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The design, fabrication, and characterization of optically switchable organic light-emitting diodes (OSOLEDs) based on the combination of the commercially available light-emitting polymer poly(9,9′-dioctylfluorene-alt-benzothiadiazole), F8BT, doped with a diarylethene derivative is reported. The photochromic activity of the dopant in the solid state has been investigated both via UV/vis absorption and photoluminescence spectroscopy, whereas the morphology of different blends is investigated via atomic force microscopy. OSOLEDs embedding dopant loadings of 1, 5, and 10 wt% exhibit optical responsivity with a maximum reversible optical threshold voltage shift of 4 V. The best performing devices containing 5 wt% dopant show a maximum current density and luminance ON/OFF ratio of ≈20 and ≈90, respectively. For the first time, the impact of the diarylethene isomerization on hole and electron transport has been decoupled and directly investigated, via the design, fabrication, and characterization of single-carrier switchable devices based on the same blends. Not only do these results confirm the photo-responsive trapping activity of the diarylethenes on both charge carriers, but they also demonstrate its asymmetry, with a predominant effect on electron transport that is over 3.4 times larger as compared to hole transport.

Das zentrale Kapitel Feldmethoden liefert einen Überblick über das breite Methodenspektrum, das während geoarchäologischer Forschungskampagnen im Gelände zum Einsatz kommt. Beschrieben werden zunächst klassische Methoden wie Bohrungen, archäologische Grabungen und Baggerschürfe, gefolgt von der damit mittlerweile häufig kombinierten, jungen Methode der Direct-Push-Sondierung, womit gleichzeitige Messungen unterschiedlicher Parameter wie Spitzendruck, Farbe oder elektrischer Leitfähigkeit möglich sind. Dazugehörige Infoboxen befassen sich mit einem Beispiel aus der Feuchtbodenarchäologie und mit dem wichtigen Thema der langfristigen Probenarchivierung. Der Abschnitt Fernerkundung führt in die Geschichte und in die aktuelle Praxis der Methodik ein und befasst sich mit dem Potenzial von Luftbildern und räumlichen Satellitendaten. Das in einem weiteren Abschnitt vorgestellte Konzept der „Digitalen Geoarchäologie“ bewegt sich an der Schnittstelle zwischen Archäologie, Geo- und Computerwissenschaften. Weiterhin werden häufig eingesetzte geophysikalische Methoden, wie Geoelektrik, Geomagnetik und Georadar vorgestellt. Am Kapitelende geht es um das Potenzial archäologischer Zeigerpflanzen und ihrer Bedeutung für die archäologische Prospektion.

The ability to dynamically control chirality remains a grand challenge in chemistry. Although many molecules possess chiral isomers, lacking their isolation, for instance during photoisomerization, results in racemic mixtures with suppressed enantiospecific chiral properties. Here, we present a nanoporous solid in which chirality and enantioselective enrichment is induced by circularly polarized light (CPL). The material is based on photoswitchable fluorinated azobenzenes attached to the scaffold of a crystalline metal–organic framework (MOF). The azobenzene undergoes trans-to-cis-photoisomerization upon irradiation with green light and reverts back to trans upon violet light. While each moiety in cis conformation is chiral, we show the trans isomer also possesses a nonplanar, chiral conformation. During photoisomerization with unpolarized light, no enantiomeric enrichment is observed and both isomers, R- and S-cis as well as R- and S-trans, respectively, are formed in identical quantities. In contrast, CPL causes chiral photoresolution, resulting in an optically active material. Right-CPL selectively excites R-cis and R-trans enantiomers, producing a MOF with enriched S-enantiomers, and vice versa. The induction of optical activity is reversible and only depends on the light-handedness. As shown by first-principle DFT calculations, while both, trans and cis, are stabilized in nonplanar, chiral conformations in the MOF, the trans isomer adopts a planar, achiral form in solution, as verified experimentally. This shows that the chiral photoresolution is enabled by the linker reticulation in the MOF. Our study demonstrates the induction of chirality and optical activity in solid materials by CPL and opens new opportunities for chiral resolution and information storage with CPL.

A 12 m sediment core from the Aiding Lake basin in the today hyper-arid Turpan depression (Autonomous Xinjiang Province, NW-China) has been studied. The core, which was drilled near the deepest point of the endorheic Turpan basin (154 m below sea level), revealed several climatic and palaeoenvironmental changes during the Late Pleistocene. The sediments which were analyzed relating to sedimentology (grain size), geochemistry (Ti/Al ratio, chemical index of weathering, total organic and inorganic carbon, sulfur, nitrogen), and magnetic susceptibility, are of fluvial, eolian, and lacustrine origin. Age control was done by five C-14 dates. Reservoir effects for the stratigraphic units were considered. Less saline conditions lasted until the end of the Pleistocene, forced by stronger westerlieS and low, but increasing temperatures. Sometime after Dansgaard-Oeschger event 1 (14.6 ka) up to present, environmental conditions were arid and Aiding became a salt lake. High sand contents indicate eolian input during a period of cold, windy and arid conditions, associated with Heinrich event 2 (-24.8-23.4 ka cal BP; HEMMING 2004), whereas high sand input of the uppermost 2 m and salt accumulation reflects a general change to drier conditions since the Pleistocene/Holocene transition. In summary, the Lake decreased from its maximum size of around 3000 km(2) during the MIS3 to a seasonal small lake today. The measured Rb/Sr ratio, generally used as an indicator for weathering conditions of lake catchments, with reduced Sr influx during arid periods due to weak chemical weathering, has to be interpreted differently for Aiding Lake: Very low Rb/Sr ratios in the uppermost 2.7m similar to that of unweathered loess represent the recent drought and Sr accumulation during the Holocene. Contrary to other studies, we found e.g. that Rb/Sr dynamics do not indicate the intensity of past chemical weathering, but allows the distinction of different source areas and the decoupling of weatherin

Nature provides much inspiration for the design of materials capable of motion upon exposure to external stimuli, and many examples of such active systems have been created in the laboratory. However, to achieve continuous motion driven by an unchanging, constant stimulus has proven extremely challenging. Here we describe a liquid crystalline polymer film doped with a visible light responsive fluorinated azobenzene capable of continuous chaotic oscillatory motion when exposed to ambient sunlight in air. The presence of simultaneous illumination by blue and green light is necessary for the oscillating behavior to occur, suggesting that the dynamics of continuous forward and backward switching are causing the observed effect. Our work constitutes an important step towards the realization of autonomous, persistently self-propelling machines and self-cleaning surfaces powered by sunlight.

Hepatocellular carcinoma is the most common primary hepatic tumor in dogs and is amenable to surgical resection in many cases. Unfortunately, overlap of sonographic findings between benign and malignant hepatic lesions typically requires more invasive diagnostic tests to be performed (e.g., biopsy for histopathology). The availability of a noninvasive diagnostic test to identify hepatocellular carcinoma would be beneficial. The use of a liver-specific magnetic resonance imaging (MRI) contrast agent such as gadoxetate disodium (Gd-EOB-DTPA; Eovist® or Primovist®) has improved lesion detection in human patients. In this descriptive study, gadoxetate disodium contrast-enhanced MRI characteristics in dogs were evaluated in seven dogs (total of eight lesions). The imaging characteristics were variable with the exception of all lesions being hypointense to surrounding normal hepatic parenchyma on 3D T1-weighted gradient recalled echo images at all postcontrast time points. All lesions displayed signal intensity ratios less than 1, consistent with retained but impaired hepatocyte function. Hepatic lesions not identified on previous imaging were found in 3/7 patients which may affect surgical planning. In two patients, several hepatic nodules were identified during surgery which had not been visualized on MRI and were found to be benign on histopathology. This descriptive study reports the MRI characteristics of hepatocellular carcinoma in dogs using the liver-specific contrast agent gadoxetate disodium.