9,102 research outputs found
Aging-induced stem cell mutations as drivers for disease and cancer
Aging is characterized by a decrease in genome integrity, impaired organ maintenance, and an increased risk of cancer, which coincide with clonal dominance of expanded mutant stem and progenitor cell populations in aging tissues, such as the intestinal epithelium, the hematopoietic system, and the male germline. Here we discuss possible explanations for age-associated increases in the initiation and/or progression of mutant stem/progenitor clones and highlight the roles of stem cell quiescence, replication-associated DNA damage, telomere shortening, epigenetic alterations, and metabolic challenges as determinants of stem cell mutations and clonal dominance in aging
Characterizing entanglement with geometric entanglement witnesses
We show how to detect entangled, bound entangled, and separable bipartite
quantum states of arbitrary dimension and mixedness using geometric
entanglement witnesses. These witnesses are constructed using properties of the
Hilbert-Schmidt geometry and can be shifted along parameterized lines. The
involved conditions are simplified using Bloch decompositions of operators and
states. As an example we determine the three different types of states for a
family of two-qutrit states that is part of the "magic simplex", i.e. the set
of Bell-state mixtures of arbitrary dimension.Comment: 19 pages, 4 figures, some typos and notational errors corrected. To
be published in J. Phys. A: Math. Theo
Direct current superconducting quantum interferometers with asymmetric shunt resistors
We have investigated asymmetrically shunted Nb/Al-AlO/Nb direct current
(dc) superconducting quantum interference devices (SQUIDs). While keeping the
total resistance identical to a comparable symmetric SQUID with , we shunted only one of the two Josephson junctions with
. Simulations predict that the optimum energy resolution
and thus also the noise performance of such an asymmetric SQUID can
be 3--4 times better than that of its symmetric counterpart. Experiments at a
temperature of 4.2\,K yielded for an asymmetric
SQUID with an inductance of . For a comparable symmetric device
was achieved, confirming our simulation results.Comment: 5 pages, 4 figure
Particle alignments and shape change in Ge and Ge
The structure of the nuclei Ge and Ge is studied
by the shell model on a spherical basis. The calculations with an extended
Hamiltonian in the configuration space
(, , , ) succeed in reproducing
experimental energy levels, moments of inertia and moments in Ge isotopes.
Using the reliable wave functions, this paper investigates particle alignments
and nuclear shapes in Ge and Ge.
It is shown that structural changes in the four sequences of the positive-
and negative-parity yrast states with even and odd are caused by
various types of particle alignments in the orbit.
The nuclear shape is investigated by calculating spectroscopic moments of
the first and second states, and moreover the triaxiality is examined by
the constrained Hatree-Fock method.
The changes of the first band crossing and the nuclear deformation depending
on the neutron number are discussed.Comment: 18 pages, 21 figures; submitted to Phys. Rev.
Further results on the cross norm criterion for separability
In the present paper the cross norm criterion for separability of density
matrices is studied. In the first part of the paper we determine the value of
the greatest cross norm for Werner states, for isotropic states and for Bell
diagonal states. In the second part we show that the greatest cross norm
criterion induces a novel computable separability criterion for bipartite
systems. This new criterion is a necessary but in general not a sufficient
criterion for separability. It is shown, however, that for all pure states, for
Bell diagonal states, for Werner states in dimension d=2 and for isotropic
states in arbitrary dimensions the new criterion is necessary and sufficient.
Moreover, it is shown that for Werner states in higher dimensions (d greater
than 2), the new criterion is only necessary.Comment: REVTeX, 19 page
Simultaneous observation of high order multiple quantum coherences at ultralow magnetic fields
We present a method for the simultaneous observation of heteronuclear
multi-quantum coherences (up to the 3rd order), which give an additional degree
of freedom for ultralow magnetic field (ULF) MR experiments, where the chemical
shift is negligible. The nonequilibrium spin state is generated by Signal
Amplification By Reversible Exchange (SABRE) and detected at ULF with
SQUID-based NMR. We compare the results obtained by the heteronuclei Correlated
SpectroscopY (COSY) with a Flip Angle FOurier Series (FAFOS) method. COSY
allows a quantitative analysis of homo- and heteronuclei quantum coherences
A quantum protocol for cheat-sensitive weak coin flipping
We present a quantum protocol for the task of weak coin flipping. We find
that, for one choice of parameters in the protocol, the maximum probability of
a dishonest party winning the coin flip if the other party is honest is
1/sqrt(2). We also show that if parties restrict themselves to strategies
wherein they cannot be caught cheating, their maximum probability of winning
can be even smaller. As such, the protocol offers additional security in the
form of cheat sensitivity.Comment: 4 pages RevTex. Differs from the journal version only in that the
sentences: "The ordering of the authors on this paper was chosen by a coin
flip implemented by a trusted third party. TR lost." have not been remove
The Uniqueness Theorem for Entanglement Measures
We explore and develop the mathematics of the theory of entanglement
measures. After a careful review and analysis of definitions, of preliminary
results, and of connections between conditions on entanglement measures, we
prove a sharpened version of a uniqueness theorem which gives necessary and
sufficient conditions for an entanglement measure to coincide with the reduced
von Neumann entropy on pure states. We also prove several versions of a theorem
on extreme entanglement measures in the case of mixed states. We analyse
properties of the asymptotic regularization of entanglement measures proving,
for example, convexity for the entanglement cost and for the regularized
relative entropy of entanglement.Comment: 22 pages, LaTeX, version accepted by J. Math. Phy
New Rotation Periods in the Pleiades: Interpreting Activity Indicators
We present results of photometric monitoring campaigns of G, K and M dwarfs in the Pleiades carried out in 1994, 1995 and 1996. We have determined rotation periods for 18 stars in this cluster. In this paper, we examine the validity of using observables such as X-ray activity and amplitude of photometric variations as indicators of angular momentum loss. We report the discovery of cool, slow rotators with high amplitudes of variation. This contradicts previous conclusions about the use of amplitudes as an alternate diagnostic of the saturation of angular momentum loss. We show that the X-ray data can be used as observational indicators of mass-dependent saturation in the angular momentum loss proposed on theoretical grounds
Charm Correlation as a Diagnostic Probe of Quark Matter
The use of correlation between two open-charm mesons is suggested to give
information about the nature of the medium created in heavy-ion collisions.
Insensitivity to the charm production rate is achieved by measuring normalized
cumulant. The acollinearity of the D momenta in the transverse plane is a
measure of the medium effect. Its dependence on nuclear size or E_T provides a
signature for the formation of quark matter.Comment: 12 pages, no figure
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