The hadronic width of the ground state of pionic hydrogen has been redetermined by X-ray spectroscopy to be
Γ
1
s
π
H
=
(
856
±
16
stat
±
22
sys
)
meV. The experiment was performed at the ...high-intensity low-energy pion beam of the Paul Scherrer Institute by using the cyclotron trap and a high-resolution Bragg spectrometer with spherically bent crystals. Coulomb de-excitation was studied in detail by comparing its influence on the line shape by measuring the three different transitions K
α
, K
β
, and K
γ
at various hydrogen densities. The pion-nucleon scattering lengths and other physical quantities extracted from pionic-atom data are in good agreement with the results obtained from pion-nucleon and nucleon-nucleon scattering experiments and confirm that a consistent picture is achieved for the low-energy pion-nucleon sector with respect to the expectations of chiral perturbation theory.
Macroscopic X-ray fluorescence analysis (MA-XRF) is a non-destructive analytical technique that allows for the rapid and thorough investigation of paintings; therefore, it is nowadays increasingly ...involved in relevant studies. In the present work, a state-of-the-art MA-XRF set-up is utilized to identify the painting materials and techniques and document the state of preservation of an early 19th-century AD Greek religious panel painting (“icon”). The artifact in consideration has received extensive restoration interventions in the past and is considerably decayed; for these reasons, the interpretation of the relevant MA-XRF elemental intensity distribution maps is challenging. In this framework, it is demonstrated how the elemental distribution maps can be explored and interpreted to lead to a thorough investigation of the painting in consideration. In particular, the MA-XRF data interpretation allowed for the identification of the original palette that includes the rather rarely employed–in icon painting-yellow lead-antimonate pigment, led to the spotting of an invisible inscription, to the documentation of the preparation/gesso layer and the preliminary drawing. Additionally, it was possible to discriminate between the original painting and the later interventions, while the collected data revealed that the painting originally had two cross-bars attached to its back. Ultimately, the presented case study can be utilized as a guide for the proper interpretation of MA-XRF data from decayed and altered icons.
Abstract
With this study, we present the development of a transportable x‐ray emission spectrometer (XES) that was realized in a net time of 20 h, in order to verify the presence of Platinum (Pt) in ...gold Celtic coins belonging to 3rd–1st century BCE. Prior to the XES study, measurements using Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM‐EDS) revealed that the coins were made of highly concentrated gold (Au) alloy with trace amounts of bismuth (Bi) and, in one case, osmium (Os) and iridium (Ir). Os and Ir together with Pt and other components belong to the Platinum Group Elements (PGE). They form inclusions in ancient gold alloys and their presence is significant in provenance studies since they indicate the use of alluvial gold. Detection of platinum trace elements in a golden matrix is not possible using energy dispersive x‐ray emission techniques (SEM‐EDS, ED‐XRF, or PIXE) because of the limited energy resolution of the Si detectors. A way to overcome this problem is by using a high‐resolution wavelength dispersive x‐ray emission technique. For this purpose, we built a crystal spectrometer in Von‐Hamos geometry. In the framework of this study three samples/coins have been measured, and the presence of Pt was verified in one of them. The limitations of our spectrometer are critically evaluated and ways to optimize the performance of the spectrometer are discussed.
The emergence of Localized Surface Plasmon Resonance (LSPR) in nanocomposite films consisting of a hydrogen-free amorphous Carbon (a-C) matrix and Ag is considered theoretically and experimentally. ...While in theory it could be manifested for highly tetrahedral (>90% sp3) matrices, Auger electron spectroscopy and neutron reflectivity have shown that the incorporation of Ag into the a-C matrix induces severe graphitization that eliminates the LSPR; nonetheless, the dielectric damping of graphitized a-C, in combination with the π−π⁎ electronic transitions of carbon and the defect states introduced by Ag, cumulatively result in a strong broadband optical absorption in the near infrared, visible and UVA/UVB spectral ranges, revealed by optical reflectivity spectra, that coincides with the solar emission spectrum. The incorporation of Ag into a-C at room temperature thus proves to be an energy-efficient pathway for the controlled graphitization and the tailored optical absorption of novel nanocomposite films for solar photothermal applications.
•We provide the optical response of amorphous Carbon/Silver nanocomposite layers, whose absorbance is tailored to coincide with the solar emittance.•We identify the mechanism lying behind the atomical dispersion or nanoparticle formation of Ag into amorphous Carbon.•We manufacture a black carbon material at room temperature and without ion damage.
X-ray fluorescence (XRF) spectrometry has proven to be a core, non-destructive, analytical technique in cultural heritage studies mainly because of its non-invasive character and ability to rapidly ...reveal the elemental composition of the analyzed artifacts. Being able to penetrate deeper into matter than the visible light, X-rays allow further analysis that may eventually lead to the extraction of information that pertains to the substrate(s) of an artifact. The recently developed scanning macroscopic X-ray fluorescence method (MA-XRF) allows for the extraction of elemental distribution images. The present work aimed at comparing two different analysis methods for interpreting the large number of XRF spectra collected in the framework of MA-XRF analysis. The measured spectra were analyzed in two ways: a merely spectroscopic approach and an exploratory data analysis approach. The potentialities of the applied methods are showcased on a notable 18th-century Greek religious panel painting. The spectroscopic approach separately analyses each one of the measured spectra and leads to the construction of single-element spatial distribution images (element maps). The statistical data analysis approach leads to the grouping of all spectra into distinct clusters with common features, while afterward dimensionality reduction algorithms help reduce thousands of channels of XRF spectra in an easily perceived dataset of two-dimensional images. The two analytical approaches allow extracting detailed information about the pigments used and paint layer stratigraphy (i.e., painting technique) as well as restoration interventions/state of preservation.
Scanning micrο X-ray fluorescence (μ-XRF) and multispectral imaging (MSI) were applied to study philately stamps, selected for their small size and intricate structures. The μ-XRF measurements were ...accomplished using the M6 Jetstream Bruker scanner under optimized conditions for spatial resolution, while the MSI measurements were performed employing the XpeCAM-X02 camera. The datasets were acquired asynchronously. Elemental distribution maps can be extracted from the μ-XRF dataset, while chemical distribution maps can be obtained from the analysis of the multispectral dataset. The objective of the present work is the fusion of the datasets from the two spectral imaging modalities. An algorithmic co-registration of the two datasets is applied as a first step, aiming to align the multispectral and μ-XRF images and to adapt to the pixel sizes, as small as a few tens of micrometers. The dataset fusion is accomplished by applying k-means clustering of the multispectral dataset, attributing a representative spectrum to each pixel, and defining the multispectral clusters. Subsequently, the μ-XRF dataset within a specific multispectral cluster is analyzed by evaluating the mean XRF spectrum and performing k-means sub-clustering of the μ-XRF dataset, allowing the differentiation of areas with variable elemental composition within the multispectral cluster. The data fusion approach proves its validity and strength in the context of philately stamps. We demonstrate that the fusion of two spectral imaging modalities enhances their analytical capabilities significantly. The spectral analysis of pixels within clusters can provide more information than analyzing the same pixels as part of the entire dataset.
It has been argued that sleep disturbances are a risk factor for depression but previous longitudinal studies have had limitations and not addressed alternative explanations. The aim of this study ...was to examine the longitudinal association between sleep disturbances and depressive symptoms in a nationally representative sample.
Data from the 18-month follow-up of the UK National Psychiatric Morbidity survey were used (n = 2406). Sleep disturbances, depressive and other psychiatric symptoms (fatigue, concentration problems, irritability, anxiety and pain symptoms) were assessed using the Revised Clinical Interview Schedule (CIS-R). The bidirectional association between symptoms was investigated with logistic regression analyses and path analysis.
Sleep disturbances and depressive symptoms were correlated with each other cross-sectionally (r = 0.52, p < 0.001). In the longitudinal analysis, sleep disturbances at baseline did not predict depressive symptoms at follow-up odds ratio (OR) 1.27, 95% confidence interval (CI) 0.51-3.19 and the same was observed for the reciprocal association (OR 0.87, 95% CI 0.56-1.35). In the path analysis, the reciprocal model did not have a better fit compared to the simpler first-order model without cross-lagged paths. The path from sleep disturbances at baseline to depressive symptoms at follow-up had a minimal contribution to the explained variance of the latter (<1%).
Previous studies may have overestimated the importance of sleep disturbances as an independent risk factor of depression. The strong cross-sectional association is compatible with sleep disturbances being either a prodromal or a residual symptom of depression and this may have implications for recognition and treatment of depression.
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