180 research outputs found
<i>Salmonella</i> Flagellum
Flagella-driven motility contributes to effective bacterial invasion. The bacterial flagellum of Salmonella enterica is a rotary motor powered by an electrochemical potential difference of protons across the cytoplasmic membrane. The flagellum is composed of several basal body rings and an axial structure consisting of the rod as a drive shaft, the hook as a universal joint and the filament as a helical propeller. The assembly of the axial structure begins with the rod, followed by the hook and finally the filament. A type III protein export apparatus is located at the flagellar base and transports flagellar axial proteins from the cytoplasm to the distal end of the growing flagellar structure where their assembly occurs. The protein export apparatus coordinates flagellar gene expression with assembly, allowing the hierarchy of flagellar gene expression to exactly parallel the flagellar assembly process. The basal body can accommodate a dozen stator complexes around a rotor ring complex in a load-dependent manner. Each stator unit conducts protons and pushes the rotor. In this book chapter, we will summarize our current understanding of the structure and function of the Salmonella flagellum
Effect of Dy substitution in the giant magnetocaloric properties of HoB
Recently, a massive magnetocaloric effect near the liquefaction temperature
of hydrogen has been reported in the ferromagnetic material HoB. Here we
investigate the effects of Dy substitution in the magnetocaloric properties of
HoDyB alloys ( = 0, 0.3, 0.5, 0.7, 1.0). We
find that the Curie temperature () gradually increases upon
Dy substitution, while the magnitude of the magnetic entropy change || at = decreases from 0.35 to 0.15
J cm K for a field change of 5 T. Due to the presence of two
magnetic transitions in these alloys, despite the change in the peak magnitude
of ||, the refrigerant capacity () and
refrigerant cooling power () remains almost constant in all
doping range, which as large as 5.5 J cm and 7.0 J cm for a field
change of 5 T. These results imply that this series of alloys could be an
exciting candidate for magnetic refrigeration in the temperature range between
10-50 K.Comment: 19 pages, 5 figures, 2 table
Pressure-Induced Antiferromagnetic Bulk Superconductor EuFeAs
We present the magnetic and superconducting phase diagram of EuFeAs
for and . The antiferromagnetic phase of the
Eu moments is completely enclosed in the superconducting phase. The
upper critical field vs. temperature curves exhibit strong concave curvatures,
which can be explained by the Jaccarino-Peter compensation effect due to the
antiferromagnetic exchange interaction between the Eu moments and
conduction electrons.Comment: submitted to the proceedings of the M2S-IX Toky
Phase Diagram of Pressure-Induced Superconductivity in EuFe2As2 Probed by High-Pressure Resistivity up to 3.2 GPa
We have constructed a pressuretemperature () phase diagram of
-induced superconductivity in EuFeAs single crystals, via
resistivity () measurements up to 3.2 GPa. As hydrostatic pressure is
applied, an antiferromagnetic (AF) transition attributed to the FeAs layers at
shifts to lower temperatures, and the corresponding resistive
anomaly becomes undetectable for 2.5 GPa. This suggests that the
critical pressure where becomes zero is about 2.5
GPa. We have found that the AF order of the Eu moments survives up to
3.2 GPa without significant changes in the AF ordering temperature
. The superconducting (SC) ground state with a sharp transition
to zero resistivity at 30 K, indicative of bulk
superconductivity, emerges in a pressure range from 2.5
GPa to 3.0 GPa. At pressures close to but outside the SC phase, the
curve shows a partial SC transition (i.e., zero resistivity is not
attained) followed by a reentrant-like hump at approximately
with decreasing temperature. When nonhydrostatic pressure with a uniaxial-like
strain component is applied using a solid pressure medium, the partial
superconductivity is continuously observed in a wide pressure range from 1.1
GPa to 3.2 GPa.Comment: 7 pages, 6 figures, accepted for publication in Physical Review B,
selected as "Editors' Suggestion
Experimental exploration of ErB and SHAP analysis on a machine-learned model of magnetocaloric materials for materials design
Stimulated by a recent report of a giant magnetocaloric effect in HoB
found via machine-learning predictions, we have explored the magnetocaloric
properties of a related compound ErB, that has remained the last
ferromagnetic material among the rare-earth diboride (REB) family with
unreported magnetic entropy change |{\Delta}SM|. The evaluated
at field change of 5 T in ErB turned out to be as high as 26.1 (J kg
K) around the ferromagnetic transition () of 14 K. In this
series, HoB is found to be the material with the largest as
the model predicted, while the predicted values showed a deviation with a
systematic error compared to the experimental values. Through a coalition
analysis using SHAP, we explore how this rare-earth dependence and the
deviation in the prediction are deduced in the model. We further discuss how
SHAP analysis can be useful in clarifying favorable combinations of constituent
atoms through the machine-learned model with compositional descriptors. This
analysis helps us to perform materials design with aid of machine learning of
materials data.Comment: 9 pages, 10 figures. Accepted manuscript. Published by Taylor &
Francis in STAM:Methods, available at
https://doi.org/10.1080/27660400.2023.221747
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