2,460 research outputs found
Laboratory and observational study of the interrelation of the carbonaceous component of interstellar dust and solar system materials
By studying the chemical and isotopic composition of interstellar ice and dust, one gains insight into the composition and chemical evolution of the solid bodies in the solar nebula and the nature of the material subsequently brought into the inner part of the solar system by comets and meteorites. It is now possible to spectroscopically probe the composition of interstellar ice and dust in the mid-infrared, the spectral range which is most diagnostic of fundamental molecular vibrations. We can compare these spectra of various astronomical objects (including the diffuse and dense interstellar medium, comets, and the icy outer planets and their satellites) with the spectra of analogs we produce in the laboratory under conditions which mimic those in these different objects. In this way one can determine the composition and abundances of the major constituents of the various ices and place general constraints on the types of organics coating the grains in the diffuse interstellar medium. In particular we have shown the ices in the dense clouds contain H2O, CH3OH, CO, perhaps some NH3 and H2CO, we well as nitriles and ketones or esters. Furthermore, by studying the photochemistry of these ice analogs in the laboratory, one gains insight into the chemistry which takes place in interstellar/precometary ices. Chemical and spectroscopic studies of photolyzed analogs (including deuterated species) are now underway. The results of some of these studies will be presented and implications for the evolution of the biogenic elements in interstellar dust and comets will be discussed
Safe nights out: Workers’ perspectives on tackling violence against women and girls
Existing research focused on workers within the night-timeeconomy (NTE) is limited. In this unique study, research was conducted with workers from a wide range of professions and occupations. The study garnered important insights into NTE workers’ understanding and experience of violence against women and girls (VAWG).
Workers observed a strong relationship between alcohol consumption and VAWG and were knowledgeable about spiking, perceiving this practice to be growing. Strong protocols were in place to support women when spiking was alleged. The understanding of VAWG was, in contrast, broad but inconsistent. NTE workers provide myriad ways to support and protect women who are out at night. However, responses to potential incidents of VAWG are shaped by intuition, rather than being rooted in formal knowledge and institutional protocols. The decision to intervene is usually based on NTE workers’ levels of experience, confidence, and subjective perception of risk – described as ‘going with your gut’.
There were, however, some good examples of where formal training had been provided and found to be useful. Specifically,there was evidence that many of the initiatives established as part of the Safer Streets project were making a difference. Respondents valued the training that they had received (such as zero-tolerance), and they recognised the important role that Street Pastors provide. Nevertheless, several training gaps were identified. Specifically, workers reported that they wanted to be better equipped to identify potential perpetrators of crime and would welcome advice on how to enhance personal and customer safety. NTE workers would also benefit from knowing more about the location and
value of safe havens.
The study showed that while many venues offer support to customers, there is some inconsistency in the way that safety measures are advertised and enacted
Laboratory simulation of the photoprocessing and warm-up of cometary and pre-cometary ices: Production of complex organic molecules
The recent missions to Comet Halley detected large quantities of organic material on grains as well as organic molecules in the gas phase. A possible origin of these materials is the energetic processing of ice mantles on the grains prior to comet formation, either in the pre-solar nebula or the interstellar medium. This process was simulated in the laboratory by depositing interstellar ice analogs (H2O/CH3OH/CO/NH3) on a cold (10 K) substrate with simultaneous UV irradiation. The material evaporating during warm-up of the photolyzed ice as well as the residue remaining at room temperature was analyzed by a number of techniques. It was found that a large number of organic molecules of various complexity are synthesized during the simulation process, stressing the possible significance of UV photolysis for producing the organic Comet material
Molecular and mass spectroscopic analysis of isotopically labeled organic residues
Experimental studies aimed at understanding the evolution of complex organic molecules on interstellar grains were performed. The photolysis of frozen gas mixtures of various compositions containing H2O, CO, NH3, and CH4 was studied. These species were chosen because of their astrophysical importance as deducted from observational as well as theoretical studies of ice mantles on interstellar grains. These ultraviolet photolyzed ices were warmed up in order to produce refractory organic molecules like the ones formed in molecular clouds when the icy mantles are being irradiated and warmed up either by a nearby stellar source or impulsive heating. The laboratory studies give estimates of the efficiency of production of such organic material under interstellar conditions. It is shown that the gradual carbonization of organic mantles in the diffuse cloud phase leads to higher and higher visual absorptivity - yellow residues become brown in the laboratory. The obtained results can be applied to explaining the organic components of comets and their relevance to the origin of life
Report of the International Society of Hypertension (ISH) Hypertension Teaching Seminar organized by the ISH Africa Regional Advisory Group: Maputo, Mozambique, 2016
The International Society of Hypertension (ISH), in fulfilment of its mission of promoting hypertension control and prevention and also of advancing knowledge globally, organizes hypertension teaching seminars or ‘summer schools’ worldwide through the ISH Regional Advisory Groups. In Africa, seven of such seminars have been organized. This is a report of the eighth seminar held in Maputo, Mozambique, April, 2016. The seminar was attended by over 65 participants from 11 African countries. The Faculty consisted of 11 international hypertension experts. The eighth African hypertension seminar was a great success as confirmed by a pre- and post-test questionnaire
Orbiting Resonances and Bound States in Molecular Scattering
A family of orbiting resonances in molecular scattering is globally described
by using a single pole moving in the complex angular momentum plane. The
extrapolation of this pole at negative energies gives the location of the bound
states. Then a single pole trajectory, that connects a rotational band of bound
states and orbiting resonances, is obtained. These complex angular momentum
singularities are derived through a geometrical theory of the orbiting. The
downward crossing of the phase-shifts through pi/2, due to the repulsive region
of the molecular potential, is estimated by using a simple hard-core model.
Some remarks about the difference between diffracted rays and orbiting are also
given.Comment: 18 pages, 3 figures, to appear in Physical Review
A Variational Approach to Bound States in Quantum Field Theory
We consider here in a toy model an approach to bound state problem in a
nonperturbative manner using equal time algebra for the interacting field
operators. Potential is replaced by offshell bosonic quanta inside the bound
state of nonrelativistic particles. The bosonic dressing is determined through
energy minimisation, and mass renormalisation is carried out in a
nonperturbative manner. Since the interaction is through a scalar field, it
does not include spin effects. The model however nicely incorporates an
intuitive picture of hadronic bound states in which the gluon fields dress the
quarks providing the binding between them and also simulate the gluonic content
of hadrons in deep inelastic collisions.Comment: latex, revtex, 22 page
Methanol masers : Reliable tracers of the early stages of high-mass star formation
The GLIMPSE and MSX surveys have been used to examine the mid-infrared
properties of a statistically complete sample of 6.7 GHz methanol masers. The
GLIMPSE point sources associated with methanol masers are clearly distinguished
from the majority, typically having extremely red mid-infrared colors, similar
to those expected of low-mass class 0 young stellar objects. The intensity of
the GLIMPSE sources associated with methanol masers is typically 4 magnitudes
brighter at 8.0 micron than at 3.6 micron. Targeted searches towards GLIMPSE
point sources with [3.6]-[4.5] > 1.3 and an 8.0 micron magnitude less than 10
will detect more than 80% of class II methanol masers. Many of the methanol
masers are associated with sources within infrared dark clouds (IRDC) which are
believed to mark regions where high-mass star formation is in its very early
stages. The presence of class II methanol masers in a significant fraction of
IRDC suggests that high-mass star formation is common in these regions.
Different maser species are thought to trace different evolutionary phases of
the high-mass star formation process. Comparison of the properties of the
GLIMPSE sources associated with class II methanol masers and other maser
species shows interesting trends, consistent with class I methanol masers
tracing a generally earlier evolutionary phase and OH masers tracing a later
evolutionary phase.Comment: 45 pages, 19 figures, accepted for publication in Ap
Infrared spectroscopy of HCOOH in interstellar ice analogues
Context: HCOOH is one of the more common species in interstellar ices with
abundances of 1-5% with respect to solid H2O. Aims: This study aims at
characterizing the HCOOH spectral features in astrophysically relevant ice
mixtures in order to interpret astronomical data. Methods: The ices are grown
under high vacuum conditions and spectra are recorded in transmission using a
Fourier transform infrared spectrometer. Pure HCOOH ices deposited at 15 K and
145 K are studied, as well as binary and tertiary mixtures containing H2O, CO,
CO2 and CH3OH. The mixture concentrations are varied from 50:50% to ~10:90% for
HCOOH:H2O. Binary mixtures of HCOOH:X and tertiary mixtures of HCOOH:H2O:X with
X = CO, CO2, and CH3OH, are studied for concentrations of ~10:90% and
~7:67:26%, respectively. Results: Pure HCOOH ice spectra show broad bands which
split around 120 K due to the conversion of a dimer to a chain-structure. Broad
single component bands are found for mixtures with H2O. Additional spectral
components are present in mixtures with CO, CO2 and CH3OH. The resulting peak
position, full width at half maximum and band strength depend strongly on ice
structure, temperature, matrix constituents and the HCOOH concentration.
Comparison of the solid HCOOH 5.9, 7.2, and 8.1 micron features with
astronomical data toward the low mass source HH 46 and high mass source W 33A
shows that spectra of binary mixtures do not reproduce the observed ice
features. However, our tertiary mixtures especially with CH3OH match the
astronomical data very well. Thus interstellar HCOOH is most likely present in
tertiary or more complex mixtures with H2O, CH3OH and potentially also CO or
CO2, providing constraints on its formation.Comment: 11 pages, 10 figures, accepted by A&
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