The iron-related molecular toxicity mechanism of synthetic asbestos nanofibres: a model study for high-aspect-ratio nanoparticles

Asbestos shares with carbon nanotubes some morphological and physico-chemical features. An asbestos-like behaviour has been recently reported by some authors, though the mechanism of toxicity may be very different. To identify at the atomic level the source of toxicity in asbestos, the effect of progressive iron loading on a synthetic iron-free model nanofibre previously found non-toxic in cellular tests was studied. A set of five synthetic chrysotile nanofibres [(Mg,Fe)3(Si2O5)(OH)4] has been prepared with Fe ranging from 0 to 1.78?wt?%. The relationship between fibre-induced free-radical generation and the physico-chemical characteristics of iron active sites was investigated with spin-trapping techniques on an aqueous suspension of the fibres and M?ssbauer and EPR spectroscopies on the solids, respectively. The fully iron-free fibre was inert, whereas radical activity arose with even the smallest amount of iron. Surprisingly, such activity decreased upon increasing iron loading. M?ssbauer and EPR revealed isolated iron ions in octahedral sites that undergo both axial and rhombic distortion and the occurrence of aggregated iron ions and/or extra-framework clustering. The isolated ions largely prevailed at the lowest loadings. Upon increasing the loading, the amount of isolated iron was reduced and the aggregation increased. A linear relationship between the formation of carbon-centred radicals and the amount of rhombic-distorted isolated iron sites was found. Even the smallest iron contamination imparts radical reactivity, hence toxicity, to any chrysotile outcrop, thereby discouraging the search for non-toxic chrysotile. The use of model solids that only differ in one property at a time appears to be the most successful approach for a molecular understanding of the physico-chemical determinants of toxicity. Such findings could also be useful in the design of safer nanofibres.     

Spontaneous vesicles of single-chain sugar-based fluorocarbon surfactants

The synthesis and physico-chemical investigation of a cationic, water-soluble surfactant of formula C₈F₁₇CH₂CH(OH)CH₂NH₂⁺CH₂CH(OH)CH₂OH, Lac⁻ (Lac = lactobionate), bearing a single-fluorocarbon tail and the lactobionate moiety as a counterion is reported. It forms spontaneously in water bilayer vesicles with a polydisperse distribution in size. This behavior could be attributed to a possible asymmetry of the bilayers due to an excess of the counterion outside the vesicles and possible stabilization by hydrogen bond interactions between the aminoalcohol polar heads of the cationic surfactant inside the vesicle.     

Characterization of a Two-Photon Quantum Battery: Initial Conditions,Stability and Work Extraction

We consider a quantum battery that is based on a two-level system coupled with a cavity radiation by means of a two-photon interaction. Various figures of merit, such as stored energy, average charging power, energy fluctuations, and extractable work are investigated, considering, as possible initial conditions for the cavity, a Fock state, a coherent state, and a squeezed state. We show that the first state leads to better performances for the battery. However, a coherent state with the same average number of photons, even if it is affected by stronger fluctuations in the stored energy, results in quite interesting performance, in particular since it allows for almost completely extracting the stored energy as usable work at short enough times.     

On a multidimensional model for the codiffusion of isotopes: existence and uniqueness

The paper deals with the existence and uniqueness of classical solutions of the homogeneous Neumann problem for a class of parabolic–hyperbolic system of partial differential equations in n dimensions. The problem arises from a model of the diffusion of N species of radioactive isotopes of the same element. Copyright © 2014 John Wiley & Sons, Ltd.     

L-α-Aminoadipic Acid from L-Glutamic Acid

A convenient procedure for the preparation of L-α-aminoadipic acid from L-glutamic acid is described.     

Sequential and dynamic frameproof codes

There are many schemes in the literature for protecting digital data from piracy by the use of digital fingerprinting, such as frameproof codes and traitor-tracing schemes. The concept of traitor-tracing has been applied to a digital broadcast setting in the form of dynamic traitor-tracing schemes and sequential traitor-tracing schemes, which could be used to combat piracy of pay-TV broadcasts, for example. In this paper, we extend the properties of frameproof codes to this dynamic model, defining and constructing both l-sequential c-frameproof codes and l-dynamic c-frameproof codes. We also give bounds on the number of users supported by such schemes.      

Showing by Avowing

Dorit Bar-On aims to account for the distinctive security of avowals by appealing to expression. She officially commits herself only to a negative characterization of expression, contending that expressive behavior is not epistemically based in self-judgments. I argue that her account of avowals, if it relies exclusively on this negative account of expression, can't achieve the explanatory depth she claims for it. Bar-On does explore the possibility that expression is a kind of perception-enabling showing. If she endorsed this positive account, her argument would re-gain an explanatory advantage over its rivals. But extending this account to linguistic expressive behavior would bring Bar-On very close to constitutive accounts of first-person authority.     

Review of recent advances in analytical techniques for the determination of neurotransmitters

Methods and advances for monitoring neurotransmitters in vivo or for tissue analysis of neurotransmitters over the last five years are reviewed. The review is organized primarily by neurotransmitter type. Transmitter and related compounds may be monitored by either in vivo sampling coupled to analytical methods or implanted sensors. Sampling is primarily performed using microdialysis, but low-flow push-pull perfusion may offer advantages of spatial resolution while minimizing the tissue disruption associated with higher flow rates. Analytical techniques coupled to these sampling methods include liquid chromatography, capillary electrophoresis, enzyme assays, sensors, and mass spectrometry. Methods for the detection of amino acid, monoamine, neuropeptide, acetylcholine, nucleoside, and soluble gas neurotransmitters have been developed and improved upon. Advances in the speed and sensitivity of these methods have enabled improvements in temporal resolution and increased the number of compounds detectable. Similar advances have enabled improved detection at tissue samples, with a substantial emphasis on single cell and other small samples. Sensors provide excellent temporal and spatial resolution for in vivo monitoring. Advances in application to catecholamines, indoleamines, and amino acids have been prominent. Improvements in stability, sensitivity, and selectivity of the sensors have been of paramount interest.