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Search Results: 1 - 10 of 1663 matches for " Eisuke Abe "
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Pituitary intratumoral hemorrhage during radiation therapy following partial removal of giant pituitary adenoma: A case report  [PDF]
Junyang Liu, Yuichiro Yoneoka, Kensuke Tanaka, Hiraku Satou, Eisuke Abe, Naoto Watanabe, Yukihiko Fuji, Hitoshi Takahashi, Hidefumi Aoyama
Case Reports in Clinical Medicine (CRCM) , 2014, DOI: 10.4236/crcm.2014.31010
Abstract:


We report a rare case of intratumoral hemorrhage during postoperative radiotherapy for pituitary adenoma. A 57-year-old Asian male, complaining of long-standing eye strain, underwent a medical checkup of the brain. Magnetic resonance imaging showed a multicystic giant pituitary adenoma. The patient underwent an endoscopic endonasal transsphenoidal partial removal of the adenoma to provide optic pathway decompression and got relief from the visual symptoms. Just before completion of the postoperative radiotherapy for residual adenoma, the patient developed right hemiparesis, mild motor aphasia, and right oculomotor palsy. A cranial CT scan showed intratumoral hemorrhage into the intratumoral cyst. The patient therefore had to undergo three additional craniotomies for evacuation of cyst contents over the next 8 months. The follow-up MRI at 11 months after the initial hemorrhage showed that the new oozing of blood in the intratumoral cyst was still appearing. Intratumoral hemorrhage is a rare, albeit life-threatening, complication of pituitary adenoma. We reviewed relevant literature and suggested that the cystic component in pituitary adenoma could be a key pathogenesis of this rare complication. In conclusion, we suggest that it may be necessary to realize that cases which have cystic giant pituitary adenoma may cause hemorrhage by chance with the foreseeability.


Detection of spin polarization with a side coupled quantum dot
Tomohiro Otsuka,Eisuke Abe,Yasuhiro Iye,Shingo Katsumoto
Physics , 2009, DOI: 10.1103/PhysRevB.79.195313
Abstract: We propose realistic methods to detect local spin polarization, which utilize a quantum dot side coupled to the target system. By choosing appropriate states in the dot, we can put spin selectivity to the dot and detect spins in the target with small disturbance. We also present an experiment which realizes one of the proposed spin detection schemes in magnetic fields.
Probing local electronic states in the quantum Hall regime with a side coupled quantum dot
Tomohiro Otsuka,Eisuke Abe,Yasuhiro Iye,Shingo Katsumoto
Physics , 2009, DOI: 10.1103/PhysRevB.81.245302
Abstract: We demonstrate a new method for locally probing the edge states in the quantum Hall regime utilizing a side coupled quantum dot positioned at an edge of a Hall bar. By measuring the tunneling of electrons from the edge states into the dot, we acquire information on the local electrochemical potential and electron temperature of the edge states. Furthermore, this method allows us to observe the spatial modulation of the electrostatic potential at the edge state due to many-body screening effect.
Excited-state spectroscopy on a quantum dot side-coupled to a quantum wire
Tomohiro Otsuka,Eisuke Abe,Yasuhiro Iye,Shingo Katsumoto
Physics , 2008, DOI: 10.1063/1.2987424
Abstract: We report excited-state spectroscopy on a quantum dot side-coupled to a quantum wire with accurate energy estimation. Our method utilizes periodic voltage pulses on the dot, and the energy calibration is performed with reference to the bias voltage across the wire. We demonstrate the observation of the orbital excited state and the Zeeman splitting in a single dot.
Electron spin ensemble strongly coupled to a three-dimensional microwave cavity
Eisuke Abe,Hua Wu,Arzhang Ardavan,John J. L. Morton
Physics , 2011, DOI: 10.1063/1.3601930
Abstract: We demonstrate the strong coupling between an electron spin ensemble and a three-dimensional cavity in a reflection geometry. We also find that an anticrossing in the cavity/spin spectrum can be observed under conditions that the collective coupling strength $g_c$ is smaller than the spin linewidth $\gamma_s$ or the cavity linewidth. We identify a ratio of $g_c$ to $\gamma_s$ ($g_c/\gamma_s >$ 0.64) as a condition to observe a splitting in the cavity frequency. Finally, we confirm that $g_c$ scales with $\sqrt{N}$, where $N$ is the number of polarized spins.
Electron spin phase relaxation of phosphorus donors in nuclear spin enriched silicon
Eisuke Abe,Kohei M. Itoh,Junichi Isoya,Satoshi Yamasaki
Physics , 2004, DOI: 10.1103/PhysRevB.70.033204
Abstract: We report a pulsed EPR study of the phase relaxation of electron spins bound to phosphorus donors in isotopically purified 29^Si and natural abundance Si single crystals measured at 8 K.
Observation of Spin-Orbit Berry's Phase in Magnetoresistance of a Two-Dimensional Hole Anti-dot System
Ning Kang,Eisuke Abe,Yoshiaki Hashimoto,Yasuhiro Iye,Shingo Katsumoto
Physics , 2007, DOI: 10.1143/JPSJ.76.083704
Abstract: We report observation of spin-orbit Berry's phase in the Aharonov-Bohm (AB) type oscillation of weak field magnetoresistance in an anti-dot lattice (ADL) of a two-dimensional hole system. An AB-type oscillation is superposed on the commensurability peak, and the main peak in the Fourier transform is clearly split up due to variation in Berry's phase originating from the spin-orbit interaction. A simulation considering Berry's phase and the phase arising from the spin-orbit shift in the momentum space shows qualitative agreement with the experiment.
Towards All Optical, Universal Quantum Computation using Trapped Electron Spins and Cavity Polariton Resonance
Shruti Puri,Na Young Kim,Eisuke Abe,Yoshihisa Yamamoto
Physics , 2012,
Abstract: We propose an all optical quantum computation scheme, with trapped electron spin qubits, using their Coulomb exchange interaction with optically excited microcavity exciton-polaritons. This paper describes a single qubit rotation, which together with two-qubit controlled-z gate presented in PRB 85, 241403(R) (2012), form a set of universal logic gates. The errors due to finite cavity lifetime and incorrect orientation of the rotation axis are minimized by optimizing pump pulse parameters. With projective homodyne phase measurement and initialization, our scheme is a promising candidate for the physical realization of a universal quantum computer.
Fano Effect in a Few-Electron Quantum Dot
Tomohiro Otsuka,Eisuke Abe,Shingo Katsumoto,Yasuhiro Iye,Gyong Luck Khym,Kicheon Kang
Physics , 2007, DOI: 10.1143/JPSJ.76.084706
Abstract: We have studied the Fano effect in a few-electron quantum dot side-coupled to a quantum wire. The conductance of the wire, which shows an ordinal staircase-like quantization without the dot, is modified through the interference (the Fano effect) and the charging effects. These effects are utilized to verify the exhaustion of electrons in the dot. The "addition energy spectrum" of the dot shows a shell structure, indicating that the electron confinement potential is fairly circular. A rapid sign inversion of the Fano parameter on the first conductance plateau with the change of the wire gate voltage has been observed, and explained by introducing a finite width of dot-wire coupling.
Line Broadening and Decoherence of Electron Spins in Phosphorus-Doped Silicon Due to Environmental 29^Si Nuclear Spins
Eisuke Abe,Akira Fujimoto,Junichi Isoya,Satoshi Yamasaki,Kohei M. Itoh
Physics , 2005, DOI: 10.1103/PhysRevB.82.121201
Abstract: Phosphorus-doped silicon single crystals with 0.19 % <= f <= 99.2 %, where f is the concentration of 29^Si isotopes, are measured at 8 K using a pulsed electron spin resonance technique, thereby the effect of environmental 29^Si nuclear spins on the donor electron spin is systematically studied. The linewidth as a function of f shows a good agreement with theoretical analysis. We also report the phase memory time T_M of the donor electron spin dependent on both f and the crystal axis relative to the external magnetic field.
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