Arctic Ocean evidence for late Quaternary initiation of northern Eurasian ice sheets

A high-resolution multiparameter stratigraphy allows the identification of late Quaternary glacial and interglacial cycles in a central Arctic Ocean sediment core. Distinct sandy layers in the upper part of the otherwise fine-grained sediment core from the Lomonosov Ridge (lat 87.5°N) correlate to four major glacials since ca. 0.7 Ma. The composition of these ice-rafted terrigenous sediments points to a glaciated northern Siberia as the main source. In contrast, lithic carbonates derived from North America are also present in older sediments and indicate a northern North American glaciation since at least 2.8 Ma. We conclude that large-scale northern Siberian glaciation began much later than other Northern Hemisphere ice sheets

Arctic Ocean evidence for late Quaternary initiation of northern Eurasian ice sheets

A high-resolution multiparameter stratigraphy allows the identification of late Quaternary glacial and interglacial cycles in a central Arctic Ocean sediment core. Distinct sandy layers in the upper part of the otherwise fine-grained sediment core from the Lomonosov Ridge (lat 87.5°N) correlate to four major glacials since ca. 0.7 Ma. The composition of these ice-rafted terrigenous sediments points to a glaciated northern Siberia as the main source. In contrast, lithic carbonates derived from North America are also present in older sediments and indicate a northern North American glaciation since at least 2.8 Ma. We conclude that large-scale northern Siberian glaciation began much later than other Northern Hemisphere ice sheets

Climate change effects on winter chill for tree crops with chilling requirements on the Arabian Peninsula

Fruit production systems that rely on winter chill for breaking of dormancy might be vulnerable to climatic change. We investigated decreases in the number of winter chilling hours (0–7.2°C) in four mountain oases of Oman, a marginal area for the production of fruit trees with chilling requirements. Winter chill was calculated from long-term hourly temperature records. These were generated based on the correlation of hourly temperature measurements in the oases with daylength and daily minimum and maximum temperatures recorded at a nearby weather station. Winter chill was estimated for historic temperature records between 1983 and 2008, as well as for three sets of synthetic 100-year weather records, generated to represent historic conditions, and climatic changes likely to occur within the next 30 years (temperatures elevated by 1°C and 2°C). Our analysis detected a decrease in the numbers of chilling hours in high-elevation oases by an average of 1.2–9.5 h/year between 1983 and 2008, a period during which, according to the scenario analysis, winter chill was sufficient for most important species in most years in the highest oasis. In the two climate change scenarios, pomegranates, the most important tree crop, received insufficient chilling in 13% and 75% of years, respectively. While production of most traditional fruit trees is marginal today, with trees barely fulfilling their chilling requirements, such production might become impossible in the near future. Similar developments are likely to affect other fruit production regions around the world

Der modifizierte Yankauer - ein alternatives Applikationsinstrument für die Ballondilatation der Tuba auditiva

Einleitung: Untersuchungen weisen die Tubendilatation als eine erfolgreiche Methode zur Behandlung der Tubenfunktionsstörung aus. Der Ballonkatheter wird endoskopisch kontrolliert mit einem Einführinstrument über die Nase in das Tubenostium eingeführt. Verletzungen der Nasenschleimhaut mit nachfolgenden Blutungen sowie Verlegungen der Nasenhaupthöhle durch z.B. anatomische Veränderungen können die Bedingungen für die Applikation des Ballonkatheters über den Zugangsweg der Nasenhaupthöhle in das Tubenostium erschweren.Methode: Die Epipharyngoskopie kann, wie die der Adenotomie üblich, mit einem McIVOR Spatel und Optik erfolgen. Der Zugang bietet ausreichend Platz und eine ungehinderte Sicht auf das Tubenostium. Ein durchsichtiger Yankauer Sauger wurde durch zwei zusätzliche Biegungen so modifiziert, dass dieser das Absaugen des Nasopharynx, die Positionierung am Tubenostium und die Applikation des Ballonkatheters unter Sicht des Einführvorgangs ermöglicht. Ergebnisse: Die Herstellung einer alternativen Einführhilfe zur Ballondilatation ist einfach und kostengünstig. Durch ein weiteres Loch am Schaft konnte eine Saugung integriert werden, die für gute Sicht während der gesamten Prozedur sorgte. Dadurch entfallen Instrumentenwechsel, es ergibt sich eine Zeitersparnis sowie ein erhöhter Komfort für dieses Verfahren. Die Handhabbarkeit wird vereinfacht durch die Verwendung von durchsichtigem Kunststoff durch den die Insertion des Katheters beobachtet werden.Schlussfolgerung: Die einfache und kostengünstige Herstellung des alternativen Einführinstrumentes lassen den modifizierten Yankauer für die Ballokatheterapplikation nicht nur bei anatomisch erschwerenden Bedingungen sondern auch im Regelfall geeignet erscheinen.Der Erstautor gibt keinen Interessenkonflikt an

AraC-like transcriptional activator CuxR binds c-di-GMP by a PilZ-like mechanism to regulate extracellular polysaccharide production

Cyclic dimeric GMP (c-di-GMP) has emerged as a key regulatory player in the transition between planktonic and sedentary biofilm-associated bacterial lifestyles. It controls a multitude of processes including production of extracellular polysaccharides (EPSs). The PilZ domain, consisting of an N-terminal "RxxxR" motif and a β-barrel domain, represents a prototype c-di-GMP receptor. We identified a class of c-di-GMP-responsive proteins, represented by the AraC-like transcription factor CuxR in plant symbiotic α-proteobacteria. In Sinorhizobium meliloti, CuxR stimulates transcription of an EPS biosynthesis gene cluster at elevated c-di-GMP levels. CuxR consists of a Cupin domain, a helical hairpin, and bipartite helix-turn-helix motif. Although unrelated in sequence, the mode of c-di-GMP binding to CuxR is highly reminiscent to that of PilZ domains. c-di-GMP interacts with a conserved N-terminal RxxxR motif and the Cupin domain, thereby promoting CuxR dimerization and DNA binding. We unravel structure and mechanism of a previously unrecognized c-di-GMP-responsive transcription factor and provide insights into the molecular evolution of c-di-GMP binding to proteins

Arctic Ocean evidence for late Quaternary initiation of northern Eurasian sheets

A high-resolution multiparameter stratigraphy allows the identification of late Quaternary glacial and interglacial cycles in a central Arctic Ocean sediment core. Distinct sandy layers in the upper part of the otherwise fine-grained sediment core from the Lomonosov Ridge (lat 87.5°N) correlate to four major glacials since ca. 0.7 Ma. The composition of these ice-rafted terrigenous sediments points to a glaciated northern Siberia as the main source. In contrast, lithic carbonates derived from North America are also present in older sediments and indicate a northern North American glaciation since at least 2.8 Ma. We conclude that large-scale northern Siberian glaciation began much later than other Northern Hemisphere ice sheets