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141.
This article provides a systematic study of several important parameters of the Associative Neural Network (ASNN), such as the number of networks in the ensemble, distance measures, neighbor functions, selection of smoothing parameters, and strategies for the user-training feature of the algorithm. The performance of the different methods is assessed with several training/test sets used to predict lipophilicity of chemical compounds. The Spearman rank-order correlation coefficient and Parzen-window regression methods provide the best performance of the algorithm. If additional user data is available, an improved prediction of lipophilicity of chemicals up to 2-5 times can be calculated when the appropriate smoothing parameters for the neural network are selected. The detected best combinations of parameters and strategies are implemented in the ALOGPS 2.1 program that is publicly available at http://www.vcclab.org/lab/alogps. 相似文献
142.
Igor Djerdj Georg Garnweitner Markus Niederberger 《Journal of solid state chemistry》2007,180(7):2154-2165
The preparation of lanthanum hydroxide and manganese oxide nanoparticles is presented, based on a nonaqueous sol-gel process involving the reaction of La(OiPr)3 and KMnO4 with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. The lanthanum manganese oxide system is highly complex and surprising results with respect to product composition and morphology were obtained. In dependence of the reaction parameters, the La(OH)3 nanoparticles undergo a shape transformation from short nanorods with an average aspect ratio of 2.1 to micron-sized nanofibers (average aspect ratio is more than 59.5). Although not directly involved, KMnO4 plays a crucial role in determining the particle morphology of La(OH)3. The reason lies in the fact that KMnO4 is able to oxidize the benzyl alcohol to benzoic acid, which presumably induces the anisotropic particle growth in [0 0 1] direction upon preferential coordination to the ±(1 0 0), ±(0 1 0) and ±(−110) crystal facets. By adjusting the molar La(OiPr)3-to-KMnO4 ratio as well as by using the appropriate solvent mixture it is possible to tailor the morphology, phase purity and microstructure of the La(OH)3 nanoparticles. Postsynthetic thermal treatment of the sample containing La(OH)3 nanofibers and β-MnOOH nanoparticles at the temperature of 800 °C for 8 h yielded polyhedral LaMnO3 and worm-like La2O3 nanoparticles as final products. 相似文献
143.
Khoroshko LO Takhistov VV Petrova VN Viktorovskii IV Lahtiperä M Paasivirta J 《European journal of mass spectrometry (Chichester, England)》2004,10(5):731-736
Structures of six cyclic polysulfides, previously unknown as organic environmental pollutants, were analyzed from a sediment sample from the Eastern Gulf of Finland. The determinations were done by gas chromatography connected to mass spectrometry. High resolution (HRMS) measurements of the isotopic composition of four compounds could be done to confirm their molecular formulae. Total low resolution (LRMS) spectra were used to elucidate structures of all six compounds by thermochemical approach, application of fragmentation rules and by ICLU simulation of the spectra. The compounds were deduced to be (in the order of GC- retention) 1,2,4-trithiacycloheptane, tetrathiacyclopentane, 1,2,4,5-tetrathia-cyclohexane, 1,2,3,4- tetrathiacycloheptane, 1,2,3,4-tetrathiacyclohexane and 1,2,4,6-tetrathiacyclooctane. 相似文献
144.
Thermal analysis supported by kinetic calculations was applied exhaustively to these compounds. Under dynamic conditions, tetrafluorometallates(III), which as intermediates, could not be isolated, for the first three compounds. In each case, the final step was the pure metal(III) fluoride. Ammonium hexafluorochromate(III) decomposed directly to the pure chromium(III) fluoride. The decomposition rate of all compounds slowed down towards the end, probably for kinetic reasons. Polymorphic transitions of ammonium hexafluorotitanate(III) were observed at 35 and 100°C. Ammoniumhexafluoroscandate(III) underwent polymorphic transition at 47°C. The decomposition patterns for all these compounds were similar. Conditions for the preparation of pure ammonium tetrafluorometallates(III) of Sc, Ti and V are described. 相似文献
145.
The diffusion length of charge carriers in the active layer of a perovskite solar cell (PSC) of the structure Glass/PEDOT: PSS/CH3NH3PbI3/PC60BM/Al is modelled. It is found that the diffusion length depends on the position x in the active layer measured from the PEDOT: PSS interface, Urbach energy and temperature. By varying the voltage in the range from zero to , it is shown that the dependence of diffusion length on the position x in the active layer reduces at higher voltage. The combined influence of applied voltage and temperature on the diffusion length of charge carriers is investigated and it is found that in the low voltage range the diffusion length is temperature independent, but it becomes significantly temperature dependent at higher voltages. Also, it is found that the diffusion length decreases as the applied voltage increases and this reduction becomes much more significant at higher voltage and temperatures. The combined influence of applied voltage and Urbach energy on diffusion length of charge carriers reveals that the diffusion length decreases when both the applied voltage and Urbach energy increase. However, the reduction in the diffusion length due to the increase in Urbach energy becomes less significant at higher voltage. 相似文献
146.
Praic M. Keane Kyra O'Sullivan Fergus E. Poynton Bjrn C. Poulsen Igor V. Sazanovich Michael Towrie Christine J. Cardin Xue-Zhong Sun Michael W. George Thorfinnur Gunnlaugsson Susan J. Quinn John M. Kelly 《Chemical science》2020,11(32):8600
Ruthenium polypyridyl complexes which can sensitise the photo-oxidation of nucleic acids and other biological molecules show potential for photo-therapeutic applications. In this article a combination of transient visible absorption (TrA) and time-resolved infra-red (TRIR) spectroscopy are used to compare the photo-oxidation of guanine by the enantiomers of [Ru(TAP)2(dppz)]2+ in both polymeric {poly(dG-dC), poly(dA-dT) and natural DNA} and small mixed-sequence duplex-forming oligodeoxynucleotides. The products of electron transfer are readily monitored by the appearance of a characteristic TRIR band centred at ca. 1700 cm−1 for the guanine radical cation and a band centered at ca. 515 nm in the TrA for the reduced ruthenium complex. It is found that efficient electron transfer requires that the complex be intercalated at a G-C base-pair containing site. Significantly, changes in the nucleobase vibrations of the TRIR spectra induced by the bound excited state before electron transfer takes place are used to identify preferred intercalation sites in mixed-sequence oligodeoxynucleotides and natural DNA. Interestingly, with natural DNA, while it is found that quenching is inefficient in the picosecond range, a slower electron transfer process occurs, which is not found with the mixed-sequence duplex-forming oligodeoxynucleotides studied.Efficient electron transfer requires the complex to be intercalated at a G-C base-pair. Identification of preferred intercalation sites is achieved by TRIR monitoring of the nucleobase vibrations before electron transfer. 相似文献
147.
We employ dissipative particle dynamics (DPD) to examine the self‐assembly behavior of A2‐star‐(B‐alt‐C) molecules. We successfully observe various types of hierarchical structure‐within‐structures, such as A‐formed spheres in the matrix formed by B and C alternating layers, hexagonally packed A‐formed cylinders in the matrix with B and C segregated layers, B and C alternating layers‐within‐lamellae, coaxial B and C alternating domains within hexagonally packed BC‐formed cylinders in the A‐matrix, and co‐centric BC‐alternating domains within BC‐formed spheres in the A‐matrix, by increasing the A composition. Generally speaking, the small length‐scale B and C segregated domains are in parallel to the large length‐scale structures. This hierarchical periodicity along the same axis as well as the various characteristic structures, that the A2‐star‐(B‐alt‐C) copolymers display, are quite different from those in A‐block‐(B‐graft‐C) coil‐comb copolymers. Moreover, it is interesting to find that when the copolymer chain length increases, though the hierarchical structure type is maintained, the number of small length‐scale lamellae that can form within the large length‐scale structure increases. These hierarchical structures under various compositions are reported theoretically for the first time in the copolymer systems consisting of the alternating blocks, and are in good agreement with the most recent experimental work by Matsushita and co‐workers (Macromolecules 2007 , 40, 4023). 相似文献
148.
149.
Amperometric urea biosensor based on urease and electropolymerized toluidine blue dye as a pH-sensitive redox probe 总被引:4,自引:0,他引:4
Vostiar I Tkac J Sturdik E Gemeiner P 《Bioelectrochemistry (Amsterdam, Netherlands)》2002,56(1-2):113-115
The electropolymerized toluidine blue film deposited on the glassy carbon electrode show amperometrically detectable pH sensitivity. This feature of polytoluidine blue (PTOB) film was used for a construction of an amperometric urea biosensor. We have observed a linear shift of the formal redox potential with increasing pH value between 4 and 8 giving the slope of 81 mV(Delta) pH(-1). Polytoluidine blue film has had a significantly increased stability and higher electrochemical activity compared to the adsorbed monomeric dye. The polytoluidine blue urea biosensor has been operating at a working potential of -200 mV vs. SCE. The sensitivity of the biosensor was 980 nA mM(-1) cm(-2). The biosensor showed linearity in concentration range up to 0.8 mM with the detection limit of 0.02 mM (S/N=3). 相似文献
150.
Prof. Dr. Hans Nowotny Josef Tomiska László Erdélyi Adolf Neckel 《Monatshefte für Chemie / Chemical Monthly》1977,108(1):7-19
By means of vapor pressure measurements using theTorker method (Torsion-Knudsen Effusion Recoil) as well as theKnudsen tanspiration technique in connection with a mass spectrometer, the heats of formation of the following compounds were found to be –6.5±0.7 kcal/g atom (Mn0.366Si0.634), –7.8±0.6 kcal/g atom (Mn0.50Si0.50), –7.3±0.6 kcal/g atom (Mn0.625Si0.375), and –6.6±0.6 kcal/g atom (Mn0.75Si0.25).
Mit 7 Abbildungen 相似文献
Mit 7 Abbildungen 相似文献