Connecticut State The Connecticut Agricultural Experiment Station

Christian (Chris) O. Dimkpa

 

 

Head and Chief Scientist

Department of Analytical Chemistry

The Connecticut Agricultural Experiment Station (CAES)

123 Huntington Street,

New Haven, Connecticut, 06511

Email: Christian.Dimkpa@ct.gov

Voice: 203-974-8523

 

Expertise:

Christian Dimkpa has 25 years of pre -and post- doctoral engagement in plant-environmental sciences with strong nexus with chemicals. Since 2009, he has been involved in agricultural and environmental nanoscience research, including plant and microbial nanotoxicology, development of enhanced efficiency chemical fertilizers based on coating with nanoparticles, and studies of plant beneficial responses to mineral nutrients as a function of particle size (nano and bulk) and solubility state. He has expertise in investigating crop response to differently packaged micronutrients (zinc, copper, boron, iron and manganese) for yield enhancement, acceleration of phenological development, resilience to drought and disease stress, and fortification of edible tissues with nutrients critical for human health. He also studies the role of micronutrients in improving plant use efficiency of nitrogen, with implications for mitigating nutrient loss and associated climatic effects. An important aspect of Christian’s expertise involves examining how micronutrients influence plant uptake of phosphorus. Experience prior to 2009 include serving as a Technician and Supervisor in banana crop improvement research. He has published over 75 journal articles, book chapters and technical reports. He has given presentations and attended national and international conferences/workshops in multiple countries, including United States, Germany, Belgium, Canada, China, Brazil, Uganda, Kenya, India, Myanmar, Nigeria and Morocco.

 

Education:

- PhD in Bioenvironmental Science (Microbe-Plant-Metals Interaction), Friedrich Schiller University/International Max Planck Research School Jena, Germany (2009).

- MS in Plant Molecular Biology, Interuniversity Program of Vrije University Brussels and Katholieke University Leuven (KUL), Belgium (2005)

- HND (BS equivalent) in Crop Production, Imo State Polytechnic Owerri, Nigeria (1998)

- Diploma in Agriculture, Federal College of Agriculture, Umudike, Nigeria (1992)

 

Career Timeline:

- Head and Chief Scientist, Department of Analytical Chemistry, CAES (2020-current)

- Senior Scientist, International Fertilizer Development Center (IFDC), Muscle Shoals, Alabama (2016-2020)

- Research Scientist, Virtual Fertilizer Development Center, Washington, D.C. (2014-2016)

- Research Assistant Professor, Department of Biology, Utah State University, Logan (2012-2014)

- Post-doctoral Fellow, Department of Biological Engineering, Utah State University, Logan (2009-2011)

- Research Supervisor, International Institute of Tropical Agriculture, Nigeria (2000-2003)

- Research Technician, International Institute of Tropical Agriculture, Nigeria (1995-2000)

 

Secondary Affiliations and Professional Activities:

- Senior Review Editor for the Journal of Basic Microbiology (environmental interactions) (since 2011)

- Member of the USDA NIFA-AFRI Center for Nanotechnology and Agricultural Pathogens Suppression (since 2015).

- External Graduate Dissertation Examiner, Faculty of Natural and Agricultural Sciences, North West University, South Africa (since 2019).

- Collaborative development research projects in Africa with IFDC (future prospect)

 

Selected Publications (journal articles only):

  1. Dimkpa, C. O., Deng, C., Wang, Y., Adisa, I. O., Zhou, J., and White. J. C. (2023). Chitosan and zinc oxide nanoparticle-enhanced tripolyphosphate modulate phosphorus leaching in soil. ACS Agricultural Science and Technology. DOI: 10.1021/acsagscitech.3c00054

  2. Karmous, K., Vaidya, S., Dimkpa, C., Zuverza-Mena, N., da Silva, W., Barroso, K. A., Milagres, J., Bharadwaj, A., Abdelraheem, W., White, J. C., and Elmer, W. H. (2023). Biologically synthesized zinc and copper oxide nanoparticles using Cannabis sativa L. enhance soybean (Glycine max) defense against Fusarium virguliforme. Pesticide Biochemistry and Physiology, 194, DOI: 10.1016/j.pestbp.2023.105486

  3. Dimkpa, C., Adzawla, W., Pandey, R., Atakora W. K., Kouame, A. K., Jemo, M., and Bindraban, P. S. (2023). Fertilizers for food and nutrition security in sub-Saharan Africa: an overview of soil health implications. Frontiers in Soil Science, 3. DOI: 10.3389/fsoil.2023.1123931

  4. Awio, T., Struik, P. C., Senthilkumar, K., Dimkpa, C. O., Otim-Nape, G. W., and Stomph, T. J. (2023). Indigenous nutrient supply, weeding and fertilisation strategies influence on-farm N, P and K use efficiency in lowland rice. Nutrient Cycling in Agroecosystems, 126, 163–180. DOI: 10.1007/s10705-023-10275-z

  5. Sharma, S., Pandey, R., Dimkpa, C. O. Kumar, A., and Bindraban, P. S. (2023). Growth stage-dependent foliar application of iron improves its mobilisation towards grain and enhances Fe use efficiency in rice.  Journal of Plant Growth Regulation. DOI: 10.1007/s00344-023-10944-x

  6. Giri, V. P., Shukla, P., Tripathi, A., Verma, P., Kumar, N., Pandey, S., Dimkpa, C. O., and Mishra, A. A. (2023). Review of sustainable use of biogenic nanoscale agro-materials to enhance stress tolerance and nutritional value of plants. Plants, 12, 815. DOI: 10.3390/plants12040815

  7. Karmous, I., Taheur, F. B., Zuverza-Mena, N., Jebahi, S., Vaidya, S., Tlahig, S., Mhadhbi, M., Gorai, M., Raouafi, A., Debara, M., Bouhamda, T., and Dimkpa, C. O. (2022). Phytosynthesis of zinc oxide nanoparticles using Ceratonia siliqua L. and evidence of antimicrobial activity. Plants, 11. DOI: 10.3390/plants11223079

  8. Wang, Y., Deng, C., Shen, Y., Borgatta, J., Dimkpa, C. O., Xing, B., Dhankher, O. P., Wang, Z., White, J. C., and Elmer, W. (2022). Surface coated sulfur nanoparticles suppress fusarium disease in field grown tomato: increased yield and nutrient biofortification. J. Agric. Food Chem. 70(45), 14377–14385. DOI: 10.1021/acs.jafc.2c05255

  9. Wang, Y., Deng, C., Elmer, W., Dimkpa, C. O., Sharma, S., Navarro, G., Wang, Z., LaReau, J., Steven, B. T., Wang, Z., Zhao, L., Li, C., Dhankher, O. P., Gardea-Torresdey, J., Xing, B., and White, J. C. (2022). Therapeutic delivery of nanoscale sulfur to suppress disease in tomatoes: in vitro imaging and orthogonal mechanistic investigation. ACS Nano, 16(7). DOI: 10.1021/acsnano.2c04073

  10. Deng, C., Wang, Y., Cantu, J. M., Navarro, C. V. G., Cota-Ruiz, K., Hernandez-Viezcas, J. A., Li, C., Elmer, W. H., Dimkpa, C. O., White, J. C., and Gardea-Torresdey, J. (2022). Soil and foliar exposure of soybean (Glycine max) to CuO nanoparticles: Coating and particle size-dependent Cu accumulation. NanoImpact. DOI: 10.1016/j.impact.2022.100406

  11. Prajapati, D., Pal, A., Dimkpa, C., Harish, V., Singh, U., Devi, K. A., Choudhary, J. L., and Saharan, V. (2022). Chitosan nanomaterials: A prelim of next-generation fertilizers, existing and future prospects. Carbohydrate Polymers, 288. DOI: 10.1016/j.carbpol.2022.119356

  12. Awio, T., Senthilkumar, K., Dimkpa, C. O., Otim-Nape, G. W., Struik, P. C., and Stomph, T. J. (2022). Yields and yield gaps in lowland rice systems and options to improve smallholder production. Agronomy, 12, 552. DOI: 10.3390/agronomy12030552

  13. Dimkpa, C. O., Campos, M. G. N., Fugice, J., Glass, K., Ozcan, A., Huang, Z., Singh, U., and Santra, S. (2022). Synthesis and characterization of novel dual-capped Zn-urea nanofertilizers and application in nutrient delivery in wheat. Environmental Science: Advances. http://dx.doi.org/10.1039/D1VA00016K
  14. Wang, Y., Dimkpa, C., Deng, C., Elmer, W. H., Jorge Gardea-Torresdey, J., and White, J. C. (2022). Impact of engineered nanomaterials on rice (Oryza sativa L.): A critical review of current knowledge. Environmental Pollution, 297, 118738. 
  15. Sigmon, L. R., Adisa, I.O., Liu, B., Elmer, W. H., White, J. C., Dimkpa, C. O., and Fairbrother, D. H. (2021). Biodegradable polymer nanocomposites provide effective delivery and reduce phosphorus loss during plant growth. ACS Agricultural Science and Technology, 1, 529–539. 
  16. Elmer W. H., De La Torre-Roche R., Zuverza-Mena N., Dimkpa C. O., Gardea-Torresdey J. L., and White J. C. (2021). Influence of single and combined mixtures of metal oxide nanoparticles on eggplant growth, yield, and Verticillium wilt severity. Plant Disease, 105, 1153-1161. 
  17. Dimkpa, C. O., Fugice, J., Singh, U., and Lewis, T. (2020). Development of fertilizers for enhanced nitrogen use efficiency – trends and perspectives. Science of the Total Environment, 731, 139113.
  18. Dimkpa, C. O., Andrews, J., Sanabria, J., Bindraban, P. S., Singh, U., Elmer, W. H., Gardea-Torresdey, J. L., and White, J. C. (2020). Interactive effects of drought, organic fertilizer, and zinc oxide nanoscale and bulk particles on wheat performance and grain nutrient accumulation. Science of the Total Environment. 722, 137808. DOI:  10.1016/j.scitotenv.2020.137808.
  19. Dimkpa, C. O., Andrews, J., Fugice, J., Singh, U., Bindraban, P. S., Elmer, W. H., Gardea-Torresdey, J. L., and White, J. C. (2020). Facile coating of urea with low-dose ZnO nanoparticles promotes wheat performance and enhances Zn uptake under drought stress. Frontiers in Plant Science, 11, 168.
  20. Adisa I. O., Rawat S., Pullagurala V. L. R., Dimkpa C. O., Elmer W. H., White J. C., Peralta-Videa J. R., and Gardea-Torresdey J. L. (2020). Nutritional status of tomato (Solanum lycopersicum) fruit grown in Fusarium infested soil: impact of cerium oxide nanoparticles. Journal of Agricultural and Food Chemistry, 68(7), 1986-1997.
  21. Bindraban, P. S., Dimkpa, C. O., and Pandey, R. (2020). Exploring phosphorus fertilizers and fertilization strategies for improved human and environmental health. Biology and Fertility of Soils, DOI: 10.1007/s00374-019-01430-2.
  22. Bindraban, P. S., Dimkpa, C. O., White, J. C., Franklin, F. A., Melse-Boonstra, A., Koele, N., Pandey, R., Rodenburg, J., Senthilkumar, K. Demokritou, P., and Schmidt, S. (2020). Safeguarding human and planetary health demands a fertilizer sector transformation. Plants, People, Planet, 2, 302-309.
  23. Dimkpa, C. O., Singh, U., Bindraban, P. S., Elmer, W. H., Gardea-Torresdey, J. L., and White, J. C. (2019). Zinc oxide nanoparticles alleviate drought-induced alterations in sorghum performance, nutrient acquisition, and grain fortification. Science of the Total Environment, 688, 926-934.
  24. Adisa, I. O., Pullagurala, V. L. R.., Peralta-Videa, J. R., Dimkpa, C. O., Elmer, W. H., Gardea-Torresdey, J. L., and White, J. C. (2019). Recent advances in nano-enabled fertilizers and pesticides: A critical review of mechanisms of action. Environmental Science: Nano, 6, 2002-2030.
  25. Comer, B. A., Fuentes, P., Dimkpa, C. O., Liu, Y-H., Fernandez, C., Arora, P., Realff, M., Singh, U. P., Hatzell, M. C., and Medford, A. J. (2019). Prospects and challenges for solar fertilizers. Joule, 3, 1578-1605.
  26. Dimkpa, C. O., Singh, U., Bindraban, P. S., Adisa, I. O., Elmer, W. H., Gardea-Torresdey, J. L., and White, J. C. (2019). Addition-omission of zinc, copper, and boron nano and bulk particles demonstrate element and size -specific response of soybean to micronutrients exposure. Science of the Total Environment, 665, 606-616.
  27. Dimkpa, C. O., Singh, U., Bindraban, P. S., Elmer, W. H., Gardea-Torresdey, J. L., and White, J. C. (2018). Exposure to weathered and fresh nanoparticle and ionic Zn in soil promotes grain yield and modulates nutrient acquisition in wheat (Triticum aestivum L.) Journal of Agricultural and Food Chemistry, 66, 9645–9656.
  28. Dimkpa, C. O., Singh, U., Adisa, I. O., Bindraban, P. S., Elmer, W. H., Gardea-Torresdey, J. L., and White, J. C. (2018). Effects of manganese nanoparticle exposure on nutrient acquisition in wheat (Triticum aestivum L.). Agronomy, 8, 158.
  29. Dimkpa, C. O. (2018). Soil properties influence the response of terrestrial plants to metallic nanoparticles exposure. Current Opinion in Environmental Science and Health, 6, 1-8.
  30. Adisa, I. O., Pullagurala, V. L. R., Rawat, S., Hernandez-Viezcas, J. A., Dimkpa, C. O., Elmer, W. H., White, J. C., Peralta-Videa, J. R., and Gardea-Torresdey, J. L. (2018). Role of cerium compounds in Fusarium wilt suppression and growth enhancement in tomato (Solanum lycopersicum). Journal of Agricultural and Food Chemistry, 66, 5959-5970.
  31. Bindraban, P. S., Dimkpa, C. O., Angle, S., and Rabbinge, R. (2018). Unlocking the multiple public good services from balanced fertilizers. Food Security, 10, 273-285.
  32. Elmer, W., De La Torre-Roche, R., Pagano, L., Majumdar, S., Zuverza-Mena, N., Dimkpa, C., Gardea-Torresdey, J. and White, J. C. (2018). Effect of metalloid and metallic oxide nanoparticles on Fusarium wilt of watermelon. Plant Disease, 102, 1394-1401.
  33. Rietra, R. P. J. J., Heinen, M., Dimkpa, C. O., and Bindraban, P. S. (2017). Effects of nutrient antagonism and synergism on yield and fertilizer use efficiency. Communications in Soil Science and Plant Analysis, 48, 16.
  34. Dimkpa, C. O., White, J. C. Elmer, W. H. and Gardea-Torresdey J. (2018). Nanoparticle and ionic Zn promote nutrient loading of sorghum grain under low NPK fertilization. Journal of Agricultural and Food Chemistry, 65, 8552-8559.
  35. Raliya R., Saharan V., Dimkpa C. Biswas P. (2017). Nanofertilizer for precision and sustainable agriculture: current state and future perspectives. Journal of Agricultural and Food Chemistry, 66, 6487-6503.
  36. Dimkpa, C. (2017). Balanced plant nutrition and the future of micronutrients. Fertilizer Focus, pp. 59-61.
  37. Dimkpa, C., andBindraban P. (2018). Nanofertilizers: new products for the industry? Journal of Agricultural and Food Chemistry, 66, 6462–6473.
  38. Dimkpa, C., Bindraban P., Fugice J., Agyin-Birikorang S., Singh U., and Hellums D. (2017). Composite micronutrient nanoparticles and salts decrease drought stress in soybean. Agronomy for Sustainable Development, 37, 5.
  39. Dimkpa, C., Bindraban, P., McLean, J. E., Gatere, L., Singh, U., and Hellums, D. (2017). Methods for rapid testing of plant and soil nutrients. In: Sustainable Agriculture Reviews (Lichtfouse E., Ed.) Springer International Publishers. DOI: 10.1007/978-3-319-58679-3_1.
  40. Dimkpa C. (2016). Microbial Siderophores: Production, Detection and Application in Agriculture and Environment. Endocytobiosis and Cell Research, 2, 7-16.
  41. Dimkpa, C. O., and Bindraban, P. S. (2016). Micronutrients fortification for efficient agronomic production. Agronomy for Sustainable Development, 36, 1-26.
  42. Monreal, C. M., DeRosa, M., Mallubhotla, S. C., Bindraban, P. S., andDimkpa, C. (2016). Nanotechnologies for increasing the crop use efficiency of fertilizer-micronutrients. Biology and Fertility of Soils, 52, 423–437.
  43. Bindraban, P. S., Dimkpa, C., Nagarajan, L., Roy, A., and Rabbinge R. (2015). Revisiting fertilisers and fertilisation strategies for improved nutrient uptake by plants. Biology and Fertility of Soils, 51, 897-911.
  44. Zabrieski, Z., Morrell, E., Horton J., Dimkpa, C., McLean, J., Britt, D., and Anderson, A. (2015). Pesticidal activity of metal oxide nanoparticles on plant pathogenic isolates of Pythium. Ecotoxicology, 24, 1305-1314.
  45. Stewart, J., Hansen, T., McLean, J. E., McManus, P., Das, S., Britt, D. W., Anderson, A. J., and Dimkpa, C. O. (2015). Salts affect the interaction of ZnO or CuO nanoparticles with wheat. Environmental Chemistry and Toxicology, 34, 2116-2125.
  46. Servin, A., Elmer, W., Mukherjee, A., De La Torre-Roche, R., Hamdi, H., White, J. C., Bindraban P., and Dimkpa, C. (2015). A review of the use of engineered nanomaterials to suppress plant disease and enhance crop yield. Journal of Nanoparticle Research, 17, 92.
  47. Watson, J.-L., Fang, T., Dimkpa, C. O., Britt, D. W., McLean, J. E., Jacobson, A., and Anderson, A. J. (2015). The phytotoxicity of ZnO nanoparticles on wheat varies with soil properties. Biometals, 28, 101-112. https://doi.org/10.1007/s10534-014-9806-8
  48. Dimkpa, C. O., McLean, J. E., Britt, D. W., and Anderson, A. J. (2015). Nano-CuO and interaction with nano-ZnO or soil bacterium provide evidence for the interference of nanoparticles in metal nutrition of plants. Ecotoxicology, 24, 119-129.
  49. Dimkpa, C. O., Hansen, T., Stewart, J., McLean, J. E., Britt, D. W., and Anderson, A. J. (2015). ZnO nanoparticles and root colonization by a beneficial pseudomonad influence metal responses in bean (Phaseolus vulgaris). Nanotoxicology, 9, 271-278.
  50. Dimkpa, C. O. (2014). Can nanotechnology deliver the promised benefits without negatively impacting soil microbial life? Journal of Basic Microbiology, 54, 889-904
  51. Martineau, N., McLean, J. E., Dimkpa, C. O., Britt, D. W., and Anderson, A. J. (2014). Components from wheat roots modify the bioactivity of ZnO and CuO NPs in a soil bacterium. Environmental Pollution, 187, 65-72.
  52. Dimkpa, C. O., McLean, J. E., Britt, D. W., and Anderson, A. J. (2013). Antifungal activity of ZnO nanoparticles and their interactive effect with a biocontrol bacterium on growth antagonism of the plant pathogen, Fusarium graminearum. Biometals, 26, 913-924.
  53. Dimkpa, C. O., Latta, D. E., McLean, J. E., Britt, D. W., Boyanov, M. I., and Anderson, A. J. (2013). Fate of CuO and ZnO nano and micro particles in the plant environment. Environmental Science & Technology, 47, 4734-4742.
  54. Dimkpa, C. O., McLean, J. E., Martineau, N., Britt, D. W., Haverkamp, R., and Anderson, A. J. (2013). Silver nanoparticles disrupt wheat (Triticum aestivum L.) growth in a sand matrix. Environmental Science & Technology, 47, 1082-1090.
  55. McLean, J. E., Pabst, M. W., Miller, C. D., Dimkpa, C. O., and Anderson, A. J. (2013). Effect of complexing ligands on the surface adsorption, internalization, and bioresponse of copper and cadmium in a soil bacterium, Pseudomonas putida. Chemosphere, 91, 374-382.
  56. Fang, T., Watson, J.-L., Goodman, J., Dimkpa, C. O., Martineau, N., Das, S., McLean, J. E., David, W. Britt, D., Anderson, A.J. (2013). Does doping with aluminum alter the effects of ZnO nanoparticles on the metabolism of soil pseudomonads? Microbiological Research, 168, 91-98.
  57. Calder, A. J., Dimkpa, C. O., McLean, J. E., Britt D. W., Johnson W., and Anne J. Anderson, A. J. (2012). Soil components mitigate the antimicrobial effects of silver nanoparticles towards a beneficial soil bacterium, Pseudomonas chlororaphis O6. Science of the Total Environment, 429, 215-222.
  58. Dimkpa, C. O., McLean, J. E., Britt, D. W., Johnson, J. P., Arey, B., Lea, S. A., Anderson, A. J. (2012). Nanospecific inhibition of pyoverdine siderophore production in Pseudomonas chlororaphisO6 by CuO nanoparticles. Chemical Research in Toxicology, 25, 1066-1074.
  59. Dimkpa, C. O., Zeng, J., McLean, J. E., Britt, D. W., Zhan, J., Anderson, A. J. (2012). Production of indole-3-acetic acid via the indole-3-acetamide pathway in the plant-beneficial bacterium, Pseudomonas chlororaphis O6 is inhibited by ZnO nanoparticles but enhanced by CuO nanoparticles. Applied & Environmental Microbiology, 78, 1404-1410.
  60. Dimkpa, C. O., McLean, J. E., Britt, D. W., Anderson, A. J. (2012). Bioactivity and biomodification of Ag, ZnO and CuO nanoparticles with relevance to plant performance in agriculture. Industrial Biotechnology, 8, 344-357
  61. Dimkpa, C. O., McLean, J. E., Latta, D. E., Manangón, E., Britt, D. W., Johnson, W. P., Boyanov, M. I., Anderson, A. J. (2012). CuO and ZnO nanoparticles: phytotoxicity, metal speciation and induction of oxidative stress in sand-grown wheat. Journal of Nanoparticle Research, 14(9), 1125. DOI: 10.1007/s11051-012-1125-9
  62. Dimkpa, C. O., McLean, J. E., Britt, D. W., Anderson, A. J. (2012). CuO and ZnO nanoparticles differently affect the secretion of fluorescent siderophores in the beneficial root colonizer Pseudomonas chlororaphis O6. Nanotoxicology, 6, 635-642.
  63. Dimkpa, C. O., Calder, A., Britt, D. W., McLean, J. E., Anderson, A. J. (2011). Responses of a soil bacterium, Pseudomonas chlororaphis O6 to commercial metal oxide nanoparticles compared with their metal ions. Environmental Pollution, 159, 1749-1756
  64. Dimkpa, C. O., Calder, A., Huang, W., Merugu, S., Britt, D. W., McLean, J., Johnson, W. P., Anderson, A. J. (2011). Interaction of silver nanoparticles with an environmentally beneficial bacterium, Pseudomonas chlororaphis. Journal of Hazardous Materials, 188, 428-435.
  65. Pabst, M. W., Anderson, A. J., Miller, C. D., Dimkpa, C., McLean, J. E. (2010). Defining the surface adsorption and internalization of copper and cadmium in a soil bacterium, Pseudomonas Putida. Chemosphere, 81, 904-910.
  66. Dimkpa, C., Weinand, T., Asch, F. (2009). Plant-rhizobacteria interactions alleviate abiotic stress conditions, Plant Cell & Environment, 32, 1682-1694.
  67. Dimkpa, C. O., Merten, D., Svatoš, A., Büchel, G., Kothe, E. (2009). Siderophores mediate reduced and increased uptake of cadmium by Streptomyces tendae F4 and sunflower (Helianthus annuus), respectively. Journal of Applied Microbiology, 107, 1687-1696.
  68. Dimkpa, C. O., Merten, D., Svatoš, A., Büchel, G,. Kothe, E. (2009). Metal-induced oxidative stress impacting plant growth in contaminated soil is alleviated by microbial siderophores. Soil Biology & Biochemistry, 41, 154-162.
  69. Dimkpa, C. O., Svatoš, A., Dabrowska, P., Schmidt, A., Boland, W., Kothe, E. (2008). Involvement of siderophores in the reduction of metal-induced inhibition of auxin synthesis in Streptomyces spp. Chemosphere, 74, 19-25.
  70. Dimkpa, C. O., Merten, D., Svatoš, A., Büchel, G., Kothe, E. (2008). Hydroxamate siderophores produced by Streptomyces acidiscabies E13 bind nickel and promote growth in cowpea (Vigna unguiculata L.) under nickel stress. Canadian Journal of Microbiology, 54, 163-172.