Impact of lunar oxygen production on direct manned Mars missions

A manned Mars program made up of six missions is evaluated to determine the impact of using lunar liquid oxygen (LOX) as a propellant. Two departure and return nodes, low Earth orbit and low lunar orbit, are considered, as well as two return vehicle configurations, a full 70,000-kg vehicle and a 6800-kg capsule. The cost of lunar LOX delivered to orbit is expressed as a ratio of Earth launch cost

The adenomatous polyposis coli protein unambiguously localizes to microtubule plus ends and is involved in establishing parallel arrays of microtubule bundles in highly polarized epithelial cells

Loss of full-length adenomatous polyposis coli (APC) protein correlates with the development of colon cancers in familial and sporadic cases. In addition to its role in regulating β-catenin levels in the Wnt signaling pathway, the APC protein is implicated in regulating cytoskeletal organization. APC stabilizes microtubules in vivo and in vitro, and this may play a role in cell migration (Näthke, I.S., C.L. Adams, P. Polakis, J.H. Sellin, and W.J. Nelson. 1996. J. Cell Biol. 134:165–179; Mimori-Kiyosue, Y., N. Shiina, and S. Tsukita. 2000. J. Cell Biol. 148:505–517; Zumbrunn, J., K. Inoshita, A.A. Hyman, and I.S. Näthke. 2001. Curr. Biol. 11:44–49) and in the attachment of microtubules to kinetochores during mitosis (Fodde, R., J. Kuipers, C. Rosenberg, R. Smits, M. Kielman, C. Gaspar, J.H. van Es, C. Breukel, J. Wiegant, R.H. Giles, and H. Clevers. 2001. Nat. Cell Biol. 3:433–438; Kaplan, K.B., A. Burds, J.R. Swedlow, S.S. Bekir, P.K. Sorger, and I.S. Näthke. 2001. Nat. Cell Biol. 3:429–432). The localization of endogenous APC protein is complex: actin- and microtubule-dependent pools of APC have been identified in cultured cells (Näthke et al., 1996; Mimori-Kiyosue et al., 2000; Reinacher-Schick, A., and B.M. Gumbiner. 2001. J. Cell Biol. 152:491–502; Rosin-Arbesfeld, R., G. Ihrke, and M. Bienz. 2001. EMBO J. 20:5929–5939). However, the localization of APC in tissues has not been identified at high resolution. Here, we show that in fully polarized epithelial cells from the inner ear, endogenous APC protein associates with the plus ends of microtubules located at the basal plasma membrane. Consistent with a role for APC in supporting the cytoskeletal organization of epithelial cells in vivo, the number of microtubules is significantly reduced in apico-basal arrays of microtubule bundles isolated from mice heterozygous for APC

Applications of flight control system methods to an advanced combat rotorcraft

Advanced flight control system design, analysis, and testing methodologies developed at the Ames Research Center are applied in an analytical and flight test evaluation of the Advanced Digital Optical Control System (ADOCS) demonstrator. The primary objectives are to describe the knowledge gained about the implications of digital flight control system design for rotorcraft, and to illustrate the analysis of the resulting handling-qualities in the context of the proposed new handling-qualities specification for rotorcraft. Topics covered in-depth are digital flight control design and analysis methods, flight testing techniques, ADOCS handling-qualities evaluation results, and correlation of flight test results with analytical models and the proposed handling-qualities specification. The evaluation of the ADOCS demonstrator indicates desirable response characteristics based on equivalent damping and frequency, but undersirably large effective time-delays (exceeding 240 m sec in all axes). Piloted handling-qualities are found to be desirable or adequate for all low, medium, and high pilot gain tasks; but handling-qualities are inadequate for ultra-high gain tasks such as slope and running landings

Gone But Not Forgotten: The HST Non-Detection of SN Ia 2011fe 11.5yr After Explosion Further Restricts Single-Degenerate Progenitor Systems

We present deep Hubble Space Telescope imaging of the nearby Type Ia supernova (SN Ia) 2011fe obtained 11.5yr after explosion. No emission is detected at the SN location to a $1\sigma$ ($3\sigma$) limit of ${F555W > 30.2 \;(29.0)}~$mag, or equivalently $M_V > 1.2 \;(-0.1)~$mag, neglecting the distance uncertainty to M101. We constrain the presence of donor stars impacted by the SN ejecta with the strictest limits thus far on compact (i.e., $\log \,g \gtrsim 4$) companions. H-rich zero-age main-sequence companions with masses $\geq 2~\rm M_\odot$ are excluded, a significant improvement upon the pre-explosion imaging limit of $\approx 5~\rm M_\odot$. Main-sequence He stars with masses $\geq 0.5~\rm M_\odot$ and subgiant He stars with masses $\lesssim 1~\rm M_\odot$ are also disfavored by our late-time imaging. Synthesizing our limits on post-impact donors with previous constraints from pre-explosion imaging, early-time radio and X-ray observations, and nebular-phase spectroscopy, essentially all formation channels for SN2011fe invoking a non-degenerate donor star at the time of explosion are unlikely.Comment: 5 pages excluding references, 4 figures, 1 table. Submitted to ApJ

Case studies to enhance online student evaluation: Bond University – Surveying students online to improve learning and teaching

One of the most sensible ways of improving learning and teaching is to ask the students for feedback. At the end of each teaching period (i.e. semester or term) all universities and many schools survey their students. Usually these surveys are managed online. Questions ask for student perceptions about teaching, assessment and workload. The survey administrators report four common problems

Lack of Z-DNA Conformation in Mitomycin-Modified Polynucleotides Having Inverted Circular Dichroism

Poly(dG-dC)· poly(dG-dC) and Micrococcus lysodeikticus DNA were modified by exposure to reductively activated mitomycin C, an antitumor antibiotic. The resulting covalent drug-polynucleotide complexes displayed varying degrees of CD inversions, which are strikingly similar to the inverted spectrum observed with Z-DNA. The following criteria have been used to establish, however, that the inverted CD pattern seen in mitomycin C-polynucleotide complexes does not reflect a Z-DNA conformation. (i) The ethanol-induced transition of poly(dG-dC)· poly(dG-dC) from B to Z conformation is not facilitated but rather is inhibited by mitomycin C modification. This may be due to the presence of crosslinks. (ii) Radioimmunoassay indicated no competition for Z-DNA-specific antibody by any of the mitomycin C-modified polynucleotides. (iii) 31P NMR of the complexes yielded a single relatively narrow resonance, which is inconsistent with the dinucleotide repeat characteristic of Z-DNA. Alternative explanations for the inverted CD pattern include a drug-induced left-handed but non-Z conformational change or the superposition of an induced CD onto the CD of B-DNA due to drug-base electronic interactions. These results illustrate the need for caution in interpreting CD changes alone as an indication of Z-DNA conformation