The new field of spin cavitronics focuses on the interaction between the magnon excitation of a magnetic element and the electromagnetic wave in a microwave cavity. In the strong interaction regime, ...such an interaction usually gives rise to the level anticrossing for the magnonic and the electromagnetic mode. Recently, the attractive level crossing has been observed, and it is explained by a non-Hermitian model Hamiltonian. However, the mechanism of such attractive coupling is still unclear. We reveal the secret by using a simple model with two harmonic oscillators coupled to a third oscillator with large dissipation. We further identify this dissipative third party as the invisible cavity mode with large leakage in cavity-magnon experiments. This understanding enables one to design dissipative coupling in all sorts of coupled systems.
Plants in infertile habitats are thought to have a high rate of nutrient resorption to enable them reuse nutrients more efficiently than those in fertile habitats. However, there is still much debate ...on how plant nutrient resorption responds to nutrient availability. Here we used a meta-analysis from a global data set of 9703 observations at 306 sites from 508 published articles to examine the effects of nitrogen (N) and phosphorus (P) fertilization on plant foliar N and P concentrations and resorption efficiency. We found that N fertilization enhanced N concentration in green leaves by 27% and P fertilization enhanced green-leaf P by 73% on average. The N and P concentrations in senesced leaves also increased with respective nutrient fertilization. Resorption efficiencies (percentage of nutrient recovered from senescing leaves) of both N and P declined in response to respective nutrient fertilization. Combined N and P fertilization also had negative effects on both N and P resorption efficiencies. Whether nutrient resorption efficiency differs among plant growth types and among ecosystems, however, remains uncertain due to the limited sample sizes when analyzed by plant growth types or ecosystem types. Our analysis indicates that fertilization decreases plant nutrient resorption and the view that nutrient resorption is a critical nutrient conservation strategy for plants in nutrient-poor environments cannot be abandoned. The response values to fertilization presented in our analysis can help improve biogeochemical models.
Health information sharing has become especially important during the COVID-19 (coronavirus disease 2019) pandemic because people need to learn about the disease and then act accordingly. This study ...examines the perceived trust of different COVID-19 information sources (health professionals, academic institutions, government agencies, news media, social media, family, and friends) and sharing of COVID-19 information in China. Specifically, it investigates how beliefs about sharing and emotions mediate the effects of perceived source trust on source-specific information sharing intentions. Results suggest that health professionals, academic institutions, and government agencies are trusted sources of information and that people share information from these sources because they think doing so will increase disease awareness and promote disease prevention. People may also choose to share COVID-19 information from news media, social media, and family as they cope with anxiety, anger, and fear. Taken together, a better understanding of the distinct psychological mechanisms underlying health information sharing from different sources can help contribute to more effective sharing of information about COVID-19 prevention and to manage negative emotion contagion during the pandemic.
An optical frequency comb consists of a set of discrete and equally spaced frequencies and has found wide applications in the synthesis over a broad range of spectral frequencies of electromagnetic ...waves and precise optical frequency metrology. Despite the analogies between magnons and photons in many aspects, the analog of an optical frequency comb in magnonic systems has not been reported. Here, we theoretically study the magnon-skyrmion interaction and find that a magnonic frequency comb (MFC) can be generated above a threshold driving amplitude, where the nonlinear scattering process involving three magnons prevails. The mode spacing of the MFC is equal to the breathing-mode frequency of the skyrmion and is thus tunable by either electric or magnetic means. The theoretical prediction is verified by micromagnetic simulations, and the essential physics can be generalized to a large class of magnetic solitons. Our findings open a new pathway to observe frequency comb structures in magnonic devices that may inspire the study of fundamental nonlinear physics in spintronic platforms in the future.
We show that parity-time (PT) symmetry can be spontaneously broken in the recently reported energy level attraction of magnons and cavity photons. In the PT-broken phase, the magnon and photon form a ...high-fidelity Bell state with maximum entanglement. This entanglement is steady and robust against the perturbation of the environment, which is in contrast to the general wisdom that expects instability of the hybridized state when the symmetry is broken. This anomaly is further understood by the compete of non-Hermitian evolution and particle number conservation of the hybrid system. As a comparison, neither PT-symmetry breaking nor steady magnon-photon entanglement is observed inside the normal level repulsion case. Our results may open an exciting window to utilize magnon-photon entanglement as a resource for quantum information science.
Aims To investigate the relationships between a known history of diabetes and ambient fasting plasma glucose (FPG) levels with death and morbidity rates in patients with severe acute respiratory ...syndrome (SARS).
Methods In this retrospective analysis, the clinical and biochemical characteristics of 135 patients who had died from SARS, 385 survivors of SARS and 19 patients with non‐SARS pneumonia were compared.
Results All patients were treated according to a predefined protocol. Before steroid treatment, the mean FPG level was significantly higher in the SARS group (deceased vs. survivors vs. non‐SARS pneumonia group: 9.7 ± 5.2 vs. 6.5 ± 3.0 vs. 5.1 ± 1.0 mmol/l, P < 0.01). In the SARS group, the percentage of patients with a known history of diabetes was significantly higher in the deceased patients than in the survivors (21.5% vs. 3.9%, P < 0.01). Among patients with no known history of diabetes and before commencement of steroid therapy, those who had hypoxaemia (SaO2 < 93%) had higher FPG levels than those who did not have hypoxia in both the survivor (8.7 ± 4.9 vs. 6.3 ± 2.1 mmol/l, P < 0.001) and deceased (9.8 ± 4.8 vs. 7.2 ± 1.5 mmol/l, P < 0.001) groups. A known history of diabetes odds ratio (OR) 3.0, 95% confidence interval (CI) 1.4, 6.3; P = 0.005 and FPG ≥ 7.0 mmol/l before steroid treatment (OR 3.3, 95% CI 1.4, 7.7, P = 0.006) were independent predictors of death. During the course of the illness, FPG levels were negatively associated with SaO2 (β =−0.682 ± 0.305, P = 0.025, general estimation equation model) in SARS patients. Survival analysis showed that FPG was independently associated with an increased hazard ratio (HR) of mortality (HR = 1.1, 95% CI 1.0, 1.1, P = 0.001) and hypoxia (HR = 1.1, 95% CI 1.0, 1.1, P = 0.002) after controlling for age and gender.
Conclusions A known history of diabetes and ambient hyperglycaemia were independent predictors for death and morbidity in SARS patients. Metabolic control may improve the prognosis of SARS patients.
A theory on skyrmion size Wang, X. S.; Yuan, H. Y.; Wang, X. R.
Communications physics,
07/2018, Volume:
1, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
A magnetic skyrmion is a topological object consisting of a skyrmion core, an outer domain, and a wall that separates the skyrmion core from the outer domain. The skyrmion size and wall ...width are two fundamental quantities of a skyrmion that depend sensitively on material parameters such as exchange energy, magnetic anisotropy, Dzyaloshinskii–Moriya interaction, and magnetic field. However, quantitative understanding of the two quantities is still very poor. Here we present a general theory on skyrmion size and wall width. The two formulas we obtained agree almost perfectly with simulations and experiments for a wide range of parameters, including most of the existing materials that support skyrmions.
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