645 research outputs found
M. Mazoyer et L. Roudard, Histoire des agricultures du monde. Du néolithique à la crise contemporaine, 1997
No full textGrantham George W., Postel-Vinay Gilles. M. Mazoyer et L. Roudard, Histoire des agricultures du monde. Du néolithique à la crise contemporaine, 1997. In: Cahiers d'Economie et sociologie rurales, N°48, 3e trimestre 1998. pp. 129-131
Geology of the Nelson Limestone, Postel Nunatak, Patuxent Range, Antarctica
No full textPostel Nunatak in the Patuxent Range has been previously mapped as Nelson Limestone but there was no biostratigraphic support for that interpretation until now. We confirm that limestone exposures at Postel Nunatak are at least partly correlated with the Nelson Limestone of the Neptune Range, 160 km north-east, and are not correlative with the lower Cambrian Schneider Hills Limestone of the Argentina Range. Upper beds have yielded the trilobites Suludella? davnii Palmer & Gatehouse, 1972 and Solenopleura pruina Palmer & Gatehouse, 1972, which provide a basis for assignment to Cambrian Series 3 (late middle Cambrian), within the Drumian or lower Guzhangian stages. Limestone beds were deposited in a shallow marine setting, ranging from supratidal to lagoonal facies with rare subtidal intervals. These settings contrast with deeper water facies of the Neptune Range. Despite limitations in sampling density, isotopic analysis indicates that a greater than +2.5‰ shift in δ13C is consistent with δ13C trends documented for the Drumian Stage. Because the upper and lower contacts at Postel Nunatak are covered by snow and ice, the relationship with rocks mapped as the Patuxent Formation in the Patuxent Range remains uncertain, but part of it may belong to the Precambrian Hannah Ridge Formation
An analysis of the structure and performance of organic dairy farms in the Northeast, U.S.A.
No full textDue to the restructuring and trend toward consolidation that has been taking place in the dairy industry for the past several decades; the number of dairy farms in the U.S. has been steadily declining. Smaller dairy farms have been disappearing at a disproportionate rate. At the same time, demand for organic milk has been consistently rising. There is some evidence to suggest that organic dairy may be a viable economic alternative for dairy farmers, but there is little empirical evidence to verify such claims. This study analyzed the financial performance of U.S. organic dairy farms in comparison to conventional dairy farms in the Northeast, highlighted significant structural differences between profitable and unprofitable organic dairy farms, and examined the factors affecting dairy farm profitability in the Northeast. This study shows that organic dairy farms in the Northeast were profitable and that small organic dairy farms were more economically viable than small conventional dairy farms. It was found that farm size, organic milk price, production efficiency, extra income in addition to milk sales, operator's age and expectations regarding the future of the dairy enterprise, and production efficiency had a positive correlation with organic dairy farm profitability. Factors that had a negative influence on organic dairy farm profitability were variable costs per cow, the debt-to-asset ratio of the farm, the average age of the milking herd, family farm status, the hours per day the milking system was in operation, and the choice to dry off milk cows seasonally. The results suggest that transitioning to certified organic status is an economically viable alternative for small conventional dairy farms in the Northeast.M.S.Includes bibliographical references (p. 121-127)
Gel gradient electrophoresis, isoelectric focusing and two-dimensional techniques in horizontal, ultrathin polycrylamide layers
No full textAn ultrathin layer, horizontal polyacrylamide gel system for electrophoresis, isoelectric focusing and two-dimensional techniques is described. Gel slabs 240 micron thin for unidimensional, or 360 micron thin for two-dimensional runs are cast on cellophane foils as support. The sample is loaded in pockets pre-cast in the gel (2--3 microliter size) or in trenches for two-dimensional experiments. The second dimension is routinely performed in concave exponential gel gradients, spanning an acrylamide concentration from 4% to 22.5%. The sensitivity with the common Coomassie Blue stain is very high, well below 0.1 microgram protein/band. Zymogram detections can be developed within a few minutes, thus retaining the band sharpness of the focused zones or of the bands separated in pore gradient electrophoresis. Sample handling, staining and destaining and gel drying and storage are greatly simplified and performed in a fraction of the time needed for conventional, thick gels in the 1-2 mm thickness range
Geology of the Nelson Limestone, Postel Nunatak, Patuxent Range, Antarctica
No full textAbstractPostel Nunatak in the Patuxent Range has been previously mapped as Nelson Limestone but there was no biostratigraphic support for that interpretation until now. We confirm that limestone exposures at Postel Nunatak are at least partly correlated with the Nelson Limestone of the Neptune Range, 160 km north-east, and are not correlative with the lower Cambrian Schneider Hills Limestone of the Argentina Range. Upper beds have yielded the trilobitesSuludella? davniiPalmer & Gatehouse, 1972 andSolenopleura pruinaPalmer & Gatehouse, 1972, which provide a basis for assignment to Cambrian Series 3 (late middle Cambrian), within the Drumian or lower Guzhangian stages. Limestone beds were deposited in a shallow marine setting, ranging from supratidal to lagoonal facies with rare subtidal intervals. These settings contrast with deeper water facies of the Neptune Range. Despite limitations in sampling density, isotopic analysis indicates that a greater than +2.5‰ shift in δ13C is consistent with δ13C trends documented for the Drumian Stage. Because the upper and lower contacts at Postel Nunatak are covered by snow and ice, the relationship with rocks mapped as the Patuxent Formation in the Patuxent Range remains uncertain, but part of it may belong to the Precambrian Hannah Ridge Formation.</jats:p
Isoelectric focusing in immobilized pH gradients: principle, methodology and some applications
No full textA new technique for generating pH gradients in isoelectric focusing is described, based on the principle that the buffering groups are covalently linked to the matrix used as anticonvective medium. For the generation of this type of pH gradient in polyacrylamide gels, a set of buffering monomers, called Immobiline (in analogy with Ampholine), is used. The pH gradient gels are cast in the same way as pore gradient gels, but instead of varying the acrylamide content, the light and heavy solutions are adjusted to different pH values with the aid of the Immobiline buffers. Available Immobiline species make it possible to generate any narrow linear pH gradient between pH 3 and 10. The behaviour of these types of gradients in isoelectric focusing is described. Immobilized pH gradients show a number of advantages compared with carrier ampholyte generated pH gradients. The most important are: (1) the cathodic drift is completely abolished; (2) they give higher resolution and higher loading capacity; (3) they have uniform conductivity and buffering capacity; (4) they represent a milieu of known and controlled ionic strength
Entre linhas
No full textIn a publication on current science, an author is included whose author, Olivier Postel-Vinay (2003), following the opinion of what he calls "a surgeon of the spirit", Adolf Grübaum, questions the relevance of the Freudian discovery.En una publicación sobre la actualidad de la ciencia se incluye un artícilo cuyo autor, Olivier Postel-Vinay (2003), siguiendo la opinión de quien él llama "un cirujano del espíritu", Adolf Grübaum, cuestiona la pertinencia del descubrimiento freudiano.Em uma publicação sobre a ciência atual, é incluído um autor cujo autor, Olivier Postel-Vinay (2003), seguindo a opinião do que ele chama de "cirurgião do espírito", Adolf Grübaum, questiona a relevância da descoberta freudiana
La faucille et la faux.
No full textThe sickle and the scythe. An instance of path dependence -
The morphological characteristics of the domesticated cereals have been affected by the techniques of harvest at the time they were domesticated. Wheat was domesticated under the regime of the sickle; oats under the much later regime of the scythe. Because the sickle selected for a comparatively loose attachment of the seed to the stalk, while the scythe for a strong attachment, farmers could not profitably employ the more rapid technique of scything in harvesting the bread cereals without suffering unacceptable loss of seed from spillage. At the same time, there was no reason to employ the sickle to reap oats when they could be more efficiently mowed using the scythe. The simultaneous use of both techniques in harvesting the small grains is a case of path dependence, in which an initial condition - here the difference in the date at which the cereals were domesticated - had long-lasting consequences for the technology and economic organization of the grain harvest.Les céréales cultivées ont tiré certaines de leurs caractéristiques de la façon dont elles étaient récoltées lors de leur domestication - à la faucille pour le blé, à la faux pour l'avoine. Comme le choix de la faucille allait de pair avec celui de grains dont l'attache à la tige était plus fragile, les cultivateurs n'ont ensuite pu moissonner le blé qu'à la faucille. La faux, plus rapide, aurait provoqué trop de pertes et n'était donc utilisée que pour l'avoine. La coexistence de ces deux instruments est un exemple frappant de dépendance temporelle dans la mesure où les conditions initiales - ici le fait que la domestication du blé est antérieure de plusieurs millénaires à celle de l'avoine - ont eu des conséquences très durables sur le choix des techniques et sur l'organisation sociale en Europe du néolithique au XIXe siècle.Grantham George W., Adam Michel, Postel-Vinay Gilles. La faucille et la faux. In: Études rurales, n°151-152, 1999. Autres temps, autres lieux. pp. 103-131
Severance Packages
Get PDFJob-to-job turnover provides a way for employers to escape statutory firing costs, as unprofitable workers may willfully quit their job on receiving an outside offer, thus sparing their incumbent employer the firing costs. Furthermore, employers can induce their unprofitable workers to accept outside job offers that they would otherwise reject by offering voluntary severance packages, which are less costly than the full statutory firing cost. We formalize those mechanisms within an extension of the Diamond-Mortensen-Pissarides (DMP) matching model that allows for employed job search and negotiation over severance packages. We find that, while essentially preserving most standard qualitative predictions of the DMP model without employed job search, our model explains why higher firing costs intensify job-to-job turnover at the expense of transitions out of unemployment. We further find that allowing for on-the-job search markedly changes the quantitative predictions of the DMP model regarding the impact of firing costs on unemployment and employment flows: ignoring on-the-job search leads one to strongly underestimate the negative impact of firing costs on unemployment.firing costs, on-the-job search, mutual consent, minimum wage
Microeconometric search-matching models and matched employer-employee data
No full textThe recent advent of matched employer-employee data as part of the labor market scholar’s
toolbox has allowed a great deal of progress in our understanding of individual labor earnings.
A growing number of empirical analyzes of available matched employer-employee
data sets now combine with the already voluminous literature on empirical wage equations
based on individual or household survey data to draw an ever richer picture of wage
dispersion, individual wage dynamics, and the productivity-wage relationship.
In this chapter we tour the empirical wage equations literature along these three lines
and make a case that viewing it through the lens of structural job search models can
help clarify and unify some of its recurring findings. Among other things, we emphasize
and quantify the role of matching frictions in explaining the share of “residual” wage
dispersion that is left unexplained by the reduced-form approach. Secondly, we quantitatively
assess the importance of labor market competition between employers relative
to non-competitive wage formation mechanisms (namely, wage bargaining) as a theoretical
underpinning of the wage-productivity relationship. Thirdly, we show how search
frictions combined with a theoretically founded wage formation rule based on renegotiation
by mutual consent can account for the widely documented dynamic persistence of
individual wages. We conclude with a list of questions that are open to further research
- …
