1,008 research outputs found
Electropolishing of medical-grade stainless steel in preparation for surface nano-texturing
The purpose of this work is to investigate the electropolishing of medical grade 316L stainless steel to obtain a clean, smooth and defect free surface in preparation for surface nano-texturing. Electropolishing of steel was conducted under stationary conditions in four electrolyte mixtures: A) 4.5 M H2SO4 + 11 M H3PO4, B) 7.2 M H2SO4 + 6.5 M H3PO4, C) 6.4 M glycerol + 6.1 M H3PO4 and D) 6.1 M H3PO4. The influence of electrolyte composition and concentration, temperature and electropolishing time, in conjunction with linear sweep voltammetry and chronoamperometry, on the stainless steel surface was studied. The activation energies for dissolution of steel in the four electrolyte solutions were calculated. The resulting surfaces of unpolished and optimally-polished stainless steel were characterised in terms of contamination, defects, topography, roughness, hydrophilicity and chemical composition by optical and atomic force microscopies, contact angle goniometry and x-ray photoelectron spectroscopy. It was found that the optimally polished surfaces were obtained with the following parameters: electrolyte mixture A at 2.1 V applied potential, 80 °C for 10 minutes. This corresponded to the diffusion-limited dissolution of the surface. The root mean square surface roughness of the electropolished surface achieved was 0.4 nm over 2 x 2 Όm2. Surface analysis showed that electropolishing led to ultraclean surfaces with reduced roughness and contamination thickness, and with Cr, P, S, Mo, Ni and O enrichment compared to untreated surfaces
Deep XMM-Newton observations of the northern disc of M31. I. Source catalogue
We carried out new observations of two fields in the northern ring of M31
with XMM-Newton with two exposures of 100 ks each and obtained a complete list
of X-ray sources down to a sensitivity limit of ~7 x 10^34 erg s^-1 (0.5 - 2.0
keV). The major objective of the observing programme was the study of the hot
phase of the ISM in M31. The analysis of the diffuse emission and the study of
the ISM is presented in a separate paper. We analysed the spectral properties
of all detected sources using hardness ratios and spectra if the statistics
were high enough. We also checked for variability. We cross-correlated the
source list with the source catalogue of a new survey of the northern disc of
M31 carried out with Chandra and Hubble (Panchromatic Hubble Andromeda
Treasury, PHAT) as well as with other existing catalogues. We detected a total
of 389 sources, including 43 foreground stars and candidates and 50 background
sources. Based on the comparison to the Chandra/PHAT survey, we classify 24
hard X-ray sources as new candidates for X-ray binaries (XRBs). In total, we
identified 34 XRBs and candidates and 18 supernova remnants (SNRs) and
candidates. Three of the four brightest SNRs show emission mainly below 2 keV,
consistent with shocked ISM. The spectra of two of them also require an
additional component with a higher temperature. The SNR [SPH11] 1535 has a
harder spectrum and might suggest that there is a pulsar-wind nebula inside the
SNR. We find five new sources showing clear time variability. We also studied
the spectral properties of the transient source SWIFT J004420.1+413702, which
shows significant variation in flux over a period of seven months (June 2015 to
January 2016) and associated change in absorption. Based on the likely optical
counterpart detected in the Chandra/PHAT survey, the source is classified as a
low-mass X-ray binary.Comment: Accepted for publication in A&
The nature and current status of Transgenic Atlantic Salmon
This study was commissioned by the Irish Marine Institute in response to a Ministerial request from the Department of the Marine. The definition of Genetically Modified fish
(GMO) that we use throughout this report is of fish that have a gene added from the same or another species, i.e. transgenics. This is a narrow definition, in that it excludes products of sex manipulation or ploidy manipulation, but is the one accepted by, for example, the European Union (Council Directive 90/220/EEC, Anon. 1990).
We were asked to address a number of questions, viz.
1. Current "state of the art" in salmon genetic engineering.
2. What is available commercially and what commercial strains would be attractive to Irish interests?
3. What is the potential impact of transgenic Atlantic salmon (Salmo salar) in general?
4. What particular concerns would there be if a strain currently being reared in Scotland, were to be introduced to Ireland?
5. Are current ED Directives sufficient to protect Irish interests. If not what changes should be proposed?
6. What research is required to clarify the issues?
This report was produced within twenty days of the initial request and thus we were confined largely to the literature that was available locally, though we were able to talk to some people who have various areas of expertise in the field and these people, who are listed in the acknowledgements, provided useful discussion and additional literature. One other point that should be made is that this is a very rapidly expanding field and the material described here will rapidly become dated.Funder: Marine Institut
Isotopic Composition of Solar Wind Calcium: First in Situ Measurement by CELIAS/MTOF on Board SOHO
We present first results on the Ca isotopic abundances derived from the high
resolution Mass Time-of-Flight (MTOF) spectrometer of the charge, element, and
isotope analysis system (CELIAS) experiment on board the Solar and Heliospheric
Observatory (SOHO). We obtain isotopic ratios 40Ca/42Ca = (128+-47) and
40Ca/44Ca = (50+-8), consistent with terrestrial values. This is the first in
situ determination of the solar wind calcium isotopic composition and is
important for studies of stellar modeling and solar system formation since the
present-day solar Ca isotopic abundances are unchanged from their original
isotopic composition in the solar nebula.Comment: 14 pages, 3 figure
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Altered dynamics of visual contextual interactions in Parkinson\u27s disease.
Over the last decades, psychophysical and electrophysiological studies in patients and animal models of Parkinson\u27s disease (PD), have consistently revealed a number of visual abnormalities. In particular, specific alterations of contrast sensitivity curves, electroretinogram (ERG), and visual-evoked potentials (VEP), have been attributed to dopaminergic retinal depletion. However, fundamental mechanisms of cortical visual processing, such as normalization or gain control computations, have not yet been examined in PD patients. Here, we measured electrophysiological indices of gain control in both space (surround suppression) and time (sensory adaptation) in PD patients based on steady-state VEP (ssVEP). Compared with controls, patients exhibited a significantly higher initial ssVEP amplitude that quickly decayed over time, and greater relative suppression of ssVEP amplitude as a function of surrounding stimulus contrast. Meanwhile, EEG frequency spectra were broadly elevated in patients relative to controls. Thus, contrary to what might be expected given the reduced contrast sensitivity often reported in PD, visual neural responses are not weaker; rather, they are initially larger but undergo an exaggerated degree of spatial and temporal gain control and are embedded within a greater background noise level. These differences may reflect cortical mechanisms that compensate for dysfunctional center-surround interactions at the retinal level
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LC/MS based detection and semi-quantitative analysis of INSL5 in human and murine tissues
RATIONALE: Insulin Like Peptide 5 (INSL5) is a hormone produced by enteroendocrine L-cells in the colon that has recently been implicated in the control of metabolic homeostasis. However, research into its physiology has been hindered by the reported unreliability of commercially available immunoassays and additional detection assays would benefit this emerging field. METHODS: Peptides from purified murine L-cells and homogenates from both human and mouse colonic tissues were extracted by precipitating larger proteins with acetonitrile. Untargeted LC/MS/MS analyses followed by database searching, was used to detect and identify various INSL5 gene derived peptides and characterize their precise sequence. A similar approach was developed to quantify INSL5 levels in primary intestinal culture supernatants after purification and concentration by solid phase extraction. RESULTS: Mass spectral analysis of purified enteroendocrine cells and tissue homogenates identified the exact sequence of A- and B-chains of INSL5 endogenously expressed in L-cells. Differences in the endogenously processed peptide and the Swissprot database entry were observed for murine INSL5, whereas the human sequence matched previous predictions from heterologous expression experiments. INSL5 was detected in the supernatant of human and mouse primary colonic cultures and concentrations increased after treatment with a known L-cell stimulus. CONCLUSIONS: The first LC/MS/MS based method capable of the detection and semi-quantitative analysis of endogenous INSL5 using MS based techniques has been demonstrated. The methodology will enable the identification of stimulants for INSL5 secretion from murine and human primary colonic epithelial cultures.The Human Research Tissue Bank is supported by the NIHR Cambridge Biomedical Research Centre. This work was funded by grants from the WellcomeTrust (106262/Z/14/Z, 106 263/Z/14/Z), theMRC Metabolic Diseases Unit (MRC MCUU 12012/3, MRC MC UU 12012/5). The MS instrument was obtained using the MRC âEnhancing UK clinical researchâ grant (MR/M009041/1).The work was also supported by a project grant from Medimmune
Solar-Wind Bulk Velocity Throughout the Inner Heliosphere from Multi-Spacecraft Measurements
We extrapolate solar-wind bulk velocity measurements for different in-ecliptic heliospheric positions by calculating the theoretical time lag between the locations. The solar-wind bulk velocity dataset is obtained from in-situ plasma measurements by STEREO A and B, SOHO, Venus Express, and Mars Express. During their simultaneous measurements between 2007 and 2009 we find typical solar activity minimum conditions. In order to validate our extrapolations of the STEREO A and B data, we compare them with simultaneous in-situ observations from the other spacecraft. This way of cross-calibration we obtain a measure for the goodness of our extrapolations over different heliospheric distances. We find that a reliable solar-wind dataset can be provided in case of a longitudinal separation less than 65 degrees. Moreover, we find that the time lag method assuming constant velocity is a good basis to extrapolate from measurements in Earth orbit to Venus or to Mars. These extrapolations might serve as a good solar-wind input information for planetary studies of magnetospheric and ionospheric processes. We additionally show how the stream-stream interactions in the ecliptic alter the bulk velocity during radial propagation
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Intermittent release of transients in the slow solar wind: 2. In situ evidence
In paper 1, we showed that the Heliospheric Imager (HI) instruments on the pair of NASA STEREO spacecraft can be used to image the streamer belt and, in particular, the variability of the slow solar wind which originates near helmet streamers. The observation of intense intermittent transient outflow by HI implies that the corresponding in situ observations of the slow solar wind and corotating interaction regions (CIRs) should contain many signatures of transients. In the present paper, we compare the HI observations with in situ measurements from the STEREO and ACE spacecraft. Analysis of the solar wind ion, magnetic field, and suprathermal electron flux measurements from
the STEREO spacecraft reveals the presence of both closed and partially disconnected interplanetary magnetic field lines permeating the slow solar wind. We predict that one of the transients embedded within the second CIR (CIRâD in paper 1) should impact the nearâEarth ACE spacecraft. ACE measurements confirm the presence of a transient at the time of CIR passage; the transient signature includes helical magnetic fields and bidirectional suprathermal electrons. On the same day, a strahl electron dropout is observed at STEREOâB, correlated with the passage of a high plasma beta structure. Unlike ACE, STEREOâB observes the transient a few hours ahead of the CIR. STEREOâA, STEREOâB, and ACE spacecraft observe very different slow solar wind properties ahead of and during the CIR analyzed in this paper, which we associate with the intermittent release of transients
The Spectral Energy Distribution of Powerful Starburst Galaxies I: Modelling the Radio Continuum
We have acquired radio continuum data between 70\,MHz and 48\,GHz for a
sample of 19 southern starburst galaxies at moderate redshifts () with the aim of separating synchrotron and free-free emission
components. Using a Bayesian framework we find the radio continuum is rarely
characterised well by a single power law, instead often exhibiting low
frequency turnovers below 500\,MHz, steepening at mid-to-high frequencies, and
a flattening at high frequencies where free-free emission begins to dominate
over the synchrotron emission. These higher order curvature components may be
attributed to free-free absorption across multiple regions of star formation
with varying optical depths. The decomposed synchrotron and free-free emission
components in our sample of galaxies form strong correlations with the
total-infrared bolometric luminosities. Finally, we find that without
accounting for free-free absorption with turnovers between 90 to 500\,MHz the
radio-continuum at low frequency (\,MHz) could be overestimated by
upwards of a factor of twelve if a simple power law extrapolation is used from
higher frequencies. The mean synchrotron spectral index of our sample is
constrained to be , which is steeper then the canonical value of
for normal galaxies. We suggest this may be caused by an intrinsically
steeper cosmic ray distribution
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