Allgemeine Untersuchungsverfahren und Laboratoriumstechnik

Ohne Zusammenfassung     

Molecular changes during learning: Behavioral strategy: A comment on Gaito and Bonnet.

Discusses J. Gaito and K. Bonnet's (see record 1971-07612-001) recent review which suggests that there is no conclusive evidence linking macromolecular changes to learning and memory. It is contended that current experiments in this field are not properly designed to test the hypothesis that a general macromolecular process underlies learning and memory, since the control group designated "nonlearning" is not achieved with the typical control procedures. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intracellular localisation of urea-cycle enzymes in liver (author's transl)

Enzymes of the Krebs-Henseleit urea-cycle were localized by means of differential centrifugation and fractional tissue extraction in rat liver and in human liver. Argininosuccinatlyase (ASAL) and Argininosuccinatsynthetase (ASAS) represent enzymes of the soluble cytoplasmic fraction. Ornithine-ketoacid-transaminase(OKT), carbamyl-phosphate-synthetase (CPS) and ornithine-carbamyl-transferase (OCT) are localized in the mitochondrial and nuclei fractions of the liver cell. Most of the arginase activity is bound to subcellular structures (probably to nuclei). A small portion of arginase-activity was found in the soluble cytoplasmatic fraction. The enzymes of the Krebs-Henseleit urea-cycle are equally distributed in rat liver and in human liver. Differences in the subcellular localisation of (mitochondrial) enzymes in human liver could be attributed to mitochondrial breakage during tissue preparation and do not represent in-vivo conditions.     

Comparative investigation of the biocompatibility of various silicon nitride ceramic qualities in vitro

There is a controversy about the biocompatibility of silicon nitride ceramics contained in the literature, which appears to be related to a factor of the individual chemical composition of different qualities of silicon nitride ceramics and of the different surface properties. This study attempts to investigate the cytotoxicity of different qualities of industrial silicon nitride ceramics applying an L929-cell culture model in a direct contact assay combined with a cell viability assessment. Five different qualities of industrial standard silicon nitride ceramics were chosen for in vitro testing. The chemical composition was determined by EDS analysis. Different biomedically approved aluminium oxide qualities, a titanium alloy, glass and polyvinylchloride (PVC) served as control materials. L929 mice fibroblasts were incubated directly on the materials for 24 h, stained with bisbenzimide and propidium iodine for double fluorochromasia viability testing, and evaluated by inversion-fluorescence microscopy to control cell morphology, viability and cell counts compared to empty well values. Scanning electron microscopy was applied to additionally investigate cell morphology. There was no observation of cytotoxic effects on the silicon nitride ceramic samples; moreover cell morphology remained the same as on aluminium oxide and titanium. Viability testing revealed the presence of avital cells exclusively on PVC, which served as a negative control. Cell counts on all polished surfaces showed significantly higher numbers, whereas some rough surface samples showed significantly lower numbers. We conclude that silicon nitride ceramics show no cytotoxic effects and should be considered for biomedical application owing to its favourable physiochemical properties, especially its superior resistance to mechanical stress, which would be useful for compression loaded conditions. Polished surfaces would appear to promote advanced biocompatibility.     

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.     

On-line coupling of size exclusion chromatography with electrospray ionization-tandem mass spectrometry for the analysis of aquatic fulvic and humic acids

A method was developed for the analysis of humic and fulvic acids by size-exclusion chromatography-electrospray ionization-tandem mass spectrometry using a completely volatile eluent. Humic and fulvic acids were separated into three peaks. These fractions occupied different mass ranges and showed differences in the fine structure of their mass spectra. The low-molecular-weight (LMW) fraction of fulvic acids is most sensitively determined by ESI-MS, and it appears that previous results obtained by infusion-ESI-MS were primarily determined by this fulvic acid fraction. The average molecular weight of this fractions turned out to be lower than that reported from infusion-ESI-MS measurements. Its scan spectra and the product ion spectra of some of its molecular anions perfectly match those previously obtained from whole fulvic acid mixtures. Obviously, a class of well-defined polycarboxylated molecules exist that occurs in all fulvic acid fractions thus far investigated. With decreasing elution time and increasing molecular weight, detection by ESI-MS loses sensitivity as compared to the parallel UV recording, and the fine structure of the scan spectra becomes increasingly uniform for both fulvic and humic acids. The average molecular weight of the HMW fraction exceeds those values calculated from infusion experiments. Scan spectra and product ion spectra of the high-molecular-weight (HMW) fraction of both the humic and the fulvic acids suggest that the HMW fraction consists of several subunits that originate from the LMW fraction.     

Computational aspects of prospect theory with asset pricing applications

We develop an algorithm to compute asset allocations for Kahneman and Tversky’s (Econometrica, 47(2), 263–291, 1979) prospect theory. An application to benchmark data as in Fama and French (Journal of Financial Economics, 47(2), 427–465, 1992) shows that the equity premium puzzle is resolved for parameter values similar to those found in the laboratory experiments of Kahneman and Tversky (Econometrica, 47(2), 263–291, 1979). While previous studies like Benartzi and Thaler (The Quarterly Journal of Economics, 110(1), 73–92, 1995), Barberis, Huang and Santos (The Quarterly Journal of Economics, 116(1), 1–53, 2001), and Grüne and Semmler (Asset prices and loss aversion, Germany, Mimeo Bielefeld University, 2005) focussed on dynamic aspects of asset pricing but only used loss aversion to explain the equity premium puzzle our paper explains the unconditional moments of asset pricing by a static two-period optimization problem. However, we incorporate asymmetric risk aversion. Our approach allows reducing the degree of loss aversion from 2.353 to 2.25, which is the value found by Tversky and Kahneman (Journal of Risk and Uncertainty, 5, 297–323, 1992) while increasing the risk aversion from 1 to 0.894, which is a slightly higher value than the 0.88 found by Tversky and Kahneman (Journal of Risk and Uncertainty, 5, 297–323, 1992). The equivalence of these parameter settings is robust to incorporating the size and the value portfolios of Fama and French (Journal of Finance, 47(2), 427–465, 1992). However, the optimal prospect theory portfolios found on this larger set of assets differ drastically from the optimal mean-variance portfolio.     

Component-based end-user database design for ecologists

To solve today’s ecological problems, scientists need well documented, validated, and coherent data archives. Historically, however, ecologists have collected and stored data idiosyncratically, making data integration even among close collaborators difficult. Further, effective ecology data warehouses and subsequent data mining require that individual databases be accurately described with metadata against which the data themselves have been validated. Using database technology would make documenting data sets for archiving, integration, and data mining easier, but few ecologists have expertise to use database technology and they cannot afford to hire programmers. In this paper, we identify the benefits that would accrue from ecologists’ use of modern information technology and the obstacles that prevent that use. We describe our prototype, the Canopy DataBank, through which we aim to enable individual ecologists in the forest canopy research community to be their own database programmers. The key feature that makes this possible is domain-specific database components, which we call templates. We also show how additional tools that reuse these components, such as for visualization, could provide gains in productivity and motivate the use of new technology. Finally, we suggest ways in which communities might share database components and how components might be used to foster easier data integration to solve new ecological problems.     

Structural Engineering with NiTi. II: Mechanical Behavior and Scaling

This paper continues to address the overarching goal to provide a more unified understanding of NiTi shape memory alloys intended for use in structural applications by attempting to link standard processing practice and basic materials characterization to the deformation behavior of large diameter bars. Results from cyclic tensile tests performed on large diameter Ni-rich polycrystalline NiTi bars are presented. Coupon specimens taken from deformation processed bars with diameters of 12.7, 19.1, and 31.8?mm are tested along with their respective full-scale specimens. The coupon tests results reveal small and highly variable differences between specimens taken from the different size bars. The full-scale specimen tests continue to show the presence of the R phase, but lack a Lüders-like transformation. A comparison of the results suggests that coupon specimens provide only limited information in terms of the full-scale behavior. Full-scale tests using an earthquake-type loading then show similar behavior to the tensile cyclic tests suggesting the ability to use NiTi in structural applications. Overall, this paper and Tyber et al. 2007 provide a multiscale analysis of NiTi shape memory alloys to be used by both material scientist and civil engineers in the development of applications for NiTi.