Magnetization models for particle-based simulations of magnetorheological fluids

In this study, three-dimensional particle-based simulations are used to model magnetorheological fluids. The numerical model of the MRF is implemented in the framework of the Discrete Element Method (DEM) and takes into account the coupling of the magnetic dipoles, the hydrodynamic drag forces and steric forces between particles. To accurately treat the magnetic interaction between particles, the magnetic field at the particles’ position is computed and an appropriate magnetization model is implemented. DEM simulations with different volume fractions of the MRF are carried out and the resulting magnetization curves are put in comparison with experimental data

Magnetization models for particle-based simulations of magnetorheological fluids

In this study, three-dimensional particle-based simulations are used to model magnetorheological fluids. The numerical model of the MRF is implemented in the framework of the Discrete Element Method (DEM) and takes into account the coupling of the magnetic dipoles, the hydrodynamic drag forces and steric forces between particles. To accurately treat the magnetic interaction between particles, the magnetic field at the particles’ position is computed and an appropriate magnetization model is implemented. DEM simulations with different volume fractions of the MRF are carried out and the resulting magnetization curves are put in comparison with experimental data

Generation of OH radicals at palladium oxide nanoparticle modified electrodes, and scavenging by fluorescent probes and antioxidants

The reduction of palladium oxide nanoparticles in the presence of hydrogen peroxide or dissolved oxygen gives rise to a catalytic reduction current dependent on the hydrogen peroxide concentration or the oxygen concentration. Using terephthalic acid as an OH radical scavenger yielding the fluorescent 2-hydroxyterephthalic acid, we demonstrate that the catalytic current stems from the freshly exposed palladium metal re-oxidation by OH radicals. A kinetic model is presented to account for these catalytic reactions. We also demonstrate that the measurement of the catalytic reduction current in the presence of antioxidant molecules can be used to measure the OH scavenging properties of antioxidants

Antioxidant Redox Sensors Based on DNA Modified Carbon Screen-Printed Electrodes

Antioxidant redox sensors based on DNA modified carbon screen-printed electrodes were developed. The carbon ink was doped with TiO2 nanoparticles, onto which double- strand DNA was adsorbed. A redox mediator, namely, tris- 2,2′-bipyridine ruthenium(II) [Ru(bpy)32+] was electro- oxidized on the electrode surface to subsequently oxidize both the adsorbed ds-DNA and the antioxidants in solu- tion. The resulting oxidation damage of the adsorbed ds- DNA was then detected by square wave voltammetry in a second solution containing only Ru(bpy)3Cl2 at a low con- centration (μM). A kinetic model was developed to study the protecting role of antioxidants in aqueous solutions. The electrochemical sensor has been applied to evaluate the redox antioxidant capacity of different molecules

Hydrovoltaic cells. Part II: Thermogalvanic cells and numerical simulations of thermal diffusion potentials

When two electrolyte solutions of different temperature are placed in contact, a thermal diffusion potential (TDP) is established. The phenomenon is studied numerically using finite element simulations of the temperature distribution within a hydrodynamic cell. Experimentally, the hydrovoltaic flow cell is used to demonstrate how a temperature difference can induce redox reactions at electrodes placed in the two liquids in order to extract a current continuously in an external circuit resulting in a power-generating unit. When the concentration of the redox couple introduced in the solution is moderated, it is shown that the TDP is not negligible, even if the main driving force is due to the temperature effect on the standard potential of the couple present. The numerical model may also be applied in more general situations involving thermal effects in microsystems

Antioxidant Sensors Based on DNA-Modified Electrodes

TiO2/ITO modified electrodes were developed to quantitatively photooxidize adsorbed ds-DNA and to study the effect of antioxidants as ds-DNA protecting agents. TiO2 films are used for efficient ds-DNA immobilization, for ds- DNA oxidation through photogenerated hydroxyl radicals, and as electrodes for amperometric sensing. The films, prepared by a sol-gel process, are deposited on ITO glass electrodes. Damages occurring after ds-DNA oxidation by ROS are detected by adding MB as an intercalant probe and by monitoring the electrochemical reduction current of the intercalated redox probe. The MB electrochemical signal is found to be sensitive enough to monitor ds-DNA structure changes, and the electrochemical sensor has been applied to the evaluation of the antioxidant properties of glutathione and gallic acid

Caracterización de las explotaciones lecheras de La Pampa

En la cuenca lechera de la provincia de la Pampa, al igual que en el resto de las cuencas argentinas, existe un proceso de concentración de la producción, con reducción en la cantidad de establecimientos y aumento de la producción de leche. El conocimiento de la variabilidad de la estructura productiva como indicador estratégico permitirá implementar acciones de investigación y desarrollo para la permanencia de las explotaciones en el sector lechero. El objetivo de este trabajo fue caracterizar la estructura productiva de los establecimientos lecheros de la provincia de La Pampa. Durante el año 2017, se encuestaron 45 explotaciones distribuidos en las tres cuencas, norte, centro y sur de la provincia de La Pampa. En promedio las explotaciones lecheras producen 3.509,82 Lts/día ± 1.040,61 (C.V. 198,89%) en una superficie ganadera de 215,20 ha ± 57,90 (C.V.180,47%) con un total de vacas de 201,78 ± 58,00 (C.V. 192,83%). La mortalidad en la cría fue de 5,42% ± 0,38 (C.V. 47,26) superior al 3% recomendado y la edad al primer parto de 26,6 meses ± 0,35 (C.V. 8,87) levemente superior al intervalo de 24 – 26 meses destacado como óptimo para no acrecentar los costos por tiempo ocioso. La producción de leche hallada concuerda con un sistema de producción pastoril, como el que predomina en La Pampa, con variables factibles de mejorar tales como las halladas en mortandad de la cría y edad al primer part

Amperometric tape ion sensors for cadmium(II) ion analysis

This paper describes a novel tape platform ion sensing methodology specific to the detection of cadmium(II) ions in aqueous solution based on assisted ion transfer reactions across a polarized water | organic gel micro-interface. The tape ion sensors were constructed to incorporate the microwater | polyvinylchloride-2-nitrophenylethyl ether (PVC–NPOE) gel interfaces referred to as ionodes. The sensors have overall thicknesses less than $300\mu m$, allowing their packaging in a disposable tape format. The detection methodology is based on the selective assisted transfer of the cadmium ion in aqueous phase by ETH 1062 present in the PVC–NPOE gel layer and was first investigated using cyclic voltammetry. Quantitative analysis of cadmium(II) ions in aqueous solution using the tape sensors was then conducted under stop-flow conditions. Detection limits as low as 20 ppb (178 nM) for Cd(II) ions in very small volumes as low as a single 20ul droplet without any sample preconcentration was achieved in an analysis time of approximately 20 s, which could be easily employed for the direct measurement of Cd(II) ion levels in various field applications. The tape ion sensor can also be used in a flow-cell geometry to preconcentrate Cd(II) ions from aqueous samples and further improve the detection limit

Mutants in the Mouse NuRD/Mi2 Component P66α Are Embryonic Lethal

The NuRD/Mi2 chromatin complex is involved in histone modifications and contains a large number of subunits, including the p66 protein. There are two mouse and human p66 paralogs, p66alpha and p66beta. The functions of these genes are not clear, in part because there are no mutants available, except in invertebrate model systems.We made loss of function mutants in the mouse p66alpha gene (mp66alpha, official name Gatad2a, MGI:2384585). We found that mp66alpha is essential for development, as mutant embryos die around day 10 of embryogenesis. The gene is not required for normal blastocyst development or for implantation. The phenotype of mutant embryos and the pattern of gene expression in mutants are consistent with a role of mp66alpha in gene silencing.mp66alpha is an essential gene, required for early mouse development. The lethal phenotype supports a role in execution of methylated DNA silencing