Landscape structure planning and the urban forest in polycentric city regions

© Published under licence by IOP Publishing Ltd. The World is continuing to urbanise at an increasing and some say alarming rate, and although urbanism is not uniform in all countries, without a doubt the 21 st century is the century of the Polycentric City Region. By the year 2007, for the first time in history, the world hosted more urban dwellers than rural, and in order to deal with this urban expansion in an environmentally acceptable way, the concept of the "sustainable compact city" was advocated. There is now an increasing canon of research however that suggests that such cities may not be quite as sustainable as they are claimed to be. As a consequence, the concept of "urban green infrastructure", which includes the concept of urban forestry, is being incorporated into new thinking on the landscape structure planning of expanding cities and city regions to ensure that they provide an acceptable quality of life for their inhabitants. The environmental, economic, social, health, well-being and cultural benefits that emanate from such an approach to promoting resilient landscape structure planning are considerable. Such an approach to landscape structure planning is well-able to repair the beneficial relationship that people once had with their landscapes, a relationship that has arguably suffered as our scientific and economic cultures have tended to gain the upper hand in the post-industrial times in which we live. Human beings have had a long, deep, cultural relationship with trees, woodlands and the landscape - a relationship which transcends national cultures. The use of the term "landscape" does not refer to the rather shallow modern concept of 'the landscape as a view", but to the more fundamental concept of "landscape as the composition of our world". Thus it refers to both urban, peri-urban and rural areas, and the urban forest is the prime spatial articulator of a landscape structure plan. Although the words "forest" and "forestry" are now generally understood to be connected with trees, the words have arguably been derived from the Latin word "foris", meaning "out of doors" or "unenclosed land" (Porteous, 1928 p34). Thus urban forestry could be described as the "urban out of doors". This presentation will consider the benefits that can be achieved from developing a viable urban forest structure as the backbone of a polycentric city region landscape structure plan. It will focus upon the Leeds Polycentric City Region in the UK and its emerging Leeds City Region Green and Blue Infrastructure Strategy 2017 - 2036 as a case study

Rupture of multiple parallel molecular bonds under dynamic loading

Biological adhesion often involves several pairs of specific receptor-ligand molecules. Using rate equations, we study theoretically the rupture of such multiple parallel bonds under dynamic loading assisted by thermal activation. For a simple generic type of cooperativity, both the rupture time and force exhibit several different scaling regimes. The dependence of the rupture force on the number of bonds is predicted to be either linear, like a square root or logarithmic.Comment: 8 pages, 2 figure

Cycle-finite module categories

We describe the structure of module categories of finite dimensional algebras over an algebraically closed field for which the cycles of nonzero nonisomorphisms between indecomposable finite dimensional modules are finite (do not belong to the infinite Jacobson radical of the module category). Moreover, geometric and homological properties of these module categories are exhibited

Descriptions of membrane mechanics from microscopic and effective two-dimensional perspectives

Mechanics of fluid membranes may be described in terms of the concepts of mechanical deformations and stresses, or in terms of mechanical free-energy functions. In this paper, each of the two descriptions is developed by viewing a membrane from two perspectives: a microscopic perspective, in which the membrane appears as a thin layer of finite thickness and with highly inhomogeneous material and force distributions in its transverse direction, and an effective, two-dimensional perspective, in which the membrane is treated as an infinitely thin surface, with effective material and mechanical properties. A connection between these two perspectives is then established. Moreover, the functional dependence of the variation in the mechanical free energy of the membrane on its mechanical deformations is first studied in the microscopic perspective. The result is then used to examine to what extent different, effective mechanical stresses and forces can be derived from a given, effective functional of the mechanical free energy.Comment: 37 pages, 3 figures, minor change

Gorenstein homological algebra and universal coefficient theorems

We study criteria for a ring—or more generally, for a small category—to be Gorenstein and for a module over it to be of finite projective dimension. The goal is to unify the universal coefficient theorems found in the literature and to develop machinery for proving new ones. Among the universal coefficient theorems covered by our methods we find, besides all the classic examples, several exotic examples arising from the KK-theory of C*-algebras and also Neeman’s Brown–Adams representability theorem for compactly generated categories

Elastic deformation of a fluid membrane upon colloid binding

When a colloidal particle adheres to a fluid membrane, it induces elastic deformations in the membrane which oppose its own binding. The structural and energetic aspects of this balance are theoretically studied within the framework of a Helfrich Hamiltonian. Based on the full nonlinear shape equations for the membrane profile, a line of continuous binding transitions and a second line of discontinuous envelopment transitions are found, which meet at an unusual triple point. The regime of low tension is studied analytically using a small gradient expansion, while in the limit of large tension scaling arguments are derived which quantify the asymptotic behavior of phase boundary, degree of wrapping, and energy barrier. The maturation of animal viruses by budding is discussed as a biological example of such colloid-membrane interaction events.Comment: 14 pages, 9 figures, REVTeX style, follow-up on cond-mat/021242

On Arnold's 14 `exceptional' N=2 superconformal gauge theories

We study the four-dimensional superconformal N=2 gauge theories engineered by the Type IIB superstring on Arnold's 14 exceptional unimodal singularities (a.k.a. Arnold's strange duality list), thus extending the methods of 1006.3435 to singularities which are not the direct sum of minimal ones. In particular, we compute their BPS spectra in several `strongly coupled' chambers. From the TBA side, we construct ten new periodic Y-systems, providing additional evidence for the existence of a periodic Y-system for each isolated quasi-homogeneous singularity with $\hat c<2$ (more generally, for each N=2 superconformal theory with a finite BPS chamber whose chiral primaries have dimensions of the form N/l).Comment: 73 pages, 7 figure