Distinct complexing trends of chitosan with toxic metals (PO1-24)

We have been able to prove that not only adsorption but also complexation of different metals (Pb, Cd, Mo, Cu, Zn and Cr) actually takes place in acetate buffer (pH=4) with Chitosans of different molecular weights and deacetylation degrees. Depending on the different electrochemical behaviour on mercury electrode of studied metals and the nature of the resulting complexes, diverse approaches have been used. Chitosan molecular weight and concentration had been seen to play a key role in the Chitosan binding activity with Zn, Pb and Cd, as reported elsewhere[1]. Length of Chitosan chains influences the degree of complexation with both Cr and Mo, while Cu binding capacity remains independent of the molecular weight of the assayed polymers. The larger the polymer chain length the higher the number of amino group available for the retention of both Cr and Mo within the tridimensional structure of the acting ligand. This is consistent with a predominant intra-chain linkage of both metal atoms. On the contrary, in the case of Cu, an inter-layer binding mechanism is proposed as the main retention factor by Chitosan

Fiber-optic lossy mode resonance sensors

In the last 4 years, experimental evidences about the potential use of optical sensors based on Lossy Mode Resonances (LMR) have been presented in the literature. These LMR sensors have some similarities with Surface Plasmon Resonance (SPR) sensors, the gold standard in label-free, real-time biomolecular interaction analysis. In these new LMR sensors, if the non-metallic nanocladding of an optical waveguide fulfills the conditions explained in this work, coupling of light to the cladding modes happens at certain resonance wavelengths, which enables the use of LMR devices as refractometers and opens the door to diverse applications such as in biology and proteomics research. These highly sensitive refractometers have already shown sensitivities higher than 20,000 nm/RIU or 5x10-7 RIU and, given the youth of this field, it is expected to achieve even better values

Optical sensors based on lossy-mode resonances

Lossy-mode resonance (LMR)–based optical sensing technology has emerged in the last two decades as a nanotechnological platform with very interesting and promising properties. LMR complements the metallic materials typically used in surface plasmon resonance (SPR)–based sensors, with metallic oxides and polymers. In addition, it enables one to tune the position of the resonance in the optical spectrum, to excite the resonance with both transverse electric (TE) and transverse magnetic (TM) polarized light, and to generate multiple resonances. The domains of application are numerous: as sensors for detection of refractive indices voltage, pH, humidity, chemical species, and antigens, as well as biosensors. This review will discuss the bases of this relatively new technology and will show the main contributions that have permitted the optimization of its performance to the point that the question arises as to whether LMR–based optical sensors could become the sensing platform of the near future

Nb Substitution Effects on Superconducting Properties of Ru

In order to gain further insight into the role of substitution of Ru by Nb on superconductivity, polycrystalline samples of Ru1−xNbxSr2Eu1.4Ce0.6Cu2O10−δ  (0.0 ≤ x ≤ 1.0) have been synthesized by solid-state reaction method. Substitution of Nb at the Ru site in the system takes place isostructurally in the tetragonal structure (space group I4/mmm) with full solubility (x = 1.0). Superconductivity exists for all compositions. Resistivity measurements in function of temperature from 0 to 300 K were done using the four-probe technique. It is found that the substitution of Ru5+ for Nb5+ depresses the superconductivity of samples from Tc = 29 K for x = 0.0 to Tc = 5 K for x = 1.0 (where Tc is the critical temperature, when resistivity becomes equal to zero). In the normal state, the dependence of resistivity with temperature, for compositions with x = 0.0 and 0.2, shows a metallic behavior, while for compositions between x = 0.4 and x = 1 it shows a semiconducting behavior. In that way, the density of charge carriers is reduced with niobium doping, leading to the semiconducting behavior. The resistive transition to the superconducting state of all samples is found to be affected by granularity. Samples undergo double superconducting transition

The contact angle of nanofluids as thermophysical property

Droplet volume and temperature affect contact angle significantly. Phase change heat transfer processes of nanofluids – suspensions containing nanometre-sized particles – can only be modelled properly by understanding these effects. The approach proposed here considers the limiting contact angle of a droplet asymptotically approaching zero-volume as a thermophysical property to characterise nanofluids positioned on a certain substrate under a certain atmosphere. Graphene oxide, alumina, and gold nanoparticles are suspended in deionised water. Within the framework of a round robin test carried out by nine independent European institutes the contact angle of these suspensions on a stainless steel solid substrate is measured with high accuracy. No dependence of nanofluids contact angle of sessile droplets on the measurement device is found. However, the measurements reveal clear differences of the contact angle of nanofluids compared to the pure base fluid. Physically founded correlations of the contact angle in dependency of droplet temperature and volume are obtained from the data. Extrapolating these functions to zero droplet volume delivers the searched limiting contact angle depending only on the temperature. It is for the first time, that this specific parameter, is understood as a characteristic material property of nanofluid droplets placed on a certain substrate under a certain atmosphere. Together with the surface tension it provides the foundation of proper modelling phase change heat transfer processes of nanofluids

Contrasting CO2 and water vapour fluxes in dry forest and pasture sites of central Argentina

The dry forests of South America are a key player of the global carbon cycle and the regional water cycle, but they are being intensively deforested. We used eddy covariance measurements to compare the temporal patterns of CO2 and water vapour fluxes and their relationships with environmental variables in dry forest and pastures sites of central Argentina. Ecosystem fluxes showed clear contrasts in magnitude, timing and response to environmental controls between ecosystems. The dry forest displayed higher daily gross primary productivity (GPP, 10.6 vs. 7.8 g CO2 m−2 d−1) and ecosystem respiration (Reco, 9.1 vs. 7.0 g CO2 m−2 d−1) and lower net ecosystem exchange (NEE, −1.5 vs. −0.7 g CO2 m−2 d−1) than the pasture. These differences were explained by a lower tolerance of the pasture to cool temperatures and drought. The lowest NEE rates were observed between 26°C and 34°C in the pasture, but below this range, NEE increased sharply, switching to a carbon source with temperatures <20°C. By contrast, the dry forest remained as a strong carbon sink down to 18°C. The pasture also showed a stronger drop of GPP with drought compared with the dry forest, becoming a carbon source with soil wetness <25% of soil available water. Rainfall was strongly coupled with GPP in both ecosystems, but the dry forest responded to longer rainfall integration periods. This study helps to understand how ecosystems can respond to climate change, improve global scale modelling and increase the productivity and resilience of rangelands.Fil: Nosetto, Marcelo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Luna Toledo, Emanuel Santiago. Instituto Nacional de Tecnología Agropecuaria; Argentina. Universidad Nacional de Chilecito; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Magliano, Patricio Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Figuerola, Patricia Irene. Universidad Nacional de Chilecito; ArgentinaFil: Blanco, Lisandro Javier. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Jobbagy Gampel, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentin

Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles can providemultiple benefits for biomedical applications in aqueous environments such asmagnetic separation or magnetic resonance imaging. To increase the colloidal stability and allow subsequent reactions, the introduction of hydrophilic functional groups onto the particles’ surface is essential. During this process, the original coating is exchanged by preferably covalently bonded ligands such as trialkoxysilanes. The duration of the silane exchange reaction, which commonly takes more than 24 h, is an important drawback for this approach. In this paper, we present a novel method, which introduces ultrasonication as an energy source to dramatically accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove the generic character, different functional groups were introduced on the surface including polyethylene glycol chains, carboxylic acid, amine, and thiol groups. Their colloidal stability in various aqueous buffer solutions as well as human plasma and serum was investigated to allow implementation in biomedical and sensing applications.status: publishe

Albiglutide and cardiovascular outcomes in patients with type 2 diabetes and cardiovascular disease (Harmony Outcomes): a double-blind, randomised placebo-controlled trial

Background: Glucagon-like peptide 1 receptor agonists differ in chemical structure, duration of action, and in their effects on clinical outcomes. The cardiovascular effects of once-weekly albiglutide in type 2 diabetes are unknown. We aimed to determine the safety and efficacy of albiglutide in preventing cardiovascular death, myocardial infarction, or stroke. Methods: We did a double-blind, randomised, placebo-controlled trial in 610 sites across 28 countries. We randomly assigned patients aged 40 years and older with type 2 diabetes and cardiovascular disease (at a 1:1 ratio) to groups that either received a subcutaneous injection of albiglutide (30–50 mg, based on glycaemic response and tolerability) or of a matched volume of placebo once a week, in addition to their standard care. Investigators used an interactive voice or web response system to obtain treatment assignment, and patients and all study investigators were masked to their treatment allocation. We hypothesised that albiglutide would be non-inferior to placebo for the primary outcome of the first occurrence of cardiovascular death, myocardial infarction, or stroke, which was assessed in the intention-to-treat population. If non-inferiority was confirmed by an upper limit of the 95% CI for a hazard ratio of less than 1·30, closed testing for superiority was prespecified. This study is registered with ClinicalTrials.gov, number NCT02465515. Findings: Patients were screened between July 1, 2015, and Nov 24, 2016. 10 793 patients were screened and 9463 participants were enrolled and randomly assigned to groups: 4731 patients were assigned to receive albiglutide and 4732 patients to receive placebo. On Nov 8, 2017, it was determined that 611 primary endpoints and a median follow-up of at least 1·5 years had accrued, and participants returned for a final visit and discontinuation from study treatment; the last patient visit was on March 12, 2018. These 9463 patients, the intention-to-treat population, were evaluated for a median duration of 1·6 years and were assessed for the primary outcome. The primary composite outcome occurred in 338 (7%) of 4731 patients at an incidence rate of 4·6 events per 100 person-years in the albiglutide group and in 428 (9%) of 4732 patients at an incidence rate of 5·9 events per 100 person-years in the placebo group (hazard ratio 0·78, 95% CI 0·68–0·90), which indicated that albiglutide was superior to placebo (p&lt;0·0001 for non-inferiority; p=0·0006 for superiority). The incidence of acute pancreatitis (ten patients in the albiglutide group and seven patients in the placebo group), pancreatic cancer (six patients in the albiglutide group and five patients in the placebo group), medullary thyroid carcinoma (zero patients in both groups), and other serious adverse events did not differ between the two groups. There were three (&lt;1%) deaths in the placebo group that were assessed by investigators, who were masked to study drug assignment, to be treatment-related and two (&lt;1%) deaths in the albiglutide group. Interpretation: In patients with type 2 diabetes and cardiovascular disease, albiglutide was superior to placebo with respect to major adverse cardiovascular events. Evidence-based glucagon-like peptide 1 receptor agonists should therefore be considered as part of a comprehensive strategy to reduce the risk of cardiovascular events in patients with type 2 diabetes. Funding: GlaxoSmithKline

Estudio de la interacción quitosano-metales pesados y su inmovilización en matrices cementicias

El desarrollo de nuevos composites cemento-aditivo para la obtención de morteros con propiedades mejoradas es una de las líneas con mayor perspectiva de investigación en la química de los conglomerantes para la construcción. El presente trabajo propone el estudio de un nuevo aditivo polimérico, el quitosano, y la investigación de su influencia en las propiedades de los morteros de cemento. El estudio se extiende a tres derivados de este biopolímero: dos no-iónicos (hidroxipropil e hidroxietilquitosano) y uno iónico (carboximetilquitosano). El trabajo se completa con la evaluación de la capacidad de estos sistemas para servir como agentes para la solidificación/estabilización de metales pesados. En primer lugar, se ha evaluado la capacidad del quitosano para retener metales pesados mediante estudios electroquímicos. Este polímero ha demostrado ser capaz de complejar de manera efectiva los metales seleccionados (Zn, Pb, Cd, Cu, Mo y Cr) a pH4, siendo determinantes el peso molecular y la dilución. El estudio del carboximetilquitosano ha manifestado su capacidad para unir Pb y Zn a pH cercano a la neutralidad, mientras que en valores alcalinos la complejación resulta casi nula. La influencia de la adición de los polímeros en los morteros de cemento se ha evaluado mediante ensayos normalizados en estado fresco y en endurecido. Adicionalmente, para la elucidación de los mecanismos se han realizado experimentos en pastas de cemento. La incorporación de quitosano modifica el comportamiento reológico del mortero, incrementando su viscosidad. La naturaleza del grupo introducido en la cadena de los derivados resulta determinante de cara a los efectos producidos. Los derivados no-iónicos apenas modifican las propiedades, mientras que el derivado iónico es, entre los aditivos estudiados, el que tiene mayor influencia en las propiedades de mortero. La presencia de carboximetilquitosano, incluso a baja dosificación, aumenta drásticamente la viscosidad de la muestra, reduce el periodo de trabajabilidad, retrasa la hidratación de las fases de cemento e incrementa la cantidad de poros del mortero endurecido. Se han utilizado estudios de potencial zeta y tamaño de partícula para esclarecer el mecanismo de acción, que en este caso apunta a la formación de aglomerados entre el polímero y las partículas de cemento. La presencia de metales pesados produce una notable influencia en las propiedades del estado fresco y en la resistencia a compresión de los morteros. La adición de los polímeros ha atenuado los efectos contraproducentes de los metales, especialmente en la trabajabilidad. Cabe destacar la gran mejora en la resistencia a compresión aportada por los quitosanos en aquellos morteros en los que se ha incorporado Zn a la mezcla. La efectividad de la retención de los metales en morteros aditivados se ha llevado a cabo mediante un test de lixiviación semi-dinámico. Los datos obtenidos reflejan que la lixiviación en presencia de los polímeros apenas se ve modificada, por lo que se puede afirmar que los quitosanos pueden utilizarse para compensar los efectos de la incorporación de Cr, Pb y Zn sin comprometer la eficacia de su retención. De hecho, la retención de Zn en presencia del quitosano de menor peso molecular se ve aumentada. Por último, se ha evaluado la lixiviación en probetas en las que el metal se incorpora tras la formación previa en disolución del complejo CMCH-metal. Este test ha revelado una disminución de la cantidad de Pb y Zn liberada por lo que puede afirmarse que la retención de estos elementos metálicos en morteros de cemento mejora al añadirlos complejados