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141.
Milne AJ Elliott JA Zabeti P Zhou J Amirfazli A 《Physical chemistry chemical physics : PCCP》2011,13(36):16208-16219
Despite the practical need, no models exist to predict contact angles or wetting mode of surfactant solutions on rough hydrophobic or superhydrophobic surfaces. Using Gibbs' adsorption equation and a literature isotherm, a new model is constructed based on the Wenzel and Cassie equations. Experimental data for aqueous solutions of sodium dodecyl sulfate (SDS) contact angles on smooth Teflon surfaces are fit to estimate values for the adsorption coefficients in the model. Using these coefficients, model predictions for contact angles as a function of topological f (Cassie) and r (Wenzel) factors and SDS concentration are made for different intrinsic contact angles. The model is also used to design/tune surface responses. It is found that: (1) predictions compare favorably to data for SDS solutions on five superhydrophobic surfaces. Further, the model predictions can determine which wetting mode (Wenzel or Cassie) occurred in each experiment. The unpenetrated or partially penetrated Cassie mode was the most common, suggesting that surfactants inhibit the penetration of liquids into rough hydrophobic surfaces. (2) The Wenzel roughness factor, r, amplifies the effect of surfactant adsorption, leading to larger changes in contact angles and promoting total wetting. (3) The Cassie solid area fraction, f, attenuates the lowering of contact angles on rough surfaces. (4) The amplification/attenuation is understood to be due to increased/decreased solid-liquid contact-area. 相似文献
142.
Contrast agents based on lanthanide tetra-propargyl DOTAM complexes suitable for temperature mapping by magnetic resonance spectroscopy (MRS) are reported. Sensitivity values from 1.05 ppm/°C to 1.76 ppm/°C were determined which represents an improvement of 2-3 times over currently available lanthanide temperature-responsive contrast agents. 相似文献
143.
Tadesse M Strøm MB Svenson J Jaspars M Milne BF Tørfoss V Andersen JH Hansen E Stensvåg K Haug T 《Organic letters》2010,12(21):4752-4755
Bioassay-guided fractionation of the sub-Arctic ascidian Synoicum pulmonaria collected off the Norwegian coast led to the isolation of a novel family of brominated guanidinium oxazolidinones named synoxazolidinones A and B (1 and 2). The backbone of the compounds contains a 4-oxazolidinone ring rarely seen in natural products. The structure of the compounds was determined by spectroscopic methods. The synoxazolidinones exhibited antibacterial and antifungal activities. 相似文献
144.
A novel method, combining isotope dilution with standard additions, was developed for the analysis of eight elements (Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb) in seawater. The method requires just 12 mL of sample and employs an off-line pre-concentration step using the commercially available chelating resin Toyopearl AF-Chelate-650M prior to determination by high resolution inductively coupled plasma magnetic sector mass spectrometry (ICP-MS). Acidified samples were spiked with a multi-element standard of six isotopes (57Fe, 62Ni, 65Cu, 68Zn, 111Cd and 207Pb) enriched over natural abundance. In addition, standard additions of a mixed Co and Mn standard were performed on sub-sets of the same sample. All samples were irradiated using a low power (119 mW cm−2; 254 nm) UV system, to destroy organic ligands, before pre-concentration and extraction from the seawater matrix. Ammonium acetate was used to raise the pH of the 12 mL sub-samples (off-line) to pH 6.4 ± 0.2 prior to loading onto the chelating resin. The extracted metals were eluted using 1.0 M Q-HNO3 and determined using ICP-MS. The method was verified through the analysis of certified reference material (NASS-5) and the SAFe inter-comparison samples (S1 and D2), the results of which are in good agreement with the certified and reported consensus values. We also present vertical profiles of the eight metals taken from the Bermuda Atlantic Time Series (BATS) station collected during the GEOTRACES inter-comparison cruise in June 2008. 相似文献
145.
Tsang‐Lin Hwang Michael Ronk Jacqueline E. Milne 《Magnetic resonance in chemistry : MRC》2013,51(2):89-94
In the pharmaceutical industry, regulatory expectations driven by patient safety considerations make structure elucidation of impurities at levels greater than 0.1% in the active pharmaceutical ingredient (API) of primary interest. Impurities can be generated from isomers in starting materials, or produced from different process steps toward the final API. Proton peaks belonging to different impurities could be potentially identified in the one‐dimensional 1H NMR spectrum, when evaluated in combination with two‐dimensional (2‐D) COSY and HSQC data. However, in 2‐D HMBC data, correlation responses from different impurities may overlap with those from the major component, causing uncertainty of long‐range proton to carbon correlations and quaternary carbon assignments. This observation prompts us to design the 2‐D selective‐TOCSY HMBC experiment to distinguish responses from different impurities in mixtures to obtain 2‐D NMR data for each impurity, thus eliminating the use of a chromatographic isolation step to obtain material for NMR analysis. This methodology is demonstrated for structure elucidation of impurities ranging from 8.2% in the raw material to 0.4% in the API in this study, and would be particularly useful for industrial samples in which the solubility and availability of material are not an issue. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
146.
147.
Möhr-Vorobeva E Johnson SL Beaud P Staub U De Souza R Milne C Ingold G Demsar J Schaefer H Titov A 《Physical review letters》2011,107(3):036403
We use time-resolved optical reflectivity and x-ray diffraction with femtosecond resolution to study the dynamics of the structural order parameter of the charge density wave phase in TiSe2. We find that the energy density required to melt the charge density wave nonthermally is substantially lower than that required for thermal suppression and is comparable to the charge density wave condensation energy. This observation, together with the fact that the structural dynamics take place on an extremely fast time scale, supports the exciton condensation mechanism for the charge density wave in TiSe2. 相似文献
148.
Bruce F. Milne Robson P. Pereira Ana Maria Rocco Janet M. S. Skakle Anthony J. Travis James L. Wardell Solange M. S. V. Wardell 《应用有机金属化学》2005,19(3):363-371
The MeCOCH2CMe2 ligand in X3SnCMe2CH2COMe ( 2 ; X = halide) acts as a C,O‐chelating group both in the solid state and in non‐coordinating solutions. The intramolecular Sn? O bond lengths in trigonal bipyramidal 2 (X = Cl and I), as determined by X‐ray crystallography, indicate that the stronger interaction occurs in 2 X = Cl. Comparisons with the Sn? O bond lengths in the estertin trihalides, X3SnCH2CH2CO2R ( 1 ; R = Me), suggest that the latter form stronger chelates than do 2 . In chlorocarbon solution, 2 (X = Cl, I) undergoes exchange reactions, as shown by NMR spectra, to give all possible halide derivatives, ∑(ClnI3?nSnCMe2CH2COMe) (n = 0–3). Various ab initio calculations on 2 and X3SnCH2CH2COMe ( 3 ) have been carried out. Comparisons of the theoretical and experimental structures of 2 for X = Cl or I are reported. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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