Diffusing Wave Spectroscopy Measurements of Colloidal Suspension Dynamics.

Diffusing wave spectroscopy (DWS) is used to measure the dynamics of charged silica particles between the volume fractions 0.065 ≤ ϕ ≤ 0.352 (weight percentages from 12.7 to 55.8 wt %). The short-time diffusivity averaged over the scattering vectors sampled by DWS D¯(ϕ) decreases with an increasing concentration. An effective hard-sphere model that accounts for hydrodynamic interactions and a double-layer repulsion fits the values up to an effective volume fraction ϕeff=ϕb^3≈0.6, where b^ is the excluded shell radius normalized by the particle radius b^ = b/a = 1.3. While DWS measurements of diffusivity are sensitive to repulsive interactions, we show that they are relatively insensitive to attraction, such as those due to secondary minima in the interaction potential or weak depletion interaction.

Guar Gel Binders for Silicon Nanoparticle Anodes: Relating Binder Rheology to Electrode Performance.

Binding agents are a critical component of Si-based anodes for lithium-ion batteries. Herein, we introduce a composite hydrogel binder consisting of carbon black (CB) and guar, which is chemically cross-linked with glutaraldehyde as a means to reinforce the electrode structure during lithiation and improve electronic conductivity. Dynamic rheological measurements are used to monitor the cross-linking reaction and show that rheology plays a significant role in binder performance. The cross-linking reaction occurs at a faster rate and produces stronger networks in the presence of CB, as evidenced from higher gel elastic modulus in guar + CB gels than guar gels alone. Silicon nanoparticle (SiNP) electrodes that use binders with low cross-link densities (trxn < 2 days) demonstrate discharge capacities ∼1200 mAh g-1 and Coulombic efficiencies >99.8% after 300 cycles at 1-C rate. Low cross-link densities likely increase the capacity of SiNP anodes because of binder-Si hydrogen-bonding interactions that accommodate volume expansions. In addition, the cross-linked binder demonstrates the potential for self-healing, as evidenced by an increased elastic modulus after the gel was mechanically fragmented, which may preserve the electrode microstructure during lithiation and increase capacity retention. The composite hydrogel with integrated conductive additives gives promise to a new type of binder for next-generation lithium-ion batteries.

On-chip recalcification of citrated whole blood using a microfluidic herringbone mixer.

In vitro assays of platelet function and coagulation are typically performed in the presence of an anticoagulant. The divalent cation chelator sodium citrate is among the most common because its effect on coagulation is reversible upon reintroduction of divalent cations. Adding divalent cations into citrated blood by batch mixing leads to platelet activation and initiation of coagulation after several minutes, thus limiting the time blood can be used before spontaneously clotting. In this work, we describe a herringbone microfluidic mixer to continuously introduce divalent cations into citrated blood. The mixing ratio, defined as the ratio of the volumetric flow rates of citrated blood and recalcification buffer, can be adjusted by changing the relative inlet pressures of these two solutions. This feature is useful in whole blood assays in order to account for differences in hematocrit, and thus viscosity. The recalcification process in the herringbone mixer does not activate platelets. The advantage of this continuous mixing approach is demonstrated in microfluidic vascular injury model in which platelets and fibrin accumulate on a collagen-tissue factor surface under flow. Continuous recalcification with the herringbone mixer allowed for flow assay times of up to 30 min, more than three times longer than the time achieved by batch recalcification. This continuous mixer allows for measurements of thrombus formation, remodeling, and fibrinolysis in vitro over time scales that are relevant to these physiological processes.

Promising Results for Cross-Systems Collaborative Efforts to Meet the Needs of Families Impacted by Substance Use.

This study is based on data regarding more than 15,000 families served by 53 federal grantees showing that child safety and permanency, parental recovery, and family well-being improve when agencies work together to address the complex needs of families at the intersection of substance abuse treatment and child welfare. Strategies summarized here offer promising collaborative approaches to mitigate the negative outcomes too often experienced by families impacted by substance use disorders.

Communicating with pediatricians about complementary/alternative medicine: perspectives from parents of children with down syndrome.

OBJECTIVES: Barriers to communication about complementary/alternative medicine (CAM) between parents and pediatricians are frequently documented, yet the scope of these barriers remains poorly understood. Such barriers are especially troubling when they involve children with special health needs, among whom CAM use is especially common. This pilot study of parents of children with Down syndrome (DS) used qualitative methods to explore parents' perceptions of the extent and quality of communication about CAM with pediatricians, to elicit parents' recommendations for improvement, and to formulate new research questions. DESIGN: Semistructured interviews were conducted with parents from 30 families with children with DS. Data were audiotaped and analyzed with assistance from qualitative data analysis software. RESULTS: Parents described how they advocated vigorously with their pediatricians about biomedical concerns such as the American Academy of Pediatrics healthcare guidelines for DS, but often avoided discussion of nonbiomedical concerns such as CAM. Many parents looked to pediatricians to initiate conversations about CAM. DISCUSSION: Even parents who assertively advocate for biomedical concerns in their children's health care may be unlikely to disclose and discuss CAM use with their pediatricians. Attending to parents' experiences helps to illuminate the nature and scope of current communication barriers and poses new research questions for assessing and improving parent-physician collaboration about health-related issues that may be prioritized differently by parents and pediatricians.