A5054347808- Atomic and Subatomic Physics Research
- Quantum, superfluid, helium dynamics
- Physics of Superconductivity and Magnetism
- Magnetic Field Sensors Techniques
- High-pressure geophysics and materials
- Advanced Thermodynamic Systems and Engines
- Advanced MRI Techniques and Applications
- Functional Brain Connectivity Studies
- Refrigeration and Air Conditioning Technologies
- Characterization and Applications of Magnetic Nanoparticles
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Thermodynamics and Statistical Mechanics
- EEG and Brain-Computer Interfaces
- Thermodynamic and Exergetic Analyses of Power and Cooling Systems
- Spacecraft and Cryogenic Technologies
- Iron Metabolism and Disorders
- Heat Transfer and Optimization
- Superconducting Materials and Applications
- Advanced NMR Techniques and Applications
- Advanced Memory and Neural Computing
- Transcranial Magnetic Stimulation Studies
- Non-Destructive Testing Techniques
- Phase Equilibria and Thermodynamics
- Neural dynamics and brain function
- Optical Polarization and Ellipsometry
Tristan Technologies (United States)
2003-2024
Mayo Clinic in Arizona
2007
Universität Hamburg
1989
University Medical Center Hamburg-Eppendorf
1989
University of California, San Diego
1973-1981
University of Turku
1978
The response of the orbital degrees freedom superfluid $^{3}\mathrm{He}$-$A$ to a magnetic field suddenly rotated through small angle is decaying exponential rather than an oscillatory response. Analysis and temperature dependence time constant supports Cross-Anderson orbital-viscosity theory as complemented by Pethick-Smith relaxation-time but reveals discrepancy in susceptibility-anisotropy energy near ${T}_{c}$.
Measurements of attenuation and velocity sound in the collisionless regime have been made normal extraordinary phases liquid $^{3}\mathrm{He}$ at several pressures. The has a frequency-independent component with sharp maximum just below ${T}_{c}$ BCS-like temperature dependence. velocity, frequency dependent very near ${T}_{c}$, becomes independent lower $T$ may be approaching first sound.
In the presence of a magnetic field $^{3}\mathrm{He} A$ phase is interposed between normal liquid and B$ for all pressures measured, including below that polycritical point. This can be understood on basis known nuclear paramagnetic properties if at given pressure both have same critical temperature there are plausible small differences in heat capacties two phases.
Static-nuclear-magnetization measurements show temperature-independent magnetization in the "$A$" phase of $^{3}\mathrm{He}$, temperature-dependent "$B$" and at boundary between these phases a discontinuity which approaches zero polycritical point.
We developed a 375-channel, whole-head magnetoencephalography (MEG) system (“BabyMEG”) for studying the electrophysiological development of human brain during first years life. The helmet accommodates heads up to 95% 36-month old boys in USA. unique two-layer sensor array consists of: (1) 270 magnetometers (10 mm diameter, ∼15 coil-to-coil spacing) inner layer, (2) thirty-five three-axis (20 × 20 mm) outer layer 4 cm away from layer. Additionally, there are three reference magnetometers....
Following suitable preparation the intensity of zero sound propagated through $^{3}\mathrm{He}$-$A$ in magnetic field varies periodically with time. This implies an oscillatory motion orbital axis $\stackrel{^}{l}$, which is probably driven by a residual heat flow.
In this work, we demonstrate the ability to fabricate superconducting quantum interference devices (SQUIDs) by directly writing Josephson junctions into plane of YBa2Cu3O7−δ thin films with a focused helium ion beam. This technique allows for control barrier transport properties through single parameter, dose. SQUIDs written dose 4 × 1016 ions/cm2 had metallic that exhibited nearly ideal electrical characteristics at 50 K and flux noise 20 μΦ0/Hz 10 Hz. At higher irradiation doses,...
Multichannel Transcranial Magnetic Stimulation (mTMS) arrays enable multiple sites to be stimulated simultaneously or sequentially under electronic control without moving the system's stimulation coils. Here, we build and characterize performance of a novel modular 3-axis TMS coil that can utilized as unit element in large-scale multichannel arrays. We determined basic physical characteristics x-, y- z-elements using custom 2-channel programmable stimulator prototype. mapped temporal...
Pressure waves propagate through a superleak in both $^{3}\mathrm{He}$-$A$ and $^{3}\mathrm{He}$-$B$, showing that are superfluids below ${T}_{c}$. Superfluid relative density is obtained from velocity measurements over wide pressure range above the polycritical point.
In a heat-flow experiment at zero field we have found that the phase diagram of liquid $^{3}\mathrm{He}$ below second-order transition ${T}_{c}$ divides into two regions. one heat flow is linear and enhanced by an amount predicted two-fluid model; other shows nonlinearity, history dependence, critical-velocity effects. The are separated line thermal-resistance discontinuities which extrapolates to what may be polycritical point possibly "$B$" feature melting line.
A major motivation in designing the new infant and child magnetoencephalography (MEG) system described this manuscript is premise that electrophysiological signatures (resting activity evoked responses) may serve as biomarkers of neurodevelopmental disorders, with neuronal abnormalities conditions such autism spectrum disorder (ASD) potentially detectable early development. Whole-head MEG systems are generally optimized/sized for adults. Since magnetic field produced by currents decreases a...
We developed a prototype of mobile, high-resolution, multichannel magnetoencephalography (MEG) system, called babySQUID, for assessing brain functions in newborns and infants. Unlike electroencephalography, MEG signals are not distorted by the scalp or fontanels sutures skull. Thus, activity can be measured localized with as if sensors were above an exposed brain. The babySQUID is housed moveable cart small enough to transported from one room another. To assess functions, places baby on bed...
We have fabricated HTS dc-SQUID flip-chip sensors with a large area multilayer flux transformers. Different layouts of the transformers provide variety magnetometers and planar gradiometers. For resolution /spl sim/6 fT//spl radic/Hz gradiometers about sim/30 fT/cm./spl were routinely obtained at 77 K. The noise was nearly white down to frequencies few Hz. vacuum-tight encapsulated together heater feedback coil. This makes handling more reproducible convenient. Production in small series proven.
A novel SQUID magnetometer for noninvasive measurements of hepatic (liver) iron stores is discussed. Placement the SQUID, detection coil, and magnet in dewar vacuum region significantly reduced system noise. In addition, incorporates multiple magnets coils which may allow discrimination surface skin layer from deeper (weaker signal) true liver concentration. Measurements indicate an instrumental noise level that <20 mu g/g equivalent
We have optimized the preparation of submicrometer wide symmetric 20° bicrystal Josephson junctions on basis YBa2Cu3O7−x (YBCO) films and integrated them in SQUID magnetometers gradiometers with multilayer flux transformers. The achieved reduction curvature grain boundary leads to an improvement homogeneity current flow junction due d-wave symmetry order parameter YBCO. typical normal resistance Rn above 10 Ω a IcRn product about 0.4 mV at 77.4 K. high has required extensive use low pass...
Experiments on $^{3}\mathrm{He}$-$A$ show that the orientation of orbital field $\stackrel{^}{l}$ depends sign applied magnetic field, as if there were a ferromagnetic magnetization along estimated by $|(10 \mathrm{mG})(1\ensuremath{-}\frac{T}{{T}_{c}}){\ensuremath{\chi}}_{N}|$, in agreement with recent prediction Leggett.
The melting curve of pure ${\mathrm{He}}^{3}$ has been measured in the region "$A$" and "$B$" phenomena discovered by Osheroff, Richardson, Lee. Within a 2% precision there is no effect phenomenon on slope equilibrium curve. This indicates that not related to properties solid ${\mathrm{He}}^{3}$. Also, we describe new thermal relaxation powdered-cerium-magnesium-nitrate thermometer immersed
An understanding of the maturation auditory cortex responses in typically developing infants and toddlers is needed to later identify processing abnormalities at risk for neurodevelopmental disorders. The availability infant young child magnetoencephalography (MEG) systems may now provide near optimal assessment left right hemisphere neuromagnetic populations. To assess performance a novel whole-head MEG system, cross-sectional study examined children 6- 59-months age.Blocks 1000 Hz (1st 3rd...
The use of a magnetometer or gradiometer as quantitative instrument requires the proper calibration output voltage measure magnetic field. methods used to calibrate conventional and SQUID-based detection systems depend upon configuration coils environment. Calibration procedures for number different coil designs their mathematical foundations are addressed. Many these can be applied wide variety measurement technologies.