931 research outputs found
Assessment of seasonal winter temperature forecast errors in the regcm model over northern Vietnam
This study verified the seasonal six-month forecasts for winter temperatures for northern Vietnam in 1998–2018 using a regional climate model (RegCM4) with the boundary conditions of the climate forecast system Version 2 (CFSv2) from the National Centers for Environmental Prediction (NCEP). First, different physical schemes (land-surface process, cumulus, and radiation parameterizations) in RegCM4 were applied to generate 12 single forecasts. Second, the simple ensemble forecasts were generated through the combinations of those different physical formulations. Three subclimate regions (R1, R2, R3) of northern Vietnam were separately tested with surface observations and a reanalysis dataset (Japanese 55-year reanalysis (JRA55)). The highest sensitivity to the mean monthly temperature forecasts was shown by the land-surface parameterizations (the biosphere−atmosphere transfer scheme (BATS) and community land model version 4.5 (CLM)). The BATS forecast groups tended to provide forecasts with lower temperatures than the actual observations, while the CLM forecast groups tended to overestimate the temperatures. The forecast errors from single forecasts could be clearly reduced with ensemble mean forecasts, but ensemble spreads were less than those root-mean-square errors (RMSEs). This indicated that the ensemble forecast was underdispersed and that the direct forecast from RegCM4 needed more postprocessing
Cyclopropanation using flow-generated diazo compounds.
We have devised a room temperature process for the cyclopropanation of electron-poor olefins using unstabilised diazo compounds, generated under continuous flow conditions. This protocol was applied to a wide range of different diazo species to generate functionalised cyclopropanes which are valuable 3D building blocks.We are grateful to Pfizer Worldwide Research and Development
(CB, RJI and JMH), the Swiss National Science Foundation
(DNT), CAPES (RL, no 9865/13-6) and the EPSRC (SVL,
grant no EP/K0099494/1 and no EP/K039520/1) for financial
support.This is the final published article, originally published in Organic & Biomolecular Chemistry, 2015,13, 2550-2554 DOI: 10.1039/C5OB00019
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A Schrödinger Equation for Evolutionary Dynamics
We establish an analogy between the Fokker–Planck equation describing evolutionary landscape dynamics and the Schrödinger equation which characterizes quantum mechanical particles, showing that a population with multiple genetic traits evolves analogously to a wavefunction under a multi-dimensional energy potential in imaginary time. Furthermore, we discover within this analogy that the stationary population distribution on the landscape corresponds exactly to the ground-state wavefunction. This mathematical equivalence grants entry to a wide range of analytical tools developed by the quantum mechanics community, such as the Rayleigh–Ritz variational method and the Rayleigh–Schrödinger perturbation theory, allowing us not only the conduct of reasonable quantitative assessments but also exploration of fundamental biological inquiries. We demonstrate the effectiveness of these tools by estimating the population success on landscapes where precise answers are elusive, and unveiling the ecological consequences of stress-induced mutagenesis—a prevalent evolutionary mechanism in pathogenic and neoplastic systems. We show that, even in an unchanging environment, a sharp mutational burst resulting from stress can always be advantageous, while a gradual increase only enhances population size when the number of relevant evolving traits is limited. Our interdisciplinary approach offers novel insights, opening up new avenues for deeper understanding and predictive capability regarding the complex dynamics of evolving populations
A Schr\"odinger Equation for Evolutionary Dynamics
We establish an analogy between the Fokker-Planck equation describing
evolutionary landscape dynamics and the Schr\"{o}dinger equation which
characterizes quantum mechanical particles, showing how a population with
multiple genetic traits evolves analogously to a wavefunction under a
multi-dimensional energy potential in imaginary time. Furthermore, we discover
within this analogy that the stationary population distribution on the
landscape corresponds exactly to the ground-state wavefunction. This
mathematical equivalence grants entry to a wide range of analytical tools
developed by the quantum mechanics community, such as the Rayleigh-Ritz
variational method and the Rayleigh-Schr\"{o}dinger perturbation theory,
allowing us to not only make reasonable quantitative assessments but also
explore fundamental biological inquiries. We demonstrate the effectiveness of
these tools by estimating the population success on landscapes where precise
answers are elusive, and unveiling the ecological consequences of
stress-induced mutagenesis -- a prevalent evolutionary mechanism in pathogenic
and neoplastic systems. We show that, even in a unchanging environment, a sharp
mutational burst resulting from stress can always be advantageous, while a
gradual increase only enhances population size when the number of relevant
evolving traits is limited. Our interdisciplinary approach offers novel
insights, opening up new avenues for deeper understanding and predictive
capability regarding the complex dynamics of evolving populations
Spectroscopy of Luminous Compact Blue Galaxies in Distant Clusters I. Spectroscopic Data
We used the DEIMOS spectrograph on the Keck II Telescope to obtain spectra of
galaxies in the fields of five distant, rich galaxy clusters over the redshift
range 0.5 < z < 0.9 in a search for luminous, compact, blue galaxies (LCBGs).
Unlike traditional studies of galaxy clusters, we preferentially targeted blue
cluster members identified via multi-band photometric pre-selection based on
imaging data from the WIYN telescope. Of the 1288 sources that we targeted, we
determined secure spectroscopic redshifts for 848 sources, yielding a total
success rate of 66%. Our redshift measurements are in good agreement with those
previously reported in the literature, except for 11 targets which we believe
were previously in error. Within our sample, we confirm the presence of 53
LCBGs in the five galaxy clusters. The clusters all stand out as distinct peaks
in the redshift distribution of LCBGs with the average number density of LCBGs
ranging from 1.65+-0.25 Mpc^-3 at z=0.55 to 3.13+-0.65 Mpc^-3 at z=0.8. The
number density of LCBGs in clustes exceeds the field desnity by a factor of
749+-116 at z=0.55; at z=0.8, the corresponding ratio is E=416+-95. At z=0.55,
this enhancement is well above that seen for blue galaxies or the overall
cluster population, indicating that LCBGs are preferentially triggered in
high-density environments at intermediate redshifts.Comment: 45 pages, 19 figures, accepted to ApJ. For Full resolution figure and
data tables, see http://www.salt.ac.za/~crawford/projects/deimos
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