A multiscale model for collagen alignment in wound healing

It is thought that collagen alignment plays a significant part in scar tissue formation during dermal wound healing. We present a multiscale model for collagen deposition and alignment during this process. We consider fibroblasts as discrete units moving within an extracellular matrix of collagen and fibrin modelled as continua. Our model includes flux induced alignment of collagen by fibroblasts, and contact guidance of fibroblasts by collagen fibres. We can use the model to predict the effects of certain manipulations, such as varying fibroblast speed, or placing an aligned piece of tissue in the wound. We also simulate experiments which alter the TGF-β concentrations in a healing dermal wound and use the model to offer an explanation of the observed influence of this growth factor on scarring

Cancer modelling: Getting to the heart of the problem

Paradoxically, improvements in healthcare that have enhanced the life expectancy of humans in the Western world have, indirectly, increased the prevalence of certain types of cancer such as prostate and breast. It remains unclear whether this phenomenon should be attributed to the ageing process itself or the cumulative effect of prolonged exposure to harmful environmental stimuli such as ultraviolet light, radiation and carcinogens (Franks and Teich, 1988). Equally, there is also compelling evidence that certain genetic abnormalities can predispose individuals to specific cancers (Ilyas et al., 1999). The variety of factors that have been implicated in the development of solid tumours stems, to a large extent, from the fact that ‘cancer’ is a generic term, often used to characterize a series of disorders that share common features. At this generic level of description, cancer may be viewed as a cellular disease in which controls that usually regulate growth and maintain homeostasis are disrupted. Cancer is typically initiated by genetic mutations that lead to enhanced mitosis of a cell lineage and the formation of an avascular tumour. Since it receives nutrients by diffusion from the surrounding tissue, the size of an avascular tumour is limited to several millimeters in diameter. Further growth relies on the tumour acquiring the ability to stimulate the ingrowth of a new, circulating blood supply from the host vasculature via a process termed angiogenesis (Folkman, 1974). Once vascularised, the tumour has access to a vast nutrient source and rapid growth ensues. Further, tumour fragments that break away from the primary tumour, on entering the vasculature, may be transported to other organs in which they may establish secondary tumours or metastases that further compromise the host. Invasion is another key feature of solid tumours whereby contact with the tissue stimulates the production of enzymes that digest the tissue, liberating space into which the tumour cells migrate. Thus, cancer is a complex, multiscale process. The spatial scales of interest range from the subcellular level, to the cellular and macroscopic (or tissue) levels while the timescales may vary from seconds (or less) for signal transduction pathways to months for tumour doubling times The variety of phenomena involved, the range of spatial and temporal scales over which they act and the complex way in which they are inter-related mean that the development of realistic theoretical models of solid tumour growth is extremely challenging. While there is now a large literature focused on modelling solid tumour growth (for a review, see, for example, Preziosi, 2003), existing models typically focus on a single spatial scale and, as a result, are unable to address the fundamental problem of how phenomena at different scales are coupled or to combine, in a systematic manner, data from the various scales. In this article, a theoretical framework will be presented that is capable of integrating a hierarchy of processes occurring at different scales into a detailed model of solid tumour growth (Alarcon et al., 2004). The model is formulated as a hybrid cellular automaton and contains interlinked elements that describe processes at each spatial scale: progress through the cell cycle and the production of proteins that stimulate angiogenesis are accounted for at the subcellular level; cell-cell interactions are treated at the cellular level; and, at the tissue scale, attention focuses on the vascular network whose structure adapts in response to blood flow and angiogenic factors produced at the subcellular level. Further coupling between the different spatial scales arises from the transport of blood-borne oxygen into the tissue and its uptake at the cellular level. Model simulations will be presented to illustrate the effect that spatial heterogeneity induced by blood flow through the vascular network has on the tumour’s growth dynamics and explain how the model may be used to compare the efficacy of different anti-cancer treatment protocols

Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 156)

This bibliography lists 170 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1976

Steps towards "Quantum Gravity" and the practice of science: will the merger of mathematics and physics work?

The author recalls general tendencies of the "mathematization" of the sciences and derives challenges and tentative obstructions for a successful merger of mathematics and physics on fancied steps towards "Quantum Gravity". This is an edited version of the author's opening words to an international workshop "Quantum Gravity: An Assessment", Denmark, May 17-18, 2008. It followed immediately after the Quantum Gravity Summer School 2008, see http://QuantumGravity.ruc.dk/Comment: To appear as part of a Springer Lecture Notes in Physics publication: "Quantum Gravity - New Paths towards Unification" (B. Booss-Bavnbek, G. Esposito, M. Lesch, Eds.

Neuroprotection by Chitosan and Chitosan Nanoparticles

In the U.S., about 200,000 people are currently living with spinal cord injury (SCI). An estimated of 50%-70% of all SCI cases occurs in the range of ages between 15-35 years old. The destructive neurotrauma results in the majority of adult disability, even after patients suffering with SCI survived from the acute death. There are two stages involved in the progression of SCI, the primary stage and the secondary stage. The primary stage is mainly the mechanical damage to the central nervous system. The rapid collapse of the integrity of cell membrane and tissue is often one of the initial onsets. Centered by the cascade of biochemical disruption, such as aldehyde toxins, the secondary injury is responsible for the major clinical deficits in sensory and motor functions. Available pharmacological treatment for SCI includes high doses of steroids. However, the side effects of steroid therapy leave patients more susceptible for complications, such as infections, chronic pain and blood clots. The absence of standard of care have triggered waves of intense research leading to finding a cure for SCI . Based on our previous successful explorations of the neuroprotection by chitosan and chitosan nanoparticles (Chi-NPs) in SCI related cell and tissue studies, we further investigated the neuroprotective effects based on two major characteristics of chitosan: (1) molecular weight (MW) and (2) degree of acetylation (DA). Our results demonstrated that chitosan polymer blocked the random exchange of a probe, tetramethyl-rodamine (TMR) and an endogenous protein, lactate dehydrogenase (LDH), across mechanically compromised cell membrane, while a significant difference of the membrane sealing effect was not suggested among different MWs and DAs of chitosan polymer. A similar affinity of FITC-chitosan polymer at intact and injured spinal tissues was also suggested. To push the use of chitosan a step towards clinical tests, we incorporated the advantage of nanomedicine with our promising chitosan material . Different factors were investigated during the formation and the storage of Chi F-NPs. Two types of Chi-NPs (chitosan-triphosphate, Chi-TPPNPs and chitosan-dextran sulfate, Chi-DSNPs) were synthesized, with a range of size at 100-300nm and zeta-potentials of 30.65mV and -47.4mV, based on an ionic gelation method. Chi-DSNPs were shown to rescue necrotic BV-2 cells induced by a short incubation of hydrogen peroxide at 5.5mM. In addition, the conduction of somatosensory evoked potentials (SSEPs) through the lesion produced by the compression injury was partially restored after 1 week of the subcutaneous administration of Chi-DSNPs. We also found that polyethylene glycol (PEG)-coated silica NPs were significantly accumulated at the compression injured spinal tissues. The affinity of NPs at severed cell membranes was guided by PEG. Our experimental findings suggested that chitosan and Chi-NPs provided neuroprotective effects using both in vitro and in vivo models

Hydrodynamics

The phenomena related to the flow of fluids are generally complex, and difficult to quantify. New approaches - considering points of view still not explored - may introduce useful tools in the study of Hydrodynamics and the related transport phenomena. The details of the flows and the properties of the fluids must be considered on a very small scale perspective. Consequently, new concepts and tools are generated to better describe the fluids and their properties. This volume presents conclusions about advanced topics of calculated and observed flows. It contains eighteen chapters, organized in five sections: 1) Mathematical Models in Fluid Mechanics, 2) Biological Applications and Biohydrodynamics, 3) Detailed Experimental Analyses of Fluids and Flows, 4) Radiation-, Electro-, Magnetohydrodynamics, and Magnetorheology, 5) Special Topics on Simulations and Experimental Data. These chapters present new points of view about methods and tools used in Hydrodynamics

Charged Carbon Nanotubes

As the degree of functionalization on CNTs greatly affects its properties, the structure and dynamics of water confined inside pristine and functionalized/charged carbon nanotubes (CNTs) is of prime importance. The presence of charges on the surface of CNTs results in hydrophobic to hydrophilic transitions which increase its occupancy of the water molecules thereby breaking down 1D water wires, as seen in pristine CNTs

Synthesis of formation control for an aquatic swarm robotics system

Formations are the spatial organization of objects or entities according to some predefined pattern. They can be found in nature, in social animals such as fish schools, and insect colonies, where the spontaneous organization into emergent structures takes place. Formations have a multitude of applications such as in military and law enforcement scenarios, where they are used to increase operational performance. The concept is even present in collective sports modalities such as football, which use formations as a strategy to increase teams efficiency. Swarm robotics is an approach for the study of multi-robot systems composed of a large number of simple units, inspired in self-organization in animal societies. These have the potential to conduct tasks too demanding for a single robot operating alone. When applied to the coordination of such type of systems, formations allow for a coordinated motion and enable SRS to increase their sensing efficiency as a whole. In this dissertation, we present a virtual structure formation control synthesis for a multi-robot system. Control is synthesized through the use of evolutionary robotics, from where the desired collective behavior emerges, while displaying key-features such as fault tolerance and robustness. Initial experiments on formation control synthesis were conducted in simulation environment. We later developed an inexpensive aquatic robotic platform in order to conduct experiments in real world conditions. Our results demonstrated that it is possible to synthesize formation control for a multi-robot system making use of evolutionary robotics. The developed robotic platform was used in several scientific studies.As formações consistem na organização de objetos ou entidades de acordo com um padrão pré-definido. Elas podem ser encontradas na natureza, em animais sociais tais como peixes ou colónias de insetos, onde a organização espontânea em estruturas se verifica. As formações aplicam-se em diversos contextos, tais como cenários militares ou de aplicação da lei, onde são utilizadas para aumentar a performance operacional. O conceito está também presente em desportos coletivos tais como o futebol, onde as formações são utilizadas como estratégia para aumentar a eficiência das equipas. Os enxames de robots são uma abordagem para o estudo de sistemas multi-robô compostos de um grande número de unidades simples, inspirado na organização de sociedades animais. Estes têm um elevado potencial na resolução de tarefas demasiado complexas para um único robot. Quando aplicadas na coordenação deste tipo de sistemas, as formações permitem o movimento coordenado e o aumento da sensibilidade do enxame como um todo. Nesta dissertação apresentamos a síntese de controlo de formação para um sistema multi-robô. O controlo é sintetizado através do uso de robótica evolucionária, de onde o comportamento coletivo emerge, demonstrando ainda funcionalidadeschave tais como tolerância a falhas e robustez. As experiências iniciais na síntese de controlo foram realizadas em simulação. Mais tarde foi desenvolvida uma plataforma robótica para a condução de experiências no mundo real. Os nossos resultados demonstram que é possível sintetizar controlo de formação para um sistema multi-robô, utilizando técnicas de robótica evolucionária. A plataforma desenvolvida foi ainda utilizada em diversos estudos científicos

Protein Crystallization under the Presence of an Electric Field

This book entitled “Protein Crystallization under the Presence of an Electric Field” covers recent trends and original contributions on the use of electric fields (internal and external) for applications for nucleation control and the effect on the kinetics of crystallization processes. This book also includes basic strategies for growing crystals of biological macromolecules for characterization via X-ray and neutron diffraction as well as using modern X-ray-free electron-lasers. There are six main topics covered on this book, including recent insights into the crystallization process from nucleation and growth peculiarities, when using different kinds of electric fields; the effect of external electric fields on the kinetics of the dislocation-free growth of model proteins; the use of very strong external electric fields for the crystallization of a model protein glucose isomerase; and the use of alternant electric fields using different kinds of pulses and their combination with strong magnetic fields. There are also contributions related to applications in developing electron-transfer devices as well as graphene-based platforms for electrocrystallization and in situ X-ray diffraction characterization