High energy resolution fluorescence detection XANES - an in situ method to study the interaction of adsorbed molecules with metal catalysts in the liquid phase

The change in the Pt electronic structure following the adsorption of an a,ß-unsaturated aldehyde and ketone was followed by in situ HERFD-XANES in the liquid phase. The resulting shift in the Pt Fermi energy is in good agreement with the molecule adsorption energy trends calculated by DFT and provides insight into the reaction selectivity.

Laser-driven x-ray and neutron source development for industrial applications of plasma accelerators

Pulsed beams of energetic x-rays and neutrons from intense laser interactions with solid foils are promising for applications where bright, small emission area sources, capable of multi-modal delivery are ideal. Possible end users of laser-driven multi-modal sources are those requiring advanced non-destructive inspection techniques in industry sectors of high value commerce such as aerospace, nuclear and advanced manufacturing. We report on experimental work that demonstrates multi-modal operation of high power laser-solid interactions for neutron and x-ray beam generation. Measurements and Monte Carlo radiation transport simulations show that neutron yield is increased by a factor ∼2 when a 1 mm copper foil is placed behind a 2 mm lithium foil, compared to using a 2 cm block of lithium only. We explore x-ray generation with a 10 picosecond drive pulse in order to tailor the spectral content for radiography with medium density alloy metals. The impact of using >1 ps pulse duration on laser-accelerated electron beam generation and transport is discussed alongside the optimisation of subsequent bremsstrahlung emission in thin, high atomic number target foils. X-ray spectra are deconvolved from spectrometer measurements and simulation data generated using the GEANT4 Monte Carlo code. We also demonstrate the unique capability of laser-driven x-rays in being able to deliver single pulse high spatial resolution projection imaging of thick metallic objects. Active detector radiographic imaging of industrially relevant sample objects with a 10 ps drive pulse is presented for the first time, demonstrating that features of 200 μm size are resolved when projected at high magnification.

ROSA: A High-cadence, Synchronized Multi-camera Solar Imaging System

The Rapid Oscillations in the Solar Atmosphere (ROSA) instrument is a synchronized, six-camera high-cadence solar imaging instrument developed by Queen's University Belfast. The system is available on the Dunn Solar Telescope at the National Solar Observatory in Sunspot, New Mexico, USA, as a common-user instrument. Consisting of six 1k x 1k Peltier-cooled frame-transfer CCD cameras with very low noise (0.02 -aEuro parts per thousand 15 e s(-1) pixel(-1)), each ROSA camera is capable of full-chip readout speeds in excess of 30 Hz, or 200 Hz when the CCD is windowed. Combining multiple cameras and fast readout rates, ROSA will accumulate approximately 12 TB of data per 8 hours observing. Following successful commissioning during August 2008, ROSA will allow for multi-wavelength studies of the solar atmosphere at a high temporal resolution.

ROSA: A High-cadence, Synchronized Multi-camera Solar Imaging System

The Rapid Oscillations in the Solar Atmosphere (ROSA) instrument is a synchronized, six-camera high-cadence solar imaging instrument developed by Queen's University Belfast and recently commissioned at the Dunn Solar Telescope at the National Solar Observatory in Sunspot, New Mexico, USA, as a common-user instrument. Consisting of six 1k x 1k Peltier-cooled frame-transfer CCD cameras with very low noise (0.02 - 15 e/pixel/s), each ROSA camera is capable of full-chip readout speeds in excess of 30 Hz, and up to 200 Hz when the CCD is windowed. ROSA will allow for multi-wavelength studies of the solar atmosphere at a high temporal resolution. We will present the current instrument set-up and parameters, observing modes, and future plans, including a new high QE camera allowing 15 Hz for Halpha. Interested parties should see https://habu.pst.qub.ac.uk/groups/arcresearch/wiki/de502/ROSA.html

CaII K interstellar observations towards early-type disc and halo stars - distances to intermediate- and high-velocity clouds

We compare existing high spectral resolution (R = lambda/Deltalambda similar to 40 000) Ca II Kobservations (lambda(air) = 3933.66 Angstrom) towards 88 mainly B-type stars, and new observations taken using the Intermediate dispersion Spectrograph and Imaging System (ISIS) on the William Herschel Telescope at R similar to 10 000 towards three stars taken from the Palomar-Green Survey, with 21-cm HI emission-line profiles, in order to search for optical absorption towards known intermediate- and high-velocity cloud complexes. Given certain assumptions, limits to the gas phase abundance of Ca II are estimated for the cloud components. We use the data to derive the following distances from the Galactic plane (z). (i) Tentative lower z-height limits of 2800 and 4100 pc towards complex C using lack of absorption in the spectra of HD341617 and PG 0855 + 294, respectively. (ii) A weak lower z-height of 1400 pc towards complex WA-WB using lack of absorption in EC 09470-1433 and a weak lower limit of 2470 pc using lack of absorption in EC 09452-1403. (iii) An upper z- height of 2470 pc towards a southern intermediate- velocity cloud (IVC) with v(LSR) = -55 km s(-1) using PG 2351 + 198. (iv) Detection of a possible IVC in Ca II absorption at v(LSR) = +52 km s(-1) using EC 20104-2944. No associated HI in emission is detected. At this position, normal Galactic rotation predicts velocities of up to similar to+ 25 km s(-1). The detection puts an upper z-height of 1860 pc to the cloud. (v) Tentative HI and Ca II K detections towards an IVC at similar to+70 km s(-1) in the direction of high-velocity cloud (HVC) complex WE, sightline EC 06387-8045, indicating that the IVC may be at a z-height lower than 1770 pc. (vi) Detection of Ca II K absorption in the spectrum of PG 0855 + 294 in the direction of IV20, indicating that this IVC has a z-height smaller than 4100 pc. (vii) A weak lower z-height of 4300 pc towards a small HVC with v(LSR) = +115 km s(-1) at l, b = 200degrees, + 52degrees, using lack of absorption in the Ca II K spectrum of PG 0955 + 291.

High-resolution spectroscopic observations of B-type stars from the Edinburgh-Cape Survey - III. Completion of a magnitude range limited survey

High spectral resolution (R similar to 40 000) and signal-to- noise ratio observations of five high Galactic latitude early- type stars taken from the Edinburgh-Cape (EC) Faint Blue Object Survey are presented. These were required to complete a magnitude range-limited survey of young B-type objects with 11 <V <15. Of the five stars, four were rejected on the grounds that they are either subluminous (subdwarf or horizontal branch), were part of a binary system or possessed colours later than the (U - B) = -0.5 cut-off employed. The remaining star in the data set, EC 19596-5356, is found to exhibit normal young B-type stellar properties. A kinematic analysis reveals that an origin in the Galactic disc appears likely for all the stars in the sample. Some statistics are drawn about the number density of young stars in the Galactic halo.

High-resolution spectroscopic observations of post-asymptotic giant branch candidates from the Edinburgh-Cape Survey

High spectral resolution ( R similar to 40 000) and signal-to-noise optical spectra, obtained at the Very Large Telescope ( VLT), are presented for three post-asymptotic giant branch ( AGB) candidates selected from the Edinburgh-Cape ( EC) Faint Blue Object Survey. The stellar atmospheric parameters and chemical compositions, derived using sophisticated non-local thermodynamic equilibrium calculations, reveal that EC 14102-1337 and EC 20068-7324 are both in an evolved post-horizontal branch ( HB) evolutionary state. However, EC 11507-2253 is most likely a post-AGB star.

Geophysical imaging of stimulated microbial biomineralization

Understanding how microorganisms influence the physical and chemical properties of the subsurface is hindered by our inability to observe microbial dynamics in real time and with high spatial resolution. Here, we investigate the use of noninvasive geophysical methods to monitor biomineralization at the laboratory scale during stimulated sulfate reduction under dynamic flow conditions. Alterations in sediment characteristics resulting from microbe-mediated sulfide mineral precipitation were concomitant with changes in complex resistivity and acoustic wave propagation signatures. The sequestration of zinc and iron in insoluble sulfides led to alterations in the ability of the pore fluid to conduct electrical charge and of the saturated sediments to dissipate acoustic energy. These changes resulted directly from the nucleation, growth, and development of nanoparticulate precipitates along grain surfaces and within the pore space. Scanning and transmission electron microscopy (SEM and TEM) confirmed the sulfides to be associated with cell surfaces, with precipitates ranging from aggregates of individual 3-5 nm nanocrystals to larger assemblages of up to 10-20 m in diameter. Anomalies in the geophysical data reflected the distribution of mineral precipitates and biomass over space and time, with temporal variations in the signals corresponding to changes in the aggregation state of the nanocrystalline sulfides. These results suggest the potential for using geophysical techniques to image certain subsurface biogeochemical processes, such as those accompanying the bioremediation of metal-contaminated aquifers.

Phase and space resolved optical emission spectroscopic investigations of an inductively coupled RF plasma using an imaging acousto-optic spectrometer

A novel acousto-optic spectrometer (IfU Diagnostic Systems GmbH) for 2-dimensional (2D) optical emission spectroscopy with high spectral resolution has been developed. The spectrometer is based on acousto-optic tuneable filter technology with fast random wavelength access. Measurements for characterisation of the imaging quality, the spatial resolution, and the spectral resolution are presented. The applicability for 2D-space and phase resolved optical emission spectroscopy (2D-PROES) is shown. 2D-PROES has been applied to an inductively coupled plasma with radio frequency excitation at 13.56 MHz.

Aligning conservation priorities across taxa in Madagascar with high-resolution planning tools

Globally, priority areas for biodiversity are relatively well known, yet few detailed plans exist to direct conservation action within them, despite urgent need. Madagascar, like other globally recognized biodiversity hot spots, has complex spatial patterns of endemism that differ among taxonomic groups, creating challenges for the selection of within-country priorities. We show, in an analysis of wide taxonomic and geographic breadth and high spatial resolution, that multitaxonomic rather than single-taxon approaches are critical for identifying areas likely to promote the persistence of most species. Our conservation prioritization, facilitated by newly available techniques, identifies optimal expansion sites for the Madagascar government's current goal of tripling the land area under protection. Our findings further suggest that high-resolution multitaxonomic approaches to prioritization may be necessary to ensure protection for biodiversity in other global hot spots.

Nuclear activation as a high dynamic range diagnostic of laser-plasma interactions

Proton imaging has become a common diagnostic technique for use in laser-plasma research experiments due to their ability to diagnose electric field effects and to resolve small density differences caused through shock effects. These interactions are highly dependent on the use of radiochromic film (RCF) as a detection system for the particle probe, and produces very high-resolution images. However, saturation effects, and in many cases, damage to the film limits the usefulness of this technique for high-flux particle probing. This paper outlines the use of a new technique using contact radiography of (p,n)-generated isotopes in activation samples to produce high dynamic range 2D images with high spatial resolution and extremely high dynamic range, whilst maintaining both energy resolution and absolute flux measurements. (C)007 Elsevier B.V. All rights reserved.

High-resolution electron energy-loss spectroscopy of Ba Ti O 3∕ Sr Ti O 3 multilayers

The dielectric properties of BaTiO3 thin films and multilayers are different from bulk materials because of nanoscale dimensions, interfaces, and stress-strain conditions. In this study, BaTiO3/SrTiO3 multilayers deposited on SrTiO3 substrates by pulsed laser deposition have been investigated by high-energy-resolution electron energy-loss spectroscopy. The fine structures in the spectra are discussed in terms of crystal-field splitting and the internal strain. The crystal-field splitting of the BaTiO3 thin layer is found to be a little larger than that of bulk BaTiO3, which has been interpreted by the presence of the internal strain induced by the misfit at the interface. This finding is consistent with the lattice parameters of the BaTiO3 thin layer determined by the selected area diffraction pattern. The near-edge structure of the oxygen K edge in BaTiO3 thin layers and in bulk BaTiO3 are simulated by first-principle self-consistent full multiple-scattering calculations. The results of the simulations are in a good agreement with the experimental results. Moreover, the aggregation of oxygen vacancies at the rough BaTiO3/SrTiO3 interface is indicated by the increased [Ti]/[O] element ratio, which dominates the difference of dielectric properties between BaTiO3 layer and bulk materials.

Zooming In on the Progenitors of Superluminous Supernovae With the HST

We present Hubble Space Telescope (HST) rest-frame ultraviolet imaging of the host galaxies of 16 hydrogen-poor superluminous supernovae (SLSNe), including 11 events from the Pan-STARRS Medium Deep Survey. Taking advantage of the superb angular resolution of HST, we characterize the galaxies' morphological properties, sizes, and star formation rate (SFR) densities. We determine the supernova (SN) locations within the host galaxies through precise astrometric matching and measure physical and host-normalized offsets as well as the SN positions within the cumulative distribution of UV light pixel brightness. We find that the host galaxies of H-poor SLSNe are irregular, compact dwarf galaxies, with a median half-light radius of just 0.9 kpc. The UV-derived SFR densities are high ([Sigma(SFR)] similar or equal to 0.1M(circle dot) yr(-1) kpc(-1)), suggesting that SLSNe form in overdense environments. Their locations trace the UV light of their host galaxies, with a distribution intermediate between that of long-duration gamma-ray bursts (LGRBs; which are strongly clustered on the brightest regions of their hosts) and a uniform distribution (characteristic of normal core-collapse SNe), though cannot be statistically distinguished from either with the current sample size. Taken together, this strengthens the picture that SLSN progenitors require different conditions than those of ordinary core-collapse SNe to form and that they explode in broadly similar galaxies as do LGRBs. If the tendency for SLSNe to be less clustered on the brightest regions than are LGRBs is confirmed by a larger sample, this would indicate a different, potentially lower-mass progenitor for SLSNe than LRGBs.