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121.
122.
为实现PTS系列频率综合器的微机控制,设计了一种简单的控制电路。在微机的控制下,通过该电路与微机的并行通讯口,用C语言编写的控制程序可以很方便的控制频率综合器的输出频率。控制程序采用菜单操作,电路所需的+5V电源由微机提供,整个控制系统简单实用,值得推广。 相似文献
123.
活性酚醛树脂中羟甲基含量的测定 总被引:12,自引:0,他引:12
本文提出一种酚醛树脂中羟甲基含量的化学分析法,分别以^13CNMR和化学分析法测定酚醛树脂的羟甲基含量。将两种测试结果与已知的投料量进行比较,证明所建立的化学分析法可行。 相似文献
124.
The synthesis and characterisation of five newβ-aminodiketones is reported: (a) 3,3,5,8,10,10-hexamethyl-5,8-diazadodecane-2,11-dione; (b) 3,3,11,11-tetramethyl-5,8-diazatridecane-2,12-dione;
(c) 3,3,12,12-tetramethyl-5,10-diazatetradecane-2,13-dione; (d) 3,3,10,10-tetramethyl-5,8-diphenyl-5,8-diazadodecane-2,11,dione
and (e) 6,7-benzo-3,3,10,10-tetramethyl-5,8-diazadodecane-2,11-dione. These compounds are discussed as potential precursors
in the synthesis of tetra-aza macrocyclic complexes. 相似文献
125.
126.
HeinzD. Roth 《Helvetica chimica acta》2006,89(12):2847-2860
Chemically induced dynamic nuclear polarization (CIDNP) observed during electron transfer (ET) reactions of tertiary amines such as DABCO ( 1 ) or Et3N ( 2 ) with a wide range of electron acceptors support the involvement of amine radical‐cations (e.g., 1. + or 2. + ) as key intermediates. Radical ions such as 2. + may be deprotonated, generating neutral aminoalkyl radicals (e.g., 2. ). When generated by reaction with an electron acceptor of energetically low triplet state such as naphthalene (1Naph*), the resulting pair 2. + /Naph.? reacts mostly by reverse electron transfer (RET) from triplet pairs populating the naphthalene triplet state. 相似文献
127.
《Arabian Journal of Chemistry》2022,15(1):103472
As a representative of traditionally fermented Chinese medicine, Massa Medicata Fermentata (MMF) shows the functions of invigorating the spleen and stomach and promoting digestion, which plays an important role in the treatment of gastrointestinal diseases. The fermentation mechanism and the key factors that affect the quality of MMF have not been revealed yet, which has become an urgent issue that limits its clinical application. This article aims to systematically and comprehensively reveal the transformation of physical properties and the dynamic trend of chemical components including substrate components, volatile components, and lactic acid as anaerobic fermentation product during MMF fermentation. Along with obvious hyphae growth observed for MMF, the weight of MMF decreased, and the moisture and temperature increased. Through the quantified 14 components from substrate, ferulic acid increased from 45.53 ± 6.94 to 141.89 ± 78.40 μg/g, while glycosides and phenolic acids declined except caffeic acid. Also, within the 66 volatile components analyzed, alcohols and acids increased, while aldehydes and ketones decreased. Lactic acid was not detected in the fermentation substrate, but an apparent increase in lactic acid content was observed along with the increased fermentation days, resulting in 2.54 ± 0.15 mg/g on day 8. Based on the tested components, the fermentation process of MMF was discriminated into three distinct stages by principal component analysis, and an optimal fermentation time of four days was proposed. The results of this study will be of great significance to clarify the characteristics of fermentation and conduce to improving quality standards of MMF. 相似文献
128.
The conformational transformation of a 30-residue peptide H(Ala-Gly-Ser-Gly-AIa-Gly)5OH, i.e., (AGSGAG)5, extracted from highly crystalline region of Bombyx mori (B. mori) silk fibroin was described by using the high resolution solid state 13^C NMR, and CD spectroscopies. Based on the conformation-dependent 13^C NMR chemical shifts of the Ala, Gly and Ser residues and the line-shape analysis of the conformation sensitive Ala Cβ resonance, the peptide revealed a strong preference for silk Ⅱ structural form, i,e,, an antiparallel fl-sheet structure (φ= - 140±20°and ψ= 135±20°) in solid state. On the contrary, the CD spectra of this peptide in the two non-native hexafluorinated fibre spinning solvents, hexafluoroisopropanol (HFIP) and hexafluoroacetone (HFA), exhibited the existence of an unusual tightly-folded conformation resembling 310-helix (φ=- 60±20° and ψ=-30±20°), as judged from the R ratio of [θ]222/[θ]203 in HFIP solution, whereas a dynamically averaged unordered structure in HFA, Taken together, the information inclined to hypothesis that the primary structure of the highly crystalline regions of B. mori silk fibroin may be easily accessible to the large conformational changes, which in turn may be critical for facilitating the structural transformation from unprocessed silk fibroin (silk I form) to processed silk fiber (silk Ⅱform). 相似文献
129.
Some gauge invariant atomic orbitals-coupled-perturbed Hartree-Fock (GIAO-CPHF) calculations were performed for seven indolizine derivatives and their monoprotonated forms. Chemical shift, molecular geometry, and charge distribution data are reported for each molecule. The calculations support the results of nuclear magnetic resonance (NMR) spectroscopy measurements showing that protonation occurs preferentially at N1. The good agreement between the calculated and observed 13C and 15N chemical shifts show that such calculations can be used for chemical shift assignment purposes. Cation structures and probable sites for electrophilic reaction or second protonation are also discussed. 相似文献
130.
Impact Responses of Prismatic Lithium-Ion Battery Based on the Membrane Factor Method北大核心CSCD 下载免费PDF全文
Aimed at the internal short circuit problem due to large deformation of the prismatic lithium-ion battery cell under impact loadings, a simplified battery model was first established. Then the motion equations of velocity and displacement based on the membrane factor method were proposed. With the effects of the face-sheet thickness and the densification region on the normalized final deflection, impact response characteristics of prismatic battery cells were investigated in detail. The results show that, the improved motion equations involving the membrane factor can reflect the dynamic response mechanisms of the prismatic battery cell under impact loadings, and the large deflection under high-speed impact can be predicted. With the increase of the face-sheet thickness, the deflection of the battery cell’s lower part decreases obviously. However, the densification region expands with the face-sheet thickness. The deflection and the densification region of the cell’s lower part both increase with the inner core density of the battery. This proposed impact model provides a theoretical guidance for the multi-functional integrated dynamic design of prismatic battery cells. © 2022 Editorial Office of Applied Mathematics and Mechanics. All rights reserved. 相似文献