Concave holographic grating for spectrographic applications: Study of the aberrations

An analysis of reflecting diffraction gratings by the application of holographic techniques is presented. The subjects discussed are: (1) holographic grating properties, (2) calculation of aberrant optical path, (3) analytical expression of stigmatic points, (4) spherical aberration and limitation of grating width, and (5) determination of construction parameters

Interregional transfers, group loyalty and the decentralization of redistribution

We study the decentralization of redistributive taxation in a political economy model assuming regional heterogeneity regarding both group identity and average income. If a centralized system permits a beneficial pooling of national resources, it might also decrease the degree of solidarity in the society. With no group loyalty, centralization Pareto-dominates decentralization even when regions are not identical. Furthermore, increased heterogeneity need not increase the relative efficiency of decentralization. If regions are equally rich, centralization Pareto-dominates decentralization whenever group loyalty is not perfect. Finally, centralization is always more efficient than decentralization even when allowing for interregional transfers

Macroeconomic News 'Surprises' and the Rand/Dollar Exchange Rate

Economic theory in the context of floating exchange rates has focussed on underlying medium and long term direction of exchange rate movements. Daily volatility is less well understood. One theory that offers an explanation for short term exchange rate movements is that of the efficient market hypothesis or EMH. Its application to the forex market allows exchange rate movements to be understood as the reaction of traders to relevant news. In an efficient market traders react to news and specifically to surprise news events which necessitate a re-evaluation of the currency value. We test for the validity of this hypothesis in the context of the daily rand/dollar forex market over a three year period, adding an emerging market case to the literature. We test the significance of macroeconomic news surprises -measured by the difference between actual and forecast data - in driving daily exchange rates. We find that surprises in both real and nominal variables cause a statistically significant reaction in the exchange rate. The results support an asymmetry between news of different origin as only surprises that originate in the U.S. prove significant. Good news also seems to receive greater attention from traders than bad news in our sample. Finally, we find that the statistical significance of variables is time-varying.

Strategic choice of sharing rules in collective contests

Competition between groups often involves prizes that have both a public and a private component. The exact nature of the prize not only affects the strategic choice of the sharing rules determining its allocation but also gives rise to an interesting phenomenon not observed when the prize is either purely public or purely private. Indeed, we show that in the two-groups contest, for most degrees of privateness of the prize, the large group uses its sharing rule as a mean to exclude the small group from the competition, a situation called monopolization. Conversely, there is a degree of relative privateness above which the small group, besides being active, even outperforms the large group in terms of winning probabilities, giving rise to the celebrated group size paradox

A 64mW DNN-based Visual Navigation Engine for Autonomous Nano-Drones

Fully-autonomous miniaturized robots (e.g., drones), with artificial intelligence (AI) based visual navigation capabilities are extremely challenging drivers of Internet-of-Things edge intelligence capabilities. Visual navigation based on AI approaches, such as deep neural networks (DNNs) are becoming pervasive for standard-size drones, but are considered out of reach for nanodrones with size of a few cm${}^\mathrm{2}$. In this work, we present the first (to the best of our knowledge) demonstration of a navigation engine for autonomous nano-drones capable of closed-loop end-to-end DNN-based visual navigation. To achieve this goal we developed a complete methodology for parallel execution of complex DNNs directly on-bard of resource-constrained milliwatt-scale nodes. Our system is based on GAP8, a novel parallel ultra-low-power computing platform, and a 27 g commercial, open-source CrazyFlie 2.0 nano-quadrotor. As part of our general methodology we discuss the software mapping techniques that enable the state-of-the-art deep convolutional neural network presented in [1] to be fully executed on-board within a strict 6 fps real-time constraint with no compromise in terms of flight results, while all processing is done with only 64 mW on average. Our navigation engine is flexible and can be used to span a wide performance range: at its peak performance corner it achieves 18 fps while still consuming on average just 3.5% of the power envelope of the deployed nano-aircraft.Comment: 15 pages, 13 figures, 5 tables, 2 listings, accepted for publication in the IEEE Internet of Things Journal (IEEE IOTJ

Innate immune basis for rift valley fever susceptibility in mouse models

Rift Valley fever virus (RVFV) leads to varied clinical manifestations in animals and in humans that range from moderate fever to fatal illness, suggesting that host immune responses are important determinants of the disease severity. We investigated the immune basis for the extreme susceptibility of MBT/Pas mice that die with mild to acute hepatitis by day 3 post-infection compared to more resistant BALB/cByJ mice that survive up to a week longer. Lower levels of neutrophils observed in the bone marrow and blood of infected MBT/Pas mice are unlikely to be causative of increased RVFV susceptibility as constitutive neutropenia in specific mutant mice did not change survival outcome. However, whereas MBT/Pas mice mounted an earlier inflammatory response accompanied by higher amounts of interferon (IFN)-α in the serum compared to BALB/cByJ mice, they failed to prevent high viral antigen load. Several immunological alterations were uncovered in infected MBT/Pas mice compared to BALB/cByJ mice, including low levels of leukocytes that expressed type I IFN receptor subunit 1 (IFNAR1) in the blood, spleen and liver, delayed leukocyte activation and decreased percentage of IFN-γ-producing leukocytes in the blood. These observations are consistent with the complex mode of inheritance of RVFV susceptibility in genetic studies

The Redistributive Effects Of The EU Budget: An Analysis And A Proposal Reform

This paper analyzes the redistributive effects of the EU budget during the period 1986-98, explores the implications of the Berlin budget agreement and advances a proposal for setting member countries' budgetary balances in a manner consistent with a simple equity criterion based on relative income per capita. Using an extension of a standard methodology, we find that the redistributive impact of the EU budget has been considerable in view of its small size, that it has tended to increase over time, and that it is mostly due to the effects of structural programmes. We also find that, in spite of the relative loss of weight of structural transfers, the expenditure side of the Berlin budget agreement represents a noticeable (but small) improvement over the previous financial perspectives in terms of both its redistributive impact and its horizontal equity properties. Our proposed allocation criterion involves the correction of horizontal inequities while preserving the current degree of redistribution. This would involve a sizable reallocation of net contributions across rich countries and only a modest reduction in north-south fiscal flows.This paper was written as part of a research project cofinanced by the European Fund for Regional Development and Fundación Caixa Galicia. Additional financial support was provided by the Spanish Ministry of Education and Culture under grants SEC99-1189 and SEC99-0820