Modifying the surface electronic properties of YBa2Cu3O7-delta with cryogenic scanning probe microscopy

We report the results of a cryogenic study of the modification of YBa2Cu3O7-delta surface electronic properties with the probe of a scanning tunneling microscope (STM). A negative voltage applied to the sample during STM tunneling is found to modify locally the conductance of the native degraded surface layer. When the degraded layer is removed by etching, the effect disappears. An additional surface effect is identified using Scanning Kelvin Probe Microscopy in combination with STM. We observe reversible surface charging for both etched and unetched samples, indicating the presence of a defect layer even on a surface never exposed to air.Comment: 6 pages, 4 figures. To appear in Superconductor Science and Technolog

Search For Trapped Antihydrogen

We present the results of an experiment to search for trapped antihydrogen atoms with the ALPHA antihydrogen trap at the CERN Antiproton Decelerator. Sensitive diagnostics of the temperatures, sizes, and densities of the trapped antiproton and positron plasmas have been developed, which in turn permitted development of techniques to precisely and reproducibly control the initial experimental parameters. The use of a position-sensitive annihilation vertex detector, together with the capability of controllably quenching the superconducting magnetic minimum trap, enabled us to carry out a high-sensitivity and low-background search for trapped synthesised antihydrogen atoms. We aim to identify the annihilations of antihydrogen atoms held for at least 130 ms in the trap before being released over ~30 ms. After a three-week experimental run in 2009 involving mixing of 10^7 antiprotons with 1.3 10^9 positrons to produce 6 10^5 antihydrogen atoms, we have identified six antiproton annihilation events that are consistent with the release of trapped antihydrogen. The cosmic ray background, estimated to contribute 0.14 counts, is incompatible with this observation at a significance of 5.6 sigma. Extensive simulations predict that an alternative source of annihilations, the escape of mirror-trapped antiprotons, is highly unlikely, though this possibility has not yet been ruled out experimentally.Comment: 12 pages, 7 figure

An in-vitro screening assay for the detection of inhibitors of proinflammatory cytokine synthesis: a useful tool for the development of new antiarthritic and disease modifying drugs

AbstractObjective This work targets the development of a new tool to help develop new anticytokine drugs that prevent or reduce the progression of arthritic diseases. The specific aim of our study was to establish a fast and reliable in vitro screening assay of cytokine synthesis inhibitors (TNFα, IL-1β) which shows better correlation with enzyme assays than previously reported in vitro assays. The test system should be able to detect p38-MAP kinase inhibitors.Material and methods Human peripheral blood mononuclear cells (PBMCs) were isolated by Ficoll density gradient centrifugation from human EDTA-potassium whole blood. Cells were adjusted at 1×106 cells/ml. PBMCs were stimulated with lipopolysaccharide (LPS; E. coli serotype 026:B6: 1μg/ml) in the presence of test compound (10−5–10−8M) for 4h at 37°C in a 5% CO2-incubator. Induced TNFα and IL-1β protein were measured by ELISA.Results The following are representative examples of inhibitors which effect cytokine synthesis. Corticoid Dexamethasone inhibits IL-1β and TNFα synthesis at IC50 of 38nM and 25nM, respectively. ERK1/ERK2 inhibitor U0126 effects cytokine synthesis at IC50 of 0.34μM for IL-1β production and 0.26μM for TNFα synthesis.p38-MAP kinase inhibitor SB 203580 inhibits IL-1β- and TNF-α-synthesis (IC50sof 0.052μM and 0.46μM) in the same degree as p38-MAP kinase activity (IC50: 0.34μM). Same results could be shown for SB 210313, which had same efficacy on IL-1β and TNFα biosynthesis (IC50's: 1.88μM and 1.01μM) and on p38-MAP kinase (IC50: 6.85μM). Also for SB 202190 this correlation in inhibition of IL-1β and TNFα synthesis (IC50's: 0.055μM and 1.01μM) and p38-MAP kinase inhibition (IC50: 0.088μM) could be shown.Conclusion This study shows the screening assay using PBMCs stimulated with LPS for IL-1β and TNFα synthesis is a reliable test system for the quantification of the effectiveness of new drugs modulating IL-1β and TNFα synthesis which is mainly mediated by p38-MAP Kinase. These assay allows fast detection of IL-1β and TNFα synthesis inhibitors with different modes of action, including p38-MAP kinase inhibitors. The results obtained with our in-vitro screening assay show good correlation with results from enzyme assays. Copyright 2002 OsteoArthritis Research Society International. Published by Elsevier Science Ltd. All rights reserved

Centrifugal separation and equilibration dynamics in an electron-antiproton plasma

Charges in cold, multiple-species, non-neutral plasmas separate radially by mass, forming centrifugally-separated states. Here, we report the first detailed measurements of such states in an electron-antiproton plasma, and the first observations of the separation dynamics in any centrifugally-separated system. While the observed equilibrium states are expected and in agreement with theory, the equilibration time is approximately constant over a wide range of parameters, a surprising and as yet unexplained result. Electron-antiproton plasmas play a crucial role in antihydrogen trapping experiments

Status of the Super-B factory Design

The SuperB international team continues to optimize the design of an electron-positron collider, which will allow the enhanced study of the origins of flavor physics. The project combines the best features of a linear collider (high single-collision luminosity) and a storage-ring collider (high repetition rate), bringing together all accelerator physics aspects to make a very high luminosity of 10$^{36}$ cm$^{-2}$ sec$^{-1}$. This asymmetric-energy collider with a polarized electron beam will produce hundreds of millions of B-mesons at the $\Upsilon$(4S) resonance. The present design is based on extremely low emittance beams colliding at a large Piwinski angle to allow very low $\beta_y^\star$ without the need for ultra short bunches. Use of crab-waist sextupoles will enhance the luminosity, suppressing dangerous resonances and allowing for a higher beam-beam parameter. The project has flexible beam parameters, improved dynamic aperture, and spin-rotators in the Low Energy Ring for longitudinal polarization of the electron beam at the Interaction Point. Optimized for best colliding-beam performance, the facility may also provide high-brightness photon beams for synchrotron radiation applications

Antihydrogen and mirror-trapped antiproton discrimination: Discriminating between antihydrogen and mirror-trapped antiprotons in a minimum-B trap

Recently, antihydrogen atoms were trapped at CERN in a magnetic minimum (minimum-B) trap formed by superconducting octupole and mirror magnet coils. The trapped antiatoms were detected by rapidly turning off these magnets, thereby eliminating the magnetic minimum and releasing any antiatoms contained in the trap. Once released, these antiatoms quickly hit the trap wall, whereupon the positrons and antiprotons in the antiatoms annihilated. The antiproton annihilations produce easily detected signals; we used these signals to prove that we trapped antihydrogen. However, our technique could be confounded by mirror-trapped antiprotons, which would produce seemingly-identical annihilation signals upon hitting the trap wall. In this paper, we discuss possible sources of mirror-trapped antiprotons and show that antihydrogen and antiprotons can be readily distinguished, often with the aid of applied electric fields, by analyzing the annihilation locations and times. We further discuss the general properties of antiproton and antihydrogen trajectories in this magnetic geometry, and reconstruct the antihydrogen energy distribution from the measured annihilation time history.Comment: 17 figure

Alpha Antihydrogen Experiment

ALPHA is an experiment at CERN, whose ultimate goal is to perform a precise test of CPT symmetry with trapped antihydrogen atoms. After reviewing the motivations, we discuss our recent progress toward the initial goal of stable trapping of antihydrogen, with some emphasis on particle detection techniques.Comment: Invited talk presented at the Fifth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 28-July 2, 201

On the formation of trappable antihydrogen

Study, using extensive simulations, of the fraction of trappable antihydrogen under typical experimental conditions. Discovery that positron collisions can influence the magnetic moment of the antihydrogen after formation to promote the trappable fraction. Thus attempting experiments at higher positron densities should be beneficial