Automorphisms of Partially Commutative Groups II: Combinatorial Subgroups

We define several "standard" subgroups of the automorphism group Aut(G) of a partially commutative (right-angled Artin) group and use these standard subgroups to describe decompositions of Aut(G). If C is the commutation graph of G, we show how Aut(G) decomposes in terms of the connected components of C: obtaining a particularly clear decomposition theorem in the special case where C has no isolated vertices. If C has no vertices of a type we call dominated then we give a semi-direct decompostion of Aut(G) into a subgroup of locally conjugating automorphisms by the subgroup stabilising a certain lattice of "admissible subsets" of the vertices of C. We then characterise those graphs for which Aut(G) is a product (not necessarily semi-direct) of two such subgroups.Comment: 7 figures, 63 pages. Notation and definitions clarified and typos corrected. 2 new figures added. Appendix containing details of presentation and proof of a theorem adde

The Aggregation Kinetics of a Simulated Telechelic Polymer

We investigate the aggregation kinetics of a simulated telechelic polymer gel. In the hybrid Molecular Dynamics (MD) / Monte Carlo (MC) algorithm, aggregates of associating end groups form and break according to MC rules, while the position of the polymers in space is dictated by MD. As a result, the aggregate sizes change every time step. In order to describe this aggregation process, we employ master equations. They define changes in the number of aggregates of a certain size in terms of reaction rates. These reaction rates indicate the likelihood that two aggregates combine to form a large one, or that a large aggregate splits into two smaller parts. The reaction rates are obtained from the simulations for a range of temperatures. Our results indicate that the rates are not only temperature dependent, but also a function of the sizes of the aggregates involved in the reaction. Using the measured rates, solutions to the master equations are shown to be stable and in agreement with the aggregate size distribution, as obtained directly from simulation data. Furthermore, we show how temperature induced variations in these rates give rise to the observed changes in the aggregate distribution that characterizes the sol-gel transition.Comment: 9 pages, 10 figure

Proposed Vertical Expansion Tunnel

It is proposed that the adverse effects from secondary diaphragm rupture in an expansion tunnel may be reduced or eliminated by orienting the tunnel vertically, matching the test gas pressure and the accelerator gas pressure, and initially separating the test gas from the accelerator gas by density stratification. This proposed configuration is termed the vertical expansion tunnel. Two benefits are 1) the removal of the diaphragm particulates in the test gas after its rupture, and 2) the elimination of the wave system that is a result of a real secondary diaphragm having a finite mass and thickness. An inviscid perfect-gas analysis and quasi-one-dimensional Euler computations are performed to find the available effective reservoir conditions (pressure and mass specific enthalpy) and useful test time in a vertical expansion tunnel for comparison to a conventional expansion tunnel and a reflected-shock tunnel. The maximum effective reservoir conditions of the vertical expansion tunnel are higher than the reflected-shock tunnel but lower than the expansion tunnel. The useful test time in the vertical expansion tunnel is slightly longer than the expansion tunnel but shorter than the reflected-shock tunnel. If some sacrifice of the effective reservoir conditions can be made, the vertical expansion tunnel could be used in hypervelocity ground testing without the problems associated with secondary diaphragm rupture

Fluid Mechanics of Everyday Objects

High speed Schlieren videos were produced highlighting the fluid mechanics found in everyday objects. This video (entry 102369) was submitted as part of the Gallery of Fluid Motion 2013, which is a showcase of fluid dynamics videos.Comment: Both a high-resolution version and a low-resolution version of the submitted video are available for downloa

落ちそむる梧桐(あおぎり)の葉 : 稲賀恵四郎（南畝, 1865-1901）の漢詩

The heart of this piece is a series of annotated translations of kanshi (poems in Chinese) by Inaga Keishirō (Nanpo, 1865–1901), an educator and amateur poet from Tottori prefecture. Eighty-six of Nanpo’s poems were rediscovered in 2000. The translators have deciphered the holograph poem texts and placed the poetry in context. Their introductory essay offers a biography of the poet and an outline of Meiji kanshi practice, and comments on developments in the world of kangaku. Kanshi during this period experienced its final flowering, remaining popular despite the trend toward modernity and Westernization and Japan’s gradual retreat from its Sinitic traditions. The kanshi renaissance of the Meiji era produced a large volume of appealing and lively poetry and reflected kanshi’s broadened demographic appeal. Several factors were at work, including educational reform and growth in the literacy rate, the reopening of contacts with China, expansion of the media, and a conservative reaction against modernization that set in during the 1880s. Much of Nanpo’s verse, like late Edo kanshi generally, displays a distinctively Japanese flavor; Chinese allusions are infrequent, as are conspicuous efforts to imitate past poets. His kanshi tend to be more conventional than novel or political in theme; in tone, the poems range from grave or melancholy to contented, even jocular. The introduction concludes with an analysis of Nanpo’s poetic style, topoi, diction, and his poetic persona. Despite the profusion of socio-political changes occurring around them, many kanshi poets in Meiji Japan remained content with traditional themes, even while giving the occasional nod to modernity. Nanpo was among these poets, who outnumbered the better known modernists of the kanshi world

East Asia and the global/transatlantic/Western crisis

This paper introduces the special collection on East Asia and the Global Crisis. After justifying why a focus on East Asia is appropriate, it draws out the main themes that run through the individual contributions. These are the extent to which the region is decoupling from the global economy (or the West), the increasing legitimacy of statist alternatives to neoliberal development strategies, and the impact of crises on the definition of ―region‖ and the functioning of regional institutions and governance mechanisms