Efficiency, costs and trade-offs in marine reserve system design

With marine biodiversity conservation the primary goal for reserve planning initiatives, a site's conservation potential is typically evaluated on the basis of the biological and physical features it contains. By comparison, socio-economic information is seldom a formal consideration of the reserve system design problem and generally limited to an assessment of threats, vulnerability or compatibility with surrounding uses. This is perhaps surprising given broad recognition that the success of reserve establishment is highly dependent on widespread stakeholder and community support. Using information on the spatial distribution and intensity of commercial rock lobster catch in South Australia, we demonstrate the capacity of mathematical reserve selection procedures to integrate socio-economic and biophysical information for marine reserve system design. Analyses of trade-offs highlight the opportunities to design representative, efficient and practical marine reserve systems that minimise potential loss to commercial users. We found that the objective of minimising the areal extent of the reserve system was barely compromised by incorporating economic design constraints. With a small increase in area (< 3%) and boundary length (< 10%), the economic impact of marine reserves on the commercial rock lobster fishery was reduced by more than a third. We considered also how a reserve planner might prioritise conservation areas using information on a planning units selection frequency. We found that selection frequencies alone were not a reliable guide for the selection of marine reserve systems, but could be used with approaches such as summed irreplaceability to direct conservation effort for efficient marine reserve design.

N-Substituent effect of maleimides on acrylate polymerization initiated by three-component systems

In this paper, the relative photopolymerization efficiency for polymerization of a difunctional acrylate initiated by various N-substituted maleimides in the presence of amine and benzophenone are compared on the basis of a photo-differential scanning calorimetry (photo-DSC) study. The trends in the polymerization rates were obtained from the photopolymerization profiles and expressed in terms of a photoinitiation index, I-p. An N-substituent index, I-s, which indicates whether each N-substituent plays either a positive (when I-s > 1) or a negative (when I-s < 1) role in the initiation process relative to MI (unsubstituted maleimide), was determined. (C) 2003 Society of Chemical Industry.

The plasticisation effect of glycerol and water on the gelatinisation of wheat starch

In the extrusion manufacture of starch-based thermoplastics, such as biodegradable packaging materials, glycerol is an effective additive as a plasticiser, that is, to diminish the brittle nature of the product and provide the desired extent of flexibility. However, the addition of glycerol may also affect the gelatinisation behaviour of the starch-water mixture, and hence the required processing conditions for producing a homogeneously gelatinised starch-based material. The effect of glycerol on the gelatinisation of wheat starch was studied using differential scanning calorimetry (DSC). Mixtures of starch, water and glycerol were investigated with a water content ranging from 12 - 40% and a glycerol concentration up to 75%. Dependent on composition, the enthalpy of gelatinisation ranged from 1.7 - 12.6 J/g (on a dry starch basis), while the onset and peak temperatures varied from 54 to 86 degreesC and 60 to 90 degreesC, respectively. As expected, water acted as a plasticiser in that the onset temperature for gelatinisation (TO) decreased with increasing moisture content. Glycerol, however, increased To. It is shown that the T-0 of starch-glycerol-water mixtures may be predicted on the basis of the effective moisture content of the starch fraction of these mixtures resulting from the relative speed of moisture absorption by glycerol and starch, respectively. Moisture sorption kinetics of wheat starch and glycerol in 100% relative humidity were determined and used to predict the preferential water absorption by glycerol in starch-glycerol-water mixtures and hence the resulting T-0 of the system.

Nanostructures, Semicrytalline Morphology, and Nanoscale Confinement Effect on the Crystallization Kinetics in Self-Organized Block Copolymer/Thermoset Blends

This work reports the first instance of self-organized thermoset blends containing diblock copolymers with a crystallizable thermoset-immiscible block. Nanostructured thermoset blends of bisphenol A-type epoxy resin (ER) and a low-molecular-weight (M-n = 1400) amphiphilic polyethylene-block-poly(ethylene oxide) (EEO) symmetric diblock copolymer were prepared using 4,4'-methylenedianiline (MDA) as curing agent and were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and differential scanning calorimetry (DSC). All the MDA-cured ER/EEO blends do not show macroscopic phase separation but exhibit microstructures. The ER selectively mixes with the epoxy-miscible PEO block in the EEO diblock copolymer whereas the crystallizable PE blocks that are immiscible with ER form separate microdomains at nanoscales in the blends. The PE crystals with size on nanoscales are formed and restricted within the individual spherical micelles in the nanostructured ER/EEO blends with EEO content up to 30 wt %. The spherical micelles are highly aggregated in the blends containing 40 and 50 wt % EEO. The PE dentritic crystallites exist in the blend containing 50 wt % EEO whereas the blends with even higher EEO content are completely volume-filled with PE spherulites. The semicrystalline microphase-separated lamellae in the symmetric EEO diblock copolymer are swollen in the blend with decreasing EEO content, followed by a structural transition to aggregated spherical micellar phase morphology and, eventually, spherical micellar phase morphology at the lowest EEO contents. Three morphological regimes are identified, corresponding precisely to the three regimes of crystallization kinetics of the PE blocks. The nanoscale confinement effect on the crystallization kinetics in nanostructured thermoset blends is revealed for the first time. This new phenomenon is explained on the basis of homogeneous nucleation controlled crystallization within nanoscale confined environments in the block copolymer/thermoset blends.

On a resampling approach for tests on the number of clusters with mixture model-based clustering of tissue samples

We consider the problem of assessing the number of clusters in a limited number of tissue samples containing gene expressions for possibly several thousands of genes. It is proposed to use a normal mixture model-based approach to the clustering of the tissue samples. One advantage of this approach is that the question on the number of clusters in the data can be formulated in terms of a test on the smallest number of components in the mixture model compatible with the data. This test can be carried out on the basis of the likelihood ratio test statistic, using resampling to assess its null distribution. The effectiveness of this approach is demonstrated on simulated data and on some microarray datasets, as considered previously in the bioinformatics literature. (C) 2004 Elsevier Inc. All rights reserved.

Relation between cell disruption conditions, cell debris particle size, and inclusion body release

The efficiency of physical separation of inclusion bodies from cell debris is related to cell debris size and inclusion body release and both factors should be taken into account when designing a process. In this work, cell disruption by enzymatic treatment with lysozyme and cellulase, by homogenization, and by homogenization with ammonia pretreatment is discussed. These disruption methods are compared on the basis of inclusion body release, operating costs, and cell debris particle size. The latter was measured with cumulative sedimentation analysis in combination with membrane-associated protein quantification by SDS-PAGE and a spectrophotometric pepticloglycan quantification method. Comparison of the results obtained with these two cell debris quantification methods shows that enzymatic treatment yields cell debris particles with varying chemical composition, while this is not the case with the other disruption methods that were investigated. Furthermore, the experiments show that ammonia pretreatment with homogenization increases inclusion body release compared to homogenization without pretreatment and that this pretreatment may be used to control the cell debris size to some extent. The enzymatic disruption process gives a higher product release than homogenization with or without ammonia pretreatment at lower operating costs, but it also yields a much smaller cell debris size than the other disruption process. This is unfavorable for centrifugal inclusion body purification in this case, where cell debris is the component going to the sediment and the inclusion body is the floating component. Nevertheless, calculations show that centrifugal separation of inclusion bodies from the enzymatically treated cells gives a high inclusion body yield and purity. (C) 2004 Wiley Periodicals, Inc.

Comparative study of Li, Na, and K adsorptions on graphite by using ab initio method

A comprehensive study has been conducted to compare the adsorptions of alkali metals (including Li, Na, and K) on the basal plane of graphite by using molecular orbital theory calculations. All three metal atoms prefer to be adsorbed on the middle hollow site above a hexagonal aromatic ring. A novel phenomenon was observed, that is, Na, instead of Li or K, is the weakest among the three types of metal atoms in adsorption. The reason is that the SOMO (single occupied molecular orbital) of the Na atom is exactly at the middle point between the HOMO and the LUMO of the graphite layer in energy level. As a result, the SOMO of Na cannot form a stable interaction with either the HOMO or the LUMO of the graphite. On the other hand, the SOMO of Li and K can form a relatively stable interaction with either the HOMO or the LUMO of graphite. Why Li has a relatively stronger adsorption than K on graphite has also been interpreted on the basis of their molecular-orbital energy levels.

On the steady-state assumption and its application to the rotating disk voltammetry of adsorbed enzymes

Rotating disk voltammetry is routinely used to study electrochemically driven enzyme catalysis because of the assumption that the method produces a steady-state system. This assumption is based on the sigmoidal shape of the voltammograms. We have introduced an electrochemical adaptation of the King-Altman method to simulate voltammograms in which the enzyme catalysis, within an immobilized enzyme layer, is steadystate. This method is readily adaptable to any mechanism and provides a readily programmable means of obtaining closed form analytical equations for a steady-state system. The steady-state simulations are compared to fully implicit finite difference (FIFD) simulations carried out without any steady-state assumptions. On the basis of our simulations, we conclude that, under typical experimental conditions, steady-state enzyme catalysis is unlikely to occur within electrode-immobilized enzyme layers and that typically sigmoidal rotating disk voltammograms merely reflect a mass transfer steady state as opposed to a true steady state of enzyme intermediates at each potential.

Improvement of the Derjaguin-Broekhoff-de Boer theory for capillary condensation/evaporation of nitrogen in mesoporous systems and its implications for pore size analysis of MCM-41 silicas and related materials

In this work, we propose an improvement of the classical Derjaguin-Broekhoff-de Boer (DBdB) theory for capillary condensation/evaporation in mesoporous systems. The primary idea of this improvement is to employ the Gibbs-Tolman-Koenig-Buff equation to predict the surface tension changes in mesopores. In addition, the statistical film thickness (so-called t-curve) evaluated accurately on the basis of the adsorption isotherms measured for the MCM-41 materials is used instead of the originally proposed t-curve (to take into account the excess of the chemical potential due to the surface forces). It is shown that the aforementioned modifications of the original DBdB theory have significant implications for the pore size analysis of mesoporous solids. To verify our improvement of the DBdB pore size analysis method (IDBdB), a series of the calcined MCM-41 samples, which are well-defined materials with hexagonally ordered cylindrical mesopores, were used for the evaluation of the pore size distributions. The correlation of the IDBdB method with the empirically calibrated Kruk-Jaroniec-Sayari (KJS) relationship is very good in the range of small mesopores. So, a major advantage of the IDBdB method is its applicability for small mesopores as well as for the mesopore range beyond that established by the KJS calibration, i.e., for mesopore radii greater than similar to4.5 nm. The comparison of the IDBdB results with experimental data reported by Kruk and Jaroniec for capillary condensation/evaporation as well as with the results from nonlocal density functional theory developed by Neimark et al. clearly justifies our approach. Note that the proposed improvement of the classical DBdB method preserves its original simplicity and simultaneously ensures a significant improvement of the pore size analysis, which is confirmed by the independent estimation of the mean pore size by the powder X-ray diffraction method.

On the optimal ratio of heavy to light chain genes for efficient recombinant antibody production by CHO cells

Monoclonal antibodies (Mab) are heterotetramers consisting of an equimolar ratio of heavy chain (HC) and light chain (LC) polypeptides. Accordingly, most recombinant Mab expression systems utilize an equimolar ratio of heavy chain (he) to light chain (lc) genes encoded on either one or two plasmids. However, there is no evidence to suggest that this gene ratio is optimal for stable or transient production of recombinant Mab. In this study we have determined the optimal ratio of hc:lc genes for production of a recombinant IgG(4) Mab, cB72.3, by Chinese hamster ovary (CHO) cells using both empirical and mathematical modeling approaches. Polyethyleneimine-mediated transient expression of cB72.3 at varying ratios of hc:lc genes encoded on separate plasmids yielded an optimal Mab titer at a hc:lc gene ratio of 3:2; a conclusion confirmed by separate mathematical modeling of the Mab folding and assembly process using transient expression data. On the basis of this information, we hypothesized that utilization of he genes at low hc:lc gene ratios is more efficient. To confirm this, cB72.3 Mab was transiently produced by CHO cells at constant he and varying lc gene dose. Under these conditions, Mab yield was increased with a concomitant increase in lc gene dose. To determine if the above findings also apply to stably transfected CHO cells producing recombinant Mab, we compared the intra- and extracellular ratios of HC and LC polypeptides for three GS-CHO cells lines transfected with a 1:1 ratio of hc:lc genes and selected for stable expression of the same recombinant Mab, cB72.3. Intra- and extracellular HC:LC polypeptide ratios ranged from 1:2 to 1:5, less than that observed on transient expression of the same Mab in parental CHO cells using the same vector. In conclusion, our data suggest that the optimal ratio of hc:lc genes used for transient and stable expression of Mab differ. In the case of the latter, we infer that optimal Mab production by stably transfected cells represents a compromise between HC abundance limiting productivity and the requirement for excess LC to render Mab folding and assembly more efficient.

Effect of carbon/noncarbon addition on hydrogen storage behaviors of magnesium hydride

Various Mg/carbon and Mg/noncarbon composite systems were prepared by mechanical milling and their hydrogen storage behaviors were investigated. It was found that all the carbon additives exhibited prominent advantage over the noncarbon additives, such as BN nanotubes (BNNTs) or asbestos in improving the hydrogen capacity and dehydriding/hydriding kinetics of Mg. And among the various carbon additives, purified single-walled carbon nanotubes (SWNTs) exhibited the most prominent catalytic effect on the hydrogen storage properties of Mg. The hydrogen capacities of all Mg/C composites at 573 K reached more than 6.2 wt.% within 10 min, about 1.5 wt.% higher than that of pure MgH2 at the identical operation conditions. Under certain operation temperatures, H-absorption/desorption rates of Mg/carbon systems were over one order of magnitude higher than that of pure Mg. Furthermore, the starting temperature of the desorption reaction of MgH2 has been lowered to 60 K by adding SWNTs. On the basis of the hydrogen storage behavior and structure/phase investigations, the possible mechanism involved in the property improvement of Mg upon adding carbon materials was discussed. (c) 2005 Elsevier B.V. All rights reserved.

Get the picture? The effects of iconicity on toddlers' reenactment from picture books

What do toddlers learn from everyday picture-book reading interactions? To date, there has been scant research exploring this question. In this study, the authors adapted a standard imitation procedure to examine 18- to 30-month-olds' ability to learn how to reenact a novel action sequence from a picture book. The results provide evidence that toddlers can imitate specific target actions on novel real-world objects on the basis of a picture-book interaction. Children's imitative performance after the reading interaction varied both as a function of age and the level of iconicity of the pictures in the book. These findings are discussed in terms of children's emerging symbolic capacity and the flexibility of the cognitive representation.

Strain energies due to nonplanar distortion of fullerenes and their dependence on structural motifs

Accurate strain energies due to nonplanar distortion of 114 isolated pentagon rule (IPR) fullerenes with 60-102 carbon atoms have been calculated based on B3LYP/6-31G(d) optimized structures. The calculated values of strain energy due to nonplanar distortion (E-np) are reproduced by three simple schemes based upon counts of 8, 16, and 30 distinct structural motifs composed of hexagons and pentagons. Using C-180 (I-h) and CN (I-h) (N is very large) as test molecules, the intrinsic limitations of the motif model based on six-membered rings (6-MRs) as the central unit have been discussed. On the basis of the relationship between the contributions of motifs to E-np and the number of five-membered rings (5-MRs) in motifs, we found that IPR fullerenes with dispersed 5-MRs present smaller nonplanar distortions.