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排序方式: 共有775条查询结果,搜索用时 11 毫秒
1.
Hiroshi Yamauchi Keiko Takahashi Mari Mashiko Juichiro Saitoh Yukio Yamamura 《应用有机金属化学》1992,6(4):383-388
We calculated the intake of each chemical species of dietary arsenic by typical Japanese, and determined urinary and blood levels of each chemical species of arsenic. The mean total arsenic intake by 35 volunteers was 195±235 (15.8-1039) μg As day?1, composed of 76% trimethylated arsenic (TMA), 17.3% inorganic arsenic (Asi), 5.8% dimethylated arsenic (DMA), and 0.8% monomethylated arsenic (MA): the intake of TMA was the largest of all the measured species. Intake of Asi characteristically and invariably occurred in each meal. Of the intake of Asi, 45-75% was methylated in vivo to form MA and DMA, and excreted in these forms into urine. The mean measured urinary total arsenic level in 56 healthy volunteers was 129±92.0 μg As dm?3, composed of 64.6% TMA, 26.7% DMA, 6.7% Asi and 2.2% MA. The mean blood total arsenic level in the 56 volunteers was 0.73±0.57 μg dl?1, composed of 73% TMA, 14% DMA and 9.6% Asi. The urinary TMA levels proved to be significantly correlated with the whole-blood TMA levels (r = 0.376; P<0.01). 相似文献
2.
Mari Carmen Domingo 《Wireless Personal Communications》2011,57(4):607-627
The design of routing protocols for Underwater Wireless Sensor Networks (UWSNs) poses many challenges due to the intrinsic properties of underwater environments. In this paper we present DUCS (Distributed Underwater Clustering Scheme), a new GPS-free routing protocol that does not use flooding techniques, minimizes the proactive routing message exchange and uses data aggregation to eliminate redundant information. Besides, DUCS assumes random node mobility and compensates the high propagation delays of the underwater medium using a continually adjusted timing advance combined with guard time values to minimize data loss. The theoretical and simulation studies carried out demonstrate its effectiveness. 相似文献
3.
4.
L.?Marié J.?Burguete F.?DaviaudEmail author J.?Léorat 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(4):469-485
A numerical study of the magnetic induction equation has
been performed on von Kármán type flows. These flows are
generated by two co-axial counter-rotating propellers in
cylindrical containers. Such devices are currently used in the
von Kármán sodium (VKS) experiment designed to study dynamo
action in an unconstrained flow. The mean velocity fields have
been measured for different configurations and are introduced in
a periodic cylindrical kinematic dynamo code. Depending on the
driving configuration, on the poloidal to toroidal flow ratio
and on the conductivity of boundaries, some flows are observed
to sustain growing magnetic fields for magnetic Reynolds numbers
accessible to a sodium experiment. The response of the flow to
an external magnetic field has also been studied: The results
are in excellent agreement with experimental results in the
single propeller case but can differ in the two propellers case. 相似文献
5.
Stephan?Dahlke Filippo?De Mari Ernesto?De Vito S?ren?H?userEmail author Gabriele?Steidl Gerd?Teschke 《Journal of Geometric Analysis》2016,26(3):1693-1729
Recently, shearlet groups have received much attention in connection with shearlet transforms applied for orientation sensitive image analysis and restoration. The square integrable representations of the shearlet groups provide not only the basis for the shearlet transforms but also for a very natural definition of scales of smoothness spaces, called shearlet coorbit spaces. The aim of this paper is twofold: first we discover isomorphisms between shearlet groups and other well-known groups, namely extended Heisenberg groups and subgroups of the symplectic group. Interestingly, the connected shearlet group with positive dilations has an isomorphic copy in the symplectic group, while this is not true for the full shearlet group with all nonzero dilations. Indeed we prove the general result that there exist, up to adjoint action of the symplectic group, only one embedding of the extended Heisenberg algebra into the Lie algebra of the symplectic group. Having understood the various group isomorphisms it is natural to ask for the relations between coorbit spaces of isomorphic groups with equivalent representations. These connections are examined in the second part of the paper. We describe how isomorphic groups with equivalent representations lead to isomorphic coorbit spaces. In particular we apply this result to square integrable representations of the connected shearlet groups and metaplectic representations of subgroups of the symplectic group. This implies the definition of metaplectic coorbit spaces. Besides the usual full and connected shearlet groups we also deal with Toeplitz shearlet groups. 相似文献
6.
Ai Jia Yang Xiao Jianying Hu Mari Asami Shoichi Kunikane 《Journal of chromatography. A》2009,1216(22):4655-4662
A sensitive method was developed for the trace determination of six tetracyclines and ten of their degradation products in influent, effluent, and river waters using liquid chromatography–electrospray tandem mass spectrometry detection, combined with Oasis hydrophilic–lipophilic balance (HLB) cartridge extraction and Oasis mixed-mode strong anion exchange (MAX) cartridge cleanup. Tetracyclines and their products were separated by liquid chromatography in 9.5 min, and the instrument detection limits were generally between 0.03 and 0.1 μg/L except for minocycline (0.5 μg/L). The chromatograms were improved through the MAX cleanup and no apparent matrix effect was found. The recoveries of all the target compounds except for 4-epianhydrochlortetracycline and anhydrochlortetracycline (34–52%) were 75–120% for influent, 61–103% for effluent, and 64–113% for river waters. The method detection limits (MDLs) of the analytes varied in the range of 0.8–17.5 ng/L in all studied matrices. The method was applied for the determination of tetracyclines and their products in a sewage treatment plant (STP) and surface waters in Beijing, China. Oxytetracycline (3.8–72.5 ng/L), tetracycline (1.9–16.5 ng/L), and five products including 4-epitetracycline, 4-epioxytetracycline, isochlortetracycline, anhydrotetracycline, and 4-epianhydrochlortetracycline (5.7–25.3 ng/L) were detected in wastewater, while only oxytetracycline and tetracycline (2.2 and 2.1 ng/L) were detected in surface water samples. 相似文献
7.
Ab initio calculations are performed to understand the geometry, electronic structure, and vibrational frequencies of nickel
porphyrin (NiP). Hartree-Fock (HF) and second-order perturbation (MP2) theories are applied with polarized basis sets. The
calculated geometrical parameters are in very good agreement with the crystal structure determination. The electronic structure
and bonding are analyzed in terms of complexation and correlation effects. Not unexpectedly, the HF depiction of the metal-porphyrin
interaction is rather ionic while ligand σ donation is dominant at the MP2 level. Scaled HF frequencies of NiP and its isotopomers
are in very good agreement with observed infrared and resonance Raman data.
Received: 7 January 1997 / Accepted: 6 May 1997 相似文献
8.
Mariko Kitajima Tomomi Yanagisawa Mari Tsukahara Yasuka Yamaguchi Noriyuki Kogure Ruri Kikura-Hanajiri Yukihiro Goda Osamu Iida Yasushi Sugimura Nobuo Kawahara Hiromitsu Takayama 《Tetrahedron》2018,74(4):441-452
Three new biphenyl ether quinolizidine lactone alkaloids (1–3) and 13 new biphenyl quinolizidine lactone alkaloids (4–16) were isolated from Heimia salicifolia (Lythraceae) together with seven known alkaloids. Their structures were determined by spectroscopic analyses and chemical conversions. 相似文献
9.
Ryuji Hirase Koji Honda Mari Ishihara Hideki Yoshioka Hirosato Monobe 《Tetrahedron letters》2018,59(5):469-472
We have investigated synthesis as well as purification of 5,5?-bis(tridecafluorohexyl)-2,2′:5′,2″:5″,2?-quaterthiophene (BFH-4?T, n-type organic semiconducting material) using supercritical carbon dioxide (scCO2) as a green solvent. BFH-4T was obtained in good selectivity and high yield by TDAE/PdCl2-catalyzed reductive coupling reaction of 5-bromo-5′-(tridecafluorohexyl)-2,2′-bithiophene in scCO2. We have also successfully established purification of the reaction mixture by passing scCO2 in the reaction vessel. The product was yellow powder of BFH-4T with purity of more than 99% and Pd catalyst was not contained. 相似文献
10.
Kinumi T Goto M Eyama S Kato M Kasama T Takatsu A 《Analytical and bioanalytical chemistry》2012,404(1):13-21
A certified reference material (CRM) is a higher-order calibration material used to enable a traceable analysis. This paper describes the development of a C-peptide CRM (NMIJ CRM 6901-a) by the National Metrology Institute of Japan using two independent methods for amino acid analysis based on isotope-dilution mass spectrometry. C-peptide is a 31-mer peptide that is utilized for the evaluation of β-cell function in the pancreas in clinical testing. This CRM is a lyophilized synthetic peptide having the human C-peptide sequence, and contains deamidated and pyroglutamylated forms of C-peptide. By adding water (1.00 ± 0.01) g into the vial containing the CRM, the C-peptide solution in 10 mM phosphate buffer saline (pH 6.6) is reconstituted. We assigned two certified values that represent the concentrations of total C-peptide (mixture of C-peptide, deamidated C-peptide, and pyroglutamylated C-peptide) and C-peptide. The certified concentration of total C-peptide was determined by two amino acid analyses using pre-column derivatization liquid chromatography-mass spectrometry and hydrophilic chromatography-mass spectrometry following acid hydrolysis. The certified concentration of C-peptide was determined by multiplying the concentration of total C-peptide by the ratio of the relative area of C-peptide to that of the total C-peptide measured by liquid chromatography. The certified value of C-peptide (80.7 ± 5.0) mg/L represents the concentration of the specific entity of C-peptide; on the other hand, the certified value of total C-peptide, (81.7 ± 5.1) mg/L can be used for analyses that does not differentiate deamidated and pyroglutamylated C-peptide from C-peptide itself, such as amino acid analyses and immunochemical assays. 相似文献