Are Antiprotons Forever?

Up to one million antiprotons from a single LEAR spill have been captured in a large Penning trap. Surprisingly, when the antiprotons are cooled to energies significantly below 1 eV, the annihilation rate falls below background. Thus, very long storage times for antiprotons have been demonstrated in the trap, even at the compromised vacuum conditions imposed by the experimental set up. The significance for future ultra-low energy experiments, including portable antiproton traps, is discussed.Comment: 12 pages, latex; 4 figures, uufiled. Slightly expanded discussion of expected energy dependence of annihilation cross section and rate, and of estimates of trap pressure, plus minor text improvement

Supersymmetric particle mass measurement with invariant mass correlations

The kinematic end-point technique for measuring the masses of supersymmetric particles in R-Parity conserving models at hadron colliders is re-examined with a focus on exploiting additional constraints arising from correlations in invariant mass observables. The use of such correlations is shown to potentially resolve the ambiguity in the interpretation of quark+lepton end-points and enable discrimination between sequential two-body and three-body lepton-producing decays. The use of these techniques is shown to improve the SUSY particle mass measurement precision for the SPS1a benchmark model by at least 20-30% compared to the conventional end-point technique.Comment: 29 pages, 23 .eps figures, JHEP3 style; v2 adds some references and small clarifications to text; v3 adds some more clarifications to the tex

Rifampin and Triclosan but not Silver is Effective in Preventing Bacterial Infection of Vascular Dacron Graft Material

AbstractObjectives. To evaluate the efficacy of silver- or Triclosan-coated prosthetic material compared to Rifampin bonded Dacron concerning their resistance to infection following subcutaneous implantation and contamination with Staphylococcus aureus.Design. Animal experimental study in mice.Material and methods. Thirty-six C3H/HcN mice (Charles River Lab., Sulzfeld, Germany) with a weight between 24 and 27 g were randomised into six groups counting six animals each. Group I: control, gel-sealed dacron graft, group II: gel-sealed dacron graft and local contamination, group III: Intergard®-Silver-prosthesis and contamination, group IV: silver/gel-sealed dacron prosthesis (test graft) and contamination, group V: Rifampin-bonded gel-sealed graft and contamination, group VI: Triclosan/collagen-coated dacron graft and contamination. Dacron graft material 0.8×1 cm was subcutaneously implanted in mice. Local contamination with 2×107/0.2 ml S. aureus ATCC 25923 was carried out in groups II to VI. On day 14 the animals were killed and the grafts were explanted. The microscopic, histologic and microbiological evaluation of the graft material and the perigraft tissue was performed.Results. In control group I no case of infection was detected. In group II, 6 of 6 animals showed infection. In group III (Intergard®-Silver) and group IV (silver/gel-test graft) were 6 of 6, in group V (Rifampin) only 1 of 6 grafts and in group VI (Triclosan) 4 of 6 grafts were infected. The difference between the low rate of infection in group V (Rifampin) in comparison to the completely infected groups III and IV (Silver) as well as the control group II was significant. Treatment of grafts with Triclosan could prevent infection only in 1/3 of the cases in group IV.Conclusion. Silver coating failed to prevent graft infection material. A potential antimicrobial property was evident for Triclosan whereas Rifampin-bonded grafts exhibit a significantly reduced infection rate. Thus, silver-coated vascular grafts cannot ensure protection from vascular graft infection

Measurement of the Gluino Mass via Cascade Decays for SPS 1a

If R-parity conserving supersymmetry is realised with masses below the TeV scale, sparticles will be produced and decay in cascades at the LHC. In the case of a neutral LSP, which will not be detected, decay chains cannot be fully reconstructed, complicating the mass determination of the new particles. In this paper we extend the method of obtaining masses from kinematical endpoints to include a gluino at the head of a five-sparticle decay chain. This represents a non-trivial extension of the corresponding method for the squark decay chain. We calculate the endpoints of the new distributions and assess their applicability by examining the theoretical distributions for a variety of mass scenarios. The precision with which the gluino mass can be determined by this method is investigated for the mSUGRA point SPS 1a. Finally we estimate the improvement obtained from adding a Linear Collider measurement of the LSP mass.Comment: 40 pages; extended discussion of error

Critical exponents of directed percolation measured in spatiotemporal intermittency

A new experimental system showing a transition to spatiotemporal intermittency is presented. It consists of a ring of hundred oscillating ferrofluidic spikes. Four of five of the measured critical exponents of the system agree with those obtained from a theoretical model of directed percolation.Comment: 7 pages, 12 figures, submitted to PR

Tuuurbine: A Generic CBR Engine over RDFS

International audienceThis paper presents Tuuurbine, a case-based reasoning (CBR) system for the Semantic Web. Tuuurbine is built as a generic CBR system able to reason on knowledge stored in RDF format; it uses Semantic Web technologies like RDF/RDFS, RDF stores, SPARQL, and optionally Semantic Wikis. Tuuurbine implements a generic case-based inference mechanism in which adaptation consists in retrieving similar cases and in replacing some features of these cases in order to obtain one or more solutions for a given query. The search for similar cases is based on a generalization/specialization method performed by means of generalization costs and adaptation rules. The whole knowledge (cases, domain knowledge, costs, adaptation rules) is stored in an RDF store

Measurement of SUSY masses via cascade decays for SPS 1a

If R-parity conserving supersymmetry exists below the TeV-scale, new particles will be produced and decay in cascades at the LHC. The lightest supersymmetric particle will escape the detectors, thereby complicating the full reconstruction of the decay chains. In this paper we expand on existing methods for determining the masses of the particles in the cascade from endpoints of kinematical distributions. We perform scans in the mSUGRA parameter space to delimit the region where this method is applicable. From the examination of theoretical distributions for a wide selection of mass scenarios it is found that caution must be exerted when equating the theoretical endpoints with the experimentally obtainable ones. We provide analytic formulae for the masses in terms of the endpoints most readily available. Complications due to the composite nature of the endpoint expressions are discussed in relation to the detailed analysis of two points on the SPS 1a line. Finally we demonstrate how a Linear Collider measurement can improve dramatically on the precision of the masses obtained

Semiclassical theory of transport in a random magnetic field

We study the semiclassical kinetics of 2D fermions in a smoothly varying magnetic field $B({\bf r})$. The nature of the transport depends crucially on both the strength $B_0$ of the random component of $B({\bf r})$ and its mean value $\bar{B}$. For $\bar{B}=0$, the governing parameter is $\alpha=d/R_0$, where $d$ is the correlation length of disorder and $R_0$ is the Larmor radius in the field $B_0$. While for $\alpha\ll 1$ the Drude theory applies, at $\alpha\gg 1$ most particles drift adiabatically along closed contours and are localized in the adiabatic approximation. The conductivity is then determined by a special class of trajectories, the "snake states", which percolate by scattering at the saddle points of $B({\bf r})$ where the adiabaticity of their motion breaks down. The external field also suppresses the diffusion by creating a percolation network of drifting cyclotron orbits. This kind of percolation is due only to a weak violation of the adiabaticity of the cyclotron rotation, yielding an exponential drop of the conductivity at large $\bar{B}$. In the regime $\alpha\gg 1$ the crossover between the snake-state percolation and the percolation of the drift orbits with increasing $\bar{B}$ has the character of a phase transition (localization of snake states) smeared exponentially weakly by non-adiabatic effects. The ac conductivity also reflects the dynamical properties of particles moving on the fractal percolation network. In particular, it has a sharp kink at zero frequency and falls off exponentially at higher frequencies. We also discuss the nature of the quantum magnetooscillations. Detailed numerical studies confirm the analytical findings. The shape of the magnetoresistivity at $\alpha\sim 1$ is in good agreement with experimental data in the FQHE regime near $\nu=1/2$.Comment: 22 pages REVTEX, 14 figure

Stricture and perforation of the esophagus: Overlooked threats in the Zollinger-Ellison syndrome

This study was undertaken to assess the frequency of significant esophageal involvement in the Zollinger-Ellison syndrome (ZES). In a consecutive series of 24 patients with this disease, 9 (37%) showed endoscopic evidence of acid-induced esophageal lesions ranging from erosive inflammation to ulceration with massive bleeding, severe stricture formation, and perforation. In 3 cases, pronounced esophagitis was known 1–5 years before the underlying disease was diagnosed. Severe esophageal complications developed despite treatment with antisecretory drugs. It is emphasized that the best way to limit such complications is by excision of the underlying gastrin-secreting tumor(s) when possible . Nous avons entrepris cette étude pour établir la fréquence de participation oesophagienne dans le syndrome de Zollinger-Ellison. Pour une série de 24 patients présentant cette maladie, 9 (37%) avaient à l'endoscopie des lésions oesophagiennes dues à l'acidité allant de l'érosion inflammatoire à l'ulcération avec saignement important, sténose sévère, et perforation. Dans 3 cas, une oesophagite importante était connue 1–5 ans avant que la maladie sous-jacente soit diagnostiquée. Des complications oesophagiennes sévères se sont produites malgré le traitement antisécrétoire. Nous insistons sur le fait que le meilleur moyen de limiter ces complications est d'exciser chaque fois que possible la ou les tumeurs sous-jacentes sécrétant la gastrine. El presente estudio fue emprendido con el propósito de determinar la frecuencia de afección ácido péptica significativa del esófago en pacientes con síndrome de Zollinger-Ellison. En una serie de 24 pacientes consecutivos con esta enfermedad, 9 (37%) exhibieron evidencia endoscópica de lesiones esofágicas inducidas por ácido, las cuales variaron entre inflamación erosiva y ulceración con sangrado masivo, estrechez severa, y perforación. En 3 pacientes se conocía la existencia de esofagitis severa entre 1 y 5 años antes del diagnóstico de la enfermedad de base. Se desarrollaron graves complicaciones esofágicas a pesar del tratamiento con drogas antisecretorias en 3 pacientes. Se hace enfasis en que la mejor manera de disminuir tales complicaciones es mediante la resección del tumor(es) secretor de gastrina, cuando ello sea posible.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41287/1/268_2005_Article_BF01658528.pd