Quality Factor Improvement of a Thin-Film Piezoelectric-on-Silicon Resonator Using a Radial Alternating Material Phononic Crystal.

This paper studies the radial alternating material phononic crystal (RAM-PnC). By simulating the band gap structure of the phononic crystal, a complete acoustic band gap was verified at the resonant frequency of 175.14 MHz, which can prevent the propagation of elastic waves in a specific direction. The proposed alternately arranged radial phononic crystal structure is applied to the thin-film piezoelectric-on-silicon (TPOS) MEMS resonator. The finite element simulation method increases the anchor quality factor (Qanchor) from 60,596 to 659,536,011 at the operating frequency of 175.14 MHz, which is about 10,000 times higher. The motion resistance of the RAM-PnC resonator is reduced from 156.25 Ω to 48.31 Ω compared with the traditional resonator. At the same time, the insertion loss of the RAM-PnC resonator is reduced by 1.1 dB compared with the traditional resonator.

Nonconventional Tether Structure for Quality Factor Enhancement of Thin-Film-Piezoelectric-on-Si MEMS Resonator.

This article presents a new design of supporting tethers through the concept of force distribution. The transmitted force applied on tethers will be distributed on the new tether design area, resulting in low acoustic energy transferred to anchor boundaries and stored energy enhancement. This technique achieves an anchor quality factor of 175,000 compared to 58,000 obtained from the conventional tether design, representing a three-fold enhancement. Furthermore, the unloaded quality factor of the proposed design improved from 23,750 to 27,442, representing a 1.2-fold improvement.

Reem-Shape Phononic Crystal for Q Anchor Enhancement of Thin-Film-Piezoelectric-on-Si MEMS Resonator.

This paper proposes a reem-shaped phononic crystal for the performance enhancement of TPoS resonators. The proposed phononic crystal offers an ultra-wide acoustic band gap that prevents energy leakage through the supporting substrate upon its placement at the anchoring boundary, resulting in significant improvements in the resonator quality factor. Simulated results show reem-shape phononic crystals generate a band gap up to 175 MHz with a BG of 90% and enhance the anchor quality factor from 180,000 to 6,000,000 and the unloaded quality factor from 133,000 to 160,000, representing 33.3-fold and 1.2-fold improvements, respectively.

Combination of Tetragonal Crystals With LiTaO3 Thin Plate for Transverse Resonance Suppression of Surface Acoustic Wave Devices.

This article discusses combination of tetragonal crystals with LiTaO3 (LT) thin plate for complete transverse resonance suppression of surface acoustic wave (SAW) devices without k2 deterioration by manipulating the slowness shape. Besides, better lateral energy confinement is achieved as well by the use of a double bus-bar structure. First, the mechanism of slowness shape manipulation by combining tetragonal crystals is studied. By comparison, YZ-lithium tetraborate (LBO) shows better performance than 69°Y90°X quartz. Then, numerical simulations are carried out using a periodic 3-D finite method assisted by a hierarchical cascading technique (HCT), and the effectiveness of transverse mode suppression by flattening the slowness shape is revealed. Also, the possibility to realize temperature compensation (TC) is discussed owing to the unique material property of LBO. Moreover, the capability of other tetragonal crystals for slowness manipulation is compared, and LBO is the best choice among these tetragonal crystals.

Bibliometric analysis of fibroblast growth factor 21 research over the period 2000 to 2021.

Background: Fibroblast growth factor 21 (FGF-21) is an evolutionarily conserved protein that plays multiple roles in metabolic regulation. Over the past two decades, numerous studies have deepened our understanding of its various functions and its pharmacological value. Nevertheless, most clinical trials have not achieved the desired results, which raises issues regarding its clinical value. In this bibliometric analysis, we evaluated the state of FGF-21 research over the last 20 years and identified important topics, achievements, and potential future directions. Methods: Publications related to FGF-21 were collected from the Web of Science Core Collection-Science Citation Index Expanded. HistCite, VOSviewer, and CiteSpace were used for bibliometric analysis and visualization, including the analysis of annual publications, leading countries, active institutions and authors, core journals, co-cited references, and keywords. Results: Altogether, 2,490 publications related to FGF-21 were obtained. A total of 12,872 authors from 2,628 institutions in 77 countries or regions reported studies on FGF-21. The United States of America was the most influential country in FGF-21 research. Alexei Kharitonenkov, Steven A. Kliewer, and David J. Mangelsdorf were the most influential scholars, and endocrinology journals had a core status in the field. The physiological roles, clinical translation, and FGF-21-based drug development were the main topics of research, and future studies may concentrate on the central effects of FGF-21, FGF-21-based drug development, and the effects of FGF-21 on non-metabolic diseases. Conclusion: The peripheral metabolic effects of FGF-21, FGF-21-based drug development, and translational research on metabolic diseases are the three major topics in FGF-21 research, whereas the central metabolic effects of FGF-21 and the effects of FGF-21 on metabolic diseases are the emerging trends and may become the following hot topics in FGF-21 research.

First-Order Perturbation Analysis of Nonlinear Signal Generation in Surface Acoustic Wave Resonators on LiTaO3/SiO2/Si Structure Based on Coupling-of-Modes Theory.

This article describes the first-order perturbation analysis of nonlinear responses in surface acoustic wave (SAW) resonators on the LiTaO3/SiO2/Si structure, where bulk wave radiation is negligible near the main resonance while the longitudinal resonances are not. The coupling-of-modes (COMs) theory is employed as the platform for both the linear and nonlinear response analyses. Stress and dielectric flux are assumed to be generated by nonlinear mixture of linear strain and electric fields proportional to the SAW displacement and applied voltage, respectively, and they are newly introduced to the extended COM equations as excitation sources. The simulated third harmonic (H3) responses agree well with the experimental ones including that caused by longitudinal resonances, and effectiveness of the present method is demonstrated. Furthermore, this theory is applied to the infinitely long interdigital transducer (IDT) to highlight the impact of longitudinal resonances.

A Bibliometric and Visualized Analysis of Uremic Cardiomyopathy From 1990 to 2021.

Background: Uremic cardiomyopathy is commonly presented in chronic kidney disease (CKD), and it severely affects the prognosis of patients with CKD. In the past few decades, the investigation of uremic cardiomyopathy has developed rapidly. However, no report has summarized the situation of uremic cardiomyopathy research to date. This study aimed to evaluate the state of uremic cardiomyopathy research in the last 30 years and identify important topics and achievements, as well as emerging trends through bibliometric analysis. Materials and Methods: Publications related to uremic cardiomyopathy were collected from Science Citation Index Expanded. HistCite, VOSviewer, CiteSpace, and the Bibliometrix Package were used for bibliometric analysis and visualization, including the analysis of the overall distribution of the annual publication, leading countries, and active institutions and authors, core journals, co-cited references, and keywords. Results: A total of 2,403 studies related to uremic cardiomyopathy were obtained, and progress related to uremic cardiomyopathy was slower in past 3 years. A total of 10,077 authors from 2,697 institutions in 89 countries or regions reported investigations on uremic cardiomyopathy. The United States of America was the most productive and the most cited country. Myles Wolf, Joseph I Shapiro, and Carmine Zoccali published most articles in uremic cardiomyopathy, and journals in nephrology possessed core status in the field. Phosphate metabolism was the hotspot in uremic cardiomyopathy research in recent years, and future progress may concentrate on phosphate metabolism, endogenous natriuretic factors, and novel biomarkers. Conclusion: The United States of America and European countries played central roles in uremic cardiomyopathy research, while Chinese scholars should be more involved in this field. Global publications on uremic cardiomyopathy have entered platform stage, and the fibroblast growth factor-23-klotho axis remained a hotspot in this field. Endogenous natriuretic factors and novel biomarkers may be potential directions in future investigations.

Irisin, a fascinating field in our times.

Irisin is a muscle-secreted hormone that is generated by cleavage of membrane protein FNDC-5 (fibronectin type III domain-containing protein 5). Irisin is considered to be a mediator of exercise-induced metabolic improvements, such as browning of white adipose tissue, and is known to alleviate several chronic non-metabolic diseases. Thus, irisin may be an ideal therapeutic target for metabolic and non-metabolic diseases. However, several controversies regarding irisin have hindered its clinical translation. We review the generation, regulation (especially in exercise), and metabolic as well as therapeutic effects of irisin on metabolic and non-metabolic diseases. Furthermore, we discuss controversies regarding irisin and highlight potential future research directions.

Fibroblast growth factor 21: A "rheostat" for metabolic regulation?

Fibroblast growth factor 21 is an evolutionarily conserved factor that plays multiple important roles in metabolic homeostasis. During the past two decades, extensive investigations have improved our understanding of its delicate metabolic roles and identified its pharmacological potential to mitigate metabolic disorders. However, most clinical trials have failed to obtain the desired results, which raises issues regarding its clinical value. Fibroblast growth factor 21 is dynamically regulated by nutrients derived from food intake and hepatic/adipose release, which in turn act on the central nervous system, liver, and adipose tissues to influence food preference, hepatic glucose, and adipose fatty acid output. Based on this information, we propose that fibroblast growth factor 21 should not be considered merely an anti-hyperglycemia or anti-obesity factor, but rather a means of balancing of nutrient fluctuations to maintain an appropriate energy supply. Hence, the specific functions of fibroblast growth factor 21 in glycometabolism and lipometabolism depend on specific metabolic states, indicating that its pharmacological effects require further consideration.

Double Busbar Structure for Transverse Energy Leakage and Resonance Suppression in Surface Acoustic Wave Resonators Using 42°YX-Lithium Tantalate Thin Plate.

This article describes a new transverse edge structure with double busbar for surface acoustic wave (SAW) devices employing a 42°YX-lithium tantalate thin plate such as incredible high-performance (I.H.P.) SAW. This design offers good energy confinement and scattering loss suppression for a wide frequency range. First, preexisting transverse edge designs are reviewed, and their difficulties are pointed out using the dispersion relation for lateral SAW propagation. Then, numerical simulations are performed using the periodic 3-D finite-element method (FEM) powered by the hierarchical cascading technique, and effectiveness of the proposed structure is revealed. In addition, we also provide a possible solution to expand the frequency range giving well energy confinement and demonstrate effectiveness of manipulating the SAW slowness curve shape for transverse mode suppression.

Figure of Merit Enhancement of Laterally Vibrating RF-MEMS Resonators via Energy-Preserving Addendum Frame.

This paper examines a new technique to improve the figure of merit of laterally vibrating RF-MEMS resonators through an energy-preserving suspended addendum frame structure using finite element analysis. The proposed suspended addendum frame on the sides of the resonant plate helps as a mechanical vibration isolator from the supporting substrate. This enables the resonator to have a low acoustic energy loss, resulting in a higher quality factor. The simulated attenuation characteristics of the suspended addendum frame are up to an order of magnitude larger than those achieved with the conventional structure. Even though the deployed technique does not have a significant impact on increasing the effective electromechanical coupling coefficient, due to a gigantic improvement in the unloaded quality factor, from 4106 to 51,136, the resonator with the suspended frame achieved an 11-folds improvement in the figure of merit compared to that of the conventional resonator. Moreover, the insertion loss was improved from 5 dB down to a value as low as 0.7 dB. Furthermore, a method of suppressing spurious mode is demonstrated to remove the one incurred by the reflected waves due to the proposed energy-preserving structure.

Electron-Ion Coupling Mechanism to Construct Stable Output Performance Nanogenerator.

Recently, triboelectric nanogenerators (TENGs) have been promoted as an effective technique for ambient energy harvesting, given their large power density and high energy conversion efficiency. However, traditional TENGs based on the combination of triboelectrification effect and electrostatic induction have proven susceptible to environmental influence, which intensively restricts their application range. Herein, a new coupling mechanism based on electrostatic induction and ion conduction is proposed to construct flexible stable output performance TENGs (SOP-TENGs). The calcium chloride doped-cellulose nanofibril (CaCl2-CNF) film made of natural carrots was successfully introduced to realize this coupling, resulting from its intrinsic properties as natural nanofibril hydrogel serving as both triboelectric layer and electrode. The coupling of two conductive mechanisms of SOP-TENG was comprehensively investigated through electrical measurements, including the effects of moisture content, relative humidity, and electrode size. In contrast to the conventional hydrogel ionotronic TENGs that require moisture as the carrier for ion transfer and use a hydrogel layer as the electrode, the use of a CaCl2-CNF film (i.e., ion-doped natural hydrogel layer) as a friction layer in the proposed SOP-TENG effectively realizes a superstable electrical output under varying moisture contents and relative humidity due to the compound transfer mechanism of ions and electrons. This new working principle based on the coupling of electrostatic induction and ion conduction opens a wider range of applications for the hydrogel ionotronic TENGs, as the superstable electrical output enables them to be more widely applied in various complex environments to supply energy for low-power electronic devices.

PTEN alleviates maladaptive repair of renal tubular epithelial cells by restoring CHMP2A-mediated phagosome closure.

Phosphatase and Tensin Homolog on chromosome Ten (PTEN) has emerged as a key protein that governs the response to kidney injury. Notably, renal adaptive repair is important for preventing acute kidney injury (AKI) to chronic kidney disease (CKD) transition. To test the role of PTEN in renal repair after acute injury, we constructed a mouse model that overexpresses PTEN in renal proximal tubular cells (RPTC) by crossing PTENfl-stop-fl mice with Ggt1-Cre mice. Mass spectrometry-based proteomics was performed after subjecting these mice to ischemia/reperfusion (I/R). We found that PTEN was downregulated in renal tubular cells in mice and cultured HK-2 cells subjected to renal maladaptive repair induced by I/R. Renal expression of PTEN negatively correlated with NGAL and fibrotic markers. RPTC-specific PTEN overexpression relieved I/R-induced maladaptive repair, as indicated by alleviative tubular cell damage, apoptosis, and subsequent renal fibrosis. Mass spectrometry analysis revealed that differentially expressed proteins in RPTC-specific PTEN overexpression mice subjected to I/R were significantly enriched in phagosome, PI3K/Akt, and HIF-1 signaling pathway and found significant upregulation of CHMP2A, an autophagy-related protein. PTEN deficiency downregulated CHMP2A and inhibited phagosome closure and autolysosome formation, which aggravated cell injury and apoptosis after I/R. PTEN overexpression had the opposite effect. Notably, the beneficial effect of PTEN overexpression on autophagy flux and cell damage was abolished when CHMP2A was silenced. Collectively, our study suggests that PTEN relieved renal maladaptive repair in terms of cell damage, apoptosis, and renal fibrosis by upregulating CHMP2A-mediated phagosome closure, suggesting that PTEN/CHMP2A may serve as a novel therapeutic target for the AKI to CKD transition.

PTEN protects kidney against acute kidney injury by alleviating apoptosis and promoting autophagy via regulating HIF1-α and mTOR through PI3K/Akt pathway.

Phosphatase and tensin homolog (PTEN) deleted on human chromosome 10 is a tumor suppressor with bispecific phosphatase activity, which is often involved in the study of energy metabolism and tumorigenesis. PTEN is recently reported to participate in the process of acute injury. However, the mechanism of PTEN in Ischemia-Reperfusion Injury (IRI) has not yet been clearly elucidated. In this study, mice with bilateral renal artery ischemia-reperfusion and HK-2 cells with hypoxia/reoxygenation (H/R) were used as acute kidney injury models. We demonstrated that PTEN was downregulated in IRI-induced kidney as well as in H/R-induced HK-2 cells. By silencing and overexpressing PTEN with si-PTEN RNA and PHBLV-CMV-PTEN-flag lentivirus before H/R, we found that PTEN protected HK-2 cells against H/R-induced injury reflected by the change in cell activity and the release of LDH. Furthermore, we inhibited HIF1-α with PX-478 and inactivated mTOR with Rapamycin before the silence of PTEN in H/R model. Our data indicated that the renoprotective effect of PTEN worked via PI3K/Akt/mTOR pathway and PI3K/Akt/HIF1-α pathway, hence alleviating apoptosis and improving autophagy respectively. Our findings provide valuable insights into the molecular mechanism underlying renoprotection of PTEN on autophagy and apoptosis induced by renal IRI, which offers a novel therapeutic target for the treatment of AKI.

Flexible Hybrid Photo-Thermoelectric Generator Based on Single Thermoelectric Effect for Simultaneously Harvesting Thermal and Radiation Energies.

Wearable electronic devices have great potential in the fields of the Internet of Things (IoT), sports and entertainment, and healthcare, and they are essential in advancing the development of next-generation electronic information technology. However, conventional lithium batteries, which are currently the main power supply of wearable electronic devices, have some critical issues, such as frequent charging, environmental pollution, and no surface adaptability, which limit the further development of wearable electronic devices. To address these challenges, we present a flexible hybrid photothermoelectric generator (PTEG) with a simple structure composed of a thermoelectric generator (TEG) and a light-to-thermal conversion layer to simultaneously harvest thermal and radiation energies based on a single working mechanism. The mature mass-fabrication technology of screen printing was applied to successively prepare n-type (i.e., Bi2Te2.7Se0.3) and p-type (i.e., Sb2Te3) thermoelectric inks atop a polyimide substrate to form the TEG with a serpentine thermocouple chain, which was further covered by a light-to-thermal conversion layer to constitute the PTEG. The resulting PTEG with five pairs of thermocouples generated a direct-current output of 82.4 mV at a temperature difference of 50 °C and a direct-current output of 41.2 mV under 20 mW/cm2 infrared radiation. Meanwhile, the remarkable mechanical reliability and output stability were experimentally demonstrated through a systematic test, which indicated the feasibility and potential of the developed PTEG as a reliable power source. In addition, as desirable application prototypes, the fabricated PTEGs have been successfully demonstrated to harvest biothermal energy and infrared radiation to drive portable electronic devices (e.g., a calculator and a clock). Hybrid energy harvesting technology based on a simple structure may provide a new solution to current power supply issues of wearable electronic device.

MicroRNA-30 regulates left ventricular hypertrophy in chronic kidney disease.

Left ventricular hypertrophy (LVH) is a primary feature of cardiovascular complications in patients with chronic kidney disease (CKD). miRNA-30 is an important posttranscriptional regulator of LVH, but it is unknown whether miRNA-30 participates in the process of CKD-induced LVH. In the present study, we found that CKD not only resulted in LVH but also suppressed miRNA-30 expression in the myocardium. Rescue of cardiomyocyte-specific miRNA-30 attenuated LVH in CKD rats without altering CKD progression. Importantly, in vivo and in vitro knockdown of miRNA-30 in cardiomyocytes led to cardiomyocyte hypertrophy by upregulating the calcineurin signaling directly. Furthermore, CKD-related detrimental factors, such as fibroblast growth factor-23, uremic toxin, angiotensin II, and transforming growth factor-ß, suppressed cardiac miRNA-30 expression, while miRNA-30 supplementation blunted cardiomyocyte hypertrophy induced by such factors. These results uncover a potentially novel mechanism of CKD-induced LVH and provide a potential therapeutic target for CKD patients with LVH.

Roles for fibroblast growth factor-23 and α-Klotho in acute kidney injury.

Acute kidney injury is a global disease with high morbidity and mortality. Recent studies have revealed that the fibroblast growth factor-23-α-Klotho axis is closely related to chronic kidney disease, and has multiple biological functions beyond bone-mineral metabolism. However, although dysregulation of fibroblast growth factor-23-α-Klotho has been observed in acute kidney injury, the role of fibroblast growth factor-23-α-Klotho in the pathophysiology of acute kidney injury remains largely unknown. In this review, we describe recent findings regarding fibroblast growth factor-23-α-Klotho, which is mainly involved in inflammation, oxidative stress, and hemodynamic disorders. Further, based on these recent results, we put forth novel insights regarding the relationship between the fibroblast growth factor-23-α-Klotho axis and acute kidney injury, which may provide new therapeutic targets for treating acute kidney injury.

Single-Layer Triboelectric Nanogenerators Based on Ion-Doped Natural Nanofibrils.

As emerging ambient energy harvesting technology, triboelectric nanogenerators (TENGs) have proven to be a robust power source and have demonstrated the unique ability to power micro-nano electronics autonomously to form self-powered devices. Although four working modes of TENGs have been developed to promote the feasibility of self-powered micro-nano systems, the relatively complicated structure composed of multilayer and movable components limits the practical applications of TENGs. Herein, we propose a single-layer triboelectric nanogenerator (SL-TENG) based on ion-doped natural nanofibrils. Compared with the simplest mode of currently existing TENGs, i.e., the single-electrode type, this novel single-electrode TENG further simplifies the configuration by the removal of the dielectric layer. The underlying mechanism of the proposed SL-TENG is comprehensively investigated through electrical measurements and the analysis of the effect of ion species at different concentrations. In contrast to conventional TENGs that require electrodes to realize charge transfer, it is revealed that the ions doped into natural nanofibrils effectively realize charge transfer due to the separation and migration of cations and anions. This new working principle based on the combination of electrons and ions enables TENGs to show greater potential for applications since the ultrasimple single-layer configuration enables them to be more easily integrated with other electronic components; additionally, the whole device of the proposed SL-TENG is biodegradable because the natural nanofibrils are completely extracted from carrots.

A Land of Controversy: Fibroblast Growth Factor-23 and Uremic Cardiac Hypertrophy.

Cardiac hypertrophy is a common feature in patients with CKD. Recent studies revealed that two phosphate regulators, fibroblast growth factor-23 and α-Klotho, are highly involved in the pathophysiologic process of CKD-induced cardiac hypertrophy. With decreasing renal function, elevated fibroblast growth factor-23 and decreased α-Klotho may contribute to cardiac hypertrophy by targeting the heart directly or by inducing systemic changes, such as vascular injury, hemodynamic disorders, and inflammation. However, several studies have demonstrated that disturbances in the fibroblast growth factor-23/α-Klotho axis do not lead to cardiac hypertrophy. In this review, we describe the cardiac effects of the fibroblast growth factor-23/α-Klotho axis and summarize recent progress in this field. In addition, we present not only the main controversies in this field but also provide possible directions to resolve these disputes.