Combined two-dimensional velocity and temperature measurements of natural convection using a high-speed camera and temperature-sensitive particles

This paper proposes a combined method for two-dimensional temperature and velocity measurements in liquid and gas flows using temperature-sensitive particles (TSPs), a pulsed ultraviolet laser, and a high-speed camera. TSPs respond to temperature changes in the flow and can also serve as tracers for the velocity field. The luminescence from the TSPs was recorded at 15,000 frames per second as sequential images for a lifetime-based temperature analysis. These images were also used for the particle image velocimetry calculations. The temperature field was estimated using several images, based on the lifetime method. The decay curves for various temperature conditions fit well to exponential functions, and from these the decay constants at each temperature were obtained. The proposed technique was applied to measure the temperature and velocity fields in natural convection driven by a Marangoni force and buoyancy in a rectangular tank. The accuracy of the temperature measurement of the proposed technique was ±0.35–0.40°C.     

Theoretical Investigation of an Eddy-Viscosity-Type Expression of the Reynolds Stress with Low-Reynolds-Number Effect

In low-Reynolds-number turbulent flows, the influence of the molecular viscosity is important. The turbulence models which are applied to those flows should include the low-Reynolds-number effect. In this study, turbulent flow with the molecular viscosity effect is analyzed theoretically with the aid of a two-scale direct-interaction approximation (TSDIA) and the energy spectrum and a new low-Reynolds-number-type eddy-viscosity representation are derived. An priori test for the model expression on the basis of the result of direct numerical simulation (DNS) for turbulent Couette flows is performed. Received 5 July 2002 and accepted 8 January 2003 Published online 25 March 2003 Communicated by T.B. Gatski     

二氧化硅负载[C5Me5]2SmMe(THF)引发甲基丙烯酸甲酯聚合

近年来 ,有许多文献报道茂金属催化剂的负载化及其在烯烃聚合中的应用 ,这对发展新型茂金属催化剂和开发新型高分子材料有重要意义 [1,2 ] .我们 [3]曾报道壳聚糖负载稀土催化剂用于甲基丙烯酸甲酯的配位聚合有优良性能 .以五甲基环戊二烯为配体的有机稀土配合物 ,如 [Sm H( C5Me5) ]2 ,[C5Me5]Ln Me( THF) ( Ln=Sm,Yb)等在甲苯中单组分引发甲基丙烯酸甲酯聚合及内酯开环聚合具有许多优异性能[4 ,5] ,但是经负载化的该类催化剂的聚合性能尚未见报道 .本文报道将 [C5Me5]2 Sm Me·( THF)负载于二氧化硅 ,引发甲基丙烯酸甲酯聚合的结…     

PRODAN-conjugated DNA: synthesis and photochemical properties

A solvatochromic fluorophore, PRODAN, has been used as a microenvironment-sensitive reporter. Based on the chemistry of PRODAN, we designed and synthesized four novel fluorescent nucleosides, PDNX (X = U, C, A, and G), to which a PRODAN fluorophore was attached at pyrimidine C5 or purine C8. The fluorescent nucleosides sensitively varied the Stokes shift values depending on the orientational polarizability of the solvent. The PDNX incorporated into DNA also changed the Stokes shift values depending on the DNA structure. In particular, the excitation spectrum of the PDNX-containing duplex shifted to a longer wavelength and gave a smaller Stokes shift value when the base opposite PDNX could form a Watson-Crick base pair with PDNX. A lower energy excitation of PDNX-containing DNA resulted in a strong fluorescence emission selective to the Watson-Crick pairing base. This unique photochemical character was applicable to the efficient typing of single-nucleotide polymorphisms of genes.     

Phase-ordering kinetics of the liquid-liquid transition in single-component molecular liquids

Recently it has been revealed that even a single-component liquid can have more than two liquid states. The transition between these liquid states is called the "liquid-liquid transition." Most known liquid-liquid transitions occur at temperatures and pressures which are difficult to access experimentally, so the physical nature of the transition, particularly the kinetics, has remained elusive. However, the recent discovery of liquid-liquid transitions in molecular liquids opens up a possibility to study the kinetics in detail. Here, we report the first phase field simulation on the kinetics of a liquid-liquid transition and its direct comparison with experimental results of the molecular liquids. Both nucleation-growth-type and spinodal-decomposition-type liquid-liquid transformation observed experimentally are well reproduced by numerical simulation based on a two-order-parameter model of liquid that regards the liquid-liquid transition as the cooperative formation of locally favored structures. Thus, phase field calculations may allow us to predict the kinetics of liquid-liquid transitions and the resulting spatiotemporal change of various physical properties of the liquid, such as density and refractive index.     

Conformational transitions of cyclic D,L-peptides

Conformational transitions of cyclic D,L-hexapeptides have been studied by first-principles calculations. Geometry optimizations for 20 types of homoresidue cyclic D,L-hexapeptide revealed that the cyclic peptides have two types of energetically stable backbone (extended (E) and bound (B) types); and for each type, the amino acid side chains have two orientations (equatorial and axial). Among the four types of isomer [E-type equatorial (E(eq)), B-type equatorial (B(eq)), E-type axial (E(ax)), and B-type axial (B(ax))], B(ax) is the energetically most preferred by most of the 20 encoded amino acid residues, whereas E(ax) is the least preferred. A search for transition states indicated that six types of conformational transition are possible between the isomers of the cyclic peptide, i.e., the backbone-backbone conversions (E(eq)-B(eq) and E(ax)-B(ax) transitions), the side chain-side chain conversions (E(eq)-E(ax) and B(eq)-B(ax) transitions), and the simultaneous conversions of the backbone and the side-chain orientation (E(eq)-B(ax) and E(ax)-B(eq) transitions). All the six transitions proceed with the breaking of the high molecular symmetry (S(6)) and go through the triangular (C(3)) intermediate structure with either equatorial or axial side-chain orientation.     

Synthesis and chiral recognition of helical poly(phenylacetylene)s bearing l‐phenylglycinol and its phenylcarbamates as pendants

A series of novel stereoregular one‐handed helical poly(phenylacetylene) derivatives ( PPA‐1 and PPA‐1a～g ) bearing l ‐phenylglycinol and its phenylcarbamate residues as pendants was synthesized for use as chiral stationary phases (CSPs) for HPLC, and their chiral recognition abilities were evaluated using 13 racemates. The phenylcarbamate residues include an unsubstituted phenyl, three chloro‐substituted phenyls (3‐Cl, 4‐Cl, 3,5‐Cl₂), and three methyl‐substituted phenyls (3‐CH₃, 4‐CH₃, 3,5‐(CH₃)₂). The acidity of the phenylcarbamate N‐H proton and the hydrogen bonds formed between the N‐H groups of the phenylcarbamate residues were dependent on the type, position, and the number of substituents on the phenylcarbamate residues. The chiral recognition abilities of these polymers significantly depended on the dynamic helical conformation of the main chain with more or less regularly arranged pendants. The chiral recognition abilities seem to be improved by the introduction of substituents on the phenylcarbamate residues, and PPA‐1d bearing the more acidic N‐H groups due to the 3,5‐dichloro substituents, exhibited a higher chiral recognition than the others. PPA‐1d showed an efficient chiral recognition for some racemates, and baseline separation was possible for racemates 5 , 11 , 12 , and 15 . © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 809–821     

Thermal activation of KF/alumina catalyst for double bond isomerization and Michael addition

KF/alumina catalyst exhibits activity for double bond isomerization of 1-pentene at 273 K when pretreatedin vacuo in the temperature range 573–673 K, while the activity for Michael addition of nitromethane to butene-2-one does not change much with the pretreatment temperature.