83 research outputs found

    Designing cascades of electron transfer processes in multicomponent graphene conjugates

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    A novel family of nanocarbon-based materials was designed, synthesized, and probed within the context of charge-transfer cascades. We integrated electron-donating ferrocenes with light-harvesting/electron-donating (metallo)porphyrins and electron-accepting graphene nanoplates (GNP) into multicomponent conjugates. To control the rate of charge flow between the individual building blocks, we bridged them via oligo-p-phenyleneethynylenes of variable lengths by β-linkages and the Prato-Maggini reaction. With steady-state absorption, fluorescence, Raman, and XPS measurements we realized the basic physico-chemical characterization of the photo- and redox-active components and the multicomponent conjugates. Going beyond this, we performed transient absorption measurements and corroborated by single wavelength and target analyses that the selective (metallo)porphyrin photoexcitation triggers a cascade of charge transfer events, that is, charge separation, charge shift, and charge recombination, to enable the directed charge flow. The net result is a few nanosecond-lived charge-separated state featuring a GNP-delocalized electron and a one-electron oxidized ferrocenium

    Improved understanding of self-sustained, sub-micrometric multi-composition surface Constantan wires interacting with H2 at high temperatures: experimental evidence of Anomalous Heat Effects

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    This article is an extension of what presented by our team at 17th International Conference on Cold Fusion, ICCF-17, in Daejon, Korea, in 2012 [1]. It documents the improvements on Constantan-related experiments, started in 2011, in order to study the feasibility of new Nickel based alloys that are able to absorb proper amounts of Hydrogen (H2) and/or Deuterium (D2) and that have, in principle, some possibility to generate anomalous thermal effects at temperatures >100°C. The interest in Ni comes in part because there is the possibility to use also H2 instead of expensive D2. Moreover, cross-comparison of results using H2 instead of D2 can be made and could help the understanding of the phenomena involved (atomic, nuclear, super-chemical origin?) due to the use of such isotopes. Keywords: calorimeter, LENR, Nickel based alloys, sub-micrometric surface

    Carbon nanotubes toxicology and effects on metabolism and immunological modification in vitro and in vivo

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    The aim of this research is focused on the biological effects of multi wall carbon nanotubes (MWCNTs) on three different human cell types, laboratory animals in vivo, and immunological effects. Large numbers of researchers are directly involved in the handling of nanostructured materials such as MWCNTs and nanoparticles. It is important to assess the potential health risks related to their daily exposure to carbon nanotubes. The administration of sterilized nanosamples has been performed on laboratory animals, in both acute and chronic administration, and the pathological effects on the parenchymal tissues have been investigated. We studied the serum immunological modifications after intraperitoneal administration of the MWCNTs. We did not observe any antigenic reaction; the screening of ANA, anti-ENA, anti-cardiolipin, C-ANCA and P-ANCA was negative. No quantitative modification of immunoglobulins was observed, hence no modification of humoral immunity was documented. We also studied the effects of MWCNTs on the proliferation of three different cell types. MCF-7 showed a significant inhibition of proliferation for all conditions studied, whereas hSMCs demonstrated a reduction of cell growth only for the highest MWCNTs concentrations after 72 h. Also, no growth modification was observed in the Caco-2 cell line. We observed that a low quantity of MWCNTs does not provoke any inflammatory reaction. However, for future medical applications, it is important to realize prosthesis based on MWCNTs, through studying the corresponding implantation effects. Moreover, it has to be emphasized that this investigation does not address, at the moment, the carcinogenicity of MWCNTs, which requires a detailed follow-up investigation on the specific topic. In view of the subsequent and more extensive use of MWCNTs, especially in applications where carbon nanotubes are injected into the human body for drug delivery, as a contrast agent carrying entities for MRI, or as the basic material of a new prosthesis generation, more extended tests and experiments are necessary. © 2008 IOP Publishing Ltd

    The Apical Hook: Positive Gravitropism and Circumnutation

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    Hook formation in sunflower seedlings is directed by both positive gravitropism and a form of circumnutation

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    The apical hook that forms at the apex of most dicotyledonous seedlings during germination has in the past been variously described either as the consequence of positive gravitropism or as an autonomous process. Recently, however, emphasis has shifted more on the role of positive gravitropism as the inducer of this structure. To address the question on the nature and origin of the hook, experiments were performed on sunflower seedlings, not only under gravitational conditions but also by means of a clinostat, i.e. in the presence of multidirectionally compensated gravitational stimulation. The results of this work show that at least two processes are involved in the formation of a hook: positive gravitropism and an autonomous movement. Consequently, both Darwin, with his conviction that an innate process such as circumnutation was involved, and the supporters of positive gravitropism, were partly correct. Moreover, it was found that, in contrast to the hook formed under normal unidirectional gravitational conditions, the one formed on the clinostat showed a preferential plane for its development: the plane that passes parallel to the closed cotyledons. This characteristic also suggests that a form of circumnutation may be part of the basic mechanism for hook formation
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