Alternative Synthesis of the Alkaloid Guvacine and Its Derivatives

Russian Journal of Organic Chemistry - The reaction of nicotinic acid ethyl ester with phenacyl bromides containing electron-donating substituents in the benzene ring afforded the corresponding...     

The investigation of the optics of shock-compressed strongly correlated plasma

Rare gas plasmas at high temperatures and pressures, produced by explosive shock fronts, are explored using laser diagnostics. The analysis of the response of a dense plasma to an electromagnetic wave of moderate-intensity proves successful for investigating properties and the validity of physical models describing the behaviour of dense and non-ideal plasmas. We present new experimental data for the reflectivity of oblique incidence of polarized electromagnetic waves on the front of shock-compressed xenon plasmas. The optical properties of strongly correlated plasma were studied in the near-infrared and green spectral regions at a plasma mass density ρ = 0.83 g/cm³ and temperature T = 32900 K. The spatial parameters of the plasma transition shock-front layer are determined by solving numerically the electromagnetic field equations.     

Solid-phase-spectrophotometric and test determination of simultaneously present phosphorus forms (phosphorus speciation) in water

Solid-phase-spectrophotometric and test procedures are proposed to determine phosphorus as its ion associate with a quaternary ammonium salt and molybdoantimonophosphoric acid immobilized on silica gel in the concentration range 1.9–124 μg P/L. The determination of 4 μmol of phosphorus is not affected by (in μmol) alkali and alkaline-earth metals (≤2 × 10⁴), NH ₄ ⁺ (≤1 × 10³), Co²⁺ (≤1.0), Cu²⁺ (≤100), Mn²⁺ (≤10), Fe³⁺ (≤300), NO ₃ ^? and SO ₄ ^2? (≤2 × 10⁴), CO ₃ ^2? (≤1 × 10⁴), As (≤20), and Si (≤1 × 10³). The procedure was tested in the determination of various phosphorus forms in natural waters.     

Investigation of some oxygen-containing chromium (III) complexes by epr and optical spectroscopy

EPR and electronic absorption spectra of chrome alum solutions in sulphuric and phosphoric acids have been studied. Broadening of the EPR lines and shifts in the positions of the electronic spectra absorption bands were observed at low acid concentrations. In concentrated acids the ⁴T_2g band splits into several well resolved components and the EPR spectra show two resolved areas of fine structure. Each structure may be described by a spinHamiltonian of the form

where D is the zero-field splitting parameter due to the action of the axial crystal fields. The changes in the spectra as the acid concentration is increased are explained by changes in the internal environment of the Cr^III complexes as a result of the substitution of H₂O by anions of the acid residue. The symmetry of the complexes predominating at particular acid concentrations and the parameters D, g and Dt have been determined from an analysis of the EPR and optical absorption spectra. The character of the bond of the Cr^III ion with the surrounding ligands has also been estimated.     

Determination of total iodine in samples with an organic matrix by solid-phase spectrophotometry

A solid-phase spectrophotometry method is proposed for determining total iodine in samples with an organic matrix. The method involves the sorption of I₂ formed in oxidation of iodide with oxone (active ingredient potassium peroxomonosulfate) by polyurethane foams, followed by the registration of the adsorbent absorbance at 360 nm. Sample preparation includes treatment with an aqueous methanolic solution of tetramethylammonium hydroxide followed by thermostation at 90 ± 2°C for 3 h. The detection limit for iodine calculated using the 3s-test is 0.03 μg in a sample aliquot portion of ≤8 cm³. The relative standard deviation is 8–12% for iodine concentration in the range 0.3–5.0 μg/g.     

X-ray photoelectronic spectroscopy of the processes of interaction between elements in contact layers on InP

Using the method of x-ray photoelectronic spectroscopy, we investigated of the interaction of gold-containing contact layers and indium phosphide in the process of thermal burning-in. We determined the dependence of the depth of the InP layer that had entered into interaction with the metal of the contact on the type of alloying admixture and the gold layer thickness. Institute of Electronics, National Academy of Sciences of Belarus, 22, Logoiskii Trakt, Minsk, 220090, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 144–147, January–February, 1999.     

Xylenol orange adsorbed on silica surface as a solid phase reagent for lead determination using diffuse reflectance spectroscopy

The solid-phase reagents on the base of xylenol orange and its complex with Fe(III) immobilized on silica surface were obtained. The interaction of Pb(II) with developed reagents was studied. The conditions of quantitative recovery of Pb(II) from diluted solutions, such as acidity of aqueous phase, the amount of the sorbent, the volume of solutions and the time of equilibrium reaching, were examined. The tolerance limits of metal ions in the sorption of Pb(II) at pH 4.5-5.5 are reported. The capabilities of immobilized xylenol orange for Pb(II) pre-concentration prior to its diffusion reflectance spectroscopic detection was evaluated. The detection limit was 2 mug l(-1). The developed method was applied to Pb(II) determination in natural water and foodstuffs.     

Predicting noise from aircraft operated on the ground

Averaged data for sound levels due to aircraft engine testing out to a distance of 3 km obtained under low wind speed conditions are presented. Predictions of standard analytical approximations are compared with these averaged data. The measured average sound levels are shown to be consistent with the predicted influence of ground effect including impedance discontinuities. There is a noticeable influence of directionality also.     

Determination of Fe(II), Cu(II) and Ag(I) by using silica gel loaded with 1,10-phenanthroline

The modified silica gel with 1,10-phenanthroline adsorbed was obtained. The adsorption from aqueous solutions onto loaded silica gel of Fe(II), Cu(II) and Ag(I) and their complexes was studied. The loaded silica gel was applied to Fe(II), Cu(II) and Ag(I) reflectance spectroscopy determinations in water (detection limits 0.08, 0.03 and 0.01 ppm respectively). Visual test scales for Fe, Cu and Ag ion determinations in water were worked out.