Ultra-low-density digitally architected carbon with a strutted tube-in-tube structure

Porous materials with engineered stretching-dominated lattice designs, which offer attractive mechanical properties with ultra-light weight and large surface area for wide-ranging applications, have recently achieved near-ideal linear scaling between stiffness and density. Here, rather than optimizing the microlattice topology, we explore a different approach to strengthen low-density structural materials by designing tube-in-tube beam structures. We develop a process to transform fully dense, three-dimensional printed polymeric beams into graphitic carbon hollow tube-in-tube sandwich morphologies, where, similar to grass stems, the inner and outer tubes are connected through a network of struts. Compression tests and computational modelling show that this change in beam morphology dramatically slows down the decrease in stiffness with decreasing density. In situ pillar compression experiments further demonstrate large deformation recovery after 30-50% compression and high specific damping merit index. Our strutted tube-in-tube design opens up the space and realizes highly desirable high modulus-low density and high modulus-high damping material structures

the fire assay reloaded

The fire assay process is still the most accurate and precise method for measuring the gold content in gold alloys. Scanning electron microscopy and transmission electron microscopy have been applied to observe the change in microstructure of the samples undergoing the fire assay process. The performed observations reveal that the microstructure of the specimen is more complex than expected. Before the parting stage, the specimen is not a perfect gold–silver binary alloy but contains also copper–silver oxides and other residual compounds. The parting stage appears to be a dealloying process leading to a nanoporous gold nanostructure. What observed after partition explains the evolution of the shape and colour of the specimen and may allow for a better comprehension of the procedure and an improvement in the method

Optical spin-to-orbital angular momentum conversion in inhomogeneous anisotropic media

We demonstrate experimentally an optical process in which the spin angular momentum carried by a circularly polarized light beam is converted into orbital angular momentum, leading to the generation of helical modes with a wavefront helicity controlled by the input polarization. This phenomenon requires the interaction of light with matter that is both optically inhomogeneous and anisotropic. The underlying physics is also associated with the so-called Pancharatnam-Berry geometrical phases involved in any inhomogeneous transformation of the optical polarization

ALD Functionalized Nanoporous Gold: Thermal Stability, Mechanical Properties, and Catalytic Activity

Nanoporous metals have many technologically promising applications but their tendency to coarsen limits their long-term stability and excludes high temperature applications. Here, we demonstrate that atomic layer deposition (ALD) can be used to stabilize and functionalize nanoporous metals. Specifically, we studied the effect of nanometer-thick alumina and titania ALD films on thermal stability, mechanical properties, and catalytic activity of nanoporous gold (np-Au). Our results demonstrate that even only one-nm-thick oxide films can stabilize the nanoscale morphology of np-Au up to 1000 C, while simultaneously making the material stronger and stiffer. The catalytic activity of np-Au can be drastically increased by TiO{sub 2} ALD coatings. Our results open the door to high temperature sensor, actuator, and catalysis applications and functionalized electrodes for energy storage and harvesting applications

The impact of televised tobacco control advertising content on campaign recall: evidence from the International Tobacco Control (ITC) United Kingdom Survey

BACKGROUND: Although there is some evidence to support an association between exposure to televised tobacco control campaigns and recall among youth, little research has been conducted among adults. In addition, no previous work has directly compared the impact of different types of emotive campaign content. The present study examined the impact of increased exposure to tobacco control advertising with different types of emotive content on rates and durations of self-reported recall. METHODS: Data on recall of televised campaigns from 1,968 adult smokers residing in England through four waves of the International Tobacco Control (ITC) United Kingdom Survey from 2005 to 2009 were merged with estimates of per capita exposure to government-run televised tobacco control advertising (measured in GRPs, or Gross Rating Points), which were categorised as either “positive” or “negative” according to their emotional content. RESULTS: Increased overall campaign exposure was found to significantly increase probability of recall. For every additional 1,000 GRPs of per capita exposure to negative emotive campaigns in the six months prior to survey, there was a 41% increase in likelihood of recall (OR = 1.41, 95% CI: 1.24–1.61), while positive campaigns had no significant effect. Increased exposure to negative campaigns in both the 1–3 months and 4–6 month periods before survey was positively associated with recall. CONCLUSIONS: Increased per capita exposure to negative emotive campaigns had a greater effect on campaign recall than positive campaigns, and was positively associated with increased recall even when the exposure had occurred more than three months previously

Nanoporous Metal - Combining Strength and Porosity

Recent nanomechanical tests on submicron metal columns and wires have revealed a dramatic increase in yield strength with decreasing sample size. This effect seems to be related to the increased strength observed in metals on decreasing grain size or film thickness, and has been explained by a dislocation nucleation/activation controlled plasticity regime in small sample volumes. The question arises whether one can utilize this new size effect to design materials with improved bulk properties. Here, we demonstrate that nanoporous metal foams can be envisioned as a three-dimensional network of ultrahigh-strength nanocolumns/wires, thus bringing together two seemingly conflicting properties: high strength and high porosity. Specifically, we studied the mechanical properties of nanoporous (np) Au using a combination of nanoindentation and column microcompression tests, as well as supplemental molecular dynamics simulations. We find that np-Au can be as strong as bulk Au, despite being a highly porous material, and that the ligaments in np-Au approach the theoretical yield strength of Au. The combination of high yield strength and high porosity can be used to design a new generation of energy absorbing materials for various engineering applications

The relationship between smokers' motivation to quit and intensity of tobacco control at the population level: a comparison of five European countries

Background: Smoking prevalence differs significantly across Europe. In addition, there are considerable differences in tobacco control activities across European countries. The relationship between prevalence and policy is under-researched. The present analysis examines the motivation to change smoking behaviour across 5 different European countries that differ considerably in their tobacco control activities. Methods: A population-based, representative survey of 1750 smokers, aged 16–59, from 5 different European countries (Germany, Greece, Poland, Sweden, UK) was used. Demographic variables, smoking status and the motivation to stop smoking were assessed. Motivation was assessed as, first, intending to quit (using the stages of change plus a modified stage for Precontemplation), and second, the desire to quit. Results: The majority of smokers want to stop smoking (73.5%), while only 35.0% want to stop definitely. Across countries, 10.2% definitely do not want to stop. Most of the smokers can be categorised in the Precontemplation stage (between 62.6% and 77.7% depending on the country), one of the stages of change categories. The relationship between the stages of change and the country under examination is statistically significant (chi-square = 43.466, p < 0.001). In countries with a high level of tobacco control, the proportion of people in Precontemplation is lower than in countries with low tobacco control activity. Conclusion: There are differences in the stages of change between the countries under examination. However, the categorisation of the countries into low, medium and high tobacco control activity used in this analysis does not explain these differences. Most smokers want to stop smoking, but a high proportion cannot indicate a time-frame when this is going to happen. Tobacco control efforts or other kinds of support might encourage these smokers to actually try to stop. Longitudinal studies at the population level are needed to assess, relate or monitor tobacco control activities and the intention to stop