The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Paul C. Mcafee - One of the best experts on this subject based on the ideXlab platform.
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biomechanical and anatomical considerations in lumbar spinous process fixation an in vitro human cadaveric model
The Spine Journal, 2014Co-Authors: Ashley A Murgatroyd, Kathleen P. Mullinix, Bryan W Cunningham, Paul C. McafeeAbstract:Abstract Background context Although multiple mechanisms of device attachment to the spinous processes exist, there is a paucity of Data regarding lumbar spinous process morphology and peak failure loads. Purpose Using an in vitro human cadaveric spine model, the primary objective of the present study was to compare the peak load and mechanisms of lumbar spinous process failure with variation in spinous process hole location and pullout direction. A secondary objective was to provide an in-depth characterization of spinous process morphology. Study design Biomechanical and anatomical considerations in lumbar spinous process fixation using an in vitro human cadaveric model. Methods A total of 12 intact lumbar spines were used in the current investigation. The vertebral Segments (L1–L5) were randomly assigned to one of five treatment groups with variation in spinous process hole placement and pullout direction: (1) central hole placement with superior pullout (n=10), (2) central hole placement with inferior pullout (n=10), (3) inferior hole placement with inferior pullout (n=10), (4) superior hole placement with superior pullout (n=10), and (5) intact spinous process with superior pullout (n=14). A 4-mm diameter pin was placed through the hole followed by pullout testing using a material testing system. As well, the bone mineral density (BMD) (g/cm 3 ) was measured for each Segment. Data were quantified in terms of anatomical dimensions (mm), peak failure loads (newtons [N]), and fracture mechanisms, with linear regression analysis to identify relationships between anatomical and biomechanical Data. Results Based on anatomical comparisons, there were significant differences between the anteroposterior and cephalocaudal dimensions of the L5 spinous process versus L1–L4 (p .05). However, a significant linear correlation was observed between peak failure load and anteroposterior and cephalocaudal dimensions (p Conclusions The present study demonstrated that variation in spinous process hole placement did not significantly influence failure load. However, there was a strong linear correlation between peak failure load and the anteroposterior and cephalocaudal anatomical dimensions. From a clinical standpoint, the findings of the present study indicate that attachment through the spinous process provides a viable alternative to attachment around the spinous processes. In addition, the anatomical dimensions of the lumbar spinous processes have a greater influence on biomechanical fixation than either hole location or BMD.
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Biomechanical and anatomical considerations in lumbar spinous process fixation—an in vitro human cadaveric model
The Spine Journal, 2014Co-Authors: Ashley A Murgatroyd, Kathleen P. Mullinix, Xinlong Ma, Bryan W Cunningham, Paul C. McafeeAbstract:Abstract Background context Although multiple mechanisms of device attachment to the spinous processes exist, there is a paucity of Data regarding lumbar spinous process morphology and peak failure loads. Purpose Using an in vitro human cadaveric spine model, the primary objective of the present study was to compare the peak load and mechanisms of lumbar spinous process failure with variation in spinous process hole location and pullout direction. A secondary objective was to provide an in-depth characterization of spinous process morphology. Study design Biomechanical and anatomical considerations in lumbar spinous process fixation using an in vitro human cadaveric model. Methods A total of 12 intact lumbar spines were used in the current investigation. The vertebral Segments (L1–L5) were randomly assigned to one of five treatment groups with variation in spinous process hole placement and pullout direction: (1) central hole placement with superior pullout (n=10), (2) central hole placement with inferior pullout (n=10), (3) inferior hole placement with inferior pullout (n=10), (4) superior hole placement with superior pullout (n=10), and (5) intact spinous process with superior pullout (n=14). A 4-mm diameter pin was placed through the hole followed by pullout testing using a material testing system. As well, the bone mineral density (BMD) (g/cm 3 ) was measured for each Segment. Data were quantified in terms of anatomical dimensions (mm), peak failure loads (newtons [N]), and fracture mechanisms, with linear regression analysis to identify relationships between anatomical and biomechanical Data. Results Based on anatomical comparisons, there were significant differences between the anteroposterior and cephalocaudal dimensions of the L5 spinous process versus L1–L4 (p .05). However, a significant linear correlation was observed between peak failure load and anteroposterior and cephalocaudal dimensions (p Conclusions The present study demonstrated that variation in spinous process hole placement did not significantly influence failure load. However, there was a strong linear correlation between peak failure load and the anteroposterior and cephalocaudal anatomical dimensions. From a clinical standpoint, the findings of the present study indicate that attachment through the spinous process provides a viable alternative to attachment around the spinous processes. In addition, the anatomical dimensions of the lumbar spinous processes have a greater influence on biomechanical fixation than either hole location or BMD.
Shiwon Song - One of the best experts on this subject based on the ideXlab platform.
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The Informational Value of Segment Data Disaggregated by Underlying Industry: Evidence from the Textual Features of Business Descriptions
The Accounting Review, 2021Co-Authors: Shiwon SongAbstract:I examine a fundamental determinant of disclosure quality: how underlying Data are disaggregated. For this, I create a measure of industry disaggregation, which is the extent to which Segment disclosures are disaggregated based on underlying industries. To identify underlying industries, I apply a deep learning algorithm that extracts textual features from Item 1 business descriptions, in which firms are required to accurately describe their products and services. Industry disaggregation captures the disclosure of underlying industries and the adherence to industry-based disaggregation criteria. Consistent with capital markets being informationally Segmented by industry, I find that industry disaggregation is negatively associated with analyst forecast error and dispersion, and positively associated with analyst following and information transfers among analysts and investors. These findings indicate that financial information is more informative, and thus of higher quality, when disaggregated by standardized criteria that achieve comparability and match the information-processing strategies of capital market participants.
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the informational value of disaggregated Segment Data evidence from the textual features of business descriptions
Social Science Research Network, 2020Co-Authors: Shiwon SongAbstract:I examine a fundamental determinant of accounting information: how underlying Data are disaggregated. For this, I create a measure of industry disaggregation, which is the extent to which underlying industries map onto Segment disclosures. To identify underlying industries, I apply a deep learning algorithm that extracts textual features from Item 1 business descriptions, in which firms are required to accurately describe their products and services. My industry disaggregation measure captures both the disclosure of underlying industries and the avoidance of using non-industry disaggregation criteria. Consistent with analysts’ industry specialization and reliance on Segment disclosures, I find that industry disaggregation is negatively associated with analyst forecast error and dispersion, and positively associated with analyst following and intra-industry information transfers among analysts. Collectively, these findings indicate that financial information is more informative when disaggregated by standardized criteria that achieve comparability and match the information processing strategies of capital market participants.
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The Informational Value of Disaggregated Segment Data: Evidence from the Textual Features of Business Descriptions
SSRN Electronic Journal, 2017Co-Authors: Shiwon SongAbstract:I examine a fundamental determinant of disclosure quality: how underlying Data are disaggregated. For this, I create a measure of industry disaggregation, which is the extent to which Segment disclosures are disaggregated based on underlying industries. To identify underlying industries, I apply a deep learning algorithm that extracts textual features from Item 1 business descriptions, in which firms are required to accurately describe their products and services. Industry disaggregation captures the disclosure of underlying industries and the adherence to industry-based disaggregation criteria. Consistent with capital markets being informationally Segmented by industry, I find that industry disaggregation is negatively associated with analyst forecast error and dispersion, and positively associated with analyst following and information transfers among analysts and investors. These findings indicate that financial information is more informative, and thus of higher quality, when disaggregated by standardized criteria that achieve comparability and match the information-processing strategies of capital market participants.
Ashley A Murgatroyd - One of the best experts on this subject based on the ideXlab platform.
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biomechanical and anatomical considerations in lumbar spinous process fixation an in vitro human cadaveric model
The Spine Journal, 2014Co-Authors: Ashley A Murgatroyd, Kathleen P. Mullinix, Bryan W Cunningham, Paul C. McafeeAbstract:Abstract Background context Although multiple mechanisms of device attachment to the spinous processes exist, there is a paucity of Data regarding lumbar spinous process morphology and peak failure loads. Purpose Using an in vitro human cadaveric spine model, the primary objective of the present study was to compare the peak load and mechanisms of lumbar spinous process failure with variation in spinous process hole location and pullout direction. A secondary objective was to provide an in-depth characterization of spinous process morphology. Study design Biomechanical and anatomical considerations in lumbar spinous process fixation using an in vitro human cadaveric model. Methods A total of 12 intact lumbar spines were used in the current investigation. The vertebral Segments (L1–L5) were randomly assigned to one of five treatment groups with variation in spinous process hole placement and pullout direction: (1) central hole placement with superior pullout (n=10), (2) central hole placement with inferior pullout (n=10), (3) inferior hole placement with inferior pullout (n=10), (4) superior hole placement with superior pullout (n=10), and (5) intact spinous process with superior pullout (n=14). A 4-mm diameter pin was placed through the hole followed by pullout testing using a material testing system. As well, the bone mineral density (BMD) (g/cm 3 ) was measured for each Segment. Data were quantified in terms of anatomical dimensions (mm), peak failure loads (newtons [N]), and fracture mechanisms, with linear regression analysis to identify relationships between anatomical and biomechanical Data. Results Based on anatomical comparisons, there were significant differences between the anteroposterior and cephalocaudal dimensions of the L5 spinous process versus L1–L4 (p .05). However, a significant linear correlation was observed between peak failure load and anteroposterior and cephalocaudal dimensions (p Conclusions The present study demonstrated that variation in spinous process hole placement did not significantly influence failure load. However, there was a strong linear correlation between peak failure load and the anteroposterior and cephalocaudal anatomical dimensions. From a clinical standpoint, the findings of the present study indicate that attachment through the spinous process provides a viable alternative to attachment around the spinous processes. In addition, the anatomical dimensions of the lumbar spinous processes have a greater influence on biomechanical fixation than either hole location or BMD.
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Biomechanical and anatomical considerations in lumbar spinous process fixation—an in vitro human cadaveric model
The Spine Journal, 2014Co-Authors: Ashley A Murgatroyd, Kathleen P. Mullinix, Xinlong Ma, Bryan W Cunningham, Paul C. McafeeAbstract:Abstract Background context Although multiple mechanisms of device attachment to the spinous processes exist, there is a paucity of Data regarding lumbar spinous process morphology and peak failure loads. Purpose Using an in vitro human cadaveric spine model, the primary objective of the present study was to compare the peak load and mechanisms of lumbar spinous process failure with variation in spinous process hole location and pullout direction. A secondary objective was to provide an in-depth characterization of spinous process morphology. Study design Biomechanical and anatomical considerations in lumbar spinous process fixation using an in vitro human cadaveric model. Methods A total of 12 intact lumbar spines were used in the current investigation. The vertebral Segments (L1–L5) were randomly assigned to one of five treatment groups with variation in spinous process hole placement and pullout direction: (1) central hole placement with superior pullout (n=10), (2) central hole placement with inferior pullout (n=10), (3) inferior hole placement with inferior pullout (n=10), (4) superior hole placement with superior pullout (n=10), and (5) intact spinous process with superior pullout (n=14). A 4-mm diameter pin was placed through the hole followed by pullout testing using a material testing system. As well, the bone mineral density (BMD) (g/cm 3 ) was measured for each Segment. Data were quantified in terms of anatomical dimensions (mm), peak failure loads (newtons [N]), and fracture mechanisms, with linear regression analysis to identify relationships between anatomical and biomechanical Data. Results Based on anatomical comparisons, there were significant differences between the anteroposterior and cephalocaudal dimensions of the L5 spinous process versus L1–L4 (p .05). However, a significant linear correlation was observed between peak failure load and anteroposterior and cephalocaudal dimensions (p Conclusions The present study demonstrated that variation in spinous process hole placement did not significantly influence failure load. However, there was a strong linear correlation between peak failure load and the anteroposterior and cephalocaudal anatomical dimensions. From a clinical standpoint, the findings of the present study indicate that attachment through the spinous process provides a viable alternative to attachment around the spinous processes. In addition, the anatomical dimensions of the lumbar spinous processes have a greater influence on biomechanical fixation than either hole location or BMD.
Guochang Zhang - One of the best experts on this subject based on the ideXlab platform.
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Heterogeneous investment opportunities in multiple-Segment firms and the incremental value relevance of Segment accounting Data
The Accounting Review, 2003Co-Authors: Peter F. Chen, Guochang ZhangAbstract:Applying a real‐options‐based valuation approach, we develop and test a model that addresses the incremental value relevance of Segment Data beyond firmlevel accounting Data. Prior studies (e.g., Zhang 2000; Biddle et al. 2001) show that equity valuation requires accounting Data (in part) because accounting provides signals that guide capital investments underlying value creation. In this study, we establish that the usefulness of Segment Data beyond aggregate Data relates to heterogeneity of investment opportunities across Segments, caused by divergences of Segment profitability and growth potential. Empirical results are consistent with the model's predictions. We also assess the magnitude of the valuation impact of Segment information relative to that of firm‐level information.
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Heterogeneous Investment Opportunities in Multiple-Segment Firms and the Incremental Value Relevance of Segment Accounting Data
SSRN Electronic Journal, 2001Co-Authors: Peter F. Chen, Guochang ZhangAbstract:Applying an option-based valuation approach, we develop and test a model that addresses the incremental value relevance of Segment Data beyond firm-level accounting Data. Prior studies (e.g., Zhang 2000; Biddle et al. 2001) show that firm value relates to accounting Data (in part) because accounting Data are useful for guiding capital investment decisions that underlie value creation. In this study, we establish that the incremental value relevance of Segment Data relates to the heterogeneity of investment decisions across Segments, as informed by Segmental profitability and investment opportunities. Equity value is predicted to depend not only on aggregate firm-level accounting Data but also on the extent to which Segments differ in profitability and investment opportunities. Our empirical tests confirm the predicted incremental effect of Segment Data.
Marc Baldus - One of the best experts on this subject based on the ideXlab platform.
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Plasticity of the PAS domain and a potential role for signal transduction in the histidine kinase DcuS
Nature Structural & Molecular Biology, 2008Co-Authors: Manuel Etzkorn, Holger Kneuper, Pia Dünnwald, Vinesh Vijayan, Jens Krämer, Christian Griesinger, Stefan Becker, Gottfried Unden, Marc BaldusAbstract:DcuS is a multidomain membrane sensor kinase important for Escherichia coli interactions with its environment. A new approach combining solution- and solid-state NMR with in silico modeling and mutagenesis has provided a three-dimensional model for most of this large membrane protein and suggests a mechanism for DcuS activation. The mechanistic understanding of how membrane-embedded sensor kinases recognize signals and regulate kinase activity is currently limited. Here we report structure-function relationships of the multidomain membrane sensor kinase DcuS using solid-state NMR, structural modeling and mutagenesis. Experimental Data of an individual cytoplasmic Per-Arnt-Sim (PAS) domain were compared to structural models generated in silico . These studies, together with previous NMR work on the periplasmic PAS domain, enabled structural investigations of a membrane-embedded 40-kDa construct by solid-state NMR, comprising both PAS Segments and the membrane domain. Structural alterations are largely limited to protein regions close to the transmembrane Segment. Data from isolated and multidomain constructs favor a disordered N-terminal helix in the cytoplasmic domain. Mutations of residues in this region strongly influence function, suggesting that protein flexibility is related to signal transduction toward the kinase domain and regulation of kinase activity.
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Plasticity of the PAS domain and a potential role for signal transduction in the histidine kinase DcuS.
Nature structural & molecular biology, 2008Co-Authors: Manuel Etzkorn, Holger Kneuper, Pia Dünnwald, Vinesh Vijayan, Jens Krämer, Christian Griesinger, Stefan Becker, Gottfried Unden, Marc BaldusAbstract:The mechanistic understanding of how membrane-embedded sensor kinases recognize signals and regulate kinase activity is currently limited. Here we report structure-function relationships of the multidomain membrane sensor kinase DcuS using solid-state NMR, structural modeling and mutagenesis. Experimental Data of an individual cytoplasmic Per-Arnt-Sim (PAS) domain were compared to structural models generated in silico. These studies, together with previous NMR work on the periplasmic PAS domain, enabled structural investigations of a membrane-embedded 40-kDa construct by solid-state NMR, comprising both PAS Segments and the membrane domain. Structural alterations are largely limited to protein regions close to the transmembrane Segment. Data from isolated and multidomain constructs favor a disordered N-terminal helix in the cytoplasmic domain. Mutations of residues in this region strongly influence function, suggesting that protein flexibility is related to signal transduction toward the kinase domain and regulation of kinase activity.