2,833 research outputs found
Transmission Resonance in an Infinite Strip of Phason-Defects of a Penrose Approximant Network
An exact method that analytically provides transfer matrices in finite
networks of quasicrystalline approximants of any dimensionality is discussed.
We use these matrices in two ways: a) to exactly determine the band structure
of an infinite approximant network in analytical form; b) to determine, also
analytically, the quantum resistance of a finite strip of a network under
appropriate boundary conditions. As a result of a subtle interplay between
topology and phase interferences, we find that a strip of phason-defects along
a special symmetry direction of a low 2-d Penrose approximant, leads to the
rigorous vanishing of the reflection coefficient for certain energies. A
similar behavior appears in a low 3-d approximant. This type of ``resonance" is
discussed in connection with the gap structure of the corresponding ordered
(undefected) system.Comment: 18 pages special macros jnl.tex,reforder.tex, eqnorder.te
Copepod (Crustacea) distribution in the freshwater and hyposaline lakes of the Pantanal of Nhecolandia (Mato Grosso do Sul, Brazil).
Eighteen freshwater and hyposaline lakes of the Nhecolândia floodplain were sampled in two periods, April/03 (beginning of dry period) and March/04 (end of wet period). Dezoito lagoas de água doce e de água hiposalina do Pantanal da Nhecolândia foram amostrados em dois perĂodos, abril/03 (inĂcio da seca) e março/04(fim da cheia)
Essential facts of the monitoring of the sand extraction and its impact on the Flemish banks on the Belgian Continental Shelf from 2003 to 2012
The monitoring of sand extraction on the Flemish sandbanks of the Belgian continental shelf is based on multiple types of data: statistics derived from the extraction registers, data from the Electronic Monitoring System (EMS = “black-boxes”) on board the dredging vessels (complete records are available since 2003), and regular bathymetric surveys with the multibeam echosounders MBES) EM1002 and EM3002D (installed on the R/V Belgica) across the sandbanks along parallel lines and on specific areas. The analysis of the various types of data provides a 4D (space and time) view of the evolution of the extraction and admits robust and pragmatic conclusions about the real impact of the sand extraction on the marine environment. From 2003 to 2012, the global bathymetric evolution, based on MBES EM1002 and EM3002D measurements along lines across the control zones, confirms thestraightforward relation between the extraction and the bathymetrical evolution. On a larger scale, virtually all ofthe bathymetric variation can be explained by the extraction itself. In areas without any extraction, no significanttrend of the bathymetry is observed
Composition of Kinetic Momenta: The U_q(sl(2)) case
The tensor products of (restricted and unrestricted) finite dimensional
irreducible representations of \uq are considered for a root of unity.
They are decomposed into direct sums of irreducible and/or indecomposable
representations.Comment: 27 pages, harvmac and tables macros needed, minor TeXnical revision
to allow automatic TeXin
Deep Mid-Infrared Silicate Absorption as a Diagnostic of Obscuring Geometry Toward Galactic Nuclei
The silicate cross section peak near 10um produces emission and absorption
features in the spectra of dusty galactic nuclei observed with the Spitzer
Space Telescope. Especially in ultraluminous infrared galaxies, the observed
absorption feature can be extremely deep, as IRAS 08572+3915 illustrates. A
foreground screen of obscuration cannot reproduce this observed feature, even
at large optical depth. Instead, the deep absorption requires a nuclear source
to be deeply embedded in a smooth distribution of material that is both
geometrically and optically thick. In contrast, a clumpy medium can produce
only shallow absorption or emission, which are characteristic of
optically-identified active galactic nuclei. In general, the geometry of the
dusty region and the total optical depth, rather than the grain composition or
heating spectrum, determine the silicate feature's observable properties. The
apparent optical depth calculated from the ratio of line to continuum emission
generally fails to accurately measure the true optical depth. The obscuring
geometry, not the nature of the embedded source, also determines the far-IR
spectral shape.Comment: To appear in ApJ
U.S. pregnant women's knowledge and attitudes about behavioral strategies and vaccines to prevent Zika acquisition
INTRODUCTION:
Zika virus infection during pregnancy can cause significant infant morbidity. Little is known about pregnant women's attitudes regarding behavioral strategies and hypothetical vaccination to prevent Zika infections and sequelae.
METHODS:
Pregnant women across the United States (N = 362) completed an online questionnaire regarding attitudes about Zika, including six behavioral prevention strategies (i.e., abstaining from sex, using condoms, not traveling to an area with Zika, their partner not traveling into an area with Zika, using mosquito repellant, wearing long pants and sleeves) and vaccination.
RESULTS:
Most women (91%) were married/living with the baby's father, 65% were non-Hispanic White, and 71% had been pregnant. Seventy-four percent were worried about Zika, while 30% thought they were knowledgeable about Zika. The mean knowledge score was 5.0 out of 8 (SD = 2.09), and the mean behavioral strategies score was 4.9 out of 12 (SD = 3.7) with a range of 0 (none would be hard to do) to 12 (all would be hard to do). In a multivariable model, having had a sexually transmitted infection, living/traveling in an area with Zika, and worrying about Zika were significantly related to reporting behavioral strategies as hard to do. Seventy-two percent would be willing to be vaccinated. In the multivariable model, living/traveling in an area with Zika, believing they knew a lot about Zika, worrying about Zika, and considering Zika vaccine development as important were significantly associated with willingness to get vaccinated.
CONCLUSIONS:
Pregnant women were worried about Zika, yet had gaps in their factual knowledge. Most women reported they would get vaccinated if a vaccine was available. Pregnant women who reported themselves as vulnerable (being worried, having lived in or traveled to a Zika area) were more likely to view behavioral strategies as hard to do and to accept vaccination
Resolved Mid-IR Emission in the Narrow Line Region of NGC 4151
We present subarcsecond resolution mid infrared images of NGC 4151 at 10.8
micron and 18.2 micron. These images were taken with the University of Florida
mid-IR camera/spectrometer OSCIR at the Gemini North 8-m telescope. We resolve
emission at both 10.8 micron and 18.2 micron extending ~ 3.5" across at a P.A.
of ~ 60 degrees. This coincides with the the narrow line region of NGC 4151 as
observed in [OIII] by the Hubble Space Telescope. The most likely explanation
for this extended mid-IR emission is dust in the narrow line region heated by a
central engine. We find no extended emission associated with the proposed torus
and place an upper limit on its mid-IR size of less than or equal to ~ 35 pc.Comment: accepted for publication in the Astrophysical Journal, 19 pages
including 5 figure
Centre and Representations of U_q(sl(2|1)) at Roots of Unity
Quantum groups at roots of unity have the property that their centre is
enlarged. Polynomial equations relate the standard deformed Casimir operators
and the new central elements. These relations are important from a physical
point of view since they correspond to relations among quantum expectation
values of observables that have to be satisfied on all physical states. In this
paper, we establish these relations in the case of the quantum Lie superalgebra
U_q(sl(2|1)). In the course of the argument, we find and use a set of
representations such that any relation satisfied on all the representations of
the set is true in U_q(sl(2|1)). This set is a subset of the set of all the
finite dimensional irreducible representations of U_q(sl(2|1)), that we
classify and describe explicitly.Comment: Minor corrections, References added. LaTeX2e, 18 pages, also
available at http://lapphp0.in2p3.fr/preplapp/psth/ENSLAPP583.ps.gz . To
appear in J. Phys. A: Math. Ge
Impact evaluation of marine aggregate extraction through adaptive monitoring of bottom shear stress in bedform areas
Dedicated monitoring programmes are needed for the evaluation of the effects of the exploitation of non-living resources on the territorial sea and the continental shelf. Related to physical impacts, hydrodynamics and sediment transport, together with sedimentological and morphological evolution, need investigation. Overall aim is to increase process and system knowledge of both natural and exploited areas, with a particular focus on thecompliancy of extraction activities with respect to European Directives (e.g., European Marine Strategy Framework Directive and Habitat Directive). More specifically assessments are needed of changes in seafloor integrity and hydrographic conditions, two descriptors to define Good Environmental Status within Europe’sMarine Strategy Framework Directive.An important parameter is the bottom shear stress, with knowledge needed on both natural and anthropogenically induced variability. Bottom shear stress measurements are used for the validation of numerical models, necessary for impact quantification in the far field. Extensive data-model integration is critical for adequate assessments of the status of the marine environment, a prerequisite for sustainable use of living, and non-living resources
HST and UKIRT imaging observations of z~1 6C radio galaxies - II. Galaxy morphologies and the alignment effect
(abridged) Powerful radio galaxies often display enhanced optical/UV emission
regions, elongated and aligned with the radio jet axis. The aim of this series
of papers is to separately investigate the effects of radio power and redshift
on the alignment effect, together with other radio galaxy properties. In this
second paper, we present a deeper analysis of the morphological properties of
these systems, including both the host galaxies and their surrounding aligned
emission. The host galaxies of our 6C subsample are well described as de
Vaucouleurs ellipticals, with typical scale sizes of ~10kpc. This is comparable
to the host galaxies of low-z radio sources of similar powers, and also the
more powerful 3CR sources at the same redshift. The contribution of nuclear
point source emission is also comparable, regardless of radio power. The 6C
alignment effect is remarkably similar to that seen around more powerful 3CR
sources at the same redshift in terms of extent and degree of alignment with
the radio source axis, although it is generally less luminous. The bright,
knotty features observed in the case of the z~1 3CR sources are far less
frequent in our 6C subsample; neither do we observe such strong evidence for
evolution in the strength of the alignment effect with radio source size/age.
However, we do find a very strong link between the most extreme alignment
effects and emission line region properties indicative of shocks, regardless of
source size/age or power. In general, the 6C alignment effect is still
considerably stronger than that seen around lower redshift galaxies of similar
radio powers. (abridged)Comment: 23 pages, 15 figures, accepted for publication in MNRAS. See
http://www.mrao.cam.ac.uk/~kji/MorphPaper/ for version of paper with full
resolution images of Figs 1-1
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