505 research outputs found
Quantitative phase contrast imaging of a shock-wave with a laser-plasma based X-ray source
X-ray phase contrast imaging (XPCI) is more sensitive to density variations than X-ray absorption radiography, which is a crucial advantage when imaging weakly-absorbing, low-Z materials, or steep density gradients in matter under extreme conditions. Here, we describe the application of a polychromatic X-ray laser-plasma source (duration ~0.5 ps, photon energy >1 keV) to the study of a laser-driven shock travelling in plastic material. The XPCI technique allows for a clear identification of the shock front as well as of small-scale features present during the interaction. Quantitative analysis of the compressed object is achieved using a density map reconstructed from the experimental data
Perspectives on the Trypanosoma cruzi-host cell receptor interaction
Chagas disease is caused by the parasite Trypanosoma cruzi. The critical initial event is the interaction of the trypomastigote form of the parasite with host receptors. This review highlights recent observations concerning these interactions. Some of the key receptors considered are those for thromboxane, bradykinin, and for the nerve growth factor TrKA. Other important receptors such as galectin-3, thrombospondin, and laminin are also discussed. Investigation into the molecular biology and cell biology of host receptors for T. cruzi may provide novel therapeutic targets
The Robinson Gravitational Wave Background Telescope (BICEP): a bolometric large angular scale CMB polarimeter
The Robinson Telescope (BICEP) is a ground-based millimeter-wave bolometric
array designed to study the polarization of the cosmic microwave background
radiation (CMB) and galactic foreground emission. Such measurements probe the
energy scale of the inflationary epoch, tighten constraints on cosmological
parameters, and verify our current understanding of CMB physics. Robinson
consists of a 250-mm aperture refractive telescope that provides an
instantaneous field-of-view of 17 degrees with angular resolution of 55 and 37
arcminutes at 100 GHz and 150 GHz, respectively. Forty-nine pair of
polarization-sensitive bolometers are cooled to 250 mK using a 4He/3He/3He
sorption fridge system, and coupled to incoming radiation via corrugated feed
horns. The all-refractive optics is cooled to 4 K to minimize polarization
systematics and instrument loading. The fully steerable 3-axis mount is capable
of continuous boresight rotation or azimuth scanning at speeds up to 5 deg/s.
Robinson has begun its first season of observation at the South Pole. Given the
measured performance of the instrument along with the excellent observing
environment, Robinson will measure the E-mode polarization with high
sensitivity, and probe for the B-modes to unprecedented depths. In this paper
we discuss aspects of the instrument design and their scientific motivations,
scanning and operational strategies, and the results of initial testing and
observations.Comment: 18 pages, 11 figures. To appear in Millimeter and Submillimeter
Detectors and Instrumentation for Astronomy III, Proceedings of SPIE, 6275,
200
X-ray phase-contrast imaging for laser-induced shock waves
X-ray phase-contrast imaging (XPCI) is a versatile technique with applications in many fields, including fundamental physics, biology and medicine. Where X-ray absorption radiography requires high density ratios for effective imaging, the image contrast for XPCI is a function of the density gradient. In this letter, we apply XPCI to the study of laser-driven shock waves. Our experiment was conducted at the Petawatt High-Energy Laser for Heavy Ion EXperiments (PHELIX) at GSI. Two laser beams were used: one to launch a shock wave and the other to generate an X-ray source for phase-contrast imaging. Our results suggest that this technique is suitable for the study of warm dense matter (WDM), inertial confinement fusion (ICF) and laboratory astrophysics
Propagation-based imaging phase-contrast enhanced imaging setup for single shot acquisition using laser-generated X-ray sources
The development of new diagnostics is important to improve the interpretation of experiments. Often well-known physical processes and techniques originally developed in unrelated fields of science can be applied to a different area with a significant impact on the quality of the produced data. X-ray phase-contrast imaging (XPCI) is one techniques which has found many applications in biology and medicine. This is due to its capability to emphasise the presence of strong density variations normally oriented with respect to the X-ray propagation direction. With the availability of short energetic X-ray pulses XPCI extends to time-resolved pump-probe measurements of laser-matter interaction where strong density gradient are also present. In this work we present the setup for XPCI tested at the laser PHELiX at GSI in Germany
In-situ characterization of the Hamamatsu R5912-HQE photomultiplier tubes used in the DEAP-3600 experiment
The Hamamatsu R5912-HQE photomultiplier-tube (PMT) is a novel high-quantum
efficiency PMT. It is currently used in the DEAP-3600 dark matter detector and
is of significant interest for future dark matter and neutrino experiments
where high signal yields are needed.
We report on the methods developed for in-situ characterization and
monitoring of DEAP's 255 R5912-HQE PMTs. This includes a detailed discussion of
typical measured single-photoelectron charge distributions, correlated noise
(afterpulsing), dark noise, double, and late pulsing characteristics. The
characterization is performed during the detector commissioning phase using
laser light injected through a light diffusing sphere and during normal
detector operation using LED light injected through optical fibres
White Matter Tract Pathology in Pediatric Anoxic Brain Injury from Drowning
ABSTRACT BACKGROUND AND PURPOSE: Although drowning is a leading cause of mortality and morbidity in young children, the neuropathologic consequences have not been fully determined. The purpose of this article was to quantitatively characterize white matter microstructural abnormalities in pediatric anoxic brain injury from nonfatal drowning and investigate the correlation with motor function
Search for astrophysical sources of neutrinos using cascade events in IceCube
The IceCube neutrino observatory has established the existence of a flux of
high-energy astrophysical neutrinos inconsistent with the expectation from
atmospheric backgrounds at a significance greater than . This flux has
been observed in analyses of both track events from muon neutrino interactions
and cascade events from interactions of all neutrino flavors. Searches for
astrophysical neutrino sources have focused on track events due to the
significantly better angular resolution of track reconstructions. To date, no
such sources have been confirmed. Here we present the first search for
astrophysical neutrino sources using cascades interacting in IceCube with
deposited energies as small as 1 TeV. No significant clustering was observed in
a selection of 263 cascades collected from May 2010 to May 2012. We show that
compared to the classic approach using tracks, this statistically-independent
search offers improved sensitivity to sources in the southern sky, especially
if the emission is spatially extended or follows a soft energy spectrum. This
enhancement is due to the low background from atmospheric neutrinos forming
cascade events and the additional veto of atmospheric neutrinos at declinations
.Comment: 14 pages, 9 figures, 1 tabl
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