Developments in quantitative luminescence techniques

Developments in quantitative luminescence technique

Fundamental Differences in Mechanical Behavior between Two Types of Crystals at the Nanoscale

We present differences in the mechanical behavior of nanoscale gold and molybdenum single crystals. A significant strength increase is observed as the size is reduced to 100 nm. Both nanocrystals exhibit discrete strain bursts during plastic deformation. We postulate that they arise from significant differences in the dislocation behavior. Dislocation starvation is the predominant mechanism of plasticity in nanoscale fcc crystals, while junction formation and hardening characterize bcc plasticity. A statistical analysis of strain bursts is performed as a function of size and compared with stochastic models

Solution to the problem of the poor cyclic fatigue resistance of bulk metallic glasses

The recent development of metallic glass-matrix composites represents a particular milestone in engineering materials for structural applications owing to their remarkable combination of strength and toughness. However, metallic glasses are highly susceptible to cyclic fatigue damage, and previous attempts to solve this problem have been largely disappointing. Here, we propose and demonstrate a microstructural design strategy to overcome this limitation by matching the microstructural length scales (of the second phase) to mechanical crack-length scales. Specifically, semisolid processing is used to optimize the volume fraction, morphology, and size of second-phase dendrites to confine any initial deformation (shear banding) to the glassy regions separating dendrite arms having length scales of ≈2 μm, i.e., to less than the critical crack size for failure. Confinement of the damage to such interdendritic regions results in enhancement of fatigue lifetimes and increases the fatigue limit by an order of magnitude, making these “designed” composites as resistant to fatigue damage as high-strength steels and aluminum alloys. These design strategies can be universally applied to any other metallic glass systems

Microprobe Attachment for Quantitative Studies of Cathode Luminescence

Monochromator photomultiplier attachment to electron microprobe for measuring luminescence of enstatit

Mounting Materials for Automated Image Analysis of Coals Using Backscattered Electron Imaging

In order to apply SEM-based automated image analysis (AIA) to the characterization of not only minerals in coal but to the coal itself, sample preparation methods need to be developed beyond common practice. A significant consideration is the degree of contrast achievable between the mount media chosen and the coal. Four low-atomic number materials (epoxy, polyethylene, polystyrene and carnauba wax) were compared for their potential as suitable mounting media for coal samples. Epoxy is satisfactory only for characterization of mineral particles since the contrast between epoxy and coal particles is negligible. Polyethylene or polystyrene have marginal application for use as mounting material for coal characterization due to limited contrast and sample preparation artifacts. Carnauba wax appears satisfactory as a mounting material since it provides good contrast with coal particles with minimal artifacts

Stimuli Responsive Shape Memory Microarchitectures

Shape memory polymers (SMPs) respond to heat by generating programmable movement in devices that require substantial deformation and operate at transient temperatures, including stents and embolization coils. To enable their use in small‐scale applications like retinal vasculature stenting, shape transformations must occur in SMPs with complex 3D geometries with nanoscale features. This work describes the synthesis and sculpting of a benzyl methacrylate‐based SMP into 3D structures with <800 nm characteristic critical dimensions via two photon lithography. Dynamic nanomechanical analysis of 8 µm‐diameter cylindrical pillars reveal the initiation of this SMP's glass transition at 60 °C. Shape memory programming of the characterized pillars as well as complex 3D architectures, including flowers with 500 nm thick petals and cubic lattices with 2.5 µm unit cells and overall dimensions of 4.5 µm × 4.5 µm × 10 µm, demonstrate an 86 +/− 4% characteristic shape recovery ratio. These results reveal a pathway toward SMP devices with nanoscale features and arbitrary 3D geometries changing shape in response to temperature

Teaching climate change and sustainability: A survey of teachers in England

This report shares detailed findings as to the current state of climate change and sustainability education in England in 2022-23, with a particular focus on teachers’ practice and professional development. The results reveal both strengths and gaps in the provision of climate change and sustainability education in England. The report serves as an evidence base for researchers, policymakers and practitioners who seek to support teachers to fulfil their important roles in society’s transformation to a sustainable future. UCL’s Centre for Climate Change and Sustainability Education (CCCSE) conducted a survey of teachers in England entitled ‘What do climate change and sustainability education have to do with me?’. Between October and December 2022, teachers were invited to respond to an online questionnaire about their views and experiences. Teachers were recruited through email lists, professional networks, social media and via the CCCSE website. The questionnaire investigated their teaching practice, professional development, and sense of confidence and preparedness to incorporate climate change and sustainability into their teaching. It included a range of question types and generated quantitative and qualitative data. The survey gathered 870 responses, with over two thirds (70.7%) teaching at secondary level, and geography (41.3%) and science (37.2%) being the most frequently reported subjects taught. Those who responded represented a wide range of teaching experience, from one year to 20+ years, with university-led PGCE programmes the most commonly reported route into teaching (87.2%). The significant majority of respondents were female (73.9%) and from white backgrounds (90.5%)

Labelling, Deviance and Media

Labelling theory is a perspective that emerged as a distinctive approach to criminology during the 1960s, and was a major seedbed of the radical and critical perspectives that became prominent in the 1970s. It represented the highpoint of an epistemological shift within the social sciences away from positivism – which had dominated criminological enquiry since the late-1800s – and toward an altogether more relativistic stance on the categories and concepts of crime and control. It inspired a huge amount of work throughout the 1960s and 1970s, and still resonates powerfully today. This short chapter maps out some of the ways in which labelling, deviance, media and justice interact at the levels of definition and process. It presents an overview and analysis of key mediatised labelling processes, such as the highly influential concept of moral panics. It discusses how the interconnections between labelling, crime and criminal justice are changing in a context of technological development, cultural change and media proliferation. The conclusion offers an assessment and evaluation of labelling theory’s long-term impact on criminology