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31.
Paul Becher Suzanne E. Trifiletti Pamela C. Petty 《Journal of Dispersion Science and Technology》2013,34(1):53-66
Isotherms for the adsorption of sodium dodecyl benzene sulfonate, sodium POE (4) nonyl phenol sulfate, and POE (25) nonyl phenol, on the hydrophobic crystalline herbicides atrazine and cyanazine were determined. Anionic surfactants were measured at 5°, 25°, and 50° C; the nonionic surfactant at 25° C only. Low degrees of surface coverage were observed; in only one case (atra-zine/NaDBS) was monolayer coverage approached. On the other hand, adsorption was accompanied by a significant increase in negative zeta potential. Although DLVO calculations suggest that this adsorption should lead to stable aggregates, these are of such size that gravitational effects overpower the DLVO terms. 相似文献
32.
pH‐controlled reaction divergence of decarboxylation versus fragmentation in reactions of dihydroxyfumarate with glyoxylate and formaldehyde: parallels to biological pathways
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Christopher J. Butch Jing Wang Jiande Gu Rebeca Vindas Jacob Crowe Pamela Pollet Leslie Gelbaum Jerzy Leszczynski Ramanarayanan Krishnamurthy Charles L. Liotta 《Journal of Physical Organic Chemistry》2016,29(7):352-360
The reactions of dihydroxyfumarate with glyoxylate and formaldehyde exhibit a unique pH‐controlled mechanistic divergence leading to different product suites by two distinct pathways. The divergent reactions proceed via a central intermediate (2,3‐dihydroxy‐oxalosuccinate, 3 , in the reaction with glyoxylate and 2‐hydroxy‐2‐hydroxymethyl‐3‐oxosuccinate, 14 , in the reaction with formaldehyde). At pH 7–8, products ( 7 , 8 , and 15 ) exclusively from a decarboxylation of the intermediate are observed, while at pH 13–14, products ( 9 , 10 , and 16 ) solely derived from a hydroxide‐promoted fragmentation of the intermediate are formed. The decarboxylative and fragmentation pathways are mutually exclusive and do not appear to coexist under the range of pH (7–14) conditions investigated. Herein, we employ a combination of quantitative 13C NMR measurements and density functional theory calculations to provide a rationale for this pH‐driven reaction divergence. These rationalizations also hold true for the reactions of dihydroxyfumarate produced in situ by the catalytic cyanide‐mediated dimerization of glyoxylate. In addition, the non‐enzymatic decarboxylation and fragmentation transformations of these central intermediates ( 3 and 14 ) appear to have intriguing parallels to the enzymatic reactions of oxalosuccinate and formation of glyceric acid derivatives in extant metabolism – the high and low pH mimicking the precise control exerted by the enzymes over reaction pathways. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
33.
Determination of nicotine,glycerol, propylene glycol and water in electronic cigarette fluids using quantitative 1H NMR
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We describe measurements of colloidal transport through arrays of micrometer-scale potential wells created with holographic optical tweezers. Varying the orientation of the trap array relative to the external driving force results in a hierarchy of lock-in transitions analogous to symmetry-selecting processes in a wide variety of systems. Focusing on colloid as a model system provides the first opportunity to observe the microscopic mechanisms of kinetic lock-in transitions and reveals a new class of statistically locked-in states. This particular realization also has immediate applications for continuously fractionating particles, biological cells, and macromolecules. 相似文献
36.
Marina Quartu Maria Pina Serra Marianna Boi Viviana Ibba Tiziana Melis Marina Del Fiacco 《BMC neuroscience》2008,9(1):108
Background
The polysialylated neuronal cell adhesion molecule (PSA-NCAM) is considered a marker of developing and migrating neurons and of synaptogenesis in the immature vertebrate nervous system. However, it persists in the mature normal brain in some regions which retain a capability for morphofunctional reorganization throughout life. With the aim of providing information relevant to the potential for dynamic changes of specific neuronal populations in man, this study analyses the immunohistochemical occurrence of PSA-NCAM in the human trigeminal ganglion (TG) and brainstem neuronal populations at prenatal and adult age. 相似文献37.
Douglas J. Raber Milton D. Johnston Catherine M. Campbell Christopher M. Janks Pamela Sutton 《Magnetic resonance in chemistry : MRC》1978,11(7):323-328
The use of lanthanide shift reagents (LSR's) to obtain additional structural information from nuclear magnetic resonance studies has gained widespread acceptance. However, there has not been general agreement with regard to the most appropriate methodology for analysis of the shifted NMR spectra. We present arguments that only the bound shifts (Δ1) corresponding to the LS complex should be used for correlation of lanthanide-induced shifts with molecular structure by means of the pseudocontact equation. Several examples are discussed of compounds for which the relative induced shifts are dependent on the concentration of LSR. For such cases it is not possible for both Δ1 and Δ2 (the bound shift corresponding to the LS2 complex) to correlate successfully with the correct structure. Alternative methods of obtaining bound shifts are critically evaluated. 相似文献
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Abstract— Near ultraviolet (365 nm) and green-yellow (546-579nm) radiations repress the growth of liquid cell cultures of Ginkgo pollen and of monolayer cultures of HeLa. The deleterious effects of green-yellow wavelengths can be negated by red radiation; near-u.v.-induced growth repressions are insensitive to visible light photorestoration. These wavelengths do not interact synergistically and evoke different kinetics of response. 相似文献
40.
Vrba J Robinson SE Mccubbin J Lowery CL Eswaran H Wilson JD Murphy P Preissl H 《IEEE transactions on bio-medical engineering》2004,51(7):1207-1218
The fetal magnetoencephalogram (fMEG) is measured in the presence of large interference from the maternal and fetal magnetocardiograms. This interference can be efficiently attenuated by orthogonal projection of the corresponding spatial vectors. However, the projection operators redistribute the fMEG signal among sensors. Although redistribution can be readily accounted for in the forward solution, visual interpretation of the fMEG signal topography is made difficult. We have devised a general, model-independent method for correction of the redistribution effect that utilizes the assumption that we know in which channels the fMEG should be negligible (such channels are distant from the known fetal head position). In a simplified case where the fMEG can be explained by equivalent current dipoles, the correction can also be obtained from fitting the dipoles to the fMEG signal. The corrected fMEG signal topography then corresponds to the dipole forward solution, but without orthogonal projection. We illustrate the redistribution correction on an example of experimentally measured flash evoked fMEG. 相似文献