Simulating P systems with membrane dissolution in a chemical calculus

We present a transformation of membrane systems, possibly with promoter/inhibitor rules, priority relations, and membrane dissolution, into formulas of the chemical calculus such that terminating computations of membranes correspond to terminating reduction sequences of formulas and vice versa. In the end, the same result can be extracted from the underlying computation of the membrane system as from the reduction sequence of the chemical term.     

A Digital Breeder for Designing Cities

The idea that inspired designs mirror processes of biological evolution is fast gaining ground as we learn more about how complex systems such as cities function. Michael Batty illustrates how cities can now be grown in ‘digital laboratories’ and, by imposing realistic constraints on their form, begin to breed ‘good designs’ that emerge from continual feedbacks that reinforce the best and iron out the worst. Copyright © 2009 John Wiley & Sons, Ltd.     

Polymers from acrylonitrile polymerized in the presence of vinylsulphone dyes

The properties of a series of ‘copolymers’ of acrylonitrile and various vinylsulphone dyes are discussed. Information relating to molecular size, the nature of the linkage between the chromophore and the backbone and the reactivity ratios of the two ‘monomers’ is given. These reactivity ratios are calculated from extinction coefficients on the assumption that there is no appreciable breakdown of the chromophore during polymerization. Factors governing the role of the dye in the polymerization process are considered in some detail. Thermal analysis techniques have been used to investigate the thermal stability of the products of polymerization. The thermograms have been used to assess the potential of these materials as pigments and to study the nature of their decomposition.     

The Potential Importance of Mine Sites for Biodiversity

Abstract  Abandoned mine sites are typically viewed as environmental problems due to their negative impacts on local ecosystems. This paper presents an alternative viewpoint providing evidence of the potential importance of mine sites for supporting rare and threatened species from many of the major taxonomic orders. The potential importance of these species in remediation of polluted environments is also highlighted.     

Suppression of wind-induced hydrodynamics in ponds

Significant economies of scale are an incentive for the design of large salt gradient solar ponds; however, wind induced mixing is more difficult to suppress on larger ponds because of the greater distance (or fetch) between dikes. Quantitative data are needed on the hydrodynamic effects of wind action on ponds protected with wave suppression systems.Experiments conducted at the Utah Water Research Laboratory measured wave height, wave length, and depth of disturbance of water in a test flume exposed to various air flows and wave suppression devices. Water depth was 30 cm in the 12.2-m-long test flume having a cross section 61 cm square. Air velocities ranged from 4.50 to 11.8 m/s. Experiments also were conducted with a sharply stratified system consisting of 15 cm of fresh water floating on 15 cm of salt brine in which the air velocities were observed at the point where gravity return currents and wave motion occur at the density interface.Results indicate that circulation currents may persist even if waves are effectively suppressed.     

Modification of the fastness properties of dyed wool through grafting

Methods are described whereby the light fastness and wash fastness properties of dyed wool can be improved through grafting small quantities of acrylonitrile onto the wool. Four dye classes are covered together with six techniques of copolymerization. Preliminary data from studies of the fading of dyes in solution with and without acrylonitrile are presented. These show that acrylonitrile reduces the rate of fading of most of the dyes investigated, irrespective of the chromophore structure. Radiation induced processes are more successful than those based on chemical initiation whilst post-irradiation induced grafting of acrylonitrile onto wool, followed by conventional dyeing offers particular promise for effectiveness and industrial exploitation.     

Diffusion-limited aggregation and the fractal nature of urban growth

This paper introduces the mechanism of diffusion-limited aggregation (DLA) as a new basis for understanding urban growth. Through DLA, urban form is related to the processes of rural-to-urban migration and contiguous growth. However, despite being based on very simple principles, DLA simulations are shown to have properties found in most urban areas such as negative density gradients and ordered chaotic structures. The paper examines variations in the simulated urban structures produced by different assumptions regarding the rural-to-urban migration mechanism. An important finding is that urban density gradients can occur independently of the generally accepted reasons for their presence. We also comment on boundary effects in the measurement of urban density gradients.     

Graduate Student Literature Review: The milk behind the mustache: A review of milk and bone biology

Exploring the relationship between nutrition, skeletal development, and aging is important in maintaining bone health. Even further, understanding the complexity of skeletal homeostasis may assist in reducing the prevalence of skeletal disease, especially osteoporosis. The skeleton is unique in that it can adapt to various physical pressures, maintain shape, and remodel itself to increase integrity and strength. For decades, it was thought that increasing skeletal health was as simple as drinking three 8-oz. glasses of milk per day due to high levels of bioavailable calcium. New research into the bioactive components of milk have revealed other roles in promoting skeletal health. Milk contains various bioactive peptides, houses genetic information in milk-derived exosomes, and supplies relevant amounts of nutrients important for bone health. In this review, we discuss the basics of skeletal formation and homeostasis, dive into the potential effects of milk on the growing skeleton, and present contrasting findings.     

The quest for the qualitative: New directions in planning theory and analysis

Abstract

This paper argues that new methods of understanding current planning problems might be found in recent advances in qualitative structural analysis. The case for qualitative rather than quantitative analysis per se is presented in terms of the history of systematic modelling in planning, and these ideas are illustrated using the popular development of catastrophe theory applied to problems of urban riots, and land speculations in the central city.