2,098 research outputs found
Comparing key compositional indicators in Jupiter with those in extra-solar giant planets
Spectroscopic transiting observations of the atmospheres of hot Jupiters
around other stars, first with Hubble Space Telescope and then Spitzer, opened
the door to compositional studies of exoplanets. The James Webb Space Telescope
will provide such a profound improvement in signal-to-noise ratio that it will
enable detailed analysis of molecular abundances, including but not limited to
determining abundances of all the major carbon- and oxygen-bearing species in
hot Jupiter atmospheres. This will allow determination of the carbon-to-oxygen
ratio, an essential number for planet formation models and a motivating goal of
the Juno mission currently around JupiterComment: Submitted to the Astro2020 Decadal Survey as a white paper; thematic
areas "Planetary Systems" and "Star and Planet Formation
Ferromagnetic resonance force microscopy on microscopic cobalt single layer films
We report mechanical detection of ferromagnetic resonance signals from
microscopic Co single layer thin films using a magnetic resonance force
microscope (MRFM). Variations in the magnetic anisotropy field and the
inhomogeneity of were clearly observed in the FMR spectra of microscopic Co
thin films 500 and 1000 angstrom thick and 40 X 200 micron^2 in lateral extent.
This demonstrates the important potential that MRFM detection of FMR holds for
microscopic characterization of spatial distribution of magnetic properties in
magnetic layered materials and devices.Comment: 4 pages, 2 figures, RevTex. To be published in Applied Physics
Letters, October 5, 199
Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy
Lateral one-dimensional imaging of cobalt (Co) films by means of microscopic ferromagnetic resonance (FMR) detected using the magnetic resonance force microscope (MRFM) is demonstrated. A novel approach involving scanning a localized magnetic probe is shown to enable FMR imaging in spite of the broad resonance linewidth. We introduce a spatially selective local field by means of a small, magnetically polarized spherical crystallite of yttrium iron garnet (YIG). Using MRFM-detected FMR signals from a sample consisting of two Co films, we can resolve the ∼20 μm lateral separation between the films. The results can be qualitatively understood by consideration of the calculated spatial profiles of the magnetic field generated by the YIG sphere
An optical method for carbon dioxide isotopes and mole fractions in small gas samples: Tracing microbial respiration from soil, litter, and lignin
Rationale
Carbon dioxide isotope (δ13C value) measurements enable quantification of the sources of soil microbial respiration, thus informing ecosystem C dynamics. Tunable diode lasers (TDLs) can precisely measure CO2 isotopes at low cost and high throughput, but are seldom used for small samples (≤5 mL). We developed a TDL method for CO2 mole fraction ([CO2]) and δ13C analysis of soil microcosms. Methods
Peaks in infrared absorbance following constant volume sample injection to a carrier were used to independently measure [12CO2] and [13CO2] for subsequent calculation of δ13C values. Using parallel soil incubations receiving differing C substrates, we partitioned respiration from three sources using mixing models: native soil organic matter (SOM), added litter, and synthetic lignin containing a 13C label at Cβ of the propyl side chain. Results
Once-daily TDL calibration enabled accurate quantification of δ13C values and [CO2] compared with isotope ratio mass spectrometry (IRMS), with long-term external precision of 0.17 and 0.31‰ for 5 and 1 mL samples, respectively, and linear response between 400 and 5000 μmol mol−1CO2. Production of CO2 from native soil C, added litter, and lignin Cβ varied over four orders of magnitude. Multiple-pool first-order decay models fitted to data (R2 \u3e 0.98) indicated substantially slower turnover for lignin Cβ (17 years) than for the dominant pool of litter (1.3 years) and primed soil C (3.9 years). Conclusions
Our TDL method provides a flexible, precise, and high-throughput (60 samples h−1) alternative to IRMS for small samples. This enables the use of C isotopes in increasingly sophisticated experiments to test biogeochemical controversies, such as the fate of lignins in soil
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