Environment Constrains Fitness Advantages of Division of Labor in Microbial Consortia Engineered for Metabolite Push or Pull Interactions.

Fitness benefits from division of labor are well documented in microbial consortia, but the dependency of the benefits on environmental context is poorly understood. Two synthetic Escherichia coli consortia were built to test the relationships between exchanged organic acid, local environment, and opportunity costs of different metabolic strategies. Opportunity costs quantify benefits not realized due to selecting one phenotype over another.

Quantitative analysis of macroscopic solute transport in the murine brain.

Background: Understanding molecular transport in the brain is critical to care and prevention of neurological disease and injury. A key question is whether transport occurs primarily by diffusion, or also by convection or dispersion. Dynamic contrast-enhanced (DCE-MRI) experiments have long reported solute transport in the brain that appears to be faster than diffusion alone, but this transport rate has not been quantified to a physically relevant value that can be compared to known diffusive rates of tracers.

Antimicrobial laser-activated sealants for combating surgical site infections.

Surgical-site infections (SSIs) occur in 2-5% of patients undergoing surgery in the US alone, impacting 300 000-500 000 lives each year, and presenting up to 11 times greater risk of death compared to patients without SSIs. The most common cause of SSI is Staphylococcus aureus, and methicillin-resistant S. aureus (MRSA) is the most common pathogen in community hospitals.

In response to "Is solute movement within the extracellular spaces of brain gray matter brought about primarily by diffusion or flow?".

In our work, "Analysis of Convective and Diffusive Transport in the Brain Interstitium", published in this journal (2019, 16:6), we estimate the interstitial superficial velocity by comparison of transport model simulations to published experimental Real-Time Iontophoresis (RTI) data. In the Discussion section, we calculate a value for perfusion rate, or volumetric flow rate per unit mass of tissue, from these fundamental results of superficial velocity. Drs.

Analysis of convective and diffusive transport in the brain interstitium.

Background: Despite advances in in vivo imaging and experimental techniques, the nature of transport mechanisms in the brain remain elusive. Mathematical modelling verified using available experimental data offers a powerful tool for investigating hypotheses regarding extracellular transport of molecules in brain tissue. Here we describe a tool developed to aid in investigation of interstitial transport mechanisms, especially the potential for convection (or bulk flow) and its relevance to interstitial solute transport, for which there is conflicting evidence.

Competitive resource allocation to metabolic pathways contributes to overflow metabolisms and emergent properties in cross-feeding microbial consortia.

Resource scarcity is a common stress in nature and has a major impact on microbial physiology. This review highlights microbial acclimations to resource scarcity, focusing on resource investment strategies for chemoheterotrophs from the molecular level to the pathway level. Competitive resource allocation strategies often lead to a phenotype known as overflow metabolism; the resulting overflow byproducts can stabilize cooperative interactions in microbial communities and can lead to cross-feeding consortia.

Effects of Spatial Localization on Microbial Consortia Growth.

Microbial consortia are commonly observed in natural and synthetic systems, and these consortia frequently result in higher biomass production relative to monocultures. The focus here is on the impact of initial spatial localization and substrate diffusivity on the growth of a model microbial consortium consisting of a producer strain that consumes glucose and produces acetate and a scavenger strain that consumes the acetate. The mathematical model is based on an individual cell model where growth is described by Monod kinetics, and substrate transport is described by a continuum-based, non-equilibrium reaction-diffusion model where convective transport is negligible (e.

Combining existing numerical models with data assimilation using weighted least-squares finite element methods.

A new approach has been developed for combining and enhancing the results from an existing computational fluid dynamics model with experimental data using the weighted least-squares finite element method (WLSFEM). Development of the approach was motivated by the existence of both limited experimental blood velocity in the left ventricle and inexact numerical models of the same flow. Limitations of the experimental data include measurement noise and having data only along a two-dimensional plane.

Simulation of nanoparticle transport in airways using Petrov-Galerkin finite element methods.

The transport and deposition properties of nanoparticles with a range of aerodynamic diameters ( 1 nm ≤ d ≤ 150 nm) were studied for the human airways. A finite element code was developed that solved both the Navier-Stokes and advection-diffusion equations monolithically. When modeling nanoparticle transport in the airways, the finite element method becomes unstable, and, in order resolve this issue, various stabilization methods were considered in terms of accuracy and computational cost.

Left ventricular flow analysis: recent advances in numerical methods and applications in cardiac ultrasound.

The left ventricle (LV) pumps oxygenated blood from the lungs to the rest of the body through systemic circulation. The efficiency of such a pumping function is dependent on blood flow within the LV chamber. It is therefore crucial to accurately characterize LV hemodynamics.

A model of filiform hair distribution on the cricket cercus.

Crickets and other orthopteran insects sense air currents with a pair of abdominal appendages resembling antennae, called cerci. Each cercus in the common house cricket Acheta domesticus is covered with between 500 to 750 filiform mechanosensory hairs. The distribution of the hairs on the cerci, as well as the global patterns of their movement axes, are very stereotypical across different animals in this species, and the development of this system has been studied extensively.

Effect of model selection on prediction of periodic behavior in gene regulatory networks.

One of the current challenges for cell biology is understanding of the system level cellular behavior from the knowledge of a network of the individual subcellular agents. We address a question of how the model selection affects the predicted dynamic behavior of a gene network. In particular, for a fixed network structure, we compare protein-only models with models in which each transcriptional activation is represented both by mRNA and protein concentrations.

Weighted least-squares finite element method for cardiac blood flow simulation with echocardiographic data.

As both fluid flow measurement techniques and computer simulation methods continue to improve, there is a growing need for numerical simulation approaches that can assimilate experimental data into the simulation in a flexible and mathematically consistent manner. The problem of interest here is the simulation of blood flow in the left ventricle with the assimilation of experimental data provided by ultrasound imaging of microbubbles in the blood. The weighted least-squares finite element method is used because it allows data to be assimilated in a very flexible manner so that accurate measurements are more closely matched with the numerical solution than less accurate data.

Quantitative characterization of the filiform mechanosensory hair array on the cricket cercus.

Background: Crickets and other orthopteran insects sense air currents with a pair of abdominal appendages resembling antennae, called cerci. Each cercus in the common house cricket Acheta domesticus is approximately 1 cm long, and is covered with 500 to 750 filiform mechanosensory hairs. The distribution of the hairs on the cerci, as well as the global patterns of their movement vectors, have been characterized semi-quantitatively in studies over the last 40 years, and have been shown to be very stereotypical across different animals in this species.

Particle transport modeling in pulmonary airways with high-order elements.

Inhaled particles can be either harmful (e.g., smoke, exhaust, viruses) or beneficial (e.

Flow velocity vector fields by ultrasound particle imaging velocimetry: in vitro comparison with optical flow velocimetry.

Objectives: We performed an in vitro study to assess the precision and accuracy of particle imaging velocimetry (PIV) data acquired using a clinically available portable ultrasound system via comparison with stereo optical PIV.

Methods: The performance of ultrasound PIV was compared with optical PIV on a benchmark problem involving vortical flow with a substantial out-of-plane velocity component. Optical PIV is capable of stereo image acquisition, thus measuring out-of-plane velocity components.

Impact of pericardial adhesions on diastolic function as assessed by vortex formation time, a parameter of transmitral flow efficiency.

Background: Pericardial adhesions are a pathophysiological marker of constrictive pericarditis (CP), which impairs cardiac filling by limiting the total cardiac volume compliance and diastolic filling function. We studied diastolic transmitral flow efficiency as a new parameter of filling function in a pericardial adhesion animal model. We hypothesized that vortex formation time (VFT), an index of optimal efficient diastolic transmitral flow, is altered by patchy pericardial-epicardial adhesions.

Spatiotemporal temperature distribution and cancer cell death in response to extracellular hyperthermia induced by gold nanorods.

Plasmonic nanoparticles have shown promise in hyperthermic cancer therapy, both in vitro and in vivo. Previous reports have described hyperthermic ablation using targeted and nontargeted nanoparticles internalized by cancer cells, but most reports do not describe a theoretical analysis for determining optimal parameters. The focus of the current research was first to evaluate the spatiotemporal temperature distribution and cell death induced by extracellular hyperthermia in which gold nanorods (GNRs) were maintained in the dispersion outside human prostate cancer cells.

Revisiting the simplified bernoulli equation.

Background: The assessment of the severity of aortic valve stenosis is done by either invasive catheterization or non-invasive Doppler Echocardiography in conjunction with the simplified Bernoulli equation. The catheter measurement is generally considered more accurate, but the procedure is also more likely to have dangerous complications.

Objective: The focus here is on examining computational fluid dynamics as an alternative method for analyzing the echo data and determining whether it can provide results similar to the catheter measurement.

Impact of acute moderate elevation in left ventricular afterload on diastolic transmitral flow efficiency: analysis by vortex formation time.

Background: The formation of a vortex alongside a diastolic jet signifies an efficient blood transport mechanism. Vortex formation time (VFT) is an index of the optimal conditions for vortex formation. It was hypothesized that left ventricular (LV) afterload impairs diastolic transmitral flow efficiency and therefore shifts the VFT out of its optimal range.

Increase in the late diastolic filling force is associated with impaired transmitral flow efficiency in acute moderate elevation of left ventricular afterload.

Objective: Analysis of intraventricular flow force and efficiency is a novel concept of quantitatively assessing left ventricular (LV) hemodynamic performance. We have parametrically characterized diastolic filling flow by early inflow force, late inflow force, and total inflow force and by vortex formation time (VFT), a fundamental parameter of fluid transport efficiency. The purpose of this study was to determine what changes in inflow forces characterize a decrease in diastolic blood transport efficiency in acute moderate elevation of LV afterload.

Optimizing delivery of multivalent targeting constructs for detection of secondary tumors.

Targeting drugs or imaging molecules to specific cells by conjugating them to antibodies or ligands for cell surface receptors may allow earlier detection of pathology, better localization for intervention, and fewer side effects. Delivery of these molecules to the target is complicated by construct size, which cannot cross typical endothelial barriers such as the vascular wall, and lack of a priori knowledge of the location of secondary tumor sites to which the construct is targeted. Here we develop mathematical models for diffusive and convection-enhanced delivery of a trivalent construct.

Modeling 3-D compliant blood flow with FOSLS.

Blood flow in large vessels is typically modeled using the Navier-Stokes equations for the fluid domain and elasticity equations for the vessel wall. As the wall deforms, additional complications are introduced because the shape of the fluid domain changes, necessitating the use of a re-mapping or re-griding process for the fluid region. Typically, this system (fluid, solid, mapping) is solved using an iterative approach in which the fluid, elastic, and mapping equations are solved in series until the iterations converge.

First-order system least squares for elastohydrodynamics with application to flow in compliant blood vessels.

Mathematical modeling of compliant blood vessels generally involves the Navier-Stokes equations on the evolving fluid domain and constitutive structural equations on the tissue domain. Coupling these systems while accounting for the changing shape of the fluid domain is a major challenge in numerical simulation. Many techniques have been developed to model compliant vessels, but all suffer from disproportionate increase in computational cost as problem complexity increases (i.

A boussinesq model of natural convection in the human eye and the formation of Krukenberg's spindle.

The cornea of the human eye is cooled by the surrounding air and by evaporation of the tear film. The temperature difference between the cornea and the iris (at core body temperature) causes circulation of the aqueous humor in the anterior chamber of the eye. Others have suggested that the circulation pattern governs the shape of the Krukenberg spindle, a distinctive vertical band of pigment on the posterior cornea surface in some pathologies.