330 research outputs found
Montecarlo simulation of the role of defects as the melting mechanism
We study in this paper the melting transition of a crystal of fcc structure
with the Lennard-Jones potential, by using isobaric-isothermal Monte Carlo
simulations.
Local and collective updates are sequentially used to optimize the
convergence. We show the important role played by defects in the melting
mechanism in favor of modern melting theories.Comment: 6 page, 10 figures included. Corrected version to appear in Phys.
Rev.
Supersymmetric Electroweak Corrections to Charged Higgs Boson Production in Association with a Top Quark at Hadron Colliders
We calculate the and supersymmetric electroweak corrections to the cross section
for the charged Higgs boson production in association with a top quark at the
Tevatron and the LHC. These corrections arise from the quantum effects which
are induced by potentially large Yukawa couplings from the Higgs sector and the
chargino-top(bottom)-sbottom(stop) couplings,
neutralino-top(bottom)-stop(sbottom) couplings and charged Higgs-stop-sbottom
couplings. They can decrease or increase the cross section depending on
but are not very sensitive to the mass of the charged Higgs boson
for high . At low the corrections decrease the total
cross sections significantly, which exceed -12% for below
at both the Tevatron and the LHC, but for the
corrections can become very small at the LHC. For high
these corrections can decrease or increase the total cross sections, and the
magnitude of the corrections are at most a few percent at both the Tevatron and
the LHC.Comment: 28 pages including 4 eps figure
Phenomenology of non-standard Z couplings in exclusive semileptonic b -> s transitions
The rare decays , and
are analyzed in a generic scenario where New Physics effects
enter predominantly via penguin contributions. We show that this
possibility is well motivated on theoretical grounds, as the vertex
is particularly susceptible to non-standard dynamics. In addition, such a
framework is also interesting phenomenologically since the coupling
is rather poorly constrained by present data. The characteristic features of
this scenario for the relevant decay rates and distributions are investigated.
We emphasize that both sign and magnitude of the forward-backward asymmetry of
the decay leptons in , , carry sensitive information on New Physics. The observable is proposed as a useful probe of
non-standard CP violation in couplings.Comment: Minor modifications; version to appear in Phys. Rev.
A systematic account of the genus Plagiostoma (Gnomoniaceae, Diaporthales) based on morphology, host-associations, and a four-gene phylogeny
Members of the genus Plagiostoma inhabit leaves, stems, twigs, and
branches of woody and herbaceous plants predominantly in the temperate
Northern Hemisphere. An account of all known species of Plagiostoma
including Cryptodiaporthe is presented based on analyses of
morphological, cultural, and DNA sequence data. Multigene phylogenetic
analyses of DNA sequences from four genes (ÎČ-tubulin, ITS,
rpb2, and tef1-α) revealed eight previously
undescribed phylogenetic species and an association between a clade composed
of 11 species of Plagiostoma and the host family Salicaceae.
In this paper these eight new species of Plagiostoma are described,
four species are redescribed, and four new combinations are proposed. A key to
the 25 accepted species of Plagiostoma based on host, shape, and size
of perithecia, perithecial arrangement in the host, and microscopic
characteristics of the asci and ascospores is provided. Disposition of
additional names in Cryptodiaporthe and Plagiostoma is also
discussed
Workplace productivity and office type: an evaluation of office occupier differences based on age and gender
Purpose
Open plan office environments are considered to offer workplace productivity benefits because of the opportunities that they create for interaction and knowledge exchange, but more recent research has highlighted noise, distraction and loss of privacy as significant productivity penalties with this office layout. This study aims to investigate if the purported productivity benefits of open plan outweigh the potential productivity penalties.
Design/methodology/approach
Previous research suggests that office environments are experienced differently according to the gender and age of the occupier across both open-plan and enclosed configurations. Empirical research undertaken with office occupiers in the Middle East (N=220) led to evaluations to establish the impact different offices had on perceived productivity. Factor analysis was used to establish five underlying components of office productivity. The five factors are subsequently used as the basis for comparison between office occupiers based on age, gender and office type.
Findings
This research shows that benefits and penalties to workplace productivity are experienced equally across open-plan and enclosed office environments. The greatest impact on perceived workplace productivity however was availability of a variety of physical layouts, control over interaction and the 'downtime' offered by social interaction points. Male occupiers and those from younger generations were also found to consider the office environment to have more of a negative impact on their perceived workplace productivity compared to female and older occupiers.
Originality/value
The originality of this paper is that it develops the concept of profiling office occupiers with the aim of better matching office provision. This paper aims to establish different occupier profiles based on age, gender and office type. Data analysis techniques such as factor analysis and t-test analysis identify the need for different spaces so that occupiers can choose the most appropriate space to best undertake a particular work task. In addition, it emphasises the value that occupiers place on âdowntimeâ leading to the need for appropriate social space
A rotação de cultura reduz a matocompetição e aumenta o teor de clorofila e a produtividade do arroz
Planck 2015 results. XXVII. The Second Planck Catalogue of Sunyaev-Zeldovich Sources
We present the all-sky Planck catalogue of Sunyaev-Zeldovich (SZ) sources detected from the 29 month full-mission data. The catalogue (PSZ2) is the largest SZ-selected sample of galaxy clusters yet produced and the deepest all-sky catalogue of galaxy clusters. It contains 1653 detections, of which 1203 are confirmed clusters with identified counterparts in external data-sets, and is the first SZ-selected cluster survey containing > confirmed clusters. We present a detailed analysis of the survey selection function in terms of its completeness and statistical reliability, placing a lower limit of 83% on the purity. Using simulations, we find that the Y5R500 estimates are robust to pressure-profile variation and beam systematics, but accurate conversion to Y500 requires. the use of prior information on the cluster extent. We describe the multi-wavelength search for counterparts in ancillary data, which makes use of radio, microwave, infra-red, optical and X-ray data-sets, and which places emphasis on the robustness of the counterpart match. We discuss the physical properties of the new sample and identify a population of low-redshift X-ray under- luminous clusters revealed by SZ selection. These objects appear in optical and SZ surveys with consistent properties for their mass, but are almost absent from ROSAT X-ray selected samples
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
Planck intermediate results. VIII. Filaments between interacting clusters
About half of the baryons of the Universe are expected to be in the form of
filaments of hot and low density intergalactic medium. Most of these baryons
remain undetected even by the most advanced X-ray observatories which are
limited in sensitivity to the diffuse low density medium. The Planck satellite
has provided hundreds of detections of the hot gas in clusters of galaxies via
the thermal Sunyaev-Zel'dovich (tSZ) effect and is an ideal instrument for
studying extended low density media through the tSZ effect. In this paper we
use the Planck data to search for signatures of a fraction of these missing
baryons between pairs of galaxy clusters. Cluster pairs are good candidates for
searching for the hotter and denser phase of the intergalactic medium (which is
more easily observed through the SZ effect). Using an X-ray catalogue of
clusters and the Planck data, we select physical pairs of clusters as
candidates. Using the Planck data we construct a local map of the tSZ effect
centered on each pair of galaxy clusters. ROSAT data is used to construct X-ray
maps of these pairs. After having modelled and subtracted the tSZ effect and
X-ray emission for each cluster in the pair we study the residuals on both the
SZ and X-ray maps. For the merging cluster pair A399-A401 we observe a
significant tSZ effect signal in the intercluster region beyond the virial
radii of the clusters. A joint X-ray SZ analysis allows us to constrain the
temperature and density of this intercluster medium. We obtain a temperature of
kT = 7.1 +- 0.9, keV (consistent with previous estimates) and a baryon density
of (3.7 +- 0.2)x10^-4, cm^-3. The Planck satellite mission has provided the
first SZ detection of the hot and diffuse intercluster gas.Comment: Accepted by A&
Leaf-inhabiting genera of the Gnomoniaceae, Diaporthales
The Gnomoniaceae are characterised by ascomata that are generally
immersed, solitary, without a stroma, or aggregated with a rudimentary stroma,
in herbaceous plant material especially in leaves, twigs or stems, but also in
bark or wood. The ascomata are black, soft-textured, thin-walled, and
pseudoparenchymatous with one or more central or eccentric necks. The asci
usually have a distinct apical ring. The Gnomoniaceae includes
species having ascospores that are small, mostly less than 25 ÎŒm long,
although some are longer, and range in septation from non-septate to
one-septate, rarely multi-septate. Molecular studies of the
Gnomoniaceae suggest that the traditional classification of genera
based on characteristics of the ascomata such as position of the neck and
ascospores such as septation have resulted in genera that are not
monophyletic. In this paper the concepts of the leaf-inhabiting genera in the
Gnomoniaceae are reevaluated using multiple genes, specifically
nrLSU, translation elongation factor 1-alpha (tef1-α), and RNA
polymerase II second largest subunit (rpb2) for 64 isolates. ITS sequences
were generated for 322 isolates. Six genera of leaf-inhabiting
Gnomoniaceae are defined based on placement of their type species
within the multigene phylogeny. The new monotypic genus
Ambarignomonia is established for an unusual species, A.
petiolorum. A key to 59 species of leaf-inhabiting Gnomoniaceae is
presented and 22 species of Gnomoniaceae are described and
illustrated
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