Prediction and reconstruction of on-orbit acceleration

As the number of acceleration sensitive experiments to be carried on each Shuttle or Space Station mission increases, the requirement for either low-g environment or for accelerometry at each experiment location also increases. Preflight planning of such experiments in the past has not always included detailed analyses of the acceleration environment at the experiment location that had a serious impact on the experiment. Careful modeling of the mission activities and their effect on the experiment in many cases would have been beneficial to these experiments. In some cases, the experiment was not comprised, but insufficient instrumentation was available onboard to directly measure accelerations at the experiment location. The type of preflight modeling available to assist in experiment design and mission integration is described, as well as the use of that tool postflight to enhance flight data when sensors are not ideally suited to experiment analysis. Examples of recent shuttle flight experiments are presented

Design of an Inexpensive PVC Shock Tube for Educational Use

Herein is described the design and function of a low-cost, easy-to-assemble, -operate, and -disassemble shock tube platform experiment that can generate shock waves approaching Mach 2 at maximum pressures of ~100 psig with a helium driver gas. The experiment uses several inexpensive (\u3c$5), unamplified piezoelectric sensors attached to a multichannel oscilloscope to monitor the passage of key features of the flow (i.e., incident shock and reflected shock) through the tube, constructed from inexpensive and easy to work with schedule 40 PVC pipe and fittings. From the fixed sensor displacements along the tube and relative differences in respective transit times, the velocities of these flow features can be determined. This permits (1) comparison of experimental results to the theoretical predictions of 1-D transient gas dynamics and (2) a leaping off point for discussion and quantification of non-idealities in the flow, including the shock wave development length, shock attenuation and boundary layer growth, and interactions of the reflected shock and contact surface. Experimental accessories (future work) for study of shock focusing and steady 2-D high speed flows are also briefly discussed. Assuming both pressurized, conditioned air at ~80-100 psig and a modern multi-channel oscilloscope are available at most institutions, the total cost to construct this experiment is around$500

An approach to CMG steering using feedback linearization

This paper presents an approach for controlling spacecraft equipped with control moment gyroscopes. A technique from feedback linearization theory is used to transform the original nonlinear problem to an equivalent linear form without approximating assumptions. In this form, the spacecraft dynamics appear linearly, and are decoupled from redundancy in the system of gyroscopes. A general approach to distributing control effort among the available actuators is described which includes provisions for redistribution of rotors, explicit bounds in gimbal rates, and guaranteed operation at or near singular configurations. A particular algorithm is developed for systems of double-gimbal devices, and demonstrated in two examples for which existing approaches fail to give adequate performance

A new spacecraft autopilot.

Thesis. 1976. M.S. cn--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics.MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO.Includes bibliographical references.M.S.c

Spacecraft System Design for an Advanced X-Ray Monitor (AXM) Mission

This paper describes a system concept for a NASA Small Explorer Mission to develop an all-skyviewing Advanced X-ray Monitor (AXM). The spacecraft is configured to be launched from a Pegasus XL vehicle. AXM is designed to provide unprecedented sensitivity to cosmic explosions seen in X-rays. These include the ejections of relativistic jets by black holes in the Galaxy, and the fireballs of gamma ray bursts that originate in distant Galaxies. Such events are captured with 31 cameras mounted on the AXM spacecraft to continuously view 97% of the celestial sphere, excluding occultations by the Earth. The camera detectors are Gas Electron Multiplier (GEM) devices, developed at CERN and used with coded masks for X-ray astronomy. The pointing orientations for the cameras presented a challenge to provide 4p steradian viewing, while accommodating spacecraft subsystems and deployable solar arrays for power. The mounting orientation resembles the 32 faces and vertices of a soccer ball, with one camera eliminated to avoid the saturating effect of solar X-rays. The objective of continuous, all-sky viewing is accomplished with a three-axis stabilized attitude control subsystem with the solar panels pointed close to the Sun. The AXM mission is designed for launch into a ~600-km altitude, circular, equatorial orbit. An approximately 1 degree spacecraft maneuver once per day will maintain the solar panels aligned with the Sun. The spacecraft is powered by solar arrays that deploy after launch and are then fixed for the mission duration. Within limitations, the AXM spacecraft has been designed to gracefully tolerate many kinds of anomalies

Metalloprotein entatic control of ligand-metal bonds quantified by ultrafast x-ray spectroscopy

The multifunctional protein cytochrome c (cyt c) plays key roles in electron transport and apoptosis, switching function by modulating bonding between a heme iron and the sulfur in a methionine residue. This Fe-S(Met) bond is too weak to persist in the absence of protein constraints. We ruptured the bond in ferrous cyt c using an optical laser pulse and monitored the bond reformation within the protein active site using ultrafast x-ray pulses from an x-ray free-electron laser, determining that the Fe-S(Met) bond enthalpy is ~4 kcal/mol stronger than in the absence of protein constraints. The 4 kcal/mol is comparable with calculations of stabilization effects in other systems, demonstrating how biological systems use an entatic state for modest yet accessible energetics to modulate chemical function

B cell survival, surface BCR and BAFFR expression, CD74 metabolism, and CD8-dendritic cells require the intramembrane endopeptidase SPPL2A

Druggable proteins required for B lymphocyte survival and immune responses are an emerging source of new treatments for autoimmunity and lymphoid malignancy. In this study, we show that mice with an inactivating mutation in the intramembrane protease signal peptide peptidase-like 2A (SPPL2A) unexpectedly exhibit profound humoral immunodeficiency and lack mature B cell subsets, mirroring deficiency of the cytokine B cell-activating factor (BAFF). Accumulation of Sppl2a-deficient B cells was rescued by overexpression of the BAFF-induced survival protein B cell lymphoma 2 (BCL2) but not BAFF and was distinguished by low surface BAFF receptor and IgM and IgD B cell receptors. CD8-negative dendritic cells were also greatly decreased. SPPL2A deficiency blocked the proteolytic processing of CD74 MHC II invariant chain in both cell types, causing dramatic build-up of the p8 product of Cathepsin S and interfering with earlier steps in CD74 endosomal retention and processing. The findings illuminate an important role for the final step in the CD74-MHC II pathway and a new target for protease inhibitor treatment of B cell diseases.R01 AI052127/AI/NIAID NIH HHS/United States U19 AI100627/AI/NIAID NIH HHS/United States Medical Research Council/United Kingdom Wellcome Trust/United Kingdo

Functional dissection of the chickpea (Cicer arietinum l.) stay-green phenotype associated with molecular variation at an ortholog of mendel’s i gene for cotyledon color: Implications for crop production and carotenoid biofortification

“Stay-green” crop phenotypes have been shown to impact drought tolerance and nutritional content of several crops. We aimed to genetically describe and functionally dissect the particular stay-green phenomenon found in chickpeas with a green cotyledon color of mature dry seed and investigate its potential use for improvement of chickpea environmental adaptations and nutritional value. We examined 40 stay-green accessions and a set of 29 BC2F4-5 stay-green introgression lines using a stay-green donor parent ICC 16340 and two Indian elite cultivars (KAK2, JGK1) as recurrent parents. Genetic studies of segregating populations indicated that the green cotyledon trait is controlled by a single recessive gene that is invariantly associated with the delayed degreening (extended chlorophyll retention). We found that the chickpea ortholog of Mendel’s I locus of garden pea, encoding a SGR protein as very likely to underlie the persistently green cotyledon color phenotype of chickpea. Further sequence characterization of this chickpea ortholog CaStGR1 (CaStGR1, for carietinum stay-green gene 1) revealed the presence of five different molecular variants (alleles), each of which is likely a loss-of-function of the chickpea protein (CaStGR1) involved in chlorophyll catabolism. We tested the wild type and green cotyledon lines for components of adaptations to dry environments and traits linked to agronomic performance in different experimental systems and different levels of water availability. We found that the plant processes linked to disrupted CaStGR1 gene did not functionality affect transpiration efficiency or water usage. Photosynthetic pigments in grains, including provitaminogenic carotenoids important for human nutrition, were 2–3-fold higher in the stay-green type. Agronomic performance did not appear to be correlated with the presence/absence of the stay-green allele. We conclude that allelic variation in chickpea CaStGR1 does not compromise traits linked to environmental adaptation and agronomic performance, and is a promising genetic technology for biofortification of provitaminogenic carotenoids in chickpea