Spin-dependent recombination in Czochralski silicon containing oxide precipitates

Electrically detected magnetic resonance is used to identify recombination centers in a set of Czochralski grown silicon samples processed to contain strained oxide precipitates with a wide range of densities (~ 1e9 cm-3 to ~ 7e10 cm-3). Measurements reveal that photo-excited charge carriers recombine through Pb0 and Pb1 dangling bonds and comparison to precipitate-free material indicates that these are present at both the sample surface and the oxide precipitates. The electronic recombination rates vary approximately linearly with precipitate density. Additional resonance lines arising from iron-boron and interstitial iron are observed and discussed. Our observations are inconsistent with bolometric heating and interpreted in terms of spin-dependent recombination. Electrically detected magnetic resonance is thus a very powerful and sensitive spectroscopic technique to selectively probe recombination centers in modern photovoltaic device materials.Comment: 8 pages, 8 figure

Interactions Between the Effects of Nitrogen, and Phosphorus, Potassium and Sulphur on Grass Production

The interactions between rates of nitrogen (N) and rates of phosphorus (P), potassium (K) or sulphur (S) on yield of ryegrass dominant swards were measured with no return of mown clippings in Southland, New Zealand. In the second year of the trial, the yield response to 176 kg N ha-1 compared with no N increased only slightly with increasing soil Olsen P from 8 to 91 µg g-1 soil. At 352 and 704 kg N ha-1 there was a large increase in the yield response (from 5 to 9.4 and 11 t DM ha-1 respectively) up to an Olsen P of 55 µg g-1 soil. At 176 kg N ha-1, there was a linear yield response (from 3.5 to 6.5 t DM ha-1) as ammonium acetate extracted soil K increased from 80 to 120 µg g-1 soil. A larger yield response to K (from 3.5 to 13.5 t DM ha-1) was measured up to but not above 240 µg K g-1 soil at 352 and 704 kg N ha-1. The yield response to 352 and 704 kg N ha-1 increased with soil S status (from 8.2 to 11.8 t DM ha-1) up to 15 µg calcium phosphate extractable S g-1 soil. These results demonstrated that yield responses to increasing rates of N do not increase above a threshold level of other soil nutrients

Higher Order Terms in the Melvin-Morton Expansion of the Colored Jones Polynomial

We formulate a conjecture about the structure of `upper lines' in the expansion of the colored Jones polynomial of a knot in powers of (q-1). The Melvin-Morton conjecture states that the bottom line in this expansion is equal to the inverse Alexander polynomial of the knot. We conjecture that the upper lines are rational functions whose denominators are powers of the Alexander polynomial. We prove this conjecture for torus knots and give experimental evidence that it is also true for other types of knots.Comment: 21 pages, 1 figure, LaTe

Abelian link invariants and homology

We consider the link invariants defined by the quantum Chern-Simons field theory with compact gauge group U(1) in a closed oriented 3-manifold M. The relation of the abelian link invariants with the homology group of the complement of the links is discussed. We prove that, when M is a homology sphere or when a link -in a generic manifold M- is homologically trivial, the associated observables coincide with the observables of the sphere S^3. Finally we show that the U(1) Reshetikhin-Turaev surgery invariant of the manifold M is not a function of the homology group only, nor a function of the homotopy type of M alone.Comment: 18 pages, 3 figures; to be published in Journal of Mathematical Physic

High cooperativity coupling of electron-spin ensembles to superconducting cavities

Electron spins in solids are promising candidates for quantum memories for superconducting qubits because they can have long coherence times, large collective couplings, and many quantum bits can be encoded into the spin-waves of a single ensemble. We demonstrate the coupling of electron spin ensembles to a superconducting transmission-line resonator at coupling strengths greatly exceeding the cavity decay rate and comparable to spin linewidth. We also use the enhanced coupling afforded by the small cross-section of the transmission line to perform broadband spectroscopy of ruby at millikelvin temperatures at low powers. In addition, we observe hyperfine structure in diamond P1 centers and time domain saturation-relaxation of the spins.Comment: 4pgs, 4 figure

Quantum computing with an electron spin ensemble

We propose to encode a register of quantum bits in different collective electron spin wave excitations in a solid medium. Coupling to spins is enabled by locating them in the vicinity of a superconducting transmission line cavity, and making use of their strong collective coupling to the quantized radiation field. The transformation between different spin waves is achieved by applying gradient magnetic fields across the sample, while a Cooper Pair Box, resonant with the cavity field, may be used to carry out one- and two-qubit gate operations.Comment: Several small corrections and modifications. This version is identical to the version published in Phys. Rev. Let

The gathering firestorm in southern Amazonia.

Wildfires, exacerbated by extreme weather events and land use, threaten to change the Amazon from a net carbon sink to a net carbon source. Here, we develop and apply a coupled ecosystem-fire model to quantify how greenhouse gas-driven drying and warming would affect wildfires and associated CO2 emissions in the southern Brazilian Amazon. Regional climate projections suggest that Amazon fire regimes will intensify under both low- and high-emission scenarios. Our results indicate that projected climatic changes will double the area burned by wildfires, affecting up to 16% of the region's forests by 2050. Although these fires could emit as much as 17.0 Pg of CO2 equivalent to the atmosphere, avoiding new deforestation could cut total net fire emissions in half and help prevent fires from escaping into protected areas and indigenous lands. Aggressive efforts to eliminate ignition sources and suppress wildfires will be critical to conserve southern Amazon forests

Dynamic analysis of a lithium-boiling potassium refractory metal Rankine cycle power system for the Jet Propulsion Laboratory

Lithium-boiling potassium refractory metal Rankine cycle power system heat transfer model

Collaborative development of diffraction-limited beamline optical systems at US DOE light sources

An ongoing collaboration among four US Department of Energy (DOE) National Laboratories has demonstrated key technology prototypes and software modeling tools required for new high-coherent flux beamline optical systems. New free electron laser (FEL) and diffraction-limited storage ring (DLSR) light sources demand wavefront preservation from source to sample to achieve and maintain optimal performance. Fine wavefront control was achieved using a novel, roomtemperature cooled mirror system called REAL (resistive element adjustable length) that combines cooling with applied, spatially variable auxiliary heating. Single-grating shearing interferometry (also called Talbot interferometry) and Hartmann wavefront sensors were developed and used for optical characterization and alignment on several beamlines, across a range of photon energies. Demonstrations of non-invasive hard x-ray wavefront sensing were performed using a thin diamond single-crystal as a beamsplitter