1,277 research outputs found
The Blood Neutrophil Count After 1 Month of Treatment Predicts the Radiologic Severity of Lung Disease at Treatment End
BACKGROUND: Post-tuberculous lung disease confers significant morbidity. However, the determinants of persistent lung damage in tuberculosis are not well established. We investigated associations between tuberculosis-associated radiological changes and socio-demographic factors, surrogates of bacillary burden and blood inflammatory markers at initiation of therapy and after 1 month. RESEARCH QUESTION: What are the predictors of radiological severity at the end of tuberculosis treatment for tuberculosis? STUDY DESIGN AND METHODS: We collected data from patients treated for drug sensitive pulmonary tuberculosis at our centre over a 5.5-year period. We recorded age, sex, ethnicity, smoking status, symptom duration, sputum smear grade, time to culture positivity and blood results (C-reactive protein and neutrophil count) at baseline and after 1 month of treatment. Chest x-rays performed at baseline, 2 months and end of treatment were assessed independently by two radiologists and scored using a validated system. Relationships between predictor variables and radiological outcomes were assessed using linear or binary logistic regression. RESULTS: We assessed 154 individuals, mean age 37 years, 63% male. In multivariate analysis, baseline radiological severity correlated with sputum smear grade (p=0.003) and neutrophil count (p<0.001). At end of treatment, only the 1-month neutrophil count was significantly associated with overall radiological severity in multivariate analysis (r=0.34, p=0.003), and remained significant after controlling for baseline radiological scores. The 1-month neutrophil count was also the only independent correlate of volume loss and pleural thickening at end of treatment and was significantly higher in patients with persistent cavitation or effusion versus those without. INTERPRETATION: Persistent neutrophilic inflammation after 1 month of tuberculosis therapy is associated with poor radiological outcome, suggesting a target for interventions to minimise post-tuberculous lung disease
Evolution of the Cluster X-ray Luminosity Function
We report measurements of the cluster X-ray luminosity function out to z=0.8
based on the final sample of 201 galaxy systems from the 160 Square Degree
ROSAT Cluster Survey. There is little evidence for any measurable change in
cluster abundance out to z~0.6 at luminosities less than a few times 10^44
ergs/s (0.5-2.0 keV). However, between 0.6 < z < 0.8 and at luminosities above
10^44 ergs/s, the observed volume densities are significantly lower than those
of the present-day population. We quantify this cluster deficit using
integrated number counts and a maximum-likelihood analysis of the observed
luminosity-redshift distribution fit with a model luminosity function. The
negative evolution signal is >3 sigma regardless of the adopted local
luminosity function or cosmological framework. Our results and those from
several other surveys independently confirm the presence of evolution. Whereas
the bulk of the cluster population does not evolve, the most luminous and
presumably most massive structures evolve appreciably between z=0.8 and the
present. Interpreted in the context of hierarchical structure formation, we are
probing sufficiently large mass aggregations at sufficiently early times in
cosmological history where the Universe has yet to assemble these clusters to
present-day volume densities.Comment: 15 pages, 10 figures, accepted for publication in Ap
Chandra Discovery of a 300 kpc X-ray Jet in the GPS Quasar PKS1127-145
We have discovered an X-ray jet with Chandra imaging of the z=1.187
radio-loud quasar PKS1127-145. In this paper we present the Chandra X-ray data,
follow-up VLA observations, and optical imaging using the HST WFPC2. The X-ray
jet contains 273+/-5 net counts in 27ksec and extends ~30 arcsec, from the
quasar core, corresponding to a minimum projected linear size of ~330/h_50 kpc.
The evaluation of the X-ray emission processes is complicated by the observed
offsets between X-ray and radio brightness peaks. We discuss the problems posed
by these observations to jet models. In addition, PKS1127-145 is a Giga-Hertz
Peaked Spectrum radio source, a member of the class of radio sources suspected
to be young or ``frustrated'' versions of FRI radio galaxies. However the
discovery of an X-ray and radio jet extending well outside the host galaxy of
PKS1127-145 suggests that activity in this and other GPS sources may be
long-lived and complex.Comment: 22 pages, 11 ps figures, 1 figure in a JPG file, 3 tables. AASTEX.
Accepted by The Astrophysical Journa
GTI-space : the space of generalized topological indices
A new extension of the generalized topological indices (GTI) approach is carried out torepresent 'simple' and 'composite' topological indices (TIs) in an unified way. Thisapproach defines a GTI-space from which both simple and composite TIs represent particular subspaces. Accordingly, simple TIs such as Wiener, Balaban, Zagreb, Harary and Randićconnectivity indices are expressed by means of the same GTI representation introduced for composite TIs such as hyper-Wiener, molecular topological index (MTI), Gutman index andreverse MTI. Using GTI-space approach we easily identify mathematical relations between some composite and simple indices, such as the relationship between hyper-Wiener and Wiener index and the relation between MTI and first Zagreb index. The relation of the GTI space with the sub-structural cluster expansion of property/activity is also analysed and some routes for the applications of this approach to QSPR/QSAR are also given
The warm absorber in NGC 5548: The lean years
We study the variability of the warm absorber and the gas responsible for the
emission lines in the Seyfert 1 galaxy NGC 5548, in order to constrain the
location and physical properties of these components. Using X-ray spectra taken
with the \textit{Chandra}LETGS in 2002 and 2005, we study variability in the
ionic column densities and line intensities. We find a lower \ion{O}{vii}
forbidden emission line flux in 2005, while the Fe K line flux stays
constant. The warm absorber is less ionized in 2005, allowing us to constrain
its location to within 7 pc of the central source. Using both the observed
variability and the limit on the FWHM of the \ion{O}{vii} f line, we have
constrained the location of the narrow line region to a distance of 1 pc from
the central source. The apparent lack of variability of the Fe K line
flux does not allow for a unique explanation.Comment: 6 pages, 6 figures, accepted by A&
Constraining dark energy with Sunyaev-Zel'dovich cluster surveys
We discuss the prospects of constraining the properties of a dark energy
component, with particular reference to a time varying equation of state, using
future cluster surveys selected by their Sunyaev-Zel'dovich effect. We compute
the number of clusters expected for a given set of cosmological parameters and
propogate the errors expected from a variety of surveys. In the short term they
will constrain dark energy in conjunction with future observations of type Ia
supernovae, but may in time do so in their own right.Comment: 5 pages, 3 figures, 1 table, version accepted for publication in PR
Cortical tau is associated with microstructural imaging biomarkers of neurite density and dendritic complexity in Alzheimer's disease
INTRODUCTION: In Alzheimer's disease (AD), hyperphosphorylated tau is closely associated with focal neurodegeneration, but the mechanism remains uncertain. METHODS: We quantified cortical microstructure using neurite orientation dispersion and density imaging in 14 individuals with young onset AD. Diffusion tensor imaging measured mean diffusivity (MD). Amyloid beta and tau positron emission tomography were acquired and associations with microstructural measures were assessed. RESULTS: When regional volume was adjusted for, in the medial temporal lobe there was a significant negative association between neurite density and tau (partial R2  = 0.56, p = 0.008) and between orientation dispersion and tau (partial R2  = 0.66, p = 0.002), but not between MD and tau. In a wider cortical composite, there was an association between orientation dispersion and tau (partial R2  = 0.43, p = 0.030), but not between other measures and tau. DISCUSSION: Our findings are consistent with tau causing first dendritic pruning (reducing dispersion/complexity) followed by neuronal loss. Advanced magnetic resonance imaging (MRI) microstructural measures have the potential to provide information relating to underlying tau deposition
Geographically touring the eastern bloc: British geography, travel cultures and the Cold War
This paper considers the role of travel in the generation of geographical knowledge of the eastern bloc by British geographers. Based on oral history and surveys of published work, the paper examines the roles of three kinds of travel experience: individual private travels, tours via state tourist agencies, and tours by academic delegations. Examples are drawn from across the eastern bloc, including the USSR, Poland, Romania, East Germany and Albania. The relationship between travel and publication is addressed, notably within textbooks, and in the Geographical Magazine. The study argues for the extension of accounts of cultures of geographical travel, and seeks to supplement the existing historiography of Cold War geography
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