Toughening of Thermoresponsive Arrested Networks of Elastin-Like Polypeptides To Engineer Cytocompatible Tissue Scaffolds

Formulation of tissue engineering or regenerative scaffolds from simple bioactive polymers with tunable structure and mechanics is crucial for the regeneration of complex tissues, and hydrogels from recombinant proteins, such as elastin-like polypeptides (ELPs), are promising platforms to support these applications. The arrested phase separation of ELPs has been shown to yield remarkably stiff, biocontinuous, nanostructured networks, but these gels are limited in applications by their relatively brittle nature. Here, a gel-forming ELP is chain-extended by telechelic oxidative coupling, forming extensible, tough hydrogels. Small angle scattering indicates that the chain-extended polypeptides form a fractal network of nanoscale aggregates over a broad concentration range, accessing moduli ranging from 5 kPa to over 1 MPa over a concentration range of 5–30 wt %. These networks exhibited excellent erosion resistance and allowed for the diffusion and release of encapsulated particles consistent with a bicontinuous, porous structure with a broad distribution of pore sizes. Biofunctionalized, toughened networks were found to maintain the viability of human mesenchymal stem cells (hMSCs) in 2D, demonstrating signs of osteogenesis even in cell media without osteogenic molecules. Furthermore, chondrocytes could be readily mixed into these gels via thermoresponsive assembly and remained viable in extended culture. These studies demonstrate the ability to engineer ELP-based arrested physical networks on the molecular level to form reinforced, cytocompatible hydrogel matrices, supporting the promise of these new materials as candidates for the engineering and regeneration of stiff tissues

A cross-sectional investigation of the relationships education, certification, and experience have with knowledge, skills, and abilities among aviation professionals

The aviation industry is a complex system with many different segments and as such, makes hiring the right person a complicated endeavor. Previous research suggested that knowledge, skills, and abilities (KSAs) are composed of elements that include education, certification, and experience (ECE). The relative importance of ECE is dependent on the type of job within the aviation sector. The objective of this mixed-methods concurrent triangulation study was to examine aviation industry professionals’ perceived relationship between their ECE and the development of their KSAs. The convenience sample consisted of 404 professionals in the aviation industry who completed the KSA Composite Measure (KCM). The study clarified relationships between ECEs and KSAs that managers in the aviation industry can apply when developing job openings, conducting interviews, reviewing applicant credentials, and building high-performance teams

Validating the Knowledge, Skills, and Abilities Composite Measure: An Aviation Industry Pilot Study

Recent research into the aviation management education paradigm shift indicated that education, certification, and experience (ECE) were all important in the aviation industry; however, the relative importance varied between managers depending on their field. Overall, the results identified experience as the most important factor, followed by certification, then education. Furthermore, the authors made a logical connection between the that study and knowledge, skills, and abilities (KSAs), which would ultimately lead managers to a hiring decision. The purpose of this mixed-methods sequential exploratory pilot study was to develop, validate, and test the reliability of the KSA composite measure (KCM), a data collection device to measure the connection between ECE and KSAs. The three phased approach consisted of (a) an expert panel review by eight research, aviation, and human resource professionals, (b) an institutional review board (IRB) review, and (c) a live pilot using 45 professionals from the aviation industry. The pilot proved to validate and confirm the reliability of the KCM for future use

Alignment and Testing of Critical Interface Fixtures for the James Webb Space Telescope

NASAs James Webb Space Telescope (JWST) is a 6.6m diameter, segmented, deployable telescope for cryogenic IR space astronomy. The JWST Observatory architecture includes the Primary Mirror Backplane Support Structure (PMBSS) and Integrated Science Instrument Module (ISIM) Electronics Compartment (IEC) which is designed to integrate to the spacecraft bus via six cupcone interfaces. Prior to integration to the spacecraft bus the JWST observatory must undergo environmental testing, handling, and transportation. Multiple fixtures were developed to support these tasks including the vibration fixture and handling and integration fixture (HIF). This work reports on the development of the nominal alignment of the six interfaces and metrology operations performed for the JWST observatory to safely integrate them for successful environmental testing

Synthesis, nanostructure, and mechanics of thermoresponsively tough biomaterials from artificial polypeptides

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2015.Cataloged from PDF version of thesis.Includes bibliographical references.Artificial protein hydrogels have attracted interest as injectable fillers and scaffolds for tissue engineering and regeneration, but the same features that enable minimally-invasive implantation of these biomaterials typically make them susceptible to mechanical degradation in the tissue environment. Achieving a rapid and sufficiently large increase in gel toughness post-injection is a crucial challenge for developing load-bearing injectable implants that persist for the needed lifetime of the implant. To address these complex goals, the objective of this thesis has been to engineer physical hydrogels that shear-thin at low temperatures but responsively assemble into a nanostructured, reinforced state at body temperature. For this purpose, the thermoresponsive aggregation of poly(N-isopropylacrylamide) (PNIPAM) and elastin-like polypeptides (ELPs) was leveraged to assemble nanostructured hydrogels from dual-associative block copolymers. Hybrid protein-polymers or protein fusions were formed by fusing PNIPAM or ELPs to the termini of a soluble artificial polypeptide decorated with self-associating [alpha]-helical domains. In cold solutions, these polypeptide block copolymers formed weak, injectable gels due to helix-associations alone; upon heating to physiological temperatures, the endblocks aggregated to form a reinforcing network of close-packed micelles throughout the gel, leading to over a 10-fold increase in elastic modulus and over 10³-fold increase in the longest stress relaxation time. Micelle packing and morphology could be tuned by endblock chemistry and block architecture, allowing for orthogonal control of gel viscoelasticity over timescales separated by four orders of magnitude. Furthermore, through the discovery of a new gelation mechanism for ELPs, simple but tough hydrogels were engineered and explored as biocompatible substrates for tissue engineering. Unlike solutions of other ELPs that have been studied extensively for decades, ELPs that have an alanine mutation in the third position of the repeat unit (i.e. VPAVG) were found to undergo arrested phase separation upon heating when formulated above a critical concentration. Solidification resulted in a bicontinuous, nanoscale network that could be manipulated by ELP design. Critically, this reversible mechanism produced extremely stiff physical gels with a relaxation time greater than 10³ seconds and shear moduli almost 10 MPa, nearly that of natural rubber despite consisting of 70% water. These ELPs were chain-extended via reversible coupling of terminal cysteine residues, leading to oxidatively-responsive increases in gel extensibility and overall toughness. Biofunctionalized gels maintained the viability of mesenchymal stem cells and chondrocytes in 2D and 3D, respectively, making these simple gel formulations a promising platform for biomedical applications. Ultimately, through controlled macromolecular synthesis and functionalization, combined with a fundamental understanding of the structure and mechanics of these new materials, this thesis has led to the development of responsively tough biomaterials that are promising for long-term performance under physiological conditions.by Matthew James Glassman.Ph. D

Validating the Knowledge, Skills, and Abilities Composite Measure: An Aviation Industry Pilot Study

Recent research into the aviation management education paradigm shift indicated that education, certification, and experience (ECE) were all important in the aviation industry; however, the relative importance varied between managers depending on their field. Overall, the results identified experience as the most important factor, followed by certification, then education. Furthermore, the authors made a logical connection between the that study and knowledge, skills, and abilities (KSAs), which would ultimately lead managers to a hiring decision. The purpose of this mixed-methods sequential exploratory pilot study was to develop, validate, and test the reliability of the KSA composite measure (KCM), a data collection device to measure the connection between ECE and KSAs. The three phased approach consisted of (a) an expert panel review by eight research, aviation, and human resource professionals, (b) an institutional review board (IRB) review, and (c) a live pilot using 45 professionals from the aviation industry. The pilot proved to validate and confirm the reliability of the KCM for future use

A cross-sectional investigation of the relationships education, certification, and experience have with knowledge, skills, and abilities among aviation professionals

The aviation industry is a complex system with many different segments and as such, makes hiring the right person a complicated endeavor. Previous research suggested that knowledge, skills, and abilities (KSAs) are composed of elements that include education, certification, and experience (ECE). The relative importance of ECE is dependent on the type of job within the aviation sector. The objective of this mixed-methods concurrent triangulation study was to examine aviation industry professionals’ perceived relationship between their ECE and the development of their KSAs. The convenience sample consisted of 404 professionals in the aviation industry who completed the KSA Composite Measure (KCM). The study clarified relationships between ECEs and KSAs that managers in the aviation industry can apply when developing job openings, conducting interviews, reviewing applicant credentials, and building high-performance teams