scholarly journals Observing---and Imaging---Active Galactic Nuclei with the Event Horizon Telescope

2016 ◽  
Author(s):  
Vincent Fish ◽  
Kazunori Akiyama ◽  
Katherine Bouman ◽  
Andrew Chael ◽  
Michael Johnson ◽  
...  
Keyword(s):  
Event Horizon ◽  
Imaging Techniques ◽  
Galactic Nuclei ◽  
High Angular Resolution ◽  
Nearby Galaxy ◽  
Reconstruction Algorithms ◽  
Sagittarius A ◽  
The Status ◽  
Image Reconstruction Algorithms ◽  
Very High

Originally developed to image the shadow region of the central black hole in Sagittarius A* and in the nearby galaxy M87, the Event Horizon Telescope (EHT) provides deep, very high angular resolution data on other AGN sources too. The challenges of working with EHT data have spurred the development of new image reconstruction algorithms. This work briefly reviews the status of the EHT and its utility for observing AGN sources, with emphasis on novel imaging techniques that offer the promise of better reconstructions at 1.3 mm and other wavelengths.

scholarly journals Bio-Inspired Multimodal Imaging in Reduced Visibility

2022 ◽  
Vol 3 ◽  
Author(s):  
Pierre-Jean Lapray ◽  
Jean-Baptiste Thomas ◽  
Ivar Farup
Keyword(s):  
Multimodal Imaging ◽  
Imaging Techniques ◽  
Biological Imaging ◽  
Imaging Systems ◽  
Reconstruction Algorithms ◽  
Benchmark Experiment ◽  
Visual Systems ◽  
Statistical Relevance ◽  
The Difference ◽  
Image Reconstruction Algorithms

The visual systems found in nature rely on capturing light under different modalities, in terms of spectral sensitivities and polarization sensitivities. Numerous imaging techniques are inspired by this variety, among which, the most famous is color imaging inspired by the trichromacy theory of the human visual system. We investigate the spectral and polarimetric properties of biological imaging systems that will lead to the best performance on scene imaging through haze, i.e., dehazing. We design a benchmark experiment based on modalities inspired by several visual systems, and adapt state-of-the-art image reconstruction algorithms to those modalities. We show the difference in performance of each studied systems and discuss it in front of our methodology and the statistical relevance of our data.

Small-Angle Electron Scattering (SAES) of Polymers

1985 ◽  
Vol 43 ◽  
pp. 78-79
Author(s):  
Ralph Oralor ◽  
Pamela Lloyd ◽  
Satish Kumar ◽  
W. W. Adams
Keyword(s):  
Electron Scattering ◽  
Small Angle ◽  
Angular Resolution ◽  
Structural Features ◽  
Objective Lens ◽  
High Angular Resolution ◽  
Push Button ◽  
First Case ◽  
Diffraction Mode ◽  
Very High

Small angle electron scattering (SAES) has been used to study structural features of up to several thousand angstroms in polymers, as well as in metals. SAES may be done either in (a) long camera mode by switching off the objective lens current or in (b) selected area diffraction mode. In the first case very high camera lengths (up to 7Ø meters on JEOL 1Ø ØCX) and high angular resolution can be obtained, while in the second case smaller camera lengths (approximately up to 3.6 meters on JEOL 1Ø ØCX) and lower angular resolution is obtainable. We conducted our SAES studies on JEOL 1ØØCX which can be switched to either mode with a push button as a standard feature.

Three dimensional deblurring of transmitted-light brightfield micrographs

1993 ◽  
Vol 51 ◽  
pp. 564-565
Author(s):  
Santosh Bhattacharyya
Keyword(s):  
Image Reconstruction ◽  
Three Dimensional ◽  
Transmitted Light ◽  
Reconstruction Algorithms ◽  
3D Image Reconstruction ◽  
Structural Details ◽  
Spread Function ◽  
Early Testing ◽  
Linearized Model ◽  
Image Reconstruction Algorithms

Three dimensional microscopic structures play an important role in the understanding of various biological and physiological phenomena. Structural details of neurons, such as the density, caliber and volumes of dendrites, are important in understanding physiological and pathological functioning of nervous systems. Even so, many of the widely used stains in biology and neurophysiology are absorbing stains, such as horseradish peroxidase (HRP), and yet most of the iterative, constrained 3D optical image reconstruction research has concentrated on fluorescence microscopy. It is clear that iterative, constrained 3D image reconstruction methodologies are needed for transmitted light brightfield (TLB) imaging as well. One of the difficulties in doing so, in the past, has been in determining the point spread function of the system.We have been developing several variations of iterative, constrained image reconstruction algorithms for TLB imaging. Some of our early testing with one of them was reported previously. These algorithms are based on a linearized model of TLB imaging.

Ionized gas kinematics and luminosity profiles of Low-z Lyman Alpha Blobs

2019 ◽  
Vol 15 (S359) ◽  
pp. 413-414
Author(s):  
María P. Agüero ◽  
Rubén Díaz ◽  
Mischa Schirmer
Keyword(s):  
Emission Line ◽  
Galactic Nuclei ◽  
Host Galaxies ◽  
Ionized Gas ◽  
Lyman Alpha ◽  
Gas Kinematics ◽  
The Universe ◽  
Very High ◽  
The Continuum

AbstractThis work is focused on the characterization of the Seyfert-2 galaxies hosting very large, ultra-luminous narrow-line regions (NLRs) at redshifts z = 0.2−0.34. With a space density of 4.4 Gcp−3 at z ∼ 0.3, these “Low Redshift Lyman-α Blob” (LAB) host galaxies are amongst the rarest objects in the universe, and represent an exceptional and short-lived phenomenon in the life cycle of active galactic nuclei (AGNs). We present the study of GMOS spectra for 13 LAB galaxies covering the rest frame spectral range 3700–6700 Å. Predominantly, the [OIII]λ5007 emission line radial distribution is as widespread as that of the continuum one. The emission line profiles exhibit FWHM between 300–700 Km s−1. In 7 of 13 cases a broad kinematical component is detected with FWHM within the range 600–1100 Km s−1. The exceptionally high [OIII]λ5007 luminosity is responsible for very high equivalent width reaching 1500 Å at the nucleus.

scholarly journals Radiation Dose Reduction in CT Torsion Measurement of the Lower Limb: Introduction of a New Ultra-Low Dose Protocol

Diagnostics ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1209
Author(s):  
Gabriel Keller ◽  
Simon Götz ◽  
Mareen Sarah Kraus ◽  
Leonard Grünwald ◽  
Fabian Springer ◽  
...  
Keyword(s):  
Radiation Dose ◽  
Radiation Exposure ◽  
Lower Limb ◽  
Low Dose ◽  
Body Volume ◽  
Reconstruction Algorithms ◽  
Pelvic Radiograph ◽  
Lower Radiation Dose ◽  
Median Total Dose ◽  
Image Reconstruction Algorithms

This study analyzed the radiation exposure of a new ultra-low dose (ULD) protocol compared to a high-quality (HQ) protocol for CT-torsion measurement of the lower limb. The analyzed patients (n = 60) were examined in the period March to October 2019. In total, 30 consecutive patients were examined with the HQ and 30 consecutive patients with the new ULD protocol comprising automatic tube voltage selection, automatic exposure control, and iterative image reconstruction algorithms. Radiation dose parameters as well as the contrast-to-noise ratio (CNR) and diagnostic confidence (DC; rated by two radiologists) were analyzed and potential predictor variables, such as body mass index and body volume, were assessed. The new ULD protocol resulted in significantly lower radiation dose parameters, with a reduction of the median total dose equivalent to 0.17 mSv in the ULD protocol compared to 4.37 mSv in the HQ protocol (p < 0.001). Both groups showed no significant differences in regard to other parameters (p = 0.344–0.923). CNR was 12.2% lower using the new ULD protocol (p = 0.033). DC was rated best by both readers in every HQ CT and in every ULD CT. The new ULD protocol for CT-torsion measurement of the lower limb resulted in a 96% decrease of radiation exposure down to the level of a single pelvic radiograph while maintaining good image quality.

scholarly journals Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

2021 ◽  
Author(s):  
Michael Janssen ◽  
Heino Falcke ◽  
Matthias Kadler ◽  
Eduardo Ros ◽  
Maciek Wielgus ◽  
...  
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
Radio Jets ◽  
Long Baseline ◽  
Wide Range ◽  
Terahertz Frequencies ◽  
Source Structure ◽  
Centaurus A

AbstractVery-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources1. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses5,6.

scholarly journals Muon Tracing and Image Reconstruction Algorithms for Cosmic Ray Muon Computed Tomography

2019 ◽  
Vol 28 (1) ◽  
pp. 426-435 ◽  
Author(s):  
Zhengzhi Liu ◽  
Stylianos Chatzidakis ◽  
John M. Scaglione ◽  
Can Liao ◽  
Haori Yang ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Image Reconstruction ◽  
Cosmic Ray ◽  
Reconstruction Algorithms ◽  
Image Reconstruction Algorithms

scholarly journals A Benchmark Dataset and Deep Learning-Based Image Reconstruction for Electrical Capacitance Tomography

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3701 ◽  
Author(s):  
Jin Zheng ◽  
Jinku Li ◽  
Yi Li ◽  
Lihui Peng
Keyword(s):  
Machine Learning ◽  
Image Reconstruction ◽  
Benchmark Dataset ◽  
Electrical Capacitance Tomography ◽  
Electrical Capacitance ◽  
Reconstruction Algorithms ◽  
Reconstruction Methods ◽  
Image Reconstruction Algorithms ◽  
Capacitance Tomography ◽  
The Relationship

Electrical Capacitance Tomography (ECT) image reconstruction has developed for decades and made great achievements, but there is still a need to find a new theoretical framework to make it better and faster. In recent years, machine learning theory has been introduced in the ECT area to solve the image reconstruction problem. However, there is still no public benchmark dataset in the ECT field for the training and testing of machine learning-based image reconstruction algorithms. On the other hand, a public benchmark dataset can provide a standard framework to evaluate and compare the results of different image reconstruction methods. In this paper, a benchmark dataset for ECT image reconstruction is presented. Like the great contribution of ImageNet that transformed machine learning research, this benchmark dataset is hoped to be helpful for society to investigate new image reconstruction algorithms since the relationship between permittivity distribution and capacitance can be better mapped. In addition, different machine learning-based image reconstruction algorithms can be trained and tested by the unified dataset, and the results can be evaluated and compared under the same standard, thus, making the ECT image reconstruction study more open and causing a breakthrough.

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