• The Korean Journal of Physiology and Pharmacology
• /
• v.19 no.4
• /
• pp.373-382
• /
• 2015

Fura-2 analogs are ratiometric fluoroprobes that are widely used for the quantitative measurement of [$Ca^{2+}$]. However, the dye usage is intrinsically limited, as the dyes require ultraviolet (UV) excitation, which can also generate great interference, mainly from nicotinamide adenine dinucleotide (NADH) autofluorescence. Specifically, this limitation causes serious problems for the quantitative measurement of mitochondrial [$Ca^{2+}$], as no available ratiometric dyes are excited in the visible range. Thus, NADH interference cannot be avoided during quantitative measurement of [$Ca^{2+}$] because the majority of NADH is located in the mitochondria. The emission intensity ratio of two different excitation wavelengths must be constant when the fluorescent dye concentration is the same. In accordance with this principle, we developed a novel online method that corrected NADH and Fura-2-FF interference. We simultaneously measured multiple parameters, including NADH, [$Ca^{2+}$], and pH/mitochondrial membrane potential; Fura-2-FF for mitochondrial [$Ca^{2+}$] and TMRE for ${\Psi}_m$ or carboxy-SNARF-1 for pH were used. With this novel method, we found that the resting mitochondrial [$Ca^{2+}$] concentration was $1.03{\mu}M$. This $1{\mu}M$ cytosolic $Ca^{2+}$ could theoretically increase to more than 100 mM in mitochondria. However, the mitochondrial [$Ca^{2+}$] increase was limited to ${\sim}30{\mu}M$ in the presence of $1{\mu}M$ cytosolic $Ca^{2+}$. Our method solved the problem of NADH signal contamination during the use of Fura-2 analogs, and therefore the method may be useful when NADH interference is expected.

• Nutrition Research and Practice
• /
• v.11 no.1
• /
• pp.64-69
• /
• 2017

BACKGROUND/OBJECTIVES: This study was performed to measure fat-soluble vitamins and minerals in breast milk of Korean lactating mothers who exclusively breastfed their babies. SUBJECTS/METHODS: Breast milk samples were collected from 334 mothers. Concentrations of retinol and ${\alpha}$-tocopherol were analyzed by high performance liquid chromatography ultraviolet spectrometry while concentrations of minerals were measured by inductively coupled plasma optical emission spectrometry. RESULTS: Retinol and ${\alpha}$-tocopherol contents of breast milk were $39.58{\pm}19.64{\mu}g/dL$ and $0.23{\pm}0.13mg/dL$, respectively. Average sodium, potassium, calcium, phosphorus, and magnesium levels in breast milk were $11.11{\pm}5.16$, $38.56{\pm}9.01$, $27.87{\pm}6.10$, $13.56{\pm}3.30$, and $3.05{\pm}0.65mg/dL$, respectively. Contents of trace elements such as iron, zinc, copper, and manganese were $40.26{\pm}46.21$, $98.40{\pm}62.47$, $24.09{\pm}9.03$, and $0.90{\pm}1.63{\mu}g/dL$, respectively. Fat-soluble vitamin concentration was positively correlated with total fat in milk samples, but no significant differences were observed in levels of retinol, ${\alpha}$-tocopherol, or minerals based on whether or not lactating women were taking dietary supplements. CONCLUSIONS: Micronutrient contents of breast milk samples from Korean lactating women were comparable to those of other nations. Retinol and ${\alpha}$-tocopherol levels were correlated and also with total fat in breast milk.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.9
• /
• pp.546-551
• /
• 2016

$SrSnO_3:Tb^{3+}$ phosphor thin films were prepared on sapphire and quartz substrates in the growth temperature range of $100{\sim}400^{\circ}C$ by using the radio frequency magnetron sputtering deposition. The resulting $SrSnO_3:Tb^{3+}$ thin films were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible-infrared spectrophotometer, and photoluminescence spectrometer. The results indicated that the morphology, optical transmittance, band gap energy, and luminescence intensity of the phosphor thin films significantly depended on the growth temperature. All the thin films, regardless of the type of substrate, showed an amorphous behavior. As for the thin films deposited on sapphire substrate, the maximum crystallite size was obtained at a growth temperature of $400^{\circ}C$ and the strongest emission was green at 544 nm arising from the $^5D_4{\rightarrow}^7F_5$ transition of Tb3+. The average optical transmittance for all the thin films grown on sapphire and quartz substrates was decreased as the growth temperature increased from 100 to $400^{\circ}C$. The results suggest that the optimum growth temperatures for depositing highly-luminescent $SrSnO_3:Tb^{3+}$ phosphor thin films on sapphire and quartz substrates are 400 and $300^{\circ}C$, respectively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.380-380
• /
• 2010

Currently, organic light-emitting diodes (OLEDs) have been proven of their readiness for commercialization in terms of lifetime and efficiency. In accordance with emerging new technologies, enhancement of light efficiency and extension of application fields are required. Particularly inverted structures, in which electron injection occurs at bottom and hole injection on top, show crucial advantages due to their easy integration with Si-based driving circuits for active matrix OLED as well as large open area for brighter illumination. In order to get better performance and process reliability, usually a proper buffer layer for carrier injection is needed. In inverted top emission OLED, the buffer layer should protect underlying organic materials against destructive particles during the electrode deposition, in addition to increasing their efficiency by reducing carrier injection barrier. For hole injection layers, there are several requirements for the buffer layer, such as high transparency, high work function, and reasonable electrical conductivity. As a buffer material, a few kinds of transition metal oxides for inverted OLED applications have been successfully utilized aiming at efficient hole injection properties. Among them, we chose 2 nm of $WO_3$ between NPB [N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] and Au (or Al) films. The interfacial energy-level alignment and chemical reaction as a function of film coverage have been measured by using in-situ ultraviolet and X-ray photoelectron spectroscopy. It turned out that the $WO_3$ interlayer substantially reduces the hole injection barrier irrespective of the kind of electrode metals. It also avoids direct chemical interaction between NPB and metal atoms. This observation clearly validates the use of $WO_3$ interlayer as hole injection for inverted OLED applications.

• Korean Journal of Materials Research
• /
• v.18 no.2
• /
• pp.92-97
• /
• 2008

In spray pyrolysis, the effects of the preparation temperature, flow rate of the carrier gas and concentration of the spray solution on characteristics such as the morphology, size, and emission intensity of $Ca_8Mg(SiO_4)_4Cl_2:Eu^{2+}$ phosphor powders under long-wavelength ultraviolet light were investigated. The phosphor powders obtained post-treatment had a range of micron sizes with regular morphologies. However, the composition, crystal structure and photoluminescence intensity of the phosphor powders were affected by the preparation conditions of the precursor powders. The $Ca_8Mg(SiO_4)_4Cl_2:Eu^{2+}$ phosphor powders prepared at temperatures that were lower and higher than $700^{\circ}C$ had low photoluminescence intensities due to deficiencies related to the of Cl component. The phosphor powders with the deficient Cl component had impurity peaks of $Ca_2SiO_4$. The optimum flow rates of the carrier gas in the preparation of the $Ca_8Mg(SiO_4)_4Cl_2:Eu^{2+}$ phosphor powders with high photoluminescence intensities and regular morphologies were between 40 and 60 l/minute. Phosphor powders prepared from a spray solution above 0.5 M had regular morphologies and high photoluminescence intensities.

• Korean Journal of Materials Research
• /
• v.29 no.5
• /
• pp.282-287
• /
• 2019

The photovoltaic properties of $TiO_2$ used for the electron transport layer in perovskite solar cells(PSCs) are compared according to the particle size. The PSCs are fabricated and prepared by employing 20 nm and 30 nm $TiO_2$ as well as a 1:1 mixture of these particles. To analyze the microstructure and pores of each $TiO_2$ layer, a field emission scanning electron microscope and the Brunauer-Emmett-Teller(BET) method are used. The absorbance and photovoltaic characteristic of the PSC device are examined over time using ultraviolet-visible-near-infrared spectroscopy and a solar simulator. The microstructural analysis shows that the $TiO_2$ shape and layer thicknesses are all similar, and the BET analysis results demonstrate that the size of $TiO_2$ and in surface pore size is very small. The results of the photovoltaic characterization show that the mean absorbance is similar, in a range of about 400-800 nm. However, the device employing 30 nm $TiO_2$ demonstrates the highest energy conversion efficiency(ECE) of 15.07 %. Furthermore, it is determined that all the ECEs decrease over time for the devices employing the respective types of $TiO_2$. Such differences in ECE based on particle size are due to differences in fill factor, which changes because of changes in interfacial resistance during electron movement owing to differences in the $TiO_2$ particle size, which is explained by a one-dimensional model of the electron path through various $TiO_2$ particles.

• Korean Journal of Materials Research
• /
• v.31 no.12
• /
• pp.665-671
• /
• 2021

A 1.8 ㎛ thick polycrystalline diamond (PCD) thin film layer is prepared on a Si(100) substrate using hot-filament chemical vapor deposition. Thereafter, its thermal conductivity is measured using the conventional laser flash analysis (LFA) method, a LaserPIT-M2 instrument, and the newly proposed light source thermal analysis (LSTA) method. The LSTA method measures the thermal conductivity of the prepared PCD thin film layer using an ultraviolet (UV) lamp with a wavelength of 395 nm as the heat source and a thermocouple installed at a specific distance. In addition, the microstructure and quality of the prepared PCD thin films are evaluated using an optical microscope, a field emission scanning electron microscope, and a micro-Raman spectroscope. The LFA, LaserPIT-M2, and LSTA determine the thermal conductivities of the PCD thin films, which are 1.7, 1430, and 213.43 W/(m·K), respectively, indicating that the LFA method and LaserPIT-M2 are prone to errors. Considering the grain size of PCD, we conclude that the LSTA method is the most reliable one for determining the thermal conductivity of the fabricated PCD thin film layers. Therefore, the proposed LSTA method presents significant potential for the accurate and reliable measurement of the thermal conductivity of PCD thin films.

• Fashion & Textile Research Journal
• /
• v.24 no.1
• /
• pp.138-145
• /
• 2022

Today, graphene loaded textiles are being considered promising smart clothing due to their high conductivity. In this study, we reported reduced graphene oxide(r-GO) deposited pure cotton fabrics fabricated with a colloidal solution of graphene(GO), using a one-step aerosol spray pyrolysis(ASP) process and their potential application on smart textiles. The ASP process is advantageous in that it is easily implementable and can be applied for continuous processing. Moreover, this process has never been applied to deposit r-GO on pure cotton fabric. The field emission-scanning microscopy (FE-SEM) observation, Fourier transform-infrared(FT-IR) analysis, Raman spectroscopy, X-ray diffraction(XRD) analysis, and ultraviolet transmittance(UVT) were used to evaluate material properties of the r-GO colloids. The resistance was also measured to evaluate the electrical conductivity of the specimens. The results revealed that the r-GO was successfully deposed on specimens, and the specimen with the highest electrical conductivity demonstrated an electrical resistance value of 2.27 kΩ/sq. Taken together, the results revealed that the ASP method demonstrated a high potential for effective deposition of r-GO on cotton fabric specimens and is a prospect for the development of conductive cotton-based smart clothing. Therefore, this study is also meaningful in that the ASP process can be newly applied by depositing r-GO on the pure cotton fabric.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1998.02a
• /
• pp.17-17
• /
• 1998

Synchrotron radiation is produced when charged particles moving with relativistic velocities a are accelerated - for example, deflected by the bending magnets which guide the electron or p positrons in circular accelerators or storage rings. By using special focusing magnetic lattices i in the particle accelerators it is possible to make the dimensions of the particle beam very small with a hi맹 charge density which results in a light source with high b디lIiance. Synchrotron light h has important properties which make it ideal for a wide range of investigations in surface s science. The fact that the spectrum of electromagnetic radiation emitted in a bending magnet e extends in a continuum from the 얹r infra red region to hard x-rays means that it is id않I for a v variety of spectroscopic studies. Since there are no convenient lasers, or other really bright l light sources, in the vacuum ultraviolet and soft x-ray re.밍ons the development of synchrotron r radiation has enabled enormous advances to be made in this di펌C비t spectr따 re밍on. P Polarization-dependent measurements, for ex없nple ellipsometry or circular dichroism studies a are possible because the radiation has a well-defined polarization - linear in the plane of orbit w with additional right-circular, or left-circular, components for emission an생es above, or below, t the horizontal, respectively. Since the synchrotron light is emitted from a bunch of charge c circulating in a ring the light is emitted with a well-defined time structure with a short flash of l light every time a bunch passes an exit port. The time structure depends on the size of the ring a and the number and sequence of filling of the bunches. A pulsed light source enables time¬r resolved studies to be performed which provide direct information on the lifetimes and decay m modes of excited states and in addition opens up the possibility of using time of flight t techniques for spectroscopic studies. The fact that synchrotron radiation is produced in a clean u ultrahi야 vacuum environment is of gr않t importance for surce science studies. The current t비rd generation synchrotron light sources provide exceptionally high baliance and stability a and open up possibilities for experiments which would have been inconceivable only a short time ago.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.2
• /
• pp.38.1-38.1
• /
• 2021

Dust polarization depends on the physical and mechanical properties of dust, as well as the properties of local environments. To understand how dust polarization varies with grain mechanical properties and the local environment, in this paper, we model the wavelength-dependence polarization of starlight and polarized dust emission by aligned grains by simultaneously taking into account grain alignment and rotational disruption by radiative torques (RATs). We explore a wide range of the local radiation field and grain mechanical properties characterized by tensile strength. We find that the maximum polarization and the peak wavelength shift to shorter wavelengths as the radiation strength U increases due to the enhanced alignment of small grains. Grain rotational disruption by RATs tends to decrease the optical-near infrared polarization but increases the ultraviolet polarization of starlight due to the conversion of large grains into smaller ones. In particular, we find that the submillimeter (submm) polarization degree at 850㎛(P850) does not increase monotonically with the radiation strength or grain temperature (Td), but it depends on the tensile strength of grain materials. Our physical model of dust polarization can be tested with observations toward star-forming regions or molecular clouds irradiated by a nearby star, which have higher radiation intensity than the average interstellar radiation field. Finally, we compare our predictions of the P850-Td relationship with Planck data and find that the observed decrease of P850 with Td can be explained when grain disruption by RATs is accounted for, suggesting that interstellar grains unlikely to have a compact structure but perhaps a composite one. The variation of the submm polarization with U (or Td)can provide a valuable constraint on the internal structures of cosmic dust