Events Archive

Nov
10
2014
The science behind animal-inspired robotics
The 21st Century has seen an explosion of bio-inspired technology and devices. Perhaps no where has this approach been more transformative than in the field of mobile robotics. Geckos, snakes, and even cockroaches have motivated new sticky, stable, steerable robots. Yet inspiration means more than curiosity. As scientists we must unravel the scientific principles and mechanisms underlying animal performance. By studying the physics of these living systems we can inform a systematic approach to animal-inspired robotics. By doing so, we discover new properties and dynamics of complex systems -- the robots themselves even...
Nov
10
2014
Ion Motion in Gases, A Colloquium in Honor of Dr. Ian Gatland
The history of drift-tube measurements of gaseous ion transport coefficients is reviewed, with an emphases on the contributions made by Dr. Gatland.  The use of experimental measurements of such coefficients in testing ion-neutral interaction potentials over wide ranges of internuclear separation is illustrated through recent tests of ab initio potentials.  Finally, the use of such data with recent theoretical advances is shown to have implications for ion-neutral reactions of importance in the ionosphere. ...
Nov
07
2014
Quantum Oscillations in Kondo Insulator SmB6
In Kondo insulator samarium hexaboride SmB6, strong correlation and band hybridization lead to a diverging resistance at low temperature. The resistance divergence ends at about 3 Kelvin, a behavior recently demonstrated to arise from the surface conductance. However, questions remain whether and where a topological surface state exists. Quantum oscillations have not been observed to map the Fermi surface. We solve the problem by resolving the Landau Level quantization and Fermi surface topology using torque magnetometry. The observed angular dependence of the Fermi surface cross section suggests two-dimensional surface...
Nov
07
2014
Accurate Modeling of Galaxy Clustering on Small Scales: Testing the Standard ΛCDM + Halo Model
The large-scale distribution of galaxies can be explained fairly simply by assuming i) all galaxies are hosted by halos and ii) a cosmological model. This simple framework, called the `halo-model', has been remarkably successful at reproducing the large-scale clustering of galaxies observed in various galaxy redshift surveys. However, none of these studies have truly tested the `halo-model' by carefully modeling the systematics. We present the results from a fully-numerical, accurate `halo-model' framework and show that the theory can not simultaneously reproduce the galaxy projected correlation function and the group...
Nov
06
2014
The measurement of the expansion rate of the Universe from gamma-ray attenuation
The extragalactic background light (EBL) that fills the Universe is mainly the result of star formation activity over cosmic time. Therefore, it contains fundamental information on galaxy evolution and cosmology. The detection of the EBL by direct methods is hampered by the strong foregrounds mainly from our own Solar System and Galaxy. Interestingly, there are other indirect methodologies that allows us its ...
Nov
06
2014
Quantum Hall effect in graphene for resistance metrology
The quantum Hall effect (QHE) observed in two dimensional electron gas at low temperature and under a strong perpendicular magnetic field has revolutionized the resistance metrology since its discovery in 1980 by Klaus von Klitzing. It provides a representation of the ohm based on the Planck constant and the electron charge only. In 2005, graphene, a purely two dimensional arrangement of carbon atoms in a honeycomb lattice, where the charge carriers behave as Dirac fermions, has revealed a new flavor of the QHE. From the metrological point of view the QHE in graphene is very promising since it...
Nov
05
2014
The Tongue as an Excitable Medium
This is a Webinar Geographic tongue (GT) is a medical condition affecting approximately 2% of the population, whereby the papillae covering the upper part of the tongue are lost due to a slowly expanding inflammation. The resultant dynamical appearance of the tongue has striking similarities with well known out-of-equilibrium phenomena observed in excitable media, such as forest fires, cardiac dynamics and chemically driven reaction-diffusion systems. We explore the dynamics associated with GT from a dynamical...
Nov
04
2014
The Viruses They are a Changin: On The Eco-evolutionary Dynamics of Virus-Host Interactions
Viruses are ubiquitous in the environment, with densities often ten-fold higher than that of their microbial hosts. Viruses can function like microbial predators, regulating the amount and diversity of hosts present in a community. However, efforts to understand the dynamics of complex virus-microbe communities are still in their infancy. Here, I present examples of the interplay between evolutionary and ecological dynamics arising due to virus-microbe interactions. In the first example, I show how rapid changes in the frequency of...
Nov
03
2014
How Nature Harvests Sunlight: The Physics of Photosynthesis
Photosynthesis is one of the great-impact inventions of biological evolution.  Indeed, life on Earth is fueled energy-wise mainly by sun light.  Many, so-called photosynthetic, life forms harvest sun light directly, for example, plants, algae and bacteria; other life forms use sun light indirectly, like herbivorous animals.  This lecture tells the story a particular simple, yet...
Nov
03
2014
The Search for Modulated Superconductivity
In the mid 60's, theoretical physicists came to the conclusion that a strong magnetic field could lead to a superconducting state where magnetism and superconductivity are interleaved on the nano-scale: tidal wave like domain walls spontaneously form in the superfluid order, trapping unpaired spins. Over the past 50 years, our theoretical understanding of this proposal has greatly advanced, yet we still have not found definitive experimental evidence of the modulated superconducting state (also known as the FFLO state, after the initials of the theorists who anticipated it). I will describe the current state of this search, with a particular focus on how...

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