301,495 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
Portrait Groups: R (Ray?), D, V, and E (Edie?)
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/247881171164
Item: [1981.0081.00276] "Portrait Groups: R (Ray?), D, V, and E (Edie?)
Time Resolved Two Dimensional X-Ray Densitometry of a Two Phase Flow Downstream of a Ventilated Cavity
No full textTo measure the void fraction distribution in gas-liquid flows, a two-dimensional x-ray densitometry system was developed. This system is capable of acquiring a two-dimensional projection with a 225 cm2 area of measurement through 21 cm of water. The images can be acquired at rates on the order of 1 kHz. Common sources of error in x-ray imaging, such as x-ray scatter, image distortion, veiling glare, and beam hardening were considered, and mitigated. The measured average void fraction was compared success fully to that of a phantom target and found to be within 1%. To evaluate the performance of the new system, the flow in and downstream of a ventilated nominally two-dimensional partial cavity was investigated and compared to measurements from dual tip fiber optical probes and high speed video. The measurements were found to have satisfactory agreement for void fractions above 5% of the selected void fraction measurement range.Office of Naval Research under grant N00014-10-1-097
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
Registration and tracking to integrate X-ray and MR images in an XMR facility
No full textWe describe a registration and tracking technique to integrate cardiac X-ray images and cardiac magnetic resonance (MR) images acquired from a combined X-ray and MR interventional suite (XMR). Optical tracking is used to determine the transformation matrices relating MR image coordinates and X-ray image coordinates. Calibration of X-ray projection geometry and tracking of the X-ray C-arm and table enable three-dimensional (3-D) reconstruction of vessel centerlines and catheters from bi-plane X-ray views. We can, therefore, combine single X-ray projection images with registered projection MR images from a volume acquisition, and we can also display 3-D reconstructions of catheters within a 3-D or multi-slice MR volume. Registration errors were assessed using phantom experiments. Errors in the combined projection images (two-dimensional target registration error--TRE) were found to be 2.4 to 4.2 mm, and the errors in the integrated volume representation (3-D TRE) were found to be 4.6 to 5.1 mm. These errors are clinically acceptable for alignment of images of the great vessels and the chambers of the heart. Results are shown for two patients. The first involves overlay of a catheter used for invasive pressure measurements on an MR volume that provides anatomical context. The second involves overlay of invasive electrode catheters (including a basket catheter) on a tagged MR volume in order to relate electrophysiology to myocardial motion in a patient with an arrhythmia. Visual assessment of these results suggests the errors were of a similar magnitude to those obtained in the phantom measurement
X-Ray micro-Computed Tomography and micro X-ray Fluorescence mapping of synthetic emerald by using a laboratory polycapillary optics X-ray tube layout
No full textThis paper relates the X-ray micro-Computed Tomography and micro X-ray Fluorescence 2D mapping of a
synthetic emerald performed by a conventional X-ray source matched with polycapillary optics. The investigated
crystals were synthesized in 1888 by Hautefeuille and Perrey starting from a stochiometric oxide mixture and using
LiMoO4 as a flux; Cr was added to the system to give the green-color to the resulting crystals. Preliminary scanning
electron microscope-backscattered electron images, coupled with wavelength-dispersive spectrometry microanalyses,
showed a peculiar ‘hourglass’ distribution of Cr across the beryl crystals. In this contribution, we show the
capability of a laboratory polycapillary lenses/X-ray tubes layout to characterize at the micrometric scale; the 3D spatial
distribution of Cr in these emerald crystals. Actually, this technique offers many opportunities to characterize natural and
technological materials where zoning of particular chemical elements occur at the micron or sub-micron scale
Fluorometric sensing of thiocyanate ions and competitive binding of anions in a family of CdII complexes of a phenol based ligand showing diverse structures
No full textA family of central phenoxido and terminal alcohol bound Cd2 complexes have been synthesized and crystallographically characterized. Reaction condition and anion coordination (NO3-, NCS- and N3-) dependent changeable structures have been identified in the four complexes 1–4 following varying coordination of the binucleating Schiff base ligand H3bemp (2,6-bis[(2-hydroxy ethylimino)-methyl]-4-methyl phenol) to cadmium(II) ions. These complexes have been characterized by X-ray crystallography, spectroscopic and analytical techniques. During the formation of 2 and 3, the phenoxido bridging unit of
H3bemp is transformed to non-bridging modes of binding following the coordination of NO3- and NCS-,while changing one imine function on each ligand to the zwitterionic form, generated through a kind of acid–base reaction for metal ion coordination. The H3bemp molecule registers as a highly selective and
sensitive fluorescent probe for Cd2+ in a PBS buffer (5 mM in pH = 7.1) at 25 C. In the presence ofCd2+, the increase in fluorescence intensity is accounted for by the formation of [Cd2(H2bemp)2](NO3)2(1) in solution. The fluorescence quantum yield of H3bemp is 0.201, and it increases more than 4-fold (0.851) in the presence of the cadmium ion. In presence of NCS, complex 1 showed coordination induced fluorescence enhancement, whereas NO3- and N3- anions quench the emission intensities significantly
A new heuristic geometrical approach for finding non-coplanar multiple edge diffraction ray paths
No full textRooftop diffraction can contribute significantly to the propagation path loss in outdoor microcellular environments. For non-coplanar multiple edges, the finding of exact ray paths requires a complex algebraic analysis that is infeasible for rapid application in deterministic ray tracing models. A new heuristic geometrical approach is reported that finds the ray paths for arbitrary height rooftop diffraction and rooftop-to-building corner diffraction. This method can be applied to any 3-D image based ray tracing model. The accuracy of the new method is first quantified using two specific test cases. The method is then implemented in an existing microcellular ray model and path loss predictions are compared with measured data. The heuristic diffraction approach is shown to be simple to implement and lowers the prediction error when compared with the traditional Vertical Plane diffraction approximatio
Ronald D. Ray Interview (part 3)
No full textAn interview with Ronald D. Ray of Crestwood, Kentucky discussing his experiences as a United States Marine Corps Infantry Battalion Advisor to the Vietnamese Marine Corps during the Vietnam War in 1967 and 1968 on August 21, 1999. Colonel Ray was a founder and chairman of the Kentucky Vietnam Veterans Memorial from 1982 to 1990
Ronald D. Ray Interview (part 2)
No full textAn interview with Ronald D. Ray of Crestwood, Kentucky discussing his experiences as a United States Marine Corps Infantry Battalion Advisor to the Vietnamese Marine Corps during the Vietnam War in 1967 and 1968 on August 21, 1999. Colonel Ray was a founder and chairman of the Kentucky Vietnam Veterans Memorial from 1982 to 1990
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