72 research outputs found
Measurement of CH2O in low and atmospheric pressure flames by Laser Induced Fluorescence and Cavity RingDown absorption
We have investigated the spatial structure of formaldehyde usinglaser-induced fluorescence (LIF), LIF imaging, and cavity ringdownspectroscopy (CRDS) in two flames. The first is an atmospheric pressureBunsen flame, into which are inserted various metal to simulatedifferent types of heat removal inserts in appliance flames. Here LIFimaging is used. The second is a low pressure flat flame that can bemodeled with a one-dimensional code. All three techniques are used. Theresults in both cases show that CH2O appears prior to CH, inlower pressure regions of the flame
Three new species of Dolichogenidea Viereck (Hymenoptera, Braconidae, Microgastrinae) from Australia with exceptionally long ovipositors
The subfamily Microgastrinae contains an extraordinarily rich diversity of parasitoid wasps which parasitise larval lepidopterans. The Australian fauna has generally been poorly studied, particularly for the very speciose genera. One such genus is Dolichogenidea Vierek, which in Australia is known from only six described species. Here we describe three new species of Dolichogenidea from Australia, which are distinguished by possessing extremely long ovipositors compared with the typical form for the genus. These are D. finchi Fagan-Jeffries & Austin, sp. n., D. mediocaudata Fagan-Jeffries & Austin, sp. n., and D. xenomorph Fagan-Jeffries & Austin, sp. n. In describing these new species we also discuss relationships within the genus, and the diversity and biology of the Australian fauna
Nitrogen atom detection in low-pressure flames by two-photon laser-excited fluorescence
Bittner J, Lawitzki A, Meier U, Kohse-Höinghaus K. Nitrogen atom detection in low-pressure flames by two-photon laser-excited fluorescence. Applied Physics, B. 1991;52(2):108-116.Nitrogen atoms have been detected in stoichiometric flat premixed H2/O2/N2 flames at 33 and 96 mbar doped with small amounts of NH3, HCN, and (CN)2 using two-photon laser excitation at 211 nm and fluorescence detection around 870 nm. The shape of the fluorescence intensity profiles versus height above the burner surface is markedly different for the different additives. Using measured quenching rate coefficients and calibrating with the aid of known N-atom concentrations in a discharge flow reactor, peak N-atom concentrations in these flames are estimated to be on the order of 10 12–5×10 13 cm –3; the detection limit is about 1×10 11 cm –3
Low-mass pre--main-sequence stars in the Magellanic Clouds
[Abridged] The stellar Initial Mass Function (IMF) suggests that sub-solar
stars form in very large numbers. Most attractive places for catching low-mass
star formation in the act are young stellar clusters and associations, still
(half-)embedded in star-forming regions. The low-mass stars in such regions are
still in their pre--main-sequence (PMS) evolutionary phase. The peculiar nature
of these objects and the contamination of their samples by the evolved
populations of the Galactic disk impose demanding observational techniques for
the detection of complete numbers of PMS stars in the Milky Way. The Magellanic
Clouds, the companion galaxies to our own, demonstrate an exceptional star
formation activity. The low extinction and stellar field contamination in
star-forming regions of these galaxies imply a more efficient detection of
low-mass PMS stars than in the Milky Way, but their distance from us make the
application of special detection techniques unfeasible. Nonetheless, imaging
with the Hubble Space Telescope yield the discovery of solar and sub-solar PMS
stars in the Magellanic Clouds from photometry alone. Unprecedented numbers of
such objects are identified as the low-mass stellar content of their
star-forming regions, changing completely our picture of young stellar systems
outside the Milky Way, and extending the extragalactic stellar IMF below the
persisting threshold of a few solar masses. This review presents the recent
developments in the investigation of PMS stars in the Magellanic Clouds, with
special focus on the limitations by single-epoch photometry that can only be
circumvented by the detailed study of the observable behavior of these stars in
the color-magnitude diagram. The achieved characterization of the low-mass PMS
stars in the Magellanic Clouds allowed thus a more comprehensive understanding
of the star formation process in our neighboring galaxies.Comment: Review paper, 26 pages (in LaTeX style for Springer journals), 4
figures. Accepted for publication in Space Science Review
Complete genome sequence of Hirschia baltica type strain (IFAM 1418T)
The family Hyphomonadaceae within the Alphaproteobacteria is largely comprised of bacteria isolated from marine environments with striking morphologies and an unusual mode of cell growth. Here, we report the complete genome sequence Hirschia baltica, which is only the second a member of the Hyphomonadaceae with a published genome sequence. H. baltica is of special interest because it has a dimorphic life cycle and is a stalked, budding bacterium. The 3,455,622 bp long chromosome and 84,492 bp plasmid with a total of 3,222 protein-coding and 44 RNA genes were sequenced as part of the DOE Joint Genome Institute Program CSP 2008
Effect of temperature, wetness duration and cultivar on the development of anthracnose in guava fruits
Fungos micorrízicos arbusculares em fitofisionomias do Pantanal da Nhecolândia, Mato Grosso do Sul
Collisional processes near the CH B 2Σ- v′=0,1 predissociation limit in laser-induced fluorescence flame diagnostics
Excitation and dispersed laser-induced fluorescence spectra of CH¿B¿2S-v'=0,1 in methane flames are analyzed using rotational relaxation models to investigate their applicability for flame diagnostics. The existence of non-predissociative and highly predissociative rotational levels in the same vibrational state provides a unique scenario to test the effects of rotational relaxation in laser-induced fluorescence measurements. Using a statistical power gap law for rotational relaxation modeling, we find that the levels with collision-free lifetimes as short as 100 ps have apparent fluorescence yields larger than expected because of the extent of rotational relaxation at atmospheric pressure. Also, vibrational (v'=1 to v'=0) and electronic energy transfer (B¿2S-v'=1 to A¿2¿) are competitive, and together are half the value for the total collisional removal rate from CH¿B¿2S-v'=0. The measured electronic energy transfer branching ratio into A¿(v'=0-3) depends on the initial rotational level pumped, and energy gap considerations can be used to explain these propensities. The combination of measurements and model calculations finds the excitation of the CH¿B¿2S-¿v'=1,N'=8 level a good candidate for laser-induced fluorescence quantitative measurements in flames at atmospheric pressure
Collisional processes near the CH B 2Σ- v′=0,1 predissociation limit in laser-induced fluorescence flame diagnostics
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