1,729 research outputs found
Mobile radio interferometric geodetic systems
Operation of the Astronomical Radio Interferometric Earth Surveying (ARIES) in a proof of concept mode is discussed. Accuracy demonstrations over a short baseline, a 180 km baseline, and a 380 km baseline are documented. Use of ARIES in the Sea Slope Experiment of the National Geodetic Survey to study the apparent differences between oceanographic and geodetic leveling determinations of the sea surface along the Pacific Coast is described. Intergration of the NAVSTAR Global Positioning System and a concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) is briefly reviewed
Elevated alpha-synuclein caused by SNCA gene triplication impairs neuronal differentiation and maturation in Parkinson's patient-derived induced pluripotent stem cells
We have assessed the impact of α-synuclein overexpression on the differentiation potential and phenotypic signatures of two neural-committed induced pluripotent stem cell lines derived from a Parkinson´s disease patient with a triplication of the human SNCA genomic locus. In parallel, comparative studies were performed on two control lines derived from healthy individuals and lines generated from the patient iPS-derived neuroprogenitor lines infected with a lentivirus incorporating a small hairpin RNA to knock down the SNCA mRNA. The SNCA triplication lines exhibited a reduced capacity to differentiate into dopaminergic or GABAergic neurons and decreased neurite outgrowth and lower neuronal activity compared with control cultures. This delayed maturation phenotype was confirmed by gene expression profiling, which revealed a significant reduction in mRNA for genes implicated in neuronal differentiation such as delta-like homolog 1 (DLK1), gamma-aminobutyric acid type B receptor subunit 2 (GABABR2), nuclear receptor related 1 protein (NURR1), G-protein-regulated inward-rectifier potassium channel 2 (GIRK-2) and tyrosine hydroxylase (TH). The differentiated patient cells also demonstrated increased autophagic flux when stressed with chloroquine. We conclude that a two-fold overexpression of α-synuclein caused by a triplication of the SNCA gene is sufficient to impair the differentiation of neuronal progenitor cells, a finding with implications for adult neurogenesis and Parkinson´s disease progression, particularly in the context of bioenergetic dysfunction.Fil: Oliveira, L. M. A.. Max-Planck-Institut fĂĽr biophysikalische Chemie; AlemaniaFil: Falomir Lockhart, Lisandro Jorge. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de Investigaciones BioquĂmicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias MĂ©dicas. Instituto de Investigaciones BioquĂmicas de La Plata ; Argentina. Max-Planck-Institut fĂĽr biophysikalische Chemie; AlemaniaFil: Botelho, M. G.. Max-Planck-Institut fĂĽr biophysikalische Chemie; Alemania. Universidade Federal do Rio de Janeiro; BrasilFil: Lin, K. H.. Max-Planck-Institut fĂĽr biophysikalische Chemie; AlemaniaFil: Wales, P.. Universität Göttingen; AlemaniaFil: Koch, J. C.. Universität Göttingen; AlemaniaFil: Gerhardt, Elizabeth. Universität Göttingen; AlemaniaFil: Taschenberger, H.. Max-Planck-Institut fĂĽr biophysikalische Chemie; AlemaniaFil: Outeiro, T. F.. Universität Göttingen; AlemaniaFil: Lingor, P.. Universität Göttingen; AlemaniaFil: SchĂĽele, B.. The Parkinson’s Institute; Estados UnidosFil: Arndt Jovin, D. J.. Max-Planck-Institut fĂĽr biophysikalische Chemie; AlemaniaFil: Jovin, T. M.. Max-Planck-Institut fĂĽr biophysikalische Chemie; Alemani
Preserving entanglement under decoherence and sandwiching all separable states
Every entangled state can be perturbed, for instance by decoherence, and stay
entangled. For a large class of pure entangled states, we show how large the
perturbation can be. Our class includes all pure bipartite and all maximally
entangled states. For an entangled state, E, the constucted neighborhood of
entangled states is the region outside two parallel hyperplanes, which sandwich
the set of all separable states. The states for which these neighborhoods are
largest are the maximally entangled ones. As the number of particles, or the
dimensions of the Hilbert spaces for two of the particles increases, the
distance between two of the hyperplanes which sandwich the separable states
goes to zero. It is easy to decide if a state Q is in the neighborhood of
entangled states we construct for an entangled state E. One merely has to check
if the trace of EQ is greater than a constant which depends upon E and which we
determine.Comment: Corrected first author's e-mail address. All the rest remains
unchange
Electrostatic Patch Effect in Cylindrical Geometry. I. Potential and Energy between Slightly Non-Coaxial Cylinders
We study the effect of any uneven voltage distribution on two close
cylindrical conductors with parallel axes that are slightly shifted in the
radial and by any length in the axial direction. The investigation is
especially motivated by certain precision measurements, such as the Satellite
Test of the Equivalence Principle (STEP). By energy conservation, the force can
be found as the energy gradient in the vector of the shift, which requires
determining potential distribution and energy in the gap. The boundary value
problem for the potential is solved, and energy is thus found to the second
order in the small transverse shift, and to lowest order in the gap to cylinder
radius ratio. The energy consists of three parts: the usual capacitor part due
to the uniform potential difference, the one coming from the interaction
between the voltage patches and the uniform voltage difference, and the energy
of patch interaction, entirely independent of the uniform voltage. Patch effect
forces and torques in the cylindrical configuration are derived and analyzed in
the next two parts of this work.Comment: 26 pages, 1 Figure. Submitted to Classical and Quantum Gravit
Multiple and Fast: The Accretion of Ordinary Chondrite Parent Bodies
Although petrologic, chemical and isotopic studies of ordinary chondrites and
meteorites in general have largely helped establish a chronology of the
earliest events of planetesimal formation and their evolution, there are
several questions that cannot be resolved via laboratory measurements and/or
experiments only. Here we propose rationale for several new constraints on the
formation and evolution of ordinary chondrite parent bodies (and by extension
most planetesimals) from newly available spectral measurements and
mineralogical analysis of main belt S-type asteroids (83 objects) and
unequilibrated ordinary chondrite meteorites (53 samples). Based on the latter,
we suggest spectral data may be used to distinguish whether an ordinary
chondrite was formed near the surface or in the interior of its parent body. If
these constraints are correct, the suggested implications include that: i)
large groups of compositionally similar asteroids are a natural outcome of
planetesimal formation and, consequently, meteorites within a given class can
originate from multiple parent bodies; ii) the surfaces of large (up to ~200km)
S-type main-belt asteroids expose mostly the interiors of the primordial
bodies, a likely consequence of impacts by small asteroids (D<10km) in the
early solar system (Ciesla et al. 2013); iii) the duration of accretion of the
H chondrite parent bodies was likely short (instantaneous or in less then ~10^5
yr but certainly not as long as 1 Myr); iv) LL-like bodies formed closer to the
Sun than H-like bodies, a possible consequence of radial mixing and size
sorting of chondrules in the protoplanetary disk prior to accretion.Comment: Accepted for publication in Ap
Sequence alignment, mutual information, and dissimilarity measures for constructing phylogenies
Existing sequence alignment algorithms use heuristic scoring schemes which
cannot be used as objective distance metrics. Therefore one relies on measures
like the p- or log-det distances, or makes explicit, and often simplistic,
assumptions about sequence evolution. Information theory provides an
alternative, in the form of mutual information (MI) which is, in principle, an
objective and model independent similarity measure. MI can be estimated by
concatenating and zipping sequences, yielding thereby the "normalized
compression distance". So far this has produced promising results, but with
uncontrolled errors. We describe a simple approach to get robust estimates of
MI from global pairwise alignments. Using standard alignment algorithms, this
gives for animal mitochondrial DNA estimates that are strikingly close to
estimates obtained from the alignment free methods mentioned above. Our main
result uses algorithmic (Kolmogorov) information theory, but we show that
similar results can also be obtained from Shannon theory. Due to the fact that
it is not additive, normalized compression distance is not an optimal metric
for phylogenetics, but we propose a simple modification that overcomes the
issue of additivity. We test several versions of our MI based distance measures
on a large number of randomly chosen quartets and demonstrate that they all
perform better than traditional measures like the Kimura or log-det (resp.
paralinear) distances. Even a simplified version based on single letter Shannon
entropies, which can be easily incorporated in existing software packages, gave
superior results throughout the entire animal kingdom. But we see the main
virtue of our approach in a more general way. For example, it can also help to
judge the relative merits of different alignment algorithms, by estimating the
significance of specific alignments.Comment: 19 pages + 16 pages of supplementary materia
Geodetic measurements with a mobile VLBI system
The Project ARIES 9 meter transportable antenna was used as one element of very long baseline interferometer (VLBI) to begin monitoring locations of six sites in California relative to large diameter fixed antennas at the NASA Deep Space Network, Goldstone, California, and at the Caltech Owens Valley Radio Observatory, Big Pine, California. An accuracy of about 6 cm in the horizontal components was demonstrated by comparison with measurements of the National Geodetic Survey. The root of mean square scatter of the lengths of the baselines between any pair of antennas was about 3 cm except for the Goldstone-JPL (Pasadena) baseline. In the period August 1974 to August 1977 the length of this baseline increased by 15 + or - 5 cm as JPL moved westward relative to Goldstone at the rate of 6 + or - 2 cm/year. The baseline lengths were unaffected by the uncertainties of UT1, polar motion, and tropospheric water vapor, which are the limitations to present three dimensional vector accuracies
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