Carbide precipitates in solution-quenched PH13-8 Mo stainless steel: A small-angle neutron scattering investigation

This paper deals with the small-angle neutron scattering (SANS) investigation on solution-quenched PH13-8 Mo stainless steel. From the nature of the variation of the functionality of the profiles for varying specimen thickness and also from the transmission electron microscopy (TEM), it has been established that the small-angle scattering signal predominantly originates from the block-like metallic carbide precipitates in the specimen. The contribution due to double Bragg reflection is not significant in the present case. The single scattering profile has been extracted from the experimental profiles corresponding to different values of specimen thickness. In order to avoid complexity and non-uniqueness of the multi-parameter minimization for randomly oriented polydisperse block-like precipitate model, the data have been analyzed assuming randomly oriented polydisperse cylindrical particle model with a locked aspect ratio.     

Isomeric ruthenium terpyridine complexes [Ru(trpy)(L)Cl]n+ containing the unsymmetrically bidentate acceptor L=3-amino-6-(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine. Synthesis, structures, electrochemistry, spectroscopy and DFT calculations

The isomeric title complexes were obtained in almost equimolar ratio from the reaction of Ru(trpy)Cl3 and L. Crystal structure analyses of the perchlorate hemihydrates, electrochemical and spectroscopic (NMR, UV/VIS, EPR) studies, supported by DFT calculations, reveal distinct differences between the isomeric redox series [1]n+(tetrazine-Nt trans to Cl) and [2]n+(pyrazolyl-Np trans to Cl; n= 0, 1, 2). The latter system with the pi acceptors trpy and tetrazine in the equatorial plane and the pyrazolyl and chloride donors in the axial positions exhibits facilitated oxidation, lower energy MLCT transitions, more balanced chelate coordination, and a higher g anisotropy in the oxidised (RuIII) state. According to partially resolved EPR spectra of one-electron reduced neutral compounds and they have the unpaired electron predominantly in the tetrazine ring of L.     

Total synchronous fluorescence scan spectra of petroleum products

Extending the two-dimensional synchronous fluorescence scan to a three-dimensional total synchronous fluorescence scan (TSFS) spectral measurement gives the total synchronous fluorescence characteristics of a multifluorophoric sample at various possible wavelength intervals (Deltalambda), which could help to characterize multifluorophoric systems better. TSFS spectra of petroleum products such as diesel, kerosene, petrol, engine oil etc., available in the Indian market, are reported. Fluorescence in these samples is due to the presence of polycyclic aromatic hydrocarbons (PAHs) of various ring sizes. The TSFS contour plot profiles of the neat samples measured at right-angle geometry is a result of various energy-degrading photophysical processes such as inner filter effect, light attenuation, resonance energy transfer, collisional quenching etc. TSFS plots make it easy to obtain the optimized Deltalambda of an unknown sample of analytical interest. TSFS and the excitation-emission matrix (EEM) techniques are similar, but the contour profiles generated are different. The response of the TSFS contour profiles to dilution is different from that in the EEM contour profiles. Thus, TSFS can provide an alternative way of presenting the fluorescence response of concentrated multifluorophoric samples.     

Pyridine and pyrimidine ring syntheses from 4-(4-morpholino)-3-pentenone and from ethyl 3-(4-morpholino)-2-butenoate

3-Substituted 2(1H)-pyridones are produced from reaction of 4-(4-morpholino)-3-pentenone 1 with each of the following carbon acids: cyanoacetamide, malononitrile, cyanothioacetamide, acetylacetamide, benzoyl-acetonitrile. Reaction of ethyl 3-(4-morpholino)-2-butenoate 2 with cyanoacetamide gives the corresponding hydroxypyridone. Pyrimidines are formed by reaction of 1 and of 2 with benzamidine and with S-benzylthio-urea; in the last case, the eliminated morpholine displaces the benzylthio group to give the final product.     

Luminescence of Ce3+ in Y2SiO5 nanocrystals: Role of crystal structure and crystal size

Here, we report the role of crystal structure and crystal size on the photoluminescence properties of Ce3+ ions in Y2SiO5 nanocrystals. The emission at 430 nm (5d1 --> 4f1) and lifetime of the excited state of Ce3+ ion doped Y2SiO5 nanocrystals are found to be sensitive to the crystal structure, crystal size, and dopant concentration. It is found that the overall lifetime tau of 0.5 mol % Ce doped Y2SiO5 nanocrystals are 8.78 and 3.45 ns for 1000 and 1100 degrees C heat-treated samples with the same crystal structure (X1-Y2SiO5 phase), respectively. However, a significant increase in the overall lifetime (35.21 ns) is observed for the 1300 degrees C annealed 0.5 mol % Ce doped Y2SiO5 sample having a different crystal structure (X2-Y2SiO5 phase). We found that the decay kinetic is biexponential. It is explained that the fast component arises due to sequential hole-electron capture on the luminescent ions and the slow component arises from isolated ions. Our analysis suggests that modifications of radiative and nonraditive relaxation mechanisms are due to local symmetry structure of the host lattice and crystal size, respectively.     

Liquid chromatographic separation of derivatives of diospyrin, a bioactive bisnaphthoquinonoid plant-product, and analogous naphthyl compounds

Isocratic reversed-phase liquid chromatography (LC) method was developed using acetonitrile and water for the determination of diospyrin, a pharmacologically important bisnaphthoquinonoid plant-product. The method was validated for precision, accuracy and reproducibility, and was found to be linear over the concentration range of 1-1000 microg/ml; the limits of detection and quantitation were 8 and 20 ng, respectively. The technique was used to determine the amount of diospyrin in plant extracts from four climatic regions in India. It was also applied for differentiation and separation of 27 naphthyl compounds. While a composition of 50:50 was preferable for dimeric compounds, the composition 40:60 was a better choice for the monomers. Also, the isomeric alpha- and beta-naphthols and their dimers could be distinguished by conversion into the respective methyl ethers.     

Total synthesis of (+/-)-stemodinone via an efficient ring-exchange strategy

A total synthesis of (+/-)-stemodinone, a tetracyclic stemodane diterpene, from the known tricyclic methyl olefin 11 is described. The key steps involve an efficient ring-exchange reaction and palladium(0)-catalyzed lactone migration. The ring-exchange strategy for controlling the stereochemistry was based on an initial Diels-Alder reaction to form a new ring followed by cleavage of the original ring. Cleavage of the original ring of the Diels-Alder adduct 9 was achieved by an initial regio- and chemoselective Baeyer-Villiger oxidation followed by the Pd(0)-catalyzed lactone-migration reaction reported by us.     

Autofluorescence characterization of advanced glycation end products of hemoglobin

This article describes the analysis of autofluorescence of advanced glycation end products of hemoglobin (Hb-AGE). Formed as a result of slow, spontaneous and non-enzymatic glycation reactions, Hb-AGE possesses a characteristic autofluorescence at 308/345 nm (lambda(ex)/lambda(em)). Even in the presence of heme as a quenching molecule, the surface presence of the glycated adduct gave rise to autofluorescence with the quantum yield of 0.19. The specificity of monoclonal antibody developed against common AGE structure with Hb-AGE was demonstrated using reduction in fluorescence polarization value due to increased molecular volume while binding. The formation of fluorescent adduct in hemoglobin in the advanced stage of glycation and the non-fluorescent HbA(1c) will be of major use in distinguishing and to know the past status of diabetes mellitus. While autofluorescence correlated highly with HbA(1c) value under in vivo condition (r = 0.85), it was moderate in the clinical samples (r = 0.55). The results suggest a non-linear relation between glycemia and glycation, indicating the application of Hb-AGE as a measure of susceptibility to glycation rather than glycation itself.