Fully autonomous navigation for the NASA cargo transfer vehicle

A great deal of attention has been paid to navigation during the close approach (less than or equal to 1 km) phase of spacecraft rendezvous. However, most spacecraft also require a navigation system which provides the necessary accuracy for placing both satellites within the range of the docking sensors. The Microcosm Autonomous Navigation System (MANS) is an on-board system which uses Earth-referenced attitude sensing hardware to provide precision orbit and attitude determination. The system is capable of functioning from LEO to GEO and beyond. Performance depends on the number of available sensors as well as mission geometry; however, extensive simulations have shown that MANS will provide 100 m to 400 m (3(sigma)) position accuracy and 0.03 to 0.07 deg (3(sigma)) attitude accuracy in low Earth orbit. The system is independent of any external source, including GPS. MANS is expected to have a significant impact on ground operations costs, mission definition and design, survivability, and the potential development of very low-cost, fully autonomous spacecraft

The Porcine Antibody Repertoire: Variations on the Textbook Theme

The genes encoding the heavy and light chains of swine antibodies are organized in the same manner as in other eutherian mammals. There are ∼30 VH genes, two functional DH genes and one functional JH gene, 14–60 Vκ genes, 5 Jκ segments, 12–13 functional Vλ genes, and two functional Jλ genes. The heavy chain constant regions encode the same repertoire of isotypes common to other eutherian mammals. The piglet models offers advantage over rodent models since the fetal repertoire develops without maternal influences and the precocial nature of their multiple offspring allows the experimenter to control the influences of environmental and maternal factors on repertoire development postnatally. B cell lymphogenesis in swine begins in the fetal yolk sac at 20 days of gestation (DG), moves to the fetal liver at 30 DG and eventually to the bone marrow which dominates until birth (114 DG) and to at least 5 weeks postpartum. There is no evidence that the ileal Peyers patches are a site of B cell lymphogenesis or are required for B cell maintenance. Unlike rodents and humans, light chain rearrangement begins first in the lambda locus; kappa rearrangements are not seen until late gestation. Dissimilar to lab rodents and more in the direction of the rabbit, swine utilize a small number of VH genes to form >90% of their pre-immune repertoire. Diversification in response to environmental antigen does not alter this pattern and is achieved by somatic hypermutation (SHM) of the same small number of VH genes. The situation for light chains is less well studied, but certain Vκ and Jκ and Vλ and Jλ are dominant in transcripts and in contrast to rearranged heavy chains, there is little junctional diversity, less SHM, and mutations are not concentrated in CDR regions. The transcribed and secreted pre-immune antibodies of the fetus include mainly IgM, IgA, and IgG3; this last isotype may provide a type of first responder mucosal immunity. Development of functional adaptive immunity is dependent on bacterial MAMPs or MAMPs provided by viral infections, indicating the importance of innate immunity for development of adaptive immunity. The structural analysis of Ig genes of this species indicate that especially the VH and Cγ gene are the result of tandem gene duplication in the context of genomic gene conversion. Since only a few of these duplicated VH genes substantially contribute to the antibody repertoire, polygeny may be a vestige from a time before somatic processes became prominently evolved to generate the antibody repertoire. In swine we believe such duplications within the genome have very limited functional significance and their occurrence is therefore overrated

How do first-year engineering students experience ambiguity in engineering design problems: The development of a self-report instrument

Citation: Dringenberg, E., & Wertz, R. E. H. (2016). How do first-year engineering students experience ambiguity in engineering design problems: The development of a self-report instrument.Design is widely recognized as a keystone of engineering practice. Within the context of engineering education, design has been categorized as a type of ill-structured problem solving that is crucial for engineering students to engage with. Improving undergraduate engineering education requires a better understanding of the ways in which students experience ill-structured problems in the form of engineering design. With special attention to the experiences of first-year engineering students, prior exploratory work identified two critical thresholds that distinguished students' ways of experiencing design as less or more comprehensive: accepting ambiguity and recognizing the value of multiple perspectives. The goal of current (work-in-progress) research is to develop and pilot a self-report instrument to assess students' relation to these two thresholds at the completion of an ill-structured design project within the context of undergraduate engineering education. The specific research questions addressed in this study are 1) if the piloted self-report instrument can be used to identify discrete constructs, and 2) how these constructs align with prior qualitative research findings. The objective of this study was addressed using a quantitative exploratory research design. Items for the self-report Likert-scaled instrument were designed to distinguish student experience that either accept or reject the presence of ambiguity and the value of multiple perspectives. The instrument was disseminated to a total of 214 first-year engineering students. Exploratory factor analysis was used to identify the constructs that emerge from the self-report data, and these constructs were checked for alignment with the previously identified thresholds. The results of this investigation will be used to help advance progress towards an easily administered instrument able to assist engineering educators with the identification of students in need of intervention or explicit instruction related to critical aspects of learning engineering design. The instrument could also be used to track student growth over time, and, with further development, to provide evidence for ABET student outcomes. © American Society for Engineering Education, 2016

Some Results of the Educational Experiment APIS (Cervantes Mission on Board ISS)

Some results of the analysis of the pictures taken along the performance of the Análisis de Propiedades Inerciales de Sólidos, Analysis of the Inertia Properties of Solid Bodies (APIS) experiment carried out in the Cervantes mission on board ISS, are presented. APIS was an educational experiment devoted to take advantage of the unique conditions of absence of relative gravity forces of a space platform such as ISS, to show some of the characteristics of the free rotational motion of a solid body, which are impossible to carry out on earth. This field of experimental research has application to aerospace engineering science (e.g. attitude control of spacecrafts), to astrophysical sciences (e.g. state of rotation and tumbling motions of asteroids) and to engineering education. To avoid the effect of the ambient atmosphere loads on the motion, the test body is placed inside a sphere, which reduces the effect of the aerodynamic forces to just friction. The drastic reduction of the effect of the surrounding air during the short duration of the experimental sequences allows us to compare the actual motion with the known solutions for the solid body rotation in vacuum. In this paper, some selected, relevant sequences of the sphere enclosing a body with a nominal cylindrical inertia tensor, put into rotation by the astronaut, are shown; the main problems to extract the information concerning the characteristic parameters of the motion are outlined, and some of the results obtained concerning the motion of the test probe are included, which show what seems to be a curious and unexpected solution of the Euler equations for the solid body rotation in vacuum, without energy dissipation, when the angular momentum is almost perpendicular to the axisymmetry axis

Detecting Key Structural Features within Highly Recombined Genes

Many microorganisms exhibit high levels of intragenic recombination following horizontal gene transfer events. Furthermore, many microbial genes are subject to strong diversifying selection as part of the pathogenic process. A multiple sequence alignment is an essential starting point for many of the tools that provide fundamental insights on gene structure and evolution, such as phylogenetics; however, an accurate alignment is not always possible to attain. In this study, a new analytic approach was developed in order to better quantify the genetic organization of highly diversified genes whose alleles do not align. This BLAST-based method, denoted BLAST Miner, employs an iterative process that places short segments of highly similar sequence into discrete datasets that are designated “modules.” The relative positions of modules along the length of the genes, and their frequency of occurrence, are used to identify sequence duplications, insertions, and rearrangements. Partial alleles of sof from Streptococcus pyogenes, encoding a surface protein under host immune selection, were analyzed for module content. High-frequency Modules 6 and 13 were identified and examined in depth. Nucleotide sequences corresponding to both modules contain numerous duplications and inverted repeats, whereby many codons form palindromic pairs. Combined with evidence for a strong codon usage bias, data suggest that Module 6 and 13 sequences are under selection to preserve their nucleic acid secondary structure. The concentration of overlapping tandem and inverted repeats within a small region of DNA is highly suggestive of a mechanistic role for Module 6 and 13 sequences in promoting aberrant recombination. Analysis of pbp2X alleles from Streptococcus pneumoniae, encoding cell wall enzymes that confer antibiotic resistance, supports the broad applicability of this tool in deciphering the genetic organization of highly recombined genes. BLAST Miner shares with phylogenetics the important predictive quality that leads to the generation of testable hypotheses based on sequence data

NF94-179 Surge Irrigation Management

This NebFact discusses surge irrigation management

NF94-177 Nebraska Surge Irrigation Trials

This NebFact discusses the Nebraska Surge Irrigation Trials