A method was developed for the determination of trace and subtrace amounts of uranium in organic substances used during the industrial process of nuclear fuel production. The method is based on decomposing 50 g of the sample by wet ashing with 25 g conc. sulfuric acid. The residue from the ashing process was ignited at 525 °C to remove all carbonaceous materials. The residue was boiled with 10 ml of 11 nitric acid. The resulting solutions was analyzed for uranium concentration using a modification of the arsenazo III method which allows for uranium determination after separating it by TBP extraction from all the interfering elements. The proposed method proved to be sensitive (detection limit: 15 ppb). The relative standard deviation of the method for a sample containing 200 ppb uranium is 5%. The dynamic range of the method is wide, since the method is applicable. for trace and subtrace levels of uranium in organic substances.
The high-precision uranium determination by reduction with ferrous sulfate in phosphoric acid and titration with dichromate, which is applicable to nuclear-grade uranium compounds in which the uranium exists nearly exclusively as U(IV), has been modified. The modification enlarges the range of applicability of the original method to include the analysis of uranium compounds in which the uranium exists as U(VI) or as a mixture of U(IV) and U(VI), such as U3O8. The modified method has the same precision, relative freedom from interferences and applicability for routine use as the original method.
Two sample treatment methods are evaluated to provide accurate boron determination at low concentrations in biological and botanical samples. The first approach is a hot 1M nitric acid extraction of boron from the sample. The second technique uses wet digestion with concentrated sulfuric acid. The accuracy of the procedures was demonstrated with botanical and animal reference materials (Corn Bran RM 8433 and Whole Egg Powder RM 8415). At least three results are given for each reference material. Two are direct measurements of B using independent 10B and 11B calibration curves with a Be internal reference, and the third is obtained by isotope dilution mass spectrometry (IDMS). The 10B and 11B values are consistent for both acid treatment procedures. The IDMS results also are consistent. Overall results for Whole Egg Powder and Corn Bran RM's match the best-estimate values within their confidence intervals. These results demonstrate the ability to measure B accurately at the 0.3 µg/g concentration range. Thus, low-level B samples can be analyzed with accuracy and precision by the two approaches. These methods introduce very little dissolved organic carbon (DOC) in the final solution and allow the use of large (2 g) sample aliquots. Direct introduction of biological fluids including whole blood serum also was evaluated critically for the determination of B.
Authors:M. E. Kassem, E. A. Ammar, A. M. El-Khatib and E. F. Elwahidy
The differential thermal analysis curves and the specific heat at constant pressure,Cp, of pure and Cu2+-doped sodium potassium sulphate crystals were studied. Different neutron fluences were used up to 2.6×1010 n/cm2, in the temperature range 300–500 K. Impurity incorporation generally increased the specific heat up to a maximum at 5% Cu2+ content. The peaks for the doped crystals were shifted to lower temperature as a result of neutron irradiation. This behaviour is discussed on the basis of defects induced by irradiation.
Authors:M. E. Kassem, A. M. El-Khatib, E. A. Ammar and M. M. Denton
Thermodynamic studies of (LixK1−x)2SO4, LKS, mixed crystals have been made in the concentration range (x=0.1, 0.2, ...,x=0.5). The thermal behaviour has been investigated by differential thermal analysis, DTA, and differential scanning calorimeter, DSC, in the vicinity of high temperature phases. Also, the effect of the thermal neutron irradiations on the thermal properties of mixed crystals was studied. The results showed a change in the transition temperatureTc, as well as the value of specific heatCp at transition temperature, due to the change of stoichiometric ratio and radiation doses. The change of enthalpy and entropy of mixed crystals have been estimated numerically.
Authors:A Ammar, H Chtourou, O Hammouda, M Turki, F Ayedi, C Kallel, O AbdelKarim, A Hoekelmann and N Souissi
The aims of the present study were to: (1) investigate the effect of a weightlifting training session and time-of-day (TOD) upon biological parameters (i.e., oral temperature, hematological, C-reactive protein (CRP), and oxidative stress) and (2) assess their possible link with muscle damage responses. Nine weightlifters (21 ± 0.5 years) performed, in a randomized order, three Olympic-Weightlifting sessions (i.e., at 08:00, 14:00, and 18:00). Blood samples were collected at rest, 3 min and 48 h after each training session. Between pre- and post-training session, ANOVA showed significant increases in oxidative stress markers at the three TODs (p < 0.01) and significant increases for creatine kinase (CK) and lactate dehydrogenase (LDH) only at 08:00 and 18:00 (p < 0.05). At rest, the results showed a significant diurnal variation for the majority of the selected parameters except for malondialdehyde (MDA), total bilirubin, and CRP with higher values observed at 18:00 (p < 0.05). After the training session, given the higher rate of increase during the morning session, these diurnal variations persisted for temperature and WBC (p < 0.01) and were suppressed for CK, LDH, uric acid (UA), catalase, and glutathione peroxidase. The main significant correlations (p < 0.001) were observed between: (1) CK and MDA (r = 0.6) and CK and UA (r = 0.66 and r = 0.82) during the morning and evening training sessions; (2) CK and CRP only during the morning session (r = 0.5); and (3) CRP and WBC during the three training sessions (r = 0.8). In conclusion, the present findings: (1) confirm that the muscle damage responses could be induced by a high level of oxidative stress and (2) suggest to avoid scheduling training sessions in the morning given the higher muscle damage, inflammatory, and oxidative responses at this TOD.