Identification of trade-offs underlying the primary strategies of plants

Question: What are the key physiological and life-history trade-offs responsible for the evolution of different suites of plant traits (strategies) in different environments? Experimental methods: Common-garden experiments were performed on physiologically realistic model plants, evolved in contrasting environments, in computer simulations. This allowed the identification of the trade-offs that resulted in different suites of traits (strategies). The environments considered were: resource rich, low disturbance (competitive); resource poor, low disturbance (stressed); resource rich, high disturbance (disturbed); and stressed environments containing herbivores (grazed). Results: In disturbed environments, plants increased reproduction at the expense of ability to compete for light and nitrogen. In competitive environments, plants traded off reproductive output and leaf production for vertical growth. In stressed environments, plants traded off vertical growth and reproductive output for nitrogen acquisition, contradicting Grime's (2001) theory that slow-growing, competitively inferior strategies are selected in stressed environments. The contradiction is partly resolved by incorporating herbivores into the stressed environment, which selects for increased investment in defence, at the expense of competitive ability and reproduction. Conclusion: Our explicit modelling of trade-offs produces rigorous testable explanations of observed associations between suites of traits and environments.

Vacuum-induced bubble formation in liquid-tempered chocolate

Bubble inclusion is one of the fastest growing operations practiced in the food industry. A variety of aerated foods is currently available in supermarkets, and newer products are emerging all the time. This paper aims to combine knowledge on chocolate aeration with studies performed on bubble formation and dispersion characteristics. More specifically, we have investigated bubble formation induced by applying vacuum. Experimental methods to determine gas hold-up (volume fraction of air), bubble section distributions along specific planes, and chocolate rheological properties are presented. This study concludes that decreasing pressures elevate gas hold-up values due to an increase in the number of bubble nuclei being formed and release of a greater volume of dissolved gases. Furthermore, bubbles are observed to be larger at lower pressures for a set amount of gas because the internal pressure needs to be in equilibrium with the surrounding pressures. Temperature-induced changes to the properties of the chocolate have less of an effect on bubble formation. On the other hand, when different fats and emulsifiers are added to a standard chocolate recipe, milk fat was found to increase, significantly, the gas hold-up values and the mean bubble-section diameters. It is hypothesized that this behavior is related to the way milk fats, which contain different fatty acids to cocoa butter, crystallize and influence the setting properties of the final product. It is highlighted that apparent viscosity values at low shear rate, as well as setting behavior, play an important role in terms of bubble formation and entrainment.

Identified consumers: an experiment on the informativeness of cross-demand price effects

Often, firms have no information on the specification of the true demand model they are faced with. It is, however, a well established fact that trial-and-error algorithms may be used by them in order to learn how to make optimal decisions. Using experimental methods, we identify a property of the information on past actions which helps the seller of two asymmetric demand substitutes to reach the optimal prices more precisely and faster. The property concerns the possibility of disaggregating changes in each product’s demand into client exit/entry and shift from one product to the other.

Perceived competence moderates the relation between performance-approach and performance-avoidance goals

In the present research, we conducted 4 studies designed to examine the hypothesis that perceived competence moderates the relation between performance-approach and performance-avoidance goals. Each study yielded supportive data, indicating that the correlation between the 2 goals is lower when perceived competence is high. This pattern was observed at the between- and within-subject level of analysis, with correlational and experimental methods and using both standard and novel achievement goal assessments, multiple operationalizations of perceived competence, and several different types of focal tasks. The findings from this research contribute to the achievement goal literature on theoretical, applied, and methodological fronts and highlight the importance of and need for additional empirical work in this area. (PsycINFO Database Record (c) 2012 APA, all rights reserved)(journal abstract)

Carbon nanotubes in nanostructured films: Potential application as amperometric and potentiometric field-effect (bio-)chemical sensors

The assembly of carbon nanotubes (CNTs) into nanostructured films is attractive for producing functionalized hybrid materials and (bio-)chemical sensors, but this requires experimental methods that allow for control of molecular architecturcs. In this study, we exploit the layer-by-layer (LbL) technique to obtain two types of sensors incorporating CNTs. In the first, LbL films of alternating layers of multi-walled carbon nanotubes (MWNTs) dispersed in polyarninoamide (PAMAM) dendrimers and nickel phthalocyanine (NiTsPc) were used in amperometric detection of the neurotransmitter dopamine (DA). The electrochemical properties evaluated with cyclic voltammetry indicated that the incorporation of MWNTs in the PAMAM-NT/NiTsPc LbL films led to a 3-fold increase in the peak current, in addition to a decrease of 50 mV in the oxidation potential of DA. The latter allowed detection of DA even in the presence of ascorbic acid (AA), a typical interferent for DA. Another LbL film was obtained with layers of PAMAM and single-walled carbon nanotubes (SWNTs) employed in field-effect-devices using a capacitive electrolyte-insulator-semiconductor structure (EIS). The adsorption of the film components was monitored by measuring the flat-band voltage shift in capacitance-voltage (C-P) curves, caused by the charges from the components. Constant capacitance (ConCap) measurements showed that the EISPAMAM/SWNT film displayed a high pH sensitivity (ca. 54.5 mV/pH), being capable of detecting penicillin G between 10(-4) mol L(-1) and 10(-2) mol L-1, when a layer of penicillinase was adsorbed atop the PAMAM/SWNT film. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of the carbon dioxide chemical fixation-activation by guanidines

Fixation of CO(2) is one of the most important priorities of the scientific community dedicated to reduce global warming. In this work, we propose new methods for the fixation of CO2 using the guanidine bases tetramethylguanidine (TMG) and 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]-pyrimidine (TBD). In order to understand the reactions occurring during the CO(2) fixation and release processes, we employed several experimental methods, including solution and solid-state NMR, FTIR, and coupled TGA-FTIR. Quantum mechanical NMR calculations were also carried out. Based on the results obtained, we concluded that CO(2) fixation with both TMG and TBD guanidines is a kinetically reversible process, and the corresponding fixation products have proved to be useful as transcarboxylating compounds. Afterward, CO(2) thermal releasing from this fixation product with TBD was found to be an interesting process for CO(2) capture and isolation purposes. (C) 2008 Elsevier Ltd. All rights reserved.

Homogenization of Precipitation Hardening Nickel Based Superalloys

Allvac 718 Plus and Haynes 282 are relatively new precipitation hardening nickel based superalloys with good high temperature mechanical properties. In addition, the weldability of these superalloys enhances easy fabrication. The combination of high temperature capabilities and superior weldability is unmatched by other precipitation hardening superalloys and linked to the amount of the γ’ hardening precipitates in the materials. Hence, it is these properties that make Allvac 718 Plus and Haynes 282 desirable in the manufacture of hot sections of aero engine components. Studies show that cast products are less weldable than wrought products. Segregation of elements in the cast results in inhomogeneous composition which consequently diminishes weldability. Segregation during solidification of the cast products results in dendritic microstructure with the segregating elements occupying interdendritic regions. These segregating elements are trapped in secondary phases present alongside γ matrix. Studies show that in Allvac 718Plus, the segregating phase is Laves while in Haynes 282 the segregating phase is not yet fully determined. Thus, the present study investigated the effects of homogenization heat treatments in eliminating segregation in cast Allvac 718 Plus and Haynes 282. Paramount to the study was the effect of different homogenization temperatures and dwell time in the removal of the segregating phases. Experimental methods used to both qualify and quantify the segregating phases included SEM, EDX analysis, manual point count and macro Vickers hardness tests. Main results show that there is a reduction in the segregating phases in both materials as homogenization proceeds hence a disappearance of the dendritic structure. In Allvac 718 Plus, plate like structures is observed to be closely associated with the Laves phase at low temperatures and dwell times. In addition, Nb is found to be segregating in the interdendritic areas. The expected trend of increase in Laves as a result of the dissolution of the plate like structures at the initial stage of homogenization is only detectable for few cases. In Haynes 282, white and grey phases are clearly distinguished and Mo is observed to be segregating in interdendritic areas.

Effect of structure-property relationships on fatigue failure in natural fibres

The fatigue behaviour of natural fibres is important for fibre processing efficiency as well as the properties and performance of products made from these fibres. This chapter presents some fibre fatigue results obtained from various experimental methods and testing conditions. It demonstrates that many factors, including fibre structure and chemical treatments, affect the fatigue failure in natural fibres. Examples of controlling fibre fatigue life for different purposes are also presented. Knowledge of the fatigue behaviour of natural fibres will help product design and care.

Social comparisons, appearance related comments, contingent self-esteem and their relationships with body dissatisfaction and eating disturbance among women

This study examined social comparisons, appearance related comments and contingent self-esteem, and their relationships with body dissatisfaction and eating disturbance in young adult women. Importantly, the role of both positive and negative appearance related comments, and upward and downward comparisons, were investigated. A self-report questionnaire assessing each of these variables was completed by one hundred and ninety-six women aged 18–35. A higher frequency of negative comments and contingent self-esteem were associated with higher upward comparisons, and more positive comments were associated with higher downward comparisons. Overall, social comparisons were shown to be more important than verbal commentary and contingent self-esteem. More upward comparisons and less downward comparisons uniquely predicted higher body dissatisfaction and eating disturbance. In addition, negative appearance comments were found to be more salient than positive comments. Negative comments and contingent self-esteem uniquely predicted more eating disturbance but positive comments were not a predictor of body dissatisfaction or eating disturbance. Longitudinal studies are now required to establish the direction of these relationships and to more fully examine the interplay among the factors. In addition, given that our study only assessed self-reported social comparisons, our findings need to be validated against experimental methods.

What were they thinking? An exploration of child sexual offenders' beliefs using a lexical decision task

Cognitive distortions have been afforded a key role in the offending behaviour of child sexual offenders. While the mechanisms underlying cognitive distortions are not fully understood, they are generally thought to reflect entrenched beliefs that distinguish child sexual offenders from other individuals. We investigated this hypothesis using a robust experimental technique called the lexical decision task. Child sexual offenders, offender controls, and non-offender controls completed a lexical decision task in which they responded to words that completed sentences in either an offence-supportive or nonoffence-supportive manner. Contrary to predictions, child sexual offenders did not respond faster to words that were consistent with offence-supportive beliefs, relative to controls. However, they did show accelerated recognition for word stems supporting external locus of control beliefs. These results highlight the need to use cognitive experimental methods to study child sexual offenders' beliefs, and the importance of investigating potential alternative drivers of cognitive distortions.

What's in a measure? A multi-method study of child sexual offenders' beliefs

The hypothesis that child sexual offenders (CSOs) hold distorted, offence-supportive beliefs is usually investigated using interview and questionnaire techniques. However, in light of various problems associated with the use of these techniques, researchers are increasingly turning to cognitive-experimental approaches. To date, no study has examined potential differences in the nature of the beliefs that are revealed using interview, questionnaire, and experimental methods. In this study, data is gathered using these three methods and the results triangulated. CSOs are interviewed and the content categorised into five belief types. CSOs and offender controls then complete a questionnaire measure of offence-supportive beliefs and an experimental task (Rapid Serial Visual Presentation-Modified, or RSVP-M), which uses sentence reading times to explore content held in cognitive structures. As hypothesised, CSOs showed evidence of holding distorted beliefs according to the interview and questionnaire measures. Against predictions, however, CSOs did not show evidence of holding distorted belief structures on the RSVP-M task. In fact, the three methods showed no agreement regarding the belief types each CSO was deemed to hold. These results raise important questions about the phenomena and potential artefacts measured by each method.

Analysis of protein sequence and interaction data for candidate disease gene prediction

Linkage analysis is a successful procedure to associate diseases with specific genomic regions. These regions are often large, containing hundreds of genes, which make experimental methods employed to identify the disease gene arduous and expensive. We present two methods to prioritize candidates for further experimental study: Common Pathway Scanning (CPS) and Common Module Profiling (CMP). CPS is based on the assumption that common phenotypes are associated with dysfunction in proteins that participate in the same complex or pathway. CPS applies network data derived from protein–protein interaction (PPI) and pathway databases to identify relationships between genes. CMP identifies likely candidates using a domain-dependent sequence similarity approach, based on the hypothesis that disruption of genes of similar function will lead to the same phenotype. Both algorithms use two forms of input data: known disease genes or multiple disease loci. When using known disease genes as input, our combined methods have a sensitivity of 0.52 and a specificity of 0.97 and reduce the candidate list by 13-fold. Using multiple loci, our methods successfully identify disease genes for all benchmark diseases with a sensitivity of 0.84 and a specificity of 0.63. Our combined approach prioritizes good candidates and will accelerate the disease gene discovery process.

Heterogeneous electrode processes and localized corrosion

This book covers the areas of electrochemical heterogeneity and electrode inhomogeneity and their effects on nonuniform electrode processes, in particular, localized corrosion. It covers the fundamentals, experimental methods, and engineering aspects of electrochemical heterogeneity.