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Catalytic Growth of 1D ZnO Nanoneedles on Glass Substrates Through Vapor Transport
摘要： In this study, one-dimensional (1D) zinc oxide (ZnO) nanoneedles are successfully fabricated on a Ag catalyst-coated glass substrate through simple physical vapor deposition via thermal evaporation of zinc (Zn) powder in the presence of oxygen (O2) gas at a low growth temperature of 450°C. The growth rate and diameter of ZnO nanoneedles increase as a function of varying silver (Ag) film thicknesses and argon (Ar) flow rates. Detailed structural investigations confirm that the synthesized nanoneedles have high crystallinity with a hexagonal wurtzite structure, and they preferentially grow along the c-axis orientation. This approach provides a simple and cost-effective method for the synthesis and controlled growth of 1D nanostructures, which can be useful in solid-state devices and various optoelectronic applications.
关键词： 1D ZnO,x-ray diffraction,UV emission enhancement,structural properties
更新于2025-09-23 15:23:52
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Fraction of Rare-Earth (Sm/Nd)-Lanthanum Ferrite-Based Perovskite Ferroelectric and Magnetic Nanopowders
摘要： Multiferroic compound, especially LaFeO3-based perovskite nanopowders that exhibit robust simultaneous ferromagnetism and ferroelectricity, are widely investigated and applied in different applications. In this work, we report the synthesis and characterization pertaining to fraction of rare-earth (Sm/Nd)-substituted lanthanum ferrite based perovskite nanopowders via solid-state technique. The multiferroic phenomenon is the fundamental approach to combine both the ferromagnetic and ferroelectric properties in a single system. Reduction in crystallite size, as well as some lattice distortion effects, are included to show the possibilities of tuning the lattice structure, electrical, optical as well as the magnetic properties which are closely connected to the ferroelectric behavior and magnetism. At room temperature, the ferroelectric behavior of La0.9(Sm/Nd)0.1FeO3 exhibiting a P-E hysteresis loop became more and more pronounced, indicating the electrical leakage is greatly reduced. The canted antiferromagnetic hysteresis loop shows that the rare-earth (Sm/Nd) ion can significantly affect the magnetic parameters of the materials.
关键词： Lanthanum ferrite,x-ray diffraction,optical and magnetic properties,solid-state reaction,ferroelectric,UV–Vis spectroscopy
更新于2025-09-23 15:23:52
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Novel method to measure the intrinsic spatial resolution in PET detectors based on monolithic crystals
摘要： The main aim of this work is to provide a method to retrieve the intrinsic spatial resolution of a gamma-ray detector block based on monolithic crystals within an assembled scanner. This method consists on a discrimination of the data using a software collimation process. The results are compared with an alternative method of separating two detector blocks far enough to produce a "virtual" source collimation due to the geometric constraints on the allowed coincidence event angles. A theoretical model has been deduced to fit the measured light distribution profiles, allowing estimating the detector intrinsic spatial resolution. The detector intrinsic spatial resolution is expected to follow a Gaussian distribution and the positron-emitter source shape, given the small size of a 22Na source with 0.25 mm in diameter, can be assumed to follow a Lorentzian profile. However, the collimation of the data modifies the source shape that is no longer a pure Lorentzian distribution. Therefore, the model is based on the convolution of a Gaussian shaped distribution (contribution of the detector) and a modified Lorentzian distribution (contribution of the collimated source profile) that takes into account the collimation effect. Three LYSO crystals geometries have been studied in the present work, namely a 10 mm thick trapezoidal monolithic block, and two rectangular monolithic blocks with thicknesses of 15 mm and 20 mm, respectively. All the blocks have size dimensions of 50 mm × 50 mm. The experimental results yielded an intrinsic detector spatial resolution of 0.64 ± 0.02 mm, 0.82 ± 0.02 and 1.07 ± 0.03 mm, for the 10 mm, 15 mm and 20 mm thick blocks, respectively, when the source was placed at the center of the detector. The detector intrinsic spatial resolution was moreover evaluated across one of the axis of each crystal. These values worsen to an average value of 0.68 ± 0.04 mm, 0.90 ± 0.14 and 1.29 ± 0.19 mm, respectively, when the whole crystal size is considered, as expected. These tests show an accurate method to determine the intrinsic spatial resolution of monolithic-based detector blocks, once assembled in the PET system.
关键词： Intrinsic spatial resolution,SiPM array,Monolithic blocks,Positron Emission Tomography,Gamma ray detectors
更新于2025-09-23 15:23:52
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Optimization of X-ray image acquisition and reconstruction for a C-arm CBCT system with a flat-panel detector
摘要： A modern cone-beam computed tomography (CBCT) system with a C-arm gantry incorporating a large-area flat-panel detector is an important imaging tool widely used for diagnosis and image-guidance in spine surgery, orthopedic and interventional suite, and image-guided radiation therapy. In this study, the experimental prototype CBCT imaging platform consists of a benchtop system that is integrated with a cone-beam X-ray tube, a collimator, an anti-scatter grid, and a large-area TFT-based flat-panel detector. The different projection images in the C-arm CT system were usually acquired at short scanning angles with a constant interval for various exposure conditions. The performance of CT imaging quality was performed using the Feldkamp, Davis and Kress (FDK) reconstruction algorithm through acquired two-dimensional projection images at different scanning angles and projection numbers. Quantitative analysis of the image quality was performed by using the cone-beam CT phantom for spatial resolution, low-contrast resolution, noise, and two different phantoms, such as the head and pelvis.
关键词： Flat-panel X-ray detector,3D image reconstruction,Cone-beam CT system,C-arm CT system
更新于2025-09-23 15:23:52
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Ru(II) and Ir(III) complexes containing ADA and DAD triple hydrogen bonding motifs: Potential tectons for the assembly of functional materials.
摘要： The synthesis and characterisation of series of [Ru(II)(bpy)2L] and [Ir(ppy)2L] complexes containing ligands L with the potential to engage in triple hydrogen bonding interactions is described. L1 and L2 comprise pyridyl triazole chelating units with pendant diaminotriazine units, capable of donor-acceptor-donor (DAD) hydrogen bonding, while L3 and L4 contain ADA hydrogen bonding units proximal to N^N and N^O cleating sites, respectively. X-ray crystallography shows the L1 and L2 containing Ru(II) complexes to assemble via R22(8) hydrogen bonding dimers, while [Ru(II)(bpy)2L4] assembles via extended hydrogen bonding motifs to form one dimensional chains. By contrast, the expected hydrogen bonding patterns are not observed for the Ru(II) and Ir(III) complexes of L3. Spectroscopic studies show that the absorption spectra of the complexes result from combinations of MLCT and LLCT transitions. The L1 and L2 complexes of Ir(III) and Ru(II) complexes are emissive in the solid state and it seems likely that hydrogen bonding to complementary species may facilitate tuning of their 3ILCT emission. Low frequency Raman spectra provide further evidence for ordered interactions in the solid state for the L4 complexes, consistent with the results from X-ray crystallography.
关键词： crystal engineering,ruthenium,Hydrogen bonding,iridium,X-ray crystallography
更新于2025-09-23 15:23:52
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An algorithmic approach to single probe Cherenkov removal in pulsed X-ray beams
摘要： Purpose: The removal of Cherenkov light in an optical dosimetry system is an important process to ensure accurate dosimetry without compromising spatial resolution. Many solutions have been presented in the literature, each with advantages and disadvantages. We present a methodology to remove Cherenkov light from a scintillator fibre optic dosimeter in a pulsed megavoltage X-ray beam using the temporal waveform across the pulse. Methods: A sample waveform of Cherenkov light can be measured by exposing only the fibre to the beam. By assuming that the Cherenkov waveform closely matches the intensity of incident radiation, this waveform can be convoluted with the instantaneous scintillation response function to generate an expected scintillation signal. By finding the least-squares fit between these two functions and the experimental data, the estimated Cherenkov contribution can be subtracted off the net signal. This can be applied for arbitrarily complex Cherenkov waveforms (within the 2 ns timing resolution of the data acquisition), and in fact the results suggest more fluctuations in the waveforms provide a better fit to data. Results: Four beam profiles for different field sizes and energies were found with this method. They closely matched references data measured with ionisation chamber with average differences across the beam no more than 4%. Noisy waveforms are assumed to be the primary cause of differences between the analysed scintillator and IC results. We propose methods for improving the results and optimising the data acquisition and analysis processes. Conclusions: These results demonstrate that it is possible and effective with a single probe to use function-fitting of expected data to experimental to remove a complicated Cherenkov signal from the net light signal in pulsed-beam optical dosimetry.
关键词： x-ray,scintillators,fiber-optic dosimetry,microbeam radiation therapy
更新于2025-09-23 15:23:52
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Evaluation of the effect of image noise on CT perfusion measurements using digital perfusion phantoms
摘要： Objectives To assess the influence of image noise on computed tomography (CT) perfusion studies, CT perfusion software algorithms were evaluated for susceptibility to image noise and results applied to clinical perfusion studies. Methods Digital perfusion phantoms were generated using a published deconvolution model to create time-attenuation curves (TACs) for 16 different combinations of blood flow (BF; 30/60/90/120 ml/100 ml/min) and flow extraction product (FEP; 10/20/30/40 ml/100 ml/min) corresponding to values encountered in clinical studies. TACs were distorted with Gaussian noise at 50 different strengths to approximate image noise, performing 200 repetitions for each noise level. A total of 160,000 TACs were evaluated by measuring BF and FEP with CT perfusion software, comparing results for the maximum slope and Patlak models with those obtained with a deconvolution model. To translate results to clinical practice, data of 23 patients from a CT perfusion study were assessed for image noise, and the accuracy of reported CT perfusion measurements was estimated. Results Perfusion measurements depend on image noise as means and standard deviations of BF and FEP over repetitions increase with increasing image noise, especially for low BF and FEP values. BF measurements derived by deconvolution show larger standard deviations than those performed with the maximum slope model. Image noise in the evaluated CT perfusion study was 26.46 ± 3.52 HU, indicating possible overestimation of BF by up to 85% in a clinical setting. Conclusions Measurements of perfusion parameters depend heavily upon the magnitude of image noise, which has to be taken into account during selection of acquisition parameters and interpretation of results, e.g., as a quantitative imaging biomarker.
关键词： Tomography, x-ray computed,Phantoms, imaging,Perfusion imaging,Software,Artifacts
更新于2025-09-23 15:23:52
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Visual assessment of calcification in solitary pulmonary nodules on chest radiography: correlation with volumetric quantification of calcification
摘要： Purpose To assess the ability of digital chest radiography (CXR) to reveal calcification in solitary pulmonary nodules (SPNs), and to examine the correlation between a visual assessment and volumetric quantification of the calcification. Materials and methods This study was a retrospective review of 220 SPNs identified by both CXR and chest CT. Eleven observers did blind review of the CXR images and scored nodule calcification on a confidence scale of 1 to 5. The area under the receiver operating characteristics (ROC) curve (AUC) was obtained to analyze the diagnostic performance. The intraclass correlation coefficient (ICC) for interrater reliability was calculated. The AUC and ICC were calculated according to the following nodule diameter groups: group 1 (< 10 mm), group 2 (≥ 10 mm and < 20 mm), and group 3 (≥ 20 mm). Results Of the 220 SPNs, 145 SPNs (65.6%) were identified as non-calcified and 75 (34.4%) as calcified. The average percentage of calcification volume in SPN > 160 HU (Vol160HU) among the 75 calcified nodules was 47.5%. The mean Vol160HU of the 68 SPNs classified as having definite calcification was 51.1%. The overall AUC was 0.71. The AUCs for groups 1, 2, and 3 was 0.835, 0.639, and 0.620, respectively. The ICCs for groups 1, 2, 3 was 0.65, 0.48, and 0.33, respectively. Conclusion The overall diagnostic performance of digital CXR to predict calcification in SPNs was moderately accurate and the diagnostic performance for predicting calcification in SPNs was significantly higher, and interobserver reproducibility was good when SPN < 10 mm compared with ≥ 10 mm in diameter.
关键词： Radiography,Solitary pulmonary nodule,Tomography,thoracic,X-ray computed
更新于2025-09-23 15:23:52
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Interpretation of linear dichroism at S L2,3 x-ray absorption edges of small organic molecules at surfaces
摘要： Resonant soft x-ray absorption was applied at the S L2,3 (2p) edges of thin films of 1,4-benzenedimethanethiol (BDMT) on gold and of sexithiophene (6 T) on flat and patterned CaF2 surfaces. Linear dichroism effects were clearly observed depending on the orientation of the electric field vector of the incoming radiation. They were related to the organization of the molecules. For the interpretation of the angular dependencies of the spectral features, density functional theory (DFT) simulations of the absorption cross sections were calculated. It was possible to confirm the generally accepted chemisorption geometry of BDMT on Au(111), composed of molecules nearly vertical at the surface with one of the S atoms participating in the bonding with Au and the other left pending at the outermost surface and contributing mostly to the measured x-ray absorption. For 6 T on CaF2 a new chemisorption phase was identified on ridge-patterned CaF2(110), coexisting with a previously known phase given by 6 T crystallites highly oriented along the ridges. The new phase being composed of molecules oriented perpendicular to the ridges and lying on their edges.
关键词： Organic thin films,X-ray absorption,Sulphur
更新于2025-09-23 15:23:52
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Structural, morphological, composition and optical properties of undoped zinc oxide thin films prepared by spray pyrolysis method: effect of solution concentrations
摘要： The aim of this paper is the study of transparent undoped zinc oxide thin films obtained by spray pyrolysis technique on glass substrates heated at 350 °C from 0.1 to 0.4 mol solution concentrations using zinc acetate dehydrate as precursor. The X-ray diffraction patterns and Raman spectrometry with respect to Urbach energy and wurtzite structure, show that the maximum value of the high frequency intensity E2 and the optimal value of the optical gap are obtained at 0.2 mol concentration. Furthermore, an appropriate transparency is obtained and that makes these films suitable for photovoltaic windows layer cells.
关键词： X-ray diffraction,ultraviolet transmission spectroscopy,Raman spectroscopy,spray pyrolysis,undoped zinc oxide
更新于2025-09-23 15:23:52