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11.
Ab initio molecular orbital calculations employing a 4-31G basis set have been used to study the minimum energy paths for the formation of HCO+, COH+, and HCOH2+ from CO by protonation. The protonation of N2 to give NNH+ and HNNH2+ and of NO+ to form HNO2+ and NOH2+ have also been investigated. All species formed have linear equilibrium geometries and the minimum energy path for approach of the proton is along the line-of-centers of the heavy atoms. Energy barriers to the formation of the various species are given, where appropriate, and changes in geometry, ordering of molecular orbitals and orbital occupancy are discussed. 相似文献
12.
3,3′-Thiobispyridine is prepared by reaction of pyridine-3-thiol with 3-bromopyridine. The base peak in the mass spectrum of 3,3′-thiobispyridine is due to the molecular ion which fragments by loss of H, HCN and CS as well as by central bond rupture. The 1,1′-dimethyl diquaternary salt of 3,3′-thiobispyridine is reduced polarographically by a one electron transfer not involving hydrogen to an unstable radical cation at a potential (Eo) of −0.72 V in the pH range 7.4–11.2. 相似文献
13.
Zhengjie Pi Joseph P. Kennedy James W. Summers 《Journal of polymer science. Part A, Polymer chemistry》2002,40(21):3644-3651
The tertiary chlorine (Clt) content of vinyl chloride/2‐chloropropene copolymers [P(VC‐co‐2CP)] was determined by NMR spectroscopy. Copolymers containing 6.8–47.0 Clt's per P(VC‐co‐2CP) chain were used to initiate the cationic grafting of α‐methylstyrene, norbornadiene, indene, and norbornene with Et2AlCl under various conditions. Grafting was demonstrated by selective solvent extraction, and the effect of the experimental conditions on the grafting efficiency was examined. Select rheological and thermal characteristics of P(VC‐co‐2CP) grafts, including the glass‐transition temperature, heat deflection temperature, and discoloration upon heating, were studied. P(VC‐co‐2CP) carrying 7–11 poly(α‐methylstyrene) or polynorbornadiene branches per chain raised the glass‐transition temperature to, or above, that of a blend control. P(VC‐co‐2CP)s fitted with polyindene or polynorbornene branches were less effective in raising the mechanical properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3644–3651, 2002 相似文献
14.
Alves GA Amato S Anjos JC Appel JA Astorga J Bracker SB Cremaldi LM Dagenhart WD Darling CL Dixon RL Errede D Fenker HC Gay C Green DR Jedicke R Karchin PE Kennedy C Kwan S Lueking LH de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Passmore D Rafatian A dos Reis AC Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wallace A Wu Z 《Physical review letters》1996,77(12):2388-2391
15.
If
(V) is a net of local von Neumann algebras satisfying standard axioms of algebraic relativistic quantum field theory and V
1
and V
2
are spacelike separated spacetime regions, then the system (
(V
1
),
(V
2
), ) is said to satisfy the Weak Reichenbach's Common Cause Principle iff for every pair of projections A
(V
1
), B
(V
2
) correlated in the normal state there exists a projection C belonging to a von Neumann algebra associated with a spacetime region V contained in the union of the backward light cones of V
1
and V
2
and disjoint from both V
1
and V
2
, a projection having the properties of a Reichenbachian common cause of the correlation between A and B. It is shown that if the net has the local primitive causality property then every local system (
(V
1
),
(V
2
), ) with a locally normal and locally faithful state and suitable bounded V
1
and V
2
satisfies the Weak Reichenbach's Common Cause Principle. 相似文献
16.
A recent result by Borchers connecting geometric modular action, modular inclusion and spectrum condition, is applied in quantum field theory on spacetimes with a bifurcate Killing horizon (these are generalizations of black-hole spacetimes, comprising the familiar black-hole spacetime models). Within this framework, we give sufficient, model-independent conditions ensuring that the temperature of thermal equilibrium quantum states is the Hawking temperature. 相似文献
17.
I.R. Summers 《Applied Acoustics》1980,13(6):441-448
Measurements were taken on four oil/air or gas/air diffusion flames to investigate the connection between fluctuations in air velocity in or near the flame zone, fluctuations in burning rate and combustion noise output. In all cases the combustion noise spectrum was found to be approximately 6 dB per octave up on the spectrum of air velocity fluctuations. The simple model of the noise generation mechanism suggested by this result was not supported by measurements on burning rate fluctuations. However, in almost all cases the transfer functions between fluctuations in air velocity, burning rate and sound output could be expressed as a function of frequency by a simple power law. 相似文献
18.
19.
In a systematic study of hybrid MR time-series with simulated "activation" (contrast-to-noise range 1-10) we investigated the power and compared the ability of the "novelty indices" (NI) kurtosis, negentropy, and 1-lag autocorrelation, to discriminate between potentially interesting ("structured") and uninteresting ("noisy") time-courses (TCs). NIs may be employed as preprocessing tools to focus only on the interesting TCs prior to any further exploratory or confirmatory approach. 相似文献
20.