Experimental evidence for fast cluster formation of chain oxygen vacancies in YBa2Cu3O7-d being at the origin of the fishtail anomaly

We report on three different and complementary measurements, namely magnetisation measurements, positron annihilation spectroscopy and NMR measurements, which give evidence that the formation of oxygen vacancy clusters is on the origin of the fishtail anomaly in YBa2Cu3O7-d. While in the case of YBa2Cu3O7.0 the anomaly is intrinsically absent, it can be suppressed in the optimally doped state where vacancies are present. We therefore conclude that the single vacancies or point defects can not be responsible for this anomaly but that clusters of oxygen vacancies are on its origin.Comment: 10 pages, 4 figures, submitted to PR

Identification de composés génotoxiques dans les eaux de boisson

Depuis la mise en évidence de trihalométhanes dans les eaux potables en 1974, de multiples travaux ont démontré la présence de nombreux composés génotoxiques dans l'eau de boisson. L'eau potable obtenue à partir d'eau de surface subit un traitement incluant généralement une étape de chloration. Il est aujourd'hui largement admis que l'activité génotoxique des eaux de boisson provient principalement de la chloration des substances humiques, composés organiques naturels contenus dans l'eau brute et issus de la dégradation des déchets animaux et végétaux. Les très faibles concentrations en composés génotoxiques dans les eaux potables nécessitent la concentration des échantillons, procédé qui risque toutefois de modifier la génotoxicité. Plusieurs tests mettant en oeuvre des cellules procaryotes ou eucaryotes, des plantes ou des mammifères, ont permis de mettre en évidence les effets génotoxiques dans des eaux potables chlorées. L'identification des composés génotoxiques est réalisée au moyen des données de la spectrométrie de masse et de la spectroscopie UV ou RMN (proton ou carbone). Ces agents sont généralement non volatils, acides et polaires. Bien que certains composés inorganiques interviennent parfois, la majeure partie de la génotoxicité est attribuée aux agents organohalogénés (bromés ou/et chlorés), les principaux étant les trihalométhanes, acides acétiques, acétonitriles, cétones, et hydroxyfuranones. La fixation de normes contribue à limiter l'exposition des populations aux agents potentiellement dangereux. La qualité des eaux de boisson peut être accrue en utilisant une eau brute moins chargée en matière organique, et en améliorant le traitement chimique tout en veillant à conserver la qualité microbiologique de l'eau produite.In 1974, two independent studies - one in the Netherlands and the other in the United States - demonstrated the occurrence of trihalomethanes in drinking water. Following studies showed that these chemicals were common contaminants of drinking water and that chloroform, i.e. one of these trihalomethanes, was carcinogenic in rodents. Further investigations demonstrated that extracts of chlorinated drinking water induced significant mutagenicity in the Ames/Salmonella assay. In the present paper we will fist discuss the methods used to detect the genotoxic activity of drinking water and, then, the methods developed to identify the compounds responsible for this activity. After this, we will present the main genotoxic chemicals identified in drinking water, before finally considering several propositions to limit the exposure of populations to these genotoxic compounds.Drinking water is usually produced through a multistage process which includes one or several chlorination steps. It is now widely accepted that the genotoxic activity of drinking water mainly originates from the reaction of chlorine with humic substances present in raw water. Humic substances are natural organic matters (resulting from the degradation of plants and animal tissues) of very complex structure with most chemical functions arranged in aromatic rings or aliphatic chains. The identification of a genotoxic activity in drinking water usually requires concentration of the water samples. Even though such a process implies a probable qualitative/quantitative alteration of the constituents of water samples, the extremely low amounts of genotoxic compounds in drinking water require concentration steps. Among the many genotoxicity tests carried out, the Ames test (which detects reverse mutations in bacteria Salmonella typhimurium) is the assay which was the most frequently used in the field of drinking water mutagenicity. Other tests were performed on eucaryotic cells. Assays detecting micronuclei or chromosomal aberrations in plants, or mutations in mold, yeast, or maize enabled the detection of genotoxic effects of drinking water extracts. Tests on mammal cells also showed that drinking water extracts induced point mutations, sister chromatid exchanges, chromosomal aberrations and micronuclei. In vivo tests on aquatic organims such as newt or mussels demonstrated the micronuclei inducing effect of unconcentrated drinking water samples.Regarding the identification of the compounds responsible for the genotoxicity, it is obviously not possible to identify all of the thousands of chemicals that may be involved. But such a process is important in order to evaluate the specific genotoxicity and the risk associated with (at least) the main chemicals occurring in drinking water. The identification process usually follows three steps: 1. concentration of the sample can be performed using reverse osmosis, freeze drying, liquid-liquid extraction, and/or adsorption on non ionic resin followed by extraction with organic solvent; 2. the purification step uses one or a combination of chromatographic techniques (TLC, packed column liquid chromatography, HPLC or GC); 3. structural identification of the chemical is performed using data from mass spectrometry, and proton and carbon NMR, or UV spectroscopy. The analysis of the genotoxic compounds of drinking water showed that they are rather non-volatile, quite acid and not stable at high pH, rather polar, and with a mean molecular weigh around 200.Turning now to the identity of these compounds, it is considered that the genotoxicity of drinking water is mainly due to organohalogenated chemicals. Some inorganic chemicals (this class of chemicals is usually not recovered in drinking water extracts) which induce genotoxic or carcinogenic effects must, however, be recalled. Arsenic, nitrates, bromates and radon are natural or human-activity-related drinking water contaminants which are responsible for cancers in rodents or in humans. Among the many genotoxic or carcinogenic organohalogenated compounds identified in drinking water, the most abundant chemicals are chlorinated and/or brominated trihalomethanes. Other important groups of compounds are chlorinated and/or brominated derivatives of acetic acids, acetonitriles, ketones, phenolic compounds. The chlorinated hydroxyfuranones, although present at concentrations lower than 0.1 µg/l in drinking water, can be responsible for more than half of the Ames mutagenicity. MX, the most potent of these chlorohydroxyfuranones, has been submitted to intensive toxicological studies worldwide and was very recently identified as a potent carcinogen in rats.Now that the presence of genotoxic compounds in drinking waters is a well documented and accepted fact, the perspectives lies in the better identification of the impact of these drinking water contaminants. The development of more sensitive tests such as the Comet assay (detection of DNA strand breaks) or the 32P postlabelling assay (detection of DNA adducts) should be pursued. Moreover, the interaction between genotoxic compounds and DNA must be investigated more thoroughly, including the identification of adduct structures. More globally, it is of interest to better assess the impact of these agents on public health and on the occurrence of specific human cancers. At present, even though a few individual water contaminants are classified as human probable carcinogens, the chlorinated drinking water (in itself) is not considered as carcinogenic to humans. Exposure to these potentially harmful agents can be limited with 1. improving drinking water quality - i.e. decreasing the formation of genotoxins - by using raw water containing lower amounts of organic matter; and 2. modifying the water chemical treatment by using lower amounts of chlorine and/or combining chlorine with other disinfectants. The public health can also be protected by the setting of guidelines for drinking water: each compound identified as dangerous would be given a concentration threshold which should never be exceeded. The Environmental Protection Agency in the U.S.A. and the World Health Organisation are authorities setting such guidelines. Finally, we believe it is important to limit the concentration of genotoxic compounds in drinking water as much as possible, and one way to do so is to use chlorine in smaller amounts and in a more efficient way. But it is of paramount importance to keep in mind that the disinfection process (in which chlorine still plays a major role) and the providing of a microbiologically safe drinking water should never be jeopardized

Observation of out-of-phase bilayer plasmons in YBa_2Cu_3O_7-delta

The temperature dependence of the c-axis optical conductivity \sigma(\omega) of optimally and overdoped YBa_2Cu_3O_x (x=6.93 and 7) is reported in the far- (FIR) and mid-infrared (MIR) range. Below T_c we observe a transfer of spectral weight from the FIR not only to the condensate at \omega = 0, but also to a new peak in the MIR. This peak is naturally explained as a transverse out-of-phase bilayer plasmon by a model for \sigma(\omega) which takes the layered crystal structure into account. With decreasing doping the plasmon shifts to lower frequencies and can be identified with the surprising and so far not understood FIR feature reported in underdoped bilayer cuprates.Comment: 7 pages, 3 eps figures, Revtex, epsfi

2D Kinematics and Physical Properties of z~3 Star-Forming Galaxies

We present results from a study of the kinematic structure of star-forming galaxies at redshift z~3 selected in the VVDS, using integral-field spectroscopy of rest-frame optical nebular emission lines, in combination with rest-frame UV spectroscopy, ground-based optical/near-IR and Spitzer photometry. We also constrain the underlying stellar populations to address the evolutionary status of these galaxies. We infer the kinematic properties of four galaxies: VVDS-20298666, VVDS-020297772, VVDS-20463884 and VVDS-20335183 with redshifts z = 3.2917, 3.2878, 3.2776, and 3.7062, respectively. While VVDS-20463884 presents an irregular velocity field with a peak in the local velocity dispersion of the galaxy shifted from the centre of the galaxy, VVDS-20298666 has a well-resolved gradient in velocity over a distance of ~4.5 kpc with a peak-to-peak amplitude of v = 91 km/s . We discovered that the nearby galaxy, VVDS-020297772 (which shows traces of AGN activity), is in fact a companion at a similar redshift with a projected separated of 12 kpc. In contrast, the velocity field of VVDS-020335183 seems more consistent with a merger on a rotating disk. However, all of the objects have a high local velocity dispersion (sigma ~ 60-70 km/s), which gives v/sigma < 1. It is unlikely that these galaxies are dynamically cold rotating disk of ionized gas.Comment: 14 pages and 16 figure

Management der oberen Atemwege beim spontan atmenden Kind: Eine Herausforderung für den Anästhesisten

Zusammenfassung: Partielle und totale Atemwegsobstruktionen treten bei spontan atmenden, bewusstlosen oder anästhesierten Kindern häufig auf und können eine adäquate Sauerstoffversorgung gefährden. Das Offenhalten der oberen Atemwege ist daher die wichtigste und effektivste Maßnahme in dieser Situation: Kinn hochheben ("chin lift"), Unterkiefer nach vorne verschieben ("jaw thrust", Esmarch-Handgriff) und kontinuierlich positiver Atemwegsdruck ("continuous positive airway pressure", CPAP) öffnen nachgewiesenermaßen den Atemweg. Neben diesen einfachen Atemwegsmanövern führen auch verschiedene Lagerungstechniken (Seitenlage oder Rückenlage unter Einnahme der "Schnüffelposition") zu einer besseren Öffnung und Stabilität des oberen Atemweg

Cluster states in nuclei as representations of a U(n+1) group

We propose a description of cluster states in nuclei in terms of representations of unitary algebras U(n+1), where n is the number of space degrees of freedom. Within this framework, a variety of situations including both vibrational and rotational spectra, soft and rigid configurations, identical and non-identical constituents can be described. As an example, we show how the method can be used to study alpha-clustering configurations in 12C with point group symmetry D(3h).Comment: 5 pages, 2 figures, Phys. Rev. C, in pres

Vaskulärer Zugang in der Kindernotfallanästhesie

Zusammenfassung: Zum Thema des schwierigen intervenösen Zugangs bei pädiatrischen Notfallsituationen existieren erstaunlich wenige Angaben in der Literatur. "Wie machen es die Anderen?" war die Motivationsgrundlage für eine Umfrage bei in Kinderanästhesie erfahrenen Anästhesisten. Insgesamt 89Fragebögen wurden an die Leiter der Weiterbildungsstätten für Anästhesie in der Schweiz und an alle Mitglieder der Schweizerischen Gesellschaft für Kinderanästhesie verschickt. Anhand von 2Fallbeispielen (FallA: nicht nüchternes Kleinkind mit einer Radiusfraktur, FallB: Säugling mit hohem Ileus) wurde das weitere Vorgehen nach 2-3 erfolglosen peripheren Punktionsversuchen erfragt. Die Beantwortung ergab, dass die meisten der Befragten in beiden Situationen zunächst weitere periphere Venenpunktionen vornehmen werden. Falls diese Versuche erfolglos bleiben, wird beim Kleinkind mit der Radiusfraktur eine intramuskuläre oder inhalative Anästhesieeinleitung befürwortet. Bei dem Säugling mit Ileus wird versucht, für die Anästhesieeinleitung einen intraossären oder zentralvenösen Zugang (V.femoralis) zu legen. Aufgrund der Resultate der Umfrage und einer Literaturrecherche wird eine Prioritätenliste zu den wichtigsten vaskulären Zugängen und alternativen Anästhesieeinleitungsmethoden in der pädiatrischen Notfallsituation vorgeschlage

Utilisation de trois tests de génotoxicité pour l'étude de l'activité génotoxique de composés organohalogénés, d'acides fulviques chlorés et d'échantillons d'eau (non concentrés) en cours de traitement de potabilisation

Il est admis aujourd'hui que la génotoxicité identifiée dans les extraits d'eau potable provient principalement de l'action du chlore sur la matière organique naturelle qui donne naissance à des dérivés organohalogénés.Dans le présent travail, nous avons comparé la sensibilité de trois essais de génotoxicité (SOS chromotest, test d'Ames-fluctuation et test micronoyau triton) lors de l'étude de composés organohalogénés, d'acides fulviques chlorés et d'échantillons d'eau (non concentrés) en cours de traitement de potabilisation.Les composés organohalogénés étudiés sont 4 trihalométhanes, 5 acétonitriles et 5 chloropropanones identifiés dans l'eau potable ou dans des solutions de substances humiques chlorées. Les résultats obtenus révèlent que le SOS chromotest est globalement le moins sensible des trois essais et que le test d'Ames-fluctuation et le test micronoyau triton permettent généralement de détecter les plus faibles concentrations de composés génotoxiques. Les essais ont également permis de démontrer que la nature des substituants halogénés (brome ou chlore), le nombre et la position des atomes de chlore influencent notablement la génotoxicité des composés organohalogénés.Toutefois, les résultats obtenus indiquent qu'aucun des trois tests réalisés n'est suffisant à lui seul pour détecter l'ensemble des produits génotoxiques. Ces observations confirment la nécessité de réaliser une batterie de tests qui mette en oeuvre divers types cellulaires et différents systèmes de métabolisation, et détecte divers évènements de génotoxicité.Les travaux portant sur les solutions concentrées d'acides fulviques chlorés montrent l'intérêt des essais sur bactéries (particulièrement le test d'Ames-fluctuation) pour la détection rapide de l'activité génotoxique de ces solutions.L'étude concemant les échantillons d'eau prélevés à différents niveaux d'une station de potabilisation, et analysés sans concentration préalable, indique que le test d'Ames- fluctuation est le seul capable de détecter une activité génotoxique dans les échantillons non concentrés étudiés. On montre, conformément à la littérature, que l'activité mutagène observée résulte de la chloration de l'eau.Since the identification of organohalides in drinking water in 1974, several investigators have detected genotoxic activity in drinking water concentrates. It is now widely admitted that the observed genotoxicity originates mainly from the reaction of chlorine on natural organic matter contained in the raw water, which leads to the formation of organohalogenated compounds.The aim of this study is to show the benefit of three short-term assays for the evaluation of the genotoxic potency of organohalogenated compounds and of complex mixtures. In a wider context, the purpose is to identify a test or a battery of tests that can contribute to the control of natural and drinking water genotoxicity.The three genotoxicity assays carried out during this work were:- the SOS chromotest, a primary DNA damage in vitro assay on Escherichia coli; - the Ames- fluctuation test, a point mutation in vitro assay on Salmonella typhimurium; - and the newt micronucleus test, a chromosomal aberration in vivo assay on the amphibian Pleurodeles waltl. These assays display a valuable advantage: the water samples under study can be analyzed without concentration prior to testing. Thus, the different concentration procedures, which may modify the original genotoxicity of the water samples, are avoided.A previous study on seven reference genotoxic chemicals had indicated that the SOS chromotest was never the most sensitive of the three tests (for a given chemical, the most sensitive assay is defined as the test which detects the lowest concentration inducing a significant genotoxic effect). On the contrary, the Ames-fluctuation test proved to be the most sensitive for compounds showing direct genotoxic activity, and the newt micronucleus test the most sensitive for chemicals with indirect genotoxic effects. None of the assays was the most sensitive for every substance analyzed. These observations suggested the need to implement a battery of tests using several cell types, different metabolization systems and detecting several genotoxicity events. This earlier study also showed, in accord with several results in the literature, that the Ames-fluctuation test (in liquid medium) demonstrated a better sensitivity than the Ames test (in agar solid medium).The first part of the present study involved testing the genotoxicity of 14 organo- halogenated compounds identified in drinking water samples or in chlorinated humic matter samples. The chemicals studied were four chlorinated and/or brominated trihalomethanes (trichloro-, bromodichloro-, chlorodibromo- and tribromomethane), five chlorinated or brominated acetonitriles with one, two or three halogens (monochloro-, dichloro-, trichloro-, monobromo- and dibromoacetonitrile) and five chlorinated propanones with one, two or three substitutions on one or two carbon atoms (monochloro-, 1,1-dichloro-, 1,3-dichloro-, 1,1,1-trichloro- and 1,1,3- trichloropropanone). Although the SOS chromotest was the most sensitive for 3 of the 14 substances analyzed, the results confirmed that this test was globally the least sensitive; the Ames-fluctuation test and the newt micronucleus test remained the most efficient assays. It is interesting to note that the Ames-fluctuation test appeared the most sensitive for all the chloropropanones tested and the newt micronucleus test, for all the haloacetonitriles analyzed. Moreover, several structure-activity relationships were demonstrated: the nature of the halogenated substituents (bromine or chlorine), the number and, above all, the position of chlorine atoms strongly influenced the genotoxicity of the organohalides studied.In the second part of the work we analyzed the effects of complex mixtures containing several organohalogenated compounds: the three tests were performed on two chlorinated fulvic acids of different origin. Pornic fulvic acid was extracted from a surface water reservoir used to produce drinking water in Vendée (France) and Pinail fulvic acid came from a forest pond near Poitiers (France). The total organic carbon was about 1 g/l in the solution subjected to chlorination and the molar chlorination ratio was 1.5 Cl2/C. The results showed the advantage of tests using bacteria: the Ames fluctuation test was the only assay able to detect the genotoxicity of both chlorinated fulvic acids; the SOS chromotest detected the genotoxic effect of only one of the chlorinated fulvic acids (Pinail). In contrast, the newt micronucleus test did not show any genotoxicity of the chlorinated fulvic acids. However, it must be pointed out that, as insufficient fulvic acid was available, the genotoxic potency of these solutions on the newt was not tested under adequate conditions (e.g., subchronic concentrations were not studied). Nevertheless, the concentrations of fulvic acid analyzed were very close to those found in the aquatic environment.The last part of the study attempted to approximate environmental and human exposure conditions: the three tests were performed on four water samples taken at several stages of a drinking water treatment plant. These samples were analyzed for genotoxicity in the three test systems without preconcentration. The plant studied is characterized by the following treatment steps: - coagulation-flocculation; - chlorination at 6 g Cl2/m3; - sand filtration; - ozonation at 1.9 g O3/m3; - final chlorination at 1.4 g Cl2/m3 before sending the treated water into the distribution system. The four samples were taken:1. before any treatment (raw water, 10 to 13 mg total organic carbon per liter), 2. between the sand layer filter and the ozonator (chlorinated water), 3. after the ozonator (ozonated water), 4. and at the end of the treatment process (treated water). The results obtained confirmed the advantage of the Ames fluctuation test, which was the only assay able to detect a genotoxic activity in the unconcentrated water samples studied. Regarding the influence of the different chemical treatments on the mutagenicity observed, it was demonstrated that the first chlorination step led to the formation of direct-acting mutagens. The treatment with ozone, at the rate used, did not significantly modify the mutagenicity of the samples that had previously been chlorinated. Similarly, the second chlorination step did not significantly increase the direct mutagenicity detected.Practically, our study indicated that the Ames-fluctuation test is the only assay, among the three performed that is able to contribute efficiently to the control of drinking water genotoxicity. In this context, the benefit of the SOS chromotest appears only in case of accidental pollution: indeed, it is the only test able to yield results within 24 hours. The implementation of the newt micronucleus test could be useful for the control of natural or drinking water genotoxicity in case of extensive pollution

Auditory skills and brain morphology predict individual differences in adaptation to degraded speech

Noise-vocoded speech is a spectrally highly degraded signal, but it preserves the temporal envelope of speech. Listeners vary considerably in their ability to adapt to this degraded speech signal. Here, we hypothesized that individual differences in adaptation to vocoded speech should be predictable by non-speech auditory, cognitive, and neuroanatomical factors. We tested eighteen normal-hearing participants in a short-term vocoded speech-learning paradigm (listening to 100 4-band-vocoded sentences). Non-speech auditory skills were assessed using amplitude modulation (AM) rate discrimination, where modulation rates were centered on the speech-relevant rate of 4 Hz. Working memory capacities were evaluated (digit span and nonword repetition), and structural MRI scans were examined for anatomical predictors of vocoded speech learning using voxel-based morphometry. Listeners who learned faster to understand degraded speech also showed smaller thresholds in the AM discrimination task. This ability to adjust to degraded speech is furthermore reflected anatomically in increased volume in an area of the left thalamus (pulvinar) that is strongly connected to the auditory and prefrontal cortices. Thus, individual non-speech auditory skills and left thalamus grey matter volume can predict how quickly a listener adapts to degraded speech