826 research outputs found
Sulphur-bearing molecules in diffuse molecular clouds: new results from SOFIA/GREAT and the IRAM 30 m telescope
We have observed five sulphur-bearing molecules in foreground diffuse
molecular clouds lying along the sight-lines to five bright continuum sources.
We have used the GREAT instrument on SOFIA to observe the 1383 GHz transitions of SH towards the star-forming regions W31C,
G29.96-0.02, G34.3+0.1, W49N and W51, detecting foreground absorption towards
all five sources; and the EMIR receivers on the IRAM 30m telescope at Pico
Veleta to detect the HS 1(10)-1(01), CS J=2-1 and SO 3(2)-2(1) transitions.
In nine foreground absorption components detected towards these sources, the
inferred column densities of the four detected molecules showed relatively
constant ratios, with N(SH)/N(HS) in the range 1.1 - 3.0, N(CS)/N(HS)
in the range 0.32 - 0.61, and N(SO)/N(HS) in the range 0.08 - 0.30. The
observed SH/H ratios - in the range (0.5-2.6) - indicate
that SH (and other sulphur-bearing molecules) account for << 1% of the
gas-phase sulphur nuclei. The observed abundances of sulphur-bearing molecules,
however, greatly exceed those predicted by standard models of cold diffuse
molecular clouds, providing further evidence for the enhancement of endothermic
reaction rates by elevated temperatures or ion-neutral drift. We have
considered the observed abundance ratios in the context of shock and turbulent
dissipation region (TDR) models. Using the TDR model, we find that the
turbulent energy available at large scale in the diffuse ISM is sufficient to
explain the observed column densities of SH and CS. Standard shock and TDR
models, however, fail to reproduce the column densities of HS and SO by a
factor of about 10; more elaborate shock models - in which account is taken of
the velocity drift, relative to H, of SH molecules produced by the
dissociative recombination of HS - reduce this discrepancy to a factor
~ 3.Comment: 30 pages, accepted for publication in A&
SUSTAINABLE DEVELOPMENT AND THE PROCESS OF JUSTIFYING CHOICES IN A CONTROVERSIAL UNIVERSE
All in all, neither the path of the generic principle nor that of the reduction to existing principles would appear to be fully satisfactory as the basis for establishing the legitimacy of sustainable development or as a way of making sustainability a principle of legitimacy by its own. We should probably resign ourselves to seeing in this idea a composite construction, still striving towards the formation of a new "superior common principle", without this principle yet being able to be completely clarified and validated. What we have here is an example of the sort of "compromise" described by Boltanski and Thévenot (1991, p.338): "In the compromise, the participants abandon the idea of clarifying the principle of their agreement but endeavour to maintain a frame of mind aiming at the common good." If we want to consolidate the compromise developing around sustainability, it would be well advised to seek the support of tests using well-formed objects. To this end, steps should be taken to move the emphasis away from long-term and unknowable sustainability requirements and closer to secondbest criteria focused on the transitional developments and possible risks of intentional human action, the ways of managing the linking of the different temporalities in play -- as regards the biophysical phenomena, their understanding and the main worlds of legitimacy (Godard, 1992) -- and the introduction of deliberation within the present generations as to what they feel best describes their identity, those things they would like to pass on
A Very Low Resource Language Speech Corpus for Computational Language Documentation Experiments
Most speech and language technologies are trained with massive amounts of
speech and text information. However, most of the world languages do not have
such resources or stable orthography. Systems constructed under these almost
zero resource conditions are not only promising for speech technology but also
for computational language documentation. The goal of computational language
documentation is to help field linguists to (semi-)automatically analyze and
annotate audio recordings of endangered and unwritten languages. Example tasks
are automatic phoneme discovery or lexicon discovery from the speech signal.
This paper presents a speech corpus collected during a realistic language
documentation process. It is made up of 5k speech utterances in Mboshi (Bantu
C25) aligned to French text translations. Speech transcriptions are also made
available: they correspond to a non-standard graphemic form close to the
language phonology. We present how the data was collected, cleaned and
processed and we illustrate its use through a zero-resource task: spoken term
discovery. The dataset is made available to the community for reproducible
computational language documentation experiments and their evaluation.Comment: accepted to LREC 201
Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
In diffuse interstellar clouds the chemistry that leads to the formation of
the oxygen bearing ions OH+, H2O+, and H3O+ begins with the ionization of
atomic hydrogen by cosmic rays, and continues through subsequent hydrogen
abstraction reactions involving H2. Given these reaction pathways, the observed
abundances of these molecules are useful in constraining both the total
cosmic-ray ionization rate of atomic hydrogen (zeta_H) and molecular hydrogen
fraction, f(H2). We present observations targeting transitions of OH+, H2O+,
and H3O+ made with the Herschel Space Observatory along 20 Galactic sight lines
toward bright submillimeter continuum sources. Both OH+ and H2O+ are detected
in absorption in multiple velocity components along every sight line, but H3O+
is only detected along 7 sight lines. From the molecular abundances we compute
f(H2) in multiple distinct components along each line of sight, and find a
Gaussian distribution with mean and standard deviation 0.042+-0.018. This
confirms previous findings that OH+ and H2O+ primarily reside in gas with low
H2 fractions. We also infer zeta_H throughout our sample, and find a log-normal
distribution with mean log(zeta_H)=-15.75, (zeta_H=1.78x10^-16 s^-1), and
standard deviation 0.29 for gas within the Galactic disk, but outside of the
Galactic center. This is in good agreement with the mean and distribution of
cosmic-ray ionization rates previously inferred from H3+ observations.
Ionization rates in the Galactic center tend to be 10--100 times larger than
found in the Galactic disk, also in accord with prior studies.Comment: 76 pages, 25 figures, 6 tables; accepted for publication in Ap
Risks, alternative knowledge strategies and democratic legitimacy: the conflict over co-incineration of hazardous industrial waste in Portugal.
The decision to incinerate hazardous industrial waste in cement plants (the socalled
‘co-incineration’ process) gave rise to one of the most heated environmental
conflicts ever to take place in Portugal. The bitterest period was between 1997 and
2002, after the government had made a decision. Strong protests by residents,
environmental organizations, opposition parties, and some members of the
scientific community forced the government to backtrack and to seek scientific
legitimacy for the process through scientific expertise. The experts ratified the
government’s decision, stating that the risks involved were socially acceptable.
The conflict persisted over a decade and ended up clearing the way for a more
sustainable method over which there was broad social consensus – a multifunctional
method which makes it possible to treat, recover and regenerate most
wastes. Focusing the analysis on this conflict, this paper has three aims: (1) to
discuss the implications of the fact that expertise was ‘confiscated’ after the
government had committed itself to the decision to implement co-incineration and
by way of a reaction to the atmosphere of tension and protest; (2) to analyse the
uses of the notions of ‘risk’ and ‘uncertainty’ in scientific reports from both
experts and counter-experts’ committees, and their different assumptions about
controllability and criteria for considering certain practices to be sufficiently safe
for the public; and (3) to show how the existence of different technical scientific
and political attitudes (one more closely tied to government and the corporate
interests of the cement plants, the other closer to the environmental values of reuse
and recycling and respect for the risk perception of residents who challenged
the facilities) is closely bound up with problems of democratic legitimacy. This
conflict showed how adopting more sustainable and lower-risk policies implies a
broader view of democratic legitimacy, one which involves both civic movements
and citizens themselves
Nitrogen hydrides in interstellar gas: Herschel/HIFI observations towards G10.6-0.4 (W31C)
The HIFI instrument on board the Herschel Space Observatory has been used to
observe interstellar nitrogen hydrides along the sight-line towards G10.6-0.4
in order to improve our understanding of the interstellar chemistry of
nitrogen. We report observations of absorption in NH N=1-0, J=2-1 and ortho-NH2
1_1,1-0_0,0. We also observed ortho-NH3 1_0-0_0, and 2_0-1_0, para-NH3 2_1-1_1,
and searched unsuccessfully for NH+. All detections show emission and
absorption associated directly with the hot-core source itself as well as
absorption by foreground material over a wide range of velocities. All spectra
show similar, non-saturated, absorption features, which we attribute to diffuse
molecular gas. Total column densities over the velocity range 11-54 km/s are
estimated. The similar profiles suggest fairly uniform abundances relative to
hydrogen, approximately 6*10^-9, 3*10^-9, and 3*10^-9 for NH, NH2, and NH3,
respectively. These abundances are discussed with reference to models of
gas-phase and surface chemistry.Comment: 5 pages, 3 figures, 2 online pages with 2 figures. Accepted for
publication in A&A July 6 (Herschel/HIFI special issue
Detection of hydrogen fluoride absorption in diffuse molecular clouds with Herschel/HIFI: a ubiquitous tracer of molecular gas
We discuss the detection of absorption by interstellar hydrogen fluoride (HF)
along the sight line to the submillimeter continuum sources W49N and W51. We
have used Herschel's HIFI instrument in dual beam switch mode to observe the
1232.4762 GHz J = 1 - 0 HF transition in the upper sideband of the band 5a
receiver. We detected foreground absorption by HF toward both sources over a
wide range of velocities. Optically thin absorption components were detected on
both sight lines, allowing us to measure - as opposed to obtain a lower limit
on - the column density of HF for the first time. As in previous observations
of HF toward the source G10.6-0.4, the derived HF column density is typically
comparable to that of water vapor, even though the elemental abundance of
oxygen is greater than that of fluorine by four orders of magnitude. We used
the rather uncertain N(CH)-N(H2) relationship derived previously toward diffuse
molecular clouds to infer the molecular hydrogen column density in the clouds
exhibiting HF absorption. Within the uncertainties, we find that the abundance
of HF with respect to H2 is consistent with the theoretical prediction that HF
is the main reservoir of gas-phase fluorine for these clouds. Thus, hydrogen
fluoride has the potential to become an excellent tracer of molecular hydrogen,
and provides a sensitive probe of clouds of small H2 column density. Indeed,
the observations of hydrogen fluoride reported here reveal the presence of a
low column density diffuse molecular cloud along the W51 sight line, at an LSR
velocity of ~ 24kms-1, that had not been identified in molecular absorption
line studies prior to the launch of Herschel.Comment: 4 pages, 3 figures, A&A Letter special issue, accepted on 07/13/201
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