Paper Session III-C - Proton Exchange Membrane Fuel Cells for the Next Generation Spacecraft Applications

This paper presents the results of an assessment of the requirements and technology for the Proton Exchange Membrane (PEM) fuel cell as the electric power source for next-generation spacecraft, and particularly as an accepted upgrade to replace the current Orbiter alkaline fuel cell. As part of the technology assessment, a commercially available 4-kW PEM fuel cell was tested for over 400 hours at NASA-Johnson Space Center using hydrogen and oxygen as reactants. The findings of this evaluation, as well as a short summary of some test facility improvements and accomplishments as they relate to fuel cell testing in general, are presented. A short status of other items in the Orbiter PEM Fuel Cell Upgrade effort is also presented

Word Length Perturbations in Certain Symmetric Presentations of Dihedral Groups

Given a finite group with a generating subset there is a well-established notion of length for a group element given in terms of its minimal length expression as a product of elements from the generating set. Recently, certain quantities called $\lambda_{1}$ and $\lambda_{2}$ have been defined that allow for a precise measure of how stable a group is under certain types of small perturbations in the generating expressions for the elements of the group. These quantities provide a means to measure differences among all possible paths in a Cayley graph for a group, establish a group theoretic analog for the notion of stability in nonlinear dynamical systems, and play an important role in the application of groups to computational genomics. In this paper, we further expose the fundamental properties of $\lambda_{1}$ and $\lambda_{2}$ by establishing their bounds when the underlying group is a dihedral group. An essential step in our approach is to completely characterize so-called symmetric presentations of the dihedral groups, providing insight into the manner in which $\lambda_{1}$ and $\lambda_{2}$ interact with finite group presentations. This is of interest independent of the study of the quantities $\lambda_{1},\; \lambda_{2}$. Finally, we discuss several conjectures and open questions for future consideration

Quantifying environmental impacts of poplar biomass production in the U.S. Pacific Northwest

The life cycle impacts were determined for poplar-managed four ways in the Pacific Northwest of the United States. Two sites had 3-yr rotations and either no irrigation (Site 1) or irrigation with river water (Site 2). The other sites had 12-yr rotations and irrigation with wastewater from a treatment facility (Site 3) or irrigation with landfill leachate (Site 4). Primary data for land preparation, plantation management, harvesting, and land restoration at each site and the production of cuttings at an additional facility were collected. A cradle to gate life cycle assessment was conducted using SimaPro PhD v8 based on the primary data and secondary data from the US life cycle inventory and ecoinvent v3 database to create a life cycle inventory. Impact indicators were provided by TRACI model. Short rotations resulted in lower global warming impact per unit output (79.5 and 54.5 kg CO2 eq/t) and energy consumption (1381.8 and 877.4 MJ/t) than long rotations (93.1 and 81 kg CO2 eq/t and 1406.9 and 1343.5 MJ/t) mainly due to reduced diesel use. Higher planting densities resulted in greater water and electrical consumption attributed to cuttings. Pesticide and herbicide use strongly affected ozone depletion and eutrophication, whereas fuel consumption had strong effects on global warming impact, smog, and acidification. Increasing biomass yield reduced impacts. When the electricity was all from biomass, global warming and acidification decreased; however, ozone depletion, smog, and eutrophication increased. The results suggested that both, herbicide application during plantation management and diesel consumed during harvesting at these sites should be optimized to decrease the environmental impacts. 

Genome-Wide Association Study for Maize Leaf Cuticular Conductance Identifies Candidate Genes Involved in the Regulation of Cuticle Development.

The cuticle, a hydrophobic layer of cutin and waxes synthesized by plant epidermal cells, is the major barrier to water loss when stomata are closed at night and under water-limited conditions. Elucidating the genetic architecture of natural variation for leaf cuticular conductance (g c) is important for identifying genes relevant to improving crop productivity in drought-prone environments. To this end, we conducted a genome-wide association study of g c of adult leaves in a maize inbred association panel that was evaluated in four environments (Maricopa, AZ, and San Diego, CA, in 2016 and 2017). Five genomic regions significantly associated with g c were resolved to seven plausible candidate genes (ISTL1, two SEC14 homologs, cyclase-associated protein, a CER7 homolog, GDSL lipase, and β-D-XYLOSIDASE 4). These candidates are potentially involved in cuticle biosynthesis, trafficking and deposition of cuticle lipids, cutin polymerization, and cell wall modification. Laser microdissection RNA sequencing revealed that all these candidate genes, with the exception of the CER7 homolog, were expressed in the zone of the expanding adult maize leaf where cuticle maturation occurs. With direct application to genetic improvement, moderately high average predictive abilities were observed for whole-genome prediction of g c in locations (0.46 and 0.45) and across all environments (0.52). The findings of this study provide novel insights into the genetic control of g c and have the potential to help breeders more effectively develop drought-tolerant maize for target environments

Left-Right Symmetry and Leading Contributions to Neutrinoless Double Beta Decay

We study the impact of the mixing (LR mixing) between the standard model W boson and its hypothetical, heavier right-handed parter WR on the neutrinoless double beta decay (0νββ decay) rate. Our study is done in the minimal left-right symmetric model assuming a type-II dominance scenario with charge conjugation as the left-right symmetry. We then show that the 0νββ decay rate may be dominated by the contribution proportional to this LR mixing, which at the hadronic level induces the leading-order contribution to the interaction between two pions and two charged leptons. The resulting long-range pion exchange contribution can significantly enhance the decay rate compared to previously considered short-range contributions. Finally, we find that even if future cosmological experiments rule out the inverted hierarchy for neutrino masses, there are still good prospects for a positive signal in the next generation of 0νββ decay experiments

Convective Fingering of an Autocatalytic Reaction Front

We report experimental observations of the convection-driven fingering instability of an iodate-arsenous acid chemical reaction front. The front propagated upward in a vertical slab; the thickness of the slab was varied to control the degree of instability. We observed the onset and subsequent nonlinear evolution of the fingers, which were made visible by a {\it p}H indicator. We measured the spacing of the fingers during their initial stages and compared this to the wavelength of the fastest growing linear mode predicted by the stability analysis of Huang {\it et. al.} [{\it Phys. Rev. E}, {\bf 48}, 4378 (1993), and unpublished]. We find agreement with the thickness dependence predicted by the theory.Comment: 11 pages, RevTex with 3 eps figures. To be published in Phys Rev E, [email protected], [email protected], [email protected]

Costo por actividades y gestión financiera en los productores de ganado vacuno. Feria ganadera Coto Coto - Chilca 2021

La presente tesis titulada Costo por Actividades y Gestión Financiera en los Productores de Ganado Vacuno. Feria Ganadera Coto Coto - Chilca 2021, planteo como problema ¿Qué relación existe entre Costo por Actividades y Gestión Financiera en los Productores de Ganado Vacuno en la Feria Ganadera Coto - Coto Chilca 2021?, respectivamente el objetivo de estudio fue: Determinar la relación existe entre el Costo por Actividades y Gestión Financiera en los Productores de Ganado Vacuno en la Feria Ganadera Coto - Coto Chilca 2021. La metodología de la investigación fue científica, de tipo básica, de nivel relacional, el diseño de la investigación está comprendido desde un nivel no experimental bajo el esquema descriptivo correlacional, la muestra de estudio estuvo conformada por 141 productores de ganado vacuno que participan en la feria, a quienes se les aplico un cuestionario bajo la escala de medición ordinal, concluyéndose: Se determinó que existe una relación directa con correlación elevada τ = 0,779 y significativa al 0,01 entre el costo por actividades y gestión financiera en los ganaderos de ganado vacuno en la feria Coto - Coto Chilca 2021, con un p-valor = 0,000 y ∝=0,01; efectuando el diagnóstico mediante la aplicación de la encuesta a los ganaderos se identificó que usan la metodología del control de sus actividades de manera empírica pues no existe un orden apropiado y control de todos los componentes que intervienen en el proceso, por lo que se está demostrando que se encontró evidencia suficiente de relación entre nuestras variables de estudio

Using Graph Algorithms to Pretrain Graph Completion Transformers

Recent work on Graph Neural Networks has demonstrated that self-supervised pretraining can further enhance performance on downstream graph, link, and node classification tasks. However, the efficacy of pretraining tasks has not been fully investigated for downstream large knowledge graph completion tasks. Using a contextualized knowledge graph embedding approach, we investigate five different pretraining signals, constructed using several graph algorithms and no external data, as well as their combination. We leverage the versatility of our Transformer-based model to explore graph structure generation pretraining tasks (i.e. path and k-hop neighborhood generation), typically inapplicable to most graph embedding methods. We further propose a new path-finding algorithm guided by information gain and find that it is the best-performing pretraining task across three downstream knowledge graph completion datasets. While using our new path-finding algorithm as a pretraining signal provides 2-3% MRR improvements, we show that pretraining on all signals together gives the best knowledge graph completion results. In a multitask setting that combines all pretraining tasks, our method surpasses the latest and strong performing knowledge graph embedding methods on all metrics for FB15K-237, on MRR and Hit@1 for WN18RRand on MRR and hit@10 for JF17K (a knowledge hypergraph dataset)

Impact of Team Formation Approach on Teamwork Effectiveness and Performance in an Upper-Level Undergraduate Chemical Engineering Laboratory Course

This study focuses on the impact of team formation approach on teamwork effectiveness and performance spanning three years of instruction of the chemical engineering unit operations laboratory, which is an upper-level undergraduate laboratory course. Team formation approaches changed each year, and assessment tools, including peer-assessment, academic performance, and course evaluations, were employed to evaluate team performance. Approaches included three cases: instructor-selected teams based on GPA with the objective of a similar cumulative average GPA for each team, student self-selected teams, and a combination of self-selected teams with instructor-selected teams for a final experiment. For the third case, new teams were assigned based on a common interest to learn about a specific final laboratory experiment or research topic, and the instructor identification of both low- and high-performing students in the prior teams. Team effectiveness and performance were assessed using CATME, a teamwork VALUE rubric developed by the Association of American Colleges and Universities (AAC&U), and numerical peer-contribution forms. In addition, assigned team leaders for each experiment provided feedback regarding individual team member performance, including contributions to reports and presentations. Results demonstrated that less than five percent of the students presented team conflicts when students self-selected teams for the laboratory course; however, strong or weak teams were formed leading to unbalanced laboratory performance. On the contrary, course evaluation outcomes were improved when students were assigned to teams based on cumulative GPA or reassigned by the instructor for the completion of a final experiment. Overall, this study demonstrates that a combination of student-selected and instructor-selected teams during the same semester led to better course outcomes and enhanced individual experiences, as shown by the students’ evaluations of the laboratory course