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  • 1
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    Winter-to-summer precipitation phasing in southwestern North America : a multicentury perspective from paleoclimatic model-data comparisons (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Atmospheres 120 (2015): 8052–8064, doi:10.1002/2015JD023085.
    Description: The phasing of winter-to-summer precipitation anomalies in the North American monsoon (NAM) region 2 (113.25°W–107.75°W, 30°N–35.25°N—NAM2) of southwestern North America is analyzed in fully coupled simulations of the Last Millennium and compared to tree ring reconstructed winter and summer precipitation variability. The models simulate periods with in-phase seasonal precipitation anomalies, but the strength of this relationship is variable on multidecadal time scales, behavior that is also exhibited by the reconstructions. The models, however, are unable to simulate periods with consistently out-of-phase winter-to-summer precipitation anomalies as observed in the latter part of the instrumental interval. The periods with predominantly in-phase winter-to-summer precipitation anomalies in the models are significant against randomness, and while this result is suggestive of a potential for dual-season drought on interannual and longer time scales, models do not consistently exhibit the persistent dual-season drought seen in the dendroclimatic reconstructions. These collective findings indicate that model-derived drought risk assessments may underestimate the potential for dual-season drought in 21st century projections of hydroclimate in the American Southwest and parts of Mexico.
    Description: NOAA. Grant Number: NA11OAR4310166, NSF. Grant Number: AGS-1243204
    Description: 2016-02-19
    Keywords: Paleoclimate ; North American monsoon ; Teleconnection
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
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    How unusual is the 2012–2014 California drought? (2015)
    John Wiley & Sons
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    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 41 (2014): 9017–9023, doi:10.1002/2014GL062433.
    Description: For the past three years (2012–2014), California has experienced the most severe drought conditions in its last century. But how unusual is this event? Here we use two paleoclimate reconstructions of drought and precipitation for Central and Southern California to place this current event in the context of the last millennium. We demonstrate that while 3 year periods of persistent below-average soil moisture are not uncommon, the current event is the most severe drought in the last 1200 years, with single year (2014) and accumulated moisture deficits worse than any previous continuous span of dry years. Tree ring chronologies extended through the 2014 growing season reveal that precipitation during the drought has been anomalously low but not outside the range of natural variability. The current California drought is exceptionally severe in the context of at least the last millennium and is driven by reduced though not unprecedented precipitation and record high temperatures.
    Description: D. G. was supported by a NOAA Climate and Global Change Postdoctoral Fellowship. Both authors also acknowledge the Woods Hole Oceanographic Institution Academic Program Office for support of this research.
    Description: 2015-06-30
    Keywords: Drought ; Tree rings ; Paleoclimate
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Toward interoperable bioscience data (2012)
    Susanna-Assunta Sansone; Philippe Rocca-Serra; Dawn Field; Eamonn Maguire; Chris Taylor; Oliver Hofmann; Hong Fang; Steffen Neumann; Weida Tong; Linda Amaral-Zettler; Kimberly Begley; Tim Booth; Lydie Bougueleret; Gully Burns; Brad Chapman; Tim Clark; Lee-Ann Coleman; Jay Copeland; Sudeshna Das; Antoine de Daruvar; Paula de Matos; Ian Dix; Scott Edmunds; Chris T Evelo; Mark J Forster; Pascale Gaudet; Jack Gilbert; Carole Goble; Julian L Griffin; Daniel Jacob; Jos Kleinjans; Lee Harland; Kenneth Haug; Henning Hermjakob; Shannan J Ho Sui; Alain Laederach; Shaoguang Liang; Stephen Marshall; Annette McGrath; Emily Merrill; Dorothy Reilly; Magali Roux; Caroline E Shamu; Catherine A Shang; Christoph Steinbeck; Anne Trefethen; Bryn Williams-Jones; Katherine Wolstencroft; Ioannis Xenarios; Winston Hide
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2012-02-16
    Description: Toward interoperable bioscience data Nature Genetics 44, 121 (2012). doi:10.1038/ng.1054 Authors: Susanna-Assunta Sansone, Philippe Rocca-Serra, Dawn Field, Eamonn Maguire, Chris Taylor, Oliver Hofmann, Hong Fang, Steffen Neumann, Weida Tong, Linda Amaral-Zettler, Kimberly Begley, Tim Booth, Lydie Bougueleret, Gully Burns, Brad Chapman, Tim Clark, Lee-Ann Coleman, Jay Copeland, Sudeshna Das, Antoine de Daruvar, Paula de Matos, Ian Dix, Scott Edmunds, Chris T Evelo, Mark J Forster, Pascale Gaudet, Jack Gilbert, Carole Goble, Julian L Griffin, Daniel Jacob, Jos Kleinjans, Lee Harland, Kenneth Haug, Henning Hermjakob, Shannan J Ho Sui, Alain Laederach, Shaoguang Liang, Stephen Marshall, Annette McGrath, Emily Merrill, Dorothy Reilly, Magali Roux, Caroline E Shamu, Catherine A Shang, Christoph Steinbeck, Anne Trefethen, Bryn Williams-Jones, Katherine Wolstencroft, Ioannis Xenarios & Winston Hide
    Print ISSN: 1061-4036
    Electronic ISSN: 1546-1718
    Topics: Biology , Medicine
    Published by Nature Publishing Group (NPG)
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  • 4
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    Strip-bark morphology and radial growth trends in ancient Pinus sibirica trees from central Mongolia (2018)
    Wiley-Blackwell
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    Publication Date: 2018-02-23
    Description: Some of the oldest and most important trees used for dendroclimatic reconstructions develop strip-bark morphology, in which only a portion of the stem contains living tissue. Yet the ecophysiological factors initiating strip bark and the potential effect of cambial dieback on annual ring widths and tree-ring estimates of past climate remain poorly understood. Using a combination of field observations and tree-ring data, we investigate the causes and timing of cambial dieback events in Pinus sibirica strip-bark trees from central Mongolia, and compare the radial growth rates and trends of strip-bark and whole-bark trees over the past 515 years. Results indicate that strip bark is more common on the southern aspect of trees and dieback events were most prevalent in the 19 th century, a cold and dry period. Further, strip-bark and whole-bark trees have differing centennial trends, with strip-bark trees exhibiting notably large increases in ring widths at the beginning of the 20 th century. We find a steeper positive trend in the strip-bark chronology relative to the whole-bark chronology when standardizing with age-dependent splines. We hypothesize that localized warming on the southern side of stems due to solar irradiance results in physiological damage and dieback, and leads to increasing tree-ring increment along the living portion of strip-bark trees. Because the impact of cambial dieback on ring widths likely varies depending on species and site, we suggest conducting a comparison of strip-bark and whole-bark ring widths before statistically treating ring-width data for climate reconstructions.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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  • 5
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    Time-varying effect moderation using the structural nested mean model: estimation using inverse-weighted regression with residuals (2013)
    Wiley-Blackwell
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    Publication Date: 2013-07-20
    Description: This article considers the problem of examining time-varying causal effect moderation using observational, longitudinal data in which treatment, candidate moderators, and possible confounders are time varying. The structural nested mean model (SNMM) is used to specify the moderated time-varying causal effects of interest in a conditional mean model for a continuous response given time-varying treatments and moderators. We present an easy-to-use estimator of the SNMM that combines an existing regression-with-residuals (RR) approach with an inverse-probability-of-treatment weighting (IPTW) strategy. The RR approach has been shown to identify the moderated time-varying causal effects if the time-varying moderators are also the sole time-varying confounders. The proposed IPTW+RR approach provides estimators of the moderated time-varying causal effects in the SNMM in the presence of an additional, auxiliary set of known and measured time-varying confounders. We use a small simulation experiment to compare IPTW+RR versus the traditional regression approach and to compare small and large sample properties of asymptotic versus bootstrap estimators of the standard errors for the IPTW+RR approach. This article clarifies the distinction between time-varying moderators and time-varying confounders. We illustrate the methodology in a case study to assess if time-varying substance use moderates treatment effects on future substance use. Copyright © 2013 John Wiley & Sons, Ltd.
    Print ISSN: 0277-6715
    Electronic ISSN: 1097-0258
    Topics: Mathematics , Medicine
    Published by Wiley-Blackwell
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  • 6
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    IJERPH, Vol. 12, Pages 7478-7490: Increased Long-Term Mortality among Black CABG Patients Receiving Preoperative Inotropic Agents (2015)
    MDPI Publishing
    Details
    Publication Date: 2015-07-07
    Description: The aim of this study was to examine racial differences in long-term mortality after coronary artery bypass grafting (CABG), stratified by preoperative use of inotropic agents. Black and white patients who required preoperative inotropic support prior to undergoing CABG procedures between 1992 and 2011 were compared. Mortality probabilities were computed using the Kaplan-Meier product-limit method. Hazard ratios (HR) and 95% confidence intervals (CI) were computed using a Cox regression model. A total of 15,765 patients underwent CABG, of whom 211 received preoperative inotropic agents within 48 hours of surgery. Long-term mortality differed by race (black versus white) among preoperative inotropic category (inotropes: adjusted HR = 1.6, 95% CI = 1.009–2.4; no inotropes: adjusted HR = 1.15, 95% CI = 1.08–1.2; Pinteraction 〈 0.0001). Our study identified an independent preoperative risk-factor for long-term mortality among blacks receiving CABG. This outcome provides information that may be useful for surgeons, primary care providers, and their patients.
    Print ISSN: 1661-7827
    Electronic ISSN: 1660-4601
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Published by MDPI Publishing
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  • 7
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    Quality and impact of appraisal for revalidation: the perceptions of London’s responsible officers and their appraisers (2015)
    BioMed Central
    Details
    Publication Date: 2015-09-22
    Description: Background: To evaluate NHS England London region’s approach to the revalidation appraisal of responsible officers in London, exploring perceptions of the quality and impact of the appraisal process. Revalidation is the process which aims to ensure doctors in the UK are up-to-date and fit to practice medicine thus improving the quality of patient care. Revalidation recommendations are largely premised on the documentation included in annual appraisals, which includes the professional development a doctor has undertaken and supporting information about their practice. Methods: A pan-London qualitative study exploring the views of responsible officers and their appraisers about the revalidation appraisal process. The study aimed to gain an in-depth understanding of the experiences and perceptions of the participants. Responsible officers were purposefully sampled to represent the broadest range of designated bodies. Data analysis generated themes pertaining to quality and impact of appraisal for revalidation with the potential to feed into and shape the evolving system under investigation. Results: The central importance of highly skilled appraisers was highlighted. Both groups reported educational opportunities embedded within the appraisal process. Independent appraisers, not matched by clinical speciality or place of work, were considered to take a more objective view of a responsible officer’s practice by providing an ‘outsider perspective’. However, covering the breadth of roles, in sufficient depth, was challenging. Participants reported a bias favouring the appraisal of the responsible officer role above others including clinical work. Appraisal and revalidation was perceived to have the potential to improve the healthcare standards and support both personal development and institutional quality improvement. Conclusions: Responsible officers play a central role in the revalidation process. Getting responsible officer appraisal right is central to supporting those individuals to in turn support doctors and healthcare organisations in continuous quality improvement. The complexity and importance of the role of responsible officer may make achieving an appraisal of all roles of such individuals problematic. This evaluation suggests responsible officer appraisal was perceived as educational and effective.
    Electronic ISSN: 1472-6920
    Topics: Medicine , Education
    Published by BioMed Central
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  • 8
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    A tutorial on propensity score estimation for multiple treatments using generalized boosted models (2013)
    Wiley-Blackwell
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    Publication Date: 2013-03-20
    Description: The use of propensity scores to control for pretreatment imbalances on observed variables in non-randomized or observational studies examining the causal effects of treatments or interventions has become widespread over the past decade. For settings with two conditions of interest such as a treatment and a control, inverse probability of treatment weighted estimation with propensity scores estimated via boosted models has been shown in simulation studies to yield causal effect estimates with desirable properties. There are tools (e.g., the twang package in R) and guidance for implementing this method with two treatments. However, there is not such guidance for analyses of three or more treatments. The goals of this paper are twofold: (1) to provide step-by-step guidance for researchers who want to implement propensity score weighting for multiple treatments and (2) to propose the use of generalized boosted models (GBM) for estimation of the necessary propensity score weights. We define the causal quantities that may be of interest to studies of multiple treatments and derive weighted estimators of those quantities. We present a detailed plan for using GBM to estimate propensity scores and using those scores to estimate weights and causal effects. We also provide tools for assessing balance and overlap of pretreatment variables among treatment groups in the context of multiple treatments. A case study examining the effects of three treatment programs for adolescent substance abuse demonstrates the methods. Copyright © 2013 John Wiley & Sons, Ltd.
    Print ISSN: 0277-6715
    Electronic ISSN: 1097-0258
    Topics: Mathematics , Medicine
    Published by Wiley-Blackwell
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