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81.
We demonstrate the possibility of creating user-defined partially coherent light pulses by means of a slight modification of the direct space-to-time pulse shaper. Specifically, we generate a mutual coherence function that corresponds to the independent-elementary-pulse representation model. The theoretical limits in the parameter of global coherence and the efficiency of the system are studied. Our result opens the door to a new way of quantum control in laser-assisted chemical reactions, namely, control by partial coherence. 相似文献
82.
Zhe Quan Yaru Song Gladys Peters Ming Shenwu Yinghong Sheng Huey-Min Hwang Yi-Ming Liu 《Analytical sciences》2005,21(2):115-119
An enantiomeric separation of dopamine-derived neurotoxins by capillary electrophoresis has been developed. Tetrahydroisoquinoline (TIQ), dopamine (DA), (R/S)-1-benzyl-TIQ (BTIQ), (R/S)-6,7-dihydroxy-1-methyl-TIQ (salsolinol, Sal), and (R/S)-6,7-dihydroxy-1, 2-dimethyl-TIQ (N-methyl-salsolinol, NMSal) were studied as model compounds. The CE running buffer (50 mM phosphate buffer at pH 3.0) contained 1.5 M urea and 12 mM beta-CD as a chiral selector. During separation, the (R)-enantiomers formed more stable inclusion complexes with beta-CD, and thus had a longer migration time than their optical antipodes. It was noticed that the recovery rates of these TIQ derivatives were very poor (< 15%) during protein precipitation, a procedure widely used for cleaning up biological samples. The recovery was significantly improved by pre-mixing the sample with a surfactant (e.g., sodium hexanesulfonate or Triton X-100) to reduce the co-precipitation. The present method in combination with electrospray ionization tandem mass spectrometry (ESI-MS/MS) was applied to study samples obtained from in vitro incubation of two catecholamines, dopamine and epinine, with aldehydes forming neurotoxins including (S)- and (R)-NMSal enantiomers. The later is known to induce Parkinsonism in rats. 相似文献
83.
Dr. Antony E. Fernandes Dr. Ali Dirani Cécile d'Haese Gladys Deumer Dr. Weiming Guo Dr. Peter Hensenne Fady Nahra Dr. Xavier Laloyaux Prof. Vincent Haufroid Prof. Bernard Nysten Prof. Olivier Riant Prof. Alain M. Jonas 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(50):16226-16233
Polymer brushes (PBs) have been used as supports for the immobilization of palladium complexes on silicon surfaces. The polymers were grown by surface‐initiated atom‐transfer radical polymerization (SI‐ATRP) and postdecorated with dipyridylamine (dpa) ligands. The pendant dpa units were in turn complexed with [Pd(OAc)2] to afford hybrid catalytic surfaces. A series of catalytic samples of various thicknesses (ca. 20–160 nm) and associated palladium loadings (ca. 10–45 nmol cm?2) were obtained by adjusting the SI‐ATRP reaction time and characterized by ellipsometry, X‐ray reflectivity, X‐ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry (ICP‐MS). ICP‐MS revealed a near‐linear relationship between thickness of the polymer brush and palladium content, which confirmed the robustness of the preparation and postmodification sequence presented herein, rendering possible the creation of functional architectures with predefined catalytic potential. The activities of the catalytic PBs were determined by systematically exploring a full range of substrate‐to‐catalyst ratios in a model palladium(0)‐catalyzed reaction. Quantitative transformations were observed for loadings down to 0.03 mol % and a maximum turnover number (TON) of around 3500 was established for the system. Comparison of the catalytic performances evidenced a singular influence of the thickness on conversions and TONs. The limited recyclability of the hairy catalysts has been attributed to palladium leaching. 相似文献
84.
Van Bael MJ Bekaert J Temst K Van Look L Moshchalkov VV Bruynseraede Y Howells GD Grigorenko AN Bending SJ Borghs G 《Physical review letters》2001,86(1):155-158
A scanning Hall probe microscope is used to study flux pinning in a thin superconducting Pb film covering a square array of single-domain Co dots with in-plane magnetization. We show that single flux quanta of opposite sign thread the superconducting film below T(c) at the opposite poles of these dipoles. Depending on the polarity of the applied field, flux lines are attracted to a specific pole of the dipoles, due to the direct interaction with the vortexlike structures induced by the local stray field. 相似文献
85.
The preparation and oxidation of 2,3-dihydroindazoles to 1H, 2H or 3H-indazoles is described. A method for the synthesis of indazole 2-oxides has been found. Oxidation of 2-acetyl-2,3-dihydro-3,3-disubstituted indazoles 5a and 5c gave quinoid compounds 20a, 20b, 24a and 24b , which could be isomerized to 3H-indazoles upon removal of the acetyl group. A quinoid compound 21 was also obtained on treatment of 5a with tetracyanoethylene. 相似文献
86.
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89.
Base catalyzed cyclization of the 2-methylazoxybenzophenone ( 4B ) obtained by condensation of the 2-nitrosobenzophenone ( 2a ) with methylhydroxylamine led to the cinnoline 2-oxide ( 7 ) which is the major product of the peracid oxidation of the corresponding cinnoline ( 5 ). 相似文献
90.
Armin Walser Gladys Silverman Thomas Flynn R. Ian Fryer 《Journal of heterocyclic chemistry》1975,12(2):351-358
Variously substituted indolo[2,3-c]quinolines, benzofurano[2,3-c]quinolines and their positional isomers indolo[3,2-c]quinolines and benzofurano[3,2-c]quinolines respectively, were prepared from both indole and quinoline derivatives by intramolecular nucleophilic displacement of aromatic fluorine. The formation of an indolo[2,3-d]benzazepine was also observed. 相似文献