On the highly reddened members in 6 young galactic star clusters - a multiwavelength study

The spectral and reddening properties of 211 highly reddened proper motion members with $V < 15$ mag in 6 young galactic star clusters are investigated using low resolution spectroscopic, broad-band $UBVRIJHK$ and mid-IR data. We report emission features in CaII HK and HI lines for a sample of 29 stars including 11 stars reported for the first time and also provide either a new or more reliable spectral class for a sample of 24 stars. CaII triplet width measurements are used to indicate the presence of an accretion disk for a dozen stars and to hint luminosity for a couple of stars. On the basis of spectral features, near-IR excesses, dereddened color-color diagrams and mid-IR spectral indices we identify a group of 28 pre-main sequence cluster members including 5 highly probable Herbig Ae/Be and 6 classical T Tauri star. A total of 25 non-emission MS stars, amounting to $\sim$ 10 % early type MS members, appears to show Vega-like characteristics or are precursors to such a phenomenon. The various membership indicators suggest that $\sim$ 16% of the PM members are non-members. A significant fraction ($>$70%) of program stars in NGC 1976, NGC 2244, NGC 6530 and NGC 6611 show anomalous reddening with $R_{V}$ = $5.11\pm0.11$, $3.60\pm0.05$, $3.87\pm0.05$ and $3.56\pm 0.02$, respectively, indicating the presence of grain size dust larger than that typical to the diffuse medium. A small number of stars in NGC 1976, NGC 2244 and NGC 6611 also show normal behavior while the cluster NGC 6823 appears to have a normal reddening. Three highly luminous late type giants, one in NGC 2244 and two in NGC 6530, appears to be member and are in post-hydrogen-core-burning stages suggesting a prolonged duration ($\sim$ 25 Myrs) of star formation.Comment: 12 pages, 13 figures, submitted to MNRA

Spoof detection using time-delay shallow neural network and feature switching

Detecting spoofed utterances is a fundamental problem in voice-based biometrics. Spoofing can be performed either by logical accesses like speech synthesis, voice conversion or by physical accesses such as replaying the pre-recorded utterance. Inspired by the state-of-the-art \emph{x}-vector based speaker verification approach, this paper proposes a time-delay shallow neural network (TD-SNN) for spoof detection for both logical and physical access. The novelty of the proposed TD-SNN system vis-a-vis conventional DNN systems is that it can handle variable length utterances during testing. Performance of the proposed TD-SNN systems and the baseline Gaussian mixture models (GMMs) is analyzed on the ASV-spoof-2019 dataset. The performance of the systems is measured in terms of the minimum normalized tandem detection cost function (min-t-DCF). When studied with individual features, the TD-SNN system consistently outperforms the GMM system for physical access. For logical access, GMM surpasses TD-SNN systems for certain individual features. When combined with the decision-level feature switching (DLFS) paradigm, the best TD-SNN system outperforms the best baseline GMM system on evaluation data with a relative improvement of 48.03\% and 49.47\% for both logical and physical access, respectively

Evaluating Explanations for Stagnation

In this paper, we evaluate four explanations for economic stagnation that have been proposed in the literature: coordination failures, ineffective mix of occupational choices, insufficient human capital accumulation, and politico-economic considerations. We calibrate models that embody these explanations in the context of the stagnant economies of sub-Saharan Africa. The methodology of calibration is ideally suited for this evaluation, given the paucity of high-quality data, the high degree of model nonlinearity, and the need for conducting counterfactual policy experiments. In addition to studying how closely and robustly these models capture the African situation, we examine the quantitative aspects of their policy implications. We find that calibrations that yield multiple equilibria -- one prosperity and the other stagnation -- are not particularly robust. This tempers optimism about the efficacy of one-shot or temporary development policies suggested by models with multiplicity. However, the calibrated models indicate that small policy interventions are sufficient to trigger development in stagnant economies.Coordination failure, Occupational choice, Human capital accumulation, Political economy, Economic Development, Calibration.

Higher Education Subsidies and Heterogeneity, A Dynamic Analysis

In this paper, we develop a simple dynamic general equilibrium framework that can be used to study issues in higher education policy. The model features heterogeneity in income of parents and academic ability of students. Liquidity constraints create persistence in educational attainment even when ability is independently distributed. A unique steady state with a positive fraction of college educated workers, or one with a development trap, or multiple steady states which feature both of these, can result in equilibrium. We add a government that is equipped with a simple tax scheme and calibrate the model to the US economy to get a benchmark for our policy analysis. The government can design a tax and subsidy scheme that guarantees equality of opportunity, but only at the expense of a decrease in the efficiency of utilization of education resources; the welfare gain is minimal. A policy that aims to maximize the fraction of college-educated labor, by sending as many children as possible to college, results in a big drop in the above-mentioned efficiency with little or no welfare gain. If the government has the political will to use any available signal on ability and provide merit-based aid, it can increase this efficiency with little decrease in welfare. Education subsidies may be a potent tool for countries that are caught in a development trap; a sufficient level of subsidy can cause the economy to emerge from the trap.Dynamic General Equilibrium, Education, College Subsidies

Education Policies to Revive a Stagnant Economy: The Case of Sub- Saharan Africa

In this paper, we argue that the condition of education and the economy of the low performing sub-Saharan African countries can be characterized as a stagnant steady state -- a "trap". We present a simple heterogeneous-agent model in which high costs of education relative to income and the skill premium can cause the economy to be trapped in such a steady state with minimal educational attainment. We calibrate the model to available data from the sub-Saharan African countries to study policies that could potentially free these trapped economies and set them on a path to a higher steady state. We find that a tax and subsidy scheme that redistributes resources at the trap from poor households with lower ability children to those with higher ability children can pry the economy out of the trap, thus freeing it from dependence on foreign aid in order to achieve the same goal. In addition to the direct cost, a portion of the indirect cost also needs to be subsidized. Moreover, such a policy outperforms the abolition of child labor and the institution and enforcement of compulsory education laws when expenditure neutral welfare comparisons are made.Dynamic heterogeneous-agent models, Economic stagnation, Education subsidies, Calibration of a trap

Nonintegrability of (2+1)-dimensional continuum isotropic Heisenberg spin system: Painlev\'e analysis

While many integrable spin systems are known to exist in (1+1) and (2+1) dimensions, the integrability property of the physically important (2+1) dimensional isotropic Heisenberg ferromagnetic spin system in the continuum limit has not been investigated in the literature. In this paper, we show through a careful singularity structure analysis of the underlying nonlinear evolution equation that the system admits logarithmic type singular manifolds and so is of non-Painlev\'e type and is expected to be nonintegrable.Comment: 11 pages. to be published in Phys. Lett. A (2006