Metallic behavior induced by potassium doping of the trigonal antiferromagnetic insulator EuMn2As2

We report magnetic susceptibility \chi, isothermal magnetization M, heat capacity C_p and electrical resistivity \rho measurements on undoped EuMn2As2 and K-doped Eu0.96K0.04Mn2As2 and Eu0.93K0.07Mn2As2 single crystals with the trigonal CaAl2Si2-type structure as a function of temperature T and magnetic field H. EuMn2As2 has an insulating ground state with an activation energy of 52 meV and exhibits antiferromagnetic (AFM) ordering of the Eu+2 spins S=7/2 at T_N1 = 15 K from C_p(T) and \chi(T) data with a likely spin-reorientation transition at T_N2 = 5.0 K. The Mn+2 3d5 spins-5/2 exhibit AFM ordering at T_N = 142 K from all three types of measurements. The M(H) isotherm and \chi(T) data indicate that the Eu AFM structure is both noncollinear and noncoplanar. The AFM structure of the Mn spins is also unclear. A 4% substitution of K for Eu in Eu0.96K0.04Mn2As2 is sufficient to induce a metallic ground state. Evidence is found for a difference in the AFM structure of the Eu moments in the metallic crystals from that of undoped EuMn2As2 versus both T and H. For metallic Eu0.96K0.04Mn2As2 and Eu0.93K0.07Mn2As2, an anomalous S-shape T dependence of \rho related to the Mn magnetism is found. Upon cooling from 200 K, \rho exhibits a strong negative curvature, reaches maximum positive slope at the Mn T_N ~ 150 K, and then continues to decrease but more slowly below T_N. This suggests that dynamic short-range AFM order of the Mn spins above the Mn T_N strongly suppresses the resistivity, contrary to the conventional decrease of \rho that is only observed upon cooling below T_N of an antiferromagnet.Comment: 21 pages, 22 figures, 4 Table

Health Employment, Medical Spending, and Long Term Health Reform

This paper explores the relationships between the growth in the medical workforce in an aging society and employment in other sectors of the economy, based on data from the United States since 1985. Employment in medical services grew, but did not displace employment in other sectors uniformly. Instead, regression analysis shows that medical workforce growth produced contemporaneous reductions in relative employment in the manufacturing, construction, and information sectors, while being associated with growth in other services and public administration. Import penetration and productivity growth mattered, but much of the displacement remains even after controlling for these factors.

Unfree Labour : did indenture reduce labour supply to tea plantations in Assam?

Migration to tea plantations in Assam in the 19th century used indentured contracts. These contracts differed by conditions of harshness. Migration under the Special Act gained notoriety by giving tea planter the right of private arrest. Using a new set of migration by types of contract, the paper assesses if harsh terms of indenture discouraged labour flows. We find that regions using the harsh contract saw lower response to rise in the price of tea. Disaggregating by types of recruiter, we find that the response to market recruitment was high in all regions, but response to recruitment using community networks is statistically insignificant, suggesting that informational asymmetries may be an explanation for continuing migration despite concerns raised by the nationalist movement, social reformers and policy makers

Enhancing Energy Minimization Framework for Scene Text Recognition with Top-Down Cues

Recognizing scene text is a challenging problem, even more so than the recognition of scanned documents. This problem has gained significant attention from the computer vision community in recent years, and several methods based on energy minimization frameworks and deep learning approaches have been proposed. In this work, we focus on the energy minimization framework and propose a model that exploits both bottom-up and top-down cues for recognizing cropped words extracted from street images. The bottom-up cues are derived from individual character detections from an image. We build a conditional random field model on these detections to jointly model the strength of the detections and the interactions between them. These interactions are top-down cues obtained from a lexicon-based prior, i.e., language statistics. The optimal word represented by the text image is obtained by minimizing the energy function corresponding to the random field model. We evaluate our proposed algorithm extensively on a number of cropped scene text benchmark datasets, namely Street View Text, ICDAR 2003, 2011 and 2013 datasets, and IIIT 5K-word, and show better performance than comparable methods. We perform a rigorous analysis of all the steps in our approach and analyze the results. We also show that state-of-the-art convolutional neural network features can be integrated in our framework to further improve the recognition performance

Contracts, Hold-Up, and Exports: Textiles and Opium in Colonial India

Trade and export, it is argued, spur economic growth. This paper studies the microeconomics of exporting. We build a heuristic model of transactions between exporters and producers and relate it to East India Company operations in colonial Bengal. Our model and the historical record stress two difficulties: the exporter and its agents might not uphold pricing agreements, and producers might not honor sales contracts. The model shows when procurement succeeds or fails, highlighting the tension between these two hold-up problems. We analyze several cases including the East India Company's textile venture, the famous Opium Monopoly, and present-day contract farming.

Contracts, Hold-Up, and Exports: Textiles and Opium in Colonial India

Trade and export, it is argued, spur economic growth. This paper studies the microeconomics of exporting. We build a heuristic model of transactions between exporters and producers and relate it to East India Company operations in colonial Bengal. Our model and the historical record stress two difficulties: the exporter and its agents might not uphold pricing agreements, and producers might not honor sales contracts. The model shows when procurement succeeds or fails, highlighting the tension between these two hold-up problems. We analyze several cases including the East India Company's textile venture, the famous Opium Monopoly, and present-day contract farming.

Antiferromagnetism in EuCu2As2 and EuCu1.82Sb2 Single Crystals

Single crystals of EuCu2As2 and EuCu2Sb2 were grown from CuAs and CuSb self-flux, respectively. The crystallographic, magnetic, thermal and electronic transport properties of the single crystals were investigated by room-temperature x-ray diffraction (XRD), magnetic susceptibility \chi versus temperature T, isothermal magnetization M versus magnetic field H, specific heat Cp(T) and electrical resistivity \rho(T) measurements. EuCu2As2 crystallizes in the body-centered tetragonal ThCr2Si2-type structure (space group I4/mmm), whereas EuCu2Sb2 crystallizes in the related primitive tetragonal CaBe2Ge2-type structure (space group P4/nmm). The energy-dispersive x-ray spectroscopy and XRD data for the EuCu2Sb2 crystals showed the presence of vacancies on the Cu sites, yielding the actual composition EuCu1.82Sb2. The \rho(T) and Cp(T) data reveal metallic character for both EuCu2As2 and EuCu1.82Sb2. Antiferromagnetic (AFM) ordering is indicated from the \chi(T), Cp(T), and \rho(T) data for both EuCu2As2 (T_N = 17.5 K) and EuCu1.82Sb2 (T_N = 5.1 K). In EuCu1.82Sb2, the ordered-state \chi(T) and M(H) data suggest either a collinear A-type AFM ordering of Eu+2 spins S=7/2 or a planar noncollinear AFM structure, with the ordered moments oriented in the tetragonal ab plane in either case. This ordered-moment orientation for the A-type AFM is consistent with calculations with magnetic dipole interactions. The anisotropic \chi(T) and isothermal M(H) data for EuCu2As2, also containing Eu+2 spins S=7/2, strongly deviate from the predictions of molecular field theory for collinear AFM ordering and the AFM structure appears to be both noncollinear and noncoplanar.Comment: 21 pages, 22 figures, 4 Table

An efficient high-order Nystr\"om scheme for acoustic scattering by inhomogeneous penetrable media with discontinuous material interface

This text proposes a fast, rapidly convergent Nystr\"{o}m method for the solution of the Lippmann-Schwinger integral equation that mathematically models the scattering of time-harmonic acoustic waves by inhomogeneous obstacles, while allowing the material properties to jump across the interface. The method works with overlapping coordinate charts as a description of the given scatterer. In particular, it employs "partitions of unity" to simplify the implementation of high-order quadratures along with suitable changes of parametric variables to analytically resolve the singularities present in the integral operator to achieve desired accuracies in approximations. To deal with the discontinuous material interface in a high-order manner, a specialized quadrature is used in the boundary region. The approach further utilizes an FFT based strategy that uses equivalent source approximations to accelerate the evaluation of large number of interactions that arise in the approximation of the volumetric integral operator and thus achieves a reduced computational complexity of $O(N \log N)$ for an $N$-point discretization. A detailed discussion on the solution methodology along with a variety of numerical experiments to exemplify its performance in terms of both speed and accuracy are presented in this paper