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571.
We study spherically symmetric solutions in a covariant massive gravity model, which is a candidate for a ghost-free nonlinear completion of the Fierz-Pauli theory. There is a branch of solutions that exhibits the Vainshtein mechanism, recovering general relativity below a Vainshtein radius given by (r(g)m(2))(1/3), where m is the graviton mass and r(g) is the Schwarzschild radius of a matter source. Another branch of exact solutions exists, corresponding to de Sitter-Schwarzschild spacetimes where the curvature scale of de Sitter space is proportional to the mass squared of the graviton. 相似文献
572.
Koyama H Siqin Zhang Z Sumi K Hatta Y Nagata H Doi H Suzuki M 《Organic & biomolecular chemistry》2011,9(11):4287-4294
Pd(0)-mediated rapid couplings of CH(3)I (and then [(11)C]CH(3)I) with excess 5-tributylstannyl-2'-deoxyuridine and -4'-thio-2'-deoxyuridine were investigated for the syntheses of [methyl-(11)C]thymidine and its stable analogue, 4'-[methyl-(11)C]thiothymidine as PET probes for cancer diagnosis. The previously reported conditions were attempted using Pd(2)(dba)(3)/P(o-CH(3)C(6)H(4))(3) (1?:?4 in molar ratio) at 130 °C for 5 min in DMF, giving desired products only in 32 and 30% yields. Therefore, we adapted the current reaction conditions developed in our laboratory for heteroaromatic compounds. The reaction using CH(3)I/stannane/Pd(2)(dba)(3)/P(o-CH(3)C(6)H(4))(3)/CuCl/K(2)CO(3) (1?:?25?:?1?:?32?:?2?:?5) at 80 °C gave thymidine in 85% yield. Whereas, CH(3)I/stannane/Pd(2)(dba)(3)/P(o-CH(3)C(6)H(4))(3)/CuBr/CsF (1?:?25?:?1?:?32?:?2?:?5) including another CuBr/CsF system promoted the reaction at a milder temperature (60 °C), giving thymidine in 100% yield. Chemo-response of thiothymidine-precursor was different from thymidine system. Thus, the above optimized conditions including CuBr/CsF system gave 4'-thiothymidine only in 40% yield. The reaction using 5-fold amount of CuBr/CsF at 80 °C gave much higher yield (83%), but unexpectedly, the reaction was accompanied by a considerable amount of undesired destannylated product. Such destannylation was greatly suppressed by changing to a CuCl/K(2)CO(3) system using CH(3)I/stannane/Pd(2)(dba)(3)/P(o-CH(3)C(6)H(4))(3)/CuCl/K(2)CO(3) (1?:?25?:?1?:?32?:?2?:?5) at 80 °C, giving the 4'-thiothymidine in 98% yield. The each optimized conditions were successfully applied to the syntheses of the corresponding PET probes in 87 and 93% HPLC analytical yields. [(11)C]Compounds were isolated by preparative HPLC after the reaction conducted under slightly improved conditions, exhibiting sufficient radioactivity of 3.7-3.8 GBq and specific radioactivity of 89-200 GBq μmol(-1) with radiochemical purity of ≥99.5% for animal and human PET studies. 相似文献
573.
574.
Ohshima N Koyama T Tanigawa H Kotsugi M Ohkouchi T Chiba D Kinoshita T Ono T 《J Phys Condens Matter》2011,23(38):382202
Current-induced magnetic domain wall (DW) displacement in a Co/Ni nano-wire with perpendicular magnetic anisotropy was investigated in real space by photoemission electron microscopy (PEEM) for the first time. DW velocity determined from the PEEM observation was 40?m?s(-1) for the current density of 2.5?×?10(12)?A?m(-2), which was consistent with the result obtained by the electrical measurement used in our previous reports. 相似文献
575.
Tamio Koyama Hiromasa Nakayama Kenta Nishiyama Nobuki Takayama 《Computational Statistics》2014,29(3-4):661-683
We propose an accelerated version of the holonomic gradient descent and apply it to calculating the maximum likelihood estimate (MLE) of the Fisher–Bingham distribution on a \(d\) -dimensional sphere. We derive a Pfaffian system (an integrable connection) and a series expansion associated with the normalizing constant with an error estimation. These enable us to solve some MLE problems up to dimension \(d=7\) with a specified accuracy. 相似文献
576.
Katsunori Tanaka Kaori Minami Tsuyoshi Tahara Eric R. O. Siwu Koichi Koyama Satoshi Nozaki 《Journal of carbohydrate chemistry》2013,32(3):118-132
A Combined 6π-Azaelectrocyclization/Staudinger Approach to Protein and Cell Engineering: Noninvasive Tumor Targeting by N-Glycan-Engineered Lymphocytes
Published online:
02 June 2010 Graphical Abstract 相似文献
577.
Toshiyuki Fujii Takeshi Uda Kazuhito Fukasawa Akihiro Uehara Nobuaki Sato Takayuki Nagai Kensuke Kinoshita Tadafumi Koyama Hajimu Yamana 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(1):255-259
As an analytical application for pyrochemical reprocessing using molten salts, quantitative analysis of uranium and lanthanides by UV/Vis/NIR absorption spectrophotometry was performed. Electronic absorption spectra of LiCl–KCl eutectic at 773 K including trivalent uranium and eight rare earth elements (Y, La, Ce, Pr, Nd, Sm, Eu, and Gd as fission product elements) were measured in the wavenumber region of 4,500–33,000 cm?1. The composition of the solutes was simulated for a reductive extraction condition in a pyroreprocessing process for spent nuclear fuels, that is, about 2 wt% U and 0.1–2 wt% rare earth elements. Since U(III) possesses strong absorption bands due to f–d transitions, an optical quartz cell with short light path length of 1 mm was adopted in the analysis. The quantitative analysis of trivalent U, Nd, Pr, and Sm was possible with their f–f transition intensities in the NIR region. The analytical results agree with the prepared concentrations within 2σ experimental uncertainties. 相似文献
578.
Kaneko S Ito T Hirabayashi Y Ozawa T Okuda T Motoizumi Y Hirai K Naganuma Y Soga M Yoshimoto M Suzuki K 《Talanta》2011,84(2):579-582
Metal oxide nanoparticles prepared by pulsed laser deposition (PLD) were applied to nonenzymatic glucose detection. NiO nanoparticles with size of 3 nm were deposited on glassy carbon (GC) and silicon substrates at room temperature in an oxygen atmosphere. Transmission electron microscope (TEM) image showed nanoparticles with the size of 3 nm uniformly scattered on the Si(0 0 1) substrate. Unlike co-sputtering nanoparticle and carbon simultaneously, the PLD method can easily control the surface coverage of nanoparticles on the surface of substrate by deposition time. Cyclic voltammetry was performed on the samples deposited on the GC substrates for electrochemical detection of glucose. The differences between peak currents with and without glucose was used to optimize the coverage of nanoparticles on carbon electrode. The results indicated that optimal coverage of nanoparticles on carbon electrode. 相似文献
579.
Ishiwari F Fukasawa K Sato T Nakazono K Koyama Y Takata T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(43):12067-12075
Directed helicity control of a polyacetylene dynamic helix was achieved by hybridization with a rotaxane skeleton placed on the side chain. Rotaxane-tethering phenylacetylene monomers were synthesized in good yields by the ester end-capping of pseudorotaxanes that consisted of optically active crown ethers and sec-ammonium salts with an ethynyl benzoic acid. The monomers were polymerized with [{RhCl(nbd)}(2)] (nbd=norbornadiene) to give the corresponding polyacetylenes in high yields. Polymers with optically active wheel components that are far from the main chain show no Cotton effect, thereby indicating the formation of racemic helices. Our proposal that N-acylative neutralization of the sec-ammonium moieties of the side-chain rotaxane moieties enables asymmetric induction of a one-handed helix as the wheel components approach the main chain is strongly supported by observation of the Cotton effect around the main-chain absorption region. A polyacetylene with a side-chain rotaxane that has a shorter axle component shows a Cotton effect despite the ammonium structure of the side-chain rotaxane moiety, thereby suggesting the importance of proximity between the wheel and the main chain for the formation of a one-handed helix. Through-space chirality induction in the present systems proved to be as powerful as through-bond chirality induction for formation of a one-handed helix, as demonstrated in an experiment using non-rotaxane-based polyacetylene that had an optically active binaphthyl group. The present protocol for controlling the helical structure of polyacetylene therefore provides the basis for the rational design of one-handed helical polyacetylenes. 相似文献
580.
We formulate a macroscopic quantum theory that can describe the macroscopic quantum tunneling (MQT) in intrinsic Josephson junctions (IJJs). The capacitively coupled IJJ model is quantized in terms of the canonical quantization method. The multi-junction effect for the MQT to the first resistive branch is clarified. It is shown that the escape rate is greatly enhanced by the capacitive coupling between junctions. 相似文献