211,138 research outputs found
Operators between subspaces and quotients of L1
We provide an unified approach of results of L. Dor on the complementation of
the range, and of D. Alspach on the nearness from isometries, of small into
isomorphisms of L1. We introduce the notion of small subspace of L1 and show
lifting theorems for operators between quotients of L1 by small subspaces. We
construct a subspace of L1 which shows that extension of isometries from
subspaces of L1 to the whole space are no longer true for isomorphisms, and
that nearly isometric isomorphisms from subspaces of L1 into L1 need not be
near from any isometry.Comment: 35 page
Fluorine Abundances of Galactic Low-Metallicity Giants
With abundances and 2{\sigma} upper limits of fluorine (F) in seven
metal-poor field giants, nucleosynthesis of stellar F at low metallicity is
discussed. The measurements are derived from the HF(1-0) R9 line at 23358{\AA}
using nearinfrared K-band high-resolution spectra obtained with CRIRES at the
Very Large Telescope. The sample reaches lower metallicities than previous
studies on F of field giants, ranging from [Fe/H] = -1.56 down to -2.13.
Effects of three-dimensional model atmospheres on the derived F and O
abundances are quantitatively estimated and shown to be insignificant for the
program stars. The observed F yield in the form of [F/O] is compared with two
sets of Galactic chemical evolution models, which quantitatively demonstrate
the contribution of Type II supernova (SN II) {\nu}-process and asymptotic
giant branch/Wolf-Rayet stars. It is found that at this low-metallicity region,
models cannot well predict the observed distribution of [F/O], while the
observations are better fit by models considering an SN II {\nu}-process with a
neutrino energy of E_{\nu} = 3 x 10^53 erg. Our sample contains HD 110281, a
retrograde orbiting low-{\alpha} halo star, showing a similar F evolution as
globular clusters. This supports the theory that such halo stars are possibly
accreted from dwarf galaxy progenitors of globular clusters in the halo.Comment: 8 pages, 8 figures, 2 tables, published in The Astrophysical Journa
Engineering a Conformant Probabilistic Planner
We present a partial-order, conformant, probabilistic planner, Probapop which
competed in the blind track of the Probabilistic Planning Competition in IPC-4.
We explain how we adapt distance based heuristics for use with probabilistic
domains. Probapop also incorporates heuristics based on probability of success.
We explain the successes and difficulties encountered during the design and
implementation of Probapop
Functional repair of the corticospinal tract by delayed transplantation of olfactory ensheathing cells in adult rats
Adult rats were trained to use their forepaws to retrieve a piece of food. Destruction of the dorsal corticospinal tract on one side at the level of the first cervical segment abolished the use of the ipsilateral forepaw for retrieval for at least 6 months after operation. Where a variable amount of the corticospinal tract was spared, there was a proportionate persistence of retrieval. In lesioned rats that had shown no retrieval for 8 weeks after operation, a suspension of olfactory ensheathing cells was injected into the lesion site. Starting between 1 and 3 weeks after transplantation, all rats with transplants bridging the lesion site resumed retrieval by the ipsilateral forepaw. Biotin dextran anterograde tracing shows regenerating corticospinal axons crossing the bridge, traveling caudally for ~10 mm in the distal part of the corticospinal tract and forming terminal arborizations in the spinal gray matter. Functional recovery can occur when only ~1% of the corticospinal tract axons are present
The zero-energy state in graphene in a high magnetic field
The fate of the charge-neutral Dirac point in graphene in a high magnetic
field has been investigated at low temperatures ( 0.3 K). In samples
with small (the gate voltage needed to access the Dirac point), the
resistance at the Dirac point diverges steeply with , signalling a
crossover to an insulating state in intense field. The approach to the
insulating state is highly unusual. Despite the steep divergence in , the
profile of vs. in fixed saturates to a -independent value
below 2 K, consistent with charge carrying gapless excitations.Comment: 4 pages, 4 figures. Four new sub-figures have been added. Text
expanded to discuss data from more sample
Unusual Nernst effect suggestive of time-reversal violation in the striped cuprate LaBaCuO
The striped cuprate LaBaCuO ( undergoes several
transitions below the charge-ordering temperature = 54 K. From Nernst
experiments, we find that, below , there exists a large, anomalous
Nernst signal that is symmetric in field , and remains
finite as . The time-reversal violating signal suggests that, below
, vortices of one sign are spontaneously created to relieve interlayer
phase frustration.Comment: 5 pages, 4 figure
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Semantics-Space-Time Cube. A Conceptual Framework for Systematic Analysis of Texts in Space and Time
We propose an approach to analyzing data in which texts are associated with spatial and temporal references with the aim to understand how the text semantics vary over space and time. To represent the semantics, we apply probabilistic topic modeling. After extracting a set of topics and representing the texts by vectors of topic weights, we aggregate the data into a data cube with the dimensions corresponding to the set of topics, the set of spatial locations (e.g., regions), and the time divided into suitable intervals according to the scale of the planned analysis. Each cube cell corresponds to a combination (topic, location, time interval) and contains aggregate measures characterizing the subset of the texts concerning this topic and having the spatial and temporal references within these location and interval. Based on this structure, we systematically describe the space of analysis tasks on exploring the interrelationships among the three heterogeneous information facets, semantics, space, and time. We introduce the operations of projecting and slicing the cube, which are used to decompose complex tasks into simpler subtasks. We then present a design of a visual analytics system intended to support these subtasks. To reduce the complexity of the user interface, we apply the principles of structural, visual, and operational uniformity while respecting the specific properties of each facet. The aggregated data are represented in three parallel views corresponding to the three facets and providing different complementary perspectives on the data. The views have similar look-and-feel to the extent allowed by the facet specifics. Uniform interactive operations applicable to any view support establishing links between the facets. The uniformity principle is also applied in supporting the projecting and slicing operations on the data cube. We evaluate the feasibility and utility of the approach by applying it in two analysis scenarios using geolocated social media data for studying people's reactions to social and natural events of different spatial and temporal scales
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