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261.
T. P. Cheng H. D. Anderson D. S. Mills V. L. Spate C. K. Baskett J. S. Morris 《Journal of Radioanalytical and Nuclear Chemistry》1997,217(2):171-174
An instrumental neutron activation analysis (INAA) technique, based on the19F(n,)20F reaction, has been development for the determination of fluoride in bone. The purpose was to study fluoride distribution in different kinds of bone samples using a rabbit model. The rationale for the study stems from the posible correlation between fluoride in bone and osteoporosis. The sodium concentration in the bone was used to correct the20F peak area for the23F(n,)20F contribution. Two secondary standards, teflon tape and teflon coated dacron line, were used to quantify fluoride concentration. They proved to be stable and consistent with respect to their fluoride concentration. Bone specimens from 10 sites and two tooth samples were analyzed for fluoride. Fluoride concentration ranged from 305 ppm in the tibia long bone to 585 ppm in the humerus trochanter end and the magnitude of fluoride concentration levels is age depdentent. The detection limit of the fluoride is approximately 5 ppm using a 100 mg bone sample. 相似文献
262.
用定量体积排除色谱方法研究了过渡金属Fe(Ⅲ)、Co(Ⅲ)、Cu(Ⅱ)、Ni(Ⅱ)的乙酰丙酮螯合物在四氢呋喃溶液中的加合和缔合行为。在溶液中乙酰丙酮钴(Ⅲ)以单个螯合物分子的形式存在,乙酰丙酮铜(Ⅱ)和乙酰丙酮铁(Ⅲ)与溶剂加合生成加合物,乙酰丙酮铁(Ⅲ)除加合物外还存在缔合度为2-10的多分散缔合物,乙酰丙酮镍(Ⅱ)水合物在四氢呋喃中产生了加合交换作用,同时存在缔合度为6左右的缔合物。色谱数据给出了螯合物、加合物及缔合物 相似文献
263.
From the wood of Taiwania cryptomerioides Hayata, two new sesquiterpenes, cadinan-3β, 9β-diol and cadinan-3β, 9α-diol were isolated as minor components. Their structures were elucidated as (I) and (II), respectively. 相似文献
264.
Effects of double substitution on the thermodynamic stabilities of nitrogen radicals 总被引:1,自引:0,他引:1
Studiesonkineticsofradicalreactions[1]andonCHbonddissociationenergies(BDE)[2]haveshownthatcarbonradicalsarestabilizedbyeitheranelectrondonatinggroup(EDG)oranelectronwithdrawinggroup(EWG),andthatifacarbonradicalissubstitutedwithbothanEDGandanEWGatthesamecen… 相似文献
265.
Propane fuel cells using H(3)PO(4)-doped polybenzimidazole polymer membranes produce low and unsustainable current densities at temperatures up to 250 degrees C under anhydrous conditions. Stable intermediate species blocked the surface of noble metal anode catalysts, and the intermediate species could not react further into desorbable final products. In contrast, when water was introduced by light humidification (S(r) 0.08%) of the propane stream, sustainable and higher current densities were achieved. Water participated in the reaction sequence to form surface-bound hydrocarbon and then oxygen-containing intermediates and thereby generated CO and CO(2) as the only carbon-containing products. 相似文献
266.
Shihui Si Fenglian Ren Wen Cheng Shouzhuo Yao 《Analytical and bioanalytical chemistry》1997,357(8):1101-1105
To obtain new coatings for the preparation of piezoelectric immunosensors, the anodic polymerization of o-aminophenol (oAP),
o-phenylenediamine (oPD) and m-phenylenediamine (mPD) onto a gold-plated crystal has been studied. The possibility of immobilizing
an antibody (anti-S. paratyphi A) onto the crystal via the electropolymerized films was investigated. The poly-mPD film gave
the best results for immobilizing the antibody. With antibodies crosslinked on the poly-mPD film, a piezoelectric immuno-assay
for the detection of S. paratyphi A was proposed. The shift (ΔF=F20s−F400s, Hz) between the frequency at 20 s after the addition of sample (F20s), and that of 400 s (F400s) was used to construct a calibration graph, and shortening of the assay time was achieved. The S. paratyphi A concentration
in the range of 105–109 cells/ml can be measured by this method.
Received: 9 May 1996/Revised: 6 September 1996/Accepted: 19 September 1996 相似文献
267.
Yee AA Savchenko A Ignachenko A Lukin J Xu X Skarina T Evdokimova E Liu CS Semesi A Guido V Edwards AM Arrowsmith CH 《Journal of the American Chemical Society》2005,127(47):16512-16517
NMR spectroscopy and X-ray crystallography, the two primary experimental methods for protein structure determination at high resolution, have different advantages and disadvantages in terms of sample preparation and data collection and analysis. It is therefore of interest to assess their complementarity when applied to small proteins. Structural genomics/proteomics projects provide an ideal opportunity to make such comparisons as they generate data in a systematic manner for large enough numbers of proteins to allow firm conclusions to be drawn. Here we report a comparison for 263 unique proteins screened by both NMR spectroscopy and X-ray crystallography in our structural proteomics pipeline. Only 21 targets (8%) were deemed amenable to both methods based on an initial 2D 15N-HSQC NMR spectrum and optimized crystallization trials. However, the use of both methods in the pipeline increased the total number of targets amenable to structure determination to 107, with 43 amenable to NMR only and 43 amenable to X-ray crystallographic methods only. We did not observe a correlation between 15N-HSQC spectral quality and the success of the same protein in crystallization screens. Similar results were found for an independent set of 159 proteins as reported in the accompanying paper by Snyder et al. Thus, we conclude that both methods are highly complementary, and in order to increase the number of proteins suited for structure determination, we suggest that both methods be used in parallel in screening of all small proteins for structure determination. 相似文献
268.
269.
The boxes contained kiwifruits were irradiated with cobalt-60 γ-rays at different dosages (0.6 , 1.8 and 3.6 KGy) and stored in a room ventilated at night, the natural ambient air being used as cool source.The results showed that the treatment which fruits irradiated with 0.6 KGy was the best after 85 days. It gave the normal-fruit rate of 95.10%, fruit flesh hardness of 4.10 Kg · cm-2, fresh and plump fruits, good quality and less Vc loss. 相似文献
270.
应用核磁共振和电子自旋共振技术研究了铜锌超氧化物歧化酶(CuZnSOD)的金属重组酶与水溶液中游离组氨酸(His)的相互作用。发现在水溶液中CuZnSOD的金属重组酶活性中心的金属可与加入的His发生作用而被部分地诱导出来,与His形成络合物。 相似文献