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Structural Constraints (structural + constraint)
Selected AbstractsExplaining union membership of temporary workers in Spain: the role of local representatives and workers' participative potentialINDUSTRIAL RELATIONS JOURNAL, Issue 1 2007David Llorente Sánchez ABSTRACT It has been widely assumed that type-of-contract segmentation represents a strong structural constraint on trade union growth. The analysis of a sample of the Spanish workforce shows, however, that the effect of contract type on union membership is not statistically significant once the availability and performance of local union representatives are introduced in the explanatory model. Additionally, the worker's participative potential, as indicated by his/her social and political capital, is also found to be a major explanatory factor. These findings are placed in comparative perspective and discussed in relation to possible union revitalisation strategies. [source] Mechanism of the Asymmetric Sulfoxidation in the Esomeprazole Process: Effects of the Imidazole Backbone for the EnantioselectionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2009Muthu Seenivasaperumal Abstract The asymmetric sulfoxidation reaction of imidazole-based prochiral sulfides was studied to explore the mechanistic details of the highly efficient esomeprazole process, which is one of the few industrial scale catalytic asymmetric procedures. The synthetic studies revealed that the smallest subunit governing the selectivity in the esomeprazole process is an imidazole ring. Thus, by using the esomeprazole procedure methyl imidazole sulfide could be oxidized as efficiently as its several functionalized derivatives, including pyrmetazol. However, alkylation of the imidazole nitrogen led to a major drop of the enantioselectivity. Our atmospheric pressure chemical ionization-mass spectrometry (APCI/MS) studies indicate that addition of small amounts of water to the reaction mixture facilitates the formation of mononuclear titanium species, which are the active catalytic intermediates of the selective oxidation reaction. One of the most important features of the esomeprazole procedure is that amine additives increase the enantioselectivity of the oxidation process. The NMR studies of the presumed reaction intermediates show that under catalytic conditions the amines are able to coordinate to titanium and dissociate the coordinated imidazole substrate. The density functional theory (DFT) modelling studies provided new insights in the mechanism of the asymmetric induction. It was found that the oxidation requires a lower activation energy if the imidazole sulfide precursor does not coordinate to titanium. Two possible reaction paths were explored for this out of sphere oxidation mechanism. The most important interaction governing the enantioselection is hydrogen bonding between the NH of the imidazole ring and the chiral tartrate ligand on titanium. Furthermore, the oxidation reaction imposes an important structural constraint to the TS structure involving a linear arrangement of the peroxide oxygens and the sulfur atom. This constraint and the N coordination of imidazole leads to a very strained structure for the inner sphere mechanism of the oxidation, which leads to a much higher activation barrier than the corresponding out of sphere process, and therefore it is unlikely. [source] Agentic Orientation as Magical VoluntarismCOMMUNICATION THEORY, Issue 1 2010Joshua Gunn In this essay we argue that the rhetoric of Foss, Waters, and Armada's recent work on "agentic orientation," as well as the rhetoric of the popular bestselling DVD and book The Secret, are typical of "magical voluntarism." Magical voluntarism is an idealist understanding of human agency in which a subject can fulfill her needs and desires by simple wish-fulfillment and the manipulation of symbols, irrelevant of structural constraint or material limitation. Embracing magical voluntarism, we argue, leads to narcissistic complacency, regressive infantilism, and elitist arrogance. A more materialist and dialectical understanding of agency is better. [source] Policy Learning: can Government discover the treasure within?EUROPEAN JOURNAL OF EDUCATION, Issue 2 2007GRAHAM LEICESTER We live in powerful times and are experiencing a conceptual emergency. The imperative to learn is evident. Yet in spite of advances in knowledge about how we learn, our application of that knowledge in practice remains patchy at best. A key part of the challenge is to encourage government itself to participate in the learning process, and to overcome the psychological and structural constraints it faces that militate against learning. The article suggests a number of measures to facilitate learning within the policy process: including first tackling denial, making space for reflection, empowering the boundary spanners and , most important , practising innovation as learning. The Delors Commission for UNESCO on education for the 21st century called learning ,the treasure within'. It is no longer possible for government to ignore the turbulence and complexity of its operating environment: it needs to find its own treasure within. This is the case for policy learning. [source] Requirement for Q226, but not multiple charged residues, in the class I MHC CD loop/D strand for TCR-activated CD8 accessory functionEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 3 2003Micheal Durairaj Abstract Activation of CD8+ cytotoxic T lymphocytes typically begins with recognition of class I MHC-peptide complexes by the TCR and CD8 as a coreceptor. In its coreceptor role, CD8 binds thesame class I-peptide antigen complex as the TCR, enhancing the strength of TCR-class I interaction. Subsequent to initial TCR engagement, CD8 acts as an accessory molecule by binding any properly conformed class I molecules on the target cell surface, leading to CD8-mediated adhesion and cosignaling functions. We expressed and isolated a number of mutant class I molecules in which one or moreacidic or polar residues in the class I ,3 domain CD loop and D strand region, or ,2 domain were altered. Using solid phase CTL adhesion and degranulation assays with isolated class I molecules, we demonstrate that multiple acidic residues in the ,3 domain, although involved in CD8 coreceptor interaction, are not required for TCR-activated CD8 accessory interactions. Instead, we show that Q226, a polar group on the end of the CD loop, is required for TCR-activated CD8 accessory functions. These results indicate that CD8 coreceptor and accessory interactions differ substantially and suggest that TCR activation results in changes that alter the structural constraints for CD8 accessory interactions. [source] Cross-National Transfer of Policy Ideas: Agencification in Britain and JapanGOVERNANCE, Issue 2 2004Koichi Nakano This study seeks to contribute to the policy transfer literature through a comparison of the British "Next Steps" initiative of agencification (i.e., organizational separation of policy implementation from policy formulation in central departments) and the Japanese reform that officially proclaimed to be inspired by the British example. In addition to confirming the crucial role played by domestic structural constraints in producing variant outputs in different countries, this article also shows that the transfer of policy ideas can be a highly proactive political process in which political actors in the learning country interpret and define both problems and solution as they "borrow" from another country. [source] Magnetic Materials: X-Ray Magnetic Circular Dichroism Picks out Single-Molecule Magnets Suitable for Nanodevices (Adv. Mater.ADVANCED MATERIALS, Issue 2 20092/2009) The surface sensitivity of X-ray magnetic circular dichroism in extreme conditions has been exploited to investigate the first layers of bulk single-molecule magnets (SMMs), as reported by Roberta Sessoli and co-workers on p. 167. Striking differences have emerged between two classes of SMM having different structural constraints, thus highlighting the importance of molecular design in the realization of molecular spintronic devices. [source] X-Ray Magnetic Circular Dichroism Picks out Single-Molecule Magnets Suitable for NanodevicesADVANCED MATERIALS, Issue 2 2009Matteo Mannini The surface sensitivity of X-ray Magnetic Circular Dichroism in extreme conditions is exploited to investigate the first layers of bulk single-molecule magnets (SMM). Striking differences emerge between two classes of SMM with different structural constraints, thus highlighting the importance of molecular design in the realization of molecular spintronic devices [source] Parental Divorce and Premarital Couples: Commitment and Other Relationship CharacteristicsJOURNAL OF MARRIAGE AND FAMILY, Issue 3 2001Susan E. Jacquet Parental divorce is thought to affect the romantic relationships of young adults, especially with respect to their certainty about the relationship and perceptions of problems in it. We examined these connections with a random sample of 464 coupled partners. Compared with women from intact families, women from divorced families reported less trust and satisfaction, but more ambivalence and conflict. For men, perceptions of relationships were contingent on the marital status of their partners' parents, although men from intact and divorced families did differ on structural constraints that affect commitment. Young adults who were casually dating showed the strongest effects of parental divorce, suggesting that the repercussions of parental divorce may be in place before the young adults form their own romantic relationships. [source] Synthesis of azobenzene-containing polythiophenes and photoinduced anisotropyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2004Francois Aubertin Abstract Three new polythiophenes containing an azobenzene moiety in the side-chain were synthesized and characterized. Two of them, which are slightly soluble in tetrahydrofuran to allow the preparation of thin films from solution casting, were used to investigate the photoinduced anisotropy arising from the photoisomerization of azobenzene in this type of polymer. The results show that, unlike other amorphous azobenzene polymers, only an extremely small anisotropy can be induced on excitation with an Ar+ laser at 488 nm in these azobenzene-containing polythiophenes, and that this photoinduced anisotropy is observable only by heating the polymer to some temperatures below glass transition temperature. It is suggested that the inability for azobenzene polythiophenes to display a significant photoinduced anisotropy may be caused by some structural constraints and/or a severe interference from conjugated thiophene chains that absorb strongly in the visible region. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3445,3455, 2004 [source] "I Never Wanted to Be a Quack!"MEDICAL ANTHROPOLOGY QUARTERLY, Issue 2 2010The Professional Deviance of Plaintiff Experts in Contested Illness Lawsuits: The Case of Multiple Chemical Sensitivities When medical practitioners act as expert witnesses for the plaintiff in contested illness lawsuits, they can be stigmatized by their professional community. Drawing on ethnographic research surrounding the condition multiple chemical sensitivities (MCS) in Australia, this article focuses on: how plaintiff experts specialize; their rationale for deviance from the professional norm; and structural constraints to medical advocacy. By diagnosing and treating the condition as organic, these experts oppose the accepted disease paradigm of the medical community and therefore face professional isolation and peer pressure. They rationalize their continued advocacy within a moral discourse, which includes a professional aspiration toward altruism, an ethical commitment to "truth," and the explicit emphasis that financial gain is not a motivation. For their deviance the experts have been confronted with professional disillusionment and emotional drain. Ultimately, the medical profession is disenfranchising experts who may be vital characters in the quest for understanding about environmental illnesses. [source] Rural market imperfections and the role of institutions in collective action to improve markets for the poorNATURAL RESOURCES FORUM, Issue 1 2008Bekele Shiferaw Abstract Many countries in sub-Saharan Africa have liberalized markets to improve efficiency and enhance market linkages for smallholder farmers. The expected positive response by the private sector in areas with limited market infrastructure has however been very limited. The functioning of markets is constrained by high transaction costs and coordination problems along the production-to-consumption value chain. New kinds of institutional arrangements are needed to reduce these costs and fill the vacuum left when governments withdrew from markets in the era of structural adjustments. One of these institutional innovations has been the strengthening of producer organizations and formation of collective marketing groups as instruments to remedy pervasive market failures in rural economies. The analysis presented here with a case study from eastern Kenya has shown that marketing groups pay 20,25% higher prices than other buyers to farmers while participation was also positively correlated with adoption of improved dryland legume varieties, crops not targeted by the formal extension system. However the effectiveness of marketing groups is undermined by external shocks and structural constraints that limit the volume of trade and access to capital and information, and require investments in complementary institutions and coordination mechanisms to exploit scale economies. Successful groups have shown high levels of collective action in the form of increased participatory decision making, member contributions and initial start-up capital. Failure to pay on delivery, resulting from lack of capital credit, is a major constraint that stifles competitiveness of marketing groups relative to other buyers. These findings call for interventions that improve governance and participation; mechanisms for improving access to operating capital; and effective strategies for risk management and enhancing the business skills of farmer marketing groups. [source] Power in telephone-advice nursingNURSING INQUIRY, Issue 1 2010Vesa Leppänen LEPPÄNEN V. Nursing Inquiry 2010; 17: 15,26 Power in telephone-advice nursing Power is a central aspect of nursing, especially in telephone-advice nursing, where nurses assess callers' medical problems and decide what measures that need to be taken. This article presents a framework for understanding how power operates in social interaction between nurses and callers in telephone-advice nursing in primary care in Sweden. Power is analysed as the result of nurses and callers being oriented to five social structures that are relevant to their actions in this context, namely the organization of telephone-advice nursing, the social stock of medical knowledge, the professional division of labour between nurses and doctors, structures of social interaction and structures of emotions. While structural constraints govern some actions to a high degree, calls take place in an organizational free room that give nurses more leeway for acting more creatively. The discussion focuses on the introduction of new technologies of control, for instance computerized decision support systems and audio recording of calls, and on how they reduce the free room. Empirical data consist of 276 audio-recorded telephone calls to 13 nurses at six primary-care centres and of qualitative interviews with 18 nurses. [source] Tissue transglutaminase modulates ,-synuclein oligomerizationPROTEIN SCIENCE, Issue 8 2008Ine M.J. Segers-Nolten Abstract We have studied the interaction of the enzyme tissue transglutaminase (tTG), catalyzing cross-link formation between protein-bound glutamine residues and primary amines, with Parkinson's disease-associated ,-synuclein protein variants at physiologically relevant concentrations. We have, for the first time, determined binding affinities of tTG for wild-type and mutant ,-synucleins using surface plasmon resonance approaches, revealing high-affinity nanomolar equilibrium dissociation constants. Nanomolar tTG concentrations were sufficient for complete inhibition of fibrillization by effective ,-synuclein cross-linking, resulting predominantly in intramolecularly cross-linked monomers accompanied by an oligomeric fraction. Since oligomeric species have a pathophysiological relevance we further investigated the properties of the tTG/,-synuclein oligomers. Atomic force microscopy revealed morphologically similar structures for oligomers from all ,-synuclein variants; the extent of oligomer formation was found to correlate with tTG concentration. Unlike normal ,-synuclein oligomers the resultant structures were extremely stable and resistant to GdnHCl and SDS. In contrast to normal ,-sheet-containing oligomers, the tTG/,-synuclein oligomers appear to be unstructured and are unable to disrupt phospholipid vesicles. These data suggest that tTG binds equally effective to wild-type and disease mutant ,-synuclein variants. We propose that tTG cross-linking imposes structural constraints on ,-synuclein, preventing the assembly of structured oligomers required for disruption of membranes and for progression into fibrils. In general, cross-linking of amyloid forming proteins by tTG may prevent the progression into pathogenic species. [source] Unfolding of the loggerhead sea turtle (Caretta caretta) myoglobin: A 1H-NMR and electronic absorbance studyPROTEIN SCIENCE, Issue 9 2002Daniela Delli Castelli Abstract The effect of urea concentration on the backbone solution structure of the cyanide derivative of ferric Caretta caretta myoglobin (at pH 5.4) is reported. By addition of urea, sequential and long-range nuclear Overhauser effects (NOEs) are gradually lost. By using the residual NOE constraints to build the molecular model, a picture of the unfolding pathway was obtained. When the urea concentration is raised to 2.2 M, helices A and B appear largely disordered; helices C, D, and F loose structural constraints at 3.0 M urea. At urea concentration >6 M, the protein appears to be fully unfolded, including the GH hairpin and helix E stabilizing the prosthetic group. Reversible and cooperative denaturation isotherms obtained by following NOE peaks are considerably different from those obtained by monitoring electronic absorption changes. The reversible and cooperative urea-dependent folding-unfolding process of C. caretta myoglobin follows the minimum three-state mechanism N,X,D, where X represents a disordered globin structure (occurring at ,4 M urea) that still binds the heme. [source] Modeling of the bacterial luciferase-flavin mononucleotide complex combining flexible docking with structure-activity dataPROTEIN SCIENCE, Issue 8 2001Leo Yen-Cheng Lin FMN, flavin mononucleotide; FMNH2, reduced FMN Abstract Although the crystal structure of Vibrio harveyi luciferase has been elucidated, the binding sites for the flavin mononucleotide and fatty aldehyde substrates are still unknown. The determined location of the phosphate-binding site close to Arg 107 on the , subunit of luciferase is supported here by point mutagenesis. This information, together with previous structure-activity data for the length of the linker connecting the phosphate group to the isoalloxazine ring represent important characteristics of the luciferase-bound conformation of the flavin mononucleotide. A model of the luciferase,flavin complex is developed here using flexible docking supplemented by these structural constraints. The location of the phosphate moiety was used as the anchor in a flexible docking procedure performed by conformation search by using the Monte Carlo minimization approach. The resulting databases of energy-ranked feasible conformations of the luciferase complexes with flavin mononucleotide, ,-phosphopentylflavin, ,-phosphobutylflavin, and ,-phosphopropylflavin were filtered according to the structure-activity profile of these analogs. A unique model was sought not only on energetic criteria but also on the geometric requirement that the isoalloxazine ring of the active flavin analogs must assume a common orientation in the luciferase-binding site, an orientation that is also inaccessible to the inactive flavin analog. The resulting model of the bacterial luciferase,flavin mononucleotide complex is consistent with the experimental data available in the literature. Specifically, the isoalloxazine ring of the flavin mononucleotide interacts with the Ala 74,Ala 75 cis -peptide bond as well as with the Cys 106 side chain in the , subunit of luciferase. The model of the binary complex reveals a distinct cavity suitable for aldehyde binding adjacent to the isoalloxazine ring and flanked by other key residues (His 44 and Trp 250) implicated in the active site. [source] Re-encountering resistance: Plantation activism and smallholder production in Thailand and Sarawak, MalaysiaASIA PACIFIC VIEWPOINT, Issue 3 2004Keith BarneyArticle first published online: 6 DEC 200 Abstract:,The emergence of social and environmental movements against plantation forestry in Southeast Asia positions rural development against local displacement and environmental degradation. Multi-scaled NGO networks have been active in promoting the notion that rural people in Southeast Asia uniformly oppose plantation development. There are potential pitfalls in this heightened attention to resistance however, as it has often lapsed into essentialist notions of timeless indigenous agricultural practices, and unproblematic local allegiances to common property and conservation. An exclusive emphasis on resistance also offers little understanding of widespread smallholder participation in plantation production across the region. A useful method of approaching the complexity of local responses to plantation development is through the history of legal and informal resource tenure, within an analysis of rural political-economic restructuring. Drawing on research in Thailand and Sarawak, I suggest that a more nuanced appreciation of both the structural constraints and deployments of agency which characterise the enrolment of rural people into plantation commodity networks, opens up new spaces for analysis and political action, which supports a geographically embedded view of relations of power, rural livelihoods and environmental politics. [source] Economic drought management index to evaluate water institutions' performance under uncertainty*AUSTRALIAN JOURNAL OF AGRICULTURAL & RESOURCE ECONOMICS, Issue 1 2007Eva Iglesias Reservoir management and intertemporal water allocation are critical issues in semiarid regions where agriculture has to confront highly variable rainfall patterns. In this paper, we derive and propose an economic drought management index (EDMI) to evaluate water institutions' performance to cope with drought risk. The EDMI is based on the optimal conditions of a stochastic dynamic optimisation problem that characterises reservoir management. The index's main advantages are its ease of interpretation and breadth of scope, as it incorporates information on hydrological processes, structural constraints, water institutions' rules, and the economic benefits of water use. An empirical application is developed to assess the institutional rules governing water allocation in two different supply systems in Andalusia (southern Spain). [source] Rhetoric and reality of corporate greening: a view from the supply chain management functionBUSINESS STRATEGY AND THE ENVIRONMENT, Issue 2 2005Lutz Preuss Abstract The increasingly important economic role of supply chain management provides the backcloth against which this article examines what contribution the function can make to environmental protection. Theoretical perspectives on greener supply are developed and then tested against a sample of manufacturing companies. Environmental policy documents published by the sample companies seem to offer surface evidence for a proactive supply chain management role in environmental protection. Yet a more detailed examination of the three elements that constitute supply chain management , the management of the transformation of materials, the management of information flows and the management of supply chain relationships , finds a suboptimal situation for all three areas. In part this gap can be explained by limits in the technical capabilities of the supply chain. More important, however, are structural constraints that prevent the supply chain manager from actively searching for environmentally friendlier alternatives. Copyright © 2005 John Wiley & Sons, Ltd and ERP Environment. [source] Molecular Structure of ProlineCHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2004Wesley D. Allen Dr. Abstract The molecular structures of the two lowest-energy conformers of proline, Pro- I and Pro- II, have been characterized by ab initio electronic structure computations. An extensive MP2/6-31G* quartic force field for Pro- I, containing 62,835 unique elements in the internal coordinate space, was computed to account for anharmonic vibrational effects, including total zero-point contributions to isotopomeric rotational constants. New re and improved r0 least-squares structural refinements were performed to determine the heavy-atom framework of Pro- I, based on experimentally measured (A. Lesarri, S. Mata, E. J. Cocinero, S. Blanco, J. C. Lopez, J. L. Alonso, Angew. Chem.2002, 114, 4867; Angew. Chem. Int. Ed.2002, 41, 4673) rotational constant sets of nine isotopomers and our ab initio data for structural constraints and zero-point vibrational (ZPV) shifts. Without the ab initio constraints, even the extensive set of empirical rotational constants cannot satisfactorily fix the molecular structure of the most stable conformer of proline, a 17-atom molecule with no symmetry. After imposing the ab initio constraints, excellent agreement between theory and experiment is found for the heavy-atom geometric framework, the root-mean-square (rms) residual of the empirical rotational constant fit being cut in half by adding ZPV corrections. The most significant disparity, about 0.07 Å, between the empirical and the best ab initio structures, concerns the r(N,,,H) distance of the intramolecular hydrogen bond. Some of the experimental quartic centrifugal distortion constants assigned to Pro- II have been corrected based on data obtained from a theoretical force field. [source] | |||||||||||||||||||||||||