Policy Scan: An Exploratory Study of National Youth Service Policy in 19 Countries in Latin America and the Caribbean

This paper presents findings from an exploratory study of government policies that involve youth in community service in 19 countries in Latin America and the Caribbean. The research, which was performed in 2004, provides descriptive information and explores the context within which national youth service policies can emerge and thrive. While it is assumed that well-designed national youth service policies provide a framework for engaging youth in pro-social activities that benefit themselves and their communities, relatively little research is available on the subject. Findings indicate that 13 of 19 countries in the study have a national youth service policy, and that the policies vary in forms and configuration. Facilitators and obstacles of these policies are discussed. The paper concludes by providing recommendations to policy makers

A theory for image persistence in HgCdTe photodiodes

Image persistence can produce systematic errors, which remain significant in some applications even when buried in noise. Ideally the image persistence amplitude, linearity and decay over time could be calibrated independently for each pixel to levels well below the noise floor, however averaging multiple measurements to characterize persistence to this accuracy is impractical due to the long time scales for the decay and the need to emulate the exposure and readout timing of the observations to be calibrated. We examine a compromise where the initial persistence response is characterized independently for each pixel but the latter parts of the decay are assumed to follow the mean decay curve. When averaged spatially, persistence increases monotonically with stimulus amplitude until the photodiodes approach forward bias. For several Teledyne 1.7 μm cutoff HgCdTe detectors tested, persistence is linear over most of the normal signal range. We characterize the temporal response, and examine the dependence of charge emission time constants on total stimulus duration. We describe the suppression of persistence by signal in the current frame and begin to examine the superposition of the decay curves from multiple stimuli

Fast and Frobenius: Rational Isogeny Evaluation over Finite Fields

Consider the problem of efficiently evaluating isogenies $\phi: E \to E/H$ of elliptic curves over a finite field $\mathbb{F}_q$, where the kernel $H = \langle G\rangle$ is a cyclic group of odd (prime) order: given $E$, $G$, and a point (or several points) $P$ on $E$, we want to compute $\phi(P)$. This problem is at the heart of efficient implementations of group-action- and isogeny-based post-quantum cryptosystems such as CSIDH. Algorithms based on V{\'e}lu's formulae give an efficient solution to this problem when the kernel generator $G$ is defined over $\mathbb{F}_q$. However, for general isogenies, $G$ is only defined over some extension $\mathbb{F}_{q^k}$, even though $\langle G\rangle$ as a whole (and thus $\phi$) is defined over the base field $\mathbb{F}_q$; and the performance of V{\'e}lu-style algorithms degrades rapidly as $k$ grows. In this article we revisit the isogeny-evaluation problem with a special focus on the case where $1 \le k \le 12$. We improve V{\'e}lu-style isogeny evaluation for many cases where $k = 1$ using special addition chains, and combine this with the action of Galois to give greater improvements when $k > 1$

Mapping erosion risk at the basin scale in a Mediterranean environment with opencast coal mines to target restoration actions

34 páginas, 9 figurasRiver basin restoration and management is crucial for assuring the continued delivery of ecosystem services and for limiting potential hazards. Human activity, whether directly or indirectly, can induce erosion processes and drastically change the landscape and alter vital ecological functions. Mapping erosion risk before future restoration-management projects will help to reveal the priority areas and develop a hierarchy ordered according to need. For this purpose, we used the Revised Universal Soil Loss Equation (RUSLE) erosion model. We also applied a novel technique called GPVI (Genetic Programming Vegetation Index) in the Martín River basin in NE Spain (2,112 km2), which has a large coalfield located in the southern part of the basin. Approximately two-thirds (69%) of the area of the Martín basin presents low and medium soil loss rates, and one-third (31%) of the area presents high (18%), very high (10%), and irreversible (3%) erosion rates. The southern part of the basin is the most degraded and is strongly influenced by the topography. This work allows us to locate areas prone to erosional degradation processes to help create a buffer around the river and locate “spots” in need of restoration. We also checked the error estimation of the methodology because our soil maps do not include rock and bare rock areas. The usefulness of applying RUSLE for predicting degraded areas and the consequent directing of soil conservation–restoration actions at the basin scale is demonstrated. We highly recommend a field survey of the selected areas to prove the goodness of the model estimations.This work is part of the research and assistance agreement between Endesa S.A. and CSICPyrenean Institute of Ecology (IPE-CSIC). Funding for this study was provided by Endesa S.A. A special acknowledge is given to Endesa Centro Minero Andorra (Teruel). Thanks are given to, J. M. Garcia Ruiz, S. Begueria, E. Nadal, E. Moran-Tejera, and J.J. Jimenez for reviewing and general advises during the development of this work, M. P. Errea, J. Zabalza, L. C. Alatorre for assistance with GIS analysis, M. Angulo for R factor map, M. Pazos with statistical analysis, and F. Reverberi for laboratory work. M. Trabucchi was in receipt of grant from JAE-CSIC (Ref. I3P-BPD-2006).Peer reviewe

Loss of Cone Molecular Markers in Rhodopsin-Mutant Human Retinas with Retinitis Pigmentosa

Purpose: To examine the effect of rhodopsin mutations on cone photoreceptors in human retinas with retinitis pigmentosa (RP). Methods: Four RP retinas with rhodopsin mutations and four normal retinas were examined by immunofluorescence with a battery of cell-specific antibodies against cone and rod cytoplasmic and outer segment membrane proteins. Areas of the retinas were studied that showed maximal preservation of photoreceptor structure. Results: All four RP retinas showed loss of rods, ranging from mild (T-17-M), to more severe (P-23-H), to advanced degeneration (Q-64-ter and G-106-R). The majority of cones in the T-17-M and P-23-H retinas were cytologically normal but showed loss of immunoreactivity for the cytoplasmic proteins 7G6, calbindin, and X-arrestin. The cone outer segments (OS) remained positive for cone opsins and peripherin-2 (rds/peripherin). All remaining cones in the Q-64-ter and G-106-R retinas were degenerate, with short to absent OS, but had strong reactivity for these cytoplasmic and OS membrane markers. Cones in the maculas of the RP retinas were degenerate, with short to absent OS, but retained strong labeling for the cytoplasmic and OS proteins. Conclusions: Even before cones show cytologic changes in response to rod cell degeneration, they lose immunoreactivity for certain cytoplasmic proteins. These cones later show shortening and loss of OS, although their OS membrane proteins remain well labeled. Cones may down regulate expression of both cytoplasmic and outer segment membrane proteins in response to mutant rod cell dysfunction and/or cell death in human RP retinas. Such cytologic and immunocytochemical changes in the cones may presage death of these critical cells in the later stages of RP

Refrigerants with Low Environmental Impact for Refrigeration Applications

New refrigerants with considerable low environmental impact are currently under evaluation by the refrigeration industry. Such refrigerants could be used in place of high global warming fluids like R404A. Among these new fluids are 1234ze, N-13, L-40 and N-40. Initial laboratory evaluations of these refrigerants showed good energy efficiency due to their good thermal properties. These initial evaluations were followed by larger scale (field) trials, refrigerant–oil property measurements, and also material compatibility. This study presents and discusses results of such evaluations, and extends the assessment to LCCP using different refrigeration technologies and refrigerants