Coaxial-to-Waveguide Matching With $varepsilon$-Near-Zero Ultranarrow Channels and Bends

We propose the use of metamaterial-inspired ultranarrow channels at cutoff to realize an interesting matching between a coaxial antenna and a waveguide. The anomalous properties of a channel at cutoff, analogous to those of zero permittivity materials, allow a simple matching design, valid for arbitrary waveguides, with large degrees of freedom in terms of geometry, length and possible bending of the connecting channel. Moreover, the static-like properties of the channel allow such matching, independent of the relative position of the antenna and possible bending and abruptions along the channel.      

Extended method of line procedure for the analysis of microwave components with bianisotropic inhomogeneous media

Method of line (MoL) procedure is very useful in the analysis of radiative and transmissive microwave components, but its standard version does not allow for the study of elements with complex substrates. In this work, we first show that components integrated into materials exhibiting the magneto-electric effect (biisotropic and general bianisotropic media) cannot be analyzed following a standard MoL algorithm. Next, we derive an extended MoL numerical tool, which allows for the analysis of components in the presence of any linear medium (even inhomogeneous, bianisotropic and lossy). Such an extension is based on the generalization of the transmission-line equations for a general linear medium, which, in the case in point, are not necessarily decoupled. Furthermore, we present the full coincidence of this new method with the standard MoL in the case of simpler media (i.e., not exhibiting the magneto-electric effect) and, finally, we show some numerical results, obtained analyzing microwave antennas and resonators with bianisotropic and chiral substrates.     

Fibromyalgia: its prevalence and impact on the quality of life on a hemodialyzed population

Fibromyalgia syndrome (FMS) is characterized by widespread musculoskeletal pain. It has negative effects on quality of life and has been poorly investigated in specific populations. Our aim was to determine the prevalence of FMS in Brazilian hemodialysis (HD) patients and to investigate its effects on the quality of life. We investigated 311 patients on HD who were submitted to physical examination towards the classification of FMS. All subjects from FMS and control groups were submitted to laboratorial investigation and completed questionnaires of quality of life. The prevalence of FMS was 3.9%, which was close to that of the general population. Most patients were females and from non-Caucasian races. No difference between FMS and control groups was observed regarding race, dialysis adequacy, nutritional status and level of schooling. Ionized calcium was higher in the FMS group than in the control group. There was no association between FMS and secondary hyperparathyroidism. On the other hand, FMS was associated with worse quality of life, depression and anxiety. In conclusion, the prevalence of FMS in HD patients was similar to that of the general population. It was associated with decreasing quality of life in HD patients, in addition to higher degrees of depression and anxiety. No laboratory tests could identify FMS patients on HD. Fibromyalgia syndrome subsequently follows without a well-established mechanism of pathogenesis, and seems to be due to multifactorial causes. Its true impact on the quality of life of HD patients deserves more attention by nephrologists.     

Apple osmotic dehydration described by three-dimensional numerical solution of the diffusion equation

ABSTRACT

In the present study, experimental data of osmotic dehydration kinetics of apple, cut into slices with parallelepiped shape, were simulated using two types of diffusion models. Model 1 considers the constant values of mass diffusivities and volume of the slices. Model 2, on the other hand, considers variable mass diffusivities and also the shrinkage of the product. The numerical solution of the three-dimensional diffusion equation in Cartesian coordinates was obtained through the finite volume method, with a fully implicit formulation and boundary condition of the first kind. Process parameters were determined by optimization using the experimental data sets, through the minimization of an objective function, called χ². The results of the osmotic dehydration kinetics were compatible with those of other studies found in the literature. Process temperature and osmotic solution concentration had influence on the phenomenon, but temperature was preponderant. A study was conducted on water and sucrose distribution during the osmotic dehydration. The results obtained through the mathematical model that considered the variable diffusivity and shrinkage showed greater adequacy to the experimental data.     

Preliminary Studies on Microbial Degradation of Plastics Used in Packaging Potable Water in Nigeria

A simple technique using proprietary solvents to solubilize and powderize Linear Low Density Polyethylene (LLDPE) used in packaging potable water in Nigeria was developed. The increased surface area created, promoted better exposure of the LLDPE to soil microbes. Using the culture enrichment techniques, eight microbial colonies were found capable of utilizing LLDPE as their sole carbon source. The most prolific organism, producing red pigment, was isolated and identified as Serratia marcescens marcescens. This organism was characterized as gram negative rod, reactivity with β-gal, β-glu, and urease was positive while indole production and H₂S was negative. Fermentation test was positive for glucose, sucrose, glycerol, fructose, sorbitol alanine and citrate. The conditions for the pigmentation could not be ascertained. However, the pigment absorbed radiation within UV region and formed a precipitate with ferric chloride. The SEM micrographs of the plastic film surfaces after exposure to S. marcescens revealed some indentations that were attributed to the degrading ability of the organisms. Micrographs of films in medium without S. marcescens (control) presented smooth surfaces. The Tg of degraded and undegraded plastics determined by Differential Scanning Calorimetry (DSC) were 52.43°C and 63.33°C respectively, suggesting a higher degree of motility of the shorter chain length produced after degradation. DSC measurement further showed AH as 89.936 J/g before and 31.945 J/g after microbial degradation. A decrease was also observed in the crystallization temperature (118.980 to 112.25°C) and the enthalpy of crystallization (-83.241 J/g to -34.776 J/g). The result of the DSC thermograph was an indication of reduced crystallinity associated with degradation processes.     

真空断路器高频电流开断特性的影响因素和研究方法

对影响真空断路器高频电流开断特性的一些因素做了介绍。认为这些因素的综合效应决定了真空断路器的高频电流开断特性;电流在零值附近的变化率和触头间隙在电流开断后的介质恢复速率是影响真空断路器高频电流开断性能的决定性参数。并指出了利用计算机模拟的方法研究真空断路器高频电流开断特性的必要性。     

Generalized transmission line equations for bianisotropic materials

The generalized transmission line equations for bianisotropic materials are derived in this paper. These equations are obtained in a general orthogonal curvilinear reference system, taking properly into account the metric factors and decomposing the field vectors into two components: a transverse component and a longitudinal one, both with respect to a reference coordinate direction. Such a general formulation is very useful in order to analyze metallic/dielectric uniform bended waveguides. On the other hand, it is very appropriate when studying conformal integrated circuits by using the method of lines (MoL). Finally, the formulation here presented leads to a straightforward derivation of the transmission line equations in the spectral domain when studying conformal integrated antennas. As particular cases of the theory here presented, transmission line equations in orthogonal curvilinear coordinates are also derived for anisotropic, bi-isotropic, and isotropic materials.     

Time‐series clustering via quasi U‐statistics

The problem of time‐series discrimination and classification is discussed. We propose a novel clustering algorithm based on a class of quasi U‐statistics and subgroup decomposition tests. The decomposition may be applied to any concave time‐series distance. The resulting test statistics are proven to be asymptotically normal for either i.i.d. or non‐identically distributed groups of time‐series under mild conditions. We illustrate its empirical performance on a simulation study and a real data analysis. The simulation setup includes stationary vs. stationary and stationary vs. non‐stationary cases. The performance of the proposed method is favourably compared with some of the most common clustering measures available.     

Characterization of phenolic compounds extracted from wheat protein fractions using high-performance liquid chromatography/liquid chromatography mass spectrometry in relation to anti-allergenic,anti-oxidant,anti-hypertension,and anti-diabetic properties

The purpose of this study was to identify novel natural bioactive phenolic compounds with anti-oxidant, anti-allergic, anti-hypertensive, and anti-diabetic properties in wheat protein fractions. Free and bound phenolic compounds were isolated from the albumin, glutelin-1, glutelin-2, prolamin, and globulin wheat protein fractions. The biological properties of the extracted phenolics were analyzed in vitro using 1,1-diphenyl-2-picryl-hydrazyl assays, enzyme-linked immunosorbent assays, angiotensin-1 converting enzyme assays, and α-amylase assays. The free and bound phenolic compounds were identified using liquid chromatography electrospray ionization tandem mass spectrometry methods. The aromatic rings in globulin were the highest in both before and after the removal of phenolic compounds (1.13 and 1.05 mg/g). The highest values of angiotensin-1 converting enzyme inhibitory and α-amylase inhibition (%) were obtained in glutelin-1 (73.17 and 96.41%, respectively) before removal phenolic compounds. The biological activity was affected by the presence or absence of phenolic compounds. Allergenicity was minimized in the presence of phenolic compounds. Correlation coefficients between wheat protein fractions and biological properties are described.     

Polygonal patch antennas for wireless communications

An effective design of polygonal patch antennas with multifrequency or broad-band operation modes for wireless communications is presented in this paper. It is shown how polygonal patches with suitable features may be obtained after a proper perturbation of conventional rectangular geometries, which inherently present poor bandwidth performances. These perturbed irregular geometries may support multiple resonances and, thus, may present a broad-band or multifrequency operation mode, even employing conventional patch antennas with a single dielectric substrate. These polygonal patches are efficiently analyzed through a numerical code based on the method of moments, with entire domain basis functions that accurately describe the radiation mechanism. After the presentation of the analysis and design techniques, some antenna layouts for modern wireless communication systems will be proposed. Such antennas are designed for both universal mobile telecommunication system and wireless local area network portable equipment with real-life finite ground planes.