The influence of two plasticizers, propylene carbonate and dimethyl sulphoxide, as well as different salt concentrations of Li(TFSI), on properties of a polymer gel electrolyte material has been studied using differential scanning calorimetry (DSC) and ac impedance and FTIR spectroscopy. Variations of glass transition temperature and the conductivity behaviours of the systems were examined, and found to be highly dependent on the amount and type of the plasticizer used. Characteristic band-shifts in FTIR spectra, indicating coordination of lithium ions, have been found for the polymer and both the plasticizers in the corresponding binary solutions. These shifts were used to study the coordination preferences in the complete ternary electrolyte system. The combined results from the three experimental techniques have been discussed.
The base-catalysed 1,3-proton transfer reactions in 1-methylindene have been studied theoretically in polar (water) and unpolar (cyclohexane) solvents, respectively, for two different choices of bases, namely ammonia and trimethylamine (TMA), using the SM
Being a major cause of eutrophication and subsequent loss of water quality, the turnover of phosphorus (P) in lake sediments is in need of deeper understanding. A major part of the flux of P to eutrophic lake sediments is organically bound or of biogenic origin. This P is incorporated in a poorly described mixture of autochthonous and allochthonous sediment and forms the primary storage of P available for recycling to the water column, thus regulating lake trophic status. To identify and quantify biogenic sediment P and assess its lability, we analyzed sediment cores from Lake Erken, Sweden, using traditional P fractionation, and in parallel, NaOH extracts were analyzed using 31P NMR. The surface sediments contain orthophosphates (ortho-P) and pyrophosphates (pyro-P), as well as phosphate mono- and diesters. The first group of compounds to disappear with increased sediment depth is pyrophosphate, followed by a steady decline of the different ester compounds. Estimated half-life times of these compound groups are about 10 yr for pyrophosphate and 2 decades for mono- and diesters. Probably, these compounds will be mineralized to ortho-P and is thus potentially available for recycling to the water column, supporting further growth of phytoplankton. In conclusion, 31P NMR is a useful tool to asses the bioavailability of certain P compound groups, and the combination with traditional fractionation techniques makes quantification possible.
This contribution describes how de novo designed synthetic helix–loop–helix polypeptides are utilized tocontrol the assembly of gold nanoparticles and as scaffolds for biosensing. The synthetic polypeptides aredesigned to fold into a four-helix bundle upon dimerization. When immobilized on gold nanoparticles,dimerization and folding occur between peptides on neighbouring particles as an effect of particleaggregation and the folded polypeptides are rigid enough to keep the particles separated at a distancecorresponding to the size of the four-helix bundle. Moreover, peptide dimerization offers a convenientroute to assemble nanoparticles into hybrid multilayers on planar substrates. The drastic change in theresonance conditions of the localized nanoparticle surface plasmon upon particle aggregation is shown tobe useful for optical detection of biomolecular interactions.
An automated liquid nano-separation system has been developed for nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) using both isocratic and gradient elution, One fused-silica nanocolumn, typically 75 mu m i x 39 cm (25 cm ef
Treatment of 1-(benzylselenenyl)-5-butyl-5-nonanoI (10) with oxalyl chloride followed by the sodium salt of N-hydroxypyridine-2-thione afforded the corresponding pyridine-2-thione-N-oxycarbonyI (PTOC) oxalate ester which was not isolated but immediately h
A highly diastereoselective reaction of 2-azanorbornyl enolates with electrophiles has been studied. Deprotonation of 4 with LDA at low temperature affords the corresponding exocyclic lithium enolate 5, which reacts with different electrophiles such as al
2-Azanorbornyl-derived amino alcohols were prepared and evaluated as ligands in the Ru(II)-catalyzed asymmetric transfer hydrogenation of aromatic ketones. To improve selectivity and rate, the structure of the ligand was optimized, Acetophenone was reduce
The mechanism of the Ru(arene)(amino alcohol)-catalyzed transfer hydrogenation of ketones using isopropyl alcohol as the hydrogen source has been studied by means of hybrid density functional methods (B3PW91). Three mechanistic alternatives were evaluated, and it was shown that the reaction takes place via a six-membered transition state, where a metal-bound hydride and a proton of a coordinated amine are transferred simultaneously to the ketone. Further calculations provided a general rationale for the rate of the reaction by comparison of steric effects in the ground and transition states of the ruthenium hydride complex. It was found that the TS has a strong preference for planarity, and this in turn is dependent on the conformational behavior of the O,N-linkage of the amino alcohol ligand. Finally, a general model, rationalizing the enantioselectivity of the reaction, was developed. Experimental studies of both rate and enantioselectivity were used in order to support the computational results.
Tryptophan and its metabolites are of great interest in understanding the pathogenesis of multiple sclerosis (MS). The total levels of tryptophan and its metabolites, kynurenine and kynurenic acid were determined in plasma by capillary liquid chromatography electrospray ionisation tandem mass spectrometry. This is the first report of the plasma levels of these analytes in healthy controls and relapsing-remitting MS patients receiving long-term and acute interferon-beta (IFN-beta) treatment. Twenty-four hours post-administration increased kynurenine levels (first IFN MS versus healthy, P = 0.042) and kynurenine/tryptophan ratio (K/T; first IFN MS versus healthy, P =0.027; first IFN MS versus long-term IFN MS, P = 0.036) were found. The long-term IFN MS group had higher K/T ratios at 4 and 12 h post-administration (P = 0.015 and 0.009, respectively). The increase of K/T ratio in the first IFN MS group indicate an induction of the enzyme indolamine-2,3-dioxygenase (IDO), as reported earlier in experimental allergic encephalomyelitis. As IDO is participating in both inflammatory and neurodegenerative processes, further knowledge of its involvement in the pathogenesis of MS is of great importance.
Four different sheathless electrospray ionization (ESI) configurations were investigated for a nano liquid chromatography (LC) system. The studied configurations were: a column with an integrated emitter, with the ESI potential applied before or after the column, and a column with separate emitter, with the ESI voltage applied at a union before the emitter or at the emitter tip. The results indicates that the efficiency of the LC system is rather independent of the configuration when using 95 μm i.d. columns, acetic mobile phase and standard peptides as a sample. Introduction of post column dead volume seems not to be a critical issue at least with flow rates down to 600 nl/min.
Magnetic susceptibility measurements indicate that rhombohedral Li3Fe2(PO4)(3), obtained by ion exchange of monoclinic Na3Fe2(PO4)(3), exhibits a paramagnetic to antiferromagnetic transition at T-N approximate to 27 K. Curie-Weiss-like behaviour is observ
The capacity and cyclability of solid-state synthesized LiFePO4-based laminate cells of type <Li \ liq. el. \ LiFePO4> have been studied at 23, 40, and 60 degrees C. Larger capacities were obtained for cells cycled at the elevated temperatures. No evidenc
A modified standard addition method for single element determination by X-ray fluorescence spectrometry has been studied. The attenuation properties of the standard added samples are kept constant by adding decreasing amounts of an attenuation modifier along with increasing amounts of a standard. In this way the standard addition curve will be a straight line in cases where the ordinary standard addition curve is non-linear, and linear regression can be used to evaluate the concentration of the analyte. Standard additions of oxides of a number of elements, with and without modifier, have been made to cellulose powder or a mixture of aluminium oxide and polyethylene as matrices in order to test the method. The method has been applied to the determination of zinc in fly-ash from a steel work and of iron in cement. The fly-ash contained about 5% of zinc and the cement samples between 2 and 5% of Fe(2)O(3). The results were compared with those obtained by ICP-AES after decomposition of samples in lithium tetraborate or lithium metaborate and dissolution of the melt in 10%(v/v) nitric acid. The results agreed within 2%, relative, for fly-ash and within 3-6%, relative, for cement samples.
Lead in fly-ash from a garbage incinerator has been determined by X-ray fluorescence spectrometry (XRFS) and a modified standard-addition method. To keep the attenuation properties of the spiked samples constant, decreasing amounts of an attenuation modifier [mercury (II) acetate] were added together with increasing amounts of the standard (lead nitrate). Linearity between fluorescence intensity and amount of lead was thus obtained, so the amount of lead in the sample could be evaluated by linear regression. The amount of modifier needed could be calculated from a simple expression. The method was validated by comparison with the results obtained by applying atomic-absorption spectrometry (AAS) to solutions made by leaching the fly-ash with strong acid. For 8 fly-ash samples, containing between 0.8 and 1.35% lead, the largest absolute difference between the two sets of results was 0.03%. Theoretical calculations based on a simplified version of the Sherman equation were performed to confirm the linearity of the modified standard-addition curves.
The crystal structures of Nb-3(Al0.84Nb0.16) and Nb-3(Al0.84Nb0.16)H-2(2.52) have been refined from neutron powder diffraction data using the Rietveld method. Nb-3(Al0.84Nb0.16) crystallizes in the cubic Cr3Si-type structure, space group Pm3n, with the un