Effect of pH and concentration on the diffusion of radiostrontium in compacted bentonite—a capillary experimental study

The effects of pH and Sr²⁺ solution concentration on diffusion and sorption of Sr²⁺ in compacted bentonite (ρ_b=1000±30 kg/m³) were studied using an “in-diffusion” method at an ionic strength of 0.1 M NaClO₄. The results (distribution coefficients, K_d, apparent and effective diffusion coefficients, D_a and D_e) 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 Sr²⁺ in compacted bentonite decreases slightly with increasing pH values and also increases slightly with increasing Sr²⁺ 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 Sr²⁺ in compacted bentonite is (1.2±0.2)×10⁻⁹ m²/s, surface diffusion effects are found for the diffusion of Sr²⁺ in compacted bentonite.     

A liquid-scintillation-based primary standardization of Pb

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 Pb²⁺ and 21 μg Bi³⁺ 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 4πβ 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 2π spectrometry with a Si surface barrier detector of separated ²¹⁰Po, and by 4πβ(LS)–γ(NaI) anticoincidence counting.     

The dependence of the counting efficiency of Marinelli beakers for environmental samples on the density of the samples.

The effect of the density of the radioactive material packed in a Marinelli beaker on the counting efficiency was studied. It was found that for all densities (0.4-1.7 g/cm(3)) studied the counting efficiency (epsilon) fits the linear log-log dependence on the photon energy (E) above 200 keV, i.e. obeying the equation epsilon=alphaE(beta) (alpha, beta-parameters). It was found that for each photon energy the counting efficiency is linearly dependent on the density (rho) of the matrix. epsilon=a-brho (a, b-parameters). The parameters of the linear dependence are energy dependent (linear log-log dependence), leading to a final equation for the counting efficiency of Marinelli beaker involving both density of the matrix and the photon energy: epsilon=alpha(1) x Ebeta1 - alpha2Ebeta2rho.     

Use of the ion exchange method for the determination of stability constants of trivalent metal complexes with humic and fulvic acids—Part I: Eu and Am complexes in weakly acidic conditions

The conditional stability constants for tracer concentrations of Eu(III) and Am(III) with a red earth humic acid (REHA), a red earth fulvic acid (REFA) and a fulvic acid from weathered coal (WFA) were determined at pH 5.2–6.4 (such values are similar to those in non-calcareous soils) in the presence of HAc/NaAc or NaNO₃ by using the cation exchange method. It was found that 1 : 1 complexes were predominately formed in weakly acidic conditions. The total exchangeable proton capacities and the degrees of dissociation of these humic substances were determined by using a potentiometric titration method.

The key parameters necessary for the experimental determination of the conditional stability constants of metal ions with humic substances in weakly acidic conditions by using the cation exchange method were discussed.

The conditional stability constants of 1 : 1 complexes obtained in this paper were compared with the literature data of Am(III) determined by using the ion exchange method and the solvent extraction method and with the stability constants of 1 : 1 complexes of UO₂²⁺ and Th⁴⁺ with the same soil humic substances. These results indicate the great stability of bivalent UO₂²⁺, trivalent Eu³⁺, Am³⁺ and tetravalent Th⁴⁺ complexes with humic and fulvic acids in weakly acidic conditions.     

The effect of contrast temperature water therapy on repeated sprint performance

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.     

Measurement of Pu γ-ray intensities between 148 and 161 keV

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.     

Indoor gamma dose measurements in Gudalore (India) using TLD

Indoor gamma radiation dose rates were measured inside residential buildings in Gudalore using a CaSO₄ : Dy thermoluminescent dosimeter for 1 year . Significant seasonal variations are observed. The highest dose rate is observed during summer and the lowest in winter. The dose rates observed are between 77.9 and 229.3 nGy h⁻¹ and may be attributed to the type of building materials used in the dwellings monitored. The calculated mean annual effective dose equivalent rates range between 477.6 μSv y⁻¹, for the inhabitants of mud houses to 1406.3 μSv y⁻¹, for those living in terrace houses made of cement and brick.     

Investigation of the NMR relaxation rate dose-response of a ceric sulphate dosimeter

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.     

Influence of exercise mode and maximal lactate-steady-state concentration on the validity of OBLA to predict maximal lactate-steady-state in active individuals

The aim of this study was to analyze the effects of exercise mode on the validity of onset of blood lactate accumulation (OBLA—3.5-mM fixed blood lactate concentration) to predict the work-rate at maximal lactate steady state (MLSS_work-rate). Eleven recreationally active males (21.3 ± 2.9 years, 72.8 ± 6.7 kg, 1.78 ± 0.1 m) performed randomly incremental tests to determine OBLA (stage duration of 3 min), and 2 to 4 constants work-rate exercise tests to directly determine maximal lactate steady state parameters on a cycle-ergometer and treadmill. For both exercise modes, the OBLA was significantly correlated to MLSS_work-rate, (cycling: r = 0.81 p = 0.002; running: r = 0.94, p < 0.001). OBLA (156.2 ± 41.3 W) was lower than MLSS_work-rate (179.6 ± 26.4 W) during cycling exercise (p = 0.007). However, for running exercise, there was no difference between OBLA (3.2 ± 0.6 m s⁻¹) and MLSS_work-rate (3.1 ± 0.4 m s⁻¹). The difference between OBLA and MLSS_work-rate on the cycle-ergometer (r = 0.86; p < 0.001) and treadmill (r = 0.64; p = 0.048) was significantly related to the specific MLSS. We can conclude that the validity of OBLA on predicting MLSS_work-rate is dependent on exercise mode and that its disagreement is related to individual variations in MLSS.     

Radiotracer technique in adsorption study: Part XVII. Removal Behaviour of Alkali Metal (K- and Li-) Titanates for Cd(II)

Alkali metal (potassium and lithium) titanates were synthesized and employed for the efficient removal of Cd(II) ions from aqueous solutions using the radiotracer technique. The possible mechanism involved at the solid/solution interface was deduced with the help of various physico–chemical data, i.e. effect of adsorptive concentration temperature and pH. The effect of added cations and H⁺ (HCl/H₂SO₄) in the uptake process was also seen. The radiation stability of these materials in the adsorption process was assessed by employing a 11.1 GBq (Ra–Be) neutron source having an integral neutron flux of 3.85×10⁶ n·cm⁻² s⁻¹ and associated with a nominal γ-dose of ca. 1.72 Gy/h.     

Bone powder exposed to the action of C and Mg ion beams as investigated by electron paramagnetic resonance spectroscopy

Bovine compact bone powder was irradiated with -particles of ²⁴¹Am, ¹²C⁶⁺ and ³⁵Mg¹²⁺ ion beams, then examined by the e.p.r. spectroscopy. The stable e.p.r. signal found is of the same characteristic as that observed in γ-irradiated bone (g = 2.0017, g = 1.9973, ΔH_pp = 0.85 mT). Thus, the structure of radiation induced paramagnetic center in bone does not depend on the LET of radiation used. The radiolytic yields of the formation of stable paramagnetic centres in bone powder irradiated with γ-rays are G_γ = 0.08 ± 0.01 while with ¹²C⁶⁺ ion beams roughly about G_c = 0.02, respectively.     

Investigating the background of a 1-cm quartz gas proportional counter

The background count rate of a 1-cm³ 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.     

Theoretical basis for long-term measurements of equilibrium factors using LR 115 detectors

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 F_p, 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 F_p=(ρ/ρ_itC₀)−1, where ρ (track/m²) is the total track density on the detector, ρ_i=0.288×10⁻² m, t is the exposure time and C₀ (Bq/m³) is the concentration of ²²²Rn. If C₀ is known (e.g. from a separate measurement), we can obtain F_p. The proxy equilibrium factor F_p 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.     

An audit of clinically relevant abnormal laboratory parameters investigating athletes with persistent symptoms of fatigue

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.     

Dependency of the [18F]fluoromisonidazole uptake on oxygen delivery and tissue oxygenation in the porcine liver

We have previously shown that the accumulation of fluorine-18-labeled fluoromisonidazole ([¹⁸F]FMISO) is inversely correlated to tissue oxygenation, allowing the quantification of porcine liver tissue hypoxia in vivo. We determined the activity from administered [¹⁸F]FMISO in relation to the hepatic oxygen availability and the partial pressure of oxygen in tissue (tPO₂) to define a critical oxygen delivery on a regional basis. [¹⁸F]FMISO was injected 2 h after onset of regional liver hypoxia due to arterial occlusion of branches of the hepatic artery in 10 domestic pigs. During the experimental procedure the fractional concentration of inspired oxygen (FiO₂) was set to 0.67 in group A ( N=5) and to 0.21 in group B ( N=5) animals. Immediately before sacrifice, the tPO₂ was determined in normal flow and flow-impaired liver segments. The standardized uptake values (SUV) for [¹⁸F]FMISO was calculated from 659 single tissue samples obtained 3 h after injection of approximately 10 MBq/kg body weight [¹⁸F]FMISO and was compared with the regional total hepatic oxygen delivery (DO₂) calculated from the regional arterial and portal venous flow (based on ¹⁴¹Ce- and ^99mTc-microspheres measurements) and the oxygen content of the arterial and portal venous blood. In 121 tPO₂-measured liver tissue samples, the mean DO₂ was significantly decreased in occluded liver tissue samples [group A: 0.063 (0.044–0.089); group B: 0.046 (0.032–0.066)] compared to normal flow segments [group A: 0.177 (0.124–0.252); group B: 0.179 (0.128–0.25) mL·min⁻¹·g⁻¹; geometric mean (95% confidence limits); p < 0.01 in group A and p < 0.001 in group B]. The tPO₂ of occluded segments [group A: 5.1 (3.2–8.1); group B: 3.9 (2.4–6.2) mm Hg] was significantly decreased compared to normal flow segments [group A: 20.2 (12.6–32.5); group B: 22.4 (14.3–35.2) mm Hg; p < 0.01 in group A and p < 0.001 in group B]. Three hours after [¹⁸F]FMISO administration, the mean [¹⁸F]FMISO SUV determined in tPO₂-measured occluded segments was significantly higher [group A: 4.08 (3.12–5.34), group B: 5.43 (4.14–7.13)] compared to normal liver tissue [group A: 1.57 (1.2–2.06), group B: 1.5 (1.16–1.93); p < 0.001 for both groups]. The [¹⁸F]FMISO SUV allowed prediction of the tPO₂ with satisfying accuracy in hypoxic regions using the exponential regression curve { [¹⁸F]FMISO=1.05+6.7^{(−0.117 tPO₂}); r²=0.75;p < 0.001}. In addition, regardless of ventilation conditions, a significant exponential relationship between the DO₂ and the [¹⁸F]FMISO SUV was found ( r²=0.39,p < 0.001). Our results suggest that the reduction of the oxygen delivery below the critical range of 0.1–0.11 mL·min⁻¹·g⁻¹ regularly causes liver tissue hypoxia. The severity of hypoxia is reflected by the [¹⁸F]FMISO accumulation and allows the in vivo estimation of the tPO₂ in hypoxic regions.     

Radiochemical purification of no-carrier-added scandium-47 for radioimmunotherapy

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%.     

Contrast water immersion hastens plasma lactate decrease after intense anaerobic exercise

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.     

Thermoluminescence and electron spin resonance properties of some travertines from Turkey

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 (CaCO₃ 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 Mn²⁺ 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 CO₃³⁻ and CO₂⁻ centres. An isochronal thermal anneal sequence experiment showed that 180 and 280°C peaks in travertines are correlated with CO₃³⁻ and CO₂⁻ centres in the same way that the peak at 330°C is correlated with SO₂⁻ centres. A model for the recombination mechanism is suggested on the basis of the TL and ESR measurements.     

Greater adenosine A(2A) receptor densities in cardiac and skeletal muscle in endurance-trained men: a [11C]TMSX PET study

We examined the densities of adenosine A_2A receptors in cardiac and skeletal muscles between untrained and endurance-trained subjects using positron emission tomography (PET) and [7-methyl-¹¹C]-(E)-8-(3,4,5-trimethoxystyryl)-1,3,7-trimethylxanthine ([¹¹C]TMSX), a newly developed radioligand for mapping adenosine A_2A receptors. Five untrained and five endurance-trained subjects participated in this study. The density of adenosine A_2A receptors was evaluated as the distribution volume of [¹¹C]TMSX in cardiac and triceps brachii muscles in the resting state using PET. The distribution volume of [¹¹C]TMSX in the myocardium was significantly greater than in the triceps brachii muscle in both groups. Further, distribution volumes [¹¹C]TMSX in the trained subjects were significantly grater than those in untrained subjects (myocardium, 3.6±0.3 vs. 3.1±0.4 ml g⁻¹; triceps brachii muscle, 1.7±0.3 vs. 1.2±0.2 ml g⁻¹, respectively). These results indicate that the densities of adenosine A_2A receptors in the cardiac and skeletal muscles are greater in the endurance-trained men than in the untrained men.     

Characterization of trace elements in Casearia medicinal plant by neutron activation analysis.

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.