Showing papers in "Journal of the Korean Physical Society in 2010"
142 citations
128 citations
TL;DR: Microneedles with below a 12:1 aspect ratio of length-to-equivalent diameter and more than 3 GPa of Young's were recommended for reducing sudden failure by buckling and for successfully inserting the microneedle into the skin.
Abstract: A polymeric microneedle has been developed for drug delivery applications The ultimate goal of the polymeric microneedle is insertion into the specified region without failure for effective transdermal drug delivery Mechanical failure of various geometries of microneedles by axial load was modeled using the Euler formula and the Johnson formula to predict the failure force of tapered-column microneedles These formulas were compared with measured data to identify the mechanical behavior of microneedles by determining the critical factors including the actual length and end-fixed factor The comparison of the two formulas with the data showed good agreement at the end-fixity (K) of 07 This value means that a microneedle column has one fixed end and one pinned end, and that part of the microneedle was overloaded by axial load When the aspect ratio of length to equivalent diameter is 12:1 at 3 GPa of Young's modulus, there is a transition from the Euler region to the Johnson region by the decreased length and increased base diameter of the microneedle A polymer having less than 3 GPa of stiffness would follow the Euler formula A 12:1 aspect ratio of length to equivalent diameter of the microneedle was the mechanical indicator determining the failure mode between elastic buckling and inelastic buckling at less than 3 GPa of Young's modulus of polymer Microneedles with below a 12:1 aspect ratio of length-to-equivalent diameter and more than 3 GPa of Young's were recommended for reducing sudden failure by buckling and for successfully inserting the microneedle into the skin
73 citations
TL;DR: In this paper, an iron oxide (Fe3O4) nanoparticles coated with chitosan were synthesized for use as an MRI (magnetic resonance imaging) contrast agent.
Abstract: Iron oxide (Fe3O4) nanoparticles coated with biocompatible chitosan were synthesized for use as an MRI (magnetic resonance imaging) contrast agent. The coating was performed simultaneously with the synthesis of the ferrite nanoparticles. A dynamic light-scattering spectrometer (DLS) and a transmission electron microscope (TEM) were used to measure the average diameter of the coated nanoparticles, which was 67.0 nm. Fourier transform infrared (FT-IR) measurements showed strong bonding of the chitosan molecules to the surfaces of the ferrite nanoparticles. The spin-lattice (T1) and the spin-spin (T2) relaxation times of the nuclear spins (hydrogen protons) in aqueous solutions of various concentrations of coated ferrite nanoparticles were determined using a nuclear magnetic resonance (NMR) spectrometer. Using these data, we found that the T1 and the T2 relaxivities of the nuclear spins in aqueous solutions of ferrite nanoparticles were 0.00291 and 0.0691 ppm−1sec−1, respectively. In particular, the value of the T2 relaxivity was much larger than that of the commercial contrast agent GD-DTPA (gadolinium diethylenetriamine penta-acetic acid). A 31.7% intensity loss in the T2 image of a rabbit liver was observed after injecting the aqueous solution of coated nanoparticles into the rabbit, which shows that our coated ferrite nanoparticles can be used as a T2 MRI contrast agent.
65 citations
TL;DR: In this paper, the authors investigated the temperature dependence of the quantum optical tran- sition of quasi-2-dimensional Landau splitting, in GaN and GaAs, using the projected Liouville equa- tion method with equilibrium average projection scheme (EAPS).
Abstract: We investigated theoretically the temperature dependence of the quantum optical tran- sition of quasi-2-dimensional Landau splitting, in GaN and GaAs. We apply the quantum transport theory (QTR) to a system of electrons confined in a potential. We use the projected Liouville equa- tion method with equilibrium average projection scheme (EAPS). Through the analysis of this work, we found increasing optical quantum transition line shapes (QTLSs) and the quantum tran- sition line widths (QTLWs) in GaN and GaAs with increasing temperature. We also found the temperature dependences of the scattering factor functions: (T) of GaN < (T) of GaAs in the temperature region 50 K < T and (T) of GaAs < (T) of GaN in the temperature T < 50 K and = 394 µm.
61 citations
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48 citations
TL;DR: In this article, the quantum corrections to the thermodynamic quantities (temperature and entropy) for a Bardeen charged regular black hole by using a quantum tunneling approach over semiclassical approximations were studied.
Abstract: In this paper, we study the quantum corrections to the thermodynamical quantities (temperature and entropy) for a Bardeen charged regular black hole by using a quantum tunneling approach over semiclassical approximations. Taking into account the quantum effects, the semiclassical Bekenstein-Hawking temperature and the area law are obtained, which are then used in the first law of thermodynamics to evaluate corrections to these quantities. It is interesting to mention here that these corrections reduce to the corresponding corrections for the Schwarzschild black hole when the charge $e=0$.
46 citations
42 citations
TL;DR: In this paper, the incorporation of Cu in the two types of thin-film solar cells was discussed and the results showed a conversion efficiency of 15.5% and 11.1% respectively.
Abstract: of 11.1%. The other prepared with a 3-step process had nearly the same In-Ga and Cu concentrations and showed a conversion eciency of 15.5%. We discuss the incorporation of Cu in the two types of thin-film solar cells.
37 citations
TL;DR: It is confirmed that cisplatin could be applied to cancer therapy that combines chemotherapeutic drugs with radiation therapy and will be used to study dose enhancement in tumor regions using various radiation modalities with high atomic number materials.
Abstract: concentrations of gold nanoparticles. Brachytherapy employs low energy photons of less than 0.5 MeV, which indeed is the optimal energy range for radiation dose enhancement by introduction of high-Z material. The present study uses the MCNPX TM code to estimate the dose enhancement by gold nanoparticles for the four common brachytherapy sources ( 137 Cs, 192 Ir, 125 I, and 103 Pd). Additionally, cisplatin (H6Cl2N2Pt), a platinum-based chemotherapeutic drug, was used to evaluate the dose enhancement. The simulated source models were evaluated with reference to the calculated TG-43 parameter values. The dose enhancement in the tumor region due to the gold nanoparticles and cisplatin was evaluated according to the dose enhancement factor (DEF). The maximum values of the average DEFs were found to be 1.03, 1.11, 3.43, and 2.17 for the 137 Cs, 192 Ir, 125 I, and 103 Pd sources, respectively. The dose enhancement values for the low-energy sources were significantly higher than those for the high-energy sources. The dose enhancement due to cisplatin was calculated by using the same approach and was found to be comparable to that of the gold nanoparticles. The maximum value of the average DEF for cisplatin was 1.12 for the 5% concentration level in water and a 192 Ir source. We confirmed that cisplatin could be applied to cancer therapy that combines chemotherapeutic drugs with radiation therapy. The results presented herein will be used to study dose enhancement in tumor regions using various radiation modalities with high atomic number materials.
TL;DR: In this article, the authors investigated the incorporation site of C and the electrical properties of Cdoped ZnO films grown by using pulsed laser deposition (PLD) under oxygen-rich and oxygen-poor conditions.
Abstract: ZnO doped with non-magnetic C has been reported to exhibit room-temperature ferromagnetism (RTF). The theoretical explanations of the RTF in ZnO:C are based on the incorporation of C at the O site and on the p-p exchange interaction between the localized C2p spins and valenceband holes. Here, we investigated the incorporation site of C and the electrical properties of Cdoped ZnO films grown by using pulsed laser deposition (PLD) under oxygen-rich and oxygen-poor conditions. Contrary to the theoretical explanations, all the C-doped ZnO films exhibited n-type conductivity. Furthermore, most of the carbons were not incorporated at the O site, but rather at the interstitial or Zn site, or formed C clusters. Although there may exist a growth method that can lead to incorporation of C at the O site, our experimental results indicate that the defect-induced ferromagnetism mechanism can better explain most of the observed RTF in the PLD-grown ZnO:C films.
TL;DR: In this article, the concentration of gallium (Ga) in the film was varied by using different RF powers for sputtering the GZO target with the DC power for the AZO target fixed.
Abstract: Films were deposited on glass substrates by sputtering gallium-doped zinc oxide (GZO) (Ga2O3: 90 wt%, ZnO: 10 wt%) and aluminum-doped zinc oxide (AZO) (Al2O3: 3 wt%, ZnO: 97 wt%) targets simultaneously using a direct-current (DC)/radio-frequency (RF) magnetron cosputtering system. The concentration of gallium (Ga) in the film was varied by using different RF powers for sputtering the GZO target with the DC power for sputtering the AZO target fixed. A minimum resistivitywas obtained at an RF sputtering power of 200 W for the GZO target when the DC sputtering power for the AZO target was fixed at 60 W. It was found that the resistivity of AZO thin films (6.40 × 10−3 Ω-cm for 0 W) could be lowered by more than one order by cosputtering AZO and GZO targets to make AGZO thin films (2.14 × 10−3Ω-cm for 200 W) without lowering their transmittance at all. In addition, the origin of the enhancement in the electrical property of the AZO by additional Ga doping is discussed.
TL;DR: In this article, a group of aluminum-doped zincoxide (AZO) films were prepared on glass substrates by directcurrent reactive magnetron sputtering at substrate temperatures (Ts) ranging from 170 C to 210 C.
Abstract: A group of aluminum-doped zinc-oxide (AZO) films were prepared on glass substrates by directcurrent reactive magnetron sputtering at substrate temperatures (Ts) ranging from 170 C to 210 C. The optical constants of the AZO films defined by using Caughy model were fitted in terms of a two-layer model by using the measured spectroscopic ellipsometric parameters. The refractive index dispersion data below the interband absorption edge of the AZO films were analyzed by using a single-oscillator model. The optical energy gap as-fitted by using the single-oscillator model demonstrated a blue and a red shift as Ts increased from 170 C to 200 C and above 200 C, respectively. This could be attributed to a change in the free electron concentration, which was related to a change in the eective Al-doping eciency. The calculated parameter , related to the crystalline structure, indicated that the as-deposited AZO films fell into an ionic class even though had a slight deviation from the ionic value. The of the as-deposited AZO film at 200 C largely remained in the range of ionic values, indicating a minimum deviation from the wurtzite structure. This denoted that Al is a very eective substitute for the zinc sites. Additionally, the calculated plasma frequency, ~!p, remained in the violet region.
TL;DR: In this article, a high-pressure reaction container for the ultrasonic transducer was newly developed, and the ultrasonically-assisted hydrothermal method was examined by using this container.
Abstract: The hydrothermal method enables the production of high-quality piezoelectric materials. In this study, we propose to irradiate the reaction solutions with ultrasonic power during the hydrothermal method to obtain a shorter reaction time and a smooth film surface. A high-pressure reaction container for the ultrasonic transducer was newly developed, and the ultrasonically-assisted hydrothermal method was examined by using this container. The effect of ultrasonic assist on the synthesis of lead-zirconate-titanate (PZT) thin films and (K,Na)NbO$_{3}$ powders was verified. Thicker PZT film, thickness around 10 ${\mu}$m, could be obtained in one process, and (K,Na)NbO$_{3}$ powder was synthesized in half the previous reaction time.