Simultaneous X-ray Research Articles

Crystallization behavior of biodegradable poly(L-lactic acid) (PLLA)/poly(butylene succinate) (PBS) blends based on in situ simultaneous wide-angle x-ray diffraction/small-angle x-ray scattering techniques and thermal analyses

Crystallization behavior of biodegradable poly(L-lactic acid) (PLLA)/poly(butylene succinate) (PBS) blends based on in situ simultaneous wide-angle x-ray diffraction/small-angle x-ray scattering techniques and thermal analyses

FRAMEx. II. Simultaneous X-Ray and Radio Variability in Active Galactic Nuclei—The Case of NGC 2992

Abstract Using simultaneous Very Long Baseline Array and Neil Gehrels Swift Observatory X-ray Telescope observations of the active galactic nucleus (AGN) in NGC 2992 over a six-month observing campaign, we observed a large drop in core 5 cm radio luminosity, by a factor of >3, in tandem with a factor of >5 increase in 2–10 keV X-ray luminosity. While NGC 2992 has long been an important object for studies of X-ray variability, our study is the first simultaneous X-ray and radio variability campaign for this object. We observe that the X-ray spectral index does not change over the course of the flare, consistent with a change in the bulk amount of Comptonizing plasma, potentially due to a magnetic reconnection event in the accretion disk. The drop in apparent radio luminosity can be explained by a change in free–free absorption, which we calculate to correspond to an ionized region with a physical extent and electron density consistent with the broad-line region (BLR). Our results are consistent with magnetic reconnection events in the dynamic accretion disk creating outbursts of ionizing material, increasing Compton up-scattering of UV accretion disk photons and feeding material into the BLR. These findings present an important physical picture for the dynamical relationship between X-ray and radio emission in AGNs.

X-Ray Coronal Properties of Swift/BAT-selected Seyfert 1 Active Galactic Nuclei

Abstract The corona is an integral component of active galactic nuclei (AGNs) which produces the bulk of the X-ray emission above 1–2 keV. However, many of its physical properties and the mechanisms powering this emission remain a mystery. In particular, the temperature of the coronal plasma has been difficult to constrain for large samples of AGNs, as constraints require high-quality broadband X-ray spectral coverage extending above 10 keV in order to measure the high-energy cutoff, which provides constraints on the combination of coronal optical depth and temperature. We present constraints on the coronal temperature for a large sample of Seyfert 1 AGNs selected from the Swift/BAT survey using high-quality hard X-ray data from the NuSTAR observatory combined with simultaneous soft X-ray data from Swift/XRT or XMM-Newton. When applying a physically motivated, nonrelativistic disk-reflection model to the X-ray spectra, we find a mean coronal temperature kT e = 84 ± 9 keV. We find no significant correlation between the coronal cutoff energy and accretion parameters such as the Eddington ratio and black hole mass. We also do not find a statistically significant correlation between the X-ray photon index, Γ, and Eddington ratio. This calls into question the use of such relations to infer properties of supermassive black hole systems.

Dark-field chest x-ray imaging: first experience in patients with alpha1-antitrypsin deficiency

BackgroundSpirometry and conventional chest x-ray have limitations in investigating early emphysema, while computed tomography, the reference imaging method in this context, is not part of routine patient care due to its higher radiation dose. In this work, we investigated a novel low-dose imaging modality, dark-field chest x-ray, for the evaluation of emphysema in patients with alpha1-antitrypsin deficiency.MethodsBy exploiting wave properties of x-rays for contrast formation, dark-field chest x-ray visualises the structural integrity of the alveoli, represented by a high signal over the lungs in the dark-field image. We investigated four patients with alpha1-antitrypsin deficiency with a novel dark-field x-ray prototype and simultaneous conventional chest x-ray. The extent of pulmonary function impairment was assessed by pulmonary function measurement and regional emphysema distribution was compared with CT in one patient.ResultsWe show that dark-field chest x-ray visualises the extent of pulmonary emphysema displaying severity and regional differences. Areas with low dark-field signal correlate with emphysematous changes detected by computed tomography using a threshold of -950 Hounsfield units. The airway parameters obtained by whole-body plethysmography and single breath diffusing capacity of the lungs for carbon monoxide demonstrated typical changes of advanced emphysema.ConclusionsDark-field chest x-ray directly visualised the severity and regional distribution of pulmonary emphysema compared to conventional chest x-ray in patients with alpha1-antitrypsin deficiency. Due to the ultra-low radiation dose in comparison to computed tomography, dark-field chest x-ray could be beneficial for long-term follow-up in these patients.

XFEL serial crystallography reveals the room temperature structure of methyl-coenzyme M reductase

Methyl-Coenzyme M Reductase (MCR) catalyzes the biosynthesis of methane in methanogenic archaea, using a catalytic Ni-centered Cofactor F430 in its active site. It also catalyzes the reverse reaction, that is, the anaerobic activation and oxidation, including the cleavage of the CH bond in methane. Because methanogenesis is the major source of methane on earth, understanding the reaction mechanism of this enzyme can have massive implications in global energy balances. While recent publications have proposed a radical-based catalytic mechanism as well as novel sulfonate-based binding modes of MCR for its native substrates, the structure of the active state of MCR, as well as a complete characterization of the reaction, remain elusive. Previous attempts to structurally characterize the active MCR-Ni(I) state have been unsuccessful due to oxidation of the redox- sensitive catalytic Ni center. Further, while many cryo structures of the inactive Ni(II)-enzyme in various substrates-bound forms have been published, no room temperature structures have been reported, and the structure and mechanism of MCR under physiologically relevant conditions is not known. In this study, we report the first room temperature structure of the MCRred1-silent Ni(II) form using an X-ray Free-Electron Laser (XFEL), with simultaneous X-ray Emission Spectroscopy (XES) and X-ray Diffraction (XRD) data collection. In celebration of the seminal contributions of inorganic chemist Dick Holm to our understanding of nickel-based catalysis, we are honored to announce our findings in this special issue dedicated to this remarkable pioneer of bioinorganic chemistry.

Long-term multi-wavelength study of temporal and spectral properties of 3C 279

We present a long-term multi-wavelength study of the flat spectrum radio quasar 3C 279 using near simultaneous observations available from July 01, 2012 and June 31, 2018 (MJD 56109-58301). The data set includes measurements from the TACTIC, Fermi-LAT, Swift-XRT, Swift-UVOT, SMARTS, Steward-SPOL, and OVRO. The TACTIC telescope has monitored the source 3C 279 for ∼ 70 h between 2013 and 2018 in the energy range of > 0.85 TeV and yields null result. We have analysed the Fermi-LAT data to obtain the 5-day binned light curve in the energy range 0.1–300 GeV. One low and six high emission states are identified in the Fermi-LAT light curve. The high emission states are modelled with an exponential rise and decay time profile using 1-day averaged flux points and have been characterized as the asymmetric flares. The spectral analysis of near simultaneous X-ray and γ-ray data from the Swift-XRT and Fermi-LAT respectively indicates harder when brighter trend during the high activity states. The time averaged broadband spectral energy distributions corresponding to the seven states are successfully reproduced under the framework of a simple one zone leptonic emission model with IR photons originating from the dusty torus as the dominant target for the inverse Compton scattering by the relativistic electrons. Results obtained from the broadband modelling suggest that the non-thermal emission region in the jet is above the broadline region. This is also supported by the average value of seed factor estimated using the derived model parameters. A positive correlation between the bulk Lorentz factor of the emission zone and average γ-ray flux measurements for each state indicates that an increase in the bulk Lorentz factor can be the dominant cause for the observed flares from 3C 279. We also discuss the implications of the obtained model parameters in detail to understand the long-term behaviour of the source.

Sgr A* X-ray flares from non-thermal particle acceleration in a magnetically arrested disc

ABSTRACT Sgr A* exhibits flares in the near-infrared and X-ray bands, with the luminosity in these bands increasing by factors of 10–100 for ≈60 min. One of the models proposed to explain these flares is synchrotron emission of non-thermal particles accelerated by magnetic reconnection events in the accretion flow. We use the results from particle-in-cell simulations of magnetic reconnection to post-process 3D two-temperature GRMHD simulations of a magnetically arrested disc (MAD). We identify current sheets, retrieve their properties, estimate their potential to accelerate non-thermal particles, and compute the expected non-thermal synchrotron emission. We find that the flux eruptions of MADs can provide suitable conditions for accelerating non-thermal particles to energies γe ≲ 106 and producing simultaneous X-ray and near-infrared flares. For a suitable choice of current-sheet parameters and a simplified synchrotron cooling prescription, the model can simultaneously reproduce the quiescent and flaring X-ray luminosities as well as the X-ray spectral shape. While the near-infrared flares are mainly due to an increase in the temperature near the black hole during the MAD flux eruptions, the X-ray emission comes from narrow current sheets bordering highly magnetized, low-density regions near the black hole, and equatorial current sheets where the flux on the black hole reconnects. As a result, not all infrared flares are accompanied by X-ray ones. The non-thermal flaring emission can extend to very hard (≲ 100 keV) X-ray energies.

The Origin of The Soft X-Ray Excess in the Seyfert 1.5 Galaxy ESO 362-G18

We review the Seyfert 1.5 Galaxy ESO 362-G18 for exploring the origin of the soft X-ray excess. The Warm Corona and Relativistic Reflection models are two main scenarios to interpret the soft X-ray excess in active galactic nuclei at present. We use the simultaneous X-ray observation data of XMM-Newton and NuSTAR on 2016 September 24 to perform spectral analysis in two steps. First, we analyze the time-average spectra by using Warm Corona and Relativistic Reflection models. Moreover, we also explore the Hybrid model, Double Reflection model and Double Warm Corona model. We find that both the Warm Corona and Relativistic Reflection models can interpret the time-average spectra well but cannot be distinguished easily based on the time-averaged spectra fit statistics. Second, we add the rms and covariance spectra to perform the spectral analysis with time-average spectra. The result shows that the warm corona could reproduce all of these spectra well. The hot, optical thin corona and neutral distant reflection will increase their contribution with the temporal frequency, meaning that the corona responsible for X-ray continuum comes from the inner compact X-ray region and the neutral distant reflection is made of some moderate scale neutral clumps.

Multiphoton imaging of melanoma 3D models with plasmonic nanocapsules

We report the synthesis of plasmonic nanocapsules and the cellular responses they induce in 3D melanoma models for their perspective use as a photothermal therapeutic agent. The wall of the nanocapsules is composed of polyelectrolytes. The inner part is functionalized with discrete gold nanoislands. The cavity of the nanocapsules contains a fluorescent payload to show their ability for loading a cargo. The nanocapsules exhibit simultaneous two-photon luminescent, fluorescent properties and X-ray contrasting ability. The average fluorescence lifetime (τ) of the nanocapsules measured with FLIM (0.3 ns) is maintained regardless of the intracellular environment, thus proving their abilities for bioimaging of models such as 3D spheroids with a complex architecture. Their multimodal imaging properties are exploited for the first time to study tumorspheres cellular responses exposed to the nanocapsules. Specifically, we studied cellular uptake, toxicity, intracellular fate, generation of reactive oxygen species, and effect on the levels of hypoxia by using multi-photon and confocal laser scanning microscopy. Because of the high X-ray attenuation and atomic number of the gold nanostructure, we imaged the nanocapsule-cell interactions without processing the sample. We confirmed maintenance of the nanocapsules’ geometry in the intracellular milieu with no impairment of the cellular ultrastructure. Furthermore, we observed the lack of cellular toxicity and no alteration in oxygen or reactive oxygen species levels. These results in 3D melanoma models contribute to the development of these nanocapsules for their exploitation in future applications as agents for imaging-guided photothermal therapy. Statement of SignificanceThe novelty of the work is that our plasmonic nanocapsules are multimodal. They are responsive to X-ray and to multiphoton and single-photon excitation. This allowed us to study their interaction with 2D and 3D cellular structures and specifically to obtain information on tumor cell parameters such as hypoxia, reactive oxygen species, and toxicity. These nanocapsules will be further validated as imaging-guided photothermal probes.

Ultrasonographic Assessment of the Proximal Femoral Ossification Center in Children Under 1 Year

Background. Developmental disorders of the secondary ossification center (SOC) of the proximal femoral epiphysis can be a marker of some childhood diseases that require timely diagnosis and treatment.
 The study aimed to assess the capabilities of ultrasonography in the diagnosis of ossification processes of the proximal femoral epiphysis.
 Material and Methods. The study is based on the results of a survey of 524 children aged 2 weeks to 1 year with normal hip joints, including 259 boys and 265 girls. All patients underwent ultrasound examination of the hip joints according to the method of R. Graf in a standard coronary section. In older children, to eliminate errors in measuring the size of the SOC, an additional cross-section was used.
 Results. The SOC was detected in isolated cases in boys aged up to 3 months and girls up to 2 months. At age 3 months, the SOC was visualized in 45% of girls and 5% of boys. By age 5 months, 81% of girls had a SOC compared with 46% of boys. By 7 months, SOC was determined in more than 90% of cases of both groups. Thus, girls showed an earlier formation of the SOC than boys. The SOC was located in the center of the femoral head in 82% of cases, lateral in 14%, and medial in 4%. In 95% of the examined children, SOC development occurred symmetrically in both joints. In addition, discrepancies were revealed with simultaneous ultrasonography and X-ray of the hip joints since the SOC becomes visible earlier during ultrasonography.
 Conclusion. Sonography is a highly informative method for determining the ossification processes of the proximal femur. Knowledge of the normal sonographic appearance of the femoral head SOC by age and sex will help clinicians diagnose and treat hip disorders.

Simultaneous Neutron and X-Ray Tomography for ex-situ 3D Visualization of Graphite Anode Degradation in Extremely Fast-Charged Lithium-Ion Batteries

Simultaneous Neutron and X-Ray Tomography for ex-situ 3D Visualization of Graphite Anode Degradation in Extremely Fast-Charged Lithium-Ion Batteries

A novel practical approach for monitoring the crosslink density of an ethylene propylene diene monomer compound: Complementary scanning acoustic microscopy and FIB-SEM-EDS analyses

Tuning of the crosslink density (CLD) in the rubber compounds is very crucial for optimizing the physical and mechanical properties of the ultimate rubber products. Conventionally, CLD can be measured via rheological methods such as moving die rheometer (MDR), via mechanical tests such as temperature scanning stress relaxation analysis (TSSR), or via direct swelling experiments using Flory–Rehner approach. In the current study, two novel techniques, focused ion beam - scanning electron microscopy (FIB-SEM) processing, with simultaneous energy dispersive X-ray spectrometry (EDS) mapping analysis and scanning acoustic microscopy (SAM) were combined and correlated to conventional methods on a model recipe of ethylene propylene diene monomer (EPDM) compound having different sulphur contents. Depending on the applied technique, the increase in the crosslink density with sulphur content was found to be 1.7 fold for the Flory–Rehner approach and 1.2 fold for both TSSR and MDR. It is directly monitored from the FIB-SEM-EDS analysis that the sulphur distribution and agglomeration behavior increased in line with ZnO content, which is an indirect indication of the rise in crosslink density. The impedance maps of the crosslinked samples obtained through SAM analysis revealed that the impedance of the samples increased with the increasing sulphur content, which can be attributed to higher level of crosslink density. A quantified correlation was obtained between SAM images and the crosslink density of the samples. It was shown that SAM is a promising tool for practical and non-destructive analysis for determining the formation of crosslink density of the rubbers.

Novel laboratory setup for realistic wellbore cement and formation integrity studies

Oilfield wellbore integrity relies on a good well cement formulation, placement, and resistance to solicitations when aging, either due to chemical or stress changes. Requirements are that the cement sheath and plugs remain as proper hydraulic barriers for all foreseeable future. Thus, to qualify the cement formulations with respect to various types of stress changes, it is important to carry out these tests in the field relevant conditions in the laboratory. These tests will contribute to improved understanding of the limiting factors influencing the well integrity and assist in design of remediation strategies. Hence, a new experimental setup designed for studying near wellbore systems in field conditions is introduced. The setup comprises of an advanced X-ray cell with the possibility of three independent pressure controls of casing, pore and formation pressures. The experiments are carried out under simultaneous X-ray Micro-CT imaging allowing to monitor the in-situ mechanical changes. Numerical calculations in the finite element domain are carried out for the same test conditions with first results showing the evolution of radial cracks in the cement sheath and the formation rock submitted to excessive well pressures. The test results confirm with the numerical simulation. These results may provide valuable input for near-wellbore integrity assessments. • A unique laboratory set-up with more relevant field conditions for study cement and near wellbore formation integrity. • X-ray imaging system can visualize radial fractures in the annular cement and formation in the laboratorysetup. • Fracture structures are qualitatively and quantitively different, with and without confinement pressure. • Using a finite element tool, OOFEM, to model the obtained experimental results.

Tuning the Morphology in the Nanoscale of NH4CN Polymers Synthesized by Microwave Radiation: A Comparative Study.

A systematic study is presented to explore the NH4CN polymerization induced by microwave (MW) radiation, keeping in mind the recent growing interest in these polymers in material science. Thus, a first approach through two series, varying the reaction times and the temperatures between 130 and 205 °C, was conducted. As a relevant outcome, using particular reaction conditions, polymer conversions similar to those obtained by means of conventional thermal methods were achieved, with the advantage of a very significant reduction of the reaction times. The structural properties of the end products were evaluated using compositional data, spectroscopic measurements, simultaneous thermal analysis (STA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). As a result, based on the principal component analysis (PCA) from the main experimental results collected, practically only the crystallographic features and the morphologies in the nanoscale were affected by the MW-driven polymerization conditions with respect to those obtained by classical syntheses. Therefore, MW radiation allows us to tune the morphology, size and shape of the particles from the bidimensional C=N networks which are characteristic of the NH4CN polymers by an easy, fast, low-cost and green-solvent production. These new insights make these macromolecular systems attractive for exploration in current soft-matter science.

Depth profiling of energetic Au ions inside P-type Si 〈1 0 0〉 substrate

Gold implanted silicon substrates are widely used for the fabrication of microelectronic devices, such as detectors for infrared imaging applications, optoelectronic devices as well as for synthesis of implanted nano-particles. The continuous down scaling of physical size of these devices motivated us to develop methodologies for the reliable depth profile studies of various implanted ion species using sensitive and non-destructive methods. In this article, we present depth profile studies for gold ions implanted in silicon substrates using simultaneous X-ray reflectivity and grazing incidence X-ray fluorescence measurements. Results obtained using the XRR-GIXRF studies were found to be fairly consistent with the experimental measurements of secondary ion mass spectrometry. Furthermore, it was noticed that energetic gold ions cause substantial amorphization of crystalline Si material in the vicinity of implanted region, which was confirmed using the GIXRD measurements. Ion implantation also induces large surface modifications and roughness effects on the top of the silicon substrate, as revealed from atomic force microscope measurements.

Simultaneous high-resolution x-ray backlighting and self-emission imaging for laser-produced plasma diagnostics using a two-energy multilayer Kirkpatrick–Baez microscope

A simultaneous high-resolution x-ray backlighting and self-emission imaging method for laser-produced plasma diagnostics is developed in which two Kirkpatrick–Baez imaging channels for high-energy and low-energy diagnostics are constructed using a combination of multilayer mirrors in near-coaxial form. By using a streak or framing camera placed on the image plane, both backlit and self-emission images of a laser-produced plasma with high spatial and temporal resolution can be obtained simultaneously in a single shot. This paper describes the details of the method with regard to its optical and multilayer design, assembly, and alignment method. In addition, x-ray imaging results with a spatial resolution better than 5 µm in the laboratory and experimental results with imploding capsules in the SG-III prototype laser facility are presented.

Radio and X-ray observations of giant pulses from XTE J1810 − 197

ABSTRACT We present the results of two years of radio and X-ray monitoring of the magnetar XTE J1810 − 197 since the radio re-activation in late 2018. Single pulse analysis of radio observations from the Lovell and MkII telescopes at 1564 MHz and the Effelsberg telescope at 6 GHz has resulted in the detection of a total of 91 giant pulses (GPs) between MJDs 58858 and 59117. These GPs appear to be confined to two specific phase ranges (0.473 ≤ ϕ ≤ 0.502 and 0.541 ≤ ϕ ≤ 0.567). We also observe that the first detection of GP emission corresponds to a minimum in the spin-down rate. Simultaneous radio and X-ray observations were performed on MJDs 59009 and 59096. The 0.5–10 keV X-ray spectrum from NICER is well characterized by a two-component blackbody model that can be interpreted as two hot spots on the polar cap of the neutron star. The blackbody temperature decreases with time, consistent with the previous outburst, while the change in the pulsed fraction does not follow the same trend as was seen in the previous outburst. The radio and X-ray flux of XTE J1810 − 197 are correlated during the initial phase of the outburst (MJD 58450 – MJD 58550) and an increase in the radio flux is observed later that may be correlated to the onset of GPs. We argue that the disparity in the evolution of the current outburst compared to the previous one can be attributed to a change in geometry of the neutron star.

Simultaneous X-ray and radio observations of the transitional millisecond pulsar candidate CXOU J110926.4–650224

We present the results of simultaneous observations of the transitional millisecond pulsar (tMSP) candidate CXOU J110926.4–650224 with the XMM-Newton satellite and the MeerKAT telescope. The source was found at an average X-ray luminosity of LX ≃ 7 × 1033 erg s−1 over the 0.3−10 keV band (assuming a distance of 4 kpc) and displayed a peculiar variability pattern in the X-ray emission, switching between high, low and flaring modes on timescales of tens of seconds. A radio counterpart was detected at a significance of 7.9σ with an average flux density of ≃33 μJy at 1.28 GHz. It showed variability over the course of hours and emitted a ≃10-min long flare just a few minutes after a brief sequence of multiple X-ray flares. No clear evidence for a significant correlated or anticorrelated variability pattern was found between the X-ray and radio emissions over timescales of tens of minutes and longer. CXOU J110926.4–650224 was undetected at higher radio frequencies in subsequent observations performed with the Australia Telescope Compact Array, when the source was still in the same X-ray sub-luminous state observed before, down to a flux density upper limit of 15 μJy at 7.25 GHz (at 3σ). We compare the radio emission properties of CXOU J110926.4–650224 with those observed in known and candidate tMSPs and discuss physical scenarios that may account for its persistent and flaring radio emissions.

Photometric Analysis of the TESS Light Curve for the Asynchronous Polar V1500 Cyg

After 40 yr of nova outburst, there are still some difficulties in completely understanding V1500 Cyg. The faintness of V1500 Cyg and its crowded field pose a challenge for high-precision photometry by TESS, while long-term intensive data from TESS provide the first opportunity to accurately model this binary system. The best-fitting model reveals that the high-temperature white dwarf illuminates the surface of its companion star, a low-mass secondary (M 2 ∼ 0.22 M ⊙), and the emission from the heated secondary star still dominates the luminosity of the system. The binary model has determined the white dwarf’s mass to be M 1 ∼ 1.4 M ⊙ and its orbital inclination i ∼ 60°. The residuals after the removal of the fitted model curve present variations in both the white dwarf’s spin period and the binary orbital period, confirming the previous claim that V1500 Cyg is still an asynchronous polar, and the observed spin period demonstrates that V1500 Cyg is approaching synchronicity with the orbital period following the prediction of the polarization ephemeris. The phasing of the spin humps indicates their cyclotron origin, and the residual orbital humps may be produced by the emission from the accretion stream. There is no evidence for the pole-switching effect, while the double-humped profile of the spin modulation suggests that the white dwarf may be accreting matter from a “ring” around it. Further simultaneous polarization and X-ray observations are urged to explore the accretion geometry of V1500 Cyg in detail.

Long-term multi-band photometric monitoring of Mrk 501

Aims. Radio-to-TeV observations of the bright nearby (z = 0.034) blazar Markarian 501 (Mrk 501), performed from December 2012 to April 2018, are used to study the emission mechanisms in its relativistic jet. Methods. We examined the multi-wavelength variability and the correlations of the light curves obtained by eight different instruments, including the First G-APD Cherenkov Telescope (FACT), observing Mrk 501 in very high-energy (VHE) gamma-rays at TeV energies. We identified individual TeV and X-ray flares and found a sub-day lag between variability in these two bands. Results. Simultaneous TeV and X-ray variations with almost zero lag are consistent with synchrotron self-Compton (SSC) emission, where TeV photons are produced through inverse Compton scattering. The characteristic time interval of 5−25 days between TeV flares is consistent with them being driven by Lense-Thirring precession.