10,344 research outputs found
Cluster expansion constructed over Jacobi-Legendre polynomials for accurate force fields
We introduce a compact cluster expansion method, constructed over Jacobi and
Legendre polynomials, to generate highly accurate and flexible machine-learning
force fields. The constituent many-body contributions are separated,
interpretable and adaptable to replicate the physical knowledge of the system.
In fact, the flexibility introduced by the use of the Jacobi polynomials allows
us to impose, in a natural way, constrains and symmetries to the cluster
expansion. This has the effect of reducing the number of parameters needed for
the fit and of enforcing desired behaviours of the potential. For instance, we
show that our Jacobi-Legendre cluster expansion can be designed to generate
potentials with a repulsive tail at short inter-atomic distances, without the
need of imposing any external function. Our method is here continuously
compared with available machine-learning potential schemes, such as the atomic
cluster expansion and potentials built over the bispectrum. As an example we
construct a Jacobi-Legendre potential for carbon, by training a slim and
accurate model capable of describing crystalline graphite and diamond, as well
as liquid and amorphous elemental carbon.Comment: 16 Pages, 8 figures, 6 Page supplementary materia
Neutron scattering studies of heterogeneous catalysis
Understanding the structural dynamics/evolution of catalysts and the related surface chemistry is essential for establishing structureâcatalysis relationships, where spectroscopic and scattering tools play a crucial role. Among many such tools, neutron scattering, though less-known, has a unique power for investigating catalytic phenomena. Since neutrons interact with the nuclei of matter, the neutronânucleon interaction provides unique information on light elements (mainly hydrogen), neighboring elements, and isotopes, which are complementary to X-ray and photon-based techniques. Neutron vibrational spectroscopy has been the most utilized neutron scattering approach for heterogeneous catalysis research by providing chemical information on surface/bulk species (mostly H-containing) and reaction chemistry. Neutron diffraction and quasielastic neutron scattering can also supply important information on catalyst structures and dynamics of surface species. Other neutron approaches, such as small angle neutron scattering and neutron imaging, have been much less used but still give distinctive catalytic information. This review provides a comprehensive overview of recent advances in neutron scattering investigations of heterogeneous catalysis, focusing on surface adsorbates, reaction mechanisms, and catalyst structural changes revealed by neutron spectroscopy, diffraction, quasielastic neutron scattering, and other neutron techniques. Perspectives are also provided on the challenges and future opportunities in neutron scattering studies of heterogeneous catalysis
Endogenous measures for contextualising large-scale social phenomena: a corpus-based method for mediated public discourse
This work presents an interdisciplinary methodology for developing endogenous measures of group membership through analysis of pervasive linguistic patterns in public discourse. Focusing on political discourse, this work critiques the conventional approach to the study of political participation, which is premised on decontextualised, exogenous measures to characterise groups. Considering the theoretical and empirical weaknesses of decontextualised approaches to large-scale social phenomena, this work suggests that contextualisation using endogenous measures might provide a complementary perspective to mitigate such weaknesses.
This work develops a sociomaterial perspective on political participation in mediated discourse as affiliatory action performed through language. While the affiliatory function of language is often performed consciously (such as statements of identity), this work is concerned with unconscious features (such as patterns in lexis and grammar). This work argues that pervasive patterns in such features that emerge through socialisation are resistant to change and manipulation, and thus might serve as endogenous measures of sociopolitical contexts, and thus of groups.
In terms of method, the work takes a corpus-based approach to the analysis of data from the Twitter messaging service whereby patterns in usersâ speech are examined statistically in order to trace potential community membership. The method is applied in the US state of Michigan during the second half of 2018â6 November having been the date of midterm (i.e. non-Presidential) elections in the United States. The corpus is assembled from the original posts of 5,889 users, who are nominally geolocalised to 417 municipalities. These users are clustered according to pervasive language features. Comparing the linguistic clusters according to the municipalities they represent finds that there are regular sociodemographic differentials across clusters. This is understood as an indication of social structure, suggesting that endogenous measures derived from pervasive patterns in language may indeed offer a complementary, contextualised perspective on large-scale social phenomena
Proceedings of FORM 2022. Construction The Formation of Living Environment
This study examines the integration of building information modelling (BIM) technologies in operation & maintenance stage in the system of managing real estate that helps to reduce transaction costs. The approach and method are based on Digital Twin technology and Model Based System Engineering (MBSE) approach.
The results of the development of a service for digital facility management and
digital expertise are presented. The connection between physical and digital objects is conceptualized
Echinoderms Metabolites: Structure, Functions and Biomedical Perspectives
The materials published in the Special Issue reflect the real diversity of echinoderm metabolites and cover most of their specific classes and biomedical potential as antioxidant, antiviral, anticancer, and even anticoagulant preparations. The metabolites include sea urchin naphtoquinoid pigments and their semi-synthetic derivatives, sea cucumber triterpene glycosides, esters of polyhydroxysteroids from starfish, sea urchins free sterols, and sea cucumber fucosylated chondroitin sulfates. This Special Issue, âEchinoderm Metabolites: Structure, Functions, and Biomedical Perspectivesâ, is a collection of articles about different scientific aspects concerning low molecular weight and biopolymer metabolites from echinoderms, including their isolation and chemical structures, biological activities, biosynthesis and evolution, biological functions, and obtaining of semi-synthetic derivatives of biologically active natural products. This Special Issue includes materials about sea urchin naphtoquinoid pigments and their semi-synthetic derivatives, sea cucumber triterpene glycosides, esters of polyhydroxysteroids from starfish, sea urchin free sterols, and sea cucumber fucosylated chondroitin sulfates
Non-covalent Interactions in Coordination and Organometallic Chemistry
Non-covalent interactions in coordination and organometallic compounds (hydrogen, halogen, chalcogen, pnictogen, tetrel, and semi-coordination bonds; agosic and anagosic interactions; stacking, anion-/cation-Ï interactions; metallophilic interactions, etc.) are topical in modern chemistry, materials science, crystal engineering, and related fields of knowledge. Both experimental and theoretical methods are widely used for investigations of the nature and various properties of such weak contacts in gas, liquid, and solid states. Non-covalent interactions could be the driving force to design smart materials with valuable redox, electronic, mechanical, magnetic, and optical properties, which is promising for the manufacture of LEDs, photovoltaic cells of solar power plants, porous structures, sensors, battery cells, and liquid crystals.This Special Issue highlights and presents an overview of modern trends in non-covalent interactions in coordination and organometallic compounds, and bringing various different types to the attention of the scientific community
Structure, Activity, and Function of Protein Methyltransferases
This collection of review articles describes the structure, function and mechanism of individual protein methyltransferase enzymes including protein lysine methyltransferases, protein arginine methyltransferases, and also the less abundant protein histidine methyltransferases and protein N-terminal end methyltransferases. The topics covered in the individual reviews include structural aspects (domain architecture, homologs and paralogs, and structure), biochemical properties (mechanism, sequence specificity, product specificity, regulation, and histone and non-histone substrates), cellular features (subcellular localization, expression patterns, cellular roles and function, biological effects of substrate protein methylation, connection to cell signaling pathways, and connection to chromatin regulation) and their role in diseases. This review book is a useful resource for scientists working on protein methylation and protein methyltransferases and those interested in joining this emerging research field
Anion Photoelectron Spectroscopic Studies: Antioxidants, Actinide Clusters, and Molecular Activation
Gas phase anion photoelectron spectroscopy is uniquely suited to study chemistry at the molecular level, as atoms, molecules, and clusters are isolated and thus unperturbed by confounding environmental effects which often complicate analyses carried out in the liquid or solid state. Photoelectron spectroscopy provides information about the electronic structure of anions, as well as the geometry of the anions and corresponding neutral species when combined with theoretical calculations. A variety of ion sources were employed to generate the anions in these studies: electrospray ionization (ESI), laser vaporization (LVS), and pulsed arc cluster ion source (PACIS). Using these techniques, two antioxidants, a range of actinide containing clusters, and multiple activation reactions were studied. Additionally, a new double rod laser vaporization source was designed and constructed to generate single atom catalyst (SAC) mimics.
Chapter III presents the studies of this thesis and is divided into three major sections based on ion source: ESI, LVS, and PACIS. ESI brought the water-soluble antioxidants (ascorbate, deprotonated ascorbate, propyl gallate, and gallate) into the gas phase. LVS ablated uranium and thorium rods to generate gas phase atoms and actinide containing clusters, as well as highlighted the reaction between iridium and hydroxylamine and the phenomenon of intramolecular electron-induced proton transfer. Finally, using PACIS, two thorium clusters were generated, and CO2 activation with two metal hydrides were studied
The physical and optical investigations of the tannic acid functionalised Cu-based oxide nanostructures
The need for a mild, low-cost, green environment that is able to produce exotic properties of output nanostructures is appealing nowadays. Employing these requirements, the copper (Cu)âbased oxide nanostructures have been successfully synthesised via one-pot reaction using biocompatible natural polyphenol, tannic acid (TA) as both the reducing agent and stabiliser at 60, 70 and 80 °C. The structural and optical studies disclosed the efect of TA on the surface morphology, phase purity, elemental composition, optical microstrain and optical intrinsic energy of this mixed Cu2O and CuO nanostructures. The optically based method describes the comparative details of the multi-band gap in the presence of more than one element with overlapping spectra from the frstderivative absorbance curve and the exponential absorbance of Urbach tail energy EU towards the conventional Tauc bandgap. The A demonstrates that the pronounced efect of TA that Cu2O and CuO nanostructures creates much sensitive frst-derivative bandgap output compared to the Tauc bandgap. The results also show that the EU reduced as the temperature reaches 70 °C and then experienced sudden increase at 80 °C. The change in the pattern is parallel to the trend observed in the Williamsonâ Hall microstrain and is evident from the variations of the mean crystallite size Dm which is also a cause response to the change in temperature or pH. Therefore, the current work has elucidated that the structural and optical correlations on the as-synthesised Cu2O and CuO nanostructures in the presence of TA were the combined reaction of pH change and the ligand complexation reactions. The acquired results suggest a more comprehensive range of studies to further understand the extent relationship between the physical and optical properties of TA functionalised Cu-based oxide nanostructures
- âŠ