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Improved Models for Metallic Nanoparticle Cores From Atomic Pair Distribution Function (PDF) Analysis
摘要： X-ray atomic pair distribution functions (PDFs) were collected from a range of canonical metallic nanomaterials, both elemental and alloyed, prepared using different synthesis methods and exhibiting drastically different morphological properties. Widely applied shape-tuned attenuated crystal (AC) fcc models proved inadequate, yielding structured, coherent, and correlated fit residuals. However, equally simple discrete cluster models could account for the largest amplitude features in these difference signals. A hypothesis testing based approach to nanoparticle structure modelling systematically ruled out effects from crystallite size, composition, shape, and surface faceting as primary factors contributing to the AC misfit. On the other hand, decahedrally twinned cluster cores were found to be the origin of the AC structure misfits for a majority of the nanomaterials reported here. It is further motivated that the PDF can readily differentiate between the arrangement of domains in these multiply-twinned motifs. Most of the nanomaterials surveyed also fall within the sub-5 nm size regime where traditional electron microscopy cannot easily detect and quantify domain structures, with sampling representative of the average nanocrystal synthesized. The results demonstrate that PDF analysis is a powerful method for understanding internal atomic interfaces in small noble metallic nanomaterials. Such core cluster models, easily built algorithmically, should serve as starting structures for more advanced models able to capture atomic positional disorder, ligand induced or otherwise, near nanocrystal surfaces.
关键词： decahedrally twinned cluster cores,PDF analysis,metallic nanomaterials,nanocrystal surfaces,X-ray atomic pair distribution functions
更新于2025-09-23 15:21:21
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Study of materials structure physics of isomorphic LiNbO <sub/>3</sub> and LiTaO <sub/>3</sub> ferroelectrics by synchrotron radiation X-ray diffraction
摘要： Electron charge density studies of stoichiometric LiNbO3 and LiTaO3 ferroelectrics have been carried out by analyzing the synchrotron radiation X-ray powder di?raction data using a combination of the Rietveld and maximum entropy methods. The clear relationships between the Nb(Ta)–O bond length, the electron charge density on the Nb(Ta)–O bond, and the phase transition temperature TC are revealed for isomorphic structures. Nb(Ta)–O bonding plays an important role in the elevation of TC. The TC in LiNbO3 being higher than that in LiTaO3 is attributed to the larger lattice distortion of the Nb–O oxygen octahedron in LiNbO3. The validity of estimating TC for LiNbO3 family crystals from the degree of lattice distortion in the ferroelectric structure is discussed.
关键词： ferroelectric,LiTaO3,X-ray diffraction,synchrotron radiation,LiNbO3,phase transition temperature,electron charge density
更新于2025-09-23 15:21:21
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Dynamic Emission Tuning of X-ray Radioluminescent Crystalline Colloidal Arrays: Coupling the Optical Stop Band with Sequential F?rster Resonance Energy Transfers
摘要： X-ray radiation exhibits diminished scattering and a greater penetration depth in tissue relative to the visible spectrum and has spawned new medical imaging techniques that exploit X-ray luminescence of nanoparticles. The majority of the nanoparticles finding applications in this field incorporate metals with high atomic numbers and pose potential toxicity effects. Here, a general strategy for the preparation of a fully organic X-ray radioluminescent colloidal platform that can be tailored to emit anywhere in the visible spectrum through a judicious choice in donor/acceptor pairing and multiple sequential F?rster resonance energy transfers (FRETs) is presented. This is demonstrated with three different types of ≈100 nm particles that are doped with anthracene as the scintillating molecule to “pump” subsequent FRET dye pairs that result in emissions from ≈400 nm out past 700 nm. The particles can be self-assembled in crystalline colloidal arrays, and the radioluminescence of the particles can be dynamically tuned by coupling the observed rejection wavelength with the dyes’ emission.
关键词： anthracene,F?rster resonance energy transfer,photonic crystals,X-ray radioluminescence,colloidal crystals
更新于2025-09-23 15:21:21
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Direct quantitative material decomposition employing grating-based X-ray phase-contrast CT
摘要： Dual-energy CT has opened up a new level of quantitative X-ray imaging for many diagnostic applications. The energy dependence of the X-ray attenuation is the key to quantitative material decomposition of the volume under investigation. This material decomposition allows the calculation of virtual native images in contrast enhanced angiography, virtual monoenergetic images for beam-hardening artifact reduction and quantitative material maps, among others. These visualizations have been proven beneficial for various diagnostic questions. Here, we demonstrate a new method of ‘virtual dual-energy CT’ employing grating-based phase-contrast for quantitative material decomposition. Analogue to the measurement at two different energies, the applied phase-contrast measurement approach yields dual information in form of a phase-shift and an attenuation image. Based on these two image channels, all known dual-energy applications can be demonstrated with our technique. While still in a preclinical state, the method features the important advantages of direct access to the electron density via the phase image, simultaneous availability of the conventional attenuation image at the full energy spectrum and therefore inherently registered image channels. The transfer of this signal extraction approach to phase-contrast data multiplies the diagnostic information gained within a single CT acquisition. The method is demonstrated with a phantom consisting of exemplary solid and fluid materials as well as a chicken heart with an iodine filled tube simulating a vessel. For this first demonstration all measurements have been conducted at a compact laser-undulator synchrotron X-ray source with a tunable X-ray energy and a narrow spectral bandwidth, to validate the quantitativeness of the processing approach.
关键词： Dual-energy CT,virtual non-contrast images,grating-based phase-contrast,electron density,effective atomic number,material decomposition,quantitative X-ray imaging,virtual monoenergetic images
更新于2025-09-23 15:21:21
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[Advances in Intelligent Systems and Computing] Emerging Trends in Expert Applications and Security Volume 841 (Proceedings of ICETEAS 2018) || Bone Fracture Detection from X-Ray Image of Human Fingers Using Image Processing
摘要： Orthopaedics deals with surgery and treatment of the human musculoskeletal system. It also involves degenerative conditions, trauma, sports injury, tumors, and congenital issues. Orthopaedic doctors are always interested to take an X-Ray image of injured parts of patient’s body for better diagnosis. In an X-Ray imaging, electronic radiation is passed in the human body for capturing bone images. After X-Ray image retrieval, a doctor examines X-Ray image manually. It is not that easy to detect most of the major diseases/issues related with the bones just by visualizing an X-Ray image, although in some cases, it is possible, but till that time, diseases may reached towards next or serious stage for example bone fracture. The main problem with X-Ray images is that they may be blurred, out of focus, improperly bright and noisy, which makes examination more dif?cult. One of the solutions to all above problems can be computerized image processing of human being’s X-Ray images. In this research paper, we have presented an algorithm to detect bone fracture from X-Ray images of human ?ngers using image processing.
关键词： Trauma,Orthopaedics,Image processing,Musculoskeletal,X-Ray,Electronic radiation
更新于2025-09-23 15:21:21
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Macroscopic effects and microscopic origins of gamma-ray irradiation on In-doped CdZnTe crystal
摘要： The effects of gamma-ray irradiation, exposed to a 60Co source with a dose of 2.7 kGy, on In-doped CdZnTe (CdZnTe:In) crystal were investigated. We combined the “macroscopic” electrical properties of CdZnTe:In sample, evaluated by current–voltage (I–V) measurements at different temperature, with the “microscopic” origins of electrically active defects induced by gamma-irradiation, characterized by thermally stimulated current spectroscopy. It reveals that the bulk resistivity at room temperature have increased from 2.7 × 109 ? cm for the as-grown CdZnTe:In sample to 5.9 × 109 ? cm for the irradiated sample. Since the microscopic origins of these macroscopic effects are linked to the electrically active defects within the material, five main defect states (I, II, III, IV and V) were characterized and identified in the CdZnTe:In crystal. In particular, the introduction of gamma-irradiation altered the trap concentrations of these defect states, such as the rapidly decreasing concentration of region I. Besides, the gamma-ray irradiation caused a further deepening of EDD level (region V) from the value of 0.717 ± 0.004 eV for the as-grown sample to the value of 0.749 ± 0.004 eV for the irradiated sample. The microscopic origin of EDD level was identified with TeCd2+ below the conduction band minimum, which is responsible for the pinning of EF level near the mid-gap, and thus for the observed high-resistivity performance of CdZnTe:In.
关键词： high-resistivity,electrical properties,defect states,gamma-ray irradiation,CdZnTe:In
更新于2025-09-23 15:21:21
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Locality estimates for Fresnel-wave-propagation and stability of x-ray phase contrast imaging with finite detectors
摘要： Coherent wave-propagation in the near-field Fresnel-regime is the underlying contrast-mechanism to (propagation-based) x-ray phase contrast imaging (XPCI), an emerging lensless technique that enables 2D- and 3D-imaging of biological soft tissues and other light-element samples down to nanometer-resolutions. Mathematically, propagation is described by the Fresnel-propagator, a convolution with an arbitrarily non-local kernel. As real-world detectors may only capture a finite field-of-view, this non-locality implies that the recorded diffraction-patterns are necessarily incomplete. This raises the question of stability of image-reconstruction from the truncated data—even if the complex-valued wave-field, and not just its modulus, could be measured. Contrary to the latter restriction of the acquisition, known as the phase-problem, the finite-detector-problem has not received much attention in literature. The present work therefore analyzes locality of Fresnel-propagation in order to establish stability of XPCI with finite detectors. Image-reconstruction is shown to be severely ill-posed in this setting—even without a phase-problem. However, quantitative estimates of the leaked wave-field reveal that Lipschitz-stability holds down to a sharp resolution limit that depends on the detector-size and varies within the field-of-view. The smallest resolvable lengthscale is found to be ≈1/–f times the detector’s aspect length, where –f is the Fresnel number associated with the latter scale. The stability results are extended to phaseless imaging in the linear contrast-transfer-function regime.
关键词： resolution,phase contrast,image reconstruction,stability,x-ray imaging,Fresnel propagation
更新于2025-09-23 15:21:21
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Characterization and application of cerium bromide spectrometers for analysis of γ-ray emitting radionuclides in food matrices
摘要： Cerium bromide (CeBr3) scintillators are useful room temperature gamma-ray detectors that provide the robustness of a scintillator with improved resolution over traditional sodium iodide (NaI) detectors. This makes them attractive for field deployment or emergency response operations especially when combined with the power of Monte-Carlo based efficiency determinations. This work documents the characterization of CeBr3 detectors and the efficiency determination of a portable CeBr3 detector based gamma-ray detection system for food measurements.
关键词： Gamma-ray measurement,Cerium bromide,Efficiency calculation,Food safety
更新于2025-09-23 15:21:21
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Ion, electron and laser beams for Cultural Heritage investigations by Czech-Italian collaboration
摘要： An overview of physical investigations of cultural heritage samples using ion and laser beams performed in the frame of the international collaboration between the University of Messina (Italy) and the Nuclear Physics Institute-ASCR (Czech Republic) is presented. Solid samples are analysed in high vacuum using particle induced X-ray emission, Rutherford backscattering spectrometry, elastic recoil detection analysis, prompt γ activation analysis, nuclear reaction analysis, laser ablation, mass spectrometry, scanning electron microscopy, and many more. The elemental composition of the sample, the trace elements, the depth pro?les, the morphology and the comparison between samples and references are reported. Both electron and ion microbeams are employed to have details of the spatial distribution maps of elements of interest.
关键词： Mass spectrometers,X-ray detectors,X-ray ?uorescence (XRF) systems
更新于2025-09-23 15:21:01
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A Combined Ray Tracing Method for Improving the Precision of the USBL Positioning System in Smart Ocean
摘要： The ultra-short baseline positioning system (USBL) has the advantages of flexible application and easy installation, and it plays an extremely important role in the underwater positioning and communication. The error of the USBL in underwater positioning is mainly caused by a ranging error due to ray tracing, a phase difference error of the USBL, and acoustic noise in the underwater communication. Most of these errors are related to the changes in the sound speed during its propagation through the ocean. Therefore, when using the USBL for underwater detection, it is necessary to correct the sound speed profile in the detection area and optimize the ray tracing. Taking into account the actual conditions, this paper aims at correcting the model of underwater sound speed propagation and improving the tracking method of sound lines when the marine environment in the shallow sea area changes. This paper proposes a combined ray tracing method that can adaptively determine whether to use the constant sound speed ray tracing method or the equal gradient ray tracing method. The theoretical analysis and simulation results show that the proposed method can effectively reduce the error of slant distance in USBL compared with the traditional acoustic tracking method and the constant sound speed ray tracing method. The proposed sound ray correction algorithm solves the contradiction between the number of iterations and the reduction of positioning error and has engineering application value.
关键词： acoustic positioning,constant sound speed ray tracing,ultra-short baseline (USBL),equal gradient ray tracing,sound speed profile
更新于2025-09-23 15:21:01