295 research outputs found
Local Magnetic Turbulence and TeV-PeV Cosmic Ray Anisotropies
In the energy range from ~ 10^12 eV to ~ 10^15 eV, the Galactic cosmic ray
flux has anisotropies both on large scales, with an amplitude of the order of
0.1%, and on scales between ~ 10 and ~ 30 degrees, with amplitudes smaller by a
factor of a few. With a diffusion coefficient inferred from Galactic cosmic ray
chemical abundances, the diffusion approximation predicts a dipolar anisotropy
of comparable size, but does not explain the smaller scale anisotropies. We
demonstrate here that energy dependent smaller scale anisotropies naturally
arise from the local concrete realization of the turbulent magnetic field
within the cosmic ray scattering length. We show how such anisotropies could be
calculated if the magnetic field structure within a few tens of parsecs from
Earth were known.Comment: 5 pages (2 columns), 3 figures. Published in Physical Review Letter
Polyvinylamine membranes containing graphene-based nanofillers for carbon capture applications
In the present study, the separation performance of new self-standing polyvinylamine (PVAm) membranes loaded with few-layer graphene (G) and graphene oxide (GO) was evaluated, in view of their use in carbon capture applications. PVAm, provided by BASF as commercial product named Lupamin\u2122, was purified obtaining PVAm films with two degrees of purification: Low Grade (PVAm-LG) and High Grade (PVAm-HG). These two-grade purified PVAm were loaded with 3 wt% of graphene and graphene oxide to improve mechanical stability: indeed, pristine tested materials proved to be brittle when dry, while highly susceptible to swelling in humid conditions. Purification performances were assessed through FTIR-ATR spectroscopy, DSC and TGA analysis, which were carried out to characterize the pristine polymer and its nanocomposites. In addition, the membranes\u2032 fracture surfaces were observed through SEM analysis to evaluate the degree of dispersion. Water sorption and gas permeation tests were performed at 35 \ub0C at different relative humidity (RH), ranging from 50% to 95%. Overall, composite membranes showed improved mechanical stability at high humidity, and higher glass transition temperature (Tg) with respect to neat PVAm. Ideal CO2/N2 selectivity up to 80 was measured, paired with a CO2 permeability of 70 Barrer. The membranes\u2019 increased mechanical stability against swelling, even at high RH, without the need of any crosslinking, represents an interesting result in view of possible further development of new types of facilitated transport composite membranes
Ultrahigh Energy Nuclei in the Galactic Magnetic Field
Observations are consistent with a significant fraction of heavy nuclei in
the cosmic ray flux above a few times 10^19 eV. Such nuclei can be deflected
considerably in the Galactic magnetic field, with important implications for
the search of their sources. We perform detailed simulations of heavy nuclei
propagation within recent Galactic magnetic field models. While such models are
not yet sufficiently constrained to predict deflection maps in detail, we find
general features of the distribution of (de-) magnified flux from sources.
Since in most theoretical models sources of heavy nuclei are located in the
local large scale structure of galaxies, we show examples of images of several
nearby galaxy clusters and of the supergalactic plane. Such general features
may be useful to develop efficient methods for source reconstruction from
observed ultrahigh energy cosmic ray arrival directions.Comment: 17 pages, 11 figures. Published in JCA
Efecto de variables meteorológicas en el rendimiento de maíz temprano en el centro oeste de Entre Ríos y potencial uso predictivo de la señal ENOS
Los objetivos de este trabajo son: I) relacionar el rendimiento de maíz temprano (siembra de septiembre) en el centro oeste de Entre Ríos con variables meteorológicas y eventos ENOS; II)jerarquizarlas según su impacto en el rendimiento; III)relacionar rendimiento del cultivo de maíz temprano con el índice ONI de ENOS, explorando su potencial uso predictivo.EEA ParanáFil: Pautasso, Juan Manuel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná. Agencia de Extensión Rural Diamante; ArgentinaFil: Barbagelata, Pedro Anibal. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná. Agencia de Extensión Rural Diamante; ArgentinaFil: Barbagelata, Pedro Anibal. Universidad Nacional de Entre Ríos. Facultad de Ciencias Agropecuarias; ArgentinaFil: Giacinti, S. Asesor privado; Argentin
Equianalytic and equisingular families of curves on surfaces
We consider flat families of reduced curves on a smooth surface S such that
each member C has the same number of singularities of fixed singularity types
and the corresponding (locally closed) subscheme H of the Hilbert scheme of S.
We are mainly concerned with analytic resp. topological singularity types and
give a sufficient condition for the smoothness of H (at C). Our results for
S=P^2 seem to be quite sharp for families of cuves of small degree d.Comment: LaTeX v 2.0
Enterotoxin genes, enterotoxin production, and methicillin resistance in Staphylococcus aureus isolated from milk and dairy products in Central Italy
AbstractA total of 227 Staphylococcus aureus colonies, isolated from 54 samples of raw milk and dairy products of bovine, ovine, caprine and bubaline origin were tested for the presence of genes coding for staphylococcal enterotoxins (SEs/SEls) and for methicillin resistance. Ninety-three colonies, from 31 of the 54 samples (57.4%) and from 18 (69.2%) of the 26 farms of origin tested positive for SEs/SEls genes. Most isolates harboured more than one toxin gene and 15 different toxinotypes were recorded. The most frequent were “sec” gene alone (28.6%), “sea, sed, ser, selj” (20%), “seg, sei” and “seh” (8.6%). The 77 colonies harbouring “classical enterotoxins” genes (sea-sed) were further tested for enterotoxin production, which was assessed for 59.2% of the colonies. Three methicillin-resistant S. aureus (MRSA) isolates were detected in three different ovine milk/dairy product samples (1.3%). All isolates belonged to spa type t127, sequence type 1, clonal complex 1, SCCmec type IVa
Human cardiac progenitor cell grafts as unrestricted source of supernumerary cardiac cells in healthy murine hearts
Human heart harbors a population of resident progenitor cells that can be isolated by stem cell antigen-1 antibody and expanded in culture. These cells can differentiate into cardiomyocytes in vitro and contribute to cardiac regeneration in vivo. However, when directly injected as single cell suspension, less than 1%-5% survive and differentiate. Among the major causes of this failure are the distressing protocols used to culture in vitro and implant progenitor cells into damaged hearts. Human cardiac progenitors obtained from the auricles of patients were cultured as scaffoldless engineered tissues fabricated using temperature-responsive surfaces. In the engineered tissue, progenitor cells established proper three-dimensional intercellular relationships and were embedded in self-produced extracellular matrix preserving their phenotype and multipotency in the absence of significant apoptosis. After engineered tissues were leant on visceral pericardium, a number of cells migrated into the murine myocardium and in the vascular walls, where they integrated in the respective textures. The study demonstrates the suitability of such an approach to deliver stem cells to the myocardium. Interestingly, the successful delivery of cells in murine healthy hearts suggests that myocardium displays a continued cell cupidity that is strictly regulated by the limited release of progenitor cells by the adopted source. When an unregulated cell source is added to the system, cells are delivered to the myocardium. The exploitation of this novel concept may pave the way to the setup of new protocols in cardiac cell therapy. STEM CELLS 2011;29:2051-206
The role of CDK9 in myogenesis
Cdk9 is a member of cyclin-dependent kinases (cdks). It is expressed in human and murine tissues with high levels in terminally differentiated cells. It is involved in the regulation of transcriptional elongation via phosphorylation of CTD of RNA polII (1). It has been demonstrated that CdK9, complexed with CyT2a, plays a role in the activation of myogenic program. Moreover Cdk9-CyT2a activity is not down-regulated in myotube formation, but its activation contributes to the transcriptional activity MyoD-mediated during myogenic program (2). Recently, a 55 kDa protein called cdk9-55 has been identified. Cdk9-55 is significantly upregulated in cells induced to differentiate, either in C2C12 cells or in satellite isolated cells. In addition, it has been demonstrated that there is a clear induction of cdk9-55 expression in injured skeletal muscles (3). In order to deepen the discussion and extend the understanding of the biological role of the two isoforms of cdk9 during skeletal muscle differentiation process, we report the role of the two isoforms during in vivo mouse myogenesis. We have analyzed the behavior of CDk9-42 and CDK9-55 in primary and secondary myogenesis. Of particular interest are the apparent inverse correlation between the two cdk9 isoforms during the events of limbs formation and how the expression of two CDK9 isoforms, in combination with specific positive (Cycline T1,T2,k) or negative regulators (7SKsnRNA/Hexim1), is associated to a specific cellular phenotype and correlated to a specific function
Search for Anisotropy of Ultra-High Energy Cosmic Rays with the Telescope Array Experiment
We study the anisotropy of Ultra-High Energy Cosmic Ray (UHECR) events
collected by the Telescope Array (TA) detector in the first 40 months of
operation. Following earlier studies, we examine event sets with energy
thresholds of 10 EeV, 40 EeV, and 57 EeV. We find that the distributions of the
events in right ascension and declination are compatible with an isotropic
distribution in all three sets. We then compare with previously reported
clustering of the UHECR events at small angular scales. No significant
clustering is found in the TA data. We then check the events with E>57 EeV for
correlations with nearby active galactic nuclei. No significant correlation is
found. Finally, we examine all three sets for correlations with the large-scale
structure of the Universe. We find that the two higher-energy sets are
compatible with both an isotropic distribution and the hypothesis that UHECR
sources follow the matter distribution of the Universe (the LSS hypothesis),
while the event set with E>10 EeV is compatible with isotropy and is not
compatible with the LSS hypothesis at 95% CL unless large deflection angles are
also assumed. We show that accounting for UHECR deflections in a realistic
model of the Galactic magnetic field can make this set compatible with the LSS
hypothesis.Comment: 10 pages, 9 figure
Cosmic rays and molecular clouds
This paper deals with the cosmic-ray penetration into molecular clouds and
with the related gamma--ray emission. High energy cosmic rays interact with the
dense gas and produce neutral pions which in turn decay into two gamma rays.
This makes molecular clouds potential sources of gamma rays, especially if they
are located in the vicinity of a powerful accelerator that injects cosmic rays
in the interstellar medium. The amplitude and duration in time of the
cosmic--ray overdensity around a given source depend on how quickly cosmic rays
diffuse in the turbulent galactic magnetic field. For these reasons, gamma-ray
observations of molecular clouds can be used both to locate the sources of
cosmic rays and to constrain the properties of cosmic-ray diffusion in the
Galaxy.Comment: To appear in the proceedings of the San Cugat Forum on Astrophysics
2012, 27 pages, 10 figure
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