Further development of a charged liquid colloid source for electrostatic propulsion Final report

Performance characteristics of charged liquid droplet electrostatic propulsion syste

Earnings inequalities and educational mobility in Brazil over two decades

This paper studies the impact of changes in educational opportunities on various definitions of labour market inequalities in Brazil over two decades (1976-96). Using four editions of the nationally representative PNAD survey, we analyze the evolution of overall inequalities and inequalities of opportunity in 40-49 year old males' earnings. We design and implement semiparametric decompositions of the respective effects of (i) schooling expansion, (ii) changes in the structure of earnings, and (iii) changes in intergenerational educational mobility. Earnings inequalities varied little over the period, with a peak in the late 1980s that can be imputed to hyperinflation. First of all, the decompositions show that changes in the distribution of education contributed to the increase in both overall earnings inequalities and inequalities of opportunity among the oldest generations, before sharply reducing them among the post-WWII cohorts. Secondly, the decrease in returns to education also contributed to equalizing labour market opportunities in the 1988-96 period. Thirdly and lastly, the changes in educational mobility were not large enough to significantly affect earnings inequalities, whereas it is shown that they should play a prominent role in equalizing opportunities in the future

Exploración de los modelos de marcaje–reavistaje–recuperación para estudiar la demografía de los árboles de sabana

Despite their sessile nature, juvenile trees in savannah ecosystems are not always easy to encounter. Here, we evaluate the applicability to plants of the remedy of choice in animal studies: capture–recapture modelling. The plant equivalents, tagging and resighting, were caried outnin 7 censuses, involving 4,145 juvenile trees of 8 dominant savannah species. Using models with joint analysis of live and dead encounters, the resighting probabilities averaged 0.88 ± 0.15 and 0.92 ± 0.10 for seedlings and resprouts respectively; while dead recovery probabilities averaged 0.71 ± 0.25 for all age–classes. An ad hoc method that did not take into account encounter probabilities yielded biased survival estimates compared with estimates obtained using the mark–resighting–recovery approaches. This bias was observed even at high encounter probabilities, and we recommend therefore capture–recapture models where plant encounter is less than one. Finally, survival probabilities estimated by models based only on live or on dead data might both differ and be less accurate than estimates based on combined data. This highlights the advantages of models with joint analysis of live and dead encounters even the value of site fidelity is one.Pese a su naturaleza sésil, los árboles jóvenes no siempre resultan fáciles de hallar en los ecosistemas de sabana. En el presente trabajo se evalua la odelización de captura–recaptura, tan utilizada en estudios de animales, para su aplicación en los estudios de plantas. El equivalente al marcaje y reavistamiento para las plantas, se llevó a cabo a lo largo de siete censos, con un total de 4.145 árboles juveniles de ocho especies de la sabana dominantes. Mediante el empleo de análisis conjuntos de hallazgos de individuos vivos y muertos, las probabilidades de reaviastamiento medias fueron de 0,88 ± 0,15 y 0,92 ± 0,10 para las plántulas y los rebrotes, respectivamente, mientras que el promedio correspondiente a las probabilidades de recuperación de individuos muertos fue de 0,71 ± 0,25 para todas las clases de edad. Un método especialmente disenyado que no tenía en cuenta las probabilidades de recaptura dio unas estimaciones de supervivencia sesgadas, en comparación con las estimas obtenidas utilizando las aproximaciones basadas en el marcaje–reavistamiento–recaptura. Este sesgo aparecía incluso con altas probabilidades de recaptura, por lo que recomendamos los modelos de captura–recaptura en los que la probabilidad de encontarr la planta es menor de uno. Por ultimo, las probabilidades de supervivencia estimadas mediante los modelos basados únicamente en datos de plantas vivas o muertas pueden tanto diferir como ser menos precisas que las estimas basadas en datos combinados. Esto realza las ventajas de los modelos que emplean análisis conjuntos de hallazgos de plantas vivas y muertas, aun cuando el valor de la fidelidad al emplazamiento sea uno

Theoretical Summary of the HADRON99 conference

The Constituent Quark Model has provided a remarkable description of the experimentally observed hadron spectrum but still has no firm theoretical basis. Attempts to provide a QCD justification discussed at Hadron99 include QCD Sum Rules, instantons, relativistic potential models and the lattice. Phenomenological analyses to clarify outstanding problems like the nature of the scalar and pseudoscalar mesons and the low branching ratio for $\psi' \to \rho-\pi$ were presented. New experimental puzzles include the observation of $\bar p p \to \phi \pi$.Comment: 10 pages, espcrc1.st

Stage-classified matrix models and age estimates

When the size of individuals is a better indicator of their chances to survive, grow, and reproduce than their age, the suitable matrix population model is stage-classified. Cochran and Ellner developed a method to assess age-based parameters from such models. We present here, for these age estimates, simplified formulas that are valid whenever there is neither retrogression nor fission: individuals may only die, survive in the same stage, or survive and recruit to the next stage. Our formulas enable one to understand better why, and under which hypotheses, it is possible to compute age estimates from a stage-classified model, and point out some limitations of the method. These limitations in fact come from the basic hypothesis of stage-classified matrix models: stage is considered to be the only variable that influences survival and recruitment rates. As a consequence, age estimates using stage-classified models should be valid if the stages describe precisely enough the life cycles of the studied species, and particularly if senescence is taken into account

Notes sur la pathologie spontanée du chien de laboratoire. 4e note : Un cas de gestation dite abdominale

A propos d’une observation de gestation abdominale secondaire, avec déchirure utérine, les auteurs envisagent le devenir expérimen tal de l’animal et les problèmes soulevés en chirurgie canine : dia gnostic radiologique et traitement chirurgical

High Hepatitis E Seroprevalence Among Displaced Persons in South Sudan.

AbstractLarge protracted outbreaks of hepatitis E virus (HEV) have been documented in displaced populations in Africa over the past decade though data are limited outside these exceptional settings. Serological studies can provide insights useful for improving surveillance and disease control. We conducted an age-stratified serological survey using samples previously collected for another research study from 206 residents of an internally displaced person camp in Juba, South Sudan. We tested serum for anti-HEV antibodies (IgM and IgG) and estimated the prevalence of recent and historical exposure to the virus. Using data on individuals' serostatus, camp arrival date, and state of origin, we used catalytic transmission models to estimate the relative risk of HEV infection in the camp compared with that in the participants' home states. The age-adjusted seroprevalence of anti-HEV IgG was 71% (95% confidence interval = 63-78), and 4% had evidence of recent exposure (IgM). We estimated HEV exposure rates to be more than 2-fold (hazard ratio = 2.3, 95% credible interval = 0.3-5.8) higher in the camp than in the participants' home states, although this difference was not statistically significant. HEV transmission may be higher than previously appreciated, even in the absence of reported cases. Improved surveillance in similar settings is needed to understand the burden of disease and minimize epidemic impact through early detection and response

Analysis and modeling of magnetocaloric effect near magnetic phase transition temperature

International audienceMagnetocaloric behavior of gadolinium near room temperature can be correctly described by the Weiss molecular field theory especially in the paramagnetic state. In this paper, this approach is generalized for binary rare earth alloys which present as Gd a second order phase transition. The magnetic entropy variation can be calculated as a function of the temperature and the applied field. This model was tested on a laboratory synthesized samples of Gd-Tb. The agreement between calculations and experiments shows that this model can be easily used for these alloys in order to optimize their composition and adjust their Curie temperatures. For first order transition materials, the observed magnetocaloric effect enhancement can be explained by magnetoelastic effects which are due to the spontaneous crystal deformation and the structure transformation. A model based on the phenomenological approach of Bean Rodbell is developed to describe such a behavior. It highlights the link between the nature of magnetic transition and the magnetocaloric effect. It can be identified by only two parameters: T 0 the Curie temperature without deformation and η an order parameter which characterizes the transition nature. In this paper we apply this model to describe the giant magnetocaloric effect exhibited by the new Mn 1-x (Ti 0.5 V 0.5) x As materials

Phenomenology of the Pentaquark Antidecuplet

We consider the mass splittings and strong decays of members of the lowest-lying pentaquark multiplet, which we take to be a parity-odd antidecuplet. We derive useful decompositions of the quark model wave functions that allow for easy computation of color-flavor-spin matrix elements. We compute mass splittings within the antidecuplet including spin-color and spin-isospin interactions between constituents and point out the importance of hidden strangeness in rendering the nucleon-like states heavier than the S=1 state. Using recent experimental data on a possible S=1 pentaquark state, we make decay predictions for other members of the antidecuplet.Comment: 12 pages LaTeX, 1 eps figur