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Projected scenarios of climate change involve general predictions about the likely changes to the magnitude and frequency of landslides, particularly as a consequence of altered precipitation and temperature regimes. Whether such landslide response to contemporary or past climate change may be captured in differing scaling statistics of landslide size distributions and the erosion rates derived thereof remains debated. We test this notion with simple Monte Carlo and bootstrap simulations of statistical models commonly used to characterize empirical landslide size distributions. Our results show that significant changes to total volumes contained in such inventories may be masked by statistically indistinguishable scaling parameters, critically depending on, among others, the size of the largest of landslides recorded. Conversely, comparable model parameter values may obscure significant, i.e. more than twofold, changes to landslide occurrence, and thus inferred rates of hillslope denudation and sediment delivery to drainage networks. A time series of some of Earth's largest mass movements reveals clustering near and partly before the last glacial-interglacial transition and a distinct step-over from white noise to temporal clustering around this period. However, elucidating whether this is a distinct signal of first-order climate-change impact on slope stability or simply coincides with a transition from short-term statistical noise to long-term steady-state conditions remains an important research challenge.
We consider the effective surface motion of a particle that intermittently unbinds from a planar surface and performs bulk excursions. Based on a random-walk approach, we derive the diffusion equations for surface and bulk diffusion including the surface-bulk coupling. From these exact dynamic equations, we analytically obtain the propagator of the effective surface motion. This approach allows us to deduce a superdiffusive, Cauchy-type behavior on the surface, together with exact cutoffs limiting the Cauchy form. Moreover, we study the long-time dynamics for the surface motion.
Hepatic steatosis is recognized as hepatic presentation of the metabolic syndrome. Hyperinsulinaemia, which shifts fatty acid oxidation to de novo lipogenesis and lipid storage in the liver, appears to be a principal elicitor particularly in the early stages of disease development. The impact of PGE(2), which has previously been shown to attenuate insulin signaling and hence might reduce insulin-dependent lipid accumulation, on insulin-induced steatosis of hepatocytes was studied. The PGE(2)-generating capacity was enhanced in various obese mouse models by the induction of cyclooxygenase 2 and microsomal prostaglandin E-synthases (mPGES1, mPGES2). PGE(2) attenuated the insulin-dependent induction of SREBP-1c and its target genes glucokinase and fatty acid synthase. Nevertheless, PGE(2) enhanced incorporation of glucose into hepatic triglycerides synergistically with insulin. This was most likely due to a combination of a PGE(2)-dependent repression of (1) the key lipolytic enzyme adipose triglyceride lipase, (2) carnitine-palmitoyltransferase 1, a key regulator of mitochondrial beta-oxidation, and (3) microsomal transfer protein, as well as (4) apolipoprotein B, key components of the VLDL synthesis. Repression of PGC1 alpha, a common upstream regulator of these genes, was identified as a possible cause. In support of this hypothesis, overexpression of PGC1 alpha completely blunted the PGE(2)-dependent fat accumulation. PGE(2) enhanced lipid accumulation synergistically with insulin, despite attenuating insulin signaling and might thus contribute to the development of hepatic steatosis. Induction of enzymes involved in PGE(2) synthesis in in vivo models of obesity imply a potential role of prostanoids in the development of NAFLD and NASH. Laboratory Investigation (2012) 92, 1597-1606; doi:10.1038/labinvest.2012.128; published online 10 September 2012
The Garzn Complex of the Garzn Massif in SW Colombia is composed of the Vergel Granulite Unit (VG) and the Las Margaritas Migmatite Unit (LMM). Previous studies reveal peak temperature conditions for the VG of about 740 A degrees C. The present study considers the remarkable exsolution phenomena in feldspars and pyroxenes and titanium-in-quartz thermometry. Recalculated ternary feldspar compositions indicate temperatures around 900-1,000 A degrees C just at or above the ultra-high temperature-metamorphism (UHTM) boundary of granulites. The calculated temperatures range of exsolved ortho- and clinopyroxenes also supports the existence of an UHTM event. In addition, titanium-in-quartz thermometry points towards ultra-high temperatures. It is the first known UHTM crustal segment in the northern part of South America. Although a mean geothermal gradient of ca 38 A degrees C km(-1) could imply additional heat supply in the lower crust controlling this extreme of peak metamorphism, an alternative model is suggested. The formation of the Vergel Granulite Unit is supposed to be formed in a continental back-arc environment with a thinned and weakened crust behind a magmatic arc (Guapotn-Mancagua Gneiss) followed by collision. In contrast, rocks of the adjacent Las Margaritas Migmatite Unit display "normal" granulite facies temperatures and are formed in a colder lower crust outside the arc, preserved by the Guapotn-Mancagu Gneiss. Back-arc formation was followed by inversion and thickening of the basin. The three units that form the modern-day Garzn Massif, were juxtaposed upon each other during collision (at ca. 1,000 Ma) and exhumation. The collision leading to the deformation of the studied area is part of the Grenville orogeny leading to the amalgamation of Rodinia.
The recent decades have witnessed the incorporation of new linguistic trends into lexicography. One of these trends is a usage-based approach, with the first major application of computer-corpus data in the Collins COBUILD English dictionary (1995) and successive adaptation in other L1-dictionaries. Another, concurrent innovation-inspired by Conceptual Metaphor Theory-is the provision of conceptual information in monolingual dictionaries of English. So far, however, only the Macmillan English dictionary for advanced learners (1st and 2nd edition) has paid tribute to the fact that understanding culturespecific metaphors and being aware of metaphoric usage are crucial for learning a foreign language. Given that most of the English as lingua franca interactions take place between L2-speakers of English (see Kachru, 1994), providing conceptual information is not only a desideratum for L1- and learner dictionaries, but especially for (L2-) variety dictionaries of English. In our paper, we follow earlier tentative proposals by Polzenhagen (2007) and Wolf (2012) and present examples from A dictionary of Hong Kong English (Cummings & Wolf, 2011), showing how culturally salient conceptual information can be made explicit and conceptual links between lexical items retrievable. The examples demonstrate that fixed expressions and idioms -a perennial problem for lexicographers are explicable by means of the proposed lexicographic design, too. Our approach is cognitive-sociolinguistic in that the Conceptual Metaphor approach is coupled with the study of regional varieties of English, more specifically Hong Kong English. Our analysis is empirically backed up by corpus-linguistic insights into this L2 variety.
Current climate warming is affecting arctic regions at a faster rate than the rest of the world. This has profound effects on permafrost that underlies most of the arctic land area. Permafrost thawing can lead to the liberation of considerable amounts of greenhouse gases as well as to significant changes in the geomorphology, hydrology, and ecology of the corresponding landscapes, which may in turn act as a positive feedback to the climate system. Vast areas of the east Siberian lowlands, which are underlain by permafrost of the Yedoma-type Ice Complex, are particularly sensitive to climate warming because of the high ice content of these permafrost deposits. Thermokarst and thermal erosion are two major types of permafrost degradation in periglacial landscapes. The associated landforms are prominent indicators of climate-induced environmental variations on the regional scale. Thermokarst lakes and basins (alasses) as well as thermo-erosional valleys are widely distributed in the coastal lowlands adjacent to the Laptev Sea. This thesis investigates the spatial distribution and morphometric properties of these degradational features to reconstruct their evolutionary conditions during the Holocene and to deduce information on the potential impact of future permafrost degradation under the projected climate warming. The methodological approach is a combination of remote sensing, geoinformation, and field investigations, which integrates analyses on local to regional spatial scales. Thermokarst and thermal erosion have affected the study region to a great extent. In the Ice Complex area of the Lena River Delta, thermokarst basins cover a much larger area than do present thermokarst lakes on Yedoma uplands (20.0 and 2.2 %, respectively), which indicates that the conditions for large-area thermokarst development were more suitable in the past. This is supported by the reconstruction of the development of an individual alas in the Lena River Delta, which reveals a prolonged phase of high thermokarst activity since the Pleistocene/Holocene transition that created a large and deep basin. After the drainage of the primary thermokarst lake during the mid-Holocene, permafrost aggradation and degradation have occurred in parallel and in shorter alternating stages within the alas, resulting in a complex thermokarst landscape. Though more dynamic than during the first phase, late Holocene thermokarst activity in the alas was not capable of degrading large portions of Pleistocene Ice Complex deposits and substantially altering the Yedoma relief. Further thermokarst development in existing alasses is restricted to thin layers of Holocene ice-rich alas sediments, because the Ice Complex deposits underneath the large primary thermokarst lakes have thawed completely and the underlying deposits are ice-poor fluvial sands. Thermokarst processes on undisturbed Yedoma uplands have the highest impact on the alteration of Ice Complex deposits, but will be limited to smaller areal extents in the future because of the reduced availability of large undisturbed upland surfaces with poor drainage. On Kurungnakh Island in the central Lena River Delta, the area of Yedoma uplands available for future thermokarst development amounts to only 33.7 %. The increasing proximity of newly developing thermokarst lakes on Yedoma uplands to existing degradational features and other topographic lows decreases the possibility for thermokarst lakes to reach large sizes before drainage occurs. Drainage of thermokarst lakes due to thermal erosion is common in the study region, but thermo-erosional valleys also provide water to thermokarst lakes and alasses. Besides these direct hydrological interactions between thermokarst and thermal erosion on the local scale, an interdependence between both processes exists on the regional scale. A regional analysis of extensive networks of thermo-erosional valleys in three lowland regions of the Laptev Sea with a total study area of 5,800 km² found that these features are more common in areas with higher slopes and relief gradients, whereas thermokarst development is more pronounced in flat lowlands with lower relief gradients. The combined results of this thesis highlight the need for comprehensive analyses of both, thermokarst and thermal erosion, in order to assess past and future impacts and feedbacks of the degradation of ice-rich permafrost on hydrology and climate of a certain region.
During life bones constantly adapt their structure to their mechanical environment via a mechanically controlled process called bone remodeling. For trabecular bone, this process modifies the thickness of each trabecula leading occasionally to full resorption. We describe the irreversible dynamics of the trabecular thickness distribution (TTD) by means of a Markov chain discrete in space and time. By using thickness data from adult patients, we derive the transition probabilities in the chain. This allows a quantification, in terms of geometrical quantities, of the control of bone remodeling and thus to determine the evolution of the TTD with age.
In this paper, we analytically study a star motif of Stuart-Landau oscillators, derive the bifurcation diagram and discuss the different forms of synchronization arising in such a system. Despite the parameter mismatch between the central node and the peripheral ones, an analytical approach independent of the number of units in the system has been proposed. The approach allows to calculate the separatrices between the regions with distinct dynamical behavior and to determine the nature of the different transitions to synchronization appearing in the system. The theoretical analysis is supported by numerical results.
We construct a new RC phase shift network based Chua's circuit, which exhibits a period-doubling bifurcation route to chaos. Using coupled versions of such a phase-shift network based Chua's oscillators, we describe a new method for achieving complete synchronization (CS), approximate lag synchronization (LS), and approximate anticipating synchronization (AS) without delay or parameter mismatch. Employing the Pecora and Carroll approach, chaos synchronization is achieved in coupled chaotic oscillators, where the drive system variables control the response system. As a result, AS or LS or CS is demonstrated without using a variable delay line both experimentally and numerically.
Quantitative estimates of sediment flux and the global cycling of sediments from hillslopes to rivers, estuaries, deltas, continental shelves, and deep-sea basins have a long research tradition. In this context, extremely large and commensurately rare sediment transport events have so far eluded a systematic analysis. To start filling this knowledge gap I review some of the highest reported sediment yields in mountain rivers impacted by volcanic eruptions, earthquake- and storm-triggered landslide episodes, and catastrophic dam breaks. Extreme specific yields, defined here as those exceeding the 95th percentile of compiled data, are similar to 10(4) t km(-2) yr(-1) if averaged over 1 yr. These extreme yields vary by eight orders of magnitude, but systematically decay with reference intervals from minutes to millennia such that yields vary by three orders of magnitude for a given reference interval. Sediment delivery from natural dam breaks and pyroclastic eruptions dominate these yields for a given reference interval. Even if averaged over 10(2)-10(3) yr, the contribution of individual disturbances may remain elevated above corresponding catchment denudation rates. I further estimate rates of sediment (re-)mobilisation by individual giant terrestrial and submarine mass movements. Less than 50 postglacial submarine mass movements have involved an equivalent of similar to 10% of the contemporary annual global flux of fluvial sediment to Earth's oceans, while mobilisation rates by individual events rival the decadal-scale sediment discharge from tectonically active orogens such as Taiwan or New Zealand. Sediment flushing associated with catastrophic natural dam breaks is non-stationary and shows a distinct kink at the last glacial-interglacial transition, owing to the drainage of very large late Pleistocene ice-marginal lakes. Besides emphasising the contribution of high-magnitude and low-frequency events to the global sediment cascade, these findings stress the importance of sediment storage for fuelling rather than buffering high sediment transport rates.