Cr2AlC MAX phase thin films prepared by radio-frequency magnetron sputtering were irradiated at room temperature by 100 keV helium ions to a fluence of 1 x 10(17)ions cm(-2). The effects of thermal annealing on the structural and mechanical properties of the helium-irradiated Cr2AlC films as well as the helium release were investigated by grazing-incidence X-ray diffraction (GIXRD), Raman spectroscopy, and scanning electron microscope (SEM) in combination with nano-indentation and elastic recoil detection (ERD) analysis. The irradiation-induced structural damage in the Cr2AlC is significantly recovered by thermal annealing at temperatures around 600celcius, attributed to high defect diffusivity. After annealing to 750celcius, the hardness of irradiated films recovered almost completely, which is ascribes to both defect recombination and reformation of damaged chemical bonds. Substantial helium release occurring at this annealing temperature is closely related to the damage recovery due to helium irradiation.

Artificially generated radiofrequency-electromagnetic energy (RF-EME) is now ubiquitous in our environment owing to the utilization of mobile phone and Wi-Fi based communication devices. While several studies have revealed that RF-EME is capable of eliciting biological stress, particularly in the context of the male reproductive system, the mechanistic basis of this biophysical interaction remains largely unresolved. To extend these studies, here we exposed unrestrained male mice to RF-EME generated via a dedicated waveguide (905 MHz, 2.2 W/kg) for 12 h per day for a period of 1, 3 or 5 weeks. The testes of exposed mice exhibited no evidence of gross histological change or elevated stress, irrespective of the RF-EME exposure regimen. By contrast, 5 weeks of RF-EME exposure adversely impacted the vitality and motility profiles of mature epididymal spermatozoa. These spermatozoa also experienced increased mitochondrial generation of reactive oxygen species after 1 week of exposure, with elevated DNA oxidation and fragmentation across all exposure periods. Notwithstanding these lesions, RF-EME exposure did not impair the fertilization competence of spermatozoa nor their ability to support early embryonic development. This study supports the utility of male germ cells as sensitive tools with which to assess the biological impacts of whole-body RF-EME exposure.

As the use of mobile phone devices is now highly prevalent, many studies have sought to evaluate the effects of the radiofrequency-electromagnetic radiation (RF-EMR) on both human health and biology. While several such studies have shown RF-EMR is capable of inducing cellular stress, the physicobiological origin of this stress remains largely unresolved. To explore the effect of RF-EMR on the male reproductive system, we exposed cultured mouse spermatogonial GC1 and spermatocyte GC2 cell lines, as well as cauda epididymal spermatozoa to a waveguide generating continuous wave RF-EMR (1.8 GHz, 0.15 and 1.5 W/kg). This study demonstrated that a 4 h exposure is capable of inducing the generation of mitochondrial reactive oxygen species (ROS) in populations of GC1 (7 vs. 18%; p < 0.001) and GC2 cells (11.5 vs. 16 %; p < 0.01), identifying Complex III of the electron transport chain (ETC) as the potential source of electrons producing ROS. Assessing the generation of ROS in the presence of an antioxidant, penicillamine, as well as measuring lipid peroxidation via 4-hydroxynonenal levels, indicated that the elevated incidence of ROS generation observed under our exposure conditions did not necessarily induce an overt cellular oxidative stress response. However, exposure to RF-EMR at 0.15 W/kg for 3 h did induce significant DNA fragmentation in spermatozoa (that was no longer significant after 4 h), assessed by the alkaline comet assay (p < 0.05). Furthermore, this fragmentation was accompanied by an induction of oxidative DNA damage in the form of 8-hydroxy-2'-deoxyguanosine, which was significant (p < 0.05) after spermatozoa were exposed to RF-EMR for 4 h. At this exposure time point, a decline in sperm motility (p < 0.05) was also observed. This study contributes new evidence toward elucidating a mechanism to account for the effects of RF-EMR on biological systems, proposing Complex III of the mitochondrial ETC as the key target of this radiation.

Useful yields from resonance ionization mass spectrometry can be extremely high compared to other mass spectrometry techniques, but uranium analysis shows strong matrix effects arising from the tendency of uranium to form strongly bound oxide molecules that do not dissociate appreciably on energetic ion bombardment. We demonstrate a useful yield of 24% for metallic uranium. Modeling the laser ionization and ion transmission processes shows that the high useful yield is attributable to a high ion fraction achieved by resonance ionization. We quantify the reduction of uranium oxide surface layers by Ar+ and Ga+ sputtering. The useful yield for uranium atoms from a uranium dioxide matrix is 0.4% and rises to 2% when the surface is in sputter equilibrium with the ion beam. The lower useful yield from the oxide is almost entirely due to uranium oxide molecules reducing the neutral atom content of the sputtered flux. We demonstrate rapid isotopic analysis of solid uranium oxide at a precision of <0.5% relative standard deviation using relatively broadband lasers to mitigate spectroscopic fractionation.

A complete model of a thermionic generator has been developed in order to optimise the technology for application in the solar thermal generation of electricity. Steady state current densities predicted by the model have been shown to agree with published experimental thermionic data. Two separate genetic algorithm optimisations have been carried out for both power density and efficiency, in which electrode temperatures and work functions, external circuit resistance and electrode separation were varied. The result of these optimisations were two configurations separately exhibiting a maximum power density of 1.66 W/cm(2), and a Maximum efficiency of 7.69% for parameter ranges applicable to concentrating solar thermal power. Examination of the optimum simulation parameters indicated that future developments in lowering collector work functions, increasing emitter service temperature and decreasing attainable electrode separations will all positively impact device performance. (C) 2017 Elsevier Ltd. All rights reserved.

The radiation damage response of Ti3SiC2 irradiated by 110 keV helium ions at room temperature (RT), the subsequent evolution of damage including helium bubble growth as a function of annealing temperatures are investigated using grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and transmission electronic microscopy (TEM). In addition to collision cascade effects leading to TiC nanocrystal formation near the surface of Ti3SiC2, He ion irradiation produces damage due to the growth of He bubbles, which cause a structural transformation into a large grain TiC crystalline phase at high temperatures. The displacement of matrix Si atoms adjacent to the He bubbles along the Si layer in Ti3SiC2 either via bubble growth or the production of inter bubble fracture is the reason for the structural transformation. Depending on the He damage level, a significant recovery of the He irradiation damage can occur at moderate temperatures. This property may play a positive role in the damage resistance of Ti3SiC2, making it a potential candidate for future nuclear reactor applications.

The ternary alloy Au7Cu5Al4 was irradiated with 0.1–10 keV Ar+ and the surface composition analyzed using laser sputter neutral mass spectrometry. Ejected clusters containing up to seven atoms, with masses up to 2000 amu, were observed. By monitoring the signals from sputtered clusters, the surface composition of the alloy was seen to change with 100 eV Ar+ dose, reaching equilibrium after 10 nm of the surface was eroded, in agreement with TRIDYN simulation and indicating that the changes were due to preferential sputtering of Al and Cu. Ejected gold containing clusters were found to increase markedly in intensity while aluminum containing clusters decreased in intensity as a result of Ar sputtering. Such an effect was most pronounced for low energy (<1 keV) Ar+ sputtering and was consistent with TRIDYN simulations of the depth profiling. The component sputter yields from the ternary alloy were consistent with previous binary alloy measurements but showed greater Cu surface concentrations than expected from TRIDYN simulations.

Mobile phone usage has become an integral part of our lives. However, the effects of the radiofrequency electromagnetic radiation (RF-EMR) emitted by these devices on biological systems and specifically the reproductive systems are currently under active debate. A fundamental hindrance to the current debate is that there is no clear mechanism of how such non-ionising radiation influences biological systems. Therefore, we explored the documented impacts of RF-EMR on the male reproductive system and considered any common observations that could provide insights on a potential mechanism. Among a total of 27 studies investigating the effects of RF-EMR on the male reproductive system, negative consequences of exposure were reported in 21. Within these 21 studies, 11 of the 15 that investigated sperm motility reported significant declines, 7 of 7 that measured the production of reactive oxygen species (ROS) documented elevated levels and 4 of 5 studies that probed for DNA damage highlighted increased damage due to RF-EMR exposure. Associated with this, RF-EMR treatment reduced the antioxidant levels in 6 of 6 studies that discussed this phenomenon, whereas consequences of RF-EMR were successfully ameliorated with the supplementation of antioxidants in all 3 studies that carried out these experiments. In light of this, we envisage a two-step mechanism whereby RF-EMR is able to induce mitochondrial dysfunction leading to elevated ROS production. A continued focus on research, which aims to shed light on the biological effects of RF-EMR will allow us to test and assess this proposed mechanism in a variety of cell types.

The radiation damage response of Ti3SiC2 heated from 120°C to 850°C during 700 keV Si+ irradiation has been investigated. The samples were analyzed using glancing incidence X‐ray diffraction, Rutherford backscattering spectrometry, Raman spectroscopy, and scanning electron microscopy. For the sample at 120°C, irradiation results in a buildup of a heterogeneous surface and the formation of TiCx. Irradiation at 200°C results in maximum microstrain, a maximum in the c lattice parameter, and the appearance of a β phase in addition to the normal α phase of Ti3SiC2. A minimum in the observed damage level near the surface was seen for irradiation at a sample temperature of 300°C but the damaged phase increases at higher temperatures. Differences between the present work and a previous C irradiation study have been ascribed to the enhanced Si defect transport at low temperatures.

The radiation damage response of Ti3SiC2 irradiated by 700keV C ions has been investigated over a range of fluences and sample temperatures. The samples were analysed using a series of experimental techniques, including glancing-incidence X-ray diffraction, Rutherford backscattering spectrometry, Raman spectroscopy and scanning electron microscopy. This material exhibits a high level of tolerance to damage, especially at high temperature. Irradiation at temperatures from room temperature to 270°C results in decomposition to TiC; however, this is not observed at temperatures above 270°C. A minimum in the observed damage level is evident for irradiation at a sample temperature of 350°C. At higher temperatures the damage level increases, and results in material which is made up of damaged Ti3SiC2.

The influence of the deposition conditions on the surface morphology, crystal structure and deuterium retention of the tungsten layers formed by rf magnetron plasma sputtering in mixed atmosphere of D2, He and Ar, has been carried out. Helium containing deuterated tungsten layers (named He-WDx) on Cu/Si substrate demonstrate serious film damages with zones of cracks, fractures, flaking-off and large surface blisters. However, these kinds of damages do not happen on the He-WDx layers performed on mechanically polished polycrystalline Cu substrates because of larger surface roughness of the substrates. The crystal structure of the W layer greatly changes with the additional He in the layer, and large amounts of defects resulting in lattice expansion and X-diffraction peak broadening were produced in the W crystal. He in the W layer has direct impacts on D retention. Both D and He concentrations vary simultaneously with He fraction, attached negative bias and substrate temperature.

Ionized and neutral clusters were desorbed from spangold, a polycrystalline ternary alloy with composition Au7Cu5Al4, using both a femtosecond laser beam and an energetic ion beam and the resulting time of flight mass spectra compared. Neutral clusters containing up to 7 atoms were ejected by the 15 key Ar+ beam whereas only smaller positively and negatively charged clusters were observed from the laser ablated spangold surface.Laser ionization mass spectrometry (LIMS) positive ion spectra were dominated by Al containing cluster ions whereas Au containing ions dominated the negative LIMS spectrum. An odd-even variation in LIMS cluster yield was observed, consistent with previous results and due to fragmentation of photoionized clusters. The laser sputtered neutral mass spectrometry (laser SNMS) spectrum showed that larger desorbed clusters were gold rich. The cluster signals also followed a power law dependence with cluster size with the exponent value of 6-7.6 for sputtered mixed clusters being greater than that found from sputtering of pure elements, similar to the result found previously in the Cu-Au system. (C) 2014 Elsevier B.V. All rights reserved.

The damage produced by a 2 MeV iodine ion beam in MAX-phase Ti3SiC2 polycrystalline targets at room temperature has been studied at doses up to 3 × 1015 ions cm−2. The evolution of microstructure and induced defects of the irradiated sample with different doses was surveyed by combining grazing incident X-ray diffraction (GIXRD) using synchrotron radiation and variable energy positron beam analysis (PBA). With increasing irradiation dose, the crystallinity degrades gradually and leads to a combination of damaged Ti3SiC2 in combination with the precipitation of a TiCx phase. For high dose irradiation, a nano-dispersed TiCx phase becomes the dominant component. The PBA measurements indicate the formation of a new large vacancy-type defect that could be a cluster or void. The combination of GIXRD and PBA demonstrates that the damage of the MAX phase is more serious in the first 10 nm surface layer than that in the deeper layers closer to the final resting position of the projectile in the solid. The possible damage mechanisms have been discussed.

We have used the surface sensitivity of laser sputter neutral mass spectrometry to make measurements of clusters sputtered from AuAl alloys surfaces with high dynamic range. Polycrystalline AuAl4 and Au4Al were bombarded with 15keV Ar+ at 60° incidence, and the resulting secondary neutral yield distributions were measured using laser postionization mass spectrometry. Neutral clusters containing up to 28 atoms were observed and exhibited an odd–even variation in signal dependent on the stability of the photoion. Clusters sputtered from Au4Al were gold rich compared to the substrate and the yield of neutral clusters containing n atoms, Yn, was found to follow a power in n, i.e. Yn∝n−δ, where the exponent δ was approximately 3.4.

The beneficial impacts of mobile-based communications on society are considerable. Health concerns over the broadcast of radio frequency electromagnetic waves, which carry the information for this medium, are now gaining momentum but are not without its controversies. Studies in the past that aim to determine whether concerns are warranted are sometimes lacking in impact because of poor understanding of radiation science. Nevertheless, the studies completed to date are important in developing the field toward the goal of confirming or disproving claims that radio frequency electromagnetic radiation (RF-EMR) is a serious health issue. We focus on what has been achieved to date, toward determining the effects of RF-EMR on the male reproductive system and information presented which may underpin the potential mechanisms at play. We suggest that oxidative stress may have a key role in the detrimental effects observed in the human spermatozoon and that this cell type may be a unique model to determine the potential mechanism of action given its sensitivities to such stressors.

The microstructure of high fluence 2 MeV I2+ irradiated Ti3SiC2 has been studied by grazing incident Xray diffraction (GIXRD) using synchrotron radiation. The shift and broadening of the observed diffraction peaks are due to a variety of defects ranging from atomic to micron scale in size. The observation of the surface micrograph reveals the microcrack formation at grain boundaries due to high irradiation damage. The Raman spectrum of Ti3SiC2 was measured and compared with that of TiC0.67. It was found that a TiC nanocrystalline phase was formed under the high dose irradiation. However, a complete decomposition by irradiation did not take place even at 10.3 dpa. Post irradiation annealing to temperatures of 500-800 degrees C results in crystal regrowth of Ti3SiC2 and TiC phases. (C) 2012 Elsevier B.V. All rights reserved.

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.