One-step microwave synthesis of palladium-carbon nanotubes hybrids with improved catalytic performance

7 páginas, 7 figuras, 3 tablas.-- El pdf del artículo es la versión pre-print.A fast and easy one-step linker-free approach for the synthesis of palladium nanoparticle/multiwall carbon nanotube (Pd-NP/MWCNT)hybrid materials is described using microwave irradiation for the effective decomposition of Pd2dba3 complex in the presence of MWCNTs. High loadings of Pd nanoparticles (up to 40 wt.%) having sizes between 3 and 5 nm are deposited on the surface of MWCNTs within a time of only 2 minutess. The Pd-NP/MWCNT materials serve as efficient catalysts in C-C coupling as well as in hydrogenation reactions, all characterized by high conversion rates using a small amount of catalysts, high turnover frequency values and good recyclbility.Financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN) and the European Regional Development Fund (ERDF) under projects CTQ2008-01784 and MAT2007-66927-C02-01, and the Gobierno de Aragón (DGAPI086- 08) is gratefully acknowledged. M.C. thanks MICINN for her Grant No. BES-2008-003503.Peer reviewe

Modélisation par Eléments Finis d'une Ligne à Retard à Ondes de Love

Les microcapteurs acoustiques à ondes de surface ont largement démontré leurs performances pour détecter des composés chimiques et biologiques en milieux gazeux et liquides. Plus précisément, les dispositifs à onde de Love font l’objet d’une attention particulière en raison de leurs bons résultats en milieux liquides notamment. La conception de ces dispositifs nécessite une phase de modélisation et de simulation indispensable à leur mise en œuvre opérationnelle. Cependant, à ce jour, en raison de la complexité de ces dispositifs, la plupart des modèles présentés simulent quelques caractéristiques de propagation de l’onde. La vitesse de phase est plus particulièrement calculée afin de permettre l’estimation de la sensibilité à l’effet de masse des capteurs. Nous proposons dans cette communication d’aller au-delà des modélisations classiques en présentant l’utilisation d’un logiciel à éléments finis pour un dispositif à ondes de Love. Nous présentons ainsi une modélisation globale permettant l’estimation d’un large champ de paramètres lors du fonctionnement du dispositif. Les premiers résultats seront présentés et analysés. Les perspectives et potentialités de l’utilisation de ce logiciel pour les capteurs à ondes de Love seront également abordées

Frequency dependence of viscous and viscoelastic dissipation in coated micro-cantilevers from noise measurement

We measure the mechanical thermal noise of soft silicon atomic force microscopy cantilevers. Using an interferometric setup, we have a resolution down to 1E-14 m/rtHz on a wide spectral range (3 Hz to 1E5 Hz). The low frequency behavior depends dramatically on the presence of a reflective coating: almost flat spectrums for uncoated cantilevers versus 1/f like trend for coated ones. The addition of a viscoelastic term in models of the mechanical system can account for this observation. Use of Kramers-Kronig relations validate this approach with a complete determination of the response of the cantilever: a power law with a small coefficient is found for the frequency dependence of viscoelasticity due to the coating, whereas the viscous damping due to the surrounding atmosphere is accurately described by the Sader model

Russian roulette with unlicensed fat-burner drug 2,4-dinitrophenol (DNP) : evidence from a multidisciplinary study of the internet, bodybuilding supplements and DNP users

BACKGROUND: 2,4-Dinitrophenol (DNP) poses serious health-risks to humans. The aims of this three-stage multidisciplinary project were, for the first time, to assess the risks to the general public from fraudulent sale of or adulteration/contamination with DNP; and to investigate motives, reasons and risk-management among DNP-user bodybuilders and avid exercisers. METHODS: Using multiple search-engines and guidance for Internet research, online retailers and bodybuilding forums/blogs were systematically explored for availability of DNP, advice offered on DNP use and user profiles. Ninety-eight pre-workout and weight-loss supplements were purchased and analysed for DNP using liquid-chromatography-mass-spectrometry. Psychosocial variables were captured in an international sample of 35 DNP users (26.06 ± 6.10 years, 94.3 % male) with an anonymous, semi-qualitative self-reported survey. RESULTS: Although an industrial chemical, evidence from the Internet showed that DNP is sold 'as is', in capsules or tablets to suit human consumption, and is used 'uncut'. Analytical results confirmed that DNP is not on the supplement market disguised under fictitious supplement names, but infrequently was present as contaminant in some supplements (14/98) at low concentration (<100mcg/kg). Users make conscious and 'informed' decisions about DNP; are well-prepared for the side-effects and show nonchalant attitude toward self-experimentation with DNP. Steps are often taken to ensure that DNP is genuine. Personal experience with performance- and appearance enhancing substances appears to be a gateway to DNP. Advice on DNP and experiences are shared online. The significant discrepancy between the normative perception and the actual visibility suggests that DNP use is-contrary to the Internet accounts-a highly concealed and lonesome activity in real life. Positive experiences with the expected weight-loss prevail over the negative experiences from side effects (all but two users considered using DNP again) and help with using DNP safely is considered preferable over scare-tactics. CONCLUSION: Legislation banning DNP sale for human consumption protects the general public but DNP is sold 'as is' and used 'uncut' by determined users who are not dissuaded from experimenting with DNP based on health threats. Further research with stakeholders' active participation is imperative for targeted, proactive public health policies and harm-reduction measures for DNP, and other illicit supplements

Association of a Love wave sensor to thin film molecularly imprinted polymers for nucleosides analogs detection

International audienceThe overall objective of this work is to develop and validate a quantitative, non-invasive therapeutic tool to detect selected urinary modified nucleosides as biomarkers of colorectal cancer chemotherapy and to monitor in fine the efficiency of the chemotherapy. Our methodology takes the advantage of high sensitivity of acoustic biosensor combined with high selectivity and robustness of thin molecularly imprinted polymer (MIP) film. In this paper we present a process based on a thin film of a MIP of adenosine 5'-monophosphate (AMP) coating on the sensor surface which is compatible with the acoustic wave propagation. Detection tests of AMP have been performed in aqueous media. The sensor response was recorded in terms of synchronous frequency and total insertion losses after both steps: extraction from, rebinding by the MIP layer. A frequency decrease of 6.875 Hz was recorded for 25μg/mL AMP concentration

Multiphase CT scanning and different intravenous contrast media concentrations in combined F-18-FDG PET/CT: Effect on quantitative and clinical assessment

PURPOSE: To evaluate the influence of multiphase CT scanning and different intravenous contrast media on contrast enhancement, attenuation correction and image quality in combined PET/CT. MATERIAL AND METHODS: 140 patients were prospectively enrolled for F-18-FDG-PET/CT including a low-dose unenhanced, arterial and venous contrast enhanced CT. The first (second) 70 patients, received contrast medium with 370 (300) mg iodine/ml. The iodine delivery rate (1.3mg/s) and total iodine load (44.4g) were identical for both groups. Contrast enhancement and maximum and mean standardized FDG uptake values (SUVmax and SUVmean) were determined for the un-enhanced, arterial and venous PET/CT at multiple anatomic sites and PET reconstructions were visually evaluated. RESULTS: Arterial contrast enhancement was significantly higher for the 300mg/ml contrast medium compared to 370mgI/ml at all anatomic sites. Venous enhancement was not different between the two contrast media. SUVmean and SUVmax were significantly higher for the contrast enhanced compared to the non-enhanced PET/CT at all anatomic sites (all P0.05). Visual assessment revealed no relevant differences between the different PET reconstructions. CONCLUSIONS: There is no relevant qualitative influence on the PET scan from the use of different intravenous contrast media in its various phases in combined multiphase PET/CT. For quantitative analysis of tracer uptake it is required to use an identical PET/CT protocol

Invited talk: CArbon and Microwave-based Ultrasensitive gas Sensors (CAMUS)

International audienceIn the areas of safety, health and environment, the detection of chemical compounds, VOCs and toxic gases, is a major societal concern. The explosion in recent years in the telecommunications market has led to the emergence of concept of sensor network. This new concept of communicating objects meets the growing need to deploy sensors for monitoring and analysing distributed applications. These systems rely on an architecture built around wireless autonomous sensors composed of nanostructured materials that are very effective in terms of sorption of chemical compounds, and of new low cost communication electronic devices printed on flexible substrates. Thus, the research effort requires a multidisciplinary approach around the engineering of new materials, transduction mechanisms and electromagnetic waves (microwaves).The CAMUS (CArbon & Microwaves-based Ultrasensitive Gas Sensors) project is proposed by a consortium of four labs with complementary skills: IMS Bordeaux UMR 5218, XLIM Limoges UMR 7252, IEMN Lille UMR 8510, CINTRA Singapore UMI 3288 CNRS-NTU-Thales.In this project, we propose the realization of a platform for microwave transduction associated with nanostructured materials, graphene and carbon nanotubes (CNTs), allowing the extraction of interference properties of conductivity and dielectric permittivity caused by the interaction of these materials with the target species. Thus, our approach aims to demonstrate the feasibility of a passive microwave resonator on a flexible substrate dedicated to the detection of chemical compounds in the vapor state