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81.
82.
Activated carbon production from almond shells using phosphoric acid activation agent was achieved by applying both conventional heating and microwave heating in succession. The morphology and surface properties of activated carbon were studied using thermogravimetric and differential gravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and Brunauer–Emmett–Teller analysis. A surface area of 1128 m2/g was achieved by optimizing the microwave power (500?W), microwave application time (15?minutes), conventional heating time (45?minutes), conventional heating temperature (500?°C), and the phosphoric acid:sample ratio (0.7:1). An adsorption capacity of methylene blue of 148?mg/g and an iodine value of 791?mg/g was obtained for the prepared activated carbon. 相似文献
83.
Comparison of phantom materials for use in quality assurance of microbeam radiation therapy 下载免费PDF全文
Matthew Cameron Iwan Cornelius Dean Cutajar Jeremy Davis Anatoly Rosenfeld Michael Lerch Susanna Guatelli 《Journal of synchrotron radiation》2017,24(4):866-876
Microbeam radiation therapy (MRT) is a promising radiotherapy modality that uses arrays of spatially fractionated micrometre‐sized beams of synchrotron radiation to irradiate tumours. Routine dosimetry quality assurance (QA) prior to treatment is necessary to identify any changes in beam condition from the treatment plan, and is undertaken using solid homogeneous phantoms. Solid phantoms are designed for, and routinely used in, megavoltage X‐ray beam radiation therapy. These solid phantoms are not necessarily designed to be water‐equivalent at low X‐ray energies, and therefore may not be suitable for MRT QA. This work quantitatively determines the most appropriate solid phantom to use in dosimetric MRT QA. Simulated dose profiles of various phantom materials were compared with those calculated in water under the same conditions. The phantoms under consideration were RMI457 Solid Water (Gammex‐RMI, Middleton, WI, USA), Plastic Water (CIRS, Norfolk, VA, USA), Plastic Water DT (CIRS, Norfolk, VA, USA), PAGAT (CIRS, Norfolk, VA, USA), RW3 Solid Phantom (PTW Freiburg, Freiburg, Germany), PMMA, Virtual Water (Med‐Cal, Verona, WI, USA) and Perspex. RMI457 Solid Water and Virtual Water were found to be the best approximations for water in MRT dosimetry (within ±3% deviation in peak and 6% in valley). RW3 and Plastic Water DT approximate the relative dose distribution in water (within ±3% deviation in the peak and 5% in the valley). PAGAT, PMMA, Perspex and Plastic Water are not recommended to be used as phantoms for MRT QA, due to dosimetric discrepancies greater than 5%. 相似文献
84.
85.
S. Karashima 《辐射效应与固体损伤》2013,168(1-3):215-219
Abstract The stopping power and range for Xe ions in high temperature matter (partially ionized plasmas) have been calculated using the dielectric response function method. Calculations have been made for a target matter Al (Z = 13) over a wide range of temperatures and densities considering a finite temperature model. The stopping powers obtained have smaller values in comparison with those of a zero temperature model. The stopping power strongly depends on the density and temperature of the target material, and the projectile ion energy. 相似文献
86.
Annihilation characteristics are calculated for positrons trapped in clean and impurity decorated vacancy clusters in Au. The positron lifetime depends strongly on the structure of the clusters. In a strongly relaxed vacancy cluster, the lifetime can become smaller than the lifetime in a single vacancy. The substitution of some neighbour atoms of a vacancy cluster by Fe atoms has only a minor effect on the positron lifetimes. 相似文献
87.
G. Brunner 《Isotopes in environmental and health studies》2013,49(9-10):328-333
Mit Berücksichtigung eines die horizontale Probeausdehnung umfassenden Geometriefaktors werden unter praktisch brauchbaren Bedingungen absolute Fluoreszens- und Streustrahlungsausbeuten für sättigungsdicke und für dünne Proben berechnet. Die aus ihnen herleitbaren Meβempfindlichkeiten zeigen, daβ sich geringe Konzentrationen von relativ leichten bis mittelschweren Elementen besonders gut messen lassen, wenn man entweder dicht oberhalb der Absorptionskanten liegenda Energien anwendel oder bei relativ hoher Anregungsenergie die Streustahlung abtrennt. Bei groβen Konzentrationen solcher Elemente kann auch ohne Streustrahlungsabtrennung mit relativ hohen Anregungsenergien gemessen werden, wobei sogar unter gewissen Bedingungen mit Zunahme der Anregungsenergie eine leichte Empfindlichkeitsverbesserung eintritt. Bei schweren Elementen ist der Gesichtspunkt der Probendicke vielfach wichtiger als die Wahl der Anregungsenergie. Für dūnne Proben lassen sich relativ recht hohe Empfindlichkeiten erzielen, was jedoch zu einem Problem der absoluten Intensitāten angesichts des Detektor-Strahlungsuntergrundes fūhren kann. 相似文献
88.
The purpose of this study was to measure the radiation exposure to operator and patient during cardiac electrophysiology study, radiofrequency catheter ablation and cardiac device implantation procedures and to calculate the allowable number of cases per year. We carried out 9 electrophysiology studies, 40 radiofrequency catheter ablation and 11 cardiac device implantation procedures. To measure occupational radiation dose and dose–area product (DAP), 13 photoluminescence glass dosimeters were placed at eyes (inside and outside lead glass), thyroids (inside and outside thyroid collar), chest (inside and outside lead apron), wrists, genital of the operator (inside lead apron), and 6 of photoluminescence glass dosimeters were placed at eyes, thyroids, chest and genital of the patient. Exposure time and DAP values were 11.7?±?11.8?min and 23.2?±?26.2?Gy?cm2 for electrophysiology study; 36.5?±?42.1?min and 822.4?±?125.5?Gy?cm2 for radiofrequency catheter ablation; 16.2?±?9.3?min and 27.8?±?16.5?Gy?cm2 for cardiac device implantation procedure, prospectively. 4591 electrophysiology studies can be conducted within the occupational exposure limit for the eyes (150?mSv), and 658-electrophysiology studies with radiofrequency catheter ablation can be carried out within the occupational exposure limit for the hands (500?mSv). 1654 cardiac device implantation procedure can be conducted within the occupational exposure limit for the eyes (150?mSv). The amounts of the operator and patient's radiation exposure were comparatively small. So, electrophysiology study, radio frequency catheter ablation and cardiac device implantation procedures are safe when performed with modern equipment and optimized protective radiation protect equipment. 相似文献
89.
G. Brunner 《Isotopes in environmental and health studies》2013,49(12):420-424
Modern radiometric analytics demands a complex consideration of nuclear and electron shell processes, if more pretentious aims are envisaged. As an example the small variation of decay rates of radionuclides presents possibilities for information on chemical situations of decaying atoms. In principle this phenomenon is well known since many years, but now the situation is such that, e.g. in 99mTc internal conversion, a full agreement of the difficult experiments and the respective theory was established. The secondary emission of X-rays as a consequence of high excitation of electron shells in combination with nuclear transitions supplies another example for a methodical progress of radiometry. Investigations on 51Cr as an electron capture nuclide have shown that chemically induced variations of the Kα to Kβ X-ray intensity ratio is at least qualitatively understood. 相似文献
90.
A. M. El-Agramy B. A. Henaish A. A. Shabaka 《Isotopes in environmental and health studies》2013,49(10):479-482
Radiophotolumenescence (RPL) of irradiated and non irradiated thin films of polymethylmethacrylate (PMMA) doped with anthracene (Anth) as a donor, and tetracyanoquinodimethane (TCNQ) as an acceptor, has been investigated. The RPL – glow spectrum was recorded to study the characterizing emission bands from the point of view of glow peak position and intensity and hence the prospective relative sensitivities. RFL – signal fading after one month storage in dark at room temperature post gamma irradiation was also studied. PMMA doped with 6:4 donor to acceptor ratio has been proved to be the most sensitive one with less fading regarding gamma detection. On the other hand 2 Anth: 8 TCNQ was found to be the proper dopant concentration ratio for thermal neutron detection. 相似文献