Search results for "Density"
showing 10 items of 4402 documents
Modeling long-range memory with stationary Markovian processes
2009
In this paper we give explicit examples of power-law correlated stationary Markovian processes y(t) where the stationary pdf shows tails which are gaussian or exponential. These processes are obtained by simply performing a coordinate transformation of a specific power-law correlated additive process x(t), already known in the literature, whose pdf shows power-law tails 1/x^a. We give analytical and numerical evidence that although the new processes (i) are Markovian and (ii) have gaussian or exponential tails their autocorrelation function still shows a power-law decay =1/T^b where b grows with a with a law which is compatible with b=a/2-c, where c is a numerical constant. When a<2(1+c) th…
Synthesis, crystal structure, DFT calculations, Hirshfeld surface, vibrational and optical properties of a novel hybrid non-centrosymmetric material …
2019
This present work undertakes the study of a novel organic–inorganic hybrid material, which has been obtained successfully by an acid-base reaction at room temperature and structurally studied by the single crystal X-ray diffraction method. (C10H15N2)2H2P2O7 crystallizes in the triclinic system with the non-centrosymmetric space group P1 with the following lattice parameters: a = 5.9159(2) Å, b = 13.8451(6) Å, c = 14.5973(5) Å, ? = 74.507(2)°, ? = 89.980(2)°, ? = 89.231(2)° with V = 1152.06(8) Å3 and Z = 2. The X-ray structural analysis supported by a detailed Hirshfeld 2D fingerprint plots has been performed to elucidate the different inter-contacts in the crystal structure mainly associate…
Effect of conjugated system extension on structural features and electron-density distribution in charge–transfer difluoroborates
2021
A comparative structural study of two related donor–acceptor pyridine-based BF2 complexes, namely, 3-(dimethylamino)-1,1-difluoro-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uide, C8H10BF2N3O (1), and 3-{(1E,3E)-4-[4-(dimethylamino)phenyl]buta-1,3-dien-1-yl}-1,1-difluoro-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uide, C18H18BF2N3O (2), containing a dimethylamino group and either the shortest (in 1) or the longest (in 2) charge-transfer path known until now in this family of compounds, is presented. Single-crystal X-ray diffraction analysis supported by computational investigations shed more light on these systems, indicating, among other aspects, the predominance of C—H...F cont…
Double-CO32− Centered [CoII5] Wheel and Modeling of Its Magnetic Properties
2010
A high-spin Co(II) cluster with a rare pentagonal molecular structure and formula [Co(5)(CO(3))(2)(bpp)(5)]ClO(4) (1; Hbpp is 2,6-bis(phenyliminomethyl)-4-methylphenolate) has been synthesized and characterized by single-crystal X-ray diffraction. This topology arises from fusing five [Co(2)(bpp)] moieties in a cyclic manner around two CO(3)(2-) central ligands, resulting in propeller-like configuration. The irregular coordination of the carbonate ions to the metal centers results in a combination of coordination numbers (CNs) of the Co(II) ions of five and six. The bulk magnetization of this complicated magnetically exchanged system has been modeled successfully by employing a matrix diago…
Crystal structure, Hirshfeld surface analysis and DFT studies of (E)-1-(4-bromophenyl)-3-(3-fluorophenyl)prop-2-en-1-one
2018
The title halogenated organic chalcone was prepared by a Claisen–Schmidt condensation reaction. A Hirshfeld surface analysis was carried out to reveal the percentage contributions of the intermolecular interactions. A theoretical study was performed using the density functional theory (DFT) at B3LYP with the 6–311 G++(d,p) basis set level to compare with the experimental results of the X-ray analysis and UV–vis absorption analysis in term of the geometrical parameters, HOMO-LUMO energy gap and charge distributions.
Substituent effects in nitro derivatives of carbazoles investigated by comparison of low-temperature crystallographic studies with density functional…
2014
The crystal structure of 9H-carbazole, C12H9N, (I), has been redetermined at low temperature for use as a reference structure in a comparative study with the structures of 1-nitro-9H-carbazole, C12H8N2O2, (II), and 9-nitrocarbazole, C12H8N2O2, (III). The molecule of (I) has crystallographically imposed mirror symmetry (Z′ = 0.5). All three solid-state structures are slightly nonplanar, the dihedral angles between the planes of the arene and pyrrole rings ranging from 0.40 (7)° in (III) to 1.82 (18)° in (II). Nevertheless, a density functional theory (DFT) study predicts completely planar conformations for the isolated molecules. To estimate the influence of nitro-group substitution on aroma…
Characterization of spatial porosity and mineral distribution of crystalline rock using X-ray micro computed tomography, C-14-PMMA autoradiography an…
2019
The spatial porosity and mineral distribution of geological materials strongly affects transport processes in them. X-ray micro computed tomography (X-mu CT) has proven to be a powerful tool for characterizing the spatial mineral distribution of geological samples in 3-D. However, limitations in resolution prevent an accurate characterization of pore space especially for tight crystalline rock samples and 2-D methods such as C-14-polymethylmethacrylate (C-14-PMMA) autoradiography and scanning electron microscopy (SEM) are needed. The spatial porosity and mineral distributions of tight crystalline rock samples from Aspo, Sweden, and Olkiluoto, Finland, were studied here. The X-mu CT were use…
Liquid structure of a choline chloride-water natural deep eutectic solvent: A molecular dynamics characterization
2021
The liquid structure of a representative of the first water-in-salt (WiS) Natural Deep Eutectic Solvents (NADES), hereinafter indicated as aquoline, a mixture of choline chloride (ChCl) and water with molar ratio 1:3.33, is ex- plored at ambient conditions. Using Molecular Dynamics (MD) simulation tools, we extract structural informa- tion at atomistic level on the nature of inter-correlations between the different moieties. Despite being a very fluid liquid, with much lower viscosity than other common ChCl-based DES, aquoline turns out to be very struc- tured. Computed X-ray and neutron weighted scattering patterns (the latter also on selectively deuterated mix- tures) highlight the existe…
Are there plenty of fish in the sea? How life history traits affect the eco-evolutionary consequences of population oscillations
2022
Understanding fish population oscillations is important for both fundamental population biology and for fisheries science. Much research has focused on the causes of population oscillations, but the eco-evolutionary consequences of population oscillations are unclear. Here, we used an empirically parametrised individual-based simulation model to explore the consequences of oscillations with different amplitudes and wavelengths. We show that oscillations with a wavelength shorter than the maximum lifespan of the fish produce marked differences in the evolutionary trajectories of asymptotic length. Wavelengths longer than the maximum lifespan of the fish, in turn, mainly manifest as ecologica…
The occurrence of Echinorhynchus salmonis Müller, 1784 in benthic amphipods in the Baltic Sea
2015
The acanthocephalan Echinorhynchus salmonis Muller, 1784 is a common parasite of salmonid fish, but it has rarely been reported from an intermediate host. Samples of benthic amphipods, Monoporeia affinis (Lindstrom), were taken from multiple, deep sites (usually below 70 m) in the Gulf of Bothnia over the course of more than a decade and examined for acanthocephalans. Overall, only 0.44% of 23 296 amphipods were infected, all with just a single worm. This prevalence is consistent with several previous reports of acanthocephalans in deep-water, benthic amphipods, but it appears low compared to that often reported for acanthocephalan species infecting littoral amphipods. Parasite occurrence d…