1,011 research outputs found
Autonomous space processor for orbital debris
This work continues to develop advanced designs toward the ultimate goal of a GETAWAY SPECIAL to demonstrate economical removal of orbital debris utilizing local resources in orbit. The fundamental technical feasibility was demonstrated last year through theoretical calculations, quantitative computer animation, a solar focal point cutter, a robotic arm design and a subscale model. During this reporting period, several improvements are made in the solar cutter, such as auto track capabilities, better quality reflectors and a more versatile framework. The major advance has been in the design, fabrication and working demonstration of a ROBOTIC ARM that has several degrees of freedom. The functions were specifically tailored for the orbital debris handling. These advances are discussed here. Also a small fraction of the resources were allocated towards research in flame augmentation in SCRAMJETS for the NASP. Here, the fundamental advance was the attainment of Mach numbers up to 0.6 in the flame zone and a vastly improved injection system; the current work is expected to achieve supersonic combustion in the laboratory and an advanced monitoring system
XO-5b: A Transiting Jupiter-sized Planet With A Four Day Period
The star XO-5 (GSC 02959-00729, V=12.1, G8V) hosts a Jupiter-sized,
Rp=1.15+/-0.12 Rjup, transiting extrasolar planet, XO-5b, with an orbital
period of P=4.187732+/-0.00002 days. The planet mass (Mp=1.15+/-0.08 Mjup) and
surface gravity (gp=22+/-5 m/s^2) are significantly larger than expected by
empirical Mp-P and Mp-P-[Fe/H] relationships. However, the deviation from the
Mp-P relationship for XO-5b is not large enough to suggest a distinct type of
planet as is suggested for GJ 436b, HAT-P-2b, and XO-3b. By coincidence XO-5
overlies the extreme H I plume that emanates from the interacting galaxy pair
NGC 2444/NGC 2445 (Arp 143).Comment: 10 pages, 9 Figures, Submitted to Ap
Hyperbaric oxygen improves engraftment of ex-vivo expanded and gene transduced human CD34+ cells in a murine model of umbilical cord blood transplantation
Delayed engraftment and graft failure represent major obstacles to successful umbilical cord blood (UCB) transplantation. Herein, we evaluated the use of hyperbaric oxygen (HBO) therapy as an intervention to improve human UCB stem/progenitor cell engraftment in an immune deficient mouse model. Six-to eight-week old NSG mice were sublethally irradiated 24 hours prior to CD34+ UCB cell transplant. Irradiated mice were separated into a non-HBO group (where mice remained under normoxic conditions) and the HBO group (where mice received two hours of HBO therapy; 100% oxygen at 2.5 atmospheres absolute). Four hours after completing HBO therapy, both groups intravenously received CD34+ UCB cells that were transduced with a lentivirus carrying luciferase gene and expanded for in vivo imaging. Mice were imaged and then sacrificed at one of 10 times up to 4.5 months post-transplant. HBO treated mice demonstrated significantly improved bone marrow, peripheral blood , and spleen (p=0.0293) retention and subsequent engraftment. In addition, HBO significantly improved peripheral, spleen and bone marrow engraftment of human myeloid and B-cell subsets. In vivo imaging demonstrated that HBO mice had significantly higher ventral and dorsal bioluminescence values. These studies suggest that HBO treatment of NSG mice prior to UCB CD34+ cell infusion significantly improves engraftment
XO-2b: Transiting Hot Jupiter in a Metal-rich Common Proper Motion Binary
We report on a V=11.2 early K dwarf, XO-2 (GSC 03413-00005), that hosts a
Rp=0.98+0.03/-0.01 Rjup, Mp=0.57+/-0.06 Mjup transiting extrasolar planet,
XO-2b, with an orbital period of 2.615857+/-0.000005 days. XO-2 has high
metallicity, [Fe/H]=0.45+/-0.02, high proper motion, mu_tot=157 mas/yr, and has
a common proper motion stellar companion with 31" separation. The two stars are
nearly identical twins, with very similar spectra and apparent magnitudes. Due
to the high metallicity, these early K dwarf stars have a mass and radius close
to solar, Ms=0.98+/-0.02 Msolar and Rs=0.97+0.02/-0.01 Rsolar. The high proper
motion of XO-2 results from an eccentric orbit (Galactic pericenter, Rper<4
kpc) well confined to the Galactic disk (Zmax~100 pc). In addition, the phase
space position of XO-2 is near the Hercules dynamical stream, which points to
an origin of XO-2 in the metal-rich, inner Thin Disk and subsequent dynamical
scattering into the solar neighborhood. We describe an efficient Markov Chain
Monte Carlo algorithm for calculating the Bayesian posterior probability of the
system parameters from a transit light curve.Comment: 14 pages, 10 Figures, Accepted in ApJ. Negligible changes to XO-2
system properties. Removed Chi^2 light curve analysis section, and simplified
MCMC light curve analysis discussio
UV Absorption Lines from High-Velocity Gas in the Vela Supernova Remnant: New insights from STIS Echelle Observations of HD72089
The star HD72089 is located behind the Vela supernova remnant and shows a
complex array of high and low velocity interstellar absorption features arising
from shocked clouds. A spectrum of this star was recorded over the wavelength
range 1196.4 to 1397.2 Angstroms at a resolving power lambda/Delta lambda =
110,000 and signal-to-noise ratio of 32 by STIS on the Hubble Space Telescope.
We have identified 7 narrow components of C I and have measured their relative
populations in excited fine-structure levels. Broader features at heliocentric
velocities ranging from -70 to +130 km/s are seen in C II, N I, O I, Si II, S
II and Ni II. In the high-velocity components, the unusually low abundances of
N I and O I, relative to S II and Si II, suggest that these elements may be
preferentially ionized to higher stages by radiation from hot gas immediately
behind the shock fronts.Comment: 11 pages, 2 figures, Latex. Submitted for the special HST ERO issue
of the Astrophysical Journal Letter
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Development and Evaluation of a 193nm Immersion Generation-Three Fluid Candidates
The need to extend 193nm immersion lithography necessitates the development of a third generation (Gen-3) of high refractive index (RI) fluids that will enable approximately 1.7 numerical aperture (NA) imaging. A multi-pronged approach was taken to develop these materials. One approach investigated the highest-index organic thus far discovered. The second approach used a very high refractive index nanoparticle to make a nanocomposite fluid. This report will describe the chemistry of the best Gen-3 fluid candidates and the systematic approach to their identification and synthesis. Images obtained with the Gen-3 fluid candidates will also be presented for a NA ≥ 1.7
Recommended from our members
Development and Evaluation of a 193nm Immersion Generation-Three Fluid Candidates
The need to extend 193nm immersion lithography necessitates the development of a third generation (Gen-3) of high refractive index (RI) fluids that will enable approximately 1.7 numerical aperture (NA) imaging. A multi-pronged approach was taken to develop these materials. One approach investigated the highest-index organic thus far discovered. The second approach used a very high refractive index nanoparticle to make a nanocomposite fluid. This report will describe the chemistry of the best Gen-3 fluid candidates and the systematic approach to their identification and synthesis. Images obtained with the Gen-3 fluid candidates will also be presented for a NA ≥ 1.7
How Universal is the Relationship Between Remotely Sensed Vegetation Indices and Crop Leaf Area Index? A Global Assessment
Leaf Area Index (LAI) is a key variable that bridges remote sensing observations to the quantification of agroecosystem processes. In this study, we assessed the universality of the relationships between crop LAI and remotely sensed Vegetation Indices (VIs). We first compiled a global dataset of 1459 in situ quality-controlled crop LAI measurements and collected Landsat satellite images to derive five different VIs including Simple Ratio (SR), Normalized Difference Vegetation Index (NDVI), two versions of the Enhanced Vegetation Index (EVI and EVI2), and Green Chlorophyll Index (CI(sub Green)). Based on this dataset, we developed global LAI-VI relationships for each crop type and VI using symbolic regression and Theil-Sen (TS) robust estimator. Results suggest that the global LAI-VI relationships are statistically significant, crop-specific, and mostly non-linear. These relationships explain more than half of the total variance in ground LAI observations (R2 greater than 0.5), and provide LAI estimates with RMSE below 1.2 m2/m2. Among the five VIs, EVI/EVI2 are the most effective, and the crop-specific LAI-EVI and LAI-EVI2 relationships constructed by TS, are robust when tested by three independent validation datasets of varied spatial scales. While the heterogeneity of agricultural landscapes leads to a diverse set of local LAI-VI relationships, the relationships provided here represent global universality on an average basis, allowing the generation of large-scale spatial-explicit LAI maps. This study contributes to the operationalization of large-area crop modeling and, by extension, has relevance to both fundamental and applied agroecosystem research
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