Structural defects created on natural graphite surface by slight treatment of oxygen plasma: – STM observations –

The creation of structural defects on natural graphite surfaces by slight treatment of oxygen plasma was studied by scanning tunneling microscopy (STM) at nanoscopic scale. Most of the defects were vacancies with the depth of one or two layers, while the mean number of defects per μm² of graphite surface and the mean area of defects increased with the increase in input power, time and temperature of the irradiation. After very slight treatment at room temperature, single carbon atom vacancies were obtained on graphite surfaces with a percentage more than 50%, though some large vacancies were formed. After slight irradiation at a high temperature (400°C), an agglomeration of defects occurred (the mean area increases whereas the defect density decreases), while the defects once formed were difficult to be annealed by heating at high temperatures up to 400°C in vacuum. The present work showed the possibility to control the modification of natural graphite surfaces for further applications by changing the condition of oxygen plasma treatment.     

Effect of Fatty Acid Composition of Monoglycerides and Shear on the Polymorph Behavior in Water-in-Palm Oil-Based Blend

Effect of the fatty acid composition of monoglycerides and shear on the polymorphic behavior in a water-in-oil (W/O) emulsion semi-solid fats blend was investigated. The bulk fat blend and the W/O emulsion fat blend with added either unsaturated or saturated monoglycerides were prepared using a rapid cooling heat exchanger, and the polymorphic transitions from β′ to β-form during storage were compared by X-ray diffraction. The peak intensity of the β-polymorph of the samples with added saturated monoglycerides was stronger than that of unsaturated monoglycerides, and the peak intensity of the β-polymorph of the W/O fat blend emulsions was stronger than that of the bulk fat blends. The polymorphic transition to the β-form during storage of the W/O emulsion fat blend was promoted by the applied shear. In contrast, that of the bulk fat blend was retarded by shear. These results suggested that fatty acids, which combined to monoglycerides on the surface of water droplets, influenced the polymorph transformation of the fat crystal network in a continuous semi-solid fat phase because of the acyl–acyl interactions between the fatty acid residues of the monoglycerides and triacylglycerols in the fat crystal network.     

Electron microscope study of the formation of graphitic nanostructures in nickel-loaded wood char

We investigated the graphitization of carbonized larch wood chars impregnated with aqueous solution of nickel acetate, using scanning electron microscopy (SEM), both in secondary and transmission modes, and high-resolution transmission electron microscopy (HRTEM). Heat treatment of the chars at 500 °C brought about homogeneous distribution of metallic Ni particles about 5 nm in size in the amorphous carbon matrix. Graphitization sporadically started at this temperature, and some of the Ni particles are aggregated. SEM observations on chars heat-treated at 900 °C suggested that graphitic nanoshells about 50–200 nm in diameter, formed by catalytic effects of the Ni particles, grow in a “meandering” manner inside the amorphous carbon matrix. Some graphitic protrusions are found to grow outwards. Upon removal of the residual amorphous carbon matrix, long chains of the graphitic nanoshells exhibited a three-dimensionally intertwined structure, while transmission SEM showed that the interior of the shells is empty. HRTEM images exhibited not only stacked graphitic layers, but also cross-sectional contrasts expected from the hexagonal net of the graphite structure. These findings are discussed from the viewpoints of processing parameters, such as the use of aqueous solutions and atmosphere, specific to the catalytic graphitization of lignocellulosic materials.     

Soil site response

The response of stiff quaternary soil sites to strong earthquake shaking is an important factor in the development of seismic siting criteria for nuclear power plants. Analytical methods for estimating this site response are in common use, but there is need for empirical verification of these modeling techniques. There are two dense 3-D strong motion arrays installed and operating in California to directly measure the response of stiff quaternary soil to earthquake shaking. These are the Hollister Earthquake Observatory and the Borrego Valley Downhole Arrays. Site response measurements from these arrays, along with detailed geotechnical and geophysical site investigations, will provide important calibration and confirmation of site response modeling techniques used for seismic siting criteria development. This paper presents an overview of the two arrays and initial results of the measurements.     

Dynamic actuation and sensing micro-device for mechanical response of cultured adhesive cells

As one of the cellular responses to external mechanical stimulation, it is presumable that the cell adjusts the cytoskeletal mechanical strength globally as well as locally. However, the methodologies to validate this hypothesis are extremely limited and expensive. In this study, a new micro device, utilizing dynamic response of a piezoelectric vibrator, is developed, which works not only to evaluate local mechanical property, but also to enforce local mechanical stimulation onto cultured living adhesive cells. Experimental studies have been carried out by applying actin (the major component of cytoskeleton) polymerization inhibitor, cytochalasin D, to normal human osteoblast. The studies show the present device’s sensing capability to detect changes of mechanical property, induced by external mechanical stimulation, of cultured normal human osteoblast. Also, the method shows that the cellular response against static and dynamic mechanical stimulation differs depending on the condition of actin cytoskeleton.     

Fabrication of Cu(Ti) Alloy Interconnects with Self-Formation of Thin Barrier Metal Layers Using a High-Pressure Annealing Process

Copper interconnects with self-formed thin TiSi _x O _y barrier layers were successfully fabricated by sequentially depositing Cu(7 at.%Ti) alloys and pure Cu films on SiO₂-based substrates with 0.1-μm-wide trenches, and embedding the samples using a high-pressure annealing technique at 550°C and 195 MPa. Microstructural analyses revealed that the self-formed Ti-rich layers with thicknesses of about 5 nm were uniformly formed on the trench bottom and sidewall. In addition, these layers were thermally stable against Cu diffusion into the SiO₂-based interlayers. The present study suggests that the Cu-Ti alloy is one of the best candidates among possible interconnect and/or seed layer materials.     

The development of computational chemistry approach to predict the viscosity of lubricants

Sophisticated machinery requires the development of new lubricants that realize friction-less contact, perfect transmittance of torque, and so on. However, experimental approaches have needed long time to find new lubricants. Therefore, the prediction of lubricant properties by computational chemistry should be crucial to accelerate the design of lubricants. This study treats precise evaluation of viscosity employing molecular dynamics simulation and prediction based on neural network.     

Regression of metastatic liver tumors in rats treated with angiogenesis inhibitor TNP-470: occurrence of apoptosis and necrosis

To clarify the mechanism of the reduction of metastatic liver tumors in rats treated with angiogenesis inhibitor TNP-470, the death of tumor cells was examined pathologically and ultrastructurally. Liver metastases were developed by intravenous injection of AH-130 cells. TNP-470 was given subcutaneously after tumor cell injection. Alterations in the size and number of metastatic tumors were examined at various time points, in association with the analysis of cell death pattern. The metastatic nodules were divided into 4 groups according to the morphological patterns of cell death; no cell death, scattered apoptosis, central necrosis, and diffuse necrosis. The number and size of the metastatic tumors at 2 weeks in untreated rats were larger than those in treated rats. The number of tumors in untreated rats decreased, but the tumor size increased. All rats treated with TNP-470 were alive and free from tumors after 4 weeks, whereas all the untreated rats died of liver metastases. The percentages of the tumors with necrosis in untreated rats (61.2% at 2 weeks and 100% at 4 weeks) were significantly higher than that (31.8% at 2 weeks) in treated rats (P < 0.01). The percentage of the tumors containing apoptotic cells in treated rats was significantly higher than that in untreated rats (54.5% vs. 30.6%; P < 0.05). The growth of metastatic tumors without treatment might be faster than the growth of vessels in untreated tumors, resulting in central necrosis due to ischemia. On the other hand, the reduction of metastatic liver tumors treated with TNP-470 might be caused by inhibition of angiogenesis, providing a weak ischemic stimulus which triggers apoptosis, rather than by a direct cytotoxic effect on tumor cells, because previous in vivo experiments demonstrated that TNP-470 affected endothelial cells but not tumor cells.     

Securing an optimum operating field without undesired tissue damage in neurosurgery

In neurosurgery, surgeons sometimes retract brain tissue to prepare an operating field around a lesion. In addition, they are required to plan a safe surgical pathway for deep-brain regions while considering tissue damage caused by excessive stress. The goal of this study is to develop a technique for automatically generating a surgery pathway for lesions in the deep-brain region, focusing on securing an operating field around the lesion as a first step and also considering brain tissue deformation. In previous studies, securing the operating field has been treated as a single-objective optimization problem in order to maximize the viewable area of the lesion. However, in this study, the task of securing the operating field is formulated as a multi-objective optimization problem. Using a technique that combines finite element analysis and an optimization method, the principal stress on the brain is constrained to less than a certain threshold value, and the position and orientation of the surgical instrument are optimized for safe retraction of the brain according to various weighting factors.