Manufacture, observation, and test of membranes with locatable single pores

A method for generating single pores down to 0.1 μm diameter in the center of a large circular foil is described, based on nuclear tracks. The foil is framed by a tension ring which enables one to handle the foils in a well‐defined precise way. The single pore has a lateral displacement of ±0.1 mm with respect to the tension ring center. The foils used are polycarbonate of the type Makrofol and have thicknesses between 2 and 10 μm. For calibration of the single pore diameters, multiple nuclear tracks between 0.1 and 3.5 μm diameter are etched and observed by microscopy. The microscopic observations are compared with gas‐flow measurements, using two alternative methods: multiple holes are tested under viscous flow conditions of N2 gas at normal temperature and pressure; single holes are tested under collisionless flow conditions of 4He gas at liquid‐nitrogen temperature, using a capacitance method.Peer reviewe

Supercooled confined water and the Mode Coupling crossover temperature

We present a Molecular Dynamics study of the single particle dynamics of supercooled water confined in a silica pore. Two dynamical regimes are found: close to the hydrophilic substrate molecules are below the Mode Coupling crossover temperature, $T_C$, already at ambient temperature. The water closer to the center of the pore (free water) approaches upon supercooling $T_C$ as predicted by Mode Coupling Theories. For free water the crossover temperature and crossover exponent $\gamma$ are extracted from power-law fits to both the diffusion coefficient and the relaxation time of the late $\alpha$ region.Comment: To be published, Phys. Rev. Lett., 4 pages, 3 figures, revTeX, minor changes in the figures, references added, changes in the tex

Aspectos de Implementação de um Servidor MMS

O objetivo deste artigo é apresentar um modelo de implementação de um servidor MMS que atue no ambiente de manufatura integrada. Esse modelo inclui um subconjunto de serviços que atendem, no mínimo, aos requisitos de comuni­cação de um dispositivo controlador lógico programável (CLP). Será apresentada inicialmente una visão geral dos serviços MMS, bem como do controlador lógico programável, seguida da definição dos serviços MMS a serem implementados com base nas funções de um CLP. Finalmente, será apresentado um modelo de implementação, incluindo a descrição da estru­tura de processos e das estruturas de dados. ABSTRACT This paper presents a MMS server implementation model that actuates in an integrated manufacturing environ­ment. This model includes a subset of services that attends, at least, the communications requirements of a programmable logic controller device (PLC). Initially, it presents a survey of MMS services and PLCs, followed by the definition of the MMS services that will be implemented based on PLC's functions. Finally, it presents the implementation model, including the process and data structures description

X-ray Absorption Near-Edge Structure (XANES) at the O K-Edge of Bulk Co₃O₄: Experimental and Theoretical Studies

We combine theoretical and experimental X-ray absorption near-edge spectroscopy (XANES) to probe the local environment around cationic sites of bulk spinel cobalt tetraoxide (Co3O4). Specifically, we analyse the oxygen K-edge spectrum. We find an excellent agreement between our calculated spectra based on the density functional theory and the projector augmented wave method, previous calculations as well as with the experiment. The oxygen K-edge spectrum shows a strong pre-edge peak which can be ascribed to dipole transitions from O 1s to O 2p states hybridized with the unoccu- pied 3d states of cobalt atoms. Also, since Co3O4 contains two types of Co atoms, i.e., Co3+ and Co2+, we find that contribution of Co2+ ions to the pre-edge peak is solely due to single spin-polarized t2g orbitals (dxz, dyz, and dxy) while that of Co3+ ions is due to spin-up and spin-down polarized eg orbitals (dx2−y2 and dz2 ). Furthermore, we deduce the magnetic moments on the Co3+ and Co2+ to be zero and 3.00 μB respectively. This is consistent with an earlier experimental study which found that the magnetic structure of Co3O4 consists of antiferromagnetically ordered Co2+ spins, each of which is surrounded by four nearest neighbours of oppositely directed spins

Prevalência e fatores de risco associados à Leptospira spp. em rebanhos bovinos da região centro-sul do estado do Paraná.

O objetivo deste trabalho foi determinar a prevalência de anticorpos anti-Leptospira spp. e os fatores de risco para infecção de Leptospira spp. na criação de rebanhos bovinos no centro-sul da região do Estado do Paraná

Exploring the performance of the spectrometer prisma in heavy zirconium and xenon mass regions

We present results from two recent runs which illustrate the performance of the PRISMA spectrometer in the proximity of the upper limit of its operational interval, namely 96Zr + 124Sn at Elab = 500 MeV and 136Xe + 208Pb at Elab = 930 MeV. In the latter run, the γ array CLARA also allowed us to identify previously unknown γ transitions in the nuclides 136Cs and 134I

Morphology of supported polymer electrolyte ultra-thin films: a numerical study

Morphology of polymer electrolytes membranes (PEM), e.g., Nafion, inside PEM fuel cell catalyst layers has significant impact on the electrochemical activity and transport phenomena that determine cell performance. In those regions, Nafion can be found as an ultra-thin film, coating the catalyst and the catalyst support surfaces. The impact of the hydrophilic/hydrophobic character of these surfaces on the structural formation of the films has not been sufficiently explored yet. Here, we report about Molecular Dynamics simulation investigation of the substrate effects on the ionomer ultra-thin film morphology at different hydration levels. We use a mean-field-like model we introduced in previous publications for the interaction of the hydrated Nafion ionomer with a substrate, characterized by a tunable degree of hydrophilicity. We show that the affinity of the substrate with water plays a crucial role in the molecular rearrangement of the ionomer film, resulting in completely different morphologies. Detailed structural description in different regions of the film shows evidences of strongly heterogeneous behavior. A qualitative discussion of the implications of our observations on the PEMFC catalyst layer performance is finally proposed