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51.
52.
Dorothy J. Park Tammy D. Fulmer Charles F. Beam 《Journal of heterocyclic chemistry》1981,18(3):649-651
C(α),O-Dilithiooximes were prepared in an excess of lithium diisopropylamide and condensed with several 2-aminobenzophenones, followed by acid hydrolysis of the oximes to the ketones, which then underwent cyclodehydration and linear dehydration to give substituted quinolines or dihydrobenz[c]acridines. 相似文献
53.
We prove that the Boolean lattice of all subsets of an n-set can be partitioned into chains of size four if and only if n9.Research supported in part by N.S.F. grant DMS-8401281.Research supported in part by N.S.F. grant DMS-8406451. 相似文献
54.
The method of differences is used to establish that every 2-regular multigraph onv– 10,2 (mod 3) points occurs as the neighbourhood graph of an element in a twofold triple system of orderv, with two exceptions: C2C3and C3C3.Dedicated to Professor Hanfried Lenz on the occasion of his seventieth birthday 相似文献
55.
Charles H. Bennett 《Foundations of Physics》1986,16(6):585-592
The observed complexity of nature is often attributed to an intrinsic propensity of matter to self-organize under certain (e.g., dissipative) conditions. In order better to understand and test this vague thesis, we define complexity as logical depth, a notion based on algorithmic information and computational time complexity. Informally, logical depth is the number of steps in the deductive or causal path connecting a thing with its plausible origin. We then assess the effects of dissipation, noise, and spatial and other symmetries of the initial conditions and equations of motion on the asymptotic complexity-generating abilities of statistical-mechanical model systems. We concentrate on discrete, spatially-homogeneous, locally-interacting systems such as kinetic Ising models and cellular automata. 相似文献
56.
The potential generated by a plastic-membrane calcium ion-selective electrode (i.s.e.) is shown to be indirectly measurable by a non-zero current method based on bipolar pulse conductance. Linear current—voltage curves are obtained using 0–5-V pulses; the current axis intercept is related to the i.s.e. potential. A simple electrical contact (e.g., platinum or stainless steel) can be used instead of a poised reference electrode as the counter electrode in this two-electrode system. Long-term exposure of the i.s.e. to calcium solutions causes an upward drift in the measured current. This drift is minimized by avoiding long exposure times to solution, rinsing the electrode between measurements, and constructing current—voltage curves for determination of the current axis intercepts. Voltage pulses lasting 100 μs are optimum for this method. Shorter pulses are subject to error from capacitive charging currents, and longer pulses yield poorer precision, and degrade the electrode through faradaic reactions. The measured signal is dependent upon Ca2+ concentration (rather than activity), making ionic strength adjustment unnecessary. The concentration dependence is induced by application of voltage pulses greater than ~ 15 mV in amplitude. Selectivities of the potentiometric and conductometric methods are shown to be comparable for a variety of interfering monovalent and divalent cations. The conductometric method yields a fast i.s.e. response because of induced migration of Ca2+ into the membrane. Response time decreases as the pulse height increases. Pulses greater than 2 V in magnitude yield response times limited by the solution mixing time rather than by the electrode. 相似文献
57.
Charles H. Womack Robert T. Gampe B. Kaye Lemke Kailash N. Sawhney Thomas L. Lemke Gary E. Martin 《Journal of heterocyclic chemistry》1982,19(5):1105-1107
Treatment of 2-pivaloyl-1,3-indandione with hydroxylamine leads to the formation of a pair of isomeric indenoisoxazoles, the product formed dependent upon the cyclization conditions. Under acidic conditions, 8-t-butylindeno[1,2-c]isoxazol-7-one ( 5 ) is formed while under neutral or basic conditions, an oxime, 2 , is generated which may then be cyclized under acidic conditions to give 3-t-butylindeno[1,2-c]isoxazol-4-one ( 4 ). Although these isomeric indenoisoxazoles may be discriminated by chemical means, we were interested in developing an unequivocal method for distinguishing these and potentially other isomeric pairs by spectroscopic means. A 13C-nmr based method for the discrimination of these isomers which is based on the utilization of chemical shift arguments and spin-lattice relaxation data is thus presented. 相似文献
58.
Abstract— Results concerning Rose Bengal sensitized photoxidation of 2,7-dimethyl-2,6-octadiene (A) are discussed. This diolefin may be considered as a model molecule of polyisoprene of polymerization number two with 1,4-4,1 addition mode.
All the mono- and dihydroperoxides apt to occur are actually obtained. One of the occurring hydroperoxides, 2,7-dimethyl-dihydroperoxy-3,5-octadiene, which has the structure of a conjugated diene, does not lead to an endoperoxide. This is contrary to Kaplan and Kelleher's hypothesis. On the other hand, no trihydroperoxide forms as a result of further addition of singlet oxygen (1 O2 ).
A complete kinetic study has allowed us to determine the rate constants of all the reactions which take place. The reactivity of (A) is twice that of 2-methyl-2-pentene and the addition of1 O2 to one of the double bonds of (A) induces deactivation of the remaining double bond. 相似文献
All the mono- and dihydroperoxides apt to occur are actually obtained. One of the occurring hydroperoxides, 2,7-dimethyl-dihydroperoxy-3,5-octadiene, which has the structure of a conjugated diene, does not lead to an endoperoxide. This is contrary to Kaplan and Kelleher's hypothesis. On the other hand, no trihydroperoxide forms as a result of further addition of singlet oxygen (
A complete kinetic study has allowed us to determine the rate constants of all the reactions which take place. The reactivity of (A) is twice that of 2-methyl-2-pentene and the addition of
59.
Razak J. Al-Essa Richard J. Puddephatt Charles F.H. Tipper Peter J. Thompson 《Journal of organometallic chemistry》1978,157(2):C40-C42
The platinacyclobutane complexes PtCl2L2(C3H5Me)], L pyridine, CD3CN, or tetrahydrofuran, exist as mixtures of isomers containing PH2 or P groups in rapid equilibrium. Decomposition occurs in some cases to give [PtCl2L(CH3CH2CHCH2)]. Stereospecific skeletal isomerisation also occurs in metallocyclobutanes containing the groups PH2 PHR, when R aryl further decomposition gives ν-allylplatinum complexes. 相似文献
60.
J. Popplewell A. Al-Qenaie S. W. Charles R. Moskowitz K. Raj 《Colloid and polymer science》1982,260(3):333-338
The thermal conductivity of a number of ferrofluids consisting of colloidally dispersed Fe3O4 particles in diester, hydrocarbon, water and fluorcarbon carriers have been measured at 38°C. The variation in thermal conductivity with particle concentration is well described by Tareef's equation (1940). This has enabled the ratio of the physical to magnetic size to be determined and compared with estimates of the ratio obtained from electron micrographs and magnetic measurements.The fit between theory and experiment is particularly good for hydrocarbon carrier fluids giving the ratio of solid to magnetic radiusR
i/R
m=1.24±0.03 compared with the value obtained from magnetic data and electron micrographs of 1.19±0.07. The corresponding value from the fluids with a diester carrier ranges between 1.1<R
d/R
m<1.3 which is again consistent with microscopy and magnetic data.The application of a magnetic field of 0.1 T had no noticeable effect on the thermal conductivities of ferrofluids. 相似文献