Infection percolation: A dynamic network model of disease spreading

Models of disease spreading are critical for predicting infection growth in a population and evaluating public health policies. However, standard models typically represent the dynamics of disease transmission between individuals using macroscopic parameters that do not accurately represent person-to-person variability. To address this issue, we present a dynamic network model that provides a straightforward way to incorporate both disease transmission dynamics at the individual scale as well as the full spatiotemporal history of infection at the population scale. We find that disease spreads through a social network as a traveling wave of infection, followed by a traveling wave of recovery, with the onset and dynamics of spreading determined by the interplay between disease transmission and recovery. We use these insights to develop a scaling theory that predicts the dynamics of infection for diverse diseases and populations. Furthermore, we show how spatial heterogeneities in susceptibility to infection can either exacerbate or quell the spread of disease, depending on its infectivity. Ultimately, our dynamic network approach provides a simple way to model disease spreading that unifies previous findings and can be generalized to diverse diseases, containment strategies, seasonal conditions, and community structures.Comment: In press, Frontiers in Physics (2021

Chemotactic smoothing of collective migration

Collective migration-the directed, coordinated motion of many self-propelled agents-is a fascinating emergent behavior exhibited by active matter with functional implications for biological systems. However, how migration can persist when a population is confronted with perturbations is poorly understood. Here, we address this gap in knowledge through studies of bacteria that migrate via directed motion, or chemotaxis, in response to a self-generated nutrient gradient. We find that bacterial populations autonomously smooth out large-scale perturbations in their overall morphology, enabling the cells to continue to migrate together. This smoothing process arises from spatial variations in the ability of cells to sense and respond to the local nutrient gradient-revealing a population-scale consequence of the manner in which individual cells transduce external signals. Altogether, our work provides insights to predict, and potentially control, the collective migration and morphology of cellular populations and diverse other forms of active matter. eLife digest Flocks of birds, schools of fish and herds of animals are all good examples of collective migration, where individuals co-ordinate their behavior to improve survival. This process also happens on a cellular level; for example, when bacteria consume a nutrient in their surroundings, they will collectively move to an area with a higher concentration of food via a process known as chemotaxis. Several studies have examined how disturbing collective migration can cause populations to fall apart. However, little is known about how groups withstand these interferences. To investigate, Bhattacharjee, Amchin, Alert et al. studied bacteria called Escherichia coli as they moved through a gel towards nutrients. The E. coli were injected into the gel using a three-dimensional printer, which deposited the bacteria into a wiggly shape that forces the cells apart, making it harder for them to move as a collective group. However, as the bacteria migrated through the gel, they smoothed out the line and gradually made it straighter so they could continue to travel together over longer distances. Computer simulations revealed that this smoothing process is achieved by differences in how the cells respond to local nutrient levels based on their position. Bacteria towards the front of the group are exposed to more nutrients, causing them to become oversaturated and respond less effectively to the nutrient gradient. As a result, they move more slowly, allowing the cells behind them to eventually catch-up. These findings reveal a general mechanism in which limitations in how individuals sense and respond to an external signal (in this case local nutrient concentrations) allows them to continue migrating together. This mechanism may apply to other systems that migrate via chemotaxis, as well as groups whose movement is directed by different external factors, such as temperature and light intensity

Chemotactic smoothing of collective migration

Collective migration -- the directed, coordinated motion of many self-propelled agents -- is a fascinating emergent behavior exhibited by active matter that has key functional implications for biological systems. Extensive studies have elucidated the different ways in which this phenomenon may arise. Nevertheless, how collective migration can persist when a population is confronted with perturbations, which inevitably arise in complex settings, is poorly understood. Here, by combining experiments and simulations, we describe a mechanism by which collectively migrating populations smooth out large-scale perturbations in their overall morphology, enabling their constituents to continue to migrate together. We focus on the canonical example of chemotactic migration of Escherichia coli, in which fronts of cells move via directed motion, or chemotaxis, in response to a self-generated nutrient gradient. We identify two distinct modes in which chemotaxis influences the morphology of the population: cells in different locations along a front migrate at different velocities due to spatial variations in (i) the local nutrient gradient and in (ii) the ability of cells to sense and respond to the local nutrient gradient. While the first mode is destabilizing, the second mode is stabilizing and dominates, ultimately driving smoothing of the overall population and enabling continued collective migration. This process is autonomous, arising without any external intervention; instead, it is a population-scale consequence of the manner in which individual cells transduce external signals. Our findings thus provide insights to predict, and potentially control, the collective migration and morphology of cell populations and diverse other forms of active matter

Controlling capillary fingering using pore size gradients in disordered media

Capillary fingering is a displacement process that can occur when a non-wetting fluid displaces a wetting fluid from a homogeneous disordered porous medium. Here, we investigate how this process is influenced by a pore size gradient. Using microfluidic experiments and computational pore-network models, we show that the non-wetting fluid displacement behavior depends sensitively on the direction and the magnitude of the gradient. The fluid displacement depends on the competition between a pore size gradient and pore-scale disorder; indeed, a sufficiently large gradient can completely suppress capillary fingering. By analyzing capillary forces at the pore scale, we identify a non-dimensional parameter that describes the physics underlying these diverse flow behaviors. Our results thus expand the understanding of flow in complex porous media, and suggest a new way to control flow behavior via the introduction of pore size gradients.Comment: In press, Physical Review Fluids (2019

Clinically Relevant Interactions between Newer Antidepressants and Second-Generation Antipsychotics

INTRODUCTION: Combinations of newer antidepressants and second-generation antipsychotics (SGAs) are frequently used by clinicians. Pharmacokinetic drug interaction (PK DI) and poorly understood pharmacodynamic (PD) drug interaction (PD DI) can occur between them. AREAS COVERED: This paper comprehensively reviews PD DI and PK DI studies. EXPERT OPINION: More PK DI studies are needed to better establish dose correction factors after adding fluoxetine and paroxetine to aripiprazole, iloperidone and risperidone. Further PK DI studies and case reports are also needed to better establish the need for dose correction factors after adding i) fluoxetine to clozapine, lurasidone, quetiapine and olanzapine; ii) paroxetine to olanzapine; iii) fluvoxamine to asenapine, aripiprazole, iloperidone, lurasidone, olanzapine, quetiapine and risperidone; iv) high sertraline doses to aripiprazole, clozapine, iloperidone and risperidone: v) bupropion and duloxetine to aripiprazole, clozapine, iloperidone and risperidone; and vi) asenapine to paroxetine and venlafaxine. Possible beneficial PD DI effects occur after adding SGAs to newer antidepressants for treatment-resistant major depressive and obsessive-compulsive disorders. The lack of studies combining newer antidepressants and SGAs in psychotic depression is worrisome. PD DIs between newer antidepressants and SGAs may be more likely for mirtazapine and bupropion. Adding selective serotonin reuptake inhibitors and SGAs may increase QTc interval and may very rarely contribute to torsades de pointes

The impact of musical improvisation on children’s creative thinking

This paper reports some findings from a doctoral thesis, which was been pursuing at the University of Granada, Spain. The author would like to thank the staff and children of Conservatory of Santiago de Compostela for welcoming the idea of this project, and specially to Maria Jos´e P´ampano and Alejandro Vargas for their collaboration as experts on the assessment of children musical thinking.This article seeks to be a contribution to the defence of the development of musical creative thinking in educational settings. This research report evaluates the efficacy of a musical improvisation workshop with 8-11-year-olds (N = 17) as aiming to develop children's creative thinking. The study was conducted with two groups of 8-9-year-olds and 10-11-year-old children over a period of three months combining collective and individual lessons. The music lessons were improvisatory activities around an upright piano as the main tool but enriched with a variety of musical instruments, objects, and proposals (musical and extra-musical assignments). Webster's Measure of Creative Thinking in Music - MCTM II (Webster, 1987, 1994) was administered before and after the six-month teaching programmes (i.e., pre-test and post-test) to assess children's creative thinking in terms of four musical factors: extensiveness, flexibility, originality, and syntax. The study demonstrated how creativity was significantly fostered in children through musical improvisation with a considerable increase of the four musical factors in both groups, with the main progress in musical originality (group of 8-9 year old) and musical syntax (group of 10-11 year old). The study also revealed that the difference between agegroups diminished after the intervention and the variability between the participants decreased after an improvisation workshop, especially in group 2 (10-11 years), indicating that because of the training, the initial differences tend to be minimized. However, individual differences highlighted the complexity of analysing the creativity paradigm

Biophysical Modeling of the Growth and Motion of Bacterial Populations

The growth and spread of bacterial populations are processes of broad significance. The coupling between cells, the structures of their environment, and the chemical makeup of their environment underlies how bacteria survive and spread. For example, the environments bacteria inhabit often confine individual cells, modifying both their individual and collective motion in previously overlooked ways. Thus, in this thesis, I first use biophysical modeling and numerical simulations to uncover new features of cell motion that arise due to confinement within a heterogeneous medium. In particular, I develop a continuum model to better understand experimental observations of traveling bacterial fronts in highly-confining porous media. Using this model, I explore the influence of confinement on (i) the dynamics of bacteria spreading, (ii) the overall morphology of a migrating population, and (iii) the robustness of the population to morphological perturbations. Then, as a step toward similarly describing the dynamics of mixed communities---which are often composed of different species requiring different chemical conditions to thrive---I use biophysical modeling and numerical simulations to study the growth of aerobes and anaerobes in an environment of shared nutrient. In this case, the coupling between nutrient consumption, oxygen consumption, and growth leads to striking new dynamics, such as hysteresis/bistability and growth oscillations, amidst varying chemical conditions. Altogether, this work establishes a quantitative framework to predict, and potentially guide strategies to control, microbial behavior for diverse applications in biomedical science and the environment

Creative musical response: The effects of teacher-student interaction on the improvisation abilities of fourth- and fifth-grade students.

This study investigated the effects of teacher-led verbal interactions with modelling techniques on student creative musical responses in melody-completion activities and tasks involving creative uses of sound. Teaching materials from the Margaret Murray edition of the Orff-Schulwerk, Volume One and Orff-related teaching procedures were used. A pilot study of fourth-graders (N = 40) indicated that limited instructional treatments had no effect on creative thinking scores, as measured by Webster's Measure of Creative Thinking in Music, Version 2 (MCTM-II) and the researcher-designed Measure of Instrumental Creative Musical Response (MICMR). Reliability coefficients and content-, construct-, and criterion-related evidence of MICMR's validity were collected through its use in the pilot study, a test-retest reliability study, and the main investigation. Results showed good test reliability and validity with children ages nine through eleven. The main investigation, a test-retest design, included a twenty-three week instructional treatment with fourth- and fifth-grade students (N = 129). Analysis of data indicated that teacher-student interactions as defined by this study neither aided nor hindered students' creative musical responses as assessed in melody-completion activities, as measured using MICMR, and in creative uses of sounds, as measured by MCTM-II. MICMR scores and music aptitude, as measured by Gordon's Intermediate Measures of Musical Audiation (IMMA), showed a significant positive relationship. Other results showed that instructional treatments had no significant effect on IMMA scores. Interest in music and family background showed no clear relationship to creative musical responses. There was an apparent increase of students' interest in music as a result of the treatments. Changes in interest levels and reactions to treatments indicated the need for further investigations regarding motivational and affective responses in students as a result of teacher-led verbal interactions with students.Ph.D.Music: Music EducationUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104585/1/9542792.pdfDescription of 9542792.pdf : Restricted to UM users only