Thermal stability of expanded perlite modified by mullite

Results of the thermal stability of expanded perlite modified by mullite are presented. Mullite was formed from alumino-silicate gel by sol–gel method. This method allowed us to obtain very homogenous and reactive gel and phase formation of mullite took place at relatively low temperatures. Expanded perlite modified with alumino-silicate gel after firing above the temperature of mullite formation had better thermal stability and durability during heating. The thermal stability of this material was examined up to 1400 °C.     

Fatigue strength of welded joints in austenitic Cr-Ni steels

Abstract

High quality corrosion resistant Cr-Ni steels are used in many branches of industry. Constructors are faced with the problem of correctly dimensioning statically and dynamically loaded parts, but have little data available for dynamically loaded welded constructions of high alloy austenitic steels. To close this gap fatigue strength tests were carried out on three different steels and five different welded joints.     

Aromatic Bis[aminomethylidenebis(phosphonic)] Acids Prevent Ovariectomy-Induced Bone Loss and Suppress Osteoclastogenesis in Mice

Osteoporosis is a skeletal disease associated with excessive bone turnover. Among the compounds with antiresorptive activity, nitrogen-containing bisphosphonates play the most important role in antiosteoporotic treatment. In previous studies, we obtained two aminomethylidenebisphosphonates—benzene-1,4-bis[aminomethylidene(bisphosphonic)] (WG12399C) acid and naphthalene-1,5-bis[aminomethylidene(bisphosphonic)] (WG12592A) acid—which showed a significant antiproliferative activity toward J774E macrophages, a model of osteoclast precursors. The aim of these studies was to evaluate the antiresorptive activity of these aminobisphosphonates in ovariectomized (OVX) Balb/c mice. The influence of WG12399C and WG12592A administration on bone microstructure and bone strength was studied. Intravenous injections of WG12399C and WG12592A bisphosphonates remarkably prevented OVX-induced bone loss; for example, they sustained bone mineral density at control levels and restored other bone parameters such as trabecular separation. This was accompanied by a remarkable reduction in the number of TRAP-positive cells in bone tissue. However, a significant improvement in the quality of bone structure did not correlate with a parallel increase in bone strength. In ex vivo studies, WG12399C and WG12592A remarkably bisphosphonates reduced osteoclastogenesis and partially inhibited the resorptive activity of mature osteoclasts. Our results show interesting biological activity of two aminobisphosphonates, which may be of interest in the context of antiresorptive therapy.     

Thermodynamic analysis of afterburning of detonation products in confined explosions

Abstract

In the paper, an attempt is undertaken to apply the thermodynamic theory of closed combustion, proposed by A. K. Oppenheim and co-workers, to analyse the process of afterburning of the detonation products of condensed explosives in a chamber filled with air. The principal assumptions of the theory are presented and the problem of combustion of fuel in a closed volume is formulated. The relations between thermodynamic parameters and fuel consumption are determined from the laws of conservation of volume, mass and energy. These relations are used to estimate the rate and heat effect of afterburning of the detonation products of some explosives in a steel chamber of 150 dm³ volume. The influence of assumed degree of mixing of the combustion products and air on the mean pressure in the chamber is discussed.     

Sensitivity and performance properties of tex explosives

Abstract

Some sensitivity and performance properties of TEX were studied experimentally and theoretically. The TEX sensitivity to electrostatic spark was determined and tests for transportation were performed. The detonation properties, like the critical diameter, detonation pressure and Gurney energy were determined. Moreover, the detonation velocities of TEX-based cast explosives were compared with those of similar NTO-based ones.     

Tribochemical Conversions of Zinc Dialkyldithiophosphate (ZDDP) Under Extremely Different Pressure Conditions

The authors performed ball-on-disk and four-ball tests. The former gave much less severe conditions than the latter. A ZDDP-containing package, blended with a mineral base oil, was tested. Completely different mechanisms of ZDDP conversions were observed. During ball-on-disk tests, ZDDP undergoes partial tribochemical decomposition. It results in a modification of the surface of test specimens—organic compounds are produced and zinc atoms diffuse into the surface. During four-ball tests, advanced structural decomposition of ZDDP takes place—S and P take part in tribochemical reactions. Probably inorganic compounds are produced, whereas there is a lack of a layer of organic ones adsorbed on the surface. The generation of inorganic compounds results from chemical reactions of decomposed ZDDP with the surface of steel specimens as well as diffusion of some elements (e.g. S) into the surface. Good antiseizure properties of such inorganic structures help to improve the tribological characteristics under severe test conditions.     

Evaluation of some physico-chemical properties of restructured trout and hake mince during cold gelation and chilled storage

Cold gelation was carried out on trout (Oncorhynchus mykiss) or on hake (Merluccius merluccius) mince with or without addition of fish oil and using microbial transglutaminase (MTGase). Products were stored at 4 °C for 6 days and lipid oxidation, protein oxidation, texture, water binding capacity, and colour were followed. Results indicated that MTGase was able to generate gels with good properties for both trout and hake. Gels prepared with trout were oxidised whilst gels prepared with hake were stable toward oxidation even in the presence of 5% fish oil. However, in the presence of oil, as an alternative for generating omega-3 enriched products, the activity of MTGase was impaired, as the gels took longer to reach maximum hardness. Furthermore, in all samples containing MTGase, protein oxidation was high.     

Changes in chemical composition during development of grass pea (Lathyrus sativus L.) seeds

The level of chemical components was determined in seeds of grass pea (Lathyrus sativus L.), cv. Krab, harvested at a dry matter content between 25.9 and 49.6 g/100 g of the raw material, and divided into five degrees of maturity. The results presented suggest that, in general, with an increasing maturity of seeds, the level of the following components increased if related to fresh matter: starch, dietary fibre, acids, total and protein nitrogen, total amino acids and sulphur amino acids, ash and its alkalinity, magnesium, calcium, total phosphorus and phytic phosphorus, and thiamine. The following components were reduced: vitamin C, riboflavin, carotenoids, beta-carotene, and chlorophylls. No such regularity could be found with respect to the accumulation of sugars, essential amino acids, and iron. By expressing the results in dry matter, increases were noted in starch, protein nitrogen, and thiamine. The content of sugars, total nitrogen, total amino acids, essential and sulphur amino acids, ash and its alkalinity, magnesium, phosphorus, vitamin C, riboflavin, carotenoids, beta-carotene, and chlorophylls were reduced while that of dietary fibre, iron, calcium, and phytic phosphorus varied.     

High-pressure treatment of cloudy apple juice

A factorial design with four factors (pressure, holding time, temperature and waiting period between crushing of apple and high-pressure (HP) treatment) was built up to study the effect of HP treatment on pectin methylesterase activity (PME, EC 3.1.1.11) in cloudy apple juice. PME activity was measured by the methanol release during the storage of samples at 4 °C for 1 month. Only the holding time of the treatment and three interactions between factors (holding time×temperature, pressure×waiting and holding time×waiting) had significant effects on the PME level. Increasing the pressure or the holding time at moderate temperatures (15-40 °C) increased the activity. PME purified from apple was pressure stable in the range 100-600 MPa at 25 °C. The soluble pectin content was not changed after HP treatment. The particles size increased with the temperature reached during the treatment, in agreement with a diffusion-limited-aggregation model but were independent of pressure and holding time. In a separate experiment we found a positive correlation between the PME activity and the residual content of the catechins suggesting that polyphenoloxidase (PPO, EC 1.14.18.1) and oxidized polyphenols play a role in the PME activity level after HP treatment.