Analysis of Subsurface Imaging and Effect of Contact Elasticity in the Ultrasonic Force Microscope

We examined, both theoretically and experimentally, the characteristics of subsurface imaging with nanometer resolution and the effect of contact elasticity in the ultrasonic force microscope (UFM). In particular, the effect of the surface energy and effective elasticity on the maximum tip-sample force and the shift of the averaged tip-sample distance were examined. Furthermore, kink formation in the cantilever deflection (z(a)) against the ultrasonic frequency vibration (UFV) amplitude (a) characteristics was predicted. This model was used to explain experimental observations in UFM, such as the features of the measured z(a)(a) curve and the damping of the cantilever torsion vibration by the UFV. Moreover. the previously reported lateral ultrasonic force microscope image of subsurface features was explained by the response of subsurface edge dislocation to a large instantaneous force enhanced by the UFV

Wear Behavior of Al₂O₃-Reinforced Aluminum Metal Matrix Composite in Water and in Ethanol

Aluminum metal matrix composite disks reinforced with alumina (Al2O3) were slid against silicon carbide (SiC) pins in water and in ethanol to evaluate the wear resistance. The wear of the composite slid against SiC in water was higher than that in ethanol. Oxidized aluminum compounds were formed by tribo-oxidation on the composite disk surfaces worn both in water and in ethanol. The amount of the oxidized aluminum compounds deposited on the wear tracks in water was much larger than that in ethanol. The significant oxidative wear took place in water, while oxidative wear and wear due to plastic deformation took place in ethanol

DC Arc Plasma Treatment for Defect Reduction in WC-Co Granulated Powder

Tungsten carbide–cobalt (WC–Co) agglomerated powder is widely used for additive manufacturing and spray coating, and a reduction in internal gaps in the powder is required to obtain a product of high quality. In this paper, we investigate plasma effects on agglomerated powder when WC–12%Co powder is directly subjected to direct current (DC) arc plasma treatment to reduce gaps in the WC–Co powder. We obtain a plasma-treated powder with reduced gaps among WC particles. Furthermore, plasma-treatment improves the sphericity of the powder particles, due to the spheroidization effect, so that the percentage of plasma-treated particles exceeding 95% sphericity is 50%, which is 1.7 times that of raw powder. Concern regarding the possible generation of W2C by plasma treatment is unfounded, with W2C levels kept very low according to X-ray diffraction (XRD) analysis, showing a value of 0.0075 for the area ratio W2C(002)/WC(100). XRD analysis also reveals that plasma treatment relaxes residual strains in the powder. From these results, the DC plasma treatment of WC agglomerated powder produces a spherical powder with fewer gaps and strains in the powder, making it more suitable for additive manufacturing while suppressing decarburization

Lub1 Participates in Ubiquitin Homeostasis and Stress Response via Maintenance of Cellular Ubiquitin Contents in Fission Yeast

Ubiquitin-dependent proteolysis plays a pivotal role in stress responses. To investigate the mechanisms of these cellular processes, we have been studying Schizosaccharomyces pombe mutants that have altered sensitivities to various stress conditions. Here, we showed that Lub1, a homologue of Ufd3p/Zzz4p/Doa1p in budding yeast, is involved in the regulation of ubiquitin contents. Disruption of the lub1(+) gene resulted in monoubiquitin as well as multiubiquitin depletion without change in mRNA level and in hypersensitivity to various stress conditions. Consistently, overexpression of genes encoding ubiquitin suppressed the defects associated with lub1 mutation, indicating that the phenotypes of the lub1 mutants under stress conditions were due to cellular ubiquitin shortage at the posttranscriptional level. In addition, the lub1-deleted cells showed aberrant functions in ubiquitin/proteasome-dependent proteolysis, with accelerated degradation of ubiquitin. Also Cdc48, a stress-induced chaperon-like essential ATPase, was found to interact with Lub1, and this association might contribute to the stabilization of Lub1. Our results indicated that Lub1 is responsible for ubiquitin homeostasis at the protein level through a negative regulation of ubiquitin degradation