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1.
Amos Korin Moshe Levy David Vofsi 《Journal of polymer science. Part A, Polymer chemistry》1980,18(1):109-121
Vinyl fluoride was polymerized by photochemical initiation in a continuous-flow cylindrical reactor at room temperature and at pressures of up to 30 atm. Copolymers with vinyl acetate were prepared in order to improve the solubility and processability of poly(vinyl fluoride) (PVF). The copolymers were hydrolyzed to the corresponding vinyl alcohol copolymers and yielded hydrophilic films that are strong and flexible only when swollen by water. It was found that on hydrolysis the Tg, Tm, and heat of fusion as well as degree of crystallinity increased. It was suggested that PVF and the copolymers with vinyl alcohol are isomorphous. 相似文献
2.
Wheeler KE Lees NS Gurbiel RJ Hatch SL Nocek JM Hoffman BM 《Journal of the American Chemical Society》2004,126(41):13459-13463
The rotational mobilities of small solute molecules encapsulated in tetramethyl orthosilicate (TMOS) sol-gels have been investigated by EPR spectroscopy of encapsulated nitroxide probes and by high-resolution NMR spectroscopic measurements of transferred NOE's (trNOE's), of T(1)'s, and of T(1)'s in the rotating frame (T(1)rho). The two spectroscopic methods are sensitive to motions on different time scales and hence, are nicely complementary. Suites of neutral, positively, and negatively charged nitroxide probes (EPR) and of simple diamagnetic small molecules (NMR) were selected to disclose influences of electrostatic interactions with the sol-gel walls and to probe the presence of multiple populations of molecules in distinct regions of the sol-gel pores. For neutral and negatively charged solute probes, both techniques disclose a single population with a significantly increased average rotational correlation time, which we interpret at least in part as resulting from exchange between free-volume and transiently immobilized surface populations. The electrostatic attraction between cationic probes and the negatively charged sol-gel walls causes the positively charged probes to be more effectively immobilized and/or causes a greater percentage of probes to undergo this transient immobilization. The EPR spectra directly disclose a population of cationic probes which are immobilized on the X-band EPR time scale: tau(c) greater than or approximately equal 10(-7) s. However, NMR measurements of trNOE's and of T(1)rho demonstrate that this population does exchange with the free-volume probes on the slower time scale of NMR. This approach is equally applicable to the study of solutes within other types of confined spaces, as well. 相似文献
3.
Vapour pressures of water over saturated solutions of dl-2-aminobutyric acid, 4-aminobutyric acid, sodium-d-gluconate, sodium hippurate, and potassium magnesium-l-aspartate were determined over the (278 to 322) K temperature range. The determined vapour pressures were used to obtain the water activities, the molar enthalpies of vaporization, and the osmotic coefficients of sodium-d-gluconate. 相似文献
4.
In this Letter we describe a novel method for tunable viscoelastic focusing of particles flowing in a microchannel. It is proposed that some elasticity, inherently present in dilute polymer solutions, may be responsible for highly nonuniform spatial distribution of flowing particles across the channel cross section, yielding their "focusing" in the midplane of the channel. A theory based on scaling arguments is presented to explain the lateral migration and is found to be in a very good agreement with the experimental observations. It was found that, in agreement with the theoretical prediction, the particles would have different spatial distribution depending on their size and rheology of the suspending medium. We demonstrate how the viscoelastic focusing can be precisely controlled by proper rheological design of the carrier solution. 相似文献
5.
Korin E. Soifer L. Mogiliyanskii D. Soifer Ya. Brodova I. Manuhin A. 《Journal of Thermal Analysis and Calorimetry》1999,58(3):663-669
Crystallization kinetics of Mg84Ni12.5Y3.5 amorphous ribbons produced by the melt-spinning method, was studied by DSC analysis and X-ray diffraction. The effect of heating rate (from 2 to 240 K min–1) was investigated in the temperature range from 298 to 673 K. The results showed that the crystallization process took place in two stages: a) crystallization of part of the amorphous matrix to an intermediate phase and hcp-Mg, and b) transformation of the intermediate phase and the remaining amorphous material to Mg2Ni+Mg (solid solution of Y in Mg). Increasing the heating rate from 2 to 240 K min–1 results in increases of the temperature difference between the two-step crystallization of the first stage transformation processes from 33 to 56 K and in increases of the temperature difference between the two-stage transformation from 62 to 97 K.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
6.
V.?F.?Kopiev V.?V.?PalchikovskiyEmail author I.?V.?Belyaev Yu.?V.?Bersenev S.?Yu.?Makashov I.?V.?Khramtsov I.?A.?Korin E.?V.?Sorokin O.?Yu.?Kustov 《Acoustical Physics》2017,63(1):113-124
The acoustic parameters of a new anechoic chamber constructed at Perm National Research Polytechnic University (PNRPU) are presented. This chamber is designed to be used, among other things, for measuring noise from aerodynamic sources. Sound-absorbing wedges lining the walls of the chamber were studied in an interferometer with normal wave incidence. The results are compared to the characteristics of sound-absorbing wedges of existing anechoic facilities. Metrological examination of the acoustic parameters of the PNRPU anechoic chamber demonstrates that free field conditions are established in it, which will make it possible to conduct quantitative acoustic experiments. 相似文献
7.
Differential scanning calorimetry (DSC) and X-ray diffraction techniques were used to study the crystallization kinetics of Al91La5Ni4 amorphous alloys prepared by a rapid quenching method. The experimental results showed that the thermal treatment of the melt — temperature regime and exposure time — had a significant effect on the crystallinity of the ribbons prepared by rapid quenching, and hence on the crystallization kinetics of the ribbon alloys in the annealing process. 相似文献
8.
Crystallization kinetics of Al91La5Ni4 amorphous ribbons produced by a melt-spinning method were studied by DSC analysis and X-ray diffraction. The effect of heating
rate (from 4 to 200°C min-1) was investigated in the temperature range from 298 to 700 K. Increases the heating rate from 4 to 200°C min-1 resulted in increases of the temperature difference between the two stages of the transformation process: crystallization
of Al and crystallization of the Al compounds from 148.9 to 167.4 K. The apparent activation energies for the first step,
related to Al crystallization, and to the second step related to crystallization of Al4La and Al3Ni, were found to be 161±9 and 199±10 kJ mol-1, respectively. The results indicate the possibility of tailoring the heating treatment to produce the required fraction of
the amorphous phase.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Kobayashi A Ohbayashi K Aoki R Chang HC Kato M 《Dalton transactions (Cambridge, England : 2003)》2011,40(14):3484-3489
We synthesized a thiosemicarbazone-functionalized flavin (Fl-(H)TSC: 2-[2-(3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(2H)-yl)ethylidene]-hydrazinecarbothioamide) and its Pt(II) complex [Pt(Fl-TSC)(2)], and characterized it using X-ray diffraction, UV-visible absorption and luminescence spectroscopy. X-ray structural analysis for [Pt(Fl-TSC)(2)] revealed that the structure of the isoalloxazine part was almost the same as that in lumiflavin (7,8,10-trimethylisoalloxazine), and the thiosemicarbazone moiety acted as a bidentate ligand to form a PtS(2)N(2) planar conformation. UV-visible absorption and luminescence spectra of these compounds were very similar to those of riboflavin, but the emission intensity and the lifetime decreased considerably. Theoretical calculations suggested that the charge-separated state (Fl˙(-)-TSC˙(+)) contributed to the faster quenching from the (1)π-π* emission state. 相似文献
10.
Steiner I Richmond K Marshall I Gray CD 《The Journal of the Acoustical Society of America》2012,131(2):EL106-EL111
This paper announces the availability of the magnetic resonance imaging (MRI) subset of the mngu0 corpus, a collection of articulatory speech data from one speaker containing different modalities. This subset comprises volumetric MRI scans of the speaker's vocal tract during sustained production of vowels and consonants, as well as dynamic mid-sagittal scans of repetitive consonant-vowel (CV) syllable production. For reference, high-quality acoustic recordings of the speech material are also available. The raw data are made freely available for research purposes. 相似文献