Chemical force microscopy of microcontact-printed self-assembled monolayers by pulsed-force-mode atomic force microscopy

A novel chemically sensitive imaging mode based on adhesive force detection by previously developed pulsed-force-mode atomic force microscopy (PFM-AFM) is presented. PFM-AFM enables simultaneous imaging of surface topography and adhesive force between tip and sample surfaces. Since the adhesive forces are directly related to interaction between chemical functional groups on tip and sample surfaces, we combined the adhesive force mapping by PFM-AFM with chemically modified tips to accomplish imaging of a sample surface with chemical sensitivity. The adhesive force mapping by PFM-AFM both in air and pure water with CH3- and COOH-modified tips clearly discriminated the chemical functional groups on the patterned self-assembled monolayers (SAMs) consisting of COOH- and CH3-terminated regions prepared by microcontact printing (microCP). These results indicate that the adhesive force mapping by PFM-AFM can be used to image distribution of different chemical functional groups on a sample surface. The discrimination mechanism based upon adhesive forces measured by PFM-AFM was compared with that based upon friction forces measured by friction force microscopy. The former is related to observed difference in interactions between tip and sample surfaces when the different interfaces are detached, while the latter depends on difference in periodic corrugated interfacial potentials due to Pauli repulsive forces between the outermost functional groups facing each other and also difference in shear moduli of elasticities between different SAMs.     

Evaluation of Anti-Wear Performance of PFPE-Soluble Additives under Sliding Contact in High Vacuum

The anti-wear performances of perfluoropolyether (PFPE)-soluble additives were evaluated under vacuum using a vacuum four-ball tribometer with 440C stainless steel balls as test specimens. PFPE derivatives having the hydroxyl, carboxyl and phosphate groups at the end of the Type D-PFPE molecules were studied. The addition of either PFPE-soluble carboxylic acid or PFPE-soluble phosphates to the PFPE base oil remarkably reduced steady wear rates in a vacuum environment, whereas the addition of PFPE-soluble alcohol did not. Contrary to the performance in vacuum, an appreciable increase in wear rate was observed in the air atmosphere with all the types of additives used. The effect of moisture is studied in explaining the high wear rates obtained with the additives in the air environment. The mechanism of boundary lubrication with PFPE-soluble additives is discussed.     

Promotion of Anti-Wear Property of Sodium Stearate by Oxygen and Surface Active Agents

The anti-wear properties of a water-based lubricant were studied using a newly designed friction tester which enabled the rubbing with nascent surface under controlled atmospheres. Sodium stearate considerably reduced the wear of steel in oxygen rich atmospheres.

Supplementary adsorption tests were performed to identify the anti-wear film formed on the rubbed surface. Surface analysis by Fourier transform infrared spectroscopy (FTIR) revealed that metal stearate film was heavily formed on the rubbed surface in oxygen rich atmospheres. The measurement of metal elements in the protective film by atomic absorption spectroscopy clarified that the main constituent of the film was iron stearate. These results of adsorption tests could support that iron stearate might prevent the wear of steel in the wear test.

It was observed that a surface active agent prevented the formation of lubricative oxide film, but when used with sodium stearate, it synergistically promoted the anti-wear property of sodium stearate. This was attributed to the fact that the surface active agent improved the permeability of recrystallized sodium stearate to the rubbing area.     

Dissolution characteristics of granulated coal ash in different saline water conditions

Granulate coal ash (GCA) has been widely used for improving both sediment and water environments in littoral regions. Dissolved ions from GCA have been pointed out to play an important role in the improvements of sediment and water environments. As the dissolution characteristics of a material in solvent depend on the solvent characteristics, this study attempts to clarify the dissolution characteristics of GCA under different saline water conditions. This may provide useful information for practical uses of GCA in different water environments. The experimental results showed that GCA dissolved more with increasing salinity of solvent. This suggests that GCA is more active in saline water environment rather than freshwater environment. Interestingly, larger releases of calcium ions were confirmed when the solvent salinity was higher than 1000?mg/L. This was because the calcium ions of calcium silicate hydrate (C–S–H) present in GCA were replaced by the sodium ions present in solvent. The solubility of C–S–H present in GCA was low comparing with that of C–S–H gels. Only 40% of the total C–S–H were influenced by the high salinity concentration (higher than 1000?mg/L). Furthermore, a higher solubility of GCA was observed after combusting GCA. Our results suggest that GCA should be combusted at 200?°C prior to use for obtaining a higher performance in improving water and sediment environments.     

Voltage-time and voltage-number characteristics of insulation elements with oil-filled transformers in EHV and UHV classes

In order to attain reduction in insulation test voltages, voltage-time (V-t) characteristics under AC voltage and voltage-number (V-N) characteristics under lightning impulse and switching impulse voltages were experimentally investigated on the turn-to-turn insulation model, section-to-section insulation model and barrier-oil-duct insulation model of core- and shell-type transformers in EHV and UHV Classes. First, V-t characteristics for AC voltage were obtained in a short time range of a few tens of milliseconds to a long time range of three to four months. The n-values (inclination) of V-t characteristics are distributed around 40 for the short time and several hundreds for the long time characteristics. These values are of essence in determining the AC withstand voltage test. Next, V-N characteristics for both lightning and switching impulse voltages were acquired for up to 1,000 times of application. The n-values (inclination) of V-N characteristics are in most cases distributed around 70 for both impulse waveforms and about 40 in only turn-to-turn insulation models This result will be useful for evaluating the effect of frequent surges on apparatus insulation. Finally, insulation coordination studies were performed based on these experimental results.     

Induction of gastric lesions and hypoglycemic response by food deprivation in streptozotocin-diabetic rats

Overnight fasting causes hemorrhagic lesions in the stomach of streptozotocin (STZ)-induced diabetic rats, but the pathogenetic mechanism remains unknown. The present study was performed to investigate the pathogenesis of such lesions developed in STZ-diabetic rats after starvation, mainly in relation to blood glucose changes. A single injection of STZ (70 mg/kg, intraperitoneally) induced hyperglycemic conditions one week after the administration, and high blood glucose levels (BGL: > 350 mg%) remained up to three weeks later. The STZ-diabetic rats developed gastric lesions with the marked reduction of BGL after 18 hr of fasting, depending upon the duration of diabetes; the lesion score and delta BGL reduction in the 3-week-old STZ rats were 32.0 +/- 7.8 mm and > 250 mg/100 ml, respectively. Acid secretion in the pylorus-ligated rats was not significantly changed in the STZ-induced diabetic conditions for the initial two weeks but slightly decreased at three weeks when compared with normal rats. Fasting of normal rats for 18 hr did not cause either BGL reduction or any lesion in the stomach. In the 3-week-old STZ animals, the severity of gastric lesions increased with the duration of fasting (4-18 hr) and was again closely associated with the degree of delta BGL reduction. These lesions induced by 18 hr of starvation in 3-week-old STZ rats were significantly inhibited by pretreatment with insulin (4 units/rat/day) for the last one week to maintain BGL within normal ranges or by intravenous infusion of 25% glucose during fasting period. Both of these treatments significantly prevented BGL reduction in response to fasting.(ABSTRACT TRUNCATED AT 250 WORDS)