Marine sponges as biomonitor of polychlorobiphenyl contamination: concentration and fate of 24 congeners

The aim of this study was first to assess the relevance of a marine sponge, Spongia officinalis, as a biomonitor of PCB. Twenty-four chlorobiphenyl congeners have been measured along a pollution gradient both in sponges and seawater. S. officinalis displays a capacity to accumulate all types of congeners. The highest concentration factors were found for hexa- and heptachlorobiphenyls. Concentrations recorded in sponges agreed quite well with the PCB concentrations of study sites. The prevalence of CB138 and CB153 definitely demonstrated the urban origin of the PCB detected, despite the ban on their production and the existence of a wastewater treatment plant since 1987. The CB138/CB153 ratio is approximately 1.2 in commercial mixtures as well as in seawater. In sponges, this ratio varies strongly in space and time, from 1 in sponges at the most polluted site to 0.3 at the reference site. This change in the ratio of these two very persistent congeners, which is not observed in seawater, indicates a metabolism of CB138 in sponges. As it was recently demonstrated for nonpersistent organic contaminants, sponges might well be able to degrade PCB, but further work is needed to identify the processes involved.     

Image Segmentation and Bruise Identification on Potatoes Using a Kohonen's Self-Organizing Map

Potato quality includes a low incidence of colored bruises resulting from bad storage or manipulation practices. We developed a procedure to process and segment potato images by using Kohonen's self‐organizing map. Anomalous regions could be distinguished on 3 potato varieties. Bruises that were very dissimilar in appearance were correctly identified, and some particular defects such as green spots could be located as well.     

Identification of odour‐active compounds in muscle of brown trout (Salmo trutta) as affected by dietary lipid sources

The effect of fatty acid composition on odour‐active compounds in brown trout (Salmo trutta) muscle was evaluated. The fillets were obtained from three groups of fish fed experimental diets containing either fish oil (FO), soybean oil (SO) or linseed oil (LO). Muscle fatty acid composition was shown to be influenced by diet. Thirty‐one odorous compounds were detected by gas chromatography/olfactometry (frequency‐of‐detection method). Most of these compounds were formed by the oxidation of unsaturated fatty acids. Independently of diet, (E)‐2‐pentenal, (E)‐2‐pentenol and (E)‐2‐hexenol contribute strongly to the odour of brown trout. (E,Z)‐2,4‐Heptadienal was detected with high frequency in fish fed diets containing high levels of n‐3 PUFAs (FO and LO groups). Hexanal, (E)‐2‐hexenal and 2‐nonanol seem to contribute most to the odour of fish fed diets containing vegetable oils. Many odorous compounds were derived from the oxidation of mono‐ and di‐unsaturated fatty acids, which could be promoted by high levels of PUFAs. © 2002 Society of Chemical Industry     

Chemical Coupling of Carbon Nanotubes and Silicon Nanoparticles for Improved Negative Electrode Performance in Lithium‐Ion Batteries

Multi‐walled carbon nanotube (MWCNT)/silicon nanocomposites obtained by a grafting technique using the diazonium chemistry are used to prepare silicon negative electrodes for lithium‐ion batteries. The covalent bonding of the two compounds is obtained via mono‐ and multi‐layers of phenyl bridges, leading to an ideal dispersion of MWCNTs and silicon nanoparticles that are bound together. The presence of MWCNTs close to silicon nanoparticles enhances the electronic pathway to the active material particles and probably helps to prevent silicon decrepitation upon repeated lithium insertion/extraction by improving the mechanical stability of the electrode at a nanoscale level. This effect results in the enhancement of cycling ability and capacity, which are demonstrated by comparing the nanocomposite electrode to a simple mixture of the two compounds. This technique can be applied to other carbon conductive additives together with silicon or other nanosized active compounds.     

Wavelength‐Emission Tuning of ZnO Nanowire‐Based Light‐Emitting Diodes by Cu Doping: Experimental and Computational Insights

The band‐gap engineering of doped ZnO nanowires is of the utmost importance for tunable light‐emitting‐diode (LED) applications. A combined experimental and density‐functional theory (DFT) study of ZnO doping by copper (Zn²⁺ substitution by Cu²⁺) is presented. ZnO:Cu nanowires are epitaxially grown on magnesium‐doped p‐GaN by electrochemical deposition. The heterojunction is integrated into a LED structure. Efficient charge injection and radiative recombination in the Cu‐doped ZnO nanowires are demonstrated. In the devices, the nanowires act as the light emitters. At room temperature, Cu‐doped ZnO LEDs exhibit low‐threshold emission voltage and electroluminescence emission shifted from the ultraviolet to violet–blue spectral region compared to pure ZnO LEDs. The emission wavelength can be tuned by changing the copper content in the ZnO nanoemitters. The shift is explained by DFT calculations with the appearance of copper d states in the ZnO band‐gap and subsequent gap reduction upon doping. The presented data demonstrate the possibility to tune the band‐gap of ZnO nanowire emitters by copper doping for nano‐LEDs.     

New insights into physiology and metabolism of Propionibacterium freudenreichii

Dairy propionibacteria are Actinobacteria, mainly isolated from dairy environments. Propionibacterium freudenreichii has been used for a long time as a ripening culture in Swiss-type cheese manufacture, and is more and more considered for its potent probiotic effects. This review summarises the knowledge on the main P. freudenreichii pathways and the main features explaining its hardiness, and focuses on recent advances concerning its applications as a cheese ripening agent and as a probiotic for human health. Propionibacteria have a peculiar metabolism, characterised by the formation of propionic acid as main fermentation end-product. They have few nutritional requirements and are able to use a variety of carbon substrates. From the sequence of P. freudenreichii CIRM-BIA1^T genome, many pathways were reconstituted, including the Wood-Werkman cycle, enzymes of the respiratory chain, synthesis pathways for all amino acids and many vitamins including vitamin B₁₂. P. freudenreichii displays features allowing its long-term survival. It accumulates inorganic polyphosphate (polyP) as energy reserve, carbon storage compounds (glycogen), and compatible solutes such as trehalose. In cheese, P. freudenreichii plays an essential role in the production of a variety of flavour compounds, including not only propionic acid, but also free fatty acids released via lipolysis of milk glycerides and methyl-butanoic acids resulting from amino acid degradation. P. freudenreichii can exert health-promoting activities, such as a bifidogenic effect in the human gut and promising immunomodulatory effects. Many P. freudenreichii properties involved in adaptation, cheese ripening, bio-preservation and probiotic effects are highly strain-dependent. The elucidation of the molecular mechanisms involved is now facilitated by the availability of genome sequence and molecular tools. It will help in the selection of the most appropriate strain for each application.     

Fruit juice-induced endothelium-dependent relaxations in isolated porcine coronary arteries: evaluation of different fruit juices and purees and optimization of a red fruit juice blend

Numerous studies have indicated that several polyphenol-rich sources such as red wine and green tea are potent inducers of endothelium-dependent relaxations in isolated arteries. As various fruits and berries are known to contain high levels of polyphenols, the aim of the present study was to assess the ability of selected pure fruit juices and purees as well as blends to cause endothelium-dependent relaxations in isolated arteries. Vascular reactivity was assessed using porcine coronary artery rings, and fruit juices, purees and blends were characterized for their content in vitamin C, total phenolic, sugar and antioxidant activity. Fruit juices and purees caused variable concentration-dependent relaxations, with blackcurrant, aronia, cranberry, blueberry, lingonberry, and grape being the most effective fruits. Several blends of red fruits caused endothelium-dependent relaxations. Relaxations to blend D involved both a NO- and an EDHF-mediated components. The present findings indicate that some berries and blends of red fruit juices are potent inducers of endothelium-dependent relaxations in the porcine coronary artery. This effect involves both endothelium-derived NO and EDHF, and appears to be dependent on their polyphenolic composition rather than on the polyphenolic content.     

Failure analysis defect location on a real case 55 nm memory using dynamic power supply emulation

Static and dynamic techniques for defect location are well established in the failure analysis flow of a failing integrated circuit. When a circuit shows an overconsumption on power supply, the useful static techniques are laser stimulation (OBIRCH, TIVA, LIVA, etc.) or photoemission. When the electrical signature is a soft fail, a functional fault or a timing issue the analyst will use dynamic techniques like dynamic laser mapping (SDL, xVM, LVI, etc.), dynamic photoemission or internal probing (Ebeam, TRE, LVP, etc.) by applying a looping test sequence which emulates the fail.In this paper we will present a real case analysis on a circuit showing a static signature (over consumption) and also a functional fault. Both static and dynamic location techniques have been used for the defect location, plus a non conventional approach by applying a clocked power supply sequence to the circuit. A comparison is done between the different signatures and we show that dynamic power supply emulation can bring some additional information on the defect location which is not detected with the conventional static/dynamic approach.