Magnetically enhanced thermoelectrics: a comprehensive review.

Thermoelectric (TE) materials have great potential for waste-energyrecycling and solid-state cooling. Their conversion efficiency has attracted huge attention to the development of TE devices, and largely depends on the thermal and electrical transport properties. Magnetically enhanced thermoelectrics open up the possibility of making thermoelectricity a future leader in sustainable energy development and offer an intriguing platform for both fundamental physics and prospective applications. In this review, state-of-the-art TE materials are summarized from the magnetism point of view, via diagrams of the charges, lattices, orbits and spin degrees of freedom. Our fundamental knowledge of magnetically induced TE effects is discussed. The underlying thermo-electro-magnetic merits are discussed in terms of superparamagnetism- and magnetic-transition-enhanced electron scattering, field-dependent magnetoelectric coupling, and the magnon- and phonon-drag Seebeck effects. After these topics, we finally review several thermal-electronic and spin current-induced TE materials, highlight future possible strategies for further improvingZT, and also give a brief outline of ongoing research challenges and open questions in this nascent field.

Detection of Transdermal Drug Delivery Efficiency by Shock Wave.

OBJECTIVE: This study aimed to observe the drug distribution ex-vivo after transdermal drug delivery (TDD) by Shock Wave (SW) and to explore the different effects of the two types of shock waves. MATERIALS AND METHODS: Nine female Sprague-Dawley (SD) rats were randomly divided into 3 groups: (i) control group; (ii) RESW group (0.35mJ/mm2, 2 Hz, 400 pulse); (iii) FESW group (0.16mJ/mm2, 2 Hz, 400 pulse). Micro positron emission tomography/computed tomography (PET/CT) was used to observe the distribution of [18]F-NaF. Furthermore, 12 SD rats were randomly divided into 4 groups: (i) control group; (ii) FESW group 1 (0.03mJ/mm2, 2 Hz, 400 pulse); (iii) FESW group 2 (0.16mJ/mm2, 2 Hz, 400 pulse); (iv) FESW group 3 (0.35mJ/mm2, 2 Hz, 400 pulse). High-performance liquid chromatography (HPLC) tested diclofenac sodium and glucose percutaneously TDD by FESW. Statistical significance was conducted by analysis of variance of repeated measurement. RESULTS: The micro PET/CT observed FESW could penetrate [18]F-NaF through the skin, while RESW could not. The second study found the higher the energy of the FESW, the more diclofenac sodium and glucose penetration. Repeated measures analysis of variance found a within-subject effect (diclofenac sodium, F = 4.77, p = 0.03), (glucose, F = 8.95, p = 0.006), significant differences between the control group, FESW group 1, and FESW group 2 (p < 0.05). CONCLUSION: The study found that FESW can penetrate [18]F-NaF, sugar and diclofenac sodium into the rat body. FESW has a good indication of drug penetration, which provides new biological evidence for route administration.

Evolution of defect structures leading to high ZT in GeTe-based thermoelectric materials.

GeTe is a promising mid-temperature thermoelectric compound but inevitably contains excessive Ge vacancies hindering its performance maximization. This work reveals that significant enhancement in the dimensionless figure of merit (ZT) could be realized by defect structure engineering from point defects to line and plane defects of Ge vacancies. The evolved defects including dislocations and nanodomains enhance phonon scattering to reduce lattice thermal conductivity in GeTe. The accumulation of cationic vacancies toward the formation of dislocations and planar defects weakens the scattering against electronic carriers, securing the carrier mobility and power factor. This synergistic effect on electronic and thermal transport properties remarkably increases the quality factor. As a result, a maximum ZT > 2.3 at 648 K and a record-high average ZT (300-798 K) were obtained for Bi0.07Ge0.90Te in lead-free GeTe-based compounds. This work demonstrates an important strategy for maximizing the thermoelectric performance of GeTe-based materials by engineering the defect structures, which could also be applied to other thermoelectric materials.

Research Trends on the Rotator Cuff Tendon: A Bibliometric Analysis of the Past 2 Decades.

BACKGROUND: Clinical research on the rotator cuff tendon is increasing, and new approaches are being applied to rotator cuff disease. Considering the integration of research resources and research trends, it is necessary to conduct an analysis of recent research on the topic. PURPOSE: To identity the research trends, influential journals, key researchers, and core countries of rotator cuff tendon research between 2000 and 2019. STUDY DESIGN: Cross-sectional study. METHODS: All the literature related to rotator cuff tendon research was retrieved from the Web of Science Core Collection on January 7, 2020. Qualitative and quantitative analyses were processed based on Web of Science and CiteSpace. RESULTS: A total of 4131 studies, which included 3830 articles and 301 reviews, were obtained. There was an upward trend of studies on the topic, with small fluctuations in the past 2 decades. The United States had the most studies, and the number of studies from other countries increased over the study period. Most of the funding sources came from the United States. Articles in the Journal of Shoulder and Elbow Surgery had the most citations for rotator cuff research. Frontier topics, such as arthroscopic repair, mesenchymal stem cell, and "platelet-rich plasma, were identified. The number of citations in 2018 (r = 0.280; P = .005) and 2019 (r = 0.307; P = .002) had a weak positive correlation with publication date, indicating that the more recently published articles had a higher number of citations. CONCLUSION: Valuable information on rotator cuff research based on bibliometric analysis was identified. Arthroscopic repair, mesenchymal stem cell, and platelet-rich plasma might be the research frontiers in this field, and researchers should focus on these topics in future studies.

Effects of electromyography biofeedback for patients after knee surgery: A systematic review and meta-analysis.

There has been no systematic review evaluating the efficacy of electromyography (EMG) biofeedback after knee surgery recently. This meta-analysis aimed to determine whether EMG-biofeedback is effective for improving the range of motion (ROM), physical function, and pain relief in patients after knee. Randomized controlled trials (RCTs) assessing the effect of EMG-biofeedback after any knee surgery were retrieved from EMBASE, PubMed, Cochrane Library, Physiotherapy Evidence Database, ClinicalTrials.gov, ProQuest. This review identified 773 unique studies, and six RCTs were in the final meta-analysis. EMG-Biofeedback treatment has a significant difference compared to other rehabilitation therapy in knee ROM improving (SMD = -0.48, 95% CI = -0.82 to -0.14, p = 0.006, I2 = 37%). Moreover, there was no significant difference in pain (SMD = -0.33, 95% CI = -0.67 to0.02, p = 0.07, I2 = 41%) and physical function scores (MD = 1.83, 95% CI = -3.48 to7.14, p = 0.50, I2 = 0%). The results illustrate that EMG-biofeedback can improve knee ROM in patients after knee surgery. However, it is not superior to other rehabilitation methods for pain relief and physical function improvement.

The effect of VNS on the rehabilitation of stroke: A meta-analysis of randomized controlled studies.

INTRODUCTION: The efficacy of vagus nerve stimulation (VNS) for the rehabilitation of stroke remains controversial. We conduct a systematic review and meta-analysis to explore the influence of VNS on the rehabilitation of stroke. METHODS: We search PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through March 2020 for randomized controlled trials (RCTs) assessing the effect of VNS on the rehabilitation of stroke. This meta-analysis is performed using the random-effect model. RESULTS: Three RCTs are included in the meta-analysis. Overall, compared with control group in stroke, VNS is associated with significantly improved FMA-UE (SMD = 3.86; 95% CI = 1.19 to 6.52; P = 0.005) and Motor Function Test (SMD = 0.33; 95% CI = 0.04 to 0.62; P = 0.03), but has no obvious impact on Box and Block Test (SMD = -0.31; 95% CI = -3.48 to 2.86; P = 0.85), Nine-Hole Peg Test (SMD = 8.35; 95% CI = -40.59 to 57.28; P = 0.74), atrial fibrillation (RR = 3.46; 95% CI = 0.39 to 30.57; P = 0.26) or adverse events (RR = 0.59; 95% CI = 0.21 to 1.61; P = 0.30). CONCLUSIONS: VNS may be beneficial to the rehabilitation of stroke.

Nanostructure Engineering and Performance Enhancement in Fe2O3-Dispersed Cu12Sb4S13 Thermoelectric Composites with Earth-Abundant Elements.

Nanostructuring and defect engineering are increasingly employed as processing strategies for thermoelectric performance enhancement, and special attention has been paid to nanostructured interfaces and dislocations that can effectively scatter low- and mid-frequency phonons. This work demonstrated that their combination was realized in Fe2O3-dispersed tetrahedrite (Cu12Sb4S13) nanocomposites, leading to significantly reduced thermal conductivities around 0.9 W m-1 K-1 at all temperatures and hence a high ZT value of ∼1.0, which increases by ∼33% compared with that of the matrix. The plausible enhancement mechanisms have been analyzed with an emphasis on the incorporation of magnetic γ-Fe2O3 nanoparticles (NPs) into Cu11.5Ni0.5Sb4S13, leading to various nanostructures (NPs, nanoprecipitates, and nanotwins) and dislocations. A calculated efficiency of ∼9.3% and an average ZT of 0.63 also reveal the potential application of tetrahedrite at medium temperatures. Additionally, the mechanical properties are improved because of a second phase strengthening and nanotwin structures.

What You Should Know About Osteoarthritis Rehabilitation: A Bibliometric Analysis of the 50 Most-Cited Articles.

BACKGROUND: Osteoarthritis is a degenerative disease that commonly occurs in middle-aged and elderly people. High-quality articles in the field of osteoarthritis rehabilitation have not been studied in detail. OBJECTIVE: To identify and conduct a qualitative and quantitative analysis of the 50 most-cited articles on osteoarthritis rehabilitation and provide valuable scientific information for researchers. METHODS: Fifty articles related to the rehabilitation of individuals with osteoarthritis were retrieved from the Web of Science Core Collection. Basic information, such as the authors, title, number of citations, year of publication, journal, country/territory, and research type, was extracted. CiteSpace was used to visualize the keywords. RESULTS: The average number of citations per article was 244.54. The top 50 articles were published in 27 journals and published by 262 authors. Most of the top 50 articles were published in the United States. The top 50 articles included 23 randomized controlled trials, 21 cohort studies, 2 case series, and 4 expert opinion articles. The most commonly studied topics in osteoarthritis rehabilitation included rehabilitation for pain, gait abnormalities, muscle strength deficiencies, and other functional impairments caused by osteoarthritis in elderly people. CONCLUSIONS: The top articles in the field of osteoarthritis rehabilitation have a high level of evidence. Collaboration between authors was high for highly-cited articles. Moreover, the eminent articles can provide important information for the education of doctors and therapists specializing in osteoarthritis rehabilitation.

Reducing Lattice Thermal Conductivity of MnTe by Se Alloying toward High Thermoelectric Performance.

Lead-free manganese telluride has been considered to be a promising candidate for mid-temperature thermoelectric materials. In this work, we report point defect scattering-induced reduction of thermal conductivity in MnTe with Se alloying, fabricated by a facile method combining mechanical alloying and spark plasma sintering. A low lattice thermal conductivity of 0.56 W/mK was obtained for MnTe0.92Se0.08, which is quite close to the amorphous limits. A detailed Debye model analysis reveals the underlying mechanism of phonon scattering and well predicts the thermal conductivity with different contents of Se. Meanwhile, a slight increase of carrier concentration was also observed after Se alloying, accompanied by a variation of energy gap that may be associated with the competition among anions in trapping charges. Further Na doping leads to enhanced electrical transport properties, achieving a maximum ZT value of 1.03 at 873 K. An average ZT of 0.52 and a calculated efficiency of more than 9% also suggest the promising application of MnTe at medium temperatures.

Highly Textured N-Type SnSe Polycrystals with Enhanced Thermoelectric Performance.

Thermoelectric materials, which directly convert heat into electricity based on the Seebeck effects, have long been investigated for use in semiconductor refrigeration or waste heat recovery. Among them, SnSe has attracted significant attention due to its promising performance in both p-type and n-type crystals; in particular, a higher out-of-plane ZT value could be achieved in n-type SnSe due to its 3D charge and 2D phonon transports. In this work, the thermoelectric transport properties of n-type polycrystalline SnSe were investigated with an emphasis on the out-of-plane transport through producing textural microstructure. The textures were fabricated using mechanical alloying and repeated spark plasma sintering (SPS), as a kind of hot pressing, aimed at producing strong anisotropic transports in n-type polycrystalline SnSe as that in crystalline SnSe. Results show that the lowest thermal conductivity of 0.36 Wm-1 K-1 was obtained at 783 K in perpendicular to texture direction. Interestingly, the electrical transport properties are less anisotropic and even nearly isotropic, and the power factors reach 681.3 µWm-1 K-2 at 783 K along both parallel and perpendicular directions. The combination of large isotropic power factor and low anisotropic thermal conductivity leads to a maximum ZT of 1.5 at 783 K. The high performance elucidates the outstanding electrical and thermal transport behaviors in n-type polycrystalline SnSe, and a higher thermoelectric performance can be expected with future optimizing texture in n-type polycrystalline SnSe.

MnS Incorporation into Higher Manganese Silicide Yields a Green Thermoelectric Composite with High Performance/Price Ratio.

Thermoelectric materials that can directly convert heat to electrical energy offer a viable solution for reducing the usage of fossil energy by harvesting waste heat resources. Higher manganese silicide (HMS) is a naturally abundant, eco-friendly, and low-cost p-type thermoelectric semiconductor with high power factor (PF); however, its figure of merit (ZT) is limited by intrinsically high thermal conductivity (κ). For effectively enhancing the thermoelectric performance of HMS and avoiding the use of expensive or toxic elements, such as Re, Te, or Pb, a green p-type MnS with high Seebeck coefficient (S) and low κ is incorporated into the HMS matrix to form MnS/HMS composites. The incorporation of MnS leads to a 31% reduction of κ and a 10% increase of S. The ZT value increases by ≈48% from 0.40 to 0.59 at 823 K. Correspondingly, performance/price ratio is first proposed to evaluate the practical value of thermoelectric materials, which is higher than those of the vast majority of current thermoelectric materials. This study provides an overview of enhancing ZT of HMS and reducing costs, which may also be applicable to other thermoelectric materials.

Melt-Centrifuged (Bi,Sb)2 Te3 : Engineering Microstructure toward High Thermoelectric Efficiency.

Microstructure engineering is an effective strategy to reduce lattice thermal conductivity (κl ) and enhance the thermoelectric figure of merit (zT). Through a new process based on melt-centrifugation to squeeze out excess eutectic liquid, microstructure modulation is realized to manipulate the formation of dislocations and clean grain boundaries, resulting in a porous network with a platelet structure. In this way, phonon transport is strongly disrupted by a combination of porosity, pore surfaces/junctions, grain boundaries, and lattice dislocations. These collectively result in a ≈60% reduction of κl compared to zone melted ingot, while the charge carriers remain relatively mobile across the liquid-fused grains. This porous material displays a zT value of 1.2, which is higher than fully dense conventional zone melted ingots and hot pressed (Bi,Sb)2 Te3 alloys. A segmented leg of melt-centrifuged Bi0.5 Sb1.5 Te3 and Bi0.3 Sb1.7 Te3 could produce a high device ZT exceeding 1.0 over the whole temperature range of 323-523 K and an efficiency up to 9%. The present work demonstrates a method for synthesizing high-efficiency porous thermoelectric materials through an unconventional melt-centrifugation technique.

Nanoporous PbSe-SiO2 Thermoelectric Composites.

Nanoporous architecture has long been predicted theoretically for its proficiency in suppressing thermal conduction, but less concerned as a practical approach for better thermoelectric materials hitherto probably due to its technical challenges. This article demonstrates a study on nanoporous PbSe-SiO2 composites fabricated by a facile method of mechanical alloying assisted by subsequent wet-milling and then spark plasma sintering. Owing to the formation of random nanopores and additional interface scattering, the lattice thermal conductivity is limited to a value as low as 0.56 W m-1 K-1 at above 600 K, almost the same low level achieved by introducing nanoscale precipitates. Besides, the room-temperature electrical transport is found to be dominated by the grain-boundary potential barrier scattering, whose effect fades away with increasing temperatures. Consequently, a maximum ZT of 1.15 at 823 K is achieved in the PbSe + 0.7 vol% SiO2 composition with >20% increase in average ZT, indicating the great potential of nanoporous structuring toward high thermoelectric conversion efficiency.

Thermoelectric SnS and SnS-SnSe solid solutions prepared by mechanical alloying and spark plasma sintering: Anisotropic thermoelectric properties.

P-type SnS compound and SnS1-xSex solid solutions were prepared by mechanical alloying followed by spark plasma sintering (SPS) and their thermoelectric properties were then studied in different compositions (x = 0.0, 0.2, 0.5, 0.8) along the directions parallel (//) and perpendicular (⊥) to the SPS-pressurizing direction in the temperature range 323-823 Κ. SnS compound and SnS1-xSex solid solutions exhibited anisotropic thermoelectric performance and showed higher power factor and thermal conductivity along the direction ⊥ than the // one. The thermal conductivity decreased with increasing contents of Se and fell to 0.36 W m-1 K-1 at 823 K for the composition SnS0.5Se0.5. With increasing selenium content (x) the formation of solid solutions substantially improved the electrical conductivity due to the increased carrier concentration. Hence, the optimized power factor and reduced thermal conductivity resulted in a maximum ZT value of 0.64 at 823 K for SnS0.2Se0.8 along the parallel direction.

Self-Tuning n-Type Bi2(Te,Se)3/SiC Thermoelectric Nanocomposites to Realize High Performances up to 300 °C.

Bi2Te3 thermoelectric materials are utilized for refrigeration for decades, while their application of energy harvesting requires stable thermoelectric and mechanical performances at elevated temperatures. This work reveals that a steady zT of ≈0.85 at 200 to 300 °C can be achieved by doping small amounts of copper iodide (CuI) in Bi2Te2.2Se0.8-silicon carbide (SiC) composites, where SiC nanodispersion enhances the flexural strength. It is found that CuI plays two important roles with atomic Cu/I dopants and CuI precipitates. The Cu/I dopants show a self-tuning behavior due to increasing solubility with increasing temperatures. The increased doping concentration increases electrical conductivity at high temperatures and effectively suppresses the intrinsic excitation. In addition, a large reduction of lattice thermal conductivity is achieved due to the "in situ" CuI nanoprecipitates acting as phonon-scattering centers. Over 60% reduction of bipolar thermal conductivity is achieved, raising the maximum useful temperature of Bi2Te3 for substantially higher efficiency. For module applications, the reported materials are suitable for segmentation with a conventional ingot. This leads to high device ZT values of ≈0.9-1.0 and high efficiency up to 9.2% from 300 to 573 K, which can be of great significance for power generation from waste heat.