Algae have attracted much interest for production of foods, bioactive compounds and also for their usefulness in cleaning the environment. In order to grow and tap the potentials of algae, efficient ...photobioreactors are required. Although a good number of photobioreactors have been proposed, only a few of them can be practically used for mass production of algae. One of the major factors that limits their practical application in algal mass cultures is mass transfer. Thus, a thorough understanding of mass transfer rates in photobioreactors is necessary for efficient operation of mass algal cultures. In this review article, various photobioreactors that are very promising for mass production of algae are discussed.
Abstract
The pseudogap phenomenon in the cuprates is arguably the most mysterious puzzle in the field of high-temperature superconductivity. The tetragonal cuprate HgBa
2
CuO
4+
δ
, with only one CuO
...2
layer per primitive cell, is an ideal system to tackle this puzzle. Here, we measure the magnetic susceptibility anisotropy within the CuO
2
plane with exceptionally high-precision magnetic torque experiments. Our key finding is that a distinct two-fold in-plane anisotropy sets in below the pseudogap temperature
T
*
, which provides thermodynamic evidence for a nematic phase transition with broken four-fold symmetry. Surprisingly, the nematic director orients along the diagonal direction of the CuO
2
square lattice, in sharp contrast to the bond nematicity along the Cu-O-Cu direction. Another remarkable feature is that the enhancement of the diagonal nematicity with decreasing temperature is suppressed around the temperature at which short-range charge-density-wave formation occurs. Our result suggests a competing relationship between diagonal nematic and charge-density-wave order in HgBa
2
CuO
4+
δ
.
Antiferroelectrics are essential ingredients for the widely applied piezoelectric and ferroelectric materials: the most common ferroelectric, lead zirconate titanate is an alloy of the ferroelectric ...lead titanate and the antiferroelectric lead zirconate. Antiferroelectrics themselves are useful in large digital displacement transducers and energy-storage capacitors. Despite their technological importance, the reason why materials become antiferroelectric has remained allusive since their first discovery. Here we report the results of a study on the lattice dynamics of the antiferroelectric lead zirconate using inelastic and diffuse X-ray scattering techniques and the Brillouin light scattering. The analysis of the results reveals that the antiferroelectric state is a 'missed' incommensurate phase, and that the paraelectric to antiferroelectric phase transition is driven by the softening of a single lattice mode via flexoelectric coupling. These findings resolve the mystery of the origin of antiferroelectricity in lead zirconate and suggest an approach to the treatment of complex phase transitions in ferroics.
Phonon-phonon scattering dominates the thermal properties in nonmetallic materials, and it directly influences device performance in applications. The understanding of the scattering has been ...progressing using computational approaches, and the direct and systematic observation of phonon modes that include momentum dependences is desirable. We report experimental data on the phonon dispersion curves and lifetimes in an epitaxially grown ScN film using inelastic x-ray scattering measurements. The momentum dependence of the optical phonon lifetimes is estimated from the spectral width, and the highest-energy phonon mode around the zone center is found to possess a short lifetime of 0.21 ps. A comparison with first-principles calculations shows that our observed phonon lifetimes are quantitatively explained by three-body phonon-phonon interactions.
Anisotropic behavior has been studied for some 3d transition metal monoxides (MnO, FeO, CoO, and NiO) in the framework of classical and density functional theories. The calculations suggest that ...deviation of potential and energy from spherical symmetry around the metal and oxygen atoms is required to describe the behavior, which corresponds to symmetry breaking of the system. As for the symmetry breaking along the antiferromagnetic order, it is confirmed only for MnO that superexchange interaction between the nearest-neighboring metal atoms induces the symmetry breaking. In contrast, for NiO, this symmetry breaking is mainly caused by charge transfer from metal to oxygen ions. For FeO, it is predominantly caused by Jahn-Teller effects. The calculations suggest that the anisotropic behavior of CoO is affected by two mechanisms, namely, the Jahn-Teller and charge-transfer effects.
Elastic properties of B2‐Fe0.67Ni0.06Si0.27 (15 wt.% Si) alloy have been investigated by combined high‐resolution inelastic X‐ray scattering and powder X‐ray diffraction in diamond anvil cells up to ...100 GPa at room temperature. Densities (ρ), compressional (VP) and shear (VS) wave velocities were extrapolated to inner core conditions to enable comparison with the preliminary reference Earth model. The modeled aggregate compressional and shear wave velocities and densities of the two‐phase mixture of B2‐Fe0.67Ni0.06Si0.27 and hcp‐Fe‐Ni are consistent with inner core PREM values of VP, VS, and ρ based on a linear mixing model with 30(5) vol % B2‐Fe0.67Ni0.06Si0.27 and 70(5) vol % hcp Fe‐Ni, which corresponds to ∼3–5 wt.% Si and ∼5–12 wt.% Ni.
Plain Language Summary
The composition of the inner core holds key information about how Earth evolved and how current processes such as the geomagnetic field work. Because the core cannot be directly sampled, our best estimates of its composition are based on the comparison of geophysical data with laboratory measurements of candidate materials. Decades of study have shown the inner core to be composed mainly of iron (with a minor amount of nickel) alloyed with one or more light elements, such as silicon. However, the effect of Si on the geophysical properties of Fe‐Ni alloys is not well established. In this study, we performed laboratory experiments to determine the density and sound velocity of Fe‐Ni‐Si alloy under extreme pressure conditions. We compared our results with seismological determinations and found that Earth's inner core can be accounted for by a mechanical mixture of cubic Fe‐Ni‐Si and hexagonal Fe‐Ni alloys. This mixture has a bulk composition of ∼3–5 weight % Si and ∼5–12 weight % Ni and is consistent with geophysical constraints.
Key Points
Sound velocities and densities of B2‐Fe‐Ni‐Si alloy are determined at high pressure, up to 100 GPa, using inelastic X‐ray scattering and X‐ray diffraction
Seismologically observed compressional and shear wave velocities and density of Earth's inner core can be accounted for by a two‐phase mixture of 30 vol % B2‐Fe‐Ni‐Si and 70 vol % hcp Fe‐Ni alloys
Extrapolated results at inner core boundary conditions are consistent with an inner core composition containing ∼3–5 wt.% Si and ∼5–12 wt.% Ni
Ewald-parameter dependence of Coulomb interaction in ionic crystals was studied using a point-charge model. In the presence of the long-range interaction, the ion configuration breaks spherical ...symmetry of local potential and charge at each ion site, and gives non-scalar contributions to them. This non-scalar potential has similar effects to Heisenberg interaction, while is intrinsically distinct from conventional multipole expansions of the scalar potential. Symmetry and magnitude of the scalar and non-scalar potentials are similar for most materials despite the different definitions, but one exception can be seen in parent materials of hole-doped high-Tc cuprates.
•The Ewald method for point charges was reexamined.•There is another, non-scalar, contribution in the Coulomb potential.•The non-scalar and scalar contributions are similar for most materials.•An exception is found in the parent material of hole-doped high-Tc cuprates.
Thermoelectric conversion devices based on group IV semiconductor elements can improve conversion efficiency by reducing the thermal conductivity of the material. In particular, it is known that ...introducing Sn into the system can dramatically reduce the conductivity. It has been experimentally shown that the thermal conductivity of polycrystalline Ge and polycrystalline Si
1−x
Ge
x
can be reduced by introduction of Sn. However, there is no experimental report on the effect of Sn atoms on the phonons responsible for thermal conduction. In this study, we investigated the mechanism of thermal conductivity reduction due to the introduction of Sn by inelastic x-ray scattering measurements on a Ge
1−
x
Sn
x
single-crystalline thin film with 9% Sn composition. The phonon dispersion of Ge
1−
x
Sn
x
was obtained as a result of the measurements, and the slope of the acoustic mode in the phonon dispersion curve of Ge
1−
x
Sn
x
was smaller than that of Ge. The phonon group velocity is expressed as the slope of the dispersion curves of the acoustic mode. Therefore, it was suggested that the reduction of the phonon group velocity by the introduction of Sn partly contributes to the reduction of the thermal conductivity of Ge
1−
x
Sn
x
. Local vibration mode (LVM), which was independent of wavenumber, was also observed in the low-energy region, and we attribute the origin to the local structure of Sn–Sn pairs formed in Ge
1−
x
Sn
x
. Such LVM has also been reported in bulk single- and polycrystalline Si
1−
x
Ge
x
and polycrystalline Si
1−
x
−
y
Ge
x
Sn
y
and is considered to influence the thermal conductivity reduction.
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