Использование двухчастотного намагничивания для получения кривой дифференциальной динамической проницаемости

Анализ процесса перемагничивания ферромагнетика в сложном поле позволил путем разложения в ряд Фурье получить полное выражение э. д. с. измерительной обмотки датчика. Показано, что огибающая сигнала, изменяющегося с частотой возбуждающего высокочастотного поля при определенных соотношениях параметров полей, повторяют по форме временную зависимость дифференциальной динамической проницаемости. Приводится блок-схема установки, реализующей указанный метод

NFATc2 and NFATc3 transcription factors play a crucial role in suppression of CD4+ T lymphocytes by CD4+ CD25+ regulatory T cells

The phenotype of NFATc2−/− c3−/− (double knockout [DKO]) mice implies a disturbed regulation of T cell responses, evidenced by massive lymphadenopathy, splenomegaly, and autoaggressive phenomena. The population of CD4+ CD25+ T cells from DKO mice lacks regulatory capacity, except a small subpopulation that highly expresses glucocorticoid-induced tumor necrosis factor receptor family–related gene (GITR) and CD25. However, neither wild-type nor DKO CD4+ CD25+ regulatory T cells (T reg cells) are able to suppress proliferation of DKO CD4+ CD25− T helper cells. Therefore, combined NFATc2/c3 deficiency is compatible with the development of CD4+ CD25+ T reg cells but renders conventional CD4+ T cells unresponsive to suppression, underlining the importance of NFAT proteins for sustaining T cell homeostasis

Homo- and Heterotypic Cell Contacts in Malignant Melanoma Cells and Desmoglein 2 as a Novel Solitary Surface Glycoprotein

During progression of melanomas, a crucial role has been attributed to alterations of cell–cell adhesions, specifically, to a “cadherin switch” from E- to N-cadherin (cad). We have examined the adhesion of melanoma cells to each other and to keratinocytes. When different human melanoma cell lines were studied by protein analysis and immunofluorescence microscopy, six of eight lines contained N-cad, three E-cad, and five P-cad, and some lines had more than one cad. Surprisingly, two N-cad-positive lines, MeWo and C32, also contained desmoglein 2 (Dsg2), a desmosomal cad previously not reported for melanomas, whereas other desmosome-specific proteins were absent. This finding was confirmed by reverse transcriptase–PCR, immunoprecipitation, and matrix-assisted laser desorption ionization–time of flight analyses. Double-label confocal and immunoelectron microscopy showed N-cad, α- and β-catenin in plaque-bearing puncta adhaerentia, whereas Dsg2 was distributed rather diffusely over the cell surface. In cocultures with HaCaT keratinocytes Dsg2 was found in heterotypic cell contact regions. Correspondingly, immunohistochemistry revealed Dsg2 in five of 10 melanoma metastases. Together, we show that melanoma cell adhesions are more heterogeneous than expected and that certain cells devoid of desmosomes contain Dsg2 in a non-junction-restricted form. Future studies will have to clarify the diagnostic and prognostic significance of these different adhesion protein subtypes

"Hier entsteht eine neue Internetpräsenz" - Weblogs im Bundestagswahlkampf 2005

"Mit dem Bundestagswahlkampf 2005 entstand in der deutschsprachigen Blogosphäre ein neues 'Netz im Netz'. Politikerinnen und Politiker, Journalistinnen und Journalisten sowie interessierte Bürgerinnen und Bürger begannen gleichermaßen damit, in Weblogs über die Wahl im Besonderen und Politik im Allgemeinen zu posten, Sachverhalte zu kommentieren und vor allem auch: Personen, Themen und Meinungen zu diskutieren. Die vorliegende Forschungsnotiz informiert über Methodik und erste Ergebnisse einer Studie zu Weblogs im Bundestagswahlkampf 2005, welche derzeit am Arbeitsbereich Technikbewertung und Technikgestaltung der Technischen Universität Hamburg-Harburg durchgeführt wird. Ziel der Studie ist es insbesondere, ein möglichst genaues Bild der zwischen einzelnen Weblogs bestehenden Verbindungen zu zeichnen. Diese basieren auf Links, wie sie in Blogrolls, Weblog-Einträgen oder Kommentaren enthalten sind. Neben der Diskussion methodischer Probleme von Untersuchungen der 'Blogosphäre' werden weiterführende Fragestellungen präsentiert, die von der Theorie kommunikationsorientierter Modellierung (COM) ausgehen." (Autorenreferat

On synchronous supereruptions

The Youngest Toba Tuff (YTT) supereruption from Toba Caldera in Sumatra at ca. 74,000 years BP is the largest volcanic event recorded in the Pleistocene. Intriguingly, recent radioisotopic dating of the near antipodal Los Chocoyos (LCY) supereruption from the Atitlán caldera in Guatemala finds an identical age within uncertainties to that of YTT. This opens the question of whether these synchronous supereruptions may be a coincidence or could be a consequence of each other? Using the known eruptive record from the past 2 Myr, we find that the likelihood of having two near antipodal supereruptions (>1,000 km3 tephra volume) within centuries (<400 years), as suggested by volcanic proxies and annual counting layer chronology in the ice core records, is very small (0.086%), requiring a non-random cause and effect. Considering this analysis, we speculate that one potential physical mechanism that could explain the temporal relationship between these supereruptions is that seismic energy released during YTT eruption focused on the antipodal region, where concentrated stresses ultimately promoted the eruption of the perched LCY magma system (or vice versa). This supereruption “double-whammy” may thus be the more compelling source of the significant environmental impacts often attributed individually to the YTT supereruption. Improving the existing age information of YTT and LCY, and a better understanding of caldera collapse events will enable further testing of the hypothesis that synchronous supereruptions do not result by pure chance

Homogeneous conversion of NOx_{x} and NH3_{3} with CH4_{4}, CO, and C2_{2}H4_{4} at the diluted conditions of exhaust-gases of lean operated natural gas engines

Understanding gas‐phase reactions in model gas mixtures approximating pre‐turbine heavy‐duty natural gas engine exhaust compositions containing NO, NH$_{3}$, NO$_{2}$, CH$_{4}$, CO, and C$_{2}$H$_{4}$ is extremely relevant for aftertreatment procedure and catalyst design and is thus addressed in this work. In a plug‐flow reactor at atmospheric pressure, five different model gas mixtures were investigated in the temperature range of 700‐1 200 K, using species analysis with electron ionization molecular‐beam mass spectrometry. The mixtures were designed to reveal influences of individual components by adding NO$_{2}$, CH$_{4}$, CO, and C$_{2}$H$_{4}$ sequentially to a highly argon‐diluted NO/NH$_{3}$ base mixture. Effects of all components on the reactivity for NO$_{x}$ conversion were investigated both experimentally as well as by comparison with three selected kinetic models. Main results show a significantly increased reactivity upon NO$_{2}$ and hydrocarbon addition with lowered NO conversion temperatures by up to 200 K. Methane was seen to be of dominant influence in the carbon‐containing mixtures regarding interactions between the carbon and nitrogen chemistry as well as formaldehyde formation. The three tested mechanisms were capable to overall represent the reaction behavior satisfactorily. On this basis, it can be stated that significant gas‐phase reactivity was observed among typical constituents of pre‐turbine natural gas engine exhaust at moderate temperature

Surveying lichen diversity in forests: A comparison of expert mapping and eDNA metabarcoding of bark surfaces

Lichens are an important part of forest ecosystems, contributing to forest biodiversity, the formation of micro-niches and nutrient cycling. Assessing the diversity of lichenised fungi in complex ecosystems, such as forests, requires time and substantial skills in collecting and identifying lichens. The completeness of inventories thus largely depends on the expertise of the collector, time available for the survey and size of the studied area. Molecular methods of surveying biodiversity hold the promise to overcome these challenges. DNA barcoding of individual lichen specimens and bulk collections is already being applied; however, eDNA methods have not yet been evaluated as a tool for lichen surveys. Here, we assess which species of lichenised fungi can be detected in eDNA swabbed from bark surfaces of living trees in central European forests. We compare our findings to an expert floristic survey carried out in the same plots about a decade earlier. In total, we studied 150 plots located in three study regions across Germany. In each plot, we took one composite sample based on six trees, belonging to the species Fagus sylvatica, Picea abies and Pinus sylvestris. The eDNA method yielded 123 species, the floristic survey 87. The total number of species found with both methods was 167, of which 48% were detected only in eDNA, 26% only in the floristic survey and 26% in both methods. The eDNA contained a higher diversity of inconspicuous species. Many prevalent taxa reported in the floristic survey could not be found in the eDNA due to gaps in molecular reference databases. We conclude that, currently, eDNA has merit as a complementary tool to monitor lichen biodiversity at large scales, but cannot be used on its own. We advocate for the further development of specialised and more complete databases