The Multidimensional Study of Viral Campaigns as Branching Processes

Viral campaigns on the Internet may follow variety of models, depending on the content, incentives, personal attitudes of sender and recipient to the content and other factors. Due to the fact that the knowledge of the campaign specifics is essential for the campaign managers, researchers are constantly evaluating models and real-world data. The goal of this article is to present the new knowledge obtained from studying two viral campaigns that took place in a virtual world which followed the branching process. The results show that it is possible to reduce the time needed to estimate the model parameters of the campaign and, moreover, some important aspects of time-generations relationship are presented.Comment: In proceedings of the 4th International Conference on Social Informatics, SocInfo 201

Identifying structure-selectivity correlations in the electrochemical reduction of CO₂: a comparison of well-ordered atomically-clean and chemically-etched Cu single crystal surfaces

Despite significant theoretical efforts, the identification of the active sites for the electrochemical reduction of CO2 (CO2RR) to specific chemical products has remained elusive. This is partially due to insufficient experimental data gathered on clean and atomically well-ordered electrode surfaces. Here, ultrahigh vacuum based preparation methods and surface science characterization techniques are used together with gas chromatography to demonstrate that subtle changes in the preparation of well-oriented Cu(100) and Cu(111) single crystal surfaces drastically affect their CO2RR selectivity. Copper single crystals with clean, flat, and atomically ordered surfaces are theoretically predicted to yield hydrocarbons. However, these were found experimentally to favour the production of H2. Only when roughness and defects are introduced, for example through an electrochemical etchingor a plasmatreatment, significant amounts of hydrocarbons are generated. These results clearly indicate that structural and morphological effects are the key factors determining the catalytic selectivity of CO2RR

Identifying structure-selectivity correlations in the electrochemical reduction of CO₂: a comparison of well-ordered atomically-clean and chemically-etched Cu single crystal surfaces

Despite significant theoretical efforts, the identification of the active sites for the electrochemical reduction of CO2(CO2RR) to specific chemical products has remained elusive. This is partially due to insufficient experimental data gathered on clean and atomically well-ordered electrode surfaces. Here, ultrahigh vacuum based preparation methods and surface science characterization techniques are used together with gas chromatography to demonstrate that subtle changes in the preparation of well-oriented Cu(100) and Cu(111) single crystal surfaces drastically affect their CO2RR selectivity. Copper single crystals with clean, flat, and atomically ordered surfaces are theoretically predicted to yield hydrocarbons. However, these were found experimentally to favour the production of H2. Only when roughness and defects are introduced, for example through an electrochemical etching or a plasma treatment, significant amounts of hydrocarbons are generated. These results clearly indicate that structural and morphological effects are the key factors determining the catalytic selectivity of CO2RR

SU(4) symmetry in the extended proton-neutron interacting boson model: multiplets and symmetry breaking

The manifestation of $SU(4)$ symmetry within an interacting boson model including particle-like and hole-like $\pi$- and $\nu$-bosons is shown for light nuclei around the Z=N=8 shell. We also present a consistent description of the particle-hole (intruder spin or $I$ spin) multiplets in the Extended Interacting Boson Model (EIBM) and of $\pi$-$\nu$ ($F$ spin) multiplets in the IBM-2 as a breaking of this $SU(4)$ symmetry

Quadrupole collective variables in the natural Cartan-Weyl basis

The matrix elements of the quadrupole collective variables, emerging from collective nuclear models, are calculated in the natural Cartan-Weyl basis of O(5) which is a subgroup of a covering $SU(1,1)\times O(5)$ structure. Making use of an intermediate set method, explicit expressions of the matrix elements are obtained in a pure algebraic way, fixing the $\gamma$-rotational structure of collective quadrupole models.Comment: submitted to Journal of Physics

Der Verbleib Quartärer Ammoniumverbindungen im Boden - Ergebnisse aus Studien mit Modellsubstanzen

Quartäre Alkylammoniumverbindungen (QAAV) sind eine Gruppe amphiphiler organischer Verbindungen, welche weltweit als Tensid und zur Desinfektion, beispielsweise in der Tierhaltung eingesetzt werden. Aufgrund ihres Einsatzes in der Tierhaltung oder als Formulierung in Pflanzenschutzmittel gelangen diese Stoffe mit hoher Wahrscheinlichkeit in Böden. Bislang sind Daten zum Verbleib der QAAVs in Böden in der Literatur allerdings kaum dokumentiert. Aufgrund des positiv geladenen Stickstoffatoms in ihrer Struktur, sowie bekannter Anwendung der QAAVs in Organotonen, ist von einem Eindringen in die Zwischenschichten aufweitbarer Tonminerale im Boden auszugehen. Eine langsame Desorption aus den Zwischenschichten könnte zu sub-inhibitorischen QAAV-Konzentrationen in der Bodenlösung führen, die zu einer Resistenzgenentwickung und Co-Selektion für Antibiotikaresistenzgene von Mikroorganismen beitragen. Eine höhere Affinität der Schichtsilikate im Vergleich zu anderen Bodenbestandteilen wird für die Sorption von QAAVs angenommen. Um zu prüfen, in welchem Umfang und mit welcher Rate QAAVs in Zwischenschichten von Tonmineralen wandern, werden Experimente zur Sorptionskinetik in Gegenwart von Smektit (Wyoming-Bentonit) in 8 Stufen im Konzentrationsbereich 0 mmol*g-1 Ton bis 1.5 mmol*g-1 Ton durchgeführt. Basierend auf diesen Ergebnissen wurde in Batch Sorptionsversuchen bei kontrolliertem pH die Affinität der QAAVs zu den Modellsubstanzen Huminsäure(Aldrich), Smektit und Eisenoxid (Goethit) und der Einfluss variabler Ionenstärke auf das Adsorptionsverhalten untersucht. Anschließend sind mit denselben Substanzen Desorptionsexperimente zur Ermittlung von Desorptionskinetiken durchgeführt worden. Das Eindringen von QAAVs in die Zwischenschichten aufweitbarer Tonminerale wurde mittels Röntgendiffraktometrie überprüft. Die Ergebnisse der Desorptions- und Sorptionsstudien liefern eine Grundlage zum Verständnis für den Verbleib und Transport von QAAVs in Böden

Intruder bands and configuration mixing in the lead isotopes

A three-configuration mixing calculation is performed in the context of the interacting boson model with the aim to describe recently observed collective bands built on low-lying $0^+$ states in neutron-deficient lead isotopes. The configurations that are included correspond to the regular, spherical states as well as two-particle two-hole and four-particle four-hole excitations across the Z=82 shell gap.Comment: 20 pages, 4 figures, accepted by PRC, reference added for section 1 in this revised versio

The Structure of a Silica Thin Film on Oxidized Cu(111): Conservation of Honeycomb Lattice and Role of the Interlayer

There is a crucial role of the metal-oxide interface in determining the growth ofsilica thin films. However, only a few metallic substrates have been explored so far.In previous studies, metal substrates exhibiting unreconstructed surfaces under oxygenexposure have been analyzed. In this work, we study the structure of a silica thinfilm grown on Cu(111) and propose that a copper oxide film formed at the interfaceinhibits the appearance of defects and domain boundaries. Our results suggest that thesilica film structure has flexible connections with the copper oxide interlayer leadingto a lattice solely composed of six-membered rings. This honeycomb configuration iscertainly of importance in the design of well-defined two-dimensional oxide thin films onmetallic substrates as well as for catalysis applications involving metal-oxide interfaces

The effect of cognition on the visually-induced illusion of self-motion (vection)

INTRODUCTION: The illusion of self-motion induced by moving visual stimuli has typically been attributed to bottom-up perceptual processes. Here, we investigated whether a cognitive factor such as spatial presence can contribute to the illusion. Spatial presence was indirectly manipulated by presenting either a photorealistic image of a natural scene or modified versions of the same stimulus. Those were created by either scrambling image parts in a mosaic-like manner or by slicing the original image horizontally and randomly reassembling it. We expected scene modifications to decrease spatial presence and thus impair vection. METHODS: Twelve observers viewed stimuli projected onto a curved projection screen (FOV: 54 ×40.5 ). Dependent measures included vection onset time, vection intensity, and convincingness of the illusion (0–100 ratings). Spatial presence was assessed with presence questionnaires. RESULTS: Scene modification led to both reduced presence scores and impaired vection: Modified stimuli yielded significantly longer vection onset times, lower perceived intensity, and lower convincingness ratings than the intact market scene. No clear difference was found between the sliced and scrambled stimuli or among the number of slices or mosaics (2, 8, or 32). Results suggest that high level information (consistent reference frame for the intact market scene) dominated over the low-level information (more contrast edges in the scrambled stimulus, which are known to facilitate vection). CONCLUSIONS: Results suggest a direct relation between spatial presence and self-motion perception. We posit that stimuli depicting naturalistic scenes provide observers with a convincing reference frame for the simulated environment which enables them to feel “spatially present”. This, in turn, facilitates the self-motion illusion. This work has important implications for both self-motion perception and motion simulator design and applications

Particle-hole excitations in the interacting boson model; 4, the U(5)-SU(3) coupling

In the extended interacting boson model (EIBM) both particle- and hole-like bosons are incorporated to encompass multi-particle-multi-hole excitations at and near to closed shells.We apply the group theoretical concepts of the EIBM to the particular case of two coexisting systems in the same nucleus exhibiting a U(5) (for the regular configurations) and an SU(3) symmetry (for the intruder configurations).Besides the description of ``global'' symmetry aspects in terms of I-spin , also the very specific local mixing effects characteristic for the U(5)-SU(3) symmetry coupling are studied.The model is applied to the Po isotopes and a comparison with a morerealistic calculation is made