3,636 research outputs found
Distributions and abundances of Pacific sardine (Sardinops sagax) and other pelagic fishes in the California Current Ecosystem during spring 2006, 2008, and 2010, estimated from acoustic–trawl surveys
The abundances and distributions of coastal pelagic fish
species in the California Current Ecosystem from San Diego to southern Vancouver Island, were estimated from combined acoustic and trawl surveys conducted in the spring of 2006, 2008, and 2010. Pacific sardine (Sardinops sagax), jack mackerel (Trachurus symmetricus), and Pacific mackerel (Scomber japonicus) were the dominant coastal pelagic fish species, in that order. Northern anchovy (Engraulis mordax) and Pacific herring (Clupea pallasii) were sampled only sporadically and therefore estimates for these species were
unreliable. The estimates of sardine biomass compared well with those of the annual assessments and confirmed a declining trajectory of the “northern stock” since 2006. During the sampling period, the biomass of jack mackerel was stable or increasing, and that of Pacific mackerel was
low and variable. The uncertainties in these estimates are mostly the result of spatial patchiness which increased
from sardine to mackerels to anchovy and herring. Future surveys of coastal pelagic fish species in the California
Current Ecosystem should benefit from adaptive sampling based on modeled habitat; increased echosounder and trawl sampling, particularly for the most patchy and nearshore species; and directed-trawl sampling for improved species identification and estimations of their acoustic target
stre
Noether symmetries, energy-momentum tensors and conformal invariance in classical field theory
In the framework of classical field theory, we first review the Noether
theory of symmetries, with simple rederivations of its essential results, with
special emphasis given to the Noether identities for gauge theories. Will this
baggage on board, we next discuss in detail, for Poincar\'e invariant theories
in flat spacetime, the differences between the Belinfante energy-momentum
tensor and a family of Hilbert energy-momentum tensors. All these tensors
coincide on shell but they split their duties in the following sense:
Belinfante's tensor is the one to use in order to obtain the generators of
Poincar\'e symmetries and it is a basic ingredient of the generators of other
eventual spacetime symmetries which may happen to exist. Instead, Hilbert
tensors are the means to test whether a theory contains other spacetime
symmetries beyond Poincar\'e. We discuss at length the case of scale and
conformal symmetry, of which we give some examples. We show, for Poincar\'e
invariant Lagrangians, that the realization of scale invariance selects a
unique Hilbert tensor which allows for an easy test as to whether conformal
invariance is also realized. Finally we make some basic remarks on metric
generally covariant theories and classical field theory in a fixed curved
bakground.Comment: 31 pa
Effect of anisotropic impurity scattering on a density of states of a d-wave superconductor
We discuss the effect of an anisotropic impurity potential on the critical
temperature, local density of states in the vicinity of a single impurity, and
the quasiparticle density of states for a finite impurity concentration in a
d-wave superconductor. Different scattering regimes are concerned.Comment: 3 pages, revtex4, 4 figure
Local Electronic Structure of a Single Magnetic Impurity in a Superconductor
The electronic structure near a single classical magnetic impurity in a
superconductor is determined using a fully self-consistent Koster-Slater
algorithm. Localized excited states are found within the energy gap which are
half electron and half hole. Within a jellium model we find the new result that
the spatial structure of the positive-frequency (electron-like) spectral weight
(or local density of states), can differ strongly from that of the negative
frequency (hole-like) spectral weight. The effect of the impurity on the
continuum states above the energy gap is calculated with good spectral
resolution for the first time. This is also the first three-dimensional
self-consistent calculation for a strong magnetic impurity potential.Comment: 13 pages, RevTex, change in heuristic picture, no change in numerical
result
Non-magnetic impurities in two dimensional superconductors
A numerical approach to disordered 2D superconductors described by BCS mean
field theory is outlined. The energy gap and the superfluid density at zero
temperature and the quasiparticle density of states are studied. The method
involves approximate self-consistent solutions of the Bogolubov-deGennes
equations on finite square lattices. Where comparison is possible, the results
of standard analytic approaches to this problem are reproduced. Detailed
modeling of impurity effects is practical using this approach. The {\it range}
of the impurity potential is shown to be of {\it quantitative importance} in
the case of strong potential scatterers. We discuss the implications for
experiments, such as the rapid suppression of superconductivity by Zn doping in
Copper-Oxide superconductors.Comment: 16 pages, latex, 8 figures( available upon request
Obtaining Stakeholder Consensus on the Core Components of a Parent Support and Training Model for Parents of Children With Serious Emotional Disturbances
This is the publisher's version, also available electronically from http://alliance1.metapress.com/content/y66232237182170g/?genre=article&id=doi%3a10.1606%2f1044-3894.4317Parent-to-parent peer interventions are nationally recognized as an important service within children's community-based mental health systems of care. Despite rapid growth, clearly defined models of professional parent services for statewide application do not exist. In this study, concept mapping was used to achieve stakeholder consensus on the core components of the Parent Support and Training (PST) peer intervention model developed within the Kansas community mental health system. Participants rated the importance and observed frequency of 49 distinct statements related to the service and sorted them into conceptual groups. Analyses reflected a high level of agreement across stakeholders on statements identified as most important and most frequently demonstrated in PST services statewide
Extended Impurity Potential in a d_{x^2-y^2} Superconductor
We investigate the role of a finite potential range of a nonmagnetic impurity
for the local density of states in a d_{x^2-y^2} superconductor. Impurity
induced subgap resonances are modified by the appearance of further scattering
channels beyond the --wave scattering limit. The structure of the local
density of states (DOS) in the vicinity of the impurity is significantly
enhanced and therefore improves the possibility for observing the
characteristic anisotropic spatial modulation of the local DOS in a d_{x^2-y^2}
superconductor by scanning tunneling microscopy.Comment: 4 pages, Revtex, with 4 embedded eps figures. Submitted to Phys. Rev.
Let
Permanent current from non-commutative spin algebra
We show that a spontaneous electric current is induced in a nano-scale
conducting ring just by putting three ferromagnets. The current is a direct
consequence of the non-commutativity of the spin algebra, and is proportional
to the non-coplanarity (chirality) of the magnetization vectors. The
spontaneous current gives a natural explanation to the chirality-driven
anomalous Hall effect.Comment: 7 pages, 4 figures on separate pag
Quantitative LSPR Imaging for Biosensing with Single Nanostructure Resolution
AbstractLocalized surface plasmon resonance (LSPR) imaging has the potential to map complex spatio-temporal variations in analyte concentration, such as those produced by protein secretions from live cells. A fundamental roadblock to the realization of such applications is the challenge of calibrating a nanoscale sensor for quantitative analysis. Here, we introduce a new, to our knowledge, LSPR imaging and analysis technique that enables the calibration of hundreds of individual gold nanostructures in parallel. The calibration allowed us to map the fractional occupancy of surface-bound receptors at individual nanostructures with nanomolar sensitivity and a temporal resolution of 225 ms. As a demonstration of the technique’s applicability to molecular and cell biology, the calibrated array was used for the quantitative LSPR imaging of anti-c-myc antibodies harvested from a cultured 9E10 hybridoma cell line without the need for further purification or processing
- …