Integrated Calendar

I will present recent developments in the deceleration and velocity filtering of polar neutral molecules in electric fields. Via the Stark effect, electric fields can be used to produce forces on neutral molecules. If these forces are perpendicular to the translational motion of the molecule they provide access to guiding structures. If they are along the direction of translation, they allow for the acceleration or deceleration of the molecules.
The latter has lead to a method called Stark-deceleration that has proven extremely powerful in applications to the investigation of both the spectroscopy and dynamics of polar molecules. We have recently developed a new Stark decelerator where the molecules are picked up and confined in moving three-dimensional electrostatic traps. The velocity of these traps can be modified, allowing the deceleration of the trapped molecules.
As an alternative to decelerators, electrostatic guides can be used to extract the slow molecules from a thermal sample, resulting in a technically simpler approach than most deceleration methods. Since the Stark effect depends on the rotational state of a molecule, the guiding probability will also depend on the rotational quantum numbers.

A hallmark of Nanoscience is the variety of wonderful new properties of matter when it is reduced to nanometer dimensions. Scientists and engineers around the world are working hard to exploit these properties in a broad range of applications, ranging from electronics to energy, as well as biology and medicine. One of the great challenges in this effort is controlling the organization of such small objects. We are presently exploring strategies which combine traditional lithographic patterning with new surface chemistries and biomolecular assembly to control the placement of individual molecules and electronically functional nanostructures over macroscopic dimensions. One direction we are pursuing involves lithographically directed DNA assembly. In this approach, we bind DNA molecules and DNA nanostructures to molecular-scale anchors on a surface in a way that retains the DNA shape and function. This provides a platform to study biomolecular interactions and to explore ways in which DNA can be used to organize the assembly of electronically and optically functional nanostructures, in order to take full advantage of their unique properties. We use a similar approach to create biomimetic surfaces which simulate specific physical properties of the extracellular matrix down to the single-molecule level. Developing an understanding of the factors required to elicit a given cellular response will yield insight into the functional complexes involved in specific cell behaviors and how these may be altered. Potential applications range from adoptive immunotherapy to the rational design of tissue scaffolds that can optimize healing without scarring.

The "Faint Young Sun Paradox" poses the problem of reconciling evidence for climates not colder than present on ancient Earth and Mars with the knowledge that the Sun has become more luminous with time by 20-30%. The common solution to this apparent paradox involves thicker greenhouse atmospheres, composed primarily of CO2, with small abundances of other infrared absorbers. However, theoretical and observational problems with such solutions exist for both planets. For example, geochemical proxies for the atmospheric concentration of CO2 indicate that it did not reach the values required in global climate models to account for a mild climate on early Earth. For Mars, formation of CO2 clouds and scattering of incoming solar radiation to space hinder a mild climate solution, in disagreement widespread evidence for the existence of liquid water on the planet's early surface. With an eye towards understanding early planetary climate, I will survey flaws in the observations and models and attempt to bridge knowledge and idea gaps with the aim of reconciling between them.