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61.
Denis A. Brosnan John P. Sanders Stephanie A. Hart 《Journal of Thermal Analysis and Calorimetry》2011,106(1):109-115
Thermal analysis techniques have been used in characterizing building materials from significant historic properties in the
Charleston, South Carolina area. Determining the chemical and physical effects of deterioration resulting from long periods
of exposure is a first step in formulating preservation strategies. In this regard, simultaneous thermal analysis coupled
with evolved gas analysis has been used to study reactions between air, seawater, and masonry materials. Further, the traditional
petrographic identification of mortar composition is greatly facilitated through use of thermal analysis. Simultaneous thermal
analysis allows for an exact determination of the calcium carbonate content in mortars as an alternative to the use of an
inferred value based on chemical analysis data. The partial dissolution of calcium carbonate in the presence of sea salt is
a major deterioration process. Further, natural cements manufactured in the United States are identified, in part, based on
their thermogravimetric (TG) traces and their evolved gases. The data indicates that natural cements form some carbonate phases
in addition to the major hydrate phases. Clay bricks are found to exhibit interaction with sea water, with uptake of bicarbonate
suggested. Additionally, there is evidence of re-hydroxylation in the 160 year old bricks. The bricks made in coastal zones
contain a considerable free silica fraction that is composed of a small percentage of cristobalite. The silica content of
the clay bricks is seen to result in very high thermal expansion coefficients in the area of 10 × 10−6 to 12 × 10−6 K−1. These studies provide guidance in restoration efforts where authenticity of cements is important. In the event that replacement
bricks are required, matching the thermal expansion coefficient of the original bricks is a requirement for preservation of
the masonry structure. 相似文献
62.
Clifton LA Sanders MR Castelletto V Rogers SE Heenan RK Neylon C Frazier RA Green RJ 《Physical chemistry chemical physics : PCCP》2011,13(19):8881-8888
The self-assembly in solution of puroindoline-a (Pin-a), an amphiphilic lipid binding protein from common wheat, was investigated by small angle neutron scattering, dynamic light scattering and size exclusion chromatography. Pin-a was found to form monodisperse prolate ellipsoidal micelles with a major axial radius of 112 ± 4.5 ? and minor axial radius of 40.4 ± 0.18 ?. These protein micelles were formed by the spontaneous self-assembly of 38 Pin-a molecules in solution and were stable over a wide pH range (3.5-11) and at elevated temperatures (20-65 °C). Pin-a micelles could be disrupted upon addition of the non-ionic surfactant dodecyl-β-maltoside, suggesting that the protein self-assembly is driven by hydrophobic forces, consisting of intermolecular interactions between Trp residues located within a well-defined Trp-rich domain of Pin-a. 相似文献
63.
[reaction: see text] A series of diimide-based macrocycles have been prepared using Mitsunobu-mediated alkylation as the macrocyclization step. These macrocycles could not be incorporated into [2]catenanes using previously established building blocks and coupling methodology. However, when one of the macrocycle syntheses was conducted in the presence of a dinaphtho crown ether, catenane formation was achieved. This result is discussed in terms of the ability of the components to establish intermolecular C-H...O hydrogen-bonding contacts. 相似文献
64.
Sanders L Halder M Xiao TL Ding J Armstrong DW Petrich JW 《Photochemistry and photobiology》2005,81(1):183-186
We report the first separation of the enantiomers of hypericin. Their steady-state optical spectra and ultrafast primary photoprocesses are investigated in chiral environments. Within experimental error, there is no difference between the two enantiomers in any of the systems considered. This is consistent with the emerging picture that the rich and extended absorption spectrum of hypericin is not a result of ground-state heterogeneity. It is also consistent with the observation that the spectra and photophysics of hypericin are generally insensitive to environments in which it does not aggregate. 相似文献
65.
S. B. Ellis S. J. Kiehl W. S. Hughes K. Schwabe W. C. Gardiner H. L. Sanders H. Yoshimura Hanna Jablezynska-Jedrzewska J. Domański W. A. Dorfman P. Nylén Barbara Stone F. Hovorka W. C. Dearing E. Biilmann W. Kordatzki P. Wulff G. Florence A. Drilhon P. Szigeti O. Tomiček F. Poupě O. Redlich W. Stricks 《Analytical and bioanalytical chemistry》1937,111(2-4):94-104
66.
67.
68.
Fluorescence lifetime imaging of oxygen in living cells 总被引:1,自引:0,他引:1
H. C. Gerritsen R. Sanders A. Draaijer C. Ince Y. K. Levine 《Journal of fluorescence》1997,7(1):11-15
The usefulness of the fluorescent probe ruthenium tris(2,2′-dipyridyl) dichloride hydrate (RTDP) for the quantitative imaging
of oxygen in single cells was investigated utilizing fluorescence lifetime imaging. The results indicate that the fluorescence
behavior of RTDP in the presence of oxygen can be described by the Stem-Volmer equation. This shows that fluorescence quenching
by oxygen is a dynamic quenching process. In addition, it was demonstrated that the fluorescence lifetime of RTDP is insensitive
to pH, ion concentration, and cellular contents. This implies that a simple calibration procedure in buffers can be used to
quantify oxygen concentrations within cells. First fluorescence imaging experiments on J774 macrophages show a nonuniform
fluorescence intensity and a uniform fluorescence lifetime image. This indicates that the RTDP is heterogeneously partitioned
throughout the cells, while the oxygen concentration is constant. 相似文献
69.
Ultraviolet broadband light spanning 337–405 nm was produced in a single-mode optical fiber primarily by stimulated Raman scattering. Pulses of 4 ns duration at 337 nm were coupled into a 50 m long ultraviolet-grade fiber featuring single-mode operation in the 320–450 nm range. Significant spectral broadening was achieved with pulses of only ∼10 W peak power. Our experiments demonstrate the potential for a source with ∼104 times the spectral radiance of a quartz tungsten halogen lamp, which is currently used for many applications in this wavelength range. PACS 42.65.Ky; 42.81.Wg 相似文献
70.