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  • 1
    Dissertation
    Dissertation
    University of Essex
    Language: English
    Description: The recent and rapid expansion of nanotechnology is expected to benefit mankind, yet certain nanomaterials have the potential to disrupt in situ microbial communities following their rel ease into the environment. This study characterised four engineered nanomaterials (capped and uncapped silver nanoparticles (cAgNP and uAgNP), titanium dioxide nanoparticles (TiO,NP) and multi-walled carbon nanotubes (MWCNT)) and measured their toxicity to bacterial pure cultures and aquatic microbial communities, with focus on two key processes (i.e. hydrocarbon-degradation and ammonia oxidation). Whilst the TiO,NP and MWCNT were non-toxic up to 50 mg both the cAgNP and uAgNP demonstrated bacterial toxicity between 5-50 mg with differential toxic responses obseNed by a range of different bacterial species tested. In general, a greater toxic response was elicited by the smaller cAgNP compared to the larger uAgNP. Freshwater and marine microbial communities demonstrated some resilience to AgNP in terms of cell viability, enzyme activity and hydrocarbon biodegradation rates. Furthermore, microbial nitrification potential in estuarine sediments demonstrated recovery following an initial decline in response to 50 mg L·1 cAgNP. Aquatic microbial community compositions were in general, sensitive to uAgNP and cAgNP between 0.5 to 50 mg. Since the nanoparticle concentrations tested herein are greater than current predicted environmental concentrations, it is suggested that microbial-mediated processes such as hydrocarbon-deg radation and ammonia oxidation are unlikely to be impacted by exposure to AgNP at present. However, aquatic microbial community compositions may be at risk in the event of a point-source AgNP spillage, or by future environmental concentrations, if the production and use of AgNP is not properly regulated.
    Keywords: 620.5
    Source: The British Library
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  • 2
    In: Physical Chemistry Chemical Physics, 2016, Vol.18(4), pp.2574-2579
    Description: We study the motion of a doped charge in a -conjugated polymer chain in solution subject to Brownian fluctuations. Specifically, we take poly( para -phenylene) to be our model system where the Brownian fluctuations cause rotational motion of the phenylene rings. The instantaneous torsional fluctuations cause Anderson localization of the charge wavefunction, with the lower-energy spectrum being composed of local ground states and the higher-energy spectrum being composed of quasi-extended states. At low temperatures, additional charge localization occurs via torsional relaxation. The dynamical torsional fluctuations lead to two distinct modes of motion of the charge: adiabatic and non-adiabatic. Adiabatic motion is a crawling motion of the charge along the polymer chain while the charge remains in its local ground state. Non-adiabatic motion is a rapid hopping motion as the charge is excited into higher energy quasi-extended states and travels ballistically along the chain before relaxing into a local ground state. The adiabatic motion dominates at low temperatures, and exhibits a linear temperature dependence and thus a constant zero-field charge mobility. Non-adiabatic motion begins to dominate as the temperature is increased, as the charge is thermally excited into higher energy states. At high temperatures the diffusion constant becomes almost temperature independent, indicating a decrease in the charge mobility with increasing temperature, which we attribute to the charge localization length being a decreasing function of temperature at high temperatures.
    Keywords: Grundzustand ; Mobilität ; Niedertemperatur ; Temperaturabhängigkeit ; Drehbewegung ; Konjugiertes Polymer ; Phenylen ; Niederenergie ; Adiabatische Zustandsänderung ; Wellenfunktion ; Hochtemperatur ; Erhöhte Temperatur ; Diffusionskonstante ; Chemistry;
    ISSN: 1463-9076
    E-ISSN: 1463-9084
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  • 3
    Language: English
    In: Journal of Infectious Diseases, Sept 1, 2013, Vol.208(5), p.720(8)
    Keywords: Haemophilus Influenzae -- Genetic Aspects ; Haemophilus Influenzae -- Research ; Genetic Variation -- Research
    ISSN: 0022-1899
    Source: Cengage Learning, Inc.
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  • 4
    Dissertation
    Dissertation
    University of Essex
    Description: The recent and rapid expansion of nanotechnology is expected to benefit mankind, yet certain nanomaterials have the potential to disrupt in situ microbial communities following their rel ease into the environment. This study characterised four engineered nanomaterials (capped and uncapped silver nanoparticles (cAgNP and uAgNP), titanium dioxide nanoparticles (TiO,NP) and multi-walled carbon nanotubes (MWCNT)) and measured their toxicity to bacterial pure cultures and aquatic microbial communities, with focus on two key processes (i.e. hydrocarbon-degradation and ammonia oxidation). Whilst the TiO,NP and MWCNT were non-toxic up to 50 mg both the cAgNP and uAgNP demonstrated bacterial toxicity between 5-50 mg with differential toxic responses obseNed by a range of different bacterial species tested. In general, a greater toxic response was elicited by the smaller cAgNP compared to the larger uAgNP. Freshwater and marine microbial communities demonstrated some resilience to AgNP in terms of cell viability, enzyme activity and hydrocarbon biodegradation rates. Furthermore, microbial nitrification potential in estuarine sediments demonstrated recovery following an initial decline in response to 50 mg L·1 cAgNP. Aquatic microbial community compositions were in general, sensitive to uAgNP and cAgNP between 0.5 to 50 mg. Since the nanoparticle concentrations tested herein are greater than current predicted environmental concentrations, it is suggested that microbial-mediated processes such as hydrocarbon-deg radation and ammonia oxidation are unlikely to be impacted by exposure to AgNP at present. However, aquatic microbial community compositions may be at risk in the event of a point-source AgNP spillage, or by future environmental concentrations, if the production and use of AgNP is not properly regulated.
    Keywords: 620.5
    Source: Networked Digital Library of Theses and Dissertations
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  • 5
    Language: English
    In: Nature reviews. Microbiology, July 2018, Vol.16(7), pp.440-452
    Description: Many important interactions between bacterial pathogens and their hosts are highly specific binding events that involve host or pathogen carbohydrate structures (glycans). Glycan interactions can mediate adhesion, invasion and immune evasion and can act as receptors for toxins. Several bacterial pathogens can also enzymatically alter host glycans to reveal binding targets, degrade the host cell glycans or alter the function of host glycoproteins. In recent years, high-throughput screening technologies, such as lectin, glycan and mucin microarrays, have transformed the field by identifying new bacterial-host glycointeractions, which are crucial for colonization, persistence and disease. In this Review, we discuss interactions involving both host and bacterial glycans that have a role in bacterial pathogenesis. We also highlight recent technological advances that have illuminated the glycoscience of microbial pathogenesis.
    Keywords: Bacterial Infections – Genetic Aspects ; Bacterial Infections – Development and Progression ; Bacterial Infections – Care and Treatment ; Protein-Protein Interactions – Observations;
    ISSN: 17401526
    E-ISSN: 1740-1534
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  • 6
    Language: English
    In: Biochemical and Biophysical Research Communications, 05 September 2018, Vol.503(2), pp.1103-1107
    Description: Non-typeable (NTHi) is a human-adapted bacterial pathogen, responsible for infections of the human respiratory tract. This pathogen expresses a range of adhesins that mediate binding to host cells. Most NTHi strains can express the related adhesins HMW1 and HMW2. Expression of HMW proteins is phase-variable: changes in the length of simple-sequence repeats located in the encoding genes promoter regions results in changes in expression levels of these adhesins. HMW expression is also controlled by epigenetic regulation. HMW1 has been previously demonstrated to bind α 2–3 sialyl-lactosamine, but affinity of this interaction has not been investigated. The host receptor(s) for HMW2 is currently unknown. We hypothesized that host glycans may act as receptors for HMW2-mediated adherence. We examined the glycan-binding activity of HMW2 using glycan arrays and Surface Plasmon Resonance (SPR). These studies demonstrate that HMW2 binds 2–6 linked -acetylneuraminic acid with high affinity. HMW2 did not bind glycan structures containing the non-human form of sialic acid, -glycolylneuraminic acid. Thus, the specificity of HMW1 and HMW2 have complementary lectin activities that may allow NTHi distinct niches in the human host.
    Keywords: Biology ; Chemistry ; Anatomy & Physiology
    ISSN: 0006-291X
    E-ISSN: 1090-2104
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  • 7
    Language: English
    In: Appetite, 2006, Vol.47(2), pp.277-277
    Keywords: Anatomy & Physiology ; Diet & Clinical Nutrition
    ISSN: 0195-6663
    E-ISSN: 1095-8304
    Source: ScienceDirect Journals (Elsevier)
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  • 8
    Language: English
    In: The Journal of infectious diseases, 01 September 2013, Vol.208(5), pp.720-7
    Description: Studies of nontypeable Haemophilus influenzae (NTHi) have demonstrated that a number of genes associated with infectivity have long repeat regions associated with phase variation in expression of the respective gene. The purpose of this study was to determine the genes that underwent phase variation during a 6-day period of experimental human nasopharyngeal colonization. Strain NTHi 2019Str(R)1 was used to colonize the nasopharynx of human subjects in a study of experimental colonization. Thirteen phase-variable genes were analyzed in NTHi 2019Str(R)1. Samples of NTHi 2019Str(R)1 were cultured from subjects during the 6-day colonization period. We used capillary electrophoresis and Roche 454 pyrosequencing to determine the number of repeats in each gene from each sample. A significant number of samples switched licA and igaB from phase off in the inoculated strain to phase on during the 4-day period of observation. lex2A also showed variability as compared to baseline, but the differences were not significant. The remaining genes showed no evidence of phase variation. Our studies suggest that the phase-on genotypes of licA and igaB are important for early human nasopharynx colonization. lex2A showed a trend from phase off to phase on, suggesting a potentially important role in the colonization process.
    Keywords: Haemophilus Influenzae ; Igab ; Lex2a Nasopharyngeal Colonization ; Lica ; Phase Variation ; Antigenic Variation ; Gene Expression Profiling ; Antigens, Bacterial -- Biosynthesis ; Carrier State -- Microbiology ; Haemophilus Infections -- Microbiology ; Haemophilus Influenzae -- Genetics ; Nasopharynx -- Microbiology
    ISSN: 00221899
    E-ISSN: 1537-6613
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  • 9
    Language: English
    In: The Journal of Chemical Physics, 14 August 2019, Vol.151(6)
    Description: Charge transfer processes and charge mobility are investigated in the poly( p -phenylenevinylene) model system. Realistic disordered polymer conformations are created and used in a coarse-grained model. Localized and quasiextended states are obtained using the Holstein Hamiltonian. Charge transport is modeled as an incoherent hopping mechanism in the framework of unimolecular and bimolecular Marcus theory for intramolecular and intermolecular processes, respectively, to account for the electron-phonon coupling present in π -conjugated polymer systems. Static and quasidynamic disorder effects are both considered using the “fluctuating bridges” approach. Charge mobility is calculated using kinetic Monte Carlo simulations for a range of physically relevant parameters. We examine the relative importance of intramolecular and intermolecular mechanisms and the role of localized and extended states in the transport process. We discuss the role of disorder and temperature and show that a log   μ ∝ − F electric field dependence in the high field regime naturally emerges from our model. We show that disorder significantly reduces the mobility at low fields but slightly increases it at high fields. We also show that the mobility is dominated by interchain charge transfer between low energy localized states at low fields, but at higher fields, intrachain transfer to more delocalized higher energy states becomes equally important. This crossover is the cause of anisotropic charge mobility at intermediate field strengths.
    Keywords: Articles
    ISSN: 0021-9606
    E-ISSN: 1089-7690
    Source: © 2019 Author(s) (AIP)
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  • 10
    Language: English
    In: Canadian Journal of Rural Medicine, Wntr, 2010, Vol.15(1), p.14(5)
    Description: Introduction: The group practice physicians in Marathon, a small rural community in northwestern Ontario, discovered general lifestyle dissatisfaction with the traditional model for obstetric practice. The old model of doing the follow-up and delivery for one's own patients created perceived onerous on-call responsibilities. The providers created a new model of obstetric care. This involved the local providers of obstetric care each taking 1 month of the year in rotation and following up any woman due in that month for prenatal and intrapartum services. This study is an investigation of patient and provider satisfaction with this model. Methods: Patient survey: We surveyed all 73 women who received obstetric care under the new model during its first 14 months of implementation. We collected data on patient demographics and patients' satisfaction with their obstetric experience using Likert scale, yes/no and short-answer questions. Physician survey: We surveyed the 9 physicians of Marathon Family Practice using Likert scale, yes/no and shortanswer questions. We collected information on demographics, history of involvement with obstetric service, and comparison of old and new models with regard to patient care, and professional and personal issues. Results: Patient survey: The response rate was 56%. Of the respondents, 97% reported their expectations for their obstetric care were met, if not surpassed, and 100% were satisfied with their obstetric care. Physician survey: All the physicians responded and found the new model to cause less disruption of their family practice (Wilcoxon signed rank test, p = 0.041), to improve scheduling of personal activities (p = 0.017) and to improve their satisfaction with on-call hours (p = 0.027). Overall, the physicians were satisfied with the new model and preferred it to the old model. Conclusion: This obstetric care model meets patients' expectations and provides patient satisfaction. It provides practitioners with an increased quality of life and greater satisfaction. It is a viable paradigm for the provision of obstetric care in the appropriate setting. Introduction : Les medecins d'une pratique de groupe de Marathon, petite communaute rurale du Nord-Ouest de l'Ontario, a constate une insatisfaction generalisee vis-a-vis du style de vie que lui imposait le modele de pratique obstetricale classique. Les medecins percevaient comme tres lourd sur le plan des heures de garde ce modele ou chacun assure le suivi et l'accouchement de ses propres patientes. Les medecins ont donc imagine un nouveau modele de soins obstetricaux dans lequel les medecins de la localite qui font de l'obstetrique assument a tour de role un mois de garde pour faire le suivi des femmes dont l'accouchement est prevu au cours du mois en question. Pour ces patientes et durant ce mois, les medecins fournissent les services prenataux necessaires et veillent aux accouchements. La presente etude s'est penchee sur le degre de satisfaction des patientes et des medecins a l'endroit de ce modele. Methodes : Sondage aupres des patientes : nous avons interroge les 73 femmes qui ont recu des soins obstetricaux selon le nouveau modele durant ses 14 premiers mois d'application. Nous avons recueilli les donnees demographiques des patientes et mesure leur degre de satisfaction a l'endroit de leur experience obstetricale au moyen de l'echelle de Likert et de questions breves a reponse oui ou non. Sondage aupres des medecins : nous avons interroge les neuf medecins de la clinique de medecine familiale de Marathon en utilisant l'echelle de Likert et des questions breves a reponse oui ou non. Nous avons recueilli des donnees demographiques et des donnees sur leur experience en obstetrique, et nous avons ensuite compare le nouveau modele a l'ancien pour ce qui est des soins aux patientes et des enjeux d'ordre professionnel et personnel. Resultats : Sondage aupres des patientes : le taux de reponse a ete de 56 %. Parmi les repondantes, 97 % ont declare que leurs attentes en matiere de soins obstetricaux avaient ete comblees sinon depassees et 100 % se sont dites satisfaites de leurs soins obstetricaux. Sondage aupres des medecins : tous les medecins ont participe et ont note que le nouveau modele perturbait moins leur pratique en medecine familiale (test de Wilcoxon pour observation appariee, p = 0,041), facilitait la planification de leurs activites personnelles (p = 0,017) et ameliorait leur degre de satisfaction vis-a-vis des heures de garde (p = 0,027). Dans l'ensemble, les medecins se sont dits satisfaits du nouveau modele et l'ont prefere a l'ancien. Conclusion : Ce modele de soins obstetricaux repond aux attentes des patientes et les satisfait. Il offre aux professionnels de la sante une meilleure qualite de vie et un degre de satisfaction plus eleve. Dans un contexte approprie, il s'agit d'un modele viable pour assurer les soins obstetricaux.
    Keywords: Family Medicine -- Surveys ; Medical Practice -- Surveys ; Marathons -- Surveys ; Health Surveys -- Surveys ; Medical Research -- Surveys ; Pregnant Women -- Surveys
    ISSN: 1203-7796
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