1,431 research outputs found
Women in pediatric radiology
Women represent a significant proportion of pediatric radiologists in the United States, as shown on surveys by the American College of Radiology (ACR) and the Society for Pediatric Radiology (SPR). This review discusses the characteristics of this subgroup of specialists and issues uniquely related to them
Geodesic Flow on the Diffeomorphism Group of the circle
We show that certain right-invariant metrics endow the infinite-dimensional
Lie group of all smooth orientation-preserving diffeomorphisms of the circle
with a Riemannian structure. The study of the Riemannian exponential map allows
us to prove infinite-dimensional counterparts of results from classical
Riemannian geometry: the Riemannian exponential map is a smooth local
diffeomorphism and the length-minimizing property of the geodesics holds.Comment: 15 page
Disfluency in dialogue:an intentional signal from the speaker?
Disfluency is a characteristic feature of spontaneous human speech, commonly seen as a consequence of problems with production. However, the question remains open as to why speakers are disfluent: Is it a mechanical by-product of planning difficulty, or do speakers use disfluency in dialogue to manage listeners' expectations? To address this question, we present two experiments investigating the production of disfluency in monologue and dialogue situations. Dialogue affected the linguistic choices made by participants, who aligned on referring expressions by choosing less frequent names for ambiguous images where those names had previously been mentioned. However, participants were no more disfluent in dialogue than in monologue situations, and the distribution of types of disfluency used remained constant. Our evidence rules out at least a straightforward interpretation of the view that disfluencies are an intentional signal in dialogue. © 2012 Psychonomic Society, Inc
Optimal quantum cloning of orbital angular momentum photon qubits via Hong-Ou-Mandel coalescence
The orbital angular momentum (OAM) of light, associated with a helical
structure of the wavefunction, has a great potential for quantum photonics, as
it allows attaching a higher dimensional quantum space to each photon.
Hitherto, however, the use of OAM has been hindered by its difficult
manipulation. Here, exploiting the recently demonstrated spin-OAM information
transfer tools, we report the first observation of the Hong-Ou-Mandel
coalescence of two incoming photons having nonzero OAM into the same outgoing
mode of a beam-splitter. The coalescence can be switched on and off by varying
the input OAM state of the photons. Such effect has been then exploited to
carry out the 1 \rightarrow 2 universal optimal quantum cloning of OAM-encoded
qubits, using the symmetrization technique already developed for polarization.
These results are finally shown to be scalable to quantum spaces of arbitrary
dimension, even combining different degrees of freedom of the photons.Comment: 5 pages, 3 figure
A surface-patterned chip as a strong source of ultracold atoms for quantum technologies
Laser-cooled atoms are central to modern precision measurements. They are also increasingly important as an enabling technology for experimental cavity quantum electrodynamics, quantum information processing and matter–wave interferometry. Although significant progress has been made in miniaturizing atomic metrological devices, these are limited in accuracy by their use of hot atomic ensembles and buffer gases. Advances have also been made in producing portable apparatus that benefits from the advantages of atoms in the microkelvin regime. However, simplifying atomic cooling and loading using microfabrication technology has proved difficult. In this Letter we address this problem, realizing an atom chip that enables the integration of laser cooling and trapping into a compact apparatus. Our source delivers ten thousand times more atoms than previous magneto-optical traps with microfabricated optics and, for the first time, can reach sub-Doppler temperatures. Moreover, the same chip design offers a simple way to form stable optical lattices. These features, combined with simplicity of fabrication and ease of operation, make these new traps a key advance in the development of cold-atom technology for high-accuracy, portable measurement devices
Analytic Results for Higgs Production in Bottom Fusion
We evaluate analytically the cross section for Higgs production plus one jet
through bottom quark fusion. By considering the small pT limit we derive
expressions for the resummation coefficients governing the structure of large
logarithms, and compare these expressions with those available in the
literature.Comment: 14 pages, 7 figure
The Light Stop Scenario from Gauge Mediation
In this paper we embed the light stop scenario, a MSSM framework which
explains the baryon asymmetry of the universe through a strong first order
electroweak phase transition, in a top-down approach. The required low energy
spectrum consists in the light SM-like Higgs, the right-handed stop, the
gauginos and the Higgsinos while the remaining scalars are heavy. This spectrum
is naturally driven by renormalization group evolution starting from a heavy
scalar spectrum at high energies. The latter is obtained through a
supersymmetry-breaking mix of gauge mediation, which provides the scalars
masses by new gauge interactions, and gravity mediation, which generates
gaugino and Higgsino masses. This supersymmetry breaking also explains the \mu\
and B_\mu\ parameters necessary for electroweak breaking and predicts small
tri-linear mixing terms A_t in agreement with electroweak baryogenesis
requirements. The minimal embedding predicts a Higgs mass around its
experimental lower bound and by a small extension higher masses m_H\lesssim 127
GeV can be accommodated.Comment: 20 pages, 3 figures; v2: changes in the conventions; v3: more details
on the Higgs mass prediction, version published in JHE
Naturalised Vitis Rootstocks in Europe and Consequences to Native Wild Grapevine
The genus Vitis is represented by several coexisting species in Europe. Our study focuses on naturalised rootstocks that originate in viticulture. The consequences of their presence to the landscape and to native European species (Vitis vinifera ssp. silvestris) are evaluated. This study compares ecological traits (seven qualitative and quantitative descriptors) and the genetic diversity (10 SSR markers) of populations of naturalised rootstocks and native wild grapevines. 18 large naturalised rootstock populations were studied in the Rhône watershed. Wild European grapevines are present in four main habitats (screes, alluvial forests, hedges, and streamside hedges). In contrast, naturalised rootstock populations are mainly located in alluvial forests, but they clearly take advantage of alluvial system dynamics and connectivity at the landscape level. These latter populations appear to reproduce sexually, and show a higher genetic diversity than Vitis vinifera ssp. silvestris. The regrouping of naturalised rootstocks in interconnected populations tends to create active hybrid swarms of rootstocks. The rootstocks show characters of invasive plants. The spread of naturalised rootstocks in the environment, the acceleration of the decline of the European wild grapevine, and the propagation of genes of viticultural interest in natural populations are potential consequences that should be kept in mind when undertaking appropriate management measures
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