Application of single poise counterweight method in adjusting grinding uniformity of silicon wafer

为提高硅片研磨的均匀性,提出了一种通过改变调节砝码位置的新方法。对单砝码配重法的原理、步骤及物理模型进行了详细的论述,并基于lAbVIEW软件对该方法进行了可视化。在精密研磨抛光机上进行实验,并用膜厚仪进行均匀性测量。结果表明:在给定的条件下使9.9 CM硅片的均匀性从单靠自重研磨的20μM提高到用配重法调节后的3μM,显著提高了硅片研磨的均匀性。单砝码配重法为解决硅片研磨均匀性问题提供了一种既精确又简便的方法。To improve the grinding uniformity of silicon wafer,this paper proposed a new approach by changing the position of poise.The principle,procedure and physical model of the single poise counterweight method were described in detail,and then the visualization of this method basing on LabVIEW software was realized.Experiment was carried out on a precision grinding and polishing machine,and the thickness uniformity was measured on the thickness monitor.Experimental results show that the uniformity of three inches silicon wafer is improved from 20 μm to 3 μm comparing to conventional deadweight grinding,so the grinding uniformity of silicon wafer is enhanced markedly.Therefore,the single poise counterweight method provides a precise and convenient way to solve the grinding uniformity problem of silicon wafer.航空科学基金(20110868001

间充质细胞外泌体促进小鼠胰岛内皮细胞血管生成的研究

目的探讨间充质细胞（MSC）外泌体对低氧条件下胰岛内皮细胞（MS-1）血管生成的影响。方法 MSC无血清低氧条件培养48 h,超滤离心法富集条件培养基中的外泌体,采用电镜和Western Blot的方法进行鉴定;通过血管形成试验比较分析不同条件下:常氧培养组（NOR组,21%O2、5%CO2）、低浓度氧培养组（HYP组,2%O2、5%CO2）、外泌体+低浓度氧共培养组（HYP+EXO组,2%O2、5%CO2）,MS-1细胞的血管形成能力;image J软件分析血管形成长度;PCR、Q-PCR检测血管内皮生长因子（VEGF） RNA水平的表达,Western Blot检测VEGF、HIF1α蛋白水平表达以及mTOR信号通路激活情况。采用单因素方差分析和SNK-q检验统计学分析。结果超滤离心法富集的MSC条件培养基中的外泌体,大小为30～100 nm,表达CD9,CD63,CD81等外泌体表面标志物;血管形成试验结果显示,低氧促进MS-1血管生成,HYP+EXO组形成明显的血管网状结构;HYP+EXO组血管形成相对长度（2386.0±137.7）像素与NOR组（393.3±174.2）像素和HYP组（1467.0±230.0）像素相比增强,差异有统计学意义（t=12.30,P=0.0065;t=15.74,P=0.0040）; PCR结果显示,HYP+EXO组VEGF相对表达量（20.26±9.972）较常氧对照组（1.000）和低氧组（6.521±3.501）均增强,差异有统计学意义（t=5.462,P=0.0009;t=4.238,P=0.0038）;同时,Western Blot结果显示VEGF蛋白水平表达升高,HIF1-α表达上调,mTOR发生磷酸化。结论 MSC外泌体可促进低氧条件下的小鼠胰岛内皮细胞血管生成。MSC外泌体可能通过上调HIF1-α,调节VEGF表达,激活mTOR信号通路,促进胰岛内皮细胞血管生成。国家自然科学基金青年项目(81601618);;福建省自然科学基金面上项目(2016J01582、2016J01580、2018J01349);;福建省科技创新联合资金重大项目(2017Y9127

骨髓间充质细胞联合PDMS支架构建移植胰岛微环境的实验研究

目的为了提高移植胰岛的活性和功能,构建适合移植胰岛生存的微环境。方法采用聚二甲基硅氧烷(PDMS)和氯化钠晶体构建三维支架,联合骨髓间充质细胞(MSCs)、纤维蛋白和胰岛共同构建迷你\"人工胰腺\"。采用链脲佐菌素(STZ)诱导的糖尿病大鼠移植模型评价效果,将\"人工胰腺\"移植到糖尿病大鼠大网膜内,对照组行假手术,术后隔天监测移植大鼠血糖水平;数据采用t检验和曼-惠特尼U检验。结果用PDMS构建的三维巨孔支架,支架内可见大量不规则孔洞空间。胰岛和MSCs可成功装载入支架内,HE染色结果显示,支架孔内存在胰岛,胰岛周围包绕有MSCs。糖尿病大鼠大网膜内移植结果显示,移植后各时间点(1,3,5,7 d),\"人工胰腺\"移植组糖尿病大鼠血糖水平分别为(278.70±86.06) mg/dl、(323.50±44.29) mg/dl、(283.30±74.00) mg/dl、(304.80±13.33) mg/dl,较假手术对照组(606.00±52.40) mg/dl、(589.70±55.78) mg/dl、(615.00±54.84) mg/dl、(630.30±48.17) mg/dl均降低,差异具有统计学意义(t=7.96、9.15、8.82,U=0.00,P均<0.01)。结论 MSCs联合PDMS三维支架构建的微环境,可为移植胰岛提供生存的环境,为临床开展胰岛移植提供新的策略

磷与水分互作的根土界面效应及其高效利用机制研究进展

【目的】磷与水分利用率低是制约作物生产的重要因子。磷必须在水分的作用下通过根土界面才能被作物吸收利用,磷和水分在根土界面的互作效应是影响其高效利用的关键环节。本文以根际为核心,重点综述了磷与水分在根土界面的互作机制,并剖析了通过强化根土界面磷与水分的协同,提高农田水肥资源利用效率的根际调控途径。【主要进展】根系的形态和生理变化深刻影响磷和水分的有效性,而根系生长和根际过程依赖于植物的营养和水分供应状况,作物根层适宜的水分和养分供应水平能最大化根系和根际过程的效率,从而促进作物对磷与水资源的高效利用。作物根系除了能对根层土壤中磷和水分的系统供应做出响应外,也对局部磷和水分的变化产生形态和生理上的反应。根系响应磷和水分的表型可塑性与植物激素的调控作用密切相关。ABA、乙烯、NO均参与磷和水分互作的调控过程,质外体p H在调控植物抵抗水分胁迫过程中具有重要作用,并与植物的营养状况密切相关。【展望】深入理解根土界面水与磷互作的协同过程及其调控机制是提高集约化作物体系水分和磷利用效率的关键。未来的研究方向与重点包括:进一步揭示磷和水分互作与激素信号途径之间的关系,探明农田生态系统中磷与水分互作的根土界面效应及其高效利用的协同机制,建立不同种植条件下水肥资源高效利用的根际调控途径,为通过根系、根际的定向调控,发挥其生物学潜力,提高集约化农田水肥资源的利用效率提供科学依据

Research on user privacy leakage in mobile social messaging applications

智能移动终端以其强大的处理能力和丰富的功能应用迅速得到普及,成为人们日常生活中存储和处理个人信息必不可少的工具.在众多的移动应用中,社交通信类应用致力于为人们提供便捷的日常通信服务,这类应用相比移动通信运营商提供的传统短消息服务更加经济实用,同时提供多媒体通信方式进一步增强用户的社交体验,从而迅速地被广泛接受.为了进一步巩固自身的用户群体,增加用户黏度,这类应用在其内部增添了一种称为“通讯录匹配”的功能.该功能能够向用户推荐其手机通讯录中已经注册过该应用的线下联系人为好友,从而帮助用户快速地将线下社交圈移植到应用线上.然而,用户在获得便利的同时也面临着潜在的隐私泄露风险.文中首次提出了一种独立于各移动智能平台的、能有效利用移动社交通信类应用的通讯录匹配功能实现大规模收集用户私人数据的方法,该方法能够收集到存储于目标应用服务器的用户个人资料,包括手机号码和虚拟应用账户资料以及两者之间的映射关系;其次,为了获取规模更大,内容更全面、更真实的用户资料,文本提出了基于多款社交通信类应用的跨应用整合分析方法以及针对不同应用来源的用户资料数据一致性与真实性分析;最后,在信息获取和分析方法的指导下,文中建立了利用上述漏洞的原型系统,进行了大规模数据实验,最终验证了上述方法的有效性和良好的可扩展性.Due to their powerful processing capability and diverse equipped applications, smart mobile devices have become the rage to store and manage personal information in people's daily work and lives. This dominant prevalence to a large extent benefits from those various kinds of applications running on the mobile platform. Among them, a staple category of applications have devoted themselves to provide daily social communication service for regular users, which called social messaging applications. It offers users wonderful user experience and various ways of communication via multi-media, such as text, audios, pictures and videos. Comparing to the SMS and MMS, social messaging applications are more widely accepted for their fantastic social experience and economical manner. In order to aggregate user basis and increase their stickiness, social messaging applications incorporate a new functionality component called Address Book Matching which recommends registered user accounts from the address book in one's phone and facilitates the transplantation of users' social circle from offline to online. However, this novel feature brings not only convenience but also potential privacy leakage issues. This paper proposes a novel platform-independent method to collect users' personal information in large scale, including their phone numbers and the corresponding application accounts, by means of abusing Address Book Matching. Besides, based on the user information we obtained, two approaches of further analysis are presented, i. e. single application analysis and cross application integration. In order to pursue more authentic user information, we propose the conformity and authentic analysis of user personal information gathered from different social messaging applications. Finally, on the basis of our collection and analysis approaches, we also build up a prototype system to leverage above mentioned vulnerability. The experiment results demonstrate the effectiveness of our method of taking advantage of Address Book Matching to collect user personal information from social messaging applications in large scale

An anti-obfuscation method for detecting similarity among Android applications in large scale

随着代码混淆、加壳技术的应用,基于行为特征的Android应用相似性检测受到的影响愈加明显.提出了一种抗混淆的大规模Android应用相似性检测方法,通过提取应用内特定文件的内容特征计算应用相似性,该方法不受代码混淆的影响,且能有效抵抗文件混淆带来的干扰.对5.9万个应用内的文件类型进行统计,选取具有普遍性、代表性和可度量性的图片文件、音频文件和布局文件作为特征文件.针对3种特征文件的特点,提出了不同内容特征提取方法和相似度计算方法,并通过学习对其相似度赋予权重,进一步提高应用相似性检测的准确性.使用正版应用和已知恶意应用作为标准,对5.9万个应用进行相似性检测实验,结果显示基于文件内容的相似性检测可以准确识别重打包应用和含有已知恶意代码的应用,并且在效率和准确性上均优于现有方案.Code obfuscation exerts a huge impact on similarity detection among Android applications based on behavior characteristics. In order to deal with the situation, we propose a novel way of similarity detection among Android applications based on file content characteristics, which computes the similarity of file content features and can be applied to large-scale scenario in real world. Our method is not subject to code obfuscation or file obfuscation. We choose to utilize the characteristics of image, audio and layout files which are shown in our statistics as the most representative features in Android applications. Meanwhile, different weights are given to these features through machine learning, which further enhances the accuracy of our method. In addition, we implement a prototype system and particularly optimize each step to speed up the calculation, making our system suitable for large-scale scenario and give a good calculation performance. The experiments dataset contains 59 000 applications. And for both legitimate application and malware applications, our system successfully detects those repackaged pirate applications and those with the similar malicious component, which prove the effectiveness of our method. The experiment results demonstrate that similarity detection based on file content characteristics could resist the file obfuscation and give better performance in both accuracy and efficiency

一氧化氮在植物发育及植物–微生物互作中的作用机制研究进展

一氧化氮(NO)作为高活性信号分子,是调控植物生长发育的关键因子。NO可提高植物对非生物胁迫及生物胁迫的抗性,增强植物的免疫能力。最新的研究表明,NO在植物根系与微生物的互作过程中发挥着重要作用,NO能够促进植物根系与根瘤菌及丛枝菌根真菌形成共生体,从而提高植物对土壤氮磷养分的获取。NO作为信号物质调控植物对生物胁迫和非生物胁迫抗性的主要机制有:1) NO与活性氧系统互作,调节活性氧的水平,缓解氧化应激反应对植物的伤害;2) NO通过蛋白质的翻译后修饰,对植物免疫及抗逆过程进行调节;3) NO与多种植物激素互作,参与激素对植物生长发育的调节过程。而且NO可促进共生体的形成及发育相关基因表达,抑制免疫基因表达,通过NO与植物球蛋白(phytoglobin)的循环维持共生体的氧化还原水平及能量状态,从而促进植物–微生物共生关系。以往关于NO的研究主要集中在前3个方面,有关NO在植物–微生物互作中的作用机制的研究较少,NO参与植物–微生物互作机制的研究亟待加强。揭示NO增强植物抗逆性及其调节根系发育的机制,深入探究NO调控植物–微生物互作的机理,对于提高集约化作物生产体系中养分利用效率和作物生产力具有重要的理论与实践意义

黄土区不同地类土壤容水量与渗水率的试验研究/Soil Infiltration Rate and Soil Moisture Content Under Different Land Use of Loess Region[J]

通过对研究区12种不同土地利用类型土壤容水量和渗水率的试验研究,分析了相同土地利用和不同土地利用方式下土壤容水量和渗水率的差异。结果表明,相同土地利用方式下,农坡地土壤容水量差异约1倍,差异较大;旱梯田土壤容水量差异可达35.23%,差异明显;荒坡地相差仅为5.84%,差异较小;沟台地差异不明显。不同土地利用方式下,土壤入渗性能差异显著。在连续入渗180min时,YL（人工杨树林地）、HF（荒地整地后封管1a自然草地）、NT（人工柠条林）、SJ（人工沙棘林）、YS（人工油松林）、ZK（针阔混交林）土壤容水量分别是HP（荒地）的108.19%,173.43%,157.76%,192.28%,93.64%和129.67%。沙棘林、柠条林等人工灌木林地的土壤容水量大于人工乔木林地。荒坡经过隔坡水平台整地封闭保护自然恢复植被1a后,土壤容水量高于多数乔、灌木林地,是一种经济有效的水土保持措施。土壤容重是影响土壤容水量的主要土壤物理特性指标,土壤容重越大,土壤容水量越小。土壤含水率在9.60%～19.02%范围内对土壤容水量的影响不明显

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel