1,374 research outputs found
Long-Term, Seasonal, and Event-Driven Sediment Movement on East Beach, San Salvador Island, Bahamas
East Beach is a modern, medium-energy shoreline located on the northeast coast of San Salvador Island, Bahamas. Stake and horizon profiles were made at 9 sites along a 1-km section of the beach in June, 1990, and every six months thereafter through January,1992. These observations appear to confirm that East Beach is a prograding shoreline, building onto the eastern shelf of the island. Seasonally corrected volume calculations indicate that between June, 1990 and January, 1992 approximately 14,000 m3 of new sand per kilometer were added to the East Beach system, with most of the sand likely derived from the nearshore shelf area. Visual evidence for progradation could be seen in the formation of a heavily vegetated berm along the backshore, that by June, 1991 had reached a maximum height of 40 cm before its destruction by the powerful storm that hit San Salvador in late October, 1991. Seasonal topographic measurements and volume calculations indicate a minimum of 8,600 m3/km of sediment moving offshore in response to higher average wave energies in the winter, and returning to build a wide foreshore and pronounced berm during the summer months. The late October storm battered East Beach with waves that entrained meter-sized blocks of coral, cut back the primary dune line by an average of 5.1 m, and washed over approximately 1,500 m3of sediment into the primary dune swale. Storm damage was measurably less severe at northern stations, possibly because of sheltering by Northeast Point and Man Head Cay, or by baffling action of the dense patch reefs offshore, or both
Development and Scale-Up of a New Sulfone-Based Bismacycle as a Universal Precursor for Bi(V)-Mediated Electrophilic Arylation
The scope and practical utility of bismuth(V)-mediated electrophilic arylation have been greatly improved by the recent development of user-friendly protocols based on modular bismacycle reagents. Here, we report the scalable synthesis of a new bench-stable bismacycle bromide and demonstrate that it can be used as a âuniversal precursorâ in electrophilic arylation. Relative to established syntheses of related bismacycles, the new protocol benefits from improved step- and vessel-economy, reduced production time, and the complete elimination of cryogenic temperatures and undesirable solvents (Et2O and CH2Cl2). The synthesis is complemented by a robust, chromatography-free purification procedure that was developed by using design of experiments. We show that this process is highly reproducible at the 100 mmol scale, with two independent experiments giving 61 and 62% yields of isolated material. We anticipate that this efficient method for the synthesis of a new bismacycle precursor will expedite both (a) wider uptake of existing bismuth-mediated arylation methods by the synthetic community and (b) ongoing efforts to develop new bismuth-mediated transformations
The prevalence and impact of thrombocytopenia, anaemia and leucopenia on sustained virological response in patients receiving hepatitis C therapy: evidence from a large âreal worldâ cohort
Draft Nuclear Genome Sequence of the Liquid Hydrocarbon-Accumulating Green Microalga Botryococcus braunii Race B (Showa).
Botryococcus braunii has long been known as a prodigious producer of liquid hydrocarbon oils that can be converted into combustion engine fuels. This draft genome for the B race of B. braunii will allow researchers to unravel important hydrocarbon biosynthetic pathways and identify possible regulatory networks controlling this unusual metabolism
Multi-phase High-Velocity Clouds toward HE 0226-4110 and PG 0953+414
We study the physical conditions, elemental abundances, and kinematics of the
high-velocity clouds (HVCs) along the sight lines toward active galaxies
HE0226-4110 and PG0953+414 using Hubble Space Telescope Imaging Spectrograph
and Far Ultraviolet Spectroscopic Explorer data. Our observations reveal
multiple components of HVC absorption in lines of HI, CII, CIII, CIV, OVI,
SiII, SiIII, and SiIV in both directions. We investigate whether
photoionization by the extragalactic background radiation or by escaping Milky
Way radiation can explain the observed ionization pattern. We find that
photoionization is a good explanation for the CII, CIII, SiII, and SiIII
features, but not for the OVI or CIV associated with the HVCs, suggesting that
two principal phases exist: a warm (T~10^4K), photoionized phase and a hotter
(T=1-3x10^5K), collisionally-ionized phase. The warm HVCs toward HE0226-4110
have high levels of ionization (97-99%), and metallicities ([Z/H] between -0.9
and -0.4) close to those in the Magellanic Stream, which lies eleven degrees
away on the sky at similar velocities. These HVCs have thermal pressures that
would place them close to equilibrium in a fully ionized 10^6 K Galactic corona
with n_H=4-9x10^{-5}cm^{-3} at 50 kpc. A mini-survey of the hot, collisionally
ionized HVC components seen here and in five other sight lines finds that in
11/12 cases, the high ions have kinematics and ionic ratios that are consistent
with an origin in conductive interfaces. However, the broad absorption wing on
the OVI profile toward PG0953+414 is not completely explained by the interface
scenario, and may be tracing the outflow of hot gas into the Milky Way halo as
part of a Galactic fountain or wind.Comment: 27 pages, 12 figures (9 in color), accepted for publication in Ap
The Addition of Vitamin D Supplementation to Interferon and Ribavirin in the Treatment of Hepatitis C Virus Infection:A Randomised Double-Blind PlaceboControlled Pilot Study
Web-Based Software for Managing Research
aeroCOMPASS is a software system, originally designed to aid in the management of wind tunnels at Langley Research Center, that could be adapted to provide similar aid to other enterprises in which research is performed in common laboratory facilities by users who may be geographically dispersed. Included in aeroCOMPASS is Web-interface software that provides a single, convenient portal to a set of project- and test-related software tools and other application programs. The heart of aeroCOMPASS is a user-oriented document-management software subsystem that enables geographically dispersed users to easily share and manage a variety of documents. A principle of "write once, read many" is implemented throughout aeroCOMPASS to eliminate the need for multiple entry of the same information. The Web framework of aeroCOMPASS provides links to client-side application programs that are fully integrated with databases and server-side application programs. Other subsystems of aeroCOMPASS include ones for reserving hardware, tracking of requests and feedback from users, generating interactive notes, administration of a customer-satisfaction questionnaire, managing execution of tests, managing archives of metadata about tests, planning tests, and providing online help and instruction for users
Consumer Willingness-To-Pay for a Resilient Electrical Grid
The research objective is to estimate consumer willingness to pay (WTP) for electricity grid fortification. Data are from a representative survey of Oklahoma citizens. Extreme weather events, aging utility infrastructure, increased demand for affordable energy, and terrorism threaten the safety and security of the way most citizens access electricity. This study is a first look at public willingness to support energy grid security measures in the United States Southern Great Plains. Findings suggest that consumers would pay an additional 14 initiated by local electricity providers. The findings provide policymakers and energy providers with information on consumer willingness to support efforts to modernize the current grid
Exploring the Optical Transient Sky with the Palomar Transient Factory
The Palomar Transient Factory (PTF) is a wide-field experiment designed to
investigate the optical transient and variable sky on time scales from minutes
to years. PTF uses the CFH12k mosaic camera, with a field of view of 7.9 deg^2
and a plate scale of 1 asec/pixel, mounted on the the Palomar Observatory
48-inch Samuel Oschin Telescope. The PTF operation strategy is devised to probe
the existing gaps in the transient phase space and to search for theoretically
predicted, but not yet detected, phenomena, such as fallback supernovae,
macronovae, .Ia supernovae and the orphan afterglows of gamma-ray bursts. PTF
will also discover many new members of known source classes, from cataclysmic
variables in their various avatars to supernovae and active galactic nuclei,
and will provide important insights into understanding galactic dynamics
(through RR Lyrae stars) and the Solar system (asteroids and near-Earth
objects). The lessons that can be learned from PTF will be essential for the
preparation of future large synoptic sky surveys like the Large Synoptic Survey
Telescope. In this paper we present the scientific motivation for PTF and
describe in detail the goals and expectations for this experiment.Comment: 15 pages, 6 figures, submitted to PAS
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