Labor Court Inputs, Judicial Cases Outcomes and Labor Flows: Identifying Real EPL.

Using a data set of individual labor disputes brought to court over the years 1990 to 2003 in France, we examine the impact of the enforcement of Employment Protection Legislation on labor market outcomes. First, we present a simple theoretical model showing that judicial case outcomes cannot be directly interpreted in terms of EPL. A large fraction of cases that go to trials may well be a sign of low firing costs when firms face low litigation costs and are therefore willing to go to court or a sign of high firing costs when workers face low litigation costs and are therefore willing to sue the firm. Second, we exploit our model as well as the French institutional setting to generate instruments for these endogenous outcomes. Using these instruments, we show that labor courts decisions have a causal effect on labor flows. More dropped cases and more trials cause more job destructions: more trials indeed are a sign of lower separation costs. More settlements, higher filing rates, a larger fraction of workers represented at trial, large lawyer density dampen job destruction. A larger judge density causes less job creation, in particular on the extensive margin.Employment protection legislation, Labor flows, Labor judges, Unfair dismissal, France

Cyclical budget balance measurement

Government balances are often adjusted for changes in economic activity in order to draw a clearer picture of the underlying fiscal situation and to use this as a guide to fiscal policy analysis. International organisations estimate the cyclical component of economic activity by the current level of the output gap. Using elasticities of tax and public expenditures to GDP, they compute the cyclical part of budget balance. The structural budget balance is defined as the remainder. Our approach is different, as it rests on the estimation of a bivariate VAR. Variables used are the budget balance in percents of GDP, and the annual rate of growth of GDP. The structural part of the budget balance is defined as the one which would have occurred had GDP never deviated from its trend. Hence, past business cycles affect the cyclical part of the budget balance, contrary to what more traditional methods assume. In our method, systematic cyclical policies de facto affect the cyclical balance. Our estimated changes in structural balances are consistent with previous methods, given the fairly large standard errors. However, these methods yield significantly different predictions at the peaks and troughs of business cycles : according to our method, structural balances consolidated by more in 1990-1991 and deteriorated by more in 1994-1995.fiscal policy, VAR, cycles, structural budget balance

Transverse instability of the antiproton beam in the Recycler Ring

The brightness of the antiproton beam in Fermilab's 8 GeV Recycler ring is limited by a transverse instability. This instability has occurred during the extraction process to the Tevatron for large stacks of antiprotons even with dampers in operation. This paper describes observed features of the instability, introduces the threshold phase density to characterize the beam stability, and finds the results to be in agreement with a resistive wall instability model. Effective exclusion of the longitudinal tails from Landau damping by decreasing the depth of the RF potential well is observed to lower the threshold density by up to a factor of two.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1 Apr 2011. New York, US

Modélisation de l'hydrodynamique d'un décanteur primaire de station d'épuration

Les qualités de fonctionnement d'un décanteur primaire de station d'épuration d'eaux usées dépendent essentiellement de ses caractéristiques hydrauliques. Le but de ce travail est la caractérisation et la modélisation de l'hydrodynamique d'un décanteur réel d'une station d'épuration d'eaux usées urbaines.Cette opération s'effectue par la détermination de la Distribution des Temps de Séjour (DTS) de la phase liquide du décanteur par traçage au chlorure de lithium. Simultanément, les évolutions des débits d'effluent à traiter et des rendements d'épuration en Matières En Suspension (MES) ont été suivis.La courbe de DTS obtenue a permis une modélisation de l'hydrodynamique du décanteur primaire par des associations en série ou en parallèle de Réacteurs Parfaitement Agités (RPA). Le modèle hydrodynamique proposé, dont les résultats sont en très bonne concordanoe avec les résultats expérimentaux, est composé de 2 branches associées en parallèle: l'une traversée par une fraction a = 0,14 d'effluent entrant dans le décanteur est une cascade de 7 RPA d'un volume total de 77 m3. L'autre branche traversée par la fraction de débit restante (l-a) est composée de 2 modules en série: le premier module, caractérisant une zone de recirculation, est un RPA de 645 m3 en échange avec un second RPA de 1935 m3, la fraction de débit ß échangée est de 28. Le deuxième module de cette branche, représentant un écoulement uniforme, est une cascade de 7 RPA d'un volume total de 1 183 m3.Ce modèle hydrodynamique permet d'analyser les résultats obtenus quant à l'évolution des rendements d'épuration en MES mesurés dans le décanteur.The operating performances of wastewater treatment plant primary clarifiers essentially depend on hydraulic conditions. The aim of this paper is to characterize and to simulate the hydraulic flow regime of an existing sedimentaton tank.This study was carried out on a wastewater treatment plant primary clarifier. It is a circular clarifier of 3900 m3 in volume, 42 m in diameter, 2.1 m in straight useful height, and, 2.1m in height for the conical part. The inlet flow rate is between 1400 and 2700 m3/h, whereas the sequental (3 primary clarifiers) sludge extraction flow rate is about 20 m3/h.To characterize the liquid phase residence time distribution (RTD) in the clarifier, we did a tracing operation (pulse injection) with lithium chloride as tracer (20 kg of lithium chloride dissolved in 120 litres of tap-water). After the tracer injection, the lithium concentration at the outlet of the clarifier was measured as a function of time. During this experiment we also followed the evolution of inlet flow rates and the suspended solid (SS) retention efliciency ofthe clarifier. For 350 min of experimental time, the recuperation of lithium was 92.7%.The experimental RTD curve allowed us to develop a model for the primary clarifier hydrodynarnics by association of elementary units (completely stirred reactors, CSTR) in series or in parallel. The transfer function in the LAPLACE domain, G (s), and the mathematical expressions of the first order and second central order moments were determined for this model. The nurnerical simulation of RTD between the inlet and the outlet of the system was performed with the help of a general computer code which numerically calculates the RTD, using Fast Fourier Trandormation techniques, from a given transfer fucnction.The hydrodynamic model proposed in this study matches very well with the experimental results. It comprises two trranches associated in parallel. The first one, which is drived by an effluent flow rate fraction α (α=0,14), is treated as 7 CSTR's in series of 77 m3 in total volume. The second branch, which is drived by the remaining eflluent flow rate fraction (1-α), is composed of two modules associated in series. The first module, which characterizes a recycling zone, is treated as a CSTR of 645 m3 in volume exchanging with a second CSTR of 1935 m3 in volume, the exchanged flow rate fraction, ß, being equal to 28. The second module of this branch. which characterize a uniform flow zone, is represented by 7 CSTR's in series of 1183 m3 in total volume.These results are confirmed by the comparison of the first order and the second central order moments. Indeed, between t = 0 and t = 350 min., we find for the experimental curve µ1=l27 min and µ2=6957, and, for the proposed hydrodynamic model curve µ1=129 min and µ2=7154 which are equivalent values. Finally, the proposed hydrodynamic model makes possible the analysis of the primary clarifier performance with respect to suspended solid removal

Factors Responsible for the Stability and the Existence of a Clean Energy Gap of a Silicon Nanocluster

We present a critical theoretical study of electronic properties of silicon nanoclusters, in particular the roles played by symmetry, relaxation, and hydrogen passivation on the the stability, the gap states and the energy gap of the system using the order-N [O(N)] non-orthogonal tight-binding molecular dynamics and the local analysis of electronic structure.Comment: 26 pages including figure

Influence d'une alimentation séquentielle sur l'épuration par boues activées d'un effluent fortement chargé

Cet article présente les résultats d'une étude menée sur le traitement d'effluents fortement chargés (DCO > 1,5 kg.m-3) par un procédé à boues activées. L'objectif principal de ce travail est de montrer qu'une alimentation séquentielle d'un réacteur parfaitement agité avec maintien permanent du recyclage des boues et de l'oxygénation permet d'obtenir une bonne épuration tant du point de vue de l'élimination de la pollution carbonée que de la maîtrise de la décantabilité des flocs microbiens. Les essais sont menés sur un pilote de laboratoire constitué d'une colonne à bulles et d'un décanteur, alimenté avec un substrat synthétique. Contrairement à une alimentation continue, la mise en place de cycles d'alimentation permet d'obtenir des flocs de bonne décantabilité de manière constante dans le temps. Ainsi une concentration élevée en biomasse peut être maintenue dans le réacteur. De plus, le suivi d'un cycle 1 h/1 h confirme que la mise en œuvre d'un cycle court n'entraîne pas de variations importantes des performances d'épuration. Par ailleurs, le suivi d'un long cycle (24 h/24 h) montre des variations significatives des concentrations en DCO, polysaccharides dans la phase liquide et exopolysaccharides dans les flocs microbiens. Ceci semble indiquer que des produits microbiens sont relargués des flocs vers la phase liquide pendant l'arrêt de l'alimentation et que des exopolysaccharides sont produits dans les flocs pendant l'alimentation.The overall efficiency of an activated sludge wastewater treatment system depends both on the ability of the activated sludge culture to remove the soluble organic pollution and on the efficiency of the separation of the treated water from the biomass. In the treatment of a high-strength wastewater (COD > 1.5 kg .m-3), ultrafiltration or crossflow filtration systems can sometimes substitute for the final clarifier, the separation of the sludge from the effluent water being very good regardless of changes in sludge settleability. Because of the high pollutant concentrations, the biomass must be more concentrated in the bioreactor than in the usual aerobic processes (10 to 20 kg.m-3 rather than 4 kg.m-3), whatever the separation system (settler or filtration system). Thus, with this biomass concentration, the volumetric loading rate can be increased while the organic loading rate is maintained at a low level.The use of a clarifier is preferable because it is cheaper than ultrafiltration or crossflow filtration systems, which have very high investment and operation costs, on the other hand, and some fouling problems, on the other hand. However, its use requires a very good biomass settleability. Results from the literature show that there is no general relation between sludge settleability and such wastewater treatment operating parameters as dissolved oxygen concentration in the aeration basin, organic loading rates, pH, or low relative influent nitrogen and phosphorus contents. On the other hand, the separation ability of the clarifier depends on the hydraulic configuration of the aerated reactor: biomass settleability can be controlled by completely stirred reactors in series, plug-flow reactors or intermittently-fed systems. Indeed, this spatial or temporal staggering should allow microorganisms to consume their accumulated substrate and thus restore their accumulation capacity. In the case of high-strength wastewater treatment, temporal staggering is better than spatial staggering. Indeed, higher organic loading rates require a higher number of reactors. Thus, the COD concentration significantly increases in the first reactors of the cascade and some toxic or inhibitory problems could appear. For this reason, a temporal staggering was chosen.Biomass settleability is linked to the extracellular polymers that are the third component of the sludge flocs, after the cells and the water. These polymers are composed largely of microbial exopolysaccharides. Measurements of exopolysaccharides could be used to characterize sludge settleability. A too low level of exopolysaccharides indicates a sludge defloculation problem, whereas a too high level of exopolysaccharides means that sludge settleability could be hindered because of an excessive growth of filamentous organisms.The purpose of the present work is to show that the use of only one completely stirred reactor, fed in a cyclic way with permanent oxygenation and return sludge flow, leads to good sludge settleability and effluent quality. The experiments have been performed with a laboratory pilot-plant composed of a 11.3 litre bubble column, which is a completely stirred reactor, and a secondary settling tank of 14.8 litres. The reactor is fed with an equilibrated synthetic substrate consisting mainly of meat extract, saccharose and ethanol (COD:N:P=100:5:1 and 1 kg COD=1 kg meat extract + 0.444 kg saccharose + 0.2 kg ethanol). The feeding cycle is a set of consecutive periods of feeding and starvation. For example, during a 1h/2h feeding cycle, the substrate feeding is continuous during 1 hour and stopped during 2 hours.The sludge comes from the Nancy-Maxéville wastewater treatment plant and its acclimation to the synthetic substrate begins with an aeration without feeding during 12 hours. Afterwards, the experimental system is fed during 1 hour every 2 hours with the substrate (first concentration of COD=0.1 kg.m-3). Then, the inlet COD is increased by steps of 0.1 kg.m-3 every day until the required concentration is reached. Once the biomass is acclimated to the influent and sufficiently concentrated, the experiment can begin.In order to show the positive influence of cyclic feeding on wastewater treatment quality, we have carried out one experiment with continuous feeding and two experiments with cyclic feeding (see Table 1). For these experiments, the volumetric loading rate is about 4 kg COD.m-3.d-1. With an appropriate feeding cycle, the settleability of the sludge and the effluent quality remain good: the diluted sludge volume index is 56 cm3.g-1 and 96% of the inlet COD is removed. Thus, the biomass concentration remains high in the reactor (19 kg.m-3). This is not the case with a continuous feeding where the biomass settleability rapidly deteriorates. The principal advantage of sequential feeding is the maintenance of good sludge settleability and a high biomass concentration in the aeration basin. Moreover, during the short feeding cycles, the variations of the concentrations of COD, polysaccharides in the bulk phase and extracellular polysaccharides in the microbial aggregates are very low. This augurs well for system stability.In contrast, monitoring of a long cycle (24 h of feeding and 24 h of starvation) shows great variations in the concentrations of COD, polysaccharides and extracellular polysaccharides in the system. When the feeding is stopped, the COD and polysaccharide concentrations in the bulk phase increase whereas the exopolysaccharide concentration in sludge flocs decreases. Reciprocally, after the feeding is begun, the COD and polysaccharide concentrations in the bulk phase decrease, and then remain constant, whereas the exopolysaccharide concentration increases. As 1 kg of measured polysaccharides represents 0.9 kg COD, and as in the bulk phase the COD concentration is equivalent to 4 times the polysaccharide concentration, it seems that microbial products other than polysaccharides are released in the bulk phase during starvation, these products being slowly biodegradable. Extracellular polysaccharides in the microbial aggregates are formed during the feeding phase

Anomalous fluctuations of active polar filaments

Using a simple model, we study the fluctuating dynamics of inextensible, semiflexible polar filaments interacting with active and directed force generating centres such as molecular motors. Taking into account the fact that the activity occurs on time-scales comparable to the filament relaxation time, we obtain some unexpected differences between both the steady-state and dynamical behaviour of active as compared to passive filaments. For the statics, the filaments have a {novel} length-scale dependent rigidity. Dynamically, we find strongly enhanced anomalous diffusion.Comment: 5 pages, 3 figure

Self-organized Beating and Swimming of Internally Driven Filaments

We study a simple two-dimensional model for motion of an elastic filament subject to internally generated stresses and show that wave-like propagating shapes which can propel the filament can be induced by a self-organized mechanism via a dynamic instability. The resulting patterns of motion do not depend on the microscopic mechanism of the instability but only of the filament rigidity and hydrodynamic friction. Our results suggest that simplified systems, consisting only of molecular motors and filaments could be able to show beating motion and self-propulsion.Comment: 8 pages, 2 figures, REVTe

An experimental test of the dose-dependent effect of carotenoids and immune activation on sexual signals and antioxidant activity.

Carotenoid-based sexual traits are thought to be reliable indicators of male quality because they might be scarce and therefore might indicate the ability of males to gather high-quality food and because they are involved in important physiological functions (as immune enhancers and antioxidants). We performed an experiment where male and female zebra finches (Taeniopygia guttata) were provided with increasing carotenoid doses in the drinking water during 4 weeks (bill color of this species is a carotenoid-based sexual signal). Simultaneously, birds were split into two groups: one receiving weekly injections of Escherichia coli lipopolysaccharide in order to activate the immune system, the other being injected with the same volume of phosphate buffered saline. We assessed how carotenoid availability and immune activation affected the amount of circulating plasma carotenoids, the beak color, and the antioxidant defenses (assessed as the resistance of red blood cells to a controlled free radical attack). Carotenoid availability affected the amount of circulating carotenoids and beak color; both variables reached a plateau at the highest carotenoid doses. Immune activation diverted carotenoids from plasma, and this in turn affected the expression of the sexual trait. Finally, we found a positive correlation between the change in circulating carotenoids and antioxidant defenses. These results support the idea that carotenoids have important physiological properties that ensure the honesty of carotenoid-based sexual traits