Kinetic energy and angular distributions of instantaneous fission fragments in a classical model

The process of instantaneous fission in deep inelastic collisions is investigated in a classical model. Kinetic energies and angular distributions of the fragments are calculated for the proposed reaction Pb+U atE _cm ^inc =750 MeV; an experimental setup for the separation of the fragments originating from instantaneous fission from the fragments of thermal fission is explained. We also discuss fusion following instantaneous fission as a mechanism for the production of superheavy elements and arrive at rather promising estimates.     

Speciation of chromium in wastewater and sludge by extraction with liquid anion exchanger Amberlite LA-2 and electrothermal atomic absorption spectrometry

A simple, integrated method for the speciation of chromium in wastewater and sewage sludge was developed, utilising liquid anion exchange by Amberlite LA-2 (LAES) and final determination by electrothermal atomic absorption spectrometry (ETAAS). Samples were filtered through a 0.45 μm membrane filter and chromium species were determined in filtered water samples and in sludge on the filters. In the former case (filtrate), total Cr was determined directly by ETAAS, while for the determination of Cr(VI) the filtrate was buffered to pH 6.4, extracted with LAES and Cr(VI) was determined in the organic extract. Cr(III) was determined by the difference. In the latter case (filter), the filters were leached with an alkaline buffer solution (pH 12.7) and the supernatant was subjected to the same extraction procedure. For the determination of total leachable Cr, the filters were subjected to acid leaching with dilute HNO₃ (pH 1) and the supernatant was subjected to ETAAS, after appropriate dilution with water. Then, Cr(III) was determined by the difference. The limits of detection (LOD) were 0.39 and 0.45 μg l⁻¹ for total Cr and Cr(VI), respectively, in the dissolved phase and 2.10 and 0.87 ng g⁻¹ for total Cr and Cr(VI) in the suspended solids. The recoveries of total Cr and Cr(VI) in filtrated wastewater samples and filters were quantitative, ranged from 93 to 106%. The effect of time and temperature of sonication and suspended solids concentration on total Cr and Cr(VI) recovery was studied. No significant difference in recoveries was obtained for sonication temperatures between 30 and 70 °C. However, sonication time equal to or higher than 30 min and concentration of suspended solids equal to or less than 30 mg significantly improved Cr recovery. The ETAAS program for the determination of Cr(VI) in Amberlite/MIBK extract was carefully optimised in the absence of a chemical modifier to avoid memory effects. The developed analytical method was applied for the determination of chromium species in wastewater and suspended solids of a municipal and a lab-scale wastewater treatment plant.     

Determination of the antifouling booster biocides irgarol 1051 and diuron and their metabolites in seawater by high performance liquid chromatography-diode array detector

A method for the simultaneous determination of two antifouling booster biocides, diuron (1-(3,4 dichlorophenyl) 3,3 dimethyl urea) and irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine), and their metabolites, DCPMU (1-(3,4 dichlorophenyl)-3 methyl urea), DCPU (1-(3,4 dichlorophenyl) urea), DCA (3,4 dichloroaniline) and M1 (2-methylthio-4-tert-butylamino-s-triazine) in seawater by high performance liquid chromatography-diode array detector (HPLC-DAD) was developed. The optimization of the extraction procedure included the type of sorbent and the type of the organic solvent for the elution. Optimization of the liquid chromatography (LC) separation was also performed and the robustness of the developed separation was tested, in respect to the effect of three factors (column temperature, flow rate and initial strength of acetonitrile) on the retention times, peak resolution and peak area of the six compounds. The optimized procedure included off-line extraction of these compounds from seawater samples using C18 solid phase extraction (SPE) cartridges. The inter-day precision of the developed procedure was less than 14% (as R.S.D.s) for all the tested compounds. Satisfactory recoveries (higher than 82%) were obtained for all substances, except for DCA, for which low recovery was obtained (30.5%). The limits of detection (LODs) of the substances varied between 0.005 (DCPMU) and 0.026 (M1) μg L⁻¹.     

Stereoselectivity in rhodium antibiotics

The biological activities of the enantiomeric rhodium(III)-nicotine complexes trans-[Rh(S-(–)-nicH⁺)₄Cl₂](PF₆)₅, trans-[Rh(R-(+)-nicH⁺)₄Cl₂](PF₆)₅ (97% enantiomerically pure) and trans-[Rh(RS-(±)-nicH⁺)₄Cl₂](PF₆)₅ were examined in detail on the Gram positive bacteria B. subtilis. Minimal inhibitory concentrations and exponential phases for each complex were calculated: the complexes were bactericidal at certain concentrations. Novel stereoselective phenomena are reported.     

Stochastic oscillations induced by colored noise

We investigate the effect of additive colored noise on Hopf-bifurcating systems in the limit of small correlation times. It is shown that it results in an advancement of the oscillating regime. Several examples are studied.     

Complex compounds with rhodium(III) of enantiomers of nicotine

The synthesis, characterization and comparison of the enantiomeric transition metal complexes, trans-[Rh-(S-(–)-nicH⁺)₄Cl₂](PF₆)₅ and trans-[Rh-(R-(+)-nicH⁺)₄Cl₂](PF₆)₅, and of the racemic mixture trans-[Rh-(RS-(±)-nicH⁺)₄Cl₂](PF₆)₅ are described.     

Application of different analytical methods for determination of volatile chlorination by-products in drinking water

Four analytical methods have been applied for the determination of volatile chlorination by-products in drinking water, based on the following techniques: liquid-liquid extraction-gas chromatography-electron capture detection (LLE-GC-ECD); liquid-liquid extraction-gas chromatography-mass spectrometry (LLE-GC-MS); purge and trap-gas chromatography-mass spectrometry (purge and trap-GC-MS); and headspace-gas chromatography-mass spectrometry (headspace-GC-MS). The compounds studied were trihalomethanes, haloacetonitriles, haloketones, chloral hydrate and chloropicrin. LLE-GC-ECD method proved to be the most sensitive for determination of all compounds studied, followed by LLE-GC-MS. Purge and trap-GC-MS method gave good results in the case of trihalomethanes, but had high detection limits for the other volatile chlorination by-products. Headspace-GC-MS method had acceptable recoveries for trihalomethanes, but the detection limits were higher.     

A Simple Method for the Speciation of Organotin Compounds in Water Samples Using Ethylation and GC-QFAAS

 A simple method for the extraction of organotin compounds from water samples was developed in which both the instrumental parameters and the extraction/derivatization step were optimized. Organotin compounds (butyl-, phenyl- and octyl-) in tap water samples were ethylated with the addition of 2.5 ml of 0.4% w/v NaBEt₄ at pH 5.00 and subsequently extracted two times, for 10 min, with 3 and 2 ml of hexane. The combined extracts were analyzed with on-column capillary GC-QFAAS. The recoveries were quantitative for di- and tri- alkyltin compounds, whereas between 67 and 86% of the monoalkyltin compounds were recovered. The detection limits obtained ranged from 110 pg for monobutyltin to 500 pg for triphenyltin, as sensitivities were found to be compound dependent. The preparation of ethylated standards was also optimized. It was found that two subsequent extractions, with 1.0 and 0.5 ml of hexane were necessary for the quantitative recovery of the ethylated organotin compounds.     

The influence of mercury(II) on the extraction efficiency of herbicides from water

In this work, the effect of Hg(II) on the extraction efficiency of triazine and phenylurea herbicides from water samples was tested. The results showed that in the presence of Hg(II), the recoveries of the s-triazine herbicides (except hexazinon) from styrene divinylbenzene (SDVB) cartridges were significantly reduced using acetonitrile as the elution solvent, whereas acidified methanol quantitatively eluted all the herbicides. Consequently, the loss in the recoveries was not due to degradation of the compounds but rather due to irreversible adsorption onto the resin. The adsorption is probably due to ternary complex formation between the compounds, Hg(II) and the polymeric resin. The chemical structure and the basicity of the compounds affected their interaction with Hg(II). When using octadecyl (C18) cartridges, only atraton was affected. Mercury did not affect the liquid–liquid extraction of the herbicides. The findings suggest that acidic methanol is a suitable elution solvent of s-triazines from mercury-loaded water samples.     

The neutron-proton scattering length in the reaction9Be(p,np)8Be at 7.5 MeV

The relative differential cross section of the⁹Be(p, np)⁸Be _gs reaction at 7.5 MeV has been measured in an FSI geometry. A strongn-p FSI peak was observed with virtually no sequential decay modes interfering. The Watson-Migdal analysis of this peak yields the scattering lengtha _np =–23.8_–1.2 ^–1.1 fm with the effective ranger _np =2.76 fm.