Application of the inhomogeneous Lippmann-Schwinger equation to inverse scattering problems

In this paper we present a hybrid approach to numerically solve two-dimensional electromagnetic inverse scattering problems, whereby the unknown scatterer is hosted by a possibly inhomogeneous background. The approach is `hybrid' in that it merges a qualitative and a quantitative method to optimize the way of exploiting the a priori information on the background within the inversion procedure, thus improving the quality of the reconstruction and reducing the data amount necessary for a satisfactory result. In the qualitative step, this a priori knowledge is utilized to implement the linear sampling method in its near-field formulation for an inhomogeneous background, in order to identify the region where the scatterer is located. On the other hand, the same a priori information is also encoded in the quantitative step by extending and applying the contrast source inversion method to what we call the `inhomogeneous Lippmann-Schwinger equation': the latter is a generalization of the classical Lippmann-Schwinger equation to the case of an inhomogeneous background, and in our paper is deduced from the differential formulation of the direct scattering problem to provide the reconstruction algorithm with an appropriate theoretical basis. Then, the point values of the refractive index are computed only in the region identified by the linear sampling method at the previous step. The effectiveness of this hybrid approach is supported by numerical simulations presented at the end of the paper.Comment: accepted in SIAM Journal on Applied Mathematic

Rol Ecológico Del Zorro Pampeano (Lycalopex Gymnocercus) Como Dispersor De Semillas En Ambientes De Agroecosistema Y Bosques Serranos De Argentina

El zorro pampeano (Lycalopex gymnocercus) es un carnívoro de amplia distribución que posee una dieta omnívora donde los frutos/semillas conforman una parte muy importante de la misma. El objetivo de este trabajo fue conocer y describir las especies de frutos/semillas que el zorro pampeano dispersa en ambientes de agroecosistemas y bosques serranos de la provincia de CórdobaArgentina. Para ello se realizaron muestreos mensuales y se recolectaron fecas frescas de zorro en ambos ambientes. Las fecas fueron procesadas bajo lupa estereoscópica y los frutos/semillas fueran separados e identificados a nivel específico. De acuerdo con nuestros resultados se contabilizaron 46 especies diferentes de frutos/semillas en el ambiente de agroecosistemas de los cuales el 37% correspondieron a especies autóctonas. En el ambiente de bosque serrano se contabilizaron 26 especies diferentes de las cuales el 61.5% eran de especies autóctonas. El 69% y 84% de los frutos/semillas de agroecosistema y bosque serrano respectivamente estaban sanas. En ambos ambientes el zorro pampeano juega un rol esencial en la dispersión “legítima” de semillas mediante endozoocoria. Pampas fox (Lycalopex gymnocercus) is a widely distributed carnivore with an omnivorous diet, with fruits and seeds being a very important part of this diet. The aim of this research was to study and describe the fruits and seeds dispersed by the Pampas fox in the agroecosystems and hill forests of Córdoba province in Argentina. For this, monthly samplings were carried out in order to collect fresh fox feces in both environments. The feces were analyzed under a stereoscopic magnifying glass and fruits and seeds were separated and identified at the species level. In the agroecosystem environment, 46 fruit and seed species were counted, and from those, 37% corresponded to autochthonous species. Furthermore, in the hill forest environment, 26 different species were counted, of which 61.5% were autochthonous. This study showed that 69% of the fruits and seeds from the agroecosystem and 84% from the mountain forest were healthy. In both environments, the Pampas fox plays an essential role in the dispersal of seeds through endozoochory

Attenuation of Lightning-Induced Effects on Overhead Distribution Systems in Urban Areas

Overhead distribution systems can be strongly affected and damaged by indirect lightning. The induced voltages are usually computed neglecting the surrounding geometry and the presence of buildings in urban areas. Buildings can strongly change the behavior of the measured lighting-induced electromagnetic (EM) fields in the proximity of the point of impact. As a consequence, induced voltages can deviate from what would be measured in the absence of buildings. This work proposes an analysis of the main variables, which affect the deviation of the EM fields and of the consequent induced voltages along an overhead distribution line due to the presence of a building. Different distances between the line and the building and different building heights are considered

A network meta-analysis comparing effects of various antidepressant classes on the Digit Symbol substitution test (DSST) as a measure of cognitive dysfunction in patients with major depressive disorder

Background: Major depressive disorder is a common condition that often includes cognitive dysfunction. A systematic literature review of studies and a network meta-analysis were carried out to assess the relative effect of antidepressants on cognitive dysfunction in major depressive disorder. Methods: MEDLINE, Embase, Cochrane, CDSR, and PsychINFO databases; clinical trial registries; and relevant conference abstracts were searched for randomized controlled trials assessing the effects of antidepressants/placebo on cognition. A network meta-analysis comparing antidepressants was conducted using a random effects model. Results: The database search retrieved 11337 citations, of which 72 randomized controlled trials from 103 publications met the inclusion criteria. The review identified 86 cognitive tests assessing the effect of antidepressants on cognitive functioning. However, the Digit Symbol Substitution Test, which targets multiple domains of cognition and is recognized as being sensitive to change, was the only test that was used across 12 of the included randomized controlled trials and that allowed the construction of a stable network suitable for the network meta-analysis. The interventions assessed included selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, and other non-selective serotonin reuptake inhibitors/serotonin-norepinephrine reuptake inhibitors. The network meta-analysis using the Digit Symbol Substitution Test showed that vortioxetine was the only antidepressant that improved cognitive dysfunction on the Digit Symbol Substitution Test vs placebo {standardized mean difference: 0.325 (95% CI = 0.120; 0.529, P=.009}. Compared with other antidepressants, vortioxetine was statistically more efficacious on the Digit Symbol Substitution Test vs escitalopram, nortriptyline, and the selective serotonin reuptake inhibitor and tricyclic antidepressant classes. Conclusions: This study highlighted the large variability in measures used to assess cognitive functioning. The findings on the Digit Symbol Substitution Test indicate differential effects of various antidepressants on improving cognitive function in patients with major depressive disorder.Bernhard T Baune, Mélanie Brignone, Klaus Groes Larse

Engineering models for the design of long-lasting, sustainable, cost-efficient and climate-responsive pavements for Ashghal road projects in the State of Qatar

The planning, design, construction and management of modern transportation infrastructures is based on the use of continuously updated methodologies that consider, among others, the concept of sustainability. In such a context, for the specific case of road pavements, it is of crucial importance to carry out quantitative analyses based on the use of optimized engineering models. These models explicitly consider environment-pavement interactions, environmental impacts generated by all the components involved in the supply chain, and financial flows associated to pavement construction and maintenance. Such an approach is being adopted by the Public Works Authority (Ashghal) of the State of Qatar, that is developing and implementing models tailored for its infrastructure projects and local environmental conditions. This paper provides an overview of some of the employed models and methodologies that are based on the physics of pavement structures and on the assessment of environmental and economic indicators. It is shown that such an approach leads to significant improvements to current practice and to the enhanced use of recycled materials, while still guaranteeing required pavement performance