Gezielte Variation des Beanspruchungskollektivs zur Verbesserung des Einlaufverhaltens im Trockenlauf

Forschung im Ingenieurwesen - Präzise steuer- und regelbaren Kupplungen wird eine Schlüsselrolle in der Transformation der Automobilwirtschaft zugesprochen. Als Grundlage der...     

Immunochemical quantification of human plasma Lp(a) lipoprotein

The Lp(a) lipoprotein was purified from human plasma by ultracentrifugation and gel filtration on 6% agarose. It contained 27% protein, 65% lipid, and 8% carbohydrate. Quantification of the Lp(a) lipoprotein was performed by radial immunodiffusion. Both within-assay and between-assay coefficients of variation were inversely concentration dependent, decreasing from 20% and 27%, respectively, at 3 mg/100 ml to 7% and 12%, respectively, at concentrations above 8 mg/100 ml. The lower limit of sensitivity of the assay was 1.5 mg/100 ml. Of 340 unrelated fasting subjects tested, 81% had levels of the Lp(a) lipoprotein exceeding this lower limit. The distribution of Lp(a) concentrations in this population was skewed with a mean of 14 mg/100 ml and a median of 8 mg/100 ml. Lp(a) lipoprotein was not significantly correlated with age, sex, or cholesterol or glyceride concentrations.     

Mesoscopic structure and swelling properties of crosslinked polyethylene glycol in water

In this paper, we present our efforts in modeling and simulation of polyethylene glycol crosslinked with an isocyanate tHDI. The polymer, by its nature, is hydrophilic and has strong hydrogen bond interactions with water. The simulations are performed at coarse-grained scale by using a dissipative particle dynamics (DPD) simulation method. The effect of hydrogen bond between water and polymer beads on the structure of the crosslinked hydrophilic polymer structure is studied. The polymer is observed to phase separate with water in the absence of hydrogen bonds in DPD simulations. In the reverse case, where hydrogen bonds are explicitly included in DPD simulations, polymer mixes with water. This behavior is investigated by plotting the density profiles. Moreover, the volumetric swelling behavior in mixtures with different water contents is estimated from simulations and extrapolated by a polynomial fit to compare with experiments. It is observed that the predicted swelling ratio is in good agreement with the experimental measurements.     

Soil to plant uptake of fallout 137Cs by plants from boreal areas polluted by industrial emissions from smelters.

To study the impact of industrial pollution on the soil-to-plant uptake of fallout-radiocesium in a boreal forest ecosystem, four study sites were selected at distances of 7, 16, 21 and 28 km from the large copper-nickel smelter at Monchegorsk on the Kola Peninsula (Russia). At each site, soil and selected plant species were sampled from five plots and analysed separately for 137Cs and 40K. The data show that the root-uptake of 137Cs, as characterised by the median aggregated transfer-factor T(ag), decreased significantly (P < 0.05) with decreasing distance from the smelter for the plants Vaccinium myrtillus (from 0.023 to 0.007 m2 kg-1) and Empetrum nigrum (from 0.015 to 0.007 m2 kg-1), but increased for Deschampsia flexuosa (from 0.013 to 0.031 m2 kg-1). For Vaccinium vitis-idaea a significant trend for the T(ag) was not observed. The median 40K activity concentrations in these plants also decreased significantly (P < 0.001) with decreasing distance from the smelter for Vaccinium myrtillus (from approx. 140 to 20 Bq kg-1 dry wt.), Empetrum nigrum (from approx. 90 to 40 Bq kg-1 dry wt.), and also for Deschampsia flexuosa (from approx. 270 to 40 Bq kg-1 dry wt.). For Vaccinium vitis-idaea such a continuous significant trend was not observed. The results for the Cu-Ni polluted soils thus show: (1) that the soil-to-plant transfer of radiocesium can be significantly modified; (2) that these modifications are quite specific; and (3) that modifications of the uptake of potassium do not always correspond to those of radiocesium.     

Automated detection and quantitation of bacterial RNA by using electrical microarrays

Low-density electrical 16S rRNA specific oligonucleotide microarrays and an automated analysis system have been developed for the identification and quantitation of pathogens. The pathogens are Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, and Staphylococcus epidermidis, which are typically involved in urinary tract infections. Interdigitated gold array electrodes (IDA-electrodes), which have structures in the nanometer range, have been used for very sensitive analysis. Thiol-modified oligonucleotides are immobilized on the gold IDA as capture probes. They mediate the specific recognition of the target 16S rRNA by hybridization. Additionally three unlabeled oligonucleotides are hybridized in close proximity to the capturing site. They are supporting molecules, because they improve the RNA hybridization at the capturing site. A biotin labeled detector oligonucleotide is also allowed to hybridize to the captured RNA sequence. The biotin labels enable the binding of avidin alkaline phophatase conjugates. The phosphatase liberates the electrochemical mediator p-aminophenol from its electrically inactive phosphate derivative. The electrical signals were generated by amperometric redox cycling and detected by a unique multipotentiostat. The read out signals of the microarray are position specific current and change over time in proportion to the analyte concentration. If two additional biotins are introduced into the affinity binding complex via the supporting oligonucleotides, the sensitivity of the assays increase more than 60%. The limit of detection of Escherichia coli total RNA has been determined to be 0.5 ng/microL. The control of fluidics for variable assay formats as well as the multichannel electrical read out and data handling have all been fully automated. The fast and easy procedure does not require any amplification of the targeted nucleic acids by PCR.     

Effect of local restaurant smoking regulations on progression to established smoking among youths

Background: While smoke-free restaurant laws are intended to protect the public from secondhand smoke exposure, they may also discourage smoking among adolescents. There is no evidence from longitudinal studies to test this hypothesis. Objective: To examine the effect of local restaurant smoking regulations on progression to established smoking among adolescents. Design, setting, and subjects: A cohort of 2623 Massachusetts youths, ages 12–17 years at baseline, was interviewed via random digit dial telephone survey in 2001–2002 and followed up two years later. A generalised estimating equations (GEE) logistic regression analysis was used and controlled for potential individual, household, and town level confounding factors. Main outcome measure: Progression to established smoking during the two year follow up period (defined as having smoked 100 or more cigarettes in one''s life). Results: Compared to youths living in towns with weak regulations, those living in towns with strong regulations (complete restaurant smoking bans) had less than half the odds of progression to established smoking (odds ratio (OR) 0.39, 95% confidence interval (CI) 0.24 to 0.66). The association was stronger for youths in towns with strong regulations in effect for two or more years (OR 0.11, 95% CI 0.03 to 0.37), although it was still present for those in towns with strong regulations in effect for less than two years (OR 0.55, 95% CI 0.33 to 0.90). No relationship was found between living in a town with a medium restaurant smoking regulation (restriction of smoking to enclosed, separately ventilated areas) and rates of progression to established smoking. Conclusions: Local restaurant smoking bans may be an effective intervention to prevent youth smoking.     

Effects of Compression and Filler Particle Coating on the Electrical Conductivity of Thermoplastic Elastomer Composites

Elastomeric polymers can be filled with metallic micro- or nanoparticles to obtain electrical conductivity, in which the conductivity is largely determined by the intrinsic conductivity of and contact resistance between the particles. Electrons will flow through the material effectively when the percolation threshold for near-neighbor contacts is exceeded and sufficiently close contacts between the filler particles are realized for electron tunneling to occur. Silver-coated glass microparticles of two types (fibers and spheres) were used as fillers in a thermoplastic elastomer composite based on styrene–ethylene–butylene–styrene copolymer, and the direct-current (DC) resistance and radiofrequency impedance were significantly reduced by coating the filler particles with octadecylmercaptan. Not only was the resistance reduced but also the atypical positive piezoresistivity effect observed in these elastomers was strongly reduced, such that resistivity values below 0.01 Ω cm were obtained for compression ratios up to 20%. In the DC measurements, an additional decrease of resistivity was obtained by inclusion of π-extended aromatic compounds, such as diphenylhexatriene. Some qualitative theories are presented to illuminate the possible mechanisms of action of these surface coatings on the piezoresistivity.     

Impurities block the alpha to omega martensitic transformation in titanium

Impurities control phase stability and phase transformations in natural and man-made materials, from shape-memory alloys to steel to planetary cores. Experiments and empirical databases are still central to tuning the impurity effects. What is missing is a broad theoretical underpinning. Consider, for example, the titanium martensitic transformations: diffusionless structural transformations proceeding near the speed of sound. Pure titanium transforms from ductile alpha to brittle omega at 9 GPa, creating serious technological problems for beta-stabilized titanium alloys. Impurities in the titanium alloys A-70 and Ti-6Al-4V (wt%) suppress the transformation up to at least 35 GPa, increasing their technological utility as lightweight materials in aerospace applications. These and other empirical discoveries in technological materials call for broad theoretical understanding. Impurities pose two theoretical challenges: the effect on the relative phase stability, and the energy barrier of the transformation. Ab initio methods calculate both changes due to impurities. We show that interstitial oxygen, nitrogen and carbon retard the transformation whereas substitutional aluminium and vanadium influence the transformation by changing the d-electron concentration. The resulting microscopic picture explains the suppression of the transformation in commercial A-70 and Ti-6Al-4V alloys. In general, the effect of impurities on relative energies and energy barriers is central to understanding structural phase transformations.     

The h,x-diagram as a Representation of Measurements of Ranges of Comfort in a Long-Duration Test

It is well known that the inhabitants of dwellings use the room heating and ventilation to build up their own individual climatic zone in which they feel comfortable. To date individual measurements have been conducted to investigate these climatic zones, or line charts have been drawn up with a thermohygrograph in long-duration tests. Compared with the form of presentation used previously, the possibilities for evaluation have been substantially improved by the use of measured data-recording installations for the long-term investigation and presentation of results in the form of dots (temperature/humidity value pairs) in an h,x-diagram. The h,x-diagram is a type of psychrometric chart which is widely used in Germany. The advantage of this chart is that all thermodynamic properties of moist air can be determined without calculation. The dry bulb temperature, the wet bulb temperature, the dew point, the relative humidity, the humidity ratio, the specific enthalpy and the specific volume of moist air can be read directly from the diagram.