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[en] Inorganic bromide residues and ¹⁴C-labelled methylated products (expressed as CH₃Br equivalent) in cocoa beans fumigated with [¹⁴C]-methyl bromide have been determined by radiometric and chemical methods. Determination of ¹⁴C by direct combustion in an oxygen chamber followed by liquid scintillation counting confirmed previous findings with respect to the magnitude, distribution and chemical nature of the residues. Although recovery of added bromide was good, the values of total bromide obtained by the chemical method were only half of those estimated from the total residual ¹⁴C-activity. This is attributed to loss of organic (presumably, protein-bound) bromide. In agreement with the total ¹⁴C-labelled residue contents, total bromide in shells was 20 times greater than that in nibs. The low levels of residues in the nib (12ppm as CH₃Br equivalent, 10ppm Br) and the further reduction of organic residues by roasting suggest that no toxicological and nutritional hazards may be expected from fumigation of cocoa beans with methyl bromide. (author)

[en] A fiber-optic sensor system is described for the on-line determination of bromide in spent brine. In this method, the bromide is selectively oxidized to bromine in a flow reactor containing a packed bed of chloramine-T; the optical absorption of the resulting bromine is then used for quantification. The technique exhibits a dynamic range from 20 to 5000 mg l^-1 bromide, provides continuous readout, is not affected by the presence of high concentrations of chloride and has a response time of about 2 min. (author). 13 refs.; 8 figs.; 1 tab

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[en] The photodissociation dynamics of cyclopropyl bromide (C-3H₅Br) and cyclobutyl bromide (C₄H₇Br) at 234 nm was investigated. A two-dimensional photofragment ion-imaging technique coupled with a [2+1] resonance enhanced multiphoton ionization scheme was utilized to obtain speed and angular distributions of the nascent Br(²P_3/2) and Br*(²P_1/2) atoms. The recoil anisotropies for the Br and Br* channels were measured to be βBr = 0.92 ± 0.03 and βBr* = 1.52 ± 0.04 for C₃H₅Br and βBr = 1.10 ± 0.03 and βBr* = 1.49 ± 0.05 for C₄H₇Br. The relative quantum yield for Br was found to be ΦBr = 0.13 ± 0.03 and for C₃H₅Br and C₄H₇Br, respectively. The soft radical limit of the impulsive model adequately modeled the related energy partitioning. The nonadiabatic transition probability from the 3A' and 4A' potential energy surfaces was estimated and discussed

[en] Biopurification systems treating pesticide contaminated water are very efficient, however they operate as a black box. Processes inside the system are not yet characterized. To optimize the performance, knowledge of degradation and retention processes needs to be generated. Therefore, displacement experiments were carried out for four pesticides (isoproturon, bentazone, metalaxyl, linuron) in columns containing different organic mixtures. Bromide, isoproturon and bentazone breakthrough curves (BTCs) were well described using the convection-dispersion equation (CDE) and a first-order degradation kinetic approach. Metalaxyl and linuron BTCs were well described using the CDE model expanded with Monod-type kinetics. Freundlich sorption, first-order degradation and Monod kinetics coefficients were fitted to the BTCs. Fitted values of the distribution coefficient K_f,column were much lower than those determined from batch experiments. Based on mobility, pesticides were ranked as: bentazone > metalaxyl - isoproturon > linuron. Based on degradability, pesticides were ranked as: linuron > metalaxyl - isoproturon > bentazone. - Transport of pesticides in column experiments containing organic substrates

[en] Microchip produced by a plastic material such as poly(dimethylsiloxane) (PDMS) has shown a good material of choice since PDMS has good biocompatibility, facile bonding ability, high transparency for UV and fluorescence detection, and is cost-effective for the production. In addition, it is much less fragile compared to quartz or glass, and can be constructed easily by molding or embossing. However, there are several problems associated with PDMS microchips. For example, many organic molecules and biomolecules are easily adsorbed on the PDMS surface due to the nature of hydrophobicity of a PDMS chip. Moreover, this hydrophobicity limits the use of many organic solvents in the buffer except several alcohols. The electrosmotic flow (EOF) produced under high electric field tends to become unstable as a function of time

[en] Evolution of spiral waves in light-sensitive media described with the two variable oregonator model is investigated. The intensity of external illumination is modulated by a weak chaotic signal, which is introduced into the whole system, the additional bromide production is influenced and the dynamics thus changed. The results are confirmed within our numerical simulation and it may give useful information in pattern formation and suppression of spiral waves. It can be an example for anti-control of chaos

[en] Selection of the most informative molecular descriptors from the original data set is a key step for development of quantitative structure activity/property relationship models. Recently, mutual information (MI) has gained increasing attention in feature selection problems. This paper presents an effective mutual information-based feature selection approach, named mutual information maximization by replacing collinear variables (MIMRCV), for nonlinear quantitative structure-property relationship models. The proposed variable selection method was applied to three different QSPR datasets, soil degradation half-life of 47 organophosphorus pesticides, GC-MS retention times of 85 volatile organic compounds, and water-to-micellar cetyltrimethylammonium bromide partition coefficients of 62 organic compounds.The obtained results revealed that using MIMRCV as feature selection method improves the predictive quality of the developed models compared to conventional MI based variable selection algorithms

No abstract available