296 research outputs found

    CFD analysis of an ALD reactor: gaseous species distribution and cycle time

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    A three-dimensional Computational Fluid Dynamics (CFD) model is built for a Cambridge Nanotech® ALD reactor, considering the Atomic Layer Deposition process of aluminum oxide (Al2O3), using trimethyl aluminum (TMA, Al(CH3)3) and water vapor (H2O) as precursors and argon as inert gas. The developed model investigates the transport phenomena during the reactant pulses of the ALD cycle, while no reactions are taken into account. Due to the lack of measurements of the reactants inlet flows into the reactor, a model for the precursor feeding system is also built. Its results are used as transient inlet boundary conditions of the reactor model. Results about the gas flow field, temperature and species distributions inside the ALD reactor are obtained during each pulse. A good agreement between the experimental and calculated pressure pulses at the reactor exit is observed, which allows validating the approach. The simulations show the effect of the reactor loading door, resulting to flow regimes that affect the gaseous species distribution close to the substrate surface. As illustrated in Fig. 1, it is shown that for the side of the wafer close to the loading door, the gas phase reactant concentration above the substrate is always lower. Finally, the ALD purging steps of a complete cycle are simulated. The results show that the purging steps can be reduced to a time period smaller than the operated one, thus minimizing the ALD total cycle time

    Computational mechanistic investigation of the initial growth of Alumina ALD: Effect of substrate pretreatment on nucleation period reduction

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    In this work, the surface mechanisms including reaction, adsorption and desorption steps during the ALD of Al2O3 from TMA and H2O on Si substrates are investigated. The analysis is performed using a surface chemistry model, coupled to a CFD model for a commercial reactor treating 20 cm Si wafers. [4] This model is used to feed a geometric model that simulates island growth on a surface. The model predictions are validated by comparing its results with experimental measurements and literature data. It is shown that for ALD exposures in the range of ms, no reactions between a perfect Si substrate and reactants take place due to the low activation energy of the desorption step. The effect of initial long duration TMA exposures before deposition is investigated, showing that they clearly lead to an increase of nucleation sites on the surface by allowing TMA adsorption and reaction to occur, thus producing methyl groups transformed in active hydroxyl bonds by the subsequent H2O exposure. This significantly reduces the nucleation period, hence decreasing the number of ALD cycles needed to obtain a conformal continuous film

    Impact of perioperative chemotherapy on survival in patients with advanced primary urethral cancer: results of the international collaboration on primary urethral carcinoma

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    This is the first series that suggests a prognostic benefit of neoadjuvant treatment in a consecutive series of patients who underwent perioperative chemotherapy plus surgery for advanced primary urethral carcinoma. Further studies should yield a better understanding of how perioperative chemotherapy exerts a positive effect on survival in order to selectively advocate its use in advanced primary urethral carcinom

    Metadata stewardship in nanosafety research: learning from the past, preparing for an "on-the-fly" FAIR future

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    Introduction: Significant progress has been made in terms of best practice in research data management for nanosafety. Some of the underlying approaches to date are, however, overly focussed on the needs of specific research projects or aligned to a single data repository, and this “silo” approach is hampering their general adoption by the broader research community and individual labs. Methods: State-of-the-art data/knowledge collection, curation management FAIRification, and sharing solutions applied in the nanosafety field are reviewed focusing on unique features, which should be generalised and integrated into a functional FAIRification ecosystem that addresses the needs of both data generators and data (re)users. Results: The development of data capture templates has focussed on standardised single-endpoint Test Guidelines, which does not reflect the complexity of real laboratory processes, where multiple assays are interlinked into an overall study, and where non-standardised assays are developed to address novel research questions and probe mechanistic processes to generate the basis for read-across from one nanomaterial to another. By focussing on the needs of data providers and data users, we identify how existing tools and approaches can be re-framed to enable “on-the-fly” (meta) data definition, data capture, curation and FAIRification, that are sufficiently flexible to address the complexity in nanosafety research, yet harmonised enough to facilitate integration of datasets from different sources generated for different research purposes. By mapping the available tools for nanomaterials safety research (including nanomaterials characterisation, non-standard (mechanistic-focussed) methods, measurement principles and experimental setup, environmental fate and requirements from new research foci such as safe and sustainable by design), a strategy for integration and bridging between silos is presented. The NanoCommons KnowledgeBase has shown how data from different sources can be integrated into a one-stop shop for searching, browsing and accessing data (without copying), and thus how to break the boundaries between data silos. Discussion: The next steps are to generalise the approach by defining a process to build consensus (meta)data standards, develop solutions to make (meta)data more machine actionable (on the fly ontology development) and establish a distributed FAIR data ecosystem maintained by the community beyond specific projects. Since other multidisciplinary domains might also struggle with data silofication, the learnings presented here may be transferable to facilitate data sharing within other communities and support harmonization of approaches across disciplines to prepare the ground for cross-domain interoperability. Visit WorldFAIR online at http://worldfair-project.eu. WorldFAIR is funded by the EC HORIZON-WIDERA-2021-ERA-01-41 Coordination and Support Action under Grant Agreement No. 101058393

    Metadata stewardship in nanosafety research: learning from the past, preparing for an "on-the-fly" FAIR future

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    Introduction: Significant progress has been made in terms of best practice in research data management for nanosafety. Some of the underlying approaches to date are, however, overly focussed on the needs of specific research projects or aligned to a single data repository, and this "silo" approach is hampering their general adoption by the broader research community and individual labs.Methods: State-of-the-art data/knowledge collection, curation management FAIrification, and sharing solutions applied in the nanosafety field are reviewed focusing on unique features, which should be generalised and integrated into a functional FAIRification ecosystem that addresses the needs of both data generators and data (re)users.Results: The development of data capture templates has focussed on standardised single-endpoint Test Guidelines, which does not reflect the complexity of real laboratory processes, where multiple assays are interlinked into an overall study, and where non-standardised assays are developed to address novel research questions and probe mechanistic processes to generate the basis for read-across from one nanomaterial to another. By focussing on the needs of data providers and data users, we identify how existing tools and approaches can be re-framed to enable "on-the-fly" (meta) data definition, data capture, curation and FAIRification, that are sufficiently flexible to address the complexity in nanosafety research, yet harmonised enough to facilitate integration of datasets from different sources generated for different research purposes. By mapping the available tools for nanomaterials safety research (including nanomaterials characterisation, nonstandard (mechanistic-focussed) methods, measurement principles and experimental setup, environmental fate and requirements from new research foci such as safe and sustainable by design), a strategy for integration and bridging between silos is presented. The NanoCommons KnowledgeBase has shown how data from different sources can be integrated into a one-stop shop for searching, browsing and accessing data (without copying), and thus how to break the boundaries between data silos.Discussion: The next steps are to generalise the approach by defining a process to build consensus (meta)data standards, develop solutions to make (meta)data more machine actionable (on the fly ontology development) and establish a distributed FAIR data ecosystem maintained by the community beyond specific projects. Since other multidisciplinary domains might also struggle with data silofication, the learnings presented here may be transferrable to facilitate data sharing within other communities and support harmonization of approaches across disciplines to prepare the ground for cross-domain interoperability
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