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41.
Samuel O. Asekomhe Janet A. W. Elliott 《Colloids and surfaces. A, Physicochemical and engineering aspects》2003,220(1-3):271-278
Much research has been done on line tension measurement and interpretation, and attempts have also been made to measure line tension with simple, cheap and reliable methods that do not require excessive sophistication. Of particular interest is the method of determining line tensions of solid–liquid–vapor systems from the capillary rise in a conical tube. This simple and relatively inexpensive method gives line tension values comparable to those reported in the literature obtained via highly sophisticated instruments or techniques such as the well known axisymmetric drop shape analysis technique. The absolute value of line tension obtained using the conical tube method and assuming a spherical liquid–vapor interface is larger but of the same order of magnitude (1 μJ m−1) as that reported in the literature. A theoretical analysis presented herein shows that by including the deformation of the liquid–vapor interface due to gravity in the conical capillary analysis, the line tension value inferred from the experimental data is reduced by approximately 50% and compares better with values in the literature obtained using other sophisticated methods. Thus a relatively simple, cheap, accurate and reliable method of line tension measurement has been advanced. 相似文献
42.
John A. Montgomery James R. Piper Robert D. Elliott Eugene C. Roberts Carroll Temple Y. Fulmer Shealy 《Journal of heterocyclic chemistry》1979,16(3):537-539
Eighteen derivatives of 2,4-diamino-6-methylpteridine related to methotrexate and aminopterin have been prepared from 6-(bromomethyl)-2,4-pteridinediamine by nucleophilic displacement reactions. None of these compounds showed any antileukemic acitivity. 相似文献
43.
Minimum action solutions of some vector field equations 总被引:2,自引:0,他引:2
The system of equations studied in this paper is –u
i
=g
i
(u) on
d
,d2, withu:
d
n
andg
i
(u)=G/u
i
. Associated with this system is the action,S(u)={1/2|u|2–G(u)}. Under appropriate conditions onG (which differ ford=2 andd3) it is proved that the system has a solution,u 0, of finite action and that this solution also minimizes the action within the class {v is a solution,v has finite action,v 0}.Work partially supported by U.S. National Science Foundation Grant PHY-81-16101-A02 相似文献
44.
Hsuan-Yin Lan-Hargest John D. Elliott Drake S. Eggleston Brian W. Metcalf 《Tetrahedron letters》1987,28(52):6557-6560
Photolysis of the steroidal dienol triflate
in pyridine solution using a medium pressure mercury lamp leads to the formation of 6β-trifluoromethyl enone
in 78% yield. The structure of compound
was confirmed by x-ray analysis. 相似文献
45.
Summary The following [(NH3)5RhLH]Cl3 salts were preparedvia the [(NH3)5Rh(O3SCF3)](O3SCF3)2 synthetic route; LH=1-methylimidazole (1CH3imH), 2-methylimidazole (2CH3imH), 4-methylimidazole (4CH3imH), 5-methylimidazole(5CH3imH), and pyrazole (pyzH). pKa's at 25.0°C were determined for [(NH3)5RhLH]3+ complexes as follows: 2CH3imH, 10.4±0.1; 5CH3imH/4CH3imH isomer mixture, 10.3±0.1; pyzH, 6.54±0.05. The influence on the pKa's of imidazoles is dominated by withdrawal of the rhodium(III) centre and may be compensated by the presence of ring methylation by only 0.5log units for cobalt(III) and rhodium(III) derivatives, compared to 1.3 units for the -withdrawing ruthenium(III) centre. In the case of the -acceptor pyrazole ring, [(NH3)5Rh]3+ is observed to serve as a slight -donor and raises the pKa above the cobalt(III) analogue. The1H n.m.r. spectra of [(NH3)5RhLH]3+ complexes of the substituted imidazoles and pyrazole exhibit a deshielding order. C–2H>C–5H>C–4H for imidazoles and C–3H>C–5H>C–4H for pyrazole, as do their cobalt(III) analogues. The magnitude of values (=free L-complex) are virtually the same as in the cobalt(III) systems which shows that TIP influences are unimportant compared to ring rehybridization in estabilishing chemical shifts for both the cobalt(III) and rhodium(III) complexes. The imidazolato and pyrazolato complexes exhibit resonances upfield of the respective substituted imidazole or pyrazole complex in keeping with more negative charge on the rings; the influence is largest at C–2H of imidazolates and C–3H of pyrazolate. 相似文献
46.
Catalytic hydrogenation of some 4-arylidene-1,3-(2H,4H)isoquinolinediones (1) afforded the corresponding 4-arylmethyl-1,3-(2H,4H)isoquinolinediones (2) , but reduction of 1 by sodium borohydride gave 4-arylmethyl-1(2H)isoquinolones (isocarbostyrils, 3). Compounds of type 1 studied had aryl substituents phenyl, 3,4-dimethoxyphenyl, 3,4-methyleneoxyphenyl and 2-furyl. In one example of sodium borohydride reduction of an N-methylisoquinolinedione derivative (1) the heterocylic ring was opened, and 2-(1-hydroxymethyl-2-phenylethenyl)-N-methylbenzamide (4) was obtained from 4-benzylidene-2-methyl-1,3-(2H,4H)isoquinolinedione. 相似文献
47.
Ola Bratteli George A. Elliott Richard H. Herman 《Communications in Mathematical Physics》1980,74(3):281-295
A simpleC*-algebra and a continuous one-parameter automorphism group are constructed such that the set of inverse temperatures at which there exist equilibrium states (i.e., KMS states, or, for =±, ground or ceiling states) is an arbitrary closed subset of IR{±}.With partial support of the National Science Foundation 相似文献
48.
Elliott H. Lieb 《Communications in Mathematical Physics》1980,77(2):127-135
A general formulation is given of Simon's Ising model inequality:
whereB is any set of spins separating from . We show that
b
can be replaced by
b
A
whereA is the spin system insideB containing . An advantage of this is that a finite algorithm can be given to compute the transition temperature to any desired accuracy. The analogous inequality for plane rotors is shown to hold if a certain conjecture can be proved. This conjecture is indeed verified in the simplest case, and leads to an upper bound on the critical temperature. (The conjecture has been proved in general by Rivasseau. See notes added in proof.)Work partially supported by U.S. National Science Foundation grant PHY-7825390 A01 相似文献
49.
Correlation of antioxidant depletion and mechanical performance during thermal degradation of an HTPB elastomer 总被引:1,自引:0,他引:1
M. Celina J.M. Skutnik Elliott S.T. Winters R.A. Assink L.M. Minier 《Polymer Degradation and Stability》2006,91(8):1870-1879
Thermal degradation studies of a stabilized HTPB based elastomer were conducted at temperatures from 50 °C to 110 °C. The concentration of extractable antioxidant (AO2246) in the polymer was quantified via AO extraction and a gas chromatography-based method using internal standards. The decrease in extractable AO levels as a function of time and temperature was evaluated and correlated with mechanical property changes. Most importantly, AO depletion features were found to be temperature dependent. At elevated temperatures (>80 °C) extractable AO levels decreased rapidly and faster than the concurrent loss in mechanical properties. While extractable AO concentrations decrease quickly, the material is able to maintain some useful mechanical properties, perhaps via non-extractable or grafted AO species formed during degradation providing additional protection. At lower aging temperatures extractable or free AO levels decreased more slowly than the mechanical properties. Therefore, for condition monitoring purposes a universal correlation between AO levels and aging state or material condition could not be established. Most importantly, however, loss of mechanical properties and oxidative degradation is observed at lower temperatures despite significant levels of free antioxidant in the material. The antioxidant appears to be limited in its effectiveness to completely prevent degradation reactions, or only fractions of the total AO available are actually involved in the inhibition process. 相似文献
50.
Mitrovski SM Elliott LC Nuzzo RG 《Langmuir : the ACS journal of surfaces and colloids》2004,20(17):6974-6976
We describe the fabrication and performance of a passive, microfluidics-based H2-O2 microfluidic fuel cell using thin film Pt electrodes embedded in a poly(dimethylsiloxane) (PDMS) device. The electrode array is fully immersed in a liquid electrolyte confined inside the microchannel network, which serves also as a thin gas-permeable membrane through which the reactants are fed to the electrodes. The cell operates at room temperature with a maximum power density of around 700 microW/cm(2), while its performance, as recorded by monitoring the corresponding polarization curves and the power density plots, is affected by the pH of the electrolyte, its concentration, the surface area of the Pt electrodes, and the thickness of the PDMS membrane. The best results were obtained in basic solutions using electrochemically roughened Pt electrodes, the roughness factor, R(f), of which was around 90 relative to a smooth Pt film. In addition, the operating lifetime of the fuel cell was found to be longer for the one using higher surface area electrodes. 相似文献