Comparison of green algae Cladophora sp. and Enteromorpha sp. as potential biomonitors of chemical elements in the southern Baltic

The contents of Cd, Cu, Ni, Pb, Zn, Mn, K, Na, Ca and Mg were determined in the green algae Cladophora sp. from coastal and lagoonal waters of the southern Baltic. Factor analysis demonstrated spatial differences between concentration of chemical elements. The algae from the southern Baltic contained more Na and K while the anthropogenic impact of Cu, Pb and Zn was observed in the case of Cladophora sp. and Enteromorpha sp. from the Gulf of Gdansk at the vicinity of Gdynia. This area is exposed to emission of heavy metals from municipal and industrial sources with the main contribution of shipbuilding industry and seaport. The statistical evaluation of data has demonstrated that there exists a correlation between concentrations of Cu, Pb and Zn in both green algae collected at the same time and sampling sites of the Gulf of Gdansk. Our results show that in the case of absence of one species in the investigated area it is still possible to continue successfully the biomonitoring studies with its replacing by second one, i.e. Cladophora sp. by Enteromorpha sp. and vice versa; in consequence reliable results may be obtained.     

Thienyl analogues of acyclic monoterpene alcohols and their biological activity

BACKGROUND: Thienyl analogues of linalool, geraniol, nerol and citronellol were synthesised and their sensory and anti‐ microbial activities were investigated. RESULTS: The thienyl analogues of linalool, geraniol, nerol and citronellol, in which the isobutenyl moiety was replaced by a thiophene substituent, were synthesised from commercially available 2‐ and 3‐methylthiophenes and 2‐ and 3‐thiophenecarboxaldehydes. The olfactory properties of the new compounds were generally of the corresponding parent terpene type; however, their relative volatility determined by the headspace gas chromatography method was lower by a factor of 34–42 compared with the parent alcohols. Antimicrobial activity against Aspergillus niger and Penicillium expansum of some thienyl analogues of linalool was 1.5–3 times higher than that of linalool, with a minimum inhibitory concentration of 0.2–0.1 µL mL^?1. CONCLUSION: Replacement of the isobutenyl moiety in acyclic monoterpene alcohols by a thienyl substituent results in the formation of new terpene analogues, some of which are interesting for perfumery and cosmetology because of their odour quality, tenacity and antimicrobial action. Copyright © 2009 Society of Chemical Industry     

Excess-methane dry and oxidative reforming on Ni-containing hydrotalcite-derived catalysts for biogas upgrading into synthesis gas

The activity of Ni-containing hydrotalcite-derived catalysts was assayed in the excess-methane dry reforming of different CH₄-CO₂ mixtures, aiming to simulate biogas upgrading to hydrogen and/or syngas. These catalysts yielded methane conversions quite far away from the thermodynamically predicted values, pointing to the inhibition of important methane consuming reactions, such as direct methane decomposition (DMD). Adding oxygen to the gas mixture (12.5%) results in increased methane conversions. Almost constant H₂/CO ratios, around 1.5, were measured at any temperature (600–850 °C). However, solid carbon formation was found to take place to a higher extent. The intrinsic properties of the hydrotalcite-derived catalysts tested results in favored reverse water gas shift reaction, leading to CO₂ and H₂ conversion.     

The solution algorithms for the multiprocessor scheduling with workspan criterion

In this paper, we consider multiprocessor scheduling problems, where each job (task) must be executed simultaneously by the specified number of processors, but the indices of the processors allotted to each job do not have to be contiguous (i.e., jobs can be fragmentable). Unlike other research in this domain, we analyse the problem under the workspan criterion, which is defined as the product of the maximum job completion time (makespan) and the number of used processors. Moreover, the job processing times can be described by non-increasing or non-decreasing functions dependent on the start times of jobs that model improvement (learning) or degradation (deteriorating), respectively. To solve the problems, we construct some polynomial time algorithms and analyse numerically their efficiency.     

Microstructure,chemical composition,wear, and corrosion resistance of FeB–Fe<Subscript>2</Subscript>B–Fe<Subscript>3</Subscript>B surface layers produced on Vanadis-6 steel using CO<Subscript>2</Subscript> laser

The paper presents the study results of laser modification of FeB–Fe₂B surface layers produced on Vanadis-6 steel using pack cementation method. Microstructure, x-ray phase analysis, chemical composition study using wave dispersive spectrometry method, microhardness, corrosion resistance as well as surface condition, roughness, and wear resistance were investigated. The diffusion boronizing processes were performed at 900 °C for 5 h in the EKabor® powder mixture. The boronized layers had a dual-phase microstructure composed of two types of iron borides, FeB and Fe₂B, and their microhardness ranged from 1800 to 1400 HV. The laser surface modification was carried out on specimens after diffusion boronizing process using CO₂ laser with a nominal power of 2600 W. Laser beam power used in this experiment was equal to 1040 W and was constant. While the three values of scanning speed were used: 19, 48, and 75 mm/s. During laser modification, the multiple tracks were made where distance between of axis tracks was equal to 0.5 mm. As a result of this process, microstructure consisted of remelted zone, heat-affected zone, and substrate was obtained. In remelted zone, the boron-martensite eutectic was observed. Boronized layers after laser modification were characterized by the mild gradient of microhardness from surface to the substrate and their value was dependent on the scanning speed used and was between 1700 and 1100 HV. Corrosion resistance tests revealed reducing the current of corrosion in case of laser modification process. Wear resistance of laser modified specimens was improved in comparison to diffusion boronized layers.