942 research outputs found
An interview study of pregnant women who were provided with indoor air quality measurements of second hand smoke to help them quit smoking
Background: Maternal smoking can cause health complications in pregnancy. Particulate matter (PM2.5) metrics applied to second hand smoke (SHS) concentrations provide indoor air quality (IAQ) measurements and have been used to promote smoking behaviour change among parents of young children. Here, we present the qualitative results from a study designed to use IAQ measurements to help pregnant women who smoke to quit smoking. Methods: We used IAQ measurements in two centres (Aberdeen and Coventry) using two interventions: 1. In Aberdeen, women made IAQ measurements in their homes following routine ultrasound scan; 2. In Coventry, IAQ measurements were added to a home-based Stop Smoking in Pregnancy Service. All women were invited to give a qualitative interview to explore acceptability and feasibility of IAQ measurements to help with smoking cessation. A case study approach using grounded theory was applied to develop a typology of pregnant women who smoke. Results: There were 39 women recruited (18 in Aberdeen and 21 in Coventry) and qualitative interviews were undertaken with nine of those women. Diverse accounts of smoking behaviours and experiences of participation were given. Many women reported changes to their smoking behaviours during pregnancy. Most women wanted to make further changes to their own behaviour, but could not commit or felt constrained by living with a partner or family members who smoked. Others could not envisage quitting. Using themes emerging from the interviews, we constructed a typology where women were classified as follows: 'champions for change'; 'keen, but not committed'; and 'can't quit, won't quit'. Three women reported quitting smoking alongside participation in our study. Conclusions: Pregnant women who smoke remain hard to engage,. Although providing IAQ measurements does not obviously improve quit rates, it can support changes in smoking behaviour in/around the home for some individuals. Our typology might offer a useful assessment tool for midwives
Ground-based aerosol characterization during the South American Biomass Burning Analysis (SAMBBA) field experiment
This paper investigates the physical and chemical
characteristics of aerosols at ground level at a site
heavily impacted by biomass burning. The site is located
near Porto Velho, Rondônia, in the southwestern part of the
Brazilian Amazon rainforest, and was selected for the deployment
of a large suite of instruments, among them an
Aerosol Chemical Speciation Monitor. Our measurements
were made during the South American Biomass Burning
Analysis (SAMBBA) field experiment, which consisted of
a combination of aircraft and ground-based measurements
over Brazil, aimed to investigate the impacts of biomass
burning emissions on climate, air quality, and numerical
weather prediction over South America. The campaign took
place during the dry season and the transition to the wet season
in September/October 2012.
During most of the campaign, the site was impacted by
regional biomass burning pollution (average CO mixing ratio
of 0.6 ppm), occasionally superimposed by intense (up
to 2 ppm of CO), freshly emitted biomass burning plumes.
Aerosol number concentrations ranged from ∼ 1000 cm−3
to
peaks of up to 35 000 cm−3
(during biomass burning (BB)
events, corresponding to an average submicron mass mean
concentrations of 13.7 µg m−3
and peak concentrations close
to 100 µg m−3
. Organic aerosol strongly dominated the submicron
non-refractory composition, with an average concentration
of 11.4 µg m−3
. The inorganic species, NH4, SO4,
NO3, and Cl, were observed, on average, at concentrations
of 0.44, 0.34, 0.19, and 0.01 µg m−3
, respectively. Equivalent
black carbon (BCe) ranged from 0.2 to 5.5 µg m−3
,
with an average concentration of 1.3 µg m−3
. During BB
peaks, organics accounted for over 90 % of total mass (submicron
non-refractory plus BCe), among the highest values
described in the literature.
We examined the ageing of biomass burning organic
aerosol (BBOA) using the changes in the H : C and O : C
ratios, and found that throughout most of the aerosol processing
(O : C ∼= 0.25 to O : C ∼= 0.6), no remarkable change
is observed in the H : C ratio (∼ 1.35). Such a result contrasts
strongly with previous observations of chemical ageing
of both urban and Amazonian biogenic aerosols. At higher
levels of processing (O : C > 0.6), the H : C ratio changes
with a H : C/O : C slope of −0.5, possibly due to the development
of a combination of BB (H : C/O : C slope =
0) and biogenic (H : C/O : C slope = −1) organic aerosol
(OA). An analysis of the 1OA/1CO mass ratios yields
very little enhancement in the OA loading with atmospheric
processing, consistent with previous observations. These
results indicate that negligible secondary organic aerosol
(SOA) formation occurs throughout the observed BB plume
Published by Copernicus Publications on behalf of the European Geosciences Union.
12070 J. Brito et al.: Ground-based aerosol characterization during SAMBBA
processing, or that SOA formation is almost entirely balanced
by OA volatilization.
Positive matrix factorization (PMF) of the organic aerosol
spectra resulted in three factors: fresh BBOA, aged BBOA,
and low-volatility oxygenated organic aerosol (LV-OOA).
Analysis of the diurnal patterns and correlation with external
markers indicates that during the first part of the campaign,
OA concentrations are impacted by local fire plumes
with some chemical processing occurring in the near-surface
layer. During the second part of the campaign, long-range
transport of BB plumes above the surface layer, as well as
potential SOAs formed aloft, dominates OA concentrations
at our ground-based sampling site.
This manuscript describes the first ground-based deployment
of the aerosol mass spectrometry at a site heavily impacted
by biomass burning in the Amazon region, allowing
a deeper understanding of aerosol life cycle in this important
ecosystem.This work was supported by the Foundation
for Research Support of the State of São Paulo (FAPESP,
projects 2012/14437-9 and 2013/05014-0), CNPq project 475735-
2012-9, INCT Amazonia, and Natural Environment Research
Council (NERC) project NE/J010073/1. We thank A. Ribeiro,
A. L. Loureiro, F. Morais, F. Jorge, and S. Morais for technical and
logistics support. We thank the National Institute of Meteorology
for providing valuable meteorological data. We gratefully acknowledge
S. Hacon, J. Silva, and W. Bastos for support in the successful
operation of the sampling site
Observations of SN 2017ein Reveal Shock Breakout Emission and A Massive Progenitor Star for a Type Ic Supernova
We present optical and ultraviolet observations of nearby type Ic supernova
SN 2017ein as well as detailed analysis of its progenitor properties from both
the early-time observations and the prediscovery Hubble Space Telescope (HST)
images. The optical light curves started from within one day to 275 days
after explosion, and optical spectra range from 2 days to 90 days
after explosion. Compared to other normal SNe Ic like SN 2007gr and SN 2013ge,
\mbox{SN 2017ein} seems to have more prominent C{\footnotesize II} absorption
and higher expansion velocities in early phases, suggestive of relatively lower
ejecta mass. The earliest photometry obtained for \mbox{SN 2017ein} show
indications of shock cooling. The best-fit obtained by including a shock
cooling component gives an estimate of the envelope mass as 0.02
M and stellar radius as 84 R. Examining the
pre-explosion images taken with the HST WFPC2, we find that the SN position
coincides with a luminous and blue point-like source, with an
extinction-corrected absolute magnitude of M8.2 mag and
M7.7 mag.Comparisons of the observations to the theoretical models
indicate that the counterpart source was either a single WR star or a binary
with whose members had high initial masses, or a young compact star cluster. To
further distinguish between different scenarios requires revisiting the site of
the progenitor with HST after the SN fades away.Comment: 28 pages, 19 figures; accepted for publication in The Astrophysical
Journa
Direct Introduction of a Dimesitylboryl Group Using Base-Mediated Substitution of Aryl Halides with Silyldimesitylborane
The first dimesitylboryl substitution of aryl halides with a silylborane bearing a dimesitylboryl group in the presence of alkali-metal alkoxides is described. The reactions of aryl bromides or iodides with Ph2MeSi-BMes(2) and Na(OtBu) afforded the desired aryl dimesitylboranes in good to high yields and with high borylation/silylation ratios. Selective reaction of the sterically less-hindered C-Br bond of dibromoarenes provided monoborylated products. This reaction was used to rapidly construct a D-pi-A aryl dimesityl borane with a non-symmetrical biphenyl spacer
The escape of ionising radiation from high-redshift dwarf galaxies
The UV escape fraction from high-redshift galaxies plays a key role in models
of cosmic reionisation. Because it is currently not possible to deduce the
escape fractions during the epoch of reionisation from observations, we have to
rely on numerical simulations. Our aim is to better constrain the escape
fraction from high-redshift dwarf galaxies, as these are the most likely
sources responsible for reionising the Universe. We employ a N-body/SPH method
that includes realistic prescriptions for the physical processes that are
important for the evolution of dwarf galaxies. These models are post-processed
with radiative transfer to determine the escape fraction of ionising radiation.
We perform a parameter study to assess the influence of the spin parameter, gas
fraction and formation redshift of the galaxy and study the importance of
numerical parameters as resolution, source distribution and local gas clearing.
We find that the UV escape fraction from high-redshift dwarf galaxies that have
formed a rotationally supported disc lie between 1e-5 and 0.1. The mass and
angular momentum of the galaxy are the most important parameters that determine
the escape fraction. We compare our results to previous work and discuss the
uncertainties of our models. The low escape fraction we find for high-redshift
dwarf galaxies is balanced by their high stellar content, resulting in an
efficiency parameter for stars that is only marginally lower than the values
found by semi-analytic models of reionisation. We therefore conclude that dwarf
galaxies play an important role in cosmic reionisation also after the initial
starburst phase, when the gas has settled into a disc.Comment: 19 pages, 14 figures. Accepted for publication in A&
Suizidprävention: Vorgehensweisen und Wirksamkeit
According to official statistics every year 11,000 persons in Germany die from suicide. 20 years ago nearly 19,000 suicides were registered. What are the causes for this decrease? Do suicide preventive measures contribute to the reduction of suicide rates? Different universal prevention strategies ( e. g. restriction of access to means) and selective approaches ( programs for special high-risk groups; e. g. patients after attempted suicide) are presented and discussed regarding their preventive value. In most cases it is hardly possible to scientifically prove the efficacy of suicide prevention strategies. Neither the role of psychosocial interventions nor the impact of psychotropic agents can be sufficiently quantified. Due to various methodological reasons ( e. g. small sample sizes and the lack of randomization), interpretation of the data is difficult. In terms of a comprehensive approach of suicide prevention a combination of different activities should be most adequate in the long run
Evaluation of diffusion models in breast cancer.
Purpose The purpose of this study is to investigate whether the microvascular pseudodiffusion effects resulting with non-monoexponential behavior are present in breast cancer, taking into account tumor spatial heterogeneity. Additionally, methodological factors affecting the signal in low and high diffusion-sensitizing gradient ranges were explored in phantom studies.Methods The effect of eddy currents and accuracy of b-value determination using a multiple b-value diffusion-weighted MR imaging sequence were investigated in test objects. Diffusion model selection and noise were then investigated in volunteers (n = 5) and breast tumor patients (n = 21) using the Bayesian information criterion.Results 54.3% of lesion voxels were best fitted by a monoexponential, 26.2% by a stretched-exponential, and 19.5% by a biexponential intravoxel incoherent motion (IVIM) model. High correlation (0.92) was observed between diffusion coefficients calculated using mono- and stretched-exponential models and moderate (0.59) between monoexponential and IVIM (medians: 0.96/0.84/0.72 × 10(-3) mm(2)/s, respectively). Distortion due to eddy currents depended on the direction of the diffusion gradient and displacement varied between 1 and 6 mm for high b-value images. Shift in the apparent diffusion coefficient due to intrinsic field gradients was compensated for by averaging diffusion data obtained from opposite directions.Conclusions Pseudodiffusion and intravoxel heterogeneity effects were not observed in approximately half of breast cancer and normal tissue voxels. This result indicates that stretched and IVIM models should be utilized in regional analysis rather than global tumor assessment. Cross terms between diffusion-sensitization gradients and other imaging or susceptibility-related gradients are relevant in clinical protocols, supporting the use of geometric averaging of diffusion-weighted images acquired with diffusion-sensitization gradients in opposite directions
Multi-centre reproducibility of diffusion MRI parameters for clinical sequences in the brain.
The purpose of this work was to assess the reproducibility of diffusion imaging, and in particular the apparent diffusion coefficient (ADC), intra-voxel incoherent motion (IVIM) parameters and diffusion tensor imaging (DTI) parameters, across multiple centres using clinically available protocols with limited harmonization between sequences. An ice-water phantom and nine healthy volunteers were scanned across fives centres on eight scanners (four Siemens 1.5T, four Philips 3T). The mean ADC, IVIM parameters (diffusion coefficient D and perfusion fraction f) and DTI parameters (mean diffusivity MD and fractional anisotropy FA), were measured in grey matter, white matter and specific brain sub-regions. A mixed effect model was used to measure the intra- and inter-scanner coefficient of variation (CV) for each of the five parameters. ADC, D, MD and FA had a good intra- and inter-scanner reproducibility in both grey and white matter, with a CV ranging between 1% and 7.4%; mean 2.6%. Other brain regions also showed high levels of reproducibility except for small structures such as the choroid plexus. The IVIM parameter f had a higher intra-scanner CV of 8.4% and inter-scanner CV of 24.8%. No major difference in the inter-scanner CV for ADC, D, MD and FA was observed when analysing the 1.5T and 3T scanners separately. ADC, D, MD and FA all showed good intra-scanner reproducibility, with the inter-scanner reproducibility being comparable or faring slightly worse, suggesting that using data from multiple scanners does not have an adverse effect compared with using data from the same scanner. The IVIM parameter f had a poorer inter-scanner CV when scanners of different field strengths were combined, and the parameter was also affected by the scan acquisition resolution. This study shows that the majority of diffusion MRI derived parameters are robust across 1.5T and 3T scanners and suitable for use in multi-centre clinical studies and trials
A simple, reproducible method for monitoring the treatment of tumours using dynamic contrast-enhanced MR imaging
Dynamic contrast-enhanced MR imaging (DCE-MRI) may act as a biomarker for successful cancer therapy. Simple, reproducible techniques may widen this application. This paper demonstrates a single slice imaging technique. The image acquisition is performed in less than 500 ms making it relatively insensitive to respiratory motion. Data from phantom studies and a reproducibility study in solid human tumours are presented. The reproducibility study showed a coefficient of variation (CoV) of 19.1% for Ktrans and 15.8% for the initial area under the contrast enhancement curve (IAUC). This was improved to 16 and 13.9% if tumours of diameter less than 3 cm were excluded. The individual repeatability (the range within which individual measurements are expected to fall) was 30.6% for Ktrans and 26.5% for IAUC for tumours greater than 3 cm diameter. This approach to DCE–MRI image acquisition can be performed with standard clinical scanners, and data analysis is straightforward. For treatment trials with 10 patients in a cohort, the CoV implies that the method would be sensitive to a treatment effect of greater than 18%. The individual repeatability is well inside the 40% change shown to be important in clinical studies using this DCE–MRI technique
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