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Tao, S,Trzasko, J D,Gunter, J L,Weavers, P T,Shu, Y,Huston III, J,Lee, S K,Tan, E T,Bernstein, M A Institute of Physics in association with the Ameri 2017 Physics in medicine & biology Vol.62 No.2
<P>Due to engineering limitations, the spatial encoding gradient fields in conventional magnetic resonance imaging cannot be perfectly linear and always contain higher-order, nonlinear components. If ignored during image reconstruction, gradient nonlinearity (GNL) manifests as image geometric distortion. Given an estimate of the GNL field, this distortion can be corrected to a degree proportional to the accuracy of the field estimate. The GNL of a gradient system is typically characterized using a spherical harmonic polynomial model with model coefficients obtained from electromagnetic simulation. Conventional whole-body gradient systems are symmetric in design; typically, only odd-order terms up to the 5th-order are required for GNL modeling. Recently, a high-performance, asymmetric gradient system was developed, which exhibits more complex GNL that requires higher-order terms including both odd- and even-orders for accurate modeling. This work characterizes the GNL of this system using an iterative calibration method and a fiducial phantom used in ADNI (Alzheimer’s Disease Neuroimaging Initiative). The phantom was scanned at different locations inside the 26 cm diameter-spherical-volume of this gradient, and the positions of fiducials in the phantom were estimated. An iterative calibration procedure was utilized to identify the model coefficients that minimize the mean-squared-error between the true fiducial positions and the positions estimated from images corrected using these coefficients. To examine the effect of higher-order and even-order terms, this calibration was performed using spherical harmonic polynomial of different orders up to the 10th-order including even- and odd-order terms, or odd-order only. The results showed that the model coefficients of this gradient can be successfully estimated. The residual root-mean-squared-error after correction using up to the 10th-order coefficients was reduced to 0.36 mm, yielding spatial accuracy comparable to conventional whole-body gradients. The even-order terms were necessary for accurate GNL modeling. In addition, the calibrated coefficients improved image geometric accuracy compared with the simulation-based coefficients.</P>
Shannon Weaver,Zainub Hussaini,Virginia Lynn Valentin,Samin Panahi,Sarah Elizabeth Levitt,Jeanie Ashby,Akiko Kamimura 한국보건의료인국가시험원 2019 보건의료교육평가 Vol.16 No.-
Volunteering at a free clinic may influence career choice among health profession students. The purpose of this study was to explore knowledge, skills, attitudes, self-efficacy, interest in future work with the underserved, and interest in primary care among physician assistant (PA) students through an analysis of demographic characteristics of PA students at a student-run free clinic in the United States. Data were collected from 56 PA students through a quantitative survey in October 2018 after their participation at a student-run free clinic in Salt Lake City, Utah, in the intermountain west region of the USA. Out of the 3 sub-scales (attitudes, effect, and readiness), students responded most positively to items exploring the effect of their experiences of volunteering at the free clinic. Students who spoke Spanish showed higher levels of self-efficacy and readiness for a future career than non-Spanish speakers.
New Era Nutrition and Food Research is Leading Us Beyond Essential Nutrients
Connie M. Weaver 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10
Dietary guidance and nutrient recommendations have traditionally been based on meeting essential nutrient needs to prevent nutrient deficiencies. The explosion of interest in bioactive constituents and functional foods for promoting health and resiliency to prevent chronic disease is raising questions about what kind of research is needed to create a rigorous evidence based for setting food guidance policy and what the process should be for developing the policies. A chronic disease risk reduction category was developed and applied first to sodium and potassium. A Dietary Reference Intake-type proposed process for bioactive foods and beverages was recently developed. Best practices for designing and conducting human nutrition clinical trials were published in a series of articles in Advances in Nutrition in 2020 and 2021. Key elements will be highlighted from our dose response randomized, controlled trial of blueberries and bone health in postmenopausal women that will be featured in Frontiers in Nutrition. New tools for identifying biomarkers of exposure and outcome measures are launching an era of personalized nutrition.
In Vitro Transcription Analysis of Autographa californica Nuclear Polyhedrosis Virus Genes
HUH, NAM-EUNG,WEAVER, ROVERT F. 한국미생물 · 생명공학회 1994 Journal of microbiology and biotechnology Vol.4 No.3
Cell-free extracts prepared from cultured insect cells, Spodoptera frugiperda, were analyzed for activation of early gene transcription of an insect baculovirus, Autographa californica nuclear polyhedrosis virus (AcNPV). The template DNA used for in vitro transcription assays contained promoter sites for the baculovirus genes that have been classified as immediate early (α) or early genes. These genes are located in the HindⅢ-K/Q region of the AcNPV genome. Nuclei isolated from the AcNPV-infected Spodoptera frugiperda cells were also used for in vitro transcription analysis by RNase-mapping the Labeled RNA synthesized from in vitro run-on reaction in the isolated nuclei. The genes studied by this technique were p26 and p10 genes which were classified as delayed early and late gene, respectively. We found that transcription of the genes from the HindⅢ-K region was accurately initiated and unique in the whole cell extract obtained from uninfected cells, although abundance of the in vitro transcripts was reverse to that of in vivo RNA. With isolated nuclei transcription of the p26 gene was inhibited by α-amanitin suggesting that the p26 gene was transcribed by host RNA polymerase Ⅱ. However, transcription of the p10 gene in isolated nuclei was not inhibited by α-amanitin, but rather stimulated by the inhibitor. We also found that the synthesis of α-amanitin-resistant RNA polymerase was begun before 6 hr p.i., the time point at which the onset of viral DNA replication as well as the appearance of α-amanitin-resistant viral transcripts were detected. These studies give us strong evidence to support the previous data that early genes of AcNPV were transcribed by host RNA polymerease Ⅲ, while transcription of late genes was mediated at least by a novel α-amanitin-resistant RNA polymerase.
HUBBLE SPACE TELESCOPE INVESTIGATION OF MAIN-BELT COMET 133P/ELST-PIZARRO
Jewitt, David,Ishiguro, Masateru,Weaver, Harold,Agarwal, Jessica,Mutchler, Max,Larson, Steven American Institute of Physics 2014 The Astronomical journal Vol.147 No.5
<P>We report new observations of the prototype main-belt comet (active asteroid) 133P/Elst-Pizarro taken at high angular resolution using the Hubble Space Telescope. The object has three main components: (1) a point-like nucleus; (2) a long, narrow antisolar dust tail; and (3) a short, sunward anti-tail. There is no resolved coma. The nucleus has a mean absolute magnitude H<SUB>V</SUB> = 15.70 ± 0.10 and a light curve range ΔV = 0.42 mag, the latter corresponding to projected dimensions 3.6 × 5.4 km (axis ratio 1.5:1) at the previously measured geometric albedo of 0.05 ± 0.02. We explored a range of continuous and impulsive emission models to simultaneously fit the measured surface brightness profile, width, and position angle of the antisolar tail. Preferred fits invoke protracted emission, over a period of 150 days or less, of dust grains following a differential power-law size distribution with index 3.25 ≤q ≤ 3.5 and with a wide range of sizes. Ultra-low surface brightness dust projected in the sunward direction is a remnant from emission activity occurring in previous orbits, and consists of the largest (≥cm-sized) particles. Ejection velocities of one-micron-sized particles are comparable to the ~1.8 m s<SUP>–1</SUP> gravitational escape speed of the nucleus, while larger particles are released at speeds less than the gravitational escape velocity. The observations are consistent with, but do not prove, a hybrid hypothesis in which mass loss is driven by gas drag from the sublimation of near-surface water ice, but escape is aided by centripetal acceleration from the rotation of the elongated nucleus. No plausible alternative hypothesis has been identified.</P>
FRAGMENTATION KINEMATICS IN COMET 332P/IKEYA-MURAKAMI
Jewitt, David,Mutchler, Max,Weaver, Harold,Hui, Man-To,Agarwal, Jessica,Ishiguro, Masateru,Kleyna, Jan,Li, Jing,Meech, Karen,Micheli, Marco,Wainscoat, Richard,Weryk, Robert American Astronomical Society 2016 ASTROPHYSICAL JOURNAL LETTERS - Vol.829 No.1
<P>We present initial time-resolved observations of the split comet 332P/Ikeya-Murakami taken using the Hubble Space Telescope. Our images reveal a dust-bathed cluster of fragments receding from their parent nucleus at projected speeds in the range 0.06-3.5 m s(-1) from which we estimate ejection times from 2015 October to December. The number of fragments with effective radii greater than or similar to 20 m follows a differential power law with index gamma = -3.6 +/- 0.6, while smaller fragments are less abundant than expected from an extrapolation of this power law. We argue that, in addition to losses due to observational selection, torques from anisotropic outgassing are capable of destroying the small fragments by driving them quickly to rotational instability. Specifically, the spin-up times of fragments. 20 m in radius are shorter than the time elapsed since ejection from the parent nucleus. The effective radius of the parent nucleus is re <= 275 m (geometric albedo 0.04 assumed). This is about seven times smaller than previous estimates and results in a nucleus mass at least 300 times smaller than previously thought. The mass in solid pieces, 2 x 10(9) kg, is about 4% of the mass of the parent nucleus. As a result of its small size, the parent nucleus also has a short spin-up time. Brightness variations in time-resolved nucleus photometry are consistent with rotational instability playing a role in the release of fragments.</P>