Demixing and orientational ordering in mixtures of rectangular particles

Using scaled-particle theory for binary mixtures of two-dimensional hard particles with rotational freedom, we analyse the stability of nematic phases and the demixing phase behaviour of a variety of mixtures, focussing on cases where at least one of the components consists of hard rectangles or hard squares. A pure fluid of hard rectangles may exhibit, aside from the usual uniaxial nematic phase, an additional (tetratic) oriented phase, possessing two directors, which is the analogue of the biaxial or cubatic phases in three- dimensional fluids. There is computer simulation evidence that the tetratic phase might be stable with respect to phases with spatial order for rectangles with low aspect ratios. As hard rectangles are mixed with other particles not possessing stable tetratic order by themselves, the tetratic phase is destabilised, via a first- or second-order phase transition, to uniaxial nematic or isotropic phases; for hard rectangles of low aspect ratio tetratic order persists in a relatively large range of volume fractions. The order of these transitions depends on the particle geometry, dimensions and thermodynamic conditions of the mixture. The second component of the mixture has been chosen to be hard discs or disco-rectangles, the geometry of which is different from that of rectangles, leading to packing frustration and demixing behaviour, or simply rectangles of different aspect ratio. These mixtures may be good candidates for observing thermodynamically stable tetratic phases in monolayers of hard particles. Finally, demixing between fluid (isotropic--tetratic or tetratic--tetratic) phases is seen to occur in mixtures of hard squares of different sizes when the size ratio is sufficiently large.Comment: 27 pages, 9 figure

Research activities on radioactive waste management and on the back-end of the nuclear fuel cycle performed by the Joint Research Centre of the European Commission

The Euratom Research and Training Programme contributes, within its portfolio of activities, to establish and improve the scientific basis of knowledge for the safe management of spent nuclear fuel and radioactive waste. This includes research and innovation activities undertaken by the Joint Research Centre (or JRC, the European Commission’s science and knowledge service) in its laboratories. This paper provides an overview and some highlights of the Joint Research Centre (JRC) activities which are dedicated to the safety of spent fuel and high level radioactive waste forms. The fields of experimental and modelling research address various stages of spent fuel management after discharge from the reactor core: cooling in the spent fuel pool; handling, transport, extended interim storage and retrieval thereafter; disposal in a deep geological repository and long term behaviour of the spent fuel/waste form after disposal. The safety of the “back-end” of nuclear fuel cycles which include U-Pu recycling and/or a “fully closed” cycle with minor actinides separation and transmutation is also a major area of research. Both normal operation and accident scenarios, which cause fuel degradation/melting, are investigated. Possible applications for legacy waste management, decommissioning, and safeguards are considered. The relevance of the research is linked to the possibility of investigating “real” spent fuel and highly radioactive compounds using JRC’s research infrastructure, which includes hot cells and shielded facilities, and state of the art experimental methods that are (in some cases) rare or even unique. The activities are performed in collaboration with partners and/or in the context of international initiatives. Opportunities and perspectives for enhanced cooperation, including access and sharing of infrastructure are being developed

NyctiDB: A non-relational bioprocesses modeling database supported by an ontology

Strategies to exploit and enable the digitalization of industrial processes are on course to become game-changers in optimizing (bio)chemical facilities. To achieve this, these industries face an increasing need for process models and, as importantly, an efficient way to store the models and data/information. Therefore, this work proposes developing an online information storage system that can facilitate the reuse and expansion of process models and make them available to the digitalization cycle. This system is named NyctiDB, and it is a novel non-relational database coupled with a bioprocess ontology. The ontology supports the selection and classification of bioprocess models focused information, while the database is in charge of the online storage of said information. Through a series of online collections, NyctiDB contains essential knowledge for the design, monitoring, control, and optimization of a bioprocess based on its mathematical model. Once NyctiDB has been implemented, its applicability and usefulness are demonstrated through two applications. Application A shows how NyctiDB is integrated inside the software architecture of an online educational bioprocess simulator. This implies that NyctiDB provides the information for the visualization of different bioprocess behaviours and the modifications of the models in the software. Moreover, the information related to the parameters and conditions of each model is used to support the users’ understanding of the process. Additionally, application B illustrates that NyctiDB can be used as AI enabler to further the research in this field through open-source and reliable data. This can, in fact, be used as the information source for the AI frameworks when developing, for example, hybrid models or smart expert systems for bioprocesses. Henceforth, this work aims to provide a blueprint on how to collect bioprocess modeling information and connect it to facilitate and empower the Internet-of-Things paradigm and the digitalization of the biomanufacturing industries