An unusual 1,2-N→C acyl migration in urea derivatives of α-aminoorganolithiums

Transmetalation of urea derivatives of α-aminoorganostannanes with alkyllithiums provides α-aminoorganolithiums which undergo rapid N to C acyl migration to afford α-aminocarboxamides. The stereochemical course of the transmetalation/migration process depends on the substituents on the urea and varies from complete retention of configuration to complete racemization.     

辽河冷家油田特稠油降粘剂LJVR-1及其性能评价

采用荧光法测定了辽河冷家油田冷47-556井特稠油乳化HLB值,然后以混合型表面活性剂、非离子型表面活性剂为主剂,快速渗透剂为辅剂按一定比例制备了水基降粘剂LJVR-1.实验结果表明,该降粘剂具有良好的乳化降粘性能,开采后易于破乳脱水,是一种较为理想的特稠油降粘剂.     

A first-principles study of surface and subsurface H on and in Ni(1 1 1): diffusional properties and coverage-dependent behavior

Periodic, self-consistent, density functional theory (GGA-PW91) calculations are performed for both surface and subsurface atomic hydrogen on and in Ni(1 1 1). At a low coverage (θ=0.25 ML), the binding energies (BEs) of a hydrogen atom in surface fcc, subsurface octahedral (first layer), and subsurface octahedral (second layer) sites are −2.89, −2.18, and −2.11 eV, respectively. The activation energy barriers for hydrogen diffusion from the surface to the first subsurface layer and from the first to the second subsurface layer are estimated to be 0.88 and 0.52 eV, respectively. In the entire coverage range studied, hydrogen occupies surface fcc and hcp sites and subsurface octahedral sites. In addition, the magnitude of the BE per hydrogen atom and the magnetization of the nickel slabs both decrease as hydrogen coverage increases. Vibrational frequencies of hydrogen at various surface and subsurface sites are calculated and are in reasonable agreement with experimental data. A phase stability calculation with a 2 × 2 surface unit cell shows that a p(2 × 2)-2H overlayer structure (θ=0.5 ML) and a p(1 × 1)-1H structure (θ=1.0 ML) are stable at low hydrogen pressures, in agreement with numerous experimental results. A very large increase in pressure is required to populate subsurface sites. After such an increase occurs, the first subsurface layer is filled completely.     

Behavior of zirconium in the ZrOW(100) system at high temperature, studied by ISS, AES and work-function measurements

The behavior of zirconium atoms at the W(100) surface associated with oxygen adsorption at different sample temperatures has been studied by Auger electron spectroscopy (AES), ion scattering spectroscopy (ISS), and the relative change of the work function (Δф) measured by the onset of the secondary electron energy distribution. The results have revealed: (i) adsorption of zirconium onto the W(100) surface followed by the elevation of the sample temperature up to 1710 K in an oxygen partial pressure of 2.7 × 10⁻⁴ induces complete diffusion of zirconium atoms into the W(100) substrate; (ii) further exposure of oxygen induces co-existence of oxygen and tungsten on the surface at 1710 K, resulting in a work function of 4.37 eV; (iii) keeping the sample temperature at 1710 K, simple evacuation of the system has resulted in surface segregation of zirconium atoms to the surface to form a zirconium atomic layer on the top-most surface, reducing the work function to 2.7 eV. The results have revealed that this specific behavior of zirconium atoms at high temperature assures, with very good reproducibility, the highly stable performance and long service life of Zr---O/W(100)-emitters in practical use, even in a low vacuum of 10⁻⁶ Pa.     

离子表面活性剂胶团对阿斯匹林碱水解反应的影响

离子表面活性剂胶团对阿斯匹林碱水解反应的影响史振民＊刘生昆张祝莲巩育军（延安大学化学系延安７１６０００）关键词表面活性剂，阿斯匹林，碱水解反应，胶团，抑制作用１９９６－０５－０４收稿，１９９６－０８－１２修回阿斯匹林（ＡＳＰ），学名为乙酰水杨酸，有较...     

考虑流体湿润性影响的核沸腾RohsenoW修正模型

添加界面活性剂的核沸腾在改变蒸气泡生长特性的同时，主要是强化了对流换热．本文考虑流体湿润性影响，对核沸腾换热沿用最广的对流类比模型－Ｒｏｈｓｅｎｏｗ模型进行了修正．通过对实验数据的检验，表明修正后的模型预示值与实测结果吻合很好．     

Vowel Intelligibility in Classical Singing

Vowel intelligibility during singing is an important aspect of communication during performance. The intelligibility of isolated vowels sung by Western classically trained singers has been found to be relatively low, in fact, decreasing as pitch rises, and it is lower for women than for men. The lack of contextual cues significantly deteriorates vowel intelligibility. It was postulated in this study that the reduced intelligibility of isolated sung vowels may be partly from the vowels used by the singers in their daily vocalises. More specifically, if classically trained singers sang only a few American English vowels during their vocalises, their intelligibility for American English vowels would be less than for those classically trained singers who usually vocalize on most American English vowels. In this study, there were 21 subjects (15 women, 6 men), all Western classically trained performers as well as teachers of classical singing. They sang 11 words containing 11 different American English vowels, singing on two pitches a musical fifth apart. Subjects were divided into two groups, those who normally vocalize on 4, 5, or 6 vowels, and those who sing all 11 vowels during their daily vocalises. The sung words were cropped to isolate the vowels, and listening tapes were created. Two listening groups, four singing teachers and five speech-language pathologists, were asked to identify the vowels intended by the singers. Results suggest that singing fewer vowels during daily vocalises does not decrease intelligibility compared with singing the 11 American English vowels. Also, in general, vowel intelligibility was lower with the higher pitch, and vowels sung by the women were less intelligible than those sung by the men. Identification accuracy was about the same for the singing teacher listeners and the speech-language pathologist listeners except for the lower pitch, where the singing teachers were more accurate.     

表面活性剂增敏阴极溶出伏安法测定痕量的碘

本介绍在ＫＮＯ３－ＶＣ－ＥＤＴＡ－Ｔｒｉｔｏｎ Ｘ－１００混合底液中，用悬汞电极２．５次微分阴极溶出伏安法测定痕量碘的方法及其最佳条件。引入表面活性剂Ｔｒｉｔｏｎ Ｘ－１００可显提高灵敏度，Ｉ＾－的检测下限达０．１ｎｇ·ｍＬ＾－１（电积１８０ｓ）；引入ＶＣ可提高Ｉ＾－的稳定性（抗氧化性）；ＥＤＴＡ和ＶＣ有效率地提高了方法的抗干扰能力。用于饮水中痕量碘的分析，其相对标准偏差为３．３％（ｎ＝７），     

聚电解质与相反电荷表面活性剂的相互作用

通过透光度测定、电导滴定和粘度法考察了阳离子聚电解质聚苯乙烯 4 乙烯基吡啶硫酸甲酯盐与阴离子表面活性剂十二烷基硫酸钠 (SDS)的相互作用。研究表明 ,在表面活性剂未过量时 ,二者之间的静电作用占主导地位 ,并且当二者电荷总量相等时 ,生成的复合物沉淀最多 ;在表面活性剂过量后 ,复合物可部分溶解 ,溶解的原因是疏水相互作用。本文初步阐述了二者的作用机理     

Synthesis of polystyrene latex with amphoteric surfactant and its characterization

An emulsion polymerization of styrene in the presence of an amphoteric surfactant; N,N-dimethyl-n-laurylbetaine (LNB) was carried out at pH 7.0. The polymerization rate and the concentration of the latex particle were proportional to the LNB concentration of 0.6 power. The latex particle sizes became smaller with increasing concentrations of LNB. The molecular weights of polystyrene latices increased with the concentration of LNB. The zeta-potentials of latex particles were significantly dependent on the pH, and showed the existence of an isoelectric point.