• Seminar Announcement

    Friday, September 23rd, 2016
    3:30 p.m. in Olin 04

    James Smith, University of California-Irvine, “Aitken nuclei: Little things in the world working great effects by virtue of their numbers”.

    The quote in the title is paraphrased from the writing of John Aitken, a Scottish scientist at the turn of the 20th century who is considered to be the founding father of the fields of cloud physics and aerosol science. Today Aitken’s name is given to the smallest aerosol particles in the atmosphere, Aitken nuclei, with diameters smaller than 100 nm. These particles can be emitted from cars and factories, but are also formed directly in the atmosphere in a process, first identified by Aitken, called “nucleation.” Despite the passage of a century since its discovery, the chemical species and mechanisms responsible for atmospheric nucleation and the subsequent growth of nanometer-sized particles remain mysterious. We know, however, that these processes occur nearly everywhere in locales spanning from megacities to isolated forests. While the impacts are not well understood, aerosol nucleation and growth are the dominate formation processes of particles in remote regions and could play a crucial role in the Earth’s climate by regulating the number and activity of cloud condensation nuclei. This effect of aerosol particles on clouds is recognized in the most recent assessment of the Intergovernmental Panel on Climate Change as the largest single contributor to uncertainty in predicting climate change.

    In this talk I will describe the efforts of my research team in solving the mysteries of the formation and growth of Aitken nuclei using an instrument called the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). We developed the TDCIMS 15 years ago specifically for the study of the composition of nanometer-sized particles; today it remains the only instrument capable of measuring the molecular constituents in the smallest particles in our atmosphere. With an understanding of the capabilities and limitations of the TDCIMS, I will present some key observations from recent laboratory and field studies.  These studies seek answers to such questions as “What are the mechanisms and species responsible for the formation of new particles in the atmosphere?” and “What are the effects of atmospheric nanoparticles on human health and climate?”

  • Journal Club Meets This Week

    Thursday, September 22nd, 2016
    12:00 – 1:00 pm / Mudd 171

    Have lunch and discuss the work of this week’s seminar speaker. The paper we’ll be discussing will be found here.

  • GRE Subject Test Registration Reminder

    The deadline to register for the 10/29/16 GRE subject tests is this Friday, 9/23/16. (The deadline for late registration is 9/30/16). Find more information about test centers and dates.

  • Lunch with Seminar Speaker

    Lunch with this week’s seminar speaker will be Friday, 1:10-2:20 p.m., in the LDC.  Meet in the hallway outside Mudd 169.  If you are off board, the department will cover your lunch.