Experimental demonstrations of high-Q superconducting coplanar waveguide resonators

We designed and successfully fabricated an absorption-type of superconducting coplanar waveguide (CPW) resonators. The resonators are made from a Niobium film (about 160 nm thick) on a high-resistance Si substrate, and each resonator is fabricated as a meandered quarter-wavelength transmission line (one end shorts to the ground and another end is capacitively coupled to a through feedline). With a vector network analyzer we measured the transmissions of the applied microwave through the resonators at ultra-low temperature (e.g., at 20 mK), and found that their loaded quality factors are significantly high, i.e., up to 10^6. With the temperature increases slowly from the base temperature (i.e., 20 mK), we observed the resonance frequencies of the resonators are blue shifted and the quality factors are lowered slightly. In principle, this type of CPW-device can integrate a series of resonators with a common feedline, making it a promising candidate of either the data bus for coupling the distant solid-state qubits or the sensitive detector of single photons.Comment: Accepted by Chinese Science Bulleti

Critical charge and spin instabilities in superconducting La3_3Ni2_2O7_7

Motivated by the recent discovery of superconductivity in La$_3$Ni$_2$O$_7$ under high pressure, we explore its potential charge and spin instabilities through combined model analysis and first-principles calculations. Taking into account the negative charge-transfer nature of high valence nickel, a fully correlated two-cluster model identifies a lattice-coupled rocksalt-type charge instability characterized by substantial fluctuations of oxygen holes. This instability is corroborated by density-functional-theory plus $U$ calculations that also reveal a strong tendency towards concurrent antiferromagnetic ordering. The charge, spin, and associated lattice instabilities are significantly suppressed with increasing external pressure, contributing to the emergence of superconductivity in pressurized La$_3$Ni$_2$O$_7$. Carrier doping is found to effectively suppress these instabilities, suggesting a viable strategy to stabilize a superconducting phase under ambient pressure

Unusual linewidth dependence of coherent THz emission measured from intrinsic Josephson junction stacks in the hot-spot regime

We report on measurements of the linewidth {\Delta}f of THz radiation emitted from intrinsic Josephson junction stacks, using a Nb/AlN/NbN integrated receiver for detection. Previous resolution limited measurements indicated that {\Delta}f may be below 1 GHz - much smaller than expected from a purely cavity-induced synchronization. While at low bias we found {\Delta}f to be not smaller than ? 500 MHz, at high bias, where a hotspot coexists with regions which are still superconducting, {\Delta}f turned out to be as narrow as 23 MHz. We attribute this to the hotspot acting as a synchronizing element. {\Delta}f decreases with increasing bath temperature, a behavior reminiscent of motional narrowing in NMR or ESR, but hard to explain in standard electrodynamic models of Josephson junctions.Comment: 4 figures, 5 page

Effects of Montmorillonite on the Mineralization and Cementing Properties of Microbiologically Induced Calcium Carbonate

Carbonate mineralization microbe is a microorganism capable of decomposing the substrate in the metabolic process to produce the carbonate, which then forms calcium carbonate with calcium ions. By taking advantage of this process, contaminative uranium tailings can transform to solid cement, where calcium carbonate plays the role of a binder. In this paper, we have studied the morphology of mineralized crystals by controlling the mineralization time and adding different concentrations of montmorillonite (MMT). At the same time, we also studied the effect of carbonate mineralized cementation uranium tailings by controlling the amount of MMT. The results showed that MMT can regulate the crystal morphology of calcium carbonate. What is more, MMT can balance the acidity and ions in the uranium tailings; it also can reduce the toxicity of uranium ions on microorganisms. In addition, MMT filling in the gap between the uranium tailings made the cement body more stable. When the amount of MMT is 6%, the maximum strength of the cement body reached 2.18 MPa, which increased by 47.66% compared with that the sample without MMT. Therefore, it is reasonable and feasible to use the MMT to regulate the biocalcium carbonate cemented uranium tailings

Risk Factors Associated with Pain Severity in Patients with Non-specific Low Back Pain in Southern China

Study Design A prospective cross-sectional study. Purpose To evaluate the risk factors associated with the severity of pain intensity in patients with non-specific low back pain (NSLBP) in Southern China. Overview of Literature Low back pain (LBP) is the leading cause of activity limitation and work absence throughout the world, so a firm understanding of the risk factor associated with NSLBP can provide early and prompt interventions that are aimed at attaining long-term results. Methods Participants were recruited from January 2014 to January 2016 and were surveyed using a self-designed questionnaire. Anonymous assessments included Short Form 36-Item Health Survey (SF-36) and Visual Analogue Scale (VAS). The association between the severity of NSLBP and these potential risk factors were evaluated. Results A total of 1,046 NSLBP patients were enrolled. The patients with primary school education, high body mass index (BMI), those exposed to sustained durations of driving and sitting, smoking, recurrent LBP had increased VAS and Oswestry Disability Index (ODI) scores with lower SF-36 scores (p 10 kg objects in a quarter of their work time for >10 years had higher VAS and ODI scores with lower SF-36 scores (p <0.01). Multiple logistic regression showed lower levels of education, LBP for 1–7 days, long-lasting LBP in last year, smoking, long duration driving, and higher BMI were associated with more severe VAS score. Conclusions The severity of NSLBP is associated with lower levels of education, poor standards of living, heavy physical labor, long duration driving, and sedentary lifestyle. Patients with recurrent NSLBP have more severe pain. Reducing rates of obesity, the duration of heavy physical work, driving or riding, and attenuating the prevalence of sedentary lifestyles and smoking may reduce the prevalence of NSLBP