• 대한화학회지
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• 제17권4호
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• pp.262-268
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• 1973

p-Phenylenediamine을 과량의 진한 염산 및 과염소산을 매질로하여 거의 완전히 tetrazo화 하였다. Tetrazonium염의 두 diazo기를 할로겐으로 치환하여 생긴 dihalobenzene의 수량으로 반응의 정도를 알아 보았다. 이 반응의 성패는 tetrazonium염의 안정도에 의하여 죄우되었으며, 그 안정도는 매질의 종류, 산도(농도) 및 그양과 밀접한 관계가 있음을 알았다. 즉 산매질의 농도가 너무 묽으면 tetrazonium염은 불안정하여 완전히 분해되었으며, 매질의 농도가 너무 진하면 tetrazonium염은 안정한 반면에 tetrazo화 반응이 방해되었다. 이 상반되는 두 경향을 조화시키기 위해서는 tetrazonium염이 안정하게 존재할 수 있는 가장 낮은 농도의 산을 매질로 써야함을 알 수 있었다. p-Phenylenediamine의 tetrazo화에서는 약$40{\sim}45$%의 산매질이 적당하였다. $H^+$이온이 부촉매로 작용하는 것으로 보아 diazo화 반응이 아민의 염의 상태에서 일어나는 것이아니고 유리상태의 아민과 nitroso group 사이에서 일어난다는 설이 타당함을 알 수 있었다. Tetrazo화 반응을 diazo화 반응의 kinetics 및 mechanism과 관련시켜서 설명하였다.

• Journal of Chest Surgery
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• 제20권3호
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• pp.451-457
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• 1987

Reoperations following cardiac surgery have an increased risk of the danger of damaging the heart, great vessels or extracardiac grafts because of adhesions to the sternum. We experimentally evaluated 3 different methods for pericardial closure. A standardized procedure for induction of pericardial adhesions was carried out in 30 rabbits. For closure of pericardium, animals were divided into 3 groups, 10 animals respectively: Croup 1 [simple pericardial closure]The pericardium was primarily resuture; Group 2 [Core-Tex surgical membrane as a pericardial substitute]- A Gore-Tex surgical membrane was interposed between the sternum and the heart; and Group 3 [pericardial tension releasing technique]-Three longitudinal overlapping incisions were made on the right side of the pericardium while the midline incison was sutured. Animals were put to death 4 weeks postoperatively and the pericardial space was examined for pericardial adhesions and epicardial reactions. The extent of adhesions and reactions were graded as: I-none; II-minimal; III-moderate; and IV-severe. Histologic studies of the pericardium, the pericardial substitute and the epicardium were also performed. The results were as follows: 1. In group 1 [simple pericardial closure], the degree of pericardial adhesions were grade I in 1 animal, grade II in 2, grade III in 4 and grade IV in 3. Epicardial reactions were grade I in 1 animal, grade II in 3, grade III in 5 and grade IV in 1. Histologic examination revealed thick fibrous tissue that obliterated the pericardial space in 7 animals. 2. In group 2 [Gore-Tex surgical membrane as a pericardial substitute], the degree of pericardial adhesions were grade I in 3 animals, grade II in 3, grade III in 2 and grade IV in 2. The degree of epicardial reactions were grade II in 1 animal, grade III in 5 and grade IV in 4. Histologic studies revealed a thin layer of dense fibrous tissue which covered the Gore-Tex surgical membrane and thick loose fibrous tissue on the epicardium just beneath the substitute. 3. In group 3 [pericardial tension releasing technique], the degree of pericardial adhesions were grade I in 3 animals, grade II in 4, grade III in 2 and grade IV in 1. The degree of epicardial reactions were grade 1 in 4 animals, grade II in 4 and grade III in 2. Severe epicardial reactions were not observed in this group. Histologic examination showed normal epicardium in 4 animals and the epicardium of the other 6 animals only revealed very thin fibrous layer compared to group I and group II. Pericardial adhesions more than grade III were 70% in group 1, 40% in group 2 and 30% in group 3. Pericardial adhesions were reduced in group 2 and group 3 compared to group 1, but statistically not significant. Epicardial reactions more than grade III were 60% in group 1, 90% in group 2 and 20% in group 3. Epicardial reactions were significantly reduced in group 3 compared to group 2. Author`s modified pericardial releasing technique provides marked augment of pericardial surface area and facilitates tension-free pericardial closure. Furthermore, pericardial adhesion and epicardial reaction will be reduced with the pericardial tension releasing technique.

• Restorative Dentistry and Endodontics
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• 제29권4호
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• pp.386-398
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• 2004

Objectives: The purpose of this study was to observe the reaction kinetics and the degree of polymerization of composite resins when cured by different light sources and to evaluate the effectiveness of the blue Light Emitting Diode Light Curing Units (LED LCUs) compared with conventional halogen LCUs. Materials and Methods: First, thermal analysis was performed by a differential scanning calorimeter (DSC). The LED LCU (Elipar Freelight, $320{\;}mW/\textrm{cm}^2$) and the conventional halogen LCU (XL3000, $400{\;}mV/\textrm{cm}^2$) were used in this study for curing three composite resins (SureFil, Z-250 and AEliteFLO). Second. the degree of conversion was obtained in the composite resins cured according to the above curing mode with a FTIR. Third, the measurements of depth of cure were carried out in accordance with ISO 4049 standards. Statistical analysis was performed by two-way ANOVA test at 95% levels of confidence and Duncan's procedure for multiple comparisons. Results: The heat of cure was not statistically different among the LCUs (p > 0.05). The composites cured by the LED (Exp) LCUs were statistically more slowly polymerized than by the halogen LCU and the LED (Std) LCU (p < 0.05). The composite resin groups cured by the LED (Exp) LCUs had significantly greater degree of conversion value than by the halogen LCU and the LED (Std) LCU (p =0.0002). The composite resin groups cured by the LED (Std) LCUs showed significantly greater depth of cure value than by the halogen LCU and the LED (Exp) LCU (p < 0.05).

• Journal of Chest Surgery
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• 제13권4호
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• pp.507-511
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• 1980

Most cases of plasma-cell granuloma occur in adult skeleton system. They usually present as a single lesion, but multiple lesions are not uncommon. Roentgenographically, the lesions are lytic, sclerotic or mixed, but in the majority there is some degree of sclerosis. No specific etiologic agent is known, but it is postulated that the reaction may be associated with a variety of organisms of low-grade virulence. Certain organisms have long been known to produce predominantly plasmacytic infiltrate, notably spirochetes, mycobacteria and some exotic viruses. It is most important, however, that this entity, plasma-cell granuloma, be distinguished from multiple myeloma so those potentially life-threatening chemotherapeutic agents are not prescribed. Histologically, aggregates of chronic inflammatory cells are intermingled with the meets of plasma cells, and note the markedly thickened bone trabeculae in surrounding bone. We experienced a case of plasma-cell granuloma of right 7th. rib, occurring in 32 year old male and reported it with review of literatures.

• International Journal of Concrete Structures and Materials
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• 제2권1호
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• pp.49-55
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• 2008

The disadvantage of PMM's (polymer-modified mortars) that are currently on the market is the utilization of expensive polymer additives and also the cost of the other components. One of the possibilities how to decrease this price is the effective utilization of waste materials which are very inexpensive in spite of their good properties. The combinations of different degree in polymer adhesiveness and waste secondary raw materials - fly ash - are experimentally verified in the paper. The use of fly ash in adhesive materials for ceramic tiles is limited by unsatisfactory initial adhesiveness to sintered ceramic sherd as a result of a running pozzolanic reaction that lowers the efficiency of polymer additives. On the other hand, the use of adhesive and backfill coating materials for gluing ETICS board insulation materials has brought very good results.

• 대한화학회지
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• 제15권3호
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• pp.109-116
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• 1971

The mechanical degradation of poly (${\alpha}$-methyl styrene) in several mixed solvents (toluene-n-butyl alcohol, toluene-sec-butyl alcohol, toluene-kerosene, toluene-methyl ethyl ketone), from $1^{\circ}C to $45^{\circ}C$, was studied using the capillary flow method. The velocity constant of scission reaction (k) and the limited degree of polymerization (g) were compared at the same value of [${\eta}$] at each temperatures. As results, mechanical degradation of polymer in dilute mixed solutions is affected by composition of solvents around the polymer chains.

• International Journal of Concrete Structures and Materials
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• 제8권2호
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• pp.173-182
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• 2014

An experimental investigation was carried out to evaluate the mechanical properties of concrete mixtures in which coarse aggregate was partially (30, 50 or 70 %) replaced with pre-washed municipal solid waste incineration (MSWI) bottom ash. Results indicated that bottom ash reduced the compressive strength, elastic modulus, and levels of heavy metals in leachate when used as a replacement for gravel, and that the maximum amount of MSWI bottom ash in concrete should not exceed 50 %. To analyze the effect mechanism of bottom ash in concrete, the degree of hydration and the following pozzolanic reaction characterized by the pozzolanic activity index, and the porosity distribution in cement mortar. The study indicates that improved properties of concrete are not solely later strength gain and reduced levels of heavy metals in leachate but also the progression of pozzolanic reactions, where a dense structure contains a higher proportion of fine pores that are related to durability.

• Bulletin of the Korean Chemical Society
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• 제33권10호
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• pp.3274-3278
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• 2012

The kinetic studies on the reactions of phenyl N-phenyl phosphoramidochloridate (8) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) have been carried out in acetonitrile at $60.0^{\circ}C$. The obtained deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) are huge secondary inverse ($k_H/k_D$ = 0.52-0.69). A concerted mechanism is proposed with a backside attack transition state (TS) on the basis of the secondary inverse DKIEs and the variation trends of the $k_H/k_D$ values with X. The degree of bond formation in the TS is really extensive taking into account the very small values of the DKIEs. The steric effects of the two ligands on the rates are extensively discussed for the aminolyses of the chlorophosphate-type substrates on the basis of the Taft equation.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1973-1975
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• 2010

The electronic and adsorption structure of o-phthalaldehyde (OPA) on the H-Si(100) surface was investigated by using Near Edge X-ray Fine Structure (NEXAFS) and high resolution photoemission spectroscopy (HRPES). We confirmed that the OPA grown on the H-Si(100) surface showed good dependency with about 60 degree tilting angle using NEXAFS and a single O 1s peak by using HRPES. Hydrogen atom passivated on the Si(100) surface was found to be a seed for making one dimensional organic line that uses a chain reaction as the H-Si(100) surface was compared with the hydrogen free Si(100) surface.

• Corrosion Science and Technology
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• 제2권5호
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• pp.219-224
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• 2003

Crevice corrosion of stainless steels in natural seawater was investigated for several post weld treatments; as-annealed, as-welded, pickled, and ground. The results confirmed the effect of the biofilm on the cathodic reaction leading to an ennoblement of the rest potential. The degree of ennoblement of corrosion potential depends on the surface finish. As-annealed and pickled samples show stable corrosion potential approaching to 200 ~ 300 mV (SCE) while as-welded and ground samples show the fluctuating corrosion potential. This points to a situation where there are conflicting effects determining the trend in free corrosion potential. Crevice corrosion initiation will tend to pull the free corrosion potential in the active direction, whereas the presence of biofilm will tend to ennoble corrosion potential. There was no visible attack on UNS S31803, S32550, and 2205W. Therefore, those stainless steel grades appeared to be resistant to crevice corrosion in natural seawater on condition of weld metal.