• Restorative Dentistry and Endodontics
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• v.14 no.1
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• pp.41-56
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• 1989

The purpose of this study was to examine the effect of temperature dependence of the behavior on the physical properties of posterior composite resins. Three light cure posterior composite resins (Heliomolar, Litefil-P, and P-50) and one chemical cure posterior composite resin (Bisfil-II) were used as experimental materials. Composite resin was placed in a cylindrical brass mold (2.5 mm high and 6.5 mm inside diameter) that was rested on a glass plate. Another flat glass was placed on top of the mold, and the plate was tightly clamped together. After the mold had been filled with the light cure composite material, the top surface was cured for 30 seconds with a light source. Chemical cure resin specimens were made in the same manner as above. Three hundreds and twenty composite resin specimens were constructed from the four composite materials. One hundred and sixty specimens of them were placed in a heater at $50^{\circ}C$, $75^{\circ}C$, $100^{\circ}C$, $125^{\circ}C$, $150^{\circ}C$, $175^{\circ}C$ and $200^{\circ}C$ for 5 minutes or 10 minutes respectively before compressive strengths were measured. Another one hundred and sixty specimens were tested for the diametral tensile strengths in the same way as above. They were randomly divided into eight groups according to the mode of heating methods as follows and stored in distilled water at $37^{\circ}C$ for 24 hours. Group $37^{\circ}C$ - specimens were stored at $37^{\circ}C$ in distilled water for 24 hours. Group $50^{\circ}C$ - specimens were heated at $50^{\circ}C$ after curing. Group $75^{\circ}C$ - specimens were heated at $75^{\circ}C$ after curing. Group $100^{\circ}C$ - specimens were heated at $100^{\circ}C$ after curing. Group $125^{\circ}C$ - specimens were heated at $125^{\circ}C$ after curing. Group $150^{\circ}C$ - specimens were heated at $150^{\circ}C$ after curing. Group $175^{\circ}C$ - specimens were heated at $175^{\circ}C$ after curing. Group $200^{\circ}C$ - specimens were heated at $200^{\circ}C$ after curing. Twenty specimens of each of four composite resins were respectively made by insertion of materials into same mold for examining the dimensional changes between before and after heating. The final eighty specimens were stored in distilled water at $37^{\circ}C$ for 24 hours before testing the dimensional changes. Compressive and diametral tensile strengths were measured crosshead speed 1mm/minute and 500Kg in full scale with a mechanical testing machine (DLC 500 Type, Shimadzu Co., Japan). Dimensional changes were determined by measuring the diametral changes of eighty specimens with micrometer (Mitutoyo Co., Japan). Results were as follows: 1. Diametral tensile strengths of specimens in all groups were increased with time heated compared with control group except for that in group $50^{\circ}C$ and the maximum diametral tensile strength was appeared in the specimen of Litefil-P heated for 10 minutes at $100^{\circ}C$. In heliomolar and P-50, it could be seen in the specimen heated for 10 minutes at $150^{\circ}C$, but in Bisfil-II, it could be found in the specimen heated for 5 minutes at $150^{\circ}C$. 2. Compressive strengths of specimens in all groups was tended to be also increased with time heated but that in group $50^{\circ}C$ and the maximum compressive strengths were showed in the same specimens conditioned as the diametral tensile strengths of four composite materials tested. 3. In Heliomolar, Litefil-P, and Bisfil-II, it was decreased in diameters of resin specimens between before heating and increased in diameters of resin specimens after storing in distilled water, but it was not in P-50. 4. There is little difference in diametral tensile strengths, compressive strengths, and dimensional changes followed by heating the resin specimens for 5 minutes and 10 minutes, but there is no statistical significances.

• Journal of Chest Surgery
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• v.36 no.1
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• pp.7-14
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• 2003

Cyclin I plays a pivotal role in the regulation of G1-S transition and could consequently be a deregulated molecule in tumors. The activity of the cdk2-cyclin E complex is increased by degradation of cdk inhibitor p27kip1. Little is known about the expression and prognostic significance of cyclin E and p27 in non-small cell lung cancer(NSCLC). Material and Method: The expression of cyclin E and p27 in eighty-one cases of resected stage I NSCLC tissues and its relation to major clinico-pathological factors, including histology, differentiation, size of tumor, pleural invasion and survival rate were studied and analyzed. Immunohistochemical analysis with monoclonal antibodies specific for cyclin E and p27 were performed by ABC method. Result: Expression rates of cyclin E and p27 in stage I NSCLC tissues were 29.6% and 28.4% respectively. Cyclin E was expressed higher in cases of pleural invasion(p=0.04), and p27 was expressed higher in diameter of tumor less than 3cm(p=0.015). The 5-years survival rate was lower in cases of Positive expression of cyclin E than in cases of negative expression of cyclin E(44.4% vs 68.2%, p=0.015), and the 5-years survival rate was 72.2% in positive expression of p27 and 56.2% in negative expression of p27(p=0.09). The 5-years survival rate was higher in negative expression of cyclin E and positive expression of p27 than in cases of positive expression of cyclin I and negative expression of p27 (73.5% vs 36.3%, p=0.0029). In multivariate analysis, expression of cyclin I was an unfavorable prognostic factor(RR=3.578, p=0.006) and p27 was a favorable prognostic factor(RR=0.183, p=0.019) independently. Conclusion: Cyclin E and p27 may play a pivotal role for the biological behavior of stage I NSCLC, so that the expressions of cyclin I and p27 nay be new prognostic markers.

• Journal of Chest Surgery
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• v.37 no.8
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• pp.684-690
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• 2004

Background: Primary thymic epithelial neoplasm is a type of mediastinal tumors that have various biologic and morphologic features. In this study, we reclassified 59 cases of thymic epithelial tumors by the new WHO classification. We inquired whether the new WHO classification has independent prognostic relevance by analyzing clinical characteristics of thymic epithelial tumors including Masaoka's clinical stage. Material and Method: From December 1986 to August 2003, 59. patients who underwent surgery in the Keimyung University Dongsan Medical Center with definite diagnosis of thymic epithelial tumor were studied. We analyzed the histologic subtype (WHO classification). clinical stage (Masaoka's clinical stage) and patient's characteristics (sex, age, myasthenia gravis, tumor size, invasion. recurrence, metastasis) as prognostic factors. We analyzed the relationship between histologic subtype and clinical stage. Result: 32 patients were male and 27 were female. Mean age was 50.1$\pm$14.2. From WHO A to C, all thymic epithelial tumors were reclassified by the new WHO classification. Six patients (10.2%) had Type A, 7 (11.9%) had Type AB, 7 (11.9%) had Type B$_1$, 10 (16.9%) had Type B$_2$ and 7 (11.9%) had Type B$_3$, 22 (37.3%) had Type C. Two factors were shown by multivariate analysis to be associated with a favorable prognosis: completeness of resection (p=0.003) and non-invasiveness (p=0.001). The overall 5-year survival of the 59 patients was 53%, subtype A and AB were 92.3%, B$_1$ and B$_2$ were 70.2%, and B$_3$ and C were 26.1%. The association between histologic subtype and invasive behavior (stage) was statistically significant (p<0.001). Conclusion: The WHO classfication is not only a histologic classfication of the thymic epithelial tumors but also a significant prognostic factor that influence the survival of thymic epithelial tumors.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.625-639
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• 2019

Microplastics are one of the substances threatening the marine ecosystem. Here, we summarize the status of research on the effect of microplastics on marine life and suggest future research directions. Microplastics are synthetic polymeric compounds smaller than 5 mm and these materials released into the environment are not only physically small but do not decompose over time. Thus, they accumulate extensively on land, from the coast to the sea, and from the surface to the deep sea. Microplastic can be ingested and accumulated in marine life. Furthermore, the elution of chemicals added to plastic represents another risk. Microplastics accumulated in the ocean affect the growth, development, behavior, reproduction, and death of marine life. However, the properties of microplastics vary widely in size, material, shape, and other aspects and toxicity tests conducted on several properties of microplastics cannot represent the hazards of all other microplastics. It is necessary to evaluate the risks according to the types of microplastic, but due to their variety and the lack of uniformity in research results, it is difficult to compare and analyze the results of previous studies. Therefore, it is necessary to derive a standard test method to estimate the biological risk from different types of microplastics. In addition, while most of the previous studies were conducted mostly on spheres for the convenience of the experiments, they do not properly reflect the reality that fibers and fragments are the main forms of microplastics in the marine environment and in fish and shellfish. Furthermore, studies have been conducted on additives and POPs (persistent organic pollutants) in plastics, but little is known about their toxic effects on the body. The effects of microplastics on the marine ecosystems and humans could be identified in more detail if standard testing methods are developed, microplastics in the form of fibers and fragments rather than spheres are tested, and additives and POPs are analyzed. These investigations will allow us to identify the impact of microplastics on marine ecosystems and humans in more detail.

• Korean Journal of Head & Neck Oncology
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• v.14 no.2
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• pp.182-190
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• 1998

Background: Most of the cancers of maxillary sinus are the squamous variety, but various histopathologic types of malignant tumor can occur in the maxillary sinus. These non-squamous cell tumors have quite different patterns of clinical behavior compared with squamous variety, such as invasive characters, route of metastasis, treatment modality, and so on. Objectives: The authors intend to establish the clinical characteristics and treatment modalities of non-squamous cell tumors of the maxillary sinus. Material and Methods: We experienced 16 cases of non-squamous cell tumors arisen from the maxillary sinus during the 10-year period from 1987 to 1996. We analyzed their clinical features, therapeutic modalities and results with review of literatures. Results: According to AJCC TNM system, 13 patients presented with $T_{1-2}$, 3 with $T_{3-}4$, Two patients were treated with surgery after radiotherapy, 3 patients with surgery after chemotherapy and radiotherapy, 4 patients with chemotherapy and radiotherpy, 5 patients with chemotherapy and radiotherapy after surgery. Conclusion: In cases of adenoid cystic carcinoma, adenocarcinoma and sarcoma, we believe that the best form of therapy is wide surgical excision. If there is microscopic evidence of disease at or close to the resection margin, postoperative radiation was used to achieve better local control. In cases of undifferentiated carcinoma, preoperative chemotherapy and radiation therapy showed improved outcomes.

• Journal of the Korean Chemical Society
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• v.47 no.6
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• pp.614-618
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• 2003

$Sr_2Ru_{1-x}Cu_xO_{4-y}(0.0{\le}x{\le}0.5)$ compounds were prepared using a conventional solid state reaction. Based on the Rietveld refinements of X-ray diffraction results, it is revealed that $Sr_2Ru_{1-x}Cu_xO_{4-y}$ compounds are the single phases with K2NiF4 type tetragonal system in the range of 0=x=0.3, while the mixed phases of$Sr_2RuO_4$ and $Sr_2CuO_3$ in the range of $0.4{\le}x{\le}0.5$. By means of X-ray photoelectron spectroscopy, the valence states of Ru and Cu in $Sr_2Ru_{1-x}Cu_xO_{4-y}$, have been confirmed to 4+ and 2+, respectively. The bond length difference between $Ru-O_1 ({\times}4)\;and\;Ru-O_2 ({\times}2)\;in\;RuO_6$ octahedron is gradually decreased with increasing Cu content in $Sr_2Ru_{1-x}Cu_xO_{4-y}$, which results in the lower c/a ratio. So, it might be assured that the variation of local symmetry of $RuO_6$ octahedron is very closely related to the transporting property of $Sr_2Ru_{1-x}Cu_xO_{4-y}$ compounds. The behavior of resistivity discloses that the metallic property in $Sr_2RuO_4$ changes into the semiconducting one in proportion to the Cu content in $Sr_2Ru_{1-x}Cu_xO_{4-y}$.

• Management & Information Systems Review
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• v.3
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• pp.287-316
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• 1999

Cyberspace permits us to more beyond traditional face-to-face, mail and telephone surveys, yet still to examine basic issues regarding the quality of data collection: sampling, questionnaire design, survey distribution, means of response, and database creation. This article address each of these issues by contrasting and comparing traditional survey methods(Paper-and-Pencil) with Internet or Personal Computer networks-mediated (Screen-and-Keyboard) survey methods also introduces researchers to this revolutionary and innovative tool and outlines a variety of practical methods for using the Internet or Personal Computer Networks. The revolution in telecommunications technology has fostered the rapid growth of the Internet all over the world. The Internet is a massive global network and comprising many national and international networks of interconnected computers. The Internet or Personal Computer Networks could be the comprehensive interactive tool that will facilitate the development of the skills. The Internet or Personal Computer Networks provides a virtual frontier to expand our access to information and to increase our knowledge and understanding of public opinion, political behavior, social trends and lifestyles through survey research. Comparable to other technological advancements, the Internet or Personal Computer Networks presents opportunities that will impact significantly on the process and quality of survey research now and in the twenty-first century. There are trade-offs between traditional and the Internet or Personal Computer Networks survey. The Internet or Personal Computer Networks is an important channel for obtaining information for target participants. The cost savings in time, efforts, and material were substantial. The use of the Internet or Personal Computer Networks survey tool will increase the quality of research environment. There are several limitations to the Internet or Personal Computer Network survey approach. It requires the researcher to be familiar with Internet navigation and E-mail, it is essential for this process. The use of Listserv and Newsgroup result in a biased sample of the population of corporate trainers. However, it is this group that participates in technology and is in the fore front of shaping the new organizations of interest, and therefore it consists of appropriate participants. If this survey method becomes popular and is too frequently used, potential respondents may become as annoyed with E-mail as the sometimes are with mail survey and junk mail. Being a member of the Listserv of Newsgroup may moderate that reaction. There is a need to determine efficient, effective ways for the researcher to strip identifiers from E-mail, so that respondents remain anonymous, while simultaneously blocking a respondent from responding to a particular survey instrument more than once. The optimum process would be on that is initiated by the researcher : simple, fast and inexpensive to administer and has credibility with respondents. This would protect the legitimacy of the sample and anonymity. Creating attractive Internet or Personal Computer Networks survey formats that build on the strengths of standardized structures but also capitalize on the dynamic and interactive capability of the medium. Without such innovations in survey design, it is difficult to imagine why potential survey respondents would use their time to answer questions. More must be done to create diverse and exciting ways of building an credibility between respondents and researchers on the Internet or Personal Computer Networks. We believe that the future of much exciting research is based in the Electronic survey research. The ability to communicate across distance, time, and national boundaries offers great possibilities for studying the ways in which technology and technological discourse are shaped. used, and disseminated ; the many recent doctoral dissertations that treat some aspect of electronic survey research testify to the increase focus on the Internet or Personal Computer Networks. Thus, scholars should begin a serious conversation about the methodological issues of conducting research In cyberspace. Of all the disciplines, Internet or Personal Computer Networks, emphasis on the relationship between technology and human communication, should take the lead in considering research in the cyberspace.

• Journal of the Korean Magnetics Society
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• v.18 no.3
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• pp.109-114
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• 2008

The samples were synthesized by using a solid state reaction. The X-ray diffraction pattern for $Ti_{0.96}Co_{0.02}Fe_{0.02}O_2$ showed a pure rutile phase with tetragonal structure, Mixtures of the proper proportions of the elements sealed in evacuated quartz ampoule were heated at $870{\sim}930^{\circ}C$ for one day and then slowly cooled down to room temperature at a rate of $10^{\circ}C$/h. In order to obtain single phase material, it was necessary to grind the sample after the first firing and to press the powders into pellets before annealing them for a second time in evacuated and sealed quartz ampoule. Magnetic properties have been investigated using the vibrating sample magnetometer (VSM). Room temperature magnetic hysteresis (M-H) curve showed an obvious ferromagnetic behavior and the magnetic moment per Fe atom under the applied of 0.8 T was estimated to be about $1.5\;{\mu}_B$/CoFe. But the magnetic moment per Fe atom under the applied of 0.8 T was estimated to be about $0.02\;{\mu}_B$/CoFe without Ti-getter. Size of particles is about $1\;{\mu}m$ using the transmission electron microscope (TEM). The ingredients of sample are distributed irregular in particles. Only Fe get shown on the surface of particles.

• Korean Journal of Food Science and Technology
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• v.44 no.4
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• pp.428-433
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• 2012

Probiotics and their products, such as yogurt and cheese have been widely consumed in many countries with proven health benefits including anti-microbial activity and anti-diarrheal activity. LHFM (Lactobacillus helveticus - fermented milk) is a processed skim milk powder, fermented by a probiotics, L. helveticus IDCC3801. In the present study, we aimed to investigate the neuroprotective effects and the cognitive improvements of LHFM. LHFM itself did not show any cytotoxicity to the human neuroblastoma cell line, SH-SY5Y; however, it dose-dependently protected against glutamate-induced neuronal cell death. LHFM also attenuated scopolamine-induced memory deficit in Y-maze and Morris-water maze. In the analysis of hippocampus after a behavior test, LHFM significantly increased the acetylcholine level and also inhibited acetylcholine esterase activity. Therefore, the raised acetylcholine release partially contributes to the improvement of learning and memory by a treatment with LHFM. These results suggest that LHFM is an effective material for prevention or improvement of cognitive impairments caused by neuronal cell damage and central cholinergic dysfunction.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.06a
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• pp.16-23
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• 2000

The increasing functional needs of top-quality printing papers and packaging paperboards, and especially the rapid developments in electronic printing processes and various computer printers during past few years, set new targets and requirements for modern paper quality. Most of these paper grades of today have relatively high filler content, are moderately or heavily calendered , and have many coating layers for the best appearance and performance. In practice, this means that many of the traditional quality assurance methods, mostly designed to measure papers made of pure. native pulp only, can not reliably (or at all) be used to analyze or rank the quality of modern papers. Hence, introduction of new measurement techniques is necessary to assure and further develop the paper quality today and in the future. Paper formation , i.e. small scale (millimeter scale) variation of basis weight, is the most important quality parameter of paper-making due to its influence on practically all the other quality properties of paper. The ideal paper would be completely uniform so that the basis weight of each small point (area) measured would be the same. In practice, of course, this is not possible because there always exists relatively large local variations in paper. However, these small scale basis weight variations are the major reason for many other quality problems, including calender blacking uneven coating result, uneven printing result, etc. The traditionally used visual inspection or optical measurement of the paper does not give us a reliable understanding of the material variations in the paper because in modern paper making process the optical behavior of paper is strongly affected by using e.g. fillers, dye or coating colors. Futhermore, the opacity (optical density) of the paper is changed at different process stages like wet pressing and calendering. The greatest advantage of using beta transmission method to measure paper formation is that it can be very reliably calibrated to measure true basis weight variation of all kinds of paper and board, independently on sample basis weight or paper grade. This gives us the possibility to measure, compare and judge papers made of different raw materials, different color, or even to measure heavily calendered, coated or printed papers. Scientific research of paper physics has shown that the orientation of the top layer (paper surface) fibers of the sheet paly the key role in paper curling and cockling , causing the typical practical problems (paper jam) with modern fax and copy machines, electronic printing , etc. On the other hand, the fiber orientation at the surface and middle layer of the sheet controls the bending stiffness of paperboard . Therefore, a reliable measurement of paper surface fiber orientation gives us a magnificent tool to investigate and predict paper curling and coclking tendency, and provides the necessary information to finetune, the manufacturing process for optimum quality. many papers, especially heavily calendered and coated grades, do resist liquid and gas penetration very much, bing beyond the measurement range of the traditional instruments or resulting invonveniently long measuring time per sample . The increased surface hardness and use of filler minerals and mechanical pulp make a reliable, nonleaking sample contact to the measurement head a challenge of its own. Paper surface coating causes, as expected, a layer which has completely different permeability characteristics compared to the other layer of the sheet. The latest developments in sensor technologies have made it possible to reliably measure gas flow in well controlled conditions, allowing us to investigate the gas penetration of open structures, such as cigarette paper, tissue or sack paper, and in the low permeability range analyze even fully greaseproof papers, silicon papers, heavily coated papers and boards or even detect defects in barrier coatings ! Even nitrogen or helium may be used as the gas, giving us completely new possibilities to rank the products or to find correlation to critical process or converting parameters. All the modern paper machines include many on-line measuring instruments which are used to give the necessary information for automatic process control systems. hence, the reliability of this information obtained from different sensors is vital for good optimizing and process stability. If any of these on-line sensors do not operate perfectly ass planned (having even small measurement error or malfunction ), the process control will set the machine to operate away from the optimum , resulting loss of profit or eventual problems in quality or runnability. To assure optimum operation of the paper machines, a novel quality assurance policy for the on-line measurements has been developed, including control procedures utilizing traceable, accredited standards for the best reliability and performance.