Effects of gelatine type and concentration on the shelf-life stability and quality of marshmallows

The effects of gelatine concentration, bloom strength, and origin on the quality and shelf-life stability of marshmallows were studied. All six sample treatments were carried out under accelerated storage conditions of 25 °C and 75% relative humidity (RH) for 25 weeks. Gelatine A 150 bloom had the highest viscosity because of its highest concentration (2.54%), lowest density and greatest amount of moisture loss producing the hardest marshmallows. Hardness and water activity measurements correlate for all sample treatments indicating that moisture loss is the main mechanism for hardening. With the exception of Gelatine B 2.2%, sugar crystallisation may have occurred in all sample treatments at week 20 which would have an impact on hardness as well. Gel network formation may be contributing towards hardness in Gelatine B 2.2% as there was an increase in hardness but no changes were perceived in water activity.     

Synthesis of cobalt nanoparticles to enhance magnetic permeability of metal–polymer composites

Metallic cobalt nanoparticles were synthesized by hydrogen reduction method. Particles were coated in situ with carbon by adding ethene to reaction flow. Particles were characterized by transmission electron microscopy, energy dispersive X-ray emission, X-ray diffraction, X-ray fluorescence and BET method. The observed cobalt particle size distributions in different cobalt batches produced with unvarying reaction parameters was reproducible: The mean diameter of primary cobalt particle varied only 5% from the mean value of 76 nm in different batches. Increased carbon precursor concentration decreased mean diameter of cobalt particles to 17 nm. The produced nanoparticles were used as filler material in 0–3 type metal–polymer composites. Composite samples with varying filler loading were fabricated with mixing extrusion and injection moulding techniques. The magnetic properties of the fabricated composites were measured up to 1 GHz. In order to analyse the particle distribution in composite matrix and its effect on magnetic properties the microstructure was studied.     

Membrane response model for ion-selective electrodes operated by controlled-potential thin-layer coulometry

The electrochemical response behavior of controlled-potential thin-layer coulometric sensors based on solvent polymeric membranes doped with ionophores is elucidated by numerical simulation. This treatment forms the theoretical basis for the design of potentially recalibration-free ion-selective chemical sensors that operate by exhaustive coulometry. Mass transport is assumed to occur primarily by diffusion in each bulk phase, and interfacial ion exchange with interfering ions is described with modern ion-selective electrode theory. The ion-selective membrane is assumed to contain an ion exchanger that can form concentration gradients as a result of transmembrane ion fluxes. It is shown that the diffusion of ions in the membrane phase will become rate limiting for membrane components with diffusion coefficients of 10(-8) cm(2) s(-1) that are typical for traditional ion-selective electrode formulations. This characteristic may be advantageous for sample thicknesses of 20 μm or less, where otherwise exhaustive depletion occurs too quickly to be distinguishable from nonfaradic processes. In most other cases, however, it will be necessary to formulate membrane materials that permit much faster diffusion characteristics. Indeed, the simulations give guidance on sensor design for sample concentrations that approach millimolar levels. The treatment also considers interferences from ions of the same charge sign as the analyte ion, and it is shown that the required selectivity for a given analysis must be about 1 order of magnitude higher than in direct potentiometry. This is because the coulometric exhaustive depletion process occurs only for the analyte ion, not for the interfering one, and to avoid interference, the required selectivity must be maintained even if the sample contains a fraction of the original analyte levels.     

Bone transplantation and bone replacement materials

There is a growing need for immediately available material with appropriate qualities for reconstruction of large bone defects. Autologous spongy bone grafts are optimal as to biocompatibility, but are in short supply. Allogenic and xenogenic bone grafts evoke an immunological reaction after implantation and are not biocompatible. In the last thirty years ceramic implants and composites have been developed for bone substitution. New calcium phosphate bone substitutes undergo processes of resorption and precipitation of carbonate apatite that play a part in formation of new bone. These materials are easy to use because of their pastelike consistence. Resorption properties are influenced by particle size, crystallinity and composition. So far, no serious adverse reactions were reported. More clinical experience is necessary especially with composites and combinations with antibiotics, bone growth factors and collagen, to specify the place of these modern calcium phosphates in bone replacement and bone substitution.     

Permissive effect of nitric oxide in arachidonic acid induced dilation in isolated rat arterioles

OBJECTIVE: Prostaglandins and nitric oxide play an important role in the regulation of arteriolar tone. L-Arginine analogues inhibit nitric oxide formation, but may also inhibit arachidonic-acid induced dilation. Nitric oxide was found to stimulate cyclooxygenase activity in cultured endothelial cells. Therefore, we hypothesized that the non-specific inhibition of prostaglandin-related dilation by L-arginine analogues is a consequence of the absence of nitric oxide. METHODS: To test this hypothesis, arteriolar segments from rat cremaster muscle were studied in a pressure myograph at 75 mmHg. Segments developed spontaneous tone, the diameter reduced from 179 +/- 3 to 98 +/- 3 microns (n = 41). In this condition, responses to exogenous arachidonic acid (1 microM) were recorded and compared with responses after addition of L-NNA, and addition of either SNAP, nitroprusside or 8-Br-cGMP in the presence of L-NNA. RESULTS: Inhibition of basal nitric oxide production with L-NNA (0.1 mM) reduced arachidonic acid-induced dilation (from 52 +/- 9 to 31 +/- 6 microns). In the presence of L-NNA, responses to arachidonic acid were augmented when exogenous nitric oxide was also present (SNAP, 31 +/- 6 microns vs. 75 +/- 5 microns; nitroprusside, 31 +/- 8 microns vs. 42 +/- 7 microns). Responses were not augmented with the second messenger of nitric oxide-mediated dilation 8-Br-cGMP (37 +/- 9 microns vs. 32 +/- 9 microns). CONCLUSIONS: These results indicate that nitric oxide directly increases arachidonic acid-induced dilation. Thus, the non-specific effect of L-arginine analogues can be explained by a permissive effect of nitric oxide on endothelial arachidonic acid metabolism.     

Rendez-vous with metric semantics

A comparative semantic study is made of an element of the family of concurrent object-oriented programming languages. Particular attention is paid to two notions: (i) dynamically evolving process structures, including a mechanism to name and refer to processes and a means to create new processes, and (ii) rendez-vous between processes involving the sending and answering of messages and the induced execution of method calls. The methodology of metric semantics is applied in the design of operational and denotational semantics, as well as in the proof of their equivalence. Both semantics employ domains which are determined as fixed points of a contracting functor in the category of complete metric spaces. Moreover, fruitful use is made of the technique of defining semantic meaning functions as fixed points of contracting higher-order mappings. Finally. syntactic and semantic continuations play a pervasive role.     

Free volume changes in mechanically milled PS and PC studied by positron annihilation lifetime spectroscopy (PALS)

The effect of mechanical milling on free volume was studied by means of positron annihilation lifetime spectroscopy (PALS) in polystyrene (PS) as a typical brittle polymer and in polycarbonate (PC) as a tough representative. Long‐time milling increases the free volume, while a decrease is observed for short milling times. The changes are mostly irreversible in PS. The irreversible fraction is much smaller for PC. Gel permeation chromatography (GPC) measurements show a decrease of the molecular weight, which is much more pronounced in PS. The milling‐induced irreversible changes in free volume are attributed to chain‐end defects resulting from chain scission. In PC, other deformation‐induced defects that anneal upon heat treatment above the glass transition temperature dominate. Polym. Eng. Sci. 44:1351–1359, 2004. © 2004 Society of Plastics Engineers.     

Effect of purified Trichoderma reesei cellulases on formation of cotton powder from cotton fabric

The mode of action of monocomponent purified Trichoderma reesei cellobiohydrolases (CBHI and CBHII) and endoglucanases (EGI and EGII) on cotton fabrics was studied by analyzing the weight loss of the fabric, the reducing sugars, the soluble oligosaccharides and the molecular weight of the cotton powder formed. The impact of mechanical action on these factors was also evaluated. EGI and EGII released the highest amounts of reducing sugars and soluble oligosaccharides in both treatments with or without additional mechanical action. After cellulase treatment without additional mechanical action, all of the cellulases were found to have reduced the molecular weight of cotton poplin powder. When mechanical action was combined with enzyme treatments, only EGII reduced the molecular weight. The weight loss of EG‐treated fabrics was clearly higher than the weight loss of CBH‐treated fabrics with both low and high mechanical action levels. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1917–1922, 2003