250 research outputs found

    Series Bosch System Development

    Get PDF
    State-of-the-art (SOA) carbon dioxide (CO2) reduction technology for the International Space Station produces methane as a byproduct. This methane is subsequently vented overboard. The associated loss of hydrogen ultimately reduces the mass of oxygen that can be recovered from CO2 in a closed-loop life support system. As an alternative to SOA CO2 reduction technology, NASA is exploring a Series-Bosch system capable of reducing CO2 with hydrogen to form water and solid carbon. This results in 100% theoretical recovery of oxygen from metabolic CO2. In the past, Bosch-based technology did not trade favorably against SOA technology due to a high power demand, low reaction efficiencies, concerns with carbon containment, and large resupply requirements necessary to replace expended catalyst cartridges. An alternative approach to Bosch technology, labeled "Series-Bosch," employs a new system design with optimized multi-stage reactors and a membrane-based separation and recycle capability. Multi-physics modeling of the first stage reactor, along with chemical process modeling of the integrated system, has resulted in a design with potential to trade significantly better than previous Bosch technology. The modeling process and resulting system architecture selection are discussed

    Optical Tracking Telemetry and Commanding (TT&C) for Small Satellites

    Get PDF
    This paper presents information on the current state of technology and potential subsystem and operational concepts to allow the use of low power optical communication systems to perform tracking, telemetry and commanding (IT &C) for small satellites. The mantra of \u27smaller, faster, better (& cheaper)\u27 has been realized, at least partially, for many aspects of small satellite design, construction and operations. Most small spacecraft systems have become smaller, lighter and more power efficient while offering greater performance. Unfortunately, one area that has not followed this general trend is IT &C. In many ways, this situation takes on greater significance due to the successes in other areas relating to processors, memory and sensor capability. Technology improvements in these areas have increased the capabilities of small satellites to collect, process and store data on-board the satellite to such a point that the ability of the spacecraft to generate data has outpaced its ability to communicate it to the ground. One approach to resolving this situation is to make use of optical communications technology for IT&C

    A revision and key to the genera of Afrotropical Mantispidae (Neuropterida, Neuroptera), with the description of a new genus

    Get PDF
    The Afrotropical Mantispidae genera have previously been neglected and are poorly known. The genera are revised and redescribed. A new genus Afromantispa Snyman and Ohl is described with Afromantispa tenella comb. n. as type species. Perlamantispa (Handschin, 1960) is synonymised with Sagittalata Handschin, 1959. The new combinations within the genus include S. austroafrica comb. n., S. bequaerti comb. n., S. dorsalis comb. n., S. girardi comb. n., S. nubila comb. n., S. perla comb. n., S. pusilla comb. n., S. similata comb. n., S. royi comb. n., S. tincta comb. n. and S. vassei comb. n. An illustrated key to the genera Afromantispa gen. n., Sagittalata Handschin, 1959, Mantispa Illiger, 1798, Cercomantispa Handschin, 1959, Rectinerva Handschin, 1959, Nampista NavĂĄs, 1914, and Pseudoclimaciella Handschin, 1960 is provided. The wing venation of Mantispidae is redescribed. Similarities between the genera are discussed. Subsequent studies will focus on revising the taxonomic status of species, which are not dealt with in this study.The University of Pretoria and the Scarab Research Group (University of Pretoria)http://www.pensoft.net/journals/zookeysab201

    Lessons in Membrane Engineering for Octanoic Acid Production from Environmental Escherichia coli Isolates

    Get PDF
    Fermentative production of many attractive biorenewable fuels and chemicals is limited by product toxicity in the form of damage to the microbial cell membrane. Metabolic engineering of the production organism can help mitigate this problem, but there is a need for identification and prioritization of the most effective engineering targets. Here, we use a set of previously characterized environmental Escherichia coli isolates with high tolerance and production of octanoic acid, a model membrane-damaging biorenewable product, as a case study for identifying and prioritizing membrane engineering strategies. This characterization identified differences in the membrane lipid composition, fluidity, integrity, and cell surface hydrophobicity from those of the lab strain MG1655. Consistent with previous publications, decreased membrane fluidity was associated with increased fatty acid production ability. Maintenance of high membrane integrity or longer membrane lipids seemed to be of less importance than fluidity. Cell surface hydrophobicity was also directly associated with fatty acid production titers, with the strength of this association demonstrated by plasmid-based expression of the multiple stress resistance outer membrane protein BhsA. This expression of bhsA was effective in altering hydrophobicity, but the direction and magnitude of the change differed between strains. Thus, additional strategies are needed to reliably engineer cell surface hydrophobicity. This work demonstrates the ability of environmental microbiological studies to impact the metabolic engineering design-build-test-learn cycle and possibly increase the economic viability of fermentative bioprocesses

    New insight into the causes, consequences, and correction of hematopoietic stem cell aging

    Get PDF
    Aging of hematopoietic stem cells (HSCs) is characterized by lineage bias, increased clonal expansion, and functional decrease. At the molecular level, aged HSCs typically display metabolic dysregulation, upregulation of inflammatory pathways, and downregulation of DNA repair pathways. Cellular aging of HSCs, driven by cell-intrinsic and cell-extrinsic factors, causes a predisposition to anemia, adaptive immune compromise, myelodys, plasia, and malignancy. Most hematologic diseases are strongly associated with age. But what is the biological foundation for decreased fitness with age? And are there therapeutic windows to resolve age-related hematopoietic decline? These questions were the focus of the International Society for Experimental Hematology (ISEH) New Investigator Committee Fall 2022 Webinar. This review touches on the latest insights from two leading laboratories into inflammatory- and niche-driven stem cell aging and includes speculation on strategies to prevent or correct age-related decline in HSC function

    Mediators of Treatment Effect in the Back In Action Trial:Using Latent Growth Modeling to Take Change Over Time Into Account

    Get PDF
    Objectives: To test whether change in fear-avoidance beliefs was a mediator of the effect of treatment on disability outcome, and to test an analytical approach, latent growth modeling, not often applied to mediation analysis. Methods: Secondary analysis was carried out on a randomized controlled trial designed to compare an intervention addressing fear-avoidance beliefs (n=119) with treatment as usual (n=121) for patients with low back pain, which found the intervention to be effective. Latent growth modelling was used to perform a mediation analysis on the trial data to assess the role of change in fear-avoidance beliefs on disability outcome. The product of coefficients with bias-corrected bootstrapped confidence intervals was used to calculate the mediating effect. Results: A statistically significant mediating effect of fear-avoidance beliefs on the effect of treatment on disability outcome was found (standardized indirect effect −0.35; bias-corrected 95% CI, −0.47 to −0.24). Poor fit of the model to the data suggested that other factors not accounted for in this model are likely to be part of the same mediating pathway. Discussion: Fear-avoidance beliefs were found to mediate the effect of treatment on disability outcome. Measurement of all potential mediator variables in future studies would help to more strongly identify which factors explain observed treatment effects. Latent growth modelling was found to be a useful technique to apply to studies of treatment mediation, suggesting that future studies could use this approach

    Uranium(III) coordination chemistry and oxidation in a flexible small-cavity macrocycle

    Get PDF
    U(III) complexes of the conformationally flexible, small-cavity macrocycle trans-calix[2]benzene[2]pyrrolide (L)2–, [U(L)X] (X = O-2,6-tBu2C6H3, N(SiMe3)2), have been synthesized from [U(L)BH4] and structurally characterized. These complexes show binding of the U(III) center in the bis(arene) pocket of the macrocycle, which flexes to accommodate the increase in the steric bulk of X, resulting in long U–X bonds to the ancillary ligands. Oxidation to the cationic U(IV) complex [U(L)X][B(C6F5)4] (X = BH4) results in ligand rearrangement to bind the smaller, harder cation in the bis(pyrrolide) pocket, in a conformation that has not been previously observed for (L)2–, with X located between the two ligand arene rings

    On Afromantispa and Mantispa (Insecta, Neuroptera, Mantispidae) : elucidating generic boundaries

    Get PDF
    The genus Afromantispa Snyman & Ohl, 2012 was recently synonymised with Mantispa Illiger, 1798 by Monserrat (2014). Here morphological evidence is presented in support of restoring the genus Afromantispa stat. rev. to its previous status as a valid and morphologically distinct genus. Twelve new combinations (comb. n.) are proposed as species of Afromantispa including three new synonyms.Werner StrĂŒmpher is thanked for his valuable and critical comments on the manuscript. We would also like to extend our gratitude to Johan Saayman for his enthusiasm and willingness to help with the photography, as well as Morgan Trimble for some of the photos used in this publication. Mervyn Mansell is thanked for his willingness to discuss and for his meaningful advice. We are also grateful for all the staff of SANC, MRAC and ZMB who helped with the curation and lending of specimens.The National Research Foundationhttp://zookeys.pensoft.net/am201
    • 

    corecore