Degradation of MMEA at absorber and stripper conditions

This study examines the degradation of N-methylethanolamine (MMEA) under different experimental conditions. Thermal degradation with and without CO₂, and oxidative degradation are investigated. Samples of the degraded solution were taken at regular intervals and analyzed. The percentage of amine loss was determined by Liquid Chromatography–Mass Spectrometry (LC–MS) while the degradation compounds were identified and quantified by Gas Chromatography–Mass Spectrometry (GC–MS). MMEA degradation at absorber and stripper conditions is compared with previous work on 2-ethanolamine (MEA). Degradation mechanisms are proposed and discussed in order to understand the differences compared to MEA.     

Fine root biomass, necromass and chemistry during seven years of elevated aluminium concentrations in the soil solution of a middle-aged Picea abies stand

Toxic effects of aluminium (Al) on Picea abies (L.) Karst. (Norway spruce) trees are well documented in laboratory-scale experiments, but field-based evidence is scarce. This paper presents results on fine root growth and chemistry from a field manipulation experiment in a P. abies stand that was 45 years old when the experiment started in 1996. Different amounts of dissolved aluminium were added as AlCl3 by means of periodic irrigation during the growing season in the period 1997-2002. Potentially toxic concentrations of Al in the soil solution were obtained. Fine roots were studied from direct cores (1996) and sequential root ingrowth cores (1999, 2001, 2002) in the mineral soil (0-40 cm). We tested two hypotheses: (1) elevated concentration of Al in the root zone leads to significant changes in root biomass, partitioning into fine, coarse, living or dead fractions, and distribution with depth; (2) elevated Al concentration leads to a noticeable uptake of Al and reduced uptake of Ca and Mg; this results in Ca and Mg depletion in roots. Hypothesis 1 was only marginally supported, as just a few significant treatment effects on biomass were found. Hypothesis 2 was supported in part; Al addition led to increased root concentrations of Al in 1999 and 2002 and reduced Mg/Al in 1999. Comparison of roots from subsequent root samplings showed a decrease in Al and S over time. The results illustrated that 7 years of elevated Al(tot) concentrations in the soil solution up to 200 microM are not likely to affect root growth. We also discuss possible improvements of the experimental approach.     

Covariances between gamma-ray energies

Covariances between experimental data are as significant as variances both in the evaluation of uncertainties and to perform statistical tests. If standard data are used in calibrations, covariances must be taken into account. Covariances are also necessary in order to update values every time when new data are obtained. In this paper we determined covariances between the most important gamma-ray energies for use in Ge-semiconductor detectors calibration recently published by Helmer and van der Leun (Nucl. Instr. Meth. A 450 (2000) 35).     

Effects of hot spices on energy intake,appetite and sensory specific desires in humans

This study investigated the effect of hot spices on energy intake and appetite. Forty participants received five meals of fixed portion sizes, served with or without five hot spices followed by a buffet. Spices were used in doses perceived as moderately hot, ensuring that the meals were palatable. Food intake (kJ), appetite and liking (before, during, after the meal and after the buffet), mood (before, after the meal and after the buffet) and desire to eat sweet, sour, fatty, salty, bitter and hot foods (after the meal and after the buffet) were measured on 9-point scales. Hot spices did not affect energy intake (p > 0.05). Desire for sweet foods was increased by chili (0.6 point, p < 0.05) whereas desire to eat salty foods was decreased by mustard (1 point, p < 0.01), suggesting that hot spices can induce changes in sensory specific desires. Liking of the meals tended to increase during the buffet when compared to the relatively constant liking of the fixed starter meals, suggesting that traditional sensory specific satiety does not play a large role in determining eating behaviour with complex meals.     

Influence of racemization on stereocomplex‐induced gelation of water‐soluble polylactide–poly(ethylene glycol) block copolymers

Ring‐opening polymerization of L ‐ or D ‐lactide was realized at 140 °C for a period of 7 days in the presence of dihydroxyl poly(ethylene glycol) (PEG), with M?_n = 4000 g mol^?1, using zinc lactate as initiator. The resulting poly(L ‐lactide)–PEG–poly(L ‐lactide) and poly(D ‐lactide)–PEG–poly(D ‐lactide) triblock copolymers are water soluble with polylactide (PLA) block length ranging from 11 to 17 units. Both the tube inverting method and rheological measurements were used to evaluate the gelation properties of aqueous solutions containing single copolymers or L /D copolymer pairs. Stereocomplexation between poly(L ‐lactide) and poly(D ‐lactide) blocks is observed for mixed solutions. Hydrogel formation is detected in the case of relatively long PLA blocks (DP _PLA = 17), but not for copolymers with shorter PLA blocks (DP _PLA = 11–13) due to partial racemization of L ‐lactyl units. Racemization is largely reduced when the reaction time is shortened to 1 day. Under these conditions, DP _PLA of 8 is sufficient for the stereocomplexation of PLA–PEG block copolymers, and DP _PLA above 10 leads to the formation of hydrogels of PLA–PEG block copolymers. On the other hand, racemization appears as a general phenomenon in the (co)polymerization of L ‐lactide with Zn(Lac)₂ as initiator, although it is negligible or undetectable in the case of high molar mass polymers. Therefore, racemization is the limiting factor for the stereocomplexation‐induced gelation of water‐soluble PLA–PEG block copolymers where the PLA block length generally ranges from 10 to 30. Reaction conditions including initiator, time and temperature should be strictly controlled to minimize racemization. Copyright © 2010 Society of Chemical Industry     

Papain-specific activating esters in aqueous dipeptide synthesis

Enzymatic peptide synthesis has the potential to be a viable alternative for chemical peptide synthesis. Because of the increasing commercial interest in peptides, new and improved enzymatic synthesis methods are desirable. In recently developed enzymatic strategies such as substrate mimetic approaches and enzyme-specific activation, use of the guanidinophenyl ester (OGp) group has been shown to suffer from some drawbacks. OGp esters are sensitive to spontaneous chemical hydrolysis and the group is expensive to synthesize and therefore not suitable for large-scale applications. On the basis of earlier computational studies, we hypothesized that OGp might be replaceable by simpler ester groups to make the enzyme-specific activation approach to peptide bond formation more accessible. To this end, a set of potential activating esters (Z-Gly-Act) was designed, synthesized, and evaluated. Both the benzyl (OBn) and the dimethylaminophenyl (ODmap) esters gave promising results. For these esters, the scope of a model dipeptide synthesis reaction under aqueous conditions was investigated by varying the amino acid donor. The results were compared with those obtained from a previous study of Z-X(AA) -OGp esters. Computational docking analysis of the set of esters was performed in order to provide insight into the differences in the reactivities of all the potential activating esters. Finally, selected ODmap- and OBn-activated amino acids were applied in the synthesis of two biologically active dipeptides on preparative scales.     

Sensory evaluation of precooked chicken meat with mate (<Emphasis Type="Italic">Ilex paraguariensis</Emphasis>) added as antioxidant

Dried mate leaves or aqueous extract of dried mate leaves added to chicken meat balls prior to cooking for antioxidant protection was found not to affect taste or smell of the product significantly for addition corresponding to 0.050% of dried mate leaves, while 0.10% changed the smell but not the taste and more significantly for dried leaves. Addition of aqueous mate extract corresponding to 0.050% of mate is recommended as an alternative to more strongly flavoured herbs for oxidative protection of meat products.     

Statistical analysis of the Doppler broadening coincidence spectrum of electron–positron annihilation radiation in silicon

We report a statistical analysis of Doppler broadening coincidence data of electron–positron annihilation radiation in silicon using a ²²Na source. The Doppler broadening coincidence spectrum was fit using a model function that included positron annihilation at rest with 1s, 2s, 2p, and valence band electrons. In-flight positron annihilation was also fit. The response functions of the detectors accounted for backscattering, combinations of Compton effects, pileup, ballistic deficit, and pulse-shaping problems. The procedure allows the quantitative determination of positron annihilation with core and valence electron intensities as well as their standard deviations directly from the experimental spectrum. The results obtained for the core and valence band electron annihilation intensities were 2.56(9)% and 97.44(9)%, respectively. These intensities are consistent with published experimental data treated by conventional analysis methods. This new procedure has the advantage of allowing one to distinguish additional effects from those associated with the detection system response function.     

Improvements in Cryptosporidium recovery and variability through modifications to United States Environmental Protection Agency Method 1623

The use of United States Environmental Protection Agency (USEPA) Method 1623 for the detection of Cryptosporidium in water often results in low and variable rates of recovery. According to data disseminated in Method 1623, less than a quarter of tested surface water samples had Cryptosporidium recoveries of 60% or greater. This research explored various method modifications in order to produce a method with higher recovery and less variability. Once method modifications were implemented, recoveries of C. parvum in reagent water increased by greater than 20% to an average recovery of 76%. In surface water, a significantly higher (P = 0.049) mean recovery of 67% for C. parvum was achieved with the modified method. Giardia is simultaneously detected when using Method 1623. The method modifications significantly increased the recovery of Giardia in reagent water by 37% (P = 0.0002) while also allowing for a 17% higher recovery in surface water samples (P = 0.21).