A5088360011- Terahertz technology and applications
- Glaucoma and retinal disorders
- Flow Measurement and Analysis
- Ultrasonics and Acoustic Wave Propagation
- Superconducting and THz Device Technology
- Spectroscopy and Laser Applications
- Ultrasound Imaging and Elastography
- Ultrasound and Hyperthermia Applications
- Semiconductor Quantum Structures and Devices
- 2D Materials and Applications
- Retinal Diseases and Treatments
- Gyrotron and Vacuum Electronics Research
- Traumatic Brain Injury and Neurovascular Disturbances
- Scientific Measurement and Uncertainty Evaluation
- Sensor Technology and Measurement Systems
- Electronic and Structural Properties of Oxides
- Quantum and electron transport phenomena
- Photonic and Optical Devices
- Perovskite Materials and Applications
- Retinal and Optic Conditions
- Molecular Junctions and Nanostructures
- Metamaterials and Metasurfaces Applications
- Ultrasound and Cavitation Phenomena
- Corneal surgery and disorders
- Cerebral Venous Sinus Thrombosis
Okinawa Institute of Science and Technology Graduate University
2021-2023
University of Leeds
2016-2020
National Physical Laboratory
1984-2003
Legacy Health
1992-1999
Oregon Health & Science University
1988-1996
Oregon National Primate Research Center
1988-1996
Oregon Medical Research Center
1989-1996
Legacy Good Samaritan Medical Center
1992-1995
Good Samaritan Regional Medical Center
1992-1995
Good Samaritan Hospital
1992-1995
Abstrocr-The experimental determination of the frequency response, directionality, and electrical characteristics membrane hydrophones are reported. These interpreted in terms theoretical models, based mainly on published values for properties polyvinylidene fluoride (pvdf). The response was determined using both linear nonlinear acoustic fields. directionality is affected by angular variation piezoelectric sensitivity also, large angles incidence, Lamb wave propagation membrane. shown to be...
We visualize the distribution of electron around hole in an exciton and observe its elusive anomalous dispersion.
Three basic types of membrane hydrophone made from the piezoelectric polymer polyvinylidene fluoride (PVDF) are described. These have been developed as instruments for characterisation ultrasonic fields in megahertz frequency range. Performance properties such sensitivity, directional response, reflection, linearity and signal-to-noise ratio considered various devices films thicknesses between 0.006 mm 0.080 with active elements 0.5 to 4 diameter.
A primary calibration method for ultrasonic hydrophones which uses a Michelson interferometer to determine the particle displacement in an field is discussed. The acoustic pressure derived from this measurement and used free-field sensitivity of hydrophone frequency range 0.5-15 MHz. random uncertainty typically 1%, whereas systematic varies 2.3 6.6% over range. To obtain accuracy, performance system has been carefully examined appropriate correction factors derived. greatest difficulty lies...
We demonstrate a significant enhancement in the sensitivity of split ring resonator terahertz metamaterial dielectric sensors by introduction etched trenches into their inductive-capacitive gap area, both through finite element simulations and experiments performed using time-domain spectroscopy. The enhanced is demonstrated observation an increased frequency shift response to overlaid material thicknesses up 18 µm deposited on sensor surface. show that factor ∼2.7 times incorporation...
Abstract Conceived over 30 years ago, photoconductive (PC) emitters have proved essential in the development and spread of terahertz technology. Since then, not only they been used extensively a wide range spectroscopic imaging applications, also undergone significant improvements performance, leading to their use for broadband or non-linear spectroscopy. In this review article, we provide an overview literature, highlighting key milestones progression PC emitter. We investigate future...
The purpose of this study was to evaluate flow reduction the optic nerve after chronic administration endothelin-1 in primates.Endothelin-1 (three rhesus monkeys), a dosage 0.1 microgram/day, or balanced salt solution monkeys) delivered perineural region anterior via osmotically driven minipumps. Optic blood determined by means colored microspheres technique 7 days local administration. effect on analyzed analysis convariance (ANCOVA) 2 (between groups: endothelin-1, solution) x (within...
The purpose of this study was to evaluate the effects induced by chronic microapplication endothelin-l on anterior optic nerve microvasculature and determine dose-response characteristics endothelin-1 vascular bed. Daily dosages between 4.69×10−4 9.0×10−1 μg/day were delivered continually over 3 days, at a constant flow rate, perineural region 15 albino rabbits via osmotically-driven minipumps. vasomotor effect local examined using intraluminal microvascular corrosion casting technique....
A method is described for comparing the sensitivity of two hydrophones over frequency range 1-15 MHz. This technique forms basis dissemination national ultrasonic standards in U.K. this range. reference hydrophone placed an field and then device being calibrated substituted output voltages are compared. substitution utilizes a broadband produced by nonlinear propagation. Thus it possible to cover whole with single measurement on each hydrophone. The overall uncertainty intercomparison...
A beam-plotting facility has been developed to provide a reference measurement system for determining the acoustic output of medical ultrasonic equipment. It consists two coordinate-positioning systems controlled by stepping motors and minicomputer. One is used holding manipulating an transducer other hydrophone. membrane hydrophone made from polyvinylidene fluoride 9-mum thickness with active element 0.5-mm diameter most measurements. The connected amplifier digitizer, also minicomputer,...
The heating of tissues by the absorption ultrasound is an important safety consideration in use diagnostic ultrasound. This paper shows that models ultrasonic for this situation need to take account nonlinear propagation. Measurements were made temperature rise a sample tissue-mimicking gel, caused application 3.6-MHz focused beams 3 min. propagation path focus was water, mimic where fetus scanned through full bladder. effect seen changing pressure amplitude pulse, while altering pulsing...
The gain recovery time of a bound-to-continuum terahertz frequency quantum cascade laser, operating at 1.98 THz, has been measured using broadband terahertz-pump-terahertz-probe spectroscopy. is found to reduce as function current density, attaining value 18 ps the laser brought close threshold. We attribute this reduction improved coupling efficiency between injector state and upper lasing level active region aligns.
We demonstrate an electrically tunable polarizer for terahertz (THz) frequency electromagnetic waves formed from a hybrid graphene-metal metasurface. Broadband (>3 THz) polarization-dependent modulation of THz transmission is demonstrated as function the graphene conductivity various wire grid geometries, each tuned by gating using overlaid ion gel. show strong enhancement (up to ∼17 times) compared grids in range 0.2-2.5 upon introduction metallic elements. Theoretical calculations,...
Predictions of the absorption focused finite amplitude waves based on weak shock theory have been tested experimentally. The characteristics this are qualitatively different from those associated with small signal losses. Under appropriate conditions, ultrasound is determined largely by source amplitude, field geometry, and nonlinear properties medium only weakly dependent upon coefficient material. These effects seen most dramatically in sharply sound fields. To emphasize an experimental...
A pulsed photoconductive terahertz (THz) source is presented that able to radiate milliwatt (mW) level average power over a large bandwidth, by exploiting both the optical and electrical properties of sources ultrawideband connected antenna arrays. An system composed microlenses array splits laser beam into <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{N \times N}$</tex-math></inline-formula>...
Increasingly, it is recognised that diagnostic ultrasound capable of causing temperature rises sufficient to damage tissue. Predictions this heating are often based on simplified models both the in vivo conditions and relevant physical effects. Few measurements have been made verify these predictions, however, particularly for tightly focused beams employed diagnosis. Furthermore, non-linear effects acoustic field surrounding medium largely ignored calculations. To provide an alternative way...
Abstract We have refined the technique of vascular corrosion casting with methacrylate to permit reproduction physiological states tone and produce sturdy castings ocular microvasculature. The method entails careful maintenance homeostasis up moment plastic perfusion, avoidance rinsing or fixation attendant anoxia, reduction viscosity resin without impairing properties resultant polymer, addition a cross‐linking agent increase strength plastic, injection at temperature pressure. This regimen...