887 resultados para Structure-Activity Relationship


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Orthodox contingency theory links effective organisational performance to compatible relationships between the environment and organisation strategy and structure and assumes that organisations have the capacity to adapt as the environment changes. Recent contributions to the literature on organisation theory claim that the key to effective performance is effective adaptation which in turn requires the simultaneous reconciliation of efficiency and innovation which is afforded by an unique environment-organisation configuration. The literature on organisation theory recognises the continuing confusion caused by the fragmented and often conflicting results from cross-sectional studies. Although the case is made for longitudinal studies which comprehensively describe the evolving relationship between the environment and the organisation there is little to suggest how such studies should be executed in practice. Typically the choice is between the approaches of the historicised case study and statistical analysis of large populations which examine the relationship between environment and organisation strategy and/or structure and ignore the product-process relationship. This study combines the historicised case study and the multi-variable and ordinal scale approach of statistical analysis to construct an analytical framework which tracks and exposes the environment-organisation-performance relationship over time. The framework examines changes in the environment, strategy and structure and uniquely includes an assessment of the organisation's product-process relationship and its contribution to organisational efficiency and innovation. The analytical framework is applied to examine the evolving environment-organisation relationship of two organisations in the same industry over the same twenty-five year period to provide a sector perspective of organisational adaptation. The findings demonstrate the significance of the environment-organisation configuration to the scope and frequency of adaptation and suggest that the level of sector homogeneity may be linked to the level of product-process standardisation.

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Purpose: To analyse the relationship between measured intraocular pressure (IOP) and central corneal thickness (CCT), corneal hysteresis (CH) and corneal resistance factor (CRF) in ocular hypertension (OHT), primary open-angle (POAG) and normal tension glaucoma (NTG) eyes using multiple tonometry devices. Methods: Right eyes of patients diagnosed with OHT (n=47), normal tension glaucoma (n=17) and POAG (n=50) were assessed, IOP was measured in random order with four devices: Goldmann applanation tonometry (GAT); Pascal(R) dynamic contour tonometer (DCT); Reichert(R) ocular response analyser (ORA); and Tono-Pen(R) XL. CCT was then measured using a hand-held ultrasonic pachymeter. CH and CRF were derived from the air pressure to corneal reflectance relationship of the ORA data. Results: Compared to the GAT, the Tonopen and ORA Goldmann equivalent (IOPg) and corneal compensated (IOPcc) measured higher IOP readings (F=19.351, p<0.001), particularly in NTG (F=12.604, p<0.001). DCT was closest to Goldmann IOP and had the lowest variance. CCT was significantly different (F=8.305, p<0.001) between the 3 conditions as was CH (F=6.854, p=0.002) and CRF (F=19.653, p<0.001). IOPcc measures were not affected by CCT. The DCT was generally not affected by corneal biomechanical factors. Conclusion: This study suggests that as the true pressure of the eye cannot be determined non-invasively, measurements from any tonometer should be interpreted with care, particularly when alterations in the corneal tissue are suspected.

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Orthodox depictions of a fraught labour–environmental relationship privileging class, ideological and programmatic differences are problematised by newly quantified evidence of British unions' pro-environmental policy-making since 1967. The following narrative blends widely accepted accounts of the fortunes of both movements with an evaluation of Britain's shifting political opportunity structure and coalition theory to identify an alternative range of constraints and opportunities influencing the propensity and capacity of both movements to interact effectively, culminating recently in unions' emergence as environmental actors in their own right.

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Redox regulation of signalling pathways is critical in proliferation and apoptosis; redox imbalance can lead to pathologies such as inflammation and cancer. Vaccinia H1-related protein (VHR; DUSP3) is a dual-specificity phosphatase important in controlling MAP kinase activity during cell cycle. the active-site motif contains a cysteine that acts as a nucleophile during catalysis. We used VHR to investigate the effect of oxidation in vitro on phosphatase activity, with the aim of determining how the profile of site-specific modification related to catalytic activity. Recombinant human VHR was expressed in E. coli and purified using a GST-tag. Protein was subjected to oxidation with various concentrations of SIN-1 or tetranitromethane (TNM) as nitrating agents, or HOCl. the activity was assayed using either 3-O-methylfluorescein phosphate with fluorescence detection or PIP3 by phosphate release with malachite green. the sites of oxidation were mapped using HPLC coupled to tandem mass spectrometry on an ABSciex 5600TripleTOF following in-gel digestion. More than 25 different concentration-dependent oxidative modifications to the protein were detected, including oxidations of methionine, cysteine, histidine, lysine, proline and tyrosine, and the % oxidized peptide (versus unmodified peptide) was determined from the extracted ion chromatograms. Unsurprisingly, methionine residues were very susceptible to oxidation, but there was a significant different in the extent of their oxidation. Similarly, tyrosine residues varied greatly in their modifications: Y85 and Y138 were readily nitrated, whereas Y38, Y78 and Y101 showed little modification. Y138 must be phosphorylated for MAPK phosphatase activity, so this susceptibility impacts on signalling pathways. Di- and tri- oxidations of cysteine residues were observed, but did not correlate directly with loss of activity. Overall, the catalytic activity did not correlate with redox state of any individual residue, but the total oxidative load correlated with treatment concentration and activity. This study provides the first comprehensive analysis of oxidation modifications of VHR, and demonstrates both heterogenous oxidant effects and differential residue susceptibility in a signalling phosphatase.

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Corporate governance has become increasingly important in developed and developing countries just after a series of corporate scandals and failures in a number of countries. Corporate governance structure is often viewed as a means of corporate success despite prior studies reveal mixed, somewhere conflicting and ambiguous, and somewhere no relationship between governance structure and performance. This study empirically investigates the relationship between corporate governance mechanisms and financial performance of listed banking companies in Bangladesh by using two multiple regression models. The study reveals that a good number of companies do not comply with the regulatory requirements indicating remarkable shortfall in corporate governance practice. The companies are run by the professional managers having no duality and no ownership interest for which they are compensated by high remuneration to curb agency conflict. Apart from some inconsistent relationship between some corporate variables, the corporate governance mechanisms do not appear to have significant relationship with financial performances. The findings reveal an insignificant negative impact or somewhere no impact of independent directors and non-independent non-executive directors on the level of performance that strongly support the concept that the managers are essentially worthy of trust and earn returns for the owners as claimed by stewardship theory. The study provides support for the view that while much emphasis on corporate governance mechanisms is necessary to safeguard the interest of stakeholders; corporate governance on its own, as a set of codes or standards for corporate conformance, cannot make a company successful. Companies need to balance corporate governance mechanisms with performance by adopting strategic decision and risk management with the efficient utilization of the organization’s resources.

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In recent years, a surprising new phenomenon has emerged in which globally-distributed online communities collaborate to create useful and sophisticated computer software. These open source software groups are comprised of generally unaffiliated individuals and organizations who work in a seemingly chaotic fashion and who participate on a voluntary basis without direct financial incentive. ^ The purpose of this research is to investigate the relationship between the social network structure of these intriguing groups and their level of output and activity, where social network structure is defined as (1) closure or connectedness within the group, (2) bridging ties which extend outside of the group, and (3) leader centrality within the group. Based on well-tested theories of social capital and centrality in teams, propositions were formulated which suggest that social network structures associated with successful open source software project communities will exhibit high levels of bridging and moderate levels of closure and leader centrality. ^ The research setting was the SourceForge hosting organization and a study population of 143 project communities was identified. Independent variables included measures of closure and leader centrality defined over conversational ties, along with measures of bridging defined over membership ties. Dependent variables included source code commits and software releases for community output, and software downloads and project site page views for community activity. A cross-sectional study design was used and archival data were extracted and aggregated for the two-year period following the first release of project software. The resulting compiled variables were analyzed using multiple linear and quadratic regressions, controlling for group size and conversational volume. ^ Contrary to theory-based expectations, the surprising results showed that successful project groups exhibited low levels of closure and that the levels of bridging and leader centrality were not important factors of success. These findings suggest that the creation and use of open source software may represent a fundamentally new socio-technical development process which disrupts the team paradigm and which triggers the need for building new theories of collaborative development. These new theories could point towards the broader application of open source methods for the creation of knowledge-based products other than software. ^

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Zinc is essential for the activity of thymulin, a thymic hormone involved in T-lymphocyte differentiation and activation. Zinc deficiency is widespread in populations with HIV infection, and HIV+ drug users are particularly susceptible to zinc deficiency and immune suppression. This dissertation explored the relationship of zinc-bound active thymulin to plasma zinc, CD4+ and CD8+ cell count, the CD4+/CD8+ ratio, and drug use in HIV-infected drug users. Zinc-bound active thymulin was assessed in plasma of HIV+ drug users who were participating in a 30 month zinc supplementation trial. Plasma from 80 participants at the 12 month visit, and 40 of these same participants, randomly selected, at the baseline visit were assessed for zinc-bound active thymulin levels using a modification of the rosette inhibition assay. Thymulin activity was directly associated with CD4+ cell count (β = 0.127, p = 0.002) and inversely associated with cocaine use (β = −0.908, p = 0.026; R2 = 0.188, p = 0.019) independent of HIV viral load, age, gender and antiretroviral use. An increase in thymulin activity was 1.4 times more likely when CD4+ cell count increased (OR = 1.402, 95%CI: 1.006–1.956), independent of change in viral load, antiretroviral use, and age. Participants who used cocaine consistently, were 7.6 times less likely to have an increase in thymulin activity (OR = 0.133, 95%CI: 0.017–1.061). There was a direct correlation between change in plasma zinc and change in zinc-bound active thymulin (r = 0.243, p = 0.13). Analysis of CD4+ cell count decline in 222 participants in the zinc supplementation trial across the 30 months showed that both crack cocaine use and heavy alcohol use accelerated CD4+ cell count decline. Thymulin activity is directly associated with HIV disease progression, measured by CD4+ cell count, and is depressed with cocaine use independent of antiretroviral use and HIV viral load. Cocaine and heavy alcohol accelerate CD4+ cell count decline. The effect of cocaine on thymic output requires further evaluation as a mechanism for the association of cocaine use with faster HIV disease progression.

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The purpose of this study was to examine the relationship between the structure of jobs and burnout, and to assess to what extent, if any this relationship was moderated by individual coping methods. This study was supported by the Karasek's (1998) Job Demand-Control-Support theory of work stress as well as Maslach and Leiter's (1993) theory of burnout. Coping was examined as a moderator based on the conceptualization of Lazarus and Folkman (1984). ^ Two overall overarching questions framed this study: (a) what is the relationship between job structure, as operationalized by job title, and burnout across different occupations in support services in a large municipal school district? and (b) To what extent do individual differences in coping methods moderate this relationship? ^ This study was a cross-sectional study of county public school bus drivers, bus aides, mechanics, and clerical workers (N = 253) at three bus depot locations within the same district using validated survey instruments for data collection. Hypotheses were tested using simultaneous regression analyses. ^ Findings indicated that there were statistically significant and relevant relationships among the variables of interest; job demands, job control, burnout, and ways of coping. There was a relationship between job title and physical job demands. There was no evidence to support a relationship between job title and psychological demands. Furthermore, there was a relationship between physical demands, emotional exhaustion and personal accomplishment; key indicators of burnout. ^ Results showed significant correlations between individual ways of coping as a moderator between job structure, operationalized by job title, and individual employee burnout adding empirical evidence to the occupational stress literature. Based on the findings, there are implications for theory, research, and practice. For theory and research, the findings suggest the importance of incorporating transactional models in the study of occupational stress. In the area of practice, the findings highlight the importance of enriching jobs, increasing job control, and providing individual-level training related to stress reduction.^

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In recent years, a surprising new phenomenon has emerged in which globally-distributed online communities collaborate to create useful and sophisticated computer software. These open source software groups are comprised of generally unaffiliated individuals and organizations who work in a seemingly chaotic fashion and who participate on a voluntary basis without direct financial incentive. The purpose of this research is to investigate the relationship between the social network structure of these intriguing groups and their level of output and activity, where social network structure is defined as 1) closure or connectedness within the group, 2) bridging ties which extend outside of the group, and 3) leader centrality within the group. Based on well-tested theories of social capital and centrality in teams, propositions were formulated which suggest that social network structures associated with successful open source software project communities will exhibit high levels of bridging and moderate levels of closure and leader centrality. The research setting was the SourceForge hosting organization and a study population of 143 project communities was identified. Independent variables included measures of closure and leader centrality defined over conversational ties, along with measures of bridging defined over membership ties. Dependent variables included source code commits and software releases for community output, and software downloads and project site page views for community activity. A cross-sectional study design was used and archival data were extracted and aggregated for the two-year period following the first release of project software. The resulting compiled variables were analyzed using multiple linear and quadratic regressions, controlling for group size and conversational volume. Contrary to theory-based expectations, the surprising results showed that successful project groups exhibited low levels of closure and that the levels of bridging and leader centrality were not important factors of success. These findings suggest that the creation and use of open source software may represent a fundamentally new socio-technical development process which disrupts the team paradigm and which triggers the need for building new theories of collaborative development. These new theories could point towards the broader application of open source methods for the creation of knowledge-based products other than software.

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The relationship between the frequency of eating, physical activity and Body Mass Index (BMI) was investigated. Seventy five women, aged 24 to 55, were recruited from Florida International University. Via interview, subjects provided information regarding demographics and habitual eating frequency over 24-hours, and completed both the Baecke Questionnaire of Habitual Physical Activity and the Health Insurance Plan of New York Questionnaire on Physical Activity. Pearson correlations and partial correlation coefficients were used to assess the relationship between eating frequency, physical activity, age, and BMI. Results revealed significant positive correlations between eating frequency and total physical activity scores, and leisure time physical activity scores, but not between eating frequency and physical activity on the job. Partial correlations suggest that there may be an effect of eating frequency on BMI both through an effect on physical activity and through another mechanism. These results suggest that more frequent eaters tend to be more physically active, which may partially explain why lower body weights is associated with more frequent eating.

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Chitosan gel films were successfully obtained by evaporation cast from chitosan solutions in aqueous acidic solutions of organic acids (lactic and acetic acid) as gel film bandages, with a range of additives that directly influence film morphology and porosity. We show that the structure and composition of a wide range of 128 thin gel films, is correlated to the antimicrobial properties, their biocompatibility and resistance to biodegradation. Infrared spectroscopy and solid-state 13C nuclear magnetic resonance spectroscopy was used to correlate film molecular structure and composition to good antimicrobial properties against 10 of the most prevalent Gram positive and Gram negative bacteria. Chitosan gel films reduce the number of colonies after 24 h of incubation by factors of ∼105–107 CFU/mL, compared with controls. For each of these films, the structure and preparation condition has a direct relationship to antimicrobial activity and effectiveness. These gel film bandages also show excellent stability against biodegradation with lysozyme under physiological conditions (5% weight loss over a period of 1 month, 2% in the first week), allowing use during the entire healing process. These chitosan thin films and subsequent derivatives hold potential as low-cost, dissolvable bandages, or second skin, with antimicrobial properties that prohibit the most relevant intrahospital bacteria that infest burn injuries.

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This dissertation explores the complex interactions between organizational structure and the environment. In Chapter 1, I investigate the effect of financial development on the formation of European corporate groups. Since cross-country regressions are hard to interpret in a causal sense, we exploit exogenous industry measures to investigate a specific channel through which financial development may affect group affiliation: internal capital markets. Using a comprehensive firm-level dataset on European corporate groups in 15 countries, we find that countries

with less developed financial markets have a higher percentage of group affiliates in more capital intensive industries. This relationship is more pronounced for young and small firms and for affiliates of large and diversified groups. Our findings are consistent with the view that internal capital markets may, under some conditions, be more efficient than prevailing external markets, and that this may drive group affiliation even in developed economies. In Chapter 2, I bridge current streams of innovation research to explore the interplay between R&D, external knowledge, and organizational structure–three elements of a firm’s innovation strategy which we argue should logically be studied together. Using within-firm patent assignment patterns,

we develop a novel measure of structure for a large sample of American firms. We find that centralized firms invest more in research and patent more per R&D dollar than decentralized firms. Both types access technology via mergers and acquisitions, but their acquisitions differ in terms of frequency, size, and i\ntegration. Consistent with our framework, their sources of value creation differ: while centralized firms derive more value from internal R&D, decentralized firms rely more on external knowledge. We discuss how these findings should stimulate more integrative work on theories of innovation. In Chapter 3, I use novel data on 1,265 newly-public firms to show that innovative firms exposed to environments with lower M&A activity just after their initial public offering (IPO) adapt by engaging in fewer technological acquisitions and

more internal research. However, this adaptive response becomes inertial shortly after IPO and persists well into maturity. This study advances our understanding of how the environment shapes heterogeneity and capabilities through its impact on firm structure. I discuss how my results can help bridge inertial versus adaptive perspectives in the study of organizations, by

documenting an instance when the two interact.