Broadside wide-angle seismic studies and three-dimensional structure of the crust in the southeast Canadian Cordillera

1997 ◽  
Vol 34 (8) ◽  
pp. 1156-1166 ◽  
Author(s):  
M. J. A. Burianyk ◽  
E. R. Kanasewich ◽  
N. Udey
Keyword(s):  
Signal To Noise Ratio ◽  
Seismic Refraction ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
High Signal ◽  
Canadian Cordillera ◽  
Wide Angle ◽  
Low Velocity ◽  
Seismic Properties ◽  
High Degree

Broadside, or fan, recordings of a Lithoprobe seismic refraction – wide-angle reflection experiment in the southeastern Canadian Cordillera show several features further illuminating the crustal structure beyond that previously derived from SCoRE '90 (Southern Cordillera Refraction Experiment of 1990) in-line data. Analysis of a nearly in-line profile centred on Castlegar, British Columbia, shows lower velocities in the upper crust associated with the Purcell Anticlinorium as well as velocity variations that may have some association with the Purcell fault zone. The depth to Moho is almost 38 km, somewhat deeper and on trend with the structure that has been established farther north. The broadside records show high signal-to-noise ratio PmP arrivals (i.e., reflections from the bottom of the crust). These PmP fan picks were analysed in regions away from in-line profiles, providing further measurements of the depth to Moho in the southeastern Cordillera. The analysis of the broadside records combined with the earlier in-line interpretations as well as older crustal seismic measurements make up a relatively high resolution database, compared with most other regions in Canada, from which we have generated maps of depth to Moho and average crustal velocity in the southeastern Cordillera of Canada. The maps show thin, low-velocity crust over much of the region and indicate a high degree of correlation between current crustal seismic properties and regional isotherms.

Seismic studies of the crust under the Williston Basin

1987 ◽  
Vol 24 (11) ◽  
pp. 2160-2171 ◽  
Author(s):  
E. R. Kanasewich ◽  
Z. Hajnal ◽  
A. G. Green ◽  
G. L. Cumming ◽  
R. F. Mereu ◽  
...  
Keyword(s):  
Seismic Refraction ◽  
Three Dimensional ◽  
Good Evidence ◽  
Dimensional Structure ◽  
Williston Basin ◽  
Mobile Belt ◽  
Low Velocity ◽  
Reflection Data ◽  
Yield Information ◽  
Seismic Recording

The seismic refraction method was used in 1981 to study the crust under the northern half of the Williston Basin, in Saskatchewan. A new method of spatial seismic recording, based on a triangular arrangement of receivers, was used for the first time to obtain three-dimensional structure and velocity information. The broadside seismic refraction and wide-angle reflection data obtained by the technique were of particular value in defining several faulted blocks. These blocks are also characterized by aeromagnetic anomalies trending in a northerly direction. The crustal thickness in the southern part of the western provinces shows large variation ranging from 35 to 50 km. Much of the area is also notable for the presence of one or more low-velocity layers and a high-velocity lower crust. There is good evidence for significant lateral heterogeneity, and detailed deep seismic reflection and refraction studies would likely yield information on dips and strikes of beds and faults around the basin as well as define the properties of the various terranes of the Hudsonian mobile belt.

scholarly journals Radial Carboxyterminal Peptides of Tubulin Directly Imaged in Microtubules by Electron Microscopy Tomography Exploiting Emplitude Contrast

2021 ◽  
Author(s):  
Andrea Fera ◽  
Thomas Reese ◽  
Joshua Zimmerberg ◽  
Dan Sackett
Keyword(s):  
Electron Microscopy ◽  
Outer Surface ◽  
Electron Beam Irradiation ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
High Signal ◽  
High Electron ◽  
Microscopy Image ◽  
Multiple Samples

Abstract Tubulin carboxyterminal tails (CTT) are peptides of 10-20 amino acids, unstructured and acidic, that vary in sequence between tubulin isotypes and are exposed on the outer surface of microtubules (MTs). These peptides have, so far, eluded direct visualization. In this report, electron microscopy tomography was applied to isolated MTs stained with Uranyl and tungstate salts demonstrated to resist sustained electron beam irradiation. Such resistance of high electron doses allows each electron microscopy image to be recorded with a high signal-to-noise ratio. Corresponding tomograms reconstructed from tilt series at high magnification show exceptional resolution of details, revealing features of average dimension ~ 1 nm without the need of averaging multiple samples. The known three-dimensional structure of the MT wall is apparent. But now images also reveal small stalks on the outer surface of MTs. Inspection of virtual sections demonstrates that the stalks are up to ~2.5 nm long and ~1 nm wide (at half length), protruding every 4 ± 0.8 (22) nm along the microtubule. This spacing corresponds to one stalk per tubulin monomer. The grafting point on each monomer is not random but is positioned at one end of each monomer, identifying that end as toward the (-) end of the MT. The stalks are not observed following CTT removal with subtilisin. We conclude that these stalks are the CTT peptides of tubulin.

scholarly journals Ab initiostructure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector

2016 ◽  
Vol 72 (2) ◽  
pp. 236-242 ◽  
Author(s):  
E. van Genderen ◽  
M. T. B. Clabbers ◽  
P. P. Das ◽  
A. Stewart ◽  
I. Nederlof ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Direct Methods ◽  
Liquid Nitrogen Temperature ◽  
High Dynamic Range ◽  
Electron Diffraction Data ◽  
High Signal

Until recently, structure determination by transmission electron microscopy of beam-sensitive three-dimensional nanocrystals required electron diffraction tomography data collection at liquid-nitrogen temperature, in order to reduce radiation damage. Here it is shown that the novel Timepix detector combines a high dynamic range with a very high signal-to-noise ratio and single-electron sensitivity, enablingab initiophasing of beam-sensitive organic compounds. Low-dose electron diffraction data (∼0.013 e− Å−2 s−1) were collected at room temperature with the rotation method. It was ascertained that the data were of sufficient quality for structure solution using direct methods using software developed for X-ray crystallography (XDS,SHELX) and for electron crystallography (ADT3D/PETS,SIR2014).

scholarly journals Studies of the ISM in the LMC using SN1987A

1991 ◽  
Vol 148 ◽  
pp. 431-431
Author(s):  
Max Pettini
Keyword(s):  
High Resolution ◽  
Interstellar Medium ◽  
Large Scale ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Large Magellanic Cloud ◽  
Absorption Lines ◽  
High Signal ◽  
Hii Region ◽  
Sn 1987A

The exceptional brightness of SN1987A provided a wealth of opportunities for probing not only the interstellar medium in our Galaxy and in the Large Magellanic Cloud (LMC), but also any intergalactic matter between the two. Spectroscopic work has been directed both towards searches for very weak absorption lines, which require data of exceptionally high signal-to-noise ratio, and towards recording spectra of known features at unprecedentedly high resolution. Both approaches have yielded exciting and unexpected results. The first detection of [FeX] absorption has revealed the presence of million-degree gas in the interstellar medium of the LMC, possibly resulting from the explosions of previous supernovae in the 30-Doradus HII region. The ultra-high-resolution observations have been successful in resolving the hyperfine structure of the sodium D lines in several interstellar clouds along the line of sight to the supernova. This implies that the clouds are at temperatures of, at most, 170 K and have internal turbulent velocities of not more than 0.2 km s−1; large-scale motions thus appear to be mainly subsonic in these clouds. Radio observations of HI emission at 21-cm with the Parkes telescope have been combined with measurements of a variety of ultraviolet absorption lines, obtained with the International Ultraviolet Explorer satellite, to give the most detailed picture yet of the chemical composition of the gas between the Galaxy and the LMC. Finally, photographic monitoring of the light echo of SN 1987A over the last two years has provided a three-dimensional view of the interstellar environment in which SN 1987A exploded, complementing vividly the information deduced from the spectroscopic results.

scholarly journals 3D MPRAGE improves classification of cortical lesions in multiple sclerosis

2008 ◽  
Vol 14 (9) ◽  
pp. 1214-1219 ◽  
Author(s):  
F Nelson ◽  
A Poonawalla ◽  
P Hou ◽  
JS Wolinsky ◽  
PA Narayana
Keyword(s):  
Multiple Sclerosis ◽  
White Matter ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Inversion Recovery ◽  
High Signal ◽  
Cortical Lesions ◽  
Rapid Acquisition ◽  
Lesion Morphology

Background Gray matter lesions are known to be common in multiple sclerosis (MS) and are suspected to play an important role in disease progression and clinical disability. A combination of magnetic resonance imaging (MRI) techniques, double-inversion recovery (DIR), and phase-sensitive inversion recovery (PSIR), has been used for detection and classification of cortical lesions. This study shows that high-resolution three-dimensional (3D) magnetization-prepared rapid acquisition with gradient echo (MPRAGE) improves the classification of cortical lesions by allowing more accurate anatomic localization of lesion morphology. Methods 11 patients with MS with previously identified cortical lesions were scanned using DIR, PSIR, and 3D MPRAGE. Lesions were identified on DIR and PSIR and classified as purely intracortical or mixed. MPRAGE images were then examined, and lesions were re-classified based on the new information. Results The high signal-to-noise ratio, fine anatomic detail, and clear gray-white matter tissue contrast seen in the MPRAGE images provided superior delineation of lesion borders and surrounding gray-white matter junction, improving classification accuracy. 119 lesions were identified as either intracortical or mixed on DIR/PSIR. In 89 cases, MPRAGE confirmed the classification by DIR/PSIR. In 30 cases, MPRAGE overturned the original classification. Conclusion Improved classification of cortical lesions was realized by inclusion of high-spatial resolution 3D MPRAGE. This sequence provides unique detail on lesion morphology that is necessary for accurate classification.

AAT Observations of the Interstellar Medium towards SN 1987A

1988 ◽  
Vol 7 (4) ◽  
pp. 527-534 ◽  
Author(s):  
M. Pettini
Keyword(s):  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Large Magellanic Cloud ◽  
High Spectral Resolution ◽  
High Signal ◽  
Interstellar Matter ◽  
Interstellar Clouds ◽  
Sn 1987A ◽  
Light Echoes ◽  
Dimensional Distribution

AbstractThe exceptional brightness of SN 1987A has provided a unique opportunity to probe intervening gas clouds in the disk and halo of our Galaxy and in the Large Magellanic Cloud, as well as intergalactic matter between the two. At the AAO we have exploited this opportunity in two ways: in searches for very weak interstellar features requiring exceptionally high signal-to-noise ratio spectra, and in recording known interstellar lines with unprecedentedly high spectral resolution. We are also monitoring photographically the evolution of the light-echoes to map the three-dimensional distribution of interstellar matter near the supernova. Surprisingly high column densities of million-degree gas have been found in the LMC through the first detection of [Fe X] in absorption. The hot gas may fill the interior of a ‘superbubble’, created by the combined effects of previous supernovae in this active region of star-formation; this cavity may be related to the shells of interstellar matter giving rise to the light-echoes. The ultra-high resolution observations, which required the rapid construction of a dedicated new spectrograph, were successful in resolving the hyperfine structure of the sodium D lines in several interstellar clouds. This implies that the clouds are at temperatures of at most 170 K and have internal turbulent velocities of no more than 0.3 km s−1, even though some are moving with high velocities relative to the Sun.

Three-Dimensional Optical Bit Memory in Sm(DBM)3Phen-Doped and Un-Doped Poly(methyl methacrylate)

2011 ◽  
Vol 284-286 ◽  
pp. 2251-2254
Author(s):  
Zhao Gang Nie ◽  
Xin Zhong Li ◽  
Yu Ping Tai ◽  
Ki Soo Lim ◽  
Myeongkyu Lee
Keyword(s):  
Refractive Index ◽  
Methyl Methacrylate ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Pulsed Laser ◽  
High Signal ◽  
Signal To Noise ◽  
Fluorescent Signal ◽  
Poly Methyl Methacrylate ◽  
Noise Ratio

The feasibility of three-dimensional optical bit memory is demonstrated by using the change of fluorescence and refractive index in Sm(DBM)3Phen-doped and un-doped Poly(methyl methacrylate). After a femtosecond pulsed laser irradiation, a refractive-index bit and a fluorescent bit can be formed at the same position inside the bulk sample. Multilayer patterns recorded by tightly focusing the pulsed laser beam were read out by a reflection-type fluorescent confocal microscope, which can detect the reflection signal and also the fluorescent signal of the stored bits. The signal-to-noise ratio via the two retrieval modes was compared as a function of recording depth. The stored bits were retrieved with a high signal-to-noise ratio in the absence of any crosstalk and the detection of the fluorescent signal enables retrieval of the stored bits with a higher S/N ratio.

DEVELOPMENT OF PHANTOM FOR PERFORMANCE EVALUATION OF MICRO-CT

2008 ◽  
Vol 20 (03) ◽  
pp. 177-184 ◽  
Author(s):  
Kevin Wen-Kai Tsai ◽  
Ho-Shiang Chueh ◽  
Jyh-Cheng Chen
Keyword(s):  
Performance Evaluation ◽  
Spatial Resolution ◽  
Evaluation Method ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Research Field ◽  
High Signal ◽  
Micro Ct ◽  
Analytic Methods ◽  
American Society

Micro-X-ray computed tomography (micro-CT) has several characters such as non-invasive, high spatial resolution, high signal-to-noise ratio, providing three-dimensional volume information. Because micro-CT was utilized in many kinds of research field such as preclinical biomedical study, designing a performance phantom and developing analytic methods to objectively evaluate the performance of micro-CT are very important. In this study, the performance phantom and the analytic methods were developed for performance evaluation of micro-CT. The performance parameters extracted from different CT images including noise, linearity, spatial resolution, and hardware alignment were defined in the American Association of Physicists in Medicine (AAPM) Report No. 1 and the American Society for Testing and Materials (ASTM) E1695-95. Standard deviation, Pearson's correlation coefficient, edge response function, and visualization method were utilized to evaluate noise, linearity, spatial resolution, and hardware alignment, respectively. A digital uniform disk image was utilized to evaluate the accuracy of spatial resolution evaluation method. The physical phantom study was performed to evaluate a home-made micro-CT and a commercial micro-CT (Skyscan 1076). According to these results, the performance phantom and the analytic methods developed in this study have demonstrated their capability to evaluate performance of any micro-CT.

Flexoelectricity in Bulk and Nanoscale Polar and Non-Polar Dielectrics

2015 ◽  
Vol 232 ◽  
pp. 213-233
Author(s):  
Ashok Kumar ◽  
Hitesh Borkar
Keyword(s):  
Strain Gradient ◽  
Signal To Noise Ratio ◽  
Basic Mechanism ◽  
Dielectric Materials ◽  
Device Fabrication ◽  
Dimensional Structure ◽  
High Signal ◽  
Nanoscale Materials ◽  
Epitaxial Thin Films ◽  
History Of

Piezoelectricity (PE) is defined as the polarization under homogeneous application of stress on polar/non-centrosymmetry/no-inversion symmetry dielectrics, whereas it has been commonly accepted that flexoelectricity (FLX) is the induced polarization due to strain gradient in any polar/nonpolar dielectrics, the latter effect is universal and can be generated in any materials under inhomogeneous stress. Flexoelectricity is inversely proportional to the size of materials and devices which further suggests that giant FLX effects may develop in nanoscale materials. Flexoelectricity represents the polarization due to strain gradient and have significant effects on the functional properties of nanoscale materials, epitaxial thin films, one-dimensional structure with various shape and size, liquid crystals, polymers, nanobio-hybrid materials, etc. Till late sixties, very few works on flexoelectricity have been reported due to very weak magnitude compared to piezoelectricity. Advancement in nanoscale materials and device fabrication process and highly sophisticated electronics with detection of data with high signal to noise ratio lead the scientists/researchers to get several orders of higher flexoelectric coefficients compared to the proposed theoretical limits. Recently, giant FLX have been observed in nanoscale materials and their magnitudes are six to seven orders larger than the theoretical limits. In this review article, we describe the basic mechanism of flexoelectricity, brief history of discovery, theoretical modeling, experimental procedures, and results reported by several authors for bulk and nanoscale ferroelectric and dielectric materials.

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