X-ray production cross sections at incident photon energies across the M{sub i} (i=1-5) edges of {sub 90}Th

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaur, Rajnish; Shehla,; Kumar, Anil

2015-08-28

The X-ray production cross sections for the M{sub k} (k= ξ, δ, α, β, ζ, γ, m{sub 1}, m{sub 2}) groups of X-rays have been evaluated at incident photon energies across the M{sub i} (i =1-5) edges of {sub 90}Th using the relativistic Hartree-Fock-Slater model based photoionisation cross sections and recently reported values of the M-shell X-ray emission rates, fluorescence and Coster Kronig yields. Further, the energies of the prominent (M{sub i}-S{sub j}) (S{sub j}=N{sub j}, O{sub j} and i =1-3, j =1-7) resonant Raman scattered (RRS) peaks at different incident photon energies have also been evaluated using the neutral-atommore » electron binding energies (E{sub sj}) based on the relaxed orbital relativistic Hartree-Fock-Slater model.« less

Monte Carlo study of x-ray cross talk in a variable resolution x-ray detector

NASA Astrophysics Data System (ADS)

Melnyk, Roman; DiBianca, Frank A.

2003-06-01

A variable resolution x-ray (VRX) detector provides a great increase in the spatial resolution of a CT scanner. An important factor that limits the spatial resolution of the detector is x-ray cross-talk. A theoretical study of the x-ray cross-talk is presented in this paper. In the study, two types of the x-ray cross-talk were considered: inter-cell and inter-arm cross-talk. Both types of the x-ray cross-talk were simulated, using the Monte Carlo method, as functions of the detector field of view (FOV). The simulation was repeated for lead and tungsten separators between detector cells. The inter-cell x-ray cross-talk was maximum at the 34-36 cm FOV, but it was low at small and the maximum FOVs. The inter-arm x-ray cross-talk was high at small and medium FOVs, but it was greatly reduced when variable width collimators were placed on the front surfaces of the detector. The inter-cell, but not inter-arm, x-ray cross-talk was lower for tungsten than for lead separators. From the results, x-ray cross-talk in a VRX detector can be minimized by imaging all objects between 24 cm and 40 cm in diameter with the 40 cm FOV, using tungsten separators, and placing variable width collimators in front of the detector.

Dimethylarsinic acid in drinking water changed the morphology of urinary bladder but not the expression of DNA repair genes of bladder transitional epithelium in F344 rats.

PubMed

Wang, Amy; Wolf, Douglas C; Sen, Banalata; Knapp, Geremy W; Holladay, Steven D; Huckle, William R; Caceci, Thomas; Robertson, John L

2009-06-01

Inorganic arsenic increases urinary bladder transitional cell carcinoma in humans. In F344 rats, dimethylarsinic acid (DMA[V]) increases transitional cell carcinoma. Arsenic-induced inhibition of DNA repair has been reported in cultured cell lines and in lymphocytes of arsenic-exposed humans, but it has not been studied in urinary bladder. Should inhibition of DNA damage repair in transitional epithelium occur, it may contribute to carcinogenesis or cocarcinogenesis. We investigated morphology and expression of DNA repair genes in F344 rat transitional cells following up to 100 ppm DMA(V) in drinking water for four weeks. Mitochondria were very sensitive to DMA(V), and swollen mitochondria appeared to be the main source of vacuoles in the transitional epithelium. Real-time reverse transcriptase polymerase chain reaction (Real-Time RT PCR) showed the mRNA levels of tested DNA repair genes, ataxia telangectasia mutant (ATM), X-ray repair cross-complementing group 1 (XRCC1), excision repair cross-complementing group 3/xeroderma pigmentosum B (ERCC3/XPB), and DNA polymerase beta (Polbeta), were not altered by DMA(V). These data suggested that either DMA(V) does not affect DNA repair in the bladder or DMA(V) affects DNA repair without affecting baseline mRNA levels of repair genes. The possibility remains that DMA(V) may lower damage-induced increases in repair gene expression or cause post-translational modification of repair enzymes.

Self-association and domain rearrangements between complement C3 and C3u provide insight into the activation mechanism of C3.

PubMed

Li, Keying; Gor, Jayesh; Perkins, Stephen J

2010-10-01

Component C3 is the central protein of the complement system. During complement activation, the thioester group in C3 is slowly hydrolysed to form C3u, then the presence of C3u enables the rapid conversion of C3 into functionally active C3b. C3u shows functional similarities to C3b. To clarify this mechanism, the self-association properties and solution structures of C3 and C3u were determined using analytical ultracentrifugation and X-ray scattering. Sedimentation coefficients identified two different dimerization events in both proteins. A fast dimerization was observed in 50 mM NaCl but not in 137 mM NaCl. Low amounts of a slow dimerization was observed for C3u and C3 in both buffers. The X-ray radius of gyration RG values were unchanged for both C3 and C3u in 137 mM NaCl, but depend on concentration in 50 mM NaCl. The C3 crystal structure gave good X-ray fits for C3 in 137 mM NaCl. By randomization of the TED (thioester-containing domain)/CUB (for complement protein subcomponents C1r/C1s, urchin embryonic growth factor and bone morphogenetic protein 1) domains in the C3b crystal structure, X-ray fits showed that the TED/CUB domains in C3u are extended and differ from the more compact arrangement of C3b. This TED/CUB conformation is intermediate between those of C3 and C3b. The greater exposure of the TED domain in C3u (which possesses the hydrolysed reactive thioester) accounts for the greater self-association of C3u in low-salt conditions. This conformational variability of the TED/CUB domains would facilitate their interactions with a broad range of antigenic surfaces. The second dimerization of C3 and C3u may correspond to a dimer observed in one of the crystal structures of C3b.

Elucidating the Wavelength Dependence of Phonon Scattering in Nanoparticle-Matrix Composites using Phonon Spectroscopy

DTIC Science & Technology

2016-07-11

composites with x - ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Rutherford backscattering spectroscopy...RBS), particle-induced x - ray emission (PIXE), and energy dispersive x - ray spectroscopy (EDX). This work complements earlier works on CdSe...sample shows only In2Se3 and CdIn2Se4 XRD peaks (Figure 1.4e), it is stoichiometrically   Figure 1.4. X - ray diffraction patterns of (a) γ-In2Se3

Noninvasive Synchrotron-Based X-ray Raman Scattering Discriminates Carbonaceous Compounds in Ancient and Historical Materials [ In situ synchrotron-based X-Ray Raman scattering discriminates carbonaceous compounds in ancient and historical materials

DOE PAGES

Gueriau, Pierre; Rueff, Jean -Pascal; Bernard, Sylvain; ...

2017-09-13

Carbon compounds are ubiquitous and occur in a diversity of chemical forms in many systems including ancient and historic materials ranging from cultural heritage to paleontology. Determining their speciation cannot only provide unique information on their origin but may also elucidate degradation processes. Synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy at the carbon K-edge (280–350 eV) is a very powerful method to probe carbon speciation. However, the short penetration depth of soft X-rays imposes stringent constraints on sample type, preparation, and analytical environment. A hard X-ray probe such as X-ray Raman scattering (XRS) can overcome many of these difficulties. Heremore » we report the use of XRS at ~6 keV incident energy to collect carbon K-edge XANES data and probe the speciation of organic carbon in several specimens relevant to cultural heritage and natural history. This methodology enables the measurement to be done in a nondestructive way, in air, and provides information that is not compromised by surface contamination by ensuring that the dominant signal contribution is from the bulk of the probed material. Using the backscattering geometry at large photon momentum transfer maximizes the XRS signal at the given X-ray energy and enhances nondipole contributions compared to conventional XANES, thereby augmenting the speciation sensitivity. The capabilities and limitations of the technique are discussed. As a result, we show that despite its small cross section, for a range of systems the XRS method can provide satisfactory signals at realistic experimental conditions. XRS constitutes a powerful complement to FT-IR, Raman, and conventional XANES spectroscopy, overcoming some of the limitations of these techniques.« less

Novel detector design for reducing intercell x-ray cross-talk in the variable resolution x-ray CT scanner: a Monte Carlo study.

PubMed

Arabi, Hosein; Asl, Ali Reza Kamali; Ay, Mohammad Reza; Zaidi, Habib

2011-03-01

The variable resolution x-ray (VRX) CT scanner provides substantial improvement in the spatial resolution by matching the scanner's field of view (FOV) to the size of the object being imaged. Intercell x-ray cross-talk is one of the most important factors limiting the spatial resolution of the VRX detector. In this work, a new cell arrangement in the VRX detector is suggested to decrease the intercell x-ray cross-talk. The idea is to orient the detector cells toward the opening end of the detector. Monte Carlo simulations were used for performance assessment of the oriented cell detector design. Previously published design parameters and simulation results of x-ray cross-talk for the VRX detector were used for model validation using the GATE Monte Carlo package. In the first step, the intercell x-ray cross-talk of the actual VRX detector model was calculated as a function of the FOV. The obtained results indicated an optimum cell orientation angle of 28 degrees to minimize the x-ray cross-talk in the VRX detector. Thereafter, the intercell x-ray cross-talk in the oriented cell detector was modeled and quantified. The intercell x-ray cross-talk in the actual detector model was considerably high, reaching up to 12% at FOVs from 24 to 38 cm. The x-ray cross-talk in the oriented cell detector was less than 5% for all possible FOVs, except 40 cm (maximum FOV). The oriented cell detector could provide considerable decrease in the intercell x-ray cross-talk for the VRX detector, thus leading to significant improvement in the spatial resolution and reduction in the spatial resolution nonuniformity across the detector length. The proposed oriented cell detector is the first dedicated detector design for the VRX CT scanners. Application of this concept to multislice and flat-panel VRX detectors would also result in higher spatial resolution.

A Flash X-Ray Facility for the Naval Postgraduate School

DTIC Science & Technology

1985-06-01

ionizing radiation, *• NPS has had active programs with a Van de Graaff generator, a reactor, radioactive sources, X-ray machines and a linear electron ...interaction of radiation with matter and with coherent radiation. Currently the most active program is at the linear electron accelerator which over...twenty years has produced some 75 theses. The flash X-ray machine was obtained to expan-i and complement the capabilities of the linear electron

Association study between XRCC1 gene polymorphisms and sporadic amyotrophic lateral sclerosis.

PubMed

Coppedè, Fabio; Migheli, Francesca; Lo Gerfo, Annalisa; Fabbrizi, Maria Rita; Carlesi, Cecilia; Mancuso, Michelangelo; Corti, Stefania; Mezzina, Nicoletta; del Bo, Roberto; Comi, Giacomo P; Siciliano, Gabriele; Migliore, Lucia

2010-01-01

The aim of the present study was to investigate the possible contribution of three common functional polymorphisms in the DNA repair protein X-ray repair cross-complementing group 1 (XRCC1), namely Arg194Trp (rs1799782), Arg280His (rs25489) and Arg399Gln (rs25487), to sporadic amyotrophic lateral sclerosis (SALS). We genotyped 206 Italian SALS patients and 203 matched controls for XRCC1 Arg194Trp, Arg280His and Arg399Gln polymorphisms by means of PCR/RFLP technique, searching for association between any of the studied polymorphisms and disease risk, age and site of onset. We observed a statistically significant difference in XRCC1 Gln399 allele frequencies between SALS cases and controls (0.39/0.28; p=0.001). The present study suggests that the XRCC1 Arg399Gln polymorphism might contribute to SALS risk.

X-Ray Weak Broad-Line Quasars: Absorption or Intrinsic X-Ray Weakness

NASA Technical Reports Server (NTRS)

Risaliti, Guido; Mushotzky, Richard F. (Technical Monitor)

2004-01-01

XMM observations of X-ray weak quasars have been performed during 2003. The data for all but the last observation are now available (there has been a delay of several months on the initial schedule, due to high background flares which contaminated the observations: as a consequence, most of them had to be rescheduled). We have reduced and analyzed these data, and obtained interesting preliminary scientific results. Out of the eight sources, 4 are confirmed to be extrimely X-ray weak, in agreement with the results of previous Chandra observations. 3 sources are confirmed to be highly variable both in flux (by factors 20-50) and in spectral properties (dramatic changes in spectral index). For both these groups of objects, an article is in preparation. Preliminary results have been presented at an international workshop on AGN surveys in December 2003, in Cozumel (Mexico). In order to further understand the nature of these X-ray weak quasars, we submitted proposals for spectroscopy at optical and infrared telescopes. We obtained time at the TNG 4 meter telescope for near-IR observations, and at the Hobby-Eberly Telescope for optical high-resolution spectroscopy. These observations will be performed in early 2004, and will complement the XMM data, in order to understand whether the X-ray weakness of these sources is an intrinsic property or is due to absorption by circumnuclear material.

Pressure induced structural transitions in CuSbS 2 and CuSbSe 2 thermoelectric compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker, Jason; Kumar, Ravhi S.; Sneed, Daniel

Here, we investigate the structural behavior of CuSbS 2 and CuSbSe 2 thermoelectric materials under high pressure conditions up to 80 GPa using angle dispersive X-ray diffraction in a diamond anvil cell (DAC). We also perform high pressure Raman spectroscopy measurements up to 16 GPa. We observed a pressure-induced structural transformation from the ambient orthorhombic structure with space group Pnma to a triclinic type structure with space group P1 beginning around 8 GPa in both samples and completing at 13 GPa and 10 GPa in CuSbS 2 and CuSbSe 2, respectively. High pressure Raman experiments complement the transitions observed bymore » high pressure X-ray diffraction (HPXRD). Finally, the transitions were found to be reversible on releasing the pressure to ambient in the DAC. The bulk modulus and compressibility of these materials are further discussed.« less

Pressure induced structural transitions in CuSbS 2 and CuSbSe 2 thermoelectric compounds

DOE PAGES

Baker, Jason; Kumar, Ravhi S.; Sneed, Daniel; ...

2015-04-27

Here, we investigate the structural behavior of CuSbS 2 and CuSbSe 2 thermoelectric materials under high pressure conditions up to 80 GPa using angle dispersive X-ray diffraction in a diamond anvil cell (DAC). We also perform high pressure Raman spectroscopy measurements up to 16 GPa. We observed a pressure-induced structural transformation from the ambient orthorhombic structure with space group Pnma to a triclinic type structure with space group P1 beginning around 8 GPa in both samples and completing at 13 GPa and 10 GPa in CuSbS 2 and CuSbSe 2, respectively. High pressure Raman experiments complement the transitions observed bymore » high pressure X-ray diffraction (HPXRD). Finally, the transitions were found to be reversible on releasing the pressure to ambient in the DAC. The bulk modulus and compressibility of these materials are further discussed.« less

A Genetic and Molecular Analysis of the 46c Chromosomal Region Surrounding the Fmrfamide Neuropeptide Gene in Drosophila Melanogaster

PubMed Central

O'Brien, M. A.; Roberts, M. S.; Taghert, P. H.

1994-01-01

We have analyzed the FMRFamide neuropeptide gene region of Drosophila melanogaster. This gene maps to the 46C region of chromosome 2R; this interval previously was not well characterized. For this genetic and molecular analysis, we have used X-ray mutagenesis, EMS mutagenesis, and the recently reported local P element transposition method. We identified four overlapping deletions, two of which have proximal breakpoints that define a 50-60-kb region surrounding the FMRFamide gene in 46C. To this small region, we mapped three lethal complementation groups; 10 additional lethal complementation groups were mapped to more distal regions of 46CD. One of these groups corresponds to even-skipped, the other 12 are previously unidentified. Using various lines of evidence we excluded the possibility that FMRFamide corresponds to any of the three lethal complementation groups mapping to its immediate 50-60-kb vicinity. The positions of two of the three lethal complementation groups were identified with P elements using a local transposition scheme. The third lethal complementation group was excluded as being FMRFamide mutants by sequence analysis and by immunocytochemistry with proFMRFamide precursor-specific antibodies. This analysis has (1) provided a genetic map of the 46CD chromosomal region and a detailed molecular map of a portion of the 46C region and (2) provided additional evidence of the utility of local transposition for targeting nearby genes. PMID:8056304

Results from Multiwavelength Workshop for Next Generation Gamma Ray Experiments

NASA Astrophysics Data System (ADS)

Fortson, L.

2002-12-01

The next few years will see the build up of several new gamma-ray detectors both on the ground and in space. By 2006 VERITAS, HESS and MAGIC expect to be operational and GLAST will be in orbit. At the same time, a number of X-ray satellites will be in operation, complementing these new gamma-ray instruments. A better understanding of many high-energy sources can be obtained by making contemporaneous observations with multiple x-ray and gamma-ray instruments. A workshop was recently held at the Adler Planetarium and Astronomy Museum in Chicago to discuss the future of multiwavelength campaigns. The workshop was intended as an opportunity for information exchange within the community to get the best possible science returns from the wealth of data that is expected to come in from the next generation of experiments. By the end of the workshop participants gained a general understanding of the capabilities of the various instruments and their observational strategies. We also came up with a good start on some concrete mechanisms for coordinating gamma-ray observations with ground based and space based observatories at other wavelengths - including X-ray and optical groups. I will report on the results from this workshop in my presentation at the AAS. The workshop was sponsored by the Adler Planetarium and Astronomy Museum.

Complementation and Genetic Recombination in Candida lipolytica

PubMed Central

Bassel, John; Warfei, Jean; Mortimer, Robert

1971-01-01

Nutritional requirements were introduced into wild-type, heterothallic strains of Candida lipolytica by exposing the cells to X rays. Complementing hybrids were recovered from mixtures of the auxotrophic strains, and genetic recombination was observed in individually isolated ascospores from the hybrid strains. PMID:5122814

X-Raying the Star Formation History of the Universe.

PubMed

Cavaliere; Giacconi; Menci

2000-01-10

The current models of early star and galaxy formation are based upon the hierarchical growth of dark matter halos, within which the baryons condense into stars after cooling down from a hot diffuse phase. The latter is replenished by infall of outer gas into the halo potential wells; this includes a fraction previously expelled and preheated because of momentum and energy fed back by the supernovae which follow the star formation. We identify such an implied hot phase with the medium known to radiate powerful X-rays in clusters and in groups of galaxies. We show that the amount of the hot component required by the current star formation models is enough to be observable out to redshifts z approximately 1.5 in forthcoming deep surveys from Chandra and X-Ray Multimirror Mission, especially in case the star formation rate is high at such and earlier redshifts. These X-ray emissions constitute a necessary counterpart and will provide a much-wanted probe of the star formation process itself (in particular, of the supernova feedback) to parallel and complement the currently debated data from optical and IR observations of the young stars.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arabi, Hosein; Asl, Ali Reza Kamali; Ay, Mohammad Reza

Purpose: The variable resolution x-ray (VRX) CT scanner provides substantial improvement in the spatial resolution by matching the scanner's field of view (FOV) to the size of the object being imaged. Intercell x-ray cross-talk is one of the most important factors limiting the spatial resolution of the VRX detector. In this work, a new cell arrangement in the VRX detector is suggested to decrease the intercell x-ray cross-talk. The idea is to orient the detector cells toward the opening end of the detector. Methods: Monte Carlo simulations were used for performance assessment of the oriented cell detector design. Previously publishedmore » design parameters and simulation results of x-ray cross-talk for the VRX detector were used for model validation using the GATE Monte Carlo package. In the first step, the intercell x-ray cross-talk of the actual VRX detector model was calculated as a function of the FOV. The obtained results indicated an optimum cell orientation angle of 28 deg. to minimize the x-ray cross-talk in the VRX detector. Thereafter, the intercell x-ray cross-talk in the oriented cell detector was modeled and quantified. Results: The intercell x-ray cross-talk in the actual detector model was considerably high, reaching up to 12% at FOVs from 24 to 38 cm. The x-ray cross-talk in the oriented cell detector was less than 5% for all possible FOVs, except 40 cm (maximum FOV). The oriented cell detector could provide considerable decrease in the intercell x-ray cross-talk for the VRX detector, thus leading to significant improvement in the spatial resolution and reduction in the spatial resolution nonuniformity across the detector length. Conclusions: The proposed oriented cell detector is the first dedicated detector design for the VRX CT scanners. Application of this concept to multislice and flat-panel VRX detectors would also result in higher spatial resolution.« less

X1908+075: A Late O-Type Supergiant with a Neutron Star Companion

NASA Astrophysics Data System (ADS)

Morel, Thierry; Grosdidier, Yves

2006-08-01

X1908 + 075 is a highly-absorbed Galactic X-ray source likely made up of a pulsar accreting wind material from a massive companion. We have used near-IR photometric data complemented by follow-up spectroscopy to identify the likely counterpart to this X-ray source and to assign a spectral type O7.5 9.5 If to the primary. Further details can be found in Morel and Grosdidier (2005).

Directly Characterizing the Relative Strength and Momentum Dependence of Electron-Phonon Coupling Using Resonant Inelastic X-Ray Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devereaux, T. P.; Shvaika, A. M.; Wu, K.

The coupling between lattice and charge degrees of freedom in condensed matter materials is ubiquitous and can often result in interesting properties and ordered phases, including conventional superconductivity, charge-density wave order, and metal-insulator transitions. Angle-resolved photoemission spectroscopy and both neutron and nonresonant x-ray scattering serve as effective probes for determining the behavior of appropriate, individual degrees of freedom—the electronic structure and lattice excitation, or phonon dispersion, respectively. However, each provides less direct information about the mutual coupling between the degrees of freedom, usually through self-energy effects, which tend to renormalize and broaden spectral features precisely where the coupling is strong,more » impacting one’s ability to quantitatively characterize the coupling. Here, we demonstrate that resonant inelastic x-ray scattering, or RIXS, can be an effective tool to directly determine the relative strength and momentum dependence of the electron-phonon coupling in condensed matter systems. Using a diagrammatic approach for an eight-band model of copper oxides, we study the contributions from the lowest-order diagrams to the full RIXS intensity for a realistic scattering geometry, accounting for matrix element effects in the scattering cross section, as well as the momentum dependence of the electron-phonon coupling vertex. A detailed examination of these maps offers a unique perspective into the characteristics of electron-phonon coupling, which complements both neutron and nonresonant x-ray scattering, as well as Raman and infrared conductivity.« less

Directly Characterizing the Relative Strength and Momentum Dependence of Electron-Phonon Coupling Using Resonant Inelastic X-Ray Scattering

DOE PAGES

Devereaux, T. P.; Shvaika, A. M.; Wu, K.; ...

2016-10-25

The coupling between lattice and charge degrees of freedom in condensed matter materials is ubiquitous and can often result in interesting properties and ordered phases, including conventional superconductivity, charge-density wave order, and metal-insulator transitions. Angle-resolved photoemission spectroscopy and both neutron and nonresonant x-ray scattering serve as effective probes for determining the behavior of appropriate, individual degrees of freedom—the electronic structure and lattice excitation, or phonon dispersion, respectively. However, each provides less direct information about the mutual coupling between the degrees of freedom, usually through self-energy effects, which tend to renormalize and broaden spectral features precisely where the coupling is strong,more » impacting one’s ability to quantitatively characterize the coupling. Here, we demonstrate that resonant inelastic x-ray scattering, or RIXS, can be an effective tool to directly determine the relative strength and momentum dependence of the electron-phonon coupling in condensed matter systems. Using a diagrammatic approach for an eight-band model of copper oxides, we study the contributions from the lowest-order diagrams to the full RIXS intensity for a realistic scattering geometry, accounting for matrix element effects in the scattering cross section, as well as the momentum dependence of the electron-phonon coupling vertex. A detailed examination of these maps offers a unique perspective into the characteristics of electron-phonon coupling, which complements both neutron and nonresonant x-ray scattering, as well as Raman and infrared conductivity.« less

An X-Ray Analysis Database of Photoionization Cross Sections Including Variable Ionization

NASA Technical Reports Server (NTRS)

Wang, Ping; Cohen, David H.; MacFarlane, Joseph J.; Cassinelli, Joseph P.

1997-01-01

Results of research efforts in the following areas are discussed: review of the major theoretical and experimental data of subshell photoionization cross sections and ionization edges of atomic ions to assess the accuracy of the data, and to compile the most reliable of these data in our own database; detailed atomic physics calculations to complement the database for all ions of 17 cosmically abundant elements; reconciling the data from various sources and our own calculations; and fitting cross sections with functional approximations and incorporating these functions into a compact computer code.Also, efforts included adapting an ionization equilibrium code, tabulating results, and incorporating them into the overall program and testing the code (both ionization equilibrium and opacity codes) with existing observational data. The background and scientific applications of this work are discussed. Atomic physics cross section models and calculations are described. Calculation results are compared with available experimental data and other theoretical data. The functional approximations used for fitting cross sections are outlined and applications of the database are discussed.

The Soft X-ray Spectrophotometer SphinX for the CORONAS-Photon Mission

NASA Astrophysics Data System (ADS)

Sylwester, Janusz; Kowalinski, Miroslaw; Szymon, Gburek; Bakala, Jaroslaw; Kuzin, Sergey; Kotov, Yury; Farnik, Frantisek; Reale, Fabio

The purpose, construction details and calibration results of the new design, Polish-led solar X-ray spectrophotometer SphinX will be presented. The instrument constitutes a part of the Russian TESIS X-ray and EUV complex aboard the forthcoming CORONAS-Photon solar mission to be launched later in 2008. SphinX uses Si-PIN detectors for high time resolution (down to 0.01 s) measurements of solar spectra in the energy range between 0.5 keV and 15 keV. The spectral resolution allows separating 256 individual energy channels in this range with particular groups of lines clearly distinguishable. Unprecedented accuracy of the instrument calibration at the XACT (Palermo) and BESSY (Berlin) synchrotron will allow for establishing the solar soft X-ray photometric reference system. The cross-comparison between SphinX and the other instruments presently in orbit like XRT on Hinode, RHESSI and GOES X-ray monitor, will allow for a precise determination of the coronal emission measure and temperature during both very low and very high activity periods. Examples of the detectors' ground calibration results as well as the calculated synthetic spectra will be presented. The operation of the instrument while in orbit will be discussed allowing for suggestions from other groups to be still included in mission planning.

Low-energy proton induced M X-ray production cross sections for 70Yb, 81Tl and 82Pb

NASA Astrophysics Data System (ADS)

Shehla; Mandal, A.; Kumar, Ajay; Roy Chowdhury, M.; Puri, Sanjiv; Tribedi, L. C.

2018-07-01

The cross sections for production of Mk (k = Mξ, Mαβ, Mγ, Mm1) X-rays of 70Yb, 81Tl and 82Pb induced by 50-250 keV protons have been measured in the present work. The experimental cross sections have been compared with the earlier reported values and those calculated using the ionization cross sections based on the ECPSSR (Perturbed (P) stationary(S) state(S), incident ion energy (E) loss, Coulomb (C) deflection and relativistic (R) correction) model, the X-ray emission rates based on the Dirac-Fock model, the fluorescence and Coster-Kronig yields based on the Dirac-Hartree-Slater (DHS) model. In addition, the present measured proton induced X-ray production cross sections have also been compared with those calculated using the Dirac-Hartree-Slater (DHS) model based ionization cross sections and those based on the Plane wave Born Approximation (PWBA). The measured M X-ray production cross sections are, in general, found to be higher than the ECPSSR and DHS model based values and lower than the PWBA model based cross sections.

M sub-shell X-ray fluorescence cross-section measurements for six elements in the range Z = 78-92 at tuned synchrotron photon energies 5, 7 and 9 keV.

NASA Astrophysics Data System (ADS)

Bansal, Himani; Tiwari, M. K.; Mittal, Raj

2018-01-01

M sub-shell X-ray fluorescence cross-sections of elements Pt, Au, Hg, Pb, Th and U have been measured with linearly polarized photon beams from Indus-II synchrotron source at Raja Ramanna Centre for Advanced Technology (RRCAT), India at tuned 5, 7 and 9 keV energies less than the L3 edge energy of elements. Measurements at present energies and elements are not available in literature. Therefore, measured cross-sections for Mξ, Mδ, Mα, Mβ, Mγ, Mm1 and Mm2 group of X-rays were compared with calculated theoretical values based upon Non Relativistic Hartree-Slater (NRHS) and relativistic Dirac-Fork (DF) and Dirac-Hartree-Slater (DHS) models. The measured cross-sections along with our earlier quoted measurements at 8 and 10 keV by Kaur et al. [Nucl. Instrum. Meth. B, 2014; 320: 37] are found in good agreement with DF and DHS values around 20% deviations and are highly deviated from NRHS values. Most of the spots of observed high deviations in measured and theoretical cross-sections are found to coincide with the presence of crisscrosses/sharp variations in contributing physical parameters photo-ionization cross-sections σMi's and Coster-Kronig yields fij's with Zs.

Cross-correlation of the X-ray background with nearby galaxies

NASA Technical Reports Server (NTRS)

Jahoda, Keith; Mushotzky, Richard F.; Boldt, Elihu; Lahav, Ofer

1991-01-01

The detection of a signal in the cross-correlation of the diffuse 2-10 keV HEAO 1 A-2 X-ray surface brightness with the galaxy surface density derived from diameter-limited samples from the Uppsala General Catalogue is reported. An ad hoc relationship between the X-ray flux and the galaxy counts is used to estimate the local X-ray volume emissivity at 2.8 + or - 1.0 x 10 to the 38th ergs/s/cu Mpc. This result implies that unevolved populations of X-ray sources correlated with present-epoch galaxies can contribute only 13 + or - 5 percent of the cosmic X-ray background.

High-resolution x-ray diffraction microscopy of specifically labeled yeast cells

PubMed Central

Nelson, Johanna; Huang, Xiaojing; Steinbrener, Jan; Shapiro, David; Kirz, Janos; Marchesini, Stefano; Neiman, Aaron M.; Turner, Joshua J.; Jacobsen, Chris

2010-01-01

X-ray diffraction microscopy complements other x-ray microscopy methods by being free of lens-imposed radiation dose and resolution limits, and it allows for high-resolution imaging of biological specimens too thick to be viewed by electron microscopy. We report here the highest resolution (11–13 nm) x-ray diffraction micrograph of biological specimens, and a demonstration of molecular-specific gold labeling at different depths within cells via through-focus propagation of the reconstructed wavefield. The lectin concanavalin A conjugated to colloidal gold particles was used to label the α-mannan sugar in the cell wall of the yeast Saccharomyces cerevisiae. Cells were plunge-frozen in liquid ethane and freeze-dried, after which they were imaged whole using x-ray diffraction microscopy at 750 eV photon energy. PMID:20368463

High-resolution x-ray diffraction microscopy of specifically labeled yeast cells

DOE PAGES

Nelson, Johanna; Huang, Xiaojing; Steinbrener, Jan; ...

2010-04-20

X-ray diffraction microscopy complements other x-ray microscopy methods by being free of lens-imposed radiation dose and resolution limits, and it allows for high-resolution imaging of biological specimens too thick to be viewed by electron microscopy. We report here the highest resolution (11-13 nm) x-ray diffraction micrograph of biological specimens, and a demonstration of molecular-specific gold labeling at different depths within cells via through-focus propagation of the reconstructed wavefield. The lectin concanavalin A conjugated to colloidal gold particles was used to label the α-mannan sugar in the cell wall of the yeast Saccharomyces cerevisiae. Cells were plunge-frozen in liquid ethane andmore » freeze-dried, after which they were imaged whole using x-ray diffraction microscopy at 750 eV photon energy.« less

XMM-Newton observations of NGC 3268 in the Antlia Galaxy Cluster: characterization of a hidden group of galaxies at z ≈ 0.41

NASA Astrophysics Data System (ADS)

Gargiulo, I. D.; García, F.; Combi, J. A.; Caso, J. P.; Bassino, L. P.

2018-05-01

We report on a detailed X-ray study of the extended emission of the intracluster medium (ICM) around NGC 3268, in the Antlia cluster of galaxies, together with a characterization of an extended source in the field, namely a background cluster of galaxies at z ≈ 0.41, which was previously accounted as an X-ray point source. The spectral properties of the extended emission of the gas present in Antlia were studied using data from the XMM-Newton satellite complemented with optical images of CTIO-Blanco telescope, to attain for associations of the optical sources with the X-ray emission. The XMM-Newton observations show that the intracluster gas is concentrated in a region centred in one of the main galaxies of the cluster, NGC 3268. By means of a spatially-resolved spectral analysis we derived the abundances of the ICM plasma. We found a wall-like feature in the northeast direction where the gas is characterized by a lower temperature with respect to the rest of the ICM. Furthermore, using combined optical observations we inferred the presence of an elliptical galaxy in the centre of the extended X-ray source considered as a background cluster, which favours this interpretation.

In vivo X-ray fluorescence of lead in bone: review and current issues.

PubMed Central

Todd, A C; Chettle, D R

1994-01-01

Bone lead measurements can assess long-term lead dosimetry because the residence time of lead in bone is long. Bone lead measurements thus complement blood and plasma lead measurements, which reflect more short-term exposure. Although the noninvasive, in vivo measurement of lead in bone by X-ray fluorescence (XRF) has been under development since the 1970s, its use is still largely confined to research institutions. There are three principal methods used that vary both in the how lead X-rays are fluoresced and in which lead X-rays are fluoresced. Several groups have reported the independent development of in vivo measurement systems, the majority adopting the 109Cd K XRF method because of its advantages: a robust measurement, a lower detection limit (compared to 57Co K XRF), and a lower effective (radiation) dose (compared to L XRF) when calculated according to the most recent guidelines. These advantages, and the subsequent widespread adoption of the 109Cd method, are primarily consequences of the physics principles of the technique. This paper presents an explanation of the principles of XRF, a description of the practical measurement systems, a review of the human bone lead studies performed to date; and a discussion of some issues surrounding future application of the methods. Images p172-a PMID:8033846

Structure of Mycobacterium tuberculosis phosphopantetheine adenylyltransferase in complex with the feedback inhibitor CoA reveals only one active-site conformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wubben, T.; Mesecar, A.D.; UIC)

Phosphopantetheine adenylyltransferase (PPAT) catalyzes the penultimate step in the coenzyme A (CoA) biosynthetic pathway, reversibly transferring an adenylyl group from ATP to 4'-phosphopantetheine to form dephosphocoenzyme A (dPCoA). To complement recent biochemical and structural studies on Mycobacterium tuberculosis PPAT (MtPPAT) and to provide further insight into the feedback regulation of MtPPAT by CoA, the X-ray crystal structure of the MtPPAT enzyme in complex with CoA was determined to 2.11 {angstrom} resolution. Unlike previous X-ray crystal structures of PPAT-CoA complexes from other bacteria, which showed two distinct CoA conformations bound to the active site, only one conformation of CoA is observedmore » in the MtPPAT-CoA complex.« less

Spatially resolved density and ionization measurements of shocked foams using x-ray fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, M. J.; Keiter, P. A.; Montgomery, D. S.

2016-09-28

We present experiments at the Trident laser facility demonstrating the use of x-ray fluorescence (XRF) to simultaneously measure density, ionization state populations, and electron temperature in shocked foams. An imaging x-ray spectrometer obtained spatially resolved measurements of Ti K-α emission. Density profiles were measured from K-α intensity. Ti ionization state distributions and electron temperatures were inferred by fitting K-α spectra to spectra from CRETIN simulations. This work shows that XRF provides a powerful tool to complement other diagnostics to make equation of state measurements of shocked materials containing a suitable tracer element.

Catalytic Adventures in Space and Time Using High Energy X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newton, Mark A.; Di Michiel, Marco; Ferri, Davide

2014-09-16

Very high energy X-rays have long offered great promise in providing great insight into the inner workings of catalysts; insights that may complement the array of techniques available to researchers in catalysis either in the laboratory or at more conventional X-ray wavelengths. This contribution aims to critically assess the diverse possibilities now available in the high energy domain as a result of the maturation of third generation synchrotron facilities and to look forward to the potential that forthcoming developments in synchrotron source technology may offer the world of catalysis in the near future.

The Imaging X-ray Polarimetry Explorer (IXPE)

NASA Astrophysics Data System (ADS)

Weisskopf, Martin C.; Ramsey, Brian; O'Dell, Stephen; Tennant, Allyn; Elsner, Ronald; Soffitta, Paolo; Bellazzini, Ronaldo; Costa, Enrico; Kolodziejczak, Jeffrey; Kaspi, Victoria; Muleri, Fabio; Marshall, Herman; Matt, Giorgio; Romani, Roger

2016-07-01

The Imaging X-ray Polarimetry Explorer (IXPE) expands observation space by simultaneously adding polarization measurements to the array of source properties currently measured (energy, time, and location). IXPE will thus open new dimensions for understanding how X-ray emission is produced in astrophysical objects, especially systems under extreme physical conditions—such as neutron stars and black holes. Polarization singularly probes physical anisotropies—ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin—that are not otherwise measurable. Hence, IXPE complements all other investigations in high-energy astrophysics by adding important and relatively unexplored information to the parameter space for studying cosmic X-ray sources and processes, as well as for using extreme astrophysical environments as laboratories for fundamental physics.

Cross-Linking/Mass Spectrometry for Studying Protein Structures and Protein-Protein Interactions: Where Are We Now and Where Should We Go from Here?

PubMed

Sinz, Andrea

2018-05-28

Structural mass spectrometry (MS) is gaining increasing importance for deriving valuable three-dimensional structural information on proteins and protein complexes, and it complements existing techniques, such as NMR spectroscopy and X-ray crystallography. Structural MS unites different MS-based techniques, such as hydrogen/deuterium exchange, native MS, ion-mobility MS, protein footprinting, and chemical cross-linking/MS, and it allows fundamental questions in structural biology to be addressed. In this Minireview, I will focus on the cross-linking/MS strategy. This method not only delivers tertiary structural information on proteins, but is also increasingly being used to decipher protein interaction networks, both in vitro and in vivo. Cross-linking/MS is currently one of the most promising MS-based approaches to derive structural information on very large and transient protein assemblies and intrinsically disordered proteins. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

X-ray Weak Broad-line Qquasars: Absorption or Intrinsic X-ray Weakness

NASA Technical Reports Server (NTRS)

Mushotzky, Richard (Technical Monitor); Risaliti, Guida

2005-01-01

XMM observations of X-ray weak quasars have been performed during 2003 and 2004. The data for all the observations have become available in 2004 (there has been a delay of several months on the initial schedule, due to high background flares which contaminated the observations: as a consequence, most of them had to be rescheduled). We have reduced and analyzed all the data, and obtained interesting scientific results. Out of the eight sources, 4 are confirmed to be extremely X-ray weak, in agreement with the results of previous Chandra observations. 3 sources are confined to be highly variable both in flux (by factor 20-50) and in spectral properties (dramatic changes in spectral index). For both these groups of objects we are completing a publication: 1) For the X-ray weak sources, a paper is submitted with a complete analysis of the X-ray spectra both from Chandra and XMM-Newton, and a comparison with optical and near-IR photometry obtained from all-sky surveys. Possible models for the unusual spectral energy distribution of these sources are also presented. 2) For the variable sources, a paper is being finalized where the X-ray spectra obtained with XMM-Newton are compared with previous X-ray observations and with observations at other wavelengths. It is shown that these sources are high luminosity and extreme cases of the highly variable class of narrow-line Seyfert Is. In order to further understand the nature of these X-ray weak quasars, we submitted proposals for spectroscopy at optical and infrared telescopes. We obtained time at the TNG 4 meter telescope for near-IR observations and at the Hobby-Eberly Telescope for optical high-resolution spectroscopy. These observations have been performed in early 2004. They will complement the XMM data and will lead to understanding of whether the X-ray weakness of these sources is an intrinsic property or is due to absorption by circum-nuclear material. The infrared spectra of the variable sources have been already analyzed and are discussed in the paper by Memola et al. which will be soon submitted.

Effect of Pressure on Valence and Structural Properties of YbFe 2 Ge 2 Heavy Fermion Compound—A Combined Inelastic X-ray Spectroscopy, X-ray Diffraction, and Theoretical Investigation

DOE PAGES

Kumar, Ravhi S.; Svane, Axel; Vaitheeswaran, Ganapathy; ...

2015-10-19

We measured the crystal structure and the Yb valence of the YbFe 2Ge 2 heavy fermion compound at room temperature and under high pressures using high-pressure powder X-ray diffraction and X-ray absorption spectroscopy via both partial fluorescence yield and resonant inelastic X-ray emission techniques. Moreover, the measurements are complemented by first-principles density functional theoretical calculations using the self-interaction corrected local spin density approximation investigating in particular the magnetic structure and the Yb valence. Finally, while the ThCr 2Si 2-type tetragonal (I4/mmm) structure is stable up to 53 GPa, the X-ray emission results show an increase of the Yb valence frommore » v = 2.72(2) at ambient pressure to v = 2.93(3) at ~9 GPa, where at low temperature a pressure-induced quantum critical state was reported.« less

Observations of the structure and evolution of solar flares with a soft X-ray telescope

NASA Technical Reports Server (NTRS)

Vorpahl, J. A.; Gibson, E. G.; Landecker, P. B.; Mckenzie, D. L.; Underwood, J. M.

1975-01-01

Soft X ray flare events were observed with the S-056 X-ray telescope that was part of the ATM complement of instruments aboard SKYLAB. Analyses of these data are reported. The observations are summarized and a detailed discussion of the X-ray flare structures is presented. The data indicated that soft X-ray emitted by a flare come primarily from an intense well-defined core surrounded by a region of fainter, more diffuse emission. An analysis of flare evolution indicates evidence for preliminary heating and energy release prior to the main phase of the flare. Core features are found to be remarkably stable and retain their shape throughout a flare. Most changes in the overall configuration seem to be result of the appearance, disappearance or change in brightness of individual features, rather than the restructuring or reorientation of these features. Brief comparisons with several theories are presented.

Secret Lives of Cepheids: beta Dor as a Test of Cepheid X-ray Heating Mechanisms

NASA Astrophysics Data System (ADS)

Engle, Scott

2017-09-01

We propose two 40 ksec phase-constrained ACIS-I observations of the 9.8 day Cepheid beta Dor. This will fill its uncharted 0.9-0.2 phase gap to confirm and define (Lx, kT) its pulsation-driven X-ray variations and help identify the mechanism (shocks, magnetic fields, turbulent dynamos) responsible, in complement to our recent confirmation of pulsation-induced X-ray variations from delta Cep (Engle et al. 2017). Beta Dor has different properties than delta Cep (P = 9.8/5.4d; R = 61/44Rsun), and the proposed visits are crucial to combine with existing X-ray and FUV data and test the X-ray heating mechanisms. This program is the culmination of several years of work, and the resulting nearly complete phase coverage of beta Dor makes this Cepheid the timeliest and most promising target.

Ultrafast Science Opportunities with Electron Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durr, Hermann

X-rays and electrons are two of the most fundamental probes of matter. When the Linac Coherent Light Source (LCLS), the world’s first x-ray free electron laser, began operation in 2009, it transformed ultrafast science with the ability to generate laser-like x-ray pulses from the manipulation of relativistic electron beams. This document describes a similar future transformation. In Transmission Electron Microscopy, ultrafast relativistic (MeV energy) electron pulses can achieve unsurpassed spatial and temporal resolution. Ultrafast temporal resolution will be the next frontier in electron microscopy and can ideally complement ultrafast x-ray science done with free electron lasers. This document describes themore » Grand Challenge science opportunities in chemistry, material science, physics and biology that arise from an MeV ultrafast electron diffraction & microscopy facility, especially when coupled with linac-based intense THz and X-ray pump capabilities.« less

Low-hazard metallography of moisture-sensitive electrochemical cells.

PubMed

Wesolowski, D E; Rodriguez, M A; McKenzie, B B; Papenguth, H W

2011-08-01

A low-hazard approach is presented to prepare metallographic cross-sections of moisture-sensitive battery components. The approach is tailored for evaluation of thermal (molten salt) batteries composed of thin pressed-powder pellets, but has general applicability to other battery electrochemistries. Solution-cast polystyrene is used to encapsulate cells before embedding in epoxy. Nonaqueous grinding and polishing are performed in an industrial dry room to increase throughput. Lapping oil is used as a lubricant throughout grinding. Hexane is used as the solvent throughout processing; occupational exposure levels are well below the limits. Light optical and scanning electron microscopy on cross-sections are used to analyse a thermal battery cell. Spatially resolved X-ray diffraction on oblique angle cut cells complement the metallographic analysis. Published 2011. This article is a US Government work and is in the public domain in the USA.

Structural Model for Covalent Adhesion of the Streptococcus pyogenes Pilus through a Thioester Bond*

PubMed Central

Linke-Winnebeck, Christian; Paterson, Neil G.; Young, Paul G.; Middleditch, Martin J.; Greenwood, David R.; Witte, Gregor; Baker, Edward N.

2014-01-01

The human pathogen Streptococcus pyogenes produces pili that are essential for adhesion to host surface receptors. Cpa, the adhesin at the pilus tip, was recently shown to have a thioester-containing domain. The thioester bond is believed to be important in adhesion, implying a mechanism of covalent attachment analogous to that used by human complement factors. Here, we have characterized a second active thioester-containing domain on Cpa, the N-terminal domain of Cpa (CpaN). Expression of CpaN in Escherichia coli gave covalently linked dimers. These were shown by x-ray crystallography and mass spectrometry to comprise two CpaN molecules cross-linked by the polyamine spermidine following reaction with the thioester bonds. This cross-linked CpaN dimer provides a model for the covalent attachment of Cpa to target receptors and thus the streptococcal pilus to host cells. Similar thioester domains were identified in cell wall proteins of other Gram-positive pathogens, suggesting that thioester domains are more widely used and provide a mechanism of adhesion by covalent bonding to target molecules on host cells that mimics that used by the human complement system to eliminate pathogens. PMID:24220033

SODART telescopes on the Spectrum X-Gamma (SRG) and their complement of instruments

NASA Astrophysics Data System (ADS)

Schnopper, Herbert W.

1994-11-01

Two SODART thin foil X-ray telescopes will fly on SRG. In the focal plane of one telescope there are: HEPC/LEPC (high- and low energy imaging proportional counters), SIXA (solid state spectrometer array), and FRD (focal plane X-ray detector). In the other, there are: another HEPC/LEPC pair, SXRP (stellar X-ray polarimeter), and another FRD. Mounted alongside and co-aligned with the SODART telescopes is TAUVEX (UV telescope). An objective Bragg spectrometer is mounted in front of one of the telescopes. These instruments and their scientific goals will be described briefly. More detailed discussions will be given by the relevant PIs in the poster session.

Characteristics of light reflected from a dense ionization wave with a tunable velocity.

PubMed

Zhidkov, A; Esirkepov, T; Fujii, T; Nemoto, K; Koga, J; Bulanov, S V

2009-11-20

An optically dense ionization wave (IW) produced by two femtosecond (approximately 10/30 fs) laser pulses focused cylindrically and crossing each other may become an efficient coherent x-ray converter in accordance with the Semenova-Lampe theory. The resulting velocity of a quasiplane IW in the vicinity of pulse intersection changes with the angle between the pulses from the group velocity of ionizing pulses to infinity allowing a tuning of the wavelength of x rays and their bunching. The x-ray spectra after scattering of a lower frequency and long coherent light pulse change from the monochromatic to high order harmoniclike with the duration of the ionizing pulses.

A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time.

PubMed

Schweitzer, Mary H; Zheng, Wenxia; Cleland, Timothy P; Goodwin, Mark B; Boatman, Elizabeth; Theil, Elizabeth; Marcus, Matthew A; Fakra, Sirine C

2014-01-22

The persistence of original soft tissues in Mesozoic fossil bone is not explained by current chemical degradation models. We identified iron particles (goethite-αFeO(OH)) associated with soft tissues recovered from two Mesozoic dinosaurs, using transmission electron microscopy, electron energy loss spectroscopy, micro-X-ray diffraction and Fe micro-X-ray absorption near-edge structure. Iron chelators increased fossil tissue immunoreactivity to multiple antibodies dramatically, suggesting a role for iron in both preserving and masking proteins in fossil tissues. Haemoglobin (HB) increased tissue stability more than 200-fold, from approximately 3 days to more than two years at room temperature (25°C) in an ostrich blood vessel model developed to test post-mortem 'tissue fixation' by cross-linking or peroxidation. HB-induced solution hypoxia coupled with iron chelation enhances preservation as follows: HB + O2 > HB - O2 > -O2 > +O2. The well-known O2/haeme interactions in the chemistry of life, such as respiration and bioenergetics, are complemented by O2/haeme interactions in the preservation of fossil soft tissues.

A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time

PubMed Central

Schweitzer, Mary H.; Zheng, Wenxia; Cleland, Timothy P.; Goodwin, Mark B.; Boatman, Elizabeth; Theil, Elizabeth; Marcus, Matthew A.; Fakra, Sirine C.

2014-01-01

The persistence of original soft tissues in Mesozoic fossil bone is not explained by current chemical degradation models. We identified iron particles (goethite-αFeO(OH)) associated with soft tissues recovered from two Mesozoic dinosaurs, using transmission electron microscopy, electron energy loss spectroscopy, micro-X-ray diffraction and Fe micro-X-ray absorption near-edge structure. Iron chelators increased fossil tissue immunoreactivity to multiple antibodies dramatically, suggesting a role for iron in both preserving and masking proteins in fossil tissues. Haemoglobin (HB) increased tissue stability more than 200-fold, from approximately 3 days to more than two years at room temperature (25°C) in an ostrich blood vessel model developed to test post-mortem ‘tissue fixation’ by cross-linking or peroxidation. HB-induced solution hypoxia coupled with iron chelation enhances preservation as follows: HB + O2 > HB − O2 > −O2 ≫ +O2. The well-known O2/haeme interactions in the chemistry of life, such as respiration and bioenergetics, are complemented by O2/haeme interactions in the preservation of fossil soft tissues. PMID:24285202

Spatially resolved density and ionization measurements of shocked foams using x-ray fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, M. J.; Keiter, P. A.; Montgomery, D. S.

2016-09-22

We present experiments at the Trident laser facility demonstrating the use of x-ray fluorescence (XRF) to simultaneously measure density, ionization state populations, and electron temperature in shocked foams. An imaging x-ray spectrometer was used to obtain spatially-resolved measurements of Ti K-more » $$\\alpha$$ emission. Density profiles were measured from K-$$\\alpha$$ intensity. Ti ionization state distributions and electron temperatures were inferred by fitting K-$$\\alpha$$ spectra to spectra from CRETIN simulations. This study shows that XRF provides a powerful tool to complement other diagnostics to make equation of state measurements of shocked materials containing a suitable tracer element.« less

An XMM Investigation of Non-Thermal Phenomena in the Winds of Early-Type Stars

NASA Technical Reports Server (NTRS)

Waldron, Wayne L.; Mushotzky, Richard (Technical Monitor)

2002-01-01

The X-ray emission from early-type stars is believed to arise from a stellar wind distribution of shocks. Hence, X-ray analyses of these stars must include the effects of stellar wind X-ray absorption, which, in general dominates the ISM absorption. Although the absorption cross sections for the wind and ISM are essentially identical above 1 keV, there is substantial differences below 1 keV. Typically, if one only uses ISM cross sections to obtain fits to X-ray spectra, the fits usually indicate a model deficiency at energies below 1 keV which is attributed to the large increase in ISM cross sections at these energies. This deficiency can be eliminated by using stellar wind absorption models with a fixed ISM component. Since all early-type stars have substantial X-ray emission below 1 keV, than inclusion of wind absorption has proven to be a critical component in fitting X-ray spectra at low energies, verifying that these X-rays are indeed arising from within the stellar wind.

Mutations in XRCC4 cause primordial dwarfism without causing immunodeficiency.

PubMed

Saito, Shinta; Kurosawa, Aya; Adachi, Noritaka

2016-08-01

In successive reports from 2014 to 2015, X-ray repair cross-complementing protein 4 (XRCC4) has been identified as a novel causative gene of primordial dwarfism. XRCC4 is indispensable for non-homologous end joining (NHEJ), the major pathway for repairing DNA double-strand breaks. As NHEJ is essential for V(D)J recombination during lymphocyte development, it is generally believed that abnormalities in XRCC4 cause severe combined immunodeficiency. Contrary to expectations, however, no overt immunodeficiency has been observed in patients with primordial dwarfism harboring XRCC4 mutations. Here, we describe the various XRCC4 mutations that lead to disease and discuss their impact on NHEJ and V(D)J recombination.

X-ray imaging crystal spectrometer for extended X-ray sources

DOEpatents

Bitter, Manfred L.; Fraenkel, Ben; Gorman, James L.; Hill, Kenneth W.; Roquemore, A. Lane; Stodiek, Wolfgang; von Goeler, Schweickhard E.

2001-01-01

Spherically or toroidally curved, double focusing crystals are used in a spectrometer for X-ray diagnostics of an extended X-ray source such as a hot plasma produced in a tokomak fusion experiment to provide spatially and temporally resolved data on plasma parameters using the imaging properties for Bragg angles near 45. For a Bragg angle of 45.degree., the spherical crystal focuses a bundle of near parallel X-rays (the cross section of which is determined by the cross section of the crystal) from the plasma to a point on a detector, with parallel rays inclined to the main plain of diffraction focused to different points on the detector. Thus, it is possible to radially image the plasma X-ray emission in different wavelengths simultaneously with a single crystal.

ART: Surveying the Local Universe at 2-11 keV

NASA Technical Reports Server (NTRS)

O'Dell, S. L.; Ramsey, B. D.; Adams, M. L.; Brandt, W. N.; Bubarev, M. V.; Hassinger, G.; Pravlinski, M.; Predehl, P.; Romaine, S. E.; Swartz, D. A.;

Broad-band characteristics of seven new hard X-ray selected cataclysmic variables

NASA Astrophysics Data System (ADS)

Bernardini, F.; de Martino, D.; Mukai, K.; Russell, D. M.; Falanga, M.; Masetti, N.; Ferrigno, C.; Israel, G.

2017-10-01

We present timing and spectral analysis of a sample of seven hard X-ray selected cataclysmic variable candidates based on simultaneous X-ray and optical observations collected with XMM-Newton, complemented with Swift/BAT and INTEGRAL /IBIS hard X-ray data and ground-based optical photometry. For six sources, X-ray pulsations are detected for the first time in the range of ˜296-6098 s, identifying them as members of the magnetic class. Swift J0927.7-6945, Swift J0958.0-4208, Swift J1701.3-4304, Swift J2113.5+5422 and possibly PBC J0801.2-4625 are intermediate polars (IPs), while Swift J0706.8+0325 is a short (1.7 h) orbital period polar, the 11th hard X-ray-selected identified so far. X-ray orbital modulation is also observed in Swift J0927.7-6945 (5.2 h) and Swift J2113.5+5422 (4.1 h). Swift J1701.3-4304 is discovered as the longest orbital period (12.8 h) deep eclipsing IP. The spectra of the magnetic systems reveal optically thin multitemperature emission between 0.2 and 60 keV. Energy-dependent spin pulses and the orbital modulation in Swift J0927.7-6945 and Swift J2113.5+5422 are due to intervening local high-density absorbing material (NH ˜ 1022 - 23 cm-2). In Swift J0958.0-4208 and Swift J1701.3-4304, a soft X-ray blackbody (kT ˜ 50 and ˜80 eV) is detected, adding them to the growing group of `soft' IPs. White dwarf masses are determined in the range of ˜ 0.58-1.18 M⊙, indicating massive accreting primaries in five of them. Most sources accrete at rates lower than the expected secular value for their orbital period. Formerly proposed as a long-period (9.4 h) nova-like CV, Swift J0746.3-1608 shows peculiar spectrum and light curves suggesting either an atypical low-luminosity CV or a low-mass X-ray binary.

L x-ray production cross sections in Th and U at 17.8, 25.8 and 46.9 keV photon energies

NASA Astrophysics Data System (ADS)

Kumar, Ajay; Puri, Sanjiv; Shahi, J. S.; Garg, M. L.; Mehta, D.; Singh, Nirmal

2001-02-01

The L x-ray production (XRP) differential cross sections in Th and U have been measured at the 17.8 keV incident photon energy (E_L3

Extended X-ray emission in PKS 1718-649

NASA Astrophysics Data System (ADS)

Beuchert, T.; Rodríguez-Ardila, A.; Moss, V. A.; Schulz, R.; Kadler, M.; Wilms, J.; Angioni, R.; Callingham, J. R.; Gräfe, C.; Krauß, F.; Kreikenbohm, A.; Langejahn, M.; Leiter, K.; Maccagni, F. M.; Müller, C.; Ojha, R.; Ros, E.; Tingay, S. J.

2018-04-01

PKS 1718-649 is one of the closest and most comprehensively studied candidates of a young active galactic nucleus (AGN) that is still embedded in its optical host galaxy. The compact radio structure, with a maximal extent of a few parsecs, makes it a member of the group of compact symmetric objects (CSO). Its environment imposes a turnover of the radio synchrotron spectrum towards lower frequencies, also classifying PKS 1718-649 as gigahertz-peaked radio spectrum (GPS) source. Its close proximity has allowed the first detection of extended X-ray emission in a GPS/CSO source with Chandra that is for the most part unrelated to nuclear feedback. However, not much is known about the nature of this emission. By co-adding all archival Chandra data and complementing these datasets with the large effective area of XMM-Newton, we are able to study the detailed physics of the environment of PKS 1718-649. Not only can we confirm that the bulk of the ≲kiloparsec-scale environment emits in the soft X-rays, but we also identify the emitting gas to form a hot, collisionally ionized medium. While the feedback of the central AGN still seems to be constrained to the inner few parsecs, we argue that supernovae are capable of producing the observed large-scale X-ray emission at a rate inferred from its estimated star formation rate.

Thick-target-method study of Mα β x-ray production cross sections of Pb and Bi impacted by positrons up to 9 keV

NASA Astrophysics Data System (ADS)

Wu, Y.; Liang, Y.; Xu, M. X.; Yuan, Y.; Chang, C. H.; Qian, Z. C.; Wang, B. Y.; Kuang, P.; Zhang, P.

2018-03-01

Atomic M -shell x-ray production cross sections induced by positrons near the threshold energy have been presented in this paper. In the experiment, online monitoring technology, which utilizes a high-purity germanium detector to record the annihilation photons emitted from the pure thick target impacted by positrons, was developed to obtain the accurate number of the incident positrons. The effects of the multiple scattering of incident positrons, from the bremsstrahlung and annihilation photons and other secondary particles on the experimental characteristic x-ray yield, were eliminated by Monte Carlo simulation in combination with theoretical integral calculation. The Tikhonov regularization method was adopted to handle the ill-posed inverse problem involved in the thick-target method, i.e., x-ray production cross sections by the corrected characteristic x-ray yield. Experimental results of Mα β x-ray production cross sections for Pb and Bi impacted by 6-9-keV positrons were compared with the corresponding values predicted by the distorted-wave Born approximation (DWBA). Good agreement was found between the two. Moreover, we have presented the experimental results on the ratios of the Mα β x-ray production cross sections by electron impact in the literature to that by 6-9-keV positron impact in this work. They were also in accordance with the theoretical ratios calculated by the predictions of DWBA theory.

Ion charge state distribution effects on elastic X-ray Thomson scattering

NASA Astrophysics Data System (ADS)

Iglesias, Carlos A.

2018-03-01

Analytic models commonly applied in elastic X-ray Thomson scattering cross-section calculations are used to generate results from a discrete ion charge distribution and an average charge description. Comparisons show that interchanging the order of the averaging procedure can appreciably alter the cross-section, especially for plasmas with partially filled K-shell bound electrons. In addition, two common approximations to describe the free electron density around an ion are shown to yield significantly different elastic X-ray Thomson scattering cross-sections.

Do solar decimetric spikes originate in coronal X-ray sources?

NASA Astrophysics Data System (ADS)

Battaglia, M.; Benz, A. O.

2009-06-01

Context: In the standard solar flare scenario, a large number of particles are accelerated in the corona. Nonthermal electrons emit both X-rays and radio waves. Thus, correlated signatures of the acceleration process are predicted at both wavelengths, coinciding either close to the footpoints of a magnetic loop or near the coronal X-ray source. Aims: We attempt to study the spatial connection between coronal X-ray emission and decimetric radio spikes to determine the site and geometry of the acceleration process. Methods: The positions of radio-spike sources and coronal X-ray sources are determined and analyzed in a well-observed limb event. Radio spikes are identified in observations from the Phoenix-2 spectrometer. Data from the Nançay radioheliograph are used to determine the position of the radio spikes. RHESSI images in soft and hard X-ray wavelengths are used to determine the X-ray flare geometry. Those observations are complemented by images from GOES/SXI. Results: We find that the radio emission originates at altitudes much higher than the coronal X-ray source, having an offset from the coronal X-ray source amounting to 90´´ and to 113´´ and 131´´ from the two footpoints, averaged over time and frequency. Conclusions: Decimetric spikes do not originate from coronal X-ray flare sources contrary to previous expectations. However, the observations suggest a causal link between the coronal X-ray source, related to the major energy release site, and simultaneous activity in the higher corona.

Inner-shell/subshell photoionization cross section measurements using a gamma excited variable energy X-ray source

NASA Astrophysics Data System (ADS)

Sood, B. S.; Allawadhi, K. L.; Arora, S. K.

1982-02-01

The method developed for the determination of K/L shell photoionization cross sections in various elements, 39 ≤ Z ≤ 92, in the characteristic X-ray energy region using a gamma excited variable energy X-ray source has been used for the measurement of L III subshell photoionization cross sections in Pb, Th and U. The measurements are made at the K X-ray energies of Rb, Nb and Mo, since these are able to excite selectively the L III subshells of Pb, Th and U, respectively. The results, when compared with theoretical calculations of Scofield, are found to agree within the uncertainties of determination.

The Secret Lives of Cepheids: δ Cep—The Prototype of a New Class of Pulsating X-Ray Variable Stars

NASA Astrophysics Data System (ADS)

Engle, Scott G.; Guinan, Edward F.; Harper, Graham M.; Cuntz, Manfred; Remage Evans, Nancy; Neilson, Hilding R.; Fawzy, Diaa E.

2017-03-01

From our Secret Lives of Cepheids program, the prototype Classical Cepheid, δ Cep, is found to be an X-ray source with periodic pulsation-modulated X-ray variations. This finding complements our earlier reported phase-dependent FUV-UV emissions of the star that increase ˜10-20 times with highest fluxes at ˜ 0.90{--}0.95φ , just prior to maximum brightness. Previously δ Cep was found as potentially X-ray variable, using XMM-Newton observations. Additional phase-constrained data were secured with Chandra near X-ray emission peak, to determine if the emission and variability were pulsation-phase-specific to δ Cep and not transient or due to a possible coronally active, cool companion. The Chandra data were combined with prior XMM-Newton observations, and were found to very closely match the previously observed X-ray behavior. From the combined data set, a ˜4 increase in X-ray flux is measured, reaching a peak {L}{{X}} = 1.7 × 1029 erg s-1 near 0.45ϕ. The precise X-ray flux phasing with the star’s pulsation indicates that the emissions arise from the Cepheid and not from a companion. However, it is puzzling that the maximum X-ray flux occurs ˜0.5ϕ (˜3 days) later than the FUV-UV maximum. There are several other potential Cepheid X-ray detections with properties similar to δ Cep, and comparable X-ray variability is indicated for two other Cepheids: β Dor and V473 Lyr. X-ray generating mechanisms in δ Cep and other Cepheids are discussed. If additional Cepheids are confirmed to show phased X-ray variations, then δ Cep will be the prototype of a new class of pulsation-induced X-ray variables.

Phonon spectroscopy with sub-meV resolution by femtosecond x-ray diffuse scattering

DOE PAGES

Zhu, Diling; Robert, Aymeric; Henighan, Tom; ...

2015-08-10

We present a reconstruction of the transverse acoustic phonon dispersion of germanium from femtosecond time-resolved x-ray diffuse scattering measurements at the Linac Coherent Light Source. We demonstrate an energy resolution of 0.3 meV with a momentum resolution of 0.01 nm -1 using 10-keV x rays with a bandwidth of ~ 1 eV. This high resolution was achieved simultaneously for a large section of reciprocal space including regions closely following three of the principal symmetry directions. The phonon dispersion was reconstructed with less than 3 h of measurement time, during which neither the x-ray energy, the sample orientation, nor the detectormore » position were scanned. In conclusion, these results demonstrate how time-domain measurements can complement conventional frequency domain inelastic-scattering techniques.« less

Constructing polyamidoamine dendrons from poly(poly(ethylene glycol) monomethacrylate) brushes grafted from planar silicon hydride surfaces for biomedical applications

NASA Astrophysics Data System (ADS)

Liu, Xiang; Zheng, Hong-Ning; Yan, Qin; Wang, Cuie; Ma, Yin-Zhou; Tang, Yan-Chun; Xiao, Shou-Jun

2011-06-01

A facile approach was established to construct polyamidoamine (PAMAM) dendrons from polymer brushes of poly(poly(ethylene glycol) monomethacrylate) (Si-g-P(PEGMA-OH)) grafted from a planar silicon hydride surface. First the Si-g-P(PEGMA-OH) brushes were grown via surface-initiated atom transfer radical polymerization with robust Si-C links on silicon surfaces. The side-chain hydroxyl groups of Si-g-P(PEGMA-OH) were chlorinated with thionyl chloride and further chlorines were substituted with amino groups of ethylenediamine, giving terminal primary amines. Borrowing the solution synthesis approach, we constructed second and third generations of PAMAM dendrons on-chip by surface-initiated alternative growth of two monomers, methyl acrylate and ethylenediamine. Two applications of silicon-based PAMAM dendrons were shown: the dense amino groups were activated via a cross-linker, N-succinimidyl-6-maleimidylhexanoate, to capture a free-thiol-carrying peptide of oxytocin and the third generation of PAMAM dendrons was used as a platform to on-chip synthesize a three amino acid peptide of Arg-Gly-Asp (RGD). The above conclusions were mainly derived from a home-built multiple transmission-reflection infrared spectroscopy, and complemented by X-ray photoelectron spectroscopy, UV-Vis spectroscopy and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry.

Time-dependent nonequilibrium soft x-ray response during a spin crossover

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Veenendaal, Michel

The rapid development of high-brilliance pulsed X-ray sources with femtosecond time resolution has created a need for a better theoretical understanding of the time-dependent soft-X-ray response of dissipative many-body quantum systems. It is demonstrated how soft-X-ray spectroscopies, such as X-ray absorption and resonant inelastic X-ray scattering at transition-metal L-edges, can provide insight into intersystem crossings, such as a spin crossover. The photoinduced doublet-to-quartet spin crossover on cobalt in Fe-Co Prussian blue analogues is used as an example to demonstrate how the X-ray response is affected by the dissipative nonequilibrium dynamics. The time-dependent soft-X-ray spectra provide a wealth of information thatmore » reflect the changes in the nonequilibrium initial state via continuously changing spectral lineshapes that cannot be decomposed into initial photoexcited and final metastable spectra, strong broadenings, a collapse of clear selection rules during the intersystem crossing, strong fluctuations in the isotropic branching ratio in X-ray absorption, and crystal-field collapse/oscillations and strongly time-dependent anti-Stokes processes in RIXS.« less

Flash-Bang Detector to Model the Attenuation of High-Energy Photons

NASA Astrophysics Data System (ADS)

Pagsanjan, N., III; Kelley, N. A.; Smith, D. M.; Sample, J. G.

2015-12-01

It has been known for years that lightning and thunderstorms produce gamma rays and x-rays. Terrestrial gamma-ray flashes (TGFs) are extremely bright bursts of gamma rays originating from thunderstorms. X-ray stepped leaders are bursts of x-rays coming from the lightning channel. It is known that the attenuation of these high-energy photons is a function of distance, losing energy and intensity at larger distances. To complement gamma-ray detectors on the ground it would be useful to measure the distance to the flash. Knowing the distance would allow for the true source fluence of gamma rays or x-rays to be modeled. A flash-bang detector, which uses a micro-controller, a photodiode, a microphone and temperature sensor will be able to detect the times at which lightning and thunder occurs. Knowing the speed of sound as function of temperature and the time difference between the flash and the thunder, the range to the lightning can be calculated. We will present the design of our detector as well as some preliminary laboratory test results.

X-ray Reflectivity Characterization of Ion Distribution at Biomimetic Membrane Surfaces

NASA Astrophysics Data System (ADS)

Krüger, Peter; Pittler, Jens; Vaknin, David; Lösche, Mathias

2003-03-01

Ions at cell membrane surfaces may control the function and conformation of nearby biomolecules, thus playing an important role in inter- and intracellular transport as well as in biorecognition processes. Moreover, charge patterns at membrane surfaces may direct the growth of inorganic crystals in biomineralization. Langmuir monolayers are widely employed as model systems for studying charge distribution and growth processes at the organic/inorganic interface. We present a novel x-ray reflectivity technique that provides detailed information on ion distribution at biomembrane surfaces by using monochromatic x-rays at various energies at and away from the ion x-ray absorption edges. As a model, the interaction of Ba^2+ with DMPA^- (dimyristoyl phosphatidic acid) monolayers at the aqueous surface was studied. We find an unexpectedly large concentration of the cations near the interface where they form a Stern layer of bound ions. These studies have been complemented with conventional x-ray reflectivity measurements and extended to other anionic lipid species (DMPS, DMPG) and cations (Ca^2+).

Association of XRCC1 Trp194 allele with risk of breast cancer, and Ki67 protein status in breast tumor tissues

PubMed Central

Jalali, Chiya; Ghaderi, Bayazid; Amini, Sabrieh; Abdi, Mohammad; Roshani, Daem

2016-01-01

Objectives: To evaluate the role of this polymorphism as a risk factor for breast cancer in Kurdish patients and to investigate the possible association between Arg194Trp x-ray repair cross-complementing group 1 (XRCC1) gene polymorphisms with clinical and histopathological outcomes of patients with breast cancer. Methods: A total of 100 breast cancer patients and 200 cancer-free controls in Kurdish population of Kurdistan state admitted to Tohid Hospital, Sanandaj, Kurdistan, Iran between January 2012 and May 2015 were enrolled in this cross-sectional study. Tissue expression of estrogen receptor (ER), progesteron receptor (PR), human epidermal growth factor receptor 2 (Her2/neu), and Ki67 were evaluated by immunohistochemistry (IHC). The Arg194Trp genotypes were determined by polymerase chain reaction- restriction fragment length polymorphism method. Results: Our data showed that the risk for breast cancer increased significantly among the Trp variant of XRCC1. Statistically significant association was found between codon 194 polymorphisms and tissue expression of Ki67. Conclusion: The Trp allele of codon 194 XRCC1 is a potential risk factor for breast cancer in Kurdish ethnicity. Furthermore, effect of this polymorphism on clinical and histological features of breast cancer was significant. PMID:27279507

Modification and benchmarking of MCNP for low-energy tungsten spectra.

PubMed

Mercier, J R; Kopp, D T; McDavid, W D; Dove, S B; Lancaster, J L; Tucker, D M

2000-12-01

The MCNP Monte Carlo radiation transport code was modified for diagnostic medical physics applications. In particular, the modified code was thoroughly benchmarked for the production of polychromatic tungsten x-ray spectra in the 30-150 kV range. Validating the modified code for coupled electron-photon transport with benchmark spectra was supplemented with independent electron-only and photon-only transport benchmarks. Major revisions to the code included the proper treatment of characteristic K x-ray production and scoring, new impact ionization cross sections, and new bremsstrahlung cross sections. Minor revisions included updated photon cross sections, electron-electron bremsstrahlung production, and K x-ray yield. The modified MCNP code is benchmarked to electron backscatter factors, x-ray spectra production, and primary and scatter photon transport.

AGN in the Swift/BAT and INTEGRAL Hard X-ray Surveys

NASA Technical Reports Server (NTRS)

Beckmann, Volker; Tueller, Jack; Baumgartner, Wayne; Markwardt, Craig; Mushotzky, Richard; Skinner, Gerry

2008-01-01

Two hard X-ray surveys are in progress at this time. They provide a unique new window on compact objects and black holes. I will discuss how these two surveys complement each other and the potential for improved coordination that could yield significant near term results in both sensitivity and time coverage. I will pay particular attention to the discovery of faint sources including new results from the 36 month survey from Swift/Burst Alert Telescope (BAT).

Propagation-based x-ray phase contrast imaging using an iterative phase diversity technique

NASA Astrophysics Data System (ADS)

Carroll, Aidan J.; van Riessen, Grant A.; Balaur, Eugeniu; Dolbnya, Igor P.; Tran, Giang N.; Peele, Andrew G.

2018-03-01

Through the use of a phase diversity technique, we demonstrate a near-field in-line x-ray phase contrast algorithm that provides improved object reconstruction when compared to our previous iterative methods for a homogeneous sample. Like our previous methods, the new technique uses the sample refractive index distribution during the reconstruction process. The technique complements existing monochromatic and polychromatic methods and is useful in situations where experimental phase contrast data is affected by noise.

Association of Leukotrichia in Vitiligo and Asp148Glu Polymorphism of Apurinic/Apyrimidinic Endonuclease 1.

PubMed

Aydin, A Fatih; Aydıngöz, İkbal Esen; Doğru-Abbasoğlu, Semra; Vural, Pervin; Uysal, Müjdat

2017-01-01

Oxidative stress and increased DNA damage have been implicated in the etiopathogenesis of vitiligo. Oxidative DNA damage is mainly repaired by the base excision repair (BER) pathway. We sought to determine whether polymorphisms in DNA repair genes may have a role in the pathogenesis of vitiligo. We conducted a study including 100 patients with vitiligo and age- and sex-matched 193 control subjects to examine the role of single-nucleotide polymorphisms of BER genes, human 8-oxoG DNA N-glycosylase 1 (codon 326), apurinic/apyrimidinic endonuclease 1 (APE1) (codon 148), and X-ray repair cross-complementing group 1 (codon 399) as risk factors for vitiligo. These polymorphisms were determined by quantitative real-time polymerase chain reaction and melting curve analysis. No significant association was observed between the variant alleles of studied genes and vitiligo. However, we showed that the presence of APE1 148Glu variant allele is associated with leukotrichia. This preliminary study suggests that APE1 (codon 148) polymorphism may play a role in vitiligo pathogenesis.

X-ray and gamma-ray line production by nonthermal ions

NASA Technical Reports Server (NTRS)

Bussard, R. W.; Omidvar, K.; Ramaty, R.

1977-01-01

X-ray production was calculated at approximately 6.8 keV by the 2p to 1s transition in fast hydrogen- and helium-like iron ions, following both electron capture to excited levels and collisional excitation. A refinement of the OBK approximation was used to obtain an improved charge exchange cross section. This, and the corresponding ionization cross section were used to determine equilibrium charge fractions for iron ions as functions of their energy. The effective X-ray line production cross section was found to be sharply peaked in energy at about 8 to 12 MeV/amu. Because fast ions of similar energies can also excite nuclear levels, the ratio of selected strong gamma ray line emissivities to the X-ray line emissivity was also calculated. Limits set by this method on the intensity of gamma ray line emission from the galactic center and the radio galaxy Centaurus A are generally lower than those reported in the literature.

X-ray imaging of aggregation in silica and zeolitic precursors

NASA Astrophysics Data System (ADS)

Morrison, Graeme R.; Browne, Michael T.; Beelen, Theo P. M.; van Garderen, Harold F.

1993-01-01

The resolution available in the King's College London scanning transmission x-ray microscope (STXM) can be exploited to study aggregate structures over a length scale from 100 nm to 10 micrometers that overlaps with and complements that available from small-angle x-ray scattering (SAXS) data. It is then possible to use these combined sets of data to test between different growth models for the aggregates, using the fractal dimension of the structures as a way of distinguishing the different models. In this paper we show some of the first transmission x-ray images taken of silica gels and zeolite precursors, materials that are of great practical and economic importance for certain selective catalytic processes in the chemical industry, and yet for which there is still only limited understanding of the complicated processes involved in their preparation. These images reveal clearly the fractal aggregates that are formed by the specimens.

X-ray ptychographic and fluorescence microscopy of frozen-hydrated cells using continuous scanning

DOE PAGES

Deng, Junjing; Vine, David J.; Chen, Si; ...

2017-03-27

X-ray microscopy can be used to image whole, unsectioned cells in their native hydrated state. It complements the higher resolution of electron microscopy for submicrometer thick specimens, and the molecule-specific imaging capabilites of fluorescence light microscopy. We describe here the first use of fast, continuous x-ray scanning of frozen hydrated cells for simultaneous sub-20 nm resolution ptychographic transmission imaging with high contrast, and sub-100 nm resolution deconvolved x-ray fluorescence imaging of diffusible and bound ions at native concentrations, without the need to add specific labels. Here, by working with cells that have been rapidly frozen without the use of chemicalmore » fixatives, and imaging them under cryogenic conditions, we are able to obtain images with well preserved structural and chemical composition, and sufficient stability against radiation damage to allow for multiple images to be obtained with no observable change.« less

The Imaging X-Ray Polarimetry Explorer (IXPE)

NASA Technical Reports Server (NTRS)

Weisskopf, Martin C.; Ramsey, Brian; O’Dell, Stephen; Tennant, Allyn; Elsner, Ronald; Soffita, Paolo; Bellazzini, Ronaldo; Costa, Enrico; Kolodziejczak, Jeffery; Kaspi, Victoria;

Quantifying Mesoscale Neuroanatomy Using X-Ray Microtomography

PubMed Central

Gray Roncal, William; Prasad, Judy A.; Fernandes, Hugo L.; Gürsoy, Doga; De Andrade, Vincent; Fezzaa, Kamel; Xiao, Xianghui; Vogelstein, Joshua T.; Jacobsen, Chris; Körding, Konrad P.

2017-01-01

Methods for resolving the three-dimensional (3D) microstructure of the brain typically start by thinly slicing and staining the brain, followed by imaging numerous individual sections with visible light photons or electrons. In contrast, X-rays can be used to image thick samples, providing a rapid approach for producing large 3D brain maps without sectioning. Here we demonstrate the use of synchrotron X-ray microtomography (µCT) for producing mesoscale (∼1 µm 3 resolution) brain maps from millimeter-scale volumes of mouse brain. We introduce a pipeline for µCT-based brain mapping that develops and integrates methods for sample preparation, imaging, and automated segmentation of cells, blood vessels, and myelinated axons, in addition to statistical analyses of these brain structures. Our results demonstrate that X-ray tomography achieves rapid quantification of large brain volumes, complementing other brain mapping and connectomics efforts. PMID:29085899

The nature of X-ray selected star candidates

NASA Astrophysics Data System (ADS)

Mickaelian, A. M.; Paronyan, G. M.; Abrahamyan, H. V.; Gigoyan, K. S.; Gyulzadyan, M. V.; Kostandyan, G. R.

2016-12-01

The joint HRC/BHRC catalogue of optical identifications of ROSAT BSC and FSC X-ray sources is based on merging the Hamburg-ROSAT Catalogue (HRC) and Byurakan-Hamburg-ROSAT Catalogue (BHRC). Both have been made by optical identifications of X-ray sources based on low-dispersion spectra of the Hamburg QuasarSurvey (HQS) using the ROSAT Catalogues. HRC/BHRC contains a sample of 8132 (5341+2791) optically identified X-ray sources with count rate (CR) of photons ≥ 0.04 ct/s in the area of the low-dispersion Hamburg Quasar Survey (HQS), |b| ≥ 20° and δ ≥ 0°. Based on low-dispersion spectral classification, there are 4253 AGN, 492 galaxies, 1800 stars and 1587 unknown objects in the sample. 1800 star candidates include 1429 objects listed in SDSS DR12 photometric catalogue and 433 given in SDSS spectroscopic catalogue. Using these spectra, we have carried out classification of these star candidates to reveal new interesting objects, as well as to define the true content of our sample. 34 cataclysmic variables (including 7 new ones), 19 white dwarfs, 19 late-type stars (K-M and C types), 16 early type stars (O-B), 40 hot coronal stars (A-F types), 2 composite spectrum objects, and 17 bright stars have been revealed, as well as 286 objects which turned out to be extragalactic ones; 75 emission-line galaxies (HII/SB and AGN, including QSOs, Seyferts, and LINERs) and 211 absorption line galaxies were revealed (wrong classifications in HRC/BHRC due to their faint images and low-quality spectra). We have retrieved multiwavelength data from recent catalogues and carried out statistical investigations of the multiwavelength properties for the whole sample of stars. All stars have been found in GSC 2.3.2, as well as most of them are in GALEX, USNO-B1.0, 2MASS and WISE catalogues. Relations between the radiation fluxes in different bands from X-ray to radio for different types of sources are studied and analysis of their characteristics is made. X-ray selected stars are an important complement to the stellar populations of our Galaxy in solar neighbourhood and beyond. Keywords: X-ray sources, cross-correlations, white dwarfs, cataclysmic variables, carbon stars

The second FERMI large area telescope catalog of gamma-ray pulsars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdo, A. A.; Ajello, M.; Allafort, A.

2013-09-19

This catalog summarizes 117 high-confidence ≥0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emissionmore » for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.« less

The second fermi large area telescope catalog of gamma-ray pulsars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdo, A. A.; Ajello, M.; Allafort, A.

2013-09-19

This catalog summarizes 117 high-confidence ≥0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emissionmore » for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.« less

Semi-empirical and empirical L X-ray production cross sections for elements with 50 ⩽ Z ⩽ 92 for protons of 0.5 3.0 MeV

NASA Astrophysics Data System (ADS)

Nekab, M.; Kahoul, A.

2006-04-01

We present in this contribution, semi-empirical production cross sections of the main X-ray lines Lα, Lβ and Lγ for elements from Sn to U and for protons with energies varying from 0.5 to 3.0 MeV. The theoretical X-ray production cross sections are firstly calculated from the theoretical ionization cross sections of the L i ( i = 1, 2, 3) subshell within the ECPSSR theory. The semi-empirical Lα, Lβ and Lγ cross sections are then deduced by fitting the available experimental data normalized to their corresponding theoretical values and give the better representation of the experimental data in some cases. On the other hand, the experimental data are directly fitted to deduce the empirical L X-ray production cross sections. A comparison is made between the semi-empirical cross sections, the empirical cross sections reported in this work and the empirical ones reported by Reis and Jesus [M.A. Reis, A.P. Jesus, Atom. Data Nucl. Data Tables 63 (1996) 1] and those of Strivay and Weber [Strivay, G. Weber, Nucl. Instr. and Meth. B 190 (2002) 112].

Cell micro-irradiation with MeV protons counted by an ultra-thin diamond membrane

NASA Astrophysics Data System (ADS)

Barberet, Philippe; Pomorski, Michal; Muggiolu, Giovanna; Torfeh, Eva; Claverie, Gérard; Huss, Cédric; Saada, Samuel; Devès, Guillaume; Simon, Marina; Seznec, Hervé

2017-12-01

We report the development of thin single crystal diamond membranes suitable for dose control in targeted cell irradiation experiments with a proton microbeam. A specific design was achieved to deliver single protons with a hit detection efficiency approaching 100%. The membranes have thicknesses between 1.8 and 3 μm and are used as vacuum windows on the microbeam line. The impact of these transmission detectors on the microbeam spot size is estimated by Monte-Carlo simulations, indicating that a beam lateral resolution below 2 μm is achieved. This is confirmed by experiments showing the accumulation online of X-ray Repair Cross-Complementing protein 1 (XRCC1)-Green Fluorescent Protein (GFP) at DNA damaged sites in living cells.

Time-dependent nonequilibrium soft x-ray response during a spin crossover

NASA Astrophysics Data System (ADS)

van Veenendaal, Michel

2018-03-01

A theoretical framework is developed for better understanding the time-dependent soft-x-ray response of dissipative quantum many-body systems. It is shown how x-ray absorption and resonant inelastic x-ray scattering (RIXS) at transition-metal L edges can provide insight into ultrafast intersystem crossings of importance for energy conversion, ultrafast magnetism, and catalysis. The photoinduced doublet-to-quartet spin crossover on cobalt in Fe-Co Prussian blue analogs is used as a model system to demonstrate how the x-ray response is affected by the nonequilibrium dynamics on a femtosecond time scale. Changes in local spin and symmetry and the underlying mechanism are reflected in strong broadenings, a collapse of clear selection rules during the intersystem crossing, fluctuations in the isotropic branching ratio in x-ray absorption, crystal-field collapse and/or oscillations, and time-dependent anti-Stokes processes in RIXS.

Small scale H I structure and the soft X-ray background

NASA Technical Reports Server (NTRS)

Jahoda, K.; Mccammon, D.; Lockman, F. J.

1986-01-01

The observed anticorrelation between diffuse soft X-ray flux and H I column density has been explained as absorption of soft X-rays produced in a hot galactic halo, assuming that the neutral interstellar material is sufficiently clumped to reduce the soft X-ray absorption cross section by a factor of two to three. A 21 cm emission line study of H I column density variations at intermediate and high galactic latitudes to 10' spatial resolution has been done. The results confirm conclusions from preliminary work at coarser resolution, and in combination with other data appear to rule out the hypothesis that clumping of neutral interstellar matter on any angular scale significantly reduces X-ray absorption cross sections in the 0.13 - 0.28 keV energy range. It is concluded therefore that the observed anticorrelation is not primarily a consequence of absorption of soft X-rays produced in a hot galactic halo.

Methods development for diffraction and spectroscopy studies of metalloenzymes at X-ray free-electron lasers

PubMed Central

Kern, Jan; Hattne, Johan; Tran, Rosalie; Alonso-Mori, Roberto; Laksmono, Hartawan; Gul, Sheraz; Sierra, Raymond G.; Rehanek, Jens; Erko, Alexei; Mitzner, Rolf; Wernet, Phillip; Bergmann, Uwe; Sauter, Nicholas K.; Yachandra, Vittal; Yano, Junko

2014-01-01

X-ray free-electron lasers (XFELs) open up new possibilities for X-ray crystallographic and spectroscopic studies of radiation-sensitive biological samples under close to physiological conditions. To facilitate these new X-ray sources, tailored experimental methods and data-processing protocols have to be developed. The highly radiation-sensitive photosystem II (PSII) protein complex is a prime target for XFEL experiments aiming to study the mechanism of light-induced water oxidation taking place at a Mn cluster in this complex. We developed a set of tools for the study of PSII at XFELs, including a new liquid jet based on electrofocusing, an energy dispersive von Hamos X-ray emission spectrometer for the hard X-ray range and a high-throughput soft X-ray spectrometer based on a reflection zone plate. While our immediate focus is on PSII, the methods we describe here are applicable to a wide range of metalloenzymes. These experimental developments were complemented by a new software suite, cctbx.xfel. This software suite allows for near-real-time monitoring of the experimental parameters and detector signals and the detailed analysis of the diffraction and spectroscopy data collected by us at the Linac Coherent Light Source, taking into account the specific characteristics of data measured at an XFEL. PMID:24914169

A compact dispersive refocusing Rowland circle X-ray emission spectrometer for laboratory, synchrotron, and XFEL applications

DOE PAGES

Holden, William M.; Hoidn, Oliver R.; Ditter, Alexander S.; ...

2017-07-27

X-ray emission spectroscopy is emerging as an important complement to x-ray absorption fine structure spectroscopy, providing a characterization of the occupied electronic density of states local to the species of interest. Here, we present details of the design and performance of a compact x-ray emission spectrometer that uses a dispersive refocusing Rowland (DRR) circle geometry to achieve excellent performance for the 2-2.5 keV range, i.e., especially for the K-edge emission from sulfur and phosphorous. The DRR approach allows high energy resolution even for unfocused x-ray sources. This property enables high count rates in laboratory studies, approaching those of insertion-device beamlinesmore » at third-generation synchrotrons, despite use of only a low-powered, conventional x-ray tube. The spectrometer, whose overall scale is set by use of a 10-cm diameter Rowland circle and a new small-pixel complementary metal-oxide-semiconductor x-ray camera, is easily portable to synchrotron or x-ray free electron laser beamlines. Photometrics from measurements at the Advanced Light Source show excellent overall instrumental efficiency. In addition, the compact size of this instrument lends itself to future multiplexing to gain large factors in net collection efficiency or its implementation in controlled gas gloveboxes either in the lab or in an endstation.« less

IGR J14257-6117, a magnetic accreting white dwarf with a very strong strong X-ray orbital modulation

NASA Astrophysics Data System (ADS)

Bernardini, F.; de Martino, D.; Mukai, K.; Falanga, M.

2018-04-01

IGR J14257-6117 is an unclassified source in the hard X-ray catalogues. Optical follow-ups suggest it could be a Cataclysmic Variable of the magnetic type. We present the first high S/N X-ray observation performed by XMM-Newton at 0.3-10 keV, complemented with 10-80 keV coverage by Swift/BAT, aimed at revealing the source nature. We detected for the first time a fast periodic variability at 509.5 s and a longer periodic variability at 4.05 h, ascribed to the white dwarf (WD) spin and binary orbital periods, respectively. These unambiguously identify IGR J14257-6117 as a magnetic CV of the Intermediate Polar (IP) type. The energy resolved light curves at both periods reveal amplitudes decreasing with increasing energy, with the orbital modulation reaching ˜100% in the softest band. The energy spectrum shows optically thin thermal emission with an excess at the iron complex, absorbed by two dense media (NH ˜ 1022 - 23 cm-2), partially covering the X-ray source. These are likely localised in the magnetically confined accretion flow above the WD surface and at the disc rim, producing the energy dependent spin and orbital variabilities, respectively. IGR J14257-6117, joins the group of strongest orbitally modulated IPs now counting four systems. Drawing similarities with low-mass X-ray binaries displaying orbital dips, these IPs should be seen at large orbital inclinations allowing azimuthally extended absorbing material fixed in the binary frame to intercept the line of sight. For IGR J14257-6117, we estimate (50o ≲ i ≲ 70o). Whether also the mass accretion rate plays a role in the large orbital modulations in IPs cannot be established with the present data.

Unveiling an X-ray counterpart to the Unid. TeV source HESS J1852-000

NASA Astrophysics Data System (ADS)

Kosack, Karl

2011-10-01

We propose to use XMM-Newton to attempt to identify the hard-spectrum very-high- energy (VHE) gamma-ray source HESS J1852-000, which has currently no clear counterpart in lower-energy wavebands. The VHE source lies near the shell-type supernova remnant Kes 78, which may be associated with part of the VHE emission, e.g. through the illumination of nearby molecular clouds by escaping hadrons, via direct shock interaction, or via an as-yet-undetected nearby pulsar wind nebula. We present an analysis of archival XMM data from the region near Kes 78 that shows evidence for X-ray emission from part of the shell, and we propose a pointing that would complement the existing data while covering the peaks of the VHE gamma-ray emission as well as several weak X-ray and radio hotspots.

Comparison of DSB effects of the beta particles of iodine-131 and 6 MV X-ray at a dose of 2 Gy in the presence of 2-Methoxyestradiol, IUdR, and TPT in glioblastoma spheroids

NASA Astrophysics Data System (ADS)

Neshasteh-Riz, Ali; Eyvazzadeh, Nazila; Koosha, Fereshteh; Cheraghi, Susan

2017-02-01

Glioblastoma is one of the lethal brain tumors and one of the resistant tumors against radiotherapy. Multiple treatment methods and different types of radiation and Radiosensitizers drugs have been combined to optimize the efficacy of radiotherapy. Radiosensitizers are employed to reinforce tumor cell killing and have much fewer effects on the normal tissue. Inducing DNA double strand break in tumoral cells is a major goal of radiation sensitivity. In this study, the level of DNA double strand break in glioblastoma spheroids irradiated by 2 Gy beta particles of iodine-131 and 6 MV X-rays in the presence of 2-Methoxyestradiol (2ME2), iodo-deoxy-uridine (IUdR) and Topotecan (TPT) was measured using the PicoGreen method. Spheroids of the U87MG cell line were cultured to reach a 300 μm diameter. In the phase one of the study, the spheroids were treated in four groups individually, including 2 Gy of iodine-131, TPT+iodine-131, IUdR+iodine-131, IUdR+2ME2+iodine-131. In the next phase, the cells were treated with 2 Gy of 6 MV X-ray, TPT+6 MV X-ray, IUdR+6 MV X-ray, TPT+IUdR+6 MV X-ray. DSB lesions were measured by the Pico Green assay. The amount of DSB lesions in groups irradiated with iodine-131 individually was greater than the group irradiated with 6 MV X-ray (p<0.05). DNA double strand breaks became more significant in combination with TPT. However, the amount of DSBs in the two independent groups of TPT+IUdR+2ME2+iodine-131 and TPT+IUdR+2ME2+6 MV X-ray was approximately in the same range (P>0.05). The level of DNA double strand breaks in cells irradiated with Iodine-131 was higher than cells irradiated with 6 MV X-ray at the same dose and Topotecan had a positive effect on inducing the damage. The role of 2ME2+IUdR in increasing the damage caused by beta particles of iodine-131 was not significant. Iodine-131 could lead to major DSB damage than 6 MV X-ray at the same dose due to its cross fire effect and spatial distribution of energy in different angels. This study showed that a combination of chemotherapy and iodine-131 had better efficacy than radiotherapy with 6 MV X-ray in the treatment of glioblastoma.

Optical, Fluorescence with quantum analysis of hydrazine (1, 3- Dinitro Phenyl) by DFT and Ab initio approach

NASA Astrophysics Data System (ADS)

Cecily Mary Glory, D.; Sambathkumar, K.; Madivanane, R.; Velmurugan, G.; Gayathri, R.; Nithiyanantham, S.; Venkatachalapathy, M.; Rajkamal, N.

2018-07-01

Experimental and computational study of molecular structure, vibrational and UV-spectral analysis of Hydrazine (1, 3- Dinitrophenyl) (HDP) derivatives. The crystal was grown by slow cooling method and the crystalline perfection of single crystals was evaluated by high resolution X-ray diffractometry (HRXRD) using a multicrystal X-ray diffractometer. Fluorescence, FT-IR and FT-Raman spectra of HDP crystal were recorded. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) followed by scaled quantum force field methodology (SQMFF). NMR studies have confirmed respectively the crystal structure and functional groups of the grown crystal. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) result complements the experimental findings. The calculated MESP, UV, HOMO-LUMO energies show that charge transfer done within the molecule. And various thermodynamic parameters are studied. Fukui determines the local reactive site of electrophilic, nucleophilic, descriptor.

Homologous recombination mediates S-phase-dependent radioresistance in cells deficient in DNA polymerase eta.

PubMed

Nicolay, Nils H; Carter, Rebecca; Hatch, Stephanie B; Schultz, Niklas; Prevo, Remko; McKenna, W Gillies; Helleday, Thomas; Sharma, Ricky A

2012-11-01

DNA polymerase eta (pol η) is the only DNA polymerase causally linked to carcinogenesis in humans. Inherited deficiency of pol η in the variant form of xeroderma pigmentosum (XPV) predisposes to UV-light-induced skin cancer. Pol η-deficient cells demonstrate increased sensitivity to cisplatin and oxaliplatin chemotherapy. We have found that XP30R0 fibroblasts derived from a patient with XPV are more resistant to cell kill by ionising radiation (IR) than the same cells complemented with wild-type pol η. This phenomenon has been confirmed in Burkitt's lymphoma cells, which either expressed wild-type pol η or harboured a pol η deletion. Pol η deficiency was associated with accumulation of cells in S-phase, which persisted after IR. Cells deficient in pol η demonstrated increased homologous recombination (HR)-directed repair of double strand breaks created by IR. Depletion of the HR protein, X-ray repair cross-complementing protein 3 (XRCC3), abrogated the radioresistance observed in pol η-deficient cells as compared with pol η-complemented cells. These findings suggest that HR mediates S-phase-dependent radioresistance associated with pol η deficiency. We propose that pol η protein levels in tumours may potentially be used to identify patients who require treatment with chemo-radiotherapy rather than radiotherapy alone for adequate tumour control.

Phase contrast tomography of the mouse cochlea at microfocus x-ray sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartels, Matthias; Krenkel, Martin; Hernandez, Victor H.

2013-08-19

We present phase contrast x-ray tomography of functional soft tissue within the bony cochlear capsule of mice, carried out at laboratory microfocus sources with well-matched source, detector, geometry, and reconstruction algorithms at spatial resolutions down to 2 μm. Contrast, data quality and resolution enable the visualization of thin membranes and nerve fibers as well as automated segmentation of surrounding bone. By complementing synchrotron radiation imaging techniques, a broad range of biomedical applications becomes possible as demonstrated for optogenetic cochlear implant research.

Photodynamic synchrotron x-ray therapy in Glioma cell using superparamagnetic iron nanoparticle

NASA Astrophysics Data System (ADS)

Kim, Hong-Tae; Kim, Ki-Hong; Choi, Gi-Hwan; Jheon, Sanghoon; Park, Sung-Hwan; Kim, Bong-Il; Hyodo, Kazuyuki; Ando, Masami; Kim, Jong-Ki

2009-06-01

In order to evaluate cytotoxic effects of secondary Auger electron emission(Photon Activation Therapy:PAT) from alginate-coated iron nanoparticles(Alg-SNP), Alg-SNP-uptaken C6 glioma cell lines were irradiated with 6.89/7.2 Kev synchrotron X-ray. 0-125 Gy were irradiated on three experimental groups including No-SNP group incubating without SNP as control group, 6hr-SNP group incubating with SNP for 6hr and ON-SNP group incubating with SNP overnight. Irradiated cells were stained with Acridine Orange(AO) and Edithium Bromide(EB) to count their viability with fluorescent microscopy in comparison with control groups. AO stained in damaged DNA, giving FL color change in X-ray plus SNP group. EB did not or less enter inside the cell nucleus of control group. In contrast, EB entered inside the cell nucleus of Alg-SNP group which means more damage compared with Control groups. The results of MTT assay demonstrated a X-ray dose-dependent reduction generally in cell viability in the experimental groups. 3 or 9 times increase in cell survival loss rate was observed at 6hr-SNP and ON-SNP groups, respectively compared to No-SNP control group in first experiment that was done to test cell survival rate at relatively lower dose, from 0 to 50 Gy. In second experiment X-ray dose was increased to 125 Gy. Survival loss was sharply decreased in a relatively lower dose from 5 to 25 Gy, and then demonstrated an exponentially decreasing behavior with a convergence until 125 Gy for each group. This observation suggests PAT effects on the cell directly by X-ray in the presence of Alg-SNP occurs within lower X-ray dose, and conventional X-ray radiation effect becomes dominant in higher X-ray dose. The cell viability loss of ON-SNP group was three times higher compared with that of 6hr-SNP group. In conclusion, it is possible to design photodynamic X-ray therapy study using a monochromatic x-ray energy and metal nanoparticle as x-ray sensitizer, which may enable new X-ray PDT to disseminated tumors without side effects to normal surrounding tissue.

The origin of the X-ray, radio and H I structures in the NGC 5903 galaxy group

NASA Astrophysics Data System (ADS)

O'Sullivan, Ewan; Kolokythas, Konstantinos; Kantharia, Nimisha G.; Raychaudhury, Somak; David, Laurence P.; Vrtilek, Jan M.

2018-02-01

The NGC 5903 galaxy group is a nearby (∼30 Mpc) system of ∼30 members, dominated by the giant ellipticals NGC 5903 and NGC 5898. The group contains two unusual structures: a ∼110 kpc long H I filament crossing NGC 5903 and a ∼75 kpc wide diffuse, steep-spectrum radio source of unknown origin that overlaps NGC 5903 and appears to be partly enclosed by the H I filament. Using a combination of Chandra, XMM-Newton, Giant Meterwave Radio Telescope (GMRT) and Very Large Array (VLA) observations, we detect a previously unknown ∼0.65 keV intra-group medium filling the volume within 145 kpc of NGC 5903 and find a loop of enhanced X-ray emission extending ∼35 kpc south-west from the galaxy, enclosing the brightest part of the radio source. The northern and eastern parts of this X-ray structure are also strongly correlated with the southern parts of the H I filament. We determine the spectral index of the bright radio emission to be α _{150}^{612} = 1.03 ± 0.08, indicating a radiative age >360 Myr. We discuss the origin of the correlated radio, X-ray and H I structures, either through an interaction-triggered active galactic nucleus (AGN) outburst with enthalpy 1.8 × 1057 erg, or via a high-velocity collision between a galaxy and the H I filament. While neither scenario provides a complete explanation, we find that an AGN outburst is the most likely source of the principal X-ray and radio structures. However, it is clear that galaxy interactions continue to play an important role in the development of this relatively highly evolved galaxy group. We also resolve the question of whether the group member galaxy ESO 514-3 hosts a double-lobed radio source, confirming that the source is a superposed background AGN.

Modern Progress and Modern Problems in High Resolution X-ray Absorption from the Cold Interstellar Medium

NASA Astrophysics Data System (ADS)

Corrales, Lia; Li, Haochuan; Heinz, Sebastian

2018-01-01

With accurate cross-sections and higher signal-to-noise, X-ray spectroscopy can directly measure Milky Way gas and dust-phase metal abundances with few underlying assumptions. The X-ray energy band is sensitive to absorption by all abundant interstellar metals — carbon, oxygen, neon, silicon, magnesium, and iron — whether they are in gas or dust form. High resolution X-ray spectra from Galactic X-ray point sources can be used to directly measure metal abundances from all phases of the interstellar medium (ISM) along singular sight lines. We show our progress for measuring the depth of photoelectric absorption edges from neutral ISM metals, using all the observations of bright Galactic X-ray binaries available in the Chandra HETG archive. The cross-sections we use take into account both the absorption and scattering effects by interstellar dust grains on the iron and silicate spectral features. However, there are many open problems for reconciling X-ray absorption spectroscopy with ISM observations in other wavelengths. We will review the state of the field, lab measurements needed, and ways in which the next generation of X-ray telescopes will contribute.

Measurement of Lα and Lβ1,3,4 fluorescence cross sections of La, Ce, Pr and Nd induced by photons of energies between 7.01 keV and 8.75 keV

NASA Astrophysics Data System (ADS)

Reyes-Herrera, J.; Miranda, J.

2016-06-01

This study presents measurement results of x-ray production cross sections of Lα and Lβ1,3,4 emitted by four lanthanoid elements (La, Ce, Pr and Nd), after irradiation with Kα and Kβ X rays of the elements Co, Ni, Cu, and Zn (covering energies between 7.01 keV and 8.75 keV). Primary x-rays were induced in turn by the irradiation of thick targets of these elements with a beam of x-rays produced by a tube with an Rh anode, operating at 50 kV and 850 μA. The experimental results are compared with theoretical cross sections predicted using known tabulations of photoelectric cross sections. Dirac-Hartree-Slater (DHS) atomic parameters were used for these calculations. An acceptable match between experiment and both sets of tabulated data is found.

Nonlinear X-Ray and Auger Spectroscopy at X-Ray Free-Electron Laser Sources

NASA Astrophysics Data System (ADS)

Rohringer, Nina

2015-05-01

X-ray free-electron lasers (XFELs) open the pathway to transfer non-linear spectroscopic techniques to the x-ray domain. A promising all x-ray pump probe technique is based on coherent stimulated electronic x-ray Raman scattering, which was recently demonstrated in atomic neon. By tuning the XFEL pulse to core-excited resonances, a few seed photons in the spectral tail of the XFEL pulse drive an avalanche of resonant inelastic x-ray scattering events, resulting in exponential amplification of the scattering signal by of 6-7 orders of magnitude. Analysis of the line profile of the emitted radiation permits to demonstrate the cross over from amplified spontaneous emission to coherent stimulated resonance scattering. In combination with statistical covariance mapping, a high-resolution spectrum of the resonant inelastic scattering process can be obtained, opening the path to coherent stimulated x-ray Raman spectroscopy. An extension of these ideas to molecules and a realistic feasibility study of stimulated electronic x-ray Raman scattering in CO will be presented. Challenges to realizing stimulated electronic x-ray Raman scattering at present-day XFEL sources will be discussed, corroborated by results of a recent experiment at the LCLS XFEL. Due to the small gain cross section in molecular targets, other nonlinear spectroscopic techniques such as nonlinear Auger spectroscopy could become a powerful alternative. Theory predictions of a novel pump probe technique based on resonant nonlinear Auger spectroscopic will be discussed and the method will be compared to stimulated x-ray Raman spectroscopy.

Parabolic crossed planar polymeric x-ray lenses

NASA Astrophysics Data System (ADS)

Nazmov, V.; Reznikova, E.; Mohr, J.; Saile, V.; Vincze, L.; Vekemans, B.; Bohic, S.; Somogyi, A.

2011-01-01

The principles of design and manufacturing of the polymer planar x-ray lenses focusing in one and two directions, as well as the peculiarities of optical behaviors and the results of the lens test are reported in this paper. The methods of electron and deep x-ray lithography used in lens manufacturing allow the manufacture of ten or more x-ray lenses on one substrate; the lenses show focal lengths down to several centimeters for photon energies between 5 and 40 keV. The measured focus size was 105 nm for a linear lens with an intensity gain of about 407, and 300 × 770 nm for a crossed lens with an intensity gain of 6470.

A rapid alternative to X-ray crystallography for chiral determination: case studies of vibrational circular dichroism (VCD) to advance drug discovery projects.

PubMed

Wesolowski, Steven S; Pivonka, Don E

2013-07-15

The absolute stereochemistry of chiral drugs is usually established via X-ray crystallography. However, vibrational circular dichroism (VCD) spectroscopy coupled with quantum mechanics simulations offers a rapid alternative to crystallography and is readily applied to both crystalline and non-crystalline samples. VCD is an effective complement to X-ray analysis of drug candidates, and it can be used as a high-throughput means of assessing absolute stereochemistry at all phases of the discovery process (hundreds of assignments per year). The practical implementation (or fee-for-service outsourcing) of VCD and selected case studies are illustrated with an emphasis on providing utility and impact to pharmaceutical discovery programs. Copyright © 2013 Elsevier Ltd. All rights reserved.

High energy X-ray CT study on the central void formations and the fuel pin deformations of FBR fuel assemblies

NASA Astrophysics Data System (ADS)

Katsuyama, Kozo; Nagamine, Tsuyoshi; Matsumoto, Shin-ichiro; Sato, Seichi

2007-02-01

The central void formations and deformations of fuel pins were investigated in fuel assemblies irradiated to high burn-up, using a non-destructive X-ray CT (computer tomography) technique. In this X-ray CT, the effect of strong gamma ray activity could be reduced to a negligible degree by using the pulse of a high energy X-ray source and detecting the intensity of the transmitted X-rays in synchronization with the generated X-rays. Clear cross-sectional images of fuel assemblies irradiated to high burn-up in a fast breeder reactor were successively obtained, in which the wrapping wires, cladding, pellets and central voids could be distinctly seen. The diameter of a typical central void measured by X-ray CT agreed with the one obtained by ceramography within an error of 0.1 mm. Based on this result, the dependence of the central void diameter on the linear heating rate was analyzed. In addition, the deformation behavior of a fuel pin along its axial direction could be analyzed from 20 stepwise X-ray cross-sectional images obtained in a small interval, and the results obtained showed a good agreement with the predictions calculated by two computer codes.

X-rays and photocarcinogenesis in hairless mice.

PubMed

Lerche, Catharina M; Philipsen, Peter A; Wulf, Hans Christian

2013-08-01

It is well known that excessive X-ray radiation can cause non-melanoma skin cancers. With the increased incidence of sun-related skin cancer there is a need to investigate the combination of sunlight and X-rays. Immunocompetent C3.Cg/TifBomTac mice (n = 298) were divided into 12 groups. Mice were irradiated with 12, 29 or 50 kV X-rays. The mice received a total dose of 45 Gy. They were irradiated with 3 SED simulated solar radiation (SSR) either before or after irradiation with X-rays. The groups irradiated with X-rays alone, 0, 3, 9 and 10 mice (0, 12, 29 and 50 kV, respectively) developed squamous cell carcinoma. In the groups irradiated with SSR after X-rays the development of tumours was significantly faster in the 50 kV group than in the corresponding control group (175 vs. 194 days, p < 0.001). In the groups irradiated with SSR prior to the X-ray radiation the development of tumours was significantly faster in the 29 and the 50 kV groups than in the corresponding control group (175 vs. 202 days, p < 0.001 and 158 vs. 202 days, p < 0.001, respectively). In conclusion, X-ray radiation alone is a weak carcinogen in hairless mice. There is an added carcinogenic effect if X-ray radiation is given on prior sun-exposed skin or if the skin is sun-exposed after X-rays. We still believe that X-ray radiation is a safe and effective therapy for various dermatological diseases but caution should be observed if a patient has severely sun-damaged skin or has a high-risk sun behaviour.

Note: A disposable x-ray camera based on mass produced complementary metal-oxide-semiconductor sensors and single-board computers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoidn, Oliver R.; Seidler, Gerald T., E-mail: seidler@uw.edu

We have integrated mass-produced commercial complementary metal-oxide-semiconductor (CMOS) image sensors and off-the-shelf single-board computers into an x-ray camera platform optimized for acquisition of x-ray spectra and radiographs at energies of 2–6 keV. The CMOS sensor and single-board computer are complemented by custom mounting and interface hardware that can be easily acquired from rapid prototyping services. For single-pixel detection events, i.e., events where the deposited energy from one photon is substantially localized in a single pixel, we establish ∼20% quantum efficiency at 2.6 keV with ∼190 eV resolution and a 100 kHz maximum detection rate. The detector platform’s useful intrinsic energymore » resolution, 5-μm pixel size, ease of use, and obvious potential for parallelization make it a promising candidate for many applications at synchrotron facilities, in laser-heating plasma physics studies, and in laboratory-based x-ray spectrometry.« less

X-ray lithography source

DOEpatents

Piestrup, Melvin A.; Boyers, David G.; Pincus, Cary

1991-01-01

A high-intensity, inexpensive X-ray source for X-ray lithography for the production of integrated circuits. Foil stacks are bombarded with a high-energy electron beam of 25 to 250 MeV to produce a flux of soft X-rays of 500 eV to 3 keV. Methods of increasing the total X-ray power and making the cross section of the X-ray beam uniform are described. Methods of obtaining the desired X-ray-beam field size, optimum frequency spectrum and elminating the neutron flux are all described. A method of obtaining a plurality of station operation is also described which makes the process more efficient and economical. The satisfying of these issues makes transition radiation an exellent moderate-priced X-ray source for lithography.

Nanoscale characterization of local structures and defects in photonic crystals using synchrotron-based transmission soft X-ray microscopy

PubMed Central

Nho, Hyun Woo; Kalegowda, Yogesh; Shin, Hyun-Joon; Yoon, Tae Hyun

2016-01-01

For the structural characterization of the polystyrene (PS)-based photonic crystals (PCs), fast and direct imaging capabilities of full field transmission X-ray microscopy (TXM) were demonstrated at soft X-ray energy. PS-based PCs were prepared on an O2-plasma treated Si3N4 window and their local structures and defects were investigated using this label-free TXM technique with an image acquisition speed of ~10 sec/frame and marginal radiation damage. Micro-domains of face-centered cubic (FCC (111)) and hexagonal close-packed (HCP (0001)) structures were dominantly found in PS-based PCs, while point and line defects, FCC (100), and 12-fold symmetry structures were also identified as minor components. Additionally, in situ observation capability for hydrated samples and 3D tomographic reconstruction of TXM images were also demonstrated. This soft X-ray full field TXM technique with faster image acquisition speed, in situ observation, and 3D tomography capability can be complementally used with the other X-ray microscopic techniques (i.e., scanning transmission X-ray microscopy, STXM) as well as conventional characterization methods (e.g., electron microscopic and optical/fluorescence microscopic techniques) for clearer structure identification of self-assembled PCs and better understanding of the relationship between their structures and resultant optical properties. PMID:27087141

Considerations about projectile and target X-rays induced during heavy ion bombardment

NASA Astrophysics Data System (ADS)

Fernandes, F.; Bauer, D. V.; Duarte, A.; Ferrari, T. M.; Niekraszewicz, L. A. B.; Amaral, L.; Dias, J. F.

2018-02-01

In this work we present some results concerning the X-rays emitted by heavy ions during target bombardment. In this case, Cl4+ and Cl5+ ions with energies from 4 MeV to 10 MeV were employed to irradiate vitreous carbon planchets. Moreover, total X-ray production cross sections of titanium X-rays induced by chlorine ions were obtained as well for the same energy range. Only inner shell transitions were considered in the present work. The titanium target consisted of a thin film deposited over vitreous carbon planchets. The results indicate that the projectile X-ray yields increase as a function of the bombarding energy for the present energy range. Effects due to projectile charge state appears to be of minor importance at these low ion velocities. It is shown that a simple exponential function can represent the continuum background of such complex spectra. The chlorine transition rates Kβ/Kα obtained from chlorine acting as a projectile interacting with a carbon target are about half the value when compared to the chlorine Kβ/Kα ratios obtained when a LiCl target is bombarded with C+ and C3+ ions with energies from 2 MeV to 6 MeV. As far as the total X-ray production cross sections of Ti induced by chlorine ions are concerned, the ECPSSR theory underestimates the Ti total X-rays production cross sections by several orders of magnitude. The role of electron capture and possible mechanisms responsible for these effects are discussed.

Performance of large area x-ray proportional counters in a balloon experiment

NASA Astrophysics Data System (ADS)

Roy, J.; Agrawal, P. C.; Dedhia, D. K.; Manchanda, R. K.; Shah, P. B.; Chitnis, V. R.; Gujar, V. M.; Parmar, J. V.; Pawar, D. M.; Kurhade, V. B.

2016-10-01

ASTROSAT is India's first satellite fully devoted to astronomical observations covering a wide spectral band from optical to hard X-rays by a complement of 4 co-aligned instruments and a Scanning Sky X-ray Monitor. One of the instruments is Large Area X-ray Proportional Counter with 3 identical detectors. In order to assess the performance of this instrument, a balloon experiment with two prototype Large Area X-ray Proportional Counters (LAXPC) was carried out on 2008 April 14. The design of these LAXPCs was similar to those on the ASTROSAT except that their field of view (FOV) was 3 ∘ × 3 ∘ versus FOV of 1 ∘ × 1 ∘ for the LAXPCs on the ASTROSAT. The LAXPCs are aimed at the timing and spectral studies of X-ray sources in 3-80 keV region. In the balloon experiment, the LAXPC, associated electronics and support systems were mounted on an oriented platform which could be pre-programmed to track any source in the sky. A brief description of the LAXPC design, laboratory tests, calibration and the detector characteristics is presented here. The details of the experiment and background counting rates of the 2 LAXPCs at the float altitude of about 41 km are presented in different energy bands. The bright black hole X-ray binary Cygnus X-1 (Cyg X-1) was observed in the experiment for ˜ 3 hours. Details of Cyg X-1 observations, count rates measured from it in different energy intervals and the intensity variations of Cyg X-1 detected during the observations are presented and briefly discussed.

Searching for New γ-Ray Blazar Candidates in the Third Palermo BAT Hard X-Ray Catalog with WISE

NASA Astrophysics Data System (ADS)

Maselli, A.; Massaro, F.; Cusumano, G.; D'Abrusco, R.; La Parola, V.; Paggi, A.; Segreto, A.; Smith, Howard A.; Tosti, G.

2013-06-01

We searched for γ-ray blazar candidates among the 382 unidentified hard X-ray sources of the third Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of Swift Burst Alert Telescope (BAT) survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors that characterize the γ-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope. We used this method exploiting the data of the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources and WISE γ-ray blazar candidates located within the BAT positional uncertainty region at a 99% confidence level. We obtained a preliminary list of candidates for which we analyzed all the available data in the Swift archive to complement the information in the literature and in the radio, infrared, and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 γ-ray blazar candidates.

Physical parameters for proton induced K-, L-, and M-shell ionization processes

NASA Astrophysics Data System (ADS)

Shehla; Puri, Sanjiv

2016-10-01

The proton induced atomic inner-shell ionization processes comprising radiative and non-radiative transitions are characterized by physical parameters, namely, the proton ionization cross sections, X-ray emission rates, fluorescence yields and Coster-Kronig (CK) transition probabilities. These parameters are required to calculate the K/L/M shell X-ray production (XRP) cross sections and relative X-ray intensity ratios, which in turn are required for different analytical applications. The current status of different physical parameters is presented in this report for use in various applications.

Jaw muscles in older overdenture patients.

PubMed

Newton, James P; McManus, Frank C; Menhenick, Stephen

2004-03-01

To determine, using computer tomography (CT), whether the retention of a small number of teeth in the older adult used to support overdentures could affect the cross-sectional area (CSA) and X-ray density of two jaw closing muscles. Cross-sectional study of a group of older patients subdivided into dentate, edentulous and those wearing overdentures supported by two to five teeth. The sample consisted of 24 subjects aged 55-68 years. CSA and X-ray density of two jaw closing muscles, masseter and medial pterygoid were measured and evaluated using CT. There were no significant differences between left and right jaw muscles, but the CSA of the masseter muscles were significantly larger than the medial pterygoid muscles. The CSA of the masseter and medial pterygoid muscles was significantly smaller in edentulous subjects compared with dentate subjects but no significant difference was observed between subjects wearing overdentures and those with a natural dentition. No significant differences were observed with the X-ray density between different muscles or dental states. The retention of a small number of teeth in the older adult used to support overdentures appears to sustain the CSA of two jaw closing muscles and therefore could enhance these patients' masticatory ability compared with those who were edentulous.

Magnetic navigation system assisted percutaneous coronary intervention: a comparison to the conventional approach in daily practice.

PubMed

Li, Chun-Jian; Wang, Hui; Yang, Zhi-Jian; Cao, Ke-Jiang

2011-01-01

The benefits of the magnetic navigation system (MNS) for percutaneous coronary intervention (PCI) remain unclear, and a comparison of the MNS assisted approach to the conventional approach for PCI, when used in daily practice, is little studied. This study aimed to investigate the benefits of an MNS assisted technique as compared to the conventional technique for PCI. Forty-eight consecutive patients scheduled for PCI were recruited between December 2009 and April 2010. MNS assisted PCIs were performed on 54 target vessels. Another 45 patients with 54 target vessels undergoing conventional PCIs were selected from a historical population of patients to match the MNS group according to the coronary lesion type (ACC/AHA classification). Emergency PCIs and chronic total occlusions were excluded from both groups. Analyses were performed using Stata 9.2 statistical software. There were no significant differences between the baseline characteristics of the MNS group and the control group. The success rates were 100.0% for the MNS assisted PCI and 98.1% for the conventional PCI, which did not reach a significant difference (P = 1.000); there were also no significant differences in terms of guide wire crossing time ((51.7 ± 30.5) seconds vs. (57.5 ± 49.4) seconds, P = 0.448), operation time ((28.4 ± 15.9) minutes vs. (28.0 ± 24.7) minutes, P = 0.935), X-ray exposure ((458.1 ± 350.1) µGym(2) vs. (558.7 ± 451.7) µGym(2), P = 0.197; and (94.2 ± 80.9) mGy vs. (96.2 ± 77.3) mGy, P = 0.895) or contrast usage ((7.3 ± 4.0) ml vs. (6.1 ± 3.7) ml, P = 0.121) between the two groups. However, a trend toward shorter guide wire crossing time and less X-ray exposure were observed for the magnetic group. In daily practice, MNS assisted PCI resulted in a similar procedural success rate, operation time, and contrast usage, with a trend toward shorter guide wire crossing time and less X-ray exposure when compared to the conventional PCI.

M ξ, M αβ, M γ and M m X-ray production cross-sections for elements with 71⩽ z⩽92 at 5.96 keV photon energy

NASA Astrophysics Data System (ADS)

Sharma, Manju; Sharma, Veena; Kumar, Sanjeev; Puri, S.; Singh, Nirmal

2006-11-01

The M ξ, M αβ, M γ and M m X-ray production (XRP) cross-sections have been measured for the elements with 71⩽ Z⩽92 at 5.96 keV incident photon energy satisfying EM1< Einc< EL3, where EM1(L3) is the M 1(L 3) subshell binding energy. These XRP cross-sections have been calculated using photoionization cross-sections based on the relativistic Dirac-Hartree-Slater (RDHS) model with three sets of X-ray emission rates, fluorescence, Coster-Kronig and super Coster-Kronig yields based on (i) the non-relativistic Hartree-Slater (NRHS) potential model, (ii) the RDHS model and (iii) the relativistic Dirac-Fock (RDF) model. For the third set, the M i ( i=1-5) subshell fluorescence yields have been calculated using the RDF model-based X-ray emission rates and total widths reevaluated to incorporate the RDF model-based radiative widths. The measured cross-sections have been compared with the calculated values to check the applicability of the physical parameters based on different models.

Cross-correlating Cosmic IR and X-ray Background Fluctuations: Evidence of Significant Black Hole Populations Among the CIB Sources

NASA Technical Reports Server (NTRS)

Cappelluti, N.; Kashlinsky, A.; Arendt, R. G.; Comastri, A.; Fazio, G. G.; Finoguenov, A.; Hasinger, G.; Mather, J. C.; Miyaji, T; Moseley, S. H.

2013-01-01

In order to understand the nature of the sources producing the recently uncovered cosmic infrared background (CIB) fluctuations, we study cross-correlations between the fluctuations in the source-subtracted CIB from Spitzer/IRAC data and the unresolved cosmic X-ray background from deep Chandra observations. Our study uses data from the EGS/AEGIS field, where both data sets cover an approx = 8' x 45' region of the sky. Our measurement is the cross-power spectrum between the IR and X-ray data. The cross-power signal between the IRAC maps at 3.6 micron and 4.5 micron and the Chandra [0.5-2] keV data has been detected, at angular scales approx >20'', with an overall significance of approx = 3.8 sigma and approx. = 5.6 sigma, respectively. At the same time we find no evidence of significant cross-correlations at the harder Chandra bands. The cross-correlation signal is produced by individual IR sources with 3.6 micron and 4.5 micron magnitudes m(sub AB) approx. > 25-26 and [0.5-2] keV X-ray fluxes << 7 × 10(exp -177 erg sq. cm/ s. We determine that at least 15%-25% of the large scale power of the CIB fluctuations is correlated with the spatial power spectrum of the X-ray fluctuations. If this correlation is attributed to emission from accretion processes at both IR and X-ray wavelengths, this implies a much higher fraction of accreting black holes than among the known populations. We discuss the various possible origins for the cross-power signal and show that neither local foregrounds nor the known remaining normal galaxies and active galactic nuclei can reproduce the measurements. These observational results are an important new constraint on theoretical modeling of the near-IR CIB fluctuations. local foregrounds, nor the known remaining normal galaxies and active galactic nuclei (AGN) can reproduce the measurements. These observational results are an important new constraint on theoretical modeling of the near-IR CIB fluctuations

X-ray emission from Stephan's Quintet and other compact groups

NASA Technical Reports Server (NTRS)

Bahcall, N. A.; Harris, D. E.; Rood, H. J.

1984-01-01

A search for X-ray emission from five compact groups of galaxies with the Einstein Observatory revealed detections from three groups. Soft, extended X-ray emission was observed in Stephan's Quintet, which is most likely caused by hot intracluster gas. This provides evidence for dynamical interaction among the group galaxies. X-ray emission from the group Arp 330 may also originate in hot intracluster gas. Stephan's Quintet and Arp 330 have the largest velocity dispersions among the groups studied, suggesting a correlation between high velocity and the release (or properties) of hot gas. X-ray emission from Arp 318 may originate in its member galaxies.

MAX '91: An advanced payload for the exploration of high energy processes on the active sun

NASA Technical Reports Server (NTRS)

1986-01-01

The results of a NASA science working group established to study a follow-on to the Solar Maximum Mission are given. A complement of instruments is suggested, with the primary objective of studying the physics of energetic processes in cosmic plasmas by observing high-energy phenomena in solar flares. High-quality flare observations will be possible with these instruments during the next peak in solar activity expected to last from 1990 through at least 1995. The primary objective of MAX '91 is to study energetic processes in cosmic plasmas by observing high-energy phenomena in solar flares. These processes, which are of general astrophysical importance, include energy release, particle acceleration, and energy transport. Results from comprehensive observing programs conducted during the last solar cycle have demonstrated the great scientific potential of high-energy emissions for addressing these central physical processes. Consequently, a payload optimized for observations of high-energy solar flare phenomena is suggested for MAX '91. It consists of the following four specific instruments: (1) a Fourier-transform X-ray and gamma-ray imager covering the energy range from a few keV to 1 MeV with arcsecond spatial resolution; (2) a cooled germanium X-ray and gamma-ray spectrometer with keV spectral resolution covering the energy range from 10 keV to 50 MeV; (3) Bragg spectrometers with high spectral resolution at wavelengths between 1 and 9 angstrons; and (4) a soft X-ray, EUV, or UV imaging instrument with arcsecond spatial resolution.

Synchrotron X-ray Analytical Techniques for Studying Materials Electrochemistry in Rechargeable Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Feng; Liu, Yijin; Yu, Xiqian

Rechargeable battery technologies have ignited major breakthroughs in contemporary society, including but not limited to revolutions in transportation, electronics, and grid energy storage. The remarkable development of rechargeable batteries is largely attributed to in-depth efforts to improve battery electrode and electrolyte materials. There are, however, still intimidating challenges of lower cost, longer cycle and calendar life, higher energy density, and better safety for large scale energy storage and vehicular applications. Further progress with rechargeable batteries may require new chemistries (lithium ion batteries and beyond) and better understanding of materials electrochemistry in the various battery technologies. In the past decade, advancementmore » of battery materials has been complemented by new analytical techniques that are capable of probing battery chemistries at various length and time scales. Synchrotron X-ray techniques stand out as one of the most effective methods that allows for nearly nondestructive probing of materials characteristics such as electronic and geometric structures with various depth sensitivities through spectroscopy, scattering, and imaging capabilities. This article begins with the discussion of various rechargeable batteries and associated important scientific questions in the field, followed by a review of synchrotron X-ray based analytical tools (scattering, spectroscopy and imaging) and their successful applications (ex situ, in situ, and in operando) in gaining fundamental insights into these scientific questions. Furthermore, electron microscopy and spectroscopy complement the detection length scales of synchrotron X-ray tools, and are also discussed towards the end. We highlight the importance of studying battery materials by combining analytical techniques with complementary length sensitivities, such as the combination of X-ray absorption spectroscopy and electron spectroscopy with spatial resolution, because a sole technique may lead to biased and inaccurate conclusions. We then discuss the current progress of experimental design for synchrotron experiments and methods to mitigate beam effects. Finally, a perspective is provided to elaborate how synchrotron techniques can impact the development of next-generation battery chemistries.« less

Synchrotron X-ray Analytical Techniques for Studying Materials Electrochemistry in Rechargeable Batteries

DOE PAGES

Lin, Feng; Liu, Yijin; Yu, Xiqian; ...

2017-08-30

Rechargeable battery technologies have ignited major breakthroughs in contemporary society, including but not limited to revolutions in transportation, electronics, and grid energy storage. The remarkable development of rechargeable batteries is largely attributed to in-depth efforts to improve battery electrode and electrolyte materials. There are, however, still intimidating challenges of lower cost, longer cycle and calendar life, higher energy density, and better safety for large scale energy storage and vehicular applications. Further progress with rechargeable batteries may require new chemistries (lithium ion batteries and beyond) and better understanding of materials electrochemistry in the various battery technologies. In the past decade, advancementmore » of battery materials has been complemented by new analytical techniques that are capable of probing battery chemistries at various length and time scales. Synchrotron X-ray techniques stand out as one of the most effective methods that allows for nearly nondestructive probing of materials characteristics such as electronic and geometric structures with various depth sensitivities through spectroscopy, scattering, and imaging capabilities. This article begins with the discussion of various rechargeable batteries and associated important scientific questions in the field, followed by a review of synchrotron X-ray based analytical tools (scattering, spectroscopy and imaging) and their successful applications (ex situ, in situ, and in operando) in gaining fundamental insights into these scientific questions. Furthermore, electron microscopy and spectroscopy complement the detection length scales of synchrotron X-ray tools, and are also discussed towards the end. We highlight the importance of studying battery materials by combining analytical techniques with complementary length sensitivities, such as the combination of X-ray absorption spectroscopy and electron spectroscopy with spatial resolution, because a sole technique may lead to biased and inaccurate conclusions. We then discuss the current progress of experimental design for synchrotron experiments and methods to mitigate beam effects. Finally, a perspective is provided to elaborate how synchrotron techniques can impact the development of next-generation battery chemistries.« less

[Computation of the cross-sectional area of the cable in the power circuit of the X-ray machine].

PubMed

Meng, Xin-min; Feng, Da-yu

2007-01-01

The source impedance of the power circuit in the x-ray machine is analyzed in the paper and based on the voltage drop generated by the impedance, the cross-sectional area of the cable is calculated. In the end, the cross-sectional areas of the cables, corresponding to their respective distances between the transformers and the switchboards are given.

X-ray-induced fluorescent centers formation in zinc- phosphate glasses doped with Ag and Cu ions

NASA Astrophysics Data System (ADS)

Klyukin, D. A.; Pshenova, A. S.; Sidorov, A. I.; Stolyarchuk, M. V.

2016-08-01

Fluorescent properties of silver and copper doped zinc-phosphate glasses were studied. By X-ray irradiation of silver and copper co-doped glasses we could create and identify new emission centers which do not exist in single-doped samples. Doping of the glass with both silver and copper ions leads to the increase of quantum yield by 2.7 times. The study was complemented by quantum chemical calculations using the time-dependent density functional theory. It was shown that fluorescence may be attributed to the formation of mixed Ag-Cu molecular clusters.

In-field tests of the EURITRACK tagged neutron inspection system

NASA Astrophysics Data System (ADS)

Carasco, C.; Perot, B.; Bernard, S.; Mariani, A.; Szabo, J.-L.; Sannie, G.; Roll, Th.; Valkovic, V.; Sudac, D.; Viesti, G.; Lunardon, M.; Bottosso, C.; Fabris, D.; Nebbia, G.; Pesente, S.; Moretto, S.; Zenoni, A.; Donzella, A.; Moszynski, M.; Gierlik, M.; Batsch, T.; Wolski, D.; Klamra, W.; Le Tourneur, P.; Lhuissier, M.; Colonna, A.; Tintori, C.; Peerani, P.; Sequeira, V.; Salvato, M.

2008-04-01

The EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) inspection system has been designed to complement X-ray scanners in the detection of explosives and other illicit materials hidden in cargo containers. The containers are interrogated by a 14-MeV tagged neutron beam at any suspect position in the X-ray image. Interrogation of a specific volume element with tagged neutrons yields information about the chemical composition of the material. Implementation and performance tests of the EURITRACK system in the Port of Rijeka in Croatia are described. Cargo container inspection results are reported and discussed.

X-ray astronomical spectroscopy

NASA Technical Reports Server (NTRS)

Holt, Stephen S.

1987-01-01

The contributions of the Goddard group to the history of X-ray astronomy are numerous and varied. One role that the group has continued to play involves the pursuit of techniques for the measurement and interpretation of the X-ray spectra of cosmic sources. The latest development is the selection of the X-ray microcalorimeter for the Advanced X-ray Astrophysics Facility (AXAF) study payload. This technology is likely to revolutionize the study of cosmic X-ray spectra.

X-ray lithography source

DOEpatents

Piestrup, M.A.; Boyers, D.G.; Pincus, C.

1991-12-31

A high-intensity, inexpensive X-ray source for X-ray lithography for the production of integrated circuits is disclosed. Foil stacks are bombarded with a high-energy electron beam of 25 to 250 MeV to produce a flux of soft X-rays of 500 eV to 3 keV. Methods of increasing the total X-ray power and making the cross section of the X-ray beam uniform are described. Methods of obtaining the desired X-ray-beam field size, optimum frequency spectrum and eliminating the neutron flux are all described. A method of obtaining a plurality of station operation is also described which makes the process more efficient and economical. The satisfying of these issues makes transition radiation an excellent moderate-priced X-ray source for lithography. 26 figures.

X-ray investigation of cross-breed silk in cocoon, yarn and fabric forms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radhalakshmi, Y. C.; Kariappa,; Siddaraju, G. N.

2012-06-05

Recently Central Sericulture Research and Training Institute, Mysore developed many improved cross breeds and bivoltine hybrids. Newly developed cross breeds recorded fibre characteristics which are significantly superior over existing control hybrids. This aspect has been investigated using X-ray diffraction technique. We have employed line profile analysis to compute microstructural parameters. These parameters are compared with physical parameters of newly developed cross breed silk fibers for a better understanding of structure-property relation in these samples.

M shell X-ray production cross sections and fluorescence yields for the elements with 71 <= Z <= 92 using 5.96 keV photons

NASA Astrophysics Data System (ADS)

Puri, S.; Mehta, D.; Chand, B.; Singh, Nirmal; Mangal, P. C.; Trehan, P. N.

1993-03-01

Total M X-ray production (XRP) cross sections for ten elements in the atomic number region 71 ≤ Z ≤ 92 were measured at 5.96 keV incident photon energy. The average M shell fluorescence yields < overlineωM> have also been computed using the present measured cross section values and the theoretical M shell photoionisation cross sections. The results are compared with theoretical values.

CROSS-CORRELATION BETWEEN X-RAY AND OPTICAL/NEAR-INFRARED BACKGROUND INTENSITY FLUCTUATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchell-Wynne, Ketron; Cooray, Asantha; Xue, Yongquan

Angular power spectra of optical and infrared background anisotropies at wavelengths between 0.5 and 5 μ m are a useful probe of faint sources present during reionization, in addition to faint galaxies and diffuse signals at low redshift. The cross-correlation of these fluctuations with backgrounds at other wavelengths can be used to separate some of these signals. A previous study on the cross-correlation between X-ray and Spitzer fluctuations at 3.6 μ m and 4.5 μ m has been interpreted as evidence for direct collapse black holes present at z  > 12. Here we return to this cross-correlation and study its wavelengthmore » dependence from 0.5 to 4.5 μ m using Hubble and Spitzer data in combination with a subset of the 4 Ms Chandra observations in GOODS-S/ECDFS. Our study involves five Hubble bands at 0.6, 0.7, 0.85, 1.25, and 1.6 μ m, and two Spitzer -IRAC bands at 3.6 μ m and 4.5 μ m. We confirm the previously seen cross-correlation between 3.6 μ m (4.5 μ m) and X-rays with 3.7 σ (4.2 σ ) and 2.7 σ (3.7 σ ) detections in the soft [0.5–2] keV and hard [2–8] keV X-ray bands, respectively, at angular scales above 20 arcsec. The cross-correlation of X-rays with Hubble is largely anticorrelated, ranging between the levels of 1.4 σ –3.5 σ for all the Hubble and X-ray bands. This lack of correlation in the shorter optical/NIR bands implies the sources responsible for the cosmic infrared background at 3.6 and 4.5 μ m are at least partly dissimilar to those at 1.6 μ m and shorter.« less

X-ray fluorescence cross sections for K and L x rays of the elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krause, M.O.; Nestor, C.W. Jr.; Sparks, C.J. Jr.

1978-06-01

X-ray fluorescence cross sections are calculated for the major x rays of the K series 5 less than or equal to Z less than or equal to 101, and the three L series 12 less than or equal to Z less than or equal to 101 in the energy range 1 to 200 keV. This calculation uses Scofield's theoretical partical photoionization cross sections, Krause's evaluation of fluorescence and Coster-Kronig yields, and Scofield's theoretical radiative rates. Values are presented in table and graph format, and an estimate of their accuracy is made. The following x rays are considered: K..cap alpha../sub 1/,more » K..cap alpha../sub 1/,/sub 2/, K..beta../sub 1/, K..beta../sub 1/,/sub 3/, L..cap alpha../sub 1/, L..cap alpha../sub 1/,/sub 2/, L..beta../sub 1/, L..beta../sub 2/,/sub 15/, L..beta../sub 3/, Ll, L..gamma../sub 1/, L..gamma../sub 4/, and L/sub 1/ ..-->.. L/sub 2/,/sub 3/. For use in x-ray fluorescence analysis, K..cap alpha.. and L..cap alpha.. fluorescence cross sections are presented at specific energies: TiK identical with 4.55 keV, CrK identical with 5.46 keV, CoK identical with 7.00 keV, CuK identical with 8.13 keV, MoK..cap alpha.. identical with 17.44 keV, AgK identical with 22.5 keV, DyK identical with 47.0 keV, and /sup 241/Am identical with 59.54 keV. Supplementary material includes fluorescence and Coster--Kronig yields, fractional radiative rates, fractional fluorescence yields, total L-shell fluorescence cross sections, fluorescence and Coster-Kronig yields in condensed matter, effective fluorescence yields, average L-shell fluorescence yield, L-subshell photoionization cross section ratios, and conversion factors from barns per atom to square centimeters per gram.« less

IUE and Einstein survey of late-type giant and supergiant stars and the dividing line

NASA Technical Reports Server (NTRS)

Haisch, Bernhard M.; Bookbinder, Jay A.; Maggio, A.; Vaiana, G. S.; Bennett, Jeffrey O.

1990-01-01

Results are presented on an IUE UV survey of 255 late-type G, K, and M stars, complementing the Maggio et al. (1990) Einstein X-ray survey of 380 late-type stars. The large data sample of X-ray and UV detections make it possible to examine the activity relationship between the X-ray and the UV emissions. The results confirm previous finding of a trend involving a steeply-dropping upper envelope of the transition region line fluxes, f(line)/f(V), as the dividing line is approached. This suggests that a sharp decrease in maximum activity accompanies the advancing spectral type, with the dividing line corresponding to this steep gradient region. The results confirm the rotation-activity connection for stars in this region of the H-R diagram.

How cryo-electron microscopy and X-ray crystallography complement each other.

PubMed

Wang, Hong-Wei; Wang, Jia-Wei

2017-01-01

With the ability to resolve structures of macromolecules at atomic resolution, X-ray crystallography has been the most powerful tool in modern structural biology. At the same time, recent technical improvements have triggered a resolution revolution in the single particle cryo-EM method. While the two methods are different in many respects, from sample preparation to structure determination, they both have the power to solve macromolecular structures at atomic resolution. It is important to understand the unique advantages and caveats of the two methods in solving structures and to appreciate the complementary nature of the two methods in structural biology. In this review we provide some examples, and discuss how X-ray crystallography and cryo-EM can be combined in deciphering structures of macromolecules for our full understanding of their biological mechanisms. © 2016 The Protein Society.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Junjing; Vine, David J.; Chen, Si

X-ray microscopy can be used to image whole, unsectioned cells in their native hydrated state. It complements the higher resolution of electron microscopy for submicrometer thick specimens, and the molecule-specific imaging capabilites of fluorescence light microscopy. We describe here the first use of fast, continuous x-ray scanning of frozen hydrated cells for simultaneous sub-20 nm resolution ptychographic transmission imaging with high contrast, and sub-100 nm resolution deconvolved x-ray fluorescence imaging of diffusible and bound ions at native concentrations, without the need to add specific labels. Here, by working with cells that have been rapidly frozen without the use of chemicalmore » fixatives, and imaging them under cryogenic conditions, we are able to obtain images with well preserved structural and chemical composition, and sufficient stability against radiation damage to allow for multiple images to be obtained with no observable change.« less

Temperature-controlled cross-linking of silver nanoparticles with diels-alder reaction and its application on antibacterial property

NASA Astrophysics Data System (ADS)

Liu, Lian; Yang, Pengfei; Li, Junying; Zhang, Zhiliang; Yu, Xi; Lu, Ling

2017-05-01

Sliver nanoparticles (AgNPs) were synthesized and functionalized with furan group on their surface, followed by the reverse Diels-Alder (DA) reaction with bismaleimide to vary the particle size, so as to give different antibacterial activities. These nanoparticles were characterized using Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Ultraviolet-Visible (UV-vis), Nanoparticle Size Analyzer and X-Ray Photoelectron Spectroscopy (XPS). It was found that the cross-linking reaction with bismaleimide had a great effect on the size of AgNPs. The size of the AgNPs could be controlled by the temperature of DA/r-DA equilibrium. The antibacterial activity was assessed using the inhibition zone diameter by introducing the particles into a media containing Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, respectively. It was found that these particles were effective bactericides. Furthermore, the antibacterial activity of the nanoparticles decreased orderly as the particle size enlarged.

A cosmic and solar X-ray and gamma-ray instrument for a scout launch

NASA Technical Reports Server (NTRS)

Forrest, D. J.; Vestrand, W. T.; Chupp, E. L.

1988-01-01

An overview is presented for a set of simple and robust X-ray and gamma ray instruments which have both cosmic and solar objectives. The primary solar scientific objective is the study of the beaming of energetic electrons and ions in solar flares. The instrument will measure spectra and polarization of flare emissions up to 10 MeV. At X-ray energies both the directly emitted flux and the reflected albedo flux will be measured with a complement of six X-ray sensors. Each of these detectors will have a different high Z filter selected to optimize both the energy resolution and high rate capabilities in the energy band 10 to 300 keV. At energies greater than 100 keV seven 7.6 x 7.6 cm NaI and a set of 30 concentric plastic scattering detectors will record the spectra and polarization of electron bremsstrahlung and nuclear gamma rays. All of the components of the instrument are in existence and have passed flight tests for earlier space missions. The instrument will use a spinning solar oriented Scout spacecraft. The NaI detectors will act as a self-modulating gamma ray detector for cosmic sources in a broad angular band which lies at 90 degrees to the Sun-Earth vector and hence will scan the entire sky in 6 months.

Radioprotective activity of glutathione on cognitive ability in X-ray radiated tumor-bearing mice.

PubMed

Lu, Lina; Li, Zongli; Zuo, Yanhua; Zhao, Libo; Liu, Bin

2018-05-30

The use of X-ray for therapeutics always raises the problem of radiation hazards to living beings. In this research, we explored the radioprotective activity of glutathione (GSH) on cognitive ability of X-ray radiated tumor-bearing mice. Forty C57BL/6 mice were chosen to establish the GL261 glioma model and randomly divided into four groups: Model group, X-ray group, Pre-GSH group and Pos-GSH group. Morris water maze test was used to test cognitive ability. Moreover, histopathological observation of hippocampus was observed by hematoxylin and eosin (HE) staining. The protein expression of choline acetyl transferase (ChAT) was measured by western blot, simultaneously the contents of acetylcholinesterase (Ach), superoxide dismutase (SOD), methane dicarboxylic aldehyde (MDA),TNF-α and IL-6 were detected by the respective kit. There was a significant difference in X-ray group of the escape latency from the Model group (P<0.05). Besides, HE staining revealed that nucleus in hippocampus cells were pyknotic, glial cells were hyperplastic and the nerve cells were swelling in X-ray group. In X-ray group the expression of ChAT and Ache were decreased versus Model group. Finally, the cognitive ability in Pre-GSH and Pos-GSH group was enhanced than X-ray group, in which the cognitive ability of Pos-GSH group was higher than the Pre-GSH group. X-ray impaired the brain tissues and cognitive ability of tumor-bearing mice. The damages of brain tissues were alleviated by Pre-GSH and Pos-GSH protection and the efficacy of Pos-GSH protection was superior to Pre-GSH protection. Abbreviation Ach: Acetylcholinesterase; GSH: Glutathione; HE: Hematoxylin and eosin; MDA: methane dicarboxylic aldehyde; SOD: Superoxide dismutase; TV: Tumor volume; TW: Tumor weight.

Application of relativistic electrons for the quantitative analysis of trace elements

NASA Astrophysics Data System (ADS)

Hoffmann, D. H. H.; Brendel, C.; Genz, H.; Löw, W.; Richter, A.

1984-04-01

Particle induced X-ray emission methods (PIXE) have been extended to relativistic electrons to induce X-ray emission (REIXE) for quantitative trace-element analysis. The electron beam (20 ≤ E0≤ 70 MeV) was supplied by the Darmstadt electron linear accelerator DALINAC. Systematic measurements of absolute K-, L- and M-shell ionization cross sections revealed a scaling behaviour of inner-shell ionization cross sections from which X-ray production cross sections can be deduced for any element of interest for a quantitative sample investigation. Using a multielemental mineral monazite sample from Malaysia the sensitivity of REIXE is compared to well established methods of trace-element analysis like proton- and X-ray-induced X-ray fluorescence analysis. The achievable detection limit for very heavy elements amounts to about 100 ppm for the REIXE method. As an example of an application the investigation of a sample prepared from manganese nodules — picked up from the Pacific deep sea — is discussed, which showed the expected high mineral content of Fe, Ni, Cu and Ti, although the search for aliquots of Pt did not show any measurable content within an upper limit of 250 ppm.

Iodate in calcite and vaterite: Insights from synchrotron X-ray absorption spectroscopy and first-principles calculations

NASA Astrophysics Data System (ADS)

Podder, J.; Lin, J.; Sun, W.; Botis, S. M.; Tse, J.; Chen, N.; Hu, Y.; Li, D.; Seaman, J.; Pan, Y.

2017-02-01

Calcium carbonates such as calcite are the dominant hosts of inorganic iodine in nature and are potentially important for the retention and removal of radioactive iodine isotopes (129I and 131I) in contaminated water. However, little is known about the structural environment of iodine in carbonates. In this study, iodate (IO3-) doped calcite and vaterite have been synthesized using the gel-diffusion method at three NaIO3 concentrations (0.002; 0.004; 0.008 M) and a pH value of 9.0, under ambient temperature and pressure. Inductively coupled plasma mass spectrometry (ICP-MS) analyses show that iodine is preferentially incorporated into calcite over vaterite. Synchrotron iodine K-edge X-ray absorption near-edge structure (XANES) spectra confirm that IO3- is the dominant iodine species in synthetic calcite and vaterite. Analyses of iodine K-edge extended X-ray absorption fine structure (EXAFS) data, complemented by periodic first-principles calculations at the density functional theory (DFT) levels, demonstrate that the I5+ ion of the IO3- group in calcite and vaterite is bonded by three and two additional O atoms (i.e., coordination numbers = 6 and 5), respectively, and is incorporated via the charged coupled substitution I5+ + Na+ ↔ C4+ + Ca2+, with the Na+ cation at a nearest Ca2+ site being the most energetically favorable configuration.

Accurate Cross Sections for Microanalysis.

PubMed

Rez, Peter

2002-01-01

To calculate the intensity of x-ray emission in electron beam microanalysis requires a knowledge of the energy distribution of the electrons in the solid, the energy variation of the ionization cross section of the relevant subshell, the fraction of ionizations events producing x rays of interest and the absorption coefficient of the x rays on the path to the detector. The theoretical predictions and experimental data available for ionization cross sections are limited mainly to K shells of a few elements. Results of systematic plane wave Born approximation calculations with exchange for K, L, and M shell ionization cross sections over the range of electron energies used in microanalysis are presented. Comparisons are made with experimental measurement for selected K shells and it is shown that the plane wave theory is not appropriate for overvoltages less than 2.5 V.

X-ray crystallography over the past decade for novel drug discovery - where are we heading next?

PubMed

Zheng, Heping; Handing, Katarzyna B; Zimmerman, Matthew D; Shabalin, Ivan G; Almo, Steven C; Minor, Wladek

2015-01-01

Macromolecular X-ray crystallography has been the primary methodology for determining the three-dimensional structures of proteins, nucleic acids and viruses. Structural information has paved the way for structure-guided drug discovery and laid the foundations for structural bioinformatics. However, X-ray crystallography still has a few fundamental limitations, some of which may be overcome and complemented using emerging methods and technologies in other areas of structural biology. This review describes how structural knowledge gained from X-ray crystallography has been used to advance other biophysical methods for structure determination (and vice versa). This article also covers current practices for integrating data generated by other biochemical and biophysical methods with those obtained from X-ray crystallography. Finally, the authors articulate their vision about how a combination of structural and biochemical/biophysical methods may improve our understanding of biological processes and interactions. X-ray crystallography has been, and will continue to serve as, the central source of experimental structural biology data used in the discovery of new drugs. However, other structural biology techniques are useful not only to overcome the major limitation of X-ray crystallography, but also to provide complementary structural data that is useful in drug discovery. The use of recent advancements in biochemical, spectroscopy and bioinformatics methods may revolutionize drug discovery, albeit only when these data are combined and analyzed with effective data management systems. Accurate and complete data management is crucial for developing experimental procedures that are robust and reproducible.

Automated patient identification and localization error detection using 2-dimensional to 3-dimensional registration of kilovoltage x-ray setup images.

PubMed

Lamb, James M; Agazaryan, Nzhde; Low, Daniel A

2013-10-01

To determine whether kilovoltage x-ray projection radiation therapy setup images could be used to perform patient identification and detect gross errors in patient setup using a computer algorithm. Three patient cohorts treated using a commercially available image guided radiation therapy (IGRT) system that uses 2-dimensional to 3-dimensional (2D-3D) image registration were retrospectively analyzed: a group of 100 cranial radiation therapy patients, a group of 100 prostate cancer patients, and a group of 83 patients treated for spinal lesions. The setup images were acquired using fixed in-room kilovoltage imaging systems. In the prostate and cranial patient groups, localizations using image registration were performed between computed tomography (CT) simulation images from radiation therapy planning and setup x-ray images corresponding both to the same patient and to different patients. For the spinal patients, localizations were performed to the correct vertebral body, and to an adjacent vertebral body, using planning CTs and setup x-ray images from the same patient. An image similarity measure used by the IGRT system image registration algorithm was extracted from the IGRT system log files and evaluated as a discriminant for error detection. A threshold value of the similarity measure could be chosen to separate correct and incorrect patient matches and correct and incorrect vertebral body localizations with excellent accuracy for these patient cohorts. A 10-fold cross-validation using linear discriminant analysis yielded misclassification probabilities of 0.000, 0.0045, and 0.014 for the cranial, prostate, and spinal cases, respectively. An automated measure of the image similarity between x-ray setup images and corresponding planning CT images could be used to perform automated patient identification and detection of localization errors in radiation therapy treatments. Copyright © 2013 Elsevier Inc. All rights reserved.

Homologous recombination mediates S-phase-dependent radioresistance in cells deficient in DNA polymerase eta

PubMed Central

Sharma, Ricky A.

2012-01-01

DNA polymerase eta (pol η) is the only DNA polymerase causally linked to carcinogenesis in humans. Inherited deficiency of pol η in the variant form of xeroderma pigmentosum (XPV) predisposes to UV-light-induced skin cancer. Pol η-deficient cells demonstrate increased sensitivity to cisplatin and oxaliplatin chemotherapy. We have found that XP30R0 fibroblasts derived from a patient with XPV are more resistant to cell kill by ionising radiation (IR) than the same cells complemented with wild-type pol η. This phenomenon has been confirmed in Burkitt’s lymphoma cells, which either expressed wild-type pol η or harboured a pol η deletion. Pol η deficiency was associated with accumulation of cells in S-phase, which persisted after IR. Cells deficient in pol η demonstrated increased homologous recombination (HR)-directed repair of double strand breaks created by IR. Depletion of the HR protein, X-ray repair cross-complementing protein 3 (XRCC3), abrogated the radioresistance observed in pol η-deficient cells as compared with pol η-complemented cells. These findings suggest that HR mediates S-phase-dependent radioresistance associated with pol η deficiency. We propose that pol η protein levels in tumours may potentially be used to identify patients who require treatment with chemo-radiotherapy rather than radiotherapy alone for adequate tumour control. PMID:22822095

Three-dimensional structure determination protocol for noncrystalline biomolecules using x-ray free-electron laser diffraction imaging.

PubMed

Oroguchi, Tomotaka; Nakasako, Masayoshi

2013-02-01

Coherent and intense x-ray pulses generated by x-ray free-electron laser (XFEL) sources are paving the way for structural determination of noncrystalline biomolecules. However, due to the small scattering cross section of electrons for x rays, the available incident x-ray intensity of XFEL sources, which is currently in the range of 10(12)-10(13) photons/μm(2)/pulse, is lower than that necessary to perform single-molecule diffraction experiments for noncrystalline biomolecules even with the molecular masses of megadalton and submicrometer dimensions. Here, we propose an experimental protocol and analysis method for visualizing the structure of those biomolecules by the combined application of coherent x-ray diffraction imaging and three-dimensional reconstruction methods. To compensate the small scattering cross section of biomolecules, in our protocol, a thin vitreous ice plate containing several hundred biomolecules/μm(2) is used as sample, a setup similar to that utilized by single-molecule cryoelectron microscopy. The scattering cross section of such an ice plate is far larger than that of a single particle. The images of biomolecules contained within irradiated areas are then retrieved from each diffraction pattern, and finally provide the three-dimensional electron density model. A realistic atomic simulation using large-scale computations proposed that the three-dimensional structure determination of the 50S ribosomal subunit embedded in a vitreous ice plate is possible at a resolution of 0.8 nm when an x-ray beam of 10(16) photons/500×500 nm(2)/pulse is available.

Optical imaging for breast cancer prescreening

PubMed Central

Godavarty, Anuradha; Rodriguez, Suset; Jung, Young-Jin; Gonzalez, Stephanie

2015-01-01

Breast cancer prescreening is carried out prior to the gold standard screening using X-ray mammography and/or ultrasound. Prescreening is typically carried out using clinical breast examination (CBE) or self-breast examinations (SBEs). Since CBE and SBE have high false-positive rates, there is a need for a low-cost, noninvasive, non-radiative, and portable imaging modality that can be used as a prescreening tool to complement CBE/SBE. This review focuses on the various hand-held optical imaging devices that have been developed and applied toward early-stage breast cancer detection or as a prescreening tool via phantom, in vivo, and breast cancer imaging studies. Apart from the various optical devices developed by different research groups, a wide-field fiber-free near-infrared optical scanner has been developed for transillumination-based breast imaging in our Optical Imaging Laboratory. Preliminary in vivo studies on normal breast tissues, with absorption-contrasted targets placed in the intramammary fold, detected targets as deep as 8.8 cm. Future work involves in vivo imaging studies on breast cancer subjects and comparison with the gold standard X-ray mammography approach. PMID:26229503

The Stellar Mass-Halo Mass Relation for Low-mass X-Ray Groups At 0.5< z< 1 in the CDFS With CSI

NASA Astrophysics Data System (ADS)

Patel, Shannon G.; Kelson, Daniel D.; Williams, Rik J.; Mulchaey, John S.; Dressler, Alan; McCarthy, Patrick J.; Shectman, Stephen A.

2015-02-01

Since z˜ 1, the stellar mass density locked in low-mass groups and clusters has grown by a factor of ˜8. Here, we make the first statistical measurements of the stellar mass content of low-mass X-ray groups at 0.5\\lt z\\lt 1, enabling the calibration of stellar-to-halo mass scales for wide-field optical and infrared surveys. Groups are selected from combined Chandra and XMM-Newton X-ray observations in the Chandra Deep Field South. These ultra-deep observations allow us to identify bona fide low-mass groups at high redshift and enable measurements of their total halo masses. We compute aggregate stellar masses for these halos using galaxies from the Carnegie-Spitzer-IMACS (CSI) spectroscopic redshift survey. Stars comprise ˜3%-4% of the total mass of group halos with masses {{10}12.8}\\lt {{M}200}/{{M}⊙ }\\lt {{10}13.5} (about the mass of Fornax and one-fiftieth the mass of Virgo). Complementing our sample with higher mass halos at these redshifts, we find that the stellar-to-halo mass ratio decreases toward higher halo masses, consistent with other work in the local and high redshift universe. The observed scatter about the stellar-halo mass relation is σ ˜ 0.25 dex, which is relatively small and suggests that total group stellar mass can serve as a rough proxy for halo mass. We find no evidence for any significant evolution in the stellar-halo mass relation since z≲ 1. Quantifying the stellar content in groups since this epoch is critical given that hierarchical assembly leads to such halos growing in number density and hosting increasing shares of quiescent galaxies. This Letter includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

IGR J14257-6117, a magnetic accreting white dwarf with a very strong strong X-ray orbital modulation

NASA Astrophysics Data System (ADS)

Bernardini, F.; de Martino, D.; Mukai, K.; Falanga, M.

2018-07-01

IGR J14257-6117 is an unclassified source in the hard X-ray catalogues. Optical follow-ups suggest it could be a Cataclysmic Variable (CV) of the magnetic type. We present the first high signal-to-noise (S/N) X-ray observation performed by XMM-Newton at 0.3-10 keV, complemented with 10-80 keV coverage by Swift/BAT, aimed at revealing the source nature. We detected for the first time a fast periodic variability at 509.5 s and a longer periodic variability at 4.05 h, ascribed to the white dwarf (WD) spin and binary orbital periods, respectively. These unambiguously identify IGR J14257-6117 as a magnetic CV of the intermediate polar (IP) type. The energy-resolved light curves at both periods reveal amplitudes decreasing with increasing energy, with the orbital modulation reaching ˜ 100 per cent in the softest band. The energy spectrum shows optically thin thermal emission with an excess at the iron complex, absorbed by two dense media (NH ˜ 1022 - 23 cm-2), partially covering the X-ray source. These are likely localized in the magnetically confined accretion flow above the WD surface and at the disc rim, producing the energy-dependent spin and orbital variabilities, respectively. IGR J14257-6117 joins the group of strongest orbitally modulated IPs now counting four systems. Drawing similarities with low-mass X-ray binaries displaying orbital dips, these IPs should be seen at large orbital inclinations allowing azimuthally extended absorbing material fixed in the binary frame to intercept the line of sight. For IGR J14257-6117, we estimate 50o ≲ i ≲ 70o. Whether also the mass accretion rate plays a role in the large orbital modulations in IPs cannot be established with the present data.

The measurement capabilities of cross-sectional profile of Nanoimprint template pattern using small angle x-ray scattering

NASA Astrophysics Data System (ADS)

Yamanaka, Eiji; Taniguchi, Rikiya; Itoh, Masamitsu; Omote, Kazuhiko; Ito, Yoshiyasu; Ogata, Kiyoshi; Hayashi, Naoya

2016-05-01

Nanoimprint lithography (NIL) is one of the most potential candidates for the next generation lithography for semiconductor. It will achieve the lithography with high resolution and low cost. High resolution of NIL will be determined by a high definition template. Nanoimprint lithography will faithfully transfer the pattern of NIL template to the wafer. Cross-sectional profile of the template pattern will greatly affect the resist profile on the wafer. Therefore, the management of the cross-sectional profile is essential. Grazing incidence small angle x-ray scattering (GI-SAXS) technique has been proposed as one of the method for measuring cross-sectional profile of periodic nanostructure pattern. Incident x-rays are irradiated to the sample surface with very low glancing angle. It is close to the critical angle of the total reflection of the x-ray. The scattered x-rays from the surface structure are detected on a two-dimensional detector. The observed intensity is discrete in the horizontal (2θ) direction. It is due to the periodicity of the structure, and diffraction is observed only when the diffraction condition is satisfied. In the vertical (β) direction, the diffraction intensity pattern shows interference fringes reflected to height and shape of the structure. Features of the measurement using x-ray are that the optical constant for the materials are well known, and it is possible to calculate a specific diffraction intensity pattern based on a certain model of the cross-sectional profile. The surface structure is estimated by to collate the calculated diffraction intensity pattern that sequentially while changing the model parameters with the measured diffraction intensity pattern. Furthermore, GI-SAXS technique can be measured an object in a non-destructive. It suggests the potential to be an effective tool for product quality assurance. We have developed a cross-sectional profile measurement of quartz template pattern using GI-SAXS technique. In this report, we will report the measurement capabilities of GI-SAXS technique as a cross-sectional profile measurement tool of NIL quartz template pattern.

Regolith X-Ray Imaging Spectrometer (REXIS) Aboard the OSIRIS-REx Asteroid Sample Return Mission

NASA Astrophysics Data System (ADS)

Masterson, R. A.; Chodas, M.; Bayley, L.; Allen, B.; Hong, J.; Biswas, P.; McMenamin, C.; Stout, K.; Bokhour, E.; Bralower, H.; Carte, D.; Chen, S.; Jones, M.; Kissel, S.; Schmidt, F.; Smith, M.; Sondecker, G.; Lim, L. F.; Lauretta, D. S.; Grindlay, J. E.; Binzel, R. P.

2018-02-01

The Regolith X-ray Imaging Spectrometer (REXIS) is the student collaboration experiment proposed and built by an MIT-Harvard team, launched aboard NASA's OSIRIS-REx asteroid sample return mission. REXIS complements the scientific investigations of other OSIRIS-REx instruments by determining the relative abundances of key elements present on the asteroid's surface by measuring the X-ray fluorescence spectrum (stimulated by the natural solar X-ray flux) over the range of energies 0.5 to 7 keV. REXIS consists of two components: a main imaging spectrometer with a coded aperture mask and a separate solar X-ray monitor to account for the Sun's variability. In addition to element abundance ratios (relative to Si) pinpointing the asteroid's most likely meteorite association, REXIS also maps elemental abundance variability across the asteroid's surface using the asteroid's rotation as well as the spacecraft's orbital motion. Image reconstruction at the highest resolution is facilitated by the coded aperture mask. Through this operation, REXIS will be the first application of X-ray coded aperture imaging to planetary surface mapping, making this student-built instrument a pathfinder toward future planetary exploration. To date, 60 students at the undergraduate and graduate levels have been involved with the REXIS project, with the hands-on experience translating to a dozen Master's and Ph.D. theses and other student publications.

STELLAR AND TOTAL BARYON MASS FRACTIONS IN GROUPS AND CLUSTERS SINCE REDSHIFT 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giodini, S.; Pierini, D.; Finoguenov, A.

2009-09-20

We investigate if the discrepancy between estimates of the total baryon mass fraction obtained from observations of the cosmic microwave background (CMB) and of galaxy groups/clusters persists when a large sample of groups is considered. To this purpose, 91 candidate X-ray groups/poor clusters at redshift 0.1 <= z <= 1 are selected from the COSMOS 2 deg{sup 2} survey, based only on their X-ray luminosity and extent. This sample is complemented by 27 nearby clusters with a robust, analogous determination of the total and stellar mass inside R {sub 500}. The total sample of 118 groups and clusters with zmore » <= 1 spans a range in M {sub 500} of {approx}10{sup 13}-10{sup 15} M {sub sun}. We find that the stellar mass fraction associated with galaxies at R {sub 500} decreases with increasing total mass as M {sup -0.37+}-{sup 0.04} {sub 500}, independent of redshift. Estimating the total gas mass fraction from a recently derived, high-quality scaling relation, the total baryon mass fraction (f {sup stars+gas} {sub 500} = f {sup stars} {sub 500} + f {sup gas} {sub 500}) is found to increase by {approx}25%, when M{sub 500} increases from (M) = 5 x 10{sup 13} M{sub sun} to (M) = 7 x 10{sup 14} M{sub sun}. After consideration of a plausible contribution due to intracluster light (11%-22% of the total stellar mass) and gas depletion through the hierarchical assembly process (10% of the gas mass), the estimated values of the total baryon mass fraction are still lower than the latest CMB measure of the same quantity (WMAP5), at a significance level of 3.3sigma for groups of (M) = 5 x 10{sup 13} M{sub sun}. The discrepancy decreases toward higher total masses, such that it is 1sigma at (M) = 7 x 10{sup 14} M{sub sun}. We discuss this result in terms of nongravitational processes such as feedback and filamentary heating.« less

Reverse actin sliding triggers strong myosin binding that moves tropomyosin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bekyarova, T.I.; Reedy, M.C.; Baumann, B.A.J.

2008-09-03

Actin/myosin interactions in vertebrate striated muscles are believed to be regulated by the 'steric blocking' mechanism whereby the binding of calcium to the troponin complex allows tropomyosin (TM) to change position on actin, acting as a molecular switch that blocks or allows myosin heads to interact with actin. Movement of TM during activation is initiated by interaction of Ca{sup 2+} with troponin, then completed by further displacement by strong binding cross-bridges. We report x-ray evidence that TM in insect flight muscle (IFM) moves in a manner consistent with the steric blocking mechanism. We find that both isometric contraction, at highmore » [Ca{sup 2+}], and stretch activation, at lower [Ca{sup 2+}], develop similarly high x-ray intensities on the IFM fourth actin layer line because of TM movement, coinciding with x-ray signals of strong-binding cross-bridge attachment to helically favored 'actin target zones.' Vanadate (Vi), a phosphate analog that inhibits active cross-bridge cycling, abolishes all active force in IFM, allowing high [Ca{sup 2+}] to elicit initial TM movement without cross-bridge attachment or other changes from relaxed structure. However, when stretched in high [Ca{sup 2+}], Vi-'paralyzed' fibers produce force substantially above passive response at pCa {approx} 9, concurrent with full conversion from resting to active x-ray pattern, including x-ray signals of cross-bridge strong-binding and TM movement. This argues that myosin heads can be recruited as strong-binding 'brakes' by backward-sliding, calcium-activated thin filaments, and are as effective in moving TM as actively force-producing cross-bridges. Such recruitment of myosin as brakes may be the major mechanism resisting extension during lengthening contractions.« less

An X-ray fluorescence spectrometer and its applications in materials studies

NASA Technical Reports Server (NTRS)

Singh, J. J.; Han, K. S.

1977-01-01

An X-ray fluorescence system based on a Co(57) gamma-ray source has been developed. The system was used to calculate the atomic percentages of iron implanted in titanium targets. Measured intensities of Fe (k-alpha + k-beta) and Ti (k-alpha + k-beta) X-rays from the Fe-Ti targets are in good agreement with the calculated values based on photoelectric cross sections of Ti and Fe for the Co(57) gamma rays.

X-Ray Diffraction Wafer Mapping Method for Rhombohedral Super-Hetero-Epitaxy

NASA Technical Reports Server (NTRS)

Park, Yoonjoon; Choi, Sang Hyouk; King, Glen C.; Elliott, James R.; Dimarcantonio, Albert L.

2010-01-01

A new X-ray diffraction (XRD) method is provided to acquire XY mapping of the distribution of single crystals, poly-crystals, and twin defects across an entire wafer of rhombohedral super-hetero-epitaxial semiconductor material. In one embodiment, the method is performed with a point or line X-ray source with an X-ray incidence angle approximating a normal angle close to 90 deg, and in which the beam mask is preferably replaced with a crossed slit. While the wafer moves in the X and Y direction, a narrowly defined X-ray source illuminates the sample and the diffracted X-ray beam is monitored by the detector at a predefined angle. Preferably, the untilted, asymmetric scans are of {440} peaks, for twin defect characterization.

Solar Flares and the High Energy Solar Spectroscopic Imager (HESSI)

NASA Technical Reports Server (NTRS)

Holman, Gordon D.; Fisher, Richard R. (Technical Monitor)

2001-01-01

Solar flares are the biggest explosions in the solar system. They are important both for understanding explosive events in the Universe and for their impact on human technology and communications. The satellite-based HESSI is designed to study the explosive release of energy and the acceleration of electrons, protons, and other charged particles to high energies in solar flares. HESSI produces "color" movies of the Sun in high-energy X rays and gamma rays radiated by these energetic particles. HESSI's X-ray and gamma-ray images of flares are obtained using techniques similar to those used in radio interferometry. Ground-based radio observations of the Sun provide an important complement to the HESSI observations of solar flares. I will describe the HESSI Project and the high-energy aspects of solar flares, and how these relate to radio astronomy techniques and observations.

Bimetallic catalysis for C–C and C–X coupling reactions

PubMed Central

Pye, Dominic R.

2017-01-01

Bimetallic catalysis represents an alternative paradigm for coupling chemistry that complements the more traditional single-site catalysis approach. In this perspective, recent advances in bimetallic systems for catalytic C–C and C–X coupling reactions are reviewed. Behavior which complements that of established single-site catalysts is highlighted. Two major reaction classes are covered. First, generation of catalytic amounts of organometallic species of e.g. Cu, Au, or Ni capable of transmetallation to a Pd co-catalyst (or other traditional cross-coupling catalyst) has allowed important new C–C coupling technologies to emerge. Second, catalytic transformations involving binuclear bond-breaking and/or bond-forming steps, in some cases involving metal–metal bonds, represent a frontier area for C–C and C–X coupling processes.

SEARCHING FOR NEW {gamma}-RAY BLAZAR CANDIDATES IN THE THIRD PALERMO BAT HARD X-RAY CATALOG WITH WISE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maselli, A.; Cusumano, G.; La Parola, V.

We searched for {gamma}-ray blazar candidates among the 382 unidentified hard X-ray sources of the third Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of Swift Burst Alert Telescope (BAT) survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors that characterize the {gamma}-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope. We used this method exploiting the data of the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources andmore » WISE {gamma}-ray blazar candidates located within the BAT positional uncertainty region at a 99% confidence level. We obtained a preliminary list of candidates for which we analyzed all the available data in the Swift archive to complement the information in the literature and in the radio, infrared, and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 {gamma}-ray blazar candidates.« less

Single and double capture in F9+ + Ar collisions: Comparison of total capture with capture occurring from the Ar K shell

NASA Astrophysics Data System (ADS)

La Mantia, David; Kumara, Nuwan; Kayani, Asghar; Simon, Anna; Tanis, John

2016-05-01

Total cross sections for single and double capture, as well as the corresponding cross sections for capture resulting in the emission of an Ar K x ray, were measured. This work was performed at Western Michigan University with the use of the tandem Van de Graaff accelerator. A 45 MeV beam of fully-stripped fluorine ions was collided with argon gas molecules in a differentially pumped cell. Surface barrier detectors were used to observe the charge changed projectiles and a Si(Li) x-ray detector, placed at 90o to the incident beam, were used to measure coincidences with Ar K x rays. The total capture cross sections are compared to previously measured cross sections in the existing literature. The coincidence cross sections, considerably smaller than the total cross sections, are found to be nearly equal for single and double capture in contrast to the total cross sections, which vary by about an order of magnitude. Possible reasons for this behavior are discussed. Supported in part by the NSF.

Corrosion phenomena in electron, proton and synchrotron X-ray microprobe analysis of Roman glass from Qumran, Jordan

NASA Astrophysics Data System (ADS)

Janssens, K.; Aerts, A.; Vincze, L.; Adams, F.; Yang, C.; Utui, R.; Malmqvist, K.; Jones, K. W.; Radtke, M.; Garbe, S.; Lechtenberg, F.; Knöchel, A.; Wouters, H.

1996-04-01

A series of 89 glass fragments of Roman glass are studied using electron, proton and synchrotron radiation induced X-ray emission from microscopic areas on the sample surface. The glass originates from Qumran, Jordan and was buried for 1900 years. The weathering layers that result from the extended contact with ground water have been studied, next to the trace composition of the original glass of these pieces. The latter information indicates that at Qumran, large quantities of glass objects were being used in Ancient times. Cross-sectional profiles of the glass show a complex migration behaviour of various groups of major and trace elements.

IGR J19294+1816: a new Be-X-ray binary revealed through infrared spectroscopy

NASA Astrophysics Data System (ADS)

Rodes-Roca, J. J.; Bernabeu, G.; Magazzù, A.; Torrejón, J. M.; Solano, E.

2018-05-01

The aim of this work is to characterize the counterpart to the INTErnational Gamma-Ray Astrophysics Laboratory high-mass X-ray binary candidate IGR J19294+1816 so as to establish its true nature. We obtained H-band spectra of the selected counterpart acquired with the Near Infrared Camera and Spectrograph instrument mounted on the Telescopio Nazionale Galileo 3.5-m telescope which represents the first infrared spectrum ever taken of this source. We complement the spectral analysis with infrared photometry from UKIDSS, 2MASS, WISE, and NEOWISE data bases. We classify the mass donor as a Be star. Subsequently, we compute its distance by properly taking into account the contamination produced by the circumstellar envelope. The findings indicate that IGR J19294+1816 is a transient source with a B1Ve donor at a distance of d = 11 ± 1 kpc, and luminosities of the order of 1036-37 erg s-1, displaying the typical behaviour of a Be-X-ray binary.

Evidence for a Multiphase ISM in Early Type Galaxies and Elliptical Galaxies with Strong Radio Continuum

NASA Technical Reports Server (NTRS)

Kim, Dong Woo

1997-01-01

We have observed NGC 1316 (Fornax A) with the ROSAT HRI. In this paper, we present the results of these observations and we complement them with the spectral analysis of the archival PSPC data. The spectral properties suggest the presence of a significant component of thermal X-ray emission (greater than 60%), amounting to approx. 10(exp 9) solar mass of hot ISM. Within 3 feet from the nucleus of NGC 1316, the HRI X-ray surface brightness falls as r(exp -2) following the stellar light. In the inner approx. 30 inch., however, the X-ray surface brightness is significantly elongated, contrary to the distribution of stellar light, which is significantly rounder within 10 inch. This again argues for a non-stellar origin of the X-ray emission. This flattened X-ray feature is suggestive of either the disk-like geometry of a rotating cooling flow and/or the presence of extended, elongated dark matter. By comparing the morphology of the X-ray emission with the distribution of optical dust patches, we find that the X-ray emission is significantly reduced at the locations where the dust patches are more pronounced, indicating that at least some of the X-ray photons are absorbed by the cold ISM. We also compare the distribution of the hot and cold ISM with that of the ionized gas, using recently obtained H(sub alpha) CCD data. We find that the ionized gas is distributed roughly along the dust patches and follows the large scale X-ray distribution at r greater than 1 foot from the nucleus. However, there is no one-to-one correspondence between ionized gas and hot gas. Both morphological relations and kinematics suggest different origins for hot and cold ISM. The radio jets in projection appear to pass perpendicularly through the central X-ray ellipsoid. Comparison of thermal and radio pressures suggests that the radio jets are confined by the surrounding hot gaseous medium.

Contaminant Organic Complexes: Their Structure and Energetics in Surface Decontamination Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Satish C. B. Myneni

2005-12-13

Siderophores are biological macromolecules (400-2000 Da) released by bacteria in iron limiting situations to sequester Fe from iron oxyhydroxides and silicates in the natural environment. These molecules contain hydroxamate and phenolate functional groups, and exhibit very high affinity for Fe{sup 3+}. While several studies were conducted to understand the behavior of siderophores and their application to the metal sequestration and mineral dissolution, only a few of them have examined the molecular structure of siderophores and their interactions with metals and mineral surfaces in aqueous solutions. Improved understanding of the chemical state of different functional moieties in siderophores can assist inmore » the application of these biological molecules in actinide separation, sequestration and decontamination processes. The focus of our research group is to evaluate the (a) functional group chemistry of selected siderophores and their metal complexes in aqueous solutions, and (b) the nature of siderophore interactions at the mineral-water interfaces. We selected desferrioxamine B (desB), a hydroxamate siderophore, and its small structural analogue, acetohydroxamic acid (aHa), for this investigation. We examined the functional group chemistry of these molecules as a function of pH, and their complexation with aqueous and solid phase Fe(III). For solid phase Fe, we synthesized all naturally occurring Fe(III)-oxyhydroxides (goethite, lepidocrocite, akaganeite, feroxyhite) and hematite. We also synthesized Fe-oxides (goethite and hematite) of different sizes to evaluate the influence of particle size on mineral dissolution kinetics. We used a series of molecular techniques to explore the functional group chemistry of these molecules and their complexes. Infrared spectroscopy is used to specifically identify the variations in oxime group as a function of pH and Fe(III) complexation. Resonance Raman spectroscopy was used to evaluate the nature of hydroxamate binding in the case of Fe(III)-siderophore complexes and model ligands. Soft and hard X-ray spectroscopy techniques were used to examine the electronic structure of binding groups, and their local structural environment. The synchrotron X-ray studies were conducted at the Stanford Synchrotron Radiation Laboratory and at the Advanced Light Source (Lawrence Berkeley National Laboratory). These experimental vibrational and X-ray spectroscopy studies were complemented with density functional theory calculations. The highlight of this study is the evaluation of the fundamental electronic state information of the hydroxamate moiety in siderophores during deprotonation and Fe(III) complexation. The applications of soft X-ray studies are also new, and were applied, for the first time, to examine the chemistry of organic macromolecules in aqueous solutions.« less

Coupling of jet and accretion activity in the active galaxy NGC 1052

NASA Astrophysics Data System (ADS)

Boeck, Moritz; Kadler, Matthias; Ros, Eduardo; Weaver, Kimberly; Wilms, Joern; Brenneman, Laura; Angelakis, Emmanouil

The radio loud galaxy NGC 1052 has been monitored for the past fifteen years with Very Long Baseline Interferometry (VLBI) observations and has been the target of an intense multiwave-length monitoring campaign since 2005. This provides an excellent dataset for analyzing the relationship between properties of the relativistic jet and the accretion disk in active galactic nuclei. Components in the jet are tracked and the ejection times of new components are deter-mined. The analysis of the radio variability is complemented by the study of X-ray observations allowing us to draw conclusions on the accretion activity. The X-ray variability on weekly and monthly time scales is monitored with the Rossi X-ray Timing Explorer, whereas deep XMM-Newton and Suzaku observations provide spectra showing a broad Fe Kα line, whose variability can provide a particularly valuable probe of the inner accretion flow.

The ART-XC Instrument on Board the SRG Mission

NASA Technical Reports Server (NTRS)

Pavlinksy, M.; Akimov, V.; Levin, V.; Lapshov, I.; Tkachenko, A.; Semena, N.; Buntov, M.; Glushenko, A.; Arefiev, V.; Yaskovish, A.;

An optical and X-ray survey of s-type Markarian galaxies

NASA Technical Reports Server (NTRS)

Hutter, D. J.; Mufson, S. L.

1981-01-01

The results of a study of 23 compact, lineless Markarian galaxies using broadband optical photometry and X-ray satellite observations are reported. The photometry shows that the sample can be broken into four groups. In one group (Mrk 180, 421, and 501) are composite objects in which a BL Lacertae object is embedded in an elliptical galaxy. For this group, the results of multiepoch X-ray observations using the HEAO-1 and -2 satellites are presented. In addition, photometry is used to decompose the optical emission into nonthermal and galactic components. In the second group are objects showing a small ultraviolet excess relative to normal galaxies. The X-ray survey indicates that the X-ray luminosity of objects in group 2 is much lower than those in group 1. This suggests that there is an intrinsic difference between objects in groups 1 and 2. The third and fourth groups are objects whose colors are indistinguishable from those of normal field galaxies and those of galactic stars, respectively. No X-ray emission was detected from objects in either of these groups.

Virtual bronchoscopic navigation without X-ray fluoroscopy to diagnose peripheral pulmonary lesions: a randomized trial.

PubMed

Asano, Fumihiro; Ishida, Takashi; Shinagawa, Naofumi; Sukoh, Noriaki; Anzai, Masaki; Kanazawa, Kenya; Tsuzuku, Akifumi; Morita, Satoshi

2017-12-11

Transbronchial biopsy for peripheral pulmonary lesions is generally performed under X-ray fluoroscopy. Virtual bronchoscopic navigation (VBN) is a method in which virtual images of the bronchial route to the lesion are produced based on CT images obtained before VBN, and the bronchoscope is guided using these virtual images, improving the diagnostic yield of peripheral pulmonary lesions. VBN has the possibility of eliminating the need for X-ray fluoroscopy in the bronchoscopic diagnosis of peripheral lesions. To determine whether VBN can be a substitute for X-ray fluoroscopy, a randomized multicenter trial (non-inferiority trial) was performed in VBN and X-ray fluoroscopy (XRF) -assisted groups. The non-inferiority margin in the VBN-assisted group compared with the XRF-assisted group was set at 15%. The subjects consisted of 140 patients with peripheral pulmonary lesions with a mean diameter > 3 cm. In the VBN-assisted group, the bronchoscope was guided to the lesion using a VBN system without X-ray fluoroscopy. In the XRF-assisted group, the same bronchoscope was guided to the lesion under X-ray fluoroscopy. Subsequently, in both groups, the lesion was visualized using endobronchial ultrasonography with a guide sheath (EBUS/GS), and biopsy was performed. In this serial procedure, X-ray fluoroscopy was not used in the VBNA group. The subjects of analysis consisted of 129 patients. The diagnostic yield was 76.9% (50/65) in the VBN-assisted group and 85.9% (55/64) in the XRF-assisted group. The difference in the diagnostic yield between the two groups was -9.0% (95% confidence interval: -22.3% ~ 4.3%). The non-inferiority of the VBN-assisted group could not be confirmed. The rate of visualizing lesions by EBUS was 95.4% (62/65) in the VBN-assisted group and 96.9% (62/64) in the XRF-assisted group, being high in both groups. On EBUS/GS, a bronchoscope and biopsy instruments may be guided to the lesions using VBN without X-ray fluoroscopy, but X-ray fluoroscopy is necessary to improve the accuracy of sample collection from lesions. During transbronchial biopsy for peripheral pulmonary lesions, VBN cannot be a substitute for X-ray fluoroscopy. UMIN-CTR (UMIN000001710); registered 16 February 2009.

Temporal cross-correlation of x-ray free electron and optical lasers using soft x-ray pulse induced transient reflectivity.

PubMed

Krupin, O; Trigo, M; Schlotter, W F; Beye, M; Sorgenfrei, F; Turner, J J; Reis, D A; Gerken, N; Lee, S; Lee, W S; Hays, G; Acremann, Y; Abbey, B; Coffee, R; Messerschmidt, M; Hau-Riege, S P; Lapertot, G; Lüning, J; Heimann, P; Soufli, R; Fernández-Perea, M; Rowen, M; Holmes, M; Molodtsov, S L; Föhlisch, A; Wurth, W

2012-05-07

The recent development of x-ray free electron lasers providing coherent, femtosecond-long pulses of high brilliance and variable energy opens new areas of scientific research in a variety of disciplines such as physics, chemistry, and biology. Pump-probe experimental techniques which observe the temporal evolution of systems after optical or x-ray pulse excitation are one of the main experimental schemes currently in use for ultrafast studies. The key challenge in these experiments is to reliably achieve temporal and spatial overlap of the x-ray and optical pulses. Here we present measurements of the x-ray pulse induced transient change of optical reflectivity from a variety of materials covering the soft x-ray photon energy range from 500eV to 2000eV and outline the use of this technique to establish and characterize temporal synchronization of the optical-laser and FEL x-ray pulses.

High energy X-ray phase and dark-field imaging using a random absorption mask.

PubMed

Wang, Hongchang; Kashyap, Yogesh; Cai, Biao; Sawhney, Kawal

2016-07-28

High energy X-ray imaging has unique advantage over conventional X-ray imaging, since it enables higher penetration into materials with significantly reduced radiation damage. However, the absorption contrast in high energy region is considerably low due to the reduced X-ray absorption cross section for most materials. Even though the X-ray phase and dark-field imaging techniques can provide substantially increased contrast and complementary information, fabricating dedicated optics for high energies still remain a challenge. To address this issue, we present an alternative X-ray imaging approach to produce transmission, phase and scattering signals at high X-ray energies by using a random absorption mask. Importantly, in addition to the synchrotron radiation source, this approach has been demonstrated for practical imaging application with a laboratory-based microfocus X-ray source. This new imaging method could be potentially useful for studying thick samples or heavy materials for advanced research in materials science.

Synchrotron X-ray topographic study on nature of threading mixed dislocations in 4H–SiC crystals grown by PVT method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Jianqiu; Yang, Yu; Wu, Fangzhen

Synchrotron X-ray Topography is a powerful technique to study defects structures particularly dislocation configurations in single crystals. Complementing this technique with geometrical and contrast analysis can enhance the efficiency of quantitatively characterizing defects. In this study, the use of Synchrotron White Beam X-ray Topography (SWBXT) to determine the line directions of threading dislocations in 4H–SiC axial slices (sample cut parallel to the growth axis from the boule) is demonstrated. This technique is based on the fact that the projected line directions of dislocations on different reflections are different. Another technique also discussed is the determination of the absolute Burgers vectorsmore » of threading mixed dislocations (TMDs) using Synchrotron Monochromatic Beam X-ray Topography (SMBXT). This technique utilizes the fact that the contrast from TMDs varies on SMBXT images as their Burgers vectors change. By comparing observed contrast with the contrast from threading dislocations provided by Ray Tracing Simulations, the Burgers vectors can be determined. Thereafter the distribution of TMDs with different Burgers vectors across the wafer is mapped and investigated.« less

Can X-ray spectrum imaging replace backscattered electrons for compositional contrast in the scanning electron microscope?

PubMed

Newbury, Dale E; Ritchie, Nicholas W M

2011-01-01

The high throughput of the silicon drift detector energy dispersive X-ray spectrometer (SDD-EDS) enables X-ray spectrum imaging (XSI) in the scanning electron microscope to be performed in frame times of 10-100 s, the typical time needed to record a high-quality backscattered electron (BSE) image. These short-duration XSIs can reveal all elements, except H, He, and Li, present as major constituents, defined as 0.1 mass fraction (10 wt%) or higher, as well as minor constituents in the range 0.01-0.1 mass fraction, depending on the particular composition and possible interferences. Although BSEs have a greater abundance by a factor of 100 compared with characteristic X-rays, the strong compositional contrast in element-specific X-ray maps enables XSI mapping to compete with BSE imaging to reveal compositional features. Differences in the fraction of the interaction volume sampled by the BSE and X-ray signals lead to more delocalization of the X-ray signal at abrupt compositional boundaries, resulting in poorer spatial resolution. Improved resolution in X-ray elemental maps occurs for the case of a small feature composed of intermediate to high atomic number elements embedded in a matrix of lower atomic number elements. XSI imaging strongly complements BSE imaging, and the SDD-EDS technology enables an efficient combined BSE-XSI measurement strategy that maximizes the compositional information. If 10 s or more are available for the measurement of an area of interest, the analyst should always record the combined BSE-XSI information to gain the advantages of both measures of compositional contrast. Copyright © 2011 Wiley Periodicals, Inc.

Statistical and operational considerations for designs for x-ray tomographic spectrophotometry to detect, localize, and classify foreign objects in various systems

NASA Astrophysics Data System (ADS)

Fennelly, Alphonsus J.; Fry, Edward L.; Zukic, Muamer; Wilson, Michele M.; Janik, Tadeusz J.; Torr, Douglas G.

1994-11-01

In six companion papers we discuss a capability for x-ray tomographic spectrophotometry at three energy ranges to observe foreign objects in various systems using a novel x-ray optical and photometric approach. We describe new types of thin-film x-ray reflecting filters to provide energy-specific optical trains, inserted into existing x-ray interrogation systems. That is complemented by performing topographic imaging at a few, to several, energies in each case. That provides a full topographic and spectrophotometric analysis. Foreign objects can then be detected, localized, discriminated, and classified, so that they may be dealt with by excision, and replacement with benign system elements. We analyze statistical and operational concerns leading to the design of three systems: The first operates at x-ray energies of 1 - 10 keV; it deals with defects in microelectronic integrated circuits. The second operates at x-ray energies of 10 - 30 keV; it deals with the defects in human tissue. The chemical specificity and image resolution of the system will allow identification, localization, and mensuration of tumors without the need of biopsy. The system which we concentrate this discussion on, the third, operates at x- ray energies of 30 - 70 keV; it deals with the presence in transportation systems of explosive devices, and contraband materials and objects in luggage and cargo. We present the analysis of the statistical features of the detection problem in these types of systems, discussing the operational constraints which limits system performance. After considering the multivariate, multisignature, approach to the problem, we discuss the tomographic and spectrophotometric approach to the problem which yields a better solution to the detection problem within the operational constraints.

VizieR Online Data Catalog: X-ray line ratios for diverse ion collisions (Mullen+, 2017)

NASA Astrophysics Data System (ADS)

Mullen, P. D.; Cumbee, R. S.; Lyons, D.; Gu, L.; Kaastra, J.; Shelton, R. L.; Stancil, P. C.

2018-03-01

Charge exchange (CX) has emerged in X-ray emission modeling as a significant process that must be considered in many astrophysical environments- particularly comets. Comets host an interaction between solar wind ions and cometary neutrals to promote solar wind charge exchange (SWCX). X-ray observatories provide astronomers and astrophysicists with data for many X-ray emitting comets that are impossible to accurately model without reliable CX data. Here, we utilize a streamlined set of computer programs that incorporate the multi-channel Landau-Zener theory and a cascade model for X-ray emission to generate cross sections and X-ray line ratios for a variety of bare and non-bare ion single electron capture (SEC) collisions. Namely, we consider collisions between the solar wind constituent bare and H-like ions of C, N, O, Ne, Na, Mg, Al, and Si and the cometary neutrals H2O, CO, CO2, OH, and O. To exemplify the application of this data, we model the X-ray emission of Comet C/2000 WM1 (linear) using the CX package in SPEX and find excellent agreement with observations made with the XMM-Newton RGS detector. Our analyses show that the X-ray intensity is dominated by SWCX with H, while H2O plays a secondary role. This is the first time, to our knowledge, that CX cross sections have been implemented into a X-ray spectral fitting package to determine the H to H2O ratio in cometary atmospheres. The CX data sets are incorporated into the modeling packages SPEX and Kronos. (1 data file).

X-ray source characterization of aluminum X-pinch plasmas driven by the 0. 5 TW LION accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qi, N.; Hammer, D.A.; Kalantar, D.H.

1989-12-01

Recent experiments at Cornell have been performed to investigate X-pinch plasmas as intense x-ray sources which might be used to pump resonant photoexcitation lasers. Crossed Al wires have been driven by up to 600 kA current for 40 ns. High density bright spots are observed at the crossing point(s). Various diagnostics were used to characterize the X-pinch plasmas as a function of initial mass loading for several specific wire configurations. The optimum mass loading for different ionization stages of Al, and the total x-ray energy yields, which are on the order of hundreds of Joules, were examined. Estimates of plasmamore » density, {similar to}10{sup 20} cm{sup {minus}3}, and temperature, about 400 eV, were obtained.« less

V-V compact group of galaxies

NASA Technical Reports Server (NTRS)

Bahcall, N.

1984-01-01

A search for X-ray emission from five compact groups of galaxies with the Einstein Observatory revealed detections from three groups. Soft, extended X-ray emission was observed in Stephan's Quintet which is most likely caused by hot intracluster gas. This provides evidence for dynamical interaction among the group galaxies. X-ray emission from the group Arp 330 may also originate in hot intracluster gas. Stephan's Quintet and Arp 330 have the largest velocity dispersions among the groups studied suggesting a correlation between high velocity and the release (or properties) of hot gas. X-ray emission from Arp 318 may originate in its member galaxies.

Production cross sections of cosmic antiprotons in the light of new data from the NA61 and LHCb experiments

NASA Astrophysics Data System (ADS)

Korsmeier, Michael; Donato, Fiorenza; Di Mauro, Mattia

2018-05-01

The cosmic-ray flux of antiprotons is measured with high precision by the space-borne particle spectrometers AMS-02. Its interpretation requires a correct description of the dominant production process for antiprotons in our Galaxy, namely, the interaction of cosmic-ray proton and helium with the interstellar medium. In light of new cross section measurements by the NA61 experiment of p +p →p ¯+X and the first ever measurement of p +He →p ¯+X by the LHCb experiment, we update the parametrization of proton-proton and proton-nucleon cross sections. We find that the LHCb p He data constrain a shape for the cross section at high energies and show for the first time how well the rescaling from the p p channel applies to a helium target. By using p p , p He and p C data we estimate the uncertainty on the Lorentz invariant cross section for p +He →p ¯+X . We use these new cross sections to compute the source term for all the production channels, considering also nuclei heavier than He both in cosmic rays and the interstellar medium. The uncertainties on the total source term are up to ±20 % and slightly increase below antiproton energies of 5 GeV. This uncertainty is dominated by the p +p →p ¯+X cross section, which translates into all channels since we derive them using the p p cross sections. The cross sections to calculate the source spectra from all relevant cosmic-ray isotopes are provided in Supplemental Material. We finally quantify the necessity of new data on antiproton production cross sections, and pin down the kinematic parameter space which should be covered by future data.

YOHKOH Observations at the Y2K Solar Maximum

NASA Astrophysics Data System (ADS)

Aschwanden, M. J.

1999-05-01

Yohkoh will provide simultaneous co-aligned soft X-ray and hard X-ray observations of solar flares at the coming solar maximum. The Yohkoh Soft X-ray Telescope (SXT) covers the approximate temperature range of 2-20 MK with a pixel size of 2.46\\arcsec, and thus complements ideally the EUV imagers sensitive in the 1-2 MK plasma, such as SoHO/EIT and TRACE. The Yohkoh Hard X-ray Telescope (HXT) offers hard X-ray imaging at 20-100 keV at a time resolution of down to 0.5 sec for major events. In this paper we review the major SXT and HXT results from Yohkoh solar flare observations, and anticipate some of the key questions that can be addressed through joint observations with other ground and space-based observatories. This encompasses the dynamics of flare triggers (e.g. emerging flux, photospheric shear, interaction of flare loops in quadrupolar geometries, large-scale magnetic reconfigurations, eruption of twisted sigmoid structures, coronal mass ejections), the physics of particle dynamics during flares (acceleration processes, particle propagation, trapping, and precipitation), and flare plasma heating processes (chromospheric evaporation, coronal energy loss by nonthermal particles). In particular we will emphasize on how Yohkoh data analysis is progressing from a qualitative to a more quantitative science, employing 3-dimensional modeling and numerical simulations.

The active galactic nucleus population in X-ray-selected galaxy groups at 0.5 < Z < 1.1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oh, Semyeong; Woo, Jong-Hak; Matsuoka, Kenta

2014-07-20

We use Chandra data to study the incidence and properties of active galactic nuclei (AGNs) in 16 intermediate redshift (0.5 < z < 1.1) X-ray-selected galaxy groups in the Chandra Deep Field-South. We measure an AGN fraction of f(L{sub X,H}>10{sup 42};M{sub R}<−20)=8.0{sub −2.3}{sup +3.0}% at z-bar ∼0.74, approximately a factor of two higher than the AGN fraction found for rich clusters at comparable redshift. This extends the trend found at low redshift for groups to have higher AGN fractions than clusters. Our estimate of the AGN fraction is also more than a factor of three higher than that of lowmore » redshift X-ray-selected groups. Using optical spectra from various surveys, we also constrain the properties of emission-line selected AGNs in these groups. In contrast to the large population of X-ray AGNs (N(L{sub X,{sub H}} > 10{sup 41} erg s{sup –1}) = 25), we find only four emission-line AGNs, three of which are also X-ray bright. Furthermore, most of the X-ray AGNs in our groups are optically dull (i.e., lack strong emission-lines), similar to those found in low redshift X-ray groups and clusters of galaxies. This contrasts with the AGN population found in low redshift optically selected groups which are dominated by emission-line AGNs. The differences between the optically and X-ray-selected AGNs populations in groups are consistent with a scenario where most AGNs in the densest environments are currently in a low accretion state.« less

The HectoMAP Cluster Survey. II. X-Ray Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sohn, Jubee; Chon, Gayoung; Bohringer, Hans

Here, we apply a friends-of-friends algorithm to the HectoMAP redshift survey and cross-identify associated X-ray emission in the ROSAT All-Sky Survey data (RASS). The resulting flux-limited catalog of X-ray cluster surveys is complete to a limiting flux of ~3 × 10 –13 erg s –1 cm –2 and includes 15 clusters (7 newly discovered) with redshifts z ≤ 0.4. HectoMAP is a dense survey (~1200 galaxies deg –2) that provides ~50 members (median) in each X-ray cluster. We provide redshifts for the 1036 cluster members. Subaru/Hyper Suprime-Cam imaging covers three of the X-ray systems and confirms that they are impressivemore » clusters. The HectoMAP X-ray clusters have an L X–σ cl scaling relation similar to that of known massive X-ray clusters. The HectoMAP X-ray cluster sample predicts ~12,000 ± 3000 detectable X-ray clusters in RASS to the limiting flux, comparable with previous estimates.« less

The HectoMAP Cluster Survey. II. X-Ray Clusters

DOE PAGES

Sohn, Jubee; Chon, Gayoung; Bohringer, Hans; ...

2018-03-10

Here, we apply a friends-of-friends algorithm to the HectoMAP redshift survey and cross-identify associated X-ray emission in the ROSAT All-Sky Survey data (RASS). The resulting flux-limited catalog of X-ray cluster surveys is complete to a limiting flux of ~3 × 10 –13 erg s –1 cm –2 and includes 15 clusters (7 newly discovered) with redshifts z ≤ 0.4. HectoMAP is a dense survey (~1200 galaxies deg –2) that provides ~50 members (median) in each X-ray cluster. We provide redshifts for the 1036 cluster members. Subaru/Hyper Suprime-Cam imaging covers three of the X-ray systems and confirms that they are impressivemore » clusters. The HectoMAP X-ray clusters have an L X–σ cl scaling relation similar to that of known massive X-ray clusters. The HectoMAP X-ray cluster sample predicts ~12,000 ± 3000 detectable X-ray clusters in RASS to the limiting flux, comparable with previous estimates.« less

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin

We use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated and therebymore » the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin

Here, we use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated andmore » thereby the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

Detecting element specific electrons from a single cobalt nanocluster with synchrotron x-ray scanning tunneling microscopy

DOE PAGES

Kersell, Heath; Shirato, Nozomi; Cummings, Marvin; ...

2017-09-05

Here, we use a nanofabricated scanning tunneling microscope tip as a detector to investigate local X-ray induced tunneling and electron emission from a single cobalt nanocluster on a Au(111) surface. The tip-detector is positioned a few angstroms above the nanocluster, and ramping the incident X-ray energy across the Co photoabsorption K-edge enables the detection of element specific electrons. Atomic-scale spatial dependent changes in the X-ray absorption cross section are directly measured by taking the X-ray induced current as a function of X-ray energy. From the measured sample and tip currents, element specific X-ray induced current components can be separated andmore » thereby the corresponding yields for the X-ray induced processes of the single cobalt nanocluster can be determined. The detection of element specific synchrotron X-ray induced electrons of a single nanocluster opens a new avenue for materials characterization on a one particle at-a-time basis.« less

X-ray crystallography over the past decade for novel drug discovery – where are we heading next?

PubMed Central

Zheng, Heping; Handing, Katarzyna B; Zimmerman, Matthew D; Shabalin, Ivan G; Almo, Steven C; Minor, Wladek

2015-01-01

Introduction Macromolecular X-ray crystallography has been the primary methodology for determining the three-dimensional structures of proteins, nucleic acids and viruses. Structural information has paved the way for structure-guided drug discovery and laid the foundations for structural bioinformatics. However, X-ray crystallography still has a few fundamental limitations, some of which may be overcome and complemented using emerging methods and technologies in other areas of structural biology. Areas covered This review describes how structural knowledge gained from X-ray crystallography has been used to advance other biophysical methods for structure determination (and vice versa). This article also covers current practices for integrating data generated by other biochemical and biophysical methods with those obtained from X-ray crystallography. Finally, the authors articulate their vision about how a combination of structural and biochemical/biophysical methods may improve our understanding of biological processes and interactions. Expert opinion X-ray crystallography has been, and will continue to serve as, the central source of experimental structural biology data used in the discovery of new drugs. However, other structural biology techniques are useful not only to overcome the major limitation of X-ray crystallography, but also to provide complementary structural data that is useful in drug discovery. The use of recent advancements in biochemical, spectroscopy and bioinformatics methods may revolutionize drug discovery, albeit only when these data are combined and analyzed with effective data management systems. Accurate and complete data management is crucial for developing experimental procedures that are robust and reproducible. PMID:26177814

Conventional vs  invert-grayscale X-ray for diagnosis of pneumothorax in the emergency setting.

PubMed

Musalar, Ekrem; Ekinci, Salih; Ünek, Orkun; Arş, Eda; Eren, Hakan Şevki; Gürses, Bengi; Aktaş, Can

2017-09-01

Pneumothorax is a pathologic condition in which air is accumulated between the visceral and parietal pleura. After clinical suspicion, in order to diagnose the severity of the condition, imaging is necessary. By using the help of Picture Archiving and Communication Systems (PACS) direct conventional X-rays are converted to gray-scale and this has become a preferred method among many physicians. Our study design was a case-control study with cross-over design study. Posterior-anterior chest X-rays of patients were evaluated for pneumothorax by 10 expert physicians with at least 3years of experience and who have used inverted gray-scale posterior anterior chest X-ray for diagnosing pneumothorax. The study included posterior anterior chest X-ray images of 268 patients of which 106 were diagnosed with spontaneous pneumothorax and 162 patients used as a control group. The sensitivity of Digital-conventional X-rays was found to be higher than that of inverted gray-scale images (95% CI (2,08-5,04), p<0,01). There was no statistically significant difference between the gold standard and digital-conventional images (95% CI (0,45-2,17), p=0,20), while the evaluations of the gray-scale images were found to be less sensitive for diagnosis (95% CI (3,16-5,67) p<0,01). Inverted gray-scale imaging is not a superior imaging modality over digital-conventional X-ray for the diagnosis of pneumothorax. Prospective studies should be performed where diagnostic potency of inverted gray-scale radiograms is tested against gold standard chest CT. Further research should compare inverted grayscale to lung ultrasound to assess them as alternatives prior to CT. Copyright © 2017 Elsevier Inc. All rights reserved.

Long-term optical and X-ray variability of the Be/X-ray binary H 1145-619: Discovery of an ongoing retrograde density wave

NASA Astrophysics Data System (ADS)

Alfonso-Garzón, J.; Fabregat, J.; Reig, P.; Kajava, J. J. E.; Sánchez-Fernández, C.; Townsend, L. J.; Mas-Hesse, J. M.; Crawford, S. M.; Kretschmar, P.; Coe, M. J.

2017-11-01

Context. Multiwavelength monitoring of Be/X-ray binaries is crucial to understand the mechanisms producing their outbursts. H 1145-619 is one of these systems, which has recently displayed X-ray activity. Aims: We investigate the correlation between the optical emission and X-ray activity to predict the occurrence of new X-ray outbursts from the inferred state of the circumstellar disc. Methods: We have performed a multiwavelength study of H 1145-619 from 1973 to 2017 and present here a global analysis of its variability over the last 40 yr. We used optical spectra from the SAAO, SMARTS, and SALT telescopes and optical photometry from the Optical Monitoring Camera (OMC) onboard INTEGRAL and from the All Sky Automated Survey (ASAS). We also used X-ray observations from INTEGRAL/JEM-X, and IBIS to generate the light curves and combined them with Swift/XRT to extract the X-ray spectra. In addition, we compiled archival observations and measurements from the literature to complement these data. Results: Comparing the evolution of the optical continuum emission with the Hα line variability, we identified three different patterns of optical variability: first, global increases and decreases of the optical brightness, observed from 1982 to 1994 and from 2009 to 2017, which can be explained by the dissipation and replenishment of the circumstellar disc; second, superorbital variations with a period of Psuperorb ≈ 590 days, observed in 2002-2009, which seems to be related to the circumstellar disc; and third, optical outbursts, observed in 1998-1999 and 2002-2005, which we interpret as mass ejections from the Be star. We discovered the presence of a retrograde one-armed density wave, which appeared in 2016 and is still present in the circumstellar disc. Conclusions: We carried out the most complete long-term optical study of the Be/X-ray binary H 1145-619 in correlation with its X-ray activity. For the first time, we found the presence of a retrograde density perturbation in the circumstellar disc of a Be/X-ray binary.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Jaejin; Woo, Jong-Hak; Mulchaey, John S.

We perform a comprehensive study of X-ray cavities using a large sample of X-ray targets selected from the Chandra archive. The sample is selected to cover a large dynamic range including galaxy clusters, groups, and individual galaxies. Using β -modeling and unsharp masking techniques, we investigate the presence of X-ray cavities for 133 targets that have sufficient X-ray photons for analysis. We detect 148 X-ray cavities from 69 targets and measure their properties, including cavity size, angle, and distance from the center of the diffuse X-ray gas. We confirm the strong correlation between cavity size and distance from the X-raymore » center similar to previous studies. We find that the detection rates of X-ray cavities are similar among galaxy clusters, groups and individual galaxies, suggesting that the formation mechanism of X-ray cavities is independent of environment.« less

Young's modulus and SEM analysis of leg bones exposed to simulated microgravity by hind limb suspension (HLS)

NASA Astrophysics Data System (ADS)

Patel, Niravkumar D.; Mehta, Rahul; Ali, Nawab; Soulsby, Michael; Chowdhury, Parimal

2013-04-01

The aim of this study was to determine composition of the leg bone tissue of rats that were exposed to simulated microgravity by Hind-Limb Suspension (HLS) by tail for one week. The leg bones were cross sectioned, cleaned of soft tissues, dried and sputter coated, and then placed horizontally on the stage of a Scanning Electron Microscope (SEM) for analysis. Interaction of a 17.5 keV electron beam, incident from the vertical direction on the sample, generated images using two detectors. X-rays emitted from the sample during electron bombardment were measured with an Energy Dispersive Spectroscopy (EDS) feature of SEM using a liquid-nitrogen cooled Si(Li) detector with a resolution of 144 eV at 5.9 keV (25Mn Kα x-ray). Kα- x-rays from carbon, oxygen, phosphorus and calcium formed the major peaks in the spectrum. Relative percentages of these elements were determined using a software that could also correct for ZAF factors namely Z(atomic number), A(X-ray absorption) and F(characteristic fluorescence). The x-rays from the control groups and from the experimental (HLS) groups were analyzed on well-defined parts (femur, tibia and knee) of the leg bone. The SEM analysis shows that there are definite changes in the hydroxyl or phosphate group of the main component of the bone structure, hydroxyapatite [Ca10(PO4)6(OH)2], due to hind limb suspension. In a separate experiment, entire leg bones (both from HLS and control rats) were subjected to mechanical stress by mean of a variable force. The stress vs. strain graph was fitted with linear and polynomial function, and the parameters reflecting the mechanical strength of the bone, under increasing stress, were calculated. From the slope of the linear part of the graph the Young's modulus for HLS bones were calculated and found to be 2.49 times smaller than those for control bones.

First-Principles Predictions of Near-Edge X-ray Absorption Fine Structure Spectra of Semiconducting Polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Gregory M.; Patel, Shrayesh N.; Pemmaraju, C. D.

The electronic structure and molecular orientation of semiconducting polymers in thin films determine their ability to transport charge. Methods based on near-edge X-ray absorption fine structure (NEXAFS) spectroscopy can be used to probe both the electronic structure and microstructure of semiconducting polymers in both crystalline and amorphous films. However, it can be challenging to interpret NEXAFS spectra on the basis of experimental data alone, and accurate, predictive calculations are needed to complement experiments. Here, we show that first-principles density functional theory (DFT) can be used to model NEXAFS spectra of semiconducting polymers and to identify the nature of transitions inmore » complicated NEXAFS spectra. Core-level X-ray absorption spectra of a set of semiconducting polymers were calculated using the excited electron and core-hole (XCH) approach based on constrained-occupancy DFT. A comparison of calculations on model oligomers and periodic structures with experimental data revealed the requirements for accurate prediction of NEXAFS spectra of both conjugated homopolymers and donor–acceptor polymers. The NEXAFS spectra predicted by the XCH approach were applied to study molecular orientation in donor–acceptor polymers using experimental spectra and revealed the complexity of using carbon edge spectra in systems with large monomeric units. The XCH approach has sufficient accuracy in predicting experimental NEXAFS spectra of polymers that it should be considered for design and analysis of measurements using soft X-ray techniques, such as resonant soft X-ray scattering and scanning transmission X-ray microscopy.« less

VizieR Online Data Catalog: New gamma-ray blazar candidates in the 3PBC (Maselli+, 2013)

NASA Astrophysics Data System (ADS)

Maselli, A.; Massaro, F.; Cusumano, G.; D'Abrusco, R.; La Parola, V.; Paggi, A.; Segreto, A.; Smith, H. A.; Tosti, G.

2013-06-01

We searched for γ-ray blazar candidates among the 382 unidentified hard X-ray sources of the third Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of Swift Burst Alert Telescope (BAT) survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors that characterize the γ-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope. We used this method exploiting the data of the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources and WISE γ-ray blazar candidates located within the BAT positional uncertainty region at a 99% confidence level. We obtained a preliminary list of candidates for which we analyzed all the available data in the Swift archive to complement the information in the literature and in the radio, infrared, and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 γ-ray blazar candidates. (2 data files).

Some Like it Hot: Linking Diffuse X-Ray Luminosity, Baryonic Mass, and Star Formation Rate in Compact Groups of Galaxies

NASA Technical Reports Server (NTRS)

Desjardins, Tyler D.; Gallagher, Sarah C.; Hornschemeier, Ann E.; Mulchaey, John S.; Walker, Lisa May; Brandt, Willian N.; Charlton, Jane C.; Johnson, Kelsey E.; Tzanavaris, Panayiotis

2014-01-01

We present an analysis of the diffuse X-ray emission in 19 compact groups (CGs) of galaxies observed with Chandra. The hottest, most X-ray luminous CGs agree well with the galaxy cluster X-ray scaling relations in L(x-T) and (L(x-sigma), even in CGs where the hot gas is associated with only the brightest galaxy. Using Spitzer photometry, we compute stellar masses and classify Hickson CGs 19, 22, 40, and 42, and RSCGs 32, 44, and 86 as fossil groups using a new definition for fossil systems that includes a broader range of masses. We find that CGs with total stellar and Hi masses are great than or equal to 10(sup (11.3) solar mass are often X-ray luminous, while lower-mass CGs only sometimes exhibit faint, localized X-ray emission. Additionally, we compare the diffuse X-ray luminosity against both the total UV and 24 micron star formation rates of each CG and optical colors of the most massive galaxy in each of the CGs. The most X-ray luminous CGs have the lowest star formation rates, likely because there is no cold gas available for star formation, either because the majority of the baryons in these CGs are in stars or the X-ray halo, or due togas stripping from the galaxies in CGs with hot halos. Finally, the optical colors that trace recent star formation histories of the most massive group galaxies do not correlate with the X-ray luminosities of the CGs, indicating that perhaps the current state of the X-ray halos is independent of the recent history of stellar mass assembly in the most massive galaxies.

Evidence for an unorthodox firing sequence employed by the Berlin Painter. Deciphering ancient ceramic firing conditions through high-resolution material characterization and replication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cianchetta, I.; Trentelman, K.; Maish, J.

XANES spectroscopy was used to complement the results previously obtained with Raman spectroscopy by the same group to determine the firing conditions used in the production of a single vessel painted by the Berlin Painter in the 5th century B.C. The vessel, part of the collection of the J. Paul Getty Museum, presents a complicated layered architecture of black and red gloss, with different stratigraphies present on the interior and exterior surfaces. The study of two samples, one each from the interior and exterior surface of the vessel, was performed with the complementary analytical techniques of X-ray nano- and micro-spectroscopymore » (X-ray fluorescence spectroscopy (XRF) and full-field transmission X-ray micro-spectroscopy (FF-XANES) across the Fe K edge), and supported by a replication study. The replicates, made in a laboratory furnace providing complete control over the firing temperature and oxygen partial pressure, provided a paradigm for the comparison of the mineralogical phases observed in the ancient samples, which led to a deeper understanding of the firing conditions necessary for the production of the Berlin Painter's vessel. Our results confirm the necessity of multiple firings and painting applications to obtain the Berlin Painter's architecture and provide a further example of the multiplicity of techniques and practices employed by the potters of the Kerameikos in ancient Athens.« less

Evidence for an unorthodox firing sequence employed by the Berlin Painter. Deciphering ancient ceramic firing conditions through high-resolution material characterization and replication

DOE PAGES

Cianchetta, I.; Trentelman, K.; Maish, J.; ...

2014-12-10

XANES spectroscopy was used to complement the results previously obtained with Raman spectroscopy by the same group to determine the firing conditions used in the production of a single vessel painted by the Berlin Painter in the 5th century B.C. The vessel, part of the collection of the J. Paul Getty Museum, presents a complicated layered architecture of black and red gloss, with different stratigraphies present on the interior and exterior surfaces. The study of two samples, one each from the interior and exterior surface of the vessel, was performed with the complementary analytical techniques of X-ray nano- and micro-spectroscopymore » (X-ray fluorescence spectroscopy (XRF) and full-field transmission X-ray micro-spectroscopy (FF-XANES) across the Fe K edge), and supported by a replication study. The replicates, made in a laboratory furnace providing complete control over the firing temperature and oxygen partial pressure, provided a paradigm for the comparison of the mineralogical phases observed in the ancient samples, which led to a deeper understanding of the firing conditions necessary for the production of the Berlin Painter's vessel. Our results confirm the necessity of multiple firings and painting applications to obtain the Berlin Painter's architecture and provide a further example of the multiplicity of techniques and practices employed by the potters of the Kerameikos in ancient Athens.« less

Nighttime sensitivity of ionospheric VLF measurements to X-ray bursts from a remote cosmic source

NASA Astrophysics Data System (ADS)

Raulin, Jean-Pierre; Trottet, Gérard; Giménez de Castro, C. Guillermo; Correia, Emilia; Macotela, E. Liliana

2014-06-01

On 22 January 2009, a series of X-ray bursts were emitted by the soft gamma ray repeater SGR J1550-5418. Some of these bursts produced enhanced ionization in the nighttime lower ionosphere. These ionospheric disturbances were studied using X-ray measurements from the Anti-Coincidence Shield of the Spectrometer for Integral onboard the International Gamma-Ray Astrophysics Laboratory and simultaneous phase and amplitude records from two VLF propagation paths between the transmitter Naval Radio Station, Pearl Harbor (Hawaii) and the receivers Radio Observatorio do Itapetinga (Brazil) and Estação Antarctica Commandante Ferraz (Antarctic Peninsula). The VLF measurements have been obtained with an unprecedented high time resolution of 20 ms. We find that the illumination factor I (illuminated path length times the cosine of the zenith angle), which characterizes the propagation paths underlying the flaring object, is a key parameter which determines the sensitivity threshold of the VLF detection of X-ray bursts from nonsolar transients. For the present VLF measurements of bursts from SGR J1550-5418, it is found that for I ≥ 1.8 Mm, all X-ray bursts with fluence in the 25 keV to 2 MeV range larger than F25_min 1.0 × 10-6 erg/cm2 produce a measurable ionospheric disturbance. Such a lower limit of the X-ray fluence value indicates that moderate X-ray bursts, as opposed to giant X-ray bursts, do produce ionospheric disturbances larger than the sensitivity limit of the VLF technique. Therefore, the frequency of detection of such events could be improved, for example by increasing the coverage of existing VLF receiving networks. The VLF detection of high-energy astrophysical bursts then appears as an important observational diagnostic to complement their detection in space. This would be especially important when space observations suffer from adverse conditions, like saturation, occultation from the Earth, or the passage of the spacecraft through the South Atlantic anomaly.

Carbonate formation in non-aqueous environments by solid-gas carbonation of silicates

NASA Astrophysics Data System (ADS)

Day, S. J.; Thompson, S. P.; Evans, A.; Parker, J. E.

2012-02-01

We have produced synthetic analogues of cosmic silicates using the Sol Gel method, producing amorphous silicates of composition Mg(x)Ca(1-x)SiO3. Using synchrotron X-ray powder diffraction on Beamline I11 at the Diamond Light Source, together with a newly-commissioned gas cell, real-time powder diffraction scans have been taken of a range of silicates exposed to CO2 under non-ambient conditions. The SXPD is complemented by other techniques including Raman and Infrared Spectroscopy and SEM imaging.

Exploring Electric Polarization Mechanisms in Multiferroic Oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tyson, Trevor A.

2017-01-24

Multiferroic oxides are a class of systems which exhibit coupling between the electrical polarization and the magnetization. These materials show promise to lead to devices in which ferromagnetic memory can be written with magnetic fields or magnetic bits can be written by an electric field. The work conducted in our research focuses on single phase materials. We studied the detailed coupling of the spin and lattice correlations in these systems. In the first phase of the proposal, we explored the complex spin spiral systems and low temperature behavior of hexagonal layered REMnO 3 (RE= rare earth, Y and Sc) systemmore » following the detailed structural changes which occurred on crossing into the magnetic states. The techniques were applied to other layered materials such as superconductors and thermoelectric where the same layered motif exists. The second phase of the proposal focused on understanding the mechanisms involved in the onset high temperature ferroelectricity ion hexagonal REMnO 3 and at low temperature in E-Type magnetic ordered perovskite REMnO 3. We wsynthesized preovskite small A site multiferroics by high pressure and high temperature methods. Detailed measurement of the structural properties and dynamics were conducted over a range of length scales from atomic to mesoscopic scale using, x-ray absorption spectroscopy, x-ray diffuse scattering, x-ray and neutron pair distribution analysis and high resolution x-ray diffraction. Changes in vibration modes which occur with the onset of polarization were probed with temperature and pressure dependent infrared absorption spectroscopy. In addition the orthorhombic system (small radius RE ions) which is believed to exhibit electronically driven ferroelectricity and is also not understood was examined. The multiple length scale synchrotron based measurements may assist in developing more detailed models of these materials and possibly lead to device applications. The experimental work was complemented by density functional methods to determine the magnetic ground states and ab initio molecular dynamics methods (AIMD) to determine the high temperature structures. Simulation were carried out on supercomputers at the National Energy Research Scientific Computing Center (NERSC). An important contribution of this work was the training of graduate students and postdoctoral researchers in materials synthesis, high pressure methods and synchrotron based spectroscopy and x-ray scattering techniques.« less

Theoretical detection limit of PIXE analysis using 20 MeV proton beams

NASA Astrophysics Data System (ADS)

Ishii, Keizo; Hitomi, Keitaro

2018-02-01

Particle-induced X-ray emission (PIXE) analysis is usually performed using proton beams with energies in the range 2∼3 MeV because at these energies, the detection limit is low. The detection limit of PIXE analysis depends on the X-ray production cross-section, the continuous background of the PIXE spectrum and the experimental parameters such as the beam currents and the solid angle and detector efficiency of X-ray detector. Though the continuous background increases as the projectile energy increases, the cross-section of the X-ray increases as well. Therefore, the detection limit of high energy proton PIXE is not expected to increase significantly. We calculated the cross sections of continuous X-rays produced in several bremsstrahlung processes and estimated the detection limit of a 20 MeV proton PIXE analysis by modelling the Compton tail of the γ-rays produced in the nuclear reactions, and the escape effect on the secondary electron bremsstrahlung. We found that the Compton tail does not affect the detection limit when a thin X-ray detector is used, but the secondary electron bremsstrahlung escape effect does have an impact. We also confirmed that the detection limit of the PIXE analysis, when used with 4 μm polyethylene backing film and an integrated beam current of 1 μC, is 0.4∼2.0 ppm for proton energies in the range 10∼30 MeV and elements with Z = 16-90. This result demonstrates the usefulness of several 10 MeV cyclotrons for performing PIXE analysis. Cyclotrons with these properties are currently installed in positron emission tomography (PET) centers.

Measurement of the natHf(d,x)177Ta cross section and impact of erroneous gamma-ray intensities

NASA Astrophysics Data System (ADS)

Simonelli, F.; Abbas, K.; Bulgheroni, A.; Pommé, S.; Altzitzoglou, T.; Suliman, G.

2012-08-01

In this work, excitation functions for deuteron-induced reactions on natural hafnium have been measured in the energy range 7-17 MeV, using the stacked-foil technique. Particular attention has been paid to the reaction natHf(d,x)177Ta, because reported γ-ray intensities have been found to be in disagreement with previously published data. This discrepancy is due to an error in the 2003 ENSDF absolute γ-ray intensities of 177Hf following the decay of 177Ta, which are about a factor of three higher compared to other available data. As a consquence, some peer reviewed papers reporting on natHf(d,x)177Ta, and also on natHf(p,x) 177Ta and natW(p,x) 177Ta, need to be reviewed. An upcoming re-evaluation of the 177Ta decay data shows new significant changes in the absolute γ-ray intensities, which in turn will affect again the 177Ta producing cross sections.

Simultaneous Monitoring of X-Ray and Radio Variability in Sagittarius A*

NASA Astrophysics Data System (ADS)

Capellupo, Daniel M.; Haggard, Daryl; Choux, Nicolas; Baganoff, Fred; Bower, Geoffrey C.; Cotton, Bill; Degenaar, Nathalie; Dexter, Jason; Falcke, Heino; Fragile, P. Chris; Heinke, Craig O.; Law, Casey J.; Markoff, Sera; Neilsen, Joey; Ponti, Gabriele; Rea, Nanda; Yusef-Zadeh, Farhad

2017-08-01

Monitoring of Sagittarius A* from X-ray to radio wavelengths has revealed structured variability—including X-ray flares—but it is challenging to establish correlations between them. Most studies have focused on variability in the X-ray and infrared, where variations are often simultaneous, and because long time series at submillimeter and radio wavelengths are limited. Previous work on submillimeter and radio variability hints at a lag between X-ray flares and their candidate submillimeter or radio counterparts, with the long wavelength data lagging the X-ray. However, there is only one published time lag between an X-ray flare and a possible radio counterpart. Here we report nine contemporaneous X-ray and radio observations of Sgr A*. We detect significant radio variability peaking ≳ 176 minutes after the brightest X-ray flare ever detected from Sgr A*. We also report other potentially associated X-ray and radio variability, with the radio peaks appearing ≲ 80 minutes after these weaker X-ray flares. Taken at face value, these results suggest that stronger X-ray flares lead to longer time lags in the radio. However, we also test the possibility that the variability at X-ray and radio wavelengths is not temporally correlated. We cross-correlate data from mismatched X-ray and radio epochs and obtain comparable correlations to the matched data. Hence, we find no overall statistical evidence that X-ray flares and radio variability are correlated, underscoring a need for more simultaneous, long duration X-ray-radio monitoring of Sgr A*.

The cosmic X-ray background-IRAS galaxy correlation and the local X-ray volume emissivity

NASA Technical Reports Server (NTRS)

Miyaji, Takamitsu; Lahav, Ofer; Jahoda, Keith; Boldt, Elihu

1994-01-01

We have cross-correlated the galaxies from the IRAS 2 Jy redshift survey sample and the 0.7 Jy projected sample with the all-sky cosmic X-ray background (CXB) map obtained from the High Energy Astronomy Observatory (HEAO) 1 A-2 experiment. We have detected a significant correlation signal between surface density of IRAS galaxies and the X-ray background intensity, with W(sub xg) = (mean value of ((delta I)(delta N)))/(mean value of I)(mean value of N)) of several times 10(exp -3). While this correlation signal has a significant implication for the contribution of the local universe to the hard (E greater than 2 keV) X-ray background, its interpretation is model-dependent. We have developed a formulation to model the cross-correlation between CXB surface brightness and galaxy counts. This includes the effects of source clustering and the X-ray-far-infrared luminosity correlation. Using an X-ray flux-limited sample of active galactic nuclei (AGNs), which has IRAS 60 micrometer measurements, we have estimated the contribution of the AGN component to the observed CXB-IRAS galaxy count correlations in order to see whether there is an excess component, i.e., contribution from low X-ray luminosity sources. We have applied both the analytical approach and Monte Carlo simulations for the estimations. Our estimate of the local X-ray volume emissivity in the 2-10 keV band is rho(sub x) approximately = (4.3 +/- 1.2) x 10(exp 38) h(sub 50) ergs/s/cu Mpc, consistent with the value expected from the luminosity function of AGNs alone. This sets a limit to the local volume emissivity from lower luminosity sources (e.g., star-forming galaxies, low-ionization nuclear emission-line regions (LINERs)) to rho(sub x) less than or approximately = 2 x 10(exp 38) h(sub 50) ergs/s/cu Mpc.

The Complete Local Volume Groups Sample - I. Sample selection and X-ray properties of the high-richness subsample

NASA Astrophysics Data System (ADS)

O'Sullivan, Ewan; Ponman, Trevor J.; Kolokythas, Konstantinos; Raychaudhury, Somak; Babul, Arif; Vrtilek, Jan M.; David, Laurence P.; Giacintucci, Simona; Gitti, Myriam; Haines, Chris P.

2017-12-01

We present the Complete Local-Volume Groups Sample (CLoGS), a statistically complete optically selected sample of 53 groups within 80 Mpc. Our goal is to combine X-ray, radio and optical data to investigate the relationship between member galaxies, their active nuclei and the hot intra-group medium (IGM). We describe sample selection, define a 26-group high-richness subsample of groups containing at least four optically bright (log LB ≥ 10.2 LB⊙) galaxies, and report the results of XMM-Newton and Chandra observations of these systems. We find that 14 of the 26 groups are X-ray bright, possessing a group-scale IGM extending at least 65 kpc and with luminosity >1041 erg s-1, while a further three groups host smaller galaxy-scale gas haloes. The X-ray bright groups have masses in the range M500 ≃ 0.5-5 × 1013 M⊙, based on system temperatures of 0.4-1.4 keV, and X-ray luminosities in the range 2-200 × 1041 erg s-1. We find that ∼53-65 per cent of the X-ray bright groups have cool cores, a somewhat lower fraction than found by previous archival surveys. Approximately 30 per cent of the X-ray bright groups show evidence of recent dynamical interactions (mergers or sloshing), and ∼35 per cent of their dominant early-type galaxies host active galactic nuclei with radio jets. We find no groups with unusually high central entropies, as predicted by some simulations, and confirm that CLoGS is in principle capable of detecting such systems. We identify three previously unrecognized groups, and find that they are either faint (LX, R500 < 1042 erg s-1) with no concentrated cool core, or highly disturbed. This leads us to suggest that ∼20 per cent of X-ray bright groups in the local universe may still be unidentified.

X-ray induced mutations in jute (Corchorus capsularis L. and Corchorus olitorius L.)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, D.P.; Sharma, B.K.; Banerjee, S.C.

1973-09-30

Dry dormant seeds of three varieties of jute (C. capsularis & b. olitorius), which yield commercial fibers, were irradiated with different doses of x-rays ranging from 10 kR to 100 kR at 10 kR intervals. The percentage of germination, survival rates, the resulting morphological abnormalities in different generations, the total abnormalities, the total mutation frequency including chlorophyll mutations, and the complete, mutation spectrum are described in detail. Mutations were classified into different groups and each mutant was briefly described. Several directly useful mutations were observed with emphasis on the fiber yield. Interesting results were obtained after crossing mutants, where themore » first high yielding hybrid was evolved by the senior author. (auth)« less

X-Ray Form Factor, Attenuation and Scattering Tables

National Institute of Standards and Technology Data Gateway

SRD 66 X-Ray Form Factor, Attenuation and Scattering Tables (Web, free access)   This database collects tables and graphs of the form factors, the photoabsorption cross section, and the total attenuation coefficient for any element (Z <= 92).

FAST TRACK COMMUNICATION Far-field x-ray phase contrast imaging has no detailed information on the object

NASA Astrophysics Data System (ADS)

Kohn, V. G.; Argunova, T. S.; Je, J. H.

2010-11-01

We show that x-ray phase contrast images of some objects with a small cross-section diameter d satisfy a condition for a far-field approximation d Lt r1 where r1 = (λz)1/2, λ is the x-ray wavelength, z is the distance from the object to the detector. In this case the size of the image does not match the size of the object contrary to the edge detection technique. Moreover, the structure of the central fringes of the image is universal, i.e. it is independent of the object cross-section structure. Therefore, these images have no detailed information on the object.

Evaluation of computational models and cross sections used by MCNP6 for simulation of characteristic X-ray emission from thick targets bombarded by kiloelectronvolt electrons

NASA Astrophysics Data System (ADS)

Poškus, A.

2016-09-01

This paper evaluates the accuracy of the single-event (SE) and condensed-history (CH) models of electron transport in MCNP6.1 when simulating characteristic Kα, total K (=Kα + Kβ) and Lα X-ray emission from thick targets bombarded by electrons with energies from 5 keV to 30 keV. It is shown that the MCNP6.1 implementation of the CH model for the K-shell impact ionization leads to underestimation of the K yield by 40% or more for the elements with atomic numbers Z < 15 and overestimation of the Kα yield by more than 40% for the elements with Z > 25. The Lα yields are underestimated by more than an order of magnitude in CH mode, because MCNP6.1 neglects X-ray emission caused by electron-impact ionization of L, M and higher shells in CH mode (the Lα yields calculated in CH mode reflect only X-ray fluorescence, which is mainly caused by photoelectric absorption of bremsstrahlung photons). The X-ray yields calculated by MCNP6.1 in SE mode (using ENDF/B-VII.1 library data) are more accurate: the differences of the calculated and experimental K yields are within the experimental uncertainties for the elements C, Al and Si, and the calculated Kα yields are typically underestimated by (20-30)% for the elements with Z > 25, whereas the Lα yields are underestimated by (60-70)% for the elements with Z > 49. It is also shown that agreement of the experimental X-ray yields with those calculated in SE mode is additionally improved by replacing the ENDF/B inner-shell electron-impact ionization cross sections with the set of cross sections obtained from the distorted-wave Born approximation (DWBA), which are also used in the PENELOPE code system. The latter replacement causes a decrease of the average relative difference of the experimental X-ray yields and the simulation results obtained in SE mode to approximately 10%, which is similar to accuracy achieved with PENELOPE. This confirms that the DWBA inner-shell impact ionization cross sections are significantly more accurate than the corresponding ENDF/B cross sections when energy of incident electrons is of the order of the binding energy.

Excited state X-ray absorption spectroscopy: Probing both electronic and structural dynamics

NASA Astrophysics Data System (ADS)

Neville, Simon P.; Averbukh, Vitali; Ruberti, Marco; Yun, Renjie; Patchkovskii, Serguei; Chergui, Majed; Stolow, Albert; Schuurman, Michael S.

2016-10-01

We investigate the sensitivity of X-ray absorption spectra, simulated using a general method, to properties of molecular excited states. Recently, Averbukh and co-workers [M. Ruberti et al., J. Chem. Phys. 140, 184107 (2014)] introduced an efficient and accurate L 2 method for the calculation of excited state valence photoionization cross-sections based on the application of Stieltjes imaging to the Lanczos pseudo-spectrum of the algebraic diagrammatic construction (ADC) representation of the electronic Hamiltonian. In this paper, we report an extension of this method to the calculation of excited state core photoionization cross-sections. We demonstrate that, at the ADC(2)x level of theory, ground state X-ray absorption spectra may be accurately reproduced, validating the method. Significantly, the calculated X-ray absorption spectra of the excited states are found to be sensitive to both geometric distortions (structural dynamics) and the electronic character (electronic dynamics) of the initial state, suggesting that core excitation spectroscopies will be useful probes of excited state non-adiabatic dynamics. We anticipate that the method presented here can be combined with ab initio molecular dynamics calculations to simulate the time-resolved X-ray spectroscopy of excited state molecular wavepacket dynamics.

Line Ratios for Solar Wind Charge Exchange with Comets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mullen, P. D.; Cumbee, R. S.; Lyons, D.

Charge exchange (CX) has emerged in X-ray emission modeling as a significant process that must be considered in many astrophysical environments—particularly comets. Comets host an interaction between solar wind ions and cometary neutrals to promote solar wind charge exchange (SWCX). X-ray observatories provide astronomers and astrophysicists with data for many X-ray emitting comets that are impossible to accurately model without reliable CX data. Here, we utilize a streamlined set of computer programs that incorporate the multi-channel Landau–Zener theory and a cascade model for X-ray emission to generate cross sections and X-ray line ratios for a variety of bare and non-baremore » ion single electron capture (SEC) collisions. Namely, we consider collisions between the solar wind constituent bare and H-like ions of C, N, O, Ne, Na, Mg, Al, and Si and the cometary neutrals H{sub 2}O, CO, CO{sub 2}, OH, and O. To exemplify the application of this data, we model the X-ray emission of Comet C/2000 WM1 (linear) using the CX package in SPEX and find excellent agreement with observations made with the XMM-Newton RGS detector. Our analyses show that the X-ray intensity is dominated by SWCX with H, while H{sub 2}O plays a secondary role. This is the first time, to our knowledge, that CX cross sections have been implemented into a X-ray spectral fitting package to determine the H to H{sub 2}O ratio in cometary atmospheres. The CX data sets are incorporated into the modeling packages SPEX and Kronos .« less

Cross sections of X-ray production induced by C and Si ions with energies up to 1 MeV/u on Ti, Fe, Zn, Nb, Ru and Ta

NASA Astrophysics Data System (ADS)

Prieto, José Emilio; Zucchiatti, Alessandro; Galán, Patricia; Prieto, Pilar

2017-09-01

X-ray production differential cross sections induced by C and Si ions with energies from 1 MeV/u down to 0.25 MeV/u, produced by the CMAM 5 MV tandem accelerator, have been measured for thin targets of Ti, Fe, Zn, Nb, Ru and Ta in a direct way. X-rays have been detected by a fully characterized silicon drift diode and beam currents have been measured by a system of two Faraday cups. Measured cross sections agree in general with previously published results. The ECPSSR theory with the united atoms correction gives absolute values close to the experimental ones for all the studied elements excited by C ions and for Ta, Nb and Ru excited by Si ions. For Ti, Fe and Zn excited by Si, the matching with theory is poor since even the ionization cross section is below the measured data.

Magnetic resonance imaging analyses of varved marine sedimentary records of the Gulf of California

NASA Astrophysics Data System (ADS)

Briskin, Madeleine; Robins, Jon; Riedel, William R.; Booker, Ron

1986-08-01

Nuclear Magnetic Resonance Imaging used for the first time to analyze marine sedimentary records of the Gulf of California is a remarkable improvement over the more conventional X-ray technique in the identification of organic rich layers. Analytical results indicate that NMRI differentiates clearly between organic rich (light) and organic poor (dark) deposits. It also provides a fine resolution of sedimentary structures, laminae and stratigraphic subtleties. It may be made to yield a three-dimensional stratigraphy; the procedure is nondestructive. The organic vs. inorganic resolution provided by NMRI technology complemented by X-ray when needed should facilitate future studies of paleoceanographic, paleoclimatic and biogeochemical cycles recorded in the vast deposits of marine clays.

A Review of Recent Developments in X-Ray Diagnostics for Turbulent and Optically Dense Rocket Sprays

NASA Technical Reports Server (NTRS)

Radke, Christopher; Halls, Benjamin; Kastengren, Alan; Meyer, Terrence

2017-01-01

Highly efficient mixing and atomization of fuel and oxidizers is an important factor in many propulsion and power generating applications. To better quantify breakup and mixing in atomizing sprays, several diagnostic techniques have been developed to collect droplet information and spray statistics. Several optical based techniques, such as Ballistic Imaging and SLIPI have previously demonstrated qualitative measurements in optically dense sprays, however these techniques have produced limited quantitative information in the near injector region. To complement to these advances, a recent wave of developments utilizing synchrotron based x-rays have been successful been implemented facilitating the collection of quantitative measurements in optically dense sprays.

Arcus: Exploring the formation and evolution of clusters, galaxies, and stars

NASA Astrophysics Data System (ADS)

Smith, Randall K.

2017-08-01

Arcus, a proposed soft X-ray grating spectrometer Explorer, leverages recent advances in critical-angle transmission (CAT) gratings and silicon pore optics (SPOs), using CCDs with strong Suzaku heritage and electronics based on the Swift mission; both the spacecraft and mission operations reuse highly successful designs. To be launched in 2023, Arcus will be the only observatory capable of studying, in detail, the hot galactic and intergalactic gas that is the dominant baryonic component of the present-day Universe and ultimate reservoir of entropy, metals and the output from cosmic feedback. Its superior soft (12-50Å) X-ray sensitivity will complement forthcoming calorimeters, which will have comparably high spectral resolution above 2 keV.

Symbiotic Stars in X-rays

NASA Technical Reports Server (NTRS)

Luna, G. J. M.; Sokoloski, J. L.; Mukai, K.; Nelson, T.

2014-01-01

Until recently, symbiotic binary systems in which a white dwarf accretes from a red giant were thought to be mainly a soft X-ray population. Here we describe the detection with the X-ray Telescope (XRT) on the Swift satellite of 9 white dwarf symbiotics that were not previously known to be X-ray sources and one that was previously detected as a supersoft X-ray source. The 9 new X-ray detections were the result of a survey of 41 symbiotic stars, and they increase the number of symbiotic stars known to be X-ray sources by approximately 30%. Swift/XRT detected all of the new X-ray sources at energies greater than 2 keV. Their X-ray spectra are consistent with thermal emission and fall naturally into three distinct groups. The first group contains those sources with a single, highly absorbed hard component, which we identify as probably coming from an accretion-disk boundary layer. The second group is composed of those sources with a single, soft X-ray spectral component, which likely arises in a region where low-velocity shocks produce X-ray emission, i.e. a colliding-wind region. The third group consists of those sources with both hard and soft X-ray spectral components. We also find that unlike in the optical, where rapid, stochastic brightness variations from the accretion disk typically are not seen, detectable UV flickering is a common property of symbiotic stars. Supporting our physical interpretation of the two X-ray spectral components, simultaneous Swift UV photometry shows that symbiotic stars with harder X-ray emission tend to have stronger UV flickering, which is usually associated with accretion through a disk. To place these new observations in the context of previous work on X-ray emission from symbiotic stars, we modified and extended the alpha/beta/gamma classification scheme for symbiotic-star X-ray spectra that was introduced by Muerset et al. based upon observations with the ROSAT satellite, to include a new sigma classification for sources with hard X-ray emission from the innermost accretion region. Since we have identified the elusive accretion component in the emission from a sample of symbiotic stars, our results have implications for the understanding of wind-fed mass transfer in wide binaries, and the accretion rate in one class of candidate progenitors of type Ia supernovae.

Ionization cross sections of the Au L subshells by electron impact from the L3 threshold to 100 keV

NASA Astrophysics Data System (ADS)

Barros, Suelen F.; Vanin, Vito R.; Maidana, Nora L.; Martins, Marcos N.; García-Alvarez, Juan A.; Santos, Osvaldo C. B.; Rodrigues, Cleber L.; Koskinas, Marina F.; Fernández-Varea, José M.

2018-01-01

We measured the cross sections for Au Lα, Lβ, Lγ, Lℓ and Lη x-ray production by the impact of electrons with energies from the L3 threshold to 100 keV using a thin Au film whose mass thickness was determined by Rutherford Backscattering Spectrometry. The x-ray spectra were acquired with a Si drift detector, which allowed to separate the components of the Lγ multiplet lines. The measured Lα, Lβ, {{L}}{γ }1, L{γ }{2,3,6}, {{L}}{γ }{4,4\\prime }, {{L}}{γ }5, {{L}}{\\ell } and Lη x-ray production cross sections were then employed to derive Au L1, L2 and L3 subshell ionization cross sections with relative uncertainties of 8%, 7% and 7%, respectively; these figures include the uncertainties in the atomic relaxation parameters. The correction for the increase in electron path length inside the Au film was estimated by means of Monte Carlo simulations. The experimental ionization cross sections are about 10% above the state-of-the-art distorted-wave calculations.

Chandra-SDSS Normal and Star-Forming Galaxies. I. X-Ray Source Properties of Galaxies Detected by the Chandra X-Ray Observatory in SDSS DR2

NASA Astrophysics Data System (ADS)

Hornschemeier, A. E.; Heckman, T. M.; Ptak, A. F.; Tremonti, C. A.; Colbert, E. J. M.

2005-01-01

We have cross-correlated X-ray catalogs derived from archival Chandra X-Ray Observatory ACIS observations with a Sloan Digital Sky Survey Data Release 2 (DR2) galaxy catalog to form a sample of 42 serendipitously X-ray-detected galaxies over the redshift interval 0.03

The Temporal Development of Dust Formation and Destruction in Nova Sagittarii 2015#2 (V5668 SGR): A Panchromatic Study

NASA Astrophysics Data System (ADS)

Gehrz, R. D.; Evans, A.; Woodward, C. E.; Helton, L. A.; Banerjee, D. P. K.; Srivastava, M. K.; Ashok, N. M.; Joshi, V.; Eyres, S. P. S.; Krautter, Joachim; Kuin, N. P. M.; Page, K. L.; Osborne, J. P.; Schwarz, G. J.; Shenoy, D. P.; Shore, S. N.; Starrfield, S. G.; Wagner, R. M.

2018-05-01

We present 5–28 μm SOFIA FORECAST spectroscopy complemented by panchromatic X-ray through infrared observations of the CO nova V5668 Sgr documenting the formation and destruction of dust during ∼500 days following outburst. Dust condensation commenced by 82 days after outburst at a temperature of ∼1090 K. The condensation temperature indicates that the condensate was amorphous carbon. There was a gradual decrease of the grain size and dust mass during the recovery phase. Absolute parameter values given here are for an assumed distance of 1.2 kpc. We conclude that the maximum mass of dust produced was 1.2 × 10‑7 M ⊙ if the dust was amorphous carbon. The average grain radius grew to a maximum of ∼2.9 μm at a temperature of ∼720 K around day 113 when the shell visual optical depth was τ v ∼ 5.4. Maximum grain growth was followed by a period of grain destruction. X-rays were detected with Swift from day 95 to beyond day 500. The Swift X-ray count rate due to the hot white dwarf peaked around day 220, when its spectrum was that of a kT = 35 eV blackbody. The temperature, together with the supersoft X-ray turn-on and turn-off times, suggests a white dwarf mass of ∼1.1 M ⊙. We show that the X-ray fluence was sufficient to destroy the dust. Our data show that the post-dust event X-ray brightening is not due to dust destruction, which certainly occurred, as the dust is optically thin to X-rays.

Recent Developments in X-Ray Diagnostics for Cryogenic and Optically Dense Coaxial Rocket Sprays

NASA Technical Reports Server (NTRS)

Radke, Christopher D.; Kastengren, Alan L.; Meyer, Terrence R.

2017-01-01

The mixing and atomization of propellants is often characterized by optically dense flow fields and complex breakup dynamics. In the development of propulsion systems, the complexity of relevant physics and the range of spatio-temporal scales often makes computational simulation impractical for full scale injector elements; consequently, continued research into improved systems for experimental flow diagnostics is ongoing. One area of non-invasive flow diagnostics which has seen widespread growth is using synchrotron based x-ray diagostics. Over the past 3 years, a series of water and cryogenic based experiments were performed at the Advanced Photon Source, Argonne National Lab, on a NASA in-house designed swirl co-axial rocket injector, designed for operation using liquid oxygen and liquid methane in support of Project Morpheus. A range of techniques, such as x-ray fluorescence and time-averaged radiography were performed providing qualitative and quantitative mass and phase distributions, and were complemented by investigations using time-resolved radiography and white beam imaging, which provided information on breakup and mixing dynamics. Results of these investigations are presented, and conclusions regarding the viability of x-ray based diagnostics are discussed.

Autonomous Modelling of X-ray Spectra Using Robust Global Optimization Methods

NASA Astrophysics Data System (ADS)

Rogers, Adam; Safi-Harb, Samar; Fiege, Jason

2015-08-01

The standard approach to model fitting in X-ray astronomy is by means of local optimization methods. However, these local optimizers suffer from a number of problems, such as a tendency for the fit parameters to become trapped in local minima, and can require an involved process of detailed user intervention to guide them through the optimization process. In this work we introduce a general GUI-driven global optimization method for fitting models to X-ray data, written in MATLAB, which searches for optimal models with minimal user interaction. We directly interface with the commonly used XSPEC libraries to access the full complement of pre-existing spectral models that describe a wide range of physics appropriate for modelling astrophysical sources, including supernova remnants and compact objects. Our algorithm is powered by the Ferret genetic algorithm and Locust particle swarm optimizer from the Qubist Global Optimization Toolbox, which are robust at finding families of solutions and identifying degeneracies. This technique will be particularly instrumental for multi-parameter models and high-fidelity data. In this presentation, we provide details of the code and use our techniques to analyze X-ray data obtained from a variety of astrophysical sources.

Radiation damage in protein crystals examined under various conditions by different methods.

PubMed

Garman, Elspeth F; Nave, Colin

2009-03-01

Investigation of radiation damage in protein crystals has progressed in several directions over the past couple of years. There have been improvements in the basic procedures such as calibration of the incident X-ray intensity and calculation of the dose likely to be deposited in a crystal of known size and composition with this intensity. There has been increased emphasis on using additional techniques such as optical, Raman or X-ray spectroscopy to complement X-ray diffraction. Apparent discrepancies between the results of different techniques can be explained by the fact that they are sensitive to different length scales or to changes in the electronic state rather than to movement of atoms. Investigations have been carried out at room temperature as well as cryo-temperatures and, in both cases, with the introduction of potential scavenger molecules. These and other studies are leading to an overall description of the changes which can occur when a protein crystal is irradiated with X-rays at both cryo- and room temperatures. Results from crystallographic and spectroscopic radiation-damage experiments can be reconciled with other studies in the field of radiation physics and chemistry.

Beamline P02.1 at PETRA III for high-resolution and high-energy powder diffraction

PubMed Central

Dippel, Ann-Christin; Liermann, Hanns-Peter; Delitz, Jan Torben; Walter, Peter; Schulte-Schrepping, Horst; Seeck, Oliver H.; Franz, Hermann

2015-01-01

Powder X-ray diffraction techniques largely benefit from the superior beam quality provided by high-brilliance synchrotron light sources in terms of photon flux and angular resolution. The High Resolution Powder Diffraction Beamline P02.1 at the storage ring PETRA III (DESY, Hamburg, Germany) combines these strengths with the power of high-energy X-rays for materials research. The beamline is operated at a fixed photon energy of 60 keV (0.207 Å wavelength). A high-resolution monochromator generates the highly collimated X-ray beam of narrow energy bandwidth. Classic crystal structure determination in reciprocal space at standard and non-ambient conditions are an essential part of the scientific scope as well as total scattering analysis using the real space information of the pair distribution function. Both methods are complemented by in situ capabilities with time-resolution in the sub-second regime owing to the high beam intensity and the advanced detector technology for high-energy X-rays. P02.1’s efficiency in solving chemical and crystallographic problems is illustrated by presenting key experiments that were carried out within these fields during the early stage of beamline operation. PMID:25931084

Development of variable-magnification X-ray Bragg optics.

PubMed

Hirano, Keiichi; Yamashita, Yoshiki; Takahashi, Yumiko; Sugiyama, Hiroshi

2015-07-01

A novel X-ray Bragg optics is proposed for variable-magnification of an X-ray beam. This X-ray Bragg optics is composed of two magnifiers in a crossed arrangement, and the magnification factor, M, is controlled through the azimuth angle of each magnifier. The basic properties of the X-ray optics such as the magnification factor, image transformation matrix and intrinsic acceptance angle are described based on the dynamical theory of X-ray diffraction. The feasibility of the variable-magnification X-ray Bragg optics was verified at the vertical-wiggler beamline BL-14B of the Photon Factory. For X-ray Bragg magnifiers, Si(220) crystals with an asymmetric angle of 14° were used. The magnification factor was calculated to be tunable between 0.1 and 10.0 at a wavelength of 0.112 nm. At various magnification factors (M ≥ 1.0), X-ray images of a nylon mesh were observed with an air-cooled X-ray CCD camera. Image deformation caused by the optics could be corrected by using a 2 × 2 transformation matrix and bilinear interpolation method. Not only absorption-contrast but also edge-contrast due to Fresnel diffraction was observed in the magnified images.

Light ion induced L X-ray production cross-sections in Au and Pb

NASA Astrophysics Data System (ADS)

Ouziane, S.; Amokrane, A.; Toumert, I.

2008-04-01

Experimental proton-induced Lα, Lβ, Lγ, Lℓ and Ltot absolute X-ray production cross-sections for Au and Pb in the incident proton energy range between 1 and 2.5 MeV are presented. The experimental results for X-ray production cross-sections are compared to available data given in Sokhi and Crumpton [R.S. Sokhi, D. Crumpton, At. Data Nucl. Data Tables 30 (1984) 49], Jesus et al. [A.P. Jesus, J.S. Lopes, J.P. Ribeiro, J. Phys. B: At. Mol. Phys. 18 (1985) 2456; A.P. Jesus, T.M. Pinheiro, I.A. Nisa, J.P. Ribeiro, J.S. Lopes, Nucl. Instrum. Methods B15 (1986) 95] and Goudarzi et al. [M. Goudarzi, F. Shokouhi, M. Lamehi-Rachti, P.Olialiy, Nucl. Instrum. Methods Phys. Res. B247 (2006) 218]. The given data are also compared with the predictions of ECPSSR model [W. Brandt, G. Lapicki, Phys. Rev. A23 (1981) 1717].

Theoretical X-ray production cross sections at incident photon energies across Li (i=1-3) absorption edges of Br

NASA Astrophysics Data System (ADS)

Puri, Sanjiv

2015-08-01

The X-ray production (XRP) cross sections, σLk (k = l, η, α, β6, β1, β3, β4, β9,10, γ1,5, γ2,3) have been evaluated at incident photon energies across the Li(i=1-3) absorption edge energies of 35Br using theoretical data sets of different physical parameters, namely, the Li(i=1-3) sub-shell the X-ray emission rates based on the Dirac-Fock (DF) model, the fluorescence and Coster Kronig yields based on the Dirac-Hartree-Slater (DHS) model, and two sets of the photoionisation cross sections based on the relativistic Hartree-Fock-Slater (RHFS) model and the Dirac-Fock (DF) model, in order to highlight the importance of electron exchange effects at photon energies in vicinity of absorption edge energies.

LoCuSS: The infall of X-ray groups onto massive clusters

NASA Astrophysics Data System (ADS)

Haines, C. P.; Finoguenov, A.; Smith, G. P.; Babul, A.; Egami, E.; Mazzotta, P.; Okabe, N.; Pereira, M. J.; Bianconi, M.; McGee, S. L.; Ziparo, F.; Campusano, L. E.; Loyola, C.

2018-03-01

Galaxy clusters are expected to form hierarchically in a ΛCDM universe, growing primarily through mergers with lower mass clusters and the continual accretion of group-mass halos. Galaxy clusters assemble late, doubling their masses since z ˜ 0.5, and so the outer regions of clusters should be replete with accreting group-mass systems. We present an XMM-Newton survey to search for X-ray groups in the infall regions of 23 massive galaxy clusters ( ˜ 1015 M⊙) at z ˜ 0.2, identifying 39 X-ray groups that have been spectroscopically confirmed to lie at the cluster redshift. These groups have mass estimates in the range 2 × 1013 - 7 × 1014 M⊙, and group-to-cluster mass ratios as low as 0.02. The comoving number density of X-ray groups in the infall regions is ˜25 × higher than that seen for isolated X-ray groups from the XXL survey. The average mass per cluster contained within these X-ray groups is 2.2 × 1014 M⊙, or 19 ± 5% of the mass within the primary cluster itself. We estimate that ˜1015 M⊙ clusters increase their masses by 16 ± 4% between z = 0.223 and the present day due to the accretion of groups with M200 ≥ 1013.2 M⊙. This represents about half of the expected mass growth rate of clusters at these late epochs. The other half is likely to come from smooth accretion of matter not bound within halos. The mass function of the infalling X-ray groups appears significantly top heavy with respect to that of "field" X-ray systems, consistent with expectations from numerical simulations, and the basic consequences of collapsed massive dark matter halos being biased tracers of the underlying large-scale density distribution.

LoCuSS: The infall of X-ray groups on to massive clusters

NASA Astrophysics Data System (ADS)

Haines, C. P.; Finoguenov, A.; Smith, G. P.; Babul, A.; Egami, E.; Mazzotta, P.; Okabe, N.; Pereira, M. J.; Bianconi, M.; McGee, S. L.; Ziparo, F.; Campusano, L. E.; Loyola, C.

2018-07-01

Galaxy clusters are expected to form hierarchically in a Λ cold dark matter (ΛCDM) universe, growing primarily through mergers with lower mass clusters and the continual accretion of group-mass haloes. Galaxy clusters assemble late, doubling their masses since z ˜ 0.5, and so the outer regions of clusters should be replete with accreting group-mass systems. We present an XMM-Newton survey to search for X-ray groups in the infall regions of 23 massive galaxy clusters ( ˜ 1015 M⊙) at z ˜ 0.2, identifying 39 X-ray groups that have been spectroscopically confirmed to lie at the cluster redshift. These groups have mass estimates in the range 2 × 1013-7 × 1014 M⊙, and group-to-cluster mass ratios as low as 0.02. The comoving number density of X-ray groups in the infall regions is ˜25× higher than that seen for isolated X-ray groups from the XXL survey. The average mass per cluster contained within these X-ray groups is 2.2 × 1014 M⊙, or 19 ± 5 per cent of the mass within the primary cluster itself. We estimate that ˜1015 M⊙ clusters increase their masses by 16 ± 4 per cent between z = 0.223 and the present day due to the accretion of groups with M200 ≥ 1013.2 M⊙. This represents about half of the expected mass growth rate of clusters at these late epochs. The other half is likely to come from smooth accretion of matter not bound within haloes. The mass function of the infalling X-ray groups appears significantly top heavy with respect to that of `field' X-ray systems, consistent with expectations from numerical simulations, and the basic consequences of collapsed massive dark matter haloes being biased tracers of the underlying large-scale density distribution.

Nondestructive Imaging of Internal Structures of Frog (Xenopus laevis) Embryos by Shadow-Projection X-Ray Microtomography

NASA Astrophysics Data System (ADS)

Aoki, Sadao; Yoneda, Ikuo; Nagai, Takeharu; Ueno, Naoto; Murakami, Kazuo

1994-04-01

Nondestructive high-resolution imaging of frog ( Xenopus laevis) embryos has been developed by X-ray microtomography. Shadow-projection X-ray microtomography with a brilliant fine focus laboratory X-ray source could image fine structures of Xenopus embryos which were embedded in paraffin wax. The imaging system enabled us to not only distinguish endoderm from ectoderm at the gastrula stage, but also to obtain a cross-section view of the tail bud embryo showing muscle, notochord and neural tube without staining. Furthermore, the distribution of myosin was also imaged in combination with whole-mount immunohistochemistry.

Melatonin and roentgen irradiation-induced acute radiation enteritis in Albino rats: an animal model.

PubMed

Hussein, Mahmoud R; Abu-Dief, Eman E; Kamel, Esam; Abou El-Ghait, Amal T; Abdulwahed, Saad Rezk; Ahmad, Mohamed H

2008-11-01

Roentgen irradiation can affect normal cells, especially the rapidly growing ones such as the mucosal epithelial cells of the small intestine. The small intestine is the most radiosensitive gastrointestinal organ and patients receiving radiotherapy directed to the abdomen or pelvis may develop radiation enteritis. Although roentgen rays are widely used for both imaging and therapeutic purposes, our knowledge about the morphological changes associated with radiation enteritis is lacking. This study tries to tests the hypothesis that "the intake of melatonin can minimize the morphological features of cell damage associated with radiation enteritis". We performed this investigation to test our hypothesis and to examine the possible radioprotective effects of melatonin in acute radiation enteritis. To achieve these goals, an animal model consisting of 60 Albino rats was established. The animals were divided into five groups: Group 1, non-irradiated; Group 2, X-ray irradiated (X-ray irradiation, 8 Grays); Group 3, X-ray irradiated-pretreated with solvent (ethanol and phosphate buffered saline); Group 4, non-irradiated-group treated with melatonin, and Group 5, X-ray irradiated-pretreated with melatonin. The small intestines were evaluated for gross (macroscopic), histological, morphometric (light microscopy), and ultrastructural changes (transmission electron microscopy). We found morphological variations among the non-irradiated-group, X-ray irradiated-group and X-ray irradiated-intestines of the animals pretreated with melatonin. The development of acute radiation enteritis in X-ray irradiated-group (Groups 2 and 3) was associated with symptoms of enteritis (diarrhea and abdominal distention) and histological features of mucosal injury (mucosal ulceration, necrosis of the epithelial cells). There was a significant reduction of the morphometric parameters (villous count, villous height, crypt height and villous/crypt height ratio). Moreover, the ultrastructural features of cell damage were evident including: apoptosis, lack of parallel arrangement of the microvilli, loss of the covering glycocalyx, desquamation of the microvilli, vacuolation of the apical parts of the cells, dilatation of the rough endoplasmic reticulum, and damage of the mitochondrial cristae. In the non-irradiated-group and in X-ray irradiated-intestines of the animals pretreated with melatonin (Group 5), these changes were absent and the intestinal mucosal structure was preserved. Administration of melatonin prior to irradiation can protect the intestine against X-rays destructive effects, i.e. radiation enteritis. The clinical applications of these observations await further studies.

The X-Ray Background and the AGN Luminosity Function

NASA Astrophysics Data System (ADS)

Hasinger, G.

The deepest X-ray surveys performed with ROSAT were able to resolve as much as 70-80% of the 1-2 keV X-ray background into resolved sources. Optical follow-up observations were able to identify the majority of faint X-ray sources as active galactic nuclei (AGN) out to redshifts of 4.5 as well as a sizeable fraction as groups of galaxies out to redshifts of 0.7. A new population of X-ray luminous, optically innocent narrow emission line galaxies (NELGs) at the faintest X-ray fluxes is still a matter of debate, most likely many of them are also connected to AGN. First deep surveys with the Japanese ASCA satellite give us a glimpse of the harder X-ray background where the bulk of the energy density resides. Future X-ray observatories (XMM and AXAF) will be able to resolve the harder X-ray background. For the first time we are now in a position to study the cosmological evolution of the X-ray luminosity function of AGN, groups of galaxies and galaxies and simultaneously constrain their total luminosity output over cosmic time.

Synchrotron-based ambient pressure X-ray photoelectron spectroscopy of hydrogen and helium

DOE PAGES

Zhong, Jian-Qiang; Wang, Mengen; Hoffmann, William H.; ...

2018-03-01

Contrary to popular belief, it is possible to obtain X-ray photoelectron spectra for elements lighter than lithium, namely hydrogen and helium. The literature is plagued with claims of this impossibility, which holds true for lab-based X-ray sources. However, this limitation is merely technical and is related mostly to the low X-ray photoionization cross-sections of the 1s orbitals of hydrogen and helium. Here, we show that, using ambient pressure X-ray photoelectron spectroscopy (XPS), a bright-enough X-ray source allows the study of these elusive elements. This has important implications in the understanding of the limitations of one of the most useful techniquesmore » in materials science, and moreover, it potentially opens the possibility of using XPS to directly study the most abundant element in the universe.« less

Synchrotron-based ambient pressure X-ray photoelectron spectroscopy of hydrogen and helium

NASA Astrophysics Data System (ADS)

Zhong, Jian-Qiang; Wang, Mengen; Hoffmann, William H.; van Spronsen, Matthijs A.; Lu, Deyu; Boscoboinik, J. Anibal

2018-02-01

Contrary to popular belief, it is possible to obtain X-ray photoelectron spectra for elements lighter than lithium, namely hydrogen and helium. The literature is plagued with claims of this impossibility, which holds true for lab-based X-ray sources. However, this limitation is merely technical and is related mostly to the low X-ray photoionization cross-sections of the 1s orbitals of hydrogen and helium. In this letter, we show that, using ambient pressure X-ray photoelectron spectroscopy (XPS), a bright-enough X-ray source allows the study of these elusive elements. This has important implications in the understanding of the limitations of one of the most useful techniques in materials science, and moreover, it potentially opens the possibility of using XPS to directly study the most abundant element in the universe.

Synchrotron-based ambient pressure X-ray photoelectron spectroscopy of hydrogen and helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Jian-Qiang; Wang, Mengen; Hoffmann, William H.

Contrary to popular belief, it is possible to obtain X-ray photoelectron spectra for elements lighter than lithium, namely hydrogen and helium. The literature is plagued with claims of this impossibility, which holds true for lab-based X-ray sources. However, this limitation is merely technical and is related mostly to the low X-ray photoionization cross-sections of the 1s orbitals of hydrogen and helium. Here, we show that, using ambient pressure X-ray photoelectron spectroscopy (XPS), a bright-enough X-ray source allows the study of these elusive elements. This has important implications in the understanding of the limitations of one of the most useful techniquesmore » in materials science, and moreover, it potentially opens the possibility of using XPS to directly study the most abundant element in the universe.« less

Molecularly Designed Ultrafine/Nanostructured Materials

DTIC Science & Technology

1994-04-08

Ti. UdIOVic. R R, Cananaeh. /iXn. S. Kawi, T. Mure, and B1 C Gates STUDIIES OF- NANOSTRUCTURED M50 TYPE STEEL USING X - RAY AB3SORPTION SPFECTROSCOPY...hydrogenation of titanium or zirconium sponges and related systems and as a powerful activator for heterogeneous hydrogenation catalysts. X - ray ... X - ray diffraction). Quantitave measurements of the gas evolved during the reduction (1 mol H2 per mol Ti), protonolysis and cross experiments using K

Simultaneous Monitoring of X-ray and Radio Variability in Sagittarius A*

NASA Astrophysics Data System (ADS)

Haggard, Daryl; Capellupo, Daniel M.; Choux, Nicolas; Baganoff, Frederick K.; Bower, Geoffrey C.; Cotton, William D.; Degenaar, Nathalie; Dexter, Jason; Falcke, Heino; Fragile, P. Christopher Christopher; Heinke, Craig O.; Law, Casey J.; Markoff, Sera; Neilsen, Joseph; Ponti, Gabriele; Rea, Nanda; Yusef-Zadeh, Farhad

2017-08-01

We report on joint X-ray/radio campaigns targeting Sagittarius A*, including 9 contemporaneous Chandra and VLA observations. These campaigns are the most extensive of their kind and have allowed us to test whether the black hole’s variations in different parts of the electromagnetic spectrum are due to the same physical processes. We detect significant radio variability peaking >176 minutes after the brightest X-ray flare ever detected from Sgr A*. We also identify other potentially associated X-ray and radio variability, with radio peaks appearing <80 minutes after weaker X-ray flares. These results suggest that stronger X-ray flares lead to longer time lags in the radio. However, we also test the possibility that the variability at X-ray and at radio wavelengths are not temporally correlated, and show that the radio variations occurring around the time of X-ray flaring are not significantly greater than the overall radio flux variations. We also cross-correlate data from mismatched X-ray and radio epochs and obtain comparable correlations to the matched data. Hence, we find no overall statistical evidence that X-ray flares and radio variability are correlated, underscoring a need for more simultaneous, long duration X-ray-radio monitoring of Sgr A*.

3D morphological characterization of the polyamide active layer of RO and NF membranes using TEM and soft X-ray scattering

NASA Astrophysics Data System (ADS)

Culp, Tyler; Paul, Mou; Roy, Abhishek; Rosenberg, Steve; Behr, Michael; Kumar, Manish; Gomez, Enrique; Penn State Team; Dow Team

Polyamide-based thin-film composite (TFC) membranes used for reverse osmosis (RO) and nanofiltration (NF) separation processes are at the forefront of water desalination and purification technologies due to their high salt rejection, high energy efficiency, and ease of operation. Nevertheless, in spite of the benefits of RO and NF membranes, many open questions about the internal nanostructure of the membrane active layer remain, such as the dispersion and distribution of acid functional groups. We demonstrate that resonant soft X-ray scattering (RSOXS), where the X-ray energy is tuned to absorption edges of the constituent materials, is a powerful tool to examine the microstructure of the polyamide layer. In conjunction with complementary techniques such as transmission electron microscopy (TEM), where tomography is used to obtain a 3D reconstruction of the polyamide active layer, the effect of cross-linking can be quantified in 3D for a systematic series of membranes. This relationship can then be applied to a series of commercially available RO and NF membranes where the effect of polyamide cross-linking on their respective structure and water transport properties can be evaluated. The combination of RSOXS with traditional characterization tools provides a strategy for linking the chemical structure to the morphology and water transport properties of RO and NF membranes.

Studies in the X-Ray Emission of Clusters of Galaxies and Other Topics

NASA Technical Reports Server (NTRS)

Vrtilek, Jan; Thronson, Harley (Technical Monitor)

2001-01-01

The paper discusses the following: (1) X-ray study of groups of galaxies with Chandra and XMM. (2) X-ray properties of point sources in Chandra deep fields. (3) Study of cluster substructure using wavelet techniques. (4) Combined study of galaxy clusters with X-ray and the S-Z effect. Groups of galaxies are the fundamental building blocks of large scale structure in the Universe. X-ray study of the intragroup medium offers a powerful approach to addressing some of the major questions that still remain about almost all aspects of groups: their ages, origins, importance of composition of various galaxy types, relations to clusters, and origin and enrichment of the intragroup gas. Long exposures with Chandra have opened new opportunities for the study of X-ray background. The presence of substructure within clusters of galaxies has substantial implications for our understanding of cluster evolution as well as fundamental questions in cosmology.

MAXI/GSC 7-year Source Catalog

NASA Astrophysics Data System (ADS)

Ueda, Y.; Kawamuro, T.; Hori, T.; Shidatsu, M.; Tanimoto, A.; MAXI Team

2017-10-01

Monitor of All-sky X-ray Image (MAXI) on the International Space Station has been continuously observing the X-ray sky since its launch in 2009. The MAXI survey has achieved the best sensitivity in the 4-10 keV band as an all sky X-ray mission, and is complementary to the ROSAT all sky survey (<2 keV) and hard X-ray (>10 keV) surveys performed with Swift and INTEGRAL. Here we present the latest source catalog of MAXI/Gas Slit Camera (GSC) constructed from the first 7-year data, which is an extension of the 37-month catalog of the high Galactic-latitude sky (Hiroi et al. 2013). We summarize statistical properties of the X-ray sources and results of cross identification with other catalogs.

Mesoscale imaging with cryo-light and X-rays: Larger than molecular machines, smaller than a cell: Mesoscale imaging with cryo-light and X-rays

DOE PAGES

Ekman, Axel A.; Chen, Jian-Hua; Guo, Jessica; ...

2016-11-14

In the context of cell biology, the term mesoscale describes length scales ranging from that of an individual cell, down to the size of the molecular machines. In this spatial regime, small building blocks self-organise to form large, functional structures. A comprehensive set of rules governing mesoscale self-organisation has not been established, making the prediction of many cell behaviours difficult, if not impossible. Our knowledge of mesoscale biology comes from experimental data, in particular, imaging. Here, we explore the application of soft X-ray tomography (SXT) to imaging the mesoscale, and describe the structural insights this technology can generate. We alsomore » discuss how SXT imaging is complemented by the addition of correlative fluorescence data measured from the same cell. This combination of two discrete imaging modalities produces a 3D view of the cell that blends high-resolution structural information with precise molecular localisation data.« less

Studying Ultradisperse Diamond Structure within Explosively Synthesized Samples via X-Ray Techniques

NASA Astrophysics Data System (ADS)

Sharkov, M. D.; Boiko, M. E.; Ivashevskaya, S. N.; Belyakova, N. S.

2013-08-01

XRD (X-Ray Diffraction) and SAXS (Small-Angle X-Ray Scattering) data have been measured for a pair of samples produced with the help of explosives. XRD peaks have shown the both samples to contain crystal diamond components as well as graphite ones. Basing on SAXS analysis, possible presence of grains with radii up to 30-50 nm within all the samples has been shown. Structure components with fractal dimension between 1 and 2 in the sample have been detected, this fact being in agreement with the assumption of diamond grain coating similarity to onion shells. In order to broad rocking curves analysis, the standard SAXS treatment technique has been complemented by a Fourier filtering procedure. For the sample #1, rocking curve components corresponding to individual interplanar distances with magnitudes from 5 nm up to 15 nm have been separated. A hypothesis relating these values to the distances between concentric onion-like shells of diamond grains has been formulated.

Local structure and defects in ion irradiated KTaO3

NASA Astrophysics Data System (ADS)

Zhang, F. X.; Xi, J.; Zhang, Y.; Tong, Yang; Xue, H.; Huang, R.; Trautmann, C.; Weber, W. J.

2018-04-01

The modification of the local structure in cubic perovskite KTaO3 irradiated with 3 MeV and 1.1 GeV Au ions is studied by Raman and x-ray absorption spectroscopy, complemented by density functional theory (DFT) calculations. In the case of irradiation with 3 MeV Au ions where displacement cascade processes are dominant, the Ta L3-edge x-ray absorption measurements suggest that a peak corresponding to the Ta-O bonds in the TaO6 octahedra splits, which is attributed to the formation of TaK antisite defects that are coupled with oxygen vacancies, V O. This finding is consistent with the DFT calculations. Under irradiation with 1.1 GeV ions, the intense ionization and electronic energy deposition lead to a blue shift and an intensity reduction of active Raman bands. In the case of sequential irradiations, extended x-ray absorption fine structure measurements reveal a decrease in concentration of coupled TaK-V O defects under subsequent irradiation with 1.1 GeV Au ions.

Musculoskeletal complaints among Italian X-ray technology students: a cross-sectional questionnaire survey

PubMed Central

2010-01-01

Background There is a high prevalence of musculoskeletal disorders among healthcare professional students. Although recent studies show musculoskeletal disorders are a common problem among X-ray technologists, there are no data on these disorders among students of this healthcare profession. We have therefore estimated the prevalence of musculoskeletal complaints among a group of X-ray technology students. Methods The students (n = 109) currently attending the 3-year X-ray technologist school at a large University in the Apulia region of Southern Italy were recruited for the study, with a 100% participation rate. A questionnaire collected data concerning personal characteristics, physical exposure during training activities, and the presence of musculoskeletal symptoms in the neck, shoulders, low back, hand/wrist and legs. Results The prevalence of complaints in any body site over the previous 12 months was 37%. Low back pain was the most frequently reported symptom (27%), followed by neck (16%), shoulder (11%), leg (8%) and hand/wrist (5%) pain. Poor physical activity was associated with the complaints. Conclusions Our study showed prevalence rates of musculoskeletal complaints among X-ray technology students to be somewhat high, representing about half of those found in Italian technologists. The most common musculoskeletal problem was low back pain, which had also been found in research conducted among nursing students. Our research also showed a significant association between poor physical activity and the presence of musculoskeletal disorders in young university students. PMID:20416101

Establishment of a Photon Data Section of the BNL National Nuclear Data Center: A preliminary proposal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, A.L.; Pearlstein, S.

1992-05-01

It is proposed to establish a Photon Data Section (PDS) of the BNL National Nuclear Data Center (NNDC). This would be a total program encompassing both photon-atom and photon-nucleus interactions. By utilizing the existing NNDC data base management expertise and on-line access capabilities, the implementation of photon interaction data activities within the existing NNDC nuclear structure and nuclear-reaction activities can reestablish a viable photon interaction data program at minimum cost. By taking advantage of the on-line capabilities, the x-ray users' community will have access to a dynamic, state-of-the-art data base of interaction information. The proposed information base would include datamore » that presently are scattered throughout the literature usually in tabulated form. It is expected that the data bases would include at least the most precise data available in photoelectric cross sections, atomic form factors and incoherent scattering functions, anomalous scattering factors, oscillator strengths and oscillator densities, fluorescence yields, Auger electron yields, etc. It could also include information not presently available in tabulations or in existing data bases such as EXAFS (extended x-ray absorption fine structure) reference spectra, chemical bonding induced shifts in the photoelectric absorption edge, matrix corrections, x-ray Raman, and x-ray resonant Raman cross sections. The data base will also include the best estimates of the accuracy of the interaction data as it exists in the data base. It is proposed that the PDS would support computer programs written for calculating scattering cross sections for given solid angles, sample geometries, and polarization of incident x-rays, for calculating Compton profiles, and for analyzing data as in EXAFS and x-ray fluorescence.« less

Establishment of a Photon Data Section of the BNL National Nuclear Data Center: A preliminary proposal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, A.L.; Pearlstein, S.

1992-05-01

It is proposed to establish a Photon Data Section (PDS) of the BNL National Nuclear Data Center (NNDC). This would be a total program encompassing both photon-atom and photon-nucleus interactions. By utilizing the existing NNDC data base management expertise and on-line access capabilities, the implementation of photon interaction data activities within the existing NNDC nuclear structure and nuclear-reaction activities can reestablish a viable photon interaction data program at minimum cost. By taking advantage of the on-line capabilities, the x-ray users` community will have access to a dynamic, state-of-the-art data base of interaction information. The proposed information base would include datamore » that presently are scattered throughout the literature usually in tabulated form. It is expected that the data bases would include at least the most precise data available in photoelectric cross sections, atomic form factors and incoherent scattering functions, anomalous scattering factors, oscillator strengths and oscillator densities, fluorescence yields, Auger electron yields, etc. It could also include information not presently available in tabulations or in existing data bases such as EXAFS (extended x-ray absorption fine structure) reference spectra, chemical bonding induced shifts in the photoelectric absorption edge, matrix corrections, x-ray Raman, and x-ray resonant Raman cross sections. The data base will also include the best estimates of the accuracy of the interaction data as it exists in the data base. It is proposed that the PDS would support computer programs written for calculating scattering cross sections for given solid angles, sample geometries, and polarization of incident x-rays, for calculating Compton profiles, and for analyzing data as in EXAFS and x-ray fluorescence.« less

Protective role of Aloe vera against X-ray induced testicular dysfunction.

PubMed

Bala, S; Chugh, N A; Bansal, S C; Garg, M L; Koul, A

2017-09-01

The present investigation was carried out to evaluate the possible radioprotective potential of an Aloe vera extract against whole-body X-ray irradiation-induced testicular alterations in mice. Male balb/c mice were divided into four groups: control, A. vera, X-ray and A. vera pre-treated + X-ray irradiated. Histopathological examination revealed significant structural alterations in testes after X-ray exposure, which was also associated with the presence of apoptotic cells as assessed by TUNEL assay. X-ray irradiation resulted in elevation in the levels of reactive oxygen species, lipid peroxidation, a reduction in glutathione concentration and enhanced activities of antioxidant enzymes such as glutathione reductase, glutathione peroxidase, catalase, superoxide dismutase and glutathione-S-transferase. Sperm count/motility and testosterone levels were significantly decreased in the irradiated group. Irradiated animals pre-treated with A. vera extract revealed an improvement in antioxidant status, inhibition of lipid peroxides, apoptotic cell formation and enhanced testicular parameters when compared to the X-ray-exposed group. These findings suggest that A. vera extract could ameliorate X-ray-induced damage due to its free radical scavenging properties and its potential to boost cellular antioxidant defence machinery. © 2016 Blackwell Verlag GmbH.

New Spectral Model for Constraining Torus Covering Factors from Broadband X-Ray Spectra of Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Baloković, M.; Brightman, M.; Harrison, F. A.; Comastri, A.; Ricci, C.; Buchner, J.; Gandhi, P.; Farrah, D.; Stern, D.

2018-02-01

The basic unified model of active galactic nuclei (AGNs) invokes an anisotropic obscuring structure, usually referred to as a torus, to explain AGN obscuration as an angle-dependent effect. We present a new grid of X-ray spectral templates based on radiative transfer calculations in neutral gas in an approximately toroidal geometry, appropriate for CCD-resolution X-ray spectra (FWHM ≥ 130 eV). Fitting the templates to broadband X-ray spectra of AGNs provides constraints on two important geometrical parameters of the gas distribution around the supermassive black hole: the average column density and the covering factor. Compared to the currently available spectral templates, our model is more flexible, and capable of providing constraints on the main torus parameters in a wider range of AGNs. We demonstrate the application of this model using hard X-ray spectra from NuSTAR (3–79 keV) for four AGNs covering a variety of classifications: 3C 390.3, NGC 2110, IC 5063, and NGC 7582. This small set of examples was chosen to illustrate the range of possible torus configurations, from disk-like to sphere-like geometries with column densities below, as well as above, the Compton-thick threshold. This diversity of torus properties challenges the simple assumption of a standard geometrically and optically thick toroidal structure commonly invoked in the basic form of the unified model of AGNs. Finding broad consistency between our constraints and those from infrared modeling, we discuss how the approach from the X-ray band complements similar measurements of AGN structures at other wavelengths.

Hard X-ray quiescent emission in magnetars via resonant Compton upscattering

NASA Astrophysics Data System (ADS)

Baring, M. G.; Wadiasingh, Z.; Gonthier, P. L.; Harding, A. K.

2017-12-01

Non-thermal quiescent X-ray emission extending between 10 keV and around 150 keV has been seen in about 10 magnetars by RXTE, INTEGRAL, Suzaku, NuSTAR and Fermi-GBM. For inner magnetospheric models of such hard X-ray signals, inverse Compton scattering is anticipated to be the most efficient process for generating the continuum radiation, because the scattering cross section is resonant at the cyclotron frequency. We present hard X-ray upscattering spectra for uncooled monoenergetic relativistic electrons injected in inner regions of pulsar magnetospheres. These model spectra are integrated over bundles of closed field lines and obtained for different observing perspectives. The spectral turnover energies are critically dependent on the observer viewing angles and electron Lorentz factor. We find that electrons with energies less than around 15 MeV will emit most of their radiation below 250 keV, consistent with the turnovers inferred in magnetar hard X-ray tails. Electrons of higher energy still emit most of the radiation below around 1 MeV, except for quasi-equatorial emission locales for select pulse phases. Our spectral computations use a new state-of-the-art, spin-dependent formalism for the QED Compton scattering cross section in strong magnetic fields.

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic-Inorganic Lead Halide Perovskites.

PubMed

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina; Sadoughi, Golnaz; Habisreutinger, Severin N; Félix, Roberto; Wilks, Regan G; Snaith, Henry J; Bär, Marcus; Draxl, Claudia

2018-04-19

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3 ) hybrid inorganic-organic perovskite and its binary phase PbI 2 . The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. The theoretical analysis complementing experimental observations provides the conceptual insights required for a full characterization of this complex material.

Intermediate-energy inverse-kinematics one-proton pickup reactions on neutron-deficient fp-shell nuclei

NASA Astrophysics Data System (ADS)

McDaniel, S.; Gade, A.; Tostevin, J. A.; Baugher, T.; Bazin, D.; Brown, B. A.; Cook, J. M.; Glasmacher, T.; Grinyer, G. F.; Ratkiewicz, A.; Weisshaar, D.

2012-01-01

Background: Thick-target-induced nucleon-adding transfer reactions onto energetic rare-isotope beams are an emerging spectroscopic tool. Their sensitivity to single-particle structure complements one-nucleon removal reaction capabilities in the quest to reveal the evolution of nuclear shell structure in very exotic nuclei. Purpose: Our purpose is to add intermediate-energy, carbon-target-induced one-proton pickup reactions to the arsenal of γ-ray-tagged direct reactions applicable in the regime of low beam intensities and to apply these for the first time to fp-shell nuclei. Methods: Inclusive and partial cross sections were measured for the 12C(48Cr,49Mn+γ)X and 12C(50Fe,51Co+γ)X proton pickup reactions at 56.7 and 61.2 MeV/nucleon, respectively, using coincident particle-γ spectroscopy at the National Superconducting Cyclotron Laboratory. The results are compared to reaction theory calculations using fp-shell-model nuclear structure input. For comparison with our previous work, the same reactions were measured on 9Be targets. Results: The measured partial cross sections confirm the specific population pattern predicted by theory, with pickup into high-ℓ orbitals being strongly favored, driven by linear and angular momentum matching. Conclusion: Carbon-target-induced pickup reactions are well suited, in the regime of modest beam intensity, to study the evolution of nuclear structure, with specific sensitivities that are well described by theory.

X-ray stars observed in LAMOST spectral survey

NASA Astrophysics Data System (ADS)

Lu, Hong-peng; Zhang, Li-yun; Han, Xianming L.; Shi, Jianrong

2018-05-01

X-ray stars have been studied since the beginning of X-ray astronomy. Investigating and studying the chromospheric activity from X-ray stellar optical spectra is highly significant in providing insights into stellar magnetic activity. The big data of LAMOST survey provides an opportunity for researching stellar optical spectroscopic properties of X-ray stars. We inferred the physical properties of X-ray stellar sources from the analysis of LAMOST spectra. First, we cross-matched the X-ray stellar catalogue (12254 X-ray stars) from ARXA with LAMOST data release 3 (DR3), and obtained 984 good spectra from 713 X-ray sources. We then visually inspected and assigned spectral type to each spectrum and calculated the equivalent width (EW) of Hα line using the Hammer spectral typing facility. Based on the EW of Hα line, we found 203 spectra of 145 X-ray sources with Hα emission above the continuum. For these spectra we also measured the EWs of Hβ, Hγ, Hδ and Ca ii IRT lines of these spectra. After removing novae, planetary nebulae and OB-type stars, we found there are 127 X-ray late-type stars with Hα line emission. By using our spectra and results from the literature, we found 53 X-ray stars showing Hα variability; these objects are Classical T Tauri stars (CTTs), cataclysmic variables (CVs) or chromospheric activity stars. We also found 18 X-ray stars showing obvious emissions in the Ca ii IRT lines. Of the 18 X-ray stars, 16 are CTTs and 2 are CVs. Finally, we discussed the relationships between the EW of Hα line and X-ray flux.

Fabricating Blazed Diffraction Gratings by X-Ray Lithography

NASA Technical Reports Server (NTRS)

Mouroulis, Pantazis; Hartley, Frank; Wilson, Daniel

2004-01-01

Gray-scale x-ray lithography is undergoing development as a technique for fabricating blazed diffraction gratings. As such, gray-scale x-ray lithography now complements such other grating-fabrication techniques as mechanical ruling, holography, ion etching, laser ablation, laser writing, and electron-beam lithography. Each of these techniques offers advantages and disadvantages for implementing specific grating designs; no single one of these techniques can satisfy the design requirements for all applications. Gray-scale x-ray lithography is expected to be advantageous for making gratings on steeper substrates than those that can be made by electron-beam lithography. This technique is not limited to sawtooth groove profiles and flat substrates: various groove profiles can be generated on arbitrarily shaped (including highly curved) substrates with the same ease as sawtooth profiles can be generated on flat substrates. Moreover, the gratings fabricated by this technique can be made free of ghosts (spurious diffraction components attributable to small spurious periodicities in the locations of grooves). The first step in gray-scale x-ray lithography is to conformally coat a substrate with a suitable photoresist. An x-ray mask (see Figure 1) is generated, placed between the substrate and a source of collimated x-rays, and scanned over the substrate so as to create a spatial modulation in the exposure of the photoresist. Development of the exposed photoresist results in a surface corrugation that corresponds to the spatial modulation and that defines the grating surface. The grating pattern is generated by scanning an appropriately shaped x-ray area mask along the substrate. The mask example of Figure 1 would generate a blazed grating profile when scanned in the perpendicular direction at constant speed, assuming the photoresist responds linearly to incident radiation. If the resist response is nonlinear, then the mask shape can be modified to account for the nonlinearity and produce a desired groove profile. An example of grating grooves generated by this technique is shown in Figure 2. A maximum relative efficiency of 88 percent has been demonstrated.

In-depth study of long-term variability in the X-ray emission of the Be/X-ray binary system AX J0049.4-7323

NASA Astrophysics Data System (ADS)

Ducci, L.; Romano, P.; Malacaria, C.; Ji, L.; Bozzo, E.; Santangelo, A.

2018-06-01

AX J0049.4-7323 is a Be/X-ray binary in the Small Magellanic Cloud hosting a 750 s pulsar which has been observed over the last 17 years by several X-ray telescopes. Despite numerous observations, little is known about its X-ray behaviour. Therefore, we coherently analysed archival Swift, Chandra, XMM-Newton, RXTE, and INTEGRAL data, and we compared them with already published ASCA data, to study its X-ray long-term spectral and flux variability. AX J0049.4-7323 shows a high X-ray variability, spanning more than three orders of magnitudes, from L ≈ 1.6 × 1037 erg s-1 (0.3-8 keV, d = 62 kpc) down to L ≈ 8 × 1033 erg s-1. RXTE, Chandra, Swift, and ASCA observed, in addition to the expected enhancement of X-ray luminosity at periastron, flux variations by a factor of 270 with peak luminosities of ≈2.1 × 1036 erg s-1 far from periastron. These properties are difficult to reconcile with the typical long-term variability of Be/XRBs, traditionally interpreted in terms of type I and type II outbursts. The study of AX J0049.4-7323 is complemented with a spectral analysis of Swift, Chandra, and XMM-Newton data which showed a softening trend when the emission becomes fainter, and an analysis of optical/UV data collected by the UVOT telescope on board Swift. In addition, we measured a secular spin-up rate of Ṗ = (-3.00 ± 0.12) × 10-3 s day-1, which suggests that the pulsar has not yet achieved its equilibrium period. Assuming spherical accretion, we estimated an upper limit for the magnetic field strength of the pulsar of ≈3 × 1012 G.

HIGH PRECISION K-SHELL PHOTOABSORPTION CROSS SECTIONS FOR ATOMIC OXYGEN: EXPERIMENT AND THEORY

DOE Office of Scientific and Technical Information (OSTI.GOV)

McLaughlin, B. M.; Ballance, C. P.; Bowen, K. P.

2013-07-01

Photoabsorption of atomic oxygen in the energy region below the 1s {sup -1} threshold in X-ray spectroscopy from Chandra and XMM-Newton is observed in a variety of X-ray binary spectra. Photoabsorption cross sections determined from an R-matrix method with pseudo-states and new, high precision measurements from the Advanced Light Source (ALS) are presented. High-resolution spectroscopy with E/{Delta}E Almost-Equal-To 4250 {+-} 400 was obtained for photon energies from 520 eV to 555 eV at an energy resolution of 124 {+-} 12 meV FWHM. K-shell photoabsorption cross section measurements were made with a re-analysis of previous experimental data on atomic oxygen atmore » the ALS. Natural line widths {Gamma} are extracted for the 1s {sup -1}2s {sup 2}2p {sup 4}({sup 4} P)np {sup 3} P Degree-Sign and 1s {sup -1}2s {sup 2}2p {sup 4}({sup 2} P)np {sup 3} P Degree-Sign Rydberg resonances series and compared with theoretical predictions. Accurate cross sections and line widths are obtained for applications in X-ray astronomy. Excellent agreement between theory and the ALS measurements is shown which will have profound implications for the modeling of X-ray spectra and spectral diagnostics.« less

CXRO - Mi-Young Im, Staff Scientist

Science.gov Websites

X-Ray Database Zone Plate Education Nanomagnetism X-Ray Microscopy LDJIM EUV Lithography EUV Mask Publications Contact The Center for X-Ray Optics is a multi-disciplined research group within Lawrence Berkeley -Ray Optics X-Ray Database Nanomagnetism X-Ray Microscopy EUV Lithography EUV Mask Imaging

Study of a chemically amplified resist for X-ray lithography by Fourier transform infrared spectroscopy.

PubMed

Tan, T L; Wong, D; Lee, P; Rawat, R S; Patran, A

2004-11-01

Future applications of microelectromechanical systems (MEMS) require lithographic performance of very high aspect ratio. Chemically amplified resists (CARs) such as the negative tone commercial SU-8 provide critical advantages in sensitivity, resolution, and process efficiency in deep ultraviolet, electron-beam, and X-ray lithographies (XRLs), which result in a very high aspect ratio. In this investigation, an SU-8 resist was characterized and optimized for X-ray lithographic applications by studying the cross-linking process of the resist under different conditions of resist thickness and X-ray exposure dose. The exposure dose of soft X-ray (SXR) irradiation at the average weighted wavelength of 1.20 nm from a plasma focus device ranges from 100 to 1600 mJ/cm(2) on the resist surface. Resist thickness varies from 3.5 to 15 mum. The cross-linking process of the resist during post-exposure bake (PEB) was accurately monitored using Fourier transform infrared (FT-IR) spectroscopy. The infrared absorption peaks at 862, 914, 972, and 1128 cm(-1) in the spectrum of the SU-8 resist were found to be useful indicators for the completion of cross-linking in the resist. Results of the experiments showed that the cross-linking of SU-8 was optimized at the exposure dose of 800 mJ/cm(2) for resist thicknesses of 3.5, 9.5, and 15 microm. PEB temperature was set at 95 degrees C and time at 3 min. The resist thickness was measured using interference patterns in the FT-IR spectra of the resist. Test structures with an aspect ratio 3:1 on 10 microm thick SU-8 resist film were obtained using scanning electron microscopy (SEM).

Topics in Astrophysical X-Ray and Gamma Ray Spectroscopy. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Bussard, R. W.

1978-01-01

A number of topics relating to astrophysical observations that have already been made or are currently planned of spectral features, mostly emission lines, in the X-ray and gamma ray region of the electromagnetic spectrum are investigated. These topics include: the production of characteristic X-ray and gamma ray lines by nonthermal ions, spectral features induced by processes occurring in strong magnetic fields, and the positron annihilation line at 0.5 MeV. The rate of X-ray production at 6.8 keV by the 2p to 1s transition in fast hydrogen- and helium-like iron ions, following both electron capture to excited levels and collisional excitation is calculated. The cross section for electron-ion Coulomb collisions in strong fields is also calculated.

Advances in x-ray framing cameras at the National Ignition Facility to improve quantitative precision in x-ray imaging

DOE PAGES

Benedetti, L. R.; Holder, J. P.; Perkins, M.; ...

2016-02-26

We describe an experimental method to measure the gate profile of an x-ray framing camera and to determine several important functional parameters: relative gain (between strips), relative gain droop (within each strip), gate propagation velocity, gate width, and actual inter-strip timing. Several of these parameters cannot be measured accurately by any other technique. This method is then used to document cross talk-induced gain variations and artifacts created by radiation that arrives before the framing camera is actively amplifying x-rays. Electromagnetic cross talk can cause relative gains to vary significantly as inter-strip timing is varied. This imposes a stringent requirement formore » gain calibration. If radiation arrives before a framing camera is triggered, it can cause an artifact that manifests as a high-intensity, spatially varying background signal. Furthermore, we have developed a device that can be added to the framing camera head to prevent these artifacts.« less

Advances in x-ray framing cameras at the National Ignition Facility to improve quantitative precision in x-ray imaging.

PubMed

Benedetti, L R; Holder, J P; Perkins, M; Brown, C G; Anderson, C S; Allen, F V; Petre, R B; Hargrove, D; Glenn, S M; Simanovskaia, N; Bradley, D K; Bell, P

2016-02-01

We describe an experimental method to measure the gate profile of an x-ray framing camera and to determine several important functional parameters: relative gain (between strips), relative gain droop (within each strip), gate propagation velocity, gate width, and actual inter-strip timing. Several of these parameters cannot be measured accurately by any other technique. This method is then used to document cross talk-induced gain variations and artifacts created by radiation that arrives before the framing camera is actively amplifying x-rays. Electromagnetic cross talk can cause relative gains to vary significantly as inter-strip timing is varied. This imposes a stringent requirement for gain calibration. If radiation arrives before a framing camera is triggered, it can cause an artifact that manifests as a high-intensity, spatially varying background signal. We have developed a device that can be added to the framing camera head to prevent these artifacts.

Ultrafast absorption of intense x rays by nitrogen molecules

NASA Astrophysics Data System (ADS)

Buth, Christian; Liu, Ji-Cai; Chen, Mau Hsiung; Cryan, James P.; Fang, Li; Glownia, James M.; Hoener, Matthias; Coffee, Ryan N.; Berrah, Nora

2012-06-01

We devise a theoretical description for the response of nitrogen molecules (N2) to ultrashort and intense x rays from the free electron laser Linac Coherent Light Source (LCLS). We set out from a rate-equation description for the x-ray absorption by a nitrogen atom. The equations are formulated using all one-x-ray-photon absorption cross sections and the Auger and radiative decay widths of multiply-ionized nitrogen atoms. Cross sections are obtained with a one-electron theory and decay widths are determined from ab initio computations using the Dirac-Hartree-Slater (DHS) method. We also calculate all binding and transition energies of nitrogen atoms in all charge states with the DHS method as the difference of two self-consistent field (SCF) calculations (ΔSCF method). To describe the interaction with N2, a detailed investigation of intense x-ray-induced ionization and molecular fragmentation are carried out. As a figure of merit, we calculate ion yields and the average charge state measured in recent experiments at the LCLS. We use a series of phenomenological models of increasing sophistication to unravel the mechanisms of the interaction of x rays with N2: a single atom, a symmetric-sharing model, and a fragmentation-matrix model are developed. The role of the formation and decay of single and double core holes, the metastable states of N_2^{2+}, and molecular fragmentation are explained.

Li-Like CX

NASA Astrophysics Data System (ADS)

Dorsey, Zachary

2018-06-01

A fantastic discovery in 1996 caused an epiphany when it was realized that the charge exchange (CX) process was an important source of X-ray emission from comets. Over the last two decades, CX induced X-ray emission has been detected in a wide variety of solar and extra-solar sources. Recently, our group developed the Kronos database which contains CX cross sections and emission spectra for all H-like and most He-Like ions up to iron, based primarily on multichannel Landau-Zener calculations. Here we present preliminary results for extending Kronos to Li-like ions. Due to the incompleteness of highly-charged Li-like atomic structure data, we estimate missing energy levels and transition probabilities with a quantum defect approach and the package Autostructure.This work was support by NASA grants NNX13AF31G.

Practical application of cross correlation technique to measure jitter of master-oscillator-power-amplifier laser system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Młyńczak, J.; Sawicz-Kryniger, K.; Fry, A. R.

2014-01-01

The Linac coherent light source (LCLS) at the SLAC National Accelerator Laboratory (SLAC) is the world’s first hard X-ray free electron laser (XFEL) and is capable of producing high-energy, femtosecond duration X-ray pulses. A common technique to study fast timescale physical phenomena, various “pump/probe” techniques are used. In these techniques there are two lasers, one optical and one X-ray, that work as a pump and as a probe to study dynamic processes in atoms and molecules. In order to resolve phenomena that occur on femtosecond timescales, it is imperative to have very precise timing between the optical lasers and X-raysmore » (on the order of ~ 20 fs or better). The lasers are synchronized to the same RF source that drives the accelerator and produces the X-ray laser. However, elements in the lasers cause some drift and time jitter, thereby de-synchronizing the system. This paper considers cross-correlation technique as a way to quantify the drift and jitter caused by the regenerative amplifier of the ultrafast optical laser.« less

AXAF-1 High Resolution Assembly Image Model and Comparison with X-Ray Ground Test Image

NASA Technical Reports Server (NTRS)

Zissa, David E.

1999-01-01

The x-ray ground test of the AXAF-I High Resolution Mirror Assembly was completed in 1997 at the X-ray Calibration Facility at Marshall Space Flight Center. Mirror surface measurements by HDOS, alignment results from Kodak, and predicted gravity distortion in the horizontal test configuration are being used to model the x-ray test image. The Marshall Space Flight Center (MSFC) image modeling serves as a cross check with Smithsonian Astrophysical observatory modeling. The MSFC image prediction software has evolved from the MSFC model of the x-ray test of the largest AXAF-I mirror pair in 1991. The MSFC image modeling software development is being assisted by the University of Alabama in Huntsville. The modeling process, modeling software, and image prediction will be discussed. The image prediction will be compared with the x-ray test results.

Phase-space evolution of x-ray coherence in phase-sensitive imaging.

PubMed

Wu, Xizeng; Liu, Hong

2008-08-01

X-ray coherence evolution in the imaging process plays a key role for x-ray phase-sensitive imaging. In this work we present a phase-space formulation for the phase-sensitive imaging. The theory is reformulated in terms of the cross-spectral density and associated Wigner distribution. The phase-space formulation enables an explicit and quantitative account of partial coherence effects on phase-sensitive imaging. The presented formulas for x-ray spectral density at the detector can be used for performing accurate phase retrieval and optimizing the phase-contrast visibility. The concept of phase-space shearing length derived from this phase-space formulation clarifies the spatial coherence requirement for phase-sensitive imaging with incoherent sources. The theory has been applied to x-ray Talbot interferometric imaging as well. The peak coherence condition derived reveals new insights into three-grating-based Talbot-interferometric imaging and gratings-based x-ray dark-field imaging.

INTRAGROUP AND GALAXY-LINKED DIFFUSE X-RAY EMISSION IN HICKSON COMPACT GROUPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desjardins, Tyler D.; Gallagher, Sarah C.; Tzanavaris, Panayiotis

2013-02-15

Isolated compact groups (CGs) of galaxies present a range of dynamical states, group velocity dispersions, and galaxy morphologies with which to study galaxy evolution, particularly the properties of gas both within the galaxies and in the intragroup medium. As part of a large, multiwavelength examination of CGs, we present an archival study of diffuse X-ray emission in a subset of nine Hickson compact groups (HCGs) observed with the Chandra X-Ray Observatory. We find that seven of the groups in our sample exhibit detectable diffuse emission. However, unlike large-scale emission in galaxy clusters, the diffuse features in the majority of themore » detected groups are linked to the individual galaxies, in the form of both plumes and halos likely as a result of vigourous star formation or activity in the galaxy nucleus, as well as in emission from tidal features. Unlike previous studies from earlier X-ray missions, HCGs 31, 42, 59, and 92 are found to be consistent with the L{sub X} -T relationship from clusters within the errors, while HCGs 16 and 31 are consistent with the cluster L{sub X} -{sigma} relation, though this is likely coincidental given that the hot gas in these two systems is largely due to star formation. We find that L{sub X} increases with decreasing group H I to dynamical-mass ratio with tentative evidence for a dependence in X-ray luminosity on H I morphology whereby systems with intragroup H I indicative of strong interactions are considerably more X-ray luminous than passively evolving groups. We also find a gap in the L{sub X} of groups as a function of the total group specific star formation rate. Our findings suggest that the hot gas in these groups is not in hydrostatic equilibrium and these systems are not low-mass analogs of rich groups or clusters, with the possible exception of HCG 62.« less

Intragroup and Galaxy-linked Diffuse X-ray Emission In Hickson Compact Groups

NASA Technical Reports Server (NTRS)

Desjardins, Tyler D.; Gallagher, Sarah C.; Tzanavaris, Panayiotis; Mulchaey, John S.; Brandt, William N.; Charlton, Jane C.; Garmire, Gordon P.; Gronwall, Caryl; Cardiff, Ann; Johnson, Kelsey E.;

Importance of Doppler broadening in Compton scatter imaging techniques

NASA Astrophysics Data System (ADS)

Rao, Donepudi V.; Takeda, Tohoru; Itai, Yuji; Seltzer, S. M.; Hubbell, John H.; Zeniya, Tsutomu; Akatsuka, Takao; Cesareo, Roberto; Brunetti, Antonio; Gigante, Giovanni E.

2001-12-01

Compton scattering is a potential tool for the determination of bone mineral content or tissue density for dose planning purposes, and requires knowledge of the energy distribution of the X-rays through biological materials of medical interest in the X-ray and (gamma) -ray region. The energy distribution is utilized in a number of ways in diagnostic radiology, for example, in determining primary photon spectra, electron densities in separate volumes, and in tomography and imaging. The choice of the X-ray energy is more related to X-ray absorption, where as that of the scattering angle is more related to geometry. The evaluation of all the contributions are mandatory in Compton profile measurements and is important in X-ray imaging systems in order to achieve good results. In view of this, Compton profile cross-sections for few biological materials are estimated at nineteen K(alpha) X-ray energies and 60 keV (Am-241) photons. Energy broadening, geometrical broadening from 1 to 180 degree(s), FWHM of J(Pz) and FWHM of Compton energy broadening has been evaluated at various incident photon energies. These values are estimated around the centroid of the Compton profile with an energy interval of 0.1 keV and 1.0 keV for 60 keV photons. The interaction cross sections for the above materials are estimated using fractions-by-weight of the constituent elements. Input data for these tables are purely theoretical.

Tiger, Bengal and Domestic Cat Embryos Produced by Homospecific and Interspecific Zona-Free Nuclear Transfer.

PubMed

Moro, L N; Jarazo, J; Buemo, C; Hiriart, M I; Sestelo, A; Salamone, D F

2015-10-01

The aim of this study was to evaluate three different cloning strategies in the domestic cat (Felis silvestris) and to use the most efficient to generate wild felid embryos by interspecific cloning (iSCNT) using Bengal (a hybrid formed by the cross of Felis silvestris and Prionailurus bengalensis) and tiger (Panthera tigris) donor cells. In experiment 1, zona-free (ZP-free) cloning resulted in higher fusion and expanded blastocyst rates with respect to zona included cloning techniques that involved fusion or injection of the donor cell. In experiment 2, ZP-free iSCNT and embryo aggregation (2X) were assessed. Division velocity and blastocyst rates were increased by embryo aggregation in the three species. Despite fewer tiger embryos than Bengal and cat embryos reached the blastocyst stage, Tiger 2X group increased the percentage of blastocysts with respect to Tiger 1X group (3.2% vs 12.1%, respectively). Moreover, blastocyst cell number was almost duplicated in aggregated embryos with respect to non-aggregated ones within Bengal and tiger groups (278.3 ± 61.9 vs 516.8 ± 103.6 for Bengal 1X and Bengal 2X groups, respectively; 41 vs 220 ± 60 for Tiger 1X and Tiger 2X groups, respectively). OCT4 analysis also revealed that tiger blastocysts had higher proportion of OCT4-positive cells with respect to Bengal blastocysts and cat intracytoplasmic sperm injection blastocysts. In conclusion, ZP-free cloning has improved the quality of cat embryos with respect to the other cloning techniques evaluated and was successfully applied in iSCNT complemented with embryo aggregation. © 2015 Blackwell Verlag GmbH.

SIBYLS - a SAXS and Protein Crystallography Beamline at the ALS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trame, C.; MacDowell, A.A.; Celestre, R.S.

2004-05-12

The new Structurally Integrated BiologY for Life Sciences (SIBYLS) beamline at the Advanced Light Source will be dedicated to Macromolecular Crystallography (PX) and Small Angle X-ray Scattering (SAXS). SAXS will provide structural information of macromolecules in solutions and will complement high resolution PX studies on the same systems but in a crystalline state. The x-ray source is one of the 5 Tesla superbend dipoles recently installed at the ALS that allows for a hard x-ray program to be developed on the relatively low energy Advanced Light Source (ALS) ring (1.9 GeV). The beamline is equipped with fast interchangeable monochromator elements,more » consisting of either a pair of single Si(111) crystals for crystallography, or a pair of multilayers for the SAXS mode data collection (E/{delta}E{approx}1/110). Flux rates with Si(111) crystals for PX are measured as 2x1011 hv/sec through a 100{mu}m pinhole at 12.4KeV. For SAXS the flux is up to 3x1013photons/sec at 10KeV with all apertures open when using the multilayer monochromator elements. The performance characteristics of this unique beamline will be described.« less

Characterization of New Hard X-ray Cataclysmic Variables

NASA Technical Reports Server (NTRS)

Bernardini, F.; deMartino, D.; Falanga, M.; Mukai, K.; Matt, G.; Bonnet-Bidaud, J.-M.; Masetti, N.; Mouchet, M.

2012-01-01

Aims. We aim at characterizing a sample of nine new hard X-ray selected Cataclysmic Variable (CVs), to unambiguously identify them as magnetic systems of the Intermediate Polar (IP) type. Methods. We performed detailed timing and spectral analysis by using X-ray, and simultaneous UV and optical data collected by XMM-Newton, complemented with hard X-ray data provided by INTEGRAL and Swift. The pulse arrival time were used to estimate the orbital periods. The broad band X-ray spectra were fitted using composite models consisting of different absorbing columns and emission components. Results. Strong X-ray pulses at the White Dwarf (WD) spin period are detected and found to decrease with energy. Most sources are spin-dominated systems in the X-rays, though four are beat dominated at optical wavelengths. We estimated the orbital period in all system (except for IGR J16500-3307), providing the first estimate for IGRJ08390-4833, IGRJ18308-1232, and IGR J18173-2509. All X-ray spectra are multi-temperature. V2069 Cyg and RX J0636+3535 poses a soft X-ray optically thick component at kT approx. 80 eV. An intense K (sub alpha) Fe line at 6.4 keV is detected in all sources. An absorption edge at 0.76 keV from OVII is detected in IGR J08390-4833. The WD masses and lower limits to the accretion rates are also estimated. Conclusions. We found all sources to be IPs. IGR J08390-4833, V2069 Cyg, and IGR J16500-3307 are pure disc accretors, while IGR J18308-1232, IGR J1509-6649, IGR J17195-4100, and RX J0636+3535 display a disc-overflow accretion mode. All sources show a temperature gradient in the post-shock regions and a highly absorbed emission from material located in the pre-shock flow which is also responsible for the X-ray pulsations. Reflection at the WD surface is likely the origin of the fluorescent iron line. There is an increasing evidence for the presence of a warm absorber in IPs, a feature that needs future exploration. The addition of two systems to the subgroup of soft X-ray IPs confirms a relatively large ( 30%) incidence.

Pharmacogenetic Study in Rectal Cancer Patients Treated With Preoperative Chemoradiotherapy: Polymorphisms in Thymidylate Synthase, Epidermal Growth Factor Receptor, GSTP1, and DNA Repair Genes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paez, David, E-mail: dpaez@santpau.cat; Salazar, Juliana; Pare, Laia

Purpose: Several studies have been performed to evaluate the usefulness of neoadjuvant treatment using oxaliplatin and fluoropyrimidines for locally advanced rectal cancer. However, preoperative biomarkers of outcome are lacking. We studied the polymorphisms in thymidylate synthase, epidermal growth factor receptor, glutathione S-transferase pi 1 (GSTP1), and several DNA repair genes to evaluate their usefulness as pharmacogenetic markers in a cohort of 128 rectal cancer patients treated with preoperative chemoradiotherapy. Methods and Materials: Blood samples were obtained from 128 patients with Stage II-III rectal cancer. DNA was extracted from the peripheral blood nucleated cells, and the genotypes were analyzed by polymerasemore » chain reaction amplification and automated sequencing techniques or using a 48.48 dynamic array on the BioMark system. The germline polymorphisms studied were thymidylate synthase, (VNTR/5 Prime UTR, 2R G>C single nucleotide polymorphism [SNP], 3R G>C SNP), epidermal growth factor receptor (Arg497Lys), GSTP1 (Ile105val), excision repair cross-complementing 1 (Asn118Asn, 8092C>A, 19716G>C), X-ray repair cross-complementing group 1 (XRCC1) (Arg194Trp, Arg280His, Arg399Gln), and xeroderma pigmentosum group D (Lys751Gln). The pathologic response, pathologic regression, progression-free survival, and overall survival were evaluated according to each genotype. Results: The Asterisk-Operator 3/ Asterisk-Operator 3 thymidylate synthase genotype was associated with a greater response rate (pathologic complete remission and microfoci residual tumor, 59% in Asterisk-Operator 3/ Asterisk-Operator 3 vs. 35% in Asterisk-Operator 2/ Asterisk-Operator 2 and Asterisk-Operator 2/ Asterisk-Operator 3; p = .013). For the thymidylate synthase genotype, the median progression-free survival was 103 months for the Asterisk-Operator 3/ Asterisk-Operator 3 patients and 84 months for the Asterisk-Operator 2/ Asterisk-Operator 2 and Asterisk-Operator 2/ Asterisk-Operator 3 patients (p = .039). For XRCC1 Arg399Gln SNP, the median progression-free survival was 101 months for the G/G, 78 months for the G/A, and 31 months for the A/A patients (p = .048). Conclusions: The thymidylate synthase genotype and XRCC1 Arg399Gln polymorphism might help to identify Stage II-III rectal cancer patients with a better outcome after preoperative concomitant chemoradiotherapy.« less

A modified Rayleigh-Gans-Debye formula for small angle X-ray scattering by interstellar dust grains

NASA Astrophysics Data System (ADS)

Sharma, Subodh K.

2015-05-01

A widely used approximation in studies relating to small angle differential scattering cross-section of X-rays scattered by interstellar dust grains is the well known Rayleigh-Gans-Debye approximation (RGDA). The validity of this approximation, however, is limited only to X-ray energies greater than about 1 keV. At lower energies, this approximation overestimates the exact results. In this paper a modification to the RGDA is suggested. It is shown that a combination of the RGDA with Ramsauer approximation retains the formal simplicity of the RGDA and also yields good agreement with Mie computations at all X-ray energies.

Nuclear Bragg scattering studies in [sup 57]Fe with synchrotron radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haustein, P.E.

1993-01-01

Studies of nuclear Bragg x-ray scattering of synchrotron radiation, using crystals of [alpha]-[sup 57]Fe[sub 2]O[sub 3], have been carried out at the NSLS at Brookhaven National Laboratory and at the Cornell University CHESS facility. These studies have demonstrated that nuclear resonance states can be used to produce filtered x-ray beams which have extremely narrow bandwidth, small angular divergence and unique polarization and temporal properties. this combination of characteristics, unobtainable with radioactive sources, makes synchrotron-based Moessbauer spectroscopy feasible and is an important complement to existing methods. A review of the experimental methodology is presented. As well as come suggestions for fullermore » exploitation of this new technique.« less

Nuclear Bragg scattering studies in {sup 57}Fe with synchrotron radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haustein, P.E.

1993-03-01

Studies of nuclear Bragg x-ray scattering of synchrotron radiation, using crystals of {alpha}-{sup 57}Fe{sub 2}O{sub 3}, have been carried out at the NSLS at Brookhaven National Laboratory and at the Cornell University CHESS facility. These studies have demonstrated that nuclear resonance states can be used to produce filtered x-ray beams which have extremely narrow bandwidth, small angular divergence and unique polarization and temporal properties. this combination of characteristics, unobtainable with radioactive sources, makes synchrotron-based Moessbauer spectroscopy feasible and is an important complement to existing methods. A review of the experimental methodology is presented. As well as come suggestions for fullermore » exploitation of this new technique.« less

A parameterization scheme for the x-ray linear attenuation coefficient and energy absorption coefficient.

PubMed

Midgley, S M

2004-01-21

A novel parameterization of x-ray interaction cross-sections is developed, and employed to describe the x-ray linear attenuation coefficient and mass energy absorption coefficient for both elements and mixtures. The new parameterization scheme addresses the Z-dependence of elemental cross-sections (per electron) using a simple function of atomic number, Z. This obviates the need for a complicated mathematical formalism. Energy dependent coefficients describe the Z-direction curvature of the cross-sections. The composition dependent quantities are the electron density and statistical moments describing the elemental distribution. We show that it is possible to describe elemental cross-sections for the entire periodic table and at energies above the K-edge (from 6 keV to 125 MeV), with an accuracy of better than 2% using a parameterization containing not more than five coefficients. For the biologically important elements 1 < or = Z < or = 20, and the energy range 30-150 keV, the parameterization utilizes four coefficients. At higher energies, the parameterization uses fewer coefficients with only two coefficients needed at megavoltage energies.

L i ( i = 1-3) subshell X-ray production cross sections and fluorescence yields for some elements with 56 ⩽ Z ⩽ 68 at 22.6 keV

NASA Astrophysics Data System (ADS)

Chauhan, Yogeshwar; Tiwari, M. K.; Puri, Sanjiv

2008-01-01

The L k ( k = l, α, β 1,4, β 3,6, β 2,15,9,10,7, γ 1,5 and γ 2,3,4) X-ray production (XRP) cross sections have been measured for six elements with 56 ⩽ Z ⩽ 68 at 22.6 keV incident photon energy using the EDXRF spectrometer. The incident photon intensity, detector efficiency and geometrical factors have been determined from the K X-ray yields emitted from elemental targets with 22 ⩽ Z ⩽ 42 in the same geometrical setup and from knowledge of the K XRP cross sections. The L 1 and L 2 subshell fluorescence yields have been deduced from the present measured L k XRP cross sections using the relativistic Hartree-Fock-Slater (HFS) model based photoionization cross sections. The present deduced ω1 (exp) values have been found to be, on an average, higher by 15% and 20% than those based on the Dirac-Hartree-Slater (DHS) model and the semi-empirical values compiled by Krause, respectively, for elements with 60 ⩽ Z ⩽ 68.

Low serum immunglobulin G (IgG) during nephrosis is a predictor of urinary tract infection (UTI) in children with nephrotic syndrome.

PubMed

Afroz, S; Roy, D K; Khan, A H

2013-04-01

Low serum level of IgG, complement C3 and C4 in nephrotic syndrome children may cause increased susceptibility to infection. Serum level of IgG and complements in nephrotic children (NS) with UTI has been analyzed in this cross sectional study. It was carried out in the department of Pediatric nephrology, National Institute of Kidney Diseases & Urology (NIKDU), Dhaka, Bangladesh. The study subjects were followed up prospectively for one year to see and compare the frequency of relapse of NS and UTI. Patients were selected in a nonrandom purposive technique. Nephrotic syndrome children with initial attack between 1-12 year of age were included over a period of one year. The patients were grouped into Group I - UTI positive and Group II - UTI negative depending on urine culture positivity and colony count >10⁵ CFU/ml. Serum IgG and complements C3, C4 levels were done in both groups during nephrosis and were compared. A total of 101 children M: F 1.7:1, mean age 5.96±3.2 years were included in this study. Group I, n=45 vs. Group II, n=56. The mean serum level of IgG was low in Group I (549.91±210.71 vs. 728.64±235.81mg/dl, p<0.001). Serum IgG level less than 700mg/dl was found in 37 vs. 23 children {x² (¹) 17.52 p<0.001, OR=6.63}. Mean serum complement C3 level was also low in Group I (123.09±40.52 vs. 143.38±37.06mg/dl, p<0.05). But complement C3 and C4 level do not carry any risk of developing UTI in nephrotic children. Higher number of children in Group II were at remission (n=24) during follow up, while frequent relapsers were high in Group I (n=22). Increased frequency of UTI attack (88 episodes) was found in Group I children compared to none in Group II during follow up. So low serum level of IgG in children with NS during nephrosis can predict UTI with an odds ratio of 6.63 as well as relapse. Serum level of C3, C4 do not associated with any risk of development of UTI in NS children.

A comprehensive study of high-energy gamma-ray and radio emission from Cyg X-3

NASA Astrophysics Data System (ADS)

Zdziarski, Andrzej A.; Malyshev, Denys; Dubus, Guillaume; Pooley, Guy G.; Johnson, Tyrel; Frankowski, Adam; de Marco, Barbara; Chernyakova, Maria; Rao, A. R.

2018-06-01

We study high-energy γ-rays observed from Cyg X-3 by the Fermi Large Area Telescope and the 15-GHz emission observed by the Ryle Telescope and the Arcminute Microkelvin Imager. We measure the γ-ray spectrum averaged over strong flares much more accurately than before, and find it well modelled by Compton scattering of stellar radiation by relativistic electrons with the power law index of ≃3.5 and a low-energy cutoff at the Lorentz factor of ˜103. We find a weaker spectrum in the soft spectral state, but only upper limits in the hard and intermediate states. We measure strong orbital modulation during the flaring state, well modelled by anisotropic Compton scattering of blackbody photons from the donor by jet relativistic electrons. We discover a weaker orbital modulation of the 15 GHz radio emission, which is well modelled by free-free absorption by the stellar wind. We then study cross-correlations between radio, γ-ray and X-ray emissions. We find the cross-correlation between the radio and γ-ray emissions peaks at a lag less than 1 d, while we detect a distinct radio lag of ˜50 d with respect to the soft X-rays in the soft spectral state.

Laboratory Data for X-Ray Astronomy

NASA Technical Reports Server (NTRS)

Beiersdorfer, P.; Brown, G. V.; Chen, H.; Gu, M.-F.; Kahn, S. M.; Lepson, J. K.; Savin, D. W.; Utter, S. B.

2000-01-01

Laboratory facilities have made great strides in producing large sets of reliable data for X-ray astronomy, which include ionization and recombination cross sections needed for charge balance calculations as well as the atomic data needed for interpreting X-ray line formation. We discuss data from the new generation sources and pay special attention to the LLNL electron beam ion trap experiment, which is unique in its ability to provide direct laboratory access to spectral data under precisely controlled conditions that simulate those found in many astrophysical plasmas. Examples of spectral data obtained in the 1-160 A wavelength range are given illustrating the type of laboratory X-ray data produced in support of such missions as Chandra, X-Ray Multi-Mirror telescope (XMM), Advanced Satellite for Cosmology and Astrophysics (ASCA) and Extreme Ultraviolet Explorer Satellite (EUVE).

High performance x-ray anti-scatter grid

DOEpatents

Logan, Clinton M.

1995-01-01

An x-ray anti-scatter grid for x-ray imaging, particularly for screening mammography, and method for fabricating same, x-rays incident along a direct path pass through a grid composed of a plurality of parallel or crossed openings, microchannels, grooves, or slots etched in a substrate, such as silicon, having the walls of the microchannels or slots coated with a high opacity material, such as gold, while x-rays incident at angels with respect to the slots of the grid, arising from scatter, are blocked. The thickness of the substrate is dependent on the specific application of the grid, whereby a substrate of the grid for mammography would be thinner than one for chest radiology. Instead of coating the walls of the slots, such could be filed with an appropriate liquid, such as mercury.

Integrated image presentation of transmission and fluorescent X-ray CT using synchrotron radiation

NASA Astrophysics Data System (ADS)

Zeniya, T.; Takeda, T.; Yu, Q.; Hasegawa, Y.; Hyodo, K.; Yuasa, T.; Hiranaka, Y.; Itai, Y.; Akatsuka, T.

2001-07-01

We have developed a computed tomography (CT) system with synchrotron radiation (SR) to detect fluorescent X-rays and transmitted X-rays simultaneously. Both SR transmission X-ray CT (SR-TXCT) and SR fluorescent X-ray CT (SR-FXCT) can describe cross-sectional images with high spatial and contrast resolutions as compared to conventional CT. TXCT gives morphological information and FXCT gives functional information of organs. So, superposed display system for SR-FXCT and SR-TXCT images has been developed for clinical diagnosis with higher reliability. Preliminary experiment with brain phantom was carried out and the superposition of both images was performed. The superposed SR-CT image gave us both functional and morphological information easily with high reliability, thus demonstrating the usefulness of this system.

Probing the gravitational Faraday rotation using quasar X-ray microlensing.

PubMed

Chen, Bin

2015-11-17

The effect of gravitational Faraday rotation was predicted in the 1950s, but there is currently no practical method for measuring this effect. Measuring this effect is important because it will provide new evidence for correctness of general relativity, in particular, in the strong field limit. We predict that the observed degree and angle of the X-ray polarization of a cosmologically distant quasar microlensed by the random star field in a foreground galaxy or cluster lens vary rapidly and concurrently with flux during caustic-crossing events using the first simulation of quasar X-ray microlensing polarization light curves. Therefore, it is possible to detect gravitational Faraday rotation by monitoring the X-ray polarization of gravitationally microlensed quasars. Detecting this effect will also confirm the strong gravity nature of quasar X-ray emission.

In Vivo and In Vitro Effects of ATM/ATR Signaling Pathway on Proliferation, Apoptosis, and Radiosensitivity of Nasopharyngeal Carcinoma Cells.

PubMed

Wang, Ming; Liu, Gang; Shan, Guo-Ping; Wang, Bing-Bing

2017-08-01

The study investigated the ability of ataxia-telangiectasia mutated (ATM)/Rad3-related (ATR) signaling pathway to influence the proliferation, apoptosis, and radiosensitivity of nasopharyngeal carcinoma (NPC) cells. NPC tissues and corresponding adjacent normal tissues were collected from 143 NPC patients. The NPC CNE2 cells were assigned into a control group, X-ray group, CGK-733 group, and X-ray+CGK-733 group. The mRNA levels of ATM and ATR were evaluated using quantitative real-time polymerase chain reaction (qRT-PCR) and the protein levels of ATM and ATR using western blotting. The positive expression of ATM and ATR in tissues and nude mouse tumor tissues was determined by immunohistochemistry. Cell proliferation, migration, invasion, and apoptosis rates were analyzed by the 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT) assay, scratch test, transwell assay, and flow cytometry, respectively. A nude mouse model of NPC was established to observe tumor volume and growth. The mRNA levels of ATR and ATM and the expression of ATR and ATM protein in NPC tissues were significantly higher than those in adjacent normal tissues. The colony formation assay showed that the colony-forming rate decreased, showing radiation dose-dependent and CGK-733 concentration-dependent manners. Expression of ATM, ATR, Chk1, and Chk2 was evidently increased in the X-ray, CGK-733, and X-ray+CGK-733groups compared with the control group, and the aforementioned expression was highest in the X-ray+CGK-733 group among the four groups. The cell proliferation, invasion, and migration were decreased, tumor volume decreased and cell apoptosis increased in the X-ray, CGK-733, and X-ray+CGK-733 groups compared with the control group; the X-ray+CGK-733 group exhibited lowest cell proliferation, invasion and migration, smallest tumor volume, and highest cell apoptosis among the four groups. Inhibition of ATM/ATR signaling pathway reduces proliferation and enhances apoptosis and radiosensitivity of NPC cells.

Genetic Map of Bacteriophage α

PubMed Central

Kejzlarovà, J.; Donini, P.; Eremenko-Volpe, T.; Graziosi, F.

1970-01-01

Temperature-sensitive mutants of phage α were obtained by means of various mutagens and assigned to 25 complementation groups. Temperature-sensitive mutants belonging to 21 complementation groups and a mutant giving turbid plaques were used to perform two- and three-factor crosses. Seventeen of the cistrons and the turbid mutant were shown to belong to the same linear linkage group, which showed no signs of circularity. The remaining four unlinked cistrons showed peculiarities in their recombination properties. Genes which are known to be expressed earlier apear to be grouped together in a terminal segment of the linkage group. PMID:4990532

Contribution of inner shell Compton ionization to the X-ray fluorescence line intensity

NASA Astrophysics Data System (ADS)

Fernández, Jorge E.; Scot, Viviana; Di Giulio, Eugenio

2016-10-01

The Compton effect is a potential ionization mechanism of atoms. It produces vacancies in inner shells that are filled with the same mechanism of atomic relaxation as the one following photo-absorption. This contribution to X-ray fluorescence emission is frequently neglected because the total Compton cross-section is apparently much lower than the photoelectric one at useful X-ray energies. However, a more careful analysis suggests that is necessary to consider single shell cross sections (instead of total cross sections) as a function of energy. In this article these Compton cross sections are computed for the shells K, L1-L3 and M1-M5 in the framework of the impulse approximation. By comparing the Compton and the photoelectric cross-section for each shell it is then possible to determine the extent of the Compton correction to the intensity of the corresponding characteristic lines. It is shown that for the K shell the correction becomes relevant for excitation energies which are too high to be influent in X-ray spectrometry. In contrast, for L and M shells the Compton contribution is relevant for medium-Z elements and medium energies. To illustrate the different grades of relevance of the correction, for each ionized shell, the energies for which the Compton contribution reaches the extent levels of 1, 5, 10, 20, 50 and 100% of the photoelectric one are determined for all the elements with Z = 11-92. For practical applications it is provided a simple formula and fitting coefficients to compute average correction levels for the shells considered.

Measurements of K shell absorption jump factors and jump ratios using EDXRF technique

NASA Astrophysics Data System (ADS)

Kacal, Mustafa Recep; Han, İbrahim; Akman, Ferdi

2015-04-01

In the present work, the K-shell absorption jump factors and jump ratios for 30 elements between Ti ( Z = 22) and Er ( Z = 68) were measured by energy dispersive X-ray fluorescence (EDXRF) technique. The jump factors and jump ratios for these elements were determined by measuring the K shell fluorescence parameters such as the Kα X-ray production cross-sections, K shell fluorescence yields, Kβ-to- Kα X-rays intensity ratios, total atomic absorption cross sections and mass attenuation coefficients. The measurements were performed using an Am-241 radioactive point source and a Si (Li) detector in direct excitation and transmission experimental geometry. The results for jump factors and jump ratios were compared with theoretically calculated and the ones available in the literature.

The iron complex in high mass X-ray binaries

NASA Astrophysics Data System (ADS)

Giménez-García, A.; Torrejón, J. M.; Martínez-Núñez, S.; Rodes-Rocas, J. J.; Bernabéu, G.

2013-05-01

An X-ray binary system consists of a compact object (a white dwarf, a neutron star or a black hole) accreting material from an optical companion star. The spectral type of the optical component strongly affects the mass transfer to the compact object. This is the reason why X-ray binary systems are usually divided in High Mass X-ray Binaries (companion O or B type, denoted HMXB) and Low Mass X-ray Binaries (companion type A or later). The HMXB are divided depending on the partner's luminosity class in two main groups: the Supergiant X-ray Binaries (SGXB) and Be X-ray Binaries (BeXB). We introduce the spectral characterization of a sample of 9 High Mass X-ray Binaries in the iron complex (˜ 6-7 keV). This spectral range is a fundamental tool in the study of the surrounding material of these systems. The sources have been divided into three main groups according to their current standard classification: SGXB, BeXB and γ Cassiopeae-like. The purpose of this work is to look for qualitative patterns in the iron complex, around 6-7 keV, in order to discern between current different classes that make up the group of HMXB. We find significant spectral patterns for each of the sets, reflecting differences in accretion physics thereof.

Evaluation and Management of the Nursing Home Resident With Respiratory Symptoms and an Equivocal Chest X-Ray Report.

PubMed

McClester Brown, Mallory; Sloane, Philip D; Kistler, Christine E; Reed, David; Ward, Kimberly; Weber, David; Zimmerman, Sheryl

2016-12-01

Pneumonia is a leading cause of morbidity and mortality in nursing home (NH) residents. Chest x-ray evidence is considered a key diagnostic criterion for pneumonia by the Infectious Disease Society of America (IDSA) diagnostic guidelines, the modified McGeer diagnostic criteria, and the Loeb criteria for initiating antibiotics; however, x-ray interpretation is often equivocal. We conducted chart audits of patients in NHs who had chest x-rays for new respiratory symptoms to determine the degree of ambiguity in the radiology reports and their relationship to antibiotic prescription decisions. Cross-sectional study. Thirty-one NHs in North Carolina. Two hundred twenty-six NH residents who had a chest x-ray. Medical charts were abstracted to record (1) the patient's clinical presentation when a chest x-ray was ordered, (2) the verbatim report of the chest x-ray, and (3) the patient's course during the subsequent 7 days. To standardize the radiologist reports, a seven-category coding system was developed, which was further aggregated into three groups based on the radiologist's description of the likelihood of pneumonia. Of the 226 chest x-rays, 118 (52%) identified a very low likelihood of pneumonia, 67 (30%) indicated that pneumonia was present or highly likely, and the remaining 41 (18%) used a variety of terms to describe uncertainty regarding the presence of pneumonia. NH medical providers tended to treat ambiguous chest x-ray reports similarly to positive x-ray reports, prescribing antibiotic therapy to 71% of patients with ambiguous reports and 78% of positive reports. Also notable is that 40 (34%) of the 118 patients with a very low likelihood of pneumonia based on chest x-ray results were prescribed antibiotics, the majority of whom failed to meet criteria for a clinical diagnosis of pneumonia or chronic obstructive pulmonary disease exacerbation. The moderate rate of ambiguous x-ray interpretations in NH residents is likely a combination of the poor quality of portable x-rays, a high prevalence of chronic lung conditions, and conservative (ie, cautious) decision making by radiologists whose interpretation is based on little clinical information and a suboptimal quality film. As a result, data suggest that chest x-rays obtained in NHs may unnecessarily encourage antibiotic prescribing because a majority of readings are ambiguous or show a low likelihood of pneumonia, yet more than half of the patients are still treated. From an antibiotic stewardship standpoint, the apparent solution is to more closely rely on clinical signs and symptoms for diagnosis of pneumonia and to place less emphasis on the role of the chest x-ray given the high number of unclear readings. Copyright © 2016 AMDA – The Society for Post-Acute and Long-Term Care Medicine. Published by Elsevier Inc. All rights reserved.

X-ray Follow-ups of XSS J12270-4859: A Low-mass X-ray Binary with Gamma-ray Fermi-LAT Association

NASA Technical Reports Server (NTRS)

deMartino, D.; Belloni, T.; Falanga, M.; Papitto, A.; Motta, S.; Pellizzoni, A.; Evangelista, Y.; Piano, G.; Masetti, N.; Mouchet, M.;

Prevalence of vitamin D deficiency and rickets in children with cholestasis in Iran.

PubMed

Mohammadi, Bahram; Najafi, Mehri; Farahmand, Fateme; Motamed, Farzaneh; Ghajarzadeh, Mahsa; Mohammadi, Jamshid; Eshagh Roze, Mohammad

2012-01-01

This study was aimed to determine prevalence of vitamin D deficiency and rickets in children with cholestatic liver diseases. Forty eight children with established cholestatic liver disease who referred to gastrointestinal clinic of Children Medical Center (Tehran, Iran) between April 2010 and March 2011 were enrolled in a cross-sectional study. Laboratory analysis including calcium, phosphate, albumin, total and direct bilirubin, aminotransferases, alkalinephosphatase (ALP), prothrombin time (PT), parathyroid hormone (PTH), total protein determined by routine laboratory techniques. Mean age of participants was 299.1 ± 676.8 days (range 2-3600 days) whereas twenty one were female (43.8%) and 27 (56.3%) were male. Twenty two (45.8%) had evidences of rickets in X-ray evaluation. Three children with rickets and two with normal X-ray had vitamin D deficiency while ten in rickets group and 16 in normal group had vitamin D insufficiency. The main underlying diseases were anatomical biliary atresia in cases with rickets and idiopathic in other group. Rickets and vitamin D deficiency should be considered in chronic cholestatic children.

L i ( i=1,2,3) subshell X-ray production cross-sections and fluorescence yields for Ir, Pt, Pb and Bi

NASA Astrophysics Data System (ADS)

Singh, P.; Sharma, M.; Shahi, J. S.; Mehta, D.; Singh, N.

2003-09-01

The L i ( i=1,2,3) subshell X-ray production (XRP) cross-sections were measured for 77Ir, 78Pt, 82Pb and 83Bi following direct ionization in the L i ( i=1,2,3) subshells by the 59.54 keV γ-rays and the L 3 subshell by the Br/Rb/Sr/Y K X-rays. The photon sources consisting of an 241Am source in (i) the direct excitation mode and (ii) the secondary excitation mode together with the KBr/RbNO 3/SrCO 3 /Y secondary exciter and an Si(Li) detector were used. The L i ( i=1,2,3) subshell fluorescence yields ( ωi) for these elements were deduced using the measured XRP cross-sections and the L i subshell photoionization cross-sections based on the Hartree-Fock-Slater model. The measured ω1 values are found to be higher upto 50% than those based on the relativistic Dirac-Hartree-Slater (RDHS) calculations, while the ω2 and ω3 values exhibit good agreement. The predicted jump in the RDHS based ω1 values from 77Ir to 78Pt due to onset of intense L 1-L 3M 4 CK transition is not observed.

Young's modulus and SEM analysis of leg bones exposed to simulated microgravity by hind limb suspension (HLS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Niravkumar D.; Mehta, Rahul; Ali, Nawab

2013-04-19

The aim of this study was to determine composition of the leg bone tissue of rats that were exposed to simulated microgravity by Hind-Limb Suspension (HLS) by tail for one week. The leg bones were cross sectioned, cleaned of soft tissues, dried and sputter coated, and then placed horizontally on the stage of a Scanning Electron Microscope (SEM) for analysis. Interaction of a 17.5 keV electron beam, incident from the vertical direction on the sample, generated images using two detectors. X-rays emitted from the sample during electron bombardment were measured with an Energy Dispersive Spectroscopy (EDS) feature of SEM usingmore » a liquid-nitrogen cooled Si(Li) detector with a resolution of 144 eV at 5.9 keV ({sub 25}Mn K{sub {alpha}} x-ray). K{sub {alpha}}- x-rays from carbon, oxygen, phosphorus and calcium formed the major peaks in the spectrum. Relative percentages of these elements were determined using a software that could also correct for ZAF factors namely Z(atomic number), A(X-ray absorption) and F(characteristic fluorescence). The x-rays from the control groups and from the experimental (HLS) groups were analyzed on well-defined parts (femur, tibia and knee) of the leg bone. The SEM analysis shows that there are definite changes in the hydroxyl or phosphate group of the main component of the bone structure, hydroxyapatite [Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}], due to hind limb suspension. In a separate experiment, entire leg bones (both from HLS and control rats) were subjected to mechanical stress by mean of a variable force. The stress vs. strain graph was fitted with linear and polynomial function, and the parameters reflecting the mechanical strength of the bone, under increasing stress, were calculated. From the slope of the linear part of the graph the Young's modulus for HLS bones were calculated and found to be 2.49 times smaller than those for control bones.« less

Effect of UV-ozone treatment on poly(dimethylsiloxane) membranes: surface characterization and gas separation performance.

PubMed

Fu, Ywu-Jang; Qui, Hsuan-zhi; Liao, Kuo-Sung; Lue, Shingjiang Jessie; Hu, Chien-Chieh; Lee, Kueir-Rarn; Lai, Juin-Yih

2010-03-16

A thin SiO(x) selective surface layer was formed on a series of cross-linked poly(dimethylsiloxane) (PDMS) membranes by exposure to ultraviolet light at room temperature in the presence of ozone. The conversion of the cross-linked polysiloxane to SiO(x) was monitored by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX) microanalysis, contact angle analysis, and atomic force microscopy (AFM). The conversion of the cross-linked polysiloxane to SiO(x) increased with UV-ozone exposure time and cross-linking agent content, and the surface possesses highest conversion. The formation of a SiO(x) layer increased surface roughness, but it decreased water contact angle. Gas permeation measurements on the UV-ozone exposure PDMS membranes documented interesting gas separation properties: the O(2) permeability of the cross-linked PDMS membrane before UV-ozone exposure was 777 barrer, and the O(2)/N(2) selectivity was 1.9; after UV-ozone exposure, the permeability decreased to 127 barrer while the selectivity increased to 5.4. The free volume depth profile of the SiO(x) layer was investigated by novel slow positron beam. The results show that free volume size increased with the depth, yet the degree of siloxane conversion to SiO(x) does not affect the amount of free volume.

On the Detectability of Oxygen X-Ray Fluorescence and Its Use as a Solar Photospheric Abundance Diagnostic

NASA Astrophysics Data System (ADS)

Drake, Jeremy J.; Ercolano, Barbara

2008-08-01

Monte Carlo calculations of the O Kα line fluoresced by coronal X-rays and emitted just above the temperature minimum region of the solar atmosphere have been employed to investigate the use of this feature as an abundance diagnostic. While they are quite weak, we estimate line equivalent widths in the range 0.02-0.2 Å, depending on the X-ray plasma temperature. The line remains essentially uncontaminated by blends for coronal temperatures T <= 3 × 106 K and should be quite observable, with a flux gtrsim2 photons s-1 arcmin-2. Model calculations for solar chemical mixtures with an O abundance adjusted up and down by a factor of 2 indicate 35%-60% changes in O Kα line equivalent width, providing a potentially useful O abundance diagnostic. Sensitivity of equivalent width to differences between recently recommended chemical compositions with "high" and "low" complements of the CNO trio important for interpreting helioseismological observations is less acute, amounting to 20%-26% at coronal temperatures T <= 2 × 106 K. While still feasible for discriminating between these two mixtures, uncertainties in measured line equivalent widths and in the models used for interpretation would need to be significantly less than 20%. Provided a sensitive X-ray spectrometer with resolving power >=1000 and suitably well-behaved instrumental profile can be built, X-ray fluorescence presents a viable means for resolving the solar "oxygen crisis."

Theoretical X-ray production cross sections at incident photon energies across L{sub i} (i=1-3) absorption edges of Br

DOE Office of Scientific and Technical Information (OSTI.GOV)

Puri, Sanjiv

The X-ray production (XRP) cross sections, σ{sub Lk} (k = l, η, α, β{sub 6}, β{sub 1}, β{sub 3}, β{sub 4}, β{sub 9,10}, γ{sub 1,5}, γ{sub 2,3}) have been evaluated at incident photon energies across the L{sub i}(i=1-3) absorption edge energies of {sub 35}Br using theoretical data sets of different physical parameters, namely, the L{sub i}(i=1-3) sub-shell the X-ray emission rates based on the Dirac-Fock (DF) model, the fluorescence and Coster Kronig yields based on the Dirac-Hartree-Slater (DHS) model, and two sets of the photoionisation cross sections based on the relativistic Hartree-Fock-Slater (RHFS) model and the Dirac-Fock (DF) model, inmore » order to highlight the importance of electron exchange effects at photon energies in vicinity of absorption edge energies.« less

The effect of cold-light-activated bleaching treatment on enamel surfaces in vitro

PubMed Central

Shi, Xin-Chang; Ma, He; Zhou, Jing-Lin; Li, Wei

2012-01-01

This in vitro study aims to evaluate the crystal and surface microstructure of dental enamel after cold-light bleaching treatment. Twelve sound human premolars were cross-split into four specimens, namely, mesio-buccal (Group LP), disto-buccal (Group P), mesio-lingual (Group NP) and disto-lingual (Group L) specimens. These four groups were treated using the standard cold-light bleaching procedure, a bleaching agent, a peroxide-free bleaching agent and cold-light, respectively. Before and after treatment, all specimens were analyzed by high-resolution, micro-area X-ray diffraction and scanning electron microscopy. Using a spectrometer, tooth color of all specimens was measured before and after treatment. The phase of the enamel crystals was identified as hydroxyapatite and carbonated hydroxyapatite. After treatment, specimens in Groups LP and P showed significantly weaker X-ray diffraction peaks, significant reduction in crystal size and crystallinity, significant increase in L* but decrease in a* and b*, and obvious alterations in the surface morphology. However, specimens in Groups NP and L did not show any significant changes. The cold-light bleaching treatment leads to demineralization in the enamel surface. The acidic peroxide-containing bleaching agent was the major cause of demineralization, whereas cold-light did not exhibit significant increase or decrease effect on this demineralization. PMID:23258380

Effect of wave function on the proton induced L XRP cross sections for 62Sm and 74W

NASA Astrophysics Data System (ADS)

Shehla, Kaur, Rajnish; Kumar, Anil; Puri, Sanjiv

2015-08-01

The Lk(k= 1, α, β, γ) X-ray production cross sections have been calculated for 74W and 62Sm at different incident proton energies ranging 1-5 MeV using theoretical data sets of different physical parameters, namely, the Li(i=1-3) sub-shell X-ray emission rates based on the Dirac-Fork (DF) model, the fluorescence and Coster Kronig yields based on the Dirac- Hartree-Slater (DHS) model and two sets the proton ionization cross sections based on the DHS model and the ECPSSR in order to assess the influence of the wave function on the XRP cross sections. The calculated cross sections have been compared with the measured cross sections reported in the recent compilation to check the reliability of the calculated values.

X-ray relative intensities at incident photon energies across the L{sub i} (i=1–3) absorption edges of elements with 35≤Z≤92

DOE Office of Scientific and Technical Information (OSTI.GOV)

Puri, Sanjiv, E-mail: sanjivpurichd@yahoo.com

The intensity ratios, I{sub Lk}/I{sub Lα1} (k=l,η,α{sub 2},β{sub 1},β{sub 2,15},β{sub 3},β{sub 4},β{sub 5,7},β{sub 6},β{sub 9,10},γ{sub 1,5},γ{sub 6,8},γ{sub 2,3},γ{sub 4}) and I{sub Lj}/I{sub Lα} (j=β,γ), have been evaluated at incident photon energies across the L{sub i} (i=1–3) absorption edge energies of all the elements with 35≤Z≤92. Use is made of what are currently considered to be more reliable theoretical data sets of different physical parameters, namely, the L{sub i} (i=1–3) sub-shell photoionization cross sections based on the relativistic Hartree–Fock–Slater (RHFS) model, the X-ray emission rates based on the Dirac–Fock model, and the fluorescence and Coster–Kronig yields based on the Dirac–Hartree–Slater model.more » In addition, the Lα{sub 1} X-ray production cross sections for different elements at various incident photon energies have been tabulated so as to facilitate the evaluation of production cross sections for different resolved L X-ray components from the tabulated intensity ratios. Further, to assist evaluation of the prominent (L{sub i}−S{sub j}) (S{sub j}=M{sub j}, N{sub j} and i=1–3, j=1–7) resonant Raman scattered (RRS) peak energies for an element at a given incident photon energy (below the L{sub i} sub-shell absorption edge), the neutral-atom electron binding energies based on the relaxed orbital RHFS calculations are also listed so as to enable identification of the RRS peaks, which can overlap with the fluorescent X-ray lines. -- Highlights: •The L X-ray relative intensities and Lα{sub 1} XRP cross sections are evaluated using physical parameters based on the IPA models. •Comparison of the intensity ratios evaluated using the DHS and DF models based photoionization cross sections is presented. •Importance of many body effects including electron exchange effects is highlighted.« less

Characterization of linear accelerator X-ray source size using a laminated beam-spot camera.

PubMed

Yeboah, Collins

2011-05-10

A laminated beam-spot camera of length 20 cm and effective cross-sectional area 2.5 cm × 3 cm was designed and constructed for the measurement of X-ray beam-spot sizes on different models of Siemens accelerators. With the accelerator gantry at 180° and camera positioned on an accessory tray holder, an XV film placed in contact with the camera at the distal end of it detected those X-rays that were transmitted through the camera. The FWHM of the detected X-ray intensity profile in the gun-target (G-T) direction or the orthogonal A-B direction was used as a measure of the beam-spot size in that direction. Siemens Mevatron MXEs exhibited a beam-spot size of 1.7 ± 0.2 mm in both the in-plane and cross-plane directions for 6 MV photon beams. The beam-spot size observed for a Mevatron MDX-2 was larger by up to 1 mm, and also was different for the in-plane and cross-plane directions. For Siemens PRIMUS accelerators, the beam-spot size in the in-plane direction was found to fall in the range 2.0-2.2 ± 0.2 mm, whereas the beam-spot size in the cross-plane direction fell within 1.7-1.9 ± 0.2 mm for 6, 10, and 18 MV photon beams. Assessment of long-term stability of the beam-spot size shows the spot size remains fairly stable over time.

Planar small-angle x-ray scattering imaging of phantoms and biological samples

NASA Astrophysics Data System (ADS)

Choi, M.; Badano, A.

2017-04-01

Coherent small-angle x-ray scattering (SAXS) provides molecular and nanometer-scale structural information. By capturing SAXS data at multiple locations across a sample, we obtained planar images and observed improved contrast given by the difference in the material scattering cross sections. We use phantoms made with 3D printing techniques, with tissue-mimicking plastic (PMMA), and with a highly scattering reference material (AgBe), which were chosen because of their well characterized scattering cross section to demonstrate and characterize the planar imaging of a laboratory SAXS system. We measure 1.07 and 2.14 nm-1 angular intensity maps for AgBe, 9.5 nm-1 for PMMA, and 12.3 nm-1 for Veroclear. The planar SAXS images show material discrimination based on their cross sectional features. The image signal-to-noise ratio (SNR) of each q image was dependent on exposure time and x-ray flux. We observed a lower SNR (91 ± 48) at q angles where no characteristic peaks for either material exist. To improve the visualization of the acquired data by utilizing all q-binned data, we describe a weighted-sum presentation method with a priori knowledge of relevant cross sections to improve the SNR (10 000 ± 6400) over the SNR from a single q-image at 1.07 nm-1 (1100 ± 620). In addition, we describe planar SAXS imaging of a mouse brain slice showing differentiation of tissue types as compared to a conventional absorption-based x-ray imaging technique.

The nature of X-ray sources associated to young clusters around Sh2-296

NASA Astrophysics Data System (ADS)

Gregorio-Hetem, J.; Fernandes, B.; Montmerle, T.

2014-10-01

Aiming to unravel the star formation activity in the Canis Major R1 (CMaR1), we have studied the young (< 5 Myr) clusters associated to the arc-shaped ionized nebula Sh2-296. Based on our X-ray data complemented by optical and near-IR data, we discovered, near to GU CMa, a stellar cluster that is older by at least a few Myr than the previously known cluster, around Z CMa, where star formation is still very active. Multi-object optical spectroscopy of our X-ray sources nearby Z CMa was performed with Gemini telescopes to confirm the existence of a mixed population from both older and younger clusters around the edge of Sh2-296. In the present work we show the results for optical counterparts candidates of 45 X-ray sources. Spectral type determination was based on comparison with standard spectra library and fitting the continuum and TiO bands. Typical features of young stars were inspected to confirm the nature of the sample that is mainly classified as T Tauri stars (TTs), since their spectra show the Li I line, one of the indicators of youth. The equivalent width of Hα measured at 10% of the total flux was used to separate Classical TTs (CTTs) from weak-line TTs (WTTs). Among 51 optical counterparts candidates, 38 are young stars: 24% of them are classified as CTTs and 76% are WTTs. However the present results correspond to a small fraction (˜ 15%) of the entire sample of X-ray sources we have detected. Aiming a more representative set of spectra, additional GMOS observations have been performed, as well as another ongoing project (see Santos-Silva et al.) dedicated to studying of the X-ray properties.

Accretion Properties of a Sample of Hard X-Ray (<60 keV) Selected Seyfert 1 Galaxies

NASA Astrophysics Data System (ADS)

Wang, J.; Mao, Y. F.; Wei, J. Y.

2009-02-01

We examine the accretion properties in a sample of 42 hard (3-60 keV) X-ray selected nearby broad-line active galactic nuclei (AGNs). The energy range in the sample is harder than that usually used in similar previous studies. These AGNs are mainly complied from the RXTE All Sky Survey, and complemented by the released INTEGRAL AGN catalog. The black hole masses, bolometric luminosities of AGN, and Eddington ratios are derived from their optical spectra in terms of the broad Hβ emission line. The tight correlation between the hard X-ray (3-20 keV) and bolometric/line luminosity is well identified in our sample. Also identified is a strong inverse Baldwin relationship of the Hβ emission line. In addition, all of these hard X-ray AGNs are biased toward luminous objects with a high Eddington ratio (mostly between 0.01 and 0.1) and a low column density (<1022 cm-2), which is most likely due to the selection effect of the surveys. The hard X-ray luminosity is consequently found to be strongly correlated with the black hole mass. We believe the sample completeness will be improved in the next few years by the ongoing Swift and the International Gamma-Ray Astrophysics Laboratory missions, and by the next advanced missions, such as NuSTAR, Simbol-X, and NeXT. Finally, the correlation between RFe (= optical Fe II/Hβ) and disk temperature as assessed by T vprop (L/L Edd)M -1 BH leads us to suggest that the strength of the Fe II emission is mainly determined by the shape of the ionizing spectrum.

Laboratory Measurements of Solar-Wind/Comet X-Ray Emission and Charge Exchange Cross Sections

NASA Technical Reports Server (NTRS)

Chutjian, A.; Cadez, I.; Greenwood, J. B.; Mawhorter, R. J.; Smith, S. J.; Lozano, J.

2002-01-01

The detection of X-rays from comets such as Hyakutake, Hale-Bopp, d Arrest, and Linear as they approach the Sun has been unexpected and exciting. This phenomenon, moreover, should be quite general, occurring wherever a fast solar or stellar wind interacts with neutrals in a comet, a planetary atmosphere, or a circumstellar cloud. The process is, O(+8) + H2O --> O(+7*) + H2O(+), where the excited O(+7*) ions are the source of the X-ray emissions. Detailed modeling has been carried out of X-ray emissions in charge-transfer collisions of heavy solar-wind Highly Charged Ions (HCIs) and interstellar/interplanetary neutral clouds. In the interplanetary medium the solar wind ions, including protons, can charge exchange with interstellar H and He. This can give rise to a soft X-ray background that could be correlated with the long-term enhancements seen in the low-energy X-ray spectrum of ROSAT. Approximately 40% of the soft X-ray background detected by Exosat, ROSAT, Chandra, etc. is due to Charge Exchange (CXE): our whole heliosphere is glowing in the soft X-ray due to CXE.

Mapping High-Velocity H-alpha and Lyman-alpha Emission from Supernova 1987A

NASA Technical Reports Server (NTRS)

France, Kevin; McCray, Richard; Fransson, Claes; Larsson, Josefin; Frank, Kari A.; Burrows, David N.; Challis, Peter; Kirshner, Robert P.; Chevalier, Roger A.; Garnavich, Peter;

X-ray-selected galaxy groups in Boötes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vajgel, Bruna; Lopes, Paulo A. A.; Jones, Christine

2014-10-10

We present the X-ray and optical properties of the galaxy groups selected in the Chandra X-Boötes survey. We used follow-up Chandra observations to better define the group sample and their X-ray properties. Group redshifts were measured from the AGN and Galaxy Evolution Survey spectroscopic data. We used photometric data from the NOAO Deep Wide Field Survey to estimate the group richness (N {sub gals}) and the optical luminosity (L {sub opt}). Our final sample comprises 32 systems at z < 1.75 with 14 below z = 0.35. For these 14 systems, we estimate velocity dispersions (σ {sub gr}) and performmore » a virial analysis to obtain the radii (R {sub 200} and R {sub 500}) and total masses (M {sub 200} and M {sub 500}) for groups with at least 5 galaxy members. We use the Chandra X-ray observations to derive the X-ray luminosity (L{sub X} ). We examine the performance of the group properties σ{sub gr}, L {sub opt}, and L{sub X} , as proxies for the group mass. Understanding how well these observables measure the total mass is important to estimate how precisely the cluster/group mass function is determined. Exploring the scaling relations built with the X-Boötes sample and comparing these with samples from the literature, we find a break in the L{sub X} -M {sub 500} relation at approximately M {sub 500} = 5 × 10{sup 13} M {sub ☉} (for M {sub 500} > 5 × 10{sup 13} M {sub ☉}, M{sub 500}∝L{sub X}{sup 0.61±0.02}, while for M {sub 500} ≤ 5 × 10{sup 13} M {sub ☉}, M{sub 500}∝L{sub X}{sup 0.44±0.05}). Thus, the mass-luminosity relation for galaxy groups cannot be described by the same power law as galaxy clusters. A possible explanation for this break is the dynamical friction, tidal interactions, and projection effects that reduce the velocity dispersion values of the galaxy groups. By extending the cluster luminosity function to the group regime, we predict the number of groups that new X-ray surveys, particularly eROSITA, will detect. Based on our cluster/group luminosity function estimates, eROSITA will identify ∼1800 groups (L{sub X} = 10{sup 41}-10{sup 43} erg s{sup –1}) within a distance of 200 Mpc. Since groups lie in large-scale filaments, this group sample will map the large-scale structure of the local universe.« less

Instrumentation on Multi-Scaled Scattering of Bio-Macromolecular Solutions

PubMed Central

Chu, Benjamin; Fang, Dufei; Mao, Yimin

2015-01-01

The design, construction and initial tests on a combined laser light scattering and synchrotron X-ray scattering instrument can cover studies of length scales from atomic sizes in Angstroms to microns and dynamics from microseconds to seconds are presented. In addition to static light scattering (SLS), dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD), the light scattering instrument is being developed to carry out studies in mildly turbid solutions, in the presence of multiple scattering. Three-dimensional photon cross correlation function (3D-PCCF) measurements have been introduced to couple with synchrotron X-ray scattering to study the structure, size and dynamics of macromolecules in solution. PMID:25946340

Near-edge X-ray refraction fine structure microscopy

DOE PAGES

Farmand, Maryam; Celestre, Richard; Denes, Peter; ...

2017-02-06

We demonstrate a method for obtaining increased spatial resolution and specificity in nanoscale chemical composition maps through the use of full refractive reference spectra in soft x-ray spectro-microscopy. Using soft x-ray ptychography, we measure both the absorption and refraction of x-rays through pristine reference materials as a function of photon energy and use these reference spectra as the basis for decomposing spatially resolved spectra from a heterogeneous sample, thereby quantifying the composition at high resolution. While conventional instruments are limited to absorption contrast, our novel refraction based method takes advantage of the strongly energy dependent scattering cross-section and can seemore » nearly five-fold improved spatial resolution on resonance.« less

Refractive Optics for Hard X-ray Transmission Microscopy

NASA Astrophysics Data System (ADS)

Simon, M.; Ahrens, G.; Last, A.; Mohr, J.; Nazmov, V.; Reznikova, E.; Voigt, A.

2011-09-01

For hard x-ray transmission microscopy at photon energies higher than 15 keV we design refractive condenser and imaging elements to be used with synchrotron light sources as well as with x-ray tube sources. The condenser lenses are optimized for low x-ray attenuation—resulting in apertures greater than 1 mm—and homogeneous intensity distribution on the detector plane, whereas the imaging enables high-resolution (<100 nm) full-field imaging. To obtain high image quality at reasonable exposure times, custom-tailored matched pairs of condenser and imaging lenses are being developed. The imaging lenses (compound refractive lenses, CRLs) are made of SU-8 negative resist by deep x-ray lithography. SU-8 shows high radiation stability. The fabrication technique enables high-quality lens structures regarding surface roughness and arrangement precision with arbitrary 2D geometry. To provide point foci, crossed pairs of lenses are used. Condenser lenses have been made utilizing deep x-ray lithographic patterning of thick SU-8 layers, too, whereas in this case, the aperture is limited due to process restrictions. Thus, in terms of large apertures, condenser lenses made of structured and rolled polyimide film are more attractive. Both condenser types, x-ray mosaic lenses and rolled x-ray prism lenses (RXPLs), are considered to be implemented into a microscope setup. The x-ray optical elements mentioned above are characterized with synchrotron radiation and x-ray laboratory sources, respectively.

High performance x-ray anti-scatter grid

DOEpatents

Logan, C.M.

1995-05-23

Disclosed are an x-ray anti-scatter grid for x-ray imaging, particularly for screening mammography, and method for fabricating same, x-rays incident along a direct path pass through a grid composed of a plurality of parallel or crossed openings, microchannels, grooves, or slots etched in a substrate, such as silicon, having the walls of the microchannels or slots coated with a high opacity material, such as gold, while x-rays incident at angels with respect to the slots of the grid, arising from scatter, are blocked. The thickness of the substrate is dependent on the specific application of the grid, whereby a substrate of the grid for mammography would be thinner than one for chest radiology. Instead of coating the walls of the slots, such could be filed with an appropriate liquid, such as mercury. 4 Figs.

Probing the gravitational Faraday rotation using quasar X-ray microlensing

PubMed Central

Chen, Bin

2015-01-01

The effect of gravitational Faraday rotation was predicted in the 1950s, but there is currently no practical method for measuring this effect. Measuring this effect is important because it will provide new evidence for correctness of general relativity, in particular, in the strong field limit. We predict that the observed degree and angle of the X-ray polarization of a cosmologically distant quasar microlensed by the random star field in a foreground galaxy or cluster lens vary rapidly and concurrently with flux during caustic-crossing events using the first simulation of quasar X-ray microlensing polarization light curves. Therefore, it is possible to detect gravitational Faraday rotation by monitoring the X-ray polarization of gravitationally microlensed quasars. Detecting this effect will also confirm the strong gravity nature of quasar X-ray emission. PMID:26574051

X-ray survey of the North-America and Pelican star-forming complex (NGC 7000/IC 5070)

NASA Astrophysics Data System (ADS)

Damiani, Francesco; Pillitteri, Ignazio; Prisinzano, Loredana

2017-06-01

Aims: We present the first extensive X-ray study of the North-America and Pelican star-forming region (NGC 7000/IC 5070), with the aim of finding and characterizing the young population of this cloud. Methods: X-ray data from Chandra (four pointings) and XMM-Newton (seven pointings) were reduced and source detection algorithm applied to each image. We complement the X-ray data with optical and near-IR data from the IPHAS, UKIDSS, and 2MASS catalogs, and with other published optical and Spitzer IR data. More than 700 X-ray sources are detected, the majority of which have an optical or near-IR (NIR) counterpart. This allowed us to identify young stars in different stages of formation. Results: Less than 30% of X-ray sources are identified with a previously known young star. We argue that most X-ray sources with an optical or NIR counterpart, except perhaps for a few tens at near-zero reddening, are likely candidate members of the star-forming region, on the basis of both their optical and NIR magnitudes and colors, and of X-ray properties such as spectrum hardness or flux variations. They are characterized by a wide range of extinction, and sometimes near-IR excesses, both of which prevent derivation of accurate stellar parameters. The optical color-magnitude diagram suggests ages between 1-10 Myr. The X-ray members have a very complex spatial distribution with some degree of subclustering, qualitatively similar to that of previously known members. The detailed distribution of X-ray sources relative to the objects with IR excesses identified with Spitzer is sometimes suggestive of sequential star formation, especially near the "Gulf of Mexico" region, probably triggered by the O5 star which illuminates the whole region. We confirm that around the O5 star no enhancement in the young star density is found, in agreement with previous results. Thanks to the precision and depth of the IPHAS and UKIDSS data used, we also determine the local optical-IR reddening law, and compute an updated reddening map of the entire region. Full Tables 3-5 and reduced images (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/602/A115

Using the EXIST Active Shields for Earth Occultation Observations of X-Ray Sources

NASA Technical Reports Server (NTRS)

Wilson, Colleen A.; Fishman, Gerald; Hong, Jae-Sub; Gridlay, Jonathan; Krawczynski, Henric

2005-01-01

The EXIST active shields, now being planned for the main detectors of the coded aperture telescope, will have approximately 15 times the area of the BATSE detectors; and they will have a good geometry on the spacecraft for viewing both the leading and training Earth's limb for occultation observations. These occultation observations will complement the imaging observations of EXIST and can extend them to higher energies. Earth occultatio observations of the hard X-ray sky with BATSE on the Compton Gamma Ray Observatory developed and demonstrated the capabilities of large, flat, uncollimated detectors for this method. With BATSE, a catalog of 179 X-ray sources was monitored twice every spacecraft orbit for 9 years at energies above about 25 keV, resulting in 83 definite detections and 36 possible detections with 5-sigma detection sensitivities of 3.5-20 mcrab (20-430 keV) depending on the sky location. This catalog included four transients discovered with this technique and many variable objects (galactic and extragalactic). This poster will describe the Earth occultation technique, summarize the BATSE occultation observations, and compare the basic observational parameters of the occultation detector elements of BATSE and EXIST.

Infection control procedures used in conjunction with computed dental radiography.

PubMed

Hubar, J S; Gardiner, D M

2000-10-01

Infection control guidelines for dental radiography have been modified since 1986, when the American Dental Association and the Centers for Disease Control and Prevention supported the concept of "universal blood and body fluid precautions." With the introduction of computed digital radiography, hardware manufacturers recommend that alternative infection control techniques are necessary to prevent potential damage to the digital x-ray sensors placed inside the patient's mouth. Thirty first-year dental hygiene students were asked to insert and remove a Schick CDR number 2 size intraoral digital x-ray sensor into modified Rinn XCP bitewing bite blocks and a modified Rinn Snap-a-ray five times with each of the recommended infection control covers. Reduced rates of cross contamination are possible if the plastic barrier envelope has an additional latex finger cot stretched over it and the x-ray sensor. Sole usage of a latex finger cot will result in a reduced incidence of contamination, but still not to acceptable levels. However, a plastic barrier envelope placed over the x-ray sensor and over the modified XCP bite block together or a covered sensor in a Snap-a-ray under normal conditions does not result in a perforation and is least likely to result in cross contamination.

Hard alpha-keratin degradation inside a tissue under high flux X-ray synchrotron micro-beam: a multi-scale time-resolved study.

PubMed

Leccia, Emilie; Gourrier, Aurélien; Doucet, Jean; Briki, Fatma

2010-04-01

X-rays interact strongly with biological organisms. Synchrotron radiation sources deliver very intense X-ray photon fluxes within micro- or submicro cross-section beams, resulting in doses larger than the MGy. The relevance of synchrotron radiation analyses of biological materials is therefore questionable since such doses, million times higher than the ones used in radiotherapy, can cause huge damages in tissues, with regard to not only DNA, but also proteic and lipid organizations. Very few data concerning the effect of very high X-ray doses in tissues are available in the literature. We present here an analysis of the structural phenomena which occur when the model tissue of human hair is irradiated by a synchrotron X-ray micro-beam. The choice of hair is supported by its hierarchical and partially ordered keratin structure which can be analysed inside the tissue by X-ray diffraction. To assess the damages caused by hard X-ray micro-beams (1 microm(2) cross-section), short exposure time scattering SAXS/WAXS patterns have been recorded at beamline ID13 (ESRF) after various irradiation times. Various modifications of the scattering patterns are observed, they provide fine insight of the radiation damages at various hierarchical levels and also unexpectedly provide information about the stability of the various hierarchical structural levels. It appears that the molecular level, i.e. the alpha helices which are stabilized by hydrogen bonds and the alpha-helical coiled coils which are stabilized by hydrophobic interactions, is more sensitive to radiation than the supramolecular architecture of the keratin filament and the filament packing within the keratin associated proteins matrix, which is stabilized by disulphide bonds. (c) 2009 Elsevier Inc. All rights reserved.

Stress-induced cortisol secretion impairs detection performance in x-ray baggage screening for hidden weapons by screening novices.

PubMed

Thomas, Livia; Schwaninger, Adrian; Heimgartner, Nadja; Hedinger, Patrik; Hofer, Franziska; Ehlert, Ulrike; Wirtz, Petra H

2014-09-01

Aviation security strongly depends on screeners' performance in the detection of threat objects in x-ray images of passenger bags. We examined for the first time the effects of stress and stress-induced cortisol increases on detection performance of hidden weapons in an x-ray baggage screening task. We randomly assigned 48 participants either to a stress or a nonstress group. The stress group was exposed to a standardized psychosocial stress test (TSST). Before and after stress/nonstress, participants had to detect threat objects in a computer-based object recognition test (X-ray ORT). We repeatedly measured salivary cortisol and X-ray ORT performance before and after stress/nonstress. Cortisol increases in reaction to psychosocial stress induction but not to nonstress independently impaired x-ray detection performance. Our results suggest that stress-induced cortisol increases at peak reactivity impair x-ray screening performance. Copyright © 2014 Society for Psychophysiological Research.

X-ray-induced apoptosis of BEL-7402 cell line enhanced by extremely low frequency electromagnetic field in vitro.

PubMed

Jian, Wen; Wei, Zhao; Zhiqiang, Cheng; Zheng, Fang

2009-02-01

This study was designed to test whether extremely low frequency electromagnetic field (ELF-EMF) could enhance the apoptosis-induction effect of X-ray radiotherapy on liver cancer cell line BEL-7402 in vitro. EMF exposure was performed inside an energized solenoid coil. X-ray irradiation was performed using a linear accelerator. Apoptosis rates of BEL-7402 cells were analyzed using Annexin V-Fit Apoptosis Detection kit. Apoptosis rates of EMF group and sham EMF group were compared when combined with X-ray irradiation. Our results suggested that the apoptosis rate of BEL-7402 cells exposed to low doses of X-ray irradiation could be significantly increased by EMF. More EMF exposures obtain significantly higher apoptosis rates than fewer EMF exposures when combined with 2 Gy X-ray irradiation. These findings suggested that ELF-EMF could augment the cell apoptosis effects of low doses of X-ray irradiation on BEL-7402 cells in a synergistic and cumulative way. Copyright 2008 Wiley-Liss, Inc.

Complement research in the 18th-21st centuries: Progress comes with new technology.

PubMed

Sim, R B; Schwaeble, W; Fujita, T

2016-10-01

The complement system has been studied for about 120 years. Progress in defining this large and complex system has been dependent on the research technologies available, but since the introduction of protein chromatography, electrophoresis, and antibody-based assay methods in the 1950s and 60s, and sequencing of proteins and DNA in the 70s and 80s, there has been very rapid accumulation of data. With more recent improvements in 3D structure determination (nmr and X-ray crystallography), the structures of most of the complement proteins have now been solved. Complement research since 1990 has been greatly stimulated by the discoveries of the multiple proteins in the lectin pathway, the strong association of Factor H, C3, Factor B allelic variants with adult macular degeneration and atypical haemolytic uremic syndrome, and the introduction of the anti-C5 monoclonal antibody as a therapy for paroxysmal nocturnal hemoglobinuria and atypical haemolytic uremic syndrome. Potential new roles for complement in tissue development and the search for novel therapeutics suggest a very active future for complement research. Copyright © 2016 Elsevier GmbH. All rights reserved.

Iodine imaging in thyroid by fluorescent X-ray CT with 0.05 mm spatial resolution

NASA Astrophysics Data System (ADS)

Takeda, T.; Yu, Q.; Yashiro, T.; Zeniya, T.; Wu, J.; Hasegawa, Y.; Thet-Thet-Lwin; Hyodo, K.; Yuasa, T.; Dilmanian, F. A.; Akatsuka, T.; Itai, Y.

2001-07-01

Fluorescent X-ray computed tomography (FXCT) at a 0.05 mm in-plane spatial resolution and 0.05 mm slice thickness depicted the cross sectional distribution of endogenous iodine within thyroid. The distribution obtained from the FXCT image correlated closely to that obtained from the pathological pictures.

All five host-range variants of Xanthomonas citri carry one pthA homolog with 17.5 repeats that determines pathogenicity on citrus, but none determine host-range variation.

PubMed

Al-Saadi, Abdulwahid; Reddy, Joseph D; Duan, Yong P; Brunings, Asha M; Yuan, Qiaoping; Gabriel, Dean W

2007-08-01

Citrus canker disease is caused by five groups of Xanthomonas citri strains that are distinguished primarily by host range: three from Asia (A, A*, and A(w)) and two that form a phylogenetically distinct clade and originated in South America (B and C). Every X. citri strain carries multiple DNA fragments that hybridize with pthA, which is essential for the pathogenicity of wide-host-range X. citri group A strain 3213. DNA fragments that hybridized with pthA were cloned from a representative strain from all five groups. Each strain carried one and only one pthA homolog that functionally complemented a knockout mutation of pthA in 3213. Every complementing homolog was of identical size to pthA and carried 17.5 nearly identical, direct tandem repeats, including three new genes from narrow-host-range groups C (pthC), A(w) (pthAW), and A* (pthA*). Every noncomplementing paralog was of a different size; one of these was sequenced from group A* (pthA*-2) and was found to have an intact promoter and full-length reading frame but with 15.5 repeats. None of the complementing homologs nor any of the noncomplementing paralogs conferred avirulence to 3213 on grapefruit or suppressed avirulence of a group A* strain on grapefruit. A knockout mutation of pthC in a group C strain resulted in loss of pathogenicity on lime, but the strain was unaffected in ability to elicit an HR on grapefruit. This pthC- mutant was fully complemented by pthA, pthB, or pthC. Analysis of the predicted amino-acid sequences of all functional pthA homologs and nonfunctional paralogs indicated that the specific sequence of the 17th repeat may be essential for pathogenicity of X. citri on citrus.

The Complete Local-Volume Groups Sample (CLoGS): Early results from X-ray and radio observations

NASA Astrophysics Data System (ADS)

Vrtilek, Jan M.; O'Sullivan, Ewan; David, Laurence P.; Giacintucci, Simona; Kolokythas, Konstantinos

2017-08-01

Although the group environment is the dominant locus of galaxy evolution (in contrast to rich clusters, which contain only a few percent of galaxies), there has been a lack of reliable, representative group samples in the local Universe. In particular, X-ray selected samples are strongly biased in favor of the X-ray bright, centrally-concentrated cool-core systems. In response, we have designed the Complete Local-Volume Groups Sample (CLoGS), an optically-selected statistically-complete sample of 53 groups within 80 Mpc which is intended to overcome the limitations of X-ray selected samples and serve as a representative survey of groups in the local Universe. We have supplemented X-ray data from Chandra and XMM (70% complete to date, using both archival and new observations, with a 26-group high richness subsample 100% complete) with GMRT radio continuum observations (at 235 and 610 MHz, complete for the entire sample). CLoGS includes groups with a wide variety of properties in terms of galaxy population, hot gas content, and AGN power. We here describe early results from the survey, including the range of AGN activity observed in the dominant galaxies, the relative fraction of cool-core and non-cool-core groups in our sample, and the degree of disturbance observed in the IGM.

Accurate Modeling of X-ray Extinction by Interstellar Grains

NASA Astrophysics Data System (ADS)

Hoffman, John; Draine, B. T.

2016-02-01

Interstellar abundance determinations from fits to X-ray absorption edges often rely on the incorrect assumption that scattering is insignificant and can be ignored. We show instead that scattering contributes significantly to the attenuation of X-rays for realistic dust grain size distributions and substantially modifies the spectrum near absorption edges of elements present in grains. The dust attenuation modules used in major X-ray spectral fitting programs do not take this into account. We show that the consequences of neglecting scattering on the determination of interstellar elemental abundances are modest; however, scattering (along with uncertainties in the grain size distribution) must be taken into account when near-edge extinction fine structure is used to infer dust mineralogy. We advertise the benefits and accuracy of anomalous diffraction theory for both X-ray halo analysis and near edge absorption studies. We present an open source Fortran suite, General Geometry Anomalous Diffraction Theory (GGADT), that calculates X-ray absorption, scattering, and differential scattering cross sections for grains of arbitrary geometry and composition.

Deep diode arrays for X-ray detection

NASA Technical Reports Server (NTRS)

Zemel, J. N.

1984-01-01

Temperature gradient zone melting process was used to form p-n junctions in bulk of high purity silicon wafers. These diodes were patterned to form arrays for X-ray spectrometers. The whole fabrication processes for these X-ray detectors are reviewed in detail. The p-n junctions were evaluated by (1) the dark diode I-V measurements, (2) the diode C sub I - V measurements, and (3) the MOS C-V measurements. The results showed that these junctions were linearly graded in charge distribution with low reverse bias leakage current flowing through them (few nA at -10 volts). The X-ray detection experiments showed that an FWHM of 500 eV was obtained from these diodes with a small bias of just -5 volts (for X-ray source Fe55). A theoretical model was proposed to explain the extra peaks found in the energy spectra and a very interesting point - cross talk effect was pointed out. This might be a solution to the problem of making really high resolution X-ray spectrometers.

A Synthesis Of Cosmic X-ray And Infrared Background

NASA Astrophysics Data System (ADS)

Shi, Yong; Helou, G.; Armus, L.; Stierwalt, S.

2012-01-01

We present a synthesis model of cosmic IR and X-ray background, with the goal to derive a complete census of cosmic evolution of star formation (SF) and black-hole (BH) growth by complementing advantages of X-ray and IR surveys to each other. By assuming that individual galaxies are experiencing both SF and BH accretion, our model decomposes the total IR LF into SF and BH components while taking into account the luminosity-dependent SED and its dispersion of the SF component, and the extinction-dependent SED of the BH component. The best-fit parameters are derived by fitting to the number counts and redshift distributions at X-ray including both hard and soft bands, and mid-IR to submm bands including IRAS, Spitzer, Herschel, SCUBA, Aztec and MAMBO. Based on the fit result, our models provide a series of predictions on galaxy evolution and black-hole growth. For evolution of infrared galaxies, the model predicts that the total infrared luminosity function is best described through evolution in both luminosity and density. For evolution of AGN populations, the model predicts that the evolution of X-ray LF also shows luminosity and density dependent, that the type-1/type-2 AGN fraction is a function of both luminosity and redshift, and that the Compton-thick AGN number density evolves strongly with redshift, contributing about 20% to the total cosmic BH growth. For BH growth in IR galaxies, the model predicts that the majority of BH growth at z>1 occurs in infrared luminous galaxies and the AGN fraction as a function of IR survey is a strong function of the survey depth, ranging from >50% at bright end to below 10% at faint end. We also evaluates various AGN selection techniques at X-ray and IR wavelengths and offer predictions for future missions at X-ray and IR.

Determination of K shell absorption jump factors and jump ratios of 3d transition metals by measuring K shell fluorescence parameters.

PubMed

Kaçal, Mustafa Recep; Han, İbrahim; Akman, Ferdi

2015-01-01

Energy dispersive X-ray fluorescence technique (EDXRF) has been employed for measuring K-shell absorption jump factors and jump ratios for Ti, Cr, Fe, Co, Ni and Cu elements. The jump factors and jump ratios for these elements were determined by measuring K shell fluorescence parameters such as the Kα X-ray production cross-sections, K shell fluorescence yields, Kβ-to-Kα X-rays intensity ratios, total atomic absorption cross sections and mass attenuation coefficients. The measurements were performed using a Cd-109 radioactive point source and an Si(Li) detector in direct excitation and transmission experimental geometry. The measured values for jump factors and jump ratios were compared with theoretically calculated and the ones available in the literature. Copyright © 2014 Elsevier Ltd. All rights reserved.

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic–Inorganic Lead Halide Perovskites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3) hybrid inorganic-organic perovskite and its binary phase PbI 2. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. Furthermore, the theoretical analysis complementing experimental observationsmore » provides the conceptual insights required for a full characterization of this complex material.« less

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic–Inorganic Lead Halide Perovskites

DOE PAGES

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina; ...

2018-03-23

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3) hybrid inorganic-organic perovskite and its binary phase PbI 2. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. Furthermore, the theoretical analysis complementing experimental observationsmore » provides the conceptual insights required for a full characterization of this complex material.« less

Emission line spectra of S VII ? S XIV in the 20 ? 75 ? wavelength region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lepson, J K; Beiersdorfer, P; Behar, E

As part of a larger project to complete a comprehensive catalogue of astrophysically relevant emission lines in support of new-generation X-ray observatories using the Lawrence Livermore electron beam ion traps EBIT-I and EBIT-II, the authors present observations of sulfur lines in the soft X-ray and extreme ultraviolet regions. The database includes wavelength measurements with standard errors, relative intensities, and line assignments for 127 transitions of S VII through S XIV between 20 and 75 {angstrom}. The experimental data are complemented with a full set of calculations using the Hebrew University Lawrence Livermore Atomic Code (HULLAC). A comparison of the laboratorymore » data with Chandra measurements of Procyon allows them to identify S VII-S XI lines.« less

Mechanism of the α -ɛ phase transformation in iron

NASA Astrophysics Data System (ADS)

Dewaele, A.; Denoual, C.; Anzellini, S.; Occelli, F.; Mezouar, M.; Cordier, P.; Merkel, S.; Véron, M.; Rausch, E.

2015-05-01

The α -Fe↔ɛ -Fe pressure-induced transformation under pure hydrostatic static compression has been characterized with in situ x-ray diffraction using α -Fe single crystals as starting samples. The forward transition starts at 14.9 GPa, and the reverse at 12 GPa, with a width of α -ɛ coexistence domain of the order of 2 GPa. The elastic stress in the sample increases in this domain, and partially relaxes after completion of the transformation. Orientation relations between parent α -Fe and child ɛ -Fe have been determined, which definitely validates the Burgers path for the direct transition. On the reverse transition, an unexpected variant selection is observed. X-ray diffraction data, complemented with ex situ microstructural observations, suggest that this selection is caused by defects and stresses accumulated during the direct transition.

Synthesis of 24-phenyl-24-oxo steroids derived from bile acids by palladium-catalyzed cross coupling with phenylboronic acid. NMR characterization and X-ray structures.

PubMed

Mayorquín-Torres, Martha C; Romero-Ávila, Margarita; Flores-Álamo, Marcos; Iglesias-Arteaga, Martin A

2013-11-01

Palladium-catalyzed cross coupling of phenyboronic acid with acetylated bile acids in which the carboxyl functions have been activated by formation of a mixed anhydride with pivalic anhydride afforded moderate to good yield of 24-phenyl-24-oxo-steroids. Unambiguous assignments of the NMR signals were made with the aid of combined 1D and 2D NMR techniques. X-ray diffraction studies confirmed the obtained structures. Copyright © 2013 Elsevier Inc. All rights reserved.

Local structure and defects in ion irradiated KTaO 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fuxiang; Xi, Jianqi; Zhang, Yanwen

Here, the modification of the local structure in cubic perovskite KTaO 3 irradiated with 3 MeV and 1.1 GeV Au ions is studied by Raman and x-ray absorption spectroscopy, complemented by density functional theory (DFT) calculations. In the case of irradiation with 3 MeV Au ions where displacement cascade processes are dominant, the Ta L 3-edge x-ray absorption measurements suggest that a peak corresponding to the Ta–O bonds in the TaO 6 octahedra splits, which is attributed to the formation of Ta K antisite defects that are coupled with oxygen vacancies, V O. This finding is consistent with the DFTmore » calculations. Under irradiation with 1.1 GeV ions, the intense ionization and electronic energy deposition lead to a blue shift and an intensity reduction of active Raman bands. In the case of sequential irradiations, extended x-ray absorption fine structure measurements reveal a decrease in concentration of coupled Ta K-V O defects under subsequent irradiation with 1.1 GeV Au ions.« less

Local structure and defects in ion irradiated KTaO 3

DOE PAGES

Zhang, Fuxiang; Xi, Jianqi; Zhang, Yanwen; ...

2018-03-12

Here, the modification of the local structure in cubic perovskite KTaO 3 irradiated with 3 MeV and 1.1 GeV Au ions is studied by Raman and x-ray absorption spectroscopy, complemented by density functional theory (DFT) calculations. In the case of irradiation with 3 MeV Au ions where displacement cascade processes are dominant, the Ta L 3-edge x-ray absorption measurements suggest that a peak corresponding to the Ta–O bonds in the TaO 6 octahedra splits, which is attributed to the formation of Ta K antisite defects that are coupled with oxygen vacancies, V O. This finding is consistent with the DFTmore » calculations. Under irradiation with 1.1 GeV ions, the intense ionization and electronic energy deposition lead to a blue shift and an intensity reduction of active Raman bands. In the case of sequential irradiations, extended x-ray absorption fine structure measurements reveal a decrease in concentration of coupled Ta K-V O defects under subsequent irradiation with 1.1 GeV Au ions.« less

An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading

PubMed Central

Oswald, Benjamin B.; Schuren, Jay C.; Pagan, Darren C.; Miller, Matthew P.

2013-01-01

An experimental system with in situ thermomechanical loading has been developed to enable high energy synchrotron x-ray diffraction studies of crystalline materials. The system applies and maintains loads of up to 2250 N in uniaxial tension or compression at a frequency of up to 100 Hz. The furnace heats the specimen uniformly up to a maximum temperature of 1200 °C in a variety of atmospheres (oxidizing, inert, reducing) that, combined with in situ mechanical loading, can be used to mimic processing and operating conditions of engineering components. The loaded specimen is reoriented with respect to the incident beam of x-rays using two rotational axes to increase the number of crystal orientations interrogated. The system was used at the Cornell High Energy Synchrotron Source to conduct experiments on single crystal silicon and polycrystalline Low Solvus High Refractory nickel-based superalloy. The data from these experiments provide new insights into how stresses evolve at the crystal scale during thermomechanical loading and complement the development of high-fidelity material models. PMID:23556825

ROVIBRATIONALLY RESOLVED DIRECT PHOTODISSOCIATION THROUGH THE LYMAN AND WERNER TRANSITIONS OF H{sub 2} FOR FUV/X-RAY-IRRADIATED ENVIRONMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gay, C. D.; Porter, R. L.; Stancil, P. C.

Using ab initio potential curves and dipole transition moments, cross-section calculations were performed for the direct continuum photodissociation of H{sub 2} through the B{sup 1}{Sigma}{sup +}{sub u} <- X{sup 1}{Sigma}{sup +}{sub g} (Lyman) and C{sup 1}{Pi}{sub u} <- X{sup 1}{Sigma}{sup +}{sub g} (Werner) transitions. Partial cross-sections were obtained for wavelengths from 100 A to the dissociation threshold between the upper electronic state and each of the 301 bound rovibrational levels v''J'' within the ground electronic state. The resulting cross-sections are incorporated into three representative classes of interstellar gas models: diffuse clouds, photon-dominated regions, and X-ray-dominated regions (XDRs). The models, whichmore » used the CLOUDY plasma/molecular spectra simulation code, demonstrate that direct photodissociation is comparable to fluorescent dissociation (or spontaneous radiative dissociation, the Solomon process) as an H{sub 2} destruction mechanism in intense far-ultraviolet or X-ray-irradiated gas. In particular, changes in H{sub 2} rotational column densities are found to be as large as 20% in the XDR model with the inclusion of direct photodissociation. The photodestruction rate from some high-lying rovibrational levels can be enhanced by pumping from H Ly{beta} due to a wavelength coincidence with cross-section resonances resulting from quasi-bound levels of the upper electronic states. Given the relatively large size of the photodissociation data set, a strategy is described to create truncated, but reliable, cross-section data consistent with the wavelength resolving power of typical observations.« less

Energy dispersive X-ray analysis on an absolute scale in scanning transmission electron microscopy.

PubMed

Chen, Z; D'Alfonso, A J; Weyland, M; Taplin, D J; Allen, L J; Findlay, S D

2015-10-01

We demonstrate absolute scale agreement between the number of X-ray counts in energy dispersive X-ray spectroscopy using an atomic-scale coherent electron probe and first-principles simulations. Scan-averaged spectra were collected across a range of thicknesses with precisely determined and controlled microscope parameters. Ionization cross-sections were calculated using the quantum excitation of phonons model, incorporating dynamical (multiple) electron scattering, which is seen to be important even for very thin specimens. Copyright © 2015 Elsevier B.V. All rights reserved.

Advanced Instrumentation for Ultrafast Science at the LCLS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berrah, Nora

2015-10-13

This grant supported a Single Investigator and Small Group Research (SISGR) application to enable multi-user research in Ultrafast Science using the Linac Coherent Light Source (LCLS), the world’s first hard x-ray free electron laser (FEL) which lased for the first time at 1.5 Å on April 20, 2009. The goal of our proposal was to enable a New Era of Science by requesting funds to purchase and build Advanced Instrumentation for Ultrafast Science (AIUS), to utilize the intense, short x-ray pulses produced by the LCLS. The proposed instrumentation will allow peer review selected users to probe the ultrasmall and capture themore » ultrafast. These tools will expand on the investment already made in the construction of the light source and its instrumentation in both the LCLS and LUSI projects. The AIUS will provide researchers in the AMO, Chemical, Biological and Condensed Matter communities with greater flexibility in defining their scientific agenda at the LCLS. The proposed instrumentation will complement and significantly augment the present AMO instrument (funded through the LCLS project) through detectors and capabilities not included in the initial suite of instrumentation at the facility. We have built all of the instrumentations and they have been utilized by scientists. Please see report attached.« less

Synthesis, characterization, antimicrobial screening and computational studies of 4-[3-(4-methoxy-phenyl)-allylideneamino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one

NASA Astrophysics Data System (ADS)

Obasi, L. N.; Kaior, G. U.; Rhyman, L.; Alswaidan, Ibrahim A.; Fun, Hoong-Kun; Ramasami, P.

2016-09-01

The Schiff base, 4-[3-(4-methoxy-phenyl)-allylideneamino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (TPMC/AAP) was synthesized by the condensation of 4-aminoantipyrine (4-amino-1,5-dimethyl-2-phenylpyrazole-3-one) and trans-para-methoxycinnamaldehyde (trans-3,4-methoxyphenyl-2-propenal) in dry methanol at 75 °C. The compound was characterized using elemental microanalysis, IR, NMR, UV spectroscopies and single-crystal X-ray crystallography. The X-ray structure determination shows that the Schiff base, (TPMC/AAP) is orthorhombic with the Pbca space group. The anti-microbial screening of the compound was carried out with Escherichia coli, Bacillus subtillis, Staphylococcus aureus, Pseudemonas aeruginosa, Candida albicans and Aspergillus niger using agar well diffusion method. The Schiff base possesses significant antimicrobial activity. The minimum inhibitory concentration (MIC) of the compound was also determined and the activity was compared with that of conventional drugs ciprofloxacin and ketoconazole. The compound (TPMC/AAP) showed varying activity against the cultured bacteria and fungi used. To complement the experimental data, density functional theory (DFT) was used to have deeper understanding into the molecular parameters and infrared spectra of the compound.

DNA Damage Induced by Alkylating Agents and Repair Pathways

PubMed Central

Kondo, Natsuko; Takahashi, Akihisa; Ono, Koji; Ohnishi, Takeo

2010-01-01

The cytotoxic effects of alkylating agents are strongly attenuated by cellular DNA repair processes, necessitating a clear understanding of the repair mechanisms. Simple methylating agents form adducts at N- and O-atoms. N-methylations are removed by base excision repair, AlkB homologues, or nucleotide excision repair (NER). O6-methylguanine (MeG), which can eventually become cytotoxic and mutagenic, is repaired by O6-methylguanine-DNA methyltransferase, and O6MeG:T mispairs are recognized by the mismatch repair system (MMR). MMR cannot repair the O6MeG/T mispairs, which eventually lead to double-strand breaks. Bifunctional alkylating agents form interstrand cross-links (ICLs) which are more complex and highly cytotoxic. ICLs are repaired by complex of NER factors (e.g., endnuclease xeroderma pigmentosum complementation group F-excision repair cross-complementing rodent repair deficiency complementation group 1), Fanconi anemia repair, and homologous recombination. A detailed understanding of how cells cope with DNA damage caused by alkylating agents is therefore potentially useful in clinical medicine. PMID:21113301

Fast calculator for X-ray emission due to Radiative Recombination and Radiative Electron Capture in relativistic heavy-ion atom collisions

NASA Astrophysics Data System (ADS)

Herdrich, M. O.; Weber, G.; Gumberidze, A.; Wu, Z. W.; Stöhlker, Th.

2017-10-01

In experiments with highly charged, fast heavy ions the Radiative Recombination (RR) and Radiative Electron Capture (REC) processes have significant cross sections in an energy range of up to a few GeV / u . They are some of the most important charge changing processes in collisions of heavy ions with atoms and electrons, leading to the emission of a photon along with the formation of the ground and excited atomic states. Hence, for the understanding and planning of experiments, in particular for X-ray spectroscopy studies, at accelerator ring facilities, such as FAIR, it is crucial to have a good knowledge of these cross sections and the associated radiation characteristics. In the frame of this work a fast calculator, named RECAL, for the RR and REC process is presented and its capabilities are demonstrated with the analysis of a recently conducted experiment at the Experimental Storage Ring (ESR) at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany. A method is presented to determine unknown X-ray emission cross sections via normalization of the recorded spectra to REC cross sections calculated by RECAL.

Charge transfer between O6+ and atomic hydrogen

NASA Astrophysics Data System (ADS)

Wu, Y.; Stancil, P. C.; Liebermann, H. P.; Buenker, R. J.; Schultz, D. R.; Hui, Y.

2011-05-01

The charge exchange process has been found to play a dominant role in the production of X-rays and/or EUV photons observed in cometary and planetary atmospheres and from the heliosphere. Charge transfer cross sections, especially state-selective cross sections, are necessary parameters in simulations of X-ray emission. In the present work, charge transfer due to collisions of ground state O6+(1s2 1 S) with atomic hydrogen has been investigated theoretically using the quantum-mechanical molecular-orbital close-coupling method (QMOCC). The multi-reference single- and double-excitation configuration interaction approach (MRDCI) has been applied to compute the adiabatic potential and nonadiabatic couplings, and the atomic basis sets used have been optimized with the method proposed previously to obtain precise potential data. Total and state-selective cross sections are calculated for energies between 10 meV/u and 10 keV/u. The QMOCC results are compared to available experimental and theoretical data as well as to new atomic-orbital close-coupling (AOCC) and classical trajectory Monte Carlo (CTMC) calculations. A recommended set of cross sections, based on the MOCC, AOCC, and CTMC calculations, is deduced which should aid in X-ray modeling studies.

Effect of wave function on the proton induced L XRP cross sections for {sub 62}Sm and {sub 74}W

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shehla,; Kaur, Rajnish; Kumar, Anil

The L{sub k}(k= 1, α, β, γ) X-ray production cross sections have been calculated for {sub 74}W and {sub 62}Sm at different incident proton energies ranging 1-5 MeV using theoretical data sets of different physical parameters, namely, the Li(i=1-3) sub-shell X-ray emission rates based on the Dirac-Fork (DF) model, the fluorescence and Coster Kronig yields based on the Dirac- Hartree-Slater (DHS) model and two sets the proton ionization cross sections based on the DHS model and the ECPSSR in order to assess the influence of the wave function on the XRP cross sections. The calculated cross sections have been compared withmore » the measured cross sections reported in the recent compilation to check the reliability of the calculated values.« less

Mechanistic Understanding of Tungsten Oxide In-Plane Nanostructure Growth via Sequential Infiltration Synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Jae Jin; Suh, Hyo Seon; Zhou, Chun

Tungsten oxide (WO3-x) nanostructures with hexagonal in-plane arrangements were fabricated by sequential infiltration synthesis (SIS), using the selective interaction of gas phase precursors with functional groups in one domain of a block copolymer (BCP) self-assembled template. Such structures are highly desirable for various practical applications and as model systems for fundamental studies. The nanostructures were characterized by cross-sectional scanning electron microscopy, grazing-incidence small/wide-angle X-ray scattering (GISAXS/GIWAXS), and X-ray absorption near edge structure (XANES) measurements at each stage during the SIS process and subsequent thermal treatments, to provide a comprehensive picture of their evolution in morphology, crystallography and electronic structure. Inmore » particular, we discuss the critical role of SIS Al2O3 seeds toward modifying the chemical affinity and free volume in a polymer for subsequent infiltration of gas phase precursors. The insights into SIS growth obtained from this study are valuable to the design and fabrication of a wide range of targeted nanostructures.« less

SIBYLS - A SAXS and protein crystallography beamline at the ALS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trame, Christine; MacDowell, Alastair A.; Celestre, Richard S.

2003-08-22

The new Structurally Integrated BiologY for Life Sciences (SIBYLS) beamline at the Advanced Light Source will be dedicated to Macromolecular Crystallography (PX) and Small Angle X-ray Scattering (SAXS). SAXS will provide structural information of macromolecules in solutions and will complement high resolution PX studies on the same systems but in a crystalline state. The x-ray source is one of the 5 Tesla superbend dipoles recently installed at the ALS that allows for a hard x-ray program to be developed on the relatively low energy Advanced Light Source (ALS) ring (1.9 GeV). The beamline is equipped with fast interchangeable monochromator elements,more » consisting of either a pair of single Si(111) crystals for crystallography, or a pair of multilayers for the SAXS mode data collection (E/{Delta}E {approx} 1/110). Flux rates with Si(111) crystals for PX are measured as 2 x 10{sup 11} hv/sec/400 mA through a 100 {micro}m pinhole at 12.4 KeV. For SAXS the flux is up to 3 x 10{sup 13} photons/sec at 10 KeV with all apertures open when using the multilayer monochromator elements. The performance characteristics of this unique beamline will be described.« less

High pressure studies on group VI metal hexacarbonyl molecular solids

NASA Astrophysics Data System (ADS)

Garimella, Subrahmanyam Venkata

Group VI metal hexacarbonyls, M(CO)6 (M = Cr, Mo and W), are of extreme importance as catalysts in industry and also of fundamental interest due to the established charge transfer mechanism between the carbon monoxide and the metal. They condense to molecular solids at ambient conditions retaining the octahedral (Oh) symmetry of gas phase and have been extensively investigated by previous workers to understand their fundamental chemical bonding and possible industrial applications. However little is known about their behavior at high pressures which is the focus of this dissertation. Metal hexacarbonyls were subjected to high pressures in Diamond-Anvil cells to understand the pressure effect on chemical bonding using Raman scattering in situ. The high-pressure results on each of the three metal hexacarbonyls are presented and are followed by a critical analysis of the entire family. The Raman study was conducted at pressures up to 45 GPa and X-ray up to 58 GPa. This is followed by a discussion on infra red spectra in conjunction with Raman and X-ray analysis to provide a rationale for polymerization. Finally the probable synthesis of extremely reactive species under high-pressures and as identified via Raman is discussed. The high-pressure Raman scattering, up to 30 GPa, demonstrated the absence of pi-backbonding. The disappearance of parental Raman spectra for (M = Cr, Mo and W) at 29.6, 23.3 and 22.2 GPa respectively was attributed to the total collapse of the Oh symmetry. This collapse under high-pressure lead to metal-mediated polymeric phase characterized by Raman active delta(OCO) feature, originating from intermolecular vibrational coupling in the parent sample. Further increase in pressures up to 45 GPa, did not affect this feature. The pressure quenched Raman spectra, revealed various chemical groups non-characteristic of the parent sample and adsorption of CO in addition to the characteristic delta(OCO) feature. The thus recorded Raman, complemented with the far and mid-infrared pressure quenched spectra, reveal the formation of novel metal-mediated polymers. The X-ray diffraction on W(CO)6 up to 58 GPa revealed the generation of amorphous polymeric pattern which was retained back to ambient conditions.

Tracking ink composition on Herculaneum papyrus scrolls: quantification and speciation of lead by X-ray based techniques and Monte Carlo simulations.

PubMed

Tack, Pieter; Cotte, Marine; Bauters, Stephen; Brun, Emmanuel; Banerjee, Dipanjan; Bras, Wim; Ferrero, Claudio; Delattre, Daniel; Mocella, Vito; Vincze, Laszlo

2016-02-08

The writing in carbonized Herculaneum scrolls, covered and preserved by the pyroclastic events of the Vesuvius in 79 AD, was recently revealed using X-ray phase-contrast tomography, without the need of unrolling the sensitive scrolls. Unfortunately, some of the text is difficult to read due to the interference of the papyrus fibers crossing the written text vertically and horizontally. Recently, lead was found as an elemental constituent in the writing, rendering the text more clearly readable when monitoring the lead X-ray fluorescence signal. Here, several hypotheses are postulated for the origin and state of lead in the papyrus writing. Multi-scale X-ray fluorescence micro-imaging, Monte Carlo quantification and X-ray absorption microspectroscopy experiments are used to provide additional information on the ink composition, in an attempt to determine the origin of the lead in the Herculaneum scrolls and validate the postulated hypotheses.

Analytical transmission cross-coefficients for pink beam X-ray microscopy based on compound refractive lenses.

PubMed

Falch, Ken Vidar; Detlefs, Carsten; Snigirev, Anatoly; Mathiesen, Ragnvald H

2018-01-01

Analytical expressions for the transmission cross-coefficients for x-ray microscopes based on compound refractive lenses are derived based on Gaussian approximations of the source shape and energy spectrum. The effects of partial coherence, defocus, beam convergence, as well as lateral and longitudinal chromatic aberrations are accounted for and discussed. Taking the incoherent limit of the transmission cross-coefficients, a compact analytical expression for the modulation transfer function of the system is obtained, and the resulting point, line and edge spread functions are presented. Finally, analytical expressions for optimal numerical aperture, coherence ratio, and bandwidth are given. Copyright © 2017 Elsevier B.V. All rights reserved.

Monitoring nonadiabatic avoided crossing dynamics in molecules by ultrafast X-ray diffraction

DOE PAGES

Kowalewski, Markus; Bennett, Kochise; Mukamel, Shaul

2017-05-26

We examine time-resolved X-ray diffraction from molecules in the gas phase which undergo nonadiabatic avoided-crossing dynamics involving strongly coupled electrons and nuclei. Several contributions to the signal are identified, representing (in decreasing strength) elastic scattering, contributions of the electronic coherences created by nonadiabatic couplings in the avoided crossing regime, and inelastic scattering. The former probes the charge density and delivers direct information on the evolving molecular geometry. The latter two contributions are weaker and carry spatial information through the transition charge densities (off-diagonal elements of the charge-density operator). Furthermore, simulations are presented for the nonadiabatic harpooning process in the excitedmore » state of sodium fluoride.« less

Chandra Observations of Low Velocity Dispersion Groups

NASA Astrophysics Data System (ADS)

Helsdon, Stephen F.; Ponman, Trevor J.; Mulchaey, J. S.

2005-01-01

Deviations of galaxy groups from cluster scaling relations can be understood in terms of an excess of entropy in groups. The main effect of this excess is to reduce the density and thus the luminosity of the intragroup gas. Given this, groups should also show a steep relationship between X-ray luminosity and velocity dispersion. However, previous work suggests that this is not the case, with many measuring slopes flatter than the cluster relation. Examining the group LX-σ relation shows that much of the flattening is caused by a small subset of groups that show very high X-ray luminosities for their velocity dispersions (or vice versa). Detailed Chandra study of two such groups shows that earlier ROSAT results were subject to significant (~30%-40%) point-source contamination but confirm that a significant hot intergalactic medium is present in these groups, although these are two of the coolest systems in which intergalactic X-ray emission has been detected. Their X-ray properties are shown to be broadly consistent with those of other galaxy groups, although the gas entropy in NGC 1587 is unusually low, and its X-ray luminosity is correspondingly high for its temperature when compared with most groups. This leads us to suggest that the velocity dispersion in these systems has been reduced in some way, and we consider how this might have come about.

A deeper look at the X-ray point source population of NGC 4472

NASA Astrophysics Data System (ADS)

Joseph, T. D.; Maccarone, T. J.; Kraft, R. P.; Sivakoff, G. R.

2017-10-01

In this paper we discuss the X-ray point source population of NGC 4472, an elliptical galaxy in the Virgo cluster. We used recent deep Chandra data combined with archival Chandra data to obtain a 380 ks exposure time. We find 238 X-ray point sources within 3.7 arcmin of the galaxy centre, with a completeness flux, FX, 0.5-2 keV = 6.3 × 10-16 erg s-1 cm-2. Most of these sources are expected to be low-mass X-ray binaries. We finding that, using data from a single galaxy which is both complete and has a large number of objects (˜100) below 1038 erg s-1, the X-ray luminosity function is well fitted with a single power-law model. By cross matching our X-ray data with both space based and ground based optical data for NGC 4472, we find that 80 of the 238 sources are in globular clusters. We compare the red and blue globular cluster subpopulations and find red clusters are nearly six times more likely to host an X-ray source than blue clusters. We show that there is evidence that these two subpopulations have significantly different X-ray luminosity distributions. Source catalogues for all X-ray point sources, as well as any corresponding optical data for globular cluster sources, are also presented here.

ROSAT X-ray sources embedded in the rho Ophiuchi cloud core

NASA Astrophysics Data System (ADS)

Casanova, Sophie; Montmerle, Thierry; Feigelson, Eric D.; Andre, Philippe

1995-02-01

We present a deep ROSAT Position Sensitive Proportional Counter (PSPC) image of the central region of the rho Oph star-forming region. The selected area, about 35 x 35 arcmins in size, is rich with dense molecular cores and young stellar objects (YSOs). Fifty-five reliable X-ray sources are detected (and up to 50 more candidates may be present) above approximately 1 keV,, doubling the number of Einstein sources in this area. These sources are cross-identified with an updated list of 88 YSOs associated with the rho Oph cloud core. A third of the reliable X-ray sources do not have optical counterparts on photographic plates. Most can be cross-identified wth Class II and Class III infrared (IR) sources, which are embedded T Tauri stars, but three reliable X-ray sources and up to seven candidate sources are tentatively identified with Class I protostars. Eighteen reliable, and up to 20 candidate, X-ray sources are probably new cloud members. The overall detection rate of the bona fide cloud population is very high (73% for the Class II and Class III objects). The spatial distribution of the X-ray sources closely follows that of the moleclar gas. The visual extinctions Av estimated from near-IR data) of the ROSAT sources can be as high as 50 or more, confirming that most are embedded in the cloud core and are presumably very young. Using bolometric luminosities Lbol estimated from J-magnitudes a tight correlation between Lx and Lbol is found, similar to that seen for older T Tauri stars in the Cha I cloud: Lx approximately 10-4 Lbol. A general relation Lxproportional to LbolLj seems to apply to all T Tauri-like YSOs. The near equality of the extintion in the IR J band and in the keV X-ray rage implies that this relation is valid for the detected fluxes as well as for the dereddened fluxes. The X-ray luminosity function of the embedded sourced in rho Oph spans a range of Lx approximately 1028.5 to approximately equal to or greater than 1031.5 ergs/s and is statistically indistinguishable from that of X-ray-detected visile T Tauri stars. We estimate a total X-ray luminosity Lx, Oph approximately equal to or greater than 6 x 10 32 ergs/s from approximately equal to 200 X-ray sources in the cloud core, down to Lbol approximately 0.1 solar luminosity or Mstar approximately 0.3 solar mass. We discuss several consequences of in situ irradiation of molecular clouds by X-rays from embedded YSOs. These X-rays must partially ionize the inner regions of circumstellar disk coronae, possibly playing an important role in coupling magnetic ionize the fields and wind or bipolar outflows. Photon-stimulated deportion of large molecules by YSO X-rays may be partly responsible for the bright 12 micrometer halos seen in some molecular clouds.

A study of the cross-correlation and time lag in black hole X-ray binary XTE J1859+226

NASA Astrophysics Data System (ADS)

Pei, Songpeng; Ding, Guoqiang; Li, Zhibing; Lei, Yajuan; Yuen, Rai; Qu, Jinlu

2017-07-01

With Rossi X-ray Timing Explorer (RXTE) data, we systematically study the cross-correlation and time lag in all spectral states of black hole X-ray binary (BHXB) XTE J1859+226 in detail during its entire 1999-2000 outburst that lasted for 166 days. Anti-correlations and positive correlations and their respective soft and hard X-ray lags are only detected in the first 100 days of the outburst when the luminosity is high. This suggests that the cross-correlations may be related to high luminosity. Positive correlations are detected in every state of XTE J1859+226, viz., hard state, hard-intermediate state (HIMS), soft-intermediate state (SIMS) and soft state. However, anti-correlations are only detected in HIMS and SIMS, anti-correlated hard lags are only detected in SIMS, while anti-correlated soft lags are detected in both HIMS and SIMS. Moreover, the ratio of the observations with anti-correlated soft lags to hard lags detected in XTE J1859+226 is significantly different from that in neutron star low-mass X-ray binaries (NS LMXBs). So far, anti-correlations are never detected in the soft state of BHXBs but detected in every branch or state of NS LMXBs. This may be due to the origin of soft seed photons in BHXBs is confined to the accretion disk and, for NS LMXBs, from both accretion disk and the surface of the NS. We notice that the timescale of anti-correlated time lags detected in XTE J1859+226 is similar with that of other BHXBs and NS LMXBs. We suggest that anti-correlated soft lag detected in BHXB may result from fluctuation in the accretion disk as well as NS LMXB.

Distant Cluster Hunting. II; A Comparison of X-Ray and Optical Cluster Detection Techniques and Catalogs from the ROSAT Optical X-Ray Survey

NASA Technical Reports Server (NTRS)

Donahue, Megan; Scharf, Caleb A.; Mack, Jennifer; Lee, Y. Paul; Postman, Marc; Rosait, Piero; Dickinson, Mark; Voit, G. Mark; Stocke, John T.

2002-01-01

We present and analyze the optical and X-ray catalogs of moderate-redshift cluster candidates from the ROSA TOptical X-Ray Survey, or ROXS. The survey covers the sky area contained in the fields of view of 23 deep archival ROSA T PSPC pointings, 4.8 square degrees. The cross-correlated cluster catalogs were con- structed by comparing two independent catalogs extracted from the optical and X-ray bandpasses, using a matched-filter technique for the optical data and a wavelet technique for the X-ray data. We cross-identified cluster candidates in each catalog. As reported in Paper 1, the matched-filter technique found optical counter- parts for at least 60% (26 out of 43) of the X-ray cluster candidates; the estimated redshifts from the matched filter algorithm agree with at least 7 of 1 1 spectroscopic confirmations (Az 5 0.10). The matched filter technique. with an imaging sensitivity of ml N 23, identified approximately 3 times the number of candidates (155 candidates, 142 with a detection confidence >3 u) found in the X-ray survey of nearly the same area. There are 57 X-ray candidates, 43 of which are unobscured by scattered light or bright stars in the optical images. Twenty-six of these have fairly secure optical counterparts. We find that the matched filter algorithm, when applied to images with galaxy flux sensitivities of mI N 23, is fairly well-matched to discovering z 5 1 clusters detected by wavelets in ROSAT PSPC exposures of 8000-60,000 s. The difference in the spurious fractions between the optical and X-ray (30%) and IO%, respectively) cannot account for the difference in source number. In Paper I, we compared the optical and X-ray cluster luminosity functions and we found that the luminosity functions are consistent if the relationship between X-ray and optical luminosities is steep (Lx o( L&f). Here, in Paper 11, we present the cluster catalogs and a numerical simulation of the ROXS. We also present color-magnitude plots for several of the cluster candidates, and examine the prominence of the red sequence in each. We find that the X-ray clusters in our survey do not all have a prominent red sequence. We conclude that while the red sequence may be a distinct feature in the color-magnitude plots for virialized massive clusters, it may be less distinct in lower mass clusters of galaxies at even moderate redshifts. Multiple, complementary methods of selecting and defining clusters may be essential, particularly at high redshift where all methods start to run into completeness limits, incomplete understanding of physical evolution, and projection effects.

Genetic Polymorphisms in XRCC1, CD3EAP, PPP1R13L, XPB, XPC, and XPF and the Risk of Chronic Benzene Poisoning in a Chinese Occupational Population.

PubMed

Xue, Ping; Gao, Lin; Xiao, Sha; Zhang, Guopei; Xiao, Mingyang; Zhang, Qianye; Zheng, Xiao; Cai, Yuan; Jin, Cuihong; Yang, Jinghua; Wu, Shengwen; Lu, Xiaobo

2015-01-01

Individual variations in the capacity of DNA repair machinery to relieve benzene-induced DNA damage may be the key to developing chronic benzene poisoning (CBP), an increasingly prevalent occupational disease in China. ERCC1 (Excision repair cross complementation group 1) is located on chromosome 19q13.2-3 and participates in the crucial steps of Nucleotide Excision Repair (NER); moreover, we determined that one of its polymorphisms, ERCC1 rs11615, is a biomarker for CBP susceptibility in our previous report. Our aim is to further explore the deeper association between some genetic variations related to ERCC1 polymorphisms and CBP risk. Nine single nucleotide polymorphisms (SNPs) of XRCC1 (X-ray repair cross-complementing 1), CD3EAP (CD3e molecule, epsilon associated protein), PPP1R13L (protein phosphatase 1, regulatory subunit 13 like), XPB (Xeroderma pigmentosum group B), XPC (Xeroderma pigmentosum group C) and XPF (Xeroderma pigmentosum group F) were genotyped by the Snapshot and TaqMan-MGB® probe techniques, in a study involving 102 CBP patients and 204 controls. The potential interactions between these SNPs and lifestyle factors, such as smoking and drinking, were assessed using a stratified analysis. An XRCC1 allele, rs25487, was related to a higher risk of CBP (P<0.001) even after stratifying for potential confounders. Carriers of the TT genotype of XRCC1 rs1799782 who were alcohol drinkers (OR = 8.000; 95% CI: 1.316-48.645; P = 0.022), male (OR = 9.333; 95% CI: 1.593-54.672; P = 0.019), and had an exposure of ≤12 years (OR = 2.612; 95% CI: 1.048-6.510; P = 0.035) had an increased risk of CBP. However, the T allele in PPP1R13L rs1005165 (P<0.05) and the GA allele in CD3EAP rs967591 (OR = 0.162; 95% CI: 0039~0.666; P = 0.037) decreased the risk of CBP in men. The haplotype analysis of XRCC1 indicated that XRCC1 rs25487A, rs25489G and rs1799782T (OR = 15.469; 95% CI: 5.536-43.225; P<0.001) were associated with a high risk of CBP. The findings showed that the rs25487 and rs1799782 polymorphisms of XRCC1 may contribute to an individual's susceptibility to CBP and may be used as valid biomarkers. Overall, the genes on chromosome 19q13.2-3 may have a special significance in the development of CBP in occupationally exposed Chinese populations.

Genetic Polymorphisms in XRCC1, CD3EAP, PPP1R13L, XPB, XPC, and XPF and the Risk of Chronic Benzene Poisoning in a Chinese Occupational Population

PubMed Central

Xiao, Sha; Zhang, Guopei; Xiao, Mingyang; Zhang, Qianye; Zheng, Xiao; Cai, Yuan; Jin, Cuihong; Yang, Jinghua; Wu, Shengwen; Lu, Xiaobo

2015-01-01

Objectives Individual variations in the capacity of DNA repair machinery to relieve benzene-induced DNA damage may be the key to developing chronic benzene poisoning (CBP), an increasingly prevalent occupational disease in China. ERCC1 (Excision repair cross complementation group 1) is located on chromosome 19q13.2–3 and participates in the crucial steps of Nucleotide Excision Repair (NER); moreover, we determined that one of its polymorphisms, ERCC1 rs11615, is a biomarker for CBP susceptibility in our previous report. Our aim is to further explore the deeper association between some genetic variations related to ERCC1 polymorphisms and CBP risk. Methods Nine single nucleotide polymorphisms (SNPs) of XRCC1 (X-ray repair cross-complementing 1), CD3EAP (CD3e molecule, epsilon associated protein), PPP1R13L (protein phosphatase 1, regulatory subunit 13 like), XPB (Xeroderma pigmentosum group B), XPC (Xeroderma pigmentosum group C) and XPF (Xeroderma pigmentosum group F) were genotyped by the Snapshot and TaqMan-MGB® probe techniques, in a study involving 102 CBP patients and 204 controls. The potential interactions between these SNPs and lifestyle factors, such as smoking and drinking, were assessed using a stratified analysis. Results An XRCC1 allele, rs25487, was related to a higher risk of CBP (P<0.001) even after stratifying for potential confounders. Carriers of the TT genotype of XRCC1 rs1799782 who were alcohol drinkers (OR = 8.000; 95% CI: 1.316–48.645; P = 0.022), male (OR = 9.333; 95% CI: 1.593–54.672; P = 0.019), and had an exposure of ≤12 years (OR = 2.612; 95% CI: 1.048–6.510; P = 0.035) had an increased risk of CBP. However, the T allele in PPP1R13L rs1005165 (P<0.05) and the GA allele in CD3EAP rs967591 (OR = 0.162; 95% CI: 0039~0.666; P = 0.037) decreased the risk of CBP in men. The haplotype analysis of XRCC1 indicated that XRCC1 rs25487A, rs25489G and rs1799782T (OR = 15.469; 95% CI: 5.536–43.225; P<0.001) were associated with a high risk of CBP. Conclusions The findings showed that the rs25487 and rs1799782 polymorphisms of XRCC1 may contribute to an individual’s susceptibility to CBP and may be used as valid biomarkers. Overall, the genes on chromosome 19q13.2–3 may have a special significance in the development of CBP in occupationally exposed Chinese populations. PMID:26681190

Isolation and Characterization of Sex-Linked Female-Sterile Mutants in DROSOPHILA MELANOGASTER

PubMed Central

Gans, Madeleine; Audit, Claudie; Masson, Michele

1975-01-01

The purpose of the experiments described was to identify X chromosome genes functioning mainly or exclusively during oogenesis. Two mutagenesis experiments were carried out with ethyl methane sulfonate. Following treatment inducing 60% lethals, 9% of the treated X chromosomes carried a female sterility mutation which did not otherwise seriously affect viability. Among —95 isolated mutants, 19 were heat-sensitive and 5 cold-sensitive. The mutants have been classified as follows: I (16 mutants; 12 complementation groups): the females laid few or no eggs; the defect concerned either ovulation or oogenesis. II (37 mutants; 18 complementation groups): the female laid morphologically abnormal eggs, often with increased membrane permeability. III A (13 mutants; at least 8 complementation groups): the homozygous females were sterile if mated to mutant males; their progeny (homo- and hemizygous) died at a late embryonic stage (11 mutants), at the larval stage (1 mutant) or at the pupal stage (1 mutant). However fertility was partly restored by breeding to wild-type males as shown by survival of some heterozygous descendants. III B (29 mutants; 22 complementation groups): the fertility of the females was not restored by breeding to a wild-type male. Most of the eggs of 13 of the mutants died at a late stage of embryogenesis. The eggs of the others ceased development earlier or, perhaps, remained unfertilized. The distribution of the number of mutants per complementation group led to an estimation of a total of about 150 X-linked genes involved in female fertility. The females of three mutants, heat-sensitive and totally sterile at 29°, produced at a lower temperature descendants morphologically abnormal or deprived of germ cells. Three other mutants not described in detail showed a reduction in female fertility with many descendants lacking germ cells. A desirable mutant which was not recovered was one with normal fertile females producing descendants which, regardless of their genotype, bore specific morphological abnormalities. The value of the mutants isolated for analysis of the complex processes leading to egg formation and initiation of development is discussed. PMID:814037

Implications of XRCC1, XPD and APE1 gene polymorphism in North Indian population: a comparative approach in different ethnic groups worldwide.

PubMed

Gangwar, Ruchika; Manchanda, Parmeet Kaur; Mittal, Rama Devi

2009-05-01

Identifying risk factors for human cancers should consider combinations of genetic variations and environmental exposures. Several polymorphisms in DNA repair genes have impact on repair and cancer susceptibility. We focused on X-ray repair cross-complementing group 1 (XRCC1), Xeroderma pigmentosum D (XPD) and apurinic/apyrimidinic endonuclease (APE1) as these are most extensively studied in cancer. Present study was conducted to determine distribution of XRCC1 C26304T, G27466A, G23591A, APE1 T2197G and XPD A35931C gene polymorphisms in North Indian population and compare with different populations globally. PCR-based analysis was conducted in 209 normal healthy individuals of similar ethnicity. Allelic frequencies in wild type of XRCC1 C26304T were 91.1% C(Arg); G27466A 62.9% G(Arg); G23591A 60.3% G(Arg); APE1 T2197G 75.1% T(Asp) and XPD A35931C 71.8% A(Lys). The variant allele frequency were 8.9% T(Trp) in XRCC1 C26304T; 37.1% A(His) in G27466A; 39.7% A(Gln) in G23591A; 24.9% G(Glu) in APE1 and 28.2% C(Gln) in XPD respectively. We further compared frequency distribution for these genes with various published studies in different ethnicity. Our results suggest that frequency in these DNA repair genes exhibit distinctive pattern in India that could be attributed to ethnicity variation. This could assist in high-risk screening of humans exposed to environmental carcinogens and cancer predisposition in different ethnic groups.

X-Ray Computed Tomography Monitors Damage in Composites

NASA Technical Reports Server (NTRS)

Baaklini, George Y.

1997-01-01

The NASA Lewis Research Center recently codeveloped a state-of-the-art x-ray CT facility (designated SMS SMARTSCAN model 100-112 CITA by Scientific Measurement Systems, Inc., Austin, Texas). This multipurpose, modularized, digital x-ray facility includes an imaging system for digital radiography, CT, and computed laminography. The system consists of a 160-kV microfocus x-ray source, a solid-state charge-coupled device (CCD) area detector, a five-axis object-positioning subassembly, and a Sun SPARCstation-based computer system that controls data acquisition and image processing. The x-ray source provides a beam spot size down to 3 microns. The area detector system consists of a 50- by 50- by 3-mm-thick terbium-doped glass fiber-optic scintillation screen, a right-angle mirror, and a scientific-grade, digital CCD camera with a resolution of 1000 by 1018 pixels and 10-bit digitization at ambient cooling. The digital output is recorded with a high-speed, 16-bit frame grabber that allows data to be binned. The detector can be configured to provide a small field-of-view, approximately 45 by 45 mm in cross section, or a larger field-of-view, approximately 60 by 60 mm in cross section. Whenever the highest spatial resolution is desired, the small field-of-view is used, and for larger samples with some reduction in spatial resolution, the larger field-of-view is used.

Measurements of Atomic Rayleigh Scattering Cross-Sections: A New Approach Based on Solid Angle Approximation and Geometrical Efficiency

NASA Astrophysics Data System (ADS)

Rao, D. V.; Takeda, T.; Itai, Y.; Akatsuka, T.; Seltzer, S. M.; Hubbell, J. H.; Cesareo, R.; Brunetti, A.; Gigante, G. E.

Atomic Rayleigh scattering cross-sections for low, medium and high Z atoms are measured in vacuum using X-ray tube with a secondary target as an excitation source instead of radioisotopes. Monoenergetic Kα radiation emitted from the secondary target and monoenergetic radiation produced using two secondary targets with filters coupled to an X-ray tube are compared. The Kα radiation from the second target of the system is used to excite the sample. The background has been reduced considerably and the monochromacy is improved. Elastic scattering of Kα X-ray line energies of the secondary target by the sample is recorded with Hp Ge and Si (Li) detectors. A new approach is developed to estimate the solid angle approximation and geometrical efficiency for a system with experimental arrangement using X-ray tube and secondary target. The variation of the solid angle is studied by changing the radius and length of the collimators towards and away from the source and sample. From these values the variation of the total solid angle and geometrical efficiency is deduced and the optimum value is used for the experimental work. The efficiency is larger because the X-ray fluorescent source acts as a converter. Experimental results based on this system are compared with theoretical estimates and good agreement is observed in between them.

Femtosecond response of polyatomic molecules to ultra-intense hard X-rays.

PubMed

Rudenko, A; Inhester, L; Hanasaki, K; Li, X; Robatjazi, S J; Erk, B; Boll, R; Toyota, K; Hao, Y; Vendrell, O; Bomme, C; Savelyev, E; Rudek, B; Foucar, L; Southworth, S H; Lehmann, C S; Kraessig, B; Marchenko, T; Simon, M; Ueda, K; Ferguson, K R; Bucher, M; Gorkhover, T; Carron, S; Alonso-Mori, R; Koglin, J E; Correa, J; Williams, G J; Boutet, S; Young, L; Bostedt, C; Son, S-K; Santra, R; Rolles, D

2017-06-01

X-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions. Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 10 20 watts per square centimetre). However, fundamental investigations have focused mainly on the individual response of atoms and small molecules using soft X-rays with much lower intensities. Studies with intense X-ray pulses have shown that irradiated atoms reach a very high degree of ionization, owing to multiphoton absorption, which in a heteronuclear molecular system occurs predominantly locally on a heavy atom (provided that the absorption cross-section of the heavy atom is considerably larger than those of its neighbours) and is followed by efficient redistribution of the induced charge. In serial femtosecond crystallography of biological objects-an application of X-ray free-electron lasers that greatly enhances our ability to determine protein structure-the ionization of heavy atoms increases the local radiation damage that is seen in the diffraction patterns of these objects and has been suggested as a way of phasing the diffraction data. On the basis of experiments using either soft or less-intense hard X-rays, it is thought that the induced charge and associated radiation damage of atoms in polyatomic molecules can be inferred from the charge that is induced in an isolated atom under otherwise comparable irradiation conditions. Here we show that the femtosecond response of small polyatomic molecules that contain one heavy atom to ultra-intense (with intensities approaching 10 20 watts per square centimetre), hard (with photon energies of 8.3 kiloelectronvolts) X-ray pulses is qualitatively different: our experimental and modelling results establish that, under these conditions, the ionization of a molecule is considerably enhanced compared to that of an individual heavy atom with the same absorption cross-section. This enhancement is driven by ultrafast charge transfer within the molecule, which refills the core holes that are created in the heavy atom, providing further targets for inner-shell ionization and resulting in the emission of more than 50 electrons during the X-ray pulse. Our results demonstrate that efficient modelling of X-ray-driven processes in complex systems at ultrahigh intensities is feasible.

Femtosecond response of polyatomic molecules to ultra-intense hard X-rays

DOE PAGES

Rudenko, A.; Inhester, L.; Hanasaki, K.; ...

2017-05-31

We report x-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions. Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 10 20 watts per square centimetre). However, fundamental investigations have focused mainly on the individual response of atoms and small molecules using soft X-rays with much lower intensities. Studies with intense X-ray pulses have shown that irradiated atoms reach a very high degree of ionization, owing to multiphoton absorption, which in a heteronuclear molecularmore » system occurs predominantly locally on a heavy atom (provided that the absorption cross-section of the heavy atom is considerably larger than those of its neighbours) and is followed by efficient redistribution of the induced charge. In serial femtosecond crystallography of biological objects—an application of X-ray free-electron lasers that greatly enhances our ability to determine protein structure—the ionization of heavy atoms increases the local radiation damage that is seen in the diffraction patterns of these objects and has been suggested as a way of phasing the diffraction data. On the basis of experiments using either soft or less-intense hard X-rays, it is thought that the induced charge and associated radiation damage of atoms in polyatomic molecules can be inferred from the charge that is induced in an isolated atom under otherwise comparable irradiation conditions. Here we show that the femtosecond response of small polyatomic molecules that contain one heavy atom to ultra-intense (with intensities approaching 10 20 watts per square centimetre), hard (with photon energies of 8.3 kiloelectronvolts) X-ray pulses is qualitatively different: our experimental and modelling results establish that, under these conditions, the ionization of a molecule is considerably enhanced compared to that of an individual heavy atom with the same absorption cross-section. This enhancement is driven by ultrafast charge transfer within the molecule, which refills the core holes that are created in the heavy atom, providing further targets for inner-shell ionization and resulting in the emission of more than 50 electrons during the X-ray pulse. Fnally, our results demonstrate that efficient modelling of X-ray-driven processes in complex systems at ultrahigh intensities is feasible.« less

Femtosecond response of polyatomic molecules to ultra-intense hard X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rudenko, A.; Inhester, L.; Hanasaki, K.

We report x-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions. Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 10 20 watts per square centimetre). However, fundamental investigations have focused mainly on the individual response of atoms and small molecules using soft X-rays with much lower intensities. Studies with intense X-ray pulses have shown that irradiated atoms reach a very high degree of ionization, owing to multiphoton absorption, which in a heteronuclear molecularmore » system occurs predominantly locally on a heavy atom (provided that the absorption cross-section of the heavy atom is considerably larger than those of its neighbours) and is followed by efficient redistribution of the induced charge. In serial femtosecond crystallography of biological objects—an application of X-ray free-electron lasers that greatly enhances our ability to determine protein structure—the ionization of heavy atoms increases the local radiation damage that is seen in the diffraction patterns of these objects and has been suggested as a way of phasing the diffraction data. On the basis of experiments using either soft or less-intense hard X-rays, it is thought that the induced charge and associated radiation damage of atoms in polyatomic molecules can be inferred from the charge that is induced in an isolated atom under otherwise comparable irradiation conditions. Here we show that the femtosecond response of small polyatomic molecules that contain one heavy atom to ultra-intense (with intensities approaching 10 20 watts per square centimetre), hard (with photon energies of 8.3 kiloelectronvolts) X-ray pulses is qualitatively different: our experimental and modelling results establish that, under these conditions, the ionization of a molecule is considerably enhanced compared to that of an individual heavy atom with the same absorption cross-section. This enhancement is driven by ultrafast charge transfer within the molecule, which refills the core holes that are created in the heavy atom, providing further targets for inner-shell ionization and resulting in the emission of more than 50 electrons during the X-ray pulse. Fnally, our results demonstrate that efficient modelling of X-ray-driven processes in complex systems at ultrahigh intensities is feasible.« less

Fingerprints of the first black holes? Crosscorrelationg the Near-Infrared and X-ray background in COSMOS

NASA Astrophysics Data System (ADS)

Hasinger, Guenther

Unresolved cosmic backgrounds carry information about the populations of stars and black holes not accessible by any other current observational technique. Studies using both Spitzer and AKARI have revealed large-scale fluctuations in the Cosmic Infrared Background (CIB) after subtracting resolved sources to faint levels. The signal, which is stronger than all foreground contributions, has been attributed to the earliest light in the universe. Other teams, by using Spitzer and CIBER, suggested that this signal could originate from stars tidally stripped from their parent galaxies at low redshift as a result of mergers. Only sensitive multi-wavelength observations can distinguish between these radically different interpretations. Recently our team discovered an intriguing cross-correlation signal between the unresolved CIB and X-ray background (CXB) suggesting significant black hole populations among the CIB sources (C13). The analysis used data from Spitzer and Chandra in an overlapping 8'x45' region of the All-Wavelength Extended Groth strip International Survey (AEGIS), probing the clustering of the underlying sources to angular scales 20', but the experiment is limited by the size and the elongated configuration of the field. Here we propose to use the much more extended multiwavelength observations in the COSMOS field to obtain new constraints on this important debate. Spitzer has recently completed the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH), which observed the full 2 square degree COSMOS field to about half the depth of the AEGIS field, but a 20 times larger sky area. SPLASH, focusing on the COSMOS field with excellent multi-wavelength coverage from space and ground-based observatories, is ideally suited to study the CIB to better precision and at larger scales than available so far. We propose to cross-correlate the Spitzer unresolved CIB to the unresolved CXB observed by Chandra and XMM-Newton. Chandra has covered the full 2 deg2 COSMOS field with a total exposure of 5.6 Ms. XMM-Newton has covered the whole 2 deg2 COSMOS field with an exposure time of about 1.5 Ms . The technique for our cross-correlation analysis has been described in detail by C13. All the known instrumental and non-cosmic backgrounds are removed from the data and all discrete sources are excised using the same mask for both datasets. Then the exposure-corrected images are cross-correlated with each other. Compared to the AEGIS cross-correlation signal we expect a significantly better signal to noise ratio, which together with the larger area, will allow us to reach much larger angular scales, where different models can be constrained. The better photon statistics will also allow to separate the signal into at least four independent X-ray energy bands, thus yielding coarse spectral information allowing to discriminate between different models for the X-ray emitting sources. If the X-ray sources are High-Mass X-ray binaries with stellar-mass black holes descendent from massive Pop III stars at z>7, we would expect the X-ray emission to be only moderately absorbed. If on the other hand, the X-ray emission originates from direct collapse black holes with masses in the range 10^5-6 solar masses, we expect a significant Compton-thick absorption component, similar to the resolved X-ray background produced at lower redshifts. Finally, the new data on the CIB-CXB crosscorrelation will also strongly constrain the intrahalo light scenario proposed as an alternative interpretation. At any rate, these measurements allow diagnostics into the faintest discrete source populations right after they emerged from the dark ages or buried within halos. Until the next generation of telescopes, JWST, WFIRST, and EUCLID, the ground based 30m telescopes and later the ESA X-ray observatory Athena, this is one of the few avenues to constrain the formation and early evolution of stars and black holes in the Universe.

Experimental investigation of dynamic fragmentation of laser shock-loaded by soft recovery and X-ray radiography

NASA Astrophysics Data System (ADS)

Xin, Jianting; He, Weihua; Chu, Genbai; Gu, Yuqiu

2017-06-01

Dynamic fragmentation of metal under shock pressure is an important issue for both fundamental science and practical applications. And in recent decades, laser provides a promising shock loading technique for investigating the process of dynamic fragmentation under extreme condition application of high strain rate. Our group has performed experimental investigation of dynamic fragmentation under laser shock loading by soft recovery and X-ray radiography at SGC / ó prototype laser facility. The fragments under different loading pressures were recovered by PMP foam and analyzed by X-ray micro-tomography and the improved watershed method. The experiment result showed that the bilinear exponential distribution is more appropriate for representing the fragment size distribution. We also developed X-ray radiography technique. Owing to its inherent advantage over shadowgraph technique, X-ray radiography can potentially determine quantitatively material densities by measuring the X-ray transmission. Our group investigated dynamic process of microjetting by X-ray radiography technique, the recorded radiographic images show clear microjetting from the triangular grooves in the free surface of tin sample.

Many-Body Effects in the Mesoscopic x-Ray Edge Problem

NASA Astrophysics Data System (ADS)

Hentschel, M.; R"Oder, G.; Ullmo, D.

Many-body phenomena, a key interest in the investigation ofbulk solid state systems, are studied here in the context of the x-ray edge problem for mesoscopic systems. We investigate the many-body effects associated with the sudden perturbation following the x-ray excition of a core electron into the conduction band. For small systems with dimensions at the nanoscale we find considerable deviations from the well-understood metallic case where Anderson orthogonality catastrophe and the Mahan-Nozières-DeDominicis response cause characteristic deviations of the photoabsorption cross section from the naive expectation. Whereas the K-edge is typically rounded in metallic systems, we find a slightly peaked K-edge in generic mesoscopic systems with chaotic-coherent electron dynamics. Thus the behavior of the photoabsorption cross section at threshold depends on the system size and is different for the metallic and the mesoscopic case.

Here Be Dragons: Effective (X-ray) Timing with the Cospectrum

NASA Astrophysics Data System (ADS)

Huppenkothen, Daniela; Bachetti, Matteo

2018-01-01

In recent years, the cross spectrum has received considerable attention as a means of characterising the variability of astronomical sources as a function of wavelength. While much has been written about the statistics of time and phase lags, the cospectrum—the real part of the cross spectrum—has only recently been understood as means of mitigating instrumental effects dependent on temporal frequency in astronomical detectors, as well as a method of characterizing the coherent variability in two wavelength ranges on different time scales. In this talk, I will present recent advances made in understanding the statistical properties of cospectra, leading to much improved inferences for periodic and quasi-periodic signals. I will also present a new method to reliably mitigate instrumental effects such as dead time in X-ray detectors, and show how we can use the cospectrum to model highly variable sources such as X-ray binaries or Active Galactic Nuclei.

SU-E-J-66: Evaluation of a Real-Time Positioning Assistance Simulator System for Skull Radiography Using the Microsoft Kinect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurata, T; Ono, M; Kozono, K

2014-06-01

Purpose: The purpose of this study is to investigate the feasibility of a low cost, small size positioning assistance simulator system for skull radiography using the Microsoft Kinect sensor. A conventional radiographic simulator system can only measure the three-dimensional coordinates of an x-ray tube using angle sensors, but not measure the movement of the subject. Therefore, in this study, we developed a real-time simulator system using the Microsoft Kinect to measure both the x-ray tube and the subject, and evaluated its accuracy and feasibility by comparing the simulated and the measured x-ray images. Methods: This system can track a headmore » phantom by using Face Tracking, which is one of the functions of the Kinect. The relative relationship between the Kinect and the head phantom was measured and the projection image was calculated by using the ray casting method, and by using three-dimensional CT head data with 220 slices at 512 × 512 pixels. X-ray images were thus obtained by using a computed radiography (CR) system. We could then compare the simulated projection images with the measured x-ray images from 0 degrees to 45 degrees at increments of 15 degrees by calculating the cross correlation coefficient C. Results: The calculation time of the simulated projection images was almost real-time (within 1 second) by using the Graphics Processing Unit(GPU). The cross-correlation coefficients C are: 0.916; 0.909; 0.891; and, 0.886 at 0, 15, 30, and 45 degrees, respectively. As a result, there were strong correlations between the simulated and measured images. Conclusion: This system can be used to perform head positioning more easily and accurately. It is expected that this system will be useful for learning radiographic techniques by students. Moreover, it could also be used for predicting the actual x-ray image prior to x-ray exposure in clinical environments.« less

Future Hard X-ray and Gamma-Ray Missions

NASA Astrophysics Data System (ADS)

Krawczynski, Henric; Physics of the Cosmos (PCOS) Gamma Ray Science Interest Group (GammaSIG) Team

2017-01-01

With four major NASA and ESA hard X-ray and gamma-ray missions in orbit (Swift, NuSTAR, INTEGRAL, and Fermi) hard X-ray and gamma-ray astronomy is making major contributions to our understanding of the cosmos. In this talk, I will summarize the current and upcoming activities of the Physics of the Cosmos Gamma Ray Science Interest Group and highlight a few of the future hard X-ray and gamma-ray mission discussed by the community. HK thanks NASA for the support through the awards NNX14AD19G and NNX16AC42G and for PCOS travel support.

Final Report on Developing Microstructure-Property Correlation in Reactor Materials using in situ High-Energy X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Meimei; Almer, Jonathan D.; Yang, Yong

2016-01-01

This report provides a summary of research activities on understanding microstructure – property correlation in reactor materials using in situ high-energy X-rays. The report is a Level 2 deliverable in FY16 (M2CA-13-IL-AN_-0403-0111), under the Work Package CA-13-IL-AN_- 0403-01, “Microstructure-Property Correlation in Reactor Materials using in situ High Energy Xrays”, as part of the DOE-NE NEET Program. The objective of this project is to demonstrate the application of in situ high energy X-ray measurements of nuclear reactor materials under thermal-mechanical loading, to understand their microstructure-property relationships. The gained knowledge is expected to enable accurate predictions of mechanical performance of these materialsmore » subjected to extreme environments, and to further facilitate development of advanced reactor materials. The report provides detailed description of the in situ X-ray Radiated Materials (iRadMat) apparatus designed to interface with a servo-hydraulic load frame at beamline 1-ID at the Advanced Photon Source. This new capability allows in situ studies of radioactive specimens subject to thermal-mechanical loading using a suite of high-energy X-ray scattering and imaging techniques. We conducted several case studies using the iRadMat to obtain a better understanding of deformation and fracture mechanisms of irradiated materials. In situ X-ray measurements on neutron-irradiated pure metal and model alloy and several representative reactor materials, e.g. pure Fe, Fe-9Cr model alloy, 316 SS, HT-UPS, and duplex cast austenitic stainless steels (CASS) CF-8 were performed under tensile loading at temperatures of 20-400°C in vacuum. A combination of wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), and imaging techniques were utilized to interrogate microstructure at different length scales in real time while the specimen was subject to thermal-mechanical loading. In addition, in situ X-ray studies were complemented and benchmarked by ex situ characterization using advanced electron microscopy, atom probe tomography (APT) and micro/nano-indentation. The report presented in situ tensile test results on neutron-irradiated pure Fe, Fe-9Cr model alloy, 316 SS and CASS CF-8. These in situ experiments demonstrate the broad applications of the new capability in understanding several outstanding issues related to irradiated materials.« less

X-ray and optical observations of four polars

NASA Astrophysics Data System (ADS)

Worpel, H.; Schwope, A. D.; Granzer, T.; Reinsch, K.; Schwarz, R.; Traulsen, I.

2016-08-01

Aims: We investigate the temporal and spectral behaviour of four polar cataclysmic variables from the infrared to X-ray regimes, refine our knowledge of the physical parameters of these systems at different accretion rates, and search for a possible excess of soft X-ray photons. Methods: We obtained and analysed four XMM-Newton X-ray observations of three of the sources, two of them discovered with the SDSS and one in the RASS. The X-ray data were complemented by optical photometric and spectroscopic observations and, for two sources, archival Swift observations. Results: SDSSJ032855.00+052254.2 was X-ray bright in two XMM-Newton and two Swift observations, and shows transitions from high and low accretion states on a timescale of a few months. The source shows no significant soft excess. We measured the magnetic field strength at the main accreting pole to be 39 MG and the inclination to be 45° ≤ I ≤ 77°, and we refined the long-term ephemeris. SDSSJ133309.20+143706.9 was X-ray faint. We measured a faint phase X-ray flux and plasma temperature for this source, which seems to spend almost all of its time accreting at a low level. Its inclination is less than about 76°. 1RXSJ173006.4+033813 was X-ray bright in the XMM-Newton observation. Its spectrum contained a modest soft blackbody component, not luminous enough to be considered a significant soft excess. We inferred a magnetic field strength at the main accreting pole of 20 to 25 MG, and that the inclination is less than 77° and probably less than 63°. V808 Aur, also known as CSS081231:J071126+440405, was X-ray faint in the Swift observation, but there is nonetheless strong evidence for bright and faint phases in X-rays and perhaps in UV. Residual X-ray flux from the faint phase is difficult to explain by thermal emission from the white dwarf surface, or by accretion onto the second pole. We present a revised distance estimate of 250 pc. Conclusions: The three systems we were able to study in detail appear to be normal polars with luminosities and magnetic field strengths typical for this class of accreting binary. None of the four systems studied shows the strong soft excess thought commonplace in polars prior to the XMM-Newton era. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).

Two giant outbursts of V0332+53 observed with INTEGRAL

NASA Astrophysics Data System (ADS)

Ferrigno, Carlo; Ducci, Lorenzo; Bozzo, Enrico; Kretschmar, Peter; Kühnel, Matthias; Malacaria, Christian; Pottschmidt, Katja; Santangelo, Andrea; Savchenko, Volodymyr; Wilms, Jörn

2016-10-01

Context. In July 2015, the high-mass X-ray binary V0332+53 underwent a giant outburst, a decade after the previous one. V0332+53 hosts a strongly magnetized neutron star. During the 2004-2005 outburst, an anti-correlation between the centroid energy of its fundamental cyclotron resonance scattering features (CRSFs) and the X-ray luminosity was observed. Aims: The long (≈100 d) and bright (Lx ≈ 1038 erg s-1) 2015 outburst provided the opportunity to study the unique properties of the fundamental CRSF during another outburst and to study its dependence on the X-ray luminosity. Methods: The source was observed by the INTEGRAL satellite for ~330 ks. We exploit the spectral resolution at high energies of the SPectrometer on INTEGRAL (SPI) and the Joint European X-ray Monitors to characterize its spectral properties, focusing in particular on the CRSF-luminosity dependence. We complement the data of the 2015 outburst with those collected by SPI in 2004-2005, which have so far been left unpublished. Results: We find a highly significant anti-correlation of the centroid energy of the fundamental CRSF and the 3-100 keV luminosity of E1 ∝ -0.095(8)L37 keV. This trend is observed for both outbursts. We confirm the correlation between the width of the fundamental CRSF and the X-ray luminosity previously found in the JEM-X and IBIS dataset of the 2004-2005 outburst. By exploiting the RXTE/ASM and Swift/BAT monitoring data, we also report on the detection of a ~34 d modulation superimposed on the mean profiles and roughly consistent with the orbital period of the pulsar. We discuss possible interpretations of such variability.

The period history of the X-ray pulsar in MSH 15-52

NASA Technical Reports Server (NTRS)

Weisskopf, M. C.; Elsner, R. F.; Darbo, W.; Leahy, D.; Naranan, S.; Harnden, F. R.; Seward, F. D.; Sutherland, P. G.; Grindlay, J. E.

1983-01-01

New and refined mesurements of the pulse period of the X-ray pulsar in the supernova remnant MSH 15-52 are presented. The data were obtained with the Monitor proportional Counter on board the HEAO 2 observatory. The period measurements were obtained by analyzing pulse arrival times determined by cross-correlating sample pulse profiles with a master template. The period history for the source and a representative 0.15 s X-ray light curve are shown. The X-ray measurements alone lead to a refined value of the period derivative of (1.5382 + or -0.0024) x 10 to the -12th s/s, while including the results of more recent radio observations leads to a value of (1.54029 + or -0.00095) x 10 to the -12th s/s. These results indicate a hard-point source surrounded by diffuse nebular emission.

Advanced X-ray Astrophysics Facility (AXAF): Science working group report. [space shuttle payload

NASA Technical Reports Server (NTRS)

1980-01-01

The Advanced X-Ray Astrophysics Facility (AXAF) mission concept is examined from a scientific viewpoint. A brief description of the development of X-ray astronomy and a summary description of AXAF, the scientific objectives of the facility, a description of representative scientific instruments, requirements for X-ray ground testing, and a summary of studies related to spacecraft and support subsystems, are included.

[Frequency of diagnosis of postmenopausal osteoporosis of the spine, distant radius and extravertebral fractures in women with normal body mass, overweight and obesity].

PubMed

Popov, A A; Izmozherova, N V; Fominykh, M I; Tagil'tseva, N V; Kozulina, E V; Gavrilova, E I

2008-01-01

To assess features and peculiarities of postmenopausal osteoporosis (OP) in women with normal body mass, overweight and obesity. Dual energy X-ray absorptiometry of the lumbal spine (Lunar DPX) and distal radius X-ray absorptiometry (DTX 200) were performed during cross-section study of 730 symptomatic postmenopausal women. OP was diagnosed in 253 (34.7%) women, 30.5% of them had normal body mass, 43.2% had overweight and 26.3% were obese. Among them 227 had atraumatic fractures at the age over 50 years. Obese OP patients had significantly higher frequency of arterial hypertension, chronic heart failure, osteoarthritis and glucose metabolism disorders than osteoporotic patients with normal body mass. Fracture frequency did not differ between groups with normal body mass, overweight and obesity. Excessive body mass did not decrease fracture risk in women with postmenopausal OP.

Microtomographic images of rat's lumbar vertebra microstructure using 30 keV synchrotron X-rays: an analysis in terms of 3D visualization

NASA Astrophysics Data System (ADS)

Rao, D. V.; Takeda, T.; Kawakami, T.; Uesugi, K.; Tsuchiya, Y.; Wu, J.; Lwin, T. T.; Itai, Y.; Zeniya, T.; Yuasa, T.; Akatsuka, T.

2004-05-01

Microtomographic images of rat's lumbar vertebra of different age groups varying from 8, 56 and 78 weeks were obtained at 30 keV using synchrotron X-rays with a spatial resolution of 12 μm. The images are analyzed in terms of 3D visualization and micro-architecture. Density histogram of rat's lumbar vertebra is compared with test phantoms. Rat's lumbar volume and phantom volume are studied at different concentrations of hydroxyapatite with slice number. With the use of 2D slices, 3D images are reconstructed, in order to know the evolution and a state of decline of bone microstructure with aging. Cross-sectional μ-CT images shows that the bone of young rat has a fine trabecular microstructure while that of the old rat has large meshed structure.

Resonant inelastic x-ray scattering on iso-C₂H₂Cl₂ around the chlorine K-edge: structural and dynamical aspects.

PubMed

Kawerk, Elie; Carniato, Stéphane; Journel, Loïc; Marchenko, Tatiana; Piancastelli, Maria Novella; Žitnik, Matjaž; Bučar, Klemen; Bohnic, Rok; Kavčič, Matjaž; Céolin, Denis; Khoury, Antonio; Simon, Marc

2014-10-14

We report a theoretical and experimental study of the high resolution resonant K(α) X-ray emission lines around the chlorine K-edge in gas phase 1,1-dichloroethylene. With the help of ab initio electronic structure calculations and cross section evaluation, we interpret the lowest lying peak in the X-ray absorption and emission spectra. The behavior of the K(α) emission lines with respect to frequency detuning highlights the existence of femtosecond nuclear dynamics on the dissociative Potential Energy Surface of the first K-shell core-excited state.

Resonant inelastic x-ray scattering on iso-C2H2Cl2 around the chlorine K-edge: Structural and dynamical aspects

NASA Astrophysics Data System (ADS)

Kawerk, Elie; Carniato, Stéphane; Journel, Loïc; Marchenko, Tatiana; Piancastelli, Maria Novella; Žitnik, Matjaž; Bučar, Klemen; Bohnic, Rok; Kavčič, Matjaž; Céolin, Denis; Khoury, Antonio; Simon, Marc

2014-10-01

We report a theoretical and experimental study of the high resolution resonant Kα X-ray emission lines around the chlorine K-edge in gas phase 1,1-dichloroethylene. With the help of ab initio electronic structure calculations and cross section evaluation, we interpret the lowest lying peak in the X-ray absorption and emission spectra. The behavior of the Kα emission lines with respect to frequency detuning highlights the existence of femtosecond nuclear dynamics on the dissociative Potential Energy Surface of the first K-shell core-excited state.

Poly(iohexol) nanoparticles as contrast agents for in vivo X-ray computed tomography imaging.

PubMed

Yin, Qian; Yap, Felix Y; Yin, Lichen; Ma, Liang; Zhou, Qin; Dobrucki, Lawrence W; Fan, Timothy M; Gaba, Ron C; Cheng, Jianjun

2013-09-18

Biocompatible poly(iohexol) nanoparticles, prepared through cross-linking of iohexol and hexamethylene diisocyanate followed by coprecipitation of the resulting cross-linked polymer with mPEG-polylactide, were utilized as contrast agents for in vivo X-ray computed tomography (CT) imaging. Compared to conventional small-molecule contrast agents, poly(iohexol) nanoparticles exhibited substantially protracted retention within the tumor bed and a 36-fold increase in CT contrast 4 h post injection, which makes it possible to acquire CT images with improved diagnosis accuracy over a broad time frame without multiple administrations.

ACCURATE MODELING OF X-RAY EXTINCTION BY INTERSTELLAR GRAINS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffman, John; Draine, B. T., E-mail: jah5@astro.princeton.edu, E-mail: draine@astro.princeton.edu

Interstellar abundance determinations from fits to X-ray absorption edges often rely on the incorrect assumption that scattering is insignificant and can be ignored. We show instead that scattering contributes significantly to the attenuation of X-rays for realistic dust grain size distributions and substantially modifies the spectrum near absorption edges of elements present in grains. The dust attenuation modules used in major X-ray spectral fitting programs do not take this into account. We show that the consequences of neglecting scattering on the determination of interstellar elemental abundances are modest; however, scattering (along with uncertainties in the grain size distribution) must bemore » taken into account when near-edge extinction fine structure is used to infer dust mineralogy. We advertise the benefits and accuracy of anomalous diffraction theory for both X-ray halo analysis and near edge absorption studies. We present an open source Fortran suite, General Geometry Anomalous Diffraction Theory (GGADT), that calculates X-ray absorption, scattering, and differential scattering cross sections for grains of arbitrary geometry and composition.« less

Experimental characterization of an ultra-fast Thomson scattering x-ray source with three-dimensional time and frequency-domain analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuba, J; Slaughter, D R; Fittinghoff, D N

We present a detailed comparison of the measured characteristics of Thomson backscattered x-rays produced at the PLEIADES (Picosecond Laser-Electron Interaction for the Dynamic Evaluation of Structures) facility at Lawrence Livermore National Laboratory to predicted results from a newly developed, fully three-dimensional time and frequency-domain code. Based on the relativistic differential cross section, this code has the capability to calculate time and space dependent spectra of the x-ray photons produced from linear Thomson scattering for both bandwidth-limited and chirped incident laser pulses. Spectral broadening of the scattered x-ray pulse resulting from the incident laser bandwidth, perpendicular wave vector components in themore » laser focus, and the transverse and longitudinal phase space of the electron beam are included. Electron beam energy, energy spread, and transverse phase space measurements of the electron beam at the interaction point are presented, and the corresponding predicted x-ray characteristics are determined. In addition, time-integrated measurements of the x-rays produced from the interaction are presented, and shown to agree well with the simulations.« less

Constraints on Cosmic Rays, Magnetic Fields, and Dark Matter from Gamma-ray Observations of the Coma Cluster of Galaxies with VERITAS and FERMI

NASA Technical Reports Server (NTRS)

Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Cesarini, A.;

X-Ray Binary Populations in a Cosmological Context, Including NuSTAR Predictions

NASA Technical Reports Server (NTRS)

Cardiff, Ann Hornschemeier

2011-01-01

The new ultradeep 4 Ms Chandra Deep Field South has afforded the deepest view ever of X-ray binary populations. We report on the latest results on both LMXB and HMXB evolution out to redshifts of approximately four, including comparison with the latest theoretical models, using this deepest-ever view of the X-ray universe with Chandra. The upcoming NuSTAR mission will open up X-ray binary populations in the hard X-ray band, similar to the pioneering work of Fabbiano et al. in the Einstein era. We report on plans to study both Local Group and starburst galaxies as well as the implications those observations may have for X-ray binary populations in galaxies contributing to the Cosmic X-ray Background.

Ultraviolet germicidal irradiation and its effects on elemental distributions in mouse embryonic fibroblast cells in x-ray fluorescence microanalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Qiaoling; Vogt, Stefan; Lai, Barry

Rapidly-frozen hydrated (cryopreserved) specimens combined with cryo-scanning x-ray fluorescence microscopy provide an ideal approach for investigating elemental distributions in biological cells and tissues. However, because cryopreservation does not deactivate potentially infectious agents associated with Risk Group 2 biological materials, one must be concerned with contamination of expensive and complicated cryogenic x-ray microscopes when working with such materials. We employed ultraviolet germicidal irradiation to decontaminate previously cryopreserved cells under liquid nitrogen, and then investigated its effects on elemental distributions under both frozen hydrated and freeze dried states with x-ray fluorescence microscopy. We show that the contents and distributions of most biologicallymore » important elements remain nearly unchanged when compared with non-ultraviolet-irradiated counterparts, even after multiple cycles of ultraviolet germicidal irradiation and cryogenic x-ray imaging. This provides a potential pathway for rendering Risk Group 2 biological materials safe for handling in multiuser cryogenic x-ray microscopes without affecting the fidelity of the results.« less

Ultraviolet germicidal irradiation and its effects on elemental distributions in mouse embryonic fibroblast cells in x-ray fluorescence microanalysis

DOE PAGES

Jin, Qiaoling; Vogt, Stefan; Lai, Barry; ...

2015-02-23

Rapidly-frozen hydrated (cryopreserved) specimens combined with cryo-scanning x-ray fluorescence microscopy provide an ideal approach for investigating elemental distributions in biological cells and tissues. However, because cryopreservation does not deactivate potentially infectious agents associated with Risk Group 2 biological materials, one must be concerned with contamination of expensive and complicated cryogenic x-ray microscopes when working with such materials. We employed ultraviolet germicidal irradiation to decontaminate previously cryopreserved cells under liquid nitrogen, and then investigated its effects on elemental distributions under both frozen hydrated and freeze dried states with x-ray fluorescence microscopy. We show that the contents and distributions of most biologicallymore » important elements remain nearly unchanged when compared with non-ultraviolet-irradiated counterparts, even after multiple cycles of ultraviolet germicidal irradiation and cryogenic x-ray imaging. This provides a potential pathway for rendering Risk Group 2 biological materials safe for handling in multiuser cryogenic x-ray microscopes without affecting the fidelity of the results.« less

X-Ray Fluorescence to Determine Zn in Bolivian Children using Hair Samples

NASA Astrophysics Data System (ADS)

Tellería Narvaez, C. A.; Fernández Alcázar, S.; Barrientos Zamora, F. G.; Chungara Castro, J.; Luna Lauracia, I.; Mamani Tola, H.; Mita Peralta, E.; Muñoz Gosálvez, A. O.; Romero Bolaños, L. E.; Ramírez Ávila, G. M.

2014-06-01

As a first step in the evaluation of nutritional levels in Bolivian children (8-13 years-old), we carried out X-Ray Fluorescence measurements in hair samples of children belonging to different social classes and living either in rural areas or in cities. The aim of this study is to contribute to health policies tending to improve the global health of children and consequently avoid malnutrition. Our method intends to have maximum reliability and at the same time be as simple as possible from an experimental point of view. Additionally, we use this method to determine some other elements such as Fe, Cu, Pb, As and Hg, the latter three considered as contaminants that could be present in children living in areas which neighbor mines and industries. This work will be complemented by some biological and medical tests.

Difficult macromolecular structures determined using X-ray diffraction techniques.

PubMed

Hernández-Santoyo, Alejandra

2012-07-01

Macromolecular crystallography has been, for the last few decades, the main source of structural information of biological macromolecular systems and it is one of the most powerful techniques for the analysis of enzyme mechanisms and macromolecular interactions at the atomic level. In addition, it is also an extremely powerful tool for drug design. Recent technological and methodological developments in macromolecular X-ray crystallography have allowed solving structures that until recently were considered difficult or even impossible, such as structures at atomic or subatomic resolution or large macromolecular complexes and assemblies at low resolution. These developments have also helped to solve the 3D-structure of macromolecules from twin crystals. Recently, this technique complemented with cryo-electron microscopy and neutron crystallography has provided the structure of large macromolecular machines with great precision allowing understanding of the mechanisms of their function.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Meimei; Wang, Leyun; Almer, Jonathan D.

Deformation processes in Grade 91 (Fe–9%Cr–1%Mo–V,Nb) and Grade 92 (Fe–9%Cr–0.5%Mo–2%W–V,Nb) ferritic–martensitic steels were investigated at temperatures between 20 and 650 °C using high-energy synchrotron X-ray diffraction with in situ thermal–mechanical loading. The change of the dislocation density with strain was quantified by X-ray diffraction line profile analysis complemented by transmission electron microscopy measurements. The relationship between dislocation density and strain during uniform deformation was described by a dislocation model, and two critical materials parameters, namely dislocation mean free path and dynamic recovery coefficient, were determined as a function of temperature. Effects of alloy chemistry, thermal–mechanical treatment and temperature on themore » tensile deformation process in Grade 91 and Grade 92 steels can be well understood by the dislocation evolution behavior.« less

An X-ray image of the violent interstellar medium in 30 Doradus

NASA Technical Reports Server (NTRS)

Wang, Q.; Helfand, D. J.

1991-01-01

A detailed analysis of the X-ray emission from the largest H II region complex in the Local Group, 30 Dor, is presented. Applying a new maximum entropy deconvolution algorithm to the Einstein Observatory data, reveals striking correlations among the X-ray, radio, and optical morphologies of the region, with X-ray-emitting bubbles filling cavities surrounded by H-alpha shells and coextensive diffuse X-ray and radio continuum emission from throughout the region. The total X-ray luminosity in the 0.16-3.5 keV band from an area within 160 pc of the central cluster R136 is about 2 x 10 to the 37th ergs/sec.

Quantitative X-ray dark-field and phase tomography using single directional speckle scanning technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hongchang, E-mail: hongchang.wang@diamond.ac.uk; Kashyap, Yogesh; Sawhney, Kawal

2016-03-21

X-ray dark-field contrast tomography can provide important supplementary information inside a sample to the conventional absorption tomography. Recently, the X-ray speckle based technique has been proposed to provide qualitative two-dimensional dark-field imaging with a simple experimental arrangement. In this letter, we deduce a relationship between the second moment of scattering angle distribution and cross-correlation degradation of speckle and establish a quantitative basis of X-ray dark-field tomography using single directional speckle scanning technique. In addition, the phase contrast images can be simultaneously retrieved permitting tomographic reconstruction, which yields enhanced contrast in weakly absorbing materials. Such complementary tomography technique can allow systematicmore » investigation of complex samples containing both soft and hard materials.« less

Dimeric, trimeric and tetrameric complexes of immunoglobulin G fix complement.

PubMed Central

Wright, J K; Tschopp, J; Jaton, J C; Engel, J

1980-01-01

The binding of pure dimers, trimers and tetramers of randomly cross-linked non-immune rabbit immunoglobulin G to the first component and subcomponent of the complement system, C1 and C1q respectively, was studied. These oligomers possessed open linear structures. All three oligomers fixed complement with decreasing affinity in the order: tetramer, trimer, dimer. Complement fixation by dimeric immunoglobulin exhibited the strongest concentration-dependence. No clear distinction between a non-co-operative and a co-operative binding mechanism could be achieved, although the steepness of the complement-fixation curves for dimers and trimers was better reflected by the co-operative mechanism. Intrinsic binding constants were about 10(6)M-1 for dimers, 10(7)M-1 for trimers and 3 X 10(9)M-1 for tetramers, assuming non-co-operative binding. The data are consistent with a maximum valency of complement component C1 for immunoglobulin G protomers in the range 6-18. The binding of dimers to purified complement subcomponent C1q was demonstrated by sedimentation-velocity ultracentrifugation. Mild reduction of the complexes by dithioerythritol caused the immunoglobulin to revert to the monomeric state (S20,w = 6.2-6.5S) with concomitant loss of complement-fixing ability. Images Fig. 2. PMID:6985362

Cross-sectional structural parameters from densitometry

NASA Technical Reports Server (NTRS)

Cleek, Tammy M.; Whalen, Robert T.

2002-01-01

Bone densitometry has previously been used to obtain cross-sectional properties of bone from a single X-ray projection across the bone width. Using three unique projections, we have extended the method to obtain the principal area moments of inertia and orientations of the principal axes at each scan cross-section along the length of the scan. Various aluminum phantoms were used to examine scanner characteristics to develop the highest accuracy possible for in vitro non-invasive analysis of cross-sectional properties. Factors considered included X-ray photon energy, initial scan orientation, the angle spanned by the three scans (included angle), and I(min)/I(max) ratios. Principal moments of inertia were accurate to within +/-3.1% and principal angles were within +/-1 degrees of the expected value for phantoms scanned with included angles of 60 degrees and 90 degrees at the higher X-ray photon energy (140 kVp). Low standard deviations in the error (0.68-1.84%) also indicate high precision of calculated measurements with these included angles. Accuracy and precision decreased slightly when the included angle was reduced to 30 degrees. The method was then successfully applied to a pair of excised cadaveric tibiae. The accuracy and insensitivity of the algorithms to cross-sectional shape and changing isotropy (I(min)/I(max)) values when various included angles are used make this technique viable for future in vivo studies.

[Complement deficiencies and meningococcal disease in The Netherlands].

PubMed

Swart, A G; Fijen, C A; te Bulte, M T; Daha, M R; Dankert, J; Kuijper, E J

1993-06-05

To determine the prevalence of complement system deficiencies in patients who have survived a Neisseria meningitidis infection. Retrospective. Reference laboratory for bacterial meningitis of the University of Amsterdam and the National Institute of Public Health and Environmental Protection. Out of the files of the laboratory 187 patients who had experienced a meningococcal infection in the Netherlands between 1959-1990 were selected in two groups according to the infecting bacterial strain: 97 patients with a serogroup X, Y, Z, W135, 29E, or non-groupable strains and 90 patients with an infection due to serogroup A or C. The patients were asked for their cooperation by their family doctor and one of us visited the patients at home to take blood samples. The complement activity was studied with a haemolysis in gel test and with an assay of haemolytic activity in free solution. Complement deficiency was present in 18% of the 187 patients who had experienced a meningococcal infection. The highest prevalence was found in patients older than 10 years who had developed infections due to serogroups X, Y, W135, or non-groupable strains (45%). Of the patients with a serogroup A or C infection, 3% had an complement deficiency. Of the complement deficiencies, 42% concerned a component of the alternative pathway, 12% a deficiency of C3, and 46% a component of the terminal route. The most commonly found deficiencies were properdin deficiency (39%) and C8 deficiency (18%). 30% of the complement deficient patients reported other family members having experienced meningitis. Recurrent meningitis was only observed in patients with terminal route deficiencies. We recommend that patients with a meningococcal infection due to serogroups X, Y, W135 or non-groupable strains should be screened for complement deficiency.

Robert R. Wilson Prize: The Quest for Bright, Coherent X-Rays: A Personal Story

NASA Astrophysics Data System (ADS)

Kim, Kwang Je

2014-03-01

Stories associated with the advances in x-ray source techniques during the last several decades will be told from a personal viewpoint. I will start from the ``third-generation'' x-ray sources based on storage-ring-based undulators and a struggle to find a proper way to quantify the radiation strength. I will then discuss how the initially incoherent undulator radiation evolves into an intense-quasi-coherent radiation via free-electron laser (FEL) interaction. This so-called self-amplified spontaneous emission (SASE) in the x-ray region could be realized with the advent of laser-induced electron guns and forms the basis of the linac-driven ``fourth generation'' x-ray facilities. An x-ray FEL oscillator (XFELO) will also be feasible if Bragg reflectors, such as diamond crystals, are used as cavity mirrors. An XFELO driven by a CW superconducting linac would be a ``real x-ray laser,'' producing a steady stream of fully coherent, spectrally pure x-ray pulses. An XFELO can be mode-locked, thus producing x-ray spectral comb, if the cavity length can be fixed to a fraction of the x-ray wavelength by referencing to a narrow nuclear resonance. A mode-locked XFELO will enable x-ray quantum optics experiments, such as matter-wave interferometry, for fundamental physics. Alongside these main themes, stories for novel and ``cute'' schemes, such as a crossed undulator for polarization switching and an emittance exchanger for swapping the transverse and longitudinal phase space, will also be presented. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357.

Complex UV/X-ray variability of 1H 0707-495

NASA Astrophysics Data System (ADS)

Pawar, P. K.; Dewangan, G. C.; Papadakis, I. E.; Patil, M. K.; Pal, Main; Kembhavi, A. K.

2017-12-01

We study the relationship between the UV and X-ray variability of the narrow-line Seyfert 1 galaxy 1H 0707-495. Using a year-long Swift monitoring and four long XMM-Newton observations, we perform cross-correlation analyses of the UV and X-ray light curves, on both long and short time-scales. We also perform time-resolved X-ray spectroscopy on 1-2 ks scale, and study the relationship between the UV emission and the X-ray spectral components - soft X-ray excess and a power law. We find that the UV and X-ray variations anticorrelate on short, and possibly on long time-scales as well. Our results rule out reprocessing as the dominant mechanism for the UV variability, as well as the inward propagating fluctuations in the accretion rate. Absence of a positive correlation between the photon index and the UV flux suggests that the observed UV emission is unlikely to be the seed photons for the thermal Comptonization. We find a strong correlation between the continuum flux and the soft-excess temperature which implies that the soft excess is most likely the reprocessed X-ray emission in the inner accretion disc. Strong X-ray heating of the innermost regions in the disc, due to gravitational light bending, appears to be an important effect in 1H 0707-495, giving rise to a significant fraction of the soft excess as reprocessed thermal emission. We also find indications for a non-static, dynamic X-ray corona, where either the size or height (or both) vary with time.

Correlation Between CXB and Cib: the Nature of Cib Fluctuations

NASA Astrophysics Data System (ADS)

Kashlinsky, Alexander

2011-09-01

We will analyze the 4Ms CDFS and 2 Ms CDFN data by cross-correlating them with the maps of source-subtracted Cosmic Infrared Background (CIB) fluctuations from Spitzer/IRAC. This will provide important information about the nature of the sources contributing to these CIB fluctuations.We will carefully subtract X-ray background, construct a common mask for the X-ray and CIB IRAC maps and compute the cross- and auto-correlations. Our pilot study demonstrates conclusively that this measurement is feasible and would lead to conclusive results. The results will enable to estimate the relative contributions of accreting sources, such as black holes, to the recently discovered CIB fluctuations (significant cross-correlations), and those emitting by stellar nucleosynthesis.

Structural basis for complement evasion by Lyme disease pathogen Borrelia burgdorferi.

PubMed

Bhattacharjee, Arnab; Oeemig, Jesper S; Kolodziejczyk, Robert; Meri, Taru; Kajander, Tommi; Lehtinen, Markus J; Iwaï, Hideo; Jokiranta, T Sakari; Goldman, Adrian

2013-06-28

Borrelia burgdorferi spirochetes that cause Lyme borreliosis survive for a long time in human serum because they successfully evade the complement system, an important arm of innate immunity. The outer surface protein E (OspE) of B. burgdorferi is needed for this because it recruits complement regulator factor H (FH) onto the bacterial surface to evade complement-mediated cell lysis. To understand this process at the molecular level, we used a structural approach. First, we solved the solution structure of OspE by NMR, revealing a fold that has not been seen before in proteins involved in complement regulation. Next, we solved the x-ray structure of the complex between OspE and the FH C-terminal domains 19 and 20 (FH19-20) at 2.83 Å resolution. The structure shows that OspE binds FH19-20 in a way similar to, but not identical with, that used by endothelial cells to bind FH via glycosaminoglycans. The observed interaction of OspE with FH19-20 allows the full function of FH in down-regulation of complement activation on the bacteria. This reveals the molecular basis for how B. burgdorferi evades innate immunity and suggests how OspE could be used as a potential vaccine antigen.

Comparison of the X-Ray and Radio Light Curves of Quasar PKS 1510--089

NASA Technical Reports Server (NTRS)

Aller, M. F.; Marscher, A. P.; Marchenko-Jorstad, S. G.; McHardy, I. M.; Aller, H. D.

1998-01-01

We present results for the X-ray-bright superluminal AGN PKS 1510-089 (z=0.36) monitored weekly with the Rossi X-Ray Timing Explorer for the past four years in order to study the origin of X-ray emission from this extremely variable blazer. These RXTE data are compared with weekly cm-band flux and polarization observations from the Michigan Diameter telescope, to identify correlated activity and associated frequency-dependent time delays for constraining X-ray emission models; and bimonthly 7mm VLBA total and linearly polarized intensity imaging to identify temporal associations between X-ray events and the ejection of superluminal components and disturbances in the magnetic field, to test if the X-ray energy release is related to changes in the inner jet flow. Both the X-ray (2-20 keV) and radio flux are highly variable on timescales of weeks. The VLBA mas structure is dominated by a bright core with a weak jet; both the ejection of very fast superluminal knots and changes in the fractional polarization and EVPA of the core on timescales of one to four months are identified. Two outbursts in 1997 are well-resolved in both the centimeter and X-ray bands. Both the strong temporal association and the similar outburst shape support a causal relation, and a discrete cross-correlation analysis identifies that the X-ray lags the radio by 16 days during the bursts. Starting in 1998 the behavior changes: the correlation is weaker with the X-ray possibly leading the radio by six days. During the full time window there is a correlation between bands as expected if the radio photons are upscattered to X-ray energies. The time correlations and difference between the flat X-ray spectral index (0.0 <= alpha <= 0.5 where F(sub v) is proportional to v(exp -alpha)), and the mm-wave synchrotron spectrum (alpha = 0.8) are discussed within the framework of viable SSC models.

A comparative study on radioprotective effect of N-acetylcysteine against 12C6+ ion versus X-rays

NASA Astrophysics Data System (ADS)

Liu, Yang; Zhang, Hong; Zhang, Luwei

Purpose: The aim of this study was to evaluate the different protective efficacy of N-acetylcysteine (NAC, 200 mg/kg dose) against 12C6+ ion (4 Gy) and X-rays (4 Gy) - induced damage in vivo model. Method: Kung-Ming female mice were divided into six groups, each composed of twelve animals: control group, two irradiation groups, and two NAC-treated groups, as well as NAC alone-treated group. An acute study was carried out to determine alterations in the oxidative stress (malondialdehyde level) using with colorimetric method and cell apoptosis measuring by flow cytometry as well as DNA-single strand break analyzing by comet assay at 2h after irradiation in mouse liver. Results: Compared with respective irradiation group, NAC can significantly ameliorate injury induced by two types of ionizing irradiation, which marked by the decrease of malondialdehyde level, and the reduction of apoptosis cells percentage and DNA damage. But the greater efficacy of NAC was prominently observed to inhibit the damage induced by X-rays, suggesting that NAC-mediated protective effect is more advisable to X-rays than 12C6+ ion irradiation. Moreover, NAC treatment alone did not result in any damage as compared to the control group. Conclusion: NAC may merit development as a potential radioprotective agent. Furthermore, NAC might exert its best effort to respond X rays-caused damage.

X and Y Chromosome Complement Influence Adiposity and Metabolism in Mice

PubMed Central

Chen, Xuqi; McClusky, Rebecca; Itoh, Yuichiro; Reue, Karen

2013-01-01

Three different models of MF1 strain mice were studied to measure the effects of gonadal secretions and sex chromosome type and number on body weight and composition, and on related metabolic variables such as glucose homeostasis, feeding, and activity. The 3 genetic models varied sex chromosome complement in different ways, as follows: 1) “four core genotypes” mice, comprising XX and XY gonadal males, and XX and XY gonadal females; 2) the XY* model comprising groups similar to XO, XX, XY, and XXY; and 3) a novel model comprising 6 groups having XO, XX, and XY chromosomes with either testes or ovaries. In gonadally intact mice, gonadal males were heavier than gonadal females, but sex chromosome complement also influenced weight. The male/female difference was abolished by adult gonadectomy, after which mice with 2 sex chromosomes (XX or XY) had greater body weight and percentage of body fat than mice with 1 X chromosome. A second sex chromosome of either type, X or Y, had similar effects, indicating that the 2 sex chromosomes each possess factors that influence body weight and composition in the MF1 genetic background. Sex chromosome complement also influenced metabolic variables such as food intake and glucose tolerance. The results reveal a role for the Y chromosome in metabolism independent of testes and gonadal hormones and point to a small number of X–Y gene pairs with similar coding sequences as candidates for causing these effects. PMID:23397033

A new on-axis micro-spectrophotometer for combining Raman, fluorescence and UV/Vis absorption spectroscopy with macromolecular crystallography at the Swiss Light Source

PubMed Central

Pompidor, Guillaume; Dworkowski, Florian S. N.; Thominet, Vincent; Schulze-Briese, Clemens; Fuchs, Martin R.

2013-01-01

The combination of X-ray diffraction experiments with optical methods such as Raman, UV/Vis absorption and fluorescence spectroscopy greatly enhances and complements the specificity of the obtained information. The upgraded version of the in situ on-axis micro-spectrophotometer, MS2, at the macromolecular crystallography beamline X10SA of the Swiss Light Source is presented. The instrument newly supports Raman and resonance Raman spectroscopy, in addition to the previously available UV/Vis absorption and fluorescence modes. With the recent upgrades of the spectral bandwidth, instrument stability, detection efficiency and control software, the application range of the instrument and its ease of operation were greatly improved. Its on-axis geometry with collinear X-ray and optical axes to ensure optimal control of the overlap of sample volumes probed by each technique is still unique amongst comparable facilities worldwide and the instrument has now been in general user operation for over two years. PMID:23955041

A new on-axis micro-spectrophotometer for combining Raman, fluorescence and UV/Vis absorption spectroscopy with macromolecular crystallography at the Swiss Light Source.

PubMed

Pompidor, Guillaume; Dworkowski, Florian S N; Thominet, Vincent; Schulze-Briese, Clemens; Fuchs, Martin R

2013-09-01

The combination of X-ray diffraction experiments with optical methods such as Raman, UV/Vis absorption and fluorescence spectroscopy greatly enhances and complements the specificity of the obtained information. The upgraded version of the in situ on-axis micro-spectrophotometer, MS2, at the macromolecular crystallography beamline X10SA of the Swiss Light Source is presented. The instrument newly supports Raman and resonance Raman spectroscopy, in addition to the previously available UV/Vis absorption and fluorescence modes. With the recent upgrades of the spectral bandwidth, instrument stability, detection efficiency and control software, the application range of the instrument and its ease of operation were greatly improved. Its on-axis geometry with collinear X-ray and optical axes to ensure optimal control of the overlap of sample volumes probed by each technique is still unique amongst comparable facilities worldwide and the instrument has now been in general user operation for over two years.

Fossil Groups as Cosmological Labs

NASA Astrophysics Data System (ADS)

D'Onghia, Elena

Optical and X-ray measurements of fossil groups (FGs) suggest that they are old and relaxed systems. If FGs are assembled at higher redshift, there is enough time for intermediate-luminosity galaxies to merge, resulting in the formation of the brightest group galaxy (BGG). We carry out the first, systematic study of a large sample of FGs, the "FOssil Group Origins'' (FOGO) based on an International Time Project at the Roque de los Muchachos Observatory. For ten FOGO FGs we have been awarded time at SUZAKU Telescope to measure the temperature of the hot intragroup gas (IGM). For these systems we plan to evaluate and correlate their X-ray luminosity and X-ray temperature, Lx-Tx, optical luminosity and X-ray temperature, Lopt-Tx, and group velocity dispersion with their X-ray temperature, sigma V-Tx, as compared to the non fossil systems. By combining these observations with state-of-art cosmological hydrodynamical simulations we will open a new window into the study of the IGM and the nature of fossil systems. Our proposed work will be of direct relevance for the understanding and interpretation of data from several NASA science missions. Specifically, the scaling relations obtained from these data combined with our predictions obtained using state-of-the-art hydrodynamical simulation numerical adopting a new hydrodynamical scheme will motivate new proposal on CHANDRA X-ray telescope for fossil groups and clusters. We will additionally create a public Online Planetarium Show. This will be an educational site, containing an interactive program called: "A Voyage to our Universe''. In the show we will provide observed images of fossil groups and similar images and movies obtained from the numerical simulations showing their evolution. The online planetarium show will be a useful reference and an interactive educational tool for both students and the public.

Resonant Compton Upscattering Models of Magnetar Hard X-ray Emission and Polarization

NASA Astrophysics Data System (ADS)

Baring, Matthew G.; Wadiasingh, Zorawar; Gonthier, Peter L.; Kust Harding, Alice

2017-08-01

Non-thermal quiescent X-ray emission extending between 10 keV and around 150 keV has been seen in about 10 magnetars by RXTE, INTEGRAL, Suzaku and Fermi-GBM. For inner magnetospheric models of such hard X-ray signals, resonant Compton upscattering is anticipated to be the most efficient process for generating the continuum radiation. This is because the scattering becomes resonant at the cyclotron frequency, and the effective cross section exceeds the classical Thomson value by over two orders of magnitude. We present angle-dependent hard X-ray upscattering model spectra for uncooled monoenergetic relativistic electrons injected in inner regions of pulsar magnetospheres. These spectra are integrated over closed field lines and obtained for different observing perspectives. The spectral cut-off energies are critically dependent on the observer viewing angles and electron Lorentz factor. We find that electrons with energies less than around 15 MeV will emit most of their radiation below 250 keV, consistent with the observed turnovers in magnetar hard X-ray tails. Moreover, electrons of higher energy still emit most of the radiation below around 1 MeV, except for quasi-equatorial emission locales for select pulses phases. In such cases, attenuation mechanisms such as pair creation will be prolific, thereby making it difficult to observe signals extending into the Fermi-LAT band. Our spectral computations use new state-of-the-art, spin-dependent formalism for the QED Compton scattering cross section in strong magnetic fields. The emission exhibits strong polarization above around 30 keV that is anticipated to be dependent on pulse phase, thereby defining science agendas for future hard X-ray polarimeters.

Probing multi-scale mechanical damage in connective tissues using X-ray diffraction.

PubMed

Bianchi, Fabio; Hofmann, Felix; Smith, Andrew J; Thompson, Mark S

2016-11-01

The accumulation of microstructural collagen damage following repetitive loading is linked to painful and debilitating tendon injuries. As a hierarchical, semi-crystalline material, collagen mechanics can be studied using X-ray diffraction. The aim of the study was to describe multi-structural changes in tendon collagen following controlled plastic damage (5% permanent strain). We used small angle X-ray scattering (SAXS) to interrogate the spacing of collagen molecules within a fibril, and wide angle X-ray scattering (WAXS) to measure molecular strains under macroscopic loading. Simultaneous recordings of SAXS and WAXS patterns, together with whole-tissue strain in physiologically hydrated rat-tail tendons were made during increments of in situ tensile loading. Results showed that while tissue level modulus was unchanged, fibril modulus decreased significantly, and molecular modulus significantly increased. Further, analysis of higher order SAXS peaks suggested structural changes in the gap and overlap regions, possibly localising the damage to molecular cross-links. Our results provide new insight into the fundamental damage processes at work in collagenous tissues and point to new directions for their mitigation and repair. This article reports the first in situ loading synchrotron studies on mechanical damage in collagenous tissues. We provide new insight into the nano- and micro-structural mechanisms of damage processes. Pre-damaged tendons showed differential alteration of moduli at macro, micro and nano-scales as measured using X-ray scattering techniques. Detailed analysis of higher order diffraction peaks suggested damage is localised to molecular cross-links. The results are consistent with previous X-ray scattering studies of tendons and also with recent thermal stability studies on damaged material. Detailed understanding of damage mechanisms is essential in the development of new therapies promoting tissue repair. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Charge-equilibrium and radiation of low-energy cosmic rays passing through interstellar medium

NASA Technical Reports Server (NTRS)

Rule, D. W.; Omidvar, K.

1977-01-01

The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, is considered. Electron loss of the beam has been taken into account by means of the First Born approximation allowing for the target atom to remain unexcited, or to be excited to all possible states. Electron capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation and collisional inner-shell ionization of the ions has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated.

Screening of matrix metalloproteinases available from the protein data bank: insights into biological functions, domain organization, and zinc binding groups.

PubMed

Nicolotti, Orazio; Miscioscia, Teresa Fabiola; Leonetti, Francesco; Muncipinto, Giovanni; Carotti, Angelo

2007-01-01

A total of 142 matrix metalloproteinase (MMP) X-ray crystallographic structures were retrieved from the Protein Data Bank (PDB) and analyzed by an automated and efficient routine, developed in-house, with a series of bioinformatic tools. Highly informative heat maps and hierarchical clusterograms provided a reliable and comprehensive representation of the relationships existing among MMPs, enlarging and complementing the current knowledge in the field. Multiple sequence and structural alignments permitted better location and display of key MMP motifs and quantification of the residue consensus at each amino acid position in the most critical binding subsites of MMPs. The MMP active site consensus sequences, the C-alpha root-mean-square deviation (RMSd) analysis of diverse enzymatic subsites, and the examination of the chemical nature, binding topologies, and zinc binding groups (ZBGs) of ligands extracted from crystallographic complexes provided useful insights on the structural arrangements of the most potent MMP inhibitors.

Linear attenuation coefficients of tissues from 1 keV to 150 keV

NASA Astrophysics Data System (ADS)

Böke, Aysun

2014-09-01

The linear attenuation coefficients and three interaction processes have been computed for liver, kidney, muscle, fat and for a range of x-ray energies from 1 keV to 150 keV. Molecular photoelectric absorption cross sections were calculated from atomic cross section data. Total coherent (Rayleigh) and incoherent (Compton) scattering cross sections were obtained by numerical integration over combinations of F2m(x) with the Thomson formula and Sm(x) with the Klein-Nishina formula, respectively. For the coherent (Rayleigh) scattering cross section calculations, molecular form factors were obtained from recent experimental data in the literature for values of x<1 Å-1 and from the relativistic modified atomic form factors for values of x≥1 Å-1. With the inclusion of molecular interference effects in the coherent (Rayleigh) scattering, more accurate knowledge of the scatter from these tissues will be provided. The number of elements involved in tissue composition is 5 for liver, 47 for kidney, 44 for muscle and 3 for fat. The results are compared with previously published experimental and theoretical linear attenuation coefficients. In general, good agreement is obtained. The molecular form factors and scattering functions and cross sections are incorporated into a Monte Carlo program. The energy distributions of x-ray photons scattered from tissues have been simulated and the results are presented.

Photoelectron angular distribution from free SiO2 nanoparticles as a probe of elastic electron scattering.

PubMed

Antonsson, E; Langer, B; Halfpap, I; Gottwald, J; Rühl, E

2017-06-28

In order to gain quantitative information on the surface composition of nanoparticles from X-ray photoelectron spectroscopy, a detailed understanding of photoelectron transport phenomena in these samples is needed. Theoretical results on the elastic and inelastic scattering have been reported, but a rigorous experimental verification is lacking. We report in this work on the photoelectron angular distribution from free SiO 2 nanoparticles (d = 122 ± 9 nm) after ionization by soft X-rays above the Si 2p and O 1s absorption edges, which gives insight into the relative importance of elastic and inelastic scattering channels in the sample particles. The photoelectron angular anisotropy is found to be lower for photoemission from SiO 2 nanoparticles than that expected from the theoretical values for the isolated Si and O atoms in the photoelectron kinetic energy range 20-380 eV. The reduced angular anisotropy is explained by elastic scattering of the outgoing photoelectrons from neighboring atoms, smearing out the atomic distribution. Photoelectron angular distributions yield detailed information on photoelectron elastic scattering processes allowing for a quantification of the number of elastic scattering events the photoelectrons have undergone prior to leaving the sample. The interpretation of the experimental photoelectron angular distributions is complemented by Monte Carlo simulations, which take inelastic and elastic photoelectron scattering into account using theoretical values for the scattering cross sections. The results of the simulations reproduce the experimental photoelectron angular distributions and provide further support for the assignment that elastic and inelastic electron scattering processes need to be considered.

The Presence of Thermally Unstable X-Ray Filaments and the Production of Cold Gas in the NGC 5044 Group

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, Laurence P.; Vrtilek, Jan; O’Sullivan, Ewan

We present the results of a deep Chandra observation of the X-ray bright moderate-cooling flow group NGC 5044 along with the observed correlations between the ionized, atomic, and molecular gas in this system. The Chandra observation shows that the central AGN has undergone two outbursts in the past 10{sup 8} years, based on the presence of two pairs of nearly bipolar X-ray cavities. The molecular gas and dust within the central 2 kpc is aligned with the orientation of the inner pair of bipolar X-ray cavities, suggesting that the most recent AGN outburst had a dynamical impact on the molecularmore » gas. NGC 5044 also hosts many X-ray filaments within the central 8 kpc, but there are no obvious connections between the X-ray and H α filaments and the more extended X-ray cavities that were inflated during the prior AGN outburst. Using the line width of the blended Fe-L line complex as a diagnostic for multiphase gas, we find that the majority of the multiphase thermally unstable gas in NGC 5044 is confined within the X-ray filaments. While the cooling time and entropy of the gas within the X-ray filaments are very similar, not all filaments show evidence of gas cooling or an association with H α emission. We suggest that the various observed properties of the X-ray filaments are suggestive of an evolutionary sequence where thermally unstable gas begins to cool, becomes multiphased, develops H α emitting plasma, and finally produces cold gas.« less

From single-site tantalum complexes to nanoparticles of Ta x N y and TaO x N y supported on silica: elucidation of synthesis chemistry by dynamic nuclear polarization surface enhanced NMR spectroscopy and X-ray absorption spectroscopy.

PubMed

Mohandas, Janet C; Abou-Hamad, Edy; Callens, Emmanuel; Samantaray, Manoja K; Gajan, David; Gurinov, Andrei; Ma, Tao; Ould-Chikh, Samy; Hoffman, Adam S; Gates, Bruce C; Basset, Jean-Marie

2017-08-01

Air-stable catalysts consisting of tantalum nitride nanoparticles represented as a mixture of Ta x N y and TaO x N y with diameters in the range of 0.5 to 3 nm supported on highly dehydroxylated silica were synthesized from TaMe 5 (Me = methyl) and dimeric Ta 2 (OMe) 10 with guidance by the principles of surface organometallic chemistry (SOMC). Characterization of the supported precursors and the supported nanoparticles formed from them was carried out by IR, NMR, UV-Vis, extended X-ray absorption fine structure, and X-ray photoelectron spectroscopies complemented with XRD and high-resolution TEM, with dynamic nuclear polarization surface enhanced NMR spectroscopy being especially helpful by providing enhanced intensities of the signals of 1 H, 13 C, 29 Si, and 15 N at their natural abundances. The characterization data provide details of the synthesis chemistry, including evidence of (a) O 2 insertion into Ta-CH 3 species on the support and (b) a binuclear to mononuclear transformation of species formed from Ta 2 (OMe) 10 on the support. A catalytic test reaction, cyclooctene epoxidation, was used to probe the supported nanoparticles, with 30% H 2 O 2 serving as the oxidant. The catalysts gave selectivities up to 98% for the epoxide at conversions as high as 99% with a 3.4 wt% loading of Ta present as Ta x N y /TaO x N y .

Measurement of Kα and Kβ fluorescence cross sections for elements in the range 44<=Z<=68 at 59.5 keV

NASA Astrophysics Data System (ADS)

Budak, G.; Karabulut, A.; Demir, L.; Sahin, Y.

1999-09-01

The Kα and Kβ x-ray fluorescence cross sections have been measured for elements in the range 44<=Z<=68 at an excitation energy of 59.5-keV γ ray from 241Am radioisotope with a Si(Li) detector. A reasonable agreement is found between the present experimental results and the theoretically calculated values based on photoionization cross sections by Scofield using Hartree-Slater and Hartree-Fock central potential theory.

Detection of X-ray photons by solution-processed organic-inorganic perovskites

PubMed Central

Yakunin, Sergii; Sytnyk, Mykhailo; Kriegner, Dominik; Shrestha, Shreetu; Richter, Moses; Matt, Gebhard J.; Azimi, Hamed; Brabec, Christoph J.; Stangl, Julian; Kovalenko, Maksym V.; Heiss, Wolfgang

2017-01-01

The evolution of real-time medical diagnostic tools such as angiography and computer tomography from radiography based on photographic plates was enabled by the development of integrated solid-state X-ray photon detectors, based on conventional solid-state semiconductors. Recently, for optoelectronic devices operating in the visible and near infrared spectral regions, solution-processed organic and inorganic semiconductors have also attracted immense attention. Here we demonstrate a possibility to use such inexpensive semiconductors for sensitive detection of X-ray photons by direct photon-to-current conversion. In particular, methylammonium lead iodide perovskite (CH3NH3PbI3) offers a compelling combination of fast photoresponse and a high absorption cross-section for X-rays, owing to the heavy Pb and I atoms. Solution processed photodiodes as well as photoconductors are presented, exhibiting high values of X-ray sensitivity (up to 25 µC mGyair-1 cm-3) and responsivity (1.9×104 carriers/photon), which are commensurate with those obtained by the current solid-state technology. PMID:28553368

Tracking ink composition on Herculaneum papyrus scrolls: quantification and speciation of lead by X-ray based techniques and Monte Carlo simulations

PubMed Central

Tack, Pieter; Cotte, Marine; Bauters, Stephen; Brun, Emmanuel; Banerjee, Dipanjan; Bras, Wim; Ferrero, Claudio; Delattre, Daniel; Mocella, Vito; Vincze, Laszlo

2016-01-01

The writing in carbonized Herculaneum scrolls, covered and preserved by the pyroclastic events of the Vesuvius in 79 AD, was recently revealed using X-ray phase-contrast tomography, without the need of unrolling the sensitive scrolls. Unfortunately, some of the text is difficult to read due to the interference of the papyrus fibers crossing the written text vertically and horizontally. Recently, lead was found as an elemental constituent in the writing, rendering the text more clearly readable when monitoring the lead X-ray fluorescence signal. Here, several hypotheses are postulated for the origin and state of lead in the papyrus writing. Multi-scale X-ray fluorescence micro-imaging, Monte Carlo quantification and X-ray absorption microspectroscopy experiments are used to provide additional information on the ink composition, in an attempt to determine the origin of the lead in the Herculaneum scrolls and validate the postulated hypotheses. PMID:26854067

Atomic Processes in X-ray Photoioinzed Gas

NASA Technical Reports Server (NTRS)

Kallman, Timothy

2005-01-01

It has long been known that photoionization and photoabsorption play a dominant role in determining the state of gas in nebulae surrounding hot stars and in active galaxies. Recent observations of X-ray spectra demonstrate that these processes are also dominant in highly ionized gas near compact objects, and also affect the transmission of X-rays from the majority of astronomical sources. This has led to new insights into the understanding of what is going on in these sources. It has also pointed out the need for accurate atomic cross sections for photoionization and absorption, notably for processes involving inner shells. The xstar code can be used for calculating the heating, ionization and reprocessing of X-rays by gas in a range of ionization states and temperatures. It has recently been updated to include an improved treatment of inner shell transitions in iron. I will review the capabilities of xstar, the atomic data, and illustrate some applications to recent X-ray spectral observations.

Single-shot full strain tensor determination with microbeam X-ray Laue diffraction and a two-dimensional energy-dispersive detector.

PubMed

Abboud, A; Kirchlechner, C; Keckes, J; Conka Nurdan, T; Send, S; Micha, J S; Ulrich, O; Hartmann, R; Strüder, L; Pietsch, U

2017-06-01

The full strain and stress tensor determination in a triaxially stressed single crystal using X-ray diffraction requires a series of lattice spacing measurements at different crystal orientations. This can be achieved using a tunable X-ray source. This article reports on a novel experimental procedure for single-shot full strain tensor determination using polychromatic synchrotron radiation with an energy range from 5 to 23 keV. Microbeam X-ray Laue diffraction patterns were collected from a copper micro-bending beam along the central axis (centroid of the cross section). Taking advantage of a two-dimensional energy-dispersive X-ray detector (pnCCD), the position and energy of the collected Laue spots were measured for multiple positions on the sample, allowing the measurement of variations in the local microstructure. At the same time, both the deviatoric and hydrostatic components of the elastic strain and stress tensors were calculated.

THE XMM-NEWTON WIDE-FIELD SURVEY IN THE COSMOS FIELD (XMM-COSMOS): DEMOGRAPHY AND MULTIWAVELENGTH PROPERTIES OF OBSCURED AND UNOBSCURED LUMINOUS ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brusa, M.; Cappelluti, N.; Merloni, A.

2010-06-10

We report the final optical identifications of the medium-depth ({approx}60 ks), contiguous (2 deg{sup 2}) XMM-Newton survey of the COSMOS field. XMM-Newton has detected {approx}1800 X-ray sources down to limiting fluxes of {approx}5 x 10{sup -16}, {approx}3 x 10{sup -15}, and {approx}7 x 10{sup -15} erg cm{sup -2} s{sup -1} in the 0.5-2 keV, 2-10 keV, and 5-10 keV bands, respectively ({approx}1 x 10{sup -15}, {approx}6 x 10{sup -15}, and {approx}1 x 10{sup -14} erg cm{sup -2} s{sup -1}, in the three bands, respectively, over 50% of the area). The work is complemented by an extensive collection of multiwavelength datamore » from 24 {mu}m to UV, available from the COSMOS survey, for each of the X-ray sources, including spectroscopic redshifts for {approx}>50% of the sample, and high-quality photometric redshifts for the rest. The XMM and multiwavelength flux limits are well matched: 1760 (98%) of the X-ray sources have optical counterparts, 1711 ({approx}95%) have IRAC counterparts, and 1394 ({approx}78%) have MIPS 24 {mu}m detections. Thanks to the redshift completeness (almost 100%) we were able to constrain the high-luminosity tail of the X-ray luminosity function confirming that the peak of the number density of log L{sub X} > 44.5 active galactic nuclei (AGNs) is at z {approx} 2. Spectroscopically identified obscured and unobscured AGNs, as well as normal and star-forming galaxies, present well-defined optical and infrared properties. We devised a robust method to identify a sample of {approx}150 high-redshift (z > 1), obscured AGN candidates for which optical spectroscopy is not available. We were able to determine that the fraction of the obscured AGN population at the highest (L{sub X} > 10{sup 44} erg s{sup -1}) X-ray luminosity is {approx}15%-30% when selection effects are taken into account, providing an important observational constraint for X-ray background synthesis. We studied in detail the optical spectrum and the overall spectral energy distribution of a prototypical Type 2 QSO, caught in a stage transitioning from being starburst dominated to AGN dominated, which was possible to isolate only thanks to the combination of X-ray and infrared observations.« less

[Characteristics of specifications of transportable inverter-type X-ray equipment].

PubMed

Yamamoto, Keiichi; Miyazaki, Shigeru; Asano, Hiroshi; Shinohara, Fuminori; Ishikawa, Mitsuo; Ide, Toshinori; Abe, Shinji; Negishi, Toru; Miyake, Hiroyuki; Imai, Yoshio; Okuaki, Tomoyuki

2003-07-01

Our X-ray systems study group measured and examined the characteristics of four transportable inverter-type X-ray equipments. X-ray tube voltage and X-ray tube current were measured with the X-ray tube voltage and the X-ray tube current measurement terminals provided with the equipment. X-ray tube voltage, irradiation time, and dose were measured with a non-invasive X-ray tube voltage-measuring device, and X-ray output was measured by fluorescence meter. The items investigated were the reproducibility and linearity of X-ray output, error of pre-set X-ray tube voltage and X-ray tube current, and X-ray tube voltage ripple percentage. The waveforms of X-ray tube voltage, the X-ray tube current, and fluorescence intensity draw were analyzed using the oscilloscope gram and a personal computer. All of the equipment had a preset error of X-ray tube voltage and X-ray tube current that met JIS standards. The X-ray tube voltage ripple percentage of each equipment conformed to the tendency to decrease when X-ray tube voltage increased. Although the X-ray output reproducibility of system A exceeded the JIS standard, the other systems were within the JIS standard. Equipment A required 40 ms for X-ray tube current to reach the target value, and there was some X-ray output loss because of a trough in X-ray tube current. Owing to the influence of the ripple in X-ray tube current, the strength of the fluorescence waveform rippled in equipments B and C. Waveform analysis could not be done by aliasing of the recording device in equipment D. The maximum X-ray tube current of transportable inverter-type X-ray equipment is as low as 10-20 mA, and the irradiation time of chest X-ray photography exceeds 0.1 sec. However, improvement of the radiophotographic technique is required for patients who cannot move their bodies or halt respiration. It is necessary to make the irradiation time of the equipments shorter for remote medical treatment.

Fabrication of an X-Ray Imaging Detector

NASA Technical Reports Server (NTRS)

Alcorn, G. E.; Burgess, A. S.

1986-01-01

X-ray detector array yields mosaic image of object emitting 1- to 30-keV range fabricated from n-doped silicon wafer. In proposed fabrication technique, thin walls of diffused n+ dopant divide wafer into pixels of rectangular cross section, each containing central electrode of thermally migrated p-type metal. This pnn+ arrangement reduces leakage current by preventing transistor action caused by pnp structure of earlier version.

Probing large-scale structure with large samples of X-ray selected AGN. I. Baryonic acoustic oscillations

NASA Astrophysics Data System (ADS)

Hütsi, Gert; Gilfanov, Marat; Kolodzig, Alexander; Sunyaev, Rashid

2014-12-01

We investigate the potential of large X-ray-selected AGN samples for detecting baryonic acoustic oscillations (BAO). Though AGN selection in X-ray band is very clean and efficient, it does not provide redshift information, and thus needs to be complemented with an optical follow-up. The main focus of this study is (i) to find the requirements needed for the quality of the optical follow-up and (ii) to formulate the optimal strategy of the X-ray survey, in order to detect the BAO. We demonstrate that redshift accuracy of σ0 = 10-2 at z = 1 and the catastrophic failure rate of ffail ≲ 30% are sufficient for a reliable detection of BAO in future X-ray surveys. Spectroscopic quality redshifts (σ0 = 10-3 and ffail ~ 0) will boost the confidence level of the BAO detection by a factor of ~2. For meaningful detection of BAO, X-ray surveys of moderate depth of Flim ~ few 10-15 erg s-1/cm2 covering sky area from a few hundred to ~ten thousand square degrees are required. The optimal strategy for the BAO detection does not necessarily require full sky coverage. For example, in a 1000 day-long survey by an eROSITA type telescope, an optimal strategy would be to survey a sky area of ~9000 deg2, yielding a ~16σ BAO detection. A similar detection will be achieved by ATHENA+ or WFXT class telescopes in a survey with a duration of 100 days, covering a similar sky area. XMM-Newton can achieve a marginal BAO detection in a 100-day survey covering ~400 deg2. These surveys would demand a moderate-to-high cost in terms the optical follow-ups, requiring determination of redshifts of ~105 (XMM-Newton) to ~3 × 106 objects (eROSITA, ATHENA+, and WFXT) in these sky areas.

The Wide Field X-ray Telescope Mission

NASA Astrophysics Data System (ADS)

Murray, Stephen S.; WFXT Team

2010-01-01

To explore the high-redshift Universe to the era of galaxy formation requires an X-ray survey that is both sensitive and extensive, which complements deep wide-field surveys at other wavelengths. The Wide-Field X-ray Telescope (WFXT) is designed to be two orders of magnitude more effective than previous and planned X-ray missions for surveys. WFXT consists of three co-aligned wide-field X-ray telescopes with a 1 sq. deg. field of view and <10 arc sec (goal of 5 arc sec) angular resolution over the full field. With nearly ten times Chandra's collecting area and more than ten times Chandra's field of view, WFXT will perform sensitive deep surveys that will discover and characterize extremely large populations of high redshift AGN and galaxy clusters. In five years, WFXT will perform three extragalactic surveys: 1) 20,000 sq. deg. of extragalactic sky at 100-1000 times the sensitivity, and twenty times better angular resolution than the ROSAT All Sky Survey; 2) 3000 sq.deg. to deep Chandra sensitivity; and 3) 100 sq.deg. to the deepest Chandra sensitivity. WFXT will generate a legacy dataset of >500,000 galaxy clusters to redshifts about 2, measuring redshift, gas abundance and temperature for a significant fraction of them, and a sample of more than 10 million AGN to redshifts > 6, many with X-ray spectra sufficient to distinguish obscured from unobscured quasars. These surveys will address fundamental questions of how supermassive black holes grow and influence the evolution of the host galaxy and how clusters form and evolve, as well as providing large samples of massive clusters that can be used in cosmological studies. WFXT surveys will map systems spanning many square degrees including Galactic star forming regions, the Magellanic Clouds and the Virgo Cluster. WFXT data will become public through annual Data Releases that will constitute a vast scientific legacy.

Rate equations for nitrogen molecules in ultrashort and intense x-ray pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ji -Cai; Berrah, Nora; Cederbaum, Lorenz S.

Here, we study theoretically the quantum dynamics of nitrogen molecules (N2) exposed to intense and ultrafast x-rays at a wavelength ofmore » $$1.1\\;{\\rm{nm}}$$ ($$1100\\;{\\rm{eV}}$$ photon energy) from the Linac Coherent Light Source (LCLS) free electron laser. Molecular rate equations are derived to describe the intertwined photoionization, decay, and dissociation processes occurring for N2. This model complements our earlier phenomenological approaches, the single-atom, symmetric-sharing, and fragmentation-matrix models of 2012 (J. Chem. Phys. 136 214310). Our rate-equations are used to obtain the effective pulse energy at the sample and the time scale for the dissociation of the metastable dication $${{\\rm{N}}}_{2}^{2+}$$. This leads to a very good agreement between the theoretically and experimentally determined ion yields and, consequently, the average charge states. The effective pulse energy is found to decrease with shortening pulse duration. This variation together with a change in the molecular fragmentation pattern and frustrated absorption—an effect that reduces absorption of x-rays due to (double) core hole formation—are the causes for the drop of the average charge state with shortening LCLS pulse duration discovered previously.« less

Rate equations for nitrogen molecules in ultrashort and intense x-ray pulses

DOE PAGES

Liu, Ji -Cai; Berrah, Nora; Cederbaum, Lorenz S.; ...

2016-03-16

Here, we study theoretically the quantum dynamics of nitrogen molecules (N2) exposed to intense and ultrafast x-rays at a wavelength ofmore » $$1.1\\;{\\rm{nm}}$$ ($$1100\\;{\\rm{eV}}$$ photon energy) from the Linac Coherent Light Source (LCLS) free electron laser. Molecular rate equations are derived to describe the intertwined photoionization, decay, and dissociation processes occurring for N2. This model complements our earlier phenomenological approaches, the single-atom, symmetric-sharing, and fragmentation-matrix models of 2012 (J. Chem. Phys. 136 214310). Our rate-equations are used to obtain the effective pulse energy at the sample and the time scale for the dissociation of the metastable dication $${{\\rm{N}}}_{2}^{2+}$$. This leads to a very good agreement between the theoretically and experimentally determined ion yields and, consequently, the average charge states. The effective pulse energy is found to decrease with shortening pulse duration. This variation together with a change in the molecular fragmentation pattern and frustrated absorption—an effect that reduces absorption of x-rays due to (double) core hole formation—are the causes for the drop of the average charge state with shortening LCLS pulse duration discovered previously.« less

Observational diagnostics of accretion on young stars and brown dwarfs

NASA Astrophysics Data System (ADS)

Stelzer, Beate; Argiroffi, Costanza

I present a summary of recent observational constraints on the accretion properties of young stars and brown dwarfs with focus on the high-energy emission. In their T Tauri phase young stars assemble a few percent of their mass by accretion from a disk. Various observational signatures of disks around pre-main sequence stars and the ensuing accretion process are found in the IR and optical regime: e.g. excess emission above the stellar photosphere, strong and broad emission lines, optical veiling. At high energies evidence for accretion is less obvious, and the X-ray emission from stars has historically been ascribed to magnetically confined coronal plasmas. While being true for the bulk of the emission, new insight obtained from XMM-Newton and Chandra observations has unveiled contributions from accretion and outflow processes to the X-ray emission from young stars. Their smaller siblings, the brown dwarfs, have been shown to undergo a T Tauri phase on the basis of optical/IR observations of disks and measurements of accretion rates. Most re-cently, first evidence was found for X-rays produced by accretion in a young brown dwarf, complementing the suspected analogy between stars and substellar objects.

Discovery of a dual active galactic nucleus with ˜8 kpc separation

NASA Astrophysics Data System (ADS)

Ellison, Sara L.; Secrest, Nathan J.; Mendel, J. Trevor; Satyapal, Shobita; Simard, Luc

2017-09-01

Targeted searches for dual active galactic nuclei (AGNs), with separations 1-10 kpc, have yielded relatively few successes. A recent pilot survey by Satyapal et al. has demonstrated that mid-infrared (mid-IR) pre-selection has the potential to significantly improve the success rate for dual AGN confirmation in late stage galaxy mergers. In this Letter, we combine mid-IR selection with spatially resolved optical AGN diagnostics from the Mapping Nearby Galaxies at Apache Point Observatory survey to identify a candidate dual AGN in the late stage major galaxy merger SDSS J140737.17+442856.2 at z = 0.143. The nature of the dual AGN is confirmed with Chandra X-ray observations that identify two hard X-ray point sources with intrinsic (corrected for absorption) 2-10 keV luminosities of 4 × 1041 and 3.5 × 1043 erg s-1 separated by 8.3 kpc. The neutral hydrogen absorption (˜1022 cm-2) towards the two AGNs is lower than in duals selected solely on their mid-IR colours, indicating that strategies that combine optical and mid-IR diagnostics may complement techniques that identify the highly obscured dual phase, such as at high X-ray energies or mid-IR only.

X-ray computed tomography using curvelet sparse regularization.

PubMed

Wieczorek, Matthias; Frikel, Jürgen; Vogel, Jakob; Eggl, Elena; Kopp, Felix; Noël, Peter B; Pfeiffer, Franz; Demaret, Laurent; Lasser, Tobias

2015-04-01

Reconstruction of x-ray computed tomography (CT) data remains a mathematically challenging problem in medical imaging. Complementing the standard analytical reconstruction methods, sparse regularization is growing in importance, as it allows inclusion of prior knowledge. The paper presents a method for sparse regularization based on the curvelet frame for the application to iterative reconstruction in x-ray computed tomography. In this work, the authors present an iterative reconstruction approach based on the alternating direction method of multipliers using curvelet sparse regularization. Evaluation of the method is performed on a specifically crafted numerical phantom dataset to highlight the method's strengths. Additional evaluation is performed on two real datasets from commercial scanners with different noise characteristics, a clinical bone sample acquired in a micro-CT and a human abdomen scanned in a diagnostic CT. The results clearly illustrate that curvelet sparse regularization has characteristic strengths. In particular, it improves the restoration and resolution of highly directional, high contrast features with smooth contrast variations. The authors also compare this approach to the popular technique of total variation and to traditional filtered backprojection. The authors conclude that curvelet sparse regularization is able to improve reconstruction quality by reducing noise while preserving highly directional features.

Development study of the X-ray scattering properties of a group of optically polished flat samples

NASA Technical Reports Server (NTRS)

Froechtenigt, J. F.

1973-01-01

A group of twelve optically polished flat samples were used to study the scattering of X-rays. The X-ray beam reflected from the twelve optical flat samples was analyzed by means of a long vacuum system of special design for these tests. The scattering measurements were made at 8.34A and 0.92 deg angle of incidence. The results for ten of the samples are comparable, the two exceptions being the fire polished samples.

Photon activated therapy (PAT) using monochromatic Synchrotron x-rays and iron oxide nanoparticles in a mouse tumor model: feasibility study of PAT for the treatment of superficial malignancy

PubMed Central

2012-01-01

Background X-rays are known to interact with metallic nanoparticles, producing photoelectric species as radiosensitizing effects, and have been exploited in vivo mainly with gold nanoparticles. The purpose of this study was to investigate the potential of sensitizing effect of iron oxide nanoparticles for photon activated therapy. Methods X-rays photon activated therapy (PAT) was studied by treating CT26 tumor cells and CT26 tumor-bearing mice loaded with 13-nm diameter FeO NP, and irradiating them at 7.1 keV near the Fe K-edge using synchrotron x-rays radiation. Survival of cells was determined by MTT assay, and tumor regression assay was performed for in vivo model experiment. The results of PAT treated groups were compared with x-rays alone control groups. Results A more significant reduction in viability and damage was observed in the FeO NP-treated irradiated cells, compared to the radiation alone group (p < 0.04). Injection of FeO NP (100 mg/kg) 30 min prior to irradiation elevated the tumor concentration of magnetite to 40 μg of Fe/g tissue, with a tumor-to-muscle ratio of 17.4. The group receiving FeO NP and radiation of 10 Gy showed 80% complete tumor regression (CTR) after 15–35 days and relapse-free survival for up to 6 months, compared to the control group, which showed growth retardation, resulting in 80% fatality. The group receiving radiation of 40 Gy showed 100% CTR in all cases irrespective of the presence of FeO NP, but CTR was achieved earlier in the PAT-treated group compared with the radiation alone group. Conclusions An iron oxide nanoparticle enhanced therapeutic effect with relatively low tissue concentration of iron and 10 Gy of monochromatic X-rays. Since 7.1 keV X-rays is attenuated very sharply in the tissue, FeO NP-PAT may have promise as a potent treatment option for superficial malignancies in the skin, like chest wall recurrence of breast cancer. PMID:23111059

On the roles of close shell interactions in the structure of acyl-substituted hydrazones: An experimental and theoretical approach

NASA Astrophysics Data System (ADS)

Saeed, Aamer; Ifzan Arshad, M.; Bolte, Michael; Fantoni, Adolfo C.; Delgado Espinoza, Zuly Y.; Erben, Mauricio F.

2016-03-01

The 2-(phenyl-hydrazono)-succinic acid dimethyl ester compound was synthesized by reacting phenylhydrazine with dimethylacetylene dicarboxylate at room temperature and characterized by elemental analysis, infrared, Raman, 1H and 13C NMR spectroscopies and mass spectrometry. Its solid state structure was determined by X-ray diffraction methods. The X-ray structure determination corroborates that the molecule is present in the crystal as the hydrazone tautomer, probably favored by a strong intramolecular N-H···Odbnd C hydrogen bond occurring between the carbonyl (-Cdbnd O) and the hydrazone -Cdbnd N-NH- groups. A substantial fragment of the molecular skeleton is planar due to an extended π-bonding delocalization. The topological analysis of the electron densities (Atom in Molecule, AIM) allows characterization of intramolecular N-H···O interaction, that can be classified as a resonant assisted hydrogen bond (RAHB). Moreover, the Natural Bond Orbital population analysis confirms that a strong hyperconjugative lpO1 → σ*(N2-H) remote interaction between the C2dbnd O1 and N2-H groups takes place. Periodic system electron density and topological analysis have been applied to characterize the intermolecular interactions in the crystal. Weak intermolecular interactions determine the crystal packing, and the prevalence of non-directional dispersive contributions are inferred on topological grounds. The IR spectrum of the crystalline compound was investigated by means of density functional theory calculations carried out with periodic boundary conditions on the crystal, showing excellent agreement between theory and the experiments. The vibrational assignment is complemented with the analysis of the Raman spectrum.

X-ray screening seems to reduce gastric cancer mortality by half in a community-controlled trial in Costa Rica

PubMed Central

Rosero-Bixby, L; Sierra, R

2007-01-01

X-ray screening of gastric cancer is broadly used in Japan, although no controlled trial has proved its effectiveness. This study evaluates the impact of an X-ray screening demonstrative intervention to reduce gastric cancer mortality in a Costa Rican region. The evaluation follows a quasi-experimental, community-controlled design, with measures before and after. About 7000 individuals participated by invitation in the two-wave screening programme. X-ray screening was followed by videoendoscopy and gastric biopsies. Treatment included resection with or without lymph node dissection. Comparisons with two control groups estimate that gastric cancer mortality was halved in the period from 2 to 7 years after the first screening visit. Validity of X-rays as used in this intervention had 88% sensitivity, 80% specificity, and 3% predictive value for individuals with two screening visits. Incidence in the screened group increased up to four times. Case survival was 85% in the intervention group after 5 years, compared to 12% among the controls before the intervention and 35% among the controls in the same region after the intervention. Although X-ray mass screening seems able to reduce stomach cancer mortality, its high cost may be an obstacle for scaling up this intervention in a non-rich country like Costa Rica. PMID:17912238

X-ray absorption spectroscopy: EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alp, E.E.; Mini, S.M.; Ramanathan, M.

1990-04-01

The x-ray absorption spectroscopy (XAS) had been an essential tool to gather spectroscopic information about atomic energy level structure in the early decades of this century. It has also played an important role in the discovery and systematization of rare-earth elements. The discovery of synchrotron radiation in 1952, and later the availability of broadly tunable synchrotron based x-ray sources have revitalized this technique since the 1970's. The correct interpretation of the oscillatory structure in the x-ray absorption cross-section above the absorption edge by Sayers et. al. has transformed XAS from a spectroscopic tool to a structural technique. EXAFS (Extended X-raymore » Absorption Fine Structure) yields information about the interatomic distances, near neighbor coordination numbers, and lattice dynamics. An excellent description of the principles and data analysis techniques of EXAFS is given by Teo. XANES (X-ray Absorption Near Edge Structure), on the other hand, gives information about the valence state, energy bandwidth and bond angles. Today, there are about 50 experimental stations in various synchrotrons around the world dedicated to collecting x-ray absorption data from the bulk and surfaces of solids and liquids. In this chapter, we will give the basic principles of XAS, explain the information content of essentially two different aspects of the absorption process leading to EXAFS and XANES, and discuss the source and samples limitations.« less

[Radiation exposure of children in pediatric radiology. Part 5: organ doses in chest radiography].

PubMed

Seidenbusch, M C; Schneider, K

2009-05-01

Reconstruction of organ doses of selected organs and tissues from radiographic settings and exposure data collected during chest X-ray examinations of children of various age groups performed in Dr. von Hauner's Kinderspital (children's hospital of the University of Munich, DvHK) between 1976 and 2007. The dosimetric data of all X-ray examinations performed since 1976 at DvHK were stored electronically in a database. After 30 years of data collection, the database now includes 305 107 radiological examinations (radiographs and fluoroscopies), especially 119 150 chest radiographs of all age groups. Reconstruction of organ doses in 40 organs and tissues in X-ray examinations of the chest was performed based on the conversion factor concept. The radiation exposure of organs in projection radiography is determined by the exact site of the organs relative to the edges of the X-ray field and the beam direction of X-rays. Optimal collimation in chest radiography can reduce the exposure of organs located at the periphery of the X-ray field, e. g. thyroid gland, stomach and partially the liver, by a factor of 2 to 3, while organs located in the center of the X-ray-field, e. g. thymus, breasts, lungs, esophagus and red bone marrow, are not affected by exact collimation. The high frequency of the roentgen examination of the chest in early age groups increases the collective radiation burden to radiosensitive organs. Therefore, radiation protection of the patient during chest radiographies remains of great importance.

Effect of X-ray flux on polytetrafluoroethylene in X-ray photoelectron spectroscopy

NASA Technical Reports Server (NTRS)

Wheeler, D. R.; Pepper, S. V.

1982-01-01

The effect of the X-ray flux in X-ray photoelectron spectroscopy (STAT) on the constitution of the polytetrafluoroethylene (PTFE) surface has been examined. The radiation dose rate for our specimen was about 10 to the 7th rad/s. The structure, magnitude and binding energy of the C(1s) and F(1s) features of the XPS spectrum and the mass spectrum of gaseous species evolved during irradiation are observed. The strong time dependence of these signals over a period of several hours indicated that the surface constitution of PTFE is greatly affected by this level of radiation dose. The results are consistent with the development of a heavily cross-linked or branched structure in the PTFE surface region and the evolution of short chain fragments into the gas phase.

Flares observed by the normal incidence X-ray telescope on 1989 September 11

NASA Technical Reports Server (NTRS)

Herant, M.; Pardo, F.; Spiller, E.; Golub, L.

1991-01-01

Two solar flare events have been observed in soft X-rays during a sounding-rocket flight of the Normal-Incidence X-ray Telescope payload on September 11, 1989. The flare in X-rays involves a single bright loop crossing the neutral line, and having its footpoints at the southern ends of the ribbons; this loop accounts for more than 66 percent of the emission. Within the remainder of each of the flare ribbons, a complex coronal structure is also observed to be interacting with the main flare loop. A second event, in an active region at the limb, has a strong correlation with H-alpha images obtained at the same time. This indicates the coexistence, and indeed the close proximity, of coronal and chromospheric temperature material. Interpretations of this phenomenon are discussed.

Resonant inelastic x-ray scattering on iso-C{sub 2}H{sub 2}Cl{sub 2} around the chlorine K-edge: Structural and dynamical aspects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawerk, Elie, E-mail: eliekawerk@hotmail.com, E-mail: ekawerk@units.it; Sorbonne Universités, UPMC Université Paris 06, UMR 7614, Laboratoire de Chimie Physique-Matière et Rayonnement, F-75005 Paris; Laboratoire de Physique Appliquée, Faculté des Sciences II, Université Libanaise, 90656 Jdeidet el Metn, Liban

2014-10-14

We report a theoretical and experimental study of the high resolution resonant K{sub α} X-ray emission lines around the chlorine K-edge in gas phase 1,1-dichloroethylene. With the help of ab initio electronic structure calculations and cross section evaluation, we interpret the lowest lying peak in the X-ray absorption and emission spectra. The behavior of the K{sub α} emission lines with respect to frequency detuning highlights the existence of femtosecond nuclear dynamics on the dissociative Potential Energy Surface of the first K-shell core-excited state.

Responses of the Jovian Atmosphere to Cometary Particles and Photon Impacts

NASA Technical Reports Server (NTRS)

Dalgarno, A.

1998-01-01

Spectra of soft x-ray and EUV emissions of oxygen ions, precipitating into the Jovian atmosphere, are calculated, taking into account the dynamical character of the energy and charge distributions of the ions as they propagate. Monte-Carlo simulations are performed using experimental and theoretical cross sections of ion collisions with the atmospheric gases. The numbers of x-ray and EUV photons produced per precipitating oxygen ion are calculated as functions of the initial ion energy and charge. The energy and charge distribution functions are used to evaluate the intensities of characteristic x-ray and EUV spectral emission lines of oxygen ions in the Jovian aurora.

Opening the CHOCBOX: clumpy stellar winds in Cyg X-1

NASA Astrophysics Data System (ADS)

Grinberg, V.; Uttley, P.; Wilms, J.; Miller-Jones, J.; Pottschmidt, K.; Niu, S.; Hirsch, M.; Chocbox Collaboration

2017-10-01

Winds of O/B-stars are key drivers of enrichment and star formation and evolution. Yet, our understanding of their clumpy structure is limited. Luckily, high mass X-ray binaries, where the compact object accretes from the stellar wind of the companion, are perfect laboratories to study such winds: the X-ray radiation from the vicinity of the compact object is quasi-pointlike and effectively X-rays the clumps crossing the line of sight. We observed the high mass X-ray binary Cyg X-1 with XMM for 7 consecutive days with simultaneous coverage with NuSTAR, INTEGRAL and VLBA. One of our main aims was to probe the wind of the O-type companion in an unprecedented uninterrupted campaign, spanning more than an orbital period and including two superior conjunctions where we expect the densest wind. Here, we present first results from the CHOCBOX (Cyg X-1 Hard state Observations of a Complete Binary Orbit in X-rays) campaign and compare them to previous work, in particular multi-year studies of absorption variability and high resolution snapshots with Chandra-HETG. We argue that the clumps have a complex structure with hotter outer and colder inner layers and are not symmetrical.

Universal empirical fit to L-shell X-ray production cross sections in ionization by protons

NASA Astrophysics Data System (ADS)

Lapicki, G.; Miranda, J.

2018-01-01

A compilation published in 2014, with a recent 2017 update, contains 5730 experimental total L-shell X-ray production cross sections (XRPCS). The database covers an energy range from 10 keV to 1 GeV, and targets from 18Ar to 95Am. With only two adjustable parameters, universal fit to these data normalized to XRPCS calculated at proton velocity v1 equal to the electron velocity in the L-shell v2L, is obtained in terms of a single ratio of v1/v2L. This fit reproduces 97% of the compiled XRPCS to within a factor of 2.

Comparison Of Optical, UV, X-ray, And Gamma-ray Variations Of Selected Blazars In 2011

NASA Astrophysics Data System (ADS)

Consiglio, Santina; Marscher, A. P.; Jorstad, S. G.; Walker, G.

2012-01-01

We present multi-wavelength observations of several gamma-ray bright blazars. We combine optical data obtained at Maria Mitchell Observatory on Nantucket Island with space- and ground-based observations carried out with a variety of instruments. These include a number of other optical telescopes, the Fermi Gamma-ray Space Telescope at photon energies of 0.1-200 GeV, the Rossi X-Ray Timing Explorer at 2.4-10 keV, and the Swift satellite at 0.3-10 keV plus optical and UV wavelengths. Three of the observed blazars proved to be particularly active - BL Lac, 3C 279, and PKS 1510-089. BL Lac was of special interest, varying greatly in optical brightness from night to night. In addition, as reported by the VERITAS group, it exhibited a remarkable, short-lived flare at TeV gamma-ray energies on one of the nights. We cross-correlate the variations in the different wavebands in an effort to guide theoretical interpretations of the optical and high-energy emission from blazars. This project was supported by NSF/REU grant AST-0851892 and by the Nantucket Maria Mitchell Association. The research at Boston University was supported in part by NSF grants AST-0907893, and by NASA through Fermi grants NNX08AV65G and NNX11AQ03G.

Arcus: Exploring the Formation and Evolution of Clusters, Galaxies, and Stars

NASA Astrophysics Data System (ADS)

Smith, Randall K.; Arcus Collaboration

2017-06-01

The Large Scale Structure (LSS) of the Universe grew via the gravitational collapse of dark matter, but the visible components that trace the LSS-galaxies, groups and clusters-have a more complex history. Their baryons experience shock heating, radiative cooling and feedback from black holes and star formation, which leave faint signatures of hot (T~10^5-10^8 K), metal-enriched gas in the interstellar and intergalactic media (ISM and IGM). While recent Planck and X-ray studies support this scenario, no current mission possesses the instrumentation necessary to provide direct observational evidence for these “missing baryons." Arcus, a proposed MIDEX mission, leverages recent advances in critical-angle transmission (CAT) gratings and silicon pore optics (SPOs), using CCDs with strong Suzaku heritage and electronics based on the Swift mission; both the spacecraft and mission operations reuse highly successful designs. To be launched in 2023, Arcus will be the only observatory capable of studying, in detail, the hot galactic and intergalactic gas-the dominant baryonic component in the present-day Universe and ultimate reservoir of entropy, metals and the output from cosmic feedback. Its superior soft X-ray sensitivity will complement the forthcoming post-Hitomi and Athena calorimeters, which will have comparably high spectral resolution above 2 keV but poorer spectral resolution than XMM or Chandra in the Arcus bandpass.

Automated Classification of ROSAT Sources Using Heterogeneous Multiwavelength Source Catalogs

NASA Technical Reports Server (NTRS)

McGlynn, Thomas; Suchkov, A. A.; Winter, E. L.; Hanisch, R. J.; White, R. L.; Ochsenbein, F.; Derriere, S.; Voges, W.; Corcoran, M. F.

2004-01-01

We describe an on-line system for automated classification of X-ray sources, ClassX, and present preliminary results of classification of the three major catalogs of ROSAT sources, RASS BSC, RASS FSC, and WGACAT, into six class categories: stars, white dwarfs, X-ray binaries, galaxies, AGNs, and clusters of galaxies. ClassX is based on a machine learning technology. It represents a system of classifiers, each classifier consisting of a considerable number of oblique decision trees. These trees are built as the classifier is 'trained' to recognize various classes of objects using a training sample of sources of known object types. Each source is characterized by a preselected set of parameters, or attributes; the same set is then used as the classifier conducts classification of sources of unknown identity. The ClassX pipeline features an automatic search for X-ray source counterparts among heterogeneous data sets in on-line data archives using Virtual Observatory protocols; it retrieves from those archives all the attributes required by the selected classifier and inputs them to the classifier. The user input to ClassX is typically a file with target coordinates, optionally complemented with target IDs. The output contains the class name, attributes, and class probabilities for all classified targets. We discuss ways to characterize and assess the classifier quality and performance and present the respective validation procedures. Based on both internal and external validation, we conclude that the ClassX classifiers yield reasonable and reliable classifications for ROSAT sources and have the potential to broaden class representation significantly for rare object types.

Errata and update to ;Experimental cross sections for L-shell X-ray production and ionization by protons;

NASA Astrophysics Data System (ADS)

Miranda, J.; Lapicki, G.

2018-01-01

A compilation of experimental L-shell X-ray production and ionization cross sections induced by proton impact was published recently (Miranda and Lapicki, 2014), collecting 15 439 experimental cross sections. The database covers an energy range from 10 keV to 1 GeV, and targets from 10Ne to 95Am. A correction to several tabulated values that were in error, as well as an update including new data published after 2012 and older references not found previously are given in the present work. The updated data base increased the total number of experimental cross sections by 3.1% to 15 921. A new analysis of the total number of experimental points per year shows that the possible saturation in the cumulative total number of data is increased to 15 950 ± 110 points.

The subtle balance of weak supramolecular interactions: The hierarchy of halogen and hydrogen bonds in haloanilinium and halopyridinium salts.

PubMed

Raatikainen, Kari; Cametti, Massimo; Rissanen, Kari

2010-01-15

THE SERIES OF HALOANILINIUM AND HALOPYRIDINIUM SALTS: 4-IPhNH₃Cl (1), 4-IPhNH₃Br (5), 4-IPhNH₃H₂PO₄ (6), 4-ClPhNH₃H₂PO₄ (8), 3-IPyBnCl (9), 3-IPyHCl (10) and 3-IPyH-5NIPA (3-iodopyridinium 5-nitroisophthalate, 13), where hydrogen or/and halogen bonding represents the most relevant non-covalent interactions, has been prepared and characterized by single crystal X-ray diffraction. This series was further complemented by extracting some relevant crystal structures: 4-BrPhNH₃Cl (2, CCDC ref. code TAWRAL), 4-ClPhNH₃Cl (3, CURGOL), 4-FPhNH₃Cl (4, ANLCLA), 4-BrPhNH₃H₂PO₄, (7, UGISEI), 3-BrPyHCl, (11, CIHBAX) and 3-ClPyHCl, (12, VOQMUJ) from Cambridge Structural Database for sake of comparison. Based on the X-ray data it was possible to highlight the balance between non-covalent forces acting in these systems, where the relative strength of the halogen bonding C-X...A⁻ (X = I, Br or Cl) and the ratio between the halogen and hydrogen bonds [C-X...A⁻ : D-H...A⁻] varied across the series.

X-ray analysis of residual stress gradients in TiN coatings by a Laplace space approach and cross-sectional nanodiffraction: a critical comparison.

PubMed

Stefenelli, Mario; Todt, Juraj; Riedl, Angelika; Ecker, Werner; Müller, Thomas; Daniel, Rostislav; Burghammer, Manfred; Keckes, Jozef

2013-10-01

Novel scanning synchrotron cross-sectional nanobeam and conventional laboratory as well as synchrotron Laplace X-ray diffraction methods are used to characterize residual stresses in exemplary 11.5 µm-thick TiN coatings. Both real and Laplace space approaches reveal a homogeneous tensile stress state and a very pronounced compressive stress gradient in as-deposited and blasted coatings, respectively. The unique capabilities of the cross-sectional approach operating with a beam size of 100 nm in diameter allow the analysis of stress variation with sub-micrometre resolution at arbitrary depths and the correlation of the stress evolution with the local coating microstructure. Finally, advantages and disadvantages of both approaches are extensively discussed.

The space shuttle payload planning working groups. Volume 3: High energy astrophysics

NASA Technical Reports Server (NTRS)

1973-01-01

The findings of the High Energy Astrophysics working group of the space shuttle payload planning activity are presented. The objectives to be accomplished during space shuttle missions are defined as: (1) X-ray astronomy, (2) hard X-ray and gamma ray astronomy, and (3) cosmic ray astronomy. The instruments and test equipment required to accomplish the mission are identified. Recommendations for managing the installation of the equipment and conducting the missions are included.

X-ray microscopy with high-resolution zone plates: recent developments

NASA Astrophysics Data System (ADS)

Schneider, Gerd; Wilhein, Thomas; Niemann, Bastian; Guttman, P.; Schliebe, T.; Lehr, J.; Aschoff, H.; Thieme, Juergen; Rudolph, Dietbert M.; Schmahl, Guenther A.

1995-09-01

In order to expand the applications of x-ray microscopy, developments in the fields of zone plate technology, specimen preparation and imaging techniques have been made. A new cross- linked polymer chain electron beam resist allows us to record zone plate pattern down to 19 nm outermost zone width. High resolution zone plates in germanium with outermost zone widths down to 19 nm have been developed. In addition, phase zone plates in nickel down to 30 nm zone width have been made by electroplating. In order to enhance the image contrast for weak absorbing objects, the phase contrast method for x-ray microscopy was developed and implemented on the Gottingen x-ray microscope at BESSY. The effects of x ray absorption on the structure of biological specimen limits the maximum applicable radiation dose and therefore the achievable signal to noise ratio for an artifact-free x-ray image. To improve the stability especially of biological specimen, a cryogenic object chamber has been developed and tested. It turns out that at the operating temperature T less than or equal to 130 K unfixed biological specimen can be exposed to a radiation dose of 109 - 1010 Gy without any observable structural changes. A multiple-angle viewing stage allows us to take stereoscopic images with the x-ray microscope, giving a 3D-impression of the object. As an example for the applications of x-ray microscopy in biology, erythrocytes infected by malaria parasite have been examined. Studies of the aggregation of hematite by sodium sulfate gives an example for the application of x-ray microscopy in the field of colloid research.

The ROSAT Deep Survey. 2; Optical Identification, Photometry and Spectra of X-Ray Sources in the Lockman Field

NASA Technical Reports Server (NTRS)

Schmidt, M.; Hasinger, G.; Gunn, J.; Schneider, D.; Burg, R.; Giacconi, R.; Lehmann, I.; MacKenty, J.; Truemper, J.; Zamorani, G.

1998-01-01

The ROSAT Deep Survey includes a complete sample of 50 X-ray sources with fluxes in the 0.5 - 2 keV band larger than 5.5 x 10(exp -15)erg/sq cm/s in the Lockman field (Hasinger et al., Paper 1). We have obtained deep broad-band CCD images of the field and spectra of many optical objects near the positions of the X-ray sources. We define systematically the process leading to the optical identifications of the X-ray sources. For this purpose, we introduce five identification (ID) classes that characterize the process in each case. Among the 50 X-ray sources, we identify 39 AGNs, 3 groups of galaxies, 1 galaxy and 3 galactic stars. Four X-ray sources remain unidentified so far; two of these objects may have an unusually large ratio of X-ray to optical flux.

Charge Exchange X-Ray Emission due to Highly Charged Ion Collisions with H, He, and H2: Line Ratios for Heliospheric and Interstellar Applications

NASA Astrophysics Data System (ADS)

Cumbee, R. S.; Mullen, P. D.; Lyons, D.; Shelton, R. L.; Fogle, M.; Schultz, D. R.; Stancil, P. C.

2018-01-01

The fundamental collisional process of charge exchange (CX) has been established as a primary source of X-ray emission from the heliosphere, planetary exospheres, and supernova remnants. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly excited, high-charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays. To provide reliable CX-induced X-ray spectral models to realistically simulate these environments, line ratios and spectra are computed using theoretical CX cross sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, molecular-orbital close-coupling, and classical trajectory Monte Carlo methods for various collisional velocities relevant to astrophysics. X-ray spectra were computed for collisions of bare and H-like C to Al ions with H, He, and H2 with results compared to available experimental data. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant and the heliosphere are shown as examples with ion velocity dependence.

BL-Lacs in X-Ray Outburst

NASA Technical Reports Server (NTRS)

Remillard, Ronald A.; Urry, C. Megan; Aharonian, Felix; Pian, Elena; Sambruna, Rita; Coppi, Paolo

2000-01-01

We conducted a multifrequency campaign for the TeV blazar Markarian 421 in 1998 April. The campaign started from a pronounced high-amplitude flare recorded by BeppoSAX and Whipple; the Advanced Satellite for Cosmology and Astrophysics (ASCA) observation started three days later. In the X-ray data, we detected multiple flares, occurring on timescales of about one day. ASCA data clearly reveal spectral variability. The comparison of the data from ASCA, the Extreme Ultraviolet Explorer, and the Rossi X-Ray Timing Explorer indicates that the variability amplitudes in the low-energy synchrotron component are larger at higher photon energies. In TeV and gamma-rays, large intraday variations-which were correlated with the X-ray flux-were observed when results from three Cerenkov telescopes were combined. The rms variability of TeV and gamma-rays was similar to that observed in hard X-rays, above ten keV. The X-ray light curve reveals flares that are almost symmetric for most cases, implying that the dominant timescale is the light crossing time through the emitting region. The structure function analysis based on the continuous X-ray light curve of seven days indicates that the characteristic timescale is approx. 0.5 days. The analysis of ASCA light curves in various energy bands appears to show both soft (positive) and hard (negative) lags. These may not be real, as systematic effects could also produce these lags, which are all much smaller than an orbit. If the lags of both signs are real, these imply that the particle acceleration and X-ray cooling timescales are similar.

Clocking Femtosecond Collisional Dynamics via Resonant X-Ray Spectroscopy

NASA Astrophysics Data System (ADS)

van den Berg, Q. Y.; Fernandez-Tello, E. V.; Burian, T.; Chalupský, J.; Chung, H.-K.; Ciricosta, O.; Dakovski, G. L.; Hájková, V.; Hollebon, P.; Juha, L.; Krzywinski, J.; Lee, R. W.; Minitti, M. P.; Preston, T. R.; de la Varga, A. G.; Vozda, V.; Zastrau, U.; Wark, J. S.; Velarde, P.; Vinko, S. M.

2018-02-01

Electron-ion collisional dynamics is of fundamental importance in determining plasma transport properties, nonequilibrium plasma evolution, and electron damage in diffraction imaging applications using bright x-ray free-electron lasers (FELs). Here we describe the first experimental measurements of ultrafast electron impact collisional ionization dynamics using resonant core-hole spectroscopy in a solid-density magnesium plasma, created and diagnosed with the Linac Coherent Light Source x-ray FEL. By resonantly pumping the 1 s →2 p transition in highly charged ions within an optically thin plasma, we have measured how off-resonance charge states are populated via collisional processes on femtosecond time scales. We present a collisional cross section model that matches our results and demonstrates how the cross sections are enhanced by dense-plasma effects including continuum lowering. Nonlocal thermodynamic equilibrium collisional radiative simulations show excellent agreement with the experimental results and provide new insight on collisional ionization and three-body-recombination processes in the dense-plasma regime.

Clocking Femtosecond Collisional Dynamics via Resonant X-Ray Spectroscopy

DOE PAGES

van den Berg, Q. Y.; Fernandez-Tello, E. V.; Burian, T.; ...

2018-02-01

Electron-ion collisional dynamics is of fundamental importance in determining plasma transport properties, nonequilibrium plasma evolution, and electron damage in diffraction imaging applications using bright x-ray free-electron lasers (FELs). Here in this paper, we describe the first experimental measurements of ultrafast electron impact collisional ionization dynamics using resonant core-hole spectroscopy in a solid-density magnesium plasma, created and diagnosed with the Linac Coherent Light Source x-ray FEL. By resonantly pumping the 1s → 2p transition in highly charged ions within an optically thin plasma, we have measured how off-resonance charge states are populated via collisional processes on femtosecond time scales. We presentmore » a collisional cross section model that matches our results and demonstrates how the cross sections are enhanced by dense-plasma effects including continuum lowering. Nonlocal thermodynamic equilibrium collisional radiative simulations show excellent agreement with the experimental results and provide new insight on collisional ionization and three-body-recombination processes in the dense-plasma regime.« less

A simulation-based study on the influence of beam hardening in X-ray computed tomography for dimensional metrology.

PubMed

Lifton, Joseph J; Malcolm, Andrew A; McBride, John W

2015-01-01

X-ray computed tomography (CT) is a radiographic scanning technique for visualising cross-sectional images of an object non-destructively. From these cross-sectional images it is possible to evaluate internal dimensional features of a workpiece which may otherwise be inaccessible to tactile and optical instruments. Beam hardening is a physical process that degrades the quality of CT images and has previously been suggested to influence dimensional measurements. Using a validated simulation tool, the influence of spectrum pre-filtration and beam hardening correction are evaluated for internal and external dimensional measurements. Beam hardening is shown to influence internal and external dimensions in opposition, and to have a greater influence on outer dimensions compared to inner dimensions. The results suggest the combination of spectrum pre-filtration and a local gradient-based surface determination method are able to greatly reduce the influence of beam hardening in X-ray CT for dimensional metrology.

Thermal equation of state of Molybdenum determined from in situ synchrotron X-ray diffraction with laser-heated diamond anvil cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Xiaoli; Li, Fangfei; Zhou, Qiang

Here we report that the equation of state (EOS) of Mo is obtained by an integrated technique of laser-heated DAC and synchrotron X-ray diffraction. The cold compression and thermal expansion of Mo have been measured up to 80 GPa at 300 K, and 92 GPa at 3470 K, respectively. The P-V-T data have been treated with both thermodynamic and Mie–Gruneisen-Debye methods for the thermal EOS inversion. The results are self-consistent and in agreement with the static multi-anvil compression data of Litasov et al. (J. Appl. Phys. 113, 093507 (2013)) and the theoretical data of Zeng et al. (J. Phys. Chem.more » B 114, 298 (2010)). Furthermore, these high pressure and high temperature (HPHT) data with high precision firstly complement and close the gap between the resistive heating and the shock compression experiment.« less

Thermal equation of state of Molybdenum determined from in situ synchrotron X-ray diffraction with laser-heated diamond anvil cells

DOE PAGES

Huang, Xiaoli; Li, Fangfei; Zhou, Qiang; ...

2016-02-17

Here we report that the equation of state (EOS) of Mo is obtained by an integrated technique of laser-heated DAC and synchrotron X-ray diffraction. The cold compression and thermal expansion of Mo have been measured up to 80 GPa at 300 K, and 92 GPa at 3470 K, respectively. The P-V-T data have been treated with both thermodynamic and Mie–Gruneisen-Debye methods for the thermal EOS inversion. The results are self-consistent and in agreement with the static multi-anvil compression data of Litasov et al. (J. Appl. Phys. 113, 093507 (2013)) and the theoretical data of Zeng et al. (J. Phys. Chem.more » B 114, 298 (2010)). Furthermore, these high pressure and high temperature (HPHT) data with high precision firstly complement and close the gap between the resistive heating and the shock compression experiment.« less

Application of SEM and EDX in studying biomineralization in plant tissues.

PubMed

He, Honghua; Kirilak, Yaowanuj

2014-01-01

This chapter describes protocols using formalin-acetic acid-alcohol (FAA) to fix plant tissues for studying biomineralization by means of scanning electron microscopy (SEM) and qualitative energy-dispersive X-ray microanalysis (EDX). Specimen preparation protocols for SEM and EDX mainly include fixation, dehydration, critical point drying (CPD), mounting, and coating. Gold-coated specimens are used for SEM imaging, while gold- and carbon-coated specimens are prepared for qualitative X-ray microanalyses separately to obtain complementary information on the elemental compositions of biominerals. During the specimen preparation procedure for SEM, some biominerals may be dislodged or scattered, making it difficult to determine their accurate locations, and light microscopy is used to complement SEM studies. Specimen preparation protocols for light microscopy generally include fixation, dehydration, infiltration and embedding with resin, microtome sectioning, and staining. In addition, microwave processing methods are adopted here to speed up the specimen preparation process for both SEM and light microscopy.

Systematic study of magnetar outbursts

NASA Astrophysics Data System (ADS)

Coti Zelati, F.; Rea, N.; Pons, J. A.; Campana, S.; Esposito, P.

2017-12-01

We present the results of the systematic study of all magnetar outbursts observed to date through a reanalysis of data acquired in about 1100 X-ray observations. We track the temporal evolution of the luminosity for all these events, model empirically their decays, and estimate the characteristic decay time-scales and the energy involved. We study the link between different parameters (maximum luminosity increase, outburst peak luminosities, quiescent X-ray and bolometric luminosities, energetics, decay time-scales, magnetic field, spin-down luminosity and age), and reveal several correlations between different quantities. We discuss our results in the framework of the models proposed to explain the triggering mechanism and evolution of magnetar outbursts. The study is complemented by the Magnetar Outburst Online Catalog (http://www.magnetars.ice.csic.es), an interactive database where the user can plot any combination of the parameters derived in this work and download all reduced data.

Measurement of Preheat Due to Nonlocal Electron Transport in Warm Dense Matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Falk, K.; Holec, M.; Fontes, C. J.

This work presents a novel approach to study electron transport in warm dense matter. It also includes the first x-ray Thomson scattering (XRTS) measurement from low-density CH foams compressed by a strong laser-driven shock at the OMEGA laser facility. The XRTS measurement is combined with velocity interferometry (VISAR) and optical pyrometry (SOP) providing a robust measurement of thermodynamic conditions in the shock. Evidence of significant preheat contributing to elevated temperatures reaching 17.5–35 eV in shocked CH foam is measured by XRTS. These measurements are complemented by abnormally high shock velocities observed by VISAR and early emission seen by SOP. Thesemore » results are compared to radiation hydrodynamics simulations that include first-principles treatment of nonlocal electron transport in warm dense matter with excellent agreement. Additional simulations confirm that the x-ray contribution to this preheat is negligible.« less

Measurement of Preheat Due to Nonlocal Electron Transport in Warm Dense Matter

DOE PAGES

Falk, K.; Holec, M.; Fontes, C. J.; ...

2018-01-10

This work presents a novel approach to study electron transport in warm dense matter. It also includes the first x-ray Thomson scattering (XRTS) measurement from low-density CH foams compressed by a strong laser-driven shock at the OMEGA laser facility. The XRTS measurement is combined with velocity interferometry (VISAR) and optical pyrometry (SOP) providing a robust measurement of thermodynamic conditions in the shock. Evidence of significant preheat contributing to elevated temperatures reaching 17.5–35 eV in shocked CH foam is measured by XRTS. These measurements are complemented by abnormally high shock velocities observed by VISAR and early emission seen by SOP. Thesemore » results are compared to radiation hydrodynamics simulations that include first-principles treatment of nonlocal electron transport in warm dense matter with excellent agreement. Additional simulations confirm that the x-ray contribution to this preheat is negligible.« less

Flares, ejections, proton events

NASA Astrophysics Data System (ADS)

Belov, A. V.

2017-11-01

Statistical analysis is performed for the relationship of coronal mass ejections (CMEs) and X-ray flares with the fluxes of solar protons with energies >10 and >100 MeV observed near the Earth. The basis for this analysis was the events that took place in 1976-2015, for which there are reliable observations of X-ray flares on GOES satellites and CME observations with SOHO/LASCO coronagraphs. A fairly good correlation has been revealed between the magnitude of proton enhancements and the power and duration of flares, as well as the initial CME speed. The statistics do not give a clear advantage either to CMEs or the flares concerning their relation with proton events, but the characteristics of the flares and ejections complement each other well and are reasonable to use together in the forecast models. Numerical dependences are obtained that allow estimation of the proton fluxes to the Earth expected from solar observations; possibilities for improving the model are discussed.

Efforts to identify Te-rich nano-islands in ZnSe

NASA Astrophysics Data System (ADS)

Lau, June W.; Volkov, Vyacheslav V.; Zhu, Yimei; Kuskovsky, Igor L.; Neumark, Gertrude F.; Lin, W.; Maksimov, Oleg; Tamargo, Maria C.

2002-03-01

Much work has been done on the study of nano-island formation (“dopants”) in various systems by use of electron microscopy, often complemented by x-ray microanalysis [1]. This works well for systems involving one or more monolayers of dopants. Our system consists of Te and N dopants incorporated into ZnSe in sub-monolayer quantities [2]. This presents a challenge; our calculations show that this case is probably below the detection limit of x-ray microanalysis. Our samples do show strain contrasts but we were unable to obtain direct confirmation of nano-islands’ existence. As an alternative, dark field images from chemically sensitively reflections were used in volumetric defect density studies. The defect density in the doped samples was higher than that of the undoped samples. 1. Dorin C., U of Mich. Poster presentation at Fall MRS meeting 2001 2. Lin et al., Apple. Phys. Let., 76, 2205 (2000).

The Bragg Reflection Polarimeter On the Gravity and Extreme Magnetism Small Explorer Mission

NASA Astrophysics Data System (ADS)

Allured, Ryan; Griffiths, S.; Daly, R.; Prieskorn, Z.; Marlowe, H.; Kaaret, P.; GEMS Team

2011-09-01

The strong gravity associated with black holes warps the spacetime outside of the event horizon, and it is predicted that this will leave characteristic signatures on the polarization of X-ray emission originating in the accretion disk. The Gravity and Extreme Magnetism Small Explorer (GEMS) mission will be the first observatory with the capability to make polarization measurements with enough sensitivity to quantitatively test this prediction. Students at the University of Iowa are currently working on the development of the Bragg Reflection Polarimeter (BRP), a soft X-ray polarimeter sensitive at 500 eV, that is the student experiment on GEMS. The BRP will complement the main experiment by making a polarization measurement from accreting black holes below the main energy band (2-10 keV). This measurement will constrain the inclination of the accretion disk and tighten measurements of black hole spin.

Measurement of Preheat Due to Nonlocal Electron Transport in Warm Dense Matter

NASA Astrophysics Data System (ADS)

Falk, K.; Holec, M.; Fontes, C. J.; Fryer, C. L.; Greeff, C. W.; Johns, H. M.; Montgomery, D. S.; Schmidt, D. W.; Šmíd, M.

2018-01-01

This Letter presents a novel approach to study electron transport in warm dense matter. It also includes the first x-ray Thomson scattering (XRTS) measurement from low-density CH foams compressed by a strong laser-driven shock at the OMEGA laser facility. The XRTS measurement is combined with velocity interferometry (VISAR) and optical pyrometry (SOP) providing a robust measurement of thermodynamic conditions in the shock. Evidence of significant preheat contributing to elevated temperatures reaching 17.5-35 eV in shocked CH foam is measured by XRTS. These measurements are complemented by abnormally high shock velocities observed by VISAR and early emission seen by SOP. These results are compared to radiation hydrodynamics simulations that include first-principles treatment of nonlocal electron transport in warm dense matter with excellent agreement. Additional simulations confirm that the x-ray contribution to this preheat is negligible.

The new HMI beamline MAGS: an instrument for hard X-ray diffraction at BESSY.

PubMed

Dudzik, Esther; Feyerherm, Ralf; Diete, Wolfgang; Signorato, Riccardo; Zilkens, Christopher

2006-11-01

The Hahn-Meitner-Institute Berlin is operating the new hard X-ray diffraction beamline MAGS at the Berlin synchrotron radiation source BESSY. The beamline is intended to complement the existing neutron instrumentation at the Berlin Neutron Scattering Centre. The new beamline uses a 7 T multipole wiggler to produce photon fluxes in the 10(11)-10(12) photons s(-1) (100 mA)(-1) (0.1% bandwidth)(-1) range at energies from 4 to 30 keV at the experiment. It has active bendable optics to provide flexible horizontal and vertical focusing and to compensate the large heat load from the wiggler source. The experimental end-station consists of a six-circle Huber diffractometer which can be used with an additional (polarization) analyser and different sample environments. The beamline is intended for single-crystal diffraction and resonant magnetic scattering experiments for the study of ordering phenomena, phase transitions and materials science.

X-Ray Fluorescence to Determine Zn in Bolivian Children using Hair Samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tellería Narvaez, C.A.; Fernández Alcázar, S.; Barrientos Zamora, F.G.

As a first step in the evaluation of nutritional levels in Bolivian children (8–13 years-old), we carried out X-Ray Fluorescence measurements in hair samples of children belonging to different social classes and living either in rural areas or in cities. The aim of this study is to contribute to health policies tending to improve the global health of children and consequently avoid malnutrition. Our method intends to have maximum reliability and at the same time be as simple as possible from an experimental point of view. Additionally, we use this method to determine some other elements such as Fe, Cu,more » Pb, As and Hg, the latter three considered as contaminants that could be present in children living in areas which neighbor mines and industries. This work will be complemented by some biological and medical tests.« less

X-ray fluorescence measurements of dissolved gas and cavitation

DOE PAGES

Duke, Daniel J.; Kastengren, Alan L.; Swantek, Andrew B.; ...

2016-09-28

The dynamics of dissolved gas and cavitation are strongly coupled, yet these phenomena are difficult to measure in-situ. Both create voids in the fluid that can be difficult to distinguish. In this paper, we present an application of X-ray fluorescence in which liquid density and total noncondensible gas concentration (both dissolved and nucleated) are simultaneously measured. The liquid phase is doped with 400 ppm of a bromine tracer, and dissolved air is removed and substituted with krypton. Fluorescent emission at X-ray wavelengths is simultaneously excited from the Br and Kr with a focused monochromatic X-ray beam from a synchrotron source.more » We measure the flow in a cavitating nozzle 0.5 mm in diameter. From Br fluorescence, total displacement of the liquid is measured. From Kr fluorescence, the mass fraction of both dissolved and nucleated gas is measured. Volumetric displacement of liquid due to both cavitation and gas precipitation can be separated through estimation of the local equilibrium dissolved mass fraction. The uncertainty in the line of sight projected densities of the liquid and gas phases is 4–6 %. The high fluorescence yields and energies of Br and Kr allow small mass fractions of gas to be measured, down to 10 -5, with an uncertainty of 8 %. Finally, these quantitative measurements complement existing optical diagnostic techniques and provide new insight into the diffusion of gas into cavitation bubbles, which can increase their internal density, pressure and lifetimes by orders of magnitude.« less

New Homogeneous Standards by Atomic Layer Deposition for Synchrotron X-ray Fluorescence and Absorption Spectroscopies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butterworth, A.L.; Becker, N.; Gainsforth, Z.

2012-03-13

Quantification of synchrotron XRF analyses is typically done through comparisons with measurements on the NIST SRM 1832/1833 thin film standards. Unfortunately, these standards are inhomogeneous on small scales at the tens of percent level. We are synthesizing new homogeneous multilayer standards using the Atomic Layer Deposition technique and characterizing them using multiple analytical methods, including ellipsometry, Rutherford Back Scattering at Evans Analytical, Synchrotron X-ray Fluorescence (SXRF) at Advanced Photon Source (APS) Beamline 13-ID, Synchrotron X-ray Absorption Spectroscopy (XAS) at Advanced Light Source (ALS) Beamlines 11.0.2 and 5.3.2.1 and by electron microscopy techniques. Our motivation for developing much-needed cross-calibration of synchrotronmore » techniques is borne from coordinated analyses of particles captured in the aerogel of the NASA Stardust Interstellar Dust Collector (SIDC). The Stardust Interstellar Dust Preliminary Examination (ISPE) team have characterized three sub-nanogram, {approx}1{micro}m-sized fragments considered as candidates to be the first contemporary interstellar dust ever collected, based on their chemistries and trajectories. The candidates were analyzed in small wedges of aerogel in which they were extracted from the larger collector, using high sensitivity, high spatial resolution >3 keV synchrotron x-ray fluorescence spectroscopy (SXRF) and <2 keV synchrotron x-ray transmission microscopy (STXM) during Stardust ISPE. The ISPE synchrotron techniques have complementary capabilities. Hard X-ray SXRF is sensitive to sub-fg mass of elements Z {ge} 20 (calcium) and has a spatial resolution as low as 90nm. X-ray Diffraction data were collected simultaneously with SXRF data. Soft X-ray STXM at ALS beamline 11.0.2 can detect fg-mass of most elements, including cosmochemically important oxygen, magnesium, aluminum and silicon, which are invisible to SXRF in this application. ALS beamline 11.0.2 has spatial resolution better than 25 nm. Limiting factors for Stardust STXM analyses were self-imposed limits of photon dose due to radiation damage concerns, and significant attenuation of <1500 eV X-rays by {approx}80{micro}m thick, {approx}25 mg/cm{sup 3} density silica aerogel capture medium. In practice, the ISPE team characterized the major, light elements using STXM (O, Mg, Al, Si) and the heavier minor and trace elements using SXRF. The two data sets overlapped only with minor Fe and Ni ({approx}1% mass abundance), providing few quantitative cross-checks. New improved standards for cross calibration are essential for consortium-based analyses of Stardust interstellar and cometary particles, IDPs. Indeed, they have far reaching application across the whole synchrotron-based analytical community. We have synthesized three ALD multilayers simultaneously on silicon nitride membranes and silicon and characterized them using RBS (on Si), XRF (on Si{sub 3}N{sub 4}) and STXM/XAS (holey Si{sub 3}N{sub 4}). The systems we have started to work with are Al-Zn-Fe and Y-Mg-Er. We have found these ALD multi-layers to be uniform at {micro}m- to nm scales, and have found excellent consistency between four analytical techniques so far. The ALD films can also be used as a standard for e-beam instruments, eg., TEM EELS or EDX. After some early issues with the consistency of coatings to the back-side of the membrane windows, we are confident to be able to show multi-analytical agreement to within 10%. As the precision improves, we can use the new standards to verify or improve the tabulated cross-sections.« less

Development of Accurate Structure for Mounting and Aligning Thin-Foil X-Ray Mirrors

NASA Technical Reports Server (NTRS)

Heilmann, Ralf K.

2001-01-01

The goal of this work was to improve the assembly accuracy for foil x-ray optics as produced by the high-energy astrophysics group at the NASA Goddard Space Flight Center. Two main design choices lead to an alignment concept that was shown to improve accuracy well within the requirements currently pursued by the Constellation-X Spectroscopy X-Ray Telescope (SXT).

XRayView: a teaching aid for X-ray crystallography.

PubMed

Phillips, G N

1995-10-01

A software package, XRayView, has been developed that uses interactive computer graphics to introduce basic concepts of x-ray diffraction by crystals, including the reciprocal lattice, the Ewald sphere construction, Laue cones, the wavelength dependence of the reciprocal lattice, primitive and centered lattices and systematic extinctions, rotation photography. Laue photography, space group determination and Laue group symmetry, and the alignment of crystals by examination of reciprocal space. XRayView is designed with "user-friendliness" in mind, using pull-down menus to control the program. Many of the experiences of using real x-ray diffraction equipment to examine crystalline diffraction can be simulated. Exercises are available on-line to guide the users through many typical x-ray diffraction experiments.

Advancements and Application of Microsecond Synchrotron X-ray Footprinting at the Advanced Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Sayan; Celestre, Rich; Feng, Jun

2016-01-02

The method of synchrotron X-ray protein footprinting (XF-MS) is used to determine protein conformational changes, folding, protein-protein and protein-ligand interactions, providing information which is often difficult to obtain using X-ray crystallography and other common structural biology methods [1 G. Xu and M.R. Chance, Chemical Reviews 107, 3514–3543 (2007). [CrossRef], [PubMed], [Web of Science ®], [Google Scholar] –3 V.N. Bavro, Biochem Soc Trans 43, 983–994 (2015). [CrossRef], [PubMed], [Web of Science ®], [Google Scholar] ]. The technique uses comparative in situ labeling of solvent-accessible side chains by highly reactive hydroxyl radicals (•OH) in buffered aqueous solution under different assay conditions. Inmore » regions where a protein is folded or binds a partner, these •OH susceptible sites are inaccessible to solvent, and therefore protected from labeling. The •OH are generated by the ionization of water using high-flux-density X-rays. High-flux density is a key factor for XF-MS labeling because obtaining an adequate steady-state concentration of hydroxyl radical within a short irradiation time is necessary to minimize radiation-induced secondary damage and also to overcome various scavenging reactions that reduce the yield of labeled side chains.« less

THE STELLAR MASS–HALO MASS RELATION FOR LOW-MASS X-RAY GROUPS AT 0.5< z< 1 IN THE CDFS WITH CSI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Shannon G.; Kelson, Daniel D.; Williams, Rik J.

2015-01-30

Since z∼1, the stellar mass density locked in low-mass groups and clusters has grown by a factor of ∼8. Here, we make the first statistical measurements of the stellar mass content of low-mass X-ray groups at 0.5

SEARCHING FOR BULK MOTIONS IN THE INTRACLUSTER MEDIUM OF MASSIVE, MERGING CLUSTERS WITH CHANDRA CCD DATA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ang; Yu, Heng; Tozzi, Paolo

2016-04-10

We search for bulk motions in the intracluster medium (ICM) of massive clusters showing evidence of an ongoing or recent major merger with spatially resolved spectroscopy in Chandra CCD data. We identify a sample of six merging clusters with >150 ks Chandra exposure in the redshift range 0.1 < z < 0.3. By performing X-ray spectral analysis of projected ICM regions selected according to their surface brightness, we obtain the projected redshift maps for all of these clusters. After performing a robust analysis of the statistical and systematic uncertainties in the measured X-ray redshift z{sub X}, we check whether or not themore » global z{sub X} distribution differs from that expected when the ICM is at rest. We find evidence of significant bulk motions at more than 3σ in A2142 and A115, and less than 2σ in A2034 and A520. Focusing on single regions, we identify significant localized velocity differences in all of the merger clusters. We also perform the same analysis on two relaxed clusters with no signatures of recent mergers, finding no signs of bulk motions, as expected. Our results indicate that deep Chandra CCD data enable us to identify the presence of bulk motions at the level of v{sub BM} > 1000 km s{sup −1} in the ICM of massive merging clusters at 0.1 < z < 0.3. Although the CCD spectral resolution is not sufficient for a detailed analysis of the ICM dynamics, Chandra CCD data constitute a key diagnostic tool complementing X-ray bolometers on board future X-ray missions.« less

Organic Photonics: Toward a New Generation of Thin Film Photovoltaics and Lasers

DTIC Science & Technology

2011-03-07

plane. 39 Both electron and x - ray diffraction confirm the existence of crystalline domains of CuPc and C60. Crystalline domain sizes range from 5...nanocrystalline domains indicated by white curves that locate the domain boundaries. Scale bar=5 nm. b, X - ray diffraction pattern of an OVPD grown A... ray diffraction (XRD) and atomic force microscopy (AFM), as shown in Fig. 8. A cross-sectional TEM image of [CuPc(6.1nm)/C60(6.1nm)]10 is shown in

XRCC3 Thr241Met Polymorphism is not Associated with Lung Cancer Risk in a Romanian Population.

PubMed

Catana, Andreea; Pop, Monica; Marginean, Dragos Horea; Blaga, Ioana Cristina; Porojan, Mihai Dumitru; Popp, Radu Anghel; Pop, Ioan Victor

2016-01-01

Deoxyribonucleic Acid (DNA) repair mechanisms play a critical role in protecting the cellular genome against carcinogens. X-ray cross-complementing gene 3 (XRCC3) is involved in DNA repair and therefore certain genetic polymorphisms that occur in DNA repair genes may affect the ability to repair DNA defects and may represent a risk factor in carcinogenesis. The purpose of our study was to investigate the association between XRCC3 gene substitution of Threonine with Methionine in codon 241 of XRCC3 gene (Thr241Met) polymorphism and the risk of lung cancer, in a Romanian population. We recruited 93 healthy controls and 85 patients with lung cancer, all smokers. Thr241Met, XRCC3 gene genotyping was determined by multiplex Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP). Statistical analysis (OR, recessive model), did not revealed an increased risk for lung cancer, for the variant 241Met allele and Thr241Met genotypes (p=0.138, OR=0.634, CI=0.348-1.157; p=0.023, OR=0.257, CI=0.085-6.824). Also, there were no positive statistical associations between Thr241Met polymorphism of XRCC3 gene, gender, tobacco and various histopathological tumor type of lung cancer. In conclusion, the results of the study suggest that the XRCC3 gene Thr241Met polymorphism is not associated with an increased risk for the development of lung cancer in this Romanian group.

XRCC1 Polymorphisms and Pancreatic Cancer: A Meta-Analysis

PubMed Central

Shen, Wei-dong; Chen, Hong-lin; Liu, Peng-fei

2011-01-01

Objective To assess the association between X-ray repair cross-complementating group 1 (XRCC1) polymorphisms and pancreatic cancer. Methods We searched MEDLINE, Web of Science and HuGE Navigator at June 2010, and then quantitatively summarized associations of the XRCC1 polymorphisms with pancreatic cancer risk using meta-analysis. Results Four studies with 1343 cases and 2302 controls were included. Our analysis found: at codon 194, the Trp allele did not decrease pancreatic cancer risk (Arg/Arg versus Trp/Trp: OR=0.97; 95% CI: 0.48-1.96; P=0.97; Arg/Arg versus Arg/Trp: OR=0.89; 95% CI: 0.70-1.13; P=0.55; Arg/Trp versus Trp/Trp: OR=1.06; 95% CI: 0.52-2.16; P=0.90); at codon 280, only a study showed a nonsignificant association between single nucleotide polymorphism with pancreatic cancer risk; at codon 399, the Gln allele also showed no significant effect on pancreatic cancer compared to Arg allele (Arg/Arg versus Gln/Gln: OR=0.94; 95% CI: 0.74-1.18; Arg/Arg versus Arg/Gln: OR=0.97; 95% CI: 0.83-1.13; Arg/Gln versus Gln/Gln: OR=0.97; 95% CI: 0.77-1.22). The shape of the funnel plot and the Egger’s test did not detect any publication bias. Conclusion There is no evidence that XRCC1 polymorphisms (Arg194Trp, Arg280His, and Arg399Gln) are associated with pancreatic cancer risk. PMID:23467456

Contribution of DNA double-strand break repair gene XRCC3 genotypes to oral cancer susceptibility in Taiwan.

PubMed

Tsai, Chia-Wen; Chang, Wen-Shin; Liu, Juhn-Cherng; Tsai, Ming-Hsui; Lin, Cheng-Chieh; Bau, Da-Tian

2014-06-01

The DNA repair gene X-ray repair cross complementing protein 3 (XRCC3) is thought to play a major role in double-strand break repair and in maintaining genomic stability. Very possibly, defective double-strand break repair of cells can lead to carcinogenesis. Therefore, a case-control study was performed to reveal the contribution of XRCC3 genotypes to individual oral cancer susceptibility. In this hospital-based research, the association of XRCC3 rs1799794, rs45603942, rs861530, rs3212057, rs1799796, rs861539, rs28903081 genotypes with oral cancer risk in a Taiwanese population was investigated. In total, 788 patients with oral cancer and 956 age- and gender-matched healthy controls were genotyped. The results showed that there was significant differential distribution among oral cancer and controls in the genotypic (p=0.001428) and allelic (p=0.0013) frequencies of XRCC3 rs861539. As for the other polymorphisms, there was no difference between case and control groups. In gene-lifestyle interaction analysis, we have provided the first evidence showing that there is an obvious joint effect of XRCC3 rs861539 genotype with individual areca chewing habits on oral cancer risk. In conclusion, the T allele of XRCC3 rs861539, which has an interaction with areca chewing habit in oral carcinogenesis, may be an early marker for oral cancer in Taiwanese. Copyright© 2014 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

Studies of the evolution of the x ray emission of clusters of galaxies

NASA Technical Reports Server (NTRS)

Henry, J. Patrick

1990-01-01

The x ray luminosity function of clusters of galaxies was determined at different cosmic epoches using data from the Einstein Observatory Extended Medium Survey. The sample consisted of 67 x ray selected clusters that were grouped into three redshift shells. Evolution was detected in the x ray properties of clusters. The present volume density of high luminosity clusters was found to be greater than it was in the past. This result is the first convincing evidence for evolution in the x ray properties of clusters. Investigations into the constraints provided by these data on various Cold Dark Matter models are underway.

Conjugate observation of electron microburst groups by Bremsstrahlung X-ray and riometer techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siren, J.C.; Rosenberg, T.J.; Detrick, D.

1980-12-01

The first evidence is reported of simultaneous conjugate electron microburst group precipitation. Groups of bremsstrahlung X ray microbursts (E>25 keV) were observed during a substorm recovery phase by a balloon-borne scintillation counter over Roberval, Quebec, Canada. The microburst groups were accompanied one-to-one by time-delayed and broadened pulses of ionospheric absorption measured by a high sensitivity 30-MHz riometer at Siple Station, Antarctica (Lapprox. =4.1). For the interval of highest correlation, the absolute lag between the two data sets was 4 +- 1 s, to the limit of the relative timing accuracy. Approximately 2 s of the observed lag had been introducesmore » by a low-pass filter in the riometer data acquistion unit. The remainder (2 s) was due to the ionospheric recombination process, which evidently had a response time (tauapprox.5 s) during this event much shorter than that ordinarily associated with the D region of the ionosphere. Model calculations of the ionspheric response to time-varying precipitation, derived from the profile of the measurement X ray flux, provide a consistent picture of simultaneous microburst group precipitation at conjugate points, absolute absorption and the electron spectrum derived from X rays, the degree of variation in absorption and X ray fluxes, and the characteristic ionospheric time constant at the altitude of maximum energy deposition.« less

The relationship between crystal structure and methyl and t-butyl group dynamics in van der Waals organic solids

NASA Astrophysics Data System (ADS)

Beckmann, Peter A.; Paty, Carol; Allocco, Elizabeth; Herd, Maria; Kuranz, Carolyn; Rheingold, Arnold L.

2004-03-01

We report x-ray diffractometry in a single crystal of 2-t-butyl-4-methylphenol (TMP) and low-frequency solid state nuclear magnetic resonance (NMR) proton relaxometry in a polycrystalline sample of TMP. The x-ray data show TMP to have a monoclinic, P21/c, structure with eight molecules per unit cell and two crystallographically inequivalent t-butyl group (C(CH3)3) sites. The proton spin-lattice relaxation rates were measured between 90 and 310 K at NMR frequencies of 8.50, 22.5, and 53.0 MHz. The relaxometry data is fitted with two models characterizing the dynamics of the t-butyl groups and their constituent methyl groups, both of which are consistent with the determined x-ray structure. In addition to presenting results for TMP, we review previously reported x-ray diffractometry and low-frequency NMR relaxometry in two other van der Waals solids which have a simpler structure. In both cases, a unique model for the reorientational dynamics was found. Finally, we review a similar previously reported analysis in a van der Waals solid with a very complex structure in which case fitting the NMR relaxometry requires very many parameters and serves mainly as a flag for a careful x-ray diffraction study.

The International Cometary Explorer (ICE) mission to comet Giacobini-Zinner (G/Z)

NASA Technical Reports Server (NTRS)

Brandt, J. C.; Farquhar, R. W.; Maran, S. P.; Niedner, M. B.; Von Rosenvinge, T.

1985-01-01

The primary objectives of the International Cometary Explorer (ICE) mission is to provide in situ data on the interaction between solar wind and the atmosphere of the P/Giacobini-Zinner comet (G/Z), making measurements of particles, fields, and waves while passing through the cometary tail of G/Z on September 11, 1985. Following the G/Z tail intercept, the ICE measurements will complement the later upstream measurements obtained by the Comet Halley probe. The major ICE payload includes a vector helium magnetometer, the plasma-wave experiment, the radio-wave experiment, the plasma-electron experiment, and the plasma ion experiment. Other experiments are intended to measure energetic protons, X-rays, low energy to high energy cosmic rays, cosmic ray electrons, and gamma-ray bursts. The ICE measurements of G/Z will be supplemented with ground-based measurements. Schematic diagrams are included.

RESULTS FROM LONG-TERM OPTICAL MONITORING OF THE SOFT X-RAY TRANSIENT SAX J1810.8-2609

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu Ling; Di Stefano, Rosanne; Wyrzykowski, Lukasz, E-mail: zhul04@mails.tsinghua.edu.cn

2012-12-20

In this paper, we report the long-term optical observation of the faint soft X-ray transient SAX J1810.8-2609 from the Optical Gravitational Lensing Experiment (OGLE) and Microlensing Observations in Astrophysics (MOA). We have focused on the 2007 outburst, and also cross-correlated its optical light curves and quasi-simultaneous X-ray observations from RXTE/Swift. Both the optical and X-ray light curves of the 2007 outburst show multi-peak features. Quasi-simultaneous optical/X-ray luminosity shows that both the X-ray reprocessing and viscously thermal emission can explain the observed optical flux. There is a slight X-ray delay of 0.6 {+-} 0.3 days during the first peak, while themore » X-ray emission lags the optical emission by {approx}2 days during the rebrightening stage, which suggests that X-ray reprocessing emission contributes significantly to the optical flux in the first peak, but the viscously heated disk origin dominates it during rebrightening. This implies variation of the physical environment of the outer disk, with even the source remaining in a low/hard state during the entire outburst. The {approx}2 day X-ray lag indicates a small accretion disk in the system, and its optical counterpart was not detected by OGLE and MOA during quiescence, which constrained it to be fainter than M{sub I} = 7.5 mag. There is a suspected short-time optical flare detected at MJD = 52583.5 with no detected X-ray counterpart; this single flux increase implies a magnetic loop reconnection in the outer disk, as proposed by Zurita et al. The observations cover all stages of the outburst; however, due to the low sensitivity of RXTE/ASM, we cannot conclude whether it is an optical precursor at the initial rise of the outburst.« less

Research relative to high resolution camera on the advanced X-ray astrophysics facility

NASA Technical Reports Server (NTRS)

1986-01-01

The HRC (High Resolution Camera) is a photon counting instrument to be flown on the Advanced X-Ray Astrophysics Facility (AXAF). It is a large field of view, high angular resolution, detector for the x-ray telescope. The HRC consists of a CsI coated microchannel plate (MCP) acting as a soft x-ray photocathode, followed by a second MCP for high electronic gain. The MCPs are readout by a crossed grid of resistively coupled wires to provide high spatial resolution along with timing and pulse height data. The instrument will be used in two modes, as a direct imaging detector with a limiting sensitivity of 10 to the -15 ergs sq cm sec in a 10 to the 5th second exposure, and as a readout for an objective transmission grating providing spectral resolution of several hundreds to thousands.

THE IMPACT OF ACCURATE EXTINCTION MEASUREMENTS FOR X-RAY SPECTRAL MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Randall K.; Valencic, Lynne A.; Corrales, Lia, E-mail: lynne.a.valencic@nasa.gov

Interstellar extinction includes both absorption and scattering of photons from interstellar gas and dust grains, and it has the effect of altering a source's spectrum and its total observed intensity. However, while multiple absorption models exist, there are no useful scattering models in standard X-ray spectrum fitting tools, such as XSPEC. Nonetheless, X-ray halos, created by scattering from dust grains, are detected around even moderately absorbed sources, and the impact on an observed source spectrum can be significant, if modest, compared to direct absorption. By convolving the scattering cross section with dust models, we have created a spectral model asmore » a function of energy, type of dust, and extraction region that can be used with models of direct absorption. This will ensure that the extinction model is consistent and enable direct connections to be made between a source's X-ray spectral fits and its UV/optical extinction.« less

A CATALOG OF SOLAR X-RAY PLASMA EJECTIONS OBSERVED BY THE SOFT X-RAY TELESCOPE ON BOARD YOHKOH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomczak, M.; Chmielewska, E., E-mail: tomczak@astro.uni.wroc.pl, E-mail: chmielewska@astro.uni.wroc.pl

2012-03-01

A catalog of X-ray plasma ejections (XPEs) observed by the Soft X-ray Telescope on board the Yohkoh satellite has been recently developed in the Astronomical Institute of University of Wroclaw. The catalog contains records of 368 events observed in years 1991-2001 including movies and cross-references to associated events like flares and coronal mass ejections (CMEs). One hundred sixty-three XPEs out of 368 in the catalog were not reported until now. A new classification scheme of XPEs is proposed in which morphology, kinematics, and recurrence are considered. The relation between individual subclasses of XPEs and the associated events was investigated. Themore » results confirm that XPEs are strongly inhomogeneous, responding to different processes that occur in the solar corona. A subclass of erupting loop-like XPEs is a promising candidate to be a high-temperature precursor of CMEs.« less

The location of the site of energy release in a solar X-ray subflare

NASA Technical Reports Server (NTRS)

Petrasso, R. D.; Kahler, S. W.; Krieger, A. S.; Silk, J. K.; Vaiana, G. S.

1975-01-01

A rapid sequence of high-resolution X-ray photographs was obtained by the S-054 X-ray Telescope Experiment on Skylab on 1973 September 1. During the course of this observation, photographs were obtained of a flarelike brightening in a simple, bipolar active region. Analysis reveals the following facts. The event had the form of a small, elongated bright feature whose narrowest dimension was less than seconds of arc. The brightness peak of the flarelike brightening was located within seconds of arc of the center of brightness of a preexisting loop structure that crossed the magnetic neutral line. This loop was observed to brighten gradually beginning approximately 10 minutes prior to the flarelike event. During the rise of the event, the 2-17 A X-ray brightness of the center of the subflare core rose by over a factor of 10 in a time period of 196 seconds or less.

Self-interaction-corrected time-dependent density-functional-theory calculations of x-ray-absorption spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tu, Guangde; Rinkevicius, Zilvinas; Vahtras, Olav

We outline an approach within time-dependent density functional theory that predicts x-ray spectra on an absolute scale. The approach rests on a recent formulation of the resonant-convergent first-order polarization propagator [P. Norman et al., J. Chem. Phys. 123, 194103 (2005)] and corrects for the self-interaction energy of the core orbital. This polarization propagator approach makes it possible to directly calculate the x-ray absorption cross section at a particular frequency without explicitly addressing the excited-state spectrum. The self-interaction correction for the employed density functional accounts for an energy shift of the spectrum, and fully correlated absolute-scale x-ray spectra are thereby obtainedmore » based solely on optimization of the electronic ground state. The procedure is benchmarked against experimental spectra of a set of small organic molecules at the carbon, nitrogen, and oxygen K edges.« less

Enhanced Imaging of Corrosion in Aircraft Structures with Reverse Geometry X-ray(registered tm)

NASA Technical Reports Server (NTRS)

Winfree, William P.; Cmar-Mascis, Noreen A.; Parker, F. Raymond

2000-01-01

The application of Reverse Geometry X-ray to the detection and characterization of corrosion in aircraft structures is presented. Reverse Geometry X-ray is a unique system that utilizes an electronically scanned x-ray source and a discrete detector for real time radiographic imaging of a structure. The scanned source system has several advantages when compared to conventional radiography. First, the discrete x-ray detector can be miniaturized and easily positioned inside a complex structure (such as an aircraft wing) enabling images of each surface of the structure to be obtained separately. Second, using a measurement configuration with multiple detectors enables the simultaneous acquisition of data from several different perspectives without moving the structure or the measurement system. This provides a means for locating the position of flaws and enhances separation of features at the surface from features inside the structure. Data is presented on aircraft specimens with corrosion in the lap joint. Advanced laminographic imaging techniques utilizing data from multiple detectors are demonstrated to be capable of separating surface features from corrosion in the lap joint and locating the corrosion in multilayer structures. Results of this technique are compared to computed tomography cross sections obtained from a microfocus x-ray tomography system. A method is presented for calibration of the detectors of the Reverse Geometry X-ray system to enable quantification of the corrosion to within 2%.

PREFACE: Buried Interface Sciences with X-rays and Neutrons 2010

NASA Astrophysics Data System (ADS)

Sakurai, Kenji

2011-09-01

The 2010 summer workshop on buried interface science with x-rays and neutrons was held at Nagoya University, Japan, on 25-27 July 2010. The workshop was organized by the Japan Applied Physics Society, which established a group to develop the research field of studying buried function interfaces with x-rays and neutrons. The workshop was the latest in a series held since 2001; Tsukuba (December 2001), Niigata (September 2002), Nagoya (July 2003), Tsukuba (July 2004), Saitama (March 2005), Yokohama (July 2006), Kusatsu (August 2006), Tokyo (December 2006), Sendai (July 2007), Sapporo (September 2007), Tokyo (December 2007), Tokyo-Akihabara (July 2009) and Hiratsuka (March 2010). The 2010 summer workshop had 64 participants and 34 presentations. Interfaces mark the boundaries of different material systems at which many interesting phenomena take place, thus making it extremely important to design, fabricate and analyse the structures of interfaces at both the atomic and macroscopic scale. For many applications, devices are prepared in the form of multi-layered thin films, with the result that interfaces are not exposed but buried under multiple layers. Because of such buried conditions, it is generally not easy to analyse such interfaces. In certain cases, for example, when the thin surface layer is not a solid but a liquid such as water, scientists can observe the atomic arrangement of the liquid-solid interface directly by using a scanning probe microscope, of which the tip is soaked in water. However, it has become clear that the use of a stylus tip positioned extremely close to the interface might change the structure of the water molecules. Therefore it is absolutely crucial to develop non-contact, non-destructive probes for buried interfaces. It is known that analysis using x-rays and neutrons is one of the most powerful tools for exploring near-surface structures including interfaces buried under several layers. In particular, x-ray analysis using 3rd generation synchrotron radiation is highly reliable in practice, as well as being quantitative and reproducible. The use of neutron analysis complements x-ray experiments, and helps to enhance information such as contrasts in soft materials and magnetic structures, which are not always given clearly by x-rays. The techniques ensure non-contact, non-destructive measurement, and one can also use the same specimen for further analysis by other methods. On the other hand, we are now aware that it not always straightforward to solve many realistic problems related to buried interfaces. Although advanced synchrotron x-rays and neutrons are highly useful, we still note many limitations. Collaboration with theoreticians is one of the most important directions in which to improve analysis. Over the past couple of years, scientists have argued over the existence of a depletion layer between oil and water. The argument is far from settled, even though highly sophisticated x-ray reflectometry seems to have given quite strong experimental evidence. In most cases, analysis of x-ray reflectivity depends on the model. This is good provided that one can be sure of the validity of the model, as in the case of multilayered thin films in industrial devices. However, sometimes our main interest lies in the model itself. Therefore, we should insist on introducing something new to justify the model scientifically, instead of just claiming that x-ray data can be explained by a certain model. Probably collaboration with theoretical research could be helpful. Another important direction would be to develop a method of model-free analysis. During this workshop, participants talked about the present status of their own work. The workshop was open to those who are not particular specialists in x-ray and neutron experiments, but discussions were detailed and thorough. We discussed how buried interface research by x-ray and neutron experiments can be strengthened in the future. One of the most important extensions is high resolution in space (micro area) and time (quick and realtime). Current x-ray methods can give atomic-scale information for quite a large area on a scale of mm2-cm2, but it is also important to see a specific small area rather than the average structure of the wide area. In addition, there is a need to see unstable changing structures and related phenomena in order to understand more about the mechanism of the functioning of nano materials. Quick measurements are therefore important. Another effective extension would come with combining several x-ray and neutron techniques (reflectivity, grazing-incidence small angle scattering (GISAS), diffraction, x-ray absorption and emission spectroscopy etc). The use of coherent beams and several other new approaches are also significant. We do not, in this current volume, intend to present what could be termed conference proceedings in a strict sense. Some papers were contributed by those who could not attend the workshop. Other papers were written on topics that were not presented during the workshop. We have always argued in favour of the significance of publishing such collections of papers; isn't it more important for young scientists to publish their results in a good ordinary journal with a high impact factor? The answer is obvious. We have already published so many papers in leading journals, and therefore, the next step would be to share information among specialists (including those who will become specialists) at a deeper level. Young scientists should contribute their work to such collections of papers, in addition to ordinary journals. In this way, almost all specialists in this field will read and respond to them. Publishing papers here will become a starting point for new discussions. I would also like to mention that almost all the papers included in this issue were reviewed thoroughly by four reviewers, who mainly make up the specialist group of the Japan Applied Physics Society. I sincerely acknowledge the efforts and assistance of all my colleagues during the editing of this issue. This publication was financially supported by National Institute for Materials Science, Japan. Kenji Sakurai National Institute for Materials Science Chairman of the workshop A list of previous publications by our group: 1. J. Phys.: Condens. Matter 22 (2010) http://iopscience.iop.org/0953-8984/22/47 2. Trans MRS Japan 34 No 4 (2009) 3. 'Introduction to X-ray reflectivity' (Kodansha, 2009) [in Japanese] 4. Trans MRS Japan 33 No 3 (2008) 5. J. Phys.: Conf. Ser. 83 (2007) http://www.iop.org/EJ/toc/1742-6596/83/1 6. Trans MRS Japan 32 No 1 (2007) 7. Report on buried interface sciences with X-rays and neutrons (2006) http://www.nims.go.jp/xray/lab/hot/kaimen.pdf [in Japanese] 8. KEK Proceedings, 2006-3, 'Buried Interface Science with X-rays and Neutrons' (2006) 9. KEK Proceedings, 2004-5, 'Nano science/technology with synchrotron and neutron reflectivity' (2004) [in Japanese] 10. Trans MRS Japan 28 special issue (2003) 11. KEK Proceedings, 2001-25, 'Structural analysis of thin films and multilayers by X-ray and neutron reflectivity' (2002) [in Japanese

A Search for Hyperluminous X-Ray Sources in the XMM-Newton Source Catalog

NASA Astrophysics Data System (ADS)

Zolotukhin, I.; Webb, N. A.; Godet, O.; Bachetti, M.; Barret, D.

2016-02-01

We present a new method to identify luminous off-nuclear X-ray sources in the outskirts of galaxies from large public redshift surveys, distinguishing them from foreground and background interlopers. Using the 3XMM-DR5 catalog of X-ray sources and the SDSS DR12 spectroscopic sample of galaxies, with the help of this off-nuclear cross-matching technique, we selected 98 sources with inferred X-ray luminosities in the range 1041 < LX < 1044 erg s-1, compatible with hyperluminous X-ray objects (HLX). To validate the method, we verify that it allowed us to recover known HLX candidates such as ESO 243-49 HLX-1 and M82 X-1. From a statistical study, we conservatively estimate that up to 71 ± 11 of these sources may be foreground- or background sources, statistically leaving at least 16 that are likely to be HLXs, thus providing support for the existence of the HLX population. We identify two good HLX candidates and using other publicly available data sets, in particular the VLA FIRST in radio, UKIRT Infrared Deep Sky Survey in the near-infrared, GALEX in the ultraviolet and Canada-France-Hawaii Telescope Megacam archive in the optical, we present evidence that these objects are unlikely to be foreground or background X-ray objects of conventional types, e.g., active galactic nuclei, BL Lac objects, Galactic X-ray binaries, or nearby stars. However, additional dedicated X-ray and optical observations are needed to confirm their association with the assumed host galaxies and thus secure their HLX classification.

Effects of X-ray on the metacestodes of Echinococcus granulosus in vitro.

PubMed

Mao, Rui; Wu, Ge; Wang, Hui; Lu, Pengfei; Li, Jun; Li, Haitao; Ainiwaer, Aimudula; Bai, Yiwei; Shu, Mingyang; Bao, Yongxing; Zhang, Wenbao

2017-09-21

Radiotherapy may represent an alternative treatment modality for cystic echinococcosis (CE), but there is no adequate evidence for it up to now. In this study, we aim to investigate the parasiticidal effects of X-ray on the metacestodes of Echinococcus granulosus in vitro. Protoscoleces obtained from sheep naturally infected with CE were cultivated in RPMI 1640 medium containing 10% fetal bovine serum (FBS) at 37 °C in 5% CO 2 . Upon encystation on day 14, the metacestodes were subjected to various intensities of X-ray. Metacestode structures were observed using light microscope and transmission electron microscopy (TEM), and Real-Time PCR was carried out to determine the expression of EgTPX, EgHSP70, EgEPC1 and Caspase-3. On day 14, encystation was noticed in the majority of protoscoleces in the control group. In the X-ray groups, the encystation rate showed significant decrease compared with that of the control group (P < 0.05), especially the groups subjected to a dose of ≥40 Gy (P < 0.01). Light microscope findings indicated the hooklets on the rostellum were deranged in the irradiation group, and malformation was noticed in the suckers in a dose dependent manner. For the TEM findings, the cellular structure of the germinal layer of the cysts was completely interrupted by X-ray on day 7. The expression of EgTPX, EgHSP70, EgEPC1 and Caspase-3 was up-regulated after irradiation, especially at a dose of ≥45Gy (P < 0.05). X-ray showed parasiticidal effects on the metacestodes of E. granulosus. Irradiation triggered increased expression of EgTPX, EgHSP70, EgEPC1 and Caspase-3.

Impact of DNA repair genes polymorphism (XPD and XRCC1) on the risk of breast cancer in Egyptian female patients.

PubMed

Hussien, Yousry Mostafa; Gharib, Amal F; Awad, Hanan A; Karam, Rehab A; Elsawy, Wael H

2012-02-01

The genes involved in DNA repair system play a crucial role in the protection against mutations. It has been hypothesized that functional deficiencies in highly conserved DNA repair processes resulting from polymorphic variation may increase genetic susceptibility to breast cancer (BC). The aim of the present study was to evaluate the association of genetic polymorphisms in 2 DNA repair genes, XPD (Asp312Asn) and XRCC1 (A399G), with BC susceptibility. We further investigated the potential combined effect of these DNA repair variants on BC risk. Both XPD (xeroderma pigmentosum group D) and XRCC1 (X-ray repair cross-complementing group 1) polymorphisms were characterized in 100 BC Egyptian females and 100 healthy women who had no history of any malignancy by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) method and PCR with confronting two-pair primers (PCR-CTPP), using DNA from peripheral blood in a case control study. Our results revealed that the frequencies of AA genotype of XPD codon 312 polymorphism were significantly higher in the BC patients than in the normal individuals (P ≤ 0.003), and did not observe any association between the XRCC1 Arg399Gln polymorphism and risk of developing BC. Also, no association between both XPD Asp312Asn and XRCC1 A399G polymorphisms and the clinical characteristics of disease. Finally, the combination of AA(XPD) + AG(XRCC1) were significantly associated with BC risk. Our results suggested that, XPD gene is an important candidate gene for susceptibility to BC. Also, gene-gene interaction between XPD(AA) + XRCC1(AG) polymorphism may be associated with increased risk of BC in Egyptian women.

Charge equilibrium and radiation of low-energy cosmic rays passing through interstellar medium

NASA Technical Reports Server (NTRS)

Rule, D. W.; Omidvar, K.

1979-01-01

The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, are considered. Electron loss of the beam has been taken into account by means of the first Born approximation, allowing for the target atom to remain unexcited or to be excited to all possible states. Electron-capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms and capture into all excited states of the projectile. The capture and loss cross sections are found to be within 20%-30% of the existing experimental values for most of the cases considered. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation, and collisional inner-shell ionization, taking into account the fluorescence yield of the ions, has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated, and error estimates made for the results.

Atomic Processes in X-ray Photoionized Gas

NASA Technical Reports Server (NTRS)

Kallman, Timothy

2005-01-01

It has long been known that photoionization and photoabsorption play a dominant role in determining the state of gas in nebulae surrounding hot stars and in active galaxies. Recent observations of X-ray spectra demonstrate that these processes are also dominant in highly ionized gas near compact objects, and also affect the transmission of X-rays from the majority of astronomical sources. This has led to new insights into the understanding of what is going on in these sources. It has also pointed out the need for a better atomic cross sections for photoionization and absorption, notably for processes involving inner shells. In this talk I will discuss these issues, what is known and where more work is needed.

Molecular interactions between photosystem I and ferredoxin: an integrated energy frustration and experimental model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cashman, Derek J.; Zhu, Tuo; Simmerman, Richard F.

2014-08-01

The stromal domain (PsaC, PsaD, and PsaE) of photosystem I (PSI) reduces transiently bound ferredoxin (Fd) or flavodoxin. Experimental structures exist for all of these protein partners individually, but no experimental structure of the PSI/Fd or PSI/flavodoxin complexes is presently available. Molecular models of Fd docked onto the stromal domain of the cyanobacterial PSI site are constructed here utilizing X-ray and NMR structures of PSI and Fd, respectively. Moreover, predictions of potential protein-protein interaction regions are based on experimental site-directed mutagenesis and cross-linking studies to guide rigid body docking calculations of Fd into PSI, complemented by energy landscape theory tomore » bring together regions of high energetic frustration on each of the interacting proteins. Results identify two regions of high localized frustration on the surface of Fd that contain negatively charged Asp and Glu residues. Our study predicts that these regions interact predominantly with regions of high localized frustration on the PsaC, PsaD, and PsaE chains of PSI, which include several residues predicted by previous experimental studies.« less

Oligomerization state in solution of the cell cycle regulators p13suc1 from the fission yeast and p9cksphy from the myxomycete Physarum, two members of the cks family.

PubMed

Birck, C; Raynaud-Messina, B; Samama, J P

1995-04-17

The cks proteins (for cdc2 kinase subunit) are essential cell cycle regulators. They interact strongly with the mitotic cdc2 kinase, but the mechanism and the biological function of this association still await understanding. The oligomerization state in solution of two members of this ubiquitous protein family, the suc1 gene product from the fission yeast and the newly cloned cksphy gene product from the myxomycete Physarum, was investigated by small-angle X-ray scattering (SAXS) and biochemical methods. We found that the major molecular species are monodispersed monomeric proteins. Minor amounts of dimeric suc1 proteins were also found, but no equilibrium between the two forms was observed and surprisingly, the hexameric assemblies observed in the crystal structure of the human ckshs2 homolog were not detected. These apparent discrepancies between proteins that display cross-complementation address the question of the control of the cks oligomerization process and its link to the biological function.

Cross-Correlation of the X-Ray Background with Nearby Galaxies: Erratum

NASA Astrophysics Data System (ADS)

Jahoda, Keith; Lahav, Ofer; Mushotzky, Richard F.; Boldt, Elihu

1992-11-01

In the Letter "Cross-Correlation of the X-Ray Background with Nearby Galaxies" by Keith Jahoda, Ofer Lahav, Richard F. Mushotzky, & Elihu Boldt (ApJ, 378, L37, [1991]) there is an error in the evaluation of equation(5): the numerical constant is too small by a factor of 4.5 (the solid angle of the HEAO 1 A2 beam). The revised X-ray emissivity values (over the volume sampled by the UGC and ESO galaxies) are as follows. For UGC (using the median of Table 1) ρ_x_ = (10.5 +/- 6.0) x 10^38^ h_50_ ergs s^-1^ Mpc^-3^, where the error reflects the scatter in Table 1 and the uncertainty in R_*_, the effective depth of the catalogs (the Hubble constant is in units of H_0_ = 50 h_50_ km s^-1^ Mpc^-1^). Similarly for ESO ρ_x = (14.5 +/- 8.0) x 10^38^ h_50_ ergs s^-1^ Mpc^-3^. For the combined data (UGC and ESO)our revised value is the mean of the two samples,ρ_x_ = (12.5 +/- 7.0) x 10^38^ h_50_ ergs s^-1^ Mpc^-3^. This correction has important consequences for the discussion section of the paper. First, the fraction of the X-ray background which can be produced by nonevolving X-ray sources distributed out to high redshift (assuming a look-back factor of f=0.5) can be as large as 50% +/- 30% and 70% +/- 40% for UGC and ESO, respectively. Second, this measurement of ρ_x_ exceeds the upper limit calculated by E. Boldt (IAU Colloq. 123,451 [1990]) based on an approximation of the total extragalactic X-ray dipole, unless b{OMEGA}^-0.6^<~ 1.3, less than about half the value derived for bright X-ray AGNs by T. Miyaji & E. Boldt (ApJ, 353, L3 [1990]) and T. Miyaji, K. Jahoda, & E. Boldt (AIP Conf. Proc. 222,431 [1991]). However, an improved determination of the extragalactic X-ray dipole, now obtained by performing a direct vector sum of the all-sky X-ray data (excluding only points near known Galactic point sources and their antipodes and points with |b| < 20^deg^), and subtracting the high-latitude contribution predicted by the Galactic model of D. Iwan et al. (ApJ, 260,111 [1982]) and that arising from the Compton-Getting effect, gives an estimate (rather than an upper limit) that ρ_x_ ~ 30 x 10^38^ h_50_(b{OMEGA}^- 0.6^)^-1^ ergs s^-1^ Mpc^-3^, consistent with the revised volume emissivity estimated in this work and the same bias parameter deduced for the bright AGNs. These two results suggest that a substantial fraction of the X-ray background could be produced by present-epoch objects and that these have a bias parameter similar to or only slightly smaller than the X-ray bright AGNs. We would also like to point out a minor error after equation (3). The correct sentence should be "where W_gg_, a galaxy autocorrelation estimator defined in analogy to equation (1), is, for example, 023 and 0.24 for UGC and ESO, respectively (for 17 deg^2^ cells)." The rest of the calculation is as before. We thank Andy Fabian for bringing the error to our attention and Takamitsu Miyaji for discussion.

Application of X-Ray Computer Tomography for Observing the Central Void Formations and the Fuel Pin Deformations of Irradiated FBR Fuel Assemblies

NASA Astrophysics Data System (ADS)

Katsuyama, Kozo; Nagamine, Tsuyoshi; Furuya, Hirotaka

2010-10-01

In order to observe the structural change in the interior of irradiated fuel assemblies, a non-destructive post-irradiation examination (PIE) technique using X-ray computer tomography (X-ray CT) was developed. This X-ray CT technique was applied to observe the central void formations and fuel pin deformations of fuel assemblies which had been irradiated at high linear heat rating. The central void sizes in all fuel pins were measured on five cross sections of the core fuel column as a parameter for evaluating fuel thermal performance. In addition, the fuel pin deformations were analyzed from X-ray CT images obtained along the axial direction of a fuel assembly at the same separation interval. A dependence of void size on the linear heat rating was seen in the fuel assembly irradiated at high linear heat rating. In addition, significant undulations of the fuel pin were observed along the axial direction, coinciding with the wrapping wire pitch in the core fuel column. Application of the developed technique should provide enhanced resolution of measurements and simplify fuel PIEs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castillo-Mejia, Fermin; Herrera-Velazquez, J. Julio E.; Gamboa-deBuen, I.

The Fuego Nuevo II (FN-II) dense plasma focus device is a small machine (4.6 kJ), operating at the Instituto de Ciencias Nucleares, UNAM, in which neutrons, as well as soft and hard X rays have been studied with a number of diagnostics. Neutrons are studied with silver activation counters, and scintillator-photomultiplier detectors, while their angular distribution inside and outside the discharge chamber have been studied with CR-39 plastic track detectors. The soft X rays are studied with a multiple-pin-hole camera and PIN diodes, while the hard X-rays are observed with the scintillator-photomultiplier detectors mentioned above. When a needle is insertedmore » on the inner electrode, a bright spot of hard x-rays can be concentrated, and used for the production of high-contrast radiography. Dosimetric measurements have been made for X-rays crossing a 300 micron aluminum window, through the axis of the machine, showing an average dose of 0.11{+-}0.01 mGy per shot. In contrast, the average dose with a hollow cathode is 0.077{+-}0.006 mGy per shot.« less

A hyperspectral X-ray computed tomography system for enhanced material identification

NASA Astrophysics Data System (ADS)

Wu, Xiaomei; Wang, Qian; Ma, Jinlei; Zhang, Wei; Li, Po; Fang, Zheng

2017-08-01

X-ray computed tomography (CT) can distinguish different materials according to their absorption characteristics. The hyperspectral X-ray CT (HXCT) system proposed in the present work reconstructs each voxel according to its X-ray absorption spectral characteristics. In contrast to a dual-energy or multi-energy CT system, HXCT employs cadmium telluride (CdTe) as the x-ray detector, which provides higher spectral resolution and separate spectral lines according to the material's photon-counter working principle. In this paper, a specimen containing ten different polymer materials randomly arranged was adopted for material identification by HXCT. The filtered back-projection algorithm was applied for image and spectral reconstruction. The first step was to sort the individual material components of the specimen according to their cross-sectional image intensity. The second step was to classify materials with similar intensities according to their reconstructed spectral characteristics. The results demonstrated the feasibility of the proposed material identification process and indicated that the proposed HXCT system has good prospects for a wide range of biomedical and industrial nondestructive testing applications.

Atomic Calculations and Laboratory Measurements Relevant to X-ray Warm Absorbers

NASA Technical Reports Server (NTRS)

Kallman, Tim; Bautista, M.; Palmeri, P.

2007-01-01

This viewgraph document reviews the atomic calculations and the measurements from the laboratory that are relevant to our understanding of X-Ray Warm Absorbers. Included is a brief discussion of the theoretical and the experimental tools. Also included is a discussion of the challenges, and calculations relevant to dielectronic recombination, photoionization cross sections, and collisional ionization. A review of the models is included, and the sequence that the models were applied.