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101.
Summary The addition of organic solvents (light aliphatic, heavy aliphatic and aromatic hydrocarbons) in Brazilian gasoline is unfortunately very frequent, and this illicit practice impares gasoline quality. Gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS) analyses can be used as a procedure to improve the detection of adulterated gasoline. The results showed that adulterated samples and also the type of organic solvent used in adulteration can be detected by comparison of chromatographic profiles (standard samples versus adulterated samples). However, a single GC analysis can detect an adulterated gasoline, and so decrease the number of adulterated samples approved as presenting good quality. 相似文献
102.
103.
We report ab initio computations with the Vienna Ab initio Simulation Package (VASP) aimed at elucidating the adsorption mechanism of graphene-like structures on (111) Pd, Pt, and Ni surfaces. To study the adsorption properties, we simulate an already-formed graphene layer. We present a comparative discussion of the graphene interactions with the three metals, focusing on the very particular adsorption of graphene over Pd. 相似文献
104.
New primary amine-guanidines derived from the monoguanylation of (1S,2S)- and (1R,2R)-cyclohexane-1,2-diamine have been prepared and used as chiral organocatalysts for the enantioselective conjugate addition of α,α-disubstituted aldehydes to maleimides. The corresponding Michael adducts bearing a new stereocenter were generally obtained in high or quantitative yields and with good enantioselectivities (up to 93% ee). 相似文献
105.
Prof. Dr. Theodor Doll Dr. Juan J. Velasco‐Velez Dr. Dirk Rosenthal Dr. Jonathan Avila Prof. Dr. Victor Fuenzalida 《Chemphyschem》2013,14(11):2505-2510
Microchemical sensors and catalytic reactors make use of gases during adsorption in specific ways on selected materials. Fine‐tuning is normally achieved by morphological control and material doping. The latter relates surface properties to the electronic structure of the bulk, and this suggests the possibility of electronic control. Although unusual for catalytic surfaces, such phenomena are sometimes reported for microsensors, but with little understanding of the underlying mechanisms. Herein, direct observation of the electroadsorptive effect by a combination of X‐ray photoelectron spectroscopy and conductivity analysis on nanometre‐thick semiconductor films on buried control electrodes is reported. For the SnO2/NO2 model system, NO3 surface species, which normally decay at the latest within minutes, can be kept stable for 1.5 h with a high coverage of 15 % under appropriate electric fields. This includes uncharged states, too, and implies that nanoelectronic structures provide control over the predominant adsorbate conformation on exterior surfaces and thus opens the field for chemically reactive interfaces with in situ tunability. 相似文献
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107.
Vega-Hissi Esteban G. Andrada Matias F. Díaz Mario G. Garro Martinez Juan C. 《Molecular diversity》2019,23(4):985-995
Molecular Diversity - Although many sulfur containing garlic compounds present antioxidant activity, little is known about molecular mechanisms through which these compounds react with reactive... 相似文献
108.
Mauricio Gomes Constantino Luiz Gonzaga de Oliveira Matias Gil Valdo José da Silva Vladimir Constantino Gomes Heleno Maria Teresa do Prado Gambardella 《合成通讯》2013,43(24):4285-4295
Abstract: In this paper we describe a very short stereoselective synthesis of the β-ethoxylactone 13, a model structure for compounds isolated from Otoba parvifolia. The method, which also produces β-hydroxy-esters and β-hydroxy-lactones, is based on a chemo- and stereoselective Reformatsky reaction. 相似文献
109.
MISTRAL: a transmission soft X‐ray microscopy beamline for cryo nano‐tomography of biological samples and magnetic domains imaging
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Andrea Sorrentino Josep Nicolás Ricardo Valcárcel Francisco Javier Chichón Marc Rosanes Jose Avila Andrei Tkachuk Jeff Irwin Salvador Ferrer Eva Pereiro 《Journal of synchrotron radiation》2015,22(4):1112-1117
The performance of MISTRAL is reported, the soft X‐ray transmission microscopy beamline at the ALBA light source (Barcelona, Spain) which is primarily dedicated to cryo soft X‐ray tomography (cryo‐SXT) for three‐dimensional visualization of whole unstained cells at spatial resolutions down to 30 nm (half pitch). Short acquisition times allowing for high‐throughput and correlative microscopy studies have promoted cryo‐SXT as an emerging cellular imaging tool for structural cell biologists bridging the gap between optical and electron microscopy. In addition, the beamline offers the possibility of imaging magnetic domains in thin magnetic films that are illustrated here with an example. 相似文献