726 research outputs found
Optimising computer aided detection to identify intra-thoracic tuberculosis on chest x-ray in South African children
Diagnostic tools for paediatric tuberculosis remain limited, with heavy reliance on clinical algorithms which include chest x-ray. Computer aided detection (CAD) for tuberculosis on chest x-ray has shown promise in adults. We aimed to measure and optimise the performance of an adult CAD system, CAD4TB, to identify tuberculosis on chest x-rays from children with presumptive tuberculosis. Chest x-rays from 620 children <13 years enrolled in a prospective observational diagnostic study in South Africa, were evaluated. All chest x-rays were read by a panel of expert readers who attributed each with a radiological reference of either 'tuberculosis' or 'not tuberculosis'. Of the 525 chest x-rays included in this analysis, 80 (40 with a reference of 'tuberculosis' and 40 with 'not tuberculosis') were allocated to an independent test set. The remainder made up the training set. The performance of CAD4TB to identify 'tuberculosis' versus 'not tuberculosis' on chest x-ray against the radiological reference read was calculated. The CAD4TB software was then fine-tuned using the paediatric training set. We compared the performance of the fine-tuned model to the original model. Our findings were that the area under the receiver operating characteristic curve (AUC) of the original CAD4TB model, prior to fine-tuning, was 0.58. After fine-tuning there was an improvement in the AUC to 0.72 (p = 0.0016). In this first-ever description of the use of CAD to identify tuberculosis on chest x-ray in children, we demonstrate a significant improvement in the performance of CAD4TB after fine-tuning with a set of well-characterised paediatric chest x-rays. CAD has the potential to be a useful additional diagnostic tool for paediatric tuberculosis. We recommend replicating the methods we describe using a larger chest x-ray dataset from a more diverse population and evaluating the potential role of CAD to replace a human-read chest x-ray within treatment-decision algorithms for paediatric tuberculosis
1q21.1 distal copy number variants are associated with cerebral and cognitive alterations in humans
Low-frequency 1q21.1 distal deletion and duplication copy number variant (CNV) carriers are predisposed to multiple neurodevelopmental disorders, including schizophrenia, autism and intellectual disability. Human carriers display a high prevalence of micro- and macrocephaly in deletion and duplication carriers, respectively. The underlying brain structural diversity remains largely unknown. We systematically called CNVs in 38 cohorts from the large-scale ENIGMACNV collaboration and the UK Biobank and identified 28 1q21.1 distal deletion and 22 duplication carriers and 37,088 non-carriers (48% male) derived from 15 distinct magnetic resonance imaging scanner sites. With standardized methods, we compared subcortical and cortical brain measures (all) and cognitive performance (UK Biobank only) between carrier groups also testing for mediation of brain structure on cognition. We identified positive dosage effects of copy number on intracranial volume (ICV) and total cortical surface area, with the largest effects in frontal and cingulate cortices, and negative dosage effects on caudate and hippocampal volumes. The carriers displayed distinct cognitive deficit profiles in cognitive tasks from the UK Biobank with intermediate decreases in duplication carriers and somewhat larger in deletion carriers—the latter potentially mediated by ICV or cortical surface area. These results shed light on pathobiological mechanisms of neurodevelopmental disorders, by demonstrating gene dose effect on specific brain structures and effect on cognitive function
The distribution of water in the high-mass star-forming region NGC 6334I
We present observations of twelve rotational transitions of H2O-16, H2O-18,
and H2O-17 toward the massive star-forming region NGC 6334 I, carried out with
Herschel/HIFI as part of the guaranteed time key program Chemical HErschel
Surveys of Star forming regions (CHESS). We analyze these observations to
obtain insights into physical processes in this region.
We identify three main gas components (hot core, cold foreground, and
outflow) in NGC 6334 I and derive the physical conditions in these components.
The hot core, identified by the emission in highly excited lines, shows a
high excitation temperature of 200 K, whereas water in the foreground component
is predominantly in the ortho- and para- ground states. The abundance of water
varies between 4 10^-5 (outflow) and 10^-8 (cold foreground gas). This
variation is most likely due to the freeze-out of water molecules onto dust
grains. The H2O-18/H2O-17 abundance ratio is 3.2, which is consistent with the
O-18/O-17 ratio determined from CO isotopologues. The ortho/para ratio in water
appears to be relatively low 1.6(1) in the cold, quiescent gas, but close to
the equilibrium value of three in the warmer outflow material (2.5(0.8)).Comment: 7 pages, 3 figures, accepted by A&
The CHESS chemical Herschel surveys of star forming regions: Peering into the protostellar shock L1157-B1. I. Shock chemical complexity
We present the first results of the unbiased survey of the L1157-B1 bow
shock, obtained with HIFI in the framework of the key program Chemical Herschel
surveys of star forming regions (CHESS). The L1157 outflow is driven by a
low-mass Class 0 protostar and is considered the prototype of the so-called
chemically active outflows. The bright blue-shifted bow shock B1 is the ideal
laboratory for studying the link between the hot (around 1000-2000 K) component
traced by H2 IR-emission and the cold (around 10-20 K) swept-up material. The
main aim is to trace the warm gas chemically enriched by the passage of a shock
and to infer the excitation conditions in L1157-B1. A total of 27 lines are
identified in the 555-636 GHz region, down to an average 3 sigma level of 30
mK. The emission is dominated by CO(5-4) and H2O(110-101) transitions, as
discussed by Lefloch et al. (2010). Here we report on the identification of
lines from NH3, H2CO, CH3OH, CS, HCN, and HCO+. The comparison between the
profiles produced by molecules released from dust mantles (NH3, H2CO, CH3OH)
and that of H2O is consistent with a scenario in which water is also formed in
the gas-phase in high-temperature regions where sputtering or grain-grain
collisions are not efficient. The high excitation range of the observed tracers
allows us to infer, for the first time for these species, the existence of a
warm (> 200 K) gas component coexisting in the B1 bow structure with the cold
and hot gas detected from ground
First detection of ND in the solar-mass protostar IRAS16293-2422
In the past decade, much progress has been made in characterising the
processes leading to the enhanced deuterium fractionation observed in the ISM
and in particular in the cold, dense parts of star forming regions such as
protostellar envelopes. Very high molecular D/H ratios have been found for
saturated molecules and ions. However, little is known about the deuterium
fractionation in radicals, even though simple radicals often represent an
intermediate stage in the formation of more complex, saturated molecules. The
imidogen radical NH is such an intermediate species for the ammonia synthesis
in the gas phase. Herschel/HIFI represents a unique opportunity to study the
deuteration and formation mechanisms of such species, which are not observable
from the ground. We searched here for the deuterated radical ND in order to
determine the deuterium fractionation of imidogen and constrain the deuteration
mechanism of this species. We observed the solar-mass Class 0 protostar
IRAS16293-2422 with the heterodyne instrument HIFI as part of the Herschel key
programme CHESS (Chemical HErschel Surveys of Star forming regions). The
deuterated form of the imidogen radical ND was detected and securely identified
with 2 hyperfine component groups of its fundamental transition in absorption
against the continuum background emitted from the nascent protostar. The 3
groups of hyperfine components of its hydrogenated counterpart NH were also
detected in absorption. We derive a very high deuterium fractionation with an
[ND]/[NH] ratio of between 30 and 100%. The deuterium fractionation of imidogen
is of the same order of magnitude as that in other molecules, which suggests
that an efficient deuterium fractionation mechanism is at play. We discuss two
possible formation pathways for ND, by means of either the reaction of N+ with
HD, or deuteron/proton exchange with NH.Comment: Accepted; To appear in A&A Herschel/HIFI Special Issu
Nitrogen hydrides in the cold envelope of IRAS16293-2422
Nitrogen is the fifth most abundant element in the Universe, yet the
gas-phase chemistry of N-bearing species remains poorly understood. Nitrogen
hydrides are key molecules of nitrogen chemistry. Their abundance ratios place
strong constraints on the production pathways and reaction rates of
nitrogen-bearing molecules. We observed the class 0 protostar IRAS16293-2422
with the heterodyne instrument HIFI, covering most of the frequency range from
0.48 to 1.78~THz at high spectral resolution. The hyperfine structure of the
amidogen radical o-NH2 is resolved and seen in absorption against the continuum
of the protostar. Several transitions of ammonia from 1.2 to 1.8~THz are also
seen in absorption. These lines trace the low-density envelope of the
protostar. Column densities and abundances are estimated for each hydride. We
find that NH:NH2:NH3=5:1:300. {Dark clouds chemical models predict steady-state
abundances of NH2 and NH3 in reasonable agreement with the present
observations, whilst that of NH is underpredicted by more than one order of
magnitude, even using updated kinetic rates. Additional modelling of the
nitrogen gas-phase chemistry in dark-cloud conditions is necessary before
having recourse to heterogen processes
Herschel/HIFI observations of spectrally resolved methylidyne signatures toward the high-mass star-forming core NGC6334I
In contrast to extensively studied dense star-forming cores, little is known
about diffuse gas surrounding star-forming regions. We study molecular gas in
the high-mass star-forming region NGC6334I, which contains diffuse, quiescent
components that are inconspicuous in widely used molecular tracers such as CO.
We present Herschel/HIFI observations of CH toward NGC6334I observed as part of
the CHESS key program. HIFI resolves the hyperfine components of its J=3/2-1/2
transition, observed in both emission and absorption. The CH emission appears
close to the systemic velocity of NGC6334I, while its measured linewidth of 3
km/s is smaller than previously observed in dense gas tracers such as NH3 and
SiO. The CH abundance in the hot core is 7 10^-11, two to three orders of
magnitude lower than in diffuse clouds. While other studies find distinct
outflows in, e.g., CO and H2O toward NGC6334I, we do not detect outflow
signatures in CH. To explain the absorption signatures, at least two absorbing
components are needed at -3.0 and +6.5 km/s with N(CH)=7 10^13 and 3 10^13
cm^-2. Two additional absorbing clouds are found at +8.0 and 0.0 km/s, both
with N(CH)=2 10^13 cm^-2. Turbulent linewidths for the four absorption
components vary between 1.5 and 5.0 km/s in FWHM. We constrain physical
properties of our CH clouds by matching our CH absorbers with other absorption
signatures. In the hot core, molecules such as H2O and CO trace gas that is
heated and dynamically influenced by outflow activity, whereas CH traces more
quiescent material. The four CH absorbers have column densities and turbulent
properties consistent with diffuse clouds: two are located near NGC6334, and
two are unrelated foreground clouds. Local density and dynamical effects
influence the chemical composition of physical components of NGC6334, causing
some components to be seen in CH but not in other tracers, and vice versa.Comment: Accepted by A&A Letters; 5 pages, 1 figure; v2: minor textual and
typographical change
Ortho-to-para ratio of interstellar heavy water
Despite the low elemental deuterium abundance in the Galaxy, enhanced
molecular D/H ratios have been found in the environments of low-mass star
forming regions, and in particular the Class 0 protostar IRAS 16293-2422. The
CHESS (Chemical HErschel Surveys of Star forming regions) Key Program aims at
studying the molecular complexity of the interstellar medium. The high
sensitivity and spectral resolution of the HIFI instrument provide a unique
opportunity to observe the fundamental 1,1,1 - 0,0,0 transition of the
ortho-D2O molecule, inaccessible from the ground, and to determine the
ortho-to-para D2O ratio. We have detected the fundamental transition of the
ortho-D2O molecule at 607.35 GHz towards IRAS 16293-2422. The line is seen in
absorption with a line opacity of 0.62 +/- 0.11 (1 sigma). From the previous
ground-based observations of the fundamental 1,1,0 - 1,0,1 transition of
para-D2O seen in absorption at 316.80 GHz we estimate a line opacity of 0.26
+/- 0.05 (1 sigma). We show that the observed absorption is caused by the cold
gas in the envelope of the protostar. Using these new observations, we estimate
for the first time the ortho to para D2O ratio to be lower than 2.6 at a 3
sigma level of uncertainty, to be compared with the thermal equilibrium value
of 2:1.Comment: 5 pages, 5 figures, accepted the A&A HIFI Special Issue as a lette
CHESS, Chemical Herschel surveys of star forming regions:Peering into the protostellar shock L1157-B1
The outflow driven by the low-mass class 0 protostar L1157 is the prototype
of the so-called chemically active outflows. The bright bowshock B1 in the
southern outflow lobe is a privileged testbed of magneto-hydrodynamical (MHD)
shock models, for which dynamical and chemical processes are strongly
interdependent. We present the first results of the unbiased spectral survey of
the L1157-B1 bowshock, obtained in the framework of the key program "Chemical
Herschel Surveys of Star Forming Regions" (CHESS). The main aim is to trace the
warm and chemically enriched gas and to infer the excitation conditions in the
shock region. The CO 5-4 and H2O lines have been detected at high-spectral
resolution in the unbiased spectral survey of the HIFI-Band 1b spectral window
(555-636 GHz), presented by Codella et al. in this volume. Complementary
ground-based observations in the submm window help establish the origin of the
emission detected in the main-beam of HIFI, and the physical conditions in the
shock.}{Both lines exhibit broad wings, which extend to velocities much higher
than reported up to now. We find that the molecular emission arises from two
regions with distinct physical conditions: an extended, warm (100K), dense (3e5
cm-3) component at low-velocity, which dominates the water line flux in Band~1;
a secondary component in a small region of B1 (a few arcsec) associated with
high-velocity, hot (> 400 K) gas of moderate density ((1.0-3.0)e4 cm-3), which
appears to dominate the flux of the water line at 179mu observed with PACS. The
water abundance is enhanced by two orders of magnitude between the low- and the
high-velocity component, from 8e-7 up to 8e-5. The properties of the
high-velocity component agree well with the predictions of steady-state C-shock
models.Comment: Accepted for Publication in Astronomy and Astrophysics (Herschel
Special Issue
Crime among irregular immigrants and the influence of internal border control
Both the number of crime suspects without legal status and the number of irregular or undocumented immigrants held in detention facilities increased substantially in theNetherlands between 1997 and 2003. In this period, theDutch state increasingly attempted to exclude irregular immigrants from the formal labour market and public provisions. At the same time the registered crime among irregular migrants rose. The 'marginalisation thesis' asserts that a larger number of migrants have become involved in crime in response to a decrease in conventional life chances. Using police and administrative data, the present study takes four alternative interpretations into consideration based on: 1) reclassification of immigrant statuses by the state and redefinition of the law, 2) criminal migration and crossborder crime, 3) changes in policing, and 4) demographic changes. A combination of factors is found to have caused the rise in crime, but the marginalisation thesis still accounts for at least 28%. These findings accentuate the need for a more thorough discussion on the intended and unintended consequences of border control for immigrant crime
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