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61.
Subramanian S Devasahayam N McMillan A Matsumoto S Munasinghe JP Saito K Mitchell JB Chandramouli GV Krishna MC 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2012,214(1):244-251
Oxygen maps derived from electron paramagnetic resonance spectral-spatial imaging (EPRI) are based upon the relaxivity of molecular oxygen with paramagnetic spin probes. This technique can be combined with MRI to facilitate mapping of pO(2) values in specific anatomic locations with high precision. The co-registration procedure, which matches the physical and digital dimensions of EPR and MR images, may present the pO(2) map at the higher MRI resolution, exaggerating the spatial resolution of oxygen, making it difficult to precisely distinguish hypoxic regions from normoxic regions. The latter distinction is critical in monitoring the treatment of cancer by radiation and chemotherapy, since it is well-established that hypoxic regions are three or four times more resistant to treatment compared to normoxic regions. The aim of this article is to describe pO(2) maps based on the intrinsic resolution of EPRI. A spectral parameter that affects the intrinsic spatial resolution of EPRI is the full width at half maximum (FWHM) height of the gradient-free EPR absorption line in frequency-encoded imaging. In single point imaging too, the transverse relaxation times (T(2)(?)) limit the resolution since the signal decays by exp(-t(p)/T(2)(?)) where the delay time after excitation pulse, t(p), is related to the resolution. Although the spin densities of two point objects may be resolved at this separation, it is inadequate to evaluate quantitative changes of pO(2) levels since the linewidths are proportionately affected by pO(2). A spatial separation of at least twice this resolution is necessary to correctly identify a change in pO(2) level. In addition, the pO(2) values are blurred by uncertainties arising from spectral dimensions. Blurring due to noise and low resolution modulates the pO(2) levels at the boundaries of hypoxic and normoxic regions resulting in higher apparent pO(2) levels in hypoxic regions. Therefore, specification of intrinsic resolution and pO(2) uncertainties are necessary to interpret digitally processed pO(2) illustrations. 相似文献
62.
Sakakibara K Nakatsubo F French AD Rosenau T 《Chemical communications (Cambridge, England)》2012,48(62):7672-7674
Right-handedness derived from bisporphyrins attached to a cellotriose backbone at O-6 and O'-6 positions is revealed for the first time. This cellotriose is proposed as a model of alternatingly functionalized cellulosics, which have promising properties for applications in optoelectronics and molecular receptors owing to the chirality and rigid backbone effects. 相似文献
63.
Shusuke Yamanaka Keita Kanda Toru Saito Yasutaka Kitagawa Takashi Kawakami Masahiro Ehara Mitsutaka Okumura Haruki Nakamura Kizashi Yamaguchi 《Chemical physics letters》2012
We assessed the applicability and basis set dependency of the B3LYP functional to investigate magnetic interactions of Mn complexes. For the purpose, we constructed a test set consisting of 16 Mn complexes with various oxidation states and structural motifs.The B3LYP results correctly reproduced magnetism and magneto–redox correlation of the standard μ-oxo motifs with superexchange paths, while it does not work for weak magnetic complexes. We also showed that a modest basis set yields results similar to those of triple-zeta plus diffuse-and-polarization functions. This basis set is expected to be a standard basis set for investigating magnetism of manganese complexes. 相似文献
64.
Keita Sakakibara Yasuhiro Ogawa Fumiaki Nakatsubo 《Macromolecular rapid communications》2007,28(11):1270-1275
Langmuir‐Blodgett films of a cellulose derivative containing porphyrins, porphyrin‐cellulose, were fabricated in order to construct a cellulose‐based molecular photocurrent generation system. On visible light illumination of the LB monolayer film deposited on an ITO electrode, anodic photocurrents were observed with a quantum yield of 1.6% at an applied potential of 0 V versus SCE, and 3.8–4.6% at 0.2–0.3 V versus SCE. These values indicate that the self‐quenching of the photoexcited porphyrins in the cellulose LB film was suppressed, while porphyrin moieties in the LB film had a densely packed structure. This is because the porphyrins are located at a distance of approximately 1.0 nm along the cellulose backbone.
65.
Keita Saito Yoshiyuki Tokorodani Chihiro Sakamoto Hiroyuki Kataoka 《Molecules (Basel, Switzerland)》2021,26(19)
The odors and emanations released from the human body can provide important information about the health status of individuals and the presence or absence of diseases. Since these components often emanate from the body surface in very small quantities, a simple sampling and sensitive analytical method is required. In this study, we developed a non-invasive analytical method for the measurement of the body odor component 2-nonenal by headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry by selective ion monitoring. Using a StableFlex PDMS/DVB fiber, 2-nonenal was efficiently extracted and enriched by fiber exposition at 50 °C for 45 min and was separated within 10 min using a DB−1 capillary column. Body odor sample was easily collected by gauze wiping. The limit of detection of 2-nonenal collected in gauze was 22 pg (S/N = 3), and the linearity was obtained in the range of 1–50 ng with a correlation coefficient of 0.991. The method successfully analyzed 2-nonenal in skin emissions and secretions and was applied to the analysis of body odor changes in various lifestyles, including the use of cosmetics, food intake, cigarette smoking, and stress load. 相似文献
66.
Bineta Keita Essadik Abdeljalil François Girard Sophie Gerschwiler Louis Nadjo Roland Contant Christian Haut 《Journal of Solid State Electrochemistry》1999,3(7-8):446-456
New oxide films have been electrodeposited from [P2Mo18O62]6− by potential cycling in mildly acidic aqueous media. To obtain an adherent and persistent film, it is necessary that more
than six electrons/molecule be fixed on the framework of the heteropolyanion. The film is then studied in pure supporting
electrolyte. In this medium, a remarkable current increase is observed during the potential cycling. Whether the film is deposited
on a glassy carbon electrode or on the gold electrode of an electrochemical quartz crystal microbalance (EQCM), exactly the
same steady current increase up to a maximum is obtained in cyclic voltammetric measurements. The EQCM reveals a steady mass
increase during the continuous cycling of the film in the supporting electrolyte. This behaviour is interpreted as featuring
an irreversible water and electrolyte intake into the film, up to a maximum, after which the phenomena observed during reduction
and oxidation processes are taken as featuring intercalation/deintercalation, respectively. This behaviour is much the same
as described in the literature for WO3 and MoO3 bronzes, except that the present films seem very stable and have shown no tendency to dissolve or deactivate.
Received: 2 December 1998 / Accepted: 26 January 1999 相似文献
67.
Keita Yokoyama 《Mathematical Logic Quarterly》2007,53(2):132-146
This research is motivated by the program of reverse mathematics and non‐standard arguments in second‐order arithmetic. Within a weak subsystem of second‐order arithmetic ACA0, we investigate some aspects of non‐standard analysis related to sequential compactness. Then, using arguments of non‐standard analysis, we show the equivalence of the Riemann mapping theorem and ACA0 over WKL0. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
68.
Strain‐Induced Double Carbon–Carbon Bond Activations of Cycloparaphenylenes by a Platinum Complex: Application to the Synthesis of Cyclic Diketones 下载免费PDF全文
Dr. Eiichi Kayahara Toshiki Hayashi Dr. Katsuhiko Takeuchi Prof. Dr. Fumiyuki Ozawa Keita Ashida Prof. Dr. Sensuke Ogoshi Prof. Dr. Shigeru Yamago 《Angewandte Chemie (International ed. in English)》2018,57(35):11418-11421
The carbon–carbon (C?C) bond activation of [n]cycloparaphenylenes ([n]CPPs) by a transition‐metal complex is herein reported. The Pt0 complex Pt(PPh3)4 regioselectively cleaves two C?C σ bonds of [5] CPP and [6]CPP to give cyclic dinuclear platinum complexes in high yields. Theoretical calculations reveal that the relief of ring strain drives the reaction. The cyclic complex was further transformed into a cyclic diketone by using a CO insertion reaction. 相似文献
69.
Keita Sakamoto Akihiro Hakamata Prof. Dr. Masashi Tsuda Prof. Dr. Haruhiko Fuwa 《Angewandte Chemie (International ed. in English)》2018,57(14):3801-3805
Total syntheses of the proposed and correct structures of iriomoteolide‐2a, a cytotoxic marine macrolide natural product with an unusual 23‐membered macrolactone skeleton, have been accomplished for the first time. The synthesis of the correct structure involves an asymmetric epoxidation/diepoxide cyclization cascade for the construction of the bis(tetrahydrofuran) moiety, a Suzuki–Miyaura coupling for the fragment assembly, and a ring‐closing metathesis for the closure of the macrocyclic backbone. In addition, the original stereochemical assignment of iriomoteolide‐2a was revised. 相似文献
70.