1,976 research outputs found
Modeling the Development of Early Rice Agriculture: Ethnoecological Perspectives from Northeast Thailand
Ethnoecological research in northeast Thailand suggests that both wedand and upland rice cultivation emerged from a common beginning in manipulation of wild rice in seasonal swamps. The field research revealed extensive variants of wedand rice cultivation that show how it can be viewed as mimicking wild rice ecology and hence as an extension of rice's natural environment. This picture contrasts with the traditional portrayal of wedand rice cultivation as necessarily labor intensive, technologically advanced, and environmentally transformative. Upland cultivation of rice would have emerged as rice was grown in increasingly dry locales, necessitating genetic and physiological adaptations in nutrient absorption and timing of maturity. It is hypothesized that upland rice was then integrated into a preexisting swidden cultivation strategy. Furthermore, it is suggested that the early subsistence strategies of northeast Thailand included cultivation of wedand rice in permanent fields using extensive strategies, cultivation of uplands (of species yet to be determined) probably using shifting field strategies, as well as collection of diverse wild resources. KEYWORDS: rice, agriculture, swiddening, Ban Chiang cultural tradition, ethnoecology, Thailand
Linear theory and violent relaxation in long-range systems: a test case
In this article, several aspects of the dynamics of a toy model for longrange
Hamiltonian systems are tackled focusing on linearly unstable unmagnetized
(i.e. force-free) cold equilibria states of the Hamiltonian Mean Field (HMF).
For special cases, exact finite-N linear growth rates have been exhibited,
including, in some spatially inhomogeneous case, finite-N corrections. A random
matrix approach is then proposed to estimate the finite-N growth rate for some
random initial states. Within the continuous, , approach,
the growth rates are finally derived without restricting to spatially
homogeneous cases. All the numerical simulations show a very good agreement
with the different theoretical predictions. Then, these linear results are used
to discuss the large-time nonlinear evolution. A simple criterion is proposed
to measure the ability of the system to undergo a violent relaxation that
transports it in the vicinity of the equilibrium state within some linear
e-folding times
A prescription for the asteroseismic surface correction
In asteroseismology, the surface effect is a disparity between the observed
and the modelled oscillation frequencies. It originates from improper modelling
of the surface layers in stars with solar-like oscillations. Correcting the
surface effect usually requires using functions with free parameters, which are
conventionally fitted to the observed frequencies. On the basis that the
correction should vary smoothly across the H--R diagram, we parameterize it as
a simple function of three stellar surface properties: surface gravity,
effective temperature, and metallicity. We determine this function by fitting
stars ranging from main-sequence dwarfs to red-giant-branch stars. The absolute
amount of the surface correction increases with surface gravity, but the ratio
between it and decreases. Applying the prescription has an
advantage of eliminating unrealistic surface correction, which improves
parameter estimations with stellar modelling. Using two open clusters, we found
that adopting the prescription can help reduce the scatter of the model-derived
ages for each star in the same cluster. For an application, we provide a new
revision for the scaling relation, using our prescription to
account for the surface effect in models. The values of the correction factor,
, are up to 2\% smaller than those determined without the
surface effect considered, suggesting decreases of up to 4\% in asteroseismic
scaling radii and up to 8\% in asteroseismic scaling masses. This revision
brings the asteroseismic properties into agreement with those determined from
eclipsing binaries. Finally, the new correction factor and the stellar models
with the corrected frequencies are made publicly available.Comment: 11 pages, 9 figures. Submitted to MNRAS. All comments (including on
refs) are welcom
TSS-1R Mission Failure Investigation Board
Reasons for the tether separation during the Tethered Satellite System (TSS-1) Mission are investigated. Lessons learned are presented
Deficiency of the zinc finger protein ZFP106 causes motor and sensory neurodegeneration
Acknowledgements We are indebted to Jim Humphries, JennyCorrigan, LizDarley, Elizabeth Joynson, Natalie Walters, Sara Wells and the whole necropsy, histology, genotyping and MLC ward 6 teams at MRC Harwell for excellent technical assistance. We thank the staff of the WTSI Illumina Bespoke Team for the RNA-seq data, the Sanger Mouse Genetics Project for the initial mouse characterization and Dr David Adams for critical reading of the manuscript. We also thank KOMP for the mouse embryonic stem cells carrying the knockout first promoter-less allele (tm1a(KOMP)Wtsi) within Zfp016. Conflict of Interest statement. None declared. Funding This work was funded by the UK Medical Research Council (MRC) to A.A.-A. and a Motor Neurone Disease Association (MNDA) project grant to A.A.-A. and EMCF. D.L.H.B. is a Wellcome Trust Senior Clinical Scientist Fellow and P.F. is a MRC/MNDA Lady Edith Wolfson Clinician Scientist Fellow. Funding to pay the Open Access publication charges for this article was provided by the MRC grant number: MC_UP_A390_1106.Peer reviewedPublisher PD
Changes in the Frontotemporal Cortex and Cognitive Correlates in First-Episode Psychosis
Background: Loss of cortical volume in frontotemporal regions has been reported in patients with schizophrenia and their relatives. Cortical area and thickness are determined by different genetic processes, and measuring these parameters separately may clarify disturbances in corticogenesis relevant to schizophrenia. Our study also explored clinical and cognitive correlates of these parameters.Methods: Thirty-seven patients with first-episode psychosis (34 schizophrenia, 3 schizoaffective disorder) and 38 healthy control subjects matched for age and sex took part in the study. Imaging was performed on an magnetic resonance imaging 1.5-T scanner. Area and thickness of the frontotemporal cortex were measured using a surface-based morphometry method (Freesurfer). All subjects underwent neuropsychologic testing that included measures of premorbid and current IQ, working and verbal memory, and executive function.Results: Reductions in cortical area, more marked in the temporal cortex, were present in patients. Overall frontotemporal cortical thickness did not differ between groups, although regional thinning of the right superior temporal region was observed in patients. There was a significant association of both premorbid IQ and IQ at disease onset with area, but not thickness, of the frontotemporal cortex, and working memory span was associated with area of the frontal cortex. These associations remained significant when only patients with schizophrenia were considered.Conclusions: Our results suggest an early disruption of corticogenesis in schizophrenia, although the effect of subsequent environmental factors cannot be excluded. In addition, cortical abnormalities are subject to regional variations and differ from those present in neurodegenerative diseases
Structure formation with a self-tuning scalar field
A scalar field with an exponential potential has the particular property that
it is attracted into a solution in which its energy scales as the dominant
component (radiation or matter) of the Universe, contributing a fixed fraction
of the total energy density. We study the growth of perturbations in a CDM
dominated universe with this extra field, with an initial flat
spectrum of adiabatic fluctuations. The observational constraints from
structure formation are satisfied as well, or better, than in other models,
with a contribution to the energy density from the scalar field which is small enough to be consistent with entry into the attractor
prior to nucleosynthesis.Comment: 4 pages, uses RevTex, 2 figure
Quintessence and Gravitational Waves
We investigate some aspects of quintessence models with a non-minimally
coupled scalar field and in particular we show that it can behave as a
component of matter with . We study the
properties of gravitational waves in this class of models and discuss their
energy spectrum and the cosmic microwave background anisotropies they induce.
We also show that gravitational waves are damped by the anisotropic stress of
the radiation and that their energy spectrum may help to distinguish between
inverse power law potential and supergravity motivated potential. We finish by
a discussion on the constraints arising from their density parameter
\Omega_\GW.Comment: 21 pages, 18 figures, fianl version, accepted for publication in PR
- …