Controlling the extrudate swell in melt extrusion additive manufacturing of 3D scaffolds: a designed experiment.

Tissue engineering using three-dimensional porous scaffolds has shown promise for the restoration of normal function in injured and diseased tissues and organs. Rigorous control over scaffold architecture in melt extrusion additive manufacturing is highly restricted mainly due to pronounced variations in the deposited strand diameter upon any variations in process conditions and polymer viscoelasticity. We have designed an I-optimal, split-plot experiment to study the extrudate swell in melt extrusion additive manufacturing and to control the scaffold architecture. The designed experiment was used to generate data to relate three responses (swell, density, and modulus) to a set of controllable factors (plotting needle diameter, temperature, pressure, and the dispensing speed). The fitted regression relationships were used to optimize the three responses simultaneously. The swell response was constrained to be close to 1 while maximizing the modulus and minimizing the density. Constraining the extrudate swell to 1 generates design-driven scaffolds, with strand diameters equal to the plotting needle diameter, and allows a greater control over scaffold pore size. Hence, the modulus of the scaffolds can be fully controlled by adjusting the in-plane distance between the deposited strands. To the extent of the model's validity, we can eliminate the effect of extrudate swell in designing these scaffolds, while targeting a range of porosity and modulus appropriate for bone tissue engineering. The result of this optimization was a predicted modulus of 14 MPa and a predicted density of 0.29 g/cm3 (porosity ≈ 75%) using polycaprolactone as scaffold material. These predicted responses corresponded to factor levels of 0.6 µm for the plotting needle diameter, plotting pressure of 2.5 bar, melt temperature of 113.5 °C, and dispensing speed of 2 mm/s. The validation scaffold enabled us to quantify the percentage difference for the predictions, which was 9.5% for the extrudate swell, 19% for the density, and 29% for the modulus.

Parenting skills and parent readiness for treatment are associated with child disruptive behavior and parent participation in treatment.

OBJECTIVE: Parent management training programs for parents of children with disruptive behaviors are efficacious treatments; however, in order to maximize efficiency it is necessary to develop approaches to understand which parents are most likely to participate in treatment. Accordingly, the present study used a person-centered methodology to determine clinically relevant parenting profiles that capture the breadth of parents' readiness to engage in parenting treatment, and their self-reported parenting skills. Further, identified profiles were compared on the severity of children's behavior problems and used to predict participation in parent management training. METHOD: One hundred and forty-three parents completed assessments at an urban children's mental health clinic. Parents were given measures to assess personal readiness to participate in parenting treatment, parenting skills, and child behavior. A subset of these parents participated in parent management training. RESULTS: Three profiles emerged that differed in parents' treatment readiness and level of skills. Forty-one percent of parents were classified as "ready." They showed relatively higher rates of inconsistent discipline, but also somewhat higher levels of positive parenting. Thirty-nine percent of parents were classified as "less in need." These parents reported relatively less inconsistent discipline and poor supervision skills and greater positive parenting. Finally, approximately 20% of parents were classified as "almost ready." They showed high levels of inconsistent discipline and poor supervision skills, and low levels of positive parenting. Almost ready and ready parents reported the most problems with their children's behavior. Further, parents classified as less in need participated in the fewest treatment sessions. CONCLUSIONS: Consideration of parent readiness and skills, in addition to symptom severity, may inform clinical decision making and screening procedures.