Neural Cell Response to Nanostructured Biosensor Surfaces

AbstractIn our work we investigate the interaction of cells and nanotextured surfaces as a model of implanted device surface and living tissue interaction. We developed a maskless nanostructuring method, which can be integrated into our neural biosensor fabrication process. Morphology of the fabricated nanograss was characterised using SEM. The nanorods are 520-800nm in height and their density is 18-70/μm2. Electrochemical impedance spectroscopy and contact angles of different surfaces were measured. The specific surface area is 30 times larger than the reference. The contact-angle can be tuned. The samples will be tested in viability and adhesion assays using neural cell cultures

Seasonal and diurnal variations in Martian surface ultraviolet irradiation: biological and chemical implications for the Martian regolith

The issue of the variation of the surface ultraviolet (UV) environment on Mars was investigated with particular emphasis being placed on the interpretation of data in a biological context. A UV model has been developed to yield the surface UV irradiance at any time and place over the Martian year. Seasonal and diurnal variations were calculated and dose rates evaluated. Biological interpretation of UV doses is performed through the calculation of DNA damage effects upon phage T7 and Uracil, used as examples for biological dosimeters. A solar UV 'hotspot' was revealed towards perihelion in the southern hemisphere, with a significant damaging effect upon these species. Diurnal profiles of UV irradiance are also seen to vary markedly between aphelion and perihelion. The effect of UV dose is also discussed in terms of the chemical environment of the Martian regolith, since UV irradiance can reach high enough levels so as to have a significant effect upon the soil chemistry. We show, by assuming that H2O is the main source of hydrogen in the Martian atmosphere, that the stoichiometrically desirable ratio of 2:1 for atmospheric H and O loss rates to space are not maintained and at present the ratio is about 20:1. A large planetary oxygen surface sink is therefore necessary, in contrast with escape to space. This surface oxygen sink has important implications for the oxidation potential and the toxicology of the Martian soil. UV-induced adsorption of {\rm O}_{2}^{-} super-radicals plays an important role in the oxidative environment of the Martian surface, and the biologically damaging areas found in this study are also shown to be regions of high subsurface oxidation. Furthermore, we briefly cover the astrobiological implications for landing sites that are planned for future Mars missions

Nanomechanical properties of Mg–Al intermetallic compounds produced by packed powder diffusion coating (PPDC) on the surface of AZ91E

A packed powder diffusion coating (PPDC) treatment produced two intermetallic layers on the surface of the commercial magnesium alloy AZ91E. The beta-phase (Mg17Al12) was immediately on top of the AZ91E, on top of which was the tau-phase (Mg-32(Al,Zn)(49)). Nanoindentation showed that the elastic modulus and hardness of each of the intermetallic compounds was significantly greater than that of the AZ91E substrate. Staircase displacement bursts occurred during nanoindentation of the intermetallic compounds, attributed to the combination of incipient plasticity at low loads, and the development of dislocation networks due to dislocation pile ups around the indentation at higher loads. Crystallographic analysis of beta phase orientations using EBSD showed that the nanomechanical properties of the intermetallic compound produced through PPDC treatment were isotropic. (C) 2013 Elsevier B.V. All rights reserved

Splitting ‘intervocalic’: Expanding the typology of lenition environments

The basic types of lenition environments (‘initial’, ‘intervocalic’, ‘final’) need to be separately evaluated as they differ along parameters like word position (e.g., pre-consonantal vs. final codas) or stress relations. This paper argues that we need to recognise an additional such parameter: the length of the vowel preceding an intervocalic consonant. We show that a number of phenomena from varieties of English and German show lenition patterns which draw a distinction between reflexes found in post-short (vc) and post-long (vvc) environments. The theoretical consequence of our observations is that phonological theory needs to be able to account for the post-short vs. post-long distinction in the form of a parametrically-determined representational difference

Density functional theory study of the multimode Jahn-Teller effect – ground state distortion of benzene cation

The multideterminental-DFT approach performed to analyze Jahn-Teller (JT) active molecules is described. Extension of this method for the analysis of the adiabatic potential energy surfaces and the multimode JT effect is presented. Conceptually a simple model, based on the analogy between the JT distortion and reaction coordinates gives further information about microscopic origin of the JT effect. Within the harmonic approximation the JT distortion can be expressed as a linear combination of all totally symmetric normal modes in the low symmetry minimum energy conformation, which allows calculating the Intrinsic Distortion Path, IDP, exactly from the high symmetry nuclear configuration to the low symmetry energy minimum. It is possible to quantify the contribution of different normal modes to the distortion, their energy contribution to the total stabilization energy and how their contribution changes along the IDP. It is noteworthy that the results obtained by both multideterminental-DFT and IDP methods for different classes of JT active molecules are consistent and in agreement with available theoretical and experimental values. As an example, detailed description of the ground state distortion of benzene cation is given

Sodium ion interactions with aqueous glucose: Insights from quantum mechanics, molecular dynamics, and experiment

In the last several decades, significant efforts have been conducted to understand the fundamental reactivity of glucose derived from plant biomass in various chemical environments for conversion to renewable fuels and chemicals. For reactions of glucose in water, it is known that inorganic salts naturally present in biomass alter the product distribution in various deconstruction processes. However, the molecular-level interactions of alkali metal ions and glucose are unknown. These interactions are of physiological interest as well, for example, as they relate to cation-glucose cotransport. Here, we employ quantum mechanics (QM) to understand the interaction of a prevalent alkali metal, sodium, with glucose from a structural and thermodynamic perspective. The effect on B-glucose is subtle: a sodium ion perturbs bond lengths and atomic partial charges less than rotating a hydroxymethyl group. In contrast, the presence of a sodium ion significantly perturbs the partial charges of α-glucose anomeric and ring oxygens. Molecular dynamics (MD) simulations provide dynamic sampling in explicit water, and both the QM and the MD results show that sodium ions associate at many positions with respect to glucose with reasonably equivalent propensity. This promiscuous binding nature of Na + suggests that computational studies of glucose reactions in the presence of inorganic salts need to ensure thorough sampling of the cation positions, in addition to sampling glucose rotamers. The effect of NaCl on the relative populations of the anomers is experimentally quantified with light polarimetry. These results support the computational findings that Na + interacts similarly with a- and B-glucose

Forty years of carabid beetle research in Europe - from taxonomy, biology, ecology and population studies to bioindication, habitat assessment and conservation

Volume: 100Start Page: 55End Page: 14