Preparation and Enzymatic Degradation of Porous Crosslinked Polylactides of Biomass Origin

To understand the enzymatic degradation behavior of crosslinked polylactide (PLA), the preparation and enzymatic degradation of both thermoplastic (linear) and crosslinked PLAs that have pore structures with different dimensions were carried out. The porous structures of the linear PLA samples were of micro and nanoporous nature, and prepared by batch foaming with supercritical CO₂ and compared with the porous structures of crosslinked PLA (Lait-X) created by the salt leaching method. The surface and cross-sectional morphologies of the porous structures were investigated by using scanning electron microscopy. The morphological analysis of porous Lait-X showed a rapid loss of physical features within 120 h of exposure to proteinase-K enzymatic degradation at 37 °C. Due to the higher affinity for water, enhanced enzymatic activity as compared to the linear PLA porous structures in the micro and nanoporous range was observed.     

Fatty acids of a whitefish (Coregonus albula) flesh lipids

Using gas chromatographic-mass spectrometric methods 50 fatty acid components of the flesh lipids of a fresh-water whitefish have been examined in detail. The total lipids represented, on average, 3.0% of the wet weight of whitefish fillets. Saturated, monoenoic and polyenoic fatty acids were present in proportions of 31.4, 22.4 and 44.2%, respectively. About half of the total saturated acids was composed of palmitic acid (16:0, 16.1 %), which is generally abundant in fish lipids. The proportion of saturated iso- and anteiso-acids was 2.9%. The major monoenoic acid was oleic acid (18:1,ω9 10.6%), whereas the monoenoic C₂₀-acids were present only in minor amounts and the monenoic C₂₂-acids were not detected at all. The polyenoic fatty acids were predominantly of ω3 series with docosahexaenoic (22:6ω3, 9.4%) and cicosapentaenoic (20:5ω3, 7.7%) acids as the major components. Linoleic (18:2ω6), linolenic (18:3ω3), octadecatetraenoic (18:4ω3) and arachidonic (20:4ω6) acids were also present in remarkable proportions each amounting to about 4.5% of the total fatty acids.     

Effects of diameter, length, and circuit pressure on sound conductance through endotracheal tubes

We evaluated the acoustic frequency response of endotracheal tubes (ETs) to assess their effect on respiratory system sound transmission studies. White noise 150-3300 Hz was introduced into 4.0-, 6.0-, and 8.0-mm ETs and recorded at their proximal and distal ends. Four tubes of each size were studied at their original and normalized lengths, in straight and bent configurations, and at circuit pressures from 0 to 20 cmH2O. The characteristics of the sound transmission were compared using an analysis of variance for repeated measures. The average transmission amplitude varied directly with tube diameter. The position of peaks and troughs on the amplitude frequency distribution depended on tube length but not on tube diameter. The angle of the phase-frequency plot correlated well with the length of the tube and was independent of its diameter. A 90 degrees bend in the tube had no effect on its sound transmission. Increasing the circuit pressure above ambient modified the frequency response only if volume changes occurred in the test lung. When used to conduct sound into the respiratory system an ET affects the incident signal predictably depending on its length and diameter but not on its curvature or circuit pressure.     

Distribution of (210)Pb and (210)Po in boreal forest soil

Vertical distribution and activity contents of ²¹⁰Pb and ²¹⁰Po were investigated in forest soils of Scots pine-dominated (Pinus sylvestris L.) stands from seven different locations in Finland. The mean total inventory in the soil profile, up to 20 cm, of ²¹⁰Pb was 4.0 kBq m^− 2 (range 3.1-5.0 kBq m^− 2) and ²¹⁰Po 5.5 kBq m^− 2 (range 4.0-7.4 kBq m^− 2), the organic soil layer containing 45% of the total inventory of both nuclides. In both the organic and the mineral layers the ²¹⁰Po/²¹⁰Pb ratio was close to unity indicating a radioactive equilibrium between them. In the litter layer there was, however, a clear excess of ²¹⁰Po suggesting that polonium is recycled via root uptake from the root zone to the ground surface. The activity concentration (Bq kg^− 1) of ²¹⁰Pb clearly correlated with organic matter and the Fe, Al and Mn concentrations in soil indicating that radioactive lead is associated both with humic substances and the oxides of iron, aluminium and manganese. Radioactive lead was also seen to follow the behavior of stable lead. No systematic correlation between polonium and soil properties was seen.     

Hydrogen and methane production in extreme thermophilic conditions in two-stage (upflow anaerobic sludge bed) UASB reactor system

Two-stage hydrogen and methane production in extreme thermophilic (70 °C) conditions was demonstrated for the first time in UASB-reactor system. Inoculum used in hydrogen and methane reactors was granular sludge from mesophilic internal circulation reactor and was first acclimated for extreme thermophilic conditions. In hydrogen reactor, operated with hydraulic retention time (HRT) of 5 h and organic loading rate (OLR) of 25.1 kg COD/m³/d, hydrogen yield was 0.73 mol/mol glucose_added. Methane was produced in second stage from hydrogen reactor effluent. In methane reactor operated with HRT of 13 h and OLR of 7.8 kg COD/m³/d, methane yield was 117.5 ml/g COD_added. These results prove that hydrogen and methane can be produced in extreme thermophilic temperatures, but as batch experiments confirmed, for methane production lower temperature would be more efficient.     

Lactic acid based poly(ester-urethanes): Use of hydroxyl terminated prepolymer in urethane synthesis

We studied a two step process for lactic acid polymerization: in the first step, the lactic acid is condensation polymerized to a low molecular weight hydroxyl terminated prepolymer and then the molecular weight is raised by joining prepolymer chains together using diisocyanate as the chain extender. The resulting polymer is a thermoplastic poly(ester-urethane). The polymer samples were carefully characterized with ¹³C-NMR, GPC, DSC, and IR. The results indicate that high conversions of lactic acid can be achieved, as well as independent control of the stereostructure, long chain branches, molecular weight average, and molecular weight distribution. Lactic acid is converted into a poly(ester-urethane) with a weight average molecular weight as high as 390,000 g/mol and a glass transition temperature of 53.7°C. The analyzed content of the monomer in the prepolymer is less than 1 mol % and the lactide content 2.4 mol %, while the final poly(ester-urethane) is essentially monomer and lactide free. The mechanical properties of the poly(ester-urethane) are comparable to those of polylactides. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1091–1100, 1997     

High-Pressure Gelatinization of Barley Starch at Low Moisture Levels and Elevated Temperature

High-pressure gelatinization of barley starch at low water contents and at elevated temperature was performed in a differential scanning calorimeter equipped with a pressure chamber. Microscopic examination of the samples showed complete loss of birefringence and rupture of granular structure in most samples. The results indicated that enthalpy levels much higher than those in high-moisture gelatinization are needed to attain proper gelatinization and plastification of starch at low water contents.     

Evaluating the basic performance of the Intel iPSC/860 parallel computer

We evaluate the basic performance of the Intel iPSC/860 computer, which can have up to 128 Intel i860-based nodes connected together with a hypercube network topology. After giving a brief overview of the system, the properties and bottlenecks of the hardware architecture and software environment are discussed. Basic memory, scalar and vector performance of a single node is evaluated, and the communication performance and the overlap of computation and communication are analysed.