142 research outputs found
Simultaneous self-organization of arterial and venous networks driven by the physics of global power optimization
Understanding of vascular organization is a long-standing problem in
quantitative biology and biophysics and is essential for the growth of large
cultured tissues. Approaches are needed that (1) make predictions of optimal
arteriovenous networks in order to understand the natural vasculatures that
originate from evolution (2) can design vasculature for 3D printing of cultured
tissues, meats, organoids and organs. I present a method for determining the
globally optimal structure of interlocking arterial and venous (arteriovenous)
networks. The core physics is comprised of the minimization of total power
associated with the whole vascular network, with penalties to stop arterial and
venous segments from intersecting. Specifically, the power needed for
Poiseuille flow through vessels and the metabolic power cost for blood
maintenance are optimized. Simultaneous determination of both arterial and
venous vasculatures is essential to avoid intersections between vessels that
would bypass the capillary network. As proof-of-concept, I examine the optimal
vascular structure for supplying square- and disk-like tissue shapes that would
be suitable for bioprinting in multi-well plates. Features in the trees are
driven by the bifurcation exponent and metabolic constant which affect whether
arteries and veins follow the same or different routes through the tissue. They
also affect the level of tortuosity in the vessels. The method could be used to
understand the distribution of blood vessels within organs, to form the core of
simulations, and combined with 3D printing to generate vasculatures for
arbitrary volumes of cultured tissue and cultured meat
Determination of metal ion content of beverages and estimation of target hazard quotients : a comparative study
Background: Considerable research has been directed towards the roles of metal ions in nutrition with metal ion toxicity attracting particular attention. The aim of this study is to measure the levels of metal ions found in selected beverages (red wine, stout and apple juice) and to determine their potential detrimental effects via calculation of the Target Hazard Quotients (THQ) for 250 mL daily consumption. Results: The levels (mean ± SEM) and diversity of metals determined by ICP-MS were highest for red wine samples (30 metals totalling 5620.54 ± 123.86 ppb) followed by apple juice (15 metals totalling 1339.87 ± 10.84 ppb) and stout (14 metals totalling 464.85 ± 46.74 ppb). The combined THQ values were determined based upon levels of V, Cr, Mn, Ni, Cu, Zn and Pb which gave red wine samples the highest value (5100.96 ± 118.93 ppb) followed by apple juice (666.44 ± 7.67 ppb) and stout (328.41 ± 42.36 ppb). The THQ values were as follows: apple juice (male 3.11, female 3.87), stout (male 1.84, female 2.19), red wine (male 126.52, female 157.22) and ultra-filtered red wine (male 110.48, female 137.29). Conclusion: This study reports relatively high levels of metal ions in red wine, which give a very high THQ value suggesting potential hazardous exposure over a lifetime for those who consume at least 250 mL daily. In addition to the known hazardous metals (e.g. Pb), many metals (e.g. Rb) have not had their biological effects systematically investigated and hence the impact of sustained ingestion is not known
Rapid prediction of lab-grown tissue properties using deep learning
The interactions between cells and the extracellular matrix are vital for the
self-organisation of tissues. In this paper we present proof-of-concept to use
machine learning tools to predict the role of this mechanobiology in the
self-organisation of cell-laden hydrogels grown in tethered moulds. We develop
a process for the automated generation of mould designs with and without key
symmetries. We create a large training set with cases by running
detailed biophysical simulations of cell-matrix interactions using the
contractile network dipole orientation (CONDOR) model for the self-organisation
of cellular hydrogels within these moulds. These are used to train an
implementation of the \texttt{pix2pix} deep learning model, reserving
cases that were unseen in the training of the neural network for training and
validation. Comparison between the predictions of the machine learning
technique and the reserved predictions from the biophysical algorithm show that
the machine learning algorithm makes excellent predictions. The machine
learning algorithm is significantly faster than the biophysical method, opening
the possibility of very high throughput rational design of moulds for
pharmaceutical testing, regenerative medicine and fundamental studies of
biology. Future extensions for scaffolds and 3D bioprinting will open
additional applications.Comment: 26 Pages, 11 Figure
High-throughput design of cultured tissue moulds using a biophysical model
The technique presented here identifies tethered mould designs, optimised for
growing cultured tissue with very highly-aligned cells. It is based on a
microscopic biophysical model for polarised cellular hydrogels. There is an
unmet need for tools to assist mould and scaffold designs for the growth of
cultured tissues with bespoke cell organisations, that can be used in
applications such as regenerative medicine, drug screening and cultured meat.
High-throughput biophysical calculations were made for a wide variety of
computer-generated moulds, with cell-matrix interactions and tissue-scale
forces simulated using a contractile-network dipole-orientation model.
Elongated moulds with central broadening and one of the following tethering
strategies are found to lead to highly-aligned cells: (1) tethers placed within
the bilateral protrusions resulting from an indentation on the short edge, to
guide alignment (2) tethers placed within a single vertex to shrink the
available space for misalignment. As such, proof-of-concept has been shown for
mould and tethered scaffold design based on a recently developed biophysical
model. The approach is applicable to a broad range of cell types that align in
tissues and is extensible for 3D scaffolds
Simulated annealing approach to vascular structure with application to the coronary arteries
Do the complex processes of angiogenesis during organism development ultimately lead to a near optimal coronary vasculature in the organs of adult mammals? We examine this hypothesis using a powerful and universal method, built on physical and physiological principles, for the determination of globally energetically optimal arterial trees. The method is based on simulated annealing, and can be used to examine arteries in hollow organs with arbitrary tissue geometries. We demonstrate that the approach can generate in silico vasculatures which closely match porcine anatomical data for the coronary arteries on all length scales, and that the optimized arterial trees improve systematically as computational time increases. The method presented here is general, and could in principle be used to examine the arteries of other organs. Potential applications include improvement of medical imaging analysis and the design of vascular trees for artificial organs
The role of vascular complexity on optimal junction exponents
We examine the role of complexity on arterial tree structures, determining globally optimal vessel arrangements using the Simulated AnneaLing Vascular Optimization algorithm, a computational method which we have previously used to reproduce features of cardiac and cerebral vasculatures. In order to progress computational methods for growing arterial networks, deeper understanding of the stability of computational arterial growth algorithms to complexity, variations in physiological parameters (such as metabolic costs for maintaining and pumping blood), and underlying assumptions regarding the value of junction exponents is needed. We determine the globally optimal structure of two-dimensional arterial trees; analysing how physiological parameters affect tree morphology and optimal bifurcation exponent. We find that considering the full complexity of arterial trees is essential for determining the fundamental properties of vasculatures. We conclude that optimisation-based arterial growth algorithms are stable against uncertainties in physiological parameters, while optimal bifurcation exponents (a key parameter for many arterial growth algorithms) are affected by the complexity of vascular networks and the boundary conditions dictated by organs
Gap modification of atomically thin boron nitride by phonon mediated interactions
A theory is presented for the modification of bandgaps in atomically thin
boron nitride (BN) by attractive interactions mediated through phonons in a
polarizable substrate, or in the BN plane. Gap equations are solved, and gap
enhancements are found to range up to 70% for dimensionless electron-phonon
coupling \lambda=1, indicating that a proportion of the measured BN bandgap may
have a phonon origin
Rise of the centrist: from binary to continuous opinion dynamics
We propose a model that extends the binary ``united we stand, divided we
fall'' opinion dynamics of Sznajd-Weron to handle continuous and multi-state
discrete opinions. Disagreement dynamics are often ignored in continuous
extensions of the binary rules, so we make the most symmetric continuum
extension of the binary model that can treat the consequences of agreement
(debate) and disagreement (confrontation) within a population of agents. We use
the continuum extension as an opportunity to develop rules for persistence of
opinion (memory). Rules governing the propagation of centrist views are also
examined. Monte Carlo simulations are carried out. We find that both memory
effects and the type of centrist significantly modify the variance of average
opinions in the large timescale limits of the models. Finally, we describe the
limit of applicability for Sznajd-Weron's model of binary opinions as the
continuum limit is approached. By comparing Monte Carlo results and long
time-step limits, we find that the opinion dynamics of binary models are
significantly different to those where agents are permitted more than 3
opinions
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High-throughput design of cultured tissue moulds using a biophysical model: optimising cell alignment
The technique presented here identifies tethered mould designs, optimised for growing cultured tissue with very highly-aligned cells. It is based on a microscopic biophysical model for polarised cellular hydrogels. There is an unmet need for tools to assist mould and scaffold designs for the growth of cultured tissues with bespoke cell organisations, that can be used in applications such as regenerative medicine, drug screening and cultured meat. High-throughput biophysical calculations were made for a wide variety of computer-generated moulds, with cell-matrix interactions and tissue-scale forces simulated using a contractile network dipole orientation model. Elongated moulds with central broadening and one of the following tethering strategies are found to lead to highly-aligned cells: (1) tethers placed within the bilateral protrusions resulting from an indentation on the short edge, to guide alignment (2) tethers placed within a single vertex to shrink the available space for misalignment. As such, proof-of-concept has been shown for mould and tethered scaffold design based on a recently developed biophysical model. The approach is applicable to a broad range of cell types that align in tissues and is extensible for 3D scaffolds
Technology Platform for Sampling Water with Electrolyte-Gated Organic Transistors Sensitised with Langmuiur-Deposited Calixarene Surface Layers.
We demonstrate a technology platform that enables the development of new, surface-sensitised organic transistor sensors. We show that an organic semiconductor can still be gated by an electric double layer within the electrochemical window of water after the deposition of up to four Langmuir- Schäfer calixarene layers onto its surface. Since many calixarenes are known to selectively bind waterborne cations, this facilitates sensitising a conventional organic semiconductor with a physically deposited layer for specific cation recognition. When at least two Langmuir-Schäfer layers are deposited, these also block the electrochemical doping of the organic semiconductor, which otherwise competes with the field effect in water-gated organic transistors. Carrier mobility is reduced by the application of calixarene layers, but transistor current measurement remains accessible by simple methods. We find that for the present purpose, Langmuir-Schäfer-printed surface layers perform better than those deposited by Langmuir-Blodgett deposition
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