Despite biological variability the spectral characteristics of undiluted human urine show relatively low autofluorescence at short UV (250-300 nm) excitation. However with dilution the fluorescence intensity remarkably increases. This paper examines the mechanisms behind this effect, by using excitation-emission matrices. Corrections for the inner filter effect were made for improved understanding of the spectral patterns. We focused on three major fluorophores (tryptophan, indoxyl sulfate and 5-hydroxyindole-3-acetate) that are excited at these wavelengths, and whose content in urine is strongly linked with various health conditions. Their fluorescence was studied both individually and in combinations. We also examined the effect of ammonium on the fluorescence of these major fluorophores individually and in combinations. Through these studies we have identified the leading effects that reduce the UV fluorescence, namely higher concentration of indoxyl sulfate producing the inner filter effect and concentration quenching and quenching of fluorophores by ammonium. This result will assist in broader utilisation of UV fluorescence in medical diagnostics. 相似文献
Magtrieve™ (CrO2) and MnO2 mediated oxidation of aldoximes to nitrile oxides were studied in details. In presence of external radical source, TEMPO, these reagents did not furnish nitrile oxides, instead favoured deoximation to aldehydes. A common trend of deoximation was established from electronically tuned aldoximes, which is: aliphatic>aromatic>aldoximes with strong electron-withdrawing group, though the extent of deoximation was less in case of CrO2. Above effects were not observed with chloramine-T and diacetoxyiodobenzene, reagents known to produce nitrile oxides via hydroximoyl halide or equivalent ionic intermediates. A putative reaction mechanism is proposed for MO2 (M=Cr, Mn) mediated oxidation of aldoximes through formation of a nitroso-oxime tautomeric pair. Formation of nitrile oxide is possibly occurred from the oxime tautomer via a σ-type iminoxy radical intermediate. The deoximation process, dominating in presence of external radical environment, is explained following decomposition of the nitroso tautomer. 相似文献
Redox-active ferrocene was assembled on gold surfaces through the hydrogen bonding interactions between adenine-substituted ferrocene and a uracil-terminated organothiol monolayer. The surface coverage of ferrocene Γ could be varied from ca. 4 × 10? 11 to 2.0 × 10? 10 mol cm? 2 by diluting the thiol-modified uracil derivative with inert 1-octanethiol. A decrease in the apparent electron transfer rate constant for ferrocene, kapp, from ca. 50 to 10 s? 1 was observed upon increasing Γ. 相似文献
The triplet state of positronium, o-Ps, is used as a probe to characterize a starch-20% w/w sucrose matrix as a function of temperature (T). A two-step decomposition (of sucrose, and then starch) starts at 440 K as shown by a decrease in the o-Ps intensity (I(3)) and lifetime (τ(3)), the latter also disclosing the occurrence of a glass transition. Upon sucrose decomposition, the matrix acquires properties (reduced size and density of nanoholes) that are different from those of pure starch. A model is successfully established, describing the variations of both I(3) and τ(3) with T and yields a glass transition temperature, T(g) = (446 ± 2) K, in spite of the concomitant sucrose decomposition. Unexpectedly, the starch volume fraction (as probed through thermal gravimetry) decreases with T at a higher rate than the free volume fraction (as probed through PALS). 相似文献
Suzuki-Miyaura cross coupling was successfully used for C5-arylation in 4-amino-2-chloroquinoline-3-carbaldehyde using arylbornic acid and tetrakistriphenylphosphine palladium catalyst in water. Friedländer condensation reaction on 4-amino-2-chloro/2-arylquinoline-3-carbaldehyde and aromatic ketones gave novel aryl and diarylbenzo[h] [1, 6]naphthyridines in good yields. Fluorescence quantum yields were increased by introducing C2 and C5 π donor aryl benzo[h][1, 6]naphthyridines derivatives.
The study of superconductivity, dual superconductivity and color superconductivity has been undertaken through the breaking
of super symmetric gauge theory in restricted chromo dynamics (RCD) which automatically incorporates the condensation of monopoles
and dyons leading to confining and superconducting phases. Dyonic supermultiplets in N=1 super symmetry have been obtained quantum mechanically in RCD and it has been shown that dyon appears in RCD theory only
through restricted part of the generalized potential and it is only this part of this potential which is responsible for quark
confinement and the resulting superconductivity through the mechanism of dyonic condensation. 相似文献