Vibrational and AFM studies of adsorption of glycine on DLC and silicon-doped DLC

A better understanding of protein adsorption onto surfaces of materials is required to control biocompatibility and bioactivity. Diamond-like carbon (DLC) is known to have excellent biocompatibility. Various samples of a-C:H and silicon-doped a-C:H thin films (Si-DLC) were deposited onto silicon substrates using plasma-enhanced chemical vapour deposition (PECVD). Subsequently, the adsorption of the simplest amino acid glycine onto the surfaces of the thin films was investigated to elucidate the mechanisms involved in protein adhesion. The physicochemical characteristics of the surfaces, before and after adsorption of glycine, were investigated using Raman spectroscopy and atomic force microscopy (AFM). The Raman study highlighted a slight decrease in the I D/I G ratio with increasing the silicon dopant levels. Following exposure to glycine solutions, the presence of bands at ~1735 and ~1200 cm−1 indicates that the adsorption of glycine onto the surfaces has taken place. Glycine was bound to the surfaces via both deprotonated carboxyl and protonated amino groups whilst, as the silicon content in the DLC film increased the adsorption of glycine decreased. AFM analysis showed that the surface roughness increased following exposure to glycine. These results show that at low silicon doping the adsorption of the amino acid was enhanced whilst increased doping levels led to a reduced adsorption compared to undoped DLC. Therefore, doping of DLC may provide an approach to control the protein adsorption

Search for diphoton events with large missing transverse momentum in 1 fb(-1) of 7 TeV proton-proton collision data with the ATLAS detector ATLAS Collaboration

A search for diphoton events with large missing transverse momentum has been performed using 1.07 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ATLAS detector. No excess of events was observed above the Standard Model prediction and 95% Confidence Level (CL) upper limits are set on the production cross section for new physics. The limits depend on each model parameter space and vary as follows: sigma < (22-129) fb in the context of a generalised model of gauge-mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, sigma < (27-91) fb in the context of a minimal model of gauge-mediated supersymmetry breaking (SPS8), and sigma < (15-27) fb in the context of a specific model with one universal extra dimension (UED). A 95% CL lower limit of 805 GeV, for bino masses above 50 GeV, is set on the GGM gluino mass. Lower limits of 145 TeV and 1.23 TeV are set on the SPS8 breaking scale Lambda and on the UED compactification scale 1/R, respectively. These limits provide the most stringent tests of these models to date. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved