Rheology of bidisperse non-Brownian suspensions.

We study the rheology of bidisperse non-Brownian suspensions using particle-based simulation, mapping the viscosity as a function of the size ratio of the species, their relative abundance, and the overall solid content. The variation of the viscosity with applied stress exhibits shear-thickening phenomenology irrespective of composition, though the stress-dependent limiting solids fraction governing the viscosity and its divergence point are nonmonotonic in the mixing ratio. Contact force data demonstrate an asymmetric exchange in the dominant stress contribution from large-large to small-small particle contacts as the mixing ratio of the species evolves.

Women in dental education and their desire to lead: A follow-up.

The aim of this study was to provide a follow-up to the 2015 national survey of women in dental education to re-examine factors and perceived barriers to pursuing administrative and leadership roles. At the beginning of 2023, a survey was administered to full-time women faculty in predoctoral dental programs in the United States. The survey instrument employed a structured format along with open-ended questions to capture qualitative data.

Shear flow of non-Brownian rod-sphere mixtures near jamming.

We use the discrete element method, taking particle contact and hydrodynamic lubrication into account, to unveil the shear rheology of suspensions of frictionless non-Brownian rods in the dense packing fraction regime. We find that, analogously to the random close packing volume fraction, the shear-driven jamming point of this system varies in a nonmonotonic fashion as a function of the rod aspect ratio. The latter strongly influences how the addition of rodlike particles affects the rheological response of a suspension of frictionless non-Brownian spheres to an external shear flow.

Scaling Description of Frictionless Dense Suspensions under Inhomogeneous Flow.

Predicting the rheology of dense suspensions under inhomogeneous flow is crucial in many industrial and geophysical applications, yet the conventional "μ(J)" framework is limited to homogeneous conditions in which the shear rate and solids fraction are spatially invariant. To address this shortcoming, we use particle-based simulations of frictionless dense suspensions to derive new constitutive laws that unify the rheological response under both homogeneous and inhomogeneous conditions. By defining a new dimensionless number associated with particle velocity fluctuations and combining it with the viscous number, the macroscopic friction, and the solids fraction, we obtain scaling relations that collapse data from homogeneous and inhomogeneous simulations.

Impact of granular inclusions on the phase behavior of colloidal gels.

Colloidal gels formed from small attractive particles are commonly used in formulations to keep larger components in suspension. Despite extensive work characterising unfilled gels, little is known about how the larger inclusions alter the phase behavior and microstructure of the colloidal system. Here we use numerical simulations to examine how larger 'granular' particles can alter the gel transition phase boundaries.

Bulk rheology of sticky DNA-functionalized emulsions.

We measure by experiment and particle-based simulation the rheology of concentrated, non-Brownian droplet emulsions functionalized with surface-bound single-stranded (ss), "sticky," DNA. In the absence of ssDNA, the emulsion viscosity increases with the dispersed phase volume fraction ϕ, before passing through a liquid-solid transition at a critical ϕ_{c} related to random close packing. Introducing ssDNA leads to a liquid-solid transition at ϕ<ϕ_{c}, the onset being set by the droplet valency N and the ssDNA concentration (or simulated binding strength ε).

Expert consensus on Didactic Clinical Skills Development for orthodontic curricula.

Purpose/objective: Competence is expected of each beginning dentist and orthodontist. However, the broad definition of competence presents a challenge to academic programs in identifying the level of cognition for students to achieve competence. This study aimed to determine the Didactic Clinical Skills Development curriculum content and competency in predoctoral and advanced education orthodontic programs.

Reliability of a grading rubric designed to evaluate the reflective ability of predoctoral dental students.

Introduction: Reflection and self-assessment are critical skills for healthcare providers. Identification of gaps in knowledge, skills and attitudes, along with the ability to critically think and problem solve to fill gaps, is the ultimate outcome for lifelong learning. The aims of this study were to (a) refine an instrument used for measuring reflective ability, and conduct comprehensive reliability testing, and (b) describe a process for rater calibration.

Nonequilibrium master kinetic equation modeling of colloidal gelation.

We present a detailed study of the kinetic cluster growth process during gelation of weakly attractive colloidal particles by means of experiments on critical Casimir attractive colloidal systems, simulations, and analytical theory. In the experiments and simulations, we follow the mean coordination number of the particles during the growth of clusters to identify an attractive-strength independent cluster evolution as a function of mean coordination number. We relate this cluster evolution to the kinetic attachment and detachment rates of particles and particle clusters.

Stokes at 200 (part 2).

We present the second half of the papers from the Stokes symposium celebrating the bicentenary of George Gabriel Stokes. This article is part of the theme issue 'Stokes at 200 (part 2)'.

Nonequilibrium continuous phase transition in colloidal gelation with short-range attraction.

The dynamical arrest of attractive colloidal particles into out-of-equilibrium structures, known as gelation, is central to biophysics, materials science, nanotechnology, and food and cosmetic applications, but a complete understanding is lacking. In particular, for intermediate particle density and attraction, the structure formation process remains unclear. Here, we show that the gelation of short-range attractive particles is governed by a nonequilibrium percolation process.

Stokes at 200: a celebration of the remarkable achievements of Sir George Gabriel Stokes two hundred years after his birth.

Sir George Gabriel Stokes PRS was for 30 years an inimitable Secretary of the Royal Society and its President from 1885 to 1890. Two hundred years after his birth, Stokes is a towering figure in physics and applied mathematics; fluids, asymptotics, optics, acoustics among many other fields. At the Stokes meeting, held at Pembroke College, Cambridge from 15-18th September 2019, an invited audience of about 100 discussed the state of the art in all the modern research fields that have sprung from his work in physics and mathematics, along with the history of how we have got from Stokes' contributions to where we are now.

Tunable solidification of cornstarch under impact: How to make someone walking on cornstarch sink.

Hundreds of YouTube videos show people running on cornstarch suspensions demonstrating that dense shear thickening suspensions solidify under impact. Such processes are mimicked by impacting and pulling out a plate from the surface of a thickening cornstarch suspension. Here, using both experiments and simulations, we show that applying fast oscillatory shear transverse to the primary impact or extension directions tunes the degree of solidification.

On the role of flexibility in linker-mediated DNA hydrogels.

Three-dimensional DNA networks, composed of tri- or higher valent nanostars with sticky, single-stranded DNA overhangs, have been previously studied in the context of designing thermally responsive, viscoelastic hydrogels. In this work, we use linker-mediated gels, where the sticky ends of two trivalent nanostars are connected through the complementary sticky ends of a linear DNA duplex. We can design this connection to be either rigid or flexible by introducing flexible, non-binding bases.

Testing the Wyart-Cates model for non-Brownian shear thickening using bidisperse suspensions.

There is a growing consensus that shear thickening of concentrated dispersions is driven by the formation of stress-induced frictional contacts. The Wyart-Cates (WC) model of this phenomenon, in which the microphysics of the contacts enters solely via the fraction f of contacts that are frictional, can successfully fit flow curves for suspensions of weakly polydisperse spheres. However, its validity for "real-life", polydisperse suspensions has yet to be seriously tested.

Expert Consensus on Growth and Development Curricula for Predoctoral and Advanced Education Orthodontic Programs.

Dental students and orthodontic residents must demonstrate competence in various areas prior to graduation. However, the Commission on Dental Accreditation (CODA) definition of competence is broad. The aims of this study were to obtain expert consensus on Growth and Development topics and subtopics in predoctoral and advanced education programs in orthodontics and to determine the level of cognition on the subtopics necessary to demonstrate learner competence.

Parameter-free predictions of the viscoelastic response of glassy polymers from non-affine lattice dynamics.

We study the viscoelastic response of amorphous polymers using theory and simulations. By accounting for internal stresses and considering instantaneous normal modes (INMs) within athermal non-affine theory, we make parameter-free predictions of the dynamic viscoelastic moduli obtained in coarse-grained simulations of polymer glasses at non-zero temperatures. The theoretical results show very good correspondence with rheology data collected from molecular dynamics simulations over five orders of magnitude in frequency, with some instabilities that accumulate in the low-frequency part on approach to the glass transition.

Nonmonotonic dependence of polymer-glass mechanical response on chain bending stiffness.

We investigate the mechanical properties of amorphous polymers by means of coarse-grained simulations and nonaffine lattice dynamics theory. A small increase of polymer chain bending stiffness leads first to softening of the material, while hardening happens only upon further strengthening of the backbones. This nonmonotonic variation of the storage modulus G^{'} with bending stiffness is caused by a competition between additional resistance to deformation offered by stiffer backbones and decreased density of the material due to a necessary decrease in monomer-monomer coordination.

Linking attractive interactions and confinement to the rheological response of suspended particles close to jamming.

We study the response to simple shear start-up of an overdamped, athermal assembly of particles with tuneable attractive interactions. We focus on volume fractions close to the jamming point, where such systems can become disordered elastoplastic solids. By systematically varying the strength of the particle-particle attraction and the volume fraction, we demonstrate how cohesion and confinement individually contribute to the shear modulus and yield strain of the material.

Student Preparation for the National Board Dental Hygiene Examination: A national survey of dental hygiene program directors.

Dental hygiene students nearing completion of their educational programs are required to take written and clinical examinations in order to be eligible for licensure. The written licensure exam, the National Board Dental Hygiene Examination (NBDHE), is administered by the Joint Commission of National Dental Examinations (JCNDE). Failing a licensing examination is a costly experience for students and has the potential for a negative impact on a program's accreditation status.

Program Evaluation of a Distance Master's Degree Dental Hygiene Program: A Program Effectiveness Study.

The purpose of this study was to conduct a program evaluation of the University of Missouri-Kansas City Master of Science in Dental Hygiene Education Program (MSDH). This evaluation examined long-term outcomes in the context of stakeholders (the profession, the student, and the degree-granting institution). A mixed-methods approach was used to gather data from the 28 graduates from the MSDH program.