50 research outputs found

    Elevated CO2 degassing rates prevented the return of Snowball Earth during the Phanerozoic

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    The Cryogenian period (~720–635 Ma) is marked by extensive Snowball Earth glaciations. These have previously been linked to CO₂ draw-down, but the severe cold climates of the Cryogenian have never been replicated during the Phanerozoic despite similar, and sometimes more dramatic changes to carbon sinks. Here we quantify the total CO₂ input rate, both by measuring the global length of subduction zones in plate tectonic reconstructions, and by sea-level inversion. Our results indicate that degassing rates were anomalously low during the Late Neoproterozoic, roughly doubled by the Early Phanerozoic, and remained comparatively high until the Cenozoic. Our carbon cycle modelling identifies the Cryogenian as a unique period during which low surface temperature was more easily achieved, and shows that the shift towards greater CO₂ input rates after the Cryogenian helped prevent severe glaciation during the Phanerozoic. Such a shift appears essential for the development of complex animal life

    Measuring efficiency and productivity in professional football teams: Evidence from the English Premier League

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    Professional football clubs are unusual businesses, their performance judged on and off the field of play. This study is concerned with measuring the efficiency of clubs in the English Premier League. Information from clubs’ financial statements is used as a measure of corporate performance. To measure changes in efficiency and productivity the Malmquist non-parametric technique has been used. This is derived from the Data Envelopment Analysis (DEA) linear programming approach, with Canonical Correlation Analysis (CCA) being used to ensure the cohesion of the input-output variables. The study concludes that while clubs operate close to efficient levels for the assessed models, there is limited technological advance in their performance in terms of the displacement of the technological frontier

    Cancer Biomarker Discovery: The Entropic Hallmark

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    Background: It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods. Methodology/Principal Findings: Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer. Conclusions/Significance: We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-throughput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases

    Warm and cold wet states in the western United States during the Pliocene–Pleistocene

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    The size distribution of lakes records the competition between precipitation delivery and evaporation. Lakes were abundant in the terminally draining basins of the western United States (USA) during both the colder-than-preindustrial latest Pleistocene glacial period (ca. 14–29 ka) and the warmer-than-preindustrial mid-Pliocene (ca. 2.9–3.3 Ma). To understand the hydroclimatic conditions that permitted lakes, we couple lake mass balance equations with a water and energy balance framework (sensu Budyko). Further, we compare paleo-lake area distributions to forward-modeled lake areas using climate model simulations of the Last Glacial Maximum (LGM, 19–26 ka) and mid-Pliocene. We conclude that both warmer- and colder-than-modern periods of the Pliocene–Pleistocene resulted in wetter-than-modern conditions in the terminally draining basins of the western USA through similar mechanisms. Specifically, the presence of lakes during the LGM reflects increased precipitation in addition to decreased evaporative demand. In the southern Great Basin, LGM lakes require large increases in precipitation across the region. During the mid-Pliocene, increased evaporative demand necessitated increased precipitation to maintain lakes. Further, the increase in precipitation and dominantly southwestern distribution of mid-Pliocene lake deposits is consistent with proposed mean “El Niño–like” conditions altering regional hydroclimate during this period. These observations suggest that during interglacial periods, the western USA resides within a local aridity maximum, and both long-term increases and decreases in global temperatures have been associated with wetter conditions across much of the western USA in the past

    The Risk Preferences of U.S. Executives

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