Understanding the Radio Emission from ϵ\epsilon Eridani

Some solar-type stars are known to present faint, time-variable radio continuum emission whose nature is not clearly established. We report on Jansky Very Large Array observations of the nearby star $\epsilon$ Eridani at 10.0 and 33.0 GHz. We find that this star has flux density variations on scales down to days, hours and minutes. On 2020 Apr 15 it exhibited a radio pulse at 10.0 GHz with a total duration of about 20 minutes and a peak four times larger than the plateau of 40 $\mu$Jy present in that epoch. We were able to model the time behavior of this radio pulse in terms of the radiation from shocks ramming into the stellar wind. Such shocks can be produced by the wind interaction of violently expanding gas heated suddenly by energetic electrons from a stellar flare, similar to the observed solar flares. Because of the large temperature needed in the working surface to produce the observed emission, this has to be non thermal. It could be gyrosynchrotron or synchrotron emission. Unfortunately, the spectral index or polarization measurements from the radio pulse do not have enough signal-to-noise ratio to determine its nature.Comment: 7 pages, 4 figures. To appear in Astronomy & Astrophysic

MICROFINANCE MARKET NICHES AND CLIENT PROFILES IN BOLIVIA

This paper presents and interprets descriptive statistics generated from data obtained in a survey of clients of five microfinance organizations believed to be among the best in Bolivia. These lenders represent different combinations of organizational design, lending technology, and market area of operations. Two are regulated financial intermediaries and three are NGOs. Two operate in rural areas (PRODEM and Sartawi) and three operate in urban areas (BancoSol, FIE, and Caja Los Andes). Two offer individual loans and three grant loans through joint liability groups. The paper discusses household-enterprise profiles of a sample of 622 clients and identifies terms and conditions of loan contracts with these organizations to evaluate the depth and quality of their outreach. The interpretation seeks to establish connections between key characteristics of the clients and features of the lending technologies that lead to the matching of classes of borrowers with particular organizations and that influence the choice of market niches. Data on loan sizes suggest the existence of different but broadly overlapping market niches associated with three tiers of clients. The sharpest distinction is between urban and rural clients. The matching between clients and organizations also reflects a weak but positive correlation between levels of poverty and loan sizes. According to an index of basic needs fulfillment of their clients, these organizations can be ranked as: FIE and Caja Los Andes (first tier), BancoSol (second tier), and PRODEM and Sartawi (third tier). The same ranking is obtained when clients are ordered according to loan size, the ratio of loan size to the value of sales, and the value of monthly sales. The three tiers of clients are associated with different socio-economic features of their household-enterprises: sex, education, household size, access to electricity, water supplies, and sewage facilities, employment-generating capacity of the enterprise, informality and separation of household and enterprise, occupations and the like. The development of lending technologies that do not rely on standard financial statements and collateralizable assets is a formidable innovation that explains the outreach and sustainability of these organizations. Differences in the guarantees required for loans dominate distinctions in lending technology. Trade-offs between loan size, interest rates, and guarantee requirements attract different subsets of the clientele. Joint liability seems to be appropriate for very poor people, but group borrowers eventually outgrow this relationship. Caja Los Andes and FIE have shown that it is possible to supply individual loans to poor people and be profitable. Most clients are satisfied with the services received. The lowest satisfaction concerns loan sizes and loan-size rationing may be widespread. At least in urban areas, increasing competition will force these organizations to improve their services and adjust loan sizes. All of these organizations are expanding the frontier of microfinance by developing lending technologies for a much poorer clientele than is reached by collateral-based lenders. This is a formidable achievement.Financial Economics,

Hybrid Resolvent Kernel Calibration Technique for Microwave Imaging Systems

This work assesses a hybrid calibration technique that uses together measured and simulated data to compensate modeling errors such as fabrication tolerances and positioning inaccuracies. Here, as a proof-of-concept, it is considered a virtual microwave imaging experiment of a human brain stroke condition. The test involves a full-wave software based on the finite element method and 3-D highly realistic system models, including a set of 24 monopoles immersed in a solid brick-shaped matching medium and a single-cavity anthropomorphic head phantom. The studied case shows that under favorable assumptions, the calibration procedure improves the quality of the retrieved images compared to the non-calibrated-kernel approach

El Fact Checking en España. Plataformas, prácticas y rasgos distintivos

Las plataformas de verificación de datos se han convertido en un movimiento que, nacido en Estados Unidos, se ha extendido por todo el mundo. Su objetivo es luchar contra la desinformación, las percepciones erróneas y las falsas noticias en el nuevo ecosistema comunicativo en el que las redes sociales adquieren relevancia como fuente de información, y en el que es cada vez más fácil –y asequible a miles de millones de ciudadanos– producir, editar y distribuir (falsa) información. Casi toda la bibliografía y los casos de estudio se han centrado en Estados Unidos. Sobre la verificación de datos en castellano, solo se han investigado las plataformas de verificación en español que el Duke reporter´s Lab incluía en 2018 en su base de datos, así como nueve iniciativas en español surgidas desde 2010 en media docena de países latinoamericanos. En este artículo, después de un marco teórico, abordamos la realidad del fact checking en España. Mediante un análisis cualitativo, identificamos y analizamos las webs de verificación y las actividades de chequeo de información en nuestro país. Ello se complementa con entrevistas a los periodistas que han llevado a cabo iniciativas de fact checking en nuestro entorno. La realidad del fact checking en España, como se demuestra, se haya todavía en una fase incipiente.Fact Checking platforms have become a movement that, born in the United States, has spread throughout the world. It is now a tool to fight against misinformation, misperceptions and fake news in the new communicative ecosystem in which social media acquire relevance as a source of information, and in which it is increasingly easy - and accessible to millions of citizens - produce, edit and distribute (false) information. Almost all literature and case studies have focused on the United States. About fact checking in Spanish, only have been investigated those included in the Duke reporter’s Lab in 2018; and nine initiatives in Spanish that have emerged since 2010 in six Latin American countries. In this article, after a theoretical framework, through a qualitative analysis, we identify and analyze the verification websites and information check activities in our country. This is complemented by interviews with journalists who have carried out fact checking initiatives in our environment. The reality of the fact checking in Spain, as will be shown, is yet in its begginings

Ground- and excited-state electronic structure of an iron-containing molecular spin photoswitch

The electronic structure of the cation of [Fe(ptz)(6)](BF4)(2), a prototype of a class of complexes that display light-induced excited-state spin trapping (LIESST), has been investigated by time-independent and time-dependent density-functional theories. The density of states of the singlet ground state reveals that the highest occupied orbitals are metal centered and give rise to a low spin configuration Fe2+(3d(xy)(up arrow down arrow)3d(xz)(up arrow down arrow)3d(yz)(up arrow down arrow)) in agreement with experiment. Upon excitation with light in the 2.3-3.3 eV range, metal-centered spin-allowed but parity-forbidden ligand field (LF) antibonding states are populated which, in conjunction with electron-phonon coupling, explain the experimental absorption intensities. The computed excitation energies are in excellent agreement with experiment. Contrary to simpler models we show that the LF absorption bands, which are important for LIESST, do not originate in transitions from the ground to a single excited state but from transitions to manifolds of nearly degenerate excited singlets. Consistent with crystallography, population of the LF states promotes a drastic dilation of the ligand cage surrounding the iron. (C) 2005 American Institute of Physics

The influence of numerical parameters on tidally triggered bar formation

The joint influence of numerical parameters such as the number of particles N, the gravitational softening length $\epsilon$ and the time-step $\Delta t$ is investigated in the context of galaxy simulations. For isolated galaxy models we have performed a convergence study and estimated the numerical parameters ranges for which the relaxed models do not deviate significantly from its initial configuration. By fixing N, we calculate the range of the mean interparticle separation $\lambda(r)$ along the disc radius. We have found that in the simulations with N=1310720 particles $\lambda$ varies by a factor of 6, and the corresponding final Toomre's parameters Q change by only about 5 per cent. By decreasing N, the $\lambda$ and Q ranges broaden. Large $\epsilon$ and small N cause an earlier bar formation. For a given set of parameters the disc heating is smaller with the Plummer softening than with the spline softening. For galaxy collision models numerical simulations indicate that the properties of the formed bars strongly depend upon the selection of N and $\epsilon$. Large values of the gravitational softening parameter and a small number of particles results in the rapid formation of a well defined, slowly rotating bar. On the other hand, small values of $\epsilon$ produce a small, rapidly rotating disc with tightly wound spiral arms, and subsequently a weak bar emerges. We have found that by increasing N, the bar properties converge and the effect of the softening parameter diminishes. Finally, in some cases short spiral arms are observed at the ends of the bar that change periodically from trailing to leading and vice-versa - the wiggle.Comment: 17 pages, 13 figures, 3 tables. Accepted for publication in A&A. A high resolution version of the paper is found at http://www.astro.inin.mx/ruslan/tidal_bars/gabbasov.pd

Microfinance Market Niches and Client Profiles in Bolivia

This paper presents and interprets descriptive statistics generated from data obtained in a survey of clients of five microfinance organizations believed to be among the best in Bolivia. These lenders represent different combinations of organizational design, lending technology, and market area of operations. Two are regulated financial intermediaries and three are NGOs. Two operate in rural areas (PRODEM and Sartawi) and three operate in urban areas (BancoSol, FIE, and Caja Los Andes). Two offer individual loans and three grant loans through joint liability groups. The paper discusses household-enterprise profiles of a sample of 622 clients and identifies terms and conditions of loan contracts with these organizations to evaluate the depth and quality of their outreach. The interpretation seeks to establish connections between key characteristics of the clients and features of the lending technologies that lead to the matching of classes of borrowers with particular organizations and that influence the choice of market niches. Data on loan sizes suggest the existence of different but broadly overlapping market niches associated with three tiers of clients. The sharpest distinction is between urban and rural clients. The matching between clients and organizations also reflects a weak but positive correlation between levels of poverty and loan sizes. According to an index of basic needs fulfillment of their clients, these organizations can be ranked as: FIE and Caja Los Andes (first tier), BancoSol (second tier), and PRODEM and Sartawi (third tier). The same ranking is obtained when clients are ordered according to loan size, the ratio of loan size to the value of sales, and the value of monthly sales. The three tiers of clients are associated with different socio-economic features of their household-enterprises: sex, education, household size, access to electricity, water supplies, and sewage facilities, employment-generating capacity of the enterprise, informality and separation of household and enterprise, occupations and the like. The development of lending technologies that do not rely on standard financial statements and collateralizable assets is a formidable innovation that explains the outreach and sustainability of these organizations. Differences in the guarantees required for loans dominate distinctions in lending technology. Trade-offs between loan size, interest rates, and guarantee requirements attract different subsets of the clientele. Joint liability seems to be appropriate for very poor people, but group borrowers eventually outgrow this relationship. Caja Los Andes and FIE have shown that it is possible to supply individual loans to poor people and be profitable. Most clients are satisfied with the services received. The lowest satisfaction concerns loan sizes and loan-size rationing may be widespread. At least in urban areas, increasing competition will force these organizations to improve their services and adjust loan sizes. All of these organizations are expanding the frontier of microfinance by developing lending technologies for a much poorer clientele than is reached by collateral-based lenders. This is a formidable achievement