Channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories

The channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories is investigated. While the trapped charge profile-dependent overerasure is observed in 10-μm-wide device, it is suppressed in 0.22-μm-wide device. Both the overerasure suppression and gradual positive threshold voltage shift in narrow device are explained as an elevated hot hole injection efficiency followed by more pronounced redistribution of the hole profile in the channel-center and the suppression of the lateral migration of injected holes in the channel-edge, by combining the measured endurance characteristics and TCAD simulation results. Main physical mechanisms are three-dimensional distribution of the electric field by gate/drain voltage, increasing interface states, and their trapped charge with cycling in the channel-edge.     

Characterization and antimicrobial activity of sweetpotato starch-based edible film containing origanum (Thymus capitatus) oil

The objectives of this research were to characterize the mechanical and barrier properties of sweetpotato starch (SPS)-based film (SPSF) and to investigate the antimicrobial activity of SPSF containing origanum oil (OG) against foodborne pathogenic bacteria. The SPSF was fabricated with the SPS extracted from commercial sweetpotato roots. Tensile strength (TS), percent elongation at break (E), and water vapor permeability (WVP) were determined to characterize the SPSF fabricated with selected SPS concentrations, plasticizers, and the concentrations of plasticizers. The agar diffusion assay was used to determine the antimicrobial activity of SPSF containing selective concentrations of OG against Salmonella Enteritidis, Escherichia coli O157:H7, and Listeria monocytogenes. The SPSF fabricated with 2.5% SPS exhibited the greatest TS (4.58 MPa). The TS, E, and WVP of SPSF plasticized with 40% sorbitol exhibited 7.96 MPa, 77.92%, 0.212 ng m/m(2) S Pa, respectively. Therefore, the SPSF fabricated with 2.5% SPS and 40% sorbitol was determined as the optimum film. The antimicrobial activity of the SPSF containing OG increased as the concentration of OG increased. And the SPSF containing OG exhibited greater inhibitory effects against the gram-negative bacteria such as S. Enteritidis and E. coli O157:H7 than the gram-positive L. monocytogenes. The greatest antimicrobial activity was observed against S. Enteritidis when the SPSF containing 2% OG was applied, and the maximum square of zone width was 18.43 mm(2).     

Controlled synthesis of gold nanoparticles by fluorescent light irradiation

A novel photochemical synthesis of size-controlled gold nanoparticles was reliably accomplished via both a direct reduction and a seeded-growth method at room temperature under the irradiation of fluorescent light. These methods utilized the intensity of fluorescent light that closely resembles daily sunlight (～100 mW cm(-2)). This effectively allowed for the formation of gold nanoparticles with tunable sizes simply by controlling the concentration of trisodium citrate and gold chloride. The broad band fluorescent light was found to be an efficient source for inducing the formation of gold nanoparticles at ambient conditions. The size distribution and absorption property of the resulting nanoparticles were thoroughly characterized by scanning/transmission electron microscopy, dynamic light scattering, UV-visible spectroscopy and powder x-ray diffraction. This photochemical synthesis demonstrates, for the first time, the reliable preparation of gold nanoparticles at room temperature upon irradiation with fluorescent light.     

Thermally tunable catalytic and optical properties of gold-hydrogel nanocomposites

We have developed a very simple approach for preparing physically embedded gold cores in a temperature-responsive hydrogel polymer nanoparticle under fluorescent light irradiation. The complete encapsulation of the multiple gold core nanoparticles is confirmed by the catalytic reduction of 4-nitrophenol, whose reactivity is significantly retarded above the lower critical solution temperature (LSCT) due to the deswelled polymer structure; its increased hydrophobicity slows the access of hydrophilic reactants to the cores. Since these gold cores are physically embedded in the polymer nanoparticles, further growth of the cores is reliably achieved in situ under light irradiation. Interestingly, the resulting composite nanoparticles exhibit reversible solution color changes as well as absorption bands from the visible to near-IR regions below and above the LSCT.     

High-throughput analysis of thin-film stresses using arrays of micromachined cantilever beams

We report on a technique for making high-throughput residual stress measurements on thin films by means of micromachined cantilever beams and an array of parallel laser beams. In this technique, the film of interest is deposited onto a silicon substrate with micromachined cantilever beams. The residual stress in the film causes the beams to bend. The curvature of the beams, which is proportional to the residual stress in the film, is measured by scanning an array of parallel laser beams generated with a diffraction grating along the length of the beams. The reflections of the laser beams are captured using a digital camera. A heating stage enables measurement of the residual stress as a function of temperature. As the curvature of each beam is determined by the local stress in the film, the film stress can be mapped across the substrate. This feature makes the technique a useful tool for the combinatorial analysis of phase transformations in thin films, especially when combined with the use of films with lateral composition gradients. As an illustration, we apply the technique to evaluate the thermomechanical behavior of Fe-Pd binary alloys as a function of composition.     

Single walled carbon nanotube based biosensor for detection of peanut allergy-inducing protein ara h1

Food allergies are global trending issues in the food industry. Peanut allergy is an especially serious problem with emerging allergen symptoms because peanuts are utilized worldwide as a processing food source. Arachis hypogaea 1 (Ara h1) is a main seed storage protein from peanut materials that derives allergic medical symptoms. In this study, a single-walled carbon nanotube (SWCNT)-based biosensor was developed to detect Ara h1. The developed biosensor utilizes an Ara h1 antibody as a receptor for the target material, SWCNTs as a signal transfer, and 1-pyrenebutanoic acid succinimidyl ester (1-PBSE) as a linker between the SWCNTs and the receptors. SWCNTs dramatically transferred the biological reaction between the antibody and the antigen into measurable signals of electrical responses. The sensor capacity of the developed SWCNT-based biosensor, including the limit of detection (LOD, 1 ng/mL), the detection range (1-1,000 ng/mL), and the washing amounts (three times), was confirmed.     

Wet surface heat transfer and pressure drop of aluminum parallel flow heat exchangers at different inclination angles

The effect of inclination angle on the heat transfer and pressure drop characteristics of brazed aluminum heat exchangers was experimentally investigated under wet conditions. Three samples having different fin pitches (1.25, 1.5 and 2.0 mm) were tested. Results show that heat transfer coefficients are not affected by the inclination angle. However, friction factors increase as the inclination angle increases with negligible difference between the forward and backward inclination. The effect of fin pitch on the heat transfer coefficient and on the pressure drop is also discussed. Comparison of the dry and wet surface heat transfer coefficients reveals that dry surface heat transfer coefficients are significantly larger than wet surface heat transfer coefficients. Possible explanation is provided by considering the condensate drainage pattern. The data are also compared with the existing correlation. This paper was recommended for publication in revised form by Associate Editor Man-Yeong Ha Nae-Hyun Kim is a Professor of Mechanical Engineering, University of Incheon. His area of interest spans boiling and condensation, heat transfer enhancement and heat exchanger design. He has been active in heat transfer community, and was a Chairman of Thermal Engineering Division of KSME. He holds several editorial position including Journal of Enhanced Heat Transfer. He is a recipient of Asian Academic Award awarded by SAREK and JSRAE.     

The study on the selective oxidation of H<Subscript>2</Subscript>S over the mixture zeolite NaX-WO<Subscript>3</Subscript> catalysts

At temperatures lower than 250 °C the deactivation of zeolite NaX catalyst occurred in the presence of water vapor. The gradual accumulation of water vapor on the surface of catalyst could cause deactivation of catalyst. The zeolite NaX-WO₃ catalysts were prepared to study a method preventing deactivation of catalysts from the adsorption of water vapor. The zeolite NaX-WO₃ (9 : 1) with a low content of WO₃ showed the highest conversion of H₂S. It is believed that the addition of WO₃ caused either a decrease of the strong adsorption of water vapor on the zeolite NaX or an increase of the reducibility of WO₃ by some interactions between zeolite NaX and WO₃. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

HPLC-MS/MS analysis of 9 artificial sweeteners in imported foods

An analytical method for the simultaneous determination of 9 artificial sweeteners (acesulfame-K, cyclamate, sodium saccharin, aspartame, alitame, neotame, sucralose, dulcin, and neohesperidine dihydrochalcone) in imported foods by HPLC-MS/MS was developed. Samples were extracted with buffer solution (pH 4.5). The supernatant was analyzed by HPLC-MS/MS after centrifugation and filtration. The sample was separated on a thermo hypersil BPS C₁₈ (250×3 mm, 5-μm) column, and detected by MS/MS with selective reaction monitoring (SRM) mode. The correlation coefficients (r ²) of the calibration curve were >0.99. The recoveries were 90.0–107.5% with good coefficients of variation of 1.8–8.6%. The limits of detection and limits of quantification were between 0.001 and 0.375 mg/mL and between 0.003 and 1.125 mg/mL, respectively. The proposed method has been successfully applied to the determination of the 9 sweeteners in various foods.

     

Stabilizing polymorphic transitions of tristearin using diacylglycerols and sucrose polyesters

The polymorphic transitions of synthesized tristearin in the presence of selected DAG or commercial sucrose polyesters (SPE) were investigated using DSC and X-ray diffractiometry. The stabilizing effects of DAG and SPE on α to β transitions of tristearin were dependent on the chemical structures of additives such as FA chain length, saturation of FA, positions and number of FA on backbones. The addition of 1,2-distearin (DS) or SPE containing 70% stearic acid with a hydrophile-lipophile balance value of 1 (S-170) to tristearin resulted in a significant stabilizing effect on the α to β transition during constant heating and storage of α forms at 53°C. The addition of 1,2-DS or S-170 also stabilized the β′ to β transitions of tristearin during constant heating and storage at 59°C. The addition of S-170 exhibited greater stabilizing effects than the addition of 1,2-DS during early stages of storage of α or β′ forms of tristearin. This study provides evidence of potential uses for SPE as additives to improve the quality and shelf life of foods containing fats by stabilizing the desirable α or β′ forms of fats.