Thermofraktographie zur Schnellanalyse von Kunststoffen. 4. Mitt.: Identifizierung der Basiskomponenten von Epoxidharzen

Thermofractography is suitable for the rapid identification of the basic components of epoxy resins. 2–3 mg of the polymer sample are being heated in the temperature gradient of 200 to 450°C. The thus forming decomposition products are being transferred as a starting line onto the separating thin layer by means of a carrier gas. After development the thermofractogram (TFG) shows in the temperature range of 200 to approx. 350°C the free oligomeres. The resulting phenols and their subsequent products appear on the TFG from 350°C. A cycloaliphatic type does not give phenolic fragments. The degradation mechanisms of epoxy resins are being discussed in regard to the TFG results and are being confirmed by establishing TGA curves. For the rapid evaluation of the thermofractograms of epoxy resins a questioning scheme is given as an evaluation key.     

On-road measurement of particle emission in the exhaust plume of a diesel passenger car

Particle size distributions were measured under real world dilution conditions in the exhaust plume of a diesel passenger car closely followed by a mobile laboratory on a high speed test track. Under carefully controlled conditions the exhaust plume was continuously sampled and analyzed inside the mobile laboratory. Exhaust particle size distribution data were recorded together with exhaust gas concentrations, i.e., CO, CO2, and NO(x), and compared to data obtained from the same vehicle tested on a chassis dynamometer. Good agreement was found for the soot mode particles which occurred at a geometric mean diameter of approximately 50 nm and a total particle emission rate of 10(14) particles km(-1). Using 350 ppm high sulfur fuel and the standard oxidation catalyst a bimodal size distribution with a nucleation mode at 10 nm was observed at car velocities of 100 km h(-1) and 120 km h(-1), respectively. Nucleation mode particles were only present if high sulfur fuel was used with the oxidation catalyst installed. This is in agreement with prior work that these particles are of semivolatile nature and originate from the nucleation of sulfates formed inside the catalyst. Temporal effects of the occurrence of nucleation mode particles during steady-state cruising and the dynamical behavior during acceleration and deceleration were investigated.     

Application of mid-infrared spectroscopy: measuring hydrogen peroxide concentrations in bleaching baths

The presented work applies mid-infrared attenuated total reflection (ATR) spectroscopy to the measurment of hydrogen peroxide in aqueous matrices. The performance of different ATR crystals mounted in flow cells was investigated in the presence of aqueous hydrogen peroxide solutions. Quantitative determination has been achieved by evaluation of specific OH stretching and deformation vibrations with linear correlation between peak areas or peak heights and hydrogen peroxide concentration in the range of 1-10% (weight in water). Important aspects such as chemical stability of the waveguide material and influences of pH and ionic strength on the performance are discussed. Feasibility for the investigation of real world samples is demonstrated by measuring industrial bleaching solutions with known concentrations of hydrogen peroxide fitting well with calibration graphs established with neat hydrogen peroxide solutions. The presented sensor system is capable of determining hydrogen peroxide within complex matrices and clearly corroborates the potential of providing an in situ measurement concept for on-line hydrogen peroxide detection.     

Classification of rheumatoid joint inflammation based on laser imaging

We describe a classification system for a novel imaging method for arthritic finger joints. The basis of this system is a laser imaging technique which is sensitive to the optical characteristics of finger joint tissue. From the laser images acquired at baseline and follow-up, finger joints can automatically be classified according to whether the inflammatory status has improved or worsened. To perform the classification task, various linear and kernel-based systems were implemented and their performances were compared. Based on the results presented in this paper, we conclude that the laser-based imaging permits a reliable classification of pathological finger joints, making it a sensitive method for detecting arthritic changes.     

Separation of plutonium and neptunium species by capillary electrophoresis-inductively coupled plasma-mass spectrometry and application to natural groundwater samples

Capillary electrophoresis (CE) was coupled to ICPMS in order to combine the good performance of this separation technique with the high sensitivity of the ICPMS for the analysis of plutonium and neptunium oxidation states. The combination of a fused-silica capillary with a MicroMist AR 30-I-FM02 nebulizer and a Cinnabar small-volume cyclonic spray chamber yielded the best separation results. With this setup, it was possible to separate a model element mixture containing neptunium (NpO2(+)), uranium (UO2(2+)), lanthanum (La3+), and thorium (Th4+) in 1 M acetic acid. The same conditions were also suitable for the separation of various oxidation states of plutonium and neptunium in different aqueous samples. All separations were obtained within less than 15 min. A detection limit of 50 ppb identical with 2 x 10(-7) M (3-fold standard deviation of a blank) was achieved. To prove the negligible disturbance of the plutonium and neptunium redox equilibria during the CE separations, plutonium and neptunium speciation by CE-ICPMS in acidic solutions was compared with the results of UV/visible absorption spectroscopy and was found to be in good agreement. The CE-ICPMS system was also applied to study the reduction of Pu(VI) in a humic acid-containing groundwater at different pH values.     

Evaluation of bacterial RNase P RNA as a drug target

RNA has gained increasing importance as a therapeutic target. However, so far mRNAs rather than stable cellular RNAs have been considered in such studies. In bacteria, the tRNA-processing enzyme RNase P has a catalytic RNA subunit. Fundamental differences in structure and function between bacterial and eukaryotic RNase P, and its indispensability for cell viability make the bacterial enzyme an attractive drug target candidate. Herein we describe two approaches utilized to evaluate whether the catalytic RNA subunit of bacterial RNase P is amenable to inactivation by antisense-based strategies. In the first approach, we rationally designed RNA hairpin oligonucleotides targeted at the tRNA 3'-CCA binding site (P15 loop region) of bacterial RNase P RNA by attempting to include principles derived from the natural CopA-CopT antisense system. Substantial inactivation of RNase P RNA was observed for Type A RNase P RNA (such as that in Escherichia coli) but not for Type B (as in Mycoplasma hyopneumoniae). Moreover, only an RNA oligonucleotide (Eco 3') complementary to the CCA binding site and its 3' flanking sequences was shown to be an efficient inhibitor. Mutation of Eco 3' and analysis of other natural RNase P RNAs with sequence deviations in the P15 loop region showed that inhibition is due to interaction of Eco 3' with this region and occurs in a highly sequence-specific manner. A DNA version of Eco 3' was a less potent inhibitor. The potential of Eco 3' to form an initial kissing complex with the P15 loop did not prove advantageous. In a second approach, we tested a set of oligonucleotides against E. coli RNase P RNA which were designed by algorithms developed for the selection of suitable mRNA targets. This approach identified the P10/11-J11/12 region of bacterial RNase P RNA as another accessible region. In conclusion, both the P15 loop and P10/11-J11/12 regions of Type A RNase P RNAs seem to be promising antisense target sites since they are easily accessible and sufficiently interspersed with nonhelical sequence elements, and oligonucleotide binding directly interferes with substrate docking to these two regions.     

Expert Recommender: Designing for a Network Organization

Recent knowledge management initiatives focus on expertise sharing within formal organizational units and informal communities of practice. Expert recommender systems seem to be a promising tool in support of these initiatives. This paper presents experiences in designing an expert recommender system for a knowledge-intensive organization, namely the National Industry Association (NIA). Field study results provide a set of specific design requirements. Based on these requirements, we have designed an expert recommender system which is integrated into the specific software infrastructure of the organizational setting. The organizational setting is, as we will show, specific for historical, political, and economic reasons. These particularities influence the employees’ organizational and (inter-)personal needs within this setting. The paper connects empirical findings of a long-term case study with design experiences of an expertise recommender system.     

Transparent conducting indium oxide thin films grown by low-temperature metal organic chemical vapor deposition

We have grown indium oxide thin films on silicon substrates at low temperature by metal organic chemical vapor deposition. Polycrystalline film growth could only be obtained at temperatures below 400 °C. Above 400 °C, metallic indium deposition dominated. We have investigated the effect of substrate temperature and reactor pressure on the film growth and structural properties in the range of 250-350 °C and 5 ^? 10³-4 ^? 10⁴ Pa. The film grown at 300 °C exhibited a resistivity of about 3.6 × 10^− 3 Ω cm and a maximal optical transmittance of more than 95% in the visible range. The film showed an optical band gap of about 3.6 eV.