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991.
Formation, structure, and stability of titanate nanotubes and their proton conductivity 总被引:2,自引:0,他引:2
Thorne A Kruth A Tunstall D Irvine JT Zhou W 《The journal of physical chemistry. B》2005,109(12):5439-5444
High-yield H-form trititanate nanotubes have been synthesized, and their structures have been characterized by using X-ray diffraction and high-resolution transmission electron microscopy. According to combined TGA/XRD studies, the nanotubes are not stable at high temperature. Thermal analysis suggests that the stoichiometry of the material is H(2)Ti(3)O(7).0.8H(2)O(abs). Conductivity measurements indicate that mainly protonic transport occurs at temperatures below 150 degrees C and that with increasing temperature and progressive breakdown of nanotubes and formation of crystalline TiO(2) phases protonic conductivity is lost, leaving only residual defect electronic conduction. The proton conductivity is ca. 5.5 x 10(-6) S cm(-1) at 300 K. The structural protons and trapped water were confirmed by solid-state NMR. 相似文献
992.
The ability of a Brazilian strain ofThermoascus aurantiacus, a thermophilic fungus, to produce extracellular phenol oxidases and to degradeEucalyptus grandis sawdust was studied.T. aurantiacus was capable of good growth in liquid culture containing 1.5% (w/v) of various lignocellulosic substrates (sugar cane bagasse, rice hulls, and chips and sawdust ofE. grandis) plus 5 mg/mL of glucose. When lignocellulosic substrates were used, enzymes involved in cellulose and hemicellulose metabolism were stimulated inT. aurantiacus. It was also found that these substrates have an inductive effect on phenol oxidase production. The most effective inducer of phenol oxidase activity wasE. grandis sawdust, which led to the production of 0.80 U/mL (o-dianisidine oxidation) on day 12. Low phenol oxidase activity was observed at cultures when only glucose was used. Cultures ofT. aurantiacus also exhibited cellobiose-quinone oxidoreductase activity when lignocellulosic materials were used as substrate. However, under our experimental conditions, lignin peroxidase activity was not detected.E. grandis sawdust supplemented with 5 mg/mL of glucose suffered a total weight loss of 6.7% accompanied by 15% lignin loss and 64.4% extractive loss after 21 d incubation withT. aurantiacus. 相似文献
993.
Carlo Bicchi Giuseppe Artuffo Angela D'Amato Gian Mario Nano Anna Galli Mario Galli 《Journal of separation science》1991,14(5):301-305
The chromatographic separation of racemic mixtures of volatile compounds by 2,3,6-trimethyl-α-, β- and γ-cyclodextrins is discussed. Columns were prepared by mixing the derivatized cyclodextrin with OV-1701 or hydroxy-terminated OV-1701 (OV-1701-OH) following Schurig's method [1]. About 130 racemates with widely differing structures were used to test the performances of 2,3,6-permethylated-α, β- and, γ-cyclodextrins mixed with the polysiloxane polymers in different ratios. The influence of the different types of cyclodextrin on racemate separation is shown, and some phenomena which might be helpful in the elucidation of the chromatographic behavior involved are also described. The influence both of the percentage of cyclodextrin in the polysiloxane, and of the operating conditions (carrier gas, flow rate, and temperature) in the separation of flavor and fragrance racemates is also evaluated. 相似文献
994.
Bauer EM Donzello MP Ercolani C Masetti E Panero S Ricciardi G Rosa A Chiesi-Villa A Rizzoli C 《Inorganic chemistry》2003,42(2):283-293
Recrystallization of the previously reported monosolvated bis(phthalocyaninato)niobium(IV), [Pc2Nb].CINP (CINP = 1-chloronaphthalene), has allowed isolation of a single crystal of a new solvated form, i.e. [Pc2Nb]. 3.5CINP, whose structure has been elucidated by X-ray work: space group P2(1)/n (No. 14); a = 16.765(3), b = 23.800(4), c = 19.421(4) A; alpha = gamma = 90 degrees, beta = 92.51(2) degrees; Z = 4. The sandwiched material is a "stapled" molecule, characterized by the presence of two intramolecular interligand C-C sigma bonds and highly strained phthalocyanine units, as formerly observed by crystallographic work for its Ti(IV) analogue, [Pc2Ti], and the +1 corresponding fragment, [Pc2Nb]+, present in the species [Pc2Nb](l3)(l2)0.5.3.5CINP. [Pc2Nb] appears to be reluctant to undergo further oxidation above the +1 oxidation state. Detailed theoretical studies by DFT and TDDFT methods have been developed on [Pc2Nb] and [Pc2Nb]+, also extended for comparison to the Ti(IV) complex [Pc2Ti], and an adequate picture of the ground-state electronic structure of these species has been achieved. Moreover, the excitation energies and oscillator strengths calculated for the closed-shell systems, [Pc2Ti] and [Pc2Nb]+, provide a satisfactory interpretation of their characteristic visible optical spectra and help to rationalize the similar features observed in the visible spectrum of the open-shell "stapled" complex, [Pc2Nb]. Thin solid films (100-250 nm) of [Pc2Nb] deposited on ITO (indium-doped tin oxide) show a reversible redox process in neutral or acidic aqueous electrolytes. The electrochemical and electrochromic properties of the sandwiched complex, combined with impedance and UV/visible spectral measurements, are presented and discussed. The achieved electrochemical information, while substantially in keeping with the observed chemical redox behavior and theoretical predictions, qualifies [Pc2Nb] as an "optically passive" electrode and a promising material for its use in electrochromic devices. 相似文献
995.
996.
Sorption properties of olive husk were investigated under equilibrium (batch tests) and dynamic (column tests) conditions
in order to assess the possibility of using such a waste material for removing heavy metals from aqueous streams. Husk samples
were contacted, at 25°C, with aqueous solutions of nitric salts of Pb, Cd, Cu, and Zn. Sorption isotherms obtained from equilibrium
data were fitted and interpreted by the Freundlich model. Metals-saturated husk samples resulting from column tests were air-dried
and incinerated to simulate combustion in order to assess the fate of sorbed metals. The results demonstrated that, under
both equilibrium and dynamic conditions, metal sorption capacity of the husk was in the sequence Pb>Cd>Cu>Zn. For all the
metals, calculated Freundlich constants decreased by increasing initial metal concentration or decreasing solution pH. In
dynamic tests, a significant reduction of sorption capacity was recorded (except for copper) when a metal was fed simultaneously
to the others: Pb (77%); Cd (93%); Zn (68%). Combustion tests carried out on metals-saturated husk samples showed that the
average losses of lead and cadmium, as volatile species, were always three to four times greater than the losses of copper
and zinc, in both single-metal- and multimetal-saturated samples. 相似文献
997.
Gooding EA Ramajo AP Wang J Palmer C Fouts E Volk M 《Chemical communications (Cambridge, England)》2005,(48):5985-5987
Nanosecond temperature jump experiments coupled to time-resolved infrared spectroscopy were carried out on a series of alanine-based peptides containing different guest amino acids to study the effects of residues with different helix propensities on the helix-coil dynamics. 相似文献
998.
Göbel Aa Thomsen A McArdell CS Alder AC Giger W Theiss N Löffler D Ternes TA 《Journal of chromatography. A》2005,1085(2):179-189
Pressurized liquid extraction (PLE) was optimized and validated for the determination of sulfonamide and macrolide antimicrobials and trimethoprim in sewage sludge samples. A mixture of water/methanol (50:50, v/v) was found as the most efficient extraction solvent. A temperature of 100 degrees C and a pressure of 100 bar were chosen for extraction. Two cycles of 5 min each efficiently extracted at least 97% of the total extractable amount of all studied analytes from activated sludge. The limits of quantification (S/N= 10) varied between 3 and 41 microg/kg dry weight (dw) and the relative recoveries ranged between 78 and 142%. Additionally, the influence of pH and different LC/MS/MS systems on the absolute recoveries was assessed. Of the investigated antimicrobials sulfapyridin, sulfamethoxazole, trimethoprim, azithromycin, clarithromycin and roxithromycin were detected in municipal sewage sludge samples. Concentrations in activated sludge ranged up to 197 microg/kgdw. In comparison, results obtained by ultrasonic solvent extraction were significantly lower for sulfonamides and in tendency lower for macrolides. 相似文献
999.
Protein A-Sepharose CL-4B was used as a solid phase for antibodies in the radioimmunoassay of progesterone and estriol. The
method was fast and easily standardizable. Immobilized antibodies had the same binding capacity as free antibodies and gave
good correlation curves (r = 0.996 for progesterone andr = 0.989 for estriol). Sensitivity was 12.5 pg/tube for progesterone and 8.0 pg/tube for estriol. Comparison of progesterone
radioimmunoassay with chemically immobilized antibody onto Sepharose CL-4B was also carried out. 相似文献
1000.
The First T5‐Supertetrahedron in Oxide Chemistry: Na26Mn39O55 Na26Mn39O55 has been obtained from a redox reaction between manganese metal, CdO in the presence of Na2O and Na2SO4 as a flux component as red single crystals with octahedral shape. The crystal structure has been determined from single crystal data (Fd3¯m, Z = 8, a = 2377.4(3) pm at 293 K and a = 2372.5(2) pm at 130 K). The rare characteristic structural feature of a T5‐Supertetrahedron, [Mn35O56], is observed for this new mixed‐valent sodium‐oxomanganat(II, III), Na26Mn39O55. First investigations of the magnetic properties are reported. 相似文献