The Experts below are selected from a list of 250860 Experts worldwide ranked by ideXlab platform
Tanveer Ali Dar - One of the best experts on this subject based on the ideXlab platform.
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manifestations of native topology in the denatured state ensemble of rhodopseudomonas palustris cytochrome c
Biochemistry, 2011Co-Authors: Tanveer Ali Dar, Dustin R Schaeffer, Valerie Daggett, Bruce E BowlerAbstract:To provide insight into the role of local sequence in the nonrandom coil behavior of the denatured state, we have extended our measurements of histidine−heme loop formation equilibria for cytochrome c′ to 6 M guanidine hydrochloride. We observe that there is some reduction in the scatter about the best fit Line of loop stability versus loop size data in 6 M versus 3 M guanidine hydrochloride, but the scatter is not eliminated. The scaling exponent, ν3, of 2.5 ± 0.2 is also similar to that found previously in 3 M guanidine hydrochloride (2.6 ± 0.3). Rates of histidine−heme loop breakage in the denatured state of cytochrome c′ show that some histidine−heme loops are significantly more persistent than others at both 3 and 6 M guanidine hydrochloride. Rates of histidine−heme loop formation more closely approximate random coil behavior. This observation indicates that heterogeneity in the denatured state ensemble results mainly from contact persistence. When mapped onto the structure of cytochrome c′, the hist...
Michael L. Oelze - One of the best experts on this subject based on the ideXlab platform.
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characterization of tissue microstructure using ultrasonic backscatter theory and technique for optimization using a gaussian form factor
Journal of the Acoustical Society of America, 2002Co-Authors: Michael L. Oelze, James F. Zachary, William D ObrienAbstract:Characterization of tissue microstructure through ultrasonic backscatter is hypothesized to aid in detection and classification of diseased tissues. Radio frequency signals backscattered from tissues can be modeled according to the assumed shape, size, and distribution of scatterers in tissues. Power spectra of rf backscattered signals describe the frequency dependence of scatterers. Experimental measurements of ultrasonic backscatter from spontaneous mammary tumors in rats are obtained over the frequency range of 4 to 12 MHz. The power spectra measured from rat tumors are compared to theoretical power spectra derived from a 3D spatial autocorrelation function assuming a Gaussian distribution. Independent values of average scatterer diameter and acoustic concentration are obtained by approximating the measured power spectrum with a Best-Fit Line. Enhanced B-mode images are made of the rat tumors and surrounding tissues with superimposed regions of interest quantified by estimated average scatterer sizes a...
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Ultrasonic rf-based imaging for the purposes of characterizing the microstructure of solid tumors
Medical Imaging 2002: Ultrasonic Imaging and Signal Processing, 2002Co-Authors: Michael L. Oelze, James F. Zachary, William D. O'brienAbstract:Eight retired breeder rats were acquired that had developed spontaneous mammary tumors. Tumors were diagnosed microscopically as mammary gland fibroadenomas. Two-dimensional gray-scale B-mode images of the tumors in the rats were constructed from backscattered echoes using an 8 MHz (90% bandwidth) single element ultrasonic transducer. From the gray-scale B-mode images, regions-of-interest (ROIs) were selected in the tumors and surrounding tissues. The power spectra of backscattered RF echoes gated from the ROIs were used to estimate the average scatterer diameters and concentrations. A unique estimation scheme was used to obtain the average scatterer diameters and concentrations. The average scatterer diameter was related to the slope of the Best-Fit Line to the reduced measured power spectrum versus the frequency squared. The scatterer concentration was determined from the intercept of the Best-Fit Line. The reduced measured power spectrum is the measured power spectrum minus 40 log of the frequency. Parametric B-mode images were constructed by converting ROI boxes into colored pixels. The color of the pixels was related to the estimated scatterer properties. The images showed a distinct difference between the tumor and surrounding healthy tissues. Scatterer sizes inside the tumor were on average 30% larger than scatterer sizes in surrounding normal tissues.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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B-mode images of spontaneous rat mammary tumors enhanced by estimated scatterer parameters
2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263), 2001Co-Authors: Michael L. Oelze, James F. Zachary, William D. O'brienAbstract:B-mode images of tissues enhanced by information about the microstructure can aid in the diagnosis of diseased (cancerous) tissues. Four retired breeder rats were acquired that had developed spontaneous mammary tumors. Tumors were diagnosed microscopically as mammary gland fibroadenomas. Two-dimensional B-mode images of the tumors in the rats were constructed from backscattered echoes using a 8 MHz (90% bandwidth) single element transducer. From the B-mode images, regions-of-interest (ROIs) were selected in the tumors and surrounding tissues. The power spectra of backscattered echoes gated from the ROIs were used to estimate the average scatterer diameter and scatterer concentration. The ROIs are boxes with sides of 10 wavelengths at the central frequency of the signal. The tissue microstructure is related to the average scatterer diameter and concentration. A unique estimation scheme is used to obtain the average scatterer diameter and the scatterer concentration. The average scatterer diameter is related to the slope of the Best-Fit Line to the reduced measured power spectrum versus the frequency squared. The scatterer concentration is determined from the intercept of the Best-Fit Line. The reduced measured power spectrum is the measured power spectrum minus 40 log of the frequency. Enhanced B-mode images are constructed by converting ROI boxes into colored pixels. The color of the pixels is related to the estimated scatterer parameters. For each tumor three images are constructed: the normal B-mode image, the B-mode image with superimposed scatterer diameter pixels, and the B-mode image with superimposed scatterer concentration pixels. The images show a distinct difference between the tumor and surrounding healthy tissues.
Terry Wilson - One of the best experts on this subject based on the ideXlab platform.
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New criteria for systematic mapping and reliability assessment of monogenetic volcanic vent alignments and elongate volcanic vents for crustal stress analyses
Tectonophysics, 2009Co-Authors: Timothy Paulsen, Terry WilsonAbstract:Abstract Linear arrays of monogenetic volcanic vent alignments represent an important source of stress/strain data from volcanic regions of the Earth and other planets. Currently, however, there is no standard methodology for mapping vent alignments or for assessing alignment reliability, which are essential to defining a robust stress datum from vent alignments. Here we define a systematic method for defining monogenetic vent alignments by mapping the locations and shapes of vents. Elongation of vents into elliptical shapes is directly related to the trend of subsurface fissures that control alignments. Elongated vents therefore are critical for defining reliable regional vent alignments, and also provide an independent means for assessing stress directions. Our reliability assessment system (A > B > C > D) for vent alignments is based on the number of vents, the standard deviation of vent center points from a Best-Fit Line, the numbers and types of elongate vents, the standard deviation of long axes of elliptical vents from a Best-Fit Line, and, in cases where alignments lack elongate vents, by vent spacing distances. We quantified morphometric parameters of well-defined fissure-fed vent alignments from polygenetic volcanoes and platform volcanic fields to establish appropriate threshold values for reliability assessments. In this new method, the combined analysis of vent locations and shapes optimizes the process of alignment mapping and the assessment of the reliability of alignments to be incorporated in stress analyses. We provide quality-ranking schemes for stress data derived from reliability-assessed vent alignments and from elongate vents. We demonstrate the utility of this new mapping and assessment methodology by analyzing monogenetic cinder cone fields within a platform volcanic field (the San Francisco volcanic field in Arizona) and within a volcanic field on the flank of a polygenetic volcano (Mount Morning in Antarctica).
Bruce E Bowler - One of the best experts on this subject based on the ideXlab platform.
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manifestations of native topology in the denatured state ensemble of rhodopseudomonas palustris cytochrome c
Biochemistry, 2011Co-Authors: Tanveer Ali Dar, Dustin R Schaeffer, Valerie Daggett, Bruce E BowlerAbstract:To provide insight into the role of local sequence in the nonrandom coil behavior of the denatured state, we have extended our measurements of histidine−heme loop formation equilibria for cytochrome c′ to 6 M guanidine hydrochloride. We observe that there is some reduction in the scatter about the best fit Line of loop stability versus loop size data in 6 M versus 3 M guanidine hydrochloride, but the scatter is not eliminated. The scaling exponent, ν3, of 2.5 ± 0.2 is also similar to that found previously in 3 M guanidine hydrochloride (2.6 ± 0.3). Rates of histidine−heme loop breakage in the denatured state of cytochrome c′ show that some histidine−heme loops are significantly more persistent than others at both 3 and 6 M guanidine hydrochloride. Rates of histidine−heme loop formation more closely approximate random coil behavior. This observation indicates that heterogeneity in the denatured state ensemble results mainly from contact persistence. When mapped onto the structure of cytochrome c′, the hist...
William D. O'brien - One of the best experts on this subject based on the ideXlab platform.
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Ultrasonic rf-based imaging for the purposes of characterizing the microstructure of solid tumors
Medical Imaging 2002: Ultrasonic Imaging and Signal Processing, 2002Co-Authors: Michael L. Oelze, James F. Zachary, William D. O'brienAbstract:Eight retired breeder rats were acquired that had developed spontaneous mammary tumors. Tumors were diagnosed microscopically as mammary gland fibroadenomas. Two-dimensional gray-scale B-mode images of the tumors in the rats were constructed from backscattered echoes using an 8 MHz (90% bandwidth) single element ultrasonic transducer. From the gray-scale B-mode images, regions-of-interest (ROIs) were selected in the tumors and surrounding tissues. The power spectra of backscattered RF echoes gated from the ROIs were used to estimate the average scatterer diameters and concentrations. A unique estimation scheme was used to obtain the average scatterer diameters and concentrations. The average scatterer diameter was related to the slope of the Best-Fit Line to the reduced measured power spectrum versus the frequency squared. The scatterer concentration was determined from the intercept of the Best-Fit Line. The reduced measured power spectrum is the measured power spectrum minus 40 log of the frequency. Parametric B-mode images were constructed by converting ROI boxes into colored pixels. The color of the pixels was related to the estimated scatterer properties. The images showed a distinct difference between the tumor and surrounding healthy tissues. Scatterer sizes inside the tumor were on average 30% larger than scatterer sizes in surrounding normal tissues.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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B-mode images of spontaneous rat mammary tumors enhanced by estimated scatterer parameters
2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263), 2001Co-Authors: Michael L. Oelze, James F. Zachary, William D. O'brienAbstract:B-mode images of tissues enhanced by information about the microstructure can aid in the diagnosis of diseased (cancerous) tissues. Four retired breeder rats were acquired that had developed spontaneous mammary tumors. Tumors were diagnosed microscopically as mammary gland fibroadenomas. Two-dimensional B-mode images of the tumors in the rats were constructed from backscattered echoes using a 8 MHz (90% bandwidth) single element transducer. From the B-mode images, regions-of-interest (ROIs) were selected in the tumors and surrounding tissues. The power spectra of backscattered echoes gated from the ROIs were used to estimate the average scatterer diameter and scatterer concentration. The ROIs are boxes with sides of 10 wavelengths at the central frequency of the signal. The tissue microstructure is related to the average scatterer diameter and concentration. A unique estimation scheme is used to obtain the average scatterer diameter and the scatterer concentration. The average scatterer diameter is related to the slope of the Best-Fit Line to the reduced measured power spectrum versus the frequency squared. The scatterer concentration is determined from the intercept of the Best-Fit Line. The reduced measured power spectrum is the measured power spectrum minus 40 log of the frequency. Enhanced B-mode images are constructed by converting ROI boxes into colored pixels. The color of the pixels is related to the estimated scatterer parameters. For each tumor three images are constructed: the normal B-mode image, the B-mode image with superimposed scatterer diameter pixels, and the B-mode image with superimposed scatterer concentration pixels. The images show a distinct difference between the tumor and surrounding healthy tissues.