On the auxetic behaviour of metamaterials with re-entrant cell structures

In the present paper a two dimensional plate, made by structural straight elements and showing an auxetic behaviour, is considered. Theoretical, experimental and numerical analyses for the characterisation of its mechanical properties are presented and compared. The main geometrical parameters of an elementary cell affecting the deformation behaviour are highlighted, with emphasis to the negative values of the Poisson’s ratio

Mechanical characterization of additively manufactured photopolymerized polymers

Photopolymerization, based on light-induced radical polymerization, is nowadays exploited in additive manufacturing (AM) technologies enabling to achieve high dimensional quality. The mechanical properties of the obtained material are heavily dependent on the chemistry of the photopolymer and on the way the AM process is performed. Here we study, through experiments and theoretical modeling, how the mechanical properties of liquid crystal shutter (LCD) printed photopolymers depend on the printing process setup, namely UV exposure time and layer thickness. To this end, a multi-physics simulation tool considering the light diffusion, chemical kinetics, and the micro-mechanics at the network level, has been developed

Involvement of recreational anglers in the eradication of alien brook trout from high altitude lakes

Stocking programmes for recreational angling are primarily responsible for the spread and ecological impact of introduced sh in high-altitude, originally shless lakes. In 2013, the Gran Paradiso National Park started an eradication campaign of brook trout by intensive gill-netting. Local anglers were invited to attend two angling sessions to start the eradication before gill-netting in an experimental lake, as part of an education action devoted to these critical stakeholders. The angling sessions turned out to be a valuable help for the eradication campaign and the aim of this study is to report on the outcomes of these angling sessions. Angling techniques were highly size-selective, removing a substantial part of the adult population and of the sh biomass, but their contribution to the eradication of small sh (<15cm) was irrelevant. Therefore, angling cannot completely eradicate age-structured populations. However, there is scope to use angling sessions as a support for eradication campaigns and as an emergency measure for recent sh introduc- tions. Similar actions should be considered whenever a sh eradication programme is planned. These ndings, however, do not imply a general endorsement for angling within protected areas

Behind the impact of introduced trout in high altitude lakes: adult, not juvenile fish are responsible of the selective predation on crustacean zooplankton

Introduced fish seriously affect zooplankton communities in mountain lakes, often leading to the loss of large species. Selective predation is recognized to be the ultimate cause of such a strong impact. Here we describe the selection of zooplankton prey by analyzing the stomach contents of more than 300 brook trout (Salvelinus fontinalis) inhabiting seven alpine lakes in the Gran Paradiso National Park (western Italian Alps). Our results show that planktivory is much more common in young fish, which feed on a larger number of taxa, but also adult fish maintain the ability to feed on zooplankton. There is a direct dependence between the length of zooplankton prey and the length of their fish predators, and adult, not juvenile fish are responsible of the selective predation on large crustacean zooplankton, which drive the impact of introduced fish throughout the entire zooplankton community. In some rare cases, large zooplankton populations develop in the presence of brook trout, and planktivory can become an important temporary resource for adult fish during the ice-free season. Thus, in the early stages of the establishment of non-native trout in alpine lakes, large-bodied zooplankton may represent an important food resource

Use of a Zwitterionic Surfactant to Improve the Biofunctional Properties of Wool Dyed with an Onion (Allium cepa L.) Skin Extract

To improve the loadability and antioxidant properties of wool impregnated with onion skin extract, the introduction of SB3-14 surfactant in the dyeing process was evaluated. A preliminary investigation on the surfactant–quercetin interaction indicated that the optimal conditions for dye solubility, stability, and surfactant affinity require double-distilled water (pH = 5.5) as a medium and SB3-14 in a concentration above the c.m.c. (2.5 × 10−3 M). The absorption profile of textiles showed the flavonoid absorption band (390 nm) and a bathochromic feature (510 nm), suggesting flavonoid aggregates. The higher absorbance for the sample dyed with SB3-14 indicated greater dye uptake, which was further confirmed by HPLC analysis. The Folin–Ciocalteu method was applied to evaluate the total phenol content (TPC) released from the treated wool, while the assays FRAP, DPPH, ABTS, and ORAC were applied to evaluate the corresponding total antioxidant activity (TAC). Higher TPCs (about 20%) and TACs (5–55%) were measured with SB3-14, highlighting textiles with improved biofunctional properties. Spectrophotometric analyses were also performed with an artificial sweat. The potential cytotoxic effect of SB3-14 in both monomeric and aggregated forms, cell viability, and induction of apoptosis were evaluated in RAW 264.7 cells. These analyses revealed that SB3-14 is safe at concentrations below the c.m.c

Chemotherapy-associated thromboembolic risk in cancer outpatients and effect of nadroparin thromboprophylaxis: results of a retrospective analysis of the PROTECHT study

<p>Abstract</p> <p>Background</p> <p>Cancer patients receiving chemotherapy are at increased risk of thrombosis. Nadroparin has been demonstrated to reduce the incidence of venous and arterial thrombotic events (TEs) by about 50% in cancer outpatients receiving chemotherapy. The aims of this retrospective analysis were to evaluate the thromboembolic risk and the benefit of thromboprophylaxis according to type of chemotherapy.</p> <p>Methods</p> <p>Cancer outpatients were randomly assigned to receive subcutaneous injections of nadroparin or placebo. The incidence of symptomatic TEs was assessed according to the type of chemotherapy. Results were reported as risk ratios with associated 95% CI and two-tailed probability values.</p> <p>Results</p> <p>769 and 381 patients have been evaluated in the nadroparin and placebo group, respectively. In the absence of thromboprophylaxis, the highest rate of TEs was found in patients receiving gemcitabine- (8.1%) or cisplatin-based chemotherapy (7.0%). The combination of gemcitabine and cisplatin or carboplatin increased the risk to 10.2%. Thromboprophylaxis reduced TE risk by 68% in patients receiving gemcitabine; with a further decrease to 78% in those receiving a combination of gemcitabine and platinum.</p> <p>Conclusions</p> <p>This retrospective analysis confirms that patients undergoing chemotherapy including gemcitabine, platinum analogues or their combination are at higher risk of TEs. Our results also suggest that outpatients receiving chemotherapy regimens including these agents might achieve an increased benefit from thromboprophylaxis with nadroparin. Clinical Trial registration number: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00951574">NCT 00951574</a></p

Cause and Effect of Feedback: Multiphase Gas in Cluster Cores Heated by AGN Jets

Multiwavelength data indicate that the X-ray emitting plasma in the cores of galaxy clusters is not cooling catastrophically. To large extent, cooling is offset by heating due to active galactic nuclei (AGN) via jets. The cool-core clusters, with cooler/denser plasmas, show multiphase gas and signs of some cooling in their cores. These observations suggest that the cool core is locally thermally unstable while maintaining global thermal equilibrium. Using high-resolution, three-dimensional simulations we study the formation of multiphase gas in cluster cores heated by highly-collimated bipolar AGN jets. Our key conclusion is that spatially extended multiphase filaments form only when the instantaneous ratio of the thermal instability and free-fall timescales (t_TI/t_ff) falls below a critical threshold of \approx 10. When this happens, dense cold gas decouples from the hot ICM phase and generates inhomogeneous and spatially extended Halpha filaments. These cold gas clumps and filaments `rain' down onto the central regions of the core, forming a cold rotating torus and in part feeding the supermassive black hole. Consequently, the self-regulated feedback enhances AGN heating and the core returns to a higher entropy level with t_TI/t_ff > 10. Eventually the core reaches quasi-stable global thermal equilibrium, and cold filaments condense out of the hot ICM whenever t_TI/t_ff \lesssim 10. This occurs despite the fact that the energy from AGN jets is supplied to the core in a highly anisotropic fashion. The effective spatial redistribution of heat is enabled in part by the turbulent motions in the wake of freely-falling cold filaments. Increased AGN activity can locally reverse the cold gas flow, launching cold filamentary gas away from the cluster center. Our criterion for the condensation of spatially extended cold gas is in agreement with observations and previous idealized simulations.Comment: Submitted to ApJ; 16 pages, 11 figure

Cosmic Ray Generation by Quasar Remnants: Constraints and Implications

The quasar remnant cores of nearby giant elliptical galaxies NGC 4486 (M87), NGC 1399, NGC 4649 and NGC 4472 are the sites of supermassive (greater than one billion solar masses) black holes. These objects are investigated as to the viability of the conjecture that they could harbor compact dynamos capable of generating the highest energy cosmic rays. For an accretion process involving an equipartition magnetic field near the event horizons of the underlying putative spun-up black holes, the energy achievable in accelerating protons could well be greater or equal than 100 EeV for all these when only considering the drag induced by curvature radiation. Estimates of the SED (spectral energy distribution) of ambient core photons lead to the conclusion that the energy losses arising from photo-pion production in proton collisions with these target photons are relatively small for all but M87. For M87, the ambient photon field is likely to be a limiting factor. Accretion rates on the order of one solar mass per year, comparable to the Bondi rates and to the stellar mass loss rates, are associated with (greater than 100 EeV) cosmic ray generation in the other (electromagnetically dark) galactic core sites. If these sites are found to be sources of such cosmic rays, it would suggest the presence of a global inflow of interstellar gas all the way into the center of the host galaxy.Comment: 11 pages Latex, no figures, uses mn and amssymb style files, accepted for publication in MNRA

Combining Semi-analytic Models with Simulations of Galaxy Clusters: the Need for Heating from Active Galactic Nuclei

We present hydrodynamical N-body simulations of clusters of galaxies with feedback taken from semi-analytic models of galaxy formation. The advantage of this technique is that the source of feedback in our simulations is a population of galaxies that closely resembles that found in the real universe. We demonstrate that, to achieve the high entropy levels found in clusters, active galactic nuclei must inject a large fraction of their energy into the intergalactic/intracluster media throughout the growth period of the central black hole. These simulations reinforce the argument of Bower et al., who arrived at the same conclusion on the basis of purely semi-analytic reasoning.Comment: 25 pages and 10 colour figures. Accepted by Ap