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Search Results: 1 - 10 of 220719 matches for " Kacey C Ernst "
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Malaria hotspot areas in a highland Kenya site are consistent in epidemic and non-epidemic years and are associated with ecological factors
Kacey C Ernst, Samson O Adoka, Dickens O Kowuor, Mark L Wilson, Chandy C John
Malaria Journal , 2006, DOI: 10.1186/1475-2875-5-78
Abstract: To address this issue, spatial distribution of malaria incidence and the relationship of ecological factors to malaria incidence were assessed in the highland area of Kipsamoite, Kenya, from 2001–2004.Clustering of disease in a single geographic "hotspot" area occurred in epidemic and non-epidemic years, with a 2.6 to 3.2-fold increased risk of malaria inside the hotspot, as compared to outside the area (P < 0.001, all 4 years). Altitude and proximity to the forest were independently associated with increased malaria risk in all years, including epidemic and non-epidemic years.In this highland area, areas of high malaria risk are consistent in epidemic and non-epidemic years and are associated with specific ecological risk factors. Ongoing interventions in areas of ecological risk factors could be a cost-effective method of significantly reducing malaria incidence and blunting or preventing epidemics, even in the absence of malaria early warning systems. Further studies should be conducted to see if these findings hold true in varied highland settings.It has been estimated that 34 million individuals in highland areas of East Africa are at risk for malaria [1] and malaria in these highland areas has been responsible for numerous deaths [2]. However, the levels of variation in malaria risk within these highland areas are not well described and only a few studies have investigated risk factors for malaria there [3-5]. Previous studies have demonstrated that malaria cases aggregate from the household to the countrywide level [3,6,7]. The determinants of such clustering are likely due to shared anthropogenic and environmental variables, as well as factors related to contagion such as population density and human interactions [8,9]. Brooker et al demonstrated that there was spatial clustering of malaria cases in children during an epidemic in a single year in highland area of Kenya [3]. However, without data from multiple years, it is difficult to discern if clusters of
Health status of southern Arizona border counties: a Healthy Border 2010 midterm review
Robinson,Keisha L.; Ernst,Kacey C.; Johnson,Babs L.; Rosales,Cecilia;
Revista Panamericana de Salud Pública , 2010, DOI: 10.1590/S1020-49892010001100004
Abstract: objective: the region on the united states (us) side of the us-mexico border consists of 44 counties in four states; populations on both sides of the border have similar health problems. healthy border 2010: an agenda for improving health on the us-mexico border (hb 2010) is a binational agenda of health promotion and disease prevention for individuals in the region. this study reports on the health status of the four southern arizona border counties. methods: data on health indicators for cochise, pima, santa cruz, and yuma counties were collected from the arizona department of health services vital records and statistics. progress was calculated as a percentage made toward or away from the 2010 target. comparisons were made between the border counties and arizona. results: progress toward the hb 2010 targets varied among the border counties. all border counties made progress toward the targets with the cervical cancer, hepatitis a, and teenage birthrate objectives. most border counties moved toward the goals for breast cancer, diabetes mortality, tuberculosis, motor vehicle crashes, infant mortality from congenital abnormalities, and prenatal care. border counties moved away from the target with the human immunodeficiency virus and infant mortality objectives. conclusions: assessment of the hb 2010 objectives provided a comprehensive description of the health status of the population. although the southern arizona border counties have shown improvement in some areas, monitoring is still needed to identify the disparities that remain.
Local topographic wetness indices predict household malaria risk better than land-use and land-cover in the western Kenya highlands
Justin M Cohen, Kacey C Ernst, Kim A Lindblade, John M Vulule, Chandy C John, Mark L Wilson
Malaria Journal , 2010, DOI: 10.1186/1475-2875-9-328
Abstract: The topographic wetness index, an estimate of predicted water accumulation in a defined area, was generated from a digital terrain model of the landscape surrounding households in two neighbouring western Kenyan highland communities. Variables determined to best encompass the variance in this topographic wetness surface were calculated at a household level. Land-cover/land-use information was extracted from a high-resolution satellite image using an object-based classification method. Topographic and land-cover variables were used individually and in combination to predict household-level malaria in the communities through an iterative split-sample model fitting and testing procedure. Models with only topographic variables were compared to those with additional predictive factors related to land-cover/land-use to investigate whether these environmental factors improved prediction of malaria based on the shape of the land alone.Variables related to topographic wetness proved most useful in predicting the households of individuals contracting malaria in this region of rugged terrain. Other variables related to human modification of the environment also demonstrated clear associations with household malaria. However, these land-cover/land-use variables failed to produce unambiguous improvements in statistical predictive models controlling for important topographic factors, with none improving prediction of household-level malaria more than 75% of the time.Topographic wetness values in this region of highly varied terrain more accurately predicted houses at greater risk of malaria than did consideration of land-cover/land-use characteristics. As such, those planning control or local elimination strategies in similar highland regions may use topographic and geographic characteristics to effectively identify high-receptivity regions that may require enhanced vigilance.Local elimination of malaria requires identification of residual transmission foci [1], while optimal tar
Topography-derived wetness indices are associated with household-level malaria risk in two communities in the western Kenyan highlands
Justin M Cohen, Kacey C Ernst, Kim A Lindblade, John M Vulule, Chandy C John, Mark L Wilson
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-40
Abstract: Hydrologic modelling techniques were adapted to predict the flow of water across the landscape surrounding households in two communities in the western Kenyan highlands. These surface analyses were used to generate indices describing predicted water accumulation in regions surrounding the study area. Households with and without malaria were compared for their proximity to regions of high and low predicted wetness. Predicted wetness and elevation variables were entered into bivariate and multivariate regression models to examine whether significant associations with malaria were observable at small spatial scales.On average, malaria case households (n = 423) were located 280 m closer to regions with very high wetness indices than non-malaria "control" households (n = 895) (t = 10.35, p < 0.0001). Distance to high wetness indices remained an independent predictor of risk after controlling for household elevation in multivariate regression (OR = 0.93 [95% confidence interval = 0.89–0.96] for a 100 m increase in distance). For every 10 m increase in household elevation, there was a 12% decrease in the odds of the house having a malaria case (OR = 0.88 [0.85–0.90]). However, after controlling for distance to regions of high predicted wetness and the community in which the house was located, this reduction in malaria risk was not statistically significant (OR = 0.98 [0.94–1.03]).Proximity to terrain with high predicted water accumulation was significantly and consistently associated with increased household-level malaria incidence, even at small spatial scales with little variation in elevation variables. These results suggest that high wetness indices are not merely proxies for valley bottoms, and hydrologic flow models may prove valuable for predicting areas of high malaria risk in highland regions. Application in areas where malaria surveillance is limited could identify households at higher risk and help focus interventions.Elevation has long been recognized to be ass
Meteorologically Driven Simulations of Dengue Epidemics in San Juan, PR
Cory W. Morin?,Andrew J. Monaghan?,Mary H. Hayden?,Roberto Barrera?,Kacey Ernst
PLOS Neglected Tropical Diseases , 2015, DOI: 10.1371/journal.pntd.0004002
Abstract: Meteorological factors influence dengue virus ecology by modulating vector mosquito population dynamics, viral replication, and transmission. Dynamic modeling techniques can be used to examine how interactions among meteorological variables, vectors and the dengue virus influence transmission. We developed a dengue fever simulation model by coupling a dynamic simulation model for Aedes aegypti, the primary mosquito vector for dengue, with a basic epidemiological Susceptible-Exposed-Infectious-Recovered (SEIR) model. Employing a Monte Carlo approach, we simulated dengue transmission during the period of 2010–2013 in San Juan, PR, where dengue fever is endemic. The results of 9600 simulations using varied model parameters were evaluated by statistical comparison (r2) with surveillance data of dengue cases reported to the Centers for Disease Control and Prevention. To identify the most influential parameters associated with dengue virus transmission for each period the top 1% of best-fit model simulations were retained and compared. Using the top simulations, dengue cases were simulated well for 2010 (r2 = 0.90, p = 0.03), 2011 (r2 = 0.83, p = 0.05), and 2012 (r2 = 0.94, p = 0.01); however, simulations were weaker for 2013 (r2 = 0.25, p = 0.25) and the entire four-year period (r2 = 0.44, p = 0.002). Analysis of parameter values from retained simulations revealed that rain dependent container habitats were more prevalent in best-fitting simulations during the wetter 2010 and 2011 years, while human managed (i.e. manually filled) container habitats were more prevalent in best-fitting simulations during the drier 2012 and 2013 years. The simulations further indicate that rainfall strongly modulates the timing of dengue (e.g., epidemics occurred earlier during rainy years) while temperature modulates the annual number of dengue fever cases. Our results suggest that meteorological factors have a time-variable influence on dengue transmission relative to other important environmental and human factors.
Aging Field Collected Aedes aegypti to Determine Their Capacity for Dengue Transmission in the Southwestern United States
Teresa K. Joy,Eileen H. Jeffrey Gutierrez,Kacey Ernst,Kathleen R. Walker,Yves Carriere,Mohammad Torabi,Michael A. Riehle
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046946
Abstract: Aedes aegypti, the primary vector of dengue virus, is well established throughout urban areas of the Southwestern US, including Tucson, AZ. Local transmission of the dengue virus, however, has not been reported in this area. Although many factors influence the distribution of the dengue virus, we hypothesize that one contributing factor is that the lifespan of female Ae. aegypti mosquitoes in the Southwestern US is too short for the virus to complete development and be transmitted to a new host. To test this we utilized two age grading techniques. First, we determined parity by analyzing ovarian tracheation and found that only 40% of Ae. aegypti females collected in Tucson, AZ were parous. The second technique determined transcript levels of an age-associated gene, Sarcoplasmic calcium-binding protein 1 (SCP-1). SCP-1 expression decreased in a predictable manner as the age of mosquitoes increased regardless of rearing conditions and reproductive status. We developed statistical models based on parity and SCP-1 expression to determine the age of individual, field collected mosquitoes within three age brackets: nonvectors (0–5 days post-emergence), unlikely vectors (6–14 days post-emergence), and potential vectors (15+ days post-emergence). The statistical models allowed us to accurately group individual wild mosquitoes into the three age brackets with high confidence. SCP-1 expression levels of individual, field collected mosquitoes were analyzed in conjunction with parity status. Based on SCP-1 transcript levels and parity data, 9% of collected mosquitoes survived more than 15 days post emergence.
Chronic Teacher Turnover in Urban Elementary Schools
Kacey Guin
Education Policy Analysis Archives , 2004,
Abstract: This study examines the characteristics of elementary schools that experience chronic teacher turnover and the impacts of turnover on a school’s working climate and ability to effectively function. Based on evidence from staff climate surveys and case studies, it is clear that high turnover schools face significant organizational challenges. Schools with high teacher turnover rates have difficulty planning and implementing a coherent curriculum and sustaining positive working relationships among teachers. The reality of these organizational challenges is particularly alarming, given that high turnover schools are more likely to serve low-income and minority students. The negative relationship between teacher turnover and school functioning, and the fact that turbulent schools are disproportionately likely to serve lowincome and minority students have important implications for both district and school-level policies. Specifically: Teacher turnover rates are one indicator of school health, which school districts should consider when focusing on school improvements. Districts need to begin by developing the means to identify individual schools that experience high levels of teacher turnover. Current district policies in implementing professional development for teachers in low-performing schools are inefficient when teachers do not remain in the schools in which they are trained. In order for low-performing schools to improve, districts need to consider providing incentive programs so that high quality teachers apply for, and remain in, these schools. Future research is needed to address the causal link between turnover, organizational functioning and student outcomes. Additionally, there is a need for research examining district policies that may facilitate teacher turnover within a district, including how districts place and transfer teachers, as well as how teachers’ salaries are budgeted.
Diagram calculus for a type affine $C$ Temperley--Lieb algebra, II
Dana C. Ernst
Mathematics , 2011,
Abstract: In a previous paper, we presented an infinite dimensional associative diagram algebra that satisfies the relations of the generalized Temperley--Lieb algebra having a basis indexed by the fully commutative elements of the Coxeter group of type affine $C$. We also provided an explicit description of a basis for the diagram algebra. In this paper, we show that the diagrammatic representation is faithful and establish a correspondence between the basis diagrams and the so-called monomial basis of the Temperley--Lieb algebra of type affine $C$.
Diagram calculus for a type affine $C$ Temperley--Lieb algebra, I
Dana C. Ernst
Mathematics , 2009,
Abstract: In this paper, we present an infinite dimensional associative diagram algebra that satisfies the relations of the generalized Temperley--Lieb algebra having a basis indexed by the fully commutative elements (in the sense of Stembridge) of the Coxeter group of type affine $C$. Moreover, we provide an explicit description of a basis for the diagram algebra. In the sequel to this paper, we show that this diagrammatic representation is faithful. The results of this paper and its sequel will be used to construct a Jones-type trace on the Hecke algebra of type affine $C$, allowing us to non-recursively compute leading coefficients of certain Kazhdan--Lusztig polynomials.
Cell Complexes for Arrangements with Group Actions
Dana C. Ernst
Mathematics , 2009,
Abstract: For a real oriented hyperplane arrangement, we show that the corresponding Salvetti complex is homotopy equivalent to the complement of the complexified arrangement. This result was originally proved by M. Salvetti. Our proof follows the framework of a proof given by L. Paris and relies heavily on the notation of oriented matroids. We also show that homotopy equivalence is preserved when we quotient by the action of the corresponding reflection group. In particular, the Salvetti complex of the braid arrangement in $\ell$ dimensions modulo the action of the symmetric group is a cell complex which is homotopy equivalent to the space of unlabelled configurations of $\ell$ distinct points. Lastly, we describe a construction of the orbit complex from the dual complex for all finite reflection arrangements in dimension 2. This description yields an easy derivation of the so-called "braid relations" in the case of braid arrangement.
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