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971.
在粗糙表面上用液晶空间光调制器进行振动测量 总被引:2,自引:2,他引:0
为实现在一段时间内连续实时观测振动物体的全息干涉图形,采用覆盖铝箔的喇叭作为振动物体,利用铝箔原有未经特殊处理表面反射的漫反射光成像,并用光寻址液晶空间光调制器(Liquid crystal-sparial lightmodulator,LC-SLM)作为全息记录载体,来实现振动测量。实验中采用时间平均干涉测量法,得到了不同振动频率下物体的干涉图形。同时在连续改变振动物体的振动频率时,可以清晰地观察到物体振动全息干涉图形的变化过程,即近实时的全息干涉图形。 相似文献
972.
973.
为了获得CH分子束及其相关特性,以氦气为载气,利用直流脉冲放电技术产生了CH分子束.实验记录了放电时间相对于脉冲分子束不同延时CH光谱信号强度的变化,放电相对延时为460μs左右获得最大的信号强度.研究了在保持CH4/He总气压3 atm和放电电压-4 kV不变的条件下CH分子束强度与不同配比的关系,建立了理论模型,对实验数据进行了理论拟合,拟合曲线与实验结果符合较好,配比为1%(甲烷与氦的气压比为1:99)左右能够维持较稳定的放电现象和较强的放电强度而获得较强的CH自由基束流.在这一配比下对CH(A2△-X2П)(0,0)带发射光谱进行探测和分析,获得CH(A2△)转动温度和振动温度分别为2455 K和4575 K,并估计此时每个脉冲中大约包含1013~1014个CH自由基. 相似文献
974.
975.
He-Xia Huang Hui-Jun Tan Zheng-Kang Lin Zi-Jie Li Shu Sun Hao Chen Zhi-Xiang Xiao 《Acta Mechanica Sinica》2021,37(1):156-168
The submerged inlet is an attractive configuration for advanced helicopters due to its high stealth performance and low external drag.In this paper,a submerged ... 相似文献
976.
Tributylstibine can mediate the olefination of carbonyl compounds with bromomalonic ester and with dibromomalonic ester. An initial halophilic attack of tributylstibine on the bromine of bromomalonic or dibromomalonic ester forming an ion pair of bromotributylstibonium cation and malonic (A) or bromomalonic ester carbanion (B) , respectively, is proposed. These ion pairs react with carbonyl compounds to achieve subsequent olefination. Alternatively, 2 equiv of A collapse, with elimination of malonic ester, to form stiborane D , and the ion pair B reacts with another equivalent of tributylstibine to form stiborane D. This last undergoes a Wittig-type reaction with carbonyl compound to achieve olefination. 相似文献
977.
Dong-Zhao Yang Zhen-Zhen Chen Mei Chi Ying-Ying Dong Shou-Zhi Pu Qi Sun 《Molecules (Basel, Switzerland)》2022,27(3)
5-Hydroxymethyl-2′-deoxycytidine (5hmdC) phosphoramidite and triphosphate are important building blocks in 5hmdC-containing DNA synthesis for epigenetic studies. However, efficient and practical methods for the synthesis of these compounds are still limited. The current research provides an intensively improved synthetic method that enables the preparation of commercially available cyanoethyl-protected 5hmdC phosphoramidite with an overall yield of 39% on 5 g scale. On the basis of facile and efficient accesses to cyanoethyl protected-5hmdU and 5hmdC intermediates, two efficient synthetic routes for 5hmdC triphosphate were also developed. 相似文献
978.
With the increasing application of deep-learning-based generative models for de novo molecule design, the quantitative estimation of molecular synthetic accessibility (SA) has become a crucial factor for prioritizing the structures generated from generative models. It is also useful for helping in the prioritization of hit/lead compounds and guiding retrosynthesis analysis. In this study, based on the USPTO and Pistachio reaction datasets, a chemical reaction network was constructed for the identification of the shortest reaction paths (SRP) needed to synthesize compounds, and different SRP cut-offs were then used as the threshold to distinguish a organic compound as either an easy-to-synthesize (ES) or hard-to-synthesize (HS) class. Two synthesis accessibility models (DNN-ECFP model and graph-based CMPNN model) were built using deep learning/machine learning algorithms. Compared to other existing synthesis accessibility scoring schemes, such as SYBA, SCScore, and SAScore, our results show that CMPNN (ROC AUC: 0.791) performs better than SYBA (ROC AUC: 0.76), albeit marginally, and outperforms SAScore and SCScore. Our prediction models based on historical reaction knowledge could be a potential tool for estimating molecule SA. 相似文献
979.
Chia-Yu Hung Chih-Han Chang Tzu-Jung Lin Hsin-Hui Yi Nian-Zhen Tsai Yu-Ru Chen Yng-Tay Chen 《Molecules (Basel, Switzerland)》2022,27(3)
Acrylamide (ACR) is present in high-temperature-processed high-carbohydrate foods, cigarette smoke, and industrial pollution. Chronic exposure to ACR may induce neurotoxicity from reactive oxygen species (ROS); however, the mechanisms underlying ACR-induced neurotoxicity remain unclear. We studied 28-day subacute ACR toxicity by repeatedly feeding ACR (0, 15, or 30 mg/kg) to rats. We conducted RNA sequencing and Western blot analyses to identify differences in mRNA expression in the blood and in protein expression in the brain tissues, respectively, of the rats. AQP4 transient transfection was performed to identify potential associations with protein regulation. The rats treated with 30 mg/kg ACR exhibited hind-limb muscle weakness. Matrix metalloproteinase (MMP9) expression was higher in the ACR-treated group than in the control group. ACR induced MMP-9 and AQP4 protein expression in the brain tissues of the rats, which subsequently presented with neurotoxicity. In the in vitro study, Neuro-2a cells were transiently transfected with AQP4, which inhibited MMP-9 and TNF receptor-associated factor 6 (TRAF6) expression, and inhibited ACR induced expression of TRAF6, IκBα, and nuclear factor κB (NFκB). Using a combination of in vivo and in vitro experiments, this study revealed that depressive symptoms associated with ACR-induced neurotoxicity are associated with downregulation of AQP4 and induction of the TRAF6 pathway. 相似文献
980.
Meccanica - This paper introduces an analytical approach to optimize the textured bearing with cavitation to improve the load support. For this purpose, a grooved parallel slider bearing is... 相似文献