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51.
JPC – Journal of Planar Chromatography – Modern TLC - Cu(II) complexes of l-threonine, l-serine, and l-tartaric acid were prepared and used as ligand exchange reagents for enantiomeric... 相似文献
52.
Amino acids are unique in terms of their structural features and multidimensional uses. With their simple structures and the ready availability of both enantiomers, amino acids not only serve as a chiral pool for synthesis but also provide an inexpensive pool for resolution studies. There has been no attempt to review the application of amino acids as chiral selectors for chromatographic enantioresolution of pharmaceuticals and other compounds. The present paper deals with application of l-amino acids and complexes of l-amino acids with a metal ion, particularly Cu(II), as an impregnating reagent in thin-layer chromatography or as a chiral ligand exchange reagent or a chiral mobile phase additive in both thin-layer chromatography and high-performance liquid chromatography. Enantiomeric resolution of β-blockers, nonsteroidal anti-inflammatories, amino acids (and their derivatives) and certain other compounds is discussed. 相似文献
53.
Enantioresolution of (R,S)-baclofen was accomplished using a newly synthesized set of three chiral derivatizing reagents (CDRs) having amines [(S)-(-)-α,4-dimethylbenzylamine, (-)-cis-myrtanylamine and (R)-(-)-1-cyclohexylethylamine] as chiral auxiliaries in cyanuric chloride and another set of five CDRs having amino acids (L-Leu, D-Phg, L-Val, L-Met and L-Ala) as chiral auxiliaries. These eight CDRs were used for synthesis of diastereomers of (R,S)-baclofen under microwave irradiation. The diastereomers were separated on a reversed-phase C(18) column using mixtures of methanol with aqueous trifluoroacetic acid with UV detection at 230 nm. Chromatographic data obtained for the two sets of diastereomers were compared among themselves and among the two groups. The method was validated for limit of detection, linearity, accuracy and precision. 相似文献
54.
Bora Yalkinoglu 《Inventiones Mathematicae》2013,191(2):383-425
This paper has two parts. In the first part we construct arithmetic models of Bost-Connes systems for arbitrary number fields, which has been an open problem since the seminal work of Bost and Connes (Sel. Math. 1(3):411–457, 1995). In particular our construction shows how the class field theory of an arbitrary number field can be realized through the dynamics of a certain operator algebra. This is achieved by working in the framework of Endomotives, introduced by Connes, Consani and Marcolli (Adv. Math. 214(2):761–831, 2007), and using a classification result of Borger and de Smit (arXiv:1105.4662) for certain Λ-rings in terms of the Deligne-Ribet monoid. Moreover the uniqueness of the arithmetic model is shown by Sergey Neshveyev in an appendix. In the second part of the paper we introduce a base-change functor for a class of algebraic endomotives and construct in this way an algebraic refinement of a functor from the category of number fields to the category of Bost-Connes systems, constructed recently by Laca, Neshveyev and Trifkovic (arXiv:1010.4766). 相似文献
55.
Sezgin Bakırdere Selin Bora E. Gülhan Bakırdere Fırat Aydın Yasin Arslan O. Tarık Komesli Işıl Aydın Emrah Yıldırım 《Central European Journal of Chemistry》2012,10(3):675-685
Carcinogenic and mutagenic properties of aflatoxin species are known in literature. Their intake over a long time period might
be health-dangerous for human even at trace levels. It is well known that different foodstuffs can be contaminated by aflatoxin
species through growing and storage. Due to the serious health effects, sensitive determination of aflatoxin species in any
matrices related with the human being is very crucial at trace levels. In literature, there are sensitive techniques to analyze
the different samples for the contents of their aflatoxin species. Each technique has some advantages and disadvantages over
the other techniques. This review aims to summarize the different health effects of aflatoxin species, development of analytical
techniques and applications of developed techniques in a variety of matrices.
相似文献
56.
Shuchi Tiwari Kallol K. Ghosh Jan Marek Kamil Kuca 《Journal of Physical Organic Chemistry》2010,23(6):519-525
Nucleophilic reactivity of some functionalized surfactants, i.e. quaternary pyridinium aldoximes towards the hydrolysis of p‐nitrophenyl acetate (PNPA), p‐nitrophenyl benzoate (PNPB), p‐nitrophenyldiphenyl phosphate (PNPDPP) and p‐nitrophenyl p‐toluene sulphonate (PNPTS) has been studied at pH 7.1 and 27 °C. Addition of functionalized surfactant to reaction medium causes progressive increase in the rate of hydrolysis and reaches a maximum and then decreases due to further addition of surfactant. An increase in the alkyl chain length of functionalized surfactants resulted in an increase in the first‐order rate constant. The apparent pKa and CMC of functionalized surfactants have also been determined by spectrophotometric and conductometric methods, respectively. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
57.
In the present investigation, attempts have been made to obtain the spectral signature of the fruit jamun and to estimate the changes in biochemical composition that take place in the process of ripening of the fruits. The changes in exocarp, mesocarp, and seed of the fruit in raw and ripe stages have been investigated with the help of label-free, nondestructive, and rapid techniques: laser-induced fluorescence and attenuated total reflectance Fourier transform infrared spectroscopy. For this, the fluorescence spectra of the different parts (exocarp, mesocarp, and seed) of the raw and ripe fruits of jamun excited by 405?nm violet diode laser have been recorded in the spectral region 400–900?nm. The spectrum shows the spectral signature of anthocyanin, flavonoids, carotenoid, and chlorophyll. The observed decrease in the intensity of chlorophyll bands and simultaneous increase in the intensity of anthocyanin and carotenoid bands is regarded as indicator of the ripening of the fruit of jamun. Also, attenuated total reflectance Fourier transform infrared spectra have been recorded in the spectral region 4000–485?cm?1 for the identification of functional groups associated with different biochemical altered during ripening process of the fruits of jamun. The analyses of the recorded infrared spectra show the presence of carbohydrates, cell wall components, phenolic compounds, nucleic acid, and amide. The quantitative estimation of the biochemical content in the different parts of jamun fruit during the ripening process has been done through calculating the area of the band by curve fitting. The determined spectral signatures can be utilized for the effective monitoring of jamun fruit. 相似文献
58.
Some unusual and unexplained events (the so-called Kolar events) were interpreted in Pramana – J. Phys. 82, 609 (2014). This article is a corrigendum to it. 相似文献
59.
Serkan Dag E. Erhan Arman Bora Yildirim 《International Journal of Solids and Structures》2010,47(25-26):3480-3488
This article introduces a computational method based on the Jk-integral for mixed-mode fracture analysis of orthotropic functionally graded materials (FGMs) that are subjected to thermal stresses. The generalized definition of the Jk-integral is recast into a domain independent form composed of line and area integrals by utilizing the constitutive relations of plane orthotropic thermoelasticity. Implementation of the domain independent Jk-integral is realized through a numerical procedure developed by means of the finite element method. The outlined computational approach enables the evaluation of the modes I and II stress intensity factors, the energy release rate, and the T-stress. The developed technique is validated numerically by considering two different problems, the first of which is the problem of an embedded crack in an orthotropic FGM layer subjected to steady-state thermal stresses; and the second one is that of periodic cracks under transient thermal loading. Comparisons of the mixed-mode stress intensity factors evaluated by the Jk-integral based method to those calculated through the displacement correlation technique (DCT) and to those available in the literature point out that, the proposed form of the Jk-integral possesses the required domain independence and leads to numerical results of high accuracy. Further results are presented to illustrate the influences of the geometric and material constants on the thermal fracture parameters. 相似文献
60.