920 resultados para Gut passage


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Der Wechsel von der Volksschule in die weiterführende Schule ist für alle Kinder ein wichtiges Lebensereignis. Nichtsdestotrotz ist nur wenig darüber bekannt, wie Kinder diesen Übergang erleben. Durch den biografischen Zugang der hier vorgestellten Arbeit werden Einblicke in die Wahrnehmungen und die Gefühlswelt der Kinder eröffnet und ihre Erwartungen, Freuden und Ängste dokumentiert. Der Grossteil der SchülerInnen sieht dem Schulwechsel freudig entgegen. Diese Freude bleibt auch am Beginn der Sekundarstufe I bestehen. Die überwiegend positiven Einstellungen schliessen aber nicht aus, dass sich Kinder um bestimmte Themen in der neuen Schule sorgen.

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A three-dimensional, regional coupled atmosphere-ocean model with full physics is developed to study air-sea interactions during winter storms off the U. S. east coast. Because of the scarcity of open ocean observations, models such as this offer valuable opportunities to investigate how oceanic forcing drives atmospheric circulation and vice versa. The study presented here considers conditions of strong atmospheric forcing (high wind speeds) and strong oceanic forcing (significant sea surface temperature (SST) gradients). A simulated atmospheric cyclone evolves in a manner consistent with Eta reanalysis, and the simulated air-sea heat and momentum exchanges strongly affect the circulations in both the atmosphere and the ocean. For the simulated cyclone of 19-20 January 1998, maximum ocean-to-atmosphere heat fluxes first appear over the Gulf Stream in the South Atlantic Bight, and this results in rapid deepening of the cyclone off the Carolina coast. As the cyclone moves eastward, the heat flux maximum shifts into the region near Cape Hatteras and later northeast of Hatteras, where it enhances the wind locally. The oceanic response to the atmospheric forcing is closely related to the wind direction. Southerly and southwesterly winds tend to strengthen surface currents in the Gulf Stream, whereas northeasterly winds weaken the surface currents in the Gulf Stream and generate southwestward flows on the shelf. The oceanic feedback to the atmosphere moderates the cyclone strength. Compared with a simulation in which the oceanic model always passes the initial SST to the atmospheric model, the coupled simulation in which the oceanic model passes the evolving SST to the atmospheric model produces higher ocean-to-atmosphere heat flux near Gulf Stream meander troughs. This is due to wind-driven lateral shifts of the stream, which in turn enhance the local northeasterly winds. Away from the Gulf Stream the coupled simulation produces surface winds that are 5 similar to 10% weaker. Differences in the surface ocean currents between these two experiments are significant on the shelf and in the open ocean.

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A simple technique was developed to measure the bacteriolytic activities of the digestive fluids of the deposit-feeding polychaete Arenicola marina. Lysis of a cultured environmental isolate, incubated with extracts of gut luminal contents, was monitored spectrophotometrically. Concurrent direct counts were used to verify cell lysis. The ability of extracts from 8 longitudinal sections of the gut to lyse the bacterium was monitored. The digestive ceca, anterior stomach, and posterior stomach regions exhibited high lytic activities, whereas bacteriolytic activities in all other regions of the gut were negligible. Similarly, extracts of surface sediments and fecal castings showed negligible lytic capabilities. The sharply limited distribution of lytic activity implicates the ceca as the source of bacteriolytic agent and suggests a true plug-flow system, with little axial mixing. Questions regarding the fate of lytic agents, which disappear abruptly posterior to the stomach, remain unanswered. Localization of lysis in the gut coupled with estimates of gut residence time permit the calculation that ingested bacteria are exposed to strong lytic activity for approximately 20 min. Incubation of in situ sediment samples with gut fluids corroborates the distributional findings of the in vitro work although the efficiency of lysis is much reduced, possibly due to exopolymer capsules and slimes of natural sedimentary bacteria. Cross-phyletic comparisons of bacteriolytic activities reveal both qualitative and quantitative differences. Much less demarcation of lytic activity is observed in the guts of a holothuroid (Caudina arenata) and a hemichordate (Stereobalanus canadensis), with a pattern more similar to that of A. marina observed in another polychaete, Amphitrite johnstoni. Quantitatively, the polychaetes showed higher levels of activity with rates in A. marina exceeding those of the hemichordate and holothuroid by more than 10-fold.

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Marine invertebrate deposit feeders secrete surfactants into their gut fluid in concentrations sufficient to induce micelle formation, enhancing solubilization of sedimentary lipids. We isolated and identified 3 related surfactant molecules from the deposit-feeding polychaete lugworm Arenicola marina. Surfactants were isolated and separated by a combination of solvent extraction and thin-layer and gas chromatography. Identification was performed using mass and infrared spectrometry, coupled to various derivatization and hydrolysis reactions. A. marina produces a mixture of related yet distinct anionic surfactants composed of branched, C9, saturated and unsaturated fatty acids that are amide linked to leucine or glycine residues, showing some similarity to crustacean surfactants. The critical micelle concentration of the mixture of these surfactants in gut fluid was about 2 mM, and total concentrations ranged from 5.5 to 19.5 mM. The hydrophilic amide linkage helps to explain previous observations that gut surfactants do not adsorb onto sediment transiting the gut.

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Microbial exposures and sex hormones exert potent effects on autoimmune diseases, many of which are more prevalent in women. We demonstrate that early-life microbial exposures determine sex hormone levels and modify progression to autoimmunity in the nonobese diabetic (NOD) mouse model of type 1 diabetes (T1D). Colonization by commensal microbes elevated serum testosterone and protected NOD males from T1D. Transfer of gut microbiota from adult males to immature females altered the recipient's microbiota, resulting in elevated testosterone and metabolomic changes, reduced islet inflammation and autoantibody production, and robust T1D protection. These effects were dependent on androgen receptor activity. Thus, the commensal microbial community alters sex hormone levels and regulates autoimmune disease fate in individuals with high genetic risk.

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Die europäischen Alpen sind in den Hochlagen trotz einem immensen Rückgang in den letzten Jahrzehnten immer noch stark vergletschert. Früher dachte man, dass die alpine Zone über rund 2000 m über Meer vom prähistorischen Menschen nicht begangen wurde. 1991 zeigte die Entdeckung des Mannes aus dem Eis beim Tisenjoch („Ötzi“) in über 3000 m Höhe, dass schon im Neolithikum Vorstösse bis in die vergletscherten Gebiete der Alpen stattgefunden haben. Die ältesten Spuren am Schnidejoch, einem Pass in den Berner Alpen der Schweiz, reichen bis in die Zeit zwischen 4800 und 4500 v.Chr. zurück. Der Pass wurde auch in der Frühen Bronzezeit benutzt, wie zahlreiche Objekte aus der Zeit zwischen etwa 2200 und 1600 v.Chr. belegen. Frühbronzezeitliche Funde liegen auch vom Lötschenpass, einem zweiten Passübergang in den Berner Alpen vor. Nördlich dieser Übergänge befinden sich die bekannten frühbronzezeitlichen Gräber des Berner Oberlandes (Region des unteren Thunersees), südlich davon stammen zahlreiche frühbronzezeitliche Funde aus Gräbern und Nekropolen im Rhonetal. Dank der Erhaltung von organischem Material bieten die Eisfundstellen wertvolle Einblicke zur Frequentierung der Hochalpen. Neben Bohlenwegen, Strassen und Brücken bilden Pässe wichtige Elemente des prähistorischen terrestrischen Transportsystems.

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von Vögele der Maggid

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von E. Flanter