Implicit leadership theories in applied settings:factor structure, generalizability, and stability over time

The present empirical investigation had a 3-fold purpose: (a) to cross-validate L. R. Offermann, J. K. Kennedy, and P. W. Wirtz's (1994) scale of Implicit Leadership Theories (ILTs) in several organizational settings and to further provide a shorter scale of ILTs in organizations; (b) to assess the generalizability of ILTs across different employee groups, and (c) to evaluate ILTs' change over time. Two independent samples were used for the scale validation (N 1 = 500 and N 2 = 439). A 6-factor structure (Sensitivity, Intelligence, Dedication, Dynamism, Tyranny, and Masculinity) was found to most accurately represent ILTs in organizational settings. Regarding the generalizability of ILTs, although the 6-factor structure was consistent across different employee groups, there was only partial support for total factorial invariance. Finally, evaluation of gamma, beta, and alpha change provided support for ILTs' stability over time.

The effect of lignin and inorganic species in biomass on pyrolysis oil yields, quality and stability

This paper investigates four reference fuels and three low lignin Lolium Festuca grasses which were subjected to pyrolysis to produce pyrolysis oils. The oils were analysed to determine their quality and stability, enabling the identification of feedstock traits which affect oil stability. Two washed feedstocks were also subjected to pyrolysis to investigate whether washing can enhance pyrolysis oil quality. It was found that the mineral matter had the dominate effect on pyrolysis in compared to lignin content, in terms of pyrolysis yields for organics, char and gases. However the higher molecular weight compounds present in the pyrolysis oil are due to the lignin derived compounds as determined by results of GPC and liquid-GC/MS. The light organic fraction also increased in yield, but reduced in water content as metals increased at the expense of the lignin content. It was found that the fresh oil and aged oil had different compound intensities/concentrations, which is due to a large number of reactions occurring when the oil is aged day by day. These findings agree with previous reports which suggest that a large amount of re-polymerisation occurs as levoglucosan yields increase during the aging progress, while hydroxyacetaldehyde decrease. In summary the paper reports a window for producing a more stable pyrolysis oil by the use of energy crops, and also show that washing of biomass can improve oil quality and stability for high ash feedstocks, but less so for the energy crops.

Delivery and stability of antisense oligonucleotide conjugates in vitro

The efficacy of antisense oligonucleotide (ODN) therapy is dependent on four major parameters: delivery to cells, intracellular stability and localisation and efficient action at the target site.The aim of this project was to study the delivery of ODNs to macrophages and to assess the stability of two ODN conjugates, in vitro. The first conjugate aimed to improve uptake of ODNs via mannose receptor mediated delivery, the second investigated the improved delivery of ODN conjugates via non-specific lipophilic interaction with the cell membrane. A mono-mannose phosphoramidite derivative was designed and synthesised and a mono-mannose ODN conjugate synthesised by standard phosphoramidite chemistry. Delivery of this conjugate was enhanced to RAW264.7 and J774 macrophage cell lines via a mechanism of receptor mediated endocytosis. The delivery of three lipophilic ODN conjugates, cholesterol (cholhex), 16-carbon alkyl chain (C16) and hexa-ethylene glycol (HEG) moieties and an unconjugated ODN were assessed in RAW264.7 macrophages. All three conjugates increased the lipophilicity of the ODN as assessed from partition coefficient data. Both the cholhex and unconjugated ODNs were found to have higher degrees of cellular association than the C16 and HEG conjugates. Cellular uptake studies implicated internalisation of these ODNs by an adsorptive endocytosis mechanism. Following endocytosis, ODNs must remain stable during their residence in endosomal/lysosomal compartments prior to exiting and exerting their biological action in either the cytosol or nucleus. Assessment of in vitro stability in a lysosomal extract revealed the cholhex conjugate and unconjugated ODNs to have a longer half-life than the C16 and HEG conjugated ODNs, highlighting the influence of conjugate moieties on lysosomal stability. The effects of base composition and length on stability in a lysosomal extract revealed the longest half-life for homo-cytidine ODNs and ODNs over 20 nucleotides in length. These studies suggest that the above conjugates can enhance cellular association and delivery of antisense ODNs to cultured macrophages. This may lead to their use in treating disorders such as HIV infection, which affects this cell type.

Techniques for determining bias and stability in satellite altimeters

The case for monitoring large-scale sea level variability is established in the context of the estimation of the extent of anthropogenic climate change. Satellite altimeters are identified as having the potential to monitor this change with high resolution and accuracy. Possible sources of systematic errors and instabilities in these instruments which would be hurdles to the most accurate monitoring of such ocean signals are examined. Techniques for employing tide gauges to combat such inaccuracies are proposed and developed. The tide gauge at Newhaven in Sussex is used in conjunction with the nearby satellite laser ranger and high-resolution ocean models to estimate the absolute bias of the TOPEX, Poseidon, ERS 1 and ERS 2 altimeters. The theory which underlies the augmentation of altimeter measurements with tide gauge data is developed. In order to apply this, the tide gauges of the World Ocean Circulation Experiment are assessed and their suitability for altimeter calibration is determined. A reliable subset of these gauges is derived. A method of intra-altimeter calibration is developed using these tide gauges to remove the effect of variability over long time scales. In this way the long-term instability in the TOPEX range measurement is inferred and the drift arising from the on-board ultra stable oscillator is thus detected. An extension to this work develops a method for inter-altimeter calibration, allowing the systematic differences between unconnected altimeters to be measured. This is applied to the TOPEX and ERS 1 altimeters.

The development and stability analysis of a nonlinear growth model for microorganisms

A nonlinear dynamic model of microbial growth is established based on the theories of the diffusion response of thermodynamics and the chemotactic response of biology. Except for the two traditional variables, i.e. the density of bacteria and the concentration of attractant, the pH value, a crucial influencing factor to the microbial growth, is also considered in this model. The pH effect on the microbial growth is taken as a Gaussian function G0e-(f- fc)2/G1, where G0, G1 and fc are constants, f represents the pH value and fc represents the critical pH value that best fits for microbial growth. To study the effects of the reproduction rate of the bacteria and the pH value on the stability of the system, three parameters a, G0 and G1 are studied in detail, where a denotes the reproduction rate of the bacteria, G0 denotes the impacting intensity of the pH value to microbial growth and G1 denotes the bacterial adaptability to the pH value. When the effect of the pH value of the solution which microorganisms live in is ignored in the governing equations of the model, the microbial system is more stable with larger a. When the effect of the bacterial chemotaxis is ignored, the microbial system is more stable with the larger G1 and more unstable with the larger G0 for f0 > fc. However, the stability of the microbial system is almost unaffected by the variation G0 and G1 and it is always stable for f0 < fc under the assumed conditions in this paper. In the whole system model, it is more unstable with larger G1 and more stable with larger G0 for f0 < fc. The system is more stable with larger G1 and more unstable with larger G0 for f0 > fc. However, the system is more unstable with larger a for f0 < fc and the stability of the system is almost unaffected by a for f0 > fc. The results obtained in this study provide a biophysical insight into the understanding of the growth and stability behavior of microorganisms.

Results of the IEA round robin on viscosity and stability of fast pyrolysis bio-oils

An international round robin study of the stability of fast pyrolysis bio-oil was undertaken. Fifteen laboratories in five different countries contributed. Two bio-oil samples were distributed to the laboratories for stability testing and further analysis. The stability test was defined in a method provided with the bio-oil samples. Viscosity measurement was a key input. The change in viscosity of a sealed sample of bio-oil held for 24 h at 80 °C was the defining element of stability. Subsequent analyses included ultimate analysis, density, moisture, ash, filterable solids, and TAN/pH determination, and gel permeation chromatography. The results showed that kinematic viscosity measurement was more generally conducted and more reproducibly performed versus dynamic viscosity measurement. The variation in the results of the stability test was great and a number of reasons for the variation were identified. The subsequent analyses proved to be at the level of reproducibility, as found in earlier round robins on bio-oil analysis. Clearly, the analyses were more straightforward and reproducible with a bio-oil sample low in filterable solids (0.2%), compared to one with a higher (2%) solids loading. These results can be helpful in setting standards for use of bio-oil, which is just coming into the marketplace. © 2012 American Chemical Society.

Polymer degradation and stability

This edition of Polymer Degradation and Stability is dedicated to papers which were presented in the session on ‘Chemical Modification’ at the Third International Conference on Modification Degradation and Stabilisation of Polymers (MoDeSt) held in Lyon in August 2004. This was the third meeting of the MoDeSt Society which was set up in the year 2000 under the chairmanship of Professor Franco LaMantia; the earlier meetings were held in Palermo (2000) and Budapest (2002). The overall goal of the MoDeSt Society is to promote the latest research carried out in University laboratories, in public organisations and in industry through publications, and organisation of biannual scientific conferences and workshops that act as forums for scientific developments and for promoting networking between academics and industrialists from across the field of polymer modification, degradation and stabilisation. In September 2004, Professor Norman Billingham was elected as Chairman of the Society. The conference was organised by Dr Alain Michel and Veronique Bounor-Legare of the University Claude Bernard, Lyon 1, attracting over 250 delegates with the ‘Chemical Modification’ Session alone enjoying 54 oral presentations and many more poster presentations. We are all very grateful to the organisers for running such a successful and enjoyable meeting. I wish to thank my co-editors, Professors Philippe Dubois and Domenico Acierno and Dr Alain Michel, for their cooperation in the editorial task of the papers published in this special issue. On behalf of the editors of this issue, I wish to express our appreciation to the Editor-in-Chief of Polymer Degradation and Stability, Professor Norman Billingham, for the support and help received during the preparation of this special issue.

Evaluation of the activity and stability of alkali-doped metal oxide catalysts for application to an intensified method of biodiesel production

A series of alkali-doped metal oxide catalysts were prepared and evaluated for activity in the transesterification of rapeseed oil to biodiesel. Of those evaluated, LiNO3/CaO, NaNO3/CaO, KNO3/CaO and LiNO3/MgO exhibited >90% conversion in a standard 3 h test. There was a clear correlation between base strength and activity. These catalysts appeared to be promising candidates to replace conventional homogeneous catalysts for biodiesel production as the reaction times are low enough to be practical in continuous processes and the preparations are neither prohibitively difficult nor costly. However, metal leaching from the catalyst was detected, and this resulted in some homogeneous activity. This would have to be resolved before these catalysts would be viable for large-scale biodiesel production facilities.

Influence of processing and clay type on nanostructure and stability of polypropylene-clay nanocomposites

Melt processing is a critical step in the manufacture of polymer articles and is even more critical when dealing with inhomogeneous polymer-clay nanocomposites systems. The chemical composition, and in particular the clay type and its organic modification, also plays a major contribution in determining the final properties and in particular the thermal and long-term oxidative stability of the resulting polymer nanocomposites. Proper selection and tuning of the process variable should, in principle, lead to improved characteristics of the fabricated product. With multiphase systems containing inorganic nanoclays, however, this is not straightforward and it is often the case that the process conditions are chosen initially to improve one or more desired properties at the expense of others. This study assesses the influence of organo-modified clays and the processing parameters (extrusion temperature and screw speed) on the rheological and morphological characteristics of polymer nanocomposites as well as on their melt and thermo-oxidative stability. Nanocomposites (PPNCs) based on PP, maleated PP and organically modified clays were prepared in different co-rotating twin-screw extruders ranging from laboratory scale to semi-industrial scale. Results show that the amount of surfactant present in similar organo-modified clays affects differently the thermo-oxidative stability of the extruded PPNCs and that changes in processing conditions affect the clay morphology too. By choosing an appropriate set of tuned process variables for the extrusion process it would be feasible to selectively fabricate polymer-clay nanocomposites, with the desired mechanical and thermo-oxidative characteristics. © 2013 Elsevier Ltd. All rights reserved.

Bifurcation and stability in a low-dimensional model for multiple-frequency mode-locked lasers

Recent theoretical investigations have demonstrated that the stability of mode-locked solutions of multiple frequency channels depends on the degree of inhomogeneity in gain saturation. In this article, these results are generalized to determine conditions on each of the system parameters necessary for both the stability and the existence of mode-locked pulse solutions for an arbitrary number of frequency channels. In particular, we find that the parameters governing saturable intensity discrimination and gain inhomogeneity in the laser cavity also determine the position of bifurcations of solution types. These bifurcations are completely characterized in terms of these parameters. In addition to influencing the stability of mode-locked solutions, we determine a balance between cubic gain and quintic loss, which is necessary for the existence of solutions as well. Furthermore, we determine the critical degree of inhomogeneous gain broadening required to support pulses in multiple-frequency channels. © 2010 The American Physical Society.

Ash control methods to limit biomass inorganic content and its effect on fast pyrolysis bio-oil stability

This research investigates specific ash control methods to limit inorganic content within biomass prior to fast pyrolysis and effect of specific ash components on fast pyrolysis processing, mass balance yields and bio-oil quality and stability. Inorganic content in miscanthus was naturally reduced over the winter period from June (7.36 wt. %) to February (2.80 wt. %) due to a combination of senescence and natural leaching from rain water. September harvest produced similar mass balance yields, bio-oil quality and stability compared to February harvest (conventional harvest), but nitrogen content in above ground crop was to high (208 kg ha.-1) to maintain sustainable crop production. Deionised water, 1.00% HCl and 0.10% Triton X-100 washes were used to reduce inorganic content of miscanthus. Miscanthus washed with 0.10% Triton X-100 resulted in the highest total liquid yield (76.21 wt. %) and lowest char and reaction water yields (9.77 wt. % and 8.25 wt. % respectively). Concentrations of Triton X-100 were varied to study further effects on mass balance yields and bio-oil stability. All concentrations of Triton X-100 increased total liquid yield and decreased char and reaction water yields compared to untreated miscanthus. In terms of bio-oil stability 1.00% Triton X-100 produced the most stable bio-oil with lowest viscosity index (2.43) and lowest water content index (1.01). Beech wood was impregnated with potassium and phosphorus resulting in lower liquid yields and increased char and gas yields due to their catalytic effect on fast pyrolysis product distribution. Increased potassium and phosphorus concentrations produced less stable bio-oils with viscosity and water content indexes increasing. Fast pyrolysis processing of phosphorus impregnated beech wood was problematic as the reactor bed material agglomerated into large clumps due to char formation within the reactor, affecting fluidisation and heat transfer.

Metallocene ethylene-1-octene copolymers:influence of comonomer content on thermo-mechanical, rheological, and thermo-oxidative behaviours before and after melt processing in an internal mixer

The influence of the comonomer content in a series of metallocene-based ethylene-1-octene copolymers (m-LLDPE) on thermo-mechanical, rheological, and thermo-oxidative behaviours during melt processing were examined using a range of characterisation techniques. The amount of branching was calculated from 13C NMR and studies using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were employed to determine the effect of short chain branching (SCB, comonomer content) on thermal and mechanical characteristics of the polymer. The effect of melt processing at different temperatures on the thermo-oxidative behaviour of the polymers was investigated by examining the changes in rheological properties, using both melt flow and capillary rheometry, and the evolution of oxidation products during processing using infrared spectroscopy. The results show that the comonomer content and catalyst type greatly affect thermal, mechanical and oxidative behaviour of the polymers. For the metallocene polymer series, it was shown from both DSC and DMA that (i) crystallinity and melting temperatures decreased linearly with comonomer content, (ii) the intensity of the ß-transition increased, and (iii) the position of the tan δmax peak corresponding to the a-transition shifted to lower temperatures, with higher comonomer content. In contrast, a corresponding Ziegler polymer containing the same level of SCB as in one of the m-LLDPE polymers, showed different characteristics due to its more heterogeneous nature: higher elongational viscosity, and a double melting peak with broader intensity that occurred at higher temperature (from DSC endotherm) indicating a much broader short chain branch distribution. The thermo-oxidative behaviour of the polymers after melt processing was similarly influenced by the comonomer content. Rheological characteristics and changes in concentrations of carbonyl and the different unsaturated groups, particularly vinyl, vinylidene and trans-vinylene, during processing of m-LLDPE polymers, showed that polymers with lower levels of SCB gave rise to predominantly crosslinking reactions at all processing temperatures. By contrast, chain scission reactions at higher processing temperatures became more favoured in the higher comonomer-containing polymers. Compared to its metallocene analogue, the Ziegler polymer showed a much higher degree of crosslinking at all temperatures because of the high levels of vinyl unsaturation initially present.

Spatiotemporal optical bullets in two-dimensional fiber arrays and their stability

Long-lived light bullets fully localized in both space and time can be generated in novel photonic media such as multicore optical fiber or waveguide arrays. In this paper we present detailed theoretical analysis on the existence and stability of the discrete-continuous light bullets using a very generic model that occurs in a number of applications.

Fullerene-capped copolymers for bulk heterojunctions: device stability and efficiency improvements

A fullerene end-capped polymer-compatibilizer based on poly(3-hexylthiophene) (P3HT) was synthesized and demonstrated to have a remarkable effect on both the stability and efficiency of devices made from exemplar P3HT and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). P3HT with ethynyl chain-ends and α-azido-ω-bromo-PS were prepared via Grignard metathesis (GRIM) and atom transfer radical polymerisation, respectively. “Click” chemistry resulted in the preparation of poly(3-hexylthiophene)-block-ω-bromo-polystyrene (P3HT-b-PS-Br), and subsequent atom transfer radical addition chemistry with fullerene (C60) yielded the donor–acceptor block copolymer P3HT-b-PS-C60. Both P3HT-b-PS-Br and P3HT-b-PS-C60 were considered as compatibilizers with P3HT/PCBM blends, with the study detailing effects on active-layer morphology, device efficiency and stability. When used at low concentrations, both P3HT-b-PS-Br (1%) and P3HT-b-PS-C60 (0.5%) resulted in considerable 28% and 35% increases in efficiencies with respect to devices made from P3HT/PCBM alone. Furthermore, P3HT-b-PS-C60 (0.5%) resulted in an important improvement in device stability.

Eating behaviours of preadolescent children over time:stability, continuity and the moderating role of perceived parental feeding practices

The links between childhood eating behaviours and parental feeding practices are well-established in younger children, but there is a lack of research examining these variables in a preadolescent age group, particularly from the child's perspective, and longitudinally. This study firstly aimed to examine the continuity and stability of preadolescent perceptions of their parents' controlling feeding practices (pressure to eat and restriction) over a 12 month period. The second aim was to explore if perceptions of parental feeding practices moderated the relationship between preadolescents' eating behaviours longitudinally. Two hundred and twenty nine preadolescents (mean age at recruitment 8.73 years) completed questionnaires assessing their eating behaviours and their perceptions of parental feeding practices at two time points, 12 months apart (T1 and T2). Preadolescents' perceptions of their parental feeding practices remained stable. Perceptions of restriction and pressure to eat were continuous. Perceptions of parental pressure to eat and restriction significantly moderated the relationships between eating behaviours at T1 and T2. The findings from this study suggest that in a preadolescent population, perceptions of parental pressure to eat and restriction of food may exacerbate the development of problematic eating behaviours.