4,451 research outputs found
Boundary regularity for manifold constrained p(x)-harmonic maps
We prove partial and full boundary regularity for manifold constrained (Formula presented.) -harmonic maps
Effects of the electron-phonon coupling near and within the insulating Mott phase
The role of the electron-phonon interaction in the Holstein-Hubbard model is
investigated in the metallic phase close to the Mott transition and in the
insulating Mott phase. The model is studied by means of a variational slave
boson technique. At half-filling, mean-field static quantities are in good
agreement with the results obtained by numerical techniques. By taking into
account gaussian fluctuations, an analytic expression of the spectral density
is derived in the Mott insulating phase showing that an increase of the
electron-phonon coupling leads to a sensitive reduction of the Mott gap through
a reduced effective repulsion. The relation of the results with recent
experimental observations in strongly correlated systems is discussed.Comment: 4 pages, 4 figure
Spin polarization of electrons with Rashba double-refraction
We demonstrate how the Rashba spin-orbit coupling in semiconductor
heterostructures can produce and control a spin-polarized current without
ferromagnetic leads. Key idea is to use spin-double refraction of an electronic
beam with a nonzero incidence angle. A region where the spin-orbit coupling is
present separates the source and the drain without spin-orbit coupling. We show
how the transmission and the beam spin-polarization critically depend on the
incidence angle. The transmission halves when the incidence angle is greater
than a limit angle and a significant spin-polarization appears. Increasing the
spin-orbit coupling one can obtain the modulation of the intensity and of the
spin-polarization of the output electronic current when the input current is
unpolarized. Our analysis shows the possibility to realize a spin-field-effect
transistor based on the propagation of only one mode with the region with
spin-orbit coupling. Where the original Datta and Das device [Appl.Phys.Lett.
{\bf 56}, 665 (1990)] use the spin-precession that originates from the
interference between two modes with orthogonal spin.Comment: 12 pages with 7 figure
Animal rennets as sources of dairy lactic acid bacteria
The microbial composition of artisan and industrial animal rennet pastes was studied by using both culture-dependent and -independent
approaches. Pyrosequencing targeting the 16S rRNA gene allowed to identify 361 operational taxonomic units
(OTUs) to the genus/species level. Among lactic acid bacteria (LAB), Streptococcus thermophilus and some lactobacilli, mainly
Lactobacillus crispatus and Lactobacillus reuteri, were the most abundant species, with differences among the samples. Twelve
groups of microorganisms were targeted by viable plate counts revealing a dominance of mesophilic cocci. All rennets were able
to acidify ultrahigh-temperature-processed (UHT) milk as shown by pH and total titratable acidity (TTA). Presumptive LAB
isolated at the highest dilutions of acidified milks were phenotypically characterized, grouped, differentiated at the strain level
by randomly amplified polymorphic DNA (RAPD)-PCR analysis, and subjected to 16S rRNA gene sequencing. Only 18 strains
were clearly identified at the species level, as Enterococcus casseliflavus, Enterococcus faecium, Enterococcus faecalis, Enterococcus
lactis, Lactobacillus delbrueckii, and Streptococcus thermophilus, while the other strains, all belonging to the genus Enterococcus,
could not be allotted into any previously described species. The phylogenetic analysis showed that these strains might
represent different unknown species. All strains were evaluated for their dairy technological performances. All isolates produced
diacetyl, and 10 of them produced a rapid pH drop in milk, but only 3 isolates were also autolytic. This work showed that animal
rennet pastes can be sources of LAB, mainly enterococci, that might contribute to the microbial diversity associated with dairy
productions
A 10-3 drift velocity monitoring chamber
The MEG-II experiment searches for the lepton flavor violating decay: mu in
electron and gamma. The reconstruction of the positron trajectory uses a
cylindrical drift chamber operated with a mixture of He and iC4H10 gas. It is
important to provide a stable performance of the detector in terms of its
electron transport parameters, avalanche multiplication, composition and purity
of the gas mixture. In order to have a continuous monitoring of the quality of
gas, we plan to install a small drift chamber, with a simple geometry that
allows to measure very precisely the electron drift velocity in a prompt way.
This monitoring chamber will be supplied with gas coming from the inlet and the
outlet of the detector to determine if gas contaminations originate inside the
main chamber or in the gas supply system. The chamber is a small box with
cathode walls, that define a highly uniform electric field inside two adjacent
drift cells. Along the axis separating the two drift cells, four staggered
sense wires alternated with five guard wires collect the drifting electrons.
The trigger is provided by two 90Sr weak calibration radioactive sources placed
on top of a two thin scintillator tiles telescope. The whole system is designed
to give a prompt response (within a minute) about drift velocity variations at
the 0.001 level
Joining participatory approach and spatially-based modelling tools for groundwater resource management.
Although a lot of science has been produced on Water Resource Management (WRM) in the Information and
Communication Technology (ICT) sector, WRM is still poorly addressed via scientific means. Some reasons for
this may be: the underrated importance given to this topic at political and decision-making level; the low-capacity
of the research environment to transfer results; and missing numerical modelling capacities at agencies and
governing authorities.
ICT may provide tools for water planning and management, as discussed within the ICT4WATER cluster initiative.
Among these, GIS-integrated numerical modeling is a robust method to represent hydrological systems and to
provide answers to problems of protection of groundwater resources. Because these tools require a high level
of knowledge pertaining to various disciplines, they are often disregarded as complex âtricky gamesâ providing
unrealistic results. This is a barrier to the uptake of technologies for water management.
To overcome this issue, the application of ICT tools has been combined with an innovative participatory approach,
and large capacity building activities, in the framework of the H2020 FREEWAT project (FREE and open source
software tools for WATer resource management; www.freewat.eu). The major result of the project consists in an
open source and public domain, QGIS-integrated modeling platform for promoting WRM.
FREEWAT capabilities have been demonstrated at 14 case studies in EU and non-EU Countries, where the
effectiveness of few measures foreseen in River Basin Management Plans for achieving good status of water
bodies was tested.
At each case study, a Focus Group (FG) participated by local stakeholders (e.g., river basin authorities, research
institutions, environmental protection agencies, environmental associations) was formed and seven meetings were
organized. During these meetings, the objective of each case study, the methodology to be adopted, including
definition of the conceptual model and of data needed, were discussed. The FG also took decisions on scenarios
to be simulated for testing the feasibility of the foreseen measures. FGs aimed at demonstrating that WRM may
be performed with open source and public domain software and participantsâ perception on using ICT tools for
WRM was discussed.
Some of the implemented models are now being used for operational purposes: Vrbansky plato (Slovenia),
where FREEWAT is used to monitor remediation of heating oil spillage and the water supply company intends to
maintain and use developed groundwater flow model for managed groundwater recharge with induced riverbank
filtration; the Bremerhaven case study (Germany), where the local water authority intends to use the developed
groundwater flow model for predictions; the Scarlino-Follonica case study (Italy), where the model will be used by
the regional authority to manage private groundwater remediation projects in a large industrial contaminated site;
the Gozo case study (Malta), where the model is being developed to support the assessment of good groundwater
quantitative status as part of the implementation of the Water Framework Directive
AC 114: a cluster with a soft X-ray tail
We present Chandra observations of the galaxy cluster AC114, which shows a
strongly irregular morphology, with signs of multiple merging activity. We
report the discovery of a soft X-ray filament originating close to the core of
the cluster. We confirm that X-ray emission is associated with two of three
mass concentrations identified in previous gravitational lensing studies of
this object. These two mass concentrations are located at opposite ends of the
soft filament, evidence for interaction between them. In the northern part, the
cluster shows two sharp discontinuities, both in surface brightness and in
temperature, evincing another, more recent merger event which took place in, or
close, to the cluster core. In spite of the merger activity, a combined mass
and lensing analysis shows remarkably good agreement between lensing and X-ray
masses. We therefore advocate for the robustness of the X-ray mass estimates,
and conclude that the assumption of hydrostatic equilibrium can yield accurate
mass estimates even in clusters as dynamically active as AC 114, once the gas
density distribution is properly mapped.Comment: 11 pages; to appear in ApJ 10 August 2004 issu
CMS Monte Carlo production in the WLCG computing Grid
Monte Carlo production in CMS has received a major boost in performance and
scale since the past CHEP06 conference. The production system has been re-engineered in order
to incorporate the experience gained in running the previous system and to integrate production
with the new CMS event data model, data management system and data processing framework.
The system is interfaced to the two major computing Grids used by CMS, the LHC Computing
Grid (LCG) and the Open Science Grid (OSG).
Operational experience and integration aspects of the new CMS Monte Carlo production
system is presented together with an analysis of production statistics. The new system
automatically handles job submission, resource monitoring, job queuing, job distribution
according to the available resources, data merging, registration of data into the data
bookkeeping, data location, data transfer and placement systems. Compared to the previous
production system automation, reliability and performance have been considerably improved. A
more efficient use of computing resources and a better handling of the inherent Grid unreliability
have resulted in an increase of production scale by about an order of magnitude, capable of
running in parallel at the order of ten thousand jobs and yielding more than two million events
per day
Distribution of antibiotic resistance genes in the saliva of healthy omnivores, ovo-lacto-vegetarians, and vegans
Food consumption allows the entrance of bacteria and their antibiotic resistance (AR) genes into the human oral cavity. To date, very few studies have examined the influence of diet on the composition of the salivary microbiota, and even fewer investigations have specifically aimed to assess the impact of different long-term diets on the salivary resistome. In this study, the saliva of 144 healthy omnivores, ovo-lacto-vegetarians, and vegans were screened by nested PCR for the occurrence of 12 genes conferring resistance to tetracyclines, macrolide-lincosamide-streptogramin B, vancomycin, and \u3b2-lactams. The tet(W), tet(M), and erm(B) genes occurred with the highest frequencies. Overall, no effect of diet on AR gene distribution was seen. Some differences emerged at the recruiting site level, such as the higher frequency of erm(C) in the saliva of the ovo-lacto-vegetarians and omnivores from Bologna and Turin, respectively, and the higher occurrence of tet(K) in the saliva of the omnivores from Bologna. A correlation of the intake of milk and cheese with the abundance of tet(K) and erm(C) genes was seen. Finally, when the occurrence of the 12 AR genes was evaluated along with geographical location, age, and sex as sources of variability, high similarity among the 144 volunteers was seen
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