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| 2. |
- Artini, Cristina, et al.
(författare)
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Roadmap on thermoelectricity
- 2023
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Ingår i: Nanotechnology. - : IOP Publishing Ltd. - 0957-4484 .- 1361-6528. ; 34:29
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Tidskriftsartikel (refereegranskat)abstract
- The increasing energy demand and the ever more pressing need for clean technologies of energy conversion pose one of the most urgent and complicated issues of our age. Thermoelectricity, namely the direct conversion of waste heat into electricity, is a promising technique based on a long-standing physical phenomenon, which still has not fully developed its potential, mainly due to the low efficiency of the process. In order to improve the thermoelectric performance, a huge effort is being made by physicists, materials scientists and engineers, with the primary aims of better understanding the fundamental issues ruling the improvement of the thermoelectric figure of merit, and finally building the most efficient thermoelectric devices. In this Roadmap an overview is given about the most recent experimental and computational results obtained within the Italian research community on the optimization of composition and morphology of some thermoelectric materials, as well as on the design of thermoelectric and hybrid thermoelectric/photovoltaic devices.
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| 3. |
- Dupin, Nathalie, et al.
(författare)
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Implementation of an Effective Bond Energy Formalism in the Multicomponent Calphad Approach
- 2018
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Ingår i: Journal of research of the National Institute of Standards and Technology. - : NATL INST STANDARDS & TECHNOLOGY-NIST. - 1044-677X .- 2165-7254. ; 123
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Tidskriftsartikel (refereegranskat)abstract
- Most models currently used for complex phases in the calculation of phase diagrams (Calphad) method are based on the compound energy formalism. The way this formalism is presently used, however, is prone to poor extrapolation behavior in higher-order systems, especially when treating phases with complex crystal structures. In this paper, a partition of the Gibbs energy into effective bond energies, without changing its configurational entropy expression, is proposed, thereby remarkably improving the extrapolation behavior. The proposed model allows the use of as many sublattices as there are occupied Wyckoff sites and has great potential for reducing the number of necessary parameters, thus allowing shorter computational time. Examples for face centered cubic (fcc) ordering and the sigma phase are given.
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| 4. |
- Haglöf, Fredrik, 1979-
(författare)
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Transition Metals and their Carbides, Nitrides and Carbonitrides : from a CALPHAD Perspective
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The CALPHAD (CALculation of PHAse Diagrams) method consists of three cornerstones, i.e. experiments, computational methods (e.g. Density Functional Theory (DFT)) and thermodynamic models, which together are used to build CALPHAD descriptions. In this thesis the CALPHAD method, including all three parts, is used to study transition metals and their carbides, nitrides and carbonitrides. The focus is mainly on transition metals important for the steel and cemented carbide industries. Some of the weaknesses or uncertainties in existing thermodynamic descriptions of these transition metals are identified and investigated with either experiments or computational methods whereupon new descriptions are presented.A method for calculation of the molar Gibbs energy as a function of temperature (Gm(T)) for metastable magnetic components is developed. The method uses DFT in combination with the Debye-Grüneisen model and the empirical magnetic model often used in CALPHAD. The developed method is also able to estimate the magnetic transition temperature (TC or TN). Furthermore, two new approaches for how to treat calculations on dynamically unstable allotropes are presented. This is important since this often is the reason why DFT calculations on metastable components fail. The method is developed and verified on bcc, fcc and hcp allotropes of Fe, Co and Ni, and is then used to calculate Gm(T) descriptions for fcc-TiC, fcc-CrC, fcc-CrN, hcp-Cr2C and hcp-Cr2N. Furthermore, the same method is also used to calculate the excess Gibbs energy at 0 K for the interactions CrC-TiC (fcc), CrC-CrN (fcc) and Cr2C-Cr2N (hcp), as well as TC and TN as a function of composition for the same composition ranges.Experiments are performed at 1673 and 1773 K to determine the solubility of Cr in MC (M = Ti, Cr) and of Ti in M3C2 and M7C3, in the equilibria MC-M3C2-M7C3 and MC-M3C2-graphite of the C-Cr-Ti system. The solubilities are measured with EDS/WDS and verified with XRD/Rietveld refinement.The experimental and computational results for the C-Cr-Ti system are used together with literature data to perform a reassessment of this system. Compared to the previous CALPHAD description, the new description also includes updated descriptions for two of the three constituent binary systems (C-Ti and Cr-Ti) and reproduces the experimental results in the TiC-Cr3C2 isoplethal section found in literature.In summary, the outcome of this thesis is an updated CALPHAD description of the C-Cr-Ti system and calculated Gm(T) descriptions, including magnetic properties, for allotropes of Fe, Co, Ni, and several parameters in the C-Cr-N system. The developed method for calculation of Gm(T) for metastable magnetic compounds is also a useful tool for calculation of Gm(T) for many other transition metals and their carbides, nitrides, and carbonitrides.
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| 5. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 7. |
- van Rheenen, W, et al.
(författare)
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Common and rare variant association analyses in amyotrophic lateral sclerosis identify 15 risk loci with distinct genetic architectures and neuron-specific biology
- 2021
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Ingår i: Nature genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 53:12, s. 1636-
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Tidskriftsartikel (refereegranskat)abstract
- Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with a lifetime risk of one in 350 people and an unmet need for disease-modifying therapies. We conducted a cross-ancestry genome-wide association study (GWAS) including 29,612 patients with ALS and 122,656 controls, which identified 15 risk loci. When combined with 8,953 individuals with whole-genome sequencing (6,538 patients, 2,415 controls) and a large cortex-derived expression quantitative trait locus (eQTL) dataset (MetaBrain), analyses revealed locus-specific genetic architectures in which we prioritized genes either through rare variants, short tandem repeats or regulatory effects. ALS-associated risk loci were shared with multiple traits within the neurodegenerative spectrum but with distinct enrichment patterns across brain regions and cell types. Of the environmental and lifestyle risk factors obtained from the literature, Mendelian randomization analyses indicated a causal role for high cholesterol levels. The combination of all ALS-associated signals reveals a role for perturbations in vesicle-mediated transport and autophagy and provides evidence for cell-autonomous disease initiation in glutamatergic neurons.
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