2,970 research outputs found
Dolphin Conservation in the Tuna Industry: The United States\u27 Role in an International Problem
Thousands of dolphin die annually in the international tuna fishery. This Comment explores the history of that problem and the domestic and international attempts to alleviate it. Foreign legislation, positions of international organizations, and documents of the United Nations Law of the Sea Conference are reviewed as potential sources of an international solution. The Comment emphasizes the need for active United States involvement in international programs, comprehensive data on the dolphin populations, and immediate action to avoid excessive exploitation. It concludes with a suggestion that increased public concern for dolphin may be utilized effectively to support conservation initiatives
Phylloplane fungi in Hong Kong mangroves: evaluation of study methods
Many methods have been used to study phylloplane fungi, most of which have constraints and may result in biased results. This study used light microscopy and scanning electron microscopy (SEM) to investigate fungal abundance on the leaves of the most common mangrove trees in Hong Kong, Kandelia candel and Aegiceras corniculatum. Species richness was investigated using light microscopy and a leaf washing method. Methods to study phylloplane fungi are discussed and the performances of these three investigation methods are evaluated. Seven mitosporic fungal taxa were found by light microscopy, while 30 sporulating taxa and 18 Mycelia sterilia were isolated using the leaf washing method. Fungal abundance in terms of percentage cover investigated with light microscopy was similar using the SEM method, and was significantly higher on Aegiceras corniculatum than on Kandelia candel. Fungal abundance peaked in the summer and was lowest in the winter. This study indicates that light microscopy reveals the most typical phylloplane fungi and is more efficient than SEM, while the leaf washing method reveals many casual species and is not quantitative.published_or_final_versio
NASA's CubeQuest Challenge - From Ground Tournaments to Lunar and Deep Space Derby
The First Flight of NASA's Space Launch System will feature 13 CubeSats that will launch into cis-lunar space. Three of these CubeSats are winners of the CubeQuest Challenge, part of NASA's Space Technology Mission Directorate (STMD) Centennial Challenge Program. In order to qualify for launch on EM-1, the winning teams needed to win a series of Ground Tournaments, periodically held since 2015. The final Ground Tournament, GT-4, was held in May 2017, and resulted in the Top 3 selection for the EM-1 launch opportunity. The Challenge now proceeds to the in-space Derbies, where teams must build and test their spacecraft before launch on EM-1. Once in space, they will compete for a variety of Communications and Propulsion-based challenges. This is the first Centennial Challenge to compete in space and is a springboard for future in-space Challenges. In addition, the technologies gained from this challenge will also propel development of deep space CubeSats
Tur\'an Colourings in Off-Diagonal Ramsey Multiplicity
The Ramsey multiplicity constant of a graph is the limit as tends to
infinity of the minimum density of monochromatic labelled copies of in a
colouring of the edges of with two colours. Fox and Wigderson recently
identified a large family of graphs whose Ramsey multiplicity constants are
attained by sequences of "Tur\'an colourings;" i.e. colourings in which one of
the colour classes forms the edge set of a balanced complete multipartite
graph. The graphs in their family come from taking a connected non-3-colourable
graph with a critical edge and adding many pendant edges. We extend their
result to an off-diagonal variant of the Ramsey multiplicity constant which
involves minimizing a weighted sum of red copies of one graph and blue copies
of another. We also apply the flag algebra method to investigate the minimum
number of pendant edges required for Tur\'an colourings to become optimal when
the underlying graphs are small cliques.Comment: 48 pages, 2 figure
Hybrid architecture active wavefront sensing and control system, and method
According to various embodiments, provided herein is an optical system and method that can be configured to perform image analysis. The optical system can comprise a telescope assembly and one or more hybrid instruments. The one or more hybrid instruments can be configured to receive image data from the telescope assembly and perform a fine guidance operation and a wavefront sensing operation, simultaneously, on the image data received from the telescope assembly
Dust Grain Orbital Behavior Around Ceres
Many asteroids show indications they have undergone impacts with meteoroid
particles having radii between 0.01 m and 1 m. During such impacts, small dust
grains will be ejected at the impact site. The possibility of these dust grains
(with radii greater than 2.2x10-6 m) forming a halo around a spherical asteroid
(such as Ceres) is investigated using standard numerical integration
techniques. The orbital elements, positions, and velocities are determined for
particles with varying radii taking into account both the influence of gravity,
radiation pressure, and the interplanetary magnetic field (for charged
particles). Under the influence of these forces it is found that dust grains
(under the appropriate conditions) can be injected into orbits with lifetimes
in excess of one year. The lifetime of the orbits is shown to be highly
dependent on the location of the ejection point as well as the angle between
the surface normal and the ejection path. It is also shown that only particles
ejected within 10 degrees relative to the surface tangential survive more than
a few hours and that the longest-lived particles originate along a line
perpendicular to the Ceres-Sun line.Comment: 8 pages, Presented at COSPAR '0
Magnetic and quadrupole moments of light spin-1 mesons in light cone QCD sum rules
The magnetic and quadrupole moments of the light-vector and axial-vector
mesons are calculated in the light cone QCD sum rules. Our results for the
static properties of these mesons are compared with the predictions of lattice
QCD as well as other approaches existing in the literature.Comment: 11 pages, NO figures, LaTeX formatte
Use of waveform lidar and hyperspectral sensors to assess selected spatial and structural patterns associated with recent and repeat disturbance and the abundance of sugar maple (Acer saccharum Marsh.) in a temperate mixed hardwood and conifer forest.
Abstract
Waveform lidar imagery was acquired on September 26, 1999 over the Bartlett Experimental Forest (BEF) in New Hampshire (USA) using NASA\u27s Laser Vegetation Imaging Sensor (LVIS). This flight occurred 20 months after an ice storm damaged millions of hectares of forestland in northeastern North America. Lidar measurements of the amplitude and intensity of ground energy returns appeared to readily detect areas of moderate to severe ice storm damage associated with the worst damage. Southern through eastern aspects on side slopes were particularly susceptible to higher levels of damage, in large part overlapping tracts of forest that had suffered the highest levels of wind damage from the 1938 hurricane and containing the highest levels of sugar maple basal area and biomass. The levels of sugar maple abundance were determined through analysis of the 1997 Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) high resolution spectral imagery and inventory of USFS Northern Research Station field plots. We found a relationship between field measurements of stem volume losses and the LVIS metric of mean canopy height (r2 = 0.66; root mean square errors = 5.7 m3/ha, p \u3c 0.0001) in areas that had been subjected to moderate-to-severe ice storm damage, accurately documenting the short-term outcome of a single disturbance event
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