bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased mast cell number in human hypertensive nephropathy
Authors: Welker Pia , Krämer Stephanie , Groneberg David A. , Neumayer Hans H. , Bachmann Sebastian , Amann Kerstin , Peters Harm
Published: August 2008

Mast cells have recently been related to nonallergic chronic organ damage and fibrosis. In the present study, we analyzed mast cell number, localization, and maturation in the kidney of a relatively unique group of middle-aged accident victims with primary essential hypertension and in normotensive controls ( n = 8 per group, Caucasians, predominantly male). Hypertensive kidneys showed a significantly higher degree of arteriolosclerosis. However, glomerular and tubulointerstitial matrix accumulation did not differ significantly to normotensive controls indicating a relatively early stage of hypertensive nephropathy. Using toluidine blue staining, renal mast cell number was found to be fivefold higher in hypertensive subjects compared with normotensive controls. Mast cells were primarily located in the peritubular interstitial spaces, some perivascular, but not in glomeruli. In a series of immunohistological staining studies, mast cell maturation grading showed that expression of early hematopoietic precursor cell marker CD34 did not differ between both groups. In contrast, mast cells were mostly positive for IgE receptor, tryptase, and chymase indicating a mature, differentiated cell phenotype in hypertensive nephropathy. Renal expression of stem cell factor was markedly upregulated in primary hypertension. Kidney macrophage and lymphocyte numbers were similar in both groups. In conclusion, human hypertensive kidney disease shows an early and conspicuous upregulation of stem cell factor along with an increased number of mature mast cells. The results suggest that renal mast cell accumulation may play a role in the pathogenesis of human hypertensive nephropathy.
TRPV4 mediates hypotonicity-induced ATP release by the thick ascending limb
Authors: Silva Guillermo B. , Garvin Jeffrey L.
Published: August 2008

Extracellular ATP is an autocrine/paracrine factor that regulates renal function. Transient receptor potential vanilloid (TRPV) 4 is a cation channel that mediates release of autocrine/paracrine factors by acting as an osmosensor. The renal medulla, and therefore the thick ascending limb, is exposed to osmotic stress. We hypothesize that reduced osmolality stimulates ATP release from the thick ascending limb via transient receptor potential vanilloid (TRPV) 4 activation. We measured ATP release by medullary thick ascending limb suspensions after reducing bath osmolality from 350 to 323 mosmol/kgH2O, using the luciferin-luciferase assay. Decreasing osmolality stimulated ATP release compared with control (38.9 ± 7.2 vs. 2.4 ± 1.0 pmol/mg protein; n = 6, P < 0.01). To examine the role of TRPV4, we used 1) Ca-free solutions, 2) a TRPV4 inhibitor, 3) small interfering (si) RNA against TRPV4, and 4) a TRPV4 activator. Removal of Ca completely blocked osmolality-induced ATP release (42.2 ± 5.9 vs. 2.6 ± 1.5 pmol/mg protein; n = 6, P < 0.01). In the presence of the TRPV4-selective inhibitor ruthenium red, osmolality-induced ATP release was blocked by 73% (56.4 ± 19.9 vs. 8.8 ± 2.3 pmol/mg protein; n = 6; P < 0.03). In vivo treatment of thick ascending limbs with siRNA against TRPV4 decreased osmolality-induced ATP release by 62% (31.5 ± 3.4 vs. 12.4 ± 1.1 pmol/mg protein; n = 6; P < 0.01), while reducing TRPV4 expression by 74% compared with the nontreated kidney. Treatment with scrambled siRNA did not affect TRPV4 expression and/or osmolality-induced ATP release. Finally, in the absence of changes in osmolality, the specific TRPV4 agonist 4α-PDD increased ATP release (3.6 ± 0.9 vs. 25.4 ± 7.4 pmol/mg protein; n = 6; P < 0.04). We concluded that decreases in osmolality stimulate ATP release by thick ascending limbs and this effect is mediated by TRPV4 activation.
Complex genetic regulation of bone mineral density and insulin-like growth factor-I in C57BL/6J-Chr #A/J/NaJ chromosome substitution strains
Authors: Govoni K. E. , Donahue L. R. , Marden C. , Mohan S.
Published: August 2008

Low bone mineral density (BMD) is a phenotype associated with osteoporosis and increased risk of fracture. Since 60–80% of variation in BMD is associated with genetic factors, we used the novel approach of chromosome substitution strains (CSS) to identify chromosomes that harbor genes that regulate BMD. Specifically, we evaluated 24 wk old C57BL/6J-Chr #A/J/NaJ CSS ( n = 7 to 18) in which each chromosome in the host C57BL/6J strain is replaced by a corresponding chromosome from the donor A/J strain (19 autosomes, X, Y). We determined several A/J chromosomes contribute to body weight (BW), percent body fat (BF), whole body areal BMD (aBMD), and serum insulin-like growth factor (IGF)-I in both a positive and negative manner when compared with C57BL/6J. Specifically, C57BL/6J-Chr 5A/J/NaJ (B.A-5) (males) and B.A-13 (females) contributed to increased BW, whereas B.A-3, 4, 8, 9, 12, and 18 (males) and B.A-3, 4, and 11 (females) contributed to reduced BW. B.A-5 (males) and B.A-13 (females) contributed to increased BF, whereas B.A-12 (males) and B.A-3, 4, 10, and 11 (females) contributed to reduced BF. B.A-14 (females) contributed to increased aBMD and B.A-1, 2, 6, 9, 10, and 18 (males) and B.A-8, 9, and 10 (females) contributed to reduced aBMD. To determine if similar chromosomes regulate aBMD and IGF-I, we determined serum concentrations of IGF-I. B.A-14 and Y (males) and B.A-6 (females) contributed to increased IGF-I and male B.A-3 and female B.A-8 contributed to reduced IGF-I. Overall, we identified several sex-dependent and -independent chromosomes that regulate aBMD and IGF-I in adult mice.
Genomic organization, expression, and phylogenetic analysis of Ca2+channel β4 genes in 13 vertebrate species
Authors: Ebert Alicia M. , McAnelly Catherine A. , Handschy Anne V. , Mueller Rachel Lockridge , Horne William A. , Garrity Deborah M.
Published: August 2008

The Ca2+channel β-subunits, encoded by CACNB genes 1–4, are membrane-associated guanylate kinase (MAGUK) proteins. As auxiliary subunits of voltage-gated Ca2+channels, the β-subunits facilitate membrane trafficking of the pore-forming α1 subunits and regulate voltage-dependent channel gating. In this report, we investigate whether two zebrafish β4 genes, β4.1 and β4.2, have diverged in structure and function over time. Comparative expression analyses indicated that β4.1 and β4.2 were expressed in separable domains within the developing brain and other tissues. Alternative splicing in both genes was subject to differential temporal and spatial regulation, with some organs expressing different subsets of β4.1 and β4.2 transcript variants. We used several genomic tools to identify and compare predicted cDNAs for eight teleost and five tetrapod β4 genes. Teleost species had either one or two β4 paralogs, whereas each tetrapod species contained only one. Teleost β4.1 and β4.2 genes had regions of sequence divergence, but compared with tetrapod β4s, they exhibited similar exon/intron structure, strong conservation of residues involved in α1 subunit binding, and similar 5′ alternative splicing. Phylogenetic results are consistent with the duplicate teleost β4 genes resulting from the teleost whole genome duplication. Following duplication, the β4.1 genes have evolved faster than β4.2 genes. We identified disproportionately large second and third introns in several β4 genes, which we propose may provide regulatory elements contributing to their differential tissue expression. In sum, both mRNA expression data and phylogenetic analysis support the evolutionary divergence of β4.1 and β4.2 subunit function.
Polymer Embedded Nanocrystalline Titania Sorbent for 99Mo-99mTc Generator
Authors: Chakravarty Rubel , Shukla Rakesh , Gandhi Shyamla , Ram Ramu , Dash Ashutosh , Venkatesh Meera , Tyagi A. K.
Published: August 2008

A new sorbent material, polymer embedded nano crystalline titania (Titanium Polymer-TiP) has been developed, from titanium (IV) chloride and isopropyl alcohol, for the adsorption of 99Mo, which is a precursor to 99mTc, a workhorse in radio-pharmaceuticals. The
infrared absorption spectra of the TiP showed peaks corresponding to Ti-O groups. X-ray diffraction pattern of the adsorbent corresponded to rutile TiO2. The surface area of this polymer was 30 m2/g with an average pore size of 40 nm. The average crystallite size of TiO2,
embedded in polymer, was found to be 5 nm. TEM micrograph of the adsorbent revealed the networkof polymer with dispersed titania phase. Potential of this adsorbent for the preparation of 99Mo-99mTc generator has been explored. 99Mo could be adsorbed on to the
adsorbent column containing TiP at pH 1 from which 99mTc could be eluted with normal (0.9%) saline solution with an elution yield of ∼80%. The quality of the 99mTcO−4 obtained was in accordance with the international specifications applicable
for radiopharmaceutical use. A process demonstration run was carried out with 1.1 GBq (30 mCi) 99Mo activity level making use of the above adsorbent and consistent results were obtained over a period of one week, which is generally the shelf life of 99Mo-99mTc
generator.
Synthesis and Characterization of Radially-Aligned Carbon Filaments Spontaneously Grown on a Carbon Yarn
Authors: Muradov Nazim , Ur Rahman Zia
Published: August 2008

The synthesis and characterization of radially-aligned carbon filaments (RACF) produced from light hydrocarbons are reported. RACF grow spontaneously on the surface of a resistively heated (1100–1700 °C) carbon yarn exposed to C1–C3 hydrocarbons
(methane, ethylene, propane) as carbon precursors. The diameter of the RACF depends on the temperature, exposure time, nature of hydrocarbon, and it ranges from 700 nm to 40 μm, with the length of the carbon filaments reaching up to 800 μm. The morphology and microstructure
of the produced carbon filaments were analyzed by a number of materials characterization techniques, and it was shown that they feature a tree-ring type structure made of turbostratic carbon layers. RACF are characterized by the presence of cracks (50–100 nm in width) between the consecutive
"tree-rings" and a crenulated structure of the exterior surface of the filaments. The RAFC growth mechanism is yet to be fully understood. Pros and cons for the catalytic versus non-catalytic growth models for the RACF are discussed in the paper.
Silica-Polypyrrole Core–Shell Nanocomposites as Active Materials for Dielectrophoretic Displays
Authors: Miomandre F. , Audebert P. , Bonnet J. P. , Brosseau A. , Perriat P. , Weisbuch C. , Wen W. , Sheng P.
Published: August 2008

A direct route to silica-polypyrrole core–shell nanoparticles has been used to design new nanocomposites, in which the conducting part is then wrapped by an external silica shell in order to have finally neutral nanoparticles. The nanocomposites are characterized by TEM, spectroscopy,
electrochemistry and thermal gravimetric analysis, demonstrating that the external silica shell actually insulates the conjugated polymer from the outer medium. Finally the electrorheological properties of these nanocomposites are checked in a dielectrophoretic device in which the motion of
the particles induced by an external electric field can be used to monitor a switch of the light transmission properties.
Structure and Microwave Characteristics of Co/TiO2 Nanocomposites Prepared by Ball Milling
Authors: Ni Xia , Ma Ji , Li Jiangong , Huang Juanjuan , Jiao Dongmao , Lu Zhibin
Published: August 2008

Co/TiO2 nanocomposites were fabricated via direct ball milling. The structure and microwave characteristics of the Co/TiO2 nanocomposites were investigated. The results show that the hcp and fcc Co phases coexist in the nanocomposites for a long milling duration.
The accumulation of the stacking faults in Co and the increase of the Co/TiO2 interfaces were detected by nuclear magnetic resonance. The measured relative complex permittivity of the Co/TiO2 nanocomposite-paraffin wax mixture indicates that a high electrical resistivity
and a dielectric loss exist in the Co/TiO2 nanocomposites. The dielectric loss mainly results from the polarisation of the metal/insulator interfaces. The imaginary part of the relative complex permeability of the mixture exhibits a broad resonance peak at 5.1 GHz which originates
from the natural resonance in Co. The broadening of the resonance peak can be attributed to the fluctuating magnetocrystalline anisotropy at the stacking faults and interfaces regions. The calculated reflection loss curves show that the minimal reflection loss value of the Co/TiO2
nanocomposite-paraffin wax mixture can reach −32 dB at 4.0 GHz with a 3 mm sample thickness. The improved microwave absorption properties may result from the high electrical resistivity, dielectric loss and natural resonance.
Factors Affecting Formation of Metastable Ni3C Phase in a Solution-Based Method
Authors: Leng Yonghua , Liu Yang , Song Xubo , Li Xingguo
Published: August 2008

Ni3C nanoparticles are synthesized over a wide range of reaction conditions by thermal decomposition of organometallic precursors in the organic solution medium. It is found that Ni3C nanoparticles are formed using Ni nanoparticles as an intermediate. The carbon
component originating from the organic solution medium to enter into Ni metal lattice is identified as a diffusion-controlled reaction, which is speeded up by increasing the reaction temperature and completed by prolonging the reaction time. Any organic molecule which contains active carbon
atoms is found to be a good candidate as carbon source and combine with nickel nanoparticles to form Ni3C phase. Although this paper emphasizes on the preparation of metastable Ni3C phase, at the same time, this work could effectively direct the synthesis of Ni nanoparticles
in organic solution, by avoiding the formation of Ni3C phase.
Investigation on the Surface Passivation of Intrinsic a-Si:H Thin Films Prepared by Inductively Coupled Plasma-Chemical Vapor Deposition for Heterojunction Solar Cell Applications
Authors: Jeong Chaehwan , Jeon Minsung , Kim Tae-Won , Boo Seongjae , Kamisako Koichi
Published: August 2008

Intrinsic a-Si:H thin films, which can have passivation functions on the surface of crystalline Si, were deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD). The properties of the films were investigated at deposition temperatures ranging from 50 to 400 °C.
The Si—H stretching mode at 2000 cm−1, which indicates good film quality, was found in the range of 150∼400 °C, but the film quality was not good at deposition temperatures below 150 °C. The passviation quality was determined by measuring the effective carrier
lifetime using the quasi-steady state photoconductance (QSS-PC) technique. Two, 5, 7.5 and 10 nm thick films were deposited at 150 °C and annealed at 200 °C for 1 hour. The carrier lifetime of these films was approximately 3 times higher than that observed before annealing. A p
a-SiC:H/i a-Si:H/n c-Si hetero-structure solar cell with a 7.8% efficiency and approximately 85% quantum efficiency (QE) was obtained by inserting an intrinsic a-Si:H thin film (5 nm) between the interfaces. These results highlight the potential applications of a passivation
layer to heterojunction solar cells.
Effects of the Neutralization Degree on Morphologies in "Drying-Mediated" Samples of Sodium Neutralized Poly(styrene-ran-methacrylic acid) Copolymers in THF
Authors: Yu Jeong-A , Park Yu-Ri , Kim Joon-Seop
Published: August 2008

To understand the effect of neutralization degree on surface morphologies of drying-mediated samples, un-neutralized, partially and fully Na-neutralized poly(styrene-ran-methacrylic acid) (PSMAA) prepared from THF solutions were investigated using a scanning electron microscope
(SEM). We varied the content of acid groups as well as the degree of neutralization of the PSMAA copolymers. The neutralization degree changed the surface morphologies of the polymers significantly. When the acid group content was low (<9.4 mol%), the morphologies of PSMAA were found to
be very similar to that of homo-PS, forming a continuous matrix with a number of circular pores. Upon neutralization, the shape of the pores changed to non-circular form and the porous matrix was mingled with the congregated aggregates. With increasing neutralization degrees, the boundary
between porous films and deformed sphere-shaped aggregates became unclear. For fully neutralized forms, only highly porous layered films were formed, indicating micro phase separation between solvent and aggregated copolymer networks.
Thermal Stability of Cu and Cu2O Nanoparticles in a Polyimide Film
Authors: Choi Jae-Youn , Dong Wenguo , Choi Dong Joo , Yoon Chong S. , Kim Young-Ho
Published: August 2008

Nanoparticles of Cu or Cu oxide dispersed in a polyimide (PI) film were fabricated by reaction of polyamic acid with a thin Cu film during imidization. In this paper, the thermal stability of the Cu or Cu oxide nanoparticles was investigated under various atmospheres. The PI/nanoparticle
composites were heat-treated at 140 °C and 250 °C in air, N2, Ar, and 5% H2 atmospheres. Nanoparticles in the PI film were characterized by UV-VIS spectroscopy and transmission electron microscopy. The optical absorption peaks originating from Cu or Cu2O
nanoparticles were changed by heat-treatment in different atmospheres. When Cu nanoparticles were oxidized by heat-treatment in air, the surface plasmon resonance (SPR) peak originating from the Cu nanoparticles disappeared. The quantum confined absorption peak of Cu2O was not affected
by heat-treatment in N2 or Ar. Cu2O nanoparticles were reduced by heat-treatment at 250 °C in 5% H2 atmosphere and a new SPR peak appeared. Our results show that Cu nanoparticles are easily oxidized and highly dense Cu nanoparticles can be formed by reducing
Cu2O nanoparticles.
Synthesis of Carbon Containing TiO2 Nano Powders by Aerosol Flame Deposition for Photocatalyst
Authors: Lim Gyeong-Taek , Kim Yeon-Hong , Jeong Hyung-Gon , Woo Hee-Gweon , Ohk Seung-Ho , Kim Do-Heyoung
Published: August 2008

In-situ carbon-doped-TiO2 nano-powder was prepared by an AFD (aerosol flame deposition) technique using ethanol and isopropanol, and the photocatalytic activity of the prepared powder was examined. There were no significant effect of the solvents on the phase of the
prepared TiO2, but the level of carbon in the deposits prepared with ethanol was lower than that prepared with isopropanol. Also, the average sizes of the particles prepared with ethanol were slightly smaller than that formed with isopropanol. All the samples showed excellent photocatalytic
activity in the decomposing of methylene blue (MB). We even observed photocatalytic activity of the powder under visible light irradiation, although the decomposition rate of MB under this irradiation was slightly slower than under UV-A light irradiation.
Molecular Scale Photodiode Composed of Recombinant Ferredoxin/Chlorophyll a Heterostructure
Authors: Choi Jeong-Woo , Lee Doo-Bong , Oh Byung-Keun , Min Junhong , Kim Kun Soo
Published: August 2008

Photoelectrical rectifying property of biomolecular heterostructures is investigated in molecular scale. Recombinant ferredoxin and chlorophyll a were used as an electron acceptor and a sensitizer respectively in the molecular layer by mimicking photosynthesis. A self-assembled monolayer
of recombinant ferredoxin was formed on Au surface, and then chlorophyll a was deposited onto the recombinant ferredoxin layer by Langmuir-Blodgett method. The formation of recombinant ferredoxin/chlorophyll a hetero-layers was confirmed by the SPR (surface plasmon resonance) spectroscopy,
and the surface was observed by the STM (scanning tunneling microscopy). The rectifying property by the STS (scanning-tunneling-spectroscopy) based current–voltage characteristics was achieved in the recombinant ferredoxin/chlorophyll a hetero-layers. Thus, proposed hetero-layers functioned
as a rectifier that can be useful property for the development of molecular-scale bioelectronic devices.
Photo-Patternable Titanium Doped Organic–Inorganic Hybrid Gate Dielectric in Organic Thin Film Transistors
Authors: Choi Chaun Gi , Bae Byeong-Soo
Published: August 2008

Solution processable and photo-patternable titanium doped organic–inorganic hybrid material (MDT hybrimer) was prepared by simple sol–gel reaction for the gate dielectrics in organic thin film transistors (OTFTs). The MDT hybrimer is a typical nanocomposite which is fabricated
via UV cross-linking of the nano-sized organo-oligosiloxanes. The photo-patternability of the MDT thin films was investigated using the UV light. The surface and electrical properties of MDT thin film were also investigated. The pentacene-based OTFT with MDT gate dielectrics was fabricated
by using the top contact geometry. It is found that the OTFT with the MDT gate dielectrics showed a small hysteresis and good performance. The filed-effect mobility, threshold voltage, subthreshold slope and on/off current ratio of OTFT with MDT gate dielectric were 0.66 cm2V−1s−1,
−14 V, 1.6 Vdec.−1, and 3 × 106, respectively.
Growth and Electrochromic Properties of Poly(3,4-ethylenedioxythiophene) Layer on TiO2 Nanoparticles
Authors: Baek Jehoon , Kim Yuna , Kim Eunkyoung
Published: August 2008

The growth of the conductive layer on TiO2 nanoparticles was examined. Poly(3,4-ethylenedioxythiophene)(PEDOT)was deposited on the mesoporous TiO2 nanoparticle by the chemical polymerization of 3,4-ethylenedioxythiophene (EDOT)under oxidative conditions, to afford
PEDOT coated particles having average diameter of ∼75 nm. The growth of PEDOT on TiO2 was confirmed by a field emission-scanning electron microscopy (FE-SEM) and electrochemistry. All-solid-state electrochromic devices were fabricated using the PEDOT-on-TiO2 coated
electrode and the solid polymer electrolyte as the ion conduction layer. Evaluation of the optical and electrochromic (EC) response was performed by monitoring the intensity of absorbance at the absorption wavelength of 600 nm under different conditions of applied potential. A fast electrochromic
response and an efficient EC process with a blue color change was observed from the device constructed with nano-structured PEDOT.
Synthesis of Carbazole-Based Polymers with 1,3,4-Oxadiazole Pendant Group and Their Application in Organic Light-Emitting Diodes
Authors: Wang Hui , Ryu Jeong-Tak , Cao Chao , Kwon Younghwan
Published: August 2008

Structurally well-defined copolymers with high solubility were prepared via palladium-catalyzed polycondensation of N-(2-ethylhexyl)-3,6-dibromocarbazole with 2-aryl-5-(4-aminophenyl)-1,3,4-oxadiazole (aryl = phenyl, p-methylphenyl, p-methoxyphenyl). Copolymers
consisted of alkylcarbazole groups in the main chain and 1,3,4-oxadiazole pendants in the side chain. The influence of their aryl substituents on physical, optical, band gaps and electroluminescent characteristics of the copolymers was investigated. Both UV-Visible absorption and photoluminescence
emission peaks of the copolymers were similar to each other. The band gap energy of the polymers was measured in the range of 2.84∼2.88 eV, and HOMO energy in the range of −5.13∼−5.18 eV. These copolymers were used as hole-transporting layers (HTL) in the light-emitting
diodes with Alq3 as an emitting layer. Compared to devices with P-H and P-OCH3 used as HTL, it should be noted that device with P-CH3 used as HTL showed higher luminescence. Maximum luminescence of devices was measured to be 276cd/m2 at 14 V with
P-H, 625 cd/m2 at 15 V with P-CH3, and 471 cd/m2 at 14 V with P-OCH3. This might be due to effect of subtle changes in HOMO energy level of polymers with changing substituent groups. Phosphorescent polymer light emitting diodes were also fabricated
with an emitting layer consisting of P-CH3 matrix and a red phosphorescent dopant (Ir-PIQCH).
Organic Thin Film Transistor Using a Photo-Curable Organic/Inorganic Hybrid Material as a Gate Dielectric
Authors: Hwang Do-Hoon , Yang Yong Suk , Lee Jeong-Ik , Kim Seong Hyun , Park Oun-Ho , Kim Ho-Cheol , Lee Victor , Dubois Geraud , Miller Robert D.
Published: August 2008

A polyhedral oligomeric silsesquioxane derivative (POSS-OXT) containing photo-curable 4-membered cyclic oxetane functional groups was used as a gate dielectric of organic field effect transistor. The POSS-OXT was cross-linked and completely solidified by UV irradiation in the presence
of a selected photo acid generator, and pinhole free uniform thin film was obtained. We fabricated a metal/insulator/metal device of Au/POSS-OXT (300 nm)/Au with area of 0.7 mm2 and the measured leakage current and capacitance of the device to evaluate the insulating properties
of the POSS-OXT thin film. The maximum current was about 0.25 nA when 40 V was applied to the device. The observed values of the capacitance per unit area and dissipation factor were 11.4 nF/cm2 and 0.025, respectively. We fabricated an organic thin film transistor with pentacene
as the active semiconductor and the photo-cross-linked POSS-OXT as an insulator. A field effect carrier mobility of 0.03 cm2/V·s was obtained with the device.
Electrochemical Properties of Poly(3,4-ethylenedioxythiophene) Nanofiber Non-Woven Web Formed by Electrospinning
Authors: Nguyen Hoang Dung , Ko Jung Min , Kim Hong Jung , Kim Seok Ki , Cho Seung Hyun , Nam Jae Do , Lee Jun Young
Published: August 2008

Electrically conducting nano (micro) poly(3,4-ethylenedioxythiophene) (PEDOT) fiber non-woven web was fabricated using the electrospinning technique by applying high voltage of 10 to 30 kV to the electrospinning solution. To investigate the effects of various conditions on formation
and properties of PEDOT fiber non-woven web, we changed the solvent or other components and their concentrations. We used 1-propanol or 1-butanol as a solvent and poly(vinyl pyrrolidone) (PVP) as a matrix polymer to prepare the electrospinning solution. The electrical conductivity of the electrospun
PEDOT non-woven web was as high as 7.5 S/cm when 1-propanol was used as the solvent. Electrochemical capacitor was assembled using one pair of the PEDOT non-woven webs as the electrodes by a simple stack method, where metal plates were used as current collectors. We observed the electrochemical
charge and discharge behavior of the capacitor, confirming that the PEDOT non-woven web can be used as the electrode for flexible electrochemical capacitor.
New Strategy and Easy Fabrication of Solid-State Supercapacitor Based on Polypyrrole and Nitrile Rubber
Authors: Lee Sangyool , Lee Youngkwan , Cho Mi-Suk , Nam Jae-Do
Published: August 2008

Solid state redox supercapacitors were fabricated using a solid polymer electrolyte, nitrile butadiene rubber (NBR)-KCl and chemically deposited polypyrrole (PPy) as the conducting polymer electrodes on both surfaces of a NBR film. The optimal conditions for the preparation of the PPy/NBR
electrode were confirmed as functions of the uptake of pyrrole monomer into the NBR matrix as well as the immersion time in an oxidant solution. The morphology of the PPy-NBR-KCl capacitor was observed using scanning electron microscopy. The performance of the capacitors was characterized
using a galvanostatic charge–discharge technique.
Effect of MMT Concentration on Tribological Behavior of MMT/Epoxy Nanocomposite
Authors: Ha Sung-Rok , Rhee Kyong-Yop , Shin Hyunho
Published: August 2008

Numerous studies have investigated the material properties of clay/polymer nanocomposites, such as their fracture toughness, elastic modulus, and hardness. However, only a few researchers have studied the tribological properties of clay/polymer nanocomposites. This study investigated
the effect of the montmorillonite (MMT) concentration on the tribological behavior of MMT/epoxy nanocomposites. Wear tests were performed on MMT/epoxy nanocomposites with four different clay concentration levels to characterize the improvement in wear behavior due to the MMT concentration.
In order to examine the tribological mechanism depending on the clay concentration level, SEM analysis was performed on the worn surfaces after the wear tests. The results showed that the friction coefficient of an MMT/epoxy nanocomposite with a low MMT concentration was larger than that of
a nanocomposite with a high MMT concentration. It is believed that the phenomena occur due to the action of MMT as a reinforcement and lubricant material and reduce the wear rate with increasing MMT concentration.
A Facile Route to Nano-Sized Nickel Sulfide via Thermolysis of Nickel Alkanethiolate
Authors: Sung Kiwhan , Lee Sang Hyun , Chung Taek-Mo , Kim Chang Gyoun
Published: August 2008

Nano-sized nickel sulfides were synthesized by the thermolysis of nickel alkanethiolates in the presence of coordinating ligands. Nickel alkanethiolates were synthesized by the reaction of the square planar nickel 1-dimethylamino-2-methyl-2-propanolate [Ni(dmamp)2] with various n-alkanethiols.
The effect of ligands in the reaction system has been investigated to control the size and shape of nano-sized nickel sulfides. TEM images show that the products are nano-sized nickel sulfides in rod and plate shapes. Nickel alkanethiolates and nano-sized nickel sulfides have been characterized
by means of X-ray diffraction and transmission electron microscopy.
Sensitivity Enhancement by Au Nanoparticles in Surface Plasmon Resonance Chemical Sensors
Authors: Choi Sung-Wook , Kim Hyo-Sop , Kang Won-Seok , Kim Jin-Ho , Cho Yong-Jin , Kim Jae-Ho
Published: August 2008

We investigated the sensitivity enhancement in chemical sensors by coupling Au nanoparticles that have the specific size and surface density on sensor chips as those found in label-free detection systems. The Au particles with 10, 30, 60 nm diameter were conjugated by amine groups of
cystamine modified chips. The surface density of Au particles was controlled by the reaction time and the concentration of the solution containing the particles. In order to investigate the sensitivity enhancement, we compared the resonance angle shifts with or without Au particles in a methanol
aqueous solution. We know that the sensitivity depends on the size and surface density of particles. The sensitivity increased by 57% with the adsorption of 30 nm diameter particles and low surface density due to the coupling effect of localized surface plasmon derived by the size and density
of specific Au nanoparticles and surface plasmon waves.
Synthesis and Characterization of Poly(amido amine) Dendrimer Containing Fluorene as a Core Chromophore
Authors: Lee Jae Wook , Kim Hee Joo , Han Seung Choul , Kim Ji Hyeon , Jin Sung-Ho
Published: August 2008

The synthetic strategy for the convergent synthesis of emissive poly(amido amine) (PAMAM) dendrimers having the core chromophore via the copper-catalyzed 1,3-dipolar cycloaddition reaction between alkyne and azide was described. 2,7-Diazido-9H-fluorene, designed and synthesized to serve
as the core in dendrimer, was stitched with the propargyl-functionalized PAMAM dendrons by the click chemistry leading to the formation of fluorescent PAMAM dendrimers in high yields. The absorption and emission of the dendrimers were investigated. Their photophysical studies indicated that
2,7-diazido-9H-fluorene showed no fluorescence due to the quenching effect from the electron-rich α-nitrogen of the azido group but the dendrimers fluoresced due to the elimination of the quenching through the formation of the triazole ring.
Decrease in Work Function of Transparent Conducting ZnO Thin Films by Phosphorus Ion Implantation
Authors: Heo Gi-Seok , Hong Sang-Jin , Park Jong-Woon , Choi Bum-Ho , Lee Jong-Ho , Shin Dong-Chan
Published: August 2008

To confirm the possibility of engineering the work function of ZnO thin films, we have implanted phosphorus ions into ZnO thin films deposited by radio-frequency magnetron sputtering. The fabricated films show n-type characteristics. It is shown that the electrical and optical
properties of those thin films vary depending sensitively on the ion dose and rapid thermal annealing time. Compared to as-deposited ZnO films, the work-function of phosphorus ion-implanted ZnO thin films is observed to be lower and decreases with increasing ion doses. It is likely that the
zinc or oxygen vacancies are firstly filled with the implanted phosphorus ions. With further increased ions, free electrons are generated as Zn2+ sites are replaced by those ions or interstitial phosphorus ions increase at the lattice sites, the fermi level by which approaches the
conduction band and thus the work function decreases. Those films exhibit the optical transmittance higher than 85% within the visible wavelength range (up to 800 nm).
Characterization of Nafion®/Zirconium Sulphophenyl Phosphate Nanocomposite Membrane for Direct Methanol Fuel Cells
Authors: Kim Young-Sang , Cho Hyun-Seok , Song Min-Kyu , Ghil Li-Jin , Kang Jung-Soo , Rhee Hee-Woo
Published: August 2008

Layered structure zirconium sulphophenyl phosphate (ZrSPP) was prepared from the precipitation of Zr4+ ion and m-sulphophenyl phosphonic (SPP) acid at a mole ratio of P to Zr = 2.0. The reflective index measurement indicated that the methanol permeability of unmodified
Nafion® 117 was 2.3 × 10−6 cm2/s at RT while that of the Nafion®/ZrSPP membrane (∼50 μm thick) decreased to 6.5 × 10−7 cm2/s. Nafion®/ZrSPP (10 wt%) nanocomposite
membranes delivered constant power output 104 mW/cm2 @ 0.4 V under 1 M MeOH/dry air at 70 °C even in the wide range of air stoichiometry from 1.5 to 3.0.
Subharmonic Gap Structure of Normal-State Conductance and Thermoelectric Effect in a Graphene-Based Nano Device
Authors: Park K.-S. , Park Joonho , Yi K. S.
Published: August 2008

Using the quantum transport of chiral Dirac fermions in graphene, we investigate the normal-state conductance and thermoelectric effect of a nano device under the ballistic superconductor-graphene-superconductor (SGS) model. Because of the Josephson effect and Andreev reflections, there
exists an oscillatory behavior of the normal-state conductance flowing through the successive discrete energy levels on a finite-sized graphene contacted to the superconducting leads. The normal-state conductance displays a rich structure of subharmonic gaps controlled by means of a gate voltage
on the discrete energy levels near the Fermi energy. Since the Fermi energy is an essential factor in determining the nature of conduction such as n or p type, we study the thermoelectric effect over the graphene-based nano device. It is shown that the thermoelectric effect can
provide information on the location of the Fermi energy with respect to the energy levels of the finite-sized graphene.
Effects of Post Thermal Annealing on the Electrical Properties of Vertical Type Organic Thin Film Transistors Using Poly(3-hexylthiophene) and Its Application in Organic Light Emitting Transistor
Authors: Oh Se Young , Hwang Sun Kak , Kim Young Do , Park Jong Wook , Kang In Nam
Published: August 2008

We have fabricated the vertical type organic thin film transistor (OTFT) using electrically conductive poly(3-hexylthiophene) (P3HT) as a p-type organic material. Effects of post thermal annealing and thickness of active layer on the performance of vertical type transistors were
investigated. Especially, the correlation between carrier mobility of P3HT after post thermal annealing and static characteristics of the transistor was studied. Carrier mobility was calculated by space charge limited current (SCLC) model from the I–V curves of the prepared
device. The vertical type OTFT after post thermal annealing at 120 °C (Tg) showed high current of 0.383 mA and on–off ratio of 22.5 at a low gate voltage of +2.0 V. Additionally, we report on emission characteristics from the vertical type transistor using P3HT.
ProteinVista: A Fast Molecular Visualization System Using Microsoft Direct3D
Authors: Park Chan-Yong , Park Sung-Hee , Park Soo-Jun , Park Sun-Hee , Hwang Chi-Jung
Published: August 2008

Many tools have been developed to visualize protein and molecular structures. Most high quality protein visualization tools use the OpenGL graphics library as a 3D graphics system. Currently, the performance of recent 3D graphics hardware has rapidly improved. Recent high-performance
3D graphics hardware support Microsoft Direct3D graphics library more than OpenGL and have become very popular in personal computers (PCs). In this paper, a molecular visualization system termed ProteinVista is proposed. ProteinVista is well-designed visualization system using the Microsoft
Direct3D graphics library. It provides various visualization styles such as the wireframe, stick, ball and stick, space fill, ribbon, and surface model styles, in addition to display options for 3D visualization. As ProteinVista is optimized for recent 3D graphics hardware platforms and because
it uses a geometry instancing technique, its rendering speed is 2.7 times faster compared to other visualization tools.
Fabrication of Nanocomposite Based on ZnO Nanowire
Authors: Lee Sun Sook , Kim Hyun Jin , Chung Taek-Mo , Lee Young Kuk , Kim Chang Gyoun , An Ki-Seok
Published: August 2008

ZnO-NiO core–shell nanowires and Ni-ZnO nanoparticle–nanowire composites have been synthesized by atomic layer deposition (ALD) and H2 thermal reduction, respectively. Grown ZnO nanowires on Si substrates by vapor transport method were used as templates for the
growth of NiO layers. In order to prevent interfacial interaction between deposited NiO and ZnO nanowires templates by the reaction at low temperature and to precisely control the thickness of NiO layer, ALD technique was suitably employed to form the ZnO-NiO core–shell nanowires. All
surface area of ZnO nanowires was completely and uniformly covered by amorphous NiO layers at low temperature of 130 °C. The Ni-ZnO nanoparticle–nanowire composites were achieved by the thermal reduction of the ZnO-NiO core–shell nanowires at H2 atmosphere. The density
of Ni nanoparticles on ZnO nanowires was roughly related to the pre-deposited NiO thickness and the inter-diffusion of Ni into the ZnO nanowire was not observed.
Optical Characteristics of CdSe Quantum Dots Depending on Growth Conditions and Surface Passivation
Authors: Jung Soon Il , Yeo Hyun Young , Yun Ilgu , Cho Sung M. , Han Il Ki , Lee Joo In
Published: August 2008

We investigated the effects of different growth conditions and surface passivation on the growth of CdSe quantum dots (QDs). The synthesis of CdSe QDs by pyrolysis of organometallic reagents was performed by using the hot-matrix method. In order to modify the size and quality of CdSe
QDs, we controlled the growth temperature from 250 °C to 350 °C and the relative amount of trioctylphosphin (as the ligand of the Cd and Se precursors) to be injected into the coordinating solvent trioctylphosphineoxide. Moreover, an effective surface passivation of mono-disperse CdSe
QDs was achieved by overcoating them with a larger band gap material, such as ZnS.
Epitaxial Growth of ZnO Nanowires Over the ZnO Thin Films Depositedon the Si and Sapphire Substrates
Authors: Park No-Kuk , Lee You Jin , Jung Ji Young , Lee Won Guen , Bae Young Je , Yoon Suk Hoon , Han Gi Bo , Ryu Si Ok , Lee Tae Jin
Published: August 2008

Epitaxial growth of ZnO nanowires was carried out using a modified thermal evaporation method with inexpensive experimental setup. ZnO nanowires were synthesized using ZnO thin films. The ZnO thin films were deposited as a buffer layer on silicon and sapphire using an impinging flow
reactor (IFR). The IFR system is a modified version of a chemical bath deposition (CBD). Films can be created at low temperature, without any metallic catalysts. The properties of Zinc Oxide films are dependant upon the type of substrate used. The same deposition process with a different substrates
yields two films with different properties. The most critical effect on growth of ZnO nanowires were dependent the properties of the buffer layer deposited on the substrate. It was not the type of substrate used. A cost-efficient method for epitaxial growth of single crystal ZnO nanowires
is proposed in this work.
Microfabricated In-Channel Structured Polydimethylsiloxane Microfluidic System for a Lab-on-a-Chip
Authors: Ra Gyu-Sik , Yoo Jong-Chul , Kang C. J. , Kim Yong-Sang
Published: August 2008

In this paper, the fabrication of microfluidic system integrated with micropump and microvalve on the same substrate and its high performance are described. The microfabricated microfluidic system has been optimized for application in capillary electrophoresis–electrochemical
detector (CE-ECD), polymerase chain reaction (PCR) and microcantilever. The system is realized by means of a polydimethylsiloxane (PDMS)-glass chip and indium tin oxide heater. The pumping rates of the proposed micropump are measured as functions of the frequency and the duty-ratio of applied
voltage. The performances of the microvalves are characterized under the on/off alternation with the applied power of the indium tin oxide (ITO) heater. The flow rate gradually decreases as the applied heater power increase. The optimized membrane thickness for microfluidic system is 350 μm.
At this condition, the power of the cut-off flow in microvalve is 400 mW and the 70 nl/min of maximum pumping rate is observed at a duty ratio of 4% and a frequency of 4 Hz for the applied pulse power.
Cluster Analysis of North Atlantic–European Circulation Types and Links with Tropical Pacific Sea Surface Temperatures
Authors: Fereday D. R. , Knight J. R. , Scaife A. A. , Folland C. K. , Philipp A.
Published: August 2008

Observed atmospheric circulation over the North Atlantic–European (NAE) region is examined using cluster analysis. A clustering algorithm incorporating a “simulated annealing” methodology is employed to improve on solutions found by the conventional k-means technique. Clustering is applied to daily mean sea level pressure (MSLP) fields to derive a set of circulation types for six 2-month seasons. A measure of the quality of this clustering is defined to reflect the average similarity of the fields in a cluster to each other. It is shown that a range of classifications can be produced for which this measure is almost identical but which partition the days quite differently. This lack of a unique set of circulation types suggests that distinct weather regimes in NAE circulation do not exist or are very weak. It is also shown that the stability of the clustering solution to removal of data is not maximized by a suitable choice of the number of clusters. Indeed, there does not appear to be any robust way of choosing an optimum number of circulation types. Despite the apparent lack of preferred circulation types, cluster analysis can usefully be applied to generate a set of patterns that fully characterize the different circulation types appearing in each season. These patterns can then be used to analyze NAE climate variability. Ten clusters per season are chosen to ensure that a range of distinct circulation types that span the variability is produced. Using this classification, the effect of forcing of NAE circulation by tropical Pacific sea surface temperature (SST) anomalies is analyzed. This shows a significant influence of SST in this region on certain circulation types in almost all seasons. A tendency for a negative correlation between El Niño and an anomaly pattern resembling the positive winter North Atlantic Oscillation (NAO) emerges in a number of seasons. A notable exception is November–December, which shows the opposite relationship, with positive NAO-like patterns correlated with El Niño.
On Scatterometer Ocean Stress
Authors: Portabella M. , Stoffelen A.
Published: August 2008

Scatterometers estimate the relative atmosphere–ocean motion at spatially high resolution and provide accurate inertial-scale ocean wind forcing information, which is crucial for many ocean, atmosphere, and climate applications. An empirical scatterometer ocean stress (SOS) product is estimated and validated using available statistical information. A triple collocation dataset of scatterometer, and moored buoy and numerical weather prediction (NWP) observations together with two commonly used surface layer (SL) models are used to characterize the SOS. First, a comparison between the two SL models is performed. Although their roughness length and the stability parameterizations differ somewhat, the two models show little differences in terms of stress estimation. Second, a triple collocation exercise is conducted to assess the true and error variances explained by the observations and the SL models. The results show that the uncertainty in the NWP dataset is generally larger than in the buoy and scatterometer wind/stress datasets, but it depends on the spatial scales of interest. The triple collocation analysis also shows that scatterometer winds are as close to real winds as to equivalent neutral winds, provided that the appropriate scaling is used. An explanation for this duality is that the small stability effects found in the analysis are masked by the uncertainty in SL models and their inputs. The triple collocation analysis shows that scatterometer winds can be straightforwardly and reliably transformed to wind stress. This opens the door for the development of wind stress swath (level 2) and gridded (level 3) products for the Advanced Scatterometer (ASCAT) on board Meterological Operation (MetOp) and for further geophysical development.
The Temporal Aliasing Formulas for the Tandem Mission of Jason-1 and TOPEX/Poseidon
Authors: Tai Chang-Kou
Published: August 2008

The temporal aliasing formulas are derived for the Tandem Mission of Jason-1 and the Ocean Topography Experiment (TOPEX)/Poseidon. Previously, aliasing formulas were derived for a single satellite or a constellation of coordinated satellites, wherein the coordination is such that the collective samplings appear as if they were carried out by a single satellite. In this vein, Jason-1 and TOPEX/Poseidon are coordinated spatially but not temporally. The problem is treated as a general problem about the temporal phasing between any two satellites that are coordinated spatially so that the Tandem Mission is just one special case, whereas the temporally coordinated case is another special case. The present results do agree with the formulas for a constellation of coordinated satellites when the temporal phasing yields temporal coordination, as they should. The benefit of temporal coordination shows itself as having a higher spatial resolution for temporally aliased features. The physical implication is twofold. First, a high-frequency and low-wavenumber feature (e.g., the barotropic Rossby waves) has a better chance of being aliased as a low-frequency and higher-wavenumber feature in a perfectly coordinated mission than it has in the Tandem Mission. Second, in a perfectly coordinated mission, a high-frequency and high-wavenumber feature could be aliased as a low-frequency and high-wavenumber feature rather than as a low-frequency and low-wavenumber feature in the Tandem Mission. Despite the extreme mathematical complexity, the physical case is rather intuitive. Namely, the two satellites need temporal coordination to work as one in fending off temporal aliasing. Without it, the two satellites behave as two independent satellites, thus each reverting to their original (i.e., lower) spatial resolution capability in dealing with temporal aliasing.