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151.
Dissolved organic matter is an important component of the global carbon cycle that allows the distribution of carbon and nutrients. Therefore, analysis of soil dissolved organic matter helps us to better understand climate change impacts as it is the most dynamic and reactive fraction in terrestrial ecosystems. Its characterization at the molecular level is still challenging due to complex mixtures of hundreds of compounds at low concentration levels in percolating water. This work presents simple methods, such as thermochemolysis– or derivatization–gas chromatography, as an alternative for the analysis of fatty acids in dissolved organic matter without any purification step. The variables of the protocols were examined to optimize the processing conditions for the C9–C18 range. As a proof of concept, fatty acid distributions of soil percolating water samples from a long-term field experiment were successfully assessed. The variability of dissolved organic acid distributions was pronounced through depth profile and soil treatment but no major change in composition was observed. However, although the optimization was done from C9 to C18, detection within the C6-C32 fatty acids range was performed for all samples. 相似文献
152.
153.
Emily Kerr David J. Hayne Lachlan C. Soulsby Joseph C. Bawden Steven J. Blom Egan H. Doeven Luke C. Henderson Conor F. Hogan Paul S. Francis 《Chemical science》2022,13(2):469
The classic and most widely used co-reactant electrochemiluminescence (ECL) reaction of tris(2,2′-bipyridine)ruthenium(ii) ([Ru(bpy)3]2+) and tri-n-propylamine is enhanced by an order of magnitude by fac-[Ir(sppy)3]3− (where sppy = 5′-sulfo-2-phenylpyridinato-C2,N), through a novel ‘redox mediator’ pathway. Moreover, the concomitant green emission of [Ir(sppy)3]3−* enables internal standardisation of the co-reactant ECL of [Ru(bpy)3]2+. This can be applied using a digital camera as the photodetector by exploiting the ratio of R and B values of the RGB colour data, providing superior sensitivity and precision for the development of low-cost, portable ECL-based analytical devices.A water-soluble Ir(iii) complex is shown to enhance the ‘remote’ mechanism of the most widely used co-reactant ECL reaction of tris(2,2′-bipyridine)ruthenium(ii) with tripropylamine. 相似文献
154.
A transitive triple, (a,b,c), is defined to be the set {(a,b), (b,c), (a,c)} of ordered pairs. A directed triple system of order v, DTS(v), is a pair (D,β), where D is a set of v points and β is a collection of transitive triples of pairwise distinct points of D such that any ordered pair of distinct points of D is contained in precisely one transitive triple of β. An antiautomorphism of a Directed triple system, (D,β), is a permutation of D that maps β to β−1, where β −1 = {(c,b,a)|(a,b,c) E β}. In this article we give necessary and sufficient conditions for the existence of a Directed triple system of order v admitting an antiautomorphism consisting of a single cycle of length d and having v − d fixed points. Further, we give a more general result for partial Directed triple systems in which the missing ordered pairs are precisely those containing two fixed points. © 1996 John Wiley & Sons, Inc. 相似文献
155.
156.
Venkataraman Vishwanathan Gajula Balakrishna Balraj Rajesh Venkatreddy Jayasri Lucky Sikhwivhilu Neil J. Coville 《Reaction Kinetics and Catalysis Letters》2007,92(2):311-317
A series of sulphate-promoted ZrO2 solid acid catalysts with different contents of SO4
2− were calcined at 450°C in air for 4 h and tested for the liquid-phase alkylation of catechol to guaiacol in a fixed-bed down-flow
reactor. The 5 wt.% SO4
2− on ZrO2 showed the best conversion (82%) and selectivity for guaiacol (84%) at 200°C and 1 bar pressure. A smooth correlation was
observed between the catalytical activity and surface acidity of sulphated zirconia. Based on our results, a surface mechanism
is proposed. 相似文献
157.
Neil L. Kelleher Colleen A. Costello Tadhg P. Begley Fred W. McLafferty 《Journal of the American Society for Mass Spectrometry》1995,6(10):981-984
Thiaminase I (E.C. 2.5. 1.2) from Bacillus thiaminolyticus catalyzes the degradation of thiamin (vitamin B1). Unexpected mass heterogeneity (MW 42,127, 42,197, and 42,254; 1:2:1) in recombinant thiaminase I from Escherichia coli was detected by electrospray ionization Fourier-transform mass spectrometry, resolving power 7×104. Nozzle-skimmer fragmentation data reveal an extra Ala (+71.02; 71.04=theory) and GlyAla (+128.04; 128.06=theory) on the N-terminus, in addition to the fully processed enzyme. However, the fragment ion masses were consistent only with this sequence through 330 N-terminal residues; resequencing of the last 150 bps of the thiaminase I gene yields a sequence consistent with the molecular weight values and all 61 fragment ion masses. Covalently labeling the active site with a 108-Da pyrimidine moiety via mechanism-based inhibition produces a corresponding molecular weight increase in all three thiaminase I components, which indicates that they are all enzymatically active. Inspection of the fragment ions that do and do not increase by 108 Da indicates that the active site nucleophile is located between Pro79 and Thr177 in the 379 amino acid enzyme. 相似文献
158.
In this letter we describe the advantages of a dynamic optical interconnection system for parallel information processing applications. The system is based on a liquid crystal television which acts as a binary phase-only spatial light modulator. We describe example algorithms where reconfigurable interconnects would be useful and present results of several interconnection topologies which have been implemented.Presented at the International Commission for Optics Topical Meeting, Kyoto, 1994. 相似文献
159.
Robert A. Valentine Alexander Whyte Kunio Awaga Neil Robertson 《Tetrahedron letters》2012,53(6):657-660
We have prepared two new C3-symmetric, substituted-triazatruxene molecules using a facile one-pot trimerisation of 5-carboxyindole and 6-bromoindole in acetic acid using Br2, giving 2a and 3a, respectively. These were subsequently modified by the addition of six alkyl chains to the N- and carboxyl-positions of 2a giving 2b and three alkyl chains to the N-positions of 3a giving 3b. The new molecules were characterised using cyclic voltammetry, UV/vis and emission spectroscopy, DFT calculations and in the case of 3b, field-effect transistor measurements showing gate-modulated source-drain current. These represent a straightforward route to large polyaromatic molecules with easily-modified side groups and are suitable as building blocks for synthesis of functional molecules for materials. 相似文献
160.