3,187 research outputs found
Amino Acids in the Haemolymph of Smaller European Elm Bark Beetle Larvae, Scolytus Multistriatus (Marsham) (Coleoptera: Scolytidae)
Author Institution: Northeastern Forest Experiment Station, Forest Service, U. S. Dept. Agriculture, Delaware, Ohio 43015Nineteen amino acids and two amides were detected in the haemolymph of last-instar Scolytus multistriatus larvae by thin-layer chromatography. Glycine, arginine, glutamine, lysine, ornithine, histidine, asparagine, glutamic acid, serine, proline, alanine, valine, isoleucine, and leucine were readily detected. Taurine, phenylalanine, tyrosine, a- and B- amino butyric acid, and aspartic acid were less readily detected on some chromatograms, and at times were apparently absent in the haemolymph extract. Cysteine, cystine, and cysteic acid were not adequately separated by any of the methods tried, but their presence was confirmed through co-chromatography
The Photophysics of the Carrier of Extended Red Emission
Interstellar dust contains a component which reveals its presence by emitting
a broad, unstructured band of light in the 540 to 950 nm wavelength range,
referred to as Extended Red Emission (ERE). The presence of interstellar dust
and ultraviolet photons are two necessary conditions for ERE to occur. This is
the basis for suggestions which attribute ERE to an interstellar dust component
capable of photoluminescence. In this study, we have collected all published
ERE observations with absolute-calibrated spectra for interstellar
environments, where the density of ultraviolet photons can be estimated
reliably. In each case, we determined the band-integrated ERE intensity, the
wavelength of peak emission in the ERE band, and the efficiency with which
absorbed ultraviolet photons are contributing to the ERE. The data show that
radiation is not only driving the ERE, as expected for a photoluminescence
process, but is modifying the ERE carrier as manifested by a systematic
increase in the ERE band's peak wavelength and a general decrease in the photon
conversion efficiency with increasing densities of the prevailing exciting
radiation. The overall spectral characteristics of the ERE and the observed
high quantum efficiency of the ERE process are currently best matched by the
recently proposed silicon nanoparticle (SNP) model. Using the experimentally
established fact that ionization of semiconductor nanoparticles quenches their
photoluminescence, we proceeded to test the SNP model by developing a
quantitative model for the excitation and ionization equilibrium of SNPs under
interstellar conditions for a wide range of radiation field densities.Comment: 42 p., incl. 8 fig. Accepted for publication by Ap
Elucidating the genetic basis of antioxidant status in lettuce (Lactuca sativa).
A diet rich in phytonutrients from fruit and vegetables has been acknowledged to afford protection against a range of human diseases, but many of the most popular vegetables are low in phytonutrients. Wild relatives of crops may contain allelic variation for genes determining the concentrations of these beneficial phytonutrients, and therefore understanding the genetic basis of this variation is important for breeding efforts to enhance nutritional quality. In this study, lettuce recombinant inbred lines, generated from a cross between wild and cultivated lettuce (Lactuca serriola and Lactuca sativa, respectively), were analysed for antioxidant (AO) potential and important phytonutrients including carotenoids, chlorophyll and phenolic compounds. When grown in two environments, 96 quantitative trait loci (QTL) were identified for these nutritional traits: 4 for AO potential, 2 for carotenoid content, 3 for total chlorophyll content and 87 for individual phenolic compounds (two per compound on average). Most often, the L. serriola alleles conferred an increase in total AOs and metabolites. Candidate genes underlying these QTL were identified by BLASTn searches; in several cases, these had functions suggesting involvement in phytonutrient biosynthetic pathways. Analysis of a QTL on linkage group 3, which accounted for >30% of the variation in AO potential, revealed several candidate genes encoding multiple MYB transcription factors which regulate flavonoid biosynthesis and flavanone 3-hydroxylase, an enzyme involved in the biosynthesis of the flavonoids quercetin and kaempferol, which are known to have powerful AO activity. Follow-up quantitative RT-PCR of these candidates revealed that 5 out of 10 genes investigated were significantly differentially expressed between the wild and cultivated parents, providing further evidence of their potential involvement in determining the contrasting phenotypes. These results offer exciting opportunities to improve the nutritional content and health benefits of lettuce through marker-assisted breeding
Infrared Spectroscopic Study of a Selection of AGB and Post-AGB Stars
We present here near-infrared spectroscopy in the H and K bands of a
selection of nearly 80 stars that belong to various AGB types, namely S type, M
type and SR type. This sample also includes 16 Post-AGB (PAGB) stars. From
these spectra, we seek correlations between the equivalent widths of some
important spectral signatures and the infrared colors that are indicative of
mass loss. Repeated spectroscopic observations were made on some PAGB stars to
look for spectral variations. We also analyse archival SPITZER mid-infrared
spectra on a few PAGB stars to identify spectral features due to PAH molecules
providing confirmation of the advanced stage of their evolution. Further, we
model the SEDs of the stars (compiled from archival data) and compare
circumstellar dust parameters and mass loss rates in different types.
Our near-infrared spectra show that in the case of M and S type stars, the
equivalent widths of the CO(3-0) band are moderately correlated with infrared
colors, suggesting a possible relationship with mass loss processes. A few PAGB
stars revealed short term variability in their spectra, indicating episodic
mass loss: the cooler stars showed in CO first overtone bands and the hotter
ones showed in HI Brackett lines. Our spectra on IRAS 19399+2312 suggest that
it is a transition object. From the SPITZER spectra, there seems to be a
dependence between the spectral type of the PAGB stars and the strength of the
PAH features. Modelling of SEDs showed among the M and PAGB stars that the
higher the mass loss rates, the higher the [K-12] colour in our sample.Comment: 14 pages; accepted in MNRAS, 200
The Anomalous Infrared Emission of Abell 58
We present a new model to explain the excess in mid and near infrared
emission of the central, hydrogen poor dust knot in the planetary nebula (PN)
Abell 58. Current models disagree with ISO measurement because they apply an
average grain size and equilibrium conditions only. We investigate grain size
distributions and temperature fluctuations affecting infrared emission using a
new radiative transfer code and discuss in detail the conditions requiring an
extension of the classical description. The peculiar infrared emission of V605
Aql, the central dust knot in Abell 58, has been modeled with our code. V605
Aql is of special interest as it is one of only three stars ever observed to
move from the evolutionary track of a central PN star back to the post-AGB
state.Comment: 17 pages, 4 figures; accepted and to be published in Ap
Extended view on the dust shells around two carbon stars
Stars on the asymptotic giant branch (AGB) lose considerable amounts of
matter through their dust-driven stellar winds. A number of such sources have
been imaged by Herschel/PACS, revealing a diverse sample of different
morphological types. Among them are a few examples which show geometrically
thin, spherically symmetric shells which can be used to probe the mass loss
history of their host stars. We aim to determine the physical properties of the
dust envelope around the two carbon stars U Hya and W Ori. With the
much-improved spatial constraints from the new far-infrared maps, our primary
goal is to measure the dust masses contained in the shells and see how they fit
the proposed scenarios of shell formation. We calculated the radiative transfer
of the circumstellar dust envelope using the 1D code More of DUSTY (MoD).
Adopting a parametrised density profile, we obtained a best-fit model in terms
of the photometric and spectroscopic data, as well as a radial intensity
profile based on Herschel/PACS data. For the case of U Hya, we also computed a
grid of circumstellar envelopes by means of a stationary wind code and compare
the results of the two modelling approaches. The Herschel/PACS maps show U Hya
surrounded by a detached shell of in radius,
confirming the observations from previous space missions. The dust masses
calculated for the shell by the two approaches are consistent with respect to
the adopted dust grain properties. In addition, around W Ori, we detect for the
first time a weak spherically symmetric structure with a radius of $92''\
(0.17\,\mathrm{pc})(3.5\pm0.3)\times10^{-6}\,\mathrm{M_\odot}$
Transforming community prevention systems for sustained impact: embedding active implementation and scaling functions
Traditional efforts to translate evidence-based prevention strategies to communities, at scale, have not often produced socially significant outcomes or the local capacity needed to sustain them. A key gap in many efforts is the transformation of community prevention systems to support and sustain local infrastructure for the active implementation, scaling, and continuous improvement of effective prevention strategies. In this paper, we discuss (1) the emergence of applied implementation science as an important type 3â5 translational extension of traditional type 2 translational prevention science, (2) active implementation and scaling functions to support the full and effective use of evidence-based prevention strategies in practice, (3) the organization and alignment of local infrastructure to embed active implementation and scaling functions within community prevention systems, and (4) policy and practice implications for greater social impact and sustainable use of effective prevention strategies
The Spectral Energy Distribution of Self-gravitating Interstellar Clouds I. Spheres
We derive the spectral energy distribution (SED) of dusty, isothermal, self
gravitating, stable and spherical clouds externally heated by the ambient
interstellar radiation field. For a given radiation field and dust properties,
the radiative transfer problem is determined by the pressure of the surrounding
medium and the cloud mass expressed as a fraction of the maximum stable cloud
mass above which the clouds become gravitational unstable.
To solve the radiative transfer problem a ray-tracing code is used to
accurately derive the light distribution inside the cloud. This code considers
both non isotropic scattering on dust grains and multiple scattering events.
The dust properties inside the clouds are assumed to be the same as in the
diffuse interstellar medium in our galaxy. We analyse the effect of the
pressure, the critical mass fraction, and the ISRF on the SED and present
brightness profiles in the visible, the IR/FIR and the submm/mm regime with the
focus on the scattered emission and the thermal emission from PAH-molecules and
dust grains.Comment: accepted for publication in ApJS, May 2008, v176n1 issu
Spatially Resolved 3 um Spectroscopy of IRAS 22272+5435: Formation and Evolution of Aliphatic Hydrocarbon Dust in Proto-Planetary Nebula
We present medium-resolution 3 um spectroscopy of the carbon-rich
proto-planetary nebula IRAS 22272+5435. Spectroscopy with the Subaru Telescope
adaptive optics system revealed a spatial variation of hydrocarbon molecules
and dust surrounding the star. The ro-vibrational bands of acetylene (C2H2) and
hydrogen cyanide (HCN) at 3.0 um are evident in the central star spectra. The
molecules are concentrated in the compact region near the center. The 3.3 and
3.4 um emission of aromatic and aliphatic hydrocarbons is detected at 600--1300
AU from the central star. The separation of spatial distribution between gas
and dust suggests that the small hydrocarbon molecules are indeed the source of
solid material, and that the gas leftover from the grain formation is being
observed near the central star. The intensity of aliphatic hydrocarbon emission
relative to the aromatic hydrocarbon emission decreases with distance from the
central star. The spectral variation is well matched to that of a laboratory
analog thermally annealed with different temperatures. We suggest that either
the thermal process after the formation of a grain or the variation in the
temperature in the dust-forming region over time determines the chemical
composition of the hydrocarbon dust around the proto-planetary nebula.Comment: 14 pages, 7 figures, Accepted for publication in the Astrophyical
Journa
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