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Search Results: 1 - 10 of 429890 matches for " John M Miller "
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Principles of Electroanatomic Mapping
Deepak Bhakta,John M Miller
Indian Pacing and Electrophysiology Journal , 2008,
Abstract: Electrophysiologic testing and radiofrequency ablation have evolved as curative measures for a variety of rhythm disturbances. As experience in this field has grown, ablation is progressively being used to address more complex rhythm disturbances. Paralleling this trend are technological advancements to facilitate these efforts, including electroanatomic mapping (EAM). At present, several different EAM systems utilizing various technologies are available to facilitate mapping and ablation. Use of these systems has been shown to reduce fluoroscopic exposure and radiation dose, with less significant effects on procedural duration and success rates. Among the data provided by EAM are chamber reconstruction, tagging of important anatomic landmarks and ablation lesions, display of diagnostic and mapping catheters without using fluoroscopy, activation mapping, and voltage (or scar) mapping. Several EAM systems have specialized features, such as enhanced ability to map non-sustained or hemodynamically unstable arrhythmias, ability to display diagnostic as well as mapping catheter positions, and wide compatibility with a variety of catheters. Each EAM system has its strengths and weaknesses, and the system chosen must depend upon what data is required for procedural success (activation mapping, substrate mapping, cardiac geometry), the anticipated arrhythmia, the compatibility of the system with adjunctive tools (i.e. diagnostic and ablation catheters), and the operator's familiarity with the selected system. While EAM can offer significant assistance during an EP procedure, their incorrect or inappropriate application can substantially hamper mapping efforts and procedural success, and should not replace careful interpretation of data and strict adherence to electrophysiologic principles.
A quasi-experimental evaluation of an interpersonal communication intervention to increase insecticide-treated net use among children in Zambia
Keating Joseph,Hutchinson Paul,Miller John M,Bennett Adam
Malaria Journal , 2012, DOI: 10.1186/1475-2875-11-313
Abstract: Background This paper presents results from an evaluation of the effect of a community health worker (CHW) –based, interpersonal communication campaign (IPC) for increasing insecticide-treated mosquito net (ITN) use among children in Luangwa District, Zambia, an area with near universal coverage of ITNs and moderate to low malaria parasite prevalence. Methods A quasi-experimental community randomized control trial was conducted from 2008 to 2010. CHWs were the unit of randomization. Cross-sectional data were collected from houses in both 2008 and 2010 using simple random sampling of a complete household enumeration of the district. A difference-in -differences approach was used to analyse the data. Results ITN use among children <5 years old in households with ≥1 ITN increased overall from 54% in 2008 to 81% in 2010 (χ2 = 96.3, p <0.01); however, there was no difference in increase between the treatment and control arms in 2010 (p >0.05). ITN use also increased among children five to 14 years old from 37% in 2008 to 68% in 2010. There was no indication that the CHW-based intervention activities had a significant effect on increasing ITN use in this context, over and above what is already being done to disseminate information on the importance of using an ITN to prevent malaria infection. Discussion ITN use increased dramatically in the district between 2008 and 2010. It is likely that IPC activities in general may have contributed to the observed increase in ITN use, as the increased observed in this study was far higher than the increase observed between 2008 and 2010 malaria indicator survey (MIS) estimates. Contamination across control communities, coupled with linear settlement patterns and subsequent behavioural norms related to communication in the area, likely contributed to the observed increase in net use and null effect in this study.
Association between early childhood exposure to malaria and children’s pre-school development: evidence from the Zambia early childhood development project
Fink Günther,Olgiati Analia,Hawela Moonga,Miller John M
Malaria Journal , 2013, DOI: 10.1186/1475-2875-12-12
Abstract: Background Despite major progress made over the past 10 years, malaria remains one of the primary causes of ill health in developing countries in general, and in sub-Saharan Africa in particular. Whilst a large literature has documented the frequency and severity of malaria infections for children under-five years, relatively little evidence is available regarding the impact of early childhood malaria exposure on subsequent child development. Methods The objective of the study was to assess the associations between early childhood exposure to malaria and pre-school development. Child assessment data for 1,410 children in 70 clusters collected through the 2010 Zambian Early Childhood Development Project was linked with malaria parasite prevalence data from the 2006 Zambia Malaria Indicator Survey. Linear and logistic models were used to estimate the effect of early childhood exposure to malaria on anthropometric outcomes as well as on a range of cognitive and behavioural development measures. Results No statistically significant associations were found between parasite exposure and children’s height and weight. Exposure to the malaria parasite was, however, associated with lower ability to cope with cognitive tasks administered by interviewers (z-score difference 1.11, 95% CI 2.43–0.20), as well as decreased overall socio-emotional development as assessed by parents (z-score difference 1.55, 95% CI 3.13–0.02). No associations were found between malaria exposure and receptive vocabulary or fine-motor skills. Conclusions The results presented in this paper suggest potentially large developmental consequences of early childhood exposure to malaria. Continued efforts to lower the burden of malaria will not only reduce under-five mortality, but may also have positive returns in terms of the long-term well-being of exposed cohorts.
Warm Absorbers and Outflows in the Seyfert-1 Galaxy NGC 4051
Ashley L. King,Jon M. Miller,John Raymond
Physics , 2011, DOI: 10.1088/0004-637X/746/1/2
Abstract: We present both phenomenological and more physical photoionization models of the Chandra HETG spectra of the Seyfert-1 AGN NGC 4051. We detect 40 absorption and emission lines, encompassing highly ionized charge states from O, Ne, Mg, Si, S and the Fe L-shell and K-shell. Two independent photoionization packages, XSTAR and Cloudy, were both used to self-consistently model the continuum and line spectra. These fits detected three absorbing regions in this system with densities ranging from 10^{10} to 10^{11} cm^{-3}. In particular, our XSTAR models require three components that have ionization parameters of log \xi = 4.5, 3.3, & 1.0, and are located within the BLR at 70, 300, and 13,000 R_g, respectively, assuming a constant wind density. Larger radii are inferred for density profiles which decline with radius. The Cloudy models give a similar set of parameters with ionization parameters of log \xi = 5.0, 3.6, & 2.2 located at 40, 200, and 3,300 R_g. We demonstrate that these regions are out-flowing from the system, and carry a small fraction of material out of the system relative to the implied mass accretion rate. The data suggest that magnetic fields may be an important driving mechanism.
The Stability of a Stochastic CaMKII Switch: Dependence on the Number of Enzyme Molecules and Protein Turnover
Paul Miller,Anatol M. Zhabotinsky,John E. Lisman,Xiao-Jing Wang
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0030107
Abstract: Molecular switches have been implicated in the storage of information in biological systems. For small structures such as synapses, these switches are composed of only a few molecules and stochastic fluctuations are therefore of importance. Such fluctuations could potentially lead to spontaneous switch reset that would limit the lifetime of information storage. We have analyzed a model of the calcium/calmodulin-dependent protein kinase II (CaMKII) switch implicated in long-term memory in the nervous system. The bistability of this switch arises from autocatalytic autophosphorylation of CaMKII, a reaction that is countered by a saturable phosphatase-1-mediated dephosphorylation. We sought to understand the factors that control switch stability and to determine the functional relationship between stability and the number of molecules involved. Using Monte Carlo simulations, we found that the lifetime of states of the switch increase exponentially with the number of CaMKII holoenzymes. Switch stability requires a balance between the kinase and phosphatase rates, and the kinase rate must remain high relative to the rate of protein turnover. Thus, a critical limit on switch stability is set by the observed turnover rate (one per 30 h on average). Our computational results show that, depending on the timescale of fluctuations in enzyme numbers, for a switch composed of about 15 CaMKII holoenzymes, the stable persistent activation can span from a few years to a human lifetime.
Payer leverage and hospital compliance with a benchmark: a population-based observational study
John M Hollingsworth, Sarah L Krein, David C Miller, Sonya DeMonner, Brent K Hollenbeck
BMC Health Services Research , 2007, DOI: 10.1186/1472-6963-7-112
Abstract: Nationally representative discharge data for kidney (n = 29,272), liver (n = 7,988), heart (n = 3,530), and lung (n = 1,880) transplants from the Nationwide Inpatient Sample (1993 – 2003) were employed. Logistic regression techniques with robust variance estimators were used to examine the relationship between hospital volume compliance and Medicare market share; generalized estimating equations were used to explore the association between patient-level operative mortality and hospital volume compliance.Medicare's transplant market share varied by organ [57%, 28%, 27%, and 18% for kidney, lung, heart, and liver transplants, respectively (P < 0.001)]. Volume-based benchmark compliance varied by transplant type [85%, 75%, 44%, and 39% for kidney, liver, heart, and lung transplants, respectively (P < 0.001)], despite a lower odds of operative mortality at compliant hospitals. Adjusting for organ supply, high market leverage was independently associated with compliance at hospitals transplanting kidneys (OR, 143.00; 95% CI, 18.53 – 1103.49), hearts (OR, 2.84; 95% CI, 1.51 – 5.34), and lungs (OR, 3.24; 95% CI, 1.57 – 6.67).These data highlight the influence of payer leverage–an important contextual factor in value-based purchasing initiatives. For uncommon diagnoses, these data suggest that at least 30% of a provider's patients might need to be "at risk" for an incentive to motivate compliance.Recently, an article in the Los Angeles Times cited that "about a fifth of federally funded (heart, liver, and lung) transplant programs fail to meet the government's minimum standards" and "perform too few operations to ensure competency" [1]. After being picked up by the Associated Press and several other major media outlets, the Times' article garnered the attention of Senator Charles Grassley (Chairman of the Senate Finance Committee), prompting him to begin a federal inquiry. Senator Grassley "has ordered investigations (and) demanded answers after ... reports detailing danger
Ovipositional periodicity of caged Anopheles gambiae individuals
Megan L Fritz, Juan Huang, Edward D Walker, M Nabie Bayoh, John Vulule, James R Miller
Journal of Circadian Rhythms , 2008, DOI: 10.1186/1740-3391-6-2
Abstract: Battery-powered wall clocks were modified so as to present a unique section of dark and wet ovipositional substrate at hourly intervals over two consecutive 12 h periods. Ovipositional periodicity of mosquito groups (Kisumu laboratory strain or feral females) and individuals was determined by counting the number of eggs present on each section of the ovipositional substrate. Capacity for mid-afternoon oviposition by groups of Kisumu laboratory strain A. gambiae was determined by presenting hypergravid females with an ovipositional substrate exclusively between 1200 and 1600 h.On equatorial time, caged laboratory strain A. gambiae groups deposited 65% of their total eggs between 1800 and 0 h, and the remaining 35% were spread between 0 and 1000 h. Caged house-collected A. gambiae groups deposited 74% of their total eggs between 1800 and 200 h, ceased oviposition for 3 h, and then spread the remaining 26% of their eggs near or after dawn. Ninety-six percent of individual A. gambiae females spread their eggs over a continuous 2–4 h period without interruption. In tests of capacity for mid-afternoon oviposition, females given evening access to an ovipositional resource deposited 2% of their total eggs between 1200 and 1700 h. A. gambiae females given only access to an ovipositional resource between 1200 and 1700 h deposited 3 times more eggs during that time period than did females previously given evening access.Confined individual A. gambiae oviposit in a single ca. 2–4 h continuous bout per 24 h. Oviposition is most probable in early scotophase, mid scotophase, or early photophase. However, some oviposition can occur at any hour during 24 h, especially if females were previously deprived of ovipositional substrate.Diel ovipositional patterns have been studied in various Diptera, including Drosophila melanogaster [1-4], D. pseudoobscura [5], Delia antiqua [6], Chrysomya bezziana [7], Aedes aegypti [8], Anopheles albimanus [9], A. freeborni [9], A. albitarsis [10] and
A novel method to detect unlabeled inorganic nanoparticles and submicron particles in tissue by sedimentation field-flow fractionation
Cassandra E Deering, Soheyl Tadjiki, Shoeleh Assemi, Jan D Miller, Garold S Yost, John M Veranth
Particle and Fibre Toxicology , 2008, DOI: 10.1186/1743-8977-5-18
Abstract: Laboratory nanoparticles that have been labeled by fluorescence, radioactivity, or rare elements have provided important information regarding nanoparticle uptake and translocation, but most nanomaterials that are commercially produced for industrial and consumer applications do not contain a specific label.Both nitric acid digestion and enzyme digestion were tested with liver and lung tissue as well as with cultured cells. Tissue processing with a mixture of protease enzymes is preferred because it is applicable to a wide range of particle compositions. Samples were visualized via fluorescence microscopy and transmission electron microscopy to validate the SdFFF results. We describe in detail the tissue preparation procedures and discuss method sensitivity compared to reported levels of nanoparticles in vivo.Tissue digestion and SdFFF complement existing techniques by precisely identifying unlabeled metal oxide nanoparticles and unambiguously distinguishing nanoparticles (diameter<100 nm) from both soluble compounds and from larger particles of the same nominal elemental composition. This is an exciting capability that can facilitate epidemiological and toxicological research on natural and manufactured nanomaterials.The toxicology of nano-sized (diameter < 100 nm) particles is a topic of current interest because there have been rapid advances in the synthesis of novel nanomaterials for research, consumer, and industrial applications. Recent reviews have discussed nanoparticle health effects [1,2]. The growing evidence of adverse health effects from exposure to incidentally produced ultrafine particles from combustion and atmospheric processes motivates concern about manufactured nanomaterials. There is epidemiological evidence for cardiovascular effects of ambient ultrafine particulate matter (PM) [3]. Indications that inhaled particles can translocate to the other organs [4] suggest a link between nanoparticles and neurodegenerative diseases [5] and other systemi
The Stability of a Stochastic CaMKII Switch: Dependence on the Number of Enzyme Molecules and Protein Turnover
Miller Paul,Zhabotinsky Anatol M,Lisman John E,Wang Xiao-Jing
PLOS Biology , 2005, DOI: 10.1371/journal.pbio.0030107.20050521
Abstract: Molecular switches have been implicated in the storage of information in biological systems. For small structures such as synapses, these switches are composed of only a few molecules and stochastic fluctuations are therefore of importance. Such fluctuations could potentially lead to spontaneous switch reset that would limit the lifetime of information storage. We have analyzed a model of the calcium/calmodulin-dependent protein kinase II (CaMKII) switch implicated in long-term memory in the nervous system. The bistability of this switch arises from autocatalytic autophosphorylation of CaMKII, a reaction that is countered by a saturable phosphatase-1-mediated dephosphorylation. We sought to understand the factors that control switch stability and to determine the functional relationship between stability and the number of molecules involved. Using Monte Carlo simulations, we found that the lifetime of states of the switch increase exponentially with the number of CaMKII holoenzymes. Switch stability requires a balance between the kinase and phosphatase rates, and the kinase rate must remain high relative to the rate of protein turnover. Thus, a critical limit on switch stability is set by the observed turnover rate (one per 30 h on average). Our computational results show that, depending on the timescale of fluctuations in enzyme numbers, for a switch composed of about 15 CaMKII holoenzymes, the stable persistent activation can span from a few years to a human lifetime.
Measuring Disease Severity in Duchenne and Becker Muscular Dystrophy
Melinda F. Davis,Katalin H. Scherer,Timothy M. Miller,F. John Meaney
Journal of Methods and Measurement in the Social Sciences , 2010,
Abstract: Medical investigations use a wide variety of outcome indicators that are often not comparable. It can be challenging to integrate results across multiple studies that do not share a common metric. Some conditions such as Duchenne and Becker muscular dystrophy have a predictable course of disease progression. Severity can be inferred from a patient's medical history. This paper describes the development of a disease severity measure using common markers of disease progression. Rasch modeling was used to estimate severity using dichotomous events that indicate disease progression. Caregivers of 34 young men with Duchenne or Becker muscular dystrophy completed structured interviews about their care and medical history. Interview questions included surgeries (tendon release, scoliosis, tracheostomy), respiratory equipment (assisted ventilation, cough assist devices), and the use of other medical equipment (e.g., braces, walkers, wheelchairs, transfer boards, hospital beds). The resulting measure had a reliability of .83. The correlation between the severity measure and the Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS) was .68. Preliminary results and item calibrations are provided for the severity measure that can be estimated from caregiver reports or administrative data.
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