Plasma wake inhibition at the collision of two laser pulses in an underdense plasma

An electron injector concept for laser-plasma accelerator was developed in ref [1] and [2] ; it relies on the use of counter-propagating ultrashort laser pulses. In [2], the scheme is as follows: the pump laser pulse generates a large amplitude laser wakefield (plasma wave). The counter-propagating injection pulse interferes with the pump laser pulse to generate a beatwave pattern. The ponderomotive force of the beatwave is able to inject plasma electrons into the wakefield. We have studied this injection scheme using 1D Particle in Cell (PIC) simulations. The simulations reveal phenomena and important physical processes that were not taken into account in previous models. In particular, at the collision of the laser pulses, most plasma electrons are trapped in the beatwave pattern and cannot contribute to the collective oscillation supporting the plasma wave. At this point, the fluid approximation fails and the plasma wake is strongly inhibited. Consequently, the injected charge is reduced by one order of magnitude compared to the predictions from previous models.Comment: 4 pages, 4 figure

Repetition and difference: Lefebvre, Le Corbusier and modernity's (im)moral landscape: a commentary

This article engages with the relationship between social theory, architectural theory and material culture. The article is a reply to an article in a previous volume of the journal in question (Smith, M. (2001) ‘Repetition and difference: Lefebvre, Le Corbusier and modernity’s (im)moral landscape’, Ethics, Place and Environment, 4(1), 31-34) and, consequently, is also a direct engagement with another academic's scholarship. It represents a critique of their work as well as a recasting of their ideas, arguing that the matter in question went beyond interpretative issues to a direct critique of another author's scholarship on both Le Corbusier and Lefebvre. A reply to my article from the author of the original article was carried in a later issue of the journal (Smith, M. (2002) ‘Ethical Difference(s): a Response to Maycroft on Le Corbusier and Lefebvre’, Ethics, Place and Environment, 5(3), 260-269)

Quasimonoenergetic electron beams produced by colliding cross-polarized laser pulses in underdense plasmas

The interaction of two laser pulses in an underdense plasma has proven to be able to inject electrons in plasma waves, thus providing a stable and tunable source of electrons. Whereas previous works focused on the "beatwave" injection scheme in which two lasers with the same polarization collide in a plasma, this present letter studies the effect of polarization and more specifically the interaction of two colliding cross-polarized laser pulses. It is shown both theoretically and experimentally that electrons can also be pre-accelerated and injected by the stochastic heating occurring at the collision of two cross-polarized lasers and thus, a new regime of optical injection is demonstrated. It is found that injection with cross-polarized lasers occurs at higher laser intensities.Comment: 4 pages, 4 figure

Modification de la matière organique lors des traitements conventionnels de potabilisation

La filtration successive des eaux, préalablement filtrées sur membrane de porosité 0,45 µm puis acidifiées à pH 2, sur deux colonnes de résines XAD8 et XAD4 placées en série, caractérise la matière organique en trois grandes classes : les substances hydrophobes, les acides hydrophiles et les hydrophiles non retenus. Cette étude s'est intéressée à déterminer et à analyser l'impact sur la distribution hydrophobe/hydrophile des traitements conventionnels utilisés dans les usines de production d'eau potable.En ce qui concerne l'effet de la clarification, la distribution hydrophobe/hydrophile du COD a été inchangée dans le cas de sept prélèvements sur dix, indiquant une isoélimination de chaque fraction. Dans le cas des eaux R1.2, R4 et R6.1, une diminution de la fraction hydrophobe est obtenue entre l'eau brute et son eau clarifiée. L'étude de différents coagulants indique que la distribution de la matière organique des eaux clarifiées dépend de sa composition initiale mais aussi de la nature du coagulant mis en oeuvre. Le chlorure ferrique permet une meilleure élimination de chaque fraction comparativement à un sel d'aluminium.Un traitement d'oxydation à un taux de 1,5 mg Oxydant/mg COD et quel que soit l'oxydant mis en oeuvre (O3, Cl2, ClO2) diminue significativement les substances hydrophobes et augmente les substances hydrophiles. Ces résultats sont logiques si nous nous référons au mode d'action de ces trois oxydants. L'ozonation d'eaux brute et clarifiée s'accompagne aussi d'une augmentation du CODB, soulignant que les substances hydrophiles générées par l'étape d'ozonation seraient biodégradables.Des campagnes de prélèvements ont indiqué que les traitements de finition (ozonation, filtration sur CAG) en configuration industrielle ont une légère influence sur la distribution interne de la matière organique. Les résultats, du fait de taux de traitement plus faibles, sont moins nets que ceux obtenus en laboratoire. Une filtration sur CAG, précédée d'une étape d'ozonation, conduit à une augmentation de la fraction hydrophobe et à une diminution du CODB.Dissolved organic matter (DOM) in natural waters is a mixture of compounds. Some authors have fractionated this organic matter into large classes (humic substances, hydrophilic acids . . .). Humic substances have been defined as the fraction of organic matter retained on XAD8 resin at acidic pH (THURMAN and MALCOLM 1981); this isolation procedure is recommended by the International Humic Substances Society. Only a few investigators have dealt specifically with hydrophilic substances which are not adsorbed on XAD8 resin at acidic pH. The "hydrophobic/hydrophilic" distribution can be determined by a simple method of organic matter fractionation, using two superimposed XAD8 and XAD4 resin columns (CROUE et al. 1993). This procedures, carried out at pH 2, consists of first isolating hydrophobic substances (essentially humic acids) on an XAD8 resin and then isolating the hydrophilic acids from the XAD8 effluent on an XAD4 resin.The aim of this work was to study the evolution of the hydrophobic/hydrophilic distribution during water treatment steps as applied in waterworks. The analytical procedure was first applied to determine the change in the DOM distribution of ten surface waters after clarification. The results obtained after clarification were completed by the study of the effect of the coagulant nature (ferric chloride, aluminium sulphate, prehydrolyzed salt (WAC)). In the second phase, oxidation experiments using ozone, chlorine and chlorine dioxide were conducted on raw and clarified waters to determine their effect on the DOM distribution. Finally the fractionation procedures were carried out on two water treatment plants to compare our laboratory data with results obtained in a working plant and to observe the change in DOM distribution during granular activated carbon (GAC) filtration.Dissolved organic carbon (DOC) concentrations were analysed using a Dohrman DC 80 apparatus. UV absorbance was measured with a one or five centimeter cell using an Uvikon spectrophotometer. Oxidation experiments were carried out in a batch procedure. The study of different coagulants was made in the laboratory with a Jar Test procedure described elsewhere (LEFEBVRE 1990). Biodegradable dissolved organic carbon (BDOC) was analyzed according to the suspended bacteria method (SERVAIS et al. 1987, 1989).The hydrophobic/hydrophilic distributions of raw and clarified waters were found to be unchanged by the clarification step in seven of ten test waters. These results indicate that for a studied water, the relative reduction in DOC of one fraction was of the same order of magnitude as the other fraction. The distributions of R1.2, R4 and R6.1 were significantly modified by the clarification treatment. In these three cases, the hydrophobic substances showed the greater DOC reduction. The "non-retained" hydrophilic substances became predominant in the R6.1 clarified water, whereas in the cases of R4 and R1.2 the total hydrophilic fraction and the hydrophilic acids increased, respectively.The results obtained in the laboratory on three different raw waters, clarified by different coagulants (ferric chloride or aluminium salts), showed that the nature of the coagulant (iron or alum) can influence the hydrophobic/hydrophilic distribution. A marked influence was found in the case of R6 and less significant results were obtained for R1.2. Powdered activated carbon had no real effect on the DOC distribution, under our experimental conditions (applied dosage 25 mg/L). If the removal of each fraction is considered, and if it is assumed that each removal is independent from the others, ferric chloride appears to be the best coagulant. It removes humic substances efficiently as well as hydrophilic acids (> 72%), but is less efficient for the "non-retained" hydrophilic fraction. The DOC distribution of a clarified water depends on the distribution in the original raw water and the nature of the coagulant.Under our experimental conditions (applied dosage: 1.5 mg oxidant / mg DOC), ozone, chlorine and chlorine dioxide significantly affected the DOM distribution of the R1.2 water. The hydrophobic substances showed the higher relative DOC reduction, which can be correlated with an increase in the hydrophilic fraction. The greatest change was obtained for treatment with ozone. In the case of chlorine and chlorine dioxide, an increase of the "non-retained" hydrophilic fraction was observed whereas for ozone the two hydrophilic fractions increased. These results are in agreement with current knowledge about the action of ozone, chlorine and chlorine dioxide.An increase in the BDOC fraction was observed with the applied ozone dosage. In the case of R1, ozonation of raw and clarified waters appeared to shift the dissolved organic carbon distribution towards the "non-retained" hydrophilics. A good correlation exists between the BDOC increase (BDOC/BDOCo) and the decrease of hydrophobic acids or the increase of "non-retained" hydrophilics (slopes are respectively 12.3 ; - 16.5 and 15.5). In the case of another sample of R1.2, the comparison of BDOC in the XAD4 effluents of raw and ozonated waters indicated that at least 62% of BDOC produced by ozonation was in this fraction. This result indicates that the "non-retained" hydrophilics of this raw water are not biodegradable compared with those induced by ozonation.Results obtained on samples taken on two water treatment plants indicate that ozonation and GAC filtration have a small effect on the hydrophobic/hydrophilic DOM distribution. Intermediate ozonation at the industrially applied dose slightly modifies the distribution; a slight decrease of hydrophobic substances is observed. GAC filtration induces an increase of the hydrophobic fraction. The water treatment process includes clarification (EFS), inter-ozonation (EFSO3), and GAC filtration (EFCAG). GAC filters A and B had been respectively running for one and three years; filter C has been regenerated one month before. Good organic matter removal is obtained during clarification (removal of DOC and UV-absorbance: 75% and 88%). This treatment step changes the DOM distribution: increase of the hydrophobic fraction and decrease of the hydrophilic fraction. BDOC was completely removed. Intermediate ozonation (0.7 mg O3/mg DOC) modifies the DOC distribution and creates BDOC. This BDOC, in absolute value (0.36 mg/l), is equal to the increase of hydrophilic fraction. On the oldest filters (A and B) BDOC was completely removed, but this was not the case for filter C, probably because the bacterial biomass was insufficient. On GAC filters hydrophilic substances were found to be better removed than humic substances. The age of the GAC bed seems to have an effect on DOC distribution: the effluent from the oldest GAC filter contained less of the hydrophobic fraction than did the effluent from the youngest filter

The Collaborative Development of New CFD Methods Adapted for Tilt Rotor Aircraft in the HiPerTilt Project

No abstract available

Tuning the exciton g-factor in single InAs/InP quantum dots

Photoluminescence data from single, self-assembled InAs/InP quantum dots in magnetic fields up to 7 T are presented. Exciton g-factors are obtained for dots of varying height, corresponding to ground state emission energies ranging from 780 meV to 1100 meV. A monotonic increase of the g-factor from -2 to +1.2 is observed as the dot height decreases. The trend is well reproduced by sp3 tight binding calculations, which show that the hole g-factor is sensitive to confinement effects through orbital angular momentum mixing between the light-hole and heavy-hole valence bands. We demonstrate tunability of the exciton g-factor by manipulating the quantum dot dimensions using pyramidal InP nanotemplates

Medicaid spending burden among beneficiaries with treatment-resistant depression.

AIM: To evaluate Medicaid spending and healthcare resource utilization (HRU) in treatment-resistant depression (TRD). MATERIALS & METHODS: TRD beneficiaries were identified from Medicaid claims databases (January 2010-March 2017) and matched 1:1 with major depressive disorder (MDD) beneficiaries without TRD (non-TRD-MDD) and randomly selected patients without MDD (non-MDD). Differences in HRU and per-patient-per-year costs were reported in incidence rate ratios (IRRs) and cost differences (CDs), respectively. RESULTS: TRD beneficiaries had higher HRU than 1:1 matched non-TRD-MDD (e.g., inpatient visits: IRR = 1.41) and non-MDD beneficiaries (N = 14,710 per cohort; e.g., inpatient visits: IRR = 3.42, p \u3c 0.01). TRD beneficiaries incurred greater costs versus non-TRD-MDD (CD = US$4382) and non-MDD beneficiaries (CD = US$8294; p \u3c 0.05). CONCLUSION: TRD is associated with higher HRU and costs versus non-TRD-MDD and non-MDD. TRD poses a significant burden to Medicaid

The Urban Political Ecology of Post-industrial Scottish Towns: Examining Greengairs and Ravenscraig

Urban ecological politics is shaped by both moments of concerted action and more silent perceptions and responses. Instead of only being evident in situations of organised protest, the politics of urban ecology is also manifested, in material and symbolic terms, in the daily life of the residents. The fragmentation of urban political ecology turns out to be an important element in the affirmation of post-political forms of urban governance. Those issues were the object of fieldwork research carried out in Greengairs and Ravenscraig, two towns in North Lanarkshire, near Glasgow, with the goal of unravelling the understanding and the coping mechanisms of environmentally deprived residents. The towns are permeated by a widespread, often dissimulated, political ecology that is nonetheless always present. Empirical results demonstrate that a more comprehensive handling of the political ecology of the urban is crucial in order to halt the sources of marginalisation and ecological degradation