• Journal of Information Display
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• v.9 no.4
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• pp.35-38
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• 2008

This paper reports the electrical characteristics of polyvinylpyrrolidone (PVPy) and the performance of organic thin-film transistors (OTFTs) with PVPy as a gate insulator. PVPy shows a dielectric constant of about 3 and contributes to the upright growth of pentacene molecules with $15.3\AA$ interplanar spacing. OTFT with PVPy exhibited a field-effect mobility of 0.23 $cm^2$/Vs in the saturation regime and a threshold voltage of -12.7 V. It is notable that there was hardly any threshold voltage shift in the gate voltage sweep direction. Based on this reliable evidence, PVPy is proposed as a new gate insulator for reliable and high-performance OTFTs.

• Journal of radiological science and technology
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• v.1 no.1
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• pp.55-59
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• 1978

The photographic characteristics have been studied in relation with various molecular weights of Polyvinylpyrrolidone(PVP). The shape of silver halogen crystals by physical ripening of mixture of photographic gelatine and various molecular weights of PVP were observed. Then, the photographic characteristics have been studied by chemical ripening. Results were concluded as follows: 1. All of the crystals have formed in the shape of (100) or (111). 2. Photographic characteristics were inferior by using PVP of higher molecular weight. 3. Photographic characteristics were superior by using PVP of lower molecular weight. 4. Photographic characteristic were compared with various Emulsion thickness and Tested Resolving power.

• Bulletin of the Korean Chemical Society
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• v.29 no.4
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• pp.866-868
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• 2008

• The Journal of Advanced Prosthodontics
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• v.7 no.5
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• pp.392-399
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• 2015

PURPOSE. The aim of this study was to evaluate the effect of metal primers on the bonding of dental alloys and veneer resin. Polyvinylpyrrolidone solution's tarnish effect on bonding strength was also investigated. MATERIALS AND METHODS. Disk-shape metal specimens (diameter 8 mm, thickness 1.5 mm) were made from 3 kinds of alloy (Co-Cr, Ti and Au-Ag-Pd alloy) and divided into 4 groups per each alloy. Half specimens (n=12 per group) in tarnished group were immersed into polyvinylpyrrolidone solution for 24 hours. In Co-Cr and Ti-alloy, Alloy Primer (MDP + VBATDT) and MAC-Bond II (MAC-10) were applied, while Alloy Primer and V-Primer (VBATDT) were applied to Au-Ag-Pd alloys. After surface treatment, veneering composite resin were applied and shear bond strength test were conducted. RESULTS. Alloy Primer showed higher shear bond strength than MAC-Bond II in Co-Cr alloys and Au-Ag-Pd alloy (P<.05). However, in Ti alloy, there was no significant difference between Alloy Primer and MAC-Bond II. Tarnished Co-Cr and Au-Ag-Pd alloy surfaces presented significantly decreased shear bond strength. CONCLUSION. Combined use of MDP and VBATDT were effective in bonding of the resin to Co-Cr and Au-Ag-Pd alloy. Tarnish using polyvinylpyrrolidone solution negatively affected on the bonding of veneer resin to Co-Cr and Au-Ag-Pd alloys.

• YAKHAK HOEJI
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• v.23 no.2
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• pp.81-94
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• 1979

Rifampicin-polyvinylpyrrolidone coprecipitates were prepared by the solvent method to increase the solubility and dissolution rate, thereby improving absorption of rifampicin. It was found that the solubility and dissolution rate were greater with the 1 : 5 (w/w) coprecipitate than with the pure drug, physical mixtures or coprecipitates of any other ratio of the two components. The blood concentration data in non-fasted rats showed that the extent of absorption of rifampicin were significantly enhanced following the oral administration of the 1 : 5 coprecipitate; The area under the serum concentration curve (0-8hr) was 1.3 times greater with the 1 : 5 coprecipitate than with the pure drug. The blood concentration reached its peak (4. 38$\pm$1.36mcg/ml) within two hours in the case of oral administration of the 1 : 5 coprecipitate and, on the other hand, it reached the maximum (3.77$\pm$0.90mcg/ml) after four hours of oral administration of the pure drug. It was observed that there was no significant difference between the 1 : 5 coprecipitate and the pure drug in the extent and rate of absorption of rifampicin when fasted rats were used. When the 1 : 5 coprecipitate was orally administered to human subjects 20 minutes after meal, it was found that the blood concentration reached the maximum after one hour; in the case of the pure drug, it reached its peak after four hours.

• Korean Journal of Materials Research
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• v.18 no.8
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• pp.401-405
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• 2008

Pt-loaded carbon black for the catalyst of a PEM fuel cell was synthesized with different molar ratios of polyvinylpyrrolidone and $H_2PtCl_6$ solution to improve the dispersion of Pt nanoparticles on carbon black and decrease the size of Pt nanoparticles. From transmission electron microscopy results, Pt nanoparticles of a size of approximately 2 nm were highly dispersed when the polyvinylpyrrolidone concentration was 10mM. The electrochemical activity of the synthesized Pt/C catalysts was investigated by cyclic voltammetry, showing that the as-synthesized Pt-loaded carbon black catalyst had the best activity at a polyvinylpyrrolidone concentration of 10 mM.

• Journal of Embryo Transfer
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• v.21 no.2
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• pp.121-128
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• 2006

In this study, we examined the effects of molecular weight, concentrations and treat the duration of polyvinylpyrrolidone (PVP) in vitro maturation (IVM) medium (Experiment 1), and the effect of PVP in IVM, in vitro fertilization (IVF) and in vitro culture (IVC) medium on the development and cell number of porcine embryos (Experiment 2). The base mediums were NCSU 23 solution for IVM, mTBM solution for IVF and PZM3 solution for IVC. In experiment 1, the development rates to 2 cell and blastocyst stage were not differ from the different molecular weight (MW), concentration and duration of PVP in IVM medium. However, the hatching rate of blastocyst was significantly higher in the group of MW 40,000, 0.5% and $0{\sim}44hr$ than in the other groups (p<0.05). In experiment 2, the results of IVM, IVF and IVC medium with (W) or without (W/O) 0.5% MW 40,000 PVP are follows. The development rate to 2 cell stage was highest in the group of W-W/O-W (p<0.05). The development rate to blastocyst and hatching rate was higher in the group of W-W/O-W and W-W/O-W/O than that of other treatments (p<0.05).

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1741-1744
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• 2013

A new polymeric catalyst was prepared by supporting $GaCl_3$ on cross-linked polyvinylpyrrolidone ($GaCl_3$/PVP). This catalyst was employed for efficient and regioselective ring-opening reaction of epoxides by various alcohols under solvent-free conditions at room temperature. In our procedure, this heterogeneous catalyst was used at neutral and mild reaction conditions to afford high yields of ${\beta}$-alkoxy alcohols. Also, regioselective conversion of epoxides to ${\beta}$-azidohydrines was accomplished by sodium azide in MeOH in the presence of $GaCl_3$/PVP at room temperature. $GaCl_3$/PVP is a non-hygroscopic and recoverable catalyst and is easily separated from reaction mixture by a simple filtration and re-used repeatedly. Also, this catalyst has good handling and can be stored for long time without any reducing of its reactivity.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2575-2580
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• 2010

We present a method for chemically reducing silver alkylcarbamate complex with hydrazine to synthesize silver nanocolloids in an organic solvent using polyvinylpyrrolidone (PVP) as the stabilizer. To determine the optimal conditions for preparing stable silver colloids of controlled size and shape, the silver 2-ethylhexylcarbamate (Ag-EHCB) complex, PVP, hydrazine, and 2-propanol solvent concentrations in the reaction mixture were varied. The initial colloid has a mean particle diameter of 5-80 nm, and it exhibits an absorption band with various shapes in the UV region with a maximum near 420 nm. UV-vis spectroscopy, TEM, and X-ray diffraction techniques were used to investigate the formation and growth process of the metallic silver nanocolloids.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.5
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• pp.289-295
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• 2010

In this study, the enhancement of the thermal conductivity of water in the presence of multi-walled carbon nanotubes, MWCNT, was investigated. Sodium Dodecyl Sulfate, SDS, and Polyvinylpyrrolidone, PVP, were employed as the dispersant. SDS or PVP was added in pure water. And then, MWCNT of 0.0005, 0.001, 0.002, 0.003, 0.004, 0.005, 0.01, and 0.02 vol% was dispersed respectively. The thermal conductivity and the viscosity were measured with a transient hot-wire instrument built for this study and the DV II+ Pro viscometer. The results showed that PVP had good thermal conductivity at 300 wt% and this was better than that of SDS 100 wt%, also, the viscosity of nano fluid added PVP rapidly increased until 0.02 vol%.