723 research outputs found
The momentum and photon energy dependence of the circular dichroic photoemission in the bulk Rashba semiconductors BiTeX (X = I, Br, Cl)
Bulk Rashba systems BiTeX (X = I, Br, Cl) are emerging as important
candidates for developing spintronics devices, because of the coexistence of
spin-split bulk and surface states, along with the ambipolar character of the
surface charge carriers. The need of studying the spin texture of strongly
spin-orbit coupled materials has recently promoted circular dichroic Angular
Resolved Photoelectron Spectroscopy (cd-ARPES) as an indirect tool to measure
the spin and the angular degrees of freedom. Here we report a detailed photon
energy dependent study of the cd-ARPES spectra in BiTeX (X = I, Br and Cl). Our
work reveals a large variation of the magnitude and sign of the dichroism.
Interestingly, we find that the dichroic signal modulates differently for the
three compounds and for the different spin-split states. These findings show a
momentum and photon energy dependence for the cd-ARPES signals in the bulk
Rashba semiconductor BiTeX (X = I, Br, Cl). Finally, the outcome of our
experiment indicates the important relation between the modulation of the
dichroism and the phase differences between the wave-functions involved in the
photoemission process. This phase difference can be due to initial or final
state effects. In the former case the phase difference results in possible
interference effects among the photo-electrons emitted from different atomic
layers and characterized by entangled spin-orbital polarized bands. In the
latter case the phase difference results from the relative phases of the
expansion of the final state in different outgoing partial waves.Comment: 6 pages, 4 figure
Thermodynamics of the coupled spin-dimer system TlCuCl3 close to a quantum phase transition
We present thermal expansion alpha, magnetostriction and specific heat C
measurements of \tal, which shows a quantum phase transition from a spin-gap
phase to a Neel-ordered ground state as a function of magnetic field around
H_{C0}->4.8T. Using Ehrenfest's relation, we find huge pressure dependencies of
the spin gap for uniaxial as well as for hydrostatic pressure. For T->0 and
H->H_{C0} we observe a diverging Grueneisen parameter Gamma(T)=alpha/C, in
qualitative agreement with theoretical predictions. However, the predicted
individual temperature dependencies alpha(T) and C(T) are not reproduced by our
experimental data.Comment: 6 pages including 7 figures, contribution to the III Joint European
Magnetic Symposia 2006, San Sebastia
aMMP-8 Point-of-Care/Chairside Oral Fluid Technology as a Rapid, Non-Invasive Tool for Periodontitis and Peri-Implantitis Screening in a Medical Care Setting
This communication article addresses currently available rapid non-invasive methods to screen and detect periodontitis and dental peri-implantitis. In this regard, oral fluid biomarkers have been researched extensively but self-reported oral health (SROH)-questionnaires have also been developed. Both alternatives may offer a quick and easy way to screen and detect diseased patients. Active matrix metalloproteinase (aMMP-8) is one of the most validated biomarkers for screening and detecting periodontal breakdown related to periodontitis and peri-implantitis and monitoring their treatment effects revealing successful, less- and non-successful treatment results. Currently available aMMP-8 lateral-flow technologies allow this kind of analysis, as demonstrated here, to be conducted quantitatively online and real-time as point-of-care/chairside testing in dental and even medical care settings. In this study, an aMMP-8 peri-implant sulcular fluid point-of-care-test diagnosed peri-implantitis and healthy implants far more accurately than bleeding-on-probing or the other biomarkers, such as polymorphonuclear (PMN)/neutrophil elastase, myeloperoxidase and MMP-9. Although, SROH-questionnaires allow screening in similar settings but they lack the information about the current disease activity of periodontitis and peri-implantitis, which is of essential value in periodontal diagnostics and treatment monitoring. Thus, both methods can be considered as adjunct methods for periodontitis and peri-implant diagnostics, but the value of oral fluid biomarkers analysis does not seem to be substitutable.Peer reviewe
Modelling the black hole silhouette in Sgr A* with ion tori
We calculate the "observed at infinity" image and spectrum of the accretion
structure in Sgr A*, by modelling it as an optically thin, constant angular
momentum ion torus in hydrodynamic equilibrium. The physics we consider
includes a two-temperature plasma, a toroidal magnetic field, as well as
radiative cooling by bremsstrahlung, synchrotron and inverse Compton processes.
Our relativistic model has the virtue of being fully analytic and very simple,
depending only on eight tunable parameters: the black hole spin and the
inclination of the spin axis to our line of sight, the torus angular momentum,
the polytropic index, the magnetic to total pressure ratio, the central values
of density and electron temperature and the ratio of electron to ion
temperatures. The observed image and spectrum are calculated numerically using
the ray-tracing code GYOTO. Our results demonstrate that the ion torus model is
able to account for the main features of the accretion structure surrounding
Sgr A*.Comment: 11 pages, 10 figures, submitted to A &
Three-body Faddeev Calculation for 11Li with Separable Potentials
The halo nucleus Li is treated as a three-body system consisting of an
inert core of Li plus two valence neutrons. The Faddeev equations are
solved using separable potentials to describe the two-body interactions,
corresponding in the n-Li subsystem to a p resonance plus a
virtual s-wave state. The experimental Li energy is taken as input and
the Li transverse momentum distribution in Li is studied.Comment: 6 pages, RevTeX, 1 figur
Binary black hole shadows, chaotic scattering and the Cantor set
We investigate the qualitative features of binary black hole shadows using the model of two
extremally charged black holes in static equilibrium (a MajumdarâPapapetrou solution). Our
perspective is that binary spacetimes are natural exemplars of chaotic scattering, because they
admit more than one fundamental null orbit, and thus an uncountably infinite set of perpetual null
orbits which generate scattering singularities in initial data. Inspired by the three-disc model, we
develop an appropriate symbolic dynamics to describe planar null geodesics on the double black
hole spacetime. We show that a one-dimensional (1D) black hole shadow may constructed through
an iterative procedure akin to the construction of the Cantor set; thus the 1D shadow is self-similar.
Next, we study non-planar rays, to understand how angular momentum affects the existence and
properties of the fundamental null orbits. Taking slices through 2D shadows, we observe three
types of 1D shadow: regular, Cantor-like, and highly chaotic. The switch from Cantor-like to
regular occurs where outer fundamental orbits are forbidden by angular momentum. The highly
chaotic part is associated with an unexpected feature: stable and bounded null orbits, which exist
around two black holes of equal mass M separated by a1 < a < â
2a1, where a1 = 4M/â
27. To
show how this possibility arises, we define a certain potential function and classify its stationary
points. We conjecture that the highly chaotic parts of the 2D shadow possess the Wada property.
Finally, we consider the possibility of following null geodesics through event horizons, and chaos in
the maximally extended spacetime
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