Raman spectroscopy as a tool for measuring mutual-diffusion coefficients in hydrogels

Raman spectroscopy has been exploited to characterize the diffusion properties of solutes in hydrogels. Raman active vibrations were used as intrinsic probes of the solute concentration along gel cylinders. The resulting one-dimensional solute distribution, characterized as a function of both time and space, could be analyzed with a model based on Fick's diffusion law, and the mutual-diffusion coefficient (Dm) was then determined. To illustrate the potential of this approach, we measured the Dm of two polyethylene glycols (PEG) in Ca-alginate gels. In this case, the intensity of the CH stretching band was used to obtain the concentration profiles of PEGs, whereas the OH stretching band of water was used as an internal intensity standard. In addition to providing a straightforward approach to measuring diffusion coefficients, the Raman profile analysis provides information relative to the accessibility of gels to large molecules. As an example, it was found that the PEG penetration in Ca-alginate gels was restricted, a phenomenon that was dependent on PEG size. The Raman technique presented here effectively characterizes transport properties of solutes in gels, and such characterization is required for developing several technical applications of gels, such as their use as materials for controlled release of drugs.     

Enrichment of (8,4) Single‐Walled Carbon Nanotubes Through Coextraction with Heparin

Heparin sodium salt is investigated as a dispersant for dispersing single‐walled carbon nanotubes (SWNTs). Photoluminescence excitation (PLE) spectroscopy is used for identification and abundance estimation of the chiral species. It is found that heparin sodium salt preferentially disperses larger‐diameter Hipco SWNTs. When used to disperse CoMoCAT nanotube samples, heparin has a strong preference for (8,4) tubes, which have larger diameter than the predominant (6,5) in pristine CoMoCAT samples. PLE intensity due to (8,4) tubes increases from 7% to 60% of the total after threefold extractions. Computer modeling verifies that the complex of (8,4) SWNTs and heparin has the lowest binding energy amongst the four semiconducting species present in CoMoCAT. Network field‐effect transistors are successfully made with CoMoCAT/heparin and CoMoCAT/sodium dodecylbenzene sulfonate (SDBS)–heparin (x3), confirming the easy removability of heparin.     

Detection of Methomyl,a Carbamate Insecticide,in Food Matrices Using Terahertz Time-Domain Spectroscopy

The aim of this study was to investigate the feasibility of detecting methomyl, a carbamate insecticide, in food matrices (wheat and rice flours) using terahertz time-domain spectroscopy (THz-TDS). In the frequency range 0.1–3 THz, the characteristic THz absorption peaks of methomyl at room temperature were detected at 1 (33.4 cm^?1), 1.64 (54.7 cm^?1), and 1.89 (63.0 cm^?1)?THz. For detailed spectral analysis, the vibrational frequency and intensity of methomyl were calculated using solid-state density functional theory to mimic molecular interactions in the solid state. Qualitatively, the simulated spectrum was in good agreement with the experimental spectrum. Analysis of the individual absorption modes revealed that all of the features in the THz spectrum of methomyl were mainly generated from intermolecular vibrations. The peak appearing at 1 THz (33.4 cm^?1) was then selected and tested for its suitability as a fingerprint for detecting methomyl in food matrices. Its absorbance was dose-dependently distinguishable from that of wheat and rice flours. The calibration curve of methomyl had a regression coefficient of >0.974 and a detection limit of <3.74 %. Accuracy and precision expressed as recovery and relative standard deviation in interday repeatability were in the ranges 78.0–96.5 and 2.83–4.98 %, respectively. Our results suggest that THz-TDS can be used for the rapid detection of methomyl in foods, but its sensitivity needs to be improved.     

Preparation and evaluation of poly(2-hydroxyethyl aspartamide)-hexadecylamine-iron oxide for MR imaging of lymph nodes

The purpose of this study was to synthesize biocompatible poly(2-hydroxyethyl aspartamide)–C₁₆-iron oxide (PHEA-C₁₆-iron oxide) nanoparticles and to evaluate their efficacy as a contrast agent for magnetic resonance imaging of lymph nodes. The PHEA-C₁₆-iron oxide nanoparticles were synthesized by coprecipitation method. The core size of the PHEA-C₁₆-iron oxide nanoparticles was about 5 to 7 nm, and the overall size of the nanoparticles was around 20, 60, and 150 nm in aqueous solution. The size of the nanoparticles was controlled by the amount of C₁₆. The 3.0-T MRI signal intensity of a rabbit lymph node was effectively reduced after intravenous administration of PHEA-C₁₆-iron oxide with the size of 20 nm. The in vitro and in vivo toxicity tests revealed the high biocompatibility of PHEA-C₁₆-iron oxide nanoparticles. Therefore, PHEA-C₁₆-iron oxide nanoparticles with 20-nm size can be potentially useful as T2-weighted MR imaging contrast agents for the detection of lymph nodes.     

Electrical conductivity of the Al-stabilized La<Subscript>2/3</Subscript>TiO<Subscript>3</Subscript>

A-site deficient lanthanum titanate (La_2/3TiO₃) materials with perovskite structure are attractive due to their electrical applications such as ion conductors and dielectrics. However, its stability at room temperature in air is obtained only if Na or Li etc. is incorporated into La site or Al into Ti site. In this study, the electrical conductivities of La_0.683(Ti_0.95Al_0.05)O₃ have been measured in oxygen partial pressure (Po₂) between 1 and 10⁻¹⁸ atm at 1000~1400°C. The electrical conductivity exhibited −1/4, −1/6 and −1/5 dependence (log σ ∝ log , n = −1/4, −1/6, −1/5) depending upon temperature and Po₂. The defect model explaining the observation was proposed and discussed. The chemical diffusion coefficient was estimated from the electrical conductivity relaxation.     

Discomfort luminance level of head-mounted displays depending on the adapting luminance

The Images in an immersive head-mounted display (HMD) for virtual reality provide the sole source for visual adaptation. Thus, significant, near-instantaneous increases in luminance while viewing an HMD can result in visual discomfort. Therefore, the current study investigated the luminance change necessary to induce this discomfort. Based on the psychophysical experiment data collected from 10 subjects, a prediction model was derived using four complex images and one neutral image, with four to six levels of average scene luminance. Result showed that maximum area luminance has a significant correlation with the discomfort luminance level than average, median, or maximum pixel luminance. According to the prediction model, the discomfort luminance level of a head-mounted display was represented as a positive linear function in log₁₀ units using the previous adaptation luminance when luminance is calculated as maximum area luminance.     

Fabrication of a pilot scale module of thin film composite hollow fiber membrane for osmotic pressure‐driven processes

Polyamide thin film composite hollow fiber membranes have advantages in their unique structure compared to flat sheet membranes. This study examined interfacial polymerization methods for fabricating pilot scale hollow fiber membranes (membrane area: 1.2 m², number of hollow fiber strands: 1200). For use in osmotic pressure‐driven processes, a one‐pot hydrophilic interfacial polymerization procedure was developed simultaneously to modify the surface property and synthesize polyamide thin film. With the procedure, a pilot scale module has a water flux of 13 LMH using a draw solution of 0.6M NaCl and a feed solution of distilled water through the design of the module configuration. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46110.     

Maximum production of methanol in a pilot-scale process

Mathematical models for both bench- and pilot-scale methanol synthesis reactors were developed by estimating the overall heat transfer coefficients due to different heat transfer characteristics, while the effectiveness factor was fixed because the same catalysts were used in both reactors. The overall heat transfer coefficient of a pilot-scale reactor was approximately twice that of a bench-scale reactor, while the estimate from the correlation reported for the heat transfer coefficient was 1.8-times higher, indicating that the values determined in the present study are effective. The model showed that the maximum methanol production rate of approximately 16 tons per day was achievable with peak temperature maintained below 250 °C in the open-loop case. Meanwhile, when the recycle was used to prevent the loss of unreacted gas, peak temperature and production rate decreased due to low CO and CO₂ fraction in the recycled stream at the same space velocity as the open-loop operation. Further analysis showed that, since the reaction was in the kinetic regime, the production rate could be maximized up to 18.7 tons per day by increasing the feed flowrate and inlet temperature despite thermodynamically exothermic reaction.     

Aromatization of propane over Zn/HZSM-5 catalysts prepared by chemical vapor deposition

Zinc was introduced into HZSM-5 by chemical vapor deposition (CVD) to investigate the catalytic properties of Zn/HZSM-5 for propane conversion. Irrespective of catalytic precursor or ion exchange method, protons were found to be replaced by Zn ions. However, Zn species in the zeolite were different depending on the precursors used. Although the addition of Zn decreased the intensity of the BrÕnsted acidity, it did not caused the apparent formation of Lewis acid sites unlike Ga/HZSM-5 catalysts. On Zn/HZSM-5, both Zn and protons intervene in propane activation step.