1,721,101 research outputs found
Nanofabrication of a three‐level hierarchical surface, mimickingthe lotus leaf: from hydrophilic to hydrophobic behavior
No full textMemristive devices based on single ZnO nanowires-from material synthesis to neuromorphic functionalities
Full text linkMemristive and resistive switching devices are considered promising building blocks for the realization of artificial neural networks and neuromorphic systems. Besides conventional top-down memristive devices based on thin films, resistive switching devices based on nanowires (NWs) have attracted great attention, not only for the possibility of going beyond current scaling limitations of the top-down approach, but also as model systems for the localization and investigation of the physical mechanism of switching. This work reports on the fabrication of memristive devices based on ZnO NWs, from NW synthesis to single NW-based memristive cell fabrication and characterization. The bottom-up synthesis of ZnO NWs was performed by low-pressure chemical vapor deposition according to a self-seeding vapor-solid (VS) mechanism on a Pt substrate over large scale (∼cm2), without the requirement of previous seed deposition. The grown ZnO NWs are single crystalline with wurtzite crystal structure and are vertically aligned respect to the growth substrate. Single NWs were then contacted by means of asymmetric contacts, with an electrochemically active and an electrochemically inert electrode, to form NW-based electrochemical metallization memory cells that show reproducible resistive switching behaviour and neuromorphic functionalities including short-term synaptic plasticity and paired pulse facilitation. Besides representing building blocks for NW-based memristive and neuromorphic systems, these single crystalline devices can be exploited as model systems to study physicochemical processing underlaying memristive functionalities thanks to the high localization of switching events on the ZnO crystalline surface
Preparation and properties of PTFE/PAI nanocomposites
No full textPolytetrafluoroethylene/poly(amide-imide) PTFE/PAI nanocomposites were prepared by precipitation of TORLON® 4000TF (PAI) into a PTFE latex containing nanoparticles with average diameters of 41 nm and spherical shape. Several samples were obtained by varying the relative ratio between PAI and PTFE. SEM and PCS analysis indicates that the precipitation of PAI in the presence of PTFE leads mainly, if not exclusively, to bimodal mixtures of the two homoparticles. The PTFE crystallization process was quite complex and, depending on the sample composition, single or multiple crystallization exotherms were observed. This behavior, discussed within the fractionated crystallization frame, was revealing of the PTFE dispersion degree within the PAI matrix. When the PTFE amount is lower than 20%, a perfect PTFE nanoparticle dispersion is obtained. Partial aggregation is observed for PTFE amounts ranging from 20 to 40% whereas extensive aggregation is found for PTFE amount higher that 40%. The dynamic-mechanical behavior indicates that the interactions at nanoparticle/polymer interface are rather weak. A greater increase in the relative modulus (Ec/Em) in the rubbery state region with respect to the glassy region is observed and was explained in terms of the particle aggregation state
Quantum confinement and disorder in porous silicon: Effects on the optical and transport properties
No full text
Geometrically induced DOS effect on electronic transport properties of Si nanowires
Full text linkSemiconducting nanowires (NW) have recently been extensively studied and developed for applications in nanoelectronics, optoelectronics, solar cells and sensors using carriers confinement. The Si and Ge NWs, in particular, can be promising candidates for one-dimensional superconductor-semiconductor hybrid systems3,4. However, their electronic transport properties are strongly dependent on their surface and core structure. Hence, a detailed study on their possible effects on these properties are necessary prior to utilization of such hybrid systems. Here, we have studied electronic transport properties as a function of the temperature of Si NWs with two distinct structures. One with embedded Si quantum dots and the other with a percolative crystalline path. We show that the predesigned structure of the wires results in a prominent single distinct conduction mechanism such as tunneling in the former case and variable range hopping in the latter case5. We demonstrate that measured transport properties are the result of the geometry of the systems, with a large internal surface having a significantly high density of states. These results improve the understanding of the basis of the different electronic transport mechanisms in silicon nanowires and can lead to advanced hybrid systems design with a high controllability and precision
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Memristive devices based on single ZnO nanowires—from material synthesis to neuromorphic functionalities
Full text linkMemristive and resistive switching devices are considered promising building blocks for the realization of artificial neural networks and neuromorphic systems. Besides conventional top-down memristive devices based on thin films, resistive switching devices based on nanowires (NWs) have attracted great attention, not only for the possibility of going beyond current scaling limitations of the top-down approach, but also as model systems for the localization and investigation of the physical mechanism of switching. This work reports on the fabrication of memristive devices based on ZnO NWs, from NW synthesis to single NW-based memristive cell fabrication and characterization. The bottom-up synthesis of ZnO NWs was performed by low-pressure chemical vapor deposition according to a self-seeding vapor-solid (VS) mechanism on a Pt substrate over large scale (∼cm2), without the requirement of previous seed deposition. The grown ZnO NWs are single crystalline with wurtzite crystal structure and are vertically aligned respect to the growth substrate. Single NWs were then contacted by means of asymmetric contacts, with an electrochemically active and an electrochemically inert electrode, to form NW-based electrochemical metallization memory cells that show reproducible resistive switching behaviour and neuromorphic functionalities including short-term synaptic plasticity and paired pulse facilitation. Besides representing building blocks for NW-based memristive and neuromorphic systems, these single crystalline devices can be exploited as model systems to study physicochemical processing underlaying memristive functionalities thanks to the high localization of switching events on the ZnO crystalline surface
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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