The XRF-CT technique continues to gain attention with respect to both its development and applications. The emergence of fast scanning approaches in conjunction with ED-detectors of high counting ...rate capability has allowed XRF-CT to evolve towards a truly 3D elemental imaging technique. At SR sources, the technique is regularly applied at sub-μm resolution together with complementary imaging modalities such as absorption and phase-contrast CT, XRD-CT, 2D/3D XAS and ptychography. The TXRF spectrometric analysis of suspensions and undigested samples (
e.g.
clay, cosmetics and nanoparticles) continues to receive much attention. In the analysis of fly ash samples, elemental sensitivities were affected by the angle of the measurement. In the use of TXRF spectrometry for the analysis of particle-like large specimens, the influence of the standing wave field was considered to be negligible. However, more work needs to be done on this source of uncertainty to improve our understanding of the influence of the standing wave field on these kind of samples. Novel equipment capable of very good angle resolution will be useful for such studies. Pre-concentration procedures are becoming more sophisticated with the introduction of new substrates for ligands capable of binding heavy metals and, in some cases, of being applied directly on the TXRF spectrometry reflector for immediate analysis. A sophisticated explanation of the excitation spectrum reported for μ-XRF spectrometry included a new description of the energy distribution of electrons in the target. Another highlight was the application of high-resolution monochromatic μ-XRF spectrometry using DCC optics for excitation and focusing as well as for increasing the spectral resolution of the Pu and U L-lines. Although the use of portable XRF spectrometry systems is now well established, new dedicated systems continue to be developed including those with a triaxial configuration. The focus is now primarily on the development and use of portable TXRF spectrometry systems for an expanding range of applications. In the area of cultural heritage applications, macroXRF spectrometry is a well-established imaging technique for the analysis of paintings that is now also being used to image stained-glass panels. The extensive study using a number of micro- and macro-techniques of Vermeer's painting of The Girl with a Pearl Earring illustrated the power of this approach. Not only could the different shades of blue in the painting be characterised but also the materials and techniques used to achieve various effects in the painting.
This review covers developments in and applications of XRF techniques such as EDXRF, WDXRF, TXRF, XRF microscopy using technologies such as synchrotron sources, X-ray optics, X-ray tubes and detectors in laboratory, mobile and hand-held systems.
That the boundaries of analysis using XRF spectrometry performed at SR sources continues to be pushed back is evidenced by the nanoscale spatial resolution with near single-atom sensitivity for the ...most efficiently detected elements in nanobeam applications and high speed 2D/3D imaging capabilities. The 4
th
generation SR facilities currently under development, such as the ESRF Extremely Brilliant Source (EBS), will be at the forefront of these advances. A clear trend is that SR-XRF spectrometry is increasingly applied with complementary X-ray spectroscopic/imaging techniques to combine spatially resolved elemental information with speciation and structural/morphological imaging. The wide range of applications of scanning (sub)microXRF spectrometry for elemental imaging published in the period covered by this review included biomedical, environmental, materials science and cultural heritage studies. Most applications involved XAS and XRD methods at hard X-ray micro- and nano-probe facilities. Full field microXRF spectrometry has made very promising advances with respect to the optics used. Coded apertures have potential for overcoming the low count rates that often restrict the full potential of laboratory-based full-field setups. The availability of commercial full-field detectors will increase the user community and thereby foster advancement in full field microXRF spectrometry. The TXRF spectrometry of ambient air is becoming more and more sophisticated and the advantages of this micro analytical tool over ICP-MS in terms of short sampling times with high particle size resolution are becoming ever more apparent. For example, the optimal sampling time for aerosols for TXRF analysis was well below 12 hours, whereas that for ICP-MS analysis was about 24 hours. High-quality grazing incidence XRF analysis in the laboratory has become more feasible with the development of prototype TXRF instrumentation and the availability of commercial XRD setups with energy dispersive detectors. Portable XRF spectrometry has undergone significant technological improvements in recent years and is now applied in a wide range of applications. This is reflected in a significant number of valuable review papers dealing with different aspects of the portable XRF technique. The growth in the use of macroXRF scanning systems in cultural heritage investigations has required development of new software and methodologies for efficient handling of the huge data files generated. In several contributions the possibilities of a new scanning station equipped with real time macroXRF spectrometry was demonstrated.
This review covers developments in and applications of XRF techniques such as EDXRF, WDXRF, TXRF, XRF microscopy using technologies such as synchrotron sources, X-ray optics, X-ray tubes and detectors, in laboratory, mobile and hand-held systems.
A highlight this year was the construction of elemental maps of microalgae cells at the organelle level using XRF-CT with a beam size of just 15 nm. These probably represent the highest ever spatial ...resolution achieved for XRF-CT images. An innovative approach for reconstruction algorithms used a deep convolutional neural network to correct for the self-absorption effects in the XRF-CT sinogram domain. Such corrections will enable the use of conventional tomographic reconstruction algorithms for XRF-CT analysis. A remarkable advantage of the proposed method was that it could correct for self-absorption effects without any prior knowledge of the scanning setups. A particularly innovative dual-energy X-ray-beam ptycho-fluorescence imaging method combined XRF spectrometry and X-ray ptychography scanning with simultaneous data-collection. To overcome the incompatibility of the different excitation and scanning conditions required for fast ptychography and high spatial resolution XRF spectrometry, two coaxial beams of different sizes were used on the sample simultaneously. In comparison to sequential scans, this combined approach has the potential to reduce the data collection time by a factor of 25. The very good performance of laboratory 2D-XRF spectrometry for the analysis of minute amounts of radioactive material has made it a potential alternative to TXRF spectrometry. Reconstruction algorithms are now capable of significantly enhancing imaging resolution in μXRF spectrometry. The forensic classification of incredibly small amounts of samples such as single fibres was accomplished using elemental profiles determined by TXRF spectrometry. Although characterisation of the low-Z matrix in milk and polymers by conventional TXRF spectrometry is challenging, it was successfully achieved by studying the Compton and Rayleigh scatter with both univariate and multivariate approaches. Portable XRF spectrometry is a well-established technique for a wide range of applications. Emphasis continues to be placed on improving calibration and reducing matrix and inter-element effects. The sample type remains a challenge for portable XRF analysis. Computer vision and statistical methods such as spectral angle mapper are being increasingly applied to maximise the information that can be extracted from the data. For example, an innovative approach exploited the elemental features from XRF spectra to improve the interpretation of molecular information provided by reflectance spectroscopy, and
vice versa
.
This review covers developments in and applications of XRF techniques such as EDXRF, WDXRF, TXRF, XRF microscopy using technologies such as synchrotron sources, X-ray optics, X-ray tubes and detectors in laboratory, mobile and hand-held systems.
ABSTRACT
We present an improved measurement of the Hubble constant (H0) using the ‘inverse distance ladder’ method, which adds the information from 207 Type Ia supernovae (SNe Ia) from the Dark ...Energy Survey (DES) at redshift 0.018 < z < 0.85 to existing distance measurements of 122 low-redshift (z < 0.07) SNe Ia (Low-z) and measurements of Baryon Acoustic Oscillations (BAOs). Whereas traditional measurements of H0 with SNe Ia use a distance ladder of parallax and Cepheid variable stars, the inverse distance ladder relies on absolute distance measurements from the BAOs to calibrate the intrinsic magnitude of the SNe Ia. We find H0 = 67.8 ± 1.3 km s−1 Mpc−1 (statistical and systematic uncertainties, 68 per cent confidence). Our measurement makes minimal assumptions about the underlying cosmological model, and our analysis was blinded to reduce confirmation bias. We examine possible systematic uncertainties and all are below the statistical uncertainties. Our H0 value is consistent with estimates derived from the Cosmic Microwave Background assuming a ΛCDM universe.
The utilisation of SR sources has significantly enhanced the analytical capabilities of XRF spectrometry techniques. With the latest generation of facilities, SR-XRF spectrometry achieves remarkably ...high nm-scale resolution with excellent LODs at ppb levels. A noteworthy trend is the increasing use of SR-XRF spectrometry together with other X-ray spectroscopic and imaging techniques. This provides complementary information on elemental speciation as well as structural and morphological characteristics of samples. Sub-μm SR-XRF spectrometry has been extensively applied in diverse fields such as environmental and planetary studies, biomedical research, materials science and cultural heritage investigations. Methods for handling the huge datasets produced by macroXRF spectrometry have become essential for processing and classifying the element distributions collected from the analysis of paintings. Machine-learning-based correlations of element maps have been developed for the automatic identification of patterns as an alternative method of processing macroXRF spectrometry data from cultural heritage samples. The microanalytical capabilities of TXRF spectrometry have led to a steep increase in applications to biomedical problems with successful analyses of minute amounts of samples (
ca.
20 mg) of,
e.g.
, blood, placenta and heart tissue. The suspension-assisted preparation of theses samples and of mineralogical materials was improved in many studies by extending the common internal standard calibration with uni- and multivariate approaches. The development of a scan-free grazing-exit XRF spectrometer improved accuracy in the analysis of periodic surface structures. The degree of protonation of different thiol- or hydroxyl-bearing organic monolayers was successfully determined using grazing-incidence XRF and TXRF spectrometries in combination with other techniques.
This review covers developments in and applications of XRF techniques such as EDXRF, WDXRF, TXRF, XRF microscopy using technologies such as synchrotron sources, X-ray optics, X-ray tubes and detectors in laboratory, mobile and hand-held systems.
Convulsive status epilepticus (CSE) is the most common life-threatening neurological emergency in childhood. These children are also at risk of significant morbidity, with acute and chronic impact on ...the family and the health and social care systems. The current recommended first-choice, second-line treatment in children aged 6 months and above is intravenous phenytoin (fosphenytoin in the USA), although there is a lack of evidence for its use and it is associated with significant side effects. Emerging evidence suggests that intravenous levetiracetam may be effective as a second-line agent for CSE, and fewer adverse effects have been described. This trial therefore aims to determine whether intravenous phenytoin or levetiracetam is more effective, and safer, in treating childhood CSE.
This is a phase IV, multi-centre, parallel group, randomised controlled, open-label trial. Following treatment for CSE with first-line treatment, children with ongoing seizures are randomised to receive either phenytoin (20 mg/kg, maximum 2 g) or levetiracetam (40 mg/kg, maximum 2.5 g) intravenously. The primary outcome measure is the cessation of all visible signs of CSE as determined by the treating clinician. Secondary outcome measures include the need for further anti-seizure medications or rapid sequence induction for ongoing CSE, admission to critical care areas, and serious adverse reactions. Patients are recruited without prior consent, with deferred consent sought at an appropriate time for the family. The primary analysis will be by intention-to-treat. The primary outcome is a time to event outcome and a sample size of 140 participants in each group will have 80% power to detect an increase in CSE cessation rates from 60% to 75%. Our total sample size of 308 randomised and treated participants will allow for 10% loss to follow-up.
This clinical trial will determine whether phenytoin or levetiracetam is more effective as an intravenous second-line agent for CSE, and provide evidence for management recommendations. In addition, this trial will also provide data on which of these therapies is safer in this setting.
ISRCTN identifier, ISRCTN22567894 . Registered on 27 August 2015 EudraCT identifier, 2014-002188-13 . Registered on 21 May 2014 NIHR HTA Grant: 12/127/134.
It is well known that the probability distribution function (PDF) of galaxy density contrast is approximately lognormal; whether the PDF of mass fluctuations derived from weak lensing convergence ...(...WL) is lognormal is less well established. We derive PDFs of the galaxy and projected matter density distributions via the counts-in-cells (CiC) method. We use maps of galaxies and weak lensing convergence produced from the Dark Energy Survey Science Verification data over 139 deg2. We test whether the underlying density contrast is well described by a lognormal distribution for the galaxies, the convergence and their joint PDF. We confirm that the galaxy density contrast distribution is well modelled by a lognormal PDF convolved with Poisson noise at angular scales from 10 to 40 arcmin (corresponding to physical scales of 3-10 Mpc). We note that as ...WL is a weighted sum of the mass fluctuations along the line of sight, its PDF is expected to be only approximately lognormal. We find that the ...WL distribution is well modelled by a lognormal PDF convolved with Gaussian shape noise at scales between 10 and 20 arcmin, with a best-fitting X2/dof of 1.11 compared to 1.84 for a Gaussian model, corresponding to p-values 0.35 and 0.07, respectively, at a scale of 10 arcmin. Above 20 arcmin a simple Gaussian model is sufficient. The joint PDF is also reasonably fitted by a bivariate lognormal. As a consistency check, we compare the variances derived from the lognormal modelling with those directly measured via CiC. Our methods are validated against maps from the MICE Grand Challenge N-body simulation. (ProQuest: ... denotes formulae/symbols omitted.)
The range of ticks in North America has been steadily increasing likely, in part, due to climate change. Along with it, there has been a rise in cases of tick-borne disease. Among those medically ...important tick species of particular concern are Ixodes scapularis Say (Acari: Ixodidae), Dermacentor variabilis Say (Acari: Ixodidae), and Amblyomma americanum Linneaus (Acari: Ixodidae). The aim of this study was to determine if climate factors explain existing differences in abundance of the three aforementioned tick species between two climatically different regions of Illinois (Central and Southern), and if climate variables impact each species differently. We used both zero-inflated regression approaches and Bayesian network analyses to assess relationships among environmental variables and tick abundance. Results suggested that the maximum average temperature and total precipitation are associated with differential impact on species abundance and that this difference varied by region. Results also reinforced a differential level of resistance to desiccation among these tick species. Our findings help to further define risk periods of tick exposure for the general public, and reinforce the importance of responding to each tick species differently.
This review describes advances in the XRF group of techniques published approximately between April 2018 and March 2019. The review is selective with the aim of providing a critical insight into ...developments in instrumentation, methodologies and data handling that represent a significant advance in XRF spectrometry. It is not the intention of the review to cover comprehensively the applications of XRF techniques except in those cases where the non-destructive and remote sensing nature of XRF analysis makes it particularly valuable and the method of choice. These applications concern samples which are irreplaceable and of great cultural value such as works of art and archaeological artefacts.
This 2019 review covers developments in and applications of XRF techniques such as EDXRF, WDXRF, TXRF, XRF microscopy using technologies such as synchrotron sources, X-ray optics, X-ray tubes and detectors in laboratory, mobile and hand-held systems.
We present the first constraints on cosmology from the Dark Energy Survey (DES), using weak lensing measurements from the preliminary Science Verification (SV) data. We use 139 square degrees of SV ...data, which is less than 3% of the full DES survey area. Using cosmic shear 2-point measurements over three redshift bins we find sigma sub(8)(Omega sub(m)/0.3 ) super(0.5) = 0.81+ or -0.06 (68% confidence), after marginalizing over 7 systematics parameters and 3 other cosmological parameters. We examine the robustness of our results to the choice of data vector and systematics assumed, and find them to be stable. About 20% of our error bar comes from marginalizing over shear and photometric redshift calibration uncertainties. The current state-of-the-art cosmic shear measurements from CFHTLenS are mildly discrepant with the cosmological constraints from Planck CMB data; our results are consistent with both data sets. Our uncertainties are ~ 30% larger than those from CFHTLenS when we carry out a comparable analysis of the two data sets, which we attribute largely to the lower number density of our shear catalogue. We investigate constraints on dark energy and find that, with this small fraction of the full survey, the DES SV constraints make negligible impact on the Planck constraints. The moderate disagreement between the CFHTLenS and Planck values of sigma sub(8)(Omega sub(m)/0.3 ) super(0.5) is present regardless of the value of w.
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