134 research outputs found
AGN feedback works both ways
Simulations of galaxy growth need to invoke strong negative feedback from
active galactic nuclei (AGN) to suppress the formation of stars and thus
prevent the over-production of very massive systems. While some observations
provide evidence for such negative feedback, other studies find either no
feedback, or even positive feedback, with increased star formation associated
with higher AGN luminosities. Here we report an analysis of several hundred AGN
and their host galaxies in the Chandra Deep Field South using X-ray and radio
data for sample selection. Combined with archival far infrared data as a
reliable tracer of star formation activity in the AGN host galaxies, we find
that AGN with pronounced radio jets exhibit a much higher star formation rate
than the purely X-ray selected ones, even at the same X-ray luminosities. This
difference implies that positive AGN feedback plays an important role, too, and
therefore has to be accounted for in all future simulation work. We interpret
this to indicate that the enhanced star formation rate of radio selected AGN
arises because of jet-induced star formation, as is hinted by the different jet
powers among our AGN samples, while the suppressed star formation rate of X-ray
selected AGN is caused by heating and photo-dissociation of molecular gas by
the hot AGN accretion disc.Comment: 21 pages, 9 figures, 3 tables, accepted for publication by Ap
The kinematics of the diffuse ionized gas in NGC 4666
The global properties of the interstellar medium with processes such as
infall and outflow of gas and a large scale circulation of matter and its
consequences for star formation and chemical enrichment are important for the
understanding of galaxy evolution. In this paper we studied the kinematics and
morphology of the diffuse ionized gas (DIG) in the disk and in the halo of the
star forming spiral galaxy NGC 4666 to derive information about its kinematical
properties. Especially, we searched for infalling and outflowing ionized gas.
We determined surface brightness, radial velocity, and velocity dispersion of
the warm ionized gas via high spectral resolution (R ~ 9000) Fabry-P\'erot
interferometry. This allows the determination of the global velocity field and
the detection of local deviations from this verlocity field. We calculated
models of the DIG distribution and its kinematics for comparison with the
measured data. In this way we determined fundamental parameters such as the
inclination and the scale height of NGC 4666, and established the need for an
additional gas component to fit our observed data. We found individual areas,
especially along the minor axis, with gas components reaching into the halo
which we interpret as an outflowing component of the diffuse ionized gas. As
the main result of our study, we were able to determine that the vertical
structure of the DIG distribution in NGC 4666 is best modeled with two
components of ionized gas, a thick and a thin disk with 0.8 kpc and 0.2 kpc
scale height, respectively. Therefore, the enhanced star formation in NGC 4666
drives an outflow and also maintains a thick ionized gas layer reminiscent of
the Reynold's layer in the Milky Way.Comment: 12 pages, 10 figures, 3 table
Reflux Revisited: Advancing the Role of Pepsin
Gastroesophageal reflux disease is mediated principally by acid. Today, we recognise reflux reaches beyond the esophagus, where pepsin, not acid, causes damage. Extraesophageal reflux occurs both as liquid and probably aerosol, the latter with a further reach. Pepsin is stable up to pH 7 and regains activity after reacidification. The enzyme adheres to laryngeal cells, depletes its defences, and causes further damage internally after its endocytosis. Extraesophageal reflux can today be detected by recognising pharyngeal acidification using a miniaturised pH probe and by the identification of pepsin in saliva and in exhaled breath condensate by a rapid, sensitive, and specific immunoassay. Proton pump inhibitors do not help the majority with extraesophageal reflux but specifically formulated alginates, which sieve pepsin, give benefit. These new insights may lead to the development of novel drugs that dramatically reduce pepsinogen secretion, block the effects of adherent pepsin, and give corresponding clinical benefit
The effect of dietary intake, physical activity and posture on pepsin concentrations detected in the saliva of free-living, healthy individuals
Introduction: Diet and lifestyle are believed to be major causes of gastric reflux. The occurrence of reflux is associated with a number of respiratory, oesophageal and airways conditions. Previous studies have used oesophageal monitoring to assess the occurrence of reflux events. Such measurements may only measure "bulk" rather than "microreflux" events. Such technology is also likely to impact on both habitual dietary intake and physical activity due to the nature of the assessment. Aim: To assess the impact of meal intake and physical activity on pepsin concentrations in saliva collected from free-living individuals throughout the day. Methods: Fifty-one participants (aged 18+, non-smokers with no current chronic or acute respiratory conditions, bloodborne diseases, or diagnosis of reflux disease) provided saliva samples before (< 30 min) and after (< 1 h) meals and physical activity bouts or before and after sleep. Dietary intake and physical activity were monitored by diary over this time. Dietary intake was analyzed using Windiets® software, while physical activity output was calculated from pre-existing tables of energy expenditure. Saliva samples were analyzed for pepsin content using a previously described ELISA methodology. Wilcoxon matched pairs rank sign tests were performed on before- and after-meal/physical activity/sleep samples. Results: Fifty-seven paired pre-and post-meal,48 paired pre- and post-physical activity samples and 168 pre- and post-sleep samples were analyzed. Mean(standard deviation) pepsin concentrations in saliva were significantly higher (P=0.037) in the pre-meal samples (44.2(42.2)) than the post-meal samples (32.8(29.6)). Post-sleep pepsin concentrations (196.4(323.4)) were significantly higher (P< 0.001) than pre-sleep (102.3(152.8)). There was no significant difference (P=0.491) between pre-(45.2(56.8)) and post-(40.8(38.6)) physical activity saliva samples. Conclusions: Analysis of pepsin in saliva is a useful method to assess the impact of lifestyle on reflux event occurrence. Increased preprandial salivary pepsin concentrations may be due to microreflux events driven by the cephalic phase of digestion
Detecting Quasars in Large-Scale Astronomical Surveys
We present a classification-based approach to identify quasi-stellar radio
sources (quasars) in the Sloan Digital Sky Survey and evaluate its performance
on a manually labeled training set. While reasonable results can already be
obtained via approaches working only on photometric data, our experiments
indicate that simple but problem-specific features extracted from spectroscopic
data can significantly improve the classification performance. Since our
approach works orthogonal to existing classification schemes used for building
the spectroscopic catalogs, our classification results are well suited for a
mutual assessment of the approaches' accuracies.Comment: 6 pages, 8 figures, published in proceedings of 2010 Ninth
International Conference on Machine Learning and Applications (ICMLA) of the
IEE
Gastroesophageal reflux and idiopathic pulmonary fibrosis: A prospective study
Background and Objective: Idiopathic pulmonary fibrosis (IPF) is the most common of the idiopathic interstitial pneumonias. There is evidence of the increased prevalence of gastroesophageal reflux disease in patients with IPF. The aim of this prospective study was to evaluate reflux in patients with IPF by analyzing the scores of the reflux cough questionnaire, measurement of pepsin in exhaled breath condensate (EBC) to detect extraesophageal reflux, and Helicobacter pylori serology to evaluate the prevalence of this stomach bacterium in patients with IPF. Material and Methods: The Hull airway reflux questionnaire (HARQ) was completed by 40 patients with IPF and 50 controls in order to evaluate reflux symptoms. EBC was collected from 23 patients (17 patients with IPF and 6 controls) for measurement of pepsin by the lateral flow technique. A prospective study of 57 subjects (34 patients with IPF and 23 controls) for H. pylori antibody detection by ELISA was performed. Results: Significantly higher HARQ scores (maximum score, 70) were recorded in patients with IPF compared with controls (19.6 [SD, 12.4] vs. 3 [SD, 2.9],
Evidence for a large off-centered galactic outflow and its connection to the extraplanar diffuse ionized gas in IC 1553
Aims. We analyze a MUSE optical integral field spectrum of the star-forming
edge-on galaxy IC 1553 in order to study its extraplanar diffuse ionized gas
(eDIG) and the processes shaping its disk-halo interface. Methods. We extracted
the optical emission line properties from the integral field spectrum and
generated the commonly used emission line diagnostic diagrams in order to
analyze the ionization conditions and the distribution of the eDIG.
Furthermore, we performed gravitational potential fitting to investigate the
kinematics of a suspected galactic outflow. Results. We find that the eDIG
scale height has a maximum value of approximately 1.0 kpc and decreases roughly
linearly with the radial distance from the galactic center in projection. The
ionization state of the eDIG is not consistent with a pure photoionization
scenario and instead requires a significant contribution from shock ionization.
This, in addition to the gas kinematics, strongly suggests the presence of a
galactic scale outflow, the origin of which lies at least 1.4 kpc away from the
galactic center. The inferred shock velocity in the eDIG of approximately 225
km s-1 is comparable to the escape velocity estimated from our potential
modelling. The asymmetric distribution of currently star-forming clusters
produces a range of different ionization conditions in the eDIG. As a result,
the vertical emission line profiles vary quantitatively and qualitatively along
the major axis of the galaxy. This analysis illustrates that it is crucial in
studies of the eDIG to use observations that take the spatial and kinematical
distributions into account, such as those done with integral field units, to
form an accurate picture of the relevant physical properties.Comment: Accepted for publication by Astronomy & Astrophysics on August 1,
202
Alginates: From the ocean to gastroesophageal reflux disease treatment
Reckitt Benckiser Turke
Alginate reduces the increased uptake of cholesterol and glucose in overweight male subjects: a pilot study
Dietary fibers are of particular interest in the prevention and management of obesity and consequent pathologies. Among the proposed mechanisms of action of fiber is the modulation of nutrient uptake from the small intestine. We have used a crossover study design in human subjects to monitor the uptake of glucose, cholesterol, and triacylglycerols in human subjects with normal and high body mass index. Our data demonstrate that uptakes of glucose, triacylglycerols, and cholesterol are all increased with increasing body fat. We demonstrate that treatment with a 1.5-g dose of a strong-gelling alginate may restore uptake of cholesterol and glucose to the levels of healthy subjects. These data indicate a potential therapeutic application of gelling fibers. (C) 2008 Published by Elsevier Inc
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