Research on microstructure of copper coatings on AlN ceramic surface by laser cladding and brazing

The preparation of Cu-based coatings on AlN ceramic surface was accomplished by laser cladding and brazing technology. The Cu-based coating was prepared by both copper powder and titanium powder on ceramic surface. The microstructure and properties were tested by x-ray diffraction, metallurgical microscope, scanning electron microscope, energy dispersive spectrometer and microhardness tester. The novelties of this paper in the method of laser cladding and brazing were used to prepare Cu-coating on ceramic surface and the addition of Ti could improve the properties of Cu-based coating. The addition of Ti improved the wettability of ceramic surface. According to the results of EDS, Ti could better get into the Cu-based coating and formed metallurgical bonding in the laser cladding. The microhardness of laser cladding was higher than brazing, which could be concluded that it was due to the rapid cooling rate during the laser cladding could restrain grain growth and element segregation

Ultrahigh Frequency Ultrasonic Transducers (150MHz) Based on Silicon Lenses

Acoustic microscopes and acoustic tweezers have great value in the application of microparticle manipulation, biomedical research and non-destructive testing. Ultrahigh frequency (UHF) ultrasonic transducers act as the key component in acoustic microscopes, and acoustic tweezers and acoustic lenses are essential parts of UHF ultrasonic transducers. Therefore, the preparation of acoustic lenses is crucial. Silicon is a suitable material for preparing acoustic lenses because of its high acoustic velocity, low acoustic attenuation and excellent machinability. In previous research, silicon lenses were mainly prepared by etching. However, etching has some drawbacks. The etching of large sizes is complex, time-consuming and expensive. Furthermore, vertical etching is preferred to spherical etching. Thus, a new method of ultra-precision machining was introduced to prepare silicon lenses. In this paper, silicon lenses with an aperture of 892 μm and a depth of 252 μm were prepared. Then, UHF ultrasonic transducers with a center frequency of 157 MHz and a −6-dB bandwidth of 52% were successfully prepared based on silicon lenses. The focal distance of the transducers was 736 μm and the F-number was about 0.82. The transducers had a lateral resolution of 11 μm and could distinguish the 13 μm slots on silicon wafers clearly

Acute Antibody-Mediated Rejection in Liver Transplant Recipients with Autoimmune Liver Disease: A Clinical and Pathologic Study of 4 Cases

Background: Acute antibody-mediated rejection (AMR) is an uncommon complication after ABO-compatible liver transplantation (LT). This case series investigated the clinicopathologic characteristics and outcomes of acute AMR in LT recipients with autoimmune liver disease (ALD). Patients and Methods: Among 809 patients who underwent LT from January 2014 to December 2020, four ALD patients developed AMR, which was confirmed based on clinical features, histopathology of liver biopsy, donor-specific antibodies (DSA) or panel reactive antibody (PRA) level. Therapies were individualized based on clinical manifestations. Results: The incidence of acute AMR was 0.49%, and the incidence of acute AMR with ALD and non-ALD recipients was 11.1% and 0%, respectively. Three patients had strongly positive HLA class II DSA, and one patient was with the PRA class I and II sensitivities, which were >80%; complement component 4d (C4d) staining was negative in all patients. The first patient underwent re-LT, and the other three patients had good prognoses with treatments. Conclusions: ALD patients are prone to acute AMR after LT, thus should be kept vigilant against the occurrence of acute AMR

A Review on Additive Manufacturing of Pure Copper

With the development of the aerospace and automotive industries, high heat exchange efficiency is a challenge facing the development of various industries. Pure copper has excellent mechanical and physical properties, especially high thermal conductivity and electrical conductivity. These excellent properties make pure copper the material of choice for the manufacture of heat exchangers and other electrical components. However, the traditional processing method is difficult to achieve the production of pure copper complex parts, so the production of pure copper parts through additive manufacturing has become a problem that must be overcome in industrial development. In this article, we not only reviewed the current status of research on the structural design and preparation of complex pure copper parts by researchers using selective laser melting (SLM), selective electron beam melting (SEBM) and binder jetting (BJ) in recent years, but also reviewed the forming, physical properties and mechanical aspects of pure copper parts prepared by different additive manufacturing methods. Finally, the development trend of additive manufacturing of pure copper parts is also prospected

Enhancing catalytic performance of Fe-based metallic glasses by selective laser melting and electrochemical dealloying

Herein, a Fenton-like catalyst with hierarchical porous structure for the degradation of azo dye with no illumination is reported. Selective laser melting (SLM) fabrication method and electrochemical dealloying are used to enhance degradation efficiency. Even in the absence of light, the degradation efficiency can reach 0.062 (k, reaction kinetic constant) and the durability of catalysts is good. Various properties of the SLM-produced porous metallic glass (SPMG) catalysis, such as the amorphous phase fraction and relaxation, which not only affect the degradation efficiency of the catalyst, but also the dealloying process of the catalyst. To investigate this issue, a series of SLM experiments and electrochemical experiments were performed. The result showed that crystallization occurs during electrochemical dealloying, and more pronounced ligaments and less ‘Grain Region’ on the surface of high initial amorphous fraction SPMG than the one of low initial amorphous fracion, indicating that the structure of the precursor alloy affects the final formation of the nano-porous structure. Subsequently, more pronounced ligaments and less ‘Grain Region’ result in greater catalytic. However, the ‘Grain Region’ in SPMG with a low initial amorphous fraction is not decrease and its azo catalytic ability deteriorates even when electrochemical dealloying was extended to 6 h

Fabrication and characterization of thick-film piezoelectric lead zirconate titanate ceramic resonators by tape-casting

In this paper, thick-film piezoelectric lead zirconate titanate (PZT) ceramic resonators with thicknesses down to tens of micrometers have been fabricated by tapecasting processing. PZT ceramic resonators with composition near the morphotropic phase boundary and with different dopants added were prepared for piezoelectric transducer applications. Material property characterization for these thick-film PZT resonators is essential for device design and applications. For the property characterization, a recently developed normalized electrical impedance spectrum method was used to determine the electromechanical coefficient and the complex piezoelectric, elastic, and dielectric coefficients from the electrical measurement of resonators using thick films. In this work, nine PZT thick-film resonators have been fabricated and characterized, and two different types of resonators, namely thickness longitudinal and transverse modes, were used for material property characterization. The results were compared with those determined by the IEEE standard method, and they agreed well. It was found that depending on the PZT formulation and dopants, the relative permittivities T 33/0 measured at 2 kHz for these thick-films are in the range of 1527 to 4829, piezoelectric stress constants (e33 in the range of 15 to 26 C/m2, piezoelectric strain constants (d 31) in the range of-169 10-12 C/N to-314 10-12 C/N, electromechanical coupling coefficients (kt) in the range of 0.48 to 0.53, and k31 in the range of 0.35 to 0.38. The characterization results shows tape-casting processing can be used to fabricate high-quality PZT thick-film resonators, and the extracted material constants can be used to for device design and application. 漏 2012 IEEE

Fabrication and Characterization of Lead-Free BNT-6BT Ultrasonic Transducers Designed by an Intelligent Optimization Algorithm

Lead-free piezoelectric material-based ultrasonic transducers have been researched for several years, but the inefficient properties and design difficulties have troubled lead-free ultrasonic transducers for a long time. To improve the performance and design efficiency of lead-free ultrasonic transducers, in this work, an equivalent circuit model and intelligent optimization algorithm were combined for use in a transducer design. Firstly, 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3(BNT-6BT) lead-free piezoelectric ceramics were prepared and characterized. Then, BNT-6BT ceramics were used to fabricate the ultrasonic transducers. An equivalent circuit model-based software, PiezoCAD, and a genetic algorithm-based back-propagation neural network were used to optimize the design of the transducers. A 3.03 MHz center frequency and 60.3% −6 dB bandwidth of the optimized transducers were achieved, which were consistent with the neural networks optimization results. To verify the application potential of the lead-free transducers, tungsten rods phantom imaging and polystyrene spheres with 300 μm diameter manipulation were completed by the transducers, and the experiment results indicate that the BNT-6BT lead-free transducers have great potential in further biological and biomedical applications

A novel organ preservation solution with efficient clearance of red blood cells improves kidney transplantation in a canine model

Abstract Organ preservation solutions are designed to minimize organ damage during transplantation. A novel preservation solution, WMO-II, was developed to have a low viscosity and to improve microvasculature perfusion for kidneys. In an autologous canine transplantation model, kidney function and recovery were evaluated after organs were flushed and cold-stored with WMO-II or HTK solution, a perfusate currently approved for clinical use. The average number of red blood cells remaining in a single glomerulus after flushing with WMO-II was significantly reduced when compared with HTK solution. Additionally, WMO-II reduced the number of apoptotic bodies in stored kidneys compared to HTK treated tissue after 48 h of cold storage by reducing expression of Caspase-9, BiP, Chop, and Caspase-12. WMO-II solution reduced serum creatinine levels and serum potassium in kidneys stored for 48 h when compared to HTK perfusion. WMO-II preserves kidney function as evidenced by the reduction in serum creatinine and potassium during graft transplantation

SUMOylation of Pdia3 exacerbates proinsulin misfolding and ER stress in pancreatic beta cells

SUMOylation has long been recognized to regulate multiple biological processes in pancreatic beta cells, but its impact on proinsulin disulfide maturation and endoplasmic reticulum (ER) stress remains elusive. Herein, we conducted comparative proteomic analyses of SUMOylated proteins in primary mouse/human islets following proinflammatory cytokine stimulation. Cytokine challenge rendered beta cells to undergo a SUMOylation turnover manifested by the changes of SUMOylation substrates and SUMOylation levels for multiple substrates. Our data support that SUMOylation may play a crucial role to regulate proinsulin misfolding and ER stress at least by targeting Protein Disulfide Isomerase a3 (Pdia3). SUMOylation regulates Pdia3 enzymatic activity, subcellular localization, and protein binding ability. Furthermore, SUMOylation of Pdia3 exacerbated proinsulin misfolding and ER stress, and repressed Stat3 activation. In contrast, disruption of Pdia3 SUMOylation markedly rescued the outcomes. Collectively, our study expands the understanding how SUMOylation regulates ER stress in beta cells, which shed light on developing potential strategies against beta cell dysfunction.SCOPUS: ar.jinfo:eu-repo/semantics/publishe