Catalysis by Gold: Why Size Matters

Bulk gold is the most inert metal of all, however, when gold is finely dispersed on a support, it can be a very active catalyst for oxidation and hydrogenation reactions. X-ray absorption spectroscopy showed that the smaller the gold particles are, the shorter the gold–gold bond length is. The smaller particles also have an altered electronic structure, as they undergo less hybridization between the s, p, and d orbitals than the larger particles. The d band narrows and moves closer to the Fermi level. As a result, hydrogen, oxygen, and CO adsorb on the metal surface and the nano-sized metal particles can become catalytic

On the formation of cyclones and anticyclones in a rotating fluid

It is commonly observed that the columnar vortices that dominate the large scales in homogeneous, rapidly rotating turbulence are predominantly cyclonic. This has prompted us to ask how this asymmetry arises. To provide a partial answer to this we look at the process of columnar vortex formation in a rotating fluid and, in particular, we examine how a localized region of swirl (an eddy) can convert itself into a columnar structure by inertial wave propagation. We show that, when the Rossby number (Ro) is small, the vortices evolve into columnar eddies through the radiation of linear inertial waves. When the Rossby number is large, on the other hand, no such column is formed. Rather, the eddy bursts radially outward under the action of the centrifugal force. There is no asymmetry between cyclonic and anticyclonic eddies for these two regimes. However, cyclones and anticyclones behave differently in the intermediate regime of Ro~1. Here we find that the transition from columnar vortex formation to radial bursting occurs at lower values of Ro for anticyclones, with the transition for anticyclones occurring at Ro~0.5, and that for cyclones at Ro~2. Thus, in a homogeneous turbulence experiment conducted at, say, Ro=1, we would expect to see more cyclones than anticyclones. The reason for this asymmetry at Ro~1 is explained

Understanding a Heterogeneous Catalyst in Action

The role of catalysis in the clean production of energy and chemicals will become increasingly important and new catalysts must be developed. To improve the activity, selectivity, and stability of a heterogeneous catalyst, the electronic and geometric structure of the catalytically active site must be controlled. In situ characterization combined with kinetic analysis provides insights into the functioning of a heterogeneous catalyst. This aids the synthesis of a new generation of catalysts that converts new feedstocks, which are derived from sustainable sources, into energy and chemicals

Героическое в произведениях А.А. Фета о Крымской войне в контексте эстетической полемики ХIХ века

Проблемы героического в военной прозе и поэзии А.А Фета рассматриваются в контексте эстетической полемики второй половины Х1Х века. В ходе исследования литературно-критических материалов и произведений поэта делается попытка пересмотреть существование традиционных стереотипов относительно творчества и личной жизни художника-эстета и прийти к выводу: военная тематика поэта "чистого искусства" не была обособленной от всего его литературного наследия, она органически вписывалась в его эстетическую программу. Героическое в эстетике и творчестве А. Фета представлено наравне с категорией красоты как составляющей категории прекрасного.Проблеми героiчного в военiй прозi та поезii А.А.Фета разглядаються в контекстi літературної полемікі другоїї половини Х1Х сторіччя. В ході дослiдництва лiтературно-крiтичних матерiалiв та творiв поета робиться спроба переглянути iснування традицiйних стереотипiв вiдносно творчостi та особистого життя художника- естета та прийти до висновка: вiйськова тематика поета "чистого мистецтва" не була вiдокремленою вiд всii його спадщини, вона органiчно вписувалась в його естетичну програму. Героiчне в естетицi та творчостi А.Фета надано нарiвнi з категорiєю красоти, як складовоi категорii прекрасного.Heroic problems in war prose and poetry of A.A.Fet are examined in the context of literal controversy of the second part of the 19thcenturi. In the way of research of literal and critical materials and works of the poet the attempt is making to reexamine existence of formed stereotypes which are related to creative work and personal life of artist-design and go up to the conclusion that poet?s war subject-matter of "pure art" was not isolated from all his legacy. It enters organically into his aesthetic program

The decay of Batchelor and Saffman rotating turbulence

The decay rate of isotropic and homogeneous turbulence is known to be affected by the large-scale spectrum of the initial perturbations, associated with at least two cannonical self-preserving solutions of the von K\'arm\'an-Howarth equation: the so-called Batchelor and Saffman spectra. The effect of long-range correlations in the decay of anisotropic flows is less clear, and recently it has been proposed that the decay rate of rotating turbulence may be independent of the large-scale spectrum of the initial perturbations. We analyze numerical simulations of freely decaying rotating turbulence with initial energy spectra $\sim k^4$ (Batchelor turbulence) and $\sim k^2$ (Saffman turbulence) and show that, while a self-similar decay cannot be identified for the total energy, the decay is indeed affected by long-range correlations. The decay of two-dimensional and three-dimensional modes follows distinct power laws in each case, which are consistent with predictions derived from the anisotropic von K\'arm\'an-Howarth equation, and with conservation of anisotropic integral quantities by the flow evolution

Catalytic Conversion of Methane to Methanol Using Cu-Zeolites

The conversion of methane to value-added liquid chemicals is a promising answer to the imminent demand for fuels and chemical synthesis materials in the advent of a dwindling petroleum supply. Current technology requires high energy input for the synthesis gas production, and is characterized by low overall selectivity, which calls for alternative reaction routes. The limitation to achieve high selectivity is the high C–H bond strength of methane. High-temperature reaction systems favor gas-phase radical reactions and total oxidation. This suggests that the catalysts for methane activation should be active at low temperatures. The enzymatic-inspired metal-exchanged zeolite systems apparently fulfill this need, however, methanol yield is low and a catalytic process cannot yet be established. Homogeneous and heterogeneous catalytic systems have been described which stabilize the intermediate formed after the first C–H activation. The understanding of the reaction mechanism and the determination of the active metal sites are important for formulating strategies for the upgrade of methane conversion catalytic technologies