Near-infrared spectroscopy (NIRS) was originally designed for clinical monitoring of tissue oxygenation, and it has also been developed into a useful tool in neuroimaging studies, with the so-called ...functional NIRS (fNIRS). With NIRS, cerebral activation is detected by measuring the cerebral hemoglobin (Hb), where however, the precise correlation between NIRS signal and neural activity remains to be fully understood. This can in part be attributed to the situation that NIRS signals are inherently subject to contamination by signals arising from extracerebral tissue. In recent years, several approaches have been investigated to distinguish between NIRS signals originating in cerebral tissue and signals originating in extracerebral tissue. Selective measurements of cerebral Hb will enable a further evolution of fNIRS. This chapter is divided into six sections: first a summary of the basic theory of NIRS, NIRS signals arising in the activated areas, correlations between NIRS signals and fMRI signals, correlations between NIRS signals and neural activities, and the influence of a variety of extracerebral tissue on NIRS signals and approaches to this issue are reviewed. Finally, future prospects of fNIRS are described.
Structural and electrical properties of a Ge(111) layer directly grown on a Si(111) substrate are studied. Via optimized two-step growth manner, we form a high-quality relaxed Ge layer, where ...strain-relieving dislocations are confined close to a Ge/Si interface. Consequently, a density of holes, which unintentionally come from crystal defects, is highly suppressed below 4×1016cm−3, which leads to significantly high hole Hall mobility exceeding 1500cm2/Vs at room temperature. By layer transfer of the grown Ge layer, we also fabricate a Ge(111)-on-Insulator, which is a promising template for high-performance Ge-based electronic and photonic devices.
•A high-quality Ge layer is epitaxially grown on a Si(111) by two-step growth manner.•Growth conditions, such as growth temperatures, are optimized.•Very high hole mobility is obtained from Ge(111) grown on Si(111).•High-quality thin Ge-on-Insulator with (111) orientation is obtained.
We investigate the average location of magnetic reconnection on the Earth's dayside magnetopause, based on spatial distributions of northward and southward reconnection jets observed by the THEMIS ...spacecraft at the near‐noon (10–14 magnetic local time) magnetopause. A total of 711 reconnection jets were identified by applying the Walén relation, the tangential stress balance relation to be satisfied for a reconnected (rotational discontinuity) magnetopause, to magnetopause crossings identified from 10 years of THEMIS observations. The directions and positions of jets indicate that during southward interplanetary magnetic field (IMF) conditions, the dayside X‐line location shifts from the subsolar point toward the winter hemisphere by about 6 Earth radii under the largest tilt of the geomagnetic dipole axis. The X‐line location also shifts northward (southward) by at most 2.5 Earth radii when the IMF is predominantly radial and its x component is positive (negative). The dipole tilt effect on the shift of the X‐line location becomes smaller for higher solar wind Alfvén Mach numbers. The dipole tilt effect being larger than the IMF Bx effect suggests that the X‐line location has a seasonal dependence. Since models and theory show that the reconnection rate away from the subsolar magnetopause is lower than that at the subsolar magnetopause, the dipole tilt dependence of the X‐line location suggests that the efficiency of solar wind energy transfer into the magnetosphere may decrease under larger dipole tilt; this may partially account for seasonal variations of geomagnetic activity, which is known to decrease under larger dipole tilts.
Plain Language Summary
The near‐Earth space environment is strongly affected by solar wind energy that comes from the Sun. Entry of the energy into the near‐Earth space occurs as a result of merging the magnetic fields of the Sun and the Earth on the dayside of the Earth through a physical process known as magnetic reconnection. The location of magnetic reconnection is expected to control the efficiency of energy influx; however, the average location is not well understood. In this study, the average location of the reconnection process is statistically investigated from 10 years of THEMIS spacecraft observations. We revealed how much the reconnection position shifts depending on the season. In addition, the average reconnection location is affected by the magnitude of the Sun's magnetic fields along the Sun‐Earth line just outside of the near‐Earth space. We also discuss a possibility that the reconnection location changes the amount of the Sun's energy flux flowing into the near‐Earth space.
Key Points
The X‐line location on the dayside magnetopause is estimated from observed locations of northward and southward reconnection jets
The X‐line shifts poleward from the subsolar point under tilted dipole or finite IMF Bx when IMF By is small and Bz is negative
The dipole tilt effect is larger than that of IMF Bx, suggesting that the X‐line location has a seasonal dependence
Abstract
Electron spins confined in quantum dots are an attractive system to realize high-fidelity qubits owing to their long coherence time. With the prolonged spin coherence time, however, the ...control fidelity can be limited by systematic errors rather than decoherence, making characterization and suppression of their influence crucial for further improvement. Here we report that the control fidelity of Si/SiGe spin qubits can be limited by the microwave-induced frequency shift of electric dipole spin resonance and it can be improved by optimization of control pulses. As we increase the control microwave amplitude, we observe a shift of the qubit resonance frequency, in addition to the increasing Rabi frequency. We reveal that this limits control fidelity with a conventional amplitude-modulated microwave pulse below 99.8%. In order to achieve a gate fidelity >99.9%, we introduce a quadrature control method, and validate this approach experimentally by randomized benchmarking. Our finding facilitates realization of an ultra-high-fidelity qubit with electron spins in quantum dots.
To establish rapid and stable Sphagnum growth, capitulum culture of a selected strain of S. palustre was carried out using a floating culture method. Four planting treatments were tested at mountain ...and urban sites in Kumamoto Prefecture on Kyushu Island, south-west Japan. Capitula were planted in colonies of different sizes on 30 cm square floating rafts, but with strict control of the number (75–77) of capitula per raft. The initial cover of live green Sphagnum ranged from 15 to 20 %. Growth of the colonies was followed throughout the growing season (April to November) of 2008. After three months, green coverage rates reached 40–50 % in all planting treatments. At the end of the growing season, the highest Sphagnum cover (almost 90 % at the urban site) was recorded in the planting treatment with eleven re-introduced colonies of seven capitula (‘11×7cap’), while the highest capitulum number and biomass (dry weight) gain occurred in the ‘4×19cap’ planting treatment. Average stem elongation ranged from 5 cm to 7 cm in the ‘77×1cap’ and ‘4×19cap’planting treatments, respectively, indicating that the larger sized colony grew longer stems. However, contrary to expectation, the ‘4×19cap’planting treatment - which had the largest colony size - did not deliver the highest number of newly formed side shoots.
We examined the laser-induced discharge (LID) in medium-vacuum air. The time-averaged discharge energy W d of a primary discharge prior to an arc discharge was affected by the number of initial ...electrons. The initial electrons were produced by the laser irradiation of electrodes. The number of electrons was proportional to the energy of the laser, L p . Thus, it was adjusted by changing L p . Although the experimental conditions were rather limited, i.e., air at 200-Pa pressure, we demonstrated a simple relationship, W d ∝ V s 2 × L p s , where Vs is the applied voltage and s is an exponent determined empirically. Note that the number of initial electrons is a function of L p . Such a simple relationship for the behavior of LID that incorporates W d is proposed for the first time in this paper.
We demonstrate the (111)-oriented Ge-on-Insulator (GOI) formed by Ge epitaxial growth on a Si(111) and the layer transfer technique. The two-step growth manner, involving low-temperature growth of a ...thin Ge layer and subsequent high-temperature growth of a thick Ge layer, enables us to obtain high-quality tensile-strained epitaxial Ge(111) on Si(111). It is found that the strain amount straongly depends on the growth temperatures and we find an optimal growth temperature. We also developed a chemical mechanical polishing (CMP) method modified for Ge, offering the ultra-smooth Ge(111) surface. The polished epitaxial Ge is bonded on a SiO2/Si, followed by the selective etching of Si and the final CMP of Ge. As a result, we achieve the high-quality 200-nm-thick tensile-strained Ge(111)-OI with an ultra-smooth surface, on which, furthermore, we demonstrate the growth of an epitaxial metallic silicide for the metal source/drain in spintronic devices as well as advanced Ge channel devices.
•A high-quality Ge layer is epitaxially grown on a Si(111) by two-step growth manner.•Ultra-smooth Ge surface is obtained with modified chemical mechanical polishing.•Epitaxially grown Ge is transferred onto a SiO2/Si.•High-quality tensile-strained Ge-on-Insulator with (111) orientation is obtained.
Phosphorus doping of BaSi2 epitaxial films by means of P implantation and rapid thermal annealing has been investigated from a structural viewpoint. Raman spectroscopy and X-ray diffraction show that ...the crystal structure of BaSi2 is destroyed, at least partially, by P implantation. This irradiation damage increases with increasing the P dose from 1.0×1013 to 1.0×1015cm−2 and can be removed by rapid thermal annealing for 30s at 600–800°C, as evidenced by the variation of the full width at half-maximum of the A1-mode Raman peak. In addition to the recovery of the irradiation damage, the metastable trigonal phase of BaSi2, which is metallic and undesirable to exist in the semiconductor film, is found to form by annealing at 800°C after P implantation of 1.0×1015cm−2. Furthermore, by annealing at 600 and 700°C, P atoms have been revealed to segregate into the surface and BaSi2/Si interface while the P segregation is suppressed at 800°C, according to the depth profile of P determined by secondary ion mass spectroscopy. Thus, we have obtained a useful guide of the P implantation dose and annealing temperature to effectively dope P atoms into the semiconducting BaSi2 film.
► P doping of BaSi2 by ion implantation and rapid thermal annealing is studied. ► The crystal structure of BaSi2 is destroyed, at least partially, by P implantation. ► The annealing condition to remove the irradiation damage is revealed. ► The trigonal BaSi2 phase forms from the highly damaged film by annealing. ► P atoms segregate at 600–800°C.
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