28 results on '"Mitsuo Kitamura"'
Search Results
2. Polar-Coded Transmission over 7.8-km Terrestrial Free-Space Optical Links
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Shingo Fujita, Eiji Okamoto, Hideki Takenaka, Hiroyuki Endo, Mikio Fujiwara, Mitsuo Kitamura, Ryosuke Shimizu, Masahide Sasaki, and Morio Toyoshima
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free space optics ,transmission experiments ,polar code ,low-density parity-check code ,channel equalization ,Applied optics. Photonics ,TA1501-1820 - Abstract
Free-space optical (FSO) communications can offer high-capacity transmission owing to the properties of the laser beams. However, performance degradation caused by atmospheric turbulence is an urgent issue. Recently, the application of polar codes, which can provide capacity-achieving error-correcting performance with low computational cost for decoding, to FSO communications has been studied. However, long-distance and real-field experiments have not been conducted in these studies. To the best of our knowledge, this study is the first to present the experimental results of polar-coded transmission over 7.8-km FSO links. Using experimental data, we investigated the performance of polar codes over atmospheric channels, including their superiority to regular low-density parity-check codes. We expect that our results will offer a path toward the application of polar codes in high-speed optical communication networks including satellites.
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- 2023
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3. Exposure to an Extremely-Low-Frequency Magnetic Field Stimulates Adrenal Steroidogenesis via Inhibition of Phosphodiesterase Activity in a Mouse Adrenal Cell Line.
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Kazuyoshi Kitaoka, Shiyori Kawata, Tomohiro Yoshida, Fumiya Kadoriku, and Mitsuo Kitamura
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Medicine ,Science - Abstract
Extremely low-frequency magnetic fields (ELF-MFs) are generated by power lines and household electrical devices. In the last several decades, some evidence has shown an association between ELF-MF exposure and depression and/or anxiety in epidemiological and animal studies. The mechanism underlying ELF-MF-induced depression is considered to involve adrenal steroidogenesis, which is triggered by ELF-MF exposure. However, how ELF-MFs stimulate adrenal steroidogenesis is controversial. In the current study, we investigated the effect of ELF-MF exposure on the mouse adrenal cortex-derived Y-1 cell line and the human adrenal cortex-derived H295R cell line to clarify whether the ELF-MF stimulates adrenal steroidogenesis directly. ELF-MF exposure was found to significantly stimulate adrenal steroidogenesis (p < 0.01-0.05) and the expression of adrenal steroid synthetic enzymes (p < 0.05) in Y-1 cells, but the effect was weak in H295R cells. Y-1 cells exposed to an ELF-MF showed significant decreases in phosphodiesterase activity (p < 0.05) and intracellular Ca2+ concentration (p < 0.01) and significant increases in intracellular cyclic adenosine monophosphate (cAMP) concentration (p < 0.001-0.05) and cAMP response element-binding protein phosphorylation (p < 0.05). The increase in cAMP was not inhibited by treatment with NF449, an inhibitor of the Gs alpha subunit of G protein. Our results suggest that ELF-MF exposure stimulates adrenal steroidogenesis via an increase in intracellular cAMP caused by the inhibition of phosphodiesterase activity in Y-1 cells. The same mechanism may trigger the increase in adrenal steroid secretion in mice observed in our previous study.
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- 2016
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4. Free-space optical channel estimation for physical layer security.
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Hiroyuki Endo, Mikio Fujiwara, Mitsuo Kitamura, Toshiyuki Ito, Morio Toyoshima, Yoshihisa Takayama, Hideki Takenaka, Ryosuke Shimizu, Nicola Laurenti, Giuseppe Vallone, Paolo Villoresi, Takao Aoki, and Masahide Sasaki
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- 2016
5. Free-space optical secret key agreement with post-selection based on channel state information
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Mikio Fujiwara, Masahide Sasaki, Hiroyuki Endo, Masahiro Takeoka, Orie Tsuzuki, Mitsuo Kitamura, and Ryosuke Shimizu
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Wireless network ,Computer science ,business.industry ,Channel state information ,Key (cryptography) ,Wireless ,Fading ,Communications system ,business ,Information-theoretic security ,Computer network ,Free-space optical communication - Abstract
Free-space optical (FSO) communications are becoming promising schemes for high-capacity wireless links due to their plentiful characteristics originated from higher carrier frequency. These characteristics also yield a greater security advantage over radio frequency counterparts: the physical ability of a wiretapper is reasonably restricted due to the high directionality of communication beam and the line-of-sight configuration of the link. Secret key agreement over FSO links (FSO-SKA) employs this security advantage as well as the post-processing over an authenticated public channel to establish an information-theoretic secure key which cannot be broken even with unbounded computer resources. In the previous works, the authors demonstrated the full-field implementations of FSO-SKA with a 7.8-km FSO link testbed including a probing station to estimate the possible wiretapping risks from the sidelobe of the communication beam. In the demonstration, however, there is still room to improve the secret key rate by exploiting the optical fading which contains additional information about random states of the FSO links. We here propose a novel protocol for FSO-SKA employing such channel state information. In the protocol, the legitimate receiver decides whether to discard the received symbols or not according to the received optical power at the time. Based on the experimental data from the FSO link testbed, we demonstrate that the proposed protocol improves the secret key rate compared with our previous result. To our best knowledge, this is the first demonstration that exploits the effect of atmospheric turbulences to improve the security performance of communication systems. We anticipate that this idea will be applicable on the broader areas of FSO communications and opens a way toward practical wireless network spanned by FSO links.
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- 2019
6. Experimental Evaluation of Polar Code Transmission in Terrestrial Free-Space Optics
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Mikio Fujiwara, Masahide Sasaki, Ryosuke Shimizu, Hiroyuki Endo, Keita Ito, Shinya Fujita, Hiroo Kunimori, Mitsuo Kitamura, Hideki Takenaka, Eiji Okamoto, and M. Toyoshima
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Scintillation ,Transmission (telecommunications) ,Polar code ,Computer science ,Electronic engineering ,Satellite ,Error detection and correction ,Burst error ,Free-space optical communication ,Communication channel - Abstract
In recent years, the demand for high-speed communication has been increasing. Satellite laser communication is one of the infrastructures that can realize this demand. However, in free-space optics (FSO) that use satellite laser communications, a scintillation occurs when the light passes through the atmosphere, resulting in a burst error. To prevent this, a strong error correction code is required. The polar code, one of such channel coding schemes, has been recently proposed. We have considered applying polar codes into FSO channels and have evaluated its performances through computer simulations. However, the experiments of polar code transmission in an outdoor FSO channel has not been studied. Therefore, in this paper, we conduct an experiment in polar code transmission in a terrestrial FSO channel instead of a satellite FSO as the first step of study, and then analyze the performance from the transmission results.
- Published
- 2019
7. Research and development of highly secure free-space optical communication system for mobile platforms in NICT
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Yoshihiko Saito, Alberto Carrasco-Casado, Toshihiro Kubooka, Mikio Fujiwara, Hideki Takenaka, Mitsuo Kitamura, Masahiro Takeoka, Phuc V. Trinh, Yasushi Munemasa, Hiroyuki Endo, Masahide Sasaki, and Morio Toyoshima
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Vibration ,Development (topology) ,business.industry ,Computer science ,Electrical engineering ,Optical communication ,Tracking system ,Atmospheric turbulence ,Quantum key distribution ,business ,Physics::Atmospheric and Oceanic Physics ,Free-space optical communication ,Beam divergence - Abstract
Research and development of a novel method for a secure free-space optical communication system has been done in NICT since 2018, and demonstration experiments between an aircraft and a transportable optical ground station are planned in near future. In order to establish a stable and highly accurate optical communication link, the system must have a fine pointing mechanism in both the aircraft and the ground station. A compact and light-weight tracking system is required to be mounted on the aircraft, and there will be needed to have an adjustment function of the beam divergence control to allow stable communication under various altitude and atmospheric conditions. The transportable optical ground station should maintain vibration resistance when moving, and it must be easily deployed on each site where is the appropriate optical ground station site with respect to atmospheric turbulence condition.
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- 2019
8. Group key agreement over free-space optical links
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Mitsuo Kitamura, Hiroyuki Endo, Mikio Fujiwara, Masahiro Takeoka, Masahide Sasaki, Orie Tsuzuki, and Ryosuke Shimizu
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Signal processing ,business.industry ,Computer science ,Keying ,Quantum key distribution ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Information leakage ,Electrical and Electronic Engineering ,business ,Key exchange ,Free-space optical communication ,Computer network ,Group key ,Communication channel - Abstract
Free-space optical (FSO) communications can offer secure connectivity thanks to the high directionality of the laser beam and the line-of-sight configuration. These security advantages are employed to realize high-speed key establishment between two distant parties, which is provably secure against an eavesdropper with unlimited computational resources. Besides, a well-maintained laser beam divergence allows group key agreement (GKA) among multiple parties. Here, we propose a novel method of GKA over FSO link—FSO-GKA. After numerically characterizing fundamental behaviors, we present a proof-of-concept demonstration of FSO-GKA using a 7.8-km terrestrial link. We achieve a group key rate of roughly 8 Mbps over a 58dB-loss channel based on 10-MHz on-off keying. We also investigate information leakage risks under several atmospheric conditions, which provides the basis for security certification of FSO-GKA. Our proposed scheme shows a new way to construct high-speed key exchange platforms.
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- 2020
9. QKD from a microsatellite: The SOTA experience
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Alberto Carrasco-Casado, Morio Toyoshima, Hideki Takenaka, Mitsuo Kitamura, Masahide Sasaki, and Mikio Fujiwara
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Quantum Physics ,Physics - Instrumentation and Detectors ,business.industry ,Computer science ,Electrical engineering ,Optical communication ,FOS: Physical sciences ,Cassegrain reflector ,Instrumentation and Detectors (physics.ins-det) ,Quantum channel ,Quantum key distribution ,Telecommunications network ,Key (cryptography) ,Communications satellite ,Quantum Physics (quant-ph) ,business ,Free-space optical communication - Abstract
The transmission and reception of polarized quantum-limited signals from space is of capital interest for a variety of fundamental-physics experiments and quantum-communication protocols. Specifically, Quantum Key Distribution (QKD) deals with the problem of distributing unconditionally-secure cryptographic keys between two parties. Enabling this technology from space is a critical step for developing a truly-secure global communication network. The National Institute of Information and Communications Technology (NICT, Japan) performed the first successful measurement on the ground of a quantum-limited signal from a satellite in experiments carried out on early August in 2016. The SOTA (Small Optical TrAnsponder) lasercom terminal onboard the LEO satellite SOCRATES (Space Optical Communications Research Advanced Technology Satellite) was utilized for this purpose. Two non-orthogonally polarized signals in the ~800-nm band and modulated at 10 MHz were transmitted by SOTA and received in the single-photon regime by using a 1-m Cassegrain telescope on a ground station located in an urban area of Tokyo (Japan). In these experiments, after compensating the Doppler effect induced by the fast motion of the satellite, a QKD-enabling QBER (Quantum Bit Error Rate) below 5% was measured with estimated key rates in the order of several Kbit/s, proving the feasibility of quantum communications in a real scenario from space for the first time., 10 pages, 14 figures
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- 2018
10. Quantum photonic network and physical layer security
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Hiroyuki Endo, Toshiyuki Ito, Ryosuke Shimizu, Morio Toyoshima, Mikio Fujiwara, Masahide Sasaki, and Mitsuo Kitamura
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Scheme (programming language) ,Quantum network ,Computer science ,General Mathematics ,General Engineering ,Physical layer ,General Physics and Astronomy ,02 engineering and technology ,Data_CODINGANDINFORMATIONTHEORY ,Articles ,Quantum key distribution ,020210 optoelectronics & photonics ,Quantum cryptography ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Quantum information science ,computer ,Quantum ,computer.programming_language ,Data transmission ,Computer Science::Information Theory ,Computer Science::Cryptography and Security - Abstract
Quantum communication and quantum cryptography are expected to enhance the transmission rate and the security (confidentiality of data transmission), respectively. We study a new scheme which can potentially bridge an intermediate region covered by these two schemes, which is referred to as quantum photonic network. The basic framework is information theoretically secure communications in a free space optical (FSO) wiretap channel, in which an eavesdropper has physically limited access to the main channel between the legitimate sender and receiver. We first review a theoretical framework to quantify the optimal balance of the transmission efficiency and the security level under power constraint and at finite code length. We then present experimental results on channel characterization based on 10 MHz on–off keying transmission in a 7.8 km terrestrial FSO wiretap channel. This article is part of the themed issue ‘Quantum technology for the 21st century’.
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- 2016
11. Research and development of highly secure free-space optical communication system for mobile platforms in NICT.
- Author
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Yoshihiko Saito, Hiroyuki Endo, Hideki Takenaka, Yasushi Munemasa, Mikio Fujiwara, Carrasco-Casado, Alberto, Trinh, Phuc V., Mitsuo Kitamura, Kubo-oka, Toshihiro, MasahiroTakeoka, Masahide Sasaki, and Morio Toyoshima
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- 2018
- Full Text
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12. Free-space optical channel estimation for physical layer security
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Giuseppe Vallone, Masahide Sasaki, Yoshihisa Takayama, Morio Toyoshima, Nicola Laurenti, Mitsuo Kitamura, Mikio Fujiwara, Hideki Takenaka, Takao Aoki, Toshiyuki Ito, Paolo Villoresi, Ryosuke Shimizu, and Hiroyuki Endo
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FOS: Computer and information sciences ,Computer science ,Computer Science - Information Theory ,Data_CODINGANDINFORMATIONTHEORY ,02 engineering and technology ,020210 optoelectronics & photonics ,PHY ,Atomic and Molecular Physics ,0202 electrical engineering, electronic engineering, information engineering ,Fading ,Computer Science::Information Theory ,Computer Science::Cryptography and Security ,business.industry ,Information Theory (cs.IT) ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,Testbed ,Physical layer ,020206 networking & telecommunications ,Enterprise information security architecture ,Atomic and Molecular Physics, and Optics ,Transmission (telecommunications) ,and Optics ,business ,Computer network ,Free-space optical communication ,Communication channel - Abstract
We present experimental data on message transmission in a free-space optical (FSO) link at an eye-safe wavelength, using a testbed consisting of one sender and two receiver terminals, where the latter two are a legitimate receiver and an eavesdropper. The testbed allows us to emulate a typical scenario of physical-layer (PHY) security such as satellite-to-ground laser communications. We estimate information-theoretic metrics including secrecy rate, secrecy outage probability, and expected code lengths for given secrecy criteria based on observed channel statistics. We then discuss operation principles of secure message transmission under realistic fading conditions, and provide a guideline on a multi-layer security architecture by combining PHY security and upper-layer (algorithmic) security., Comment: 16 pages, 8 figures
- Published
- 2016
13. Effects of a 1.5 T time-varying magnetic field on cell volume regulation of bovine adrenal chromaffin cells in hyposmotic media
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Hiromi Ichinose, Kazuyoshi Kawazoe, Yuki Minami, Kazuo Minakuchi, Kazuo Yoshizaki, Hitoshi Houchi, Hirotaka Nishisako, Hiroshi Miyamoto, Tairoh Shiraishi, Mitsuo Kitamura, Toshitaka Ikehara, Yohsuke Kinouchi, and Masayuki Shono
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medicine.medical_specialty ,Cytochalasin D ,Time Factors ,Osmotic shock ,Chromaffin Cells ,General Biochemistry, Genetics and Molecular Biology ,eddy current ,Magnetics ,chemistry.chemical_compound ,Osmotic Pressure ,Internal medicine ,cytoskeletal protein ,medicine ,Animals ,Cytoskeleton ,hyposmotic stress ,Cells, Cultured ,Actin ,Cell Size ,Chemistry ,General Medicine ,Actin cytoskeleton ,Actins ,Endocrinology ,Hypotonic Solutions ,Volume (thermodynamics) ,Biophysics ,regulatory volume decrease ,Tonicity ,Calcium ,Cattle ,actin ,Intracellular - Abstract
Effects of a time-varying magnetic field on cell volume regulation by hyposmotic stress in cultured bovine adrenal chromaffin cells were examined. Through regulatory volume decrease (RVD), cell volume of chromaffin cells that were incubated in a hypotonic medium initially increased, reached a peak and finally recovered to the initial value. Two hour exposure to a magnetic field and addition of cytochalasin D increased peak value and delayed return to initial value. Intracellular F-actin contents initially decreased but returned to normal levels after 10 sec. Two hour exposure to the magnetic field and addition of cytochalasin D continuously reduced the F-actin content. Results suggest that exposure to the magnetic field stimulated disruption of the actin cytoskeleton and that the disruption delayed the recovery to the volume prior to osmotic stress.
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- 2011
14. Effects of exposure to a time-varying 1.5 T magnetic field on the neurotransmitter-activated increase in intracellular Ca2+ in relation to actin fiber and mitochondrial functions in bovine adrenal chromaffin cells
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Hiromi Ichinose, Masayuki Shono, Yohsuke Kinouchi, Kazuo Yoshizaki, Mitsuo Kitamura, Tairo Shiraishi, Toshitaka Ikehara, Yuki Minami, Hitoshi Houchi, Kazuyoshi Kawazoe, Kazuo Minakuchi, Hirotaka Nishisako, and Hiroshi Miyamoto
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Cytochalasin D ,Time Factors ,Chromaffin Cells ,Immunoblotting ,Intracellular Space ,Biophysics ,Biology ,Mitochondrion ,Endoplasmic Reticulum ,Biochemistry ,chemistry.chemical_compound ,Adenosine Triphosphate ,Electromagnetic Fields ,Oxygen Consumption ,Depsipeptides ,Adrenal Glands ,Animals ,Cytochalasin ,Molecular Biology ,Cells, Cultured ,Nucleic Acid Synthesis Inhibitors ,Membrane Potential, Mitochondrial ,Calcium metabolism ,Membrane potential ,Neurotransmitter Agents ,Microscopy, Confocal ,Endoplasmic reticulum ,Acetylcholine ,Actins ,Tubulin Modulators ,Mitochondria ,Cell biology ,Intracellular signal transduction ,Actin Cytoskeleton ,chemistry ,Calcium ,Cattle ,Colchicine ,Cation transport ,Intracellular - Abstract
Background It has been reported that exposure to electromagnetic fields influences intracellular signal transduction. We studied the effects of exposure to a time-varying 1.5 T magnetic field on membrane properties, membrane cation transport and intracellular Ca2+ mobilization in relation to signals. We also studied the mechanism of the effect of exposure to the magnetic field on intracellular Ca2+ release from Ca2+ stores in adrenal chromaffin cells. Methods We measured the physiological functions of ER, actin protein, and mitochondria with respect to a neurotransmitter-induced increase in Ca2+ in chromaffin cells exposed to the time-varying 1.5 T magnetic field for 2 h. Results Exposure to the magnetic field significantly reduced the increase in [Ca2+]i. The exposure depolarized the mitochondria membrane and lowered oxygen uptake, but did not reduce the intracellular ATP content. Magnetic field-exposure caused a morphological change in intracellular F-actin. F-actin in exposed cells seemed to be less dense than in control cells, but the decrease was smaller than that in cytochalasin D-treated cells. The increase in G-actin (i.e., the decrease in F-actin) due to exposure was recovered by jasplakinolide, but inhibition of Ca2+ release by the exposure was unaffected. Conclusions and general significance These results suggest that the magnetic field-exposure influenced both the ER and mitochondria, but the inhibition of Ca2+ release from ER was not due to mitochondria inhibition. The effect of eddy currents induced in the culture medium may indirectly influence intracellular actin and suppress the transient increase in [Ca2+]i.
- Published
- 2010
15. Free space optical secret key agreement
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Hiroyuki Endo, Toshiyuki Ito, Masahide Sasaki, Masahiro Takeoka, Mikio Fujiwara, Orie Tsuzuki, Ryosuke Shimizu, and Mitsuo Kitamura
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Wireless network ,business.industry ,Computer science ,Eavesdropping ,02 engineering and technology ,Quantum channel ,Quantum key distribution ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Optics ,0103 physical sciences ,Key (cryptography) ,Electronic engineering ,010306 general physics ,0210 nano-technology ,business ,Free-space optical communication - Abstract
Free space optical (FSO) communications are enabling high-speed global wireless networks. Thanks to the highly directional nature of laser beam, they also yield a greater security advantage over radio frequency counterparts. When combined with a scheme of secret key agreement (SKA), FSO-SKA can establish at high speed a symmetric secret key which cannot be decrypted even by unbounded computer resources. Although there have been many theoretical studies on SKA, experimental investigations have been quite lacking, especially on quantifying eavesdropping risks and secret key rates in realistic environment. Here, we report the first full-field implementations of FSO-SKA in a 7.8-km terrestrial link with a probing station, enabling the estimation of eavesdropping risks. We attain the final key rates from 100 kbps to 7.77 Mbps under various atmospheric and beaming conditions even with total losses of 55dB or higher, in which known quantum key distribution schemes attain impractically low key rates.
- Published
- 2018
16. Free-space optical wiretap channel and experimental secret key agreement in 78 km terrestrial link
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Masahiro Takeoka, Morio Toyoshima, Masahide Sasaki, Hideki Takenaka, Mitsuo Kitamura, Ryutaroh Matsumoto, Toshiyuki Ito, Hiroyuki Endo, Orie Tsuzuki, Yoshihisa Takayama, Ryosuke Shimizu, and Mikio Fujiwara
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010302 applied physics ,business.industry ,Computer science ,02 engineering and technology ,Quantum channel ,Quantum key distribution ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,020210 optoelectronics & photonics ,Optics ,Alice and Bob ,Quantum cryptography ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Bit error rate ,Key (cryptography) ,Wireless ,business ,Computer network ,Communication channel - Abstract
Secret key agreement using physical properties of a wireless channel is becoming a promising scheme to establish a secret key between two users, especially in short-distance radio frequency (RF) communications. In this scheme, the existence of codes or key distillation that can make the leaked information to an eavesdropper arbitrarily small can be derived in an information theoretical way, given a priori knowledge on the channel linking a sender (Alice), a legitimate receiver (Bob), and an eavesdropper (Eve), which is called the wiretap channel. In practice, however, it is often difficult for Alice and Bob to get sufficient knowledge on Eve. In this study, we implement a free-space optical wiretap channel in a 7.8 km-terrestrial link and study how to estimate Eve's tapping ability, demonstrating high speed secret key agreement in the optical domain under a certain restricted condition of line-of-sight.
- Published
- 2018
17. QKD from a microsatellite: The SOTA experience.
- Author
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Carrasco-Casado, Alberto, Hideki Takenaka, Mikio Fujiwara, Mitsuo Kitamura, Masahide Sasaki, and Morio Toyoshima
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- 2018
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18. Effects of a time varying strong magnetic field on release of cytosolic free Ca2+ from intracellular stores in cultured bovine adrenal chromaffin cells
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Ki Ho Park, Hisao Yamaguchi, Hitoshi Houchi, Hiroshi Miyamoto, Mami Azuma, Keiko Hosokawa, Mitsuo Kitamura, Hideki Kashimoto, Kazuo Minakuchi, Toshitaka Ikehara, Yohsuke Kinouchi, and Kazuo Yoshizaki
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medicine.medical_specialty ,Time Factors ,Thapsigargin ,Physiology ,Cells ,Chromaffin Cells ,Biophysics ,Inositol 1,4,5-Trisphosphate ,Bradykinin ,Cell membrane ,chemistry.chemical_compound ,Electromagnetic Fields ,Internal medicine ,Adrenal Glands ,medicine ,Animals ,Radiology, Nuclear Medicine and imaging ,Inositol ,Receptor ,Calcium metabolism ,Biological Transport ,General Medicine ,Inositol trisphosphate receptor ,Cytosol ,medicine.anatomical_structure ,Endocrinology ,chemistry ,Calcium ,Cattle ,Intracellular ,Signal Transduction - Abstract
This study was made to explain the mechanisms for the effects of exposure to a time varying 1.51 T magnetic field on the intracellular Ca(2+) signaling pathway. The exposure inhibited an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in bovine chromaffin cells induced by addition of bradykinin (BK) to a Ca(2+) free medium. The exposure did not change BK induced production of inositol 1,4,5-trisphosphate (IP(3)). [Ca(2+)](i) was markedly increased in IP(3) loaded cells, and this increase was inhibited by the magnetic field exposure. A similar increase in [Ca(2+)](i) by other drugs, which stimulated Ca(2+) release from intracellular Ca(2+) stores, was again inhibited by the same exposure. However, transmembrane Ca(2+) fluxes caused in the presence of thapsigargin were not inhibited by the magnetic field exposure in a Ca(2+) containing medium. Inhibition of the BK induced increase in [Ca(2+)](i) by the exposure for 30 min was mostly recovered 1 h after exposure ended. Our results reveal that the magnetic field exposure inhibits Ca(2+) release from intracellular Ca(2+) stores, but that BK bindings to BK receptors of the cell membrane and intracellular inositol IP(3) production are not influenced.
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- 2002
19. Erratum: Low-Frequency Magnetic Field Induces Depression-Like Behavior and Corticosterone Secretion Without Enhancement of the Hypothalamic-Pituitary-Adrenal Axis in Mice
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Kazuo Yoshizaki, Mitsuo Kitamura, Shun Aoi, Noriyuki Shimizu, and Kazuyoshi Kitaoka
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medicine.medical_specialty ,Physiology ,Biophysics ,General Medicine ,Low frequency magnetic field ,chemistry.chemical_compound ,Endocrinology ,medicine.anatomical_structure ,chemistry ,Corticosterone ,Internal medicine ,medicine ,Radiology, Nuclear Medicine and imaging ,Secretion ,Depression (differential diagnoses) ,Hypothalamic–pituitary–adrenal axis - Published
- 2013
20. Chronic exposure to an extremely low-frequency magnetic field induces depression-like behavior and corticosterone secretion without enhancement of the hypothalamic-pituitary-adrenal axis in mice
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Shun Aoi, Mitsuo Kitamura, Noriyuki Shimizu, Kazuyoshi Kitaoka, and Kazuo Yoshizaki
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Male ,medicine.medical_specialty ,Hypothalamo-Hypophyseal System ,Time Factors ,Tyrosine 3-Monooxygenase ,Physiology ,medicine.drug_class ,Emotions ,Biophysics ,Adrenocorticotropic hormone ,Gene Expression Regulation, Enzymologic ,chemistry.chemical_compound ,Mice ,Norepinephrine ,Electromagnetic Fields ,Adrenocorticotropic Hormone ,Corticosterone ,Internal medicine ,Adrenal Glands ,medicine ,Animals ,Body Size ,Radiology, Nuclear Medicine and imaging ,Secretion ,Mice, Inbred ICR ,Behavior, Animal ,Chemistry ,Depression ,General Medicine ,respiratory system ,medicine.anatomical_structure ,Endocrinology ,CYP17A1 ,Corticosteroid ,Hypothalamic–pituitary–adrenal axis ,Glucocorticoid ,Behavioural despair test ,medicine.drug - Abstract
An extremely low-frequency magnetic field (ELF-MF) is generated by power lines and household electrical devices. Many studies have suggested an association between chronic ELF-MF exposure and anxiety and/or depression. The mechanism of these effects is assumed to be a stress response induced by ELF-MF exposure. However, this mechanism remains controversial. In the present study, we investigated whether chronic ELF-MF exposure (intensity, 3 mT; total exposure, 200 h) affected emotional behavior and corticosterone synthesis in mice. ELF-MF-treated mice showed a significant increase in total immobility time in a forced swim test and showed latency to enter the light box in a light–dark transition test, compared with sham-treated (control) mice. Corticosterone secretion was significantly high in the ELF-MF-exposed mice; however, no changes were observed in the amount of the adrenocorticotropic hormone and the expression of genes related to stress response. Quantification of the mRNA levels of adrenal corticosteroid synthesis enzymes revealed a significant reduction in Cyp17a1 mRNA in the ELF-MF-exposed mice. Our findings suggest the possibility that high intensity and chronic exposure to ELF-MF induces an increase in corticosterone secretion, along with depression- and/or anxiety-like behavior, without enhancement of the hypothalamic–pituitary–adrenal axis. Bioelectromagnetics 34:43–51, 2013. © 2012 Wiley Periodicals, Inc.
- Published
- 2011
21. Quantum photonic network and physical layer security.
- Author
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Masahide Sasaki, Hiroyuki Endo, Mikio Fujiwara, Mitsuo Kitamura, Toshiyuki Ito, Ryosuke Shimizu, and Morio Toyoshima
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QUANTUM communication (Optics) ,QUANTUM cryptography ,LASER communication systems ,OPTICAL communications ,PHOTONICS ,PHYSICAL layer security - Abstract
Quantum communication and quantum cryptography are expected to enhance the transmission rate and the security (confidentiality of data transmission), respectively. We study a new scheme which can potentially bridge an intermediate region covered by these two schemes, which is referred to as quantum photonic network. The basic framework is information theoretically secure communications in a free space optical (FSO) wiretap channel, in which an eavesdropper has physically limited access to the main channel between the legitimate sender and receiver. We first review a theoretical framework to quantify the optimal balance of the transmission efficiency and the security level under power constraint and at finite code length. We then present experimental results on channel characterization based on 10MHz on-off keying transmission in a 7.8km terrestrial FSO wiretap channel. [ABSTRACT FROM AUTHOR]
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- 2017
- Full Text
- View/download PDF
22. Effects of a time-varying strong magnetic field on transient increase in Ca2+ release induced by cytosolic Ca2+ in cultured pheochromocytoma cells
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Hitoshi Houchi, Keiko Hosokawa, Hisao Yamaguchi, Hideki Kashimoto, Kazuo Minakuchi, Ki Ho Park, Kazuo Yoshizaki, Mitsuo Kitamura, Yohsuke Kinouchi, Hiroshi Miyamoto, and Toshitaka Ikehara
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Time Factors ,Cations, Divalent ,Biophysics ,Receptors, Cytoplasmic and Nuclear ,Endoplasmic Reticulum ,Biochemistry ,PC12 Cells ,Cell membrane ,chemistry.chemical_compound ,Magnetics ,Adenosine Triphosphate ,Cytosol ,ATP hydrolysis ,Caffeine ,medicine ,Animals ,Inositol 1,4,5-Trisphosphate Receptors ,Lactic Acid ,Molecular Biology ,Cyclic ADP-Ribose ,Ryanodine receptor ,Chemistry ,Endoplasmic reticulum ,Hydrolysis ,Cell Membrane ,Ryanodine Receptor Calcium Release Channel ,Inositol trisphosphate receptor ,Rats ,medicine.anatomical_structure ,Thapsigargin ,Calcium ,Calcium Channels ,Intracellular - Abstract
Exposure of pheochromocytoma (PC 12) cells to a time-varying 1.51 T magnetic field inhibited an increase in the intracellular Ca2+ concentration ([Ca2+]i) induced by addition of caffeine to Ca2+-free medium. This inhibition occurred after a 15-min exposure and was maintained for at least 2 h. [Ca2+]i sharply increased in cells loaded with cyclic ADP-ribose, and 2-h exposure significantly suppressed the increase. Addition of ATP induced a transient increase in intracellular Ca2+ release mediated by IP3 receptor, and this increase was strongly inhibited by the exposure. Results indicated that the magnetic field exposure strongly inhibited Ca2+ release mediated by both IP3 and ryanodine receptors in PC 12 cells. However, thapsigargin-induced Ca2+ influx (capacitative Ca2+ entry) across the cell membrane was unaffected. The ATP content was maintained at the normal level during the 2-h exposure, suggesting that ATP hydrolysis was unchanged. Therefore, Mg2+ which is known to be released by ATP hydrolysis and inhibit intracellular Ca2+ release may not relate the exposure-caused inhibition. Eddy currents induced in culture medium appear to change cell membrane properties and indirectly inhibit Ca2+ release from endoplasmic reticulum and other Ca2+ stores in PC 12 cells.
- Published
- 2004
23. 3TA4-04 Histamine and exocytosis in mast cells studied with ^1H-NMR(The 47th Annual Meeting of the Biophysical Society of Japan)
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Mitsuo Kitamura, Naoki Arizono, Kazuo Yoshizaki, and Takashi Hayano
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chemistry.chemical_compound ,chemistry ,Mast (botany) ,Biology ,Exocytosis ,Histamine ,Cell biology - Published
- 2009
24. Studies on Shiraki (Sapium Japonicum) Oil
- Author
-
Tetsujiro Obara and Mitsuo Kitamura
- Subjects
biology ,Linoleic acid ,Drying oil ,Medicine (miscellaneous) ,Halogenation ,biology.organism_classification ,Palmitic acid ,chemistry.chemical_compound ,Oleic acid ,Iodine value ,chemistry ,Chemistry (miscellaneous) ,Organic chemistry ,lipids (amino acids, peptides, and proteins) ,Food science ,Stearic acid ,Sapium ,Food Science ,Biotechnology - Abstract
We found out the following fact as the results of our study on Shiraki (Sapium Japonicum) oil from Niigata prefecture. (1) Shiraki fruit contains 66% drying oil. (Iodine value 162.4). (2) This oil is composed of about 5.9% solid fatty acids and about 90. 6% liquid fatty acids. (3) The solid fatty acids consist of about 66% palmitic acid, about 24% stearic acid and about 10% fatty acids higher than stearic acid. (4) As the result of oxidation and bromination tests, it is clear that the liquid fatty acids consist of about 21% oleic acid, 66% linoleic acid and 9% linolneic acid. (5) In short, the real yields of Shiraki oil components show that it consists of about 55% linoleic acid, about 19% oleic acid, about 8%linolenic acid, about 4% palmitic acid, about 1% stearic acid and small quantities of higher saturated fatty acids.
- Published
- 1951
25. Studies on Sawafutagi (Symplocos cratalgoides) Oil
- Author
-
Tetsujiro Obara and Mitsuo Kitamura
- Subjects
Symplocos ,biology ,Traditional medicine ,Chemistry (miscellaneous) ,Medicine (miscellaneous) ,biology.organism_classification ,Food Science ,Biotechnology - Published
- 1952
26. On the Fat of Buck Wheat
- Author
-
Mitsuo Kitamura and Tetsujiro Obara
- Subjects
chemistry.chemical_classification ,Saponification value ,Interesterified fat ,Drying oil ,food and beverages ,Medicine (miscellaneous) ,Fatty acid ,Palmitic acid ,chemistry.chemical_compound ,Oleic acid ,Iodine value ,chemistry ,Chemistry (miscellaneous) ,Organic chemistry ,Food science ,Food Science ,Biotechnology ,Polyunsaturated fatty acid - Abstract
We found out the following fact as the results of our study of buck wheat. Buck wheat contains 3.08% crude fat and this is semi-drying oil (iodine value 102.08) and closely approaches to drying oil. This oil is composed of about 18% solid fatty acids and about 79% liquid fatty acids. Solid fatty acids consist of palmitic acid, carnaubic acid, and fatty acids higher than C18 acid. Liquid fatty acids consist of oleic acid and linolic acid. It seems, in short, that the fatty acids composing the fat of buck wheat consist of about 55% oleic acid, 20% linolic acid, and 13% palmitic acid, and the rest consists of carnaubic acid and saturated fatty acids higher than C18.
- Published
- 1951
27. Studies on the Lecithin and Cephalin in the Fat of Sawa-Millet (Panicum Crus-golli L.) Oil
- Author
-
Tetsujiro Obara and Mitsuo Kitamura
- Subjects
food.ingredient ,food ,Biochemistry ,biology ,Chemistry (miscellaneous) ,Chemistry ,Medicine (miscellaneous) ,Food science ,biology.organism_classification ,Lecithin ,Panicum ,Food Science ,Biotechnology - Abstract
The author investigated the phosphatide of Sawa-Millet oil and found out the following results: 1. Sawa-Millet oil contains about 0.14% phophatide. 2. This phosphatide is composed of about 23% lecithin and about 76% cephalin.
- Published
- 1955
28. Studies on the Wax and Hydrocarbon in Sawamillet Bran Oil
- Author
-
Mitsuo Kitamura and Tetsujiro Obara
- Subjects
chemistry.chemical_classification ,Wax ,Castor wax ,Hydrocarbon ,chemistry ,Bran ,Chemistry (miscellaneous) ,visual_art ,visual_art.visual_art_medium ,Medicine (miscellaneous) ,Food science ,Food Science ,Biotechnology - Published
- 1958
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