192 research outputs found
Tracing high density gas in M 82 and NGC 4038
We present the first detection of CS in the Antennae galaxies towards the NGC
4038 nucleus, as well as the first detections of two high-J (5-4 and 7-6) CS
lines in the center of M 82. The CS(7-6) line in M 82 shows a profile that is
surprisingly different to those of other low-J CS transitions we observed. This
implies the presence of a separate, denser and warmer molecular gas component.
The derived physical properties and the likely location of the CS(7-6) emission
suggests an association with the supershell in the centre of M 82.Comment: 10 pages, 3 figures, ApJ Letter - ACCEPTE
Molecular tracers of PDR-dominated galaxies
Photon-dominated regions (PDRs) are powerful molecular line emitters in
external galaxies. They are expected in galaxies with high rates of massive
star formation due to either starburst (SB) events or starburst coupled with
active galactic nuclei (AGN) events. We have explored the PDR chemistry for a
range of physical conditions representing a variety of galaxy types. Our main
result is a demonstration of the sensitivity of the chemistry to changes in the
physical conditions. We adopt crude estimates of relevant physical parameters
for several galaxy types and use our models to predict suitable molecular
tracers of those conditions. The set of recommended molecular tracers differs
from that which we recommended for use in galaxies with embedded massive stars.
Thus, molecular observations can in principle be used to distinguish between
excitation by starburst and by SB+AGN in distant galaxies. Our recommendations
are intended to be useful in preparing Herschel and ALMA proposals to identify
sources of excitation in galaxies.Comment: 18 pages, 6 figures, Accepted in Ap
The influence of cosmic rays in the circumnuclear molecular gas of NGC1068
We surveyed the circumnuclear disk of the Seyfert galaxy NGC1068 between the
frequencies 86.2 GHz and 115.6 GHz, and identified 17 different molecules.
Using a time and depth dependent chemical model we reproduced the observational
results, and show that the column densities of most of the species are better
reproduced if the molecular gas is heavily pervaded by a high cosmic ray
ionization rate of about 1000 times that of the Milky Way. We discuss how
molecules in the NGC1068 nucleus may be influenced by this external radiation,
as well as by UV radiation fields.Comment: 6 pages. Conference proceeding for the workshop on "Cosmic-ray
induced phenomenology in star-forming environments" held in Sant Cugat,
Spain, on April 16-19, 201
Flavonoids of Aerial Parts of an Endemic Species of the Apiaceae of Algeria, Ammoides atlantica
Modulation of P-glycoprotein activity by acridones and coumarins from Citrus sinensis
Bioguided fractionation of the roots of Citrus sinensis (Rutaceae) led to the isolation and identification of five coumarins, namely, clausarin, suberosin, poncitrin, xanthyletin and thamnosmonin, seven acridones, namely, acrimarine B, 2-methoxycitpressine I, citpressine I, buntanine, acrimarine E, honyumine and acrimarine C, and one terpenoid, namely, limonin. Among these compounds, clausarin, 2-methoxycitpressine I and acrimarine E inhibited P-glycoprotein-mediated drug efflux in K562/R7 human leukemic cells over-expressing P-glycoprotein
Selective modulation of P-glycoprotein activity by steroidal saponines from Paris polyphylla
Bio-guided fractionation of the roots of Paris polyphylla (Trilliaceae), based on inhibition of P-glycoprotein-mediated daunorubicin efflux in K562/R7 cell line, led to isolation and identification of the three saponins 3-O-Rha(1 → 2)[Ara(1 → 4)]Glc-pennogenine, gracillin and polyphyllin D, and the two ecdysteroids 20-hydroxyecdysone and pinnatasterone. These compounds were tested for multidrug reversion on P-glycoprotein (ABCB1) with both drug-selected and transfected cell lines, and also on Breast Cancer Resistance Protein (BCRP/ABCG2). By contrast to a weak efficiency on BCRP, the three saponins displayed significant effects as inhibitors of P-glycoprotein-mediated drug efflux
Etude de l’extrait hexanique de l’espèce Ferula vesceritensis par les techniques couplées LC-UV-DAD, LC-MS et GC-MS
Molecular tracers of high mass star-formation in external galaxies
Hot core molecules should be detectable in external active galaxies out to
high redshift. We present here a detailed study of the chemistry of
star-forming regions under physical conditions that differ significantly from
those likely to be appropriate in the Milky Way Galaxy. We examine, in
particular, the trends in molecular abundances as a function of time with
respect to changes in the relevant physical parameters. These parameters
include metallicity, dust:gas mass ratio, the H formation rate, relative
initial elemental abundances, the cosmic ray ionization rate, and the
temperature of hot cores. These trends indicate how different tracers provide
information on the physical conditions and on evolutionary age. We identify hot
core tracers for several observed galaxies that are considered to represent
spirals, active galaxies, low-metallicity galaxies, and high-redshift galaxies.
Even in low-metallicity examples, many potential molecular tracers should be
present at levels high enough to allow unresolved detection of active galaxies
at high redshift containing large numbers of hot cores.Comment: 11 pages, 8 figures, accepted in Ap
A Census of the High-Density Molecular Gas in M82
We present a three-pointing study of the molecular gas in the starburst
nucleus of M82 based on 190 - 307 GHz spectra obtained with Z-Spec at the
Caltech Submillimeter Observatory. We present intensity measurements,
detections and upper limits, for 20 transitions, including several new
detections of CS, HNC, C2H, H2CO, and CH3CCH lines. We combine our measurements
with previously-published measurements at other frequencies for HCN, HNC, CS,
C34S, and HCO+ in a multi-species likelihood analysis constraining gas mass,
density and temperature, and the species' relative abundances. We find some 1.7
- 2.7 x 10^8 M_sun of gas with n_H2 between 1 - 6 x 10^4 cm^-3 and T > 50 K.
While the mass and temperature are comparable to values inferred from mid-J CO
transitions, the thermal pressure is a factor of 10 - 20 greater. The molecular
interstellar medium is largely fragmented and is subject to ultraviolet
irradiation from the star clusters. It is also likely subject to cosmic rays
and mechanical energy input from the supernovae, and is warmer on average than
the molecular gas in the massive star formation regions in the Milky Way. The
typical conditions in the dense gas in M82's central kpc appear unfavorable for
further star formation; if any appreciable stellar populations are currently
forming, they are likely biased against low mass stars, producing a top-heavy
initial mass function.Comment: 15 pages (using emulateapj.cls), 6 figures, Astrophysical Journal, in
pres
Sesquiterpenes from aerial parts of Ferula vesceritensis
From the dichloromethane extract of aerial parts of Ferula vesceritensis (Apiaceae), 11 sesquiterpene derivatives were isolated. Among them five were compounds designated as 10-hydroxylancerodiol-6-anisate, 2,10-diacetyl-8-hydroxyferutriol-6-anisate, 10-hydroxylancerodiol-6-benzoate, vesceritenone and epoxy-vesceritenol. The six known compounds were identified as feselol, farnesiferol A, lapidol, 2-acetyl-jaeschkeanadiol-6-anisate, lasidiol-10-anisate and 10-oxo-jaesckeanadiol-6-anisate. All the structures were determined by extensive spectroscopic studies including 1D and 2D NMR experiments and mass spectroscopy analysis. Two of the compounds, the sesquiterpene coumarins farnesiferol A and feselol, bound to the model recombinant nucleotide-binding site of an MDR-like efflux pump from the enteropathogenic protozoan Cryptosporidium parvum
- …