Estimating Expected Individual Treatment Outcomes by Using Nonparametric Evaluation Methods

Consider the situation faced by an individual which has to choose among different treatments available to him. For selecting the optimal treatment he needs to conjecture for each treatment how his situation after treatment would likely to be. This article proposes a semiparametric method to estimate heterogeneous potential treatment outcomes with respect to individual characteristics. These are important in at least two respects. They can be used ex-ante to improve treatment choices and targeting of programmes to heterogeneous individuals. They also allow an ex-post examination whether each individual received the treatment most adequate to him, therewith allowing an assessment of the efficiency of the selection process. While the evaluation literature has mostly concentrated on average treatment outcomes and has promoted nonparametric techniques for their estimation, the systems proposed for targeting programmes have predominantly relied on fully parametric models. The model proposed in this article combines nonparametric and parametric elements into a GMM estimator to attain more robust estimates. Root-n consistency and asymptotic normality are shown. Furthermore, since usually more than one outcome variable is necessary to describe the after-treatment situation, different ways to summarize the numerous estimates, whose number grows quickly with the number of outcome variables and the number of treatments, are considered. Based on the asymptotic distribution of the estimated expected potential outcomes, stochastic dominance probabilities that certain treatments dominate others in one or all outcome variables are derived. Finally the proposed estimator is applied to Swedish rehabilitation programmes.

Teacher Shortages, Teacher Contracts and their Impact on Education in Africa

Primary school enrolment rates are very low in francophone Africa. In order to enhance education supply, many countries have launched large teacher recruitment programmes in recent years, whereby teachers are no longer engaged on civil servant positions, but on the basis of (fixed-term) contracts typically implying considerably lower salaries and a sharply reduced duration of professional training. While this policy has led to a boost of primary enrolment, there is a concern about a loss in the quality of education. In this paper we analyse the impact on educational quality, by estimating nonparametrically the quantile treatment effects for Niger, Togo and Mali, based on very informative data, comparable across these countries. We find that contract teachers do relatively better for low ability children in low grades than for high ability children in higher grades. When positive treatment effects were found, they tended to be more positive at the low to medium quantiles; when negative effects were found they tended to be more pronounced at the high ability quantiles. Hence, overall it seems that contract teachers do a relatively better job for teaching students with learning difficulties than for teaching the ‘more advanced’ children. This implies that contract teachers tend to reduce inequalities in student outcomes. At the same time, we also observe clear differences between the countries. We find that, overall, effects are positive in Mali, somewhat mixed in Togo (with positive effects in 2nd and negative effects in 5th grade) and negative in Niger. This ordering is consistent with theoretical expectations derived from a closer examination of the different ways of implementation of the contract teacher programme in the three countries. In Mali and, to some extent, in Togo, the contract teacher system works more through the local communities. This may have led to closer monitoring and more effective hiring of contract teachers. In Niger, the system was changed in a centralized way with all contract teachers being public employees, so that there is no reason to expect much impact on local monitoring. In addition, the extremely fast hiring of huge numbers of contract teachers may also have contributed to relatively poor performance in Niger. These results are expected to be relevant for other sub-Saharan African countries, too, as well as for the design of new contract teacher programmes in the future.

State of the art of plastic sorting and recycling : Feedback to vehicle design

Today car manufacturers are beginning to integrate recycling constraints in the first stages of the design of a new car due to their concern regarding the effects of car design on the recovery of material after End-of-Life Vehicle treatment. Improved understanding of the recycling process can help designers to avoid contaminants in the recycled product and improve the efficiency of current and new sorting methods. The main goal of this paper is to describe the state of the art of the technical efficiency of recovery channels for plastics in Europe in order to define requirements for automotive plastic part design. This paper will first present the results of a survey on industrial and innovative recycling technologies mainly originating from the mining sector, and secondly a simplified methodology for car design integrating plastic recycling constraints. This methodology concerns material association and compatibility, the type of assemblies favourable to better recycling, and better reuse of recycled products in cars.Renault Research Direction FR TCR LAB 1 13, Service 641000-Recycling Engineering, 1 avenue du Golf, 78288 Guyancourt Cedex, Franc

Resonance spectroscopy of gravitational states of antihydrogen

We study a method to induce resonant transitions between antihydrogen quantum states above a material surface in the gravitational field of the Earth. The method consists in applying a gradient of magnetic field which is temporally oscillating with the frequency equal to a frequency of a transition between gravitational states of antihydrogen. Corresponding resonant change in a spatial density of antihydrogen atoms can be measured as a function of the frequency of applied field. We estimate an accuracy of measuring antihydrogen gravitational states spacing and show how a value of the gravitational mass of the antihydrogen atom can be deduced from such a measurement.Comment: 5 pages, 2 figures, LEAP 2013 conference proceeding

Was the Late Paleocene-Early Eocene Hot Because Earth Was Flat? An Ocean Lithium Isotope View of Mountain Building, Continental Weathering, Carbon Dioxide, and Earth's Cenozoic Clima

Hothouse climates in Earth’s geologic past, such as the Eocene epoch, \ud are thought to have been caused by the release of large amounts of carbon dioxide \ud and/or methane, which had been stored as carbon in biogenic gases and organic \ud matter in sediments, to the ocean-atmosphere system. However, to avoid runaway \ud temperatures, there must be long-term negative feedbacks that consume CO 2 on \ud time scales longer than the ~ 100,000 years generally ascribed to ocean uptake of \ud CO 2 and burial of marine organic carbon. Here, we argue that continental chemical \ud weathering of silicate rocks, the ultimate long-term (multi-million year) sink for \ud CO 2 , must have been almost dormant during the late Paleocene and early Eocene, \ud allowing buildup of atmospheric CO 2 to levels exceeding 1,000 ppm. This reduction \ud in the strength of the CO 2 sink was the result of minimal global tectonic uplift of \ud silicate rocks that did not produce mountains susceptible to physical and chemical \ud weathering, an inversion of the Uplift-Weathering Hypothesis. There is lack of \ud terrestrial evidence for absence of uplift; however, the δ 7 Li chemistry of the Paleogene \ud ocean indicates that continental relief during this period of the Early Cenozoic was \ud one of peneplained (flat) continents characterized by high chemical weathering \ud intensity and slow physical and chemical weathering rates, yielding low river fluxes \ud of suspended solids, dissolved cations, and clays delivered to the sea. Only upon \ud re-initiation of mountain building in the Oligocene-Miocene (Himalayas, Andes, \ud Rockies) and drifting of these continental blocks to low-latitude locations near the \ud Inter-Tropical Convergence Zone and monsoonal climate belts did continental \ud weathering take on modern characteristics of rivers with high suspended loads and \ud incongruent weathering, with much of the cations released during weathering being \ud sequestered into secondary clay minerals. The δ 7 Li record of the Cenozoic ocean \ud provides another piece of circumstantial evidence in support of the Late Cenozoic \ud Uplift-Weathering Hypothesis

Addition of X-ray fluorescent tracers into polymers, new technology for automatic sorting of plastics : proposal for selecting some relevant tracers

A description of a new technology for automatic sorting of plastics, based on X-ray fluorescence detection of tracers, added in such materials is presented. This study describes the criteria for the selection of tracers, and concluded that the most adapted for XRF are some rare earth oxides. The plastics chosen for tracing and identification are the ones contained in ELV and WEEE from which discrimination is difficult for the existing sorting techniques due to their black colour.A description of a new technology for automatic sorting of plastics, based on X-ray fluorescence detection of tracers, added in such materials is presented. This study describes the criteria for the selection of tracers, and concluded that the most adapted for XRF are some rare earth oxides. The plastics chosen for tracing and identification are the ones contained in ELV and WEEE from which discrimination is difficult for the existing sorting techniques due to their black colour