Direct esterification of fatty acids with phenylalkanols by using dicyclohexylcarbodiimide

A mild one‐pot esterification method of fatty acids with alcohols at room temperature is described. The reaction of undec‐10‐enoic acid (I) with 1‐phenylethanol in the presence of N,N'‐di‐cyclohexylcarbodiimide and 4‐(N,N‐dimethylamino)pyridine gave 1'‐phenylethyl undec‐10‐enoate in quantitative yield. Similar reactions were also carried out with (Z)‐octadec‐9‐enoic acid, (Z)‐12‐hydroxyoctadec‐9‐enoic and (Z)‐9‐hydroxyoctadec‐12‐enoic acids. In addition, compound (I) was allowed to react with diphenyl methanol to form its corresponding ester. The structure elucidation of the prepared esters is based on the elemental analysis and spectral data (IR, ¹H‐ and ¹³C‐NMR, MS).     

化学-酶法合成RGD三肽

采用化学法和酶法相结合的合成策略,合成具有高生物活性肽RGD。先采用DCC合成GD二肽(HCl·Gly Asp(oBzl)2),然后利用胰蛋白酶(trypsin)催化合成RGD三肽(Z Arg GlyAsp(oBzl)2)。实验结果表明,其中GD二肽在反应10h,两底物G与D的摩尔比为1 5∶1时,得率为77 7%;RGD三肽在微水-1,4-丁二醇反应体系中得率为41 9%。     

An all‐digital DLL with duty‐cycle correction using reusable TDC

This paper presents the design of an all‐digital delay‐locked loop (ADDLL) with duty‐cycle correction using reusable time‐to‐digital converter (TDC). The proposed ADDLL uses a reusable TDC for achieving a wide‐operating frequency range. In addition, it achieves the frequency doubling output clock easily by changing the quantization interval. It is implemented in a 0.18‐µm complementary metal‐oxide semiconductor technology. This circuit corrects the duty cycle and synchronizes the input and output clocks in 10 clock cycles. The output duty cycle is corrected to 50 ± 1.5% as the input duty cycle ranges from 25% to 75%. The acceptable input frequency range is from 300 to 900 MHz without frequency doubling. The acceptable input frequency range is from 150 to 450 MHz when using frequency doubling. It dissipates 6.2 mW from a 1.8‐V supply at 900 MHz. The peak‐to‐peak and RMS jitters at 900 MHz are 14 and 1.8 ps, respectively. Copyright © 2015 John Wiley & Sons, Ltd.     

基于知识蒸馏的深度无监督离散跨模态哈希

跨模态哈希因其低存储花费和高检索效率得到了广泛的关注。现有的大部分跨模态哈希方法需要额外的手工标签来提供实例间的关联信息,然而,预训练好的深度无监督跨模态哈希方法学习到的深度特征同样能提供相似信息;且哈希码学习过程中放松了离散约束,造成较大的量化损失。针对以上两个问题,提出基于知识蒸馏的深度无监督离散跨模态哈希（DUDCH）方法。首先,结合知识蒸馏中知识迁移的思想,利用预训练无监督老师模型潜藏的关联信息以重构对称相似度矩阵,从而代替手工标签帮助有监督学生模型训练;其次,采用离散循环坐标下降法（DCC）迭代更新离散哈希码,以此减少神经网络学习到的实值哈希码与离散哈希码间的量化损失;最后,采用端到端神经网络作为老师模型,构建非对称神经网络作为学生模型,从而降低组合模型的时间复杂度。在两个常用的基准数据集MIRFLICKR-25K和NUS-WIDE上的实验结果表明,该方法相较于深度联合语义重构哈希（DJSRH）方法在图像检索文本/文本检索图像两个任务上的平均精度均值（mAP）分别平均提升了2.83个百分点/0.70个百分点和6.53个百分点/3.95个百分点,充分体现了其在大规模跨模态数据检索中的有效性。     

Effect of pH on the drug release rate from a new polymer–drug conjugate system

The corresponding N‐hydroximide and N‐methyl‐N‐hydroximide of poly[ethylene‐alt‐(maleic anhydride)] (weight average molecular weight (M_w) of 100–500 g mol^?1) were prepared as a new oral drug delivery system. Syntheses of N‐hydroximide and N‐methylhydroxamic acid of poly[ethylene‐alt‐(maleic anhydride)] were carried out by chemical modification of polymer with hydroxylamine and N‐methylhydroxylamine, respectively, to give water‐soluble polymers. These activated polymers were immobilized with ketoprofen in the presence of dicyclohexylcarbodiimide to give the corresponding water‐insoluble ketoprofen conjugates. All products were characterized by elemental analysis as well as Fourier transform infrared and ¹H NMR spectra. In vitro release of ketoprofen was studied by measuring UV absorption at λ_max = 260 nm as a function of time. This study demonstrated the potential use of N‐hydroximide and N‐methyl‐N‐hydroxamic acid of poly[ethylene‐alt‐(maleic anhydride)] as a drug delivery system. Controlled release was studied at different pH values and at different temperatures. At physiological temperature, the amount of drug released increased with increasing pH. The copolymer‐drug adducts released the drug very slowly at the low pH found in the stomach thus protecting the drug from the action of high acid conditions and resident digestive enzymes. These N‐hydroxamic acid polymer‐drug conjugates were found to be potentially useful in the delivery of macromolecular drugs to targeted sites in the lower gastrointestinal tract and the colon area. Copyright © 2007 Society of Chemical Industry     

DOCSIS协议中的DCC技术浅析

以HFC网络为背景,简要介绍了DOCSIS3.0的主要特点,并对DOCSIS协议中DCC(Dynamic Channel Change)技术原理及应用进行了分析,以进一步了解DOCSIS协议及其在HFC网络建设中的应用。     

电视连续剧《醒悟》拍摄技术纪实

青海电视台藏语中心 2008年6月,历时两个月摄制了首部藏语电视连续剧<醒悟>.本文从数字摄像机的应用技巧出发.就本剧拍摄过程中遇到的一些特殊问题及解决办法作了阐述.     

降低催化裂解汽油苯含量的研究及工业实践

中海油东方石化有限责任公司催化裂解汽油苯含量较高，受加工流程限制，通过调整装置操作参数以降低汽油苯含量。简述了催化裂解汽油中苯的生成机理，汽油中的苯主要来自芳烃的侧链裂解反应、环烷烃的氢转移反应和烯烃的环化脱氢反应；分析了催化裂解装置原料性质、操作条件及催化剂性质对汽油苯含量的影响，通过操作参数的调整，使催化裂解汽油苯体积分数由1.60%降至1.40%。将降低汽油苯含量的的理论成功应用于生产实践，取得良好的应用效果。     

催化裂化工艺在提高汽油质量中的作用

针对我国车用汽油质量偏低、FCC汽油所占比例大的状况,重点探讨了提高FCC汽油质量的几项措施,论述了FCC及其相关工艺在提高汽油质量中的作用。     

String Block Vs Superblock Patterns of Dispersal in China

The superblock in China has become the dominant unit of urban planning, allowing for rapid urban growth while also meeting the needs of state and property developer alike. Kjersti Monson explains the conditions that have given rise to the superblock, while challenging it by proposing an alternative ‘stringblock’ approach, rooted more in collective culture and addressing the demands of the market-driven economy. Copyright © 2008 John Wiley & Sons, Ltd.