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Optical clocks have been applied to the generation of time scales since they provide superb uncertainty and instability in recent years. This paper presents the simulations about the impact of the optical clock’s operational strategies on the performance of the generated time scale through two distinct steering algorithms. By post-processing the measured frequency difference between the 87Sr optical lattice clock and the hydrogen maser at the National Time Service Center, we realized an “optically steered” time scale TS(Sr), and the variation of the time difference TT(BIPM22)-TS(Sr) is 0.1 ns during the modified Julian date 59794–59819. [ABSTRACT FROM AUTHOR]

Heterointegration of graphene with silicon has attracted growing interest, because the resulting unique heterojunction allows for efficient collection of light generated electron–hole pairs. This study aims to understand the role of device fabrication conditions and electronic properties of chemically doped graphene on the efficiency variations and stability of graphene/silicon solar cells. We observed significant variations in the efficiency between the devices doped with metal chloride and organic molecules. A strong degradation in the hole carrier mobility by the formation of metal particles/clusters, which could act like charge puddles, accounts for the limited efficiency in the former. Molecular doping, on the other hand, offered good doping homogeneity and no mobility degradation, leading to solar cells with efficiency as high as 9.2%. Our results demonstrate that the droop in efficiency over time observed in the chemically doped devices is due to oxidation limited charge carrier separation rather than doping reversal. The prospects of molybdenum oxide (MoOx) as a multifunctional layer in improving the device stability and efficiency are also discussed based on preliminary experimental findings. [ABSTRACT FROM AUTHOR]

This study presents an optimization of the detection coil of high-Tc superconducting quantum interference device (SQUID)-based nuclear magnetic resonance (NMR) in microtesla fields for discriminating a minimum amount of liver tumor in rats by characterizing the longitudinal relaxation rate, T1-1, of tested samples. The detection coil, which was coupled to the SQUID through a flux transformer, was optimized by varying the copper wires' winding turns and diameters. When comparing the measured NMR signals, we found that the simulated NMR signal agrees with simulated signals. When discriminating liver tumors in rats, the averaged longitudinal relaxation rate was observed to be T1-1 = 3.3 s-1 for cancerous liver tissue and T1-1 = 6.6 s-1 for normal liver tissue. The results suggest that it can be used to successfully discriminate cancerous liver tissue from normal liver tissues in rats. The minimum amount of samples that can be detected is 0.2 g for liver tumor and 0.4 g for normal liver tissue in 100 μT fields. The specimen was not damaged; it can be used for other pathological analyses. The proposed method provides more possibilities for examining undersized specimens. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the field-dependent T1-relaxation and T1-contrast imaging of ferrofluids using high-Tc superconducting quantum interference device (SQUID)-detected nuclear magnetic resonance and imaging in low magnetic fields, where T1 is the spin-lattice relaxation time. It was found that the 1/T1 of ferrofluids increases when the prepolarization field increases. We attribute this to the enhanced magnetic-field gradients generated from the induced magnetization that accelerates the T1-relaxation more in a high strength of fields in comparison to a low strength of fields. Using phantoms with different relaxation times, the T1-contrast images are demonstrated in low magnetic fields, which can be promising for discriminating tumors. [ABSTRACT FROM AUTHOR]

Shortening spin-lattice relaxation rates (1/T1) or spin-spin relaxation rates (1/T2) is the purpose of magnetic resonance imaging contrast agents. In this work, an ultralow field nuclear magnetic resonance spectrometer and imager are set up to characterize the spin relaxation rates of Fe3O4 superparamagnetic iron oxide (SPIO) for image contrast. It was found that both 1/T1 and 1/T2 increase linearly when the magnetic susceptibility χ of SPIO increases by increasing the concentration of SPIO dispersed in water. In an applied field, magnetic moments of SPIO generate microscopic field gradients that weaken the field homogeneity, in turn de-phasing the proton's nuclear spin and enhancing the relaxation rates. A T1-contrast image is demonstrated, using SPIO as the contrast agent and high-Tc superconducting quantum interference devices as the detector. T1-contrast imaging in microtesla fields might provide a potential modality for discriminating cancer. [ABSTRACT FROM AUTHOR]

In this study, we present a compact and sensitive SQUID-detected nuclear magnetic resonance spectrometer and imager (NMR/MRI) using flux coupling in microtesla fields. The pre-polarization coil, measuring coil, pulsed coil, and gradient coils were set up inside a three-layer aluminum box while the SQUID-detector was shielded with a high-Tc superconducting vessel. A compensation field was applied to improve the field homogeneity in magnetically unshielded environments. The spin precession of protons was inductively coupled to the SQUID magnetometer via a resonant flux transformer. We obtained a signal-to-noise ratio of 120 in one measurement, a spectral resolution better than 1 Hz, and a spatial resolution of 1.3 mm in the images. [ABSTRACT FROM AUTHOR]

The dislocations and the strength of a nickel bicrystal are investigated in present study. There are three kinds of crystalline orientations of the nickel bicrystal, namely (100), (110), and (111). Misfit dislocations are presented on the interface between two nickel grains when a compression process is utilized on the bicrystal. The misfit dislocations on a Ni(100) interface form a square-latticed network and those on a Ni(111) form a triangle-latticed network. When a large twist angle is applied to the Ni bicrystal, the square- and triangle-latticed unit of the misfit dislocation networks will shrink or even disappear. Thus, a plane defects distribute over the interface. If the bicrystal is compressed further, dislocations within each grain are developed from the defects on the interface between grains. The configuration of the dislocations within grains is more regular when the applied twist angle is smaller. A Ni(111) bicrystal owns the largest amount of maximal stress no matter what the twist angle is. Those of a Ni(110) bicrystal is the second and of a Ni(100) bicrystal is the smallest. [ABSTRACT FROM AUTHOR]

Superconducting quantum interference device (SQUID), which is a very sensitive magnetic sensor, has been widely used to detect the ultra-small magnetic signals in many different territories, especially in the biomagnetic measurement. In this study, a 128-channel SQUID first-order axial gradiometer system for whole-head magnetoencephalography (MEG) measurements was setup to characterize the auditory evoked magnetic fields (AEFs). A 500 Hz monaural pure tone persisting 425 ms with the sound pressure level of 80 dB was randomly applied to the left ear of subject with the inter-stimulus interval of 1.5 ∼ 2.8 s to prevent fatigue of nerves. We demonstrated the characteristic waveforms of AEFs can be accurately recorded and analyzed. Using source localization processes, the origins of AEFs were successfully calculated to be at the auditory cortices which are brain areas known for responsive to sound stimulus. A phantom experiment also proved the good localization accuracy of the established MEG system and measurement procedures. The validated performance of the SQUID system suggests that this technique can also be employed in other brain research. [ABSTRACT FROM AUTHOR]

A nuclear magnetic resonance and imaging system was constructed to study spin-lattice relaxation time T1, spin-spin relaxation time T2, and effective relaxation time T2* of gadolinium (Gd) chelates using a high-Tc superconducting quantum interference device in microtesla magnetic fields. In the presence of the magnetic contrast T2* is related to T2 by the relation: 1/T2*=1/T2+γΔB+ΓGd-chelates, where γ=42.58 kHz/mT and γΔB is the relaxation rate due to the inhomogeneity field ΔB in measuring coil at the sample position and ΓGd-chelates is the intrinsic relaxation rate of Gd chelates. It is found that T1, T2, and 1/ΓGd-chelates decay exponentially as the concentration (or magnetic susceptibility) of Gd chelates increases. The Gd chelates cause a diffusive motion of nuclear spins and hence enhance the relaxation rates. Enhanced image contrast has been demonstrated in a water phantom with Gd chelates in microtesla magnetic fields. [ABSTRACT FROM AUTHOR]

The dual first-order planar gradiometers of high transition temperature (high-Tc) superconducting quantum interference devices (SQUIDs) were designed and fabricated on a 10×10 mm2 SrTiO3 bicrystal substrate. Each gradiometer consists of four bare SQUIDs which are connected to two symmetric pickup loops. Any two of the SQUIDs can be connected in series to obtain better performance. In this study, by selecting the coupling direction of SQUID, a balance resolution of 0.08% was achieved. And, a second-order electronic planar gradiometer was composed of these two first-order gradiometers. Experimental data showed that the noise performance of the second-order electronic planar gradiometer composed of two planar first-order gradiometers can reach 15 μ[uppercase_phi_synonym]0/Hz1/2 at 1 kHz in an unshielded environment, which is comparable to the noise level of a magnetometer in a shielded environment. [ABSTRACT FROM AUTHOR]

A high-temperature superconducting (HTS) radio-frequency (rf) coil has been proposed as a promising tool in the investigation of tissue microscopy with high resolution due to its low-resistant characteristic for magnetic resonance (MR) probe design. In this work, a 200 mm in diameter Bi2Sr2Ca2Cu3Ox (Bi-2223) tape HTS rf coil was built; and a signal-to-noise ratio (SNR) with the HTS tape coil having 2.22 folds higher than that of a home-made copper coil for a phantom MR study was demonstrated. Testing results were in agreement with predicted ones, and the difference between the predicted SNR gains and measured SNR gains is 0.9%. Using in vivo imaging, a SNR with the HTS tape coil having 1.95 folds higher than that of a home-made copper coil for a human hand MR study was presented. The HTS coil is expected to generate a higher SNR gain after optimization. Further applications of a functional magnetic resonance imaging system are under investigation to test the applicability of this HTS coil system in a 3T system. [ABSTRACT FROM AUTHOR]

Via immunomagnetic reduction assay, biomolecules can be quantitatively detected with aid of biofunctionalized magnetic nanoparticles, which are used as labeling markers for specific biomolecules. To achieve ultra-high sensitivity in detecting biomolecules, superconducting quantum interference device (SQUID) is a promising candidate to act as a sensor to the magnetic signal related to the concentration of detected biomolecules. In the past, we developed a single channel SQUID-based magnetosusceptometry. In order to increase the detection through-put, multichannel SQUID-based magnetosusceptometry is developed. In this work, the design and working principle of four-channel SQUID-based magnetosusceptometry are introduced. Using utilizing scanning technology, four samples can be simultaneously logged into the SQUID-based magnetosusceptometry. Notably, only single SQUID magnetometer is used in the magnetosusceptometry. The precision and sensitivity in detecting biomolecules using the four-channel SQUID-based magnetosusceptometry are investigated. [ABSTRACT FROM AUTHOR]

In this work, we present a design that improves signals produced by nuclear magnetic resonance (NMR) and magnetic resonance imaging by using optical pumping and a high-Tc superconducting quantum interference device (SQUID) magnetometer. In our design for a NMR detection system, a pickup coil is coupled to the spin procession of a 3He nucleus; the input coil is coupled to a high-Tc SQUID magnetometer; and the capacitor is connected in series to form a tank circuit resonating at the Larmor frequency of the 3He nucleus in the measuring field. A signal-to-noise ratio gain of 2.67 over a conventional Faraday detection coil was obtained with the high-Tc SQUID detection system in a measuring magnetic field equaling 0.1128 mT, at which the central frequency was 3.66 kHz for 3He nucleus. The improvement in the NMR signal for large-size, hyperpolarized 3He coupled to a high-Tc SQUID-based spectrometer in low magnetic fields at room temperature is significant compared to that without flux coupling. This result may be of interest given its potential for use in a low field imager. [ABSTRACT FROM AUTHOR]

In this paper, an overview of the current status of high-Tc superconducting quantum interference devices (SQUIDs), from device engineering to biomagnetic applications, is given. The authors offer a description of the current status of SQUID sensors, challenges encountered, and the solution of fabricating SQUID sensors with low flux noises. The current challenge that we face is to fabricate high-Tc SQUIDs that are not only more reproducible than the current technology but also capable of providing a high IcRn product and fabricating SQUID with high yield. Improvement of flux noises and fabrication yield in the integrated multichoices directly coupled SQUID magnetometer or gradiometer with series SQUID array are presented. High-Tc SQUID magnetometers exhibiting magnetic field sensitivity of ∼30–50 fT/Hz1/2 or better at 100 Hz was demonstrated by incorporating serial SQUID into the pickup loop of the magnetometers. New technologies currently being developed and applications for high-Tc SQUIDs are addressed. [ABSTRACT FROM AUTHOR]

We report on the fabrication of organic field-effect transistors (OFETs) using perylene single crystal as the active material and their electrical characteristics. Perylene single crystals were directly grown from perylene powder in a furnace using a relatively short growth time of 1–3 h. The crystalline structure of the perylene single crystals was characterized by means of a single-crystal x-ray diffractometer. In order to place the perylene single crystal onto the Au electrodes of the field-effect transistor, a polymethlymethacrylate thin layer was spin-coated on top of the crystal surface. The OFETs fabricated using the perylene single crystal showed a typical p-type operating mode. The field-effect mobility of the perylene crystal based OFETs was measured to be ∼9.62×10-4 cm2/V s at room temperature. The anisotropy of the mobility implying the existence of different mobilities when applying currents in different directions was observed for the OFETs, and the existence of traps in the perylene crystal was found through the measurements of the temperature-dependent mobility at various operating drain voltages. [ABSTRACT FROM AUTHOR]

The parameters to optimize the measurement of longitudinal relaxation time detection using a high-Tc superconductive quantum interference device magnetometer are investigated. These parameters include the prepolarization field, Bp, the prepolarization time, TBp, and the delay time, Td, to turn on pulses after turning off the prepolarization field. Furthermore, the decreasing of magnetization with the increasing Td of the applied pulse was analyzed to determine the longitudinal relaxation time. We estimated the longitudinal relaxation time to be 2.11±0.04 s and 2.29±0.04 s, respectively, for water determined from nuclear magnetic resonance signals as a function of TBp and Td at 24 °C in a measuring field of 95 μT. The data are consistent with the derived longitudinal relaxation time of water measured from the increase of magnetization with the duration of the polarizing field. [ABSTRACT FROM AUTHOR]

We characterized the current-voltage, voltage-flux, and the field sensitivity of integrated high-Tc series superconducting quantum interference device (SQUID) magnetometers and gradiometers. The series two-SQUID magnetometers shows field sensitivities of ∼30–40 fT/Hz1/2 at 1 kHz and ∼80–100 fT/Hz1/2 at 1 Hz over that of a one-SQUID magnetometer in shielded environment. The field sensitivity of a series two-SQUID gradiometers is ∼60 fT/Hz1/2 cm, while the one-SQUID gradiometer shows a gradient sensitivity of ∼80–150 fT/Hz1/2 cm at 1 kHz in an unshielded laboratory environment. The series two-SQUID magnetometers or gradiometers show a significant improvement in flux noises over that of one-SQUID magnetometers or gradiometers. [ABSTRACT FROM AUTHOR]

In this work, we studied the engineering of high-transition-temperature superconductor Josephson junctions and superconducting quantum interference device (SQUID) by using step-edge or the bicrystal grain-boundary technologies. Serial Josephson junctions and bare SQUID array reveal high quality device characteristics. A high-Tc SQUID magnetometer exhibiting magnetic field sensitivity of 33 fT/Hz1/2 in the white regime and 80 fT/Hz1/2 at 1 Hz was demonstrated by incorporating the flux dams and serial SQUID into the pickup loop of magnetometer. Furthermore, we demonstrate the opening of the flux dams by applying an external magnetic field to induce a current higher than the critical current of the serial flux dams. We show that the serial flux dams effectively suppress the low frequency 1/f-like noises. [ABSTRACT FROM AUTHOR]

Here, a report on diffusion tensor imaging (DTI) using a 125.3 MHz high-temperature superconducting (HTS) surface resonator for magnetic resonance imaging (MRI) is presented. A 40 mm in diameter Bi2Sr2Ca2Cu3Ox (Bi-2223) tape surface resonator was built. Using a HTS surface resonator at 77 K than a similar copper surface resonator at 300 K, the capacity to save the accuracy of DTI in a reduced scan time (11 min) was demonstrated. The standard deviation of deviation angles of DTI fiber tracking was also improved by 2.5 gains. The use of HTS surface resonator may improve the reliability of fiber tracking experiments. [ABSTRACT FROM AUTHOR]

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Low-temperature atomic layer deposition (ALD) was employed to deposit Al2O3 as a gate dielectric in amorphous In-Ga-Zn-O thin-film transistors fabricated at temperatures below 120 °C. The devices exhibited a negligible threshold voltage shift (ΔVT) during negative bias stress, but a more pronounced ΔVT under positive bias stress with a characteristic turnaround behavior from a positive ΔVT to a negative ΔVT. This abnormal positive bias instability is explained using a two-process model, including both electron trapping and hydrogen release and migration. Electron trapping induces the initial positive ΔVT, which can be fitted using the stretched exponential function. The breakage of residual AlO-H bonds in low-temperature ALD Al2O3 is triggered by the energetic channel electrons. The hydrogen atoms then diffuse toward the In-Ga-Zn-O channel and induce the negative ΔVT through electron doping with power-law time dependence. A rapid partial recovery of the negative ΔVT after stress is also observed during relaxation. [ABSTRACT FROM AUTHOR]

In this paper, we report on the active filtering and amplification of a single mode from an optical femtosecond laser comb with mode spacing of 250MHz by optical injection of two external-cavity diode lasers operating in cascade to build a narrow linewidth laser for laser cooling of the strontium atoms in an optical lattice clock. Despite the low injection of individual comb mode of approximately 50 nW, a single comb line at 689 nm could be filtered and amplified to reach as high as 10 mW with 37 dB side mode suppression and a linewidth of 240 Hz. This method could be applied over a broad spectral band to build narrow linewidth lasers for various applications. [ABSTRACT FROM AUTHOR]

Ferrite composites of nominal composition Ba3Co2+xIrxFe24-2xO41 were studied in order to achieve low magnetic and dielectric losses and equivalent permittivity and permeability over a frequency range of 0.3-1 GHz. Crystallographic structure was characterized by X-ray diffraction, which revealed a Z-type phase accompanied by increasing amounts of Y-type phase as the iridium amount was increased. The measured microwave dielectric and magnetic properties showed that the loss tan δε and loss tan δμ decreased by 80% and 90% at 0.8 GHz with the addition of iridium of x = 0.12 and 0.15, respectively. An effective medium approximation was adopted to analyze the composite ferrites having mixed phase structures. Moreover, adding Bi2O3 enabled equivalent values of real permittivity and real permeability over the studied frequency range. The resultant data give rise to low loss factors, i.e., tan δε/έ = 0.008 and tan δμ/μ = 0.037 at 0.8 GHz, while characteristic impedance was the same as that of free space. [ABSTRACT FROM AUTHOR]

We measure the transverse velocity distribution in a thermal Sr atomic beam precisely by velocity-selective saturated fluorescence spectroscopy. The use of an ultrastable laser system and the narrow intercombination transition line of Sr atoms mean that the resolution of the measured velocity can reach 0.13 m/s, corresponding to 90 μK in energy units. The experimental results are in very good agreement with the results of theoretical calculations. Based on the spectroscopic techniques used here, the absolute frequency of the intercombination transition of 88Sr is measured using an optical-frequency comb generator referenced to the SI second through an H maser, and is given as 434 829 121 318(10) kHz. [ABSTRACT FROM AUTHOR]

We report the characteristics of graphene-based terahertz (THz) photodetector based on noise thermometry technique by measuring its noise power at frequency from 4 to 6 GHz. Hot electron system in graphene microbridge is generated after THz photon pumping and creates extra noise power. The equivalent noise temperature and electron temperature increase rapidly in low THz pumping regime and saturate gradually in high THz power regime which is attributed to a faster energy relaxation process involved by stronger electron-phonon interaction. Based on this detector, a conversion efficiency around 0.15 from THz power to noise power in 4–6 GHz span has been achieved. [ABSTRACT FROM AUTHOR]

This study investigates the peri-tumor signal abnormalities of a spontaneous brain tumor in a rat by using a 4 cm high-temperature superconducting (HTS) surface resonator. Fractional anisotropy (FA) values derived from diffusion tensor imaging reflect the interstitial characteristic of the peri-lesional tissues of brain tumors. Low FA indicates interstitial tumor infiltration and tissue injury, while high FA indicates better tissue integrity. Better delineation of tissue contents obtained by the HTS surface resonator at 77 K may facilitate therapeutic strategy and improve clinical outcomes. [ABSTRACT FROM AUTHOR]

In this work, the spin-spin relaxation of protons in ferrofluids is characterized using a high-Tc SQUID-based detector in microtesla fields. We found that spin-spin relaxation rate is enhanced in the presence of superparamagnetic nanoparticles. The enhanced relaxation rates are attributed to the microscopic field gradients from magnetic nanoparticles that dephase protons' spins nearby. The relaxation rates decrease when temperatures increase. Additionally, the alternating current magnetic susceptibility was inversely proportional to temperature. Those characteristics explained the enhanced Brownian motion of nanoparticles at high temperatures. Characterizing the relaxation will be helpful for assaying bio-molecules and magnetic resonance imaging in microtesla fields. [ABSTRACT FROM AUTHOR]

We investigated the relaxation of protons in magnetic fluids using a high-Tc SQUID magnetometer. It was found that the longitudinal relaxation rate, 1/T1, is slower than the transverse relaxation rate, 1/T2, for ferrofluids in the same field. This is due to the fact that the 1/T1 process involves returning the magnetization to the z-direction, which automatically involves the loss of magnetization in the x-y plane governed by the 1/T2 process. Additionally, 1/T1 and 1/T2 at high temperatures are slower than the corresponding relaxation rates at low temperatures, which is due to the enhanced Brownian motion of nanoparticles at high temperatures. [ABSTRACT FROM AUTHOR]

This letter reports on the implementation of multilayer graphene (MLG) as a current spreading electrode in GaN-based blue light-emitting diodes. We demonstrate two facile strategies to maneuver the electrical coupling between p-GaN layer and MLG. Using a work-function-tuned MLG and a thin gold (Au) metal interlayer, the current spreading and thus the device forward voltage are considerably improved. We attribute these improvements to the diminution in work function difference between p-GaN and MLG, the decrease of specific contact resistance, and the enhancement in the conductivity of MLG film as a result of doping. In addition, rapid thermal annealing at elevated temperature is found to provide additional pathway for enhanced carrier injection. [ABSTRACT FROM AUTHOR]

In this paper, an instrumentation of the Earth's field nuclear magnetic resonance (EFNMR) inside a laboratory is presented. A lock-in analysis (LIA) technique was proposed to enhance the signal-to-noise ratio (SNR). A SNR of 137.8 was achieved in a single measurement for 9 ml tap water, and the LIA technique significantly enhanced the SNR to 188 after a 10-average in a noisy laboratory environment. The proton-phosphorus coupling in trimethyl phosphate ((CH3O)3PO) with J-coupling J[H,F]=(10.99±0.013) Hz has been demonstrated. The LIA technique improves the SNR, and a 2.6-fold improvement in SNR over that of the frequency-adjusted averaging is achieved. To reduce the noise in EFNMR, it was suggested that the LIA technique and the first order gradient shim be used to achieve a subhertz linewidth. [ABSTRACT FROM AUTHOR]

It has been shown that focused ultrasound (FUS) is capable of noninvasive and reversible disruption of the blood-brain barrier (BBB) at target regions when applied in the presence of ultrasound contrast agent (UCA). The purpose of this study was to investigate the effects of UCA dose on the reversibility of BBB disruption induced by the same acoustical power of FUS. Sonications were applied at an ultrasound frequency of 1 MHz with a 5% duty cycle and a repetition frequency of 1 Hz. The brains of 66 male Sprague-Dawley rats were subjected to sonications with three doses of UCA. BBB integrity was evaluated via femoral vein injection of Evans Blue (EB) while the rats were anesthetized. The relationship between UCA dose and the region of EB extravasation was evaluated at an acoustic power of 1.43 W. The BBB disruption, as indexed by the amount of EB extravasation, was the largest immediately after the sonications. The quantity of Evans blue extravasation decreased as a function of time at various UCA doses. This study demonstrates that the appropriate dose of UCA not only enhance the BBB opening but also effectively aid in controlling the duration of BBB disruption. [ABSTRACT FROM AUTHOR]

The effect of the combination of triangular prisms and cones as air-void structures arrays on the enhancement of light extraction efficiency of InGaN light-emitting diodes (LEDs) is investigated. The arrays embedded at the sapphire/GaN interface act as light reflectors and refractors, and thereby improve the light output power due to the redirection of light into escape cones on both the front and back sides of the LED. Enhancement in radiometric power as high as 74% and far-field angle as low as 125° is realized with a compact arrangement of arrays compared with that of a conventional LED. [ABSTRACT FROM AUTHOR]

The characterization of cancerous livers in rats using nuclear magnetic resonance and magnetic resonance imaging (NMR/MRI) based on high-Tc superconducting quantum interference devices (SQUIDs) is presented. The T1-1 were observed to be 6.5±0.5 s-1 for controlled livers and 2.85±0.2 s-1 for cancerous livers, which indicate that the T1 can be used to distinguish the cancerous tissues from controlled liver tissues. The intensity ratio for tap water, cancerous tissue, and controlled tissue, respectively, is 1:1.15:0.56 at TBp=1 s. The SQUID-detected NMR/MRI exhibits potential applications in research and clinics. [ABSTRACT FROM AUTHOR]

We report our experimental studies of interplays between four-wave mixing (FWM) processes in multidressed two- and three-level atomic systems. The Autler–Townes splitting of the FWM signal within the electromagnetically induced transparency window has been experimentally observed. Under the same experimental conditions in different energy-level systems, the dressing effects strongly depend on the dipole moments of the transitions, which can provide an easy and qualitative way to determine the orders of magnitude of the effective dipole moments for different transitions by comparing the FWM suppressing effects. [ABSTRACT FROM AUTHOR]

We investigated spatial light emission from a periodic inverted polygonal deflector, which included six {10-1-1} facets and six {11-2-2} facets embedded in an InGaN/GaN light emitting diode by using confocal scanning electroluminescence microscopy. We found a noticeable crown shape with the contrast of luminescence intensity and wavelength observed on these facets mainly due to the variation of growth rate for the InGaN quantum wells. In addition, a very low intensity and blueshifted emission wavelength on the {11-2-2} facets indicated the deficiency of indium incorporation and/or much thinner well thickness as compared to that of the {10-1-1} facets. [ABSTRACT FROM AUTHOR]

We characterize the balance and noise properties of directly coupled high-Tc superconducting quantum interference device (SQUID) gradiometers with a series array. The gradiometer consisted of symmetrical pickup loops, in which a series of SQUID was symmetrically configured and directly coupled to pickup loops. We characterize the balance resolution B from the following formula: B=Aeff,uniform field/Aeff,gradient field, where Aeff,uniform field and Aeff,gradient field are the parasitic effective area and the effective area of the gradiometer, respectively. We obtained B=1.25×10-2 which was comparable to the typical balance resolution of ∼10-2 for a gradiometer fabricated onto the 10×10 mm2 substrate. This discrepancy was probably due to the many superconducting pads inside the pickup loops which deteriorated the uniformity of applied uniform magnetic fields. The gradient field sensitivity of ∼40 fT/Hz1/2 cm at 1 kHz for two-SQUID gradiometers was demonstrated in a magnetically unshielded environment, which was comparable to the best gradient sensitivity of 30 fT/Hz1/2 cm, with gradiometric flip-chip flux transformer with a length of 24 mm and a base line of 10 mm in shielded environment. [ABSTRACT FROM AUTHOR]

This letter proposes a concept of InGaN/GaN light emitting diodes with periodic deflector embedded structure (PDE-LED). The PDE-LED was grown on a sapphire substrate with SiO2 hexagonal patterned mask using selective metal-organic chemical deposition. More than 200 artificial inverted polygonal pyramids (AIPPs), which included six R planes and six N planes deflectors with inclined angles of 57° and 61°, respectively, were formed and periodically distributed on masked area. These AIPP deflectors revealed a superior capability of enhancing light extraction efficiency mainly because the AIPP deflector structure could provide multiple chances for photons to escape from the LED sidewall as opposed to a rectangular conventional LED. Thus, the light output power of the PDE-LED was 1.51 times higher than that of a conventional LED at an injection current of 20 mA, while forward bias voltage and leakage current were compatible to those of conventional LEDs. [ABSTRACT FROM AUTHOR]

In contrast to the previous high-TC radio frequency (rf) superconducting quantum interference device (SQUID) magnetometer, in which the rf SQUID is placed face to face with the substrate resonator, a simple integrated washer-type rf SQUID magnetometer based on a single SrTiO3 bicrystal substrate resonator is designed and fabricated in this work. The magnetometer combines the rf SQUID, flux focusing, and resonator into a single chip. This integrated washer-type rf SQUID magnetometer offers a superior advantage in integrating the device to a scanning SQUID detection system in which the distance between the sample and SQUID can be minimized. [ABSTRACT FROM AUTHOR]

Absorption spectra of trilayer rhombohedral graphite are studied with the tight-binding model. The interlayer interactions cause a tiny energy gap and band-edge states in electronic structures. The band-edge states exhibit logarithmic divergences and discontinuities in the density of states. The frequencies of the absorption peaks correspond to the vertical transition energies of the band-edge states. Optical spectra of trilayer simple hexagonal and orthorhombic graphites are also investigated. The stacking effects on the density of states and absorption spectra are presented and discussed in detail. [ABSTRACT FROM AUTHOR]

In the title compounds the oxygen voids have a significant influence over the transport properties, compared with the parent stoichiometric compounds (Sr2FeMoO6 and Sr2CoMoO6) where the oxygen defects have little impact on the crystallographic and magnetic properties. For Sr2FeMoO6-d and Sr2Fe0.95Co0.05MoO6-d, the oxygen voids simply decrease the magnetoresistance (MR) without altering the contours, and for x>=0.1 at the expense of the decreased low field MR, the oxygen voids enhance MR at high applied field, which is 6%–8% larger than the parent compounds for 0.2≤=x≤=0.7. Remarkably enough, the antiferromagnetic Sr2Fe0.1Co0.9MoO6-d exhibits record negative magnetoresistance ratio MR=((R(H,T)-R(0,T))/R(0,T))×100% as high as 99% [ABSTRACT FROM AUTHOR]

In the title compounds the oxygen voids have a significant influence over the transport properties, compared with the parent stoichiometric compounds (Sr2FeMoO6 and Sr2CoMoO6) where the oxygen defects have little impact on the crystallographic and magnetic properties. For Sr2FeMoO6-d and Sr2Fe0.95Co0.05MoO6-d, the oxygen voids simply decrease the magnetoresistance (MR) without altering the contours, and for x>=0.1 at the expense of the decreased low field MR, the oxygen voids enhance MR at high applied field, which is 6%–8% larger than the parent compounds for 0.2≤=x≤=0.7. Remarkably enough, the antiferromagnetic Sr2Fe0.1Co0.9MoO6-d exhibits record negative magnetoresistance ratio MR=((R(H,T)-R(0,T))/R(0,T))×100% as high as 99% [ABSTRACT FROM AUTHOR]

We applied prepolarization field and high-Tc superconducting quantum interference device (SQUID) detector to enhance nuclear magnetic resonance signal in a microtesla magnetic field. The minimum measuring magnetic field is 8.9 μT at which the proton resonance frequency is 380 Hz. The specificity instrumentation and the difficulty of using a high-Tc SQUID with prepolarization field were investigated. We applied gradient field to perform one-dimensional proton imaging in a microtesla magnetic field. Additionally, low field high-Tc SQUID-based NMR systems are promising in biomagnetic research due to its use, for example, in imaging with hyperpolarized noble gas. [ABSTRACT FROM AUTHOR]