5,268 research outputs found

    Compact modes in quasi one dimensional coupled magnetic oscillators

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    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

    Regulation of Indian Traders: A Historical Perspective

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    Effects of power ultrasound treatments on properties of Longissimus beef muscle

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    This study was conducted to determine the effects of power ultrasound treatments on properties of Longissimus beef muscle. Twenty pairs of loins from steer carcasses, USDA Choice, maturity A were obtained 24hrs after slaughter for this study. Two experiments will be conducted at different intensity/time levels: (1) Control, 1.5 w/cm2, 3 w/cm2, and 5 w/cm2 for 3 minutes/side. (2) Control, 20 w/cm2, 40 w/cm2, and 60 w/cm2 for 45s/side (at 20 kHz) under refrigerated conditions. Each steak (four pieces) will be randomly allotted among these two experiments. Each loin was divided into at least 12 steaks and each steak was divided into 4 pieces, labeled, vacuum packed individually, and divided into groups: Day 1 and Day 7. Ultrasound treatments were applied using a direct probe commercial ultrasonic system. Cooking yields, shear force (Warner-Bratzler), and ultrasonic power entering the samples was measured. In addition, microscopy and SDS PAGE tests were conducted on the samples. No difference in shear force was observed for day 1, however at day seven the 5 w/cm2 treatment required a lower force (P \u3c 0.05) to shear the sample. Histological cross-sectional samples for all treatments showed separation of the muscle bundles when compared with the control. SDS PAGE did not show any difference between treatments. Shear force values for day 1 were not significant, but showed a tendency toward lower shear values for the treated samples. At day 7, the shear force values were significant for the 40 w/cm2 treatment. The histological samples showed an evident separation of the muscle fibers. 5% gels indicated a possible degradation of titin at day 7

    A DYNAMIC MODEL OF MICROLENDING IN THE DEVELOPING COUNTRIES

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    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

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    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

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    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 250”m 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%/250”m. 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)

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    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 RegiĂłn de AysĂ©n, Provincia de AysĂ©n (46°40â€Č11.9″S, 74°00â€Č54.0″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

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    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

    The Role of Water Solubility and Diffusion Coefficient in Air of Chlorine Dioxide Gas during Surface Decontamination and Compatibility of Selected Plastics and Elastomers

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    Food safety is a concern for all individuals involved in the food supply chain. Besides controlling the food product itself to improve safety, washing and sanitizing surfaces and equipment are critical. Chlorine dioxide (ClO2) is a green-yellow gas, known as a strong antimicrobial agent against multiple pathogenic microorganisms and effective on biofilms. Plastics such as polypropylene (PP), polyester (PET), cast nylon, ultra-high-molecular-weight polyethylene (UHMWPE), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) and white Acetal; and elastomers like nitrile rubber (Buna-N), ethylene propylene diene monomer (EPDM), and fluoroelastomer (FKM) are widely used in food processing surfaces and equipment. However, few studies have been conducted to address the depletion of gas by materials that might be present during the decontamination procedure nor the change in mechanical properties of plastics and elastomers. The objective of this study was to develop a model to simulate ClO2 transport into stainless steel crevices during surface decontamination. Also, to determine the resistance to ClO2 gas for selected materials. The gas was circulated inside a closed chamber with three different volumes of deionized water (20, 40, and 60 mL), and 0 mL (control). The gas decay was monitored and recorded until the concentration dropped below the detection limit. A physics-based simulation model was developed using COMSOL and validated by previously reported results in the literature, and the data obtained at the first stage of this experiment. A mathematical model was proposed for analyzing the time needed for ClO2 gas to reach the bottom at any possible crevice during equipment surface decontamination, which is depth-dependent. Additionally, selected material were exposed to 3000 ppm [parts per million] for 7 days inside a chamber following ASTM International Standards. This investigation showed an increase in the reaction rate due to water presence at different water volume and exposure surface area. After 7 days’ exposure at 3000 ppm of ClO2 gas, none of the plastics nor elastomers selected showed a significance difference (p\u3c0.05) in the hardness value. This can help the food processing industry in constructing an effective system and establishing optimum sanitizing treatment conditions
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