Solid-supported solution-phase synthesis of 4-amino-1,2,4,5-tetrahydro-2-benzazepine-3-ones

Starting from Boc-o-aminomethylphenylalanine, a solution-phase parallel synthesis of 2,4-substituted 4-amino-1,2,4,5-tetrahydro-2-benzazepine-3-ones is described. This heterocycle has two nitrogen functions, which are differentiated and can be selectively substituted. The sources of diversity are aldehydes for the R(1) position and carboxylic acids, sulfonyl chlorides, or isocyanates for the R(2) position. High-throughput synthesis and purification of this multistep synthetic sequence was accomplished using polymer-bound reagents and scavengers and liquid-liquid extraction protocols, and a small library of compounds was prepared. Polymer-bound cyanoborohydride was found to work well for the reductive amination. Scavenging of excess of amine was performed by polymer-bound benzaldehyde, and cyclization was performed in the presence of polymer-bound coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). After Boc-deprotection, the second nitrogen can be acylated using carboxylic acids, sulfonylated or converted to a urea. The acylation is again performed by polymer-bound EDC. Excellent yields and purities were obtained.     

基于波动模态耦合的铝电解槽磁流体稳定性傅立叶级数法分析

铝电解槽内磁流体稳定性对铝电解生产有重要影响。本文结合铝电解槽实体仿真的电磁场计算结果,应用傅立叶级数法对槽内磁流体波动稳定性进行数值计算,并对波动的模态耦合问题进行了重点分析。在此基础上,本文以某320kA铝电解槽为研究载体分析了槽长宽比设计对磁流体稳定性的影响,结果表明:波动的不稳定分量集中分布在频谱图中重力波模态密集的低频区域;不考虑母线对体系的影响,增大槽的长宽比,有利于提高磁流体的稳定性。     

Students’ self-regulation of emotions in mathematics: an analysis of meta-emotional knowledge and skills

Over the past decade, the concept of self-regulated learning has broadened to include motivational, volitional, and emotional components next to (meta-)cognitive ones. In this article, we present a meta-emotion perspective as an essential component of a conceptual framework on self-regulation that fully acknowledges the role of emotions. Against this background, a study is presented that attempts to contribute to the clarification of the relevance and the functioning of students’ meta-emotional knowledge and emotional regulation skills in school-related mathematical activities. It investigates the coping strategies that 393 students of the second (age 14) and fourth (age 16) year of secondary school report to use to regulate their emotions in three different mathematical school settings (i.e., a mathematics test, a difficult mathematics homework, and a difficult mathematics lesson). More specifically, it aims (1) to document the nature and frequency of the reported coping strategies, and (2) to explore—for the three different mathematical school settings—relationships between these reported coping strategies and personal characteristics (i.e., students’ familiarity with the particular school settings, their track in secondary education, their achievement level, their age, and gender). The results indicate that students report to know and to make use of several coping strategies in school-related mathematical activities, and reveal that the use of these strategies is related to specific person-related characteristics. In conclusion, we elaborate on how schools and teachers can stimulate students to acquire appropriate strategies and skills to self-regulate their emotions.     

200 MHz CW mode-locked KTP intracavity frequency-doubled Nd:YAG laser

Experimental results of 200 MHz CW actively mode-locked KTP two-pass in-tracavity frequency-doubled Nd:YAG laser are reported.The primary factors influencingthe continuous-wave frequency-doubled conversion efficiency are analyzed.High efficiencylaser output was achieved by L-type folded-arm-cavity two-pass frequency-doubling.15 Waverage mode-locked power and 1.5W average mode-locked SHG green light output were ob-tained at 3.5kW single lamp input power respectively.     

Sn(II)/PN@AC catalysts: synthesis,physical-chemical characterization,and applications

In this study, the novel tin-based catalysts (Sn(II)/PN@AC) were prepared using the phosphorus and nitrogen dual-modified activated carbon as support and SnCl₂ as active compounds, as well as then evaluated in acetylene hydrochlorination. Under the reaction temperature of 180 °C and an acetylene gas hourly space velocity (GHSV-C₂H₂) of 30 h^–1, the 15%Sn(II)/PN@AC-550 showed the initial acetylene conversion of 100% and vinyl chloride selectivity over 98.5%. Additionally, the deactivation rate of 15%Sn(II)/PN@AC-550 reached 0.47% h^–1, which was lower than that of 15%Sn(II)/AC-550 (1.02% h^–1), suggesting that PN@AC-550 as novel support can retarded the deactivation of Sn(II)/AC-550 catalysts during acetylene hydrochlorination. Based on the catalytic tests and characterization results (XRD, Raman, BET surface area, TEM, C₂H₂-TPD, H₂-TPR, XPS, FT-IR, TGA, and ICP), it demonstrated that PN@AC-550 as support could effectively improve the dispersion of tin species, retard the formation of coke deposition, lessen the oxidation of SnCl₂ during the preparation process, as well as relatively inhibit the leach of tin species during the reaction. By combing the FTIR results and Rideal–Eley mechanism, we proposed that that HSnCl₃ was transition state of SnCl₂ in catalysis acetylene hydrochlorination and then adsorbed the acetylene to produce the vinyl chloride.     

Stereochemistry at tin and mechanism of three cleavage reactions of carbontin bonds

The cleavages of the trityltin bond by NaFe(CO)₂Cp, LiBHEt₃ and Ph₃-SnLi are not stereoselective. This is explained in terms of a one-electron transfer mechanism leading to a triorganostannyl radical which can undergo inversion before reacting with another radical to give the product.     

近化学计量比铌酸锂晶体的研究进展

本文总结了近化学计量比铌酸锂晶体的不同生长方法及它们各自的特色,分析了锂铌摩尔比对晶体性能的影响及Li含量的各种表征方法.通过比较看出,采用K2O助熔剂生长近化学计量比铌酸锂晶体是一种较为实用的途径.基于此,我们采用K2O助熔剂提拉法和助熔剂-坩埚下降法生长了近化学计量比铌酸锂晶体,所得晶体的最大尺寸分别达到45mm×60mm和25mm×40mm.     

Evidence of simple intramolecular rearrangement at polymer end groups in secondary ion mass spectrometry

Polystyrenes with various end groups were analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). These end groups were obtained by termination of the active anionic group by sulfonate or chlorosilane derivatives. Characteristic end group fragments for each sulfonate derivative were observed. On the one hand, for PS capped by methyl sulfonate, or -(CH(2))(4)-O-SO(2)-CH(3), almost complete end group fragment is observed at m/z 95 and a [O-SO(2)-CH(3)](-) molecular structure. On the other hand, when PS is terminated by silyl methyl sulfonate, or -Si(CH(3))(2)-(CH(2))(3)-O-SO(2)-CH(3), the most characteristic fragment in the fingerprint secondary ion mass spectrum is located at m/z 153 with [Si(CH(3))(2)-O-SO(2)-CH(3)](+) and the complete end group peak, [Si(CH(3))(2)-(CH(2))(3)-O-SO(2)-CH(3)](+), at m/z 201, is absent. According to the molecular structure, characteristic end group secondary ions can be emitted as complete or rearranged fragments. Various silylalkyl alcohol or sulfonate functionalities are analyzed and fragmentation pathways are discussed. To our knowledge, this is the first time that such rearrangement at silyl functions has been observed and demonstrated in fingerprint secondary ion mass spectra. Copyright 1999 John Wiley & Sons, Ltd.