The MICE facility – a new tool to study plant–soil C cycling with a holistic approach

Plant–soil interactions are recognized to play a crucial role in the ecosystem response to climate change. We developed a facility to disentangle the complex interactions behind the plant–soil C feedback mechanisms. The MICE (‘Multi-Isotope labelling in a Controlled Environment’) facility consists of two climate chambers with independent control of the atmospheric conditions (light, CO₂, temperature, humidity) and the soil environment (temperature, moisture). Each chamber holds 15 plant–soil systems with hermetical separation of the shared above ground (shoots) from the individual belowground compartments (roots, rhizosphere, soil). Stable isotopes (e.g. ¹³C, ¹⁵N, ²H, ¹⁸O) can be added to either compartment and traced within the whole system. The soil CO₂ efflux rate is monitored, and plant material, leached soil water and gas samples are taken frequently. The facility is a powerful tool to improve our mechanistic understanding of plant–soil interactions that drive the C cycle feedback to climate change.     

Raman spectroscopy of n‐pentyl methyl ether and deuterium labelled analogues

The Raman spectra of n‐pentyl methyl ether, C₅H₁₁OCH₃, and six selectively deuteriated analogues are reported and discussed. Correlations between the observed ν(sp³CH) stretching and bending bands and the position of the deuterium atoms in the alkyl chain are developed and refined. Similar progress is possible in associating specific skeletal vibrations with bands in the Raman spectra. The relevance of this study to improving the assignment of bands in the Raman spectra of larger systems of biological interest is highlighted. Copyright © 2010 John Wiley & Sons, Ltd.     

On (d,1)-total numbers of graphs

A (d,1)-total labelling of a graph G assigns integers to the vertices and edges of G such that adjacent vertices receive distinct labels, adjacent edges receive distinct labels, and a vertex and its incident edges receive labels that differ in absolute value by at least d. The span of a (d,1)-total labelling is the maximum difference between two labels. The (d,1)-total number, denoted , is defined to be the least span among all (d,1)-total labellings of G. We prove new upper bounds for , compute some for complete bipartite graphs K_m,n, and completely determine all for d=1,2,3. We also propose a conjecture on an upper bound for in terms of the chromatic number and the chromatic index of G.     

Edge irregular total labellings for graphs of linear size

As an edge variant of the well-known irregularity strength of a graph G=(V,E) we investigate edge irregular total labellings, i.e. functions f:V∪E→{1,2,…,k} such that f(u)+f(uv)+f(v)≠f(u^′)+f(u^′v^′)+f(v^′) for every pair of different edges uv,u^′v^′∈E. The smallest possible k is the total edge irregularity strength of G. Confirming a conjecture by Ivan?o and Jendrol’ for a large class of graphs we prove that the natural lower bound is tight for every graph of order n, size m and maximum degree Δ with m>111000Δ. This also implies that the probability that a random graph from G(n,p(n)) satisfies the Ivan?o-Jendrol’ Conjecture tends to 1 as n→∞ for all functions p∈[0,1]^N. Furthermore, we prove that is an upper bound for every graph G of order n and size m≥3 whose edges are not all incident to a single vertex.     

Edge colouring by total labellings

We introduce the concept of an edge-colouring total k-labelling. This is a labelling of the vertices and the edges of a graph G with labels 1,2,…,k such that the weights of the edges define a proper edge colouring of G. Here the weight of an edge is the sum of its label and the labels of its two endvertices. We define to be the smallest integer k for which G has an edge-colouring total k-labelling. This parameter has natural upper and lower bounds in terms of the maximum degree Δ of . We improve the upper bound by 1 for every graph and prove . Moreover, we investigate some special classes of graphs.     

关于图的具有标号型约束条件的正常全着色

数学的拓扑图可以自然地表示编码关系结构,也叫做拓扑图编码,这种关系结构在许多领域里得到应用.本文将图的全着色和图的边魔幻标号结合产生特殊的全着色,边魔幻tcn-纯全着色和均匀魔幻tcn-纯全着色.研究了树的边魔幻tcn-纯全着色,均匀魔幻tcn-纯全着色,以及具有极值性质的边魔幻全着色数,确定了特殊全着色在树上的精确着...     

Novel formal synthesis of stereospecifically C-6 deuterated d-glucose employing configurationally stable alkoxymethyllithiums

The synthesis and testing of configurational stability of chirally monodeuterated PMB- and THP-substituted oxymethyllithiums are described. Macroscopically they are configurationally stable up to −35 °C, the limit of their chemical stability, and microscopically even up to 0 °C. Furthermore, THP-protected oxy-[D₁]methyllithium has been applied in the formal synthesis of (6R)-[6-D₁]-d-glucose (four steps, 40% yield), an example of its use as a homochiral hydroxymethyl synthon.     

A convergent synthesis of (17R,5Z,8Z,11Z,14Z)-17-hydroxyeicosa-5,8,11,14-tetraenoic acid analogues and their tritiated derivatives

17(R)-OH-AA and 14,15-dehydro-17(R)-OH-AA were synthesized from a common tetraacetylenic precursor and their azide derivatives were obtained in moderate yields via the corresponding p-toluenesulfonates. Since the azido group remained stable during tritiation procedure on Lindlar's catalyst in benzene, both 14,15-dehydro-17(S)-N₃-AA and 14,15-dehydro-17(R)-OH-AA constitute useful intermediates in the synthesis of radio-labelled 17(S)-N₃-AA and 17(R)-OH-AA. In contrast, reduction of azide in methanol afforded 17(S)-NH₂-AA with 95% yield.     

First synthesis of (1,2-C2)-monolignol glucosides

The monolignol glucosides (1,2-¹³C₂)-p-glucocoumaryl alcohol, (1,2-¹³C₂)-coniferin and (1,2-¹³C₂)-syringin, and the glucosides of (1,2-¹³C₂)-p-coumaric, (1,2-¹³C₂)-ferulic and (1,2-¹³C₂)-sinapic acids were synthesized by condensation of the corresponding aldehydes with (1,2,3-¹³C₃)-malonic acid. The free acids were converted to the acyl chlorides prior to their reduction to alcohols.     

Gold(III)‐Induced Oxidation of Amino Acids and Malonic Acid: Reaction Pathways Studied by NMR Spectroscopy with Isotope Labelling

Reactions of Au(III) with biomolecules are of interest in relation to understanding the mechanism of action of therapeutic gold compounds. NMR investigations of ¹³C and ¹⁵N isotopically‐labelled glycine and alanine show that Au(III) induces deamination and subsequent decarboxylation of both amino acids with the same mechanism. For comparison, reactions of Au(III) with sarcosine and the dicarboxylic acid malonic acid were also investigated. The major intermediates and products have been identified.