1,465 research outputs found
Acquisition of computer research equipment
Issued as Final report, Project no. G-36-61
Analysis and synthesis of communication protocols and systems
Includes GIT-ICS report no. 85/32Issued as Quarterly progress reports [nos. 1-5], and Final report, Project no. G-36-62
The Middeck Active Control Experiment (MACE)
The Middeck Active Control Experiment (MACE) is a NASA In-Step and Control Structure Interaction (CSI) Office funded Shuttle middeck experiment. The objective is to investigate the extent to which closed-loop behavior of flexible spacecraft in zero-gravity (0-g) can be predicted. This prediction becomes particularly difficult when dynamic behavior during ground testing exhibits extensive suspension and direct gravity coupling. On-orbit system identification and control reconfiguration is investigated to improve performance which would otherwise be limited due to errors in prediction. The program is presently in its preliminary design phase with launch expected in the summer of 1994. The MACE test article consists of three attitude control torque wheels, a two axis gimballing payload, inertial sensors and a flexible support structure. With the acquisition of a second payload, this will represent a multiple payload platform with significant structural flexibility. This paper presents on-going work in the areas of modelling and control of the MACE test article in the zero and one-gravity environments. Finite element models, which include suspension and gravity effects, and measurement models, derived from experimental data, are used as the basis for Linear Quadratic Gaussian controller designs. Finite element based controllers are analytically used to study the differences in closed-loop performance as the test article transitions between the 0-g and 1-g environments. Measurement based controllers are experimentally applied to the MACE test article in the 1-g environment and achieve over an order of magnitude improvement in payload pointing accuracy when disturbed by a broadband torque disturbance. The various aspects of the flight portion of the experiment are also discussed
An Extreme X-ray Disk Wind in the Black Hole Candidate IGR J17091-3624
{\it Chandra} spectroscopy of transient stellar-mass black holes in outburst
has clearly revealed accretion disk winds in soft, disk--dominated states, in
apparent anti-correlation with relativistic jets in low/hard states. These disk
winds are observed to be highly ionized, dense, and to have typical velocities
of 1000 km/s or less projected along our line of sight. Here, we present
an analysis of two {\it Chandra} High Energy Transmission Grating spectra of
the Galactic black hole candidate IGR J170913624 and contemporaneous EVLA
radio observations, obtained in 2011. The second {\it Chandra} observation
reveals an absorption line at 6.910.01 keV; associating this line with
He-like Fe XXV requires a blue-shift of km/s (0.03, or
the escape velocity at 1000 R). This projected outflow velocity is an
order of magnitude higher than has previously been observed in stellar-mass
black holes, and is broadly consistent with some of the fastest winds detected
in active galactic nuclei. A potential feature at 7.32 keV, if due to Fe XXVI,
would imply a velocity of km/s (0.05), but this putative
feature is marginal. Photoionization modeling suggests that the accretion disk
wind in IGR J170913624 may originate within 43,300 Schwarzschild radii of
the black hole, and may be expelling more gas than accretes. The
contemporaneous EVLA observations strongly indicate that jet activity was
indeed quenched at the time of our {\it Chandra} observations. We discuss the
results in the context of disk winds, jets, and basic accretion disk physics in
accreting black hole systems.Comment: 6 pages, 2 figures, Accepted to ApJLetter
Nicotianamine, a Novel Enhancer of Rice Iron Bioavailability to Humans
Background: Polished rice is a staple food for over 50 % of the world’s population, but contains little bioavailable iron (Fe) to meet human needs. Thus, biofortifying the rice grain with novel promoters or enhancers of Fe utilization would be one of the most effective strategies to prevent the high prevalence of Fe deficiency and iron deficiency anemia in the developing world. Methodology/Principal Findings: We transformed an elite rice line cultivated in Southern China with the rice nicotianamine synthase gene (OsNAS1) fused to a rice glutelin promoter. Endosperm overexpression of OsNAS1 resulted in a significant increase in nicotianamine (NA) concentrations in both unpolished and polished grain. Bioavailability of Fe from the high NA grain, as measured by ferritin synthesis in an in vitro Caco-2 cell model that simulates the human digestive system, was twice as much as that of the control line. When added at 1:1 molar ratio to ferrous Fe in the cell system, NA was twice as effective when compared to ascorbic acid (one of the most potent known enhancers of Fe bioavailability) in promoting more ferritin synthesis. Conclusions: Our data demonstrated that NA is a novel and effective promoter of iron utilization. Biofortifying polished rice with this compound has great potential in combating global human iron deficiency in people dependent on rice for thei
BLAST: the Redshift Survey
The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) has recently
surveyed ~8.7 deg^2 centered on GOODS-South at 250, 350, and 500 microns. In
Dye et al. (2009) we presented the catalogue of sources detected at 5-sigma in
at least one band in this field and the probable counterparts to these sources
in other wavebands. In this paper, we present the results of a redshift survey
in which we succeeded in measuring redshifts for 82 of these counterparts. The
spectra show that the BLAST counterparts are mostly star-forming galaxies but
not extreme ones when compared to those found in the Sloan Digital Sky Survey.
Roughly one quarter of the BLAST counterparts contain an active nucleus. We
have used the spectroscopic redshifts to carry out a test of the ability of
photometric redshift methods to estimate the redshifts of dusty galaxies,
showing that the standard methods work well even when a galaxy contains a large
amount of dust. We have also investigated the cases where there are two
possible counterparts to the BLAST source, finding that in at least half of
these there is evidence that the two galaxies are physically associated, either
because they are interacting or because they are in the same large-scale
structure. Finally, we have made the first direct measurements of the
luminosity function in the three BLAST bands. We find strong evolution out to
z=1, in the sense that there is a large increase in the space-density of the
most luminous galaxies. We have also investigated the evolution of the
dust-mass function, finding similar strong evolution in the space-density of
the galaxies with the largest dust masses, showing that the luminosity
evolution seen in many wavebands is associated with an increase in the
reservoir of interstellar matter in galaxies.Comment: Accepted for publication in the Astrophysical Journal. Maps and
associated results are available at http://blastexperiment.info
Chronic Wasting Disease Prions in Elk Antler Velvet
Residue 226 of cervid prion proteins may be a determinant of CWD pathogenesis
Alzheimer\u27s Therapeutics Targeting Amyloid Beta 1-42 Oligomers I: Abeta 42 Oligomer Binding to Specific Neuronal Receptors is Displaced by Drug Candidates That Improve Cognitive Deficits
Synaptic dysfunction and loss caused by age-dependent accumulation of synaptotoxic beta amyloid (Abeta) 1-42 oligomers is proposed to underlie cognitive decline in Alzheimer\u27s disease (AD). Alterations in membrane trafficking induced by Abeta oligomers mediates reduction in neuronal surface receptor expression that is the basis for inhibition of electrophysiological measures of synaptic plasticity and thus learning and memory. We have utilized phenotypic screens in mature, in vitro cultures of rat brain cells to identify small molecules which block or prevent the binding and effects of Abeta oligomers. Synthetic Abeta oligomers bind saturably to a single site on neuronal synapses and induce deficits in membrane trafficking in neuronal cultures with an EC50 that corresponds to its binding affinity. The therapeutic lead compounds we have found are pharmacological antagonists of Abeta oligomers, reducing the binding of Abeta oligomers to neurons in vitro, preventing spine loss in neurons and preventing and treating oligomer-induced deficits in membrane trafficking. These molecules are highly brain penetrant and prevent and restore cognitive deficits in mouse models of Alzheimer\u27s disease. Counter-screening these compounds against a broad panel of potential CNS targets revealed they are highly potent and specific ligands of the sigma-2/PGRMC1 receptor. Brain concentrations of the compounds corresponding to greater than 80% receptor occupancy at the sigma-2/PGRMC1 receptor restore cognitive function in transgenic hAPP Swe/Ldn mice. These studies demonstrate that synthetic and human-derived Abeta oligomers act as pharmacologically-behaved ligands at neuronal receptors--i.e. they exhibit saturable binding to a target, they exert a functional effect related to their binding and their displacement by small molecule antagonists blocks their functional effect. The first-in-class small molecule receptor antagonists described here restore memory to normal in multiple AD models and sustain improvement long-term, representing a novel mechanism of action for disease-modifying Alzheimer\u27s therapeutics
Addendum to ASNC/AHA/ASE/EANM/HFSA/ISA/SCMR/SNMMI expert consensus recommendations for multimodality imaging in cardiac amyloidosis:Part 1 of 2-evidence base and standardized methods of imaging
There are 2 primary reasons for an addendum. The first is that the document reviewer list is being updated to include Dr Richard Cheng and Dr Roy John, who have critically reviewed the document, but were inadvertently not listed as reviewers. In addition, since the publication of this document and the introduction of approved therapies for transthyretin cardiac amyloidosis, the clinical use of bone tracer cardiac scintigraphy has been extended to populations with a lower prevalence of transthyretin cardiac amyloidosis. Numerous observations have raised concerns about (1) incorrect diagnosis of transthyretin cardiac amyloidosis based on 99mTc-pyrophosphate (PYP) planar imaging and heart-to-contralateral lung (H/CL) ratio without confirmation of diffuse myocardial uptake on single photon emission computed tomography (SPECT) imaging at some sites; (2) excess blood pool activity on the 1-hour planar and SPECT images being interpreted as positive scans; and (3) missed diagnosis of light chain amyloidosis, as serum-free light chain studies and serum and urine immunofixation electrophoresis studies may not be recommended in the 99mTc-PY P/-3,3-diphosphono-1,2-propanodicarboxylic acid/hydroxymethylene diphosphonate (99mTc-PYP/DPD/HMDP) report. Incorrect diagnosis leads to inappropriate therapy and worse patient outcomes. SPECT and planar imaging performed at 3-hour maximize specificity. 1 , 2 , 3 Additionally, technical parameters have been updated
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