Från koja till plan

This thesis concerns questions regarding how children’s perspectives on the outdoor environment can be approached in a planning context. Attention is drawn to the general understanding of childhood and the definition of outdoor environment as variables in different planning contexts. Together these variables define in which way children become visible in the planning context. Children’s participation is emphasized in contemporary planning. This thesis argues that understanding and insights concerning children’s experiences and understanding of their own places can create complementary lines of communication. The first article provides the empirical and methodological point of departure. Through walkabouts with children, questions are developed concerning children’s use and experiences of outdoor environments. These questions are compared and related to problems, insights and experiences that planners have concerning environments for children. Parts of two perspectives are described in order to elucidate some of the problems that can arise due to differences between a child’s perspective and a planner’s perspective. In the second article children’s own places is the pivot. Through in depth studies of children’s dens it is shown that finding a suitable place, collecting, sorting and manipulating with environment and accessible materials are crucial parts of starting a den making process and appropriating a place as one’s own. Specific examples are put forward which show the close relationship between children’s experience and understanding of the outdoor environment and their construction and design of dens. Children’s dens are used to exemplify and clarify the difference between children’s perspectives and planner’s perspectives. The last article is concerned with the theoretical and practical analysis of these questions. Through interviews, studies of planning documents and reflections on my own planning experience an analysis is made of the importance of maps and plans as tools in the planning process. It is argued that the bias of these tools emphasizes and reinforces the visual point of departure to the physical environment and outdoor places, while children’s multi-sensuous and acting oriented point of departure is difficult to handle and process in maps and plans. A practical contribution is suggested on how to improve insights and understanding of children’s perspectives in planning contexts

Knots, links, anyons and statistical mechanics of entangled polymer rings

The field theory approach to the statistical mechanics of a system of N polymer rings linked together is extended to the case of links whose paths in space are characterized by a fixed number 2s of maxima and minima. Such kind of links are called 2s-plats and appear for instance in the DNA of living organisms or in the wordlines of quasiparticles associated with vortices nucleated in a quasi-two-dimensional superfluid. The path integral theory describing the statistical mechanics of polymers subjected to topological constraints is mapped here into a field theory of quasiparticles (anyons). In the particular case of s=2, it is shown that this field theory admits vortex solutions with special self-dual points in which the interactions between the vortices vanish identically. The topological states of the link are distinguished using two topological invariants, namely the Gauss linking number and the so-called bridge number which is related to s. The Gauss linking number is a topological invariant that is relatively weak in distinguishing the different topological configurations of a general link. The addition of topological constraints based on the bridge number allows to get a glimpse into the non-abelian world of quasiparticles, which is relevant for important applications like topological quantum computing and high-TC superconductivity. At the end an useful connection with the cosh-Gordon equation is shown in the case s=2. © 201

MAP4K family kinases act in parallel to MST1/2 to activate LATS1/2 in the Hippo pathway.

The Hippo pathway plays a central role in tissue homoeostasis, and its dysregulation contributes to tumorigenesis. Core components of the Hippo pathway include a kinase cascade of MST1/2 and LATS1/2 and the transcription co-activators YAP/TAZ. In response to stimulation, LATS1/2 phosphorylate and inhibit YAP/TAZ, the main effectors of the Hippo pathway. Accumulating evidence suggests that MST1/2 are not required for the regulation of YAP/TAZ. Here we show that deletion of LATS1/2 but not MST1/2 abolishes YAP/TAZ phosphorylation. We have identified MAP4K family members--Drosophila Happyhour homologues MAP4K1/2/3 and Misshapen homologues MAP4K4/6/7-as direct LATS1/2-activating kinases. Combined deletion of MAP4Ks and MST1/2, but neither alone, suppresses phosphorylation of LATS1/2 and YAP/TAZ in response to a wide range of signals. Our results demonstrate that MAP4Ks act in parallel to and are partially redundant with MST1/2 in the regulation of LATS1/2 and YAP/TAZ, and establish MAP4Ks as components of the expanded Hippo pathway

Topologically Linked Polymers are Anyon Systems

We consider the statistical mechanics of a system of topologically linked polymers, such as for instance a dense solution of polymer rings. If the possible topological states of the system are distinguished using the Gauss linking number as a topological invariant, the partition function of an ensemble of N closed polymers coincides with the 2N point function of a field theory containing a set of N complex replica fields and Abelian Chern-Simons fields. Thanks to this mapping to field theories, some quantitative predictions on the behavior of topologically entangled polymers have been obtained by exploiting perturbative techniques. In order to go beyond perturbation theory, a connection between polymers and anyons is established here. It is shown in this way that the topological forces which maintain two polymers in a given topological configuration have both attractive and repulsive components. When these opposite components reach a sort of equilibrium, the system finds itself in a self-dual point similar to that which, in the Landau-Ginzburg model for superconductors, corresponds to the transition from type I to type II superconductivity. The significance of self-duality in polymer physics is illustrated considering the example of the so-called $4-plat$ configurations, which are of interest in the biochemistry of DNA processes like replication, transcription and recombination. The case of static vortex solutions of the Euler-Lagrange equations is discussed.Comment: 7 pages, 1 figure, LaTeX +Revtex

Combinatorics of Link Diagrams and Volume

We show that the volumes of certain hyperbolic A-adequate links can be bounded (above and) below in terms of two diagrammatic quantities: the twist number and the number of certain alternating tangles in an A-adequate diagram. We then restrict our attention to plat closures of certain braids, a rich family of links whose volumes can be bounded in terms of the twist number alone. Furthermore, in the absence of special tangles, our volume bounds can be expressed in terms of a single stable coefficient of the colored Jones polynomial. Consequently, we are able to provide a new collection of links that satisfy a Coarse Volume Conjecture.Comment: 17 pages. 15 figure

Lorentzian Flat Lie Groups Admitting a Timelike Left-Invariant Killing Vector Field

We call a connected Lie group endowed with a left-invariant Lorentzian flat metric Lorentzian flat Lie group. In this Note, we determine all Lorentzian flat Lie groups admitting a timelike left-invariant Killing vector field. We show that these Lie groups are 2-solvable and unimodular and hence geodesically complete. Moreover, we show that a Lorentzian flat Lie group $(\mathrm{G},\mu)$ admits a timelike left-invariant Killing vector field if and only if $\mathrm{G}$ admits a left-invariant Riemannian metric which has the same Levi-Civita connection of $\mu$. Finally, we give an useful characterization of left-invariant pseudo-Riemannian flat metrics on Lie groups $\mathrm{G}$ satisfying the property: for any couple of left invariant vector fields $X$ and $Y$ their Lie bracket $[X,Y]$ is a linear combination of $X$ and $Y$

Corn and oats experiments, 1893.

Caption title.Experiments with corn / G.E. Morrow, F.D. Gardner -- Rate of growth and chemical composition of the corn plant / E.H. Farrington -- Experiments with oats, 1893 / G.E. Morrow, F.D. Gardner