1,315 research outputs found
Detailed analysis of radiation data from the Gemini 4 and Gemini 7 proton-electron spectrometer experiments Final report, 13 Jun. 1967 - 30 Dec. 1968
Detailed analysis of radiation data from Gemini 4 and 7 proton-electron spectrometer experiment
On Aharonov-Casher bound states
In this work bound states for the Aharonov-Casher problem are considered.
According to Hagen's work on the exact equivalence between spin-1/2
Aharonov-Bohm and Aharonov-Casher effects, is known that the
term cannot be neglected in the
Hamiltonian if the spin of particle is considered. This term leads to the
existence of a singular potential at the origin. By modeling the problem by
boundary conditions at the origin which arises by the self-adjoint extension of
the Hamiltonian, we derive for the first time an expression for the bound state
energy of the Aharonov-Casher problem. As an application, we consider the
Aharonov-Casher plus a two-dimensional harmonic oscillator. We derive the
expression for the harmonic oscillator energies and compare it with the
expression obtained in the case without singularity. At the end, an approach
for determination of the self-adjoint extension parameter is given. In our
approach, the parameter is obtained essentially in terms of physics of the
problem.Comment: 11 pages, matches published versio
On the influence of a Coulomb-like potential induced by the Lorentz symmetry breaking effects on the Harmonic Oscillator
In this work, we obtain bound states for a nonrelativistic spin-half neutral
particle under the influence of a Coulomb-like potential induced by the Lorentz
symmetry breaking effects. We present a new possible scenario of studying the
Lorentz symmetry breaking effects on a nonrelativistic quantum system defined
by a fixed space-like vector field parallel to the radial direction interacting
with a uniform magnetic field along the z-axis. Furthermore, we also discuss
the influence of a Coulomb-like potential induced by Lorentz symmetry violation
effects on the two-dimensional harmonic oscillator.Comment: 14 pages, no figure, this work has been accepted for publication in
The European Physical Journal Plu
Variability in Protoplanetary Nebulae: IX. Evidence for Evolution in a Decade
We have carried out a new photometric V,Rc study of 12 protoplanetary
nebulae, objects in the short-lived transition between the AGB and PN phases of
stellar evolution. These had been the subjects of an earlier study, using data
from 1994-2007, that found that all 12 varied periodically, with pulsation
periods in the range of ~38 to ~150 days. They are all carbon-rich, with F-G
spectral types. We combined our new (2008-2018) data with publicly-available
ASAS-SN data and determined new periods for their variability. The older and
newer period values were compared to investigate evidence of period change, for
which there is theoretical support that it might be detectable in a decade or
two in some cases. Such a detection is challenging since the light curves are
complicated, with multiple periods, changing amplitudes, and evidence of
shocks. Nevertheless, we found one, and possibly two, such cases, which are
associated with the higher temperature stars in the sample (7250 and 8000 K).
These results are most consistent with the evolution of stars at the lower end
of the mass range of carbon stars, ~1.5-2 M(sun). Several of the stars show
longer-term trends of increasing (six cases) or decreasing (one case)
brightness, which we think most likely due to changes in the circumstellar dust
opacity. There is one case of a possible ~1.8 yr period in addition to the
shorter pulsation. This is interpreted as possible evidence of an orbiting
companion.Comment: 26 pages, 9 figures. Accepted September 16, 2022 for publication in
the Ap
Interacting damage models mapped onto Ising and percolation models
We introduce a class of damage models on regular lattices with isotropic
interactions, as e.g. quasistatic fiber bundles. The system starts intact with
a surface-energy threshold required to break any cell sampled from an
uncorrelated quenched-disorder distribution. The evolution of this
heterogeneous system is ruled by Griffith's principle which states that a cell
breaks when the release in elastic energy in the system exceeds the
surface-energy barrier necessary to break the cell. By direct integration over
all possible realizations of the quenched disorder, we obtain the probability
distribution of each damage configuration at any level of the imposed external
deformation. We demonstrate an isomorphism between the distributions so
obtained and standard generalized Ising models, in which the coupling constants
and effective temperature in the Ising model are functions of the nature of the
quenched-disorder distribution and the extent of accumulated damage. In
particular, we show that damage models with global load sharing are isomorphic
to standard percolation theory, that damage models with local load sharing rule
are isomorphic to the standard Ising model, and draw consequences thereof for
the universality class and behavior of the autocorrelation length of the
breakdown transitions corresponding to these models. We also treat damage
models having more general power-law interactions, and classify the breakdown
process as a function of the power-law interaction exponent. Last, we also show
that the probability distribution over configurations is a maximum of Shannon's
entropy under some specific constraints related to the energetic balance of the
fracture process, which firmly relates this type of quenched-disorder based
damage model to standard statistical mechanics.Comment: 16 pages, 3 figure
Noninertial effects on a Dirac neutral particle inducing an analogue of the Landau quantization in the cosmic string spacetime
We discuss the behaviour of external fields that interact with a Dirac
neutral particle with a permanent electric dipole moment in order to achieve
relativistic bound states solutions in a noninertial frame and in the presence
of a topological defect spacetime. We show that the noninertial effects of the
Fermi-Walker reference frame induce a radial magnetic field even in the absence
of magnetic charges, which is influenced by the topology of the cosmic string
spacetime. We then discuss the conditions that the induced fields must satisfy
to yield the relativistic bound states corresponding to the
Landau-He-McKellar-Wilkens quantization in the cosmic string spacetime. Finally
we obtain the Dirac spinors for positive-energy solutions and the Gordon
decomposition of the Dirac probability current.Comment: 15 pages, no figure, this paper will be published in volume 42 of the
Brazilian Journal of Physic
Proton-electron spectrometer experiments on Gemini-4 and Gemini-7 Final report, 27 May 1963 - 30 Sep. 1966
Fluxes and spectra of electrons and protons in atmosphere measured by spectrometer experiments on Gemini spacecraf
Efficacy and safety of 4 weeks' treatment with combined fluticasone furoate/vilanterol in a single inhaler given once daily in COPD: a placebo-controlled randomised trial
Background: Fluticasone furoate/vilanterol (FF/VI) is a novel once-daily (OD) inhaled corticosteroid/long-acting beta(2) agonist combination in development for chronic obstructive pulmonary disease (COPD) and asthma. Trial design: A multicentre, randomised, double-blind, parallel-group, placebo-controlled study. Methods: Participants were patients with moderate-to-severe COPD treated with placebo or FF/VI 400/25 mu g OD for 4 weeks. Study objectives were to assess the safety and efficacy of FF/VI 400/25 mg OD administered for 4 weeks via a novel dry powder inhaler. Co-primary end points were change from baseline in weighted mean (wm) heart rate 0-4 h postdose at day 28 and the incidence of adverse events (AEs). Secondary end points included change from baseline in trough forced expiratory volume in one second (FEV1) (23-24 h postdose; day 29) and wm FEV1 (0-4 h postdose; day 28). Patients were randomised to receive FF/VI 400/25 mg or placebo in a 2: 1 ratio; all patients and investigators were blinded to active or placebo treatment. Results: 60 patients (mean age 64 years) were randomised (FF/VI: n=40; placebo: n=20), and all contributed data to the analysis. Mean screening post-bronchodilator FEV1 per cent predicted was comparable between groups (FF/VI: 58.5%; placebo: 60.1%). The wm heart rate 0-4 h postdose was similar between groups (difference: 0.6 beats per minute; 95% CI -3.9 to 5.1). More on-treatment AEs were reported in the FF/VI group (68%) compared with the placebo group (50%). The most common drug-related AEs in the FF/VI group were oral candidiasis (8%) and dysphonia (5%). There were no clinically relevant effects on laboratory values, including glucose and potassium, or on vital signs or ECGs/Holters. The FF/VI group had statistically greater improvements compared with placebo in trough FEV1 (mean difference 183 ml) and 0-4 h postdose wm FEV1 (mean difference 236 ml). Conclusion: FF/VI has a good safety and tolerability profile and improves lung function compared with placebo in patients with COPD. Trial registration number: clinical trials. gov-NCT00731822
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