New aspects of deglaciation in southern Norway : Climate variability derived from surface exposure ages of Late Quaternary and Holocene landforms

The investigation of periglacial and related landforms in South Norway is of high interest for exploring timings of deglaciation and to assess their geomorphological connectivity to palaeoclimatic changes during the Late Quaternary and the Holocene. The ice margins of the Scandinavian Ice Sheet during the Last Glacial Maximum (LGM) are fairly well known, the palaeo-ice thickness, however, which can only be estimated by modelling, remains unclear over large parts of Norway owing to rare field based evi-dences. Due to the significant influence of the former horizontal and vertical ice-sheet extent on sea-level rise, atmospheric and oceanic circulation patterns, erosive properties of glaciers and ice sheets, englacial thermal boundaries and deglaciation dynamics, it is crucial to better understand the topograph-ic features of the LGM ice sheet. Despite recent advances, there is a lack of terrestrial evidences from numerical data in South Norway. In this thesis two high-mountain regions and their surroundings in west (Dalsnibba, 1476 m a.s.l.) and east (Blåhø, 1617 m a.s.l.) South Norway were used to reconstruct palaeoclimatic conditions and deglaciation patterns. Terrestrial cosmogenic nuclides (10Be) and Schmidt-hammer exposure-age dating (SHD) have been utilized to determine the surface exposure of glacially transported boulders as well as of boulder-dominated glacial, periglacial and paraglacial landforms and bedrock outcrops. By developing calibration curves at both study sites for the first time, through young and old control points of known age, it was possible to obtain landform age estimates from Schmidt hammer R-(rebound) values. Beside age estimates, the formation and stabilization of those landforms and the involved processes have provided indications about the Late Quaternary and Holocene climate variability and its connectivity to landform development. The first deglaciation chronology for the western study area could be constructed based on 10Be sur-face exposure ages. Final local deglaciation on the summit of Dalsnibba probably started between 13.3 ± 0.6 and 12.7 ± 0.5 ka and progressed down to the valley bottom of Opplendskedalen (~1050 m a.s.l.) with an SHD age estimate of 7.47 ± 0.73 ka. Deglaciation during the Bølling–Allerød Interstadial (~14.7 – 12.9 ka) indicates that the summit was not ice-covered during the Younger Dryas (12.9 – 11.7 cal. ka BP). A glacially transported boulder in the summit area and summit bedrock ages without cos-mogenic nuclide inheritance further imply a minimum vertical ice extent of 1476 m and the presence of erosive warm-based ice. The SHD Dalsnibba results show that most landforms stabilized during the Holocene Thermal Maximum (~8.0 – 5.0 ka) and that their R-value characteristics with negative skew-ness were indicative for the reworking of boulders or continuous debris supply. The SHD ages from Dalsnibba imply that periglacial landforms in the western maritime setting sensitively reacted to Holo-cene climate variability. Rock-slope failures investigated at both study sites demonstrate that they do not necessarily occur shortly after local deglaciation as often inferred. Furthermore, most of the recorded rock-slope failures appear to have occurred during warm climatic conditions. Most likely, prevailing warm conditions led to permafrost degradation, enhanced snow melt and increasing cleftwater pres-sure contributed to slope instabilities probably resulting in rock-slope failures. The Blåhø SHD ages also suggest landform response on climate variations, though, in a different tem-poral context. Landforms above 1450 m a.s.l. largely shared overlapping ages and therefore appear to have stabilized during the Karmøy/Bremanger readvance (∼18.5 – 16.5 ka). This, however, seems to have been the last major geomorphic activity of these landforms as they were not reactivated by several, partly severe cold climate events such as the Younger Dryas. The SHD ages from landforms above 1450 m a.s.l. are in contrast to the previous deglaciation chronology which suggested cold-based ice coverage and slow thinning down to ∼1450 m a.s.l. at 15.0 ± 1.0 10Be ka. Based on the results from this thesis, a severe periglacial climate without ice coverage since about 18 ka is proposed for the sum-mit area of Blåhø. The 10Be ages from Blåhø with 20.9 ± 0.8 ka for the erratic boulder and 46.4 ± 1.7 ka for the bedrock, which extend the previous deglaciation chronology, are discussed within the framework of the two most popular scenarios. Within the first scenario the boulder age represented the timing of deglaciation and the bedrock age showed inherited cosmogenic nuclides, suggesting the pres-ence of low erosive cold-based ice at Blåhø during the LGM. In the second scenario, the boulder age was affected by post-depositional disturbance, frost heave processes or shielding, potentially indicating ice-free conditions on Blåhø since at least 46.4 ± 1.7 ka. Analyzing the different onset of deglaciation in the study areas within a rather short west-east distance, together with the timing of deglaciation in neighboring regions, demonstrates complex deglaciation dynamics in southern Norway. Not only the timing of deglaciation was highly variable, the results also imply diverse basal ice temperatures within this relatively small area. In general, this thesis positively contributes new evidences pointing to a more complex and dynamic Scandinavian Ice Sheet throughout the last glacial cycle than previously assumed

Age, origin and palaeoclimatic implications of peri- and paraglacial boulder-dominated landforms in Rondane, South Norway

Boulder-dominated landforms of periglacial, paraglacial and related origin constitute a valuable, but often unexplored source of palaeoclimatic and morphodynamic information. The timing of landform development initiation and its subsequent stabilization can be linked to past climatic conditions offering the potential to reconstruct cold climatic periods. In this study, Schmidt-hammer exposure-age dating (SHD) was applied to a variety of boulder-dominated landforms (sorted stripes, blockfield, rock-slope failure, paraglacial alluvial fan) in Rondane, eastern South Norway for the first time. On the basis of old and young control points a regional SHD calibration curve was established and successively utilized for the calculation of surface exposure ages for individual landforms. The chronological investigation of development and stabilization of the respective landforms permitted an assessment of Holocene climate variability in Rondane and its impact on overall landform evolution. Our obtained SHD age estimates ranged from 11.44 ± 1.22 ka (ST-D2) to 4.09 ± 1.51 ka (AF1) showing their inactive and relict character. Most surface exposure ages for sorted stripes clustered between 9.88 ± 1.35 ka and 9.25 ± 1.21 ka, hence indicating stabilization during the late stage of the Erdalen Event or shortly thereafter. It is inferred that the blockfield formed prior to the Last Glacial Maximum, was protected by cold-based ice throughout glaciation and shortly reactivated during the Erdalen Event only to subsequently becoming inactive. The surface exposure age of a rock-slope failure (7.58 ± 0.73 ka) falls into the early phase of the Holocene Thermal Maximum (HTM, ~8.0–5.0 ka). This indicates permafrost degradation and/or increasing hydrological pressure negatively influencing slope stability. The paraglacial alluvial fan with its four subsites yielded ages between 8.73 ± 1.63 ka and 4.09 ± 1.51 ka. The old exposure ages point to fan aggradation following regional deglaciation due to paraglacial processes, whereas the younger ages can be explained by increasing precipitation during the onset neoglaciation at ~4.0 ka. Our results underline the importance of meltwater for the activation of periglacial landforms in a continental climate and indicate that the Erdalen Event and immediately following onset of the HTM had major impact on landscape evolution in Rondane. Our obtained surface exposure ages from boulder-dominated landforms in Rondane give important insights into the local palaeoclimatic variability during the Holocene.publishedVersio

The line-of-sight distribution of the gas in the inner 60 pc of the Galaxy

2MASS K_S band data of the inner 60 pc of the Galaxy are used to reconstruct the line-of-sight distances of the giant molecular clouds located in this region. Using the 2MASS H band image of the same region, two different populations of point sources are identified according to their flux ratio in the two bands. The population of blue point sources forms a homogeneous foreground that has to be subtracted before analyzing the K_S band image. The reconstruction is made using two basic assumptions: (i) an axis-symmetric stellar distribution in the region of interest and (ii) optically thick clouds with an area filling factor of ~1 that block all light of stars located behind them. Due to the reconstruction method, the relative distance between the different cloud complexes is a robust result, whereas it is not excluded that the absolute distance with respect to Sgr A* of structures located more than 10 pc in front of Sgr A* are understimated by up to a factor of 2. It is shown that all structures observed in the 1.2 mm continuum and in the CS(2-1) line are present in absorption. We place the 50 km s^-1 cloud complex close to, but in front of, Sgr A*. The 20 km s^-1 cloud complex is located in front of the 50 km s^-1 cloud complex and has a large LOS distance gradient along the direction of the galactic longitude. The bulk of the Circumnuclear Disk is not seen in absorption. This leads to an upper limit of the cloud sizes within the Circumnuclear Disk of ~0.06 pc.Comment: 12 pages with 17 figures. Accepted for publication in A&

Virtual Machine Support for Many-Core Architectures: Decoupling Abstract from Concrete Concurrency Models

The upcoming many-core architectures require software developers to exploit concurrency to utilize available computational power. Today's high-level language virtual machines (VMs), which are a cornerstone of software development, do not provide sufficient abstraction for concurrency concepts. We analyze concrete and abstract concurrency models and identify the challenges they impose for VMs. To provide sufficient concurrency support in VMs, we propose to integrate concurrency operations into VM instruction sets. Since there will always be VMs optimized for special purposes, our goal is to develop a methodology to design instruction sets with concurrency support. Therefore, we also propose a list of trade-offs that have to be investigated to advise the design of such instruction sets. As a first experiment, we implemented one instruction set extension for shared memory and one for non-shared memory concurrency. From our experimental results, we derived a list of requirements for a full-grown experimental environment for further research

TOM40 Mediates Mitochondrial Dysfunction Induced by α-Synuclein Accumulation in Parkinson's Disease.

Alpha-synuclein (α-Syn) accumulation/aggregation and mitochondrial dysfunction play prominent roles in the pathology of Parkinson's disease. We have previously shown that postmortem human dopaminergic neurons from PD brains accumulate high levels of mitochondrial DNA (mtDNA) deletions. We now addressed the question, whether alterations in a component of the mitochondrial import machinery -TOM40- might contribute to the mitochondrial dysfunction and damage in PD. For this purpose, we studied levels of TOM40, mtDNA deletions, oxidative damage, energy production, and complexes of the respiratory chain in brain homogenates as well as in single neurons, using laser-capture-microdissection in transgenic mice overexpressing human wildtype α-Syn. Additionally, we used lentivirus-mediated stereotactic delivery of a component of this import machinery into mouse brain as a novel therapeutic strategy. We report here that TOM40 is significantly reduced in the brain of PD patients and in α-Syn transgenic mice. TOM40 deficits were associated with increased mtDNA deletions and oxidative DNA damage, and with decreased energy production and altered levels of complex I proteins in α-Syn transgenic mice. Lentiviral-mediated overexpression of Tom40 in α-Syn-transgenic mice brains ameliorated energy deficits as well as oxidative burden. Our results suggest that alterations in the mitochondrial protein transport machinery might contribute to mitochondrial impairment in α-Synucleinopathies

Stellar Processes Near the Massive Black Hole in the Galactic Center

A massive black hole resides in the center of most, perhaps all galaxies. The one in the center of our home galaxy, the Milky Way, provides a uniquely accessible laboratory for studying in detail the connections and interactions between a massive black hole and the stellar system in which it grows; for investigating the effects of extreme density, velocity and tidal fields on stars; and for using stars to probe the central dark mass and probe post-Newtonian gravity in the weak- and strong-field limits. Recent results, open questions and future prospects are reviewed in the wider context of the theoretical framework and physical processes that underlie them. Contents: [1] Introduction (1.1) Astrophysical context (1.2) Science questions (1.3) Scope and connections to related topics [2] Observational overview: Stars in the Galactic center (2.1) The central 100 parsecs (2.2) The central parsec [3] Stellar dynamics at extreme densities (3.1) Physical processes and scales (3.2) The stellar cusp in the Galactic center (3.3) Mass segregation (3.4) Stellar Collisions [4] Probing the dark mass with stellar dynamics (4.1) Weighing and pinpointing the dark mass (4.2) Constraints on non-BH dark mass alternatives (4.3) Limits on MBH binarity (4.4) High-velocity runaway stars [5] Probing post-Newtonian gravity near the MBH (5.1) Relativistic orbital effects (5.2) Gravitational lensing [6] Strong star-MBH interactions (6.1) Tidal disruption (6.2) Dissipative interactions with the MBH [7] The riddle of the young stars (7.1) The difficulties of forming or importing stars near a MBH (7.2) Proposed solutions (7.3) Feeding the MBH with stellar winds [8] Outlook (8.1) Progress report (8.2) Future directionsComment: Invited review article, to appear in Physics Reports. 101 p

Non-holistic coding of objects in lateral occipital complex with and without attention

A fundamental issue in visual cognition is whether high-level visual areas code objects in a part-based or a view-based (holistic) format. By examining the viewpoint invariance of object recognition, previous behavioral and neuroimaging studies have yielded ambiguous results, supporting both types of representational formats. A critical factor distinguishing the two formats could be the availability of attentional resources, as a number of studies have found greater viewpoint invariance for attended compared to unattended objects. It has therefore been suggested that attention is necessary to enable part-based representations, whereas holistic representations are automatically activated irrespective of attention. In this functional magnetic resonance imaging study we used a multivariate approach to probe the format of object representations in human lateral occipital complex (LOC) and its dependence on attention. We presented human participants with intact and half-split versions of objects that were either attended or unattended. Cross-classifying between intact and split objects, we found that the objectrelated information coded in activation patterns of intact objects is fully preserved in the patterns of split objects and vice versa. Importantly, the generalization between intact and split objects did not depend on attention. Our findings demonstrate that LOC codes objects in a non-holistic format, both in the presence and absence of attention

Parasitoids indicate major climate-induced shifts in arctic communities

Climatic impacts are especially pronounced in the Arctic, which as a region is warming twice as fast as the rest of the globe. Here, we investigate how mean climatic conditions and rates of climatic change impact parasitoid insect communities in 16 localities across the Arctic. We focus on parasitoids in a widespread habitat,Dryasheathlands, and describe parasitoid community composition in terms of larval host use (i.e., parasitoid use of herbivorous Lepidoptera vs. pollinating Diptera) and functional groups differing in their closeness of host associations (koinobionts vs. idiobionts). Of the latter, we expect idiobionts-as being less fine-tuned to host development-to be generally less tolerant to cold temperatures, since they are confined to attacking hosts pupating and overwintering in relatively exposed locations. To further test our findings, we assess whether similar climatic variables are associated with host abundances in a 22 year time series from Northeast Greenland. We find sites which have experienced a temperature rise in summer while retaining cold winters to be dominated by parasitoids of Lepidoptera, with the reverse being true for the parasitoids of Diptera. The rate of summer temperature rise is further associated with higher levels of herbivory, suggesting higher availability of lepidopteran hosts and changes in ecosystem functioning. We also detect a matching signal over time, as higher summer temperatures, coupled with cold early winter soils, are related to high herbivory by lepidopteran larvae, and to declines in the abundance of dipteran pollinators. Collectively, our results suggest that in parts of the warming Arctic,Dryasis being simultaneously exposed to increased herbivory and reduced pollination. Our findings point to potential drastic and rapid consequences of climate change on multitrophic-level community structure and on ecosystem functioning and highlight the value of collaborative, systematic sampling effort

Establishing a multi-proxy approach to alpine blockfield evolution in south-central Norway

Blockfields in high latitude mountain areas are a wide spread proxy for glaciation history. Their origin is debated since decades, especially in south-central Norway, where glaciation had a major global climate implication. Some authors explain old blockfield features by protection of cold-based ice, others claim they persisted as nunataks during the LGM (~20 kyr), or were formed throughout the Holocene. In order to clarify the origin of alpine blockfields we established a multi-method approach to combining lichenometry, stratigraphy, granulometry, and geochemistry (XRD, XRF). Our lichenometric dating results in conjunction with our factors indicate landscape stability for at least ~12.5 kyr. Frequent climatic shifts are evident in our profiles by varying color, LOI content and grain sizes. On the basis of geochemical analyses we were able to identify a long-term (chemical) weathering history and in situ blockfield formation. The field evidences and the climatic setting of the study area leave the possibility that our location was not covered by cold-based ice during the Late-Quaternary

Establishing a multi-proxy approach to alpine blockfield evolution in south-central Norway

Blockfields in high latitude mountain areas are a wide spread proxy for glaciation history. Their origin is debated since decades, especially in south-central Norway, where glaciation had a major global climate implication. Some authors explain old blockfield features by protection of cold-based ice, others claim they persisted as nunataks during the LGM (~20 kyr), or were formed throughout the Holocene. In order to clarify the origin of alpine blockfields we established a multi-method approach to combining lichenometry, stratigraphy, granulometry, and geochemistry (XRD, XRF). Our lichenometric dating results in conjunction with our factors indicate landscape stability for at least ~12.5 kyr. Frequent climatic shifts are evident in our profiles by varying color, LOI content and grain sizes. On the basis of geochemical analyses we were able to identify a long-term (chemical) weathering history and in situ blockfield formation. The field evidences and the climatic setting of the study area leave the possibility that our location was not covered by cold-based ice during the Late-Quaternary.21923