Helicobacter pylori is consistently reported with high prevalence in HIV-negative patients with chronic gastritis and active ulcer disease. This study is an evaluation of the prevalence of H. pylori ...in AIDS patients, and the association with chronic gastritis, erosions, and ulcer disease. Seventy-three AIDS patients referred for the evaluation of gastrointestinal symptoms underwent upper endoscopy and antral gastric biopsy. Histologic gastritis was diagnosed and degree of activity graded on hematoxylin-eosin stain. H. pylori organisms were identified by acridine orange stain. A single pathologist evaluated the biopsy specimens. H. pylori was found in 15% (11 of 73) of AIDS patients. Histologic chronic active gastritis was evident in 94.5% (69 of 73) of the study group. H. pylori was identified in 15.9% (11 of 69) of biopsy specimens with histologic chronic active gastritis. The organism was more common in biopsy specimens with a higher grade of activity in the chronic gastritis. Endoscopic erosions or ulcers were noted in 11 patients (seven gastric, four duodenal). H. pylori was present in 18% (2 of 11) of AIDS patients with erosions or ulcers. The prevalence of H. pylori in AIDS patients with histologic chronic active gastritis is much lower than the prevalence previously reported for HIV-negative patients with similar pathology. The low prevalence observed does not implicate H. pylori as the causal agent in most chronic active gastritis in the AIDS population. Impaired acid secretion may reduce colonization of gastric mucosa and explain the low rate of H. pylori observed.
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•Inter-laboratory quantitative PCR results of effluent-derived ARGs were compared.•The inter-laboratory gene quantification varied from 3% to 28%.•The 16S rRNA gene was the most ...abundant, followed by intI1, sul1, qnrS and blaTEM.•The genes blaCTXM-32 and vanA were below the limit of quantification.•Inter-laboratory calibrations increase ARGs quantification reliability.
Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are widely distributed in the environment where they represent potential public health threats. Quantitative PCR (qPCR) is a suitable approach to detect and quantify ARGs in environmental samples. However, the comparison of gene quantification data between different laboratories is challenging since the data are predominantly obtained under non-harmonized conditions, using different qPCR protocols. This study aimed at carrying out an inter-laboratory calibration in order to assess the variability inherent to the qPCR procedures for quantification of ARGs. With this aim, samples of treated wastewater collected in three different countries were analysed based on common DNA extract pools and identical protocols as well as distinct equipment, reagents batches, and operators. The genes analysed were the 16S rRNA, vanA, blaTEM, qnrS, sul1, blaCTXM-32 and intI1 and the artificial pNORM1 plasmid containing fragments from the seven targeted genes was used as a reference. The 16S rRNA gene was the most abundant, in all the analysed samples, followed by intI1, sul1, qnrS, and blaTEM, while blaCTXM-32 and vanA were below the limit of quantification in most or all the samples. For the genes 16S rRNA, sul1, intI1, blaTEM and qnrS the inter-laboratory variation was below 28% (3–8%, 6–18%, 8–21%, 10–24%, 15–28%, respectively). While it may be difficult to fully harmonize qPCR protocols due to equipment, reagents and operator variations, the inter-laboratory calibration is an adequate and necessary step to increase the reliability of comparative data on ARGs abundance in different environmental compartments and/or geographic regions.
The VIMOS VLT deep survey Paltani, S.; Le Fèvre, O.; Ilbert, O. ...
Astronomy and astrophysics (Berlin),
03/2007, Letnik:
463, Številka:
3
Journal Article
Recenzirano
Aims. We study the luminosity function of the high-redshift galaxy population with redshifts 3\le z \le 4 using a purely I-band magnitude- selected spectroscopic sample obtained in the framework of ...the VIMOS VLT Deep Survey (VVDS). Methods. We determine the luminosity function from the VVDS, taking care to add as few assumptions and as simple corrections as possible, and compare our results with those obtained from photometric studies, based on Lyman-break selections or photometric-redshift measurements. Results. We find that in the redshift range 3\le z \le 4, the VVDS luminosity function is parameterized by \phi angle =1.24_\times10 mag super(-1) Mpc super(-3) and M super(*) =-21.49 super(+0.19) sub(-0.19), assuming a slope \alpha=-1.4 consistent with most previous studies. While \phi angle is comparable to previously found values, M super(*) is significantly brighter by about 0.5 mag at least. Using the conservative slope \alpha=-1.4, we find a luminosity density at 1700 Aa {\cal L}_(M<-18.5) =2.4\times10 W Mpc super(-3) and {\cal L}_{\mathrm{Total}}=3.1\times10 W Mpc super(-3), comparable to that estimated in other studies. Conclusions. The unexpectedly large number of very bright galaxies found in the VVDS indicates that the color-selection and photometric-redshift techniques that are generally used to build high- redshift galaxy samples may be affected by a significant fraction of color- measurement failures or by incomplete modelling of the mix of stellar emission, AGN contribution, dust absorption and intergalactic extinction assumed to identify high-redshift galaxies, making pure magnitude selection better able to trace the full population. Because of the difficulty to identify all low-luminosity galaxies in a spectroscopic survey, the luminosity density could still be significantly underestimated. We also find that the relative contribution of the most luminous galaxies compared to the fainter ones is at least twice as large in the VVDS compared to former estimates. Therefore, the VVDS paints a quite different picture of the role of the most actively star-forming galaxies in the history of star formation.
Renewable energy penetration is increasing in last years, covering a more and more important role in both electrical and thermal supply. Nowadays, the photovoltaic conversion is a consolidated ...technology and can be efficiently combined with solar concentration. In this study, a new concept of photovoltaic solar concentrator based on non-conventional mirrors coupled with high efficiency triple-junctions cells is described and discussed. More in details, as for the optical design, deformations are applied to classical spherical mirrors to control solar aberrations and boost efficiency of a receiver consisting in a dense array of cells. The efficiency enhance is obtained by high matching between the collected solar irradiance and the receiver electrical features. The concentrator is able to produce both electrical and thermal energy: the system requires in fact an active cooling circuit to maintain the cells performance. This behavior makes the system suitable for combined heat and power applications with particular reference to high direct irradiance environments. An analytical study, considering a residential utility has been performed in order to understand the energetic and economic performance of the system. In particular, a simulation has been carried out by the use of an in-house-developed calculation code considering a whole year of operation.
The prevalence of Helicobacter pylori (HP) has previously been reported to be lower in AIDS patients. This study evaluated the prevalence of HP and peptic ulcer disease in relation to absolute CD4 ...counts in HIV-seropositive patients with GI symptoms.
Seventy-two patients (48 HIV-positive and 24 HIV-negative) with GI symptoms were evaluated with upper endoscopy and antral gastric biopsy. Samples were prepared with Giemsa stain and reviewed by a single pathologist to determine status of HP infection. The patients were stratified on the basis of HIV status and CD4 count: group A, HIV-positive patients with a CD4 count greater than 200, group B, HIV-positive patients with CD4 counts less than 200, and group C, an HIV-negative control group.
The prevalence of HP infection in the three groups was as follows: group A 69% (11/16), group B 13% (4/32), and group C 63% (15/24). Peptic ulcer prevalence in group A was 19% (3/16), group B 3% (1/32), and group C 25% (6/24).
The prevalence of HP in HIV-positive patients with a CD4 count less than 200 is significantly lower (p < 0.001) than that found in HIV-negative patients. The number of peptic ulcers in the HIV-positive group with CD4 < 200 was significantly less (p = 0.035) than that of the HIV-negative patients. These results suggest a role of CD4 cell and immune function in sustaining HP infection and HP-related peptic ulcer disease.
The VIMOS VLT Deep Survey Vergani, D.; Scodeggio, M.; Pozzetti, L. ...
Astronomy and astrophysics (Berlin),
08/2008, Letnik:
487, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Aims. Our aim is to investigate the history of mass assembly for galaxies of different stellar masses and types. Methods. We selected a mass-limited sample of 4048 objects from the VIMOS VLT Deep ...Survey (VVDS) in the redshift interval $0.5 \le z \le 1.3$. We then used an empirical criterion, based on the amplitude of the 4000 ÅBalmer break (Dn4000), to separate the galaxy population into spectroscopically early- and late-type systems. The equivalent width of the OII3727 line is used as proxy for the star formation activity. We also derived a type-dependent stellar mass function in three redshift bins. Results. We discuss to what extent stellar mass drives galaxy evolution, showing for the first time the interplay between stellar ages and stellar masses over the past 8 Gyr. Low-mass galaxies have small Dn4000 and at increasing stellar mass, the galaxy distribution moves to higher Dn4000 values as observed in the local Universe. As cosmic time goes by, we witness an increasing abundance of massive spectroscopically early-type systems at the expense of the late-type systems. This spectral transformation of late-type systems into old massive galaxies at lower redshift is a process started at early epochs (z > 1.3) and continuing efficiently down to the local Universe. This is also confirmed by the evolution of our type-dependent stellar mass function. The underlying stellar ages of late-type galaxies apparently do not show evolution, most likely as a result of a continuous and efficient formation of new stars. All star formation activity indicators consistently point towards a star formation history peaked in the past for massive galaxies, with little or no residual star formation taking place in the most recent epochs. In contrast, most of the low-mass systems show just the opposite characteristics, with significant star formation present at all epochs. The activity and efficiency of forming stars are mechanisms that depend on galaxy stellar mass, and the stellar mass assembly becomes progressively less efficient in massive systems as time elapses. The concepts of star formation downsizing and mass assembly downsizing describe a single scenario that has a top-down evolutionary pattern in how the star formation is quenched, as well as how the stellar mass is grown. The role of (dry) merging events seems to be only marginal at z < 1.3, as our estimated efficiency in stellar mass assembly can possibly account for the progressive accumulation of observed passively evolving galaxies.
The VIMOS VLT Deep Survey (VVDS), designed to measure 150,000 galaxy redshifts, requires a dedicated data reduction and analysis pipeline to process in a timely fashion the large amount of ...spectroscopic data being produced. This requirement has lead to the development of the VIMOS Interactive Pipeline and Graphical Interface (VIPGI), a new software package designed to simplify to a very high degree the task of reducing astronomical data obtained with VIMOS (Visible Multi–Object Spectrograph), the imaging spectrograph built by the VIRMOS Consortium for the European Southern Observatory and mounted on Unit 3 (Melipal) of the VLT (Very Large Telescope) at Paranal Observatory (Chile). VIPGI provides the astronomer with specially designed VIMOS data‐reduction functions, a VIMOS‐centric data organizer, and dedicated data browsing and plotting tools, which can be used to verify the quality and accuracy of the various stages of the data‐reduction process. The quality and accuracy of the data‐reduction pipeline are comparable to those obtained using well‐known IRAF tasks, but the speed of the data‐reduction process is significantly increased, because of the dedicated nature of VIPGI. In this paper we discuss the details of the multiobject spectroscopy (MOS) data‐reduction pipeline that has been implemented in VIPGI, as applied to the reduction of some 20,000 VVDS spectra, quantitatively assessing the accuracy of the various reduction steps. We also provide a more general overview of VIPGI capabilities, a tool that can be used for the reduction of any kind of VIMOS data.
In this paper we present the optical and near-infrared identifications of the 1054 radio sources detected in the 20 cm deep radio survey down to a 5sigma flux limit of ~80 muJy obtained with the VLA ...in the VIMOS VLT Deep Survey VVDS-02h deep field. Using U,B,V,R,I and K data, with limiting magnitudes of UAB~25.4, BAB~26.5, VAB~26.2, RAB~25.9 IAB~25.0, JAB~24.2, KAB~23.9 (50% completeness) we identified 718 radio sources (~74% of the whole sample). The photometric redshift analysis shows that, in each magnitude bin, the radio sample has a higher median photometric redshift than the whole optical sample, while the median (V-I)AB color of the radio sources is redder than the median color of the whole optical sample. These results suggest that radio detection is preferentially selecting galaxies with higher intrinsic optical luminosity. From the analysis of the optical properties of the radio sources as function of the radio flux, we found that while about 35% of the radio sources are optically unidentified in the higher radio flux bin (S> 1.0 mJy), the percentage of unidentified sources decreases to about 25% in the faintest bins (S< 0.5 mJy). The median IAB magnitude for the total sample of radio sources, i.e. including also the unidentified ones, is brighter in the faintest radio bins than in the bin with higher radio flux. This suggests that most of the faintest radio sources are likely to be associated to relatively lower radio luminosity objects at relatively modest redshift, rather than radio-powerful, AGN type objects at high redshift. Using a classification in early-type and late-type galaxies based on the (B-I)AB color and the photometric redshift, we found that the majority of the radio sources below ~0.15 mJy are indeed late-type star forming galaxies. Finally, the radio sources without optical counterpart in our deep imaging have a median radio flux of 0.15 mJy, equal to that of identified sources. Given the very faint optical limits, these unidentified radio sources probably contain a significant fraction of obscured and/or high redshift galaxies.
Aims. Our aim is to investigate the history of mass assembly for galaxies of different stellar masses and types. Methods. We selected a mass-limited sample of 4048 objects from the VIMOS VLT Deep ...Survey (VVDS) in the redshift interval 0.5 le z le 1.3. We then used an empirical criterion, based on the amplitude of the 4000 AaBalmer break (D_{\rm n}4000), to separate the galaxy population into spectroscopically early- and late-type systems. The equivalent width of the OII3727 line is used as proxy for the star formation activity. We also derived a type-dependent stellar mass function in three redshift bins. Results. We discuss to what extent stellar mass drives galaxy evolution, showing for the first time the interplay between stellar ages and stellar masses over the past 8 Gyr. Low-mass galaxies have small D_{\rm n}4000 and at increasing stellar mass, the galaxy distribution moves to higher D_{\rm n}4000 values as observed in the local Universe. As cosmic time goes by, we witness an increasing abundance of massive spectroscopically early-type systems at the expense of the late-type systems. This spectral transformation of late-type systems into old massive galaxies at lower redshift is a process started at early epochs (z > 1.3) and continuing efficiently down to the local Universe. This is also confirmed by the evolution of our type-dependent stellar mass function. The underlying stellar ages of late-type galaxies apparently do not show evolution, most likely as a result of a continuous and efficient formation of new stars. All star formation activity indicators consistently point towards a star formation history peaked in the past for massive galaxies, with little or no residual star formation taking place in the most recent epochs. In contrast, most of the low-mass systems show just the opposite characteristics, with significant star formation present at all epochs. The activity and efficiency of forming stars are mechanisms that depend on galaxy stellar mass, and the stellar mass assembly becomes progressively less efficient in massive systems as time elapses. The concepts of star formation downsizing and mass assembly downsizing describe a single scenario that has a top-down evolutionary pattern in how the star formation is quenched, as well as how the stellar mass is grown. The role of (dry) merging events seems to be only marginal at z < 1.3, as our estimated efficiency in stellar mass assembly can possibly account for the progressive accumulation of observed passively evolving galaxies.
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