Application of spherical nanoindentation to determine the pressure of cavitation impacts from pitting tests

This article focuses on the use of spherical nanoindentation measurements to estimate the pressure of cavitation impacts and its statistical distribution. Indeed, nanoindentation techniques are supposed to represent an effective tool in this field due to the similarities between substrate deformation under liquid impact and indentation testing. First, nanoindentation experiments were used to extract the mechanical parameters of a Nickel-Aluminum-Bronze alloy; second, pitting tests were performed at different operating pressures, and the geometrical characteristics of the pits were measured; and finally, the spectra of impact pressure and loads responsible for material erosion were obtained by coupling the findings of indentation tests with the analysis of pitting tests. Results assessed the capability of the proposed methodology to quantify the hydrodynamic aggressiveness of the cavitating flow. This procedure, which assumes the material itself as a sensor that is able to detect the impact loads, could represent an alternative solution to pressure transducers in estimating the cavitation intensit

Mission Analysis for the Don Quijote Phase-A Study

The Don Quijote Phase-A study is a definition study funded by ESA and devoted to the analysis of the possibilities to deflect a Near Earth Object (NEO) in the range of 300-800 m diameter. DEIMOS Space S.L. and EADS Astrium have teamed up within this study to form one of the three consortia that have analyzed these aspects for ESA. Target asteroids for the mission are 1989 ML, 2002 AT4 and Apophis. This paper presents the mission analysis activities within the consortium providing: low-thrust interplanetary rendezvous Orbiter trajectories to the target asteroids, ballistic interplanetary trajectories for the Impactor, Orbiter arrival description at the asteroids, Orbiter stable orbits characterization at the asteroid, deflection determination by means of a Radio Science Experiment (RSE) as well as the mission timelines and overall mission scenarios

The SIROCO Asteroid Deflection Demonstrator

There is evidence of past Near-Earth-Objects (NEOs) impacts on Earth and several studies indicating that even relatively small objects are capable of causing large local damage, either directly or in combination with other phenomena, e.g. tsunamis. This paper describes a space mission concept to demonstrate some of the key technologies to rendezvous with an asteroid and accurately measure its trajectory during and after a deflection maneuver. The mission, called SIROCO, makes use of the recently proposed ion beam shepherd (IBS) concept where a stream of accelerated plasma ions is directed against the surface of a small NEO resulting in a net transmitted deflection force. We show that by carefully selecting the target NEO a measurable deflection can be obtained in a few weeks of continuous thrust with a small spacecraft and state of the art electric propulsion hardware

Assessment of GNC Impacts of Chemical Plume Impingement in the Case of Prisma Irides Experiment

This paper presents the preliminary analysis of an in-orbit demonstration opportunity to test plume impingement as a viable means to change the attitude state of a space debris based on the Prisma and Picard missions. This technique has been proposed as part of the COBRA concept studied by ESA in collaboration with GMV, Politecnico di Milano and Thales-Alenia Space, as an active debris removal concept relying on the exhaust plume of a monopropellant chemical propulsion system as a means to impart momentum and ultimately modify the orbit of a space debris object in a contactless manner. The feasibility of the experiment is presented as well as its critical areas, no showstoppers are identified

Orientation and size-dependent mechanical modulation within individual secondary osteons in cortical bone tissue

Anisotropy is one of the most peculiar aspects of cortical bone mechanics; however, its anisotropic mechanical behaviour should be treated only with strict relationship to the length scale of investigation. In this study, we focus on quantifying the orientation and size dependence of the spatial mechanical modulation in individual secondary osteons of bovine cortical bone using nanoindentation. Tests were performed on the same osteonal structure in the axial (along the long bone axis) and transverse (normal to the long bone axis) directions along arrays going radially out from the Haversian canal at four different maximum depths on three secondary osteons. Results clearly show a periodic pattern of stiffness with spatial distance across the osteon. The effect of length scale on lamellar bone anisotropy and the critical length at which homogenization of the mechanical properties occurs were determined. Further, a laminate-composite-based analytical model was applied to the stiffness trends obtained at the highest spatial resolution to evaluate the elastic constants for a sub-layer of mineralized collagen fibrils within an osteonal lamella on the basis of the spatial arrangement of the fibrils. The hierarchical arrangement of lamellar bone is found to be a major determinant for modulation of mechanical properties and anisotropic mechanical behaviour of the tissue.MIT-Italy ProgramMIT-Italy Program. Progetto Rocca FellowshipUnited States. Office of Naval Research (Grant N00014-08-1-0510)Singapore-MIT Alliance Advanced Materials for Micro and Nano Systems Programm

Engineered yeast for enhanced CO2 mineralization

In this work, a biologically catalysed CO2 mineralization process for the capture of CO2 from point sources was designed, constructed at a laboratory scale, and, using standard chemical process scale-up protocols, was modelled and evaluated at an industrial scale. A yeast display system in Saccharomyces cerevisae was used to screen several carbonic anhydrase isoforms and mineralization peptides for their impact on CO2 hydration, CaCO3 mineralization, and particle settling rate. Enhanced rates for each of these steps in the CaCO3 mineralization process were confirmed using quantitative techniques in lab-scale measurements. The effect of these enhanced rates on the CO2 capture cost in an industrial scale CO2 mineralization process using coal fly ash as the CaO source was evaluated. The model predicts a process using bCA2-yeast and fly ash is [similar]10% more cost effective per tonne of CO2 captured than a process with no biological molecules, a savings not realized by wild-type yeast and high-temperature stable recombinant CA2 alone or in combination. The levelized cost of electricity for a power plant using this process was calculated and scenarios in which this process compares favourably to CO2 capture by MEA absorption process are presented.MIT Energy InitiativeEni S.p.A. (Firm)National Institutes of Health (U.S.) (NIH Biotechnology Training Program)Thomas and Stacey Siebel Foundatio

Could Aeromonas spp. be considered a vector of resistance genes from the environment to human intestinal flora?

Work carried out at the Laboratory of Applied Microbiology, Bellinzona, CHopenAntibiotic resistant bacteria and antibiotic resistance genes cause increasing problems in clinical setting and are considered emerging environmental contaminants. In the environment, antibiotic resistant bacteria may be inactivated but their resistance determinants may become part of the environmental gene pool and may move back to human and animal intestinal flora via food and drinking water. In order to assess the role of Aeromonas spp. in the flow of resistant determinants, we analyzed by resistance profiles, plasmidic and integrons content and characterization, 231 Aeromonas spp. and 250 Fecal Coliforms isolated from different aquatic environments. Resistance patterns could be related to both the presence of multiple plasmids and to the origin of the strains. The 31.7% of the plasmids carried by the Aeromonas strains were mobilizable as assess by dot-blot of MOB-subfamily covering the BHR (Broad Host Range) incompatibility groups. The majority (75%) of the Class 1 integrons were chromosomally locate and were found in the 27.7% of the Aeromonas spp. tested. The number and type of resistance genes identified so far on Aeromonas spp. Support the hypothesis of considering these bacteria as a "reservoir" of resistance genes. The capability of some Aeromonas strains to transfer their resistance to Fecal Coliform has been demonstrated, thus allowing to assert its role as a “vector” of resistance genes to members of the human intestinal flora.openAnalisi, Protezione e Gestione delle BiodiversitàCarnelli, AlessandroCarnelli, Alessandr

Pond Secrets: Reflections for Thought and Virtue

Pond secrets is an original play designed to create a context for motivating children to learn and practice critical thinking in its strongest sense through reflective dialogue and improvisational drama. The story\u27s design, content, and suggested methodology are theoretically consistent with Brain-based learning theory, which asserts that memorable learning occurs when children can integrate concepts, emotions, and values in a meaningful context and environment. Using a mythical setting and features of classical literature, Pond secrets invites children to join the animals of Pond as they gather to examine their thinking and affirm the meaning of friendship, citizenship, and justice. Not settling on any one definition of critical thinking, Pond secrets reflects a synthesis of expert descriptions that advances the following modified definition: Critical thinking is used to make decisions, form beliefs, solve problems, and learn new concepts. It is a dialogical questioning process that uses reasonable and imaginative reflection. Additionally, it is a purposive and disciplined process that relies on criteria, is self-correcting, and is sensitive to context. In its strongest sense, critical thinking is fair-minded and caring. Moreover, Pond secrets targets the following critical thinking skills for development : making a reliable observation, evaluating a source of information forming a reliable framework for perspectives, and examining cause and effect relationships. The target skills are infused and interwoven in the story to enable children to develop skill using them individually and together as a process transferable through subject domain. Pond secrets models a community of inquiry that provokes integrative learning while promoting the application of critical and creative thinking to the moral domain of reasoning. As a framework for deliberation and dialogue, Pond secrets develops a model of justice that balances the principles of equal treatment and beneficence; Pond secrets replaces beneficence with the ethic of caring as a more accurate description of the orientation of empathic underscoring the promotion of goodness. Pond secrets is accompanied by a theoretical guide that discusses the main ideas relevant to its implementation. The guide reviews cognitive development, issues of indoctrination, the psychological and philosophical underpinning of the justice model, and critical and creative thinking as relevant to Pond secret\u27s content and methodology. Pond secrets offers the educator free imaginative reign to design lesson plans that suit the needs of the learning environment, provided that the criteria of critical thinking and the justice model are adhered to in methodology that is neutral and accordance with Brain based learning theory

ASIME 2018 White Paper. In-Space Utilisation of Asteroids: Asteroid Composition -- Answers to Questions from the Asteroid Miners

In keeping with the Luxembourg government's initiative to support the future use of space resources, ASIME 2018 was held in Belval, Luxembourg on April 16-17, 2018. The goal of ASIME 2018: Asteroid Intersections with Mine Engineering, was to focus on asteroid composition for advancing the asteroid in-space resource utilisation domain. What do we know about asteroid composition from remote-sensing observations? What are the potential caveats in the interpretation of Earth-based spectral observations? What are the next steps to improve our knowledge on asteroid composition by means of ground-based and space-based observations and asteroid rendez-vous and sample return missions? How can asteroid mining companies use this knowledge? ASIME 2018 was a two-day workshop of almost 70 scientists and engineers in the context of the engineering needs of space missions with in-space asteroid utilisation. The 21 Questions from the asteroid mining companies were sorted into the four asteroid science themes: 1) Potential Targets, 2) Asteroid-Meteorite Links, 3) In-Situ Measurements and 4) Laboratory Measurements. The Answers to those Questions were provided by the scientists with their conference presentations and collected by A. Graps or edited directly into an open-access collaborative Google document or inserted by A. Graps using additional reference materials. During the ASIME 2018, first day and second day Wrap-Ups, the answers to the questions were discussed further. New readers to the asteroid mining topic may find the Conversation boxes and the Mission Design discussions especially interesting.Comment: Outcome from the ASIME 2018: Asteroid Intersections with Mine Engineering, Luxembourg. April 16-17, 2018. 65 Pages. arXiv admin note: substantial text overlap with arXiv:1612.0070