Convergent-Beam EMCD: Benefits, Pitfalls, and Applications

Energy-loss magnetic chiral dichroism (EMCD) is a versatile method for studying magnetic properties on the nanoscale. However, the classical EMCD technique is notorious for its low signal to noise ratio (SNR). Here, we study the theoretical possibilities of using a convergent beam for EMCD. In particular, we study the influence of detector positioning as well as convergence and collection angles on the detectable EMCD signal. In addition, we analyze the expected SNR and give guidelines for achieving optimal EMCD results

Electron vortices in crystals

The propagation of electron beams carrying angular momentum in crystals is studied using a multislice approach for the model system Fe. It is found that the vortex beam is distorted strongly due to elastic scattering. Consequently, the expectation value of the angular momentum as well as the local vortex components change with the initial position of the vortex and the propagation depth, making numerical simulations indispensable when analyzing experiments

Comment on "Quantized Orbital Angular Momentum Transfer and Magnetic Dichroism in the Interaction of Electron Vortices with Matter"

It was claimed (Lloyd et al., PRL 108 (2012) 074802) that energy loss magnetic chiral dichroism (EMCD) with electron vortex beams is feasible, and has even advantages over the standard setup with Bragg diffracted waves. In this Comment, we show that Lloyd et al. ignored an important constraint on the proposed selection rule for the transfer of angular momentum in the interaction, namely that it is only valid for an atom located in the very center of the vortex. As an experimental consequence, the EMCD signal will only be strong for extremely small nanoparticles of 1 to 2 nm diameter.Comment: Submitted to Physical Review Letters 11 July 2012. Accepted for publication 3 April 2013. "Copyright (2013) by the American Physical Society." http://prl.aps.org

Framing Sports’ Corporate Social Responsibility: U.S. Women’s Vs. Men’s Soccer Leagues

Professional sports are a rich industry for corporate social responsibility (CSR) research because today’s sports organizations are big businesses that generate shared identities and strong affective connections among fans, teams, and players. Further, today’s professional sports consumers expect organizations to behave in socially responsible ways and to give back to their communities. While nearly every sports organization, like most other major businesses, practices CSR, sports teams are in a unique position because they receive greater media coverage than other businesses. Not all of this coverage is positive, however, as news reports about the controversy over compensation inequities in women’s soccer have elevated conversations about gender equity not just in sports, but also in society at large. Moreover, research suggests that men’s team sports receive much greater coverage than their women counterparts. These differences in media coverage and compensation create a compelling context for comparing news reports of the National Women’s Soccer League (NWSL) and Major League Soccer (MLS) team’s socially responsible behaviors. Specifically, this quantitative content analysis compared local newspaper coverage of three NWSL and three MLS teams’ corporate social responsibility (CSR) behaviors. The results indicate that there were significant differences in the quantity, tone, and framing of the CSR coverage. Not only did the MLS receive significantly greater and more positive coverage than the NWSL, but also the issue, source, and visual frames differed significantly between leagues. These findings’ implications in terms of CSR, framing, and gender theories in the context of the professional sports industry as well as practical suggestions for journalists and news consumers are also discussed

The nucleotide-binding sub-proteome of mustard chloroplasts and its involvement in plastid redox signaling

The actual keen about redox signal development at the plastid photosynthetic apparatus, transmission and the reply to the signal was highlighted by the contribution of three review article to this work. Pfannschmidt et al. 2008 summarizes short and long term acclimation responses (STR and LTR respectively) to redox signals of the Plastoquinone (PQ) pool and the involvement of putative phosphorylation cascades and thioredoxins as well as the influence of the redox state on primary target genes in plastids and nucleus. Further on experimental approaches for the generation of a defined redox state at the photosynthetic electron transport (PET) chain was discussed. Dietzel et al. 2008 reviews the different types of retrograde signals between plastids and nucleus as well as the complexity and interaction of the signaling cascades and networks and in Pfalz et al. 2012 the environmental influences on gene expression and recent findings within plastid redox signaling were discussed. For a detailed investigation of the adaption of plastid gene expression responding to plastid redox signals the gene expression machinery of chloroplasts itself was studied. An experimental approach was used for the generation of a defined redox signal in mustard cotyledons, the following isolation of its chloroplasts and further on the nucleotide binding sub-proteome using heparin-Sepharose (HS) (Steiner et al. 2009; Schröter et al. 2010). The characterization and comparison of mustard cotyledons acclimated to redox signal inducing Light-qualities with Arabidopsis thaliana cotyledons was important for the integration of new findings within Sinapis alba into established models (Steiner et al. 2009). An effect on the transcriptional regulation of the two plastome-encoded genes psaAB and psbA was studied here concerning promoter recognition and specificity (Steiner et al. 2009). The impact of phosphorylation events on gene expression was surveyed and confirmed by determination of the phosphorylation state of the HS fractions, the endogenous kinase activity and the cooperative influence of kinase activity and thiol redox state on Chloroplast transcription (Steiner et al. 2009). HS proteins fractions contain a high degree of DNA and especially psaA and psbA binding proteins which were identified using mass spectrometry and Brassicales databases (Steiner et al. 2009; Schröter et al. 2010; Steiner et al. 2011). Special emphasis was on the analysis of the essential subunits of the plastid-encoded plastid RNA-polymerase (PEP) which was well to prepare by 2 dimensional (2D) blue native (BN) gel electrophoresis (Schröter et al. 2010; Steiner et al. 2011). The degree of proteins involved in gene expression was strongly increased by the use of a second chromatographic step with Phosphocellulose (PC) additional to HS (Schröter et al. 2014). Visualization and identification of this nucleotide binding sub-proteome was the aim of the last publication included into this work giving access to a precise view on the gene expression related proteome of mustard plastids (Schröter et al. 2014).Drei review Artikel beleuchten das aktuelle Wissen über die Redoxsignalentwicklung im plastidären Photosyntheseapparat, die Signalübermittlung und –beantwotung. Pfannschmidt et al. 2008 fasst Kurzzeitund Langzeitantworten auf Redoxsignale des Plastochinonpools zusammen und darüberhinaus die Einbeziehung von Phosphorylierungskaskaden und Thioredoxinen sowie den Einfluss des Redoxstatus auf primäre Zielgene in Plastiden und dem Zellkern. Desweiteren wurden experimentelle Ansätze für die Erzeugung eines definierten Redoxstatus in der photosynthetischen Elektronentransportkette diskutiert. Dietzel et al. 2008 fasst die verschiedenen Typen retrograder Signale zwischen Plastiden und Zellkern zusammen sowie die Komplexität und Interaktion der Signalkaskaden und –netzwerke und in Pfalz et al. 2012 werden die Umwelteinflüsse auf die Genexpression und aktuelle Erkenntnisse über Redoxsignale diskutiert. Für eine detailierte Untersuchung der Genexpressionsadaption als Antwort auf plastidäre Redoxsignale wurde die Genexpressionsmaschinerie der Chloroplasten direkt studiert. Ein definiertes Redoxsignal wurde in Senfkeimlingen generiert, anschließend die Chloroplasten und schließlich die nukleotidbindenden Proteine mittels Chromatographie über Heparinsepharose (HS) isoliert (Steiner et al. 2009; Schröter et al. 2010). Der Vergleich und die Charakterisierung der Senfkeimlinge, die an das Redoxsignal induzierende Licht akklimatisiert waren, mit Arabidopsis thaliana Keimlingen war wichtig für die Integration neuer Erkenntnisse über Sinapis alba in etablierte Modelle (Steiner et al. 2009). Der Effekt auf die transkriptionale Regulierung der zwei plastomkodierten Gene psaAB und psbA wurde hinsichtlich Promotererkennung und –spezifität untersucht (Steiner et al. 2009). Die Auswirkung von Phosphorylierungen auf die Genexpression wurde, durch die Bestimmung des Phosphorylierungsgrades der HS Fraktionen, der endogene Kinaseaktivität und des kooperativen Einflusses der Kinaseaktivität und des Thiolredoxstatus auf die Chloroplastentranskription, untersucht (Steiner et al. 2009). HS Fraktionen besitzen einen hohen Grad an DNA- und speziell psaA- und psbA-bindenden Proteinen, die durch Massenspektrometrie und Analyse mit Brassicales-Datenbanken identifiziert werden können (Steiner et al. 2009; Schröter et al. 2010; Steiner et al. 2011). Der Schwerpunkt lag bei der Analyse der essentiellen Untereinheiten der plastidenkodierten plastidären RNAPolymerase (PEP), die gut durch 2 dimensionale (2D) blue native (BN) Gelelektrophorese präpariert werden konnte (Schröter et al. 2010; Steiner et al. 2011). Der Anteil an Proteinen der Genexpression konnte durch eine zweite Chromatographie über Phosphocellulose (PC) zusätzlich zur HSChromatographie erzielt werden (Schröter et al. 2014). In der letzten Publikation dieser Arbeit geht es vorrangig um die Visualisierung und Identifizierung dieses nukleotidbindenden Teilproteoms, wodurch ein Zugang zu einem detaillierteren Einblick in das genexpressionsrelevante Proteom der Senfplastiden erzielt wurde (Schröter et al. 2014)

Polyominoes and Polyiamonds as Fundamental Domains of Isohedral Tilings with Rotational Symmetry

We describe computer algorithms that produce the complete set of isohedral tilings by n-omino or n-iamond tiles in which the tiles are fundamental domains and the tilings have 3-, 4-, or 6-fold rotational symmetry. The symmetry groups of such tilings are of types p3, p31m, p4, p4g, and p6. There are no isohedral tilings with symmetry groups p3m1, p4m, or p6m that have polyominoes or polyiamonds as fundamental domains. We display the algorithms' output and give enumeration tables for small values of n. This expands on our earlier works (Fukuda et al 2006, 2008)

Observation of the Larmor and Gouy Rotations with Electron Vortex Beams

Electron vortex beams carrying intrinsic orbital angular momentum (OAM) are produced in electron microscopes where they are controlled and focused using magnetic lenses. We observe various rotational phenomena arising from the interaction between the OAM and magnetic lenses. First, the Zeeman coupling, proportional to the OAM and magnetic field strength, produces an OAM-independent Larmor rotation of a mode superposition inside the lens. Second, hen passing through the focal plane, the electron beam acquires an additional Gouy phase dependent on the absolute value of the OAM. This brings about the Gouy rotation of the superposition image proportional to the sign of the OAM. A combination of the Larmor and Gouy effects can result in the addition (or subtraction) of rotations, depending on the OAM sign. This behaviour is unique to electron vortex beams and has no optical counterpart, as Larmor rotation occurs only for charged particles. Our experimental results are in agreement with recent theoretical predictions.Comment: 5 pages, 5 figure