排序方式: 共有41条查询结果,搜索用时 31 毫秒
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Sanford TW Allshouse GO Marder BM Nash TJ Mock RC Spielman RB Seamen JF McGurn JS Jobe D Gilliland TL Vargas M Struve KW Stygar WA Douglas MR Matzen MK Hammer JH De Groot JS Eddleman JL Peterson DL Mosher D Whitney KG Thornhill JW Pulsifer PE Apruzese JP Maron Y 《Physical review letters》1996,77(25):5063-5066
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A group additivity method is described which provides heat capacity estimates of the condensed phase. The data base consists of 810 liquids and 446 solids. Group values for carbon in various common substitution and hybridization states and for 47 functional groups are provided. The standard error of estimation using this approach on this data base is 19.5 (liquids) and 26.9 J/ (mole K) (solids). This can be compared to typical experimental uncertainties of 8.12 and 23,4 J/ (mole K) associated with these measurements, respectively. Experimental uncertainties were estimated from the numerical differences obtained for a given substance from multiple independent literature reports. 相似文献
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This essay is the introductory paper for a special issue of Structural Chemistry explicitly dedicated to the premier Spanish calorimetrist and thermochemist, our colleague and friend, María Victoria Roux. The studies in this issue were written on the occasion of her recent retirement from the CSIC Institute of Physical Chemistry “Rocasolano,” Madrid. 相似文献
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The thermolysis of both dl and -3,4-dideuterio-cyclobutane-1,2-dione at 250°C yields ethylene and carbon monoxide in which 79% of the stereochemistry of the reactant is retained in the ethylene. 相似文献
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An integral equation formulation for buoyancy-driven convection problems is developed and illustrated. Buoyancy-driven convection in a bounded cylindrical geometry with a free surface is studied for a range of aspect ratios and Nusselt numbers. The critical Rayleigh number, the nature of the cellular motion, and the heat transfer enhancement are computed using linear theory. Green's functions are used to convert the linear problem into linear Fredholm integral equations. Theorems are proved which establish the properties of the eigenvalues and eigenfunctions of the linear integral operator which appears in these equations. 相似文献
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A semiempirical MO method was used to calculate potential energy surfaces for ketene dimerization. One supra-supra and two supra-antara pathways were investigated. Six parameters were used to characterize the relative motion of individual groups. Two levels of approximation for the motion were considered. First, synchronous reaction pathways were followed, and a set of single-dimensional potential curves generated. Then, deviations from these synchronous reaction pathways were considered for each parameter and five two-dimensional potential surfaces for each pathway generated. Agreement with the available experimental data is satisfactory. However, we conclude that contrary to the Woodward-Hoffmann rules [1] the supra-supra pathway is allowed and the supra-antara pathways essentially forbidden. In the former case the local symmetry of the orbitals involved in the ring formation is not conserved during the reaction, in the latter case the nuclear repulsion is dominating. 相似文献
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The first measurements of the enthalpies of combustion, sublimation, and fusion of an organo-phosphorus sulfide, triphenylphosphine sulfide, are reported: c
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(C18H15PS, cr)=–(10752.58 ±2.90), sub
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(C18H15PS, 403 K)=(136.80±6.09), and fus
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(C18H15PS, Tm=435.92 K) =(30.53±0.21) kJ·mol–1. Correction of the phase change enthalpies toT=298.15K and po =0.1 MPa results in the standard phase change enthalpy values of sub
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m
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(298.15 K)=(142.8 ±6.8) and fus
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(298.15 K)=(19.28±0.21) kj·mol–1. Accordingly, the enthalpies of formation of solid, liquid, and gaseous triphenylphosphine sulfide are derived: f
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(C18H15PS, cr) =(63.20±2.56), fH
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(C18H15PS, l)=(82.48±2.57), and fH
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(C18H15PS, g)=(206.0±7.3) kJ·mol–1. From these ancillary data, the P=S double-bond enthalpy is 394 kJ-mol–1 and in good agreement with earlier reaction calorimetry results. These phosphorus sulfide values are compared with those for the arsenic sulfides. Plausibility arguments are given for our results. 相似文献
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Fernández P Durand JS Pérez-Conde C Paniagua G 《Analytical and bioanalytical chemistry》2003,375(8):1020-1023
This paper reports a new flow-through fluoroimmunosensor, the function of which is based on antibodies immobilized on an inmunoreactor of controlled-pore glass (CPG), for determination of digoxin, used in the treatment of congestive heart failure and artery disease. The immunosensor has a detection limit of 1.20 microg L(-1) and provides high reproducibility (RSD=4.5% for a concentration of 0.0025 mg L(-1), and RSD=6.7% for 0.01 mg L(-1)). The optimum working concentration range was found to be 1.2 x 10(-3)-4.0 x 10(-2) mg L(-1). The lifetime of the immunosensor was about 50 immunoassays; if stored unused its lifetime can be extended to three months. A sample speed of about 10-12 samples per hour can be attained. Possible interference from substances with structures similar to digoxin (morphine, heroin, tebaine, codeine, pentazocine and narcotine) was investigated. No cross-reactivity was seen at the highest digoxin: interferent ratio studied (1:100). The proposed fluoroimmunosensor was successfully used to determine digoxin concentrations in human serum samples. 相似文献