1,830 research outputs found
Searching for Faint Comoving Companions to the α Centauri system in the VVV Survey Infrared Images
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2017 Crown Copyright. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.The VVV survey has observed the southern disk of the Milky Way in the near infrared, covering 240 deg in the filters. We search the VVV Survey images in a 19 deg field around Centauri, the nearest stellar system to the Sun, to look for possible overlooked companions that the baseline in time of VVV would be able to uncover. The photometric depth of our search reaches 19.3 mag, 19 mag, and 17 mag. This search has yielded no new companions in Centauri system, setting an upper mass limit for any unseen companion well into the brown dwarf/planetary mass regime. The apparent magnitude limits were turned into effective temperature limits, and the presence of companion objects with effective temperatures warmer than 325K can be ruled out using different state-of-the-art atmospheric models. These limits were transformed into mass limits using evolutionary models, companions with masses above 11 M were discarded, extending the constraints recently provided in the literature up to projected distances of dPeer reviewedFinal Published versio
Variational collocation for systems of coupled anharmonic oscillators
We have applied a collocation approach to obtain the numerical solution to
the stationary Schr\"odinger equation for systems of coupled oscillators. The
dependence of the discretized Hamiltonian on scale and angle parameters is
exploited to obtain optimal convergence to the exact results. A careful
comparison with results taken from the literature is performed, showing the
advantages of the present approach.Comment: 14 pages, 10 table
Transient, unsettling and creative space: Experiences of liminality through the accounts of Chinese students on a UK-based MBA
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ The Author(s) 2009.This article explores the experiences of liminality through the accounts of Chinese students on a UK-based MBA programme. The transient nature of the MBA experience, as well as the international status of the Chinese student, is resonant with conceptualizations of liminality as âin betweenâ space. Based on semi-structured interviews with 20 MBA graduates who had subsequently returned to China with their qualification, we explored their perceptions of outcomes from the course and their experiences as international students on a programme imbued with western norms and values. Results support the unsettling yet creative implications of liminality, as well as the fragmented insecure nature of identities, as individuals pass through the MBA ârite of passageâ in terms of âbecomingâ a manager and entering a new phase of career. Accounts suggest the creation of hierarchical structures within liminal space whereby Chinese students, through their positioning at the margin, have uncomfortable yet illuminating encounters with alterity. At the same time, they experience levels of ambiguity and uncertainty in the post-liminal phase of China-located employments, as new western-based managerial identities collide with dominant discourses of Chinese organization
A transcriptomic time-series reveals differing trajectories during pre-floral development in the apex and leaf in winter and spring varieties of Brassica napus
Oilseed rape (Brassica napus) is an important global oil crop, with spring and winter varieties grown commercially. To understand the transcriptomic differences between these varieties, we collected transcriptomes from apex and leaf tissue from a spring variety, Westar, and a winter variety, Tapidor, before, during, and after vernalisation treatment, until the plants flowered. Large transcriptomic differences were noted in both varieties during the vernalisation treatment because of temperature and day length changes. Transcriptomic alignment revealed that the apex transcriptome reflects developmental state, whereas the leaf transcriptome is more closely aligned to the age of the plant. Similar numbers of copies of genes were expressed in both varieties during the time series, although key flowering time genes exhibited expression pattern differences. BnaFLC copies on A2 and A10 are the best candidates for the increased vernalisation requirement of Tapidor. Other BnaFLC copies show tissue-dependent reactivation of expression post-cold, with these dynamics suggesting some copies have retained or acquired a perennial nature. BnaSOC1 genes, also related to the vernalisation pathway, have expression profiles which suggest tissue subfunctionalisation. This understanding may help to breed varieties with more consistent or robust vernalisation responses, of special importance due to the milder winters resulting from climate change
Non-Abelian Excitations of the Quark-Gluon Plasma
We present new, non-abelian, solutions to the equations of motion which
describe the collective excitations of a quark-gluon plasma at high
temperature. These solutions correspond to spatially uniform color
oscillations.Comment: 8 pages LaTex, 1 figure (not included; available upon request),
Saclay preprint T94/0
An application of the finite-discrete element method in the simulation of ceramic breakage: methodology for a validation study for alumina specimens
Alumina (aluminum oxide, Al2O3) particles are pelletised and ïŹred to produce high porosity catalyst pellets of complex shapes. These pellets ïŹll cylindrical reactor columns with particulate packing structures that are key to the in-service performance, but will suïŹer breakages which impact on catalyst performance. The combined FiniteDiscrete Element Method (FEMDEM) is ideally suited to the simulation of both the multi-body pellet dynamic packing and quasi-static interactions as well as the stress ïŹeld of each individual pellet, its deformations and fragmentation. The application of FEMDEM fracture modelling to a ïŹne-grained brittle and porous material is novel. This paper presents a methodology for a validation study through comparison with three pointbending and Brazilian tests and discusses FEMDEM's potential in modelling multi-body fragile systems
Experimental ionization of atomic hydrogen with few-cycle pulses
We present the first experimental data on strong-field ionization of atomic
hydrogen by few-cycle laser pulses. We obtain quantitative agreement at the 10%
level between the data and an {\it ab initio} simulation over a wide range of
laser intensities and electron energies
Gibbs attractor: a chaotic nearly Hamiltonian system, driven by external harmonic force
A chaotic autonomous Hamiltonian systems, perturbed by small damping and
small external force, harmonically dependent on time, can acquire a strange
attractor with properties similar to that of the canonical distribution - the
Gibbs attractor. The evolution of the energy in such systems can be described
as the energy diffusion. For the nonlinear Pullen - Edmonds oscillator with two
degrees of freedom the properties of the Gibbs attractor and their dependence
on parameters of the perturbation are studied both analytically and
numerically.Comment: 8 pages RevTeX, 3 figure
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