Incorporating nano-carbon phases into metal-matrix composites is a promising strategy for simultaneously enhancing electrical conductivity and mechanical properties of metals. Here, we describe the ...manufacture of novel nano-carbon-aluminum composites by an electro-charging-assisted process (EAP) that show 5.6% ± 1.7% increase in electrical conductivity compared to the base metal alloy. The source of nano-carbon that was used in this study is activated carbon with particle size less than 100 nm. The enhancement is attributed to nano-graphitic structures that extend through the lattice of the metal. Through electron transfer from the metal to the nano-structures the electron density at the interface of nano-crystalline graphite and the metal lattice increases thereby enhancing the bulk electrical conductivity. We identify the important fabrication parameters of the EAP for a reaction system employing a tapered graphite cathode. A high current density of 100 A/cm2 causes ionization and crystallization of the carbon in the liquid metal. The increase in electrical conductivity of the composite is directly related to the incorporation of the nanocrystalline carbon in the metal lattice. The superior performance of these nano-carbon aluminum composites makes them promising candidates for power transmission lines and other applications.
Incorporating nano-carbon phases into metal-matrix composites is a promising strategy for enhancing electrical conductivity of metals. Here, we describe the manufacture of novel nano-carbon-aluminum composites (known as covetics) by an electro-charging assisted process (EAP) that show 5.6% increased electrical conductivity compared to the alloy matrix. We identify the important fabrication parameters of the EAP for a reaction system with a tapered graphite cathode. A high current density of 100 A/cm2, reaction time of 10 min, and reaction volume hemisphere of 4 mm radius around the electrode are responsible for the formation of graphitic nanostructures within the metal which contribute to the enhancement of electrical conductivity. The superior performance of these nano-carbon aluminum composites makes them promising candidates for power transmission lines and other conducting wires or cables in many applications. Display omitted
A method for the fabrication of thick films of porous anodic alumina on rigid substrates is described. The anodic alumina film was generated by the anodization of an aluminum film evaporated on the ...substrate. The morphology of the barrier layer between the porous film and the substrate was different from that of anodic films grown on aluminum substrates. The removal of the barrier layer and the electrochemical growth of nanowires within the ordered pores were accomplished without the need to remove the anodic film from the substrate. We fabricated porous anodic alumina samples over large areas (up to 70 cm2), and deposited in them nanowire arrays of various materials. Long nanowires were obtained with lengths of at least 9 μm and aspect ratios as high as 300. Due to their mechanical robustness and the built‐in contact between the conducting substrate and the nanowires, the structures were useful for electrical transport measurements on the arrays. The method was also demonstrated on patterned and non‐planar substrates, further expanding the range of applications of these porous alumina and nanowire assemblies.
Large‐area porous anodic alumina films lacking a barrier layer, and nanowire arrays of high aspect ratio nanowires (∼102) in direct contact with a conductive film, have been formed on rigid substrates. The effect of different substrates on the morphology of the film and the barrier layer was examined, and the ease of manipulation of the structures was demonstrated by patterning the films and by nanowire transport measurements.
The problem of plasmon resonances in metallic nanoparticles can be formulated as an eigenvalue problem under the condition that the wavelengths of the incident radiation are much larger than the ...particle dimensions. As the nanoparticle size increases, the quasistatic condition is no longer valid. For this reason, the accuracy of the electrostatic approximation may be compromised and appropriate radiation corrections for the calculation of resonance permittivities and resonance wavelengths are needed. In this paper, we present the radiation corrections in the framework of the eigenvalue method for plasmon mode analysis and demonstrate that the computational results accurately match analytical solutions (for nanospheres) and experimental data (for nanorings and nanocubes). We also demonstrate that the optical spectra of silver nanocube suspensions can be fully assigned to dipole-type resonance modes when radiation corrections are introduced. Finally, our method is used to predict the resonance wavelengths for face-to-face silver nanocube dimers on glass substrates. These results may be useful for the indirect measurements of the gaps in the dimers from extinction cross-section observations.
We address the problem of the-security of cryptographic protocols in face of future advances in computing technology and algorithmic research. The problem stems from the fact may be deemed that ...computations which at a given point in time may be deemed infeasible, can, in the course of years or decades, be made possible with improved hardware and/or breakthroughs in code-breaking algorithms. In such cases, the security of historical , but nonetheless highly confidential data may be in jeopardy. We present a scheme for efficient secure two-party communication with provable everlasting security. The security is guaranteed in face of any future technological advances, given the current state of of the art. Furthermore, the security of the messages is also guaranteed even if the secret encryption/decryption key is revealed in the future, The scheme is based on the bounded storage model and provides information-theoretic security in this model. The bounded storage model postulates an adversary who is computationally unbounded, and is only bounded in the amount of storage (not computation space) available to store the output of his computation. The bound on the storage can be arbitrarily large (e.g., 100 Tbytes), as long as it is fixed. Given this storage bound, our protocols guarantee that even a computationally all powerful adversary gains no information about a message (except with a probability that is exponentially small in the security parameter k). The bound on storage space need only hold at the time of the message transmission. Thereafter, no additional storage space or, computational power can help the adversary in deciphering the message. We present two protocols. The first protocol, which elaborates on the autoregressive (AR) protocol of Aumann and Rabin (see Advances in Cryptology-Crypto '99, p. 65-79, 1999), employs a short secret key whose size is independent of the length of the message, but uses many public random bits. The second protocol uses an optimal number of public random bits, but employs a longer secret key. Our proof of security utilizes a novel linear algebraic technique.
Despite strong educational messages from sports authorities insisting that a balanced diet is sufficient to cover all the nutritional requirements of elite level athletes, it is considered that ...between 50 and 80% of athletes regularly consume one or more nutritional supplements. Several studies conducted by anti-doping authorities over the years indicate that up to 20% of the nutritional supplements contain substances covered by the List of Prohibited Substances, which can generate an adverse result in anti-doping tests. Under the rule of strict liability as established by the World Anti-Doping Code, this is a significant risk for the athletes subject to anti-doping control in their sport practice. The nutritional supplement industry is largely unregulated and several examples of mislabeling or absence of labeling of active ingredients contained in commercial products led to sanctions of athletes and occasionally to serious consequences for some nutritional supplement manufacturers.
This presentation will explore the current regulation applied by anti-doping authorities and provide some concrete examples of risks associated to the consumption of nutritional supplements by athletes in the context of anti-doping testing.
Nanomaterials have become increasingly important in the development of new molecular probes for in vivo imaging, both experimentally and clinically. Nanoparticulate imaging probes have included ...semiconductor quantum dots, magnetic and magnetofluorescent nanoparticles, gold nanoparticles and nanoshells, among others. However, the use of nanomaterials for one of the most common imaging techniques, computed tomography (CT), has remained unexplored. Current CT contrast agents are based on small iodinated molecules. They are effective in absorbing X-rays, but non-specific distribution and rapid pharmacokinetics have rather limited their microvascular and targeting performance. Here we propose the use of a polymer-coated Bi2S3 nanoparticle preparation as an injectable CT imaging agent. This preparation demonstrates excellent stability at high concentrations (0.25 M Bi3+), high X-ray absorption (fivefold better than iodine), very long circulation times (>2 h) in vivo and an efficacy/safety profile comparable to or better than iodinated imaging agents. We show the utility of these polymer-coated Bi2S3 nanoparticles for enhanced in vivo imaging of the vasculature, the liver and lymph nodes in mice. These nanoparticles and their bioconjugates are expected to become an important adjunct to in vivo imaging of molecular targets and pathological conditions.
Incorporating nano-carbon phases into metal-matrix composites is a promising strategy for simultaneously enhancing electrical conductivity and mechanical properties of metals. Here, we describe the ...manufacture of novel nano-carbonaluminum composites by an electro-charge-assisted process (EAP) that show 5.6% ± 1.7% increase in electrical conductivity compared to the base metal alloy. The source of nano-carbon that we used in this study is activated carbon with particle size less than 100 nm. The enhancement is attributed to nano-graphitic structures that extend through the lattice of the metal. Through electron transfer from the metal to the nanostructures the electron density at the interface of nano-crystalline graphite and the metal lattice increases thereby enhancing the bulk electrical conductivity. We identify the important fabrication parameters of the EAP for a reaction system employing a tapered graphite cathode. Here, a high current density of 100 A/cm2 causes ionization and crystallization of the carbon in the liquid metal. The increase in electrical conductivity of the composite are directly related to the incorporation of the nanocrystalline carbon in the metal lattice. The superior performance of these nano-carbon aluminum composites makes them promising candidates for power transmission lines and other applications.
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