CHAP Enhances Versatility in Colloidal Probe Fabrication

A colloidal probe, comprising a colloidal particle attached to an atomic force microscope cantilever, is employed to measure directly interaction forces between the particle and a surface. It is possible to change or even destroy a particle while attaching it to a cantilever, thus limiting the types of systems to which the colloidal probe technique may be applied. Here we present the Controlled Heating and Alignment Platform (CHAP) for fabricating colloidal probes without altering the original characteristics of the attached particle. The CHAP applies heat directly to the atomic force microscope chip to rapidly and precisely control cantilever temperature. This minimizes particle heating and enables control over the viscosity of thermoplastic adhesive, to prevent it from contaminating the particle surface. 3D-printed components made the CHAP compatible with standard optical microscopes and streamlined the fabrication process while increasing the platforms versatility. Using the CHAP with a thermoplastic wax adhesive, colloidal probes were fabricated using polystyrene and silica particles between 0.7 and 40 m in diameter. We characterized the properties and interactions of the adhesive and particles, as well as the properties of the completed probes, to demonstrate the retention of particle features throughout fabrication. Pull-off tests with CHAPs probes measured adhesive force values in the expected ranges and demonstrated that particles were firmly attached to the cantilevers

Flow Resistance Dynamics in Step-pool Stream Channels: 1. Large Woody Debris and Controls on Total Resistance

Flow resistance dynamics in step-pool channels were investigated through physical modeling using a laboratory flume. Variables contributing to flow resistance in step-pool channels were manipulated in order to measure the effects of various large woody debris (LWD) configurations, steps, grains, discharge, and slope on total flow resistance. This entailed nearly 400 flume runs, organized into a series of factorial experiments. Factorial analyses of variance indicated significant two-way and three-way interaction effects between steps, grains, and LWD, illustrating the complexity of flow resistance in these channels. Interactions between steps and LWD resulted in substantially greater flow resistance for steps with LWD than for steps lacking LWD. LWD position contributed to these interactions, whereby LWD pieces located near the lip of steps, analogous to step-forming debris in natural channels, increased the effective height of steps and created substantially higher flow resistance than pieces located farther upstream on step treads. Step geometry and LWD density and orientation also had highly significant effects on flow resistance. Flow resistance dynamics and the resistance effect of bed roughness configurations were strongly discharge-dependent; discharge had both highly significant main effects on resistance and highly significant interactions with all other variables

Combining genomics and epidemiology to track mumps virus transmission in the United States

Unusually large outbreaks of mumps across the United States in 2016 and 2017 raised questions about the extent of mumps circulation and the relationship between these and prior outbreaks. We paired epidemiological data from public health investigations with analysis of mumps virus whole genome sequences from 201 infected individuals, focusing on Massachusetts university communities. Our analysis suggests continuous, undetected circulation of mumps locally and nationally, including multiple independent introductions into Massachusetts and into individual communities. Despite the presence of these multiple mumps virus lineages, the genomic data show that one lineage has dominated in the US since at least 2006. Widespread transmission was surprising given high vaccination rates, but we found no genetic evidence that variants arising during this outbreak contributed to vaccine escape. Viral genomic data allowed us to reconstruct mumps transmission links not evident from epidemiological data or standard single-gene surveillance efforts and also revealed connections between apparently unrelated mumps outbreaks

Patch Plate Materials Compatibility Assessment

Lunar dust proved to be a greater problem during the Apollo missions than was originally anticipated. The highly angular, charged dust particles stuck to seals, radiators, and visors; clogged mechanisms; and abraded space suits. As reported by Apollo 12 astronaut Pete Conrad "We must have had more than a hundred hours suited work with the same equipment, and the wear was not as bad on the training suits as it is on these flight suits in just the eight hours we were out.". Dust clinging to surfaces was also transport-ed into habitable spaces leading to lung and eye irritation of the astronauts. The Apollo astronauts were on the Lunar surface less than 24 hours and experienced many dust related problems. With the Artemis program, we are planning longer stays on the surface, with more activities that have the potential to put the astronauts and equipment in contact with greater quantities of Lunar dust. The success of these missions will depend on our understanding of material interactions with Lunar dust and the development of ways to mitigate dust effects in cases where exposure to dust will lead to failure of components, unacceptable loss of power or thermal control, unacceptable loss of visibility, or health issues. Through the Lunar Surface In-novation Initiative (LSII), we are initiating a Patch Plate Materials Compatibility Assessment project. The overall goal of the three year project is to develop passive approaches to mitigate Lunar dust adhesion to surfaces for technologies that are currently at TRL levels 2-3 to bring them to TRL level 5 through ground-based assessment, culminating in a demonstration flight experiment on a Commercial Lunar Payload Services (CLPS) lander in 2022-2023. This paper discusses the detailed technical objectives and approach for this project. References: Gaier, J.R. "The Effects of Lunar Dust on EVA Systems During the Apollo Missions," NASA/TM-2005-213610/REV1, (2005), Apollo 12 Technical Crew Debriefing, December 1, 1969, pp. 10-54

Flow Resistance Dynamics in Step-pool Channels: 2. Partitioning Between Grain, Spill, and Woody Debris Resistance

In step-pool stream channels, flow resistance is created primarily by bed sediments, spill over step-pool bed forms, and large woody debris (LWD). In order to measure resistance partitioning between grains, steps, and LWD in step-pool channels we completed laboratory flume runs in which total resistance was measured with and without grains and steps, with various LWD configurations, and at multiple slopes and discharges. Tests of additive approaches to resistance partitioning found that partitioning estimates are highly sensitive to the order in which components are calculated and that such approaches inflate the values of difficult-to-measure components that are calculated by subtraction from measured components. This effect is especially significant where interactions between roughness features create synergistic increases in resistance such that total resistance measured for combinations of resistance components greatly exceeds the sum of those components measured separately. LWD contributes large proportions of total resistance by creating form drag on individual pieces and by increasing the spill resistance effect of steps. The combined effect of LWD and spill over steps was found to dominate total resistance, whereas grain roughness on step treads was a small component of total resistance. The relative contributions of grain, spill, and woody debris resistance were strongly influenced by discharge and to a lesser extent by LWD density. Grain resistance values based on published formulas and debris resistance values calculated using a cylinder drag approach typically underestimated analogous flume-derived values, further illustrating sources of error in partitioning methods and the importance of accounting for interaction effects between resistance components

Creativity and Affective Traits Across the Life Span: Developmental Influences Among Adolescents and Older Adults

In recent years, empirical research has consistently supported an association between susceptibility to affective illness and creativity at the level of eminent achievement and at the non-eminent, or "everyday creativity" level. Although this research has provided greater evidence for the existence of this link, it has simultaneously unearthed more questions about how and why such an association exists. The purpose of this research was twofold: first, to provide further analysis of the nature of the relationship between hypomanic traits and creativity by employing a longitudinal study to determine the extent to which inter-individual differences over time in creativity are predicted by hypomanic traits. Second, the purpose of the cross-sectional analysis in the present study was to further determine how developmental components such as age and expertise may help unravel the ways in which hypomanic traits contribute to creativity and to further describe inter-individual differences among these variables. The first hypothesis, which proposed that the direction of the relationship between hypomanic traits and creativity could be predicted, was not supported by these results. The second research hypothesis was partially supported: hypomanic traits predict creativity in the combined adolescent and older adult samples. However, upon further examination of the regression analyses, the data indicate that the relationship between hypomanic traits and creativity is also influenced by age and developmental factors. Furthermore, the way in which the relationship is influenced by these other factors depends on the way in which the creativity construct is measured (e.g., process or personality. The findings suggest that the antecedents of creativity may differ between adolescents and older adults. In adolescents, the hypomanic traits measure is the only variable that predicts creative personality and creative process, while expertise is the only variable to predict creative personality and creative process among the older adults in this study. It appears expertise significantly and uniquely contributes to at least two areas of creativity in older adults, while hypomanic traits significantly and uniquely contributes to the same two areas of creativity in adolescents. Implications of these findings and limitations to this study are discussed

Flight evaluation of two segment approaches for jet transport noise abatement

A 75 flight-hour operational evaluation was conducted with a representative four-engine fan-jet transport in a representative airport environment. The flight instrument systems were modified to automatically provide pilots with smooth and continuous pitch steering command information during two-segment approaches. Considering adverse weather, minimum ceiling and flight crew experience criteria, a transition initiation altitude of approximately 800 feet AFL would have broadest acceptance for initiating two-segment approach procedures in scheduled service. The profile defined by the system gave an upper glidepath of approximately 6 1/2 degrees. This was 1/2 degree greater than inserted into the area navigation system. The glidepath error is apparently due to an erroneous along-track, distance-to-altitude profile

Hydraulics, Morphology, and Energy Dissipation in an Alpine Step-pool Channel

To investigate the relationship between hydraulics and channel morphology in step‐pool channels, we combined three‐dimensional velocity measurements with an acoustic Doppler velocimeter and topographic surveys in a steep step‐pool channel, the Rio Cordon, Italy. Measurements were organized around step, pool, and tread units and occurred within a range of 36%–57% of bankfull discharges. As flow moved from steps to their downstream pools in our study reach, an average of approximately two thirds of the total energy was dissipated, as measured by relative head loss through step‐pool sequences. Much of this head loss was achieved by elevation (potential energy) loss rather than velocity reductions. Although an overall, expected pattern of flow acceleration toward step crests and deceleration in pools was present, pool velocities were high, especially where upstream step crests were irregular and where residual pool depths were low. Many steps were porous or “leaky,” with irregular cross‐channel bed and water surface topography, producing high‐velocity jets and less flow resistance than channel‐spanning dammed steps. Longitudinal variations in hydraulics are thus often overshadowed by lateral variations arising from morphologic complexities. Velocity and turbulence characteristics in the Rio Cordon show marked differences from data we have collected in a more stable and wood‐rich channel in the Colorado Rockies, in which “ponded” steps are more prevalent and pools are slower and more turbulent. Comparison of these channels illustrates that step‐pool structure and hydraulics are strongly influenced by flow regime, sediment supply, lithology, time since the last step‐forming flood, and availability of in‐stream wood

The fate of sediment, wood and organic carbon eroded during an extreme flood, Colorado Front Range, USA

Identifying and quantifying the dominant processes of erosion and tracking the fate of sediment, wood, and carbon eroded during floods is important for understanding channel response to floods, downstream sediment and carbon loading, and the influence of extreme events on landscapes and the terrestrial carbon cycle. We quantify sediment, wood, and organic carbon (OC) from source to local sink following an extreme flood in the tectonically quiescent, semi-arid Colorado (USA) Front Range. Erosion of >500,000 m3 or as much as ~115 yr of weathering products occurred through landsliding and channel erosion during September 2013 flooding. More than half of the eroded sediment was deposited at the inlet and delta of a water supply reservoir, resulting in the equivalent of 100 yr of reservoir sedimentation and 2% loss in water storage capacity. The flood discharged 28 Mg C/km2, producing an event OC flux equivalent to humid, tectonically active areas. Post-flood remobilization resulted in a further ~100 yr of reservoir sedimentation plus export of an additional 1.3 Mg C/km2 of wood, demonstrating the ongoing impact of the flood on reservoir capacity and carbon cycling. Pronounced channel widening during the flood created accommodation space for 40% of flood sediment and storage of wood and eroded carbon. We conclude that confined channels, normally dismissed as transport reaches, can store and export substantial amounts of flood constituents

Laser Surface Preparation and Bonding of Aerospace Structural Composites

Adhesive bonds are critical to the integrity of built-up structures. Disbonds can often be detected but the strength of adhesion between surfaces in contact is not obtainable without destructive testing. Typically the number one problem in a bonded structure is surface contamination, and by extension, surface preparation. Standard surface preparation techniques, including grit blasting, manual abrasion, and peel ply, are not ideal because of variations in their application. Etching of carbon fiber reinforced plastic (CFRP) panels using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser appears to be a highly precise and promising way to both clean a composite surface prior to bonding and provide a bond-promoting patterned surface akin to peel ply without the inherent drawbacks from the same (i.e., debris and curvature). CFRP surfaces prepared using laser patterns conducive to adhesive bonding were compared to typical prebonding surface treatments through optical microscopy, contact angle goniometry, and post-bonding mechanical testing