897 research outputs found
Remittances and temporary migration
In this paper we study the remittance behavior of immigrants and how it relates to temporary versus permanent migration plans. We use a unique data source that provides unusual detail on remittances and return plans, and follows the same household over time. Our data allows us also to distinguish between different purposes of remittances. We analyze the association between individual and household characteristics and the geographic location of the family as well as return plans, and remittances. The panel nature of our data allows us to condition on household fixed effects. To address measurement error and reverse causality, we use an instrumental variable estimator. Our results show that changes in return plans are related to large changes in remittance flows
Essays on temporary migration
My thesis dissertation focuses on the temporariness of migration, its diverse effects as
well as on migration selection.
The first paper, A Dynamic Model of Return Migration analyzes the decision process
underlying return migration using a dynamic model. We explain how migrants
decide whether to stay or to go back to their home country together with their savings
and consumption decisions. We simulate our model with return intentions and perform
policy simulations.
The second paper, Remittances and Temporary Migration, studies the remittance
behaviour of immigrants and how it relates to temporary versus permanent migration
plans. We use a unique data source that provides unusual detail on the purpose of
remittances, savings, and return plans, and follows the same household over time. Our
results suggest that changes in return plans lead to large changes in remittance flows.
The third paper, Savings, Asset Holdings, and Temporary, analyzes how return
plans affect not only remittances but also savings and the accumulation of assets. We
show that immigrants with temporary return plans place a higher proportion of savings
in the home country and have accumulated a higher amount and share of assets and
housing value in the home country (compared to the host country).
Finally, the fourth paper, Migrant Selection to the U.S.: Evidence from the Mexican
Family Life Survey (MxFLS), studies the selection in terms of skills of recent
migrants to the United States using the MxFLS. We highlight the important age gradient
of migration, the different education attainment between age cohorts in Mexico
and show the implications when analyzing migrant selection. Our claim is that in order
to properly study the self-selection of migrants, it is necessary to compare migrants to
non-migrants of the same age cohort
Selective epitaxial growth of graphene on SiC
We present an innovative method of selective epitaxial growth of few layers
graphene (FLG) on a pre-patterned SiC substrate. The methods involves,
successively, the sputtering of a thin AlN layer on top of a mono-crystalline
SiC substrate and, then, patterning it with e-beam lithography (EBL) and wet
etching. The sublimation of few atomic layers of Si from the SiC substrate
occurs only through the selectively etched AlN layer. The presence of the Raman
G-band at ~1582 cm-1 in the AlN-free areas is used to validate the concept, it
gives absolute evidence of the selective FLG growth.Comment: comments: 3 pages, reference 3 replace
Invariance Violation Extends the Cosmic Ray Horizon ?
We postulate in the present paper that the energy-momentum relation is
modified for very high energy particles to violate Lorentz invariance and the
speed of photon is changed from the light velocity c. The violation effect is
amplified, in a sensitive way to detection, through the modified kinematical
constraints on the conservation of energy and momentum, in the absorption
process of gamma-rays colliding against photons of longer wavelengths and
converting into an electron-positron pair. For gamma-rays of energies higher
than 10 TeV, the minimum energy of the soft photons for the reaction and then
the absorption mean free path of gamma-rays are altered by orders of magnitude
from the ones conventionally estimated. Consideration is similarly applied to
high energy cosmic ray protons. The consequences may require the standard
assumptions on the maximum distance that very high energy radiation can travel
from to be revised.Comment: 14 pages, 1 figure, to be published in Ap J Letter
Inspecting absorption in the spectra of extra-galactic gamma-ray sources for insight into Lorentz invariance violation
We examine what the absorbed spectra of extra-galactic TeV gamma-ray sources,
such as blazars, would look like in the presence of Lorentz invariance
violation (LIV). Pair-production with the extra-galactic background light
modifies the observed spectra of such sources, and we show that a violation of
Lorentz invariance would generically have a dramatic effect on this absorption
feature. Inspecting this effect, an experimental task likely practical in the
near future, can provide unique insight on the possibility of LIV.Comment: Published in Phys. Rev.
Small scale production and storage quality of drymilled degermed maize products for tropical countries
The present study aims to propose a comprehensive appropriate technological package for small-scale processing of maize flour, which meets consumer demand for quality and achieves extended shelf life.One traditional soft cultivar was processed by the conventional method (direct grinding with disc mill) and was compared with flours obtained under various degerming and grinding intensities; two types of grinder (disc mill and hammer mill, already present on the market) were tested in parallel. Consumer satisfaction scores were registered for the different products after increasing storage duration (0 to 6 months). It was shown that combining degerming and hammer milling produce high quality flour from hard grains, which can be stored up to 6 months without significant deterioration. In parallel, physicochemical and rheological haracterizations showed that the main reaction occurring during storage is lipid degradation, which slightly increased fat acidity, hence decreasing taste and elasticity acceptability of the paste
Scanning Electron Microscopy of the Lateral Ventricle of the Pigeon Brain
Adult pigeons of both sexes were used for this study. Depending upon the distribution of various surface profiles, for example cilia, microvilli and blebs, ependymal areas with differing surface patterns were distinguished in the lateral ventricle. The topographical locations of these areas with respect to the underlying forebrain nuclei were determined in accord with the atlas of Karten and Hodos (1967). The medial surface (A) of the ventricle was much more densely ciliated than the lateral surface (B). There did not appear to be any correlation between a given surface pattern and a specific type of underlying nervous tissue. Comparison of the cell patterns seen in the pigeon brain with those seen in the analogous areas of the rat brain showed that it is not feasible to extrapolate from one zoological group to another.
With the exception of the Kolmer cells populating the choroid plexus, there were remarkably few supraependymal cells in the pigeon lateral ventricle. Supraependymal nerve fibers were also extremely rare. Particular attention was given to the ependyma associated with the nucleus stria terminalis, to that of the lateral septal organ and to the choroid plexus. The possible classification of these areas into the group of the circumventricular organs is considered
Optimisation de la fermentation en milieu semi-solide pour la production dâablo, pain cuit a la vapeur dâAfrique de lâouest
Objectif : Evaluer trois Ă©quipements pour la fermentation de la pĂąte destinĂ©e Ă prĂ©parer lâablo (pĂąte cuite Ă Â la vapeur) puis, lâinfluence de la tempĂ©rature, de la durĂ©e de fermentation et du taux de levure ajoutĂ©e Ă la pĂąte.MĂ©thodologie et rĂ©sultats : La pĂąte semi-solide a Ă©tĂ© fermentĂ©e durant quatre heures Ă tempĂ©rature ambiante (26-27 °C) dans du bac en verre, glaciĂšre et bassine en aluminium (TĂ©moin). En outre, lâeffet de la tempĂ©rature, de la durĂ©e de fermentation et du taux de levure a Ă©tĂ© Ă©valuĂ© Ă travers un dispositif factoriel complet dont les niveaux bas et hauts des facteurs rangeaient entre 2 et 6 heures, 22 et 30 °C et 1 et 3 g/Kg de farine. La pousse, le pH, lâaciditĂ© titrable et la charge en levures/moisissures ont Ă©tĂ© dĂ©terminĂ©s. A lâexception de la quantitĂ© de mousse produite et de la matiĂšre sĂšche, aucun effet significatif (P>0,05) du matĂ©riel de fermentation nâa Ă©tĂ© mis en Ă©vidence sur les paramĂštres mesurĂ©s. Le taux de levure, la tempĂ©rature et la durĂ©e de fermentation avaient une influence positive significative (P<0,05) sur la quantitĂ©Â de mousse produite.Conclusion et application : Le dispositif en verre, suivi de la glaciĂšre, avaient gĂ©nĂ©rĂ© la plus grande quantitĂ©Â de mousse, probablement Ă cause dâune relative hermĂ©ticitĂ© ou de la forme gĂ©omĂ©trique rĂ©guliĂšre des deux dispositifs. Au rendement en pĂąte voisin de 180, la fermentation dans les conditions optimales validĂ©es exigeait 30 °C, 3 g de levure par Kg de farine de riz et 4 h de conditionnement ; ce qui donne une pĂąte fermentĂ©e possĂ©dant un pH compris entre 4,42 et 4,64, une teneur de matiĂšre sĂšche variant entre 29,99 et 38,79% et la variation de hauteur de la mousse comprise entre 4,85 et 5,62 cm. Il serait intĂ©ressant de tester ces conditions optima de fermentation sur autres matiĂšres premiĂšres (maĂŻs, mĂ©lange riz-maĂŻs) intervenant dans la production dâablo.Mots clĂ©s : Ablo, levures, optimisation, fermentation, rizOptimization of semi-solid state fermentation for processing ablo, a wet steamed bread from West AfricaObjective: To test three equipments for the fermentation of rice semi-solid dough to produce ablo (a steamy and foamy bread) and then, to investigate the effect of fermentation temperature and duration and the rate of yeast on some critical parametersMethodology and results: The semi-solid dough was fermented for four hours in glass box, icebox and aluminum bowls (Control) at ambient temperature (26-27 °C). In addition, the effect of fermentation temperature and duration and the rate of yeast were investigated using full factorial design, with values ranging between 2 and 6 hours, 22 and 30 °C and 1 and 3 g/Kg flour. The pH, titrable acidity, the dry matter content and the quantity of moss/foam were determined as well as the yeast and fungi counts. Except for the moss produced and the dry matter content, no significant effect was evidenced on all other parameters measured as far as the equipment is considered. Significant and positive effects of temperature, duration and the rate of yeast (P<0.05) were observed on the quantity of moss producedConclusion and application: The glass box, followed by icebox were the best fermenting equipments of the dough, giving great amount of moss produced, probably due the airtight or the regular form of both equipments. At the dough yield of 180, the optimal values of these factors for upgrading fermentation of the rice dough included 30 °C, 3 g of yeast per Kg of flour and 4 hours of resting. These conditions was validated and lead to the fermented dough with pH ranging between 4.42 and 4.64, dry matter between 29.99 et 38.79% and moss height varying from 4.85 to 5.62 cm. In further work, it will be appreciated to test these optima conditions on maize or the mix rice-maize flour since they are raw materials for ablo productionKeywords: Yeast, optimization, fermentation, Abl
Growth of monolayer graphene on 8deg off-axis 4H-SiC (000-1) substrates with application to quantum transport devices
Using high temperature annealing conditions with a graphite cap covering the
C-face of an 8deg off-axis 4H-SiC sample, large and homogeneous single
epitaxial graphene layers have been grown. Raman spectroscopy shows evidence of
the almost free-standing character of these monolayer graphene sheets, which
was confirmed by magneto-transport measurements. We find a moderate p-type
doping, high carrier mobility and half integer Quantum Hall effect typical of
high quality graphene samples. This opens the way to a fully compatible
integration of graphene with SiC devices on the wafers that constitute the
standard in today's SiC industry.Comment: 11 pages, 4 figures , Submitted in AP
Could CODA methodology be useful in control chart techniques?
On standard control charts, the hypothesis of normality is usually assumed without any additional
veri cation. Nevertheless, in some cases this assumption is not accurate and might cause errors in
process quality monitoring. In particular, for the control of the proportion of nonconforming units
(p-chart) the normality is doubtful when p is small and consequently, lower control limit less than or
equal to zero are frequent. Some authors have proposed new techniques to de ne limits in the p-chart.
Others have proposed transformations to improve the detection of special causes
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