948 research outputs found
Coal, cumulative impacts, and the Great Barrier Reef
The Great Barrier Reef World Heritage Area, Australia, covers over 348,000 km 2 of tropical marine ecosystems of global significance. In July 2015, the World Heritage Committee called attention to the cumulative impacts of climate change, poor water quality, and coastal development on the region's outstanding universal value, but stopped short of inscribing the Great Barrier Reef on the List of World Heritage in Danger. Restoring the region's values is hindered by an environmental decision-making process that fails to incorporate cumulative impacts, including the climate change impacts of greenhouse gas emissions sourced from one of Australia's largest exports, thermal coal. We identify policy and processes that enable a more comprehensive consideration of the cumulative effects of coal mining by environmental decision-makers. Implementing cumulative impact assessment requires a collaborative and transparent program of planning and monitoring independent of Government and mine proponents that evaluates local, regional, and global impacts. The future of the Great Barrier Reef depends on transformational change in the cumulative assessment of Australian coal mines
Categorical formulation of quantum algebras
We describe how dagger-Frobenius monoids give the correct categorical
description of certain kinds of finite-dimensional 'quantum algebras'. We
develop the concept of an involution monoid, and use it to construct a
correspondence between finite-dimensional C*-algebras and certain types of
dagger-Frobenius monoids in the category of Hilbert spaces. Using this
technology, we recast the spectral theorems for commutative C*-algebras and for
normal operators into an explicitly categorical language, and we examine the
case that the results of measurements do not form finite sets, but rather
objects in a finite Boolean topos. We describe the relevance of these results
for topological quantum field theory.Comment: 34 pages, to appear in Communications in Mathematical Physic
A glassy contribution to the heat capacity of hcp He solids
We model the low-temperature specific heat of solid He in the hexagonal
closed packed structure by invoking two-level tunneling states in addition to
the usual phonon contribution of a Debye crystal for temperatures far below the
Debye temperature, . By introducing a cutoff energy in the
two-level tunneling density of states, we can describe the excess specific heat
observed in solid hcp He, as well as the low-temperature linear term in the
specific heat. Agreement is found with recent measurements of the temperature
behavior of both specific heat and pressure. These results suggest the presence
of a very small fraction, at the parts-per-million (ppm) level, of two-level
tunneling systems in solid He, irrespective of the existence of
supersolidity.Comment: 11 pages, 4 figure
Sums over Graphs and Integration over Discrete Groupoids
We show that sums over graphs such as appear in the theory of Feynman
diagrams can be seen as integrals over discrete groupoids. From this point of
view, basic combinatorial formulas of the theory of Feynman diagrams can be
interpreted as pull-back or push-forward formulas for integrals over suitable
groupoids.Comment: 27 pages, 4 eps figures; LaTeX2e; uses Xy-Pic. Some ambiguities
fixed, and several proofs simplifie
Integration of genetics into a systems model of electrocardiographic traits using humanCVD BeadChip
<p>Background—Electrocardiographic traits are important, substantially heritable determinants of risk of arrhythmias and sudden cardiac death.</p>
<p>Methods and Results—In this study, 3 population-based cohorts (n=10 526) genotyped with the Illumina HumanCVD Beadchip and 4 quantitative electrocardiographic traits (PR interval, QRS axis, QRS duration, and QTc interval) were evaluated for single-nucleotide polymorphism associations. Six gene regions contained single nucleotide polymorphisms associated with these traits at P<10−6, including SCN5A (PR interval and QRS duration), CAV1-CAV2 locus (PR interval), CDKN1A (QRS duration), NOS1AP, KCNH2, and KCNQ1 (QTc interval). Expression quantitative trait loci analyses of top associated single-nucleotide polymorphisms were undertaken in human heart and aortic tissues. NOS1AP, SCN5A, IGFBP3, CYP2C9, and CAV1 showed evidence of differential allelic expression. We modeled the effects of ion channel activity on electrocardiographic parameters, estimating the change in gene expression that would account for our observed associations, thus relating epidemiological observations and expression quantitative trait loci data to a systems model of the ECG.</p>
<p>Conclusions—These association results replicate and refine the mapping of previous genome-wide association study findings for electrocardiographic traits, while the expression analysis and modeling approaches offer supporting evidence for a functional role of some of these loci in cardiac excitation/conduction.</p>
Classical Evolution of Quantum Elliptic States
The hydrogen atom in weak external fields is a very accurate model for the
multiphoton excitation of ultrastable high angular momentum Rydberg states, a
process which classical mechanics describes with astonishing precision. In this
paper we show that the simplest treatment of the intramanifold dynamics of a
hydrogenic electron in external fields is based on the elliptic states of the
hydrogen atom, i.e., the coherent states of SO(4), which is the dynamical
symmetry group of the Kepler problem. Moreover, we also show that classical
perturbation theory yields the {\it exact} evolution in time of these quantum
states, and so we explain the surprising match between purely classical
perturbative calculations and experiments. Finally, as a first application, we
propose a fast method for the excitation of circular states; these are
ultrastable hydrogenic eigenstates which have maximum total angular momentum
and also maximum projection of the angular momentum along a fixed direction. %Comment: 8 Pages, 2 Figures. Accepted for publication in Phys. Rev.
Systematic behaviour of 3He/4He in Earth’s continental mantle
Helium isotopes are unrivalled tracers of the origins of melts in the Earth’s convecting mantle but their role in determining melt contributions from the shallower and rigid lithospheric mantle is more ambiguous. We have acquired new 3He/4He data for olivine and pyroxene separates from 47 well-characterised mantle xenoliths from global on- and off-craton settings. When combined with existing data they demonstrate a new systematic relationship between fluid-hosted 3He/4He and major and trace element composition of host minerals and whole rock. We show that a significant proportion (>70 %) of mantle peridotites from continental off-craton settings with depleted major element compositions (e.g., olivine Mg# ≥ 89.5) have 3He/4He in the range of modern-day mid-ocean ridge basalt (MORB) source mantle (7–9 Ra) and we propose that they represent underplated melt residues, which initially formed in the convecting upper mantle. Furthermore, we observe that off-craton mantle xenoliths with signatures often attributed to enrichment by melts or fluids from ‘ancient’ subducted oceanic lithosphere have lower 3He/4He (<7 Ra). Modest correlations between 3He/4He and whole rock incompatible trace element signatures commonly used as proxies for metasomatism by small-fraction carbonatite and silicate melts or C-O-H fluids characterise lithospheric mantle with 3He/4He ranging from 5 to 8 Ra. [...
Serum Neu5Gc biomarkers are elevated in primary cutaneous melanoma
Cutaneous melanoma is one of the most aggressive and deadly types of skin cancer and rates of disease are continuing to increase worldwide. Currently, no serum biomarkers exist for the early detection of cutaneous melanoma. Normal human cells cannot make the sialic acid sugar, Neu5Gc, yet human tumor cells express Neu5Gc and Neu5Gc-containing glycoconjugates have been proposed as tumor biomarkers. We engineered a Neu5Gc-specific lectin based on the pentameric B-subunit of the Shiga toxigenic Escherichia coli subtilase cytotoxin, termed SubB2M. We have detected elevated Neu5Gc-containing biomarkers in the sera of ovarian and breast cancer patients in a highly sensitive surface plasmon resonance (SPR)-based assay using our SubB2M lectin. Here, we used the SubB2M-SPR assay to investigate Neu5Gc-containing glycoconjugates in the serum of cutaneous melanoma patients. We found elevated total serum Neu5Gc levels in primary (n ¼ 24) and metastatic (n ¼ 38) patients compared to cancer-free controls (n ¼ 34). Serum Neu5Gc levels detected with SubB2M can distinguish cutaneous melanoma patients from cancer-free controls with high sensitivity and specificity as determined by ROC curve analysis. These data indicate that serum Neu5Gc-containing glycoconjugates are a novel class of biomarkers for cutaneous melanoma, particularly for primary melanoma, and have the potential to contribute to the early diagnosis of this disease.Lucy K. Shewell, Christopher J. Day, Tiana Hippolite, Xavier De Bisscop, James C. Paton, Adrienne W. Paton, Michael P. Jenning
Rigidity percolation in a field
Rigidity Percolation with g degrees of freedom per site is analyzed on
randomly diluted Erdos-Renyi graphs with average connectivity gamma, in the
presence of a field h. In the (gamma,h) plane, the rigid and flexible phases
are separated by a line of first-order transitions whose location is determined
exactly. This line ends at a critical point with classical critical exponents.
Analytic expressions are given for the densities n_f of uncanceled degrees of
freedom and gamma_r of redundant bonds. Upon crossing the coexistence line, n_f
and gamma_r are continuous, although their first derivatives are discontinuous.
We extend, for the case of nonzero field, a recently proposed hypothesis,
namely that the density of uncanceled degrees of freedom is a ``free energy''
for Rigidity Percolation. Analytic expressions are obtained for the energy,
entropy, and specific heat. Some analogies with a liquid-vapor transition are
discussed. Particularizing to zero field, we find that the existence of a
(g+1)-core is a necessary condition for rigidity percolation with g degrees of
freedom. At the transition point gamma_c, Maxwell counting of degrees of
freedom is exact on the rigid cluster and on the (g+1)-rigid-core, i.e. the
average coordination of these subgraphs is exactly 2g, although gamma_r, the
average coordination of the whole system, is smaller than 2g. gamma_c is found
to converge to 2g for large g, i.e. in this limit Maxwell counting is exact
globally as well. This paper is dedicated to Dietrich Stauffer, on the occasion
of his 60th birthday.Comment: RevTeX4, psfig, 16 pages. Equation numbering corrected. Minor typos
correcte
Viraemia and HIV-1 drug resistance mutations among patients receiving antiretroviral treatment in Mozambique.
This study was conducted among individuals taking first-line antiretroviral treatment (ART) for at least 12 months under programme conditions in Maputo, Mozambique in order to report on the level of detectable viraemia and the proportion and types of drug resistance mutations among those with detectable viral loads. HIV-1 RNA viral load levels (lower detection limit <50 copies/ml) were measured, and resistance mutations were sequenced. One hundred and forty-nine consecutive patients (69% females, median age 36 years) were included after a mean follow-up time of 23 months. One hundred and seven (72%; 95% CI 64-79) had undetectable viral load, while in 42 (28%, 95% CI 21-36) viral load was detectable (range 50-58884 copies/ml). From 15 patients with viral load >1000 copies/ml, 12 viruses were sequenced: eight were C subtypes and four were circulating recombinant forms (CRF08). Eight (5%; 95% CI 2-9) patients with detectable viral load had one or more major resistance mutations. Nucleoside reverse transcriptase inhibitor (NRTI) and non-NRTI mutations were observed. There were no major mutations for resistance to protease inhibitors. In Maputo, the level of detectable viraemia is reassuringly low. While embarking on ART scale-up, wider surveillance is warranted to monitor programme quality and limit the development of drug resistance, which remains a major potential challenge for the future of ART in Africa
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