Non-collapsing in fully non-linear curvature flows

We consider compact, embedded hypersurfaces of Euclidean spaces evolving by fully non-linear flows in which the normal speed of motion is a homogeneous degree one, concave or convex function of the principal curvatures, and prove a non-collapsing estimate: Precisely, the function which gives the curvature of the largest interior ball touching the hypersurface at each point is a subsolution of the linearized flow equation if the speed is concave. If the speed is convex then there is an analogous statement for exterior balls. In particular, if the hypersurface moves with positive speed and the speed is concave in the principal curvatures, the curvature of the largest touching interior ball is bounded by a multiple of the speed as long as the solution exists. The proof uses a maximum principle applied to a function of two points on the evolving hypersurface. We illustrate the techniques required for dealing with such functions in a proof of the known containment principle for flows of hypersurfaces.     

Insights into the hydration of Portland cement under hydrothermal curing

Journal of Thermal Analysis and Calorimetry - The combined effect of temperature and vapor pressure on hydration reactions of three different types of Portland cements was studied using a...     

The Arrow of Time: From Universe Time-Asymmetry to Local Irreversible Processes

In several previous papers we have argued for a global and non-entropic approach to the problem of the arrow of time, according to which the “arrow” is only a metaphorical way of expressing the geometrical time-asymmetry of the universe. We have also shown that, under definite conditions, this global time-asymmetry can be transferred to local contexts as an energy flow that points to the same temporal direction all over the spacetime. The aim of this paper is to complete the global and non-entropic program by showing that our approach is able to account for irreversible local phenomena, which have been traditionally considered as the physical origin of the arrow of time.     

Influence of nozzle area ratio on the gas-particle flow for single-hose dry ice blasting nozzle

Journal of Thermal Analysis and Calorimetry - In this paper, a numerical study was performed to examine the effect of divergent nozzle length of single-hose dry ice blasting on the development of...     

Cage-like structure formation during sol–gel polymerization of glycidyloxypropyltrimethoxysilane

The sol–gel polymerization of 3-glycidyloxypropyltrimethoxysilane (GTMS) was followed by size exclusion chromatography and ²⁹Si NMR. Extensive non-random cyclization under formation of polyhedral cycles – cubic cages – predominates at the beginning of the reaction. Structure growth of polysilsesquioxanes proceeds by combining the incompletely condensed cage frameworks. The extent of the cage formation increases with dilution and the amount of water and depends appreciably on a catalyst. The cage fraction was isolated from a reaction mixture using preparative size exclusion chromatography and identified by ²⁹Si NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS). High content of polyhedral cages prevents gelation of the trifunctional GTMS monomer. Reaction of pendant epoxy groups is much slower; however, at a late reaction stage the epoxy hydrolysis can be significant. Under some conditions, like base catalysis, polysilsesquioxane clusters are crosslinked by intermolecular condensation of SiOH with hydrolyzed epoxy groups and the system gels. The cage with epoxide functionalities may serve as a rigid precursor of crosslinking.     

Analysis of phosphate and phosphate containing headgroups enzymatically cleaved from phospholipids of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> by capillary electrophoresis

A new, fast, selective, and reliable capillary electrophoresis method has been developed for analysis of selected phosphoesters (phosphoserine, phosphoethanolamine, phosphoglycerol) and phosphate. The method is based on separation of specific phosphate containing headgroups (phosphoesters) which are cleaved from the glycerol skeleton of a phospholipid by a regioselective enzyme (phospholipase C). Analysis of intact phospholipids with the same polar headgroup but different fatty acids shows that fatty acid composition has a high impact on separation of phospholipids, so analysis of separated polar headgroups, which avoids this influence, represents a much more suitable approach for phospholipid class research. Optimization of method parameters results in running buffers of relatively narrow pH interval (pH about 10) where all phosphoesters are separated. Further method validation has shown that direct UV detection has a sufficient detection limit for all analytes to perform suitable analyses of cell membrane lipids. The optimized method was tested on the lysate of cell membrane of Bacillus subtilis, where all analytes were determined.