Antarctic krill (Euphausia superba) are swarming, oceanic crustaceans, up to two inches long, and best known as prey for whales and penguins - but they have another important role. With their large ...size, high biomass and daily vertical migrations they transport and transform essential nutrients, stimulate primary productivity and influence the carbon sink. Antarctic krill are also fished by the Southern Ocean's largest fishery. Yet how krill fishing impacts nutrient fertilisation and the carbon sink in the Southern Ocean is poorly understood. Our synthesis shows fishery management should consider the influential biogeochemical role of both adult and larval Antarctic krill.
In metals, orbital motions of conduction electrons on the Fermi surface are quantized in magnetic fields, which is manifested by quantum oscillations in electrical resistivity. This Landau ...quantization is generally absent in insulators. Here, we report a notable exception in an insulator-ytterbium dodecaboride (YbB
). The resistivity of YbB
, which is of a much larger magnitude than the resistivity in metals, exhibits distinct quantum oscillations. These unconventional oscillations arise from the insulating bulk, even though the temperature dependence of the oscillation amplitude follows the conventional Fermi liquid theory of metals with a large effective mass. Quantum oscillations in the magnetic torque are also observed, albeit with a lighter effective mass.
Abstract
In this study, we develop a novel method for determining electron transport coefficients from electron swarm maps measured by a scanning drift-tube experiment. In our method, two types of ...electron continuity equations that describe either the spatial or the temporal evolution of an electron swarm are discovered in the electron swarm map. The electron transport coefficients can be determined from the coefficients in the discovered equations. Therefore, we can determine the Townsend ionization coefficient, ionization rate coefficient, center-of-mass drift velocity, mean arrival-time drift velocity, longitudinal diffusion coefficient, and longitudinal third-order transport coefficient. These transport coefficients in argon are determined over a wide range of reduced electric fields,
E
/
N
, from 29.7 to 1351.6 Td (1 Td = 10
−21
Vm
2
) using our method. We establish that the consideration of high-order transport coefficients, which have been systematically ignored so far, is important for the proper determination of low-order transport coefficients, specifically the electron drift velocity and longitudinal diffusion coefficient, in the presence of ionization growth.
An overview of the recently renovated high-pressure X-ray diffraction (XRD) BL10XU beamline for the diamond anvil cell at SPring-8 is presented. The renovation includes the replacement of the X-ray ...source and monochromator, enhanced focusing systems for high-energy XRD, and recent progress in the sample environment control techniques that are available for high-pressure studies. Other simultaneous measurement techniques for combination with XRD, such as Raman scattering spectroscopy and Mössbauer spectroscopy, have been developed to obtain complementary information under extreme conditions. These advanced techniques are expected to make significant contributions to in-depth understanding of various and complicated high-pressure phenomena. The experience gained with the BL10XU beamline could help promote high-pressure research in future synchrotron radiation facilities.
A novel direct numerical method to calculate the electron velocity distribution function (EVDF) in hydrodynamic equilibrium under a uniform DC electric field is presented. In the present method, an ...artificial feedforward neural network learns the EVDF governed by both the Boltzmann equation and boundary conditions. The present method dost not require the expansion of the EVDF in the Legendre polynomials and the discretization of both the EVDF and the Boltzmann equation. As a benchmark, the EVDF in Reid's ramp model gas and Ar gas was calculated by the present method, and then the validity of the present method was demonstrated by comparing electron energy distributions and electron transport coefficients deduced from the EVDF with those calculated by Monte Carlo simulation.
Abstract
Electron collision cross section set for N
2
is proposed. The proposed set consists of vibrational elastic momentum transfer cross section and cross sections for 31 rotational excitation, 29 ...rotational deexcitation, 10 vibrational excitation, 17 electronic excitation, 2 neutral dissociation, and 5 ionization collision processes. Electron transport coefficients in N
2
, N
2
/He, and N
2
/Ar are calculated by Monte Carlo method with considering anisotropic inelastic electron scattering and partitioning of the residual energy after the ionization collision on the basis of experimental results. The reliability of the proposed electron collision cross section set is demonstrated by comparing the calculated and measured electron transport coefficients in a wide range of reduced electric fields,
E
/
N
(
E
: electric field strength,
N
: number density of gas molecules). Comparison of the values of the electron transport coefficients in N
2
calculated from eight individual cross section sets partly provided on LXCat with the measured values is also carried out. Furthermore, the effect of anisotropic inelastic electron scattering on the electron transport coefficients is examined. The electron transport coefficients in N
2
are found to be affected by considering anisotropic electron scattering with increasing
E
/
N
values, and the longitudinal third-order transport coefficient is found to be sensitive to considering anisotropic electron scattering even at middle
E
/
N
values.
The aim of the study was to determine the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in a university student population.
This was a cross-sectional survey ...study based on the World Health Organization population-based seroepidemiological investigational protocol for SARS-CoV-2 conducted between April 29, 2020, and May 8, 2020, examining SARS-CoV-2 antibody prevalence among 790 university students in Los Angeles, CA. Participants completed a questionnaire on potential risk factors before blood sampling. Samples were analyzed using the EUROIMMUN Anti-SARS-CoV-2 ELISA (IgG) for the qualitative detection of IgG class antibodies to SARS-CoV-2 in human serum or plasma.
The estimated prevalence of SARS-CoV-2 antibody was 4.0% (3.0%, 5.1%). Factors associated with having a positive test included history of anosmia and/or loss of taste (95% CI: 1.4–9.6). A history of respiratory symptoms, with or without fever, was not associated with a positive antibody test.
Prevalence of SARS-CoV-2 antibodies in the undergraduate and graduate student university population was similar to community prevalence.
Bridgmanite, the most abundant mineral in the Earth's lower mantle, can be found in meteorites that experienced instantaneous high shock pressure during parent body impact. However, the presence of ...bridgmanite in meteorites is unusual because bridgmanite grains should be amorphized under residual post‐shock temperatures at ambient pressure. Here, we report the results of time‐resolved synchrotron X‐ray diffraction measurements at high temperatures to analyze the amorphization mechanisms and kinetics of bridgmanite. The thermal expansion coefficient of bridgmanite before the amorphization is 2.1 × 10−5 K−1. At higher temperatures, our results show that the significant volume expansion due to the amorphization induces static stress that can reach up to ∼0.5 GPa, which prevents the progress of the amorphization. This time‐insensitive amorphization kinetics may have enabled the preservation of bridgmanite in the shocked meteorite that fell on Earth. Also, the reaction progress estimated based on the amorphous fraction provides the residual post‐shock temperature.
Plain Language Summary
Bridgmanite is the most abundant mineral in the Earth's lower mantle. Natural bridgmanite in the shocked meteorite is used to constrain the impact histories of parent bodies since this mineral can form at very high pressure. However, the presence of bridgmanite in meteorites is mysterious because it should be easily amorphized at atmospheric pressure after the shock events. This study reports the amorphization mechanisms and kinetics of bridgmanite based on time‐resolved synchrotron X‐ray diffraction techniques. We found that the significant volume expansion due to the amorphization induces static stress, which hinders the amorphization from progressing. The preservation of bridgmanite in meteorites can be explained by this unique amorphization kinetics.
Key Points
Amorphization kinetics of bridgmanite was studied via time‐resolved synchrotron X‐ray diffraction measurements
Significant volume expansion due to the bridgmanite amorphization induces static stress, which prevents the progress of the amorphization
Preservation of bridgmanite in the meteorites can be explained by the unique amorphization kinetics
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