A preconditioned domain decomposition algorithm for the solution of the elliptic Neumann problem

A new preconditioned conjugate gradient (PCG)-based domain decomposition method is given for the solution of linear equations arising in the finite element method applied to the elliptic Neumann problem. The novelty of the proposed method is in the recommended preconditioner which is constructed by using cyclic matrix. The resulting preconditioned algorithms are well suited to parallel computation.     

Mössbauer study of iron reduction in hematite containing mineral originated from Aswan area in Egypt

Mössbauer spectroscopy was used to study iron reduction in mineral originated from Aswan area in Egypt. The Mössbauer spectra of samples heat treated at 1000 °C in hydrogen atmosphere show a gradually reduction process of hematite. The main phase of sample aged for 1 h is magnetite, while alpha-iron as well as some silicates and wustite type oxide can be detected in sample aged for 3 h. Further aging of sample results in dissolution of alloying elements /Si, Al/, being present in the samples. This process starts already in samples aged at 1000 °C for 4 h, but it is more expressive in minerals heat treated at 1200 °C or 1300 °C, when all paramagnetic phases disappeared.     

Cystine and cysteine analysis as the same phenylthiocarbamyl derivatives by HPLC in protein hydrolyzates

Summary A new approach is described, and a novel explanation presented, for the high performance liquid chromatographic analysis of cystine and cysteine as their phenylthiocarbamyl derivatives. PTC cystine and cysteine have been eluted with the same retention times and molar responses, most probably due to electrophilic attack of phenylisothiocyanate on cystine resulting in the scission of the disulfide bond yielding two moles of cysteine. Further, total PTC cystine and cysteine have been measured both in model solutions and in standard protein hydrolyzates (lysozyme, bovine albumin, ribonuclease) with the same linearity as the other ineteen amino acids. The reproducibility of the measurements, at the 250–750 pmole level, proved to be 4.1% (Relative Standard Deviation %) or less.     

On triazoles. VII Synthesis of novel tri- and tetracyclic ring systems

The ring-closure of the 5-amino-1-(2-aminophenyl)-3-methylthio-1H-1,2,4-triazole derivatives 3 and 4 with different simple and cyclic C₁ components lead to the formation of 1,2,4-triazolo[1,5-α]-1,3,5-benzotriazepines 5–6 , their 4,5-dihydro- 7 , different 5-spiro-homocyclic- 8–13 , and 5-spiro-heterocyclic- 14-15 analogues. The structure of the compounds obtained was proved with the use of their ir, uv, ¹H-nmr and ¹³C-nmr spectra.     

Esterification of C1−C8 carboxylic acids to n-butyl esters in aqueous solutions for their gas chromatographic analysis

Summary The esterification of C₁–C₈ fatty acid in aqueous solutions and in the presence of sulfuric or hydrochloric acid and with n-butanol is described. It has been established that the esterification can be used for the quantitative determination of these fatty acids in the concentration ratio range of [H₂O]/[n-BuOH]=0.01–5.3. In the concentration ratio range of 0.01–0.8 the water present does not interfere. In the concentration range of above 0.8 anhydrous sodium sulfate is used for binding the water, in the amount of [Na₂SO₄.anh.]/[H₂O]0.2.     

Prompt gamma activation analysis using a chopped neutron beam

A beam chopper has been developed at the cold neutron PGAA facility of the Budapest Research Reactor. In the open phase of the chopper the usual prompt gamma-spectrum is recorded, while in the decay phase short-lived decay lines can be collected with good counting statistics on an extremely low baseline. A series of elements has been measured with the chopped beam technique to assess the capabilities of the new technique. An archaeological sample was also examined, to demonstrate how spectral interferences can be resolved.     

Dynamical behavior of the multiplicative diffusion coupled map lattices

We report a dynamical study of multiplicative diffusion coupled map lattices with the coupling between the elements only through the bifurcation parameter of the mapping function. We discuss the diffusive process of the lattice from an initially random distribution state to a homogeneous one as well as the stable range of the diffusive homogeneous attractor. For various coupling strengths we find that there are several types of spatiotemporal structures. In addition, the evolution of the lattice into chaos is studied. A largest Lyapunov exponent and a spatial correlation function have been used to characterize the dynamical behavior. (c) 1996 American Institute of Physics.     

Mercury determination by CV-AAS in wastewater and sewage sludge from a stabilization pond system

The mercury concentrations in wastewater and sewage sludge of a stabilization pond system have been evaluated. The system is built by three parallel facultative ponds followed by two systems of three maturation ponds in series. The samples of wastewater and sludge were digested using nitric acid and placed into a Parr-type bomb for 4 h at 110° C. Mercury was measured by Cold Vapour Atomic Absorption Spectrometry (CV-AAS) at 253.7 nm with sodium tetrahydroborate as reductant. The methodologies were checked with an USEPA quality control sample, a standard reference material from NIST and with another method of mineralization (cold mineralization) showing good results. Concentrations of mercury in wastewater between 1.47 ± 0.75 gl^–1 have been found at the entrance of the system and 0.74 ± 0.0 gl^–1 at the exit, while in sludge the results were between 0.29 ± 0.12 gkg^–1 in the facultative pond and 0.04 ± 0.02 gkg^–1 in the second maturation pond (exit).     

Behavior and characteristics of biogenic amines, ornithine and lysine derivatized with the o-phthalaldehyde-ethanethiol-fluorenylmethyl chloroformate reagent

The stability and characteristics of the ornithine (Orn), lysine (Lys), putrescine (Put), cadaverine (Cad), 1,7-diaminoheptane (Diah), spermidine (Spd) and spermine (Spm) derivatives obtained with the o-phthalaldehyde (OPA)-ethanethiol (ET)-fluorenylmethyl chloroformate (FMOC) reagent has been investigated. The stoichiometry of the introduced, two-step derivatization process has been followed by photodiode array (DAD) and fluorescence (FL) detections, simultaneously, while the composition of derivatives was confirmed by on-line HPLC-electrospray ionization (ESI) MS measurements. Depending on the composition of the OPA reagents, in addition to the secondary amino group-containing Spd and Spm, under common aqueous conditions also Orn and Lys do react with FMOC resulting in derivatives of various compositions. Applying the OPA-ET reagent of increasing methanol (Met) content (38-80%, v/v) the formation of the FMOC group containing Orn and Lys derivatives could be considerably decreased. Optimum elution condition (18 min, including equilibration) was developed for the simultaneous quantitation of Orn, Lys, Put, Cad, Diah, Spd and Spm, in the presence of the rest of protein amino acids. The practical utility of the method was demonstrated by the analysis of mouse tissues. Average reproducibility of quantitations, characterized with the relative standard deviation percentages of fluorescence intensities and UV responses, in order of listing, proved to be 2.1% and 2.1%, respectively.