Empowering Local Communities? An International Review of Community Land Trusts

This paper aims to investigate the premise that community land trusts (CLTs) offer a method of delivering affordable housing that empowers local communities and provides democratic management of community assets. The paper provides a comparative analysis of CLT developments in England, Scotland and the USA, reviewing the policy and literature to identify two key approaches that underpin CLTs: an approach to property development that emphasises resale restrictions used to preserve housing use for the CLT's target clientele, and an approach to citizen governance that privileges local communities. The paper identifies a variation of practices that underpin the operation of CLTs in each country and uses the advanced developments in Scotland and the USA to illustrate some of the challenges that remain if the CLT sector in England is to continue its recent growth.     

Robustness of differentiation cascades with symmetric stem cell division

Stem cells (SCs) perform the task of maintaining tissue homeostasis by both self-renewal and differentiation. While it has been argued that SCs divide asymmetrically, there is also evidence that SCs undergo symmetric division. Symmetric SC division has been speculated to be key for expanding cell numbers in development and regeneration after injury. However, it might lead to uncontrolled growth and malignancies such as cancer. In order to explore the role of symmetric SC division, we propose a mathematical model of the effect of symmetric SC division on the robustness of a population regulated by a serial differentiation cascade and we show that this may lead to extinction of such population. We examine how the extinction likelihood depends on defining characteristics of the population such as the number of intermediate cell compartments. We show that longer differentiation cascades are more prone to extinction than systems with less intermediate compartments. Furthermore, we have analysed the possibility of mixed symmetric and asymmetric cell division against invasions by mutant invaders in order to find optimal architecture. Our results show that more robust populations are those with unfrequent symmetric behaviour.     

Data Work: How Energy Advisors and Clients Make IoT Data Accountable

We present fieldwork findings from the deployment of an interactive sensing system that supports the work of energy advisors who give face-to-face advice to low-income households in the UK. We focus on how the system and the data it produced are articulated in the interactions between professional energy advisors and their clients, and how they collaboratively anticipate, rehearse, and perform data work. In addition to documenting how the system was appropriated in advisory work, we elaborate the ‘overhead cost’ of building collaborative action into connected devices and sensing systems, and the commensurate need to support discrete workflows and accountability systems to enable the methodical incorporation of the IoT into collaborative action. We contribute an elaboration of the social, collaborative methods of data work relevant to those who seek to design and study collaborative IoT systems.     

Comparative behavior of glucose oxidase and oxalate oxidase immobilized in mucin/chitosan hydrogels for biosensors applications

The analytical response of amperometric glucose electrodes was explained in the framework of the properties of hydrogels with different muc/chit ratio at pH = 7.00 used as immobilization matrix for glucose oxidase. The continuous increase in the sensitivity of the electrodes with the amount of chitosan was attributed to a more efficient crosslinking without affecting the enzyme activity. The results were compared with those obtained using the same matrices to immobilize Oxalate Oxidase at pH = 2.85 where it has the highest activity. A maximum sensitivity at muc/chit 70/30 ratio for these oxalate electrodes was observed. Decrease in permeability of negatively charged oxalate with the chitosan content in the matrices, in spite of the high partition coefficient, explains the analytical differences with glucose electrodes. Swelling and viscoelasticity of the hydrogels allowed to asses the importance of a hydrophilic environment for the enzyme in both cases.     

Computing all subtree repeats in ordered trees

We consider the problem of computing all subtree repeats in a given labeled ordered tree. We first transform the tree to a string representing its postfix notation, and then present an algorithm based on the bottom-up technique to solve it. The proposed algorithm consists of two phases: the preprocessing phase and the phase where all subtree repeats are computed. The linear time and space complexity of the proposed algorithm are important parts of its quality.     

The effect of physical aging on the embrittlement of steam-sterilized polycarbonate

Polycarbonate is known to suffer from dramatic reductions in ductility upon exposure to hot, humid environments, such as during steam sterilization. Two phenomena have been proposed to be the main causes of this embrittlement: hydrolysis and microcavity formation. The present study focuses on a third phenomenon, whose contribution to the embrittlement has until now been considered insignificant: (physical) aging. By studying the influence of steam sterilization on the tensile deformation behavior of polycarbonate, it is shown that aging actually is one of the dominant factors in the embrittlement.     

Conjugate-order systems for signal processing: stability, causality, boundedness, compactness

The fundamental system theory is presented for a class of real systems whose derivative order is complex. It is demonstrated that these so-called conjugate-order systems have a scale-invariance property in both the time and frequency domains, which makes them useful for describing certain phenomena in continuous media. The conditions for which these systems are guaranteed to be causal and stable are reviewed. The compactness properties of their Hankel operators, which allow them to admit finite-order approximations, are also discussed. A procedure is developed for choosing appropriate transfer-function parameter values to design a stable conjugate-order system whose frequency response meets given bandwidth, resonance, and ripple specifications.