• Polymer(Korea)
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• v.25 no.1
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• pp.1-5
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• 2001

Monomer casting nylons were synthesized by casting anionic polymerization of ${\varepsilon}$-caprolactam. Polymerization rates, molecular weights of the products and the conversions were determined while varying the content of catalysts in the range of 0.2~0.6 mol% and 0.1~1.0 mol% for initiator. The polymerization rates were enhanced as the ratio of catalysts to initiator increased. The maximum molecular weight was observed when the ratio of catalysts to initiator was 0.8, and as the ratio increased the molecular weight decreased. On the other hand, when the ratio of catalysts to initiator was below 0.8, the conversions and the molecular weights were abruptly diminished due to the termination of growing chains.

• Journal of Periodontal and Implant Science
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• v.49 no.5
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• pp.310-318
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• 2019

Purpose: Surface alterations of titanium discs following instrumentation with either a nylon brush or a metal brush were evaluated. Methods: A total of 27 titanium discs with 3 surface types (9 discs for each type), including machined (M) surfaces, sandblasted and acid-etched (SA) surfaces, and surfaces treated by resorbable blast media (RBM), were used. Three discs were instrumented with a nylon brush, another 3 discs were instrumented with a metal brush, and the remaining 3 discs were used as controls for each surface type. Surface properties including the arithmetic mean value of a linear profile (Ra), maximum height of a linear profile (Rz), skewness of the assessed linear profile (Rsk), arithmetic mean height of a surface (Sa), maximum height of a surface (Sz), developed interfacial area ratio (Sdr), skewness of a surface profile (Ssk), and kurtosis of a surface profile (Sku) were measured using confocal microscopy. Results: Instrumentation with the nylon brush increased the Ra, Sa, and Sdr of the M surfaces. On the SA surfaces, Ra, Sa and Sdr decreased after nylon brush use. Meanwhile, the roughness of the RBM surface was not affected by the nylon brush. The use of the metal brush also increased the Ra, Sa, and Sdr of the M surface; however, the increase in Sdr was not statistically significant (P=0.119). The decreases in the Rz, Sz, Ra, Sa, and Sdr of the SA surfaces were remarkable. On the RBM surfaces, the use of the metal brush did not cause changes in Ra and Sa, whereas Rz, Sz, and Sdr were reduced. Conclusions: Titanium surfaces were altered when instrumented either with a nylon brush or a metal brush. Hence, it is recommended that nylon or metal brushes be used with caution in order to avoid damaging the implant fixture/abutment surface.

• Korean Journal of Food Science and Technology
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• v.49 no.1
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• pp.28-34
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• 2017

Biocatalytic modification of natural resources can be used to generate novel compounds with specific properties, such as higher viscosity and reactivity. The production of hydroxy fatty acids (HFAs), originally found in low quantities in plants, is a good example of the biocatalytic modification of natural vegetable oils. HFAs show high potential for application in a wide range of industrial products, including resins, waxes, nylons, plastics, lubricants, cosmetics, and additives in coatings and paintings. In a recent study, Pseudomonas aeruginosa strain PR3 was used to produce 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) from oleic acid. This present study focused primarily on the utilization of three natural nut oils obtained from the Philippines -pili nut oil (PNO), palm oil (PO), and virgin coconut oil (VCO)- to produce DOD by P. aeruginosa strain PR3. Strain PR3 produced DOD from PNO and PO only, with PNO being the more efficient substrate. An optimization study to achieve the maximum DOD yield from PNO revealed the optimal incubation time and medium pH to be 48 h and 8.0, respectively. Among the carbon sources tested, fructose was the most efficiently used, with a maximum DOD production of 130 mg/50 mL culture. Urea was the optimal nitrogen source, with a maximum product yield of 165 mg/50 mL culture. The results from this study demonstrated that PNO could be used as an efficient substrate for DOD production by microbial bioconversion.