161 research outputs found
Dimensionally reduced gravity theories are asymptotically safe
4D Einstein gravity coupled to scalars and abelian gauge fields in its
2-Killing vector reduction is shown to be quasi-renormalizable to all loop
orders at the expense of introducing infinitely many essential couplings. The
latter can be combined into one or two functions of the `area radius'
associated with the two Killing vectors. The renormalization flow of these
couplings is governed by beta functionals expressible in closed form in terms
of the (one coupling) beta function of a symmetric space sigma-model.
Generically the matter coupled systems are asymptotically safe, that is the
flow possesses a non-trivial UV stable fixed point at which the trace anomaly
vanishes. The main exception is a minimal coupling of 4D Einstein gravity to
massless free scalars, in which case the scalars decouple from gravity at the
fixed point.Comment: 47 pages, Latex, 1 figur
Experimental and computational studies of Criegee Intermediate Reactions with NH<sub>3</sub> and CH<sub>3</sub>NH<sub>2</sub>
The state of the Martian climate
60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes
Release of Spring 2013 Spanish-Language MCAS Test Items
Trace atmospheric concentrations
of carboxylic acids have a potent
effect upon the environment, where they modulate aqueous chemistry
and perturb Earth’s radiative balance. Halogenated carboxylic
acids are produced by the tropospheric oxidation of halocarbons and
are considered persistent pollutants because of their weak tropospheric
and aqueous sinks. However, recent studies reported rapid reactions
between selected carboxylic acids and Criegee intermediates, which
may provide an efficient gas-phase removal process. Accordingly, absolute
rate coefficients of two Criegee intermediates, CH<sub>2</sub>OO and
(CH<sub>3</sub>)<sub>2</sub>COO, with a suite of carboxylic acids
(HCOOH, CH<sub>3</sub>COOH, CClF<sub>2</sub>COOH, CF<sub>3</sub>CF<sub>2</sub>COOH, and pyruvic acid) were measured with a view to develop
a structure–activity relationship (SAR). This SAR is based
upon the dipole-capture model and predicts the reactivity of many
further combinations of Criegee intermediates and carboxylic acids.
Complementary synchrotron-based photoionization mass spectrometry
measurements demonstrate that these reactions produce stable ester
adducts, with a reaction coordinate involving transfer of the acidic
hydrogen from the carboxylic acid to the terminal oxygen of the Criegee
intermediate. The adduct products are predicted to have low vapor
pressures, and coupling of this chemistry with a global atmospheric
chemistry and transport model shows significant production of secondary
organic aerosol at locations rich in biogenic alkene emissions
The higher-level phylogeny of Archosauria (Tetrapoda:Diapsida)
Crown group Archosauria, which includes birds, dinosaurs, crocodylomorphs, and several extinct Mesozoic groups, is a primary division of the vertebrate tree of life. However, the higher-level phylogenetic relationships within Archosauria are poorly resolved and controversial, despite years of study. The phylogeny of crocodile-line archosaurs (Crurotarsi) is particularly contentious, and has been plagued by problematic taxon and character sampling. Recent discoveries and renewed focus on archosaur anatomy enable the compilation of a new dataset, which assimilates and standardizes character data pertinent to higher-level archosaur phylogeny, and is scored across the largest group of taxa yet analysed. This dataset includes 47 new characters (25% of total) and eight taxa that have yet to be included in an analysis, and total taxonomic sampling is more than twice that of any previous study. This analysis produces a well-resolved phylogeny, which recovers mostly traditional relationships within Avemetatarsalia, places Phytosauria as a basal crurotarsan clade, finds a close relationship between Aetosauria and Crocodylomorpha, and recovers a monophyletic Rauisuchia comprised of two major subclades. Support values are low, suggesting rampant homoplasy and missing data within Archosauria, but the phylogeny is highly congruent with stratigraphy. Comparison with alternative analyses identifies numerous scoring differences, but indicates that character sampling is the main source of incongruence. The phylogeny implies major missing lineages in the Early Triassic and may support a Carnian-Norian extinction event.Marshall Scholarship for study in the United KingdomJurassic FoundationUniversity of BristolPaleontological Societ
The institutions of archaic post-modernity and their organizational and managerial consequences: The case of Portugal
The long march of modernization of the Western societies tends to be presented as following a regular sequence: societies and institutions were pre-modern, and then they were modernized, eventually becoming post-modern. Such teleology may provide an incomplete or distorted narrative of societal evolution in many parts of the world, even in the ‘post-modern heartland’ of Western Europe, with Portugal being a case in point. The concept of archaic post-modernity has been developed by a philosopher, José Gil, to show how Portuguese institutions and organizations combine elements of pre-modernity and post-modernity. The notion of an archaic post-modernity is advanced in order to provide an alternative account of the modernization process, which enriches discussion of the varieties of capitalism. Differences in historical experiences create singularities that may be considered in the analysis of culture, management and organization
Documenting the initial appearance of domestic cattle in the Eastern Fertile Crescent (northern Iraq and western Iran)
In this paper we address the timing of and mechanisms for the appearance of domestic cattle in the Eastern Fertile Crescent (EFC) region of SW Asia through the analysis of new and previously published species abundance and biometric data from 86 archaeofaunal assemblages. We find that Bos exploitation was a minor component of animal economies in the EFC in the late Pleistocene and early Holocene but increased dramatically in the sixth millennium BC. Moreover, biometric data indicate that small-sized Bos, likely representing domesticates, appear suddenly in the region without any transitional forms in the early to mid sixth millennium BC. This suggests that domestic cattle were imported into the EFC, possibly associated with the spread of the Halaf archaeological culture, several millennia after they first appear in the neighboring northern Levant
Correction to: Cluster identification, selection, and description in Cluster randomized crossover trials: the PREP-IT trials
An amendment to this paper has been published and can be accessed via the original article
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