4,134 research outputs found
The ecology of Hypericum gramineum with reference to biological control of H. perforatum by the mite, Aculus hyperici
A chemoenzymatic route to the (+)-form of the amaryllidaceae alkaloid narseronine
The enzymatically derived and enantiopure cis-1,2-dihydrocatechol 1 has been converted, over 14 one-pot operations, into the (+)-form of the alkaloid narseronine (2). The present study, which complements earlier work that established a route from metabolite 1 to enantiomer (–)-2, involves an N-bromosuccinimide/tri-n-butyltin hydride-mediated cyclisation reaction to construct the unsaturated B-ring lactone of the target compound.We thank the Australian Research Council and the Institute of Advanced Studies for generous financial support
Energy allocation in a reef coral under varying resource availability
An organism's pattern of resource allocation to reproduction and growth over time critically impacts on its lifetime reproductive success. During times of low resource availability, there are two fundamental, mutually exclusive strategies of energy investment: maintenance of somatic tissues to support survival and later reproduction or investment into an immediate reproductive event at the risk of subsequent death. Here, we examine energy allocation patterns in the coral Montipora digitata to determine whether energy investment during periods of resource shortage favours growth or reproduction in a sessile, modular marine species. We manipulated light regimes (two levels of shading) on plots within a shallow reef flat habitat (Orpheus Island, Great Barrier Reef, Australia) and quantified energy uptake (rates of net photosynthesis), energy investment into reproduction (E R ), tissue growth per unit surface area (E T ) and energy channelled into calcification (E C ). With declining resource availability (i.e. reduced photosynthesis), relative energy investment shifted from high (~80%) allocation to tissue growth (E R :E T :E C =11:81:8%) to an increasing proportion channelled into reproduction and skeletal growth (20:31:49%). At the lowest light regime, calcification was maintained but reproduction was halted and thus energy content per unit surface area of tissue declined, although no mortality was observed. The changing hierarchy in energy allocation among life functions with increasing resource limitation found here for an autotrophic coral, culminating in cessation of reproduction when limitations are severe, stands in contrast to observations from annual plants. However, the strategy may be optimal for maximising fitness components (growth, reproduction and survival) through time in marine modular animal
Thioxoethenylidene (CCS) as a bridging ligand
The reaction of [Mo(≡CBr)(CO)2(Tp*)] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with [Fe2(μ-SLi)2(CO)6] affords, inter alia, the unsymmetrical binuclear thioxoethenylidene complex [Mo2(μ,σ(C):η2(C′S)-CCS)(CO)4(Tp*)2], which may be more directly obtained from [Mo(≡CBr)(CO)2(Tp*)] and Li2S. The reaction presumably proceeds via the intermediacy of the bis(alkylidynyl)thioether complex S{C≡Mo(CO)2(Tp*)}2, which was, however, not directly observed but explored computationally and found to lie 78.6 kJ mol–1 higher in energy than the final thioxoethenylidene product. Computational interrogation of the molecules [M2(μ-C2S)(CO)2(Tp*)2] (M = Mo, W, Re, Os) reveals three plausible coordination modes for a thioxoethenylidene bridge which involve a progressive strengthening of the C–C bond and weakening of the M–C and M–S bonds, as might be expected from simple effective atomic number considerations.This work was supported by the Australian Research Council (DP130102598 and DP110101611)
Structures of New Alkaloids from Rain Forest Trees Galbulimima belgraveana and Galbulimima baccata in Papua New Guinea, Indonesia, and Northern Australia
Following on our 60-year research on the chemical constituents of the rain forest trees Galbulimima belgraveana and Galbulimima baccata, we report the isolation of seven new alkaloids: GB14 (14), GB22 (15), GB25 (16), GB21 (17), GB23 (18), GB24 (19), and GB26 (20). Their structures were elucidated by a combination of spectroscopic analyses and single-crystal X-ray crystallography, as well as structure degradation and interconversion. The newly isolated alkaloids are precursors or derivatives of the known family members from our early studies and could be intermediates in the biosynthesis of the Galbulimima alkaloids. Therefore, the present study has expanded the range of structures in this family of alkaloids and provided some missing links in the biosynthetic sequences.This study was supported by the Fundamental Research Funds
for the Central Universities, Chin
Modeling of a Building Scale Liquid Air Energy Storage and Expansion System with ASPEN HYSYS
Liquid Air Energy Storage (LAES) is a potential solution to mitigate renewable energy intermittency on islanded microgrids. Renewable microgrid generation in excess of the immediate load runs a cryogenic cycle to create and store liquid air. LAES systems can be combined with an expansion turbine to recover the stored energy. Using analytic methods to design a LAES and expansion system is complex and time consuming, suggesting modeling and simulation as a more efficient approach. Aspen HYSYS, an industrial process modeling software package, was used to model a combined Linde- Hampson cryogenic cycle (for liquefaction of air) and an expansion cycle (to convert the energy from liquid air vaporization to mechanical energy). The model was validated against previous analytic work. The validated model will be used to implement a model-based systems engineering (MBSE) approach to design an LAES and expansion system to reduce intermittency on an experimental microgrid at the Naval Postgraduate School in Monterey, CA, USA. Data from this facility will be used to further modify and validate the HYSYS model
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Algorithmic music as intelligent game music
Current game music systems typically involve the playback of prerecorded audio tracks which are crossfaded in response to game events such as level changes. However, crossfading can limit the expressive power of musical transitions, and can make fine grained structural variations difficult to achieve. We therefore describe an alternative approach in which music is algorithmically generated based on a set of high-level musical features that can be controlled in real-time according to a player’s progression through a game narrative. We outline an implementation of the approach in an actual game, focusing primarily on how the music system traces the game’s emotional narrative by periodically querying certain narrative parameters and adjusting the musical features of its output accordingly
Methodological approaches to the evaluation of game music systems
Despite an emerging interest in the application of dynamic computer music systems to computer games, currently there are no commonly accepted approaches to empirically evaluating game music systems. In this paper we pose four questions that researchers could assess in order to evaluate different aspects of a game music system. They focus on the music's effect on the game playing experience (whether the music leads to a more enjoyable experience, and whether it affects the player in the intended way during the game), and how the music itself is perceived (whether it reaches a certain aesthetic standard, and whether it accurately conveys the intended narrative). We examine each of these questions in turn, for each one establishing a theoretical background as well as reviewing and comparing relevant research methodologies in order to show how it could be addressed in practice
gem-Dibromocyclopropanes and enzymatically derived cis-1,2-dihydrocatechols as building blocks in alkaloid synthesis
The application of the title building blocks, the 6,6-dibromobicyclo[3.1.0]hexanes
and the cis-1,2-dihydrocatechols, to the total synthesis of crinine and lycorinine alkaloids is
described.We thank the Australian Research Council and the Institute of Advanced Studies for generous financial
support
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