Initial stages of oxidation at noble metal surfaces: The cases of Ag and Cu

The initial stages of oxide nucleation and surface oxide formation are hot topics at the moment due to the possible application of these materials in many fields of science and technology. The understanding of the parameters controlling these processes is therefore pivotal not only for the fundamental knowledge of the physical phenomenon but also for enabling the growth of better quality oxide phases, with a higher degree of order and/or a lower density of contaminants. Here I will summarize the main results obtained by a collaboration between experimental groups in Genova and Osaka and between the experimentalists in Genova and theoretical groups in Trieste and Ljubljana, on the initial oxidation of the noble metals Ag and Cu. I will show that the local morphology of surface defects and/or the dosing conditions are essential elements to determine the nature of the oxide form which starts to nucleate upon exposure to O2. On stepped Ag we find that, under vacuum conditions, the stoichiometry of the initial oxide nuclei is tuned by the atomic geometry at the low coordination site, while on Cu(410) the oxidation efficiency comes out to be highly enhanced both by the presence of steps and by exposure to hyperthermal oxygen. The relative amount of cuprous and cupric oxide formed depends on oxidation temperature

Comparison of experimental and numerical sloshing loads in partially filled tanks

Sloshing phenomenon consists in the movement of liquids inside partially filled tanks, whichgenerates dynamic loads on the tank structure. Resulting impact pressures are of great importance in assessingstructural strength, and their correct evaluation still represents a challenge for the designer due to the highnonlinearities involved, with complex free surface deformations, violent impact phenomena and influence of airtrapping. In the present paper a set of two-dimensional cases for which experimental results are available areconsidered to assess merits and shortcomings of different numerical methods for sloshing evaluation, namely twocommercial RANS solvers (FLOW-3D and LS-DYNA), and two own developed methods (Smoothed ParticleHydrodynamics and RANS). Impact pressures at different critical locations and global moment induced by watermotion for a partially filled tank with rectangular section having a rolling motion have been evaluated and resultsare compared with experiments

Application of computer vision techniques to measure cavitation bubble volume and cavitating tip vortex diameter.

In present paper application of computer vision techniques to propeller cavitation experiments is presented. These techniques are widely adopted in many different environments and therefore they are well documented. They are also attractive from an economic point of view, due to relative low cost of the hardware involved. Nevertheless their application to study propeller behavior in cavitation tunnel is not straightforward, because of the nonstandard environment. However the adoption of these techniques may open a wide field of investigation and can result in a deepening of knowledge in propeller cavitation phenomena. In particular, obtained data can be linked to connected topics, such as propeller radiated noise or pressure signature, providing a better understanding on the sources of these effects, and invaluable information for validation of computer simulations. Present paper traces a possible path to develop an experimental technique, covering theoretical points as well as data analysis strategies and other practical aspects. All techniques are presented through practical application, thus making clearer their points of strength and their shortcomings. Besides achieved results, possible improvements and future developments are outlined.http://deepblue.lib.umich.edu/bitstream/2027.42/84235/1/CAV2009-final35.pd

Hydrogen induced optically-active defects in silicon photonic nanocavities

This work was supported by Era-NET NanoSci LECSIN project coordinated by F. Priolo, by the Italian Ministry of University and Research, FIRB contract No. RBAP06L4S5 and by the EPSRC UKSp project. Partial financial support by the Norwegian Research Council is also acknowledged.We demonstrate intense room temperature photoluminescence (PL) from optically active hydrogen- related defects incorporated into crystalline silicon. Hydrogen was incorporated into the device layer of a silicon on insulator (SOI) wafer by two methods: hydrogen plasma treatment and ion implantation. The room temperature PL spectra show two broad PL bands centered at 1300 and 1500 nm wavelengths: the first one relates to implanted defects while the other band mainly relates to the plasma treatment. Structural characterization reveals the presence of nanometric platelets and bubbles and we attribute different features of the emission spectrum to the presence of these different kind of defects. The emission is further enhanced by introducing defects into photonic crystal (PhC) nanocavities. Transmission electron microscopy analyses revealed that the isotropicity of plasma treatment causes the formation of a higher defects density around the whole cavity compared to the ion implantation technique, while ion implantation creates a lower density of defects embedded in the Si layer, resulting in a higher PL enhancement. These results further increase the understanding of the nature of optically active hydrogen defects and their relation with the observed photoluminescence, which will ultimately lead to the development of intense and tunable crystalline silicon light sources at room temperature.Publisher PDFPeer reviewe

PRIVATE CHOICES, PUBLIC ISSUES. THE ETHICS OF HEALTH POLICY IN THE FACE OF DIET RELATED DISEASES.

The epidemic of diet related disease is a fundamental fact of epidemiology that our societies are increasingly facing. It calls for policy responses and amendments of our systems of health care. These actions and reforms intersect several loci of moral and political disagreement in the public sphere: the acceptability of public paternalism, the appropriate consideration of personal responsibility in health care and the moral and political significance of social health inequalities. I offer a treatment of these three broad normative issues in order to inform discussions about appropriate responses to diet related diseases. (1) I argue that antipaternalism is overstated if not understood in welfarist terms: within the latter framework, evidence for poor capability in dietary choices is a sound reason for intervention. (2) I distinguish distributive and efficiency concerns regarding personal responsibility for health, arguing that there is no defensible conception of the former. (3) I dismiss efforts to understand the moral importance of social health inequalities in terms of health entitlements and reject investment-like approaches to inequalities framed in terms of \u201cequality of opportunity\u201d: the fight against health inequalities is vivified by a renewed interest in the social goods attached to robust socio-economic egalitarianism. Together, these three theses lead away from policies focused on individuals, their responsibility and their productive importance for society and support both public health interventions on the environment where people live and continuous defense of traditional unconditional health care provision

Influence of growing conditions on the reactivity of Ni supported graphene towards CO

Free standing graphene is chemically inert but, as recently demonstrated, CO chemisorption occurs at low crystal temperature on the single layer grown by ethene dehydrogenation on Ni(111). Such layer is inhomogeneous since different phases coexist, the relative abundance of which depends on the growth conditions. Here we show by X ray photoemission and high resolution electron energy loss spectroscopies that the attained CO coverage depends strongly on the relative weight of the different phases as well as on the concentration of carbon in the Ni subsurface region. Our data show that the chemical reactivity is hampered by the carbon content in the substrate. The correlation between the amount of adsorbed CO and the weight of the different graphene phases indicates that the top-fcc configuration is the most reactive

Nanoscale magnetic field mapping with a single spin scanning probe magnetometer

We demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique on the electron spin resonance frequency of a single nitrogen-vacancy defect placed at the apex of an atomic force microscope tip. In addition, we report an all-optical magnetic imaging technique which is sensitive to large off-axis magnetic fields, thus extending the operation range of diamond-based magnetometry. Both techniques are illustrated by using a magnetic hard disk as a test sample. Owing to the non-perturbing and quantitative nature of the magnetic probe, this work should open up numerous perspectives in nanomagnetism and spintronics

Optimization of surface textures in hydrodynamic lubrication through the adjoint method

In this work we assess the applicability of the adjoint optimization technique for determining optimal surface topographies of two surfaces in relative motion in presence of a thin lubricant films that can cavitate. Among the existing numerical tools for topology optimization in engineering problems, the adjoint method represents a promising and versatile technique, which can also be applied to the field of full film tribology. In particular, the design of surfaces with complex textures can thoroughly benefit from this method, as it allows dealing with a large number of degrees of freedom at low computational cost. We show that this optimization method can be successfully applied to cavitating lubricant flows such as in pin-on-disc tribometers, giving the possibility to extend the results also to other typical applications such as journal and slider bearings. It is shown that the adjoint method can optimize the whole gap height distribution point by point in a more efficient way than traditional optimization approaches and parametric studies. In particular, thanks to the sensitivity analysis the adjoint method is able to find the placement and depth profile of each texture element

Boschi vetusti e riserve forestali nel Veneto: patrimoni di biodiversita\u300

Vengono sintetizzate le criticita\u300 emergenti legate alle dinamiche di cambiamento della biodiversita\u300 nelle foreste del Veneto anche esaminando i dati delle politiche forestali degli ultimi decenni e delle trasformazioni di boschi e foreste di montagna, collina e pianura conseguenti all\u2019abbandono colturale e ad iniziative locali di contrasto alle alterazioni del paesaggio forestale, di miglioramento ambientale ed estetico e di difesa della biodiversita\u300 forestale e naturalistica dei territori del Veneto. Seppur in un confronto europeo l'Italia e\u300 forse uno degli stati piu\u300 virtuosi nella gestione del patrimonio boschivo, sia in termini di risparmio di biomassa (35% di prelievo sull'incremento contro la media europea di oltre 60%) che per modalita\u300 di prelievo (e\u300 uno dei pochi stati dove il taglio a raso e\u300 vietato e, a differenza di molti paesi europei, non ammette l'imboschimento con specie esotiche), in questo approfondimento vengono esaminati gli scenari possibili di riferimento per una programmazione piu\u300 mirata, incisiva ed innovativa delle politiche di tutela della biodiversita\u300 forestale del Veneto, guardando ad alcune esperienze europee volte alla tutela e valorizzazione dei boschi antichi o vetusti. Boschi e foreste si stanno espandendo nel Veneto anche in pianura: ma questo trend e\u300 frutto dell\u2019abbandono colturale e/o conseguenza di una programmazione territoriale adeguata? Si propongono linee guida per iniziative locali di contrasto alla banalizzazione estetica ed ambientale del paesaggio e per contro di miglioramento della difesa della biodiversita\u300 forestale e naturalistica dei territori del Veneto partendo dalla tutela del patrimonio genetico dei \u201cboschi vetusti\u201d

Keeping track of phaeodactylum tricornutum (Bacillariophyta) culture contamination by potentiometric e-tongue

The large-scale cultivation of microalgae provides a wide spectrum of marketable bioproducts, profitably used in many fields, from the preparation of functional health products and feed supplement in aquaculture and animal husbandry to biofuels and green chemistry agents. The commercially successful algal biomass production requires effective strategies to maintain the process at desired productivity and stability levels. Hence, the development of effective early warning methods to timely indicate remedial actions and to undertake countermeasures is extremely important to avoid culture collapse and consequent economic losses. With the aim to develop an early warning method of algal contamination, the potentiometric E-tongue was applied to record the variations in the culture environments, over the whole growth process, of two unialgal cultures, Phaeodactylum tricornutum and a microalgal contaminant, along with those of their mixed culture. The E-tongue system ability to distinguish the cultures and to predict their growth stage, through the application of multivariate data analysis, was shown. A PLS regression method applied to the E-tongue output data allowed a good prediction of culture growth time, expressed as growth days, with R-2 values in a range from 0.913 to 0.960 and RMSEP of 1.97-2.38 days. Moreover, the SIMCA and PLS-DA techniques were useful for cultures contamination monitoring. The constructed PLS-DA model properly discriminated 67% of cultures through the analysis of their growth media, i.e., environments, thus proving the potential of the E-tongue system for a real time monitoring of contamination in microalgal intensive cultivation