Faculty Scholarship
Showing 1 - 10 of 733 Items
Observation of the charmed baryon c+ and measurement of the isospin mass splittings of the c
Date: 1993-01-01
Creator: G. Crawford, C. M. Daubenmier, R. Fulton, D. Fujino, K. K., Gan, K. Honscheid, H. Kagan, R. Kass, J. Lee, R. Malchow, F. Morrow, Y. Skovpen, M. Sung, C. White, J. Whitmore, P. Wilson, F. Butler, X. Fu, G. Kalbfleisch, M. Lambrecht, W. R. Ross, P. Skubic, J. Snow, P. L. Wang, M. Wood, D. Bortoletto, D. N. Brown, J. Fast, R. L. McIlwain, T. Miao, D. H. Miller
Access: Open access
- We observe the c+ baryon decaying to Λc+π0 and measure the mass difference M(c+)-M(Λc+) to be 168.5±0.2 MeV/c2. We also measure the mass differences M(c++)-M(Λc+) and M(c0-M(Λc+) with improved precision and determine the isospin mass splittings M(c++)-M(c0) and M(c+)-M(c0) to be 1.1±0.4±0.1 MeV/c2 and 1.4±0.5±0.3 MeV/c2, respectively. Our results indicate that the light quark mass difference does not dominate the isospin mass splitting in c. © 1993 The American Physical Society.
The efficiency of voluntary incentive policies for preventing biodiversity loss
Date: 2011-01-01
Creator: David J. Lewis, Andrew J. Plantinga, Erik Nelson, Stephen Polasky
Access: Open access
- Habitat loss is a primary cause of loss of biodiversity but conserving habitat for species presents challenges. Land parcels differ in their ability to produce returns for landowners and landowners may have private information about the value of the land to them. Land parcels also differ in the type and quality of habitat and the spatial pattern of land use across multiple landowners is important for determining the conservation value of parcels. This paper analyzes the relative efficiency of simple voluntary incentive-based policies in achieving biodiversity conservation objectives. This topic is important not just for biodiversity conservation but for any effort to provide a public good requiring coordination across multiple decision-makers who have some degree of private information. We develop a method that integrates spatially explicit data, an econometric model of private land-use decisions, landscape simulations, a biological model of biodiversity as a function of landscape pattern, and an algorithm that estimates the set of efficient solutions. These methods allow us to simulate landowner responses to policies, measure the consequences of these decisions for biodiversity conservation, and compare these outcomes to efficient outcomes to show the relative efficiency of various policy approaches. We find substantial differences in biodiversity conservation scores generated by simple voluntary incentive-based policies and efficient solutions. The performance of incentive-based policies is particularly poor at low levels of the conservation budget where spatial fragmentation of conserved parcels is a large concern. Performance can be improved by encouraging agglomeration of conserved habitat and by incorporating basic biological information, such as that on rare habitats, into the selection criteria. © 2010 Elsevier B.V.
An overview of approaches and challenges for retrieving marine inherent optical properties from ocean color remote sensing
Date: 2018-01-01
Creator: P. Jeremy Werdell, Lachlan I.W. McKinna, Emmanuel Boss, Steven G. Ackleson, Susanne E., Craig, Watson W. Gregg, Zhongping Lee, Stéphane Maritorena, Collin S. Roesler, Cécile S. Rousseaux, Dariusz Stramski, James M. Sullivan, Michael S. Twardowski, Maria Tzortziou, Xiaodong Zhang
Access: Open access
- Ocean color measured from satellites provides daily global, synoptic views of spectral water-leaving reflectances that can be used to generate estimates of marine inherent optical properties (IOPs). These reflectances, namely the ratio of spectral upwelled radiances to spectral downwelled irradiances, describe the light exiting a water mass that defines its color. IOPs are the spectral absorption and scattering characteristics of ocean water and its dissolved and particulate constituents. Because of their dependence on the concentration and composition of marine constituents, IOPs can be used to describe the contents of the upper ocean mixed layer. This information is critical to further our scientific understanding of biogeochemical oceanic processes, such as organic carbon production and export, phytoplankton dynamics, and responses to climatic disturbances. Given their importance, the international ocean color community has invested significant effort in improving the quality of satellite-derived IOP products, both regionally and globally. Recognizing the current influx of data products into the community and the need to improve current algorithms in anticipation of new satellite instruments (e.g., the global, hyperspectral spectroradiometer of the NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission), we present a synopsis of the current state of the art in the retrieval of these core optical properties. Contemporary approaches for obtaining IOPs from satellite ocean color are reviewed and, for clarity, separated based their inversion methodology or the type of IOPs sought. Summaries of known uncertainties associated with each approach are provided, as well as common performance metrics used to evaluate them. We discuss current knowledge gaps and make recommendations for future investment for upcoming missions whose instrument characteristics diverge sufficiently from heritage and existing sensors to warrant reassessing current approaches.
Environmental issues in Russia
Date: 2008-12-01
Creator: Laura A. Henry, Vladimir Douhovnikoff
Access: Open access
- This review examines the literature available on the state of the environment and environmental protection in the Russian Federation. As the largest country on Earth, rich in natural resources and biodiversity, Russia's problems and policies have global consequences. Environmental quality and management are influenced by the legacy of Soviet economic planning and authoritarian governance, as well as by Russia's post-Soviet economic recession and current strategies of economic development. Russia achieved a reduction in some pollutants owing to the collapse of industrial production in the 1990s, but many environmental indicators suggest growing degradation. Russia has signed on to a number of international environmental agreements, but its record on implementation is mixed, and it discourages environmental activism. Scholarship on the Russian environment is a limited, but growing, field, constrained by challenges of data availability, yet it offers great potential for testing scientific and social scientific hypotheses. ©2008 by Annual Reviews.
Color-factor symmetry and BCJ relations for QCD amplitudes
Date: 2016-11-01
Creator: Robert W. Brown, Stephen G. Naculich
Access: Open access
- Tree-level n-point gauge-theory amplitudes with n − 2k gluons and k pairs of (massless or massive) particles in the fundamental (or other) representation of the gauge group are invariant under a set of symmetries that act as momentum-dependent shifts on the color factors in the cubic decomposition of the amplitude. These symmetries lead to gauge-invariant constraints on the kinematic numerators. They also directly imply the BCJ relations among the Melia-basis primitive amplitudes previously obtained by Johansson and Ochirov.
Observation of a new charmed strange meson
Date: 1994-01-01
Creator: Y. Kubota, M. Lattery, J. K. Nelson, S. Patton, D., Perticone, R. Poling, V. Savinov, S. Schrenk, R. Wang, M. S. Alam, I. J. Kim, B. Nemati, J. J. O'Neill, H. Severini, C. R. Sun, M. M. Zoeller, G. Crawford, C. M. Daubenmier, R. Fulton, D. Fujino, K. K. Gan, K. Honscheid, H. Kagan, R. Kass, J. Lee, R. Malchow, F. Morrow, Y. Skovpen, M. Sung, C. White, F. Butler
Access: Open access
- Using the CLEO II detector, we have obtained evidence for a new meson decaying to D0K+. Its mass is 2573.2-1.6+1.7±0.8±0.5 MeV/c2 and its width is 16-4+5±3 MeV/c2. Although we do not establish its spin and parity, the new meson is consistent with predictions for an L=1, S=1, JP=2+ charmed strange state. © 1994 The American Physical Society.
Stolen Future, Broken Present: The Human Significance of Climate Change
Date: 2014-01-01
Creator: David A Collings
Access: Open access
- This book argues that climate change has a devastating effect on how we think about the future. Once several positive feedback loops in Earth’s dynamic systems, such as the melting of the Arctic icecap or the drying of the Amazon, cross the point of no return, the biosphere is likely to undergo severe and irreversible warming. Nearly everything we do is premised on the assumption that the world we know will endure into the future and provide a sustaining context for our activities. But today the future of a viable biosphere, and thus the purpose of our present activities, is put into question. A disappearing future leads to a broken present, a strange incoherence in the feel of everyday life. We thus face the unprecedented challenge of salvaging a basis for our lives today. That basis, this book argues, may be found in our capacity to assume an infinite responsibility for ecological disaster and, like the biblical Job, to respond with awe to the alien voice that speaks from the whirlwind. By owning disaster and accepting our small place within the inhuman forces of the biosphere, we may discover how to live with responsibility and serenity whatever may come. (Publisher's Description) Freely available online at: http://dx.doi.org/10.3998/ohp.12832550.0001.001
Conical wave propagation and diffraction in two-dimensional hexagonally packed granular lattices
Date: 2016-01-25
Creator: C. Chong, P. G. Kevrekidis, M. J. Ablowitz, Yi Ping Ma
Access: Open access
- Linear and nonlinear mechanisms for conical wave propagation in two-dimensional lattices are explored in the realm of phononic crystals. As a prototypical example, a statically compressed granular lattice of spherical particles arranged in a hexagonal packing configuration is analyzed. Upon identifying the dispersion relation of the underlying linear problem, the resulting diffraction properties are considered. Analysis both via a heuristic argument for the linear propagation of a wave packet and via asymptotic analysis leading to the derivation of a Dirac system suggests the occurrence of conical diffraction. This analysis is valid for strong precompression, i.e., near the linear regime. For weak precompression, conical wave propagation is still possible, but the resulting expanding circular wave front is of a nonoscillatory nature, resulting from the complex interplay among the discreteness, nonlinearity, and geometry of the packing. The transition between these two types of propagation is explored.
Multistable solitons in higher-dimensional cubic-quintic nonlinear Schrödinger lattices
Date: 2009-01-15
Creator: C. Chong, R. Carretero-González, B. A. Malomed, P. G. Kevrekidis
Access: Open access
- We study the existence, stability, and mobility of fundamental discrete solitons in two- and three-dimensional nonlinear Schrödinger lattices with a combination of cubic self-focusing and quintic self-defocusing onsite nonlinearities. Several species of stationary solutions are constructed, and bifurcations linking their families are investigated using parameter continuation starting from the anti-continuum limit, and also with the help of a variational approximation. In particular, a species of hybrid solitons, intermediate between the site- and bond-centered types of the localized states (with no counterpart in the 1D model), is analyzed in 2D and 3D lattices. We also discuss the mobility of multi-dimensional discrete solitons that can be set in motion by lending them kinetic energy exceeding the appropriately defined Peierls-Nabarro barrier; however, they eventually come to a halt, due to radiation loss. © 2008 Elsevier B.V. All rights reserved.
All-loop infrared-divergent behavior of most-subleading-color gauge-theory amplitudes
Date: 2013-04-19
Creator: Stephen G. Naculich, Horatiu Nastase, Howard J. Schnitzer
Access: Open access
- The infrared singularities of gravitational amplitudes are one-loop exact, in that higher-loop divergences are characterized by the exponential of the one-loop divergence. We show that the contributions to SU(N) gauge-theory amplitudes that are mostsubleading in the 1/N expansion are also one-loop exact, provided that the dipole conjecture holds. Possible corrections to the dipole conjecture, beginning at three loops, could violate one-loop-exactness, though would still maintain the absence of collinear divergences. We also demonstrate a relation between L-loop four-point N = 8 supergravity and mostsubleading-color N = 4 SYM amplitudes that holds for the two leading IR divergences, (Formula presented.) and (Formula presented.), but breaks down at (Formula presented.).