Anaerobic microbial and photochemical degradation of 4,4'-dibromodiphenyl ether

The anaerobic microbial and photochemical degradation pathways of 4,4'-dibromodiphenyl ether (BDE15) were examined. BDE15 was reductively debrominated within a fixed-film plug-flow biological reactor at hydraulic retention times of 3.4 and 6.8 h, leading to exclusive production of 4-bromodiphenyl ether (BDE3) and diphenyl ether (DE). A suite of potential BDE15 metabolites arising from reductive debromination, hydroxylation, and methoxylation of the aromatic C-Br and C-H bonds were not observed. Following initial debromination of BDE15, degradation of BDE3 to DE readily occurs, suggesting the rate-limiting step for anaerobic BDE15 degradation is conversion of BDE15 to BDE3. The photochemical degradation of BDE15 was also examined in organic (CH3CN and CH3OH) and aqueous (H2O:CH3CN; 1:1 v/v) solvent systems at 300 nm. Only photochemically induced reductive debromination was found to occur via homolytic C-Br bond cleavage, with no evidence of C-O bond cleavage or products arising from heterolytic bond cleavage.     

Oral administration of two probiotic strains, Lactobacillus gasseri CECT5714 and Lactobacillus coryniformis CECT5711, enhances the intestinal function of healthy adults

Modifications in gastrointestinal parameters, intestinal colonization and tolerance are some of the main goals claimed for probiotics. However, although healthy people are the common target for these new functional food products, the number of clinical trials analysing the effects of probiotics in gastrointestinal parameters of healthy subjects is very scarce. A randomized, double blind, placebo-controlled human clinical trial involving 30 healthy adults was performed to investigate the effect of a fermented product containing two probiotic strains, Lactobacillus gasseri CECT5714 and Lactobacillus coryniformis CECT5711, on several blood and fecal parameters, most of them related to the host intestinal function. The volunteers were randomly distributed into two groups, one receiving a standard yogurt and the other a similar dairy fermented product in which the Lactobacillus delbreuckii subsp. bulgaricus yogurt strain had been replaced by a combination of the probiotic strains L. gasseri CECT5714 and L. coryniformis CECT5711. The volunteers that received the probiotic strains reported no adverse effects and the strains could be isolated from their feces at a relatively high level. In fact, the concentration of fecal lactic acid bacteria significantly increased in the probiotic group. Additionally, the oral administration of the probiotic strains led to an improvement of parameters such as the production of short chain fatty acids, the fecal moisture and the frequency and volume of the stools. As a result, the volunteers assigned to the probiotic group perceived a clear improvement in their intestinal habits. The study revealed that probiotics may exert a positive effect on healthy adults.     

High solar energy concentration with a Fresnel lens

The high solar energy density achieved in our simple and cheap Fresnel installation has been used for several surface modifications of metallic materials. This equipment is a very useful tool to apply concentrated solar energy in the field of high and very high temperatures (1500–2000 K). These temperatures are achieved in a few seconds and usually the materials treatments are completed in minutes. Fresnel lens installation is a serious alternative to the conventional equipment for material treatment and even to the large solar installations. In this work we review the surface modifications produced by concentration of solar energy with a Fresnel lens.     

A method to compensate the influence of speech codec in speaker recognition

The recognition of a person by his voice or “speaker recognition”, is a biometric specialty increasingly used in electronic commerce and electronic banking transactions and forensic investigations, among others. Speaker recognition is supported by the discriminative information contained in the speech of a person and its main challenge is the variability that exists between different speech samples of the same person, used for training and evaluation, or “session variability”. When a speech communication is transmitted over the internet, for example, the coding–decoding process “codec” of the speech causes loss of such information and affects the effectiveness of the speaker recognition. Some methods have been proposed to mitigate this effect. This work makes a study of the degree of affectation of this information for some commonly used codec types and proposes our own solution, to compensate the session variability provoked by the codec. The influence of some types of codec in the quality of the sample was evaluated first with a set of synthesized speech samples. Later, experiments were carried out with speech samples of international competitions, retransmitted over two different codecs, and the effect on the speaker recognition effectiveness was checked. Finally, the variability compensation was applied, with an improvement of the recognition effectiveness, measured by the equal error rate, of 20.8% for the g.722 codec and 27.8% for the gsm 6.20 codec.     

Biodegradability of poly(vinyl alcohol)

Plastic waste increases at a rate of several tons per year and the time required for their biodegradation is often unknown. The Phanerochaete chysosporium fungus oxidizes a wide variety of toxic organic compounds to nontoxic compounds or CO₂ and H₂O. The biodegradability of the poly(vinyl alcohol) (PVOH) caused by this fungus was analyzed by gel permeation chromatography (GPC) with differential refractive index (Δn) and ultraviolet (UV) detectors. During the GPC analyses, the PVOH is in contact with the components of the culture medium. These components can interact with the stationary phase and also with the polymer producing erroneous results in the molecular weight determination. Therefore, we compare results using differnt mobile phases. A phosphate-acetate buffer of pH 7.4 was found to be appropriate mobile phase to follow the degree of degradation of the PVOH by the change in the average molecular weight determined by GPC in this culture medium. UV detection enabled us to identify structural changes associated with transformations of the carbonyl groups, mainly to enolized β-diketones groups. Infrared absorption (FTIR) confirmed these changes and also showed important modifications in the C-O stretching region probably due-to apertures of cyclic ether groups or transformations of the OH groups by oxidation reactions.     

Unity for all

It is quite paradoxical that, in spite of the strong energy dimension of the first European Union treaties and of the relevance of energy for the European economy, until very recently it has been difficult to identify a common European energy policy. Several factors make defining a common European energy policy particularly difficult. There is a conflict between economic efficiency, which has led to the creation of common European gas and electricity markets, and national sovereignty, which makes member states reluctant to leave their supply security in others' hands. Another conflict is the one arising because of policies favoring the so-called "national champions." It is difficult to reach a consensus on these highly political issues. Nuclear energy is yet another problem. Until recently, most of the measures adopted at the European level have lacked an integral vision: usually policies have focused on a particular aspect, fuel, or technology, ignoring the rest. The outcome has been an unbalanced, nonharmonized development of different energy aspects that harms effectiveness and perdurability.     

The influence of manufacturing and drying conditions on the survival and toxinogenesis of Staphylococcus aureus in two Spanish dry sausages (chorizo and salchichón)

The effects of formulation, starter culture and fermentation temperature on growth and synthesis of toxin A (SEA) and TNase by Staphylococcus aureus during fermentation and drying of Spanish chorizo were investigated. Inhibitory factors able to inhibit SEA synthesis in culture media were unable to prevent SEA production in chorizo fermented at 20 and 30°C, though a lower temperature and starter culture SP318 (Lactobacillus sake, Pediococcus pentosaceous and Staphylococcus xylosus) decreased staphylococcal growth and SEA formation. Reduction and even disappearance of the SEA during ripening was observed. In most batches, TNase was a reliable indicator of staphylococcal growth and SEA production. Dextrose added to the salchichón formulation repressed S. aureus growth during drying. Lactobacillus curvatus in combination with dextrose was an effective anti-staphylococcal agent during fermentation.