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111.
Pai SC 《Journal of chromatography. A》2002,950(1-2):271-279
The deformation of a flow injection analysis peak from a Gaussian shape has two components: spatial and temporal. The former is mainly attributed to the Poisseulie effect in the tubular flow, whereas the latter is related to the observing position (of a fixed detector) at which signal is measured. The combination of the two makes a skewed peak track on the recorder chart. Therefore, an observed peak may imply a substantial fraction of a “false” tail due to the effect of non-simultaneous detection. An expanding-Gaussian model is proposed to simulate the purely temporal effect, and the asymmetric factors were compared with that of the experimental peak shapes. In most cases the peak deformation occurring in flow injection analysis should be regarded as “temporal”. The contribution of the spatial effects (Poisseulie profile and others) might not be as significant as it was thought previously. 相似文献
112.
T. R. Govindachari P. C. Parthasarathy B. R. Pai P. S. Subramaniam 《Tetrahedron》1965,21(12):3715-3720
On the basis of degradative and spectral evidence and synthesis, echioidin, the new flavone glucoside isolated from Andrographis echioides Nees, is shown to be 5-hydroxy-2′-β-
-glucosidoxy-7-methoxyflavone (echioidinin-2′-β-
-glucoside). 相似文献
113.
114.
Pai Tang Can Zhang En Chen Binhui Chen Wenteng Chen Yongping Yu 《Tetrahedron letters》2017,58(22):2157-2161
MnIII-catalyzed functionalization of vinyl azides via phosphorylation was developed to synthesize various β-keto phosphine oxides in high yields. The transformation is operated in mild conditions and tolerant of a range of functional groups. Control reaction indicates that the reaction mechanism might proceed via the generation of a phosphonated iminyl radical intermediate. 相似文献
115.
We formulate the data analysis problem for the detection of the Newtonian coalescing-binary signal by a network of laser interferometric
gravitational wave detectors that have arbitrary orientations, but are located at the same site. We use the maximum likelihood
method for optimizing the detection problem. We show that for networks comprising of up to three detectors, the optimal statistic
is just the matched network-filter. Alternatively, it is simply a linear combination of the signal-to-noise ratios of the
individual detectors. This statistic, therefore, can be interpreted as the signal-to-noise ratio of the network. The overall
sensitivity of the network is shown to increase roughly as the square-root of the number of detectors in the network. We further
show that these results continue to hold even for the restricted post-Newtonian filters. Finally, our formalism is general
enough to be extended, in a straightforward way, to address the problem of detection of such waves from other sources by some
other types of detectors, eg., bars or spheres, or even by networks of spatially well-separated detectors. 相似文献
116.
In this paper we review some of the recently introduced hypertopologies on collections of nonempty closed subsets of a metrizable space in the context of continuity properties of the prox map and the restricted center map. We identify here suitable families A, B of nonempty closed sets equipped with natural topologies, as coordinate spaces for the gap functional and the restricted radius functional, with a view to explore bivariate continuity of these functionals. This leads us to sharpenings of many known results as well as to some new results for upper semicontinuity of the prox map and the restricted center map. This, in turn, also leads us to improvements of certain best approximation results for convex-valued multifunctions and fixed point theorems for such multifunctions. 相似文献
117.
A simple and analytical pair potential function was developed to represent the osmotic pressures in aqueous protein/salt systems under various conditions. Based on a hard core Lennard-Jones (HCLJ) potential model, the new potential function considers various interactions by extending the attractive Lennard-Jones potential. A temperature-dependent coefficient term was introduced to take into account the specific properties of given materials. Comparison of the new potential function with the HCLJ model in hydrocarbon and water systems showed that consideration of the temperature dependence in the potential function was effective, especially for strong polar systems such as water. To predict the osmotic pressures of aqueous lysozyme/(NH(4))(2)SO(4) solutions of various ionic strength and pH, the energy parameters of lysozyme were correlated with the experimental cloud point temperature. The proposed model agreed fairly well with the experimental osmotic pressure data with only previously obtained parameters. 相似文献
118.
Pai SS Przybycien TM Tilton RD 《Langmuir : the ACS journal of surfaces and colloids》2010,26(23):18231-18238
Covalent grafting of poly(ethylene glycol) chains to proteins ("PEGylation") is emerging as an effective technique to increase the in vivo circulation time and efficacy of protein drugs. PEGylated protein adsorption at a variety of solid/aqueous interfaces is a critical aspect of their manufacture, storage, and delivery. A special category of block copolymer, PEGylated proteins have one or more water-soluble linear polymer (PEG) blocks and a single globular protein block that each exert distinct intermolecular and surface interaction forces. We report the impact of PEGylation on protein adsorption at the interface between aqueous solutions and solid films of poly(lactide-co-glycolide) (PLG), a moderately hydrophobic and negatively charged polymer. Using the model protein lysozyme with controlled degrees of PEGylation, we employ total internal reflection fluorescence techniques to measure adsorption isotherms, adsorption reversibility, and the extent of surface-induced aggregation. Lysozyme PEGylation reduces the extent of protein adsorption and surface-induced aggregation and increases the reversibility of adsorption compared to the unconjugated protein. Results are interpreted in terms of steric forces among grafted PEG chains and their effects on protein-protein interactions and protein orientation on the surface. 相似文献
119.
Fifteen liquid chromatographic experiments were investigated using a whole‐column detection (WCD) system and a conventional post‐column UV/Vis detector. The peak widths obtained from chromatograms were found dependent on the retention factor; the larger the retention factor was the greater the peak width. However, the on‐column spatial peak widths were dependent on the locations where they were measured in the column. The peak widths monitored at 17 cm from the column inlet were found essentially the same no matter what their retention factors were. In addition, a linear relationship was found between the chromatographic peak width and the reciprocal of the average linear rate of the solute migration. The peak widths on chromatograms did not reflect how they appeared in the column; instead, the widths were determined by the solute speed passing the detector. 相似文献
120.
Sahai MA Fejer SN Viskolcz B Pai EF Csizmadia IG 《The journal of physical chemistry. A》2006,110(40):11527-11536
First-principle computations were carried out on the conformational space of trans and cis peptide bond isomers of HCO-Thr-NH2. Using the concept of multidimensional conformational analysis (MDCA), geometry optimizations were performed at the B3LYP/6-31G(d) level of theory, and single-point energies as well as thermodynamic functions were calculated at the G3MP2B3 level of theory for the corresponding optimized structures. Two backbone Ramachandran-type potential energy surfaces (PESs) were computed, one each for the cis and trans isomers, keeping the side chain at the fully extended orientation (chi1=chi2=anti). Similarly, two side chain PESs for the cis and trans isomers were generated for the (phi=psi=anti) orientation corresponding to approximately the betaL backbone conformation. Besides correlating the relative Gibbs free energy of the various stable conformations with the number of stabilizing hydrogen bonds, the process of trans-->cis isomerization is discussed in terms of intrinsic stabilities as measured by the computed thermodynamic functions. 相似文献