Compact modes in quasi one dimensional coupled magnetic oscillators

In this work we study analytically and numerically the spectrum and localization properties of three quasi-one-dimensional (ribbons) split-ring resonator arrays which possess magnetic flatbands, namely, the stub, Lieb and kagome lattices, and how their spectra is affected by the presence of perturbations that break the delicate geometrical interference needed for a magnetic flatband to exist. We find that the Stub and Lieb ribbons are stable against the three types of perturbations considered here, while the kagome ribbon is, in general, unstable. When losses are incorporated, all flatbands remain dispersionless but become complex, with the kagome ribbon exhibiting the highest loss rate.Comment: 11 pages, 15 figure

A DYNAMIC MODEL OF MICROLENDING IN THE DEVELOPING COUNTRIES

In this paper, we examine the contract design problem of banks that extend loans to poor borrowers and seek to maximize outreach while remaining financially sustainable. A dynamic model is developed that shows how interest rates can be determined based on information about productivity and diligence characteristics of borrowers, investment opportunities, correlation of business activities, peer monitoring costs, and social sanctions. The results indicate that relative to the traditional static models, the dynamic model explains better the current experience in individual and group lending in developing countries.Financial Economics,

Social Preferences for Management of Rural Forests in the Iberian Atlantic Region

This article presents results from an experiment into attribute perception and relevant levels for management of woodland and mountain areas typical of the Iberian Peninsula's Atlantic region. The aim, which the authors argue has been robustly reached, was to identify those aspects of forestry policy clearly perceived by citizens. This is useful for defining enlargement of areas protected under Natura 2000 Network. Results show clear preference for an increase in woodland to over half the current surface area, with replanting of traditional trees, in woodlands of low density and trees of different age and, preferably in irregular shaped plots.Landscape preference, Visual quality, Non-market goods, Preference models, Economic valuation, Landscape Management, Resource /Energy Economics and Policy,

Mechanical analysis of encapsulated metal interconnects under transversal load

Novel insights regarding the ability of encapsulated metal interconnections to deform due to bending are presented. Encapsulated metal interconnections are used as electric conductor or measurement system within a wide range of applications fields, e.g. biomedical, wearable, textile applications. Nevertheless the mechanical analysis remains limited to reliability investigation of these configurations. Different papers and research groups claim that meander-shaped metal interconnections are predisposed for these applications fields due to their deformability while, to the author’s knowledge, no reports are found about this ability. An analysis based on the work needed to bend interconnections to a certain curvature will be used to compare different interconnection configurations with each other. The experimental as well as the simulation setup is based on PDMS encapsulated PI-enhanced Cu tracks. The results and conclusions are specific for this type of interconnections, but can be extended to a global conclusion about stretchable interconnections. From the obtained insights it is proven that periodically meander-shaped interconnections need significant less work, up to more than 10 times less, to bend the interconnection to the same curvature compared to straight interconnection lines. Furthermore it shows out, for the meander-shaped interconnection, that per increase of 250µm encapsulation thickness the work raises with a factor 2. For straight interconnection lines the work in function of the encapsulation thickness is limited to 20%/250µm. The bendability of the straight interconnection lines is determined by the shape of the interconnection, where for meandered tracks the encapsulation will determine this factor, for an encapsulation thickness of maximum 1mm. For encapsulations > 1mm, the encapsulation thickness will become the predominant factor which determines the deformability for both interconnection shapes

Redescription of Pelecorhynchus kroeberi (Lindner), a Patagonian species rediscovered after more than 100 years in Chile (Diptera: Pelecorhynchidae)

An adult female of Pelecorhynchus kroeberi (Lindner, 1925) is newly recollected after more than 100 years and it is herein redescribed, including, for the first time, illustrations of genitalia. The specimen was collected in the Región de Aysén, Provincia de Aysén (46°40′11.9″S, 74°00′54.0″W), in the extreme south of Chile, and the specimen is deposited in the Entomological Collection of Museo Nacional de Historia Natural, Santiago, Chile

Essays in labor economics and applied econometrics

This dissertation consists of three essays in applied econometrics. The first two explore how students and parents respond to changes in educational policies. The last one implements bias corrections for nonlinear panel data models with fixed effects. The first essay addresses the effect of decreasing the age at which compulsory schooling begins in Mexico. A policy change in 2002 required all children between ages 3 and 5 to attend preschool before entering first grade. School entry laws create a discontinuity that induces a sharp increase in preschool enrollment at the expected birthday cutoff. Using this sharp increase, I find that requiring children to attend preschool increases their achievement in elementary and middle school. There is also an increase in parental investments during elementary school. Only parents who would not send their kids to preschool influence the results, as access to preschool was free and universal prior to this policy change. The second essay uses an experiment in Mexican high schools to analyze how estimates of peer effects change under different types of monetary incentives aimed at increasing math achievement. I find that the estimated peer effect differs between incentivized and non-incentivized groups, and across incentivized groups. I argue that changes in the impact of classroom peers' ability (measured by their individual fixed effects) resulting from the experimental intervention should be interpreted as evidence of peer effects. The third essay (with Ivan Fernandez-Val and Martin Weidner) develops two Stata commands that provide bias-corrected estimates of panel probit and logit models with two-way fixed effects. Nonlinear panel data models with individual fixed effects can be severely biased because of the incidental parameter problem, and yet these models are used in many empirical applications. The commands developed in this essay correct for both the bias arising from the inclusion of individual fixed effects and the additional bias arising from the inclusion of time fixed effects. They also provide corrected estimates of the average partial effects

Fixing the U-band photometry of Type Ia supernovae

We present previously unpublished photometry of supernovae 2003gs and 2003hv. Using spectroscopically-derived corrections to the U-band photometry, we reconcile U-band light curves made from imagery with the Cerro Tololo 0.9-m, 1.3-m and Las Campanas 1-m telescopes. Previously, such light curves showed a 0.4 mag spread at one month after maximum light. This gives us hope that a set of corrected ultraviolet light curves of nearby objects can contribute to the full utilization of rest frame U-band data of supernovae at redshift ~0.3 to 0.8. As pointed out recently by Kessler et al. in the context of the Sloan Digital Sky Survey supernova search, if we take the published U-band photometry of nearby Type Ia supernovae at face value, there is a 0.12 mag U-band anomaly in the distance moduli of higher redshift objects. This anomaly led the Sloan survey to eliminate from their analyses all photometry obtained in the rest frame U-band. The Supernova Legacy Survey eliminated observer frame U-band photometry, which is to say nearby objects observed in the U-band, but they used photometry of high redshift objects no matter in which band the photons were emitted.Comment: 25 pages, 9 figures, accepted for publication in the Astronomical Journa