Soil erosion in the northwestern Amhara region,Ethiopia has been a subject of anxiety,resulting in a major environmental threat to the sustainability and productive capacity of agricultural areas.This study tried to e...Soil erosion in the northwestern Amhara region,Ethiopia has been a subject of anxiety,resulting in a major environmental threat to the sustainability and productive capacity of agricultural areas.This study tried to estimate soil erodibility factor(Kfactor)using Universal Soil Loss Equation(USLE)nomograph,and evaluate the spatial distribution of the predicted K-factor in a mountainous agricultural watershed.To investigate the K-factor,the 54 km2 study watershed was divided into a 500 m by 500 m square grid and approximately at the center of each grid,topsoil samples(roughly 10 to 20 cm depth)were collected over 234 locations.Sand,silt,clay and organic matter(OM)percentage were analyzed,while soil permeability and structure class codes were obtained using the United States Department of Agriculture(USDA)document.The resulting coefficient of variation(CV)of the estimated K-factor was 0.31,suggesting a moderate variability.Meanwhile,the value of nugget to sill ratio of K-factor was 0.32,which categorized as moderate spatial autocorrelation.Prediction accuracy and model fitting effect of the Gaussian semivariogram approach was best,suggesting that the Gaussian ordinary Kriging model was more appropriate for predicting Kfactor.The resulting value of the mean error(ME)was 0 and the mean squared deviation ratio(MSDR)was nearly 1,which indicates the Gaussian model was unbiased and reproduced the experimental variance sufficiently.The values of K-factor were smaller(0.0217 to 0.0188)in the northern part and gradually increased(0.0273 to 0.033 Mg h MJ^(-1)mm^(-1))towards the central and south of the study watershed.展开更多
基金This research was financed by the Austrian Development Agency(ADA)as well as the Consultative Group for International Agricultural Research(CGIAR)Water Land and Ecosystems(WLE)project.
文摘Soil erosion in the northwestern Amhara region,Ethiopia has been a subject of anxiety,resulting in a major environmental threat to the sustainability and productive capacity of agricultural areas.This study tried to estimate soil erodibility factor(Kfactor)using Universal Soil Loss Equation(USLE)nomograph,and evaluate the spatial distribution of the predicted K-factor in a mountainous agricultural watershed.To investigate the K-factor,the 54 km2 study watershed was divided into a 500 m by 500 m square grid and approximately at the center of each grid,topsoil samples(roughly 10 to 20 cm depth)were collected over 234 locations.Sand,silt,clay and organic matter(OM)percentage were analyzed,while soil permeability and structure class codes were obtained using the United States Department of Agriculture(USDA)document.The resulting coefficient of variation(CV)of the estimated K-factor was 0.31,suggesting a moderate variability.Meanwhile,the value of nugget to sill ratio of K-factor was 0.32,which categorized as moderate spatial autocorrelation.Prediction accuracy and model fitting effect of the Gaussian semivariogram approach was best,suggesting that the Gaussian ordinary Kriging model was more appropriate for predicting Kfactor.The resulting value of the mean error(ME)was 0 and the mean squared deviation ratio(MSDR)was nearly 1,which indicates the Gaussian model was unbiased and reproduced the experimental variance sufficiently.The values of K-factor were smaller(0.0217 to 0.0188)in the northern part and gradually increased(0.0273 to 0.033 Mg h MJ^(-1)mm^(-1))towards the central and south of the study watershed.
文摘目的 探讨影响急性缺血性脑卒中(acute ischemic stroke,AIS)替奈普酶静脉溶栓疗效的相关因素,构建列线图模型,为临床决策提供依据。方法 选取接受替奈普酶静脉溶栓治疗的93例AIS患者作为研究对象,治疗90 d后,根据改良Rankin量表(modified Rankin scale,mRS)评分将患者分为预后良好组(54例)和预后不良组(39例)。收集患者的性别、年龄、体质量指数、既往史、发病至溶栓时间、血压、入院时美国国立卫生研究院卒中量表(national institute of health stroke scale,NIHSS)评分以及溶栓前血红蛋白、血小板计数、白细胞计数、肌酐、血糖、国际标准化比值、凝血酶原时间、活化部分凝血活酶时间,采用多因素Logistic回归分析替奈普酶静脉溶栓疗效的影响因素,并据此构建列线图模型。结果 预后良好组和预后不良组的年龄、饮酒史、发病至溶栓时间、溶栓前收缩压、溶栓前NIHSS评分、血红蛋白、血糖、凝血酶原时间、活化部分凝血活酶时间等资料比较,差异有统计学意义(P<0.05)。多因素Logisitc分析结果显示,饮酒史、发病至溶栓时间、溶栓前收缩压、溶栓前NIHSS评分、血糖、凝血酶原时间、活化部分凝血活酶时间是不良预后的危险因素(P<0.05)。由危险因素构建的列线图预测模型中,受试者工作特征曲线下面积为0.863(95%CI:0.776~0.925),特异度为87.04%,敏感度为71.79%。结论 基于危险因素构建的列线图能为AIS患者替奈普酶静脉溶栓临床决策提供参考。
