New coupling reagents for homogeneous esterification of cellulose

A group of known, but in cellulose chemistry new coupling reagents for homogeneous esterification has been investigated: 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride, N-methyl-2-bromopyridinium iodide, N-methyl-2-chloropyridinium iodide, and N-methyl-2-bromopyridinium tosylate. In order to study their ability to activate carboxylic acids in esterifications of cellulose they have been employed in synthesis of cellulose adamantate esters. Their effectiveness has been estimated in terms of degree of substitution of resulting esters and compared to that obtained with the commonly used N,N′-carbonyldiimidazole.     

Line-by-line calculations of thermal infrared radiation representative for global condition: CFC-12 as an example

We estimate a current direct radiative forcing due to CFC-12 of 0.18 Wm^-2, which is likely to be the peak radiative forcing for CFC-12. Global measurements of CFC-12 show at present an almost negligible trend for CFC-12 and measurement in an industrialized region show evidence that the peak concentration is reached. It is expected that concentration of CFC-12 in industrialized regions begins to decline 1-3 years before the global concentration.Our radiative forcing calculations are based on a line-by-line model appropriate for simulation of global mean radiative forcing, including clouds and stratospheric temperature adjustment. The radiative forcing of 0.33 Wm^-2/ppbv is close to earlier published results for this compound. New spectroscopic measurements for CFC-12 are performed and compared to previously published results.     

Surface features of synthetic silicate garnets

Crystals of Ca₃Al₂Si₃O₁₂-Mg₃Al₂Si₃O₁₂ solid solution have been synthesized with excess water at various high temperature-high pressure conditions. Surface features observed on the faces of the synthetic garnets and the habit variations caused by changes in Ca/Mg concentration of bulk compositions are described. The garnet crystal product are bounded predominantly by {110} faces and occasionally by small {211} and {321} faces when grown from Ca-rich bulk compositions.     

The analysis of organic mercury compounds using liquid chromatography with on-line atomic fluorescence spectrometric detection

A new method for the analysis of organic mercury compounds is reported. The organomercurials are separated by high-performance liquid chromatography (HPLC). The compounds are converted to mercury(0) in a continuous-flow system by means of an oxidizing and a subsequent reducing solution. The elemental mercury generated is swept into the cell of an atomic fluorescence spectrometer (AFS) by a stream of argon. The compositions of the oxidizing solution, which contains peroxodisulphate and copper(II) in dilute sulphuric acid, and the reducing solution, which contains alkaline tin(II) chloride, were optimized, as were the gas–liquid separator (GLS), the condensing system and the geometry of the reaction coils. The method is applied to extracts of certified reference material (CRM) and to river sediments. High concentrations of methylmercury were found in the sediment samples. At one location, the presence of ethylmercury is derived from the sample chromatogram.     

Total assignment of the 13C-NMR spectra of 5H-indolo[1,7-ab][1]benzazepine and 6,7-dihydro-5H-indolo[1,7-ab][1]benzazepine using two-dimensional proton-carbon chemical shift correlation experiments

¹³C-nmr chemical shift assignments for 5H-Indolo[1,7-ab][1]benzazepine and 6,7-Dihydro-5H-indolo-[1,7-ab][1]benzazepine, made on the basis of two-dimensional ¹H-¹³C chemical shift correlation experiments are reported.     

Controlled fed-batch fermentations of dilute-acid hydrolysate in pilot development unit scale

Inhibitors formed during wood hydrolysis constitute a major problem in fermenting dilute-acid hydrolysates. By applying a fed-batch technique, the levels of inhibitory compounds may be held low, enabling high ethanol productivity. In this study, a previously developed fed-batch strategy was modified and implemented for use in pilot development unit (PDU) scale. The rate of total gas formation, measured with a mass flow meter, was used as input variable in the control algorithm. The feed rate in the PDU-scale experiments could be properly controlled based on the gas evolution from the reactor. In fed-batch experiments utilizing TMB 3000, an inhibitor-tolerant strain of Saccharomyces cerevisiae, close to 100% of the hexoses in the hydrolysate was converted.