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International audience; The identification and measurement of biomarkers is critical to a broad range of methods that diagnose and monitor many diseases. Serum auto-antibodies are rapidly becoming interesting targets because of their biological and medical relevance. This paper describes a highly sensitive, label-free approach for the detection of p53-antibodies, a prognostic indicator in ovarian cancer as well as a biomarker in the early stages of other cancers. This approach uses impedance measurements on gold microelectrodes to measure antibody concentrations at the picomolar level in undiluted serum samples. The biosensor shows high selectivity as a result of the optimization of the epitopes responsible for the detection of p53-antibodies and was validated by several techniques including microcontact printing, self-assembled-monolayer desorption ionization (SAMDI) mass spectrometry, and adhesion pull-off force by atomic force microscopy (AFM). This transduction method will lead to fast and accurate diagnostic tools for the early detection of cancer and other diseases.

14 pages, 6 figures, 1 table, supplementary data https://doi.org/10.1016/j.protis.2010.10.003, In recent years, a substantial amount of data on aquatic protists has been obtained from culture-independent molecular approaches, unveiling a large diversity and the existence of new lineages. However, sequences affiliated with minor groups (in terms of clonal abundance) have often been under-analyzed, and this hides a potentially relevant source of phylogenetic information. Here we have searched public databases for 18S rDNA sequences of chrysophytes, choanoflagellates and bicosoecids retrieved from molecular surveys of protists. These three groups are often considered to account for most of the heterotrophic flagellates, an important functional component in microbial food webs. They represented a significant fraction of clones in freshwater studies, whereas their relative clonal abundance was low in marine studies. The novelty displayed by this dataset was notable. Most environmental sequences were distant to sequences of cultured organisms, indicating a significant bias in the representation of taxa in culture. Moreover, they were often distant to sequences from other molecular surveys, suggesting an insufficient sequencing effort to characterize the in situ diversity of these groups. Phylogenetic trees with complete sequences present the most accurate representation of the diversity of these groups, with the emergence of several new clades formed exclusively by environmental sequences. Exhaustive data mining in sequence databases allowed the identification of new diversity hidden inside chrysophytes, choanoflagellates and bicosoecids, This study was supported by projects GEMMA (CTM2007-63753-C02-01/MAR, MEC) and MICROVIS (CTM2007-62140/MAR, MEC) and the European Funding Agencies from the ERA-net program BiodivERsA under the BioMarKs project. Javier del Campo was funded by I3P program (I3PPRE-06-00676, CSIC). We thank Raquel Rodríguez-Martínez for her help in the unamended incubations, Vanessa Balagué for her laboratory assistance and Joseph Jr. Campo for his help in the English

Testosterone is one of the androgenic steroid hormones, the consumption of which is considered doping in most sports. Here, we present powerful 3D sensing platforms using novel disc-ring microelectrode array devices and exploit them for the competitive immunosensing of testosterone. Each device contains a microelectrode array that consists of a large number of individual microdiscs and is used as the substrate for immunofunctionalization and assay performance. One micrometer above it, a second microelectrode array, this time consisting of microrings, is used as the working electrode for electrochemical monitoring. The physical separation of these two functions allows the incorporation of relatively thick biocomponent layers during immunofunctionalization of the microdiscs without negatively affecting electrochemical detection at the rings. Moreover, it permits electrochemical activation of the latter immediately before substrate addition and hence enables optimal electrode performance. The optimized assay showed a linear range between 0.01 and 10 ng/mL and a limit of detection of 12.5 pg/mL testosterone with detection times of 45 min.

12 pages, 6 figures, 1 table Despite the ecological importance of marine pico-size eukaryotes, the study of their in situ diversity using molecular tools started just a few years ago. These studies have revealed that marine picoeukaryotes are very diverse and include many novel taxa. However, the amount and structure of their phylogenetic diversity and the extent of their sequence novelty still remains poorly known, as a systematic analysis has been seldom attempted. In this study, we use a coherent and carefully curated data set of 500 published 18S ribosomal DNA sequences to quantify the diversity and novelty patterns of picoeukaryotes in the Indian Ocean. Our phylogenetic tree showed many distant lineages. We grouped sequences in OTUs (operational taxonomic units) at discrete values delineated by pair-wise Jukes–Cantor (JC) distances and tree patristic distances. At a distance of 0.01, the number of OTUs observed (237/242; using JC or patristic distances, respectively) was half the number of sequences analyzed, indicating the existence of microdiverse clusters of highly related sequences. At this distance level, we estimated 600–800 OTUs using several statistical methods. The number of OTUs observed was still substantial at higher distances (39/82 at 0.20 distance) suggesting a large diversity at high-taxonomic ranks. Most sequences were related to marine clones from other sites and many were distant to cultured organisms, highlighting the huge culturing gap within protists. The novelty analysis indicated the putative presence of pseudogenes and of truly novel high-rank phylogenetic lineages. The identified diversity and novelty patterns among marine picoeukaryotes are of great importance for understanding and interpreting their ecology and evolution This study was supported by the projects GEMMA (CTM2007–63753-C02–01/MAR, MEC), the NSF grant DEB-0816638 and the European Funding Agencies from the ERA-net program BiodivERsA, under the BioMarKs project

Photosynthetic microbial mats are sources of microbial diversity and physiological strategies that reflect the physical and metabolic interactions between their resident species. This study focused on the diversity and activity of polyhydroxyalkanoate-producing and -degrading bacteria and their close partnership with cyanobacteria in an estuarine and a hypersaline microbial mat. The aerobic heterotrophic population was characterized on the basis of lipid biomarkers (respiratory quinones, sphingoid bases), polyhydroxyalkanoate determination, biochemical analysis of the isolates, and interaction assays. Most of the polyhydroxyalkanoate-producing isolates obtained from an estuarine mat belonged to the Halomonas and Labrenzia genera, while species of Sphingomonas and Bacillus were more prevalent in the hypersaline mat. Besides, the characterization of heterotrophic bacteria coisolated with filamentous cyanobacteria after selection suggested a specific association between them and diversification of the heterotrophic partner belonging to the Halomonas genus. Preliminary experiments suggested that syntrophic associations between strains of the Pseudoalteromonas and Halomonas genera explain the dynamics of polyhydroxyalkanoate accumulation in some microbial mats. These metabolic interactions and the diversity of the bacteria that participate in them are most likely supported by the strong mutual dependence of the partners.

This work features the design, fabrication and characterisation of a miniaturised electroanalytical lab on a chip that allows the performance of a complete bioassay, from the capture of magnetic particles through their functionalisation and sample incubation to the detection of electroactive reaction products. The system is built using mainly polymeric materials such as PMMA and PDMS and fast prototyping techniques such as milling and moulding. The system also includes a set of microelectrodes, photo-lithographed on a silicon chip. The novelty lies in the design of the rotary microvalve, which contains a microreactor so that various reaction and incubation steps can be carried out in isolation from the detection event with zero dead volume. This avoids contamination and fouling of the electrodes by proteins or other organic matter, and extends the useful lifetime of the detector. The system operation is demonstrated by a model example, consisting in the functionalisation of streptavidin-coated magnetic particles with biotinylated beta-galactosidase over periods ranging from 5 to 15 min, at which point the particles saturate. Although the system is intended for the development of enzyme-based electrochemical bioassays, the concept of its rotary microreactor can be applied more broadly.

La exigua rentabilidad media de los fondos de inversión en España en los últimos 3, 5 y 10 años (0,51%; 2,23% y 0,85%) fue inferior a la inversión en bonos del estado a cualquier plazo y a la inflación. A pesar de estos resultados, los 2.586 fondos existentes tenían un patrimonio de €163 millardos en diciembre de 2009. Sólo 14 de los 368 fondos con 15 años de historia y 16 de los 1.117 con 10 años tuvieron una rentabilidad superior a la de los bonos del estado a 10 años. Sólo 4 de de los 1.117 fondos con 10 años de historia proporcionaron a sus partícipes una rentabilidad superior al 10%: Bestinver bolsa (15,7%), Bestinfond (14,6%), Bestinver mixto (11,3%) y Metavalor (10,0%). 263 fondos con 10 años de historia (7 eran garantizados) proporcionaron a sus partícipes unarentabilidad ¡negativa! y su patrimonio en dici embre de 2009 fue 5.816 millones de euros. En el periodo 1991-2009 los fondos destruyeron €118 millardos de sus partícipes. El total de comisiones y gastos repercutidos en este periodo ascendió a €39 millardos.During the last 10 years (1999-2009), the average return of the mutual funds in Spain (0.85%) was smaller than the average inflation. Nevertheless, on December 31, 2009, 5.6 million investors had 163 billion euros in the 2,586 existing mutual funds. Only 1 of the 368 mutual funds with 15-year history outperformed the Spanish Index (ITBM).

We compute the shareholder value creation and the return of the companies in the IBEX 35 for the 18-year period 1991-2009. The average return was 12.5%, but 4.4% was due to the decline in interest rates (from 13% to 4%). The shareholder value creation in the whole period was 101 billion euros, despite a value destruction of 238 billion euros in 2008.

We rank the 61 companies operating in 2009 in the Pension Fund Industry in Spain using data from 1994 to 2009 for the 1,393 existing individual mutual funds. The best companies according to the ranking were: Bestinver, Caja Manresa, Cajasur, Merchbanc and Ibercaja. The worst, according to the ranking, was Caja Cataluna.

Only 23 Spanish companies out of 125 had positive return in 2010. The companies destroyed value for their shareholders in 2010 (155 billion euros), created value in 2009 (100 billion euros), and also destroyed value in 2008 (420 billion euros) and in 2007 (17 billion euros). The average return of the 125 companies was -27% in 2010, 30% in 2009 and -40% in 2008.

The average MRP used by analysts in the USA and Canada (5.1%) was similar to the one used by their colleagues in Europe (5.0%), and UK (5.2%). But the average MRP used by companies in the USA and Canada (5.3%) was smaller than the one used by companies in Europe (5.7%), and UK (5.6%). The dispersion of the MRP used was high, but lower than the one of the professors: the average range of MRP used by analysts (companies) for the same country was 5.7% (4.1%) and the average standard deviation was 1.7% (1.2%). These statistics were 7.4% and 2.4% for the professors. Most previous surveys have been interested in the Expected MRP, but this survey asks about the Required MRP. The paper also contains the references that analysts and companies use to justify their MRP, and comments from 89 respondents that illustrate the various interpretations of what is the required MRP.

During the last 10 years (1999-2009), the average return of the mutual funds in Spain (0.85%) was smaller than the average inflation. Nevertheless, on December 31, 2009, 5.6 million investors had 163 billion euros in the 2,586 existing mutual funds. Only 1 of the 368 mutual funds with 15-year history outperformed the Spanish Index (ITBM).

During the last 3, 5 and 10 years, the average return of the pension funds in Spain was lower than the inflation and than the return of Government Bonds. Nevertheless, on December 31, 2009, 10.7 million investors had 84.8 billion euros in the 3,308 existing pension funds. Note: Document in Spanish.

The average Market Risk Premium (MRP) used in 2010 by professors in the United States (6.0%) was higher than the one used by their colleagues in Europe (5.3%). We also report statistics for 33 countries: the average MRP used in 2010 ranges from 3.6% (Denmark) to 10.9% (Mexico). 29% of the professors decreased the MRP in 2010, 16% increased it and 55% used the same MRP. The dispersion of the MRP used was high: the average range of MRP used by professors for the same country was 7.4% and the average standard deviation was 2.4%. Most previous surveys have been interested in the Expected MRP, but this survey asks about the Required MRP. The paper also contains the references that professors use to justify their MRP, and comments from 85 professors that illustrate the various interpretations of what is the required MRP.

We demonstrate, with the example of the electroanalytical sensing of chromium(vi) using ultra-microelectrode arrays, that a larger number of microelectrodes comprising an array do not necessarily provide improved electroanalytical performance. Using a low density array, which consists of 256 microdiscs where each microdisc comprising the array has a radius of 10 microns in a cubic arrangement separated from their nearest neighbour by 100 microns, the electroanalytical sensing of chromium(vi) is shown to be possible over the range 13-428 microM with a limit of detection of 3.4 microM readily achievable. Using a high density microelectrode, consisting of 2597 microdiscs where each microdisc has a radius of 2.5 microns in a hexagonal pattern which are separated from their nearest neighbour by 55 microns, the electroanalytical performance, in terms of linear range and sensitivity, is considerably lower going against the misconception that a high density array should produce a superior analytical response. The reason for this disparity is discussed and it is shown that the arrangement of the microelectrodes on the array is critical due to the interaction of diffusion zones between neighbouring electrodes allowing analysts to make informed decisions on the conscientious choice of microelectrode arrays.

The fabrication, characterization, and use of arrays of ring recessed disk microelectrodes are reported. These devices are operated in generator-collector mode with a disk acting as the generator and the ring as the collector. We report experiments and simulations relating to time-of flight experiments in which material electrogenerated at a disk is diffusionally transported to the ring. Analysis of the current transient measured at the latter when it is potentiostatted at a value to ensure diffusionally controlled “collection” is shown to sensitively reflect the diffusion coefficients of the species forming the redox couple being driven at the generator electrode. The method is applied to the ferrocene/ferrocenium couple in the room temperature ionic liquid [N6, 2, 2, 2][NTf2], and the results are found to agree with independent measurements.

7 pages, 1 figure, 1 table, Over the last decade, culture-independent surveys of marine picoeukaryotic diversity based on 18S ribosomal DNA clone libraries have unveiled numerous sequences of novel high-rank taxa. This newfound diversity has significantly altered our understanding of marine microbial food webs and the evolution of eukaryotes. However, the current picture of marine eukaryotic biodiversity may be significantly skewed by PCR amplification biases, occurrence of rDNA genes in multiple copies within a single cell, and the capacity of DNA to persist as extracellular material. In this study we performed an analysis of the metagenomic dataset from the Global Ocean Survey (GOS) expedition, seeking eukaryotic ribosomal signatures. This PCR-free approach revealed similar phylogenetic patterns to clone library surveys, suggesting that PCR steps do not impose major biases in the exploration of environmental DNA. The different cell size fractions within the GOS dataset, however, displayed a distinct picture. High protistan diversity in the

13 pages, 4 pages, 5 tables, supplementary material https://doi.org/10.1007/s00248-010-9645-2, Microbial mats are stratified microbial communities composed by highly inter-related populations and therefore are frequently chosen as model systems to study diversity and ecophysiological strategies. The present study describes an integrated approach to analyze microbial quinones and intact polar lipids (IPLs) in microbial mats within layers as thin as 500 μm by liquid chromatography-tandem mass spectrometry. Quinone profiles revealed important depth-related differences in community composition in two mat systems. The higher abundance of ubiquinones, compared to menaquinones, reflected the clear predominance of microorganisms belonging to aerobic α-, β-, and γ-Proteobacteria in Ebro delta estuarine mats. Hypersaline photosynthetic Camargue mats (France) showed a predominance of menaquinone-9 at the top of the mat, which is consistent with an important contribution of facultative aerobic or anaerobic bacteria in its photic zone. Quinone indices also indicated a higher diversity of non-phototrophs and a more anaerobic character in the hypersaline mats. Besides, the dissimilarity index suggested that the samples were greatly influenced by a depth-related redox state gradient. In the analysis of IPLs, there was a predominance of phosphatidylglycerols and sulfoquinovosyldiacylglycerols, the latter being an abundant biomarker of Cyanobacteria. This combined approach based on quinone and IPL analysis has proven to be a useful method to establish differences in the microbial diversity and redox state of highly structure microbial mat systems at a fine-scale level, LV was recipient of a scholarship from the Spanish MECD (AP2001-0953). This research was supported by the grant CGL2005-04990/BOS from the Spanish Ministry of Science and Technology

En este trabajo demostramos el uso de redes de microelectrodos como base para el desarrollo de biosensores. La principal ventaja está en que las biomoléculas empleadas para reconocer los analitos se inmovilizan en la parte inerte de la red. Es decir, en el espacio entre microelectrodos. De este modo los electrodos pueden mantenerse activos y conservar su alta sensibilidad., Biosensor performance depends on the effective functionalisation of a transducer with suitable biorecognition elements. During functionalisation, surface blocking steps are normally carried out to avoid later binding of undesirable molecules and thus guarantee biosensor specificity. However, these blocking steps may be deleterious in electrochemical systems where transduction ultimately relies on electron transfer between the electrode and a redox species in solution. This work presents a novel approach to develop improved amperometric biosensing platforms using microfabricated disk microelectrode arrays, based on the functionalisation of the inert surface surrounding the active microdisks. These devices more than doubled assay sensitivity compared to conventional biosensors produced using the same arrays. This approach benefits from three advantages: the functionalisation of a broader surface, the possibility to activate the microelectrodes immediately before detection, and access to enhanced rates of mass transport to microelectrodes that improve device sensitivity. To demonstrate this, we first studied the electrochemical behaviour of tetramethylbenzidine (TMB) at gold disk microelectrode arrays, and then used TMB as the redox mediator for the amperometric biosensing of HRP/H2O2. Down to 0.54 pM H2O2 or as little as 25 pM HRP were detected within 5 seconds of enzyme activity in just 10 μl of enzyme substrate solution. We postulate that microelectrode arrays may be used to develop novel electrochemical biosensing platforms that are faster and more sensitive than conventional biosensors.

12 pages, 5 figures, 1 table, Molecular surveys of marine picoeukaryotes have revealed a large number of sequences unrelated to cultured organisms, such as those forming the marine stramenopile (MAST)-4 clade. Recent FISH (fluorescent in situ hybridization) data have shown that MAST-4 cells are uncultured heterotrophic flagellates of 2–3 μm in size that have a global distribution in non-polar marine waters. However, FISH is time-consuming and hard to apply to the many samples generated during oceanographic cruises, so we developed a real-time quantitative polymerase chain reaction (Q-PCR) protocol to determine rapidly the abundance of this group using environmental DNA. We designed a primer set targeting the 18S rRNA genes (rDNA) of MAST-4 and optimized and calibrated the Q-PCR protocol using a plasmid with the target sequence as insert. The Q-PCR was then applied to quantify MAST-4 rDNA molecules along three marine transects, longitudinal in the Indian Ocean, latitudinal in the Drake Passage and coastal–offshore in the Mediterranean Sea, and to a temporal study in a Mediterranean Sea coastal station. MAST-4 was detected in all samples processed (averaged abundances between 500 and 1000 rDNA molecules ml−1) except in mesopelagic and Antarctic samples, where it was virtually absent. In general, it was more abundant in the coast than offshore and in the deep chlorophyll maximum than at surface. A comparison of Q-PCR and FISH signals in well-controlled microbial incubations indicated that MAST-4 cells have around 30 copies of the rDNA operon. This Q-PCR assay quickly yielded quantitative data of uncultured MAST-4 cells and confirmed their wide distribution and putative ecological importance, We thank the captains and crews of Research Vessels Hespérides and Melville and the chief scientists (T. Calafat, C. Pedrós-Alió and D. Blackman) for providing an optimal environment for sampling. This study was supported by projects TRANSINDICO (REN2000-1471-CO2-01/MAR), ESTRAMAR (CTM2004-12631/MAR, MEC) and PROTAL (HA2004-088, MCyT) to R.M. and by an F.P.I. fellowship from the Spanish Ministry of Education and Science to R.R.M.

Here a novel electrochemical method for the rapid detection of anti-HIV antibodies in serum is presented. The novelty lies in the combination of allosteric enzymes and coulometry to yield a fast, simple and reliable HIV diagnostic method. We have used a previously developed β -galactosidase enzyme that is efficiently activated by anti-HIV antibodies directed against a major B-cell epitope of the gp41 glycoprotein. When these antibodies bind the enzyme, the 3D conformation changes positively affecting the performance of the active site and, consequently, the enzyme activity is stimulated. Using 4-aminophenyl β - d -galactopyranoside (PAPG) as substrate yields p-aminophenol (PAP), which is reversibly oxidised at a very mild potential, ca. 0.37 V vs. Ag/AgCl over a range of electrode materials within the working pH range of β -galactosidase. In the present case, photolithographically produced microelectrode arrays resulted in a detection limit of 4 μM for 4-aminophenol (PAP). The presence of anti-HIV antibodies results in enzyme activity increases above 50% which, combined with the sensitivity and response time afforded by the microelectrode arrays, allowed for the diagnosis of HIV in sera samples within an hour.

6 pages, 4 figures, 1 table.-- PMID: 18552178 [PubMed].-- Supporting information available at: http://www.pnas.org/content/105/25/8724/suppl/DCSupplemental, Analysis of marine cyanobacteria and proteobacteria genomes has provided a profound understanding of the life strategies of these organisms and their ecotype differentiation and metabolisms. However, a comparable analysis of the Bacteroidetes, the third major bacterioplankton group, is still lacking. In the present paper, we report on the genome of Polaribacter sp. strain MED152. On the one hand, MED152 contains a substantial number of genes for attachment to surfaces or particles, gliding motility, and polymer degradation. This agrees with the currently assumed life strategy of marine Bacteroidetes. On the other hand, it contains the proteorhodopsin gene, together with a remarkable suite of genes to sense and respond to light, which may provide a survival advantage in the nutrient-poor sun-lit ocean surface when in search of fresh particles to colonize. Furthermore, an increase in CO2 fixation in the light suggests that the limited central metabolism is complemented by anaplerotic inorganic carbon fixation. This is mediated by a unique combination of membrane transporters and carboxylases. This suggests a dual life strategy that, if confirmed experimentally, would be notably different from what is known of the two other main bacterial groups (the autotrophic cyanobacteria and the heterotrophic proteobacteria) in the surface oceans. The Polaribacter genome provides insights into the physiological capabilities of proteorhodopsin-containing bacteria. The genome will serve as a model to study the cellular and molecular processes in bacteria that express proteorhodopsin, their adaptation to the oceanic environment, and their role in carbon-cycling. Copyright © 2008 National Academy of Sciences, This work was supported by the European Union (contract EU-FP6-505403NoE Marine Genomics Europe), the Spanish Ministry of Education and Science (Grant CTM2004-02586/MAR), and the Swedish Research Council (Grant 621-2003-2692)

11 pages, 6 figures, 3 tables.-- PMID: 18553187 [PubMed].-- Printed version published Aug 2008., Functionalisation of the sensing surface is a key factor in immunosensor fabrication as it allows target-selective capture and prevents nonspecific adsorption of undesired components. Gold immunofunctionalisation using self-assembled monolayers (SAM) has been widely exploited to this end for the detection of small targets. However, we recently demonstrated that this strategy fails when detecting whole bacteria cells (Baldrich et al., Anal Bioanal Chem 390: 1557–1562, 2008). We now investigate different physisorption-based alternatives using E. coli as the target organism. Our results demonstrate that physisorption generates the appropriate substrate for the specific detection of bacteria on gold surfaces, providing detection limits down to 10^5 cells mL−1 in an ELISA-type colorimetric assay. Additionally, surface coverage is highly reproducible when assayed by impedance spectroscopy and the inter- and intra-assay coefficients of variation are below 10–15% in all cases. These surfaces were stable, retained functionality and did not suffer from significant biomolecule desorption after 10 days storage in PBS at 37°C, hence confirming physisorption as a cheap, simple and efficient strategy for the detection of bacteria., This work has been funded in the context of the project MICROBACTOMETER (TEC2006-13109-C03-02/MIC) from the Spanish Ministry of Education. Eva Baldrich is supported by an I3P fellowship from the Consejo Superior de Investigaciones Científicas (CSIC, Spain). Olivier Laczka and F. Javier del Campo are respectively supported by and FP1 and a Ramón y Cajal fellowship from the Spanish Ministry of Education.

10 pages, 6 figures, 1 table.-- PMID: 18534611 [PubMed].-- Printed version published Jul 31, 2008., Surface functionalisation is of extreme importance in assay and biosensor development because it ensures the selective capture and detection of the targets of interest. In the present report, we compare the performance of several gold functionalisation strategies/chemistries, based on SAM self-assembly and Ab conjugation, for protein and bacteria detection., The first part of the work summarises the optimisation of the various protocols considered. Their efficiency was initially evaluated in terms of reduction of biomolecule non-specific adsorption and specific detection competence impairment, using as a model-target an enzyme-labelled protein. With this purpose, the effect of several parameters, such as thiomolecule length and concentration, self-assembly time and temperature, polymer incorporation, or Ab conjugation strategy was determined. The three best performing strategies consisted of antibody (Ab) conjugation to self-assembled monolayers (SAM) containing mercaptoundecanoic acid alone, or conjugated to either long-chain hydrophilic diamines or CM-dextran. In the three cases, results demonstrated that Abs had been successfully incorporated and remained functional for protein detection. Nevertheless, as showed in the second part of the work, we demonstrate for the first time that these chemistries can be inadequate for bacteria detection. The possible reasons and implications will be discussed. Ab physisorption is proposed as a cost-effective gold immuno-functionalisation strategy alternative to SAM-based Ab incorporation for bacteria detection., This work has been funded in the context of the project MICROBACTOMETER (TEC2006-13109-C03-02/MIC) from the Spanish Ministry of Education. Eva Baldrich is supported by an I3P fellowship from the Consejo Superior de Investigaciones Científicas (CSIC, Spain). Olivier Laczka and F. Javier del Campo are respectively supported by FP1 and a Ramón y Cajal fellowship from the Spanish Ministry of Education.

Electrochemical impedance spectroscopy (EIS) is an important detection technique for biosensors. In the field of immunosensors, and particularly pathogen detection, it is one of the preferred electrochemical techniques because it does away with the use of enzyme labels or redox mediators. This chapter provides an introduction to the fundamentals of EIS and basic data analysis, with an emphasis on the most common features found in immunosensors and possible experimental limitations.

A reversible electron transfer is studied at a microdisk electrode which is partially blocked by an inert particle at the disk center. The inert particle is either a cylinder of a sphere. The size of a cylinder located at the center of the microdisk electrode is determined with the help of a simple electrochemical procedure. Cyclic voltammograms for the reduction of a reversible redox system are recorded as a function of scan rate and compared to simulations. Excellent agreement between theory and experiment was found. Modelling diffusion to a microdisk electrode modified with a sphere or cylinder at its center by numerical simulations gives physical support for the transition in diffusion-layer shape and size, therefore allowing to size not only particles of known shape but also, in principle, to determine their shape and size simultaneously. © 2007 Elsevier B.V. All rights reserved.

This article reviews the literature dealing with electroanalytical applications of ultramicroelectrode arrays over the past twenty years. A brief theoretical description of the mass transport mode governing their behavior is given, after which the main fabrication methods are described. The applications described in the later sections of this review range from conventional electroanalysis, namely trace metal stripping methods, using mercury modified arrays to more recent advances in the field of biosensors (enzymatic, immunosensors and nucleic acid based ones). © 2007 Wiley-VCH Verlag GmbH and Co. KGaA.

Microband electrode arrays are useful tools for the electrochemist, offering the enhanced sensitivity associated with microelectrodes but with a higher total current output. For optimum performance, the array may be designed such that space is used efficiently but the individual microbands behave as isolated electrodes on the time scale of the experiment. For a linear sweep experiment, the optimum specifications of a microband array depend on the scan rate used and the diffusion coefficient of the electroactive species. A two-dimensional simulation method is used to examine the nature of the diffusion to a regular array of microbands. Cyclic voltammetry of hexaammineruthenium(III)chloride is performed at a regularly spaced microband array to test the theory. © 2007 American Chemical Society.

The size of microdroplets of dodecane of approximately 5 μm diameter immobilised on a regular array of hydrophobic polymer blocks of a partially blocked electrode is determined by comparison of a simple electrochemical procedure with simulations. The electrochemical procedure is based on a simple Cottrellian-like potential-step experiment, where the current response is monitored as a function of time. Excellent agreement is found between theory and experiment thus giving physical support for the expected transition in diffusion layer shape and size. © 2006 Elsevier B.V. All rights reserved.

This article describes the direct detection of Bromate, but also of chlorate and iodate, using modified arrays of platinum ultramicroelectrodes. The detection limits for these ions are IO3- = 0.76 μM; BrO3- = 2.34 μM and ClO3- = 133.2 μM. The formation of a suitable tungsten oxide layer and the optimum analytical conditions are described. These oxide layers are formed electrochemically from hydrogen peroxide-tungstanate solutions in acid conditions. Although film stability may be an issue, particularly at pH > 3, these modified arrays of microelectrodes can be used for analytical purposes. After the analysis, the modifying oxide is easily removed and the Pt microelectrode array recovers its original properties. Finally, the detection limit is calculated using a propagation of errors approach which in the present context turned out more appropriate than IUPAC's 3σ. © 2006 Wiley-VCH Verlag GmbH and Co. KGaA.

The sections in this article are Introduction to Power Ultrasound Approaches to the Coupling of Ultrasound with Electrochemical Methods The Influence of Ultrasound on Mass Transport at the Electrode Ultrasound-Induced Surface Effects The Influence of Ultrasound on Chemical Processes Generation of Active Radical Species Rates of Heterogeneous Electron Transfer Sonovoltammetric Study of Homogeneous Chemical Reactions Extreme Conditions and Deviation from Hydrodynamic Behavior The Effects of High-Frequency Power Ultrasound

The sections in this article are Introduction Cell Design in Sonoelectrosynthesis Examples of Sonoelectrosynthetic Reactions Electrochemical Reductions in Ultrasonically Emulsified Media: Electroreduction of Maleates, Fumarates, and Acetylenes Electrodimerization of 2-Nitrobenzylchloride in the Presence of Ultrasound Ultrasonically Enhanced Birch Reductions Ultrasonically Induced Electrode Depassivation: Reduction of Methylene Green Ultrasonically Enhanced Kolbe Processes Inorganic Sonoelectrosynthesis: Production of Metallic Nanopowders Sonoelectrosynthesis: An Overview

The United States Department of Energy's Savannah River Site has approximately 5000 55-gallon drums of {sup 238}Pu contaminated waste in interim storage. These may not be shipped to WIPP in TRUPACT-II containers due to the high rate of hydrogen production resulting from the radiolysis of the organic content of the drums. In order to circumvent this problem, the {sup 238}Pu needs to be separated from the organics--either by mineralization of the latter or by decontamination by a chemical separation. We have conducted ''cold'' optimization trials and surrogate tests in which a combination of a mediated electrochemical oxidation process (SILVER II{trademark}) and ultrasonic mixing have been used to decontaminate the surrogate waste materials. The surrogate wastes were impregnated with copper oxalate for plutonium dioxide. Our process combines both mineralization of reactive components (such cellulose, rubber, and oil) and surface decontamination of less reactive materials such as polyethylene, polystyrene and polyvinylchloride. By using this combination of SILVER II and ultrasonic mixing, we have achieved 100% current efficiency for the destruction of the reactive components. We have demonstrated that: The degree of decontamination achieved would be adequate to meet both WIPP waste acceptance criteria and TRUPACT II packaging and shipping requirements; The systemmore » can maintain near absolute containment of the surrogate radionuclides; Only minimal pre-treatment (coarse shredding) and minimal waste sorting are required; The system requires minimal off gas control processes and monitoring instrumentation; The laboratory trials have developed information that can be used for scale-up purposes; The process does not produce dioxins and furans; Disposal routes for secondary process arisings have already been demonstrated in other programs. Based on the results from Phase 1, the recommendation is to proceed to Phase 2 and use the equipment at Savannah River Site to demonstrate the processing of genuine plutonium contaminated wastes.« less

Fuel cells convert chemical energy into electrical energy. Their high energy density together with the possibility to operate at room temperature using liquid fuels identified them as potentially suitable for portable applications more than a decade ago. Despite their promising capabilities, they have failed to oust lithium batteries from the consumer electronics market: batteries have successfully evolved into tiny packages that are very easy to use, rechargeable and that can meet the power demands of current portable appliances. In contrast, fuel cells have to be fed with a liquid fuel and require an ion-conducting membrane that prevents mixing of oxidant and reducing species, which has to be permanently hydrated to ensure optimal performance. The complexity associated to the use of this membrane was overcome some years ago with the development of the so-called microfluidic fuel cells, in which the separation of reactants is achieved by forcing them to flow in parallel in a microfluidic channel at low Reynolds numbers. Microfluidic fuel cells yield significant amounts of energy with a very simple architecture. In her presentation, Dr. Sabaté will talk about what are the challenges and opportunities for micro fuel cells to find a market niche where they can take advantage over other miniaturised power sources.

It is demonstrated for electrochemical processes in aqueous solution enhanced by ultrasound from a glass-horn transducer (24 kHz, 8 W cm-2) that the mass transport limited current is essentially independent of the diffusion coefficient. An explanation is proposed for this phenomenon, which allows, at low ultrasound power, considerable enhancements of the mass transport of 'slow diffusers' with small D, to be achieved via interfacial cavitation. An application of this effect in the anodic destruction of an aqueous Procion Blue dye solution at boron-doped diamond electrodes is discussed. © 2001 Elsevier Science B.V. All rights reserved.

Vacuum-annealed highly boron-doped diamond (BDD) thin-film electrodes are shown to allow reversible voltammetric responses for the reduction of nitrobenzene, 3,5-difluoronitrobenzene, and for the generation of solvated electrons in liquid ammonia at -60°C. In liquid ammonia (0.1 M KI) a considerably extended positive potential window at BDD electrodes compared to platinum is observed. At the negative end of the potential scale facile generation of solvated electrons occurs at both platinum and BDD electrodes. After exposure to solvated electrons in liquid ammonia, the surface of the diamond becomes hydrophilic and nitrogen functionalities were detected by X-ray photoelectron spectroscopy.

The use of high frequency ultrasound in electrochemical systems is of major interest for the optimisation of electrosynthetic and electroanalytical procedures, especially when the strong mechanical effects of 20 kHz ultrasound are detrimental. The characterisation of a 500 kHz ultrasound reactor for sonoelectrochemical experiments by voltammetric and potentiometric measurements revealed the presence of considerable thermal, as well as mass transport, effects depending on geometric parameters and the material used for the construction of the working electrode. Micromixing and cavitation processes govern the mass transport to and from the electrode surface and are shown by atomic force microscopy (AFM) to cause erosion on the electrode surface. Electrochemically active films of Prussian blue are shown to be gradually removed by cavitation erosion. Degassing the solution prior to sonication increases the efficiency of cavitation processes.

Biofuel cells typically yield lower power and are more difficult to fabricate than conventional fuel cells using inorganic catalysts. This work presents a glucose/O2 microfluidic biofuel cell (MBFC) featuring pyrolyzed photoresist film (PPF) electrodes made on silicon wafers using a rapid thermal process, and subsequently encapsulated by rapid prototyping techniques into a double-Y-shaped microchannel made entirely of plastic. A ferrocenium-based polyethyleneimine polymer linked to glucose oxidase (GOx/Fc-C6-LPEI) was used in the anode, while the cathode contained a mixture of laccase, anthracene-modified multi-walled carbon nanotubes, and tetrabutylammonium bromide-modified Nafion (MWCNTs/laccase/TBAB-Nafion). The cell performance was studied under different flow-rates, obtaining a maximum open circuit voltage of 0.54 ± 0.04 V and a maximum current density of 290 ± 28 μA cm(-2) at room temperature under a flow rate of 70 μL min(-1) representing a maximum power density of 64 ± 5 μW cm(-2). Although there is room for improvement, this is the best performance reported to date for a bioelectrode-based microfluidic enzymatic biofuel cell, and its materials and fabrication are amenable to mass production.

Germanium–based photodetectors are the standard technology used for radiometric measurement in the IR spectral range. Shallow PN+ junctions were obtained by using ion implantation in p–type germanium. N–type doping was achieved by phosphorus implantation at a dose of 1 × 1015 cm−2 doses and an energy of 150 keV followed by annealing at 600°C for 2 h. In order for the new detector to be used as a standard for radiometric measurement, a porous layer is introduced on the active surface. After metallisation by thermal evaporation of indium (In) on the front side and gold (Au) on the back side, the new porous germanium–based photodetector is essentially done. The electrical behaviour of this porous germanium photodiode is characterised by current–voltage measurements that are compared to the I–V characteristic of classical germanium photodiodes. The results of this study show a huge increase of the photocurrent, a significant increase of the shunt resistance and low series resistance. Effects of low shunt resistance are also discussed. AFM showed that the porous layer contributes to trap the incident optical radiation and to reduce the reflection coefficient fluctuations of the front face of the photodiode.