College of Science and Technology

Biological Physics

Physics is defined by the style of inquiry, believing that the book of Nature is written in the language of mathematics, and there is only one book that can be summarized in a few pages. Biology, on the other hand, is defined by the objects of study, that all disciplines of biology study different aspects of living objects. It is not hard to see that biological physics approaches the living objects using our unified book of Nature written in mathematics. In other physics subdisciplines, physicists have used the book of Nature to predict a lot of phenomena. In biological physics, through more quantitative experiments, we aim to reach the same level of predictive power in living systems. Through the study of biological physics, you learn how physics is applied in areas completely out of the traditional definition of “physical science,” and learn to use this “one book of Nature” to further extent. Training in biological physics leads to career opportunities in medical imaging and instrumentation, biotechnology, and so much more.

The biological physics group at NC A&T uses experimental, theoretical and computational approaches to understand how the physical environment influences behavior and how organisms process physical signals to make sense of their surroundings.

Faculty

Dr. Chih Kuan Tung uses microfluidic devices to study how physical environments such as fluid flow and the mechanical properties of the fluid influence sperm motility. On the physics front, his research uses sperm collective swimming in viscoelastic fluid as a model system for polar active matter. On the biology front, he studies the role of mucus fluid viscoelasticity in sperm migration, including the collective swimming of sperm cells and swims against fluid flow.

Dr. Vijay Singh uses theoretical, computational, and human psychophysics experimental techniques to understand signal processing in cellular, olfactory, and visual systems. His visual color perception research aims to identify the computations that lead to stable color perception in humans. In his biological signal processing research, he develops biophysical models to understand the encoding and decoding of chemical signals by biological receptor networks.

Projects

A lot of predictions have been made for polar active matters either theoretically or numerically. In this project, we seek to examine them experimentally with our swimming sperm. This shines light on the natural noise structure within a biological system and its impact on statistical physics. Funded by NSF HRD 1665004.

Relevant Publications:

  1. Tung, C.-K., Lin, C., Harvey, B., Fiore, A. G., Ardon, F., Wu, M., & Suarez, S. S. (2017). Fluid viscoelasticity promotes collective swimming of sperm. Sci. Rep., 7, 3152. link
  2. Lin, C., Marks, T. K., Pajovic, M., Watanabe, S., & Tung, C.-k. (2018). Model parameter learning using Kullback–Leibler divergence. Physica A: Statistical Mechanics and its Applications, 491(Supplement C), 549-559. link

cell swimmingHere, we try to use a microfluidic device to model the liquid-liquid interface to see how sperm enter viscoelastic fluid and form collective swimming. Also, through imaging and analyses, we aim to find whether and how the collective swimming of sperm can be a biological advantage. This line of research advances our understanding in the context of evolutionary biology. Funded by NIH/NICHD R15HD095411.

Relevant Publications:

  1. Tung, C.-K., Ardon, F., Fiore, A. G., Suarez, S. S., & Wu, M. (2014). Cooperative roles of biological flow and surface topography in guiding sperm migration revealed by a microfluidic model. Lab Chip, 14, 1348. link
  2. Walker, B. J., Phuyal, S., Ishimoto, K., Tung, C.-K., & Gaffney, E. A. (2020). Computer-assisted beat-pattern analysis and the flagellar waveforms of bovine spermatozoa. Royal Society Open Science, 7(6), 200769. link

balls in front of a colorful backgroundThe color of an object depends on its surface reflectance, but the light reflected to the eye depends on the context. For example, the reflected light depends on the source of illumination and the background of the object. Thus, the light reflected from the same object changes from one context to the other. Despite such changes, our visual system has the ability to discard such context-dependent variations and give a stable perception of the object color, a property called color constancy. We use computational methods and human psychophysics experiments to identify the computations that can lead to such context-independent color perception in humans.

We are looking for undergraduate and graduate students to work with experimental and computational aspects of this project. Contact: singh@ncat.edu

Relevant Publications:

1. Singh, V., Cottaris, N. P., Heasly, B. S., Brainard, D. H., & Burge, J. (2018). Computational luminance constancy from naturalistic images. Journal of vision, 18(13), 19-19. link

receptor networkBiological systems sense their chemical environments by binding to the chemical molecules through their receptors. While most natural chemical signals are complex mixtures of a large number of individual chemicals, biological systems have a limited number of receptors to sense these mixtures. What are the principles of processing of such complex high-dimensional signals through sensory bottlenecks? We develop biophysical models of encoding and decoding of chemical mixtures to identify such principles. We are currently interested in understanding signal processing in cellular networks and the olfactory system.

Contact: vsingh@ncat.edu

Relevant Publications:

1. Singh, V., & Nemenman, I. (2020). Universal properties of concentration sensing in large ligand-receptor networks. Physical review letters, 124(2), 028101. link

2. Singh, V., Murphy, N. R., Balasubramanian, V., & Mainland, J. D. (2019). Competitive binding predicts nonlinear responses of olfactory receptors to complex mixtures. Proceedings of the National Academy of Sciences, 116(19), 9598-9603. link

3. Singh, V., & Nemenman, I. (2017). Simple biochemical networks allow accurate sensing of multiple ligands with a single receptor. PLoS computational biology, 13(4), e1005490. link

Opportunities

1. Human Psychophysics Experiments: We are looking for motivated undergraduate students interested in human vision and color perception to join our group to conduct color perception experiments. Students from Physics, Psychology, Computer Science, Engineering, and other related fields are welcome to apply. Some Matlab programing experience will be helpful. Contact vsingh@ncat.edu

2. Automated Cell Tracking: We are looking for motivated students from Physics, Computer Science, Engineering, and other related fields to join our group to develop computational tools to track bovine sperm cells. Students with good programming skills should contact send their CV to vsingh@ncat.edu or ctung@ncat.edu.

 

Contact ctung@ncat.edu or vsingh@ncat.edu to inquire about open positions.