442 research outputs found
Genetic Assimilation and Canalisation in the Baldwin Effect
The Baldwin Effect indicates that individually learned behaviours acquired during an organism’s lifetime can influence the evolutionary path taken by a population, without any direct Lamarckian transfer of traits from phenotype to genotype. Several computational studies modelling this effect have included complications that restrict its applicability. Here we present a simplified model that is used to reveal the essential mechanisms and highlight several conceptual issues that have not been clearly defined in prior literature. In particular, we suggest that canalisation and genetic assimilation, often conflated in previous studies, are separate concepts and the former is actually not required for non-heritable phenotypic variation to guide genetic variation. Additionally, learning, often considered to be essential for the Baldwin Effect, can be replaced with a more general phenotypic plasticity model. These simplifications potentially permit the Baldwin Effect to operate in much more general circumstances
A Gaussian distribution for refined DT invariants and 3D partitions
We show that the refined Donaldson-Thomas invariants of C3, suitably
normalized, have a Gaussian distribution as limit law. Combinatorially these
numbers are given by weighted counts of 3D partitions. Our technique is to use
the Hardy-Littlewood circle method to analyze the bivariate asymptotics of a
q-deformation of MacMahon's function. The proof is based on that of E.M. Wright
who explored the single variable case.Comment: 11 pages and 3 figure
Boundary Liouville theory at c=1
The c=1 Liouville theory has received some attention recently as the
Euclidean version of an exact rolling tachyon background. In an earlier paper
it was shown that the bulk theory can be identified with the interacting c=1
limit of unitary minimal models. Here we extend the analysis of the c=1-limit
to the boundary problem. Most importantly, we show that the FZZT branes of
Liouville theory give rise to a new 1-parameter family of boundary theories at
c=1. These models share many features with the boundary Sine-Gordon theory, in
particular they possess an open string spectrum with band-gaps of finite width.
We propose explicit formulas for the boundary 2-point function and for the
bulk-boundary operator product expansion in the c=1 boundary Liouville model.
As a by-product of our analysis we also provide a nice geometric interpretation
for ZZ branes and their relation with FZZT branes in the c=1 theory.Comment: 37 pages, 1 figure. Minor error corrected, slight change in result
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Soil-landscape and climatic relationships in the middle Miocene of the Madrid Basin
The Miocene alluvial-lacustrine sequences of the Madrid Basin, Spain, formed in highly varied landscapes. The presence of various types of palaeosols allows assessment of the effects of local and external factors onsedimentation, pedogenesis and geomorphological development. In the northern, more arid, tectonicallyactive arca, soils were weakly developed in aggrading alluvial fans, dominated by mass flows. reflecting high sedimentation rates. In more distal parts of the fans and in playa lakes calcretes and dolocretes developed: the former were associated with Mg-poor fan sediments whitc: the latter formed on Mg-rich lake clays exposed during minar lake lowstands. The nonh-east part of the basin had a less arid climate. Alluvial fans in this area were dominated by stream Aood deposits, sourced by carbonate terrains. Floodplain and freshwater lakc deposits formed in distal areas. The high local supply of calcium carbonate may have contributed to the preferential developmenl on calcretes on the fans. Both the fan and floodplain palaeosols exhibit pedofacies relationships and more mature soils developed in settings more distant from the sediment sources. Palaeosols also developed on pond and lake margin carbonates, and led to the formation of palustrine limestones. The spatial distributions and stratigraphies of palaeosols in the Madrid Basin alluvial fans suggest that soil formation was controlled by local factors. These palaeosols differ from those seen in Quatemary fans. Which are characterized by climatically induced periods of stability and instability
Ramond-Ramond Fields, Fractional Branes and Orbifold Differential K-Theory
We study D-branes and Ramond-Ramond fields on global orbifolds of Type II
string theory with vanishing H-flux using methods of equivariant K-theory and
K-homology. We illustrate how Bredon equivariant cohomology naturally realizes
stringy orbifold cohomology. We emphasize its role as the correct cohomological
tool which captures known features of the low-energy effective field theory,
and which provides new consistency conditions for fractional D-branes and
Ramond-Ramond fields on orbifolds. We use an equivariant Chern character from
equivariant K-theory to Bredon cohomology to define new Ramond-Ramond couplings
of D-branes which generalize previous examples. We propose a definition for
groups of differential characters associated to equivariant K-theory. We derive
a Dirac quantization rule for Ramond-Ramond fluxes, and study flat
Ramond-Ramond potentials on orbifolds.Comment: 46 pages; v2: typos correcte
Formation of a White-Light Jet within a Quadrupolar Magnetic Configuration
We analyze multi-wavelength and multi-viewpoint observations of a large-scale
event viewed on 7 April 2011 originating from an active region complex. The
activity leads to a white-light jet being formed in the outer corona. The
topology and evolution of the coronal structures were imaged in high resolution
using the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
Observatory (SDO). In addition, large field-of-view images of the corona were
obtained using the Sun Watcher using Active Pixel System detector and Image
Processing (SWAP) telescope onboard the PRoject for Onboard Autonomy (PROBA2)
microsatellite, providing evidence for the connectivity of the coronal
structures with outer coronal features that were imaged with the Large Angle
Spectrometric Coronagraph (LASCO) C2 on Solar and Heliospheric Observatory
(SOHO). The data-sets reveal an Eiffel-tower type jet configuration extending
into a narrow jet in the outer corona. The event starts from the growth of a
dark area in the central part of the structure. The darkening was also observed
in projection on the disk by the Solar TErrestrial RElations Observatory-Ahead
(STEREO-A) spacecraft from a different point of view. We assume that the dark
volume in the corona descends from a coronal cavity of a flux rope that moved
up higher in the corona but still failed to erupt. The quadrupolar magnetic
configuration corresponds to a saddle-like shape of the dark volume and
provides a possibility for the plasma to escape along the open field lines into
the outer corona, forming the white-light jet.Comment: 15 pages, 10 figure
Photospheric and Subphotospheric Dynamics of Emerging Magnetic Flux
Magnetic fields emerging from the Sun's interior carry information about
physical processes of magnetic field generation and transport in the convection
zone. Soon after appearance on the solar surface the magnetic flux gets
concentrated in sunspot regions and causes numerous active phenomena on the
Sun. This paper discusses some properties of the emerging magnetic flux
observed on the solar surface and in the interior. A statistical analysis of
variations of the tilt angle of bipolar magnetic regions during the emergence
shows that the systematic tilt with respect to the equator (the Joy's law) is
most likely established below the surface. However, no evidence of the
dependence of the tilt angle on the amount of emerging magnetic flux, predicted
by the rising magnetic flux rope theories, is found. Analysis of surface plasma
flows in a large emerging active region reveals strong localized upflows and
downflows at the initial phase of emergence but finds no evidence for
large-scale flows indicating future appearance a large-scale magnetic
structure. Local helioseismology provides important tools for mapping
perturbations of the wave speed and mass flows below the surface. Initial
results from SOHO/MDI and GONG reveal strong diverging flows during the flux
emergence, and also localized converging flows around stable sunspots. The wave
speed images obtained during the process of formation of a large active region,
NOAA 10488, indicate that the magnetic flux gets concentrated in strong field
structures just below the surface. Further studies of magnetic flux emergence
require systematic helioseismic observations from the ground and space, and
realistic MHD simulations of the subsurface dynamics.Comment: 21 pages, 15 figures, to appear in Space Science Review
Primary, allied health, geriatric, pain and palliative healthcare service utilisation by aged care residents, 2012-2017.
OnlinePublObjectives To examine the incidence and trends in primary care, allied health, geriatric, pain and palliative care service use by permanent residential aged care (PRAC) residents and the older Australian population. Methods Repeated cross-sectional analyses on PRAC residents (N = 318,484) and the older (≥65 years) Australian population (N ~ 3.5 million). Outcomes were Medicare Benefits Schedule (MBS) subsidised primary care, allied health, geriatric, pain and palliative services between 2012-13 and 2016-17. GEE Poisson models estimated incidence rates and incidence rate ratios (IRR). Results In 2016-17, PRAC residents had a median of 13 (interquartile range [IQR] 5-19) regular general medical practitioner (GP) attendances, 3 (IQR 1-6) after-hours attendances and 5% saw a geriatrician. Highlights of utilisation changes from 2012-13 to 2016-17 include the following: GP attendances increased by 5%/year (IRR = 1.05, 95% confidence interval [CI] 1.05-1.05) for residents compared to 1%/year (IRR = 1.01, 95%CI 1.01-1.01) for the general population. GP after-hours attendances increased by 15%/year (IRR = 1.15, 95%CI 1.14-1.15) for residents and 9%/year (IRR = 1.08, 95%CI 1.07-1.20) for the general population. GP management plans increased by 12%/year (IRR = 1.12, 95%CI 1.11-1.12) for residents and 10%/year (IRR = 1.10, 95%CI 1.09-1.11) for the general population. Geriatrician consultations increased by 28%/year (IRR = 1.28, 95%CI 1.27-1.29) for residents compared to 14%/year (IRR = 1.14, 95%CI 1.14-1.15) in the general population. Conclusions The utilisation of most examined services increased in both cohorts over time. Preventive and management care, by primary care and allied health care providers, was low and likely influences the utilisation of other attendances. PRAC residents' access to pain, palliative and geriatric medicine services is low and may not address the residents' needs.Maria C. Inacio, Luke Collier, Tracy Air, Kailash Thapaliya, Maria Crotty, Helena Williams, Steve L. Wesselingh, Andrew Kellie, David Roder, Adrienne Lewis, Gillian Harvey, Janet K. Sluggett, Monica Cations, Tiffany K. Gill, Jyoti Khadka, Gillian E. Caughe
The 22-Year Hale Cycle in cosmic ray flux: evidence for direct heliospheric modulation
The ability to predict times of greater galactic cosmic ray (GCR) fluxes is important for reducing the hazards caused by these particles to satellite communications, aviation, or astronauts. The 11-year solar-cycle variation in cosmic rays is highly correlated with the strength of the heliospheric magnetic field. Differences in GCR flux during alternate solar cycles yield a 22-year cycle, known as the Hale Cycle, which is thought to be due to different particle drift patterns when the northern solar pole has predominantly positive (denoted as qA>0 cycle) or negative (qA0 cycles than for qA0 and more sharply peaked for qA0 solar cycles, when the difference in GCR flux is most apparent. This suggests that particle drifts may not be the sole mechanism responsible for the Hale Cycle in GCR flux at Earth. However, we also demonstrate that these polarity-dependent heliospheric differences are evident during the space-age but are much less clear in earlier data: using geomagnetic reconstructions, we show that for the period of 1905 - 1965, alternate polarities do not give as significant a difference during the declining phase of the solar cycle. Thus we suggest that the 22-year cycle in cosmic-ray flux is at least partly the result of direct modulation by the heliospheric magnetic field and that this effect may be primarily limited to the grand solar maximum of the space-age
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