Variational approach to renormalized phonon in momentum-nonconserving nonlinear lattices

A previously proposed variational approach for momentum-conserving systems [J. Liu et.al., Phys. Rev. E 91, 042910 (2015)] is extended to systematically investigate general momentum-nonconserving nonlinear lattices. Two intrinsic identities characterizing optimal reference systems are revealed, which enables us to derive explicit expressions for optimal variational parameters. The resulting optimal harmonic reference systems provide information for the band gap as well as the dispersion of renormalized phonons in nonlinear lattices. As a demonstration, we consider the one-dimensional \phi^?4 lattice. By combining the transfer integral operator method, we show that the phonon band gap endows a simple power-law temperature dependence in the weak stochasticity regime where predicted dispersion is reliable by comparing with numerical results. In addition, an exact relation between ensemble averages of the \phi^?4 lattice in the whole temperature range is found, regardless of the existence of the strong stochasticity threshold.Comment: 8 pages, 3 figure

Triggering waves in nonlinear lattices: Quest for anharmonic phonons and corresponding mean free paths

Guided by a stylized experiment we develop a self-consistent anharmonic phonon concept for nonlinear lattices which allows for explicit "visualization." The idea uses a small external driving force which excites the front particles in a nonlinear lattice slab and subsequently one monitors the excited wave evolution using molecular dynamics simulations. This allows for a simultaneous, direct determination of the existence of the phonon mean free path with its corresponding anharmonic phonon wavenumber as a function of temperature. The concept for the mean free path is very distinct from known prior approaches: the latter evaluate the mean free path only indirectly, via using both, a scale for the phonon relaxation time and yet another one for the phonon velocity. Notably, the concept here is neither limited to small lattice nonlinearities nor to small frequencies. The scheme is tested for three strongly nonlinear lattices of timely current interest which either exhibit normal or anomalous heat transport

Sini San inhibits breast cancer cell migration and angiogenesis via the HIF 1 /VEGF pathway

Purpose: To investigate the effects of Sini San (SNS) on breast cancer (BC), and the mechanism of action.Methods: MDA-MB-231 and SK-BR-3 cells were used as breast cancer cell models. Cell viability, migration, and invasion were determined by CCK-8, Transwell and wound healing assays, respectively. SNS mechanism of action and its anti-cancer effect were investigated by network pharmacological analysis, and further verified by Immunoblot.Results: Sini San inhibited the proliferation of the breast cancer (BC) cells., and also suppressed the migration as well as the invasion of BC cells, and also restrained the angiogenesis of BC cells. In performing the network pharmacological analysis of Sini Powder in the treatment of BC, 337 drugdisease targets were obtained. PPI network was established through String, and GO and KEGG enrichment analysis was performed on the target sites. KEGG analysis showed that genes were enriched in HIF-1 and VEGF pathways.Conclusion: Sini San suppressed cell migration as well as angiogenesis via the HIF-1 /VEGF pathway&nbsp

Temperature and frequency dependent mean free paths of renormalized phonons in nonlinear lattices

In the regime of strong nonlinearity, the validity of conventional perturbation based phonon transport theories is questionable. In particular, the renormalized phonons instead of phonons are responsible for heat transport in nonlinear lattices. In this work, we directly study the temperature and frequency dependent Mean Free Path (MFP) of renormalized phonons with the newly developed numerical tuning fork method. The typical 1D nonlinear lattices such as Fermi-Pasta-Ulam $\beta$ (FPU-$\beta$) lattice and $\phi^4$ lattice are investigated in details. It is found that the MFPs are inversely proportional to the frequencies of renormalized phonons rather than the square of phonon frequencies predicted by existing phonon scattering theory

Active spintronic-metasurface terahertz emitters with tunable chirality

The ability to manipulate the electric-field vector of broadband terahertz waves is essential for applications of terahertz technologies in many areas, and can open up new possibilities for nonlinear terahertz spectroscopy and coherent control. Here, we propose a novel laser-driven terahertz emitter, consisting of metasurface-patterned magnetic multilayer heterostructures. Such hybrid terahertz emitters can combine the advantages of spintronic emitters for being ultrabroadband, efficient and flexible, as well as those of metasurfaces for the unique capability to manipulate terahertz waves with high precision and degree of freedom. Taking a stripe-patterned metasurface as an example, we demonstrate the generation of broadband terahertz waves with tunable chirality. Based on experimental and theoretical studies, the interplay between the laser-induced spintronic-origin currents and the metasurface-induced transient charges/currents are investigated, revealing the strong influence on the device functionality originated from both the light-matter interactions in individual metasurface units and the dynamic coupling between them. Our work not only offers a flexible, reliable and cost-effective solution for chiral terahertz wave generation and manipulation, but also opens a new pathway to metasurface-tailored spintronic devices for efficient vector-control of electromagnetic waves in the terahertz regime

Developing Eighth-Grade Students’ Computational Thinking with Critical Reflection

As computer science has become a vital power in facilitating the rapid and sustainable development of various fields, equipping everyone with computational thinking (CT) has been recognized as one of the core pillars supporting the sustainable development of individuals and our digital world. However, it remains challenging for secondary school students to assimilate CT. Recently, critical reflection has been proposed as a useful metacognitive strategy for regulating students’ thinking to solve current and future problems. In this study, a quasi-experiment was conducted to investigate the role of critical reflection in advancing eighth-grade students’ CT. The participants were 95 eighth-grade students, comprising an experimental group (n = 49) and a control group (n = 46). The students’ CT was evaluated based on their learning performance in computational concepts, computational practices, and computational perspectives. The results showed that critical reflection, compared with traditional instruction from teachers, could significantly advance eighth-grade students’ CT. Interestingly, the two groups showed significantly different learning performance in computational practices during the learning process. Furthermore, interaction with peers and instructors played an essential role in helping students engage as active agents in critical reflection. The results of this study emphasize the need to develop students’ CT by practicing critical reflection in eighth-grade education

Investigating Learners’ Engagement and Chinese Writing Learning Outcomes with Different Designs of SVVR-Based Activities

The goal of this study is to explore the affordances of spherical video-based virtual reality (SVVR)-based learning activities by comparing the students’ learning engagement models and their writing learning outcomes in a double-loop SVVR-based (DL-SVVR) learning activity and a single-loop SVVR-based (SL-SVVR) learning activity, respectively. For this purpose, we conduct an empirical study involving 82 fourth-grade students. The statistical results show that the students in the DL-SVVR group had higher learning behavioral engagement and better writing learning outcomes than those in the SL-SVVR group. Furthermore, as for the interrelationship between the subscales of students’ learning engagement, we find that, for the students in SL-SVVR group, their behavioral engagement can be positively predicted by the emotional engagement, while in the DL-SVVR group, students’ behavioral engagement can be positively predicted by their social engagement. For both groups, their social engagement can positively predict the emotional engagement. Importantly, our empirical results also show that the double-loop learning approach can potentially promote students’ writing learning outcomes by shifting their social engagement and behavioral engagement. The qualitative analysis results indicate that peer interaction has a positive impact on improving students’ learning interest and writing outcomes