471 resultados para Stabilisation
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Using panel data for twenty-seven post-communist economies between 1987-2003, we examine the nexus of relationships between inequality, fiscal capacity (defined as the ability to raise taxes efficiently) and the political regime. Investigating the impact of political reform we find that full political freedom is associated with lower levels of income inequality. Under more oligarchic (authoritarian) regimes, the level of inequality is conditioned by the state’s fiscal capacity. Specifically, oligarchic regimes with more developed fiscal systems are able to defend the prevailing vested interests at a lower cost in terms of social injustice. This empirical finding is consistent with the model developed by Acemoglu (2006). We also find that transition countries undertaking early macroeconomic stabilisation now enjoy lower levels of inequality; we confirm that education fosters equality and the suggestion of Commander et al (1999) that larger countries are prone to higher levels of inequality.
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This edition of Polymer Degradation and Stability comprises selected papers presented at the 27th Polymer Degradation Discussion Group (PDDG) Conference, affiliated to the Macromolecular Group of the Royal Society of Chemistry, held at Aston University, Birmingham (UK), September 2007, in honour of Professor Norman Billingham for lifelong career in Polymer Science. Norman Billingham was one of the main founders of the PDDG meetings which have been held annually at different venues in the UK since 1976, and biennially since 1998. The PDDG meetings are forums for scientific developments and open discussion of all aspects of polymer degradation and stabilisation and have always provided younger researchers a platform for presenting and discussing their work in the field. This 27th PDDG meeting, chaired by Sahar Al-Malaika (Aston University), was dedicated to Norman Billingham, the Guest of Honour, in recognition for his distinguished contributions to Polymer Science particularly in the area of polymer degradation and stabilisation. The meeting was attended by 65 delegates from 15 countries in Europe, USA and Australia, many of whom have worked and collaborated with Norman at some points of their career. The guest editors of this issue wish to add their Congratulations to Norman Billingham for his outstanding contributions and achievements in the field of polymer degradation and stabilisation and to wish him very happy years ahead. We wish also to express our gratitude to Elsevier for sponsoring the 27th PDDG event and our appreciation to Professor Norman Billingham in his capacity as the Editor-in-Chief of Polymer Degradation and Stability, for the support and help received during the preparation of this special issue.
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Liposomes provide an efficient delivery system for solubilisation and delivery of both small and macro molecules. However, they suffer from the disadvantage of instability when stored as aqueous dispersions. Cryoprotection of the liposomal systems provides an effective approach to overcome poor stability whilst maintaining formulation characteristics, although, the formulation of a freeze-dried product requires the consideration of not only the selection of an appropriate cryoprotectant, but also needs careful consideration of the processing parameters including pre-freezing conditions, primary and secondary drying protocols along with optimisation of cryoprotectant concentration. This current work investigates the application of amino acids as potential cryoprotectants for the stabilisation of liposomes, and results indicate that amino acids show biphasic nature of stabilisation with 4 mol of cryoprotectant per mole of the lipid exhibiting optimum cryoprotection. The investigations of process parameters showed that the pre-freezing temperatures below the glass transition of the amino acids followed by drying for over 6 h resulted in stable formulations. Studies investigating the efficiency of drug retention showed that the cryoprotection offered by lysine was similar to that shown by trehalose, suggesting that amino acids act as effective stabilisers. ESEM analysis was carried out to monitor morphology of the rehydrated liposomes. © 2007 Elsevier B.V. All rights reserved.
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The extraordinary growth of the Irish economy since the mid-1990s—the ‘Celtic Tiger’—has attracted a great deal of interest, commentary and research. Indeed, many countries look to Ireland as an economic development role model, and it has been suggested that Ireland might provide key lessons for other EU members as they seek to achieve the objectives set out in the Lisbon Agenda. Much of the discussion of Ireland’s growth has focused on its possible triggers: the long-term consequences of the late 1980s fiscal stabilisation, EU structural funds, education, wage moderation and devaluation of the Irish punt. The industrial policy perspective has highlighted the importance of inflows of foreign direct investment, but a notable absence from the discourse on the ‘Celtic Tiger’ has been any mention of the role of new business venture creation and entrepreneurship. In this paper we use unpublished Irish VAT data for the years 1988–2004 to provide the first detailed look at national trends in business birth and death rates in Ireland over the ‘take-off’ period. We also use sub-national VAT data to shed light on spatial trends in new venture creation. Our overall conclusions are that new business formation made no detectable contribution to the acceleration of Ireland’s growth in the late 1990s, although we do find evidence of spatial convergence in per capita business stocks.
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Electronic commerce (e-commerce) has become an increasingly important initiative among organisations. The factors affecting adoption decisions have been well-documented, but there is a paucity of empirical studies that examine the adoption of e-commerce in developing economies in the Arab world. The aim of this study is to provide insights into the salient e-commerce adoption issues by focusing on Saudi Arabian businesses. Based on the Technology-Organisational-Environmental framework, an integrated research model was developed that explains the relative influence of 19 known determinants. A measurement scale was developed from prior empirical studies and revised based on feedback from the pilot study. Non-interactive adoption, interactive adoption and stabilisation of e-commerce adoption were empirically investigated using survey data collected from Saudi manufacturing and service companies. Multiple discriminant function analysis (MDFA) was used to analyse the data and research hypotheses. The analysis demonstrates that (1) regarding the non-interactive adoption of e-commerce, IT readiness, management team support, learning orientation, strategic orientation, pressure from business partner, regulatory and legal environment, technology consultants‘ participation and economic downturn are the most important factors, (2) when e-commerce interactive adoption is investigated, IT readiness, management team support, regulatory environment and technology consultants‘ participation emerge as the strongest drivers, (3) pressure from customers may not have much effect on the non-interactive adoption of e-commerce by companies, but does significantly influence the stabilisation of e-commerce use by firms, and (4) Saudi Arabia has a strong ICT infrastructure for supporting e-commerce practices. Taken together, these findings on the multi-dimensionality of e-commerce adoption show that non-interactive adoption, interactive adoption and stabilisation of e-commerce are not only different measures of e-commerce adoption, but also have different determinants. Findings from this study may be valuable for both policy and practice as it can offer a substantial understanding of the factors that enhance the widespread use of B2B e-commerce. Also, the integrated model provides a more comprehensive explanation of e-commerce adoption in organisations and could serve as a foundation for future research on information systems.
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We apply simple econometric methods to evaluate the factors that determined the length and depth of the post-Communist recessions. Early implementation of the stabilisation and liberalisation programmes made the recessions weaker. Wars had strong negative impact. Initial trade dependence made recessions more serious. The results are discussed with reference to the existing explanations of the 'transitional recessions', in particular Calvo and Coricelli (1992, 1993), Blanchard and Kremer (1997) and Blanchard (1997).
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Responsive core-shell latex particles are used to prepare colloidosome microcapsules using thermal annealing and internal cross-linking of the shell, allowing production of the microcapsules at high concentrations. The core-shell particles are composed of a polystyrene core and a shell of poly[2-(dimethylamino)ethyl methacrylate]-b-poly[methyl methacrylate] (PDMA-b-PMMA) chains adsorbed onto the core surface, providing steric stabilisation. The PDMA component of adsorbed polymer shell confers the latex particle thermal and pH responsive characteristics, it also provides glass transitions at lower temperatures than that of the core and reactive amine groups. These features facilitate the formation of stable Pickering emulsion droplets and the immobilisation of the latex particle monolayer on these droplets to form colloidosome microcapsules. The immobilisation is achieved through thermal annealing or cross-linking of the shell at mild conditions feasible for large scale economic production. We demonstrate here that it is possible to anneal the particle monolayer on the emulsion drop surface at 75-86 ºC by using the lower glass transition temperature of the shell compared to that of the polystyrene cores (~108 ºC). The colloidosome microcapsules formed have a rigid membrane basically composed of a monolayer of particles. Chemical cross-linking has also been successfully achieved by confining a cross-linker within the disperse droplet. This approach leads to the formation of single-layered stimulus-responsive soft colloidosome membranes and provides the advantage of working at very high emulsion concentrations since inter-droplet cross-linking is thus avoided. The porosity and mechanical strength of microcapsules are also discussed here in terms of the observed structure of the latex particle monolayers forming the capsule membrane.
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The authors study experimentally ~10 ps return-to-zero pulse propagation near the net dispersion zero of an optical fibre transmission line. Stable near-jitter-free propagation was observed over 70 Mm. Pulse stabilisation and ASE suppression were achieved through the saturable aborber mechanism of nonlinear polarisation rotation.
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The article looks first into the nature of the relations between Germany and the CEE countries a decade since the accession of the CEE countries to the EU. The relations are characterized as normalised and intensive with diverse levels of closeness and co-operation reflecting of the conceptual and ideological compatibility/differences. Next, the article focuses on the German attitude to the euro zone crisis. Germany has become a hegemon in the rescue effort aimed at stabilisation and economic invigoration of the euro zone. However, German hegemony has developed by default, not by design: her leading position is linked with considerable political and financial costs. Germany moved central stage and took the position of a reluctant hegemon. However, German role is contested internationally (it has not the support of the French government in key areas) as well as internally (particularly by the Federal Constitutional Court and the Bundesbank).The article argues that the new situation makes the German-CEE relations increasingly relevant for both sides. The German leadership of the EU increasing split along the north-south divide requires backing by the Northern group countries to which the CEE in general belongs. Given a number of reasons the CEE countries implement three distinctive strategies of co-operation with Germany in European politics. Also military co-operation, which remained rather limited so far, may receive new impulses, given the financial austerity. © 2013 The Regents of the University of California.
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Introduction: Diabetic nephropathy (DN) is the leading cause of chronic kidney failure, however the mechanisms underlying the characteristic expansion of the extracellular matrix (ECM) in diabetic kidneys remain controversial and unclear. In non-diabetic kidney scarring the protein crosslinking enzyme tissue transglutaminase (tTg) has been implicated in this process by the formation of increased ε-(γ-glutamyl)lysine bonds between ECM components in both experimental and human disease. Studies in db/db diabetic mice and in streptozotocin-treated rats have suggested a similar mechanism, although the relevance of this to human disease has not been addressed. Methods: We have undertaken a retrospective analysis of renal biopsies from 16 DN patients with type 2 diabetes mellitus using an immunohistochemical and immunofl uorescence approach, with tTg and ε-(γ-glutamyl)lysine crosslink quantified by confocal microscopy. Results: Immunofl uorescent analysis of human biopsies (confocal microscopy) showed increases in levels of tTg (+1,266%, p <0.001) and ε-(γ-glutamyl)lysine (+486%, p <0.001) in kidneys with DN compared to normal. Changes were predominantly in the extracellular periglomerular and peritubular areas. tTg staining correlated with e-(?-glutamyl)lysine (r = 0.615, p <0.01) and renal scarring (Masson's trichrome, r = 0.728, p <0.001). Significant changes in e-(?-glutamyl)lysine were also noted intracellularly in some (=5%) tubular epithelial cells. This is consistent with cells undergoing a novel transglutaminase-mediated cell death process in response to Ca influx and subsequent activation of intracellular tTg. Conclusion: Changes in tTg and ε-(γ- glutamyl)lysine occur in human DN. Cellular export of tTg may therefore be a factor in the perpetuation of DN by crosslinking and stabilisation of the ECM, while intracellular activation may lead to cell death contributing towards tubular atrophy. Copyright © 2004 S. Karger AG, Basel.
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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.
Resumo:
Gold nanoparticles with diameters of ca. 13 nm were synthesised by UV irradiation of a supramolecular organogel into which HAuCl4 and tetraoctylammonium bromide had been diffused—the gel network plays an essential role in nanoparticle stabilisation. © The Royal Society of Chemistry 2005.
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Oral liquid formulations are ideal dosage forms for paediatric, geriatric and patient with dysphagia. Dysphagia is prominent among patients suffering from stroke, motor neurone disease, advanced Alzheimer’s and Parkinson’s disease. However oral liquid preparations are particularly difficult to formulate for hydrophobic and unstable drugs. Therefore current methods employed in solving this issue include the use of ‘specials’ or extemporaneous preparations. In order to challenge this, the government has encouraged research into the field of oral liquid formulations, with the EMEA and MHRA publishing list of drugs of interest. The current work investigates strategic formulation development and characterisation of select API’s (captopril, gliclazide, melatonin, L-arginine and lansoprazole), each with unique obstacles to overcome during solubilisation, stabilisation and when developing a palatable dosage from. By preparing a validated calibration protocol for each of the drug candidates, the oral liquid formulations were assessed for stability, according to the ICH guidelines along with thorough physiochemical characterisation. The results showed that pH and polarity of the solvent had the greatest influence on the extent of drug solubilisation, with inclusion of antioxidants and molecular steric hindrance influencing the extent of drug stability. Captopril, a hydrophilic ACE inhibitor (160 mg.mL-1), undergoes dimerisation with another captopril molecule. It was found that with the addition of EDTA and HP-β-CD, the drug molecule was stabilised and prevented from initiating a thiol induced first order free radical oxidation. The cyclodextrin provided further steric hindrance (1:1 molar ratio) resulting in complete reduction of the intensity of sulphur like smell associated with captopril. Palatability is a crucial factor in patient compliance, particularly when developing a dosage form targeted towards paediatrics. L-arginine is extremely bitter in solution (148.7 g.L-1). The addition of tartaric acid into the 100 mg.mL-1 formulation was sufficient to mask the bitterness associated with its guanidium ions. The hydrophobicity of gliclazide (55 mg.L-1) was strategically challenged using a binary system of a co-solvent and surfactant to reduce the polarity of the medium and ultimately increase the solubility of the drug. A second simpler method was developed using pH modification with L-arginine. Melatonin has two major obstacles in formulation: solubility (100 μg.mL-1) and photosensitivity, which were both overcome by lowering the dielectric constant of the medium and by reversibly binding the drug within the cyclodextrin cup (1:1 ratio). The cyclodextrin acts by preventing UV rays from reaching the drug molecule and initiated the degradation pathway. Lansoprazole is an acid labile drug that could only be delivered orally via a delivery vehicle. In oral liquid preparations this involved nanoparticulate vesicles. The extent of drug loading was found to be influenced by the type of polymer, concentration of polymer, and the molecular weight. All of the formulations achieved relatively long shelf-lives with good preservative efficacy.
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The emerging role of the multifunctional enzyme, Transglutaminase 2 (TG2) in Cystic Fibrosis (CF) has been linked to its increased expression and intracellular transamidating activity. However, a full understanding of the molecular mechanisms involved still remains unclear despite numerous studies that have attempted to delineate this process. These mechanisms include the NFκB and TGFβ1 pathway amongst others. This study reveals for the first time that the development of fibrosis in CF is due to a TG2-driven epithelial to mesenchymal transition (EMT) via a mechanism involving the activation of the pro-fibrotic cytokine TGFβ1. Using a human ΔF508/W1282X CFTR CF mutant bronchial cell (IB3-1), its CFTR corrected “add-back” cell (C38) as well as a primary human bronchial epithelial cell (HBEC), elevated TG2 levels in the CFTR mutant IB3 cell were shown to activate latent TGFβ1 leading to increased levels found in the culture medium. This activation process was blocked by the presence of cell-permeable and impermeable TG2 inhibitors while inhibition of TGFβ1 receptors blocked TG2 expression. This demonstrates the direct link between TG2 and TGFβ1 in CF. The presence of active cell surface TG2 correlated with an increase in the expression of EMT markers, associated with the CF mutant cells, which could be blocked by the presence of TG2 inhibitors. This was mimicked using the “addback” C38 cell and the primary human bronchial epithelial cell, HBEC, where an increase in TG2 expression and activity in the presence of TGFβ1 concurred with a change in cell morphology and an elevation in EMT marker expression. Conversely, a knockdown of TG2 in the CF mutant IB3 cells illustrated that an inhibition of TG2 blocks the increase in EMT marker expression as well as causing an increase in TEER measurement. This together with an increase in the migration profile of the CF mutant IB3 cell against the “add-back” C38 cell suggests that TG2 drives a mesenchymal phenotype in CF. The involvement of TG2 activated TGFβ1 in CF was further demonstrated with an elevation/inhibition of p- SMAD 2 and 3 activation in the presence of TGFβ1/TG2 cell-permeable/impermeable inhibitors respectively. The use of a comparative airway cell model where bronchial epithelial cells were cultured at the air liquid interface (ALI) confirmed the observations in submerged culture depicting the robustness of the model and reiterated the importance of TG2 in CF. Using a CFTR corrector combined with TG2 inhibitors, this study showed that the correction and stabilisation of the ΔF508 CFTR mutation in the mutant cell forged an increase in matured CFTR copies trafficking to the apical surface by circumventing proteosomal degradation. Thus the results presented here suggests that TG2 expression is elevated in the CFTR mutant bronchial cell via a TGFβ1 driven positive feedback cycle whereby activation of latent TGFβ1 by TG2 leads in turn to an elevation in its own expression by TGFβ1. This vicious cycle then drives EMT in CF ultimately leading to lung remodelling and fibrosis. Importantly, TG2 inhibition blocks TGFβ1 activation leading to an inhibition of EMT and further blocks the emerging fibrosis, thus stabilizing and supporting the maturation, trafficking and conductance of CFTR channels at the apical surface.
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A family of tungstated zirconia solid acid catalysts were synthesised via wet impregnation and subsequent thermochemical processing for the transformation of glucose to 5-hydroxymethylfurfural (HMF). Acid strength increased with tungsten loading and calcination temperature, associated with stabilisation of tetragonal zirconia. High tungsten dispersions of between 2 and 7 W atoms·nm−2 were obtained in all cases, equating to sub-monolayer coverages. Glucose isomerisation and subsequent dehydration via fructose to HMF increased with W loading and calcination temperature up to 600 °C, indicating that glucose conversion to fructose was favoured over weak Lewis acid and/or base sites associated with the zirconia support, while fructose dehydration and HMF formation was favoured over Brönsted acidic WOx clusters. Aqueous phase reforming of steam exploded rice straw hydrolysate and condensate was explored heterogeneously for the first time over a 10 wt% WZ catalyst, resulting in excellent HMF yields as high as 15% under mild reaction conditions.