An analysis of nonlinear thickness vibration frequencies of multi-layered film bulk acoustic resonators.

The fast reduction of the physical size of film bulk acoustic wave resonators as a layered structure implies the intensification of the electric field which can induce large deformation in the functioning state of devices as a circuit element. Consequently, the nonlinear behavior of the resonator and accompanying properties are to be included and evaluated in the development and optimization for performance improvement. With this objective, the nonlinear formulation of a multilayered film bulk acoustic resonator is presented for the analysis of vibration frequencies and mode shapes with the consideration of larger mechanical deformation. The dominantly linear relationship between the voltage or deformation and frequency is obtained to understand the nonlinear behavior and properties which have been subjected to extensive research analytically and experimentally to satisfy the application needs in all modes of communications and network technology.

A Comparative Study of Temporomandibular Joints in Adults with Definite Sleep Bruxism on Magnetic Resonance Imaging and Cone-Beam Computer Tomography Images.

OBJECTIVE: The aim was to study the imaging characteristics of the temporomandibular joint (TMJ) of definite sleep bruxers through magnetic resonance imaging (MRI) and cone-beam computer tomography (CBCT). METHODS: Nineteen definite sleep bruxers diagnosed by polysomnography and twenty asymptomatic non-bruxers matched by age, gender, and education level participated in this study. After obtaining MRI and CBCT images of all TMJs of the subjects, evaluation and measurement were conducted, respectively. The analyzed parameters included disc position, disc configuration, joint effusion (JE), joint space or condyle position, and condylar bony changes. RESULTS: Of the 38 joints in the study group, disc deformity and disc displacement of TMJs were both 57.9% when the mouth was closed, and 76.3% showed condylar bony changes, while when the mouth was open, 82% of all TMJs showed physiological biconcave discs. Comparison of joint space revealed that the anterior space was larger in the study group. There was no significant difference between the mild and the moderate to severe sleep bruxism subgroups in the changes of TMJ. CONCLUSION: The results demonstrated that a higher prevalence of disc deformity, disc displacement, JE, and condylar bony changes occurred in temporomandibular joints of sleep bruxers. These changes were not related to the severity of sleep bruxism.

Biofabrication of poly(l-lactide-co-ε-caprolactone)/silk fibroin scaffold for the application as superb anti-calcification tissue engineered prosthetic valve.

In this study, electrospun scaffolds were fabricated by blending poly(l-lactide-co-ε-caprolactone) (PLCL) and silk fibroin (SF) with different ratios, and further the feasibility of electrospun PLCL/SF scaffolds were evaluated for application of tissue engineered heart valve (TEHV). Scanning electron microscopy (SEM) results showed that the surface of PLCL/SF electrospun scaffolds was smooth and uniform while the mechanical properties were appropriate as valve prosthesis. In vitro cytocompatibility evaluation results demonstrated that all of the PLCL/SF electrospun scaffolds were cytocompatible and valvular interstitial cells (VICs) cultured on PLCL/SF scaffolds of 80/20 & 70/30 ratios exhibited the best cytocompatibility. The in vitro osteogenic differentiation of VICs including alkaline phosphatase (ALP) activity and quantitative polymerase chain reaction (qPCR) assays indicated that PLCL/SF scaffolds of 80/20 & 90/10 ratios behaved better anti-calcification ability. In the in vivo calcification evaluation model of rat subdermal implantation, PLCL/SF scaffolds of 80/20 & 90/10 ratios presented better anti-calcification ability, which was consistent with the in vitro results. Moreover, PLCL/SF scaffolds of 80/20 & 70/30 ratios showed significantly enhanced cell infiltration and M2 macrophage with higher CD206+/CD68+ ratio. Collectively, our data demonstrated that electrospun scaffolds with the PLCL/SF ratio of 80/20 hold great potential as TEHV materials.

Research on horizontal compensation of ecological economic benefits under differential responsibility.

Given that compensation for ecological and economic benefits is an effective way to address the imbalance between the coordinated development of regional ecological environment and economic growth, this study aims to explore the horizontal ecological compensation mechanism under the differentiated responsibilities of different regions in China. In this paper, the ecological deficit and surplus zones are divided by ecological footprint analysis, and the evolution of the ecological deficit and surplus zones and their per capita coal consumption in 30 provinces (municipalities and autonomous regions) from 2004 to 2018 are analyzed. Afterwards, the panel threshold model is used to validate the conclusion. The results show that there is an inverted U-shaped feature between ecological environment and economic growth in each region, which further verifies the environmental Kuznets curve (EKC). In addition, we also find that the eastern regions are mostly ecological deficit areas, while the central and western regions are mostly ecological surplus areas. In other words, the economically developed eastern regions should give a certain amount of ecological compensation to the underdeveloped central and western regions. The research results can provide new ideas and methods for the study of regional horizontal ecological compensation.

MWCNT-mediated combinatorial photothermal ablation and chemo-immunotherapy strategy for the treatment of melanoma.

Melanoma, the most aggressive skin cancer with a high metastatic index, causes almost 90% of skin cancer mortality. Currently available conservative therapies, including chemotherapy, radiotherapy and immunotherapy, have shown little effect against metastatic melanoma, leading to a very poor prognosis. The present study was aimed at developing a more efficient therapeutic strategy by combining MWCNT mediated photothermal ablation with both chemotherapy and immunotherapy. For this purpose, DOX and CpG were loaded onto MWCNTs via physical adhesion. The diameters of the resultant MWCNT-CpG and MWCNT-DOX were 197.3 ± 5.45 nm and 263.8 ± 7.36 nm, with zeta potentials of -48 ± 4.93 mV and 58 ± 2.42 mV, respectively. Loading with either CpG or DOX significantly enhanced the water dispersibility of the MWCNTs and showed no obvious impact on the physical structure of the MWCNTs. MWCNT loading facilitated the uptake of CpG by bone marrow derived dendritic cells (BMDCs), as well as the maturation of BMDCs. Intratumoral injection of MWCNT-DOX and MWCNT-CpG with subsequent NIR irradiation resulted in a significant delay in tumor progression in melanoma bearing mice, along with an increased number of CD4+ and CD8+ T cells in the spleen, draining lymph nodes and tumor tissues. The regimen promoted TAM shifting from M2 to M1 while decreasing the number of Treg cells in the tumor microenvironment, which probably contributed to the enhanced anti-tumor efficacy of the regimen. Hopefully, the invented strategy might find potential applications for the therapy of melanoma in the future.

Curcumin-crosslinked acellular bovine pericardium for the application of calcification inhibition heart valves.

Glutaraldehyde (GA) crosslinked bovine or porcine pericardium tissues exhibit high cell toxicity and calcification in the construction of bioprosthetic valves, which accelerate the failure of valve leaflets and motivate the exploration for alternatives. Polyphenols, including curcumin, procyanidin and quercetin, etc, have showed great calcification inhibition potential in crosslinking collagen and elastin scaffolds. Herein, we developed an innovative phenolic fixing technique by using curcumin as the crosslinking reagent for valvular materials. X-ray photoelectron spectroscopy and Fourier transform infrared spectrometry assessments confirmed the hydrogen bond between curcumin and acellular bovine pericardium. Importantly, the calcification inhibition capability of the curcumin-crosslinked bovine pericardium was proved by the dramatically reduced Ca2+ content in the curcumin-fixed group in in vitro assay, a juvenile rat subcutaneous implants model, as well as an osteogenic differentiation model. In addition, the results showed that the curcumin-fixed bovine pericardium exhibited better performance in the areas of mechanical performance, hemocompatibility and cytocompatibility, in comparison with the GA group and the commercialized product. In summary, we demonstrated that curcumin was a feasible crosslinking reagent to fix acellular bovine pericardium, which showed great potential for biomedical applications, particularly in cardiovascular biomaterials with calcification inhibition capacity.

Epoxy Chitosan-Crosslinked Acellular Bovine Pericardium with Improved Anti-calcification and Biological Properties.

Glutaraldehyde (GA) was conventionally used to crosslink bovine pericardium to prepare bioprosthetic heart valves (BHVs), which usually fail within 10 years because of valve deterioration and calcification. To overcome the high cytotoxicity and severe calcification of GA-crosslinked BHVs, a quaternary ammonium salt of epoxy chitosan (epoxy group-modified 3-chlorine-2-hydroxypropyl trimethyl chitosan, abbreviated as "eHTCC") was developed to modify the acellular bovine pericardium to substitute GA and improve its anti-calcification and biocompatible properties. Mechanical test, enzymatic stability test, blood compatibility assay, and cytocompatibility assay were used to investigate its mechanical property and biocompatibility. The anti-calcification effect of the eHTCC-modified bovine pericardium (eHTCC-BP) was assessed by in vitro assay and rat subcutaneous implantation assay. The results showed that eHTCC-BP could improve the mechanical properties and anti-enzymolysis ability of BP, as well as retain the original three-dimensional structure, compared with the uncrosslinked-BP group. Moreover, the in vivo calcification level of the eHTCC-BP group was much lower than that of the GA-BP group, which was 5.1% (2 weeks), 2.3% (4 weeks), and 0.8% (8 weeks) of the GA-BP group. In summary, this study demonstrated that eHTCC could be a potential crosslinking agent for the extracellular matrix for its favorable crosslinking effects, anti-enzymolysis, anti-calcification, and biocompatibility.

Swim Bladder as a Novel Biomaterial for Cardiovascular Materials with Anti-Calcification Properties.

Calcification is a major cause of cardiovascular materials failure and deterioration, which leads to the restriction of their wide application. To develop new materials with anti-calcification capability is an urgent clinical requirement. Herein, a natural material derived from swim bladders as one promising candidate is introduced, which is prepared by decellularization and glutaraldehyde (GA) crosslinking. Data show that the swim bladder is mainly composed of collagen I, glycosaminoglycan (GAG), and elastin, especially rich in elastin, in accordance with higher elastic modulus in comparison to bovine pericardium. Moreover, the calcification of this material is proved dramatically lower than that of bovine pericardium by in vitro calcification assessments and in vivo assay using a rat subcutaneous implantation model. Meanwhile, good cytocompatibility, hemocompatibility, and enzymatic stability are demonstrated by in vitro assays. Further, a small diameter vascular graft using this material is successfully developed by rolling method and in situ implantation assay using a rat abdominal artery replacement model shows great performances in the aspect of higher patency and lower calcification. Taken together, these superior properties of swim bladder-derived material in anti-calcification, proper mechanical strength and stability, and excellent hemocompatibility and cytocompatibility endow it a great candidate as cardiovascular biomaterials.

Nonglutaraldehyde Fixation for off the Shelf Decellularized Bovine Pericardium in Anticalcification Cardiac Valve Applications.

In valvular replacement surgery, especially in the construction of bioprosthetic valves with decellularized pericardial xenograft, glutaraldehyde (GA) is routinely utilized as the golden standard reagent to fix bovine or porcine pericardial tissues. However, the apparent defects of GA, including cytotoxicity and calcification, increase the probability of leaflet failure and motivate the exploration for alternatives. Thus, the aim of this study is to develop nonglutaraldehyde combined-cross-linking reagents composed of alginate-EDC/NHS (Alg) or oxidized alginate-EDC/NHS (Alg-CHO) as substitute for GA, which is confirmed to be less toxic and more biocompatible. Evaluations of the fixed acellular bovine pericardial tissues included mechanical performance, thermodynamics/enzymatic/in vivo stability tests, blood compatibility assay, cytocompatibility assay, in vitro anticalcification, and in vivo anticalcification assay by subcutaneous implantation in juvenile Wistar rats. The data revealed that the tissues fixed with the combined cross-linking reagents were superior to GA control and commercially available Sino product in terms of better in vitro hemocompatibility and cytocompatibility, lower calcification levels, better thermodynamics stability, and better regenerative capacity in subcutaneous implants, while the mechanical strength and in vivo stability were comparable. Considering all above performances, it indicated that both Alg and Alg-CHO are appropriate to replace GA as the cross-linkers for biological tissue, particularly as a nonglutaraldehyde fixation for off the shelf decellularized bovine pericardial tissue in the anticalcification cardiac valve applications. Nevertheless, studies on the long-term durability and calcification-resistance capacity in large animal model are further needed.

The surrounding tissue contributes to smooth muscle cells' regeneration and vascularization of small diameter vascular grafts.

Small diameter vascular grafts have been promising substitutes for bypass surgery to treat cardiovascular disease. However, no ideal product is available in the clinic. In order to design improved, next generation vascular grafts, it is essential to understand the cellular and molecular mechanisms underlying tissue regeneration after vascular graft implantation. Two diverse microenvironments, circulating blood and the surrounding tissue, are involved in the regeneration process after vascular graft implantation in situ. However, their regenerative functions are not completely understood. To elucidate their roles in regeneration, we used electrospinning to fabricate four types of tubular scaffolds with a structure consisting of a microfiber layer (fiber diameter ∼ 6 µm) and a nanofiber layer (fiber diameter < 1 µm): microfiber scaffold, nanofiber scaffold, outer microfiber bilayer scaffold and inner microfiber bilayer scaffold. In the outer microfiber scaffold, cells from the surrounding tissue were allowed into the scaffold but not cells from the circulating blood while it was opposite in the inner microfiber scaffold. The processes of endothelium formation, smooth muscle cell regeneration, neo-tissue formation and vascularization of these scaffolds were analyzed with a rat left common carotid artery replacement model. Our data showed that smooth muscle cells' regeneration and vascularization were different among the four types of scaffolds. The thickest neo-tissue and α-SMA+ cell layers were detected in the microfiber scaffold group while the thinnest in the nanofiber scaffold group, and thicker neo-tissue and α-SMA+ cell layers were found in the outer microfiber bilayer scaffold group compared to the inner microfiber bilayer scaffold group. In addition, vascularization in the outer microfiber bilayer scaffold group and microfiber group was dramatically better than the inner microfiber bilayer scaffold group and the nanofiber group. Furthermore, we demonstrated that the regenerated SMCs were associated with the CD206+ macrophages in the graft wall. In all, the microfiber scaffold showed the best neo-tissue regeneration in vivo. These results indicate that the surrounding tissue contributes more to vascular regeneration than circulating blood. This finding gives a significant design clue that modulating the vascular surrounding tissue will be an alternative strategy for designing advanced and feasible small diameter vascular grafts.