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151.
研究型大学对学生科研思维的培养至关重要,有机化学实验作为近化学专业类学生重要的基础实验课程,对学生操作技能、创新能力和科研思维培养有重要作用。本文以非化学专业本科生有机化学实验"大学化学实验(O)"的教学实践为例,从学生学习方式、教师教学方法、实验教学内容设置等方面阐述如何在教学过程中完成对学生科研思维的培养。 相似文献
152.
P. Belli R. Bernabei F. Cappella R. Cerulli F.A. Danevich S. dʼAngelo M.L. Di Vacri A. Incicchitti M. Laubenstein S.S. Nagorny S. Nisi A.V. Tolmachev V.I. Tretyak R.P. Yavetskiy 《Nuclear Physics A》2011
A search for double β decay of dysprosium was realized for the first time with the help of an ultra-low background HP Ge γ detector. After 2512 h of data taking with a 322 g sample of dysprosium oxide limits on double beta processes in 156Dy and 158Dy have been established on the level of T1/2?1014–1016 yr. Possible resonant double electron captures in 156Dy and 158Dy were restricted on a similar level. As a by-product of the experiment we have measured the radioactive contamination of the Dy2O3 sample and set limits on the α decay of dysprosium isotopes to the excited levels of daughter nuclei as T1/2?1015–1017 yr. 相似文献
153.
《应用光谱学评论》2013,48(3):355-394
Abstract Prior to an asbestos removal the work requires first a substantiation, an identification, that asbestos is indeed present. This is known as a bulk analysis. Microscopical methods, particularly polarized light microscopy, can be used to measure the physical properties of fibers in the sampled material to identify and substantiate the presence of asbestos. Then, throughout the asbestos abatement process, the air is continuously monitored for asbestos fibers to minimize the risk exposure to the abatement worker as well as the general public. The measurement of air fiber levels throughout the abatement process is done primarily by phase contrast microscopy. When needed, electron microscopy is employed either in bulk asbestos analysis or the fiber in air measurements. In the USA, the usual methods that are followed are essentially prescribed. Laboratories and, under certain conditions the individual doing such work, should continuously meet performance criteria. The laboratory should be accredited and, for limited work, the individual certified. The overall procedure of asbestos analysis is reviewed; the possible current shortcoming in the methodology are discussed. 相似文献
154.
Wen Fu Edison P. Liang Milad Fatenejad Donald Q. Lamb Michael Grosskopf Hye-Sook Park Bruce Remington Anatoly Spitkovsky 《High Energy Density Physics》2013,9(2):336-340
Supersonic plasma outflows driven by multi-beam, high-energy lasers, such as Omega and NIF, have been and will be used as platforms for a variety of laboratory astrophysics experiments. Here we propose a new way of launching high density and high velocity, plasma jets using multiple intense laser beams in a hollow ring formation. We show that such jets provide a more flexible and versatile platform for future laboratory astrophysics experiments. Using high resolution hydrodynamic simulations, we demonstrate that the collimated jets can achieve much higher density, temperature and velocity when multiple laser beams are focused to form a hollow ring pattern at the target, instead of focused onto a single spot. We carried out simulations with different ring radii and studied their effects on the jet properties. Implications for laboratory collisionless shock experiments are discussed. 相似文献
155.
A.C. Vandaele C. Hermans S. Fally 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(18):2115-2126
This paper is the second of a series that reports results on the measurements of the absorption cross section of SO2 in the UV/visible region at high resolution and that investigates high temperatures in support to planetary applications. Absorption cross sections of SO2 have been obtained in the 29 000–44 000 cm−1 spectral range (227–345 nm) with a Fourier transform spectrometer at a resolution of 2 cm−1 (0.4500 cm MOPD and boxcar apodisation). Pure SO2 samples were used and measurements were performed at room temperature (298 K) as well as at 318, 338 and 358 K. Temperature effects in this spectral region are investigated and are favorably compared to existing studies in the literature. Comparison of the absorption cross section at room temperature shows good agreement in intensity with most of the literature data, but shows that most of the latter suffer from inaccurate wavelength scale definition. Moreover, literature data are often given only on restricted spectral intervals. Combined with the data described in the first part of this series of papers on SO2, this new data set offers the considerable advantage of covering the large spectral interval extending from 24 000 to 44 000 cm−1 (227–420 nm), at the four temperatures investigated. 相似文献
156.
Philip L.Cole 《中国物理 C》2009,33(12):1222-1229
In this paper we discuss the reasons for our work towards establishing a new collaboration between Jefferson Lab (JLab) and the Institute of High Energy Physics (IHEP) in Beijing. We seek to combine experimentalists and theorists into a dedicated group focused on better understanding the current and future data from JLab and from the Beijing Electron Positron Collider (BEPC). Recent JLab results on the extraction of single- and double-polarization observables in both the lπ- and 2π-channel show their high sensitivity to small production amplitudes and therefore their importance for the extraction of resonance parameters. The Beijing Electron Spectrometer (BES) at the BEPC has collected high statistics data on J/ψ production. Its decay into baryon-antibaryon channels offers a unique and complementary way of probing nucleon resonances. The CEBAF Large Acceptance Spectrometer, CLAS, has access to N* form factors at high Q2 which is advantageous for the study of dynamical properties of nucleon resonances, while the low-background BES results will be able to provide guidance for the search for less-dominant excited states at JLab. Moreover, with the recently approved experimental proposal Nucleon Resonance Studies with CLAS12 and the high-quality data streaming from BES-Ⅲand CLAS, the time has come for forging a new Trans-Pacific collaboration of theorists and experimentalists on NSTAR physics. 相似文献
157.
A series of laboratory experiments were conducted to investigate the damping effect of net cages in waves. The wave transmission coefficient of the net cage was investigated with different wave periods, wave heights, numbers of net cages, net solidities, measurement positions, geometrical shapes of the net cage and Reynolds numbers. The experimental results show that the net cage has noticeable influence on wave propagation and the damping effect of net cages has a close relationship with many parameters. For multiple net cages, the transmission coefficient tends to increase as the wave period increases. The transmission coefficient of net cages decreases with increasing wave height. As the number of net cages increases, the wave transmission coefficient will decrease gradually. The damping effect of net cages on wave propagation tends to increase with increasing net solidity. The measurement position has an effect on the value of wave transmission coefficient. For net cages with different geometrical shapes, the circular net cage has more noticeable damping effect than the square net cage. A numerical model is introduced to simulate the interaction between waves and net cages with the fishing net treated as the porous media fluid model. The wave transmission coefficient downstream from net cages shows good agreement between experimental and numerical results. The study will contribute to understanding of the damping effect of a large fish farm on wave propagation. 相似文献
158.
Jiahong Li Jie Han Zechao Lin Lei Tang Qingfei Huang Qiwei Wang Jin Zhu Jingen Deng 《Tetrahedron》2019,75(3):422-428
The influence factors of surfactant-type catalysts system on the asymmetric transfer hydrogenation (ATH) of ketones in water, including the length of aliphatic tail, the concentration of catalysts and the solvent, have been investigated. These factors played significant roles on reaction activity and stereo control. With single-chain surfactant-type catalyst Rh-L4, α, β-unsaturated ketones especially the aliphatic derivatives affords excellent regioselectivities and enantioselectivities. 相似文献
159.
Hongbo Wei Hongli Zhang Shoule Han Shan Mu Ke Huang Guzhou Chen Weiqing Xie 《Tetrahedron letters》2019,60(35):150973
Asymmetric synthesis of the marine nor-sesquiterpenoid (+)-austrodoric acid and (+)-austrodoral in seven and nine steps respectively from Wieland-Miescher ketone was described herein. The synthesis featured an oxidative ring contraction of α-formyl cyclic ketone mediated by H2O2 to forge the hydrindane scaffold together with the contiguous quaternary carbon centers simultaneously. 相似文献
160.
Caizhu Chang Jialin Geng Yuguo Du Qingwei Lv ZhiBing Dong Jun Liu 《Tetrahedron》2019,75(29):3933-3938
Stereoselective total synthesis of aspinolides B, E and J, naturally occurring 10-membered lactones, were accomplished by divergent strategies starting from the commercially available 2,3-O-isopropylidene-d-ribose and methyl d-lactate. The synthesis features rapid access to the both key fragments from chiral pool and the formation of 10-membered ring lactones containing trans double bond employing cross-metathesis reaction (CM) and intramolecular Shiina macrolactonization. 相似文献