Technique for fast and accurate prediction of antenna far-field patterns

A technique for the fast prediction of antenna far-field patterns is described in which a pillbox antenna is used as the probe. The processing involves transformation of 1-D arrays, and the validation is provided by comparing the measured and predicted patterns of a parabolic reflector.     

Intrinsic viscosity of cellulose derivatives and the persistent cylinder model of Yamakawa

By using the chain model proposed by Yamakawa, intrinsic viscosity measurements allow characterization of cellulose derivatives in dilute solution by persistence length and hydrodynamic diameter as a function of different parameters such as temperature of solvents, degree of substitution and type of substituent.     

An adaptive scheme for a class of interpolatory model reduction methods for frequency response problems

Frequency sweep problems arise in many structural dynamic, acoustic, and structural acoustic applications. In each case, they incur the evaluation of a frequency response function for a typically large number of frequencies. Because each function evaluation requires the solution of an often large‐scale system of equations, frequency sweep problems are computationally intensive. Interpolatory model order reduction is a powerful tool for reducing their cost. However, the performance of this tool depends on the location and number of the interpolation frequency points. It also depends on the number of consecutive frequency derivatives of the response function that are matched at each frequency point. So far, these two choices have been made in the literature in a heuristic manner. In contrast, this paper proposes an automatic adaptive strategy based on monitoring the Euclidean norm of the relative residual associated with the function to be evaluated over the frequency band of interest. More specifically, the number of interpolation points and the number of matched frequency derivatives are adaptively increased until the global Euclidean norm of the relative residual is reduced below a user‐specified tolerance. The robustness, accuracy, and computational efficiency of this adaptive strategy are highlighted with the solution of several frequency sweep problems associated with large‐scale structural dynamic, acoustic, and structural acoustic finite element models. Copyright © 2012 John Wiley & Sons, Ltd.     

Optical realization of bioinspired spiking neurons in the electron trapping material thin film

A thin film of electron-trapping material (ETM), when combined with suitable optical bistability, is considered as a medium for optical implementation of bioinspired neural nets. The optical mechanism of ETM under blue light and near-infrared exposure has the inherent ability at the material level to mimic the crucial components of the stylized Hodgkin-Huxley model of biological neurons. Combining this unique property with the high-resolution capability of ETM, a dense network of bioinspired neurons can be realized in a thin film of this infrared stimulable storage phosphor. When combined with suitable optical bistability and optical interconnectivity, it has the potential of producing an artificial nonlinear excitable medium analog to cortical tissue.     

Raman spectroscopy and in situ Raman spectroelectrochemistry of bilayer ¹²C/¹³C graphene

Bilayer graphene was prepared by the subsequent deposition of a (13)C single-layer graphene and a (12)C single-layer graphene on top of a SiO(2)/Si substrate. The bilayer graphene thus prepared was studied using Raman spectroscopy and in situ Raman spectroelectrochemistry. The Raman frequencies of the (13)C graphene bands are significantly shifted with respect to those of (12)C graphene, which allows us to investigate the single layer components of bilayer graphene individually. It is shown that the bottom layer of the bilayer graphene is significantly doped from the substrate, while the top layer does not exhibit a signature of the doping from the environment. The electrochemical doping has the same effect on the charge carrier concentration at the top and the bottom layer despite the top layer being the only layer in contact with the electrolyte. This is here demonstrated by essentially the same frequency shifts of the G and G' bands as a function of the electrode potential for both the top and bottom layers. Nevertheless, analysis of the intensity of the Raman modes showed an anomalous bleaching of the Raman intensity of the G mode with increasing electrode potential, which was not observed previously in one-layer graphene.     

Effect of material ionicity on the performance of daily disposable contact lenses.

The surface of hydrophilic contact lenses is intrinsically hydrophobic. Biocompatibility requires the contact lens surface to be coated with a lipoproteinic biofilm produced by the ocular secretion. For daily disposable modality of wear it is essential that biocompatibility, clinically represented by good in vivo wettability and subjective acceptance, is achieved as quickly as possible following insertion, as the process needs to be repeated daily. It has been hypothesised that non-ionic materials will not achieve biocompatibility as rapidly as ionic materials owing to the latter's ability to attract high levels of adsorbed proteins. The current investigation was a double-masked crossover study that evaluated, over 1 week of wear, a new non-ionic material (Nelfilcon A) and a current ionic material (Etafilcon A) under daily disposable modality. The results obtained showed that overall, both contact lens materials achieved good in vivo tear stability over the first 30 min of wear and good subjective acceptance that remained stable over the period of wear. The results obtained demonstrate that a non-ionic material can achieve rapid biocompatibility and subjective acceptance in a similar manner to an ionic material.     

Competition between the spring force constant and the phonon energy renormalization in electrochemically doped semiconducting single-walled carbon nanotubes

A detailed analysis of the in situ Raman spectroelectrochemical behavior of individual semiconducting single-walled carbon nanotubes (SWCNTs) is presented. Special attention has been paid to the development of the tangential (TG) mode frequency, which shifts when the externally applied potential Ve is shifted away from Ve=0. The magnitude and direction (upshift or downshift) of the tangential mode band has been found to be dependent on the diameter of the semiconducting tubes. For negative charging, the small-diameter tubes exhibit a downshift while the large-diameter tubes exhibit an upshift. This behavior is explained by a competition between two effects which cause opposite shifts in the TG mode frequency during negative charging: a phonon renormalization effect and a C-C bond weakening during the charging process. Positive charging always causes an upshift of the TG mode frequency. However, the magnitude of the upshift is dependent on the tube diameter.     

A domain decomposition method for discontinuous Galerkin discretizations of Helmholtz problems with plane waves and Lagrange multipliers

A nonoverlapping domain decomposition (DD) method is proposed for the iterative solution of systems of equations arising from the discretization of Helmholtz problems by the discontinuous enrichment method. This discretization method is a discontinuous Galerkin finite element method with plane wave basis functions for approximating locally the solution and dual Lagrange multipliers for weakly enforcing its continuity over the element interfaces. The primal subdomain degrees of freedom are eliminated by local static condensations to obtain an algebraic system of equations formulated in terms of the interface Lagrange multipliers only. As in the FETI‐H and FETI‐DPH DD methods for continuous Galerkin discretizations, this system of Lagrange multipliers is iteratively solved by a Krylov method equipped with both a local preconditioner based on subdomain data, and a global one using a coarse space. Numerical experiments performed for two‐ and three‐dimensional acoustic scattering problems suggest that the proposed DD‐based iterative solver is scalable with respect to both the size of the global problem and the number of subdomains. Copyright © 2009 John Wiley & Sons, Ltd.     

Gene Expression Detects the Factors Influencing the Reproductive Success and the Survival Rates of Paracentrotus lividus Offspring

The increase in the demand for Paracentrotus lividus roe, a food delicacy, causes increased pressure on its wild stocks. In this scenario, aquaculture facilities will mitigate the effects of anthropogenic pressures on the wild stocks of P. lividus. Consequently, experimental studies should be conducted to enhance techniques to improve efficient aquaculture practices for these animals. Here, we for the first time performed molecular investigations on cultured sea urchins. We aimed at understanding if maternal influences may significantly impact the life of future offspring, and how the culture conditions may impact the development and growth of cultured specimens. Our findings demonstrate that the outcomes of in vitro fertilization of P. lividus are influenced by maternal influences, but these effects are largely determined by culture conditions. In fact, twenty-three genes involved in the response to stress and skeletogenesis, whose expressions were measured by Real Time qPCR, were differently expressed in sea urchins cultured in two experimental conditions, and the results were largely modified in offspring deriving from two groups of females. The findings herein reported will be critical to develop protocols for the larval culture of the most common sea urchin, both for research and industrial production purposes for mass production.     

Identification and Characterization of Malate Dehydrogenases in Tomato (Solanum lycopersicum L.)

Malate dehydrogenase, which facilitates the reversible conversion of malate to oxaloacetate, is essential for energy balance, plant growth, and cold and salt tolerance. However, the genome-wide study of the MDH family has not yet been carried out in tomato (Solanum lycopersicum L.). In this study, 12 MDH genes were identified from the S. lycopersicum genome and renamed according to their chromosomal location. The tomato MDH genes were split into five groups based on phylogenetic analysis and the genes that clustered together showed similar lengths, and structures, and conserved motifs in the encoded proteins. From the 12 tomato MDH genes on the chromosomes, three pairs of segmental duplication events involving four genes were found. Each pair of genes had a Ka/Ks ratio < 1, indicating that the MDH gene family of tomato was purified during evolution. Gene expression analysis exhibited that tomato MDHs were differentially expressed in different tissues, at various stages of fruit development, and differentially regulated in response to abiotic stresses. Molecular docking of four highly expressed MDHs revealed their substrate and co-factor specificity in the reversible conversion process of malate to oxaloacetate. Further, co-localization of tomato MDH genes with quantitative trait loci (QTL) of salt stress-related phenotypes revealed their broader functions in salt stress tolerance. This study lays the foundation for functional analysis of MDH genes and genetic improvement in tomato.