Validity of the Cauchy-Born rule applied to discrete cellular-scale models of biological tissues.

The development of new models of biological tissues that consider cells in a discrete manner is becoming increasingly popular as an alternative to continuum methods based on partial differential equations, although formal relationships between the discrete and continuum frameworks remain to be established. For crystal mechanics, the discrete-to-continuum bridge is often made by assuming that local atom displacements can be mapped homogeneously from the mesoscale deformation gradient, an assumption known as the Cauchy-Born rule (CBR). Although the CBR does not hold exactly for noncrystalline materials, it may still be used as a first-order approximation for analytic calculations of effective stresses or strain energies. In this work, our goal is to investigate numerically the applicability of the CBR to two-dimensional cellular-scale models by assessing the mechanical behavior of model biological tissues, including crystalline (honeycomb) and noncrystalline reference states. The numerical procedure involves applying an affine deformation to the boundary cells and computing the quasistatic position of internal cells. The position of internal cells is then compared with the prediction of the CBR and an average deviation is calculated in the strain domain. For center-based cell models, we show that the CBR holds exactly when the deformation gradient is relatively small and the reference stress-free configuration is defined by a honeycomb lattice. We show further that the CBR may be used approximately when the reference state is perturbed from the honeycomb configuration. By contrast, for vertex-based cell models, a similar analysis reveals that the CBR does not provide a good representation of the tissue mechanics, even when the reference configuration is defined by a honeycomb lattice. The paper concludes with a discussion of the implications of these results for concurrent discrete and continuous modeling, adaptation of atom-to-continuum techniques to biological tissues, and model classification

Designing the vertigo experience: vertigo as a design resource for digital bodily play

Vertigo can be described as an attempt to momentarily destroy the stability of perception and inflict a kind of voluptuous panic upon an otherwise lucid mind. Vertigo has, however, not been generally considered as a design resource and we believe it to be under-explored in the area of digital bodily play. To investigate how vertigo could be considered as a design resource in this context, we conducted a review of relevant literature and held a design workshop with nine students to explore the potential of vertigo as a design resource for digital bodily play. From our exploration we identify five key design themes that designers might consider when designing a Vertigo Experience. Through this work we hope to encourage designers of bodily play experiences to consider vertigo as a design resource in their games

Inner disturbance: towards understanding the design of vertigo games through a novel balancing game

The design space of vertigo games is under-explored, despite vertigo underlying many unique body based game experiences, such as rock climbing and dancing. In this paper we articulate the design and evaluation of a novel vertigo experience, Inner Disturbance, which uses Galvanic Vestibular Stimulation to affect the player’s balance. Following study observations and a thematic analysis of Inner Disturbance (N=10), we present four themes and associated design sensitivities that can be used to aid designers of future digital vertigo games. With this work we aim to encourage others to experiment within this exciting new design space for digital games

Balance ninja: towards the design of digital vertigo games via galvanic vestibular stimulation

Vertigo – the momentary disruption of the stability of perception – is an intriguing game element that underlies many unique play experiences, such as spinning in circles as children to rock climbing as adults, yet vertigo is relatively unexplored when it comes to digital play. In this paper we explore the potential of Galvanic Vestibular Stimulation (GVS) as a game design tool for digital vertigo games. We detail the design and evaluation of a novel two player GVS game, Balance Ninja. From study observations and analysis of Balance Ninja (N=20), we present three design themes and six design strategies that can be used to aid game designers of future digital vertigo games. With this work we aim to highlight that vertigo can be a valuable digital game element that helps to expand the range of games we play

The Potential of Vibrational Spectroscopy in the Early Detection of Cervical Cancer: an Exciting Emerging Field

The application of vibrational spectroscopy to disease diagnosis is a relatively new, rapidly evolving scientific field. Techniques such as Raman and infrared spectroscopy have shown great promise in this regard over the past number of years. This study directly compared Raman spectroscopy and synchrotron infrared (SR-IR) spectroscopy on parallel cervical cancer samples. Both frozen and dewaxed formalin fixed paraffin preserved tissue sections were examined. Both tissue types produced good quality Raman and SR-IR spectra, although the lesser processed, frozen tissue sections displayed the most detailed spectra. Spectroscopy was shown capable of discriminating between different cell types in normal cervical tissue. Spectra recorded from invasive carcinoma showed a marked difference from those recorded from normal cervical epithelial cells. Spectral differences identified with the onset of carcinogenesis include increased nucleic acid contributions and decreased glycogen levels. These investigations pave the way for an enlarged study into this exciting new diagnostic field

Casting a shadow: harm from known drinkers

Abstract Introduction: This paper examines the negative consequences of having a known drinker in one’s life. Method: The first dedicated national survey on alcohol’s harm to others (AH20) in Ireland was undertaken in 2015. Data was gathered by a cross sectional probability sample of 2,005 adults (18+yrs). Using a 12 month time-frame, respondents were asked about adverse effects they experienced due to known drinkers. Results: Overall, two in five people experiencing harm from known drinkers. Intangible harm was more common (38%) than tangible harm (24%). Stress/anxiety was the most common harm. The youngest age group was most at risk of tangible harm, those under 60 were most at risk of intangible harm. Closeness of the relationship to known heavy drinkers increased the risk of harm, with partners and household members of heavy drinkers most at risk. Respondents who were risky drinkers were more likely to report harm from known drinkers. Respondents with a close relationship to heavy drinkers and those with both a close and an extended relationship to heavy drinkers reported lower life satisfaction than those who did not know heavy drinkers. Conclusion: Having a known drinker in one’s life can cast a shadow on an individual’s health and well-being and the closer the proximity relationship to known heavy drinkers the greater the shadow. To reduce AH20, a broad alcohol policy framework is needed, that incorporates effective measures to reduce harm across the population and improve relevant services in local communities. The implementation of the recently passed Public Health Alcohol Act can help identify and implement the necessary actions to reduce alcohol-related harm in Ireland

Using a probabilistic approach to derive a two-phase model of flow-induced cell migration

Interstitial fluid flow is a feature of many solid tumors. In vitro experiments have shown that such fluid flow can direct tumor cell movement upstream or downstream depending on the balance between the competing mechanisms of tensotaxis (cell migration up stress gradients) and autologous chemotaxis (downstream cell movement in response to flow-induced gradients of self-secreted chemoattractants). In this work we develop a probabilistic-continuum, two-phase model for cell migration in response to interstitial flow. We use a kinetic description for the cell velocity probability density function, and model the flow-dependent mechanical and chemical stimuli as forcing terms that bias cell migration upstream and downstream. Using velocity-space averaging, we reformulate the model as a system of continuum equations for the spatiotemporal evolution of the cell volume fraction and flux in response to forcing terms that depend on the local direction and magnitude of the mechanochemical cues. We specialize our model to describe a one-dimensional cell layer subject to fluid flow. Using a combination of numerical simulations and asymptotic analysis, we delineate the parameter regime where transitions from downstream to upstream cell migration occur. As has been observed experimentally, the model predicts downstream-oriented chemotactic migration at low cell volume fractions, and upstream-oriented tensotactic migration at larger volume fractions. We show that the locus of the critical volume fraction, at which the system transitions from downstream to upstream migration, is dominated by the ratio of the rate of chemokine secretion and advection. Our model also predicts that, because the tensotactic stimulus depends strongly on the cell volume fraction, upstream, tensotaxis-dominated migration occurs only transiently when the cells are initially seeded, and transitions to downstream, chemotaxis-dominated migration occur at later times due to the dispersive effect of cell diffusion

Utilizing gravity in movement-based games and play

This paper seeks to expand the understanding of gravity as a powerful but underexplored design resource for movement-based games and play. We examine how gravity has been utilized and manipulated in digital, physical, and mixed reality games and sports, considering five central and gravity-related facets of user experience: realism, affect, challenge, movement diversity, and sociality. For each facet, we suggest new directions for expanding the field of movement-based games and play, for example through novel combinations of physical and digital elements. Our primary contribution is a structured articulation of a novel point of view for designing games and interactions for the moving body. Additionally, we point out new research directions, and our conceptual framework can be used as a design tool. We demonstrate this in 1) creating and evaluating a novel gravity-based game mechanic, and 2) analyzing an existing movement-based game and suggesting future improvements

Using a probabilistic approach to derive a two-phase model of flow-induced cell migration

Interstitial fluid flow is a feature of many solid tumours. In vitro experiments have shown that such fluid flow can direct tumour cell movement upstream or downstream depending on the balance between the competing mechanisms of tensotaxis and autologous chemotaxis. In this work we develop a probabilistic-continuum, two-phase model for cell migration in response to interstitial flow. We use a Fokker-Planck type equation for the cell-velocity probability density function, and model the flow-dependent mechanochemical stimulus as a forcing term which biases cell migration upstream and downstream. Using velocity-space averaging, we reformulate the model as a system of continuum equations for the spatio-temporal evolution of the cell volume fraction and flux, in response to forcing terms which depend on the local direction and magnitude of the mechanochemical cues. We specialise our model to describe a one-dimensional cell layer subject to fluid flow. Using a combination of numerical simulations and asymptotic analysis, we delineate the parameter regime where transitions from downstream to upstream cell migration occur. As has been observed experimentally, the model predicts downstream-oriented, chemotactic migration at low cell volume fractions, and upstream-oriented, tensotactic migration at larger volume fractions. We show that the locus of the critical volume fraction, at which the system transitions from downstream to upstream migration, is dominated by the ratio of the rate of chemokine secretion and advection. Our model predicts that, because the tensotactic stimulus depends strongly on the cell volume fraction, upstream migration occurs only transiently when the cells are initially seeded, and transitions to downstream migration occur at later times due to the dispersive effect of cell diffusion.Comment: 20 pages, 6 figures. Submitted to Biophysical Journa

Resonant Mie Scattering (RMieS) correction of infrared spectra from highly scattering biological samples

Infrared spectra of single biological cells often exhibit the “dispersion artefact” observed as a sharp decrease in intensity on the high wavenumber side of absorption bands, in particular the Amide I band at ~1655 cm-1, causing a downward shift of the true peak position. The presence of this effect makes any biochemical interpretation of the spectra unreliable. Recent theory has shed light on the origins of the ‘dispersion artefact’ which has been attributed to resonant Mie scattering (RMieS). In this paper a preliminary algorithm for correcting RMieS is presented and evaluated using simulated data. Results show that the ‘dispersion artefact’ appears to be removed, however, the correction is not perfect. An iterative approach was subsequently implemented whereby the reference spectrum is improved after each iteration, resulting in a more accurate correction. Consequently the corrected spectra become increasingly more representative of the pure absorbance spectra. Using this correction method reliable peak positions can be obtained