59 research outputs found
Physics of Solar Prominences: I - Spectral Diagnostics and Non-LTE Modelling
This review paper outlines background information and covers recent advances
made via the analysis of spectra and images of prominence plasma and the
increased sophistication of non-LTE (ie when there is a departure from Local
Thermodynamic Equilibrium) radiative transfer models. We first describe the
spectral inversion techniques that have been used to infer the plasma
parameters important for the general properties of the prominence plasma in
both its cool core and the hotter prominence-corona transition region. We also
review studies devoted to the observation of bulk motions of the prominence
plasma and to the determination of prominence mass. However, a simple inversion
of spectroscopic data usually fails when the lines become optically thick at
certain wavelengths. Therefore, complex non-LTE models become necessary. We
thus present the basics of non-LTE radiative transfer theory and the associated
multi-level radiative transfer problems. The main results of one- and
two-dimensional models of the prominences and their fine-structures are
presented. We then discuss the energy balance in various prominence models.
Finally, we outline the outstanding observational and theoretical questions,
and the directions for future progress in our understanding of solar
prominences.Comment: 96 pages, 37 figures, Space Science Reviews. Some figures may have a
better resolution in the published version. New version reflects minor
changes brought after proof editin
Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results
The chromosphere is a thin layer of the solar atmosphere that bridges the
relatively cool photosphere and the intensely heated transition region and
corona. Compressible and incompressible waves propagating through the
chromosphere can supply significant amounts of energy to the interface region
and corona. In recent years an abundance of high-resolution observations from
state-of-the-art facilities have provided new and exciting ways of
disentangling the characteristics of oscillatory phenomena propagating through
the dynamic chromosphere. Coupled with rapid advancements in
magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly
investigate the role waves play in supplying energy to sustain chromospheric
and coronal heating. Here, we review the recent progress made in
characterising, categorising and interpreting oscillations manifesting in the
solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review
D* Production in Deep Inelastic Scattering at HERA
This paper presents measurements of D^{*\pm} production in deep inelastic
scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The
data have been taken with the ZEUS detector at HERA. The decay channel
(+ c.c.) has been used in the study. The
cross section for inclusive D^{*\pm} production with
and is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region
{ GeV and }. Differential cross
sections as functions of p_T(D^{*\pm}), and are
compared with next-to-leading order QCD calculations based on the photon-gluon
fusion production mechanism. After an extrapolation of the cross section to the
full kinematic region in p_T(D^{*\pm}) and (D^{*\pm}), the charm
contribution to the proton structure function is
determined for Bjorken between 2 10 and 5 10.Comment: 17 pages including 4 figure
Observation of Scaling Violations in Scaled Momentum Distributions at HERA
Charged particle production has been measured in deep inelastic scattering
(DIS) events over a large range of and using the ZEUS detector. The
evolution of the scaled momentum, , with in the range 10 to 1280
, has been investigated in the current fragmentation region of the Breit
frame. The results show clear evidence, in a single experiment, for scaling
violations in scaled momenta as a function of .Comment: 21 pages including 4 figures, to be published in Physics Letters B.
Two references adde
Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA
In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10-4 \u3c xBJ \u3c 6 · 10-3 and 10 \u3c Q2 \u3c 100 GeV2
Propriedades biomecânicas da fáscia lata e do ligamento cruzado cranial de cães Biomechanical properties of canine fascia lata and cranial cruciate ligament
Preparações bilaterais do ligamento cruzado cranial e da fáscia lata de 15 cães foram testadas na máquina Instron, modelo 4482. Os animais, de ambos os sexos, idade entre um e quatro anos, pesavam em média 11,80 ± 1,99kg. Os retalhos de fáscia lata foram testados retilíneos e torcidos e o ligamento cruzado cranial foi testado mantendo um ângulo de 135° entre a tíbia e o fêmur e 0°, 15° de rotação externa e 15° de rotação interna da tíbia em relação ao fêmur. A velocidade dos testes de tração foi de 8,47mm por segundo. A força máxima dos retalhos de fáscia lata foi aproximadamente de 290 Newtons, e a tensão máxima, 28 Megapascal. A torção não influenciou na resistência dos retalhos de fáscia lata. A rotação externa e interna da tíbia de 15º também não influenciou na força máxima do ligamento cruzado cranial, que foi aproximadamente de 660 Newtons, nem na tensão máxima, que foi cerca de 75 Megapascal. Os retalhos de fáscia lata apresentaram 44% da força máxima e 37% da tensão máxima do ligamento, no entanto, os retalhos torcidos mostraram maior deformação do que os retalhos retilíneos, alcançando cerca de 70% da deformação do ligamento, sendo essa forma a mais indicada na substituição do ligamento cruzado cranial.<br>Bilateral preparations of fascia lata and cranial cruciate ligament from 15 dogs were tested in Instron machine, model 4482. Dogs were from both sexes, between one and four years of age and weighing in average about 11.80 ± 1.99kg. Fascia lata strips were tested straight and twisted and the cranial cruciate ligaments were tested with an angle of 135° between the femur and tibia and 0°, 15° of external tibial rotation and 15° of internal tibial rotation in relation to femur. The traction test velocity was 8.47mm per second. The maximum force of fascia lata strips was of approximately 290 Newtons and the maximum stress, 28 Megapascal. Similar results of strength and stress properties were found for the strips of fascia lata straight and twisted, although twisted strips presented a higher deformation than straight ones. External and internal tibial rotation did not influence the maximum force and maximum stress of the cranial cruciate ligament, that were of about 660 Newtons and 75 Megapascal, respectively. Fascia lata strips reached 44% of ligaments maximum force and 37% of maximum strain, and twisted strips reached 70% of ligaments maximum deformation, deserving straight strips to be recommended for cranial cruciate ligament substitution in dogs
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