Isotopic fractionation of carbon, deuterium and nitrogen : a full chemical study

Context. The increased sensitivity and high spectral resolution of millimeter telescopes allow the detection of an increasing number of isotopically substituted molecules in the interstellar medium. The 14N/ 15N ratio is difficult to measure directly for carbon containing molecules. Aims. We want to check the underlying hypothesis that the 13C/ 12C ratio of nitriles and isonitriles is equal to the elemental value via a chemical time dependent gas phase chemical model. Methods. We have built a chemical network containing D, 13C and 15N molecular species after a careful check of the possible fractionation reactions at work in the gas phase. Results. Model results obtained for 2 different physical conditions corresponding respectively to a moderately dense cloud in an early evolutionary stage and a dense depleted pre-stellar core tend to show that ammonia and its singly deuterated form are somewhat enriched in 15N, in agreement with observations. The 14N/ 15N ratio in N2H+ is found to be close to the elemental value, in contrast to previous models which obtain a significant enrichment, as we found that the fractionation reaction between 15N and N2H+ has a barrier in the entrance channel. The large values of the N2H+/15NNH+ and N2H+/ N15NH+ ratios derived in L1544 cannot be reproduced in our model. Finally we find that nitriles and isonitriles are in fact significantly depleted in 13C, questioning previous interpretations of observed C15N, HC15N and H15NC abundances from 13C containing isotopologues.Comment: 21 pages, 9 figures in the text, 3 Figures in the appendices. 7 tables in the text, 4 tables in the appendices. Accepted for publication by Astronomy Astrophysic

Discrimination of hot versus cold avalanche deposits: Implications for hazard assessment at Mount Meager, B.C.

The surficial deposits surrounding the Mount Meager volcanic complex include numerous avalanche deposits. These deposits share many attributes: (a) they are nearly monolithologic and comprise mainly intermediate volcanic rock clasts, (b) they lack internal structure, and (c) they are very poorly sorted. Despite these similarities, the avalanche deposits represent two distinct processes. Mass wasting of the Mount Meager volcanic edifice has produced cold rock avalanche deposits, whereas gravitational collapse of active lava domes and flows has produced hot block and ash avalanche deposits. The ability to discriminate between these "hot" and "cold" avalanche deposits is a critical component in the assessment of hazards in volcanic terranes. Hot block and ash avalanche deposits can be distinguished by the presence of radially-oriented joints, breadcrust textures, and incipient welding, which are features indicative of high emplacement temperatures. Conversely, rock avalanche deposits resulting from mass wasting events may be distinguished by the presence of clasts that preserve pre-depositional weathering and jointing surfaces. Volcanic avalanches are mechanically similar to rock avalanches but pose a greater hazard due to high temperatures, increased fluidization from degassing and the potential to decouple highly mobile elutriated ash clouds. The increasing use of hazardous regions such as the Lillooet River valley requires more reliable risk assessment in order to minimize losses from future hazardous events

Close contact restriction periods for patients who received iodine-131 therapy for differentiated thyroid cancer

Objective. Patients treated with radionuclide therapy may require restrictions on certain activities for a period of time following treatment to optimise protection of the public and ensure the legal dose limit is not exceeded. Software may be used to calculate necessary restriction periods for an individual based on longitudinal dose rate measurements from the time of radiopharmaceutical administration. A spreadsheet program has been used for this purpose in Australian hospitals for the last two decades. However, this spreadsheet has a limitation in that it uses an approximation in the calculation of dose from a contact pattern, which affects the calculated restriction period. A computer program called Dorn was developed that provides the same functionality as the spreadsheet but without this approximation. Proffered radiation safety advice from Dorn and the spreadsheet were compared. Approach. Advice from the spreadsheet and Dorn were compared for 55 patients who underwent iodine-131 therapy for differentiated thyroid cancer. Main results. The restriction periods for caring for infants, close contact with children and sleeping with a partner were typically about 13 hours longer in Dorn than in the spreadsheet, but in some cases were over a week shorter or a month longer. Significance. If the Dorn program is used clinically in place of the spreadsheet, some patients will enjoy shorter restriction periods and the therapy provider can be more confident in their compliance with regulatory requirements and best practice. Dorn is freely available from https://doi.org/jg5f.Comment: 17 pages, 16 figure

Dynamical effects of interactions and the Tully-Fisher relation for Hickson compact groups

We investigate the properties of the B-band Tully-Fisher (T-F) relation for 25 compact group galaxies, using Vmax derived from 2-D velocity maps. Our main result is that the majority of the Hickson Compact Group galaxies lie on the T-F relation. However, about 20% of the galaxies, including the lowest-mass systems, have higher B luminosities for a given mass, or alternatively, a mass which is too low for their luminosities. We favour a scenario in which outliers have been brightened due to either enhanced star formation or merging. Alternatively, the T-F outliers may have undergone truncation of their dark halo due to interactions. It is possible that in some cases, both effects contribute. The fact that the B-band T-F relation is similar for compact group and field galaxies tells us that these galaxies show common mass-to-size relations and that the halos of compact group galaxies have not been significantly stripped inside R25. We find that 75% of the compact group galaxies studied (22 out of 29) have highly peculiar velocity fields. Nevertheless, a careful choice of inclination, position angle and center, obtained from the velocity field, and an average of the velocities over a large sector of the galaxy enabled the determination of fairly well-behaved rotation curves for the galaxies. However, two of the compact group galaxies which are the most massive members in M51--like pairs, HCG 91a and HCG 96a, have very asymmetric rotation curves, with one arm rising and the other one falling, indicating, most probably, a recent perturbation by the small close companions.Comment: 15 pages, 4 figures, accepted for publication in the Astronomical Journa

When white people experience the weight of the past:The role of white identity strategies in linking colonialism to current racial inequalities

How do White Europeans address racial inequalities in times of burgeoningdiscussions about colonialism? The current research explores the strategies that White people in the Netherlands use to manage their racial-ethnic identity in relation to linking colonialism and current racial inequalities. With this, we examined how White identity strategies were related to ideologies legitimizing racial inequalities. Using mixed-methods consisting of qualitative interviews (N = 24) and quantitative surveys (N = 564), we found that White people exhibited different combinations of prideful (“I am a proud person of our ethnic heritage”), dissociated (“My ethnic group does not have a significant impact on how I see the world”), and power-cognizant (“I am a White person with privileges because of my ethnic group”) identity strategies. Moreover, these White identity strategies were associated withlinking colonialism and racial inequalities and, thereby, with ideologies legitimizing them. Specifically, White people holding prideful and dissociated strategies were less likely to link colonialism and racial inequalities than White people who exclusively endorsed powercognizance. Furthermore, power-cognizant people challenged current-day racial inequalities the most. We conclude by discussing how White European people legitimize or question racial inequalities by managing their whiteness and the theoretical and practical implications of these findings

How Can eHealth Meet the Hearing and Communication Needs of Adults With Hearing Impairment and their Significant Others? A Group Concept Mapping Study

Objectives: To seek the perspectives of key stakeholders regarding: (1) how eHealth could help meet the hearing and communication needs of adults with hearing impairment and their significant others; and (2) how helpful each aspect of eHealth would be to key stakeholders personally. / Design: Group concept mapping, a mixed-methods participatory research method, was used to seek the perspectives of key stakeholders: adults with hearing impairment (n = 39), significant others (n = 28), and hearing care professionals (n = 56). All participants completed a short online survey before completing one or more of the following activities: brainstorming, sorting, and rating. Brainstorming required participants to generate ideas in response to the focus prompt, “One way I would like to use information and communication technologies to address the hearing and communication needs of adults with hearing loss and their family and friends is to….” The sorting task required participants to sort all statements into groups that made sense to them. Finally, the rating task required participants to rate each of the statements according to “How helpful would this idea be to you?” using a 5-point Likert scale. Hierarchical cluster analysis was applied to the “sorting” data to develop a cluster map using the Concept Systems software. The “rating” data were subsequently analyzed at a cluster level and an individual-item level using descriptive statistics. Differences in cluster ratings between stakeholder groups were examined using Kruskal-Wallis tests. / Results: Overall, 123 statements were generated by participants in response to the focus prompt and were included in subsequent analyses. Based on the “sorting” data and hierarchical cluster analysis, a seven-cluster map was deemed to be the best representation of the data. Three key themes emerged from the data, including using eHealth to (1) Educate and Involve Others; (2) Support Aural Rehabilitation; and (3) Educate About and Demonstrate the Impacts of Hearing Impairment and Benefits of Hearing Rehabilitation. Overall median rating scores for each cluster ranged from 3.97 (educate and involve significant others) to 3.44 (empower adults with hearing impairment to manage their hearing impairment from home). / Conclusions: These research findings demonstrate the broad range of clinical applications of eHealth that have the capacity to support the implementation of patient- and family-centered hearing care, with self-directed educational tools and resources typically being rated as most helpful. Therefore, eHealth appears to be a viable option for enabling a more biopsychosocial approach to hearing healthcare and educating and involving significant others in the hearing rehabilitation process without adding more pressure on clinical time. More research is needed to inform the subsequent development of eHealth interventions, and it is recommended that health behavior change theory be adhered to for such interventions

Extented ionized gas emission and kinematics of the compact group galaxies in HCG 16: Signatures of mergers

We report on kinematic observations of Ha emission line from four late-type galaxies of Hickson Compact Group 16 (H16a,b,c and d) obtained with a scanning Fabry-Perot interferometer and samplings of 16 km/s and 1". The velocity fields show kinematic peculiarities for three of the four galaxies: H16b, c and d. Misalignments between the kinematic and photometric axes of gas and stellar components (H16b,c,d), double gas systems (H16c) and severe warping of the kinematic major axis (H16b and c) were some of the peculiarities detected. We conclude that major merger events have taken place in at least two of the galaxies group. H16c and d, based on their significant kinematic peculiarities, their double nuclei and high infrared luminosities. Their Ha gas content is strongly spatially concentred - H16d contains a peculiar bar-like structure confined to the inner $\sim$ 1 h^-1 kpc region. These observations are in agreement with predictions of simulations, namely that the gas flows towards the galaxy nucleus during mergers, forms bars and fuel the central activity. Galaxy H16b, and Sb galaxy, also presents some of the kinematic evidences for past accretion events. Its gas content, however, is very spare, limiting our ability to find other kinematic merging indicators, if they are present. We find that isolated mergers, i.e., they show an anormorphous morphology and no signs of tidal tails. Tidal arms and tails formed during the mergers may have been stripped by the group potential (Barnes & Hernquist 1992) ar alternatively they may have never been formed. Our observations suggest that HCG 16 may be a young compact group in formation throught the merging of close-by objects in a dense environment.Comment: Accepted for publication in ApJ. 35 pages, 13 figures. tar file gzipped and uuencode

HI Observations of the Stephan's Quintet

Using the VLA, we have made spectral-line and continuum observations of the neutral hydrogen in the direction of the compact group of galaxies Stephan's Quintet. The high-velocity clouds between 5600 and 6600 km/s, the disk of the foreground galaxy, NGC 7320, at 800 km/s, the extended continuum ridge near the center of the group, and 3 faint dwarf-like galaxies in the surrounding field were imaged with C, CS, and D arrays. Four of the HI clouds previously detected are confirmed. The two largest HI features are coincident with and concentrated mainly along separate large tidal tails that extend eastward. The most diffuse of the four clouds is resolved into two clumps, one coincide with tidal features south of NGC 7318a and the other devoid of any detectable stellar or Halfa sources. The two compact clouds, along the same line of sight, have peak emission at luminous infrared and bright Halfa sources probably indicative of star-forming activity. The total amount of HI detected at high redshifts is ~ 10**10Msol. As in previous HI studies of the group, no detectable emission was measured at the positions of any high-redshift galaxies so that any HI still bound to their disks must be less than 2.4 x 10**7Msol.Comment: Accepted for publication in AJ and tentatively scheduled for the May 2002 issue. High-resolution ps figures are available at: http://www.iaa.es/~lourdes/bw/bw-paper.tar.g

Detection of ethanol, acetone, and propanal in TMC-1: New O-bearing complex organics in cold sources

We present the detection of ethanol (C2H5OH), acetone (CH3COCH3), and propanal (C2H5CHO) toward the cyanopolyyne peak of TMC-1. These three O-bearing complex organic molecules are known to be present in warm interstellar clouds, but had never been observed in a starless core. The addition of these three new pieces to the puzzle of complex organic molecules in cold interstellar clouds stresses the rich chemical diversity of cold dense cores in stages prior to the onset of star formation. The detections of ethanol, acetone, and propanal were made in the framework of QUIJOTE, a deep line survey of TMC-1 in the Q band that is being carried out with the Yebes 40m telescope. We derive column densities of (1.1 +/- 0.3)e12 cm-2 for C2H5OH, (1.4 +/- 0.6)e11 cm-2 for CH3COCH3, and (1.9 +/- 0.7)e11 cm-2 for C2H5CHO. The formation of these three O-bearing complex organic molecules is investigated with the aid of a detailed chemical model which includes gas and ice chemistry. The calculated abundances at a time around 2e5 yr are in reasonable agreement with the values derived from the observations. The formation mechanisms of these molecules in our chemical model are as follows. Ethanol is formed on grains by addition of atomic carbon on methanol followed by hydrogenation and non-thermal desorption. Acetone and propanal are produced by the gas-phase reaction between atomic oxygen and two different isomers of the C3H7 radical, where the latter follows from the hydrogenation of C3 on grains followed by non-thermal desorption. A gas-phase route involving the formation of (CH3)2COH+ through several ion-neutral reactions followed by its dissociative recombination with electrons do also contribute to the formation of acetone.Comment: Accepted for publication in A&