Viscoelastic and Viscoplastic Materials

This book introduces numerous selected advanced topics in viscoelastic and viscoplastic materials. The book effectively blends theoretical, numerical, modeling and experimental aspects of viscoelastic and viscoplastic materials that are usually encountered in many research areas such as chemical, mechanical and petroleum engineering. The book consists of 14 chapters that can serve as an important reference for researchers and engineers working in the field of viscoelastic and viscoplastic materials

Second Microgravity Fluid Physics Conference

The conference's purpose was to inform the fluid physics community of research opportunities in reduced-gravity fluid physics, present the status of the existing and planned reduced gravity fluid physics research programs, and inform participants of the upcoming NASA Research Announcement in this area. The plenary sessions provided an overview of the Microgravity Fluid Physics Program information on NASA's ground-based and space-based flight research facilities. An international forum offered participants an opportunity to hear from French, German, and Russian speakers about the microgravity research programs in their respective countries. Two keynote speakers provided broad technical overviews on multiphase flow and complex fluids research. Presenters briefed their peers on the scientific results of their ground-based and flight research. Fifty-eight of the sixty-two technical papers are included here

Cargo Transport By Myosin Va Molecular Motors Within Three-Dimensional In Vitro Models Of The Intracellular Actin Cytoskeletal Network

Intracellular cargo transport involves the movement of critical cellular components (e.g. vesicles, organelles, mRNA, chromosomes) along cytoskeletal tracks by tiny molecular motors. Myosin Va motors have been demonstrated to play a vital role in the transport of cargos destined for the cell membrane by navigating their cargos through the three-dimensional actin networks of the cell. Transport of cargo through these networks presents many challenges, including directional and physical obstacles which teams of myosin Va-bound to a single cargo must overcome. Specifically, myosin Va motors are presented with numerous actin-actin intersections and dense networks of filaments which can act as a physical barrier to transport. Due to the complexities of studying myosin Va cargo transport in cells, much effort has been focused on the in vitro observation and analysis of myosin Va transport along single actin filaments or simple actin cytoskeletal models. However, these model systems often rely on non-physiological cargos (e.g. beads, quantum dots) and two-dimensional arrangements of actin attached to glass surfaces. Interestingly, a disconnect exists between the transport of cargo on these simple model systems and studies of myosin Va transport on suspended 3D actin arrangements or cellular networks which show longer run lengths, increased velocities, and straighter, more directed trajectories. One solution to this discrepancy is that the cell may use the fluidity of the cargo surface, the recruitment of myosin Va motor teams, and the 3D geometry of the actin, to finely tune the transport of intracellular cargo depending on cellular need. To understand how myosin Va motors transport their cargo through 3D networks of actin, we investigated myosin Va motor ensembles transporting fluorescent 350 nm lipid-bilayer cargo through arrangements of suspended 3D actin filaments. This was accomplished using single molecule fluorescent imaging, three-dimensional super resolution Stochastic Optical Reconstruction Microscopy (STORM), optical tweezers, and in silico modeling. We found that when moving along 3D actin filaments, myosin motors could be recruited from across the fluid lipid cargo’s surface to the filaments which enabled dynamic teams to be formed and explore the full actin filaments binding landscape. When navigating 3D actin-actin intersections these teams capable of maneuvering their cargo through the intersection in a way that encouraged the vesicles to continue straight rather than switch filaments and turn at the intersection. We hypothesized that this finding may be the source of the relatively straight directed runs by myosin Va-bound cargo observed in living cells. To test this, we designed 3D actin networks where the vesicles interacted with 2-6 actin filaments simultaneously. Actin forms polarized filaments, which, in cells, generally have their plus-ends facing the exterior of the cell; the same direction in which myosin Va walks. We found that to maintain straight directed trajectories and not become stationary within the network, vesicles needed to move along filaments with a bias in their polarity. This allows for cargo-bound motors to align their motion along the polarized networks and produced productive motion despite physical and directional obstacles. Together this work demonstrates the physical properties of the cargo, the geometric arrangement of the actin, and the mechanical properties of the motor are all critical aspects of a robust myosin Va transport system

Microgravity Science and Applications. Program Tasks and Bibliography for FY 1993

An annual report published by the Microgravity Science and Applications Division (MSAD) of NASA is presented. It represents a compilation of the Division's currently-funded ground, flight and Advanced Technology Development tasks. An overview and progress report for these tasks, including progress reports by principal investigators selected from the academic, industry and government communities, are provided. The document includes a listing of new bibliographic data provided by the principal investigators to reflect the dissemination of research data during FY 1993 via publications and presentations. The document also includes division research metrics and an index of the funded investigators. The document contains three sections and three appendices: Section 1 includes an introduction and metrics data, Section 2 is a compilation of the task reports in an order representative of its ground, flight or ATD status and the science discipline it represents, and Section 3 is the bibliography. The three appendices, in the order of presentation, are: Appendix A - a microgravity science acronym list, Appendix B - a list of guest investigators associated with a biotechnology task, and Appendix C - an index of the currently funded principal investigators

Microgravity Science and Applications: Program Tasks and Bibliography for Fiscal Year 1996

NASA's Microgravity Science and Applications Division (MSAD) sponsors a program that expands the use of space as a laboratory for the study of important physical, chemical, and biochemical processes. The primary objective of the program is to broaden the value and capabilities of human presence in space by exploiting the unique characteristics of the space environment for research. However, since flight opportunities are rare and flight research development is expensive, a vigorous ground-based research program, from which only the best experiments evolve, is critical to the continuing strength of the program. The microgravity environment affords unique characteristics that allow the investigation of phenomena and processes that are difficult or impossible to study an Earth. The ability to control gravitational effects such as buoyancy driven convection, sedimentation, and hydrostatic pressures make it possible to isolate phenomena and make measurements that have significantly greater accuracy than can be achieved in normal gravity. Space flight gives scientists the opportunity to study the fundamental states of physical matter-solids, liquids and gasses-and the forces that affect those states. Because the orbital environment allows the treatment of gravity as a variable, research in microgravity leads to a greater fundamental understanding of the influence of gravity on the world around us. With appropriate emphasis, the results of space experiments lead to both knowledge and technological advances that have direct applications on Earth. Microgravity research also provides the practical knowledge essential to the development of future space systems. The Office of Life and Microgravity Sciences and Applications (OLMSA) is responsible for planning and executing research stimulated by the Agency's broad scientific goals. OLMSA's Microgravity Science and Applications Division (MSAD) is responsible for guiding and focusing a comprehensive program, and currently manages its research and development tasks through five major scientific areas: biotechnology, combustion science, fluid physics, fundamental physics, and materials science. FY 1996 was an important year for MSAD. NASA continued to build a solid research community for the coming space station era. During FY 1996, the NASA Microgravity Research Program continued investigations selected from the 1994 combustion science, fluid physics, and materials science NRAS. MSAD also released a NASA Research Announcement in microgravity biotechnology, with more than 130 proposals received in response. Selection of research for funding is expected in early 1997. The principal investigators chosen from these NRAs will form the core of the MSAD research program at the beginning of the space station era. The third United States Microgravity Payload (USMP-3) and the Life and Microgravity Spacelab (LMS) missions yielded a wealth of microgravity data in FY 1996. The USMP-3 mission included a fluids facility and three solidification furnaces, each designed to examine a different type of crystal growth

Research and Technology 1996

This report selectively summarizes the NASA Lewis Research Center's research and technology accomplishments for fiscal year 1996. It comprises 116 short articles submitted by the staff scientists and engineers. The report is organized into six major sections: Aeronautics, Aerospace Technology, Space Flight Systems, Engineering & Computational Support, Lewis Research Academy, and Technology Transfer. The diversity of topics attests to the breadth of research and technology being pursued and to the skill mix of the staff that makes it possible. This report is not intended to be a comprehensive summary of all research and technology work done over the past fiscal year

Microgravity science & applications. Program tasks and bibliography for FY 1995

This annual report includes research projects funded by the Office of Life and Microgravity Sciences and Applications, Microgravity Science and Applications Division, during FY 1994. It is a compilation of program tasks (objective, description, significance, progress, students funded under research, and bibliographic citations) for flight research and ground based research in five major scientific disciplines: benchmark science, biotechnology, combustion science, fluid physics, and materials science. Advanced technology development (ATD) program task descriptions are also included. The bibliography cites the related principle investigator (PI) publications and presentations for these program tasks in FY 1994. Three appendices include a Table of Acronyms, a Guest Investigator index and a Principle Investigator index