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Search Results: 1 - 10 of 23670 matches for " Paul Milligan "
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Using fractional differentiation in astronomy
Amelia Carolina Sparavigna,Paul Milligan
Physics , 2009,
Abstract: In a recent paper, published at arXiv:0910.2381, we started a discussion on the new possibilities arising from the use of fractional differential calculus in image processing. We have seen that the fractional calculation is able to enhance the quality of images, with interesting possibilities in edge detection and image restoration. Here, we want to discuss more deeply its role as a tool for the processing of astronomical images. In particular, the fractional differentiation can help produce a 'content-matter' based image from a pretty astronomical image that can be used for more research and scientific purposes, for instance to reveal faint objects galactic matter, nebulosity, more stars and planetary surface detail.
Surplus Photosynthetic Antennae Complexes Underlie Diagnostics of Iron Limitation in a Cyanobacterium
Paul S. Schrader,Allen J. Milligan,Michael J. Behrenfeld
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018753
Abstract: Chlorophyll fluorescence from phytoplankton provides a tool to assess iron limitation in the oceans, but the physiological mechanism underlying the fluorescence response is not understood. We examined fluorescence properties of the model cyanobacterium Synechocystis PCC6803 and a ΔisiA knock-out mutant of the same species grown under three culture conditions which simulate nutrient conditions found in the open ocean: (1) nitrate and iron replete, (2) limiting-iron and high-nitrate, representative of natural high-nitrate, low-chlorophyll regions, and (3) iron and nitrogen co-limiting. We show that low variable fluorescence, a key diagnostic of iron limitation, results from synthesis of antennae complexes far in excess of what can be accommodated by the iron-restricted pool of photosynthetic reaction centers. Under iron and nitrogen co-limiting conditions, there are no excess antennae complexes and variable fluorescence is high. These results help to explain the well-established fluorescence characteristics of phytoplankton in high-nutrient, low-chlorophyll ocean regions, while also accounting for the lack of these properties in low-iron, low-nitrogen regions. Importantly, our results complete the link between unique molecular consequences of iron stress in phytoplankton and global detection of iron stress in natural populations from space.
An epidemiological study of RSV infection in the Gambia
Weber Martin W.,Milligan Paul,Sanneh Mariama,Awemoyi Agnes
Bulletin of the World Health Organization , 2002,
Abstract: OBJECTIVE: To describe the epidemiology of respiratory syncytial virus (RSV) infection in a developing country. METHODS: The work was carried out in three hospitals for primary cases and in the community for secondary cases in the western region of the Gambia, West Africa. RSV infection was diagnosed by immunofluorescence of nasopharyngeal aspirate samples in children younger than two years admitted to hospital with acute lower respiratory infection (ALRI). Routine records of all children with ALRI were analysed, and the incidence rates of ALRI, severe RSV-associated respiratory illness and hypoxaemic RSV infections were compared. A community-based study was undertaken to identify secondary cases and to obtain information about spread of the virus. FINDINGS: 4799 children with ALRI who were younger than two years and lived in the study area were admitted to the study hospitals: 421 had severe RSV-associated respiratory illness; 55 of these were hypoxaemic. Between 1994 and 1996, the observed incidence rate for ALRI in 100 children younger than one year living close to hospital was 9.6 cases per year; for severe RSV-associated respiratory illness 0.83; and for hypoxaemic RSV-associated respiratory illness 0.089. The proportion of all ALRI admissions due to RSV was 19%. Overall, 41% of children younger than five years in compounds in which cases lived and 42% in control compounds had evidence of RSV infection during the surveillance period. CONCLUSION: RSV is an important cause of ALRI leading to hospital admission in the Gambia. Morbidity is considerable and efforts at prevention are worthwhile.
A Randomised Trial to Compare the Safety, Tolerability and Efficacy of Three Drug Combinations for Intermittent Preventive Treatment in Children
Kalifa Bojang,Francis Akor,Ousman Bittaye,David Conway,Christian Bottomley,Paul Milligan,Brian Greenwood
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0011225
Abstract: Results from trials of intermittent preventive treatment (IPT) in infants and children have shown that IPT provides significant protection against clinical malaria. Sulfadoxine-pyrimethamine (SP) given alone or in combination with other drugs has been used for most IPT programmes. However, SP resistance is increasing in many parts of Africa. Thus, we have investigated whether SP plus AQ, SP plus piperaquine (PQ) and dihydroartemisinin (DHA) plus PQ might be equally safe and effective when used for IPT in children in an area of seasonal transmission.
Study protocol for a three-armed randomized controlled trial to assess whether house screening can reduce exposure to malaria vectors and reduce malaria transmission in The Gambia
Matthew J Kirby, Paul J Milligan, David J Conway, Steve W Lindsay
Trials , 2008, DOI: 10.1186/1745-6215-9-33
Abstract: A 3-armed randomised-controlled trial will be conducted in and around Farafenni town in The Gambia, West Africa, to assess whether screening windows, doors and closing eaves or installing netting ceilings in local houses can substantially reduce malaria transmission and anaemia compared to homes with no screening. Eligible houses will be sorted and stratified by location and the number of children in each house, then randomly allocated to the interventions in blocks of 5 houses (2 with full screening, 2 with screened ceilings and 1 control house without screening). Risk of malaria transmission will be assessed in each house by routine collections of mosquitoes using light traps and an anaemia prevalence study in children at the end of the main transmission period.Practical issues concerning intervention implementation, as well as the potential benefits and risks of the study, are discussed.ISRCTN51184253 – Screening-homes to prevent malariaMalaria remains one of the greatest childhood killers in the world[1] and is a substantial obstacle to social and economic development[2]. We know from historical accounts that in the early 1900s malaria was controlled using environmental management (EM) for vector control in many parts of the tropics [3-5]. EM was effective and sustainable in controlling and eradicating malaria, but was forgotten during the DDT campaigns of the 1950s and 1960s. Today most control tools rely exclusively on chemicals (anti-malarial drugs and insecticides), not on environmental modifications, nor on strengthened social systems to perform effective environmental manipulation. Whilst drugs and insecticides are extremely effective weapons, their initial promise has been compromised by the development of resistance [6-10] and growing concerns about long-term environmental impacts[11]. It is therefore of considerable strategic importance to reduce our dependency on antimalarials and insecticides by developing effective and sustainable methods of control.
Gametocytaemia after Drug Treatment of Asymptomatic Plasmodium falciparum
Samuel Dunyo, Paul Milligan, Tansy Edwards, Colin Sutherland, Geoffrey Targett, Margaret Pinder
PLOS ONE , 2006, DOI: 10.1371/journal.pctr.0010020
Abstract: Objectives Treatment of Plasmodium falciparum malaria with sulfadoxine-pyrimethamine (SP) is followed by a sharp rise in the prevalence and density of gametocytes. We did a randomized trial to determine the effect of treatment of asymptomatic infections with SP or SP plus one dose of artesunate (SP+AS) on gametocyte carriage. Design The study was a three-arm open-label randomized trial. We randomized asymptomatic carriers of P. falciparum to receive antimalarial treatment or placebo, and recorded the prevalence and density of gametocytes over the next 2 mo. Setting The trial was conducted during the dry (low malaria transmission) season in four rural villages in Gambia. Participants Participants were adults and children aged over 6 mo with asexual P. falciparum infection and confirmed free of clinical symptoms of malaria over a 2-d screening period. Interventions Participants were randomized to receive a single dose of SP or SP+AS or placebo. Outcome Measures The outcome measures were the presence of gametocytes 7 and 56 d after treatment, and the duration and density of gametocytaemia over 2 mo. Results In total, 372 asymptomatic carriers were randomized. Gametocyte prevalence on day 7 was 10.5% in the placebo group, 11.2% in the SP group (risk difference to placebo 0.7%, 95% confidence interval ?7.4% to 8.7%, p = 0.87), and 7.1% in the SP+AS group (risk difference to placebo 4.1%, 95% confidence interval ?3.3% to 12%, p = 0.28). By day 56, gametocyte prevalence was 13% in the placebo group and 2% in both drug-treated groups. Gametocyte carriage (the area under the curve of gametocyte density versus time), was reduced by 71% in the SP group, and by 74% in the SP+AS group, compared to placebo. Gametocyte carriage varied with age and was greater among children under 15 than among adults. Conclusions Treatment of asymptomatic carriers of P. falciparum with SP does not increase gametocyte carriage or density. Effective treatment of asexual parasitaemia in the dry season reduces gametocyte carriage to very low levels after 4 wk. Trial Registration ClinicalTrials.gov NCT00289250
Duration of Protection against Malaria and Anaemia Provided by Intermittent Preventive Treatment in Infants in Navrongo, Ghana
Matthew Cairns, Ilona Carneiro, Paul Milligan, Seth Owusu-Agyei, Timothy Awine, Roly Gosling, Brian Greenwood, Daniel Chandramohan
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002227
Abstract: Background Intermittent preventive treatment for malaria in Infants (IPTi) has been shown to give effective and safe protection against malaria. It has been suggested that IPTi might have long-lasting beneficial effects but, in most settings, the protection provided by IPTi appears to be short-lived. Knowledge of the duration of protection given by IPTi would help interpret the results of existing trials and suggest optimal delivery schedules for IPTi. This study investigated how the protective efficacy of IPTi against malaria and anaemia changes over time. Methods and Findings A secondary analysis of data from a cluster-randomised, placebo-controlled trial of IPTi using sulfadoxine-pyrimethamine (SP) in Ghana was conducted. In this trial IPTi was given to 2485 infants at 3, 4, 9 and 12 months of age; children remained in follow-up until two years of age. Poisson regression with a random effect to adjust for the cluster-randomised design was used to determine protective efficacy of IPTi against clinical malaria and anaemia in defined time strata following administration of IPTi. Analysis of first-or-only clinical malaria episode following the individual IPTi doses showed that some protection against malaria lasted between 4 to 6 weeks. A similar pattern was seen when the incidence of all malaria episodes up to 2 years of age was analysed in relation to the most recent IPT, by pooling the incidence of malaria after the individual IPTi doses. Protective efficacy within four weeks of IPTi was 75.2% (95% CI: 66–82) against malaria, 78.9% (95% CI: 69–86) against high parasite density malaria, and 93.8% (95% CI: 73–99) against anaemia. Protection against these outcomes was short-lived, with evidence of any effect lasting for only 6, 6 and 4 weeks respectively. Protection in children who were parasitaemic when receiving IPTi appeared to be of shorter duration than in uninfected children. There was no evidence of any benefit of IPTi after the immediate period following the IPTi doses. Conclusions Intermittent preventive treatment provides considerable protection against malaria and anaemia for short periods, even in an area of intense seasonal transmission. Due to the relatively short duration of protection provided by each dose of IPTi, this treatment will be of most benefit when delivered at the time of peak malaria incidence.
A trial of intermittent preventive treatment and home-based management of malaria in a rural area of The Gambia
Sanie Sesay, Paul Milligan, Ensa Touray, Maimuna Sowe, Emily L Webb, Brian M Greenwood, Kalifa A Bojang
Malaria Journal , 2011, DOI: 10.1186/1475-2875-10-2
Abstract: During the 2008 malaria transmission season, 1,277 children under five years of age resident in villages within the rural Farafenni demographic surveillance system (DSS) in North Bank Region, The Gambia were randomized to receive monthly IPTc with a single dose of sulphadoxine/pyrimethamine (SP) plus three doses of amodiaquine (AQ) or SP and AQ placebos given by village health workers (VHWs) on three occasions during the months of September, October and November, in a double-blind trial. Children in all study villages who developed an acute febrile illness suggestive of malaria were treated by VHWs who had been taught how to manage malaria with artemether-lumefantrine (Coartem?). The primary aims of the project were to determine whether IPTc added significant benefit to HMM and whether VHWs could effectively combine the delivery of both interventions.The incidence of clinical attacks of malaria was very low in both study groups. The incidence rate of malaria in children who received IPTc was 0.44 clinical attacks per 1,000 child months at risk while that for control children was 1.32 per 1,000 child months at risk, a protective efficacy of 66% (95% CI -23% to 96%; p = 0.35). The mean (standard deviation) haemoglobin concentration at the end of the malaria transmission season was similar in the two treatment groups: 10.2 (1.6) g/dL in the IPTc group compared to 10.3 (1.5) g/dL in the placebo group. Coverage with IPTc was high, with 94% of children receiving all three treatments during the study period.Due to the very low incidence of malaria, no firm conclusion can be drawn on the added benefit of IPTc in preventing clinical episodes of malaria among children who had access to HMM in The Gambia. However, the study showed that VHWs can successfully combine provision of HMM with provision of IPTc.ClinicalTrials.gov NCT00944840Although the incidence of malaria appears to be declining in a number of African countries, it remains an important cause of mortality and morbid
Risk factors for house-entry by malaria vectors in a rural town and satellite villages in The Gambia
Matthew J Kirby, Clare Green, Paul M Milligan, Charalambos Sismanidis, Momadou Jasseh, David J Conway, Steven W Lindsay
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-2
Abstract: Mosquitoes were sampled using CDC light traps in 976 houses, each on one night, in Farafenni town and surrounding villages during the malaria-transmission season in The Gambia. Catches from individual houses were both (a) left unadjusted and (b) adjusted relative to the number of mosquitoes caught in four sentinel houses that were operated nightly throughout the period, to allow for night-to-night variation. Houses were characterized by location, architecture, human occupancy and their mosquito control activities, and the number and type of domestic animals within the compound.106,536 mosquitoes were caught, of which 55% were Anopheles gambiae sensu lato, the major malaria vectors in the region. There were seven fold higher numbers of An. gambiae s.l. in the villages (geometric mean per trap night = 43.7, 95% confidence intervals, CIs = 39.5–48.4) than in Farafenni town (6.3, 5.7–7.2) and significant variation between residential blocks (p < 0.001). A negative binomial multivariate model performed equally well using unadjusted or adjusted trap data. Using the unadjusted data the presence of nuisance mosquitoes was reduced if the house was located in the town (odds ratio, OR = 0.11, 95% CIs = 0.09–0.13), the eaves were closed (OR = 0.71, 0.60–0.85), a horse was tethered near the house (OR = 0.77, 0.73–0.82), and churai, a local incense, was burned in the room at night (OR = 0.56, 0.47–0.66). Mosquito numbers increased per additional person in the house (OR = 1.04, 1.02–1.06) or trapping room (OR = 1.19, 1.13–1.25) and when the walls were made of mud blocks compared with concrete (OR = 1.44, 1.10–1.87).This study demonstrates that the risk of malaria transmission is greatest in rural areas, where large numbers of people sleep in houses made of mud blocks, where the eaves are open, horses are not tethered nearby and where churai is not burnt at night. These factors need to be considered in the design and analysis of intervention studies designed to reduce malaria trans
Estimating and Analyzing Demographic Models Using the popbio Package in R
Chris Stubben,Brook Milligan
Journal of Statistical Software , 2007,
Abstract: A complete assessment of population growth and viability from field census data often requires complex data manipulations, statistical routines, mathematical tools, programming environments, and graphical capabilities. We therefore designed an R package called popbio to facilitate both the construction and analysis of projection matrix models. The package consists primarily of the R translation of MATLAB code found in Caswell (2001) and Morris and Doak (2002) for the analysis of projection matrix models. The package also includes methods to estimate vital rates and construct projection matrix models from census data typically collected in plant demography studies. In these studies, vital rates can often be estimated directly from annual censuses of tagged individuals using transition frequency tables. Because the construction of projection matrix models requires careful management of census data, we describe the steps to construct a projection matrix in detail.
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