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Zhongnan Guo Michael Hindler Wenxia Yuan Adolf Mikula 《Monatshefte für Chemie / Chemical Monthly》2011,102(3):579-584
Abstract
The density and surface tension of binary In–Sn and ternary Cu–In–Sn alloys have been measured by a sessile-drop method. Decrease of the density and of the surface tension was observed with rising temperature. With increased Sn content in the alloys, the density increased while the surface tension reduced slightly. Addition of Cu could significantly increase the density and surface tension in the Cu–In–Sn system. The surface tension of the Cu–In–Sn alloys was also calculated by means of Butler’s equation, and compared with experimental values, showing good agreement. 相似文献3.
V. P. Korolev 《Journal of Structural Chemistry》2016,57(5):947-954
With an increase in the concentration of additives, the hydration numbers of compounds decrease. Thus, in a saturated 54.6% solution, urea loses approximately 3/4 of the initial amount of water, forming an aquacomplex of the composition (NH2)2CO?H2O. In a supersaturated 44% solution, the sodium chloride aquacomplex is dehydrated by 2/3, and in a supersaturated 67% solution, sodium sulfate is dehydrated by 5/6. The density of these solutions is 1.354÷1.360 g/cm3 (44% NaCl) and 1.800÷1.849 g/cm3 (67% Na2SO4). In a saturated urea solution, NaNO3, NaCl, and Na2SO4 complexes lose 53÷55% of hydration water. It is shown that the interactions in the binary water–urea system somewhat increase the hydration number of the salts (structural hydration). The hydration water density, a structurally important characteristic, increases in the series of solutions of urea, NaNO3, NaCl, and Na2SO4. In the same series of additives, the excess volume of binary water–urea and water–salt systems becomes more negative. 相似文献
4.
《Fluid Phase Equilibria》2001,178(1-2):239-257
Bubble points of the HCl–water–isopropanol and the HCl–water–isopropanol–benzene systems and liquid–liquid equilibria (LLE) of the HCl–water–benzene and the HCl–water– isopropanol–benzene systems were measured at 25–85°C and 30–70°C, respectively. The electrolyte nonrandom two-liquid model proposed by Chen et al. [C.-C. Chen, H.I. Britt, J.F. Boston, L.B. Evans, AIChE J. 28 (1982) 588–596] can satisfactorily correlate bubble points and liquid–liquid equilibria of the present mixed-solvent electrolyte systems over the entire range of temperature and concentrations using only binary adjustable parameters. 相似文献
5.
Elise A. Dennis Alexander W. Gundlach–Graham Christie G. Enke Steven J. Ray Anthony J. Carado Charles J. Barinaga David W. Koppenaal Gary M. Hieftje 《Journal of the American Society for Mass Spectrometry》2013,24(5):690-700
Resolution in time–of–flight mass spectrometry (TOFMS) is ordinarily limited by the initial energy and space distributions within an instrument’s acceleration region and by the length of the field–free flight zone. With gaseous ion sources, these distributions lead to systematic flight–time errors that cannot be simultaneously corrected with conventional static–field ion–focusing devices (i.e., an ion mirror). It is known that initial energy and space distributions produce non–linearly correlated errors in both ion velocity and exit time from the acceleration region. Here we reinvestigate an old acceleration technique, constant–momentum acceleration (CMA), to decouple the effects of initial energy and space distributions. In CMA, only initial ion energies (and not their positions) affect the velocity ions gain. Therefore, with CMA, the spatial distribution within the acceleration region can be manipulated without creating ion–velocity error. The velocity differences caused by a spread in initial ion energy can be corrected with an ion mirror. We discuss here the use of CMA and independent focusing of energy and space distributions for both distance–of–flight mass spectrometry (DOFMS) and TOFMS. Performance characteristics of our CMA–DOFMS and CMA–TOFMS instrument, fitted with a glow–discharge ionization source, are described. In CMA–DOFMS, resolving powers (FWHM) of greater than 1000 are achieved for atomic ions with a flight length of 285 mm. In CMA–TOFMS, only ions over a narrow range of m/z values can be energy–focused; however, the technique offers improved resolution for these focused ions, with resolving powers of greater than 2000 for a separation distance of 350 mm. 相似文献
6.
LC–DAD coupled with electrospray tandem mass spectrometry (LC–ESI–MS–MS) has been used to evaluate the quality of the traditional Chinese medicine Huang-Lian-Jie-Du-Tang (HLJDT). Twenty-five chromatographic peaks were obtained from a C18 analytical column by gradient elution with acetonitrile and formate buffer (containing 0.5% formic acid) at a flow rate of 1.0 mL min?1. The linearity, precision, and accuracy of the data obtained were acceptable. Thirteen components were identified by ESI–MS, and seven of these were quantitatively analyzed by LC–DAD. The method was used to analyze ten batches of HLJDT, and both chromatographic fingerprints and quantitative data were used to evaluate the quality of the HLJDT. It was concluded that this LC–DAD–ESI–MS method enables more fully validated and complete evaluation and monitoring of the quality of HLJDT. 相似文献
7.
Laurynas Staišiūnas Konstantinas Leinartas Meilutė Samulevičienė Povilas Miečinskas Asta Grigucevičienė Remigijus Juškėnas Eimutis Juzeliūnas 《Journal of Solid State Electrochemistry》2013,17(6):1649-1656
Nanocrystalline Mg–Nb and Mg–Nb–Al–Zn alloy films were deposited by dc magnetron sputtering on glass and quartz substrates in a wide range of niobium concentrations from 6 to 80 at.%. Structural, electrochemical and corrosion properties of the films were studied by X-ray diffraction, dc voltammetry, electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance. Development of body-centred cubic Nb structure in the Mg–Nb alloy matrix yielded the effects of lattice contraction, grain refining and electrochemical passivity. The measurements showed high corrosion resistance of the films in alkaline solutions when niobium content was one third or more. An increased corrosion resistance was achieved by introducing minor amounts of Al (ca. 2 at.%). In particular, such Al effect was pronounced at lower Nb concentrations (20 to 30 at.%). Semiconductor properties of spontaneously formed oxide on Mg–Nb alloy were studied by Mott–Schottky plots, which indicated highly doped n-type oxide structures on Mg–Nb surface. The paper fills some gap in understanding of niobium–magnesium systems, which show potential for applications in hydrogen storage, switchable mirrors and corrosion protection. 相似文献
8.
This is a study of adenine–Au and adenine–uracil–Au (neutral, anionic and cationic), applying the B3LYP density-functional approach. In these systems, the interaction is directly related to the charge; so that as the metal atomic charge increases, the bond strength also increases. Neutral molecules are weakly bonded, the interaction in the case of cations is mainly electrostatic and in the case of the anions, the extra electron is localized on the metal atom and consequently, non-conventional hydrogen bonds are formed. In the case of adenine–Au (anion), the H dissociation energy is similar to the electron dissociation energy, and therefore both reactions may be possible. Moreover, the Au anionic atom modifies the hydrogen bonds of the uracil–adenine base pair. This may be significant in the study of point mutations that may occur in the Watson–Crick dimmer of nucleic basis. The electron-donator properties of these compounds are analyzed with the aid of the donator–acceptor map (DAM), previously described. Adenine–Au, uracil–Au and adenine–uracil–Au are more effective electron donors, but poorer electron acceptors than adenine, uracil and adenine–uracil. If the electron acceptor properties of carotenoids such as β-carotene and astaxanthin are compared, there are indications that astaxanthin may act as an oxidant instead of an antioxidant with the uracil–adenine base pair. The oxidation of nucleic acid bases by carotenoids may have important consequences, as oxidative damage of DNA and RNA appears to be linked to cancer. This is something that demands further studies and for this reason, work concerning the reactivity of carotenoids with DNA-nitrogen bases is in progress. 相似文献
9.
《Physics and Chemistry of Liquids》2012,50(3):245-259
Thermodynamic and surface properties of Ge–Ga and Ge–Sb liquid alloys have been studied using statistical mechanical formulations based on complex formation and that based on the concept of layered structure near the interface. The study showed that low level of complex formation of the form Ge 2 Sb exists in Ge–Sb toward the Ge-rich end of the concentration range and the surface properties of Ge–Ga are almost equal to their corresponding bulk equivalent. 相似文献
10.
Yu. A. Mikheev L. N. Guseva Yu. A. Ershov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(4):715-726
The changes in the UV–Vis absorption spectra of dimethylaminoazobenzene (DAB) in the cellulose triacetate (CTA) matrix during the absorption of gaseous hydrogen chloride and protonation of DAB in weakly and strongly acid solutions of hydrochloric and sulfuric acids were studied. The yellow-orange color of DAB and its analog aminoazobenzene (AAB) was shown to be due to the dimers, whose structure involves phenylaminyl type cations formed due to the promotion of the sp 2 electrons of the azo groups to the Rydberg R 3s orbitals of the azo groups and possessing Vis bands at 400–417 nm. The cations exist immanently as the dimers due to the Rydberg intermonomer bonds; the Vis bands of the dimers shifted toward 500–520 nm under the action of HCl (in CTA) and weakly acid media as a result of the formation of phenyl aminyl type pair cations, whose π* levels are split by Simpson’s mechanism, during the protonation of interrelated monomers. In the concentrated sulfuric acid, the Vis bands at 500–520 nm vanished because of the decomposition of the dimers into diprotonated monomers possessing Vis bands at 400–417 nm. The mechanism of transformations of chromogens responsible for the spectral transformation was given. 相似文献
11.
Hohyun Kim Hyeongjin Roh Seung-Bock Yeom Hee Joo Lee Sang Beom Han 《Chromatographia》2003,58(3-4):235-240
Summary A sensitive and selective liquid chromatographic method coupled with electrospray ionization tandem mass spectrometry (LC–ESI–MS–MS) has been developed for quantification of felodipine in human and dog plasma. Compounds were separated on a 2.0 mm × 150 mm, 5.0 m particle, C8 column with 1 m m ammonium acetate–acetonitrile, 20:80, pH 6.0, as mobile phase at a flow rate of 200 L min–1. Nifedipine was used as internal standard. Plasma samples were extracted with diethyl ether, the centrifuged upper layer was evaporated, the residue was reconstituted with mobile phase, and the reconstituted samples were injected. The analytical column lasted for at least 1000 injections. By use of multiple reaction monitoring (MRM) mode in MS–MS felodipine and nifedipine were detected without severe interference from the human or dog plasma matrix. Felodipine produced a protonated precursor ion ([M + H]+) at m/z 384 and a corresponding product ion at m/z 338. And internal standard (nifedipine) produced a protonated precursor ion ([M + H]+) at m/z 347 and a corresponding product ion at m/z 315. Detection of felodipine in human and dog plasma was accurate and precise, with a limit of quantification of 0.05 ng mL–1. The method has been successfully applied to preliminary pharmacokinetic study of felodipine in human and dog plasma. 相似文献
12.
The Morita–Baylis–Hillman (MBH) acetates derived from nitroalkenes and ethyl glyoxylate have been transformed in one pot at room temperature to highly fused and functionalized furans and pyrans in good to excellent yield. The reaction involves a cascade Michael–oxa-Michael addition of β-dicarbonyl compounds to the MBH acetates in the presence of an amine base such as DABCO. An unusual switching of selectivity in the oxa-Michael addition from 5-exo-trig to 6-endo-trig was observed when the β-dicarbonyl compound was changed from acyclic or six-membered ring cyclic to five-membered ring cyclic system. 相似文献
13.
《Electrochemistry communications》2000,2(7):471-474
Poly(dibutylstannylene-co-dibutylsilylene) and poly(dibutylstannylene-co-dibutylgermylene) were synthesized for the first time, by electrochemical reduction of dibutyldichlorostannane together with dibutyldichlorosilane and dibutyldichlorogermane, respectively, in a one-compartment cell equipped with a platinum cathode and a silver anode, using tetrabutylammonium perchlorate and 1,2-dimethoxyethane as the supporting electrolyte and the solvent, respectively. Most of absorption peaks observed for the copolymers were located between those of polystannylene and polysilylene/polygermylene. A copolymer with relatively high stannane content had a relatively long absorption peak, which is close to that of a homopolymer polydibutylstannylene. A copolymer with a higher stannane content was more sensitive to the moisture in air. 相似文献
14.
Tomáš Grygar Petr Bezdička Pawel Piszora Emilia Wolska 《Journal of Solid State Electrochemistry》2001,5(7-8):487-494
Electrochemical reductive dissolution of Li–Mn–O and Li–Fe–Mn–O spinels and Li+ extraction/insertion in these oxides were performed using voltammetry of microparticles. Both electrochemical reactions are
sensitive to the Fe/(Fe+Mn) ratio, specific surface area, Li content in tetrahedral positions, and Mn valence, and can be
used for electrochemical analysis of the homogeneity of the elemental and phase composition of synthetic samples. The peak
potential (E
P) of the reductive dissolution of the Li–Mn–O spinel is directly proportional to the logarithm of the specific surface area. E
P of Li–Fe–Mn–O spinels is mainly controlled by the Fe/(Fe+Mn) ratio. Li+ insertion/extraction can be performed with Mn-rich Li–Fe–Mn–O spinels in aqueous solution under an ambient atmosphere and
it is sensitive to the regularity of the spinel structure, in particularly to the amount of Li in tetrahedral positions and
the Mn valence.
Electronic Publication 相似文献
15.
Yu Ogawa Hitomi Hidaka Satoshi Kimura Ung-Jin Kim Shigenori Kuga Masahisa Wada 《Cellulose (London, England)》2014,21(2):999-1006
We investigated the crystal structure of alkali-celluloses, Na-cellulose IIA and II(Cu), formerly known as Na-cellulose IIB, by synchrotron X-ray diffraction. Na-cellulose IIA, formed from cellulose I by high-concentration NaOH treatment, has a fiber repeat of 15 Å and a threefold-like helical conformation. Na-cellulose II(Cu), prepared by treating cellulose I with copper-saturated alkali solution, also has a fiber repeat of 15 Å with threefold helical symmetry. Incorporation of Cu(II) ions into cellulose was confirmed by multiwavelength anomalous diffraction. Monitoring by X-ray diffraction revealed that the formation of this complex from cellulose I is remarkably slow, probably because of the involvement of copper ion. The stability of alkali-cellulose II(Cu) was tested to estimate the influence of the presence of copper in the crystal. Na-cellulose II(Cu) characteristically dissolved in aqueous ammonia solution, indicating strong coordination of copper ion to cellulose. 相似文献
16.
Vibronic interactions have received increasing attention in modern structural chemistry. Edward Teller played a pioneering
role in understanding and describing them during the “molecular physics” period of his scientific career. Very little is known
about the two scientists who contributed significantly to our knowledge about these effects and whose names have become associated
with Teller’s. This Editorial is devoted to Hermann Jahn and Rudolf Renner and attempts to lift them out of oblivion by paying
them tribute for their contributions.
相似文献
István Hargittai (Corresponding author)Email: |
17.
Two covalently linked diphenyl ethyne bridged unsymmetrical dyads containing porphyrin and BF2–oxasmaragdyrin and Zn(II)porphyrin and BF2–oxasmaragdyrin units and one covalently linked triad containing Zn(II)porphyrin, porphyrin and BF2–oxasmaragdyrin units were synthesized by coupling appropriate functionalized macrocycles under Pd(0) coupling reaction conditions. The dyads and triad were freely soluble in common organic solvents and confirmed by ES-MS spectra. 1D and 2D NMR techniques were used to characterize the dyads and triad. Absorption and electrochemical studies of dyads and triad showed the overlapping features of the constituted macrocycles indicating that the macrocycles retain their basic features in the dyads and triad. The BF2–oxasmaragdyrin absorbs at lower energy and emits strongly in the visible region compared to porphyrin/Zn(II)porphyrin. Thus, BF2–oxasmaragdyrin acts as energy acceptor and porphyrin/Zn(II) porphyrin act as energy donor in dyads and triad. The steady state and time-resolved fluorescence studies supported an efficient energy transfer from porphyrin/Zn(II)porphyrin to BF2–oxasmaragdyrin unit in dyads and triad. 相似文献
18.
A stability indicating RP-HPLC method for cephalexin has been developed and validated to identify and characterize potential degradation products. Drug was subjected to hydrolytic (acidic, basic, and neutral), oxidative, thermal, and photolytic stresses as per ICH guidelines Q1A (R2) and Q1B. Chromatographic separation was achieved on C8 column with mixture of ammonium acetate buffer pH 4.5 and acetonitrile in gradient mode as a mobile phase with PDA detection. Specificity of the method was established by peak purity studies. Method was validated as per ICH guideline Q2 (R1) for accuracy, precision, linearity, sensitivity, and robustness. Kinetics for each degradation condition was studied with respect to order of reaction and rate constant. Method was found to comply with acceptance criteria of validation parameters with respect to specificity (peak purity greater than 0.999) linearity (r 2 greater than 0.99), accuracy (% recovery in the range of 98–102%), and precision (% RSD not more than 2). A total of six degradation products were generated in different stress conditions; these were identified and structures were proposed using LC–MS/MS. Cephalexin undergoes degradation in almost all the conditions. The developed stability indicating method is suitable for analysis of stability samples as it adequately separates all degradation products. Degradation products generated in photolytic and oxidative conditions are reported for the first time. 相似文献
19.
Dmitri V. Drobot Gulaim A. Seisenbaeva Vadim G. Kessler P. A. Scheglov O. A. Nikonova S. N. Michnevich O. V. Petrakova 《Journal of Cluster Science》2009,20(1):23-36
The paper represents a listing of results obtained by developing the original methods of controlled synthesis of cluster and
mono-, bi- and trimetallic oxo-alkoxide derivatives of rhenium and d-elements of V–VI groups. The developed techniques of
the synthesis of metal alkoxides include: (1) anodic dissolution of the metals in the alcohol media; (2) direct reaction of
the rhenium (VII) oxide with alkoxide derivatives of the transition elements. By such techniques were obtained: Re4O4(OEt)12, Re4O6(OiPr)10; individual rhenium alkoxocomplexes: Re4O2(OMe)16, Re4O6(OMe)12, Re4O6−y(OMe)12+y; bimetallic ReMoO2(OMe)7, Re4−xMoxO6−y(OMe)12+y, Re4−xWxO6−y(OMe)12+y; Nb2(OMe)8(ReO4)2, Ta2(OMe)8(ReO4)2, Nb4O2(OMe)14(ReO4)2, Ta4O2(OMe)14(ReO4)2, Nb4O2(OEt)14(ReO4)2, Ta4O2(OEt)14(ReO4)2, alkoxocomplexes: Nb2−xTax(OMe)8(ReO4)2, Nb4−xTaxO2(OMe)14(ReO4)2, Nb4−xTaxO2(OEt)14(ReO4)2. All compounds mentioned above are characterized with X-ray single crystal study, IR-spectroscopy, DTG. It has been shown,
that thermal decomposition of alkoxide derivatives in inert or hydrogen atmosphere leads to formation nano-size powders of
individual rhenium and its alloys at low temperature. Thermal decomposition in air leads to formation individual metal oxides
or its solid solutions. It has been demonstrated that the alkoxide derivatives could be promising precursors for next generation
catalysts manufacturing. 相似文献
20.
A. AlZahrani Y. Alhamed L. Petrov S. Armyanov E. Valova J. Georgieva J. Dille 《Journal of Solid State Electrochemistry》2014,18(7):1951-1961
Two types of electroless Ni–W–P coatings: nanocrystalline with low P and amorphous with higher P content are investigated. Scanning probe microscopy is applied to study their morphology. Textured nanocrystalline coatings consist of coarse pyramids built of nanometer thick lamellas. The surface morphology of amorphous coatings is much finer and uniform. Nanohardness of all coatings depends on W content. Microhardness is increasing during the heat treatment up to 350 °C due to nickel phosphide precipitation affected by tungsten also. The wear resistance of nanocrystalline Ni–W–P coatings is much higher than that of amorphous in spite of the similar tungsten content in both. Lower corrosion resistance of amorphous Ni–W–P coatings is found by weight loss method during long-term immersion in 5 % NaCl. Electrochemical tests by potentiodynamic polarization curves in two model corrosion media—solutions of 0.5 M H2SO4 and 5 % NaCl—are performed. The corrosion of bi-layered Ni–W–P/Ni–P and Ni–W–P/Ni–Cu–P deposits on mild steel is also investigated. The results prove that an electroless Ni–W–P coating on mild steel extremely improves its mechanical and corrosion behavior. It is demonstrated that in addition to deposit’s structure and composition, the distribution and chemical state of alloy ingredients are also responsible for its properties. 相似文献