Investigation of oxidation inhibition properties of vaporized self-assembled multilayers on copper nanopowders

Stability against oxidation was investigated for vaporized self-assembled multilayers on nano-sized Cu powders. 100 nm-sized copper powders were coated with 1-octanethiol to make a passivation layer against oxidation.As a result, the surface resistivity of the coated and uncoated nano-sized copper powders differed by two orders of magnitude. XPS analysis was used to monitor changes in the amount of sulfur and oxygen on the surface of octanethiol-coated Cu nano powders over a period of time. While sulfur was detected for up to 75 days, the amount of oxygen increased dramatically after 35 days, indicating sign of partial oxidation. Furthermore, HR-TEM images showed that the octanethiol film was consistently 10 nm thick, for up to 35 days. After 35 days exposure to the air, the octanethiol film was partially damaged and its diffraction pattern detected the presence of Cu₂O. Based on these findings, vaporized octanethiol coating protected the copper nano powders from oxidation for up to 35 days. Therefore this oxidation inhibition property of VSAMs coating method on Cu powders achieves a great milestone toward inkjet printing technology.     

LC-UV Column-Switching for Quantitation of Vitamin K1 in Infant Formula

This study was undertaken in order to develop an analytical method for vitamin K₁ in infant formula. The content of vitamin K₁ was investigated by using a column-switching LC-UV method. A Certified Reference Material sample of infant formula containing 0.94 ± 0.04 mg kg^?1 of vitamin K₁ was extracted with hexane followed by enzymatic digestion of fat and precipitation of the fatty acids. The linearity of this method was calculated using five consecutive standard curves, and the coefficient of determination (r ²) was found to be 0.9995. The limit of detection (LOD) and the limit of quantitation (LOQ) was 3.31 and 11.12 μg L^?1, respectively. The accuracy of intra- and inter-day measurements was in the range from 96.67 to 108.67%, and the precision of intra- and inter-day measurements was less than 5.13%. The recoveries were 109.27 ± 5.92%, and the recoveries of inter-laboratory results were in the range from 97.59 ± 1.29 to 109.27 ± 5.92%. The newly developed method uses the optimum conditions required to determine the content of vitamin K₁ in infant formula.     

Non-Invasive Measurements of Thickness of Superconductor Films by Using Two-Resonant-Mode Rutile Resonator

The film thickness should be known for extrazting the intrinsic surface resistance from the effective surface resistance as measured by using the dielectric resonator method. Thicknesses of 70 nm to 360 nm are measured for YBa2 Cu3 O7-δ films in a non-invasive way by using the two-resonant-mode dielectric resonator （TDR） method. A futile resonator with the respective resonant frequencies of 15.25-15.61 GHz and 15.10-15.37 GHz for the TE021 and the TE012 modes is used for this purpose. Differences between the values as measured by using the TDR technique and those measured by using a step profilometer appear to be less than 3%, which is smaller than the previous value of 5% as measured by using a 8. 6 GHz single-resonance mode futile resonator [Lee et al. J. Korean Phys. Soc. 54（2009）1619]. Merits of using the TDR method are discussed.     

Photoreversibly switchable superhydrophobic surface with erasable and rewritable pattern

We report the facile fabrication of a functional nanoporous multilayer film with wettability that is reversibly tunable between superhydrophobicity and superhydrophilicity with UV/visible irradiation. Our approach controls surface roughness with an electrostatic self-assembly process and makes use of the photoresponsive molecular switching of fluorinated azobenzene molecules. Selective UV irradiation onto the nanostructured substrate was used to realize substrates with erasable and rewritable patterns of extreme wetting properties. Our findings will open up new avenues for external stimuli-responsive smart surfaces.     

Soft ordered semigroups

Molodtsov introduced 1999 the concept of soft set as a new mathematical tool for dealing with uncertainties that is free from the difficulties that have troubled the usual theoretical approaches. In this paper we apply the notion of soft sets by Molodtsov to ordered semigroups. The notions of (trivial, whole) soft ordered semigroup, soft ordered subsemigroup, soft left (right) ideal, and left (right) idealistic soft ordered semigroup are introduced, and various related properties are investigated (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Evaluation of radioactivity induced by patient-specific devices in proton therapy

Journal of the Korean Physical Society - Estimating the radioactivity induced by patient-specific devices installed near the patient skin is important, because patients are directly exposed during...     

Radiation-induced thermoluminescence characteristics of feldspar upon different heat and microwave treatments

Feldspar minerals are well-known markers for thermoluminescence (TL)-based identification of irradiated foodstuff because of their high TL sensitivity and characteristic TL glow curves. Post-irradiation processing, particularly heating, may affect luminescence properties. In the present study, the effect of boiling, roasting, and microwave treatments on TL properties of irradiated (0, 5, and 10 kGy) feldspar was investigated. The TL glow peak faded (TL peak maxima shift towards higher temperature) upon boiling or roasting, which was mainly dependent upon treatment temperature and time. This effect was most apparent in the roasted samples. Liquid samples showed more changes in TL characteristics than solid samples upon microwave treatment; however, the effect was less prominent compared to those of roasting and boiling. TL ratios could not confirm the TL results when boiled and roasted samples were treated at ≥100 °C, whereas the microwave treatment showed a negligible effect on the TL ratio.     

Critical Evaluation of the Microwave Effect on Radical (Co)Polymerizations

Critical evaluations of the microwave effect on initiation, propagation, and termination during conventional radical polymerizations (RPs) of methyl methacrylate (MMA) and random copolymerization of styrene (St) with (meth)acrylates are examined by comparing microwave heating (MWH) and conventional heating (CH). Poly(methyl methacrylate) with similar , / , and conversion are obtained under precisely controlled temperature, indicating very small changes of propagation rate constant. Rate enhancement in the absence of precise temperature control is mostly due to the higher reaction temperature of the reaction mixture than the apparent value indicated on display. Rates of initiator decomposition under well‐controlled temperature are essentially the same for MWH and CH.