Abstract
Our colleague Tanya Leise passed away on 18 January 2023. She will be remembered in the field of chronobiology for her multiple contributions to our understanding of the complex dynamics of systems of coupled oscillators. She developed and shared tools for quantitative analysis, and, in her role on the Education Committee for the Society for Research on Biological Rhythms (SRBR), highlighted tools developed by others. She was a patient and dedicated teacher, a much-valued collaborator, and a kind and constructive reviewer. Tanya will be sorely missed by her family, friends, and colleagues.
Tanya was born in Omaha, NE, on 27 October 1971. She grew up with her sister Carisa, her parents Marcia and Cyril Leise, and numerous cats. She is remembered as a child who loved math and would read a book while walking. Her childhood writings included poems about nature and numbers. She attended Stanford University to study for her B.S. in Mathematics, meeting her future spouse, Andrew Cohen, among other good friends. Tanya and Andrew moved to Texas A&M University for graduate study. Their daughter Adira was born in 2001.
Following the completion of her PhD in mathematics in 1998, Tanya taught mathematics at Indiana University, Rose-Hulman Institute of Technology, and, starting in 2004, Amherst College. She secured a tenure-track appointment at Amherst in 2007, was awarded tenure in 2013, and promoted to full professor in 2018. By 2020, she was a chaired professor serving on the faculty governance “Committee of Six,” helping to build a strong department, and continuing to teach 4 courses a year. Below we include memories from several colleagues.
Kurt Bryan (Rose-Hulman Institute Of Technology)
I met Tanya in the spring of 1999 when she interviewed for a position at the Rose-Hulman Institute of Technology. I was assigned to be her faculty mentor. Tanya and I were both cyclists, so we began taking bike rides a couple times each week in the afternoon, to talk about teaching, research, and many other things. It was clear from the start that she was an exceptional and creative teacher. She prepared meticulously and brought countless interesting applications and projects into her classes. I got a lot of great ideas from her, for example, using a planimeter in a multivariable calculus class to illustrate Green’s Theorem. Our 2006 paper on Google’s eigenvector-based PageRank algorithm (Bryan and Leise, 2006) stemmed from a project that she developed in our differential equations class, which I then adopted for my use. Despite the fact that I was the senior colleague, I think she informed my teaching more than I did hers.
We stayed in touch after she left Rose in 2004, and that’s when we began writing papers for the SIAM Review education section, first the Google paper, then a paper on cloaking and invisibility, then another on compressed sensing (Bryan and Leise, 2006, 2010, 2013). We both found that it was great fun to pick a hot topic in applied mathematics, take a year or two to discuss and learn about it, and then distill the ideas down to something that students can work through and digest. All of this was aided by the fact that Tanya was a wonderful writer with a passion for communicating ideas to undergraduates.
Over the years, we continued to exchange emails about teaching, mathematics, and our lives. I always looked forward to getting together with her for dinner at the Joint Math Meetings in January. When I contacted her last December [2022] to see if she was going, she said she was not, but that her daughter Adira would present at the conference, and that it was “time to pass the torch to the next generation.” Even through her illness, I’ve never known anyone with a more positive outlook or greater equanimity than Tanya, and I will miss her.
Rob Benedetto (Amherst College)
I met Tanya in 2004, when she interviewed for a visiting faculty position in math at Amherst College. She brought a fresh take on applied math to our department. By the time Tanya’s 3-year visiting term approached its end, we realized how much we needed applied math in our curriculum and conducted a national search for an applied mathematician. Tanya quickly rose to the top of the pile of candidates, and in Fall 2007, she became both the first applied mathematician and the first woman to become a tenure-track professor of mathematics at Amherst College.
In 2013, she became the first tenured female mathematician at Amherst, and first tenured applied mathematician; the analogous set of firsts accompanied her promotion to full professor in 2018 and then a named professorship soon after.
It’s no exaggeration to say that Tanya built Amherst’s applied math curriculum single-handedly and completely from scratch. She introduced 7 applied math courses to our curriculum, spanning a wide range of topics and levels, while adding an applied wrinkle to many other courses that she taught regularly: multivariable calculus, differential equations, and real analysis, among others. The number of students taking math courses at Amherst tripled during her years with us, and our ranks of majors grew more than 6-fold.
At the same time, Tanya was an accomplished researcher, with nearly 50 published papers. She used whatever mathematical tools were most appropriate: if differential equations failed to capture certain granular effects, she shifted to agent-based models; or when Fourier analysis stumbled on disruptions to the periodicity, she introduced wavelets to her field. Tanya also welcomed undergraduates into her research program. Over the course of her 19 years at Amherst, she supervised more than 50 college students’ research experiences, some in summer research projects, and some for honors senior theses. About a dozen of those students became Tanya’s co-authors on papers appearing in refereed journals.
During her 3-year term as chair of Amherst’s Department of Mathematics and Statistics, she was a key factor in moving us from our growing pains to a more stable path forward, including the hiring of multiple colleagues in that time. After she was diagnosed with cancer, Tanya took a single semester of medical leave, but she pushed to return to the department quickly. Even in Fall 2022, she was teaching a full course load—lecturing sitting down, but in the classroom until the end.
Mary Harrington (Smith College)
I first got to know Tanya in 2005. We started from that point to share a keen interest in some core research problems. One question we circled was related to the data indicating some shifts of rhythms could be harmful to your health. Were all shifts harmful? Only some? What characterized the shifts associated with negative health impacts? This led us to many studies of varieties of circadian disruption. “Jet lag vs cruise ships,” was how we sometimes talked about this.
Tanya saw that our field did not have the analysis tools to allow quantification of properties of the rhythms we studied. For instance, we had tools for measuring stable rhythms, but not for capturing dynamic changes in rhythms. Over several years, she mastered wavelet analysis and applied this to various data sets. She and I published a paper together introducing this analysis approach to our colleagues (Leise and Harrington, 2011). One example developed in this paper used behavioral rhythms recorded from female mice showing changes that track the 4- to 5-day hormonal fluxes. This served as an excellent case for her wavelets, tools that allow measures of rapidly changing circadian periods. She continued to develop and apply these tools (Leise, 2017; Smith et al., 2022) and also occasionally to identify sex differences in biological rhythms (Martin-Burgos et al., 2022).
Alec Davidson (Morehouse School Of Medicine)
Tanya was an absolutely critical part of the success of projects that were the focus of my lab in its early days (2006-2012). We were engaged in bioluminescence imaging of the adult acute SCN slice, having recently introduced stage automation into the data acquisition process to, for the first time, acquire multiple slices to be imaged simultaneously (from the same donor mouse) without the loss of spatial resolution. These imaging data were much more complex than the photomultiplier tube (PMT) or LumiCycle (luminometer) data that we had experience with. Establishing unbiased and efficient methods for detection and isolation of cell-specific signals in these slice recordings and fully characterizing the rhythmicity of each was a new problem. Tanya developed novel, highly-efficient MATLAB-based tools to deal with these data in absolute record time. Our first paper together was published in 2009 (Davidson et al., 2009) and launched an amazing collaboration that never ended (9 papers over 13 years). Another leap forward made possible by Tanya’s genius was the combined analysis of multiple cells from multiple slices, aligned with each other and compiled into comprehensive phase maps. The first time this was done was in our second paper together (Evans et al., 2011). Since then, this or similar approaches to analyze and visualize rhythms across the nucleus has become commonplace. Not only did Tanya provide for quantification of rhythms from single cells, and create novel methods to visualize large amounts of such data, but she also provided to us the means to statistically compare rhythms in cells from one region to another, across 3D space. These skillsets, creativity, and hard work that Tanya brought to our projects were absolutely critical to our ability to publish this work and acquire grants to continue our research.
Jennifer Evans (Marquette University)
Tanya was an incredible scholar and friend. I met Tanya in 2009, when we started working together to map the dynamics of SCN organization using real-time bioluminescence imaging data. She took me under her wing, teaching me how to use the incredible tools that she had built to extract the complex information in a comprehensive and unbiased manner. We worked together closely to validate and expand these tools. She was brilliant and patient. She could speak fluently in math and biology, so she was able to describe the complexity of the analyses to me while also engaging in rigorous discussions of the biological meaning. Over all the years that I knew her, I was struck by her meticulous logic, her ability to dismantle and get to the heart of an issue so incisively. She never rushed to a conclusion or stuck with an approach that was flawed or built on faulty assumptions. She had a quiet strength, always on the verge of saying something that would solve everything. It is a blessing to have known her and worked with her.
Todd Holmes (University Of California, Irvine)
My path to meeting Tanya Leise began in 2003, when I set out to visualize the light responses of single cell oscillators in the entire circadian circuit in fly brains. Logan Roberts, a graduate student in my laboratory, was able to image the fly brain circadian circuit at single cell resolution with the help of David Welsh at UCSD. The complexity of the data of optical recordings of hundreds of cellular oscillators in a single brain was bewildering. David without hesitation said, “we should call Tanya Leise.” Tanya found the project exciting, and with her help, our project quickly came into focus. I can say with complete confidence that without her contributions, our observations would only have been qualitative.
Shortly after our first paper was published (Roberts et al., 2015), Tanya and I attended the Chronobiology Gordon Research Conference in Spain. Tanya and I had lunch, and I commented how hard it was to describe a highly dynamic complex process and how helpful it would be to express the data with an animated movie. Tanya then asked what that animation might look like, and I made a few sketches. She nodded and added several improvements to the sketches, and she then appeared to be deep in thought. My wife and daughter joined us at our table, and I invited Tanya to join us after lunch for a jaunt to the nearby town of Caldes de Malavella. Tanya declined the invitation and said she had something she wanted to work on. Several hours later, I returned, and opening my email found the animations that we had just discussed hours before. It was simultaneously one of the most emotional and intellectually satisfying moments in my scientific life. I think of Tanya every time I reflect on this work, and I am reminded of her keen intellect, her remarkable gifts of being able to visualize and rigorously analyze complex data, and her profound generosity of spirit.
Stephanie Taylor (Colby College)
Tanya was an amazing mentor and friend to me. I first met her in person when she invited me to be a presenter in a session she organized for the Third World Congress of Chronobiology, Puebla, Mexico in May 2011. After that trip, I regularly emailed her with questions about data sets I was analyzing and papers and talks I was writing. She always replied quickly with insightful feedback, drawing on her understanding, both deep and broad, of tremendous amounts of math and circadian biology. Her knowledge was current and her advice was always invaluable. Tanya welcomed me into her wide network. She seemed to know everyone. Together, we co-organized a session at the Association of Women in Mathematics Research Symposium in April 2017; that was one of many things I couldn’t have done without her.
Closing Comments (Mary Harrington)
One of Tanya’s coolest studies was on polar bears. She collaborated with folks who were attaching radio collars to female polar bears and recorded from about 150 bears over multiple years (Ware et al., 2020). Males could not be used because their necks were larger than their heads! She found that even in the months of continuous light or darkness, bears maintained circadian rhythms. They also showed flexibility, able to shift between night active or day active depending on the presence of their prey.
When the COVID-19 pandemic hit, we worked together to prepare an online course, the 2020 International Chronobiology Summer School. This was held as weekly meetings all summer long, with many guest lecturers. Tanya connected with several students in India who were developing a way to analyze smartphone use to track rhythms in students pre- and post-pandemic. This later became a collaboration between researchers in India, Argentina, and the United States, with Tanya’s analysis scripts being central to the success of the project.
Tanya developed several “Shiny Apps” (CIRCADA-E and CIRCADA-S) to allow ease in data exploration, simulations, and analysis (Cenek et al., 2020). She recently added a new one, CIRCADA-I (https://circada.shinyapps.io/circada-i/) to allow the user to upload their own data. She worked hard to make these tools easy to use but also packed with her good advice for the biologists who often might be trying to use the tool on a data set for which it was inappropriate. Her work will continue to benefit our field profoundly.
