Transitions in a West African labour market : the role of social networks

Dans cet article, nous analysons le rôle des réseaux sociaux dans la dynamique d'un marché du travail en Afrique de l'Ouest, en nous intéressant aux transitions du chômage vers l'emploi, de l'emploi salarié vers l’emploi indépendant et enfin de l’emploi indépendant vers l’emploi salarié. Les données d’une enquête originale que nous utilisons permettent d’appréhender les réseaux sociaux dans trois de leurs dimensions, à savoir sa structure, la force des liens et des ressources intégrées dans le réseau, et d’analyser les effets différenciés de chacune de ces dimensions sur ces transitions. Ces données, collectées à Ouagadougou en 2009, rassemblent les biographies professionnelles de 2000 ménages et sont représentatives à l’échelle de la ville. En nous appuyant sur des modèles de risques proportionnels, nous constatons que les réseaux sociaux ont un effet significatif sur la dynamique des travailleurs et que cet effet diffère selon le type de transition et la dimension considérée du réseau social. La taille du réseau semble joué un rôle mineur au regard des deux autres dimensions. Des liens forts jouent un rôle stabilisateur en limitant les grandes transitions. Leur effet négatif sur les transitions est renforcé quand ces liens forts sont combinés à un niveau élevé de ressources du réseau

Vocational education, on-the-job training and labour market integration of young workers in urban West Africa

Background paper prepared for the Education for All Global Monitoring Report 2012 “Youth and skills: Putting education to work”Using surveys covering seven West African economic capitals in the early 2000s, this paper describes the labour market integration of youth with regard to their level of formal education and to the type of vocational training they received. We particularly focus on the informal sector and look at activity rates, unemployment, earnings, job quality and small firm performance in order to identify the key features of youth labour market integration. To our knowledge, these features of Africa’s labour markets are rarely documented at a sectoral level using representative samples of urban areas. The overall results suggest that the youth are the most disadvantaged in terms of unemployment, access to the formal sector, and earnings. We provide some evidence that vocational education might be a good instrument for integrating the formal sector and that it is often more profitable than general education in terms of earnings and firm performance, especially at higher levels of schooling. Generally, education, especially at high levels, provides a substantial growth in earnings in informal jobs in most of the cities studied. Regarding the incidence of vocational education and training (VET), the main form observed is traditional apprenticeship. Overall, young workers without any formal VET are the more disadvantaged in terms of working conditions, while workers who benefited from a traditional apprenticeship in a small firm occupy an intermediate position. Apprenticeship training for young workers seems to be fairly prevalent in the informal sector, but the associated working conditions are bad, and kinship ties seem to be there a crucial channel for training access

A Wearable Sensor Network for Gait Analysis: A 6-Day Experiment of Running Through the Desert

International audienceThis paper presents a new system for analysis of walking and running gaits. The system is based on a network of wireless nodes with various types of embedded sensors. It has been designed to allow long-term recording in outdoor environments and was tested during the 2010 "Sultan Marathon des Sables" desert race. A runner was fitted with the sensory network for six days of the competition. Although technical problems have limited the amount of data recorded, the experiment was nevertheless suc- cessful: the system did not interfere with the runner, who finished with a high ranking, the concept was validated and high quality data were ac- quired. It should be noted that the loss of some of the measurements was mainly due to problems with the cable connectors between the nodes and batteries. In this paper, we describe the technical aspects of the system developed, the experimental conditions under which it was validated, and give examples of the data obtained with some preliminary processing

Evolution of Total and Integrated HIV-1 DNA and Change in DNA Sequences in Patients with Sustained Plasma Virus Suppression

AbstractBlood samples from patients with plasma HIV-1 RNA <20 copies/ml for more than 2 years were studied. Significant decreases in total and integrated HIV-1 DNA were observed during the first 15 months of suppressive therapy before the concentrations became stable. Clonal analysis of HIV-1 pol demonstrated that the proportions of resistance mutations in DNA sequences after 2 years were lower than those in baseline DNA and RNA sequences. The changes in the clonal composition of HIV-1 env populations in three patients with evidence of changes in HIV-1 pol populations indicated a shift from predominantly R5-like viruses to predominantly X4-like viruses in two patients and the persistence of predominantly X4-like viruses in the third. Our analyses indicate the reemergence of ancestral sequences from long-lived cells or the residual production of wild-type virus from anatomic sites with limited access to antiretroviral drugs and the preferential infection of cells expressing CXCR4

Comparison of Matrix Pencil Extracted Features in Time Domain and in Frequency Domain for Radar Target Classification

Feature extraction is a challenging problem in radar target identification. In this paper, we propose a new approach of feature extraction by using Matrix Pencil Method in Frequency Domain (MPMFD). The proposed method takes into account not only the magnitude of the signal, but also its phase, so that all the physical characteristics of the target will be considered. With this method, the separation between the early time and the late time is not necessary. The proposed method is compared to Matrix Pencil Method in Time Domain (MPMTD). The methods are applied on UWB backscattered signal from three canonical targets (thin wire, sphere, and cylinder). MPMFD is applied on a complex field (real and imaginary parts of the signal). To the best of our knowledge, this comparison and the reconstruction of the complex electromagnetic field by MPMFD have not been done before. We show the effect of the two extraction methods on the accuracy of three different classifiers: Naïve bayes (NB), K-Nearest Neighbor (K-NN), and Support Vector Machine (SVM). The results show that the accuracy of classification is better when using extracted features by MPMFD with SVM

Baryon Acoustic Oscillations in the Ly{\alpha} forest of BOSS DR11 quasars

We report a detection of the baryon acoustic oscillation (BAO) feature in the flux-correlation function of the Ly{\alpha} forest of high-redshift quasars with a statistical significance of five standard deviations. The study uses 137,562 quasars in the redshift range $2.1\le z \le 3.5$ from the Data Release 11 (DR11) of the Baryon Oscillation Spectroscopic Survey (BOSS) of SDSS-III. This sample contains three times the number of quasars used in previous studies. The measured position of the BAO peak determines the angular distance, $D_A(z=2.34)$ and expansion rate, $H(z=2.34)$, both on a scale set by the sound horizon at the drag epoch, $r_d$. We find $D_A/r_d=11.28\pm0.65(1\sigma)^{+2.8}_{-1.2}(2\sigma)$ and $D_H/r_d=9.18\pm0.28(1\sigma)\pm0.6(2\sigma)$ where $D_H=c/H$. The optimal combination, $\sim D_H^{0.7}D_A^{0.3}/r_d$ is determined with a precision of $\sim2\%$. For the value $r_d=147.4~{\rm Mpc}$, consistent with the CMB power spectrum measured by Planck, we find $D_A(z=2.34)=1662\pm96(1\sigma)~{\rm Mpc}$ and $H(z=2.34)=222\pm7(1\sigma)~{\rm km\,s^{-1}Mpc^{-1}}$. Tests with mock catalogs and variations of our analysis procedure have revealed no systematic uncertainties comparable to our statistical errors. Our results agree with the previously reported BAO measurement at the same redshift using the quasar-Ly{\alpha} forest cross-correlation. The auto-correlation and cross-correlation approaches are complementary because of the quite different impact of redshift-space distortion on the two measurements. The combined constraints from the two correlation functions imply values of $D_A/r_d$ and $D_H/r_d$ that are, respectively, 7% low and 7% high compared to the predictions of a flat $\Lambda$CDM cosmological model with the best-fit Planck parameters. With our estimated statistical errors, the significance of this discrepancy is $\approx 2.5\sigma$.Comment: Accepted for publication in A&A. 17 pages, 18 figure

The Baryon Oscillation Spectroscopic Survey of SDSS-III

The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the scale of baryon acoustic oscillations (BAO) in the clustering of matter over a larger volume than the combined efforts of all previous spectroscopic surveys of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7. Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000 quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5. Early results from BOSS include the first detection of the large-scale three-dimensional clustering of the Lyman alpha forest and a strong detection from the Data Release 9 data set of the BAO in the clustering of massive galaxies at an effective redshift z = 0.57. We project that BOSS will yield measurements of the angular diameter distance D_A to an accuracy of 1.0% at redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the same redshifts. Forecasts for Lyman alpha forest constraints predict a measurement of an overall dilation factor that scales the highly degenerate D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey is complete. Here, we provide an overview of the selection of spectroscopic targets, planning of observations, and analysis of data and data quality of BOSS.Comment: 49 pages, 16 figures, accepted by A

The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey

The Sloan Digital Sky Survey III (SDSS-III) presents the first spectroscopic data from the Baryon Oscillation Spectroscopic Survey (BOSS). This ninth data release (DR9) of the SDSS project includes 535,995 new galaxy spectra (median z=0.52), 102,100 new quasar spectra (median z=2.32), and 90,897 new stellar spectra, along with the data presented in previous data releases. These spectra were obtained with the new BOSS spectrograph and were taken between 2009 December and 2011 July. In addition, the stellar parameters pipeline, which determines radial velocities, surface temperatures, surface gravities, and metallicities of stars, has been updated and refined with improvements in temperature estimates for stars with T_eff<5000 K and in metallicity estimates for stars with [Fe/H]>-0.5. DR9 includes new stellar parameters for all stars presented in DR8, including stars from SDSS-I and II, as well as those observed as part of the SDSS-III Sloan Extension for Galactic Understanding and Exploration-2 (SEGUE-2). The astrometry error introduced in the DR8 imaging catalogs has been corrected in the DR9 data products. The next data release for SDSS-III will be in Summer 2013, which will present the first data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) along with another year of data from BOSS, followed by the final SDSS-III data release in December 2014.Comment: 9 figures; 2 tables. Submitted to ApJS. DR9 is available at http://www.sdss3.org/dr

The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since July 2014. This paper describes the second data release from this phase, and the fourteenth from SDSS overall (making this, Data Release Fourteen or DR14). This release makes public data taken by SDSS-IV in its first two years of operation (July 2014-2016). Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey (eBOSS); the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data driven machine learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS website (www.sdss.org) has been updated for this release, and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020, and will be followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14 happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov 2017 (this is the "post-print" and "post-proofs" version; minor corrections only from v1, and most of errors found in proofs corrected