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21.
James P. Kutney Eugene Dimitriadis Gary M. Hewitt Philip J. Salisbury Mahatam Singh James A. Servizi Dennis W. Martens Robert W. Gordon 《Helvetica chimica acta》1982,65(5):1343-1350
One of the fish-toxic chlorinated resin acids, 14-chlorodehydroabietic acid ( 5 ), found in kraft mill effluent is examined. When exposed to the fungus Mortierella isabellina, 5 is converted into a number of hydroxylated derivatives which show low levels of toxicity to fish. These biotransformation products were isolated and characterized. 相似文献
22.
New Oxoplumbates(II) A2PbO2 (A = K, Rb, Cs), with Binuclear Groups [OPbO2PbO] Unknown K2PbO2, Rb2PbO2 and Cs2PbO2 (yellowish powder, yellowish transparent single crystals, respectively) have been prepared, The compounds crystallize triclinic with a = 10.901 Å, b = 7.606 Å, c = 7.328 Å, α = 119.35°, β = 88.42°, γ =117,73°, (K2PbO2); a = 10.907 Å, b = 8.510 Å, c = 7.815 Å, α = 124.00°, β = 84.97°, γ = 120.68° (Rb2PbO2) and a = 11.644 Å, b = 8.905 Å, c = 8.040 Å, α = 123.32°, β = 85.70°, γ = 120.49° Z = 4, space group P1 -C/i1. For K2PbO2 we find R = 8.65% and Rw = 9.32% (2283 independent reflections). Parameters see text. There are isolated [Pb2O4]groups, which are connected in a complicated way by mutual K+ ions forming layers. The Madelung Part of the Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these by means of mean Fictive Ionic Radii, MEFIR, are calculated and discussed. 相似文献
23.
Frost RL Ding Z Martens WN Johnson TE Kloprogge JT 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(2):321-328
Infrared and Raman spectroscopy have been used to characterise synthetic hydrotalcites of formula Cu(x)Zn(6 - x)Al2(OH)16(CO3) x 4H2O. The spectra have been used to assess the molecular assembly of the cations in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features based (a) upon the carbonate anion (b) the hydroxyl units (c) water units. The Raman spectra of the hydroxyl-stretching region enable bands to be assigned to the CuOH, ZnOH and AlOH units. It is proposed that in the hydrotalcites with minimal cationic replacement that the cations are arranged in a regular array. For the Cu(x)Zn(6 - x)Al2(OH)16(CO3) x 4H2O hydrotalcites, spectroscopic evidence suggests that 'islands' of cations are formed in the structure. In a similar fashion, the bands assigned to the interlayer water suggest that the water molecules are also in a regular well-structured arrangement. Bands are assigned to the hydroxyl stretching vibrations of water. Three types of water are identified (a) water hydrogen bonded to the interlayer carbonate ion (b) water hydrogen bonded to the hydrotalcite hydroxyl surface and (c) interlamellar water. It is proposed that the water is highly structured in the hydrotalcite as it is hydrogen bonded to both the carbonate anion and the hydroxyl surface. 相似文献
24.
Brake JM Daschner MK Abbott NL 《Langmuir : the ACS journal of surfaces and colloids》2005,21(6):2218-2228
This paper reports an experimental investigation of the self-assembly of phospholipids (l-alpha-phosphatidylcholine-beta-oleoyl-gamma-palmitoyl (l-POPC), dipalmitoyl phosphatidylcholine (DPPC), and l-alpha-dilauroyl phosphatidylcholine (l-DLPC)) at interfaces between aqueous phases and the nematic liquid crystal (LC) 4'-pentyl-4-cyanobiphenyl. Stable planar interfaces between the aqueous phases and LCs were created by hosting the LCs within gold grids (square pores with widths of 283 microm and depths of 20 microm). At these interfaces, the presence and lateral organization of the phospholipids leads to interface-driven orientational transitions within the LC. By doping the phospholipids with a fluorescently labeled lipid (Texas Red-1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (TR-DPPE)), quantitative epifluorescence microscopy revealed the saturation coverage of phospholipid at the interface to be that of a monolayer with an areal density of approximately 49 +/- 8% relative to hydrated lipid bilayers. By adsorbing phospholipids to the aqueous-LC interface from either vesicles or mixed micelles of dodecyltrimethylammonium and phospholipid, control of the areal density of phospholipid from 42 +/- 10 to 102 +/-18% of saturation monolayer coverage was demonstrated. Fluorescence recovery after photobleaching (FRAP) experiments performed by using laser scanning confocal microscopy (LSCM) revealed the lateral mobility of fluorescently labeled DPPE in l-DLPC assembled at the interface with the liquid crystal to be (6 +/- 1) x 10(-12) m(2)/s for densely packed monolayers. Variation of the surface coverage and composition of phospholipid led to changes in lateral diffusivity between (0.2 +/- 0.1) x 10(-12) and (15 +/- 2) x 10(-12) m(2)/s. We also observed the phospholipid-laden interface to be compartmentalized by the gold grid, thus allowing for the creation of patterned arrays of phospholipids at the LC-aqueous interface. 相似文献
25.
Martens WN Kloprogge JT Frost RL Bartlett JR 《Journal of colloid and interface science》2002,247(1):132-137
A model for pseudoboehmite crystallite packing formed during the hydrolysis of trisecbutoxyaluminium is postulated. The model describes platelike crystallites of pseudoboehmite stacked in a sharing edges only configuration. With this type of stacking, the pore sizes detected are approximately equal to the crystallite sizes of the hydrolysates. The hydrolysates age via a dissolution re-precipitation reaction. This increases the size of the crystallite size of the pseudoboehmite formed, speeding peptization by allowing nitrate ions to enter pores and access the surfaces of the crystallites. This type of model also allows an explanation for the peptization kinetics of systems containing sec-butanol formed during the hydrolysis of trisecbutoxyaluminium. 相似文献
26.
Summary A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to
study the thermal decomposition of liebigite. Water is lost in two steps at 44 and 302°C. Two mass loss steps are observed
for carbon dioxide evolution at 456 and 686°C. The product of the thermal decomposition was found to be a mixture of CaUO4 and Ca3UO6. The thermal decomposition of liebigite was followed by hot-stage Raman spectroscopy. Two Raman bands are observed in the
50°C spectrum at 3504 and 3318 cm-1 and shift to higher wavenumbers upon thermal treatment; no intensity remains in the bands above 300°C. Three bands assigned
to the υ1 symmetric stretching modes of the (CO3)2- units are observed at 1094, 1087 and 1075 cm-1 in agreement with three structurally distinct (CO3)2- units. At 100°C, two bands are found at 1089 and 1078 cm-1. Thermogravimetric analysis is undertaken as dynamic experiment with a constant heating rate whereas the hot-stage Raman
spectroscopic experiment occurs as a staged experiment. Hot stage Raman spectroscopy supports the changes in molecular structure
of liebigite during the proposed stages of thermal decomposition as observed in the TG-MS experiment. 相似文献
27.
[reaction: see text] Whereas cyclopentenylcarbenes resulting from photocycloaddition of 4-alk-1-ynylcoumarins to 2,3-dimethylbut-2-ene undergo tandem cyclization to hitherto unknown tetracyclic (4-hetera)cyclopent[b,c]acenaphthylenes, the corresponding cyclopentenylnitrenes stemming from 4-cyanocoumarins and the same alkene are converted into tricyclic imines via H-abstraction. 相似文献
28.
Ozerov OV Pink M Watson LA Caulton KG 《Journal of the American Chemical Society》2004,126(7):2105-2113
Both (PNP)Re(H)(4) and (PNP)ReH(cyclooctyne) (PNP(i)(Pr) = ((i)Pr(2)PCH(2)SiMe(2))(2)N) react with alkylpyridines NC(5)H(4)R to give first (PNP)ReH(2)(eta(2)-pyridyl) and cyclooctene and then, when not sterically blocked, (PNP)Re(eta(2)-pyridyl)(2) and cyclooctane. The latter are shown by NMR, X-ray diffraction, and DFT calculations to have several energetically competitive isomeric structures and pyridyl N donation in preference to PNP amide pi-donation. DFT studies support NMR solution evidence that the most stable bis pyridyl structure is one that is doubly eta(2)- with the pyridyl N donating to the metal center. When both ortho positions carry methyl substituents, cyclooctane and the carbyne complex (PNP)ReH(tbd1;C-pyridyl) are produced. Excess 2-vinyl pyridine reacts with (PNP)Re(H)(4) preferentially at the vinyl group, to give 2-ethyl pyridine and the sigma-vinyl complex (PNP)ReH[eta(2)-CH=CH(2-py)]. The DFT and X-ray structures show, by various comparisons, the ability of the PNP amide nitrogen to pi-donate to an otherwise unsaturated d(4) Re(III) center, showing short Re-N distances consistent with the presence of pi-donation. 相似文献
29.
Craig C. Martens 《Journal of statistical physics》1992,68(1-2):207-237
We describe our work on qualitative methods for visualizing the quantum eigenstates of systems with nonlinear classical dynamics. For two-degree-of-freedom systems, our approach is based on the use of generalized coherent states, and allows systems with nonoscillator kinematics to be investigated. The general approach is illustrated with two examples involving vibration-rotation interaction in polyatomic molecules. We apply the coherent states of the Lie groupH
4SU(2) to define quantum surfaces of section for a model involving centrifugal coupling of a harmonic bend with molecular rotation, andSU(2)SU(2) coherent states to study two harmonic normal modes coupled to overall molecular rotation through coriolis interaction. In both systems, quantum states are visualized on the rotational surface of section and compared with the corresponding classical phase space structure. Striking classical-quantum correspondence is observed. We then describe recent results on the quantum states of (N 3)-dimensional systems of coupled nonlinear oscillators, which reveal a quantum delocalization that is reminiscent of classical Arnold diffusion. 相似文献
30.
Fabrication of three-dimensional photonic crystals with tunable photonic properties by biotemplating
Daniel Van Opdenbosch Maren Johannes Xia Wu Helge Fabritius Cordt Zollfrank 《Photonics and Nanostructures》2012,10(4):516-522
Photonic crystals with tunable D-surface structures for possible high-temperature gas- and temperature-sensing applications were prepared by a biotemplating method. This included infiltrating colored scales of the beetle Entimus imperialis with an organopolysiloxane mixture followed by simultaneous combustion of the template and calcination of the cured organopolysiloxane. A high-yield inorganic silica-based replica of the original structure was obtained, which is capable of withstanding temperatures up to 600 °C. Light- and scanning electron microscopy combined with focused ion beam milling showed a precise replication of the whole scales and their internal D-surface structure. Fourier-transform infrared spectroscopy and X-ray diffraction analysis confirmed the complete curing of the organopolysiloxanes and their transformation into amorphous silica during calcination. The dielectric constant of the manufactured materials determined by Abbé refractometry was ? = 2.3180 and used to perform band structure calculations utilizing the plane wave expansion method. By changing the chain length and degree of crosslinking of the organopolysiloxane precursor mixture, the lattice parameters and filling factors, and therefore the photonic properties of the replicas, could be tuned. 相似文献