按提交时间
按主题分类
按作者
按机构
  • 纤枝金丝桃化学成分研究

    分类: 生物学 >> 植物学 >> 应用植物学 提交时间: 2022-07-05 合作期刊: 《广西植物》

    摘要:为了探究滇产植物纤枝金丝桃的物质基础、寻找活性化合物,该文用80%乙醇对纤枝金丝桃地上部分浸渍提取,应用HP-20大孔吸附树脂、硅胶、葡聚糖凝胶、半制备高效液相等色谱技术对纤枝金丝桃的化学成分进行分离纯化,根据波谱数据鉴定化合物的结构。结果表明:从纤枝金丝桃中分离得到15个化合物,分别鉴定为attenuatumione G (1)、uralodin B (2)、chipericumin C (3)、2,5-二羟基-1-甲氧基氧杂蒽酮(4)、1,7-二羟基氧杂蒽酮(5)、1,7-二羟基-4-甲氧基氧杂蒽酮(6)、槲皮苷(7)、芹菜素-7-O-β-D-葡萄糖苷(8)、芹菜素􀀁-7-O-β-D-(6''-O-乙酰基)-葡萄糖苷(9)、木犀草素(10)、槲皮素(11)、白桦脂酸(12)、白桦脂酸甲酯(13)、白桦脂酮酸(14)、β-谷甾醇(15)。化合物1-14首次从该植物中分离得到。采用MTT法对化合物1-14进行体外抗乳腺癌活性测试,结果仅显示化合物3、6、13对2种乳腺癌细胞株MCF-7和MDA-MB-231有一定的抑制作用,它们的IC50值分别为48.6~123.5 μg·mL-1。该研究结果对综合开发利用纤枝金丝桃资源具有理论和应用意义。

  • 焦虑中的安全行为及其影响

    分类: 心理学 >> 临床与咨询心理学 提交时间: 2022-03-03

    摘要:

    安全行为是个体用于预防或者减轻恐惧后果的行为,它被认为是焦虑障碍维持的重要机制之一,也会对焦虑的暴露治疗产生干扰。安全行为与焦虑水平、焦虑相关的认知偏差存在联系,错误归因假说、注意资源偏离假说和行为信息假说对这种联系做出了解释。此外,安全行为的使用会削弱焦虑暴露治疗的效果、提高暴露的接受性。未来研究应对安全行为做出更清晰的界定和准确的测量,进一步改进研究设计,借鉴第三代行为治疗的理论解释安全行为与焦虑的关系;同时还需要考察安全行为的双重作用,开发聚焦于安全行为的治疗方案并评估其效果。

  • 儿童青少年同伴侵害与内化问题的双向关系:纵向研究的元分析

    分类: 心理学 >> 发展心理学 分类: 心理学 >> 教育心理学 提交时间: 2022-02-08

    摘要:

    本研究采用元分析技术探讨儿童青少年同伴侵害与内化问题的纵向关系,检验人际风险模型、症状驱动模型与相互作用模型在两者关系中的适用性。共纳入89篇文献,包含99个独立效应量,涉及被试70598人。随机效应模型分析结果表明,同伴侵害可以预测内化问题(β = 0.097, 95% CI [0.083, 0.110]),内化问题对同伴侵害也存在预测作用(β = 0.119, 95% CI [0.104, 0.135]),结果支持同伴侵害与内化问题的相互作用模型。同伴侵害对内化问题的预测作用中,年龄与侵害类型存在调节效应,测量时间间隔、侵害类型、评定方式与问题类型在内化问题对同伴侵害的预测中起调节作用,中西文化类型在两者相互预测模型中均不存在调节作用,各调节因素在同伴侵害及其亚类型外显侵害、关系侵害与内化问题双向关系中的作用基本一致。

  • 孤芳自赏还是乐于助人?员工自恋对亲社会行为的影响研究

    分类: 心理学 >> 管理心理学 提交时间: 2021-11-22

    摘要:本研究通过整合自恋双元理论和特质激活理论,探讨欣赏型自恋、敌对型自恋对员工亲社会行为的影响机制,深入分析了员工关系趋近型动机和关系回避型动机的中介作用以及任务相互依赖性的调节作用。通过对来自员工-同事二阶段配对的235份数据进行分析,结果发现:欣赏型自恋对员工亲社会行为具有显著的正向影响,敌对型自恋对员工亲社会行为具有显著负向影响;关系趋近型动机在欣赏型自恋与员工亲社会行为之间发挥着中介作用,关系回避型动机在敌对型自恋与员工亲社会行为之间没有发挥中介作用;任务相互依赖性不仅正向调节欣赏型自恋与员工关系趋近型动机的直接效应,而且还正向调节着欣赏型自恋通过关系趋近型动机对亲社会行为的间接效应。

  • Synergistic effects of multiple driving factors on the runoff variations in the Yellow River Basin, China

    分类: 地球科学 >> 地理学 提交时间: 2021-09-08 合作期刊: 《干旱区科学》

    摘要:River runoff plays an important role in watershed ecosystems and human survival, and it is controlled by multiple environmental factors. However, the synergistic effects of various large-scale circulation factors and meteorological factors on the runoff on different time-frequency scales have rarely been explored. In light of this, the underlying mechanism of the synergistic effects of the different environmental factors on the runoff variations was investigated in the Yellow River Basin of China during the period 1950–2019 using the bivariate wavelet coherence (WTC) and multiple wavelet coherence (MWC) methods. First, the continuous wavelet transform (CWT) method was used to analyze the multiscale characteristics of the runoff. The results of the CWT indicate that the runoff exhibited significant continuous or discontinuous annual and semiannual oscillations during the study period. Scattered inter-annual time scales were also observed for the runoff in the Yellow River Basin. The meteorological factors better explained the runoff variations on seasonal and annual time scales. The average wavelet coherence (AWC) and the percent area of the significant coherence (PASC) between the runoff and individual meteorological factors were 0.454 and 19.89%, respectively. The circulation factors mainly regulated the runoff on the inter-annual and decadal time scales with more complicated phase relationships due to their indirect effects on the runoff. The AWC and PASC between the runoff and individual circulation factors were 0.359 and 7.31%, respectively. The MWC analysis revealed that the synergistic effects of multiple factors should be taken into consideration to explain the multiscale characteristic variations of the runoff. The AWC or MWC ranges were 0.320–0.560, 0.617–0.755, and 0.819–0.884 for the combinations of one, two, and three circulation and meteorological factors, respectively. The PASC ranges were 3.53%–33.77%, 12.93%–36.90%, and 20.67%–39.34% for the combinations one, two, and three driving factors, respectively. The combinations of precipitation, evapotranspiration (or the number of rainy days), and the Arctic Oscillation performed well in explaining the variability in the runoff on all time scales, and the average MWC and PASC were 0.847 and 28.79%, respectively. These findings are of great significance for improving our understanding of hydro-climate interactions and water resources prediction in the Yellow River Basin.

  • A Temnospondyl Tooth from the Middle Triassic of the Ordos Basin, Shaanxi Province

    分类: 生物学 >> 动物学 提交时间: 2021-08-11 合作期刊: 《古脊椎动物学报》

    摘要:An isolated large temnospondyl tooth was discovered from the Middle Triassic Tongchuan Formation, Weibei Oilfield, Ordos Basin, Shaanxi Province of China. Compared with the teeth of crocodylomorphs, plesiosaurs and temnospondyls, the tooth can be referred to temnospondyl based on the following features: the crown is elongated and recurved with a circular cross-section; there are no denticles or carinae on the crown; well-marked apicobasal grooves are shown on the crown surface. This tooth represents the first temnospondyl found in the Middle Triassic Tongchuan Formation and is the youngest fossil record of temnospondyls in the North China Block.

  • 念青唐古拉山西段冰湖时空变化分析

    分类: 地球科学 >> 地理学 提交时间: 2021-06-13 合作期刊: 《干旱区研究》

    摘要:基于多源、多期遥感影像与DEM提取的冰湖数据,分析了念青唐古拉山西段1991—2017年冰湖不同维度的分布变化,在此基础上研究了冰湖数量、面积变化与气温、降水变化的关系。结果表明:(1)近年来,研究区的冰湖数量与面积均呈上升趋势,冰湖数量增加161个,面积增加1.185 km2。其中,1991—2006年平稳增长,2006—2017年大幅增长。(2)冰湖面积与数量在中高海拔范围内均呈增长趋势。新增冰湖主要分布在海拔5400~5700 m,冰湖数量占整体数量的72.41%。(3)分布在不同朝向冰湖的增长速率不同。西南向冰湖增长较为迅速,朝北向冰湖增长相对缓慢。(4)气温上升引起的冰川消融是冰湖生长的间接因素,降水是冰湖生长的重要因素。面积小的冰湖对气候的响应更灵敏,变化更显著,面积大的冰湖,变化幅度小,表明冰湖的动态变化与气候变化紧密相关。通过探究念青唐古拉山西段冰湖变化对冰湖溃决灾害的预测具有重要的指示意义。

  • Potential of Arbidol for Post-exposure Prophylaxis of COVID-19 Transmission

    分类: 医学、药学 >> 临床医学 提交时间: 2020-02-26

    摘要: Background: The efficient transmission of Severe Acute Respiratory Syndrome-2 Coronavirus (SARS-CoV-2) from patients to healthcare workers or family members has been a worrisome and prominent feature of the ongoing outbreak. On the basis of clinical practice and in-vitro studies, we postulated that post-exposure prophylaxis (PEP) using Arbidol is associated with decreased infection among individuals exposed to confirmed cases of COVID-19 infection. Methods: We conducted a retrospective case-control study on family members and health care workers who were exposed to patients confirmed to have SARS-CoV-2 infection by real-time RT-PCR and Chest CT from January 1 to January 16, 2020. We collected demographic information, work location of exposure, post-exposure prophylaxis information, and symptoms, if any, 24 days after exposure. The relation between post-exposure prophylaxis and infection in household contacts and healthcare workers were respectively analyzed. Results: 27 families and 124 health care workers had evidence of close exposure to patients with confirmed COVID-19. There were no differences in age, profession and sex distribution in the two groups with different post-exposure prophylaxis, table 1. Logistic regression based on the data of the family members and health care workers with Arbidol or Oseltamivir prophylaxis showed that Arbidol PEP was a strong protective factor against the development of COVID-19 (Odds ratio 0·011 , 95% CI 0·001-0·125, P=0·0003 for family members and Odds ratio 0·049, 95%CI 0·003-0·717), P= 0·0276 for health care workers). On the contrary, Oseltamivir was associated with an increase in COVID-19 infection (Odds ratio 20·446, 95% CI 1·407-297·143, P= 0·0271). Conclusions: Our findings suggest Arbidol could reduce the infection risk of the novel coronavirus in hospital and family settings. This treatment should be promoted for PEP use and should be the subject of further investigation.

  • Perspectives on Active Preventive Measures of Wuhan People against COVID-19 Epidemic at Home: A Comparative Study

    分类: 计算机科学 >> 计算机应用技术 提交时间: 2020-02-24

    摘要: Background:The COVID-19 Epidemic emerged in Wuhan, Hubei province, China. Ever since Wuhan lockdown on January 23rd, mass quarantines were exercised on Wuhan and other epidemic areas of China. We aimed to clarify how ordinary Wuhan people defend against COVID-19 epidemic at home through the Internet survey. Methods:A questionnaire survey, consisting of 30 questions were posted on the Internet. The following aspects were investigated: household preventive measures, self-monitoring of discomfort symptoms, immunity boosting against the epidemic, frequency and reasons of outgoing and mental status of the isolated people. The questionnaire was circulated on Wechat. We marked the areas based on the surveyed network IP addresses and categorized respondents into group A(Wuhan), B(Hubei Province excluding Wuhan ), C, and D based on the epidemic severity of their areas announced by Baidu.com at 17:00 on February 8, 2020. And a comparative study was conducted to illustrate how Wuhan people took the anti-COVID-19 strategies and how efficient these preventive measures were. Findings:In terms of discomfort symptoms, Wuhan, as Group A, had the lowest asymptomatic percentages (70.2%), compared to the average 78.5% (±7%). Considering the three typical symptoms for the COVID-19, i.e., cough, fever and fatigue, Wuhan (9.67%) greatly deviated from the average (7.68%). The fatigue was the most significant factor in the deviation, exceeding the average by 1.35%. In terms of household protection measures, most people or families were able to take effective protection measures with very low frequency of going out, but the percentage of those who took this practice was obviously smaller in Wuhan and Hubei Province. From the aspect of going out, most of the people in Wuhan only went out for shopping and work, with a small number of people for social gathering. In terms of immunity boosting, compared with Group C and D, it was relatively lower in Wuhan. Overall, most people chose to enhance their immunity through regular schedule, exercise, sufficient nutrition. Only 33.44% of people in Group A did not go out, and 59.97% had to go out for living supplies, which was the highest level among the four groups. However, the percentage of people who went out for work and unnecessary activities remains the lowest while 1% of the population went out for public welfare activities, higher than other groups. Worry about the family health topped all the parameters for all the groups. Among them, Wuhan has reached a maximum of 49.61%, higher than the average level of 36.62% (± 10.69%). Mental status except for feeling bored and lonely were the highest in Wuhan. Suggestions:When the epidemic prevention and control is still in a sticky state, and Wuhan started a stricter control measure, the closed management of communities, on Feb 11, 2020, it is expected that our findings can provide some insights into the current household preventive actions and arouse more attentions of the public to some ignored preventive precautions. Unnecessary outgoing should be strictly abandoned. Regular schedule, exercises and nutrition were the top 3 measures participants would choose to enhance their own immunity system. It seems that people in Wuhan would choose nutrition and regular scheduler rather than exercises as the primary immunity-boosting ways. Exercise should be especially advocated as an effective way to enhance the immunity system. In terms of physical condition, people in Wuhan should take more active measures when symptoms occurred. The mentality is also an important aspect requiring intensive attention with the conduct of stricter control management in Wuhan while the rest groups gradually resume to work and ordinary life.

  • 新型冠状病毒(2019-nCoV)时空数据集及其典型应用

    分类: 测绘科学技术 >> 摄影测量与遥感技术 分类: 医学、药学 >> 预防医学与公共卫生学 分类: 统计学 >> 生物与医学统计学 提交时间: 2020-02-19

    摘要: 目前,新型冠状病毒(2019-nCoV)疫情正受到全球各科研工作者的广泛关注。然而,当前尚没有一个官方的渠道对2019-nCoV疫情数据进行实时开源,为了促进本次疫情相关的科研工作,本研究旨在为广大科研工作者提供权威的、开放的和多尺度的新型冠状病毒(2019-nCoV)时空数据集,为疫情监测、防控、预测和预警提供重要的数据来源。此外,该数据集还能应用于2019-nCoV疫情的多尺度、多时相制图和可视化,为疫情的空间分布、演化、趋势分析和模拟预测提供指导。

  • 新型冠状病毒(2019-nCoV)时空数据集及其典型应用

    分类: 测绘科学技术 >> 摄影测量与遥感技术 分类: 统计学 >> 生物与医学统计学 提交时间: 2020-02-17

    摘要: 目前,新型冠状病毒(2019-nCoV)疫情正受到全球各科研工作者的广泛关注。然而,当前尚没有一个官方的渠道对2019-nCoV疫情数据进行实时开源,为了促进本次疫情相关的科研工作,本研究旨在为广大科研工作者提供权威的、开放的和多尺度的新型冠状病毒(2019-nCoV)时空数据集,为疫情监测、防控、预测和预警提供重要的数据来源。此外,该数据集还能应用于2019-nCoV疫情的多尺度、多时相制图和可视化,为疫情的空间分布、演化、趋势分析和模拟预测提供指导。

  • 父子(女)间面孔相似性的进化适应机制及其影响

    分类: 心理学 >> 社会心理学 提交时间: 2019-11-11 合作期刊: 《心理科学进展》

    摘要: 由于受精和孕育过程发生在母亲体内,人类受孕具有一定的隐蔽性,同时人类早期社会存在着通奸行为,因而,父亲面临着父亲身份不确定性的风险。为了应对这种风险,人类男性在生活中往往会寻求一些能表征父亲身份的线索,其中亲子间面孔相似性被证明是辨别个体间是否存在基因关联(或血缘关系)的有效线索之一。morph软件合成、第三方评定以及当事人的主观评定是研究亲子间面孔相似性的三种基本范式。以往的研究表明当父子(女)间面孔相似性越高时,父亲对子女的亲子投资水平越高,父亲感知到的焦虑水平越低,父亲的身体也越健康,与此同时,当父子(女)间面孔相似性越高时,父亲对女儿会表现出更高的性厌恶水平。未来的研究可以进一步关注文化因素在该效应中的调节作用、影响亲子间面孔相似性感知的因素以及探寻新的研究范式以提高研究的内部效度和外部效度。

  • 换流站接地网替代直流接地极运行的方案研究

    分类: 动力与电气工程 >> 电气工程 提交时间: 2019-03-05 合作期刊: 《电气工程学报》

    摘要:直流输电无接地极运行有助于尽早实现双极送电,换流站接地网替代直流 接地极是目前最有效的措施。换流站接地网替代直流接地极情况下可能存在人身和二 次设备安全问题、变压器直流偏磁危害、接地网发热和腐蚀问题。论文对这些问题进 行逐一分析,最后综合各影响因素提出了直流输电控制策略的要求,即单极故障联跳 双极、不平衡电流控制和双极同步解闭锁。研究工作为直流输电新型的无接地极运行 方式提供了有效参考,相关控制策略在南方电网普侨特高压直流输电工程中得到了良 好的应用。

  • 基于基准态的断路器可靠性分析方法

    分类: 动力与电气工程 >> 电气工程 提交时间: 2019-03-05 合作期刊: 《电气工程学报》

    摘要:利用基准态的概念,针对高压断路器的可靠性分析,提出了一套完整的理 论方法。首先,根据基准态建立过程中选取的关键状态量,开展关键状态量分析技术, 深入分析关键状态量性能的好坏。并引入电网强度、设备强度和设备老化程度 3 个维 度的性能,评判设备分性能状况,得到设备基准态值。接着,基准态预测过程作为基 准态分析的延伸,以经典统计学理论获取预测模型,为设备基准态发展趋势提供参考。 最后,可靠性分析则是基准态分析的最终目的和落脚点,利用经典可靠性理论,构建 可靠度模型,绘制设备可靠性曲线。从曲线中可方便获取设备当前及未来的可靠度, 为用户的运维及检修工作提供决策支持。

  • 木聚糖酶和甘露聚糖酶在毕赤酵母中的共表达及产酶分析

    分类: 生物学 >> 生物工程 提交时间: 2018-11-24 合作期刊: 《中国生物工程杂志》

    摘要:木聚糖酶和甘露聚糖酶是两种重要的半纤维素酶,也是两种重要的饲用酶制剂,本研究利用毕赤酵母表达系统中的体外串联表达盒构建多拷贝的方法构建了木聚糖酶DSB和甘露聚糖酶ManA共表达重组质粒pPICZαA/DSB-ManA,将该重组质粒电转化至宿主菌毕赤酵母X33中获得共表达两种酶的重组菌X33/ DSB-ManA,实现了两种酶的共分泌表达,经诱导表达后木聚糖酶和甘露聚糖酶的酶活分别为273.6 U/mL和256.8 U/mL,为单独表达重组菌X33/DSB和X33/ManA酶活的30.4%和73.4%。酶学性质的分析显示DSB和ManA的最适反应温度均为75℃,在45℃-75℃范围内具有较好的温度稳定性,酶活可保持最高酶活的60%以上;DSB最适pH为6.5,ManA最适pH为6.0,在pH 3.0、40℃条件下,ManA处理1 h能保持最高酶活的80%以上,DSB处理1 h时能保持最高酶活的50%以上;DSB和ManA对多种金属离子和化学试剂(浓度为1 mM)具有较好的耐受性,均可保留60%以上的酶活力。本研究利用单一菌株成功完成了不同酶的共表达,为复合酶饲料添加剂的生产和应用研究提供了一定的理论依据。

  • BIM在铁路四电工程的适应性分析

    分类: 土木建筑工程 >> 土木建筑工程基础学科 提交时间: 2018-10-26 合作期刊: 《土木建筑工程信息技术》

    摘要:目前的BIM应用与各种新兴信息技术相结合,在多领域均有其身影,而铁路四电工程因其多专业交叉、施工难、跨自然区域大等特点,迫切地需要BIM来提高设计、施工的效率。为使BIM在铁路四电工程中更好地应用

  • BIM在铁路四电工程的适应性分析

    分类: 土木建筑工程 >> 土木建筑工程基础学科 提交时间: 2018-10-26 合作期刊: 《土木建筑工程信息技术》

    摘要:目前的BIM应用与各种新兴信息技术相结合,在多领域均有其身影,而铁路四电工程因其多专业交叉、施工难、跨自然区域大等特点,迫切地需要BIM来提高设计、施工的效率。为使BIM在铁路四电工程中更好地应用

  • 工程管理专业BIM虚拟仿真实训平台构建研究

    分类: 土木建筑工程 >> 土木建筑工程设计 提交时间: 2018-07-18 合作期刊: 《土木建筑工程信息技术》

    摘要:推行实践教学改革,提升学生的工程实践能力和专业综合素质是全面落实国家中长期教育改革的重要举措,是培养复合型、应用型、创新创业人才的重要手段。但是,目前实践教学存在深度不够,关联性不强等问题。普遍采用的去建筑企业或工程项目现场实习、实践教学方式,又存在安全隐患且受时间和空间的限制。本文首先总结了BIM在国内外教育领域中的应用现状,然后提出BIM虚拟仿真实训平台的构建目标,设计了总体系统结构图,将平台分为建筑结构设计实训子平台、施工虚拟模拟仿真实训子平台、BIM工程造价实训子平台、BIM一体化项目管理实训子平台等,最后给出了实训平台的云架构示意图原理,列举了主要的软硬件构成,以供同行建立类似实训平台参考。

  • 基于BIM的管线数字化管理系统在杨泗港长江大桥工程中的应用研究

    分类: 土木建筑工程 >> 土木建筑工程设计 提交时间: 2018-07-18 合作期刊: 《土木建筑工程信息技术》

    摘要:随着城市现代化的不断发展,当前老城区地下管线信息管理存在着管线权属关系复杂、地下管线布置不清晰等问题。为了解决这些问题,提出了构建基于BIM的地下管线数字化管理系统,对其在管线项目全过程起到的作用进行了分析。最后,将该地下管线数字化管理系统应用于武汉杨泗港长江大桥项目中,实现对地下管线的信息分类、信息检索、信息可视化和碰撞检测功能。该系统切实提高了管理效率,增加了项目收益,为BIM技术结合地下管线信息管理提供了有益借鉴。

  • 云南被子植物新资料

    分类: 农、林、牧、渔 >> 植物保护学 提交时间: 2018-07-18 合作期刊: 《广西植物》

    摘要:植物资源调查是探讨系统发育、植物区系进化历史和亲缘关系的基础,是我国植物研究工作的重要任务之一。虽然我国在植物资源调查方面有了丰富的积累,并以《中国植物志》和各地方植物志为代表,但部分偏远地区的植 物资源状况仍然缺乏数据。通过形态特征比较分析,发现云南省被子植物新记录 3 种。柳叶黄肉楠 (ActinodaphnelecomteiAllen)原分布四川、贵州、广东(乳源)、广西,云南省丘北县为其新记录点;八角樟(Cinnamomum ilicioidesA.Chev.)原分布广东、海南、广西,越南北部,云南省西双版纳傣族自治州勐腊县为其新记录点;贵州山 核桃(CaryakweichowensisKuangA.M.Lu exChangetLu)原分布贵州安龙、望谟、册亨、兴义等,云南省丘北县为 其新记录点。柳叶黄肉楠和八角樟在云南的新分布点是对我国樟科薄弱地带的补充,为分析滇产原始种类对相关属的起源发生和中国樟科分类学研究提供了新材料;贵州山核桃在物种层面上对确定贵州山核桃与喙核桃 (Annamocaryasinensis)两者之间的联系提供了新的案例,并为云南发展山核桃(C.cathayensis)生产提供了种质资源。