Reducing channel spatial correlation by rotating planar antenna array

Takashi Akao,Koya Watanabe,Shun Kojima,Masato Katsuno,Kazuki Maruta,안창준 한국통신학회 2019 ICT Express Vol.5 No.4

This paper newly proposes a direct antenna array control approach to reduce channel spatial correlation for multiuser spatial multiplexing. Conventional rectangular arrays can form three dimensional beams and have superior signal separation performance compared to linear arrays. However, when the arrival angles of some signals are close, the signal separation (interference cancellation) performance deteriorates since the projection points onto horizontal/vertical axes of several antenna elements overlap and spatial resolution along each axis is degenerated. The key proposal is to improve signal separation performance by mechanically changing the positional relationship of antenna elements. The proposed scheme can achieve better Bit Error Rate (BER) performance by searching the optimal antenna rotation angle.

Dynamic Coronary 320-Row CT Angiography Using Low-Dose Contrast and Temporal Maximum Intensity Projection: A Comparison with Standard Coronary CT Angiography

Kojima Tsukasa,Yamasaki Yuzo,Kamitani Takeshi,Yabuuchi Hidetake,Shirasaka Takashi,Shimomiya Yamato,Kondo Masatoshi,Hamasaki Hiroshi,Kato Toyoyuki,Nagao Michinobu,Honda Hiroshi 아시아심장혈관영상의학회 2019 Cardiovascular Imaging Asia Vol.3 No.1

Objective: The smallest diagnostically sufficient amount of contrast media (CM) should be used for coronary computed tomography angiography (CCTA) to minimize the risk of contrast- induced nephrotoxicity in elderly patients with coronary artery disease. The purpose of this study was to propose dynamic-CCTA using a low dose of CM and temporal maximum intensity projection (TMIP) and to investigate its image quality compared to standard-CCTA. Materials and Methods: Participants comprised 30 patients with coronary artery disease who underwent dynamic-CCTA and standard-CCTA using 320-row CT. Dynamic-CCTA was continuously performed at mid-diastole throughout 15–25 cardiac cycles after bolus injection of CM [103 mg iodine/kg body weight (mgI/kg)]. TMIP-CCTA was reconstructed from three-phase dynamic-CCTA data, including a phase with peak enhancement of the ascending aorta. Standard-CCTA was performed using a standard CM dose (259 mgI/kg). Image quality of both TMIP-CCTA and standard-CCTA was analyzed. Results: The amount of CM used in TMIP-CCTA and standard-CCTA was 16.2±2.6 mL and 40.1±7.3 mL, respectively. The mean effective radiation dose was not significantly different between the two methods. Mean coronary attenuation was significantly lower for TMIP-CCTA than standard-CCTA [346.9±82.8 Hounsfield units (HU) vs. 455.4±75.3 HU, p<0.05]. Image noise was significantly lower for TMIP-CCTA than standard-CCTA (20.0±3.2 HU vs. 28.1± 3.6 HU, p<0.05). There were no differences in signal-to-noise ratio and visual assessment scores between the two methods. Conclusion: TMIP-CCTA can be performed using more than 50% less CM with the same image quality as standard-CCTA.

Formation of a Ruthenium(IV)-Oxo Complex by Electron-Transfer Oxidation of a Coordinatively Saturated Ruthenium(II) Complex and Detection of Oxygen-Rebound Intermediates in C–H Bond Oxygenation

Kojima, Takahiko,Nakayama, Kazuya,Ikemura, Kenichiro,Ogura, Takashi,Fukuzumi, Shunichi American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.30

<P>A coordinatively saturated ruthenium(II) complex having tetradentate tris(2-pyridylmethyl)amine (TPA) and bidentate 2,2′-bipyridine (bpy), [Ru(TPA)(bpy)]<SUP>2+</SUP> (<B>1</B>), was oxidized by a Ce(IV) ion in H<SUB>2</SUB>O to afford a Ru(IV)-oxo complex, [Ru(O)(H<SUP>+</SUP>TPA)(bpy)]<SUP>3+</SUP> (<B>2</B>). The crystal structure of the Ru(IV)-oxo complex <B>2</B> was determined by X-ray crystallography. In <B>2</B>, the TPA ligand partially dissociates to be in a facial tridentate fashion and the uncoordinated pyridine moiety is protonated. The spin state of <B>2</B>, which showed paramagnetically shifted NMR signals in the range of 60 to −20 ppm, was determined to be an intermediate spin (<I>S</I> = 1) by the Evans’ method with <SUP>1</SUP>H NMR spectroscopy in acetone-<I>d</I><SUB>6</SUB>. The reaction of <B>2</B> with various oraganic substrates in acetonitrile at room temperature afforded oxidized and oxygenated products and a solvent-bound complex, [Ru(H<SUP>+</SUP>TPA)(bpy)(CH<SUB>3</SUB>CN)], which is intact in the presence of alcohols. The oxygenation reaction of saturated C–H bonds with <B>2</B> proceeds by two-step processes: the hydrogen abstraction with <B>2</B>, followed by the dissociation of the alcohol products from the oxygen-rebound complexes, Ru(III)-alkoxo complexes, which were successfully detected by ESI-MS spectrometry. The kinetic isotope effects in the first step for the reaction of dihydroanthrathene (DHA) and cumene with <B>2</B> were determined to be 49 and 12, respectively. The second-order rate constants of C–H oxygenation in the first step exhibited a linear correlation with bond dissociation energies of the C–H bond cleavage.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-30/ja2037645/production/images/medium/ja-2011-037645_0013.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja2037645'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja2037645'>ACS Electronic Supporting Info</A></P>

Photochemical Activation of Ruthenium(II)–Pyridylamine Complexes Having a Pyridine-<i>N</i>-Oxide Pendant toward Oxygenation of Organic Substrates

Kojima, Takahiko,Nakayama, Kazuya,Sakaguchi, Miyuki,Ogura, Takashi,Ohkubo, Kei,Fukuzumi, Shunichi American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.44

<P>Ruthenium(II)–acetonitrile complexes having η<SUP>3</SUP>-tris(2-pyridylmethyl)amine (TPA) with an uncoordinated pyridine ring and diimine such as 2,2′-bipyridine (bpy) and 2,2′-bipyrimidine (bpm), [Ru<SUP>II</SUP>(η<SUP>3</SUP>-TPA)(diimine)(CH<SUB>3</SUB>CN)]<SUP>2+</SUP>, reacted with <I>m</I>-chloroperbenzoic acid to afford corresponding Ru(II)–acetonitrile complexes having an uncoordinated pyridine-<I>N</I>-oxide arm, [Ru<SUP>II</SUP>(η<SUP>3</SUP>-TPA-O)(diimine)(CH<SUB>3</SUB>CN)]<SUP>2+</SUP>, with retention of the coordination environment. Photoirradiation of the acetonitrile complexes having diimine and the η<SUP>3</SUP>-TPA with the uncoordinated pyridine-<I>N</I>-oxide arm afforded a mixture of [Ru<SUP>II</SUP>(TPA)(diimine)]<SUP>2+</SUP>, intermediate-spin (<I>S</I> = 1) Ru(IV)–oxo complex with uncoordinated pyridine arm, and intermediate-spin Ru(IV)–oxo complex with uncoordinated pyridine-<I>N</I>-oxide arm. A Ru(II) complex bearing an oxygen-bound pyridine-<I>N</I>-oxide as a ligand and bpm as a diimine ligand was also obtained, and its crystal structure was determined by X-ray crystallography. Femtosecond laser flash photolysis of the isolated <I>O</I>-coordinated Ru(II)–pyridine-<I>N</I>-oxide complex has been investigated to reveal the photodynamics. The Ru(IV)–oxo complex with an uncoordinated pyridine moiety was alternatively prepared by reaction of the corresponding acetonitrile complex with 2,6-dichloropyridine-<I>N</I>-oxide (Cl<SUB>2</SUB>py-O) to identify the Ru(IV)–oxo species. The formation of Ru(IV)–oxo complexes was concluded to proceed via intermolecular oxygen atom transfer from the uncoordinated pyridine-<I>N</I>-oxide to a Ru(II) center on the basis of the results of the reaction with Cl<SUB>2</SUB>py-O and the concentration dependence of the consumption of the starting Ru(II) complexes having the uncoordinated pyridine-<I>N</I>-oxide moiety. Oxygenation reactions of organic substrates by [Ru<SUP>II</SUP>(η<SUP>3</SUP>-TPA-O)(diimine)(CH<SUB>3</SUB>CN)]<SUP>2+</SUP> were examined under irradiation (at 420 ± 5 nm) and showed selective allylic oxygenation of cyclohexene to give cyclohexen-1-ol and cyclohexen-1-one and cumene oxygenation to afford cumyl alcohol and acetophenone.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-44/ja207572z/production/images/medium/ja-2011-07572z_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja207572z'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja207572z'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja207572z'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja207572z'>ACS Electronic Supporting Info</A></P>

Modified pilot selection for channel estimation of systematic polar coded MIMO-OFDM

Koya Watanabe,Shun Kojima,Takashi Akao,Masato Katsuno,Kazuki Maruta,안창준 한국통신학회 2019 ICT Express Vol.5 No.4

This paper proposes a modified pilot selection for channel estimation of systematic polar coded MIMO-OFDM. Polar codes provably achieve the theoretical limit for communication systems and systematic polar codes generate the codeword that has the same value of information bit. Using this property, an efficient channel estimation scheme was proposed; values of some information bits are fixed to zeros or ones and utilized for pilot symbols. Similarly, we also can fix values of some frozen bit as zeros or ones by exploiting features of the encoding generator. By combining these advantages, pilot signals are selected from the systematic polar coded symbols themselves and we do not need add and insert pilot symbols just to estimate the channel. Leveraging this, we apply the proposed systematic polar coding scheme to MIMO-OFDM system under frequency selective fading channel.

Risk factors for severity of colonic diverticular hemorrhage

Ken Kinjo,Toshiyuki Matsui,Takashi Hisabe,Hiroshi Ishihara,Toshiki Kojima,Kenta Chuman,Shigeyoshi Yasukawa,Tsuyoshi Beppu,Akihiro Koga,Satoshi Ishikawa,Masahiro Kishi,Noritaka Takatsu,Fumihito Hirai,K 대한장연구학회 2018 Intestinal Research Vol.16 No.3

Background/Aims: Colonic diverticular hemorrhage (DH) was a rare disease until the 1990s, and its incidence has increased rapidly since 2000 in Japan. In recent years, colonic DH has been the most frequent cause of lower gastrointestinal bleeding (LGIB). Nearly all cases of DH are mild, with the bleeding often stopping spontaneously. Some cases, however, require surgery or arterial embolization. In this study, using a cohort at Fukuoka University Chikushi Hospital, we investigated factors associated with severe colonic DH. Methods: Among patients with LGIB who underwent colonoscopy at our hospital between 1995 and 2013, DH was identified in 273 patients. Among them, 62 patients (22.7%) were defined as having severe colonic DH according to recurrence of bleeding in a short period, and/or the necessity of transfusion, arterial embolization, or surgery. We then evaluated risk factors for severe DH among DH patients in this retrospective cohort. Results: Among the 273 patients with DH, use of non-steroidal anti-inflammatory drugs (NSAIDs) (odds ratio [OR], 2.801; 95% confidence interval [CI], 1.164–6.742), Charlson Risk Index (CRI) ≥2 (OR, 3.336; 95% CI, 1.154–7.353), right-sided colonic DH (OR, 3.873; 95% CI, 1.554–9.653), and symptoms of cerebral hypoperfusion (such as light-headedness, dizziness, or syncope) (OR, 2.926; 95% CI, 1.310–6.535) showed an increased risk of severe DH even after controlling for other factors. Conclusions: Severe DH occurred in 23% of DH patients, and NSAID use, CRI ≥2, right-sided colonic DH, and symptoms of cerebral hypoperfusion are suggested to be predictors of severe DH.

Time evolution of radical deposition rate and cluster amount

Masaharu SHIRATANI,Susumu TOKO,Yoshihiro TORIGOE,Kimitaka KEYA,Takashi KOJIMA,Hyunwoong SEO,Naho ITAGAKI,Kazunori KOGA 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8