Isotope pattern deconvolution as a tool to study iron metabolism in plants

Isotope pattern deconvolution is a mathematical technique for isolating distinct isotope signatures from mixtures of natural abundance and enriched tracers. In iron metabolism studies measurement of all four isotopes of the element by high-resolution multicollector or collision cell ICP–MS allows the determination of the tracer/tracee ratio with simultaneous internal mass bias correction and lower uncertainties. This technique was applied here for the first time to study iron uptake by cucumber plants using ⁵⁷Fe-enriched iron chelates of the o,o and o,p isomers of ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA) and ethylenediamine tetraacetic acid (EDTA). Samples of root, stem, leaves, and xylem sap, after exposure of the cucumber plants to the mentioned ⁵⁷Fe chelates, were collected, dried, and digested using nitric acid. The isotopic composition of iron in the samples was measured by ICP–MS using a high-resolution multicollector instrument. Mass bias correction was computed using both a natural abundance iron standard and by internal correction using isotope pattern deconvolution. It was observed that, for plants with low ⁵⁷Fe enrichment, isotope pattern deconvolution provided lower tracer/tracee ratio uncertainties than the traditional method applying external mass bias correction. The total amount of the element in the plants was determined by isotope dilution analysis, using a collision cell quadrupole ICP–MS instrument, after addition of ⁵⁷Fe or natural abundance Fe in a known amount which depended on the isotopic composition of the sample.     

Latest Developments in the Catalytic Application of Nanoscaled Neutral Group 8–10 Metals

In the last few decades, the synthesis and catalytic application of nanoscaled particles prepared from Group 8–10 (formerly Group VIIIB) elements have been widely explored and have achieved promising results. The innovative use of these nanoparticle catalysts may provide new opportunities in the efficient combination of conventionally used homogenous and heterogeneous catalysts. Conventional homogeneous catalysts pose extraction and recycling difficulties when dealing with metal complexes and/or ligands, whereas heterogeneous catalysts generally require more pressing experimental conditions, such as high temperatures and high pressures, to be effective. Therefore, to solve these problems, the synthesis and use of nanoparticle catalysts as replacements for conventional catalytic systems is a breakthrough owing to their improved handling and environmental and economic aspects. This Focus Review primarily addresses the catalytic applications of neutral Group 8–10 nanoparticles with an average size of less than 10 nm, and also includes a discussion of commonly used synthetic methodology.     

The intersection of all maximum stable sets of a tree and its pendant vertices

A stable set in a graph G is a set of mutually non-adjacent vertices, α(G) is the size of a maximum stable set of G, and is the intersection of all its maximum stable sets. It is known that if G is a connected graph of order n≥2 with 2α(G)>n, then , [V.E. Levit, E. Mandrescu, Combinatorial properties of the family of maximum stable sets of a graph, Discrete Applied Mathematics 117 (2002) 149-161; E. Boros, M.C. Golumbic, V.E. Levit, On the number of vertices belonging to all maximum stable sets of a graph, Discrete Applied Mathematics 124 (2002) 17-25]. When we restrict ourselves to the class of trees, we add some structural properties to this statement. Our main finding is the theorem claiming that if T is a tree of order n≥2, with 2α(T)>n, then at least two pendant vertices an even distance apart belong to .     

Stable equivalences of graded algebras

We extend the notion of stable equivalence to the class of locally finite graded algebras. For such an algebra Λ, we focus on the Krull–Schmidt category gr_Λ of finitely generated -graded Λ-modules with degree 0 maps, and the stable category obtained by factoring out those maps that factor through a graded projective module. We say that Λ and Γ are graded stably equivalent if there is an equivalence that commutes with the grading shift. Adapting arguments of Auslander and Reiten involving functor categories, we show that a graded stable equivalence α commutes with the syzygy operator (where defined) and preserves finitely presented modules. As a result, we see that if Λ is right noetherian (resp. right graded coherent), then so is any graded stably equivalent algebra. Furthermore, if Λ is right noetherian or k is artinian, we use almost split sequences to show that a graded stable equivalence preserves finite length modules. Of particular interest in the nonartinian case, we prove that any graded stable equivalence involving an algebra Λ with socΛ=0 must be a graded Morita equivalence.     

Electron paramagnetic resonance (EPR) and stable isotope records of paleoenvironmental conditions during peat formation

EPR spectroscopy was performed on four peat cores (1-2.5 m depth) collected from Yellowstone National Park (USA), Scotland (UK) and Lower Silesia (Poland) to study peat formation process. The stable free radicals identified in all investigated samples are semiquinone type and g-parameters range from 2.0030 to 2.0048. The highest g-values are characteristic of upper well-aerated peat layers and gradually decrease with depth. The lowest g-values are typical of relatively old fens and bogs where anaerobic conditions are expected and carbonization processes are advanced. The decrease in g-parameter value is connected with conjugation of semiquinone units with gradually augmented polyaromatic units in the peat substance. Generally the radical concentration increases with depth (0.05-5x10(17) spins/gram). However the g-values, line width parameters, and spin concentrations exhibit strong variations in some peat layers. Variation of these parameters observed for certain peat horizons correlate with the variation of carbon stable isotopic composition. For the old well-conserved peat deposits (e.g. Scotland/UK, approximately 5600 BP), variation of EPR parameters may be used to study paleo redox conditions.     

β-Crystallisation tendency and structure of polypropylene grafted by maleic anhydride and its blends with isotactic polypropylene

Crystallization, melting and structure of three different commercial types of isotactic polypropylene (iPP) grafted by maleic anhydride (PP-g-MAH) with different maleic anhydride content (AC) and their β-nucleated versions were studied by X-ray diffractometry (WAXS), differential scanning calorimetry (DSC), polarised light microscopy (PLM) and scanning electron microscopy (SEM). The presence of maleic anhydride units disturbs the chain regularity, hereby decreases the crystallization tendency of iPP in general and the β-crystallisation ability in particular. β-modification of iPP (β-iPP) forms only in β-nucleated PP-g-MAH polymers studied if the anhydride content is not larger than 0.5 mass%. The influence of AC of PP-g-MAH on the feature the spherulitic structure is demonstrated by PLM and SEM micrographs. The β-nucleated iPP/PP-g-MAH blends containing 10 mass% PP-g-MAH crystallise predominantly in β-form independently of AC of the latter. The β-nuceated blends of iPP and PP-g-MAH with lowest AC crystallise in β-form in whole concentration range. The interaction parameter between iPP and PP-g-MAH polymers calculated by Nishi-Wang equation indicate limited interaction between the components.     

A macroporous polymer-supported cyclic anhydride for efficient sequestration of amines

The efficient removal of primary and secondary amines from organic solutions using a macroporous polymer-supported anhydride is described. The sequestering of primary amines by the anhydride via polymer-bound amide formation is completed within 2-4 h at room temperature. Secondary amines require typically 4 h for complete sequestration.