3,582 research outputs found
Detection of Jovian seismic waves: a new probe of its interior structure
Knowledge of Jupiter's deep interior would provide unique constraints on the
formation of the Solar System. Measurement of its core mass and global
composition would shed light on whether the planet formed by accretion or by
direct gravitational collapse. At present, the inner structure of Jupiter is
poorly constrained and seismology, which consists of identifying acoustic
eigenmodes, offers a way to directly measure its deep sound speed profile, and
thus its physical properties. Seismology of Jupiter has been considered since
the mid 1970s, but hitherto the various attempts to detect global modes led, at
best, to ambiguous results. We report the detection of global modes of Jupiter,
based on radial velocity measurements performed with the SYMPA Fourier
spectro-imager. The global seismic parameters that we measure include the
frequency of maximum amplitude 1213+/-50 \mu Hz, the mean large frequency
spacing between radial harmonics 155.3+/-2.2 \mu Hz and the mode maximum
amplitude 49 (-10/+8) cm/s, all values that are consistent with current models
of Jupiter. This result opens the way to the investigation of the inner
structure of the Solar System's giant planets based on seismology techniques.Comment: Accepted in Astronomy & Astrophysics (8 pages, 9 figures
Transformation properties and entanglement of relativistic qubits under space-time and gauge transformations
We revisit the properties of qubits under Lorentz transformations and, by considering Lorentz invariant quantum states in the Heisenberg formulation, clarify some misleading notation that has appeared in the literature on relativistic quantum information theory. We then use this formulation to consider the transformation properties of qubits and density matrices under space-time and gauge transformations. Finally we use our results to understand the behaviour of entanglement between different partitions of quantum systems. Our approach not only clarifies the notation, but provides a more intuitive and simple way of gaining insight into the behaviour of relativistic qubits. In particular, it allows us to greatly generalize the results in the current literature as well as substantially simplifying the calculations that are needed
Thinking about national plans
The last decade saw the revival of national plans in African policy parlance. Kenya, Uganda and Tanzania are amongst the list of countries who revitalised their planning efforts and brought national plans back to the heart of their national policy agendas. Most of these plans aim at charting the trajectory for the low-income country in question to achieve ‘middle-income status’. Developing a national plan that outlines the envisaged growth path of all major socioeconomic sectors of the economy, along with a possible allocation of budget and the identification of priority sectors/investments, is an intricate policy exercise. The sheer number of stakeholders to be consulted and the possible overlapping of topics make it mind-blowingly complicated
The Circumgalactic Medium of Submillimeter Galaxies. II. Unobscured QSOs within Dusty Starbursts and QSO Sightlines with Impact Parameters below 100 Kiloparsec
We present Atacama Large Millimeter/submillimeter Array (ALMA) 870um
observations of 29 bright Herschel sources near high-redshift QSOs. The
observations confirm that 20 of the Herschel sources are submillimeter-bright
galaxies (SMGs) and identify 16 new SMG-QSO pairs that are useful to studies of
the circumgalactic medium (CGM) of SMGs. Eight out of the 20 SMGs are blends of
multiple 870um sources. The angular separations for six of the Herschel-QSO
pairs are less than 10", comparable to the sizes of the Herschel beam and the
ALMA primary beam. We find that four of these six "pairs" are actually QSOs
hosted by SMGs. No additional submillimeter companions are detected around
these QSOs and the rest-frame ultraviolet spectra of the QSOs show no evidence
of significant reddening. Black hole accretion and star formation contribute
almost equally in bolometric luminosity in these galaxies. The SMGs hosting
QSOs show similar source sizes, dust surface densities, and SFR surface
densities as other SMGs in the sample. We find that the black holes are growing
3 faster than the galaxies when compared to the present-day
black-hole-galaxy mass ratio, suggesting a QSO duty cycle of 30% in
SMGs at z ~ 3. The remaining two Herschel-detected QSOs are undetected at 870um
but each has an SMG "companion" only 9" and 12" away (71 and 95 kpc at z = 3).
They could be either merging or projected pairs. If the former, they would
represent a rare class of "wet-dry" mergers. If the latter, the QSOs would, for
the first time, probe the CGM of SMGs at impact parameters below 100 kpc.Comment: ApJ accepte
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Application of Compressed Sensing to the Simulation of Atomic Systems
Compressed sensing is a method that allows a significant reduction in the number of samples required for accurate measurements in many applications in experimental sciences and engineering. In this work, we show that compressed sensing can also be used to speed up numerical simulations. We apply compressed sensing to extract information from the real-time simulation of atomic and molecular systems, including electronic and nuclear dynamics. We find that, compared to the standard discrete Fourier transform approach, for the calculation of vibrational and optical spectra the total propagation time, and hence the computational cost, can be reduced by approximately a factor of five.Chemistry and Chemical Biolog
Figures de la filiation littéraire dans Bourlinguer de Blaise Cendrars
Ce mémoire de maîtrise se penche sur les différentes figures de la filiation littéraire dans Bourlinguer de Blaise Cendrars. Le premier chapitre aborde les rapports intertextuels qu’entretient Bourlinguer avec un certain nombre d’œuvres, notamment celle de Rudyard Kipling, et montre bien que Cendrars emploie la connaissance à des fins de compréhension du réel et de sa propre identité. Il met aussi en lumière un procédé étonnant : un double mouvement d’invocation et de rejet des intertextes, permettant la récupération d’un héritage prestigieux et la posture désinvolte de l’auteur épris de liberté. Le second chapitre analyse la bibliothèque, la lecture et les maîtres de Cendrars. Il met en relief la place capitale qu’occupent dans Bourlinguer l’expérience et la lucidité dans l’exercice de la lecture. L’analyse des relations aux maîtres (surtout Rémy de Gourmont) soulève l’importance de l’émancipation de l’autorité, paternelle ou littéraire, qui traverse l’œuvre de Cendrars.The main objective of this thesis is to explain the intricacies of the representations of literary heritage in Blaise Cendrars’ Bourlinguer. The first chapter studies the intertextual relationships between Bourlinguer and a handful of texts (mainly Rudyard Kipling’s Kim) and thus shows how Cendrars uses knowledge as a tool to understand his identity and reality. The same chapter also sheds light on a peculiar process by which Cendrars simultaneously invokes and rejects literary influences, granting him prestige and impertinence at the same time. The second chapter analyses several types of libraries, the act of reading itself and Cendrars’ esthetic masters. Bourlinguer insists on experience and lucidity in reading, as well as on the importance of liberating oneself from authorities, paternal, literary or otherwise
QuesNet: A Unified Representation for Heterogeneous Test Questions
Understanding learning materials (e.g. test questions) is a crucial issue in
online learning systems, which can promote many applications in education
domain. Unfortunately, many supervised approaches suffer from the problem of
scarce human labeled data, whereas abundant unlabeled resources are highly
underutilized. To alleviate this problem, an effective solution is to use
pre-trained representations for question understanding. However, existing
pre-training methods in NLP area are infeasible to learn test question
representations due to several domain-specific characteristics in education.
First, questions usually comprise of heterogeneous data including content text,
images and side information. Second, there exists both basic linguistic
information as well as domain logic and knowledge. To this end, in this paper,
we propose a novel pre-training method, namely QuesNet, for comprehensively
learning question representations. Specifically, we first design a unified
framework to aggregate question information with its heterogeneous inputs into
a comprehensive vector. Then we propose a two-level hierarchical pre-training
algorithm to learn better understanding of test questions in an unsupervised
way. Here, a novel holed language model objective is developed to extract
low-level linguistic features, and a domain-oriented objective is proposed to
learn high-level logic and knowledge. Moreover, we show that QuesNet has good
capability of being fine-tuned in many question-based tasks. We conduct
extensive experiments on large-scale real-world question data, where the
experimental results clearly demonstrate the effectiveness of QuesNet for
question understanding as well as its superior applicability
Græsmarksafgrødernes sammensætning – en kompleks sag
Ønsker man at producere mælk med
en given sammensætning, er det vigtigt
både at fokusere på anvendelsen af forskellige
græssorter samt at have fokus på
planternes udviklingstrin
Trans-equatorial migration and mixing in the wintering areas of a pelagic seabird
Despite increasing interest in long-distance migration, the wintering areas, migration corridors, and population mix in winter quarters of most pelagic marine predators are unknown. Here, we present the first study tracking migration movements of shearwaters through the non-breeding period. We used geolocators (global location sensing [GLS] units based on ambient light levels) to track 22 Cory's shearwaters (Calonectris diomedea) breeding in three different areas. Most birds wintered in one or more of three relatively small areas, all clearly associated with major coastal upwelling systems of the tropical and south Atlantic. Trans-equatorial movements were dominated by prevailing trade winds and westerlies, while calm, oligotrophic areas were avoided. Breeding populations clearly differed in their preference amongst the three major wintering areas, but showed substantial mixing. This illustrates the exceptional value of GLS, not only for determining and describing the influence of oceanographic features on migration patterns, but also for assessing population mix in winter quarters. This knowledge is essential to understanding the impacts of population-level threats, such as longlining, offshore windfarms, and oil spills on multiple breeding sites, and will be critical in devising conservation policies that guarantee the sustainable exploitation of the oceans
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