Fibrinogen-to-albumin ratio predicts overall survival of hepatocellular carcinoma

BACKGROUND Fibrinogen-to-albumin ratio(FAR)has been found to be of prognostic significance for several types of malignant tumors.However,less is known about the association between FAR and survival outcomes in hepatocellular carcinoma(HCC)patients.AIM To explore the association between FAR and prognosis and survival in patients with HCC.METHODS A total of 366 histologically confirmed HCC patients diagnosed between 2013 and 2018 in a provincial cancer hospital in southwestern China were retrospectively selected.Relevant data were extracted from the hospital information system.The optimal cutoff for baseline serum FAR measured upon disease diagnosis was established using the receiver operating characteristic(ROC)curve.Univariate and multivariate Cox proportional hazards models were used to determine the crude and adjusted associations between FAR and the overall survival(OS)of the HCC patients while controlling for various covariates.The restricted cubic spline(RCS)was applied to estimate the dose-response trend in the FAR-OS association.RESULTS The optimal cutoff value for baseline FAR determined by the ROC was 0.081.Multivariate Cox proportional hazards model revealed that a lower baseline serum FAR level was associated with an adjusted hazard ratio of 2.43(95%confidence interval:1.87–3.15)in the OS of HCC patients,with identifiable dose-response trend in the RCS.Subgroup analysis showed that this FAR-OS association was more prominent in HCC patients with a lower baseline serum aspartate aminotransferase or carbohydrate antigen 125 level.CONCLUSION Serum FAR is a prominent prognostic indicator for HCC.Intervention measures aimed at reducing FAR might result in survival benefit for HCC patients.

HFACS-MI改进模型在危险化学品仓储事故人因分析中的应用

为了研究危险化学品仓储事故的关键人因,通过人因分析与分类系统-煤矿(Human Factors Analysis and Classification System-Mine,HFACS-MI)改进模型从员工的不安全行为、影响不安全行为的前提条件、监督行为、组织影响和企业外部因素5个层次系统地分析65起危险化学品仓储事故,并运用卡方检验和让步比分析了产生不安全行为的原因和各层次间的内在关系。结果表明,外部管理、组织过程、监督不充分、个人因素、技能差错和违规是导致危险化学品仓储事故发生的重要因素。HFACS-MI改进模型上下层级的人为因素间存在显著的因果关系,且主要的危险化学品仓储事故致因路径共有5条,其中“外部管理因素—组织过程漏洞—监督不充分—个人因素—违规”是最关键的致因路径。改进的HFACS-MI模型可以有效分析危险化学品仓储事故人因因素。

环境样品中铀的HR-ICP-MS测定

高分辨电感耦合等离子体质谱法(HR-ICP-MS)是痕量元素分析的有效手段。本文采用HR-ICP-MS对环境样品(土壤、底泥、茶叶、地表水)中铀浓度和同位素比值进行了测定。土壤、底泥、茶叶样品采用微波消解法进行溶解;水样采用45μm滤膜过滤后直接测定。实验对样品制备、仪器参数设定、记忆效应消除、质量歧视效应修正等进行了探索,建立了环境样品中痕量铀浓度和同位素比值测定方法。土壤制样过程中铀的加标回收率为97.7%,铀检出限0.51ng·L^(-1)。

高分辨率气体同位素质谱法测定氢同位素丰度

氢同位素丰度的准确定量对验证氢同位素分离装置的分离效果非常重要,为此,本研究建立了高分辨率气体同位素质谱(HR-IRMS)法测量全范围氢同位素丰度。确定了质谱的线性进样压强范围4~33 Pa与三原子离子产生率的影响因素,三原子离子产生率与进样压强的平方成正比,与离子源加速电压负相关,加速电压应大于8 V;通过自制标准气体制备装置,配制了平衡态的氢同位素标准气,并校正了进样系统分馏效应和各组分灵敏度的差异,验证了该质谱进样方式为严格的分子流进样。采用所建立的方法测量低、中、高不同氘丰度的样品气体。结果表明:对于天然氘丰度的样品,测量外精度小于1%;对于中、高丰度的样品,测量外精度小于0.5%;测量值与标称值吻合良好。与低分辨率的质谱分析方法相比,该方法简单可靠、无需解析质量重叠峰、测量结果准确性不依赖于样品中氢同位素的平衡程度。

脑血管病急性期血尿酸/血肌酐比值与脑血管事件复发及死亡的关系:一项前瞻性队列研究

背景脑卒中在世界各地有较高的死亡率和复发率。血尿酸(SUA)是嘌呤代谢的产物,已被认为是心脑血管病的危险因素。血尿酸/血肌酐比值(SUA/Scr)是代表肾功能标准化的SUA,目前有关SUA/Scr在急性脑血管病中的作用仍有争议。目的探讨脑血管病急性期SUA/Scr与脑血管事件复发和死亡的关系。方法本研究为前瞻性队列研究,选取2006年9月—2019年9月天津市环湖医院连续收治的首次发生脑血管事件的13313例患者为研究队列,并对患者进行随访,随访截至2020年9月。随访方式为门诊及电话相结合。随访主要终点事件为全因死亡,次要终点事件为脑血管事件复发、心血管事件复发、其他血管事件发生(如下肢动静脉栓塞)。采用Cox比例风险回归模型探究SUA/Scr与脑血管事件复发与死亡的关系。结果根据脑血管病急性期SUA/Scr四分位数,将患者分为Q1组(SUA/Scr≤3.16,n=3520)、Q2组(3.16<SUA/Scr≤3.94,n=3280)、Q3组(3.94<SUA/Scr≤4.92,n=3270)、Q4组(SUA/Scr>4.92,n=3243)。截至随访结束,774例(5.8%)患者死亡,2064例(15.5%)患者复发脑血管事件。脑血管病急性期SUA/Scr位于Q1~Q4的患者中,男性复发脑血管病的例数依次为302、375、408、337例,女性依次为99、125、169、249例;男性复发脑梗死的例数依次为261、314、345、283例,女性依次为90、101、142、205例;男性复发大动脉粥样硬化型脑梗死的例数依次为154、191、214、183例,女性依次为58、52、45、31例;男性全因死亡的例数依次为165、128、131、88例,女性依次为57、63、62、80例;男性因脑梗死死亡的例数依次为93、72、70、46例,女性依次为31、33、36、44例;男性因大动脉粥样硬化型脑梗死死亡的例数依次为58、52、45、31例,女性依次为17、18、27、24例。调整多项混杂因素后,SUA/Scr位于Q4相较于Q1是男性急性脑梗死复发的影响因素(HR=0.690,95%CI=0.500~0.953,P=0.026);SUA/Scr位于Q4相较于Q1是男性脑梗死亚组患者大动脉粥样硬化型脑梗死复发的影响因素(HR=0.740,95%CI=0.578~0.947,P=0.017)。SUA/Scr位于Q4相较于Q1是男性全因死亡、因脑梗死死亡的影响因素(HR=0.575,95%CI=0.368~0.901,P=0.003;HR=0.610,95%CI=0.353~0.814,P=0.011)。SUA/Scr位于Q3、Q4相较于Q1是男性出院后死亡的影响因素(HR=0.656,95%CI=0.476~0.904,P=0.010;HR=0.582,95%CI=0.409~0.829,P=0.001)。SUA/Scr位于Q4相较于Q1是男性脑梗死亚组患者因大动脉粥样硬化型脑梗死死亡的影响因素(HR=0.580,95%CI=0.386~0.873,P=0.007)。结论一定范围内,脑血管病急性期SUA/Scr升高对男性患者脑血管事件复发及死亡有一定的保护作用,低SUA/Scr与男性大动脉粥样硬化型脑梗死的死亡和复发风险升高有关,但与小动脉闭塞型脑梗死和心源性卒中复发和死亡无关。在女性患者中没有观察到SUA/Scr与脑血管事件复发及死亡的关系。

Effect of smoking on the risk of gastrointestinal cancer after cholecystectomy: A national population-based cohort study

BACKGROUND The role of smoking in the incidence of colorectal cancer(CRC)or gastric cancer(GC)in populations undergoing cholecystectomy has not been investigated.AIM To evaluate the effect of smoking on CRC or GC development in cholecystectomy patients.METHODS A total of 174874 patients who underwent cholecystectomy between January 1,2010 and December 31,2017 were identified using the Korean National Health Insurance Service claims database.These patients were matched 1:1 with mem-bers of a healthy population according to age and sex.CRC or GC risk after cholecystectomy and the association between smoking and CRC or GC risk in cholecystectomy patients were evaluated using adjusted hazard ratios(HRs)and 95%CIs.RESULTS The risks of CRC(adjusted HR:1.15;95%CI:1.06-1.25;P=0.0013)and GC(adjusted HR:1.11;95%CI:1.01-1.22;P=0.0027)were significantly higher in cholecystectomy patients.In the population who underwent cholecystectomy,both CRC and GC risk were higher in those who had smoked compared to those who had never smoked.For both cancers,the risk tended to increase in the order of non-smokers,ex-smokers,and current smokers.In addition,a positive correlation was observed between the amount of smoking and the risks of both CRC and GC.CONCLUSION Careful follow-up and screening should be performed,focusing on the increased risk of gastrointestinal cancer in the cholecystectomy group,particularly considering the individual smoking habits.

Optimal Insurance with Background Risk under the Ambiguity and Belief Heterogeneity Structure

In this paper, we discuss the optimal insurance in the presence of background risk while the insured is ambiguity averse and there exists belief heterogeneity between the insured and the insurer. We give the optimal insurance contract when maxing the insured’s expected utility of his/her remaining wealth under the smooth ambiguity model and the heterogeneous belief form satisfying the MHR condition. We calculate the insurance premium by using generalized Wang’s premium and also introduce a series of stochastic orders proposed by [1] to describe the relationships among the insurable risk, background risk and ambiguity parameter. We obtain the deductible insurance is the optimal insurance while they meet specific dependence structures.

月度防控视角下韩江下游城镇地质灾害危险性评价

华南山区地质环境条件复杂,地质灾害频发,亟需开展区域地质灾害危险性评价,解决“地质灾害最可能发生月度及相应易发区在哪里”的问题,以针对性地分级、分阶段部署相应防控措施,有效降低地质灾害可能造成的损失。以韩江下游广东省梅州市留隍镇为例,选取坡度、坡形、高程、工程地质岩组、土层厚度、距断裂距离、植被NDVI值与用地类型共8个评价指标,通过灾害频率比(FR)模型对指标分级赋值;采用灰色关联度法计算指标权重,结合信息量模型完成研究区地质灾害易发性评价,并通过ROC曲线对结果进行验证;在易发性评价的基础上,将月度作为最小时间评价尺度,以历史发灾记录最大月均降雨量作为激发极值优化降雨假设模型,计算1~12月地质灾害发生概率,并完成各月度地质灾害危险性评价及分区。结果表明:①总体上,留隍镇地质灾害共划分为低易发区、中易发区、高易发区、极高易发区4类易发区,各区面积占比分别为58.60%,22.99%,13.39%,5.02%,经ROC曲线检验评价精度达到0.81,表明评价结果客观有效。②月度地质灾害危险性评价结果显示,5~8月留隍镇地质灾害发生概率最大,建议将其作为全年重点防御时段;且集中分布于留隍镇北部、中部及南部,建议将上述区域作为重点防御区。研究成果可为研究区域年内不同月度地灾防控工作安排及防控措施动态调整提供参考。

青海省湟水流域潜在地质灾害识别与易发性评价

[目的]明确青海省湟水流域地质灾害空间分布特征与规律,为该地区防灾减灾提供数据支撑与科学依据。[方法]通过小基线子集干涉测量(small baseline subset interferometric synthetic aperture radar,SBAS-InSAR)技术识别地质灾害点,结合地形因素、地质因素、环境因素、气象因素、人类活动因素进行灾害空间分布规律分析,建立逻辑回归(logistic regression,LR)—频率比(frequency response,FR)模型并检验,利用返回概率值进行易发性评价。[结果]①湟水流域所分布的潜在地质灾害以滑坡、崩塌为主,多种类型潜在地质灾害并生。滑坡与不稳定斜坡通常发育于坡度较缓的山坡上,通常伴有大量张拉与剪切裂缝,尤其在雨季发育明显,对山体下方交通、居民安全构成威胁。发育于河谷两岸的滑坡与不稳定斜坡还可能阻塞河流,形成堰塞湖,进一步加剧灾害风险。崩塌多发育在岩石结构较为疏松或风化严重的陡峭山壁,因地质脆弱,加之降雨等自然因素刺激,易使山体土块、岩石块下落,对下方的居民区和交通线路构成威胁。②研究区2425—3650 m高程区间的地质灾害分布较多,东北向为地质灾害易发坡向;地质灾害易发性随归一化植被指数(normalized digital vegetation index,NDVI)增加而降低,随坡度、地形起伏度、日降水量增加而升高,随距断层距离增加而减少。③湟水流域高易发区及较高易发区,面积约5937.60 km 2,占研究区总面积约38.78%,主要集中在湟水流域南、北边缘地区,湟中、大通、海晏交界处,以及建筑区周边边坡上。④对评价结果进行检验,模型预测性能受试者特征曲线(receiver operating characteristic curve,ROC曲线)线下面积(area under curve,AUC)为0.787,易发区由高至低FR逐级减小,与实际灾害点的分布具有良好的一致性。⑤断层核密度为湟水流域地质灾害发育的主控因子,坡向、地形起伏度、道路核密度次之,剖面曲率对地质灾害发育影响最小。[结论]①利用SBAS-InSAR技术能有效识别湟水流域潜在地质灾害,LR-FR模型获得的易发性评价结果可靠。②湟水流域地质灾害易发区的分布具有明显的空间差异性,主要分布在海拔较高、植被覆盖率较低、降雨量较大、距离断层近的地区,断层核密度为地质灾害易发性的主控因子。③湟水流域的地质灾害具有多发性、突发性和高风险性的特点,给当地居民生活、区域经济发展及生态环境带来了严重的影响。因此,对其进行监测、预警和防治工作显得尤为重要。

HR-HPV在宫颈病变中的表达及不同治疗方法的转阴率分析

目的分析高危型人乳头状瘤病毒（HR-HPV）在宫颈病变中的表达及不同治疗方法对转阴率的影响。方法选择2010年至2015年在四川省攀枝花市妇幼保健院就诊并经病理检查确诊的400例HR-HPV阳性妇女,根据各患者不同的宫颈病变情况予以相应的治疗,其中50例患者未进行任何治疗,其余350例患者经单纯放置干扰素栓、宫颈锥切术、子宫全切术及宫颈癌根治术等不同治疗方法,3个月后复查各HR-HPV亚型转阴率情况。结果 400例HR-HPV患者中,共检出亚型13种,其中检出率最高的5个为HPV16型82例（20.05%）,HPV58型62例（15.50%）,HPV52型50例（12.50%）,HPV53型37例（9.25%）和HPV18型39例（9.75%）;HPV16的检出率随着CIN分级逐渐升高（χ2=6.720,P=0.035）;治疗后CINⅠ转阴率为59.39%,CINⅡ~Ⅲ转阴率为56.47%,宫颈癌转阴率为69.23%,组间差异无统计学意义（χ2=3.918,P=0.202）;不同宫颈病变治疗后HRHPV亚型转阴率组间比较差异有统计学意义（χ2=18.625,P=0.001）,宫颈癌根治术后转阴率高于其他治疗方式（χ2=4.443,P=0.038）;HPV16亚型患者未经治疗以及经干扰素栓治疗、宫颈锥切术治疗、子宫全切术治疗和宫颈癌根治术治疗后转阴率分别为29.41%、42.86%、81.82%、80.00%、84.00%,组间差异具有统计学意义（χ2=4.810,P=0.031）,手术治疗患者转阴率高于单纯干扰素治疗和未经治疗者（χ2=6.013,P=0.015）。结论 HPV16是各类宫颈病变中为常见的亚型,检出率随着CIN分级逐渐升高,手术治疗后转阴率高于保守治疗,对宫颈病变筛查以及预后判断具有积极意义。

Performance-based system seismic assessment for long-span suspension bridges under two-level seismic hazard

Since there are few studies on the performance-based seismic evaluation of the long-span suspension bridge system under two-level earthquake hazard in Chinese code,the developed procedure of this study can be regarded as a general program to assess the seismic performance of the overall system for long-span suspension bridges.In the procedure,the probabilistic seismic demand models of multiple bridge components were developed by nonlinear time-history analyses incorporating the related uncertainties,and the component-level fragility curves were calculated by the reasonable definition of limit states of the corresponding components in combination with seismic hazard analysis.The bridge repair cost ratios used to evaluate the system seismic performance were derived through the performance-based methodology and the damage probability of critical components.Furthermore,the repair cost ratios of the overall bridge system that was retrofitted with fluid viscous dampers for the main bridge and changed restraint systems for the approach bridges were compared.The results show that peak ground velocity and peak ground acceleration can be selected as the optimal intensity measurements of long-span suspension bridges using the TOPSIS(technique for order preference by similarity to an ideal solution).The bridge repair cost ratios can serve as accurate evaluation indicators to provide an efficient evaluation of retrofit measures.The seismic evaluation of long-span bridges is misled when ignoring the interaction of adjacent structures.However,the repair cost ratios of a bridge system that has optimum seismic performance are less sensitive to the relative importance of adjacent structures.

Biomechanical Considerations in the Unruptured Cerebral Aneurysm Study (UCAS Japan): Rupture Risk and True Stress of Wall

When an unruptured aneurysm is found, deciding whether to operate or follow up is one of the most important issues. There are guidelines for making the best final decision on treatment, taking into account the effectiveness of diagnostic and therapeutic devices and the risk-benefit ratio of patients, caregivers, and healthcare professionals. The guidelines evidence-based of large clinical data for this purpose are presented by national medical societies. As one of the rupture risk indicators, there is the hazard risk ratio derived by the UCAS Japan research group based on the statistical method of 6697 aneurysms in 5720 patients with cerebral aneurysms of 3 mm or more. Therefore, we investigated the biomechanical significance of this hazard risk ratio using a spherical aneurysm model. It was revealed that 1) the reason why the frequency of aneurysm rupture is relatively high up to about 10 mm, 2) the UCAS hazard risk ratio corresponds to stress of the aneurysm wall, and the true stress can be calculated by multiplying the patient’s blood pressure, and 3) the factors that cause the daughter’s sac (irregular protrusion of the aneurysm wall). In addition, our two methods for measuring the strength of the blood vessel wall of an individual patient were described.

The Cox Proportional Hazard Regression Model Vis-à-Vis ITN-Factor Impact on Mortality Due to Malaria

This study has provided a starting point for defining and working with Cox models in respect of multivariate modeling. In medical researches, there may be situations, where several risk factors potentially affect patient prognosis, howbeit, only one or two might predict patient’s predicament. In seeking to find out which of the risk factors contribute the most to the survival times of patients, there was the need for researchers to adjust the covariates to realize their impact on survival times of patients. Aside the multivariate nature of the covariates, some covariates might be categorical while others might be quantitative. Again, there might be cases where researchers need a model that has the capability of extending survival analysis methods to assessing simultaneously the effect of several risk factors on survival times. This study unveiled the Cox model as a robust technique which could accomplish the aforementioned cases. An investigation meant to evaluate the ITN-factor vis-à-vis its contribution towards death due to Malaria was exemplified with the Cox model. Data were taken from hospitals in Ghana. In doing so, we assessed hospital in-patients who reported cases of malaria (origin state) to time until death or censoring (destination stage) as a result of predictive factors (exposure to the malaria parasites) and some socioeconomic variables. We purposefully used Cox models to quantify the effect of the ITN-factor in the presence of other risk factors to obtain some measures of effect that could describe the relationship between the exposure variable and time until death adjusting for other variables. PH assumption holds for all three covariates. Sex of patient was insignificant to deaths due to malaria. Age of patient and user status were both significant. The magnitude of the coefficient (0.384) of ITN user status depicts its high contribution to the variation in the dependent variable.

足尺HR-EPS模块剪力墙抗震性能试验研究

为评价HR-EPS(Hai Rong-Expanded Polystyrene)模块剪力墙结构的抗震性能,通过试验与数值模拟相结合的方法,对配筋率及轴压比不同的足尺HR-EPS模块剪力墙试件进行抗震性能研究。研究结果表明:墙体配筋率的提高,可以大幅增强足尺HR-EPS模块剪力墙的水平承载力;随着墙体配筋率的增加,墙体的刚度、位移延性系数以及耗能能力均有所增加,刚度退化速率有所降低;模拟结果与试验数据基本吻合,适当地增加轴压比可提高试件的耗能能力及其刚度,使其抗震性能有所提升;并根据试验结果对已有公式进行修正,给出了足尺HR-EPS模块剪力墙抗剪承载力计算公式。

Understanding Dependent Competing Risks： A Simulation Study to Illustrate the Relationship Between Cause-Specific Hazard and Marginal Hazard

In the analysis of competing risk data, the observed effect of a covariate can be obtained via a Fine and Gray sub-distribution hazard ratio. Sometimes, it is also desirable to obtain the virtual effect of a covariate as if the competing risks were non-existent. Under the latent failure time scenario, when the event of interest and the competing risk event are independent, the cause-specific hazard ratio obtained from the Cox model where the competing events are censored represents the ratio of the marginal hazards and can be interpreted as the virtual effect of the covariate. However, when the two events are not independent, the cause-specific hazard ratio is not the ratio of the marginal hazards as the ratio depends not only on the marginal hazards but also on the correlation between the competing risk and the event of interest. Using simulation, we investigated the degree to which the cause-specific hazard ratio changes relative to the marginal hazard with this correlation. It was found that the discrepancy between the cause-specific hazard ratio and the theoretical marginal hazard ratio increased as the proportion of competing risk events and the correlation between the events increased （〉0.2）. Depending on the direction of the correlation, the cause-specific hazard ratio can over- or under-estimate the marginal hazard ratio. Using real-life datasets, we show how these results can be used to make inferences on the virtual effects.

Seismic Hazard Matrix of Buildings in Yunnan

Seismologists have begun to investigate the earthquake damage and assess the economic losses on the spot in the Yunnan area since the earthquakes with M_S6.7 and M_S6.9 that occurred on the boundary between China and Myanmar west of Menglian county,Yunnan Province,on April 23,1992.From 1992 to 2003,50 destructive earthquakes occurred in Yunnan,and large amounts of data on seismic hazard have been accumulated.With focus on the major building structures,the paper makes statistical analysis on the earthquake damage ratio,loss ratio and seismic hazard index in the areas with different seismic intensity of the 50 events,and presents the seismic hazard matrix of buildings for the Yunnan area.

不同轴压比下HR-EPS模块剪力墙抗震性能研究

为研究足尺HR-EPS模块剪力墙试件在不同轴压比下的抗震性能,文中通过低周往复荷载试验和有限元模拟结合的方法,开展了足尺HR-EPS模块剪力墙试件在不同轴压比下的抗震性能分析,获得试件的不同抗震性能指标,结果表明增大轴压比可以在一定程度上使试件的极限承载力增强,但会有一个上限值,超过这个上限值会使破坏具有一定脆性;与小轴压比墙体相比,大轴压比墙体的刚度退化速度在加载的前期稍显迅速;模拟结果与试验数据基本一致,适当增大轴压比使滞回曲线更加圆滑。获得不同轴压比下剪力墙的耗能能力和位移延性,为HR-EPS模块剪力墙的抗震性能提供数据依据,在实际工程应用奠定基础。

川藏交通廊道崩滑灾害分布及其危险性评价

川藏交通廊道雅安到林芝段位于青藏高原东南部,沿线地质条件复杂、河流切割强烈、地质环境脆弱、新构造运动活跃,具有山高谷深、坡体稳定性差等特点,是我国崩滑灾害最发育、危害最严重的地区之一。为了保障廊道内相关工程的顺利建设和后期安全运营,本文以线路两侧一级分水岭为界,通过遥感解译和野外调查,获得川藏交通廊道雅安—林芝段崩滑灾害共4509处,在此基础上,选取高程、坡度、坡向、工程地质岩组、断裂、水系、公路、地震动峰值加速度、降雨共9个因子分析了灾害的空间分布规律及发育特征,建立了频率比法与逻辑回归方法耦合模型,并运用到高原山区重大交通廊道崩滑灾害危险性评价中。研究结果表明:(1)廊道沿线各县区段的崩滑灾害面密度在空间上总体呈从西向东递减的趋势。(2)有利于灾害发生的条件分别是:高程1~4 km,坡度大于20°,S、SW和W坡向,较软弱、较坚硬和坚硬岩组,距断裂6.4 km范围内,距水系3.2 km范围内,距公路800 m范围内,地震动峰值加速度0.20g,年均降雨量大于1100 mm。(3)将研究区危险性等级划分为极低危险(18.64%)、低危险(26.18%)、中等危险(24.75%)、高危险(19.82%)、极高危险(10.61%)5级,其中:极高危险区与高危险区主要分布在断裂附近和坡度较陡的区域。(4)耦合模型的AUC值达到了0.737,优于单一的频率比模型的0.712,表明耦合模型的评价结果具有更高的精度。该研究可为川藏交通廊道雅安到林芝段相关工程的规划、建设和未来运营过程中的防灾减灾工作提供重要参考。

基于频率比模型和随机森林模型耦合的地质灾害易发性评价

目前利用机器学习进行易发性评价时,非地质灾害单元通常是在研究区范围内随机选取,会导致部分非地质灾害单元落在潜在地质灾害单元之上,造成模型评价结果偏差,所以非地质灾害单元的有效选取成为当前易发性评价的难点问题。以浙江省长兴县李家巷镇为研究区,选取高程、坡度、坡向、剖面曲率、岩组、距水系距离、距断层距离、归一化植被指数和土地利用这9个环境因子作为评价指标,利用频率比模型(frequency radio,FR)进行非地质灾害单元的选取,然后选用随机森林模型(random forest,RF)进行地质灾害易发性评价,并与未经有效筛选非地质灾害单元的RF模型结果进行对比分析。结果表明,与RF模型相比,FR-RF模型的特异性(Specificity)提升了9.51%,说明对非地质灾害单元的预测能力显著提升,同时敏感性(Recall)提升了13.71%,说明对地质灾害单元的预测性能也大幅提升,受试者工作特征曲线下的面积(area under curve,AUC)和准确率(Accuracy)分别提高了6%、11.66%,模型整体性能及预测能力得到改进;地质灾害极高和高易发区主要分布于存在碎屑岩和坡度较大的区域,总面积为7.35 km 2,相较于RF模型结果,面积增加了25.98%,而极低和低易发区面积减少了16.7%;坡度、工程岩组是该研究区地质灾害的主控因素,相对重要性占比分别为37.7%和28.0%。

基于贝叶斯Cox回归模型分析耐多药肺结核患者死亡的影响因素

目的:耐多药肺结核(multidrug-resistant tuberculosis,MDR-TB)具有较高的病死率,一直以来都是全球结核病防控工作的难点之一。分析MDR-TB患者不良结局的影响因素有助于改善MDR-TB患者的程序化管理,优化MDR-TB的治疗策略。在分析随访数据时,Cox比例风险回归模型是一种重要的多因素分析方法,但其存在较大的应用局限性,如难以处理样本量小等实际问题对模型的影响。基于此,本研究分别采用贝叶斯Cox回归模型和常规Cox回归模型,分析MDR-TB患者在抗结核治疗期间死亡的影响因素,并比较这2种方法在应用中的差异。方法:数据资料来自2017年11月1日至2021年3月31日在兰州市肺科医院接受治疗的388例MDR-TB患者。采用生存分析方法分析MDR-TB患者在治疗期间的死亡情况及其影响因素。分别构建常规Cox回归模型和贝叶斯Cox回归模型来估计MDR-TB患者死亡影响因素的风险比(hazard ratio,HR)及其95%置信区间(95%confidence interval,95%CI),模型的参数估计可靠性通过各自变量的参数标准差和HR值的95%CI来判断,参数标准差和95%CI范围越小,模型的估计结果越可靠。结果:纳入研究的388例MDR-TB患者的生存时间为10.18(4.26,18.13)个月,最长生存时间为31.90个月。观察期间共有12例因肺结核死亡,病死率为3.1%,死亡患者的生存时间为4.78(2.63,6.93)个月。50%的死亡患者出现在抗结核治疗的前5个月,最后一个死亡患者出现在治疗的第13个月。常规Cox回归模型分析结果显示:有合并症的患者死亡风险约为无合并症者的6.96倍(HR=6.96,95%CI 2.00~24.24;P=0.002);接受定期随访患者的死亡风险比未接受定期随访患者降低约81%(HR=0.19,95%CI 0.05~0.77;P=0.020)。贝叶斯Cox回归模型中,各参数的迭代历史图和BGR图(Blue/Green/Red plot)均提示模型的收敛效果良好,其参数估计结果显示:首次痰培养结果阳性的患者死亡风险低于阴性患者(HR=0.33,95%CI 0.08~0.87);相对于无合并症患者,有合并症患者的死亡风险提高了约6.80倍(HR=7.80,95%CI 1.90~21.91);与未接受定期随访者相比,接受定期随访的患者死亡风险降低了90%(HR=0.10,95%CI 0.01~0.30)。2个模型的结果比较显示:贝叶斯Cox模型中除接受定期随访参数的标准差(贝叶斯模型为0.77;常规模型为0.72)和肺部空洞参数的标准差(贝叶斯模型为0.73;常规模型为0.73)不小于常规模型外,其他参数的标准差和对应HR的95%CI均明显小于常规模型。结论:抗结核治疗的第1年是MDR-TB患者死亡的高风险期。合并症是影响MDR-TB患者死亡的主要危险因素,而首次痰培养阳性、接受定期随访的患者死亡风险更小。在样本量较小且结局发生率较低的数据中贝叶斯Cox回归模型的参数估计较常规Cox模型更可靠。