A Student-Driven Approach to Course Revitalization.

A first-year foundational science course grew beyond its scope. Revitalization of the course was driven by second and third-year medical students, who created new learning objectives and edited cases that were well-received by course facilitators and students. The students' role in the course revitalization is a novel approach.

Breaking Binaries: The Critical Need for Feminist Bioethics in Pediatric Gender-Affirming Care.

This commentary responds to Moti Gorin's article "What Is the Aim of Pediatric 'Gender-Affirming' Care?" We argue that Gorin's case against pediatric gender-affirming care rests upon numerous false conceptual binaries: female/male, public/private, objective/subjective, and medically necessary/elective. Drawing on feminist bioethics, we show how such dichotomous thinking is both inaccurate and marginalizing of gender minorities.

Leveraging the Polymer Glass Transition to Access Thermally Switchable Shear Jamming Suspensions.

Suspensions of polymeric nano- and microparticles are fascinating stress-responsive material systems that, depending on their composition, can display a diverse range of flow properties under shear, such as drastic thinning, thickening, and even jamming (reversible solidification driven by shear). However, investigations to date have almost exclusively focused on nonresponsive particles, which do not allow tuning of the flow properties. Polymeric materials possess rich phase transitions that can be directly tuned by their chemical structures, which has enabled researchers to engineer versatile adaptive materials that can respond to targeted external stimuli.

Designing Stress-Adaptive Dense Suspensions Using Dynamic Covalent Chemistry.

The non-Newtonian behaviors of dense suspensions are central to their use in technological and industrial applications and arise from a network of particle-particle contacts that dynamically adapt to imposed shear. Reported herein are studies aimed at exploring how dynamic covalent chemistry between particles and the polymeric solvent can be used to tailor such stress-adaptive contact networks, leading to their unusual rheological behaviors. Specifically, a room temperature dynamic thia-Michael bond is employed to rationally tune the equilibrium constant ( ) of the polymeric solvent to the particle interface.

The role of solvent molecular weight in shear thickening and shear jamming.

The application of stress can drive a dense suspension into a regime of highly non-Newtonian response, characterized by discontinuous shear thickening (DST) and potentially shear jamming (SJ), due to the formation of a frictionally stabilized contact network. Investigating how the molecular weight of the suspending solvent affects the frictional particle-particle interactions, we report on experiments with suspensions of fumed silica particles in polyethylene glycol (PEG). Focusing on the monomer-to-oligomer limit, with n = 1 to 8 ethylene oxide repeat units, we find that increasing n enhances shear thickening under steady-state shear and even elicits rapidly propagating shear jamming fronts, as assessed by high-speed ultrasound imaging of impact experiments.

Ultrathin Porous Hydrocarbon Membranes Templated by Nanoparticle Assemblies.

Porous polymer membranes are widely desired as catalyst supports, sensors, and active layers for separation membranes. We demonstrate that electron beam irradiation of freely suspended gold or FeO nanoparticle (NP) monolayer sheets followed by wet chemical etching is a high-fidelity strategy to template two-dimensional (2D) porous cross-linked hydrocarbon membranes. This approach, which relies on secondary electrons generated by the NP cores, can further be used to transform three-dimensional (3D) terraced gold NP supercrystals into 3D porous hydrocarbon membranes.

Aqueous Lyotropic Mesophase Behavior of Gemini Dicarboxylate Surfactants Swollen with -Decane.

We report detailed small-angle X-ray scattering (SAXS) studies of the impact of variable -decane loadings on the lyotropic liquid crystalline (LLC) phase behaviors of homologous bis(tetramethylammonium) gemini didecanoate surfactants , which derive from dimerizing decanoic acid through its α-carbon with hydrocarbyl linkers -(CH)- where = 3, 4, 5, and 6. amphiphiles with = 3 or 5 exhibit a strong propensity to form normal double gyroid (G) LLC network mesophases over wide surfactant hydration ranges, as compared to homologues with = 4 or 6. On swelling aqueous LLC mesophases with up to 35 wt % -decane, we demonstrate that odd-carbon linked surfactants ( = 3 or 5) form G and normal double diamond (D) phases over wide water concentration windows with = 22-100 °C.

Consequences of Convex Nanopore Chemistry on Confined Water Dynamics.

A fundamental understanding of confined water is crucial for developing selective ion transport and water purification membranes, yet the roles of nanopore geometry and functionality on confined water dynamics remain unresolved. We report the synthesis of perdeuterated ionic alkylsulfonate amphiphiles and their water-induced self-assembly into lyotropic liquid crystal (LLC) mesophases with well-defined, convex, sulfonate-lined nanopores. Quasielastic neutron scattering (QENS) measurements demonstrate that the water self-diffusion coefficients within these sulfonate-lined convex nanopores depend on the hydration level and amphiphile counterion identity (H, K, NMe).

A new framework for X-ray photon correlation spectroscopy analysis from polycrystalline materials.

We report a new analytical framework for interpreting data from X-ray photon correlation spectroscopy measurements on polycrystalline materials characterized by strong scattering intensity variations at fixed wavevector magnitude (i.e., anisotropic scattering).

Dynamics of a Supercooled Disordered Sphere-Forming Diblock Copolymer as Determined by X-ray Photon Correlation and Dynamic Mechanical Spectroscopies.

We report the dynamic behavior of a sphere-forming poly(styrene)--poly(1,4-butadiene) (PS-PB) diblock copolymer comprising 20 vol % PB below the order-disorder transition temperature ( = 153 °C) using dynamic mechanical spectroscopy (DMS) and X-ray photon correlation spectroscopy (XPCS). A time-temperature transformation diagram was constructed by monitoring the elasticity of the sample as a function of time following rapid quenches of the disordered melt to various temperatures < . Isothermal frequency spectra acquired prior to nucleation of the ordered BCC phase were time-temperature superposed, and the shift factors were fit using the Williams-Landel-Ferry (WLF) equation.

Ion-Specific Confined Water Dynamics in Convex Nanopores of Gemini Surfactant Lyotropic Liquid Crystals.

The impact of pore geometry and functionality on the dynamics of water nanoconfined in porous media are the subject of some debate. We report the synthesis and small-angle X-ray scattering (SAXS) characterization of a series of perdeuterated gemini surfactant lyotropic liquid crystals (LLCs), in which convex, water-filled nanopores of well-defined dimensions are lined with carboxylate functionalities. Quasielastic neutron scattering (QENS) measurements of the translational water dynamics in these dicarboxylate LLC nanopores as functions of the surfactant hydration state and the charge compensating counterion (Na, K, NMe) reveal that the measured dynamics depend primarily on surfactant hydration, with an unexpected counterion dependence that varies with hydration number.

Counterion-Regulated Dynamics of Water Confined in Lyotropic Liquid Crystalline Morphologies.

The dynamics of confined water is of fundamental and long-standing interest. In technologically important forms of confinement, such as proton-exchange membranes, electrostatic interactions with the confining matrix and counterions play significant roles on the properties of water. There has been recent interest on the dynamics of water confined to the lyotropic liquid crystalline (LLC) morphologies of Gemini dicarboxylate surfactants.

Roles of Chemical Functionality and Pore Curvature in the Design of Nanoporous Proton Conductors.

Nanoporous proton-transporting media are critical components in fuel cells and other electrochemical devices, yet general molecular design criteria for new materials with enhanced performance remain obscure. Aqueous lyotropic liquid crystals (LLCs) comprise a platform for detailed studies of the molecular-level features governing proton transport in monodisperse, water-filled nanopores lined with well-defined chemical functionalities. We report new alkylsulfonic acid LLCs that exhibit H conductivities as high as σ = 380 mS/cm at 80 °C, which rival those of more acidic, perfluorinated polymers, thus demonstrating that the acidity of the pore functionality is not the sole determinant of proton transport.