Scaling (Biology)

Generative Structures in Cities

by Kinda Al Sayed

Co-authored with Alasdair Turner and Sean Hanna

Research in the area of Space syntax tends to be centred on static representations of the built environment and its... more Research in the area of Space syntax tends to be centred on static representations of the built environment and its embedded social logic. Lacking for the most part the element of time, this synchronous representation cannot capture the evolutionary dynamics of urban systems. In this paper, we argue that the abstract values of space-time as a dual dimension play a key role as generators of city systems. Hence, we explore the driving forces that help reproduce growing spatial networks and yet preserve their structural properties. In two case studies; Manhattan and Barcelona, synchronic states of the growing systems are analysed. The states are separated by a certain radius of time. The analysis leads to regularities that may outline a generative model embedded in the pattern of growth and marked by alternating periods of expansion and pruning. In periods of expansion, a positive feedback process operates and takes the form of exponential addition of elements. The emergence of patches on the edges follows high values of choice and is subject to the temporal configurations of the grid. Once we observe the long-term time dimensionality, we note a change in the trend of the system as it reaches its maximum boundary. Following this change, another process of reinforcing feedback is introduced to the spatial network. This process involves intensifying sparse grid structures that have witnessed high gains in centrality in prior states and a process of pruning of poorly integrated elements. Both processes aim to differentiate the spatial structure of a city hence matching that of an organic grid. The findings yield that even at events of large scale planning interventions; cities adapt the local configurations of the new uniform parts to deform in such a way as to reproduce natural growth. In this manner, cities embody the intelligent collective minds of individuals. They are trade-off products of individuals’ decisions and they adapt their behaviour by prioritising a maximum parts-whole relationship that optimises access in the spatial network. We introduce these feedback processes under a framework of a plausible generative model to simulate city growth. The model is expected to both provide a better understanding of city growth and to aid design decision making on urban and regional scales.

Allometry and heterochrony in Alouatta palliate and Alouatta seniculus

by Callum Ross

Ravosa, M. and Ross, C.F. (1994) Allometry and heterochrony in Alouatta palliata and Alouatta seniculus. American Journal of Primatology 33: 277-299.

Allometric and functional influences on primate orbit orientation and the origins of the Anthropoidea

by Callum Ross

Ross, C.F. (1995) Allometric and functional influences on primate orbit orientation and the origins of the Anthropoidea. Journal of Human Evolution 29: 201-227

Scaling of reduced physiologic cross-sectional area in primate muscles of mastication

by Callum Ross

Anapol, F., Shahnoor, N., and Ross, C.F. (2008) Scaling of reduced physiologic cross-sectional area in primate muscles of mastication. In: Primate Craniofacial Function and Biology. Vinyard C.J., Ravosa M.J. and Wall C.E., (eds.). Springer: New York, pp. 201-216.

Scaling of chew cycle duration in primates

by Callum Ross

Ross, C. F., Reed, D. A., Washington, R. L., Eckhardt, A., Anapol, F., Shahnoor, N. (2009) Scaling of chew cycle duration in Primates. American Journal of Physical Anthropology 138: 30-44.

The primate cranial base: ontogeny, function, and integration

by Callum Ross

Lieberman, D.E., Ross, C.F., Ravosa, M.J. (2000) The primate cranial base: ontogeny, function and integration. Yrbk Phys. Anthropol. 43: 117-169.

Note: The values for AOA and AFK for Homo sapiens in Table 7 of Lieberman et al. (2000) were incorrectly given as 163... more Note: The values for AOA and AFK for Homo sapiens in Table 7 of Lieberman et al. (2000) were incorrectly given as 163 and 154, respectively, instead of 115 and 122 (Ross and Henneberg, 1995).

Allometry of masticatory loading parameters in mammals

by Callum Ross

Ravosa, M.J., Ross, C.F., Williams, S.H., Costley, D.B (2010) Allometry of masticatory loading patterns in mammals. Anatomical Record 293: 557-571.

Crossover from endogenous to exogenous activity in opensource software development

by Sergi Valverde

EPL, 77 (2007) 20002

We have investigated the origin of fluctuations in the aggregated behaviour of an open- source software community. In... more We have investigated the origin of fluctuations in the aggregated behaviour of an open- source software community. In a recent series of papers (de Menezes M. A. and Barabasi A.-L., Phys. Rev. Lett., 92 (2004) 28701; 93 (2004) 68701; Yook S. H. and de Menezes M. A., Europhys. Lett., 72 (2005) 541), de Menezes and co-workers have shown how to separate internal dynamics from external fluctuations by capturing the simultaneous activity of many system’s components. In spite of software development being a planned activity, the analysis of fluctuations reveals how external driving forces can be only observed at weekly and higher time scales. Hourly and higher change frequencies mostly relate to internal maintenance activities. There is a crossover from endogenous to exogenous activity depending on the average number of file changes. This new evidence suggests that software development is a non-homogeneous design activity where stronger efforts focus in a few project files. The crossover can be explained with a Langevin equation associated to the cascading process, where changes to any file trigger additional changes to its neighbours in the software network. In addition, analysis of fluctuations enables us to detect whether a software system can be decomposed into several subsystems with different development dynamics.

Emergence of scale-free syntax networks

by Sergi Valverde

Bernat Corominas-Murtra, Sergi Valverde and Ricard V. Solé
Evolution of Communication and Language in Embodied Agents, Springer Artificial Intelligence Series (2010)

The evolution of human language allowed the efficient propagation of nongenetic information, thus creating a new form... more The evolution of human language allowed the efficient propagation of nongenetic information, thus creating a new form of evolutionary change. Language development in children offers the opportunity of exploring the emergence of such complex communication system and provides a window to understanding the transition from protolanguage to language. Here we present the first analysis of the emergence of syntax in terms of complex networks. A previously unreported, sharp transition is shown to occur around two years of age from a (pre-syntactic) tree-like structure to a scale-free, small world syntax network. The observed combinatorial patterns provide valuable data to understand the nature of the cognitive processes involved in the acquisition of syntax, introducing a new ingredient to understand the possible biological endowment of human beings which results in the emergence of complex language. We explore this problem by using a minimal, data-driven model that is able to capture several statistical traits, but some key features related to the emergence of syntactic complexity display important divergences.

Discerning Electricity Consumption Patterns from Urban Allometric Scaling

by Sergi Valverde

Ricard Horta, Marti Rosas Casals and Sergi Valverde
COMPENG '10., 49-51 (2010)

Allometric scaling relations are characteristic of all living organisms. Metabolic and heart rates, lifespan and many... more Allometric scaling relations are characteristic of all living organisms. Metabolic and heart rates, lifespan and many other physiological properties vary with body mass in systematic and interrelated ways, which usually take the form of a power law. Scaling laws have been recently observed also in the metabolic rate of a particular kind of living system: the city. Scaling exponents of urban indicators present a remarkable variability, mainly associated with fundamentally different underlying dynamics. In this paper allometric scaling is used to detect dissimilar behaviors in one particularly important urban indicator: electricity consumption. Different scaling relations between electricity consumption and economical and social sectors found in southern Spain region of Andalucia, indicate variability in these sectors' basal energy consumption processes. The usefulness of these findings for urban modeling is finally outlined and some practical implications are suggested.

The impact of long-distance horizontal gene transfer on prokaryotic genome size

by Otto X. Cordero Sanchez

Otto X. Cordero & Paulien Hogeweg, (2009) PNAS

Horizontal gene transfer (HGT) is one of the most dominant forces molding prokaryotic gene repertoires. These... more Horizontal gene transfer (HGT) is one of the most dominant forces molding prokaryotic gene repertoires. These repertoires can be as small as ≈200 genes in intracellular organisms or as large as ≈9,000 genes in large, free-living bacteria. In this article we ask what is the impact of HGT from phylogenetically distant sources, relative to the size of the gene repertoire. Using different approaches for HGT detection and focusing on both cumulative and recent evolutionary histories, we find a surprising pattern of nonlinear enrichment of long-distance transfers in large genomes. Moreover, we find a strong positive correlation between the sizes of the donor and recipient genomes. Our results also show that distant horizontal transfers are biased toward those functional groups that are enriched in large genomes, showing that the trends in functional gene content and the impact of distant transfers are interdependent. These results highlight the intimate relationship between environmental and genomic complexity in microbes and suggest that an ecological, as opposed to phylogenetic signal in gene content gains relative importance in large-genomed bacteria.