• Title/Summary/Keyword: pressure history

Search Result 637, Processing Time 0.092 seconds

Relationship between HsCRP and Pulse Transit Time (HsCRP와 맥파전달시간에 대한 연구)

  • Kim, Yun-Jin;Min, Hong-Gi;Kim, Young-Joo;Jeon, Ah-Young;Jeon, Gye-Rok;Ye, Soo-Young
    • Journal of Life Science
    • /
    • v.17 no.2 s.82
    • /
    • pp.218-222
    • /
    • 2007
  • The purpose of this study is to evaluate the relationship between high sensitive C-reactive protein (hsCRP) and pulse transit time (PPT). Apparently healthy 233 subjects had been enrolled in the health promotion center of the Pusan National University Hospital from Jan. 29 to Feb. 26, 2004. They had no previous history of diabetes, hypertension and hyperlipidemia. Subjects were categorized according to tertiles of hsCRP level [Group 1: first tertile $(0.01\;{\sim}\;0.02\;mg/dl)$, Group 2: second tertile $(0.03\;{\sim}\;0.05\;mg/dl)$, Group 3: third tertile $(0.06\;{\sim}\;0.12\;mg/dl)$, and Group 4: Fourth tertile $(0.13\;{\sim}\;16.8\;mg/dl)$]. PTT body mass index (BMI), total cholesterol (T-C), LDL-cholesterol(LDL-C), blood sugar (BS), systolic blood pressure (sBP) and diastolic blood pressure (dBP) were significantly different among hsCRP groups (p<0.05). HsCRP is positively related with BMI, tryglyceride (TG), LDL, sBP and dBP (p<0.05), and negatively related with PTT and HDL-cholesterol (HDL-C) (p<0.05). PTT is significantly negatively related with hsCRP, T-C, TG, LDL-C, BS, dBP and sBP (p<0.05). The hsCRP and PTT were related before controlling BMI, T-C, LDL-C, sBP, and dBP, but not related after conkolling. The relationship between hsCRP and PTT depends on cardiovascular disease risk factors.

Social Networks and hypertension in Some rural residents Aged 60-64 (일부 60~64세 농촌 인구에서 사회조직망과 고혈압)

  • Lee, Choong-Won;Cho, Hee-Young;Lee, Mi-Young;Kim, Gui-Yeon;Park, Jong-Won;Kang, Mi-Jung;Suh, Suk-Kwon
    • Journal of agricultural medicine and community health
    • /
    • v.23 no.2
    • /
    • pp.229-242
    • /
    • 1998
  • Face-to-face interviews were carried out to investigate the relationship between social networks and hypertension in 958 rural residents(males=440, females=518) aged 60-64 of a community-dwelling sample of Dalsung County from April to September in 1996. Eight elements of social network were measured : marital status, regular religious attendance, membership in groups, number of friends, relatives, siblings, children, grandchildren. Hypertensives were defined as meeting at least one of following criteria : hypertension history, systolic blood pressure more than 160 mmHg, diastolic blood pressure more than 95 mmHg. In univariate logistic regression for males, having 1-4 friends vs. none showed odds ratio 0.43 (95% Confidence interval CI 0.19-0.96) and having 2-3, 4 and more than 5 children had reduced prevalence of hypertension with odds ratios 0.21 (95% CI 0.06-0.72), 0.14 (95% CI 0.04-0.49), 0.24 (95% CI 0.07-0.82), respectively when compared with persons without children. In females, there was no elements of social network statistically significant. Having 5-9 grandchildren vs. none showed a marginally significant odds ratio 0.42. In multivariate logistic regression models for males with adjustment for age, education, body mass index, smoking and drinking, number of friends and children showed increased odds ratios and number of close relatives gained a statistically significant odds ratios (0.44-0.50). In females, the adjustment yielded little changes of odds ratios except number of grandchildren which gained a statistically significance. These results suggest that only a certain elements of social network may be associated with reduced risk of hypertension and they may be different between genders in rural resident aged 60-64.

  • PDF

The Changes of Pulmonary Function and Systemic Blood Pressure in Patients with Obstructive Sleep Apnea Syndrome (폐쇄성 수면 무호흡증후군 환자에서 혈압 및 폐기능의 변화에 관한 연구)

  • Moon, Hwa-Sik;Lee, Sook-Young;Choi, Young-Mee;Kim, Chi-Hong;Kwon, Soon-Seog;Kim, Young-Kyoon;Kim, Kwan-Hyoung;Song, Jeong-Sup;Park, Sung-Hak
    • Tuberculosis and Respiratory Diseases
    • /
    • v.42 no.2
    • /
    • pp.206-217
    • /
    • 1995
  • Background: In patients with obstructive sleep apnea syndrome(OSAS), there are several factors increasing upper airway resistance and there is a predisposition to compromised respiratory function during waking and sleep related to constitutional factors including a tendency to obesity. Several recent studies have suggested a possible relationship between sleep apnea(SA) and systemic hypertension. But the possible pathophysiologic link between SA and hypertension is still unclear. In this study, we have examined the relationship among age, body mass index(BMI), pulmonary function parameters and polysomnographic data in patients with OSAS. And also we tried to know the difference among these parameters between hypertensive OSAS and normotensive OSAS patients. Methods: Patients underwent a full night of polysomnography and measured pulmonary function during waking. OSAS was diagnosed if patients had more than 5 apneas per hour(apnea index, AI). A careful history of previously known or present hypertension was obtained from each patient, and patients with systolic blood pressure $\geq$ 160mmHg and/or diastolic blood pressure $\geq$ 95mmHg were classified as hypertensives. Results: The noctural nadir of arterial oxygen saturation($SaO_2$ nadir) was negatively related to AI and respiratory disturbance index(RDI), and the degree of noctural oxygen desaturation(DOD) was positively related to AI and RDI. BMI contributed to AI, RDI, $SaO_2$ nadir and DOD values. And also BMI contributed to $FEV_1,\;FEV_1/FVC$ and DLco values. There was a correlation between airway resistance(Raw) and AI, and there was a inverse correlation between DLco and DOD. But there was no difference among these parameters between hypertensive OSAS and normotensive OSAS patients. Conclusion: The obesity contributed to the compromised respiratory function and the severity of OSAS. AI and RDI were important factors in the severity of hypoxia during sleep. The measurement of pulmonary function parameters including Raw and DLco may be helpful in the prediction and assessment of OSAS patients. But we could not find clear difference between hypertensive and normotensive OSAS patients.

  • PDF

Leukocyte count and hypertension in the health screening data of some rural and urban residents (일부 농촌과 도시의 건강선별조사 자료로 본 백혈구수와 고혈압과의 관계)

  • Lee, Choong-Won;Yoon, Nung-Ki;Lee, Sung-Kwan
    • Journal of Preventive Medicine and Public Health
    • /
    • v.24 no.3 s.35
    • /
    • pp.363-372
    • /
    • 1991
  • We used the health screening data of some rural and urban residents to examine the cross-sectional association between leukocyte count and hypertension. The 206 male and 203 female rural residents were selected by multi-stage cluster sampling method in Kyungsan-Kun area of Kyungbuk province in 1985 and 600 urban residents were selected by the same sampling method as the rural residents in Daegu city of the same province in 1986 compatible with age-sex distribution of Daegu city of 1985 census, but of whom 384 actually responded. The rest of 600 were replaced by age and sex with those who were members of the medical insurance plan visiting the health management department of the university hospital to get the biannual preventive medical checkups. Excluded in the analysis were those having hypertensive history, diseases and extreme outlying values of the screening tests, leaving 373 rural and 571 urban residents. Leukocyte count was measured with ELT-8 Laser shadow method and the unit $cells/mm^3$, Blood pressures were determined with an aneroid sphygmomanometer with pre-standardized method and hypertensives were defined as those showing systolic blood pressure more than 140mmHg and/or diastolic blood pressure more than 90mmHg. Total residents pooled (N=944) showed a significant difference between hypertensives and normotensives ($6965.93{\pm}1997.01\;vs\;6490.61{\pm}1941.32,\;P=0.00$) and in rural residents was noted the similar significant difference (P=0.03). None of significant differences were noted in any stratum stratified by residency and sex. Compared to the lowest quintile of WBC, 2/5 quintile showed odds ratio 0.99 (95% Confidence interval, Ci 0.62-1.59), 3/5 quintile 1.41 (95% CI 0.90-2.21), 4/5 quintile 1.76 (95% CI. 1.14-2.72), and highest quintile 1.80 (1.15-2.82) in the total residents. Likelihood ratio test for linear trend for it indicated a significant trend ($X^2_{trend}=5.53,\;df=1,\;P<0.05$). There were no other significant odds ratios compared to the lowest quintile of WBC in strata stratified by residency and sex. The odds ratios in total residents which had showed significant odds ratios became nonsignificant and of reduced magnitude after controlling age, frequency of smoking and drinking with multiple logistic. regression. In each stratum, it changed magnitudes of odds ratios slightly and unstably. None of the trend tests showed any significant trend. These results suggest that the Friedman et al's finding of association between leukocyte count and hypertension may be due to an statistical type I error resulting from the data dredging in an exploratory study, in which more than 800 variables were screened as possible predictors of hypertension.

  • PDF

The Effect of VDT Work on Vision and Eye Symptoms among Workers in a TV Manufacturing Plant (텔레비젼(TV)생산업체 근로자들의 영상단말기(VDT)작업이 시력과 안증상에 미치는 영향)

  • Woo, Kuck-Hyeun;Choi, Gwang-Seo;Jung, Young-Yeon;Han, Gu-Wung;Park, Jung-Han;Lee, Jong-Hyeob
    • Journal of Preventive Medicine and Public Health
    • /
    • v.25 no.3 s.39
    • /
    • pp.247-268
    • /
    • 1992
  • This study was conducted to evaluate the effect of VDT work on eyes and vision among workers in a TV manufacturing plant. The study subjects consisted of 264 screen workers and 74 non-screen workers who were less than 40 years old male and had no history of opthalmic diseases such as corneal opacities, trauma, keratitis, etc and whose visual acuity on pre-employment health examination by Han's test chart was 1.0 or above. The screen workers were divided into two groups by actual time for screen work in a day : Group I, 60 workers, lesser than 4 hours a day and group II, 204 workers, more than 4 hours a day. From July to October 1992 a questionnaire was administered to all the study subjects for the general charateristics and subjective eye symptoms after which the opthalmologic tests such as visual acuity, spherical equivalent, lacrimal function, ocular pressure, slit lamp test, fundoscopy were conducted by one opthalmologist. The proportion of workers whose present visual acuity was decreased more than 0.15 in comparison with that on the pre-employment health examination by Han's test chart was 20.6% in Group II. 15.0% in Group I and 14.9% in non-screen workers. However, the differences in proportion were not statistically significant. The proportion of workers with decreased visual acuity was not associated with the age, working duration, use of magnifying glass and type of shift work (independent variables) in all of the three groups. However, screen workers working under poor illumination had a higher proportion of persons with decreased visual acuity than those working under adequate illumination (P<0.05) . The proportion of workers whose near vision was decreased was 27.5% in Group II, 18.3% in Group I, and 28.4% in non-screen workers and these differences in proportion were not statistically significant. Changes of near vision were not associated with 4 independent variables in all of the three groups. Six out of seven subjective eye symptoms except tearing were more common in Group I than in non-screen workers and more common in Group II than in Group I (P<0.01). Mean of the total scores for seven subjective symptoms of each worker(2 points for always, 1 point for sometimes, 0 point for never) was not significantly different between workers with decreased visual acuity and workers with no vision change. However, mean of the total scores for Group II was higher than those for the Group I and non-screen workers (P<0.01). Total eye symptom scores were significantly correlated with the grade of screen work, use of magnifying glass, and type of shift work. There was no independent variable which was correlated with the difference in visual acuity between the pre-employment health examination and the present state, the difference between far and near visions, lacrimal function, ocular pressure, and spherical equivalent. Multiple linear regression analysis for the subjective eye symptom scores revealed a positive linear relationship with actual time for screen work and shift work(P<0.01). In this study it was not observed that the VDT work decreased visual acuity but it induces subjective eye symptoms such as eye fatigue, blurred vision, ocular discomfort, etc. Maintenance of adequate illumination in the work place and control of excessive VDT work are recommended to prevent such eye symptoms.

  • PDF

The crenulation of Ogcheon metasedimentary rocks near the Ogcheon granite and the Honam shearing, Korea (옥천화강암 부근 옥천 변성퇴적암류의 파랑습곡구조와 호남전단운동)

  • Kang, Ji-Hoon
    • The Journal of the Petrological Society of Korea
    • /
    • v.19 no.2
    • /
    • pp.157-165
    • /
    • 2010
  • The age unknown Ogcheon metasedimentary rocks and the Jurassic Ogcheon granite (Jocgr) intruding it are distributed in the Ogcheon area, which is located in the central part of the Ogcheon Belt, Korea, This paper newly examines the timing of Honam shearing on the basis of the microstructural researches on time-relationship between the crenulation of Ogcheon metasedimentary rocks and the contact metamorphism by the intrusion of Jocgr. The D2 crenulation phase, which is defined by the microfolding of the S1 foliation in the metasedimentary rocks, is divided into two sub-phases. The one is a sub-phase of Early crenulation (D2a) which is included within old andalusite porphyroblasts, and the other is that of Late crenulation (D2b) which warps around the old andalusite. But they show the same dextral shear sense, the axial planes parallel to each other, and a single crenulation at outcrop scale. The contact metamorphism of andalusite-sillimanite type by the Jocgr occurred during the inter-phases of D2a and D2b, and crystallized the old andalusite masking the D2a crenulation and fibrous sillimanites replacing the D2a crenulation-forming muscovites. New andalusite porphyroblasts synkinematically grew in pressure shadows around the old andalusite or in its outermost mantles during the early stage of the D2b. The D2b occurred still continuously after the growth of the andalusite ceased (= later stage of the D2b). It indicates that the D2b occurred continuously during the period when the Ogcheon granite was still hot and cool. From this study, the crenulation history of Ogcheon metasedimentary rocks and the timing of Honam shearing would be newly established and reviewed as follows. (1) Early Honam shearing; formative period of Early crenulation, (2) main magmatic period of Jurassic granitoids; growth of the old andalusite and fibrous sillimanite by the intrusion of Jocgr, (3) main cooling period of Jurassic granitoids; formative period of Late crenulation related to Late Honam shearing, growth of the new andalusite in the early stage of D2b. Thus, this study proposes that the Honam shear movement would occur two times at least before and after the intertectonic phase which corresponds to the main magmatic period of Jurassic granitoids.

자궁외 임신 환자의 임상적 고찰

  • 신현선
    • Journal of Korean Academy of Nursing
    • /
    • v.1 no.1
    • /
    • pp.64-76
    • /
    • 1970
  • This report will present a clinical and statistical analysis of 210 case of Ectopic pregnancies who were treated at the Department of Obstetrics and Gynecology at Chung Nam Medical Center from January, 1966 to March, 1970. The results obtained are as follows; 1. The total number of Ectopic pregnancies was 8.22%. 2. The occurrence of Ectopic pregnancy was high in June(13.81%), low in October(2.98%). There was a higher occurrence of Ectopic pregnancy in the summer than in the winter. 3. The average age of all patients was 33.25 years. The most frequent age for this type of pregnancy was 31-35 years (32.86%) . The youngest patient was 18 years old and the oldest was 50. 4. Multipara occurred in 82.38% of the cases; Mulipara in 17. 62% and the occurrence of primipara was especially high, 20.95%. 5. 48.09% of the women had previously experienced normal deliveries; 42.8% had received artificial abortions and 5.23% had experienced spontaneous abortions. 3.8% had a previous history of Ectopic pregnancy. It was found that the occurrence of Ectopic pregnancy was more frequent in those women who had a D & C in the Past. 6. The average length of infertility was 21.7 months. The shortest length was 60 days; longest period of infertility was 19 years. 7. The occurrence of Ectopic pregnancy is higher (29.27%) in patient who have experienced only one previous D & C. The total number of patients who received a D & C was 58.57%. 3. Ectopic symptoms appeared during the first 4.7 weeks (mean) and most frequently occurred between the 5th and 6th weeks (48.57%) of pregnancy. The Symptoms were: -99.04% complained of lower abdominal pains. -80.95% experienced abnormal uttering bleeding. -42.38% experienced bleeding before the occurrence of pain. -18.57% experienced pain before the occurrence of bleeding. -8.57% experienced both pain and bleeding. -7.62% experienced only bleeding. -22.86% experienced only pain. 9. In-77.62% of the cases the annexal mass palpated. 91.42% complained of abdominal tenderness. 42.38% complained of pain when the cervix was examined. 10. Culdocentesis was performed in 86.19% of the cases. In 92.82% of the cases the presence of an Ectopic pregnancy was accurately diagnosed 11. 71.90% of the Ectopic pregnancies occurred in the ampule portion of the ovarian tube, of the total number of gestations, 40.95% were tubal abortions and 59.05% were ruptured. The ruptured group occurred more frequently in the islamic portion and interstitial portion of the tube than the aborted group. The aborted group occurred more frequently in the fimbrial extremities of the tube. 12. The blood pressure (systolic) was noted at 119-80mmHg in 81.89% of the total cases. Hemoglobin value was noted at over 8gm/㎗ in 58.57% of the cases. The average blood transfusion was 2.3 pints. 13. In 52.86% of the Ectopic pregnancies the right side of the ovarian tube was affected. The left side of the tube was affected in 47.14% of the cases. 14. 3.33% of the patients were not given an accurate diagnosis. 15. The kinds of operation performed were as follows; Salpingectomy, 41.43%; Adnectomy, 38.57% and Adnectomy with total hysterectomy, 19.05%. 16. The patient mortality rate was significantly small; only 1 case out of 210 died. This patient most likely had a profuse hemorrhage because of a ruptured tube before her admission to the hospital. 17. The patients personal feelings and attitudes must be treated with care. Particularly patients who are concerned about vaginal bleeding or the impossibility of another pregnancy.

  • PDF

Long-term Clinical Outcomes after Primary Percutaneous Coronary Intervention in Patients with Acute Myocardial Infarction-on the basis of 65 Years (급성 심근경색증 환자에서 일차적 관상동맥 중재술 후 장기적 임상 경과-65세를 기준으로)

  • Lee, Han-Ol;Jang, Seong-Joo;Kim, In-Soo;Han, Jae-Bok;Park, Soo-Hwan;Kim, Jeong-Hun;Jang, Young-Ill
    • The Journal of the Korea Contents Association
    • /
    • v.14 no.5
    • /
    • pp.251-261
    • /
    • 2014
  • Primary percutaneous coronary intervention (PCI) has been found to be superior, in terms of hospital mortality and long-term outcome, compared with thrombolytic therapy in patients with acute myocardial infarction (AMI). However, the clinical benefits of primary PCI have not been precisely evaluated in elderly patients.1,974 patients (Group I: n=1,018, $age{\geq}65years$, $73.8{\pm}5.99years$; Group II: n=956, age<65years, $52.8{\pm}7.96years$) who underwent primary PCI for AMI at Chonnam National University Hospital between 2006 and 2010 were analyzed according to their clinical, angiographic characteristics for hospital and one-year survival. Group I had a higher percentage of women, diabetes mellitus, hypertension, multi-vessel disease and lower prevalence of current smoking, hyperlipidemia, familial history than Group II. Culprit lesions were at the left anterior descending artery, left circumflex artery, right coronary artery and left main artery in 42.8% vs. 45.0%, 34.1% vs. 29.6%, 14.6% vs 14.6, 2.7% vs. 1.6%, respectively (p=0.007). Stent diameter was smaller in group I ($3.17{\pm}0.39$ vs. $3.29{\pm}0.42mm$, p=0.001). In-hospital mortality was higher in group I (8.4 vs. 1.9%, p<0.001). There were significant differences in the rates of major adverse cardiac events between the two groups during one-year clinical follow-up (20.1 vs.14.0%, p<0.001). On multiple logistic regression analysis, systolic blood pressure<100mmHg, serum $creatinine{\geq}1.3mg/dL$, Killip class> I, multivessel disease, left ventricular ejection fraction <40% and cerebro vascular disease were independent predictors of one-year motality in patients over 65 years after PCI.

Petrochemistry of Garnet-bearing Metabasite in Marble at Shinri area in Hongseong and its Tectonic Implication (홍성 신리 지역 대리암 내 함석류석 변성염기성암의 암석지화학 연구 및 그 지구조적 의미)

  • Kim, Sung-Won;Koh, Hee-Jae
    • The Journal of the Petrological Society of Korea
    • /
    • v.19 no.3
    • /
    • pp.209-225
    • /
    • 2010
  • The Shinri area near the Yedang Lake, the eastern part of the Hongseong area in SW Gyeonggi Massif, consists of the Neoproterozoic Duckjeongri granodiorite-tonalite, mylonitized amphibole-bearing orthogneiss and impure marble with lens-shaped garnet-bearing metabasites. In this paper, we report mineralogical and geochemical data of Neoproterozoic lens-shaped garnet-bearing metabasites within marble of the Shinri area. The $SiO_2$ contents of garnet-bearing metabasites in marble vary between ~46.98 and 51.17 wt%, and the $Na_2O$ + $K_2O$ contents fall between ~1.95 and 2.85 wt%, similar to the tholeiitic sub-alkaline basaltic rocks. In the Zr/Y vs. Zr diagram, garnet-bearing metabasites also plot in the subalkaline basaltic rocks. The chondrite-normalized REE patterns for Shinri garnet-bearing metabasites show relatively flat patterns to that of chondrite. They show slight LREE-enriched and depleted patterns. The major and trace element data from lens-shaped garnet-bearing metabasites in marble of the Shinri area suggest that these rocks were formed in within plate. In contrast, previous major and trace element data of high pressure type garnet-bearing metabasites from the mafic-ultramafic complex in the Baekdong and Bibong areas suggest that these rocks were formed in a nascent arc to backarc spreading center within subduction zone setting. Based on mineral assemblage and mineral chemistry, P-T estimates for Shinri garnet-bearing metabasites are 9.6-12.7 kb, $695-840^{\circ}C$ for inclusions in the core, and 9.6-13.6 kb, $630-755^{\circ}C$ for those in the rim. These P-T estimates are distinct from those of the Baekdong and Bibong garnet-bearing metabasites with isothermal decompressional retrograde P-T path. In addition to Triassic tectonic activity previously reported in the Shinri area of Hongseong, the details of metamorphic history such as protolith age and Neo-Proterozoic metamorphic episode need to be solved.

Examination of the Current Situations of Security Dogs and it's Development Plans (경호탐지견의 운용실태 및 발전방안)

  • Park, Hyung-Kyu;Kim, Doo-Hyun
    • Korean Security Journal
    • /
    • no.14
    • /
    • pp.215-234
    • /
    • 2007
  • Our country security industry 1960's service expense of the beginning U.S. army unit it accomplishes the growth which is quick with start, currently about 2,500 triumph the security enterprises which it goes over are being active. But the majority in these enterprise about lower cotton can a forever characteristic with pressure and the manpower civil official ability insufficient back of faithlessness management and capital power. To sleep with afterwords it presents the security dogs deployment plan for an efficient security together from the research which it sees hereupon and it does. First, it cultivates the domestic mountain progress dog which is a breed which is suitable with the security dogs and the shovel flesh dog back with the security dogs. Specially the Jindo of the breed which is excellent training which is suitable in task of the security dogs it leads and if it uses appropriately, it industrializes our specific the Jindo and protection there is a possibility of getting the effect which falls to also the gist which it rears rightly. It cultivate the second, security dogs and it magnifies training. The security dogs consequently is it will be able to accomplish the task above 2 branches to training method. Namely, after finishing obedience training, it is to be in security activity it will execute guard or detection back special training which is suitable in task and it will be able to commit. Third, it uses the security dogs which is trained rightly in task. The security dogs the adult escorts, facility expense, the explosive and narcotic drug detection, it will be able to use with the other blind man guidance dogs back. The narcotic drug detection dogs which currently is used specially technique intelligence anger, when considering the tendency of the narcotic drug smuggling offense field which becomes diversification that the role very it is important is a possibility of saying at day. It cultivate a fourth, escort relation specialty manpower and it improves the breed of the security dogs. The hazard which cultivate the security dogs use necessary personnel the breed of security dogs, the security dogs training center it opens the security crane relation subject of the college which stands and (university) it improves it establishes and training which is suitable in task it is to do to execute letting in the training map company. Specially, the hazard which improves the breed of security dogs in the progress mind quality which stands against the portion where the breed improvement is demanded as the portion where the internal organs research and investment are necessary sees. The security dogs compares in labor cost and the expense holds few, if it uses the our specific domestic dogs it will be able to use efficiently in the task which is various it solves the multi branch plans for wisly with the security dogs industrial development security of course contemporary history sliced raw fish sees demands compared to being immediacy and the life which is happy business the place where it does it sees it will be able to contribute a lot as.

  • PDF