居民就诊次数的Hurdle模型分析

目的介绍Hurdle模型及其在医学零过多计数资料中的应用。方法采用logit-Poisson Hurdle模型分析2周内居民就诊次数的数据。结果居民决定是否去医院就诊存在性别和年龄的差异;居民的收入、两周内患病次数、疾病导致的活动减少天数是影响过去2周内就诊次数多少的主要因素。结论 Hurdle模型可有效分析零过多计数资料。

Hurdle模型及其在居民就诊影响因素中的应用

目的阐明Hurdle模型原理及其在计数资料中的应用。方法利用logit-Poisson Hurdle模型分析两周内居民就诊次数的影响因素。结果 Hurdle模型logistic回归部分结果表明,性别、年龄和经济收入是决定居民是否去医院就诊的主要因素,零截尾Poisson部分结果表明两周内患病次数、由疾病而导致活动天数减少是影响两周内居民就诊次数的主要因素。结论 Hurdle模型是处理零频数过多计数资料一种有效可行的方法 ,其参数估计准确,分析结果切合实际、解释合理。

基于logit-NB Hurdle模型阳性过敏原数的影响因素分析

目的应用Hurdle模型分析具有零膨胀数据阳性过敏原数的影响因素，为预防过敏反应及过敏性疾病提供依据。方法收集2014年就诊变态反应科的患者1855例，以问卷调查方式获得患者基本信息，测定血清过敏原特异性IgE获得阳性过敏原数；应用logit．NBHurdle模型分析阳性过敏原数的影响因素。结果在就诊患者中，阳性过敏原数为0的患者占72．29％，数据具零膨胀现象。两次Voung检验的y值分别为3．90、2．77，P值均小于0．05，logit—PoissonHurdle和logit．NBHurdle优于传统计数模型；logit-PoissonHurdle和logit—NBHurdle的似然比检验LR=205，P〈0．05，结合AIC=1898．6、AICC=1900．3、肌=2042．4的结果，选择logit．NBHurdle为最优模型。Logit部分结果为女性比男性更易发生过敏反应；零截尾负二项部分结果为过敏原数目与文化程度、母亲有过敏史有关，文化程度低、母亲有过敏史的患者过敏原数多。结论分析零膨胀过离散数据前需要进行最优模型的选择；女性是过敏反应的好发人群，预防人群的阳性过敏原数多更应关注母亲有过敏史及文化程度低的人群。

孤独症研究中Hurdle模型的变量选择方法

【目的】在研究孤独症等心理学课题的研究过程中,我们经常会碰到一类计数数据,它们会呈现过度离散和零度膨胀等特征。为了探索影响孤独症的真正影响因素,本文提出一种全新的基于Hurdle模型基础上的自适应LASSO变量选择方法 Hurdle-ALASSO,用于实现对这类计数数据的变量选择。【方法】对24名孤独症患者、26名精神发育迟滞患者和28名正常人士分别进行面部识别实验,分别记录他们的眼动轨迹计数数据。利用Hurdle-ALASSO方法对三组具有过度离散和零膨胀特征的眼动轨迹计数数据进行重要变量的筛选。【结果】影响参与者面孔识别的主要因素包括观察路径、注视面孔时间和注视脸部各部位的时间比例。孤独症患者脸部识别的认知过程与精神发育迟滞患者和正常人士相比存在差异,且路径扫视次数并不是导致差异的因素。【结论】Hurdle-ALASSO方法能有效地实现对具有零膨胀和过度离散特征的心理学类计数数据进行变量选择。

Effect of socio-demographic status on dental caries in pupils by using a multilevel hurdle model

Introduction: Dental caries is the most prevalent chronic disease among schoolchildren. We aimed to investigate the association between dental caries index and socio-demographic status in schoolchildren by using a multilevel hurdle model. Materials and Methods: A cross-sectional epidemiological study was carried out on 906 primary school pupils in Kerman, Iran in 2012. The subjects were selected through a stratified cluster random sampling. At first, the whole target area was stratified according to two geographic areas, the north and south area. Then each area was stratified according to gender. In the next step, several schools were considered as clusters, which were selected randomly in each geographic area and gender strata. All the schoolchildren in these schools were included in this study as samples. Twelve-year-old pupils were examined for dental caries. The dependent variable in this study was the dmft/DMFT index. Eight variables, including socio-demographic information, were collected. Multilevel negative binomial hurdle model was employed for data analysis. Results: The prevalence of caries-free pupils was 30.1% and the mean dmft/DMFT was 3.6 ± 2.2. Negative binomial part of the adjusted model showed that the dmft/DMFT adjusted rate for females was 1.36 (95% CI: 1.10-1.79) times higher than males. Also, the dmft/DMFT adjusted rate for overweight pupils was 0.86 (95% CI: 0.74-0.98) times lower than those with normal weight. Logistic part of the adjusted model showed that the posibility of caries-free state in overweight pupils was 1.95 (95% CI: 1.22-3.11) times higher than those with normal weight. In addition, pupils whose fathers and mothers were workers and housewives, respectively, and those with a high maternal age were at a greater risk for caries experience than others (p < 0.05). Conclusion: BMI, gender, parent’s job and mother’s age at delivery were factors effecting on dental caries in schoolchildren. These pupils need more attention to dental care.

Russia Clears Last Hurdle for W.T.O. Membership

Russia on November 10 cleared the last major obstacle in its 18-year effort to join the World Trade Organization in what the head of the institution called a milestone for global trade. "It’s a victory for Russia, a victory for W.T.O. members, and a victory

Application of hurdle technology for the shelf life extension of European eel(Anguilla anguilla)fillets

Fresh fish,and especially fatty species,are highly perishable due to oxidative deterioration of fish flesh and the elevated microbial load on fish surface.The implementation of a variety of“mild hurdles”may significantly decrease the rates of fish chemical degradation and microbiological spoilage,by better retaining the initial quality,compared to more intense preservation techniques.The aim of this work is the comparative study of different,single or combined,treatments at 15℃on the quality and shelf life of chilled eel fillets.Fish fillets were treated using osmotic solutions consisting of glycerol(30%–40%–45%)and 5%NaCl with and without former antioxidant impregnation by using Rosemary Serum.In all cases,water activity decreased to approximately 0.90 after 420 min of osmotic treatment.Untreated and osmotically treated fish fillets were subsequently stored at 4℃and their stability under chill conditions was assessed based on microbial growth and oxidative deterioration.Microbial growth of treated samples was significantly delayed,especially due to the osmotic step(OS)and the derived water activity decrease.Lipid oxidation,a major cause of rejection for fatty fish such as eel,was greatly inhibited in treated fillets,owing to both‘hurdles’,aw lowering(OS)and antioxidant impregnation with rosemary serum(RS/OS),showing the synergistic effect of these successive procedures.Shelf life of treated eel fillets exhibited a more than 10-fold increase,as compared to the untreated samples,based on chemical composition and a 2 to 3-fold shelf life improvement,in terms of microbial growth.

农户病虫害综合防治技术的采纳决策和采纳密度研究——基于Double-Hurdle模型的实证分析

本文利用安徽省7个县402户农户的调研数据,基于Double-Hurdle模型对农户IPM技术的采纳决策和采纳密度进行了实证分析。研究结果表明,显著影响农户IPM技术的采纳决定和采纳密度的因素具有一定的差异。户主文化程度、环保意识、参加IPM技术的培训、非农收入占比、农业信息的获取及贷款的可获性显著促进农户对IPM技术的采纳,而户主性别与风险偏好类型则显著负向影响农户对IPM技术的采纳。显著促进农户IPM技术采纳密度的因素有户主性别、文化程度及农业信息的获取,而农户风险偏好类型则呈负向作用。最后根据实证研究结果提出相应的政策建议。

Structural insights on anti-biofilm mechanism of heated slightly acidic electrolyzed water technology against multi-resistant Staphylococcus aureus biofilm on food contact surface

Slightly acidic electrolyzed water(SAEW)has proven to be an efficient and novel sanitizer in food and agriculture field.This study assessed the efficacy of SAEW(30 mg/L)at 40℃on the inactivation of foodbome pathogens and detachment of multi-resistant Staphylococcus aureus(MRSA)biofilm.Furthermore.the underlying mechanism of MRS A biofilm under heated SAEW at 40℃treatment on metabolic profiles was investigated.The results showed that the heated SAEW at 40℃significantly effectively against foodbome pathogens of 1.96-7.56(lg(CFU/g))reduction in pork,chicken,spinach,and lettuce.The heated SAEW at 40℃treatment significantly reduced MRS A biofilm cells by 2.41(lg(CFU/cm^(2))).The synergistic effect of SAEW treatment showed intense anti-biofilm activity in decreasing cell density and impairing biofilm cell membranes.Global metabolic response of MRSA biofilms,treated by SAEW at 40℃,revealed the alterations of intracellular metabolites,including amino acids,organic acid,fatty acid,and lipid.Moreover,signaling pathways involved in amino acid metabolism,energy metabolism,nucleotide synthesis,carbohydrate metabolites,and lipid biosynthesis were functionally disrupted by the SAEW at 40℃treatment.As per our knowledge,this is the first research to uncover the potential mechanism of heated SAEW treatment against MRSA biofilm on food contact surface.

Hurdle technology for fish preservation

Fresh fish is a highly perishable product due to the chemical composition of fish flesh and the high microbial load on fish surface.The natural microflora that is more adopted to low temperatures results also in lower thermal bacterial shock from natural temperature to the preservation temperature range.The development of new fish processing(e.g.high hydrostatic pressure,osmotic dehydration,high-intensity pulsed light)and packaging(e.g.modified atmospheres,active and intelligent packaging)methods or novel combinations of existing technologies is sought by the industry in the pursuit of producing alternative products,achieving shelf life extension,and management and reducing food waste.In 2014,processed fish was among the most active new product categories.The lack of dissemination of validated laboratory results for the seafood industry is one of the major issues preventing the uptake of minimal and nonthermal processing for fresh fish.However,it has been reported that some bacteria become more resistant under stress(e.g.psychrotolerant lactobacilli).At the same time,the application of some processing methods(e.g.thermal processing)may affect significantly the nutritional and sensory profile of the target food product.The application of several“soft hurdles”may reduce the rate of fish deterioration and spoilage caused by microbial growth.The objective of this article is to review the preservative effect of alternative hurdles on fish quality and shelf life,focusing on recent,combined applications.

Modeling fire ignition probability and frequency using Hurdle models: a crossregional study in Southern Europe

Background:Wildfires play a key role in shaping Mediterranean landscapes and ecosystems and in impacting species dynamics.Numerous studies have investigated the wildfire occurrences and the influence of their drivers in many countries of the Mediterranean Basin.However,in this regard,no studies have attempted to compare different Mediterranean regions,which may appear similar under many aspects.In response to this gap,climatic,topographic,anthropic,and landscape drivers were analyzed and compared to assess the patterns of fire ignition points in terms of fire occurrence and frequency in Catalonia(Spain),Sardinia,and Apulia(Italy).Therefore,the objectives of the study were to(1)assess fire ignition occurrence in terms of probability and frequency,(2)compare the main drivers affecting fire occurrence,and(3)produce fire probability and frequency maps for each region.Results:In pursuit of the above,the probability of fire ignition occurrence and frequency was mapped using Negative Binomial Hurdle models,while the models’performances were evaluated using several metrics(AUC,prediction accuracy,RMSE,and the Pearson correlation coefficient).The results showed an inverse correlation between distance from infrastructures(i.e.,urban roads and areas)and the occurrence of fires in all three study regions.This relationship became more significant when the frequency of fire ignition points was assessed.Moreover,a positive correlation was found between fire occurrence and landscape drivers according to region.The land cover classes more significantly affected were forest,agriculture,and grassland for Catalonia,Sardinia,and Apulia,respectively.Conclusions:Compared to the climatic,topographic,and landscape drivers,anthropic activity significantly influences fire ignition and frequency in all three regions.When the distance from urban roads and areas decreases,the probability of fire ignition occurrence and frequency increases.Consequently,it is essential to implement long-to medium-term intervention plans to reduce the proximity between potential ignition points and fuels.In this perspective,the present study provides an applicable decision-making tool to improve wildfire prevention strategies at the European level in an area like the Mediterranean Basin where a profuse number of wildfires take place.

Online Hurdle

Will a new regulation requiring online sellersto obtain business licenses impede the growth of consumer-to-consumer e-commerce?

One Hurdle Too Far

We sat around the office TV watching. All work had ground to a halt. The Bird’s Nest Olympic stadium was a full house and 90,000 pairs of eyes were

基于计数模型方法的林分枯损研究

利用吉林省汪清林业局金沟岭林场落叶松林分连续观测数据,分别利用Poisson回归模型、负二项模型、零膨胀模型和Hurdle模型拟合林木枯损株数,并通过AIC值以及Vuong检验对这些模型进行详细分析比较。结果表明:Poisson回归模型不适用于模拟林木枯损株数,负二项回归模型相对于Poisson回归模型比较适用;但是对于零枯损过多的数据,这2类模型拟合效果较差。零膨胀模型和Hurdle模型对这类数据有很好的解决办法,其中,零膨胀负二项模型和Hurdle-NB模型拟合效果优于其他几种模型,且Hurdle-NB模型略好于零膨胀负二项模型。

黔南地区气象因子与森林火灾发生次数之间的关系

对黔南区春季防火期森林火灾数据进行分析,分别引入Poisson回归模型、负二项模型、零膨胀负二项模型和Hurdle模型拟合该地区火险天气森林火灾发生数,并对这些模型进行逐步筛选。结果表明:Poisson回归模型不适用于处理过度离散的数据,负二项回归模型相对于Poisson回归模型,比较适用于过离散数据;但是对于零个数过多的数据,这2类模型拟合效果较差,零膨胀负二项模型和Hurdle模型对这类数据有很好的解决办法。零膨胀负二项模型和Hurdle模型拟合效果优于其他2种模型,而且Hurdle模型好于零膨胀负二项模型。

中国城乡居民茶叶消费对比研究

基于CHNS 2011年的数据,本文利用Double hurdle模型,从参与消费和消费多少两个角度对比分析了中国城乡居民的茶叶消费。结果表明,中国城乡居民中分别有2.61亿和1.67亿的饮茶者,日均饮茶量分别为3.19杯和2.81杯,城乡的茶叶消费普及率分别达到46.5%和33.0%,城镇居民和农村居民的茶叶消费收入弹性分别为11.19%和7.9%。城镇居民参与茶叶消费受年龄和收入影响,农村居民参与茶叶消费受收入和家庭规模影响,城乡居民中男性消费者的饮茶量更多,在茶叶消费量的影响上,年龄、收入、家庭规模和受教育程度对城乡居民茶叶消费量具有显著的正向影响。推动中国国内茶叶消费的政策建议是考虑政策的适用性、加快提升城乡居民收入和准确寻找缝隙市场。

长白落叶松林分进界模型的研究

利用吉林省汪清林业局金沟岭林场落叶松林分连续观测数据,以计数类模型为基础,分别利用Poisson回归模型、负二项模型、零膨胀模型和Hurdle模型拟合林木进界株数,并通过AIC值,Pearson残差图以及Vuong检验对这些模型进行了详细分析比较。结果表明:Poisson回归模型不适用于模拟林木枯损株数;负二项回归模型相对于Poisson回归模型比较适用,但是对于零枯损过多的数据,这两类模型拟合效果较差;零膨胀模型和Hurdle模型对这类数据有很好的解决办法,而且,零膨胀负二项模型拟合效果最好。

交通事故人员伤亡的影响因素分析

为探究交通事故各影响因素对人员伤亡的影响,并根据影响情况给出减少事故伤亡的合理建议,通过收集、统计某市2013年4—9月的交通事故数据,采用Poisson、负二项(NB)、HurdlePoisson(HP)、Hurdle-NB(HNB)、零膨胀Poisson(ZIP)和零膨胀负二项(ZINB)回归模型,对交通事故计数资料进行回归拟合,通过似然比(LR)检验、Vuong检验和拟合优度检验准则比较与选择模型。结果显示,ZINB回归模型拟合效果最佳,肇事车辆有无牌照、车损情况、驾驶人驾驶资历和天气状况等因素对事故中伤亡人数的影响显著,采取限制无牌照车辆出行,保障车辆性能和尽量让驾驶资历高的人驾驶并控制车速等措施能够减少事故伤亡。

零膨胀计数资料模型选择与比较

目的阐明处理零膨胀计数资料的Hurdle模型和零膨胀模型原理,并探讨模型选择与比较。方法拟合心肌缺损节段数资料的基础计数模型、Hurdle模型和零膨胀模型,通过似然比检验、Vuong检验和AIC、BIC信息准则进行模型选择与比较。结果心肌缺损节段数资料拟合ZINB和NBH模型要优于其他计数模型;ZINB与NBH进行模型选择时,Vuong检验结果尚不能判断哪个模型更优,但由于数据中零计数包括结构零和抽样零,结合AIC、BIC和专业解释,可以认为ZINB模型更合适。结论 Hurdle模型和零膨胀模型是处理零膨胀计数资料的有效方法。模型选择时需要考虑数据结构和专业解释。

零膨胀泊松模型的改进在零次索赔建模中的应用

零膨胀是非寿险精算中的一种常见现象,国内外许多学者对此进行了研究分析,而最具影响力的方法是零膨胀泊松模型与Hurdle模型,但这两个方法在区分零之间的差别时存在不足。实际中,产生零次索赔的保单持有人并非全部同质,如何提取零中所包含的信息对保险公司来说是重要的。鉴此,基于零膨胀泊松模型与Hurdle模型的思想,提出修正的零膨胀泊松模型,并利用非寿险精算中的实际数据,对新模型进行了拟合分析。与零膨胀泊松模型拟合结果的比较说明,修正的零膨胀模型在零的处理上更符合实际情况,更能体现零中所包含的信息。