OALib Journal期刊

ISSN: 2333-9721




2017 ( 5 )

2016 ( 11 )

2015 ( 121 )

2014 ( 291 )


匹配条件: “ Jessica Neilands” ,找到相关结果约2874条。
Bacterial Biofilm Formation on Resorbing Magnesium Implants  [PDF]
Olga Charyeva, Jessica Neilands, Gunnel Svens?ter, Ann Wennerberg
Open Journal of Medical Microbiology (OJMM) , 2015, DOI: 10.4236/ojmm.2015.51001
Abstract: Background: Implant-associated infections are a result of bacterial adhesion to an implant surface and subsequent biofilm formation at the implantation site. This study compares different magnesium materials based on their ability to resist bacterial adhesion as well as further biofilm formation. Material and Methods: The surfaces of four magnesium-based materials (Mg2Ag, Mg10Gd, WE43 and 99.99% pure Mg) were characterized using atomic force microscope. In addition, the samples were tested for their ability to resist biofilm formation. Planktonic bacteria of either S. epidermidis or E. faecalis were allowed to adhere to the magnesium surfaces for two hour followed by rinsing and, for S. epidermidis, further incubation of 24, 72 and 168 h was carried out. Results: E. faecalis had a significantly stronger adhesion to all magnesium surfaces compared to S. epidermidis (p = 0.001). Biofilm growth of S. epidermidis was different on various magnesium materials: the amount of bacteria increased up to 72 h but interestingly a significant decrease was seen at 168 h on Mg2Ag and WE43 surfaces. For pure Mg and Mg10Gd the biofilm formation reached plateau at 72 h. Surface characteristics of resorbable magnesium materials were changing over time, and the surface was generally less rough at 168 h compared to earlier time points. No correlation was found between the surface topology and the amount of adherent bacteria. Conclusion: In early stages of biofilm adhesion, no differences between magnesium materials were observed. However, after 72 h Mg2Ag and WE43 had the best ability to suppress S. epidermidis’ biofilm formation. Also, bacterial adhesion to magnesium materials was not dependent on samples’ surface topology.
Accumulation and modeling of particles in drinking water pipe fittings
K. Neilands, M. Bernats,J. Rubulis
Drinking Water Engineering and Science (DWES) & Discussions (DWESD) , 2012, DOI: 10.5194/dwes-5-47-2012
Abstract: The effect of pipe fittings (mainly T-pieces) on particle accumulation in drinking water distribution networks were shown in this work. The online measurements of flow and turbidity for cast iron, polyethylene and polyvinyl chloride pipe sections were linked with analysis of pipe geometry. Up to 0.29 kg of the total amount mobilized in T-pieces ranging from DN 100/100–DN 250/250. The accumulated amount of particles in fittings was defined as J and introduced into the existing turbidity model PODDS (prediction of discoloration in distribution systems) proposed by Boxall et al. (2001) which describes the erosion of particles leading to discoloration events in drinking water network viz sections of straight pipes. However, this work does not interpret mobilization of particles in pipe fittings which have been considered in this article. T-pieces were the object of this study and depending of the diameter or daily flow velocity, the coefficient J varied from 1.16 to 8.02. The study showed that pipe fittings act as catchment areas for particle accumulation in drinking water networks.
Accumulation and modeling of particles in drinking water pipe fittings
K. Neilands,M. Bernats,J. Rubulis
Drinking Water Engineering and Science Discussions , 2012, DOI: 10.5194/dwesd-5-139-2012
Abstract: The effect of pipe fittings – mainly T-pieces – on particle accumulation in drinking water distribution networks is shown in this work. The online measurements of flow and turbidity for cast iron, polyethylene and polyvinylchloride pipe sections have been linked with the analysis of pipe geometry. Up to 0.29 kg of the total mass of particles was found to be accumulated in T-pieces ranging from DN 100/100–DN 250/250. The accumulated amount of particles in the fittings was defined as J and introduced into the existing turbidity model PODDS (Prediction of Discolouration in Distribution Systems) proposed by Boxall et al. (2001), which describes the erosion of particles leading to discoloration events in drinking water networks, viz. sections, of straight pipes. It does not interpret the mobilization of particles in pipe fittings, however, which have been considered in this article. T-pieces were the object of this study and depending on the diameter or daily flow velocity, the coefficient J varied from 1.16 to 8.02.
Space Technology for Decarbonising City Precincts  [PDF]
Jessica Bunning
Journal of Geographic Information System (JGIS) , 2013, DOI: 10.4236/jgis.2013.55042
Abstract: Space technology is a powerful tool for climate research. Satellite data improve knowledge of the human impact on the Planet’s physical geography. Similarly, remote sensing technology enhances understanding of the human impact on rising global carbon emissions. However, so far satellites have been principally limited to measuring the carbon emissions of cities from space. Standing alone, satellite technology is incapable of advancing the goal of decarbonisation. This will be achieved only if cities create local methodologies that significantly enhance the carbon reduction process. There exists enormous potential to bridge remote sensing for earth observation and global environmental change with local action towards decarbonised urban renewal and redevelopment. Satellite remote sensing has the ability to demonstrate if local remedial strategies are succeeding, and assist with planning, developing, and monitoring low and zero carbon infrastructure systems. Satellite-derived data can facilitate informed discussion and decision-making between community stakeholders to deliver low carbon outcomes at the precinct scale. Satellite-based systems can be integrated within the urban fabric to assist climate change mitigation. This paper is based on current work implemented jointly with municipalities to ascertain where within city precincts carbon emissions originate and how they can ultimately be reduced. It presents space technology as an instrumental tool for understanding the carbon impact of citiesin terms of the carbon intensive patterns and processes that shape human society, as well as having great potential for providing end-user products to communities to enhance the process of decarbonising city precincts.
An Experimental Study of Microbial Fuel Cells for Electricity Generating: Performance Characterization and Capacity Improvement  [PDF]
Jessica Li
Journal of Sustainable Bioenergy Systems (JSBS) , 2013, DOI: 10.4236/jsbs.2013.33024

This paper studies the electricity generating capacity of microbial fuel cells (MFCs). Unlike most of MFC research, which targets the long term goals of renewable energy production and wastewater treatment, this paper considers a niche application that may be used immediately in practice, namely powering sensors from soils or sediments. There are two major goals in this study. The first goal is to examine the performance characteristics of MFCs in this application. Specifically we investigate the relationship between the percentage of organic matter in a sample and the electrical capacity of MFCs fueled by that sample. We observe that higher percentage of organic matter in a sample results in higher electricity production of MFCs powered by that sample. We measure the thermal limits that dictate the temperature range in which MFCs can function, and confirm that the upper thermal limit is 40℃. The new observation is that the lower thermal limit is -5℃, which is lower than 0℃ reported in the literature. This difference is important for powering environmental sensors. We observe that the electricity production of MFCs decreases almost linearly over a period of 10 days. The second goal is to determine the conditions under which MFCs work most efficiently to generate electricity. We compare the capacity under a variety of conditions of sample types (benthic mud, top soil, and marsh samples), temperatures (0℃, 40℃, and room temperature), and sample sizes (measuring 3.5 cm × 3.5 cm × 4.6 cm, 10.2 cm × 10.2 cm × 13.4 cm, and 2.7 cm × 2.7 cm × 3.8 cm), and find that the electricity capacity is greatest at 0℃, powered by benthic mud sample with the largest chamber size. What seems surprising is that 0℃ outperforms both room temperature and benthic mud sample outperforms marsh sample, which appears to be richer in organic matter. In addition, we notice that although the largest chamber size produces the greatest capacity, it suffers

Control Schemes to Reduce Risk of Extinction in the Lotka-Volterra Predator-Prey Model  [PDF]
Jessica Li
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.27071

The Lotka-Volterra predator-prey model is widely used in many disciplines such as ecology and economics. The model consists of a pair of first-order nonlinear differential equations. In this paper, we first analyze the dynamics, equilibria and steady state oscillation contours of the differential equations and study in particular a well-known problem of a high risk that the prey and/or predator may end up with extinction. We then introduce exogenous control to reduce the risk of extinction. We propose two control schemes. The first scheme, referred as convergence guaranteed scheme, achieves very fine granular control of the prey and predator populations, in terms of the final state and convergence dynamics, at the cost of sophisticated implementation. The second scheme, referred as on-off scheme, is very easy to implement and drive the populations to steady state oscillation that is far from the risk of extinction. Finally we investigate the robustness of these two schemes against parameter mismatch and observe that the on-off scheme is much more robust. Hence, we conclude that while the convergence guaranteed scheme achieves theoretically optimal performance, the on-off scheme is more attractive for practical applications.

Preliminary support for the construct of health care empowerment in the context of treatment for human immunodeficiency virus
Johnson MO, Sevelius JM, Dilworth SE, Saberi P, Neilands TB
Patient Preference and Adherence , 2012, DOI: http://dx.doi.org/10.2147/PPA.S30040
Abstract: eliminary support for the construct of health care empowerment in the context of treatment for human immunodeficiency virus Original Research (1649) Total Article Views Authors: Johnson MO, Sevelius JM, Dilworth SE, Saberi P, Neilands TB Published Date May 2012 Volume 2012:6 Pages 395 - 404 DOI: http://dx.doi.org/10.2147/PPA.S30040 Received: 19 January 2012 Accepted: 10 February 2012 Published: 11 May 2012 Mallory O Johnson, Jeanne M Sevelius, Samantha E Dilworth, Parya Saberi, Torsten B Neilands Department of Medicine, University of California, San Francisco, CA, USA Background: The Model of Health Care Empowerment (HCE) defines HCE as the process and state of being engaged, informed, collaborative, committed, and tolerant of uncertainty regarding health care. We examined the hypothesized antecedents and clinical outcomes of this model using data from ongoing human immunodeficiency virus (HIV)-related research. The purpose of this paper is to explore whether a new measure of HCE offers direction for understanding patient engagement in HIV medical care. Using data from two ongoing trials of social and behavioral aspects of HIV treatment, we examined preliminary support for hypothesized clinical outcomes and antecedents of HCE in the context of HIV treatment. Methods: This was a cross-sectional analysis of 12-month data from study 1 (a longitudinal cohort study of male couples in which one or both partners are HIV-seropositive and taking HIV medications) and 6-month data from study 2, a randomized controlled trial of HIV-seropositive persons not on antiretroviral therapy at baseline despite meeting guidelines for treatment. From studies 1 and 2, 254 and 148 participants were included, respectively. Hypothesized antecedents included cultural/social/environmental factors (demographics, HIV-related stigma), personal resources (social problem-solving, treatment knowledge and beliefs, treatment decision-making, shared decision-making, decisional balance, assertive communication, trust in providers, personal knowledge by provider, social support), and intrapersonal factors (depressive symptoms, positive/negative affect, and perceived stress). Hypothesized clinical outcomes of HCE included primary care appointment attendance, antiretroviral therapy use, adherence self-efficacy, medication adherence, CD4+ cell count, and HIV viral load. Results: Although there was no association observed between HCE and HIV viral load and CD4+ cell count, there were significant positive associations of HCE scores with likelihood of reporting a recent primary care visit, greater treatment adherence self-efficacy, and higher adherence to antiretroviral therapy. Hypothesized antecedents of HCE included higher beliefs in the necessity of treatment and positive provider relationships.
Predicting Use of Lights and Siren for Patient Illnesses  [PDF]
Jessica Mueller, Laura Stanley
Open Journal of Safety Science and Technology (OJSST) , 2013, DOI: 10.4236/ojsst.2013.33008

Lights and siren are frequently used by Emergency Medical Service (EMS) groups to reduce response times and increase a patient’s chance for survival. However, the use of lights and siren in EMS patient transport has been associated with occasional inappropriate use, higher crash rates involving the ambulance, and a potential “wake effect” increasing crash rates in ambient traffic. This study examines types of patient illnesses and their involvement with either emergency (lights and siren engaged) or non-emergency transport. Patient care records were analyzed from a five-year period from a private medical transportation company. A binary logistic regression model was built to predict the transportation mode (lights and siren or non-emergency-mode) most likely to accompany each unique primary patient illness. Patient illnesses were identified that showed a higher probability of transport using lights and siren. Fifteen illness descriptions were identified from the records as being more likely to result in emergency mode travel, including airway obstruction, altered level of consciousness, breathing problems, cardiac arrest, cardiac symptoms, chest pain, congestive heart failure/pulmonary embolism, heart/cardiac, obstetrics, respiratory arrest, respiratory distress, stroke/cerebrovascular accident, trauma, unconscious, and patients where data was not entered. The patient illnesses associated with lights and siren were not limited to cardiac conditions and symptoms, which suggest that response-time goals based solely on cardiac arrest patients may need to be expanded to include other illnesses such as respiratory conditions. Expanded studies could assess whether or not lights and sirens result in a clinically significant time savings across the spectrum of illnesses that are currently being transported using lights and siren. The list of illnesses identified here as more commonly utilizing lights and siren could be useful to untrained EMS or dispatch workers to assist in minimizing unnecessary emergency mode travel, thereby increasing safety for EMS workers, patients, and the general public.

Gender Inequality within the U.S. Land-Grant Agricultural Sciences Professoriate
Jessica Goldberger,Jessica Crowe
International Journal of Gender, Science and Technology , 2010,
Abstract: This paper focuses on gender inequality in the agricultural sciences in colleges of agriculture at U.S. land-grant universities. We ask two questions: (1) What degree of gender inequality exists in the agricultural sciences? (2) Can gender inequality be attributed to differences in human capital; professional networking; means of scientific production1; and/or, research productivity? Drawing on data from a 2005 nationwide survey of land-grant agricultural scientists, we find evidence of significant gender inequality despite few gender differences in scientists’ human capital, professional networking, means of scientific production, and research productivity. Our most robust findings relate to gender differences in scientists’ doctoral training, farming experience, and ties with private industry. Male agricultural scientists’ stronger linkages with land-grant universities, the farming world, and private industry may result in superior career outcomes (in terms of promotion and salary) compared to their female counterparts.
Social, Structural and Behavioral Determinants of Overall Health Status in a Cohort of Homeless and Unstably Housed HIV-Infected Men
Elise D. Riley, Torsten B. Neilands, Kelly Moore, Jennifer Cohen, David R. Bangsberg, Diane Havlir
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035207
Abstract: Background Previous studies indicate multiple influences on the overall health of HIV-infected persons; however, few assess and rank longitudinal changes in social and structural barriers that are disproportionately found in impoverished populations. We empirically ranked factors that longitudinally impact the overall health status of HIV-infected homeless and unstably housed men. Methods and Findings Between 2002 and 2008, a cohort of 288 HIV+ homeless and unstably housed men was recruited and followed over time. The population was 60% non-Caucasian and the median age was 41 years; 67% of study participants reported recent drug use and 20% reported recent homelessness. At baseline, the median CD4 cell count was 349 cells/μl and 18% of eligible persons (CD4<350) took antiretroviral therapy (ART). Marginal structural models were used to estimate the population-level effects of behavioral, social, and structural factors on overall physical and mental health status (measured by the SF-36), and targeted variable importance (tVIM) was used to empirically rank factors by their influence. After adjusting for confounding, and in order of their influence, the three factors with the strongest negative effects on physical health were unmet subsistence needs, Caucasian race, and no reported source of instrumental support. The three factors with the strongest negative effects on mental health were unmet subsistence needs, not having a close friend/confidant, and drug use. ART adherence >90% ranked 5th for its positive influence on mental health, and viral load ranked 4th for its negative influence on physical health. Conclusions The inability to meet food, hygiene, and housing needs was the most powerful predictor of poor physical and mental health among homeless and unstably housed HIV-infected men in an urban setting. Impoverished persons will not fully benefit from progress in HIV medicine until these barriers are overcome, a situation that is likely to continue fueling the US HIV epidemic.

Copyright © 2008-2017 Open Access Library. All rights reserved.