Obrazovanje

DODIPLOMSKI STUDIJ:

1998-2004. Prirodno-matematički fakultet, Univerzitet u Sarajevu. Diplomski rad pod naslovom „Pripremanje i karakterizacija adicionog jedinjenja RuCl3 sa N,N-dimetilformamidom“;

POSTDIPLOMSKI STUDIJ:

2007-2011. Prirodno-matematički fakultet, Univerzitet u Sarajevu. Magistarski rad pod naslovom ” Određivanje tiamina (vitamina B1) u uzorcima različitih vrsta brašna”

DOKTORSKI STUDIJ:

2012-2018. Prirodno-matematički fakultet, Univerzitet u Sarajevu. Doktorska disertacija pod naslovom “Uticaj hemijskog sastava ekstrakata sjemena izabranih vrsta familija Ranunculaceae i Apiaceae na enzimsku aktivnost “

Kretanje u zaposlenju

2005-2008. Tehnolog za finalnu obradu kože, Prevent Sarajevo d.o.o. Visoko.

2008-danas Prirodno-matematički fakultet, Univerzitet u Sarajevu

Akademsko iskustvo

IZBOR U NASTAVNIČKO ZVANJE:

Docent

DATUM I OBLAST POSLJEDNJEG IZBORA U NASTAVNIČKO ZVANJE: 

2019 – danas docent na oblastima Organska hemija i Biohemija

DATUM I OBLAST POSLJEDNJEG IZBORA U ZVANJE:

2011- 2019 viši asistent na oblastima Organska hemija i Biohemija

2008 – 2011 asistent na oblasti Organska hemija i biohemija

Naučni radovi

  • Ligata, E., Fazlić, A., Dizdar, M., Ćavar Zeljković, S., Topčagić, A. (2022) Binding constants setermination of the interaction of albumin with 6-substituted-4-methylcoumarins, 4th International Congress of Chemists and Chemical Engineers of Bosnia and
    Herzegovina, 30 June-02 July 2022, Sarajevo, Bosnia and Herzegovina, Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, Special Issue 2022, Book of Abstracts, 51.
  • Fazlić, A., Ligata, E., Dizdar, M.a, Ćavar Zeljković, S., Topčagić, A. (2022) Fluorimetric interaction studies of albumin with 7-substituted-4-methylcoumarins, 4th International Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, 30 June-02 July 2022, Sarajevo, Bosnia and Herzegovina, Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, Special Issue 2022, Book of Abstracts, 52.
  •  Marković, I., Čulum, D., Vidic, D., Čopra- Janićijević, A., Topčagić, A, Klepo, L. (2022) Identification of chemical constituents from two Fraxinus species by GC-MS and HPLCDAD methods, 4th International Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, 30 June-02 July 2022, Sarajevo, Bosnia and Herzegovina, Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, Special Issue 2022, Book of Abstracts, 84.
  •  Sulejmanović, J., Zrno, A., Omanović, R., Topčagić, A., Begić, S., Jurković, J. (2022) Novel approach for effective removal of methylene blue dye from water using grapefruit peel as a potential biosorbent, 4th International Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, 30 June-02 July 2022, Sarajevo, Bosnia and Herzegovina, Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, Special Issue 2022, Book of Abstracts,105.
  • Delibasic, M., Kovac, K., Milicevic, V., Ostrakovic, L., Ostojic, J., Topcagic, A., Klepo, L. (2022) Determination of the antioxidative activity of selected cosmetic preparations, 4th International Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, 30 June-02 July 2022, Sarajevo, Bosnia and Herzegovina, Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, Special Issue 2022, Book of Abstracts,164.
  •  Sulja, R., Dizdar, M., Topčagič, A. (2021) Determination of total proteins, starch, and gluten in cereal foods. 1st International Scientific Conference Food and Climate Changes, 15-16 October 2021, Koprivnica, Croatia, Book of Abstracts, 63.
  •  Bošković, A., Dizdar, M., Topčagić, A. (2021) Macronutrients quanification and antioxidant acivity of soy products. 1st International Scientific Conference Food and Climate Changes, 15-16 October 2021, Koprivnica, Croatia, Book of Abstracts, 65.
  • Topčagić, A., Ćavar Zeljković, S., Kezić, M., Sofić, E. (2021) Fatty acids and phenolic compounds composition of anise seed, VII International Congress “Engineering, Environment and Materials in Process Industry“, 17-19 March 2021, Jahorina, Bosnia and Herzegovina, Book of Abstracts, 157.
  • Dizdar, M., Topčagić, A., Brković, M., Vidic, D.,Štefane, B., Požgan, F., Maksimović, M. (2018) Antioxidant and Butyrylcholinesterase Inhibitory Activity of Selected Phenolic Acids and Their Derivatives. 3rd International Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, 19-21 October 2018, Sarajevo, Bosnia and Herzegovina, Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, Special Issue 2018, Book of Abstracts, 62.
  •  Turulja, M., Topčagić, A., Toromanović, J., Ajanović, A., Dizdar, M., Tahirović, I. (2018) UV Spectrophotometric Method in Quantification of the Total Protein Content in Food Samples. 3rd International Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, 19-21 October 2018, Sarajevo, Bosnia and Herzegovina, Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, Special Issue 2018, Book of Abstracts, 57.
  • Etminam, A., Uzunović, A., Topčagić, A., Žero, S., Dizdar, M., Klepo, L., Čulum, D., Tahirović, I. (2018) Utilisaion of Derivative UV/Vis Spectrophotometry in Determination of
    Active Pharmaceutical Ingredient Content in Some Drugs, 3rd International Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, 19-21 October 2018, Sarajevo, Bosnia and Herzegovina, Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, Special Issue 2018, Book of Abstracts, 24.
  • Topčagić, A., Ćavar Zeljković, S., Kezić, M., Sofić, E. (2018) Chemical profile of black cumin seed oils and extracts. 7th Balkan Botanical Congress, 10-14 September 2018, Novi Sad, Serbia, Botanica Serbica, Vol. 42 (supplement 1), 7BBC Book of abstracts, 141.
  • Topčagić, A., Ćavar Zeljković, S., Karalija, E., Galijašević, S., Sofić, E. (2018) Phenolic content and biological acivities of anise seed extracts. 7th Balkan Botanical Congress, 10- 14 September 2018, Novi Sad, Serbia, Botanica Serbica, Vol. 42 (supplement 1), 7BBC Book of abstracts, 135
  • Klarić-Došlić, I., Klepo, L., Čopra-Janićijević, A., Sofić, E., Topčagić, A. (2014) Spectrophotometric Determination of Ascorbic Acids with 2,6-Dichlorophenolindophenol in Selected Pharmaceutical Preparations. 1st Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, 10-12 October 2014, Sarajevo, Bosnia and Herzegovina, Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, Special Issue 2014, 123.
  • Čengić, L., Čopra-Janićijević, A., Sofić, E., Topčagić, A., Ašimović, Z. (2014) Fluorimetric Determination of Thiamine in Baby Cereal Food. 1st Congress of Chemists and Chemical Engineers of Bosnia and Herzegovina, 10-12 October 2014, Sarajevo, Bosnia and Herzegovina Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, Special Issue 2014, 72.
  • Topčagić, A., Ćavar, S., Sofić, E. (2014) Antioxidant and Antimicrobial Properties of Extracts from Black Cumin Seeds. Young Scientists Meeting, Trends in Natural Products Research, June 23-25, 2014, Olomouc, Czech Republic, Book of Abstracts, 36.
  • Ćavar, S., Topčagić, A., Sofić, E. (2014) Antioxidant and Antibacterial Activity of Thymoquinone and Its Derivatives. Young Scientists Meeting, Trends in Natural Products Research, June 23-25, 2014, Olomouc, Czech Republic, Book of Abstracts, 35-36.
  • Toromanovic, J., Selman, S., Topcagic, A., Klepo, L., Tahirovic, I., Sofic, E. (2013) The content of total phenolics and total flavonoids in native leaf extracts of houseleek, Sempervivum tectorum L., (Crassulaceae). 1st Mediterranean Symposium on Medicinal ad Aromatic Plants, 17-20 April 2013, Gazimagosa (Famagusta) Turkish Republic of Northern Cyprus, MESMAP-2013, Abstract book, 230.
  • Delić, D., Briga, M., Čopra-Janićijević,A., Klepo, L., Topčagić, A., Sofić, E., Tahirović I. (2012) Spectrophotometric and titrimetric determination of ascorbic acid in some biological samples, 7th CMAPSEEC, Conference on Medicinal and Aromatic Plants of Southeast European Countries, 27-31 May 2012, Subotica, Republic of Serbia, Book of Abstracts, 62.
  • Briga, M., Delić, D., Čopra-Janićijević, A., Klepo, L., Sofić, E., Topčagić, A., Tahirović, I. (2012) Fluorimetric determination of ascorbic acid using methylene blue, 7th CMAPSEEC, Conference on Medicinal and Aromatic Plants of Southeast European Countries, 27-31 May 2012, Subotica, Republic of Serbia, Book of Abstracts, 61.
  • Čalkić, S., Topčagić, A., Huseinović, Š., Sofić, E. (2012) Fluorimetric determination of thiamine in some fruits and vegetables. IX susret mladih kemijskih inženjera, 16-17 Februar 2012, Zagreb, Hrvatska, Book of abstracts, 125.
  • Briga, M., Topčagić, A., Klepo, L., Čopra-Janićijević, A. (2012) Spectrophotometric quantification of total ascorbic acid contents in common sea-buckthorn and rosehip fruits,  IX susret mladih kemijskih inženjera, 16-17 Februar 2012, Zagreb, Hrvatska, Book of abstracts, 121.
  • Kapur, A., Čopra-Janićijević, A., Klepo, L., Topčagić, A., Hasković, A., Tahirović, I., Sofić, E. (2011) Spectrophotometric analysis of total ascorbic acid and content in various fruits and vegetables. 22nd International Scientific-Expert Conference of Agruculture and Food Industry, 28 September-1 October 2011, Sarajevo, Bosna and Herzegovina, Book of Abstracts, 154.
  • Sofic, E., Copra-Janicijevic, A., Maksimovic, M., Tahirovic, I., Klepo, L., Topcagic, A., Huseinovic, S., Vidic, D., Cavar, S., Kroyer, G. (2011) Determination of Hypericin in St. John's Wort (Hypericum perforatum L.) extracts using HPLC-ED. 59th International Congress and Annual Meeting of the Society for Medicinal Plant and Natural Product Research, 4-9 September 2011, Antalya, Turkey, Planta Medica 77, SL51. doi: 10.1055/s0031-1282174.
  • Haskovic, A., Copra Janicijevic, A., Topcagic, A., Klepo, L., Kapur, A., Huseinovic, S., Tahirovic, I., Sofic, E. (2011) Analysis of ascorbic acid content in various fruits and vegetables by spectrofluorimetric methods. 59th International Congress and Annual Meetings of the Society for Medicinal Plant and Natural Product Research, 4-9 September 2011, Antalya, Turkey, Planta Medica 77, PJ17. doi: 10.1055/s-0031-1282624
  • Topcagic, A., Uzunovic, A., Husenovic, S., Sofic, E. (2011) Comparation of fluorimetric and high-performance liquid chromatographic methods for thiamine determination in fluors. 1st National Argiculture Congress and Exposition on behalf of Ali Numan Kiraç with International Participation, 27-30 April 2011, Eskişehir, Turkey, Abstracts, 278.
  • Topcagic, A., Husenovic, S., Sofic, E. (2010) Analysis of thaimine (vitamin B1) in the grain fluors anf fluors and seeds of buckwheat by fluorimetric method. 1st CONAHE, the first conference on natural health, 07-09 December 2010, Mostaganem, Algeria, Abstract Book, 121.
  • Ćavar, S., Topčagić, A., Kulenović, A., Šolić, M. E., Maksimović, M. (2010) Total phenolic and antioxidant activity of extract of endemic Centaurea gloriosa var. multiflora Radic. IX savjetovanje hemičara i tehnologa Republike Srpske, 12-13 Novembar 2010, Banja Luka, Bosna i Hercegovina, Zbornik izvoda radova, 32-33.
  • Čopra-Janićijević, A., Sofić, E. Topčagić, A., Klepo, L, Hasković, A., Tahirović, I. (2010) Fluorometric determination of ascorbic acid with o-phenylendiamine. IX savjetovanje hemičara i tehnologa Republike Srpske, 12-13 Novembar 2010, Banja Luka, Bosna i Hercegovina, Zbornik izvoda radova, 1.
  • Copra-Janicijevic, A., Sofic, E. Klepo, L., Topcagic, A., Tahirovic, I., Haskovic, A. (2010) Fluorometric determination of ascorbic acid in the absence of the oxidant in juices of common citrus. 58th International Congress and Annual Meetings of the Society for Medicinal Plant and Natural Product Research, 29 August-2 September 2010, Berlin, Germany, Planta Medica 76, P547. doi: 10.1055/s-0030-1264845.
  • Huseinovic, S., Salihovic, M., Topcagic, A., Kalcher, K., Cavar, S., Sofic, E. (2010) Screening of sage and thyme plant extracts for some phenolic acids and rutin. 58th International Congress and Annual Meetings of the Society for Medicinal Plant and Natural Product Research, 29 August-2 September 2010, Berlin, Germany, Planta Medica 76, P294. doi: 10.1055/s-0030-1264592.
  • Tahirović, I., Salihović, M., Toromanović, J., Dilberović, B., Topčagić, A., Selman, S., Kalcher, K., Sofić, E. (2010) Determination of chlorogenic acid in some fruits using high performance liquid chromatography with electrochemical detection. 6th Conference on Aromatic and Medical Plants of Southeast European Countries, 18-22 April 2010, Antalya, Turkey, Abstracts Book, PP-350, S150.
  • Ćavar, S., Topčagić, A., Vidic, D., Maksimović, M. (2010) Chemical composition and antioxidant activity of Teucrium arduini L. 6th Conference on Aromatic and Medical Plants of Southeast European Countries, 18-22 April 2010, Antalya, Turkey, Abstracts Book, PP-292, S135.
  • Topčagić, A., Ćavar, S., Maksimović, M. (2010) Total phenolic contents and antioxidant activity of some Salvia species, VIII Susret mladih kemijskih inženjera, 18.-19. veljače 2010, Zagreb, Croatia, Knjiga sažetaka, 113
  • Ćavar, S., Vidic, D., Topčagić, A., Šolić, M. A., Maksimović, M. (2009) Chemical Composition and Antioxidant Activity of Essential Oil of Salvia Sclarea L., 5th Balkan Botanical Congress, 7-11 September 2009, Belgrade, Serbia, Book of Abstracts, 143.
  • Sofic, E., Sapcanin, A., Jazic, E., Cavar, S., Salihovic, M., Topcagic, A., Duric, K. (2009) High Performance Liquid Chromatography (HPLC) Quantification of Rutin in Ruta, Rosemary and Pelargonium Extracts, 69th International Congress of FIP, World Congress of Pharmacy and Pharmaceutical Sciences 2009, 3-8 September 2009, Istanbul, Turkey, Book of Abstracts, 183.

Izlaganja na konferencijama

  • Topčagić, A., Ćavar Zeljković, S., Kezić, M., Sofić, E. (2021) Fatty acids and phenolic compounds composition of anise seed, Journal of Food Processing and Preservation, 46(19), e15872.
  • Etminan, A., Uzunović, A., Topčagić, A., Žero, S., Dizdar, M., Klepo, K., Čulum, D., Džudžević-Čančar, H., Tahirović, I. (2019) Quantification of Active Substances in Some Drugs Using by Derivative UV/Vis spectroscopy. In: Badnjevic A., Škrbić R., Gurbeta Pokvić L. (eds) CMBEBIH 2019. CMBEBIH 2019. IFMBE Proceedings, vol 73. Springer
  • Topcagic, A., Cavar Zeljkovic, S., Karalija, E., Galijasevic, S., Sofic, E. (2017) Evaluation of phenolic profile, enzyme inhibitory and antimicrobial activities of Nigella sativa L. seed extracts. Bosnian Journal of Basic Medical Science, 17(4), 286-294. doi: 10.17305/bjbms.2017.2049
  • Tahirović, I., Helbet, Dž., Gaštan, A., Buza, N., Dizdar, M., Topčagić, A., Toromanović, J., Čopra-Janićijević, A., Kurtagić, H. (2017) Hydrophilic antioxidant scores against hydroxyl and peroxyl radicals in honey samples from Bosnia and Herzegovina. CMBEBIH 2017, International Conference on Medical and Biological Engineering 2017, 16-18 March 2017,čSarajevo, Bosnia and Herzegovina, IFMBE Proceedings, 62, 429-434. doi:10.1007/978- 981-10-4166-2_66(SCOPUS)
  •  Ćavar Zeljković, S., Topčagić, A., Požgan, F., Štefane, B., Tarkowski, P., Maksimović, M. (2015) Antioxidant activity of natural and modified phenolic extracts from Satureja montana L. Industrial Crops and Products, 76, 1094-1099. doi: 10.1016/j.indcrop.2015.08.009
  • Tahirović, I., Kožljak, M., Toromanović, J., Čopra-Janićijević, A., Klepo, L., Topčagić, A., Demirović, H. (2014) Total Phenolic Content and Antioxidant Capacity in Infusions of
    Various Herbal Teas. Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, 42, 51-55.
  •  Keskin-Šašić, I., Tahirović, I., Topčagić, A., Klepo, L., Salihović, M., Ibragić, S., Toromanović, J., Ajanović, A., Velispahić, E. (2012) Total Phenolic Content and Antioxidant Capacity of Fruit Juices. Bulletin of the Chemists and Technologists of Bosnia and Herzegovina, 39, 25-28.
  • A., Hasković, A., Čopra-Janićijević, A., Klepo, L., Topčagić, A., Tahirović, I., Sofić, E. (2012) Spectrophotometric analysis of total ascorbic acid content in various fruits and
    vegetables. Bulleten of the Chemists and Tehnologists of Bosnia and Herzegovina, 38, 39- 42.
  •  Briga, M., Delic, D., Copra-Janicijevic, A., Klepo, L., Sofic, E., Topcagic, A., Tahirovic, I. (2012) Fluorimetric determination of ascorbic acid using methylene blue. 7th CMAPSEEC, Conference on Medicinal and Aromatic Plants of Southeast European Countries, 27-31 May 2012, Subotica, Republic of Serbia, Proceedings, 104-109.
  •  Delic, D., Briga, M., Copra-Janicijevic, A., Klepo, L., Topcagic, A., Sofic, E., Tahirovic, I. (2012) Spectrophotometric and titrimetric determination of ascorbic acid in some fruits and vegetables. 7th CMAPSEEC, Conference on Medicinal and Aromatic Plants of Southeast European Countries, 27 -31 May 2012, Subotica, Republic of Serbia, Proceedings, 110- 116.
  • Čopra-Janićijević, A., Sofić, E., Topčagić, A., Klepo, L., Hasković, A., Tahirović, I. (2011) Fluorimetrijsko određivanje askorbinske kiseline sa o-fenilendiaminom. Glasnik hemičara, tehnologa i ekologa Republike Srpske, 5, 5-10.
  •  Tahirovic, I., Salihovic, M., Toromanovic, J., Dilberovic, B., Topcagic, A., Selman, S., Kalcher, K., Sofic, E. (2011) Determination of chlorogenic acid in some fruits using high performance liquid chromatography with electrochemical detection. 6th CMAPSEEC, Conference on Aromatic and Medical Plants of Southeast European Countries, 18-22 April 2010, Antalya, Turkey, Proceeding, 551-559.
  •  Ćavar, S., Vidic, D., Topčagić, A., Šolić, M. E., Maksimović, M. (2010) Chemical composition and antioxidant activity of Teucrium arduini L. 6th CMAPSEEC, Conference on Aromatic and Medical Plants of Southeast European Countries, 18-22 April 2010, Antalya, Turkey, Proceeding, 1065-1076.
  • Ćavar, S., Vidic, D., Topčagić, A., Šolić, M. E., Maksimović, M. (2009) Kemijski sastav I antioksidacijska aktivnost eteričnog ulja biljne vrste Salvia sclarea L. (Chemical composition and antioxidant activity of the essential oil of Salvia sclarea L.). Radovi Hrvatskog Društva za Znanost i Umjetnost, XI, 167-176. UDK: 547.913:582.929.4 (497.6)

Objavljene knjige i udžbenici

  •  Maksimović Milka, Čopra-Janićijević Amira, Vidic Danijela, Topčagić Anela, Klepo Lejla, Dizdar Muamer, Čulum Dušan, OSNOVE ORGANSKE HEMIJE ZBIRKA ZADATAKA,
    Univerzitet u Sarajevu-Prirodno-matematički fakultet, Sarajevo, 2019. ISBN 978-9926-453- 21-3; COBISS.BH-ID 27380998
  •  Tahirović Ismet, Topčagić Anela Buza Nermin, ZBIRKA ZADATAKA IZ BIOHEMIJE I, Univerzitet u Sarajevu-Prirodno-matematički fakultet, Sarajevo, 2018. ISBN 978-9926-543- 00-8; COBISS.BH-ID 25331462
  •  Čopra-Janićijević Amira Klepo Lejla, Topčagić Anela, PRAKTIKUM ORGANSKE HEMIJE, Univerzitet u Sarajevu-Prirodno-matematički fakultet, Sarajevo, 2013. ISBN 978-9958-592- 42-3; COBISS.BH-ID 20595974
  • Tahirović Ismet, Topčagić Anela, PRAKTIKUM IZ BIOHEMIJE I, Univerzitet u SarajevuPrirodno-matematički fakultet, Sarajevo, 2012. ISBN 978-9958-592-32-4; COBISS.BH-ID 19948294

Naučno-istraživački projekti

  • 2021-danas Izolacija, identifikacija i antioksidativna aktivnost biološki aktivnih spojeva vrsta roda Fraxinus L.; Federalno ministarstvo obrazovanja i nauke (broj: 0101-10016-4/21 od 14.10.2021 i broj 05-35- 1967/21 od 07.10.2021); član projekta
  • 2021-danas Kompleksi vanadija s hidrazonima kao potencijalni anti-SARS-CoV-2 agensi, Federalno ministarstvo obrazovanja i nauke; Federalno ministarstvo obrazovanja i nauke; član projekta
  • 2021-danas Fluorimetrijske i in silico studije interakcije albumina sa sintetskim kumarinima, voditelj projekta, Ministarstvo za nauku, visoko obrazovanje i mlade Kantona Sarajevo (27-02-11-41251-18/21), voditelj projekta
  • 2021-danas Adsorpcija i uklanjanje organofosfatnog pesticida iz uzoraka vode upotrebom filosilikatnog minerala, Ministarstvo za nauku, visoko obrazovanje i mlade Kantona Sarajevo (27-02-11-
    41250-6/21); član projekta
  • 2021-danas Istraživanje inhibitorskog uticaja dervata boronske kiseline na aktivnost enzima u svrhu otkrivanja potencijalnih antitumornih lijekova; Ministarstvo za nauku, visoko obrazovanje i mlade Kantona Sarajevo (27-02-11-12880/21); član projekta
  • 2018-danas Procjena stanja prirode i upravljanja prirodnim resursima u Bosni i Hercegovini World Conservation Monitoring Centre,član projekta
  • 2012-2013. Hemijsko istraživanje fenolskih kiselina iz nekih biljaka familije Lamiaceae i njihova modifikacija u cilju unaprijeđivanja njihovog biološkog djelovanja; (2012-2013); Institucija koja je finansirala/sufinansirala projekat: Federalno ministarstvo za obrazovanje i nauku (BI-BA/12-13- 007); član projekta

Biografija - PDF