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1.
In this study we examined the unsteady and chaotic characteristics of the natural convection field in vertical slots at large
Prandtl number. In the computation, temperature dependence of viscosity was partially taken into consideration. As a result
we discovered that the spatial region where a significant temperature fluctuation is detected corresponds to the spatial region
where the secondary cells exist. The largest Lyapunov exponents calculated from the temperature on the center line have a
local maximum at the lower region of the enclosure when the viscosity change was considered. These characteristics agree well
with the experimental ones that have been observed by authors (Ishida, Kure and Kimoto 2001). 相似文献
2.
Treatment of aromatic aldehyde with lithium pentamethylcyclopentadienide provided the corresponding carbinol in excellent yield. The carbinol returns to the parent aldehyde and pentamethylcyclopentadiene upon exposure to an acid or due to heating. The combination of the two reactions can represent a protection of aromatic aldehyde. 相似文献
3.
Summary The mechanical property of aqueous gel was studied using the PVA having the content of syndiotacticity in diad from 58.4 and 66.2%. The elastic modulus of gels was 105–106 dyne/cm2 and the variation of the elastic modulus of gel with the rise of temperature was corresponded with the variation of the concentration of PVA in gel accompanying syneresis. The elastic modulus of gel having the same content of syndiotacticity and concentration of PVA increased in the order as follows, the first is the gel chilled at room temperature, the second is the gel chilled at 60 °C and last is the gel chilled at 0 °C. The variation of the elastic modulus of gel with the rise of temperature became smaller with increasing content of syndiotacticity. The increase of elastic modulus is considered to be attributed to the further growth of stronger junctions through the recrystallization followed by syneresis rather than the entropic effect of polymer networks with the rise of temperature.
With 6 figures and 2 tables
Part 2. cf. reference 2. 相似文献
Zusammenfassung Es wurden die mechanischen Eigenschaften wßriger Gele aus Polyvinylalkohol untersucht, mit Gehalten an Syndioaktizität in Diaden zwischen 58,4 und 66,2%. Die elastischen Moduln der Gele lagen bei 105 bis 106 dyn/cm2 und die Variation der elastischen Moduln der Gele mit Steigerung der Temperatur entsprach der Konzentrationsänderung von Polyvinylalkohol im Gele gemäß der stattgefundenen Synärese. Der elastische Modul des Gels mit konstantem Gehalt an Syndiotaktizität und Konzentration des PVA steigen in folgender Weise: Zuerst das Gel abgekühlt bei Raumtemperatur, dann das Gel abgekühlt bei 60 °C und zuletzt das Gel erstarrt bei 0 °C. Die Variation der elastischen Moduln mit steigender Temperatur wird kleiner mit steigendem Gehalt an Syndiotaktizität. Das Anwachsen der Moduln sollte vermutlich dem weiteren Wachstum strengerer Kopp lungen durch Rekristallisation infolge der Synärese zuzuschreiben sein mehr als einem Entropieeffekt der polymeren Netzwerke mit steigender Temperatur.
With 6 figures and 2 tables
Part 2. cf. reference 2. 相似文献
4.
In order to know the potential merits of 99mTc-pyrophosphate (99mTc-PYP) skeletal imaging, a comparative study was carried out by administering to the rabbit 85Sr-chloride (85Sr), classical bone-seeking agent, and 99mTc-PY simultaneously. Radioisotopic distribution was investigated as regards their deposition in the pelvic bones, and sharpness of the skeletal scintigrams, too. Both agents were remarkably affinitive to the skeletal system and there were remarkably differences in their temporal deposition pattern. Marked deposition was observed of either agent in the metaphyses. With 99mTc-PYP, the vertebral and costal systems were delineated symmetrically and each vertebral body was distinctly depicted as such 99mTc-PYP many possess the following merits over 85Sr; (1) owing to its physical properties, sufficiently large radioactivity of 99mTc-can be administered; (2) body burden of radiation absorption is reduced; (3) skeletal scintigrams of high quality are obtainable in a short period of time. 相似文献
5.
Raman spectra of intramolecular vibration mode for each guest species in the methane + tetrafluoromethane (CF4) mixed-gas hydrate crystal have been measured at 291.1 K. Both of pure guest species generate the structure-I hydrate in the present pressure ranges. Isothermal phase-equilibrium curve exhibits two discontinuous points around the equilibrium methane compositions (water-free) in the gas phase of 0.3 and 0.8. At the above points, the Raman spectra of both guest molecules have been drastically changed. One of the most important findings is that the crystal of methane + tetrafluoromethane mixed-gas hydrate shows the structural phase-transition (from the structure-I to the structure-II and back to the structure-I) caused by composition changes. 相似文献
6.
Ishikawa A Takata T Kondo JN Hara M Kobayashi H Domen K 《Journal of the American Chemical Society》2002,124(45):13547-13553
A Ti-based oxysulfide, Sm(2)Ti(2)S(2)O(5), was studied as a visible light-driven photocatalyst. Under visible light (440 nm < or = lambda < or = 650 nm) irradiation, Sm(2)Ti(2)S(2)O(5) with a band gap of approximately 2 eV evolved H(2) or O(2) from aqueous solutions containing a sacrificial electron donor (Na(2)S-Na(2)SO(3) or methanol) or acceptor (Ag(+)) without any noticeable degradation. This oxysulfide is, therefore, a stable photocatalyst with strong reduction and oxidation abilities under visible-light irradiation. The electronic band structure of Sm(2)Ti(2)S(2)O(5) was calculated using the plane-wave-based density functional theory (DFT) program. It was elucidated that the S3p orbitals constitute the upper part of the valence band and these orbitals make an essential contribution to the small band gap energy. The conduction and valence bands' positions of Sm(2)Ti(2)S(2)O(5) were also determined by electrochemical measurements. It indicated that conduction and valence bands were found to have satisfactory potentials for the reduction of H(+) to H(2) and the oxidation of H(2)O to O(2) at pH = 8. This is consistent with the results of the photocatalytic reactions. 相似文献
7.
γ-Butyrolactone (hereafter abbreviated GBL) is produced by the two-stage hydrogenation of maleic anhydride(MAH) in the liquid phase: the hydrogenation of MAH to succinic anhydride(SAH) in the first stage and the subsequent hydrogenation of SAH to GBL in the second stage. A novel ruthenium catalyst system consisting of Ru salts, trialkylphosphine and p-toluene sulfonic acid (p-TsOH) was found very effective for the hydrogenation of SAH affording GBL, which exhibited excellent catalyst performance, exceeding 97% selectivity for GBL and high activity. 相似文献
8.
Intramolecular tandem Michael-type addition/aldol cyclization induced by TiCl(4)-R(4)NX combinations
[reaction: see text] Treatment of formyl alpha,beta-enones with a TiCl(4)-R(4)NX combination induces an intramolecular aldol cyclization to furnish 2-acyl-3-halocyclohexanol with three controlled consecutive stereogenic centers. The reaction of bis-alpha,beta-enones with the combination provides cyclic diketones with high stereoselectivity via an intramolecular Michael addition reaction. 相似文献
9.
Kazuyoshi Tanaka Kazunari Yoshizawa Tokio Yamabe 《International journal of quantum chemistry》1991,40(3):305-314
We studied the midgap levels appearing in the photoexcited conductive polymers such as trans- and cis-polyacetylenes, poly(p-phenylene), polypyrrole, and polyacene based on the molecular orbital analysis. The midgap levels are constructed from the transformation of the highest occupied molecular orbital and the lowest unoccupied molecular orbital of the ground state. As the result of the localization of the wave functions associated with these midgap levels, large polarization is induced between adjacent carbon atoms. Based on the examination of the energy gap between the two midgap levels, the polymers with a nondegenerate ground state such as cis-polyacetylene, poly(p-phenylene), and polypyrrole would show no sizable photoconductivities. 相似文献
10.
Fukuyama T Yamaura R Higashibeppu Y Okamura T Ryu I Kondo T Mitsudo TA 《Organic letters》2005,7(26):5781-5783
[reaction: see text] Catalytic [2 + 2 + 1 + 1] cocyclization reaction of an alkyne, an alkene, and two molecules of carbon monoxide, leading to functionalized hydroquinones, was studied. Using [Cp*RuCl2]2 as a catalyst, we found that a variety of electron-deficient alkenes, such as alpha,beta-unsaturated ketones, esters, amides, and nitriles, can be employed as an alkene coupling partner to give the corresponding hydroquinones. 相似文献