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result(s) for
"Wu, W. B."
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Asymmetry of collective excitations in electron- and hole-doped cuprate superconductors
High-temperature superconductivity emerges on doping holes or electrons into antiferromagnetic copper oxides. The large energy scale of magnetic excitations, for example, compared with phonon energies, is thought to drive superconductivity with high transition temperatures (
T
c
). Comparing high-energy magnetic excitations of hole- and electron-doped superconductors provides an opportunity to test this hypothesis. Here, we use resonant inelastic X-ray scattering at the Cu L
3
-edge to reveal collective excitations in the electron-doped cuprate Nd
2−
x
Ce
x
CuO
4
. Surprisingly, magnetic excitations harden significantly across the antiferromagnetic high-temperature superconductivity phase boundary despite short-ranged antiferromagnetic correlations, in contrast to the hole-doped cuprates. Furthermore, we find an unexpected branch of collective modes in superconducting compounds, absent in hole-doped cuprates. These modes emanate from the zone centre and possess a higher temperature scale than
T
c
, signalling a distinct quantum phase. Despite their differences, the persistence of magnetic excitations and the existence of a distinct quantum phase are apparently universal in both hole- and electron-doped cuprates.
Cuprate superconductors are created by adding electrons or holes to a ‘parent’ compound. They have dissimilar phase diagrams and the asymmetry is further highlighted by unexpected collective modes measured using resonant inelastic X-ray scattering.
Journal Article
Magnetic and compressive properties of ternary Ni–Fe–Ti eutectic alloy processed by electromagnetic levitation technique
The magnetic and compressive properties of the ternary Ni
40.6
Fe
36.4
Ti
23
eutectic alloys solidified under electromagnetic levitation condition were investigated. An undercooling range from 32 to 141 K was achieved, and a ternary eutectic consisting of a fibrous Fe
2
Ti phase and lamellar γ-Fe(Ni) + Ni
3
Ti phases formed. In the ternary eutectic, the γ-Fe(Ni) and Ni
3
Ti phases kept cooperative growth, while the Fe
2
Ti phase grew either cooperatively with these two phases or sometimes independently. Theoretical calculations showed that there existed a vertical flow field and temperature gradient in the center of the levitated alloy droplet, contributing to the directional growth behavior of eutectic grain. The growth velocity of primary Ni
3
Ti dendrite increased by 2.4 times, while that of ternary eutectic increased by 77% as undercooling rose, and consequently, the microstructures were significantly refined. The temperature stability of coercivity and residual magnetization below ambient temperature was improved once alloy undercooling reached 128 K, ascribed to the enhancement of the exchange coupling effect between the magnetic domains inside refined grains. The fracture strain of the ternary eutectic alloy increased with undercooling because microcrack propagation was further hindered and the plastic deformation was more homogeneous. Meanwhile, the fracture was dominated by transgranular (TG) mode at an undercooling of 132 K because the bonding force of grain boundaries became stronger.
Journal Article
Jahn-Teller distortion driven magnetic polarons in magnetite
The first known magnetic mineral, magnetite, has unusual properties, which have fascinated mankind for centuries; it undergoes the Verwey transition around 120 K with an abrupt change in structure and electrical conductivity. The mechanism of the Verwey transition, however, remains contentious. Here we use resonant inelastic X-ray scattering over a wide temperature range across the Verwey transition to identify and separate out the magnetic excitations derived from nominal Fe
2+
and Fe
3+
states. Comparison of the experimental results with crystal-field multiplet calculations shows that the spin–orbital
dd
excitons of the Fe
2+
sites arise from a tetragonal Jahn-Teller active polaronic distortion of the Fe
2+
O
6
octahedra. These low-energy excitations, which get weakened for temperatures above 350 K but persist at least up to 550 K, are distinct from optical excitations and are best explained as magnetic polarons.
The Verwey transition of magnetite is complex due to the coexistence of strong correlations and electron-phonon coupling. Here, the authors use resonant inelastic X-ray scattering to show evidence for magnetic polarons in magnetite and provide insight into the nature of the transition.
Journal Article
Arginine deiminase PEG20 inhibits growth of small cell lung cancers lacking expression of argininosuccinate synthetase
Background:
Some cancers have been shown to lack expression of argininosuccinate synthetase (ASS), an enzyme required for the synthesis of arginine and a possible biomarker of sensitivity to arginine deprivation. Arginine deiminase (ADI) is a microbial enzyme capable of efficiently depleting peripheral blood arginine.
Methods:
Argininosuccinate synthetase expression was assessed in human small cell lung cancer (SCLC) by immunohistochemistry (IHC), with expression also assessed in a panel of 10 human SCLC by qRT-PCR and western blot. Proliferation assays and analyses of apoptosis and autophagy assessed the effect of pegylated ADI (ADI-PEG20)
in vitro
. The
in vivo
efficacy of ADI-PEG20 was determined in mice bearing SCLC xenografts.
Results:
Approximately 45% of SCLC tumours and 50% of cell lines assessed were negative for ASS. Argininosuccinate synthetase-deficient SCLC cells demonstrated sensitivity to ADI-PEG20, which was associated with the induction of autophagy and caspase-independent cell death. Arginine deiminase-PEG20 treatment of ASS-negative SCLC xenografts caused significant, dose-dependent inhibition of tumour growth of both small and established tumours.
Conclusion:
These results suggest a role for ADI-PEG20 in the treatment of SCLC, and a clinical trial exploring this therapeutic approach in patients with ASS-negative SCLC by IHC has now been initiated.
Journal Article
Characteristics of young rural Chinese suicides: a psychological autopsy study
Patterns of suicide rates in China differ in many ways from those in the West. This study aimed to identify the risk factors characteristic for young rural Chinese suicides.
This was a case-control psychological autopsy (PA) study. The samples were suicides and living controls (both aged 15-34 years) from 16 rural counties of China. We interviewed two informants for each suicide and each control with pretested and validated instruments to estimate psychosocial, psychiatric and other risk factors for suicides.
The prevalence of mental disorders was higher among the young Chinese who died by suicide than among the living controls, but was lower than among suicides in the West. Marriage was not a protecting factor for suicide among young rural Chinese women, and never-married women who were involved in relationships were about three times more likely to commit suicide than single women who were unattached. Religion/religiosity was not a protecting factor in Chinese suicide, as it tended to be stronger for suicides than for controls. Impulsivity was significantly higher for suicides than for controls. Psychological strain, resulting from conflicting social values between communist gender equalitarianism and Confucian gender discrimination, was associated significantly with suicide in young rural Chinese women, even after accounting for the role of psychiatric illness.
Risk factors for suicide in rural China are different from those in the West. Psychological strain plays a role in suicide. Suicide prevention programs in China should incorporate culture-specific considerations.
Journal Article
How similar is “similar,” or what is the best measure of soil spectral and physiochemical similarity?
Spectral similarity indices were used to select similar soil samples from a spectral library and improve the predictive accuracy of target samples. There are many similarity indices available, and precisely how to select the optimum index has become a critical question. Five similarity indices were evaluated: Spectral angle mapper (SAM), Euclidean distance (ED), Mahalanobis distance (MD), SAM_pca and ED_pca in the space of principal components applied to a global soil spectral library. The accordance between spectral and compositional similarity was used to select the optimum index. Then the optimum index was evaluated if it can maintain the greatest predictive accuracy when selecting similar samples from a spectral library for the prediction of a target sample using a partial least squares regression (PLSR) model. The evaluated physiochemical properties were: soil organic carbon, pH, cation exchange capacity (CEC), clay, silt, and sand content. SAM and SAM_pca selected samples were closer in composition compared to the target samples. Based on similar samples selected using these two indices, PLSR models achieved the highest predictive accuracy for all soil properties, save for CEC. This validates the hypothesis that the accordance information between spectral and compositional similarity can help select the appropriate similarity index when selecting similar samples from a spectral library for prediction.
Journal Article
Generation mechanism and remedy method of rail corrugation at a sharp curved metro track with Vanguard fasteners
In Chinese metro lines, Vanguard fastener system is widely used as vibration damping fastener. However, the rails mounted with this fastener system are deeply affected by rail corrugation. The generation mechanism of corrugation wear at a metro track mounted with Vanguard fastening is revealed through the numerical simulation method. A finite element model including two rails, the track system, and a leading wheelset is set up. The parameter sensitivity analysis is conducted to identify the dominant factors affecting the rail corrugation. Then, the remedy method to suppress the corrugation wear is put forward on the basis of the parameter analysis results. The results indicate that the severe corrugation wear on the inner rail is attributed to the self-sustained vibration of the wheelset–track system aroused by the saturated wheel–rail creep force. The frequency of the rail corrugation calculated by the model is very close to the measured data. The elastic modulus and the damping coefficient of the rubber rest pad in the Vanguard fasteners have a high impact on rail corrugation. Increasing the elastic modulus and the damping coefficient can effectively restrain or even eliminate the rail corrugation. Bringing the damping coefficient of the rubber rest pad above 0.0001 can significantly alleviate the rail corrugation. The influence of the damping and stiffness of the rubber pad under the floating slab track bed is negligible.
Journal Article
Long-term prediction intervals of economic time series
We construct long-term prediction intervals for time-aggregated future values of univariate economic time series. We propose computational adjustments of the existing methods to improve coverage probability under a small sample constraint. A pseudo-out-of-sample evaluation shows that our methods perform at least as well as selected alternative methods based on model-implied Bayesian approaches and bootstrapping. Our most successful method yields prediction intervals for eight macroeconomic indicators over a horizon spanning several decades.
Journal Article
Enhanced Perpendicular Exchange Bias in Co/Pd Antidot Arrays
Magnetic nanostructures revealing the exchange bias (EB) effect have attracted much interest in recent years due to their promising applications in spintronics, magnetic sensing and recording devices with various functionalities. In this paper, we report on the perpendicular exchange bias effect in a multilayered thin film composed of [Co/Pd] ferromagnetic multilayers exchange-coupled to an antiferromagnetic IrMn. The film was deposited on a porous anodized titania template. Influences of the films’ surface morphology as well as the order of layers deposited on the EB effect were studied. The enhancements of the EB field HEB (up to 30%) and the coercive field HC (two times) were achieved in the nanoporous films relative to their continuous film counterparts, which could be attributed to the specific morphology of the porous surfaces.
Journal Article