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Medicine and Health Sciences

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2015

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Articles 601 - 607 of 607

Full-Text Articles in Physical Sciences and Mathematics

Spin-Exchange Optical Pumping At High Xenon Densities And Laser Fluxes: Principles And Practice, Boyd M. Goodson, Nicholas Whiting, Hayley Newton, Jason G. Skinner, Kaili Ranta, Panayiotis Nikolaou, Michael J. Barlow, Eduard Y. Chekmenev Dec 2014

Spin-Exchange Optical Pumping At High Xenon Densities And Laser Fluxes: Principles And Practice, Boyd M. Goodson, Nicholas Whiting, Hayley Newton, Jason G. Skinner, Kaili Ranta, Panayiotis Nikolaou, Michael J. Barlow, Eduard Y. Chekmenev

Nicholas Whiting

Once limited to the realm of fundamental physics experiments, hyperpolarized (HP) noble gases have been exploited for a wide range of applications across NMR and MRI. In most cases, hyperpolarized noble gases are prepared by spin-exchange optical pumping (SEOP)...

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Hyperpolarization Methods For Mrs, Boyd M. Goodson, Nicholas Whiting, Aaron M. Coffey, Panayiotis Nikolaou, Fan Shi, Brogan M. Gust, Maxwell E. Gemeinhardt, Roman Shchepin, Jason G. Skinner, Jonathan R. Birchall, Michael J. Barlow, Eduard Y. Chekmenev Dec 2014

Hyperpolarization Methods For Mrs, Boyd M. Goodson, Nicholas Whiting, Aaron M. Coffey, Panayiotis Nikolaou, Fan Shi, Brogan M. Gust, Maxwell E. Gemeinhardt, Roman Shchepin, Jason G. Skinner, Jonathan R. Birchall, Michael J. Barlow, Eduard Y. Chekmenev

Nicholas Whiting

This article covers the fundamental principles and practice of NMR hyperpolarization techniques, which are proving useful for in vivo magnetic resonance spectroscopy (MRS) studies of metabolism in animal models, and clinical trials with hyper-enhanced sensitivity. Fundamentally, hyperpolarization methods enhance nuclear spin polarization by orders-of-magnitude, resulting in concomitant improvement in NMR detection sensitivity. The hyperpolarization methods described here – dynamic nuclear polarization (DNP), para-hydrogen induced polarization (PHIP), signal amplification by reversible exchange (SABRE), and spin-exchange optical pumping (SEOP) – are capable of achieving nuclear spin polarization approaching the theoretical maximum of unity on nuclear spin sites of molecular or atomic agents …

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Quantile Rank Maps: A New Tool For Understanding Individual Brain Development, Huaihou Chen, Clare Kelly, F. Xavier Castellanos, Ye He, Xi-Nian Zuo, Philip T. Reiss Dec 2014

Quantile Rank Maps: A New Tool For Understanding Individual Brain Development, Huaihou Chen, Clare Kelly, F. Xavier Castellanos, Ye He, Xi-Nian Zuo, Philip T. Reiss

Philip T. Reiss

We propose a novel method for neurodevelopmental brain mapping that displays how an individual’s values for a quantity of interest compare with age-specific norms. By estimating smoothly age-varying distributions at a set of brain regions of interest, we derive age-dependent region-wise quantile ranks for a given individual, which can be presented in the form of a brain map. Such quantile rank maps could potentially be used for clinical screening. Bootstrap-based confidence intervals are proposed for the quantile rank estimates. We also propose a recalibrated Kolmogorov-Smirnov test for detecting group differences in the age-varying distribution. This test is shown to be …

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Cross-Validation And Hypothesis Testing In Neuroimaging: An Irenic Comment On The Exchange Between Friston And Lindquist Et Al., Philip T. Reiss Dec 2014

Cross-Validation And Hypothesis Testing In Neuroimaging: An Irenic Comment On The Exchange Between Friston And Lindquist Et Al., Philip T. Reiss

Philip T. Reiss

The “ten ironic rules for statistical reviewers” presented by Friston (2012) prompted a rebuttal by Lindquist et al. (2013), which was followed by a rejoinder by Friston (2013). A key issue left unresolved in this discussion is the use of cross-validation to test the significance of predictive analyses. This note discusses the role that cross-validation-based and related hypothesis tests have come to play in modern data analyses, in neuroimaging and other fields. It is shown that such tests need not be suboptimal and can fill otherwise-unmet inferential needs.

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Epidemiology Of Latency And Relapse In Plasmodium Vivax Malaria, Andrew A. Lover Dec 2014

Epidemiology Of Latency And Relapse In Plasmodium Vivax Malaria, Andrew A. Lover

Andrew Lover

Malaria is a major contributor to health burdens throughout the regions where it is endemic. Historically, it was believed that there was limited morbidity and essentially no mortality associated with Plasmodium vivax; however, evidence from diverse settings now suggests that infections with P. vivax can be both severe and fatal. This awareness has highlighted a critical gap: the vast majority of research has been directed towards P. falciparum, leading to a decades-long neglect of epidemiological and clinical studies of P. vivax. There exists a large body of historical data on human experimental infections with P. vivax; these studies in controlled …

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Considerations For Comprehensive Analyses Of Sporozoite-Based Controlled Human Malaria Infection Studies, Andrew A. Lover Dec 2014

Considerations For Comprehensive Analyses Of Sporozoite-Based Controlled Human Malaria Infection Studies, Andrew A. Lover

Andrew Lover

There has been renewed interest in the use of sporozoite-based approaches for controlled human malaria infections (CHMIs), and several sets of human challenge studies have recently completed. A study undertaken in Tanzania and published in 2014 found dose dependence between 10,000 and 25,000 sporozoite doses, as well as divergent times-to-parasitemia relative to earlier studies in European volunteers, with important implications for planning future studies. Analysis of time-to-event data has had extensive development in recent years, but these methods have had limited exposure outside biostatistics. Expansion of the published analyses to include recent methodological approaches optimized for the types of data …

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Short Report: Study Variability In Recent Human Challenge Experiments With Plasmodium Falciparum Sporozoites (Pfspz Challenge), Andrew A. Lover Dec 2014

Short Report: Study Variability In Recent Human Challenge Experiments With Plasmodium Falciparum Sporozoites (Pfspz Challenge), Andrew A. Lover

Andrew Lover

There has been renewed interest in the use of sporozoite-based approaches for malaria vaccination and controlled human infections, and several sets of human challenge studies have recently completed. A study undertaken in Tanzania and published in 2014 found dose-dependence between 10,000 and 25,000 sporozoite doses, as well as divergent times-to-parasitemia relative to earlier studies in European volunteers. However, this analysis shows that these conclusions are based upon suboptimal analytical methods; with more optimal analysis, there is no evidence for dose-dependence within this dose range; and more importantly, no evidence for differences in event times between Dutch and Tanzanian study sites. …

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