14,965 research outputs found
Demystification of Mizusaki’s α-factor for the positively-deviated defect behavior of hyperstoichiometric oxides
Many hyperstoichiometric (p-type) ternary or higher oxides of present technological interests, e.g., La1-xSrxCrO3-δ exhibit a positive deviation from the ideal defect structure. Mizusaki et al. [1] could beautifully explain the positively-deviated defect structure by introducing an empirical factor α such as
ΔHxs=αδ.
Here, ΔHxs stands for the excess enthalpy of oxidation reaction involving oxygen vacancies and holes or
1/2 O2+VO••=OOx+2h• .
The authors[1] interpreted this α-factor as representing the interactions among lattice ions and defects, but its true physico-chemical face has since remained a mystery notwithstanding so frequent invoking to the defect chemistry stage.
It has recently turned out that this factor corresponds to the first order approximation of the hole-degeneracy effect. We will demystify this α-factor in this line.
[1] J. Mizusaki, S, Yamauchi, K. Fueki, and A. Ishikawa, “Nonstoichiometry of the perovskite-type oxide La1-xSrxCrO3-δ,” Solid State Ionics 12 (1984) 119
Monolithic arrays of surface emitting laser NOR logic devices
Monolithic, cascadable, laser-logic-device arrays have been realized and characterized. The monolithic surface-emitting laser logic (SELL) device consists of an AlGaAs superlattice lasing around 780 nm connected to a heterojunction phototransistor (HPT) in parallel and a resistor in series. Arrays up to 8×8 have been fabricated, and 2×2 arrays show uniform characteristics. The optical logic output is switched off with 40 μW incident optical input
Monolithic arrays of surface emitting laser NOR logic devices
Monolithic, cascadable, laser-logic-device arrays have been realized and characterized. The monolithic surface-emitting laser logic (SELL) device consists of an AlGaAs superlattice lasing around 780 nm connected to a heterojunction phototransistor (HPT) in parallel and a resistor in series. Arrays up to 8×8 have been fabricated, and 2×2 arrays show uniform characteristics. The optical logic output is switched off with 40 μW incident optical input
Control of carbon nanotube morphology by change of applied bias field during growth
Carbon nanotube morphology has been engineered via simple control of applied voltage during dc plasma chemical vapor deposition growth. Below a critical applied voltage, a nanotube configuration of vertically aligned tubes with a constant diameter is obtained. Above the critical voltage, a nanocone-type configuration is obtained. The strongly field-dependent transition in morphology is attributed primarily to the plasma etching and decrease in the size of nanotube-nucleating catalyst particles. A two-step control of applied voltage allows a creation of dual-structured nanotube morphology consisting of a broad base nanocone (~200 nm dia.) with a small diameter nanotube (~7 nm) vertically emanating from the apex of the nanocone, which may be useful for atomic force microscopy
Magnetic levitation force between a superconducting bulk magnet and a permanent magnet
The current density in a disk-shaped superconducting bulk magnet and the
magnetic levitation force exerted on the superconducting bulk magnet by a
cylindrical permanent magnet are calculated from first principles. The effect
of the superconducting parameters of the superconducting bulk is taken into
account by assuming the voltage-current law and the material law. The magnetic
levitation force is dominated by the remnant current density, which is induced
by switching off the applied magnetizing field. High critical current density
and flux creep exponent may increase the magnetic levitation force. Large
volume and high aspect ratio of the superconducting bulk can enhance the
magnetic levitation force further.Comment: 18 pages and 8 figure
The prenylated rab GTPase receptor PRA1.F4 contributes to protein exit from the golgi apparatus
Prenylated Rab acceptor1 (PRA1) functions in the recruitment of prenylated Rab proteins to their cognate organelles. Arabidopsis (Arabidopsis thaliana) contains a large number of proteins belonging to the AtPRA1 family. However, their physiological roles remain largely unknown. Here, we investigated the physiological role of AtPRA1.F4, a member of the AtPRA1 family. A T-DNA insertion knockdown mutant of AtPRA1.F4, atpra1.f4, was smaller in stature than parent plants and possessed shorter roots, whereas transgenic plants overexpressing HA:AtPRA1.F4 showed enhanced development of secondary roots and root hairs. However, both overexpression and knockdown plants exhibited increased sensitivity to high-salt stress, lower vacuolar Na+/K+-ATPase and plasma membrane ATPase activities, lower and higher pH in the vacuole and apoplast, respectively, and highly vesiculated Golgi apparatus. HA:AtPRA1.F4 localized to the Golgi apparatus and assembled into high-molecular-weight complexes. atpra1.f4 plants displayed a defect in vacuolar trafficking, which was complemented by low but not high levels of HA:AtPRA1.F4. Overexpression of HA:AtPRA1.F4 also inhibited protein trafficking at the Golgi apparatus, albeit differentially depending on the final destination or type of protein: trafficking of vacuolar proteins, plasma membrane proteins, and trans-Golgi network (TGN)-localized SYP61 was strongly inhibited; trafficking of TGN-localized SYP51 was slightly inhibited; and trafficking of secretory proteins and TGN-localized SYP41 was negligibly or not significantly inhibited. Based on these results, we propose that Golgi-localized AtPRA1.F4 is involved in the exit of many but not all types of post-Golgi proteins from the Golgi apparatus. Additionally, an appropriate level of AtPRA1.F4 is crucial for its function at the Golgi apparatus. ? 2017 American Society of Plant Biologists. All rights reserved.111Ysciescopu
On the Reported Death of the MACHO Era
We present radial velocity measurements of four wide halo binary candidates
from the sample in Chaname & Gould (2004; CG04) which, to date, is the only
sample containing a large number of such candidates. The four candidates that
we have observed have projected separations >0.1 pc, and include the two widest
binaries from the sample, with separations of 0.45 and 1.1 pc. We confirm that
three of the four CG04 candidates are genuine, including the one with the
largest separation. The fourth candidate, however, is spurious at the 5-sigma
level. In the light of these measurements we re-examine the implications for
MACHO models of the Galactic halo. Our analysis casts doubt on what MACHO
constraints can be drawn from the existing sample of wide halo binaries.Comment: 6 Pages, 4 Figures, Accepted for MNRAS Letter
Dislocation-induced superfluidity in a model supersolid
Motivated by recent experiments on the supersolid behavior of He, we
study the effect of an edge dislocation in promoting superfluidity in a Bose
crystal. Using Landau theory, we couple the elastic strain field of the
dislocation to the superfluid density, and use a linear analysis to show that
superfluidity nucleates on the dislocation before occurring in the bulk of the
solid. Moving beyond the linear analysis, we develop a systematic perturbation
theory in the weakly nonlinear regime, and use this method to integrate out
transverse degrees of freedom and derive a one-dimensional Landau equation for
the superfluid order parameter. We then extend our analysis to a network of
dislocation lines, and derive an XY model for the dislocation network by
integrating over fluctuations in the order parameter. Our results show that the
ordering temperature for the network has a sensitive dependence on the
dislocation density, consistent with numerous experiments that find a clear
connection between the sample quality and the supersolid response.Comment: 10 pages, 6 figure
- …