Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 18.961
Filtrar
1.
Environ Pollut ; 292(Pt A): 118324, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34637827

RESUMO

Traditional soil heavy metal (HM) investigation usually costs a lot of human and material resources. In-situ portable X-ray fluorescence spectrometry (PXRF) is a cheap and rapid HM analysis method, but its analysis accuracy is usually affected by spatially non-stationary field environment factors. In this study, residual sequential Gaussian co-simulation (RCoSGS) was first proposed to incorporate both continuous and categorical auxiliary variables for spatial simulation of soil Cu. Next, additional in-situ PXRF sampling sites (n = 300) were allocated in the subareas with high, medium, and low conditional variances in the proportions of 50%, 33.33%, and 16.67%, respectively. Then, robust geographically weighted regression (RGWR) was established to correct the spatially non-stationary effects of field environmental factors on in-situ PXRF and further compared with the traditionally-used multiple linear regression (MLR) and basic GWR in correction accuracy. Finally, RCoSGS with the RGWR-corrected in-situ PXRF as part of hard data (RCoSGS-PXRF) was established and further compared with the model with one or multiple auxiliary variables in the spatial simulation accuracy. Results showed that (i) RCoSGS effectively incorporated both SOM and land-use types and obtained higher spatial simulation accuracy (RI = 37.52%) than residual sequential Gaussian simulation with land-use types (RI = 19.44%) and sequential Gaussian co-simulation with SOM (RI = 20.92%); (ii) RGWR significantly weakened the spatially non-stationary effects of field environmental factors on in-situ PXRF, and RGWR (RI = 58.96%) and GWR (RI = 39.61%) obtained higher correction accuracy than MLR; (iii) the RGWR-corrected in-situ PXRF (RI = 66.57%) brought higher spatial simulation accuracy than both land-use types and SOM (RI = 37.52%); (iv) RCoSGS-PXRF obtained the highest spatial simulation accuracies (RI = 83.74%). Therefore, the proposed method is cost-effective for the rapid and high-precision investigation of soil HMs at a regional scale.


Assuntos
Metais Pesados , Poluentes do Solo , Monitoramento Ambiental , Humanos , Metais Pesados/análise , Solo , Poluentes do Solo/análise , Espectrometria por Raios X , Raios X
2.
J Intensive Care Med ; 37(1): 5-11, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33611954

RESUMO

Pneumothoraces are a common and potentially fatal complication for critically ill patients in the trauma and intensive care units. Since its use for pneumothorax detection was first reported in 1987, ultrasound has been increasingly used for the detection of thoracic injuries. As ultrasound imaging has improved and operators have potentially become more proficient, it is important to analyze more recent trends in the sensitivities and specificities of ultrasound for the detection of pneumothorax. This literature review and meta-analysis identifies 17 studies that directly compare the sensitivity and specificity of ultrasound and anterior-posterior chest x-ray in the identification of pneumothorax among 2955 patients who developed 793 pneumothoraces as detected by gold standard CT scanning. For the 17 articles analyzed, the pooled sensitivity of trans-thoracic ultrasound was 75.07% (64.92%-85.22%), and the pooled specificity was 98.36% (97.45%-99.26%). The pooled sensitivity of CXR was 45.65% (36.04%-55.26%), and pooled specificity was 99.62% (99.00%-100%). While this review demonstrates an improved sensitivity in the detection of pneumothorax with ultrasound over AP chest x-rays, it did not find a significant trend or improvement in the sensitivity or specificity of ultrasound for detecting pneumothorax over time.


Assuntos
Pneumotórax , Síndrome do Desconforto Respiratório , Humanos , Unidades de Terapia Intensiva , Pneumotórax/diagnóstico por imagem , Estudos Prospectivos , Radiografia Torácica , Ultrassonografia , Raios X
3.
J Synchrotron Radiat ; 28(Pt 6): 1801-1810, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34738933

RESUMO

The real-space Green's function code FEFF has been extensively developed and used for calculations of X-ray and related spectra, including X-ray absorption (XAS), X-ray emission (XES), inelastic X-ray scattering, and electron energy-loss spectra. The code is particularly useful for the analysis and interpretation of the XAS fine-structure (EXAFS) and the near-edge structure (XANES) in materials throughout the periodic table. Nevertheless, many applications, such as non-equilibrium systems, and the analysis of ultra-fast pump-probe experiments, require extensions of the code including finite-temperature and auxiliary calculations of structure and vibrational properties. To enable these extensions, we have developed in tandem a new version FEFF10 and new FEFF-based workflows for the Corvus workflow manager, which allow users to easily augment the capabilities of FEFF10 via auxiliary codes. This coupling facilitates simplified input and automated calculations of spectra based on advanced theoretical techniques. The approach is illustrated with examples of high-temperature behavior, vibrational properties, many-body excitations in XAS, super-heavy materials, and fits of calculated spectra to experiment.


Assuntos
Corvos , Animais , Raios X
4.
J Synchrotron Radiat ; 28(Pt 6): 1839-1844, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34738937

RESUMO

Toxic disinfection byproducts such as trihalomethanes (e.g. CHCl3) are often found after chlorination of drinking water. It has been found that photocatalytic degradation of trace CHCl3 in drinking water generally lacks an expected relationship with the crystalline phase, band-gap energy or the particle sizes of the TiO2-based photocatalysts used such as nano TiO2 on SBA-15 (Santa Barbara amorphous-15), TiO2 clusters (TiO2-SiO2) and atomic dispersed Ti [Ti-MCM-41 (Mobil Composition of Matter)]. To engineer capable TiO2 photocatalysts, a better understanding of their photoactive sites is of great importance and interest. Using in situ X-ray absorption near-edge structure (XANES) spectroscopy, the A1 (4969 eV), A2 (4971 eV) and A3 (4972 eV) sites in TiO2 can be distinguished as four-, five- and six- coordinated Ti species, respectively. Notably, the A2 Ti sites that are the main photocatalytic species of TiO2 are shown to be accountable for about 95% of the photocatalytic degradation of trace CHCl3 in drinking water (7.2 p.p.m. CHCl3 gTiO2-1 h-1). This work reveals that the A2 Ti species of a TiO2-based photocatalyst are mainly responsible for the photocatalytic reactivity, especially in photocatalytic degradation of CHCl3 in drinking water.


Assuntos
Água Potável , Dióxido de Silício , Catálise , Domínio Catalítico , Titânio , Raios X
5.
J Synchrotron Radiat ; 28(Pt 6): 1845-1849, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34738938

RESUMO

Oxygen K-edge X-ray absorption spectroscopy is used routinely to study a range of solid materials. However, liquid samples are studied less frequently at the oxygen K-edge due to the combined challenges of high-vacuum conditions and oxygen contamination of window materials. A modular sample holder design with a twist-seal sample containment system that provides a simple method to encapsulate liquid samples under high-vacuum conditions is presented. This work shows that pure silicon nitride windows have lower oxygen contamination than both diamond- and silicon-rich nitride windows, that the levels of oxygen contamination are related to the age of the windows, and provides a protocol for minimizing the background oxygen contamination. Acid-washed 100 nm-thick silicon nitride windows were found to give good quality oxygen K-edge data on dilute liquid samples.


Assuntos
Oxigênio , Radiografia , Espectroscopia por Absorção de Raios X , Raios X
6.
Igaku Butsuri ; 41(3): 111-116, 2021.
Artigo em Japonês | MEDLINE | ID: mdl-34744120

RESUMO

Fuji Photo Film (then), a chemical manufacturer that manufactures film, succeeded in digitizing X-ray photographs for the first time in the world, and commercialized Computed Radiography (CR) in 1983. In addition to eliminating darkroom work from X-ray work and improving the efficiency of X-ray work and diagnosis, this CR also played a role in paving the way for networking of image information in hospitals and for computer-added diagnostic support. Nowadays, the mechanism of digital X-rays has been established and is known to many people, but there was no precedent in the latter half of the 1970s when the development of CR was started. In this paper, we will look back on the development process of such CR first, then we will outline the evolution of digital X-ray detectors and image processing technology, and introduce the technology we have challenged to estimate scattered X-rays in the human body.


Assuntos
Intensificação de Imagem Radiográfica , Filme para Raios X , Humanos , Processamento de Imagem Assistida por Computador , Radiografia , Raios X
7.
Pulm Med ; 2021: 4496488, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34721903

RESUMO

When managing coronavirus disease 2019 (COVID-19) patients, radiological imaging complements clinical evaluation and laboratory parameters. We aimed to assess the sensitivity of chest radiography findings in detecting COVID-19, describe those findings, and assess the association of positive chest radiography findings with clinical and laboratory findings. A multicentre, cross-sectional study was conducted involving all primary health care corporation-registered patients (2485 patients) enrolled over a 1-month period during the peak of the 2020 pandemic wave in Qatar. These patients had reverse transcription-polymerase chain reaction-confirmed COVID-19 and underwent chest radiography within 72 hours of the swab test. A positive result on reverse transcription-polymerase chain reaction was the gold standard for diagnosing COVID-19. The sensitivity of chest radiography was calculated. The airspace opacities were mostly distributed in the peripheral and lower lung zones, and most of the patients had bilateral involvement. Pleural effusion was detected in some cases. The risk of having positive chest X-ray findings increased with age, Southeast Asian nationality, fever, or a history of fever and diarrhoea. Patients with cardiac disease, obesity, hypertension, diabetes, and chronic kidney disease were at a higher risk of having positive chest X-ray findings. There was a statistically significant increase in the mean serum albumin, white blood cell count, neutrophil count, and serum C-reactive protein, hepatic enzymes, and total bilirubin with an increase in the radiographic severity score.


Assuntos
COVID-19/diagnóstico , Pulmão/diagnóstico por imagem , Adolescente , Adulto , Fatores Etários , Idoso , Bilirrubina/sangue , Proteína C-Reativa/análise , COVID-19/epidemiologia , Criança , Pré-Escolar , Estudos Transversais , Feminino , Febre , Humanos , Contagem de Leucócitos , Masculino , Pessoa de Meia-Idade , Neutrófilos/metabolismo , Doenças não Transmissíveis , Pandemias , Derrame Pleural/diagnóstico por imagem , Atenção Primária à Saúde , Catar/epidemiologia , Fatores Raciais , Estudos Retrospectivos , Sensibilidade e Especificidade , Albumina Sérica , Raios X , Adulto Jovem
8.
Sensors (Basel) ; 21(21)2021 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-34770423

RESUMO

COVID-19 frequently provokes pneumonia, which can be diagnosed using imaging exams. Chest X-ray (CXR) is often useful because it is cheap, fast, widespread, and uses less radiation. Here, we demonstrate the impact of lung segmentation in COVID-19 identification using CXR images and evaluate which contents of the image influenced the most. Semantic segmentation was performed using a U-Net CNN architecture, and the classification using three CNN architectures (VGG, ResNet, and Inception). Explainable Artificial Intelligence techniques were employed to estimate the impact of segmentation. A three-classes database was composed: lung opacity (pneumonia), COVID-19, and normal. We assessed the impact of creating a CXR image database from different sources, and the COVID-19 generalization from one source to another. The segmentation achieved a Jaccard distance of 0.034 and a Dice coefficient of 0.982. The classification using segmented images achieved an F1-Score of 0.88 for the multi-class setup, and 0.83 for COVID-19 identification. In the cross-dataset scenario, we obtained an F1-Score of 0.74 and an area under the ROC curve of 0.9 for COVID-19 identification using segmented images. Experiments support the conclusion that even after segmentation, there is a strong bias introduced by underlying factors from different sources.


Assuntos
COVID-19 , Aprendizado Profundo , Inteligência Artificial , Humanos , Pulmão/diagnóstico por imagem , SARS-CoV-2 , Raios X
9.
Sensors (Basel) ; 21(21)2021 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-34770457

RESUMO

This research concerns a design and construction of a bone mineral density (BMD) and bone mineral content (BMC) measurement system based on dual energy X-ray absorptiometry (DEXA). An indirect X-ray detector is designed by optical coupling CMOS sensor with image on the intensifying screen. A dedicated microcontroller X-ray apparatus is used as an X-ray source to capture two energy level X-ray of middle phalanges bone of middle finger. The captured image is processed based on modified Beer-Lambert law to compute bone mineral density. Bone mineral content is also computed by determining the area of the phalanges bone using active contour. The designed bone mineral density (BMD) and bone mineral content (BMC) measurement system is low-cost and hence can be distributed at district hospital for screening purposes of Osteoporosis of the elderly. Compared with BMD measured from commercial model, BMD measurement of our system acquires linear relation with R2 equals 0.969. The mean square error between the normalized BMD value and that of the commercial model is 0.0000981.


Assuntos
Falanges dos Dedos da Mão , Osteoporose , Absorciometria de Fóton , Idoso , Densidade Óssea , Humanos , Osteoporose/diagnóstico por imagem , Raios X
10.
Sensors (Basel) ; 21(21)2021 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-34770600

RESUMO

Custom inspection using X-ray imaging is a very promising application of modern pattern recognition technology. However, the lack of data or renewal of tariff items makes the application of such technology difficult. In this paper, we present a data augmentation technique based on a new image-to-image translation method to deal with these difficulties. Unlike the conventional methods that convert a semantic label image into a realistic image, the proposed method takes a texture map with a special modification as an additional input of a generative adversarial network to reproduce domain-specific characteristics, such as background clutter or sensor-specific noise patterns. The proposed method was validated by applying it to backscatter X-ray (BSX) vehicle data augmentation. The Fréchet inception distance (FID) of the result indicates the visual quality of the translated image was significantly improved from the baseline when the texture parameters were used. Additionally, in terms of data augmentation, the experimental results of classification, segmentation, and detection show that the use of the translated image data, along with the real data consistently, improved the performance of the trained models. Our findings show that detailed depiction of the texture in translated images is crucial for data augmentation. Considering the comparatively few studies that have examined custom inspections of container scale goods, such as cars, we believe that this study will facilitate research on the automation of container screening, and the security of aviation and ports.


Assuntos
Aprendizado Profundo , Processamento de Imagem Assistida por Computador , Radiografia , Raios X
11.
Igaku Butsuri ; 41(3): 87-91, 2021.
Artigo em Japonês | MEDLINE | ID: mdl-34744139

RESUMO

In Japan, mammography was introduced in 2000 for the early detection of breast cancer. In quality control of mammography, dosimetry is one of the most important items. For accurate dosimetry, calibration of dosimeters is necessary because radiation quality (target-filter combination) of mammography x-ray is different from that of general radiography. Therefore, development of dosimetry standard based on radiation quality of mammography x-ray was required. AIST/NMIJ developed an air-kerma standard for mammography x-rays and started its dissemination in 2009. Since then, the air-kerma standard has been extended to various radiation qualities that have come to be used in digital mammography. In this paper, an overview of the air-kerma standard for mammography x-ray together with a future plan is briefly presented.


Assuntos
Mamografia , Radiometria , Calibragem , Japão , Doses de Radiação , Raios X
12.
Dentomaxillofac Radiol ; 50(8): 20210276, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34739304

RESUMO

The mathematical theory of CT was proposed by J. Radon in 1917. It was declared that the projection of whole data sets was needed to reconstruct CT images. Therefore, according to J. Radon's original theory, local cone beam CT (local CBCT) was impossible to achieve.In this paper, I discuss how local CBCT was discovered and developed. Its development required many technical elements, such as a turntable and X-ray television system, for basic experiments such as those on which narrow collimation theory and multifunctional panoramic tomography were based. These experiments endured many failures during development.Now, local CBCT is extremely popular in dental practice because local CBCT has a low radiation dose and high resolution. This paper introduces the technical elements and outlines the important stages during the development of local CBCT in the 1990s.


Assuntos
Tomografia Computadorizada de Feixe Cônico , Imagens de Fantasmas , Raios X
13.
Biomed Res Int ; 2021: 1896762, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34782860

RESUMO

The proposed method introduces algorithms for the preprocessing of normal, COVID-19, and pneumonia X-ray lung images which promote the accuracy of classification when compared with raw (unprocessed) X-ray lung images. Preprocessing of an image improves the quality of an image increasing the intersection over union scores in segmentation of lungs from the X-ray images. The authors have implemented an efficient preprocessing and classification technique for respiratory disease detection. In this proposed method, the histogram of oriented gradients (HOG) algorithm, Haar transform (Haar), and local binary pattern (LBP) algorithm were applied on lung X-ray images to extract the best features and segment the left lung and right lung. The segmentation of lungs from the X-ray can improve the accuracy of results in COVID-19 detection algorithms or any machine/deep learning techniques. The segmented lungs are validated over intersection over union scores to compare the algorithms. The preprocessed X-ray image results in better accuracy in classification for all three classes (normal/COVID-19/pneumonia) than unprocessed raw images. VGGNet, AlexNet, Resnet, and the proposed deep neural network were implemented for the classification of respiratory diseases. Among these architectures, the proposed deep neural network outperformed the other models with better classification accuracy.


Assuntos
COVID-19/patologia , COVID-19/virologia , Processamento de Imagem Assistida por Computador/métodos , Pulmão/patologia , Pulmão/virologia , Algoritmos , Aprendizado Profundo , Sistemas Especialistas , Humanos , Aprendizado de Máquina , Pneumonia/patologia , Pneumonia/virologia , Raios X
14.
Phys Med ; 91: 121-130, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34785490

RESUMO

PURPOSE: We developed an x-ray-opaque-marker (XOM) system with inserted fiducial markers for patient-specific quality assurance (QA) in CyberKnife (Accuray) and a general-purpose linear accelerator (linac). The XOM system can be easily inserted or removed from the existing patient-specific QA phantom. Our study aimed to assess the utility of the XOM system by evaluating the recognition accuracy of the phantom position error and estimating the dose perturbation around a marker. METHODS: The recognition accuracy of the phantom position error was evaluated by comparing the known error values of the phantom position with the values measured by matching the images with target locating system (TLS; Accuray) and on-board imager (OBI; Varian). The dose perturbation was evaluated for 6 and 10 MV single-photon beams through experimental measurements and Monte Carlo simulations. RESULTS: The root mean squares (RMSs) of the residual position errors for the recognition accuracy evaluation in translations were 0.07 mm with TLS and 0.30 mm with OBI, and those in rotations were 0.13° with TLS and 0.15° with OBI. The dose perturbation was observed within 1.5 mm for 6 MV and 2.0 mm for 10 MV from the marker. CONCLUSIONS: Sufficient recognition accuracy of the phantom position error was achieved using our system. It is unnecessary to consider the dose perturbation in actual patient-specific QA. We concluded that the XOM system can be utilized to ensure quantitative and accurate phantom positioning in patient-specific QA with CyberKnife and a general-purpose linac.


Assuntos
Aceleradores de Partículas , Planejamento da Radioterapia Assistida por Computador , Humanos , Método de Monte Carlo , Imagens de Fantasmas , Raios X
15.
J Craniofac Surg ; 32(8): e780-e783, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34727454

RESUMO

OBJECTIVES: To determine the densitometric quality of regenerated bone at the site of bone marrow and platelet-rich membrane grafting technique at unilateral alveolar cleft region using dual energy x-ray bone density scan (DEXA). METHODS: The present prospective cohort study included 16 unilateral alveolar cleft patients who were selected randomly from the outpatient maxillofacial surgery clinic and suffered from unilateral alveolar cleft. Bone marrow aspirate and platelet-rich fibrin (PRF) (bone marrow stem cells + PRF) were used as the grafting material. Six months of follow-up have been conducted for all patients' including clinical and radiographic assessments with (DEXA scan). RESULTS: Sixteen unilateral patients with a mean age of 12.56 ±â€Š1.71 years were included in the sample and the majority of patients were females with a frequency of 56.2 percent. The current research revealed no infection or wound dehiscence. After surgery, the pain and edema scores were reasonable. Our findings showed that, after 6 months of regenerative graft, the average bone mineral density of the cleft side DEXA scan value was 1.56 ±â€Š0.32 gm/cm2, compared to 1.51 ±â€Š0.488 gm/cm2 on the normal side of the noncleft scan. There was no statistically significant difference in DEXA bone mineral content measurements between the cleft and standard sides (P = 0.461). CONCLUSIONS: The bone marrow stem cells + PRF regenerative graft technique has been successfully integrated, and the DEXA scan approach for measuring regenerated grafted bone mineral content was found to be appropriate for simple and inexpensive follow-up of alveolar cleft lip patients.


Assuntos
Enxerto de Osso Alveolar , Fenda Labial , Fissura Palatina , Fibrina Rica em Plaquetas , Adolescente , Densidade Óssea , Células da Medula Óssea , Transplante Ósseo , Criança , Fenda Labial/diagnóstico por imagem , Fenda Labial/cirurgia , Fissura Palatina/diagnóstico por imagem , Fissura Palatina/cirurgia , Feminino , Humanos , Estudos Prospectivos , Raios X
16.
Wiad Lek ; 74(9 cz 1): 2082-2086, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34725280

RESUMO

OBJECTIVE: The aim: On the basis of radiological data to evaluate the effectiveness of our developed treatment complex of patients with temporomandibular joint dysfunction after mandibular fractures. PATIENTS AND METHODS: Materials and methods: To achieve this goal, 92 patients hospitalized in the department of surgical dentistry of the Chernivtsi Regional Clinical Hospital were examined for traumatic fractures of the mandible with functional disorders of the TMJ. 46 patients (main group) were treated according to the treatment method developed by us, and 46 patients (control group) were treated with the traditional method. Patients underwent orthopanthography and radiography of the temporomandibular joint according to Schuller. Statistical processing of research results was carried out using commonly used methods of variation statistics. RESULTS: Results: After 12 months of studies in patients of the main group, unilateral narrowing of the joint space was determined in 6,52 ± 1,83% of persons p, p1 0.05.The number of persons with unilateral expansion of the joint space according to Rtg, in the main group decreased by 2,3 times relative to the data before treatment. CONCLUSION: Conclusions: Timely treatment of musculoskeletal disorders with the help of pharmacological and physiotherapeutic methods proposed by us, allowed, to a large extent, to eliminate clinical, radiological and ultrasound symptoms of temporomandibular joint dysfunction in patients with post-traumatic lesions of mandibule. This was confirmed by the improvement of the data of the conducted functional researches.


Assuntos
Fraturas Mandibulares , Transtornos da Articulação Temporomandibular , Humanos , Fraturas Mandibulares/complicações , Fraturas Mandibulares/diagnóstico por imagem , Fraturas Mandibulares/terapia , Radiografia , Articulação Temporomandibular/diagnóstico por imagem , Transtornos da Articulação Temporomandibular/diagnóstico por imagem , Transtornos da Articulação Temporomandibular/etiologia , Transtornos da Articulação Temporomandibular/terapia , Raios X
17.
J Synchrotron Radiat ; 28(Pt 6): 1672-1683, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34738921

RESUMO

Uranium speciation and redox behaviour is of critical importance in the nuclear fuel cycle. X-ray absorption near-edge spectroscopy (XANES) is commonly used to probe the oxidation state and speciation of uranium, and other elements, at the macroscopic and microscopic scale, within nuclear materials. Two-dimensional (2D) speciation maps, derived from microfocus X-ray fluorescence and XANES data, provide essential information on the spatial variation and gradients of the oxidation state of redox active elements such as uranium. In the present work, we elaborate and evaluate approaches to the construction of 2D speciation maps, in an effort to maximize sensitivity to the U oxidation state at the U L3-edge, applied to a suite of synthetic Chernobyl lava specimens. Our analysis shows that calibration of speciation maps can be improved by determination of the normalized X-ray absorption at excitation energies selected to maximize oxidation state contrast. The maps are calibrated to the normalized absorption of U L3 XANES spectra of relevant reference compounds, modelled using a combination of arctangent and pseudo-Voigt functions (to represent the photoelectric absorption and multiple-scattering contributions). We validate this approach by microfocus X-ray diffraction and XANES analysis of points of interest, which afford average U oxidation states in excellent agreement with those estimated from the chemical state maps. This simple and easy-to-implement approach is general and transferrable, and will assist in the future analysis of real lava-like fuel-containing materials to understand their environmental degradation, which is a source of radioactive dust production within the Chernobyl shelter.


Assuntos
Acidente Nuclear de Chernobyl , Urânio , Síncrotrons , Espectroscopia por Absorção de Raios X , Raios X
18.
J Synchrotron Radiat ; 28(Pt 6): 1858-1864, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34738940

RESUMO

X-ray absorption and optical luminescence can both provide valuable but very different information on the chemical and physical properties of materials. Although it is known that the spectral characteristics of many materials are highly heterogeneous on the micro- and/or nanoscale, no methodology has so far been shown to be capable of spatially resolving both full X-ray absorption and X-ray excited optical luminescence (XEOL) spectra on the nanoscale in a correlative manner. For this purpose, the scanning transmission X-ray microscope at the HERMES beamline of the SOLEIL synchrotron was equipped with an optical detection system capable of recording high-resolution XEOL spectra using a 40 nm soft X-ray probe. The functionality of the system was demonstrated by analyzing ZnO powder dispersions - showing simultaneously the X-ray linear dichroism and XEOL behavior of individual submicrometric ZnO crystallites.


Assuntos
Luminescência , Síncrotrons , Radiografia , Espectroscopia por Absorção de Raios X , Raios X
19.
J Synchrotron Radiat ; 28(Pt 6): 1881-1890, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34738943

RESUMO

Recent improvements in both X-ray detectors and readout speeds have led to a substantial increase in the volume of X-ray fluorescence data being produced at synchrotron facilities. This in turn results in increased challenges associated with processing and fitting such data, both temporally and computationally. Herein an abridging approach is described that both reduces and partially integrates X-ray fluorescence (XRF) data sets to obtain a fivefold total improvement in processing time with negligible decrease in quality of fitting. The approach is demonstrated using linear least-squares matrix inversion on XRF data with strongly overlapping fluorescent peaks. This approach is applicable to any type of linear algebra based fitting algorithm to fit spectra containing overlapping signals wherein the spectra also contain unimportant (non-characteristic) regions which add little (or no) weight to fitted values, e.g. energy regions in XRF spectra that contain little or no peak information.


Assuntos
Algoritmos , Síncrotrons , Fluorescência , Radiografia , Raios X
20.
J Synchrotron Radiat ; 28(Pt 6): 1916-1920, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34738946

RESUMO

X-ray ptychography and X-ray fluorescence are complementary nanoscale imaging techniques, providing structural and elemental information, respectively. Both methods acquire data by scanning a localized beam across the sample. X-ray ptychography processes the transmission signal of a coherent illumination interacting with the sample, to produce images with a resolution finer than the illumination spot and step size. By enlarging both the spot and the step size, the technique can cover extended regions efficiently. X-ray fluorescence records the emitted spectra as the sample is scanned through the localized beam and its spatial resolution is limited by the spot and step size. The requisites for fast ptychography and high-resolution fluorescence appear incompatible. Here, a novel scheme that mitigates the difference in requirements is proposed. The method makes use of two probes of different sizes at the sample, generated by using two different energies for the probes and chromatic focusing optics. The different probe sizes allow to reduce the number of acquisition steps for the joint fluorescence-ptychography scan compared with a standard single beam scan, while imaging the same field of view. The new method is demonstrated experimentally using two undulator harmonics, a Fresnel zone plate and an energy discriminating photon counting detector.


Assuntos
Imagem Óptica , Fótons , Radiografia , Raios X
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...