4,801 research outputs found
Study of the impact of the post-MS evolution of the host star on the orbits of close-in planets. I. Sample definition and physical properties
Context: To date, more than 30 planets have been discovered around giant
stars, but only one of them has been found to be orbiting within 0.6 AU from
the host star, in direct contrast to what is observed for FGK dwarfs. This
result suggests that evolved stars destroy/engulf close-in planets during the
red giant phase.
Aims: We are conducting a radial velocity survey of 164 bright G and K giant
stars in the southern hemisphere with the aim of studying the effect of the
host star evolution on the inner structure of planetary systems. In this paper
we present the spectroscopic atmospheric parameters (\Teff, \logg, ,
[Fe/H]) and the physical properties (mass, radius, evolutionary status) of the
program stars. In addition, rotational velocities for all of our targets were
derived.
Methods: We used high resolution and high S/N spectra to measure the
equivalent widths of many Fe{\sc\,i} and Fe{\sc\,ii} lines, which were used to
derive the atmospheric parameters by imposing local thermodynamic and
ionization equilibrium. The effective temperatures and metallicities were used,
along with stellar evolutionary tracks to determine the physical properties and
evolutionary status of each star.
Results: We found that our targets are on average metal rich and they have
masses between \,1.0\,M and 3.5\,M. In addition, we found
that 122 of our targets are ascending the RGB, while 42 of them are on the HB
phase.Comment: Accepted for publication in A&
On the elastic moduli of three-dimensional assemblies of spheres: characterization and modeling of fluctuations in the particle displacement and rotation
The elastic moduli of four numerical random isotropic packings of Hertzian
spheres are studied. The four samples are assembled with different preparation
procedures, two of which aim to reproduce experimental compaction by vibration
and lubrication. The mechanical properties of the samples are found to change
with the preparation history, and to depend much more on coordination number
than on density.
Secondly, the fluctuations in the particle displacements from the average
strain are analysed, and the way they affect the macroscopic behavior analyzed.
It is found that only the average over equally oriented contacts of the
relative displacement these fluctuations induce is relevant at the macroscopic
scale. This average depends on coordination number, average geometry of the
contact network and average contact stiffness. As far as the separate
contributions from particle displacements and rotations are concerned, the
former is found to counteract the average strain along the contact normal,
while the latter do in the tangential plane. Conversely, the tangential
components of the center displacements mainly arise to enforce local
equilibrium, and have a small, and generally stiffening effect at the
macro-scale.
Finally, the fluctuations and the shear modulus that result from two
approaches available in the literature are estimated numerically. These
approaches are both based on the equilibrium of a small-sized representative
assembly. The improvement of these estimate with respect to the average strain
assumption indicates that the fluctuations relevant to the macroscopic behavior
occur with short correlation length.Comment: Submitted to IJS
Recommended from our members
Epitaxial growth of few-layer MoS2(0001) on FeS2{100}.
Physical vapour deposition of Mo on an FeS2{100} surface was performed at 170 K. Near-epitaxial growth of MoS2(0001) overlayers of the order of 1 nm thickness was observed when the Mo-covered substrate was subsequently heated to 600 K.The authors thank the EPSRC (grant ref. EP/E039782/1) for
funding.This is the final published version. It first appeared at http://pubs.rsc.org/en/Content/ArticleLanding/2015/CC/c4cc06628f#!divAbstract
A utilitarian antagonist: the zombie in popular video games
This article takes as its starting point the prevalence of the zombie in video games. I argue that, although the zombie games often superficially resemble filmic texts in their use of aesthetic and narrative, they must be understood, less as a set of conventions and thematic metaphors in the way that the zombie text has been read in film and television scholarship, and more as a utilisation of the zombie as a utilitarian antagonist that facilitates and permits the pleasures of violence and fantasy in video game play. Beginning with the Resident Evil and Left 4 Dead series of games I examine the way that games necessarily update the notion zombie as mass antagonist via the need to vary gameplay activity through different styles of adversary for players. At the same time I will demonstrate that, far from simply being the province of the survival horror genre, the zombie appears across an array of game forms, game cultures and game productions. The zombie highlights the participatory nature of game culture in the array of zombie 'mods' that users create to transform existing games into zombie based games, in particular in relation to titles such as the Call of Duty series. At the other end of the production spectrum the zombie features heavily in the little studied area of online flash games where the zombie can be found in a variety of game genres and forms. The zombie here often operates as a pastiche of popular zombie narratives in survival games (The Last Stand), parodic engagements with zombie conventions (Jetpacks and Zombies) or play with the notion of zombie pandemics (the Infectionator games). Here I situate the zombie game as a aesthetic genre that works to provide an easily understandable context for such interactive genres as survival horror, text adventures, shooting games, physics games and driving games, with the popularity of these enough to drive numerous dedicated hosting and link sites such as zombiegames.net. The pastiche element of these games extends into gamers social engagement with games. Online debates over the the appropriate actions or preparation for a zombie holocaust are commonplace on the internet in such spaces as Zombieresearch.net. Whilst many of these sites feature decidedly tongue in cheek engagement with the notion of the zombie apocalypse, the users of fora for games like Left 4 Dead and Dead Island tend to debate this directly in the terms of the games themselves, discussing their relative merits or realism. Some of these games also highlight the specific pleasures of identifying the zombie as protagonist of sorts. In discussing this I will return to online gaming and the Left 4 Dead games in which players may compete online as part of the zombie horde. Such games raise major questions for the issues of identification and immersion that are said to be at the centre of the game experience. I will also explore the parodic pleasures of many flash games that situate the player in the role of spreading zombie infections. Throughout this article I aim to demonstrate that the zombie in game culture is less a cultural metaphor than a combination of utilitarian antagonist and a persistent aesthetic; a means of providing style or pleasure to many games that relies on the intertextual and flexible nature of the zombie as popular cultural phenomenon
Spatial variability in the diversity and structure of faunal assemblages associated with kelp holdfasts (<i>Laminaria hyperborea</i>) in the northeast Atlantic
<p>Map indicating the locations of the four study regions in the UK, northeast Atlantic: (A) northern Scotland, (B) western Scotland, (C) southwest Wales and (D) southwest England. Smaller panels show the positions of the 3 study sites within each region.</p
Probabilistic Offline Policy Ranking with Approximate Bayesian Computation
In practice, it is essential to compare and rank candidate policies offline
before real-world deployment for safety and reliability. Prior work seeks to
solve this offline policy ranking (OPR) problem through value-based methods,
such as Off-policy evaluation (OPE). However, they fail to analyze special
cases performance (e.g., worst or best cases), due to the lack of holistic
characterization of policies performance. It is even more difficult to estimate
precise policy values when the reward is not fully accessible under sparse
settings. In this paper, we present Probabilistic Offline Policy Ranking
(POPR), a framework to address OPR problems by leveraging expert data to
characterize the probability of a candidate policy behaving like experts, and
approximating its entire performance posterior distribution to help with
ranking. POPR does not rely on value estimation, and the derived performance
posterior can be used to distinguish candidates in worst, best, and
average-cases. To estimate the posterior, we propose POPR-EABC, an Energy-based
Approximate Bayesian Computation (ABC) method conducting likelihood-free
inference. POPR-EABC reduces the heuristic nature of ABC by a smooth energy
function, and improves the sampling efficiency by a pseudo-likelihood. We
empirically demonstrate that POPR-EABC is adequate for evaluating policies in
both discrete and continuous action spaces across various experiment
environments, and facilitates probabilistic comparisons of candidate policies
before deployment.Comment: 19 pages with 7 pages main paper, 10 pages appendix. Accepted to AAAI
2024 main trac
Chiral Perturbation Theory in Few-Nucleon Systems
The low-energy effective theory of nuclear physics based on chiral symmetry
is reviewed. Topics discussed include the nucleon-nucleon force, few-body
potentials, isospin violation, pion-deuteron scattering, proton-neutron
radiative capture, pion photoproduction on the deuteron, and pion production in
proton-proton collisions.Comment: 15 pages, 2 figures, Latex, aipproc.sty and epsfig, invited talk at
the 6th Conference on the Intersections of Particle and Nuclear Physics, Big
Sky, May 199
A comparison between bright field and phase-contrast image analysis techniques in activated sludge morphological characterization
Different approaches using microscopy image analysis procedures were employed for characterization of activated sludge systems. The approaches varied mainly on the type of visualization and acquisition method used for collection of data. In this context, this study focused on the comparison of the two most common acquisition methods: bright field and phase-contrast microscopy. Images were acquired from seven different wastewater treatment plants for a combined period of two years. Advantages and disadvantages of each acquisition technique and the results are discussed. Bright field microscopy proved to be more simple and inexpensive and provided the best overall results.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/32329/2006, POCI/AMB/57069/200
Effects of Invertebrate Iridescent Virus 6 in Phyllophaga vandinei and Its Potential as a Biocontrol Delivery System
Invertebrate iridescent virus 6 (IIV6) was determined to cause infection in Phyllophaga vandinei Smyth (Coleoptera: Scarabaeidae) through a range of modes of transmissions. This is the first evidence of IIV6 infection in P. vandinei that caused both patent and sub-lethal infections in larvae and adults. Mortality rates were determined to be ∼30% when virus inoculum was injected into larvae or adults. Adults injected with virus showed dramatically altered behavior; injected beetles were not observed feeding or mating compared with adults injected with buffer or adults that were not injected. Tissue collected from infected adults resulted in infection when injected into healthy adults, as confirmed with PCR. PCR also confirmed that frass of infected larvae and adults contained virus, and when reconstituted frass from infected individuals was injected into healthy adults or larvae they become infected. Healthy adults could be infected by coming into contact with soil or plant material that had been exposed to infected adults as much as two weeks prior to introduction of nonvirus exposed adults. Although relatively low mortality resulted when adults or larvae were injected with the virus, the demonstration of horizontal transmission, potentially through frass of infected individuals, identifies a mode of transmission that may be exploited as a potential management tool to reduce P. vandinei
Dilution and magnification effects on image analysis applications in activated sludge characterization
The properties of activated sludge systems can be characterized using image analysis procedures.
When these systems operate with high biomass content, accurate sludge characterization requires samples to be
diluted. Selection of the best image acquisition magnification is directly related to the amount of biomass
screened. The aim of the present study was to survey the effects of dilution and magnification on the assessment
of aggregated and filamentous bacterial content and structure using image analysis procedures. Assessments of
biomass content and structure were affected by dilutions. Therefore, the correct operating dilution requires
careful consideration. Moreover, the acquisition methodology comprising a 100 magnification allowed data
on aggregated and filamentous biomass to be determined and smaller aggregates to be identified and
characterized, without affecting the accuracy of lower magnifications regarding biomass representativeness.AGERE (Empresa de
Águas, Efluentes e Resíduos de Braga – EM) and AGS(Administração e Gestão de Sistemas de Salubridade, S.A.)Fundação para a Ciência e Tecnologia (FCT
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