Two Lawrence Livermore researchers awarded early career funding

Lawrence Livermore National Laboratory (LLNL) scientists Jennifer Pett-Ridge and Todd Gamblin have been selected by the U.S. Department of Energy's Office of Science Early Career Research Program to receive funding for proposed projects.

Jennifer Pett-Ridge was selected for her work titled, "Microbial Carbon Tranformations in Wet Tropical Soils: The Importance of Redox Fluctuations," by the DOE Office of Biological & Environmental Research (OBER).

"I'm thrilled about this award," she said. "It's a huge honor, a validation for my research ideas and all of the excellent environmental science work being done at LLNL. It's also a real opportunity to expand our currently limited knowledge of soil microbial communities and carbon cycling in the tropics."

Pett-Ridge, 42, who works in the Lab's Chemical Sciences Division, has long been interested intropical biomes,and said the award willin a sense "allow her to return to her roots" (her training is in soil microbiology).

She said her early career research, in which she will receive up to $2.5 million over five years, will focus on understanding how changes in climate (rainfall and temperature regimes) in the tropics may affect the capacities of soil microbial communities that drive decomposition, nutrient availability and carbon stabilization. This will involve both field-scale ecosystem manipulations and controlled lab experiments. Her research will take advantage of unique LLNL resources such as the NanoSIMS and the Center for Accelerator Mass Spectrometry (CAMS) and collaborations with the DOE's Joint Genome Institute and Environmental Molecular Sciences Laboratory user facilities.

The tropics have been relatively ignored in terms of microbiology, and scientists have a poor understanding of how climate change will affect carbon and energy cycle feedbacks in tropical forests. But since these systems store more carbon than any other terrestrial system, and produce greenhouse gases like methane and nitrous oxide, it's critical to understand how projected warming and drying will affect them.

The work Pett-Ridge has proposed links focus areas in the DOE's Genomic Science and Terrestrial Ecosystem Science divisions as well as the largeNext Generation Ecosystem Experiment-Tropics effort that DOE-OBER recently announced.

Pett-Ridge earned her Ph.D. in soil microbial ecology from the University of California, Berkeley, and her master's in forest science and her bachelor's in biology from Yale University. She is the lead scientist of LLNL's Genomic Science Biofuels Scientific Focus Area (SFA), holds a courtesy appointment at Oregon State University and is a deputy group leader of the Isotopic Signatures Group within LLNL's Chemical Sciences Division.

Todd Gamblin, a computer scientist in LLNL's Center for Applied Scientific Computing, will receive up to $2.5 million in funding over five years for a project to accelerate the adaptation of scientific simulation codes to increasingly powerful supercomputers, a process that currently can take up to six months for complex applications. Increasingly complex machine architectures and applications are making this process even slower.

Gamblin's research is particularly important as the high performance computing(HPC) community prepares to ramp up computing speeds from petascale (quadrillions of floating point operation per second) to exascale systems that will be as much as 1,000 times faster. HPC experts believe the first exascale systems will come online in the 2020 timeframe.

The dynamically changing behavior of modern simulation codes makes existing techniques for modeling their performance difficult to apply. Under a project entitled "Statistical Methods for Exascale Performance Modeling," Gamblin proposes to develop statistical models of applications that can represent adaptive, data-dependent code behavior in a manner that can be scaled up for more powerful computing systems. In addition, the project will develop techniques to reduce the complexity of application models, so that application developers understand them.

"The idea is for these new models to provide simulation developers with insights that allow them to quickly optimize the performance of their code, ensuring that applications can take full advantage of the performance of future exascale machines," Gamblin said.

Gamblin earned his M.S. and Ph.D. in computer science from the University of North Carolina in Chapel Hill. He first came to Lawrence Livermore as a student in 2008, returned as a post-doc in 2009 and was hired as staff in 2010. For his undergraduate work, Gamblin completed a double major in computer science and Japanese at Williams College in Massachusetts. Subsequently, he worked as a software developer in Japan and held graduate research internships at the University of Tokyo and IBM Research.

"Disbelief" was how he initially reacted to learning he had been selected for an award by DOE's Advanced Scientific Computing Research program. "It seemed like slim odds," Gamblin said. "I'm grateful and I'm happy to be able to work on projects I've had on the back burner as part of the early career program."