Influence of crystallinity and chain interactions on the electrical properties of polyamides/carbon nanotubes nanocomposites

This work evaluates the effects of the crystallinity degree and π–π interactions between nanoparticles and a polymeric matrix on the electrical properties of polyamides and carbon nanotubes (CNT) nanocomposites. Two polymeric matrices were chosen; polyamide (PA) 6.6, a semi-crystalline polymer, and PA 6I-6T (here called aPA), a semi-aromatic and amorphous polyamide. The PA 6.6 crystallinity degree did not significantly change. Both lamellar thicknesses, amorphous (L_a) and crystalline (L_c), were estimated through Small-angle X-ray scattering. L_a increased significantly when CNTs were added. Both nanocomposites presented almost the same percolation threshold. In aPA nanocomposites, the π–π interaction between aromatic groups of CNTs and aPA is not only responsible for a homogeneous CNT dispersion, but also creates a direct path, parallel to the electrodes, for electron conduction after the percolation limit. In the PA 6.6 nanocomposites, the CNTs preferably disperse in the amorphous regions, forming a conductive network.     

A glance at violet LED sensitive photoinitiators based on the spiroxanthene scaffold

A novel photoinitiator based on a spiroxanthene scaffold in the presence of an iodonium salt is proposed for the cationic ring‐opening polymerization of a diepoxide, as well as for the free‐radical polymerization of an acrylate upon violet LED exposure (385 and 405 nm). Good‐to‐excellent rates of polymerization and final conversions are obtained. These systems are characterized by a higher reactivity compared with that of anthracene/iodonium salt used as reference for cationic near UV polymerization. The addition of a poly(ionic liquid) improves the cationic polymerization profiles. The photochemical mechanisms are studied by steady‐state photolysis, fluorescence, and electron spin resonance spin‐trapping techniques. Molecular orbital calculations give an insight into the light absorption properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43213.     

Targeting EphA2‐Sam and Its Interactome: Design and Evaluation of Helical Peptides Enriched in Charged Residues

The EphA2 receptor controls diverse physiological and pathological conditions and its levels are often upregulated in cancer. Targeting receptor overexpression, through modulation of endocytosis and consequent degradation, appears to be an appealing strategy for attacking tumor malignancy. In this scenario, the Sam domain of EphA2 plays a pivotal role because it is the site where protein regulators of endocytosis and stability are recruited by means of heterotypic Sam–Sam interactions. Because EphA2‐Sam heterotypic complexes are largely based on electrostatic contacts, we have investigated the possibility of attacking these interactions with helical peptides enriched in charged residues. Several peptide sequences with high predicted helical propensities were designed, and detailed conformational analyses were conducted by diverse techniques including NMR, CD, and molecular dynamics (MD) simulations. Interaction studies were also performed by NMR, surface plasmon resonance (SPR), and microscale thermophoresis (MST) and led to the identification of two peptides capable of binding to the first Sam domain of Odin. These molecules represent early candidates for the generation of efficient Sam domain binders and antagonists of Sam–Sam interactions involving EphA2.     

Inhibition of melanin synthesis pathway by tricyclazole increases susceptibility of Fonsecaea pedrosoi against mouse macrophages

Fonsecaea pedrosoi produces melanin, a pigment related to virulence in pathogenic fungi. To understand the involvement of melanin in the protection of fungi, the authors used tricyclazole to inhibit the melanin pathway in F. pedrosoi. Experiments of pigmentation suggested that F. pedrosoi uniquely produces dihydroxynaphthalene-melanin. Pigments produced on cultures modified or not with tricyclazole were extracted by an alkali-acid method and submitted to infrared and ion exchange chromatography analysis; also cytochemistry analysis for cationized ferritin of whole cells was carried out. This group of experiments showed that the tricyclazole treatment on F. pedrosoi produced a melanin-like pigment, but less negatively charged and with less affinity for iron ions than that without the tricyclazole treatment, and this in turn lead to a less negatively charge cell wall surface. Scanning electron microscopy of such pigments showed that the melanin from control cultures maintained their hyphae-like structures, which have been described as "melanin-ghosts," whereas the tricyclazole pigment showed an amorphous surface. Interaction of conidia from cultures of F. pedrosoi, modified by tricyclazole or not, with peritoneal activated macrophages suggested that tricyclazole causes higher association of fungus with macrophages, weakens the fungus capacity to destroy the macrophages, and diminishes the resistance to dry fracture procedures on samples prepared for high resolution scanning electron microscopy.     

Sand Liquefaction Phenomena During the Seismic Crisis of May 2012 in Emilia,Northern Italy

In May 2012,the Emilia region of the Po Valley was struck by a seismic crisis with two major events of magnitude M_w 6.1and M_w 5.9.The first event induced widespread sand blows formed along buried channels and old crevasse splay deposits.In the days immediately following the events,the detailed mapping and sampling of the erupted sand was fundamental to record all the seismically-induced phenomena.The study of a trench dug across large fractures at San Carlo(Ferrara)provided also valuable information on the sand blows mechanism and regome.The sedimentological and compositional characteristics of the fracture-filling materials indicate that the sands were erupted from a layer located between 6.8 and 7.5 m depth.Older and deeper Holocene and Pleistocene sand layers were not apparently involved in the liquefaction phenomena.     

Multi‐analytical approach for the morphological,molecular, and mechanical characterization after photo‐oxidation of polymers used in artworks

For a proper preservation of plastics objects, it is essential to study the degradation processes involved in both exposed and hidden areas of the polymeric materials. In fact, surface properties can differ significantly from the bulk and can have a strong effect on the artistic perception and the correct conservation strategy. In this work, a multi‐analytical investigation, including spectroscopic techniques, optical, and electronic microscopic observations and mechanical tests, was carried out to deeply investigate changes in the physic‐chemical and mechanical surface properties of selected polymers used in design objects and contemporary artworks. Accelerated photo‐oxidative ageing was performed on acrylonitrile butadiene styrene (ABS), poly(vinyl chloride) (PVC), polypropylene (PP), high density polyethylene, and linear low density polyethylene. Overall, the analyzed materials have shown different behaviors following photo‐oxidation. The molecular and microscopic analyses highlighted the formation of different products of oxidation due to the dissimilar patterns of ageing leading to surface cracking and strong yellowing of the specimen, mainly for ABS, PVC, and PP. Moreover, mechanical properties, such as the variation of hardness and elastic modulus, were investigated at different depth scales (from 100 down to 1 µm) by using different techniques such as microscratch, micro‐, and nanoindentation. The selected polymers showed different mechanical behavior at different depth scales. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46194.     

Inhibitory Effects of Semiochemicals on the Attraction of an Ambrosia Beetle <Emphasis Type="Italic">Euwallacea</Emphasis> nr. <Emphasis Type="Italic">fornicatus</Emphasis> to Quercivorol

The Euwallacea fornicatus (Eichhoff) species complex includes the polyphagous shot hole borer (PSHB), an ambrosia beetle infesting avocado limbs, Persea americana Mill. Synthetic quercivorol, a monoterpene alcohol, is known to attract females (males are flightless) over a range of release rates spanning three orders of magnitude. The upper release dose was extended 10-fold using sticky traps baited with quercivorol released at 1× (0.126 mg/day), 10×, and 108× relative rates to obtain a dose?response curve fitting a kinetic formation function. Naturally infested limbs of living avocado trees were wrapped with netting to exclude the possibility of catching emerging beetles on the encircling sticky traps. The results indicate PSHB are significantly attracted to infested limbs. Ethanol released over a 64-fold range (lowest rate of 7.5 mg/day) was moderately inhibitory of PSHB attraction to 1× quercivorol. β-caryophyllene and eucalyptol did not appear to affect attraction at the rates tested. A field test of potential inhibitors of 1× quercivorol was done using ~1 mg/day releases of monoterpene ketones: (?)-(S)-verbenone, (+)-(R)-verbenone, 3-methyl-2-cyclo-hexen-1-one (MCH or seudenone), piperitone, (+)-(S)-carvone, and racemic cryptone. Only piperitone and the two enantiomers of verbenone were strongly inhibitory. A blend of piperitone and verbenone tested together at different distances (0, 0.5, 1, 2, and 4 m) from a 1× quercivorol baited sticky trap became increasingly ineffective in inhibiting the attractant as separation distance increased. Due to the relatively short-range repellency (<1 m), the inhibitors would need to be released from several places on each tree to effectively repel PSHB from avocado trees. Effective attraction radii, EAR, and circular EARc are estimated for the quercivorol baits released at 1×, 10× and 108× rates. Push-pull simulations of moving beetles were performed in 1 ha plots with 2, 4, or 16 traps of 10× EARc and 400 trees (0, 1, or 3 inhibitors per tree) of which ten had an infested limb (EARc?=?0.5 m). The simulations indicate that push-pull methods would be more effective in reducing PSHB mating than simply using mass-trapping alone.     

Moving network based on mmWave technology: a promising solution for 5G vehicular users

Mobile connectivity is a vital requirement for people’s everyday life. Users would like to have unlimited access to information for anyone, anywhere, and anytime, especially in public means of transport where they spend a lot of time travelling. The connectivity to Internet becomes difficult for passengers because public transportation vehicles suffer from the low quality signal from the outside wireless network. A first solution to improve the broadband connectivity is to deploy more eNodeBs close to busses or train routes, but it requires high investment for providers and a higher complexity in managing the increasing number of handover. The rapid growth in the deployment of LTE femtocells for indoor use and their benefits have led many authors to propose using them even in vehicles, implementing the so-called Moving Networks. This paper shows that the use of pure LTE mobile femtocells exhibits relevant issues in terms of interference and consequently poor performance in a realistic use. In order to overcome these issues, we propose to adopt the millimeter Wave (mmWave) technology in the Moving Networks, creating the Hybrid Mobile Femtocells. In the paper we discuss the concerns arising from applying mmWave communications at 60 GHz inside vehicles. We provide a new throughput analysis in order to benchmark our proposal to the solutions presented in literature. Furthermore, we analyse the system performance in two different scenarios: a sub-urban setup and in an urban configuration where different kind of cells are deployed. The results obtained by Matlab simulations, show a noticeable improvement of the global system throughput by using Hybrid Mobile Femtocells.