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Search Results: 1 - 10 of 229303 matches for " Larry R. Brown "
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Will tidal wetland restoration enhance populations of native fishes?
Larry R. Brown
San Francisco Estuary and Watershed Science , 2003,
Abstract: Restoration of tidal wetlands might enhance populations of native fishes in the San Francisco Estuary of California. The purpose of this paper is to: (1) review the currently available information regarding the importance of tidal wetlands to native fishes in the San Francisco Estuary, (2) construct conceptual models on the basis of available information, (3) identify key areas of scientific uncertainty, and (4) identify methods to improve conceptual models and reduce uncertainty. There are few quantitative data to suggest that restoration of tidal wetlands will substantially increase populations of native fishes. On a qualitative basis, there is some support for the idea that tidal wetland restoration will increase populations of some native fishes; however, the species deriving the most benefit from restoration might not be of great management concern at present. Invasion of the San Francisco Estuary by alien plants and animals appears to be a major factor in obscuring the expected link between tidal wetlands and native fishes. Large-scale adaptive management experiments (>100 hectares) appear to be the best available option for determining whether tidal wetlands will provide significant benefit to native fishes. Even if these experiments are unsuccessful at increasing native fish populations, the restored wetlands should benefit native birds, plants, and other organisms.
Potential effects of organic carbon production on ecosystems and drinking water quality
Larry R. Brown
San Francisco Estuary and Watershed Science , 2003,
Abstract: Restoration of tidal wetlands in the Sacramento-San Joaquin Delta (Delta) is an important component of the Ecosystem Restoration Program of the CALFED Bay-Delta Program (CALFED). CALFED is a collaborative effort among state and federal agencies to restore the ecological health and improve water management of the Delta and San Francisco Bay (Bay). Tidal wetland restoration is intended to provide valuable habitat for organisms and to improve ecosystem productivity through export of various forms of organic carbon, including both algae and plant detritus. However, the Delta also provides all or part of the drinking water for over 22 million Californians. In this context, increasing sources of organic carbon may be a problem because of the potential increase in the production of trihalomethanes and other disinfection by-products created during the process of water disinfection. This paper reviews the existing information about the roles of organic carbon in ecosystem function and drinking water quality in the Bay-Delta system, evaluates the potential for interaction, and considers major uncertainties and potential actions to reduce uncertainty. In the last 10 years, substantial progress has been made on the role of various forms of organic carbon in both ecosystem function and drinking water quality; however, interactions between the two have not been directly addressed. Several ongoing studies are beginning to address these interactions, and the results from these studies should reduce uncertainty and provide focus for further research.
An introduction to the San Francisco Estuary tidal wetlands restoration series
Larry R. Brown
San Francisco Estuary and Watershed Science , 2003,
Abstract: Restoration of tidal wetlands may provide an important tool for improving ecological health and water management for beneficial uses of the San Francisco Estuary (hereafter Estuary ). Given the large losses of tidal wetlands from San Francisco Bay and the Sacramento-San Joaquin Delta in the last 150 years, it seems logical to assume that restoring tidal wetlands will have benefits for a variety of aquatic and terrestrial native species that have declined during the same time period. However, many other changes have also occurred in the Estuary concurrent with the declines of native species. Other factors that might be important in species declines include the effects of construction of upstream dams, large and small water diversions within the Sacramento-San Joaquin Delta, agricultural pesticides, trace elements from industrial and agricultural activities, and invasions of alien species. Discussions among researchers, managers, and stakeholders have identified a number of uncertainties regarding the potential benefits of tidal wetland restoration. The articles of the Tidal Wetlands Restoration Series address four major issues of concern. Stated as questions, these are: 1. Will tidal wetland restoration enhance populations of native fishes? 2. Will wetland restoration increase rates of methylation of mercury? 3. Will primary production and other ecological processes in restored tidal wetlands result in net export of organic carbon to adjacent habitats, resulting in enhancement of the food web? Will the carbon produced contribute to the formation of disinfection byproducts when disinfected for use as drinking water? 4. Will restored tidal wetlands provide long-term ecosystem benefits that can be sustained in response to ongoing physical processes, including sedimentation and hydrodynamics? Reducing the uncertainty surrounding these issues is of critical importance because tidal wetland restoration is assumed to be a critical tool for enhancement of native species and ecosystem processes in the Estuary.
A summary of the San Francisco tidal wetlands restoration series
Larry R. Brown
San Francisco Estuary and Watershed Science , 2003,
Abstract: The four topical articles of the Tidal Wetlands Restoration Series summarized and synthesized much of what is known about tidal wetlands and tidal wetland restoration in the San Francisco Estuary (hereafter Estuary ). Despite a substantial amount of available information, major uncertainties remain. A major uncertainty with regard to fishes is the net benefit of restored tidal wetlands relative to other habitats for native fishes in different regions of the Estuary given the presence of numerous invasive alien species. With regard to organic carbon, a major uncertainty is the net benefit of land use change given uncertainty about the quantity and quality of different forms of organic carbon resulting from different land uses. A major challenge is determining the flux of organic carbon from open systems like tidal wetlands. Converting present land uses to tidal wetlands will almost certainly result in increased methylation of mercury at the local scale with associated accumulation of mercury within local food webs. However, it is unclear if such local accumulation is of concern for fish, wildlife or humans at the local scale or if cumulative effects at the regional scale will emerge. Based on available information it is expected that restored tidal wetlands will remain stable once constructed; however, there is uncertainty associated with the available data regarding the balance of sediment accretion, sea-level rise, and sediment erosion. There is also uncertainty regarding the cumulative effect of many tidal restoration projects on sediment supply. The conclusions of the articles highlight the need to adopt a regional and multidisciplinary approach to tidal wetland restoration in the Estuary. The Science Program of the CALFED effort provides an appropriate venue for addressing these issues.
Stream Macroinvertebrate Response Models for Bioassessment Metrics: Addressing the Issue of Spatial Scale
Ian R. Waite, Jonathan G. Kennen, Jason T. May, Larry R. Brown, Thomas F. Cuffney, Kimberly A. Jones, James L. Orlando
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090944
Abstract: We developed independent predictive disturbance models for a full regional data set and four individual ecoregions (Full Region vs. Individual Ecoregion models) to evaluate effects of spatial scale on the assessment of human landscape modification, on predicted response of stream biota, and the effect of other possible confounding factors, such as watershed size and elevation, on model performance. We selected macroinvertebrate sampling sites for model development (n = 591) and validation (n = 467) that met strict screening criteria from four proximal ecoregions in the northeastern U.S.: North Central Appalachians, Ridge and Valley, Northeastern Highlands, and Northern Piedmont. Models were developed using boosted regression tree (BRT) techniques for four macroinvertebrate metrics; results were compared among ecoregions and metrics. Comparing within a region but across the four macroinvertebrate metrics, the average richness of tolerant taxa (RichTOL) had the highest R2 for BRT models. Across the four metrics, final BRT models had between four and seven explanatory variables and always included a variable related to urbanization (e.g., population density, percent urban, or percent manmade channels), and either a measure of hydrologic runoff (e.g., minimum April, average December, or maximum monthly runoff) and(or) a natural landscape factor (e.g., riparian slope, precipitation, and elevation), or a measure of riparian disturbance. Contrary to our expectations, Full Region models explained nearly as much variance in the macroinvertebrate data as Individual Ecoregion models, and taking into account watershed size or elevation did not appear to improve model performance. As a result, it may be advantageous for bioassessment programs to develop large regional models as a preliminary assessment of overall disturbance conditions as long as the range in natural landscape variability is not excessive.
Determinants of Multimethod Contraceptive Use in a Sample of Adolescent Women Diagnosed with Psychological Disorders
Delia L. Lang,Jessica M. Sales,Laura F. Salazar,Ralph J. DiClemente,Richard A. Crosby,Larry K. Brown,Geri R. Donenberg
Infectious Diseases in Obstetrics and Gynecology , 2011, DOI: 10.1155/2011/510239
Abstract: Objective. Despite recommendations for concurrent use of contraceptives and condoms to prevent unintended pregnancy and STIs, multimethod contraceptive use among women is poor. This study examined individual-, interpersonal-, and environmental-level factors that predict multimethod use among sexually active adolescent women diagnosed with psychological disorders. Methods. This multisite study analyzed data from 288 sexually active adolescent women who provided sociodemographic, psychosocial, and behavioral data related to birth control and condom use. Results. 34.7% of the participants reported multimethod use in the past three months. Controlling for empirically and theoretically relevant covariates, a multivariable logistic regression identified self-efficacy, multiple partners, pregnancy history, parental communication, parental norms about sex, and neighborhood cohesion as significant predictors of multimethod use. Conclusions. While continued targeted messages about multi-method contraceptive use are imperative at the individual level, an uptake in messages targeting interpersonal- and environmental-level factors such as adolescents' parents and the broader community is urgently needed. 1. Introduction Sexually transmitted infections (STIs) and unintended pregnancy are two significant public health issues that continue to affect adolescent women in the US today. Current estimates by the Centers of Disease Control and Prevention (CDC) suggest that 25% of adolescent women in the US have an STI [1], a prevalence twice as high as that among adolescent men of the same age [2]. Similarly, an estimated 82% of adolescent pregnancies are unintended despite widespread accessibility of safe, effective, and affordable contraceptive technology [3]. While a national decline in unintended pregnancies among adolescent women between 1991 and 2009 has been documented, the US continues to have higher rates of unintended teen pregnancies compared to other developed nations, particularly among adolescents residing in southern states [4]. Data on the prevalence of STIs and unintended pregnancy among adolescent women diagnosed with psychological disorders are largely lacking, although extant research among adolescents demonstrates an association between mental illness and high-risk sexual behavior including early initiation of sexual activity, sex with multiple partners, and unprotected sex [5–11]. Results from these studies suggest that this vulnerable population is at great risk for acquiring STIs including HIV as well as experiencing unintended pregnancy. Adolescents
A controlled trial of automated classification of negation from clinical notes
Peter L Elkin, Steven H Brown, Brent A Bauer, Casey S Husser, William Carruth, Larry R Bergstrom, Dietlind L Wahner-Roedler
BMC Medical Informatics and Decision Making , 2005, DOI: 10.1186/1472-6947-5-13
Abstract: 41 Clinical Documents (Medical Evaluations; sometimes outside of Mayo these are referred to as History and Physical Examinations) were parsed using the Mayo Vocabulary Server Parsing Engine. SNOMED-CT? was used to provide concept coverage for the clinical concepts in the record. These records resulted in identification of Concepts and textual clues to Negation. These records were reviewed by an independent medical terminologist, and the results were tallied in a spreadsheet. Where questions on the review arose Internal Medicine Faculty were employed to make a final determination.SNOMED-CT was used to provide concept coverage of the 14,792 Concepts in 41 Health Records from John's Hopkins University. Of these, 1,823 Concepts were identified as negative by Human review. The sensitivity (Recall) of the assignment of negation was 97.2% (p < 0.001, Pearson Chi-Square test; when compared to a coin flip). The specificity of assignment of negation was 98.8%. The positive likelihood ratio of the negation was 81. The positive predictive value (Precision) was 91.2%Automated assignment of negation to concepts identified in health records based on review of the text is feasible and practical. Lexical assignment of negation is a good test of true Negativity as judged by the high sensitivity, specificity and positive likelihood ratio of the test. SNOMED-CT had overall coverage of 88.7% of the concepts being negated.A great wealth of patient specific medical data is stored as transcribed free text. While this format is useful for individuals reading the medical record, information stored as free-text is difficult to use in decision support systems or automated cross population studies [1]. Efforts to extract computer-usable information from free text archives vary widely. Traditionally, teams of trained abstractors have manually reviewed patients' charts. String matching is a simple algorithmic approach. Identifying concepts is a much more complex process. Algorithmic natural langu
The General Stationary Gaussian Markov Process
Larry Brown,Philip Ernst,Larry Shepp,Bob Wolpert
Mathematics , 2014,
Abstract: We find the class, ${\cal{C}}_k, k \ge 0$, of all zero mean stationary Gaussian processes, $Y(t), ~t \in \reals$ with $k$ derivatives, for which \begin{equation} Z(t) \equiv (Y^{(0)}(t), Y^{(1)}(t), \ldots, Y^{(k)}(t) ), ~ t \ge 0 \end{equation} \noindent is a $(k+1)$-vector Markov process. (here, $Y^{(0)}(t) = Y(t)$).
Projected Evolution of California's San Francisco Bay-Delta-River System in a Century of Climate Change
James E. Cloern, Noah Knowles, Larry R. Brown, Daniel Cayan, Michael D. Dettinger, Tara L. Morgan, David H. Schoellhamer, Mark T. Stacey, Mick van der Wegen, R. Wayne Wagner, Alan D. Jassby
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0024465
Abstract: Background Accumulating evidence shows that the planet is warming as a response to human emissions of greenhouse gases. Strategies of adaptation to climate change will require quantitative projections of how altered regional patterns of temperature, precipitation and sea level could cascade to provoke local impacts such as modified water supplies, increasing risks of coastal flooding, and growing challenges to sustainability of native species. Methodology/Principal Findings We linked a series of models to investigate responses of California's San Francisco Estuary-Watershed (SFEW) system to two contrasting scenarios of climate change. Model outputs for scenarios of fast and moderate warming are presented as 2010–2099 projections of nine indicators of changing climate, hydrology and habitat quality. Trends of these indicators measure rates of: increasing air and water temperatures, salinity and sea level; decreasing precipitation, runoff, snowmelt contribution to runoff, and suspended sediment concentrations; and increasing frequency of extreme environmental conditions such as water temperatures and sea level beyond the ranges of historical observations. Conclusions/Significance Most of these environmental indicators change substantially over the 21st century, and many would present challenges to natural and managed systems. Adaptations to these changes will require flexible planning to cope with growing risks to humans and the challenges of meeting demands for fresh water and sustaining native biota. Programs of ecosystem rehabilitation and biodiversity conservation in coastal landscapes will be most likely to meet their objectives if they are designed from considerations that include: (1) an integrated perspective that river-estuary systems are influenced by effects of climate change operating on both watersheds and oceans; (2) varying sensitivity among environmental indicators to the uncertainty of future climates; (3) inevitability of biological community changes as responses to cumulative effects of climate change and other drivers of habitat transformations; and (4) anticipation and adaptation to the growing probability of ecosystem regime shifts.
Addressing the Dual Challenges of Meeting Demand for Minerals and Sustainable Development
R. Larry Grayson
Minerals , 2011, DOI: 10.3390/min1010001
Abstract: In recent decades, excellent progress has been made globally in finding mineral resources, extracting them efficiently and effectively, dramatically reducing environmental degradation, and preventing adverse health and safety impacts on workers and stakeholders. The industry has realized tremendous advances in technology and applied science; has met changing and more stringent environmental performance criteria; has made remarkable reductions in fatality, illness, and lost-time accident rates; and has connected better than ever before with the communities in which mining, milling, and smelting are housed. A new era focused on continuous improvement in tackling key sustainable development parameters has come and is intensifying [1].? In order to maintain the social licenses needed to enlist broad public support for mining businesses, continued progress must be visible to national, provincial, and local governments as well as the people who live in the areas blessed with the mineral resources that the global economy and growing population will demand. [...]
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