634 research outputs found

    Missing Attention to Power Dynamics in Collaborative Multi-Actor Business Models for Sustainability

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    Advances within the Sustainability Business Models (SBMs) literature from the perspective of boundary-spanning business models have received limited attention. Further, discourse within the SBMs literature exploring collaborative practices adopts the perspective that collaborative forums are always a ‘force for good’. This paper reviews important theories and relevant literature and calls into question the dearth of research examining business models for sustainability and focuses on the role that power, and power relations, play in the shaping and steering of value creation. In advancing research on sustainable operations, we assess the implications of ignoring uneven power, and draw attention to the affects and consequences of this omission in the study of SBMs. By embracing an alternative, deliberative democracy perspective, we challenge the sub-literature on collaborative multi-actor business models. In taking an inquisitive and critical stance on omnipresent power dynamics, we shine a light on the consequences of uneven power across multi-actor structures by augmenting research with practical insights from selected vignettes. Our proposed concept of a democratic business model for sustainability offers a new strand of theoretical development and a fresh perspective on the sustainability and business models literature

    File Specification for the MERRA Aerosol Reanalysis (MERRAero): MODIS AOD Assimilation based on a MERRA Replay

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    This document describes the gridded output files produced by the Goddard Earth Observing System version 5 (GEOS-5) Goddard Aerosol Assimilation System (GAAS) from July 2002 through December 2014. The MERRA Aerosol Reanalysis (MERRAero) is produced with the hydrostatic version of the GEOS-5 Atmospheric Global Climate Model (AGCM). In addition to standard meteorological parameters (wind, temperature, moisture, surface pressure), this simulation includes 15 aerosol tracers (dust, sea-salt, sulfate, black and organic carbon), ozone, carbon monoxide and carbon dioxide. This model simulation is driven by prescribed sea-surface temperature and sea-ice, daily volcanic and biomass burning emissions, as well as high-resolution inventories of anthropogenic emission sources. Meteorology is replayed from the MERRA Reanalysis

    Numerical Simulations of Highly Porous Dust Aggregates in the Low-Velocity Collision Regime

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    A highly favoured mechanism of planetesimal formation is collisional growth. Single dust grains, which follow gas flows in the protoplanetary disc, hit each other, stick due to van der Waals forces and form fluffy aggregates up to centimetre size. The mechanism of further growth is unclear since the outcome of aggregate collisions in the relevant velocity and size regime cannot be investigated in the laboratory under protoplanetary disc conditions. Realistic statistics of the result of dust aggregate collisions beyond decimetre size is missing for a deeper understanding of planetary growth. Joining experimental and numerical efforts we want to calibrate and validate a computer program that is capable of a correct simulation of the macroscopic behaviour of highly porous dust aggregates. After testing its numerical limitations thoroughly we will check the program especially for a realistic reproduction of various benchmark experiments. We adopt the smooth particle hydrodynamics (SPH) numerical scheme with extensions for the simulation of solid bodies and a modified version of the Sirono porosity model. Experimentally measured macroscopic material properties of silica dust are implemented. We calibrate and test for the compressive strength relation and the bulk modulus. SPH has already proven to be a suitable tool to simulate collisions at rather high velocities. In this work we demonstrate that its area of application can not only be extended to low-velocity experiments and collisions. It can also be used to simulate the behaviour of highly porous objects in this velocity regime to a very high accuracy.The result of the calibration process in this work is an SPH code that can be utilised to investigate the collisional outcome of porous dust in the low-velocity regime.Comment: accepted by Astronomy & Astrophysic

    Collisions between equal sized ice grain agglomerates

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    Following the recent insight in the material structure of comets, protoplanetesimals are assumed to have low densities and to be highly porous agglomerates. It is still unclear if planetesimals can be formed from these objects by collisional growth. Therefore, it is important to study numerically the collisional outcome from low velocity impacts of equal sized porous agglomerates which are too large to be examined in a laboratory experiment. We use the Lagrangian particle method Smooth Particle Hydrodynamics to solve the equations that describe the dynamics of elastic and plastic bodies. Additionally, to account for the influence of porosity, we follow a previous developed equation of state and certain relations between the material strength and the relative density. Collisional growth seems possible for rather low collision velocities and particular material strengths. The remnants of collisions with impact parameters that are larger than 50% of the radius of the colliding objects tend to rotate. For small impact parameters, the colliding objects are effectively slowed down without a prominent compaction of the porous structure, which probably increases the possibility for growth. The protoplanetesimals, however, do not stick together for the most part of the employed material strengths. An important issue in subsequent studies has to be the influence of rotation to collisional growth. Moreover, for realistic simulations of protoplanetesimals it is crucial to know the correct material parameters in more detail.Comment: 7 pages, 11 figures, accepted by A&

    Ion size effects at ionic exclusion from dielectric interfaces and slit nanopores

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    A previously developed field-theoretic model [R.D. Coalson et al., J. Chem. Phys. 102, 4584 (1995)] that treats core collisions and Coulomb interactions on the same footing is investigated in order to understand ion size effects on the partition of neutral and charged particles at planar interfaces and the ionic selectivity of slit nanopores. We introduce a variational scheme that can go beyond the mean-field (MF) regime and couple in a consistent way pore modified core interactions, steric effects, electrostatic solvation and image-charge forces, and surface charge induced electrostatic potential. We show that in the dilute limit, the MF and the variational theories agree well with MC simulation results, in contrast to a recent RPA method. The partition of charged Yukawa particles at a neutral dielectric interface (e.g air-water or protein-water interface) is investigated. It is shown that as a result of the competition between core collisions that push the ions towards the surface, and repulsive solvation and image forces that exclude them from the interface, a concentration peak of finite size ions sets in close to the dielectric interface. We also characterize the role played by the ion size on the ionic selectivity of neutral slit nanopores. We show that the complex interplay between electrostatic forces, excluded volume effects induced by core collisions and steric effects leads to an unexpected reversal in the ionic selectivity of the pore with varying pore size: while large pores exhibits a higher conductivity for large ions, narrow pores exclude large ions more efficiently than small ones

    The MERRA-2 Aerosol Reanalysis, 1980 Onward. Part I: System Description and Data Assimilation Evaluation

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    The Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) updates NASA's previous satellite era (1980 - onward) reanalysis system to include additional observations and improvements to the Goddard Earth Observing System, Version 5 (GEOS-5) Earth system model. As a major step towards a full Integrated Earth Systems Analysis (IESA), in addition to meteorological observations, MERRA-2 now includes assimilation of aerosol optical depth (AOD) from various ground- and space-based remote sensing platforms. Here, in the first of a pair of studies, we document the MERRA-2 aerosol assimilation, including a description of the prognostic model (GEOS-5 coupled to the GOCART aerosol module), aerosol emissions, and the quality control of ingested observations. We provide initial validation and evaluation of the analyzed AOD fields using independent observations from ground, aircraft, and shipborne instruments. We demonstrate the positive impact of the AOD assimilation on simulated aerosols by comparing MERRA-2 aerosol fields to an identical control simulation that does not include AOD assimilation. Having shown the AOD evaluation, we take a first look at aerosol-climate interactions by examining the shortwave, clear-sky aerosol direct radiative effect. In our companion paper, we evaluate and validate available MERRA-2 aerosol properties not directly impacted by the AOD assimilation (e.g. aerosol vertical distribution and absorption). Importantly, while highlighting the skill of the MERRA-2 aerosol assimilation products, both studies point out caveats that must be considered when using this new reanalysis product for future studies of aerosols and their interactions with weather and climate

    Building a DMU e-Biology resource for health sciences’ students.

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    The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI linkThe BSc Biomedical Science (BMS) programme at De Montfort University (DMU, Leicester, UK) is accredited by the Institute of Biomedical Science (IBMS). Students enrolled within this programme acquire highly sought after skills related with human health sciences to work in: pathology departments in hospitals; research institutions; biotechnology and pharmaceutical industries; and the education sector to name a few. The degree recruits a large number of students with currently around 600 students enrolled on this programme at DMU. Despite pre-entry requirements of knowledge of subjects related to human biology, biology or chemistry, we have noted that first year students require basic support in STEM subjects (biology, chemistry and mathematics) in modules such as “Basic Microbiology”, “Basic Anatomy and Physiology” and “Chemistry for the Biosciences”. This support is especially necessary for students that come from non-traditional routes such as Business and Technology Education Council (BTEC) routes. Moreover, usually topics related with microbiology and human diseases are challenging for students, often causing stress impacting their overall performance and experience. A group of BMS academics at DMU in conjunction with universities in the European Union (EU; e.g. University of San Pablo CEU, Spain) have started to design, create and develop a series of e-learning resources or units in human biology and BMS for undergraduate students that study health sciences degrees in the EU. These units are being uploaded onto the DMU web server (http://parasitology.dmu.ac.uk/) and will be only accessible for students from participating universities during the first phase of this project (2017/18 course) in which comprehensive feedback will be collected. This web server space has three sections or modules (theoretical section, virtual laboratory and microscope) in which the new e-learning resources will be preliminary accommodated. These units will be interactive and easy to follow, and will cover basic human biology (e.g. cells, cell structure), human anatomy and physiology, histology and basic microbiology, which will be embedded in a theoretical module named DMU e-Biology within the above URL link. They will include formative assessments and case studies throughout each unit. In addition, a series of practical units are being developed which describe routine practical elements in any biomedical laboratory such as laboratory materials, pipetting, molecular techniques (e.g. PCR), cell culture (e.g. use of biological safety cabinet) and histological techniques (e.g. use of microtome, staining techniques). The development of this teaching and learning resource will cover a gap in the traditional teaching and learning methods that are currently used and provided in the participating universities. The DMU e-Biology will aid to our undergraduate students to gain knowledge in human biology and microbiology by promoting self-learning. We consider that the DMU e-Biology will help overcome spatiotemporal, equipment and resource barriers. Additionally, it may help student retention as currently about a 10% of our first year students fail to continue BMS at DMU. Finally, the creation of the DMU e-Biology will also provide support to the DMU Student Retention and Attainment Strategy 2016-2020 through the DMU Student Learning Hub, which is currently under development
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