Addition of hyaluronic acid improves cellular infiltration and promotes early-stage chondrogenesis in a collagen-based scaffold for cartilage tissue engineering.

The response of mesenchymal stem cells (MSCs) to a matrix largely depends on the composition as well as the extrinsic mechanical and morphological properties of the substrate to which they adhere to. Collagen-glycosaminoglycan (CG) scaffolds have been extensively used in a range of tissue engineering applications with great success. This is due in part to the presence of the glycosaminoglycans (GAGs) in complementing the biofunctionality of collagen. In this context, the overall goal of this study was to investigate the effect of two GAG types: chondroitin sulphate (CS) and hyaluronic acid (HyA) on the mechanical and morphological characteristics of collagen-based scaffolds and subsequently on the differentiation of rat MSCs in vitro. Morphological characterisation revealed that the incorporation of HyA resulted in a significant reduction in scaffold mean pore size (93.9 μm) relative to collagen-CS (CCS) scaffolds (136.2 μm). In addition, the collagen-HyA (CHyA) scaffolds exhibited greater levels of MSC infiltration in comparison to the CCS scaffolds. Moreover, these CHyA scaffolds showed significant acceleration of early stage gene expression of SOX-9 (approximately 60-fold higher,

Development of a collagen calcium-phosphate scaffold as a novel bone graft substitute.

Previous investigations have shown that collagen shows excellent biological performance as a scaffold for tissue engineering. As a primary constituent of bone and cartilage, it demonstrates excellent cell adhesion and proliferation. However, in bone tissue engineering, it has insufficient mechanical properties for implantation in a load-bearing defect. The objective of this preliminary study was to investigate the possibility of developing a collagen/calcium-phosphate composite scaffold which would combine the biological performance and the high porosity of a collagen scaffold with the high mechanical stiffness of a calcium-phosphate scaffold. Collagen scaffolds were produced by a lyophilisation process from a collagen slurry. The scaffolds were soaked for different exposure times in solutions of 0.1 M, 0.5 M or 1.0 M NaNH4HPO4 followed by 0.1 M, 0.5 M or 1.0 M CaCl2. Mechanical tests of each scaffold were performed on a uniaxial testing system. Young\u27s moduli were determined from stress-strain curves. The pore structure and porosity of the scaffolds were investigated using micro-computed tomography. A pure collagen scaffold served as a control. All scaffolds showed a significantly increased compressive stiffness relative to the pure collagen scaffolds. The exposure to the 0.5 M solutions showed significantly superior results compared to the other groups. Analysis of the pore structure indicated a decrease in the overall porosity of the composite scaffolds relative to the controls. Regarding mechanical stiffness and porosity, scaffolds after 1 hour exposure to the 0.5 M solutions showed the best properties for bone tissue engineering. Further work will involve producing a scaffold with a more homogeneous calcium phosphate distribution

Interprofessional Collaboration Between Occupational Therapists and Registered Nurses in Acute Care Settings: An Exploratory Study

Background. Collaboration between occupational therapists and nurses is key to a positive prognosis for their patients. Currently, there is a gap in the research on professional relationships between occupational therapists and registered nurses in acute care settings. Purpose. To examine interprofessional collaboration between registered nurses and occupational therapy in an acute care setting. Methods. A phenomenological, qualitative design with use of semi-structured interviews was used. Interviewees were four occupational therapists and four registered nurses who currently work in acute care settings in Northern California and were recruited through a snowball, convenience and purposive sampling. Themes and subthemes that emerged from the data answered the research questions. Findings. The key factors preventing collaboration were: Time constraints, role confusion and overlap, personality factors, and lack of occupational therapy advocacy. Implications. This study may guide the development of interprofessional education to improve the collaborative relationship between occupational therapists and nurses to ultimately improve quality of care.https://scholar.dominican.edu/ug-student-posters/1005/thumbnail.jp

An empirically observed pitch-angle diffusion eigenmode in the Earth\u27s electron belt near L* = 5.0

Abstract Using data from NASA\u27s Van Allen Probes, we have identified a synchronized exponential decay of electron flux in the outer zone, near L* = 5.0. Exponential decays strongly indicate the presence of a pure eigenmode of a diffusion operator acting in the synchronized dimension(s). The decay has a time scale of about 4 days with no dependence on pitch angle. While flux at nearby energies and L* is also decaying exponentially, the decay time varies in those dimensions. This suggests the primary decay mechanism is elastic pitch angle scattering, which itself depends on energy and L *. We invert the shape of the observed eigenmode to obtain an approximate shape of the pitch angle diffusion coefficient and show excellent agreement with diffusion by plasmaspheric hiss. Our results suggest that empirically derived eigenmodes provide a powerful diagnostic of the dynamic processes behind exponential decays

Beveled Projectile Points and Ballistics Technology

Explanations for beveled blade edges on projectile points have been debated in North America archaeology since the first systematic description of lithic assemblages in the nineteenth century. Debate has centered around two opposing perspectives. One views beveled edges as features of projectile points that cause them to spin during flight. The other views beveling as a product of edge resharpening that is done unifacially to conserve scarce resources. Here we use a fluid-dynamics model to simulate the effect beveling has on projectiles. Expectations derived from this modeling are evaluated using wind-tunnel experiments. Our findings indicate that beveling produces in-flight rotation that serves as a means of increasing accuracy in relatively low-velocity flight paths.

A biomimetic multi-layered collagen-based scaffold for osteochondral repair.

Cartilage and osteochondral defects pose a significant challenge in orthopedics. Tissue engineering has shown promise as a potential method for the treatment of such defects; however, a long-lasting repair strategy has yet to be realized. This study focuses on the development of a layered construct for osteochondral repair, fabricated through a novel \u22iterative layering\u22 freeze-drying technique. The process involved repeated steps of layer addition followed by freeze-drying, enabling control over material composition, pore size and substrate stiffness in each region of the construct, while also achieving a seamlessly integrated layer structure. The novel construct developed mimics the inherent gradient structure of healthy osteochondral tissue: a bone layer composed of type I collagen and hydroxyapatite (HA), an intermediate layer composed of type I collagen, type II collagen and HA and a cartilaginous region composed of type I collagen, type II collagen and hyaluronic acid. The material properties were designed to provide the biological cues required to encourage infiltration of host cells from the bone marrow while the biomechanical properties were designed to provide an environment optimized to promote differentiation of these cells towards the required lineage in each region. This novel osteochondral graft was shown to have a seamlessly integrated layer structure, high levels of porosity (\u3e97%), a homogeneous pore structure and a high degree of pore interconnectivity. Moreover, homogeneous cellular distribution throughout the entire construct was evident following in vitro culture, demonstrating the potential of this multi-layered scaffold as an advanced strategy for osteochondral defect repair

Application of Adaptive Learning Networks to Quantitative Flaw Definition

Adaptive Learning Networks (ALNs) are algebraic, nonlinear multinomials whose structure and coefficients are learned from empirical data. Over the past several years, their application to quantitative NDE problems has become widespread. The major advantage of the ALN approach is that only a modest data base of experiments is needed, from which the ALN models can be trained. In this work, ALNs are used as a nonlinear, empirical inversion procedure for various defect geometries. Measurements from a sparselypopulated ultrasonic transducer array are input to the ALNs which estimate the defect characteristics. The defects considered are (1) elliptical cracks, (2) irregular-shaped voids, and (3) surface-breaking semielliptical cracks. The models are synthesized from theoretically-generated, forward-scattering data, then evaluated on actual experimental data recorded from titanium and carbon steel samples. The advantage of using theoretical data to train the models is that ultrasonic responses can be generated quickly and inexpensively in a digital computer, thereby avoiding, or greatly minimizing, the expense of calibration sample fabrication. The size and orientation estimates for the experimental evaluation are in excellent agreement with the true defect characteristics