Showing 1371 - 1380 of 2370 Items

Projecting global land-use change and its effect on ecosystem service provision and biodiversity with simple models

Date: 2010-12-01

Creator: Erik Nelson

Heather Sander

Peter Hawthorne

Marc Conte

Driss, Ennaanay

Stacie Wolny

Steven Manson

Stephen Polasky

Access: Open access

Background: As the global human population grows and its consumption patterns change, additional land will be needed for living space and agricultural production. A critical question facing global society is how to meet growing human demands for living space, food, fuel, and other materials while sustaining ecosystem services and biodiversity [1]. Methodology/Principal Findings: We spatially allocate two scenarios of 2000 to 2015 global areal change in urban land and cropland at the grid cell-level and measure the impact of this change on the provision of ecosystem services and biodiversity. The models and techniques used to spatially allocate land-use/land-cover (LULC) change and evaluate its impact on ecosystems are relatively simple and transparent [2]. The difference in the magnitude and pattern of cropland expansion across the two scenarios engenders different tradeoffs among crop production, provision of species habitat, and other important ecosystem services such as biomass carbon storage. For example, in one scenario, 5.2 grams of carbon stored in biomass is released for every additional calorie of crop produced across the globe; under the other scenario this tradeoff rate is 13.7. By comparing scenarios and their impacts we can begin to identify the global pattern of cropland and irrigation development that is significant enough to meet future food needs but has less of an impact on ecosystem service and habitat provision. Conclusions/Significance: Urban area and croplands will expand in the future to meet human needs for living space, livelihoods, and food. In order to jointly provide desired levels of urban land, food production, and ecosystem service and species habitat provision the global society will have to become much more strategic in its allocation of intensively managed land uses. Here we illustrate a method for quickly and transparently evaluating the performance of potential global futures.


Exchange Rate Regimes and Nominal Wage Comovements in a Dynamic Ricardian Model

Date: 2013-10-28

Creator: Yao Tang

Yoshinori Kurokawa

Jiaren Pang

Access: Open access

We construct a dynamic Ricardian model of trade with money and nominal exchange rate. The model implies that the nominal wages of the trading countries are more likely to exhibit stronger positive comovements when the countries fix their bilateral exchange rates. Panel regression results based on data from OECD countries from 1973 to 2012 suggest that countries in the European Monetary Union (EMU) experienced stronger positive wage comovements with their main trade partners. When we restrict the regression to the subsample of the EMU countries, we find a significant increase in wage comovements after these countries joined the EMU in 1999 compared to the pre-euro era. In comparison, when the sample is restricted to the non-EMU countries, we find no evidence that non-currency union pegs affected the wage comovements.


Reproducibility of Ba/Ca variations recorded by northeast Pacific bamboo corals

Date: 2017-09-01

Creator: G. Serrato Marks

M. LaVigne

T. M. Hill

W. Sauthoff

T. P., Guilderson

E. B. Roark

R. B. Dunbar

T. J. Horner

Access: Open access

Trace elemental ratios preserved in the calcitic skeleton of bamboo corals have been shown to serve as archives of past ocean conditions. The concentration of dissolved barium (Ba ), a bioactive nutrientlike element, is linked to biogeochemical processes such as the cycling and export of nutrients. Recent work has calibrated bamboo coral Ba/Ca, a new Ba proxy, using corals spanning the oxygen minimum zone beneath the California Current System. However, it was previously unclear whether Ba/Ca records were internally reproducible. Here we investigate the accuracy of using laser ablation inductively coupled plasma mass spectrometry for Ba/Ca analyses and test the internal reproducibility of Ba/Ca among replicate radial transects in the calcite of nine bamboo corals collected from the Gulf of Alaska (643–720 m) and the California margin (870–2054 m). Data from replicate Ba/Ca transects were aligned using visible growth bands to account for nonconcentric growth; smoothed data were reproducible within ~4% for eight corals (n = 3 radii/coral). This intracoral reproducibility further validates using bamboo coral Ba/Ca for Ba reconstructions. Sections of the Ba/Ca records that were potentially influenced by noncarbonate bound Ba phases occurred in regions where elevated Mg/Ca or Pb/Ca and coincided with anomalous regions on photomicrographs. After removing these regions of the records, increased Ba/Ca variability was evident in corals between ~800 and 1500 m. These findings support additional proxy validation to understand Ba variability on interannual timescales, which could lead to new insights into deep sea biogeochemistry over the past several centuries. SW SW coral coral SW coral SW


Varieties of digital authoritarianism analyzing Russia’s approach to internet governance

Date: 2021-12-01

Creator: Laura Howells

Laura A. Henry

Access: Open access

Digital authoritarianism threatens the privacy and rights of Internet users worldwide, yet scholarship on this topic remains limited in analytical power and case selection. In this article, we introduce a comprehensive analytical framework to the field of Internet governance and apply it first, briefly, to the well-known case of China and then, in more depth, to the still-understudied Russian case. We identify the extent and relative centralization of Internet governance as well as proactive versus reactive approaches to governance as notable differences between the cases, highlighting variation among digital authoritarians’ governance strategies. We conclude that Russia’s Internet governance model is less comprehensive and consistent than China’s, but its components may be more easily exported to other political systems. We then consider whether recent changes to Russia’s Internet governance suggest that it could converge with the Chinese model over time.


Saving our marine archives

Date: 2017-01-01

Creator: Emilie Dassié

Kristine Delong

Hali Kilbourne

Branwen Williams

Nerilie, Abram

Logan Brenner

Chloé Brahmi

Kim M. Cobb

Thierry Corrège

Delphine Dissard

Julien Emile-Geay

Heitor Evangelista

Michael N. Evans

Jesse Farmer

Thomas Felis

Michael Gagan

David P. Gillikin

Nathalie Goodkin

Myriam Khodri

Ana Carolina Lavagnino

Michèle Lavigne

Claire Lazareth

Braddock Linsley

Janice Lough

Helen McGregor

Intan S. Nurhati

Gilman Ouellette

Laura Perrin

Maureen Raymo

Brad Rosenheim

Michael Sandstrom

Bernd R. Schöne

Access: Open access



Assessing longitudinal pathways between maternal depressive symptoms, parenting self-esteem and infant temperament

Date: 2019-08-01

Creator: Lea Takács

Filip Smolík

Samuel Putnam

Access: Open access

Background Previous studies of relations between parenting self-concepts, parental adjustment and child temperament have been ambiguous regarding the direction of influence; and have rarely followed families from pregnancy through the first year of life. The current study examines change and stability in maternal depressive symptoms, parenting competences and child temperament through the perinatal period until nine months postpartum. Methods Czech mothers (N = 282) participated at three time points: the third trimester of pregnancy (Time 1), six weeks (Time 2) and nine months postpartum (Time 3). Questionnaire data concerned depressive symptoms (T1, T2, T3), maternal parenting self-esteem (T1, T2) and sense of competence (T3), and child temperament (T2, T3). A path model was used to examine concurrent and longitudinal relations between these variables. Results The analyses indicated longitudinal stability of all constructs, as well as concurrent relations between them. Longitudinal relations supported child-to-parent, rather than parent-to-child, effects: child difficult temperament predicted decreases in perceived maternal parenting competences, but maternal variables did not predict change in infant temperament. In addition, we observed weak mutual relations between maternal depression levels and parenting competences, such that maternal depression diminished perceived parenting competences that in turn contributed to higher levels of depression. Conclusion Mothers’ confidence in their ability to parent is influenced by their experience with a difficult infant and by their depressive symptoms during the child’s first year of life. Depressive symptoms are, in turn, aggravated by mothers’ low perceived competences in the parenting role.


Cells and constructible representations in type B

Date: 2008-10-13

Creator: Thomas Pietraho

Access: Open access

We examine the partition of a finite Coxeter group of type B into cells determined by a weight function L. The main objective of these notes is to reconcile Lusztig's description of constructible representations in this setting with conjectured combinatorial descriptions of cells.


Subleading-color contributions to gluon-gluon scattering in N = 4 SYM theory and relations to N = 8 supergravity

Date: 2008-11-01

Creator: Stephen G. Naculich

Horatiu Nastase

Howard J. Schnitzer

Access: Open access

We study the subleading-color (nonplanar) contributions to the four-gluon scattering amplitudes in = 4 supersymmetric SU(N) Yang-Mills theory. Using the formalisms of Catani and of Sterman and Tejeda-Yeomans, we develop explicit expressions for the infrared-divergent contributions of all the subleading-color L-loop amplitudes up to three loops, and make some conjectures for the IR behavior for arbitrary L. We also derive several intriguing relations between the subleading-color one- and two-loop four-gluon amplitudes and the four-graviton amplitudes of = 8 supergravity. The exact one- and two-loop = 8 supergravity amplitudes can be expressed in terms of the one- and two-loop N-independent = 4 SYM amplitudes respectively, but the natural generalization to higher loops fails, despite having a simple interpretation in terms of the 't Hooft picture. We also find that, at least through two loops, the subleading-color amplitudes of = 4 SYM theory have uniform transcendentality (as do the leading-color amplitudes). Moreover, the = 4 SYM Catani operators, which express the IR-divergent contributions of loop amplitudes in terms of lower-loop amplitudes, are also shown to have uniform transcendentality, and to be the maximum transcendentality piece of the QCD Catani operators. © SISSA 2008.


An information theoretical approach to task-switching: Evidence from cognitive brain potentials in humans

Date: 2008-03-28

Creator: Francisco Barceló

José A. Periáñez

Erika Nyhus

Access: Open access

This study aimed to clarify the neural substrates of behavioral switch and restart costs in intermittently instructed task-switching paradigms. Event-related potentials (ERPs) were recorded while participants were intermittently cued to switch or repeat their categorization rule (Switch task), or else they performed two perceptually identical control conditions (NoGo and Oddball). The three tasks involved different task-sets with distinct stimulus-response associations in each, but identical visual stimulation, consisting of frequent colored shapes (p = 0.9) and randomly interspersed infrequent black shapes (p = 0.1; '+' and 'x' symbols). Behavioral restart costs were observed in the first target responses following all black shapes in the Switch and NoGo tasks - but not in the Oddball task - and corresponded with enhanced fronto-centrally distributed early cue-locked P3 activity (peak latency 325-375 ms post-cue onset at the vertex). In turn, behavioral switch costs were associated with larger late cue-locked P3 amplitudes in the Switch task only (peak latency 400-450 ms post-cue onset at mid-parietal sites). Together with our information theoretical estimations, ERP results suggested that restart and switch costs indexed two neural mechanisms related to the preparatory resolution of uncertainty: (1) the intermittent re-activation of task-set information, and (2) the updating of stimulus-response mappings within an active task set, as indexed by early and late cue-locked P3 activations, respectively. In contrast, target-locked P3 activations reflected a functionally distinct mechanism related to the implementation of task-set information. We conclude that task-switching costs consist of both switch-specific and switch-unspecific processes during the preparation and execution stages of task performance. © 2008 Barceló, Periáñez and Nyhus.


Transvection-based gene regulation in Drosophila is a complex and plastic trait

Date: 2014-01-01

Creator: Xinyang Bing

Teresa Z. Rzezniczak

Jack R. Bateman

Thomas J.S. Merritt

Access: Open access

Transvection, a chromosome pairing-dependent form of trans-based gene regulation, is potentially widespread in the Drosophila melanogaster genome and varies across cell types and within tissues in D. melanogaster, characteristics of a complex trait. Here, we demonstrate that the trans-interactions at the Malic enzyme (Men) locus are, in fact, transvection as classically defined and are plastic with respect to both genetic background and environment. Using chromosomal inversions, we show that trans-interactions at the Men locus are eliminated by changes in chromosomal architecture that presumably disrupt somatic pairing. We further show that the magnitude of transvection at the Men locus is modified by both genetic background and environment (temperature), demonstrating that transvection is a plastic phenotype. Our results suggest that transvection effects in D. melanogaster are shaped by a dynamic interplay between environment and genetic background. Interestingly, we find that cis-based regulation of the Men gene is more robust to genetic background and environment than trans-based. Finally, we begin to uncover the nonlocal factors that may contribute to variation in transvection overall, implicating Abd-B in the regulation of Men in cis and in trans in an allele-specific and tissue-specific manner, driven by differences in expression of the two genes across genetic backgrounds and environmental conditions.