The Experts below are selected from a list of 57987 Experts worldwide ranked by ideXlab platform
Yang Yang - One of the best experts on this subject based on the ideXlab platform.
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whole heart spiral simultaneous multi slice first pass myocardial perfusion imaging
Magnetic Resonance in Medicine, 2019Co-Authors: Yang Yang, Craig H Meyer, Frederick H Epstein, Christopher M Kramer, Michael SalernoAbstract:PURPOSE To develop and evaluate a simultaneous multislice (SMS) spiral perfusion pulse sequence with whole-heart coverage. METHODS An Orthogonal Set of phase cycling angles following a Hadamard pattern was incorporated into a golden-angle (GA) variable density spiral perfusion sequence to perform SMS imaging at different multiband (MB) factors. Images were reconstructed using an SMS extension of L1-SPIRiT that we have termed SMS-L1-SPIRiT. The proposed sequence was evaluated in 40 subjects (10 each for MB factors of 1, 2, 3, and 4). Images were blindly graded by 2 cardiologists on a 5-point scale (5, excellent). To quantitatively evaluate the reconstruction performance against images acquired without SMS, the MB =1 data were used to retrospectively simulate data acquired at MB factors of 2 to 4. RESULTS Analysis of the SMS point-spread function for the desired slice showed that the proposed sampling strategy significantly canceled the main-lobe energy of the other slices and has low side-lobe energy resulting in an incoherent temporal aliasing pattern when rotated by the GA. Retrospective experiments demonstrated the SMS-L1-SPIRiT method removed aliasing from the interfering slices and showed excellent agreement with the ground-truth MB =1 images. Clinical evaluation demonstrated high-quality perfusion images with average image-quality scores of 4.3 ± 0.5 (MB =2), 4.2 ± 0.5 (MB =3), and 4.4 ± 0.4 (MB =4) with no significant quality difference in image quality between MB factors (P = 0.38). CONCLUSION SMS spiral perfusion at MB factors 2, 3, and 4 produces high-quality perfusion images with whole-heart coverage in a clinical Setting with high sampling efficiency.
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ligand controlled palladium catalyzed regiodivergent suzuki miyaura cross coupling of allylboronates and aryl halides
ChemInform, 2014Co-Authors: Yang Yang, Stephen L BuchwaldAbstract:An Orthogonal Set of catalyst systems for the Suzuki—Miyaura coupling of 3,3-disubstituted and 3-monosubstituted allylboronates with aryl halides is developed.
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ligand controlled palladium catalyzed regiodivergent suzuki miyaura cross coupling of allylboronates and aryl halides
Journal of the American Chemical Society, 2013Co-Authors: Yang Yang, Stephen L BuchwaldAbstract:An Orthogonal Set of catalyst systems has been developed for the Suzuki–Miyaura coupling of 3,3-disubstituted and 3-monosubstituted allylboronates with (hetero)aryl halides. These methods allow for the highly selective preparation of either the α- or the γ-isomeric coupling product.
Stephen L Buchwald - One of the best experts on this subject based on the ideXlab platform.
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ligand controlled palladium catalyzed regiodivergent suzuki miyaura cross coupling of allylboronates and aryl halides
ChemInform, 2014Co-Authors: Yang Yang, Stephen L BuchwaldAbstract:An Orthogonal Set of catalyst systems for the Suzuki—Miyaura coupling of 3,3-disubstituted and 3-monosubstituted allylboronates with aryl halides is developed.
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ligand controlled palladium catalyzed regiodivergent suzuki miyaura cross coupling of allylboronates and aryl halides
Journal of the American Chemical Society, 2013Co-Authors: Yang Yang, Stephen L BuchwaldAbstract:An Orthogonal Set of catalyst systems has been developed for the Suzuki–Miyaura coupling of 3,3-disubstituted and 3-monosubstituted allylboronates with (hetero)aryl halides. These methods allow for the highly selective preparation of either the α- or the γ-isomeric coupling product.
Rainer Cramer - One of the best experts on this subject based on the ideXlab platform.
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production and analysis of multiply charged negative ions by liquid atmospheric pressure matrix assisted laser desorption ionization mass spectrometry
Rapid Communications in Mass Spectrometry, 2021Co-Authors: Oliver J Hale, Pavel Ryumin, Jeffery Mark Brown, Michael Morris, Rainer CramerAbstract:RATIONALE: Liquid AP-MALDI has been shown to enable the production of ESI-like multiply charged analyte ions with little sample consumption and long-lasting, robust ion yield for sensitive analysis by mass spectrometry. Previous reports have focused on positive ion production. Here, we report an initial optimisation of liquid AP-MALDI for ESI-like negative ion production and its application to the analysis of peptides/proteins, DNA and lipids. METHODS: The instrumentation employed for this study is identical to that of earlier liquid AP-MALDI MS studies for positive analyte ion production with a simple non-commercial AP ion source that is attached to a Waters Synapt G2-Si mass spectrometer and incorporates a heated ion transfer tube. The preparation of liquid MALDI matrices is similar to positive ion mode analysis but has been adjusted for negative ion mode by changing the chromophore to 3-aminoquinoline and 9-aminoacridine for further improvements. RESULTS: For DNA, liquid AP-MALDI MS analysis benefited from switching to 9-aminoacridine-based MALDI samples and the negative ion mode, increasing the number of charges by up to a factor of 2 and the analyte ion signal intensities by more than ten-fold compared to the positive ion mode. The limit of detection was recorded at around 10fmol for ATGCAT. For lipids, negative ion mode analysis provided a fully Orthogonal Set of detected lipids. CONCLUSIONS: Negative ion mode is a sensitive alternative to positive ion mode in liquid AP-MALDI MS analysis. In particular, the analysis of lipids and DNA benefited from the complementarity of the detected lipid species and the vastly greater DNA ion signal intensities in negative ion mode.
Jeffery Mark Brown - One of the best experts on this subject based on the ideXlab platform.
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production and analysis of multiply charged negative ions by liquid atmospheric pressure matrix assisted laser desorption ionization mass spectrometry
Rapid Communications in Mass Spectrometry, 2021Co-Authors: Oliver J Hale, Pavel Ryumin, Jeffery Mark Brown, Michael Morris, Rainer CramerAbstract:RATIONALE: Liquid AP-MALDI has been shown to enable the production of ESI-like multiply charged analyte ions with little sample consumption and long-lasting, robust ion yield for sensitive analysis by mass spectrometry. Previous reports have focused on positive ion production. Here, we report an initial optimisation of liquid AP-MALDI for ESI-like negative ion production and its application to the analysis of peptides/proteins, DNA and lipids. METHODS: The instrumentation employed for this study is identical to that of earlier liquid AP-MALDI MS studies for positive analyte ion production with a simple non-commercial AP ion source that is attached to a Waters Synapt G2-Si mass spectrometer and incorporates a heated ion transfer tube. The preparation of liquid MALDI matrices is similar to positive ion mode analysis but has been adjusted for negative ion mode by changing the chromophore to 3-aminoquinoline and 9-aminoacridine for further improvements. RESULTS: For DNA, liquid AP-MALDI MS analysis benefited from switching to 9-aminoacridine-based MALDI samples and the negative ion mode, increasing the number of charges by up to a factor of 2 and the analyte ion signal intensities by more than ten-fold compared to the positive ion mode. The limit of detection was recorded at around 10fmol for ATGCAT. For lipids, negative ion mode analysis provided a fully Orthogonal Set of detected lipids. CONCLUSIONS: Negative ion mode is a sensitive alternative to positive ion mode in liquid AP-MALDI MS analysis. In particular, the analysis of lipids and DNA benefited from the complementarity of the detected lipid species and the vastly greater DNA ion signal intensities in negative ion mode.
James H Burge - One of the best experts on this subject based on the ideXlab platform.
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Distortion mapping correction in aspheric null testing
Interferometry XIV: Techniques and Analysis, 2008Co-Authors: Matt Novak, Chunyu Zhao, James H BurgeAbstract:ABSTRACT We describe methods to correct both symmetric and asymmetric distortion mapping errors induced by null testing elements such as holograms or null lenses. We show experimental resu lts for direct measurement and correction of symmetric mapping distortion, as well as an example result for analytical mapping performed using an Orthogonal Set of vector polynomials for asymmetric correction. The empirical determination of symmetric distortion is made via calculation from predicted and measured changes to aberrations induced via known changes to the testing point. 1. INTRODUCTION Aspheric primary mirrors are popular for astronomical telescope systems. These mirrors are polished to aspheric shapes to help minimize the overall length of the telescope system and provide additional optical correction for improved telescope performance. Optical testing with high accuracy is necessary, from as early a point in the fabrication process as is feasible, to efficiently converge to the proper finished optical surface. One potential obstacle encount ered when fabricating aspheric su rfaces is distortion present when imaging through null elements in the optical test. Dist ortion arises due to imperfect imaging through a null lens system and other optics in an interferometer or through a transmission CGH. The presence of distortion diminishes accuracy by mapping surface features to incorrect radial positions on the image plane. In this paper, we describe a method used to determine symmetric distortion which may prove practical for large asphere testing, as well as a more general correction method for asymmetric distortion. These techniques can be used to enable efficien t testing of aspheric optical surfaces.
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orthonormal vector polynomials in a unit circle part ii completing the basis Set
Optics Express, 2008Co-Authors: Chunyu Zhao, James H BurgeAbstract:Zernike polynomials provide a well known, Orthogonal Set of scalar functions over a circular domain, and are commonly used to represent wavefront phase or surface irregularity. A related Set of Orthogonal functions is given here which represent vector quantities, such as mapping distortion or wavefront gradient. Previously, we have developed a basis of functions generated from gradients of Zernike polynomials. Here, we complete the basis by adding a complementary Set of functions with zero divergence – those which are defined locally as a rotation or curl.
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orthonormal vector polynomials in a unit circle part i basis Set derived from gradients of zernike polynomials
Optics Express, 2007Co-Authors: Chunyu Zhao, James H BurgeAbstract:Zernike polynomials provide a well known, Orthogonal Set of scalar functions over a circular domain, and are commonly used to represent wavefront phase or surface irregularity. A related Set of Orthogonal functions is given here which represent vector quantities, such as mapping distortion or wavefront gradient. These functions are generated from gradients of Zernike polynomials, made orthonormal using the Gram-Schmidt technique. This Set provides a complete basis for representing vector fields that can be defined as a gradient of some scalar function. It is then efficient to transform from the coefficients of the vector functions to the scalar Zernike polynomials that represent the function whose gradient was fit. These new vector functions have immediate application for fitting data from a Shack-Hartmann wavefront sensor or for fitting mapping distortion for optical testing. A subsequent paper gives an additional Set of vector functions consisting only of rotational terms with zero divergence. The two Sets together provide a complete basis that can represent all vector distributions in a circular domain.
