Surface oxygen triggered size change of palladium nano-crystals impedes catalytic efficacy

Palladium nano-crystals increase in size during the initial recycling in Heck cross coupling reactions. We demonstrate that oxygen adsorbed on the surface of palladium nano-crystals plays a pivotal role in driving the ripening. This in turn is associated with a loss in catalytic activity.     

Optimization Studies of Porous Carbon Preparation from Oil Shale Using Response Surface Methodology and Its Application for Phenol Adsorption

This paper discusses the elaboration of adsorbents from oil shale. The experimental designs a response surface methodology(RSM), which has been applied to optimize the significant preparation factors, such as temperature, time, and the activating agent percentage. The results obtained from central composite design(CCD) revealed that the interaction between the factors was significant for the maximum quantity of adsorption(response). Planned results have shown that a maximum quantity of adsorption for methylene blue is 65 mg/g, which could be achieved with a temperature of 275℃ over 2 h and a percentage of the activating agent of 45%. The predicted values agreed with the experimental finding, with a determination coefficient(R²) of 0.96. The model has been validated by experiments after conditions optimization. The new material(RHO) was characterized by cation exchange capacity, zero charge pH, surface functions, X-ray fluorescence, specific surface area, and electron microscopy analysis. Phenol adsorption was determined using Langmuir, Freundlich and Temkin, which were used to describe the adsorption isotherms. The adsorption capacity of the material was about 263 mg/g, and the kinetic studies showed rapid adsorption.     

A New Validated Potentiometric Method for Batch and Continuous Quality Control Monitoring of Oseltamivir Phosphate (Taminil) in Drug Formulations and Biological Fluids

A new validated potentiometric method is described for batch and continuous quality control monitoring of the drug oseltamivir phosphate (Taminil) (OST). The method involves the development of a potentiometric sensor responsive to the drug based on the use of the ion‐association complex of (OST⁺) cation with phosphomolybdate anion (PMA^?) as an electroactive material in a poly(vinyl chloride) matrix membrane plasticized with o‐nitrophenyloctyl ether (o‐NPOE). Optimization of the performance characteristics of the sensor is described. A membrane incorporating the OST‐PMA‐NPOE complex in a tubular flow through detector is used in a two channel flow injection set up for continuous monitoring of the drug at a frequency of ～30 samples h^?1. The sensor shows fast near‐Nernstian response for OST over the concentration range 5.2×10^?5–0.8×10^?2 M (21.34 µg mL^?1–3.23 mg mL^?1) with a detection limit of 9.1×10^?6 M (3.73 µg mL^?1) over the pH range 4.6–6.1. The sensor displays good selectivity for OST drug over some basic drugs, inorganic cations, excipients and diluents commonly used in the drug formulations. Validation of the assay method is tested by measuring the lower detection limit, range, linearity, bias, trueness, accuracy, precision, and between‐day‐variability, within day reproducibility, selectivity and ruggedness (robustness). The results reveal good potentiometric performance of the proposed sensor for determination of OST in pharmaceutical capsules and in biological fluid matrices as well as for testing the dissolution profile of the drug and drug homogeneity.     

THE REACTION OF DIPHENYLPHOSPHINE OXIDE WITH DIPHENYLPHOSPHINOUS CHLORIDE IN THE ABSENCE OF BASE

Abstract

Diphenylphosphinous chloride (1) and diphenylphosphine oxide (2) (2 mol. equivalent) react to form diphenylphosphinic acid (4), together with tetraphenyldiphosphine (5) (at 80°C), or its hydrochloride (6) (at 20°C), as the only products.     

Flocculants Prepared from Mixtures of Fatty Amines with Colloidal Chrysotile Asbestos

The flocculating effectiveness of mixtures of various fatty amines with colloidal chrysotile asbestos was studied to determine the extent to which the amine and the asbestos act in concert as polycations. Tallow 1,3-propylene diamine was the principal amine studied, although other fatty amines showed similar properties. Aqueous solutions of the amine defibrillate the chrysotile into primary tubules about 250 Å in diameter and several microns in length. It is believed that the amine molecules adsorb on the surface of the chrysotile tubules, promoting their defibrillation and the high stability of the resultant dispersion. The flocculating effectiveness of the arnine/asbestos mixtures was determined on several neutral or anionic mineral suspensions including titania and kaolin by measuring sedimentation rate and volume. The flocculating effectiveness was also determined on a suspension of hydrophilic organic matter, partially digested diluted municipal waste, by measuring filtration rate. The amine/asbestos mixtures are more effective flocculants than either the amine or the asbestos alone. Moreover, in contrast to behavior frequently observed with conventional polymeric flocculants, the mixtures show little tendency to restabilize the suspended matter at higher than optimum concentrations.     

Gravitational shock waves

This paper reports on and summarizes some recent progress on gravitational shocks, i.e., discontinuities in the Riemann curvature tensor. It is shown how the constraint equations play a crucial rôle in determining the nature and propagation of the shocks. Existence results are stated and are illustrated by some examples from numerical relativity.     

Highly regioselective palladium/copper-catalysed cross-coupling reactions of terminal alkynes and allenes

The Pd/Cu-catalysed cross-coupling reaction of heterocyclic terminal alkynes and allene/allenyl heterocycles affords novel trisubstituted en-ynes in good yield.     

The enclosed laser ablation of multiple stacks of laminated, metallised polymer

Enclosed laser ablation of single laminated, metallised polymer films (i.e. polymer, metal, adhesive, polymer layers respectively) has been studied in depth previously by the authors. It was found that most of the energy during this process was transmitted by the transparentised films. Therefore, it was proposed that multiple stacks of laminated metallised polymer samples could be transparentised with a single pass. In this paper, such experiments were carried out and stacks of 10 samples could be transparentised successfully with a single laser pass. The pulse energy incident upon each film was calculated from transmissivity measurements of each sample layer in a successfully demetallised stack, and the results were used to explain the behaviour observed from the experiments. Additional physical phenomena that were not present with single layer enclosed ablation have now been observed for the enclosed laser ablation of multiple layered stacks.