• Journal of the Korean Chemical Society
• /
• v.66 no.4
• /
• pp.284-297
• /
• 2022

The antibacterial activity of metallic nanoparticles (NPs), especially silver (Ag), has been investigated during the course of time in various chemical reactions for antibiotics free agents. Green synthesis of metallic NPs using either microorganisms or plant-extracts has appeared as a simple and replacement to chemical and physical methods. The synthesizing of these NPs through ecofriendly methods signifies an exceedingly applicable approach for offering economical, preferring scalability and possessing negligible ecological influences. Essential-oils are among the subordinate metabolites of plants and their antibacterial anti-inflammatory characteristics have been investigated widely and are commonly attained from the aromatic plants. The usage of essential-oils as reducing agents in biosynthesizing of Ag NPs bring together the interaction of a vital antibacterial agent that simplify the nucleation and growth process within the NPs formation. This review article is offering a progressive process of Ag NPs synthesis using essential oils along with proposing the most applicable formation mechanisms and their antibacterial activities.

• Polymer(Korea)
• /
• v.33 no.5
• /
• pp.441-445
• /
• 2009

In order to develop an intelligent delivery system for cosmetic active agents (e.g., arbutin, ascorbic acid, and adenosine), pH-responsive P(MAA-co-PEGMA) hydrogel particles having an average size of approx. $2{\mu}m$ and spherical shape were synthesized via dispersion photopolymerization. There was a drastic change in the swelling ratio of P (MAA-co-PEGMA) hydro gels at a pH 5, which is the $pK_a$ of the hydrogel. To determine the factors that have an effect on the loading of cosmetic active agents into the hydrogel, the loading efficiency of the active agents was investigated at various MAA and EG compositions of the hydrogel and the loading pH conditions. When the MAA contents in the hydrogel decreased, the loading efficiency of the active agents increased. In loading experiments with different pH conditions, the active agents showed higher loading efficiency into the hydrogel at the pH where the hydrogel was at the swollen state than at the pH where the electrostatic repulsion was minimized.

• Restorative Dentistry and Endodontics
• /
• v.18 no.2
• /
• pp.469-481
• /
• 1993

The purpose of this study was to achieve the reduction of the galvanic current between the dental amalgam alloy and gold alloy. In order to measure the galvanic current between these two metals a prep in the size of $4{\times}13mm$ which was filled with amalgam and another prep of $4{\times}2mm$ was filled with gold alloy was made in the acrylic resin. These two preps were then connected to a 2mm diameter copper wire. Using an ammeter to measure the galvanic current, six different kinds of amalgam and gold alloy were immersed in saline solution with approximately 10mm distance between the two alloys. Chemical agents that are thought to reduce the galvanic current such as hydrazine. silver nitrate, potassium chromate, and bonding agents such as Scotch bond 2(3M) and All bond 2(Bisco) were applied to the alloy surface. Cathodic inhibitor such as hydrazine was applied to gold alloy where as anodic inhibitor such as silver nitrate and potassium chromate were applied to amalgam. Both bonding agents, Scotch bond 2(3M) and All bond 2 (Bisco), were applied to amalgam. The following results were obtained when the currency on the coated alloy surface was compared to the uncoated surface. 1. The galvanic currency went down as the time elapsed and after 30 minutes no change was detected. 2. Initial currency was higher in low copper amalgam compared to high copper amalgam. Intitial currency was the highest in low copper lathe-cut amalgam. 3. Group of gold coated with hydrazine had the most reduction in galvanic currency. 4. Group of amalgam coated with silver nitrate or potassium chromate also showed significant reduction in galvanic currency. 5. The bonding agents also helped reduce galvanic currency. 6. Of all the agents used to reduce galvanic currency, silver nitrate showed the best result.

• Journal of the Korean Institute of Gas
• /
• v.8 no.2 s.23
• /
• pp.1-7
• /
• 2004

The physical properties of rigid polyurethane foam(PUF) synthesized using various types of blowing agents such as water, HFC-365mfc, HFC-245fa, HCFC-l4lb, CFC-11 and n-pentane were studied. The blending effect of blowing agents were also studied. The thermal conductivity, reaction rate, and cell morphology of the PUF with various blending ratio of blowing agents were investigated. The PUF blown by water shows the highest compressive strength among other single blowing agents. The thermal conductivity of PUFs blown by HFC-245fa and HFC-365mfc are close to that of PUFs blown by CFC-11. When HFC-365mfc was mixed with HFC-245fa(30mo1e$\%$) as coblowing agent, the mechanical property shows the highest value among other coblowing agents. It is that the thermal conductivity of PUFs depends on cell size of PUFs as well as thermal conductivity of blowing agent in gaseous form.

• Membrane and Water Treatment
• /
• v.3 no.1
• /
• pp.35-49
• /
• 2012

In membrane processes, various agents are used to enhance, protect, and recover membrane performance. Applying these agents in membrane modification could potentially be considered as a simple method to improve membrane performance without additional process. Citric acid (CI) and sodium bisulfite (SB) are two chemicals that are widely used in membrane feed water pretreatment and cleaning processes. In this work, preadsorptions of CI and SB were developed as simple methods for polysulfone ultrafiltration membrane modification. It was found that hydrogen bonding and Van Der Waals attraction could be responsible for the adsorptions of CI and SB onto membranes, respectively. After modification with CI or SB, the membrane surfaces became more hydrophilic. Membrane permeability improved when modified by SB while decreased a little when modified by CI. The modified membranes had an increase in PEG and BSA rejections and better antifouling properties with higher flux recovery ratios during filtration of a complex pharmaceutical wastewater. Moreover, membrane chlorine tolerance was elevated after modification with either agent, as shown by the mechanical property measurements.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.9
• /
• pp.3004-3008
• /
• 2012

Small molecule conjugated peptides were prepared by solid-phase synthesis as potential novel whitening agents, and their melanogenesis inhibitory activities were investigated. The conjugated small molecules were well-known materials as tyrosinase inhibitors, and peptides were selected from the sequences that are known to antagonize melanocortin receptor 1 (MC1R). Most of small molecules-peptide conjugates showed superior melanin inhibition activity to kojic acid and arbutin. Among these, almost all compounds have -AR- sequence. From this study, we concluded that the small molecule conjugated peptides containing -AR- sequence have melanogenesis inhibitory activities and have potential to be used as novel whitening agents.

• Journal of Radiation Protection and Research
• /
• v.5 no.1
• /
• pp.32-35
• /
• 1980

A number of chemical compounds that modify radiation effects are reviewed, with brief report of our own experiments on radioprotective effect of some vasoconstrictive agents and 5-Thio-D-Glucose. Sulfhydryl compounds(-SH group) and some pharmacologic compounds such as CNS depresants, vasoconstrictive agents and autonomic drugs are known to have radioprotective effect in experimental research and in limitted clinical study, whereas oxygen, hallogenated pyrimidines and metronidazole, etc. have radiosensitizing effect. Author experimentally observed some radioprotective effects of angiotensin II, a strong vasoconstrictor, and 5-Thio-D-glucose in mice.

• Proceedings of the Korean Fiber Society Conference
• /
• 2002.04a
• /
• pp.301-304
• /
• 2002

In the prior work,$\^$l)/ we introduced several chemical cross-linking agents in order to improve elastic recovery of copolyetheresters, but we are confronted by two difficulties. The first is that cross-linking agents interfere with crystal growth which acts as a physical interlocking. The second is that strain at breaking decreases with the amount of cross-linking agent. It is considered that the chemical interlocking parts couldn't be deformed like crystalline phase. (omitted)

• 보존과학연구
• /
• s.26
• /
• pp.5-25
• /
• 2005

A consideration number of investigation have begun to elucidate the essential role biological agents play in the deterioration of stone. What is becoming clear is that many factors affect the durability of stone. Physical, chemical, and biological agentsact in co-association, ranging from synergistic to antagonistic, to deteriorate stone. Biodeterioration has usually been considered to be a degradation process following the initial deterioration effects of inorganic agents, especially objects of cultural value such as pagoda, stature of Buddha etc. These agents were thought to condition stone surfaces for microbial contamination due to structural changes and enrichment of inorganic organic nutrient substrates. This report concentrates on the action of biodeteriogens from bacteria to algae and higher plants. Preventive and remedial methods are surveyed, as are a selection of chemical treatments.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 1999.04b
• /
• pp.338-342
• /
• 1999

It has been proven in previous work that rosin sizing agents are distributed relatively homogeneously on the outer surface of paper. Therefore, rosin sizing agents on paper surfaces can be characterized by macro domain measurement techniques with very thin layer from the surface. In this work, the role of rosin sizing agents on paper surface was investigated by comparing wettability from contact angle measurement with the chemical state of the outermost surface by the ESCA. Furthermore, the role of rosin on the surface of paper was discussed by the quantity of hydroxyl groups obtained from chemical modification with the TFAA-ESCA technique. It was found from the ESCA data that the fixing mechanism with soap-type rosin sizing is different from that with emulsion-type rosin sizing.