Silicon is vital to the computing industry because of the high quality of its native oxide and well-established doping technologies. Isotopic purification has enabled quantum coherence times on the ...order of seconds, thereby placing silicon at the forefront of efforts to create a solid-state quantum processor. We demonstrate strong coupling of a single electron in a silicon double quantum dot to the photonic field of a microwave cavity, as shown by the observation of vacuum Rabi splitting. Strong coupling of a quantum dot electron to a cavity photon would allow for long-range qubit coupling and the long-range entanglement of electrons in semiconductor quantum dots.
Errors in the spectroscopic parameters used in the forward radiative transfer model can introduce spatially, temporally, and altitude-dependent biases in trace gas retrievals. For well-mixed trace ...gases such as methane, where the variability of tropospheric mixing ratios is relatively small, reducing such biases is particularly important. We use aircraft observations from all five missions of the HIAPER Pole-to-Pole Observations (HIPPO) of the Carbon Cycle and Greenhouse Gases Study to evaluate the impact of updates to spectroscopic parameters for methane (CH4), water vapor (H2O), and nitrous oxide (N2O) on thermal infrared retrievals of methane from the NASA Aura Tropospheric Emission Spectrometer (TES). We find that updates to the spectroscopic parameters for CH4 result in a substantially smaller mean bias in the retrieved CH4 when compared with HIPPO observations. After an N2O-based correction, the bias in TES methane upper tropospheric representative values for measurements between 50° S and 50° N decreases from 56.9 to 25.7 ppbv, while the bias in the lower tropospheric representative value increases only slightly (from 27.3 to 28.4 ppbv). For retrievals with less than 1.6 degrees of freedom for signal (DOFS), the bias is reduced from 26.8 to 4.8 ppbv. We also find that updates to the spectroscopic parameters for N2O reduce the errors in the retrieved N2O profile.
We perform detailed magnetotransport studies on two-dimensional electron gases (2DEGs) formed in undoped Si/SiGe heterostructures in order to identify the electron mobility limiting mechanisms. By ...analyzing data from 26 different heterostructures, we observe a strong correlation between the background oxygen concentration in the Si quantum well and the maximum mobility. The highest-quality wafer supports a 2DEG with mobility mu = 160 000 cm super(2)/Vs at a density n = 2.17 x 10 super(11)/cm super(2) and exhibits a metal-to-insulator transition at a critical density n sub(c)= 0.46 x 10 super(11)/cm super(2). We extract a valley splitting Delta sub()v~ 150 mu eV at a magnetic field B = 1.8 T. These results provide evidence that undoped Si/SiGe heterostructures are suitable for the fabrication of few-electron quantum dots.
Single-footprint retrievals of carbon monoxide from the Atmospheric Infrared Sounder (AIRS) are evaluated using aircraft in situ observations. The aircraft data are from the HIAPER Pole-to-Pole ...Observations (HIPPO, 2009-2011), the first three Atmospheric Tomography Mission (ATom, 2016-2017) campaigns, and the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Laboratory (GML) Global Greenhouse Gas Reference Network aircraft program in years 2006-2017. The retrievals are obtained using an optimal estimation approach within the MUlti-SpEctra, MUlti-SpEcies, MUlti-SEnsors (MUSES) algorithm. Retrieval biases and estimated errors are evaluated across a range of latitudes from the subpolar to tropical regions over both ocean and land points.
For additive manufacturing (AM) of metallic materials, the certification and qualification paradigm needs to evolve as there is currently no broadly accepted “ASTM- or DIN-type” additive ...manufacturing certification process or AM-produced material specifications. Accordingly, design, manufacture, and subsequent implementation and insertion of AM materials to meet engineering applications requires detailed quantification of the constitutive (strength and damage) properties of these evolving materials, across the spectrum of metallic AM methods, in comparison/contrast to conventionally-manufactured metals and alloys. For this study, cylindrical samples of 316L SS were produced using a LENS MR-7 laser additive manufacturing system from Optomec (Albuquerque, NM) equipped with a 1 kW Yb-fiber laser. The microstructure of the AM-316L SS was characterized in both the “as-built” AM state and following a heat-treatment designed to obtain full recrystallization to facilitate comparison with annealed wrought 316L SS. The constitutive behavior as a function of strain rate and temperature was characterized and is compared to that of annealed wrought 316L SS plate material. The dynamic shock-loading-induced damage evolution and failure response of all three 316L SS materials was quantified using flyer-plate impact driven spallation experiments at peak stresses of 4.7 and 6.5 GPa. The spall strength of AM-produced 316L SS and the recrystallized-AM-316L SS were found to decrease with increasing peak shock stress while the annealed wrought 316L SS spall strength remained essentially constant. The damage evolution, characterized using optical metallography and electron-backscatter diffraction (EBSD), was found to vary significantly across the three 316L SS microstructures while the three samples loaded to a peak shock stress of 6.5 GPa displayed only ∼12% differences in spall strength.
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Modern data assimilation algorithms depend on accurate infrared spectroscopy in order to make use of the information related to temperature, water vapor (H2O), and other trace gases provided by ...satellite observations. Reducing the uncertainties in our knowledge of spectroscopic line parameters and continuum absorption is thus important to improve the application of satellite data to weather forecasting. Here we present the results of a rigorous validation of spectroscopic updates to an advanced radiative transfer model, the Line-By-Line Radiative Transfer Model (LBLRTM), against a global dataset of 120 near-nadir, over-ocean, nighttime spectra from the Infrared Atmospheric Sounding Interferometer (IASI). We compare calculations from the latest version of LBLRTM (v12.1) to those from a previous version (v9.4+) to determine the impact of spectroscopic updates to the model on spectral residuals as well as retrieved temperature and H2O profiles. We show that the spectroscopy in the CO2 ν2 and ν3 bands is significantly improved in LBLRTM v12.1 relative to v9.4+, and that these spectroscopic updates lead to mean changes of ~0.5 K in the retrieved vertical temperature profiles between the surface and 10 hPa, with the sign of the change and the variability among cases depending on altitude. We also find that temperature retrievals using each of these two CO2 bands are remarkably consistent in LBLRTM v12.1, potentially allowing these bands to be used to retrieve atmospheric temperature simultaneously. The updated H2O spectroscopy in LBLRTM v12.1 substantially improves the a posteriori residuals in the P-branch of the H2O ν2 band, while the improvements in the R-branch are more modest. The H2O amounts retrieved with LBLRTM v12.1 are on average 14% lower between 100 and 200 hPa, 42% higher near 562 hPa, and 31% higher near the surface compared to the amounts retrieved with v9.4+ due to a combination of the different retrieved temperature profiles and the updated H2O spectroscopy. We also find that the use of a fixed ratio of HDO to H2O in LBLRTM may be responsible for a significant fraction of the remaining bias in the P-branch relative to the R-branch of the H2O ν2 band. There were no changes to O3 spectroscopy between the two model versions, and so both versions give positive a posteriori residuals of ~ 0.3 K in the R-branch of the O3 ν3 band. While the updates to the H2O self-continuum employed by LBLRTM v12.1 have clearly improved the match with observations near the CO2 ν3 band head, we find that these updates have significantly degraded the match with observations in the fundamental band of CO. Finally, significant systematic a posteriori residuals remain in the ν4 band of CH4, but the magnitude of the positive bias in the retrieved mixing ratios is reduced in LBLRTM v12.1, suggesting that the updated spectroscopy could improve retrievals of CH4 from satellite observations.
Despite its clear importance, the monitoring of atmospheric ammonia,
including its sources, sinks, and links to the greater nitrogen cycle,
remains limited. Satellite data are helping to fill the gap ...in monitoring
from sporadic conventional ground- and aircraft-based observations to better
inform policymakers and assess the impact of any ammonia-related policies.
Presented is a description and survey that demonstrate the capabilities of
the Cross-track Infrared Sounder (CrIS) ammonia product for monitoring, air quality forecast model
evaluation, dry deposition estimates, and emission estimates from an
agricultural hotspot. For model evaluation, while there is a general
agreement in the spatial allocation of known major agricultural ammonia
hotspots across North America, the satellite observations show some high-latitude regions during peak forest
fire activity often have ammonia concentrations approaching those in
agricultural hotspots. The CrIS annual ammonia dry depositions in Canada
(excluding the territories) and the US have average and annual variability
values of ∼0.8±0.08 and
∼1.23±0.09 Tg N yr−1, respectively. These
satellite-derived dry depositions of reactive nitrogen from NH3 with NO2 show an annual ratio of NH3 compared to their sum (NH3+NO2) of ∼82 % and ∼55 % in Canada and the US, respectively. Furthermore, we show the use of CrIS satellite
observations to estimate annual and seasonal emissions near Lethbridge, Alberta,
Canada, a region dominated by high-emission
concentrated animal feeding operations (CAFOs); the satellite annual
emission estimate of 37.1±6.3 kt yr−1 is at least double the value
reported in current bottom-up emission inventories for this region.
Presently only limited sets of tropospheric ammonia (NH3) measurements in the Earth's atmosphere have been reported from satellite and surface station measurements, despite the well-documented ...negative impact of NH3 on the environment and human health. Presented here is a detailed description of the satellite retrieval strategy and analysis for the Tropospheric Emission Spectrometer (TES) using simulations and measurements. These results show that: (i) the level of detectability for a representative boundary layer TES NH3 mixing ratio value is ~0.4 ppbv, which typically corresponds to a profile that contains a maximum level value of ~1 ppbv; (ii) TES NH3 retrievals generally provide at most one degree of freedom for signal (DOFS), with peak sensitivity between 700 and 900 mbar; (iii) TES NH3 retrievals show significant spatial and seasonal variability of NH3 globally; (iv) initial comparisons of TES observations with GEOS-CHEM estimates show TES values being higher overall. Important differences and similarities between modeled and observed seasonal and spatial trends are noted, with discrepancies indicating areas where the timing and magnitude of modeled NH3 emissions from agricultural sources, and to lesser extent biomass burning sources, need further study.
Cosmic-ray muons in the deep ocean BABSON, J; BARISH, B; JAWORSKI, M ...
Physical review. D, Particles and fields,
12/1990, Letnik:
42, Številka:
11
Journal Article
Recenzirano
A string of seven optical detectors deployed from a ship was used to detect the Cherenkov light from muons at ocean depths ranging from 2000 to 4000 m in intervals of {similar to}500 m. The flux and ...angular distributions of cosmic-ray muons were measured. An effective area for fivefold coincidences of 420 m{sup 2} for downward-going muons was achieved. The results are consistent with those derived from underground observations and theoretical calculations. The measured vertical intensity ranges from (9.84{plus minus}6.5){times}10{sup {minus}8} cm{sup {minus}2} s{sup {minus}1} sr{sup {minus}1} at 2090 m of water equivalent (mwe) to (4.57{plus minus}1.37){times}10{sup {minus}9} cm{sup {minus}2} s{sup {minus}1} sr{sup {minus}1} at 4157 mwe.
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