Sevoflurane selectively increases coronary collateral blood flow independent of KATP channels in vivo

BACKGROUND: Volatile anesthetic agents produce coronary vasodilation via activation of adenosine triphosphate-sensitive potassium (KATP) channels. The authors tested the hypothesis that sevoflurane selectively increases coronary collateral blood flow and assessed the role of KATP channel activation in this process. METHODS: Experiments were conducted in dogs 8 weeks after long-term implantation of a left anterior descending coronary artery (LAD) ameroid constrictor to stimulate coronary collateral growth. Dogs were instrumented for measurement of retrograde LAD blood flow (an index of large coronary collateral blood flow) and LAD tissue flow (via radioactive microspheres; an index of small collateral blood flow). Coronary collateral perfusion and normal (left circumflex coronary artery [LCCA]) zone tissue blood flow were determined in four groups of dogs pretreated with intracoronary glyburide (50 microg/kg) or vehicle in the presence or absence of sevoflurane (1 minimum alveolar concentration). Dose-response relationships to the KATP channel agonist nicorandil were established in each dog using doses (25, 50, and 100 microg/min) previously shown to increase coronary collateral blood flow. RESULTS: Sevoflurane increased blood flow through large and small collaterals and increased collateral vascular conductance in the presence of glyburide but did not affect LCCA blood flow or conductance. In contrast, nicorandil increased blood flow through small but not large collaterals. Nicorandil also increased LCCA blood flow and conductance, actions that were attenuated by glyburide. CONCLUSIONS: The results demonstrate that sevoflurane selectively increases large and small coronary collateral blood flow via mechanism(s) independent of KATP channel activation.     

Pyrolysis oil upgrading by high pressure thermal treatment

High pressure thermal treatment (HPTT) is a new process developed by BTG and University of Twente with the potential to economically reduce the oxygen and water content of oil obtained by fast pyrolysis (pyrolysis oil), properties that currently complicate its co-processing in standard refineries. During the HPTT process, pyrolysis oil undergoes a phase split yielding a gas phase, an aqueous phase and an oil phase. In this study, HPTT experiments were carried out at different operating conditions in a continuous tubular reactor. Experimental results showed that, with increasing temperature and residence time, the release of gases (mainly CO₂) and the production of water increased, reducing the oxygen content of the oil phase and hence increasing the energy content (from 14.1 to 28.4 MJ/kg) having the temperature a larger effect when compared to the residence time. Using gel permeation chromatography (GPC), an increase of the molecular weight of the oil phase, probably due to polymerisation of the sugars present in pyrolysis oil, was observed. When water was added as solvent to dilute the feed oil, a decrease of the molecular weight of the resulting oil phase was observed. This indicated that the concentration of organic components had a direct effect on the formation of high molecular weight components. In conclusion, during HPTT an oil with lower oxygen and water content with higher energy value was produced, but adverse formation of high molecular weight components was also detected.     

Synthesis of Imidazoles by reaction of N-benzylated amidines with carboxylic acid derivatives

2-Amino-N-heterocycles, such as 2-aminopyridine 7 or 2-aminobenzimidazole 16 as well as benzamidines 19 possessing a N-(4-nitrobenzyl)-substituent react as N-C-N-C-synthons with formamide chlorides 5 , formamide acetals 2 or acetic anhydride (C₁-building blocks) with formation of imidazole compounds 9 , 17 or 22 , respectively in the presence of triethylamine. In some cases, intermediate N-acetylation ( 20 ) or N-formylation products 21 are isolated.     

Fluidized bed spray granulation: Investigation of the coating process on a single sphere

The coating and granulation of solid particles in a fluidized bed is a process which converts pumpable and atomizable liquids (solutions, slurries, melts) into granular solids in one step by means of drying. The solution to be processed is sprayed onto a fluidized bed. Particle growth can take place either via surface layering or agglomeration. In the case of surface layering the atomized droplets deposit a thin layer of liquid onto the seed particles. The solvent is then evaporated by the hot fluidizing, leaving behind the dissolved material on the surface. Although fluidized bed spray granulation and film coating have been applied in industry for several years, there is still a lack of understanding of the physical fundamentals and the mechanisms by which spherical granules are formed. Hence a new method was developed which allows the direct observation of the subsequent particle-forming mechanisms such as droplet deposition, spreading, wetting and drying. The authors present a laboratory scale apparatus in which a single freely suspended particle can be coated under well defined and constant coating and drying conditions. With this device, particle-growth-rate and the development of particle morphology were measured and investigated under various experimental conditions.     

Application of the in vitro rat hepatocyte micronucleus assay in genetic toxicology testing

The investigation of micronuclei in mitogenic stimulated hepatocytes in vitro is a quite new area of research. Nevertheless, a relatively large database comprising more than 40 tested compounds of various classes has been generated up to now. This paper reviews the available data for the in vitro rat hepatocyte micronucleus assay, showing a sensitivity of this assay in identifying mutagens and genotoxic liver carcinogens of about 85%. Additionally, all of the tested non-carcinogens gave negative results. The use of primary hepatocytes instead of permanently dividing mammalian cell lines for the investigation of micronucleus induction has several advantages. (1) The broad spectrum of metabolizing enzymes expressed in primary hepatocytes ensures an adequate activation of most xenobiotics. (2) No transfer of activated metabolites via the culture medium is necessary in this system, since the metabolizing cells are the target cells themselves. (3) Whilst in experiments with permanently dividing cells the use of S9-mix restricts the treatment period with the test compounds to 2-6 h in the hepatocyte micronucleus assay continuous treatment of up to 48 h is possible. Investigations with the pyrrolizidine alkaloids retrorsine, monocrotaline and isatidine, strong mutagens and liver carcinogens, clearly showed that at least for isatidine a prolonged exposure period is essential to detect its mutagenic potential. This compound gave positive results in rat hepatocytes but not in V79-cells/S9-mix cultures. (4) The results obtained with the hepatocyte micronucleus assay are in good agreement with the genotoxic profiles of most of the compounds tested. Only three polycyclic aromatic hydrocarbons led to 'false-negative' results, since they strongly inhibited hepatocyte proliferation and thereby prevented micronucleus formation. (5) Hepatocytes are target cells of special interest when compounds are investigated which act specifically in the liver. Especially for hepatocarcinogens classified as non-genotoxins in standard genotoxicity tests or for chemicals showing DNA-repair induction in hepatocytes but no mutagenicity in standard tests, the hepatocyte micronucleus assay can contribute to clarify the situation. (6) The rat hepatocyte micronucleus assay can be performed easily and without great efforts in parallel to the in vitro hepatocyte DNA repair test (UDS-test), using the same hepatocyte batches. (7) Similar to the two versions of the UDS-test, the hepatocyte micronucleus assay can be performed following an in vivo-in vitro protocol. In order to further validate the hepatocyte micronucleus assay, as a next step controlled interlaboratory studies should be initiated.     

Why the visual recognition system might encode the effects of illumination

A key problem in recognition is that the image of an object depends on the lighting conditions. We investigated whether recognition is sensitive to illumination using 3-D objects that were lit from either the left or right, varying both the shading and the cast shadows. In experiments 1 and 2 participants judged whether two sequentially presented objects were the same regardless of illumination. Experiment 1 used six objects that were easily discriminated and that were rendered with cast shadows. While no cost was found in sensitivity, there was a response time cost over a change in lighting direction. Experiment 2 included six additional objects that were similar to the original six objects making recognition more difficult. The objects were rendered with cast shadows, no shadows, and as a control, white shadows. With normal shadows a change in lighting direction produced costs in both sensitivity and response times. With white shadows there was a much larger cost in sensitivity and a comparable cost in response times. Without cast shadows there was no cost in either measure, but the overall performance was poorer. Experiment 3 used a naming task in which names were assigned to six objects rendered with cast shadows. Participants practised identifying the objects in two viewpoints lit from a single lighting direction. Viewpoint and illumination invariance were then tested over new viewpoints and illuminations. Costs in both sensitivity and response time were found for naming the familiar objects in unfamiliar lighting directions regardless of whether the viewpoint was familiar or unfamiliar. Together these results suggest that illumination effects such as shadow edges: (1) affect visual memory; (2) serve the function of making unambigous the three-dimensional shape; and (3) are modeled with respect to object shape, rather than simply encoded in terms of their effects in the image.     

Competition between hydrotreating and polymerization reactions during pyrolysis oil hydrodeoxygenation

Hydrodeoxygenation (HDO) of pyrolysis oil is an upgrading step that allows further coprocessing of the oil product in (laboratory‐scale) standard refinery units to produce advanced biofuels. During HDO, desired hydrotreating reactions are in competition with polymerization reactions that can lead to unwanted product properties. To suppress this polymerization, a low‐temperature HDO step, referred to as stabilization, is typically used. Small batch autoclaves have been used to study at near isothermal conditions the competition between hydrotreating and polymerization reactions. Although fast polymerization reactions take place above 200°C, hydrogen consumption was already observed for temperatures as low as 80°C. Hydrogen consumption increased with temperature and reaction time; however, when the end temperature exceeded 250°C, hydrogen consumption achieved a plateau. This was thought to be caused by the occurrence of fast polymerization reactions and the refractivity of the products to further hydrotreating reactions. The effect of the gas–liquid mass transfer was evaluated by using different stirring speeds. The results of these experiments (carried out at 300°C) showed that in the first 5 min of HDO, gas–liquid mass transfer appears to be limiting the overall rate of hydrotreating reactions, leading to undesired polymerization reactions and product deterioration. Afterward, intraparticle mass transfer/kinetics seems to be governing the hydrogen consumption rate. Estimations on the degree of utilization (effectiveness factor) for industrially sized catalysts show that this is expected to be much lower than 1, at least, in the early stage of HDO (first 30 min). Catalyst particle size should, thus, be carefully considered when designing industrial processes not only to minimize reactor volume but also to improve the ratio of hydrotreating to polymerization reactions. © 2011 American Institute of Chemical Engineers AIChE J, 2011     

Die Geschichte der Gasentladungsphysik

The History of Gas Discharge Physics Observation and study of the impressive polar lights marks the beginning of the gas discharge physics. Even though a remarkable progress was reached by the improvement of gas discharge tubes. The first constructed tube goes back to the Englishman Hauksbee. After that the German glassblower Heinrich Geißler developed more innovative discharge tubes by reducing the gas pressure and by using electrodes of aluminium. The Geißler tubes enabled a lot of scientists such as Plücker, Hittorf and Tesla to study the properties of glow discharges in more detail. At the same time Sir William Crookes developed similar tubes, which found a use in the laboratories of English physicists. Ultimately there were more seminal insights which led to the development of plasma physics as a seperate field and as foundation for many industrial applications.     

Generation and application of hyperspectral 3D plant models: methods and challenges

Hyperspectral imaging sensors have been introduced for measuring the health status of plants. Recently, they also have been used for close-range sensing of plant canopies with a highly complex architecture. However, the complex geometry of plants and their interaction with the illumination setting severely affect the spectral information obtained. Furthermore, the spatial component of analysis results gain in importance as higher plants are represented by multiple plant organs as leaves, stems and seed pods. The combination of hyperspectral images and 3D point clouds is a promising approach to face these problems. We present the generation and application of hyperspectral 3D plant models as a new, interesting application field for computer vision with a variety of challenging tasks. We sum up a geometric calibration method for hyperspectral pushbroom cameras using a reference object for the combination of spectral and spatial information. Furthermore, we show exemplarily new calibration and analysis methods enabled by the hyperspectral 3D models in an experiment with sugar beet plants. An improved normalization, a comparison of image and 3D analysis and the density estimation of infected surface points underline some of the new capabilities gained using this new data type. Based on such hyperspectral 3D models the effects of plant geometry and sensor configuration can be quantified and modeled. In future, reflectance models can be used to remove or weaken the geometry-related effects in hyperspectral images and, therefore, have the potential to improve automated plant phenotyping significantly.