Predicting phytoplankton composition in the River Thames,England

Phytoplankton were sampled fortnightly in summer and monthly in winter for 33 months to determine temporal and spatial variations in taxonomic structure and relate these to the physical and chemical environment. Using canonical correspondence analysis, environmental variables selected by stepwise regression were found to be correlated with the major variable(s) determining phytoplankton composition. An improved proportion of explained variance was achieved by classifying data into three seasonal subsets. The highest percentage of explained variance in phytoplankton composition was achieved for the months March to May (36·5%), the lowest variance explained was for the period June to September (28·6%). Within each season, general linear modelling was used to predict taxa responses to variations in particular environmental variables. Taxa responses to discharge are presented as examples for determining river management policies. The rationale of conceptual models and the empirical models used for this study are discussed. © 1997 John Wiley & Sons, Ltd.     

Extraction of parameters and their error distributions from cyclic voltammograms using bootstrap resampling enhanced by solution maps: Computational study

The conventional determination of model parameter errors in least-squares regression of experimental cyclic voltammetric data assumes validity of local approximations (e.g., linearization) in the parameter space and normal distributions of the data and parameter errors. Such assumptions may not always be satisfied in practice. Bootstrap resampling techniques present a more universally applicable approach to error estimation, which until now has not been used in cyclic voltammetric studies, owing to the high costs of the required voltammogram simulations. We demonstrate that the burden of computing voltammograms can be significantly reduced by the use of high-dimensional model representation (HDMR) solution mapping techniques, thereby making it feasible to apply the bootstrap data analysis in cyclic voltammetry. We perform computational experiments with bootstrap resampling, enhanced by HDMR maps, for a typical cyclic voltammetric model (i.e., the Eqrev Cirr Eqrev reaction mechanism at a planar macroelectrode under semi-infinite, pure diffusion transport conditions). The experiments reveal that the bootstrap distributions of the estimated parameters provide a satisfactory quantification of the parameter errors and can also be used for detecting statistical correlations of the parameters.     

Characterization of a second-generation focal-plane camera coupled to an inductively coupled plasma Mattauch-Herzog geometry mass spectrograph

A second-generation Faraday-strip array detector has been coupled to an inductively coupled plasma Mattauch-Herzog geometry mass spectrograph, thereby offering simultaneous acquisition of a range of mass-to-charge ratios. The second-generation device incorporates narrower, more closely spaced collectors than the earlier system. Furthermore, the new camera can acquire signal on all collectors at a frequency greater than 2 kHz and has the ability to independently adjust the gain level of each collector. Each collector can also be reset independently. With these improvements, limits of detection in the hundreds of picograms per liter for metals in solution have been obtained. Some additional features, such as a broader linear dynamic range (over 7 orders of magnitude), greater resolving power (up to 600), and improved isotope ratio accuracy were attained. In addition, isotope ratio precision as low as 0.018% RSD was achieved.     

Measuring cosmic-ray exposure in aircraft using real-time personal dosemeters

Aircrew exposure to radiation was measured on several long-haul flights using two small commercial electronic personal dosemeters: one was a photon dosemeter, the NRF20; the other was a neutron dosemeter, the NRY21-both manufactured by Fuji Electric Systems Co. Ltd. for radiation protection at nuclear facilities. Non-neutron doses were measured using the photon dosemeter, and neutron doses were measured using the neutron dosemeter. The measured non-neutron doses at commercial aviation altitudes agree with the EPCARD (European Program Package for the Calculation of Aviation Route Doses) dose calculation within a difference of 8 %. However, the recorded neutron doses were 5-15 times larger than the EPCARD calculation. These over-measurements are dependent on cut-off rigidities.     

Influence of modified starches on properties of gluten-free dough and bread. Part II: Quality and staling of gluten-free bread

The aim of the study was to check the quality of gluten-free bread produced basing on the recipes, in which part of native starch was replaced with high amylose corn starch (HACS), acetylated distarch adipate (ADA), and hydroxypropyl distarch phosphate (HDP). The application 10 or 15% of chemically modified starches (HDP, ADA) caused the increase in volume of the obtained gluten-free loaves. The changes were accompanied by a decrease of average cell size, and an increase in their number. Due to the addition of modified starch crumb structure became more elastic, which was revealed in the results of stress relaxation. A slight decrease in hardness and chewiness of the crumb was also observed on the day of baking, and its extent depended on the level of modified starch, and was a little more pronounced in case of starch adipate. In comparison to the chemically modified starches, HACS deteriorated structural and mechanical properties of the crumb, which is probably related to their resistance to pasting and divergence in retrogradation pattern, where amylose component is more important than amylopectin.     

New insights into loss of swelling power and pasting profiles of acid hydrolyzed starch granules

The effect of acid hydrolysis on the swelling power of pea starch granules was studied by field emission SEM (FE‐SEM). The swelling power of the native starch granules (g water absorbed/g dry starch) was 13, and this decreased to less than 2 after 1 day of acid hydrolysis. The proportion of the starch that was soluble in hot water increased from 15% for native starch to 75% after 1 day of hydrolysis. The swelling power of the starch decreased further, and solubility increased, with more extended hydrolysis. The decrease in swelling power and increase in solubility were attributed mainly to the disruption of side chains of amylopectin. Observations with FE‐SEM indicated that starch granules were still able to melt and coalesce after 1 day of acid hydrolysis, but after 2 days solubilization of starch chains occurred predominantly rather than swelling when the granules were heated in excess water. The intactness of amylopectin is proposed to play a crucial role in the swelling power of starch granules and in the structure of granule ghosts.     

47—THE EXTRACTION OF WATER FROM COTTON-YARN PACKAGES BY CENTRIFUGAL FORCE. PART II: THE DISTRIBUTION OF MOISTURE IN AXIAL SPINNING

In the axial drying of packages, there are significant differences of centrifugal field between the inside and outside of the packages. These may give rise to differences in moisture retention. Of far greater importance, however, is a zone of high retention, which lies near the outside surface of the package.     

Electromagnetic coupling between wires inside a rectangular cavityusing multiple-mode-analogous-transmission-line circuit theory

This paper examines the coupling between two arbitrarily positioned wire segments inside a rectangular enclosure. The enclosure is treated as a superposition of analogous transmission lines which have been short circuited at two positions on the propagation axis. Each analogous transmission line is associated with a particular waveguide mode in the cavity. Previous work has used this analogy to predict the coupling between two monopoles inside a small box using the dominant TE ₁₀ mode. This paper considers the general case of high-frequency coupling between two wire monopoles in a large rectangular cavity, where several higher order modes are active. By taking into account higher order modes, and the mutual coupling between the modes, a simple equivalent circuit is presented which can give a prediction for the coupling between the monopoles. Experimental results for various monopole pair positions are shown, which indicate the success of the multimode theory. The technique requires far less computer resources than traditional methods for solving such a problem (e.g., MoM, TLM or FDTD), with solution times of less than a second on an average PC. In addition, considerable insight into the coupling process can be gained by including or excluding particular waveguide modes. This is not possible with numerical methods     

Increase in copy number of an integrated vector during continuous culture of Hansenula polymorpha expressing functional human haemoglobin

Recombinant human haemoglobin A (rHbA) was produced by a leucine-requiring strain of Hansenula polymorpha which had been transformed with an integration vector containing the Saccharomyces cerevisiae LEU2 gene and cDNAs for the expression of α and β globin each driven by the H. polymorpha MOX promoter. After 40 generations in a chemostat it was found that the integrated vector had become amplified in the host strain. In some cases this led to an increase in LEU2 gene dosage, but a loss of globin expression cassettes. In other cases the globin gene dosage also increased. These changes coincided with an increase in rHbA production in the culture, which was reversed when the dilution rate was increased. Isolates from a chemostat culture producing elevated levels of rHbA were grown in fed-batch fermentations, resulting in higher productivities than when inoculated with the parent strain. The rHbA produced was purified and characterized. Oxygen binding studies and electrospray mass spectrometry showed that the rHbA had been processed and assembled correctly, and behaved as a fully functional co-operative tetramer.