Tungsten nanostructure formation in a magnetron sputtering device

Fuzzy tungsten is a phenomena that could potentially occur in future fusion reactors. There are three conditions for fuzz to form, the existence of He ions impinging on a tungsten sample for a sufficient amount of time, that these ions be of sufficient energy, and that the surface temperature of the tungsten is hot enough. These conditions will likely be fulfilled in ITER, the future flagship fusion reactor. Therefore efforts to understand and characterise the fuzz formation are of importance. A thorough literature review has been provided, bringing together for the first time works from over 100 papers on the area. The history of its discovery is explained and the characteristics of the structure are detailed. The potential for fuzz to occur in ITER is shown, and positive and negative aspects of fuzz for fusion operation are discussed. The current accepted growth mechanisms are explained and a brief summary of the current work on simulating the phenomena is given. Fuzz appearing on other metals is introduced, and evidence of creating fuzz in a tokamak is shown. Methods for removing fuzz are presented should it be deemed necessary to do so in ITER. Results are compiled from many fuzz samples created in the literature spanning four orders of magnitude of fluence. This provided the foundation for a collaboration with the UC San Diego, and lab time at their facilities. Several samples were created to complement the dataset. The compilation provides new insights into the growth equation surrounding fuzz formation. A new addition to the equation is introduced in the form of an incubation fluence, a minimum fluence required before fuzz can develop. The growth model is expanded to fuzz grown in erosive regimes, and a new equation is proposed that encompasses the competition between growth and erosion, giving good predictions for the resulting equilibrium thickness. A new method for creating fuzz has been developed in a cheap and simple way. Conventional methods involve using large scale expensive devices, only available in a select few places worldwide. Magnetrons are apparent in many laboratories around the world and a technique for making fuzz in them has been developed. The three parameters controlling fuzz formation have been studied in the magnetron by making samples at many different conditions. The results provide new insight into early fuzz formation, providing results in a fluence range often over-looked. A cross-over fluence is noted from pre-fuzz to fully formed fuzz, overlapping with the predicted incubation fluence. The results differ slightly from fuzz created in other devices at similar fluence. The most probable cause is due to the unique existence of deposition of metallic particles in a magnetron incident on the samples during the growth of fuzz

A synthesis of evidence for policy from behavioural science during COVID-19

Scientific evidence regularly guides policy decisions1, with behavioural science increasingly part of this process2. In April 2020, an influential paper3 proposed 19 policy recommendations (‘claims’) detailing how evidence from behavioural science could contribute to efforts to reduce impacts and end the COVID-19 pandemic. Here we assess 747 pandemic-related research articles that empirically investigated those claims. We report the scale of evidence and whether evidence supports them to indicate applicability for policymaking. Two independent teams, involving 72 reviewers, found evidence for 18 of 19 claims, with both teams finding evidence supporting 16 (89%) of those 18 claims. The strongest evidence supported claims that anticipated culture, polarization and misinformation would be associated with policy effectiveness. Claims suggesting trusted leaders and positive social norms increased adherence to behavioural interventions also had strong empirical support, as did appealing to social consensus or bipartisan agreement. Targeted language in messaging yielded mixed effects and there were no effects for highlighting individual benefits or protecting others. No available evidence existed to assess any distinct differences in effects between using the terms ‘physical distancing’ and ‘social distancing’. Analysis of 463 papers containing data showed generally large samples; 418 involved human participants with a mean of 16,848 (median of 1,699). That statistical power underscored improved suitability of behavioural science research for informing policy decisions. Furthermore, by implementing a standardized approach to evidence selection and synthesis, we amplify broader implications for advancing scientific evidence in policy formulation and prioritization

Switching and memory characteristics of thin films of an ambipolar organic compound: effects of device processing and electrode materials

We report on the effects of device processing conditions, and of changing the electrode materials, on the switching and negative differential resistance (NDR) behaviour of metal/organic thin film/metal structures. The organic material was an ambipolar molecule containing both electron transporting (oxadiazole) and hole transporting (carbazole) chemical groups. Switching and NDR effects are observed for device architectures with both electrodes consisting of aluminium; optimized switching behaviour is achieved for structures incorporating gold nanoparticles. If one of the Al electrodes is replaced by a higher work function metal or coated with an electron-blocking layer, switching and NDR are no longer observed. The results are consistent with a model based on the creation and destruction of Al filaments within the thin organic layer

Methylated lysine 79 of histone H3 targets 53BP1 to DNA double-strand breaks

The mechanisms by which eukaryotic cells sense DNA doublestrand breaks (DSBs) in order to initiate checkpoint responses are poorly understood. 53BP1 is a conserved checkpoint protein with properties of a DNA DSB sensor 1-5. Here, we solved the structure of the domain of 53BP1 that recruits it to sites of DSBs. This domain consists of two tandem tudor folds with a deep pocket at their interface formed by residues conserved in the budding yeast Rad9 and fission yeast Rhp9/Crb2 orthologues. In vitro, the 53BP1 tandem tudor domain bound histone H3 methylated on Lys 79 using residues that form the walls of the pocket; these residues were also required for recruitment of 53BP1 to DSBs. Suppression of DOT1L, the enzyme that methylates Lys 79 of histone H3, also inhibited recruitment of 53BP1 to DSBs. Because methylation of histone H3 Lys 79 was unaltered in response to DNA damage, we propose that 53BP1 senses DSBs indirectly through changes in higher-order chromatin structure that expose the 53BP1 binding site