A5091413823- Ultrasound Imaging and Elastography
- Photoacoustic and Ultrasonic Imaging
- Ultrasonics and Acoustic Wave Propagation
- Ultrasound and Hyperthermia Applications
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Diamond and Carbon-based Materials Research
- Hydrocarbon exploration and reservoir analysis
- Microwave Imaging and Scattering Analysis
- Petroleum Processing and Analysis
- Molecular Junctions and Nanostructures
- Flow Measurement and Analysis
- Advanced MRI Techniques and Applications
- Carbon Nanotubes in Composites
- High-pressure geophysics and materials
- Force Microscopy Techniques and Applications
- Graphene research and applications
- Optical Coherence Tomography Applications
- Porphyrin and Phthalocyanine Chemistry
- Advanced Biosensing Techniques and Applications
- Monoclonal and Polyclonal Antibodies Research
- Cardiovascular Health and Disease Prevention
- Enhanced Oil Recovery Techniques
- Synthetic Organic Chemistry Methods
- Electrical and Bioimpedance Tomography
Stanford University
2016-2025
SLAC National Accelerator Laboratory
2014-2024
Biomarker Technologies (China)
2024
Palo Alto University
2017-2023
Stanford Medicine
2015-2023
Stratford University
2023
Duke University
2007-2022
University Radiology
2022
Forest Institute
2020
Charlottesville Medical Research
2020
We exploited the exceptional thermal stability and diverse molecular shapes of higher diamondoids (C22 polymantanes) to isolate them from petroleum. Molecules containing 4 11 diamond-crystal cages were isolated crystallized, we obtained single-crystal x-ray structures for representatives three families. Rigidity, strength, remarkable assortments three- dimensional shapes, including resolvable chiral forms, multiple, readily derivatizable attachment sites make valuable nanometer-size building blocks.
Oleanane has been reported in Upper Cretaceous and Tertiary source rocks their related oils suggested as a marker for flowering plants. Correspondence of oleanane concentrations relative to the ubiquitous microbial 17alpha-hopane with angiosperm diversification (Neocomian Miocene) suggests that migrated petroleum can be used identify maximum age unknown or unavailable rock. Rare occurrences pre-Cretaceous suggest either separate lineage leads angiosperms well before Early other plant groups...
Conventional ultrasound images are formed by delay-and-sum beamforming of the backscattered echoes received individual elements transducer aperture. Although beamformer is well suited for image formation, it corrupted speckle noise and challenged acoustic clutter phase aberration. We propose an alternative method imaging utilizing short-lag spatial coherence (SLSC) echoes. Compared with matched B-mode images, SLSC demonstrate superior SNR contrast-to-noise ratio in simulated experimental...
Time-delay estimators, such as normalized cross correlation and phase-shift estimation, form the computational basis for elastography, blood flow measurements, acoustic radiation force impulse (ARFI) imaging. This paper examines performance of these algorithms small displacements (less than half ultrasound pulse wavelength). The effects noise, bandwidth, stationary echoes, kernel size, downsampling, interpolation, quadrature demodulation on accuracy time delay estimates are measured in terms...
With traditional beamforming methods, ultrasound B-mode images contain speckle noise caused by the random interference of subresolution scatterers. In this paper, we present a framework for using neural networks to beamform channel signals into speckle-reduced images. We introduce log-domain normalization-independent loss functions that are appropriate imaging. A fully convolutional network was trained with simulated were coregistered spatially ground-truth maps echogenicity. Networks...
The 18S ribosomal DNA molecular phylogeny and lipid composition of over 120 marine diatoms showed that the capability to biosynthesize highly branched isoprenoid (HBI) alkenes is restricted two specific phylogenetic clusters, which independently evolved in centric pennate diatoms. record C 25 HBI chemical fossils a large suite well-dated sediments petroleum revealed older cluster, composed rhizosolenid diatoms, 91.5 ± 1.5 million years ago (Upper Turonian), enabling an accurate dating pace...
We found monochromatic electron photoemission from large-area self-assembled monolayers of a functionalized diamondoid, [121]tetramantane-6-thiol. Photoelectron spectra the diamondoid exhibited peak at low-kinetic energy threshold; up to 68% all emitted electrons were within this single peak. The intensity emission is indicative diamondoids being negative affinity materials. With an distribution width less than 0.5 volts, source may find application in technologies such as microscopy, beam...
A full-wave equation that describes nonlinear propagation in a heterogeneous attenuating medium is solved numerically with finite differences the time domain (FDTD). Three-dimensional solutions of are verified water tank measurements commercial diagnostic ultrasound transducer and shown to be excellent agreement terms fundamental harmonic acoustic fields power spectrum at focus. The linear components algorithm also independently. In nonattenuating regime match results from Field II, well...
The metal-induced coupling of tertiary diamondoid bromides gave highly sterically congested hydrocarbon (hetero)dimers with exceptionally long central C–C bonds up to 1.71 Å in 2-(1-diamantyl)[121]tetramantane. Yet, these dimers are thermally very stable even at temperatures above 200 °C, which is not line common bond length versus strengths correlations. We suggest that the extraordinary stabilization arises from numerous intramolecular van der Waals attractions between neighboring...
Research Article| February 01, 1996 Chemostratigraphic reconstruction of biofacies: Molecular evidence linking cyst-forming dinoflagellates with pre-Triassic ancestors J. Michael Moldowan; Moldowan 1Department Geological and Environmental Sciences, Stanford University, Stanford, California 94305-2115 Search for other works by this author on: GSW Google Scholar Jeremy Dahl; Dahl 94305-21152Chevron Petroleum Technology Company, A-3126, P.O. Box 5046, San Ramon, 94583-0946 Stephen R. Jacobson;...
A model and method to accurately estimate the local speed of sound in tissue from pulse-echo ultrasound data is presented. The relates speeds along a wave propagation path average over path, allows one avoid bias sound-speed estimates that can result overlying layers subcutaneous fat muscle tissue. Herein, using approach by Anderson Trahey measured, then authors solve proposed for via gradient descent. estimator was tested series simulation ex vivo phantom experiments two-layer media as...
Phase aberration is widely considered a major source of image degradation in medical pulse-echo ultrasound. Traditionally, near-field phase correction techniques are unable to account for distributed aberrations due spatially varying speed sound the medium, while most require use point-like sources and impractical clinical applications where diffuse scattering dominant. Here, we present two that utilize estimates from tomographic estimator builds on our previous work with layered media. We...
Ace of diamonds: Cyclohexamantane (C26H30), a large diamond-like molecule containing six peri-fused adamantane cages was identified in petroleum and its structure proven by X-ray crystallography (see picture). Never synthesized because severe mechanistic difficulties, the cyclohexamantane has appeared theoretical molecular-simulation studies related to diamond; experimentally determined properties are now discussed.
Radiation force-based techniques have been developed by several groups for imaging the mechanical properties of tissue. Acoustic radiation force impulse (ARFI) is one such method that uses commercially available scanners to generate localized forces in The response tissue determined using conventional B-mode pulses track micron-scale displacements Current research ARFI focused on producing real-time images arid related properties. Obstacles a ARFl modality include data acquisition,...
The optical spectra of hydrogen-passivated diamond clusters (diamondoids) precisely defined in size and shape have been measured the gas phase, i.e., under an environment similar to boundary conditions typically assumed by theory. Characteristic properties evolve for these wide band-gap semiconductor nanocrystals as a function size, shape, symmetry subnanometer regime. These effects not previously theoretically predicted. response tetrahedral-shaped C_{26}H_{32} cluster [1(2,3)4]...
We demonstrate a novel imaging technique, named short-lag spatial coherence (SLSC) imaging, which uses short distance (or lag) values of the function backscattered ultrasound to create images. Simulations using Field II are used detection lesions varying sizes and contrasts with without acoustical clutter in data. B-mode SLSC shown be nearly equivalent lesion detection, based on contrast-to-noise ratio (CNR) lesion, noise-free conditions. The CNR image, however, can adjusted achieve an...
A full-wave equation that describes nonlinear propagation in a heterogeneous attenuating medium is solved numerically with finite differences the time domain (FDTD). This numerical method used to simulate of diagnostic ultrasound pulse through measured representation human abdomen heterogeneities speed sound, attenuation, density, and nonlinearity. Conventional delay-andsum beamforming generate point spread functions (PSF) display effects these heterogeneities. For particular imaging...