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971.
972.
The effect of different storage temperatures on the physical properties of pectin solutions and gels
Gordon A. Morris Jonathan Castile Gary G. Adams Stephen E. Harding 《Polymer Degradation and Stability》2010,95(12):2670-2673
The stability (in terms of viscosity and gel strength) of pectin solutions and gels potentially plays an important role in their behaviour and functional properties in a wide range of applications and therefore any changes over time must be understood. The gel strength of pectin gels and intrinsic viscosity of pectin solutions at different temperatures (4 °C, 25 °C and 40 °C) have been investigated using a “rolling ball” viscometer and a texture analyser respectively. Both the intrinsic viscosity ([η]) and gel strength decrease with increased storage time, although this more pronounced at elevated temperatures. The changes in intrinsic viscosity with storage time and temperature were used to determine the depolymerisation constant (k). Pectin storage conditions and particularly temperature have an influence on depolymerisation, particularly elevated storage temperatures, but whether or not this will be detrimental to its intended application will depend on the functional significance of the changes that occur. In this case based on the previous diffusion studies on a model drug (paracetamol) we conclude that the decreases in viscosity and gel strength within the range observed have no detrimental effect on the drug release properties. 相似文献
973.
Stephen G. Davies Ai M. Fletcher Gesine J. Hermann Giovanna Poce Paul M. Roberts Andrew D. Smith Miles J. Sweet James E. Thomson 《Tetrahedron: Asymmetry》2010,21(13-14):1635-1648
The doubly diastereoselective conjugate addition of the antipodes of lithium N-benzyl-N-(α-methylbenzyl)amide to a range of enantiopure N-enoyl oxazolidin-2-ones has been used as a mechanistic probe to determine that the reactive conformation is the anti-s-cis form. The β-amino carbonyl products resulting from these conjugate addition reactions are useful templates for further elaboration into an α,β,α-pseudotripeptide. 相似文献
974.
A method for fabricating infrared‐transmitting waveguides that yields low optical losses and strong confinement of light is presented. The method minimises the number of fabrication steps by exploiting the photosensitivity of arsenic trisulfide glass, using it both as a photoresist and as a waveguiding material. Controlled annealing/remelting of the waveguides minimises scattering due to fluctuations in refractive index at the interface between the waveguide and the surrounding medium, allowing low losses to be realised. Bends and Y‐splitter structures have been realised, as well as the longest As2S3 serpentine planar waveguides yet reported. 相似文献
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We prove an Ascoli theorem for capacities. This theorem which characterizes relatively compact sets of capacities is widely applicable and many Ascoli theorems for particular classes of capacities can immediately be deduced as corollaries. Indeed it is usually necessary only to demonstrate that these classes are closed and then to simplify the characterization when possible. In particular, we show that the proof of the classical Prohorov theorem can be naturally factored into the shorter proof of the Ascoli theorem for capacities and into the somewhat longer proof that the class of probability measures is closed in the class of capacities. We also deduce new and known Ascoli theorems for sup measures, upper semi-continuous functions, the Vietoris hyperspace topology, and various classes of measures. 相似文献
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