Photoprotective non-photochemical quenching (NPQ) in higher plants is the result of the formation of energy quenching traps in the light-harvesting antenna of photosystem II (PSII). It has been ...proposed that this quenching trap is a lutein molecule closely associated with the chlorophyll terminal emitter of the major light-harvesting complex LHCII. We have used a combination of time-dependent density functional theory (TD-DFT) and the semiempirical MNDO-CAS-CI method to model the chlorophyll–lutein energy transfer dynamics of the highly quenched crystal structure of LHCII. Our calculations reveal that the incoherent “hopping” of energy from Chla612 to the short-lived, dipole forbidden 21Ag – state of lutein620 accounts for the strong fluorescence quenching observed in these crystals. This adds weight to the argument that the same dissipative pathway is responsible for in vivo NPQ.
Marine geoheritage is an important but still underdeveloped concept. Field investigations in the Abrau area (Krasnodar Region, southwestern Russia) and subsequent interpretations allow for the ...characterization of its geoheritage. Two geosites, namely Abrau and Limanchik, are delineated and assessed semi-qualitatively. Their high heritage value, complexity, and appropriate “technical” properties are appraised. The Abrau geosite features Abrau Lake with its enigmatic origin and the outcrops of deformed Upper Cretaceous carbonate flysch deposits. The Limanchik geosite represents an outstanding example of coastal abrasion, Paleocene siliciclastic flysch with trace fossils, and a coastal lagoon separated from the sea by a bar. The heritage aspects of the study areas are related to the development of the Late Cretaceous, Paleocene, and Pliocene seas, as well as to the active dynamics of the Black Sea coastal zone. The duality of marine geoheritage is linked to its relation to both ancient and modern marine environments.
Some previous studies have already highlighted the importance of Quaternary sediments as geoheritage, although the related knowledge remains incomplete and geographically biased. Unique Quaternary ...features are often overlooked in areas famous for their pre-Quaternary geoheritage. Moreover, the already established high-value linked to pre-Quaternary phenomena require comprehensive descriptions; therefore, it is reasonable to analyze the related Quaternary features (even if these are only locally unique). For the purposes of the present study, three localities that form parts of larger geosites, and which represent Quaternary sediments of Mountainous Adygeya in the Western Caucasus, are characterized. They are assessed qualitatively, with a general description of sediments and attention paid to their origin, potential scientific importance, and accessibility. The Rufabgo Canyon hosts colluvial megaclast sediments. The Dakh–Sakhray Confluence exhibits typical alluvial sediment where detrital clasts are mixed with rather numerous Fe-rich concretions washed out from the parent rocks. The Stonesea Range exhibits mixed eluvial–deluvial sediment formed as a result of the karstification of carbonates and the erosion of overlaying red siliciclastics. All these sediments are of interest to scientists because they can be employed for promising research projects, revealing the peculiarities of the local patterns of Quaternary sedimentation. The localities under consideration are geoheritage points within the larger geosites and are perfectly accessible. Aside from their use by scientists, these localities can potentially be used by geosciences educators to train university students in sedimentology. In two cases, the sediments are also aesthetically important for attracting tourists. Generally, Quaternary sediments should be considered together with the other unique features represented in the geosites of Mountainous Adygeya.
We discover that hcp phases of Fe and Fe(0.9)Ni(0.1) undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through ...anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio, and Mössbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe.
Despite of significant progress in palaeobiology, the discovery of new evidence for biotic crises cannot be excluded. Various notions about the Aalenian (Middle Jurassic) biotic crisis are scattered ...in the palaeontological and geological literature. This information needs to be summarised and re-evaluated before making any further judgements. A critical analysis of the existing literature suggests the absence of solid grounds for a definitive understanding of this event. Nonetheless, it is clear that several fossil groups like foraminifers and marine reptiles were stressed (at least, regionally), and eustatic fluctuations and changing palaeoclimate can be related to perturbations in the fossil record. This view is supported by a preliminary check of the long-term fossil records and the regional evidence. The general hypothesis of the Aalenian biotic crisis is worthy of a research agenda, and future global and regional studies of many fossil groups in different palaeoenvironmental contexts will either prove or disprove this hypothesis.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
46.
The surface energy of metals Vitos, L.; Ruban, A.V.; Skriver, H.L. ...
Surface science,
08/1998, Letnik:
411, Številka:
1-2
Journal Article
Recenzirano
We have used density functional theory to establish a database of surface energies for low index surfaces of 60 metals in the periodic table. The data may be used as a consistent starting point for ...models of surface science phenomena. The accuracy of the database is established in a comparison with other density functional theory results and the calculated surface energy anisotropies are applied in a determination of the equilibrium shape of nano-crystals of Fe, Cu, Mo, Ta, Pt and Pb.
Strain-induced and chemical interactions of interstitial carbon atoms in bcc or alpha-Fe are obtained in first-principles calculations. Subsequent Monte Carlo simulations show that at low ...temperatures, carbon atoms prefer to occupy at least two different octahedral sublattices, which is due to quite strong attractive interactions of carbon atoms at the corresponding coordination shells. The direct total-energy calculations of one of the obtained ordered structures with composition Fe16C2, show that it is more stable than the predicted earlier structure with the same composition but carbon atoms occupying only one octahedral sublattice. This indicates that the long-existing thermodynamic mean-field theory of ordering of carbon in alpha-Fe assuming strong preference of carbon atoms to occupy only one octahedral sublattice is deficient. It is shown that the presence of carbon atoms only at one octahedral sublattice in the experimentally observed martensitic phase, alpha'-Fe, is a self-trapping effect. It occurs during a displacive martensitic transformation from gamma- to alpha-Fe, which kinematically transfers the carbon atoms from a single fcc octahedral sublattice to one of three octahedral sublattices, where they appear to be locked by a consequent tetragonal distortion minimizing elastic energy of the phase. The latter creates a strong preference for carbon atoms to be only at one already occupied octahedral sublattice preventing them from further distribution over the other sublattices.
Digital management issues are extensive and are often considered from a general theoretical point of view, which makes manifestation of well-systematized practical guidelines relevant. The article ...presents a review of a recent and successful work on digital governance. The book consists of two introductory sections and 12 chapters combined into three parts. The issues considered in the reviewed work relate to digitalization processes and their impact on management activities, collective intelligence, and the possibilities of its application in organizational management implementation, as well as artificial intelligence, its technologies, and prospects for their use in modern management. It is strongly recommended that these technologies be implemented as part of pilot projects with testing of their effectiveness and subsequent retrofitting. It is established that the author does not focus on purely technological aspects, but, firstly, shows the continuity and interrelation of “classical” and digital management and, secondly, focuses on a manager’s personality and new challenges for them in the context of digitalization. The book is characterized by an academic, but at the same time simple and well-structured presentation of complex material. There are a lot of specifics, examples, and recommendations. Some aspects of digital management remained out of the author’s of the book field of view, but such incompleteness is inevitable. The book can be useful for specialists, teachers, and university students, as well as managers themselves.
Catalytic autothermal reforming (ATR) of a number of hydrocarbon fuels was studied over composite RhCZ-S catalyst (0.24 wt% Rh supported on structured Ce0.75Zr0.25O2-δ-ƞ-Al2O3/FeCrAl carrier). ...Iso-octane and n-hexadecane as model compounds of gasoline and diesel fuel, respectively, showed similar properties in ATR process, indicating weak influence of molecular weight and branching degree of liquid alkanes on catalyst performance. Biodiesel ATR characteristics were similar to those of n-hexadecane ATR, as the utilized biodiesel predominantly contained alkanes, being products of fatty acid tail fragments hydrogenation. Even in the case of gasoline ATR, sufficient amount of monoaromatics did not influence a lot on the catalyst performance. Diesel ATR showed rather different situation: the catalyst tended to lose activity due to coking, and incomplete fuel conversion was observed. Analysis of unreacted fuel revealed bi- and polyaromatic compounds (mainly naphtalenes and antracenes) were difficult to convert.
•Composite Rh/Zr0.25Ce0.75O2/FeCrAl wire mesh catalyst with high Rh dispersion.•High performance in autothermal reforming (ATR) of gasoline and biodiesel.•Deactivation and coking in diesel ATR due to incomplete di-, polyaromatics conversion.•Weak influence of molecular weight and branching degree of alkanes on ATR process.•Syngas productivity in gasoline and biodiesel ATR: 2.5 m3Lcat−1h−1.
Strontium hexaferrite has achieved immense attention in industries, manufacturing crucial components for devices, technological applications, and machine making due to its high coercivity value. The ...efficient technique of sol–gel auto-combustion was espoused for the synthesis, and the morphological studies affirmed the hexagonal shape of the particles. The magnetic analysis revealed the sample being a potential substance for perpendicular recording media applications. The dielectric studies disclosed relaxations and polarization effects existing in the material. The linkage of structural, magnetic, and dielectric properties and their inter-influences are the remarkable consequences of the research work.
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