Shielding Theory of Enclosures with Apertures

This paper develops the theory of EM radiation from metallic enclosures with apertures, excited by an internal source at frequencies below the fundamental resonance of the enclosure. The enclosure with an aperture is analyzed from two different points of view: as a cavity with a small aperture in a wall, and as a waveguide section short-circuited at one end and open at the other. Rectangular geometries are used throughout, since these are by far the most commonly encountered in practical enclosures and cabinets. Using the corresponding dyadic Green's functions, the fields generated inside the enclosure by some simple sources are determined. The fields radiated through small apertures in a cavity are determined using Bethe's theory of diffraction by small holes. The radiation from an open waveguide is calculated with the help of field-equivalence theorems, with assumptions applicable to the case of evanescent waves. The final step is to derive expressions for the " insertion loss" of the shield, defined as the ratio of the field strength at a point external to the shield, before and after the insertion of the enclosure. To do so, the effect of the shield upon the input impedance of the antenna is analyzed, and expressions obtained for the applicable cases. The resulting insertion-loss expressions are numerically evaluated for some representative cases, and graphically compared with a series of measurements performed to obtain experimental confirmation. Very good agreement is obtained in all cases, establishing the validity of the analysis.     

Definition of requirements for accessing multilingual information opinions

Multimedia Tools and Applications - In this paper, we will present a study concerning the understanding of the needs of people using Internet in order to access to multilingual information. In...     

The correct application of total active reflection coefficient to evaluate MIMO antenna systems and its generalization to N ports

Several papers published by prestigious Journals on Antennas and Microwave Techniques have disseminated misconceptions about total active reflection coefficient (TARC), a meaningful metric to characterize multiple‐input multiple‐output antenna arrays, and the misapprehension has been spread over the years. In this article, an extrapolation to calculate TARC for N‐antennas systems is derived and applied to published results for illustration purposes. Moreover, the inaccurate and correct TARC equations are put in context by means of its physic and mathematical insight, demonstrating the divergence of results when the interport RF isolation is comparable or higher than the port matching. The importance of assessing multiantenna systems using TARC is explained.     

Failure Analysis of Additively Manufactured Polyester Test Specimens Exposed to Various Liquid Media

Journal of Failure Analysis and Prevention - Additive manufacturing platforms that rely on thermoplastic feedstock materials are now expected to fabricate components intended for deployment in a...     

Order-of-magnitude scaling of the cathode region in an axisymmetric transferred electric arc

A new technique of order-of-magnitude scaling (OMS) has been applied to the mathematical modeling of the cathode region of a long gas tungsten arc (GTA). The estimations obtained are combined with numerical calculations; thus, important features of both techniques are considered simultaneously: the high precision of numerical modeling and the generality and simplicity of algebraic expressions. Power-law expressions for the estimations of characteristic unknowns such as maximum pressure in the cathode spot and maximum plasma velocity are obtained and are consistent with previous analytical or asymptotic work. Dimensional analysis is used to identify dimensionless groups governing the system, and asymptotic considerations are used to identify two dimensionless groups (the Reynolds number and the dimensionless arc length) as the most significant ones governing momentum transfer in the cathode region. The estimations obtained are calibrated with functions that depend only on these two most significant dimensionless groups. It is suggested that the numerical results for different cases can be reduced to a single general map.     

CETP and LCAT Gene Polymorphisms Are Associated with High‐Density Lipoprotein Subclasses and Acute Coronary Syndrome

We evaluated whether CETP and LCAT gene polymorphisms are statistically associated with the high‐density lipoprotein (HDL) size distribution, the cholesterol level of HDL subclasses, and the acute coronary syndrome (ACS) susceptibility. Two CETP gene polymorphisms (rs4783961 and rs708272) and one LCAT polymorphism (rs2292318) were genotyped by 5′ exonuclease TaqMan assays in 619 patients with ACS and 607 control individuals. For HDL analysis, a subgroup of 100 healthy individuals was recruited; the HDL subclasses were separated via ultracentrifugation and polyacrylamide gradient gel electrophoresis under native conditions. Under a dominant model, the G allele of the rs708272 polymorphism was associated with an increased risk of ACS (odds ratios [OR] = 1.45, corrected p‐value [pC_Dom] = 0.036). The linkage disequilibrium analysis showed that one of the eight possible combinations was associated with the risk of developing ACS (OR = 1.52, pC = 0.02), which suggests that it may contribute to coronary atherosclerosis. The rs708272 G allele carriers had a lower concentration of cholesterol associated with the HDL2a and HDL3a subclasses when compared with subjects carrying the A allele. Carriers of LCAT rs2292318 A allele showed a lower concentration of high‐density lipoprotein‐cholesterol (HDL‐C) in comparison to the GG genotype; the cholesterol associated with the each one of the five HDL subclasses was significantly lower in rs2292318 A than in GG subjects. In summary, this study demonstrates that the rs708272 polymorphism is associated with a heightened risk of developing ACS. In addition, we report the association of the rs708272 and rs2292318 polymorphisms with HDL‐C levels and HDL subclasses.     

Synapsable quadruplex-mediated fibers

We have fabricated a DNA-based nanofiber created by self-assembly of guanine quadruplex (Hoogsteen base pairing) and double-stranded DNA (Watson-Crick base pairing). When duplexes containing a long stretch of contiguous guanines and single-stranded overhangs are incubated in potassium-containing buffer, the preformed duplexes create high molecular weight species that contain quadruplexes. In addition to observation of these larger species by gel electrophoresis, solutions were analyzed by atomic force microscopy to reveal nanofibers. Analysis of the atomic force microscopy images indicates that fibers form with lengths ranging from 250 to 2,000 nm and heights from 0.45 to 4.0 nm. This work is a first step toward the creation of new structurally heterogeneous (quadruplex/duplex), yet controllable, DNA-based materials exhibiting novel properties suitable for a diverse array of nanotechnology applications.