32,788 research outputs found
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Securing XML documents with author-X
No full textAuthor-X is a Java-based system that addresses the security issues of access control and policy design for XML document administration. Author-X supports the specification of policies at varying granularity levels and the specification of user credentials as a way to enforce access control. Access control is available according to both push and pull document distribution policies, and document updates are distributed through a combination of hash functions and digital signature techniques. The Author-X approach to distributed updates allows a user to verify a document's integrity without contacting the document server
X-ray tomography for lithium ion battery electrode characterisation — A review
No full textIn recent years, x-ray tomography has emerged as a powerful analytical tool for the study of lithium ion batteries and the processes occurring within. A region of specific interest is the electrode and, in particular, the heterogeneous and porous structure. The present paper is a review of studies that use x-ray tomography to characterise electrode structure, at both the cell and microstructure scales. At the cell level, x-ray tomography is used to investigate macroscopic design parameters, such as anode and cathode thicknesses, packing density and alignment of assembled cells, as well as to visualise any macroscopic structural defects, such as islanding. At the microstructure level, x-ray tomography allows for quantitative analysis of electrode structures to ascertain parameters such as particle size, tortuosity and volume fraction. The paper also explores different techniques that have been used across the field, from ex-situ, in-situ and operando techniques, to multimodal imaging methods, tomography informed design and results informed imaging
Relations between x-ray timing features and spectral parameters of galactic black hole x-ray binaries
Full text linkWe present a study of correlations between spectral and timing parameters for a sample of black hole X-ray binary candidates. Data are taken from GX
339-4, H 1743-322, and XTE J1650-500, as the Rossi X-ray Timing Explorer
(RXTE) observed complete outbursts of these sources. In our study we investigate outbursts that happened before the end of 2009 to make use of the high-energy coverage of the HEXTE detector and select observations that
show a certain type of quasi-periodic oscillations (type-C QPOs). The spectral parameters are derived using the empirical convolution model simpl to model the Comptonized component of the emission together with a disc blackbody for the emission of the accretion disc. Additional spectral features, namely a reflection component, a high-energy cut-off, and excess emission at 6.4 keV, are taken into account. Our investigations confirm the known positive
correlation between photon index and centroid frequency of the QPOs and reveal an anti-correlation between the fraction of up-scattered photons and the QPO frequency. We show that both correlations behave as expected in the “sombrero”
geometry. Furthermore, we find that during outburst decay the correlation between photon index and QPO frequency follow a general track, independent of individual outbursts
The effect of 29 W X rays on the dose response of chromosome aberrations in human lymphocytes
No full textThe induction of chromosome aberrations in human lymphocytes irradiated in vitro with X rays generated at a tube voltage of 29 kV was examined to assess the maximum low-dose RBE (RBEM) relative to higher-energy X rays or Co-60 gamma rays. Since blood was taken from the same male donor whose blood had been used for previous irradiation experiments using widely varying photon energies, the greatest possible accuracy was available for such an estimation of the RBE,, avoiding the interindividual variations in sensitivity or differences in methodology usually associated with interlaboratory comparisons. The magnitude of the linear coefficient alpha of the linear-quadratic dose-effect relationship obtained for the production of dicentric chromosomes by 29 kV X rays (alpha = 0.0655 +/- 0.0097 Gy(-1)) confirms earlier observations of a strong increase in alpha with decreasing photon energy. Relating this value to previously published values of alpha for the dose-effect curves for dicentrics obtained in our own laboratory, RBEM values of 1.6 +/- 0.3 in comparison with weakly filtered 220 kV X rays, 3.0 +/- 0.7 compared to heavily filtered 220 kV X rays, and 6.1 +/- 2.5 compared to Co-60 gamma rays have been obtained. These data emphasize that the choice of the reference radiation is of fundamental importance for the RBEM obtained. A special survey of the RBEM values obtained by different investigators in the narrow quality range from about 30 to 350 kV X rays indicates that the present RBE is in fairly good agreement with previously published findings for the induction of chromosome aberrations or micronuclei in human lymphocytes but differs from recently published findings for neoplastic transformation in a human hybrid cell line. (C) 2002 by Radiation Research Society
Chain architecture effects on the diffusion of cylinder-forming block copolymers
No full textWe investigate the effect of chain architecture on the self-diffusion of poly(styrene)-poly(ethylene) triblock (PS-PE-PS or SES) and pentablock (PS-PE-PS-PE-PS or SESES) copolymers with a cylindrical domain structure (E cylinders). Transmission electron microscopy (TEM) and grazing-incidence small-angle X-ray scattering (GISAXS) are employed to reveal the microstructure of the block copolymer films, and dynamic secondary ion mass spectroscopy (DSIMS) is used to obtain diffusion coefficients. The triblock copolymer (SES) chains diffuse through a randomly oriented cylindrical structure via a "hopping" mechanism where the normalized diffusion coefficient D/D-0 (D is the diffusion coefficient of the block copolymer and D-0 is the diffusion coefficient of a disordered (hypothetical) block copolymer of similar M-w) decreases exponentially with the thermodynamic barrier chi N-PE, where chi is the Flory interaction parameter between styrene and ethylene and N-PE is the degree of polymerization of the poly(ethylene) block. However, the pentablock copolymer (SESES) diffuses via a "walking" mechanism through an ordered cylindrical structure which involves the activation of a single E block at a time to overcome the thermodynamic barrier. Both mechanisms have been reported previously for diblock and triblock copolymers, respectively. Hence, for a similar overall M-w the pentablock copolymer diffuses faster than the corresponding triblock copolymer. Moreover, a comparison is made between perpendicular and parallel diffusion in the pentablock copolymer as both mechanisms are observed due to a change in the cylinder orientation (from parallel to perpendicular cylinders) as a function of depth. The relative independence of the parallel diffusion on chi N-PE suggests that the thermodynamic barrier for perpendicular diffusion does not affect parallel diffusion coefficients. However, the normalized parallel and perpendicular diffusion coefficients of the SESES pentablock copolymer as well as the normalized perpendicular diffusion coefficient of the SES triblock copolymer are substantially less than the corresponding diffusion coefficients of a cylinder-forming diblock copolymer investigated by Cavicchi and Lodge at the same values of chi N-cyl, where N-cyl is the degree of polymerization of the cylinder block. This comparison suggests that entangled loops in the PE midblock cylinders impose additional entropic barriers to diffusion that are absent for diblock copolymers
. 39 Tomo X (1956) Sexta Época (1939-1966). Anales del Instituto Nacional de Antropología e Historia
No full textPublicación que recopila y difunde cien años de trabajo de la antropología en México (1877-1977), integrada por documentos y manuscritos arqueológicos, antropológicos, históricos, geológicos, botánicos y lingüísticos.- Información general de las actividades del Instituto Nacional de Antropología e Historia durante el año 1956 por Eusebio Dávalos Hurtado. - Generalidades sobre la población rural y urbana de México por Venus Uribe Macip y Anselmo Marino Flores. - Exploraciones arqueológicas en Palenque: 1953 por Alberto Ruz Lhuillier. - Exploraciones arqueológicas en Palenque: 1954 por Alberto Ruz Lhuillier. - Exploraciones arqueológicas en Palenque: 1955 por Alberto Ruz Lhuillier. - Exploraciones arqueológicas en Palenque: 1956 por Alberto Ruz Lhuillier
New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619
No full textXMM–Newton observations of the supergiant fast X-ray transient IGR J17544?2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provide a refined estimate of the orbital period at 4.9272?±?0.0004?d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM–Newton observations (each lasting ?15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR J17544?2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 1033?erg?s?1 (0.5–10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544?2619 dropped to ?4?×?1032?erg?s?1 (0.5–10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544?2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544?2619 and the supergiant fast X-ray transients (SFXTs) population. We conclude that accretion under the ‘quasi-spherical accretion’ model provides a good description of the behaviour of IGR J17544?2619 and suggests an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the neutron star under the quasi-spherical formulation. Hence, we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model
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Enhanced colour encoding of materials discrimination information for multiple view dual-energy x-ray imaging
No full textThis thesis reports an investigation into dual-energy X-ray discrimination techniques. These techniques are designed to provide colour-coded materials discrimination information in a sequence of perspective images exhibiting sequential parallax. The methods developed are combined with a novel 3D imaging technique employing depth from motion or kinetic depth effect (KDE). This technique when applied to X-ray images is termed KDEX imaging and was developed previously by the university team for luggage screening applications at security checkpoints. A primary motivation for this research is that the dual-energy X-ray techniques, which are routinely incorporated into ‘standard’ 2D luggage scanners, provide relatively crude materials discrimination information. In this work it was critical that robust materials discrimination and colour encoding process was implemented as the sequential parallax exhibited by the KDEX imagery may introduce colour changes, due to the different X-ray beam paths associated with each perspective image. Any introduction of ‘colour noise’ into the resultant image sequences could affect the perception of depth and hinder the ongoing assessment of the potential utility of the dual-energy KDEX technique. Two dual-energy discrimination methods have been developed, termed K-II and W-E respectively. Employing the total amount of attenuation measured at each energy level and the weight fraction of layered structures, a combination of the K-II and the W-E techniques enables the computation and extraction of a target objects’ effective atomic number (Zeff) and its surface density (ρS) in the presence of masking layers
Author headings for the official publications of the State of Kansas
No full textIncludes bibliographical references (page x).This list of author headings covers all official agencies as found in the laws of the territory and the laws of the state of Kansas from May 30, 1854 through July 1955; also agencies created by Executive Order, and administrative divisions, or boards, created within a department of the state. Agencies included are:
1. All departments, bureaus, divisions, commissions, courts, legislative bodies and special committees created by the laws or joint resolutions of the territory or state of Kansas, or by Executive Order*
2. Subdivisions of the respective departments, bureaus, commissions and committees even though not expressly created by acts of the legislature, but which are included in the official reports of the agencies*
3. Legislative bodies and their committees, if created by law, or if their reports were published.
4. Societies supported wholly, or in part, by the state.
5. All state and territorial institutions (including educational, charitable, correctional and penal)
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