Performance Enhancement of Wideband Reflectarray Antennas Embedded on Paper Substrate Materials

This research presents an innovative solution to address the bandwidth limitation of microstrip reflectarray antennas. Organic substrate materials with controlled compositions have been characterized to be employed as substrate materials for microstrip reflectarrays. The three proposed materials show low dielectric permittivity values of 1.81, 1.64 and 1.84 along with loss tangents of 0.053, 0.047 and 0.057 respectively. The proposed substrate materials have been verified by modelling reflectarray unit elements in CST MWS and measured using a waveguide simulator technique. The comparison between measured and simulated results show a good agreement with promising broadband performance of 312, 340 and 207 MHz for S1, S2 and S3 substrate materials respectively

Superfield Approach to (Non-)local Symmetries for One-Form Abelian Gauge Theory

We exploit the geometrical superfield formalism to derive the local, covariant and continuous Becchi-Rouet-Stora-Tyutin (BRST) symmetry transformations and the non-local, non-covariant and continuous dual-BRST symmetry transformations for the free Abelian one-form gauge theory in four $(3 + 1)$-dimensions (4D) of spacetime. Our discussion is carried out in the framework of BRST invariant Lagrangian density for the above 4D theory in the Feynman gauge. The geometrical origin and interpretation for the (dual-)BRST charges (and the transformations they generate) are provided in the language of translations of some superfields along the Grassmannian directions of the six ($4 + 2)$-dimensional supermanifold parametrized by the four spacetime and two Grassmannian variables.Comment: LaTeX file, 23 page

Design and analysis of dual U slot reflectarray antenna for X-band applications

A novel design of a dual frequency single layer reflectarray antenna is presented for X-band frequency applications. Dual U slots embedded on conventional rectangular microstrip reflectarray have been designed to attain a dual frequency operation. A detailed analysis of the effect on surface current distributions with the introduction of dual U slots is presented. Moreover a parametric study on the variation of significant dimensions of the design have been carried out and analysed thoroughly using a commercially available CST computer model. Proposed design configurations were fabricated above a 0.508 mm thick substrate of Rogers Duroid 5880. The dual U slot configuration offers a significant dual frequency behavior at 8.54 and 11.56 GHz with 10% bandwidth improvement of 47 and 56 MHz with a reflection loss of -4.54 and 4.11 dB respectively

Design and analysis of dual U slot reflectarray antenna for X-band applications

A novel design of a dual frequency single layer reflectarray antenna is presented for X-band frequency applications. Dual U slots embedded on conventional rectangular microstrip reflectarray have been designed to attain a dual frequency operation. A detailed analysis of the effect on surface current distributions with the introduction of dual U slots is presented. Moreover a parametric study on the variation of significant dimensions of the design have been carried out and analysed thoroughly using a commercially available CST computer model. Proposed design configurations were fabricated above a 0.508 mm thick substrate of Rogers Duroid 5880. The dual U slot configuration offers a significant dual frequency behavior at 8.54 and 11.56 GHz with 10% bandwidth improvement of 47 and 56 MHz with a reflection loss of -4.54 and 4.11 dB respectively

Nutritional aspects of mammary carcinogenesis: a case-control study

Dietary factors are believed to play an important role in mammary carcinogenesis. International correlations, case-control and cohort studies have associated the incidence and mortality from breast cancer with high fat consumption in the form of meat, gravy and dairy products. Most of these studies have been conducted in the developed countries. Due to paucity of data from developing countries, we conducted a case-control study to evaluate the role of nutritional factors in mammary carcinogenesis. This prospective study was conducted in the oncology clinic at a university hospital. On a detailed questionnaire, information was collected from 80 patients with histologically proven breast cancer (cases) and 80 normal healthy subjects (controls). Information was collected on several patients characteristics as well as intake of 44 different food items. Special care was taken to exclude any recent changes in diet, induced in cases since learning the diagnosis of breast cancer. Interviews were conducted by the same interviewer and lasted approximately 20 minutes. Analysis of data reveal no significant difference in patients characteristics between cases and controls. Similarly, no significant difference was found in the intake of most dietary items including meat and dairy products. However, a significant difference was observed in the consumption of fish, vegetable and fruits (P = 0.05). We conclude that our study fails to support the fat-breast cancer hypothesis. It also suggests a potential role of other dietary items such as fish, vegetables and fruits in mammary carcinogenesis

Epidural spinal cord compression from metastatic cancer: clinical features and management

We retrospectively analyzed thirty-three patients (21 males, 12 females) with malignancy induced spinal cord compression (SCC). The mean age of the patients was 42.8 years and almost half (51%) of them presented with SCC. Mean duration of symptoms was 4.5 months and the mean interval between the original diagnosis of cancer and the development of SCC was 14.6 months. Back pain was the most frequent (97%) symptom with an equal number of patients having subjective or objective evidence of lower limb weakness. Majority (73%) of the patients were non-ambulatory at the time of diagnosis. Spinal level involvement was mostly thoracic (62%) followed by lumber (38%). Breast cancer was the commonest underlying malignancy (21%). Lung (12%), prostrate (12%), multiple myeloma (9%), and carcinoma with unknown primary (12%) were also frequently encountered. There was an overall response rate of 22% to the therapeutic interventions: mostly observed in the ambulatory patients. Only 7% of the non-ambulatory patients regained ability to walk. None of the responders had bladder or bowel dysfunction. Twenty-two percent of the responders are still ambulatory with a mean follow-up of six months

A simplified structure for the second order cosmological perturbation equations

Increasingly accurate observations of the cosmic microwave background and the large scale distribution of galaxies necessitate the study of nonlinear perturbations of Friedmann-Lemaitre cosmologies, whose equations are notoriously complicated. In this paper we present a new derivation of the governing equations for second order perturbations within the framework of the metric-based approach that is minimal, as regards amount of calculation and length of expressions, and flexible, as regards choice of gauge and stress-energy tensor. Because of their generality and the simplicity of their structure our equations provide a convenient starting point for determining the behaviour of nonlinear perturbations of FL cosmologies with any given stress-energy content, using either the Poisson gauge or the uniform curvature gauge.Comment: 30 pages, no figures. Changed title to the one in published version and some minor changes and addition

Cohomological Operators and Covariant Quantum Superalgebras

We obtain an interesting realization of the de Rham cohomological operators of differential geometry in terms of the noncommutative q-superoscillators for the supersymmetric quantum group GL_{qp} (1|1). In particular, we show that a unique superalgebra, obeyed by the bilinears of fermionic and bosonic noncommutative q-(super)oscillators of GL_{qp} (1|1), is exactly identical to that obeyed by the de Rham cohomological operators. A set of discrete symmetry transformation for a set of GL_{qp} (1|1) covariant superalgebras turns out to be the analogue of the Hodge duality * operation of differential geometry. A connection with an extended BRST algebra obeyed by the nilpotent (anti-)BRST and (anti-)co-BRST charges, the ghost charge and a bosonic charge (which is equal to the anticommutator of (anti-)BRST and (anti-)co-BRST charges) is also established.Comment: LaTeX file, 21 page