Interfacial phenomena and joint strength in resistance microwelding of crossed Au-plated Ni wires

Resistance microwelding (RMW) of crossed Au-plated Ni wires has been performed at welding currents from 250 to 800 A and welding times from 1 to 80 ms under 4-kg welding force. The interfacial phenomena and the joint breaking force were investigated using an optical microscope (OM), a scanning electron microscope (SEM), an energy-dispersive X-ray (EDX) spectroscope, and a tensile-shear test. The results showed that mechanisms of joint formation involve brazing at low welding current, brazing and solidstate bonding at medium welding current, and solid-state bonding and fusion welding at high welding current. The joint breaking force first increased with increasing welding current, and after reaching a peak value, subsequently decreased due to recrystallization and softening of the Ni wire. With Au plating on the wire surfaces, the joint breaking force was remarkably improved. Comparisons among the RMW of Au-plated Ni wires, Au-plated Ni sheets, and bare Ni wires are also discussed.     

Helicobacter pylori infection accelerates gene expression of glicentin in the gastric mucosa. Its association with intestinal metaplasia of the stomach

AIMS: A recent immunohistochemical analysis of the Aschoff lesions in rheumatic fever, combining immunohistochemical analysis with comparative morphology, permitted the division of the Aschoff nodules into three stages: (1) Aschoff nodule without admixed lymphocytes, (2) Aschoff nodules with a few T lymphocytes, and (3) Aschoff nodules containing many admixed lymphocytes of both B- and T-cell phenotype. It was postulated that the order of progression was from stage 1 with macrophages only, to accumulation of first T lymphocytes (stage 2) and then B lymphocytes (stage 3). This study was undertaken to determine the role and distribution of interleukin 1 (IL-1), interleukin 2 (IL-2) and tumour necrosis factor alpha (TNF alpha) in the various stages of the rheumatic Aschoff nodule to investigate our hypothesis on the progression of these nodules. METHODS AND RESULTS: Sixteen fresh valve specimens from patients with acute rheumatic fever undergoing valve surgery were obtained. Tissue sections from 14 specimens identified as containing Aschoff nodules were subjected to immunohistochemistry for (1) T and B lymphocytes, to stage the lesions according to our previously proposed criteria; (2) IL-1, IL-2 and TNF alpha; and (3) CD4 and CD8 to phenotype the T lymphocytes. The stage 1 and 2 lesions expressed IL-1 and TNF alpha in the macrophages. The stage 3 lesions showed more variable expression of all three cytokines including IL-2 within T lymphocytes. CONCLUSION: TNF alpha and IL-1 secretion in macrophages is required for T and B lymphocytes activation and aggregation; suggesting that macrophages arrive at the scene of rheumatic injury prior to the lymphocytes. IL-2 is usually expressed later in the inflammatory process and was found only in the lymphoid aggregates. This study therefore produces corroborative evidence for our previously proposed developmental stages of the Aschoff nodule.     

Reactive Plasma Spraying of Fine Al2O3/AlN Feedstock Powder

Reactive plasma spraying (RPS) is a promising technology for in situ formation of aluminum nitride (AlN) coatings. Recently, AlN-based coatings were fabricated by RPS of alumina (Al₂O₃) powder in N₂/H₂ thermal plasma. This study investigated the feasibility of RPS of a fine Al₂O₃/AlN mixture and the influence of the plasma gases (N₂, H₂) on the nitriding conversion, and coating microstructure and properties. Thick AlN/Al₂O₃ coatings with high nitride content were successfully fabricated. The coatings consist of h-AlN, c-AlN, Al₅O₆N, γ-Al₂O₃, and a small amount of α-Al₂O₃. Use of fine particles enhanced the nitriding conversion and the melting tendency by increasing the surface area. Furthermore, the AlN additive improved the AlN content in the coatings. Increasing the N₂ gas flow rate improved the nitride content and complete crystal growth to the h-AlN phase, and enhanced the coating thickness. On the other hand, though the H₂ gas is required for plasma nitriding of the Al₂O₃ particles, increasing its flow rate decreased the nitride content and the coating thickness. Remarkable influence of the plasma gases on the coating composition, microstructure, and properties was observed during RPS of the fine particles.     

Microstructure and Mechanical Properties of Warm-Sprayed Titanium Coating on Carbon Fiber-Reinforced Plastic

Polymer materials are increasingly dominating various engineering fields. Recently, polymer-based composite materials’ surface performances—in particular, surface in relative motion—have been improved markedly by thermal spray coating. Despite this recent progress, the deposition of high-strength materials—producing a coating thickness of the order of more than 500 μm—remains highly challenging. In the present work, a highly dense and thick titanium coating was successfully deposited onto the carbon fiber-reinforced plastic (CFRP) substrate using a newly developed high-pressure warm spray (WS) system. The coating properties, such as hardness (300 ± 20 HV) and adhesion strength (8.1 ± 0.5 MPa), were evaluated and correlated with the microstructures of the coating. In addition, a wipe-test and in situ particle velocity and temperature measurement were performed to validate the particle deposition behavior as a function of the nitrogen flow rate in the WS system. It was found that the microstructures, deposition efficiency, and mechanical properties of the coatings were highly sensitive to nitrogen flow rates. The coating porosity increased with increasing nitrogen flow rates; however, the highest density was observed for nitrogen flow rate of 1000 standard liters per minute (SLM) samples due to the high fraction of semi-molten particles in the spray stream.     

Cubic Aluminum Nitride Coating Through Atmospheric Reactive Plasma Nitriding

Aluminum nitride is a promising material for structural and functional applications. Cubic AlN (c-AlN) is expected to have higher thermal conductivity due to their high symmetry; however, its fabrication is difficult. In this study, c-AlN was synthesized by atmospheric plasma spray process through the reaction between Al feedstock powder and nitrogen plasma. Al powders were supplied to the plasma stream by Ar carrier gas and reacted with surrounding N₂ plasma, then deposit onto substrate. The obtained coatings were c-AlN/Al mixture at 150 mm of spray distance, and the nitride content was improved by increasing the spray distance. The coatings almost consist of c-AlN at 300 mm of spray distance. The coatings thickness decreased from 100 to 10 μm with increasing spray distance from 150 to 300 mm. Using carrier gas, N₂ enable to fabricate thick c-AlN coating with hardness 1020 Hv.     

Design of a rugged 60 V VDMOS transistor

Vertical double diffused MOSFET (VDMOS) is an established technology for high- current power-switching applications such as automotive circuits. The most serious failure mode is destructive damage during inductive switching, resulting from avalanche breakdown of the forward-blocking junction in the presence of high current flow. Improving the ruggedness of the device is achieved by enhancing its ability to absorb inductive energy under avalanche conditions. The purpose of the paper is to explore the possibility of improving the ruggedness of VDMOS through TCAD simulations. A p⁺-strip buried underneath an n⁺-source is proposed to suppress the turn-on of the parasitic bipolar transistor. VDMOS transistors with this design modification are expected to have higher ruggedness while maintaining its superior figure-of-merit.     

Cyclin-D1-gene amplification is a more potent prognostic factor than its protein over-expression in human head-and-neck squamous-cell carcinoma

Endothelins (ETs) are potent bronchoconstrictor agents postulated to contribute to the pathophysiology of asthma and other respiratory disorders. An increase in both the expression and release of immunoreactive (ir) ETs was reported in bronchial epithelial cells and the bronchoalveolar lavage fluid of asthmatic patients. We investigated whether dexamethasone (DEX), a potent anti-inflammatory and anti-asthmatic drug, regulates the basal and stimulated release of ETs from guinea-pig cultured tracheal epithelial cells. These airway epithelial cells spontaneously release ET-1 over 24 h. When incubated in the presence of 10(-7) and 10(-6) M DEX for 24 h, basal production of ET-1 decreased by 32 and 29%. Lipopolysaccharide (LPS; 1, 5, 10 micrograms/mL), tumor necrosis factor-alpha (TNF alpha; 5, 10 ng/mL), and interleukin-1 beta (IL-1 beta; 1, 5 ng/mL) significantly increased the basal release of ET-1 after 24 h. When these cells were pretreated with DEX (10(-7) M) for a 24-h period, then incubated in the presence of LPS (10 micrograms/mL), TNF alpha (10 ng/mL), or IL-1 beta (1 ng/mL) for another 24 h, the stimulated release of ET-1 was inhibited by 48, 31, and 38%, respectively. At 10(-6) M, DEX decreased the stimulated release by 45, 37, and 46%, respectively. The present results show that DEX can regulate the basal release and inhibit the pro-inflammatory cytokine-stimulated production of ET-1 from guinea-pig cultured tracheal epithelial cells. They suggest that the beneficial effect of glucocorticoids in asthma may be related to the inhibition of ET synthesis.     

A circuit technology for a self-refresh 16 Mb DRAM with less than0.5 μA/MB data-retention current

A 16M self-refresh DRAM achieving less than 0.5 μA per megabyte data retention current has been developed. Several techniques to achieve low retention current, including a relaxed junction biasing (RTB) scheme, a plate-floating leakage-monitoring (PFM) system, and a V_BB pull-down word-line driver (PDWD) are described. An extension of data-retention time by three-fold and the refresh timer period by 30-fold over previously reported self-refresh DRAMs has been achieved. This results in a reduction of the ac refresh-current to less than 0.4 μA per megabyte. Furthermore, the addition of a gate-received V_BB detector (GRD) reduces dc retention current to less than 0.1 μA per megabyte. This allows a 20-megabyte RAM disk to retain data for 2.5 years when powered by a single button-shaped 190-mAh lithium battery     

Formation process of reaction layer between aluminium alloys and stainless steel by friction welding

Differences in the nature of the thermal cycle run under welding conditions in comparison to that during conventional heat treatment are shown. The methods of investigations into microstructural changes of austenite under welding thermal cycles conditions developed and used at the Welding Institute in Gliwice are discussed. The investigation results, in the form of CTP_C-S diagrams for construction steels of grades X12CrCoWVNbl 2-2-2 (VM12-SHC), 7CrMoVTiB10-10 (P24) and 10CrMo9-10 (P22), are presented and compared with those in the form of CTP_C diagrams plotted for metallurgical conditions.