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101.
We propose a graphical method to treat dilution shift in NMR spectra to determine the monomer shift, dimer shift and dimerization constant simultaneously and consistently for the system of monomer/dimer equilibrium. The salient features include avoiding error-prone manual extrapolation to zero concentration to obtain a monomer shift, and providing consistent assessment and error estimation for the determination. The dilution shifts of 2-isopropyl phenol in C6D12 serve to demonstrate this graphical method. The enthalpy and entropy of dimerization are determined via a van't Hoff plot from the temperature variation of the dimerization constant. 相似文献
102.
J. -C. Diels J. J. Fontaine J. C. McMichael C. Y. Wang A. Andreoni R. Cubeddu S. Cova A. Longoni W. Knox G. Mourou T. M. Nordlund C. H. Brito Cruz F. De Martini P. Mataloni E. Palange J. M. Catherall P. M. Radmore G. H. C. New A. Müller F. P. Schäler Zs. Bor B. Rácz D. Relser A. Laubereau B. Pouligny J. R. Lalanne B. Couilaud A. Ducasse C. Vaucamps D. Schubert J. Schwarz H. Wabnitz B. Wilhelmi 《Applied physics. B, Lasers and optics》1982,28(2-3):172-179
103.
Retention mechanisms of an unmodified and a hydroxylated polystyrene-divinylbenzene polymer were studied by solid-phase extraction of o-phthalic acid and some of its mono- and diesters from purified water and then analysing by GC-MS. The monoesters and phthalic acid were retained only when protonated (i.e. acidified with HCI to pH 0.9). Of all elution solvents tested, ethyl acetate gave the best overall recoveries (61-89%) with both polymers. Applicability to complex matrixes (e.g. acidogenic landfill leachates) was examined by introducing a washing step with acetone in acidified water (pH 0.9) to eliminate volatile fatty acids (C2-C6) from the cartridge. Finally, the method was tested on real samples. 相似文献
104.
Wai?Chee?ShiuEmail author Peter?Che?Bor?Lam Heping?Zhang 《Journal of mathematical chemistry》2005,38(4):451-466
This paper considers the k -resonance of a toroidal polyhex (or toroidal graphitoid) with a string (p, q, t) of three integers (p ≥ 2, q ≥ 2, 0 ≤ t ≤ p − 1). A toroidal polyhex G is said to be k-resonant if, for 1≤ i ≤ k, any i disjoint hexagons are mutually resonant, that is, G has a Kekulé structure (perfect matching) M such that these hexagons are M-alternating (in and off M). Characterizations for 1, 2 and 3-resonant toroidal polyhexes are given respectively in this paper.
*This work is supported by FRG, Hong Kong Baptist University; NSFC and TRAPOYT. 相似文献
105.
A direct error vector analysis of inverse heat conduction problem is presented to detect the measured noise. Based on the reverse matrix approach that the inverse problem is solved directly in a linear domain, and the error vector is formulated from the difference between the measured temperature and the estimated temperature. There is no prior knowledge on the exact solution while the error vector is constructed. The error vector is used to investigate the consistence of the measured data in the domain and lead to detect the noise data. Furthermore, the proper number of the undetermined variable is able to suggest based on the mean value of the error vector and the value of the condition number of the reverse matrix. In the first example, a test problem with the measurement noise is presented. The estimated result is influent by the noise globally. The result shows that the value of error vector is changed significantly at the coordinate of the measurement noise appeared. In other words, the error vector analysis is able to identify the noise data. In the second example, the proper number of series expansion terms is investigated. From the result, it shows that the number of expansion terms with the small mean value and condition number can better approximate to the unknown condition. It means that the proposed method is able to suggest a proper number of expansion terms when the function of the recovered boundary is unknown. 相似文献
106.
Clouding phenomena and phase behaviors of two nonionic surfactants, Triton X-114 and Triton X-100, in the presence of either hydroxyethyl cellulose (HEC) or its hydrophobically modified counterpart (HMHEC) were experimentally studied. Compared with HEC, HMHEC was found to have a stronger effect on lowering the cloud point temperature of a nonionic surfactant at low concentrations. The difference in clouding behavior can be attributed to different kinds of molecular interactions. Depletion flocculation is the underlying mechanism in the case of HEC, while the chain-bridging effect is responsible for the large decrease of cloud point for HMHEC. Composition analyses for the formed macroscopic phases were carried out to provide support for associative phase separation for the case of HMHEC, in contrast to segregative phase separation for HEC. An interesting three-phase-separation phenomenon was reported in some HMHEC/Triton X-100 mixtures at high surfactant concentrations. 相似文献
107.
Isothiazolidinones are a rare but potentially important chemical moiety in biochemistry. We report the identification of several thiol, phosphinate, and carbon nucleophiles that form covalent adducts by addition to the sulfenamide sulfur. This reduction is selective for isothiazolidinones over similar peptide disulfides. We synthesized a coumarin-based thioacid nucleophile which shows a marked fluorescence increase after addition to an isothiazolidinone sulfenamide bond. [structure: see text] 相似文献
108.
In this paper we have proved a main theorem concerning the | $\bar N$ , p n; δ |k summability methods, which generalizes a result of Bor and Özarslan [3]. 相似文献
109.
H. Yücel A. N. Solmaz E. Köse D. Bor 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(2):305-312
In this paper, a semi-empirical method is proposed to determine true coincidence-summing (TCS) correction factors for high
resolution γ-ray spectrometry. It needs the knowledge of both full energy peak (FEP) efficiency and total-to-peak (TTP) efficiency
curves. The TTP efficiency curve is established from the measurements with a set of coincidence-free point sources. Whereas
for a volume source, the coincidence-free FEP efficiency curve is obtained iteratively by using the peaks from almost the
coincidence-free nuclides and those from the coincident nuclides in the mixed standard sources. Then the fitting parameters
obtained for both TTP and FEP efficiency curves are combined in a freely-available TCS calculation program called TrueCoinc, which yields the TCS correction factors required for any nuclide. As an application, the TCS correction factors were determined
for the particular peaks of 238U, 226Ra and 232Th in the reference materials, measured in the case of a close-in detection geometry using a well-type Ge detector. The present
TCS correction method can be applied without difficulty to all Ge detectors for any coincident nuclide. 相似文献
110.
In this paper, a recent result dealing with \(| \bar{N},p_{n}|_{k}\) summability factors, has been generalized for \(|\bar{N},p_{n},\theta_{n}|_{k}\) summability factors. Some new results have also been obtained. 相似文献