B.V. King

Mobile Phone Radiation Induces Reactive Oxygen Species Production and DNA Damage in Human Spermatozoa In Vitro

Background In recent times there has been some controversy over the impact of electromagnetic radiation on human health. The significance of mobile phone radiation on male reproduction is a key element of this debate since several studies have suggested a relationship between mobile phone use and semen quality. The potential mechanisms involved have not been established, however, human spermatozoa are known to be particularly vulnerable to oxidative stress by virtue of the abundant availability of substrates for free radical attack and the lack of cytoplasmic space to accommodate antioxidant enzymes. Moreover, the induction of oxidative stress in these cells not only perturbs their capacity for fertilization but also contributes to sperm DNA damage. The latter has, in turn, been linked with poor fertility, an increased incidence of miscarriage and morbidity in the offspring, including childhood cancer. In light of these associations, we have analyzed the influence of RF-EMR on the cell biology of human spermatozoa in vitro. Principal Findings Purified human spermatozoa were exposed to radio-frequency electromagnetic radiation (RF-EMR) tuned to 1.8 GHz and covering a range of specific absorption rates (SAR) from 0.4 W/kg to 27.5 W/kg. In step with increasing SAR, motility and vitality were significantly reduced after RF-EMR exposure, while the mitochondrial generation of reactive oxygen species and DNA fragmentation were significantly elevated (P<0.001). Furthermore, we also observed highly significant relationships between SAR, the oxidative DNA damage bio-marker, 8-OH-dG, and DNA fragmentation after RF-EMR exposure. Conclusions RF-EMR in both the power density and frequency range of mobile phones enhances mitochondrial reactive oxygen species generation by human spermatozoa, decreasing the motility and vitality of these cells while stimulating DNA base adduct formation and, ultimately DNA fragmentation. These findings have clear implications for the safety of extensive mobile phone use by males of reproductive age, potentially affecting both their fertility and the health and wellbeing of their offspring.

Fabrication of implantable microelectrode arrays by laser cutting of silicone rubber and platinum foil

A new method for fabrication of microelectrode arrays comprised of traditional implant materials is presented. The main construction principle is the use of spun-on medical grade silicone rubber as insulating substrate material and platinum foil as conductor (tracks, pads and electrodes). The silicone rubber and the platinum foil are patterned by laser cutting using an Nd:YAG laser and a microcontroller-driven, stepper-motor operated x-y table. The method does not require expensive clean room facilities and offers an extremely short design-to-prototype time of below 1 day. First prototypes demonstrate a minimal achievable feature size of about 30 microm.

A model for atomic mixing and preferential sputtering effects in SIMS depth profiling

The development of altered surface layers due to preferential sputtering can be modeled by an algorithm based on the diffusion theory of atomic mixing using a depth‐dependent diffusion coefficient. Application of the model to typical SIMS depth profiles of buried layers indicates that the effects of atomic mixing and preferential sputtering can be separated by analysis of the shift and broadening of the measured peaks.

A STM study of the effects of the ion incident angle and energy on surface damage induced by Ar+ bombardment of HOPG

Abstract Scanning tunnelling microscopy has been used to study the surface damage induced by ion bombardment of highly ordered pyrolytic graphite (HOPG). Ar ions with energies in the range from 0.5 to 3 keV were used to bombard HOPG surfaces at different angles of incidence. A low fluence ( 12 ions cm 2 ) was used to enable characterisation of single ion impacts on surfaces. It is shown that each ion impact creates a small protrusion on the HOPG surface whose average volume increases as the ion energy and the incident angle to the surface decreases in the range investigated. Statistical distributions of protrusion diameter and height are given for comparison, as well as the average diameter and height. The origin of these features on the surfaces is discussed. It is suggested that thermal spikes created by the ion in the near surface region may play a very important role in producing this surface damage.

An unusual bimetallic p4g phase induced by Pd on Cu(001)

Abstract The surface composition and structure of Pd on Cu(001) have been studied by a combination of low-energy ion scattering (LEIS) and low-energy electron diffraction (LEED). Palladium is incorporated into the surface at room temperature (≤ 50° C ). This leads to the formation of two surface alloys: an ordered c(2 × 2) structure at 0.5 ML Pd, and a p4g structure at 1.0 ML Pd. The surface composition of the top two layers was determined by 1 keV Li + ion scattering, using selective scattering geometries with calibration measurements on reference samples of Cu(001) and Pd(001). For the p4g structure, the results show a surface composition of 53at%Cu47at% Pd in the first layer, while the second layer is 58at%Cu42at%Pd. Several structural models that could be responsible for the p4g structure are proposed and investigated. The randomly mixed top CuPd layer was found to be reconstructed such that the Pd (Cu) atoms are rotated by a lateral displacement of 0.25 ± 0.10 A . The magnitude of this displacement was determined by measuring the azimuthal distributions of the PdPd double scattering peak with 2 keV K + ions. It is proposed, based on a hard-sphere model, that it is the moderate size mismatch between Cu and Pd atoms in the second c(2 × 2) mixed layer which drives the clockwise-anticlockwise rotation.

Low energy ion beam mixing of metal-copper multilayers

Abstract The efficiency of ion beam mixing of W, Pb, Pt, Ta, Ni, In, Ag, Nb, Mo, Ti and Au with Cu during 4 and 5 keV Ne + sputter depth profiling has been determined by LEIS and SIMS. Values of the mixing efficiency, ( Dt / φF d ), were found by modelling the sputtering and mixing processes by a diffusion approximation to the transport equation. Values of mixing efficiency range from 25 A 5 /eV for Ta in Cu to 350 A 5 /eV for Ag in Cu. These values are larger than those obtained in high energy mixing experiments in Cu, but scale in the same way with thermal diffusion constants. This indicates that the same processes are responsible for low and high energy ion mixing.

Towards the development of a virtual organic solar cell: An experimental and dynamic Monte Carlo study of the role of charge blocking layers and active layer thickness

Monte Carlo (MC) simulations have been used to fully model organic solar cells. The quantum efficiency and short-circuit current of these virtual devices are in excellent agreement with experimental measurements. Simulations show that, contrary to expectation, indium tin oxide/poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methylester (PCBM)/aluminium devices lack effective charge blocking layers at the electrode interfaces. X-ray photoelectron spectroscopy depth profiling shows that despite a PCBM-rich region near the cathode, interface intermixing at the electrodes combined with incomplete PCBM coverage leads to significant interface recombination. This work highlights the effectiveness of MC simulations as a predictive tool and emphasizes the need to control electrode interface processes.

The depth resolution of sputter profiling

Abstract Depth profiles of impurity markers and overlayers obtained by sputter-sectioning techniques such as secondary ion mass spectrometry (SIMS) and Auger electron spectroscopy (AES) are modeled by a diffusion theory incorporating atomic mixing and preferential sputtering effects. The model explains very well the broadening and shifts frequently observed in experimental depth profiles.

Estimation of useful yield in surface analysis using single photon ionisation

Abstract Secondary ion mass spectrometry (SIMS), laser sputter neutral mass spectrometry (SNMS) and laser desorption photoionisation (LDPI) have been used to investigate the desorption of molecules from self-assembled monolayers of phenylsulphides. LDPI, using an F2 excimer laser to single photon ionise gave the lowest fragmentation. A useful yield greater than 0.5% was found for analysis of diphenyldisulphide self-assembled monolayers. It is shown that using a free electron laser to postionise will lead, in the future, to analysis of many atoms and molecules with useful yields approaching 30%.

Mass distribution of ejected molecules and clusters in noncascade sputtering processes

A model of noncascade sputtering is proposed to explain the mass distribution observed by MacFarlane and co‐workers in the sputtering of insulin by 90 MeV 127I20+ ions. The ejection of molecular ions from insulin is considered to be induced by vibrational excitation. The ensuing calculations using RRKM theory show that the relative abundance of the ejected species can be fitted to our model yielding realistic values for both the energy deposited by the incident ion and the activation energies required for the ejection of the molecular species.