Laser photodissociation of H2O at 157 nm: rotational energy distribution in product OH(X2II)

Water molecules are photolyzed into the electronic ground states of H and OH. A non-Boltzmann distribution of OH rotational levels is found, in disagreement with a previous measurement, and with analogous results for H₂S.     

Software package for quantitative analysis of solid materials by energy-dispersive x-ray fluorescence spectrometry without absolute calibration

A software package for quantifying elements in solids from energy-dispersive x-ray fluorescence data is described. The algorithm is based on the fundamental parameter approach and facilitates the simultaneous determination of several elements at widely varying concentrations. The software comprises three programs. One program, for spectrometer control and data acquisition, resides in a dedicated microcomputer. The two other programs, for spectra deconvulution and data evaluation, reside in a larger central computer. On-line communication between the computers is feasible, and the system facilitates the implementation of new improved programs. The performance of the system was tested on standard reference materials, and satisfactory accuracy was obtained for up to 21 elements.     

Organic matter flow in the food web at a temperate heath under multifactorial climate change

The rising atmospheric CO(2) concentration, increasing temperature and changed patterns of precipitation currently expose terrestrial ecosystems to altered environmental conditions. This may affect belowground nutrient cycling through its intimate relationship with the belowground decomposers. Three climate change factors (elevated CO(2), increased temperature and drought) were investigated in a full factorial field experiment at a temperate heathland location. The combined effect of biotic and abiotic factors on nitrogen and carbon flows was traced in plant root → litter → microbe → detritivore/omnivore → predator food-web for one year after amendment with (15)N(13)C(2)-glycine. Isotope ratio mass spectrometry (IRMS) measurement of (15)N/(14)N and (13)C/(12)C in soil extracts and functional ecosystem compartments revealed that the recovery of (15)N sometimes decreased through the chain of consumption, with the largest amount of bioactive (15)N label pool accumulated in the microbial biomass. The elevated CO(2) concentration at the site for 2 years increased the biomass, the (15)N enrichment and the (15)N recovery in detritivores. This suggests that detritivore consumption was controlled by both the availability of the microbial biomass, a likely major food source, and the climatic factors. Furthermore, the natural abundance δ(13)C of enchytraeids was significantly altered in CO(2)-fumigated plots, showing that even small changes in δ(13)C-CO(2) can be used to detect transfer of carbon from primary producers to detritivores. We conclude that, in the short term, the climate change treatments affected soil organism activity, possibly with labile carbohydrate production controlling the microbial and detritivore biomass, with potential consequences for the decomposition of detritus and nutrient cycling. Hence, there appears to be a strong coupling of responses in carbon and nitrogen cycling at this temperate heath.     

Expanding the dynamic measurement range for polymeric nanoparticle pH sensors

Conventional optical nanoparticle pH sensors that are designed for ratiometric measurements in cells have been based on utilizing one sensor fluorophore and one reference fluorophore in each nanoparticle, which results in a relatively narrow dynamic measurement range. This results in substantial challenges when conducting live cell measurements, which often leads to misleading results. In the present work we provide a simple solution to this problem.     

Water‐in‐oil Emulsions Stabilized by Hydrophobized Microfibrillated Cellulose

The properties of water‐in‐toluene emulsions stabilized solely by hydrophobized microfibrillated cellulose (MFC) were investigated. By varying the degree of surface substitution (DSS), the wettability of the MFC was altered. All emulsions prepared with MFC displayed excellent stability to coalescence. The stability to gravity‐induced sedimentation increased with increasing MFC concentration, the highest stability being obtained with MFC of moderate hydrophobicity. Drop sizes increased with increasing DSS, with a corresponding decrease in stability to sedimentation. An increase in the toluene:water ratio at constant MFC concentration resulted in a decrease in the average drop size. For all emulsions, the polydispersity in drop size decreased with decreasing average drop diameter.     

Oxalate distribution in soils under rhubarb (Rheum rhaponticum)

Oxalate in soils may enhance phosphate availability, promote mineral dissolution, and increase the mobility of aluminium and heavy metal cations by complexation. Rhubarb (Rheum rhaponticum L.) has very high content of oxalate in leaves and petioles, and therefore the topsoil under rhubarb might have elevated contents of oxalate. Soil samples were collected at depths of 0–2.5 and 2.5–5?cm from 10?cm sections along 100?cm transects from rhubarb plants at four locations in Denmark, and from seven layers in a soil profile to 80?cm depth at one location. Oxalate was extracted from the soil with 0.2?M phosphate at pH 2 by reciprocal shaking for 24?h and then determined by a new fast capillary zone electrophoresis method with 300?mM KH₂PO₄ and 0.30?mM TTAB electrolyte adjusted to pH 7, developed and tested to analyse high-ionic-strength soil extracts. Rhubarb increases the oxalate content in soil under the leaves slightly. The average content of oxalate in the upper 0–5?cm soil was 444?µmol/kg at the Kaldred site, and 111–333?µmol/kg at the three other locations. In the soil profile, the content of oxalate decreased from 500?µmol/kg in 0–5?cm depth to 110?µmol/kg at 75–80?cm depth. No significant seasonal changes in oxalate contents were observed, while an annual variation of 100?µmol/kg could be observed at 0–2.5?cm depth. During plant decay in autumn, a slight increase in oxalate content was observed at 30?cm soil depth. In conclusion, the role of oxalate in weathering and metal transport appears to be limited in soils under rhubarb. Oxalate might stimulate microbiological growth and phosphate mobilisation in the rhizosphere, but concentrations observed are too low to impose any toxic effects to organisms.     

Polymer Supported Synthesis of Deoxyoligonucleotides using In Situ Prepared Deoxynucleoside 2-Cyanoethyl Phosphoramidites

Abstract

2-Cyanoethyl bis(diisopropylamino) phosphorodiamidite (1) is a stable and easily obtainable compound¹ which, when activated with 0.5 eq. tetrazole, gives solutions of deoxyribonucleoside 2-cyano-ethyl phosphoramidites (2) useful for the synthesis of deoxyoligo-nucleotides. ² Our results applying these in-situ prepared phosphoramidites for polymer-supported syntheses of a variety of deoxyoligonucleotides (DNA fragments) will be presented.     

THIATION OF CARBONYL COMPOUNDS WITH THE DIMER OF P-METHOXY-P-THIONOPHOSPHINSULFIDE

Abstract

Recent studies on thiation of carbonyl compounds with organic P,S-compounds have shown that p-methoxyphenyl-thionophosphinsulfide (1) is the most effective thiation reagent for ketones, carboxamides, esters, and thioloesters hitherto known.     

Universal flow-density relation of single-file bicycle,pedestrian and car motion

The relation between flow and density is an essential quantitative characteristic to describe the efficiency of traffic systems. We have performed experiments with single-file motion of bicycles and compared the results with previous studies for car and pedestrian motion in similar setups. In the space–time diagrams we observe three different states of motion (free flow state, jammed state and stop-and-go waves) in all these systems. Despite their obvious differences they are described by a universal fundamental diagram after proper rescaling of space and time which takes into account the size and free velocity of the three kinds of agents. This indicates that the similarities between the systems go deeper than expected.