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Objectives: To report the prevalence and distribution of nonsyndromic dental anomalies in children in eastern Saudi Arabia.Methods: This retrospective records review study involved radiographic examination of 6-18 years old pediatric patients who attended the Dental Hospital of the College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia. Four calibrated examiners recorded nonsyndromic dental anomalies from patients' digital orthopantomograms (OPG). The anomalies recorded were related to tooth number, shape, and location. Descriptive statistics, chi-square test, and Fisher exact tests were used to report prevalence and differences by gender, nationality, and medical history at the 5% significance level.Results: Of 2226 reviewed patients' records, 1897 met the inclusion criteria and were included in the study. The study sample had equal distribution of males (52.6%) and females (47.4%) and comprised 81.2% Saudi children with a mean age of 8.8 ± 1.84 years. Most study subjects (97.8%) were in mixed dentition and 88.7% were healthy. The prevalence of dental anomalies was as follows: teeth rotations (24.5%), ectopically erupted teeth (6%), congenitally missing permanent teeth (5.4%), peg lateral (1.1%), supernumerary (0.5%), gemination (0.3%), and fusion (0.1%). No statistically significant differences were found in the distribution of dental anomalies by patients' gender, medical history, and nationality (p value ≥0.05).Conclusion: This study showed that teeth rotations were the most common dental anomalies followed by ectopic eruptions and congenitally missing teeth. The study findings may guide dental practitioners to better diagnose and manage children with dental anomalies in eastern Saudi Arabia. [ABSTRACT FROM AUTHOR]

An x-ray microcalorimeter consists of an absorber and a thermometer connected to each other, and to a heat sink, via well defined thermal conductances. The standard theoretical derivation of energy resolution treats the absorber and thermometer as point elements that are internally isothermal. In reality, the finite size and internal diffusivity of the absorber and thermometer prevents these elements from instantly achieving a uniform temperature, leading to a variation in observed pulse shapes as a function of the interaction’s position within the absorber. These variations result in a distortion of the detector response and a subsequent degradation of the energy resolution. This paper presents diffusivity measurements for x-ray microcalorimeters fabricated at the NASA/GSFC. Using a diffusion model we developed, we show quantitatively how a 2 eV Gaussian response is distorted into a non-Gaussian profile roughly 12 eV wide at an energy of 6 keV for an absorber diffusivity of 104 μm2/μs. We then present a method for eliminating the effect of pulse shape variation on the detector energy response with a modified optimal filter approach. [ABSTRACT FROM AUTHOR]

An experimental study on hard x-ray Bremsstrahlung radiation due to fast electron generation from a planar solid copper target irradiated by 150 mJ, 45 fs Ti:sapphire laser pulses at I∼1018 W/cm2 is reported. Angular distribution of the hard x-ray dose rate (hν≥40 keV) is observed to be strongly forward peaked in the direction of target normal with a measured peak value of 40 μSv/h, at a distance of 500 mm from the target. Two sources of this radiation, one at the laser irradiated target and the other at the chamber wall facing the target, are inferred from the measurements of angular distribution and distance dependence of the x-ray dose rate. [ABSTRACT FROM AUTHOR]

Fresnel zone plates for x-ray focusing optics are typically made using lithographic techniques. To achieve optimum efficiency for hard x rays, a depth of several microns is required, which limits the minimum zone width and hence minimum focal spot size achievable using lithography. We are exploring the fabrication of zone plates by an alternative technique that surmounts these limitations: the growth of a multilayer film to be used in transmission (Laue) diffraction geometry, in which the thickness of consecutive layers gradually increases according to the Fresnel zone formula; the film is sectioned after growth to the required depth. For a planar multilayer, this produces a linear zone plate that can focus x rays in one dimension. Here we report the growth and characterization of a depth-graded multilayer suitable for use as a zone plate for hard x-ray focusing. The multilayer has a total of 470 alternating layers of WSi2 and Si with thicknesses increasing monotonically from 15 to 60 nm, for a total thickness of 11.33 μm. One of the major challenges is to understand and select the right material system for this kind of thick multilayer. We have found that WSi2/Si is a promising system. A comparison between WSi2/Si and W/Si multilayers is presented. [ABSTRACT FROM AUTHOR]

An experimental system has been designed to examine the assembly of nanoparticles in a variety of process engineering applications. These applications include the harvesting from solutions of nanoparticles into green parts, and the subsequent sintering into finished components. The system is based on an x-ray microtomography with a spatial resolution down to 5 μm. The theoretical limitations in x-ray imaging are considered to allow experimental optimization. A standard nondestructive evaluation type apparatus with a small focal-spot x-ray tube, high-resolution complementary metal oxide semiconductor flat-panel pixellated detector, and a mechanical rotational stage is used to image the static systems. Dynamic sintering processes are imaged using the same x-ray source and detector but a custom rotational stage which is contained in an environmental chamber where the temperature, atmospheric pressure, and compaction force can be controlled. Three-dimensional tomographic data sets are presented here for samples from the pharmaceutical, nutraceutical, biotechnology, and nanoparticle handling industries and show the microscopic features and defects which can be resolved with the system. [ABSTRACT FROM AUTHOR]

Focuses on a study which explored an x-ray photoelectron spectroscopic analysis of the interaction between polyimide film made by the Langmuir-Blodgett method and silicon. Background on silicon carbide; Description of the experimental setup; Results and discussion.

Ionizing radiation (IR) can result in serious genomic instability and genotoxicity by causing DNA damage. Carbon ion (CI) beams and X-rays are typical IRs and possess high-linear energy transfer (LET) and low-LET, respectively. In this article, a comet assay that was optimized by decreasing the electrophoresis time (8 minutes) and voltage (0.5 V/cm) was performed to elucidate and quantify the DNA damage induced by CI or X-rays radiation. Two quantitative methods for the comet assay, namely, comet score and olive tail moment, were compared, and the appropriate means and parameter values were selected for the present assay. The dose-effect relationship for CI or X-rays radiation and the DNA repair process were studied in yeast cells. These results showed that the quadratic function fitted the dose-effect relationship after CI or X-rays exposure, and the trend for the models fitted the dose-effect curves for various repair times was precisely described by the cubic function. A kinetics model was also creatively used to describe the process of DNA repair, and equations were calculated within repairable ranges that could be used to roughly evaluate the process and time necessary for DNA repair. [ABSTRACT FROM AUTHOR]

Seals are part of our cultural heritage but the study of these objects is limited because of their fragility. Terahertz and X-Ray imaging are used to analyze a collection of wax seals from the fourteenth to eighteenth centuries. In this work, both techniques are compared in order to discuss their advantages and limits and their complementarity for conservation state study of the samples. Thanks to 3D analysis and reconstructions, defects and fractures are detected with an estimation of their depth position. The path from the parchment tongue inside the seals is also detected. [ABSTRACT FROM AUTHOR]

3D woven composite materials have been recently used to design some engine structures in order to improve their impact resistance. The aim of this work is to study experimentally and numerically low-velocity/energy impact damage in such recent composites. Impact tests at different energy levels have been performed and analysed using microscopic observations and X-ray tomography in order to understand damage mechanisms occurring in this material. Finite element simulations have been performed using the continuum damage model, ODM-PMC, developed at Onera for 3D woven composites under static loadings. Through comparisons with the available experimental data, it has been demonstrated that the damage mechanisms are described correctly by the present model. Moreover, the residual depth after impact is also accurately predicted, allowing to generate, numerically, relations between impact energy, damaged area and residual depth, currently determined experimentally in aeronautical industries. [ABSTRACT FROM AUTHOR]

Some X-ray irradiation-induced electrical characteristics of the Au/anthraquinone/p-Si and the Au/pyridine/ p -Si junction devices have been investigated. The experimental ideality factors increased for both devices with increasing irradiation dose from 25 Gy to 150 Gy. These values ranged from 1.10 to 1.52 for Au/anthraquinone/ p -Si and from 1.46 to 1.77 for Au/pyridine/ p -Si, respectively. Furthermore, the barrier height of Au/anthraquinone/ p -Si increased with increasing irradiation dose from 0.75 to 0.91 eV, whereas it displayed about a constant value for Au/pyridine/ p -Si. In addition, the series resistance of both devices increased with x-ray dose too. The increase in the series resistance with x-ray irradiation has been attributed to the decrease in the active dopant densities. It was seen that the ionization damage is effective on most of the junction characteristics. The leakage current of the Au/anthraquinone/p-Si device decreased with x-ray irradiation since the irradiation induced the formation of electron-hole pairs and hydroquinone structure, and thus some of them are trapped by the interface states. The degradation of the I-V curves of Au/pyridine/ p -Si/Al device is attributed to the variation of the surface or interface states distribution for the devices. The reverse and forward bias currents relatively increased after x-ray irradiation because of the decrease in bulk lifetime. In addition, ATR-FTIR spectra of anthraquinone and pyridine films showed that pyridine is more stable than anthraquinone under x-ray irradiation. [ABSTRACT FROM AUTHOR]

The energy spectra of X-rays produced by an LiTaO 3 single crystal have been measured at pressures of 1–20 Pa. The energy spectra showed that the endpoint energy and the amount of X-rays gradually increased with the decrease of pressure at 5–8 Pa and abruptly increased around 4 Pa and below. A maximum endpoint energy of 70 keV was obtained using the LiTaO 3 single crystal with 5 mm thickness at a pressure of 3 Pa. The change of X-rays produced by the LiTaO 3 single crystal was discussed in relation to the breakdown potential at the pressures. [ABSTRACT FROM AUTHOR]

The performance of a Cadmiun Telluride (CdTe) detector for low energy photon spectrometry was evaluated. Collected data were analyzed using the basic software package available with the CdTe detector system and the COLEGRAM code developed for photopeak deconvolution at LNHB/France. Several calibrated point sources were used to determine the energy versus efficiency curve. The efficiency curve was used in the determination of main X-ray intensities of 153 Sm and 177 Lu. [ABSTRACT FROM AUTHOR]

Thin (<50 µm) and flawless diamond single crystals are essential for the realization of numerous advanced X-ray optical devices at synchrotron radiation and free-electron laser facilities. The fabrication and handling of such ultra-thin components without introducing crystal damage and strain is a challenge. Drumhead crystals, monolithic crystal structures composed of a thin membrane furnished with a surrounding solid collar, are a solution ensuring mechanically stable strain-free mounting of the membranes with efficient thermal transport. Diamond, being one of the hardest and most chemically inert materials, poses significant difficulties in fabrication. Reported here is the successful manufacture of diamond drumhead crystals in the [100] orientation using picosecond laser milling. Subsequent high-temperature treatment appears to be crucial for the membranes to become defect free and unstrained, as revealed by X-ray topography on examples of drumhead crystals with a 26 µm thick (1 mm in diameter) and a 47 µm thick (1.5 × 2.5 mm) membrane. [ABSTRACT FROM AUTHOR]

A procedure for performing x-ray structure analyses that allows data on the fine structure of carbon and polyacrylonitrile fibers to be obtained was described. It was shown that carbon fibers were heterogeneous. Their component composition was determined by the preparation conditions and depended on the orientation angle of the coherent scattering regions relative to the filament axis. The structure of crystalline polyacrylonitrile-fiber components included two types of coherent scattering regions, the average sizes of which differed by an order of magnitude. The change in the fine structure of polyacrylonitrile fibers during thermal stabilization was followed. [ABSTRACT FROM AUTHOR]

In mineral beneficiation, the mineral liberation spectrum of the plant feed conveys valuable information for adjusting operations, provided that it is available in minutes from particulate sampling. X-ray micro-tomography is the only technique available for unbiased measurement of composite particle composition (on a 3D basis). The bottleneck of current micro-tomographic systems is the X-ray scanning time (data acquisition) rather than the slice reconstruction time (data processing). An algorithm capable of reconstructing tomographic slices of composite mineral particles from a limited number of radiographic projections, thus significantly reducing the overall measurement time, is presented and demonstrated with numerical examples. The algorithm is cast around the discrete algebraical reconstruction technique and requires less than one tenth of the projection data needed by the currently used filtered back-projection methods, thus allowing a dramatic reduction of the scanning time. [ABSTRACT FROM AUTHOR]

The ultrafast electron beam X-ray tomography scanner ROFEX is used for the investigation of multiphase flows. Its functional principle allows us to obtain sequences of cross-sectional flow images, which shows local attenuation properties of the flow. Hence, the X-ray CT images mainly reveal the shape and interfaces of flow constituents, such as gas, liquid and solids via their X-ray contrast. It is, however, more difficult to obtain velocity information from multiphase flows. In this article we discuss different methods to extract information on the velocities of particles or interfaces as well as for continuous phase. For disperse phase velocity measurement, e.g. in gas–liquid or gas–solids flows, we employ cross-correlation based techniques using two imaging planes. Apart from the standard cross-correlation technique we developed a method and algorithm, which is capable to identify identical bubbles in the two planes giving us a unique Lagrangian particle-related velocity information. Eventually we give an example of velocity measurement in the continuous liquid phase using an X-ray contrast agent. [ABSTRACT FROM AUTHOR]

Past experiments and modeling with the Tmap code in [1, 2] indicated that Be-D co-deposited layers are less (time-wise) efficiently desorbed of retained D in a fixed low-temperature bake, as the layer grows in thickness. In Iter , beryllium rich co-deposited layers will grow in thickness over the life of the machine. Although, compared with the analyses in [1, 2], Iter presents a slightly different bake efficiency problem because of instances of prior tritium recover/control baking. More relevant to Iter , is the thermal release from a new and saturated co-deposit layer in contact with a thickness of previously-baked, less-saturated, co-deposit. Experiments that examine the desorption of saturated co-deposited over-layers in contact with previously baked under-layers are reported and comparison is made to layers of the same combined thickness. Deposition temperatures of ∼323 K and ∼373 K are explored. It is found that an instance of prior bake leads to a subtle effect on the under-layer. The effect causes the thermal desorption of the new saturated over-layer to deviate from the prediction of the validated Tmap model in [2]. Instead of the D thermal release reflecting the combined thickness and levels of D saturation in the over and under layer, experiment differs in that, i) the desorption is a fractional superposition of desorption from the saturated over-layer, with ii) that of the combined over and under -layer thickness. The result is not easily modeled by Tmap without the incorporation of a thin BeO inter-layer which is confirmed experimentally on baked Be-D co-deposits using X-ray micro-analysis. [ABSTRACT FROM AUTHOR]

An application of high-energy wide angle synchrotron X-ray diffraction to investigate the tensile deformation of 9Cr ferritic/martensitic (F/M) ODS steel is presented. With tensile loading and in-situ X-ray exposure, the lattice strain development of matrix was determined. The lattice strain was found to decrease with increasing temperature, and the difference in Young's modulus of six different reflections at different temperatures reveals the temperature dependence of elastic anisotropy. The mean internal stress was calculated and compared with the applied stress, showing that the strengthening factor increased with increasing temperature, indicating that the oxide nanoparticles have a good strengthening impact at high temperature. The dislocation density and character were also measured during tensile deformation. The dislocation density decreased with increasing of temperature due to the greater mobility of dislocation at high temperature. The dislocation character was determined by best-fit methods for different dislocation average contrasts with various levels of uncertainty. The results shows edge type dislocations dominate the plastic strain at room temperature (RT) and 300 °C, while the screw type dislocations dominate at 600 °C. The dominance of edge character in 9Cr F/M ODS steels at RT and 300 °C is likely due to the pinning effect of nanoparticles for higher mobile edge dislocations when compared with screw dislocations, while the stronger screw type of dislocation structure at 600 °C may be explained by the activated cross slip of screw segments. [ABSTRACT FROM AUTHOR]

Organic solid-state luminescence materials with aggregation-induced emission enhancement have attracted considerable interest in recent years. In this work, we develop a class of 2,7-diphenylfluorenone derivatives that exhibit prominent aggregation-induced emission properties with high solid-state quantum yields. Their solid-state powders show a ∼160 nm bathochromically shifted fluorescence and longer lifetime compared to their emission in dilute THF solution. The X-ray single structures and photophysical properties reveal that the mechanism of aggregation-induced emission in this class of fluorenone compounds is due to the formation of static excimers through hydrogen bonds in the solid state. The emission of their THF solution peaked at 380 nm and originates from the single molecule and the emission of their solid-state powder peaked at 550 nm originates from the excimers. The aggregation-induced emission properties and luminescence mechanism are further verified by the design of 2,7-diphenylfluorenone-diboronic acid adduct, which exhibited weak luminescence in high pH buffer and red-shifted strong luminescence in acidic buffer. [ABSTRACT FROM AUTHOR]

Characteristic K X-rays have been observed in Coulomb-excitation experiments with heavy radioactive-ion beams in the lead region ( Z = 82), produced at the REX-ISOLDE facility, and were used to identify the decay of strongly converted transitions as well as monopole 0 2 + → 0 1 + transitions. Different targets were used, and the X-rays were detected by the Miniball γ -ray spectrometer surrounding the target position. A stable mercury isotope, as well as neutron-deficient mercury, lead, polonium, and radon isotopes were studied, and a detailed description of the analysis using the radioactive 182,184,186,188 Hg isotopes is presented. Apart from strongly converted transitions originating from the decay of excited states, the heavy-ion induced K-vacancy creation process has been identified as an extra source for K X-ray production. Isolating the atomic component of the observed K X-rays is essential for a correct analysis of the Coulomb-excitation experiment. Cross sections for the atomic reaction have been estimated and are compared to a theoretical approach. [ABSTRACT FROM AUTHOR]

A theoretical description of parametric X-ray radiation (PXR) from a nanocrystal powder target is presented in terms of the orientation distribution function (ODF). Two models of ODF resulting in the analytical solution for the PXR intensity distribution are used and the characteristic features of this distribution are considered. A promising estimate of the number of the emitted photons is obtained for the case of a nanodiamond powder target using the parameters of ASTA Facility at Fermilab. The PXR spectra from polycrystal and single crystal targets are compared. The application scenarios of PXR from nanocrystals are discussed. [ABSTRACT FROM AUTHOR]

In the present work the effect of concrete incorporation with two types of nano-lead compounds on its γ-ray shielding characteristics is investigated. The concrete samples were prepared according to the local standards of building materials and doped by different percentages of PbO and PbTiO 3 nano powders which were prepared using co-precipitation and oxalate precursor techniques, respectively. In addition, commercial PbO 2 powder additive was used to check the effect of particle size on concrete attenuation properties. The phase composition and particle size of all the lead-oxide additives were confirmed by XRD and TEM imaging. The γ-rays attenuation coefficients were measured as a function of the additive percentage of lead compounds for γ-ray energies of 662, 1173 and 1332 keV using 137 Cs and 60 Co sources. The microstructure changes occurred in the concrete samples doped with Pb compounds additives were probed using the positron annihilation spectroscopy (PAS) and the results were compared with that for normal concrete. The obtained data revealed that the overall defect density of the investigated samples, as seen by the positrons, decreases with increasing the nano-PbO contents which is in agreement with the determined values of the samples apparent densities. It was found that the γ-ray attenuation coefficient of concrete doped by nano-PbO is improved. The results are explained in the view of the fine structure enhanced modification and its impact on the γ-ray interaction probability at different energies. [ABSTRACT FROM AUTHOR]

Partial melting in the Earth’s mantle involves a combination of processes such as ionic diffusion and solid–liquid transition. These processes yield an array of characteristic times for the melting kinetics. Both the magnitude and time constant of melt-induced volume strain affect seismic velocity, attenuation, and buoyancy. In situ monitoring of samples during melting are enabled by multi-anvil high-pressure devices coupled with synchrotron X-ray radiation. In this study, the volume strain induced in a sample from melting is measured as a function of time using X-ray images. We find a doubling of the effective thermal expansion for only 2% melt both from our data and from thermodynamic models of peridotite. The characteristic time of melting is determined to be less than one second. These findings have a direct impact on the effect of melting on seismic velocities. [ABSTRACT FROM AUTHOR]

We report recent progress made in a complete fiber-optic, high-precision, long-term stable timing distribution system for synchronization of next generation X-ray free-electron lasers. Timing jitter characterization of the master laser shows less than 170-as RMS integrated jitter for frequencies above 10 kHz, limited by the detection noise floor. Timing stabilization of a 3.5-km polarization-maintaining fiber link is successfully achieved with an RMS drift of 3.3 fs over 200 h of operation using all fiber-coupled elements. This all fiber-optic implementation will greatly reduce the complexity of optical alignment in timing distribution systems and improve the overall mechanical and timing stability of the system. [ABSTRACT FROM AUTHOR]

Linear accelerators, like the Free-electron LASer in Hamburg (FLASH) or the European X-Ray Free Electron Laser (E-XFEL) take advantage of the digital Low Level Radio Frequency (LLRF) system to control the phase and amplitude of an electromagnetic field inside superconducting cavities. The real-time control LLRF system, processing data within a few microseconds, has to fulfil performance requirements and provide comprehensive monitoring and diagnostics. The AMC-based controller (DAMC-TCK7) board was developed as a general purpose high-performance low-latency data processing unit designed according to the PICMG MTCA.4 spec. The module provides the processing power, data memory, communication links, reference clock, trigger and interlock signals that are required in modern LLRF control systems. The module was originally designed as a cavity field stabilizing controller for standing-wave linear accelerators. However, the application of the board is much wider because it is a general purpose data processing module suitable for systems requiring low latency and high-speed digital signal processing. According to authors’ knowledge this is the first MTCA.4 module offering 12.5 Gbps links, unified Zone 3 connectivity and advanced Module Management Controller proposed by DESY. The DAMC-TCK7 card was used as a hardware template for the development of the other AMC modules of the XFEL accelerator’s LLRF system. This paper discusses the requirements for the digital real-time data processing module, presents the laboratory performance evaluation and verification in Cryo-Module Test Bench (CMTB) at DESY. [ABSTRACT FROM PUBLISHER]

The performances of the OFFSET3 tracker (Optical Fiber Folded Scintillating Extended Tracker) are presented. It exploits a novel system for particle tracking, designed to achieve real-time particle imaging and tracking, large detection areas, and a high spatial resolution especially suitable for applications in medical diagnostics. The tracker is composed by two 288 \times 288~\mm^2 FOV position detectors stacked by 10 cm, made by 500 micron square scintillating fiber ribbons for both directions. The track position information is extracted in real-time in an innovative way, using a reduced number of readout channels, by means of which it is possible to obtain the large detection area with moderate cost and complexity. The architecture has been patented by the Istituto Nazionale di Fisica Nucleare (INFN). The performances of the tracker were investigated by beta sources, cosmic rays, 60 MeV-250 MeV proton and 400 MeV/A carbon clinical beams. [ABSTRACT FROM PUBLISHER]

In modern particle accelerators, radio frequency (RF) phase detectors have to fulfill high demands on stability and accuracy to meet the goals of state-of-the-art synchronization systems. Especially challenging are those cases where the RF signal phase shift accuracy must be measured with fs accuracy for several hours over the full 2 \pi phase detection range. In these cases special measures on the component’s nonlinearities and RF channel isolation have to be taken. The long-term stability of the phase detector is mostly affected by temperature and humidity variations. To meet the synchronization goals, we have built a phase detector that incorporates a high-speed dual analog-to-digital converter (ADC) with a special circuit for continuous phase drift calibration. In the calibration circuit we successfully combined the RF signal with an RF calibration signal (second tone) to compensate common phase drift that occurs in the microstrip lines, the RF transformers, and the ADC. The second-tone RF signals are directly converted to the digital domain by the fast ADC and, based on signal processing in the field-programmable gate array, are used to calculate the RF signal phase shift correction caused by detector drifts. In this paper, potential error sources of the analog and the digital part of the so-called two-tone calibration technique that limit the phase detector precision are discussed. Finally, the experimental results are presented showing a long-term phase measurement stability better than 0.01\ ^\circ \ pk-\ pk evaluated at an RF frequency of 1.3 GHz over a few days. [ABSTRACT FROM PUBLISHER]

High-speed X-ray imaging applications play a crucial role for non-destructive investigations of the dynamics in material science and biology. On-line data analysis is necessary for quality assurance and data-driven feedback, leading to a more efficent use of a beam time and increased data quality. In this article we present a smart camera platform with embedded Field Programmable Gate Array (FPGA) processing that is able to stream and process data continuously in real-time. The setup consists of a Complementary Metal-Oxide-Semiconductor (CMOS) sensor, an FPGA readout card, and a readout computer. It is seamlessly integrated in a new custom experiment control system called Concert that provides a more efficient way of operating a beamline by integrating device control, experiment process control, and data analysis. The potential of the embedded processing is demonstrated by implementing an image-based trigger. It records the temporal evolution of physical events with increased speed while maintaining the full field of view. The complete data acquisition system, with Concert and the smart camera platform was successfully integrated and used for fast X-ray imaging experiments at KIT’s synchrotron radiation facility ANKA. [ABSTRACT FROM PUBLISHER]

Presented here is an investigation on the geometric (molecular) structures, spectroscopic properties and electronic structures of copper(II)-nitrite complexes as a function of steric effects, utilizing a set of closely related co-ligands. The prepared complexes, with the general formula [CuL R (η 2 -ONO) 2 ] where L R is N , N -dialkyl, N ′-benzyl-ethylenediamine and R is methyl, ethyl or isopropyl moieties, were structurally characterized by physico-chemical and spectroscopic methods. An X-ray diffraction study on CuL Me (η 2 -ONO) 2 ] and CuL Et (η 2 -ONO) 2 ] reveals that the copper(II) center in both compounds is located in a distorted octahedral environment through coordination of two amine nitrogen atoms and four oxygen atoms of the nitrite ligands. Depending on the steric crowding of the co-ligand, the coordination mode is either symmetric or asymmetric bidentate, as is evident from X-ray crystallography and IR spectroscopy. The relative stability of linkage isomers of these compounds, along with a tert -butyl derivative complex, was investigated using density functional theory (DFT) calculations. The calculated results demonstrated that in all cases the bidentate η 2 -ONO isomer is more stable than the four-coordinated nitro isomer (η 1 -NO 2 ). However, the differences in the relative stability decrease as the steric hindrance in the co-ligand increases. The vibrational spectra of the complexes were assigned using DFT calculations. In support with the X-ray structure, the results reveal that ν as (N–O) splits into two bands, with the separation increasing from [CuL Me (η 2 -ONO) 2 ] through to [CuL tert-buty (η 2 -ONO) 2 ]. That is at least partially dictated by steric factors within the molecules, imposed by the alkyl groups of the co-ligand. The UV–Vis absorption spectra are presented and analyzed with the help of time-dependent density functional theory (TD-DFT) calculations. [ABSTRACT FROM AUTHOR]

This paper demonstrates an innovative simple technique to reconstruct the irregularities on the surfaces with curved geometry in stereo-PIXE (Particle Induced X-ray Emission) set-up. The method assumes that the local inclination of the topographical structure of the object results in X-ray yield asymmetries in two spectrometers mounted on both sides of the probing beam. The relief on the curved target could be quantitatively reconstructed by comparing the detected yield asymmetries and those calculated from a known non-structured cylindrical sample model of the target. The results of the relief reconstruction on a cone seashell at different radii close to its tip demonstrate that the method could reveal the relief in a region of the scanned area which is in the field of view of the two spectrometers. [ABSTRACT FROM AUTHOR]

This paper presents a new X-ray backscatter technique (XBT) for non-destructive imaging of aerospace materials with only a single-sided access. It uses a special twisted slit collimator to inspect the whole object by changing the viewing direction of the X-ray backscatter camera. For the first time, the X-ray backscatter measurements were conducted using high-energy (>500 keV) X-ray sources. Experiments were performed on thick complex structured aluminium components, stringers and honeycomb structures to validate the applicability of the present technique to image small changes in the material properties and also to detect low-density material inclusions. In order to reduce the inspection time from hours to several seconds and to improve the image quality of the X-ray backscatter image, the backscattered signals were measured using a digital detector array with high spatial resolution (200 µm). The influence of the energy of the X-ray source and the slit width of the camera on the X-ray backscatter image were also investigated. In the proposed technique, the whole object is irradiated by an un-collimated X-ray beam resulting in a low image acquisition time of 3 min that facilitates the use of XBT for the real time NDT&E of aerospace materials. [ABSTRACT FROM AUTHOR]

The use of a single stainless steel (STS) wire mesh basket as the fuel containment material for a series of pyroprocessing steps has been studied. The use of a single basket minimizes fuel loss and was enabled by transporting and using the basket containing the fuel from one test to the next without unloading it. The series of tests consisted of electrolytic reduction, LiCl distillation, electrorefining, LiCl–KCl distillation, and finally a second electrolytic reduction and a subsequent LiCl distillation step. While the electrolytic reduction of UO 2 was conducted in a LiCl–Li 2 O molten salt electrolyte at 650 °C using the STS wire mesh basket as the cathode, the electrorefining was carried out in a LiCl–KCl–UCl 3 molten salt electrolyte at 500 °C, using the STS wire mesh basket as the anode. During the salt (LiCl and LiCl–KCl) distillation processes, the product of electrolytic reduction/electrorefining in the basket, which included metallic U and residual salts, was distilled at 850 °C under vacuum. The electrolytic reduction, electrorefining, and salt distillation processes were successfully demonstrated with the use of a single STS wire mesh basket through the entire cycle. However, an unstable intermetallic U–Fe layer was observed between the reduction product and the STS basket, when a cross section of the basket was studied after the salt distillation steps. The influence of the U–Fe layer on the electrolysis steps needs to be studied further in order to understand and quantify the lifetime of a single STS wire mesh basket during pyroprocessing. [ABSTRACT FROM AUTHOR]

Two-dimensional meso-scale finite element models with realistic aggregates, cement paste and voids of concrete are developed using microscale X-ray Computed Tomography images. Cohesive elements with traction–separation laws are pre-embedded within cement paste and aggregate–cement interfaces to simulate complex nonlinear fracture. Tension tests using a large number of images were simulated with statistical analysis. The very different load-carrying capacities and crack patterns demonstrate the effects of random distribution of phases. It is found that the tensile strength decreases as the void fraction increases, and the relative strength of cement paste and interfaces dominates the microcracking behaviour, which in turn affects macrocracking and load-carrying capacity. [ABSTRACT FROM AUTHOR]

Inefficient quality assessment and control (QA&C) of spherical fuel elements for high temperature reactor-pebblebed modules (HTR-PM) has been a long-term problem, since conventional methods are labor intensive and cannot reveal the inside information nondestructively. Herein, we proposed a nondestructive, automated X-ray inspection (AXI) method to characterize spherical fuel elements including their inner structures based on X-ray digital radiography (DR). Briefly, DR images at different angles are first obtained and then the chosen important parameters such as spherical diameters, geometric and mass centers, can be automatically extracted and calculated via image processing techniques. Via evaluating sample spherical fuel elements, we proved that this AXI method can be conducted non-destructively, quickly and automatically. This method not only provides accurate physical characterization of spherical fuel elements but also reveals their inner structure with good resolution, showing great potentials to facilitate fast QA&C in HTM-PM spherical fuel element development and production. [ABSTRACT FROM AUTHOR]