Analysis of a Waveguide-Fed Metasurface Antenna

The metasurface concept has emerged as an advantageous reconfigurable antenna architecture for beam forming and wavefront shaping, with applications that include satellite and terrestrial communications, radar, imaging, and wireless power transfer. The metasurface antenna consists of an array of metamaterial elements distributed over an electrically large structure, each subwavelength in dimension and with subwavelength separation between elements. In the antenna configuration we consider here, the metasurface is excited by the fields from an attached waveguide. Each metamaterial element can be modeled as a polarizable dipole that couples the waveguide mode to radiation modes. Distinct from the phased array and electronically scanned antenna (ESA) architectures, a dynamic metasurface antenna does not require active phase shifters and amplifiers, but rather achieves reconfigurability by shifting the resonance frequency of each individual metamaterial element. Here we derive the basic properties of a one-dimensional waveguide-fed metasurface antenna in the approximation that the metamaterial elements do not perturb the waveguide mode and are non-interacting. We derive analytical approximations for the array factors of the 1D antenna, including the effective polarizabilities needed for amplitude-only, phase-only, and binary constraints. Using full-wave numerical simulations, we confirm the analysis, modeling waveguides with slots or complementary metamaterial elements patterned into one of the surfaces.Comment: Original manuscript as submitted to Physical Review Applied (2017). 14 pages, 14 figure

Early use of immunoglobulin and risk of coronary abnormalities in patients with Kawasaki's disease

Indexación: ScieloAntecedentes: La enfermedad de Kawasaki es una vasculitis sistémica de vasos de mediano calibre, que afecta principalmente a las arterias coronarias, provocando dilatación y aneurismas coronarios en un 15 - 25% de los casos no tratados. El tratamiento recomendado actualmente es el uso de inmunoglobulina intravenosa antes del décimo día de enfermedad, lo cual reduce el riesgo de aneurismas coronarios de un 20% a un 4%. Objetivos: Determinar la relación entre el tratamiento oportuno con inmunoglobulina y el riesgo de presentar alteración coronaria en la ecocardi ografía en pacientes con Enfermedad de Kawasaki. Métodos: Se revisó la base de datos de Cardiología Infantil del hospital, identificando 66 pacientes que presentaron la enfermedad entre los años 1994 y 2014. Se determinó el momento en que se inició el tratamiento con inmunoglobulina y se analizó el hallazgo ecocardiográfico de alteraciones coronarias durante el período de hospitalización. Resultados: 52 niños (79%) recibieron tratamiento precoz, antes de 10 días del comienzo de la enfermedad; en el resto el tratamiento fue tardío. El tratamiento precoz se asoció a un menor riesgo de presentar aneurismas coronarios (5.8% vs 50% de los casos, p<0.01). Conclusión: En la enfermedad de Kawasaki es de suma importancia el diagnóstico y tratamiento oportuno con inmunoglobulina intravenosa para reducir el riesgo de formación de aneurismas coronarios.Background: Kawasaki’s disease is a systemic vasculitis of the mediumsized blood vessels, primarily affecting the coronary arteries, causing coronary dilation and aneurysms in 15 - 25% of untreated children. Use of Intravenous immunoglobulin within the first 10 days of illness is the recommended treatment, redugin the risk of coronary artery aneurysm develo-pment from 20% to 4%. Objective: To determine the association of early treatment to risk of echocardiographic coronary changes on patients with the disease. Methods and Results: A review of the institutional Pediatric Cardiology Database, allowed the identification of 66 patients who had Kawasaki’s disease between 1994 and 2014. The echocardiographic findings at follow up were related to the time of treatment initiation in relation to the beginning of the disease. Treatment with im-munoglobulin within 10 days was associated to coronary artery aneurysms in 5.8% of patients, as opposed to 50% in those with a delayed initiation of therapy. Conclusión: Early treatment with immunoglobulins (within 10 days of illness) significantly reduces the short term risk of developing coronary aneurysms in patients with Kawasaki’s disease.http://www.scielo.cl/pdf/rchcardiol/v34n3/art04.pd

Sengers syndrome: six novel AGK mutations in seven new families and review of the phenotypic and mutational spectrum of 29 patients

Background: Sengers syndrome is an autosomal recessive condition characterized by congenital cataract, hypertrophic cardiomyopathy, skeletal myopathy and lactic acidosis. Mutations in the acylglycerol kinase (AGK) gene have been recently described as the cause of Sengers syndrome in nine families. Methods: We investigated the clinical and molecular features of Sengers syndrome in seven new families; five families with the severe and two with the milder form. Results: Sequence analysis of AGK revealed compound heterozygous or homozygous predicted loss-of-function mutations in all affected individuals. A total of eight different disease alleles were identified, of which six were novel, homozygous c.523_524delAT (p.Ile175Tyrfs*2), c.424-1G > A (splice site), c.409C > T (p.Arg137*) and c.877 + 3G > T (splice site), and compound heterozygous c.871C > T (p.Gln291*) and c.1035dup (p.Ile346Tyrfs*39). All patients displayed perinatal or early-onset cardiomyopathy and cataract, clinical features pathognomonic for Sengers syndrome. Other common findings included blood lactic acidosis and tachydyspnoea while nystagmus, eosinophilia and cervical meningocele were documented in only either one or two cases. Deficiency of the adenine nucleotide translocator was found in heart and skeletal muscle biopsies from two patients associated with respiratory chain complex I deficiency. In contrast to previous findings, mitochondrial DNA content was normal in both tissues. Conclusion: We compare our findings to those in 21 previously reported AGK mutation-positive Sengers patients, confirming that Sengers syndrome is a clinically recognisable disorder of mitochondrial energy metabolism

Regionalization by fuzzy expert system based approach optimized by genetic algorithm.

In recent years soft computing methods are being increasingly used to model complex hydrologic processes. These methods can simulate the real life processes without prior knowledge of the exact relationship between their components. The principal aim of this paper is perform hydrological regionalization based on soft computing concepts in the southern strip of the Caspian Sea basin, north of Iran. The basin with an area of 42,400 sq. km has been affected by severe floods in recent years that caused damages to human life and properties. Although some 61 hydrometric stations and 31 weather stations with 44 years of observed data (1961–2005) are operated in the study area, previous flood studies in this region have been hampered by insufficient and/or reliable observed rainfall-runoff records. In order to investigate the homogeneity (h) of catchments and overcome incompatibility that may occur on boundaries of cluster groups, a fuzzy expert system (FES) approach is used which incorporates physical and climatic characteristics, as well as flood seasonality and geographic location. Genetic algorithm (GA) was employed to adjust parameters of FES and optimize the system. In order to achieve the objective, a MATLAB programming code was developed which considers the heterogeneity criteria of less than 1 (H < 1) as the satisfying criteria. The adopted approach was found superior to the conventional hydrologic regionalization methods in the region because it employs greater number of homogeneity parameters and produces lower values of heterogeneity criteria