Tiling models for metadislocations in AlPdMn approximants

The AlPdMn quasicrystal approximants xi, xi', and xi'_n of the 1.6 nm decagonal phase and R, T, and T_n of the 1.2 nm decagonal phase can be viewed as arrangements of cluster columns on two-dimensional tilings. We substitute the tiles by Penrose rhombs and show, that alternative tilings can be constructed by a simple cut and projection formalism in three dimensional hyperspace. It follows that in the approximants there is a phasonic degree of freedom, whose excitation results in the reshuffling of the clusters. We apply the tiling model for metadislocations, which are special textures of partial dislocations.Comment: 7 pages, 2 figures, Proceedings of International Conference on Quasicrystals

Cyclization of an α,β-Unsaturated Hydrazone Catalyzed by a BINOL-Phosphoric Acid: Pericyclic or Not?

Density functional theory is used to study the mechanism of the title reaction, one of the first catalytic asymmetric 6π-electrocyclizations observed experimentally. The benzylideneacetone-derived phenyl hydrazone is chosen as model substrate for the cyclization reaction, both in the protonated (A) and unprotonated (B) form, while the isoelectronic carbon analogue, 1,5-diphenylpentadienyl anion (C), serves as a reference for comparisons. The barrier to cyclization is computed to be more than 15 kcal/mol lower in A compared with B, in line with the observed acid catalysis. The relevant transition states to cyclization are characterized for A and C using orbital inspection, natural bond orbital analysis, nucleus independent chemical shifts, and stereochemical indicators. The cyclization of C is confirmed to be pericyclic, while that of A can be described as pseudopericyclic ring closure involving an intramolecular nucleophilic addition

Plantevern i grønnsaker. Integrert bekjempelse

I likhet med oss mennesker kan også planter bli sjuke eller på annen måte bli forstyrret i utviklingen. Begge trenger vi de riktige næringsstoffene for å holde oss friske, og vi må ha det riktige miljøet rundt oss. For å unngå sjukdom og andre skader er dessuten forskjellige forsvarsmekanismer viktige. Planter kan forsvare seg med for eksempel torner mot beitende dyr, behåring mot krypende insektlarver eller ved glatte blad som gjør det vanskelig for soppsporer å feste seg. Dessuten inneholder planter spesielle stoffer som kan være direkte giftige mot skadegjørere. Slike stoffer kalles sekundære plantestoffer. En del sekundære plantestoffer benytter vi som plantevernmidler, medisin, krydder eller i parfyme. I naturlige økosystemer vil for eksempel insekter som spiser planter bli spist av rovinsekter eller bli drept av parasitter. Slike naturlige øko - systemer vil være stabile fordi artsmangfoldet er stort. I jordbruket derimot, dyrker vi store arealer med kun én planteart. I tillegg vil plantene som oftest være foredlet for å gi størst mulig spisbar avling. Foredling har ofte gått på bekostning av plantas forsvarsmekanismer. En slik menneskelig påvirkning i naturen får konsekvenser. Vi kan få opptreden av skadegjørere i stort antall. For å kontrollere skadegjørere i landbruket har en tatt i bruk forskjellige kontrolltiltak som for eksempel kjemiske plantevernmidler. I økologisk landbruk og ved integrert plantevern forsøker en å tilnærme seg naturlige økosystemer i åkeren. Dette kan gjøres ved å legge forholdene for nytteorganismer som rovinsekter bedre til rette i åkeren. Hvordan dette gjøres, kan du lese mer om i grunnboka i kapitlet om integrert plantevern. For plantedyrkeren er det viktig å kjenne plantas venner og fiender eller planteskadegjørere og nytteorganismer, for å: • Vite om og når det er nødvendig å sette i verk kontrolltiltak • Sette i verk riktig kontrolltiltak • For å benytte riktig plantevernmiddel om sprøyting blir nødvendigpublishedVersio

Transparenz und Evaluierbarkeit des erziehungswissenschaftlichen Publikationsaufkommens. Eine anwendungsorientierte Studie

Der Beitrag stellt Ziele und erste Ergebnisse des DFG-Projekts "Innovative bibliometrische Verfahren zur kontinuierlichen Beobachtung der sozialwissenschaftlichen Forschungsproduktion" vor. Eine Analyse des Publikationsverhaltens von Erziehungswissenschaftlern zeigt die große Bedeutung des Publikationstyps Sammelwerksbeitrag und der Publikationssprache Deutsch, aber auch eine ausgeprägte Heterogenität in der Publikationspraxis von erziehungswissenschaftlichen Institutionen. Skizziert wird schließlich der Vorschlag für einen neuen, dieser Publikationspraxis angemessenen, bibliometrischen Indikator. (DIPF/Autor

Precision mass measurements of magnesium isotopes and implications on the validity of the Isobaric Mass Multiplet Equation

If the mass excess of neutron-deficient nuclei and their neutron-rich mirror partners are both known, it can be shown that deviations of the Isobaric Mass Multiplet Equation (IMME) in the form of a cubic term can be probed. Such a cubic term was probed by using the atomic mass of neutron-rich magnesium isotopes measured using the TITAN Penning trap and the recently measured proton-separation energies of $^{29}$Cl and $^{30}$Ar. The atomic mass of $^{27}$Mg was found to be within 1.6$\sigma$ of the value stated in the Atomic Mass Evaluation. The atomic masses of $^{28,29}$Mg were measured to be both within 1$\sigma$, while being 8 and 34 times more precise, respectively. Using the $^{29}$Mg mass excess and previous measurements of $^{29}$Cl we uncovered a cubic coefficient of $d$ = 28(7) keV, which is the largest known cubic coefficient of the IMME. This departure, however, could also be caused by experimental data with unknown systematic errors. Hence there is a need to confirm the mass excess of $^{28}$S and the one-neutron separation energy of $^{29}$Cl, which have both come from a single measurement. Finally, our results were compared to ab initio calculations from the valence-space in-medium similarity renormalization group, resulting in a good agreement.Comment: 7 pages, 3 figure

Breakdown of the Isobaric Multiplet Mass Equation for the A = 20 and 21 Multiplets

Using the Penning trap mass spectrometer TITAN, we performed the first direct mass measurements of 20,21Mg, isotopes that are the most proton-rich members of the A = 20 and A = 21 isospin multiplets. These measurements were possible through the use of a unique ion-guide laser ion source, a development that suppressed isobaric contamination by six orders of magnitude. Compared to the latest atomic mass evaluation, we find that the mass of 21Mg is in good agreement but that the mass of 20Mg deviates by 3{\sigma}. These measurements reduce the uncertainties in the masses of 20,21Mg by 15 and 22 times, respectively, resulting in a significant departure from the expected behavior of the isobaric multiplet mass equation in both the A = 20 and A = 21 multiplets. This presents a challenge to shell model calculations using either the isospin non-conserving USDA/B Hamiltonians or isospin non-conserving interactions based on chiral two- and three-nucleon forces.Comment: 5 pages, 2 figure