Atomistic characterization of the active-site solvation dynamics of a model photocatalyst

The interactions between the reactive excited state of molecular photocatalysts and surrounding solvent dictate reaction mechanisms and pathways, but are not readily accessible to conventional optical spectroscopic techniques. Here we report an investigation of the structural and solvation dynamics following excitation of a model photocatalytic molecular system [Ir 2 (dimen) 4 ] 2+, where dimen is para-diisocyanomenthane. The time-dependent structural changes in this model photocatalyst, as well as the changes in the solvation shell structure, have been measured with ultrafast diffuse X-ray scattering and simulated with Born-Oppenheimer Molecular Dynamics. Both methods provide direct access to the solute-solvent pair distribution function, enabling the solvation dynamics around the catalytically active iridium sites to be robustly characterized. Our results provide evidence for the coordination of the iridium atoms by the acetonitrile solvent and demonstrate the viability of using diffuse X-ray scattering at free-electron laser sources for studying the dynamics of photocatalysis. © The Author(s) 201617111sciescopu

Repositioning of the global epicentre of non-optimal cholesterol

High blood cholesterol is typically considered a feature of wealthy western countries1,2. However, dietary and behavioural determinants of blood cholesterol are changing rapidly throughout the world3 and countries are using lipid-lowering medications at varying rates. These changes can have distinct effects on the levels of high-density lipoprotein (HDL) cholesterol and non-HDL cholesterol, which have different effects on human health4,5. However, the trends of HDL and non-HDL cholesterol levels over time have not been previously reported in a global analysis. Here we pooled 1,127 population-based studies that measured blood lipids in 102.6 million individuals aged 18 years and older to estimate trends from 1980 to 2018 in mean total, non-HDL and HDL cholesterol levels for 200 countries. Globally, there was little change in total or non-HDL cholesterol from 1980 to 2018. This was a net effect of increases in low- and middle-income countries, especially in east and southeast Asia, and decreases in high-income western countries, especially those in northwestern Europe, and in central and eastern Europe. As a result, countries with the highest level of non-HDL cholesterol—which is a marker of cardiovascular risk—changed from those in western Europe such as Belgium, Finland, Greenland, Iceland, Norway, Sweden, Switzerland and Malta in 1980 to those in Asia and the Pacific, such as Tokelau, Malaysia, The Philippines and Thailand. In 2017, high non-HDL cholesterol was responsible for an estimated 3.9 million (95% credible interval 3.7 million–4.2 million) worldwide deaths, half of which occurred in east, southeast and south Asia. The global repositioning of lipid-related risk, with non-optimal cholesterol shifting from a distinct feature of high-income countries in northwestern Europe, north America and Australasia to one that affects countries in east and southeast Asia and Oceania should motivate the use of population-based policies and personal interventions to improve nutrition and enhance access to treatment throughout the world.</p

Vegetation development in south-east Denmark during the Weichselian Late Glacial: palaeoenvironmental studies close to the Palaeolithic site of Hasselø

Eastern Denmark was an important region for the early immigration of humans into southern Scandinavia throughout the Late Glacial period. One possible explanation for this is that the landscape provided an especially favourable environment for Palaeolithic hunters. To examine this, the local and regional environment is reconstructed through the analysis of pollen and plant macrofossils from a small kettle hole and is discussed in relation to human presence in the region. The kettle hole is situated close to a Palaeolithic occupation site with artefacts belonging to the Federmesser and Bromme Cultures. The lake sediments encompass the Bølling, Allerød, Younger Dryas and the early Preboreal biostratigraphic periods. An increase in charcoal dust between c. 14,000 and 13,900 cal. BP may be related to the occupation site. This study shows that an ecotone was positioned between present-day Denmark and northern Germany during a large part of the Late Glacialperiod. This was especially the case during the Older Dryas and early Allerød periods, when woodland was expanding in northern Germany while the Danish area remained open. Later in the Allerød period, northern Germany seems to have beenthe northern limit for pine woodland. The low-lying region separating Denmark and Germany was periodically covered by the Baltic Ice Lake and this may have delayed the dispersal of plants from south to north. Areas lying between differenthabitats are known to have a high biodiversity and this may be why a high frequency of Palaeolithic finds is seen here. It has long been thought that tree birch grew in the Danish region from the beginning of the Late Glacial, but this study of both local and regional proxies clearly shows that the immigration of tree birch was delayed by more than 1000 years. A delay of c. 250 years between the climatic transition from GI-1a to GS-1 and the biostratigraphic transition from the Allerødto the Younger Dryas periods is also shown. The three 14 C ages available from the Danish Bromme Culture are from this transition phase when the birch woodland was becoming more open. Pollen analysis also shows the classical Younger Dryascold separated into an early dry phase (until c. 12,100 cal. BP) and a later wetter phase. This was most likely due to a change in atmospheric circulation and variation in the extent of sea ice in the North Atlantic. The combined analysis of bothpollen and plant macrofossils has led to a detailed and accurate reconstruction of the local environment and, in turn, the preconditions for human presence