Electrochemically reduced tungsten‐based active species as catalysts for metathesis‐related reactions: ring‐opening metathesis copolymerization of cyclopentene with cyclooctene

The ring‐opened metathesis copolymerization of cyclopentene with cyclooctene by an electrochemically generated WCl₆‐based catalyst has been prepared and ¹³C NMR spectroscopy used to analyse in detail the nature of the homo‐ and hetero‐dyad units. This copolymer was characterized by gel‐permeation chromatography (M_n = 12 900, PDI= 2.2) and differential scanning calorimetry analysis. The glass‐transition temperature T_g of the copolymer was ?18.7 °C. Homopolymerization of cyclopentene is also reported to compare with copolymers produced in this work. Copyright © 2005 John Wiley & Sons, Ltd.     

A Hybrid Meta-Heuristic for the Batching Problem in Just-In-Time Flow Shops

This paper is concerned with a batching problem encountered in the context of production smoothing in just-in-time manufacturing systems. The manufacturing system of interest is a multi-level system with a flow-shop at the final level. We develop a hybrid meta-heuristic method to solve the batching problem, which is known to be NP-hard. We hybridize strategic oscillation (SO) and path re-linking (PR) methods and compare the hybrid method's performance to two benchmark methods: a bounded dynamic programming method developed for the problem earlier and an implementation of robust tabu search (RTS) meta-heuristic. Through a computational study, we show that the proposed hybrid method is effective in solving the problem within several minutes of computer time and yielding near-optimal results.     

A Nanoparticle Catalyst for Heterogeneous Phase Para‐Hydrogen‐Induced Polarization in Water

Para‐hydrogen‐induced polarization (PHIP) is a technique capable of producing spin polarization at a magnitude far greater than state‐of‐the‐art magnets. A significant application of PHIP is to generate contrast agents for biomedical imaging. Clinically viable and effective contrast agents not only require high levels of polarization but heterogeneous catalysts that can be used in water to eliminate the toxicity impact. Herein, we demonstrate the use of Pt nanoparticles capped with glutathione to induce heterogeneous PHIP in water. The ligand‐inhibited surface diffusion on the nanoparticles resulted in a ¹H polarization of P=0.25 % for hydroxyethyl propionate, a known contrast agent for magnetic resonance angiography. Transferring the ¹H polarization to a ¹³C nucleus using a para‐hydrogen polarizer yielded a polarization of 0.013 %. The nuclear‐spin polarizations achieved in these experiments are the first reported to date involving heterogeneous reactions in water.     

Intracellular Modulation of Excited‐State Dynamics in a Chromophore Dyad: Differential Enhancement of Photocytotoxicity Targeting Cancer Cells

The photosensitized generation of reactive oxygen species, and particularly of singlet oxygen [O₂(a¹Δ_g)], is the essence of photodynamic action exploited in photodynamic therapy. The ability to switch singlet oxygen generation on/off would be highly valuable, especially when it is linked to a cancer‐related cellular parameter. Building on recent findings related to intersystem crossing efficiency, we designed a dimeric BODIPY dye with reduced symmetry, which is ineffective as a photosensitizer unless it is activated by a reaction with intracellular glutathione (GSH). The reaction alters the properties of both the ground and excited states, consequently enabling the efficient generation of singlet oxygen. Remarkably, the designed photosensitizer can discriminate between different concentrations of GSH in normal and cancer cells and thus remains inefficient as a photosensitizer inside a normal cell while being transformed into a lethal singlet oxygen source in cancer cells. This is the first demonstration of such a difference in the intracellular activity of a photosensitizer.     

Parameter Determination of Sequential Reductive Dehalogenation Reactions of Chlorinated Hydrocarbons

Chlorinated hydrocarbons such as tetrachloroethylene (PCE) and trichloroethylene (TCE) are not directly mineralized, but rather are transformed into one or more intermediate compounds before converting into a final compound. Since the biotransformation rate coefficients of each intermediate compound are different, the coefficients in each step of reductive dehalogenation must be determined to establish an effective treatment operation. These parameters can be estimated by fitting the experimental data to Michaelis–Menten equation. In this study, we introduce a methodology, using both the curve-fitting and graphical methods, to estimate the rate of maximum biotransformation and half-saturation coefficients of parent and intermediate compounds. First-order rate coefficients are also estimated by simplifying the Michaelis–Menten equation for both curve-fitting and graphical methods. The results show that both methods produce similar parameter values for each rate equation. Estimated first-order kinetic parameters are employed to predict the compound concentrations from the analytical solutions of governing equations for sequential dehalogenation. Comparisons of predicted and experimental values show favorable agreement.     

Dispersive Solid-Phase Extraction of Rhodium from Water,Street Dust,and Catalytic Converters Using a Cellulose–Graphite Oxide Composite

A cellulose–graphite oxide composite was synthesized and characterized as an adsorbent for dispersive solid-phase extraction of rhodium from various samples before atomic absorption detection. The pH, adsorbent volume, centrifugation time and rate, eluent concentration, volume and type, adsorption and elution contact time, sample volume, and matrix interferences were optimized. The developed method is simple, rapid, and inexpensive. The tolerance limits for rhodium were 10,000?mg?L^?1 sodium, 25,000?mg?L^?1 potassium, 10,000?mg?L^?1 magnesium, and 20,000?mg?L^?1 calcium. The recovery for rhodium exceeded 95%. Elution was performed with 10?mL of 2.5?mol?L^?1 H₂SO₄. The adsorption and elution contact times were 30 and 60?s, respectively. The detection limit of the method for rhodium was 5.4?µg?L^?1 and the precision as the relative standard deviation was 1.6%. A certified reference material 2556 (used auto catalyst pellets) and fortified samples were analyzed to evaluate the accuracy of the method. The optimized method was used for the preconcentration of rhodium from tap water, well water, wastewater, seawater, catalytic converters, and street dust.     

Removal of textile dye mixtures by using modified Mg–Al–Cl layered double hydroxide (LDH)

The removal of Indigo Carmin (IC) and Congo Red (CR) dye mixtures using layered double hydroxide (LDH) (modified with sodium dodecyl sulfate (SDS)) has been studied. In the experimental context of this study, LDH was synthesized under a nitrogen atmosphere at room temperature using the coprecipitation method and characterized by Fourier transform infrared specroscopy (FTIR), X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX) and scanning electron microscopy (SEM) analyses. Contact time, temperature, and initial dye concentration on the adsorption process have been investigated. Results show that the maximum removal of IC and CR was obtained as about 50% and 95%, respectively. The isothermal data were fitted to Langmuir, Freundlich, and Temkin adsorption isotherms. Elovich and other kinetic model equations were applied. Adsorption depended on the starting naphthalene concentration at investigated various temperatures (298, 308, and 318?K) significantly.     

Applications of hyperbolic numbers to the invariant theory in two-dimensional pseudo-Euclidean space

Let \({E^{2}_{1}}\) be the real 2-dimensional pseudo-Euclidean space of index 1, O(1; 1) be the group of all pseudo-orthogonal transformations of \({E^{2}_{1}}\) and SO(1; 1) = {g ∈ O(1; 1) : det g = 1}. In the present paper, complete systems of invariants of m-tuples in \({E^{2}_{1}}\) for these groups and complete systems of relations between elements of the complete systems of invariants are obtained. For solutions of the these problems, hyperbolic numbers are used.