多功能乳清酸钝化协助制备高效稳定的钙钛矿太阳能电池

空气环境中制备钙钛矿太阳能电池(PSCs)对于发展更高性价比的光伏器件具有重要意义。然而,空气环境制备的钙钛矿层存在大量的阴阳离子缺陷,严重影响器件性能。因此,采用乳清酸(OA)作为添加剂,通过添加剂工程对混合阳离子钙钛矿薄膜缺陷进行有效调控。OA中的羧基能与钙钛矿中未配位的Pb2+键合,吡啶环上的含氮基团与未配位的I-形成氢键,在降低钙钛矿薄膜缺陷态密度的同时增大钙钛矿晶粒尺寸,抑制载流子的非辐射复合。经OA钝化PSCs的光电转换效率(PCE)从19.89%提升到22.09%,在空气环境中放置1000 h还可保持93.85%的初始效率。

术前磁共振评价腹腔镜手术治疗剖宫产切口瘢痕缺陷相关异常子宫出血的价值及影响因素

目的:剖宫产率逐年上升,而剖宫产切口瘢痕缺陷的治疗具有较大挑战性。本研究旨在评估术前磁共振成像技术对于腹腔镜手术治疗剖宫产切口瘢痕缺陷相关异常子宫出血患者的临床价值并分析相关影响因素。方法:选择2018年至2022年在中南大学湘雅三医院妇科接受腹腔镜手术治疗剖宫产切口瘢痕缺陷相关异常子宫出血的患者共计57例,进行回顾性队列分析。将57例患者根据腹腔镜手术治疗剖宫产切口瘢痕缺陷相关异常子宫出血的术后临床治愈情况分为临床治愈组(n=28,49.1%)及非临床治愈组(n=29,50.9%)。对所有的受试者进行术后3个月的随访调查,通过logistic回归分析探讨患者的年龄、临床症状、孕产史、剖宫产史等基本临床信息、术前磁共振成像参数以及术后月经情况等与腹腔镜手术治疗剖宫产切口瘢痕缺陷相关异常子宫出血的临床治愈率的相关性。结果:2组患者的年龄、前次剖宫产年龄、怀孕次数、前次剖宫产时间、腹腔镜术前T2信号磁共振评估的子宫位置、缺陷长度、缺陷宽度、缺陷残余肌层厚度、缺陷邻近子宫肌层厚度及缺陷距宫颈外口距离等参数的差异均无统计学意义(均P>0.05)。患者的异常子宫出血症状出现时间(P=0.036,OR=1.019,95%CI 1.002~1.038)和术前磁共振成像的缺陷深度(P=0.010,OR=5.793,95%CI 1.635~25.210)是影响临床治愈率的危险因素。结论:患者异常子宫出血症状出现时间及术前磁共振评估的缺陷深度是腹腔镜手术治疗剖宫产切口瘢痕缺陷相关异常子宫出血临床治愈的影响因素,术前磁共振对于判断本病预后具有一定的临床意义。

基于组合权重-集对分析理论的城市湖泊水质评价模型--以玄武湖为例

全面准确地进行水质评价是城市湖泊有效治理的前提。研究基于组合权重-集对分析理论,以溶解氧(DO)、氨氮(NH 3-N)、总磷(TP)、总氮(TN)为评价指标,利用综合层次分析法和熵权法确定指标权重,选择六元联系数,建立了适用于玄武湖的水质评价模型。结果表明,玄武湖的水质尚未完全达到Ⅳ类水标准,与传统评价方法(单因子评价法、主成分分析法)相比,采用基于组合权重-集对分析理论的城市湖泊水质模型开展评价工作时,可通过主客观相结合的方法综合考虑多种指标,且能对同一片湖区不同区域的同一等级水质的进一步发展趋势进行分析,从而完成更为全面细致的水质评价工作,为后续城市湖泊分区治理提供更为可靠的依据。

“以器官系统为中心，基础与临床全线整合”教学模式解剖学知识点整合的实践与思考

回顾高等医学教育课程模式,20世纪50年代“以器官系统为中心”的课程模式问世;90年代,美国医学院校协会在全国推行“医学院校培养目标研究项目”,许多院校实行了以器官系统为中心的课程、以问题为导向的课程、以社区为基础的课程等整合课程,成为第2次医学教育改革,对世界医学教育产生了深远的影响[1-2]。我国权威的医学教育专家认为[3],根据我国国情,以“器官系统”为中心的医学整合课程教学模式更符合当前和未来各高等医科院校对临床医学人才培养的方式。2008年9月,教育部、卫生部发布的《本科医学教育标准—临床医学专业(试行)》.

民勤绿洲边缘积沙带植物群落健康分析

甘肃河西走廊经过60多年的防沙治沙,在绿洲边缘形成了一条积沙带。其中,民勤绿洲边缘积沙带相对最典型、最完整。积沙带上的植被不仅是积沙带的形成因素,更是维持积沙带稳定的重要因素。从一定意义上说,积沙带上植被的健康状况,决定着积沙带的稳定性。为了分析积沙带上的植被状况,在民勤绿洲边缘积沙带上等间距设定了11条样线,通过60多个样方的植被调查,对民勤绿洲边缘积沙带上植物群落进行了健康序列分析。结果表明:民勤绿洲边缘积沙带上的植被普遍是不健康的,民勤绿洲边缘人工固沙林积沙带上的植被健康状况相对好于天然灌丛积沙带上的植被健康状况,乔灌混交林积沙带上的植被健康状况最差。民勤绿洲下游积沙带上的优势种植物柽柳严重枯死,健康状况最差,积沙带潜在风蚀活化的危险。农田弃耕后,沙区农田边缘防护林及其积沙带的保护是一个新的值得考虑的问题。

民勤绿洲边缘阻沙带表层土壤粒度空间分布特征

土壤粒度是风沙活动的重要表征参数。通过野外调查与室内测试,分析了不同空间分布防风固沙林表层土壤粒度的空间分布特征,旨在评价民勤绿洲边缘阻沙带防风固沙功能。结果表明:(1)坝区梭梭-沙拐枣-沙蒿-沙米固沙林表层土壤粒度组成以细砂、中砂、极细砂为主,分别占33.47%、26.08%、18.18%;泉山区白刺+沙蒿+五星蒿固沙林表层土壤粒度组成以细砂、粉粒和极细砂为主,分别占29.62%、21.17%、18.87%;湖区白刺-芦苇-猪毛菜固沙林表层土壤粒度组成以细砂、粉粒和极细砂为主,分别占36.66%、27.98%、22.83%。(2)平均粒径:坝区(2.55Φ)>泉山区(3.5Φ)>湖区(3.94Φ),分选性:坝区(1.58Φ)较差,湖区(2.10Φ)和泉山区(2.29Φ)很差。(3)泉山区、湖区表层土壤粒度频率曲线为双峰型,坝区为单峰型,偏度均为极正偏态,峰度表现为很窄。粒度累计分布曲线反映出坝区风沙活动较泉山区、湖区频繁、强烈。阻沙带荒漠植被群落物种组成决定着其防风固沙功能的大小,进而影响其表层土壤的粒度分布特征。建议阻沙带生态防护体系修复时应注重选择固沙能力强的造林树种。

新月形沙丘粒度分布的交替过程——以甘肃省河西沙区绿洲边缘积沙带为例

新月形沙丘是一种常见的沙丘类型,甘肃河西走廊沙区绿洲边缘积沙带上存在大量新月形沙丘。通过对河西走廊沙区新月形沙丘全面调查取样和在民勤沙区重复取样测定,分析了新月形沙丘的粒度特征。结果表明,新月形沙丘和新月形沙丘链表层0~5 cm深度以细沙和中沙为主,其中古浪沙区沙粒较细且与金昌、临泽、金塔和民勤沙丘的粒度差异较大;主风向(NW)过程从沙丘迎风坡底部到沙丘顶部粒度由粗变细,即沙丘顶部粉沙最多,其次是背风坡中部;迎风坡底部粗沙最多,其次是迎风坡中部。反风向(SE)过程从沙丘迎风坡底部到沙丘顶部粒度由粗变细再变粗,即迎风坡中部粉沙最多,其次是沙丘顶部;迎风坡底部粗沙最多,其次是迎风坡中部。主风向过程沙丘粒度的标准差和变异系数较大,而反风向过程沙丘粒度的标准差和变异系数相对较小。主风向和反风向2种过程,导致了沙丘各部位粒度的交替变化。由于观测的季节不同,才导致了有关新月形沙丘迎风坡粒度分布的2种不同结论。

SH抑尘剂形成胶膜的紫外线老化研究

SH喷洒在弃土表面,干燥后形成一层胶膜,可达到抑尘作用.为研究日照引起胶膜的老化问题,开展紫外线老化试验,并测试胶膜的拉伸性能.结果为:老化前,在拉伸过程中胶膜经历了弹性变形—弹塑性变形—拉裂破坏三个阶段,随胶膜厚度的增加,极限拉力与极限变形均逐渐增大;老化后,胶膜的拉力-变形曲线呈抛物线型,极限拉力和极限变形均有所下降.SH抑尘剂形成的胶膜具有一定的抗拉伸性能和抗紫外线老化能力,可满足长达一年半的建设场地抑尘要求.

随机森林算法在产后抑郁风险预测中的应用

目的:探讨随机森林算法在产后抑郁影响因素的筛选和风险预测中的应用效果。方法:选取2017年6月至2018年6月在湖南省长沙市某三甲医院接受产前检查并在该医院分娩,符合纳入和排除标准的孕早期妇女为研究对象。入组时,使用自编的调查问卷、中文版爱丁堡产后抑郁量表(Edinburgh Postnatal Depression Scale,EPDS)调查研究对象的人口经济学、心理社会学、生物学和产科及其他特征;产后4~6周内,采用中文版EPDS进行抑郁评分和自编的产后资料问卷收集分娩和产后资料。采用R软件在训练数据集上建立产后抑郁风险预测的随机森林模型,在验证数据集上采用预测准确率、灵敏度、特异度、阳性预测值、阴性预测值和曲线下面积(area under curve,AUC)评价模型的预测效果。结果:共调查406例研究对象,其中150例的EPDS得分≥9,产后抑郁的发生率为36.9%。通过随机森林算法对训练集建立的模型在验证集上验证,得出预测准确度为80.10%,灵敏度为61.40%,特异度为89.10%,阳性预测值为73.00%,阴性预测值为82.80%,AUC值0.833。采用随机森林算法通过变量重要性评分对产后抑郁影响因素的重要程度进行排序,得出排名前10位的重要预测变量为产前抑郁、产后经济担忧程度、产后工作担忧程度、孕早期血清游离三碘甲腺原氨酸、孕晚期高密度脂蛋白、向婴幼儿发脾气、孕早期血清总胆固醇、孕早期三酰甘油、孕晚期血细胞比容和三酰甘油。结论:随机森林算法在产后抑郁的风险预测中具有较大优势,通过综合评价机制能从复杂的多因素中识别出产后抑郁的重要影响因素,并进行定量分析。这对识别产后抑郁关键因素,进行及时、有效干预具有重要意义。

石羊河下游人工梭梭水分利用策略季节变化

作为石羊河下游主要固沙造林树种,人工梭梭(Haloxylon ammodendron)抗逆性和生态适应性强,构成了风沙灾害防治的第一道防线。本研究基于原位观测与稳定同位素示踪的方法,研究了人工梭梭水分来源的季节性变化,以期为民勤绿洲边缘退化防护体系的修复提供理论依据。结果表明:在生长季,人工梭梭根际垂直0-200 cm土层平均土壤水分含量为0.87%,120 cm深度处土壤水分偏高;水分季节变化表现为5月(1.22%)> 4月(1.05%)> 6月(0.83%)> 7月(0.80%)> 10月(0.67%)> 8月(0.65%)。不同季节人工梭梭0-60 cm表层根际土壤水δ18O富集效应明显,变化剧烈,60-200 cm土层δ18O逐渐减小且相对稳定。Iso Source模型表明,人工梭梭春季对120-200 cm深层土壤水分利用比例为45.15%,60-120 cm中层土壤水分的利用比例为20.6%,20-60 cm浅层土壤水分的利用比例为20.1%;夏季对0-20 cm表层、60-120 cm中层、120-200 cm深层土壤水分的利用比例分别为32.5%、24.75%、22.1%;秋季主要对0-20 cm表层、120-200 cm深层土壤水分利用较多,利用比例分别为44.4%和48.75%。不同深度土壤水分是人工梭梭重要的季节水分来源,建议在日常抚育管理中可采取人工辅助降水入渗的方法来维持林地土壤水分平衡。

淮河流域中上游径流变化归因分析

为了研究与量化人类活动、下垫面和气候变化等影响因素对淮河径流变化的贡献率,以淮河流域中上游(蚌埠站以上)为研究区域,采用M-K检验、滑动t检验、R/S分析法,分析1958—2018年的降水和潜在蒸发序列及1958—2016年的径流序列的变化趋势,确定径流序列的突变点,并采用土地利用转移矩阵分析土地利用变化及其对径流变化的影响。基于Budyko水热耦合平衡理论,计算降水、潜在蒸发和下垫面参数的弹性系数,定量分析气候变化和人类活动对径流变化的贡献率。研究结果表明:蚌埠站径流序列在1990年发生突变,变化期多年平均径流深比基准期减少了20.9 mm,草地面积也在1990年出现大幅下降,占比更大的林地、水域面积对应的径流量表现为下降趋势。基准期和变化期降水、潜在蒸发、下垫面参数的弹性系数分别为2.11、-1.10、-1.10和2.36、-1.36、-1.07。在导致径流变化的各因素中,气候变化、下垫面变化、人类活动的贡献率分别为37.13%、-53.53%、-9.34%,其中下垫面变化是导致径流减少的主要原因。

多材料Terminal Steiner树拼接问题的近似算法研究

在赋权连通网络下,给定多种材料及每种材料的费用和拼接费用,以便寻找赋权网络中的一棵Terminal Steiner树,并用给定材料连接此树,使得总费用及材料根数达到最小,记此问题为多材料Terminal Steiner树拼接问题。为了解决Terminal Steiner树拼接问题,首先分析Terminal Steiner树拼接问题是NP问题,不存在多项式时间算法;然后基于Steiner树问题和变尺寸装箱问题的近似算法及算法复杂度,给出多材料的Terminal Steiner树拼接问题的一个近似算法;最后证明算法的近似值及近似算法的时间复杂度。

广义二维多项式混沌映射及其在信息传输中的应用

现有混沌映射在工程应用中存在许多缺陷,如混沌参数范围不连续、弱混沌、混沌序列输出不均匀和动力学退化等。基于此,提出了一种广义二维多项式混沌映射,通过设定不同控制参数和多项式最高次数,得到一系列特定Lyapunov指数的二维多项式混沌映射。为避免该映射第二个状态方程的输出塌陷为一个固定值,引入了一个不随时间变化的随机扰动变量。然后,通过具体的数值实例验证了该映射的有效性,动力分析表明该映射具有复杂的动力学行为。最后,将该映射应用于信息传输技术,相较于其他混沌映射,该映射可以取得更小的误码率,表明该混沌映射更适用于混沌信息传输。

医学相关类专业人体系统解剖学课程教学模式的改革与实践

医学相关类专业是指除临床医学外的医学检验技术、医学影像技术、口腔技术、护理、预防医学、临床药学等众多专业,是我国高等医药院校教育的重要组成部分,涵盖面广,且招生人数众多。而医学相关类专业解剖学课程设置没有一个全国性的指导意见,各地院校在教学内容、教材选用上“百花齐放”。教学过程中也发现学生存在学习目的不明确、自主性差、对基础学科重要性认识不足等现象。

Comparisons between Movement Speed of Main Types of Dunes:A Case Study of Desert Areas in Hexi Region of Gansu Province

In desert areas in Hexi region,11 barchan dunes,6 chains of barchan dunes,6 pyramid dunes,6 parabolic dunes and 6 accumulated sand-belts were chosen to study their movement speed based on images obtained by Google Earth in various periods.The results show that among the dunes,the movement of the barchan dunes was the fastest,followed by the chains of barchan dunes,and only the tops of the pyramid dunes swayed,while the parabolic dunes and accumulated sand-belts hardly moved forward.The higher the barchan dunes(or the chains of barchan dunes) were,the slower the movement was.On the contrary,the higher the pyramid dunes were,the faster the swing was.There was a positive correlation between the movement speed of the barchan dunes and the average wind speed of sandstorms.

城投债信用利差影响因素分析

信用利差是影响城投债投资的重要因素。本文选取2018年1月2日至2020年3月18日存续的城投债作为样本,运用回归模型,对不同行政级别城投公司债券的信用利差影响因素进行分析。研究结果表明,当投资低行政级别城投公司债券时,需要特别关注城投公司所在地区的经济指标;当投资高行政级别城投公司债券时,应重点关注城投公司的财务资质。建议加强对低行政级别城投公司债券发行的监管,有效防范城投债信用风险。

Canonical Correlation Factors Causing the Formation of Accumulated Sand-belts along the Oasis Fringe in Hexi Corridor

Accumulated sand-belts refer to those formed along the oasis fringe,especially at the upwind location,due to the accumulation of sand blocked by farmland windbreak. In the 60 years since the foundation of new China,a lot of trees have been planted for desertification combating in northwest and north China,thus,accumulated sand-belts were formed at the upwind location. The formation and the ecological effects of the accumulated sand-belts along the oasis fringe is a new scientific concern. To study the formation causes of these belts in Hexi corridor,21 samples were selected,and the height / width of the belts,as well as the vegetation,soil,soil moisture and climatic factors were investigated. This paper analyzed the correlation between the height / width of the belts and the vegetation,soil,soil moisture and climatic factors using the methods of variance analysis,correlation analysis and canonical correlation analysis. The results indicate that: the accumulated sand-belts take a trend of being high and wide in the east whereas low and narrow in the west,and most of the parts tend to be stable; the species on the belts are dominated by Tamarix austromongolica,the vegetation cover and the pure vegetation cover of different dominant species on the leeward slope of the accumulated sand-belts vary significantly. The canonical correlation analysis shows that: the height and width of accumulated sand-belt is the interaction of precipitation,distance to the sand source,leeward vegetation cover and annual average wind speed. Moreover,the height of accumulated sand-belts are negatively correlated to the soil moisture at the depth of 30- 50 cm,air humidity and leeward vegetation cover,and the width of the belts is also negatively correlated with the distance to the sand source. The ecological effects of the accumulated sand-belts are both positive( stopping sands from moving into farmland,protective role as an obstacle)and negative( when the belts decay and activate one day,they will become the new sand sources). At present,there are no signs showing the negative effects of the belts. The ecological effects of the accumulated sand-belts are: firstly the protective role as an obstacle,and secondly to intercept and reduce the sands moving into farmlands.

Two Alternating Processes of Particle Size Distribution of Barchan Dunes at the Edge of the Oasis in Hexi Corridor, Gansu

Barchan dunes are a common type of dune. There are a lot of barchan dunes at accumulated sand-belts of the oasis edge of Hexi desert area of Gansu. What is characteristic of the particle size of barchan dunes? How is this particle size characteristic formed? Characteristics of particle size were analyzed in this paper by comprehensive investigation and sampling in Hexi Corridor desert area, and repeated sampling and determination in Minqin desert area. The results showed that:(1) The particle size of 0.25–0.05 mm and particle size of 0.5–0.25 mm were the main ingredients at the surface 0–5 cm depth of barchan dunes and barchan dune chains in desert area in Hexi Corridor of Gansu. Sand in Gulang desert area was relatively finer and the particle size was quite different from that of Jinchang, Linze, Jinta and Minqin desert area;(2) The particle size was changed from coarse to fine from the bottom to the top of the dunes in the main wind direction(NW) process. i.e. there was the most silt at the top of the dunes, followed by the middle of the leeward slope. The bottom of the windward slope had the most coarse sand, followed by the middle of the windward slope. The barchan dunes were changed from coarse to fine, then from fine to coarse from the bottom to the top of the dunes in the reverse wind direction(SE) process, i.e. there was the most silt in the middle of the windward slope, followed by the top of sand dunes. The bottom of the windward slope had the most coarse sand, followed by the middle of the windward slope. The standard deviation and coefficient of variation of sand dune particle size in the main wind direction process was larger, and the standard deviation and coefficient of variation of sand dune particle size in the reverse wind direction process was smaller;(3) The two processes of the main wind direction(NW) and the reverse wind direction(SE) led to alternating changes in particle size in various parts of the dunes. Two different conclusions on particle size distribution of barchan dunes in windward slope were due to the observation season differences.

Ecological Effects of Accumulated Sand-belts along the Oasis Fringe in Hexi of Gansu

The accumulated sand-belts have formed along the oasis fringe, especially at the upwind areas of the desert area in Gansu Hexi of China during the process of desert control in recent 60 years. The accumulated sand-belt is a byproduct of desertifieation combating through afforestation and barriers-setting. This pa- per analyzed the data （ including wind velocity/direction） of 21 sites on the accumulated sand-belt to evaluate its stability and ecological effects. The results showed that the accumulated sand-belt is in a stable state. It plays a significant role in weakening wind and this effect is enhanced with the increase of wind velocity. The height of accumulated sand-belt is an important factor characterizing its windproof function. When the wind velocity is higher than 2 m/s, the windproof area in the downwind places is 20 times greater than the height of the accumulated sand-beh. When the wind velocity is higher than 8 m/s, the wind velocity on the top of the accumulated sand-belt is less than that in the upwind open areas. When the air flow reaches the windward slope, its energy is released and reduced by uplifting along the slope and diversion towards the two wings. Wind deflector reduces the velocity of the prevailing wind on the windward slope.

Regulation of"P35/P25-CDK5-Tau"signaling pathway in hippocampi and prefrontal cortex of AD rats by electroacupuncture

Fifty SD rats were randomly divided into control,sham,model and electroacupuncture treatment group in this study.AD model rats were established by injecting ABas.ss into the hippocampi,while the same amount of saline was injected into the sham rats.AD model rats were treated by electroacupuncture stimulation at"Baihui"and"Shenshu"acupoints once a day for 10 days.The behavioral experiments results showed that the learning and memory ability of the AD rats were significantly decreased compared with the controls and shams,while depression-related behaviors were significantly increased.