A5028754315- Nuclear Physics and Applications
- Radiation Detection and Scintillator Technologies
- X-ray Diffraction in Crystallography
- Nuclear reactor physics and engineering
- Ultrasound Imaging and Elastography
- Photoacoustic and Ultrasonic Imaging
- High-pressure geophysics and materials
- Ultrasound and Hyperthermia Applications
- Atomic and Subatomic Physics Research
- Microstructure and Mechanical Properties of Steels
- Particle Detector Development and Performance
- Rare-earth and actinide compounds
- Microstructure and mechanical properties
- Advanced Materials Characterization Techniques
- Thermodynamic and Structural Properties of Metals and Alloys
- Advanced Chemical Physics Studies
- Nuclear Materials and Properties
- Fusion materials and technologies
- Radiation Therapy and Dosimetry
- Surgical Simulation and Training
- Magnetic properties of thin films
- Anatomy and Medical Technology
- Theoretical and Computational Physics
- Advanced MRI Techniques and Applications
- Magnetic Properties and Applications
Oak Ridge National Laboratory
2008-2021
University College London
2014-2019
Brno University of Technology
2017
Spallation Neutron Source
2013-2015
University of Hawaii System
2009
Ball State University
2005
Spinal Research
2003
Frenchay Hospital
2003
University of Houston
1992
Kelvin Nanotechnology (United Kingdom)
1982
Anatomical models are important training and teaching tools in the clinical environment routinely used medical imaging research. Advances segmentation algorithms increased availability of three-dimensional (3D) printers have made it possible to create cost-efficient patient-specific without expert knowledge. We introduce a general workflow that can be convert volumetric data (as generated by Computer Tomography (CT)) 3D printed physical models. This process is broken up into three steps:...
Non-invasive, focal neurostimulation with ultrasound is a potentially powerful neuroscientific tool that requires effective transcranial focusing of to develop. Time-reversal (TR) using numerical simulations propagation can correct for the effect skull, but relies on accurate simulations. Here, requirements ultrasonic are established through review previously employed parameters, and consideration deep brain targets. The specific limitations finite-difference time domain (FDTD) k-space...
High intensity transcranial focused ultrasound is an FDA approved treatment for essential tremor, while low-intensity applications such as neurostimulation and opening the blood brain barrier are under active research. Simulations of propagation used both focusing through skull, predicting intracranial fields. Maps skull acoustic properties necessary accurate simulations, can be derived from medical images using a variety methods. The maps range segmented, homogeneous models, to fully...
Abstract The ordered alloy CuAu I was deformed in tension at room temperature and the deformation mechanism investigated by electron microscopy. It found that predominant is {111} mechanical twinning not slip, as has been proposed Syutkina Yakovleva (1967). microstructure composed of microtwins on {101} planes formed during ordering process interaction twins with order investigated. probable crystal structure changed to one resembling CuPt which like atoms alternate.
AbstractAbstractThe microstructural changes that occur during superplastic deformation of the Al–Cu eutectic alloy are considered. It is shown considerable modification occurs to shapes and distribution inter-metallic CuAl2 particles deformation. This effect may be understood in terms sliding diffusion-controlled shape associated with grain boundaries within intermetallic. The roles interface diffusion creep superplasticity discussed.
AbstractA prospective randomized study was undertaken to evaluate the radiological appearance and clinical effectiveness of two porous tantalum (Hedrocel) implants in achieving a stable cervical interbody fusion. A prerandomization protocol used allocate patients three arms study: ring implant containing autologous cancellous bone graft, solid block or tricortical iliac crest graft. Patients were followed for 2 years with plain studies, SF-36, Neck Disability Index questionnaires...
A single crystal of ${\mathrm{Fe}}_{0.53}$${\mathrm{Cr}}_{0.47}$, quenched to 300 K after an anneal above the \ensuremath{\sigma}-phase boundary, was studied at three x-ray energies: 5.969, 7.092, and 7.6 keV (where contrast \ensuremath{\sim}0). With our analyzer detector we were able remove Compton resonant Raman scattering experimentally leave solely diffuse from concentration fluctuations atomic displacements. Using 7.6-keV data determine combined pure static thermal scattering, other two...
Results from neutron inelastic-scattering experiments on Fe, Cr, and three bcc Fe-Cr alloys were analyzed with a Born--von K\'arm\'an model to obtain phonon density-of-states (DOS) curves. We compared the DOS of composite appropriate fractions pure metals Fe Cr. In high-temperature limit, we obtained vibrational entropy mixing Cr be 0.141, 0.201, 0.214 ${\mathit{k}}_{\mathit{B}}$/atom for ${\mathrm{Fe}}_{70}$${\mathrm{Cr}}_{30}$,${\mathrm{Fe}}_{53}$${\mathrm{Cr}}_{47}$,...
Transcranial transmission of ultrasound is increasingly used in a variety clinical and research applications, including high intensity ablation, opening the blood brain barrier, neural stimulation. Numerical simulations propagation head are to enable effective transcranial focusing predict intracranial fields. Such require maps acoustic properties head, which can be derived from CT images. However, spatial resolution these images typically coarser than scale heterogeneities within skull...
X-ray measurements show that $\mathrm{Fe}{}_{63.2}\mathrm{Ni}{}_{36.8}$ has a slight tendency toward ${L1}_{0}$ and/or ${L1}_{2}$ ordering with preference for weakly ordered ${100}$ platelets. This bias $\mathrm{Fe}\ensuremath{-}\mathrm{Ni}$ first neighbor pairs decreases the number of Fe atoms eight or more nearest neighbors. Such rich regions are strongly correlated to alloy's Invar properties. The mean separation Fe-Fe is expanded relative average lattice, and amount expansion increases...
We constructed a compact in situ polarized (3)He neutron spin filter based on spin-exchange optical pumping which is capable of continuous the gas while system place beam an instrument. The size and light weight simplifies its utilization various instruments. has been successfully tested as polarizer triple-axis spectrometer (HB3) hybrid (HYSPEC) at Oak Ridge National Laboratory. Over 70% polarization was achieved maintained during test experiments. 90% average 25% transmission for neutrons...
Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using global optimizer framework built around MCNPX particle transport code. brightness metrics were selected as figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate 1.3 GeV energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate peak...
Effective transcranial transmission of focused ultrasound is desirable for various therapeutic applications. Time-reversal (TR) focusing based on numerical simulations propagation can be used to correct the aberrating skull layer. For weakly heterogeneous media, k-space and pseudospectral time domain (PSTD) methods have been shown increased accuracy efficiency compared finite-difference (FDTD) typically in TR. However, their suitability highly heterogeneous, less clear. Here, this...
Elastic diffuse scattering of neutrons was found around various Bragg-peak positions in FeNi Invar alloys. The intensities depend on the temperature and Ni concentration. increase with decreasing decrease increasing distribution intensity changes from peak to is well explained by formation clusters a lattice deformation consisting shear wave propagating along $⟨1\text{ }1\text{ }0⟩$ direction }\ensuremath{-}1\text{ polarization vector. ranges concentration, for which observed, coincide those...
The phonon density-of-states (DOS) of elemental vanadium was measured at elevated temperatures by inelastic neutron scattering. softening predicted thermal expansion against the bulk modulus is much larger than shifts in energies. We conclude that anharmonicities associated with are largely canceled effects from phonon-phonon Prior measurements heat capacity and calculations electronic entropy assessed, consistency requires an explicit temperature dependence DOS. Using data literature,...
The analysis of neutron diffraction experiments often assumes that neutrons are elastically scattered from the sample. However, there is growing evidence a significant fraction detected in fact inelastically scattered, especially soft materials and aqueous samples. Ignoring these inelastic contributions gives rise to inaccurate experimental results. To date, has been no simple method with broad applicability for signal separation experiments. Here, we present robust believe could be suited...
The rotary subwoofer is a novel low frequency transducer capable of efficiently generating infrasound from compact source. A field-deployable version this device may find application as calibration source for arrays the International Monitoring System (IMS) [(2001). Global Verification Regime and (CTBTO Preparatory Commission Vienna Centre, Vienna, Austria)]. prototype tested at IMS array I59US demonstrated ability to insonify all elements standoff distance 3.8km. Signal-to-noise ratios...
Atomic structure is perhaps the information most critical to understanding of materials behaviour, hence great importance x-rays and neutrons as probes. Although scattering sensitive pair higher-order correlations, in applications only correlation recovered. However, inadequate for a complete description homogeneous systems thermodynamic equilibrium; all correlations are required. It often assumed that extracted from experiments either uniquely determine or greatly restrict correlations....
Abstract Very thin layers of zinc, cadmium and tin have been deposited on polished copper insulating substrates at low temperatures. The films show diffuse rings when examined by reflection electron diffraction temperatures and, annealing, crystallize, exhibiting the normal pattern associated with materials. Measurement resistance these indicates an irreversible change in annealing concomitant change. which crystallization takes place determined.
Abstract Steady state constant pressure diffusion measurements were made on a series of alumina pellets using the nitrogen‐helium system at 1 atm. and 80°F. The prepared from same powder but compressed to different densities. Pore size distribution data indicate that all had approximately micropore sizes volume, macropore volumes. Flow with nitrogen also carried out for over range, up show pellet density, or has pronounced effect On basis simplified model pellet, path lengths evaluated flow...