Showing 551 - 600 of 733 Items

Date: 2004-01-28

Creator: M. Aydin, E. S. Saltzman, W. J. De Bruyn, S. A. Montzka, J. H., Butler, M. Battle

Access: Open access

Measurements of methyl chloride (CH3Cl) in Antarctic polar ice and firn air are used to describe the variability of atmospheric CH3Cl during the past 300 years. Firn air results from South Pole and Siple Dome suggest that the atmospheric abundance of CH3Cl increased by about 10% in the 50 years prior to 1990. Ice core measurements from Siple Dome provide evidence for a cyclic natural variability on the order of 10%, with a period of about 110 years in phase with the 20th century rise inferred from firn air. Thus, the CH3Cl increase measured in firn air may largely be a result of natural processes, which may continue to affect the atmospheric CH3Cl burden during the 21st century. Copyright 2004 by the American Geophysical Union.

Date: 1992-01-01

Creator: M. Artuso, M. Goldberg, N. Horwitz, R. Kennett, G. C., Moneti, F. Muheim, S. Playfer, Y. Rozen, P. Rubin, S. Stone, M. Thulasidas, W. M. Yao, G. Zhu, A. V. Barnes, J. Bartelt, S. E. Csorna, Z. Egyed, V. Jain, P. Sheldon, D. S. Akerib, B. Barish, M. Chadha, D. F. Cowen, G. Eigen, J. S. Miller, J. Urheim, A. J. Weinstein, D. Acosta, G. Masek, B. Ong, H. Paar

Access: Open access

The decay 0 has been observed for the first time using the CLEO-II detector at the Cornell Electron Storage Ring. The measured branching ratio (0.170.020.02)%, agrees with the CVC (conserved vector current) prediction based on e+e-+- data. Upper limits on the branching ratios for other decays to final states including mesons are improved by an order of magnitude compared to previous measurements. © 1992 The American Physical Society.

Date: 1993-01-01

Creator: M. Battle, J. Ernst, H. Kroha, Y. Kwon, S., Roberts, K. Sparks, E. H. Thorndike, C. H. Wang, J. Dominick, S. Sanghera, V. Shelkov, T. Skwarnicki, R. Stroynowski, I. Volobouev, P. Zadorozhny, M. Artuso, D. He, M. Goldberg, N. Horwitz, R. Kennett, G. C. Moneti, F. Muheim, Y. Mukhin, S. Playfer, Y. Rozen, S. Stone, M. Thulasidas, G. Vasseur, G. Zhu, J. Bartelt, S. E. Csorna

Access: Open access

We report results from a search for the decays B0→π+π-, B0→K+π-, and B0→K+K-. We find 90% confidence level upper limits on the branching fractions, Bππ<2.9×10-5, BKπ<2.6×10-5, and BKK<0.7×10-5. While there is no statistically significant signal in the individual modes, the sum of Bππ and BKπ exceeds zero with a significance of more than 4 standard deviations, indicating that we have observed charmless hadronic B decays. © 1993 The American Physical Society.

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.

Date: 1992-01-01

Creator: J. Alexander, C. Bebek, K. Berkelman, D. Besson, T. E., Browder, D. G. Cassel, E. Cheu, D. M. Coffman, P. S. Drell, R. Ehrlich, R. S. Galik, M. Garcia-Sciveres, B. Geiser, B. Gittelman, S. W. Gray, D. L. Hartill, B. K. Heltsley, K. Honscheid, J. Kandaswamy, N. Katayama, P. C. Kim, D. L. Kreinick, J. D. Lewis, G. S. Ludwig, J. Masui, J. Mevissen, N. B. Mistry, S. Nandi, C. R. Ng, E. Nordberg, C. Grady

Access: Open access

Using the CLEO II detector, we have accurately measured Ds decay branching ratios relative to the mode for the and states, for which there are conflicting claims; our results are 0.540.090.06 and 1.200.150.11, respectively. © 1992 The American Physical Society.

Date: 2012-05-21

Creator: Alexander C. Edison, Stephen G. Naculich

Access: Open access

Color-ordered amplitudes for the scattering of n particles in the adjoint representation of SU(N) gauge theory satisfy constraints arising solely from group theory. We derive these constraints for n=.5 at all loop orders using an iterative approach. These constraints generalize well-known tree-level and one-loop group theory relations. © 2012 Elsevier B.V.

Date: 2006-04-17

Creator: Stephen G. Naculich, Howard J. Schnitzer

Access: Open access

The consequences of level-rank duality for untwisted D-branes on an SU(N) group manifold are explored. Relations are found between the charges of D-branes (which are classified by twisted K-theory) belonging to su (N)K and su (K)N theories, in the case of odd N + K. An isomorphism between the charge algebras is also demonstrated in this case. © 2006 Elsevier B.V. All rights reserved.

Date: 2014-01-14

Creator: S. Melville, S. G. Naculich, H. J. Schnitzer, C. D. White

Access: Open access

We examine the high energy (Regge) limit of gravitational scattering using a Wilson line approach previously used in the context of non-Abelian gauge theories. Our aim is to clarify the nature of the Reggeization of the graviton and the interplay between this Reggeization and the so-called eikonal phase which determines the spectrum of gravitational bound states. Furthermore, we discuss finite corrections to this picture. Our results are of relevance to various supergravity theories, and also help to clarify the relationship between gauge and gravity theories. © 2014 American Physical Society.

Date: 2005-05-02

Creator: Marta Gómez-Reino, Stephen G. Naculich, Howard J. Schnitzer

Access: Open access

An exact fully-localized extremal supergravity solution for N2 D2-branes and N6 D6-branes, which is dual to 3-dimensional supersymmetric SU(N2) gauge theory with N6 fundamentals, was found by Cherkis and Hashimoto. In order to consider the thermal properties of the gauge theory we present the non-extremal extension of this solution to first order in an expansion near the core of the D6-branes. We compute the Hawking temperature and the black-brane horizon area/entropy. The leading-order entropy, which is proportional to N23/2N61/2 TH2, is not corrected to first order in the expansion. This result is consistent with the analogous weak-coupling result at the correspondence point N2 ∼ N6. © 2005 Elsevier B.V. All rights reserved.

Date: 1994-01-01

Creator: M. Athanas, W. Brower, G. Masek, H. P. Paar, J., Gronberg, R. Kutschke, S. Menary, R. J. Morrison, S. Nakanishi, H. N. Nelson, T. K. Nelson, C. Qiao, J. D. Richman, A. Ryd, H. Tajima, D. Sperka, M. S. Witherell, R. Balest, K. Cho, W. T. Ford, D. R. Johnson, K. Lingel, M. Lohner, P. Rankin, J. G. Smith, J. P. Alexander, C. Bebek, K. Berkelman, K. Bloom, T. E. Browder, D. G. Cassel

Access: Open access

An examination of leptons in (4S) events tagged by reconstructed B meson decays yields semileptonic branching fractions of b-=(10.1±1.8±1. 5)% for charged and b0=(10.9±0.7±1.1)% for neutral B mesons. This is the first measurement for charged B mesons. Assuming equality of the charged and neutral semileptonic widths, the ratio b-b0=0.93±0.18±0.12 is equivalent to the ratio of lifetimes. © 1994 The American Physical Society.

Date: 2008-11-16

Creator: Nicolas Cassar, Galen A. McKinley, Michael L. Bender, Robert Mika, Mark, Battle

Access: Open access

Ar/N2 variations in the atmosphere reflect ocean heat fluxes, air-sea gas exchange, and atmospheric dynamics. Here atmospheric Ar/N2 time series are compared to paired ocean-atmosphere model predictions. Agreement between Ar/N2 observations and simulations has improved in comparison to a previous study because of longer time series and the introduction of automated samplers at several of the atmospheric stations, as well as the refinement of the paired ocean-atmosphere models by inclusion of Ar and N2 as active tracers in the ocean component. Although analytical uncertainties and collection artifacts are likely to be mainly responsible for observed Ar/N2 outliers, air parcel back-trajectory analysis suggests that some of the variability in Ar/N2 measurements could be due to the low-altitude history of the air mass collected and, by extension, the local oceanic Ar/N2 signal. Although the simulated climatological seasonal cycle can currently be evaluated with Ar/N2 observations, longer time series and additional improvements in the signal-to-noise ratio will be required to test other model predictions such as interannual variability, latitudinal gradients, and the secular increase in atmospheric Ar/N2 expected to result from ocean warming. Copyright 2008 by the American Geophysical Union.

Date: 1994-01-01

Creator: M. S. Alam, I. J. Kim, B. Nemati, J. J. ONeill, 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, X. Fu, G. Kalbfleisch, W. R. Ross, P. Skubic, J. Snow, P. L. Wang, M. Wood, D. N. Brown, J. Fast

Access: Open access

We have fully reconstructed decays of both B»0 and B- mesons into final states containing either D, D*, D**, , or c1 mesons. This allows us to obtain new results on many physics topics including branching ratios, tests of the factorization hypothesis, color suppression, resonant substructure, and the B - B»0 mass difference. © 1994 The American Physical Society.

Date: 1994-07-01

Creator: G. Crawford, C. M. Daubenmier, R. Fulton, D. Fujino, K. K., Gan, K. Honscheid, H. Kagan, R. Kass, J. Lee, R. Malchow, Y. Skovpen, M. Sung, C. White, F. Butler, X. Fu, G. Kalbfleisch, W. R. Ross, P. Skubic, M. Wood, J. Fast, R. L. McIlwain, T. Miao, D. H. Miller, M. Modesitt, D. Payne, E. I. Shibata, I. P.J. Shipsey, P. N. Wang, M. Battle, J. Ernst, L. Gibbons

Access: Open access

A measurement of absolute integrated luminosity is presented using the CLEO II detector operating at the CESR e+e- storage ring. Independent analyses of three different final states (e+e-, γγ, and μ+μ-) at √s {reversed tilde equals} 10 GeV normalize to the expected theoretical cross sections and correct for detection efficiencies. The resulting luminosities are measured with systematic errors of ±1.8%, ±1.6%, and ±2.2%, respectively, and are consistent with one another. The combined luminosity has a systematic error of ±1.0%. © 1994.

Date: 2012-09-17

Creator: Takahito Watanabe, Hiroshi Ochiai, Tetsushi Sakuma, Hadley W. Horch, Naoya, Hamaguchi, Taro Nakamura, Tetsuya Bando, Hideyo Ohuchi, Takashi Yamamoto, Sumihare Noji, Taro Mito

Access: Open access

Hemimetabolous, or incompletely metamorphosing, insects are phylogenetically relatively basal and comprise many pests. However, the absence of a sophisticated genetic model system, or targeted gene-manipulation system, has limited research on hemimetabolous species. Here we use zinc-finger nuclease and transcription activator-like effector nuclease technologies to produce genetic knockouts in the hemimetabolous insect Gryllus bimaculatus. Following the microinjection of mRNAs encoding zinc-finger nucleases or transcription activator-like effector nucleases into cricket embryos, targeting of a transgene or endogenous gene results in sequence-specific mutations. Up to 48% of founder animals transmit disrupted gene alleles after zinc-finger nucleases microinjection compared with 17% after microinjection of transcription activator-like effector nucleases. Heterozygous offspring is selected using mutation detection assays that use a Surveyor (Cel-I) nuclease, and subsequent sibling crosses create homozygous knockout crickets. This approach is independent from a mutant phenotype or the genetic tractability of the organism of interest and can potentially be applied to manage insect pests using a non-transgenic strategy. © 2012 Macmillan Publishers Limited. All rights reserved.

Date: 2011-03-01

Creator: Tess Chakkalakal

Access: Open access

Date: 2017-12-01

Creator: Anne E. McBride

Access: Open access

Candida albicans, a common commensal fungus, can cause disease in immunocompromised hosts ranging from mild mucosal infections to severe bloodstream infections with high mortality rates. The ability of C. albicans cells to switch between a budding yeast form and an elongated hyphal form is linked to pathogenicity in animal models. Hyphal-specific proteins such as cell-surface adhesins and secreted hydrolases facilitate tissue invasion and host cell damage, but the specific mechanisms leading to asymmetric protein localization in hyphae remain poorly understood. In many eukaryotes, directional cytoplasmic transport of messenger RNAs that encode asymmetrically localized proteins allows efficient local translation at the site of protein function. Over the past two decades, detailed mechanisms for polarized mRNA transport have been elucidated in the budding yeast Saccharomyces cerevisiae and the filamentous fungus Ustilago maydis. This review highlights recent studies of RNA-binding proteins in C. albicans that have revealed intriguing similarities to and differences from known fungal mRNA transport systems. I also discuss outstanding questions that will need to be answered to reach an in-depth understanding of C. albicans mRNA transport mechanisms and the roles of asymmetric mRNA localization in polarized growth, hyphal function, and virulence of this opportunistic pathogen.

Date: 2015-05-01

Creator: Mary A. Rogalski

Access: Open access

Date: 2013-11-18

Creator: Stephen M. Majercik

Access: Open access

In the Particle Swarm Optimization (PSO) algorithm, the expense of evaluating the objective function can make it difficult, or impossible, to use this approach effectively; reducing the number of necessary function evaluations would make it possible to apply the PSO algorithm more widely. Many function approximation techniques have been developed that address this issue, but an alternative to function approximation is function conservation. We describe GREEN-PSO (GR-PSO), an algorithm that, given a fixed number of function evaluations, conserves those function evaluations by probabilistically choosing a subset of particles smaller than the entire swarm on each iteration and allowing only those particles to perform function evaluations. The "surplus" of function evaluations thus created allows a greater number of particles and/or iterations. In spite of the loss of information resulting from this more parsimonious use of function evaluations, GR-PSO performs as well as, or better than, the standard PSO algorithm on a set of six benchmark functions, both in terms of the rate of error reduction and the quality of the final solution.

Date: 2013-12-01

Creator: Crystal Hall

Access: Open access

The Venetian poet and librettist Giulio Strozzi (1583 -1652) spent much of his career glorifying he Serenissima through a series of theatrical pieces. His only epic poem, the Venetia edificata (1621, 1624), while ostensibly a celebration of the republic, shows a level of commitment to alileo Galilei (1564 -1643) and to Galileo's science that is unique among poets of the time, enetian or otherwise. It is the apex of Strozzi's artistic project to incorporate Galileo's discoveries nd texts into poetic works. The Venetia edificata also represents the culmination of a fifteen-year ffort to gain patronage from the Medici Grand Dukes in Florence. While the first, incomplete ersion is dedicated to the Venetian Doge, the second, finished version is dedicated to Grand DukeFerdinando II de' Medici of Florence. More than a decade after Galileo's departure from the eneto to Florence, Strozzi cites from Galileo's early works, creates a character inspired by Galileo, ncorporates the principles of Galileo's science into the organizing structure of the poem, and nswers one of Galileo's loudest complaints about Torquato Tasso's Jerusalem Delivered (1581). trozzi's strategies both in writing the Venetia edificata and in seeking patronage for it underscore he ambivalent response to Galileo in contemporary poetry.

Date: 2009-01-01

Creator: Aviva Briefel

Access: Open access

Date: 2014-10-01

Creator: Erik Nelson, John C. Withey, Derric Pennington, Joshua J. Lawler

Access: Open access

We determine the effect of the US Endangered Species Act’s Critical Habitat designation on land use change from 1992 to 2011. We find that the rate of change in developed land (constructed material) and agricultural land is not significantly affected by Critical Habitat designation. Therefore, Sections 7 and 9 of the Endangered Species Act do not appear to be more heavily applied in lands designated as Critical Habitat areas versus lands within listed species’ ranges, but without critical habitat designation. Further, there does not appear to be any extraordinary conservation activity in critical habitat areas; for example, environmental non-profits and land trusts do not appear to be concentrating activity in these areas. Before we conclude that the opportunity cost of Critical Habitat designation is negligible we need to examine the land management impacts of designation.

Date: 2021-06-01

Creator: Tom Ichibha, Allison L. Dzubak, Jaron T. Krogel, Valentino R. Cooper, Fernando A., Reboredo

Access: Open access

CrI3 has recently been shown to exhibit low-dimensional, long-range magnetic ordering from few layers to single layers of CrI3. The properties of CrI3 bulk and few-layered systems are uniquely defined by a combination of short-range intralayer and long-range interlayer interactions, including strong correlations, exchange, and spin-orbit coupling. Unfortunately, both the long-range van der Waals interactions, which are driven by dynamic, many-body electronic correlations, and the competing strong intralayer correlations, present a formidable challenge for the local or semilocal mean-field approximations employed in workhorse electronic structure approaches like density-functional theory. In this paper we employ a sophisticated many-body approach that can simultaneously describe long- and short-range correlations. We establish that the fixed-node diffusion Monte Carlo (FNDMC) method reproduces the experimental interlayer separation distance of bulk CrI3 for the high-temperature monoclinic phase with a reliable prediction of the interlayer binding energy. We subsequently employed the FNDMC results to benchmark the accuracy of several density-functional theory exchange-correlation approximations.

Date: 2017-01-01

Creator: Sarah Harmon

Access: Open access

An author might read other written works to polish their own writing skill, just as a painter might analyze other paintings to hone their own craft. Yet, either might also visit the theatre, listen to a piece of music, or otherwise experience the world outside their particular discipline in search of creative insight. This paper explores one example of how a computational system might rely on what they have learned from analyzing another distinct form of expression to produce creative work. Specifically, the system presented here extracts semantic meaning from an input text and uses this knowledge to generate ambient music. An independent measures experiment was conducted to provide a preliminary assessment of the system and direct future work.

Date: 2021-01-01

Creator: David Collings

Access: Open access

Date: 2020-09-01

Creator: Cary Coglianese, Shana M. Starobin

Access: Open access

As much as environmental problems manifest themselves as problems with the natural environment, environmental problems—and their solutions—are ultimately social and behavioral in nature. Just as the natural sciences provide a basis for understanding the need for environmental policy and informing its design, the social sciences also contribute in significant ways to the understanding of the behavioral sources of environmental problems, both in terms of individual incentives and collective action challenges. In addition, the social sciences have contributed much to the understanding of the ways that laws and other institutions can be designed to solve environmental problems. In this review article, we distill core intellectual frameworks from among the social sciences that scaffold modern environmental policy in industrialized country contexts—focusing on key contributions principally from political science, economics, psychology, and sociology to the analysis of environmental problems and their solutions. These frameworks underlie how environmental problems are defined at multiple scales and the conceptualization and empirical testing of policy solutions that seek to shape human behavior in ways that improve environmental quality and promote sustainable economic growth. With the planet facing continued environmental threats, improving environmental policy decision-making depends on the insights and frameworks of social science research in addition to those of the natural sciences.

Date: 2019-06-18

Creator: Peter Schwerdtfeger, Jeffrey K. Nagle

Access: Open access

A 2018 update of the most accurate calculated and experimental static dipole polarizabilities of the neutral atoms in the Periodic Table from nuclear charge Z = 1 to 120 is given. Periodic trends are analyzed and discussed.

Date: 2019-01-01

Creator: Erik Nelson, Nicole Sadowsky

Access: Open access

Since 2011, the private ride-hailing (RH) app companies Uber and Lyft have expanded into more and more US urban areas. We use a dynamic entry event study to examine the impact of Uber and Lyft's entry on public transportation (PT) use in the United States' largest urban areas. In most cases, entry into urban areas was staggered: Uber entered first, followed several months later by Lyft. We generally find that PT use increased in the representative urban area, all else equal, immediately following first RH app company entry. However, this spike in PT use largely disappeared following the entry of the second RH app company. Slightly different RH app company-PT use relationships emerge when we estimate the PT use model over various subsets of urban areas and PT modes.

Date: 2017-09-01

Creator: Barbara Elias

Access: Open access

In counterinsurgency interventions, free-riding by small, local allies is persistent. Yet, the literature on free-riding by small allies is largely limited to conventional multilateral partnerships, such as the North Atlantic Treaty Organization, neglecting other types of asymmetric alliances. Using new data containing 144 US requests to local allies in Vietnam, Iraq and Afghanistan, this article tests the logic of economic theories of alliances in counterinsurgency interventions. I find even when small allies are explicitly asked to contribute to alliance-wide security goods, they are likely to free-ride almost half the time (45%), and the likelihood of free-riding is dependent on whether local allies can be excluded by larger allies. This conclusion upholds the logic of economic models, since shared defense goods that exclude local allies fail to meet the criteria of public goods.

Date: 2010-01-01

Creator: Christopher W. Proctor, Collin S. Roesler

Access: Open access

A three-channel excitation (435 nm, 470 nm, and 532 nm) Chlorophyll fluorometer (695 nm emission) was calibrated and characterized to improve uncertainty in estimated in situ Chlorophyll concentrations. Protocols for reducing sensor-related uncertainties as well as environmental-related uncertainties were developed. Sensor calibrations were performed with thirteen monospecific cultures in the laboratory, grown under limiting and saturating irradiance, and sampled at different growth phases. Resulting uncertainties in the calibration slope induced by natural variations in the in vivo fluorescence per extracted Chlorophyll yield were quantified. Signal variations associated with the sensors (i.e., dark current configurations, drift, and stability) and the environment (i.e., temperature dependent dark currents and contamination by colored dissolved organic matter [CDOM] fluorescence) yielded errors in estimating in situ Chlorophyll concentration exceeding 100%. Calibration protocols and concurrent observations of in situ temperature and CDOM fluorescence eliminate these uncertainties. Depending upon excitation channel, biomass calibration slopes varied between 6-and 10-fold between species and as a function of growth irradiance or growth phase. The largest source of slope variability was due to variations in accessory pigmentation, and thus the variance could be reduced among pigment-based taxonomic lines. Fluorescence ratios were statistically distinct among the pigment-based taxonomic groups, providing not only a means for approximating bulk taxonomic composition, but also for selecting the appropriate calibration slope to statistically improve the accuracy of in situ Chlorophyll concentration estimates. Application to 5 months of deployment in China Lake, Maine, USA reduced the error in estimating extracted Chlorophyll concentration from > 30% to < 6%. © 2010, by the American Society of Limnology and Oceanography, Inc.

Date: 2020-01-01

Creator: B. Zorina Khan

Access: Open access

Social progress depends on the realization of inventive ideas, and economic history provides valuable lessons about creativity in technology and culture. The empirical study of over one hundred thousand innovative individuals who obtained patents, copyrights, and prizes, sheds light on the relationship between institutions, incentives, and transformative ideas and expression, over the past two centuries. The European growth model assumed useful knowledge was scarce, and top-down administered innovation systems offered rights and rewards to “exclusive” groups. By contrast, American policies regarded creativity as widely distributed in the general population, and further promoted “inclusive” market-oriented mechanisms that fostered diversity in ideas and outcomes. The evidence suggests that property rights in patents facilitated markets in ideas, and ensured that returns were aligned with productivity and market demand. Whereas, such administered systems as innovation prizes and publisher’s copyrights in the “creative industries” benefited the few rather than overall social welfare.

Date: 2013-04-12

Creator: Dhiraj Murthy

Access: Open access

Date: 2012-01-01

Creator: Margaret L. Estapa, Emmanuel Boss, Lawrence M. Mayer, Collin S. Roesler

Access: Open access

We investigated the influences of organic content and mineralogical composition on light absorption by mostly mineral suspended particles in aquatic and coastal marine systems. Mass-specific absorption spectra of suspended particles and surface sediments from coastal Louisiana and the lower Mississippi and Atchafalaya rivers were measured with a centered sample-mount integrating sphere and analyzed in conjunction with organic carbon (OC), hydrochloric acid- (HCl-) extractable iron, and dithionite-extractable iron contents. Compositions and absorption properties were comparable to published values for similar particles. Dithionite-extractable iron was strongly correlated with absorption at ultraviolet (UV) and blue wavelengths, while OC and HCl-extractable iron were weakly but positively correlated. Oxidative removal of OC from sediments caused small and variable changes in absorption, while dithionite extraction of iron oxides strongly reduced absorption. Shoulders in the absorption spectra corresponded to absorption bands of iron oxide minerals, and their intensities were well correlated to dithionite-extractable iron contents of the samples. These findings support a primary role for iron oxide and hydroxide minerals in the mass-specific absorption of mostly inorganic particles from the terrestrially influenced coast of Louisiana. Riverine particles had higher dithionite-extractable iron contents and iron oxide- specific absorption features than did marine particles, consistent with current knowledge regarding differential transport of particulate iron oxides and hydroxides through estuarine salinity gradients and reductive alteration of these oxide phases on the Louisiana shelf. The quantifiable dependence of UV absorption features on iron oxide content suggests that, under certain conditions, in situ hyperspectral absorption measurements could be designed to monitor water-column iron mineral transport and transformation. © 2012, by the Association for the Sciences of Limnology and Oceanography, Inc.

Date: 2017-08-31

Creator: Erik Nelson, John M Fitzgerald, Nathan Tefft, John L. Anderson

Access: Open access

We estimate US household monthly elasticities of demand for some of the more popular organic fruits. To our knowledge, this is the first US-wide, multi-year analysis of price and income elasticities for various organic fruits. We calculate elasticities of demand for low-income, middle class, and rich income bracket households using three estimation techniques: two econometric methods and one machine learning method (least absolute shrinkage and selection operator (LASSO)). Demand estimates are based on Nielsen scanner data from approximately 60,000 households collected from 2011 to 2013. Generally, we find that own-price conditional and unconditional elasticities of demand for organic fruits are negative. Unconditional elasticity magnitudes tend to be largest in the representative middle-class household. Income elasticities of demand measurements are inconsistent and often statistically insignificant. This finding is consistent with the survey literature finding that many consumers buy organic food for mostly moral or ethical reasons. We run two policy experiments: a 10% subsidy of organic fruits, and a 10% tax on conventional fruits. Our hypothetical policies engender a stronger reaction among the general public than habitual buyers of organic fruit; unconditional purchase and expenditure elasticities are generally larger than conditional purchase and expenditure elasticities. Finally, we find that elasticities measured with the LASSO technique are not radically different than those measured with econometric methods. The most noticeable difference between the two analytical techniques is that LASSO is more likely to find price and income elasticities of demand that indistinguishable from zero, both substantively and statistically.

Date: 2002-01-01

Creator: Michael L. Littman, Stephen M. Majercik, Toniann Pitassi

Access: Open access

Date: 2013-09-29

Creator: Stephen Meardon

Access: Open access

The most notable idea of Charles P. Kindleberger’s later career is the value of a single country acting as stabilizer of an international economy prone to instability. It runs through his widely read books, The World in Depression, 1929-1939 (1973), Manias, Crises, and Panics (1978), A Financial History of Western Europe (1984), and kindred works. “Hegemonic stability,” the idea is called in the literature it inspired. This essay traces Kindleberger’s attachment to the idea back to his tenure as chief of the State Department’s Division of German and Austrian Economic Affairs from 1945 to 1947 and adviser to the European Recovery Program from 1947 to 1948. In both capacities Kindleberger observed and participated indirectly in the 1948 monetary reform in Western Germany. In the 1990s, during his octogenary decade, he revisited the German monetary reform with a fellow participant, economist, and longtime friend, F. Taylor Ostrander. Their collaborative essay marked Kindleberger’s effort to reclaim hegemonic stability theory from the scholars who developed it following his works of the 1970s and 1980s.

Date: 2007-06-01

Creator: Elizabeth A. Stemmler, Braulio Peguero, Emily A. Bruns, Patsy S. Dickinson, Andrew E., Christie

Access: Open access

In most invertebrates, multiple species-specific isoforms of tachykinin-related peptide (TRP) are common. In contrast, only a single conserved TRP isoform, APSGFLGMRamide, has been documented in decapod crustaceans, leading to the hypothesis that it is the sole TRP present in this arthropod order. Previous studies of crustacean TRPs have focused on neuronal tissue, but the recent demonstration of TRPs in midgut epithelial cells in Cancer species led us to question whether other TRPs are present in the gut, as is the case in insects. Using direct tissue matrix assisted laser desorption/ionization Fourier transform mass spectrometry, in combination with sustained off-resonance irradiation collision-induced dissociation, we found that at least one additional TRP is present in Cancer irroratus, Cancer borealis, Cancer magister, and Cancer productus. The novel TRP isoform, TPSGFLGMRamide, was present not only in the midgut, but also in the stomatogastric nervous system (STNS). In addition, we identified an unprocessed TRP precursor APSGFLGMRG, which was detected in midgut tissues only. TRP immunohistochemistry, in combination with preadsorption studies, suggests that APSGFLGMRamide and TPSGFLGMRamide are co-localized in the stomatogastric ganglion (STG), which is contained within the STNS. Exogenous application of TPSGFLGMRamide to the STG elicited a pyloric motor pattern that was identical to that elicited by APSGFLGMRamide, whereas APSGFLGMRG did not alter the pyloric motor pattern. © 2007 The Authors.

Date: 2012-12-01

Creator: Pawat Seritrakul, Eric Samarut, Tenzing T.S. Lama, Yann Gibert, Vincent, Laudet, William R. Jackman

Access: Open access

Zebrafish lost anterior teeth during evolution but retain a posterior pharyngeal dentition that requires retinoic acid (RA) cell-cell signaling for its development. The purposes of this study were to test the sufficiency of RA to induce tooth development and to assess its role in evolution. We found that exposure of embryos to exogenous RA induces a dramatic anterior expansion of the number of pharyngeal teeth that later form and shifts anteriorly the expression patterns of genes normally expressed in the posterior tooth-forming region, such as pitx2 and dlx2b. After RA exposure, we also observed a correlation between cartilage malformations and ectopic tooth induction, as well as abnormal cranial neural crest marker gene expression. Additionally, we observed that the RA-induced zebrafish anterior teeth resemble in pattern and number the dentition of fish species that retain anterior pharyngeal teeth such as medaka but that medaka do not express the aldh1a2 RA-synthesizing enzyme in tooth-forming regions. We conclude that RA is sufficient to induce anterior ectopic tooth development in zebrafish where teeth were lost in evolution, potentially by altering neural crest cell development, and that changes in the location of RA synthesis correlate with evolutionary changes in vertebrate dentitions. © FASEB.

Date: 2013-04-12

Creator: Jeffrey Treem

Access: Open access

Date: 2013-06-05

Creator: Yao Tang, Haifang Huang, Ke Pang

Access: Open access

Under the flexible exchange rate regime, the Canadian economy is constantly affected by fluctuations in exchange rates. This paper focuses on employment in Canada. We find that appreciations of the Canadian dollar have significant effects on employment in manufacturing industries; such effects are mostly associated with the export-weighted exchange rate and not the import-weighted exchange rate. The export-weighted exchange rate elasticity of employment is -0.52. However, we also find that exchange rate fluctuations have little impact on Canada’s nonmanufacturing employment. Because the manufacturing sector accounts for only about 10% of the employment in Canada, the overall employment effect of exchange rates is small. In addition, we assess the potential employment impact of a boom in the global commodity market, which often leads to appreciations of the Canadian dollar. We find that a 12.21% increase in commodity prices (one standard deviation in the 1994-2007 data) reduces Canada’s manufacturing employment by 0.98%, less than 0.1% of the total industrial employment.

Date: 2017-06-16

Creator: H. Yasuda, C. Chong, J. Yang, P. G. Kevrekidis

Access: Open access

In the present work, motivated by generalized forms of the Hertzian dynamics associated with granular crystals, we consider the possibility of such models to give rise to both dispersive shock and rarefaction waves. Depending on the value p of the nonlinearity exponent, we find that both of these possibilities are realizable. We use a quasicontinuum approximation of a generalized inviscid Burgers model in order to predict the solution profile up to times near the formation of the dispersive shock, as well as to estimate when it will occur. Beyond that time threshold, oscillations associated with the highly dispersive nature of the underlying model emerge, which cannot be captured by the quasicontinuum approximation. Our analytical characterization of the above features is complemented by systematic numerical computations.

Date: 2013-04-12

Creator: Jing Wang

Access: Open access

Microblogging is becoming increasingly pervasive in computer-supported collaboration, attracting various types of users. Organizations, as one type, are willing to leverage this social media service for their operation, but lack guidance of how to effectively manage their organizational microblogs. However, research on microblogging practices at organizational level, especially in virtual organizations, is very limited. To enhance the understanding of how virtual organizations use microblogs in similar and different ways, we investigate microblogging practices of two virtual organizations by examining the content characteristics of their Twitter posts. We identify eleven categories of microblog themes of three dimensions, consisting of both common and different categories between the two organizations. We further enumerate their potential impacts on organizational context, discuss differences between the two organizations, and compare these organizational practices with personal ones.

Date: 2019-12-01

Creator: Svetlana A. Tulaeva, Maria S. Tysiachniouk, Laura A. Henry, Leah S. Horowitz

Access: Open access

The governance of extractive industries has become increasingly globalized. International conventions and multi-stakeholder institutions set out rules and standards on a range of issues, such as environmental protection, human rights, and Indigenous rights. Companies' compliance with these global rules may minimize risks for investors and shareholders, while offering people at sites of extraction more leverage. Although the Russian state retains a significant stake in the oil and gas industries, Russian oil and gas companies have globalized as well, receiving foreign investment, participating in global supply chains, and signing on to global agreements. We investigate how this global engagement has affected Nenets Indigenous communities in Yamal, an oil-and gas-rich region in the Russian Arctic, by analyzing Indigenous protests and benefit-sharing arrangements. Contrary to expectations, we find that Nenets Indigenous communities have not been empowered by international governance measures, and also struggle to use domestic laws to resolve problems. In Russia, the state continues to play a significant role in determining outcomes for Indigenous communities, in part by working with Indigenous associations that are state allies. We conclude that governance generating networks in the region are under-developed.

Date: 2016-06-28

Creator: Marc Serra-Garcia, André Foehr, Miguel Molerón, Joseph Lydon, Christopher, Chong, Chiara Daraio

Access: Open access

Stochastic heat engines are devices that generate work from random thermal motion using a small number of highly fluctuating degrees of freedom. Proposals for such devices have existed for more than a century and include the Maxwell demon and the Feynman ratchet. Only recently have they been demonstrated experimentally, using, e.g., thermal cycles implemented in optical traps. However, recent experimental demonstrations of classical stochastic heat engines are nonautonomous, since they require an external control system that prescribes a heating and cooling cycle and consume more energy than they produce. We present a heat engine consisting of three coupled mechanical resonators (two ribbons and a cantilever) subject to a stochastic drive. The engine uses geometric nonlinearities in the resonating ribbons to autonomously convert a random excitation into a low-entropy, nonpassive oscillation of the cantilever. The engine presents the anomalous heat transport property of negative thermal conductivity, consisting in the ability to passively transfer energy from a cold reservoir to a hot reservoir.

Date: 2021-02-01

Creator: Stephen G. Naculich

Access: Open access

We examine in detail the structure of the Regge limit of the (nonplanar) N = 4 SYM four-point amplitude. We begin by developing a basis of color factors Cik suitable for the Regge limit of the amplitude at any loop order, and then calculate explicitly the coefficients of the amplitude in that basis through three-loop order using the Regge limit of the full amplitude previously calculated by Henn and Mistlberger. We compute these coefficients exactly at one loop, through O(ϵ 2) at two loops, and through O(ϵ) at three loops, verifying that the IR-divergent pieces are consistent with (the Regge limit of) the expected infrared divergence structure, including a contribution from the three-loop correction to the dipole formula. We also verify consistency with the IR-finite NLL and NNLL predictions of Caron-Huot et al. Finally we use these results to motivate the conjecture of an all-orders relation between one of the coefficients and the Regge limit of the N = 8 supergravity four-point amplitude.

Date: 2008-07-15

Creator: Erik Nelson, Stephen Polasky, David J. Lewis, Andrew J. Plantinga, Eric, Lonsdorf, Denis White, David Bael, Joshua J. Lawler

Access: Open access

We develop an integrated model to predict private land-use decisions in response to policy incentives designed to increase the provision of carbon sequestration and species conservation across heterogeneous landscapes. Using data from the Willamette Basin, Oregon, we compare the provision of carbon sequestration and species conservation under five simple policies that offer payments for conservation. We evaluate policy performance compared with the maximum feasible combinations of carbon sequestration and species conservation on the landscape for various conservation budgets. None of the conservation payment policies produce increases in carbon sequestration and species conservation that approach the maximum potential gains on the landscape. Our results show that policies aimed at increasing the provision of carbon sequestration do not necessarily increase species conservation and that highly targeted policies do not necessarily do as well as more general policies. © 2008 by The National Academy of Sciences of the USA.

Date: 2014-03-31

Creator: C. Chong, F. Li, J. Yang, M. O. Williams, I. G., Kevrekidis, P. G. Kevrekidis

Access: Open access

By applying an out-of-phase actuation at the boundaries of a uniform chain of granular particles, we demonstrate experimentally that time-periodic and spatially localized structures with a nonzero background (so-called dark breathers) emerge for a wide range of parameter values and initial conditions. We demonstrate a remarkable control over the number of breathers within the multibreather pattern that can be "dialed in" by varying the frequency or amplitude of the actuation. The values of the frequency (or amplitude) where the transition between different multibreather states occurs are predicted accurately by the proposed theoretical model, which is numerically shown to support exact dark breather and multibreather solutions. Moreover, we visualize detailed temporal and spatial profiles of breathers and, especially, of multibreathers using a full-field probing technology and enable a systematic favorable comparison among theory, computation, and experiments. A detailed bifurcation analysis reveals that the dark and multibreather families are connected in a "snaking" pattern, providing a roadmap for the identification of such fundamental states and their bistability in the laboratory. © 2014 American Physical Society.

Date: 2017-08-01

Creator: Kristi A. Olson

Access: Open access

According to the trilemma claim, we cannot have all three of equality, Pareto, and freedom of occupational choice. In response to the trilemma, John Rawls famously sacrificed equality by introducing incentives. In contrast, GA Cohen and others argued that we can, in fact, have all three provided that individuals are properly motivated by an egalitarian ethos. The incentives debate, then, concerns the plausibility of the ethos solution versus the plausibility of the incentives solution. Considerable ink has been spilled on both sides of the debate. Yet, in this essay, I argue that we cannot have this debate until we clarify the terms. Once we clarify the terms, however, we might discover that there is no debate to be had. This is because, depending on how equality, Pareto, and freedom of occupational choice are interpreted, there might not be a trilemma in the first place. Specifically, I use a small but crucial distinction in how equality, the egalitarian ethos, and Pareto are assessed – what I call the internal/external distinction – to disentangle the various paths each solution – the ethos or incentives – could take. I conclude that both solutions have gained illicit plausibility by virtue of not keeping the distinction straight.

Date: 2009-02-10

Creator: Jason Hill, Stephen Polasky, Erik Nelson, David Tilman, Hong, Huo, Lindsay Ludwig, James Neumann, Haochi Zheng, Diego Bonta

Access: Open access

Environmental impacts of energy use can impose large costs on society. We quantify and monetize the life-cycle climate-change and health effects of greenhouse gas (GHG) and fine particulate matter (PM2.5) emissions from gasoline, corn ethanol, and cellulosic ethanol. For each billion ethanol-equivalent gallons of fuel produced and combusted in the US, the combined climate-change and health costs are $469 million for gasoline, $472-952 million for corn ethanol depending on biorefinery heat source (natural gas, corn stover, or coal) and technology, but only $123-208 million for cellulosic ethanol depending on feedstock (prairie biomass, Miscanthus, corn stover, or switchgrass). Moreover, a geographically explicit life-cycle analysis that tracks PM2.5 emissions and exposure relative to U.S. population shows regional shifts in health costs dependent on fuel production systems. Because cellulosic ethanol can offer health benefits from PM2.5 reduction that are of comparable importance to its climate-change benefits from GHG reduction, a shift from gasoline to cellulosic ethanol has greater advantages than previously recognized. These advantages are critically dependent on the source of land used to produce biomass for biofuels, on the magnitude of any indirect land use that may result, and on other as yet unmeasured environmental impacts of biofuels. © 2009 by The National Academy of Sciences of the USA.

Date: 2013-08-16

Creator: Michèle LaVigne, Intan S. Nurhati, Kim M. Cobb, Helen V. McGregor, Daniel, Sinclair, Robert M. Sherrell

Access: Open access

Variations in ocean productivity are driven largely by nutrient supply to the photic zone, but temporal records of nutrient variability are sparse. Here we show scleractinian coral P/Ca proxy records of variations in phosphate concentrations during El Niño Southern Oscillation (ENSO) cycles in the central equatorial Pacific. Covarying P/Ca records in Porites corals from Christmas and Fanning Islands show a regional ∼40% decrease during the upwelling relaxation of the 1997-1998 El Niño, consistent with less frequent nutrient measurements from this area. Similar ∼35-45% skeletal P/Ca decreases occur during the 1982-1983 and 1986-1987 El Niño events, which predate satellite color and regional nutrient measurements. After each El Niño event, nutrient increases lag temperature recovery by 4-12 months, likely reflecting uptake by massive phytoplankton blooms that followed resumption of upwelling. The results support the utility of coral P/Ca to probe the mechanisms linking ENSO, equatorial upwelling, and carbon cycling in the past. © 2013. American Geophysical Union. All Rights Reserved.

Date: 2018-03-01

Creator: Robert W. Brown, Stephen G. Naculich

Access: Open access

Color-factor symmetry is used to derive a KLT-type relation for tree-level QCD amplitudes containing gluons and an arbitrary number of massive or massless quark-antiquark pairs, generalizing the expression for Yang-Mills amplitudes originally postulated by Bern, De Freitas, and Wong. An explicit expression is given for all amplitudes with two or fewer quark-antiquark pairs in terms of the (modified) momentum kernel. We also introduce the bicolor scalar theory, the “zeroth copy” of QCD, containing massless biadjoint scalars and massive bifundamental scalars, generalizing the biadjoint scalar theory of Cachazo, He, and Yuan. We derive KLT-type relations for tree-level amplitudes of biadjoint and bicolor theories using the color-factor symmetry possessed by these theories.