Published\In Press

  1. Urbanek, J., Spira, A., Di, J., Leroux, A., Crainiceanu, C., and Zipunnikov, V.. Epidemiology of objectively measured bedtime and chronotype in the US adolescents and adults: NHANES 2003-2006. arXiv: 1706.05416. Accepted by Chronobiology International. 2017.
  2. Varma, V., Dey D., Leroux A., Di, J., Urbanek, J., Xiao, L., and Zipunnikov, V.. Total volume of physical activity: TAC, TLAC, or TAC(\(\lambda\)). Preventive Medicine. 2017.
  3. Varma, V., Dey D., Leroux A., Di, J., Urbanek, J., Xiao, L., and Zipunnikov, V.. Re-evaluating the effect of age on physical activity over the lifespan. Preventive Medicine. 2017; 101: 102-108.
  4. Di, J., Li, Y., Friedman, MR., Reddy, S., Surkan, PJ., Shoptaw, S., and Plankey, M.. Determining survey satisficing of online longitudinal survey data in the Multicenter AIDS Cohort Study using a Group-Based Trajectory Analysis. Journal of Medical Internet Research Public Health and Surveillance. 2016; 2 (2): e150.


  1. Di, J., Leroux, A., Urbanek, R., Varadhan, J., Spira, A., Schrack, J., and Zipunnikov, V.. Patterns of sedentary and active time accumulation are associated with mortality in US adults: The NHANES study. bioRxiv: 182337. Under review PLoS ONE.

Under Review\Revision

  1. Zipunnikov, V., Dey, D., Leroux, A., Di, J., Urbanek, J., Harris, T., and Crainiceanu, C.. Objectively measured late-morning physical activity predicts mortality in the NHANES 2003-2006 cohorts. Resubmitted to PLoS ONE after revision.
  2. Johns, J., Di, J., Merikangas, K., Cui, L., Swendsen, J., and Zipunnikov, V.. Fragmentation as a novel measure of stability in normalized trajectories of mood and attention assessed by electronic diaries. Under review Physiological Measurement.
  3. Grigsby, M., Di, J., Leroux, A., Zipunnikov, V., Xiao, L., Crainiceanu, C., and Checkley, W.. Novel Metrics for Growth Model Selection. Resubmitted to Emerging Themes in Epidemiology after revision.
  4. Di, J., Spira, A., Urbanek, J., Bai, J., Wu, M., Resnick, S., Simonsick, E., Ferrucci, L., Schrack, J., and Zipunnikov, V.. Joint and individual representation of domains of physical activity, sleep, and circadian rhythmicity. Under review Statistics in Biosciences.

In Preparation

  1. Tensor cumulant analysis (TCA).


  1. Robust Integrative Analysis of Multi-Block Contaminated Datasets (topic contributed). 2013 JSM, Montreal, Canada.
  2. Fragmentation of Daily Physical Activity, Review and Application (poster). 2016 Baltimore Aging Showcases, Baltimore, MD.
  3. Novel Statistical Framework to Study Fragmentation of Daily Physical Activity (contributed). 2017 ENAR, Washington, DC.
  4. Fragmentation of Physical Activity and Its Application (oral). 2017 ICAMPAM, Bethesda, MD.
  5. Fragmentation of Daily Physical Activity: Prediction of Mortality in NHANES 2003-2006. 2017 IAGG, San Fracisco, CA.
  6. Analysis of Tensor Cumulant (ATC) and Its Application in NHANES. 2018 ENAR, Atlanta, GA.