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101.
Marshall M. Siegel Rushung Tsao Allan Wissner 《Journal of mass spectrometry : JMS》1993,28(11):1297-1308
A series of substituted bisaryl phosphate compounds, (R1CH2)+ ArOP = O(O?)(OArR2R3), was analyzed and characterized by fast atom bombardment mass spectrometry. Abundant fragment ions were observed and correlated with the proposed structures. From fragmentation pattersn, ‘ortho effect’ reactions were demonstrated to have occurred when the phosphoryl oxygen reacted with the (CH2R1)+ and C?O(OCH3) substituents in the ortho position, relative to the phosphate group, and displaced the R1 and OCH3 groups, respectively, to produce phosphorus containing six-membered rings fused to the aryl moiety. When the (CH2R1)+ substituents were in the meta position relative to the phosphate group, the ‘ortho effect’ reactions were not observed. However, when the C?O(OCH3) substituent was in the meta position relative to the phosphate group, an abundant fragment ion containing a five-membered phosphate ring fused to the aryl ring was detected with the original phosphoryl oxygen ortho to both the phosphate oxygen and a formyl group, formed from the original C?O(OCH3) substituent. All other fragmentations not involving the ‘ortho effect’ reactions were nearly identical for the different structural isomers of the substituted bisaryl phosphate compounds. 相似文献
102.
Lee Ching-Yi Wen Jingquan Thomas Seqwana Delgass W. Nicholas Grutzner John B. Tsao George T. 《Applied biochemistry and biotechnology》1995,53(1):29-35
In theEscherichia coli cell-free system, the modification of cell extract can be achieved by preparation of the strains carrying additional property
or those being induced with a certain gene expression prior to harvesting. In this study, we analyzed the cell-free system
with S30 extract containing T7 RNA polymerases (S30 extract-T7pol) prepared from E.coli BL21(DE3) strain, which includes T7 RNA polymerase from extrinsic genes by IPTG induction, as a model for the improvement
of the cell-free system. The fact that a significant degree of mRNA degradation was observed in the cell-free system with
S30 extract-T7pol indicates the increase of ribonuclease activity was an unfavorable influence derived from the cell-extract
modification process. We also showed that this influence was settled by the addition of an effective ribonuclease inhibitor,
such as copper (II) ion, to the reaction mixture. 相似文献
103.
The purpose of this paper is to extend the TOPSIS method based on interval-valued fuzzy sets in decision analysis. Hwang and Yoon developed the technique for order preference by similarity to ideal solution (TOPSIS) in 1981. TOPSIS has been widely used to rank the preference order of alternatives and determine the optimal choice. Considering the fact that it is difficult to precisely attach the numerical measures to the relative importance of the attributes and to the impacts of the alternatives on these attributes in some cases, therefore, the TOPSIS method has been extended for interval-valued fuzzy data in this paper. In addition, a comprehensive experimental analysis to observe the interval-valued fuzzy TOPSIS results yielded by different distance measures is presented. A comparative analysis of interval-valued fuzzy TOPSIS rankings from each distance measure is illustrated with discussions on consistency rates, contradiction rates, and average Spearman correlation coefficients. Finally, a second-order regression model is provided to highlight the effects of the number of alternatives, the number of attributes, and distance measures on average Spearmen correlation coefficients. 相似文献
104.
Sulfur-substituted azido dienes 1 and 11 , conveniently prepared from the corresponding 3-sulfolenes 5 and 10 , were thermolyzed to give pyrrolizidine and indolizidine products, 6 , 7 and 14 . 相似文献
105.
Cheng MY Chang YC Galvanauskas A Mamidipudi P Changkakoti R Gatchell P 《Optics letters》2005,30(4):358-360
We explored high-energy and high-peak-power pulse generation in large-core multimode fiber amplifiers, achieving what is to our knowledge the highest reported energies, up to 82 mJ for 500-ns pulses, 27 mJ for 50-ns pulses, and 2.4-MW peak power for 4-ns pulses at 1064 nm, using 200-microm-diameter and 0.062-N.A. core Yb-doped double-clad fiber amplifiers. The highly multimode nature of the fiber core was mitigated by use of a coiling-induced mode-filtering effect to yield a significant improvement in output-beam quality from M2 = 25 from an uncoiled fiber to M2 = 6.5 from a properly coiled fiber, with the corresponding reduction in number of propagating transverse modes from > or = 200 to < or = 20. 相似文献
106.
Effective charges of polyelectrolytes in a salt-free solution based on counterion chemical potential
The phenomenon of counterion condensation around a flexible polyelectrolyte chain with N monomers is investigated by Monte Carlo simulations in terms of the degree of ionization alpha, which is proportional to the effective charge. It is operationally defined as the ratio of observed to intrinsic counterion concentration, alpha = co/ci. The observed counterion concentration in the dilute polyelectrolyte solution is equivalent to an electrolyte solution of concentration co with the same counterion chemical potential. It can be determined directly by thermodynamic experiments such as ion-selective electrode. With the polyelectrolyte fixed at the center of the spherical Wigner-Seitz cell, the polymer conformation, counterion distribution, and chemical potential can be obtained. Our simulation shows that the degree of ionization rises as the polymer concentration decreases. This behavior is opposite to that calculated from the infinitely long charged rod model, which is often used to study counterion condensation. Moreover, we find that, for a specified line charge density, alpha decreases with an increment in chain length and chain flexibility. In fact, the degree of ionization is found to decline with increasing polymer fractal dimension, which can be tuned by varying bending modulus and solvent quality. Those results can be qualitatively explained by a simple model of two-phase approximation. 相似文献
107.
Identification of a specifically expressed modified form of novel PSP-94 protein in the secretion of benign prostatic hyperplasia. 总被引:1,自引:0,他引:1
108.
By using different regularization methods we demonstrate that supersymmetry invariance is maintained up to one-loop order in supersymmetric gauge theories and calculate the superconformal anomalies. 相似文献
109.
Hung-Sheng Tsao 《Physics letters. [Part B]》1977,68(1):79-80
By using the dimensional regularization procedure, we explicitly calculate the coefficients of conformal anomalies in a general background metric due to scalar, spin fermion, gauge and gravitation fields. 相似文献
110.
Sorption of phenols from water in column systems using surfactant-modified montmorillonite 总被引:1,自引:0,他引:1
The sorption of phenol, m-nitrophenol (m-NP), and o-cresol from water onto montmorillonite modified with cetyltrimethylammonium bromide (CTAB) in a column was studied. The sorption isotherms were fitted by the Langmuir equation. Column experiments were performed at 25 degrees C to determine the breakthrough curves at different flow rates, feed sorbate concentrations, and bed lengths. It was shown that the proposed constant-pattern wave approach with the Langmuir model could well describe the breakthrough curves. The time required when the effluent concentration reached half of the feed concentration (t(1/2)) decreased with increasing feed flow rate, but the mass transfer coefficient (KLa) increased. In addition, an increase in feed sorbate concentration led to a decrease of both values of t(1/2) and KLa. The effect of axial dispersion on breakthrough dynamics in these sorption systems was finally discussed. 相似文献