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91.
The gas-to-infinite dilution proton chemical shifts of acetonitrile in a series of non-polar, isotropic solvents have been measured. After allowance for the bulk susceptibility and van der Waals contributions, it is possible to to explain the observed shifts by the well-known reaction field theory. The existing level of experimental error in chemical shift measurement is sufficiently large that no justification exists in preferring the form of the theory based on an ellipsoidal cavity to that based on a spherical cavity. Some further observed results are given which demonstrate the existence of specific interactions between acetonitrile and each of several non-polar solvents including carbon tetrachloride. 相似文献
92.
For a square-free monomial ideal I ? S = k[x 1, x 2,…, x n ], we introduce the notion of quasi-linear quotients. By using the quasi-linear quotients, we give a new algebraic criterion for the shellability of a pure simplicial complex Δ over [n]. Also, we provide a new criterion for the Cohen–Macaulayness of the face ring of a pure simplicial complex Δ. Moreover, we show that the face ring of the spanning simplicial complex (defined in [2]) of an r-cyclic graph is Cohen–Macaulay. 相似文献
93.
Jiao Wei Asfand Fahad Ali Raza Priya Shabir Abdu Alameri 《International journal of quantum chemistry》2024,124(1):e27322
A key paradigm in contemporary research is the use of graphs to represent physical systems, molecular structures, or particularly metal frameworks. Graphs are increasingly widely used in a variety of fields, including the study of quantum and molecular systems, macromolecules and their interactions, socioeconomic and ecological systems, and technical and infra-structural systems. Understanding how these systems function, are robust, and are stable begins with structural characterization. The use of entropies and entropy-like measurements of graphs/structures of molecules/networks is crucial from both a mathematical and physical standpoint. Several entropy measures of graphs have been defined and studied extensively during the last few decades. The current paper is devoted to investigation of distance dependent entropy measures of Poly Propylene Imine (PPI) dendrimers and Zinc Porphyrin dendrimers. The analytical formulae of distance dependent entropy measures have been developed and their patterns have been presented through graphical tools. 相似文献
94.
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96.
This study describes a highly efficient method for the selective precipitation of phosphoproteins by trivalent europium, terbium,
and erbium metal ions. These metal cations belong to the group of lanthanides and are known to be hard acceptors with an overwhelming
preference for oxygen-containing anions such as phosphates to which they form very tight ionic bonds. The method could be
successfully applied to specifically precipitate phosphoproteins from complex samples including milk and egg white by forming
solid metal–protein complexes. Owing to the low solubility product of the investigated lanthanide salts, the produced metal–protein
complexes showed high stability. The protein pellets were extensively washed to remove nonphosphorylated proteins and contaminants.
For the analysis of proteins the pellets were first dissolved in 30 % formic acid and subjected to matrix-assisted laser desorption/ionization–time
of flight (MALDI-TOF) MS. For peptide mass-fingerprint analysis the precipitated phosphoproteins were enzymatically digested
using microwave-assisted digestion. The method was found to be highly specific for the isolation and purification of phosphoproteins.
Protein quantification was performed by colorimetric detection of total precipitated phosphoproteins and revealed more than
95 % protein recovery for each lanthanide salt. 相似文献
97.
It has been recognized that primary blast waves may result in neurotrauma in soldiers in theater. A new type of contrast used in magnetic resonance imaging (MRI), susceptibility-weighted imaging (SWI), has been developed that is based on the different susceptibility levels in diverse tissues and can detect decreases in cerebral blood flow (CBF) using inferred oxygen saturation changes in tissue. In addition, a continuous arterial spin-labeled (ASL) MRI sequence was used as a direct measure of regional CBF within the brain tissue. Animals were subjected to whole-body blast exposures of various overpressures within a gas-driven shock tube. When exposed to low levels of overpressure, most rats demonstrated no obvious changes between pre- and postexposure in the conventional MR images. CBF changes measured by SWI and ASL were significantly higher for the overpressure exposed groups as compared to the sham group and tended to increase with pressure increases at the highest two pressures. In the hippocampus, all blast animals had a reduction in the CBF consistently in the range of 0-27%. In summary, low levels of primary blast pressure exposure demonstrated a significant physiologic effect to the brain up to 72 h postexposure. 相似文献
98.
Nekrasov-Okounkov identity gives a product representation of the sum over partitions of a certain function of partition hook length. In this paper, we give several generalizations of the Nekrasov-Okounkov identity using the cyclic symmetry of the topological vertex. 相似文献
99.
A method of solution impregnation and calcination has been demonstrated for synthesizing nanoparticles of Ag–TiO2 composite photocatalysts for use in the disinfection of water. Only a small proportion of the TiO2 surface is covered by nano-islands of Ag corresponding to a loading of 4 wt.% of Ag; thus, most of the TiO2 surface is available for photocatalytic function. Although the primary particles of both Ag and TiO2 are in the 10- to 20-nm range, microscopic studies indicate that the primary particles of Ag are deposited on nano-agglomerates
of 30- to 70-nm-sized TiO2. It is seen that the relatively small loading of Ag has not caused any UV–vis spectral shift but has enhanced the rate of
photocatalytic antibacterial action of TiO2, presumably by electron trapping. 相似文献
100.
Muhammad Yaseen Zahid Farooq Mian H. R. Mahmood Sheikh Asrar Ahmad Shahbaz Nazir Khalid Mahmood Anjum Syed Ali Raza Naqvi 《Journal of heterocyclic chemistry》2019,56(5):1520-1529
A new convenient solid–liquid condensation reaction procedure for the synthesis of novel asymmetric and symmetric meso‐tetraarylporphyrin and metalloporphyrin Schiff bases is reported. The condensation reaction between β‐formyl porphyrin or metalloporphyrins and aromatic amines was carried out at solid–liquid interface by using neutral alumina powder as a solid support for β‐formyl porphyrin or metalloporphyrins and absolute ethanol as the carrier solvent for aromatic amines. Six different asymmetric porphyrin/metalloporphyrin Schiff bases were synthesized via solid–liquid interface reaction methodology. The same solid–liquid synthetic methodology was applied for the synthesis of six novel symmetric Schiff base porphyrin/metalloporphyrin dimers. The comparison of UV–visible spectra of porphyrin Schiff base monomers and dimers revealed that some degree of electronic perturbation has occurred upon dimerization as the Soret bands of the monomers underwent peak broadening along with red shifts. Column chromatography and crystallization were used to purify the compounds. Fourier transform infrared, UV–visible, elemental analysis, 1H NMR, and mass spectrometry were used to characterize the newly synthesized compounds. 相似文献