63 resultados para Selbst-Organisation, aromatische Amide, supramolekulare Polymere, OPBA


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Cell and tissue patterning in plant embryo development is well documented. Moreover, it has recently been shown that successful embryogenesis is reliant on programmed cell death (PCD). The cytoskeleton governs cell morphogenesis. However, surprisingly little is known about the role of the cytoskeleton in plant embryogenesis and associated PCD. We have used the gymnosperm, Picea abies , somatic embryogenesis model system to address this question. Formation of the apical-basal embryonic pattern in P. abies proceeds through the establishment of three major cell types: the meristematic cells of the embryonal mass on one pole and the terminally differentiated suspensor cells on the other, separated by the embryonal tube cells. The organisation of microtubules and F-actin changes successively from the embryonal mass towards the distal end of the embryo suspensor. The microtubule arrays appear normal in the embryonal mass cells, but the microtubule network is partially disorganised in the embryonal tube cells and the microtubules disrupted in the suspensor cells. In the same embryos, the microtubule-associated protein, MAP-65, is bound only to organised microtubules. In contrast, in a developmentally arrested cell line, which is incapable of normal embryonic pattern formation, MAP-65 does not bind the cortical microtubules and we suggest that this is a criterion for proembryogenic masses (PEMs) to passage into early embryogeny. In embryos, the organisation of F-actin gradually changes from a fine network in the embryonal mass cells to thick cables in the suspensor cells in which the microtubule network is completely degraded. F-actin de-polymerisation drugs abolish normal embryonic pattern formation and associated PCD in the suspensor, strongly suggesting that the actin network is vital in this PCD pathway.

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This article addresses the extent to which multinational companies (MNCs) in Ireland deploy practices aimed at the transfer of learning in their operations and the factors explaining inter-organisation variation in so doing. Using data from 260 MNCs, we find that comparatively large numbers of firms deploy practices to transfer learning in their Irish operations. Most notably, we find that almost half of all MNCs have a formal policy on organisational learning, while more than six in every ten MNCs in Ireland utilise three or more learning transfer mechanisms. In investigating inter-organisation variation with respect to these, we test a number of hypotheses involving nationality, sectoral, MNC (e.g. organisation structure) and HR factors. Our results show that the presence of international HR structures is a significant factor in explaining learning transfer in MNCs. We also find support that employment size, sector and integration between the MNC's global operations are useful variables in explaining variation in the deployment of practices on learning transfer in MNCs. © 2009 Blackwell Publishing Ltd.

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This article examines the relationship between the learning organisation and the implementation of curriculum innovation within schools. It also compares the extent of innovative activity undertaken by schools in the public and the private sectors. A learning organisation is characterised by long-term goals, participatory decision-making processes, collaboration with external stakeholders, effective mechanisms for the internal communication of knowledge and information, and the use of rewards for its members. These characteristics are expected to promote curriculum innovation, once a number of control factors have been taken into account. The article reports on a study carried out in 197 Greek public and private primary schools in the 1999-2000 school year. Structured interviews with school principals were used as a method of data collection. According to the statistical results, the most important determinants of the innovative activity of a school are the extent of its collaboration with other organisations (i.e. openness to society), and the implementation of development programmes for teachers and parents (i.e. communication of knowledge and information). Contrary to expectations, the existence of long-term goals, the extent of shared decision-making, and the use of teacher rewards had no impact on curriculum innovation. The study also suggests that the private sector, as such, has an additional positive effect on the implementation of curriculum innovation, once a number of human, financial, material, and management resources have been controlled for. The study concludes by making recommendations for future research that would shed more light on unexpected outcomes and would help explore the causal link between variables in the research model.

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In a recent article (J. Am. Chem. Soc. 2011, 133, 20186) we investigated the initial spatial distribution of dry excess electrons in a series of room-temperature ionic liquids (RTILs). Perhaps unexpectedly, we found that in some alkylammonium-based systems the excess negative charge resided on anions and not on the positive cations. Following on these results, in the current paper we describe the time evolution of an excess electronic charge introduced in alkylammonium- and pyrrolidinium-based ionic liquids coupled with the bis(trifluoromethylsulfonyl)amide ([TfN]) anion. We find that on a 50 fs time scale an initially delocalized excess electron localizes on a single [TfN] anion which begins a fragmentation process. Low-energy transitions have a very different physical origin on the several femtoseconds time scale when compared to what occurs on the picosecond time scale. At time zero, these are intraband transitions of the excess electron. However after 40 fs when the excess electronic charge localizes on a single anion, these transitions disappear, and the spectrum is dominated by electron-transfer transitions between the fragments of the doubly charged breaking anion. © 2013 American Chemical Society.

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Feleucins-BV1 and -BV2 are recently-described prototypes of a novel antimicrobial nonapeptide (AMP) family identified in the skin secretion of the bombinid toad, Bombina variegata. They are encoded on different precursors that also encode a novel bombinin. Here we describe the identification of feleucin-BO1 (FLGLLGSLLamide) which is co-encoded with a different novel bombinin, named feleucin precursor-associated bombinin (FPA-bombinin-BO), from the skin secretion of Bombina orientalis. Synthetic feleucin-BO1 displayed activity against a reference Gram-positive bacterium. Staphylococcus aureus (MIC 34 μM) but was inactive (> 250 μM) against the Gram-negative bacterium, Escherichia coli, and the yeast, Candida albicans. This pattern of activity was similar to that of the prototypes. Design and synthesis of a cationicity-enhanced analogue, feleucin-K3 (F-K3), in which the amino acid residues at positions 3 (G), 6 (G) and 7 (S) of feleucin-BO1 were substituted with Lys (K) residues, resulted in a peptide with significantly-enhanced potency and spectrum of activity. The MICs of F-K3 against the reference microorganisms were 7 μM (S. aureus), 14 μM (E. coli) and 7 μM (C. albicans). These data indicate that the skin secretions of amphibians can continue to provide novel peptide templates for the rational design of analogues with possible therapeutic utility.

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This special issue volume is concerned with how technology is changing the nature of work and working conditions while generating new products and new forms of service delivery. The five articles included in this volume cover service work, from the routine and clerical through to highly credentialed and professional work. Although some of the established challenges concerning the impact of Information and Communication Technology (ICT) on work and workplaces are evident in the articles, it is also clear that new service delivery processes demand new skills and training to some extent. Overall findings indicate that while ICT competencies are important, they need to be supplemented by the soft skills that are crucial for effective customer interactions and more open work systems with greater autonomy and participation whereby flexible work teams can have a positive impact on job quality outcomes. This introductory article examines technology and the changing nature of work through three strands of interpretation, prior to introducing the five articles in this special issue.

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The research project analysed the role and effectiveness of LIFT via a multi-method study which included semi-structured interviews with policy elites and users, as well as case studies and an exploratory analysis of the financial characteristics of three LIFT Companies. While the team felt that it was able to identify key aspects relating to the advantages and drawbacks surrounding LIFT, some aspects relating to the representativeness of the study was adversely affected by a reluctance of PCTs to participate in the case study analysis and commercial confidentiality restrictions. The study was nonetheless able to identify important issues in relation to the funding and procurement of primary care premises and services.