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For most wireless communication systems, the signal environment is dominated by ambient noise and interference, which means that improving the efficiency of the antenna does not increase performance much. When the signal comes from the sky (think radio astronomy and satellite communications), the situation is very different. High aperture efficiency, radiation efficiency, spillover efficiency, and low noise electronics are everything in terms of the performance of a receiver. Bent metal antennas (horns and parabolic dishes) are very efficient and for the last century have been working just fine. The catch is that these kinds of receivers are “dumb” and offer only a fixed beam pattern. We would like to use smart antennas, phased arrays, and adaptive antennas for astronomy and satellite applications to have more control over the beam and more flexibility in selectively receiving signals of interest, but existing phased array technologies are too expensive, lossy, noisy, and most of all, too inefficient. Over more than a decade, my group has used numerical modeling, antenna design optimization, network theory, microwave noise analysis, and array signal processing theory to produce some of the most sensitive phased arrays ever built. This presentation will tell the story of this research field and show how the results have enabled new sensors, satellite receivers, scientific instruments, and influenced the IEEE’s latest version of the governing standard for definitions of antenna terms.

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Understanding the fundamental relationship between atomic structure and material properties is the holy grail of the science of materials. Towards this goal we are working to develop a real-time and atomistic understanding of the mechanistic steps taken during the growth and transformation of crystalline materials. To do this we employ a combination of complementary synthetic and characterization approaches, in particular using in situ ultra-high resolution transmission electron microscopy (TEM) to observe key structural transformations in real-time. Our in situ experiments include directly performing nanomaterial synthesis in the TEM, as well as determining the kinetics of structural phase transformations of as-synthesized inorganic nanocrystals. Further, based on an unexpected observation made during one of these in situ measurements, we have developed a new approach to directly synthesize arrays of crystallographically well-defined nanoscale interfaces. Several examples will be presented to illustrate our approach, including: the real-time observation of the solid-state reaction of an individual nanowire; a post-synthetic structural phase transformation within an individual nanorod; and finally, the creation of new nanostructured architectures using liquid metal nanodroplets.

Progress over the past fifteen years in the digitization and analysis of text found in cultural objects (inscriptions, manuscripts, scrolls) has led this past year to a new and astonishing discovery. This talk will tell the story of emerging methods for imaging and analysis culminating in a personal account of the discovery, the people involved, and the technical approaches used.  The digitization of damaged objects supports a new era of collaboration and exploration that has enabled compelling new discoveries and solutions to long-standing problems.

Rydberg atoms were the focus of much of Keith MacAdam's scientific life. Why he found them so fascinating becomes obvious with a brief summary of their properties. Their properties are exaggerated compared to normal atoms, allowing the introduction of novel detection techniques and clear manifestiations of unexpected physical phenomena. Keith was one of the pioneers in the study of Rydberg atoms. His background in radio frequency resonance spectroscopy was the perfect preparation for his initial Rydberg atom work, high resolution microwave spectroscopy, and his measurements are still the best. He is best known, though, for his beautiful work on  collisions of charged particles with Rydberg atoms, particularly charge exchange, the process in which the Rydberg electron hops from its initial ion core to the incoming ion. In spite of the fact that the "modern" Rydberg atom experiments began forty years ago, Rydberg atoms, today at microKelvin temperatures, remain a subject of intense interest.

The 2016 Nobel Prize in Physics was awarded to David Thouless, John Kosterlitz, and Duncan Haldane for research broadly associated with topology in condensed matter physics. In the first half of the talk I  will describe the two-dimensional XY model which undergoes a Berezinskii-Kosterlitz-Thouless phase transition. This transition, unlike many magnetic transitions, lacks spontaneous symmetry-breaking and is driven by the proliferation of topological excitations, vortices. The analog of of this excitation in three dimensions is the "hedgehog" of the Heisenberg magnet. I will explain what this has to do with quantum phase transitions of the two-dimensional Heisenberg antiferromagnet, explicated by Haldane.

I will give a synopsis on Quantum Chromodynamics (QCD) — the fundamental theory of strong interaction, and some of its consequences.
Lattice gauge theory is introduced as a practical way of solving the theory through computer simulation with Monte Carlo methods.
I will show how the proton mass and spin are divided into their quark and glue components in lattice QCD calculations.

Exotic hidden charm pentaquarks were discovered by the LHCb Collaboration in summer 2015. I discuss  two interpretations of these  newly discovered particles. In the QCD inspired hadrocharmonium approach pentaquarks arise naturally as bound states of quarkonia excitations and ordinary baryons. Decay width of the P_c(4450) LHCb pentaquark is explained and calculated, masses and quantum numbers of new pentaquarks are predicted.  In another approach pentaquarks are interpreted as molecular-type loosely bound  states of hadrons with  open charm. Binding in this model is due to the one-pion exchange and interplay of partial waves with different angular momenta.  The hadroquarkonium and molecular approaches  to exotic hadrons are compared and their relative advantages and drawbacks are discussed.