ALBERT

Description: Scots pine ( Pinus sylvestris L.) is a widely used tree species in European dendroclimatology studies due to its common distribution across much of the continent. Almost all studies find radial growth strongly related to summer temperature, a result reflecting site selection at high elevation/latitude environments where trees grow at their ecophysiological limits. Due to the amount of attention spent on these sites there is a geographical and seasonal bias in temperature reconstructions based upon tree-ring proxies in Europe. To overcome the limited availability of tree-ring data in temperate lowlands, we present a northern Poland ring-width chronology developed from living and historic Scots pine material with a strong common growth signal going back to AD 1200. Investigations into climate-growth relationships found year-to-year ring-width variability to be more strongly correlated to cold season temperature (November to April) prior to the growing season than summer temperatures during tree-ring formation. Based on this relationship it was possible to reconstruct cold season temperature conditions for the last 810 years. Spatial field correlations with gridded instrumental records indicated that the reconstruction provides relevant cold season temperature information across the land regions bordering the North Atlantic Ocean and Baltic Sea, lowlands and uplands of western and central Europe, and the eastern and central interior of Russia. Despite an unsuccessful attempt to find a stationary relationship with the North Atlantic Oscillation, comparisons with several cold season temperature reconstructions confirmed the long-term connection between our reconstructed temperature series for northern Poland and the wider area.

Description: It has been suggested that the origin of regio- and stereoselectivity in Michael addi- tions of pyrrolidine enamines is achieved by thermodynamic rather than kinetic control through distinct conformational preferences of the enamines. We assess this proposal by elaboration of a computational protocol that warrants sufficient accuracy. The small energy differences between the conformers necessitate a high accuracy of the electronic structure method which, in addition, must allow for computationally feasible calcula- tions of a large number of conformers. Our protocol is based on density functional theory which we validated against explicitly correlated coupled cluster theory. The results are in agreement with the available experimental data, but illustrate that conformational preferences determined for one enamine are not readily transferable to other types of enamines. We found that an appropriate conformational sampling is inevitable to arrive at meaningful conclusions. Most prominently, s- cis and s- trans conformers are similarly stable for aldehyde- and ketone-derived enamines. The regio- and stereoselectivity in Michael additions of pyrrolidine-derived enamines can, however, not be explained by pronounced stability differences of the enamine isomers and conformers in general, dis- proving the thermodynamic-control hypothesis. The elucidation of the origin of regio- and stereoselectivity requires further theoretical investigations of the elementary steps of Michael additions. This article is protected by copyright. All rights reserved.

Description: By reaction of pentacarbonyltetrafluoroboratorhenium with the neutral methylated xanthine derivatives the cationic complexes [(OC) 5 Re-L] + BF 4 – (L = caffeine, isocaffeine, theophylline, theobromine) were prepared and spectroscopically characterized.

Description: The colorless solid NO(HSO 4 ), known as “lead-chamber crystals”, was investigated ever since its first preparation more than two centuries ago. Its overall ionic nature now is confirmed by X-ray crystallography [ Pna 2 1 , a = 7.3558(4), b = 6.8924(3), c = 7.7017(3) Å, Z = 4]. The next neighbors of the NO + cations are four hydrogensulfate oxygen atoms, forming a distorted square at a distance of about 2.5 Å from the nitrogen atom. The square pattern next to the nitrogen atom is the most widespread coordination figure about an NO + ion in a nitrosyl salt. Depending on the anion, the interaction goes along with a decrease of the N–O stretch's excitation energy.

Description: A series of tertiary nitriles was synthesized by alkylation of acetonitrile, primary and secondary nitriles, using alkylbromides and sodium amide in liquid ammonia. By reaction of the in situ formed organometallic Lewis acids [Cp M (CO)(PPh 3 )] + ( M = Fe, Ru) with the novel tertiary nitriles, the complexes [Cp M (CO)(PPh 3 )(N≡C–C R 1 R 2 R 3 ]BF 4 were obtained. A di-iron complex was formed with 1,6-dicyanohexane.

Description: Large Mississippi River (MR) diversions (peak water flow 〉1416 m 3 /s and sediment loads 〉165 kg/s) have been proposed as part of a suite of coastal restoration projects and are expected to rehabilitate and rebuild wetlands to alleviate the significant historic wetland loss in coastal Louisiana. These coastal wetlands are undergoing increasing eustatic sea-level rise, land subsidence, climate change, and anthropogenic disturbances. However, the effect of MR diversions on wetland soil organic carbon (SOC) sequestration in receiving basins remains unknown. The rate of SOC sequestration or carbon burial in wetlands is one of the variables used to assess the role of wetland soils in carbon cycling and also to construct wetland carbon budgets. In this study, we examined the effects of MR water and sediment diversions on landscape-scale SOC sequestration rates that were estimated from vertical accretion for the next 50 yr (2010–2060) under two environmental (moderate and less optimistic) scenarios. Our analyses were based on model simulations taken from the Wetland Morphology model developed for Louisiana's 2012 Coastal Master Plan. The master plan modeled a “future-without-action” scenario as well as eight individual MR diversion projects in two of the hydrologic basins (Barataria and Breton Sound). We examined the effects that discharge rates (peak flow) and locations of these individual diversion projects had on SOC sequestration rates. Modeling results indicate that large river diversions are capable of improving basin-wide SOC sequestration capacity (162–222 g C·m −2 ·yr −1 ) by up to 14% (30 g C·m −2 ·yr −1 ) in Louisiana deltaic wetlands compared to the future-without-action scenario, especially under the less optimistic scenario. When large river diversions are placed in the upper receiving basin, SOC sequestration rates are 3.7–10.5% higher (6–24 g C·m −2 ·yr −1 ) than when these structures are placed in the lower receiving basin. Modeling results also indicate that both diversion discharge and location have large effects on SOC sequestration in low-salinity (freshwater and intermediate marshes) as compared to high-salinity marshes (brackish and saline marshes).

Description: Epigenetic and transcriptional variability contribute to the vast diversity of cellular and organismal phenotypes and are key in human health and disease. In this review, we describe different types, sources, and determinants of epigenetic and transcriptional variability, enabling cells and organisms to adapt and evolve to a changing environment. We highlight the latest research and hypotheses on how chromatin structure and the epigenome influence gene expression variability. Further, we provide an overview of challenges in the analysis of biological variability. An improved understanding of the molecular mechanisms underlying epigenetic and transcriptional variability, at both the intra- and inter-individual level, provides great opportunity for disease prevention, better therapeutic approaches, and personalized medicine. Epigenetic and transcriptional variability mediate phenotypic plasticity, enabling adaptation to changing environments. In this review, we describe the sources of inter- and intra-individual variability and discuss epigenetic regulators of gene expression variability, including DNA methylation and chromatin structure. Understanding these molecular mechanisms will improve therapeutic approaches and personalized medicine.

Description: The Arctic coastal plain is covered with numerous thermokarst lakes. These lakes are closely linked to climate and environmental change through their heat and water budgets. We examined the intra-lake thermal structure at the local scale and investigated the water temperature pattern of lakes at the regional scale by utilizing extensive in situ measurements and multi-date Landsat-8 remote sensing data. Our analysis indicates that the lake skin temperatures derived from satellite thermal sensors during most of the ice-free summer period effectively represent the lake bulk temperature because the lakes are typically well-mixed and without significant vertical stratification. With the relatively high- resolution Landsat-8 thermal data, we were able to quantitatively examine intra-lake lateral temperature differences and gradients in relation to geographical location, topography, meteorological factors, and lake morphometry for the first time. Our results suggest that wind speed and direction not only control the vertical stratification but also influences lateral differences and gradients of lake surface temperature. Wind can considerably reduce the intra-lake temperature gradient. Interestingly, we found that geographical location (latitude, longitude, distance to the ocean) and lake morphometry (surface size, depth, volume) not only control lake temperature regionally but also affect the lateral temperature gradient and homogeneity level within each individual lake. For the Arctic coastal plain, at regional scales, inland and southern lakes tend to have larger horizontal temperature differences and gradients compared to coastal and northern lakes. At local scales, large and shallow lakes tend to have large lateral temperature differences relative to small and deep lakes.

Description: Slow seismic velocity anomalies are commonly imaged beneath subducting slabs in tomographic studies, yet a unifying explanation for their distribution has not been agreed upon. In South America two such anomalies have been imaged associated with subduction of the Nazca Ridge in Peru and the Juan Fernández Ridge in Chile. Here we present new seismic images of the sub-slab slow velocity anomaly beneath Chile, which give a unique view of the nature of such anomalies. Slow seismic velocities within a large hole in the subducted Nazca slab connect with a sub-slab slow anomaly that appears correlated with the extent of the subducted Juan Fernández Ridge. The hole in the slab may allow the sub-slab material to rise into the mantle wedge, revealing the positive buoyancy of the slow material. We propose a new model for sub-slab slow velocity anomalies beneath the Nazca slab related to the entrainment of hotspot material.