Digital simulation of thermal reactions

Simulations of the equation for thermal expansion of a reacting gas have been carried out, exploring both the (possible) steady states and time-marching solutions. The critical Frank-Kamenetskii parameter δ_cr has been evaluated to seven decimal places for the slab, cylinder and spherical geometries and the role of the critical activation parameter ? was explored. It was found that there exist one or more mathematical steady states for any δ if ?>0, the curves for steady temperature at the center of the geometry plotted against δ tending to a straight line at large δ. Critical values of ?, the values above which this plot has a single solution for a given δ, have been computed to eight decimals. Time marching simulations showed that the Crank-Nicolson method, applied consistently, produces very accurate results, compared with the implementation in which the nonlinear term is rendered explicit. Where for a given δ there are several mathematical steady states, a time march usually settles on the lowest such state (if it settles at all), regardless of where the simulation is started, within the possible limits. The mathematical multiple steady states are not attained by time marching simulations, and are also physically unlikely.     

Higher-order spatial discretisations in electrochemical digital simulations. Part 4. Discretisation on an arbitrarily spaced grid

A systematic approach to the construction of finite difference formulae for the approximation to first and second derivatives with respect to space on an arbitrarily spaced grid is presented. The finite difference formulae, combined with backward implicit (BI) and extrapolation methods, are used for electrochemical simulations and tested for efficiency. Excellent results are obtained with second and third order discretisations even for very small space intervals in the vicinity of the electrode and strongly expanding grid spacings. This ensures efficient simulation of kinetic-diffusion systems where, due to a fast homogeneous reaction, a thin reaction layer is formed adjacent to the electrode.     

Electron microscopic analysis of dairy microbes inactivated by ultrasound

Ultrasonication is a non-thermal method of food preservation that has the advantage of inactivating microbes in food without causing the common side-effects associated with conventional heat treatments, such as nutrient and flavour loss. The aim of this study was to evaluate the use of ultrasound as an alternative to heat pasteurisation and to assess cell damage using transmission electron microscopy (TEM). Three spoilage microbes, previously isolated from pasteurised milk, were used as "test" microbes. Saline solution (SSS) and UHT milk were used as suspension media and were inoculated with exponential growth phase "test" microbes at a microbial concentration of 1 x 10(4) cfu ml(-1). The samples were subjected to power ultrasound (20 kHz, 750 W), at 100%/124 microm wave amplitude for different time intervals. Both Escherichia coli and Saccharomyces cerevisiae were reduced by >99% (for both suspension media) after ultrasonication and Lactobacillus acidophilus was reduced by 72% and 84% in SSS and milk, respectively. Transmission electron microscope micrographs showed that ultrasonication inflicts extensive microbicidal/microbistatic external and internal damage on all three "test" microbes. In E. coli, sonication-induced emulsification caused the formation of unique minute lipopolysaccharide vesicles from the fragmenting cell envelope.     

Selective host-guest interaction of single-walled carbon nanotubes with functionalised fullerenes

Exohedrally functionalised fullerenes have been inserted in single-walled carbon nanotubes (SWNTs) with the aid of supercritical carbon dioxide to form peapods; C(61)(COOEt)(2) are encapsulated in SWNTs in high yield, whereas C(61)(COOH)(2) aggregate via hydrogen bonding to form a supramolecular complex, which sterically hinders encapsulation and causes it to adhere to the exterior surface of the SWNTs.     

UV-B-INDUCED INCREASE IN SPECIFIC LEAF WEIGHT OF CUCUMBER AS A CONSEQUENCE OF INCREASED STARCH CONTENT

Abstract Specific leaf weight (SLW), the ratio of leaf dry matter to area, often increases in plants exposed to elevated UV-B radiation (280–315 nm). Increased SLW can result from greater leaf thickness or increased leaf density ( e.g . accumulation of high density substances in cells). The basis for large increases in SLW was examined in the first and third leaves of cucumber differing in developmental stage at the start of UV treatment. Leaf 1 was approximately 50% fully expanded, while leaf 3 had just unfolded. It is shown here that up to 80% of the UV-generated change in SLW in leaf 1 was caused by accumulation of nonstructural carbohydrates, especially starch (increasing from 13 to 23% of total dry weight). Leaf 3 contained a much smaller proportion of nonstructural carbohydrates (less than 8%) and the effect on SLW was correspondingly less. As shown in the previous paper, UV-B inhibition of growth in leaf 3 was reversed by supplemental blue light (BL) in a fluence-dependent manner between 0.23 to 2.68 mol m ² perday. Fluence-response curves revealed that supplemental BL reversed both the UV-induced accumulation of starch and increase in SLW in leaf 1 over the same range. The data are consistent with a back-up of photosynthate into leaf 1 as a result of UV-B inhibition of growth in leaf 3. The data also demonstrate that increases in SLW cannot be assumed to represent increases in leaf thickness.     

Parameter correlations in cold fusion measurements

Cross correlations as a function of timeshift between -emissions and electrolysis cell temperature, in a cold fusion experiment by Birgül et al. are calculated and show a distinct maximum of 0.34.     

Doubly Reinforcing Cementitious Beams with Instrumented Hollow Carbon Fiber Tendons

Surface mounted strain gages are used to characterize the behavior of polymer-enhanced cementitious beams designed to withstand reverse loadings. These unique composite structures are doubly reinforced with hollow carbon fiber (graphite) tendons equipped with strain gages and the study includes section design, materials considerations, structural testing, and finite element analysis. The primary purpose of strain gage integration is to insure that the stress in the materials remains within the elastic range so that damage does not occur. A finite element model is developed to characterize the structural response in the elastic range and a hybrid approach is suggested in which displacement, strain, and stress can be obtained with a single strain gage. The ability to characterize structural performance beyond the elastic range is also demonstrated by analyzing data obtained from displacement-controlled tests.