On the internal stepsize of an extrapolation algorithm for IVP in ODE

We propose an extrapolation algorithm for initial value problems in ordinary differential equations. In the algorithm, an appropriately chosen stepsizeH is divided into smaller stepsizes by a sequence and a new stopping rule is proposed. The sequences applied to the algorithm are Romberg {2,4,8,16,32,...}, Bulirsch {2,4,6,8,16...} and Harmonic {2,4,6,8,10,12,...} types. The proposed algorithm is compared numerically with the algorithm introduced by Stoer. In view of the accuracy of numerical solutions, the relatively small number of calculations, the stability and reliability of the algorithm, we found that the algorithm with the Romberg sequence is the best.     

Development of high-repetition-rate LD pumped Nd:YAG laser and its application

High-average-power and high-energy lasers with good beam quality are fundamental tools for pumping high-peak and high-average-power ultrafast Ti:sapphire laser systems. Laser-diode (LD) pumped solid slate lasers with phase conjugation offer a unique combination of efficiency, reliability, and compactness. We present the design details and performance characteristics of a 360-W 1-kHz LD pumped Nd:YAG phase-conjugated laser. We also discuss the basic design aspects and present our preliminary experimental investigations on ultrashort-pulse laser systems.     

Effect of labile hydrogens on measurement of tritium preserved in hydrogens of cellulose

Various f-elements are separated as anionic complexes from both acidic and alkaline solutions by precipitation with alkylpyridinium salts. The precipitates are also cationic surfactants where the simple counter-ion (e.g. nitrate or chloride) is replaced by the negatively charged complex anion of an actinide or lanthanide. The low solubility of these precipitates is explained by a strong affinity of divalent complex counter-ions of f-elements to the quaternary nitrogen. Precipitations in solutions of nitric acid allow to separate tetravalent f-elements from other metals, in alkaline carbonate solutions tetravalent and hexavalent actinides are precipitated simultaneously. The last procedure yields precipitates, which are very intimate mixtures of hexavalent and tetravalent actinides. This allows to prepare mixed oxides in a simple way.     

Solid state photoreactions occurring at the interface between crystallites of two different organic compounds

This paper deals with the solid state bimolecular photoreactions occurring at the interface between crystallites of two different organic compounds prepared as a polycrystalline mixture by melting-resolidification. The photoreactions include the photoaddition of NH compounds to aromatic and olefinic double bonds, hydrogen abstraction, condensation reaction via photoelectron transfer and [2+2] photoaddition. Particular attention is focused on the characterization of the polycrystalline mixture, the selectivity of the photoreactions in the solid state compared with those in the solution phase and the factors controlling the photoreactions.     

Reducing ability of supramolecular C60 dianion toward C=O, C=C and N-N bonds

Different from C60 dianion which readily reacts with electrophiles, supramolecular C60 dianion (2) generated from gamma-cyclodextrin-bicapped C60 (1) and NaBH4 (or diborate) in DMSO-H2O (9:1, v/v) is able to reduce N-N+, C=C-EWG and C=O bonds to provide the respective dihydro derivatives; 1-mediated reduction of acetophenone with NaBH4 in the presence of (Me2N)2CH2 and EtONa gives turn over frequency (TOF)/h of 400.     

Neutron activation analysis of low level lithium in water samples

For determining low level lithium concentrations in water, a neutron activation method based on the measurement of tritium radioactivity produced by⁶Li(n,)³H reaction has been developed. This method is specific and free from interference by other chemical elements. Using a low background liquid scintillation counter for tritium measurement, the detection limit is approximately 0.3 ppm during irradiation at a thermal neutron flux density of 1.1·10⁷n·cm^–2·s^–1 for 6 hours by a small nuclear reactor and liquid scintillation counting for 2000 minutes     

Anion-exchange separation and spectrophotometric determination of vanadium in silicate rocks

A combined anion-exchange-spectrophotometric method has been developed for the determination of vanadium in silicate rocks. A rock sample weighing about 0.1 g is decomposed with a mixture of sulphuric and hydrofluoric acids and after removal of HF the residue is taken up with dilute sulphuric acid. This solution is adjusted to be 0.05M in sulphuric acid and contain 0.3% hydrogen peroxide, and is passed through a column of Amberlite CG 400 (sulphate form). The sorbed vanadium is eluted with 30 ml of 1M hydrochloric acid. The effluent is evaporated to dryness, made 0.1M in hydrochloric acid and 3% in hydrogen peroxide content, and passed through a column of Amberlite CG 400 (chloride form) to get rid of accompanying thorium and zirconium. Vanadium is stripped by elution with 20 ml of 1M hydrochloric acid and subsequently determined spectrophotometrically with 4-(2-pyridylazo)resorcinol. The detection limit is 0.4 ppm.     

Helicity Control in the Preparation of Chiral Co-crystals from Tryptamine and Achiral Carboxylic Acids by Pseudo-seeding

Abstract

Chiral crystals of tryptamine and achiral carboxylic acids such as p-chlorobenzoic acid, cinnamic acid, p-chlorocinnarnic acid and p-methylcinnamic acid were prepared by crystallization from the solutions of both components. All the crystals belonged to typical chiral space group P2₁2₁2₁. The crystal chirality is generated through the formation of a unidirectional twofold helix between the two components through quaternary ammonium salt interaction and hydrogen bonding in the lattice. This kind of spontaneous crystallization necessarily gives crystals of both clockwise and counterclockwise helicites. Here, pseudo-seeding based on utilizing these crystals as seed crystals was examined, resulting in successful helicity control in crystallization from solutions of tryptamine and different carboxylic acids.     

Immunosensor for Detection of the Textile Dye Disperse Orange 1 Based on Non‐conventional Competitive Assay

Textile dyes appear as an important class of compounds that has become a matter of public concern and a serious challenge for scientists and environmentalists due to their large‐scale production and extensive application. In this work, a non‐conventional competitive‐type amperometric immunosensor was successfully developed for detection of the textile dye Disperse Orange 1 (DO1). The DO1 was magnetically captured and separated from the sample solution using magnetic particles (MP) functionalized with the antibody anti‐DO1 and with HRP and gold electrodes were modified with the conjugate DO1‐BSA. Molecules of DO1 immobilized on the electrode surface and DO1 captured by MP compete for antibody binding sites. As a result, the amperometric signal decreases with increasing target DO1 concentration at the capture step, because this decreases, the attachment between the HRP coated MP and the electrode. This strategy allowed us to determine DO1 at the low detection limit of 0.87 ng mL^?1 with great specificity. Also, there were good recoveries for detection of the textile dye in river water samples without the need of sample pre‐treatment. The competitive amperometric immunosensor shows applicability for the determination of small molecules that cannot be determined by conventional competitive or sandwich immunosensors.