A humid electronic nose based on pulse voltammetry: A proof-of-concept design

[EN] We report herein the design, manufacture and use of a "humid electronic nose" prototype based on voltammetric techniques. It consists of an array of four working electrodes (i.e., Au, Pt, Ir and Rh) housed inside a homemade stainless steel cylinder, in contact with a fabric mesh made of nylon damped with a NaCl aqueous solution, used as the supporting humid membrane. The "humid electronic nose" was tested for the discrimination of different samples displaying different volatile compounds. The samples chosen involve aqueous solutions of different simple volatile products (i.e., ammonia, acetone, acetic acid and 6-amino-1-hexanol) and different food samples (i.e., onion, coffee and Roquefort cheese). Under working conditions, the volatile compounds from the corresponding sample were generated in the measurement chamber and were partially dissolved in the damped nylon fabric, which was in contact with the set of electrodes. It was envisioned that provided different samples offer different vapours, the application of a suitable set of pulses to the electrodes will differentiate the samples. This proof-of-concept study employed a Large Amplitude Pulse Voltammetry (LAPV) waveform. The increment for the potential steps was of 200 mV and potentials ranged from +1 to -1 V with each pulse applied for 50 ms. PCA studies from the response obtained by the "humid electronic nose" discriminated the different samples studied. The neural network Self Organized Map (SOM) was also used to analyze the electrochemical data obtained from the "humid electronic nose". © 2013 Elsevier B.VThe financial support from the Spanish Government (project MAT2012-38429-C04) and the Generalitat Valenciana (Valencian Regional Government; projects PROMETEO/2009/016 and GV/2012/094); is gratefully acknowledged.Bataller Prats, R.; Campos Sánchez, I.; Alcañiz Fillol, M.; Gil Sánchez, L.; García Breijo, E.; Martínez Mañez, R.; Pascual Vidal, L.... (2013). A humid electronic nose based on pulse voltammetry: A proof-of-concept design. Sensors and Actuators B: Chemical. 186:666-673. https://doi.org/10.1016/j.snb.2013.06.033S66667318

The discovery, distribution and diversity of DNA viruses associated with Drosophila melanogaster in Europe

International audienceDrosophila melanogaster is an important model for antiviral immunity in arthropods, but very few DNA viruses have been described from the family Drosophilidae. This deficiency limits our opportunity to use natural host-pathogen combinations in experimental studies, and may bias our understanding of the Drosophila virome. Here we report fourteen DNA viruses detected in a metagenomic analysis of approximately 6500 pool-sequenced Drosophila, sampled from 47 European locations between 2014 and 2016. These include three new nudiviruses, a new and divergent entomopoxvirus, a virus related to Leptopilina boulardi filamentous virus, and a virus related to Musca domestica salivary gland hypertrophy virus. We also find an endogenous genomic copy of galbut virus, a dsRNA partitivirus, segregating at very low frequency. Remarkably, we find that Drosophila Vesanto virus, a small DNA virus previously described as a bidnavirus, may be composed of up to 12 segments and thus represent a new lineage of segmented DNA viruses. Two of the DNA viruses, Drosophila Kallithea nudivirus and Drosophila Vesanto virus are relatively common, found in 2% or more of wild flies. The others are rare, with many likely to be represented by a single infected fly. We find that virus prevalence in Europe reflects the prevalence seen in publicly-available datasets, with Drosophila Kallithea nudivirus and Drosophila Vesanto virus the only ones commonly detectable in public data from wild-caught flies and large population cages, and the other viruses being rare or absent. These analyses suggest that DNA viruses are at lower prevalence than RNA viruses in D. melanogaster, and may be less likely to persist in laboratory cultures. Our findings go some way to redressing an earlier bias toward RNA virus studies in Drosophila, and lay the foundation needed to harness the power of Drosophila as a model system for the study of DNA viruses

Staff attitudes and the associations with treatment organisation, clinical practices and outcomes in opioid maintenance treatment

<p>Abstract</p> <p>Background</p> <p>In opioid maintenance treatment (OMT) there are documented treatment differences both between countries and between OMT programmes. Some of these differences have been associated with staff attitudes. The aim of this study was to 1) assess if there were differences in staff attitudes within a national OMT programme, and 2) investigate the associations of staff attitudes with treatment organisation, clinical practices and outcomes.</p> <p>Methods</p> <p>This study was a cross-sectional multicentre study. Norwegian OMT staff (<it>n </it>= 140) were invited to participate in this study in 2007 using an instrument measuring attitudes towards OMT. The OMT programme comprised 14 regional centres. Data describing treatment organisation, clinical practices and patient outcomes in these centres were extracted from the annual OMT programme assessment 2007. Centres were divided into three groups based upon mean attitudinal scores and labelled; "rehabilitation-oriented", "harm reduction-oriented" and "intermediate" centres.</p> <p>Results</p> <p>All invited staff (<it>n </it>= 140) participated. Staff attitudes differed between the centres. "Rehabilitation-oriented" centres had smaller caseloads, more frequent urine drug screening and increased case management (interdisciplinary meetings). In addition these centres had less drug use and more social rehabilitation among their patients in terms of long-term living arrangements, unemployment, and social security benefits as main income. "Intermediate" centres had the lowest treatment termination rate.</p> <p>Conclusions</p> <p>This study identified marked variations in staff attitudes between the regional centres within a national OMT programme. These variations were associated with measurable differences in caseload, intensity of case management and patient outcomes.</p

Perturbation of the Dimer Interface of Triosephosphate Isomerase and its Effect on Trypanosoma cruzi

Most of the enzymes of parasites have their counterpart in the host. Throughout evolution, the three-dimensional architecture of enzymes and their catalytic sites are highly conserved. Thus, identifying molecules that act exclusively on the active sites of the enzymes from parasites is a difficult task. However, it is documented that the majority of enzymes consist of various subunits, and that conservation in the interface of the subunits is lower than in the catalytic site. Indeed, we found that there are significant differences in the interface between the two subunits of triosephosphate isomerase from Homo sapiens and Trypanosoma cruzi (TcTIM), which causes Chagas disease in the American continent. In the search for agents that specifically inhibit TcTIM, we found that 2,2′-dithioaniline (DTDA) is far more effective in inactivating TcTIM than the human enzyme, and that its detrimental effect is due to perturbation of the dimer interface. Remarkably, DTDA prevented the growth of Escherichia coli cells that had TcTIM instead of their own TIM and killed T. cruzi epimastigotes in culture. Thus, this study highlights a new approach base of targeting molecular interfaces of dimers

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Photoelectrochemistry

The purpose of this work was to assess the potential of the Ru(II)(bipy)3 complexes as photogalvanic systems, using the criteria obtained from the theory for an ideal photogalvanic solar cell developed by Albery and Archer. To this end two techniques were developed to measure the rate of the thermal back reaction between the high energy photoproducts Ru(III) and Fe(II) The thermal back reaction is a serious loss process in such a cell. The first technique, the Optical Rotating Disc Electrode, was improved by the design and construction of new apparatus. It allowed measurement of most of the important parameters of a photogalvanic cell and confirmed much of the theory for such a cell. The second technique, Flash Electrolysis, first used by Perone, was developed for use with a transparent disc electrode. Further investigations of the thermal back reaction were made using the Stopped Flow technique. The results of these experiments on Ru(IIl)(bipy)3 and its derivatives show that the reaction obeys the Marcus theory of electron transfer. However the activation parameters are dominated by "compensation effects" which, at the elevated temperatures of a practical photogalvanic cell (> 60°C) , reduce the differences between different derivatives. The very similar rates of reaction so produced are much too high for the development of an efficient photogalvanic cell. Ru(II) (bipy)3 systems thus provide a useful model for other possible photogalvanic systems buc cannot be of any practical use themselves.</p

The development of electroanalytical techniques

This thesis describes the development of an electroanalytical technique for the estimation of compounds of biochemical interest. The technique involves titration with hypobromite using double electrode systems - the rotating ring disc electrode (RRDE) and the flow-through tubular double electrode (TDE). Hypobromite is continuously electregenerated at the upstream disc (generator) electrode and is transported by convection and diffusion to the downstream ring (detector) electrode where it is detected amperometrically. The presence of a reactive substrate in solution decreases the amount of titrant which reaches the ring, and from measurements of the generating and detecting currents the bulk concentration of substrate may be estimated. At pH 9.2 the amine group of amino acids reacts with two hypobromite molecules and some side chains (e.g. cystinyl, tyrosinyl, tryptophanyl) will also react. The reactivity of these side chains permits the titration of proteins. The titration response may be described theoretically which enables the calculation of the number of hypobromite molecules which react with one protein molecule ( ~500 for haemoglobin). With this chemical amplification the detection limit of the technique is ~10-8 g ml-1 for proteins and ~10-8 M for amino acids. An electronic circuit has been developed which enables the detector electrode to control the rate at which titrant is generated. This autotitrator produces a generator current which is proportional to substrate concentration, and with the TDE should enable the continuous estimation of proteins as they are eluted from a chromatographic column. Proteins have been titrated at pH 9.2 and pH 5; the ratio of a protein's titration responses reflects its amino acid composition and, when combined with the extinction coefficient, enables the identification of proteins. Patent applications for this method of identification and for the autotitration technique have been submitted.</p

Photoelectrochemistry with the optical rotating disc electrode - Part 2. Steady-state and transient studies on colloidal CdS

Results are presented for the dark and photoelectrochemistry of colloidal CdS particles studied with the optical rotating disc electrode (ORDE). The behaviour of the particles in the dark is governed by reversible electron transfer from a range of surface states superimposed over reversible electron transfer direct from the particle conduction band or shallow electron traps just below the conduction band edge. The oxidative current due to the latter effect exhibits a range of onset potentials arising from the polydisperse, Q-state nature of the particles under interrogation. The steady-state photoelectrochemistry varies from that in the dark in that (i) the surface states play a different role in determining the shape of the current voltage curve as they have been mostly oxidised by photogenerated valence band holes; and (ii) the photocurrent onset shifts to more anodic potentials as a result of a surface state-driven photocurrent attenuation and positive charge accumulation at the particle surface, both derived from hole-driven surface state oxidation. Light-on transient photocurrent measurements with the ORDE allow calculation of a pseudo-first-order rate coefficient for photogenerated electron loss, k(0), of similar to 0.07 s(-1). This suggests that the loss process being interrogated is not photogenerated electron-valence band hole recombination, but the loss of electrons left on the particle after some valence band hole filling reaction has occurred. Transient experiments also allow calculation of phi, the quantum efficiency for the photogeneration of electrons detectable by the ORDE. phi is found to be similar to 0.006, indicating that the dominant processes within the particle are direct and indirect photogenerated electron-valence band hole recombination