Relations between assemblages of carpological remains and modern vegetation in a shallow reservoir in southern Poland

This paper explores relations between assemblages of carpological remains and vegetation in and around a small, shallow reservoir in southern Poland. The study was conducted from 2006 to 2008. Quantity and distribution of species in the reservoir were recorded annually during the growing season. In October 2008, 40 samples of surface sediment (top 2 cm) were collected along transects at 10 m intervals. Samples of 100 cm3 were prepared for analysis of plant macroremains. Assemblages of carpological remains generally reflect local vegetation well. In some cases, however, even analysis of numerous samples failed to fully capture the species composition or reflect plant ratios in the parent phytocenosis. Reasons for this include factors that affect seed production, transport and fossilization, which differ among species. Among the best-represented macroremains were plants of the rush phytocenosis. In analysed samples, macroremains of 68.8 % of extant rushes were identified. Sixty percent of submerged and floating-leaf taxa were found in carpological samples, whereas 26.7 % of the trees and bushes were represented in sediment deposits. Species composition of phytocenoses in the reservoir and in surrounding areas was best reflected by macroremains from the nearby reed bed. Numbers of diaspores of Mentha aquatica, Hippuris vulgaris and Carex reflected well their relative abundance in phytocenoses. Chara sp., Juncus inflexus and Eupatorium cannabinum were overrepresented, whereas Typha latifolia and Sparganium minimum were poorly represented in relation to contemporary plant cover. There were no diaspores of Phragmites australis, which dominates the contemporary reed bed. Besides the shape of a reservoir, the key factor influencing diaspore numbers is distribution of plant cover. In many cases, single diaspores (Potentilla erecta, Myosotis scorpioides, Lythrum salicaria, Scutellaria galericulata), or higher concentrations (Hippuris vulgaris, Mentha aquatica, Eleocharis palustris, Schoenoplectus tabernaemontani, Chara sp.) reflected well the location of parent vegetation. The findings indicate that carpological remains in sediments can be an important source of information about plants in and around lakes. They generally reflect well local vegetation and in some cases may be used to identify taxa that dominated in the past

On Predicting Mössbauer Parameters of Iron-Containing Molecules with Density-Functional Theory

The performance of six frequently used density functional theory (DFT) methods (RPBE, OLYP, TPSS, B3LYP, B3LYP*, and TPSSh) in the prediction of Mössbauer isomer shifts(δ) and quadrupole splittings (ΔEQ) is studied for an extended and diverse set of Fe complexes. In addition to the influence of the applied density functional and the type of the basis set, the effect of the environment of the molecule, approximated with the conducting-like screening solvation model (COSMO) on the computed Mössbauer parameters, is also investigated. For the isomer shifts the COSMO-B3LYP method is found to provide accurate δ values for all 66 investigated complexes, with a mean absolute error (MAE) of 0.05 mm s–1 and a maximum deviation of 0.12 mm s–1. Obtaining accurate ΔEQ values presents a bigger challenge; however, with the selection of an appropriate DFT method, a reasonable agreement can be achieved between experiment and theory. Identifying the various chemical classes of compounds that need different treatment allowed us to construct a recipe for ΔEQ calculations; the application of this approach yields a MAE of 0.12 mm s–1 (7% error) and a maximum deviation of 0.55 mm s–1 (17% error). This accuracy should be sufficient for most chemical problems that concern Fe complexes. Furthermore, the reliability of the DFT approach is verified by extending the investigation to chemically relevant case studies which include geometric isomerism, phase transitions induced by variations of the electronic structure (e.g., spin crossover and inversion of the orbital ground state), and the description of electronically degenerate triplet and quintet states. Finally, the immense and often unexploited potential of utilizing the sign of the ΔEQ in characterizing distortions or in identifying the appropriate electronic state at the assignment of the spectral lines is also shown

Ring-Opening of Unsymmetrical 1,2-Dioxines Using Cobalt(II) Salen Complexes

The regioselectivity of the metal-catalyzed ring opening of unsymmetrical 1,2-dioxines to cis-y-hydroxyenones was investigated using two different Co(II) salen complexes. Regioselectivity was determined by direct examination of the enone ratios and by derivitization with a stabilized phosphorus ylide. The steric influence of the substituents on the 1,2-dioxine was the primary influence on regioselectivity. Temperature played little role; however, solvent and selection of Co(II) complex could be used to mildly influence the outcome of the rearrangement for selected substrates. The origins of the selectivity for the reaction are discussed

Triphenylphosphine-Induced Ring Contraction of 1,2-Dioxines

Triphenylphosphine inserts into the peroxide bond of 1,2-dioxines, initiating ring contraction with loss of triphenylphosphine oxide. This process yields dihydrofuran oxides in 54-97% yield from oxirenyl[2,3-c][1,2]dioxines and dihydrofurans from 3,6-dihydro-1,2-dioxines with inversion of stereochemistry at either the 2 or 5 position in the furan product

Synthesis of allo-and epi-inositol via the NHC-catalyzed carbocyclization of carbohydrate-derived dialdehydes

A synthesis of carbocyclic sugars from carbohydrate-derived dialdehydes using organocatalysis has been developed. Sorbitol, mannitol, and galactitol were converted via 1,6-tritylation, perbenzylation or permethylation, detritylation, and Swern oxidation into 2,3,4,5-tetra-O-alkyl-dialdoses that were cyclized via the benzoin reaction promoted by a triazolium carbene. Manno- and galacto-configured dialdehydes gave predominantly single inosose stereoisomers in up to 75% yield if the mixture was acetylated prior to isolation while the gluco-dialdehyde afforded a mixture of three stereoisomers in 61% overall yield. The inososes were stereospecifically reduced using sodium borohydride and then deprotected to give allo- and epi-inositol in good yield that confirmed the structural and stereochemical assignments.Kieran P. Stockton, Ben W. Greatrex, and Dennis K. Taylo

Practical evaluation of compact fluorescent lamps for dye-sensitized photooxidation reactions

LetterEnergy-efficient compact fluorescent lamps (CFL) have been evaluated as a light source for the sensitized generation of singlet oxygen used in the oxidation of 1,3-butadienes and furfural derivatives using a range of dyes including rose bengal, methylene blue, and tetraphenylporphyrin. An ambient temperature water jacket was sufficient to cool reaction mixtures due to the low heat output of lamps and the reaction rates using 110 W of CFL were slower but comparable to those obtained using a 500 W tungsten halogen lamp. The conditions were applied to the photooxidation of a series of furan aldehydes and 1,3-butadienes to give products in good yield in 4–96 hours.Kieran P. Stockton, Joseph P. May, Dennis K. Taylor, Ben W. Greatre

A Domino Ring-Opening/Epoxidation of 1,2-Dioxines

When allowed to react with alkaline hydrogen peroxide, monocyclic 1,2-dioxines ring-open to their isomeric 'y'-hydroxyenone intermediates which are rapidly epoxidized to afford 'trans'-4-hydroxy-2,3-epoxyketones in 21-81% yield. In the case of 'meso'-1,2-dioxines, Co(II) complex catalyzed asymmetric ring-opening of the 1,2-dioxine may be employed to furnish enantioenriched epoxides