connected to a data acquisition system which transfers the pressure values to a PC which performs the signal processing to obtain the pressure maximum value reached during a pressing cycle, in each one of the holes. The system is completed with a control software especially developed, that permits to regulate individually the height of the first fall of each inferior punch to guarantee the uniformity of the pressure applied in all the holes. ISOPRESS®, by assuring the constancy of the bulk density of all the pieces processed, guarantees a unique piece size and minimize production problems associated to the variability of the bulk density of the pieces

Encefalopatía hepática por hernia diafragmática

Encefalopatía hepática en un perro Groendendael de 4 años, causada por una hernia diafragmática congénita.Hepatic encephalopaty in a four years oid Groendendael, caused by a congenital diafragmatic hernia

Gtdap-1 and the role of autophagy during planarian regeneration and starvation

Planarians have been established as an ideal model organism for stem cell research and regeneration. Planarian regeneration and homeostasis require an exquisite balancing act between cell death and cell proliferation as new tissues are made (epimorphosis) and existing tissues remodeled (morphallaxis). Some of the genes and mechanisms that control cell proliferation and pattern formation are known. However, studies about cell death during remodeling are few and far between. We have studied the gene Gtdap-1, the planarian ortholog of human death-associated protein-1 or DAP-1. DAP-1 together with DAP-kinase has been identified as a positive mediator of programmed cell death induced by gamma-interferon in HeLa cells. We have found that the gene functions at the interface between autophagy and cell death in the remodeling of the organism that occurs during regeneration and starvation in sexual and asexual races of planarians. Our data suggest that autophagy of existing cells may be essential to fuel the continued proliferation and differentiation of stem cells by providing the necessary energy and building blocks to neoblasts

Coupling between downstream variations of channel width and local pool–riffle bed topography

A potential control of downstream channel width variations on the structure and planform of pool–riffle sequence local bed topography is a key to the dynamics of gravel bed rivers. How established pool–riffle sequences respond to time-varying changes in channel width at specific locations, however, is largely unexplored and challenging to address with field-based study. Here, we report results of a flume experiment aimed at building understanding of how statistically steady pool–riffle sequence profiles adjust to spatially prescribed channel width changes. We find that local bed slopes near steady-state conditions inversely correlate with local downstream width gradients when the upstream sediment supply approximates the estimated transport capacity. This result constrains conditions prior to and following the imposed local width changes. Furthermore, this relationship between local channel bed slope and downstream width gradient is consistent with expectations from scaling theory and a broad set of field-based, numerical, and experimental studies (n=88). However, upstream disruptions to coarse sediment supply through actions such as dam removal can result in a transient flipping of the expected inverse correlation between bed slope and width gradient, collectively highlighting that understanding local conditions is critical before typically implemented spatial averaging schemes can be reliably applied.Postprint (published version

Light-Trap: A SiPM Upgrade for Very High Energy Astronomy and Beyond

With the development of the Imaging Atmospheric Cherenkov Technique (IACT), Gamma-ray astronomy has become one of the most interesting and productive fields of astrophysics. Current IACT telescope arrays (MAGIC, H.E.S.S, VERITAS) use photomultiplier tubes (PMTs) to detect the optical/near-UV Cherenkov radiation emitted due to the interaction of gamma rays with the atmosphere. For the next generation of IACT experiments, the possibility of replacing the PMTs with Silicon photomultipliers (SiPMs) is being studied. Among the main drawbacks of SiPMs are their limited active area (leading to an increase in the cost and complexity of the camera readout) and their sensitivity to unwanted wavelengths. Here we propose a novel method to build a relatively low-cost pixel consisting of a SiPM attached to a PMMA disc doped with a wavelength shifter. This pixel collects light over a much larger area than a single standard SiPM and improves sensitivity to near-UV light while simultaneously rejecting background. We describe the design of a detector that could also have applications in other fields where detection area and cost are crucial. We present results of simulations and laboratory measurements of a pixel prototype and from field tests performed with a 7-pixel cluster installed in a MAGIC telescope camera.Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Bexco, Busan, Korea. Id:81