A ring in a shell: the large-scale 6D structure of the Vela OB2 complex

The Vela OB2 association is a group of 10 Myr stars exhibiting a complex spatial and kinematic substructure. The all-sky Gaia DR2 catalogue contains proper motions, parallaxes (a proxy for distance) and photometry that allow us to separate the various components of Vela OB2. We characterise the distribution of the Vela OB2 stars on a large spatial scale, and study its internal kinematics and dynamic history. We make use of Gaia DR2 astrometry and published Gaia-ESO Survey data. We apply an unsupervised classification algorithm to determine groups of stars with common proper motions and parallaxes. We find that the association is made up of a number of small groups, with a total current mass over 2330 Msun. The three-dimensional distribution of these young stars trace the edge of the gas and dust structure known as the IRAS Vela Shell across 180 pc and shows clear signs of expansion. We propose a common history for Vela OB2 and the IRAS Vela Shell. The event that caused the expansion of the shell happened before the Vela OB2 stars formed, imprinted the expansion in the gas the stars formed from, and most likely triggered star formation.Comment: Accepted by A&A (02 November 2018), 13 pages, 9+2 figure

Zymomonas mobilis in Bread Dough: Characterization of Dough Leavening Performance in Presence of Sucrose

Zymomonas mobilis, because of its fermentative metabolism, has potential food applications in the development of leavened baked goods consumable by people with adverse responses to Saccharomyces cerevisiae. Since Z. mobilis is not able to utilize maltose present in flour, the effect of sucrose addition (2.5 g/100 g flour) on bread dough leavening properties was studied. For comparison purposes, leavening performances of S. cerevisiae with and without sucrose were also investigated. Doughs leavened by Z. mobilis without sucrose addition showed the lowest height development (14.95 +/- 0.21 mm) and CO2 production (855 +/- 136 mL). When sucrose was added, fermentative performances of Z. mobilis significantly (p < 0.05) improved (+80% and +85% of gas production and retention, respectively), with a dough maximum height 2.6 times higher, results indicating that Z. mobilis with sucrose can be leavened in shorter time with respect to the sample without addition. S. cerevisiae did not benefit the sucrose addition in terms of CO2 production and retention, even if lag leavening time was significantly (p < 0.05) shorter (about the half) and time of porosity appearance significantly (p < 0.05) longer (about 26%) with respect to S. cerevisiae alone. Results demonstrate that in the presence of sucrose, Z. mobilis can efficiently leaven a bread dough, thus providing innovation possibilities in the area of yeast-free leavened products

FROM FOOD WASTE TO FOOD PRESERVATION: PRODUCTION AND APPLICATION OF SAKACIN A

This thesis has been conceived in the frame of a broader project named \u201cNANOSAK- Nanocellulose\u2013sakacin A conjugates for food packaging purposes\u201d, financend by Fondazione Cariplo and developed in collaboration with several divisions of the Department of Food, Environmental and Nutritional Sciences (DeFENS), with the Department of Environmental Science and Policy (ESP) of the Universit\ue0 degli Studi di Milano and together with the Department of Food quality and preservation of the Instituto de Agroqu\uedmica y Tecnolog\ueda de Alimentos (IATA), CSIC (Valencia, Spain). NANOSAK aims at exploring the use of cheese whey and/or their derivatives as cheap substrates for growth of bacterial species that produce two families of molecules: a specific bacteriocin sakacin A, and bacterial cellulose (BC), that will be turned into nanocellulose (BNC) using sustainable procedures. In Italy most of the liquid whey is exported, often after an ultrafiltration (UF) step. The by-product of whey UF, namely permeate, still represents a valuable raw material due to the high content of lactose, minerals and vitamins. This permeate from the dairy industry is a low-cost alternative for industrial production, which can provide high yields of the antimicrobial agent. Both the molecules, sakacin A and bacterial cellulose, expected to be produced by microorganisms through whey utilization can be considered products of high added value. Bacterial cellulose also represents an emerging material with excellent intrinsic properties due to its high crystallinity, tensile strength and water holding capacity (Shoda and Sugano, 2005). On a subsequent step, NANOSAK will also aim at using sustainable procedures for turning BC into nanocellulose, in fact, bacterial cellulose has potential to be turned into bacterial nanocellulose by chemical modification, thus forming an innovative material that finds applications across several industrial sectors, including the use in the food packaging sector. Recently, more attention was given to the development of packaging materials based on bacterial nanocellulose as functional nanofiller in papers and in coatings for plastic matrices. An interesting application is related to the use of cellulose nanocomposites to extend shelf-life and enhance the quality of perishable foods, not only acting as barriers against moisture, water vapor and gasses but also serving as a carrier of active substances, such antimicrobials, in bioactive packaging (Lee et al., 2013). In particular, stand-alone BNC films and coatings incorporating sakacin A will be developed, using food-compatible biopolymers and aqueous chemistry. BNCs/sakacin A conjugates will also be applied to paper by surface sizing. The functional properties of the nanocellulose/sakacin A films and coatings will be assessed, as well as the kinetics of sakacin A release in several food simulants, in order to establish suitable mathematical release models. The results will contribute to increase shelf-life and quality of perishable food. The main significance of NANOSAK is the demonstration that application of industrial biotechnologies will achieve innovative and highly sustainable bioprocesses. The bioeconomic model approach developed by the project would give original opportunities to improve the sustainability of Lombardy economy, in the general food sector, and for what attains food packaging operators. In particular, the focus of this thesis is the optimization of the production of the bacteriocin sakacin A using cheese whey permeate, its food-grade isolation and purification and the development of active packaging solutions based on the antimicrobial activity of this molecules

Chemical Range of Stability for Self-Dusting Ladle Furnace Slags and Destabilizing Effect of Sulfur

Ladle furnace slags are characterized by volumetric expansions associated with the transition of dicalcium silicate (C2S) from β to γ phase, which generates fine dust during cooling, causing handling and storage issues that further reduce their recycling opportunities. The present work focuses on the effect of slag basicity on dusting and the role of sulfur on slag stability. Seven synthetic ladle slag precursors were made by mixing lime, magnesia, quartz and alumina in different proportions to match effective industrial compositions, increasing the binary basicity and keeping the ternary and quaternary indexes unchanged. Samples were heated to 1500 °C for 15 min and monitored during air cooling (< 5 °C/s) through thermocouples and camera to characterize the behavior, temperature, and time interval of dusting. The cooled samples were characterized chemically, mineralogically and morphologically. Starting from the chemistry of a self-stabilized slag, five additional slag precursors, characterized by increasing amounts of S, were created and analyzed using the same procedures. Experimental evidence showed the presence of three different dusting behaviors (stable, partial and complete) and stabilization of the slag once an optical basicity of 0.748 or higher was reached. In addition, mayenite was identified as the main phase capable of suppressing the β to γ transition by exerting hydrostatic pressure on C2S. Finally, although S can stabilize the β phase when dissolved in it, after saturation it precipitates as CaS, which can react with mayenite, locally decreasing the optical basicity and allowing dusting. Graphical Abstract: [Figure not available: see fulltext.]

NON-METALLIC INCLUSIONS AND CLEAN STEEL

The source, the removal and the mechanical consequences of the non-metallic inclusions depends on their types and on their engineering. The chemical composition of the non-metallic inclusions and their volume fraction are determined by the management of the different steps involved in the production process: melting, refining and casting operation. Thus, the inclusional population depends on the relation existing between the applied operative parameters and the features of the steel grades to be produced. A synthetic and critical evaluation of the main aspects involved in the control of the non-metallic inclusions has been presented pointing out the main aspect for the designing of a correct production route and the consequences on the application field

Processing and characterization of dual phase steel foam

Porous materials featuring cellular structures are known to have many interesting combinations of physical and mechanical properties. Some of them have been extensively used in the transportation field (i.e. balsa wood). Steel foams presented promising theoretical properties for both functional and structural applications in transportation, but processing of such a kind of foams is complex due to their high melting point. Recently a technique for processing Cu-based alloys open-cell foams through the molten metal infiltration of a leachable bed of amorphous SiO2 particles was proposed. A variation of the proposed technique that uses SiC particles as space holder is now presented and was recently successfully applied for dual phase steel foam processing. Results from a processing of dual phase DP500 steel foams, including some morphological, micro-structural and mechanical characterization, are here presented

Mechanical and tribo-metallurgical behavior of 17-4 precipitation hardening stainless steel affected by severe cold plastic deformation: a comprehensive review article

This article comprehensively reviews the mechanical properties and tribo-metallurgical behavior of 17-4 precipitation hardening stainless steel (17-4PH SS) during and after cold plastic deformation. Referring to the scientific literature, stainless steels are one of the few types of ferrous alloys which could be appropriately set up through cold working processes in the forms of sheets or other shapes. Likewise, some other metal alloys such as mild low-carbon-based steels, copper and its alloys, aluminum alloys, and some others are the few types of metal alloys which have this capability. On the other hand, in engineering applications, there are several types of mechanical failures, which must be taken into account to investigate the mechanical behavior and tribo-metallurgical properties of any targeted materials. For example, corrosion resistance, wear resistance, and fatigue failure are investigated according to the microstructural studies, comprising of the grain size, grain boundaries, orientations, dislocations, and so on. Based on the published results, focusing on 17-4PH SS, one of the most main effective factors on mechanical and tribo-metallurgical performance is the grain size. Also, the favorable balance of two mechanical properties of strength and ductility has been reported as a dilemma in the materials science, and the problem delineates upon the limitations of numerous structural materials potentials. Following the failure analysis of the materials, in order to diminish the damages caused by fretting fatigue some methods such as ultrasonic processes are applied for the treatment of 17-4PH SS via changing the microstructure, residual stress, and other parameters. Also, through the other cold deformation technologies, the nanostructured surface layer with highly upgraded mechanical properties of several ultrasonic surface rolling process-treated 17-4PH SS has been obtained. To this end, such cold working processes on 17-4PH SS and their subsequent results are elaborated in this review paper. Graphical abstract: [Figure not available: see fulltext.

RESEARCH OF THE BEST TECHNOLOGICAL AND METALLURGICAL PARAMETERS FOR PERFORMING THE ELECTRIC RESISTANCE WELDING OF LOW CARBON STEELS

This work deals with the research of the optimal technological and metallurgical parameters in order to implement a reliable procedure for the electric resistive welding of low carbon structural steel, in order to evaluate the conditions which can grant the best mechanical performances. Low carbon steels must be featured by high plastic formability properties, since the production process consists in the piping of a rolled band, followed by an Electric Resistance Welding (ERW) of the edges. The optimal technological parameters have been identified performing welding tests at several levels of electric power, squashing length and forward velocity of the pipe along the coil axis. Several mechanical tests have been performed for the determination of the properties of the materials under examination, in order to characterize the main mechanical properties, i.e. Young modulus, yield and the ultimate stresses, yield point elongation (the strain after which the plastic behaviour takes place), anisotropy coefficients (rm, ?r), Vickers micro-hardness and hardening coefficient of the materials analysed, while the residual stress induced in correspondence of the welded joining have been determined by X-ray diffraction. The microstructural characteristics of the steels have been obtained through micrographic analyses coupled with the use of Electron Back Scattered Diffraction techniques (EBSD). The value assumed by the hardening coefficient and by the yield elongation point has been revealed to be a strongly significant parameter for assuring the quality of the joining in order to avoid a very early formation of the cracks in the welding region

Numerical modelling of Auriga's Wheel - a new ring galaxy

We model the formation of Auriga's Wheel - a recently discovered collisional ring galaxy. Auriga's Wheel has a number of interesting features including a bridge of stars linking the neighbouring elliptical to the ring galaxy, and evidence for components of expansion and rotation within the ring. Using N-body/SPH modelling, we study collisions between an elliptical galaxy and a late-type disk galaxy. A near direct collision, with a mildy inclined disk, is found to reasonably reproduce the general system morphology ~50 Myr following the collision. The collision must have a relatively low velocity (initially ~150 km s^{-1}) in order to form the observed bridge, and simultaneously match the galaxies separation. Our best-match model suggests the total disk galaxy is ~5 times more massive than the elliptical. We find that the velocity of expansion of the ring is sensitive to the mass of the elliptical, while insensitive to the encounter velocity. We evolve our simulation beyond the current epoch to study the future destiny of the galaxy pair. In our model, the nucleus moves further away from the plane of the ring in the direction of the stellar bridge. The nucleus eventually merges with the elliptical galaxy ~100 Myr after the present time. The ring continues to expand for ~200 Myr before collapsing back. The low initial relative velocity of the two galaxies will eventually result in a complete merger.Comment: Accepted to MNRAS, March 9th, 2012. 17 pages, 16 figures, no table

Development of interconnected silicon micro-evaporators for the on-detector electronics cooling of the future ITS detector in the ALICE experiment at LHC

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The design of the future High Energy Physics (HEP) particle detectors for the upgrade of the LHC (Large Hadron Collider) experiments at CERN (European Organization for Nuclear Research) is pushing technological frontiers to the limit trying to reach unprecedented accuracy in particles identification and particle production dynamics in ultra-relativistic hadron collisions. The thermal management of the on-detector electronics and the development of low mass integrated cooling systems have become a crucial task in the design of silicon tracking detectors for HEP applications. In this paper, we present a novel concept of low mass interconnected silicon microchannel devices for the future Inner Tracking System of the ALICE (A Large Ion Collider Experiment) detector at LHC. This innovative design achieves the requirements of the detector while minimizing the total material budget