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Objective:To achieve rapid and accurate detection of trace uranium in drinking water by analyzing the factors influencing the accuracy of uranium measurement in drinking water using ultraviolet fluorescence method and by evaluating the uncertainty in measurement.Methods:The influence of acidity, Fe 3+ and Mn 2+ contents on the analitical result were studied to optimize the measurement conditions. The accuracy of the measurement method was verified in 7 laboratories. By studying the errors introduced in the process of standard preparation, sample pretreatment and measurement, the sources of uncertainty were analyzed and the uncertainty was synthesized. Results:At pH 1-11 in aqueous solution, the linear regression coefficient of the standard curve was greater than 0.995, which was in line with the linear measurement range of the instrument. At pH 12 or so, the linear regression coefficient was 0.761, which could not meet the measurement requirements. At pH<3 or pH>10, the increase in fluorescence count was lower, which might increase the measurement error. At Fe 3+ concentration ≥15 mg/L, a large deviation occurred in measurement value that could affect seriously measurement result. At Mn 2+ concentration ≥ 1.6 mg/L, the sample produced white precipitation, which could affect the measurement accuracy. Three spiked water samples with different concentrations were determined in 8 laboratories. Each water sample was measured six times in parallel. The relative standard uncertainty of the result were 6.42×10 -2, 4.48×10 -2 and 5.26×10 -2 μg/L, and the expanded uncertainties were 0.03, 0.06 and 0.12 μg/L( k=2), respectively. Conclusions:The optimum conditions for the determination of uranium in water using this method pH were in samples 3-10, the concentration of Fe 3+ less than 15 mg/L, and the concentration of Mn 2+ less than or equal to 1.6 mg/L. The main sources of uncertainty in the measurement of uranium in water using ultraviolet fluorescence method arise from the repeated measurement error and the volume of added standard solution.
RESUMO
Objective:To study the influence of source thickness and counting efficiency calibration on the measurement of gross alpha activity in water.Methods:241Am and natural uranium reference materials were spiked in drinking water to prepare source on a planchet with different thickness, for counting alpha activity on the planchet. Results:The effective thickness measured by spiking 241Am or uranium standard solution in water sample was consistent with the empirical value of 4 mg/cm 2. The alpha counting rate was in a linear increase trend from 2A-5A mg/cm 2 and was basically stable and no longer increase when thickness was higher than 10A mg/cm 2 (A was area of planchet). The result calculated by effective thickness method and thick source method were in good agreement when thickness was 10A mg/cm 2. Conclusions:In order to reduce the deviation of gross alpha counting rate caused by the source thickness and counting efficiency calibration, the source thickness is recommended to be 10A mg/cm 2.
RESUMO
Objective To present our experience and techniques with the use of autologous costal cartilage grafts in Asian rhinoplasty,and to report the surgical results and complications in 86 consecutive rhinoplasty cases.Methods All operations were performed by the first author (Liu AT) with open approach,costal cartilages and perichondrium were used to reconstruct the nasal tip projection according to the tripod theory in rhinoplasty,after removing the previous injection material,L-shaped implant or hypertrophic scar tissue in the tip.Medical charts and operative records were reviewed retrospectively to summary the complications.Nasal dorsum augmentation was done by costal cartilage or I-shaped allograft,sometimes with anterior sheath of rectus abdominis.Patients' subjective satisfaction of the postoperative nasal appearance was self-evaluated with grading (1 worse,2 no change,3 improved,and 4 much improved).Results From September 2015 to March 2017,86 patients underwent rhinoplasty at our hospital.The postoperative follow-up duration was 6 to 20 months.Overall,functional and aesthetic outcome was satisfactory in most patients,and the mean score by the patients' self-evaluation was 3.3 ± 0.6.Graft exposure,mobility,or significant resorption,pneumothorax or significant donor-site pain were not observed.Conclusions Even with minimal complications and morbidities,autologous costal cartilage grafts in Asian rhinoplasty is a versatile and reliable graft material for nasal tip surgery in severe short or saddle nose,contracted nose due to previous L-shaped augmentation and revision rhinoplasty in which the septal cartilage has already been harvested.