Energetics of Glucose Metabolism: A Phenomenological Approach to Metabolic Network Modeling

A new formalism to describe metabolic fluxes as well as membrane transport processes was developed. The new flux equations are comparable to other phenomenological laws. Michaelis-Menten like expressions, as well as flux equations of nonequilibrium thermodynamics, can be regarded as special cases of these new equations. For metabolic network modeling, variable conductances and driving forces are required to enable pathway control and to allow a rapid response to perturbations. When applied to oxidative phosphorylation, results of simulations show that whole oxidative phosphorylation cannot be described as a two-flux-system according to nonequilibrium thermodynamics, although all coupled reactions per se fulfill the equations of this theory. Simulations show that activation of ATP-coupled load reactions plus glucose oxidation is brought about by an increase of only two different conductances: a [Ca2+] dependent increase of cytosolic load conductances, and an increase of phosphofructokinase conductance by [AMP], which in turn becomes increased through [ADP] generation by those load reactions. In ventricular myocytes, this feedback mechanism is sufficient to increase cellular power output and O2 consumption several fold, without any appreciable impairment of energetic parameters. Glucose oxidation proceeds near maximal power output, since transformed input and output conductances are nearly equal, yielding an efficiency of about 0.5. This conductance matching is fulfilled also by glucose oxidation of β-cells. But, as a price for the metabolic mechanism of glucose recognition, β-cells have only a limited capability to increase their power output

Consumer exposure to biocides - identification of relevant sources and evaluation of possible health effects

<p>Abstract</p> <p>Background</p> <p>Products containing biocides are used for a variety of purposes in the home environment. To assess potential health risks, data on products containing biocides were gathered by means of a market survey, exposures were estimated using a worst case scenario approach (screening), the hazard of the active components were evaluated, and a preliminary risk assessment was conducted.</p> <p>Methods</p> <p>Information on biocide-containing products was collected by on-site research, by an internet inquiry as well as research into databases and lists of active substances. Twenty active substances were selected for detailed investigation. The products containing these substances were subsequently classified by range of application; typical concentrations were derived. Potential exposures were then estimated using a worst case scenario approach according to the European Commission's Technical Guidance Document on Risk Assessment. Relevant combinations of scenarios and active substances were identified. The toxicological data for these substances were compiled in substance dossiers. For estimating risks, the margins of exposure (MOEs) were determined.</p> <p>Results</p> <p>Numerous consumer products were found to contain biocides. However, it appeared that only a limited number of biocidal active substances or groups of biocidal active substances were being used. The lowest MOEs for dermal exposure or exposure by inhalation were obtained for the following scenarios and biocides: indoor pest control using sprays, stickers or evaporators (chlorpyrifos, dichlorvos) and spraying of disinfectants as well as cleaning of surfaces with concentrates (hydrogen peroxide, formaldehyde, glutardialdehyde). The risk from aggregate exposure to individual biocides via different exposure scenarios was higher than the highest single exposure on average by a factor of three. From the 20 biocides assessed 10 had skin-sensitizing properties. The biocides isothiazolinone (mixture of 5-chloro-2-methyl-2H-isothiazolin-3-one and 2-methyl-2H-isothiazolin-3-one, CMI/MI), glutardialdehyde, formaldehyde and chloroacetamide may be present in household products in concentrations which have induced sensitization in experimental studies.</p> <p>Conclusions</p> <p>Exposure to biocides from household products may contribute to induction of sensitization in the population. The use of biocides in consumer products should be carefully evaluated. Detailed risk assessments will become available within the framework of the EU Biocides Directive.</p

MD simulations of He evaporating from dodecane

The velocity distribution of He atoms evaporating from a slab of liquid dodecane has been simulated. The distribution composed of ∼10 000 He trajectories is shifted to fractionally faster velocities as compared to a Maxwell–Boltzmann distribution at the temperature of the liquid dodecane with an average translational energy of 1.05 × 2RT (or 1.08 × 2RT after correction for a cylindrical liquid jet), compared to the experimental work by Nathanson and co-workers (1.14 × 2RT) on liquid jets. Analysis of the trajectories allows us to infer mechanistic information about the modes of evaporation, and their contribution to the overall velocity distribution

Charakterisierung und Realisierung einer mikrokontrollerbasierten 3D-Erfassung,basierend auf einem Laserscanner und einer externen Schwenkeinheit

Gegenstand dieser Bachelorarbeit ist die Entwicklung einer 3D-Erfassung einer Messumgebung. Die 3D-Erfassung wird realisiert, indem zwei Einheiten, ein 2D-Laserscanner und eine Motorschwenkeinheit zu einer logischen 3DEinheit bzw. zu einem logischen 3D-Laserscanner zusammengefasst werden. Für diese neue logische 3D-Einheit werden in dieser Arbeit die Anforderungen analysiert und weitestgehend in einem Prototypen umgesetzt. Zentraler Punkt bei der Erstellung des Prototyps war die Charakterisierung und die Entwicklung einer modular aufgebauten und leicht erweiterbaren 3DErfassungssteuerung,die auf einem von zwei Mikrokontrollern des Laserscanners ausgeführt wird.This bachelor thesis includes the development of a 3D-measurement of a measurement environment. The 3D-measurement will be realized by a logic 3D-unit, which consists of a laser measurement system and a motorized swivel unit. The requirements of the new logic 3D-unit will be analyzed and a prototype will be created. The main focus on creating the prototype was the development and characterization of a 3D-measurement controller. The 3D-measurement controller has a modular system architecture, is easy expandable and will be executed on the second microcontroller of the laser measurement system