Accident source term and radiological consequences of a small modular reactor

Considering the growing global demand for energy and the need for countries to achieve climate goals,there is an increasing global interest in small modular reactors(SMRs)and their applications.Accident source term and radiological consequence evaluations of SMRs are key components of nuclear and radiation safety reviews,which affect the site,exclusion area(EAB),and low population zone outer boundaries.Based on the design characteristics of the SMR and accident analysis results,a theoretical model of a whole-core fuel cladding damage accident was constructed to study the radioactivity released into the environment and its consequences.The accident source term and radiation dose calculation models were established to analyze the released amounts of radionuclides and the total effective dose affecting individuals at the site boundary.The results showed that the amount of radionuclides released into the environment after a whole-core fuel cladding damage accident reached 10^(14) Bq,among which the release amount of ^(133)Xe was the largest.The total effective dose at the site boundary 30 days after the accident was 8.65 mSv.The highest total effective dose affecting individuals occurred to the east-north-east.The results of the accident source term and radiological consequence provide technical support for site boundary dose assessments and reviews of SMRs.

不同时期应激性血糖控制水平对危重患者的影响

住院期间多种应激因素影响下,危重患者的血糖水平会出现明显升高。应激性高血糖会对机体多器官造成不同程度的损害,致使患者并发症增多、病死率升高、住院时间延长、医疗花费增加等。该文以国内外近期研究为基础,对危重患者不同时期院内高血糖预后进行综合分析,并对应激性高血糖患者不同时期的血糖管理做一综述。

Monitoring models for base flow effect and daily variation of dam seepage elements considering time lag effect

Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine(SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam.Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.

Development and prospects of cervical laminoplasty

Cervical laminoplasty surgery is an alternative to laminectomy. It can increase the space of the spinal cord available by raising the lamina, and achieve the indirect decompression effect to treat cervical spondylosis. Various techniques of laminoplasty have since been developed after two prototype techniques: Hirabayashi's open-door laminoplasty and Kurokawa's double-door laminoplasty. Several studies report superior biomechanical stability of the cervical spine after laminoplasty compared with laminectomy. Recent development in laminoplasty is preservation of muscle attachment, which enabled dynamic and static stabilization of the cervical spine by neck extensor muscles. After treatment with new laminoplasty techniques with active postoperative neck muscle exercises, postoperative instability, kyphosis, axial neck pain, and loss of ROM become minimal. The development,complications and future trends of cervical laminoplasty are summarized below.

Extraordinary Electromagnetic Waves in Weakly Relativistic Degenerate Spin-1/2 Magnetized Quantum Plasmas

By using the relativistic quantum magnetohydrodynamic model, the extraordinary electromagnetic waves in magnetized quantum plasmas are investigated with the effects of particle dispersion associated with the quantum Bohm potential effects, the electron spin-1/2 effects, and the relativistic degenerate pressure effects. The electrons are treated as a quantum and magnetized species, while the ions are classical ones. The new general dispersion relations are derived and analyzed in some interesting special cases. Quantum effects are shown to affect the dispersion relations of the extraordinary electromagnetic waves. It is also shown that the relativistic degenerate pressure effects significantly modify the dispersive properties of the extraordinary electromagnetic waves. The present investigation should be useful for understanding the collective interactions in dense astrophysical bodies,such as the atmosphere of neutron stars and the interior of massive white dwarfs.

Role of Cervical Cerclage and Vaginal Progesterone in the Treatment of Cervical Incompetence with/without Preterm Birth History

Background：Preterm birth （PTB） is the leading cause of perinatal morbidity and mortality worldwide,and its prevention is an important health-care priority.The cervical incompetence is a well-known risk factor for PTB and its incidence is about 0.1-2.0%,while there is no ideal optimum treatment recommended currently.The cervical incompetence causes about 15% of habitual abortion in 16-28 weeks.This study aimed to evaluate the effectiveness and safety of cervical cerclage and vaginal progesterone in the treatment of cervical incompetence with/without PTB history.Methods：We retrospectively observed the pregnancy outcome of 198 patients diagnosed with cervical incompetence from January 2010 to October 2015 in Beijing Hospital.Among the 198 women involved,women who had at least one PTB before 32 weeks （including abortion in the second trimester attributed to the cervical competence） were assigned to the PTB history cohort,and others were assigned to the non-PTB history cohort.All women underwent cerclage placement （cervical cerclage group） or administrated with vaginal progesterone （vaginal progesterone group） until delivery.The outcomes of interest were the differences in gestational age at delivery,the rate of premature delivery,neonatal outcome,complications,and route of delivery between the two treatment groups.Results：Among the 198 patients with cervical incompetence,116 patients in PTB history cohort and 80 patients in non-PTB history cohort were included in the final analysis.In the PTB history cohort,cervical cerclage group had significantly longer cervical length at 2 weeks after the start of treatment （23.1 ± 4.6 mm vs.12.4 ± 9.1 mm,P =0.002）,higher proportion of delivery ≥37 weeks＇ gestation （63.4% vs.33.3%,P =0.008）,bigger median birth weight （2860 g vs.2250 g,P =0.031）,and lower proportion of neonates whose 1-min Apgar score 〈7 （5.9% vs.33.3%,P =0.005）,compared with vaginal progesterone group.No significant differences were found in other outcome measures between the two treatment groups.In the non-PTB history cohort,there were no significant differences in the maternal outcomes between cervical cerclage and vaginal progesterone groups,such as median gestational age at delivery （37.4 weeks vs.37.3 weeks,P =0.346） and proportion of delivery ≥37 weeks＇ gestation （55.9% vs.60.9%,P =0.569）.There were also no significant differences in the neonatal outcomes between the cervical cerclage and vaginal progesterone groups including the median birth weight （2750 g vs.2810 g,P =0.145）,perinatal mortality （5.9% vs.6.5%,P =0.908）,and 1-min Apgar scores （8.8% vs.8.7%,P =0.984）.Conclusions：Cervical cerclage showed more benefits in the maternal and neonatal outcomes than vaginal progesterone therapy for women with an asymptomatic short cervix and prior PTB history,while cervical cerclage and vaginal progesterone therapies showed similar effectiveness for women with an asymptomatic short cervix but without a history of PTB.