Residual fracture energy of high-performance and normal concrete subject to high temperatures

Test data on the residual fracture energy of two significantly different concrete types are presented. About 80 beams of high performance basalt concrete and ordinary gravel concrete have been tested in accordance with the RILEM work of fracture method. The beams are heated at 1°C per minute up to a certain maximum temperature and kept at this temperature for 8 hours before cooling them back to room temperature and testing in three-point bending. The tests show that the two concretes behave almost identifical when the fracture energyG _F is considered as a function of maximum temperature. It is found that the damage introduced by a maximum temperature of 300 to 400°C increases the fracture energy by 50% compared with the reference tests at room temperature. A more tortuous crack surface is one plausible explanation for the significant increase inG _F. The article also presents temperature and weight loss recordings from the heating scenarios and finally, the characteristic length and the cohesive tensile softening curve are shown to depend on the maximum temperature. Basically it is demonstrated that the temperature exposure makes the concrete significantly more ductile.

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Résumé Des données sur l'énergie résiduelle de rupture de deux bétons différents sont présentées. Environ 80 poutres de béton à base de basalte de très haute performance et de béton à base de gravier ordinaire ont été examinées conformément au travaux de la RILEM sur l'énergie de rupture. Les poutres sont chauffées à 1°C par minute jusqu'à une température maximale, puis maintenues à cette température pendant 8 heures avant d'être refroidies de nouveau à la température ambiante. Les poutres sont ensuite testées en flexion (système de flexion en trois points). Les essais prouvent que les deux bétons se comportent d'une manière presque identique quandG _F est considéré comme une fonction de la température maximale. On peut aussi constater que le dommage occasionné par une température maximale de 300 à 400°C augmente l'énergie de rupture de 50% par comparaison aux essais de référence réalisés à la température ambiante. Une surface de rupture plus tortueuse semble être une explication plausible pour l'augmentation significative deG _F. L'article présente également les évolutions de la température et de la perte de poids pour les scénarios de chauffage utilisés. En conclusion, cette étude montre que la longueur caractéristique et la courbe de post pic dépendent de la température maximale. Fondamentalement cela démontre que l'exposition à la température rend le béton sensiblement plus ductile.

     

The effect of cyclic stress on the physical properties of a poly(dimethylsiloxane) elastomer

The dynamic creep behavior of a filled poly(dimethylsiloxane) elastomer was studied under cyclic stress. The stress level was chosen such that the increase in the internal temperature was small and that microcracks were not observed. This work has demonstrated that cyclic stress in combination with high temperature accelerates the degradation of the elastomer. The results suggest that because of the applied force, breaks in the load-bearing chains of the network occur. These breaks, while relieving the mechanical stress, create highly reactive ionic fragments. It is believed that because of the subsequent reactions of the ionic fragments, changes in the specific gravity, storage modulus, effective crosslink density, and length of the sample (creep) are observed. The observed decrease in the storage modulus is thought to occur because of the reaction of the ionic fragments with moisture, which results in the formation of silanol chain ends that reduce the effective crosslink density. The results also show that contrary to the prediction of the Boltzmann's Superposition Principle, the rate of creep is greatly enhanced when the sample is subjected to a sinusoidally varying dynamic load as compared to a comparable static load. The polymer weight loss was found to be linear with time and strongly dependent on the level of applied dynamic and static force. In addition, the weight loss and rate of creep were also found to be strongly dependent upon temperature.     

Comparative antagonism of kainate-activated kainate and AMPA receptors in hippocampal neurons

Native kainate receptors expressed by cultured hippocampal cells were studied in the whole-cell configuration of the patch-clamp technique by using a fast perfusion system. About 80% of the neurons expressed kainate receptors independently of the time in culture (0-4 days), which coincided with the number of cells immunoreactive for a monoclonal antibody against the GluR5/6/7 subunits. Three types of cells were considered: neurons in which the rapid application of kainate induced a rapidly desensitizing current, cells in which kainate induced a more slowly rising, non-desensitizing, response and those in which a mixture of both responses was apparent. Steady responses induced by 300 microM kainate were inhibited by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) in a dose-dependent manner (IC50 = 0.92 microM). CNQX was less potent in blocking transient kainate-induced responses (IC50 = 6.1 microM). Responses to kainate, whether steady or transient, were also inhibited by NS102, showing poor selectivity for the transient response (IC50 = 4.1 and 2.2 microM respectively). The new alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) receptor antagonist NS394 was very potent in inhibiting steady kainate-induced currents (IC50 = 0.45 microM), but was even more effective in preventing peak responses (IC50 = 0.13 microM). In contrast, cyclothiazide did not affect transient kainate-induced responses but did potentiate current induced by activation of AMPA receptors by AMPA or kainate. These results demonstrate the lack of complete selectivity amongst some available competitive antagonists for AMPA and kainate receptors, and indicate that kainate receptors expressed by hippocampal cells lack the cyclothiazide modulatory site present at AMPA receptors. In addition, the present data support the idea that low-affinity kainate binding sites in the brain correspond to receptor channels selectively activated by kainate.     

Bovine IgG2a antibodies to Haemophilus somnus and allotype expression

AIMS/BACKGROUND: To characterise clinically a large kindred segregating retinitis pigmentosa and sensorineural hearing impairment in an autosomal dominant pattern and perform genetic linkage studies in this family. Extensive linkage analysis in this family had previously excluded the majority of loci shown to be involved in the aetiologies of RP, some other forms of inherited retinal degeneration, and inherited deafness. METHODS: Members of the family were subjected to detailed ophthalmic and audiological assessment. In addition, some family members underwent skeletal muscle biopsy, electromyography, and electrocardiography. Linkage analysis using anonymous microsatellite markers was performed on DNA samples from all living members of the pedigree. RESULTS: Patients in this kindred have a retinopathy typical of retinitis pigmentosa in addition to a hearing impairment. Those members of the pedigree examined demonstrated a subclinical myopathy, as evidence by abnormal skeletal muscle histology, electromyography, and electrocardiography. LOD scores of Zmax = 3.75 (theta = 0.10), Zmax = 3.41 (theta = 0.10), and Zmax = 3.25 (theta = 0.15) respectively were obtained with the markers D9S118, D9S121, and ASS, located on chromosome 9q34-qter, suggesting that the causative gene in this family may lie on the long arm (q) of chromosome 9. CONCLUSIONS: These data indicate that the gene responsible for the phenotype in this kindred is located on chromosome 9 q. These data, together with evidence that a murine deafness gene is located in a syntenic area of the mouse genome, should direct the research community to consider this area as a candidate region for retinopathy and/or deafness genes.     

Lifetime,residual strength,and quality of wood and other viscoelastic building materials

A theoretical analysis of the influence of wood quality on dead load lifetime is made on the basis of the authors DVM concept of building materials (Damaged Viscoelastic Material). It is shown that low quality structural wood and high quality clear wood lives longer than normal clear wood when loaded to the same fraction of respective strengths. At middle range qualities lifetime is practically not influenced by quality. Also considered is residual strength of wood during its lifetime experience. The results presented are valid in principle for a number of building materials applying to the DVM concept.     

Simulation of sulfide buildup in wastewater and atmosphere of sewer networks.

A model concept for prediction of sulfide buildup in sewer networks is presented. The model concept is an extension to--and a further development of--the WATS model (Wastewater Aerobic-anaerobic Transformations in Sewers), which has been developed by Hvitved-Jacobsen and co-workers at Aalborg University. In addition to the sulfur cycle, the WATS model simulates changes in dissolved oxygen and carbon fractions of different biodegradability. The sulfur cycle was introduced via six processes: 1. sulfide production taking place in the biofilm covering the permanently wetted sewer walls; 2. biological sulfide oxidation in the permanently wetted biofilm; 3. chemical and biological sulfide oxidation in the water phase; 4. sulfide precipitation with metals present in the wastewater; 5. emission of hydrogen sulfide to the sewer atmosphere and 6. adsorption and oxidation of hydrogen sulfide on the moist sewer walls where concrete corrosion may take place.     

Enzymatic biodiesel production: Technical and economical considerations

It is well documented in the literature that enzymatic processing of oils and fats for biodiesel is technically feasible. However, with very few exceptions, enzyme technology is not currently used in commercial‐scale biodiesel production. This is mainly due to non‐optimized process design and a lack of available cost‐effective enzymes. The technology to re‐use enzymes has typically proven insufficient for the processes to be competitive. However, literature data documenting the productivity of enzymatic biodiesel together with the development of new immobilization technology indicates that enzyme catalysts can become cost effective compared to chemical processing. This work reviews the enzymatic processing of oils and fats into biodiesel with focus on process design and economy.     

Monoclonal antibody-based competitive ELISA for simultaneous detection of rinderpest virus and peste des petits ruminants virus antibodies

An experimental competitive enzyme-linked immunosorbent assay (morbillivirus cELISA) using a recombinant N antigen (rRPV N) expressed in a baculovirus and a ruminant morbillivirus (RPV and PPRV)-specific monoclonal antibody (P-13A9) was developed for simultaneous detection of rinderpest virus (RPV) and peste des petits ruminants virus (PPRV) antibodies and its diagnostic performance was evaluated. A set of known reference antisera against RPV and PPRV belonging to different lineages, experimental sera from cattle vaccinated for a RPV of Asian lineage, and field sera from cattle and sheep/goat populations known to be positive (West Africa) and negative (Korea) for RPV and PPRV were used for the evaluation. Morbillivirus cELISA results on the panel of experimental RPV and PPRV antisera showed high correlation (r=0.97) between the whole virus and the rRPV N antigens, suggesting that the rRPV N contains a ruminant morbillivirus-specific antigenic determinant recognized by the P-13A9 and it may be suitable as an ELISA antigen in place of the whole virus. Morbillivirus cELISA detected anti-RPV and anti-PPRV antibodies in all reference RPV and PPRV antisera containing VN titers >/=1:8, suggesting that the assay can simultaneously detect antibodies against RPV and PPRV. Anti-RPV antibody was detected by morbillivirus cELISA in vaccinated cattle as early as the VNT and continued to be detectable by both the cELISA and the VNT until termination of the study. When applied to field samples from Africa, morbillivirus cELISA showed good agreement with a RP cELISA kit (kappa value of 0.86) in bovine sera and with a peste des petits ruminant cELISA kit (kappa value of 0.81) in caprine/ovine sera. Usefulness of morbillivirus cELISA using the rRPV N protein was discussed.     

Antithrombotic effect of recombinant truncated tissue factor pathway inhibitor (TFPI1-161) in experimental venous thrombosis--a comparison with low molecular weight heparin

The aim was to investigate whether a truncated recombinant Tissue Factor Pathway Inhibitor (TFPI1-161), which lacked the third Kunitz-type domain and the basic c-terminal region, had an antithrombotic effect comparable to LMWH in a randomised double-dummy study. The experimental thrombosis was induced in jugular veins, in a total of 40 rabbits by a combination of destruction of the endothelium and restricted blood flow. Group 1: placebo, gr 2: LMWH 60 anti-FXa IU/kg, gr 3-5: 0.1, 1.0 and 10.0 mg/kg TFPI1-161. TFPI1-161 reduced the thrombus weights in all treated groups, significantly in doses of 1.0 and 10.0 mg/kg compared to placebo. The frequency of thrombosis and occlusive thrombosis were also significantly reduced in those doses. The antithrombotic properties of TFPI1-161 (1.0-10.0 mg/kg) measured as thrombus weight, frequency of thrombosis and frequency of occlusive thrombosis was equivalent to the anti-thrombotic properties of LMWH. In the anti-FXa, APTT and PT-assays TFPI1-161 displayed a dose dependent increase of activity. Recombinant-TFPI1-161 did not influence the anti-FIIa-assay. No haemorrhagic side effects were noted.