Coupled Radiative Thermal and Nonlinear Stress Analysis for Thermal Deformation in Large Space Structures

Large space structures are capable of large thermal deformations in the space environment. A case of large-scale thermal deformation was observed in the analysis of the Near Earth Asteroid Scout solar sail, with predicted tip displacements of more than one meter in seven-meter booms. Experimental data supports the broad conclusions of the analysis, but shows poor agreement on the details of the thermal deformation. Prediction that is precise enough to drive engineering decisions will require coupled thermal-stress analysis with features that are not found in current multiphysics codes. This paper describes a simple method for stepwise coupling between commercial nonlinear stress analysis software and radiative thermal analysis software. Results are presented for a round stainless steel tube, which is a common case in existing literature

Shape Accuracy of a Joint-Dominated Deployable Mast

This paper presents a study to capture and model friction related changes in the un-loaded configuration of deployable masts with articulated joints. A finite model of a rep-resentative mast structure is described. This model includes a detailed treatment of the latching mechanism. The parameters of the computational model are based on direct mea-surements on components of a physical model. The moment-rotation relationship for a complete single bay of the physical model has been measured and the overall behavior is predicted well by the model, however the model predicts the residual rotation at zero moment to be zero and so it is concluded that a more refined model for the latch will need to be developed

Thermal Deformation of Very Slender Triangular Rollable and Collapsible Booms

Metallic triangular rollable and collapsible (TRAC) booms have deployed two Cubesat-based solar sails in low Earth orbit, making TRAC booms the most popular solar sail deployment method in practice. This paper presents some concerns and solutions surrounding the behavior of these booms in the space thermal environment. A 3.5-cm-tall, 4-meter-long TRAC boom of Elgiloy cobalt alloy, when exposed to direct sunlight in a 1 AU deep space environment, has a predicted tip motion of as much as 0.5 meters. Such large thermal deflections could generate unacceptable distortions in the shape of a supported solar sail, making attitude control of the solar sail spacecraft difficult or impossible. As a possible means of mitigating this issue, the thermal distortion behaviors of three alternative material TRAC booms are investigated and compared with the uncoated Elgiloy baseline boom. A tenfold decrease in induced curvature is shown to be possible relative to the baseline boom. Potential thermal distortions of the LightSail-A solar sail TRAC booms are also examined and compared, although inconclusively, with available on-orbit camera imagery

Durability Characterization of Mechanical Interfaces in Solar Sail Membrane Structures

The construction of a solar sail from commercially available metallized film presents several challenges. The solar sail membrane is made by seaming together strips of metallized polymer film. This requires seaming together a preselected width and thickness of a base material into the required geometry, and folding the assembled sail membranes into a small stowage volume prior to launch. The sail membranes must have additional features for connecting to rigid structural elements (e.g., sail booms) and must be electrically grounded to the spacecraft bus to prevent charge build up. Space durability of the material and mechanical interfaces of the sail membrane assemblies will be critical for the success of any solar sail mission. In this study, interfaces of polymer/metal joints in a representative solar sail membrane assembly were tested to ensure that the adhesive interfaces and the fastening grommets could withstand the temperature range and expected loads required for mission success. Various adhesion methods, such as surface treatment, commercial adhesives, and fastening systems, were experimentally evaluated and will be discussed

Advances in Low-Cost Manufacturing and Folding of Solar Sail Membranes

Solar sail membranes must have a high area-to-mass ratio and high solid volume fraction when stowed. In order to meet mission requirements, current solar sail projects, such as NASAs Near Earth Asteroid Scout, require metallized sail membranes with thicknesses on the order of 2-3 m. These very thin membranes do not retain creases like thicker membranes, solar panels, or paper models. For Cubesat-class spacecraft, volume, rather than mass, is often the driving requirement for deployable structural elements. These two factors make it both difficult and highly desirable to characterize the practical differences between solar sail membrane packaging methods with laboratory demonstrations. This paper presents lessons gathered from lab work with solar sail membranes at a 10-meter scale

Comprehensive translational assessment of human-induced pluripotent stem cell derived cardiomyocytes for evaluating drug-induced arrhythmias

Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) hold promise for assessment of drug-induced arrhythmias and are being considered for use under the comprehensive in vitro proarrhythmia assay (CiPA). We studied the effects of 26 drugs and 3 drug combinations on 2 commercially available iPSC-CM types using high-throughput voltage-sensitive dye and microelectrode-array assays being studied for the CiPA initiative and compared the results with clinical QT prolongation and torsade de pointes (TdP) risk. Concentration-dependent analysis comparing iPSC-CMs to clinical trial results demonstrated good correlation between drug-induced rate-corrected action potential duration and field potential duration (APDc and FPDc) prolongation and clinical trial QTc prolongation. Of 20 drugs studied that exhibit clinical QTc prolongation, 17 caused APDc prolongation (16 in Cor.4U and 13 in iCell cardiomyocytes) and 16 caused FPDc prolongation (16 in Cor.4U and 10 in iCell cardiomyocytes). Of 14 drugs that cause TdP, arrhythmias occurred with 10 drugs. Lack of arrhythmic beating in iPSC-CMs for the four remaining drugs could be due to differences in relative levels of expression of individual ion channels. iPSC-CMs responded consistently to human ether-a-go-go potassium channel blocking drugs (APD prolongation and arrhythmias) and calcium channel blocking drugs (APD shortening and prevention of arrhythmias), with a more variable response to late sodium current blocking drugs. Current results confirm the potential of iPSC-CMs for proarrhythmia prediction under CiPA, where iPSC-CM results would serve as a check to ion channel and in silico modeling prediction of proarrhythmic risk. A multi-site validation study is warranted

New Dynamometer Setup

The goal of this report is to go over the design and implementation of a dyno system for the WashU FSAE team. Utiliing existing infrastrucure and devices from 2008 and 2016 and learning how they work, a new system was designed and implemented. With cost in mind and the fact that the car is dissassembled each year, a water-brake engine dyno was designed, manufactured, and created for the Yamaha R6 engine used by the team. The main limitation of water-brake systems with motorcycle engines is the torque of motorcycle engines is too much for a water-brake due to the transmission being built into the engine: the water-brake attaches to the output of the transmission instead of to the crankshaft. Thus, a gear reduction is needed, a 0.4 gear ratio in this case, to decrease torque and increase speed at the water-brake. With this, many factors had to be added into consideration for the design such as vibrations, shaft misalignment, chain tensioning, engine ease of modification, and more as well as the water-brake support system. While there were some oversights in the design that became apparent as it was being assembled, these challenges were able to be overcome. While the dyno was not up and running before the semester was over, it is 95% complete and should be operational next semester

Functional diversity of chemokines and chemokine receptors in response to viral infection of the central nervous system.

Encounters with neurotropic viruses result in varied outcomes ranging from encephalitis, paralytic poliomyelitis or other serious consequences to relatively benign infection. One of the principal factors that control the outcome of infection is the localized tissue response and subsequent immune response directed against the invading toxic agent. It is the role of the immune system to contain and control the spread of virus infection in the central nervous system (CNS), and paradoxically, this response may also be pathologic. Chemokines are potent proinflammatory molecules whose expression within virally infected tissues is often associated with protection and/or pathology which correlates with migration and accumulation of immune cells. Indeed, studies with a neurotropic murine coronavirus, mouse hepatitis virus (MHV), have provided important insight into the functional roles of chemokines and chemokine receptors in participating in various aspects of host defense as well as disease development within the CNS. This chapter will highlight recent discoveries that have provided insight into the diverse biologic roles of chemokines and their receptors in coordinating immune responses following viral infection of the CNS

Promoting remyelination through cell transplantation therapies in a model of viral-induced neurodegenerative disease.

Multiple sclerosis (MS) is a central nervous system (CNS) disease characterized by chronic neuroinflammation, demyelination, and axonal damage. Infiltration of activated lymphocytes and myeloid cells are thought to be primarily responsible for white matter damage and axonopathy. Several United States Food and Drug Administration-approved therapies exist that impede activated lymphocytes from entering the CNS thereby limiting new lesion formation in patients with relapse-remitting forms of MS. However, a significant challenge within the field of MS research is to develop effective and sustained therapies that allow for axonal protection and remyelination. In recent years, there has been increasing evidence that some kinds of stem cells and their derivatives seem to be able to mute neuroinflammation as well as promote remyelination and axonal integrity. Intracranial infection of mice with the neurotropic JHM strain of mouse hepatitis virus (JHMV) results in immune-mediated demyelination and axonopathy, making this an excellent model to interrogate the therapeutic potential of stem cell derivatives in evoking remyelination. This review provides a succinct overview of our recent findings using intraspinal injection of mouse CNS neural progenitor cells and human neural precursors into JHMV-infected mice. JHMV-infected mice receiving these cells display extensive remyelination associated with axonal sparing. In addition, we discuss possible mechanisms associated with sustained clinical recovery. Developmental Dynamics 248:43-52, 2019. © 2018 Wiley Periodicals, Inc

The Road to Redemption: Reclaiming the Value in Assessment Retention Exams

A good assessment plan combines many direct and indirect measures to validate the collected data. One often controversial assessment measure comes in the form of retention exams. Although assessment retention exams may come with faults, others advocate for their inclusion in program assessment. Objective-based tests may offer insight to instructors about course objectives that students comprehend well and other concepts that need more attention. This research shows that using retention exams as an assessment measure can generate useful and meaningful data for both the students and the program. Students can learn strengths and weaknesses based on scores. Faculty and programs can learn where gaps may exist within the program. But, whenever a program decides to use retention exams as an assessment tool, faculty members need to be included in the process. Discussions about content need to occur constantly. Exams need to consistently reflect current standards and student learning objectives. And faculty need to stay involved in the process to know exactly where any inconsistencies may lie within their courses, and how they contribute to the students’ overall experience within the program