180 research outputs found
Antimicrobial resistance gene shuffling and a three-element mobilisation system in the monophasic Salmonella typhimurium strain ST1030
In this study we describe the genetic elements and the antimicrobial resistance units (RUs) harboured by the Salmonella Typhimurium monophasic variant 1,4,[5],12:i:- strain ST1030. Of the three identified RUs two were chromosomal, RU1 (IS26-blaTEM-1-IS26-strAB-sul2- IS26) and RU2 (IS26-tetR(B)-tetA(B)-ΔIS26), and one, RU3 (a sul3-associated class 1 integron with cassette array dfrA12-orfF-aadA2-cmlA1-aadA1), was embedded in a Tn21-derived element harboured by the conjugative I1 plasmid pST1030-1A. IS26 elements mediated the antimicrobial resistance gene (ARG) shuffling and this gave rise to pST1030-1A derivatives with different sets of ARGs. ST1030 also harboured two ColE1-like plasmids of which one, pST1030-2A, was mobilisable and the target of an intracellular translocation of the Tn21-derived element; the second (pST1030-3) was an orphan mob-associated oriT plasmid co-transferred with pST1030-1A and pST1030-2A. pST1030-2A and pST1030-3 also carried a parA gene and a type III restriction modification system, respectively. Overall analysis of our data reinforces the role played by IS26, Tn21-derived elements and non-conjugative plasmids in the spread of ARGs and supplies the first evidence, at least in Salmonella, for the identification of a natural isolate harbouring a three-element mobilisation system in the same cell
Optimization of cw sodium laser guide star efficiency
Context: Sodium laser guide stars (LGS) are about to enter a new range of
laser powers. Previous theoretical and numerical methods are inadequate for
accurate computations of the return flux and hence for the design of the
next-generation LGS systems.
Aims: We numerically optimize the cw (continuous wave) laser format, in
particular the light polarization and spectrum.
Methods: Using Bloch equations, we simulate the mesospheric sodium atoms,
including Doppler broadening, saturation, collisional relaxation, Larmor
precession, and recoil, taking into account all 24 sodium hyperfine states and
on the order of 100 velocity groups.
Results: LGS return flux is limited by "three evils": Larmor precession due
to the geomagnetic field, atomic recoil due to radiation pressure, and
transition saturation. We study their impacts and show that the return flux can
be boosted by repumping (simultaneous excitation of the sodium D2a and D2b
lines with 10-20% of the laser power in the latter).
Conclusions: We strongly recommend the use of circularly polarized lasers and
repumping. As a rule of thumb, the bandwidth of laser radiation in MHz (at each
line) should approximately equal the launched laser power in Watts divided by
six, assuming a diffraction-limited spot size.Comment: 15 pages, 12 figures, to be published in Astronomy & Astrophysics,
AA/2009/1310
From rings to bulges: evidence for rapid secular galaxy evolution at z~2 from integral field spectroscopy in the SINS survey
We present Ha integral field spectroscopy of well resolved, UV/optically
selected z~2 star-forming galaxies as part of the SINS survey with SINFONI on
the ESO VLT. Our laser guide star adaptive optics and good seeing data show the
presence of turbulent rotating star forming rings/disks, plus central
bulge/inner disk components, whose mass fractions relative to total dynamical
mass appears to scale with [NII]/Ha flux ratio and star formation age. We
propose that the buildup of the central disks and bulges of massive galaxies at
z~2 can be driven by the early secular evolution of gas-rich proto-disks. High
redshift disks exhibit large random motions. This turbulence may in part be
stirred up by the release of gravitational energy in the rapid cold accretion
flows along the filaments of the cosmic web. As a result dynamical friction and
viscous processes proceed on a time scale of <1 Gyr, at least an order of
magnitude faster than in z~0 disk galaxies. Early secular evolution thus drives
gas and stars into the central regions and can build up exponential disks and
massive bulges, even without major mergers. Secular evolution along with
increased efficiency of star formation at high surface densities may also help
to account for the short time scales of the stellar buildup observed in massive
galaxies at z~2.Comment: accepted Astrophysical Journal, main July 8 200
Microbiological and chemical assessment of wastewater discharged by infiltration trenches in fractured and karstified limestone (Sca.re.s. project 2019–2020)
This study investigated the environmental contamination of groundwater as a consequence of the discharge of treated wastewater into the soil. The investigation focused on a wastewater treatment plant located in an area fractured by karst in the Salento peninsula (Apulia, Italy). Water samples were collected at four sites (raw wastewater, treated wastewater, infiltration trench, and monitoring well), monthly from May to December 2019 (with the exception of August), and were tested for (1) panel of bacteria; (2) enteric viruses; and (3) chemical substances. A gradual reduction in the concentration of bacteria, viruses and contaminants of emerging concern was observed across the profile of soil fissured by karst. All monitored bacteria were absent from the monitoring well, except for Pseudomonas aeruginosa. Pepper mild mottle virus and adenovirus were detected at all sampling sites. Personal care products and X-ray contrast media showed the greatest decrease in concentration from infiltration trench to the monitoring well, while the highest residual concentrations in the monitoring well were found for anticonvulsants (78.5%), antimicrobials (41.3%), and antipsychotic drugs (38.6%). Our results show that parameters provided by current law may not always be sufficient to evaluate the sanitary risk relating to the discharge of treated wastewater to the soil
Evidence for Warped Disks of Young Stars in the Galactic Center
The central parsec around the super-massive black hole in the Galactic Center
hosts more than 100 young and massive stars. Outside the central cusp (R~1")
the majority of these O and Wolf-Rayet (WR) stars reside in a main clockwise
system, plus a second, less prominent disk or streamer system at large angles
with respect to the main system. Here we present the results from new
observations of the Galactic Center with the AO-assisted near-infrared imager
NACO and the integral field spectrograph SINFONI on the ESO/VLT. These include
the detection of 27 new reliably measured WR/O stars in the central 12" and
improved measurements of 63 previously detected stars, with proper motion
uncertainties reduced by a factor of four compared to our earlier work. We
develop a detailed statistical analysis of their orbital properties and
orientations. Half of the WR/O stars are compatible with being members of a
clockwise rotating system. The rotation axis of this system shows a strong
transition as a function of the projected distance from SgrA*. The main
clockwise system either is either a strongly warped single disk with a
thickness of about 10 degrees, or consists of a series of streamers with
significant radial variation in their orbital planes. 11 out of 61 clockwise
moving stars have an angular separation of more than 30 degrees from the
clockwise system. The mean eccentricity of the clockwise system is 0.36+/-0.06.
The distribution of the counter-clockwise WR/O star is not isotropic at the 98%
confidence level. It is compatible with a coherent structure such as stellar
filaments, streams, small clusters or possibly a disk in a dissolving state.
The observed disk warp and the steep surface density distribution favor in situ
star formation in gaseous accretion disks as the origin of the young stars.Comment: ApJ in pres
Approaching an investigation of multi-dimensional inequality through the lenses of variety in models of capitalism
After a synthetic presentation of the state of poverty and inequality in the world and the contradictions incurred by economic theory in this field after decades of globalization and in the midst of a persisting global crisis, in paragraphs 2. and 3. we outline the rational for our theoretical analysis, underlining two main aspects. First of all, in paragraph 2. we recall the reasons which makes inequality a multidimensional phenomenon, while in paragraph 3. we explore the reasons why the models of capitalism theory is relevant for studying multidimensional inequality. These paragraphs emphasise that inequality is a multidimensional and cumulative phenomenon and it should not be conceived only as the result of the processes of personal and functional distribution of income and wealth, which even by themselves are intrinsically multidimensional. The basic idea is that institutions, the cobweb of relations among them and their interaction with the economic structure define the model of capitalism which characterises a specific country and this, in turn, affects the level and the dynamics of inequality. This approach is consistent with the sociological approach by Rehbein and Souza (2014), based on the analytical framework developed by Pierre Bourdieu. In paragraph 4. we outline the rational for our empirical analysis, applying the notion of institutional complementarity and examining the relationship between institutional complementarity, models of capitalism and inequality. Besides, refining Amable’s analysis (2003), we provide empirical evidence on the relationship between inequality in income distribution and models of capitalism. Additionally, basing on cluster analysis, we identify six different models of capitalism in a sample of OECD countries, provide preliminary evidence on the different level of inequality which characterises each model and suggest that no evidence supports of the idea that a single model of capitalism is taking shape in this sphere in EU. In paragraph 5. we give some hints about issues in search for a new interpretation capable to fasten together the process of increasing inequality, the notion of symbolic violence and the models of capitalism theory. In the last paragraph we focus on conclusions useful for carrying on our research agenda
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