• Title/Summary/Keyword: rural children

Search Result 570, Processing Time 0.029 seconds

A Seroepidemiologic Study on Rubella Antibody in Pregnant Women in Kyonggi Do (경기도 지역 임신부를 대상으로 한 풍진 항체 양성률에 대한 혈청 역학적 연구)

  • Ki, Mo-Ran;Choi, Bo-Youl;Shin, Young-Jeon;Park, Hung-Bae;Youn, Bae-Joong;Hahn, Joong-Surk
    • Journal of Preventive Medicine and Public Health
    • /
    • v.30 no.2 s.57
    • /
    • pp.279-292
    • /
    • 1997
  • The vaccinations of susceptible children and postpubertal females are the major means to prevent congenital rubella syndrome(CRS). Another means for reducing the CRS is therapeutic abortion or fetal monitoring for women who are infected in the first four months of pregnancy. We could not estimate the incidence of CRS in Korea, because there was no surveillance system for rubella and CRS. Nationwide vaccination program for 15months infant had been started early 1980s. So, most women at childbearing age during study period were not received rubella vaccination. We set forth CRS management system for pregnant women in two rural county of Kyonggi province, Korea. In this system, the presence of rubella IgG and IgM antibodies for early pregnant women were examined with MEIA(Microparticle Enzyme Immunoassay) method by IMx automated analyzer $Abbott^(R)$. The infected pregnant women followed up in order to confirm their childrens CRS. This study was carried out from Mu. 1993 to Jun. 1994, and pregnant women examined were 874 persons. The results were summarized as follows. The overall positive .ate of rubella IgG antibody was 94.5%(826/874). The positive rate was significantly increase as the age increased, and reached 100% in pregnant women who were over 35 years old. This results suggest that a meaningful number of women are infected during childbearing years. The geometric mean titer of IgG of sero-positive subjects was significantly declined as the age increased. On the question about history of URI symptoms and rash in pregnancy, 20.7% of respondents checked on URI symptoms with .ash, 13.5% only URI symptoms without .ash, and 65.8% no symptoms. However there was no demonstrable association between the rubella like infection history in pregnancy and the rubella IgG and IgM antibody status. Rubella infection .ate in pregnant women was 0.9%(95% CI 0.4-1.8%). Two of these 8 infected pregnancies were terminated by therapeutic abortion. One of them was not followed. Five babies had no gross anomalies at birth. In Dec. 1996, three of five babies were normal appeared infants. Two of them were not followed. Throughout this study results, we confirmed the need of CRS management system for pregnant women, in Korea.

  • PDF

A Study on Sickness and Utilization of Medical Care in a Rural Area of Kyunggido (일부(一部) 농어촌주민(農漁村住民)의 상병(傷病) 및 의료이용도(醫療利用度)에 관(關)한 조사연구(調査硏究))

  • Chang, Yong-Tae
    • Journal of Preventive Medicine and Public Health
    • /
    • v.9 no.1
    • /
    • pp.139-146
    • /
    • 1976
  • This survey attempted to determine the overall health situation in Kyunggido in terms of sickness prevalence, sickness distribution, demand for medical care by type, and utilization of medical care. The survey was conducted on 766 households, or 4,065 people, from July 1-31, 1975. The findings from the survey are as follows: 1) In terms of age distribution, 28.7% of the sample was from 10-19, the 40-49 age group was the next largest group, and those over 60 made up 7% of the sample. 2. The education distribution is as follows, 30.4% completed primary school, 22.4% had no formal education, 20.6% attended but did not onplete primary school, and 1.8% attended unversities or higher. 3) In terms of occupation, 55.9% were unemployed or family employees, which represents a large dependent population, 30.4% of the workers were employed in farming or fisheries. 4. The marital status is as follows, 58.8% of the women were married, 32.3% unmarried, and 7.5% divorced. 5) The prevalence rate of mouthy illness was 19.7% of 100 infant, 42.8% became fatally ill within the first year of life. This is a very high percentage compared with more developed nations. 6) Of those reportion on illness, 54.6% sought treatment. The rate of treatment was highest in infants at 77.7%. Us age increased, demand for treatment decreased to 43.1% for those in the aldest age group. The oldest age group also had the highest rate of non treatment at 56.8%. 7) The demand for medical care showed that 65.6% utilized drug stores, 20.2% utilized hospitals and clinics, 5.4% used herbdrug-stores and herb clinices, and 3.9% relied upon folk medicine and withch craft. 8) The utilization of medical facilties by sex is as follows, 65.1% of the men and 66.0% of the women used drug stores, and 19.2% of the men and 20.2% of the women used hospitals and clinics. However, more men (3.5%) were hospitalized than women (1.8%) 9) In terms of out-patient care, the largest age group of males was 10-19 (28.2%), and the largest age group of females was 0-9 (30.8%). There was no sex difference in the use of western pharmacies. Menaged 30-39 and women aged 50-59 were the most frequent users of herb clinics. 10) The rate of receiving treatment at drugstore hospitals went towards declining level in the second case of what While increaing much more at herb clinics and folk medicines in the second case than the first one. 11) After primary utilization of hospitals, 32.7%. of the adults aged 20-59 used drug-stores as a secondary source of care, and 12.8% of children and youth under age 20 continued receiving care at hospitals. 12) After primary utilization of drug-stores, 32.5 % of the adults continued to seek care at drug stores and 1.8% used hospitals. 4.2% of those over age 60 utilized folk medcine and witch craft.

  • PDF

A Study on the User's Motivation and Satisfaction for Civic Garden (시민농원의 이용동기와 만족도에 관한 연구)

  • 노경아;김유일
    • Journal of the Korean Institute of Landscape Architecture
    • /
    • v.22 no.4
    • /
    • pp.133-148
    • /
    • 1995
  • This study was carried out to provide behavioral data for its planning and management of civic garden through the evaluation of user's motivation & satisfaction. The civic gardens around Seoul were surveyed. The site are located in Kwangtan-myeon, Sudong-myeon, Wonsam-myeon, Nam-myeon, Buknae-myeon, and Jumdong-myeon, A total of 244 questionnaires were completed by mail questionnaires. The results are as follows: 1. 82 percentage of users are in thirties or fourties most of them have children who go to the elementary school. 50 percentage of users are just typical house wifes. 74 percentage of users graduated form university. 60 percentage of users live in lofty apartment buildings. 2. As a result from factor analysis, their motivations are categorized into four fator groups.: 'to experience nature', 'weekend recreation', 'nostalgia', 'to provide their old parent's sparetime'. And their satisfactions are categorized into eleven fator groups.: 'psychological/intellectual component', 'recreational components', 'instruction/management', 'facility'. 'vegetable cultivation', 'social contact', 'crowing', 'aesthetic component', 'family contact', 'the terms of lease', 'visition time'. 3. The user of civic garden can be divided into four user groups by their motivation. CLUSTER1 can represent the user group who have motivations for 'leisure, relaxation'. They are considerably satisfied with all other factor 'opportunity of meeting new person'. CLUSTER2 at the age of 41 to 50 have motivation for 'health, nostalgia'. CLUSTER3 at the age of 31 to 40 have motivation for 'harvest, experiencing nature'. CLUSTER4 at the age of more than 51 want to let their parents enjoy their sparetime. They are dissatisfied with accessibility, amount of cultivation area, crowding and overall farm management. 4. The regression analysis was employed with predicting the overall satisfaction. The results of regression analysis showed that 69% of total variances was explained by six variables: The most effective variable is 'whether visiting on weekend or weekdays', the visitors on weekdays are far more satisfied than weekend visitors because of traffic congestion, and crowding. The second source of satisfactions are 'psychological/intellectual components', they are satisfied with 'family contact', 'the terms of lease' and 'instruction in farming' are sources of satisfaction or dissatisfaction, and finally 'aesthetic landscape' is the source of satisfaction. The second most important variable is psychological one. Even though the civic gardens were not well equipped, they liked the atmosphere of rural life, refreshness, nostalgia, satisfaction from cultivation plants, and sense of achievement.

  • PDF

Comparison of Leisure Activities of First-Year High School Students in Large Cities and Medium and Small Cities - Focusing on the Influence on Health Status - (대도시와 중소도시 고등학교 1학년 학생의 여가활동 실태 비교 - 건강상태에 미치는 영향력을 중심으로 -)

  • Yun Hwan Kim;Hyosang Han
    • Journal of agricultural medicine and community health
    • /
    • v.49 no.1
    • /
    • pp.50-58
    • /
    • 2024
  • Objective: The purpose of this study is to examine the factors influencing the health status of first-year high school students leisure activity time, considering of the city size. Methods: This study utilized the first cohort survey of the Korean Children and Youth Panel Survey. The analysis was used data from survey targeting first-year high school students of 2021. The city size was divided into large cities and medium and small-sized cities, and T-test was conducted to examine differences in factors by city size, and multiple regression analysis was conducted to identify factors influencing health status according to leisure activity time on weekdays and weekends by city size. Results: In large cities, exercise and physical activity time and other than that, Time to play with friends had a positive effect(+), Time to play with a smartphone had a negative effect(-) on both weekdays and weekends. In medium and small-sized cities, Exercise and physical activity time and Time to play while watching TV had a positive influence(+) on both weekdays and weekends, while Time to play with a smartphone had a negative influence(-). Conclusion: There were the same questions for factors influencing health status, but other questions also appeared. Leisure activities that have a positive(+) impact on health status by city size are supported so that leisure activities can be actively carried out, while leisure activities that have a negative(-) impact are participate in other leisure activities together to improve health. It is believed that this plan should be considered.

AGE AT MARRIAGE AND FERTILITY OF WOMEN IN THREE SELECTED AREAS IN KOREA, 1970 (한국 3개 지역의 결혼, 결혼년령 및 출산력에 관한 연구)

  • 김모임
    • Journal of Korean Academy of Nursing
    • /
    • v.3 no.3
    • /
    • pp.1-14
    • /
    • 1973
  • This study is designed to meet the following objectives: (1) To study attitude and behavior regarding marriage and age at marriage, (2) To learn correlates of age at marriage and to examine their relations, (3) To measure relative importance of the correlates of age at marriage, and (4) To study relations of age at marriage and family planning practice to fertility and their relative importance as correlates of fertility. The data are obtained by an independent cross-sectional survey in three study areas purposively selected to represent metropolitan. semihuman. rural population. The study population is confined to women age 17-50 as of survey. The overall response rate is 90%. Reliability of data is measured by . individual and aggregate inconsistency based upon a 15% subsample of the original interviews. The individual inconsistency (31%) is found to be high compared to the aggregate inconsistency (6%) for all 85 variables. However, the magnitude of differences between means is small, and the mean absolute shifts and proportional shifts are also small on the whole. In a word respondents did not change their answers too extremely or radically. The study populations of each study area are compared on some basic characteristics. It is found that the three study populations have more dissimilarities than similarities. The findings on seven different attitudinal positions of women toward marriage indicate that there have been tremendous changes in all study areas Iron "traditional" attitudes which have been prevalent for a long time in Korean society to "liberalized" or "modernized" attitudes. An apparent tendency is that women generally take a position of a "golden mean" attitude by not preferring either extreme of marriage attitudes. Nevertheless, the young, single, educated, and urbanite appears more "liberalized. " There has been some increase in ideal age at marriage from 1958 to 1970 for both sexes. No age group, marital status, or study area differentials in ideal age at marriage are found, the average ideal age at marriage in every sub-group being 24-25. Awareness of existing legal marriageable ages is low; only 4.4% are aware that "with parental permission: minimum age for males is 18 years and for females 16 years,"and only 3.7% are aware that "without parental permission: 27 years for males and 23 years for females." People in Korra tend to marry spouses who are in various social ways like themselves: the similarities include (a) education, occupational status of father, (c) economic status, (d) usual residence before marriage, and (e) religion. Both singulars and actual mean ages at marriage in this study confirm the trend of rising age at marriage previously established by other independent studies. The urban-rural differential in age at marriage is observed, but the differential narrows down gradually from 1935 to 1970. All socio-economic, demographic, and other variables pertaining to wife before and at first marriage, excluding (a) religion, (b) father′s of occupation, and (c) as: of menarche, are correlated with respondent's age at first marriage, whereas only three variables out of all socio-economic variables relating to husband before and at wife′s first marriage, viz., (a) education, (b) usual residence, and (c) economic level of his old home, are correlated with respondent′s age at marriage. Among socio-economic and modernity variables related to either husband or wife at the time of survey, only education and duration of residence are correlated with wife′s age at first marriage. Among the correlates of respondent′age at first marriage, education is in general the most important variable. However, it is found that wife′s education is more important than husband′s. The combined effects or the correlates studied explain no more than about 40% of variance for any of the selected groups of variables. Points which might counteract the effects of late marriage on fertility are not serious in Korea. For each of the correlates of the three fertility indices chosen for this study. namely, (a) number of living children, (b) number of live births, and (c) number of pregnancies, age at marriage is the major contributor to the variance in all age groups except the age group of 20-29 in which the index of family planning practice is the major contributor. The proportion of variability in fertility indices accounted for by the correlates is never more than 40% of the total variance in any age group. Based upon the findings from this study, it could be concluded that in the foreseeable future (a) celibate group will no! be increased to a point that would slow down population growth rate in Korea, (b) age at marriage will not increase continually, (c) although education stands out as the major contributing variable which independently explains the variation in age at marriage, it seems probable that education may not be the major variable in the near future, and (d) despite the fact found by this study that age at marriages has been the major contributor to the variance of each of the fertility indices used, family planning practice will play a more important role in the reduction of fertility in the Korean society. Therefore, factors interrupting practice of family planning must be eliminated and family planning program should be strengthened if further fertility reduction is needed.

  • PDF

Community development and parasite control (지역사회개발(地域社會開發)과 기생충(寄生虫))

  • Rim, Han-Jong
    • Journal of agricultural medicine and community health
    • /
    • v.1 no.1
    • /
    • pp.10-21
    • /
    • 1976
  • The traditional application of night soil to vegetable gardens and rice paddies results in a most wide spread condition of parasitism, with a variety of helminths found in Korea. In addition to the above fact, the peculiar habit of the consumption of raw vegetables, fish, crustaceans and mammals provides a means of infestations of helminths. During the last sixty years numerous reports were found on the prevalence of helminths amongst the Korean population in different parts of the country, and it was generally recognized that ascariasis, hookworm disease, filariasis, clonorchiasis and paragonimiasis constitute the important helminthic disease in Korea. In practical measures of parasite control activities the main measures are summarized as mass-treatment, night-soil disposal and transmission control. Among the three, the mass-treatment has been commonly applied, however, no reduction of transmission has been obtained by treatment of a population. Therefore, the ultimate eradication of parasites will depend upon the application of comprehensive environmental sanitation measures. The basic environmental measures will be concerned with (a) the safe disposal of human excreta, (b) the provision of adequate and safe water supplies in such a way as to promote a higher standard of personal hygiene in the population, and (c) the prevention of food contamination by faecal material. Additional environmental measures will deal with the improvement of housing and housing hygiene and with general community development. Community development means social and cultural as well as economic development. The control measures on the parasitic endemic diseases, such as clonorchiasis and paragonimiasis are the good examples for community health development in Korea. The control of Clonorchis and Paragonimus infections are theoretically very simple, as the infection can only invade the human body by way of encysted metacercaria which are taken into the body when eating passive intermediate hosts(fishes, crabs and crayfishes). Although prophylactic measures in the case of the infections deal with above merely consist the fishes in cooking or submerging in hot water before eating them, it is exceedingly difficult to carry out such simple measures in face of century old traditions, to which the relatively primitive population clings with great tenacity. There is no one universally applicable method of control. The choice of methods must be dictated by the nature of the environment. the habit and custom of the people. the pattern of transmission and the resources of the country. There must exist a well organized public health infrastructure. Since a control programme is of necessity on a longterm basis and continuity in its implementation is essential. An investigation should be made on the prevalence of the diseases and its relationships to irrigation engineering, freshwater ecology, agricultural methods, hydro-electric schemes, and the development of communities in affected areas. In conclusion, however. the control of clonorchiasis and paragonimiasis in Korea is not an impossible task. A combination of efforts with major emphasis on health education and mass chemotherapy coupled with governmental aid in enforcing legislative public health measures could reduce the diseases. Health education in particular attempts following four things: (a) It supplies a person with enough general knowledge about a disease to make the preventive measures. (b) It makes a person feel sufficiently about the importance of his own health to make him alter his behavior and adopt these preventive measure. (c) It makes him concerned for the health others. (d) It tries to make him feel so strongly about the first three that be supports and even initiates preventive action by the community. Educational efforts should be directed primarily toward school children because it is during the early years that most persons become infected, and also because children are less entrenched in their food habits so that, the educational process should be involved at various levels in successive changes of knowledge, attitude, beha viour, habit and custom of their lives. The most parasitic endemic diseases are related to community diseases. In caring for a sick community. the first stage is to gather epidemiological data, the next is to make inferences from it-to make the community diagnosis. The third is to prescribe community treatment or community health action part of a community health action programme. The community health action is the sum of the steps decided upon to remedy the critical features revealed by the community diagnosis. Action takes various forms; health education is the most important.

  • PDF

The Related Factors of Safety Behaviors and Accident in Elementary School Children (초등학생의 안전행동 및 사고 관련 요인)

  • Kim, Kyung-Sook;Lee, Moo-Sik;Hong, Jee-Young;Hwang, Hye-Jeong;Bae, Seok-Hwan
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.12 no.1
    • /
    • pp.288-293
    • /
    • 2011
  • This study was conducted to investigate the elementary school students' consciousness of safety, activities to prevent their accidents and factors causing such accidents. For this aim, a research was conducted from Nov. 19 through Dec. 22, 2007 by means of questionnaires distributed to 800 students enrolled in the 5th and 6th grades of 4 elementary schools in a urban-rural combined city. Out of the questionnaires distributed, 785 were collected and put to analysis by using SPSS 13.0 program to determine t-test, ANOVA, logistic regression, etc. 1. The maximum scores of safety consciousness revealing relatively high level of safety consciousness. There was, however, statistically significant difference by grade, type of residence, school life and academic achievements. In detail, 5th graders featured higher level of safety consciousness and those who live in apartments, lead a pleasant life at school and get better academic scores tended to keep higher level of safety consciousness. 2. The subjects of the high scored of activities to prevent accidents, with a statistically significant difference by gender, grade and individual personality. Females, 5th graders and active students were found to be more conscious of preventive activities for accidents. 3. In general, 6th graders and active students turned out to have experienced more accidents. 4. The main factors exerting influence on occurrence of accidents on the part of elementary school students are known to be preventive actions and consciousness of traffic safety in the category of safety consciousness. The significant variable in preventive actions was preventive actions of traffic accidents, burns and intoxication by category of accidents, but individual personality by category of general characters. Sixth graders and male students experienced more accidents, without significantly significant difference, though. As a result, From the above findings, prevention of safety accidents is found to be very important for elementary school students. It is therefore suggested that schools as well as homes should continue to conduct practical education to prevent accidents with priority placed on familiarizing students with preventive activities in daily life in consideration of their personal characters.

Survey on the Sodium Contents of Nursery School Meals in Gyeonggi-Do (경기도지역 어린이집의 단체급식 중 나트륨 함량 실태조사 연구)

  • Jung, Hong-Rae;Lee, Myung-Jin;Kim, Ki-Cheol;Kim, Jung-Boem;Kim, Dae-Hwan;Kang, Suk-Ho;Park, Jong-Suk;Kwon, Kwang-Il;Kim, Mee-Hye;Park, Yong-Bae
    • Journal of the Korean Society of Food Science and Nutrition
    • /
    • v.39 no.4
    • /
    • pp.526-534
    • /
    • 2010
  • The prevalence rate for chronic diseases such as obesity, diabetes, hypertension etc. caused by the increment of national income and the change of food life according to the globalization in Korea have been increased. Especially excess sodium intake may contribute to the development of hypertension, increasing cardiovascular disease risk. The objective of this study was to investigate sodium intake of nursery school meals in Gyeonggi-Do, and to construct database for lesser sodium intake policy. Survey consisted of 601 sample intakes of sodium in summer and in winter. A food weighed record method was used for measuring food intakes. Average intakes of ten children per nursery school were measured. The sodium contents of meals were analyzed by ICP-OES (inductively coupled plasma-optical emission spectrometer) after acid digestion by microwave. The sodium contents on food groups showed that sources (693 mg/100 g), grilled foods (689 mg/100 g) and kimchies (643 mg/100 g) had respectively higher sodium contents and the average sodium intake per meal was $582\pm204$ mg. The sodium contents of soups & hot soups and kimchies had 37.5% and 15.8% of total sodium intakes per meal, respectively. Sodium intakes per meal in summer and winter showed 572.3 mg and 592.3 mg, respectively. Regional ranking of sodium intakes showed the ascending order of apartment (514.3 mg/meal), rural region (540.5 mg/meal), multiplex house (635.9 mg/meal) and industrial complex (696.4 mg/ meal). A habit of excessive sodium intakes in childhood will threaten their health when they grow up to be adults; thus lesser intake of sodium per meal is needed for children in nursery school.

A Study on Comparison and Analysis of Civic Education in Place for Children -A Case Study on the United States, Britain, Finland, Japan, and South Korea- (어린이 공간교육의 국내외 사례 비교연구 -미국, 영국, 핀란드, 일본, 한국의 사례를 중심으로-)

  • Hue, Youn-Sun;Im, Seung-Bin
    • Journal of the Korean Institute of Landscape Architecture
    • /
    • v.39 no.2
    • /
    • pp.40-51
    • /
    • 2011
  • Recently, the public's interest in quality of life and good design has increased, and the opportunities for their participation in space planning and the design process are expanding. However, the public still lacks understanding of the role(and importance) of space and environment and is not experienced in expressing their opinion on improving the urban environment. At this point, 'Built Environment Education for Kids' will be the key to understanding space and environment as future citizens and to developing the ability of problem-solving and expressing their opinions. This study aims to change the awareness of the public as well as experts, and to make a better urban space through comparison and analysis of domestic and foreign 'Built Environment Education.' In 27 countries around the world(more than 110 institutions), 'Built Environment Education' from childhood is being implemented. Such movements aim to make people participate in the space design and decision-making process by understanding a fundamental element of the built environment and space perception. In this study, the United States, Britain, Finland, Japan and South Korea's 'Built Environment Education' are discussed Above all, the definition, range and target of 'Built Environment Education' are discussed For each case, the purpose and effect, laws and educational processes, systems and roles, and examples of programs are analyzed. Through reviewing each attribute and their implications, a conclusion is drawn on the aspects we have to consider in laying the foundation for implementing the 'Built Environment Education' in Korea, such as consideration of the locality, organizing systematic networks and composing a pool of experts, building proper institutions, and establishing the role of the government. This case study of 'Built Environment Education' can help increase the awareness of the public and build their strength in establishing a better future space. Through the analysis of the purpose, laws, systems, and contents, this case study is expected to provide and build the foundation for an educational system and develop an appropriate program that best suits our society.

A Study of the Degree of Obesity in Elementary School Students according to Grade and Gender (초등학생의 학년별 성별 비만실태)

  • Cho, In-sook;Park, In-hyae;Ryu, Hyun-sook;Park, Yo-sup;Hwang, Sen-lye;Ahan, hyun-hee
    • Journal of agricultural medicine and community health
    • /
    • v.31 no.2
    • /
    • pp.177-185
    • /
    • 2006
  • Objectives: This study was carried out with 31, 519(16,653 boys, 14,857 girls) of elementary school students to investigate the prevalence of obesity at a district in Gwangju City. It can be applied to develope an educational program of the obesity control as basic data in this local area Methods: The data collected from May, 2004 to July, 2004 were analyzed by SAS PC+ 8.0 program. Children were selected depending on criteria from obesity index (%) by using physical index (height, body weight), and then subjects were classified into one of three groups according to the degree of obesity: mild(20~29.9%), moderate(30~49.9%), and severe($?50%{\cdot}$) obesity. Results: It showed that male elementary school students were higher and heavier than female elementary school students(p< .001) in every grade except the 4th grade(height) and the 6th grade ( body weight). The obesity rates of male students(11.6%) showed higher(p< .001) than those of female students(8.8%). Specially the 4th grade elementary school boys were higher than any other groups in obesity(13.7%). As a whole, the prevalence of obestiy showed mild(5.9%), moderate(3.8%), and severe(0.6%). Male students showed higher rate of obesity than those of female students. The obesity of male students showed higher rate than that of female students except 2-3rd grade elementary school students(p< .001). The obesity of 4~6th grade elementary school students showed higher rate than those of 1~3rd grade students(p< .001). Conclusions: The obesity rates of male students are higher than that of female students, and the obesity rates of 4~6th grade students are higher than those of 1-3rd grade students in the elementary school. Additionally, these results suggest that the program may be needed to prevent obesity of children.

  • PDF