scholarly journals NuSTAR reveals that the heavily obscured nucleus of NGC 2785 was the contaminant of IRAS 09104+4109 in the BeppoSAX/PDS hard X-rays

2018 ◽  
Vol 619 ◽  
pp. A16
Author(s):  
C. Vignali ◽  
P. Severgnini ◽  
E. Piconcelli ◽  
G. Lanzuisi ◽  
R. Gilli ◽  
...  
Keyword(s):  
X Rays ◽  
X Ray ◽  
Star Forming ◽  
Physical Description ◽  
Enhanced Sensitivity ◽  
X Ray Imaging ◽  
First Time ◽  
In Virtue Of

Context. The search for heavily obscured active galactic nuclei has been revitalized in the last five years by NuSTAR, which has provided a good census and spectral characterization of a population of such objects, mostly at low redshift, thanks to its enhanced sensitivity above 10 keV compared to previous X-ray facilities, and its hard X-ray imaging capabilities. Aims. We aim at demonstrating how NGC 2785, a local (z = 0.009) star-forming galaxy, is responsible, in virtue of its heavily obscured active nucleus, for significant contamination in the non-imaging BeppoSAX/PDS data of the relatively nearby (≈17′) quasar IRAS 09104+4109 (z = 0.44), which was originally mis-classified as Compton thick. Methods. We analyzed ≈71 ks NuSTAR data of NGC 2785 using the MYTorus model and provided a physical description of the X-ray properties of the source for the first time. Results. We found that NGC 2785 hosts a heavily obscured (NH ≈ 3 × 1024 cm−2) nucleus. The intrinsic X-ray luminosity of the source, once corrected for the measured obscuration (L2−10keV ≈ 1042 erg s−1), is consistent within a factor of a few with predictions based on the source mid-infrared flux using widely adopted correlations from the literature. Conclusions. Based on NuSTAR data and previous indications from the Neil Gehrels Swift Observatory (BAT instrument), we confirm that NGC 2785, because of its hard X-ray emission and spectral shape, was responsible for at least one third of the 20–100 keV emission observed using the PDS instrument onboard BeppoSAX, originally completely associated with IRAS 09104+4109. Such emission led to the erroneous classification of this source as a Compton-thick quasar, while it is now recognized as Compton thin.

scholarly journals X-ray Scatter Imaging of Hepatocellular Carcinoma in a Mouse Model Using Nanoparticle Contrast Agents

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Danielle Rand ◽  
Zoltan Derdak ◽  
Rolf Carlson ◽  
Jack R. Wands ◽  
Christoph Rose-Petruck
Keyword(s):  
Hepatocellular Carcinoma ◽  
Mouse Model ◽  
Contrast Agents ◽  
Malignant Tumors ◽  
Detection Methods ◽  
X Rays ◽  
X Ray ◽  
Enhanced Sensitivity ◽  
X Ray Imaging

Abstract Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide and is almost uniformly fatal. Current methods of detection include ultrasound examination and imaging by CT scan or MRI; however, these techniques are problematic in terms of sensitivity and specificity and the detection of early tumors (<1 cm diameter) has proven elusive. Better, more specific and more sensitive detection methods are therefore urgently needed. Here we discuss the application of a newly developed x-ray imaging technique called Spatial Frequency Heterodyne Imaging (SFHI) for the early detection of HCC. SFHI uses x-rays scattered by an object to form an image and is more sensitive than conventional absorption-based x-radiography. We show that tissues labeled in vivo with gold nanoparticle contrast agents can be detected using SFHI. We also demonstrate that directed targeting and SFHI of HCC tumors in a mouse model is possible through the use of HCC-specific antibodies. The enhanced sensitivity of SFHI relative to currently available techniques enables the x-ray imaging of tumors that are just a few millimeters in diameter and substantially reduces the amount of nanoparticle contrast agent required for intravenous injection relative to absorption-based x-ray imaging.

Observations from the Hinotori mission

1991 ◽  
Vol 336 (1643) ◽  
pp. 339-347 ◽  
Keyword(s):  
Solar Flares ◽  
Bragg Diffraction ◽  
High Dispersion ◽  
X Rays ◽  
Crystal Spectrometer ◽  
Quartz Crystals ◽  
X Ray ◽  
X Ray Imaging ◽  
Imaging Telescope ◽  
First Time

The satellite Hinotori was launched in 1981 by the Institute of Space and Astronautical Science of Japan. Two major experiments on board the Hinotori satellite were a hard X-ray imaging telescope with modulation collimators, and a high dispersion soft X-ray crystal spectrometer utilizing the Bragg diffraction of X-rays on quartz crystals. These two instruments have revealed for the first time that solar flares show varying characteristics depending on the environment of flaring regions, and that flares produce plasmas as hot as 3-4 x 10 7 K.

X-ray Imaging of Surface and Internal Structure

1987 ◽  
Vol 31 ◽  
pp. 25-34
Author(s):  
John C. Russ
Keyword(s):  
Internal Structure ◽  
Bragg Diffraction ◽  
X Rays ◽  
Widespread Application ◽  
X Ray ◽  
Study Materials ◽  
X Ray Imaging ◽  
Composition Variation ◽  
Hospital Emergency Room

The most familiar result from X-ray analysis is a spectrum (on a chart recording or on film), or perhaps a short list of values (concentrations, d-spacings, etc.) taken from such a spectrum. X-ray pictures are usually associated in our minds with the hospital emergency room or the dentist's office. But images formed by X-rays are also an important tool to study materials' structures. Both conventional and unconventional uses of X-rays to study structural and compositional inhomogeneities find widespread application to materials. Applications include characterization of surface topography and composition variation, as well as internal structure. The methods make use of all types of X-ray interaction with materials, including Bragg diffraction and the fluorescence of characteristic X-rays, as well as simple X-ray attenuation due to absorption and scattering.

scholarly journals Characterization of the Percival detector with soft X-rays

2021 ◽  
Vol 28 (1) ◽  
pp. 131-145
Author(s):  
Alessandro Marras ◽  
Jonathan Correa ◽  
Sabine Lange ◽  
Vahagn Vardanyan ◽  
Tim Gerhardt ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Single Photon ◽  
Back Side ◽  
X Rays ◽  
Performance Parameters ◽  
X Ray ◽  
Discrimination Capability ◽  
First Time

In this paper the back-side-illuminated Percival 2-Megapixel (P2M) detector is presented, along with its characterization by means of optical and X-ray photons. For the first time, the response of the system to soft X-rays (250 eV to 1 keV) is presented. The main performance parameters of the first detector are measured, assessing the capabilities in terms of noise, dynamic range and single-photon discrimination capability. Present limitations and coming improvements are discussed.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

Defects of Platelet Function Recognized by X-Ray Imaging and Scanning Electron Microscopy

1985 ◽  
Vol 43 ◽  
pp. 610-613
Author(s):  
M.G. Baldini ◽  
S. Morinaga ◽  
D. Minasian ◽  
R. Feder ◽  
D. Sayre ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cell Biology ◽  
Imaging Technique ◽  
Human Platelets ◽  
X Rays ◽  
X Ray ◽  
X Ray Imaging ◽  
Complex Phenomena ◽  
Scanning Electron

Contact X-ray imaging is presently developing as an important imaging technique in cell biology. Our recent studies on human platelets have demonstrated that the cytoskeleton of these cells contains photondense structures which can preferentially be imaged by soft X-ray imaging. Our present research has dealt with platelet activation, i.e., the complex phenomena which precede platelet appregation and are associated with profound changes in platelet cytoskeleton. Human platelets suspended in plasma were used. Whole cell mounts were fixed and dehydrated, then exposed to a stationary source of soft X-rays as previously described. Developed replicas and respective grids were studied by scanning electron microscopy (SEM).

Tracing young SMBHs in the dusty distant universe – a Chandra view of DOGs

2020 ◽  
Vol 15 (S359) ◽  
pp. 17-21
Author(s):  
Karín Menéndez-Delmestre ◽  
Laurie Riguccini ◽  
Ezequiel Treister
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Far Infrared ◽  
Host Galaxy ◽  
X Ray ◽  
Star Forming ◽  
Near Ir ◽  
X Ray Imaging ◽  
Combined Use ◽  
Dusty Galaxies

AbstractThe coexistence of star formation and AGN activity has geared much attention to dusty galaxies at high redshifts, in the interest of understanding the origin of the Magorrian relation observed locally, where the mass of the stellar bulk in a galaxy appears to be tied to the mass of the underlying supermassive black hole. We exploit the combined use of far-infrared (IR) Herschel data and deep Chandra ˜160 ksec depth X-ray imaging of the COSMOS field to probe for AGN signatures in a large sample of >100 Dust-Obscured Galaxies (DOGs). Only a handful (˜20%) present individual X-ray detections pointing to the presence of significant AGN activity, while X-ray stacking analysis on the X-ray undetected DOGs points to a mix between AGN activity and star formation. Together, they are typically found on the main sequence of star-forming galaxies or below it, suggesting that they are either still undergoing significant build up of the stellar bulk or have started quenching. We find only ˜30% (6) Compton-thick AGN candidates (NH > 1024 cm–2), which is the same frequency found within other soft- and hard-X-ray selected AGN populations. This suggests that the large column densities responsible for the obscuration in Compton-thick AGNs must be nuclear and have little to do with the dust obscuration of the host galaxy. We find that DOGs identified to have an AGN share similar near-IR and mid-to-far-IR colors, independently of whether they are individually detected or not in the X-ray. The main difference between the X-ray detected and the X-ray undetected populations appears to be in their redshift distributions, with the X-ray undetected ones being typically found at larger distances. This strongly underlines the critical need for multiwavelength studies in order to obtain a more complete census of the obscured AGN population out to higher redshifts. For more details, we refer the reader to Riguccini et al. (2019).

scholarly journals Morphological and Ultrastructural Characterization of Hemocytes in an Insect Model, the Hematophagous Dipetalogaster maxima (Hemiptera: Reduviidae)

Insects ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 640
Author(s):  
Natalia R. Moyetta ◽  
Fabián O. Ramos ◽  
Jimena Leyria ◽  
Lilián E. Canavoso ◽  
Leonardo L. Fruttero
Keyword(s):  
Cell Biology ◽  
Cell Types ◽  
Transmission Electron ◽  
Ultrastructural Characterization ◽  
Current Classification ◽  
Contrast Microscopy ◽  
First Time ◽  
Controversial Aspect

Hemocytes, the cells present in the hemolymph of insects and other invertebrates, perform several physiological functions, including innate immunity. The current classification of hemocyte types is based mostly on morphological features; however, divergences have emerged among specialists in triatomines, the insect vectors of Chagas’ disease (Hemiptera: Reduviidae). Here, we have combined technical approaches in order to characterize the hemocytes from fifth instar nymphs of the triatomine Dipetalogaster maxima. Moreover, in this work we describe, for the first time, the ultrastructural features of D. maxima hemocytes. Using phase contrast microscopy of fresh preparations, five hemocyte populations were identified and further characterized by immunofluorescence, flow cytometry and transmission electron microscopy. The plasmatocytes and the granulocytes were the most abundant cell types, although prohemocytes, adipohemocytes and oenocytes were also found. This work sheds light on a controversial aspect of triatomine cell biology and physiology setting the basis for future in-depth studies directed to address hemocyte classification using non-microscopy-based markers.

scholarly journals Integration of Dental Implants in Conjunction with EDTA-Conditioned Dentin Grafts: An Experimental Study

2021 ◽  
Vol 9 (6) ◽  
pp. 63
Author(s):  
Payam Farzad ◽  
Ted Lundgren ◽  
Adel Al-Asfour ◽  
Lars Andersson ◽  
Christer Dahlin
Keyword(s):  
Direct Contact ◽  
Mineral Content ◽  
X Rays ◽  
X Ray ◽  
Dentin Surface ◽  
Significant Difference ◽  
C And N ◽  
Micro Implants ◽  
Demineralized Dentin

This study was undertaken to investigate the integration of titanium micro-implants installed in conjunction with previously dentin-grafted areas and to study the morphological appearance, mineral content, and healing pattern of xenogenic EDTA-conditioned dentin blocks and granules grafted to cavities in the tibial bone of rabbits. Demineralized and non-demineralized dentin blocks and granules from human premolars were implanted into cavities prepared on the lateral aspects of the tibias of rabbits. After a healing period of six months, micro-implants were installed at each surgical site. Histological examinations were carried out after 24 weeks. Characterization of the EDTA-conditioned dentin blocks was performed by means of light microscopy, dental X-rays, scanning electron microscopy, and energy dispersive X-ray analysis (EDX). No implants were found to be integrated in direct contact with the dentin particles or blocks. On the EDTA-conditioned dentin surface, the organic marker elements C and N dominated, as revealed by EDX. The hydroxyapatite constituents Ca and P were almost absent on the dentin surface. No statistically significant difference was observed between the EDTA-conditioned and non-demineralized dentin, as revealed by BIC and BA. The bone-inductive capacity of the dentin material seemed limited, although demineralization by means of EDTA indicated higher BIC and BA values in conjunction with the installed implants in the area. A 12 h EDTA treatment did not fully decalcify the grafts, as revealed by X-ray analysis.

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