scholarly journals Analysis of dosimetric peaks of MgB4O7:Dy (40% Teflon) versus LiF:Mg,Ti TL detectors

Nukleonika ◽  
2016 ◽  
Vol 61 (1) ◽  
pp. 49-52 ◽  
Author(s):  
Monika Paluch-Ferszt ◽  
Beata Kozłowska ◽  
Susana Oliveira de Souza ◽  
Luiza Freire de Souza ◽  
Divanizia Nascimento Souza
Keyword(s):  
Solid State ◽  
Gamma Ray ◽  
High Sensitivity ◽  
High Dose ◽  
Heating Rates ◽  
X Ray ◽  
Annealing Conditions ◽  
Wide Range ◽  
Personal Dosimetry ◽  
Potential Use

AbstractMagnesium tetraborate doped with dysprosium (MgB4O7:Dy) is known as a good thermoluminophor for personal dosimetry of gamma ray and X-ray radiation because of its high sensitivity and close tissue equivalence. This material can be produced by different routes. The sintered pastilles of magnesium tetraborate mixed with Teflon (40%) used in this work were manufactured at the Federal University of Sergipe, Department of Physics by the solid-state synthesis. Magnesium tetraborate was already used for high-dose dosimetry, exhibiting linearity for a wide range of doses. In this work, the authors examined its main characteristics prior to potential use of detectors in everyday dosimetry, comparing this material to a widely used LiF:Mg,Ti phosphor. The following tests influencing dosimetric peaks of MgB4O7:Dy were presented: (1) the shape of the glow curves, (2) annealing conditions and post-irradiation annealing and its influence for background of the detectors, (3) the choice of the heating rates at the read-out and (4) the threshold dose, that is, the lowest possible dose to be measured. Similar tests were performed with LiF:Mg,Ti detectors, produced and widely used in Poland. The results were compared and discussed.

Measurement of pulmonary edema in intact dogs by transthoracic gamma-ray attenuation

1979 ◽  
Vol 47 (6) ◽  
pp. 1228-1233 ◽  
Author(s):  
D. S. Simon ◽  
J. F. Murray ◽  
N. C. Staub
Keyword(s):  
Pulmonary Edema ◽  
Time Course ◽  
Gamma Ray ◽  
High Sensitivity ◽  
Lung Edema ◽  
Lung Water ◽  
Vascular Congestion ◽  
Isolated Lung ◽  
Wide Range ◽  
Gamma Ray Attenuation

We evaluated the attenuation of the 122 keV gamma ray of cobalt-57 across the thorax of anesthetized dogs as a method for following the time course of lung water changes in acute pulmonary edema induced by either increased microvascular permeability or increased microvascular hydrostatic pressure. The gamma rays traversed the thorax centered on the seventh rib laterally where the lung mass in the beam path was greatest. Calibration measurements in isolated lung lobes demonstrated the high sensitivity and inherent accuracy of the method over a wide range of lung water contents. In control dogs reproducibility averaged +/-3%. Increased permeability edema led to large rapid increases in the transthoracic gamma ray attenuation (TGA), while increased pressure caused an immediate, modest increase in TGA (vascular congestion) followed by a slow further increase over 2 h. There was a fairly good correlation between the increase in extravascular lung water and the change in TGA. The method is simple, safe, and noninvasive and appears to be useful for following the time course of lung water accumulation in generalized lung edema in anesthetized animals.

scholarly journals The XXL Survey

2018 ◽  
Vol 620 ◽  
pp. A18 ◽  
Author(s):  
C. H. A. Logan ◽  
B. J. Maughan ◽  
M. N. Bremer ◽  
P. Giles ◽  
M. Birkinshaw ◽  
...  
Keyword(s):  
Angular Resolution ◽  
False Positive Rate ◽  
High Sensitivity ◽  
Point Sources ◽  
Selection Function ◽  
X Rays ◽  
Cluster Emission ◽  
X Ray ◽  
Wide Range ◽  
Function Modelling

Context. The XMM-XXL survey has used observations from the XMM-Newton observatory to detect clusters of galaxies over a wide range in mass and redshift. The moderate PSF (FWHM ~ 6″ on-axis) of XMM-Newton means that point sources within or projected onto a cluster may not be separated from the cluster emission, leading to enhanced luminosities and affecting the selection function of the cluster survey. Aims. We present the results of short Chandra observations of 21 galaxy clusters and cluster candidates at redshifts z > 1 detected in the XMM-XXL survey in X-rays or selected in the optical and infra-red. Methods. With the superior angular resolution of Chandra, we investigate whether there are any point sources within the cluster region that were not detected by the XMM-XXL analysis pipeline, and whether any point sources were misclassified as distant clusters. Results. Of the 14 X-ray selected clusters, 9 are free from significant point source contamination, either having no previously unresolved sources detected by Chandra or with less than about 10% of the reported XXL cluster flux being resolved into point sources. Of the other five sources, one is significantly contaminated by previously unresolved AGN, and four appear to be AGN misclassified as clusters. All but one of these cases are in the subset of less secure X-ray selected cluster detections and the false positive rate is consistent with that expected from the XXL selection function modelling. We also considered a further seven optically selected cluster candidates associated with faint XXL sources that were not classed as clusters. Of these, three were shown to be AGN by Chandra, one is a cluster whose XXL survey flux was highly contaminated by unresolved AGN, while three appear to be uncontaminated clusters. By decontaminating and vetting these distant clusters, we provide a pure sample of clusters at redshift z > 1 for deeper follow-up observations, and demonstrate the utility of using Chandra snapshots to test for AGN in surveys with high sensitivity but poor angular resolution.

scholarly journals Gamma-Ray Burst Observations with BATSE

1998 ◽  
Vol 188 ◽  
pp. 159-162
Author(s):  
Gerald J. Fishman
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Gamma Ray Burst ◽  
New Era ◽  
X Ray ◽  
Time Profiles ◽  
Random Direction ◽  
Wide Range ◽  
New Phenomena

Gamma-ray bursts (GRBs) will be recorded as one of the outstanding new phenomena discovered in astronomy this century. About once per day, a burst of gamma rays appears from a random direction on the sky. Often, the burst outshines all other sources of gamma-rays in the sky, combined. This paper reviews some of the key observed phenomenon of bursts in the hard x-ray/gamma-ray region, as observed with the BATSE experiment on the Compton Gamma Ray Observatory. The observed time profiles, spectral properties and durations of gamma-ray bursts cover a wide range. Recent breakthroughs in the observation of gamma-ray burst counterparts and afterglows in other wavelength regions have marked the beginning of a new era in gamma-ray burst research. Those observations are described in following papers in these proceedings.

Near Edge X-Ray Absorption Fine Structure (NEXAFS) Microscopy: Chemical Analysis at Sub Visible Spatial Resolution

1997 ◽  
Vol 3 (S2) ◽  
pp. 851-852
Author(s):  
H. Ade
Keyword(s):  
Fine Structure ◽  
Compositional Analysis ◽  
High Sensitivity ◽  
Linear Dichroism ◽  
X Rays ◽  
X Ray ◽  
Absorption Fine ◽  
Nexafs Spectroscopy ◽  
Wide Range ◽  
X Ray Absorption

Infrared, Raman, and fluorescence/luminescence microspectroscopy/microscopy in many instances seek to provide high sensitivity compositional and functional information that goes beyond mere elemental composition. This goal is shared by NEXAFS microscopy, in which Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is employed to provide chemical sensitivity and can be relatively easily adopted in a scanning transmission x-ray microscope (STXM). In addition to compositional information, NEXAFS microscopy can exploit the dependence of x-ray absorption resonances on the bond orientation relative to the linearly polarized x rays (linear dichroism microscopy). For compositional analysis, NEXAFS microscopy is analogous to Electron Energy Loss Spectroscopy (EELS) in an electron microscope. However, when utilizing near edge spectral features, NEXAFS microscopy requires a considerable lower dose than EELS microscopy which makes it very suitable to studying radiation sensitive materials such as polymers. NEXAFS has shown to have excellent sensitivity to a wide range of moieties in polymers, including sensitivity to substitution isomerism.

The inactivation of α -chymotrypsin by ionizing radiations

1960 ◽  
Vol 256 (1284) ◽  
pp. 1-14 ◽  
Keyword(s):  
Electron Beam ◽  
Solid State ◽  
Low Voltage ◽  
Kinetic Equations ◽  
High Dose ◽  
X Rays ◽  
Dilute Solutions ◽  
Active Centre ◽  
Enhanced Sensitivity ◽  
Wide Range

The inactivation of α -chymotrypsin by low-voltage X-rays and by 15 meV electrons has been studied over a range of concentrations extending from the solid enzyme to dilute solutions and the sensitivity D 37 / c , where D 37 is the dose required to cause in activation to 37 % of the original at concentration c , determined under varied circumstances. The sensitivity is constant in air over a wide range of concentrations, but in the solid state is greater by a factor of about 7. That the enhanced sensitivity in the solid state is connected with disorganization of the secondary structure is shown by the fact that after partial inactivation by irradiation the enzyme is more sensitive to in activation by heating. This view is also supported by the finding that oxygen has no significant effect on the irradiation (with 15 meV electrons) in the solid state, since there is no reason to expect that oxygen will influence the breakage of hydrogen bonds within the molecule. The sensitivities of the protease and esterase activities of the enzyme are the same, showing that only one kind of active centre is involved. The sensitivity also decreases at low concentrations of the enzyme. That this is not due to recombination of the radicals is shown by the finding that the effect is uninfluenced by varying the dose rate of the electron beam over a very wide range. An enhanced sensitivity is, however, observed in solutions from which the oxygen has been removed. It follows that secondary radicals, principally O 2 H , formed in the presence of oxygen are less effective than the primary radicals. Kinetic equations are deduced which represent the main features of this behaviour. A possible reason for the greater effectiveness of H than O 2 H is the ability of the former to penetrate into the protein molecule. It was also found that in dilute solutions containing oxygen the electron beam is more effective than the X-rays. This could be accounted for if equilibrium between the primary radicals and oxygen is not reached at the very high dose rates at which the electron pulses are delivered. In vacuo no differences in sensitiveness to the X-rays and the electrons were observed.

Microstructure of barium monoferrite BaFe2O4

1990 ◽  
Vol 48 (4) ◽  
pp. 778-779
Author(s):  
J.M. González-Calbet ◽  
S. Nicolopoulos ◽  
M. Vallet-Regí
Keyword(s):  
Solid State ◽  
Solid State Reaction ◽  
Nominal Composition ◽  
Thermal Treatments ◽  
X Ray ◽  
Linear Defects ◽  
Annealing Conditions ◽  
Initial Stage ◽  
Ideal Stoichiometry ◽  
Crystallographic Shear

BaFe2O4 appears at the initial stage of the solid state reaction during the synthesis of hexaferrites with Ba as divalent cation. In the HREM study of this phase, linear defects like crystallographic shear planes are observed which could change the ideal stoichiometry. Crystals are twinned, confirming previously predicted results from X-Ray data.Although the crystal structure and superstructure of the BaFe2O4 is well established, the microstructure still remains unknown. This phase is always present during the synthesis of several hexaferrites; the study of the microstructure could help to the understanding of the solid state reaction to synthetize new ferrite phases.A series with nominal composition Ba2Cu2Fe12022 (Y type hexagonal ferrite) was prepared with different annealing conditions for each sample. Details about the thermal treatments and the final products are given elsewhere. From X-Ray powder diffraction data, the presence of BaFe204 is always identificated at the final products.

New Two-Dimensional Solid State Pixel Detectors With Dedicated Front-End Integrated Circuits for X-Ray and Gamma-Ray Imaging

2009 ◽  
Vol 56 (4) ◽  
pp. 2321-2329 ◽  
Author(s):  
Tumay O. Tumer ◽  
Victoria B. Cajipe ◽  
Martin Clajus ◽  
Satoshi Hayakawa ◽  
Alexander Volkovskii
Keyword(s):  
Solid State ◽  
Integrated Circuits ◽  
Gamma Ray ◽  
Two Dimensional ◽  
X Ray ◽  
Front End ◽  
Pixel Detectors ◽  
Gamma Ray Imaging

scholarly journals Occupational Radiation Exposure in Health Care Facilities

2013 ◽  
Vol 10 (3) ◽  
pp. 48-51 ◽  
Author(s):  
Chhavi Raj Bhatt ◽  
A Widmark ◽  
SL Shrestha ◽  
T Khanal ◽  
B Ween
Keyword(s):  
Health Care ◽  
Radiation Exposure ◽  
Background Radiation ◽  
Health Care Facilities ◽  
High Dose ◽  
Occupational Radiation Exposure ◽  
X Ray ◽  
Care Facilities ◽  
Personal Dosimetry ◽  
Occupational Radiation

Background  Radiation, which is used extensively to diagnose and treat human diseases, poses an occupational health risk for the concerned health workers. Personal dosimetry is an important tool to monitor occupational radiation exposures. Objective  This study was conducted to reveal and to describe the situation of occupational radiation exposure monitoring among staffs in different health care facilities in Nepal. Methods  A cross-sectional study was performed among the 35 Health Care Facilities. Information about types and number of X-ray procedures performed, types and number of personnel involved, workload and the availability of personal dosimetry service were collected. Results  Six Health Care Facilities had personal dosimetry service available for a total of 149 personnel. Of a total of nearly one million X-ray procedures performed in the 35 Health Care Facilities in 2007, 76 % was performed by non-monitored personnel. The majority of the facilities performing high dose procedures, like catheterisation, angiography and intestinal barium procedures did not offer personal dosimetry for the involved personnel. Conclusion  There are a limited number of personnel being monitored with personal dosimetry. There are no regulatory dose limits for occupationally exposed staff. Thus, there is an urgent need to establish a national radiation protection authority to regulate the use of radiation in Nepal. Kathmandu University Medical Journal | VOL.10 | NO. 3 | ISSUE 39 | JUL- SEP 2012 | Page 48-51 DOI: http://dx.doi.org/10.3126/kumj.v10i3.8019

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