This NSF Materials World Network Program allows research into a new class of artificial nanophotonic materials, which make use of our ability to use nanofabrication in conjunction with intrinsic materials properties to tailor the linear and nonlinear optical response of those metamaterials. The main challenges towards a comprehensive understanding and experimental realization of nonlinear optical properties of metamaterials are that a theory of surface and bulk nonlinear optics of metamaterials is yet to be developed, and a practical means to fabricate and test such a theory are missing as well. The main goal of this research program is to achieve these milestones. The program synergistically matches three collaborators, two in the UK and one in the US, with an established record of collaboration to investigate the properties and materials strategies for fabricating these materials. The central rationale for the group is that the UK group provides strong theoretical and fabrication capabilities while the US group provides fabrication, optical testing, and materials capabilities. In addition, we will make use of local instrumentation capabilities in both the UK and the US to fabricate and test these materials. The program is constructed to enable travel to and from each country by students and to a more limited extent the professors. The research to be undertaken here has several areas of broad impact. First, it is a project, which will foster an interdisciplinary examination of the fundamental materials science of artificial metamaterials, which includes fabrication, materials physics, optical physics, and theory. Second it will enable two groups in the US and the UK, with a strong history of interactions and complementary expertise and capabilities to collaborate. This work will involve the opportunity for both graduate and undergraduate students to collaborate and travel in an international setting. Third, the program has concrete plans and procedures to seek out recruitment of diverse student collaborators. Our immediate record in this area is strong including one woman PhD student in theory and two undergraduates. Recruitment for this program will be done via four outreach talks to undergrads at Columbia in Electrical Engineering and Applied Physics and Applied Mathematics Departments every year via active participation in research opportunities for undergraduates and undergraduate research opportunities program at Columbia. Fourth, the project will enable students to collaborate via extended visits and shorter trips with a major National Laboratory, i.e. Brookhaven, in their new Nanocenter, which one of the PIs was the founding director, as well as the London Centre for Nanotechnology, a facility shared by the University College London and Imperial College London.

Subduction zones are a key valve mediating global S processing and the climatic effects of arc volcanism, the economic potential of arc magmas, and the oxidation state of solid Earth reservoirs. Yet, the inputs, processing and recycling of S throughout the subduction system are still inaccurately known. This international project targets major unknowns in the sulfur cycle at subduction zones. The US-NSF focus of this project (PI Plank, LDEO) will fill a key knowledge gap in terms of S inputs to the mantle at subduction zones. It will involve extensive analysis of sedimentary sections at the Tonga, Marianas, Aleutians, Alaska and Central America trenches, chosen to represent end-member oceanic environments for sulfur deposition and diagenesis and extreme isotopic variations. Ocean Drilling Programs cores will be analyzed by XRF core scanning, a strategic approach to quantify heterogeneously disseminated pyrite and barite, major hosts of sulfur in sediment. Core scanning results will guide discrete sampling for bulk sulfur and sulfur isotope analyses at the University of Palermo, in collaboration with Prof. Aiuppa and Vizzini. Pilot data collected in Palermo demonstrate the quality of the coupled Elemental Analyzer-Mass Spectrometry technique and the clear sulfide- vs. sulfate-dominated regimes that may occur in a single sedimentary section. The outcome will be the first comprehensive estimates (with uncertainties) for the fluxes and isotopic compositions of S into end-member trenches and improved global estimates. The UK-NERC part of this project (PI Mather, Oxford) will take a novel approach to understanding volcanic arc S outputs. It will measure for the first time the sulfur isotopic composition in undegassed olivine-hosted arc melt inclusions. Pilot data collected at NERC Ion Microprobe Facility at Edinburgh demonstrate the viability of the technique, and yield positive delta(34)S in melt inclusions from Fuego volcano. Planned work will include well-studied melt inclusions suites from the same subducting systems as the sediment targets (above). This will ensure close collaboration between the US and UK parts of this project, and allow for the first-time direct tracing of sulfur isotopes from sediment input to arc output.

The Hawaiian-Emperor Seamount Chain is arguably the world's best known example of hotspot magmatism, where volcanic activity and earthquakes occur far from plate boundaries. Nevertheless, questions remain about the fundamental processes that control such magmatism and seismicity along the 5800-km-long, 0-80 Ma, chain, in part because the volume and compositions of frozen magma that has been added to the surface and base of Pacific oceanic crust is too poorly known. The aim of this study is to use 'state of the art' marine seismic imaging techniques to constrain the thickness and composition of the magmatic material created by the Hawaiian hotspot, how it varies along the seamount chain, and how the Pacific oceanic plate has deformed in response to volcano loading. This study, which is a collaborative one with US scientists at Lamont-Doherty Earth Observatory, will utilize reprocessed seismic reflection and refraction data acquired on previous research cruises (e.g. R/V Robert D. Conrad C2308, R/V Thomas Washington Roundabout 2, and R/V Maurice Ewing EW9801), together with a new data set that will be acquired onboard R/V Marcus G. Langseth during late summer, 2018 and early summer, 2019. The Langseth cruises, which have been funded by the National Science Foundation (Marine Geology and Geophysics Division), will acquire deep penetration seismic reflection data using a 15 km long streamer and a large tuned airgun array and wide-angle reflection/refraction data using 70 Ocean Bottom Seismometers spaced at 15 km intervals along four 500-km-long transects of the chain. The transect locations have been carefully chosen to represent variations in the timing of magma emplacement and volume flux, the age of oceanic lithosphere at the time of loading and the presence/absence of a mid-plate topographic swell, and are sufficiently long to capture the response of the lithosphere to volcano loading out to the flexural bulge. The reprocessed and processed seismic reflection profiles and velocity models created from wide-angle seismic data will constrain the volume and distribution of magmatic addition to the surface and base of the crust, the nature of the stratigraphic fill in the flanking flexural moats and the relative role of faulting within the flexed volcanic edifice and underlying oceanic plate. The seismic constraints will be integrated with swath bathymetry and potential field data, compared to other marine geophysical studies of hotspot magmatism and used as the basis for thermal and mechanical modeling in order to gain fundamental insights into crust and lithosphere rheology and stress state and to inform potential geohazards along the chain such as large-scale slope failures, fault slip and tsunamigenic earthquakes. The study proposed here is central to NERC's strategy especially as it involves discovery science that impacts on how planet Earth works, how it deforms in response to surface and sub-surface loads and how it might deform in the future.

United States

Brain functions such as perception, motor control, learning, and memory arise from the coordinated activation of neuronal assemblies distributed across multiple brain areas. While major progress has been made in understanding the response properties of individual cells, circuit interactions remain poorly understood. One of the fundamental obstacles to understanding these interactions has been the difficulty of observing the activity of large distributed populations of neurons in freely behaving animals. By combining highly engineered genetically encoded light-sensitive ion channels (typically Channelrhodopsins, ChRs) with fluorescent voltage or calcium sensors, it has become possible to achieve precise, non-invasive and high-speed control and monitoring of neuronal networks with optical techniques, both in cell culture and in live and awake animals. Conventional microscopy approaches have been employed for building these optical interfaces, resulting in very complex implementation which makes freely behaving animal studies difficult. In addition, conventional microscopy techniques, even those that use two photon techniques or light-sheet imaging, are limited by scattering and absorption in the brain tissue, allowing only superficial coverage for brains as small as that of the mouse. In this proposal, we will develop an approach for light delivery that surmounts these limitations. It enables complete coverage of all neurons within a target volume, permits functional imaging with cellular resolution in highly scattering brain tissue, and has long-term prospects for human applications. Our approach is based on distributing a dense 3-D lattice of emitter and detector pixels within the brain itself. These pixel arrays are embedded onto neural probes, realized as implantable, ultra-narrow shanks. These probes are readily producible though existing CMOS (complementary metal-oxide-semiconductor) foundries augmented by organic LED (OLED) technology. This hybrid device platform for optogenetic stimulation and recording combines angle-sensitive CMOS single-photon avalanche diodes (A-SPADs) for detection and angle-emitting OLEDs for light generation. Due to their amorphous morphology, the organic materials used in OLEDs can be deposited directly onto silicon chips, without lattice matching constraints, thus facilitating true monolithic integration of light sources on CMOS technology.