Natural Sciences

Professor Cohen's group addresses the connection between molecular reactions and regional or global scale atmospheric phenomena: What chemical reactions control whether ozone is locally produced or consumed in the urban and remote troposphere? How do these regional processes affect the oxidative capacity of the atmosphere on a global scale? What are the primary reactions controlling the rate of photochemical removal of ozone in the stratosphere? What are the natural and human induced variations in the concentrations of the free radicals that are rate limiting in these reactions? What is the molecular event during evaporation of water? These questions guide an interdisciplinary chemical/geophysical approach to exploring the structure and dynamics of the earth-ocean-atmosphere system. Cohen’s work emphasizes development of new technologies to obtain detailed observations of atmospheric composition and to validate and interpret large-scale records obtained from space-borne instruments.

A principal research activity of Inez Fung is the carbon dioxide cycle. Fung’s lab uses details of the atmospheric CO2 distribution (e.g. the difference in hemispheric loading, the changes in the seasonal amplitude over time), together with atmospheric transport models to deduce the location of the carbon sink. Fung hypothesizes that the terrestrial biosphere of the northern hemisphere may be as important as the oceans as a repository for anthropogenic CO2. Another research focus is the dust cycle. Fine dust particles lofted from arid surfaces are transported long distances. While airborne, they reflect sunlight, but may, depending on their sizes and composition, absorb terrestrial radiation. When deposited to the surface oceans, the iron in the dust may be the critical limiting micronutrient for marine productivity in some ocean regions. To tackle this problem, she is combining mineralogic information about soil particles, satellite and in-situ observations, atmospheric circulation models and ocean biology models to gain an appreciation of the many roles of dust.

Chemist Paul Alivisatos's pioneering research into tiny nanocrystals and nanorods is paying off in big ways. Chemically-pure clusters of anywhere from 100 to 100,000 atoms, Alivisatos's nanocystals and nanorods have myriad applications that impact the macroworld -- from tagging biological samples for genetic analysis and drug discovery to the creation of plastic solar cells that can be painted onto any surface. Alivisatos's latest small tech innovation nanotechnology is potentially a giant leap in solar energy. Several months ago, the group reported a technique to make flexible solar cells that could someday provide power for next-generation mobile phones, handheld computers, and wearable electronics. The first prototypes boast efficiencies of 1.7 percent. This means that they can only convert 1.7 percent of the energy they receive from the sun into electricity, far less than the 10 percent efficiency of today's commercial photovoltaics. The contributions of Alivisatos and his colleague Eicke Weber hold the promise to drop the cost of solar cells by an order of magnitude, with a related movement away from poly-crystalline silicon to amorphous silicon, plastic, and organic cells.