Self-Diffusion in Random-Tiling Quasicrystals

The first explicit realization of the conjecture that phason dynamics leads to self-diffusion in quasicrystals is presented for the icosahedral Ammann tilings. On short time scales, the transport is found to be subdiffusive with the exponent $\beta\approx0.57(1)$, while on long time scales it is consistent with normal diffusion that is up to an order of magnitude larger than in the typical room temperature vacancy-assisted self-diffusion. No simple finite-size scaling is found, suggesting anomalous corrections to normal diffusion, or existence of at least two independent length scales.Comment: 11 pages + 2 figures, COMPRESSED postscript figures available by anonymous ftp to black_hole.physics.ubc.ca directory outgoing/diffuse (use bi for binary mode to transfer), REVTeX 3.0, CTP-TAMU 21/9

Stability of the hard-sphere icosahedral quasilattice

The stability of the hard-sphere icosahedral quasilattice is analyzed using the differential formulation of the generalized effective liquid approximation. We find that the icosahedral quasilattice is metastable with respect to the hard-sphere crystal structures. Our results agree with recent findings by McCarley and Ashcroft [Phys. Rev. B {\bf 49}, 15600 (1994)] carried out using the modified weighted density approximation.Comment: 15 pages, 2 figures available from authors upon request, (revtex), submitted to Phys. Rev.

Phason elasticity of a three-dimensional quasicrystal: transfer-matrix method

We introduce a new transfer matrix method for calculating the thermodynamic properties of random-tiling models of quasicrystals in any number of dimensions, and describe how it may be used to calculate the phason elastic properties of these models, which are related to experimental measurables such as phason Debye-Waller factors, and diffuse scattering wings near Bragg peaks. We apply our method to the canonical-cell model of the icosahedral phase, making use of results from a previously-presented calculation in which the possible structures for this model under specific periodic boundary conditions were cataloged using a computational technique. We give results for the configurational entropy density and the two fundamental elastic constants for a range of system sizes. The method is general enough allow a similar calculation to be performed for any other random tiling model.Comment: 38 pages, 3 PostScript figures, self-expanding uuencoded compressed tar file, LaTeX using RevTeX macros and epsfig.st

Exact Eigenstates of Tight-Binding Hamiltonians on the Penrose Tiling

We investigate exact eigenstates of tight-binding models on the planar rhombic Penrose tiling. We consider a vertex model with hopping along the edges and the diagonals of the rhombi. For the wave functions, we employ an ansatz, first introduced by Sutherland, which is based on the arrow decoration that encodes the matching rules of the tiling. Exact eigenstates are constructed for particular values of the hopping parameters and the eigenenergy. By a generalized ansatz that exploits the inflation symmetry of the tiling, we show that the corresponding eigenenergies are infinitely degenerate. Generalizations and applications to other systems are outlined.Comment: 24 pages, REVTeX, 13 PostScript figures include

Surface Magnetization and Critical Behavior of Aperiodic Ising Quantum Chains

We consider semi-infinite two-dimensional layered Ising models in the extreme anisotropic limit with an aperiodic modulation of the couplings. Using substitution rules to generate the aperiodic sequences, we derive functional equations for the surface magnetization. These equations are solved by iteration and the surface magnetic exponent can be determined exactly. The method is applied to three specific aperiodic sequences, which represent different types of perturbation, according to a relevance-irrelevance criterion. On the Thue-Morse lattice, for which the modulation is an irrelevant perturbation, the surface magnetization vanishes with a square root singularity, like in the homogeneous lattice. For the period-doubling sequence, the perturbation is marginal and the surface magnetic exponent varies continuously with the modulation amplitude. Finally, the Rudin-Shapiro sequence, which corresponds to the relevant case, displays an anomalous surface critical behavior which is analyzed via scaling considerations: Depending on the value of the modulation, the surface magnetization either vanishes with an essential singularity or remains finite at the bulk critical point, i.e., the surface phase transition is of first order.Comment: 8 pages, 7 eps-figures, uses RevTex and epsf, minor correction

AN EXAMPLE OF APPLYING ALGORITHM TO CREATE THE ACTUAL PQ DIAGRAM OF A HYDROGENERATOR

U radu je prikazana provedba metodologije određivanja korisničke pogonske karte na primjeru hidroagregata br. 3 u HE Vinodol. Kao predložak u pripremi podloga i sustavnom određivanju granica dopuštenog rada agregata poslužio je blok dijagram sa slike 15 u [1], koji na pregledan način ocrtava tijek provedbe pojedinih radnji potrebnih za tvorbu korisničke pogonske karte. Svi međukoraci su dokumentirani, a dobiveni rezultati prikazani tablično i grafički. Svaka od konačno određenih granica je ucrtana u korisničku pogonsku kartu promatranog agregata. S obzirom na složenost provedbe proračuna graničnih uvjeta koje nameću elektromagnetska i toplinska zbivanja u čeonom prostoru, u radu je na konkretnom primjeru iz prakse prikazana potpuno nova metodologija utvrđivanja graničnih vrijednosti uzdužne komponente magnetske indukcije, temeljeno na rezultatima mjerenja indukcije i pripadne nadtemperature u trajnom kapacitivnom radu generatora. Predložena metoda je primjenjiva za bilo koji sinkroni generator.The work describes the application of the methodology of defining the actual PQ diagram on the example of Hydrogenerator-turbine unit No. 3 at Vinodol Hydroelectric Power Plant. Used as a basis for preparing documents and determining the unit’s operating tolerances was a block diagram in Figure 15, contained in [1], which provides a clear survey of the sequence of steps required to create an actual PQ diagram. All intermediate steps are documented and the obtained results are shown in tables and graphics. Each of finally defined limits is imported into the actual PQ diagram of the observed unit. Considering the complexity of calculating the limit conditions imposed by electromagnetic and thermal occurrences in the end region, in a concrete example from practice the present work describes an entirely new methodology of determining the limit values of the longitudinal magnetic induction component, based on the results of measuring induction and pertaining over-temperature in the generator’s permanent capacitive operation. The proposed method is applicable to any synchronous generator

AN EXAMPLE OF APPLYING ALGORITHM TO CREATE THE ACTUAL PQ DIAGRAM OF A HYDROGENERATOR

U radu je prikazana provedba metodologije određivanja korisničke pogonske karte na primjeru hidroagregata br. 3 u HE Vinodol. Kao predložak u pripremi podloga i sustavnom određivanju granica dopuštenog rada agregata poslužio je blok dijagram sa slike 15 u [1], koji na pregledan način ocrtava tijek provedbe pojedinih radnji potrebnih za tvorbu korisničke pogonske karte. Svi međukoraci su dokumentirani, a dobiveni rezultati prikazani tablično i grafički. Svaka od konačno određenih granica je ucrtana u korisničku pogonsku kartu promatranog agregata. S obzirom na složenost provedbe proračuna graničnih uvjeta koje nameću elektromagnetska i toplinska zbivanja u čeonom prostoru, u radu je na konkretnom primjeru iz prakse prikazana potpuno nova metodologija utvrđivanja graničnih vrijednosti uzdužne komponente magnetske indukcije, temeljeno na rezultatima mjerenja indukcije i pripadne nadtemperature u trajnom kapacitivnom radu generatora. Predložena metoda je primjenjiva za bilo koji sinkroni generator.The work describes the application of the methodology of defining the actual PQ diagram on the example of Hydrogenerator-turbine unit No. 3 at Vinodol Hydroelectric Power Plant. Used as a basis for preparing documents and determining the unit’s operating tolerances was a block diagram in Figure 15, contained in [1], which provides a clear survey of the sequence of steps required to create an actual PQ diagram. All intermediate steps are documented and the obtained results are shown in tables and graphics. Each of finally defined limits is imported into the actual PQ diagram of the observed unit. Considering the complexity of calculating the limit conditions imposed by electromagnetic and thermal occurrences in the end region, in a concrete example from practice the present work describes an entirely new methodology of determining the limit values of the longitudinal magnetic induction component, based on the results of measuring induction and pertaining over-temperature in the generator’s permanent capacitive operation. The proposed method is applicable to any synchronous generator

Effect of in vitro gastrointestinal digestion on the total phenolic contents and antioxidant activity of wild Mediterranean edible plant extracts

The recent interest in wild edible plants is associated with their health benefits, which are mainly due to their richness in antioxidant compounds, particularly phenolics. Nevertheless, some of these compounds are metabolized after ingestion, being transformed into metabolites frequently with lower antioxidant activity. The aim of the present study was to evaluate the influence of the digestive process on the total phenolic contents and antioxidant activity of extracts from four wild edible plants used in the Mediterranean diet (Beta maritima L., Plantago major L., Oxalis pes-caprae L. and Scolymus hispanicus L.). HPLC-DAD analysis revealed that S. hispanicus is characterized by the presence of caffeoylquinic acids, dicaffeoylquinic acids and flavonol derivatives, P. major by high amounts of verbascoside, B. maritima possesses 2,4-dihydroxybenzoic acid, 5-O-caffeoylquinic acid, quercetin derivatives and kaempferol-3-O-rutinoside, and O. pes-caprae extract contains hydroxycinnamic acids and flavone derivatives. Total phenolic contents were determined by Folin-Ciocalteu assay, and antioxidant activity by the ABTS, DPPH, ORAC and FRAP assays. Phenolic contents of P. major and S. hispanicus extracts were not affected by digestion, but they significantly decreased in B. maritima after both phases of digestion process and in O. pes-caprae after the gastric phase. The antioxidant activity results varied with the extract and the method used to evaluate the activity. Results showed that P. major extract has the highest total phenolic contents and antioxidant activity, with considerable values even after digestion, reinforcing the health benefits of this species.European Union (FEDER funds through COMPETE)European Union (EU)European Union (FEDER)European Union (EU)Programa de Cooperacion Interreg V-A Espana - Portugal (POCTEP) 2014-2020 [0377_IBERPHENOL_6_E]project INTERREG - MD. Net: When Brand Meets PeopleFCT Portuguese Foundation for Science and Technolog

Global responses to the COVID-19 pandemic by recreational anglers: considerations for developing more resilient and sustainable fisheries

The global COVID-19 pandemic resulted in many jurisdictions implementing orders restricting the movements of people to inhibit virus transmission, with recreational angling often either not permitted or access to fisheries and/or related infrastructure being prevented. Following the lifting of restrictions, initial angler surveys and licence sales suggested increased participation and effort, and altered angler demographics, but with evidence remaining limited. Here, we overcome this evidence gap by identifying temporal changes in angling interest, licence sales, and angling effort in world regions by comparing data in the 'pre-pandemic' (up to and including 2019); 'acute pandemic' (2020) and 'COVID-acclimated' (2021) periods. We then identified how changes can inform the development of more resilient and sustainable recreational fisheries. Interest in angling (measured here as angling-related internet search term volumes) increased substantially in all regions during 2020. Patterns in licence sales revealed marked increases in some countries during 2020 but not in others. Where licence sales increased, this was rarely sustained in 2021; where there were declines, these related to fewer tourist anglers due to movement restrictions. Data from most countries indicated a younger demographic of people who participated in angling in 2020, including in urban areas, but this was not sustained in 2021. These short-lived changes in recreational angling indicate efforts to retain younger anglers could increase overall participation levels, where efforts can target education in appropriate angling practices and create more urban angling opportunities. These efforts would then provide recreational fisheries with greater resilience to cope with future global crises, including facilitating the ability of people to access angling opportunities during periods of high societal stress.CG and CS received funding from the Danish Rod and Net Fish Licence funds (project 39122). CS, MSW and the German telephone survey have been cofounded by the European Commission’s Data Collection Framework (DCF). WCL and HVS received financial support from the Federal Ministry of Education and Research of Germany in the framework of marEEshift (project no. 01LC1826B). WMP and KH were supported by the One Ocean Hub, an independent programme for collaborative research for development, funded by UK Research and Innovation (UKRI) through the Global Challenges Research Fund (GCRF).Peer reviewe