Scaling of the size and temporal occurrence of burst sequences in creep rupture of fiber bundles

We present a detailed statistical analysis of the size and temporal occurrence of burst sequences in the creep rupture of a proposed linear viscoelastic fiber bundle model. According to the model, the burst sequences of fiber breaks display a power law asymptotic behavior analogous to that of the static-fracture [Kloster et al., Phys. Rev. E 56, 2615, (1997)]. Moreover, power law asymptotics apply to inter-arrival times between successive bursts with a universal exponent close to unity.     

Controlled Synthesis of Carbon‐Encapsulated Copper Nanostructures by Using Smectite Clays as Nanotemplates

Rhomboidal and spherical metallic‐copper nanostructures were encapsulated within well‐formed graphitic shells by using a simple chemical method that involved the catalytic decomposition of acetylene over a copper catalyst that was supported on different smectite clays surfaces by ion‐exchange. These metallic‐copper nanostructures could be separated from the inorganic support and remained stable for months. The choice of the clay support influenced both the shape and the size of the synthesized Cu nanostructures. The synthesized materials and the supported catalysts from which they were produced were studied in detail by TEM and SEM, powder X‐ray diffraction, thermal analysis, as well as by Raman and X‐ray photoelectron spectroscopy.     

Layered Double Hydroxide/Graphene Quantum Dots as a New Sorbent for the Dispersive Solid-Phase Microextraction of Selected Benzophenones,Phenols, and Parabens

In this study, the synthesis of a layered double hydroxide (LDH) composite with graphene quantum dots (GQDs) and its utilization for the development of a dispersive solid-phase extraction procedure are described. To this end, a carbonate-free Mg-Al LDH was synthesized. The development of the composite material made feasible the use of GQDs in a sample preparation procedure, while the incorporation of the GQDs in the LDH structure resulted in an 80% increase in extraction efficiency, compared to the bare LDH. As a proof of concept, the composite material was used for the development of an analytical method for the extraction, and preconcentration, of benzophenones, phenols, and parabens in lake water using high-performance liquid chromatography, coupled to a diode array detector. The analytical method exhibits low limits of quantification (0.10–1.33 μg L⁻¹), good recoveries (92–100%), and satisfactory enrichment factors (169–186). Due to the abovementioned merits, the easy synthesis and simple extraction, the developed method can be used for the routine analysis of the target compounds.     

Multiscale expansions avector solitons of a two-dimensional nonlocal nonlinear Schrödinger system

One- and two-dimensional solitons of a multicomponent nonlocal nonlinear Schrödinger (NLS) system are constructed. The model finds applications in nonlinear optics, where it may describe the interaction of optical beams of different frequencies. We asymptotically reduce the model, via multiscale analysis, to completely integrable ones in both Cartesian and cylindrical geometries; we thus derive a Kadomtsev-Petviashvili equation and its cylindrical counterpart, Johnson's equation. This way, we derive approximate soliton solutions of the nonlocal NLS system, which have the form of: (a) dark or antidark soliton stripes and (b) dark lumps in the Cartesian geometry, as well as (c) ring dark or antidark solitons in the cylindrical geometry. The type of the soliton, namely dark or antidark, is determined by the degree of nonlocality: dark (antidark) soliton states are formed for weaker (stronger) nonlocality. We perform numerical simulations and show that the derived soliton solutions do exist and propagate undistorted in the original nonlocal NLS system.     

Instabilities of massive scalar perturbations of a rotating black hole

We study the stability of a massive scalar field in the exterior metric of a rotating Kerr black hole. An argument based on energy conservation shows, under some strong technical assumptions, that unstable normal modes exist. These unstable modes can be interpreted as wave packets in bound, superradiant orbits. A JWKB estimate of the fastest growth rate gives 10^?7M^?1exp(?1.84Mμ) in the case Mμ ? 1, where M is the mass of the hole and μ is the mass of the field. The existence of unstable normal modes has significant implications for quantum particle creation by rotating black holes, which we attempt to assess.     

Defensive financial decisions support for retailers in Greek pharmaceutical industry

In this paper, we present a decisions support solution designed for Greek pharmacies comprising a cash flow management system for early warning of financial distress and a financial advisor based on a neural network. The cash flow monitoring system integrates accounting elements with real time transactions and a predictive linear regression model while the decision support module is developed with the help of a neural network. For any given business unit the system associates accounting entries with information about credit times to reflect the precise instants of cash flows and using inflows/outflows equations monthly, eventually build its liquidity curve and cash flow balance over time. Alongside, a linear regression module is introduced to estimate future cash reserves based on past profitability ratios. Lastly, combining the power of artificial neural networks with expertise in this sector of pharmaceutical business, the financial decision support tool focuses on the retailers that face financial difficulties and suggests alternative solutions for escaping from distress and insolvency. The model has an ambitious and useful purpose, to inform and consult the owners of the business units and other members of the pharmaceutical chain, thus reduce financial risk for the chain.     

Volcanic glass under fire – a comparison of three complementary analytical methods

The two obsidian sources from the island of Melos (Greece), Agia Nychia and Demenegakion, are chemically characterized by three complementary analytical techniques. Ion beam analysis (IBA) comprising particle induced X‐ray emission and particle induced gamma‐ray emission, neutron activation analysis (NAA) and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) is applied to the same set of geological obsidian samples. The combination of methods allows a more complete characterization of obsidian sources and reveals a highly specific chemical composition, the so‐called chemical fingerprint. This multi‐methodical approach checks also the self‐consistency of the analytical results and shows not only the most reliable and characteristic key elements Co and Sc but also Fe, Ca and Ti of Melos obsidian deposits. NAA contributes the largest number of reliable elements to the most unambiguous chemical fingerprint comprising in total of 41 elements. Therefore, NAA is the most suitable analytical method for a clear identification of Melos obsidian deposits. Moreover, the accuracy of methods is demonstrated by the excellent correspondences (calculated correlation coefficient R² = 1.00 for IBA and NAA, R² = 0.99 for LA‐ICP‐MS) between determined analytical results obained by IBA, NAA and LA‐ICP‐MS and certified values of the reference glass BAM‐S005B. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and structure of N-salicylidene-o-aminophenolato gallium(III) complexes

The reactions of Ga(acac)₃ with N-salicylidene-o-aminophenol (saphH₂) and its 5-methyl (5MesaphH₂) and 5-bromo (5BrsaphH₂) derivatives in alcohols afforded the complexes [Ga(acac)(saph)(EtOH)] (1), [Ga(acac)(5Mesaph)(MeOH)] (2) and [Ga(acac)(5Brsaph)(EtOH)] (3), respectively, in good yields. The crystal structures of 1 and 2 have been solved by single-crystal X-ray crystallography. All three complexes are mononuclear with the Ga^III atoms being surrounded by a dianionic tridentate Schiff base ligand, one bidentate acac⁻ ligand and a terminal alcohol molecule. Characteristic IR data are discussed in terms of the nature of bonding and the structures of the three complexes.     

Finite volume relaxation schemes for multidimensional conservation laws

We consider finite volume relaxation schemes for multidimensional scalar conservation laws. These schemes are constructed by appropriate discretization of a relaxation system and it is shown to converge to the entropy solution of the conservation law with a rate of in .

     

First and second order error estimates for the Upwind Source at Interface method

The Upwind Source at Interface (U.S.I.) method for hyperbolic conservation laws with source term introduced by Perthame and Simeoni is essentially first order accurate. Under appropriate hypotheses of consistency on the finite volume discretization of the source term, we prove -error estimates, , in the case of a uniform spatial mesh, for which an optimal result can be obtained. We thus conclude that the same convergence rates hold as for the corresponding homogeneous problem. To improve the numerical accuracy, we develop two different approaches of dealing with the source term and we discuss the question of deriving second order error estimates. Numerical evidence shows that those techniques produce high resolution schemes compatible with the U.S.I. method.