1,120 research outputs found
An Empirical Study on User Satisfaction with Mobile Business Applications Use and Hedonism
Numerous recent information systems (IS), such as instant messaging and mobile applications, are first developed within an individual context and then widely used in both individual and organizational contexts. The present study examines a recent IS, mobile business (m-business) applications, used within organizations and reports the impact of the usersâ pleasurable emotions or feelings on usersâ satisfaction with IS. The result from the sample survey and an existential phenomenology indicates that hedonism is a significant determinant of satisfaction with m-business applications. By providing insight into how and why individuals are satisfied or dissatisfied with m-business applications in addition to what leads to this, the authors hope the findings of this study will assist researchers and practitioners in finding major barriers to the mobile business application use in order to design better applications for improved user satisfaction
The X-ray puzzle of the L1551 IRS 5 jet
Protostars are actively accreting matter and they drive spectacular, dynamic
outflows, which evolve on timescales of years. X-ray emission from these jets
has been detected only in a few cases and little is known about its time
evolution. We present a new Chandra observation of L1551 IRS 5's jet in the
context of all available X-ray data of this object. Specifically, we perform a
spatially resolved spectral analysis of the X-ray emission and find that (a)
the total X-ray luminosity is constant over almost one decade, (b) the majority
of the X-rays appear to be always located close to the driving source, (c)
there is a clear trend in the photon energy as a function of the distance to
the driving source indicating that the plasma is cooler at larger distances and
(d) the X-ray emission is located in a small volume which is unresolved
perpendicular to the jet axis by Chandra. A comparison of our X-ray data of the
L1551 IRS 5 jet both with models as well as X-ray observations of other
protostellar jets shows that a base/standing shock is a likely and plausible
explanation for the apparent constancy of the observed X-ray emission. Internal
shocks are also consistent with the observed morphology if the supply of jet
material by the ejection of new blobs is sufficiently constant. We conclude
that the study of the X-ray emission of protostellar jet sources allows us to
diagnose the innermost regions close to the acceleration region of the
outflows.Comment: A&A accepted, 14 pages, 9 figure
Nonperturbative QED Effective Action at Finite Temperature
We advance a novel method for the finite-temperature effective action for
nonequilibrium quantum fields and find the QED effective action in
time-dependent electric fields, where charged pairs evolve out of equilibrium.
The imaginary part of the effective action consists of thermal loops of the
Fermi-Dirac or Bose-Einstein distribution for the initial thermal ensemble
weighted with factors for vacuum fluctuations. And the real part of the
effective action is determined by the mean number of produced pairs, vacuum
polarization, and thermal distribution. The mean number of produced pairs is
equal to twice the imaginary part. We explicitly find the finite-temperature
effective action in a constant electric field.Comment: RevTex4, 6pages, no figure; replaced by the version to be published
in Phys. Rev.
Schwinger Pair Production at Finite Temperature in Scalar QED
In scalar QED we study the Schwinger pair production from an initial ensemble
of charged bosons when an electric field is turned on for a finite period
together with or without a constant magnetic field. The scalar QED Hamiltonian
depends on time through the electric field, which causes the initial ensemble
of bosons to evolve out of equilibrium. Using the Liouville-von Neumann method
for the density operator and quantum states for each momentum mode, we
calculate the Schwinger pair-production rate at finite temperature, which is
the pair-production rate from the vacuum times a thermal factor of the
Bose-Einstein distribution.Comment: RevTex 10 pages, no figure; replaced by the version accepted in Phys.
Rev. D; references correcte
Massless and Massive Three Dimensional Super Yang-Mills Theory and Mini-Twistor String Theory
We propose various ways of adding mass terms to three-dimensional twistor
string theory. We begin with a review of mini-twistor space--the reduction of
D=4 twistor space to D=3. We adapt the two proposals for twistor string theory,
Witten's and Berkovits's, to D=3 super Yang-Mills theory. In Berkovits's model,
we identify the enhanced R-symmetry. We then construct B-model topological
string theories that, we propose, correspond to D=3 Yang-Mills theory with
massive spinors and massive and massless scalars in the adjoint representation
of the gauge group. We also analyze the counterparts of these constructions in
Berkovits's model. Some of our constructions can be lifted to D=4, where
infinitesimal mass terms correspond to VEVs of certain superconformal gravity
fields.Comment: 69 pages; Typos correcte
Jet rotation investigated in the near-ultraviolet with HST/STIS
We present results of the second phase of our near-ultraviolet investigation
into protostellar jet rotation using HST/STIS. We obtain long-slit spectra at
the base of five T Tauri jets to determine if there is a difference in radial
velocity between the jet borders which may be interpreted as a rotation
signature. These observations are extremely challenging and push the limits of
current instrumentation, but have the potential to provide long-awaited
observational support for the magneto-centrifugal mechanism of jet launching in
which jets remove angular momentum from protostellar systems. We successfully
detect all five jet targets (from RW Aur, HN Tau, DP Tau and CW Tau) in several
near-ultraviolet emission lines, including the strong Mg II doublet. However,
only RW Aur's bipolar jet presents sufficient signal-to-noise for analysis. The
approaching jet lobe shows a difference of 10 km/s in a direction which agrees
with the disk rotation sense, but is opposite to previously published optical
measurements for the receding jet. The near-ultraviolet difference is not found
six months later, nor is it found in the fainter receding jet. Overall, in the
case of RW Aur, differences are not consistent with a simple jet rotation
interpretation. Indeed, given the renowned complexity and variability of this
system, it now seems likely that any rotation signature is confused by other
influences, with the inevitable conclusion that RW Aur is not suited to a jet
rotation study.Comment: 13 pages, 21 figures, Accepted by The Astrophysical Journa
Quantum Entanglement and Teleportation in Higher Dimensional Black Hole Spacetimes
We study the properties of quantum entanglement and teleportation in the
background of stationary and rotating curved space-times with extra dimensions.
We show that a maximally entangled Bell state in an inertial frame becomes less
entangled in curved space due to the well-known Hawking-Unruh effect. The
degree of entanglement is found to be degraded with increasing the extra
dimensions. For a finite black hole surface gravity, the observer may choose
higher frequency mode to keep high level entanglement. The fidelity of quantum
teleporation is also reduced because of the Hawking-Unruh effect. We discuss
the fidelity as a function of extra dimensions, mode frequency, black hole mass
and black hole angular momentum parameter for both bosonic and fermionic
resources.Comment: 15 pages, 10 figures,contents expande
HST/STIS observations of the RW Aurigae bipolar jet: mapping the physical parameters close to the source
We present the results of new spectral diagnostic investigations applied to
high-resolution long-slit spectra of the RW Aur bipolar jet obtained with
HST/STIS. The spectra include the forbidden doublets [O I] 6300,6363 \AA, [S
II] 6716,6731 \AA, and [N II] 6548, 6583 \AA that we utilized to determine
electron density, electron temperature, hydrogen ionisation fraction, total
hydrogen density, radial velocity and the mass outflow rate. We were able to
extract the parameters as far as 3".9 in the red- and 2".1 in the blueshifted
beam. The RW Aur jet appears to be the second densest outflow from a T Tauri
star studied so far, but its other properties are quite similar to those found
in other jets from young stars. The overall trend of the physical parameters
along the first few arcseconds of the RW Aur jet is similar to that of HH 30
and DG Tau and this can reflect analogies in the mechanisms operating in that
region, suggesting the same engine is accelerating the jets in the T Tauri
stars with outflows. Our study of the RW Aur jet indicates for the first time
that, despite the detected marked asymmetries in physical and kinematic
properties between the two lobes, the mass outflow rates in the two lobes are
similar. This appears to indicate that the central engine has constraining
symmetries on both sides of the system, and that the observed asymmetries are
probably due to different environmental conditions.Comment: 24 pages, 10 figures, accepted for publication in the Astronomy and
Astrophysic
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