Young H. Chang

Intracellular translocation of superparamagnetic iron oxide nanoparticles encapsulated with peptide-conjugated poly(D,L lactide-co-glycolide)

In this study, we propose the use of iron oxide nanoparticle encapsulated with peptide-conjugated poly(D,L lactide-co-glycolide) (PLGA) as a potent intracellular carrier for diagnosis agent. The iron oxide (γ‐Fe2O3) nanoparticles were prepared by a chemical coprecipitation method of ferric and ferrous ions in an alkali solution. Arg peptide (RRRRRRRRCK-FITC) were conjugated to the PLGA via a simple coupling reaction between maleimide-derivatized PLGA and thiol-terminated Arg peptide. The γ‐Fe2O3-PLGA-Arg-FITC nanoparticle was then prepared by an emulsification-diffusion technique. A confocal laser scanning microscopy revealed that the γ‐Fe2O3-PLGA-Arg-FITC nanoparticle was effectively adsorbed onto the membrane of stem cells and delivered into the nuclei without cytotoxicity. Magnetic properties of the γ‐Fe2O3-PLGA-Arg-FITC nanoparticle were observed by measuring the zero-field-cooled∕field-cooled magnetization and magnetic hysteresis loop using a superconducting quantum interference device magnetometer f...

NO2-sensing properties of octa(2-ethylhexyloxy) metallophthalocyanine LB films using quartz-crystal microbalance

Abstract Octa(2-ethylhexyloxy) metallophthalocyanines (MPcs) have been stacked in a multilayered form on aquartz-crystalmicrobalance(QCM) by using a Langmuir-Blodgett (LB) method. The NO 2 -sensing characteristics of these films are investigated in terms of the adsorption and desorption of NO 2 . The patterns of NO 2 adsorption show different sensing properties depending on the kind of central metal atoms. The adsorption capacities to NO 2 obtained from the saturation feature are 1.2 for H 2 Pc, 1.9 for CuPc, 0.7 for CoPc and 1.0 for PbPc. From the empirical adsorption kinetics study, the adsorption order and rate constant are also comparable, and CoPc had better sensing properties than the other three MPcs. However, the recovery of sensing output is hardly satisfactory even at high temperature (170 °C), and the absorbance spectra for repeated NO 2 exposures can give some insights into the irreversible feature of MPcs to NO 2 .

Third-order nonlinear optical properties of phthalocyanines in solution and in polystyrene films

Abstract Degenerate four-wave mixing (DFWM) measurements of third-order nonlinear optical (NLO) coefficients of metal-free, Cu, Pt, Pb and Bi octa(2-ethylhexyloxy) phthalocyanines (MPcs) were done with 20 ps duration laser pulses under resonant conditions at 532 nm in polystyrene films and under nonresonant conditions at 1064 nm in chloroform solutions. The NLO coefficients ξ xxxx (3) show saturation with increasing incident intensity and no strong dependence on the central metal atom of the MPc below the saturation intensity. Optical delays of the probe-pulse up to 3 ns show an acoustic phonon response in both the polystyrene films and the chloroform solutions. An intensity-dependent absorption coefficient was measured by a pump/probe experiment and used in a simple model to qualitatively account for the saturation of ξ (3) measured by DFWM.

Simplified syntheses of polymerizable bis-substituted phosphatidylcholines with various chain lengths

Abstract Syntheses of new compounds, 1,2-bis[15-(2′,4′-hexadienoyloxy)pentadecanoyl]- and 1,2-bis[15-(2′,4′-hexadienoyloxy)dodecanoyl]-sn-glycero-3-phosphatidylcholines, via a simplified procedure are reported. The new approach utilizes the conversion of commercially available lactones into polymerizable bis-substituted phosphatidylcholines after two steps of reaction.

Online Phase Tracking of Interferometric Optical Fiber Sensors for Vibration Control

Online phase tracking of an extrinsic Fabry—Perot interferometer (EFPI) and experimental vibration control of a composite beam with a sensing patch are investigated. EFPI sensors have nonlinearity due to their interferometric characteristics. We propose a new sensing patch for compensation of this interferometric nonlinearity. This newly developed sensing patch consists of an EFPI sensor and another sensor that can produce directional information. Therefore, it uses the advantages of their components used in conjuction in order to overcome the disadvantages of the components used separately. A sensing patch that comprises an EFPI sensor and a piezoceramic is fabricated, and the characteristics are experimentally investigated. A simple and practical logic is applied to real-time tracking of the optical phase of an interferometer. The experimental results show that the proposed sensing patch does not suffer from the nonlinear behavior of conventional EFPI sensors and the hysteretic behavior of piezoelectric materials. Moreover, it has excellent strain resolution and a wide dynamic sensing range. The application of a sensing patch has been also investigated: vibration control with this sensing patch has been performed using a fuzzy logic controller (FLC), and the possibility of using a sensing patch as a sensoriactuator is considered.

Effect of stereochemistry on the oxidative metabolism of the cyclophosphamide metabolite aldophosphamide.

31P NMR and cell perfusion techniques were used to investigate the conversion of the individual enantiomers of aldophosphamide (AP) to carboxyphosphamide (CBP) as catalyzed by aldehyde dehydrogenase in human erythroleukemia K562 cells. R- and S-cyclophosphamides (CPs) were treated with ozone and hydrogen peroxide to yield Rp- and Sp-cis-4-hydroperoxycyclophosphamides (Rp- and Sp-cis-4-HO2-CP); reduction of each hydroperoxide gave the corresponding enantiomer of AP [along with its tautomer 4-hydroxycyclophosphamide (4-HO-CP)]. In separate experiments, K562 cells embedded in agarose gel threads were perfused at pH 7.4, 21 +/- 1 degrees, with solutions of 1.4 mM Rp- and Sp-4-HO-CP/AP, both with and without added mesna (an acrolein scavenger). A comparison of the 31P NMR spectral data derived from the experiments revealed little statistical difference (+/- 10-20% error limits) in the normalized intensities of the CBP peaks arising from the individual AP enantiomers [with added mesna, the ratio Rp-CBP:Sp-CBP was 1.00:1.24 +/- 0.13 (average deviation); without mesna, the same ratio was 1.00:1.35]. Using conventional methods for evaluating the in vitro drug toxicities, CP-resistant L1210 cells were treated in separate experiments with Rp- and Sp-cis-4-HO2-CP; there were no significant differences between the toxicities exhibited by the stereoisomers.

Optical phase estimation for a patch-type extrinsic Fabry–Perot interferometer sensor system and its application to flutter suppression

An optical phase tracking technique for an extrinsic Fabry–Perot interferometer (EFPI) is proposed in order to overcome interferometric non-linearity. The basic idea is utilizing strain rate information, which cannot be easily obtained from the EFPI sensor itself. The proposed phase tracking system consists of a patch-type EFPI sensor and a simple on-line phase tracking logic. The patch-type EFPI sensor comprises an EFPI and a piezoelectric patch. An EFPI sensor itself has non-linear behavior due to the interferometric characteristics, and a piezoelectric material has hysteresis. However, the composed patch-type EFPI sensor system overcomes the problems that can arise when they are used individually. The proposed system can extract vibration information from severely distorted EFPI sensor signals. The dynamic characteristics of the proposed phase tracking system were investigated, and then the patch-type EFPI sensor system was applied to the active suppression of flutter, dynamic aeroelastic instability, of a swept-back composite plate structure. The real time neural predictive control algorithm effectively reduces the amplitude of the flutter mode, and 6.5% flutter speed enhancement for the aeroelastic system was obtained by integrating smart materials into advanced structures.

Reaction of C60 with oxygen initiated by radicals from azo(bisisobutyronitrile)

Abstract In an o-dichlorobenzene solution exposed to an atmosphere of air or pure oxygen, C60 reacts with radicals generated by thermal decomposition of azo(bisisobutyronitrile) and with oxygen to form mixtures of highly substituted and oxygenated monomelic, dimeric, and trimeric derivatives. LSIMS, LDMS, and SIMS (Liquid Secondary Ion, Laser Desorption, and Secondary Ion Mass Spectrometry) of these mixtures give clusters of peaks for C2n from C40 to greater than C200. Elemental analyses show large H, N, and 0 contents that increase with the amount of AIBN and the partial pressure of oxygen during the reaction. 1H and 13C NMR spectra consist of broad bands assigned to complex mixtures of substituted fullerenes containing many 2-cyano-2-propyl groups derived from AIBN. Diffuse reflectance infrared spectra show hydroxyl and carbonyl functional groups. Thermal gravimetric analysis (TGA) of the mixture prepared under oxygen retained 40% of the initial weight at 640 °C, while <19 % of the initial weight remain...

Optimization of Multi-Layer Dome Structures for Enhanced Performance and Comfort of Protector Pads

A multi-material, multi-layer dome structure is proposed for desigining futuristic body protection pads that will address a safety issue prominent among the population of elderly people, patients, industry workers, military personnel, and sport players. Those people are prone to be subjected to blunt impacts due to falls, bullets, and blast waves, which can result in serious injuries, early death, and extremely high medical costs. Protector pads can effectively reduce impact force and prevent injuries in high-risk individuals. However, most currently available protection pads are bulky, heavy, or rigid. Therefore, new body protectors need to be developed to satisfy the requirements of wearing comfort, ease of fitting, ensured protection, and cost-effectiveness. Out of many different design ideas generated, the most promising ones were identified through an evaluation process based on various criteria such as performance, comfort, and manufacturability. One of those designs utilizes a dome-shaped top layer and thin fabric membrane component that is very strong in tension but flexible in bending. Such structure will make the pads excellent in dissipating shock energy by diverting normal impact force to lateral direction and minimizing the force directly transmitted to the weakest body parts. Through finite element analyses, the best combinations of materials and components were identified. The selected pad structure was optimized for light-weight and flexibility while keeping excellent resistance to the compression. The thickness of the shell element and the overall thickness of the whole pad were optimized for the same level of deflection and stress as other simple shell pads. The results showed that the dome-shaped structure could be a useful component of effective body protection pads through optimal combination of various materials and layers.

Surface Properties of Metallophthalocyanine LB Films and their Sensing Applications

Abstract Multilayer thin films of H2Pc and CuPc were coated on QCM by the LB method as to be used as NO2 sensing materials. The mechanism of NO2 desorption on both Pc sensing films was investigated using XPS and FTIR.