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661.
Emanuel A. Waddell Stephen Shreeves Christopher Perry James McKee 《Applied Surface Science》2008,254(17):5314-5318
The modification of polydimethylsiloxane (PDMS) by narrow band 254 nm excimer radiation under a nitrogen atmosphere was characterized by contact angle goniometry, attenuated total reflectance infrared spectroscopy, atomic force and scanning electron microscopy. UV irradiation results in the formation of the carboxylic acids that influences the wettability of the surface. Continued exposure results in the formation of an inorganic surface (SiOx (1 < x < 2)) which hinders the ability to continually increase the wettability. The continuity of this inorganic layer is disrupted by the formation of surface cracks. These results have implications in the fabrication and chemical modification of microfluidic or micro-electro-mechanical systems. 相似文献
662.
To elucidate the reasons underlying the poor penetration of non-viral vectors in tissues, relating transport properties to
physico-chemical parameters of vectors may be crucial. These properties can be influenced by the presence of multiples labels
that are used. Therefore utilizing a vector with minimum of labels preferably not more than one is important to studying penetration
in tissues. The cell impermeant bisintercalating dye YOYO-1 was found suitable to both monitor the formation of complexes
between DNA and an amphipathic peptide LK15 and, to track their penetration in HCT116 spheroids by confocal microscopy. The
results revealed a limited decrease of fluorescence ascribed to the high affinity of YOYO-1 to bind DNA. The residual fluorescence
of complexes can be exploited to monitor penetration into spheroids, after correction for YOYO-1 attenuation, and to revealing
hyaluronidase-induced reduced binding. Hence high affinity dyes such as YOYO-1 with inefficiently quenched fluorescence may
be important to establish a relation between novel medicines characteristics and penetration in tissues. 相似文献
663.
A systematic investigation of aluminium ion speciation at high temperature. Part 1. Solution studies
Speciation diagrams of aluminium ions in aqueous solution (0.2 M) at high temperature (90 degrees C) have been obtained from 48 h time-resolved multi-batch titration experiments monitored by 27Al NMR spectroscopy, potentiometry and dynamic light scattering. The quantitative speciation patterns and kinetic data obtained offer a dynamic picture of the distribution of soluble and insoluble Al species as a function of hydrolysis ratio h(h=[OH-]/[Al3+]) over a very broad range of conditions (-1.0 < or =h < or = 4.0). Monomeric, small oligomeric, tridecameric (the 'Al13-mer') and the recently characterised 30-meric aluminium species (the 'Al30-mer') as well as aluminium hydroxide have been identified and quantified. The Al13-mer species dominates over a relatively broad range of hydrolysis ratios (1.5 < or =h< or = 2.7) during the first 6 h of experiment, but are gradually replaced by Al30-mers at longer reaction times. Kinetic profiles indicate that the formation of the Al30-mer is limited by the disappearance of the Al13 species at mildly acidic conditions. The estimated rate constants of both hydrolytic processes show good internal correlation at h> or = 1.5. The effect of local perturbations leading to the formation of aluminium hydroxide below the electroneutrality point (h= 3.0) has been estimated quantitatively. 相似文献
664.
Douglas J. Raber Milton D. Johnston Jr. Catherine M. Campbell Anne Guida F. Jackson III Christopher M. Janks Joseph W. Perry Gary J. Propeck Nancy K. Raber Michael A. Schwalke Pamela M. Sutton 《Monatshefte für Chemie / Chemical Monthly》1980,111(1):43-52
The equilibrium binding constants have been evaluated for the association in CCl4 of the lanthanide shift reagent. Eu(fod)3, with a series of adamantane derivatives containing a variety of different functional groups. It is shown that if steric effects are held constant the binding abilities of the adamantane derivatives exhibit a good correlation with the proton affinities of the methyl analogs containing the same functional groups. The results permit the prediction of binding strength of other functional groups with Eu(dpm)3 as well as with Eu(fod)3 and thus can be of great assistance in planning and interpreting the results of experiments with lanthanide shift reagents.Part 4:D. J. Raber, M. D. Johnston, jr., C. M. Campbell, C. M. Janks, andP. Sutton, Org. Mag. Res.11, 323 (1978). 相似文献
665.
666.
Experimental data concerning the effect of varying reagent vibrational, rotational and translational energy on the rates of endothermic reactions can be obtained from the application of microscopic reversibility to the corresponding exothermic processes. A 3D classical trajectory computation has been performed to test this procedure. On the basis of this study we conclude that the ‘triangle plots’ of endothermic detailed rate constants published previously can be depended on to 5–10% theoretical accuracy (expressed as a percentage of the maximum endothermic rate constant). 相似文献
667.
Direct measurements of nonlinear absorption and refraction in solutions of phthalocyanines 总被引:1,自引:0,他引:1
T. H. Wei D. J. Hagan M. J. Sence E. W. Van Stryland J. W. Perry D. R. Coulter 《Applied physics. B, Lasers and optics》1992,54(1):46-51
We report direct measurements of the excited singlet state absorption cross section and the associated nonlinear refractive cross section using picosecond pulses at 532 nm in solutions of phthalocyanine and naphthalocyanine dyes. By monitoring the transmittance and far field spatial beam distortion for different pulsewidths in the picosecond regime, we determine that both the nonlinear absorption and refraction are fluence (energy per unit area) rather than irradiance dependent. Thus, excited state absorption (ESA) is the dominant nonlinear absorption process, and the observed nonlinear refraction is also due to real population excitation. 相似文献
668.
Raman measurements of the temperature dependence of several low-lying magnetic excitations in CoO are reported. The large q = 0 value of the lowest excitation (143 cm-1) and its q-independence are attributed to the large single-ion anisotropy of Co2+. 相似文献
669.
For molecules of the type R3SbX2, where R is methyl or phenyl, and X is a halogen, certain correlations involving the fundamental frequencies of vibration have been established. These frequencies were found to be dependent on the atomic mass and electronegativity of the halogen and the molecular weight and moment of inertia of the molecule. 相似文献
670.
Borzi RA Grigera SA Perry RS Kikugawa N Kitagawa K Maeno Y Mackenzie AP 《Physical review letters》2004,92(21):216403
We report a study of the de Haas-van Alphen (dHvA) effect on the itinerant metamagnet Sr3Ru2O7. Extremely high sample purity allows the observation of dHvA oscillations both above and below the metamagnetic transition field of 7.9 T. The quasiparticle masses are fairly large away from the transition, and are enhanced by up to an extra factor of 3 as the transition is approached, but the Fermi surface topography change is quite small. The results are qualitatively consistent with a field-induced Stoner transition in which the mass enhancement is the result of critical fluctuations. 相似文献