Analyse von Lkw-Überholmanövern auf Autobahnen für die Entwicklung kooperativer Fahrerassistenzsysteme

Forschung im Ingenieurwesen - Lkw-Überholmanöver auf Autobahnen können Konfliktsituationen provozieren. Das lange Blockieren der Überholspur und plötzliche Ausscheren kann...     

Study of the effect of BDMA catalyst in the epoxy novolac curing process by isothermal DSC

Epoxy novolac/anhydride cure kinetics has been studied by differential scanning calorimetry under isothermal conditions. The system used in this study was an epoxy novolac resin (DEN431), with nadic methyl anhydride as hardener and benzyldimethylamine as accelerator. Kinetic parameters including the reaction order, activation energy and kinetic rate constants, were investigated. The cure reaction was described with the catalyst concentration, and a normalized kinetic model developed for it. It is shown that the cure reaction is dependent on the cure temperature and catalyst concentration, and that it proceeds through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained using the Arrhenius kinetic model. A suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetics of epoxy novolac resin compositions as a function of the catalyst content and temperature. Copyright © 2003 Society of Chemical Industry     

Pretreatment of Highly Polluted Pharmaceutical Waste Broth by Wet Air Oxidation

The preoxidation of a highly polluted waste pharmaceutical fermentation broth using wet air oxidation (WAO) has been studied as a possible method for the effective removal of organics. The applied (pre)treatment method should enhance the biotreatability of the pharmaceutical fermentation broth in terms of reduced initial toxicity and higher biodegradability. Preliminary experiments in the pilot biological treatment plant were successful only at low organic loads, whereas the system collapses at higher ones. The characterization of the fermentation broth was started by common physicochemical analysis, whereas several bioassays were used to determine its impact on biological treatment plants and the environment. Toxicity prior to and after WAO was determined using the acute Vibrio fischeri test, measurement of inhibition of O2 consumption, and the Daphnia magna acute test. Ready biodegradability of the treated and untreated broth has also been assessed. WAO experiments were accomplished in the 2?L batch reactor at different temperatures (240/280°C) and operating pressures. WAO experiments confirmed reduction of the toxicity toward microorganisms, whereas oxidized wastewater was more toxic to daphnids. Biodegradability of the oxidized broth has also been enhanced. Further work has been focused on designing appropriate combination of WAO and biological processes.     

Cell death, axonal damage, and cell birth in the immature rat brain following induction of hydrocephalus

We hypothesized that hydrocephalus can cause death of brain cells and that generation of new brain cells might compensate for the cell loss. Hydrocephalus was induced in 3-week-old rats by injection of kaolin into the cisterna magna. The brains were studied 1 to 4 weeks later by histochemical, immunochemical, and ultrastructural methods. The ventricles enlarged progressively. Some axons in the corpus callosum were injured as early as 1 week, but axonal damage was not prevalent until 4 weeks when ventriculomegaly became severe. Dying cells detected by DNA end labeling and often identified as oligodendrocytes by electron microscopy were evident in white matter. Late-stage hydrocephalus was associated with a significant increase in the quantity of dying cells. Hydrocephalus was associated with increased Ki67 labeling and bromodeoxyuridine incorporation in the subependymal zone. Reactive changes were identified among astrocytes, oligodendroglia, and microglia. We conclude that hydrocephalus causes, in addition to axonal injury, gradual cell death in the cerebrum, particularly the white matter. The brain response includes production of new glial cells, but whether the new cells play any beneficial role remains unknown.     

Premature introduction of progestin-only contraceptive methods during lactation

INTRODUCTIONS: Cochlear implants are used for the rehabilitation of bilaterally deaf patients. Due to the improvements in speech processing they might be also useful for patients with residual hearing and some speech understanding. METHODS: Pre- and postoperative speech understanding scores in 26 patients receiving implants were evaluated in a retrospective study. RESULTS: The preoperative pure-tone threshold in the implanted ear was between 80 and 115 dB in the frequency range of 500 to 2000 Hz. On the contralateral side the mean threshold was 10 dB better. The mean score for the number test was 11.3%, for the monosyllables below 5%. Postoperatively speech understanding improved significantly up to 97% for numbers and 48% for monosyllables (tested with the Freiburger Speech Test). Cochlear implantation also benefits patients with residual hearing and some speech understanding with hearing aids under optimum conditions. The speech understanding scores must be below certain limits. General selection criteria cannot yet be specified. The individual decision must be based upon several criteria, especially the speech understanding scores in quiet and noise under optimum conditions. A prospective study is needed to develop generally applicable criteria.     

Diazepam alters caffeine-induced effects on beta-endorphin levels in specific rat brain regions

The present study was conducted to evaluate the effects of caffeine and the benzodiazepine agonist diazepam, and a combination of both on beta-endorphin (beta-EN) levels in specific rat brain regions. Male Sprague-Dawley rats (150-200 g) adapted to a 12-hour light: 12-hour dark illumination cycle were used in this study. Caffeine (10 mg/kg), diazepam (2 mg/kg) or a combination of caffeine (10 mg/kg) and diazepam (2 mg/kg) were administered intraperitoneally to rats at 11:00 hr. Control animals were injected with saline. Animals were sacrificed by decapitation 1 h after injection, the brains were immediately removed; the cortex, hippocampus, hypothalamus and midbrain were dissected and their B-EN levels measured by radioimmunoassay. Caffeine administration significantly increased B-EN levels in the cortex. Similarly, administration of diazepam alone resulted in a significant increase of B-EN levels in cortex. However, concurrent administration of diazepam and caffeine resulted in higher increase of B-EN levels in cortex. No significant changes in B-EN levels were detected in hippocampus and midbrain after administration of either caffeine or diazepam alone. On the other hand, when diazepam and caffeine were concurrently administered a significant increase of B-EN levels were observed in the midbrain. Moreover, administration of diazepam alone resulted in a significant increase of B-EN levels in hypothalamus. This increase was still observed following concurrent administration of diazepam and caffeine. These results clearly indicate that diazepam alters caffeine-induced effects on B-EN in specific rat brain regions.