19,240 research outputs found
LArGe: Background suppression using liquid argon (LAr) scintillation for 0 decay search with enriched germanium (Ge) detectors
Measurements with a bare p-type high purity germanium diode (HPGe) submerged
in a 19 kg liquid argon (LAr) scintillation detector at MPIK Heidelberg are
reported. The liquid argon--germanium system (LArGe) is operated as a 4
anti-Compton spectrometer to suppress backgrounds in the HPGe. This R&D is
carried out in the framework of the GERDA experiment which searches for
0 decays with HPGe detectors enriched in Ge. The goal of
this work is to develop a novel method to discriminate backgrounds in
0 search which would ultimately allow to investigate the
effective neutrino mass free of background events down to the inverse mass
hierarchy scale. Other applications in low-background counting are expected.Comment: 3 pages, 6 figures, conference proceedings of the 10th Topical
Seminar on Innovative Particle and Radiation Detectors (IPRD06) 1 - 5 October
2006 Siena, Ital
Electronic entanglement in late transition metal oxides
Here we present a study of the entanglement in the electronic structure of
the late transition metal monoxides - MnO, FeO, CoO, and NiO - obtained by
means of density-functional theory in the local density approximation combined
with dynamical mean-field theory (LDA+DMFT). The impurity problem is solved
through Exact Diagonalization (ED), which grants full access to the thermally
mixed many-body ground state density operator. The quality of the electronic
structure is affirmed through a direct comparison between the calculated
electronic excitation spectrum and photoemission experiments. Our treatment
allows for a quantitative investigation of the entanglement in the electronic
structure. Two main sources of entanglement are explicitly resolved through the
use of a fidelity based geometrical entanglement measure, and additional
information is gained from a complementary entropic entanglement measure. We
show that the interplay of crystal field effects and Coulomb interaction causes
the entanglement in CoO to take a particularly intricate form.Comment: Minor changes. Journal reference adde
Robust Unconditionally Secure Quantum Key Distribution with Two Nonorthogonal and Uninformative States
We introduce a novel form of decoy-state technique to make the single-photon
Bennett 1992 protocol robust against losses and noise of a communication
channel. Two uninformative states are prepared by the transmitter in order to
prevent the unambiguous state discrimination attack and improve the phase-error
rate estimation. The presented method does not require strong reference pulses,
additional electronics or extra detectors for its implementation.Comment: 7 pages, 2 figure
The effect of a nucleating agent on lamellar growth in melt-crystallizing polyethylene oxide
The effects of a (non co-crystallizing) nucleating agent on secondary
nucleation rate and final lamellar thickness in isothermally melt-crystallizing
polyethylene oxide are considered. SAXS reveals that lamellae formed in
nucleated samples are thinner than in the pure samples crystallized at the same
undercoolings. These results are in quantitative agreement with growth rate
data obtained by calorimetry, and are interpreted as the effect of a local
decrease of the basal surface tension, determined mainly by the nucleant
molecules diffused out of the regions being about to crystallize. Quantitative
agreement with a simple lattice model allows for some interpretation of the
mechanism.Comment: submitted to Journal of Applied Physics (first version on 22 Apr
2002
Compensating the Noise of a Communication Channel via Asymmetric Encoding of Quantum Information
An asymmetric preparation of the quantum states sent through a noisy channel
can enable a new way to monitor and actively compensate the channel noise. The
paradigm of such an asymmetric treatment of quantum information is the Bennett
1992 protocol, in which the ratio between conclusive and inconclusive counts is
in direct connection with the channel noise. Using this protocol as a guiding
example, we show how to correct the phase drift of a communication channel
without using reference pulses, interruptions of the quantum transmission or
public data exchanges.Comment: 5 pages, 3 figure
Metal chelation therapy and Parkinson\u2019s disease: A critical review on the thermodynamics of complex formation between relevant metal ions and promising or established drugs
The present review reports a list of approximately 800 compounds which have been
used, tested or proposed for Parkinson\u2019s disease (PD) therapy in the year range 2014\u20132019 (April):
name(s), chemical structure and references are given. Among these compounds, approximately 250
have possible or established metal-chelating properties towards Cu(II), Cu(I), Fe(III), Fe(II), Mn(II),
and Zn(II), which are considered to be involved in metal dyshomeostasis during PD. Speciation
information regarding the complexes formed by these ions and the 250 compounds has been collected
or, if not experimentally available, has been estimated from similar molecules. Stoichiometries and
stability constants of the complexes have been reported; values of the cologarithm of the concentration
of free metal ion at equilibrium (pM), and of the dissociation constant Kd (both computed at pH = 7.4
and at total metal and ligand concentrations of 106 and 105 mol/L, respectively), charge and
stoichiometry of the most abundant metal\u2013ligand complexes existing at physiological conditions,
have been obtained. A rigorous definition of the reported amounts is given, the possible usefulness
of this data is described, and the need to characterize the metal\u2013ligand speciation of PD drugs
is underlined
A Pedagogical Intrinsic Approach to Relative Entropies as Potential Functions of Quantum Metrics: the - Family
The so-called -z-\textit{R\'enyi Relative Entropies} provide a huge
two-parameter family of relative entropies which includes almost all well-known
examples of quantum relative entropies for suitable values of the parameters.
In this paper we consider a log-regularized version of this family and use it
as a family of potential functions to generate covariant symmetric
tensors on the space of invertible quantum states in finite dimensions. The
geometric formalism developed here allows us to obtain the explicit expressions
of such tensor fields in terms of a basis of globally defined differential
forms on a suitable unfolding space without the need to introduce a specific
set of coordinates. To make the reader acquainted with the intrinsic formalism
introduced, we first perform the computation for the qubit case, and then, we
extend the computation of the metric-like tensors to a generic -level
system. By suitably varying the parameters and , we are able to recover
well-known examples of quantum metric tensors that, in our treatment, appear
written in terms of globally defined geometrical objects that do not depend on
the coordinates system used. In particular, we obtain a coordinate-free
expression for the von Neumann-Umegaki metric, for the Bures metric and for the
Wigner-Yanase metric in the arbitrary -level case.Comment: 50 pages, 1 figur
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