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Objectives A periodic absorber can absorb incident electromagnetic waves and effectively reduce the reflectivity of a target. To this end, a novel microwave absorber based on an active frequency selective surface (AFSS) is proposed in this paper. The absorption frequency bandwidth can be dynamically adjusted by adding one PIN diode to the unit cell.Methods First, the tunable reflection performance of the proposed absorber is studied by means of a full-wave electromagnetic simulator CST in order to investigate the reflectivity of the absorber diode as the equivalent resistance of the PIN diode changes with different forward current. The propagation and reflection properties of electromagnetic waves in a multi-layer structure is then analyzed using multi-reflection interference theory so as to quantitatively illustrate the magnitude and phase condition with regard to the near unity absorption. Finally, an experiment is conducted on a fabricated absorber to verify its effectiveness in an anechoic chamber.Results The results indicate that the reflectivity of the absorber can be effectively controlled within the range of 2.5–9.1 GHz after adding the PIN diode.Conclusions The results of this paper have the potential to be applied in the electromagnetic stealth technology of weapons and equipment.

The study examines cross-linguistic influence (CLI) and voice onset time (VOT) in the production of Spanish stop consonants by native speakers of Mandarin Chinese who have learned English as their second language (L2). Six Chinese nationals studying Spanish in the United States at beginning levels and an advanced-level control were recorded reading words in their L1, L2, and L3. Results indicate a general lack of prevoicing in the speakers' production of the Spanish voiced stops. At the same time, their Spanish VOT values show great variation, with the majority of speakers having combined CLI from L1 and L2 on their L3 VOT. Results are discussed in relation to individual variation and learning context.

Background: While most undergraduate students in public health are aware of health behavior theories and models, they lack sufficient knowledge about how to apply and test them in Health Education/promotion research. Purpose: Evaluate eight new conceptual animation (CA) videos that explained theory and model testing in eight research articles from the public health literature. Methods: A convenience sample of public health faculty and undergraduate students pretested the CA video series during Summer 2019. Following pretesting, a convenience sample of 24 undergraduate public health majors completed an online evaluation survey about the CA video series to assess learning outcomes, quality, and student engagement. Results: Every CA video in the series received usability scores (>80.3) consistent with an "A" usability grade. Academic year and student usability ratings were significantly associated with perceived quality of the learning experience, R[superscript 2] = 0.18, R[superscript 2][subscript adj] = 0.14, F[subscript 9,229] = 5.28, P <0.001. Discussion: The new CA video series improved the quality of students' learning experience about select public health theories and models, especially among underclassmen. Translation to Health Education Practice: These promising findings warrant further investigation into how conceptual animation can be used as a pedagogical tool to improve student understanding of complex public health concepts.

Former college student-athletes encounter unique health-related challenges following athletic retirement. Many retired student-athletes adopt sedentary lifestyles that can lead to long-term health problems, while others struggle to maintain good mental health due to issues associated with resolving their own athletic identity. Retired student-athletes who are able to successfully transfer their athletic identity into life after college sports are less likely to engage in chronic disease risk behaviors. Unfortunately, there is a relative lack of personal health and wellness programs for this vulnerable subgroup of the college population, which is concerning given the large number and high proportion of retired college student-athletes who are highly susceptible to chronic health issues. It is important that appropriate resources are made available to dissuade retired student-athletes from living unhealthy lifestyles, while at the same time encouraging them to actively pursue wellness following college. Currently, there is a unique opportunity to improve holistic wellness among retired college student-athletes through "coaching" them to live healthy lifestyles after their athletic career is over. Certified Health Education Specialists can play a key role in planning, implementing, and evaluating multi-dimensional wellness coaching programs that address the unmet health promotion needs of retired college student-athletes.

The dynamics of polymer chains confined to a periodic cylinder is explored using molecular dynamics simulation and theoretical analysis. The cylinder is divided into two cavities in one periodicity: one cavity consists of a channel of length L1 and diameter D1 and another cavity is a channel of length L2 and diameter D2. For L1 = L2 = L/2, the diffusion coefficient D of a single confined polymer chain decreases rapidly with increase in periodicities L. For a fixed periodicity with L = L1 + L2 = constant, the diffusion coefficient D of a single confined polymer chain shows strong dependence on L1 (or L2). Moreover, for a multi-chain system with L1 = L2, the diffusion coefficient D shows strong non-monotonic dependence on the chain monomer density ρ, and the confined polymer chains diffuse fastest for ρ = 0.068, in which there are three polymer chains in two periodicities as well as two opposing effects: one is that the excluded volume effect between polymer chains can reduce the free energy barrier, and another is that when the chain monomer density ρ increases further, the entanglement effect increases, which leads to that the diffusion coefficient D decreases as ρ increases. Finally, we found that the diffusion coefficient D has a similar oscillation relationship with the ratio of R/L for different chain lengths N and different periodicity L, and the oscillation amplitude decreases gradually as R/L increases; here R is the mean end-to-end distance of a single confined polymer chain, i.e.,. From the view of free energy potential, both the width of the free energy potential well and the height of the free energy potential barrier govern simultaneously the diffusion behavior of confined polymer chains. According to the mean force potential (PMF) based on the weighted histogram analysis method (WHAM), we found that our results agree very well with the theoretical analysis using the Lifson–Jackson formula. Our investigation may help us understand the dynamics of particles in a periodic medium, which is one of the interesting problems in many different fields of science, such as physics, chemistry and biology. [ABSTRACT FROM AUTHOR]