Reconstruction of cracks of different types from far‐field measurements

In this paper, we deal with the acoustic inverse scattering problem for reconstructing cracks of possibly different types from the far‐field map. The scattering problem models the diffraction of waves by thin two‐sided cylindrical screens. The cracks are characterized by their shapes, the type of boundary conditions and the boundary coefficients (surface impedance). We give explicit formulas of the indicator function of the probe method, which can be used to reconstruct the shape of the cracks, distinguish their types of boundary conditions, the two faces of each of them and reconstruct the possible material coefficients on them by using the far‐field map. To test the validity of these formulas, we present some numerical implementations for a single crack, which show the efficiency of the proposed method for suitably distributed surface impedances. The difficulties for numerically recovering the properties of the crack in the concave side as well as near the tips are presented and some explanations are given. Copyright © 2009 John Wiley & Sons, Ltd.     

Semigroups with apartness

Proving a constructive version of the Spectral Mapping Theorem, Bridges and Havea used a constructive semigroup with inequality in 8 . This motivated us to achieve a little progress in that direction. The starting point is the structure called a semigroup with apartness. Our primary objective is to prove isomorphism theorems for such constructive semigroups. In doing so our main ideas and notions come from 10 .     

Synthesis,characterization and cytotoxic activity of organoruthenium(II)-halido complexes with 5-chloro-1H-benzimidazole-2-carboxylic acid

Three new ruthenium(II)-arene halido complexes, [(η⁶-p-cymene) RuX(L)] (1–3), were synthesized in a reaction of [(η⁶-p-cymene)RuX₂]₂ with 5-chloro-1H-benzimidazole-2-carboxylic acid (HL) in ethanol (X^– = Cl^– (1), Br^– (2), I^– (3)). The complexes were characterized by elemental analysis, mass spectrometry, IR, ¹H and ¹³C NMR spectroscopy. The cytotoxic activity of the ligand precursor and its ruthenium complexes was tested by MTT assay in human cancer cell lines: lung adenocarcinoma (A549), myelogenous leukemia (K562) as well as in one normal human fetal lung fibroblast cell line (MRC-5). The results show that ruthenium(II)-arene complexes possess enhanced cytotoxicity when compared to HL in the range of concentrations up to 300 µM. In terms of halido ligand substitution, cytotoxic activity toward A549 and K562 cell lines in 1–3 serie significantly increased (e.g., IC₅₀ values for K562: 1: 205.76 µM; 2: 174.77 µM; 3: 83.97 µM). All studied compounds were found to be ineffective toward MRC-5. Hydrolysis of 1–3 was followed by UV-vis spectroscopy at 25?°C, revealing ligand-substitution reactions at the Ru(II) center. Compounds 2 and 3 underwent rapid hydrolysis ranging from a few minutes for the aquation to ca. 20?min, confirming typical Ru-arene behavior in aqueous solutions.     

Impact of Imine Bond Orientations on the Geometric and Electronic Structures of Imine-based Covalent Organic Frameworks

Many efforts are currently devoted to improving the stability and crystallinity of imine-based two-dimensional (2D) covalent organic frameworks (COFs) given their wide range of potential applications. The variation in the relative orientations of the imine bonds has been found to be a critical factor that impacts the stacking of the 2D COF layers, leads to the formation of isomer structures, and influences the crystallinity of the final product. Most investigations to date have focused only on the structural properties, while the role of the imine orientations on the electronic properties has not been studied systematically. Here, we explore this effect by examining how the electronic band structures, electronic couplings, and effective masses evolve when considering four isomeric structures of an imine-linked tetraphenyl-pyrene naphthalene-diimide COF. Our results provide an understanding of the impact of the imine orientations and how they need to be controlled to realize COF inter-layer stackings that can lead to efficient cross-plane electron transport. They can be used to guide the design and synthesis of imine-based COFs for applications where charge transport needs to be optimized.     

Ergodic characterization of van der Corput sets

We prove an analogue to the well-known equivalence of intersective sets and Poincaré recurrent sets, in a stronger setting. We show that a set D is van der Corput, if and only if for each Hilbert space H, unitary operator U, and ${x \in H}$ such that the projection of x to the kernel of (U ? I) is nonvanishing, there exists ${d \in D\,}$ such that (U ^d x, x)≠ 0. We also characterize the smallest such d.     

Genotoxic effects of cadmium chloride on human amniotic fluid cells cultured in vitro

In this study we report the results of cytogenetic tests, namely a search for chromosome aberrations (CA) and sister chromatid exchanges (SCEs), performed on human amniotic fluid cells cultured and treated with Cadmium chloride. The cells from primary cultures were exposed to CdCl2 at 1 microM and 10 microM for 24 h. At the higher dose, no metaphases were scored and at the lower dose (1 microM) no effects were evident on cell proliferation, and no chromosome aberrations were found. In the subsequent experiments we used cells from subcultures exposed to 1 microM and 5 microM CdCl2. At the 5 microM dose was evident the induction of chromatid breaks, while the frequency of sister chromatid exchanges shows a small increase, not statistically significant at the dose of 1 microM. In this study we positively demonstrated that amniotic fluid cells grown in vitro are reliable for testing various mutagenic or teratogenic substances. With regard to cadmium treatment results, it is evident a clastogenic effect of cadmium chloride but not a significant induction of SCEs.     

Reduction of uranyl nitrate ions in a continuous flow electrochemical reactor

In a contemporary salt-free flowsheet of nuclear fuel reprocessing, uranous ions are used as a reducing agent to accomplish the separation of uranium and plutonium from each other which is normally produced electrochemically. In the present study, continuous mode electrochemical reduction of uranyl ions in nitric acid medium and in the presence of hydrazine nitrate was carried out in a divided cell at three different feed flow rates and cathodic current densities for the purpose of optimizing the process conditions for better conversion efficiency. A correlation function is described as a mathematical model in which, mass transfer parameter is expressed as a function of current density and flow rate. From the multivariable nonlinear regression of the experimental data, rate parameter was determined. The electro reduction of uranyl ions was not influenced by the initial acidity. The maximum conversion rate of 87 % was obtained for the electro-reduction of 100 g/l U(VI) in 3 M nitric acid with feed flow rate as 0.3 l/h and current density as 15 mA/cm². The results for the reduction of 100 g/l uranyl ions indicate that an optimum flow rate of about 0.5 l/h and 15 mA/cm² as cathodic current density may suffice for the conversion with efficiency better than 60 %. The calculated steady state concentrations for U(IV) were found to be in good agreement with the experimental results.     

Modified Ishikawa Iteration Process for Nonlinear Lipschitz Generalized Strongly Pseudo-Contractive Operators in Arbitrary Banach Spaces

In this paper, we modify the Ishikawa iteration process and show that such process, associated with a nonlinear Lipschitzian generalized strongly pseudo-contractive operator with a fixed point in a (not necessarily uniformly smooth) Banach space, converges strongly to the unique fixed point of this operator.     

Portfolio selection problems with Markowitz’s mean–variance framework: a review of literature

Since the pioneering work of Harry Markowitz, mean–variance portfolio selection model has been widely used in both theoretical and empirical studies, which maximizes the investment return under certain risk level or minimizes the investment risk under certain return level. In this paper, we review several variations or generalizations that substantially improve the performance of Markowitz’s mean–variance model, including dynamic portfolio optimization, portfolio optimization with practical factors, robust portfolio optimization and fuzzy portfolio optimization. The review provides a useful reference to handle portfolio selection problems for both researchers and practitioners. Some summaries about the current studies and future research directions are presented at the end of this paper.     

Electrochemical determination of nitrite based on poly(amidoamine) dendrimer-modified carbon nanotubes for nitrite oxidation

This study describes a simple and reliable method for the electrochemical determination of nitrite based on poly(amidoamine)-modified carbon nanotubes. Amine-terminated poly(amidoamine) (generation 4.0, G4-NH₄) were covalently attached onto multi-walled carbon nanotube (MWNT)-modified glass carbon (GC) electrodes (written as G4-NH₄/MWNT-modified GC) and which were used for the electrochemical determination of nitrite. The studies show that the G4-NH₄/MWNT-modified electrodes demonstrated significantly enhanced electrochemical activity towards nitrite oxidation. Chronoamperometry studies reveal that the amperometric response is rapid, stable, and offers a linear dependence over a wide range of nitrite concentrations from 5 μM to 1.5 mM. The proposed method can be used for the continuous monitoring of nitrite in real samples. The electrochemical properties of the G4-NH₄/MWNT nanocomposites are reasonably envisaged to be promising for providing a nanostructured platform in the development of electrochemical sensors or biosensors.