Uniaxial strain and high magnetic field investigation on materials with novel order parameters

At low temperatures, strongly correlated materials, which typically contain partially filled d- or f-electron shells, often exhibit phases with interesting properties, which may be of both research value and technological significance. The mechanisms of phase formation in them if could be clarified, are believed to be able to provide important insights not only into physics but also into the design of new materials. In this thesis, the experimental study of two strongly correlated materials, Sr₂RuO₄ and CeAuSb₂ is presented. Sr₂RuO₄ is an unconventional superconductor, and a strong candidate for spin-triplet superconductivity. Its potential significance in relation to quantum computing also makes it of great scientific interest. In order to clarify the role of the Van Hove singularity (VHS) in its superconductivity, experimental study has been performed with the recently developed uniaxial strain methods. The experimental results suggest that as the sample is compressed towards the VHS, the transition temperature can be enhanced by a factor of =2.3 whilst the upper critical field can be enhanced by a factor of more than ten. The experimental findings are intriguing and new possibilities are open for future study. CeAuSb₂ is a Kondo lattice system which has been speculated to be close to a quantum critical point. The similarity between some of its low temperature properties and those of a well-known quantum critical system Sr₃Ru₂O₇ makes it especially interesting. In this thesis, new magnetoresistivity and torque magnetometry measurements are used to clarify its low temperature phase diagram, and reveal the strength of its magnetic anisotropy

Existence of multiple positive solutions for a class of infinite-point singular p-Laplacian fractional differential equation with singular source terms

Based on properties of Green’s function and by Avery–Peterson fixed point theorem, the existence of multiple positive solutions are obtained for singular p-Laplacian fractional differential equation with infinite-point boundary conditions, and an example is given to demonstrate the validity of our main results

Bearing fault diagnosis and degradation analysis based on improved empirical mode decomposition and maximum correlated kurtosis deconvolution

Detecting periodic impulse signal (PIS) is the core of bearing fault diagnosis. Earlier fault detected, earlier maintenance actions can be implemented. On the other hand, remaining useful life (RUL) prediction provides important information when the maintenance should be conducted. However, good degradation features are the prerequisite for effective RUL prediction. Therefore, this paper mainly concerns earlier fault detection and degradation feature extraction for bearing. Maximum correlated kurtosis deconvolution (MCKD) can enhance PIS produced by bearing fault. Whereas, it only achieve good effect when bearing has severe fault. On the contrary, PIS produced by bearing weak fault is always masked by heavy noise and cannot be enhanced by MCKD. In order to resolve this problem, a revised empirical mode decomposition (EMD) algorithm is used to denoise bearing fault signal before MCKD processing. In revised EMD algorithm, a new recovering algorithm is used to resolve mode mixing problem existed in traditional EMD and it is superior to ensemble EMD. For degradation analysis, correlated kurtosis (CK) value is used as degradation indicator to reflect health condition of bearing. Except of theory analysis, simulated bearing fault data, injected bearing fault data, real bearing fault data and bearing degradation data are used to verify the proposed method. Simulated bearing fault data is used to explain the existed problems. Then, injected bearing fault data and real bearing fault data are used to demonstrate the effectiveness of proposed method for fault diagnosis. Finally, bearing degradation data is used to verify the degradation feature CK extracted based on proposed method. All these case studies show the effectiveness of proposed fault diagnosis and degradation tracking method

Bearing fault diagnosis and degradation analysis based on improved empirical mode decomposition and maximum correlated kurtosis deconvolution

Detecting periodic impulse signal (PIS) is the core of bearing fault diagnosis. Earlier fault detected, earlier maintenance actions can be implemented. On the other hand, remaining useful life (RUL) prediction provides important information when the maintenance should be conducted. However, good degradation features are the prerequisite for effective RUL prediction. Therefore, this paper mainly concerns earlier fault detection and degradation feature extraction for bearing. Maximum correlated kurtosis deconvolution (MCKD) can enhance PIS produced by bearing fault. Whereas, it only achieve good effect when bearing has severe fault. On the contrary, PIS produced by bearing weak fault is always masked by heavy noise and cannot be enhanced by MCKD. In order to resolve this problem, a revised empirical mode decomposition (EMD) algorithm is used to denoise bearing fault signal before MCKD processing. In revised EMD algorithm, a new recovering algorithm is used to resolve mode mixing problem existed in traditional EMD and it is superior to ensemble EMD. For degradation analysis, correlated kurtosis (CK) value is used as degradation indicator to reflect health condition of bearing. Except of theory analysis, simulated bearing fault data, injected bearing fault data, real bearing fault data and bearing degradation data are used to verify the proposed method. Simulated bearing fault data is used to explain the existed problems. Then, injected bearing fault data and real bearing fault data are used to demonstrate the effectiveness of proposed method for fault diagnosis. Finally, bearing degradation data is used to verify the degradation feature CK extracted based on proposed method. All these case studies show the effectiveness of proposed fault diagnosis and degradation tracking method

Hypoglycemic and Antioxidant Effects of Camellia nitidissima Flower on Type 2 Diabetic Mice

Objective: To comprehensively evaluate the hypoglycemic and antioxidant effects of Camellia nitidissima flower. Methods: The chemical constituents in the aqueous extract of C. nitidissima flower (CFA) were identified by high performance liquid chromatography-mass spectrometry (HPLC-MS). Next, a mouse model of type 2 diabetes was established, and the diabetic mice were randomly divided into five groups: model, positive control (acarbose at 20 mg/kg mb), low-, medium- and high-dose CFA (200, 400 and 800 mg/kg mb, respectively). After five weeks of intragastric intervention, general growth characteristics, serum glucose, fasting insulin (FINS) and lipid levels, oxidative stress in pancreas and liver tissues, tissue morphological changes and cell apoptosis were analyzed. Results: CFA had a high content of polyphenols and polysaccharides. The half-maximal inhibitory concentration (IC50) values for scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and α-glucosidase inhibition were (24.14 ± 0.64) and (69.99 ± 1.97) μg/mL, respectively. Seven compounds were identified from CFA. In addition, CFA could effectively improve the ‘three more and one less’ symptoms of diabetic mice, significantly reduce the levels of fasting blood glucose (FBG), postprandial blood glucose (PBG), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and malondialdehyde (MDA), increase the levels of insulin and high-density lipoprotein cholesterol (HDL-C), improve the activities of total superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and alleviate pathological damage in pancreas and liver tissues. Conclusion: CFA has significant hypoglycemic and antioxidant effects on type 2 diabetic mice

Field-temperature phase diagram and entropy landscape of CeAuSb2

We report a field-temperature phase diagram and an entropy map for the heavy-fermion compound CeAuSb2. CeAuSb2 orders antiferromagnetically below TN=6.6 K and has two metamagnetic transitions, at 2.8 and 5.6 T. The locations of the critical end points of the metamagnetic transitions, which may play a strong role in the putative quantum criticality of CeAuSb2 and related compounds, are identified. The entropy map reveals an apparent entropy balance with Fermi-liquid behavior, implying that above the Néel transition the Ce moments are incorporated into the Fermi liquid. High-field data showing that the magnetic behavior is remarkably anisotropic are also reported

Plasmacytoid dendritic cells promote HIV-1-induced group 3 innate lymphoid cell depletion

Group 3 innate lymphoid cells (ILC3s) have demonstrated roles in promoting antibacterial immunity, maintaining epithelial barrier function, and supporting tissue repair. ILC3 alterations are associated with chronic inflammation and inflammatory disease; however, the characteristics and relevant regulatory mechanisms of this cell population in HIV-1 infection are poorly understood due in part to a lack of a robust model. Here, we determined that functional human ILC3s develop in lymphoid organs of humanized mice and that persistent HIV-1 infection in this model depletes ILC3s, as observed in chronic HIV-1-infected patients. In HIV-1-infected mice, effective antiretroviral therapy reversed the loss of ILC3s. HIV-1-dependent reduction of ILC3s required plasmacytoid dendritic cells (pDCs), IFN-I, and the CD95/FasL pathway, as targeted depletion or blockade of these prevented HIV-1-induced ILC3 depletion in vivo and in vitro, respectively. Finally, we determined that HIV-1 infection induces CD95 expression on ILC3s via a pDC-and IFN-I-dependent mechanism that sensitizes ILC3s to undergo CD95/FasL-mediated apoptosis. We conclude that chronic HIV-1 infection depletes ILC3s through pDC activation, induction of IFN-I, and CD95-mediated apoptosis

Strong peak in Tc of Sr2RuO4 under uniaxial pressure

Sr2RuO4 is an unconventional superconductor that has attracted widespread study because of its high purity and the possibility that its superconducting order parameter has odd parity. We study the dependence of its superconductivity on anisotropic strain. Applying uniaxial pressures of up to ~1 gigapascals along a 〈100〉 direction (a axis) of the crystal lattice results in the transition temperature (Tc) increasing from 1.5 kelvin in the unstrained material to 3.4 kelvin at compression by ≈0.6%, and then falling steeply. Calculations give evidence that the observed maximum Tc occurs at or near a Lifshitz transition when the Fermi level passes through a Van Hove singularity, and open the possibility that the highly strained, Tc = 3.4 K Sr2RuO4 has an even-parity, rather than an odd-parity, order parameter.PostprintPeer reviewe

Vaccines targeting preS1 domain overcome immune tolerance in hepatitis B virus carrier mice

Strong tolerance to hepatitis B virus (HBV) surface antigens limits the therapeutic effect of the conventional hepatitis B surface antigen (HBsAg) vaccination in both preclinical animal models and patients with chronic hepatitis B (CHB) infection. In contrast, we observed that clinical CHB patients presented less immune tolerance to the preS1 domain of HBV large surface antigen. To study whether targeting the weak tolerance of the preS1 region could improve therapy gain, we explored vaccination with the long peptide of preS1 domain for HBV virions clearance. Our study showed that this preS1-polypeptide rather than HBsAg vaccination induced robust immune responses in HBV carrier mice. The anti-preS1 rapidly cleared HBV virions in vivo and blocked HBV infection to hepatocytes in vitro. Intriguingly, vaccination of preS1-polypeptide even reduced the tolerized status of HBsAg, opening a therapeutic window for the host to respond to the HBsAg vaccine. A sequential administration of antigenically distinct preS1-polypeptide and HBsAg vaccines in HBV carrier mice could finally induce HBsAg/hepatitis B surface antibody serological conversion and clear chronic HBV infection in carrier mice. Conclusion: These results suggest that preS1 can function as a therapeutic vaccine for the control of CHB. (Hepatology 2017;66:1067-1082)