Controlling the second-harmonic in a phase matched negative-index metamaterial

Nonlinear metamaterials (NLMMs) have been predicted to support new and exciting domains in the manipulation of light, including novel phase matching schemes for wave mixing. Most notable is the so-called nonlinear-optical mirror, in which a nonlinear negative-index medium emits the generated frequency towards the source of the pump. For the first time, we experimentally demonstrate the nonlinear-optical mirror effect in a bulk negative-index NLMM, along with two other novel phase matching configurations, utilizing periodic poling to switch between the three phase matching domains.Comment: 5 pages, 7 figure

All-angle negative refraction of photonic and polaritonic waves in three-dimensionally periodic structures

Thesis advisor: Krzysztof KempaThough nature provides a plethora of materials to work with, their properties are very much restricted, forcing severe limitations on the devices that are built from them. A huge portion of current technology stands to be significantly advanced and even revolutionized by the emergence of a new class of “configurable” materials. This class, generally referred to as metamaterials, has become more feasible than ever due to advancements in nanotechnology and fabrication techniques. Notable among nature’s limitations is an ever-positive index of refraction. This barrier has only recently been broken, and the known paths to negative refraction are few and limited. This paper introduces two distinct three-dimensional crystals capable of all-angle negative refraction. One uses the familiar photonic band, while the other is the first of its kind to rely on polaritonic waves. Their mode structures are examined and a set of parameters are chosen at which a negative effective index of refraction can be harnessed for unrestricted sub-wavelength lensing, demonstrated via numerical simulation. This work is expected to enable experimental observation of polaritonic negative refraction and sub-wavelength lensing at microwave frequencies.Thesis (BS) — Boston College, 2009.Submitted to: Boston College. College of Arts and Sciences.Discipline: College Honors Program.Discipline: Physics

Circular dichroism of four-wave mixing in nonlinear metamaterials

Metamaterial engineering offers a route to combine unusual and interesting optical phenomena in ways that are rare or nonexistent in nature. As an exploration of this wide parameter space, we experimentally demonstrate strong cross-phase modulation and f

Paleomagnetic evidence for modern-like plate motion velocities at 3.2 Ga

The mode and rates of tectonic processes and lithospheric growth during the Archean [4.0 to 2.5 billion years (Ga) ago] are subjects of considerable debate. Paleomagnetism may contribute to the discussion by quantifying past plate velocities. We report a paleomagnetic pole for the ~3180 million year (Ma) old Honeyeater Basalt of the East Pilbara Craton, Western Australia, supported by a positive fold test and micromagnetic imaging. Comparison of the 44°±15° Honeyeater Basalt paleolatitude with previously reported paleolatitudes requires that the average latitudinal drift rate of the East Pilbara was ≥2.5 cm/year during the ~170 Ma preceding 3180 Ma ago, a velocity comparable with those of modern plates. This result is the earliest unambiguous evidence yet uncovered for long-range lithospheric motion. Assuming this motion is due primarily to plate motion instead of true polar wander, the result is consistent with uniformitarian or episodic tectonic processes in place by 3.2 Ga ago

Multi-Terminal Superconducting Phase Qubit

Mesoscopic multi-terminal Josephson junctions are novel devices that provide weak coupling between several bulk superconductors through a common normal layer. Because of the nonlocal coupling of the superconducting banks, a current flow between two of the terminals can induce a phase difference and/or current flow in the other terminals. This "phase dragging" effect is used in designing a new type of superconducting phase qubit, the basic element of a quantum computer. Time-reversal symmetry breaking can be achieved by inserting a pi-phase shifter into the flux loop. Logical operations are done by applying currents. This removes the necessity for local external magnetic fields to achieve bistability or controllable operations.Comment: 7 pages, 3 figure

Light-Triggered Modulation of Cellular Electrical Activity by Ruthenium Diimine Nanoswitches

Ruthenium diimine complexes have previously been used to facilitate light-activated electron transfer in the study of redox metalloproteins. Excitation at 488 nm leads to a photoexcited state, in which the complex can either accept or donate an electron, respectively, in the presence of a soluble sacrificial reductant or oxidant. Here, we describe a novel application of these complexes in mediating light-induced changes in cellular electrical activity. We demonstrate that RubpyC17 ([Ru(bpy)_(2)(bpy-C17)]^(2+), where bpy is 2,2′-bipyridine and bpy-C17 is 2,2′-4-heptadecyl-4′-methyl-bipyridine), readily incorporates into the plasma membrane of cells, as evidenced by membrane-confined luminescence. Excitable cells incubated in RubpyC17 and then illuminated at 488 nm in the presence of the reductant ascorbate undergo membrane depolarization leading to firing of action potentials. In contrast, the same experiment performed with the oxidant ferricyanide, instead of ascorbate, leads to hyperpolarization. These experiments suggest that illumination of membrane-associated RubpyC17 in the presence of ascorbate alters the cell membrane potential by increasing the negative charge on the outer face of the cell membrane capacitor, effectively depolarizing the cell membrane. We rule out two alternative explanations for light-induced membrane potential changes, using patch clamp experiments: (1) light-induced direct interaction of RubpyC17 with ion channels and (2) light-induced membrane perforation. We show that incorporation of RubpyC17 into the plasma membrane of neuroendocrine cells enables light-induced secretion as monitored by amperometry. While the present work is focused on ruthenium diimine complexes, the findings point more generally to broader application of other transition metal complexes to mediate light-induced biological changes

Mahomet Aquifer Protection Task Force: Findings and Recommendations

The Mahomet Aquifer is one of Illinois’ most important groundwater resources, serving as the primary source of drinking water for more than 500,000 people in 15 Illinois counties and providing an estimated 220 million gallons of water per day to communities, agriculture, industry, and rural wells. In 2017, the Illinois General Assembly created the Mahomet Aquifer Protection Task Force (Task Force) to identify gaps in existing aquifer-protection regulations and efforts, specifically by: Developing a state plan to maintain the groundwater quality of the Mahomet Aquifer; Identifying current and potential contamination threats to the water quality of the Mahomet Aquifer; Identifying actions that might be taken to ensure the long-term protection of the Mahomet Aquifer; and Making legislative recommendations for the protection of the Mahomet Aquifer. The Task Force investigated and considered various actions, including legislative actions, to ensure the long-term protection of the Mahomet Aquifer and makes the following prioritized recommendations to the General Assembly and the Governor: 1. Provide 19.8 million dollars to the Prairie Research Institute (PRI) to use helicopter-based time-domain electromagnetics (HTEM) technology to more accurately map and characterize the Mahomet Aquifer to aid in identifying the connections with other aquifers and surface waters. 2. Use HTEM and other techniques to identify areas where the Mahomet Aquifer is recharged. 3. Integrate data collected via HTEM into next-generation groundwater flow models. 4. Develop and implement source water protection plans pursuant to 35 Ill. Adm. Code 604 Subpart C, after the effective date of adoption, for the community water supplies determined to be susceptible to groundwater contamination. 5. Implement the recommendations outlined for each identified threat and potential threat (as detailed below and in Section III.A) and provide additional funding (1 million dollars for one-time equipment acquisition and an additional 2.3 million annually) to PRI to deploy state-of-the-art monitoring networks and create the analytical capability to identify emerging contaminants of concern. 6. Improve education and outreach regarding the Mahomet Aquifer such that all stakeholders are better informed about water resources, water demand, and water supply planning and management, particularly when plans are made, reviewed, and updated. 7. Develop a group with a mission similar to the Mahomet Aquifer Protection Task Force that is a blend of other select individuals that serve in a quasi-government or government capacity to provide leadership, administrative stature, or process for regional water supply. 8. Plan cooperative research and data collection, analysis, management, and exchange by academic institutions, units of government, the private sector, and other stakeholders. 9. Use the established water supply planning process to review and update regional and local water supply plans at least every five years. 10. Ensure comprehensive use reporting by consistently and fully funding the Illinois Water Inventory Program.Illinois General AssemblyOpe

A multi-pronged approach targeting SARS-CoV-2 proteins using ultra-large virtual screening.

The unparalleled global effort to combat the continuing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic over the last year has resulted in promising prophylactic measures. However, a need still exists for cheap, effective therapeutics, and targeting multiple points in the viral life cycle could help tackle the current, as well as future, coronaviruses. Here, we leverage our recently developed, ultra-large-scale in silico screening platform, VirtualFlow, to search for inhibitors that target SARS-CoV-2. In this unprecedented structure-based virtual campaign, we screened roughly 1 billion molecules against each of 40 different target sites on 17 different potential viral and host targets. In addition to targeting the active sites of viral enzymes, we also targeted critical auxiliary sites such as functionally important protein-protein interactions