Now showing items 1-20 of 99262

• #### Flash Lidar On-Orbit Performance at Asteroid Bennu

NASA’s Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft is currently orbiting asteroid (101955) Bennu with the ultimate goal of collecting a sample from the asteroid’s surface and returning it to Earth. After launching from Cape Canaveral Air Force Station in September 2016, the OSIRIS-REx spacecraft travelled for nearly two years before arriving at asteroid Bennu in December 2018. Before entering orbit around Bennu, the spacecraft conducted a series of detailed surface scans. At the time, this achievement marked the closest orbit of a planetary body by a spacecraft, approximately 1.3 km, and set the record for Bennu as the smallest body ever orbited. Surveillance of Bennu continued in preparation for selecting a site to collect a regolith sample from the surface. The flash LIDAR is one of the navigation sensors for the Touch and Go (TAG) event. Several checkouts of the instrument were performed in flight including lasing at the surface of Bennu to verify its performance. Analyzing the LIDAR data over the asteroid surface against the shape model produced range data well within accuracy requirements. The LIDAR has performed nominally in flight as the first flash LIDAR used in a deep space mission. There has been no degradation to the laser and sensor, and no optical alignment issues have been observed.
• #### Consumption of walnuts suppresses the conversion of palmitic to palmitoleic acid and enhances omega-3 fatty acid metabolism in the heart of fructose-fed rats

Walnut consumption mostly has a positive implication for cardiovascular health. Walnut diet effects on the cardiac fatty acid (FA) metabolism of healthy rats and those with fructose diet-induced metabolic burden were analysed. Both walnuts and fructose increased CD36 transporter level and the nuclear content of some/all of Lipin 1/PPARα/PGC-1 complex partners, as well as cytosolic and nuclear FOXO1. However, fructose, independently of walnuts, increased the content of palmitic (PA), oleic, and vaccenic acid (VA), while in walnut-fed rats failed to increase palmitoleic acid (POA) level and the POA/PA ratio, as well as total MUFA content. In opposite, walnuts reduced the level of PA and VA and increased alpha-linolenic, eicosapentaenoic and docosapentaenoic acid level, regardless of fructose. In conclusion, both fructose and walnuts stimulated the uptake and oxidation of FA in the heart, but the walnuts, opposite to fructose, favourably altered cardiac FA profile in healthy and metabolically compromised rats.
• #### Cultivating a Community of Viewers in Africa: How Sissako Frames Spectatorship and Performance in His Films

Critical discussion of Abderrahmane Sissako's major films, Life on Earth (1998), Waiting for Happiness (2002), Bamako (2006), and Timbuktu (2014), explores issues related to spectatorship, live performance, and intertextuality. In particular, this essay looks at how this filmmaker frames spectatorship within his film narratives to bring the process of image-making up for reconsideration. These self-reflexive moments are examined in relation to film as an art form, issues of genre, and the history of cinema. The essay also looks at how live performances are embedded alongside scenarios of audiovisual spectatorship to draw our attention to the formation of audiences in different African settings, and to suggest an analogy between live and recorded performances. Some attention is also given to intertextuality and how Sissako references classic films by Ousmane Sembene and Djibril Diop Mambety to cultivate an awareness of film history in his viewers. By drawing on and developing insights from contributions by Karin Barber, Tsitsi Jaji, and Akin Adesokan the essay seeks to define the importance of these meta-cinematic elements in the film narratives of one of the most impactful filmmakers of his generation.
• #### Amplification of Enterocytozoon hepatopenaei in Penaeus vannamei Hepatopancreas Primary Culture and Immunofluorescence Assay for Detection of Enterocytozoon hepatopenaei

Hepatopancreatic microsporidiosis (HPM) disease leads to retarded growth in shrimp resulting in a major loss for the shrimp industry worldwide. The causative agent of HPM is a microsporidian known as Enterocytozoon hepatopenaei (EHP). It is little understood how EHP infects its host and hijacks its cellular machinery to replicate more organisms. Lack of an immortal cell line is a bottleneck in studying the cellular and molecular basis of EHP infection in shrimp. For this reason, EHP cannot be propagated in in vitro culture and must be propagated in live shrimp. The use of live EHP-infected shrimp remains the only way to study EHP infectivity. It was hypothesized that supplementing EHP with fresh host cells will aid the propagation of EHP in vitro. Further research must be done but with the data collected at this point, this hypothesis is rejected. In addition to the challenges in amplifying EHP in in vitro culture, there is no antibody-based detection method for EHP. EHP infection in a shrimp is examined by Hematoxylin and Eosin (H&E) histology and real-time polymerase chain reaction based detection methods. Monoclonal antibodies that were previously characterized by Riggs and colleagues to detect Cryptosporidium parvum (C. parvum), successfully detected other parasites. Based on this, it was hypothesized that monoclonal antibodies against C. parvum may also detect EHP.
• #### Numerical Investigations of Receptivity, Stability and Transition for High-Speed Boundary Layers

Numerical tools for receptivity and stability investigations in high-speed boundary layers were developed: A local Linear Stability Theory (LST) solver applicable for axisymmetric geometries as well as linear and nonlinear disturbance flow formulation solvers suitable for complex geometries. Explicit, implicit and time-spectral time-integration schemes were considered. Although explicit methods are comparatively simpler to implement for disturbance flow formulation solvers, the allowable time-step for stability reasons can be much smaller than that required by accuracy considerations. This is especially the case for receptivity problems involving sharp nose geometries, such as cones or wedges, because the resolution requirements in the nose region can lead to severe restrictions of the time-step for explicit schemes. The new solvers were verified and validated for a variety of flow conditions, geometries, and instabilities. Three investigations are presented. First, the effects of (small) leading edge bluntness on the linear stability of flat-plate boundary layers was investigated. For the conditions investigated, it was found that very small nose radii had already a significant effect on the stability characteristics. Second, the receptivity of a Mach 10 boundary layer on a 7 degree half-angle cone to freestream acoustic disturbances was considered. A detailed analysis as well as comparisons with LST are provided. For the case considered, slow acoustic waves converted rather naturally into the unstable mode S, while fast acoustic waves followed the trend of mode F until a specific downstream location where a switch occurred. Finally, linear and nonlinear cross-flow instability computations are presented for an infinite span swept wing with biconvex airfoil at Mach 2. The stability characteristics as well as flow structures associated with the linear, secondary instability and nonlinear regimes are presented and discussed.
• #### Germination Response of Twelve Accessions of Bouteloua curtipendula (Michx.) Torr. (Poaceae) to a Simulated Winter Temperature Regime

Twelve accessions of Bouteloua curtipendula were tested in a laboratory growth chamber to examine the effect of simulated winter temperature on the germination response of the selected accessions of B. curtipendula var. curtipendula (Michx.) Torr. and B. curtipendula var. caespitosa Gould & Kapadia, two botanical varieties of disparate origin. Accessions of the variety curtipendula had significantly higher total germination percentages compared to accessions whose variety was var. caespitosa under the winter treatment. Latitude was also significant with accessions whose origin was farther north exhibiting higher relative germination percentages under the winter treatment. Mean total germination percentage was significantly higher for accessions whose grains were from NPGS seed production facilities under the winter treatment compared to the mean of accessions from wild-collected populations. Mean seed (grain) mass was highly correlated (rs = 0.774) with relative germination percentages, suggesting seed vigor may be an important explanatory factor in germination under stressful conditions.