Search results for "wave"
showing 10 items of 6009 documents
Development of MR active contrast agents via Parahydrogen Induced Polarization
2009
Parahydrogen Induced Polarization provides dramatic MR signal enhancement that can be exploited for molecular imaging. This method allows amongst others for Magnetic Resonance Imaging of 13C and 15N, which is usually constrained by the low MR sensitivity of these nuclei. By combining hydrogenation of barbiturates with parahydrogen under special experimental conditions (PASADENA under pressure) with a polarization transfer sequence we demonstrate the transfer of the initial 1H polarization to 13C. The polarization transfer yields a signal increase for 13C of more than 1000. Hence, the role of certain target compounds such as anesthetics like the barbituric acid derivatives could be investiga…
Random quasi-phase-matched second harmonic generation in periodically poled lithium tantalate
2009
We experimentally observed and explained bulk second harmonic generation via random quasi-phase-matching, derived from a periodically poled lithium tantalate sample with a randomly patterned mark-to-space-ratio.
Hydrolysis of Phytic Acid by Microwave Treatment: Application to Phytic Acid Analysis in Pharmaceutical Preparations
1998
Abstract The acid hydrolysis of phytic acid in a Teflon reactor using a domestic microwave oven has been studied and compared with other reported procedures. In 0.44 M HCl quantitative hydrolysis was achieved with six heating stages of 2 min each. A lower yield was obtained with H 2 SO 4 and HNO 3 . The analytical use of this hydrolysis to determine phytic acid by indirect determination of phosphate has been demonstrated by analysis of three pharmaceutical formulations. No sample pretreatment other than obtaining a homogeneous suspension was necessary.
ChemInform Abstract: Green Conditions for the Suzuki Reaction Using Microwave Irradiation and a New HNT-Supported Ionic Liquid-Like Phase (HNT-SILLP)…
2014
Aryl iodides are coupled with conversions comparable to aryl bromides whereas conversions of aryl chlorides are significantly lower.
Absolute Configuration Determination of 2,3-Dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles Using Chiroptical Methods at Different Wavelengths
2016
A correlation between the absolute configuration and chiroptical properties of nonracemic 1,6,7-trisubstituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles was studied. A series of 16 novel representatives were prepared by Cu-catalyzed [3 + 2] cycloadditions of racemic (Z)-2-benzylidene-5-oxopyrazolidin-2-ium-1-ides to tert-butyl (S)-(3-oxopent-4-yn-2-yl)carbamate, and their structures were determined by NMR, VCD, ECD, and X-ray diffraction. A clear correlation between the sign of specific rotation and configuration at position C(1) allows for easy determination of the absolute configuration of 1,6,7-trisubstituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles by ECD and NMR. While VCD, requirin…
Synthesis and Electronic Spectra of Substitutedp-Distyrylbenzenes for the Use in Light-Emitting Diodes
2000
The influence of substitution on the absorption and Luminescence spectra of oligo(phenylenevinylene)s has been studied using distyrylbenzene (DSB) as a model compound. The degree, character, and pattern of substitution was varied systematically, altering the electronic properties of the DSB, the wavelength of the emitted light could be tuned over a range of 100 nm. The syntheses of 6b—h were performed by twofold Wittig Horner-olefinations of bisphoshonates 1a, b with substituted benzaldehydes 2a—i, 6ivia Heck-reaction of the dibromosulfonylbenzene 3, 6k by Siegrist-reaction of 4 with N-phenylbenzaldimine and the Knoevenagel-reaction of benzyl cyanide with 5 led to 6l.
Pyrene-fused bisphenazinothiadiazoles with red to NIR electroluminescence
2017
The synthesis and characterisation of two pyrene-fused phenazinothiadiazole derivatives with different substituents is described. Light-emitting diodes incorporating such derivatives display red to near-infrared electroluminescence with emission peaks at wavelengths as long as 721 nm, illustrating that pyrene-fused bisphenazinothiadiazoles can serve as deep red and NIR emitters.
Revision of Na 2 A1Σ+u state molecular constants by polarization labeling spectroscopy
1997
ABSTRACT. This paper contains the analysis of the A1 of Na2 based on the data obtained from thepolarization labeling spectroscopy experiment on the A' —X' transition. A set of Dunham coefficients is derived, which describes the A state in the wide range of v and J 126) quantum numbers and reproduces the positions of unperturbed rotational lines in the A-X band system towithinO.1 cm'.1. INTRODUCTION.We report' new analysis of the A' state based on the data obtained from polarization labelingspectroscopy (PLS) experiment"2, based on V-type optical—optical double resonance scheme, on the 1 : ' ; band system of sodium dimer. The diatomic alkali molecules, with their simple electronic configurat…