Friction drive of an SAW motor. Part II: analyses

The mechanics of the friction drive of a surface acoustic wave motor were investigated by means of contact mechanics theory. As a means to control the contact condition, the motor's slider had projections on its frictional surface. Assuming the projection was a rigid circular punch and the slider body was an elastic half-space allowed application of contact mechanics formulae to the analyses of the friction drive. Because the projection contacted the Rayleigh wave vibration, the projection's responses were considered dynamic; thus, the dynamics were also analyzed in the same framework of contact mechanics formulae. Moreover, the analyses were applied to measurements of the projection's displacement to examine the detailed mechanics during the friction drive. We calculated the contact/frictional forces based on the measurement and indicated the necessity of further investigation of the surface acoustic wave motor's friction drive, because the usual friction law was unable to explain the measurement.     

Dose-dependent effects of Ni (II) ions on production of three inflammatory cytokines (TNF-α, IL-1β and IL-6), superoxide dismutase (SOD) and free radical NO by murine macrophage-like RAW264 cells with or without LPS-stimulation

The effect of Ni (II) ions on macrophages is not well understood. The purpose of this study was to examine the dose-dependent effects of Ni (II) ions up to 1,000 μmol/L on production of three inflammatory cytokines (TNF-α, IL-1β and IL-6), superoxide dismutase (SOD) and nitric oxide (NO) by murine macrophage-like RAW264 cells with (+) or without (−) lipopolysaccharide (LPS) -stimulation. Ni (II) ions caused LPS (−) RAW264 cells to slightly increase production of TNF-α and IL-6, proportionally to the Ni (II) ion concentration while IL-1β was not produced, and to slightly increase production of SOD and NO. It can be concluded that Ni (II) ions dose-dependently increased the inflammatory and oxidative stress conditions of LPS (−) RAW264 cells. LPS-stimulation caused RAW264 cells to produce in abundance the three inflammatory cytokines, SOD and NO. Ni (II) ions dose-dependently reduced the three cytokine quantities and NO amounts in LPS (+) RAW264 cells, while dose-independently increasing SOD amounts. It was noted that Ni (II) ions dose-dependently reduce the resistance power against bacteria of LPS (+) macrophages, because the production of volatile NO—bacteria killer is diminished proportionally to the Ni (II) ion concentration.     

Standardization of strength evaluation methods using critical distance stress

The stress and displacement fields near the bonding edge, sharp notch, and contact edge show singularity behaviors, so methods of evaluating the strength of these points using maximum stresses calculated by a numerical stress analysis, such as the finite element method, are generally not valid. We have previously presented a new method of evaluating the strength of these singular points using two stress singularity parameters H and λ. The difficulty with this method was in obtaining the critical value of the intensity of the stress singularity parameter H_c for each order of stress singularity λ. Then we have developed a method of formularizing critical value of stress singularity parameter H_c for each order of stress singularity λ by utilizing critical distance stress theory. Firstly we apply this method to the delamination strength evaluation. The estimated delamination criteria H_c(λ) agrees well with the experimental results. Then we apply this method to general sharp notch corner and contact edge fatigue problems. In these cases the fatigue-crack initiation criteria can be derived from two typical strength parameters, namely, fatigue limit σ_w0 and threshold stress intensity factor range ΔK_th. These estimated critical H_th(λ) value agrees well with the experimentally measured value. Using this simple critical distance stress approach we estimated the fretting fatigue-crack initiation criteria for any contact edge angle and optimized the contact edge geometry. Moreover, we can apply this new strength criterion to stress singularity fields for general stress-concentration structures.     

Degradation behavior of polymer blend of isotactic polypropylenes with and without unsaturated chain end group

In this work, the relationship between the unsaturated chain end group content and the thermal oxidative degradation rate was systematically studied with binary polymer blends of isotactic polypropylene (iPP) with and without the unsaturated chain end group. The iPPs with and without the unsaturated chain end group were synthesized by a metallocene catalyst in the absence of hydrogen and by a Ziegler catalyst in the presence of one, respectively. The thermal oxidative degradation rate of the binary iPP blends was estimated from the molecular weight and the apparent activation energy (ΔE), which were obtained through size exclusion chromatography (SEC) and thermogravimetric analysis (TGA) measurements, respectively. These values exhibited a negative correlation against the mole content of the unsaturated chain end group. The thermal oxidative degradation rate apparently depends on the content of the unsaturated chain end group. This tendency suggests that the unsaturated chain end acts as a radical initiator of the iPP degradation reaction.     

Effects of various poisoning compounds on the activity and stereospecificity of heterogeneous Ziegler–Natta catalyst

A TiCl₄/ethylbenzoate/MgCl₂ Ziegler–Natta catalyst was pretreated with chemically different poisoning compounds to investigate their effects on the catalyst activity and stereospecificity for propylene polymerization. The poisoning power on the activity was in the order of methanol > acetone > ethyl acetate. A kinetic analysis using the stopped-flow method revealed that addition of the poisoning materials decreased the activity through the reduction of the number of active sites, whereas the catalyst isospecificity was hardly affected by these materials.     

Control of surface migration of gold particles on Si nanowires

On the surface of silicon nanowires (SiNWs) synthesized by gold (Au)-catalyzed chemical vapor deposition (CVD), Au particles 5-20 nm in diameter are formed if the growth conditions are within a specific range. We studied the mechanism of Au particle formation by growing SiNWs under different conditions, specifically by dynamically changing the growth parameters during the growth process. We show that insufficient supply of Si source to the Au-Si eutectic on top of the SiNWs enhances the migration of Au atoms on the surface of SiNWs in the form of Au-Si eutectic, which is precipitated on the surface as Au particles during cooling. We also show that using Au-Si eutectic on the surface of SiNWs as a catalyst enables one-step growth of branched SiNWs.     

Distribution of active impurities in single silicon nanowires

The distribution of electrically active B concentration in single SiNWs (nanowires) grown by a vapor-liquid-solid (VLS) process was studied by analyzing Fano resonance in Raman spectra. We found a gradient of active B concentration along the growth direction; the B concentration was the largest at the substrate side and the smallest at the catalyst side. The observed concentration gradient suggests the conformal growth of a high B concentration layer during a VLS process. To confirm this effect, we grew SiNWs with controlled impurity profiles, that is, p-type/intrinsic ( p-i) and intrinsic/ p-type ( i-p) SiNWs, by controlling the supply of B source during SiNWs growth. We found that p-i SiNWs can be grown by just stopping the supply of B source in the middle of the growth, while i-p SiNWs were not realized; that is, the whole region of nominal " i-p" SiNWs was B-doped even if we started the supply of B source in the middle of the growth. These results confirm the above doping model. We also found that the distribution of active B concentration was significantly modified by high temperature annealing. By annealing at 1100 degrees C for 1 min, B concentration became almost uniform along 10 mum long SiNWs irrespective of initial B profiles. This suggests very efficient diffusion of B atoms in a defective high B concentration surface layer of SiNWs.     

Theoretical and experimental analysis of leakage current in InGaAsPBH lasers with p-n-p-n current blocking layers

The dependence of the leakage current in 1.3-μm InGaAsP buried heterostructure (BH) lasers with p-n-p-n current blocking layers on well number, mesa width, and carrier density has been analyzed using a two-dimensional device simulator and compared with the electroluminescence (EL) emitted from InP layers. The analysis of the minority carrier flow reveals that the electron current flowing through the p-n-p-n current blocking layers is the dominant component of the leakage current. The measured EL intensity has two peaks at both sides of the n-blocking layer apart from the active layer. The EL intensity decreases with increasing well number and carrier density of the p-blocking layer, and increases with increasing mesa width. These results are consistent with the simulations     

Modeling and optimization of steam dryer for removal of lead–bismuth droplets

Removal of lead–bismuth droplets from steam flow is a crucial issue in the direct contact boiling lead–bismuth cooled fast reactor. Droplets are generated due to the boiling of water directly in the reactor chimney, where steam for the turbine is generated. The droplets could severely damage the turbine and therefore a steam dryer is used for their removal. This paper presents an optimization of the main steam dryer geometrical parameters and steam inlet velocity. The Lagrangian method is used, in which first the steam flow field is developed using the CFD code FrontFlow/Red and then the particle motion is simulated. It was found that the reduction of the plate spacing can improve the steam dryer performance without a significant increase of pressure drop, the wane pitch has a value after which the steam dryer performance is not significantly improved, the number of wanes of 1.5 was selected at this point, however, a more detailed model is necessary to arrive at the final conclusion. The optimum steam inlet velocity should be found using a detailed economical assessment. Velocities between 2 and 4 m/s seem to be reasonable to achieve good removal efficiency and keep the pressure drop at reasonable values.     

Development of a Method of Measuring β-D-Glucan and Its Use in Preemptive Therapy for Invasive Fungal Infections

Invasive fungal infections (IFIs) are serious infections that develop in conjunction with neutropenia after chemotherapy for acute leukemia or with hematopoietic stem cell transplantation. Conventionally, empirical antifungal therapy was recommended to treat IFIs for patient safety despite a lack of evidence of fungal infections. However, many studies have indicated that antifungals were not necessary for over half of patients, and several detriments of empirical therapy were noted, e.g., antifungals caused adverse reactions, an increase in drug-resistant fungi was a possibility, and medical costs soared. β-D-glucan (BDG) is a component of clinically important fungi such as Aspergillus and Candida. The G-test was developed in Japan as a way to measure BDG in serum using a coagulation factor from the blood of the horseshoe crab. Pre-emptive antifungal therapy based upon serodiagnosis with a BDG or galactomannan assay and CT imaging has been introduced. With pre-emptive antifungal therapy, the prognosis is equivalent to that with empirical therapy, and the dose of the antifungal has been successfully reduced. Measurement of BDG has been adopted widely as a method of diagnosing IFIs and is listed in the key guidelines for fungal infections and febrile neutropenia.