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

Deep into the structure of the first galaxies: SERRA views

We study the formation and evolution of a sample of Lyman Break Galaxies in the Epoch of Reionization by using high-resolution ($\sim 10 \,{\rm pc}$), cosmological zoom-in simulations part of the SERRA suite. In SERRA, we follow the interstellar medium (ISM) thermo-chemical non-equilibrium evolution, and perform on-the-fly radiative transfer of the interstellar radiation field (ISRF). The simulation outputs are post-processed to compute the emission of far infrared lines ([CII], [NII], and [OIII]). At $z=8$, the most massive galaxy, `Freesia', has an age $t_\star \simeq 409\,{\rm Myr}$, stellar mass $M_{\star} \simeq 4.2\times 10^9 {\rm M}_{\odot}$, and a star formation rate ${\rm SFR} \simeq 11.5\,{\rm M}_{\odot}{\rm yr}^{-1}$, due to a recent burst. Freesia has two stellar components (A and B) separated by $\simeq 2.5\, {\rm kpc}$; other 11 galaxies are found within $56.9 \pm 21.6 \, {\rm kpc}$. The mean ISRF in the Habing band is $G = 7.9\, G_0$ and is spatially uniform; in contrast, the ionisation parameter is $U = 2^{+20}_{-2} \times 10^{-3}$, and has a patchy distribution peaked at the location of star-forming sites. The resulting ionising escape fraction from Freesia is $f_{\rm esc}\simeq 2\%$. While [CII] emission is extended (radius 1.54 kpc), [OIII] is concentrated in Freesia-A (0.85 kpc), where the ratio $\Sigma_{\rm [OIII]}/\Sigma_{\rm [CII]} \simeq 10$. As many high-$z$ galaxies, Freesia lies below the local [CII]-SFR relation. We show that this is the general consequence of a starburst phase (pushing the galaxy above the Kennicutt-Schmidt relation) which disrupts/photodissociates the emitting molecular clouds around star-forming sites. Metallicity has a sub-dominant impact on the amplitude of [CII]-SFR deviations.Comment: 22 pages, 14 figures, accepted by MNRA

In vitro screening of interspecific hybrids (Malus spp.) for resistance to apple proliferation

A breeding programme was set up six years ago in Trentino as part of the Project “Scopazzi del Melo - Apple Proliferation” (SMAP) in order to obtain AP resistant apple rootstocks.Twenty-six hybrids generated from the crossings (Malus sieboldii, second generation, x Malus domestica) were micropropagated and studied in standardised conditions. An in vitro screening system for AP resistance previously set for the parents of the crosses was adopted and modified. Specific symptoms of the disease, as well as height and basal proliferation of the shoot and size of the leaves, were recorded in vitro at 3 months post-inoculation. At the same time, phytoplasma concentration was determined in the whole shoot by quantitative RT-PCR. An in vitro disease index taking into account all the above-mentioned parameters was developed.Each healthy genotype was graft-inoculated in triplicate with two different phytoplasma strains after plant rooting and acclimatisation. Phenotype and phytoplasma titre were evaluated in the roots the year after infection.Preliminary results indicated that the resistance trait segregates in the progenies. The resistant genotypes had lower phytoplasma concentrations than the susceptible controls, did not show AP-specific symptoms and their growth was not affected by infection. By comparing the resistant behaviour of the same genotypes, the in vitro screening allows for a quick selection of genotypes that are worth evaluating in the field for agronomic traits.Keywords: Apple Proliferation, Malus sieboldii, resistance screening, quantitative real-time PCR, disease inde

Lightweight error correction technique in industrial IEEE802.15.4 networks

Industrial Wireless Sensor Networks (IWSNs) are nowadays becoming more and more popular thanks to their flexibility and pervasive monitoring capabilities to support process automation and remote maintenance applications. In such a scenario, channel errors due to the wireless medium can result in data packet losses, and consequently in unreliable IWSN services. To mitigate the above reported problem, this paper presents a lightweight error correction scheme specially developed for IEEE802.15.4-based IWSNs. By adding error correction and detection information inside the IEEE802.15.4 MAC data frame, the proposed FEC scheme is able to guarantee a backward compatibility with the standard while providing advanced capabilities in recovering data packets affected by bit errors. In the paper the benefits of the proposed technique are first evaluated through simulated loss traces, then they are validated in a real environment by considering real loss traces collected in an electricity power plant. The proposed error correction scheme is able to recover around 50% of the data packets that would be lost in case of a standard communication without any error correction capability