Tips and Tricks for the Surface Engineering of Well-Ordered Morphologically Driven Silver-Based Nanomaterials

Particularly-shaped silver nanostructures are successfully applied in many scientific fields, such as nanotechnology, catalysis, (nano)engineering, optoelectronics, and sensing. In recent years, the production of shape-controlled silver-based nanostructures and the knowledge around this topic has grown significantly. Hence, on the basis of the most recent results reported in the literature, a critical analysis around the driving forces behind the synthesis of such nanostructures are proposed herein, pointing out the important role of surface-regulating agents in driving crystalline growth by favoring (or opposing) development along specific directions. Additionally, growth mechanisms of the different morphologies considered here are discussed in depth, and critical points highlighted.     

The first ruthenium-alkyne-dihydride reported is now recognized as an intermediate in the homogeneous hydrogenation of diphenylacetylene: Crystal structure of (μ-H)2Ru3(CO)9(μ3-η2-∥-C2Ph2)

The title complex (complex1) was the first alkyne-substituted triruthenium dihydrido cluster to be reported and was characterized by spectroscopy as a triangular cluster with the alkyne parallel to a Ru-Ru edge. Recently, we have found that1 is a key intermediate in the homogeneous hydrogenation of diphenylacetylene catalyzed by tetrahedral Ru₄ and FeRu₃ clusters. Since the discovery of1, a great number of complexes with alkynes parallel to a cluster edge have been reported; at present this is the more common bonding mode for alkynes on trinuclear clusters. The structural features of1 allow a comparison with those of other ruthenium-containing derivatives and help to draw suggestions of the role of1 in hydrogenation catalysis.     

CuPc molecules adsorbed on Au(1 1 0)-(1 × 2): growth morphology and evolution of valence band states

We present the growth morphology, the long-range ordering, and the evolution of the valence band electronic states of ultrathin films of copper phthalocyanine (CuPc) deposited on the Au(1 1 0)-(1 × 2) reconstructed surface, as a function of the organic molecule coverage. The low energy electron diffraction patterns present a (5 × 3) reconstruction from the early adsorption stages. High-resolution UV photoelectron spectroscopy data show the disappearance of the Au surface states related to the (1 × 2) reconstruction, and the presence of new electronic features related to the molecule-substrate interaction and to the CuPc molecular states. The CuPc highest occupied molecular orbital gradually emerges in the valence band, while the interface electronic states are quenched, upon increasing the coverage.     

Long‐range dependence and performance in telecom networks

Telecommunications systems have recently undergone significant innovations. These call for suitable statistical models that can properly describe the behaviour of the input traffic in a network. Here we use fractional Brownian motion (FBM) to model cumulative traffic network, thus taking into account the possible presence of long‐range dependence in the data. A Bayesian approach is devised in such a way that we are able to: (a) estimate the Hurst parameter H of the FBM; (b) estimate the overflow probability which is a parameter measuring the quality of service of a network: (c) develop a test for comparing the null hypothesis of long‐range dependence in the data versus the alternative of short‐range dependence. In order to achieve these inferential results, we elaborate an MCMC sampling scheme whose output enables us to obtain an approximation of the quantities of interest. An application to three real datasets, corresponding to three different levels of traffic, is finally considered. Copyright © 2004 John Wiley & Sons, Ltd.     

A non-isothermal Ginzburg–Landau model in superconductivity: Existence,uniqueness and asymptotic behaviour

In this paper we study a Ginzburg–Landau model which describes the behaviour of a superconducting material including thermal effects. We extend the traditional formulation of the problem, by introducing the temperature as an additional state variable. Accordingly, together with the Gor’kov–Eliashberg system, we introduce an evolution equation for the absolute temperature. We examine in detail the case which allows only variations of the concentration of superconducting electrons and of the temperature, neglecting the electromagnetic field. For this problem existence and uniqueness of the solution are shown. Finally we analyze the asymptotic behaviour of the solutions, proving that the system possesses a global attractor.     

Microstructured fibre Bragg gratings: analysis and fabrication

A microstructured fibre Bragg grating that relies on a partial and localised etching of the cladding layer along the grating region is proposed. The main effect is the formation of defect states inside the bandgap depending on surrounding refractive index. This leads to the possibility of realising novel optoelectronic devices for sensing and telecommunication applications.     

Concise asymmetric synthesis of (−)-halosaline and (2R,9aR)-(+)-2-hydroxy-quinolizidine by ruthenium-catalyzed ring-rearrangement metathesis

A ruthenium-catalyzed ring opening-ring closing metathesis reaction serves as the key step in the stereoselective synthesis of a new enantiopure 2-substituted-4,5-dehydropiperidine skeleton, a valuable intermediate for the synthesis of piperidine alkaloids (such as (−)-halosaline) and of hydroxylated quinolizidines (such as (2R,9aR)-(+)-2-hydroxy-quinolizidine).     

Longitudinally detected electron spin resonance: Recent developments

Multiple-quantum spectroscopies are reviewed in the frame of electron paramagnetic resonance. Some properties of different nonlinear techniques are discussed for both transverse and longitudinal detection. The connections of effects recently presented with the procedure of longitudinal detection of electron paramagnetic resonance (LODESR) in presence of double transverse irradiation are stressed. Peculiarities of LODESR spectroscopy and its capabilities in facing problems related to relaxations in presence of very slow dynamic processes are evidentiated. Recent results show the vitality of the LODESR technique, that in the future could be applied to new fields, owing to experimental updating.     

Frequency stability of an optically pumped cesium beam frequency standard

Results obtained in an experimental optically pumped cesium beam frequency standard in which a single semiconductor laser is used for the state selection and the atom detection are reported. The separation between the two interaction regions is equal to 21 cm. This gives a 500 Hz linewidth which is observed with a signal to noise ratio equal to 10,000 in a 1 Hz noise bandwidth. A quartz crystal oscillator is frequency controlled by the atomic transition. The measured short term frequency stability is given by _y()=2×10^–12–1/2 for 1 s<500 s. Prospects for improvement of this frequency stability are discussed.