612 research outputs found
Checklist of Anomuran crabs (Crustacea: Decapoda) from the Eastern Tropical Pacific
Literature dealing with anomuran crabs from the east Pacific is reviewed. Marine and brackish water species reported at least once in the Eastern Tropical Pacific zoogeographic subregion, which extends from Magdalena Bay, on the west coast of Baja California Sur, Mexico, to Paita, in Northern Peru, are listed,and their distribution range along the Pacific coast of America are provided. Unpublished records, based on material kept in the collections of the authors, were also considered to determine or confirm the presence of species, or to modify previously published distribution ranges within the study area. A total of 207 species, belonging to 56 genera, are included in the checklist, the first ever made available for the entire tropical zoogeographic subregion of the west coast of America. A list of names of species and subspecies currently recognized as invalid for the area is also included
Mission Concept for the Single Aperture Far-Infrared (SAFIR) Observatory
The Single Aperture Far-InfraRed (SAFIR) Observatory's science goals are
driven by the fact that the earliest stages of almost all phenomena in the
universe are shrouded in absorption by and emission from cool dust and gas that
emits strongly in the far-infrared and submillimeter. Over the past several
years, there has been an increasing recognition of the critical importance of
this spectral region to addressing fundamental astrophysical problems, ranging
from cosmological questions to understanding how our own Solar System came into
being. The development of large, far-infrared telescopes in space has become
more feasible with the combination of developments for the James Webb Space
Telescope and of enabling breakthroughs in detector technology. We have
developed a preliminary but comprehensive mission concept for SAFIR, as a 10
m-class far-infrared and submillimeter observatory that would begin development
later in this decade to meet the needs outlined above. Its operating
temperature (<4K) and instrument complement would be optimized to reach the
natural sky confusion limit in the far-infrared with diffraction-limited
peformance down to at least 40 microns. This would provide a point source
sensitivity improvement of several orders of magnitude over that of Spitzer or
Herschel, with finer angular resolution, enabling imaging and spectroscopic
studies of individual galaxies in the early universe. We have considered many
aspects of the SAFIR mission, including the telescope technology, detector
needs and technologies, cooling method and required technology developments,
attitude and pointing, power systems, launch vehicle, and mission operations.
The most challenging requirements for this mission are operating temperature
and aperture size of the telescope, and the development of detector arrays.Comment: 36 page
3D MHD Flux Emergence Experiments: Idealized models and coronal interactions
This paper reviews some of the many 3D numerical experiments of the emergence
of magnetic fields from the solar interior and the subsequent interaction with
the pre-existing coronal magnetic field. The models described here are
idealized, in the sense that the internal energy equation only involves the
adiabatic, Ohmic and viscous shock heating terms. However, provided the main
aim is to investigate the dynamical evolution, this is adequate. Many
interesting observational phenomena are explained by these models in a
self-consistent manner.Comment: Review article, accepted for publication in Solar Physic
SD-brane gravity fields and rolling tachyons
S(pacelike)D-branes are objects arising naturally in string theory when
Dirichlet boundary conditions are imposed on the time direction. SD-brane
physics is inherently time-dependent. Previous investigations of gravity fields
of SD-branes have yielded undesirable naked spacelike singularities. We set up
the problem of coupling the most relevant open-string tachyonic mode to
massless closed-string modes in the bulk, with backreaction and Ramond-Ramond
fields included. We find solutions numerically in a self-consistent
approximation; our solutions are naturally asymptotically flat and
time-reversal asymmetric. We find completely nonsingular evolution; in
particular, the dilaton and curvature are well-behaved for all time. The
essential mechanism for spacetime singularity resolution is the inclusion of
full backreaction between the bulk fields and the rolling tachyon. Our analysis
is not the final word on the story, because we have to make some significant
approximations, most notably homogeneity of the tachyon on the unstable branes.
Nonetheless, we provide significant progress in plugging a gaping hole in prior
understanding of the gravity fields of SD-branes.Comment: References added. Analysis for much broader range of solutions
presented. Conclusions unchanged. Time-reversal symmetric examples ruled out,
new examples are provide
Solitonic Strings and BPS Saturated Dyonic Black Holes
We consider a six-dimensional solitonic string solution described by a
conformal chiral null model with non-trivial superconformal transverse
part. It can be interpreted as a five-dimensional dyonic solitonic string wound
around a compact fifth dimension. The conformal model is regular with the
short-distance (`throat') region equivalent to a WZW theory. At distances
larger than the compactification scale the solitonic string reduces to a dyonic
static spherically-symmetric black hole of toroidally compactified heterotic
string. The new four-dimensional solution is parameterised by five charges,
saturates the Bogomol'nyi bound and has nontrivial dilaton-axion field and
moduli fields of two-torus. When acted by combined T- and S-duality
transformations it serves as a generating solution for all the static
spherically-symmetric BPS-saturated configurations of the low-energy heterotic
string theory compactified on six-torus. Solutions with regular horizons have
the global space-time structure of extreme Reissner-Nordstrom black holes with
the non-zero thermodynamic entropy which depends only on conserved (quantised)
charge vectors. The independence of the thermodynamic entropy on moduli and
axion-dilaton couplings strongly suggests that it should have a microscopic
interpretation as counting degeneracy of underlying string configurations. This
interpretation is supported by arguments based on the corresponding
six-dimensional conformal field theory. The expression for the level of the WZW
theory describing the throat region implies a renormalisation of the string
tension by a product of magnetic charges, thus relating the entropy and the
number of oscillations of the solitonic string in compact directions.Comment: 27 Pages, uses RevTeX (solution for the axion field corrected,
erratum to appear in Phys. Rev. D
Mountain maple and balsam fir early response to partial and clear-cut harvesting under aspen stands of northern Quebec
This study is a component of the Sylviculture et am
Physics of Solar Prominences: II - Magnetic Structure and Dynamics
Observations and models of solar prominences are reviewed. We focus on
non-eruptive prominences, and describe recent progress in four areas of
prominence research: (1) magnetic structure deduced from observations and
models, (2) the dynamics of prominence plasmas (formation and flows), (3)
Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and
large-scale patterns of the filament channels in which prominences are located.
Finally, several outstanding issues in prominence research are discussed, along
with observations and models required to resolve them.Comment: 75 pages, 31 pictures, review pape
Search for the glueball candidates f0(1500) and fJ(1710) in gamma gamma collisions
Data taken with the ALEPH detector at LEP1 have been used to search for gamma
gamma production of the glueball candidates f0(1500) and fJ(1710) via their
decay to pi+pi-. No signal is observed and upper limits to the product of gamma
gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have
been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) <
0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV
at 95% confidence level.Comment: 10 pages, 3 figure
Semiautomatic Assessment of the Terminal Ileum and Colon in Patients with Crohn Disease Using MRI (the VIGOR++ Project)
Rationale and Objectives: The objective of this study was to develop and validate a predictive magnetic resonance imaging (MRI) activity score for ileocolonic Crohn disease activity based on both subjective and semiautomatic MRI features. Materials and Methods: An MRI activity score (the “virtual gastrointestinal tract [VIGOR]” score) was developed from 27 validated magnetic resonance enterography datasets, including subjective radiologist observation of mural T2 signal and semiautomatic measurements of bowel wall thickness, excess volume, and dynamic contrast enhancement (initial slope of increase). A second subjective score was developed based on only radiologist observations. For validation, two observers applied both scores and three existing scores to a prospective dataset of 106 patients (59 women, median age 33) with known Crohn disease, using the endoscopic Crohn's Disease Endoscopic Index of Severity (CDEIS) as a reference standard. Results: The VIGOR score (17.1 × initial slope of increase + 0.2 × excess volume + 2.3 × mural T2) and other activity scores all had comparable correlation to the CDEIS scores (observer 1: r = 0.58 and 0.59, and observer 2: r = 0.34–0.40 and 0.43–0.51, respectively). The VIGOR score, however, improved interobserver agreement compared to the other activity scores (intraclass correlation coefficient = 0.81 vs 0.44–0.59). A diagnostic accuracy of 80%–81% was seen for the VIGOR score, similar to the other scores. Conclusions: The VIGOR score achieves comparable accuracy to conventional MRI activity scores, but with significantly improved reproducibility, favoring its use for disease monitoring and therapy evaluation
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