32 research outputs found
Could biodiversity loss have increased Australiaâs bushfire threat
Ecosystem engineers directly or indirectly affect the availability of resources
through changing the physical state of biotic and/or abiotic materials. Fossorial
ecosystem engineers have been hypothesized as affecting fire behaviour through
altering litter accumulation and breakdown, however, little evidence of this has
been shown to date. Fire is one of the major ecological processes affecting biodiversity
globally. Australia has seen the extinction of 29 of 315 terrestrial mammal
species in the last 200 years and several of these species were ecosystem engineers
whose fossorial actions may increase the rate of leaf litter breakdown. Thus, their
extinction may have altered the rate of litter accumulation and therefore fire ignition
potential and rate of spread. We tested whether a reduction in leaf litter was
associated with sites where mammalian ecosystem engineers had been reintroduced
using a pair-wise, cross-fence comparison at sites spanning the Australian continent.
At Scotia (New South Wales), Karakamia (Western Australia) and Yookamurra
(South Australia) sanctuaries, leaf litter mass ( 24%) and percentage cover
of leaf litter ( 3%) were significantly lower where reintroduced ecosystem engineers
occurred compared to where they were absent, and fire behaviour modelling
illustrated this has substantial impacts on flame height and rate of spread. This
result has major implications for fire behaviour and management globally wherever
ecosystem engineers are now absent as the reduced leaf litter volumes where they
occur will lead to decreased flame height and rate of fire spread. This illustrates
the need to restore the full suite of biodiversity globally.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-17952017-12-31hb2016Centre for Wildlife Managemen
Fluctuating Fuzzy Funnels
It is well known that a D-string ending on a D3, D5 or D7 brane is described
in terms of a non-commutative fuzzy funnel geometry. In this article, we give a
numerical study of the fluctuations about this leading geometry. This allows us
to investigate issues related to the stability and moduli space of these
solutions. We comment on the comparison to the linearized fluctuations in
supergravity.Comment: 24 pages, 3 figures; v2 references added and correcte
The implications of biodiversity loss for the dynamics of wildlife in Australia
Our study aimed to identify the broad effects of native fossorial species on leaf litter, and make
inferences about their mechanistic influence on fire behavior using simulation models (Hayward et al.,
2016). This conceptual link has long been hypothesized, but here we present empirical evidence to
support it; our results suggest that native fossorial mammals have fire-suppressive effects because
their activity results in higher levels of litter decomposition, and a reduced fuel load across the
landscape. The expert commentaries build on this study and raise pertinent points for further
consideration.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-17952017-12-31hb2016Centre for Wildlife Managemen
Edge states in Gravity and Black Hole Physics
We show in the context of Einstein gravity that the removal of a spatial
region leads to the appearance of an infinite set of observables and their
associated edge states localized at its boundary. Such a boundary occurs in
certain approaches to the physics of black holes like the one based on the
membrane paradigm. The edge states can contribute to black hole entropy in
these models. A ``complementarity principle" is also shown to emerge whereby
certain ``edge" observables are accessible only to certain observers. The
physical significance of edge observables and their states is discussed using
their similarities to the corresponding quantities in the quantum Hall effect.
The coupling of the edge states to the bulk gravitational field is demonstrated
in the context of (2+1) dimensional gravity.Comment: Revtex file, 22 pg. ( refs added , minor typos corrected
Open Dielectric Branes
We derive leading terms in the effective actions describing the coupling of
bulk supergravity fields to systems of arbitrary numbers of Dp-branes and
D(p+4)-branes in type IIA/IIB string theory. We use these actions to
investigate the physics of Dp-D(p+4) systems in the presence of weak background
fields. In particular, we construct various solutions describing collections of
Dp-branes blown up into open D(p+2)-branes ending on D(p+4)-branes. The
configurations are stabilized by the presence of background fields and
represent an open-brane analogue of the Myers dielectric effect. To deduce the
D-brane actions, we use supersymmetry to derive operators corresponding to
moments of various conserved currents in the Berkooz-Douglas matrix model of
M-theory in the presence of longitudinal M5-branes and then use dualities to
relate these operators to the worldvolume operators appearing in the
Dp-D(p+4)-brane effective actions.Comment: 55 pages, LaTeX, 6 figures, v2: references adde
The fuzzy S^2 structure of M2-M5 systems in ABJM membrane theories
We analyse the fluctuations of the ground-state/funnel solutions proposed to
describe M2-M5 systems in the level-k mass-deformed/pure Chern-Simons-matter
ABJM theory of multiple membranes. We show that in the large N limit the
fluctuations approach the space of functions on the 2-sphere rather than the
naively expected 3-sphere. This is a novel realisation of the fuzzy 2-sphere in
the context of Matrix Theories, which uses bifundamental instead of adjoint
scalars. Starting from the multiple M2-brane action, a U(1) Yang-Mills theory
on R^{2,1} x S^2 is recovered at large N, which is consistent with a single
D4-brane interpretation in Type IIA string theory. This is as expected at large
k, where the semiclassical analysis is valid. Several aspects of the
fluctuation analysis, the ground-state/funnel solutions and the
mass-deformed/pure ABJM equations can be understood in terms of a discrete
noncommutative realisation of the Hopf fibration. We discuss the implications
for the possibility of finding an M2-brane worldvolume derivation of the
classical S^3 geometry of the M2-M5 system. Using a rewriting of the equations
of the SO(4)-covariant fuzzy 3-sphere construction, we also directly compare
this fuzzy 3-sphere against the ABJM ground-state/funnel solutions and show
them to be different.Comment: 60 pages, Latex; v2: references added; v3: typos corrected and
references adde
Higher dimensional geometries related to fuzzy odd-dimensional spheres
We study covariant Matrix realizations of for even as candidate fuzzy odd spheres following hep-th/0101001. As for
the fuzzy four sphere, these Matrix algebras contain more degrees of freedom
than the sphere itself and the full set of variables has a geometrical
description in terms of a higher dimensional coset. The fuzzy is
related to a higher dimensional coset .
These cosets are bundles where base and fibre are hermitian symmetric spaces.
The detailed form of the generators and relations for the Matrix algebras
related to the fuzzy three-spheres suggests Matrix actions which admit the
fuzzy spheres as solutions. These Matrix actions are compared with the BFSS,
IKKT and BMN Matrix models as well as some others. The geometry and
combinatorics of fuzzy odd spheres lead to some remarks on the transverse
five-brane problem of Matrix theories and the exotic scaling of the entropy of
5-branes with the brane number.Comment: 32 pages, v2 : ref and acknowledgment adde
Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.
BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362
Allometric scaling of maximum metabolic rate: The influence of temperature
1. Maximum aerobic metabolic rate, measured in terms of rate of oxygen consumption during exercise (VÌO2max), is well known to scale to body mass (M) with an exponent greater than the value of 0.75 predicted by models based on the geometry of systems that supply nutrients. 2. Recently, the observed scaling for VÌO2max (âM0.872) has been hypothesized to arise because of the temperature dependence of biological processes, and because large species show a greater increase in muscle temperature when exercising than do small species. 3. Based on this hypothesis, we predicted VÌO2max that will be positively related to ambient temperature, because heat loss is restricted at high temperatures and body temperature is likely to be elevated to a greater extent than during exercise in the cold. 4. This prediction was tested using a comparative phylogenetic generalized least-squares (PGLS) approach, and 34 measurements of six species of rodent (20.5-939 g) maximally exercising at temperatures from -16 to 30°C. 5. VÌO2max is unrelated to testing temperature, but is negatively related to acclimation temperature. We conclude that prolonged cold exposure increases exercise-induced VÌO2max by acting as a form of aerobic training in mammals, and that elevated muscle temperatures of large species do not explain the scaling of VÌO2max across taxa. © 2008 The Authors.Articl