ABSTRACT
The isotopic fingerprints of plutonium are extremely important for nuclear safeguards and nuclear forensics. An analytical method was developed for direct determination of 240 Pu / 239 Pu ratio in plutonium-containing particles by laser ablation multiple collector inductively coupled plasma mass spectrometry ( LA-MC-ICP-MS). The risk of ablated particles leakage was reduced by leak detection, exhaust hood, and swiping the laser cell. Scanning mobility particle sizer (SMPS) was used to measure the effect of ablation parameters on the size distribution of ablated particles. The results showed that the majority of ablation material presented as particles from 40 -500 nm and the sweep time after laser ablation should be longer than 15 min. The particle size was evaluated to guide LA-MC-ICP-MS system. By using external normalization method for correction of the mass fractionation correction factor and ion counter efficiencies measured by nebulizer-coupled MC-ICP-MS, a LA-MC-ICP-MS method was established for analysis of 239 Pu / 240 Pu ratio in plutonium particles. Spot size, ablation rate and laser dwell time were set at 30 μm, 5 Hz and 5 s, respectively. Laser energy density was controlled to ensure that the intensities of 239 Pu for plutonium-containing particles were about 2×104 cps and 2×105 cps, respectively. The analytical results showed that the relative uncertainties for 239 Pu / 240 Pu was less than 1. 4% ( n = 6), and the measured value deviated by less than 4. 7% from the reference value. The time for adjusting system and determining 239 Pu / 240 Pu ratio in single plutonium particle was 9 h and 0. 5 h, respectively. The results demonstrated that this technique was rapid, precise and accurate, and could be used for determination of 239 Pu / 240 Pu in plutonium-containing particles.
ABSTRACT
AIM: To evaluate the safety and efficacy of intravitreal bevacizumab ( avastin ) injection in patients with exudative age related macular degeneration ( AMD) . METHODS: The records of patients treated with intravitreal injection of 1. 75mg bevacizumab for AMD were retrospectively reviewed. All patients were evaluated by complete ophthalmic examination, optical coherence tomography and fundus fluorescein and/or indocyanine green angiography. Observation was made on the best corrected visual acuity ( BCVA) , intraocular pressure, and the changes of lens, vitreous, central retinal thickness (CFT) and total macular volume (TMV), at 1d, 3d, 7d, 1mo and 6mo after the treatment and then compared with those of pre - operation. Repeated treatment with intravitreous bevacizumab occurred if there were signs of persistent or recurrent exudation. And all cases were followed up at least 6mo. An intravitreal injection of bevacizumab (1. 75mg) was given once every 6wk. RESULTS:All 50 eyes of 48 patients with the average of 58±20. 46 years old were included. The mean baseline of BCVA and CFT were 0. 82±0. 53, and 364. 97±151. 83μm respectively. Although there was no significant decrease in mean CFT and TMV one week after the injection, the mean BCVA had significant improvement. At the last visit of 9. 7mo follow - up, BCVA, CRT and TMV showed significant improvements over baseline values. BCVA was improved by at least two lines in 32 eyes (64%),remained stabilization in 18 eyes (36%) at the last visit. A total of 98 injections were performed and the average number of injections was 1. 98 for each eye in the group. About 50%of re - injections gained at least two lines of vision improvement one week postoperatively. There were no serious adverse events during the treatment. CONCLUSION: Intravitreal bevacizumab ( avastin ) injection for managing CNV due to age-related macular degeneration is safe and few side effects. Intravitreal avastin associated with improvement in visual acuity ( VA ) , which can reduce macular edema and choroidal neovascularization leakage. But a prolonged treatment effect needs further observation.
ABSTRACT
Objective To evaluate the effectiveness of nutrition and food safety educational programs on primary students from grade 4 to 6 in impoverished areas of Western China,under a school-based cluster-randomized trial.Methods Twelve primary schools were selected from 2 impoverished counties in West China and assigned to intervention or control groups,randomly,with 6 schools in each group.Self-rating knowledge,attitude and practice questionnaires were used at both baseline and final stages.Textbooks and supportive materials were designed according to the characteristics of baseline data.All students in the intervention group were treated with targeted nutrition and food safety lectures of 0.5 hour per week for 2 semesters.Generalized linear mixedeffects model was applied to fit the random effects on individual and clusters as well as to fit the fixed effect of the programs.Results Three hundred seventy-eight students from grade 4 to 6 were randomly selected at the baseline study and the differences of scores on knowledge,attitude and practice between the 2 groups were statistically insignificant (P＞0.05).No cluster was lost during the trial.In the final investigation,478 students were randomly selected at the individual level.Scores on knowledge,attitude and practice among students in the intervention group were significantly higher,when comparing to the control group (P＜0.01).At the cluster level,more schools in the intervention group showed significant changes on knowledge and practice,yet the change in attitude was less obvious.Data from the mixed-effects model demonstrated that the program served as an influential factor on scores related to knowledge after the intervention (P=0.015) but did not affect the scores on related attitude or practice (P＞0.05).Conclusion Lectures seemed to have improved the cognition of nutrition and food safety among primary students from grade 4 to 6.However,long-term observation and larger sample size were needed to evaluate the changes on attitude and practice among the students.
ABSTRACT
Objective To investigating knowledge,attitudes,current behavior among primary school students on nutrition and food safety in two State-level poverty-stricken counties,and to explore the best educational model on nutrition and food safety.Methods 478 pupils at 4-6 grades were selected,using the method of stratified cluster sampling and questionnairs.Results The average score on knowledge was 18.66 ± 3.75,with the qualified rate as 61.09％ (the highest was 60.6％).The average score in the section of attitude was 5.82 ± 1.50.More than 97％ of the students agreed that it was necessary to receive knowledge on nutrition and food safety.The average score of behavior was 8.52 ± 2.56.Conclusion Rate of awareness on knowledge of nutrition and food safety had greatly improved among the students under study.Their habit tended to be more regular.However,we also noticed the gap between knowledge and behavior on this issue.