1,258 research outputs found
PT Symmetric, Hermitian and P-Self-Adjoint Operators Related to Potentials in PT Quantum Mechanics
In the recent years a generalization of the
harmonic oscillator using a complex deformation was investigated, where
\epsilon\ is a real parameter. Here, we will consider the most simple case:
\epsilon even and x real. We will give a complete characterization of three
different classes of operators associated with the differential expression H:
The class of all self-adjoint (Hermitian) operators, the class of all PT
symmetric operators and the class of all P-self-adjoint operators.
Surprisingly, some of the PT symmetric operators associated to this expression
have no resolvent set
Evaluation of Aposphaeria amaranthi as a Bioherbicide for Pigweed (Amaranthus Spp.)
Studies were conducted to determine the potential of the fungus, Aposphaeria amaranth!, as a bioherbicide for pigweeds (Amaranthus spp.). Experiments to establish the environmental parameters necessary for control of tumble pigweed (A. albus) demonstrated that an 8-hr dew period was sufficient for control of seedlings with four to six leaves, and that temperatures ranging from 20 to 28 C were conducive for disease development. Conidial concentrations as lowas 1x 10s conidia per ml also were sufficient for plant mortality. Host range tests demonstrated pathogenicity of A. amaranthi to several other species of Amaranthus, including biotypes resistant to triazine herbicides. Disease on redroot pigweed (A. retroflexus) was enhanced by incorporation of surfactants into inoculum suspensions. Field tests conducted in 1990 resulted in 73% control of redroot pigweed and 99% control of tumble pigweed. These results suggest that Aposphaeria amaranthi has potential as a bioherbicide for controlling pigweeds
Massive Dirac particles on the background of charged de-Sitter black hole manifolds
We consider the behavior of massive Dirac fields on the background of a
charged de-Sitter black hole. All black hole geometries are taken into account,
including the Reissner-Nordstr\"{o}m-de-Sitter one, the Nariai case and the
ultracold case. Our focus is at first on the existence of bound quantum
mechanical states for the Dirac Hamiltonian on the given backgrounds. In this
respect, we show that in all cases no bound state is allowed, which amounts
also to the non-existence of normalizable time-periodic solutions of the Dirac
equation. This quantum result is in contrast to classical physics, and it is
shown to hold true even for extremal cases. Furthermore, we shift our attention
on the very interesting problem of the quantum discharge of the black holes.
Following Damour-Deruelle-Ruffini approach, we show that the existence of
level-crossing between positive and negative continuous energy states is a
signal of the quantum instability leading to the discharge of the black hole,
and in the cases of the Nariai geometry and of the ultracold geometries we also
calculate in WKB approximation the transmission coefficient related to the
discharge process.Comment: 19 pages, 11 figures. Macro package: Revtex4. Changes concern mainly
the introduction and the final discussion in section VI; moreover, Appendix D
on the evaluation of the Nariai transmission integral has been added.
References adde
Electronic States of Graphene Grain Boundaries
We introduce a model for amorphous grain boundaries in graphene, and find
that stable structures can exist along the boundary that are responsible for
local density of states enhancements both at zero and finite (~0.5 eV)
energies. Such zero energy peaks in particular were identified in STS
measurements [J. \v{C}ervenka, M. I. Katsnelson, and C. F. J. Flipse, Nature
Physics 5, 840 (2009)], but are not present in the simplest pentagon-heptagon
dislocation array model [O. V. Yazyev and S. G. Louie, Physical Review B 81,
195420 (2010)]. We consider the low energy continuum theory of arrays of
dislocations in graphene and show that it predicts localized zero energy
states. Since the continuum theory is based on an idealized lattice scale
physics it is a priori not literally applicable. However, we identify stable
dislocation cores, different from the pentagon-heptagon pairs, that do carry
zero energy states. These might be responsible for the enhanced magnetism seen
experimentally at graphite grain boundaries.Comment: 10 pages, 4 figures, submitted to Physical Review
Spectroscopy of southern Galactic disk planetary nebulae. Notes on chemical composition and emission-line stars
We present low resolution spectroscopic observations for a sample of 53
planetary nebulae (PNe) located in the southern sky between Vela and Norma
constellations and pertaining to the Galactic disk with expected Galactocentric
distance range of 5 to 10 kpc.
We derive nebular chemical composition and plasma parameters with the
classical empirical method. For most of the observed objects, this has been
done for the first time. The distributions of the chemical abundances of the
observed disk sample are generally indistinguishable from Galactic bulge and
inner-disk PNe populations. The exceptions are possible differences in the He/H
distribution, as compared to bulge PNe and Ne/Ar, compared to inner-disk PNe
sample. The derived O/H ratios for the observed disk PNe fit to the concept of
flattening of the chemical gradient in the inner parts of the Milky Way.
We use the spectra to search for emission-line central stars in the observed
sample. We found 6 new emission-line central stars comprising examples of all
known types: WEL, VL and [WR]. We confirm that these types represent three
evolutionary unconnected forms of enhanced mass-loss in the central stars of
PNe. We note on the problem of high ionisation PNe with nebular CIV emission
that can mimic the presence of WEL central stars in 1D spectra.Comment: 35 pages, 19 figures, 4 tables (Note: corrected error in measured
flux of [O II] 7325 lines in Table B.1
Properties of pedestrians walking in line: Stepping behavior
In human crowds, interactions among individuals give rise to a variety of
self-organized collective motions that help the group to effectively solve the
problem of coordination. However, it is still not known exactly how humans
adjust their behavior locally, nor what are the direct consequences on the
emergent organization. One of the underlying mechanisms of adjusting individual
motions is the stepping dynamics. In this paper, we present first quantitative
analysis on the stepping behavior in a one-dimensional pedestrian flow studied
under controlled laboratory conditions. We find that the step length is
proportional to the velocity of the pedestrian, and is directly related to the
space available in front of him, while the variations of the step duration are
much smaller. This is in contrast with locomotion studies performed on isolated
pedestrians and shows that the local density has a direct influence on the
stepping characteristics. Furthermore, we study the phenomena of
synchronization -walking in lockstep- and show its dependence on flow
densities. We show that the synchronization of steps is particularly important
at high densities, which has direct impact on the studies of optimizing
pedestrians flow in congested situations. However, small synchronization and
antisynchronization effects are found also at very low densities, for which no
steric constraints exist between successive pedestrians, showing the natural
tendency to synchronize according to perceived visual signals.Comment: 8 pages, 5 figure
Discovery of a [WO] central star in the planetary nebula Th 2-A
% context About 2500 planetary nebulae are known in our Galaxy but only 224
have central stars with reported spectral types in the Strasbourg-ESO Catalogue
of Galactic Planetary Nebulae (Acker et al. 1992; Acker et al. 1996) % aims We
have started an observational program aiming to increase the number of PN
central stars with spectral classification. % methods By means of spectroscopy
and high resolution imaging, we identify the position and true nature of the
central star. We carried out low resolution spectroscopic observations at
CASLEO telescope, complemented with medium resolution spectroscopy performed at
Gemini South and Magellan telescopes. % results As a first outcome of this
survey, we present for the first time the spectra of the central star of the PN
Th 2-A. These spectra show emission lines of ionized C and O, typical in
Wolf-Rayet stars. % conclusions We identify the position of that central star,
which is not the brightest one of the visual central pair. We classify it as of
type [WO 3]pec, which is consistent with the high excitation and dynamical age
of the nebula.Comment: 3 pages and 2 figures. Paper recommended for publication in A&
Dynamic studies of aldosterone in anephric man
Dynamic studies of aldosterone in anephric man. Aldosterone metabolism in the absence of a functioning renin-angiotensin system was evaluated in twelve anephric subjects. Plasma aldosterone concentrations determined while subjects were in a supine position were usually low, correlated with the plasma potassium concentration (r = 0.38; P < 0.01) and responded to acute alterations in plasma potassium concentration (r = 0.64; P < 0.001), thus indicating an important role for potassium in aldosterone regulation in anephric man. In contrast, plasma aldosterone concentration did not increase following volume and sodium depletion with ultrafiltration hemodialysis. Its response to angiotensin and corticotropin administration was usually diminished. We felt this was due in part to potassium depletion secondary to maintenance hemodialysis, since potassium repletion in two subjects improved aldosterone responsiveness. Another factor in the diminished aldosterone responsiveness in anephric subjects may be renin deficiency. Upright posture caused increases in plasma aldosterone concentration which could not be explained by concomitant alterations in the concentrations of adrenocorticotropic hormone (ACTH) or plasma electrolytes or metabolic clearance rate of aldosterone.Etudes dynamiques de l'aldostérone chez l'homme anéphrique. Le métabolisme de l'aldostérone en l'absence d'un système rénine angiotensine fonctionnel a été évalué chez douze sujets anéphriques. Les concentrations d'aldostérone en position debout étaient habituellement basses, corrélées avec la kaliémie (r = 0,38; P < 0,01) et répondaient aux modifications aiguës de la kaliémie (r = 0,64; P < 0,001), ce qui indique un rôle important du potassium dans la régulation de l'aldostérone chez l'homme anéphrique. Au contraire, la concentration d'aldostérone du plasma n'a pas augmenté après une déplétion d'eau et de sodium réalisée par ultrafiltration au cours de l'hémodialyse. La réponse à l'angiotensine et à l'ACTH était habituellement diminuée. Il est proposé que cela soit du en partie à la déplétion en potassium secondaire à l'hémodialyse chronique puisque la recharge en potassium chez deux sujets a amélioré la réponse aux stimuli. Un autre facteur dans la diminution de la réponse chez les sujets anéphriques peut être le déficit de rénine. La position debout a déterminé des augmentations de l'aldostérone du plasma qui ne peuvent pas être expliquées par des modifications concomitantes de l'ACTH, des électrolytes du plasma ou du débit de la clearance métabolique de l'aldostérone
Self-reported clinical pharmacy service provision in Austria: an analysis of both the community and hospital pharmacy sector: a national study.
Background: With expansion of more advanced clinical roles for pharmacists we need to be mindful that the extent to which clinical pharmacy services (CPS) are implemented varies from one country to another. To date no comprehensive assessment of number and types of CPS provided by either community or hospital pharmacies in Austria exists. Objective: To analyse and describe the number and types of CPS provided in both community and hospital pharmacies, as well as the level of clinical pharmacy education of pharmacists across Austria. Setting: Austrian community and hospital pharmacies. Method: An electronic questionnaire to determine number and types of CPS provided was issued to all chief pharmacists at all community (n=1365) and hospital pharmacies (n=40) across Austria. Besides current and future CPS provision, education and training provision were determined. Main outcome measure: Extent of and attitude towards CPS in Austria. Results: Response rates to the surveys were 19.1% (n=261/1365) in community and 92.5% (n=37/40) in hospital pharmacies. 59.0% and 89.2% of community and hospital pharmacies, respectively, indicated that CPS provision has increased substantially in the past 10 years. 51.0% of community pharmacies reported to provide a medication review service, while 97.3% of hospitals provide a range of CPS. Only 18.0% of community pharmacies offer services other than medication review services at dispensing. Binary regressions show that provision of already established medication management is a predictor for the willingness of community pharmacists to extend the range of CPS (p [less than] 0.01), while completed training in the area of clinical pharmacy is not (p [greater than] 0.05). More hospital than community pharmacists have postgraduate education in clinical pharmacy (17.4% vs 6.5%). A desire to complete postgraduate education was shown by 28.3% of community and 14.7% of hospital pharmacists. Lack of time, inadequate remuneration, lack of resources and poor relationship between pharmacists and physicians were highlighted as barriers. Conclusion: Both community and hospital pharmacists show strong willingness to expand their CPS provision and will need continued support, such as improved legislative structures, more supportive resources and practice focused training opportunities, to further these services
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