594 research outputs found
Generalized Involution Models for Wreath Products
We prove that if a finite group has a generalized involution model, as
defined by Bump and Ginzburg, then the wreath product also has a
generalized involution model. This extends the work of Baddeley concerning
involution models for wreath products. As an application, we construct a
Gelfand model for wreath products of the form with abelian, and
give an alternate proof of a recent result due to Adin, Postnikov, and Roichman
describing a particularly elegant Gelfand model for the wreath product \ZZ_r
\wr S_n. We conclude by discussing some notable properties of this
representation and its decomposition into irreducible constituents, proving a
conjecture of Adin, Roichman, and Postnikov's.Comment: 29 page
Thick tori around AGN: the case for extended tori and consequences for their X-ray and IR emission
Two families of models of dusty tori in AGNs (moderately thick and extended
versus very thick and compact) are tested against available observations. The
confrontation suggests that the former class better explains the IR broad-band
spectra of both broad and narrow line AGNs, the anisotropy of the emission
deduced by comparing IR properties of Seyfert 1 and 2 nuclei, the results of IR
spectroscopy and those of high spatial resolution observations. There is
however clear evidence for a broad distribution of optical depths. We also
examine the relationship between IR and X-ray emission. The data support a view
in which the matter responsible for the X-ray absorption is mostly dust free,
lying inside the dust sublimation radius. The consequences of these results for
the hard X-ray background as well as IR counts and background are discussed.Comment: 33 pages, 9 Postscript figures, to appear in ApJ, September 199
The Unified Model & Evolution of Active Galaxies: Implications from a Spectropolarimetric Study
We extend the analysis presented in Tran (2001) of a spectropolarimetric
survey of the CfA and 12micron samples of Seyfert 2 galaxies (S2s). We confirm
that S2s with hidden broad line regions (HBLRs) tend to have hotter
circumnuclear dust temperatures, show mid-IR spectra more characteristic of S1
galaxies, and are intrinsically more luminous than non-HBLR S2s. The level of
obscuration and circumnuclear star formation, however, appear to be similar
between HBLR and non-HBLR S2 galaxies, based on an examination of various
observational indicators. HBLR S2s, on average, share many similar large-scale,
presumably isotropic, characteristics with Seyfert 1 galaxies (S1s), as would
be expected if the unified model is correct, while non-HBLR S2s generally do
not. The active nuclear engines of non-HBLR S2s then, appear to be truly weaker
than HBLR S2s, which in turn, are fully consistent with being S1s viewed from
another direction. There is also evidence that the fraction of detected HBLR
increases with radio power of the AGN. Thus, not all Seyfert 2 galaxies may be
intrinsically similar in nature, and we speculate that evolutionary processes
may be at work.Comment: 15 pages with embedded figs, ApJ in press, vol. 583, 2003 Feb. 1. v2:
minor corrections to text, some typos removed; updated reference list: some
added, some remove
High temperatures in the terrestrial mid-latitudes during the early Palaeogene
The early Paleogene (56–48 Myr) provides valuable information about the Earth’s climate system in an equilibrium high pCO2 world. High ocean temperatures have been reconstructed for this greenhouse period, but land temperature estimates have been cooler than expected. This mismatch between marine and terrestrial temperatures has been difficult to reconcile. Here we present terrestrial temperature estimates from a newly calibrated branched glycerol dialkyl glycerol tetraether-based palaeothermometer in ancient lignites (fossilized peat). Our results suggest early Palaeogene mid-latitude mean annual air temperatures of 23–29 °C (with an uncertainty of ± 4.7 °C), 5–10 °C higher than most previous estimates. The identification of archaeal biomarkers in these same lignites, previously observed only in thermophiles and hyperthermophilic settings, support these high temperature estimates. These mid-latitude terrestrial temperature estimates are consistent with reconstructed ocean temperatures and indicate that the terrestrial realm was much warmer during the early Palaeogene than previously thought
Bell inequalities for entangled kaons and their unitary time evolution
We investigate Bell inequalities for neutral kaon systems from Phi resonance
decay to test local realism versus quantum mechanics. We emphasize the unitary
time evolution of the states, that means we also include all decay product
states, in contrast to other authors. Only this guarantees the use of the
complete Hilbert space. We develop a general formalism for Bell inequalities
including both arbitrary "quasi spin" states and different times; finally we
analyze Wigner-type inequalities. They contain an additional term, a correction
function h, as compared to the spin 1/2 or photon case, which changes
considerably the possibility of quantum mechanics to violate the Bell
inequality. Examples for special "quasi spin" states are given, especially
those which are sensitive to the CP parameters epsilon and epsilon'.Comment: REVTeX, 22 page
The Candida genome database incorporates multiple Candida species: multispecies search and analysis tools with curated gene and protein information for Candida albicans and Candida glabrata
The Candida Genome Database (CGD, http://www.candidagenome.org/) is an internet-based resource that provides centralized access to genomic sequence data and manually curated functional information about genes and proteins of the fungal pathogen Candida albicans and other Candida species. As the scope of Candida research, and the number of sequenced strains and related species, has grown in recent years, the need for expanded genomic resources has also grown. To answer this need, CGD has expanded beyond storing data solely for C. albicans, now integrating data from multiple species. Herein we describe the incorporation of this multispecies information, which includes curated gene information and the reference sequence for C. glabrata, as well as orthology relationships that interconnect Locus Summary pages, allowing easy navigation between genes of C. albicans and C. glabrata. These orthology relationships are also used to predict GO annotations of their products. We have also added protein information pages that display domains, structural information and physicochemical properties; bibliographic pages highlighting important topic areas in Candida biology; and a laboratory strain lineage page that describes the lineage of commonly used laboratory strains. All of these data are freely available at http://www.candidagenome.org/. We welcome feedback from the research community at [email protected]
Beyond altruism: British football and charity, 1877-1914
Football charity matches and tournaments played a significant part in the development of the sport in Britain, overlapping the era of friendly games and the advent of competitive leagues. The football community prided itself on its contributions to charity, raising more money than any other sport before 1914, and stakeholders within the game – associations, clubs, players and patrons – gained considerable kudos for this perceived altruism. However, this paper will demonstrate that amounts donated, though welcome, were relatively minor sources of revenue for both institutions and individuals, and that the charity match became less important to clubs in a professional, and increasingly commercial, era
Entanglement, Bell Inequalities and Decoherence in Particle Physics
We demonstrate the relevance of entanglement, Bell inequalities and
decoherence in particle physics. In particular, we study in detail the features
of the ``strange'' system as an example of entangled
meson--antimeson systems. The analogies and differences to entangled spin--1/2
or photon systems are worked, the effects of a unitary time evolution of the
meson system is demonstrated explicitly. After an introduction we present
several types of Bell inequalities and show a remarkable connection to CP
violation. We investigate the stability of entangled quantum systems pursuing
the question how possible decoherence might arise due to the interaction of the
system with its ``environment''. The decoherence is strikingly connected to the
entanglement loss of common entanglement measures. Finally, some outlook of the
field is presented.Comment: Lectures given at Quantum Coherence in Matter: from Quarks to Solids,
42. Internationale Universit\"atswochen f\"ur Theoretische Physik,
Schladming, Austria, Feb. 28 -- March 6, 2004, submitted to Lecture Notes in
Physics, Springer Verlag, 45 page
Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from
Bacteria and Archaea that are ubiquitous in a range of natural archives and especially
abundant in peat. Previous work demonstrated that the distribution of bacterial
branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors
such as mean annual air temperature (MAAT) and soil pH. However, the influence of
these parameters on brGDGT distributions in peat is largely unknown. Here we
investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the
world with a broad mean annual air temperature (−8 to 27 °C) and pH (3–8) range and
present the first peat-specific brGDGT-based temperature and pH calibrations. Our
results demonstrate that the degree of cyclisation of brGDGTs in peat is positively
correlated with pH, pH = 2.49 x CBTpeat + 8.07 (n = 51, R2 65 = 0.58, RMSE = 0.8) and
the degree of methylation of brGDGTs is positively correlated with MAAT,
MAATpeat (°C) = 52.18 x MBT5me’ – 23.05 (n = 96, R2 67 = 0.76, RMSE = 4.7 °C).
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These peat-specific calibrations are distinct from the available mineral soil
calibrations. In light of the error in the temperature calibration (~ 4.7 °C), we urge
caution in any application to reconstruct late Holocene climate variability, where the
climatic signals are relatively small, and the duration of excursions could be brief.
Instead, these proxies are well-suited to reconstruct large amplitude, longer-term
shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit
spanning the late glacial period (~15.2 kyr), we demonstrate that MAATpeat yields
absolute temperatures and relative temperature changes that are consistent with those
from other proxies. In addition, the application of MAATpeat to fossil peat (i.e.
lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We
conclude that there is clear potential to use brGDGTs in peats and lignites to
reconstruct past terrestrial climateThis research was funded through the advanced ERC grant “the greenhouse earth
system” (T-GRES, project reference 340923), awarded to RDP. All authors are part of
the “T-GRES Peat Database collaborators” collective. RDP also acknowledges the
Royal Society Wolfson Research Merit Award. We thank D. Atkinson for help with
the sample preparation. We acknowledge support from Labex VOLTAIRE (ANR-10-
22
LABX-100-01). Peat from Patagonia and Tierra del Fuego were collected thanks to a
Young Researcher Grant of the Agence National de la Recherche (ANR) to FDV,
project ANR-2011-JS56-006-01 “PARAD” and with the help of Ramiro Lopez,
Andrea Coronato and Veronica Pancotto (CADIC-CONICET, Ushuaia). Peat from
Brazil was collected with the context of CNPq project 482815/2011-6. Samples from
France (Frasne and La Guette) were collected thanks to the French Observatory of
Peatlands. The Canadian peat was collected in the context of the NSERC-Discovery
grant of L. Rochefort. Peats from China were obtained under a National Natural
Science Foundation of China grant (No. 41372033), awarded to Y. Zheng
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