Asteroid team

The purpose of this task is to support asteroid research and the operation of an Asteroid Team within the Earth and Space Sciences Division at the Jet Propulsion Laboratory (JPL). The Asteroid Team carries out original research on asteroids in order to discover, better characterize and define asteroid properties. This information is needed for the planning and design of NASA asteroid flyby and rendezvous missions. The asteroid Team also provides scientific and technical advice to NASA and JPL on asteroid related programs. Work on asteroid classification continued and the discovery of two Earth-approaching M asteroids was published. In the asteroid photometry program researchers obtained N or Q photometry for more than 50 asteroids, including the two M-earth-crossers. Compositional analysis of infrared spectra (0.8 to 2.6 micrometer) of asteroids is continuing. Over the next year the work on asteroid classification and composition will continue with the analysis of the 60 reduced infrared spectra which we now have at hand. The radiometry program will continue with the reduction of the N and Q bandpass data for the 57 asteroids in order to obtain albedos and diameters. This year the emphasis will shift to IRAS follow-up observations; which includes objects not observed by IRAS and objects with poor or peculiar IRAS data. As in previous year, we plan to give top priority to any opportunities for observing near-Earth asteroids and the support (through radiometric lightcurve observations from the IRTF) of any stellar occultations by asteroids for which occultation observation expeditions are fielded. Support of preparing of IRAS data for publication and of D. Matson for his participation in the NASA Planetary Astronomy Management and Operations Working Group will continue

Infrared observations of asteroids from earth and space

Infrared reflectances at wavelength between 1 and 4 micrometers are used for determining asteroid surface mineralogy, surface composition, diameters, and albedos. Thermal models were developed for analyzing infrared observations at longer wavelengths. The discovery of a spectral feature due to water of hydration on Ceres seems to contradict the mineralogy inferred from spectrophotometry

High Resolution Spectrometry of Leaf and Canopy Chemistry for Biochemical Cycling

High-resolution laboratory spectrophotometer and Airborne Imaging Spectrometer (AIS) data were used to analyze forest leaf and canopy chemistry. Fundamental stretching frequencies of organic bonds in the visible, near infrared and short-wave infrared are indicative of concentrations and total content of nitrogen, phosphorous, starch and sugar. Laboratory spectrophotometer measurements showed very strong negative correlations with nitrogen (measured using wet chemistry) in the visible wavelengths. Strong correlations with green wet canopy weight in the atmospheric water absorption windows were observed in the AIS data. A fairly strong negative correlation between the AIS data at 1500 nm and total nitrogen and nitrogen concentration was evident. This relationship corresponds very closely to protein absorption features near 1500 nm

IRAS asteroid families

The Infrared Astronomical Satellite (IRAS) sampled the entire asteroid population at wavelengths from 12 to 100 microns during its 1983 all sky survey. The IRAS Minor Planet Survey (IMPS) includes updated results for more recently numbered as well as other additional asteroids with reliable orbital elements. Albedos and diameters were derived from the observed thermal emission and assumed absolute visual magnitudes and then entered into the IMPS database at the Infrared Processing and Analysis Center (IPAC) for members of the Themis, Eos, Koronis and Maria asteroid families and compared with their visual colors. The IMPS results for the small (down to about 20 km) asteroids within these major families confirm trends previously noted for their larger members. Each of these dynamical families which are defined by their similar proper elements appears to have homogeneous physical properties

A decade's overview of Io's volcanic activity

Over the past decade some aspects of Io's volcanic activity have changed greatly, while others have essentially remained constant. This contrast has emerged from our study of multi-wavelength, infrared, observations of Io's thermal emission. From 1983 to 1992 we observed the disk integrated flux density of Io from the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Our spectral coverage allows us to separate out the emission components due to volcanic thermal anomalies which are warmer than the background emission caused by solar heating. Our temporal coverage allows us to resolve individual eruptions and also to obtain the disk-integrated flux density as a function of longitude (or, equivalently, orbital phase angle). Characteristics that persisted over the decade involve Loki's location and intensity of emission, the leading hemisphere emission, and the average heat flow. The variable aspects of Io over the decade include Loki's hotter area(s) and the outbursts in the leading hemisphere

IR-dust observations of Comet Tempel 2 with CRAF VIMS

Measurement strategies are now being planned for using the Visual and Infrared Mapping Spectrometer (VIMS) to observe the asteroid Hestia, and the nucleus, and the gas and dust in the coma of comet P/Tempel 2 as part of the Comet Rendezvous Asteroid Flyby (CRAF) mission. The spectral range of VIMS will cover wavelengths from 0.35 to 5.2 micrometers, with a spectral resolution of 11 nm from 0.35 to 2.4 micrometers and of 22 nm from 2.4 to 5.2 micrometers. The instantaneous field of view (IFOV) provided by the foreoptics is 0.5 milliradians, and the current design of the instrument provides for a scanning secondary mirror which will scan a swath of length 72 IFOVs. The CRAF high resolution scan platform motion will permit slewing VIMS in a direction perpendicular to the swath. This enables the building of a two dimensional image in any or all wavelength channels. Important measurements of the dust coma will include the onset of early coma activity, the mapping of gas and dust jets and correlations with active nucleus areas, observations of the dust coma from various scattering phase angles, coverage of the low wavelength portion of the thermal radiation, and the 3.4 micrometer hydrocarbon emission. A description of the VIMS instrument is presented

LcrG secretion is not required for blocking of Yops secretion in Yersinia pestis

<p>Abstract</p> <p>Background</p> <p>LcrG, a negative regulator of the <it>Yersinia </it>type III secretion apparatus has been shown to be primarily a cytoplasmic protein, but is secreted at least in <it>Y. pestis</it>. LcrG secretion has not been functionally analyzed and the relevance of LcrG secretion on LcrG function is unknown.</p> <p>Results</p> <p>An LcrG-GAL4AD chimera, originally constructed for two-hybrid analyses to analyze LcrG protein interactions, appeared to be not secreted but the LcrG-GAL4AD chimera retained the ability to regulate Yops secretion. This result led to further investigation to determine the significance of LcrG secretion on LcrG function. Additional analyses including deletion and substitution mutations of amino acids 2–6 in the N-terminus of LcrG were constructed to analyze LcrG secretion and LcrG's ability to control secretion. Some changes to the N-terminus of LcrG were found to not affect LcrG's secretion or LcrG's secretion-controlling activity. However, substitution of poly-isoleucine in the N-terminus of LcrG did eliminate LcrG secretion but did not affect LcrG's secretion controlling activity.</p> <p>Conclusion</p> <p>These results indicate that secretion of LcrG, while observable and T3SS mediated, is not relevant for LcrG's ability to control secretion.</p

Venous thromboembolism, chronic liver disease and anticoagulant choice: effectiveness and safety of direct oral anticoagulants versus warfarin

Background Little to no data exist to guide treatment decision in patients with venous thromboembolism (VTE) and chronic liver disease. Objectives To assess the effectiveness and safety of direct oral anticoagulants (DOACs)—individually and as a class—vs warfarin and between 2 DOACs in patients with acute VTE and chronic liver disease. Methods We conducted a retrospective, US claims–based, propensity score–matched cohort study in adults with acute VTE and chronic liver disease who had newly initiated oral anticoagulants between 2011 and 2017. The primary outcome was a composite of hospitalization for recurrent VTE and hospitalization for major bleeding. Results The cohorts included 2361 DOAC-warfarin, 895 apixaban-warfarin, 2161 rivaroxaban-warfarin, and 895 apixaban-rivaroxaban matched pairs. Lower risk of the primary outcome was seen with DOACs (hazard ratio [HR], 0.72; 95% CI, 0.61-0.85), apixaban (HR, 0.48; 95% CI, 0.35-0.66) or rivaroxaban (HR, 0.73; 95% CI, 0.61-0.88) vs warfarin but not apixaban-rivaroxaban (HR, 0.68; 95% CI, 0.43-1.08). The HRs of hospitalization for major bleeding were 0.69 (95% CI, 0.57-0.84) for DOAC-warfarin, 0.43 (95% CI, 0.30-0.63) for apixaban-warfarin, 0.72 (95% CI, 0.58-0.89) for rivaroxaban-warfarin, and 0.60 (95% CI, 0.35-1.06) for apixaban-rivaroxaban. Recurrent VTE risk was lower with apixaban (HR, 0.47; 95% CI, 0.26-0.86), but not DOACs (HR, 0.81; 95% CI, 0.59-1.12) or rivaroxaban vs warfarin (HR, 0.81; 95% CI, 0.57-1.14) or apixaban-rivaroxaban (HR, 0.92; 95% CI, 0.42-2.02). Conclusion While the magnitude of clinical benefit varied across individual DOACs, in adults with acute VTE and chronic liver disease, oral factor Xa inhibitors (as a class or individually) were associated with lower risk of recurrent VTE and major bleeding

Soil trace gas fluxes along orthogonal precipitation and soil fertility gradients in tropical lowland forests of Panama

Tropical lowland forest soils are significant sources and sinks of trace gases. In order to model soil trace gas flux for future climate scenarios, it is necessary to be able to predict changes in soil trace gas fluxes along natural gradients of soil fertility and climatic characteristics. We quantified trace gas fluxes in lowland forest soils at five locations in Panama, which encompassed orthogonal precipitation and soil fertility gradients. Soil trace gas fluxes were measured monthly for 1 (NO) or 2 (CO2, CH4, N2O) years (2010–2012) using vented dynamic (for NO only) or static chambers with permanent bases. Across the five sites, annual fluxes ranged from 8.0 to 10.2 Mg CO2-C, −2.0 to −0.3 kg CH4-C, 0.4 to 1.3 kg N2O-N and −0.82 to −0.03 kg NO-N ha−1 yr−1. Soil CO2 emissions did not differ across sites, but they did exhibit clear seasonal differences and a parabolic pattern with soil moisture across sites. All sites were CH4 sinks; within-site fluxes were largely controlled by soil moisture, whereas fluxes across sites were positively correlated with an integrated index of soil fertility. Soil N2O fluxes were low throughout the measurement years, but the highest emissions occurred at a mid-precipitation site with high soil N availability. Net negative NO fluxes at the soil surface occurred at all sites, with the most negative fluxes at the low-precipitation site closest to Panama City; this was likely due to high ambient NO concentrations from anthropogenic sources. Our study highlights the importance of both short-term (climatic) and long-term (soil and site characteristics) factors in predicting soil trace gas fluxes