1,349 research outputs found

    Real-time Monitoring of High-speed Spindle Operations Using Infrared Data Transmission

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    AbstractHigh-performance cutting is carried out with high cutting and feed speeds. Particularly, the use of heavy cutting tools (e.g. in planing machines), it is important to monitor the clamping and balance condition of the mounted tool, as well as the process forces. Therefore, a real-time monitoring system for high-speed operations based on the IrDA protocol was developed. It could be shown that infrared data transmission systems allow shorter reaction times compared to conventional wireless LAN applications. The presented monitoring system provides a reaction time of 7.14 ms at a bandwidth of 42.5 kHz and a data rate of 4.1 MBit/s

    Total Synthesis of an Exceptional Brominated 4-Pyrone Derivative of Algal Origin: An Exercise in Gold Catalysis and Alkyne Metathesis

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    A concise approach to the algal metabolite 1 is described, which also determines the previously unknown stereostructure of this natural product. Compound 1 is distinguished by a rare brominated 4-pyrone nucleus linked as a ketene–acetal to a polyunsaturated macrocyclic scaffold comprising an extra homoallylic bromide entity. The synthesis of 1 is based on the elaboration and selective functionalization of the linear precursor 23 endowed with no less than six different sites of unsaturation including the highly enolized oxo-alkanoate function. Key to success was the formation of the 2-alkoxy-4-pyrone ring by a novel gold-catalyzed transformation which engages only the acetylenic β-ketoester substructure of 23 but leaves all other π-bonds untouched. The synthesis was completed by a ring-closing alkyne metathesis to forge the signature cycloalkyne motif of 1 followed by selective bromination of the ketene–acetal site in the resulting product 27 without touching the skipped diene–yne substructure resident within the macrocyclic tether

    Mid - infrared interferometry of massive young stellar objects II Evidence for a circumstellar disk surrounding the Kleinmann - Wright object

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    The formation scenario for massive stars is still under discussion. To further constrain current theories, it is vital to spatially resolve the structures from which material accretes onto massive young stellar objects (MYSOs). Due to the small angular extent of MYSOs, one needs to overcome the limitations of conventional thermal infrared imaging, regarding spatial resolution, in order to get observational access to the inner structure of these objects.We employed mid - infrared interferometry, using the MIDI instrument on the ESO /VLTI, to investigate the Kleinmann - Wright Object, a massive young stellar object previously identified as a Herbig Be star precursor. Dispersed visibility curves in the N- band (8 - 13 {\mu}m) have been obtained at 5 interferometric baselines. We show that the mid - infrared emission region is resolved. A qualitative analysis of the data indicates a non - rotationally symmetric structure, e.g. the projection of an inclined disk. We employed extensive radiative transfer simulations based on spectral energy distribution fitting. Since SED - only fitting usually yields degenerate results, we first employed a statistical analysis of the parameters provided by the radiative transfer models. In addition, we compared the ten best - fitting self - consistent models to the interferometric observations. Our analysis of the Kleinmann - Wright Object suggests the existence of a circumstellar disk of 0.1M\odot at an intermediate inclination of 76\circ, while an additional dusty envelope is not necessary for fitting the data. Furthermore, we demonstrate that the combination of IR interferometry with radiative transfer simulations has the potential to resolve ambiguities arising from the analysis of spectral energy distributions alone.Comment: 12 pages, 22 figures accepted for publication in A&

    Optimal Resource Allocation to Survival and Reproduction in Parasitic Wasps Foraging in Fragmented Habitats

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    Expansion and intensification of human land use represents the major cause of habitat fragmentation. Such fragmentation can have dramatic consequences on species richness and trophic interactions within food webs. Although the associated ecological consequences have been studied by several authors, the evolutionary effects on interacting species have received little research attention. Using a genetic algorithm, we quantified how habitat fragmentation and environmental variability affect the optimal reproductive strategies of parasitic wasps foraging for hosts. As observed in real animal species, the model is based on the existence of a negative trade-off between survival and reproduction resulting from competitive allocation of resources to either somatic maintenance or egg production. We also asked to what degree plasticity along this trade-off would be optimal, when plasticity is costly. We found that habitat fragmentation can indeed have strong effects on the reproductive strategies adopted by parasitoids. With increasing habitat fragmentation animals should invest in greater longevity with lower fecundity; yet, especially in unpredictable environments, some level of phenotypic plasticity should be selected for. Other consequences in terms of learning ability of foraging animals were also observed. The evolutionary consequences of these results are discussed

    Radial Velocity Studies of Close Binary Stars. IX

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    Radial-velocity measurements and sine-curve fits to the orbital velocity variations are presented for the eighth set of ten close binary systems: AB And, V402 Aur, V445 Cep, V2082 Cyg, BX Dra, V918 Her, V502 Oph, V1363 Ori, KP Peg, V335 Peg. Half of the systems (V445 Cep, V2082 Cyg, V918 Her, V1363 Ori, V335 Peg) were discovered photometrically by the Hipparcos mission and all systems are double-lined (SB2) contact binaries. The broadening function method permitted improvement of the orbital elements for AB And and V502 Oph. The other systems have been observed for radial velocity variations for the first time; in this group are five bright (V<7.5) binaries: V445 Cep, V2082 Cyg, V918 Her, KP Peg and V335 Peg. Several of the studied systems are prime candidates for combined light and radial-velocity synthesis solutions.Comment: 17+ pages, 2 tables, 4 figure

    Comparative genomic and metabolomic analysis of Termitomyces species provides insights into the terpenome of the fungal cultivar and the characteristic odor of the fungus garden of Macrotermes natalensis termites

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    Macrotermitinae termites have domesticated fungi of the genus Termitomyces as food for their colony, analogously to human farmers growing crops. Termites propagate the fungus by continuously blending foraged and predigested plant material with fungal mycelium and spores (fungus comb) within designated subterranean chambers. To test the hypothesis that the obligate fungal symbiont emits specific volatiles (odor) to orchestrate its life cycle and symbiotic relations, we determined the typical volatile emission of fungus comb biomass and Termitomyces nodules, revealing α-pinene, camphene, and d-limonene as the most abundant terpenes. Genome mining of Termitomyces followed by gene expression studies and phylogenetic analysis of putative enzymes related to secondary metabolite production encoded by the genomes uncovered a conserved and specific biosynthetic repertoire across strains. Finally, we proved by heterologous expression and in vitro enzymatic assays that a highly expressed gene sequence encodes a rare bifunctional mono-/sesquiterpene cyclase able to produce the abundant comb volatiles camphene and d-limonene. IMPORTANCE The symbiosis between macrotermitinae termites and Termitomyces is obligate for both partners and is one of the most important contributors to biomass conversion in the Old World tropic’s ecosystems. To date, research efforts have dominantly focused on acquiring a better understanding of the degradative capabilities of Termitomyces to sustain the obligate nutritional symbiosis, but our knowledge of the small-molecule repertoire of the fungal cultivar mediating interspecies and interkingdom interactions has remained fragmented. Our omics-driven chemical, genomic, and phylogenetic study provides new insights into the volatilome and biosynthetic capabilities of the evolutionarily conserved fungal genus Termitomyces, which allows matching metabolites to genes and enzymes and, thus, opens a new source of unique and rare enzymatic transformations
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