Threading Through Macrocycles Enhances the Performance of Carbon Nanotubes as Polymer Fillers

In this work we study the reinforcement of polymers by mechanically interlocked derivatives of single-walled carbon nanotubes (SWNTs). We compare the mechanical properties of fibers made of polymers and of composites with pristine single-walled carbon nanotubes (SWNTs), mechanically interlocked derivatives of SWNTs (MINTs) and the corresponding supramolecular models. Improvements of both Young's modulus and tensile strength of up to 200 % were observed for the polystyrene-MINTs samples with an optimized loading of just 0.01 wt.%, while the supramolecular models with identical chemical composition and loading showed negligible or even detrimental influence. This behavior is found for three different types of SWNTs and two types of macrocycles. Molecular dynamics simulations show that the polymer adopts an elongated conformation parallel to the SWNT when interacting with MINT fillers, irrespective of the macrocycle chemical nature, whereas a more globular structure is taken upon facing with either pristine SWNTs or supramolecular models. The MINT composite architecture thus leads to a more efficient exploitation of the axial properties of the SWNTs and of the polymer chain at the interface, in agreement with experimental results. Our findings demonstrate that the mechanical bond imparts distinctive advantageous properties to SWNT derivatives as polymer fillers.Comment: 39 pages, 19 figure

Síntesis y caracterización de óxidos mixtos precursores de bronces tetragonales de W de potencial actividad en la oxidación de difenilsulfuro

Fases de heteropolioxometalatos (HPOM), a base de heteropolitungstatos complejos derivados de tipo Keggin de la serie [M4(H2O)2(PW9O34)2]10- (PWM) con M(II) = Cu y su precursor Na8H(PW9O34) (PW9), se han modificado químicamente mediante reacción hidrotermal, con iones Nb y V en el gel de síntesis, dando lugar a la formación de materiales del tipo (KNaCu)xP0.11WV0,2NbOx y (Na)xPWV0,2NbOx. Tanto los materiales de síntesis como los tratados a 500ºC (en atmosfera de N2) son pseudocristalinos (que tras tratamiento a 800º C, conduce a una estructura típica de bronce tetragonal). Los materiales tratados térmicamente a 500ºC se han caracterizado y estudiado como catalizadores en la oxidación parcial de difenilsulfuro. Los resultados catalíticos se han comparado con los obtenidos con los HPOM de partida, observándose que los bronces metálicos presentan una mayor actividad catalítica (con una drástica disminución del tiempo de reacción) y un marcado aumento de la selectividad a difenil-sulfona.Phases based on complex heteropolytungstates (HPOM), derived from series Keggin type [M4 (H2O)2 (PW9O34)2] 10-(PWM) with M(II) = Cu and its precursor Na8H (PW9O34) (PW9), have been chemically modified by hydrothermal reaction, with Nb and V ions in the synthesis gel, giving place materials as (KNaCu)xP0.11WV0,2NbOx and (Na)xPWV0,2NbOx. The as-synthesized and the heat-treated at 500ºC (in N2) are pseudocrystalline (although they are transformed to tetragonal bronze after heattreatment at 800ºC). The samples heat-treated at 500ºC have been characterized and tested in the partial oxidation of diphenylsulfide. The catalytic results have been compared to those achieved over pure HPOM. It has been observed that these metal oxides bronzes show a higher both catalytic activity (with a drastic reduction of the reaction time) and selectivity to diphenyl-sulfone

Thorpe method applied to planetary boundary layer data

Turbulence affects the dynamics of atmospheric processes by enhancing the transport of mass, heat, humidity and pollutants. The global objective of our work is to analyze some direct turbulent descriptors which reflect the mixing processes in the atmospheric boundary layer (ABL). In this paper we present results related to the Thorpe displacements dT , the maximum Thorpe displacement (dT )max and the Thorpe scale LT , the Ozmidov scale and their time evolution in the ABL during a day cycle. A tethered balloon was used to obtain vertical profiles of the atmospheric physical magnitudes up to 1000m. We discuss the vertical and horizontal variability and how different descriptors are related to atmospheric mixing

Continuous Plasma density measurement in TJ-II infrared interferometer-Advanced signal processing based on FPGAs

This work presents the behavioral simulation in an FPGA of a novel processing system for measuring line average electronic density in the TJ-II stellarator diagnostic, Infra-Red Two-Color Interferometer. Line average electronic density is proportional to phase difference between probing and reference signals of the interferometer, as the Appleton–Hartree cold plasma model states. The novelty of the approach is the development of a real time measuring system where research work has been carried out in two ways: a new interpolation algorithm and the implementation of a new specific processor on an FPGA. The main goal of this new system is to measure line plasma electronic density for several channels in real time, also it will be useful to eliminate intermediate mixing frequency stages (the output signals coming from the interferometer are going to be directly sampled) and finally to generate real time density signals for control purposes in TJ-II and in other diagnostics. This device is intended to be the new data acquisition-processing system for the future six channel infrared interferometer that requires at least 14 input signals. The knowledge acquired could be useful in the design of W7-X and ITER IR-interferometer data acquisition and processing systems

Influencia de la diagénesis en la mineralogía de los materiales terciarios del sector central de la depresión del Ebro (Zaragoza)

Four profiles built of sandstones, lutites and marls, dated Upper Oligocene-Lower Miocene, and located at the southern central sector of the Ebro basin have been studied, in order to know the postdepositional changes undergone by the original deposits, and the possible use of the inherited clay minerals as paleogeographic and paleoclimatic indicators for this basin. The mineralogical study concludes that illite is the main clay mineral along randon interstratified I-Sm clay minerals. The SEM study confirms that the main process in the deposil of these materials was the inheritance. The postdepositional processes are limited to early diagenesis represented by the development of interstratified I-Sm minerals in degradative processes and by carbonatic cementation of sandstones, in which the effect oí several stages of dissolution and reprecipitation oí carbonates and crystallization oí sulfates and chlorides can be observed.Se ha seleccionado el Sector Central de la Depresión del Ebro para tratar de conocer la incidencia que la diagénesis tiene sobre la asociación mineralógica primaria, considerada fundamentalmente compuesta por minerales heredados. En este contexto, se han estudiado cuatro perfiles, desarrollados en abanicos aluviales, en los que se han analizado separadamente los niveles de areniscas y de margas lutíticas. El estudio por SEM y EDAX confirma la composición mineralógica ya conocida, así como la composición bimodal de las ilitas (moscovita y fengitas). Por otra parte, se observa que las esmectitas presentes son, más bien, interestratificados al azar ilita (fengita)-esmectita (beidellita-nontronita). Este estudio confirma que la herencia es el mecanismo de depósito principal y que los procesos posteriores se limitan a una etapa de diagénesis precoz, representada por la presencia de interestratificados por degradación de ilitas y por la cementación carbonatada de las areniscas, junto con la precipitación de sulfatos y, ocasionalmente, algún cloruro

Alpha-tocopherol affects gene expression patterns of rabbit cumulus complexes and reduces apoptosis rate during in vitro maturation

Oxidative stress compromises oocyte developmental competence during in vitro maturation (IVM). Antioxidants such as vitamin E may avoid this imbalance. The aim of this study was to investigate the effect of a-Tocopherol (α-TocOH) on the relative mRNA abundance of genes involved in cumulus expansion (GJA1, PTGS2), cell cycle and viability (AKT1), cell cycle regulation and apoptosis (Tp53, CASP3) and antioxidant response (SOD2, GPX1, CAT) in rabbit cumulus oocyte complexes (COCs) in vitro matured. The apoptosis index in cumulus cells (CCs) and the hydrogen peroxide (H2O2) released by the COCs in maturation media were also assessed. For these purposes, COCs from follicles ≥1mm were recovered, selected and in vitro-matured for 16h (38ºC, 5% CO2) in a medium containing TCM-199 (Sigma, Madrid, Spain) with 0.3% bovine serum albumin (Sigma, Madrid, Spain) and 10 ng/mL Epidermal Growth Factor (EGF) (Sigma, Madrid, Spain) supplemented with 0, 100, 200 or 400 μM α- TocOH (Sigma, Madrid, Spain), named as 0E, 100E, 200E and 400E groups, respectivel

Shape-invariant quantum Hamiltonian with position-dependent effective mass through second order supersymmetry

Second order supersymmetric approach is taken to the system describing motion of a quantum particle in a potential endowed with position-dependent effective mass. It is shown that the intertwining relations between second order partner Hamiltonians may be exploited to obtain a simple shape-invariant condition. Indeed a novel relation between potential and mass functions is derived, which leads to a class of exactly solvable model. As an illustration of our procedure, two examples are given for which one obtains whole spectra algebraically. Both shape-invariant potentials exhibit harmonic-oscillator-like or singular-oscillator-like spectra depending on the values of the shape-invariant parameter.Comment: 16 pages, 5 figs; Present e-mail of AG: [email protected]

Strong magnetic response of submicron Silicon particles in the infrared

High-permittivity dielectric particles with resonant magnetic properties are being explored as constitutive elements of new metamaterials and devices in the microwave regime. Magnetic properties of low-loss dielectric nanoparticles in the visible or infrared are not expected due to intrinsic low refractive index of optical materials in these regimes. Here we analyze the dipolar electric and magnetic response of loss-less dielectric spheres made of moderate permittivity materials. For low material refractive index there are no sharp resonances due to strong overlapping between different multipole contributions. However, we find that Silicon particles with refractive index 3.5 and radius approx. 200nm present a dipolar and strong magnetic resonant response in telecom and near-infrared frequencies, (i.e. at wavelengths approx. 1.2-2 micrometer). Moreover, the light scattered by these Si particles can be perfectly described by dipolar electric and magnetic fields, quadrupolar and higher order contributions being negligible.Comment: 10 pages, 5 figure