Everhart Lecture Series

California Institute of Technology

2012 Everhart Lecturers

 

 

Janna C. Nawroth

 

Frankenstein Revisited: How a jellyfish made from rat and rubber advances engineering of artificial organs

Lab-engineered tissues designed to replace or repair damaged organs promise to provide alternatives for transplants. Organ function, however, emerges from the interaction of various cell types and scaffolding fibers. This creates a formidable design challenge, as components relevant to function must be identified and recapitulated. Conversely, while the pool of bio-engineered materials might be limited, their combinatorial powers are potentially endless and hard to predict. What is needed, therefore, is a design strategy for matching desired organ properties with bio-engineered solutions. One way of approaching this issue is to choose “intermediate” design problems that share some but not all of the features of human organs. I will present our proof-of-concept study in which we analyze propulsion in juvenile jellyfish to create a freely swimming artificial jellyfish from rat muscle and silicone rubber. Jellyfish represent muscular pumps that transport liquid through gentle and rhythmic pulsation – just like a beating heart - but they are of much simpler build and produce easily accessible flow patterns. This has allowed us to 1) identify the elements of jellyfish tissue that generate pumping function, 2) design and tissue-engineer an artificial jellyfish that shares those elements, and 3) iteratively improve the design by evaluating the performances of real and artificial jellyfish.

 

 

Keenan Crane

 

Discrete Differential Geometry: Helping Machines (and People) Think Clearly about Shape

The world around us is full of shapes: airplane wings and cell phones, brain tumors and rising loaves of bread, fossil records and freeform architectural surfaces. To a large extent, our ability to master these domains is limited by our capacity to design, process, and analyze geometry. But like much of mathematics, geometry makes liberal use of infinity – a concept that is alien to machines with finite memory and limited precision. The driving force behind discrete differential geometry (DDG) is to develop a language that can be easily understood by a computer, yet still faithfully captures the way shape behaves in nature. A valuable consequence of constructing algorithmic descriptions is that real-world phenomena like “curvature” and “holonomy” (which traditionally demand expert terminology) can now be easily conveyed to anyone whose vocabulary includes words like “sum” and “triangle.”

 

In this talk I explore recent discoveries in the rapidly growing field of DDG, and demonstrate how a clear geometric perspective can lead to simpler, more efficient algorithms that are numerically robust and exhibit good scaling behavior. A somewhat remarkable fact is that a wide variety of seemingly dissimilar questions can be answered by computing solutions to a simple linear system known as a discrete Poisson equation. For instance: what’s the shortest path from one point to another on a curved surface? How can you construct a flow with only the requested sources and sinks? And how does one manipulate surfaces without distorting important features like angles? These questions are deeply rooted in a number of classical and beautiful topics from physics and geometry such as heat flow, parallel transport, holomorphic functions, and the Dirac equation, which will all be explained in simple geometric terms.

 

 

Adler Ray Dillman

 

Navigating Without Eyes or Ears: A Worm's Tale of Survival Using the Sense of Smell

Nematodes are the most abundant animal on the earth and occupy virtually every known niche and habitat, from steamy South American jungles to the seemingly barren Antarctic Dry Valleys. Though best known by the ‘free-living’ model nematode, C. elegans, there are numerous nematode parasites, many of which cause human suffering directly through disease or indirectly through crop loss and damage.

 

Among nematode parasites is a unique group of lethal insect parasites that use pathogenic bacteria to kill their hosts. These are beneficial nematodes, commercially used across the globe as alternatives to chemical pesticides for controlling agriculturally damaging insects. It is unclear how even closely related species of insect parasitic nematodes can vary so greatly in the number and type of insect hosts they are capable of infecting and killing or how nematode parasites find their hosts, and it is on these questions that I have chosen to focus my research.

 

Being eyeless and earless, olfaction is the primary way nematodes interpret their environment. I have explored the host-seeking behavior of insect parasitic nematodes, including their unique ability to jump. All the parasitic species I have tested show a remarkable ability to detect and differentiate among potential hosts based on olfactory cues, though even closely related species differ in their odor preferences. I will discuss how comparative genomics of insect parasitic nematodes provides hypotheses and insight about differences in development, behavior, and ecology, as well as clues about differences in host range and specificity among parasites. Amid the tumult and hype that drives DNA sequencing technology forward, we are left wondering: what does a genome tell us abut the underlying differences between organisms? I will discuss what nematodes can teach us about the value of new genomes and how these microscopic animals have a major impact on biological discoveries.