941 research outputs found
Spin-1 gravitational waves. Theoretical and experimental aspects
Exact solutions of Einstein field equations invariant for a non-Abelian
2-dimensional Lie algebra of Killing fields are described. Physical properties
of these gravitational fields are studied, their wave character is checked by
making use of covariant criteria and the observable effects of such waves are
outlined. The possibility of detection of these waves with modern detectors,
spherical resonant antennas in particular, is sketched
Spin-1 gravitational waves and their natural sources
Non-vacuum exact gravitational waves invariant for a non Abelian
two-dimensional Lie algebra generated by two Killing fields whose commutator is
of light type, are described. The polarization of these waves, already known
from previous works, is related to the sources. Non vacuum exact gravitational
waves admitting only one Killing field of light type are also discussed.Comment: 10 pages, late
The UV behavior of Gravity at Large N
A first step in the analysis of the renormalizability of gravity at Large N
is carried on. Suitable resummations of planar diagrams give rise to a theory
in which there is only a finite number of primitive superficially divergent
Feynman diagrams. The mechanism is similar to the the one which makes
renormalizable the 3D Gross-Neveu model at large N. Some potential problems in
fulfilling the Slavnov-Taylor and the Zinn-Justin equations are also pointed
out.Comment: 17 pages, 9 figures. To appear on Phys. Rev. D. Two more references,
further technical details and the discussion of the KLT relations at large N
have been include
Does the Holographic Principle determine the Gravitational Interaction?
It is likely that the holographic principle will be a consequence of the
would be theory of quantum gravity. Thus, it is interesting to try to go in the
opposite direction: can the holographic principle fix the gravitational
interaction? It is shown that the classical gravitational interaction is well
inside the set of potentials allowed by the holographic principle. Computations
clarify which role such a principle could have in lowering the value of the
cosmological constant computed in QFT to the observed one.Comment: 12 pages, no figures, added reference
Therapeutic Targets in Amyotrophic Lateral Sclerosis: Focus on Ion Channels and Skeletal Muscle
Amyotrophic Lateral Sclerosis is a neurodegenerative disease caused by progressive loss of motor neurons, which severely compromises skeletal muscle function. Evidence shows that muscle may act as a molecular powerhouse, whose final signals generate in patients a progressive loss of voluntary muscle function and weakness leading to paralysis. This pathology is the result of a complex cascade of events that involves a crosstalk among motor neurons, glia, and muscles, and evolves through the action of converging toxic mechanisms. In fact, mitochondrial dysfunction, which leads to oxidative stress, is one of the mechanisms causing cell death. It is a common denominator for the two existing forms of the disease: sporadic and familial. Other factors include excitotoxicity, inflammation, and protein aggregation. Currently, there are limited cures. The only approved drug for therapy is riluzole, that modestly prolongs survival, with edaravone now waiting for new clinical trial aimed to clarify its efficacy. Thus, there is a need of effective treatments to reverse the damage in this devastating pathology. Many drugs have been already tested in clinical trials and are currently under investigation. This review summarizes the already tested drugs aimed at restoring muscle-nerve cross-talk and on new treatment options targeting this tissue
Education in Soil Science: the Italian approach
The Italian Society of Soil Science (SISS) was founded in Florence on February 18th, 1952.
It is an association legally acknowledged by Decree of the President of the Italian Republic in February 1957.
The Society is member of the International Union of Soil Sciences (IUSS) of the European Confederation of Soil
Science Societies (ECSSS) and collaborates with several companies, institutions and organizations having similar
objectives or policy aspects.
SISS promotes progress, coordination and dissemination of soil science and its applications encouraging relationships
and collaborations among soil lovers.
Within the SISS there are Working Groups and Technical Committees for specific issues of interest. In particular:
\u2022 the Working Group on Pedotechniques;
\u2022 the Working Group on Hydromorphic and Subaqueous Soils and
\u2022 the Technical Committee for Soil Education and Public Awareness.
In this communication we wish to stress the activities developed since its foundation by SISS to spread soil
awareness and education in Italy through this last Technical Committee, focusing also the aspect concerning grants
for young graduates and PhD graduates to stimulate the involvement of young people in the field of soil science
Nonlinear gravitational waves and their polarization
Vacuum gravitational fields invariant for a non Abelian Lie algebra generated
by two Killing fields whose commutator is light-like are analyzed. It is shown
that they represent nonlinear gravitational waves obeying to two nonlinear
superposition laws. The energy and the polarization of this family of waves are
explicitely evaluated.Comment: 9 pages. LateX. Minor correction
Bottom up approach to manage data privacy policy through the front end filter paradigm
An increasing number of business services for private companies and citizens are accomplished trough the web and mobile devices. Such a scenario is characterized by high dynamism and untrustworthiness, as a large number of applications exchange different kinds of data. This poses an urgent need for effective means in preserving data privacy. This paper proposes an approach, inspired to the front-end trust filter paradigm, to manage data privacy in a very flexible way. Preliminary experimentation suggests that the solution could be a promising path to follow for web-based transactions which will be very widespread in the next future
Distribution patterns of fungi and bacteria in saline soils
Saline soils are environments characterized by uneven temporal and spatial water distribution
and localized high concentrations of salts. Spatial distribution patterns of fungi and bacteria in
saline soils, and the link between microbial community dynamics and salts accumulation are
critical issues throughout the world (Ettema, Wardle 2002).
This study was focused on spatial distribution patterns of soil fungi and bacteria in a saline soil
located in Piana del Signore (Gela, Italy) where some ecological variables acted as shaping
factors in aboveground and belowground communities distribution. Bacterial, archaeal, and
fungal communities diversity and distribution in ten soil sites (A horizons, 0-10cm), were
characterized by 16S rDNA genes with T-RFLP method. Pyrosequencing-based analysis of the
V2-V3 16S rRNA gene region was performed to characterize the sites on the basis of bacterial
groups distribution, diversity and assemblage. To better investigate the ecological niches of
some of the main culturable species of this environment, it was carried out the isolation and
identification of the fungal flora from soil, using Warcup plating within two different salt
concentrations (NaCl 5% and 15%), combined with a metabolic screening of some
representative isolates (Di Lonardo et al., 2013).
A natural gradient of soil salinity shaped the distribution of microbial species in the environment.
The different concentration of salt (NaCl), and calcium sulfate (Ca2SO4) in soil influenced the
structure and distribution of the microbial communities even when comparing neighboring areas
within a 50 m scale.
Some bacterial phyla, together with some fungal species, appeared spread in the whole area,
independently of the salinity gradient, thus highlighting the presence of organisms with a very
different survival strategy in such an extreme environment.
In conclusion, the organization and diversity of microbial taxa at a spatial scale reflected the
scales of heterogeneity of physical and chemical properties of the habitat under investigation
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