2,063 research outputs found
The Bay Scallop, Argopecten irradians, in Florida Coastal Waters
The bay scallop, Argopecten irradians, supported a small commercial fishery in Florida from the late 1920’s through the 1940’s; peak landings were in 1946 (214,366 lbs of meats), but it currently supports one of the most popular and family-oriented fisheries along the west coast of Florida. The primary habitat of the short-lived (18 months) bay scallop is seagrass beds. Peak spawning occurs in the
fall. Human population growth and coastal development that caused habitat changes and reduced water quality probably are the main causes of a large decline in the scallop’s
abundance. Bay scallop restoration efforts in bays where they have become scarce have centered on releasing pediveligers and juveniles into grass beds and holding
scallops in cages where they woul
Representations of Time Coordinates in FITS
In a series of three previous papers, formulation and specifics of the
representation of World Coordinate Transformations in FITS data have been
presented. This fourth paper deals with encoding time. Time on all scales and
precisions known in astronomical datasets is to be described in an unambiguous,
complete, and self-consistent manner. Employing the well--established World
Coordinate System (WCS) framework, and maintaining compatibility with the FITS
conventions that are currently in use to specify time, the standard is extended
to describe rigorously the time coordinate. World coordinate functions are
defined for temporal axes sampled linearly and as specified by a lookup table.
The resulting standard is consistent with the existing FITS WCS standards and
specifies a metadata set that achieves the aims enunciated above.Comment: FITS WCS Paper IV: Time. 27 pages, 11 table
Development of a Computer-Controlled Polishing Process for X-Ray Optics
The future X-ray observatory missions require grazing-incidence x-ray optics with angular resolution of < 5 arcsec half-power diameter. The achievable resolution depends ultimately on the quality of polished mandrels from which the shells are replicated. With an aim to fabricate better shells, and reduce the cost/time of mandrel production, a computer-controlled polishing machine is developed for deterministic and localized polishing of mandrels. Cylindrical polishing software is also developed that predicts the surface residual errors under a given set of operating parameters and lap configuration. Design considerations of the polishing lap are discussed and the effects of nonconformance of the lap and the mandrel are presented
Quahogs in Eastern North America: Part II, History by Province and State
The northern quahog, Mercenaria mercenaria, ranges along the
Atlantic Coast of North America from the Canadian Maritimes to Florida, while the southern quahog, M. campechiensis,
ranges mostly from Florida to southern Mexico. The northern quahog was fished by native North Americans during prehistoric periods. They used the meats as food and the shells as scrapers and as utensils. The European colonists copied the Indians treading method, and they also used short
rakes for harvesting quahogs. The Indians of southern New England and Long Island, N.Y., made wampum from quahog shells, used it for ornaments and sold it to the colonists, who, in turn, traded it to other Indians for furs. During the late 1600’s, 1700’s, and 1800’s, wampum was made in small factories for eventual trading with Indians farther west for furs.
The quahoging industry has provided people in many coastal communities with a means of earning a livelihood and has
given consumers a tasty, wholesome food whether eaten raw, steamed, cooked in chowders, or as stuffed quahogs. More than a dozen methods and types of gear have been used in the last two centuries for harvesting quahogs. They include treading and using various types of rakes and dredges,
both of which have undergone continuous improvements in design. Modern dredges are equipped with hydraulic jets and one type has an escalator to bring the quahogs continuously to the boats. In the early 1900’s, most provinces and states
established regulations to conserve and maximize yields of their quahog stocks. They include a minimum size, now almost
universally a 38-mm shell width, and can include gear limitations and daily quotas.
The United States produces far more quahogs than either Canada or Mexico. The leading producer in Canada is Prince
Edward Island. In the United States, New York, New Jersey, and Rhode Island lead in quahog production in the north, while Virginia and North Carolina lead in the south. Connecticut and Florida were large producers in the 1990’s. The State of Tabasco leads in Mexican production. In the northeastern United States, the bays with large openings, and thus large exchanges of bay waters with ocean waters,
have much larger stocks of quahogs and fisheries than bays with small openings and water exchanges.
Quahog stocks in certified beds have been enhanced by transplanting stocks to them from stocks in uncertified waters and by planting seed grown in hatcheries, which grew in number from Massachusetts to Florida in the 1980’s and 1990’s
Design Considerations of Polishing Lap for Computer-Controlled Cylindrical Polishing Process
This paper establishes a relationship between the polishing process parameters and the generation of mid spatial-frequency error. The consideration of the polishing lap design to optimize the process in order to keep residual errors to a minimum and optimization of the process (speeds, stroke, etc.) and to keep the residual mid spatial-frequency error to a minimum, is also presented
Optomechanical self-structuring in cold atomic gases
The rapidly developing field of optomechanics aims at the combined control of
optical and mechanical (solid-state or atomic) modes. In particular, laser
cooled atoms have been used to exploit optomechanical coupling for
self-organization in a variety of schemes where the accessible length scales
are constrained by a combination of pump modes and those associated to a second
imposed axis, typically a cavity axis. Here, we consider a system with many
spatial degrees of freedom around a single distinguished axis, in which two
symmetries - rotations and translations in the plane orthogonal to the pump
axis - are spontaneously broken. We observe the simultaneous spatial
structuring of the density of a cold atomic cloud and an optical pump beam. The
resulting patterns have hexagonal symmetry. The experiment demonstrates the
manipulation of matter by opto-mechanical self-assembly with adjustable length
scales and can be potentially extended to quantum degenerate gases.Comment: 20 pages, 6 figure
Chemoenzymatic elaboration of monosaccharides using engineered cytochrome P450_(BM3) demethylases
Polysaccharides comprise an extremely important class of biopolymers
that play critical roles in a wide range of biological processes,
but the synthesis of these compounds is challenging because of
their complex structures. We have developed a chemoenzymatic
method for regioselective deprotection of monosaccharide substrates
using engineered Bacillus megaterium cytochrome P450
(P450_(BM3)) demethylases that provides a highly efficient means
to access valuable intermediates, which can be converted to a
wide range of substituted monosaccharides and polysaccharides.
Demethylases displaying high levels of regioselectivity toward a
number of protected monosaccharides were identified using a
combination of protein and substrate engineering, suggesting that
this approach ultimately could be used in the synthesis of a wide
range of substituted mono- and polysaccharides for studies in
chemistry, biology, and medicine
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