Art Historical Explanation Of Paintings And The Need For An Aesthetics Of Agency

Why should a person, and in the context of this conference particularly an art historian, take seriously the notion of the aesthetic, its discovery and/or rediscovery? Aesthetics might after all be considered at best something of a distraction from bread and butter historical and sociological analysis, and at worst entirely incompatible with it. Pursuing the line further it might be urged that, since on the one hand aesthetics is about 'how things appear'—i.e. is subject to individual predilection, taste and feeling—and on the other, historical analysis is about the careful and scholarly reconstruction of a past social reality, the two must be at loggerheads. What the art historian writes about on a weekday whilst wearing her hard hat at the office must not be confused with what she personally feels, wandering around a gallery in her woolly hat at the weekend

Survival of habitable planets in unstable planetary systems

Many observed giant planets lie on eccentric orbits. Such orbits could be the result of strong scatterings with other giant planets. The same dynamical instability that produces these scatterings may also cause habitable planets in interior orbits to become ejected, destroyed, or be transported out of the habitable zone. We say that a habitable planet has resilient habitability if it is able to avoid ejections and collisions and its orbit remains inside the habitable zone. Here we model the orbital evolution of rocky planets in planetary systems where giant planets become dynamically unstable. We measure the resilience of habitable planets as a function of the observed, present-day masses and orbits of the giant planets. We find that the survival rate of habitable planets depends strongly on the giant planet architecture. Equal-mass planetary systems are far more destructive than systems with giant planets of unequal masses. We also establish a link with observation; we find that giant planets with present-day eccentricities higher than 0.4 almost never have a habitable interior planet. For a giant planet with an present-day eccentricity of 0.2 and semimajor axis of 5 AU orbiting a Sun-like star, 50% of the orbits in the habitable zone are resilient to the instability. As semimajor axis increases and eccentricity decreases, a higher fraction of habitable planets survive and remain habitable. However, if the habitable planet has rocky siblings, there is a significant risk of rocky planet collisions that would sterilize the planet.Comment: Accepted to MNRA

How to form planetesimals from mm-sized chondrules and chondrule aggregates

The size distribution of asteroids and Kuiper belt objects in the solar system is difficult to reconcile with a bottom-up formation scenario due to the observed scarcity of objects smaller than $\sim$100 km in size. Instead, planetesimals appear to form top-down, with large $100-1000$ km bodies forming from the rapid gravitational collapse of dense clumps of small solid particles. In this paper we investigate the conditions under which solid particles can form dense clumps in a protoplanetary disk. We use a hydrodynamic code to model the interaction between solid particles and the gas inside a shearing box inside the disk, considering particle sizes from sub-millimeter-sized chondrules to meter-sized rocks. We find that particles down to millimeter sizes can form dense particle clouds through the run-away convergence of radial drift known as the streaming instability. We make a map of the range of conditions (strength of turbulence, particle mass-loading, disk mass, and distance to the star) which are prone to producing dense particle clumps. Finally, we estimate the distribution of collision speeds between mm-sized particles. We calculate the rate of sticking collisions and obtain a robust upper limit on the particle growth timescale of $\sim$$10^5$ years. This means that mm-sized chondrule aggregates can grow on a timescale much smaller than the disk accretion timescale ($\sim$$10^6 - 10^7$ years). Our results suggest a pathway from the mm-sized grains found in primitive meteorites to fully formed asteroids. We speculate that asteroids may form from a positive feedback loop in which coagualation leads to particle clumping driven by the streaming instability. This clumping, in turn reduces collision speeds and enhances coagulation.} Future simulations should model coagulation and the streaming instability together to explore this feedback loop further.Comment: 20 pages. Accepted for publication in A&

Toward an initial mass function for giant planets

The distribution of exoplanet masses is not primordial. After the initial stage of planet formation is complete, the gravitational interactions between planets can lead to the physical collision of two planets, or the ejection of one or more planets from the system. When this occurs, the remaining planets are typically left in more eccentric orbits. Here we use present-day eccentricities of the observed exoplanet population to reconstruct the initial mass function of exoplanets before the onset of dynamical instability. We developed a Bayesian framework that combines data from N-body simulations with present-day observations to compute a probability distribution for the planets that were ejected or collided in the past. Integrating across the exoplanet population, we obtained an estimate of the initial mass function of exoplanets. We find that the ejected planets are primarily sub-Saturn type planets. While the present-day distribution appears to be bimodal, with peaks around $\sim 1 M_{\rm J}$ and $\sim 20 M_\oplus$, this bimodality does not seem to be primordial. Instead, planets around $\sim 60 M_\oplus$ appear to be preferentially removed by dynamical instabilities. Attempts to reproduce exoplanet populations using population synthesis codes should be mindful of the fact that the present population has been depleted of intermediate-mass planets. Future work should explore how the system architecture and multiplicity might alter our results.Comment: 10 pages, 9 figures; submitted to MNRA

Expanding alliance: ANZUS cooperation and Asia–Pacific security

Is an alliance conceived as a bulwark against a resurgence of Japanese militarism and which cut its military and intelligence teeth in the Cold War is still relevant to today’s strategic concerns? Overview The alliance between Australia and the US, underpinned by the formal ANZUS Treaty of 1951, continues to be a central part of Australian defence and security thinking and an instrument of American policy in the Asia–Pacific. How is it that an alliance conceived as a bulwark against a resurgence of Japanese militarism and which cut its military and intelligence teeth in the Cold War is still relevant to today’s strategic concerns? The answer is partly—and importantly—that the core values of the ANZUS members are strongly aligned, and successive Australian governments and American presidential administrations have seen great value in working with like-minded partners to ensure Asia–Pacific security. Far from becoming a historical curiosity, today it’s not just relevant, but of greater importance than has been the case in the past few decades. To explore new ideas on how to strengthen the US–Australia alliance, ASPI conducted a high-level strategic dialogue in Honolulu in July this year. Discussions canvassed the future strategic environment; the forthcoming Australian Defence White Paper; budget, sovereignty and expectation risks; and cooperation in the maritime, land, air, cyber, space and intelligence domains. A key purpose of the Honolulu dialogue was to help ASPI develop policy recommendations on the alliance relationship for government. This report is the product of those discussions

Planetesimal formation by the streaming instability in a photoevaporating disk

Recent years have seen growing interest in the streaming instability as a candidate mechanism to produce planetesimals. However, these investigations have been limited to small-scale simulations. We now present the results of a global protoplanetary disk evolution model that incorporates planetesimal formation by the streaming instability, along with viscous accretion, photoevaporation by EUV, FUV, and X-ray photons, dust evolution, the water ice line, and stratified turbulence. Our simulations produce massive (60-130 $M_\oplus$) planetesimal belts beyond 100 au and up to $\sim 20 M_\oplus$ of planetesimals in the middle regions (3-100 au). Our most comprehensive model forms 8 $M_\oplus$ of planetesimals inside 3 au, where they can give rise to terrestrial planets. The planetesimal mass formed in the inner disk depends critically on the timing of the formation of an inner cavity in the disk by high-energy photons. Our results show that the combination of photoevaporation and the streaming instability are efficient at converting the solid component of protoplanetary disks into planetesimals. Our model, however, does not form enough early planetesimals in the inner and middle regions of the disk to give rise to giant planets and super-Earths with gaseous envelopes. Additional processes such as particle pileups and mass loss driven by MHD winds may be needed to drive the formation of early planetesimal generations in the planet forming regions of protoplanetary disks.Comment: 20 pages, 12 figures; accepted to Ap

Ten Years of Universal Primary Technology Education in England and Wales - What have we learnt?

In this paper I will attempt to outline the long and complex history of National Curriculum technology at primary level, celebrating the successes as well as analysing the mistakes. It is, in the words of the chairman of the National Curriculum Council (NCC), a 'lesson for us all' (Graham 1993) and makes salutary reading for any country or state about to embark upon the implementation of its own primary technology curriculum. The story in England and Wales is one of 'free-market curriculum making' in which: "; ... policy for technology education has emerged in an unplanned way by a process of action and reaction, involving initiatives and proposals from a variety of stakeholders ... "; (Layton 1995, p. 114

Representation of multiple engineering viewpoints in Computer Aided Design through computer-interpretable descriptive markup

The aim of this work was to find a way of representing multiple interpretations of a product design with the same CAD model and in a way that allowed reduction of the manual work of producing the viewpoint specific models of the product through automation The approach presented is the recording of multiple viewpoint-interpretations of a product design with a CAD product model using descriptive, by-reference (stand-off) computer interpretable markup of the model.EThOS - Electronic Theses Online ServiceGBUnited Kingdo