A structural basis for the selection of dominant alpha beta T cell receptors in antiviral immunity

We have examined the basis for immunodominant or public TCR usage in an antiviral CTL response. Residues encoded by each of the highly selected genetic elements of an immunodominant clonotype recognizing Epstein-Barr virus were critical to the antigen specificity of the receptor. Upon recognizing antigen the immunodominant TCR undergoes extensive conformational changes in the complementarity determining regions (CDRs), including the disruption of the canonical structures of the germline-encoded CDR1alpha and CDR2alpha loops to produce an enhanced fit with the HLA-peptide complex. TCR ligation induces conformational changes in the TCRalpha constant domain thought to form part of the docking site for CD3epsilon. These findings indicate that TCR immunodominance is associated with structural properties conferring receptor specificity and suggest a novel structural link between TCR ligation and intracellular signaling.

A partial velocity approach to subcycling structural dynamics

Subcycling, or the use of different timesteps at different nodes, can be an effective way of improving the computational efficiency of explicit transient dynamic structural solutions. The method that has been most widely adopted uses a nodal partition. extending the central difference method, in which small timestep updates are performed interpolating on the displacement at neighbouring large timestep nodes. This approach leads to narrow bands of unstable timesteps or statistical stability. It also can be in error due to lack of momentum conservation on the timestep interface. The author has previously proposed energy conserving algorithms that avoid the first problem of statistical stability. However, these sacrifice accuracy to achieve stability. An approach to conserve momentum on an element interface by adding partial velocities is considered here. Applied to extend the central difference method. this approach is simple. and has accuracy advantages. The method can be programmed by summing impulses of internal forces, evaluated using local element timesteps, in order to predict a velocity change at a node. However, it is still only statistically stable, so an adaptive timestep size is needed to monitor accuracy and to be adjusted if necessary. By replacing the central difference method with the explicit generalized alpha method. it is possible to gain stability by dissipating the high frequency response that leads to stability problems. However. coding the algorithm is less elegant, as the response depends on previous partial accelerations. Extension to implicit integration, is shown to be impractical due to the neglect of remote effects of internal forces acting across a timestep interface. (C) 2002 Elsevier Science B.V. All rights reserved.

Physicochemical and structural characterization of mesoporous aluminosilicates synthesized from leached saponite with additional aluminum incorporation

A thorough investigation was performed on the physical (mechanical, thermal, and hydrothermal stability) and chemical (ion exchange capacity and silanol number) characteristics of aluminosilicate FSMs, synthesized via a new successful short-time synthesis route using leached saponite and a low concentration of CTAB. Moreover, the influence of an additional Al incorporation, utilizing different aluminum sources, on the structure of the FSM derived from saponite is studied. A mesoporous aluminosilicate with a low Si/Al ratio of 12.8 is synthesized, and still has a very large surface area of 1130 m(2)/g and pore volume of 0.92 cm(3)/g. The aluminum-containing samples all have a high cation exchange capacity of around 1 mmol/9 while they still have a silanol number of about 0.9 OH/nm(2); both characteristics being interesting for high-yield postsynthesis modification reactions. Finally, a study is performed on the transformation of the aluminosilicates into their Bronsted acid form via the exchange with ammonium ions and a consecutive heat treatment.

Theoretical and experimental studies of unbraced tubular trusses allowing for torsional stiffness

This paper describes the buckling phenomenon of a tubular truss with unsupported length through a full-scale test and presents a practical computational method for the design of the trusses allowing for the contribution of torsional stiffness against buckling, of which the effect has never been considered previously by others. The current practice for the design of a planar truss has largely been based on the linear elastic approach which cannot allow for the contribution of torsional stiffness and tension members in a structural system against buckling. The over-simplified analytical technique is unable to provide a realistic and an economical design to a structure. In this paper the stability theory is applied to the second-order analysis and design of the structural form, with detailed allowance for the instability and second-order effects in compliance with design code requirements. Finally, the paper demonstrates the application of the proposed method to the stability design of a commonly adopted truss system used in support of glass panels in which lateral bracing members are highly undesirable for economical and aesthetic reasons.

Dynamic stability of laminated FGM plates based on higher-order shear deformation theory

This paper conducts a dynamic stability analysis of symmetrically laminated FGM rectangular plates with general out-of-plane supporting conditions, subjected to a uniaxial periodic in-plane load and undergoing uniform temperature change. Theoretical formulations are based on Reddy's third-order shear deformation plate theory, and account for the temperature dependence of material properties. A semi-analytical Galerkin-differential quadrature approach is employed to convert the governing equations into a linear system of Mathieu-Hill equations from which the boundary points on the unstable regions are determined by Bolotin's method. Free vibration and bifurcation buckling are also discussed as subset problems. Numerical results are presented in both dimensionless tabular and graphical forms for laminated plates with FGM layers made of silicon nitride and stainless steel. The influences of various parameters such as material composition, layer thickness ratio, temperature change, static load level, boundary constraints on the dynamic stability, buckling and vibration frequencies are examined in detail through parametric studies.

Impacts of structural characteristics on activated sludge floc stability

Activated sludge samples from seven full-scale plants were investigated in order to determine the relationship between floc structure and floc stability. Floc stability was determined by shear sensitivity and floc strength. Floc structure was considered in terms of two size scales, the micro- and macrostructure. The microstructure refers to the organization of the floc components, such as the individual microorganisms. The macrostructure refers to the overall floc. The floc macrostructure was characterized by filament index, sludge volume index, size, and fractal dimension. It had a significant impact on floc stability. Large and open floes with low fractal dimensions containing large number of filaments were more shear sensitive and had lower floc strength compared to small and dense floes. Fluorescent in situ hybridization analysis indicated that the organization of the bacterial cells might also have an effect on the floc stability. (C) 2003 Elsevier Ltd. All rights reserved.

Insights into the structural basis for zinc inhibition of the glycine receptor

Histidines 107 and 109 in the glycine receptor ( GlyR) alpha(1) subunit have previously been identified as determinants of the inhibitory zinc-binding site. Based on modeling of the GlyR alpha(1) subunit extracellular domain by homology to the acetylcholine-binding protein crystal structure, we hypothesized that inhibitory zinc is bound within the vestibule lumen at subunit interfaces, where it is ligated by His(107) from one subunit and His(109) from an adjacent subunit. This was tested by co-expressing alpha(1) subunits containing the H107A mutation with alpha(1) subunits containing the H109A mutation. Although sensitivity to zinc inhibition is markedly reduced when either mutation is individually incorporated into all five subunits, the GlyRs formed by the co-expression of H107A mutant subunits with H109A mutant subunits exhibited an inhibitory zinc sensitivity similar to that of the wild type alpha(1) homomeric GlyR. This constitutes strong evidence that inhibitory zinc is coordinated at the interface between adjacent alpha(1) subunits. No evidence was found for beta subunit involvement in the coordination of inhibitory zinc, indicating that a maximum of two zinc-binding sites per alpha(1)beta receptor is sufficient for maximal zinc inhibition. Our data also show that two zinc-binding sites are sufficient for significant inhibition of alpha(1) homomers. The binding of zinc at the interface between adjacent alpha(1) subunits could restrict intersubunit movements, providing a feasible mechanism for the inhibition of channel activation by zinc.

Structural characterization of respiratory syncytial virus fusion inhibitor escape mutants: homology model of the F protein and a syncytium formation assay

Respiratory syncytial virus (RSV) is a ubiquitous human pathogen and the leading cause of lower respiratory tract infections in infants. Infection of cells and subsequent formation of syncytia occur through membrane fusion mediated by the RSV fusion protein (RSV-F). A novel in vitro assay of recombinant RSV-F function has been devised and used to characterize a number of escape mutants for three known inhibitors of RSV-F that have been isolated. Homology modeling of the RSV-F structure has been carried out on the basis of a chimera derived from the crystal structures of the RSV-F core and a fragment from the orthologous fusion protein from Newcastle disease virus (NDV). The structure correlates well with the appearance of RSV-F in electron micrographs, and the residues identified as contributing to specific binding sites for several monoclonal antibodies are arranged in appropriate solvent-accessible clusters. The positions of the characterized resistance mutants in the model structure identify two promising regions for the design of fusion inhibitors. (C) 2003 Elsevier Science (USA). All rights reserved.

Structural refinement of systems specified in object-z and CSP

This paper is concerned with methods for refinement of specifications written using a combination of Object-Z and CSP. Such a combination has proved to be a suitable vehicle for specifying complex systems which involve state and behaviour, and several proposals exist for integrating these two languages. The basis of the integration in this paper is a semantics of Object-Z classes identical to CSP processes. This allows classes specified in Object-Z to be combined using CSP operators. It has been shown that this semantic model allows state-based refinement relations to be used on the Object-Z components in an integrated Object-Z/CSP specification. However, the current refinement methodology does not allow the structure of a specification to be changed in a refinement, whereas a full methodology would, for example, allow concurrency to be introduced during the development life-cycle. In this paper, we tackle these concerns and discuss refinements of specifications written using Object-Z and CSP where we change the structure of the specification when performing the refinement. In particular, we develop a set of structural simulation rules which allow single components to be refined to more complex specifications involving CSP operators. The soundness of these rules is verified against the common semantic model and they are illustrated via a number of examples.

Comparative study of the radiation-induced grafting of styrene onto poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) and polypropylene substrates. I: Kinetics and structural investigation

A comparative study has been made of the radiation grafting of styrene onto poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (PFA) and polypropylene (PP) substrates, using the simultaneous irradiation method. Effects of grafting conditions such as monomer concentrations, type of solvent, dose rate and irradiation dose on the grafting yield were investigated. Under the same grafting conditions it was found that a higher degree of grafting of styrene was obtained using a mixture of dichloromethane/methanol solvents for PFA and methanol for PP and the degree of grafting was higher in PP than in PFA at all doses. However, the micro-Raman spectroscopy analysis of the graft revealed that, for the same degree of grafting, the penetration depth of the grafted polystyrene into the substrate was higher in PFA than in PP substrates. In both polymers the crystallinity was hardly affected by the grafting process and the degree of crystallinity decreased slightly with grafting dose. The dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be 0.6 and 1.4 order for PFA and 0.15 and 2.2 for PP, respectively. The degree of grafting increased with increasing radiation dose in both polymers. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield for PFA and PP was accompanied by a proportional increase in the penetration depth of the graft into the substrates. (C) 2003 Society of Chemical Industry.

Structural variations and formation constants of first-row transition metal complexes of biologically active aroylhydrazones

Iron chelators of the 2-pyridinecarbaldehyde isonicotinoylhydrazone (HPCIH) class show high potential for the treatment of iron overload diseases. In the present study, selected first-row transition metal (from Mn to Zn) complexes with HPCIH and 2-pyridinecarbaldehyde (4'-aminobenzoyl)hydrazone (HPCAH) were synthesised and characterised. Crystallography reveals that HPCAH exclusively forms bis complexes with divalent transition metals, with each ligand coordinating meridionally through its pyridine-N, imine-N and carbonyl-O atoms, forming distorted octahedral cis-MN4O2 complexes. Complexes of HPCIH were more varied and unpredictable, with metal/ligand ratios of 1:1, 1:2, 2:2 and 3:2 obtained with different metal ions. The isonicotinoyl ring N-atom in HPCIH was found to be an effective ligand, and this resulted in the varied metal/ligand ratios observed. The formation constants of divalent metal complexes with HPCIH were determined by potentiometric titrations and the values obtained were consistent with similar tridentate ligands and with the Irving-Williams order. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

Structural definition of the low-temperature phase transition of tris(ethane-1,2-diamine)zinc(II) dinitrate

The 93 K X-ray crystal structure of tris(ethane-1,2-diamine)zinc(II) dinitrate is reported. As predicted by the spectroscopic studies of other workers, there is a reversible phase transition of the structure at low temperature. We have determined this temperature to be 143 K. The structure at this temperature and below resembles that of the room temperature structure, except the crystallographic D-3 symmetry of the complex cation (296 K) is lowered to C-2 ( below 144 K) by subtle changes in cation-anion hydrogen bonding. No change in the conformation of the cation or its bond lengths and angles was found.

Capital Intelectual: sua divulgação no setor bancário em Portugal

The importance of intangible resources has increased dramatically in recent years comparing to tangible ones. The economy in which we live is the result of competitive pressures that have imposed the implementation of business at an international level as well as a requirement in the application of sophisticated technologies that allow us to follow this fast evolution. In this age of information and innovation organizations will only survive if they are inserted in a global network of strategic relations, generically called as the network economy by Lev (2003). The service sector has stood out against the more traditional sectors of the economy. The intensive use of knowledge and a strong customer orientation created a new reality in today’s organizations: a growing importance attached to innovation, to the quality of products and services offered, to the information and communication technologies adopted, and to the creativity and particular abilities of human resources. The concept of intangible assets is more common in an accounting language and intellectual capital is most often applied in the context of management, being associated with a more comprehensive, multidimensional approach, representing all the knowledge that the institution owns and that it applies in the form of expertise, the creativity and organizational competencies that lead to innovation and to the sustained attainment of future economic benefits. An analysis of the scope of intellectual capital is fundamental to take more appropriate management decisions so that a more appropriate accounting treatment could be given by the accounting standardization organizations. This study intends to analyse the practices of information disclosure of the intellectual capital in the banking sector in Portugal, complementing the analysis of the disclosure of intangible assets in the context of accounting standards with the disclosure of intellectual capital in the context of organizational management. In particular, our main aims are to identify the extent of disclosure of intellectual capital made by banks in Portugal and also to identify the factors that determine such a disclosure. The disclosure in the context of accounting standards will be studied by checking the disclosure of intangible assets through the items listed in the International Accounting Standard 38 developed by the International Accounting Standards Board. The context of management was analysed by means of creating a voluntary disclosure index based on assumptions of the model Intellectus, developed by the Centro de Investigación sobre la Sociedad del Conocimiento – Instituto de Administración de Empresas (CIC-IADE) of the Universidad Autónoma of Madrid, and of the model Intellectual Capital Statement (made in Europe) (InCaS), both promoted by the European Commission and that we have adapted to the banking sector. When analysing the disclosure of intangible assets based on the context of accounting standards and the voluntary disclosure of intellectual capital, this study has tried to raise awareness about the importance of issuing reports on the intellectual capital as an alternative tool to take management decisions in the existing organizations and reflects the transparency and legitimacy that these institutions seek through a more extensive and more detailed information disclosure of their intellectual capital. Based on a complimentarily of economic theories, together with social and political theories, we tried to check the extent, evolution and tendencies of the compulsory disclosure of intangible assets and of the voluntary disclosure of the intellectual capital analysed in the period 2001-2011. Banks characteristics were also analysed in order to deduce those factors that determine or promote a larger disclosure in this sector. Based on these objectives, we adopted a longitudinal approach to explore the extent and the development of the disclosure of intangible assets as well as the factors that have determined it. Furthermore, we sought to assess the impact of the adoption of IAS 38 in the financial statements of the organizations in this sector. The disclosure index created on the basis of the disclosure requirements stated in IAS 38 from IASB was applied to the consolidated financial statements of the seventeen banks that rendered their statements in Portugal from 2001 to 2009. Since the information disclosed in the context of accounting standards may not have an important role as a management tool once it was not able to reflect what really contributes to the competitiveness and organizational growth, the voluntary disclosure of the intellectual capital was analysed according to the information obtained from the 2010 annual individual reports of the banks operating in Portugal in that year and from their respective websites in 2011. We tried to analyse the extent of the voluntary disclosure of the intellectual capital and of each of its components, human capital, structural capital and relational capital. The comparative analysis of their annual reports and their web pages allowed us to assess the incidence of the disclosure and discover what channel the banking sector focuses on when disclosing their intellectual capital. Also in this analysis the study of the disclosure determinants has allowed us to conclude about the influence of particular characteristics in the voluntary disclosure of the intellectual capital. The results of the analysis to the extent of the disclosure of intangible assets in the consolidated financial statements of the banking groups in Portugal in the period 2001-2009 have shown an average information disclosure of 0.24. This information disclosure evolved from an average value of 0.1940 in 2001 to 0.2778 in 2009. The average value is 0.8286 if it is only considered the disclosure of the intangible assets that the banks possessed. The evolution of this index means an increase in the average disclosure from 0.7852 in 2001 to 0.8788 in 2009. From the first results that are related to the extent of the disclosure of intangible assets in the financial statements, we can verify that the banking groups present a low disclosure level of these resources. However, when considering the disclosure of only the intangible assets that each institution owns, the disclosure level appears to be in compliance with the disclosure requirements for this sector. An evolution in the disclosure of intangible assets for the period considered was confirmed, showing an increase in the information disclosure of intangible assets in 2005, the year in which the accounting rules for intangible assets changed. The analysis that focused on the disclosure in the context of management tried to understand the extent, the incidence and the determinants of the voluntary information disclosure of intellectual capital in the annual reports of 2010 and on their web pages in 2011, studying the 32 banks operating in Portugal in this period. The average voluntary disclosure of the intellectual capital in the 2010 annual reports is 0.4342 while that in web pages is 0.2907. A review of the components of the intellectual capital allowed us to assess the importance that the banks confer to each of these components. The data obtained show that the relational capital, and more specifically the business capital, is the most disclosed component by banks in Portugal both in the annual reports and in their institutional web pages, followed by the structural capital and, finally, by the human capital. The disclosure of the human capital and the structural capital is higher in the annual reports than that in the websites, while the relational capital is more disclosed in the websites than in the annual reports. The results have also shown that the banks make a complementary use of both sources when disclosing information about their structural capital and relational capital but they do not show any information about their human capital in their websites. We tried to prove the influence of factors that could determine the accounting disclosure and the voluntary disclosure of the intellectual capital in this sector. The change in the IASB accounting rules as from January 1st 2005 gave a greater disclosure of accounting information of intangible assets in the financial statements of banks. The bank size and corporate governance measures have statistically proved to have an influence on the extent of the accounting disclosure of intangible assets and on the voluntary disclosure of the intellectual capital. Economic and financial variables such as profitability, operating efficiency or solvency were not determinants of information disclosure. The instability that the banking sector has experienced in economic and financial indicators in recent years as a result of the global financial markets imbalance has worsen indicators such as profitability, efficiency and solvency and caused major discrepancies in the economic situation between banks in Portugal. This empirical analysis has contributed to confront the disclosure required by accounting rules performed in the financial statements of organizations with that performed in the main disclosure media which is available for entities and which is increasingly requested in the process of taking management decisions. It also allowed us to verify whether there is homogeneity between institutions in the fulfilment of the requirements for information disclosure of intangible assets. However, as for voluntary disclosure of intellectual capital, there are large disparities in the disclosure extent between organizations. Regardless of this sector specific characteristics, the voluntary disclosure of intellectual capital made by banks in Portugal follows the trends in other sectors and the practices adopted in other countries, namely regarding the amount of information disclosed, the incidence of the disclosure on the indicators of relational capital and the importance of variables such as size as determinants of disclosure of intellectual capital. For a further knowledge in this field, we created a specific index for the banking sector, considering appropriate indicators for an incisive, comprehensive analysis in order to consider the most relevant indicators of intellectual capital components. Besides, confronting the analysis of disclosure in the context of accounting standards with the study of voluntary disclosure brought a new analysis approach to the research on intellectual capital disclosure. With this study, we have also intended to raise greater awareness of the need for harmonization in the intellectual capital disclosure on the part of the regulatory banking authority by means of a demanding, consistent and transparent report of intellectual capital with simple, clear, objective indicators so that those interested in disclosing intellectual capital information in the organizations in this sector may obtain more harmonized and comparable information. A research on the disclosure quality of intellectual capital, together with the application of other analysis methodologies in this sector, might be a promising approach for future research. Applying the voluntary disclosure index to the same sector in other countries may also contribute to the knowledge of disclosure practices in different geographical environments. We highlight the relevance of further studies contributing to the harmonization and consistency in the presentation of an intellectual capital report so as to enable organizations to disclose the resources that contribute most to their competitiveness and growth.