scholarly journals Model systems in heterogeneous catalysis: towards the design and understanding of structure and electronic properties

2018 ◽  
Vol 208 ◽  
pp. 307-323 ◽  
Author(s):  
Q. Pan ◽  
L. Li ◽  
S. Shaikhutdinov ◽  
Y. Fujimori ◽  
M. Hollerer ◽  
...  
Keyword(s):  
Ethylene Polymerization ◽  
Model System ◽  
The Other ◽  
Model Systems ◽  
Nano Particles ◽  
Nano Particle ◽  
Additional Information ◽  
Phillips Catalyst ◽  
Catalyst Systems ◽  
Au Nano Particles

We discuss in this paper two case studies related to nano-particle catalyst systems: one concerns a model system for the Cr/SiO2 Phillips catalyst for ethylene polymerization and the other provides additional information on Au nano-particles supported on ultrathin MgO(100)/Ag(100) films.

Synthesis of Au Nano-Particles Using Plasma Sputtering into Oil

2012 ◽  
Vol 476-478 ◽  
pp. 999-1002
Author(s):  
Hui Jun Zhang ◽  
Jing Liang Cheng ◽  
Wen Zen ◽  
Guo Min Wang ◽  
Masaru Murao ◽  
...  
Keyword(s):  
Solid Substrate ◽  
The Other ◽  
Nano Particles ◽  
Low Density ◽  
Measuring Time ◽  
Plasma Sputtering ◽  
Large Numbers ◽  
Absorbance Peak ◽  
And Shifts ◽  
Au Nano Particles

It has been examined to disperse the Au nano-particles directly into liquid by replacing the solid substrate with low-vapor oil in a plasma sputtering apparatus. The dispersing particles in oil are much smaller than the conventional methods. Under low density of particles on oil, the intense absorbance peak is detected around 325nm and the shape and peak of absorption spectra don’t almost change following time, and the size of Au particles is steady. With higher density, the absorbance peak is stronger and shifts to visible light about 20nm. With prolonging measuring time, absorption peaks fall and a new absorption locating on around 550nm gradually appears, large numbers of particles gradually convert and produce the new particles sizes around 3-5nm. under high density, the other intense absorbance peak exists around 540nm besides the peak of 350 nm. High particles density produces the particles sizes around 5-7nm, and the contents and sizes of particles are basic invariablenes against measured period.

Synthesis of Au Nano-particles under Energetic Irradiation Fields

2005 ◽  
Vol 900 ◽  
Author(s):  
Nobuhiro Maeda ◽  
Taiei Hiroki ◽  
Fuminobu Hori ◽  
Shuichi Okuda ◽  
Ryoichi Taniguchi ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Polyethylene Glycol ◽  
Aqueous Solutions ◽  
Nano Particles ◽  
Nano Particle ◽  
Carbon Ions ◽  
Transmission Electron ◽  
Dilute Aqueous Solutions ◽  
Γ Ray ◽  
Au Nano Particles

ABSTRACTDilute aqueous solutions with Au3+ ions and Polyethylene Glycol Monostearate are irradiated with ∼1 MeV γ-ray from 60Co source, 10 MeV pulsed electrons or 1.6 GeV carbon ions. After the irradiation, the color of solutions changes from buff yellow to reddish color. The UV-vis absorption spectra show that after the irradiation, light absorption around 530 nm appears, which corresponds to the excitation of the surface plasmon due to Au nano-particles. The result confirms that the irradiation reduces Au3+ ions in the aqueous solutions and synthesizes Au nano-particles. Size and shape of the nano-particles are examined by using 200kV transmission electron microscope. Effects of irradiation parameters (total dose and dose rate) on Au nano-particle synthesis are discussed.

scholarly journals Systematic ambiguity in the well-established model system insect Scathophaga stercoraria (Diptera: Scathophagidae): sister species S. soror revealed by molecular evidence

Zootaxa ◽  
2010 ◽  
Vol 2441 (1) ◽  
pp. 27 ◽  
Author(s):  
MARCO VALERIO BERNASCONI ◽  
DAVID BERGER ◽  
WOLF U. BLANCKENHORN
Keyword(s):  
Microsatellite Markers ◽  
Systematic Position ◽  
Model System ◽  
The Other ◽  
Model Systems ◽  
Valid Species ◽  
Molecular Evidence ◽  
Mitochondrial Coi ◽  
Scathophaga Stercoraria ◽  
Afrotropical Region

Even for well-established insect model systems, such as the yellow dung fly Scathophaga stercoraria (Linnaeus) (Diptera: Scathophagidae), there may be hidden systematic ambiguities that require clarification. Dung flies from the Afrotropical Region have been considered (i) as con-specific and not different from all the other Holarctic Scathophaga stercoraria; (ii) as a local and peculiar African subspecies of S. stercoraria (Scathophaga stercoraria soror Wiedemann), or (iii) as a separate valid species (Scathophaga soror Wiedemann). Our study represents an attempt, based on mitochondrial (COI, 12S, and 16S), nuclear (ITS2) as well as microsatellite markers, to clarify this problem. Results strongly suggest that S. soror is a separate taxon from S. stercoraria. Due to the importance of S. stercoraria as a model system for studies in ecology, behaviour and evolution, the systematic position of S. soror (relative to S. stercoraria) is not solely of interest for systematists, but for evolutionary ecologists as well.

Employing Exfoliated Graphite as Novel Support Material for Heterogeneous Model Catalysts

2019 ◽  
Author(s):  
Moritz Wolf ◽  
Nico Fischer ◽  
Michael Claeys
Keyword(s):  
Surface Area ◽  
Graphite Powder ◽  
Model Catalysts ◽  
Model Systems ◽  
Exfoliated Graphite ◽  
Support Material ◽  
Heterogeneous Model ◽  
Support Materials ◽  
Metal Support Interaction ◽  
Catalyst Systems

<p>The inert nature of graphitic samples allows for characterisation of rather isolated supported nanoparticles in model catalysts, as long as sufficiently large inter-particle distances are obtained. However, the low surface area of graphite and the little interaction with nanoparticles result in a challenging application of conventional preparation routes in practice. In the present study, a set of graphitic carbon materials was characterised in order to identify potential support materials for the preparation of model catalyst systems. Various sizes of well-defined Co<sub>3</sub>O<sub>4</sub> nanoparticles were synthesised separately and supported onto exfoliated graphite powder, that is graphite after solvent-assisted exfoliation <i>via</i> ultrasonication resulting in thinner flakes with increased specific surface area. The developed model catalysts are ideally suited for sintering studies of isolated nano-sized cobaltous particles as the graphitic support material does not provide distinct metal-support interaction. Furthermore, the differently sized cobaltous particles in the various model systems render possible studies on structural dependencies of activity, selectivity, and deactivation in cobalt oxide or cobalt catalysed reactions.</p>

scholarly journals Investigation of Ring and Star Polymers in Confined Geometries: Theory and Simulations

Entropy ◽  
2021 ◽  
Vol 23 (2) ◽  
pp. 242
Author(s):  
Joanna Halun ◽  
Pawel Karbowniczek ◽  
Piotr Kuterba ◽  
Zoriana Danel
Keyword(s):  
Star Polymers ◽  
Polymer Chains ◽  
The Other ◽  
Nano Particles ◽  
Dilute Solution ◽  
Confined Geometries ◽  
Density Profiles ◽  
Ideal Ring ◽  
Ring Polymer ◽  
Monomer Density

The calculations of the dimensionless layer monomer density profiles for a dilute solution of phantom ideal ring polymer chains and star polymers with f=4 arms in a Θ-solvent confined in a slit geometry of two parallel walls with repulsive surfaces and for the mixed case of one repulsive and the other inert surface were performed. Furthermore, taking into account the Derjaguin approximation, the dimensionless layer monomer density profiles for phantom ideal ring polymer chains and star polymers immersed in a solution of big colloidal particles with different adsorbing or repelling properties with respect to polymers were calculated. The density-force relation for the above-mentioned cases was analyzed, and the universal amplitude ratio B was obtained. Taking into account the small sphere expansion allowed obtaining the monomer density profiles for a dilute solution of phantom ideal ring polymers immersed in a solution of small spherical particles, or nano-particles of finite size, which are much smaller than the polymer size and the other characteristic mesoscopic length of the system. We performed molecular dynamics simulations of a dilute solution of linear, ring, and star-shaped polymers with N=300, 300 (360), and 1201 (4 × 300 + 1-star polymer with four arms) beads accordingly. The obtained analytical and numerical results for phantom ring and star polymers are compared with the results for linear polymer chains in confined geometries.

scholarly journals Singularly Perturbed Oscillators with Exponential Nonlinearities

2021 ◽  
Author(s):  
S. Jelbart ◽  
K. U. Kristiansen ◽  
P. Szmolyan ◽  
M. Wechselberger
Keyword(s):  
Limit Cycles ◽  
Space Dimension ◽  
Blow Up ◽  
Exponential Convergence ◽  
Model System ◽  
Piecewise Smooth ◽  
Singularly Perturbed ◽  
Model Systems ◽  
Smooth System ◽  
Unique Limit

AbstractSingular exponential nonlinearities of the form $$e^{h(x)\epsilon ^{-1}}$$ e h ( x ) ϵ - 1 with $$\epsilon >0$$ ϵ > 0 small occur in many different applications. These terms have essential singularities for $$\epsilon =0$$ ϵ = 0 leading to very different behaviour depending on the sign of h. In this paper, we consider two prototypical singularly perturbed oscillators with such exponential nonlinearities. We apply a suitable normalization for both systems such that the $$\epsilon \rightarrow 0$$ ϵ → 0 limit is a piecewise smooth system. The convergence to this nonsmooth system is exponential due to the nonlinearities we study. By working on the two model systems we use a blow-up approach to demonstrate that this exponential convergence can be harmless in some cases while in other scenarios it can lead to further degeneracies. For our second model system, we deal with such degeneracies due to exponentially small terms by extending the space dimension, following the approach in Kristiansen (Nonlinearity 30(5): 2138–2184, 2017), and prove—for both systems—existence of (unique) limit cycles by perturbing away from singular cycles having desirable hyperbolicity properties.

scholarly journals Correction: Measurement of number concentrations and sizes of Au nano-particles spiked into soil by laser ablation single particle ICPMS

2020 ◽  
Vol 35 (11) ◽  
pp. 2779-2779
Author(s):  
Jani Tuoriniemi ◽  
Timothy R. Holbrook ◽  
Geert Cornelis ◽  
Melanie Schmitt ◽  
Hans-Joachim Stärk ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Single Particle ◽  
Nano Particles ◽  
Au Nano Particles

Correction for ‘Measurement of number concentrations and sizes of Au nano-particles spiked into soil by laser ablation single particle ICPMS’ by Jani Tuoriniemi et al., J. Anal. At. Spectrom., 2020, 35, 1678–1686, DOI: 10.1039/D0JA00243G

scholarly journals Paracoccus denitrificans: a genetically tractable model system for studying respiratory complex I

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Owen D. Jarman ◽  
Olivier Biner ◽  
John J. Wright ◽  
Judy Hirst
Keyword(s):  
Complex I ◽  
Paracoccus Denitrificans ◽  
Model System ◽  
Proton Pumping ◽  
Model Systems ◽  
Metabolic Enzyme ◽  
Nadh:Ubiquinone Oxidoreductase ◽  
Mitochondrial Complex I ◽  
Mitochondrial Complex ◽  
Inner Mitochondrial Membrane

AbstractMitochondrial complex I (NADH:ubiquinone oxidoreductase) is a crucial metabolic enzyme that couples the free energy released from NADH oxidation and ubiquinone reduction to the translocation of four protons across the inner mitochondrial membrane, creating the proton motive force for ATP synthesis. The mechanism by which the energy is captured, and the mechanism and pathways of proton pumping, remain elusive despite recent advances in structural knowledge. Progress has been limited by a lack of model systems able to combine functional and structural analyses with targeted mutagenic interrogation throughout the entire complex. Here, we develop and present the α-proteobacterium Paracoccus denitrificans as a suitable bacterial model system for mitochondrial complex I. First, we develop a robust purification protocol to isolate highly active complex I by introducing a His6-tag on the Nqo5 subunit. Then, we optimize the reconstitution of the enzyme into liposomes, demonstrating its proton pumping activity. Finally, we develop a strain of P. denitrificans that is amenable to complex I mutagenesis and create a catalytically inactive variant of the enzyme. Our model provides new opportunities to disentangle the mechanism of complex I by combining mutagenesis in every subunit with established interrogative biophysical measurements on both the soluble and membrane bound enzymes.

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