28,837 research outputs found
Perturbations in the relaxation mechanism for a large cosmological constant
Recently, a mechanism for relaxing a large cosmological constant (CC) has
been proposed [arxiv:0902.2215], which permits solutions with low Hubble rates
at late times without fine-tuning. The setup is implemented in the LXCDM
framework, and we found a reasonable cosmological background evolution similar
to the LCDM model with a fine-tuned CC. In this work we analyse analytically
the perturbations in this relaxation model, and we show that their evolution is
also similar to the LCDM model, especially in the matter era. Some tracking
properties of the vacuum energy are discussed, too.Comment: 18 pages, LaTeX; discussion improved, accepted by CQ
Uniaxial pressure dependence of magnetic order in MnSi
We report comprehensive small angle neutron scattering (SANS) measurements
complemented by ac susceptibility data of the helical order, conical phase and
skyrmion lattice phase (SLP) in MnSi under uniaxial pressures. For all
crystallographic orientations uniaxial pressure favours the phase for which a
spatial modulation of the magnetization is closest to the pressure axis.
Uniaxial pressures as low as 1kbar applied perpendicular to the magnetic field
axis enhance the skyrmion lattice phase substantially, whereas the skyrmion
lattice phase is suppressed for pressure parallel to the field. Taken together
we present quantitative microscopic information how strain couples to magnetic
order in the chiral magnet MnSi.Comment: 23 pages, includes supplemen
Information Extraction in Illicit Domains
Extracting useful entities and attribute values from illicit domains such as
human trafficking is a challenging problem with the potential for widespread
social impact. Such domains employ atypical language models, have `long tails'
and suffer from the problem of concept drift. In this paper, we propose a
lightweight, feature-agnostic Information Extraction (IE) paradigm specifically
designed for such domains. Our approach uses raw, unlabeled text from an
initial corpus, and a few (12-120) seed annotations per domain-specific
attribute, to learn robust IE models for unobserved pages and websites.
Empirically, we demonstrate that our approach can outperform feature-centric
Conditional Random Field baselines by over 18\% F-Measure on five annotated
sets of real-world human trafficking datasets in both low-supervision and
high-supervision settings. We also show that our approach is demonstrably
robust to concept drift, and can be efficiently bootstrapped even in a serial
computing environment.Comment: 10 pages, ACM WWW 201
Design and analysis of an isotropic two-dimensional planar Composite Right/Left-Handed waveguide structure
A two-dimensional isotropic Composite Right/Left-Handed (CRLH) waveguide
structure is proposed which is designed for operation in <i>X</i>-band. The
balanced structure possesses left-handed behaviour over a large bandwidth
from 7.5 GHz up to its transition frequency at 10 GHz. Above
this region, the unit cell behaves in a right-handed manner up to
13.5 GHz. Operating the structure within these bands yields a
frequency dependent index of refraction ranging from −2.5 ≤ <i>n </i> ≤ 0.8.
Isotropic characteristics are obtained between 8.5 GHz ≤ <i>f </i> ≤ 12 GHz resulting in −1.5 ≤ <i>n</i> ≤ 0.8. The planar CRLH
structure is designed based on transmission line theory, implemented in
microstrip technology and optimized using full-wave simulation software. An
equivalent circuit model is determined describing the electromagnetic
behaviour of the structure whose element values are obtained by even and odd
mode analysis. The design of the unit cell requires an appropriate
de-embedding process in order to enable an analysis in terms of dispersion
characteristics and Bloch impedance, which are performed both
Phase Transitions in a Two-Component Site-Bond Percolation Model
A method to treat a N-component percolation model as effective one component
model is presented by introducing a scaled control variable . In Monte
Carlo simulations on , , and simple cubic
lattices the percolation threshold in terms of is determined for N=2.
Phase transitions are reported in two limits for the bond existence
probabilities and . In the same limits, empirical formulas
for the percolation threshold as function of one
component-concentration, , are proposed. In the limit a new
site percolation threshold, , is reported.Comment: RevTeX, 5 pages, 5 eps-figure
Direct photon production with effective field theory
The production of hard photons in hadronic collisions is studied using
Soft-Collinear Effective Theory (SCET). This is the first application of SCET
to a physical, observable cross section involving energetic partons in more
than two directions. A factorization formula is derived which involves a
non-trivial interplay of the angular dependence in the hard and soft functions,
both quark and gluon jet functions, and multiple partonic channels. The
relevant hard, jet and soft functions are computed to one loop and their
anomalous dimensions are determined to three loops. The final resummed
inclusive direct photon distribution is valid to next-to-next-to-leading
logarithmic order (NNLL), one order beyond previous work. The result is
improved by including non-logarithmic terms and photon isolation cuts through
matching, and compared to Tevatron data and to fixed order results at the
Tevatron and the LHC. The resummed cross section has a significantly smaller
theoretical uncertainty than the next-to-leading fixed-order result,
particularly at high transverse momentum.Comment: 42 pages, 9 figures; v2: references added, minor changes; v3: typos;
v4: typos, corrections in (16), (47), (72
Lamination And Microstructuring Technology for a Bio-Cell Multiwell array
Microtechnology becomes a versatile tool for biological and biomedical
applications. Microwells have been established long but remained
non-intelligent up to now. Merging new fabrication techniques and handling
concepts with microelectronics enables to realize intelligent microwells
suitable for future improved cancer treatment. The described technology depicts
the basis for the fabrication of a elecronically enhanced microwell. Thin
aluminium sheets are structured by laser micro machining and laminated
successively to obtain registration tolerances of the respective layers of
5..10\^Am. The microwells lasermachined into the laminate are with
50..80\^Am diameter, allowing to hold individual cells within the well.
The individual process steps are described and results on the microstructuring
are given.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/EDA-Publishing
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