14,408 research outputs found
Covid19-Pneumonia-Normal Chest X-Ray Images
No full text- It is a medical images directory structure branched into 3 subfolders (COVID, NORMAL, PNEUMONIA) containing Chest X-ray (CXR) Images.- All images are preprocessed and resized to 256x256 in PNG format.- It helps the researcher and medical community to detect and classify COVID19 and Pneumonia from Chest X-Ray Images using Deep Learning.COVID-19: 1626 imagesNORMAL: 1802 imagesPNEUMONIA: 1800 imagesReferences:-If you are using this dataset for research purposes then cite the below articles:1. Shastri, S., Kansal, I., Kumar, S. et al. CheXImageNet: a novel architecture for accurate classification of Covid-19 with chest x-ray digital images using deep convolutional neural networks. Health Technol. 12, 193–204 (2022). https://doi.org/10.1007/s12553-021-00630-x2. Kumar S, Shastri S, Mahajan S, et al. LiteCovidNet: A lightweight deep neural network model for detection of COVID-19 using X-ray images. Int J Imaging Syst Technol. 2022;1‐17. DOI: https://doi.org/10.1002/ima.22770THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619
No full textXMM–Newton observations of the supergiant fast X-ray transient IGR J17544?2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provide a refined estimate of the orbital period at 4.9272?±?0.0004?d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM–Newton observations (each lasting ?15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR J17544?2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 1033?erg?s?1 (0.5–10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544?2619 dropped to ?4?×?1032?erg?s?1 (0.5–10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544?2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544?2619 and the supergiant fast X-ray transients (SFXTs) population. We conclude that accretion under the ‘quasi-spherical accretion’ model provides a good description of the behaviour of IGR J17544?2619 and suggests an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the neutron star under the quasi-spherical formulation. Hence, we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model
Scientometric Portrait of Homi Jehangir Bhabha: The Father of Indian Nuclear Research Programme
No full textQuantitative and qualitative analysis with graphic representation of the publication productivity of a scientist facilitates easy and clear perception about the work of a scientist. Bhabha’s scientific work spanned over more than three decades (1933-1967) during which he published 104 publications, which could be classified into nine fields: Interaction of Radiation with Matter (4), Quantum Electrodynamics (5), Mathematical Physics (2), Cosmic Ray Physics (18), Elementary Particle Physics (14), Field Theory (15), General Physics (2), Nuclear Physics (4) and General (40). The highest number of publications (6) were published in 1941, 1945 and 1964 respectively. The average number of publications published per year was 3.05. His productivity coefficient was 0.05 which is a clear indicates that his publication productivity was quite consistent throughout his scientific career. He was single author in 79 of his publications and the main author in 24 publications indicates that he always preferred to work himself and lead the team as ‘mentor’. Bhabha had 22 collaborators during the period. Team of research collaborators working with a successful scientist documents the sociological aspect of history of science while generating knowledge by a leader in a domain.
Bhabha became a citable author in 1937. Bhabha received 1211 citations to his 30 publications out of 104 publications. Out of 104, 74 publications did not receive any citations. Out of 74 publications, 40 publications dealt subjects mainly of general interest. Bhabha’s 86.66 percent of cited publications received their first citations within four years of their publication indicates that his publications were noticed immediately and had direct impact among the fellow researchers working all over the world. His overall citation rate was 11.64 per cited publication. The highest citations 389 were received to the domain ‘Cosmic ray physics’. The highest number of citations received were 45 in 1938. His self-citations were only 24 (1.98%) and citations by others were 1187 (98.02%). The highest self citations were six in 1946. Bhabha’s mean diachronous self-citation rate was 1.98. The highest citation rate 28.4 was to the domain ‘Quantum electrodynamics. His single authored publications have received the highest number 863 (71.26%) of citations. Bhabha’s five publications have been cited more than 100 times each. His publications have been cited by the authors working in various diverse fields like nuclear physics, mathematical physics, instrumentation, optics, geophysics and geochemistry, condensed matter physics, applied physics, electrical and electronic engineering, mechanical engineering etc., indicating a very diverse influence and impact of Bhabha’s publications. Bhabha’s publications have also been cited by the Nobel laureates like V. L. Ginzberg, Wolfgang Pauli, H. A. Bethe, M. Born, W. Bothe, E. P. Wigner, H. Yukawa, P. M. S. Blackett and C. N. Yang which is an indication of his originality of ideas and high quality of publications
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
GPU-accelerated depth map generation for X-ray simulations of complex CAD geometries
No full textInteractive x-ray simulations of complex computer-aided design (CAD) models can provide valuable insights for better interpretation of the defect signatures such as porosity from x-ray CT images. Generating the depth map along a particular direction for the given CAD geometry is the most compute-intensive step in x-ray simulations. We have developed a GPU-accelerated method for real-time generation of depth maps of complex CAD geometries. We preprocess complex components designed using commercial CAD systems using a custom CAD module and convert them into a fine user-defined surface tessellation. Our CAD module can be used by different simulators as well as handle complex geometries, including those that arise from complex castings and composite structures. We then make use of a parallel algorithm that runs on a graphics processing unit (GPU) to convert the finely-tessellated CAD model to a voxelized representation. The voxelized representation can enable heterogeneous modeling of the volume enclosed by the CAD model by assigning heterogeneous material properties in specific regions. The depth maps are generated from this voxelized representation with the help of a GPU-accelerated ray-casting algorithm. The GPU-accelerated ray-casting method enables interactive (> 60 frames-per-second) generation of the depth maps of complex CAD geometries. This enables arbitrarily rotation and slicing of the CAD model, leading to better interpretation of the x-ray images by the user. In addition, the depth maps can be used to aid directly in CT reconstruction algorithms.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This proceeding appeared in Grandin, Robert J., Gavin Young, Stephen D. Holland, and Adarsh Krishnamurthy. "GPU-accelerated depth map generation for X-ray simulations of complex CAD geometries." In AIP Conference Proceedings, vol. 1949, no. 1, p. 190002. AIP Publishing LLC, 2018, and may be found at
DOI: 10.1063/1.5031636.
Copyright 2018 Author(s).
Posted with permission
X-ray and neutron techniques for nanomaterials characterization
No full textFifth volume of a 40 volume series on nanoscience and nanotechnology, edited by the renowned scientist Challa S.S.R. Kumar. This handbook gives a comprehensive overview about X-ray and Neutron Techniques for Nanomaterials Characterization. Modern applications and state-of-the-art techniques are covered and make this volume an essential reading for research scientists in academia and industry
Energy conversion of X-ray, ultraviolet and infrared radiation in Gd2O3 crystals doped with Er3+ ions
No full textSpectra of photoluminescence (PL) and X-ray excited luminescence (XRL) in region of 1.5-5.0 eV, PL excitation spectra (2.8-5.8 eV), PL decay kinetics were measured in Gd2O3 crystals doped both with Er3+ and Zn2+ ions. Synchrotron radiation (VEPP-3 storage ring, Novosibirsk, Russia) were used for XRL measurements. PL spectra were studied at room temperature and T= 88 K under excitation with energy Eexc: a) in fundamental absorption region (Eexc≥Eg); b) in intracenter excitation region (Eexc<Eg); c) in infrared region (Eexc<<Eg) with using laser 980 nm diode as exciting photons (up-conversion processes). The probability of radiative transitions from excited states of the impurity center depends on Eexc. The photoluminescence efficiency in Gd2O3 doped with both Er3+ and Zn2+ ions in the green region decreases, 4F9/2→4I15/2 transitions dominate in the red region both in XRL and PL spectra. This effect is also clearly manifested in the spectra of anti-Stokes luminescence. Energy transfer between the excited Er3+ states of the impurity center and the crystal lattice defect is observed. Decrease of the lifetime of 4S3/2 excited state in Gd2O3:Er3+ + Zn2+ from 120 to 10 μs is observed. This fact indicated s a nonradiative energy transfer between impurity center and defect. Otherwise, the defect concentration variation (by means of doping with heterovalent ions) provides the ability to control the energy conversion efficiency as well as the phosphorus color. © 2017 Author(s).This work was partially supported by the Ministry of Education and Science of the Russian Federation (Government task No. 3.1485.2017/4.6 and basic part of the government mandate, project No. 3.8302.2017/8.9). One of the authors (PVA) thanks Dr. S. Omelkov for their help in PL time-resolved experiments
Portable mini-chamber for temperature dependent studies using small angle and wide angle x-ray scattering
No full textThe present work describes the design and performance of a vacuum compatible portable mini chamber for temperature dependent GISAXS and GIWAXS studies of thin films and multilayer structures. The water cooled body of the chamber allows sample annealing up to 900 K using ultra high vacuum compatible (UHV) pyrolytic boron nitride heater, thus making it possible to study the temperature dependent evolution of structure and morphology of two-dimensional nanostructured materials. Due to its light weight and small size, the chamber is portable and can be accommodated at synchrotron facilities worldwide. A systematic illustration of the versatility of the chamber has been demonstrated at beamline P03, PETRA-III, DESY, Hamburg, Germany. Temperature dependent grazing incidence small angle x-ray scattering (GISAXS) and grazing incidence wide angle x-ray scattering (GIWAXS) measurements were performed on oblique angle deposited Co/Ag multilayer structure, which jointly revealed that the surface diffusion in Co columns in Co/Ag multilayer enhances by increasing temperature from RT to ∼573 K. This results in a morphology change from columnar tilted structure to densely packed morphological isotropic multilayer</p
Active X-ray optics for the next generation of X-ray space telescopes
No full textDescribed within is the design, manufacture, metrology and X-ray testing of an active X-ray
prototype intended for the next generation of X-ray telescopes. One of the challenges faced by
the X-ray telescope community is how to combine high resolution and high sensitivity into one
system, as weight limitations place constraints on the optics that can be launched. Therefore the
mandate of the active X-ray prototype is to provide high sensitivity through the ability of the optics
to be nested and to deliver high angular resolution through the active control of the optic’s form.
Piezoelectric unimorph actuators provide the active component: it is intended that they will correct
for figure errors within the optic and therefore increase the angular resolution capability.
The prototype’s design is based upon an ellipsoidal segment which provides point-to-point
focussing of an X-ray source. The prototype itself is composed of an electroformed nickel optic
where the non-reflective surface is populated with 30 piezoelectric actuators and it is the production
of the prototype that is the core of the presented research. Metrology of the actuators’ influence
functions is presented and highlight the prototype’s ability to deform its optic surface by microns.
In addition, the measured influence functions are compared against finite element models and a
distinct similarity between the functions is observed.
The prototype was tested at an X-ray beamline facility in November 2008 and the results
showed the prototype’s ability to correct the optic to achieve an improved angular resolution: from
0.786 arc-minutes to 0.686 arc-minutes in terms of full width half maximum. Finally, difficulties
in the manufacture of the prototype and X-ray testing shall be presented alongside future work in
conclusion to this thesis
Collapsar accretion and the gamma-ray burst X-ray light curve
No full texttextWe present axisymmetric hydrodynamical simulations of the long-term accretion of a rotating gamma-ray burst progenitor star, a "collapsar," onto the central compact object, which we take to be a black hole. The simulations were carried out with the adaptive mesh refinement code FLASH in two spatial dimensions and with an explicit shear viscosity. The evolution of the central accretion rate exhibits phases reminiscent of the long GRB [gamma]-ray and X-ray light curve, which lends support to the proposal by Kumar et al. (2008a,b) that the luminosity is modulated by the central accretion rate. In the first "prompt" phase, the black hole acquires most of its final mass through supersonic quasiradial accretion occurring at a steady rate of [scientific symbols]. After a few tens of seconds, an accretion shock sweeps outward through the star. The formation and outward expansion of the accretion shock is accompanied with a sudden and rapid power-law decline in the central accretion rate Ṁ [proportional to] t⁻²̇⁸, which resembles the L[subscript x] [proportional to] t⁻³ decline observed in the X-ray light curves. The collapsed, shock-heated stellar envelope settles into a thick, low-mass equatorial disk embedded within a massive, pressure-supported atmosphere. After a few hundred seconds, the inflow of low-angular-momentum material in the axial funnel reverses into an outflow from the thick disk. Meanwhile, the rapid decline of the accretion rate slows down, which is potentially suggestive of the "plateau" phase in the X-ray light curve. We complement our adiabatic simulations with an analytical model that takes into account the cooling by neutrino emission and estimate that the duration of the prompt phase can be ~ 20 s. The model suggests that the steep decline in GRB X-ray light curves is triggered by the circularization of the infalling stellar envelope at radii where the virial temperature is below 10¹⁰ K, such that neutrino cooling is inefficient and an outward expansion of the accretion shock becomes imminent; GRBs with longer prompt [gamma]-ray emission should have more slowly rotating envelopes.Astronom
- …
