Index to NASA Tech Briefs, 1972

Abstracts of 1972 NASA Tech Briefs are presented. Four indexes are included: subject, personal author, originating center, and Tech Brief number

Composites for hydraulic structures: a review

Composites for hydraulic structures: a review Composites have evolved over the years and are making major in-roads into the marine, aviation and other industries where corrosions and self-weight are the major impediments to advancing the state-of-the-art. Civil Works engineers have been reluctant to make use of these composite advantages, partially because of the absence of well documented success stories, accepted design and construction practices or specifications, and limited understanding of composites, higher initial costs and others. A few navigational structures using FRP composites have been designed, manufactured and installed in the United States of America and Netherlands, recently. US Army Corps of Engineers is embarking on higher volume applications of composites for navigational structures. This report is aimed at summarizing the state of the art of fiber reinforced polymer (FRP) composites for hydraulic structures including design, construction, evaluation and repair. After a brief review of history and introduction of fundamentals of composites, their manufacturing techniques, properties, and recent field applications are presented, including FRP rebar for bridge decks, other highway and railway structures, gratings, underground storage tank, pavement, sheet and pipe piling, FRP wraps, moveable bridges, utility poles, etc. Focus is placed on applications of composites in waterfront, marine, navigational structures including lock doors, gates, and protection systems. Design of hydraulic composite structures is presented for the cases available, such as design of FRP recess panel, Wicket Gates, Miter Gates, FRP slides and repair of corroded steel piles. This report also reviews engineering science issues such as fracture and fatigue, durability, creep and relaxation, UV degradation, impact resistance, and fire performance. The report concludes with summary remarks and recommendations after a discussion on operation and maintenance guidance including nondestructive evaluation inspection techniques. Intention is to provide up to date information on composite design, manufacturing and evaluation methodologies that are applicable for fabrication and maintenance of navigational structures. This report is a living document with advances taking place with time as waterborne transport infrastructure community makes progress with FRP systems. This report is expected to be useful for those decision-makers in government, consultants, designers, contractors, maintenance and rehab engineers whose focus is to minimize traffic interruptions while maximizing cost effectiveness

Repair of Wood Piles with Fiber Reinforced Composites

Piles made of treated wood have been traditionally used for the construction of piers and other waterfront structures. The main concern related to wood piles is deterioration due to marine borers, which limits the lifespan and requires frequent repair and replacement. Furthermore, since the use of preservative treatments for wood piles has been reduced due to environmental concerns, there is a current need for efficient methods for wood pile protection. Marine borer activity in Maine coastal waters was assessed through a survey directed to harbor masters correlated with historic data. In order to illustrate the type and extent of wood pile deterioration, two case studies in Maine harbors are presented. A special prefabricated Fiber Reinforced Polymer (FRP) composite shield or jacket was developed to repair wood piles in the field. FRP composite shells or sleeves are bonded with an underwater curing adhesive to form a shield. The main concern for durability of the adhesive bond is the resistance to freeze-thaw cycles. To assess adhesive bond durability, single lap shear tests were performed after exposure to freeze-thaw cycles. Two types of load-transfer mechanisms between the wood pile and the FRP composite shield were developed and tested: (1) cement-based structural grout; and (2) steel shear connectors with an expanding polyurethane chemical grout. Push-out tests by compression loading were performed to characterize the interfaces and discriminate the effect of the design parameters. The outcome of the push-out tests was the evaluation of the shear force-slip non-linear response and the progressive failure mechanism. The structural response of full-size pre-damaged wood piles repaired with the FRP composite shield system was characterized. A three-point bending test procedure was used to simulate the response of a pile subjected to lateral loads. The loaddeformation response, deflected shape profile, relative longitudinal displacements (slip), strain distribution, ultimate bending moment capacity and mode of failure were evaluated. Wood piles were pre-damaged by reducing approximately 60% of the crosssection over a portion of the pile. It was found that a pre-damaged wood pile repaired using the FRP composite shield with cement-based grout exceeded the bending capacity of a reference wood pile. The repair system using the FRP composite shield with steel shear connectors and polyurethane grout did not fully restore the bending capacity of a reference wood pile; however it can be used for marine borer protection when wood damage is not critical. A beam structural model to predict stiffness and strength properties of wood piles restored with FRP composite shells was developed. The model accounts for different pile dimensional properties and various amounts of pre-damage. The structural model was successfully correlated with experimental data from three-point bending tests of wood piles

Investigation of Polymeric Composites for Controlled Drug Release

The Electrospray (ES) technique is a promising particle generation method for drug delivery due to its capabilities of producing monodisperse PLGA composite particles with unique configurations and high drug encapsulation efficiency. In the dissertation work, the coaxial dual capillary ES was used to generate drug-loaded core-shell PLGA particles to study the effects of particle filling materials, drug loading locations and particle shell thicknesses on the resultant in vitro release behaviors of the hydrophilic and/ or hydrophobic model drugs. Through release profile characterization of drug-loaded PLGA particles (particle size: 400 nm and 1 μm), it was confirmed that the co-encapsulation of Budesonide (BUD, the hydrophobic small-molecule model drug) and Theophylline (THY, the hydrophilic small-molecule model drug) in the particle cores is the most effective drug loading strategy for extended release of the fixed combined BUD and THY. Particles composed of PLGA fillers with lower molecular weights and with greater shell layer thicknesses could release THY in a well controlled fashion. On the other hand, a slower release rate of Bovine Serum Albumin (BSA, the protein model drug) from PLGA particles with greater shell thickness was also observed. Sequential release of BSA and Paclitaxel (PTX, the hydrophobic small-molecule anti-cancer model drug) was achieved by the 400-nm PLGA (Mw: 7,000-17,000 g/mol, LA/GA: 50/50) particles with potential biopharmaceutical applications in cancer therapy

Development of soft tissue regenerative scaffold with antibacterial activity

With increasingly aging and sedentary populations, and with the rising incidence of diabetes and the associated diabetic ulcers, chronic wounds have been reported to be approaching pandemic proportions. Accumulation of wound bacteria forms a biofilm that can inhibit wound healing and the action of antibiotics. Conventional skin grafts can readily harbor bacterial and fungal cells while excluding penetration of larger immune cells and essential neo-vascularization. Soft tissue regenerative scaffolds with highly interconnected porosity have been developed for wound healing. In this research, scaffolds were fabricated with bioactive components to impart antibacterial activity. The interconnective porosity of the scaffold was preserved through using thermally forming composite scaffolds. Bioactive glass (45S5), bulk metallic glass (MgZnCa), and infused antibiotic (Cephazolin sodium) were utilised to form the composite antibiotic eluting scaffolds. A novel in vivo wound model was generated to simulate the wound environment. A confluent biofilm of Staphylococcus aureus was generated on polymer coupons using a bioreactor. The coupons were placed within nutrient agar dishes (simulating tissue) underneath scaffold specimens. Gravity fed perfusion flow was set up using a drip-set kit.The model successfully replicated the planktonic phase of the Staph. aureus life-cycle and infection of the scaffold from the wound model. Bioactive glass by itself did not contribute any detectable Staph.antibacterial activity whether on the scaffold or fused to a silicone substrate. However, when bioactive glass was present with MgZnCa and antibiotic, a mild synergistic improvement in antibacterial activity was observed. This strategy may facilitate soft tissue adhesion and further militate against bacterial infection. This study is the first report of an in-vitro wound model with an infusion method and planktonic bacteria phase, applied to assess antibacterial synthetic scaffold

Development of soft tissue regenerative scaffold with antibacterial activity

With increasingly aging and sedentary populations, and with the rising incidence of diabetes and the associated diabetic ulcers, chronic wounds have been reported to be approaching pandemic proportions. Accumulation of wound bacteria forms a biofilm that can inhibit wound healing and the action of antibiotics. Conventional skin grafts can readily harbor bacterial and fungal cells while excluding penetration of larger immune cells and essential neo-vascularization. Soft tissue regenerative scaffolds with highly interconnected porosity have been developed for wound healing. In this research, scaffolds were fabricated with bioactive components to impart antibacterial activity. The interconnective porosity of the scaffold was preserved through using thermally forming composite scaffolds. Bioactive glass (45S5), bulk metallic glass (MgZnCa), and infused antibiotic (Cephazolin sodium) were utilised to form the composite antibiotic eluting scaffolds. A novel in vivo wound model was generated to simulate the wound environment. A confluent biofilm of Staphylococcus aureus was generated on polymer coupons using a bioreactor. The coupons were placed within nutrient agar dishes (simulating tissue) underneath scaffold specimens. Gravity fed perfusion flow was set up using a drip-set kit.The model successfully replicated the planktonic phase of the Staph. aureus life-cycle and infection of the scaffold from the wound model. Bioactive glass by itself did not contribute any detectable Staph.antibacterial activity whether on the scaffold or fused to a silicone substrate. However, when bioactive glass was present with MgZnCa and antibiotic, a mild synergistic improvement in antibacterial activity was observed. This strategy may facilitate soft tissue adhesion and further militate against bacterial infection. This study is the first report of an in-vitro wound model with an infusion method and planktonic bacteria phase, applied to assess antibacterial synthetic scaffold

Marshall Space Flight Center Research and Technology Report 2019

Today, our calling to explore is greater than ever before, and here at Marshall Space Flight Centerwe make human deep space exploration possible. A key goal for Artemis is demonstrating and perfecting capabilities on the Moon for technologies needed for humans to get to Mars. This years report features 10 of the Agencys 16 Technology Areas, and I am proud of Marshalls role in creating solutions for so many of these daunting technical challenges. Many of these projects will lead to sustainable in-space architecture for human space exploration that will allow us to travel to the Moon, on to Mars, and beyond. Others are developing new scientific instruments capable of providing an unprecedented glimpse into our universe. NASA has led the charge in space exploration for more than six decades, and through the Artemis program we will help build on our work in low Earth orbit and pave the way to the Moon and Mars. At Marshall, we leverage the skills and interest of the international community to conduct scientific research, develop and demonstrate technology, and train international crews to operate further from Earth for longer periods of time than ever before first at the lunar surface, then on to our next giant leap, human exploration of Mars. While each project in this report seeks to advance new technology and challenge conventions, it is important to recognize the diversity of activities and people supporting our mission. This report not only showcases the Centers capabilities and our partnerships, it also highlights the progress our people have achieved in the past year. These scientists, researchers and innovators are why Marshall and NASA will continue to be a leader in innovation, exploration, and discovery for years to come

Implantable Microsystem Technologies For Nanoliter-Resolution Inner Ear Drug Delivery

Advances in protective and restorative biotherapies have created new opportunities to use site-directed, programmable drug delivery systems to treat auditory and vestibular disorders. Successful therapy development that leverages the transgenic, knock-in, and knock-out variants of mouse models of human disease requires advanced microsystems specifically designed to function with nanoliter precision and with system volumes suitable for implantation. The present work demonstrates a novel biocompatible, implantable, and scalable microsystem consisted of a thermal phase-change peristaltic micropump with wireless control and a refillable reservoir. The micropump is fabricated around a catheter microtubing (250 μm OD, 125 μm ID) that provided a biocompatible leak-free flow path while avoiding complicated microfluidic interconnects. Direct-write micro-scale printing technology was used to build the mechanical components of the pump around the microtubing directly on the back of a printed circuit board assembly. In vitro characterization results indicated nanoliter resolution control over the desired flow rates of 10–100 nL/min by changing the actuation frequency, with negligible deviations in presence of up to 10× greater than physiological backpressures and ±3°C ambient temperature variation. A biocompatibility study was performed to evaluate material suitability for chronic subcutaneous implantation and clinical translational development. A stand-alone, refillable, in-plane, scalable, and fully implantable microreservoir platform was designed and fabricated to be integrated with the micropump. The microreservoir consists two main components: a cavity for storing the drug and a septum for refilling. The cavity membrane is fabricated with thin Parylene-C layers, using a polyethylene glycol (PEG) sacrificial layer. The septum thickness is minimized by pre-compression down to 1 mm. The results of in vitro characterization indicated negligible restoring force for the optimized cavity membrane and thousands of punctures through the septum without leakage. The micropump and microreservoir were integrated into microsystems which were implanted in mice. The microtubing was implanted into the round window membrane niche for infusion of a known ototoxic compound (sodium salicylate) at 50 nL/min for 20 min. Real-time shifts in distortion product otoacoustic emission thresholds and amplitudes were measured during the infusion. The results match with syringe pump gold standard. For the first time a miniature and yet scalable microsystem for inner ear drug delivery was developed, enabling drug discovery opportunities and translation to human