New experimental test of strain-gradient plasticity theory: metal foil sandwich structures in flexure

Experimental tests of strain-gradient plasticity theory rely on studies of the size effect (smaller is stronger) in micromechanical testing. The plastic strain gradient is varied by varying the size of the specimen. This confounds the direct effects of the size and the effects of the strain gradient. We propose experiments on foil sandwich structures in which these parameters are separated. Preliminary results suggest that it is the foil thickness that determines the strength, not the strain gradient.     

In situ characterization of the martensitic transformation temperature of NiTi shape memory alloys via instrumented microindentation

A novel, instrumented microindentation technique was successfully used to measure the temperature associated with the martensitic transformation leading to the recovery of plastic strain in a Nickel–Titanium (NiTi) shape memory alloy. Following a standard indentation cycle, the indenter was partially unloaded such that a good contact was maintained between indenter and specimen surface. The onset and finish temperature of the martensitic transformation, the associated volume contraction, and the amount of the recovered plastic deformation were determined by quantifying the indenter displacement as a function of temperature. These experiments were compared to conventional measurements of the transformation temperature by differential scanning calorimetry and compression testing.     

Anisotropic thermal properties of single-wall-carbon- nanotube-reinforced nanoceramics

Dense single-wall-carbon-nanotube-(SWCNT)-reinforced alumina nanocomposites have been fabricated by a novel spark-plasma-sintering technique. Anisotropic thermal properties have been found in carbon nanotube composites. The introduction of ropes of SWCNTs gives rise to a decrease in the transverse thermal diffusivity with increasing carbon nanotube content while it does not change the in-plane thermal diffusivity. This is scientifically interesting and technologically important for the development of materials for novel thermal barrier coatings.     

Vertex interactions and film shapes in two-dimensional foam

A model of the structure of two-dimensional foam (cells separated by circular arcs (films) meeting at threefold vertices) is considered. Films that are so curved as to be nearly semicircular arcs are problematic for conventional foam structure computations, which aim to identify the pressures needed to achieve specified bubble areas. When the films have near semicircularity, tiny variations in pressure can lead to large changes in the computed bubble area, and hence a failure to meet the specified targets. A new algorithm for determining foam structure is presented. It is based on 'freezing' most of the system, except the nearly semicircular arcs, and then finding the particular bubble pressures associated with the latter via an analytic approximation. This procedure is shown to work well for structure relaxation in a small bubble cluster. Large relaxed bubble clusters are considered briefly at the end of the paper.     

Investigation of {111} stacking faults and nanotwins in epitaxial BaTiO3 thin films by high-resolution transmission electron microscopy

{111} stacking faults and nanotwins in epitaxial BaTiO₃ thin films on MgO substrates have been investigated by high-resolution transmission electron microscopy. In many cases, the stacking faults and nanotwins were found to be accompanied by partial dislocations. These partial dislocations can be classified as two different types, analogous to the situation in the fcc structure. One is of the Shockley type with the Burgers vector (a/3)<112>. The other is of the Frank type with the Burgers vector (a/3)<111>. The movements of both types of partial can lead to the {111} stacking faults and the {111} twins observed in these films.     

Thermodynamics of void nucleation in nanoparticles

The nucleation of voids at the initial stage of hollow nanoshell formation is described in terms of the thermodynamics of nucleation in systems of finite size (or small systems) pumped with vacancies by interdiffusion-driven vacancy influx. Crossovers from suppressed nucleation to metastable nucleus formation and then to stable nucleus formation are analysed, describing, in particular, the possibility of significant supersaturations with vacancies of the metallic core. It is shown that at higher temperatures it becomes more favourable to nucleate at once a large single void instead of multiple tiny voids.     

Molecular dynamics simulations of the size effect of titanium single-crystal nanopillars orientated for double prismatic slips

An inverse “smaller is stronger” trend is predicted on the basis of molecular dynamics simulations of α-titanium (Ti) single-crystal nanopillars orientated for double prismatic slips when the nanopillars are less than 7?nm wide. This trend is attributed to a significant increase in the surface energy due to the nucleation and propagation of edge dislocations on the surface of the pillars.     

Charles Darwin: Continuity,Teleology and Ideology

Climate change has mutated from being a physical phenomenon to be studied to an idea to be contested. The sites of adjudication between competing truth claims have therefore moved from the secluded academy and scientific peer review to the vociferous agora and the extended peer community. This move is illustrated here using the case of the shrinking glaciers of Mt Kilimanjaro. Both the British engineer Guy Callendar, in 1944, and the American campaigner Al Gore, in 2006, claimed that the primary cause of this glacial recession was rising world temperature. Both were passionate believers in the reality of human-induced global warming, but they had very different resources at their disposal to advance these beliefs. While Callendar's claim was revealed only to the editor of the science journal Nature, Gore's claims were visible to millions through his film An Inconvenient Truth. While the force of Callendar's claim was weighed and adjudicated by one peer reviewer, the validity of Gore's claim was tested very publicly in the British courts. Both claims about the cause of Kilimanjaro's retreating glaciers were found wanting. The paper argues that this simple, but powerful, comparison between identical claims-making drawn from two different eras of science, yet with contrasting processes of truth-adjudication, illuminates the different ‘post-normal’ world of science climate change now inhabits. The case study is used to reflect on the role of the extended peer community in establishing and validating scientific knowledge about climate change: who participates, how trust is stabilised and whether science is thereby democratised.     

State-Supported Science and Imaginary Lock-in: The Case of Regenerative Medicine in Japan

Abstract

Regenerative medicine (RM) in Japan lays strong emphasis on a specific trajectory of its development, which deploys human induced pluripotent stem (iPS) cells as the primary sources for the technology. The technique to create these stem cells was developed in 2006 by a Japanese stem cell scientist, Shinya Yamanaka, and since its applicability to human cells was established about a year later, this new type of cells has become to be considered as a potential substitute for human embryonic stem cells. While the clinical value of these cells are yet to be confirmed, the Japanese Ministry of Education, Culture, Sports, Science and Technology decided to concentrate its support on iPS cells research and turned it into a national project. This decision reflected the state's vision of initiating the transition to a knowledge-based society, which was adopted in the 1990s to tackle the prolonged deflation in the country. As the research became intertwined with this policy vision, however, the Ministry came to see bringing its success as more important than ever, while other trajectories of RM were left underrated and largely unsupported. Industrial actors counteracted this situation and developed an initiative to recognize existing technical capability in the country, but its impact has been so far negligible. This indicates that the nation is locked in the particular trajectory of RM. Hence, this Japanese RM research enterprise presents an interesting case to understand how states' commitment may not only shape the course of scientific research but also reduce flexibility in technological development.     

In the Netherlands the anti-Flynn effect is a Jensen effect

In this study, 63 observations of secular IQ changes (both Flynn and anti-Flynn effects) are collected from three demographically diverse studies of the Dutch population for the period 1975–2005 (representing the 1950–1990 birth cohorts), along with data on g loadings and subtest reliabilities. The method of correlated vectors is used to explore the association between Flynn and anti-Flynn effect magnitudes, both independently and together, and the g loadings of subtests. Despite a positive vector correlation the Flynn effects are not associated with the Jensen effect (r = .307, ns, N = 36), however the anti-Flynn effects are (r = .406, P = .05, N = 27). Combined, the vector correlation becomes negative but non-significant (r = −.111, ns, N = 63). Declines due to the anti-Flynn effect are estimated at −4.515 points per decade, whereas gains due to the Flynn effect are estimated at 2.175 points per decade. The N-weighted net of these is a loss of −1.350 points per decade, suggesting an overall tendency towards decreasing IQ in the Netherlands with respect to these cohorts. The Jensen effect on the anti-Flynn effect suggests that it may be related to bio-demographic changes within the Netherlands which have reduced ‘genetic-g’, despite the presence of large, parallel gains on subtests that may be relatively more sensitive to cultural-environmental improvements.