Weak Interaction Studies with 6He

The 6He nucleus is an ideal candidate to study the weak interaction. To this end we have built a high-intensity source of 6He delivering ~10^10 atoms/s to experiments. Taking full advantage of that available intensity we have performed a high-precision measurement of the 6He half-life that directly probes the axial part of the nuclear Hamiltonian. Currently, we are preparing a measurement of the beta-neutrino angular correlation in 6He beta decay that will allow to search for new physics beyond the Standard Model in the form of tensor currents.Comment: 5 pages, 4 figures, proceedings for the Eleventh Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2012

Study protocol : the empirical investigation of methods to correct for measurement error in biobanks with dietary assessment

Peer reviewedPublisher PD

Dynamical properties of liquid Al near melting. An orbital-free molecular dynamics study

The static and dynamic structure of liquid Al is studied using the orbital free ab-initio molecular dynamics method. Two thermodynamic states along the coexistence line are considered, namely T = 943 K and 1323 K for which X-ray and neutron scattering data are available. A new kinetic energy functional, which fulfills a number of physically relevant conditions is employed, along with a local first principles pseudopotential. In addition to a comparison with experiment, we also compare our ab-initio results with those obtained from conventional molecular dynamics simulations using effective interionic pair potentials derived from second order pseudopotential perturbation theory.Comment: 15 pages, 12 figures, 2 tables, submitted to PR

The dusty AGB star RS CrB: first mid-infrared interferometric observations with the Keck Telescopes

We report interferometric observations of the semi-regular variable star RS CrB, a red giant with strong silicate emission features. The data were among the first long baseline mid-infrared stellar fringes obtained between the Keck telescopes, using parts of the new nulling beam combiner. The light was dispersed by a low-resolution spectrometer, allowing simultaneous measurement of the source visibility and intensity spectra from 8 to 12 microns. The interferometric observations allow a non-ambiguous determination of the dust shell spatial scale and relative flux contribution. Using a simple spherically-symmetric model, in which a geometrically thin shell surrounds the stellar photosphere, we find that ~30% to ~70% of the overall mid-infrared flux - depending on the wavelength - originates from 7-8 stellar radii. The derived shell opacity profile shows a broad peak around 11 microns (tau ~ 0.06), characteristic of Mg-rich silicate dust particles.Comment: Accepted for publication in ApJ Letter

Keck Interferometer Nuller Data Reduction and On-Sky Performance

We describe the Keck Interferometer nuller theory of operation, data reduction, and on-sky performance, particularly as it applies to the nuller exozodiacal dust key science program that was carried out between 2008 February and 2009 January. We review the nuller implementation, including the detailed phasor processing involved in implementing the null-peak mode used for science data and the sequencing used for science observing. We then describe the Level 1 reduction to convert the instrument telemetry streams to raw null leakages, and the Level 2 reduction to provide calibrated null leakages. The Level 1 reduction uses conservative, primarily linear processing, implemented consistently for science and calibrator stars. The Level 2 processing is more flexible, and uses diameters for the calibrator stars measured contemporaneously with the interferometer’s K-band cophasing system in order to provide the requisite accuracy. Using the key science data set of 462 total scans, we assess the instrument performance for sensitivity and systematic error. At 2.0 Jy we achieve a photometrically-limited null leakage uncertainty of 0.25% rms per 10 minutes of integration time in our broadband channel. From analysis of the Level 2 reductions, we estimate a systematic noise floor for bright stars of ~0.2% rms null leakage uncertainty per observing cluster in the broadband channel. A similar analysis is performed for the narrowband channels. We also provide additional information needed for science reduction, including details on the instrument beam pattern and the basic astrophysical response of the system, and references to the data reduction and modeling tools

Immune correlates of CD4 decline in HIV-infected patients experiencing virologic failure before undergoing treatment interruption

<p>Abstract</p> <p>Background</p> <p>The advantage of treatment interruptions (TIs) in salvage therapy remains controversial. Regardless, characterizations of the correlates of CD4 count fall during TI are important to identify since patients with virologic failure commonly stop antiretroviral (ARV) therapy. The objective of this study was to determine the predictive value of pre-TI proliferative capacity and cell surface markers for CD4 count change in HIV-infected patients experiencing virologic failure before undergoing TI.</p> <p>Methods</p> <p>Peripheral blood mononuclear cells (PBMCs) from 13 HIV-infected patients experiencing virologic failure at baseline time points before the TI were tested for proliferation using the 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE) dilution assay and a Gag p55 peptide pool, staphylococcus enterotoxin B (SEB), cytomegalovirus (CMV) recall antigen, and anti-CD3 antibody as stimuli. CD28 and CD57 expression on CD4+ and CD8+ T-cells was measured.</p> <p>Results</p> <p>The median changes in the CD4+ T-cell count and viral load from baseline to the TI time point corresponding to the CD4 count nadir were -44 cells/mm³{Interquartile range (IQR) -17, -104} and +85,332 copies/mL (IQR +11,198, +283,327), respectively. CD4+ T-cell proliferation to CMV, pre-TI CD4+ T-cell count, and percent CD4+CD57+ cells correlated negatively with CD4 count change during TI (r = -0.59, p = 0.045, r = -0.61, p = 0.030 and r = -0.69, p = 0.0095, respectively; Spearman correlation). The presence of HIV-specific proliferative responses was not associated with a reduced decline in CD4 count during TI.</p> <p>Conclusion</p> <p>The use of pre-TI immune proliferative responses and cell surface markers may have predictive value for CD4 count decline during TI.</p

Milliarcsecond N-Band Observations of the Nova RS Ophiuchi: First Science with the Keck Interferometer Nuller

We report observations of the nova RS Ophiuchi (RS Oph) using the Keck Interferometer Nuller (KIN), approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. These observations represent the first scientific results from the KIN, which operates in N-band from 8 to 12.5 microns in a nulling mode. By fitting the unique KIN data, we have obtained an angular size of the mid-infrared continuum of 6.2, 4.0, or 5.4 mas for a disk profile, gaussian profile (FWHM), and shell profile respectively. The data show evidence of enhanced neutral atomic hydrogen emission and atomic metals including silicon located in the inner spatial regime near the white dwarf (WD) relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer spatial region, centered at ! 17 AU from the WD, that are not found in the inner regime. Our evidence suggests that these features have been excited by the nova flash in the outer spatial regime before the blast wave reached these regions. These identifications support a model in which the dust appears to be present between outbursts and is not created during the outburst event. We further discuss the present results in terms of a unifying model of the system that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock wave caused by the motion of the stars through the cool wind of the red giant star. These data show the power and potential of the nulling technique which has been developed for the detection of Earth-like planets around nearby stars for the Terrestrial Planet Finder Mission and Darwin missions.Comment: 41 pages, 10 figure

Pathomechanisms of ulnar ligament lesions of the wrist in a cadaveric distal radius fracture model

Background and purpose: Mechanisms of injury to ulnar sided ligaments, stabilizing the distal radioulnar joint and the ulna to the carpus, associated with dorsally displaced distal radius fractures are poorly described. We investigated the injury patterns in a human cadaver fracture model. Methods: Fresh frozen human cadaver arms were used. A dorsal open wedge osteotomy was made in the distal radius. In 8 specimens pressure was applied to the palm with the wrist in dorsiflexion and ulnar sided stabilizing structures subsequently severed. Dorsal angulation was measured on digitized radiographs. In 8 more specimens the triangular fibrocartilage complex was forced into rupture by axially loading the forearm with the wrist in dorsiflexion. The ulnar side was dissected and injuries were recorded. Results: Intact ulnar soft tissues limited the dorsal angulation of the distal radius fragment to a median of 32o (16-34o). A combination of bending and shearing of the distal radius fragment was needed to create TFCC injuries. Both palmar and dorsal injuries were observed simultaneously in 6/8 specimens. Interpretation: A TFCC injury can be expected when dorsal angulation of a distal radius fracture exceeds 32o. The extensor carpi ulnaris subsheath may be a functionally integral part of the TFCC. Both dorsal and palmar structures can tear simultaneously. These findings may have implications for reconstruction of ulnar sided soft tissue injuries

IVUS-based imaging modalities for tissue characterization: similarities and differences

Gray-scale intravascular ultrasound (IVUS) is the modality that has been established as the golden standard for in vivo imaging of the vessel wall of the coronary arteries. The use of IVUS in clinical practice is an important diagnostic tool used for quantitative assessment of coronary artery disease. This has made IVUS the de-facto invasive imaging method to evaluate new interventional therapies such as new stent designs and for atherosclerosis progression-regression studies. However, the gray-scale representation of the coronary vessel wall and plaque morphology in combination with the limited resolution of the current IVUS catheters makes it difficult, if not impossible, to identify qualitatively (e.g. visually) the plaque morphology similar as that of histopathology, the golden standard to characterize and quantify coronary plaque tissue components. Meanwhile, this limitation has been partially overcome by new innovative IVUS-based post-processing methods such as: virtual histology IVUS (VH-IVUS, Volcano Therapeutics, Rancho Cordova, CA, USA), iMAP-IVUS (Bostoc Scientific, Santa Clara, CA, USA), Integrated Backscatter IVUS (IB-IVUS) and Automated Differential Echogenicity (ADE)