13,322 research outputs found
Voltage controlled spin injection in a (Ga,Mn)As/(Al,Ga)As Zener diode
The spin polarization of the electron current in a
p-(Ga,Mn)As-n-(Al,Ga)As-Zener tunnel diode, which is embedded in a
light-emitting diode, has been studied theoretically. A series of
self-consistent simulations determines the charge distribution, the band
bending, and the current-voltage characteristics for the entire structure. An
empirical tight-binding model, together with the Landauer- Buttiker theory of
coherent transport has been developed to study the current spin polarization.
This dual approach allows to explain the experimentally observed high magnitude
and strong bias dependence of the current spin polarization.Comment: Submitted to Phys. Rev. B Rapid Communication
Comorbidities and Treatment-Limiting Decisions in Older Adults Dying in the Emergency Department: Is There an Association?
International audienc
d-Dimensional generalization of the point canonical transformation for a quantum particle with position-dependent mass
The d-dimensional generalization of the point canonical transformation for a
quantum particle endowed with a position-dependent mass in Schrodinger equation
is described. Illustrative examples including; the harmonic oscillator,
Coulomb, spiked harmonic, Kratzer, Morse oscillator, Poschl-Teller and Hulthen
potentials are used as reference potentials to obtain exact energy eigenvalues
and eigenfunctions for target potentials at different position-dependent mass
settings.Comment: 14 pages, no figures, to appear in J. Phys. A: Math. Ge
The bumpy light curve of supernova iPTF13z
A Type IIn supernova (SN) is dominated by the interaction of SN ejecta with
the circumstellar medium (CSM). Some SNe IIn (e.g., SN 2006jd) have episodes of
re-brightening ("bumps") in their light curves. We present iPTF13z, a SN IIn
discovered by the intermediate Palomar Transient Factory (iPTF) and
characterised by several bumps in its light curve. We analyse this peculiar
behaviour trying to infer the properties of the CSM and of the SN explosion, as
well as the nature of its progenitor star. We obtained multi-band optical
photometry for over 1000 days after discovery with the P48 and P60 telescopes
at Palomar Observatory. We obtained low-resolution optical spectra in the same
period. We did an archival search for progenitor outbursts. We analyse our
photometry and spectra, and compare iPTF13z to other SNe IIn. A simple
analytical model is used to estimate properties of the CSM. iPTF13z was a SN
IIn showing a light curve with five bumps during its decline phase. The bumps
had amplitudes between 0.4 and 0.9 mag and durations between 20 and 120 days.
The most prominent bumps appeared in all our different optical bands. The
spectra showed typical SN IIn characteristics, with emission lines of H
(with broad component FWHM ~ and narrow
component FWHM ~) and He I, but also with Fe II, Ca II,
Na I D and H P-Cygni profiles (with velocities of ~ ). A pre-explosion outburst was identified lasting days,
with mag around 210 days before discovery. Large, variable
progenitor mass-loss rates (~> 0.01 ) and CSM densities
(~> 10 g cm) are derived. We suggest that the light curve bumps
of iPTF13z arose from SN ejecta interacting with denser regions in the CSM,
possibly produced by the eruptions of a luminous blue variable star.Comment: Version 2: Update to match published paper. 21 pages, 14 figures,
abstract abridged to comply with arXiv length limit. In version 1 of the
paper on arXiv, Table 3 had some erroneous entries. Table 3 is now corrected
and available via VizieR. Version 1 comment: Accepted for publication in
Astronomy & Astrophysics (24 pages, 14 figures, abstract abridged by 20 % not
to exceed the arXiv length limit
Supersymmetric Method for Constructing Quasi-Exactly and Conditionally-Exactly Solvable Potentials
Using supersymmetric quantum mechanics we develop a new method for
constructing quasi-exactly solvable (QES) potentials with two known
eigenstates. This method is extended for constructing conditionally-exactly
solvable potentials (CES). The considered QES potentials at certain values of
parameters become exactly solvable and can be treated as CES ones.Comment: 17 pages, latex, no figure
Effects of pitch and musical sounds on body-representations when moving with sound
The effects of music on bodily movement and feelings, such as when people are dancing or engaged in physical activity, are well-documented—people may move in response to the sound cues, feel powerful, less tired. How sounds and bodily movements relate to create such effects? Here we deconstruct the problem and investigate how different auditory features affect people’s body-representation and feelings even when paired with the same movement. In three experiments, participants executed a simple arm raise synchronised with changing pitch in simple tones (Experiment 1), rich musical sounds (Experiment 2) and within different frequency ranges (Experiment 3), while we recorded indirect and direct measures on their movement, body-representations and feelings. Changes in pitch influenced people’s general emotional state as well as the various bodily dimensions investigated—movement, proprioceptive awareness and feelings about one’s body and movement. Adding harmonic content amplified the differences between ascending and descending sounds, while shifting the absolute frequency range had a general effect on movement amplitude, bodily feelings and emotional state. These results provide new insights in the role of auditory and musical features in dance and exercise, and have implications for the design of sound-based applications supporting movement expression, physical activity, or rehabilitation
First case of Chlamydia trachomatis L2b proctitis in a woman
AbstractSince 2003, outbreaks of lymphogranuloma venereum (LGV) have been reported in European countries, North America, and Australia. Current LGV cases have been caused by Chlamydia trachomatis serovar L2. This sexually transmitted infection is predominantly found among men who have sex with men, specifically men who are seropositive for human immunodeficiency virus and have clinical signs of proctitis. The current outbreak has been almost exclusively attributed to a new variant, designated L2b. Although urogenital cases of LGV have been described in the heterosexual population, we report the first case of C. trachomatis L2b proctitis in a woman
A new approach to the exact solutions of the effective mass Schrodinger equation
Effective mass Schrodinger equation is solved exactly for a given potential.
Nikiforov-Uvarov method is used to obtain energy eigenvalues and the
corresponding wave functions. A free parameter is used in the transformation of
the wave function. The effective mass Schrodinger equation is also solved for
the Morse potential transforming to the constant mass Schr\"{o}dinger equation
for a potential. One can also get solution of the effective mass Schrodinger
equation starting from the constant mass Schrodinger equation.Comment: 14 page
Analytical results for string propagation near a Kaluza-Klein black hole
This brief report presents analytical solutions to the equations of motion of
a null string. The background spacetime is a magnetically charged Kaluza-Klein
black hole. The string coordinates are expanded with the world-sheet velocity
of light as an expansion parameter. It is shown that the zeroth order solutions
can be expressed in terms of elementary functions in an appropriate large
distance approximation. In addition, a class of exact solutions corresponding
to the Pollard-Gross-Perry-Sorkin monopole case is also obtained.Comment: Revtex, 9 pages including two postscript figures, More detailed
discussion and new references adde
PT-symmetric Solutions of Schrodinger Equation with position-dependent mass via Point Canonical Transformation
PT-symmetric solutions of Schrodinger equation are obtained for the Scarf and
generalized harmonic oscillator potentials with the position-dependent mass. A
general point canonical transformation is applied by using a free parameter.
Three different forms of mass distributions are used. A set of the energy
eigenvalues of the bound states and corresponding wave functions for target
potentials are obtained as a function of the free parameter.Comment: 13 page
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