23 research outputs found
Electric quadrupole second harmonic generation revealing dual magnetic orders in a magnetic Weyl semimetal
Broken symmetries and electronic topology are nicely manifested together in
the second order nonlinear optical responses from topologically nontrivial
materials. While second order nonlinear optical effects from the electric
dipole (ED) contribution have been extensively explored in polar Weyl
semimetals (WSMs) with broken spatial inversion (SI) symmetry, they are rarely
studied in centrosymmetric magnetic WSMs with broken time reversal (TR)
symmetry due to complete suppression of the ED contribution. Here, we report
experimental demonstration of optical second harmonic generation (SHG) in a
magnetic WSM CoSnS from the electric quadrupole (EQ)
contribution. By tracking the temperature dependence of the rotation anisotropy
(RA) of SHG, we capture two magnetic phase transitions, with both the SHG
intensity increasing and its RA pattern rotating at =175K and
=120K subsequently. The fitted critical exponents for the SHG
intensity and RA orientation near and suggest that the
magnetic phase at is a 3D Ising-type out-of-plane ferromagnetism
while the other at is a 3D XY-type all-in-all-out in-plane
antiferromagnetism. Our results show the success of detection and exploration
of EQ SHG in a centrosymmetric magnetic WSM, and hence open the pathway towards
the future investigation of its tie to the band topology.Comment: 19 pages, 4 figure
Superconductivity in type-II Weyl-semimetal WTe2 induced by a normal metal contact
WTe is a material with rich topological properties: it is a 2D
topological insulator as a monolayer and a Weyl-semimetal and higher-order
topological insulator (HOTI) in the bulk form. Inducing superconductivity in
topological materials is a way to obtain topological superconductivity, which
lays at the foundation for many proposals of fault tolerant quantum computing.
Here, we demonstrate the emergence of superconductivity at the interface
between WTe and the normal metal palladium. The superconductivity has a
critical temperature of about 1.2 K. By studying the superconductivity in
perpendicular magnetic field, we obtain the coherence length and the London
penetration depth. These parameters correspond to a low Fermi velocity and a
high density of states at the Fermi level. This hints to a possible origin of
superconductivity due to the formation of flat bands. Furthermore, the critical
in-plane magnetic field exceeds the Pauli limit, suggesting a non-trivial
nature of the superconducting state.Comment: As accepted to Journal of Applied Physics, 7 pages, 4 figure
Disorder and diffuse scattering in single-chirality (TaSe)I crystals
The quasi-one-dimensional chiral compound (TaSe)I has been
extensively studied as a prime example of a topological Weyl semimetal. Upon
crossing its phase transition temperature 263 K,
(TaSe)I exhibits incommensurate charge density wave (CDW) modulations
described by the well-defined propagation vector (0.05, 0.05, 0.11),
oblique to the TaSe chains. Although optical and transport properties
greatly depend on chirality, there is no systematic report about chiral domain
size for (TaSe)I. In this study, our single-crystal scattering
refinements reveal a bulk iodine deficiency, and Flack parameter measurements
on multiple crystals demonstrate that separate (TaSe)I crystals have
uniform handedness, supported by direct imaging and helicity dependent THz
emission spectroscopy. Our single-crystal X-ray scattering and calculated
diffraction patterns identify multiple diffuse features and create a real-space
picture of the temperature-dependent (TaSe)I crystal structure. The
short-range diffuse features are present at room temperature and decrease in
intensity as the CDW modulation develops. These transverse displacements, along
with electron pinning from the iodine deficiency, help explain why
(TaSe)I behaves as an electronic semiconductor at temperatures above
and below , despite a metallic band structure calculated from
density functional theory of the ideal structure.Comment: 24 pages, 20 figures, 3 table
Actively implementing an evidence-based feeding guideline for critically ill patients (NEED): a multicenter, cluster-randomized, controlled trial
Background: Previous cluster-randomized controlled trials evaluating the impact of implementing evidence-based guidelines for nutrition therapy in critical illness do not consistently demonstrate patient benefits. A large-scale, sufficiently powered study is therefore warranted to ascertain the effects of guideline implementation on patient-centered outcomes.
Methods: We conducted a multicenter, cluster-randomized, parallel-controlled trial in intensive care units (ICUs) across China. We developed an evidence-based feeding guideline. ICUs randomly allocated to the guideline group formed a local "intervention team", which actively implemented the guideline using standardized educational materials, a graphical feeding protocol, and live online education outreach meetings conducted by members of the study management committee. ICUs assigned to the control group remained unaware of the guideline content. All ICUs enrolled patients who were expected to stay in the ICU longer than seven days. The primary outcome was all-cause mortality within 28 days of enrollment.
Results: Forty-eight ICUs were randomized to the guideline group and 49 to the control group. From March 2018 to July 2019, the guideline ICUs enrolled 1399 patients, and the control ICUs enrolled 1373 patients. Implementation of the guideline resulted in significantly earlier EN initiation (1.20 vs. 1.55 mean days to initiation of EN; difference − 0.40 [95% CI − 0.71 to − 0.09]; P = 0.01) and delayed PN initiation (1.29 vs. 0.80 mean days to start of PN; difference 1.06 [95% CI 0.44 to 1.67]; P = 0.001). There was no significant difference in 28-day mortality (14.2% vs. 15.2%; difference − 1.6% [95% CI − 4.3% to 1.2%]; P = 0.42) between groups.
Conclusions: In this large-scale, multicenter trial, active implementation of an evidence-based feeding guideline reduced the time to commencement of EN and overall PN use but did not translate to a reduction in mortality from critical illness. Trial registration: ISRCTN, ISRCTN12233792. Registered November 20th, 2017
Actively implementing an evidence-based feeding guideline for critically ill patients (NEED): a multicenter, cluster-randomized, controlled trial.
BackgroundPrevious cluster-randomized controlled trials evaluating the impact of implementing evidence-based guidelines for nutrition therapy in critical illness do not consistently demonstrate patient benefits. A large-scale, sufficiently powered study is therefore warranted to ascertain the effects of guideline implementation on patient-centered outcomes.MethodsWe conducted a multicenter, cluster-randomized, parallel-controlled trial in intensive care units (ICUs) across China. We developed an evidence-based feeding guideline. ICUs randomly allocated to the guideline group formed a local "intervention team", which actively implemented the guideline using standardized educational materials, a graphical feeding protocol, and live online education outreach meetings conducted by members of the study management committee. ICUs assigned to the control group remained unaware of the guideline content. All ICUs enrolled patients who were expected to stay in the ICU longer than seven days. The primary outcome was all-cause mortality within 28 days of enrollment.ResultsForty-eight ICUs were randomized to the guideline group and 49 to the control group. From March 2018 to July 2019, the guideline ICUs enrolled 1399 patients, and the control ICUs enrolled 1373 patients. Implementation of the guideline resulted in significantly earlier EN initiation (1.20 vs. 1.55 mean days to initiation of EN; difference - 0.40 [95% CI - 0.71 to - 0.09]; P = 0.01) and delayed PN initiation (1.29 vs. 0.80 mean days to start of PN; difference 1.06 [95% CI 0.44 to 1.67]; P = 0.001). There was no significant difference in 28-day mortality (14.2% vs. 15.2%; difference - 1.6% [95% CI - 4.3% to 1.2%]; P = 0.42) between groups.ConclusionsIn this large-scale, multicenter trial, active implementation of an evidence-based feeding guideline reduced the time to commencement of EN and overall PN use but did not translate to a reduction in mortality from critical illness.Trial registrationISRCTN, ISRCTN12233792 . Registered November 20th, 2017
Actively implementing an evidence-based feeding guideline for critically ill patients (NEED): a multicenter, cluster-randomized, controlled trial (vol 26, 46, 2022)
BackgroundPrevious cluster-randomized controlled trials evaluating the impact of implementing evidence-based guidelines for nutrition therapy in critical illness do not consistently demonstrate patient benefits. A large-scale, sufficiently powered study is therefore warranted to ascertain the effects of guideline implementation on patient-centered outcomes.MethodsWe conducted a multicenter, cluster-randomized, parallel-controlled trial in intensive care units (ICUs) across China. We developed an evidence-based feeding guideline. ICUs randomly allocated to the guideline group formed a local "intervention team", which actively implemented the guideline using standardized educational materials, a graphical feeding protocol, and live online education outreach meetings conducted by members of the study management committee. ICUs assigned to the control group remained unaware of the guideline content. All ICUs enrolled patients who were expected to stay in the ICU longer than seven days. The primary outcome was all-cause mortality within 28 days of enrollment.ResultsForty-eight ICUs were randomized to the guideline group and 49 to the control group. From March 2018 to July 2019, the guideline ICUs enrolled 1399 patients, and the control ICUs enrolled 1373 patients. Implementation of the guideline resulted in significantly earlier EN initiation (1.20 vs. 1.55 mean days to initiation of EN; difference - 0.40 [95% CI - 0.71 to - 0.09]; P = 0.01) and delayed PN initiation (1.29 vs. 0.80 mean days to start of PN; difference 1.06 [95% CI 0.44 to 1.67]; P = 0.001). There was no significant difference in 28-day mortality (14.2% vs. 15.2%; difference - 1.6% [95% CI - 4.3% to 1.2%]; P = 0.42) between groups.ConclusionsIn this large-scale, multicenter trial, active implementation of an evidence-based feeding guideline reduced the time to commencement of EN and overall PN use but did not translate to a reduction in mortality from critical illness.Trial registrationISRCTN, ISRCTN12233792 . Registered November 20th, 2017
Tuning cryogenic Jahn-Teller transition temperatures in magnetoelectric rare earth vanadates
Few materials undergo cooperative Jahn-Teller (JT) transitions at low
temperatures, but zircon-type oxides are one class that includes DyVO,
which transforms from a tetragonal to an orthorhombic structure at around 13.6
K, with a narrow transition temperature range within 0.5 K. Since many
rare-earth ions can be accommodated in the structure, there should be ample
routes to vary the transition temperature and structural effects of the
transition. We have synthesized pure DyVO and solid solutions
DyTmVO ( = 0.05, 0.1, 0.15, 0.2, and 0.5) and
DyPrVO ( = 0.03, 0.05, 0.1, 0.2, and 0.5), all by solution
precipitation. X-ray diffraction shows a systematic peak shift and a linear
change of lattice parameters with increasing substitution. We demonstrate
through heat capacity measurements that both Tm and Pr
substitutions cause a depression of the cooperative JT transition temperature.
When the substitution level increases, the JT transition is eventually
suppressed. We examine a mean-field approximation model that can explain the
both the JT transition temperature shift and its eventual disappearance. The
cooperative JT effect in these zircon-type oxides is known to exhibit a large
magnetoelectric response, which should follow from the mean-field behavior. The
structural transformation can be easily detected via diffraction and can be
used as a temperature calibration in low temperature experiments
Effect of Welding Sequence and the Transverse Geometry of the Weld Overlay on the Distribution of Residual Stress in the Weld Overlay Repair of T23 Tubes
Water-wall tubes are important components in power plants and are used to absorb the heat from the boilers, and they often fail prematurely due to corrosion, erosion, and fatigue during service. To repair the defects, weld overlay repair is often adopted by forming a compressive stress area around the susceptible area to prevent the cracks from propagating. In order to obtain reasonable process parameters of weld overlay repair, a study combining experiments and numerical simulations was performed to investigate the welding residual stress distribution on the repaired area with different welding repair methods. The results reveal that a compressive stress area is generated on the repaired area after the repair, and a center-to-outside welding sequence is better than either a right-to-left welding sequence or an outside-to-center welding sequence when overlaying a one-layer weld; with an increase in the number of weld layers, the compressive stress area of the repaired area is expanded, and the stress level is increased, which results from the upward movement of the compressive stress area of the subsequent-overlaying layer and the superposition of the compression areas of the subsequent-overlaying layer and previous-overlaying layer, respectively. In addition, the number of the weld passes of each layer should be not less than four with the center-to-outside welding sequence
Morphology and growth habit of a new flux-grown layered semiconductor KBiS2 revealed by diffraction-contrast tomography
Single crystals of rhombohedral KBiS2 were synthesized for the first time, and the structure, growth habit and properties of this layered semiconductor are presented. The single crystals form from a reactive K2S5 salt flux and are still embedded in the residual flux, without removal from the reaction vessel throughout the whole study. Laboratory diffraction contrast tomography (LabDCT) is used to identify the crystalline phase, orientation, and microstructure of crystals. Meanwhile, powder and single crystal X-ray diffraction were performed to determine detailed crystallographic information. Morphology of the crystalline assemblies observed by absorption contrast tomography reveals screw-dislocation-driven growth to be the dominant mechanism. First-principles electronic structure simulations predict rhombohedral KBiS2 to be a semiconductor with an indirect band gap, which was confirmed by experiment. This study demonstrates how non-destructive tomography imaging and 3D crystallography methods can lead to advances in discovering new materials and studying crystal growth mechanisms