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11.
Rigorous definitions are presented for the kinematic angular momentum K of a system of classical particles (a concept dual to the conventional angular momentum J), the angular momentum L(xi) associated with the moments of inertia, and the contributions to the total kinetic energy of the system from various modes of the motion of the particles. Some key properties of these quantities are described-in particular, their invariance under any orthogonal coordinate transformation and the inequalities they are subject to. The main mathematical tool exploited is the singular value decomposition of rectangular matrices and its differentiation with respect to a parameter. The quantities introduced employ as ingredients particle coordinates and momenta, commonly available in classical trajectory studies of chemical reactions and in molecular dynamics simulations, and thus are of prospective use as sensitive and immediately calculated indicators of phase transitions, isomerizations, onsets of chaotic behavior, and other dynamical critical phenomena in classical microaggregates, such as nanoscale clusters. 相似文献
12.
Mikhail Vorob''ev 《Colloids and surfaces. B, Biointerfaces》2003,31(1-4):133-140
The role of aqueous media in the stabilization of globular proteins and formation of gels was studied by absorption millimeter spectroscopy. This method allowed to measure bound water, the fraction of water which had decreased rotational mobility owing to the presence of solute. Hydration data for globular proteins were compared with data obtained previously for low-weight molecules and groups. It was found that rotational mobility of water molecules in the hydration shells of various kinds of solutes (groups) decreased in the following order: water structure breaking compounds>polar groups>unfolded proteins>globular proteins>non-polar groups. Time courses of the storage modulus were determined for the chemical acidification by glucono-δ-lactone (GDL) of milk samples prepared from skimmed milk powder (SMP). Gelation of unheated milk was a monotonous process that started at pH 4.9. Heat-treated milk from SMP (16 and 14 g per 100 ml) acidified by GDL (3 g per 100 ml) at 43 °C gave non-monotonous kinetics of gelation with two phases corresponding to the mechanisms induced by denatured whey proteins at pH>5 and by casein–casein interactions at pH 4.8–4.9. For heat-treated milk, measurement of bound water gave two stages of decrease in water mobility. Additional hydration of SMP during acidification gave 0.15–0.2 g and 0.8 g bound H2O per gram of SMP for unheated and heat-treated milk, respectively. 相似文献
13.
Vyacheslav Ya. Sosnovskikh Boris I. Usachev Mikhail I. Kodess 《Tetrahedron letters》2004,45(39):7351-7354
Reactions of chromones with dilithiooximes proceed via nucleophilic 1,2-addition to give, on acidification, 4H-chromene-4-spiro-5′-isoxazoline derivatives in high yields. On treatment with concentrated H2SO4 the isoxazoline ring of this novel spiroannulated heterocyclic system opens to give α,β-unsaturated oximes, which undergo nitrosation, bromination, and the Beckmann rearrangement to the corresponding spiroisoxazolines and α,β-unsaturated amides, respectively. The latter can be obtained directly by the Beckmann rearrangement of 4H-chromene-4-spiro-5′-isoxazolines. 相似文献
14.
Dr. Alexey S. Kiryutin Mikhail S. Panov Dr. Alexandra V. Yurkovskaya Prof. Dr. Konstantin L. Ivanov Prof. Dr. Geoffrey Bodenhausen 《Chemphyschem》2019,20(5):766-772
A study of long-lived spin order in chlorothiophene carboxylates at both high and low magnetic fields is presented. Careful sample preparation (removal of dissolved oxygen in solution, chelating of paramagnetic impurities, reduction of convection) allows one to obtain very long-lived singlet order of the two coupled protons in chlorothiophene derivatives, having lifetimes of about 130 s in D2O and 240 s in deuterated methanol, which are much longer than the T1-relaxation times (18 and 30 s, respectively, at a field =9.4 T). In protonated solvents the relaxation times become shorter, but the lifetime is still substantially longer than . In addition, long-lived coherences are shown to have lifetimes as long as 30 s. Thiophene derivatives can be used as molecular tags to study slow transport, slow dynamics and slow chemical processes, as has been shown in recent years. 相似文献
15.
Computer-optimized selective pulses are routinely used in solution-state NMR spectroscopy. At the same time, their utility and importance for solid-state applications has yet to be fully realized. We suggest a new computational approach that makes the design of soft selective pulses with desired properties relatively straightforward. By applying this technique to the generic selective excitation problem, we have arrived at a family of high performance selective excitation pulses, dubbed E-Family, that allows more flexibility and better performance than analogous pulses previously reported in the literature. The new pulses have been successfully tested in both solid- and solution-state NMR experiments. A theoretical treatment of the effects of chemical shift anisotropy (CSA) on the selective excitation in magic-angle spinning (MAS) experiments in solids is presented. The set of heuristics that comprise our new strategy were incorporated into a general NMR simulation program SPINEVOLUTION. 相似文献
16.
The energy transfer between argon atoms and ozone complexes O3*, excited in the region of the dissociation threshold, is calculated for fixed temperatures (100 K< or =T < or =2500 K) using classical trajectories. The internal energy of ozone is resolved in terms of vibrational and rotational energies. For all temperatures, energy flows from O3* to Ar. The vibrational energy transfer, relative to k(B)T, is very small below 500 K, but gradually increases towards high temperatures. The relative rotational energy transfer, on the other hand, monotonously decreases with T; around 1100 K it falls below the relative vibrational energy transfer. Thermally averaged cross sections for vibrational and rotational energy transfers are also calculated. The implications for the stabilization of ozone complexes in the energy transfer model are discussed. 相似文献
17.
Mikhail Ivanovich Barnik Ivan Vladimirovich Simdyankin Boris Alexandrovich Umanskii Serguei Petrovich Palto 《Liquid crystals》2020,47(2):273-283
ABSTRACT Electro-optical switching and the liquid crystal (LC) director distribution are studied in spatially periodic electric field for vertically aligned LC with negative dielectric anisotropy. Two electro-optical switching modes characterised by different switching times are observed. These modes are well distinguished optically by choosing proper geometry for the polarisers axes orientation. One of these modes is significantly faster as compared to the other. The fast switching is explained in terms of localised near-to-surface director reorientation. The 3D-numerical simulation shows very good agreement with the experiment: it points out the existence of the disclination lines and field-stabilised walls responsible for the localised director field switching and its relaxation. Possibilities of enhancing the fast mode for high-speed light modulators are discussed. 相似文献
18.
Khoudiakov M Parise AR Brunschwig BS 《Journal of the American Chemical Society》2003,125(15):4637-4642
Electroabsorption (Stark) spectroscopy has been used to study the dye sensitized interfacial electron transfer in an Fe(II)(CN)(6)(4)(-) donor complex bound to a TiO(2) nanoparticle. The average charge-transfer distance determined from the Stark spectra is 5.3 A. This value is similar to the estimated distance between the Fe(II) center of the complex and the Ti(IV) surface site coordinated to the nitrogen end of a bridging CN ligand in (CN)(5)Fe(II)-CN-Ti(IV)(particle). This finding suggests that the electron injection is to either an individual titanium surface site or a small number of Ti centers localized around the point of ferrocyanide coordination to the particle and not into a conduction band orbital delocalized over the nanoparticle. The polarizability change, Tr(Deltaalpha), between the ground and the excited states of the Fe(II)(CN)(6)(4)(-)-TiO(2)(particle) system is approximately 3 time larger than normally observed in mixed-valence dinuclear metal complexes. It is proposed that the large polarizability of the excited state increases the dipole-moment changes measured by Stark spectroscopy. 相似文献
19.
Lyudmila V. Chernykh Jitka Eysseltova Mikhail Y. Skripkin 《Monatshefte für Chemie / Chemical Monthly》2003,124(1):751-761
Solubility isotherms in the CuBr2−MBr−H2O (M
+ = Li+, Na+, Cs+) systems at 298.15 K were measured. The results together with other available literature data for copper chloride and bromide
systems were treated by hydration analysis, and comparative discussion of ionic processes taking place in the respective saturated
solutions was performed. 相似文献
20.
Magdalena?SkompskaEmail author Mikhail?A.?Vorotyntsev 《Journal of Solid State Electrochemistry》2004,8(6):360-368
We report electrochemical studies on the influence of a small concentration of chloride ions on the electroactivity of the polymer matrix of polypyrrole (PPy), poly(N-methylpyrrole) [p(N-MePy)] and a poly(titanocene-propyl-pyrrole) derivative, p(Tc3Py) [Tc(CH2)3NC4H4; Tc=CpCpTiCl2; Cp=C5H5; Cp=C5H4] in acetonitrile (AN), tetrahydrofuran (THF) and N,N-dimethylformamide (DMF). The polymer films were obtained on Pt disc electrodes from AN solutions of the monomers containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) as the supporting electrolyte and then transferred to the corresponding monomer-free solution. Studies in Cl–-containing solutions have shown that the p(Tc3Py) matrix is very sensitive to the presence of Cl– ions in all the above solvents, namely that it was subjected to electrochemical degradation at potentials above 0.1 V vs. a Ag/0.01 M Ag+ in AN reference electrode. Degradation of the p(Tc3Py) matrix was also observed in chloride-free DMF+TBAPF6 solutions. Addition of chloride ions to the AN solution containing pyrrole, N-methylpyrrole or Tc3Py inhibits the deposition of the polymer films. On the other hand, we have found that PPy and p(N-MePy) matrices after their deposition in chloride-free AN solutions show much more stable redox responses in contact with chloride and/or DMF solutions. Possible mechanisms of these effects are discussed.Abbreviations AN
acetonitrile
- Cp
cyclopentadienyl
- DMF
N,N-dimethylformamide
- N-MePy
N-methylpyrrole
- p(N-MePy)
poly(N-methylpyrrole)
- PPy
polypyrrole
- p(Tc3Py)
poly[Tc(CH2)3NC4H4]
- Py
pyrrole
- Tc
titanocene=bis(cyclopentadienyl)titanium dichloride, Cp2TiCl2, or its radical CpCpTiCl2 (Cp=C5H4)
- Tc3Py
titanocene-propyl-pyrrole, Tc(CH2)3NC4H4
- THF
tetrahydrofuran
Contribution to the 3rd Baltic Conference on Electrochemistry, Gdansk-Sobieszewo, Poland, 23–26 April 2003Dedicated to the memory of Harry B. Mark, Jr. (28 February 1934–3 March 2003) 相似文献