"The eastern Bering Sea bottom trawl survey has been conducted annually since 1975 by the Resource Assessment and Conservation Engineering Division of the Alaska Fisheries Science Center, National Marine Fisheries Service. The purpose of this survey is to collect data on the distribution and abundance of crab, groundfish, and other benthic resources in the eastern Bering Sea. These data are used to estimate population abundances for the management of commercially important species in the region. This document includes the time series of results from 1975 to the present. In 2017, 395 total stations (375 standard stations and 20 resampled stations in Bristol Bay) were sampled on the eastern Bering Sea shelf from 4 June to 15 August. In early June, colder bottom temperatures extended into Bristol Bay creating the need to resample 20 stations due to delaying effects of cold water temperature on red king crab reproductive cycle. There was an overall decrease in biomass and abundance in male red king and blue king crab and female red king crab. There was an overall increase in immature female blue king crab and a decrease in mature female biomass and abundance, with no mature female blue king crab being caught in the St. Matthew Island Section. There were overall increases in immature and legal male and immature and mature female biomass and abundance in Chionoecetes bairdi and C. opilio crab, and a decrease in mature male biomass and abundance in Chionoecetes bairdi and C. opilio crab. In addition to the standard eastern Bering Sea survey, in 2017, following the conclusion of the standard survey, 145 stations were sampled in the northern Bering Sea region, encompassing the region south of Bering Strait and including Norton Sound. These stations were sampled between 1 August and 2 September. We report the results of this survey separately from the eastern Bering Sea survey, within the northern Bering Sea section of this report. Blue king crabs occurred largely in the region north of St. Lawrence Isand, in greater densities than were observed for the St. Matthew and Pribilof stocks. Red king crab occurred primarily in Norton Sound, at densities roughly intermediate between those generally observed in the Bristol Bay and Pribilof Districts. Chionoecetes opilio dominated the catch, with the highest densities observed during the 2017 Bering Sea survey occurring to the south of St. Lawrence. Immature male and female opilio were predominate, although mature females were observed, primarily along the western edge of the survey grid, and in the north, near Bering Strait. Morphometrically mature (“large-clawed”) male C. opilio were scattered throughout the survey region, but most prevalent within catch near Bering Strait."--Publisher's website.

The promise of optical antennas is the ability to tame the light to behave in ways not achievable using traditional optical components. For example, our results here demonstrate that a careful engineering of optical antennas allow the strong, even perfect, absorption of light in ultra-thin geometries, i.e., geometries much thinner than the wavelength of light. Enabled by geometry-sensitive antenna resonances, this absorption behavior can also be realized for a broad selection of colors. A detailed theoretical analysis of the observed perfect absorption phenomenon reveals the role of incoherently interacting degenerate electric and magnetic resonances in overcoming the well-known absorption limit for infinitesimally thin films. With another set of experiments, we show that strongly absorbed optical energy in aluminum nanoantennas can be used to heat them efficiently above their melting temperature and stimulate an explosive exothermic oxidation reaction called melt-dispersion mechanism. Importantly, we see that engineering the specific geometry of the constituent particles allows an unprecedented control of aluminum ignition, both spectrally and spatially, through the fine tuning of the optical antenna resonances.

The technological revolution that started with digital electronics more than 50 years ago has pushed the limits of scalability in device fabrication. Device features are currently at the nanometer scale, which requires structures to be built with atomic level accuracy. Advances in nanotechnology have opened up an exciting area of research that allows for molecular level control of device surfaces. Organic molecules can provide the tailorability required to continue the progress of semiconductor technologies. Organic functionalization provides a pathway to control the surface at the molecular level. Fundamental understanding of the adsorption phenomena between organic molecules and the surface is critical to achieve a stable inorganic/organic interface for the creation of hybrid nanostructures. This thesis aims to expand our current toolkit on functionalization to molecules that have multiple functionalities that can react with the surface. The reaction mechanism of these molecules is complex as there are several driving forces that can play a role during adsorption and influence the final reaction products. This thesis covers the adsorption of multifunctional molecules on the Ge(100)-2×1 surface using a combination of experimental and theoretical techniques: Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations. We explored the adsorption of four different molecules: 1,2,3-benzenetriol (C6H6O3); 1,3,5-benzenetriol (C6H6O3); 2-hydroxymethyl-1,3-propanediol (C4H10O3); pyrazine (C4H6N2). These are the first reported studies of these molecules on the Ge(100) surface. In order to understand the extent to which molecular geometry affects surface coverage, a detailed comparison of the adsorption of two triol molecules was carried out: 1,3,5-benzenetriol which has a rigid phenyl backbone and 2-hydroxymethyl-1,3-propanediol with a flexible alkyl backbone. DFT results showed that the rigid backbone exhibits a higher degree of strain, which translates to a loss of exothermicity in the reaction coordinate. Experiments showed that the flexibility of the alkyl backbone provides higher rotational degrees of freedom and an enhancement in surface coverage. In order to understand the effect of intermolecular interactions, the adsorption of 1,2,3-benzenetriol was explored. Interestingly, we found that at high coverage, intramolecular hydrogen bonding in singly and dually adsorbate products breaks to form intermolecular hydrogen bonding with a nearby adsorbate, which provides enhanced stabilization of the surface adduct. This additional stabilization may lower the reactivity of unreacted functional groups even if an empty nearby Ge site is available for reaction. The distribution of products resulted in primarily bidentate adsorbates, leaving an unreacted moiety at the surface. We also found evidence of coverage and temperature effects on adsorbed pyrazine molecules on the Ge surface. It was observed that this molecule adsorbs on Ge through both carbon and nitrogen moieties and the product distribution changes as a function of coverage and temperature. At low coverage, incoming molecules react primarily through C-cycloaddition reactions and N dative bonds. However, as the density of adsorbates increases, new incoming molecules adsorbed primarily through the nitrogen moiety. Furthermore, as the temperature increases, the product distribution changed from primarily non-activated dative bond to activated cycloaddition products. Overall, the studies in this thesis provide new insight into competition and selectivity in adsorption of multifunctional molecules on the Ge(100)-2×1 surface.

Photochemistry studies chemical reactions caused by absorption of light. Developing theoretical and computational tools for photochemistry will not only help better understand photochemical processes such as photosynthesis and vision, but can also provide guidelines about how molecular photodevices can be better designed. Therefore, the goal of my graduate research is to develop a set of computational tools for studying photochemical processes. Physical systems have a hierarchical structure, i.e. basic particles like nuclei and electrons interact leading to the formation of molecules, and molecules interact and change conformations giving rise to chemical reactions. Naturally, the corresponding theoretical methods should also follow this hierarchy. At the bottom level, we need molecular integrals to describe different types of interactions between basic particles. I introduced the automated code engine (ACE) that generates optimized codes for computing integrals on the graphical processing units, and developed several variants of tensor hyper-contraction (THC) approximations. ACE reduces the computational prefactor of integral evaluations whereas THC reduces the formal scaling. On top of the integrals, we then need electronic structure methods to describe the energies and forces for a molecule at any given nuclear configuration; including electron correlation is the key to having an accurate description. Here, I first developed single reference THC-MP2 to capture the dynamic correlations, and then developed multi-reference THC-CASPT2 method to incorporate static correlations simultaneously. These methods were later generalized to THC-MSPT2 to enable descriptions for excited states and conical intersections, both are critical for photochemistry. Finally, given the electronic structure methods, we then need methods to explore the potential energy surfaces. In particular, critical point search methods locate the important configurations (e.g. Franck-Condon point, conical intersections), while molecular dynamics methods generate trajectories describing how the molecules move and interact with each other. By interfacing the electronic structure methods that I developed with the geomeTRIC geometry optimizer and G-AIMS non-adiabatic dynamics framework, a complete toolbox for understanding photochemistry is provided.

Silicon Photonics is considered to be essential for the sustained growth of semiconductor industry moving forward. The ubiquitous mobile devices and Internet of Things (IoT) are driving the data needs of the end user exponentially which has led to numerous data centers and perilously large power consumption in each of them. More than 3.4 billion people in the world have access to internet today and this number is increasing steadily day by day. Together, we generate more than 50 Terabytes (50,000 Gigabytes) of internet traffic per second at any given point of time. This number was just 100 Gigabytes per second in 2002 and it is expected to grow much faster going into the future. As for the power consumption, US data centers alone consumed about 70 billion kilowatt-hours of electricity in 2014, representing 2 percent of the country's total energy consumption, according to a study. That's equivalent to the amount consumed by about 6.4 million average American homes that year. This is a 4 percent increase in total data center energy consumption from 2010 to 2014, and a huge change from the preceding five years, during which total US data center energy consumption grew by 24 percent, and an even bigger change from the first half of last decade, when their energy consumption grew nearly 90 percent. It is well established that the copper cables which transfer data from one end of the data-center to the other are the bottlenecks reducing the overall bandwidth of the system and skyrocketing the power consumption on the whole. This bottleneck is getting worse day by day owing to the ever-increasing data needs. Silicon Photonics based 'optical interconnects' are the best solution to remove this bottleneck. Optical interconnects use photons instead of electrons for communication and therefore have the potential to offer very large bandwidths at minimal power consumption. In the very near future all the copper wires in the data-center ecosystem will have to be replaced by these optical interconnects if we must meet the data needs within the prescribed power budget. In order to build such a platform where conventional machines in the data center work in tandem with novel interconnects based on photon-devices, all the optical components need to be integrated seamlessly on a silicon chip. Modulators are the most important optical component of such a platform since they act as optical switches which control the flow of photons. In the first part of the dissertation, a silicon compatible germanium (Ge) electro-absorption modulator with the best reported energy-delay product is demonstrated. The figure-of-merits along with the design principles are discussed in detail while the fabrication methodology is briefly touched upon. Experimentally measured characteristics are then shown to be the best-in-class and ones that match the data requirements of the data-centers with minimal energy consumption. In the second part of the dissertation, we focus on developing an efficient silicon-compatible light emitter based on strained Ge technology. Detailed theoretical calculations lay down a roadmap for room-temperature lasing from Ge. These calculations also prove that the loss mechanisms involved in the light emission process from Ge have been inadequately modeled until now and shows that a particular loss mechanism known as the inter-valence-band absorption is a major barrier in the realization of a strained Ge laser. CMOS compatible fabrication techniques to introduce large uniaxial strain in Ge are then discussed. Finally, a low-threshold Ge laser at a temperature of 83 K is demonstrated. In the final part of the dissertation, the first demonstration of a 'truly' silicon compatible three-dimensional (3D) photonic crystals is discussed. Using the methodology developed, a broadband omnidirectional reflector is also demonstrated on silicon. This methodology is also shown to be particulary well suited for 3D waveguides and optical cavities.

Understanding the aerodynamic interactions between turbines in a wind farm is essential for maximizing power generation. In contrast to horizontal-axis wind turbines (HAWTs), for which wake interactions between turbines in arrays must be minimized to prevent performance losses, vertical-axis wind turbines (VAWTs) in arrays have demonstrated beneficial interactions that can result in net power output greater than that of turbines in isolation. These synergistic interactions have been observed in previous numerical simulations, laboratory experiments, and field work. This dissertation builds on previous work by identifying the aerodynamic mechanisms that result in beneficial turbine-turbine interactions and providing insights into potential wind farm optimization. The experimental data presented indicates increased power production of downstream VAWTs when positioned offset from the wake of upstream turbines. Comparison with three-dimensional, three-component flow measurements demonstrates that this enhancement is due to flow acceleration adjacent to the upstream turbine, which increase the incident freestream velocity on appropriately positioned downstream turbines. A low-order model combining potential flow and actuator disk theory accurately captures this effect. Laboratory and field experiments were used to validate the model's predictive capabilities, and an evolutionary algorithm was deployed to investigate array optimization. Furthermore, changes in upstream turbine performance are related to variations in the surrounding flow field due to the presence of the downstream rotor. Finally, three-dimensional vortex interactions behind pairs of VAWTs are observed to replenish momentum in the array's wake. These effects are described along with their implications for wind farm design.