155 research outputs found
The lived experience of self-intermittent catheterisation in people with spinal cord injury
Self-intermittent catheterisation (SIMC) is one of the most common and safest methods of bladder emptying in people with spinal cord injury (SCI). There is a large amount of literature relating to the biomedical aspects of SIMC, such as infection rates and renal complications. There is however, very little information about how people actually experience SIMC and its effect on their daily lives. Through a series of semi-structured interviews this study describes the lived experience of eight men with spinal cord injuries who perform self-intermittent catheterisation to empty their bladder. The study uses Husserlian phenomenology and Colaizzi\u27s method to analyse data gathered through the interviews. Clusters of similar themes were extracted from the transcribed interviews and reduced into six theme categories. The data showed that SIMC has an effect on almost all aspects of a person\u27s life including work and social lives, their personal relationships and body esteem, even what they drink and how they sleep. The themes are discussed and relevant literature provides a legitimate basis for the issues that arose for participants. New knowledge is detailed and there are recommendations for changes in practice and suggestions for further research
Negative ions formed in N<sub>2</sub>/CH<sub>4</sub>/Ar discharge – a simulation of Titan's atmosphere chemistry
The formation of negative ions produced in a negative point-to-plane corona discharge fed by a Ar/N2//CH4/ gas mixture has been studied using mass spectrometry. The measurements were carried out in flowing regime at ambient temperature and a reduced pressure of 460 mbar. The CN ? anion has been found to be the most dominant negative ion in the discharge and is believed to be the precursor of heavier negative ions such as C3/N ? and C5/N ? . The most likely pathway for the formation of such molecular anions is H-loss dissociative electron attachment to HCN, H3/CN and H5/CN formed in the discharge. These same anions have been detected in Titan's atmosphere and the present experiments may provide some novel insights into the chemical and physical mechanisms prevalent in Titan's atmosphere and hence assist in the interpretation of results from the Cassini Huygens space mission
The Chemistry of Interstellar OH+, H2O+, and H3O+: Inferring the Cosmic Ray Ionization Rates from Observations of Molecular Ions
We model the production of OH+, H2O+, and H3O+ in interstellar clouds, using
a steady state photodissociation region code that treats the freeze-out of gas
species, grain surface chemistry, and desorption of ices from grains. The code
includes PAHs, which have important effects on the chemistry. All three ions
generally have two peaks in abundance as a function of depth into the cloud,
one at A_V<~1 and one at A_V~3-8, the exact values depending on the ratio of
incident ultraviolet flux to gas density. For relatively low values of the
incident far ultraviolet flux on the cloud ({\chi}<~ 1000; {\chi}= 1= local
interstellar value), the columns of OH+ and H2O+ scale roughly as the cosmic
ray primary ionization rate {\zeta}(crp) divided by the hydrogen nucleus
density n. The H3O+ column is dominated by the second peak, and we show that if
PAHs are present, N(H3O+) ~ 4x10^{13} cm^{-2} independent of {\zeta}(crp) or n.
If there are no PAHs or very small grains at the second peak, N(H3O+) can
attain such columns only if low ionization potential metals are heavily
depleted. We also model diffuse and translucent clouds in the interstellar
medium, and show how observations of N(OH+)/N(H) and N(OH+)/N(H2O+) can be used
to estimate {\zeta}(crp)/n, {\chi}/n and A_V in them. We compare our models to
Herschel observations of these two ions, and estimate {\zeta}(crp) ~ 4-6 x
10^-16 (n/100 cm^-3) s^-1 and \chi/n = 0.03 cm^3 for diffuse foreground clouds
towards W49N
Two-dimensional AMR simulations of colliding flows
Colliding flows are a commonly used scenario for the formation of molecular
clouds in numerical simulations. Due to the thermal instability of the warm
neutral medium, turbulence is produced by cooling. We carry out a
two-dimensional numerical study of such colliding flows in order to test
whether statistical properties inferred from adaptive mesh refinement (AMR)
simulations are robust with respect to the applied refinement criteria. We
compare probability density functions of various quantities as well as the
clump statistics and fractal dimension of the density fields in AMR simulations
to a static-grid simulation. The static grid with 2048^2 cells matches the
resolution of the most refined subgrids in the AMR simulations. The density
statistics is reproduced fairly well by AMR. Refinement criteria based on the
cooling time or the turbulence intensity appear to be superior to the standard
technique of refinement by overdensity. Nevertheless, substantial differences
in the flow structure become apparent. In general, it is difficult to separate
numerical effects from genuine physical processes in AMR simulations.Comment: 6 pages, 6 figures, submitted to A&
On the Excitation and Formation of Circumstellar Fullerenes
We compare and analyze the Spitzer mid-infrared spectrum of three
fullerene-rich planetary nebulae in the Milky Way and the Magellanic Clouds;
Tc1, SMP SMC16, and SMP LMC56. The three planetary nebulae share many
spectroscopic similarities. The strongest circumstellar emission bands
correspond to the infrared active vibrational modes of the fullerene species
C60 and little or no emission is present from Polycyclic Aromatic Hydrocarbons
(PAHs). The strength of the fullerene bands in the three planetary nebulae is
very similar, while the ratio of the [NeIII]15.5um/[NeII]12.8um fine structure
lines, an indicator of the strength of the radiation field, is markedly
different. This raises questions about their excitation mechanism and we
compare the fullerene emission to fluorescent and thermal models. In addition,
the spectra show other interesting and common features, most notably in the
6-9um region, where a broad plateau with substructure dominates the emission.
These features have previously been associated with mixtures of
aromatic/aliphatic hydrocarbon solids. We hypothesize on the origin of this
band, which is likely related to the fullerene formation mechanism, and compare
it with modeled Hydrogenated Amorphous Carbon that present emission in this
region.Comment: 13 pages, 2 tables, 7 figures, Accepted for publication in Ap
Ensaio estadual de linhagens e cultivares de feijão em Santa Catarina: VCU - Safra 2009/2010.
Gas cooling within the diffuse ISM of late-type galaxies
We combine observations of spiral galaxies in the [CII] line at 158 micron,
made with the Long Wavelength Spectrometer aboard ISO, with previous data from
the Kuiper Airborne Observatory to study the origin of this line, which is the
main coolant of the interstellar medium at relatively low temperatures. We also
use HI and CO(1-0) observations of these galaxies and estimate the respective
line fluxes in the same beam as the [CII] observations. We confirm the
existence of a linear relation between the [CII] line intensity and the CO(1-0)
line intensity, that we extend to intrinsically fainter galaxies. The
dispersion around this relation is significant and due to variations in the
far-UV flux, thus in the star formation rate. We find that for the least active
galaxies of our sample, in terms of star formation, the rate of [CII] line
emission per interstellar hydrogen atom is similar to that in the Solar
neighbourhood. For those galaxies, most of the [CII] line emission comes
probably from the diffuse cold atomic medium. In more active galaxies,
considered globally, the average [CII] line emission is dominated by dense
photodissociation regions and to some extent by the warm ionized diffuse
medium. This is true in the central region of many spiral galaxies, and
probably even in the interarm regions of the most actively star-forming ones.Comment: 8 pages, 6 Postscript figures, 2 Postscript tables, accepted to A&
Photoelectric effect on dust grains across the L1721 cloud in the rho Ophiuchi molecular complex
We present ISO-LWS measurements of the main gas cooling lines, C+ 158 mum and
O 63 mum towards a moderate opacity molecular cloud (Av=3), L1721, illuminated
by the B2 star nu Sco (X = 5-10). These data are combined with an extinction
map and IRAS dust emission images to test our understanding of gas heating and
cooling in photo-dissociation regions (PDRs). This nearby PDR is spatially
resolved in the IRAS images; variations in the IRAS colors across the cloud
indicate an enhanced abundance of small dust grains within the PDR. A spatial
correlation between the gas cooling lines and the infrared emission from small
dust grains illustrates the dominant role of small dust grains in the gas
heating through the photoelectric effect. The photoelectric efficiency,
determined from the observations by ratioing the power radiated by gas and
small dust grains, is in the range 2 to 3% in close agreement with recent
theoretical estimates. The brightness profiles across the PDR in the C+ 158 mum
and O 63 mum lines are compared with model calculations where the density
profile is constrained by the extinction data and where the gas chemical and
thermal balances are solved at each position. We show that abundance variations
of small dust grains across the PDR must be considered to account for the LWS
observations.Comment: 10 pages, 15 figure
The 5.25 & 5.7 m Astronomical Polycyclic Aromatic Hydrocarbon Emission Features
Astronomical mid-IR spectra show two minor PAH features at 5.25 and 5.7
m (1905 and 1754 cm) that hitherto have been little studied,
but contain information about the astronomical PAH population that complements
that of the major emission bands. Here we report a study involving both
laboratory and theoretical analysis of the fundamentals of PAH spectroscopy
that produce features in this region and use these to analyze the astronomical
spectra. The ISO SWS spectra of fifteen objects showing these PAH features were
considered for this study, of which four have sufficient S/N between 5 and 6
m to allow for an in-depth analysis. All four astronomical spectra show
similar peak positions and profiles. The 5.25 m feature is peaked and
asymmetric, while the 5.7 m feature is broader and flatter. Detailed
analysis of the laboratory spectra and quantum chemical calculations show that
the astronomical 5.25 and 5.7 m bands are a blend of combination,
difference and overtone bands primarily involving CH stretching and CH in-plane
and CH out-of-plane bending fundamental vibrations. The experimental and
computational spectra show that, of all the hydrogen adjacency classes possible
on PAHs, solo and duo hydrogens consistently produce prominent bands at the
observed positions whereas quartet hydrogens do not. In all, this a study
supports the picture that astronomical PAHs are large with compact, regular
structures. From the coupling with primarily strong CH out-of-plane bending
modes one might surmise that the 5.25 and 5.7 m bands track the neutral
PAH population. However, theory suggests the role of charge in these
astronomical bands might also be important.Comment: Accepted ApJ, 40 pages in pre-print, 14 figures, two onlin
Organic chemistry of NH<sub>3</sub> and HCN induced by an atmospheric abnormal glow discharge in N<sub>2</sub>-CH<sub>4</sub> mixtures
The formation of the chemical products produced in an atmospheric glow discharge fed by a N2-CH4 gas mixture has been studied using Fourier Transform InfraRed (FTIR) and Optical Emission Spectrometry (OES). The measurements were carried out in a flowing regime at ambient temperature and pressure with CH4 concentrations ranging from 0.5% to 2%. In the recorded emission spectra the lines of the second positive system CN system and the first negative system of N2 were found to be the most intensive but atomic Hα, Hβ, and C (247 nm) lines were also observed. FTIR-measurements revealed HCN
and NH3 to be the major products of the plasma with traces of C2H2. These same molecules have been detected in Titan's atmosphere and the present experiments may provide some novel insights into the
chemical and physical mechanisms prevalent in Titan's atmosphere with these smaller species believed to be the precursors of heavier organic species in Titan's atmosphere and on its surface
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