Path integral regularization of QED by means of Stueckelberg fields

With the help of a Stueckelberg field we construct a regularized U(1) gauge invariant action through the introduction of cutoff functions. This action has the property that it converges formally to the unregularized action of QED when the ultraviolet cutoff goes to infinity. Integrating out exactly the Stueckelberg field we obtain a simple effective regularized action, which is fully gauge invariant and gives rise to the same prediction as QED at the tree level and to the one loop order.Comment: LaTeX file, 12 pages, 3 figures. Revised version, to be published in Phys. Lett.

Structure and thermoelectric properties of boron doped nanocrystalline Si0.8Ge0.2 thin film

The structure and thermoelectric properties of boron doped nanocrystalline Si0.8Ge0.2 thin films are investigated for potential application in microthermoelectric devices. Nanocrystalline Si0.8Ge0.2 thin films are grown by low-pressure chemical vapor deposition on a sandwich of Si3N4/SiO2/Si3N4 films deposited on a Si (100) substrate. The Si0.8Ge0.2 film is doped with boron by ion implantation. The structure of the thin film is studied by means of atomic force microscopy, x-ray diffraction, and transmission electron microscopy. It is found that the film has column-shaped crystal grains ~100 nm in diameter oriented along the thickness of the film. The electrical conductivity and Seebeck coefficient are measured in the temperature range between 80–300 and 130–300 K, respectively. The thermal conductivity is measured at room temperature by a 3 method. As compared with bulk silicon-germanium and microcrystalline film alloys of nearly the same Si/Ge ratio and doping concentrations, the Si0.8Ge0.2 nanocrystalline film exhibits a twofold reduction in the thermal conductivitity, an enhancement in the Seebeck coefficient, and a reduction in the electrical conductivity. Enhanced heat carrier scattering due to the nanocrystalline structure of the films and a combined effect of boron segregation and carrier trapping at grain boundaries are believed to be responsible for the measured reductions in the thermal and electrical conductivities, respectively

Modelling of the ICRF induced E x B convection in the scrape-off-layer of ASDEX Upgrade

In magnetic controlled fusion devices, plasma heating with radio-frequency (RF) waves in the ion cyclotron (IC) range of frequency relies on the electric field of the fast wave to heat the plasma. However, the slow wave can be generated parasitically. The electric field of the slow wave can induce large biased plasma potential (DC potential) through sheath rectification. The rapid variation of the rectified potential across the equilibrium magnetic field can cause significant convective transport (E x B drifts) in the scrape-off layer (SOL). In order to understand this phenomenon and reproduce the experiments, 3D realistic simulations are carried out with the 3D edge plasma fluid and kinetic neutral code EMC3-Eirene in ASDEX Upgrade. For this, we have added the prescribed drift terms to the EMC3 equations and verified the 3D code results against the analytical ones in cylindrical geometry. The edge plasma potential derived from the experiments is used to calculate the drift velocities, which are then treated as input fields in the code to obtain the final density distributions. Our simulation results are in good agreement with the experiments

Specific detection and quantification of virulent/avirulent Phytophthora infestans isolates using a real-time PCR assay that targets polymorphisms of the Avr3a gene.

Equipe 6International audienceMolecular tools that allow intraspecific quantification and discrimination of pathogen isolates are useful to assess fitness of competitors during mixed infections. However, methods that were developed for quantifying Phytophthora infestans are only specific at the species level. Here, we reported a TaqMan-based real-time PCR assay allowing, according to the specificity of the used probes, an accurate quantification of different proportions of two genetically distinct clones of P. infestans in mixed fractions. Indeed, in addition to a primer specific to P. infestans, two primers and two TaqMan(®) probes that target single-nucleotide polymorphisms located in the Avr3a/avr3a virulence gene sequence were designed. The reliability of the method was tested on serially diluted fractions containing plasmid DNA with either the Avr3a or the avr3a sequences at concentrations ranging from 10(2) to 10(8) copies per μl. Based on its specificity, sensitivity and repeatability, the proposed assay allowed a quantification of the targeted DNA sequence in fractions with a Avr3a/avr3a ratio in the range 1/99 to 99/1. The reliability of the test was also checked for counting zoospores. Applications for future research in P. infestans/host quantitative interactions were also discussed

Distal humerus fractures in patients over 65: Complications

SummaryIntroductionFractures of the distal humerus in patients over the age of 65 remain a therapeutic challenge. Treatment options include conservative treatment, internal fixation or total elbow arthroplasty. The complications of these different treatment options were evaluated in a multicentre study.Materials and methodsFour hundred and ninety-seven medical records were evaluated. A retrospective study was performed in 410 cases: 34 received conservative treatment, 289 internal fixation and 87 underwent total elbow arthroplasty. A prospective study was performed in 87 cases: 22 received conservative treatment, 53 internal fixation, and 12 underwent total elbow arthroplasty. Patients were evaluated after at least 6 months follow-up.ResultsThe rate of complications was 30% in the retrospective study and 29% in the prospective study. The rate of complications in the conservative treatment group was 60%, and the main complication was essentially malunion. The rate of complications was 44% in the internal fixation group and included neuropathies, mechanical failure or wound dehiscence. Although complications only developed in 23% of total elbow arthroplasties, they were often more severe than those following other treatments.DiscussionComplications develop in one out of three patients over 65 with distal humerus fractures. Three main types of complications were identified. Neuropathies especially of the ulnar nerve, especially during arthroplasty, must always be identified, the nerve requiring isolation and transposition. Bone complications, due principally to mechanical failure, were found following internal fixation. Despite technical progress, care must be taken not to favor excessive utilization of this treatment option in complex fractures on fragile bone. Although there were relatively fewer complications with total elbow arthroplasty they were more difficult to treat. Ossifications were frequent whatever the surgical option and can jeopardize the functional outcome.Level of evidenceLevel IV

Description in occam and simulation on a transputer network of a systolic processor for image processing

The most significant drawback in using neighbourhood processing (linear filtering, morphology) is the cost of ils implementation, particularly in the area of image processing where the cost grows in proportion to the kernel size squared . However, in PIR [1] it was shown that a large amount of classical algorithms could be described as a cascade of peculiar elementary tells. Being highly integrable, these tells brought about the design of a neighbourhood systolic processor. Converting a functional description (e .g . flow graph, mathematical model) into a hardware structure raises several technical problems . In addition, the cost of designing an integrated circuit requires special cure, making it necessary to perform many simulations . The first part of this paper gives a short description of the décomposition method. It then goes on ta describe the power of occam as a design formalism, applying it to the cascaded tells modelisation . Furthermore, the obtained model can be compiled into a code directly loadable into a Transputer network, resulting in a performant simulation . The hierarchy of occam allows a description at différent levels of abstraction, in order to fit the precision of the model to the desired type of simulation .L'inconvénient majeur des algorithmes de voisinage (filtrage linéaire, morphologique) réside dans le coût associé à leur mise en oeuvre, principalement dans le domaine du traitement d'images où il croît avec le carré de la taille du voisinage . Il a toutefois été montré dans PIR [1] que de nombreux algorithmes couramment utilisés pouvaient être décrits sous la forme d'une cascade de cellules élémentaires particulières . Le caractère hautement intégrable de ces cellules nous a amené à concevoir un processeur systolique de voisinage basé sur le principe de la synthèse par cascades de cellules . Le passage d'une représentation fonctionnelle (graphe de fluence, modèle mathématique) à une structure matérielle soulève un certain nombre de problèmes . En outre, le coût lié à la réalisation d'un circuit intégré exige une extrême prudence, imposant généralement le recours à de nombreuses simulations . Le présent papier fournit un bref aperçu de la méthode de synthèse par cascades de cellules . Il montre ensuite la puissance du langage occam comme outil de formalisation appliquant celui-ci à la modélisation des cascades de cellules . La compilation du modèle au moyen d'outils adéquats fournit un code directement exécutable par un réseau de Transputers, ce qui conduit à une simulation performante . La hiérarchie incluse dans le langage permet une décomposition en niveaux d'abstraction de plus en plus fins, en vue d'ajuster la précision du modèle au type de simulation désiré

Role of anion exchangers in Cl- and HCO3- secretion by the human airway epithelial cell line Calu-3

Despite the importance of airway surface liquid pH in the lung's defenses against infection, the mechanism of airway HCO3- secretion remains unclear. Our aim was to assess the contribution of apical and basolateral Cl-/HCO3- exchangers to Cl- and HCO3- transport in the Calu-3 cell line, derived from human airway submucosal glands. Changes in intracellular pH (pH(i)) were measured following substitution of Cl- with gluconate. Apical Cl- substitution led to an alkalinization in forskolin-stimulated cells, indicative of Cl-/HCO3- exchange. This was unaffected by the anion exchange inhibitor DIDS but inhibited by the CFTR blocker CFTRinh-172, suggesting that the HCO3- influx might occur via CFTR, rather than a solute carrier family 26 (SLC26) exchanger, as recently proposed. The anion selectivity of the recovery process more closely resembled that of CFTR than an SLC26 exchanger, and quantitative RT-PCR showed only low levels of SLC26 exchanger transcripts relative to CFTR and anion exchanger 2 (AE2). For pHi to rise to observed values (similar to 7.8) through HCO3- entry via CFTR, the apical membrane potential must reverse to at least + 20 mV following Cl- substitution; this was confirmed by perforated-patch recordings. Substitution of basolateral Cl- evoked a DIDS-sensitive alkalinization, attributed to Cl-/HCO3- exchange via AE2. This appeared to be abolished in forskolin-stimulated cells but was unmasked by blocking apical efflux of HCO3- via CFTR. We conclude that Calu-3 cells secrete HCO3- predominantly via CFTR, and, contrary to previous reports, the basolateral anion exchanger AE2 remains active during stimulation, providing an important pathway for basolateral Cl- uptake