Turbulence damping as a measure of the flow dimensionality

The dimensionality of turbulence in fluid layers determines their properties. We study electromagnetically driven flows in finite depth fluid layers and show that eddy viscosity, which appears as a result of three-dimensional motions, leads to increased bottom damping. The anomaly coefficient, which characterizes the deviation of damping from the one derived using a quasi-two-dimensional model, can be used as a measure of the flow dimensionality. Experiments in turbulent layers show that when the anomaly coefficient becomes high, the turbulent inverse energy cascade is suppressed. In the opposite limit turbulence can self-organize into a coherent flow.Comment: 4 pages, 4 figure

Unsheltered homelessness among veterans: correlates and profiles

We identified correlates of unsheltered status among Veterans experiencing homelessness and describe d distinct subgroups within the unsheltered homeless Veteran population using data from a screening instrument for homelessness that is administered to all Veterans accessing outpatient care at a Veterans Health Administration (VHA) facility . Correlates o f unsheltered homelessness included male gender, white race, older age, lower levels of VHA eligibility, substance use disorders, frequent use of VHA inpatient and infrequent use of VHA outpatient services, and residing in the West. We identified six disti nct subgroups of unsheltered Veterans; the tri - morbid frequent users represented the highest need group, but the largest group was comprised of Veterans who made highly infrequent use of VHA healthcare services. Differences between sheltered and unshelter ed Veterans and heterogeneity within the unsheltered Veteran population should be considered in targeting housing and other interventions.National Center on Homelessness Among Veteran

A two-fluid model for tissue growth within\ud a dynamic flow environment

We study the growth of a tissue construct in a perfusion bioreactor, focussing on its response to the mechanical environment. The bioreactor system is modelled as a two-dimensional channel containing a tissue construct through which a flow of culture medium is driven. We employ a multiphase formulation of the type presented by G. Lemon, J. King, H. Byrne, O. Jensen and K. Shakesheff in their study (Multiphase modelling of tissue growth using the theory of mixtures. J. Math. Biol. 52(2), 2006, 571–594) restricted to two interacting fluid phases, representing a cell population (and attendant extracellular matrix) and a culture medium, and employ the simplifying limit of large interphase viscous drag after S. Franks in her study (Mathematical Modelling of Tumour Growth and Stability. Ph.D. Thesis, University of Nottingham, UK, 2002) and S. Franks and J. King in their study (Interactions between a uniformly proliferating tumour and its surrounding: Uniform material properties. Math. Med. Biol. 20, 2003, 47–89).\ud \ud The novel aspects of this study are: (i) the investigation of the effect of an imposed flow on the growth of the tissue construct, and (ii) the inclusion of a mechanotransduction mechanism regulating the response of the cells to the local mechanical environment. Specifically, we consider the response of the cells to their local density and the culture medium pressure. As such, this study forms the first step towards a general multiphase formulation that incorporates the effect of mechanotransduction on the growth and morphology of a tissue construct. The model is analysed using analytic and numerical techniques, the results of which illustrate the potential use of the model to predict the dominant regulatory stimuli in a cell population

Mathematical modelling plant signalling networks

During the last two decades, molecular genetic studies and the completion of the sequencing of the Arabidopsis thaliana genome have increased knowledge of hormonal regulation in plants. These signal transduction pathways act in concert through gene regulatory and signalling networks whose main components have begun to be elucidated. Our understanding of the resulting cellular processes is hindered by the complex, and sometimes counter-intuitive, dynamics of the networks, which may be interconnected through feedback controls and cross-regulation. Mathematical modelling provides a valuable tool to investigate such dynamics and to perform in silico experiments that may not be easily carried out in a laboratory. In this article, we firstly review general methods for modelling gene and signalling networks and their application in plants. We then describe specific models of hormonal perception and cross-talk in plants. This sub-cellular analysis paves the way for more comprehensive mathematical studies of hormonal transport and signalling in a multi-scale setting

Colorectal Cancer Through Simulation and Experiment

Colorectal cancer has continued to generate a huge amount of research interest over several decades, forming a canonical example of tumourigenesis since its use in Fearon and Vogelstein’s linear model of genetic mutation. Over time, the field has witnessed a transition from solely experimental work to the inclusion of mathematical biology and computer-based modelling. The fusion of these disciplines has the potential to provide valuable insights into oncologic processes, but also presents the challenge of uniting many diverse perspectives. Furthermore, the cancer cell phenotype defined by the ‘Hallmarks of Cancer’ has been extended in recent times and provides an excellent basis for future research. We present a timely summary of the literature relating to colorectal cancer, addressing the traditional experimental findings, summarising the key mathematical and computational approaches, and emphasising the role of the Hallmarks in current and future developments. We conclude with a discussion of interdisciplinary work, outlining areas of experimental interest which would benefit from the insight that mathematical and computational modelling can provide

Wound healing angiogenesis the clinical implications of a simple mathematical model

Nonhealing wounds are a major burden for health care systems worldwide. In addition, a patient who suffers from this type of wound usually has a reduced quality of life. While the wound healing process is undoubtedly complex, in this paper we develop a deterministic mathematical model, formulated as a system of partial differential equations, that focusses on an important aspect of successful healing: oxygen supply to the wound bed by a combination of diffusion from the surrounding unwounded tissue and delivery from newly-formed blood vessels. While the model equations can be solved numerically, the emphasis here is on the use of asymptotic methods to establish conditions under which new blood vessel growth can be initiated and wound-bed angiogenesis can progress. These conditions are given in terms of key model parameters including the rate of oxygen supply and its rate of consumption in the wound. We use our model to discuss the clinical use of treatments such as hyperbaric oxygen therapy, wound bed debridement, and revascularisation therapy that have the potential to initiate healing in chronic, stalled wounds

Mangroves, garbage, fishing: Bringing everyday ecology to Sydney's industrial Georges River

Post war problems of rising urban, industrial pollution and intractable waste disposal are usually considered as technical and economic problems only, solutions to which were led by experts at State level, and filtered into Australia from the ferments occurring in the United States and Britain in the 1960s and 70s. This paper investigates the change which arose from the localities in which the impact of those effects of modern city development were occurring. In particular, this study looks at a working class, industrial area, the Georges River near Bankstown Municipality, which was severely affected by Sydneys post-war expansion. Here, action to address urgent environmental problems was initiated first at the local level, and only later were professional engineers and public health officials involved in seeking remedies. It was even later that these local experts turned from engineering strategies to environmental science, embracing the newly developed ecological analyses to craft changing approaches to local problems. This paper centres on the perspective of one local public health surveyor, employed by a local municipal council to oversee waste disposal, to identify the motives for his decisions to intervene dramatically in river health and waste disposal programs. Rather than being prompted to act by influences from higher political levels or overseas, this officer drew his motivation from careful local data collection, from local political agitation and from his own recreational knowledge of the river. It was his involvement with the living environments of the area the ways in which he knew the river - through personal and recreational experiences, which prompted him to seek out the new science and investigate emerging waste disposal technologies

Wave climate model of the Mid-Atlantic shelf and shoreline (Virginian Sea): Model development, shelf geomorphology, and preliminary results

A computerized wave climate model is developed that applies linear wave theory and shelf depth information to predict wave behavior as they pass over the continental shelf as well as the resulting wave energy distributions along the coastline. Reviewed are also the geomorphology of the Mid-Atlantic Continental Shelf, wave computations resulting from 122 wave input conditions, and a preliminary analysis of these data

Waterborne: Vietnamese Australians and river environments in Vietnam and Sydney

Vietnamese Australians who arrived in Australia as refugees since the 1970s and later as migrants, have developed complex relationships of remembering, knowing and belonging to environments in Vietnam and Sydney. Water was a frequent point of reference in our interviews with Vietnamese people in Sydney, and their relationships with water are used in this article to explore interviewees associations with places. The article focuses on cultural knowledge of environments, which people bring with them, such as their connections with rivers and oceans, central to both memories of place and the histories of Vietnam. These memories also change with return visits and experiences between these places. Vietnamese refugees experiences of escape and trauma coming across oceans from Vietnam also influence subsequent relationships with place. Finally, relationships with Sydney parks and urban waterways are explored by examining popular places for family and community get-togethers along Georges River, located near where many Sydney Vietnamese people live. These have become key places in making Sydney home for Vietnamese people. The article considers how Vietnamese Australian cultural knowledge of place could be shared and acknowledged by park managers and used in park interpretati

Robust inverse energy cascade and turbulence structure in three-dimensional layers of fluid

Here we report the first evidence of the inverse energy cascade in a flow dominated by 3D motions. Experiments are performed in thick fluid layers where turbulence is driven electromagnetically. It is shown that if the free surface of the layer is not perturbed, the top part of the layer behaves as quasi-2D and supports the inverse energy cascade regardless of the layer thickness. Well below the surface the cascade survives even in the presence of strong 3D eddies developing when the layer depth exceeds half the forcing scale. In a bounded flow at low bottom dissipation, the inverse energy cascade leads to the generation of a spectral condensate below the free surface. Such coherent flow can destroy 3D eddies in the bulk of the layer and enforce the flow planarity over the entire layer thickness.Comment: 8 pages, 6 figure