ALBERT

Beschreibung: Micro x-ray fluorescence (µXRF) core scanning is capable of measuring the elemental composition of lake sediment at sub-millimetre resolution, but bioturbation and physical mixing may degrade environmental signals at such fine scales. The aim of this research is to determine the maximum possible resolution at which meaningful environmental signals may be reconstructed from lake sediments using this method. Sediment from a coastal lake in the Outer Hebrides, Scotland, has been analysed using calibrated element measurements to reconstruct storminess since AD 200. We find that a Ca/K ratio in lake-core sediments reflects the presence of fine calcium carbonate shell fragments, a constituent of sand in the catchment that is washed and blown into the lake. Variations in this ratio are significantly correlated with instrumental records of precipitation and low pressures, suggesting it is a proxy for storminess. Furthermore, identification of a c . 60-year cycle supports a climatic influence on Ca/K, as this cycle is frequently identified in reconstructions of the North Atlantic Oscillation and North Atlantic sea-surface temperature. Comparison with weather records at different resolutions and spectral analysis indicate that µXRF data from Loch Hosta can be interpreted at sub-decadal resolutions (equivalent to core depth intervals of 3–5 mm in this location). Therefore, we suggest that sub-centimetre sampling using µXRF core scanning could be beneficial in producing environmental reconstructions in many lake settings where sediments are not varved.

Beschreibung: This study presents a new interpretation of the evidence for Holocene lake-level changes from Hawes Water in NW England constrained by detailed stratigraphic data, radiocarbon chronology and palaeo-environmental evidence. Lake levels are seen to decline gradually from the start of the Holocene through to 9960 cal. yr BP, in response to lake infilling and the prevailing dry climatic conditions. Low lake levels then persist until 6000 cal. yr BP, punctuated by two transgressive phases. Rising sea levels during the Holocene high-level sea stand are thought to be responsible for a major rise in lake level at 6000 cal. yr BP driven by changes in the local water-table. The rise in lake level is coincident with a rise in anthropogenic activity across the site, possibly reflecting the migration of coastal Mesolithic communities inland in response to rising sea levels.

Beschreibung: 〈p〉While a fraction of cancer patients treated with anti–PD-1 show durable therapeutic responses, most remain unresponsive, highlighting the need to better understand and improve these therapies. Using an in vivo screening approach with a customized shRNA pooled library, we identified DDR2 as a leading target for the enhancement of response to anti–PD-1 immunotherapy. Using isogenic in vivo murine models across five different tumor histologies—bladder, breast, colon, sarcoma, and melanoma—we show that DDR2 depletion increases sensitivity to anti–PD-1 treatment compared to monotherapy. Combination treatment of tumor-bearing mice with anti–PD-1 and dasatinib, a tyrosine kinase inhibitor of DDR2, led to tumor load reduction. RNA-seq and CyTOF analysis revealed higher CD8〈sup〉+〈/sup〉 T cell populations in tumors with DDR2 depletion and those treated with dasatinib when either was combined with anti–PD-1 treatment. Our work provides strong scientific rationale for targeting DDR2 in combination with PD-1 inhibitors.〈/p〉

Beschreibung: South-west China is an important area for determining variability of the SW Asian Monsoon; it is, however, also tectonically very active. Palaeolimnological studies in this region generally focus on climate as a direct driver of ecological change, rarely considering the effects of tectonic activity and catchment ontogeny. We present diatom and organic matter data from a Holocene sediment record from Muge Co, an alpine lake located on an active fault zone in the southeast margin of Tibet, and explore the possible drivers of ecological change. A major change occurred at 9000 cal. BP, when the diatom assemblage switched from benthic to predominantly planktonic forms, and organic matter content decreased rapidly. Comparison of the Holocene diatom record with a regional data set of lake surface sediments using detrended canonical correspondence analysis (DCCA) suggests that this change in diatom development was mainly associated with changing water depth, most likely linked to a seismically triggered landslide (which deepened the lake) rather than climate-driven hydrological change. However, diatom changes associated with principal components analysis (PCA) axis 2 agree well with inferred Holocene temperature changes. From the mid-Holocene, shifts in planktonic diatom species were probably related to indirect climate forcing, notably water column mixing depth and catchment vegetation–driven changes in dissolved organic carbon (DOC) and nutrient export. The diatom stratigraphy at Muge Co reflects a complex range of indirect climate- and catchment-controlled processes that were superimposed over a change in lake morphology resulting from tectonic activity.

Beschreibung: Historical and documentary records from the Petit Lac d’Annecy, indicate that human activities have been the dominant ‘geomorphic process’ shaping the catchment during the late Holocene, with deforestation, agriculture and artificial drainage profoundly affecting both the pace and spatial distribution of soil erosion. The impact of past climatic change on the evolution of the catchment is less certain because of the lack of long-term climate records for the site. Previous attempts to use the sediment record from the lake to investigate the role past climate change may have played were hampered by the difficulty in isolating and disentangling the climatic signal preserved within the archive, because of overprinting of human activity. This is a common problem in regions with a long history of human activity in the landscape. In this study we use a range of novel statistical techniques (including cross-correlation and cross spectral analysis) to assess the relative importance of climate in driving landscape dynamics. The statistical analysis is carried out on an updated high-resolution palaeo-environmental data set from the Petit Lac d’Annecy. The results of the statistical analysis indicate that regional climate phenomena such as the Atlantic multidecadal oscillation are partly responsible for landscape dynamics at Petit Lac d’Annecy throughout the late Holocene. We find that the Petit Lac d’Annecy catchment typically requires decades, or longer, to respond to changes in precipitation, reflecting the stochastic nature of river sediment storage and transport. The use of a 4 yr integrated lake core record effectively attenuates the ‘signal shredding’ effect of shorter-term internally generated sediment transport processes. Nonetheless, the lake record of climatically induced geormorphic process–responses is weak compared with the pervasive impact of human activities.

Beschreibung: A sediment core from an alpine lake (Muge Co) from the southeastern margin of the Tibetan Plateau was analyzed for sediment grain size distribution and the carbon isotopic composition of black carbon in order to reconstruct Asian summer monsoon variability over the last 12 ka. Five major climatic stages were identified: (1) From 12 to 10.5 cal. ka BP, a cold and dry climate prevailed, corresponding to the Younger Dryas in the North Atlantic; (2) from 10.5 to 9.2 cal. ka BP, precipitation increased rapidly but was interrupted by a pronounced cold and dry phase at about 10 cal. ka BP; (3) from 9.2 to 6.2 cal. ka BP, the Holocene climatic optimum was reached and maintained; (4) from 6.2 to 2.5 cal. ka BP, the climate gradually became cooler and drier; (5) from 2.5 cal. ka BP to the present, a climatic reversal toward wetter conditions occurred. The trend of our reconstructed Asian summer monsoon precipitation record is similar on orbital and millennium timescales to that of other records from the Asian monsoon region. Although the maximum monsoon intensity recorded in the Muge Co sediments lagged the peak of Northern Hemisphere insolation by ~3.0 ka, the strengthening trend was in phase with the rise in the Western Pacific Warm Pool sea surface temperature. Therefore, we suggest that the tropical ocean temperatures may have been the major driver of Asian summer monsoon precipitation in the southeastern Tibetan Plateau. In addition, other factors such as sea-level rise and temperature in the North Atlantic region may have played an important role in the evolution of the Asian summer monsoon since the last deglaciation. However, human activity may have affected the monsoon proxies during the last 2.5 ka, and further studies are needed to distinguish the effects of climate and human disturbance.