铁皮石斛多糖调控线虫寿命及抗氧化作用的研究

摘 要: 目的 基于秀丽隐杆线虫自然衰老模型, 探讨铁皮石斛多糖(Dendrobium candidum polysaccharides, DOP)抗衰老作用及其机制。方法 将秀丽隐杆线虫野生型N2随机分为对照组和铁皮石斛多糖组(低、中、高), 观察铁皮石斛多糖对线虫N2寿命、运动能力和咽泵能力的影响; 通过检测氧化应激、抗氧化酶试剂盒以及活性氧评估铁皮石斛多糖对N2线虫抗氧化能力的影响。基于skn-1基因缺陷型突变株(EU1)线虫及带有荧光标记的转基因线虫CL2166分析铁皮石斛多糖延长健康寿限的可能作用途径; 采用实时荧光定量聚合酶链反应技术测定铁皮石斛多糖作用下线虫抗氧化、胰岛素信号途径相关基因转录水平。结果 铁皮石斛多糖中剂量组(250 μg/mL)可显著延长线虫N2的寿命, 平均延寿率达12.73%, 可显著提高运动、咽泵、抗氧化应激能力; 显著提高过氧化氢酶(catalase, CAT)、超氧化物歧化酶(superoxide disumutase, SOD)活性和谷胱甘肽(glutathione, GSH)含量, 降低活性氧(reactive oxygen species, ROS)水平和丙二醛(malondialdehyde, MDA)含量; 铁皮石斛多糖干预处理对skn-1基因缺陷线虫的延寿效果缺失; 但能够增强CL2166线虫的荧光强度; 同时上调sod-5、sod-3、ctl-1、ctl-2、daf-16和skn-1基因的表达水平, 下调daf-2基因的表达水平。结论 铁皮石斛多糖可能通过激活Nrf2/SKN-1和DAF-16途径拮抗氧化应激从而延缓线虫衰老。     

智能合约的合约安全和隐私安全研究综述

区块链作为对等网络中的一种分布式账本技术,集成了密码学、共识机制、智能合约等多种技术,提供一种新型信任体系构建方法.智能合约具有公开透明、实时更新、准确执行等显著特点,在区块链中为信息存储、交易执行和资产管理等功能的实现提供了更安全、高效、可信的方式.但是,智能合约本身仍然存在安全问题,影响了区块链技术的进一步推广使用.所以,近年来围绕智能合约安全问题的相关研究比较多,为了帮助相关人员更好地理解和掌握其中的研究思路,本文采用Mapping Study方法,通过收集2015年以来公开发表的关于智能合约安全问题的各类文献,并进一步通过文献筛查、问题设置、信息提取、结果获取和分析等步骤,总结智能合约安全相关研究的现状和未来发展趋势如下:(1)目前智能合约自身面临的安全问题和挑战主要体现在合约安全和隐私安全两方面(问题和挑战).在调查的45篇文献中,有29篇文献针对合约安全,16篇文献针对隐私安全;(2)智能合约安全保障目前采用的方法主要包括形式化验证、模糊测试、零知识证明、可信执行环境等(保障方法);(3)针对合约安全的研究目前主要集中在合约实现、测试阶段,而针对智能合约设计、部署及运维阶段的研究比较少;针对隐私安全的研究主要集中在合约数据隐私保护,而针对合约代码隐私安全的比较少(覆盖范围);(4)智能合约安全保障研究目前主要从合约实现人员、合约测试人员的角度进行,而从合约维护人员和合约用户角度展开的研究较少(研究角度);(5)未来研究应该围绕智能合约的全生命周期的每个阶段安全问题进一步推进,先验方法和后验方法、定性方法和定量方法、静态方法和动态方法的结合是大势所趋(发展趋势).综上,本文通过调研发现了现有研究的不足,并建议了进一步的研究方向.     

Contribution of moderate overall coal-bearing basin uplift to tight sand gas accumulation: case study of the Xujiahe Formation in the Sichuan Basin and the Upper Paleozoic in the Ordos Basin, China

Tight sand gas is an important unconventional gas resource occurring widely in different petroleum basins.In coal-bearing formations of the Upper Triassic in the Sichuan Basin and the Carboniferous and Permian in the Ordos Basin,coal measure strata and tight sandstone constitute widely distributed source-reservoir assemblages and form the basic conditions for the formation of large tight sand gas fields.Similar to most tight gas basins in North America,the Sichuan,and Ordos Basins,all experienced overall moderate uplift and denudation in MesoCenozoic after earlier deep burial.Coal seam adsorption principles and actual coal sample simulation experiment results show that in the course of strata uplift,pressure drops and desorption occurs in coal measure strata,resulting in the discharge of substantial free gas.This accounts for 28%—42%of total gas expulsion from source rocks.At the same time,the free gases formerly stored in the pores of coal measure source rocks were also discharged at a large scale due to volumetric expansion resulting from strata uplift and pressure drop.Based on experimental data,the gas totally discharged in the uplift period of Upper Paleozoic in the Ordos Basin,and Upper Triassic Xujiahe Formation in the Sichuan Basin is calculated as(3-6) × 10~8 m~3/km~2.Geological evidence for gas accumulation in the uplift period is found in the gas reservoir analysis of the above two basins.Firstly,natural gas discharged in the uplift period has a lighter carbon isotope ratio and lower maturity than that formed in the burial period,belonging to that generated at the early stage of source rock maturity,and is absorbed and stored in coal measure strata.Secondly,physical simulation experiment results at high-temperature and high-salinity inclusions,and almost actual geologic conditions confirm that substantial gas charging and accumulation occurred in the uplift period of the coal measure strata of the two basins.Diffusive flow is the main mode for gas accumulation in the uplift period,which probably reached 56 × 10~(12)m~3 in the uplift period of the Xujiahe Formation of the Sichuan Basin,compensating for the diffusive loss of gas in the gas reservoirs,and has an important contribution to the formation of large gas fields.The above insight has promoted the gas resource extent and potential of the coal measure tight sand uplift area;therefore,we need to reassess the areas formerly believed unfavorable where the uplift scale is large,so as to get better resource potential and exploration prospects.     

Electronic and optical properties of superhard C–N materials: a first-principles study

The geometrical, electronic, and optical properties of 11 superhard C–N structures were investigated using density functional theory. The lattice parameters and energy bandgaps were calculated and compared with theoretical reports in literature. The absorption, reflectivity, refractivity, and conductivity were predicted and analyzed. It was found that only the \(\textit{Im2}\text {-CN}_{2}\) structure exhibits obvious absorption in the infrared and visible light range, whereas the other structures show no obvious absorption with small reflectivity but large refractivity in this range, indicating that these superhard C–N materials could be used for light harvesting, wear resistance, antireflection, or transparency applications depending on their structure. The various characteristics of the optical properties are explored based on the density of states (DOS) and partial DOS.     

铁皮石斛水提物通过激活SKN-1转录因子延长秀丽隐杆线虫寿命作用及机制研究

目的 观察铁皮石斛水提物(Dendrobiumofficinalewaterextract,DOWE)延长秀丽隐杆线虫(Caenorhabditis elegans, C. elegans)寿命作用及可能机制。方法 将野生型(N2)线虫随机分为对照组、DOWE组[高剂量组(1000μg/mL)、中剂量组(500μg/mL)、低剂量组(250μg/mL)],观察DOWE冻干粉(最终生药量0.0376 g/g)对N2线虫寿命、运动和咽泵能力的影响;通过检测氧化应激、热应激能力评估DOWE对N2线虫应激能力的影响,检测活性氧(reactive oxygen species, ROS)、过氧化氢酶(catalase, CAT)、抗氧化基因等指标评价DOWE对N2线虫抗氧化能力的影响;通过转基因线虫(LD1、CL2166)核转位情况及SKN-1转录因子相关基因表达情况来探究其在DOWE延长N2线虫寿命中的作用;通过转基因线虫(LG348、LG357)荧光表达情况来探究DOWE延长N2线虫寿命所依赖的SKN-1转录因子类型;通过检测有丝分裂原激活蛋白激酶(p38mitogen activated ...     

居住建筑光热系统一体化技术问题研究

介绍了太阳能热水器在世界住宅建筑中的应用案例,从技术和安装施工方面提出了我国住宅建筑太阳能一体化存在的问题,并借鉴国外发展经验提出了相应的建议,以期对国内太阳能热利用技术及太阳能与建筑一体化技术的发展提供基本思路.     

深度学习在手写汉字识别中的应用综述

手写汉字识别（Handwritten Chinese character recognition,HCCR）是模式识别的一个重要研究领域,最近几十年来得到了广泛的研究与关注,随着深度学习新技术的出现,近年来基于深度学习的手写汉字识别在方法和性能上得到了突破性的进展.本文综述了深度学习在手写汉字识别领域的研究进展及具体应用.首先介绍了手写汉字识别的研究背景与现状.其次简要概述了深度学习的几种典型结构模型并介绍了一些主流的开源工具,在此基础上详细综述了基于深度学习的联机和脱机手写汉字识别的方法,阐述了相关方法的原理、技术细节、性能指标等现状情况,最后进行了分析与总结,指出了手写汉字识别领域仍需要解决的问题及未来的研究方向.     

Accumulative Time Based Ranking Method to Reputation Evaluation in Information Networks

Journal of Computer Science and Technology - Due to over-abundant information on the Web, information filtering becomes a key task for online users to obtain relevant suggestions and how to extract...