Accessing aliphatic alcohols for metallaphotoredox catalyzed C(sp³)-arylation

Common cross-coupling reactions to obtain C(sp2)–C(sp3)-bonds are hampered by the abundance of nucleophilic and electrophilic functional groups. Recently in Nature, Dong and MacMillan developed a mild activation of a diverse range of alcohols with an N-heterocyclic carbene (NHC) salt and merged it with nickel photoredox dual catalytic arylation

Site‐Selective Electrochemical Oxidation of Carbohydrates

The site-selective transformation of unprotected sugars poses significant challenges to synthetic chemists but comes with a reward of step-economic and energy efficient protocols. By replacing stoichiometric oxidants with electricity, greener processes are anticipated. To date, mostly C3- and C6-selective transformations have been developed urging for further developments. Herein, we call for action to synthetic chemists to tackle the associated challenges of site-selective transformations of unprotected sugars toward challenging C2 and C4 regioisomers fueled by mild electroorganic transformations

Ergebnisse einer Befragung zum Suchtmittel- und Medienkonsum an weiterführenden Schulen in Friedrichshain-Kreuzberg 2018

ERGEBNISSE EINER BEFRAGUNG ZUM SUCHTMITTEL- UND MEDIENKONSUM AN WEITERFÜHRENDEN SCHULEN IN FRIEDRICHSHAIN-KREUZBERG 2018 Ergebnisse einer Befragung zum Suchtmittel- und Medienkonsum an weiterführenden Schulen in Friedrichshain-Kreuzberg 2018 / Beil, Sebastian (Rights reserved) ( -

Studie 60+

STUDIE 60+ Studie 60+ / Beil, Sebastian (Rights reserved) (Bericht

Neue Erkenntnisse über die paläoozeanographische und klimatische Entwicklung während des Späten Alb bis Frühen Turons aus Analysen hochauflösender Proxies aus Bohrkernen aus dem Tarfaya Becken (Süd-Morocco)

The Cretaceous with extremely high atmospheric pCO2 is one of the warmest periods in the Phanerozoic, providing an endmember to test climate models. Repeated periods of widespread dysoxic / anoxic conditions (Oceanic Anoxic Events; OAEs) were characterized by enhanced burial of organic matter and different degrees of marine faunal turnovers, that can be seen as extreme equivalents for the already observed trend of expanding Oxygen Minimum Zones (OMZ) in modern oceans caused by anthropogenic climate warming. One of the largest OAEs occurring at the Cenomanian / Turonian boundary is OAE2. This thesis presents results from Core SN°4 drilled in the Tarfaya Basin (SW Morocco). This continuous record spanning the time from the late Albian to early Turonian allowed 1) to reconstruct climatic and paleoceanographic variability during this period in the Tarfaya Basin, 2) to unravel climate processes and biospheric changes during the onset of OAE2 and 3) to study phosphorus dynamics during the Cenomanian and early Turonian.Die Kreide zeichnet sich als eine der wärmsten Perioden des Phanerozoikums durch signifikant höhere atmosphärische CO2-Konzentrationen aus, was sie zu einem idealen Vergleichsobjekt für Klimamodellierungen macht. Wiederholt auftretende Ozeanische Anoxische Events (OAEs) sind gekennzeichnet durch weiträumige dysoxische / anoxische Bedingungen, welche sich in einer starken Anreicherung organischen Kohlenstoffes in marinen Sedimenten, häufig begleitet von Aussterbeereignissen, wiederspiegeln. Diese Ereignisse können als extreme Äquivalente des sich bereits heute zu beobachtenden Trends der Expansion der Sauerstoff-Minimum-Zonen (OMZ) infolge der globalen Klimaerwärmung angesehen werden. Das OAE2 an der Cenomanium-Turonium-Grenze ist eines der bedeutendsten dieser Events. Im Rahmen dieser Dissertation wurde der Bohrkern SN°4 aus dem Tarfaya Becken (SW Marokko) untersucht. Dieser kontinuierliche Sedimentkern besteht aus offen marinen Ablagerungen der mittleren Kreise vom oberen Albium bis zum unteren Turonium und gestattete: 1) die Rekonstruktion von klimatischen und ozeanographischen Änderungen dieser Zeit, 2) eine hoch aufgelöste Studie klimatischer und sedimentärer Variabilität während der Anfangsphase des OAE2 und begleitender Umwälzungen in der Biosphäre und 3) die Rekonstruktion von Änderungen im Phosphorhaushalt während des Cenomaniums und unteren Turoniums

Oxygen minimum zone-type biogeochemical cycling in the Cenomanian-Turonian Proto-North Atlantic across Oceanic Anoxic Event 2

Highlights • We present a 5 myr record of biogeochemical cycling in a Cretaceous upwelling area. • A novel quantitative approach for the evaluation of Fe speciation proxies was applied. • Ferruginous proxy signature reflects intense chemical weathering rather than anoxia. • Water column redox conditions evolved from oxic to nitrogenous to euxinic before OAE2. • Smaller seawater nitrate inventory facilitated sedimentary H2S release and euxinia. Abstract Oceanic Anoxic Events (OAEs) in Earth's history are regarded as analogues for current and future ocean deoxygenation, potentially providing information on its pacing and internal dynamics. In order to predict the Earth system's response to changes in greenhouse gas concentrations and radiative forcing, a sound understanding of how biogeochemical cycling differs in modern and ancient marine environments is required. Here, we report proxy records for iron (Fe), sulfur and nitrogen cycling in the Tarfaya upwelling system in the Cretaceous Proto-North Atlantic before, during and after OAE2 (∼93 Ma). We apply a novel quantitative approach to sedimentary Fe speciation, which takes into account the influence of terrigenous weathering and sedimentation as well as authigenic Fe (non-terrigenous, precipitated onsite) rain rates on Fe-based paleo-redox proxies. Generally elevated ratios of reactive Fe (i.e., bound to oxide, carbonate and sulfide minerals) to total Fe (FeHR/FeT) throughout the 5 million year record are attributed to transport-limited chemical weathering under greenhouse climate conditions. Trace metal and nitrogen isotope systematics indicate a step-wise transition from oxic to nitrogenous to euxinic conditions over several million years prior to OAE2. Taking into consideration the low terrigenous sedimentation rates in the Tarfaya Basin, we demonstrate that highly elevated FeHR/FeT from the mid-Cenomanian through OAE2 were generated with a relatively small flux of additional authigenic Fe. Evaluation of mass accumulation rates of reactive Fe in conjunction with the extent of pyritization of reactive Fe reveals that authigenic Fe and sulfide precipitation rates in the Tarfaya Basin were similar to those in modern upwelling systems. Because of a smaller seawater nitrate inventory, however, chemolithoautotrophic sulfide oxidation with nitrate was less efficient in preventing hydrogen sulfide release into the water column. As terrigenous weathering and sediment flux determine how much authigenic Fe is required to generate an anoxic euxinic or ferruginous proxy signature, we emphasize that both have to be taken into account when interpreting Fe-based paleo-redox proxies

Augmented Reality for Presenting Real-Time Data During Students' Laboratory Work: Comparing a Head-Mounted Display With a Separate Display

Multimedia learning theories suggest presenting associated pieces of information in spatial and temporal contiguity. New technologies like Augmented Reality allow for realizing these principles in science laboratory courses by presenting virtual real-time information during hands-on experimentation. Spatial integration can be achieved by pinning virtual representations of measurement data to corresponding real components. In the present study, an Augmented Reality-based presentation format was realized via a head-mounted display and contrasted to a separate display, which provided a well-arranged data matrix in spatial distance to the real components and was therefore expected to result in a spatial split-attention effect. Two groups of engineering students (N = 107; Augmented Reality vs. separate display) performed six experiments exploring fundamental laws of electric circuits. Cognitive load and conceptual knowledge acquisition were assessed as main outcome variables. In contrast to our hypotheses and previous findings, the Augmented Reality group did not report lower extraneous load and the separate display group showed higher learning gains. The pre- and posttest assessing conceptual knowledge were monitored by eye tracking. Results indicate that the condition affected the visual relevancy of circuit diagrams to final problem completion. The unexpected reverse effects could be traced back to emphasizing coherence formation processes regarding multiple measurements

The Middle to Late Miocene “Carbonate Crash” in the Equatorial Indian Ocean

We integrate benthic foraminiferal stable isotopes, X‐ray fluorescence elemental ratios, and carbonate accumulation estimates in a continuous sedimentary archive recovered at International Ocean Discovery Program Site U1443 (Ninetyeast Ridge, Indian Ocean) to reconstruct changes in carbonate deposition and climate evolution over the interval 13.5 to 8.2 million years ago. Declining carbonate percentages together with a marked decrease in carbonate accumulation rates after ~13.2 Ma signal the onset of a prolonged episode of reduced carbonate deposition. This extended phase, which lasted until ~8.7 Ma, coincides with the middle to late Miocene carbonate crash, originally identified in the eastern equatorial Pacific Ocean and the Caribbean Sea. Interocean comparison reveals that intense carbonate impoverishment at Site U1443 (~11.5 to ~10 Ma) coincides with prolonged episodes of reduced carbonate deposition in all major tropical ocean basins. This implies that global changes in the intensity of chemical weathering and riverine input of calcium and carbonate ions into the ocean reservoir were instrumental in driving the carbonate crash. An increase in U1443 Log (Ba/Ti) together with a change in sediment color from red to green indicate a rise in organic export flux to the sea floor after ~11.2 Ma, which predates the global onset of the biogenic bloom. This early rise in export flux from biological production may have been linked to increased advection of nutrients and intensification of upper ocean mixing, associated with changes in the seasonality and intensity of the Indian Monsoon

Middle Pleistocene re-organization of Australian Monsoon

The sensitivity of the Australian Monsoon to changing climate boundary conditions remains controversial due to limited understanding of forcing processes and past variability. Here, we reconstruct austral summer monsoonal discharge and wind-driven winter productivity across the Middle Pleistocene Transition (MPT) in a sediment sequence drilled off NW Australia. We show that monsoonal precipitation and runoff primarily responded to precessional insolation forcing until ~0.95 Ma, but exhibited heightened sensitivity to ice volume and pCO2 related feedbacks following intensification of glacial-interglacial cycles. Our records further suggest that summer monsoon variability at the precessional band was closely tied to the thermal evolution of the Indo-Pacific Warm Pool and strength of the Walker circulation over the past ~1.6 Myr. By contrast, productivity proxy records consistently tracked glacial-interglacial variability, reflecting changing rhythms in polar ice fluctuations and Hadley circulation strength. We conclude that the Australian Monsoon underwent a major re-organization across the MPT and that extratropical feedbacks were instrumental in driving short- and long-term variability

New insights into Cenomanian paleoceanography and climate evolution from the Tarfaya Basin, southern Morocco

Highlights • Complete upper Albian to early Turonian climate archive in drilled core from Tarfaya Basin. • Eccentricity pacing of mid Cretaceous OAE isotope excursions. • MCE and OAE2 associated with climate cooling and sea level fall. Abstract A 325 m long continuous succession of uppermost Albian to lower Turonian pelagic (outer shelf) deposits was recovered from a new drill site in the central part of the Tarfaya Basin (southern Morocco). Natural gamma ray wireline logging, carbonate and organic carbon content, bulk carbonate and organic carbon stable isotopes and X-ray fluorescence (XRF)-scanner derived elemental distribution data in combination with planktonic foraminiferal biostratigraphy indicate complete recovery of the Cenomanian Stage. This exceptional sediment archive allows to identify orbitally driven cyclic sedimentation patterns and to evaluate the pacing of climatic events and regional environmental change across the Albian-Cenomanian boundary (ACB), the mid-Cenomanian Event (MCE) and Oceanic Anoxic Event 2 (OAE2) in the latest Cenomanian. The deposition of organic-rich sediments in the Tarfaya Basin, likely driven by upwelling of nutrient-rich water masses, started during the latest Albian and intensified in two major steps following the MCE and the onset of OAE2. The duration and structure of the MCE and OAE2 carbon isotope excursions exhibit striking similarities, suggesting common driving mechanisms and climate-carbon cycle feedbacks. Both events were also associated with eustatic sea level falls, expressed as prominent sequence boundaries in the Tarfaya Basin. Based on the 405 kyr signal imprinted on the Natural Gamma Ray (NGR) and XRF-scanner derived Log(Zr/Rb) records, we estimate the duration of the Cenomanian Stage to be 4.8 ± 0.2 Myr