On the use of the Coulomb gauge in solving source-excited boundaryvalue problems of electromagnetics

The advantages and difficulties associated with the use of the Coulomb gauge in solving source-excited boundary value problems of electromagnetics are examined. The correct dyadic Green's function for the Coulomb vector potential in a rectangular waveguide is derived to elucidate the discussion. The attractive feature of the Coulomb gauge is the explicit separation of the electric field into its lamellar and solenoidal constituents. A flaw in the usage of the Coulomb gauge in W.R. Smythe's text Static and Dynamic Electricity (1968) is noted and corrected     

Optimizing the Gaussian excitation function in the finitedifference time domain method

A systematic method is presented for determining the optimal pulsewidth and variance of a Gaussian excitation function in the finite difference time domain (FDTD) method. We highlight the interaction of several criteria, such as the stability condition, machine precision limits, the numerical grid cutoff frequency, and the dispersion relation, that play crucial roles in the design of the initial pulse. Optimal Gaussian pulse design is desirable if numerical dispersion, an inherent yet unavoidable property of the standard second-order FDTD Yee algorithm, is to be minimized. A method for determining the phase error of a Gaussian pulse is also presented     

Transforming potential of the adenovirus type 5 E4orf3 protein

Previous observations that the adenovirus type 5 (Ad5) E4orf6 and E4orf3 gene products have redundant effects in viral lytic infection together with the recent findings that E4orf6 possesses transforming potential prompted us to investigate the effect of E4orf3 expression on the transformation of primary rat cells in combination with adenovirus E1 oncogene products. Our results demonstrate for the first time that E4orf3 can cooperate with adenovirus E1A and E1A plus E1B proteins to transform primary baby rat kidney cells, acting synergistically with E4orf6 in the presence of E1B gene products. Transformed rat cells expressing E4orf3 exhibit morphological alterations, higher growth rates and saturation densities, and increased tumorigenicity compared with transformants expressing E1 proteins only. Consistent with previous results for adenovirus-infected cells, the E4orf3 protein is immunologically restricted to discrete nuclear structures known as PML oncogenic domains (PODs) in transformed rat cells. As opposed to E4orf6, the ability of E4orf3 to promote oncogenic cell growth is probably not linked to a modulation of p53 functions and stability. Instead, our results indicate that the transforming activities of E4orf3 are due to combinatorial effects that involve the binding to the adenovirus 55-kDa E1B protein and the colocalization with PODs independent from interactions with the PML gene product. These data fit well with a model in which the reorganization of PODs may trigger a cascade of processes that cause uncontrolled cell proliferation and neoplastic growth. In sum, our results provide strong evidence for the idea that interactions with PODs by viral proteins are linked to oncogenic transformation.     

Psychopharmacology of aggression in children and adolescents with primary neuropsychiatric disorders: A review of current and potentially promising treatment options.

Research examining the role of pharmacological therapy in the treatment of children and adolescents with clinical disorders is growing. Clinical disorders that present with comorbid aggression can add a challenge to treatment. Child and adolescent neuropsychiatric disorders associated with aggression include attention-deficit hyperactivity disorder, various mood disorders and in particular bipolar disorders/pediatric mania, schizophrenia, mental retardation, oppositional defiant disorder, conduct disorder, and autism spectrum disorders. This review describes the psychopharmacy to treat these disorders and the aggression that often appears comorbidly. Existing literature regarding the efficacy and safety of psychotropics for youth with neuropsychiatric disorders also is discussed. In addition, general guidelines for psychopharmacy of aggression in children and adolescents are presented. Studies reviewed in this article provide evidence for the use of psychostimulants, alpha-2 agonists, beta blockers, lithium, anticonvulsant mood-stabilizers, atypical antipsychotics, traditional antipsychotics, and selective serotonin reuptake inhibitors in treating pediatric aggression with the choice of medication dependent on symptomology. Despite increased support for pediatric psychotropic use, there is a need for more long-term safety and efficacy studies of existing medications and newer, safer, and more effective agents with fewer side effects for the pharmacological treatment of all childhood disorders in which aggression is prominent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microwave catheter design

A microwave antenna system for transcatheter ablation of cardiac tissue is investigated. A numerical model based on the finite-difference time-domain method incorporating a Gaussian pulse excitation has been constructed and frequency domain electric and magnetic fields are obtained through Fourier transformation. Results are presented for a coaxial line fed monopole catheter which is modified by the successive inclusion of a Teflon sheath outer coating, a terminating disk at the tip of the antenna, a sleeve choke, and a high dielectric constant cylinder surrounding the monopole antenna. The effects of these design features are characterized in terms of specific absorption rate (SAR) and return loss (RL). Numerical calculations are confirmed by comparing with the RL measurement of a Teflon-coated monopole containing a disk and choke     

An analysis of a two-dimensional dielectric covered corrugated antenna feed horn

The effect of placing a dielectric slab over a90degcorrugated feed horn is investigated. The feed horn is normally a circular waveguide with concentric grooves in the aperture plane. Here we simulate the90degfeed horn with a two-dimensional configuration which is a parallel-plate waveguidewith adjacent notches. The equivalence principle and modal analysis are used to formulate integral equations which are solved numerically by the method of moments. Numerical results for the input admittance are obtained with and without the corrugation and with and without the dielectric slab cover.     

Radiation from a dielectric coated hemispherical conductor fed by acoaxial transmission line

A dielectric-coated hemispherical conductor mounted on an infinite perfectly conducting ground plane and fed by a coaxial transmission line is investigated. Green's functions for the region above the ground line are derived with separated homogeneous and particular solution parts so as to be compatible with numerical analysis techniques. A magnetic field integral equation is constructed in terms of the unknown annular aperture tangential electric field and is solved by the method of moments. A comparison of the characteristics of the dielectric-coated hemispherical conductor and a flush-mounted coaxial line to an infinite homogeneous region above the ground plane is presented with respected to the tangential aperture electric field, with respect to the tangential aperture electric field, the coaxial line apparent input impedance, and the far radiated field