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.
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.
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.
Cannabis in sport: anti-doping perspective Huestis, Marilyn A; Mazzoni, Irene; Rabin, Olivier
Sports medicine (Auckland),
11/2011, Letnik:
41, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Since 2004, when the World Anti-Doping Agency assumed the responsibility for establishing and maintaining the list of prohibited substances and methods in sport (i.e. the Prohibited List), ...cannabinoids have been prohibited in all sports during competition. The basis for this prohibition can be found in the World Anti-Doping Code, which defines the three criteria used to consider banning a substance. In this context, we discuss the potential of cannabis to enhance sports performance, the risk it poses to the athlete's health and its violation of the spirit of sport. Although these compounds are prohibited in-competition only, we explain why the pharmacokinetics of their main psychoactive compound, Δ(9)-tetrahydrocannabinol, may complicate the results management of adverse analytical findings. Passive inhalation does not appear to be a plausible explanation for a positive test. Although the prohibition of cannabinoids in sports is one of the most controversial issues in anti-doping, in this review we stress the reasons behind this prohibition, with strong emphasis on the evolving knowledge of cannabinoid pharmacology.
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