scholarly journals Temporal Resolution Phantom: A Device and Method for Measurement of a CT Scanner’s Temporal Resolution

2008 ◽  
Vol 2 (2) ◽  
Author(s):  
Alexander H. Slocum ◽  
Stephen E. Jones ◽  
Rajiv Gupta
Keyword(s):  
Temporal Resolution ◽  
Imaging Modality ◽  
Temporal Frequency ◽  
Planetary Gear ◽  
Multiple Time ◽  
Functional Requirements ◽  
Ct Scanner ◽  
Calibration Phantom ◽  
Wide Range ◽  
Further Development

A calibration phantom that can be used to measure the temporal resolution of a CT scanner was designed utilizing a deterministic design process. The system was first defined in terms of a set of functional requirements based on parameters of the imaging modality. It was necessary to generate multiple time-varying signals visible to the scanner, each with a pre-determined temporal frequency. Roll-off in the scanner’s ability to resolve the modulation of certain signals would be used to determine the scanner’s temporal resolution. Based on size limitations imposed by the scanning environment, the phantom utilizes multiple planetary gear assemblies, driven by a common shaft, to achieve a wide range of rotational velocities. Results obtained with an alpha prototype agreed with the theory. It was determined that further development of the phantom was necessary to increase the sensitivity of the measurement. The latest prototype phantom has been used to measure the temporal resolution of two different scanners and it was shown that temporal resolution of each is different from the gantry rotation time.

Design of a Calibration Phantom for Measuring the Temporal Resolution of a Tomographic Imaging Device

2007 ◽  
Vol 1 (3) ◽  
pp. 225-232
Author(s):  
Alexander H. Slocum ◽  
Stephen E. Jones ◽  
Rajiv Gupta
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
Planetary Gear ◽  
Tomographic Imaging ◽  
Spatial Modulation ◽  
Acquisition Time ◽  
Input Frequency ◽  
Modulation Transfer ◽  
Imaging Device ◽  
Calibration Phantom

This paper describes the design and development of a calibration phantom to be used to aid in the calculation of the temporal resolution of tomographic imaging devices. Current practice for characterizing the dynamic response of a tomographic imaging device, such as a computed tomography or magnetic resonance imaging machine, uses image acquisition time as a surrogate for temporal resolution. At present, no standard method for describing the temporal resolution of a tomographic imaging device exists. Similar to the spatial modulation transfer function (MTF) used for characterizing spatial resolution, the concept of temporal MTF (t-MTF) can be used to enable characterization of temporal resolution. A scanner’s t-MTF represents the percentage amplitude modulation transfer in the image as a function of the input frequency. The calibration phantom uses slotted disks, each mounted to the rotating ring gear of a planetary gear assembly. The sun gears of each planetary gear set are driven from a common shaft to create differential speed sectors, allowing for about two decades of input frequencies to be obtained using a single motor and driveshaft. Preliminary results show a monotonic decline in the modulation transfer as the input frequency is increased. As expected, there is more modulation transfer at lower frequency and less modulation transfer at high frequency. Analogous to the spatial resolution, one can define the frequency for which there is 10% modulation transfer as the temporal resolution of a scanner.

Application of TEM to Deformation, Wear, and Fracture of Ceramics

1974 ◽  
Vol 32 ◽  
pp. 472-473
Author(s):  
B. J. Hockey
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Brittle Materials ◽  
High Temperature Strength ◽  
Wide Range ◽  
Corrosive Environments ◽  
Further Development

Ceramics, such as Al2O3 and SiC have numerous current and potential uses in applications where high temperature strength, hardness, and wear resistance are required often in corrosive environments. These materials are, however, highly anisotropic and brittle, so that their mechanical behavior is often unpredictable. The further development of these materials will require a better understanding of the basic mechanisms controlling deformation, wear, and fracture.The purpose of this talk is to describe applications of TEM to the study of the deformation, wear, and fracture of Al2O3. Similar studies are currently being conducted on SiC and the techniques involved should be applicable to a wide range of hard, brittle materials.

scholarly journals Status of Phenological Research Using Sentinel-2 Data: A Review

2020 ◽  
Vol 12 (17) ◽  
pp. 2760
Author(s):  
Gourav Misra ◽  
Fiona Cawkwell ◽  
Astrid Wingler
Keyword(s):  
Vegetation Index ◽  
Temporal Frequency ◽  
Short Wave ◽  
Current State ◽  
Red Edge ◽  
Natural Grasslands ◽  
Wide Range ◽  
Normalised Difference Vegetation Index ◽  
Satellite Sensors ◽  
Sentinel 2

Remote sensing of plant phenology as an indicator of climate change and for mapping land cover has received significant scientific interest in the past two decades. The advancing of spring events, the lengthening of the growing season, the shifting of tree lines, the decreasing sensitivity to warming and the uniformity of spring across elevations are a few of the important indicators of trends in phenology. The Sentinel-2 satellite sensors launched in June 2015 (A) and March 2017 (B), with their high temporal frequency and spatial resolution for improved land mapping missions, have contributed significantly to knowledge on vegetation over the last three years. However, despite the additional red-edge and short wave infra-red (SWIR) bands available on the Sentinel-2 multispectral instruments, with improved vegetation species detection capabilities, there has been very little research on their efficacy to track vegetation cover and its phenology. For example, out of approximately every four papers that analyse normalised difference vegetation index (NDVI) or enhanced vegetation index (EVI) derived from Sentinel-2 imagery, only one mentions either SWIR or the red-edge bands. Despite the short duration that the Sentinel-2 platforms have been operational, they have proved their potential in a wide range of phenological studies of crops, forests, natural grasslands, and other vegetated areas, and in particular through fusion of the data with those from other sensors, e.g., Sentinel-1, Landsat and MODIS. This review paper discusses the current state of vegetation phenology studies based on the first five years of Sentinel-2, their advantages, limitations, and the scope for future developments.

The functions and positions of political parties in consociational democracies: theoretical and empirical contexts

2020 ◽  
pp. 28-33
Author(s):  
O. Morhuniuk
Keyword(s):  
Political Parties ◽  
The Netherlands ◽  
Party System ◽  
Party Competition ◽  
European Countries ◽  
The Past ◽  
Democratic Regimes ◽  
Wide Range ◽  
Key Aspects ◽  
Further Development

An article is devoted to the analysis of the functions and formats of political parties in consociational democracies. In particular, it is defined that parties that represent the interests of certain subcultures in society and that reach a consensus among themselves at the level of political agreements are called segmental. At the same time, parties that encapsulate different subgroups of the society that cooperate inside the party within main features of the consociational theory (grand coalition, mutual veto, proportionality in representations, and independence of segments or society subcultures) are called consociational. The theory of consociationalism has received a wide range of theoretical additions and criticism from political scientists over the past fifty years. And while political parties should have been, by definition, one of the key aspects of research within such democratic regimes (parties are part of large coalitions and agents of representation of certain subcultures), there is very scarce number of literature that focuses on this aspect. Therefore, the presented article provides a description of the functions of political parties that could be observed as inside their subcultures as well as in interaction with other segmental parties. Based on the experience of two European countries in the period of “classical” consociationalism (Belgium and the Netherlands), we explain the functions of the parties we have defined in such societies with examples of relevant consociational practices in them. Simultaneously with the analysis of segmental parties, the article also offers the characteristics of consociational parties. The emergence of such parties has its own institutional and historical features. The way of further development of the party system and the level of preservation of consociational practices makes it possible to understand the nature of changes in the societies. Similarly, the analysis of the forms of party competition and interaction between segmental parties makes it possible to outline the forms of those consociational changes that are taking place in the research countries.

Orthopteran DCMD neuron: a reevaluation of responses to moving objects. I. Selective responses to approaching objects

1992 ◽  
Vol 68 (5) ◽  
pp. 1654-1666 ◽  
Author(s):  
F. C. Rind ◽  
P. J. Simmons
Keyword(s):  
Moving Objects ◽  
Temporal Frequency ◽  
Angular Acceleration ◽  
Spike Rate ◽  
Single Peak ◽  
Wide Field ◽  
Movement Detector ◽  
Star Wars ◽  
Wide Range ◽  
Real Objects

1. The "descending contralateral movement detector" (DCMD) neuron in the locust has been challenged with a variety of moving stimuli, including scenes from a film (Star Wars), moving disks, and images generated by computer. The neuron responds well to any rapid movement. For a dark object moving along a straight path at a uniform velocity, the DCMD gives the strongest response when the object travels directly toward the eye, and the weakest when the object travels away from the eye. Instead of expressing selectivity for movements of small rather than large objects, the DCMD responds preferentially to approaching objects. 2. The neuron shows a clear selectivity for approach over recession for a variety of sizes and velocities of movement both of real objects and in simulated movements. When a disk that subtends > or = 5 degrees at the eye approaches the eye, there are two peaks in spike rate: one immediately after the start of movement; and a second that builds up during the approach. When a disk recedes from the eye, there is a single peak in response as the movement starts. There is a good correlation between spike rate and angular acceleration of the edges of the image over the eye. 3. When an object approaches from a distance sufficient for it to subtend less than one interommatidial angle at the start of its approach, there is a single peak in response. The DCMD tracks the approach, and, if the object moves at 1 m/s or faster, the spike rate increases throughout the duration of object movement. The size of the response depends on the speed of approach. 4. It is unlikely that the DCMD encodes the time to collision accurately, because the response depends on the size as well as the velocity of an approaching object. 5. Wide-field movements suppress the response to an approaching object. The suppression varies with the temporal frequency of the background pattern. 6. Over a wide range of contrasts of object against background, the DCMD gives a stronger response to approaching than to receding objects. For low contrasts, the selectivity is greater for objects that are darker than the background than for objects that are lighter.

scholarly journals Edwardsiella tardaEndocarditis Confirmed by Indium-111 White Blood Cell Scan: An Unusual Pathogen and Diagnostic Modality

2016 ◽  
Vol 2016 ◽  
pp. 1-3
Author(s):  
Kayleigh M. Litton ◽  
Bret A. Rogers
Keyword(s):  
Blood Cell ◽  
White Blood Cell ◽  
Imaging Modality ◽  
Edwardsiella Tarda ◽  
Human Pathogen ◽  
Diagnostic Modality ◽  
Prosthetic Aortic Valve ◽  
Wide Range ◽  
The Family ◽  
Indium 111

Edwardsiella tardais a freshwater marine member of the family Enterobacteriaceae which often colonizes fish, lizards, snakes, and turtles but is an infrequent human pathogen. Indium-111- (111In-) labeled white blood cell (WBC) scintigraphy is an imaging modality which has a wide range of reported sensitivity and specificity (from 60 to 100% and from 68 to 92%, resp.) for diagnosing acute and chronic infection. We describe a case of suspectedE. tardaprosthetic aortic valve and mitral valve endocarditis with probable vegetations and new mitral regurgitation on transthoracic and transesophageal echocardiograms which was supported with the use of111In-labeled WBC scintigraphy.

Brain abnormality detection using template matching

2018 ◽  
Vol 14 (4) ◽  
Author(s):  
G.B. Praveen ◽  
Anita Agrawal ◽  
Shrey Pareek ◽  
Amalin Prince
Keyword(s):  
Magnetic Resonance ◽  
Template Matching ◽  
Imaging Modality ◽  
Brain Mri ◽  
Tumor Segmentation ◽  
Processing Unit ◽  
Brain Disorders ◽  
Brain Tumor Segmentation ◽  
Central Processing ◽  
Wide Range

Abstract Magnetic resonance imaging (MRI) is a widely used imaging modality to evaluate brain disorders. MRI generates huge volumes of data, which consist of a sequence of scans taken at different instances of time. As the presence of brain disorders has to be evaluated on all magnetic resonance (MR) sequences, manual brain disorder detection becomes a tedious process and is prone to inter- and intra-rater errors. A technique for detecting abnormalities in brain MRI using template matching is proposed. Bias filed correction is performed on volumetric scans using N4ITK filter, followed by volumetric registration. Normalized cross-correlation template matching is used for image registration taking into account, the rotation and scaling operations. A template of abnormality is selected which is then matched in the volumetric scans, if found, the corresponding image is retrieved. Post-processing of the retrieved images is performed by the thresholding operation; the coordinates and area of the abnormality are reported. The experiments are carried out on the glioma dataset obtained from Brain Tumor Segmentation Challenge 2013 database (BRATS 2013). Glioma dataset consisted of MR scans of 30 real glioma patients and 50 simulated glioma patients. NVIDIA Compute Unified Device Architecture framework is employed in this paper, and it is found that the detection speed using graphics processing unit is almost four times faster than using only central processing unit. The average Dice and Jaccard coefficients for a wide range of trials are found to be 0.91 and 0.83, respectively.

scholarly journals Fluorescence lifetime imaging of pH along the secretory pathway

2021 ◽  
Author(s):  
Peter Linders ◽  
Martin ter Beest ◽  
Geert van den Bogaart
Keyword(s):  
Temporal Resolution ◽  
Fluorescence Lifetime ◽  
Secretory Pathway ◽  
Fluorescent Protein ◽  
Excitation Wavelength ◽  
Fluorescence Lifetime Imaging ◽  
Ph Homeostasis ◽  
Ph Changes ◽  
Lifetime Imaging ◽  
Wide Range

Many cellular processes are dependent on correct pH levels, and this is especially important for the secretory pathway. Defects in pH homeostasis in distinct organelles cause a wide range of diseases, including disorders of glycosylation and lysosomal storage diseases. Ratiometric imaging of the pH-sensitive mutant of green fluorescent protein (GFP), pHLuorin, has allowed for targeted pH measurements in various organelles, but the required sequential image acquisition is intrinsically slow and therefore the temporal resolution unsuitable to follow the rapid transit of cargo between organelles. We therefore applied fluorescence lifetime imaging microscopy (FLIM) to measure intraorganellar pH with just a single excitation wavelength. We first validated this method by confirming the pH in multiple compartments along the secretory pathway. Then, we analyze the dynamic pH changes within cells treated with Brefeldin A, a COPI coat inhibitor. Finally, we followed the pH changes of newly-synthesized molecules of the inflammatory cytokine tumor necrosis factor (TNF)-α while it was in transit from the endoplasmic reticulum via the Golgi to the plasma membrane. The toolbox we present here can be applied to measure intracellular pH with high spatial and temporal resolution, and can be used to assess organellar pH in disease models.

scholarly journals Tunable aziridinium ylide reactivity: non-covalent interactions enable divergent product outcomes

2021 ◽  
Author(s):  
Kate Nicastri ◽  
Soren Zappia ◽  
Jared Pratt ◽  
Julia Duncan ◽  
Ilia Guzei ◽  
...  
Keyword(s):  
Chemical Space ◽  
Steric Effects ◽  
Computational Studies ◽  
Rapid Preparation ◽  
Rotational Barriers ◽  
Wide Range ◽  
Non Covalent Interactions ◽  
Further Development ◽  
Covalent Interactions

Methods for rapid preparation of densely functionalized and stereochemically complex N-heterocyclic scaffolds are in demand for exploring potential new bioactive chemical space. This work describes experimental and computational studies to better understand the features of aziridinium ylides as intermediates for the synthesis of highly substituted dehydromorpholines. The development of this chemistry has enabled the extension of aziridinium ylide chemistry to the concomitant formation of both a C–N and a C–O bond in a manner that preserves the stereochemical information embedded in the substrate. The chemistry is tolerant of a wide range of functionalities that can be employed for DNA-encoded library (DEL) synthesis to prepare diverse libraries of heterocycles with potential bioactivity. In addition, we have uncovered several key insights that describe the importance of steric effects, rotational barriers around the C–N bond of the aziridinium ylide, and non-covalent interactions (NCIs) on the ultimate reaction outcome. These critical insights will assist in the further development of this chemistry to generate novel and complex N-heterocycles that will further expand complex amine chemical space.

scholarly journals HIGH RESOLUTION CAMERA DESIGN PLANNING THEORETICAL FOUNDATIONS FOR DRIVING SYSTEMS

2021 ◽  
Author(s):  
Viacheslav S. Stadnichuk ◽  
Valentin G. Kolobrodov ◽  
Oleksii O. Mosolab ◽  
Denis Yu. Kondratenko ◽  
Dmytro I. Ryabokon
Keyword(s):  
High Resolution ◽  
Optical Glass ◽  
Light Sensitivity ◽  
Design Parameters ◽  
Optical Parameters ◽  
Functional Requirements ◽  
Modulation Transfer ◽  
Road Signs ◽  
Wide Range ◽  
Camera Design

Background. Analysis of statistical data showed that in most cases the cause of the accident is driver error and, as a consequence, violation of traffic rules. In this regard, over the past 10 years, active developments in the field of recognition of road signs and other obstacles in the path of a car have been actively developing. Car manufacturers offer ready-made built-in systems, mounted behind the interior rearview mirror and connected to the car’s on-board computer, which carries out further control of the car in a critical situation. The main disadvantage of these systems of this class is the low range of recognition of road signs, the dependence of optical parameters on temperature and low light sensitivity. Objective. The purpose of the paper is to model an athermal objective for a high-resolution camera, investigate the characteristics of lenses depending on the ambient temperature. Methods. Analysis and modeling of objectives, lenses, optical glass from different materials. Results. A high-resolution camera objective for all types of cars is proposed. An athermal objective was developed for a high-resolution camera. Conclusions. The optimized athermal design of the visible spectrum objective for long-range car cameras is considered. Car cameras typically have a fixed focus, and forward-facing cameras typically require relatively long focal lengths to provide information about distant objects. The optical system for these cameras should provide high resolution, as well as operate in a wide range of ambient temperatures. The camera design parameters are derived from the functional requirements of road sign recognition at a distance of 200 m. The objective design has five lenses with spherical surfaces. The objective has a relative aperture of f/2 and a modulation transfer function (MTF) of more than 0.5 at 111 l/mm over the entire temperature range.

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