3,094 research outputs found
Scalar mesons in a finite volume
Using effective field theory methods, we discuss the extraction of the mass
and width of the scalar mesons f0(980) and a0(980) from the finite-volume
spectrum in lattice QCD. In particular, it is argued that the nature of these
states can be studied by invoking twisted boundary conditions, as well as
investigating the quark mass dependence of the spectrum.Comment: 18 pages, 3 figure
Ultrasonic Fatigue Analysis on Steel Specimen with Temperature Control : Evaluation of Variable Temperature Effect
Non peer reviewe
Spatial Configuration and Vehicular Movement: a nationwide correlational study
We provide the most comprehensive study to date on the correlation between network
centrality measures and vehicular movement flows, using a model of the UK’s entire road
network (2,031,971 nodes) and a very large dataset of vehicular movement counts (20,752
instances, evenly distributed over the UK’s territory). We describe the statistical
associations between observed vehicular flows and the values of betweenness centrality of
the road-network nodes where such flows were measured, the latter calculated using
Euclidean and angular distance functions, across a number of increasing radii, from the
local to the supra-regional scales. Relations to road capacity are also discussed in principal
road networks where this is known.
The geographical comprehensiveness of our model and the size of our movement sample
allows us to state, with unprecedented statistical validity, the clear outperformance of
angular distance over Euclidean distance, on what concerns the effect sizes of the studied
correlations. We also demonstrate the existence of two clearly different regimes of
association between movement and centrality, occurring on the background and
foreground networks of cities, which may be interpreted as new evidence of the dual
structure of urban form, proposed by space syntax
Another shock for the Bullet cluster, and the source of seed electrons for radio relics
With Australia Telescope Compact Array observations, we detect a highly
elongated Mpc-scale diffuse radio source on the eastern periphery of the Bullet
cluster 1E0657-55.8, which we argue has the positional, spectral and
polarimetric characteristics of a radio relic. This powerful relic (2.3+/-0.1 x
10^25 W Hz^-1) consists of a bright northern bulb and a faint linear tail. The
bulb emits 94% of the observed radio flux and has the highest surface
brightness of any known relic. Exactly coincident with the linear tail we find
a sharp X-ray surface brightness edge in the deep Chandra image of the cluster
-- a signature of a shock front in the hot intracluster medium (ICM), located
on the opposite side of the cluster to the famous bow shock. This new example
of an X-ray shock coincident with a relic further supports the hypothesis that
shocks in the outer regions of clusters can form relics via diffusive shock
(re-)acceleration. Intriguingly, our new relic suggests that seed electrons for
reacceleration are coming from a local remnant of a radio galaxy, which we are
lucky to catch before its complete disruption. If this scenario, in which a
relic forms when a shock crosses a well-defined region of the ICM polluted with
aged relativistic plasma -- as opposed to the usual assumption that seeds are
uniformly mixed in the ICM -- is also the case for other relics, this may
explain a number of peculiar properties of peripheral relics.Comment: 10 pages, 9 figures, 1 table, accepted for publication in MNRA
Deep radio observations of the radio halo of the bullet cluster 1E 0657-55.8
We present deep 1.1-3.1 GHz Australia Telescope Compact Array observations of
the radio halo of the bullet cluster, 1E 0657-55.8. In comparison to existing
images of this radio halo the detection in our images is at higher
significance. The radio halo is as extended as the X-ray emission in the
direction of cluster merger but is significantly less extended than the X-ray
emission in the perpendicular direction. At low significance we detect a faint
second peak in the radio halo close to the X-ray centroid of the smaller
sub-cluster (the bullet) suggesting that, similarly to the X-ray emission, the
radio halo may consist of two components. Finally, we find that the distinctive
shape of the western edge of the radio halo traces out the X-ray detected bow
shock. The radio halo morphology and the lack of strong point-to-point
correlations between radio, X-ray and weak-lensing properties suggests that the
radio halo is still being formed. The colocation of the X-ray shock with a
distinctive radio brightness edge illustrates that the shock is influencing the
structure of the radio halo. These observations support the theory that shocks
and turbulence influence the formation and evolution of radio halo synchrotron
emission.Comment: 15 pages, 16 figures, 3 tables. Accepted by MNRA
Diabetes InsÃpida Como Causa de Febre
A Diabetes InsÃpida é uma das causas pouco habituais de febre de etiologia indeterminada. Descrevemos o caso de urna lactente internado aos nove meses de idade com febre, má progressão ponderal e atraso no desenvolvimento motor. As causas habituais destas situações foram excluÃdas por exames exaustivos. Alguns meses mais tarde constatámos o aparecimento de poliúria e polidipsia. A prova com desmopressina fez o diagnóstico de Diabetes InsÃpida Central que foi confirmada com a resposta à terapêutica
Sensores baseados em nanotubos de carbono funcionalizados por ligação não-covalente
A pesquisa na área dos nanomateriais de carbono, como os nanotubos de carbono (CNTs), tem crescido
muito rapidamente devido às suas propriedades térmicas, eletrónicas e mecânicas. Muitos esforços têm
sido realizados para aumentar a solubilidade destes materiais em diversos solventes e obter dispersões
estáveis. Uma das estratégias para dispersar os CNTs consiste na funcionalização quÃmica, que apresenta
como desvantagem a destruição da estrutura sp2 do carbono destes materiais. Neste últimos anos surgiram
vários estudos baseados na funcionalização não-covalente com o intuito de manter as suas propriedades
estruturais. Com este fim, tem sido utilizadas estruturas poliaromáticas substituÃdas como perilenos e
pirenos que podem estabelecer interações do tipo Ï€-Ï€ com a superfÃcie aromática dos CNTs ou do grafeno.
Neste trabalho pretende-se apresentar uma revisão bibliográfica da utilização da funcionalização nãocovalente
no desenvolvimento de sensores e biossensores eletroquÃmicos em substrato de materiais
nanoestruturados de carbono (MWCNTs, SWCNTs, grafeno)
Generalized L\"uscher Formula in Multi-channel Baryon-Meson Scattering
L\"uscher's formula relates the elastic scattering phase shifts to the
two-particle energy levels in a finite cubic box. The original formula was
obtained for elastic scattering of two massive spinless particles in the center
of mass frame. In this paper, we consider the case for the scattering of a spin
1/2 particle with a spinless particle in multi-channel scattering. A
generalized relation between the energy of two particle system and the
scattering matrix elements is established. We first obtain this relation using
quantum-mechanics in both center-of-mass frame and in a general moving frame.
The result is then generalized to quantum field theory using methods outlined
in Ref. \cite{Hansen:2012tf}. We verify that the results obtained using both
methods are equivalent up to terms that are exponentially suppressed in the box
size.Comment: One reference adde
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