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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
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
Relational Contracting and Allocation of Decision Rights in the Agri-Food Industry: Producer Contracts and Food Safety
No full textWe apply a formal theoretical model of adaptation to two empirical settings within the agri-food industry: specialized pig production and food safety in Denmark. The objective is to allocate decision rights ex ante so that actual decisions taken ex post will optimize the profit accruing to the two parties in a contractual or integrative relation. Two applications are presented in this paper: First an actual partnership between two pork producers in Denmark. Based on detailed budgets we develop detailed schedules for the “reneging temptations” of the two partners- These are the temptations to renege on the contract during the evolution of the partnership. Using a model developed by Baker, Gibbons and Murphy (2006) we calculate equilibria using the Folk theorem in order to determine which is the best allocation of decision rights. We find that the existing allocation of decision rights in the case we examine is efficient in the sense that it results into a second best allocation. Using the same modelling approach we present a second application on salmonella control related to end-feeding, that is, salmonella contamination of pork due to filled bellies of pigs fed for the last 12 hours before delivery. Based on appropriate assumptions, the parties should give the decision right (whether to end-feed or not) to the slaughterhouse in order to reach the firstbest solution which, given the assumptions, is feasibleTheory of the firm, Adaptation theory, Contracts, Decision Rights, Pig production, Food safety, Agribusiness, Agricultural and Food Policy, Farm Management, Food Consumption/Nutrition/Food Safety, Industrial Organization, D21, L2, Q1,
Warm winds from the Pacific caused extensive Arctic sea-ice melt in summer 2007
No full textDuring summer 2007 the Arctic sea-ice shrank to the lowest extent ever observed. The role of the atmospheric energy transport in this extreme melt event is explored using the state-of-the-art ERA-Interim reanalysis data. We find that in summer 2007 there was an anomalous atmospheric flow of warm and humid air into the region that suffered severe melt. This anomaly was larger than during any other year in the data (1989–2008). Convergence of the atmospheric energy transport over this area led to positive anomalies of the downward longwave radiation and turbulent fluxes. In the region that experienced unusual ice melt, the net anomaly of the surface fluxes provided enough extra energy to melt roughly one meter of ice during the melting season. When the ocean successively became ice-free, the surface-albedo decreased causing additional absorption of shortwave radiation, despite the fact that the downwelling solar radiation was smaller than average. We argue that the positive anomalies of net downward longwave radiation and turbulent fluxes played a key role in initiating the 2007 extreme ice melt, whereas the shortwave-radiation changes acted as an amplifying feedback mechanism in response to the melt
Long-term effects of perinatal nutrition on T lymphocyte kinetics in young Gambian men.
No full textBACKGROUND: Nutritional status is highly dependent on season in countries such as The Gambia. In a rural Gambian setting, individuals born during periods of seasonal nutritional deprivation ("hungry seasons") are susceptible to mortality from infectious diseases in adult life. OBJECTIVE: We investigated the hypothesis that impaired immunocompetence in those born in the hungry season results from an underlying defect in immunologic memory, similar to the immunosenescence of old age, which is likely to be reflected in the phenotype and kinetics of T lymphocytes in young adults. DESIGN: T cell phenotype in terms of CD3, CD4, CD8, CD45RA, and CD45R0 expression and in vivo dynamics measured by stable isotope labeling of T cell subsets combined with gas chromatography-mass spectrometry and frequency of T cell receptor excision circles were measured in 25 young (18-24-y-old) Gambian men. Thirteen of these 25 men were exposed to perinatal malnutrition as defined by birth season and birth weight. RESULTS: In persons born in the hungry season with low birth weight, no differences in the proportions of memory or naive T cells were found. Kinetic analysis showed higher proliferation rates in memory (CD45R0(+)) subsets of T cells than in naïve (CD45R0(-)) cells, which is consistent with previous studies, but no evidence was found for an effect of birth weight or season on T lymphocyte proliferation and disappearance rates. No significant correlations were found between in vivo T cell kinetics and frequency of T cell receptor excision circles. Only absolute numbers of granulocytes were elevated in those born in the nutritionally deprived season. CONCLUSION: In healthy young Gambian men, T lymphocyte homeostasis is extremely robust regardless of perinatal nutritional compromise
Measurement and modeling of human T cell kinetics.
No full textThe ability to measure, describe and interpret T cell kinetics is pivotal in understanding normal lymphocyte homeostasis and diseases that affect T cell numbers. Following in vivo labeling of dividing cells with 6,6-D(2)-glucose in eight healthy volunteers, peripheral blood T cells were sorted by CD4, CD8 and CD45 phenotype. Enrichment of deuterium in DNA was measured by gas chromatography-mass spectrometry. A novel model of T cell kinetics, allowing for heterogeneity within T cell pools, was used to analyze data on acquisition and loss of label and calculate proliferation and disappearance rates for each subpopulation. Proliferation rates for CD45RO(+)CD8(+) cells and CD45RO(+)CD4(+) cells were 5.1% and 2.7% /day, respectively (equivalent doubling times: 14 and 26 days). CD45RA(+)CD8(+) lymphocytes and CD45RA(+)CD4(+) lymphocytes had slower proliferation rates, 0.5% and 0.6% / day, respectively (doubling time about 4 months). Disappearance rates of labeled cells were similar for all cell types (7%-12% / day) and exceeded corresponding proliferation rates. This disparity may be understood conceptually in terms of either phenotypic heterogeneity (rapid versus slow turnover pools), or history (recently divided cells are more likely to die). The new kinetic model fits the data closely and avoids the need to postulate a large external source of lymphocytes to maintain equilibrium
Reproducibility of psychophysics and electroencephalography during offset analgesia
No full textAnesthesiolog
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