Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H\(_2^{18}\)O transitions were carried out ...towards the high-mass star-forming region G34.26+0.15 with the HIFI instrument onboard the Herschel Space Observatory, as well as with ground-based single-dish telescopes. Ten HDO lines and three H\(_2^{18}\)O lines covering a broad range of upper energy levels (22-204 K) were detected. We used a non-LTE 1D analysis to determine the HDO/H\(_2\)O ratio as a function of radius in the envelope. Models with different water abundance distributions were considered in order to reproduce the observed line profiles. The HDO/H\(_2\)O ratio is found to be lower in the hot core (\(\sim\)3.5 \(\times\) 10\(^{-4}\) - 7.5 \(\times\) 10\(^{-4}\)) than in the colder envelope (\(\sim\)1.0 \(\times\) 10\(^{-3}\) - 2.2 \(\times\) 10\(^{-3}\)). This is the first time that a radial variation of the HDO/H\(_2\)O ratio has been found to occur in a high-mass source. The chemical evolution of this source was modeled as a function of its radius and the observations are relatively well reproduced. The comparison between the chemical model and the observations leads to an age of \(\sim\)10\(^5\) years after the infrared dark cloud stage.
J. Mol. Spectrosc. 267 (2011) 100-107 Rotational transitions of $iso$-propyl cyanide, (CH$_3$)$_2$CHCN, also known
as $iso$-butyronitrile, were recorded using long-path absorption spectroscopy
in ...selected regions between 37 and 600 GHz. Further measurements were carried
out between 6 and 20 GHz employing Fourier transform microwave (FTMW)
spectroscopy on a pulsed molecular supersonic jet. The observed transitions
reach $J$ and $K_a$ quantum numbers of 103 and 59, respectively, and yield
accurate rotational constants as well as distortion parameters up to eighth
order. The $^{14}$N nuclear hyperfine splitting was resolved in particular by
FTMW spectroscopy yielding spin-rotation parameters as well as very accurate
quadrupole coupling terms. In addition, Stark effect measurements were carried
out in the microwave region to obtain a largely revised $c$-dipole moment
component and to improve the $a$-component. The hyperfine coupling and dipole
moment values are compared with values for related molecules both from
experiment and from quantum chemical calculations.
The HDO/H2O ratio is a powerful diagnostic to understand the evolution of water from the first stages of star formation to the formation of planets and comets. Our aim is to determine precisely the ...abundance distribution of HDO towards the low-mass protostar IRAS16293-2422 and learn more about the water formation mechanisms by determining the HDO/H2O abundance ratio. A spectral survey of the source IRAS16293-2422 was carried out in the framework of the CHESS Herschel Key program with the HIFI instrument, allowing the detection of numerous HDO lines. Other transitions have been observed previously with ground-based telescopes. The spherical Monte Carlo radiative transfer code RATRAN was used to reproduce the observed line profiles of HDO by assuming an abundance jump. To determine the H2O abundance throughout the envelope, a similar study was made of the H2-18O observed lines, as the H2O main isotope lines are contaminated by the outflows. We derive an inner HDO abundance of 1.7e-7 and an outer HDO abundance of 8e-11. To reproduce the HDO absorption lines, it is necessary to add an absorbing layer in front of the envelope. It may correspond to a water-rich layer created by the photodesorption of the ices at the edges of the molecular cloud. The HDO/H2O ratio is ~1.4-5.8% in the hot corino whereas it is ~0.2-2.2% in the outer envelope. It is estimated at ~4.8% in the added absorbing layer. Although it is clearly higher than the cosmic D/H abundance, the HDO/H2O ratio remains lower than the D/H ratio derived for other deuterated molecules observed in the same source. The similarity of the ratios derived in the hot corino and in the added absorbing layer suggests that water formed before the gravitational collapse of the protostar, contrary to formaldehyde and methanol, which formed later once the CO molecules had depleted on the grains.
Water plays a crucial role both in the interstellar medium and on Earth. To constrain its formation mechanisms and its evolution through the star formation process, the determination of the water ...deuterium fractionation ratios is particularly suitable. Previous studies derived HDO/H\(_2\)O ratios in the warm inner regions of low-mass protostars. We here report a detection of the D\(_2\)O 1\(_{1,0}\)-1\(_{0,1}\) transition toward the low-mass protostar NGC1333 IRAS2A with the Plateau de Bure interferometer: this represents the first interferometric detection of D\(_2\)O - and only the second solar-type protostar for which this isotopologue is detected. Using the observations of the HDO 5\(_{4,2}\)-6\(_{3,3}\) transition simultaneously detected and three other HDO lines previously observed, we show that the HDO line fluxes are well reproduced with a single excitation temperature of 218\(\pm\)21 K and a source size of \(\sim\)0.5 arcsec. The D\(_2\)O/HDO ratio is \(\sim\)(1.2\(\pm\)0.5) \(\times\) 10\(^{-2}\), while the use of previous H\(_2^{18}\)O observations give an HDO/H\(_2\)O ratio of \(\sim\)(1.7\(\pm\)0.8) \(\times\) 10\(^{-3}\), i.e. a factor of 7 lower than the D\(_2\)O/HDO ratio. These results contradict the predictions of current grain surface chemical models and indicate that either the surface deuteration processes are poorly understood or that both sublimation of grain mantles and water formation at high temperatures (\(\gtrsim\)230 K) take place in the inner regions of this source. In the second scenario, the thermal desorption of the grain mantles would explain the high D\(_2\)O/HDO ratio, while water formation at high temperature would explain significant extra production of H\(_2\)O leading to a decrease of the HDO/H\(_2\)O ratio.
Recent measurements carried out at comet 67P/C-G with the \({\it Rosetta}\) probe revealed that molecular oxygen, O\(_2\), is the fourth most abundant molecule in comets. Models show that O\(_2\) is ...likely of primordial nature, coming from the interstellar cloud from which our Solar System was formed. However, gaseous O\(_2\) is an elusive molecule in the interstellar medium with only one detection towards quiescent molecular clouds, in the \(\rho\) Oph A core. We perform a deep search for molecular oxygen, through the \(2_1 - 0_1\) rotational transition at 234 GHz of its \(^{16}\)O\(^{18}\)O isotopologue, towards the warm compact gas surrounding the nearby Class 0 protostar IRAS 16293--2422 B with the ALMA interferometer. The targeted \(^{16}\)O\(^{18}\)O transition is surrounded by two brighter transitions at \(\pm 1\) km s\(^{-1}\) relative to the expected \(^{16}\)O\(^{18}\)O transition frequency. After subtraction of these two transitions, residual emission at a 3\(\sigma\) level remains, but with a velocity offset of \(0.3 - 0.5\) km s\(^{-1}\) relative to the source velocity, rendering the detection "tentative". We derive the O\(_2\) column density for two excitation temperatures \(T_{\rm ex}\) of 125 and 300 K, as indicated by other molecules, in order to compare the O\(_2\) abundance between IRAS16293 and comet 67P/C-G. Assuming that \(^{16}\)O\(^{18}\)O is not detected and using methanol CH\(_3\)OH as a reference species, we obtain a O\(_2\)/CH\(_3\)OH abundance ratio lower than \(2-5\), depending on the assumed \(T_{\rm ex}\), a three to four times lower abundance than the O\(_2\)/CH\(_3\)OH ratio of \(5-15\) found in comet 67P/C-G. Such a low O\(_2\) abundance could be explained by the lower temperature of the dense cloud precursor of IRAS16293 with respect to the one at the origin of our Solar System that prevented an efficient formation of O\(_2\) in interstellar ices.
En este estudio se verificó las indicaciones de exodoncias en pacientes con cáncer en región de cabeza e cuello, que serán sometidos a radioterapia, en el servicio de Oncología de la Facultad de ...Odontología da Universidad Federal de Minas Gerais. Fueran evaluadas 114 historias clínicas y radiografías panorámicas y periapicales y fueran divididos de acuerdo con las indicaciones de exodoncias. Estas indicaciones fueron por caries, enfermedad periodontal, asociaciones de caries y periodontitis, falta de soporte para prótesis, diente incluidos, dientes extruidos, y en algunos casos dientes con indicaciones de extracciones exclusivamente por causa de la radioterapia. Los resultados mostraron que la mayor parte de indicaciones de exodoncias fueron debido a caries (21,05%) y enfermedades periodontales (26,31%). Debido a la predisposición a la pérdida de inserción periodontal y al riesgo de su progresión, pacientes que serán sometidos a la radioterapia de cabeza y cuello deberán ser evaluados en relación a la condición periodontal y a las indicaciones de exodoncia. Este estudio mostró que el diagnóstico de la enfermedad periodontal fue el principal factor relacionado con la indicación de exodoncias previamente al tratamiento oncológico
We report the detection of absorption lines by the reactive ions OH+, H2O+ and H3O+ along the line of sight to the submillimeter continuum source G10.6\(-\)0.4 (W31C). We used the Herschel HIFI ...instrument in dual beam switch mode to observe the ground state rotational transitions of OH+ at 971 GHz, H2O+ at 1115 and 607 GHz, and H3O+ at 984 GHz. The resultant spectra show deep absorption over a broad velocity range that originates in the interstellar matter along the line of sight to G10.6\(-\)0.4 as well as in the molecular gas directly associated with that source. The OH+ spectrum reaches saturation over most velocities corresponding to the foreground gas, while the opacity of the H2O+ lines remains lower than 1 in the same velocity range, and the H3O+ line shows only weak absorption. For LSR velocities between 7 and 50 kms\(^{-1}\) we estimate total column densities of \(N\)(OH+) \(> 2.5 \times 10^{14}\) cm\(^{-2}\), \(N\)(H2O+) \(\sim 6 \times 10^{13}\) cm\(^{-2}\) and \(N\)(H3O+) \(\sim 4.0 \times 10^{13}\) cm\(^{-2}\). These detections confirm the role of O\(^+\) and OH\(^+\) in initiating the oxygen chemistry in diffuse molecular gas and strengthen our understanding of the gas phase production of water. The high ratio of the OH+ by the H2O+ column density implies that these species predominantly trace low-density gas with a small fraction of hydrogen in molecular form.
