Browsing by Subject "Polymers"

Now showing 1 - 6 of 6
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    A Two-Stage Approach Integrating Provisional Biomaterial-Mediated Stabilization Followed by a Definitive Treatment for Managing Volumetric Muscle Loss Injuries
    (MDPI, 2024-06-06) Clark, Andrew R.; Kulwatno, Jonathan; Kanovka, Sergey S.; Klarmann, George J.; Hernandez, Claudia E.; Natoli, Roman M.; McKinley, Todd O.; Potter, Benjamin K.; Dearth, Christopher L.; Goldman, Stephen M.; Orthopaedic Surgery, School of Medicine
    Treatment of volumetric muscle loss (VML) faces challenges due to its unique pathobiology and lower priority in severe musculoskeletal injury management. Consequently, a need exists for multi-stage VML treatment strategies to accommodate delayed interventions owing to comorbidity management or prolonged casualty care in combat settings. To this end, polyvinyl alcohol (PVA) was used at concentrations of 5%, 7.5%, and 10% to generate provisional muscle void fillers (MVFs) of varying stiffness values (1.125 kPa, 3.700 kPa, and 7.699 kPa) to stabilize VML injuries as part of a two-stage approach. These were implanted into a rat model for a duration of 4 weeks, then explanted and either left untreated (control) or treated through minced muscle grafting (MMG). Additional benchmarks included acute MMG and unrepaired groups. At the MVF explant, the 7.5% PVA group exhibited superior neuromuscular function compared to the 5% and 10% PVA groups, the least fibrosis, and the largest median myofiber size among all groups at the 12-week endpoint. Despite the 7.5% PVA’s superiority amongst the two-stage treatment groups, neuromuscular function was neither improved nor impaired relative to acute treatment benchmarks. This suggests that the future success of a two-stage VML treatment strategy will necessitate a more effective definitive intervention.
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    Editorial on the Special Issue “Advances in Nanogels”
    (MDPI, 2022-12-17) Lin, Chien-Chi; Mauri, Emanuele; Rossi, Filippo; Biomedical Engineering, School of Engineering and Technology
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    The effect of inhibitor and initiator concentration on degree of conversion, flexural strength and polymerization shrinkage stress on resin-matrix composite
    (2009) Shaabin, Maram; Chu, Tien-Min Gabriel; Lund, Melvin R.; Matis, Bruce A.; Gonzalez-Cabezas, Carlos; Cochran, Michael A. (Michael Alan)
    Polymerization shrinkage is one of the most significant problems associated with resin-matrix composite. Shrinkage results in contraction stress in the resin, leading to possible debonding in certain areas of the adhesive joint and potentially adversely affecting the bond strength. The reduction in the stress may improve the adaptation of the resin restoration, and decrease the problems that are associated with contraction stress, such as postoperative pain and recurrent caries. Recently, it has been found that varying the inhibitor concentration would reduce the polymerization shrinkage without affecting mechanical properties. In this study, we investigated the effects of varying the initiator and initiator levels on polymerization shrinkage stress, strength, and degree of conversion. An experimental composite was prepared by using a blend of BisGMA: UDMA: TEGMA (1:1:1 weight ratio) with 70 wt% silanated glass fillers. Four levels of inhibitors (BHT 0.0 %, 2%, 6%, 20%) and initiators (CQ 2%, 6%, 20%, 60%) were used (total of 16 combinations). A tensiometer was used to measure the polymerization contraction stress, contraction stress rate and gel time for each resin. FTIR was used to measure the degree of conversion. The flexural strength and flexural modulus were determined using the three-point bending test. Resin-matrix composite with 0.0-percent BHT and 2.0-percent CQ showed the highest contraction stress and stress rate and the shortest gel time, while resin-matrix composite with the 6.0-percent BHT and 6-percent CQ showed the lowest contraction stress and stress rate and the longest gel time. At an extremely high concentrations of CQ (20 percent and 60 percent) and high BHT concentration (20 percent) low degree of conversion values were observed. Overall, from the collected data, group F (2-percent BHT and 6-percent CQ) and G (6-percent BHT and 6-percent CQ) provide the most desirable combination of strength (above 80 MPa) and stress (below 3 MPa) are present as a potential dose combination range of CQ and BHT. In conclusion, the effect of inhibitors and initiators appears to change in different resin formulation. Increasing the levels of both the inhibitor and the initiator decrease the polymerization contraction stress and stress rate, and the impact on the conversion is unpredictable. In this study, we found a decrease in both the conversion value and depth of cure.
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    Enhancing the speed of DNA walkers through soft confinement
    (Springer Nature, 2025-03-19) Ogieva, Mathew O.; Pfeifer, Wolfgang G.; Sensale, Sebastian; Physics, School of Science
    Over the past two decades, dynamic DNA origami structures have emerged as promising candidates for nanoscale signal and cargo transport. DNA walkers, programmable nanostructures that traverse tracks made of DNA, represent a key innovation in this field, enabling controlled and directional movement at the nanoscale. Despite relatively fast diffusion rates, the speed of DNA walkers remains constrained by the reaction-limited nature of strand exchange mechanisms, which depend both on the foothold-walker affinity and on the probability of the molecules being found close enough to bind. In this study, we explore how spatial confinement can expedite walker motion and evaluate two strategies to achieve this: the introduction of tailed DNA footholds, promoting pseudo-rotational dynamics, and the addition of walls along the DNA track, promoting pseudo-curvilinear dynamics. Using simulations and stochastic theories, we demonstrate that, by reducing the sampling of conformations far from the binding sites, tailed footholds provide the best speed enhancement, achieving a fourfold increase in speed. Trench-like confinement yields a more modest threefold increase, what, while significant, requires extensive structural modifications to the DNA track, limiting design flexibility and reducing cost-efficiency in comparison to the tailed footholds. The combination of tailed footholds and trench-like confinement turns the walker-foothold system bistable, with two distinct stable states separated by an energy barrier. By focusing on the properties of the DNA track, this study offers novel insights into leveraging soft structural motifs to optimize signal propagation rates, with implications for sensing, robotics and molecular computing in reaction-diffusion systems.
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    Evaluation of water sorption and solubility behavior of nine different polymeric luting materials
    (2009) Alsheikh, Rasha N.; Platt, Jeffrey A.; Lund, Melvin R., 1922-; Cochran, Michael A. (Michael Alan), 1944-; Moore, B. Keith; Matis, Bruce A.
    The cementation procedure is the key to long-term success of fixed restorations. The prognosis of prosthetic restoration is largely impacted by the maintenance of the luting cement and the adhesive bond. When exposed to water or saliva, most restorative materials undergo hydrolytic degradation. The purpose of this study is to evaluate the water solubility and water sorption characteristics of newly introduced acidic polymeric luting agents over a 180-day water-storage period. Nine different luting agents were tested. Fifty-two disc specimens of each material were fabricated using a mold with an internal dimension of 15[plus-minus]0.1 mm in diameter and 1.0 [plus-minus]0.1 mm deep. A constant weight, W0 [subscript zero], was reached after desiccating the specimens. Then, 13 specimens were assigned randomly to one of the four testing periods in the water for seven, 30, 90 and 180 days. After each period, the specimens were removed from the water and weighed to get W1 [subscript one]. A second period of desiccating the samples provided a constant weight W2 [subscript two]. The water sorption and solubility were determined by the following equations: WSP [subscript SP](%) = (W1 [subscript one] W2 [subscript two] ) X 100/ W0 [subscript zero] ,WSL [subscript SL](%) = (W0 [subscript zero] W2 [subscript two) X 100/ W0 [subscript zero]. The resin-modified glass-ionomers showed the highest water sorption/solubility results. The resin luting agents had the lowest sorption/solubility results. The self-adhesives showed a wide range of solubility/sorption; in general, they showed lower results compared with the resin-modified glass-ionomers. All the materials reached some sort of equilibrium after 90-days. Based on the results of our study, we conclude that self-adhesive luting materials were not all alike. Rely X Unicem was the most comparable to the resin luting materials. The resin luting materials had the lowest solubility and sorption. Resin-modified glass-ionomers showed the highest sorption/solubility results.
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    Patiromer to Enable Spironolactone in Patients with Resistant Hypertension and CKD (AMBER): Results in the Prespecified Subgroup with Diabetes
    (Wolters Kluwer, 2021) Agarwal, Rajiv; Rossignol, Patrick; Mayo, Martha R.; Conrad, Ansgar; Arthur, Susan; Williams, Bryan; White, William B.; Medicine, School of Medicine