12 research outputs found
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Indirect Tissue Scaffold Fabrication via Fused Deposition Modeling and Biomimetic Mineralization
To alleviate material limitations of the additive manufacture of tissue scaffolds, researchers have looked to
indirect fabrication approaches. The feature resolution of these processes is limited however, due to the viscous
ceramic slurries that are typically employed. To alleviate these limitations, the authors look to an indirect
fabrication process wherein a pattern, created using Fused Deposition Modeling, is biomimetically mineralized with
an aqueous simulated body fluid, which forms a bonelike hydroxyapatite throughout the scaffold pattern.
Mineralized patters are then heat treated to pyrolyze the pattern and sinter the minerals. With this process, scaffolds
were created with wall thicknesses as small as 150 m and internal channel diameters of 280-340 m, an
appropriate range for bone tissue engineering.Mechanical Engineerin
Meta-analysis of gender performance gaps in undergraduate natural science courses
To investigate patterns of gender-based performance gaps, we conducted a meta-analysis of published studies and unpublished data collected across 169 undergraduate biology and chemistry courses. While we did not detect an overall gender gap in performance, heterogeneity analyses suggested further analysis was warranted, so we investigated whether attributes of the learning environment impacted performance disparities on the basis of gender. Several factors moderated performance differences, including class size, assessment type, and pedagogy. Specifically, we found evidence that larger classes, reliance on exams, and undisrupted, traditional lecture were associated with lower grades for women. We discuss our results in the context of natural science courses and conclude by making recommendations for instructional practices and future research to promote gender equity
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe
The preponderance of matter over antimatter in the early Universe, the
dynamics of the supernova bursts that produced the heavy elements necessary for
life and whether protons eventually decay --- these mysteries at the forefront
of particle physics and astrophysics are key to understanding the early
evolution of our Universe, its current state and its eventual fate. The
Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed
plan for a world-class experiment dedicated to addressing these questions. LBNE
is conceived around three central components: (1) a new, high-intensity
neutrino source generated from a megawatt-class proton accelerator at Fermi
National Accelerator Laboratory, (2) a near neutrino detector just downstream
of the source, and (3) a massive liquid argon time-projection chamber deployed
as a far detector deep underground at the Sanford Underground Research
Facility. This facility, located at the site of the former Homestake Mine in
Lead, South Dakota, is approximately 1,300 km from the neutrino source at
Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino
charge-parity symmetry violation and mass ordering effects. This ambitious yet
cost-effective design incorporates scalability and flexibility and can
accommodate a variety of upgrades and contributions. With its exceptional
combination of experimental configuration, technical capabilities, and
potential for transformative discoveries, LBNE promises to be a vital facility
for the field of particle physics worldwide, providing physicists from around
the globe with opportunities to collaborate in a twenty to thirty year program
of exciting science. In this document we provide a comprehensive overview of
LBNE's scientific objectives, its place in the landscape of neutrino physics
worldwide, the technologies it will incorporate and the capabilities it will
possess.Comment: Major update of previous version. This is the reference document for
LBNE science program and current status. Chapters 1, 3, and 9 provide a
comprehensive overview of LBNE's scientific objectives, its place in the
landscape of neutrino physics worldwide, the technologies it will incorporate
and the capabilities it will possess. 288 pages, 116 figure
Investigation into Polyurethane at Varying Dose Rates of Ionizing Radiation for Clinical Application
Polyurethanes (PUs) are commonly used materials for medical devices. These devices are exposed repeatedly to radiation when patients undergo radiotherapy treatments. It has been found that peripherally inserted central catheters (PICCs) and central venous catheters (CVCs) fail at an increased rate (14.7% and 8.8%, respectively) when radiated. Currently, little research is available on increased failure seen in conjunction with radiation, but complex in vivo environments within a human patient make it difficult to isolate effects of individual variables. This research investigated effects of radiation in an aqueous environment to determine whether radiation combined with a mimicked in vivo environment is sufficient to change PU devices. The following dose rates were used in this study: 3.2 Gy·min−1, 4.5 Gy·min−1, 44 Gy·min−1, and 833 Gy·min−1. Samples were characterized in four main ways: cellular response, physical changes, chemical changes, and mechanical changes. Results reveal normal cellular response at all dose rates, indicating dose rate does not alter cellular adhesion or proliferation, and biocompatibility of the material is not being altered. Results from physical, chemical, and mechanical effects confirm that varying dose rates alone do not initiate material changes, which negates the hypothesis that varying dose rates of radiation contribute to the complications in PICC and CVCs
Fabrication and characterization of medical grade polyurethane composite catheters for near-infrared imaging.
Peripherally inserted central catheters (PICCs) are hollow polymeric tubes that transport nutrients, blood and medications to neonates. To determine proper PICC placement, frequent X-ray imaging of neonates is performed. Because X-rays pose severe health risks to neonates, safer alternatives are needed. We hypothesize that near infrared (NIR) polymer composites can be fabricated into catheters by incorporating a fluorescent dye (IRDye 800CW) and visualized using NIR imaging. To fabricate catheters, polymer and dye are dry mixed and pressed, sectioned, and extruded to produce hollow tubes. We analyzed surface roughness, stiffness, dye retention, NIR contrast intensity, and biocompatibility. The extrusion process did not significantly alter the mechanical properties of the polymer composites. Over a period of 23 days, only 6.35 ± 5.08% dye leached out of catheters. The addition of 0.025 wt% dye resulted in a 14-fold contrast enhancement producing clear PICC images at 1 cm under a tissue equivalent. The addition of IRDye 800CW did not alter the biocompatibility of the polymer and did not increase adhesion of cells to the surface. We successfully demonstrated that catheters can be imaged without the use of harmful radiation and still maintain the same properties as the unaltered medical grade equivalent
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Microstereolithography of Tissue Scaffolds Using a Biodegradable Photocurable Polyester
Due to its ability to create complex cellular geometries with extremely fine resolution, mask
projection microstereolithography (MPμSL) can be useful for fabricating designed tissue
scaffolds and other biological constructs for use in Tissue Engineering and Regenerative
Medicine. However, few photocurable materials with low cytotoxicity, adequate cell adhesion,
and degradability can be processed with MPμSL. In this work, we present the fabrication of
biocompatible and biodegradable tissue scaffolds with 50 μm feature sizes from a novel
polyester using MPμSL. Poly(tri(ethylene glycol)adipate) dimethacrylate (PTEGA-DMA) was
synthesized and evaluated for its printability. The curing parameters for printing were identified
and scaffolds were fabricated. Optical and electron microscopy were used to determine the
achievable feature sizes and accuracy of printed parts using the polymer in the MPμSL system.
MC3T3-E1 mouse preosteoblasts were seeded on PTEGA-DMA films to assess adhesion and
biocompatibility.Mechanical Engineerin