1,784 research outputs found
Welfare Impacts of Rural to Urban Water Transfers: An Equilibrium Displacement Approach
Food Security and Poverty,
Periodic Bursts of Coherent Radio Emission from an Ultracool Dwarf
We report the detection of periodic (p = 1.96 hours) bursts of extremely
bright, 100% circularly polarized, coherent radio emission from the M9 dwarf
TVLM 513-46546. Simultaneous photometric monitoring observations have
established this periodicity to be the rotation period of the dwarf. These
bursts, which were not present in previous observations of this target, confirm
that ultracool dwarfs can generate persistent levels of broadband, coherent
radio emission, associated with the presence of kG magnetic fields in a
large-scale, stable configuration. Compact sources located at the magnetic
polar regions produce highly beamed emission generated by the electron
cyclotron maser instability, the same mechanism known to generate planetary
coherent radio emission in our solar system. The narrow beams of radiation pass
our line of sight as the dwarf rotates, producing the associated periodic
bursts. The resulting radio light curves are analogous to the periodic light
curves associated with pulsar radio emission highlighting TVLM 513-46546 as the
prototype of a new class of transient radio source.Comment: 12 pages, 3 figures, accepted for publication in ApJ Letter
Enantioselective palladium-catalyzed allylic alkylation reactions in the synthesis of Aspidosperma and structurally related monoterpene indole alkaloids
Enantioselective Pd-catalyzed allylic alkylations of prochiral enolates represent a powerful tool for the construction of all-carbon quaternary stereocenters. This review describes the emergence of such reactions as strategic linchpins that enable efficient, stereocontrolled syntheses of Aspidosperma and related monoterpene indole alkaloids
Enantioselective palladium-catalyzed allylic alkylation reactions in the synthesis of Aspidosperma and structurally related monoterpene indole alkaloids
Enantioselective Pd-catalyzed allylic alkylations of prochiral enolates represent a powerful tool for the construction of all-carbon quaternary stereocenters. This review describes the emergence of such reactions as strategic linchpins that enable efficient, stereocontrolled syntheses of Aspidosperma and related monoterpene indole alkaloids
Nutritional strategies for post-exercise recovery: a review
Finding the optimal nutrition regimen for enhanced recovery is fundamental in enhancing exercise training and performance. Therefore, research has aimed to examine post-exercise nutritional strategies for optimal recovery. Because muscle glycogen is the primary substrate utilised during high-intensity exercise, it must be replenished. Recent research has examined the effectiveness on recovery of adding protein to a post-exercise carbohydrate beverage. This review summarises and analyses the literature on nutritional strategies aimed at enhancing various indicators of post-exercise recovery: glycogen resynthesis, muscle damage and performance. Furthermore, the literature on Medline and Pubmed comparing the effectiveness of carbohydrate-only (CHO) beverage with a carbohydrate:protein (CHO:PRO) beverage on maximising recovery was reviewed. The methods and results of studies regarding post-exercise nutritional strategies for recovery were analysed. primary results of this review suggest that the optimal timing in regard to post-exercise nutritional strategies for maximal glycogen resynthesis is within the first 30 minutes after exercise. The literature suggests that 1.0 - 1.5 g.kg-1h-1 of carbohydrate ingested at 2-hour intervals after exercise for up to 6 hours may be optimal for recovery. The addition of protein to a post-exercise meal may supply additional amino acids necessary for muscle repair creating an anabolic condition
The Total Synthesis of (–)-Scabrolide A
The first total synthesis of the norcembranoid diterpenoid scabrolide A is disclosed. The route begins with the synthesis of two chiral pool-derived fragments, which undergo a convergent coupling to expediently introduce all 19 carbon atoms of the natural product. An intramolecular Diels–Alder reaction and an enone–olefin cycloaddition/fragmentation sequence are then employed to construct the fused [5–6–7] linear carbocyclic core of the molecule and complete the total synthesis
Determining crop mixes for limited irrigation
Presented at the Central Plains irrigation conference on February 16-17, 2005 in Sterling, Colorado
Enantioselective Catalysis Coupled with Stereodivergent Cyclization Strategies Enables Rapid Syntheses of (+)-Limaspermidine and (+)-Kopsihainanine A
Enantioselective Pd-catalyzed allylic alkylations of dihydropyrido[1,2-a]indolone (DHPI) substrates were used to construct the C20-quaternary stereocenters of multiple monoterpene indole alkaloids. Stereodivergent Pictet–Spengler and Bischler–Napieralski cyclization/reduction cascades furnish the cis- and trans-fused azadecalin subunits present in Aspidosperma and Kopsia alkaloids, respectively, en route to highly efficient syntheses of (+)-limaspermidine and (+)-kopsihainanine A
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