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21.
A flow system has been developed to study relative rate coefficients of hydroxyl radicals reacting with alkanes under conditions relating to tropospheric chemistry. Relative Arrhenius parameters have been measured over the temperature range 243–328 K for pairs of alkanes from a list consisting of n-butane, 2-methylpropane, n-pentane, n-hexane, 2,2- and 2,3-dimethylbutane, 2,3,3-trimethylbutane, and 2,3,4-trimethylpentane. The results have been incorporated into a Structure-Activity Relation for hydroxylalkane reactions which leads to the following group rate coefficients for a temperature range of 240–500 K. 相似文献
22.
By photolyzing azomethane over the temperature range 331–491 K in the presence of trifluoroacetone the kinetics of the addition reaction (1), ?H3 + CF3COCH3 → CF3C(?)(CH3)2 have been studied. Detailed analyses have shown that the principal product of the adduct radical, CF3C(?)(CH3)2, is CH3COCH3 from reaction (?2), CF3C(?)(CH3)2 → CH3COCH3 + ?F3. The rate constant of the addition reaction has been determined to be k1(dm3/mol s) = (4.5 ± 1.4) × 107 exp(-(3370 ± 120)/T) over the temperature range 331–491 K, based on the value k3 = 2.2 × 1010 dm3/mol s for the reaction (3), 2?H3 → C2H6. The results are discussed in relation to existing data for radical additions to groups. 相似文献
23.
Mees FD Martens LR Janssen MJ Verberckmoes AA Vansant EF 《Chemical communications (Cambridge, England)》2003,(1):44-45
Hydrothermal stability of SAPO-34 is greatly improved by the treatment of the acidic form of the SAPO-34 with NH3. 相似文献
24.
25.
Abdullahi Mustapha Krystoff Busch Marta Patykiewicz Alistair Apedaile John Reglinski Alan R. Kennedy Timothy J. Prior 《Polyhedron》2008
The reaction of the Schiff base species tris-((2-hydroxybenzylidene)aminoethyl)-amine (TrenSal) and tris-((2-hydroxy-5-bromobenzylidene)aminoethyl)amine (Tren5BrSal) with the acetates of nickel and zinc are reported. Two trimetallic complexes (M3L2) of Tren5BrSal with nickel and zinc have been crystallographically characterised. The attempted crystallisation of bis-(tris-((2-hydroxybenzylidene)aminoethyl)amine nickel) nickel from solutions containing TMEDA lead to the production of two novel complexes: namely a nickel adduct of the partially hydrolysed TrenSal ligand and an interesting nickel bromide–carbonate salt. [(TrenSal)2Ni3] is reacted with PbCl2 to form a novel tetrametallic complex, [{(TrenSal)Ni}Pb(NC5H5)Cl]2, where a Pb2Cl2 moiety replaces the nickel at the core of the complex. Extending the study to include the related hexadentate ligand, 1,1,1-tris-((2-hydroxybenzylidene)-aminomethyl)propane (TEtSal), we were able to isolate and characterise both [(TEtSal)2Ni3] and [{(TEtSal)Ni}2Pb]. 相似文献
26.
Alistair P. D. Elfick Andrew R. Downes Rabah Mouras 《Analytical and bioanalytical chemistry》2010,396(1):45-52
Tip-enhanced optical spectroscopy is an approach that holds a good deal of promise for the nanoscale characterisation of matter. Tip-enhanced Raman spectroscopy (TERS) has been demonstrated on a variety of samples: inorganic, organic and biological. Imaging using TERS has been shown for carbon nanotubes due to their high scattering efficiency. There are a number of compelling motivations to consider alternative approaches for biological samples; most importantly, the potential for heat damage of biomolecules and long acquisition times. These issues may be addressed through the development of tip-enhanced coherent anti-Stokes Raman scattering microscopy. 相似文献
27.
Robert Reys Barbara Reys Gran Emanuelsson Bengt Johansson Alistair McIntosh Der Ching Yang 《School science and mathematics》1999,99(2):61-70
This paper reports selected findings from a study of number sense proficiency of students aged 8 to 14 years in Australia, Sweden, United States, and Taiwan. It comments on the meaning and importance of number sense, the development of the assessment instruments, and student responses to the items. Some implications for classrooms of the findings are then discussed. 相似文献
28.
This paper evaluates an algorithm for solving network flow optimization problems with quadratic cost functions. Strategies for fast implementation are discussed and the results of extensive numerical tests are given. The performance of the algorithm measured by CPU time is compared with that of the convex simplex method specialized for quadratic network programming. Performance of the two methods is analysed with respect to network size and density, and other parameters of interest. The algorithm is shown to perform significantly better on the majority of problems. We also show how the algorithm may be used to solve non-linear convex network optimization problems by the use of sequential quadratic programming. 相似文献
29.
Sawitree Saengkaew Tawatchai Charinpanitkul Hathaichanok Vanisri Loïc Mees Gérard Grehan 《Optics Communications》2006,259(1):7-13
To measure the temperature of individual droplets or the average temperature in a section of a spray, the analysis of the light scattered around the rainbow angle provides an attractive approach. Up to now, the analysis of recorded rainbow signals has been carried out in the framework of the full Lorenz-Mie theory or of the Airy theory. In this paper, we consider four approaches (Lorenz-Mie, Debye, Airy and Nussenzveig approaches) to compute the light scattered around the rainbow angle, and we compare them in terms of accuracy and time-consumption. It is shown that the Complex Angular Momentum (CAM) theory proposed by Nussenzveig, modified by using empirical coefficients, allows one to accurately compute the light scattered around the rainbow angle in a large angular domain for particles with diameters as small as 10 μm. 相似文献
30.
Sawitree Saengkaew Tawatchai Charinpanitkul Hathaichanok Vanisri Wiwut Tanthapanichakoon Yves Biscos Nicolas Garcia Gérard Lavergne Loïc Mees Gérard Gouesbet Gérard Grehan 《Experiments in fluids》2007,43(4):595-601
The rainbow refractrometry, under its different configurations (classical and global), is an attractive technique to extract
information from droplets in evaporation such as diameter and temperature. Recently a new processing strategy has been developed
which increases dramatically the size and refractive index measurements accuracy for homogeneous droplets. Nevertheless, for
mono component as well as for multicomponent droplets, the presence of temperature and/or of concentration gradients induce
the presence of a gradient of refractive index which affects the interpretation of the recorded signals. In this publication,
the effect of radial gradient on rainbow measurements with a high accuracy never reached previously is quantified. 相似文献