124,794 research outputs found
A mathematical model of Chikungunya dynamics and control: the major epidemic on Reunion Island
No full textChikungunya is a re-emerging arboviral disease transmitted by Aedes spp. mosquitoes. Although principally endemic to Africa and Asia, recent outbreaks have occurred in Europe following introductions by returning travellers. A particularly large outbreak occurred on Réunion Island in 2006, the published data from which forms the basis of the current study. A simple, deterministic mathematical model of the transmission of the virus between humans and mosquitoes was constructed and parameterised with the up-to-date literature on infection biology. The model is fitted to the large Réunion epidemic, resulting in an estimate of 4.1 for the type reproduction number of chikungunya. Although simplistic, the model provided a close approximation of both the peak incidence of the outbreak and the final epidemic size. Sensitivity analysis using Monte Carlo simulation demonstrated the strong influence that both the latent period of infection in humans and the pre-patent period have on these two epidemiological outcomes. We show why separating these variables, which are epidemiologically distinct in chikungunya infections, is not only necessary for accurate model fitting but also important in informing control
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Infectious disease and novel ecosystems
No full textThe contributions of habitat destruction, exotic species invasion and climate change on infectious disease ecology are difficult to disentangle. This chapter considers two case studies. The first, African Highland malaria, offers a case study for the multiplicity of anthropogenic changes to natural ecosystems and their effects on infectious disease epidemiology. A natural bias exists in the scientific literature towards human pathogens in linking infectious diseases with novel ecosystems because of the amenability of these subjects to observation. Inaccessibility continues to hamper the study of marine systems. Consequently, marine infectious disease understanding is less developed than it is for terrestrial systems. This issue is addressed in the second case study in the chapter: novel Caribbean coral reef ecosystems. Temporal dynamics of this drastically altered marine system demonstrates not only the effect that infectious disease can have in reshaping ecosystems, but also the recursive nature of the relationship between infectious disease and novel ecosystems
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Life histories offer a clue to the future role of infectious disease in coral reefs
No full textIncreased frequency and severity of stressors associated with climate change are drastically altering ecosystems. Caribbean coral reefs differ markedly from just 30 years ago, with much restructuring attributable to infectious disease outbreaks. Using a classic epidemiological approach, we demonstrate how density-dependent demographic rates serve as a mechanism for intrinsic coral resilience to population perturbations arising from disturbances such as disease. We explore the impact of allowing infection status to influence demographic rates and ascertain outbreak thresholds that are corroborated by epizootic patterns observed in the field. We discuss how our threshold calculations may provide metrics of coral epizootic early warning systems. Integrating our infection model with equations describing the interspecific competition for space between coral and macroalgae, we provide new mechanistic understanding of the influence that coral life history dynamism and infectious disease have on the changing face of these threatened ecosystems
Modelling knowlesi malaria transmission in humans: Vector preference and host competence
No full textBackground: Plasmodium knowlesi, a malaria species that normally infects long-tailed macaques, was recently found to be prevalent in humans in Southeast Asia. While human host competency has been demonstrated experimentally, the extent to which the parasite can be transmitted from human back to mosquito vector in nature is unclear. Methods. Using a mathematical model, the influence of human host competency on disease transmission is assessed. Adapting a standard model for vector-borne disease transmission and using an evolutionary invasion analysis, the paper explores how differential host competency between humans and macaques can facilitate the epidemiological processes of P. knowlesi infection between different hosts. Results. Following current understanding of the evolutionary route of other human malaria vectors and parasites, an increasing human population in knowlesi malaria endemic regions will select for a more anthropophilic vector as well as a parasite that preferentially transmits between humans. Applying these adaptations, evolutionary invasion analysis yields threshold conditions under which this macaque disease may become a significant public health issue. Conclusions. These threshold conditions are discussed in the context of malaria vector-parasite co-evolution as a function of anthropogenic effects
Associations between oral biofilm, periodontal disease, and systemic health : with a focus on atherosclerosis and breast cancer
No full textThe general hypothesis of this series of studies was that oral infections, particularly periodontal disease, by triggering inflammatory reactions detrimentally affect systemic health where inflammations are known to play a role in the pathogenesis, namely cardiovascular disease and cancer. Consequently, the general aim was to study the association between oral biofilm and certain oral micro-organisms, periodontal disease, and selected inflammatory markers with a focus on atherosclerosis and breast cancer (BC).In Study I, the aim was to examine the involvement of a high amount of dental plaque, severe gingival inflammation and periodontal disease in the development of early atherosclerotic lesions in women. The carotid arteries were examined with ultrasonography. Periodontal disease appeared to be a principal independent predictor in the development of atherosclerotic process women with periodontal disease. Our findings indicated that a high amount of dental plaque, severe gingival inflammation as well as periodontal disease seemed to be associated with the development of atherosclerotic lesions in women already at the early subclinical stage. In Study III, the aim was to examine early atherosclerotic changes in carotid arteries and relate the findings to the serum levels of high-sensitivity C-reactive protein (hsCRP) in subjects whose periodontal status have been followed for at least 18 years. Women had significantly lower hsCRP values and significantly higher highdensity lipoprotein (HDL) cholesterol values than men. Nevertheless, women with periodontal disease had significantly more atherosclerotic lesions than women without periodontal disease. Increased levels of hsCRP could not discriminate the patient group from the control group for either men or women. Periodontal disease was identified as the major independent predictor of increased carotid artery lesions. Hence, periodontal disease might nevertheless present a risk for atherosclerotic disease, particularly in women, irrespective of low hsCRP levels.In Study II, the aim was to evaluate the incidence of BC in subjects with periodontal disease and the characteristic tooth loss in a 16-year prospective investigation. Participants diagnosed with periodontal disease and BC had significantly more missing molars when compared with subjects with periodontal disease but without BC. The difference in the prevalence of BC in subjects with periodontal disease and with or without any missing molar in the mandible was significant. Thus, chronic periodontal disease indicated by missing molars seemed to be associated with the incidence of BC.In Study IV, the aim was to investigate in subjects with and without periodontal disease the levels of salivary albumin, total protein, and matrix metalloproteinases-8 (MMP-8), with or without the simultaneous presence of specific periodontal micro-organisms detected by polymerase chain reaction (PCR) in gingival crevicular fluid (GCF). The presence of both Treponema denticola and Tannerella forsythia associated with increased MMP-8 concentration in GCF. Furthermore, the presence of T. denticola associated with increased albumin and total protein concentrations in saliva. In Study V, the aim was to assess the association between site-specific subgingival micro-organisms and the levels of MMP-8 and MMP-9 at test sites. T. denticola was significantly more present at test sites in patients compared with the control group. Furthermore, the site -specific presence T. denticola in GCF appeared to increase the release of MMP-8 and MMP-9 at test sites. Thus, the results from Studies IV and V confirmed the assumption that periodontal micro-organisms might indeed trigger an inflammatory host-response.Summing up, periodontal disease was found to be associated with subclinical atherosclerotic lesions and also a higher incidence of BC. Furthermore, T. denticola associated with increased salivary albumin, total protein as well as with higher levels of MMP-8 and MMP-9 in GCF, indicating a possible inflammation triggering capacity of the oral biofilm. Thus, our findings did confirm our primary hypotheses. The associations indicate that periodontal disease might pose a threat to systemic health.List of scientific papersI. Söder B, Yakob M, Nowak J, Jogestrand T. Risk for the development of atherosclerosis in women with a high amount of dental plaque and severe gingival inflammation. International Journal of Dental Hygiene. 2007 Aug;5(3):133-8. https://doi.org/10.1111/j.1601-5037.2007.00256.x II. Söder B, Yakob M, Meurman JH, Andersson LC, Klinge B, Söder PÖ. Periodontal disease may associate with breast cancer. Breast Cancer Research and Treatment. 2011 Jun;127(2):497-502. https://doi.org/10.1007/s10549-010-1221-4 III. Yakob M, Meurman JH, Jogestrand T, Nowak J, Söder PÖ, Söder B. Creactive protein in relation to early atherosclerosis and periodontitis. Clinical Oral Investigations. 2010 Dec 7. https://doi.org/10.1007/s00784-010-0487-6 IV. Yakob M, Kari K, Tervahartiala T, Sorsa T, Söder P-Ö, Meurman JH, Söder B. Associations of periodontal micro-organisms with salivary proteins and MMP-8 in gingival crevicular fluid. Journal of Clinical Periodontology. 2011 Nov 21. https://doi.org/10.1111/j.1600-051X.2011.01813.x V. Yakob M, Meurman JH, Sorsa T, Söder B. Site-specific presence of Treponema denticola associates with increased levels of MMP-8 and MMP-9 in gingival crevicular fluid. [Submitted]</p
Synthesising 30 years of mathematical modelling of Echinococcus Transmission
No full textBackground: Echinococcosis is a complex zoonosis that has domestic and sylvatic lifecycles, and a range of different intermediate and definitive host species. The complexities of its transmission and the sparse evidence on the effectiveness of control strategies in diverse settings provide significant challenges for the design of effective public health policy against this disease. Mathematical modelling is a useful tool for simulating control packages under locally specific transmission conditions to inform optimal timing and frequency of phased interventions for cost-effective control of echinococcosis. The aims of this review of 30 years of Echinococcus modelling were to discern the epidemiological mechanisms underpinning models of Echinococcus granulosus and E. multilocularis transmission and to establish the need to include a human transmission component in such models
Pragmatic Case Studies as a Source of Unity in Applied Psychology
No full textTo unify or not to unify applied psychology: that is the question. In this article we review pendulum swings in the historical efforts to answer this question—from a comprehensive, positivist, “top-down,” deductive yes between the 1930s and the early 60s, to a postmodern no since then. A rationale and proposal for a limited, “bottom-up,” inductive yes in applied psychology is then presented, employing a case-based paradigm that integrates both positivist and postmodern themes and components. This paradigm is labeled “pragmatic psychology” and, its specific use of case studies, the “Pragmatic Case Study Method” (“PCS Method”). We call for the creation of peer-reviewed journal-databases of pragmatic case studies as a foundational source of unifying applied knowledge in our discipline. As one example, the potential of the PCS Method for unifying different angles of theoretical regard is illustrated in an area of applied psychology, psychotherapy, via the case of Mrs. B. The article then turns to the broader historical and epistemological arguments for the unifying nature of the PCS Method in both applied and basic psychology.Peer reviewe
Dr. Edwin Wright Collection: Author Unknown
No full textNotes - The author relates several short stories about his neighbours including Alex McDonell, homesteading and life around Meanook and Athabasca (1 page
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