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941.
Pao-Shu Chang Chien Chung Lig-Ji Yuan Pao-Shan Weng 《Journal of Radioanalytical and Nuclear Chemistry》1985,92(2):343-356
This work describes a nuclear facility forin vivo prompt gamma activation analysis (IVPGAA) using a moderated neutron beam from a 0.1 W Tsing-Hua Mobile Educational Reactor (THMER). The IVPGAA measurement is a new technique for toxic cadmium determination in organs, which can efficiently be used in clinical diagnosis. The low-power nuclear reactor provides a total neutron flux of 3.3·104 n·cm–2·s–1 on the surface of the central vertical neutron beam tube to which a liquid phantom is positioned. The capability of such partial-body irradiation facility is demonstrated. The detection limit of cadmium in the left kidney for a skin dose equivalent of 1.66 mSv (166 mrem) was 1.34 mg in a 500-s irradiation/counting period, and the sensitivity in the left kidney was 103 counts mg–1·mSv–1. The performance of IVPGAA system using the THMER nuclear facility therefore has the advantages of mobility and feasibility with high sensitivity under low neutron and gamma doses. 相似文献
942.
Instead of environmentally toxic chromium oxidant, singlet oxygen generated photcchemically was used as environmentally friendly and benign oxidizing agent to accomplish the transformation of pseudodiosgenin diacetate to diosone efficiently in a low toxic and less expensive solvent acetone. Accordingly 16-dehydropregnenolone acetate(16-DPA), an important intermediate for preparation of steroidal drugs, was prepared in good yield (75%) when photoreaction was run in acetone/acetic anhydride/pyridine system. The mild reaction condition as well as simple and environmentally friendly process made the method commercially viable and important for production of 16-DPA in industrial scale. 相似文献
943.
La2O(CN2)2 was synthesized from a 1:1:2 molar reaction mixture of LaCl3, LaOCl, and Li2(CN2) at 650 °C. Well developed single crystals were grown from a LiCl‐KCl flux. The crystal structure was refined as monoclinic (space group C2/c, Z = 2, a = 13.530(2) Å, b = 6.250(1) Å, c = 6.1017(9) Å, β = 104.81(2)°) from single crystal X‐ray diffraction data. The La3+ and (CN2)2— ions in the crystal structure of La2O(CN2)2 can be compared to Fe3+ and S22— ions in the cubic pyrite structure, being arranged like in a distorted NaCl type structure with their centers of gravity. In addition, the O2— ions in La2O(CN2)2 are occupying 1/4 of the tetrahedral voids formed by the arrangement of metal ions. 相似文献
944.
945.
B. Mahltig J.‐F. Gohy R. Jrme H.‐M. Buchhammer M. Stamm 《Journal of Polymer Science.Polymer Physics》2002,40(4):338-345
The adsorption behavior of aqueous mixtures of the homopolyelectrolytes poly(methacrylic acid) (PMAA) and poly[(dimethylamino)ethyl methacrylate] (PDMAEMA) was investigated in comparison with the adsorption of the ampholytic diblock copolymer PMAA‐b‐PDMAEMA on silicon substrates. Ellipsometry was used to determine the amount of adsorbed homopolyelectrolyte and diblock polyampholyte. Furthermore, the topography of the adsorbed polymers was investigated with atomic force microscopy (AFM) and compared with the structures observed in aqueous solutions by dynamic light scattering (DLS). For all types of investigated polyelectrolytic mixtures or the single polyampholyte, the adsorption was strongly influenced by the pH of the polymer solution. Although single homopolyelectrolytes showed only one maximum in adsorption according to their charge, the mixtures made from these homopolyelectrolytes showed two or three maxima. The third maximum near the isoelectric point of the mixture was assigned to a new species formed by aggregation of the two homopolyelectrolytes. Altogether, the adsorption behavior of the polyelectrolytic mixtures was in between the behavior of the pure homopolyelectrolytes and the analogous polyampholytes and therefore understandable from both of these polymer species. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 338–345, 2002; DOI 10.1002/polb.10091 相似文献
946.
Chen SH Su AC Chang CS Chen HL Ho DL Tsao CS Peng KY Chen SA 《Langmuir : the ACS journal of surfaces and colloids》2004,20(20):8909-8915
Morphological effects in luminescence properties of a representative semiconducting polymer, poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV), has recently attracted much attention. Previous studies indicated that short-term heat treatment of solution-cast MEH-PPV films may result in the formation of mesomorphic order that is responsible for the "red" emission around 640 nm, in contrast to the single-chromophore "yellow" emission near 590 nm from the disordered matrix. On the basis of microscopic and spectroscopic evidence for films cast from freshly prepared and aged solutions, here we show that prolonged storage of MEHyellowPPV solutions at room temperature or lower may result in retardation of the thermally induced mesophase formation in the subsequently cast films. According to small-angle neutron scattering and differential scanning calorimetric observations over aged MEH-PPV/toluene solutions, we propose that the suppressed transformation into mesomorphic order is due to further development of nanocrystalline aggregates that serve as physical cross-links among MEH-PPV chains in the solution state upon long-term storage. These solvent-induced nanocrystalline aggregates, however, do not exhibit new spectroscopic features beyond the suppression of "red" emission at 640 nm from the mesomorphic phase. 相似文献
947.
Eleven Lycopodium alkaloids with a lycopodine‐type skeleton were isolated from the basic material of the whole plant of Huperzia serrata (Thunb .) Trev. (Huperziaceae). Among them, 12‐epilycodoline N‐oxide (=(12α,15R)‐12‐hydroxy‐15‐methyllycopodan‐5‐one N‐oxide; 1 ), 7‐hydroxylycopodine (=(15S)‐7‐hydroxy‐15‐methyllycopodan‐5‐one; 2 ), and 4,6α‐dihydroxylycopodine (=(6α,15R)‐4,6‐dihydroxy‐15‐methyllycopodan‐5‐one; 3 ) are new compounds. Their structures were identified spectroscopically, especially by means of 1D‐ and 2D‐NMR. 相似文献
948.
P. Chang S. Yu T. Chen A. Ren C. Chen X. Wang 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(1):153-160
Sorption of Th(IV) on Na-rectorite as a function of pH, ionic strength, soil humic acid (HA) and fulvic acid (FA) are studied
under ambient conditions by using a batch technique. The results indicate that the sorption of Th(IV) on Na-rectorite is not
only dependent on medium pH values, but also dependent on medium ionic strength and humic substances. Surface complexation
and cation competition exchange account for Th(IV) sorption on Na-rectorite. The sorption of Th(IV) on Na-rectorite decreases
with the increase on the concentration of NaNO3, Mg(NO3)2 and Ca(NO3)2, and increases with the increasing amount of HA/FA in the suspension/adsorbed on rectorite. Soil HA/FA enhances the sorption
of Th(IV) on rectorite at medium pH<4 drastically, but the presence of FA reduces the sorption of Th(IV) at medium pH>6, and
HA has no effect on Th(IV) sorption at medium pH>6. An interpretation for the results is attempted, considering the occurrence
of different sorption mechanisms. 相似文献
949.
Two new acylated flavonol glycosides, named amurenosides A and B, together with quercetin 3-(2,6-di-O-alpha-rhamnopyranosyl-beta-galactopyranoside), have been isolated from the whole plant of Vicia amurensis. Their structures were elucidated as quercetin 3-O-alpha-L-(3-feruloylrhamnopyranosyl)(1-->6)-[alpha-L-rhamnopyra nosyl(1-->2)]-beta-D-galactopyranoside and quercetin 3-O-alpha-L-(2-feruloylrhamnopyranosyl)(1-->6)-[alpha-L-rhamnopyra nosyl(1-->2)]-beta-D-galactopyranoside on the basis of various NMR techniques, FAB mass spectrometry and chemical reactions. 相似文献
950.
Satoshi Takamizawa Dr. Chihiro Kachi‐Terajima Dr. Masa‐aki Kohbara Takamasa Akatsuka Tetsuro Jin Dr. 《化学:亚洲杂志》2007,2(7):837-848
The vapor absorbency of the series of alcohols methanol, ethanol, 1‐propanol, 1‐butanol, and 1‐pentanol was characterized on the single‐crystal adsorbents [MII2(bza)4(pyz)]n (bza=benzoate, pyz=pyrazine, M=Rh ( 1 ), Cu ( 2 )). The crystal structures of all the alcohol inclusions were determined by single‐crystal X‐ray crystallography at 90 K. The crystal‐phase transition induced by guest adsorption occurred in the inclusion crystals except for 1‐propanol. A hydrogen‐bonded dimer of adsorbed alcohol was found in the methanol‐ and ethanol‐inclusion crystals, which is similar to a previous observation in 2 ?2EtOH (S. Takamizawa, T. Saito, T. Akatsuka, E. Nakata, Inorg. Chem. 2005 , 44, 1421–1424). In contrast, an isolated monomer was present in the channel for 1‐propanol, 1‐butanol, and 1‐pentanol inclusions. All adsorbed alcohols were stabilized by hydrophilic and/or hydrophobic interactions between host and guest. From the combined results of microscopic determination (crystal structure) and macroscopic observation (gas‐adsorption property), the observed transition induced by gas adsorption is explained by stepwise inclusion into the individual cavities, which is called the “step‐loading effect.” Alcohol/water separation was attempted by a pervaporation technique with microcrystals of 2 dispersed in a poly(dimethylsiloxane) membrane. In the alcohol/water separation, the membrane showed effective separation ability and gave separation factors (alcohol/water) of 5.6 and 4.7 for methanol and ethanol at room temperature, respectively. 相似文献