Search results for " Geometry."
showing 10 items of 2189 documents
Study of High-Temperature Behaviour of ZnO by Ab Initio Molecular Dynamics Simulations and X-ray Absorption Spectroscopy
2021
Wurtzite-type zinc oxide (w-ZnO) is a widely used material with a pronounced structural anisotropy along the c axis, which affects its lattice dynamics and represents a difficulty for its accurate description using classical models of interatomic interactions. In this study, ab initio molecular dynamics (AIMD) was employed to simulate a bulk w-ZnO phase in the NpT ensemble in the high-temperature range from 300 K to 1200 K. The results of the simulations were validated by comparison with the experimental Zn K-edge extended X-ray absorption fine structure (EXAFS) spectra and known diffraction data. AIMD NpT simulations reproduced well the thermal expansion of the lattice, and the pronounced …
3D visualization of sheath folds in Ancient Roman marble wall coverings from Ephesos, Turkey
2014
Abstract Archaeological excavations and restoration of a palatial Roman housing complex in Ephesos, Turkey yielded 40 wall-decorating plates of folded mylonitic marble (Cipollino verde), derived from the internal Hellenides near Karystos, Greece. Cipollino verde was commonly used for decoration purposes in Roman buildings. The plates were serial-sectioned from a single quarried block of 1,25 m3 and provided a research opportunity for detailed reconstruction of the 3D geometry of meterscale folds in mylonitized marble. A GOCAD model is used to visualize the internal fold structures of the marble, comprising curtain folds and multilayered sheath folds. The sheath folds are unusual in that the…
Abelian varieties and theta functions associated to compact Riemannian manifolds; constructions inspired by superstring theory
2012
We look into a construction of principal abelian varieties attached to certain spin manifolds, due to Witten and Moore-Witten around 2000 and try to place it in a broader framework. This is related to Weil intermediate Jacobians but it also suggests to associate abelian varieties to polarized even weight Hodge structures. The latter construction can also be explained in terms of algebraic groups which might be useful from the point of view of Tannakian categories. The constructions depend on moduli much as in Teichm\"uller theory although the period maps in general are only real analytic. One of the nice features is how the index for certain differential operators canonically associated to …
Aromatic dicarboxylate incorporated new di- and tetranuclear cobalt(II) complexes: Synthetic and structural aspects, and evaluation of properties and…
2020
Abstract The synthetic and structural aspects as well as evaluation of magnetic properties and catalytic activity toward aerial oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylbenzoquinone of three new, two di- and one tetranuclear cobalt(II) complexes, [Co2(cpdp)(Hphth)]∙5H2O (1), [Co2(cpdp)(Hisophth)] (2) and [Co4(cpdp)2(terephth)]∙4.5CH3OH·5.5H2O (3), based on a symmetrical multidentate ligand, N,N'-Bis[2-carboxybenzomethyl]-N,N'-Bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol (H3cpdp) in combination with exogeneous aromatic dicarboxylic acids, such as phthalic acid (H2phth), isophthalic acid (H2isophth) and terephthalic acid (H2terephth) are reported. All three coordination compl…
The ionic tin(IV) complex tri-μ2-methoxy-μ3-oxo-tris[di-tert-butyltin(IV)] tri-μ2-methoxy-bis[tert-butyldimethoxystannate(IV)]
2004
The solid-state of the title compound, [Sn3(C4H9)6(CH3O)3O][Sn2(C4H9)2(CH3O)7], consists of distinct [tBu6Sn3(μ-OCH3)3(μ3-O)]+ cations and [tBu2Sn2(OCH3)4(μ-OCH3)3]− anions, apparently formed as a result of slow hydrolysis of pure di(tert-butyl)dimethoxystannane, tBu2Sn(OCH3)2. In the monocation, the coordination about the Sn atoms is distorted trigonal bipyramidal, and, in the monoanion, distorted octahedral. The trigonal bipyramidal arrangement induces planarity of the Sn3O4 motif.
Synthesis, characterization, crystal structures and magnetic exchange in dinuclear copper complexes with 3-amino-1-propanol as terminal and bridging …
1990
Abstract The synthesis, X-ray structures and spectroscopic and magnetic properties are described for two groups of dinuclear Cu(II) compounds with the ligand 3-amino-1-propanol (Hap). The formulae of the compounds are for group A: [Cu(ap)(anion)]2, in which ap is the dehydronated Hap and the anions are formate, nitrate, chloride and bromide and for group B: [Cu(ap)(Hap)]2(anion)2, with anion = iodide, bromide, chloride, nitrate and tetrafluoroborate. The structure of group A compounds consists of dinuclear units with the co-planar centrosymmetric chromophore ANCuOO′CuNA, in which the A ligands (anions) bridge to neighbouring units as axial ligands, thereby forming infinite chains. Dimer Cu……
Organotin(IV) azido and mixed azidothiocyanato complex anions; A Mössbauer and vibrational spectroscopic study
1975
Abstract Tetraphenylarsonium and tetramethylammonium salts of the complex anions Ph 3 Sn(N 3 ) − 2 , Ph 3 Sn(N 3 )(NCS) − , Me 2 Sn(N 3 ) 2− 4 and Ph 2 Sn(N 3 ) 2 (NCS) 2− 2 have been synthesized, and the solid state configuration of the complex anions has been studied by Mossbauer and vibrational spectroscopies. Trigonal bipyramidal structures are advanced for the Ph 3 Sn IV derivatives, with equatorial SnC 3 and apical pseudohalide ligands, while the R 2 Sn IV compounds are assumed to be trans -octahedral species. The NCS − ligands are observed to be N-bonded to Sn IV . Conductance and PMR (for the Me 2 Sn IV compound) data suggest the presence of the complex anions also in solution phase…
Cost-driven framework for progressive compression of textured meshes
2019
International audience; Recent advances in digitization of geometry and radiometry generate in routine massive amounts of surface meshes with texture or color attributes. This large amount of data can be compressed using a progressive approach which provides at decoding low complexity levels of details (LoDs) that are continuously refined until retrieving the original model. The goal of such a progressive mesh compression algorithm is to improve the overall quality of the transmission for the user, by optimizing the rate-distortion trade-off. In this paper, we introduce a novel meaningful measure for the cost of a progressive transmission of a textured mesh by observing that the rate-distor…
FISICA QUANTISTICA E FUNZIONI MENTALI SUPERIORI III
2010
Questo saggio riprende alcuni concetti di anatomia comparata e di fisiologia, sviluppati in una mia precedente ricerca dal titolo Termodinamica, campi quantici e funzioni mentali. Il fine è di chiarire alcuni punti controversi posti dall’analisi scientifica, in riguardo a teoremi di neuro anatomia e di neurofisiologia. Il filosofo Heiddegger H. riteneva che il pensiero umano non può affidarsi interamente all’indagine scientifica, traducendo in schemi ed in formule la vivente realtà della natura, sia fisica che biologica. La ricerca scientifica si basa su un sapere rigoroso e preciso, altamente dimostrativo che può competere con la matematica, ritenuta la scienza delle scienze. Nonostante ci…
FISICA QUANTISTICA E FUNZIONI CEREBRALI SUPERIORI (II)
2010
Data una semplice perturbazione, il processo lineare tende a rimanere leggermente alterato. Data la stessa perturbazione, un processo non lineare tende a tornare al suo punto di partenza. Huygens C. (fisico olandese del XVI sec.) inventò l’orologio a pendolo e la disciplina classica della dinamica. S’imbatté in uno dei grandi esempi di questa forma di regolazione. Huygens notò che vari orologi a pendolo, appoggiati contro una parete stavano oscillando in modo perfettamente sincronizzato. Sapeva che gli orologi non potevano essere così precisi. Huygens ipotizzò che gli orologi fossero coordinati da vibrazioni trasmesse attraverso la parete. Al presente, il fenomeno è definito agganciamento d…