Oberflaechenbearbeitung mit CO_2-Lasern. Teilvorhaben: Flexible Oberflaechenbearbeitung mit schnell modulierbaren Multikilowattlasern Abschlussbericht

Up to now, in laser hardening with CO_2-laser mainly unflexible integrating optics are in use. For complex tasks often optics are used, which are specially designed only for that particular problem. This is in contrast to the otherwise high flexibility of lasers. In this project the potential of a flexible beam shaping optic was investigated. Such a system was realized by using a fast two-dimensional beam deflection, generated by oscillating mirror optics, and by modulating simultaneously the laser power. It permits to modify the geometric shape of the laser spot as well as its intensity distribution in a wide range during the process. Various workpiece geometries have been treated including a tree-dimensional hardening with an industrial robot. Finally, suggestions were made for complements to existing standards. (orig.)Bislang werden zum Laserhaerten vor allem CO_2-Laser mit festen Integratoroptiken eingesetzt. Bei komplexen Bearbeitungsaufgaben werden oft Spezialoptiken verwendet, die nur fuer diese Aufgabe konstruiert wurden. Dies widerspricht der ansonsten hohen Flexibilitaet des Lasers. In diesem Projekt wurden nun die Moeglichkeiten untersucht, die sich durch den Einsatz einer flexiblen Strahlformungsoptik ergeben. Durch eine schnelle, zweidimensionale Ablenkung des Laserstrahls auf dem Werkstueck mittels einer Schwingspiegeloptik und durch eine gleichzeitige Modulation der Laserleistung laesst sich eine solche Strahlformung aufbauen. Diese Optik gestattet es, sowohl die geometrische Form des Laserbrennflecks als auch dessen Intensitaetsverteilung waehrend des Bearbeitungsprozesses in weiten Grenzen frei zu waehlen. Es wurden unterschiedliche Werkstueckgeometrien behandelt, wobei selbst eine dreidimensionale Haetebearbeitung mit einem Industrieroboter durchgefuehrt werden konnte. Abschliessend konnten Hinweise gegeben werden fuer die Ergaenzung bestehender Normen. (orig.)Available from TIB Hannover: F95B1531+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Absorptionsmessungen, Haerten und Schweissen Abschlussbericht

Available from TIB Hannover: RO 7154(90-34) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Hochleistungswerkstoffe fuer Temperaturen oberhalb 1500 C-Entwicklung von Testmethoden. Teilprojekt: Entwicklung der Laserheiztechnik Abschlussbericht

A laser heated furnace has been developed, where materials can be heated up by laser beams to high temperatures in vacuum or different gas atmospheres. With a special equipment it is possible to heat up the samples either from one side or from both sides simultaneously. The emissivity can be observed either orthogonal to the sample surface or in dependence of different angles. For the development of reference samples first investigations have been carried out. The experiments showed that remelting of plasma sprayed ceramic coatings on high temperature materials is possible if a suitable combination of coating and base material is used. To judge on the quality a detailed investigation of the processed samples is necessary. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(61,50) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

The cytosolic sensor STING is required for intestinal homeostasis and control of inflammation

STING (stimulator of interferon genes) is a cytosolic sensor for cyclic dinucleotides and also an adaptor molecule for intracellular DNA receptors. Although STING has important functions in the host defense against pathogens and in autoimmune diseases, its physiological relevance in intestinal homeostasis is largely unknown. In this study, we show that STING mice presented defective protective mechanisms of intestinal mucosa, including decreased number of goblet cells, diminished mucus production, and lower levels of secretory IgA, when compared with wild-type (WT) mice. Fecal content and microbiota DNA could activate STING, indicating a role of this molecule in gut. Microbiota composition was altered in STING mice toward a more inflammatory profile, evidencing a reduction in the Allobacolum and Bifidobacterium groups along with increase in Disulfovibrio bacteria. Absence of STING lead to decrease in induced intraepithelial lymphocytes (IEL) and to increase in group 1 innate lymphoid cell (ILC1) as well as ILC3 frequencies and decrease in ILC2 in the colon. Development and function of Foxp3+ and LAP+ regulatory T cells were also compromised in STING mice. Moreover, these mice were highly susceptible to dextran sodium sulfate-induced colitis, T-cell-induced colitis, and enteric Salmonella typhimurium infection when compared with WT animals. Therefore, our results identify an important role of STING in maintaining gut homeostasis and also a protective effect in controlling gut inflammation

The actomyosin systems in apicomplexa

The phylum of Apicomplexa groups obligate intracellular parasites that exhibit unique classes of unconventional myosin motors. These parasites also encode a limited repertoire of actins, actin-like proteins, actin-binding proteins and nucleators of filamentous actin (F-actin) that display atypical properties. In the last decade, significant progress has been made to visualize F-actin and to unravel the functional contribution of actomyosin systems in the biology of Toxoplasma and Plasmodium, the most genetically-tractable members of the phylum. In addition to assigning specific roles to each myosin, recent biochemical and structural studies have begun to uncover mechanistic insights into myosin function at the atomic level. In several instances, the myosin light chains associated with the myosin heavy chains have been identified, helping to understand the composition of the motor complexes and their mode of regulation. Moreover, the considerable advance in proteomic methodologies and especially in assignment of posttranslational modifications is offering a new dimension to our understanding of the regulation of actin dynamics and myosin function. Remarkably, the actomyosin system contributes to three major processes in Toxoplasma gondii: (i) organelle trafficking, positioning and inheritance, (ii) basal pole constriction and intravacuolar cell-cell communication and (iii) motility, invasion, and egress from infected cells. In this chapter, we summarize how the actomyosin system harnesses these key events to ensure successful completion of the parasite life cycle