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An objective global climatology of polar lows based on reanalysis data
No full textHere an objective global climatology of polar lows has been developed. In order to obtain objective detection criteria the efficacy of several parameters for separating polar lows from other cyclones has been investigated. This parameter efficacy has been compared for polar lows subjectively identified by experts and for all kind of extra-tropical cyclones. The comparison is based on the ERA-Interim reanalysis from 1979 - 2016 and the higher resolution Arctic System Reanalysis from 2000 - 2012. The parameters found to be the most effective at separating polar lows from all other kinds of synoptic and meso-scale cyclones were the difference between the mean sea-level pressure of the low and its surroundings, the difference in the potential temperature between the sea surface and the 500 hPa level, and the tropopause wind poleward of the system. Other parameters often used for distinguishing, such as the 10m wind speed and the temperature difference between the sea surface and the 700 hPa level were found to be less effective. Investigation of the climatologies reveals that PLs occur in all maritime basins at high latitudes, but with high density in the vicinity of the sea-ice edge and coastal zones. The regions showing the highest degree of polar-low activity are the Denmark Strait and the Nordic Seas. Especially the most intense polar lows occur in these two regions. In the North Atlantic and Pacific the main polar-low season ranges from November to March. In the Southern Hemisphere polar lows are mainly detected between 50 - 65'S from April to October, indicating that this hemisphere compared to its northern counterpart has a two months longer, but less intense, polar-low season. No significant hemispheric long-term trends are observed, although some regions, such as the Denmark Strait and the Nordic Sea experience significant downward and upward trends in polar lows, respectively, over the last decades. For intense polar lows a significant decaying trend has been observed for the northern hemisphere
Mesozoic basin inversion governed by crustal extension in the Bornholm area, Sorgenfrei-Tornquist Zone, Denmark
No full textMesozoic basin inversion governed by crustal extension in the Bornholm area, Sorgenfrei-Tornquist Zone, DenmarkOle Graversen, Department of Geosciences and Natural Resource Management, Section for Geology, University of Copenhagen, [email protected] inversion describes the deformation of asymmetric grabens characterized by folding and thrusting, i.e. horizontal shortening, associated with uplift of the sedimentary graben fill above regional (1). The compressive stress field has been interpreted in a plate tectonic concept as a result of continent-continent collision that established a compressive stress field in the orogenic foreland (2, 3). However, structural analysis of basin inversion in the Sorgenfrei – Tornquist Zone illustrates, that basin inversion was the result of superposition of asymmetric extensional fault basins dipping in opposite directions. The evolution of the graben basins, took place during successive extensional tectonic regimes separated by stillstand intervals. During subsidence of the superposed, extensional basin, the primary basin was tilted backward, and the basin was inverted during local compression between the primary footwall blocks.The Mesozoic fault block pattern of the Bornholm area illustrates, that the NW-SE trending Sorgenfrei – Tornquist Zone was extended in two directions: The main extension was in a NE-SW direction across the strike of the fault zone, and a secondary NW-SE extension along the fault zone trend. Based on the changing graben activity, the Mesozoic has been divided into Triassic, Jurassic – Early Cretaceous and Late Cretaceous extensional tectonic regimes. Graben subsidence started in the Triassic, and basin inversion was active in the Jurassic – Early Cretaceous and again in the Late Cretaceous (4, 5). The tectonic regimes were separated by turnover intervals characterized by only minor tectonic activity in the late Late Triassic and the early Late Cretaceous. References(1) Ziegler, P.A. 1987: Compressional intra-plate deformations in the Alpine foreland – an introduction. Tectonophysics 137, 1-5. (2) Ziegler, P.A. 1987: Late Cretaceous and Cenozoic intra-plate compressional deformations in the Alpine foreland – a geodynamic model. Tectonophysics 137, 389-420.(3) Kley, J. & Voigt, T. 2008: Late Cretaceous intraplate thrusting in central Europe: Effect of Africa-Iberia-Europe convergence, not Alpine collision. Geology 36, 839-842. (4) Graversen, O. 2004: Upper Triassic–Lower Cretaceous seismic sequence stratigraphy and basin tectonics at Bornholm, Denmark, Tornquist Zone, NW Europe. Marine and Petroleum Geology 21, 579–612.(5) Graversen, O. 2004: Upper Triassic – Cretaceous stratigraphy and structural inversion offshore SW Bornholm, Tornquist Zone, Denmark. Bulletin of the Geological Society of Denmark 51, 111–136
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Analysis of forensic DNA mixtures with artefacts
No full textDNA is now routinely used in criminal investigations and court cases, although DNA samples taken at crime scenes are of varying quality and therefore present challenging problems for their interpretation. We present a statistical model for the quantitative peak information obtained from an electropherogram of a forensic DNA sample and illustrate its potential use for the analysis of criminal cases. In contrast with most previously used methods, we directly model the peak height information and incorporate important artefacts that are associated with the production of the electropherogram. Our model has a number of unknown parameters, and we show that these can be estimated by the method of maximum likelihood in the presence of multiple unknown individuals contributing to the sample, and their approximate standard errors calculated; the computations exploit a Bayesian network representation of the model. A case example from a UK trial, as reported in the literature, is used to illustrate the efficacy and use of the model, both in finding likelihood ratios to quantify the strength of evidence, and in the deconvolution of mixtures for finding likely profiles of the individuals contributing to the sample. Our model is readily extended to simultaneous analysis of more than one mixture as illustrated in a case example. We show that the combination of evidence from several samples may give an evidential strength which is close to that of a single-source trace and thus modelling of peak height information provides a potentially very efficient mixture analysis
On the linkage between atmospheric circulation changes and Arctic climate change
No full textPolar amplification is a prominent feature of recent and projected climate change. The Arctic region shows some of the strongest signs of climate change, including sea-ice retreat and temperatures increasing at twice the rate averaged over the northern hemisphere. A major concern for humanity is the sea-level rise associated with the melting of the ice-sheets and glaciers due to climate change. The atmospheric circulation transports an amount of energy into to the Arctic equivalent that received by the Arctic from the Sun. Thus, the atmospheric energy transport is an important subject to study in the light of Arctic climate change. The atmospheric energy transport may be decomposed into contributions by planetary-scale waves such as Rossby waves and small-scale waves such as cyclones. The energy transport contributions by the different length-scale separated systems are shown to affect the Arctic differently. The meridional energy transport is separated into length-scale contributions using a Fourier-series-based approach. Here we evaluate this approach by comparing it to a novel wavelet-based length-scale decomposition, developed as a part of this project. Further a machine-learning-based length-scale decomposition approximator is developed. The approximator may be applied to climate model output to investigate future changes in the length-scale decomposed energy transport. From the comparisons it is apparent that both the Fourier and wavelet-based length-scale decompositions are skilled approaches, which produce physically meaningful decompositions. Additionally, the Fourier-based decomposition is further developed to yield a length-scale decomposition on a latitude-longitude grid. Once evaluated the Fourier and wavelet-based decompositions are applied to investigate the effects of recent climate change on the atmospheric energy transport, and how these changes affect the Arctic and the Greenland ice-sheet. Through these studies it is conspicuous that shifts of energy transport between length-scale components has occurred during the last decades, and that these shifts have contributed to Greenland ice-sheet melt and Arctic warming
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Pelevin’s Trinity in the novel “t”: author – protagonist – reader
No full textThe article attempts to interpret Pelevin's artistic strategy in the novel "T" by exploring its subject organization and addressing the key problems of the author, the protagonist, and the reader as they are seen by the researcher. The article analyzes the peculiarities of constructing the narrative reality in the novel "T", and goes on to discuss Pelevin's philosophic models of the development of the humankind, and the emergence of his new anthropology
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