The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
Martha L. Gray - One of the best experts on this subject based on the ideXlab platform.
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New MRI Techniques for Imaging Cartilage
The Journal of Bone and Joint Surgery-American Volume, 2003Co-Authors: Deborah Burstein, Martha L. GrayAbstract:Because of its ability to image all of the tissues in a diarthrodial joint, magnetic resonance imaging (MRI) has an ever-increasing role in the evaluation, diagnosis, and monitoring of joint disorders. Standard MRI techniques can delineate morphologic abnormalities. Techniques on the horizon offer improved morphologic analysis as well as previously unavailable information about the biochemical composition and functional properties of joint tissues. While research and development efforts are rapidly growing, the current review focuses on techniques that are most advanced and that have demonstrated feasibility in basic science and clinical studies. As such, we report mainly on cartilage imaging but hasten to add that ongoing research efforts offer promise for the imaging of all joint structures. These techniques should improve our ability to understand the healthy joint and the disease process, to provide earlier diagnoses, and to evaluate the effects of therapeutic procedures. With these capabilities, we can more effectively establish strategies to maintain joint health and to identify indications for intervention at an early stage of degeneration. We begin with an overview of the basics of MRI to provide the reader with a sense of what is measured and how an MR measurement is made. MRI is possible because nuclei with an odd number of protons and/or an odd number of neutrons have net magnetic moments. The most Abundant Nucleus in biological systems is the hydrogen Nucleus (which, in MR vernacular, is referred to as a proton because hydrogen contains a single proton), making water and fat both observable with MRI. In all of the methods that we will discuss here (and virtually all of the MR imaging done clinically), it is the hydrogen (proton) Nucleus that is being measured; indeed, the term MRI has come to be synonymous with the term proton-MRI (while MR of another Nucleus x …
Deborah Burstein - One of the best experts on this subject based on the ideXlab platform.
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New MRI Techniques for Imaging Cartilage
The Journal of Bone and Joint Surgery-American Volume, 2003Co-Authors: Deborah Burstein, Martha L. GrayAbstract:Because of its ability to image all of the tissues in a diarthrodial joint, magnetic resonance imaging (MRI) has an ever-increasing role in the evaluation, diagnosis, and monitoring of joint disorders. Standard MRI techniques can delineate morphologic abnormalities. Techniques on the horizon offer improved morphologic analysis as well as previously unavailable information about the biochemical composition and functional properties of joint tissues. While research and development efforts are rapidly growing, the current review focuses on techniques that are most advanced and that have demonstrated feasibility in basic science and clinical studies. As such, we report mainly on cartilage imaging but hasten to add that ongoing research efforts offer promise for the imaging of all joint structures. These techniques should improve our ability to understand the healthy joint and the disease process, to provide earlier diagnoses, and to evaluate the effects of therapeutic procedures. With these capabilities, we can more effectively establish strategies to maintain joint health and to identify indications for intervention at an early stage of degeneration. We begin with an overview of the basics of MRI to provide the reader with a sense of what is measured and how an MR measurement is made. MRI is possible because nuclei with an odd number of protons and/or an odd number of neutrons have net magnetic moments. The most Abundant Nucleus in biological systems is the hydrogen Nucleus (which, in MR vernacular, is referred to as a proton because hydrogen contains a single proton), making water and fat both observable with MRI. In all of the methods that we will discuss here (and virtually all of the MR imaging done clinically), it is the hydrogen (proton) Nucleus that is being measured; indeed, the term MRI has come to be synonymous with the term proton-MRI (while MR of another Nucleus x …
Thomas Brauniger - One of the best experts on this subject based on the ideXlab platform.
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frequency swept pulse sequences for 19f heteronuclear spin decoupling in solid state nmr
Journal of Magnetic Resonance, 2010Co-Authors: Vinod C Chandran, P K Madhu, Philip Wormald, Thomas BraunigerAbstract:Heteronuclear spin decoupling pulse sequences in solid-state NMR have mostly been designed and applied for irradiating 1H as the Abundant Nucleus. Here, a systematic comparison of different methods for decoupling 19F in rigid organic solids is presented, with a special emphasis on the recently introduced frequency-swept sequences. An extensive series of NMR experiments at different MAS frequencies was conducted on fluorinated model compounds, in combination with large sets of numerical simulations. From both experiments and simulations it can be concluded that the frequency-swept sequences SWf-TPPM and SWf-SPINAL deliver better and more robust spin decoupling than the original sequences SPINAL and TPPM. Whereas the existence of a large chemical shift anisotropy and isotropic shift dispersion for 19F does compromise the decoupling efficiency, the relative performance hierarchy of the sequences remains unaffected. Therefore, in the context of rigid organic solids under moderate MAS frequencies, the performance trends observed for 19F decoupling are very similar to those observed for 1H decoupling.
Robert L. Metzenberg - One of the best experts on this subject based on the ideXlab platform.
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Asm-1(+), a Neurospora Crassa Gene Related to Transcriptional Regulators of Fungal Development
Genetics, 1996Co-Authors: Rodolfo Aramayo, Yoav Peleg, Randolph Addison, Robert L. MetzenbergAbstract:This report describes the identification, cloning, and molecular analysis of Asm-1(+) (Ascospore maturation 1), the Neurospora crassa homologue of the Aspergillus nidulans stuA (stunted A) gene. The Asm-1(+) gene is constitutively transcribed and encodes an Abundant, Nucleus-localized 68.5-kD protein. The protein product of Asm-1(+) (ASM-1), contains a potential DNA-binding motif present in related proteins from A. nidulans (StuA), Candida albicans (EFGTF-1), and Saccharomyces cerevisiae (Phd1 and Sok2). This motif is related to the DNA binding motif of the Swi4/Mbp1/Res family of transcription factors that control the cell cycle. Deletion of Asm-1(+) destroys the ability to make protoperithecia (female organs), but does not affect male-specific functions. We propose that the APSES domain (ASM-1, Phd1, StuA, EFGTF-1, and Sok2) defines a group of proteins that constitute a family of related transcription factors involved in the control of fungal development.
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Meiotic Transvection in Fungi
Cell, 1996Co-Authors: Rodolfo Aramayo, Robert L. MetzenbergAbstract:Abstract The Neurospora crassa Asm-1 + (ascospore maturation 1) gene encodes an Abundant Nucleus-localized protein required for formation of female structures and for ascospore maturation. Deletion mutants of Asm-1 + are "ascus-dominant," i.e., when crossed to wild type, neither Asm-1 + nor Asm-1 Δ spores mature. To explain this behavior, we considered three models: an effect of reduced dosage of the gene product, failure of internuclear communication, and failure of transvection (regulation dependent on pairing of alleles). We found that for proper regulation of subsequent sexual sporulation, Asm-1 + must be in proximity, probably paired, to its allelic counterpart in the zygote: i.e., transvection must occur. Disruption of pairing causes failure of ascospore progeny to mature. Transvection in Neurospora, unlike in Drosophila, occurs immediately before meiosis, and can be demonstrated between wild-type alleles.
Vinod C Chandran - One of the best experts on this subject based on the ideXlab platform.
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frequency swept pulse sequences for 19f heteronuclear spin decoupling in solid state nmr
Journal of Magnetic Resonance, 2010Co-Authors: Vinod C Chandran, P K Madhu, Philip Wormald, Thomas BraunigerAbstract:Heteronuclear spin decoupling pulse sequences in solid-state NMR have mostly been designed and applied for irradiating 1H as the Abundant Nucleus. Here, a systematic comparison of different methods for decoupling 19F in rigid organic solids is presented, with a special emphasis on the recently introduced frequency-swept sequences. An extensive series of NMR experiments at different MAS frequencies was conducted on fluorinated model compounds, in combination with large sets of numerical simulations. From both experiments and simulations it can be concluded that the frequency-swept sequences SWf-TPPM and SWf-SPINAL deliver better and more robust spin decoupling than the original sequences SPINAL and TPPM. Whereas the existence of a large chemical shift anisotropy and isotropic shift dispersion for 19F does compromise the decoupling efficiency, the relative performance hierarchy of the sequences remains unaffected. Therefore, in the context of rigid organic solids under moderate MAS frequencies, the performance trends observed for 19F decoupling are very similar to those observed for 1H decoupling.
