The pion wave function in covariant light-front dynamics

The structure of the pion wave function in the relativistic constituent quark model is investigated in the explicitly covariant formulation of light-front dynamics. We calculate the two relativistic components of the pion wave function in a simple one-gluon exchange model and investigate various physical observables: decay constant, charge radius, electromagnetic and transition form factors. We discuss the influence of the full relativistic structure of the pion wave function for an overall good description of all these observables, including both low and high momentum scales.Comment: 12 pages, 10 figure

Towards a complete accounting of energy and momentum from stellar feedback in galaxy formation simulations

Stellar feedback plays a key role in galaxy formation by regulating star formation, driving interstellar turbulence and generating galactic scale outflows. Although modern simulations of galaxy formation can resolve scales of 10-100 pc, star formation and feedback operate on smaller, "subgrid" scales. Great care should therefore be taken in order to properly account for the effect of feedback on global galaxy evolution. We investigate the momentum and energy budget of feedback during different stages of stellar evolution, and study its impact on the interstellar medium using simulations of local star forming regions and galactic disks at the resolution affordable in modern cosmological zoom-in simulations. In particular, we present a novel subgrid model for the momentum injection due to radiation pressure and stellar winds from massive stars during early, pre-supernova evolutionary stages of young star clusters. Early injection of momentum acts to clear out dense gas in star forming regions, hence limiting star formation. The reduced gas density mitigates radiative losses of thermal feedback energy from subsequent supernova explosions, leading to an increased overall efficiency of stellar feedback. The detailed impact of stellar feedback depends sensitively on the implementation and choice of parameters. Somewhat encouragingly, we find that implementations in which feedback is efficient lead to approximate self-regulation of global star formation efficiency. We compare simulation results using our feedback implementation to other phenomenological feedback methods, where thermal feedback energy is allowed to dissipate over time scales longer than the formal gas cooling time. We find that simulations with maximal momentum injection suppress star formation to a similar degree as is found in simulations adopting adiabatic thermal feedback.Comment: ApJ submitted. For a high-resolution version of the paper, see http://kicp.uchicago.edu/~agertz

Social marketing: Immunizing against unethical practice

A simple approach for the catalytic conversion of primary alcohols into their corresponding esters and amides, with evolution of H2 gas using in situ formed ruthenium PNP- and PNN-pincer catalysts, is presented. The evaluation showed conversions for the esterification with turnover numbers as high as 4300, and 4400 for the amidation

Accidental Father-to-Son HIV-1 Transmission During the Seroconversion Period

A 4-year-old child born to an HIV-1 seronegative mother was diagnosed with HIV-1, the main risk factor being transmission from the child's father who was seroconverting at the time of the child's birth. In the context of a forensic investigation, we aimed to identify the source of infection of the child and date of the transmission event. Samples were collected from the father and child at two time points about 4 years after the child's birth. Partial segments of three HIV-1 genes (gag, pol, and env) were sequenced and maximum likelihood (ML) and Bayesian methods were used to determine direction and estimate date of transmission. Neutralizing antibodies were determined using a single cycle assay. Bayesian trees displayed a paraphyletic-monophyletic topology in all three genomic regions, with the father's host label at the root, which is consistent with father-to-son transmission. ML trees found similar topologies in gag and pol and a monophyletic-monophyletic topology in env. Analysis of the time of the most recent common ancestor of each HIV-1 gene population indicated that the child was infected shortly after the father. Consistent with the infection history, both father and son developed broad and potent HIV-specific neutralizing antibody responses. In conclusion, the direction of transmission implicated the father as the source of transmission. Transmission occurred during the seroconversion period when the father was unaware of the infection and was likely accidental. This case shows how genetic, phylogenetic, and serological data can contribute for the forensic investigation of HIV transmission.info:eu-repo/semantics/publishedVersio

Participation des radicaux carbonate à l’oxydation de l’atrazine lors de l’ozonation de solutions aqueuses contenant des ions hydrogénocarbonate

L’étude porte sur la détermination de la contribution des espèces O3, OH° et CO3°- dans la dégradation de l’atrazine lors de l’ozonation de solutions contenant différentes concentrations en ions hydrogénocarbonate et en carbone organique. Le suivi de la concentration en atrazine et en ozone dissous, et les expressions cinétiques ont permis de calculer les concentrations en radicaux hydroxyle et carbonate au cours des réactions. A partir des données expérimentales obtenues sur des eaux pures additionnées de carbone organique et inorganique, les résultats indiquent que l’élimination du micropolluant résulte de l’action de l’ozone (pour une faible part), des radicaux hydroxyle issus de la décomposition de l’ozone, mais aussi pour une part très significative, des radicaux carbonate. La participation des radicaux CO3°- diminue lorsque la concentration en carbone organique augmente. Les radicaux carbonate peuvent être responsable de plus de 40 % de la dégradation de l’atrazine lors de l’ozonation en présence de 7 mM d’ions hydrogénocarbonate et 129 µM d’ions glycolate utilisés comme molécule modèle pour l’apport de carbone organique. Les résultats obtenus sur des eaux naturelles confirment les conclusions déduites des expériences sur des eaux de composition connue.The inhibiting effect of bicarbonate ions on the oxidation of organic molecules by the hydroxyl radicals is well known. However, the carbonate radicals resulting from the consumption of the OH° radicals by these ions have only rarely been considered to participate in the reactions of organic pollutant removal. In this study, the contribution of O3, OH° and CO3°- radicals in the degradation of atrazine during ozonation of aqueous solutions containing various concentrations of bicarbonate ions and organic carbon, was determined.Experiments were performed in a bubble column fed continuously by ozone gas and an aqueous solution containing atrazine (0.05 µM) as the model molecule. Three sets of experiments were carried out at pH 8:1. pure water with different concentrations of bicarbonate ions (0.35-70 mM);2. pure water with different concentrations of bicarbonate ions (0.35 and 7 mM) and glycolate ions (0-129 µM) selected as the organic carbon source;3. surface and tap waters.For different contact times in the ozonation reactor, the concentrations of atrazine and dissolved ozone were determined. Inputting these data into kinetic equations enabled us to calculate the concentrations of hydroxyl and carbonate radicals during ozonation. In the absence of organic carbon, the concentration of hydroxyl radicals was determined by assuming steady state conditions (equation II). The concentration of carbonate radicals was deduced from the slope of the evolution of atrazine concentration ([A]0 -[A])/[A] versus the contact time, and the values of ozone and OH° radical concentration (equation IV). In the presence of organic matter, the concentration of OH° radicals was calculated from the evolution of ([A]0 -[A])/[A] versus the contact time, and by replacing the carbonate radical concentration by the expression involving the OH° radicals (equations VI-IX). From the steady state assumption, the concentration of carbonate radicals followed the hydroxyl radical evolution.In the absence of organic carbon, the results confirmed the global inhibiting effect of bicarbonate ions on the removal of atrazine molecules. However, the concentrations of the carbonate radicals were much higher than the OH° radical concentrations (above 4x10-10 M compared to 2x10-12 M, respectively). The concentration of these latter radicals decreased as the concentration of bicarbonate ions increased. Under these conditions, the carbonate radicals were mainly responsible for the removal of atrazine.From the experiments in pure water with given concentrations of bicarbonate and glycolate ions, the hydroxyl radical concentration increased with the concentration of glycolate ions, thus confirming the promoter property of this organic molecule, which favours the removal of atrazine. However, in most cases, the presence of organic carbon was found to be unfavourable to the concentration of carbonate radicals. Therefore, the participation of the carbonate radicals decreased with increasing organic carbon content. Nevertheless, their contribution to atrazine degradation can reach more than 40% during ozonation in the presence of bicarbonate ions (7 mM) and glycolate ions (129 µM) used as an organic carbon source.The results obtained from the experiments carried out in natural waters agree with the main conclusions from the above experiments. The removal of atrazine involved ozone, hydroxyl radicals as well as carbonate radicals. The contribution of carbonate radicals decreased when the ratio of inorganic carbon to organic carbon decreased. In the surface and tap waters tested, this contribution was found to be 10 to 40 % and 43 % respectively

Pion observables within the covariant formulation of Light-front dynamics

International audienceWithin the covariant formulation of light-front dynamics we determine the two spin components of the pion wave function in a phenomenological constituent quarkmodel. These spin components are further interpreted as a non-relativistic wave function and a purely relativistic component. The latter is determined in the one-gluon exchange approximation. We calculate in this model several observables: the pion decay constant, the electromagnetic form factor and the transition form factor

Clinical validation of an automated fluorogenic factor XIII activity assay based on isopeptidase activity

Hereditary factor XIII (FXIII) deficiency is a rare autosomal bleeding disorder which can cause life-threatening bleeding. Acquired deficiency can be immune-mediated or due to increased consumption or reduced synthesis. The most commonly used screening test is insensitive, and widely used quantitative assays have analytical limitations. The present study sought to validate Technofluor FXIII Activity, the first isopeptidase-based assay available on a routine coagulation analyser, the Ceveron s100. Linearity was evidenced throughout the measuring range, with correlation coefficients of >0.99, and coefficients of variation for repeatability and reproducibility were 5% and 10%, respectively. A normally distributed reference range of 47.0−135.5 IU/dL was derived from 154 normal donors. Clinical samples with Technofluor FXIII Activity results between 0 and 167.0 IU/dL were assayed with Berichrom® FXIII Activity, a functional ammonia release assay, and the HemosIL™ FXIII antigen assay, generating correlations of 0.950 and 0.980, respectively. Experiments with a transglutaminase inhibitor showed that Technofluor FXIII Activity can detect inhibition of enzymatic activity. No interference was exhibited by high levels of haemolysis and lipaemia, and interference by bilirubin was evident at 18 mg/dL, a level commensurate with severe liver disease. Technofluor FXIII Activity is a rapid, accurate and precise assay suitable for routine diagnostic use with fewer interferents than ammonia release FXIII activity assays

The Impact of Isospin Breaking on the Distribution of Transition Probabilities

In the present paper we investigate the effect of symmetry breaking in the statistical distributions of reduced transition amplitudes and reduced transition probabilities. These quantities are easier to access experimentally than the components of the eigenvectors and were measured by Adams et al. for the electromagnetic transitions in ^{26}Al. We focus on isospin symmetry breaking described by a matrix model where both, the Hamiltonian and the electromagnetic operator, break the symmetry. The results show that for partial isospin conservation, the statistical distribution of the reduced transition probability can considerably deviate from the Porter-Thomas distribution.Comment: 16 pages, 8 figures, submitted to PR

A Turbulent Origin for Flocculent Spiral Structure in Galaxies: II. Observations and Models of M33

Fourier transform power spectra of azimuthal scans of the optical structure of M33 are evaluated for B, V, and R passbands and fit to fractal models of continuum emission with superposed star formation. Power spectra are also determined for Halpha. The best models have intrinsic power spectra with 1D slopes of around -0.7pm0.7, significantly shallower than the Kolmogorov spectrum (slope =-1.7) but steeper than pure noise (slope=0). A fit to the power spectrum of the flocculent galaxy NGC 5055 gives a steeper slope of around -1.5pm0.2, which could be from turbulence. Both cases model the optical light as a superposition of continuous and point-like stellar sources that follow an underlying fractal pattern. Foreground bright stars are clipped in the images, but they are so prominent in M33 that even their residual affects the power spectrum, making it shallower than what is intrinsic to the galaxy. A model consisting of random foreground stars added to the best model of NGC 5055 fits the observed power spectrum of M33 as well as the shallower intrinsic power spectrum that was made without foreground stars. Thus the optical structure in M33 could result from turbulence too.Comment: accepted by ApJ, 13 pages, 10 figure

Sous-produits de réaction formés lors de la filtration sur charbon actif de composés phénoliques en présence d'ions chlorite

L'étude des interactions entre les ions chlorite, un charbon actif en grains (CAG CECA 40) et des composés phénoliques (phénol et para-nitrophénol) a été réalisée à partir d'expériences de filtration sur mini-colonnes de CAG de solutions aqueuses de chlorite et du composé organique en mélange ([C102-] inf=50 mg.l-¹; [Composé Organique]jnf=200 µmol.l-¹ ; 3 g de CAG; Vitesse de filtration: 3,7 m.h-¹). Les résultats obtenus ont permis de montrer que la présence de chlorite conduit à une augmentation des capacités du CAG vis-à-vis de l'élimination du phénol et du para-nitrophénol. Cette augmentation résulte de réactions chimiques entre le composé organique et les sous-produits de décomposition des ions chlorite par le charbon actif. Les analyses par couplage CG/SM des extraits issus des charbons actifs à la fin des filtrations ont permis de mettre en évidence la présence de nombreux composés adsorbés sur le charbon actif. Les composés identifiés résultent de réactions d'oxydation, de deshydroxylation, de carboxylation, d'halogénation, d'hydroxylation et de dimérisation. L'action des ions chlorite sur le charbon actif peut conduire à la formation de radicaux à la surface du charbon actif ou en solution capables de réagir avec les composés organiques pour former les sous-produits observés.The use of chlorine dioxide for the chemical preoxidation of potable water with high oxidant demand requires that the major inorganic byproduct, chlorite, in the treatment system be removed, owing to the potential toxicity of this oxychlorine species. Granular Activated Carbon (GAC) filtration, in converting chlorite ions into chloride, appears to be an interesting approach, but very few data are available concerning possible interactions in the presence of organic matter. The present research was designed to examine the influence of phenolic compounds on the efficiency of activated carbon in removing chlorite and to study the reactions between chlorite, activated carbon and organic molecules. Laboratory experiments have been carried out with relatively high substrate concentrations in order to identify the resulting byproducts.Materials and Methods.Filtrations of solutions containing chlorite and a phenolic compound (phenol or para nitrophenol; [Organic Compound]inf=200 µmol.L-¹;[C102-] inf=50 mg L-¹; pH=7.2); were performed using 1- cm i.d. glass columns packed with 3.0 g of GAC CECA 40 (Flow rate: 3.7 m.h-¹). Inorganic species were analysed by HPLC, with an anion column and a conductimetric detector for chloride and chlorate, and with a C-18 column and a UV detector for chlorite. Phenol and para nitrophenol were also analysed by HPLC, in the reverse mode. At the conclusion of the filtrations, the Total Organic Halogen (TOX) adsorbed on the carbon was determined after combustion of the carbon and measurement of the liberated halides with a micro coulometer (Dohrmann DX20). In order to identify organic reaction byproducts, carbon samples were Soxhlet extracted with methylene chloride and half of the extracts were methylated with diazomethane. Identification of the organic products was then carried out by gas chromatography / mass spectrometry with a DB5 capillary column and a quadrupolar hyperbolic filter system CPV/MS.Results and Discussion.Effects of phenol and p nitrophenol on removal of chlorite by GAC. The effluent curves from columns that received solutions containing both chlorite and an organic solute (columns A and B; fig. 1) showed that the presence of phenol or p nitrophenol in the influent decreases the capacity of GAC to remove chlorite.Effect of chlorite on removal of phenol and p nitrophenol. An increase in the cumulative removal of the organic solute was observed for columns A and B compared with columns that received solutions of the phenolic compound only (fig. 2; table 11). p benzoquinone was found in the eff1uent of column A fed with a chlorite phenol solution (fig. 3).Formation of organic byproducts by reactions between chlorite and phenol or p nitrophenol in the presence of GAC. TOX analyses showed that interactions between chlorite, GAC, and phenol or p nitrophenol led to the production of organohalogenated compounds. These data clearly demonstrate that halogenation reactions take place in the GAC bed and that a fraction of the total amount of phenol or p nitrophenol removed can be due to chemical reactions. GC/MS analyses of GAC extracts of columns A and B (tables IV and V) indicated that the phenol chlorite GAC reactions yield a variety of organic byproducts that are produced by hydroxylation and carboxylation of the aromatic ring by oxidation to quinones, by chlorine substitution and by dehydroxylation and dimerization reactions. Fewer products could be identified in the reaction between p nitrophenol, chlorite, and GAC. Since chlorite is unreactive with phenol and p nitrophenol in neutral aqueous solution, the formation of these organic byproducts can be attributed to reactions between phenol or p nitrophenol present in the GAC pore solution or adsorbed on GAC and the chemical species (Cl· ClO·, ClO2, HOCl (ClO-), surface free radicals ...) generated from the reaction of chlorite and carbon. Thus, aromatic acids could come from radical processes between adsorbed molecules and carbon surface functional groups oxidized by chlorite. The formation of dimers can also be explained by a freeradical mechanism. The reactions between Cl·, ClO· radicals or radicals present on the GAC surface, with organic compounds produce organic radicals via H atom abstraction or one electron transfer. Organic radicals such as phenoxy radicals or other aromatic radicals can then undergo dimerization by carbon-oxygen or carbon-carbon coupling. The formation of organochlorinated compounds can be explained by the reaction of chlorine (HOCl, ClO-) and chlorine radicals with organic molecules present in the solution. However further investigation is needed in order to evaluate if such compounds can be formed on GAC filters and then desorbed in the effluent in thc case of drinking waters pretreated with chlorine dioxide