2,760 research outputs found
Dimensional effects on the tunneling conductivity of gold-implanted nanocomposite films
We study the dependence of the electrical conductivity on the gold
concentration of Au-implanted polymethylmethacrylate (PMMA) and alumina
nanocomposite thin films. For Au contents larger than a critical concentration,
the conductivity of Au-PMMA and Au-alumina is well described by percolation in
two dimensions, indicating that the critical correlation length for percolation
is larger than the thickness of the films. Below the critical loading, the
conductivity is dominated by tunneling processes between isolated Au particles
dispersed in PMMA or alumina continuous matrices. Using an effective medium
analysis of the tunneling conductivity, we show that Au-PMMA behaves as a
tunneling system in two dimensions, as the film thickness is comparable to the
mean Au particle size. On the contrary, the conductivity of Au-alumina films is
best described by tunneling in three dimensions, although the film thickness is
only a few times larger than the particle size. We interpret the enhancement of
the effective dimensionality of Au-alumina films in the tunneling regime as due
to the larger film thickness as compared to the mean interparticle distances.Comment: 7 pages, 7 figure
Sola est non territa virgo. Il mito di Aracne e le ambigue trame della tessitura
The topic of the discussion offers an opportunity to more deeply consider a myth connected to the theme of weaving: the tragic story of the weaver Arachne, whose story depends almost exclusively on the story by Ovid, developed in the first part of Book VI of the Metamorphoses and placed inside a series of myths that deal with the theme of punished hybris. The reading of the Ovidian myth and the analysis of the evidences in the iconographic tradition lie well within the project “MetaMArS. The Metamorphoses of Ovid. Myth, Art, Society”, active in the Department of Archaeology, University of Padua, sprung from the idea of an ambitious revision of Ovid’s Metamorphoses from the perspectives of art history, with the aim to reconstruct visual models that could have influenced the Ovidian narration, or, viceversa, the effect of certain passages written by Ovid on visual interpretations of the myth. Introducing the actual contest with Pallas, the poet inserts a series of observations on Arachne’s gestures (“… it was not only worth admiring the finished product but also while she made them, it was the spectacle of making the art …”), which constitutes one of the more concrete evidences of fascination exercised by the act of weaving on an artist who creates his art through words
Exploiting the Symmetry of the Resonator Mode to Enhance PELDOR Sensitivity.
Pulsed electron paramagnetic resonance (EPR) spectroscopy using microwaves at two frequencies can be employed to measure distances between pairs of paramagnets separated by up to 10 nm. The method, combined with site-directed mutagenesis, has become increasingly popular in structural biology for both its selectivity and capability of providing information not accessible through more standard methods such as nuclear magnetic resonance and X-ray crystallography. Despite these advantages, EPR distance measurements suffer from poor sensitivity. One contributing factor is technical: since 65 MHz typically separates the pump and detection frequencies, they cannot both be located at the center of the pseudo-Lorentzian microwave resonance of a single-mode resonator. To maximize the inversion efficiency, the pump pulse is usually placed at the center of the resonance, while the observer frequency is placed in the wing, with consequent reduction in sensitivity. Here, we consider an alternative configuration: by spacing pump and observer frequencies symmetrically with respect to the microwave resonance and by increasing the quality factor, valuable improvement in the signal-to-noise ratio can be obtained
Limits on Pop III star formation with the most iron-poor stars
We study the impact of star-forming mini-haloes, and the Initial Mass
Function (IMF) of Population III (Pop III) stars, on the Galactic halo
Metallicity Distribution Function (MDF) and on the properties of C-enhanced and
C-normal stars at [Fe/H]<-3. For our investigation we use a data-constrained
merger tree model for the Milky Way formation, which has been improved to
self-consistently describe the physical processes regulating star-formation in
mini-haloes, including the poor sampling of the Pop III IMF. We find that only
when star-forming mini-haloes are included the low-Fe tail of the MDF is
correctly reproduced, showing a plateau that is built up by C-enhanced
metal-poor (CEMP) stars imprinted by primordial faint supernovae. The
incomplete sampling of the Pop III IMF in inefficiently star-forming
mini-haloes (< /yr) strongly limits the formation of Pair
Instability Supernovae (PISNe), with progenitor masses =[140-260] , even when a flat Pop III IMF is assumed.
Second-generation stars formed in environments polluted at >50% level by PISNe
are thus extremely rare, corresponding to 0.25% of the total stellar
population at [Fe/H]<-2, which is consistent with recent observations. The
low-Fe tail of the MDF strongly depends on the Pop III IMF shape and mass
range. Given the current statistics, we find that a flat Pop III IMF model with
=[10-300] is disfavoured by observations. We present
testable predictions for Pop III stars extending down to lower masses, with
=[0.1-300] .Comment: 15 pages, 11 figures. Accepted for publication in MNRAS. The only
change is the correction of a mistake in the list of author
Long-term outcome of everolimus treatment in transplant patients
Maurizio Salvadori, Elisabetta BertoniRenal Unit, Careggi University Hospital, Florence, ItalyAbstract: The authors review the use of everolimus in long-term studies both in renal and heart transplantation. The pharmacokinetic and pharmacodynamic differences between everolimus and its parent drug, sirolimus are discussed. The improved pharmacokinetic, in particular the improved bioavailability, the reduced half-time and the reduced binding to plasma protein makes everolimus the first choice among the proliferation signal inhibitors. Everolimus is given in almost all studies in association with cyclosporine, but fixed doses of this drug can cause nephrotoxicity. The first studies used everolimus and CsA in fixed doses, but later studies with reduced CsA doses revealed which revealed improved outcomes. Finally, therapeutic drug monitoring became the better choice for both drugs. Recently very high everolimus exposure allowed the use of very low CsA exposure with improvement of the worse side effects linked to the CsA standard dose. The Zeus study revealed a complete and safe CsA withdrawal, thanks to everolimus and mycophenolic acid. In heart transplantation, everolimus resulted in improved outcomes with respect to antiproliferative drugs such as mycophenolic acid and azathioprine. Along with antirejection properties, everolimus provided evidence for antiproliferative effects on several cells. This resulted in fewer viral infections (mainly CMV), anti-atherosclerotic properties (mainly important in heart transplantation, and antineoplastic effect. The latter activity resulted in lower cancer incidence in transplant patients treated by everolimus. An important piece of evidence for this activity is documented by the use of everolimus in the treatment of some cancers, including renal cancer, neuroendocrine cancers and hepatocellular cancers, also outside the field of transplantation.Keywords: everolimus, renal transplantation, heart transplantation, CNI minimization, CNI withdrawa
Radiofrequency to Microwave Coherent Manipulation of an Organometallic Electronic Spin Qubit Coupled to a Nuclear Qudit
Galaxy formation with radiative and chemical feedback
Here we introduce GAMESH, a novel pipeline which implements self-consistent
radiative and chemical feedback in a computational model of galaxy formation.
By combining the cosmological chemical-evolution model GAMETE with the
radiative transfer code CRASH, GAMESH can post process realistic outputs of a
N-body simulation describing the redshift evolution of the forming galaxy.
After introducing the GAMESH implementation and its features, we apply the code
to a low-resolution N-body simulation of the Milky Way formation and we
investigate the combined effects of self-consistent radiative and chemical
feedback. Many physical properties, which can be directly compared with
observations in the Galaxy and its surrounding satellites, are predicted by the
code along the merger-tree assembly. The resulting redshift evolution of the
Local Group star formation rates, reionisation and metal enrichment along with
the predicted Metallicity Distribution Function of halo stars are critically
compared with observations. We discuss the merits and limitations of the first
release of GAMESH, also opening new directions to a full implementation of
feedback processes in galaxy formation models by combining semi-analytic and
numerical methods.Comment: This version has coloured figures not present in the printed version.
Submitted to MNRAS, minor revision
Observações sobre a biologia de Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera-Noctuidae) em trigo.
bitstream/item/65942/1/CPAO-COM.-TEC.-8-82.pd
ICONA: Inter Cluster ONOS Network Application
Several Network Operating Systems (NOS) have been proposed in the last few
years for Software Defined Networks; however, a few of them are currently
offering the resiliency, scalability and high availability required for
production environments. Open Networking Operating System (ONOS) is an open
source NOS, designed to be reliable and to scale up to thousands of managed
devices. It supports multiple concurrent instances (a cluster of controllers)
with distributed data stores. A tight requirement of ONOS is that all instances
must be close enough to have negligible communication delays, which means they
are typically installed within a single datacenter or a LAN network. However in
certain wide area network scenarios, this constraint may limit the speed of
responsiveness of the controller toward network events like failures or
congested links, an important requirement from the point of view of a Service
Provider. This paper presents ICONA, a tool developed on top of ONOS and
designed in order to extend ONOS capability in network scenarios where there
are stringent requirements in term of control plane responsiveness. In
particular the paper describes the architecture behind ICONA and provides some
initial evaluation obtained on a preliminary version of the tool.Comment: Paper submitted to a conferenc
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