Preparation of highly substituted carboxymethyl starch using a twin‐screw extruder

Carboxymethyl starch was prepared by reacting corn starch with sodium mono chloro acetate (SMCA) in a Brabender TSE‐20 co‐rotating twin screw extruder. The effects of the SMCA/starch ratio (theoretical degrees of substitutions 2.73, 3.62, and 4.53), aqueous ethanol/(starch + SMCA) ratio (0.13 and 0.25) and the screw configuration (0, 1, and 2 kneading blocks) on the degree of substitution (DS) and reaction efficiency were studied. A 3 × 2 factorial design with 3 levels of the starch/SMCA ratio and 2 levels of the aqueous ethanol/(starch + SMCA) ratio were used. This 3 × 2 factorial design was blocked, with the screw configuration as the blocking variable. The effects of the SMCA/starch ratio and the screw configuration were found to be significant. The carboxymethylated starches were characterized using FTIR, SEM, and XRD. The microstructure of the carboxymethylated starches, studied using SEM, revealed that the integrity of the starch granules was partially preserved at low aqueous ethanol levels when no kneading block was used. However, for all other reaction conditions either granule agglomeration or fusion was observed. XRD analysis indicated substantial loss of crystallinity in the carboxymethylated starches, irrespective of the damage to the granule structure. The highest DS and the highest reaction efficiency obtained were 1.54 and 0.42, respectively.     

Monoterpene and sesquiterpene emission estimates for the United States

Biogenic volatile organic compounds (BVOC) contribute significantly to the formation of ozone and secondary organic aerosol (SOA). The Model of Emissions of Gases and Aerosols from Nature (MEGANv2.02) is used to estimate emissions of isoprene, monoterpenes (MT), and sesquiterpenes (SQT) across the United States. Compared to the Biogenic Emission Inventory System (BEIS3.0), MEGANv2.02 estimates higher isoprene but lower MT emissions for July 2001 and January 2002. A sensitivity study of SQT and MT emission factors and algorithm parameters was conducted by assigning values to four plant functional types (PFTs) using both recent measurements and literature values. The standard deviations of the emissions factors within these PFTs were two to four times the averages because of the variation in experimental basal emissions rate data. More recently published SQT and MT basal emission rates are generally lower than those reported in the literature through 2004. With the new emissions factors, monthly average SQT emission rates for the contiguous United States are equal to 16% of the MT emissions during July and 9% of the emissions during January. The SQT emissions distribution is strongly influenced by the grass and crop PFT, for which SQT emissions data are quite limited.     

Use of synthetic data to evaluate positive matrix factorization as a source apportionment tool for PM2.5 exposure data

Positive matrix factorization (PMF) was applied to synthetic datasets that simulate personal exposures to airborne PM2.5 from 12 sources. Three differentfilter analysis scenarios using different analytical chemistry techniques were considered. The full suite scenario quantified elemental carbon, organic carbon, inorganic ions, trace elements, and trace organic species including carboxylic acids and organic compounds with -OH functionality. A second scenario excluded trace elements and a third assumed that derivatization steps to quantify polar organic compounds were not performed. Similar errors in source apportionment were seen with all three scenarios. In most cases, PMF failed to separate out factors corresponding to road dust and vegetative debris, two sources that made relatively uniform contributions to the synthetic exposures. Factors representing wood smoke, natural gas combustion, and meat cooking sources were difficult to identify due to a lack of unique tracers with concentrations reliably above the detection limits assumed in the study. Factors representing cigarette smoke, candle smoke, gasoline exhaust, and secondary aerosols were comparatively easy to identify. When contributions from a pair of sources, such as diesel and gasoline exhaust, were highly correlated in the synthetic datasets, a single factor corresponding to both sources was usually found.     

Quantum states of he atoms adsorbed on surfaces of rare gas solids

Wave functions and energies for band states of helium atoms in the two-dimensional periodic potential at the surface of a semiinfinite rare gas solid have been studied. In the case of Kr and Ar substrates, the atoms are highly localized and, correspondingly, the band widths are small. In a third case, namely that of an argon crystal highly compressed to simulate the adsorption site density of the close-packed face of argon, much larger band widths were found. If this is a reasonable simulation, then band effects may be observable.     

Arsenic in stream sediments and waters of South West England

Past mining and smelting of arsenical and associated metalliferous ores in South-west England has led to widespread contamination of soils and surface drainage. The regional distribution of arsenic in both sediments and waters of tributary drainage shows anomalies in those areas underlain by mineralised granites and their metamorphic aureoles. High concentrations of arsenic in waters correspond with high concentrations in associated sediments. Detailed studies in three river systems illustrate the large degree of variation in arsenic values between individual sampling stations but confirm the relationship between sediments and waters. The work provides evidence of the potential use of geochemical reconnaissance surveys to water quality assessment.     

Shrinkage and re‐expansion of extruded starch acetate foams

The effects of concentration of steam, heating time, pretreatment, and cooling conditions on the shrinkage and re‐expansion of extruded starch acetate foam were investigated. The re‐expansion ratio was determined from the degree by which the foam cells were moistened under the condition tested. The higher the concentration of steam used, the faster and greater the foam re‐expanded. Shrinkage was a result of the negative pressure resulting from cooling and condensation of steam or ethanol inside the foam and the unbalanced osmosis of steam transported out of the foam and air transported into the foam and the resistance of foam cell walls. Quenching re‐expanded foams led to significant shrinkage, especially for foams re‐expanded with highly concentrated steam. Shrinkage cannot be avoided even if the foam is kept at the same temperature it was expanded at the nozzle. Gradually reducing the degree of concentration of steam could reduce the shrinking tendency of the re‐expanded foam. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4264–4268, 2006     

Fuel properties of tallow and soybean oil esters

Fuel properties of beef tallow, soybean oil, their esters, and blends with No. 2 diesel fuel and ethanol were determined. Fuel properties tested were viscosity, specific gravity, API gravity, distillation ranges, calculated cetane index, energy content, flash point, water content, sulfur content, carbon residue, particulate matter, acid value, copper-strip corrosion test, ash content, melting point, cloud point, and pour point. Gas-chromatographic analyses of tallow, soybean oil, and their esters were performed to determine their major constituents. Viscosities of soybean oil and tallow were significantly reduced by esterification. Other fuel properties of the esters and their blends with No. 2 diesel fuel and ethanol were similar to the properties of No. 2 diesel fuel.     

Hybrid robot control and SLAM for persistent navigation and mapping

For a mobile robot to operate autonomously in real-world environments, it must have an effective control system and a navigation system capable of providing robust localization, path planning and path execution. In this paper we describe work investigating synergies between mapping and control systems. We have integrated development of a control system for navigating mobile robots and a robot SLAM system. The control system is hybrid in nature and tightly coupled with the SLAM system; it uses a combination of high and low level deliberative and reactive control processes to perform obstacle avoidance, exploration, global navigation and recharging, and draws upon the map learning and localization capabilities of the SLAM system. The effectiveness of this hybrid, multi-level approach was evaluated in the context of a delivery robot scenario. Over a period of two weeks the robot performed 1143 delivery tasks to 11 different locations with only one delivery failure (from which it recovered), travelled a total distance of more than 40 km, and recharged autonomously a total of 23 times. In this paper we describe the combined control and SLAM system and discuss insights gained from its successful application in a real-world context.     

The effects of whitening and dust accumulation on the microclimate and canopy behaviour of rose plants (Rosa hybrida) in a greenhouse in Zimbabwe

The effects of whitening and of dust accumulation on the optical properties of materials in use as greenhouse covers in Zimbabwe were investigated. The effect of whitening was investigated in a greenhouse by measuring the transmittances for total solar, photosynthetically active radiation (PAR) and thermal radiation before and after painting the cover with lime-based whitewash paint, as used for shading in Zimbabwe. In addition, to evaluate the effect of dust, the transmittances for total solar, PAR and thermal radiation of a plastic sample were measured when dirty, due to exposure to the environment for 6 months, and again after cleaning. Whitening reduced the transmission coefficients for PAR, total solar and thermal radiation of the greenhouse cover from 0.75 to 0.53; 0.74 to 0.55 and 0.45 to 0.43, respectively. Dust and dirt accumulation due to 6 months exposure to the environment reduced the transmittances for all wavebands of the plastic sample (relative to their initial values) by 16%, 15% and 13%, respectively. To investigate the effect of these changes in the optical properties on greenhouse microclimate and canopy behaviour, the measured changes in transmittances were used in the Gembloux Dynamic Greenhouse Climate Model (GDGCM). The model showed that whitening of the greenhouse roof led to significant reductions in the maximum air temperature, vapour pressure deficit, canopy-to-air temperature difference and transpiration rate, while the canopy stomatal resistance was not significantly affected. These reductions, together with a decrease in the crop water stress index, indicate that the crop was less stressed after whitening. The model showed similar, but smaller, changes to all the microclimate and canopy parameters due to the accumulation of dust on the greenhouse roof.     

Renal histopathology in fatal cases of diarrhoea-associated haemolytic uraemic syndrome. British Association for Paediatric Nephrology

We report on a 32-year-old atopic female office employee with a moderate tree pollinosis who also suffered from indoor-related perennial rhinoconjunctivitis. Once when she repotted her two ornamental nonflowering green plants of the genus Tradescantia (synonym; Albifloxia; family Commelinaceae), she immediately experienced itching of the face, throat, and conjunctiva; swelling of the lips; and dyspnea and wheezing. Skin prick tests with the leaves of Tradescantia (T. albifloxia and T. fluminensis) (Ta and Tf) were strongly positive as was the specific IgE to Ta leaves extract. On RAST inhibition studies, no cross-reactivity was found between Ta and Ficus benjamina (weeping fig), a nonflowering green plant, which produces, in its milky sap, an important respiratory allergen. Green plants should be considered potential indoor allergens and tested in plant-keepers referred for allergologic investigation.