共查询到20条相似文献,搜索用时 31 毫秒
1.
Four types of light weight concrete (LWC) commonly used in Hong Kong, namely, autoclave aerated concrete (plus lime), autoclave aerated concrete (plus Pulverized Fuel Ash or PFA), concrete with synthetic aggregate ‘Leca’ and concrete with polystyrene bean as aggregate were measured for their 226Ra, 232Th and 40K contents using high-resolution gamma spectrometry. All the radionuclide contents except those for the PFA autoclave aerated concrete were below the world averages of building materials. The Ra-equivalents for these four LWC were 49.6, 249, 122 and 44.2 Bq kg −1, respectively, and were much smaller than a recommended limit of 370 Bq kg −1 for construction materials for dwellings. The gamma-dose rate for an indoor environment with partition walls built with LWC was estimated to be about 20 × 10 −8 Gy h −1, which corresponded to a reduction in the effective dose of about 0.25 mSv y −1 when compared to that obtained for an indoor environment built with normal concrete (NC) only. The Rn exhalation rates from the three lowest Ra-equivalent LWC were calculated as 0.509, 1.28, and 0.335 mBq m −2 s −1, respectively, which corresponded to a reduction in the indoor Rn concentration of around 14 Bq m −3 and reduction in the tracheobronchial dose reaching 1 mSv y −1 by using the James lung-dosimetry model, when compared to the case of NC. 相似文献
2.
The aim of this audit was to assess the yield of a selection of laboratory tests as part of the clinical assessment of the fatigued athlete. Clinical charts and blood test results of fifty consecutive athletes who presented with the primary complaint of fatigue were retrospectively reviewed. Blood tests results reviewed were: haematology (haemoglobin, red cell count, mean cell volume, mean cell haemoglobin content, platelets, white cell count, differential white cell count); erythrocyte sedimentation rate; serum biochemistry (urea, creatinine, electrolytes, urate, glucose, liver function tests, albumin, globulin); blood iron status (serum iron, total iron binding capacity, percent transferring saturation, and ferritin concentration); thyroid stimulating hormone; and immune measures (Epstein–Barr virus serology, cytomegalovirus serology). We identified only 3 abnormal results that contributed to the diagnosis of medical disease as a cause for fatigue. Laboratory testing identified 2 fatigued female athletes with serum ferritin concentration between 15 μg L −1 and 20 μg L −1 plus two of the other criteria of iron concentration (serum iron <10 μmol L −1, iron binding capacity >68 μmol L −1, or transferrin saturation <15%). We concluded that the yield from a selection of blood tests investigating fatigued athletes was low. Future study is needed to further define the role of laboratory testing and to study whether low iron stores in the absence of anaemia is related to symptoms in fatigued athletes. 相似文献
3.
Rn-222 is the most important source of natural radiation and is responsible for approximately half of the received dose from all sources. Most of this dose is from inhalation of the Rn-222 progeny, especially in closed atmospheres. A Lucas cell technique, using a portable device, “PRASSI” (SILENA mod. 5S), for Rn-222 measurements inside the Centre for Radiation Protection and Radioecology (ZSR), Hannover University was used. The portable radon monitor PRASSI is suitable for radon gas continuous or grab sampling measurements with the scintillation cell technique. In recognition of the wide periodic variations in concentration, measurements were made daily for extended periods. At the same time, meteorological variables, such as temperature and humidity were observed so that their influence on radon levels could be evaluated. The radon average concentration during the year was about 55.9 Bq/m 3 which gives rise to an annual effective dose 2.2 mSv y −1. The radon concentration is within the limits prescribed by the International Commission for Radiation Protection. A detailed analysis of radon distribution with seasonal variation is presented. 相似文献
4.
The background count rate of a 1-cm 3 quartz gas proportional counter (GPC) was investigated for measuring natural radioactivity levels of small samples. Using a new multiparameter digital counting system, spurious or afterpulses that contribute to background were identified by their pulse waveform and by a special event indicator defined by the time (<2000 μs) between two successive pulses. With the GPC in coincidence with a low-background NaI(Tl) scintillation guard detector, the weighted mean and standard uncertainty anticoincidence counts per day (d −1) was 6.2±0.4 d −1. 相似文献
5.
A new radioactivity solution standard of 210Pb has been developed and will be disseminated by the National Institute of Standards and Technology (NIST) as standard reference material (SRM) 4337. This new 210Pb solution standard is contained in a 5 mL flame-sealed borosilicate glass ampoule, consists of (5.133±0.002) g of a nominal 1 mol L −1 nitric acid solution, has a density of (1.028±0.002) g mL −1 at 20 °C, has carrier ion concentrations of about 11 μg Pb 2+ and 21 μg Bi 3+ per gram of solution, and is certified to contain a massic activity (9.037±0.22) kBq g −1 as of the reference time 1200 EST, 15 June 2006. All of the uncertainties cited above correspond to standard uncertainties multiplied by a coverage factor k=2. The standardization for the 210Pb content of the solution was based on 4 πβ liquid scintillation (LS) measurements using CIEMAT/NIST 3H-standard efficiency tracing (CNET). Confirmatory determinations were also performed by high-resolution HPGe γ-ray spectrometry, by 2 π spectrometry with a Si surface barrier detector of separated 210Po, and by 4 πβ(LS)– γ(NaI) anticoincidence counting. 相似文献
6.
High-energy electron-beam irradiation was used to remove phenol from aqueous solution. The variables that affected phenol decomposition were solute concentration, absorbed dose and total alkalinity. Experiments were conducted at large scale (480 L min −1), at solute concentrations of 10.6, 106 and 531 μmol L −1 (1, 10 and 50 mg L −1) over the pH range 5–9, and in the presence and absence of solids (3% w/w kaolin clay). Absorbed doses ranged from 0–7 kGy (0–700 krad). At low absorbed doses, catechol, hydroquinone and resorcinol were identified as the major reaction byproducts. These compounds are consistent with hydroxyl radical (OH·) addition to phenol. Subsequent ring cleavage of hydroxylated phenolic radicals and continued oxidative processes resulted in the formation of formaldehyde, acetaldehyde, glyoxal and formic acid. At high doses only trace amounts of the carbonyl derivatives were observed. Two recirculation experiments were conducted at higher phenol concentrations (≈950 μmol L −1) and it was shown that phenol was removed while the total organic carbon of the solution decreased only slightly. These results suggest that phenol was not mineralized but, rather, that irradiation resulted in the possible formation of higher molecular weight polymers. 相似文献
7.
The aim of this study was to compare the effectiveness of two recovery techniques on blood lactate and repeated sprint performance. In a randomised cross-over design 20 junior representative rugby players (aged 19 ± 1 years) were given either contrast temperature water therapy or active recovery after performing a repeated sprint test. The test was then repeated 1 h later to gauge the effects of the two recovery methods on subsequent repetitive sprinting performance. One week later, the two groups were reversed and the testing repeated. The test consisted of ten 40-m sprints with a 30-s turn-around between sprints. Recovery consisted of 6 min slow jogging (6.8 km h −1) for the active recovery group or 6 min of contrast temperature water therapy consisting of three 1-min hip-height immersions in cold water (8–10 °C) alternated with three 1-min hot water (38 °C) showers. Blood lactate concentration and heart rates were measured throughout the testing. Relative to the active recovery group the contrast temperature water therapy group showed a substantial decrease in blood lactate concentration 3 min after the procedure (−2.1 mmol L −1, 95% confidence limits, ±1.8 mmol L −1), and substantially lower heart rates both during the procedure (−9.1 ± 8.7 min −1) as well as 1 h later during the second set of sprints (−11.7 ± 8.6 min −1). Effects of recovery group on repeated sprint performance were small to trivial and unclear. Compared to active recovery, contrast temperature water therapy decreases blood lactate concentration and heart rate but has little effect on subsequent repetitive sprinting performance. 相似文献
8.
A procedure, adaptable to large-scale remote operation, was developed to purify no-carrier-added (NCA) 47Sc from irradiated Ti targets. Methods based on extraction chromatography and cation-exchange chromatography were compared. Results of this comparison led to the development of an optimized procedure based on cation-exchange with Dowex AG 50W-X4 and 47Sc elution with HCl/HF. This method gave 90–97% overall 47Sc recovery, with a Ti separation factor greater than 2.4×10 −5, and specific activities ≥0.9 GBq μg −1. Use of the 47Sc product, for labeling monoclonal antibodies, resulted in consistent labeling yields of ≥90%. 相似文献
9.
The relationship between the radiation absorbed dose and the NMR longitudinal and transversal relaxation rates, R1 and R2, respectively, of a ceric sulphate dosimeter was examined. By adding copper sulphate, the R1 and R2 dose-responses were found to be linear up to 60 kGy with dose sensitivities of 13×10 −6 and 15×10 −6 s −1 Gy −1, respectively. There is thus the potential for a three-dimensional ceric dosimeter for high dose applications, provided a suitable gelling substance is used. 相似文献
10.
The purpose of this study was to present a theoretical analysis of how the presence of bone in interstitial brachytherapy affects dose rate distributions. This study was carried out using a Monte Carlo simulation of the dose distribution in homogeneous medium for 3 commonly used brachytherapy seeds. The 3 seeds investigated in this study are iridium-192 ( 192Ir) iodine-125 ( 125I), and palladium-103 ( 103Pd). The computer code was validated by comparing the specific dose rate (Λ), the radial dose function g(r), and anisotropy function F(r,θ) for all 3 seeds with the AAPM TG-43 dosimetry formalism and current literature. The 192Ir seed resulted in a dose rate of 1.115 ± 0.001 cGy-hr −1-U −1, the 125I seed resulted in a dose rate of 0.965 ± 0.006 cGy/h −1/U −1, and the 103Pd seed resulted in a dose rate of 0.671 ± 0.002 cGy/h −1/U −1. The results for all 3 seeds are in good agreement with the AAPM TG-43 and current literature. The validated computer code was then applied to a simple inhomogeneous model to determine the effect bone has on dose distribution from an interstitial implant. The inhomogeneous model showed a decrease in dose rate of 2% for the 192Ir, an increase in dose rate of 84% for 125I, and an increase in dose rate of 83% for the 103Pd at the surface of the bone nearest to the source. 相似文献
11.
The benefits of rapid recovery after intense exercise are widely recognised, and lactate elimination is one indicator of recovery rate. This study examined the effect of contrast (alternating hot and cold) water immersion (CWI) on the rate of plasma lactate decrease during recovery after intense anaerobic exercise. Eleven subjects on each of two occasions undertook four successive 30-s Wingate tests separated by 30-s rest periods. On each occasion, plasma lactate concentration during recovery was measured 5 min post-exercise and thereafter at 5 min intervals for 30 min. On one occasion (determined randomly), the subjects recovered passively (PR) on a recovery bed and, on the other, they alternated partial body immersion in hot (36 °C) and cold (12 °C) water baths. Plasma lactate concentrations were analysed by repeated measures analysis of variance and by fitting a linear regression model, allowing for both gender and recovery mode differences. The rate of decrease in plasma lactate concentration over the 30-min recovery period was significantly higher ( p < 0.001) in CWI; 0.28(±0.02) mmol L −1 min −1 (CWI) compared to 0.22(±0.02) mmol L −1 min −1 (PR). These values do not differ significantly between males and females. Contrast water immersion is a valid method of hastening plasma lactate decrease during recovery after intense anaerobic exercise for both males and females. An approximately 1.8 mmol L −1 difference between the two conditions may be expected after 30 min. With differences among elite competitors as little as 1–2%, this reduction may be of practical significance. 相似文献
12.
During the routine isotope production schedule at the Australian National Medical Cyclotron thick copper plates, electroplated with enriched target materials, are bombarded with 30 MeV protons with an average beam current of 200 μA. As a result an intense high-energy, prompt neutron flux of the order of 1.72 × 10 13 neutrons·cm −2·2 −1 is generated in the immediate vicinity of the target. The stray fast neutrons were moderated using a water-filled PVC bucket placed on the target station. A maximum thermal neutron flux of 3.88 × 10 9 neutrons·cm −2·s −1 was measured in the bucket using cobalt activation discs. The thermal neutrons from this irradiation facility has been used for the neutron activation analysis of trace elements in archaeological artefacts. It has also been planned to utilize the fast neutron flux by varying the geometry of the water moderator in order to estimate oxygen concentration in high-temperature superconductors and aluminium and silicon in ceramics. 相似文献
13.
For the sake of dating certain calcite geological samples, the TL and ESR properties of travertines from Denizli (in the southwestern part of Turkey) were studied and the effects of pre-heating temperature and pre-heating time on the sensitivity of the samples to radiation evaluated. Heat treatment above 350°C increases the sensitivity of all radiation-induced TL peaks except the 330°C glow peak. Results of gamma-ray dose calibration in travertine (CaCO 3 crystal of trigonal symmetry) indicate that the 180 and 280°C TL peak amplitudes increase exponentially with dose. We show that second-order kinetics characterizes the 180 and 280°C glow peaks reasonably well. The Mn 2+ lines of the ESR spectra are used to investigate the thermal decomposition processes of travertine samples, showing very good agreement with those of thermogravimetry. Glow mechanisms of TL in travertine have also been studied using ESR analysis. The pre-heating and subsequent laboratory irradiation procedure is found to enhance the TL and ESR signals of CO 33− and CO 2− centres. An isochronal thermal anneal sequence experiment showed that 180 and 280°C peaks in travertines are correlated with CO 33− and CO 2− centres in the same way that the peak at 330°C is correlated with SO 2− centres. A model for the recombination mechanism is suggested on the basis of the TL and ESR measurements. 相似文献
14.
The effects of pH and Sr 2+ solution concentration on diffusion and sorption of Sr 2+ in compacted bentonite (ρ b=1000±30 kg/m 3) were studied using an “in-diffusion” method at an ionic strength of 0.1 M NaClO 4. The results (distribution coefficients, Kd, apparent and effective diffusion coefficients, Da and De) derived from the capillary method are in good agreement with the literature data obtained for similar bentonite dry densities and fit Fick's second law very well. The results suggest that the diffusion of Sr 2+ in compacted bentonite decreases slightly with increasing pH values and also increases slightly with increasing Sr 2+ solution concentration. The distribution coefficients are weakly dependent on the solution concentrations and show a slight increase with increasing pH values. The average effective diffusion coefficient of Sr 2+ in compacted bentonite is (1.2±0.2)×10 −9 m 2/s, surface diffusion effects are found for the diffusion of Sr 2+ in compacted bentonite. 相似文献
15.
Leaves of Casearia sylvestris, Casearia decandra and Casearia obliqua plant species, collected at the Atlantic Forest in Brazil, were analyzed by using instrumental neutron activation analysis (INAA). Short and long irradiations using thermal neutron flux of the IEA-R1 nuclear reactor were carried out for these analyses. Concentrations of Ca, K and Mg were found in these samples at the percentage levels, Br, Cl, Fe, Mn, Na, Rb and Zn at the μg g −1 levels and Co, Cr, Cs, La, and Sc at the μg kg −1 levels. Comparisons were made among the element concentrations obtained in these three Casearia species and significant differences were found for the elements Cl, Co, Cs, Cr, La, Mn, Na and Sc. The precision and the accuracy of the results were evaluated by analyzing the certified reference materials NIST-1515 Apple Leaves and NIST-1573a Tomato Leaves. 相似文献
16.
In this paper, we propose a method to determine the equilibrium factor using a bare LR 115 detector. The partial sensitivities ρ i of the LR 115 detector to 222Rn and its alpha-emitting short-lived progeny, 218Po and 214Po, were investigated. We first determined the distributions of lengths of major and minor axes of the perforated alpha tracks in the LR 115 detector produced by 222Rn, 218Po and 214Po through Monte Carlo simulations. The track parameters were calculated using a track development model with a published V function, by assuming a removed active layer of 6.54 μm. The distributions determined for different alpha emitters were found to completely overlap with one another. This implied equality of partial sensitivities for radon and its progeny, which was also confirmed through analytical considerations. Equality of partial sensitivities makes possible convenient measurements of the proxy equilibrium factor Fp, which is defined in the present work as ( F1+ F3) and is equal to the ratio between the sum of concentrations of the two alpha emitting radon progeny ( 218Po+ 214Po) to the concentration of radon gas ( 222Rn). In particular, we have found Fp=(ρ/ρ itC0)−1, where ρ (track/m 2) is the total track density on the detector, ρ i=0.288×10 −2 m, t is the exposure time and C0 (Bq/m 3) is the concentration of 222Rn. If C0 is known (e.g. from a separate measurement), we can obtain Fp. The proxy equilibrium factor Fp is also found to be well correlated with the equilibrium factor between radon gas and its progeny through the Jacobi room model. This leads to a novel method for long-term determination of the equilibrium factor. 相似文献
17.
Marinelli (reentrant) beakers are recommended for measurement of low-activity radioactive environmental samples, in both liquid and solid phase. The preparation of Marinelli beaker standards of milk powder containing 232ThO2 at secular equilibrium with its daughter radionuclides was studied. Standards were prepared by mixing of known amounts of solid ThO2 and milk powder. The densities of the standards were 0.5–0.7 kg dm−3. Measurements of calibrated Marinelli beaker standards with HPGe detector showed that the energy dependence of the efficiency is similar to that of a point source, i.e. an almost linear dependence of log-efficiency vs. log-energy in the 200–2000 keV range, however the parabolic correlation fits better. The validity of these standards was checked by comparison with certified standard reference material IAEA-152-Milk powder containing radiocesium and radiopotassium. The results obtained were found to be in a good agreement with the published certified data. The limit of detection for the determination of radiocesium by gamma ray spectrometry under the prevailing experimental conditions is 0.03 Bq (i.e. 0.8 pCi), for samples of dairy products having lower densities of 0.7 kg dm−1. 相似文献
18.
[ 11C]Choline has been under investigation as a PET ligand for imaging tumor tissue, especially prostate cancer. An improved, automated synthesis of the tracer now was established. [ 11C] Choline was produced by labeling 2-(dimethylamino)-ethanol (DMAE) with [ 11C]CH 3I in a Tefzel ® tube at room temperature without solvent. The product was purified using a cation exchange cartridge. Reaction conditions were optimized with respect to synthesis time and amount of DMAE, resulting in radiochemical yields higher than 80% using 60 μl of DMAE in 20 min, radiochemical purity was >99% and residual DMAE was below 10 ppm. After 11C-production of 1 h at 50 μA [ 11C]choline activities of 30.0±5.6 GBq ( n=29) were obtained in sterile solution ready for intravenous administration. 相似文献
19.
As per TG-43 dose calculation formalism, it is essential to obtain various dosimetric parameters such as the air-kerma strength, dose rate constant, radial dose function, and anisotropy function, as they account for accurate determination of dose rate distribution around brachytherapy sources. Most of the available reported Monte Carlo simulations were performed in liquid water phantoms with a bounded region of 30-cm diameter. In this context, an attempt was made to report the dosimetric parameters for various commercially available pulsed-dose rate (PDR) and high-dose rate (HDR) sources under unbounded phantom conditions, as the data may be used as input to treatment planning systems (TPSs) for quality control assistance. The air-kerma strength per unit activity, S k/A, was computed for various Iridium-192 ( 192Ir) sources in dry air medium. The air-kerma strength and dose rate constant for old PDR is (9.77 ± 0.03) 10 −8 U/Bq and 1.124 ± 0.001 cGyh −1U −1; for new PDR, the values are (9.96 ± 0.03) 10 −8 U/Bq and 1.124 ± 0.001 cGyh −1U −1; for old MHDR, the values are (9.80 ± 0.01) 10 −8 U/Bq and 1.115 ± 0.001 cGyh −1U −1; for new MHDR, (9.80 ± 0.01) 10 −8 U/Bq and 1.112 ± 0.001cGyh −1U −1; for old VHDR, the values are (10.32 ± 0.01) 10 −8 U/Bq and 1.035 ± 0.002 cGyh −1U −1; for new VHDR, the values are (10.34 ± 0.02) 10 −8 U/Bq and 1.096 ± 0.001 cGyh −1U −1. The computed radial dose function values and anisotropy function values are also in good agreement with available data. 相似文献
20.
Utilizing Pu isotopic standards characterized by the Institute for Nuclear Materials and Measurement (IRMM), New Brunswick Laboratory (NBL) measured the γ-ray branching ratios of the 148.567-keV 241Pu, the 152.72-keV 238Pu, the 159.995-keV 241Pu and the 160.28-keV 240Pu γ-rays. The study reported here includes the measurement of four IRMM standards, utilizing three different detectors for a total of 16 spectra, finding branching ratios of (1.863 ± 0.008) × 10 −6, (9.230 ± 0.068) × 10 −6, (6.321 ± 0.040) × 10 −8 and (4.065 ± 0.017) × 10 −6, γ/disintegration, respectively. 相似文献
|