13,907 research outputs found
Plant canopy shape and the influences on UV exposures to the canopy
The solar spectra at selected sites over hemispherical, conical and pinnacle plant canopy models has been evaluated with a dosimetric technique. The irradiance at the sites varies by up to a factor of 0.31 compared to the irradiance on a horizontal plane. The biologically effective (UVBE) exposures evaluated with the dosimetric technique at sites over the plant canopy are up to 19% of that on a horizontal plane. Compared to a spectroradiometer, the technique provides a more practicable method of measuring the UVBE exposures at multiple sites over a plant canopy. Usage of a dosimeter at one site to provide the exposures at that site for different sun angles introduces an error of more than 50%. Knowledge of the spectra allowed the UV and UVBE exposures to be calculated at each site along with the exposures to the entire canopies. These were dependent on the sun angle and the canopy shape. For plant damage, the UVBE was a maximum of about 1.4 mJ cm-2/min. Compared to the hemispherical canopy, the UVBE exposure for generalised plant damage was 45% less for the pinnacle canopy and 23% less for the conical canopy. The canopy exposures could not be determined from measurements of the ambient exposure
Symbiotic stars in the Local Group of Galaxies
Preliminary results of the ongoing search for symbiotic binary stars in the
Local Group of Galaxies are presented and discussed.Comment: Proceedings of Physics of Evolved Stars 2015: A Conference Dedicated
to the Memory of Olivier Chesneau, Nice, 8-12 June 201
Fermion masses in noncommutative geometry
Recent indications of neutrino oscillations raise the question of the
possibility of incorporating massive neutrinos in the formulation of the
Standard Model (SM) within noncommutative geometry (NCG). We find that the NCG
requirement of Poincare duality constrains the numbers of massless quarks and
neutrinos to be unequal unless new fermions are introduced. Possible scenarios
in which this constraint is satisfied are discussed.Comment: 4 pages, REVTeX; typos are corrected in (19), "Possible Solutions"
and "Conclusion" are modified; additional calculational details are included;
references are update
Gear mesh compliance modeling
A computer model has been constructed to simulate the compliance and load sharing in a spur gear mesh. The model adds the effect of rim deflections to previously developed state-of-the-art gear tooth deflection models. The effects of deflections on mesh compliance and load sharing are examined. The model can treat gear meshes composed to two external gears or an external gear driving an internal gear. The model includes deflection contributions from the bending and shear in the teeth, the Hertzian contact deformations, and primary and secondary rotations of the gear rims. The model shows that rimmed gears increase mesh compliance and, in some cases, improve load sharing
The luminosity function of Palomar 5 and its tidal tails
We present the main sequence luminosity function of the tidally disrupted
globular cluster Palomar 5 and its tidal tails. For this work we analyzed
imaging data obtained with the Wide Field Camera at the INT (La Palma) and data
from the Wide Field Imager at the MPG/ESO 2.2 m telescope at La Silla down to a
limiting magnitude of approximately 24.5 mag in B. Our results indicate that
preferentially fainter stars were removed from the cluster so that the LF of
the cluster's main body exhibits a significant degree of flattening compared to
other GCs. This is attributed to its advanced dynamical evolution. The LF of
the tails is, in turn, enhanced with faint, low-mass stars, which we interpret
as a consequence of mass segregation in the cluster.Comment: 4 pages, 3 figures, to be published in the proceedings of the
conference "Satellites and tidal streams" held at La Palma, Canary Islands,
May 26 - 30, 200
Constraints on a New Post-General Relativity Cosmological Parameter
A new cosmological variable is introduced which characterizes the degree of
departure from Einstein's General Relativity (GR) with a cosmological constant.
The new parameter, \varpi, is the cosmological analog of \gamma, the
parametrized post-Newtonian variable which measures the amount of spacetime
curvature per unit mass. In the cosmological context, \varpi measures the
difference between the Newtonian and longitudinal potentials in response to the
same matter sources, as occurs in certain scalar-tensor theories of gravity.
Equivalently, \varpi measures the scalar shear fluctuation in a dark energy
component. In the context of a "vanilla" LCDM background cosmology, a non-zero
\varpi signals a departure from GR or a fluctuating cosmological constant.
Using a phenomenological model for the time evolution \varpi=\varpi_0
\rho_{DE}/\rho_{M} which depends on the ratio of energy density in the
cosmological constant to the matter density at each epoch, it is shown that the
observed cosmic microwave background (CMB) temperature anisotropies limit the
overall normalization constant to be -0.4 < \varpi_0 < 0.1 at the 95%
confidence level. Existing measurements of the cross-correlations of the CMB
with large-scale structure further limit \varpi_0 > -0.2 at the 95% CL. In the
future, integrated Sachs-Wolfe and weak lensing measurements can more tightly
constrain \varpi_0, providing a valuable clue to the nature of dark energy and
the validity of GR.Comment: 9 pages, 7 figures; added reference
Recommended from our members
Learning in stomatopod crustaceans
The stomatopod crustaceans, or mantis shrimps, are marine predators that stalk or ambush prey and that have complex intraspecific communication behavior. Their active lifestyles, means of predation, and intricate displays all require unusual flexibility in interacting with the world around them, implying a well-developed ability to learn. Stomatopods have highly evolved sensory systems, including some of the most specialized visual systems known for any animal group. Some species have been demonstrated to learn how to recognize and use novel, artificial burrows, while others are known to learn how to identify novel prey species and handle them for effective predation. Stomatopods learn the identities of individual competitors and mates, using both chemical and visual cues. Furthermore, stomatopods can be trained for psychophysical examination of their sensory abilities, including demonstration of color and polarization vision. These flexible and intelligent invertebrates continue to be attractive subjects for basic research on learning in animals with relatively simple nervous systems
The Texas Standards for Appellate Conduct: An Annotated Guide and Commentary
The legal profession is bound by ethical rules that govern and guide our conduct and actions as lawyers. One of the under-appreciated, but profoundly important set of guidelines is the Texas Standards for Appellate Conduct. These Standards serve as an excellent practice guide for appellate practitioners and appellate courts and as a model code of conduct for the Bar as a whole.
The goal of this Article is to dissect the Texas Standards for Appellate Conduct and provide useful commentaries for the readers to better appreciate and understand each element of the Standards. The commentaries provide direct case examples and anecdotal guidance for the audience’s benefit. Lastly, the Authors hope that this Article serves as a teaching tool, refresher course, or general reminder of how important ethics are in the legal profession and how all parties involved in it can benefit by subscribing to these Standards
Cosmological milestones and energy conditions
Until recently, the physically relevant singularities occurring in FRW
cosmologies had traditionally been thought to be limited to the "big bang", and
possibly a "big crunch". However, over the last few years, the zoo of
cosmological singularities considered in the literature has become considerably
more extensive, with "big rips" and "sudden singularities" added to the mix, as
well as renewed interest in non-singular cosmological events such as "bounces"
and "turnarounds". In this talk, we present an extensive catalogue of such
cosmological milestones, both at the kinematical and dynamical level. First,
using generalized power series, purely kinematical definitions of these
cosmological events are provided in terms of the behaviour of the scale factor
a(t). The notion of a "scale-factor singularity" is defined, and its relation
to curvature singularities (polynomial and differential) is explored. Second,
dynamical information is extracted by using the Friedmann equations (without
assuming even the existence of any equation of state) to place constraints on
whether or not the classical energy conditions are satisfied at the
cosmological milestones. Since the classification is extremely general, and
modulo certain technical assumptions complete, the corresponding results are to
a high degree model-independent.Comment: 8 pages, 1 table, conference proceedings for NEB XII conference in
Nafplio, Greec
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