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91.
Marta Fernandez-Tarrio Carmen Alvarez-Lorenzo A. Concheiro 《Journal of Thermal Analysis and Calorimetry》2007,87(1):171-178
Tetronic®comprises X-shaped copolymers formed by four poly(propylene oxide) (PPO) andpoly(ethylene oxide) (PEO) block chains bonded to an ethylene diamine centralgroup. Micellization behaviour of three representative Tetronics (T304, T904and T1307) was characterized to gain an insight into the interactions betweenthe copolymer unimers and the state of water in their solutions. The enthalpyof demicellization, recorded at 37°C in an isoperibol microcalorimeter,indicated that the process was in all cases exothermic and the enthalpy rankedin the order T1307≥T904>>T304. Micellization is entropy-driven owing tohydrophobic interactions between the PPO chains.DSC analysisshowed that the crystallization and melting peaks of the free water remainingin T304 and T904 solutions were progressively shifted toward lower temperaturesas the surfactant proportion increased, owing to a colligative effect. Boundwater corresponded to 3 water molecules per EO repeating unit. In the caseof T1307, which has longer PEO chains, a splitting of the melting peak wasobserved, one peak appearing around 0°C due to free water and anotherat –15°C due to interfacial water. As T1307 proportion raised, theenthalpy of the former decreased, whilst the enthalpy of the latter increased.In 40% T1307 solutions, interfacial water overcame the proportion of freewater; there being 1 interfacial and 3 bound water molecules per EO repeatingunit. Gaussian deconvolution of FTIR spectra also enabled to characterizethe evolution of free water as a function of Tetronic proportion. The dependenceof micellization and water interaction behaviour on Tetronics structure shouldbe taken into account to use these copolymers as drug solubilizers and micellarcarriers. 相似文献
92.
A one-dimensional chain coordination polymer [Co(Ⅱ)(C6H5CH=CHCOOH)2(4,4'-bipy)(H2O)5]n has been synthesized with cinnamylic acid, 4,4'-bipy and cobaltous chloride as raw materials. Crystal data for this complex: monoclinic, space group P21/c, a - 1.1481(3), b =1.1230(2), c = 1.1759(3) nm, β = 97.054(4)°, V = 1.5046(6) nm3, Mr= 617.50, Dc = 1.363 g/cm3, Z= 2, μ(MoKα) = 0.627 mm-1, F(000) = 646, S = 1.062, R 0.0443 and wR = 0.1178. The crystal structure shows that two neighboring cobalt(Ⅱ) ions are linked together by one 4,4'-bipy, and the whole complex molecule adopts a one-dimensional chain structure. Each cobalt(Ⅱ) ion is coordinated with two nitrogen atoms from two 4,4'-bipy molecules and four oxygen atoms from four water molecules, giving a distorted octahedral coordination geometry. The electrochemical properties were analyzed by combining with the crystal structure. 相似文献
93.
河口水体中痕量稀土元素的共沉淀预富集-电感耦合等离子体质谱法测定研究 总被引:3,自引:0,他引:3
建立了氢氧化铟共沉淀预富集 -电感耦合等离子体质谱法测定河口水体中痕量稀土元素的方法。实验结果表明 ,在80mg·L -1的In3 +和pH9.5的实验条件下 ,在1.0L水样中添加5.0~200.0ng的混合稀土标准溶液 ,均能定量回收 ,回收率在82.2 %~106.9 %之间。方法的分析流程空白为0.04(Tb)~10.17(La)ng·L -1,检出限在0.17(Yb)~1.46(La)ng·L-1之间 ,精密度 (RSD ,n=3)小于11.7 % ,可满足河口淡水和海水样品中的痕量稀土元素定量分析的要求 相似文献
94.
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96.
Zdeněk Slanina 《Journal of Cluster Science》2004,15(1):3-11
Computational findings of temperature increase of clustering degree in saturated vapors are analyzed. A thermodynamic proof is presented and a simple criterion derived. Illustrations are based on saturated steam, magnesium and carbon vapor. The results are applicable to synthesis of fullerenes, metallofullerenes, and heterofullerenes, chemical vapor deposition technique, or atmospheric chemistry. 相似文献
97.
R. Hoelzl Christian Hoelzl Ludwig Kotz Lazlo Fabry 《Accreditation and quality assurance》1998,3(5):185-188
Inductively coupled plasma mass spectrometry (ICP-MS) and high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS)
are powerful methods of determining metallic impurities in the low- and sub-ppt level in process media such as ultra-pure
water used in semiconductor and wafer manufacturing. By using mass spectrometers for analysis, an isotope dilution analysis
(IDMS) is possible. The reproducibility of an IDMS is unmatched. For concentration levels near the instrument detection limit
a novel method is reported to find the optimal amount of isotopic spike solution. This optimal value can be derived by the
law of propagation of uncertainty combined with the Poisson statistics of the measured number of counts. Generally, an excess
of isotopic spike solution should be used to provide results of lowest possible uncertainty. The results are presented in
a diagram for easy practical use.
Received: 14 October 1997 · Accepted: 13 February 1998 相似文献
98.
99.
E. A. Zheligovskaya 《Journal of Structural Chemistry》2003,44(5):827-835
A computer simulation of proton-ordered ice IX and its proton-disordered analog III (768 molecules, 90 K) was carried out by the molecular dynamics method using Poltev–Malenkov's potential. For ice IX, the differences in the dynamic characteristics of molecules with O(1) and O(2) are much wider than those in the case of ice III. The libration spectrum of ice IX has a number of distinct acute peaks, and the spectrum of ice III is strongly smoothed. These peculiarities are explained by the proton ordering of ice IX and disordering of ice III. The latter is responsible for the great differences in the short- and especially long-range environment of water molecules in ice crystals and hence for the presence of many molecules with different dynamic characteristics. Thus averaging over a large number of different vibrational spectra of molecules leads to a smoothed total spectrum in the case of the proton-disordered crystal modification of ice. 相似文献
100.
Modeling Studies of the Formation and Destruction of NO in Pulsed Barrier Discharges in Nitrogen and Air 总被引:1,自引:0,他引:1
This paper presents the results of modeling studies on the formation and destruction of NO in pulsed barrier discharges in nitrogen and air. The goals of this work are to identify the major processes involved in the formation and destruction of NO in air discharges, to distinguish between oxidative and reductive paths for NO destruction, to explore the potential importance of excited state reactions, to evaluate the role of water in such systems, and to identify the final products in the absence of heterogeneous processes. In all cases, the systems were modeled with 100×10–4% (100 ppm) of added NO, with and without 3% added water. The focus in all of this work is chemistry in the post-pulse regime. 相似文献