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991.
992.
In this paper, from the index theorem, we present the Hermitian phase operator for fermion, give its eigenvalues and orthogonal, normalized and complete eigenstates. Furthermore, we also get the phase difference operator for two fermions and discuss its quantum properties. 相似文献
993.
电感耦合等离子体原子发射光谱法(ICP-OES)测定铍铀伴生矿石中的铍 总被引:1,自引:0,他引:1
建立了电感耦合等离子体原子发射光谱法(ICP-OES)测定铍铀伴生矿石中的铍的方法,研究了酸溶-碱熔融法溶样过程中加入的焦硫酸钾,对ICP-OES法测定铍铀伴生矿石中的铍含量产生的基体干扰问题。主要阐述消除基体干扰的一些措施。从实验数据可知,控制称样量、焦硫酸钾加入量、定容体积和加标稀释倍数,能够有效消除焦硫酸钾对ICP-OES法测定结果的基体干扰,6次平行测定结果的相对标准偏差为3.4%,加标回收率为98.7%~104.4%,实验表明,方法准确、可靠。 相似文献
994.
Irina Iovel Lena Golomba Juris Popelis Alexander Gaukhman Edmunds Lukevics 《应用有机金属化学》2001,15(1):67-74
The conjugate addition of some (hetero)aromatic amides to an α,β‐unsaturated ester (ethyl acrylate) proceeds efficiently in the presence of an equimolar amount of the CsF–Si(OEt)4 system to afford the corresponding ethyl esters of N‐substituted β‐amino acids. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
995.
Philipp Vana Thomas P. Davis Christopher Barner‐Kowollik 《Macromolecular theory and simulations》2002,11(8):823-835
Careful simulations of conversion vs. time plots and full molecular weight distributions have been performed using the PREDICI® program package in conjunction with the kinetic scheme suggested by the CSIRO group for the reversible addition fragmentation chain transfer (RAFT) process to probe RAFT agent mediated polymerizations. In particular, conditions leading to inhibition and rate retardation have been examined to act as a guide to optimum living polymerization behavior. It is demonstrated that an inhibition period of considerable length is induced by either slow fragmentation of the intermediate RAFT radicals appearing in the pre‐equilibrium or by slow re‐initiation of the leaving group radical of the initial RAFT agent. The absolute values of the rate coefficients governing the core equilibrium of the RAFT process – at a fixed value of the equilibrium constant – are confirmed to be crucial in controlling the polydispersity of the resulting molecular weight distributions: A higher interchange frequency effects narrower distributions. It is further demonstrated that the size of the rate coefficient controlling the addition reaction of propagating radicals to polyRAFT agent, kβ, is mainly responsible for optimizing the control of the polymerization. The fragmentation rate coefficient, k–β, of the macroRAFT intermediate radical, on the other hand, may be varied over orders of magnitude without affecting the amount of control exerted over the polymerization. On the basis of the basic RAFT mechanism, its value mainly governs the extent of rate retardation in RAFT polymerizations. 相似文献
996.
Hole transporting polymers were prepared by condensation polymerization of triphenylamine and N,N,N',N'‐tetraphenylbenzidine (TPD) having alkyl group with aldehydes in the presence of p‐toluenesulfonic acid. The obtained polymers had molecular weight higher than 10,000 and good film formation ability. It was found that the aromatic amine monomers were connected with aldehyde monomer at the p‐position of the phenyl group. TPD‐aldehyde polymers had almost the same UV absorption and redox potentials as those of TPD monomer indicating that the electronic structure of amine unit did not change by the polymerization. The hole transporting mobility was in the range of 10−3‐10−6cm2/Vs. The electroluminescent device consisting of ITO/TPD polymer/Alq/Mg‐Ag had a maximum luminance of 9000 cd/m2. 相似文献
997.
998.
Demetrio De la Calle García Manfred Reichenbcher Klaus Danzer Christian Hurlbeck Christine Bartzsch Karl-Heinz Feller 《Journal of separation science》1998,21(7):373-377
Headspace solid-phase microextraction (HS/SPME) was studied and optimized for the capillary gas chromatographic (CGC) analysis of wine aroma compounds. The results were compared with those obtained using the direct sampling mode (DI/SPME) and using liquid/liquid extraction with Kaltron. The aromatic patterns obtained by HS/SPME-CGC were applied to the chemometric classification of wine varieties. The HS/SPME-CGC standard additional method is an appropriate technique for the quantitative analysis of volatile wine aroma compounds. 相似文献
999.
J. Raúl AlvarezIdaboy Irina DíazAcosta Annik VivierBunge 《Journal of computational chemistry》1998,19(8):811-819
MP2 calculations with full geometry optimizations were performed with a double- and a triple-zeta basis set to obtain the energy profile for reactions of propene+OH and ethene+OH at low pressures. In these conditions, the β-hydroxyalkyl radicals formed after OH addition to the alkene double bond may go through a rearrangement reaction to form easily identifiable aldehydes and ketones. The theoretical results obtained reproduce the available experimental data well and shed light on the mechanism of reactions characterized by negative activation energies. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 811–819, 1998 相似文献
1000.
Aihemaiti Kayishaer Sami Fadlallah Louis M. M. Mouterde Aurlien A. M. Peru Yasmine Werghi Fanny Brunois Quentin Carbou Michel Lopez Florent Allais 《Molecules (Basel, Switzerland)》2021,26(24)
Levoglucosenone (LGO) is a cellulose-derived molecule that is present commercially on a multi-ton/year scale. Taking advantage of the α,β-conjugated ketone of LGO, a new citronellol-containing 5-membered lactone (HBO-citro) was synthesized through a one-pot two-step pathway involving oxa-Michael addition and Baeyer-Villiger oxidation. The solvent-free treatment of HBO-citro with NaBH4 at room temperature led to the full reduction of the lactone moiety which gave a novel fully renewable triol monomer having a citronellol side chain (Triol-citro). Noticeably, by simply changing the reducing agent, temperature and reaction duration, the partial reduction of HBO-citro can be achieved to yield a mixture of 5- and 6-membered Lactol-citro molecules. Triol-citro was chosen to prepare functional renewable polyesters having citronellol pendant chains via polycondensation reactions with diacyl chlorides having different chain lengths. Good thermal stability (Td5% up to 170 °C) and low glass transition temperatures (as low as −42 °C) were registered for the polyesters obtained. The polymers were then hydrolyzed using a commercial lipase from Thermomyces lanuginosus (Lipopan® 50 BG) to assess their biodegradability. A higher degradation profile was found for the polyesters prepared using co-monomers (acyl chlorides) having longer chain lengths. This is likely due to the decreased steric hindrance around the ester bonds which allowed enhanced accessibility of the enzyme. 相似文献