268 research outputs found
Molecular properties of (U)LIRGs: CO, HCN, HNC and HCO+
The observed molecular properties of a sample of FIR-luminous and OH
megamaser (OH-MM) galaxies have been investigated. The ratio of high and
low-density tracer lines is found to be determined by the progression of the
star formation in the system. The HCO+/HCN and HCO+/HNC line ratios are good
proxies for the density of the gas, and PDR and XDR sources can be
distinguished using the HNC/HCN line ratio. The properties of the OH-MM sources
in the sample can be explained by PDR chemistry in gas with densities higher
than 10^5.5 cm^-3, confirming the classical OH-MM model of IR pumped
amplification with (variable) low gains.Comment: 5 pages, 2 figures, to appear in: IAU Symposium 242 Astrophysical
Masers and their Environment
Evolution of the ISM in Luminous IR Galaxies
Molecules that trace the high-density regions of the interstellar medium may
be used to evaluate the changing physical and chemical environment during the
ongoing nuclear activity in (Ultra-)Luminous Infrared Galaxies. The changing
ratios of the HCN(1-0), HNC(1-0), HCO+(1-0), CN(1-0) and CN(2-1), and CS(3-2)
transitions were compared with the HCN(1-0)/CO(1-0) ratio, which is proposed to
represent the progression time scale of the starburst. These diagnostic
diagrams were interpreted using the results of theoretical modeling using a
large physical and chemical network to describe the state of the nuclear ISM in
the evolving galaxies. Systematic changes are seen in the line ratios as the
sources evolve from early stage for the nuclear starburst (ULIRGs) to later
stages. These changes result from changing environmental conditions and
particularly from the lowering of the average density of the medium. A
temperature rise due to mechanical heating of the medium by feedback explains
the lowering of the ratios at later evolutionary stages. Infrared pumping may
affect the CN and HNC line ratios during early evolutionary stages. Molecular
transitions display a behavior that relates to changes of the environment
during an evolving nuclear starburst. Molecular properties may be used to
designate the evolutionary stage of the nuclear starburst. The HCN(1-0)/CO(1-0)
and HCO+(1-0)/HCN(1-0) ratios serve as indicators of the time evolution of the
outburst.Comment: To be published in Astronomy and Astrophysics - 11 pages, 9 figures,
1 tabl
The irradiated ISM of ULIRGs
The nuclei of ULIRGs harbor massive young stars, an accreting central black
hole, or both. Results are presented for molecular gas that is exposed to
X-rays (1-100 keV, XDRs) and far-ultraviolet radiation (6-13.6 eV, PDRs).
Attention is paid to species like HCO+, HCN, HNC, OH, H2O and CO. Line ratios
of HCN/HCO+ and HNC/HCN discriminate between PDRs and XDRs. Very high J (>10)
CO lines, observable with HIFI/Herschel, discriminate very well between XDRs
and PDRs. In XDRs, it is easy to produce large abundances of warm (T>100 K) H2O
and OH. In PDRs, only OH is produced similarly well.Comment: 5 pages, 6 figures, to appear in: IAU Symposium 242 Astrophysical
Masers and their Environment
Facilitated engraftment of human hematopoietic cells in severe combined immunodeficient mice following a single injection of Cl²MDP liposomes
Transplantation of normal and malignant human hematopoietic cells into severe combined immunodeficient (SCID) mice allows for evaluation of long-term growth abilities of these cells and provides a preclinical model for therapeutic interventions. However, large numbers of cells are required for successful engraftment in preirradiated mice due to residual graft resistance, that may be mediated by cells from the mononuclear phagocytic system. Intravenous (i.v.) injection of liposomes containing dichloromethylene diphosphonate (Cl2MDP) may eliminate mouse macrophages in spleen and liver. In this study outgrowth of acute myeloid leukemia (AML) cells and umbilical cord blood (UCB) cells in SCID mice conditioned with a single i.v. injection of Cl2MDP liposomes in addition to sublethal total body irradiation (TBI) was compared to outgrowth of these cells in SCID mice that had received TBI alone. A two- to 10-fold increase in outgrowth of AML cells was observed in four cases of AML. Administration of 107 UCB cells reproducibly engrafted SCID mice that had been conditioned with Cl2MDP liposomes and TBI, whereas human cells were not detected in mice conditioned with TBI alone. As few as 2 x 104 purified CD34+ UCB cells engrafted in all mice treated with Cl2MDP liposomes. In SCID mice treated with macrophage depletion unexpected graft failures were not observed. Histological examination of the spleen showed that TBI and Cl2MDP liposomes i.v. resulted in a transient elimination of all macrophage subsets in the spleen, whereas TBI had a minor effect. Cl2MDP liposomes were easy to use and their application was not associated with appreciable side-effects. Cl2MDP liposome pretreatment in combination with TBI allows for reproducible outgrowth of high numbers of human hematopoietic cells in SCID mice
Diagnostics of active galaxies: I. Modeling the infrared properties of dusty cores of starburst galaxies
An evolutionary model of star formation in ULIRGs was created using existing
star formation and radiative transfer codes (STARBURST99, RADMC and RADICAL) as
building blocks. The results of the simulations are compared to data from two
IRAS catalogs. From the simulations it is found that the dust surrounding the
starburst region is made up from two components. There is a low optical depth
(tau=0.1, which corresponds to 0.1% of the total dust mass), hot (T~400K)
non-grey component close to the starburst (scale size 10pc) and a large scale,
colder grey component (100pc, 75K) with a much larger column (tau=10). The
simulations also show that starburst galaxies can be powered by massive star
formation. The parameters for this star forming region are difficult to
determine, since the IR continuum luminosity is only sensitive to the total UV
input. Therefore, there is a degeneracy between the total starburst mass and
the initial mass function (IMF) slope. A less massive star formation with a
shallower IMF will produce the same amount of OB stars and therefore the same
amount of irradiating UV flux. Assuming the stars are formed according to a
Salpeter IMF (Psi(M) ~ M^-2.35), the star formation region should produce 10^9
Msun of stars (either in one instantaneous burst, or in a continuous process)
in order to produce enough IR radiation.Comment: 37 pages, 32 figures, accepted by Astronomy and Astrophysics. Version
with Appendices can be obtained from
http://www.astro.rug.nl/~loenen/Loenen_et_al_2006.pd
Local bone metabolism during the consolidation process of spinal interbody fusion
INTRODUCTION: Although computed tomography (CT) can identify the presence of eventual bony bridges following lumbar interbody fusion (LIF) surgery, it does not provide information on the ongoing formation process of new bony structures. 18F sodium fluoride (18F-NaF) positron emission tomography (PET) could be used as complementary modality to add information on the bone metabolism at the fusion site. However, it remains unknown how bone metabolism in the operated segment changes early after surgery in uncompromised situations. This study aimed to quantify the changes in local bone metabolism during consolidation of LIF. MATERIALS AND METHODS: Six skeletally mature sheep underwent LIF surgery. 18F-NaF PET/CT scanning was performed 6 and 12 weeks postoperatively to quantify the bone volume and metabolism in the operated segment. Bone metabolism was expressed as a function of bone volume. RESULTS: Early in the fusion process, bone metabolism was increased at the endplates of the operated vertebrae. In a next phase, bone metabolism increased in the center of the interbody region, peaked, and declined to an equilibrium state. During the entire postoperative time period of 12 weeks, bone metabolism in the interbody region was higher than that of a reference site in the spinal column. CONCLUSION: Following LIF surgery, there is a rapid increase in bone metabolism at the vertebral endplates that develops towards the center of the interbody region. Knowing the local bone metabolism during uncompromised consolidation of spinal interbody fusion might enable identification of impaired bone formation early after LIF surgery using 18F-NaF PET/CT scanning
Mechanical feedback in the molecular ISM of luminous IR galaxies
Aims: Molecular emission lines originating in the nuclei of luminous
infra-red galaxies are used to determine the physical properties of the nuclear
ISM in these systems.
Methods: A large observational database of molecular emission lines is
compared with model predictions that include heating by UV and X-ray radiation,
mechanical heating, and the effects of cosmic rays.
Results: The observed line ratios and model predictions imply a separation of
the observedsystems into three groups: XDRs, UV-dominated high-density (n>=10^5
cm-3) PDRs, and lower-density (n=10^4.5 cm-3) PDRs that are dominated by
mechanical feedback.
Conclusions: The division of the two types of PDRs follows naturally from the
evolution of the star formation cycle of these sources, which evolves from
deeply embedded young stars, resulting in high-density (n>=10^5 cm-3) PDRs, to
a stage where the gas density has decreased (n=10^4.5 cm-3) and mechanical
feedback from supernova shocks dominates the heating budget.Comment: 4 pages, 3 figures, published as Letter to the Editor in A&A (see
http://www.aanda.org/articles/aa/abs/2008/34/aa10327-08/aa10327-08.html
Molecules as tracers of galaxy evolution: an EMIR survey. I. Presentation of the data and first results
We investigate the molecular gas properties of a sample of 23 galaxies in
order to find and test chemical signatures of galaxy evolution and to compare
them to IR evolutionary tracers. Observation at 3 mm wavelengths were obtained
with the EMIR broadband receiver, mounted on the IRAM 30 m telescope on Pico
Veleta, Spain. We compare the emission of the main molecular species with
existing models of chemical evolution by means of line intensity ratios
diagrams and principal component analysis. We detect molecular emission in 19
galaxies in two 8 GHz-wide bands centred at 88 and 112 GHz. The main detected
transitions are the J=1-0 lines of CO, 13CO, HCN, HNC, HCO+, CN, and C2H. We
also detect HC3N J=10-9 in the galaxies IRAS 17208, IC 860, NGC 4418, NGC 7771,
and NGC 1068. The only HC3N detections are in objects with HCO+/HCN<1 and warm
IRAS colours. Galaxies with the highest HC3N/HCN ratios have warm IRAS colours
(60/100 {\mu}m>0.8). The brightest HC3N emission is found in IC 860, where we
also detect the molecule in its vibrationally excited state.We find low HNC/HCN
line ratios (<0.5), that cannot be explained by existing PDR or XDR chemical
models. Bright HC3N emission in HCO+-faint objects may imply that these are not
dominated by X-ray chemistry. Thus the HCN/HCO+ line ratio is not, by itself, a
reliable tracer of XDRs. Bright HC3N and faint HCO+ could be signatures of
embedded starformation, instead of AGN activity
An analytical study of iboga alkaloids contained in Tabernanthe iboga-derived products offered by ibogaine treatment providers
Therapeutic properties of ibogaine in the treatment of addiction are attracting both clinicians and patients to its use. Since ibogaine is not an authorized medicine, the quality of these products is not always known, increasing the probability of adverse reactions. Objective: This study collects different types of iboga-derived samples from treatment providers, vendors and online buyers to analyse their content. Methods: Analysis of iboga products (n = 16) was performed using gas chromatography and mass spectrometry methods (GC/MS). Products included Iboga root bark, Total Alkaloids (TA), Purified Total Alkaloids (PTA HCl), ibogaine hydrochloride (ibogaine HCl) and one Voacanga africana root bark. Results: The content of ibogaine was highly variable, ranging from 0.6% to 11.2% for products sold as iboga root bark, from 8.2% to 32.9% for products sold as TA, 73.7% for one sample sold as PTA and from 61.5% to 73.4% for products sold as ibogaine HCl. One sample did not show any iboga alkaloids. Other alkaloids and unknown substances were found in almost all samples. Discussion: The purity of iboga products is highly variable. These results should be taken into consideration by suppliers and users, especially regarding correct dosing to avoid overdose, as well as potential interactions with other substances
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