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A Qualitative Study on Facilitating Factors of User-Created Contents: Based on Theories of Folklore (사용자 제작 콘텐츠의 활성화 요인에 대한 정성적 연구: 구비문학 이론을 중심으로)

  • Jung, Seung-Ki;Lee, Ki-Ho;Lee, In-Seong;Kim, Jin-Woo
    • Asia pacific journal of information systems
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    • v.19 no.2
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    • pp.43-72
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    • 2009
  • Recently, user-created content (UCC) have emerged as popular medium of on-line participation among users. The Internet environment has been constantly evolving, attracting active participation and information sharing among common users. This tendency is a significant deviation from the earlier Internet use as an one-way information channel through which users passively received information or contents from contents providers. Thanks to UCCs online users can now more freely generate and exchange contents; therefore, identifying the critical factors that affect content-generating activities has increasingly become an important issue. This paper proposes a set of critical factors for stimulating contents generation and sharing activities by Internet users. These factors were derived from the theories of folklores such as tales and songs. Based on some shared traits of folklores and UCC content, we found four critical elements which should be heeded in constructing UCC contents, which are: context of culture, context of situation, skill of generator, and response of audience. In addition, we selected three major UCC websites: a specialized contents portal, a general internet portal, and an official contents service site, They have different use environments, user interfaces, and service policies, To identify critical factors for generating, sharing and transferring UCC, we traced user activities, interactions and flows of content in the three UCC websites. Moreover, we conducted extensive interviews with users and operators as well as policy makers in each site. Based on qualitative and quantitative analyses of the data, this research identifies nine critical factors that facilitate contents generation and sharing activities among users. In the context of culture, we suggest voluntary community norms, proactive use of copyrights, strong user relationships, and a fair monetary reward system as critical elements in facilitating the process of contents generation and sharing activities. Norms which were established by users themselves regulate user behavior and influence content format. Strong relationships of users stimulate content generation activities by enhancing collaborative content generation. Particularly, users generate contents through collaboration with others, based on their enhanced relationship and specialized skills. They send and receive contents by leaving messages on website or blogs, using instant messenger or SMS. It is an interesting and important phenomenon, because the quality of contents can be constantly improved and revised, depending on the specialized abilities of those engaged in a particular content. In this process, the reward system is an essential driving factor. Yet, monetary reward should be considered only after some fair criterion is established. In terms of the context of the situation, the quality of contents uploading system was proposed to have strong influence on the content generating activities. Among other influential factors on contents generation activities are generators' specialized skills and involvement of the users were proposed. In addition, the audience response, especially effective development of shared interests as well as feedback, was suggested to have significant influence on contents generation activities. Content generators usually reflect the shared interest of others. Shared interest is a distinct characteristic of UCC and observed in all the three websites, in which common interest is formed by the "threads" embedded with content. Through such threads of information and contents users discuss and share ideas while continuously extending and updating shared contents in the process. Evidently, UCC is a new paradigm representing the next generation of the Internet. In order to fully utilize this innovative paradigm, we need to understand how users take advantage of this medium in generating contents, and what affects their content generation activities. Based on these findings, UCC service providers should design their websites as common playground where users freely interact and share their common interests. As such this paper makes an important first step to gaining better understand about this new communication paradigm created by UCC.

Therapeutic Effect of Anti-Rotavirus Chicken Egg Yolk Immunoglobulin(IgY) on Diarrhea by Infection of Rotavirus (로타바이러스 감염성 설사에 대한 항-로타바이러스 난황항체의 치료 효과)

  • Lim, In Seok;Lee, Ho Seok;Kim, Wonyong;Choi, Eung Sang;Jung, Dong Hyuk;Jung, Hoo Kil;Yun, Sung Seob;Chun, Ho Nam
    • Clinical and Experimental Pediatrics
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    • v.48 no.12
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    • pp.1354-1361
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    • 2005
  • Purpose : Rotavirus is an enteric pathogen that affects millions of children globally each year. But no specific therapy is available for the management of rotavirus diarrhea. Due to the clear need to define improved modality for treatment of rotavirus diarrhea, we evaluated the efficacy of antirotavirus IgY in the treatment of infants and children with gastroenteritis. Methods : First, the amount of viral particle in the stools of thirteen patients(seven were given IgY, 6 placebo) infected by rotavirus were evaluated for 3 days with the quantitative RT-PCR method. Second, 36 children with known rotavirus infection identified by ELISA or semi-quantitative RT-PCR were evaluated. We gave 5 g anti-rotavirus egg yolk daily in two equally divided doses for 3 days to two groups(an 18 IgY group and an 18 placebo group), respectively after parenteral consent. Daily vomiting frequency, stool frequency, oral intake and urine output were monitored for 3 days, and electrolyte and blood chemistry were checked at the first and third days. Results : First, in the placebo group, the amount of virus particles increased daily, but in the IgY group it decreased daily. Second, when IgY and placebos were given to children infected with rotavirus, diarrhea on the third day decreased significantly in the IgY group, compared with the placebo group. Conclusion : Treatment with antirotavirus immunoglobulin from immunized chicken's egg resulted in a decrease in the amount of viral particles in stools and diarrhea frequency in children. These results suggest that anti-rotavirus IgY is effective in the treatment of rotavirus gastroenteritis.

Socioeconomic Factors Relating to Obesity and Inadequate Nutrient Intake in Women in Low Income Families Residing in Seoul (서울지역 저소득층 여성의 비만 및 영양소 섭취 부족과 관련된 사회경제적 요인)

  • Hwang, Ji-Yun;Ru, Sung-Yeap;Ryu, Han-Kyoung;Park, Hee-Jung;Kim, Wha-Young
    • Journal of Nutrition and Health
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    • v.42 no.2
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    • pp.171-182
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    • 2009
  • This study was performed to investigate socioeconomic factors relating to obesity and inadequate nutrient intake in women in low income families residing in Seoul. The subjects were 125 women (aged 41-87 y) recruited from the local health center for free health examination for low income families. The socioeconomic status such as educational level, income level, and housing condition were poor. For subjects aged less than 65 years, the prevalence of obesity was 44% based on BMI (${\geq}\;25\;kg/m^2$), 48% based on WHR (${\geq}\;0.85$), and 50% based on waist circumference (${\geq}\;80\;cm$) and for those more than 65 years, these were greater and 57%, 81%, and 79%, respectively. The main food sources of daily diet were vegetables, grains, and fruits. Energy and other nutrient intake was not adequate for all subjects and the inadequacy was more profound in the elderly, showing percentages of subjects whose intake was less than EAR were greater than 50% for all nutrients except for iron and below RI were also greater than 50% for all nutrients. The prevalence of obesity and nutrient inadequacy were not associated with socioeconomic status in subjects aged less than 65 years, however, obesity was associated with household income and nutrient inadequacy was related to education (vitamin A) and housing status (protein, phosphate, and iron) in the elderly. After adjustment for ages, in the elderly, OR for obesity (BMI ${\geq}$ 25, OR = 12.601; 95% CI = 2.338-67.911) and central obesity (WC ${\geq}$ 80 cm, OR = 4.778; 95% CI = 1.103-20.696) were greater in subjects who earned less than 500 thousand Won per month than who earned more. For inadequate nutrient intake, the OR for inadequate intake of Vitamin A (OR = 4.555; 95% CI = 1.491-13.914) was greater in subjects with no education than those educated. Subjects without her own house had greater risk for inadequate intake for protein (OR = 3.660; 95% CI = 1.118-11.981), phosphate (OR = 3.428; 95% CI = 1.157-10.158), and iron (OR = 3.765; 95% CI = 1.205-11.766) than subjects possessing her house. In elderly females in low income families, the socioeconomic status was associated with the risk for obesity (income level) and inadequate nutrient intake (education level and housing status). More attention on these groups should be given for prevention of obesity and inadequate nutrient intake.

The Variation of Natural Population of Pinus densiflora S. et Z. in Korea -Characteristics of Needle and Wood of Wangsan, Bonghwa and Yangju Populations- (소나무 천연집단(天然集團)의 변이(變移)에 관(關)한 연구(硏究)(VII) -왕산(旺山), 봉화(奉化), 양주집단(楊州集團)의 침엽(針葉) 및 재질형질(材質形質)-)

  • Yim, Kyong Bin;Lee, Kyong Jae
    • Journal of Korean Society of Forest Science
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    • v.40 no.1
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    • pp.1-18
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    • 1978
  • Three Pinus densiflora populations as shown in location map (Fig. 1) were studied in 1977. These succeed the population numbers 10, 11 and 12 after the preceeding populations. Following the previous study methods, 20 trees were chosen from each population and the morphological characteristics such as tree forms, branching habit, needle and wood properties were investigated. The results are summerized as follows; 1. The mean stand ages were ranged from 40 to 45. The growth performances of trees of population 10 and 11 was similar, but 12 seemed to be inferior more or less. 2. The ratios of clear bole length was 0.53 in population 12 as the highest but 0.43 for population 10 as the lowest. 3. The population 12 was considered to be a stand of the coarser branching habit having the crown index (The maximum crown diameter/the crown length) 1.65 though the mean branching angle indicates almost horizontal. 4. The differences were observed in the clear bole length ratios and crown-indices between populations as shown in Fig. 3 and 4. 5. No inter-population differences in serration density of needle was shown but significant inter and intra-population and individual differences (within population) in number of stomata rows and resin duct. 6. Population 12 shown 0.119 of resin duct index as the maximum. 7. The pattern of diameter growth, analyses based on the width of 10-year-ring segment unit (for example, the 1st segment denotes the width between pith center and 10th year ring and the 2nd one is from 11th to 20th year ring and so on.), was alike among populations as shown in Fig. 9. 8. No significant differences between population in mean summer wood percentages as well as in wood specific gravity was observed. The values of wood specific gravity were increased with the increase of ages in population 10 and 11 however vice versa in population 12. 9. The fiber length was increased with the increase of age but no differences between populations as shown in Fig. 12.

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Microwave Vacuum Drying of Germinated Colored Rice as an Enzymic Health Food (효소식품으로서 발아유색미의 마이크로파 진공건조)

  • Kim, Suk-Shin;Kim, Sang-Yong;Noh, Bong-Soo;Chang, Kyu-Seob
    • Korean Journal of Food Science and Technology
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    • v.31 no.3
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    • pp.619-624
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    • 1999
  • This work was to study the potential health food use of germinated colored rice after germinating and drying using microwave under vacuum. Colored rice was soaked in water at $15^{\circ}C$ for 2 days and then germinated at $25^{\circ}C$ for $3{\sim}4\;days$. The germinated colored rice was dried by different drying methods: microwave vacuum drying 1, microwave vacuum drying $2\;(drying{\rightarrow}crushing{\rightarrow}drying)$, hot air drying, vacuum drying and freeze drying. Each drier except freeze drier was set to maintain the sample temperature at $60^{\circ}C$. During microwave vacuum drying 1 or 2, the sample reached $60^{\circ}C$ much faster (within 5 min) and was dried much faster ($2{\sim}3\;hrs$ than the other drying methods. The initial drying rate of microwave vacuum drying was ten times faster than that of hot air drying. The microwave vacuum drying 2 retained the highest ${\alpha}-amylase$ activity, followed by microwave vacuum drying 1, freeze drying, vacuum drying, and hot air drying.

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Regulation of Tumor Neceosis Factor-${\alpha}$ Receptors and Signal Transduction Pathways

  • Han, Hyung-Mee
    • Toxicological Research
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    • v.8 no.2
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    • pp.343-357
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    • 1992
  • Tumor necrosis factor-${\alpha}$(TNF), a polypeptide hormone secreted primarily by activated macrophages, was originally identified on the basis of its ability to cause hemorrhagic necrosis and tumor regression in vivo. Subsequently, TNF has been shown to be an important component of the host responses to infection and cancer and may mediate the wasting syndrome known as cachexia. These systemic actions of TNF are reflected in its diverse effects on target cells in vitro. TNF initiates its diverse cellular actions by binding to specific cell surface receptors. Although TNF receptors have been identified on most of animal cells, regulation of these receptors and the mechanisms which transduce TNF receptor binding into cellular responses are not well understood. Therefore, in the present study, the mechanisms how TNF receptors are being regulated and how TNF receptor binding is being transduced into cellular responses were investigated in rat liver plasma membranes (PM) and ME-180 human cervical carcinoma cell lines. $^{125}I$-TNF bound to high ($K_d=1.51{\pm}0.35nM$)affinity receptors in rat liver PM. Solubilization of PM with 1% Triton X-100 increased both high affinity (from $0.33{\pm}0.04\;to\;1.67{\pm}0.05$ pmoles/mg protein) and low affinity (from $1.92{\pm}0.16\;to\;7.57{\pm}0.50$ pmoles/mg protein) TNF binding without affecting the affinities for TNF, suggesting the presence of a large latent pool of TNF receptors. Affinity labeling of receptors whether from PM or solubilized PM resulted in cross-linking of $^{125}I$-TNF into $M_r$ 130 kDa, 90 kDa and 66kDa complexes. Thus, the properties of the latent TNF receptors were similar to those initially accessible to TNF. To determine if exposure of latent receptors is regulated by TNF, $^{125}I$-TNF binding to control and TNF-pretreated membranes were assayed. Specific binding was increased by pretreatment with TNF (P<0.05), demonstrating that hepatic PM contains latent TNF receptors whose exposure is promoted by TNF. Homologous up-regulation of TNF receptors may, in part, be responsible for sustained hepatic responsiveness during chronic exposure to TNF. As a next step, the post-receptor events induced by TNF were examined. Although the signal transduction pathways for TNF have not been delineated clearly, the actions of many other hormones are mediated by the reversible phosphorylation of specific enzymes or target proteins. The present study demonstrated that TNF induces phosphorylation of 28 kDa protein (p28). Two dimensional soidum dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE) resolved the 28kDa phosphoprotein into two isoforms having pIs of 6.2 and 6.1. The pIs and relative molecular weight of p28 were consistent with those of a previously characterized mRNA cap binding protein. mRNA cap binding proteins are a class of translation initiation factors that recognize the 7-methylguanosine cap structure found on the 5' end of eukaryotic mRNAs. In vitro, these proteins are defined by their specific elution from affinity columns composed of 7-methylguanosine 5'-triphosphate($m^7$GTP)-Sepharose. Affinity purification of mRNA cap binding proteins from control and TNF treated ME-180 cells proved that TNF rapidly stimulates phosphorylation of an mRNA cap binding protein. Phosphorylation occurred in several cell types that are important in vitro models of TNF action. The mRNA cap binding protein phosphorylated in response to TNF treatment was purifice, sequenced, and identified as the proto-oncogene product eukaryotic initiation factor-4E(eIF-4E). These data show that phosphorylation of a key component of the cellular translational machinery is a common early event in the diverse cellular actions of TNF.

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Characteristics and Immunomodulating Activity of Lactic Acid Bacteria for the Potential Probiotics (Probiotics로서의 젖산균주의 특성 및 면역활성)

  • Seo, Jae-Hoon;Lee, Ho
    • Korean Journal of Food Science and Technology
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    • v.39 no.6
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    • pp.681-687
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    • 2007
  • This study was designed to examine the suitable characteristics of potential probiotic bacteria. Possible probiotic bacteria, including Lactobacillus acidophilus DDS-1, Lb. acidophilus B-3208, Bifidobacterium bifidum KCTC 3357, Lb. plantarum, Leuconostoc mesenteroides ssp. mesenteroides ATCC 8293, and Lactococcus lactis ssp. lactis ATCC 7962 were selected. We then measured their acid and bile tolerances, adhesion properties in the gastrointestinal tract, antimicrobial activity against pathogenic bacteria, and immunomodulation activity. The acid tolerances of Lb. acidophilus DDS-1, Lb. acidophilus B-3208, Lb. plantarum, and Leu. mesenteroides ssp. mesenteroides ATCC 8293, in PBS (pH 2.5) for 2 hr, were high enough that 50% of the inocula survived. The bile tolerances of all bacteria, except Lc. lactis ssp. lactis ATCC 7962, were also observed at a 3% oxgall concentration in MRS broth. The results of the adhesion property assay showed that the total binding affinities of Lb. acidophilus DDS-1, Lb. acidophilus B-3208, and B. bifidum were about three times higher than those of the other bacteria. In testing their antimicrobial activities against pathogens, Lb. acidophilus B-3208, B. bifidum KCTC 3357, and Lb. plantarum inhibited the growth of pathogenic bacteria. For their immunomodulation activity, the cell wall fractions from Lb. acidophilus DDS-1 and Lb. acidophilus B-3208 showed the highest bone marrow cell proliferation activities. However, the cell wall fractions of Lb. acidophilus DDS-1 and B. bifidum, and the cytosol fraction of Lc. lactis ssp. lactis ATCC 7962 showed higher macrophage stimulation activities than those of the other bacteria. Since Lb. acidophilus DDS-1 and Lb. acidophilus B-3208 satisfy the requirements for probiotics, they can be considered suitable probiotic bacteria.

Cellular Localization and Translocation of Duplication and Alternative Splicing Variants of Olive Flounder Phospholipase C-δ1 (넙치 3가지 타입 인지질가수분해효소(PLC-δ1)의 세포 내 위치 및 이동)

  • Kim, Na Young;Kim, Moo-Sang;Jung, Sung Hee;Kim, Myoung Sug;Cho, Mi Young;Chung, oon Ki;Ahn, Sang Jung
    • Journal of Life Science
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    • v.27 no.11
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    • pp.1369-1375
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    • 2017
  • The purpose of this study was to investigate the cellular characterization of phospholipase C-${\delta}1$ in olive flounders (Paralichthys olivaceus). In general, phospholipase C signaling pathways are distributed in nuclei at plasma membranes and in cytoplasms, although the pathways' nuclear localization mechanisms are unclear. P. olivaceus duplicates type-A PoPLC-${\delta}1$ (PoPLC-${\delta}1A$), which has a high similarity to the human isoform PLC-${\delta}$; type-B PoPLC-${\delta}1$ (PoPLC-${\delta}1B$ [Sf]), which has a low similarity to the human isoform PLC-${\delta}$ and the alternative splice variant PoPLC-${\delta}1B$ (Lf), which has a nuclear localization signal (NLS) and a nuclear export signal (NES) for nuclear imports and exports, respectively. This study confirmed the effects of the cellular localization and translocation of GFP-tagged PoPLC-${\delta}1A$, PoPLC-${\delta}1B$ (Sf) and PoPLC-${\delta}1B$ (Lf). It administered treatments of $Ca^{2+}$ ionophore ionomycin and endoplasmic reticulum (ER)-$Ca^{2+}$ pump inhibitor thapsigargin to hirame natural-embryo (HINAE) cells. A laser-scanning confocal microscope was used. GFP-tagged PoPLC-${\delta}1A$ was distributed to the cellular organelles, rather than to the cytoplasms and cytomembranes, when PoPLC-${\delta}1B$ (Lf) and PoPLC-${\delta}1B$ (Sf) were localized at the plasma membranes. The treatments of ionomycin and thapsigargin showed the accumulation of PoPLC-${\delta}1A$ in the nuclei when PoPLC-${\delta}1B$ (Lf) nucleocytoplasmic shuttling and PoPLC-${\delta}1B$ (Sf) nucleocytoplasmic shuttling were not observed. The results were the first evidence that PoPLC-${\delta}1A$, which contains functional, intact NES sequences, has a main role in nucleocytoplasmic shuttling and translocation in fish.

Development of a Culture Medium for Growth and Sporulation of Bacillus polyfermenticus SCD (프로바이오틱 비스루트균의 아포생산을 위한 최적배지 개발)

  • Lee, Kwang-Ho;Park, Kyu-Yong;Kim, Seong-Mi;Kim, Won-Seok;Paik, Hyun-Dong
    • Korean Journal of Food Science and Technology
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    • v.34 no.2
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    • pp.263-268
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    • 2002
  • Bacillus polyfermenticus SCD, which is commonly called a 'Bisroot' strain, has been appropriately used for the treatment of long-term intestinal disorders, since the live strains, in the form of active endospores, can successfully reach the target intestine. Goal of this study was to develop an industrial medium for growth and sporulation of B. polyfermenticus SCD. From the results of effect of mixed carbon sources on growth and sporulation of B. polyfermenticus SCD, glucose 2% and starch 2% was particularly found to be the most effective for the maximum number of spore production, resulting in spore cells of $4.3{\times}10^9\;spores/mL$ with a sporulation yield of 91%. For the effect of nitrogen sources, the maximum spore cells of $5.7{\times}10^9\;spores/mL$ of B. polyfermenticus SCD with a sporulation yield of 97% was obtained when B. polyfermenticus SCD was cultivated in an optimum nitrogen source medium containing 5% soybean flour. A medium involving proper phosphate salt yielded the maximum number of a spore cells of $6.0{\times}10^9\;spores/mL$ with a sporulation yield of 95%. Finally, the efficacy of an industrial medium (KH5 medium) on growth and sporulation of B. polyfermenticus SCD was investigated in jar fermenter. The higher number of viable cells $(3.3{\times}10^{10}\;cells/mL)$ and spore cells $(3.0{\times}10^{10}\;spores/mL)$ were obtained in 5 L fermenter when compared with a 500 mL baffle flask cultivation. Thus, KH5 medium developed in this study shows promise as an industrial medium because of higher cells and sporulation yield.

THEORETICAL STUDY ON OBSERVED COLOR-MAGNITUDE DIAGRAMS

  • Lee, See-Woo
    • Journal of The Korean Astronomical Society
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    • v.12 no.1
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    • pp.41-70
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    • 1979
  • From $B\ddot{o}hm$-Vitense's atmospheric model calculations, the relations, [$T_e$, (B-V)] and [B.C, (B-V)] with respect to heavy element abundance were obtained. Using these relations and evolutionary model calculations of Rood, and Sweigart and Gross, analytic expressions for some physical parameters relating to the C-M diagrams of globular clusters were derived, and they were applied to 21 globular clusters with observed transition periods of RR Lyrae variables. More than 20 different parameters were examined for each globular cluster. The derived ranges of some basic parameters are as follows; $Y=0.21{\sim}0.33,\;Z=1.5{\times}10^{-4}{\sim}4.5{\times}10^{-3},\;age,\;t=9.5{\sim}19{\times}10^9$ years, mass for red giants, $m_{RG}=0.74m_{\odot}{\sim}0.91m_{\odot}$, mass for RR Lyrae stars, $m_{RR}=0.59m_{\odot}{\sim}0.75m_{\odot}$, the visual magnitude difference between the turnoff point and the horizontal branch (HB), ${\Delta}V_{to}=3.1{\sim}3.4(<{\Delta}V_{to}>=3.32)$, the color of the blue edge of RR Lyrae gap, $(B-V)_{BE}=0.17{\sim}0.21=(<(B-V)_{BE}>=0.18),\;[\frac{m}{L}]_{RR}=-1.7{\sim}-1.9$, mass difference of $m_{RR}$ relative to $m_{RG},(m_{RG}-m_{RR})/m_{RG}=0.0{\sim}0.39$. It was found that the ranges of derived parameters agree reasonably well with the observed ones and those estimated by others. Some important results obtained herein can be summarized as follows; (i) There are considerable variations in the initial helium abundance and in age of globular clusters. (ii) The radial gradient of heavy element abundance does exist for globular clusters as shown by Janes for field stars and open clusters. (iii) The helium abundance seems to have been increased with age by massive star evolution after a considerable amount (Y>0.2) of helium had been attained by the Big-Bang nucleosynthesis, but there is not seen a radial gradient of helium abundance. (iv) A considerable amount of heavy elements ($Z{\sim}10{-3}$) might have been formed in the inner halo ($r_{GC}$<10 kpc) from the earliest galactic co1lapse, and then the heavy element abundance has been slowly enriched towards the galactic center and disk, establishing the radial gradient of heavy element abundance. (v) The final galactic disk formation might have taken much longer by about a half of the galactic age than the halo formation, supporting a slow, inhomogeneous co1lapse model of Larson. (vi) Of the three principal parameters controlling the morphology of C-M diagrams, it was found that the first parameter is heavy clement abundance, the second age and the third helium abundance. (vii) The globular clusters can be divided into three different groups, AI, BI and CII according to Z, Y an d age as well as Dickens' HB types. BI group clusters of HB types 4 and 5 like M 3 and NGC 7006 are the oldest and have the lowest helium abundance of the three groups. And also they appear in the inner halo. On the other hand, the youngest AI clusters have the highest Z and Y, and appear in the innermost halo region and in the disk. (viii) From the result of the clean separations of the clusters into three groups, a three dimensional classification with three parameters, Z, Y and age is prsented. (ix) The anomalous C-M diagrams can be expalined in terms of the three principal parameters. That is, the anomaly of NGC 362 and NGC 7006 is accounted for by the smaller age of the order of $1{\sim}2{\times}10^9$ years rather than by the helium abundance difference, compared with M 3. (x) The difference in two Oosterhoff types I and II can be explained in terms of the mean mass difference of RR Lyrae variables rather than in terms of the helium abundance difference as suggested by Stobie. The mean mass of the variables in Oosterhoff type I clusters is smaller by $0.074m_{\odot}$ which is exactly consistent with Rood's estimate. Since it was found that the mean mass of RR Lyrae stars increases with decreasing Z, the two Oosterhoff types can be explained substantially by the metal abundance difference; the type II has Z<$3.4{\times}10^{-4}$, and the type I has higher Z than the type II.

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