Direct Visualization of Soliton CO Overlayers on Supported Pd Nanoparticles

The interaction of carbon monoxide (CO) molecules with the facets of noble metal nanoparticles forms the basis of many important catalytic reactions. Using scanning tunneling microscopy (STM), we have studied the adsorption of CO molecules on the (111) facets of Pd nanocrystals supported on a rutile TiO2(110) substrate. We observed four compact CO overlayers with coverages ranging between 0.5 and 0.6 monolayers. Examination of the positions of the CO molecules in each of the unit cells reveals that one of the overlayers has a rhombic (√7 × √7) R19.1°-4CO structure. The other three form rectangular structures, namely, (7 × √3) rect-8CO, c(5 × √3) rect-3CO, and c(9 × √3) rect-5CO. These are closely related via a soliton model previously proposed on the basis of infrared absorption spectroscopy and low-energy electron diffraction. By imaging the CO molecules, we provide direct evidence for the soliton model

Simulation of Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements of CO on Supported Pd Nanoparticles

Near edge X-ray absorption fine structure (NEXAFS) measurements of CO on Pd nanoparticles have been simulated. This was achieved by calculating the CO π* resonance signal of CO on a nanoparticle both as a function of the angle of incidence (I vs θ) and the direction of the electric field vector E of the incident photon beam (I vs β), with the nanoparticle defined as a (111) top facet with {111} and {100} side facets. The dependence of the π* resonance intensity signal of CO covered nanoparticles on the particle geometry and orientation as well as the bond orientation of CO is examined. In addition, we compare our simulations to a set of C K-edge NEXAFS experimental data obtained from a single Pd nanoparticle decorated with CO. Our simulation predicts that the nanoparticle has a high lateral aspect ratio of 37.7 ± 4.1

Probing the local electronic structure of the cross-linked (1×2) reconstruction of rutile TiO2(110)

The electronic structure of cross-linked TiO2(110)-(1×2) has been investigated using scanning tunneling spectroscopy (STS) and by monitoring changes in ultraviolet photoelectron spectroscopy (UPS) following exposure of the surface to O2. STS reveals two states located in the bandgap, at 0.7 and 1.5 eV below the Fermi level. The population of these two states varies over different parts of the (1×2)- reconstructed surface. An addition state at 1.1 eV above the Fermi level is observed at the double link part of the structure. All of the bandgap states are attenuated following exposure to O2, while the workfunction is increased. We attribute this to an electron transfer from the surface to the adsorbed oxygen

(2n×1) Reconstructions of TiO2(011) Revealed by Noncontact Atomic Force Microscopy and Scanning Tunneling Microscopy

We have used noncontact atomic force microscopy (NC-AFM) and scanning tunneling microscopy (STM) to study the rutile TiO2(011) surface. A series of (2n×1) reconstructions were observed, including two types of (4×1) reconstruction. High resolution NC-AFM and STM images indicate that the (4×1)-α phase has the same structural elements as the more widely reported (2×1) reconstruction. An array of analogous higher order (2n×1) reconstructions were also observed where n = 3-5. On the other hand, the (4×1)-β reconstruction seems to be a unique structure without higher order analogues. A model is proposed for this structure that is also based on the (2×1) reconstruction but with additional microfacets of {111} character

Variation of SMSI with the Au:Pd Ratio of Bimetallic Nanoparticles on TiO2(110)

Au/Pd nanoparticles are important in a number of catalytic processes. Here we investigate the formation of Au–Pd bimetallic nanoparticles on TiO 2 (110) and their susceptibility to encapsulation using scanning tunneling microscopy, as well as Auger spectroscopy and low energy electron diffraction. Sequentially depositing 5 MLE Pd and 1 MLE Au at 298 K followed by annealing to 573 K results in a bimetallic core and Pd shell, with TiO x encapsulation on annealing to ~ 800 K. Further deposition of Au on the pinwheel type TiO x layer results in a template-assisted nucleation of Au nanoclusters, while on the zigzag type TiO x layer no preferential adsorption site of Au was observed. Increasing the Au:Pd ratio to 3 MLE Pd and 2 MLE Au results in nanoparticles that are enriched in Au at their surface, which exhibit a strong resistance towards encapsulation. Hence the degree of encapsulation of the nanoparticles during sintering can be controlled by tuning the Au:Pd ratio

Entrepreneurial sons, patriarchy and the Colonels' experiment in Thessaly, rural Greece

Existing studies within the field of institutional entrepreneurship explore how entrepreneurs influence change in economic institutions. This paper turns the attention of scholarly inquiry on the antecedents of deinstitutionalization and more specifically, the influence of entrepreneurship in shaping social institutions such as patriarchy. The paper draws from the findings of ethnographic work in two Greek lowland village communities during the military Dictatorship (1967–1974). Paradoxically this era associated with the spread of mechanization, cheap credit, revaluation of labour and clear means-ends relations, signalled entrepreneurial sons’ individuated dissent and activism who were now able to question the Patriarch’s authority, recognize opportunities and act as unintentional agents of deinstitutionalization. A ‘different’ model of institutional change is presented here, where politics intersects with entrepreneurs, in changing social institutions. This model discusses the external drivers of institutional atrophy and how handling dissensus (and its varieties over historical time) is instrumental in enabling institutional entrepreneurship

The nuclear receptors of Biomphalaria glabrata and Lottia gigantea: Implications for developing new model organisms

© 2015 Kaur et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedNuclear receptors (NRs) are transcription regulators involved in an array of diverse physiological functions including key roles in endocrine and metabolic function. The aim of this study was to identify nuclear receptors in the fully sequenced genome of the gastropod snail, Biomphalaria glabrata, intermediate host for Schistosoma mansoni and compare these to known vertebrate NRs, with a view to assessing the snail's potential as a invertebrate model organism for endocrine function, both as a prospective new test organism and to elucidate the fundamental genetic and mechanistic causes of disease. For comparative purposes, the genome of a second gastropod, the owl limpet, Lottia gigantea was also investigated for nuclear receptors. Thirty-nine and thirty-three putative NRs were identified from the B. glabrata and L. gigantea genomes respectively, based on the presence of a conserved DNA-binding domain and/or ligand-binding domain. Nuclear receptor transcript expression was confirmed and sequences were subjected to a comparative phylogenetic analysis, which demonstrated that these molluscs have representatives of all the major NR subfamilies (1-6). Many of the identified NRs are conserved between vertebrates and invertebrates, however differences exist, most notably, the absence of receptors of Group 3C, which includes some of the vertebrate endocrine hormone targets. The mollusc genomes also contain NR homologues that are present in insects and nematodes but not in vertebrates, such as Group 1J (HR48/DAF12/HR96). The identification of many shared receptors between humans and molluscs indicates the potential for molluscs as model organisms; however the absence of several steroid hormone receptors indicates snail endocrine systems are fundamentally different.The National Centre for the Replacement, Refinement and Reduction of Animals in Research, Grant Ref:G0900802 to CSJ, LRN, SJ & EJR [www.nc3rs.org.uk]

The Pioneer Anomaly

Radio-metric Doppler tracking data received from the Pioneer 10 and 11 spacecraft from heliocentric distances of 20-70 AU has consistently indicated the presence of a small, anomalous, blue-shifted frequency drift uniformly changing with a rate of ~6 x 10^{-9} Hz/s. Ultimately, the drift was interpreted as a constant sunward deceleration of each particular spacecraft at the level of a_P = (8.74 +/- 1.33) x 10^{-10} m/s^2. This apparent violation of the Newton's gravitational inverse-square law has become known as the Pioneer anomaly; the nature of this anomaly remains unexplained. In this review, we summarize the current knowledge of the physical properties of the anomaly and the conditions that led to its detection and characterization. We review various mechanisms proposed to explain the anomaly and discuss the current state of efforts to determine its nature. A comprehensive new investigation of the anomalous behavior of the two Pioneers has begun recently. The new efforts rely on the much-extended set of radio-metric Doppler data for both spacecraft in conjunction with the newly available complete record of their telemetry files and a large archive of original project documentation. As the new study is yet to report its findings, this review provides the necessary background for the new results to appear in the near future. In particular, we provide a significant amount of information on the design, operations and behavior of the two Pioneers during their entire missions, including descriptions of various data formats and techniques used for their navigation and radio-science data analysis. As most of this information was recovered relatively recently, it was not used in the previous studies of the Pioneer anomaly, but it is critical for the new investigation.Comment: 165 pages, 40 figures, 16 tables; accepted for publication in Living Reviews in Relativit

Oxygen Vacancy Origin of the Surface Band-Gap State of TiO2(110)

Scanning tunneling microscopy and photoemission spectroscopy have been used to determine the origin of the band-gap state in rutile TiO2(110). This state has long been attributed to oxygen vacancies (O-b vac). However, recently an alternative origin has been suggested, namely, subsurface interstitial Ti species. Here, we use electron bombardment to vary the O-b vac density while monitoring the band-gap state with photoemission spectroscopy. Our results show that O-b vac make the dominant contribution to the photoemission peak and that its magnitude is directly proportional to the O-b vac density