The Experts below are selected from a list of 4263 Experts worldwide ranked by ideXlab platform
Richard D Bardgett - One of the best experts on this subject based on the ideXlab platform.
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effects of species evenness and dominant species identity on Multiple ecosystem functions in model grassland communities
Oecologia, 2014Co-Authors: Kate H Orwin, N J Ostle, Andrew Wilby, Richard D BardgettAbstract:Ecosystems provide Multiple services upon which humans depend. Understanding the drivers of the ecosystem functions that support these services is therefore important. Much research has investigated how species richness influences functioning, but we lack knowledge of how other Community attributes affect ecosystem functioning. Species evenness, species spatial arrangement, and the identity of dominant species are three attributes that could affect ecosystem functioning, by altering the relative abundance of functional traits and the probability of synergistic species interactions such as facilitation and complementary resource use. We tested the effect of these three Community attributes and their interactions on ecosystem functions over a growing season, using model grassland communities consisting of three plant species from three functional groups: a grass (Anthoxanthum odoratum), a forb (Plantago lanceolata), and a N-fixing forb (Lotus corniculatus). We measured Multiple ecosystem functions that support ecosystem services, including ecosystem gas exchange, water retention, C and N loss in leachates, and plant biomass production. Species evenness and dominant species identity strongly influenced the ecosystem functions measured, but spatial arrangement had few effects. By the end of the growing season, evenness consistently enhanced ecosystem functioning and this effect occurred regardless of dominant species identity. The identity of the dominant species under which the highest level of functioning was attained varied across the growing season. Spatial arrangement had the weakest effect on functioning, but interacted with dominant species identity to affect some functions. Our results highlight the importance of understanding the role of Multiple Community attributes in driving ecosystem functioning.
George E Woody - One of the best experts on this subject based on the ideXlab platform.
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using a latent variable approach to inform gender and racial ethnic differences in cocaine dependence a national drug abuse treatment clinical trials network study
Journal of Substance Abuse Treatment, 2010Co-Authors: Litzy Wu, Dan G Blazer, Maxine L Stitzer, George E WoodyAbstract:Abstract This study applies a latent variable approach to examine gender and racial/ethnic differences in cocaine dependence, to determine the presence of differential item functioning (DIF) or item-response bias to diagnostic questions of cocaine dependence, and to explore the effects of DIF on the predictor analysis of cocaine dependence. The analysis sample included 682 cocaine users enrolled in two national multisite studies of the National Drug Abuse Treatment Clinical Trials Network (CTN). Participants were recruited from 14 Community-based substance abuse treatment programs associated with the CTN, including 6 methadone and 8 outpatient nonmethadone programs. Factor and Multiple indicators–Multiple causes (MIMIC) procedures evaluated the latent continuum of cocaine dependence and its correlates. MIMIC analysis showed that men exhibited lower odds of cocaine dependence than women (regression coefficient, β = −0.34), controlling for the effects of DIF, years of cocaine use, addiction treatment history, comorbid drug dependence diagnoses, and treatment setting. There were no racial/ethnic differences in cocaine dependence; however, DIF by race/ethnicity was noted. Within the context of Multiple Community-based addiction treatment settings, women were more likely than men to exhibit cocaine dependence. Addiction treatment research needs to further evaluate gender-related differences in drug dependence in treatment entry and to investigate how these differences may affect study participation, retention, and treatment response to better serve this population.
Kate H Orwin - One of the best experts on this subject based on the ideXlab platform.
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effects of species evenness and dominant species identity on Multiple ecosystem functions in model grassland communities
Oecologia, 2014Co-Authors: Kate H Orwin, N J Ostle, Andrew Wilby, Richard D BardgettAbstract:Ecosystems provide Multiple services upon which humans depend. Understanding the drivers of the ecosystem functions that support these services is therefore important. Much research has investigated how species richness influences functioning, but we lack knowledge of how other Community attributes affect ecosystem functioning. Species evenness, species spatial arrangement, and the identity of dominant species are three attributes that could affect ecosystem functioning, by altering the relative abundance of functional traits and the probability of synergistic species interactions such as facilitation and complementary resource use. We tested the effect of these three Community attributes and their interactions on ecosystem functions over a growing season, using model grassland communities consisting of three plant species from three functional groups: a grass (Anthoxanthum odoratum), a forb (Plantago lanceolata), and a N-fixing forb (Lotus corniculatus). We measured Multiple ecosystem functions that support ecosystem services, including ecosystem gas exchange, water retention, C and N loss in leachates, and plant biomass production. Species evenness and dominant species identity strongly influenced the ecosystem functions measured, but spatial arrangement had few effects. By the end of the growing season, evenness consistently enhanced ecosystem functioning and this effect occurred regardless of dominant species identity. The identity of the dominant species under which the highest level of functioning was attained varied across the growing season. Spatial arrangement had the weakest effect on functioning, but interacted with dominant species identity to affect some functions. Our results highlight the importance of understanding the role of Multiple Community attributes in driving ecosystem functioning.
Neetha Morar - One of the best experts on this subject based on the ideXlab platform.
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Experiences in conducting Multiple Community-based HIV prevention trials among women in KwaZulu-Natal, South Africa
AIDS Research and Therapy, 2010Co-Authors: Gita Ramjee, Nicola Coumi, Nozizwe Dladla-qwabe, Shay Ganesh, Sharika Gappoo, Roshini Govinden, Vijayanand Guddera, Rashika Maharaj, Jothi Moodley, Neetha MorarAbstract:Background South Africa, with its scientific capacity, good infrastructure and high HIV incidence rates, is ideally positioned to conduct large-scale HIV prevention trials. The HIV Prevention Research Unit of the South African Medical Research Council conducted four phase III and one phase IIb trials of women-initiated HIV prevention options in KwaZulu-Natal between 2003 and 2009. A total of 7046 women participated, with HIV prevalence between 25% and 45% and HIV incidence ranging from 4.5-9.1% per year. Unfortunately none of the interventions tested had any impact on reducing the risk of HIV acquisition; however, extremely valuable experience was gained, lessons learned and capacity built, while the communities gained associated benefits. Experience Our experience in conducting these trials ranged from setting up Community partnerships to developing clinical research sites and dissemination of trial results. Community engagement included setting up Community-based research sites with approval from both political and traditional leaders, and developing Community advisory groups to assist with the research process. Community-wide education on HIV/sexually transmitted infection prevention, treatment and care was provided to over 90 000 individuals. Myths and misconceptions were addressed through methods such as anonymous suggestion boxes in clinic waiting areas and intensive education and counselling. Attempts were made to involve male partners to foster support and facilitate recruitment of women. Peer educator programmes were initiated to provide ongoing education and also to facilitate recruitment of women to the trials. Recruitment strategies such as door-to-door recruitment and Community group meetings were initiated. Over 90% of women enrolled were retained. Community benefits from the trial included education on HIV prevention, treatment and care and provision of ancillary care (such as Pap smears, reproductive health care and referral for chronic illnesses). Social benefits included training of home-based caregivers and sustainable ongoing HIV prevention education through peer educator programmes. Challenges Several challenges were encountered, including manipulation by participants of their eligibility criteria in order to enroll in the trial. Women attempted to co-enroll in Multiple trials to benefit from financial reimbursements and individualised care. The trials became ethically challenging when participants refused to take up referrals for care due to stigma, denial of their HIV status and inadequate health infrastructure. Lack of disclosure of HIV status to partners and family members was particularly challenging. Some of the ethical dilemmas put to the test our responsibility as researchers and our obligation to provide health care to research participants. Conclusion Conducting these five trials in a period of six years provided us with invaluable insights into trial implementation, Community participation, recruitment and retention, provision of care and dissemination of trial results. The critical mass of scientists trained as clinical trialists will continue to address the relentless HIV epidemic in our setting and ensure our commitment to finding a biomedical HIV prevention option for women in the future.
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Experiences in conducting Multiple Community-based HIV prevention trials among women in KwaZulu-Natal, South Africa
AIDS Research and Therapy, 2010Co-Authors: Gita Ramjee, Nicola Coumi, Nozizwe Dladla-qwabe, Shay Ganesh, Sharika Gappoo, Roshini Govinden, Vijayanand Guddera, Rashika Maharaj, Jothi Moodley, Neetha MorarAbstract:South Africa, with its scientific capacity, good infrastructure and high HIV incidence rates, is ideally positioned to conduct large-scale HIV prevention trials. The HIV Prevention Research Unit of the South African Medical Research Council conducted four phase III and one phase IIb trials of women-initiated HIV prevention options in KwaZulu-Natal between 2003 and 2009. A total of 7046 women participated, with HIV prevalence between 25% and 45% and HIV incidence ranging from 4.5-9.1% per year. Unfortunately none of the interventions tested had any impact on reducing the risk of HIV acquisition; however, extremely valuable experience was gained, lessons learned and capacity built, while the communities gained associated benefits. Our experience in conducting these trials ranged from setting up Community partnerships to developing clinical research sites and dissemination of trial results. Community engagement included setting up Community-based research sites with approval from both political and traditional leaders, and developing Community advisory groups to assist with the research process. Community-wide education on HIV/sexually transmitted infection prevention, treatment and care was provided to over 90 000 individuals. Myths and misconceptions were addressed through methods such as anonymous suggestion boxes in clinic waiting areas and intensive education and counselling. Attempts were made to involve male partners to foster support and facilitate recruitment of women. Peer educator programmes were initiated to provide ongoing education and also to facilitate recruitment of women to the trials. Recruitment strategies such as door-to-door recruitment and Community group meetings were initiated. Over 90% of women enrolled were retained. Community benefits from the trial included education on HIV prevention, treatment and care and provision of ancillary care (such as Pap smears, reproductive health care and referral for chronic illnesses). Social benefits included training of home-based caregivers and sustainable ongoing HIV prevention education through peer educator programmes. Several challenges were encountered, including manipulation by participants of their eligibility criteria in order to enroll in the trial. Women attempted to co-enroll in Multiple trials to benefit from financial reimbursements and individualised care. The trials became ethically challenging when participants refused to take up referrals for care due to stigma, denial of their HIV status and inadequate health infrastructure. Lack of disclosure of HIV status to partners and family members was particularly challenging. Some of the ethical dilemmas put to the test our responsibility as researchers and our obligation to provide health care to research participants. Conducting these five trials in a period of six years provided us with invaluable insights into trial implementation, Community participation, recruitment and retention, provision of care and dissemination of trial results. The critical mass of scientists trained as clinical trialists will continue to address the relentless HIV epidemic in our setting and ensure our commitment to finding a biomedical HIV prevention option for women in the future.
Junhua Chen - One of the best experts on this subject based on the ideXlab platform.
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Uncovering the effective interval of resolution parameter across Multiple Community optimization measures
International Journal of Modern Physics B, 2017Co-Authors: Qing Cheng, He-jin Mao, Huanian Wang, Junhua ChenAbstract:The study of Community structure is a primary focus of network analysis, which has attracted a large amount of attention. In this paper, we focus on two famous functions, i.e., the Hamiltonian function [Formula: see text] and the modularity density measure [Formula: see text], and intend to uncover the effective thresholds of their corresponding resolution parameter [Formula: see text] without resolution limit problem. Two widely used example networks are employed, including the ring network of lumps as well as the ad hoc network. In these two networks, we use discrete convex analysis to study the interval of resolution parameter of [Formula: see text] and [Formula: see text] that will not cause the misidentification. By comparison, we find that in both examples, for Hamiltonian function [Formula: see text], the larger the value of resolution parameter [Formula: see text], the less resolution limit the network suffers; while for modularity density [Formula: see text], the less resolution limit the network suffers when we decrease the value of [Formula: see text]. Our framework is mathematically strict and efficient and can be applied in a lot of scientific fields.
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Uncovering the effective interval of resolution parameter across Multiple Community optimization measures
International Journal of Modern Physics B, 2017Co-Authors: Qing Cheng, He-jin Mao, Huanian Wang, Junhua ChenAbstract:The study of Community structure is a primary focus of network analysis, which has attracted a large amount of attention. In this paper, we focus on two famous functions, i.e., the Hamiltonian function H and the modularity density measure D, and intend to uncover the effective thresholds of their corresponding resolution parameter γ without resolution limit problem. Two widely used example networks are employed, including the ring network of lumps as well as the ad hoc network. In these two networks, we use discrete convex analysis to study the interval of resolution parameter of H and D that will not cause the misidentification. By comparison, we find that in both examples, for Hamiltonian function H, the larger the value of resolution parameter γ, the less resolution limit the network suffers; while for modularity density D, the less resolution limit the network suffers when we decrease the value of γ. Our framework is mathematically strict and efficient and can be applied in a lot of scientific fields.
