92 research outputs found
Nocturnal energy demand in plants: insights from studying mutants impaired in β-oxidation
No full textFatty acid beta-oxidation is essential for seedling establishment of oilseed plants, but little is known about its role in leaf metabolism of adult plants. Arabidopsis thaliana plants with loss-of-function mutations in the peroxisomal ABC-transporter1 (PXA1) or the core beta-oxidation enzyme keto-acyl-thiolase 2 (KAT2) have impaired peroxisomal beta-oxidation. pxa1 and kat2 plants developed severe leaf necrosis, bleached rapidly when returned to light, and died after extended dark treatment, whereas the wild type was unaffected. Dark-treated pxa1 plants showed a decrease in photosystem II efficiency early on and accumulation of free fatty acids, mostly alpha-linolenic acid [18:3(n-3)] and pheophorbide a, a phototoxic chlorophyll catabolite causing the rapid bleaching. Isolated wild-type and pxa1 chloroplasts challenged with comparable alpha-linolenic acid concentrations both showed an 80% reduction in photosynthetic electron transport, whereas intact pxa1 plants were more susceptible to the toxic effects of alpha-linolenic acid than the wild type. Furthermore, starch-free mutants with impaired PXA1 function showed the phenotype more quickly, indicating a link between energy metabolism and beta-oxidation. We conclude that the accumulation of free polyunsaturated fatty acids causes membrane damage in pxa1 and kat2 plants and propose a model in which fatty acid respiration via peroxisomal beta-oxidation plays a major role in dark-treated plants after depletion of starch reserves
Materialien zum Thema Geschichtsfälschung
No full textWichtig sind die Hinweise von Dieter Martin: Barock um 1800 (2000), S. 449f. http://books.google.de/books?id=PlowdbAI6ioC&pg=PA449 *** Syndikus Koch erschuf Valentin Gierth "Das im Jahr 1830 erschienene Werk Denkwürdigkeiten aus dem Leben der Herzogin Dorothea Sibylla von Liegnitz und Brieg: geborenen Markgräfin von Brandenburg und ihrer Leib- und Hebeamme Margaretha Fuss. Wörtlich aus des Rothgerbers Valentin Gierths Haus-und Tagebuche mit einem Vorworte des Syndicus Koch (Falch, 1830[2]) st..
C8.4 Measurement Methods for Understanding Water Uptake Processes in Polymers
No full textS.306-307Harsh environmental conditions may cause corrosion processes in electronics. They are mainly induced by water uptake of polymer embedding, housing or molding compounds. Therefore, longtime stability of these materials is critical for many applications. This work is focusing on demonstration and discussion of suitable measurement methods to determine the water uptake of polymers. Electrochemical impedance spectroscopy (EIS) and Fourier Transform Infrared spectroscopy (FTIR) were used to investigate polymer degradation before and after multiple loading scenarios. Degradation models could have been derived from these results
Materialien zum Thema Geschichtsfälschung
No full textWichtig sind die Hinweise von Dieter Martin: Barock um 1800 (2000), S. 449f. http://books.google.de/books?id=PlowdbAI6ioC&pg=PA449 *** Syndikus Koch erschuf Valentin Gierth "Das im Jahr 1830 erschienene Werk Denkwürdigkeiten aus dem Leben der Herzogin Dorothea Sibylla von Liegnitz und Brieg: geborenen Markgräfin von Brandenburg und ihrer Leib- und Hebeamme Margaretha Fuss. Wörtlich aus des Rothgerbers Valentin Gierths Haus-und Tagebuche mit einem Vorworte des Syndicus Koch (Falch, 1830[2]) st..
Degradation studies of epoxy coatings on printed circuit boards after pressure cooker test
No full textS.1872-1884The present work focusses on the investigation of the degradation of screen-printed epoxy coatings on printed circuit board under multiple corrosion load realized by the pressure cooker test. Since methods like the common mechanical shear strength tests are destructive and limited in information, the authors´ approach used the Electrochemical impedance spectroscopy (EIS) to study the change of their electrochemical behavior and the state of degradation. Complementarily, the Fourier Transformed Infrared Spectroscopy (FTIR) was used to investigate possible molecular change of the polymer due to the exposition. The experiments were carried out after different time of load. It could be shown that the complex conditions of the pressure cooker test initiate a controversial mechanism. The harsh corrosion load already results in a degradation of the polymer after 8 h but simultaneously the enhanced test temperature leads to ongoing curing processes consuming the remaining parts of resin and curing agents. As a result, the degradation kinetic seems to be delayed and after the recommended test time (96 h) the epoxy are less degraded than it was expected based on the results after a shorter time exposition.72Nr.1
Complementary EIS/FTIR study of the degradation of adhesives in electronic packaging
No full textS.1832-1841Adhesives are widely used in electronic packaging and of vital importance of the reliability of electronic systems. A deep understanding of the degradation mechanism of adhesives under corrosion load plays a key role in life time prediction. Unfortunately, most of the common reliability test are destructive. The present approach combine the non-destructive methods Electrochemical Impedance Spectroscopy (EIS) and the Fourier Transformed Infrared Spectroscopy (FTIR) as a powerful tool in complementary manner to describe the degradation mechanism and kinetics of two epoxy based adhesives, which are commonly used in electronic packaging. It is demonstrated that the application quality is the dominating impact on the optimization of the life time.71Nr.1
Tubular electronics - Next step in system integration
No full textS.251-252Most kinds of electronic systems start on a PCB or a ceramic board. But not all kind of applications can be fulfilled with such plane substrates. Many kinds of heaters or sensors prefer a tubular shape to increase the integration level or signal quality. Therefore, the Fraunhofer IKTS is developing technologies to transfer planar layouts on tubular surface since over 20 years. Main working fields are screen printed designs on ceramic or metallic surfaces. Different application examples will be given to discuss possibilities and advantages of this technology. The work provided food for thought for useful next component generations
Laser-induced activation of Mg-doped GaN: quantitative characterization and analysis
No full textWe investigate the effectiveness of laser-induced treatment as compared to rapid-thermal annealing (RTA) for the activation of p-type dopant in Mg-doped GaN layers. The study is based on a wide set of analytical techniques, including resistivity measurements, atomic force microscopy, scanning emission microscopy (SEM), dynamic secondary ion mass spectroscopy (D-SIMS), time-of-flight (TOF) SIMS and energy dispersive X-ray spectroscopy (EDXS) in combination with scanning transmission electron microscopy (STEM). Samples are treated at different energy densities and in different atmospheres, to provide a comprehensive overview of the topic. The analysis is carried out on GaN-on-Si samples, to demonstrate the effectiveness of the treatment even in presence of high threading dislocation densitie
Wettability of rapid thermal firing silver-pastes
No full textS.1-6Photovoltaic technology is evolving rapidly with new concepts and ideas to systematically improve module efficiency. Cell metallizations based on thick film pastes have to be fired less than one minute. It has already been shown that the solder interconnection of these rapid thermal firing pastes is critical in terms of wettability [1]. Main problems are solder leaching of commercially available pastes and paste adhesion to the silicon substrate. The correlation between paste composition and solder wettability has not been investigated yet. The aim of this work is to evaluate the wettability of rapid thermal firing pastes in dependence on paste composition and firing temperature. Pastes with spherical silver particles and lead free glass composition have been developed and fired with an industrial standard rapid thermal firing profile between (760...840) °C. Thick film surfaces and cross sections have been inspected. Solder wettability was evaluated with solder dip and solder reflow tests. Correlations between resulting thick films and their wetting or leaching characteristics have been investigated to improve the solder interconnection for rapid thermal firing solar cell metallizations
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