Rotating Anode X-ray Source Research Articles

Flow-Xl: a new facility for the analysis of crystallization in flow systems.

Characterization of crystallization processes in situ is of great importance to furthering knowledge of how nucleation and growth processes direct the assembly of organic and inorganic materials in solution and, critically, understanding the influence that these processes have on the final physico-chemical properties of the resulting solid form. With careful specification and design, as demonstrated here, it is now possible to bring combined X-ray diffraction and Raman spectroscopy, coupled to a range of fully integrated segmented and continuous flow platforms, to the laboratory environment for in situ data acquisition for timescales of the order of seconds. The facility used here (Flow-Xl) houses a diffractometer with a micro-focus Cu Kα rotating anode X-ray source and a 2D hybrid photon-counting detector, together with a Raman spectrometer with 532 and 785 nm lasers. An overview of the diffractometer and spectrometer setup is given, and current sample environments for flow crystallization are described. Commissioning experiments highlight the sensitivity of the two instruments for time-resolved in situ data collection of samples in flow. Finally, an example case study to monitor the batch crystallization of sodium sulfate from aqueous solution, by tracking both the solute and solution phase species as a function of time, highlights the applicability of such measurements in determining the kinetics associated with crystallization processes. This work illustrates that the Flow-Xl facility provides high-resolution time-resolved in situ structural phase information through diffraction data together with molecular-scale solution data through spectroscopy, which allows crystallization mechanisms and their associated kinetics to be analysed in a laboratory setting.

Laboratory High-Contrast X-ray Microscopy of Copper Nanostructures Enabled by a Liquid-Metal-Jet X-ray Source.

High-resolution imaging of Cu/low-k on-chip interconnect stacks in advanced microelectronic products is demonstrated using full-field transmission X-ray microscopy (TXM). The comparison of two lens-based laboratory X-ray microscopes that are operated at two different photon energies, 8.0 keV and 9.2 keV, shows a contrast enhancement for imaging of copper nanostructures embedded in insulating organosilicate glass of a factor of 5 if 9.2 keV photons are used. Photons with this energy (Ga-Kα radiation) are generated from a Ga-containing target of a laboratory X-ray source applying the liquid-metal-jet technology. The 5 times higher contrast compared to the use of Cu-Kα radiation (8.0 keV photon energy) from a rotating anode X-ray source is caused by the fact that the energy of the Ga-Kα emission line is slightly higher than that of the Cu-K absorption edge (9.0 keV photon energy). The use of Ga-Kα radiation is of particular advantage for imaging of copper interconnects with dimensions from several 100 nm down to several 10 nm in a Cu/SiO2 or Cu/low-k backend-of-line stack. Physical failure analysis and reliability engineering in the semiconductor industry will benefit from high-contrast X-ray images of sub-μm copper structures in microchips.

Preclinical Intraoperative FLASH Radiotherapy

Intraoperative radiation therapy (IORT) is a method of delivering high radiation doses to an internal target with low dose to adjacent organs. Most organs at risk can often be moved out of the radiation field, so dose is usually limited by in-field vascular and/or nerve structures. It is known that ultra-high (FLASH) dose rate (>40 Gy/s) radiation reduces normal tissue toxicity compared to conventional, while preserving tumor control. We hypothesize that FLASH radiation can increase the dose tolerance of vascular and nerve structures, thus permitting for dose escalation in IORT. Here, we present a novel platform using orthovoltage x-rays to study FLASH effects in preclinical IORT. The experimental setup and dosimetry of the system have been established for FLASH irradiation of the abdominal aorta in rats to investigate dose tolerance. A 150 kVp rotating anode x-ray source with a 75-kW generator was used to deliver FLASH and conventional irradiation. A 3D printed immobilization platform was designed to reproducibly place a surgically exposed rat abdominal aorta at 55mm SSD. A 3-mm thick lead collimator with a 10mm x 10mm aperture was placed into a flange adapter, which docks into the immobilization platform. Phantom and in vivo dosimetry were performed using both calibrated radiographic film and thermoluminescent dosimeters (TLD). Anesthetized 2-month-old Wistar rats underwent laparotomy to expose the abdomen for irradiation. A 10x12x1 mm3 tungsten plate was placed under the aorta to reduce spinal cord dose. Animals were then docked into the irradiator using the immobilization platform. Radiation dose in the range of 20 - 50 Gy were delivered to the abdominal aorta at FLASH and conventional dose-rates. Following treatment, animals undergo MR angiography every two months for 6 months, at which a histological evaluation of aorta wall will be performed. The FLASH dose rate measured at the aorta wall in a rat carcass was 49.7 ± 1.2 Gy/s distal to the collimator. Dose measurements between the films and TLDs showed an agreement within ±3%. Positional uncertainty mainly depends on the visual localization of the aorta on the collimator window, which is verified before irradiation. Vertical uncertainty is less than 1 mm, which is important given the rapid dose fall off of the system. Eight animals went successfully through the procedure, are healthy and currently being follow up with MR angiography. More animals are being treated for meaningful statistical results. MR angiography and IORT are performed on different days to avoid longer times under anesthesia, which initially resulted on mortality. Results of the MR angiography and histological analysis will be presented. The proposed platform has been successfully utilized for precision setup for FLASH IORT in a preclinical laboratory setting. Evaluation of FLASH effects in IORT setup will be an important step in the potential translation of FLASH IORT, where only one high-dose fraction can be delivered.

FLASH Effects Induced by Orthovoltage X-Rays

This work describes the first implementation and in vivo study of ultrahigh-dose-rate radiation (>37 Gy/s; FLASH) effects induced by kilovoltage (kV) x-ray from a rotating-anode x-ray source. A high-capacity rotating-anode x-ray tube with an 80-kW generator was implemented for preclinical FLASH radiation research. A custom 3-dimensionally printed immobilization and positioning tool was developed for reproducible irradiation of a mouse hind limb. Calibrated Gafchromic (EBT3) film and thermoluminescent dosimeters (LiF:Mg,Ti) were used for in-phantom and in vivo dosimetry. Healthy FVB/N and FVBN/C57BL/6 outbred mice were irradiated on 1 hind leg to doses up to 43 Gy at FLASH (87 Gy/s) and conventional (CONV; <0.05 Gy/s) dose rates. The radiation doses were delivered using a single pulse with the widths up to 500 ms and 15 minutes at FLASH and CONV dose rates. Histologic assessment of radiation-induced skin damage was performed at 8 weeks posttreatment. Tumor growth suppression was assessed using a B16F10 flank tumor model in C57BL6J mice irradiated to 35 Gy at both FLASH and CONV dose rates. FLASH-irradiated mice experienced milder radiation-induced skin injuries than CONV-irradiated mice, visible by 4 weeks posttreatment. At 8 weeks posttreatment, normal tissue injury was significantly reduced in FLASH-irradiated animals compared with CONV-irradiated animals for histologic endpoints including inflammation, ulceration, hyperplasia, and fibrosis. No difference in tumor growth response was observed between FLASH and CONV irradiations at 35 Gy. The normal tissue sparing effects of FLASH irradiations were observed only for high-severity endpoint of ulceration at 43 Gy, which suggests the dependency of biologic endpoints to FLASH radiation dose. Rotating-anode x-ray sources can achieve FLASH dose rates in a single pulse with dosimetric properties suitable for small-animal experiments. We observed FLASH normal tissue sparing of radiation toxicities in mouse skin irradiated at 35 Gy with no sacrifice to tumor growth suppression. This study highlights an accessible new modality for laboratory study of the FLASH effect.

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Orthovoltage X-Ray Irradiator for Preclinical FLASH Studies

Flash radiotherapy, the delivery of high radiation dose (> 10 Gy) at ultrahigh dose rates (> 37 Gy/s), has been shown to reduce significantly normal tissue toxicity compared to conventional irradiation, while maintaining tumor control probability at similar level. Great excitement has since ensued about the transformative potential of FLASH radiotherapy. At present, important FLASH research employs complex accelerator technologies of limited accessibilities. Here, we study the feasibility of a novel self-shielded x-ray irradiation cabinet system, as an enabling technology to enhance the preclinical research capabilities of the radiation research community.The proposed system employs two commercially available high capacity 150 kVp fluoroscopy x-ray sources, RAD-44 or G-1592 tubes, with rotating anode technology in a parallel-opposed arrangement. Simulation was performed using a simulation toolkit. Simulated dosimetric properties of the x-ray beam for both FLASH and conventional dose-rate irradiations were characterized in terms of output, uniformity and symmetry as a function of SSD, beam current, exposure time, and external filters. Dose and dose rate from a single kV x-ray fluoroscopy source at various depths in solid water phantom were verified with measurements using radiographic films.The parallel-opposed x-ray sources can deliver doses up to 67 Gy to a 20-mm thick water equivalent medium at FLASH dose-rates of 40 - 240 Gy/s. A uniform depth dose rate within ± 5% deviation is achieved over 8-12 mm in central region of the phantom. Conventional dose-rate irradiation (≤ 0.1 Gy/s) can also be achieved by reducing the tube current and increasing the distance between the phantom and tubes. Either the RAD-44 or G-1592 x-ray source can be used to deliver FLASH and conventional dose-rate irradiations with the field larger than 25 mm and up to 200 mm in length, respectively. These field dimensions are well suitable for small animal and cell culture irradiations. For FLASH irradiation using parallel-opposed source arrangement, entrance and exit doses can be increased by 30% compared to the dose at the phantom center. Beam angling can be employed to reduce the high surface doses by minimizing the beams overlap at the phantom surfaces. For a 10 × 10 mm2 field, for example, 26degree beam angle from vertical axis reduces the entrance dose by 39%, while maintaining FLASH dose rate of 118 Gy/s spanning in 8 mm thickness.It is feasible to achieve FLASH dose rate irradiation with kV x-rays using rotating anode x-ray sources in the parallel-opposed arrangement. The system is amendable to self-shielding and readily deployable. Availability of both FLASH and conventional dose rate irradiations in the same platform enables effective comparative research. A cabinet FLASH irradiation system will greatly enhance research in the regular laboratory setting to elucidate the important biological mechanism of the FLASH effect.

Optimization of multipoint phase retrieval in edge illumination X-ray imaging: A theoretical and experimental analysis.

In this work, an analytical model describing the noise in the retrieved three contrast channels, transmission, refraction, and ultra small-angle scattering, obtained with edge illumination X-ray phase-based imaging system is presented and compared to experimentaldata. In EI, images acquired at different displacements of the presample mask (i.e., different illumination levels referred to as points on the "illumination curve"), followed by pixel-wise curve fitting, are exploited to quantitatively retrieve the three contrast channels. Therefore, the noise in the final image will depend on the error associated with the fitting process. We use a model based on the derivation of the standard error on fitted parameters, which relies on the calculation of the covariance matrix, to estimate the noise and the cross-channel correlation as a function of the position of the sampling points. In particular, we investigated the most common cases of 3 and 5 sampling points. In addition, simulations have been used to better understand the role of the integration time for each sampling point. Finally, the model is validated by comparison with the experimental data acquired with an edge illumination setup based on a tungsten rotating anode X-ray source and a photon countingdetector. We found a good match between the predictions of the model and the experimental data. In particular, for the investigated cases, an arrangement of the sampling points leading to minimum noise and cross-channel correlation can be found. Simulations revealed that, given a fixed overall scanning time, its distribution into the smallest possible number of sampling points needed for phase retrieval leads to minimum noise thanks to higher statistics perpoint. This work presents an analytical model describing the noise in the various contrast channels retrieved in edge illumination as a function of the illumination curve sampling. In particular, an optimal sampling scheme leading to minimum noise has been determined for the case where 3 or 5 sampling points are used, which represent two of the most common acquisition schemes. In addition, the correlation between noise in the different channels and the role of the number of points and exposure time have been also investigated. In general, our results suggest a series of procedures that should be followed in order to optimize the experimentalacquisitions.

Ultrahigh dose-rate (FLASH) x-ray irradiator for pre-clinical laboratory research

FLASH irradiation has been shown to reduce significantly normal tissue toxicity compared to conventional irradiation, while maintaining tumor control probability at similar level. Clinical translation of FLASH irradiation necessitates comprehensive laboratory studies to elucidate biological effects as well as pertinent technological and physical requirements. At present, FLASH research employs complex accelerator technologies of limited accessibilities. Here, we study the feasibility of a novel self-shielded x-ray irradiation cabinet system, as an enabling technology to enhance the preclinical research capabilities. The proposed system employs two commercially available high capacity 150 kVp fluoroscopy x-ray sources with rotating anode technology in a parallel-opposed arrangement. Simulation was performed with the GEANT4 Monte-Carlo platform. Simulated dosimetric properties of the x-ray beam for both FLASH and conventional dose-rate irradiations were characterized. Dose and dose rate from a single kV x-ray fluoroscopy source in solid water phantom were verified with measurements using Gafchromic films. The parallel-opposed x-ray sources can deliver over 50 Gy doses to a 20 mm thick water equivalent medium at ultrahigh dose-rates of 40–240 Gy s−1. A uniform depth-dose rate (±5%) is achieved over 8–12 mm in the central region of the phantom. Mirrored beams minimize heel effect of the source and achieve reasonable cross-beam uniformity (±3%). Conventional dose-rate irradiation (≤0.1 Gy s−1) can also be achieved by reducing the tube current and increasing the distance between the phantom and tubes. The rotating anode x-ray source can be used to deliver both FLASH and conventional dose-rate irradiations with the field dimensions well suitable for small animal and cell-culture irradiations. For FLASH irradiation using parallel-opposed sources, entrance and exit doses can be higher by 30% than the dose at the phantom center. Beam angling can be employed to minimize the high surface doses. Our proposed system is amendable to self-shielding and enhance research in regular laboratory setting.

Comparison of local crystal structure and magnetic properties of cation substituted LiNiO2 compositions

We investigate the change in local crystal structure and its impact on the magnetic ground states of LiNi0.5X0.5O2 (X = Mn, Co) and LiNi0.75Y0.25O2 (Y = Fe, Al) and contrast it against LiNiO2. The solid-state synthesis route adopted here introduces some anti-site disorder in the final compositions due to the volatile nature of Li ions. Powder X-ray diffraction (XRD) profiles were hence recorded using a rotating anode X-ray source to determine the percentage of anti-site disorder, and phase purity of all the compositions. Rietveld refinement of the XRD profiles confirms the symmetry and provides the estimation of unit cell parameters. Near-edge X-ray absorption spectra verified the oxidation state of various cations present in the compositions. Analysis of the extended X-ray absorption fine structure spectra identify the signatures of Jahn–Teller distortion in Ni3+ rich compositions. Changes in NiO6 octahedral environment has a much deeper impact on the magnetism of these compositions.

Comparison of image properties in full-field phase X-ray microscopes based on grating interferometry and Zernike's phase contrast optics

A grating interferometer (GI) system has been installed in an X-ray microscope equipped with a Zernike phase contrast (ZPC) system and a Cu rotating anode X-ray source. The GI and ZPC systems are switchable, and their performances of phase information extraction have been compared. The GI system is based on a Lau interferometer consisting of an absorption grating and a π/2 phase grating, which extracts a magnified phase shift map of a sample via a phase-stepping measurement. The ZPC system generates a phase contrast image by using a phase plate and a corresponding condenser device. The ZPC system and the GI system are compared in terms of detectability of phase objects. By the Fourier analysis of images of a logarithmic ruler pattern, the spatial resolution was found to be identical between the two systems. Although the sensitivity depends on the sample size, the signal-to-noise ratio of polystyrene spheres with a few microns in diameter was used for sensitivity comparison, showing the superior sensitivity of the GI system to that of the ZPC system. The quantitativeness of the GI system with the phase-stepping measurement was also demonstrated over the ZPC system, which generates halo and shade-off artifacts. The GI system exhibits twin image artifacts that need to be resolved for practical applications of the technique.

High-Resolution Extremity Cone-Beam CT with a CMOS Detector: Evaluation of a Clinical Prototype in Quantitative Assessment of Bone Microarchitecture.

A prototype high-resolution extremity cone-beam CT (CBCT) system based on a CMOS detector was developed to support quantitative in vivo assessment of bone microarchitecture. We compare the performance of CMOS CBCT to an amorphous silicon (a-Si:H) FPD extremity CBCT in imaging of trabecular bone. The prototype CMOS-based CBCT involves a DALSA Xineos3030 detector (99 μm pixels) with 400 μm-thick CsI scintillator and a compact 0.3 FS rotating anode x-ray source. We compare the performance of CMOS CBCT to an a-Si:H FPD scanner built on a similar gantry, but using a Varian PaxScan2530 detector with 0.137 mm pixels and a 0.5 FS stationary anode x-ray source. Experimental studies include measurements of Modulation Transfer Function (MTF) for the detectors and in 3D image reconstructions. Image quality in clinical scenarios is evaluated in scans of a cadaver ankle. Metrics of trabecular microarchitecture (BV/TV, Bone Volume/Total Volume, TbSp, Trabecular Spacing, and TbTh, trabecular thickness) are obtained in a human ulna using CMOS CBCT and a-Si:H FPD CBCT and compared to gold standard μCT. The CMOS detector achieves ~40% increase in the f20 value (frequency at which MTF reduces to 0.20) compared to the a-Si:H FPD. In the reconstruction domain, the FWHM of a 127 μm tungsten wire is also improved by ~40%. Reconstructions of a cadaveric ankle reveal enhanced modulation of trabecular structures with the CMOS detector and soft-tissue visibility that is similar to that of the a-Si:H FPD system. Correlations of the metrics of bone microarchitecture with gold-standard μCT are improved with CMOS CBCT: from 0.93 to 0.98 for BV/TV, from 0.49 to 0.74 for TbTh, and from 0.9 to 0.96 for TbSp. Adoption of a CMOS detector in extremity CBCT improved spatial resolution and enhanced performance in metrics of bone microarchitecture compared to a conventional a-Si:H FPD. The results support development of clinical applications of CMOS CBCT in quantitative imaging of bone health.

High-resolution extremity cone-beam CT with a CMOS detector: Task-based optimization of scintillator thickness.

CMOS x-ray detectors offer small pixel sizes and low electronic noise that may support the development of novel high-resolution imaging applications of cone-beam CT (CBCT). We investigate the effects of CsI scintillator thickness on the performance of CMOS detectors in high resolution imaging tasks, in particular in quantitative imaging of bone microstructure in extremity CBCT. A scintillator thickness-dependent cascaded systems model of CMOS x-ray detectors was developed. Detectability in low-, high- and ultra-high resolution imaging tasks (Gaussian with FWHM of ~250 μm, ~80 μm and ~40 μm, respectively) was studied as a function of scintillator thickness using the theoretical model. Experimental studies were performed on a CBCT test bench equipped with DALSA Xineos3030 CMOS detectors (99 μm pixels) with CsI scintillator thicknesses of 400 μm and 700 μm, and a 0.3 FS compact rotating anode x-ray source. The evaluation involved a radiographic resolution gauge (0.6-5.0 lp/mm), a 127 μm tungsten wire for assessment of 3D resolution, a contrast phantom with tissue-mimicking inserts, and an excised fragment of human tibia for visual assessment of fine trabecular detail. Experimental studies show ~35% improvement in the frequency of 50% MTF modulation when using the 400 μm scintillator compared to the standard nominal CsI thickness of 700 μm. Even though the high-frequency DQE of the two detectors is comparable, theoretical studies show a 14% to 28% increase in detectability index (d'2) of high- and ultrahigh resolution tasks, respectively, for the detector with 400 μm CsI compared to 700 μm CsI. Experiments confirm the theoretical findings, showing improvements with the adoption of 400 μm panel in the visibility of the radiographic pattern (2× improvement in peak-to-through distance at 4.6 lp/mm) and a 12.5% decrease in the FWHM of the tungsten wire. Reconstructions of the tibial plateau reveal enhanced visibility of trabecular structures with the CMOS detector with 400 μm scinitllator. Applications on CMOS detectors in high resolution CBCT imaging of trabecular bone will benefit from using a thinner scintillator than the current standard in general radiography. The results support the translation of the CMOS sensor with 400 μm CsI onto the clinical prototype of CMOS-based extremity CBCT.

Low-temperature high magnetic field powder x-ray diffraction setup for field-induced structural phase transition studies from 2 to 300 K and at 0 to 8-T field.

A low-temperature and high magnetic field powder x-ray diffractometer (XRD) has been developed at UGC-DAE CSR (UGC: University Grant Commission, DAE: Department of Atomic Energy, and CSR: Consortium for scientific research), Indore, India. The setup has been developed around an 18 kW rotating anode x-ray source delivering Cu-Kα x-rays coming from a vertical line source. It works in a symmetric θ-2θ parallel beam geometry. It consists of a liquid helium cryostat with an 8 T split-pair Nb-Ti superconducting magnet comprising two x-ray windows each covering an angular range of 65°. This is mounted on a non-magnetic type heavy duty goniometer equipped with all necessary motions along with data collection accessories. The incident x-ray beam has been made parallel using a parabolic multilayer mirror. The scattered x-ray is detected using a NaI detector through a 0.1° acceptance solar collimator. To control the motions of the goniometer, a computer programme has been developed. The wide-angle scattering data can be collected in a range of 2°-115° of 2θ with a resolution of ∼0.1°. The whole setup is tightly shielded for the scattered x-rays using a lead hutch. The functioning of the goniometer and the artifacts arising possibly due to the effect of stray magnetic field on the goniometer motions, on the x-ray source, and on the detector have been characterized by collecting powder XRD data of a National Institute of Standards and Technology certified standard reference material LaB6 (SRM-660b) and Si powder in zero-field and in-field conditions. Occurrence of field induced structural-phase transitions has been demonstrated on various samples like Pr0.5Sr0.5MnO3, Nd0.49Sr0.51MnO3-δ and La0.175Pr0.45Ca0.375MnO3 by collecting data in zero field cool and field cool conditions.

Technical assessment of a prototype cone-beam CT system for imaging of acute intracranial hemorrhage.

A cone-beam CT scanner has been developed for detection and monitoring of traumatic brain injury and acute intracranial hemorrhage (ICH) at the point of care. This work presents a technical assessment of imaging performance and dose for the scanner in phantom and cadaver studies as a prerequisite to clinical translation. The scanner incorporates a compact, rotating-anode x-ray source and a flat-panel detector (43 × 43 cm2) on a mobile U-arm gantry with source-axis distance = 550 mm and source-detector distance = 1000 mm. Central and peripheral doses were measured in 16 cm diameter CTDI phantoms using a 0.6 cm3 Farmer ionization chamber for various scan techniques and as a function of longitudinal position, including out of field. Spatial resolution, contrast, noise, and image uniformity were assessed in quantitative and anthropomorphic head phantoms. Two reconstruction protocols were evaluated, including filtered backprojection (FBP) for high-resolution bone imaging and penalized weighted least squares (PWLS) reconstruction for low-contrast soft tissue (ICH) visualization. A fresh cadaver was imaged with and without simulated ICH using the scanner as well as a diagnostic multidetector CT (MDCT) scanner using a standard head protocol. Images were interpreted by a fellowship-trained neuroradiologist for imaging tasks of ICH detection, gray-white-CSF differentiation, detection of midline shift, and fracture detection. The nominal scan protocol involved 720 projections acquired over a 360° orbit at 100 kV and 216 mAs, giving a dose (weighted CTDI) of 22.8 mGy (∼1.2 mSv effective dose). Out-of-field dose decreased to <10% within 6 cm of the field edge (approximate to the thyroid position). Image uniformity demonstrated <1% variation between the edge of the field (near the cranium) and center of the image. The high-resolution FBP reconstruction protocol showed ∼0.9 mm point spread function (PSF) full-width at half-maximum (FWHM). The smooth PWLS reconstruction protocol yielded ∼1.2 mm PSF FWHM and contrast-to-noise ratio exceeding 5.7 in ∼50 HU spherical ICH, resulting in conspicuous depiction of ICH down to ∼2 mm (the smallest diameter investigated). Cadaver images demonstrated good differentiation of brain and CSF (sufficient, but inferior to MDCT, recognizing that the CBCT dose was one-third that of MDCT), excellent visualization of cranial sutures and fracture (potentially superior to MDCT), clear detection of midline shift, and conspicuous detection of ICH. Technical assessment of the prototype demonstrates dose characteristics and imaging performance consistent with point-of-care detection and monitoring of head injury-most notably, conspicuous detection of ICH-and supports translation of the system to clinical studies.

Structural stability of ultra-incompressible Mo2B: A combined experimental and theoretical study

In the present work, we report a combined experiment and theoretical study on high pressure structural stability of Al2Cu type- Mo2B up to ∼40 GPa. Experiments using rotating anode x-ray source indicate that the ground state tetragonal structure of Mo2B (space group I4/mcm) to be stable up to the highest pressure studied. In addition, the experimental results were complemented by first principles density functional calculations within the projector augmented wave method. The calculated structural parameters are in excellent agreement with present experiments as well as previous reports. The estimated bulk modulus using Birch–Murnaghan equation of state from both experiment (302 GPa) and theory (310 GPa) reveals the ultra-incompressible nature of Mo2B. The much higher bulk modulus of this semi boride as compared to elemental Mo is discussed in terms of Mo–Mo bond distance in their crystal structures. The calculated electronic structure of Mo2B shows a strong Fermi surface nesting along P–P direction, which might also trigger lattice instability and is addressed in detail.

Crystallographic analysis of FAD-dependent glucose dehydrogenase.

An FAD-dependent glucose dehydrogenase (GDH) from Aspergillus terreus was purified and crystallized at 293 K using the sitting-drop vapour-diffusion method. A data set was collected to a resolution of 1.6 Å from a single crystal at 100 K using a rotating-anode X-ray source. The crystal belonged to space group P21, with unit-cell parameters a = 56.56, b = 135.74, c = 74.13 Å, β = 90.37°. The asymmetric unit contained two molecules of GDH. The Matthews coefficient was calculated to be 2.2 Å(3) Da(-1) and the solvent content was estimated to be 44%.

Achromatic approach to phase-based multi-modal imaging with conventional X-ray sources.

Compatibility with polychromatic radiation is an important requirement for an imaging system using conventional rotating anode X-ray sources. With a commercially available energy-resolving single-photon-counting detector we investigated how broadband radiation affects the performance of a multi-modal edge-illumination phase-contrast imaging system. The effect of X-ray energy on phase retrieval is presented, and the achromaticity of the method is experimentally demonstrated. Comparison with simulated measurements integrating over the energy spectrum shows that there is no significant loss of image quality due to the use of polychromatic radiation. This means that, to a good approximation, the imaging system exploits radiation in the same way at all energies typically used in hard-X-ray imaging.

Realtime X-ray reflectometry to see changes at buried interfaces

X-ray reflectometry is powerful in determining internal structure of multilayered thin films, such as thickness and density of each layer, as well as the roughness of surface and interfaces [1]. The measurement requires some precise angular scans near the critical angle with monochromatic parallel X-rays, and therefore it has not been thought that the technique is basically suitable to see changes. However, even without any angular scans, it is possible to obtain essentially the same data by using wide angular dispersion of the incident X-ray beam. The principle is basically known as Naudon's pioneering concept [2]. The system has been improved further by employing a monochroator, which was not used by Naudon's work. A multilayer monochromator was placed at very narrow limited space between a rotating anode X-ray source and the sample stage [3]. Use of a fast Si strip detector also contributed to improve the time-resolution. One can obtain an X-ray reflectivity curve with 4.5 decades even in 1 sec. It is possible to measure the curve down to 10-6, if 20 sec accumulation is allowed. Another advantage of the present instrument is fairly wide angular divergence, which ensures simultaneous data collection for 2 deg range. One of our recent successful applications of this method is the measurement of thermal expansion factor of the polymer thin film. It was also possible to see melting and freezing surfaces. In the presentation, such practical application will be demonstrated, in addition to the detailed description of our instruments.

High pressure structural investigation on LaGa

High pressure X-ray diffraction studies on rare-earth gallide LaGa was carried up to a pressure of ∼28 GPa using synchrotron, as well as rotating anode X-ray source in an angle dispersive mode. LaGa exhibits CrB (B33)-type orthorhombic structure (space group Cmcm) at ambient pressure. It undergoes a reversible structural phase transition from orthorhombic to tetragonal structure (Space. Group P4/mmm) at ∼5 GPa. Both the phases coexist up to the highest pressure studied. The transition to tetragonal phase has implications in predicting the new intermediate phase in the generally observed B1 to B2 transition sequence in AB type of rare-earth intermetallics. This investigation reveals that the LnX-type compounds may exhibit the structural sequence B1→ B33→ P4/mmm→ B2 under pressure. Considering the variation of lattice parameters a, b, c and also various bond lengths with pressure, the B33 to P4/mmm transition in LaGa may be displacive in nature. The zero pressure bulk modulus and its derivative for parent phase have been estimated to be B0 = 60 ± 3 GPa and = 4.6 ± 1.5. The bulk modulus for the high pressure tetragonal phase at ∼8 GPa also has been estimated to be B8 = 77 ± 8 GPa. We have also done the non-spin-polarized total energy calculations using the full potential linearized augmented plane wave method as implemented in the WIEN2 K code which confirms the experimental results.

The structure of augmenter of liver regeneration crystallized in the presence of 50 mMCdCl2reveals a novel Cd2Cl4O6cluster that aids in crystal packing

The crystal structure of the protein augmenter of liver regeneration containing a 14-residue hexahistidine purification tag (hsALR) has been determined to 2.4 Å resolution by Cd-SAD using a highly redundant data set collected on a rotating-anode home X-ray source and processed in 1998. The hsALR crystal structure is a tetramer composed of two homodimers bridged by a novel Cd(2)Cl(4)O(6) cluster via binding to the side-chain carboxylate groups of two solvent-exposed aspartic acid residues. A comparison with the native sALR tetramer shows that the cluster dramatically changes the hsALR dimer-dimer interface, which can now better accommodate the extra 14 N-terminal residues associated with the purification tag. The refined 2.4 Å resolution structure is in good agreement with both the X-ray data (R(cryst) of 0.165, R(free) of 0.211) and the expected stereochemistry (r.m.s. deviations from ideality for bond lengths and bond angles of 0.007 Å and 1.15°, respectively).