Effect of Carbon Reduction on the Toughness of 9CrWVTaN Steels

Nitride-strengthened, reduced activation, martensitic steel is anticipated to have higher creep strength because of the remarkable thermal stability of nitrides. Two nitride-strengthened, reduced activation martensitic steels with different carbon contents were prepared to investigate the microstructure and mechanical property changes with decreasing carbon content. It has been found that both steels had the microstructure of full martensite with fine nitrides dispersed homogeneously in the matrix and displayed extremely high strength but poor toughness. Compared with the steel with low carbon content (0.005 pct in wt pct), the steel with high carbon content (0.012 pct in wt pct) had not only the higher strength but also the higher impact toughness and grain coarsening temperature, which was related to the carbon content. On the one hand, carbon reduction led to Ta-rich inclusions; on the other hand, the grain grew larger when normalized at high temperature because of the absence of Ta carbonitrides, which would decrease impact toughness. The complicated Al2O3 inclusions in the two steels have been revealed to be responsible for the initiated cleavage fracture by acting as the critical cracks.

Ultimate strength of bolted moment-connections between cold-formed steel members

The behaviour and design of bolted moment-connections between cold-formed steel members, formed by using brackets bolted to the webs of the section, is considered. The particular problem of the moment-capacity of such joints being lower than that of the cold-formed steel sections being connected because of web buckling, caused by the concentration of load transfer from the bolts, is addressed. In this paper, a combination of laboratory tests and finite element analyses is used to investigate this mode of failure. It is demonstrated that there is good agreement between the measured ultimate moment-capacity and that predicted by using the finite element method. A parametric study conducted using the finite element model shows that the moment-capacity of a practical size joint can be up to 20% lower than that of the cold-formed steel sections being connected. Web buckling so-caused must therefore be considered in the design of such connections. (C) 2003 Elsevier Ltd. All rights reserved.

FhCaBP4: A Fasciola hepatica calcium binding protein with EF-hand and dynein light chain domains

In trematodes, there is a family of proteins which combine EF-hand-containing domains with dynein light chain (DLC)-like domains. A member of this family from the liver fluke, Fasciola hepatica-FhCaBP4-has been identified and characterised biochemically. FhCaBP4 has an N-terminal domain containing two imperfect EF-hand sequences and a C-terminal dynein light chain-like domain. Molecular modelling predicted that the two domains are joined by a flexible linker. Native gel electrophoresis demonstrated that FhCaBP4 binds to calcium, manganese, barium and strontium ions, but not to magnesium or zinc ions. The hydrophobic, fluorescent probe 8-anilinonaphthalene-1-sulphonate bound more tightly to FhCaBP4 in the presence of calcium ions. This suggests that the protein undergoes a conformational change on ion binding which increases the number of non-polar residues on the surface. FhCaBP4 was protected from limited proteolysis by the calmodulin antagonist W7, but not by trifluoperazine or praziquantel. Protein-protein cross-linking experiments showed that FhCaBP4 underwent calcium ion-dependent dimerisation. Since DLCs are commonly dimeric, it is likely that FhCaBP4 dimerises through this domain. The molecular model reveals that the calcium ion-binding site is located close to a key sequence in the DLC-like domain, suggesting a plausible mechanism for calcium-dependent dimerisation.

Electron-scale electrostatic solitary waves and shocks: the role of superthermal electrons

The propagation of electron-acoustic solitary waves and shock structures is investigated in a plasma characterized by a superthermal electron population. A three-component plasma model configuration is employed, consisting of inertial (“cold”) electrons, inertialess ? (kappa) distributed superthermal (“hot”) electrons and stationary ions. A multiscale method is employed, leading to a Korteweg-de Vries (KdV) equation for the electrostatic potential (in the absence of dissipation). Taking into account dissipation, a hybrid Korteweg-de Vries-Burgers (KdVB) equation is derived. Exact negative-potential pulse- and kink-shaped solutions (shocks) are obtained. The relative strength among dispersion, nonlinearity and damping coefficients is discussed. Excitations formed in superthermal plasma (finite ?) are narrower and steeper, compared to the Maxwellian case (infinite ?). A series of numerical simulations confirms that energy initially stored in a solitary pulse which propagates in a stable manner for large ? (Maxwellian plasma) may break down to smaller structures or/and to random oscillations, when it encounters a small-? (nonthermal) region. On the other hand, shock structures used as initial conditions for numerical simulations were shown to be robust, essentially responding to changed in the environment by a simple profile change (in width).

FhCaBP3: A Fasciola hepatica calcium binding protein with EF-hand and dynein light chain domains

A DNA sequence encoding a protein with predicted EF-hand and dynein light chain binding domains was identified in a Fasciola hepatica EST library. Sequence analysis of the encoded protein revealed that the most similar known protein was the Fasciola gigantica protein FgCaBP3 and so this newly identified protein was named FhCaBP3. Molecular modelling of FhCaBP3 predicted a highly flexible N-terminal region, followed by a domain containing two EF-hand motifs the second of which is likely to be a functioning divalent ion binding site. The C-terminal domain of the protein contains a dynein light chain like region. Interestingly, molecular modelling predicts that calcium ion binding to the N-terminal domain destabilises the ß-sheet structure of the C-terminal domain. FhCaBP3 can be expressed in, and purified from, Escherichia coli. The recombinant protein dimerises and the absence of calcium ions appeared to promote dimerisation. Native gel shift assays demonstrated that the protein bound to calcium and manganese ions, but not to magnesium, barium, zinc, strontium, nickel, copper or cadmium ions. FhCaBP3 interacted with the calmodulin antagonists trifluoperazine, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and chlorpromazine as well as the myosin regulatory light chain-binding drug praziquantel. Despite sequence and structural similarities to other members of the same protein family from F. hepatica, FhCaBP3 has different biochemical properties to the other well characterised family members, FH22 and FhCaBP4. This suggests that each member of this trematode calcium-binding family has discrete functional roles within the organism.

Multilevel election timing - A comparative overview

This article investigates the link between regionalization of the structure of government, regional elections and regionalism on the one hand, and the organization of state-wide political parties in Spain and the UK on the other. It particularly looks at two aspects of the relations between the central and regional levels of party organization: integration of the regional branches in central decision making and autonomy of the regional branches. It argues that the party factors are the most crucial elements explaining party change and that party leaders mediate between environmental changes and party organization. The parties' history and beliefs and the strength of the central leadership condition their ability or willingness to facilitate the emergence of meso-level elites. The institutional and electoral factors are facilitating factors that constitute additional motives for or against internal party decentralization.

Devolution and party organizational change: The British and Spanish and state-wide parties compared

This article investigates the link between regionalization of the structure of government, regional elections and regionalism on the one hand, and the organization of state-wide political parties in Spain and the UK on the other. It particularly looks at two aspects of the relations between the central and regional levels of party organization: integration of the regional branches in central decision making and autonomy of the regional branches. It argues that the party factors are the most crucial elements explaining party change and that party leaders mediate between environmental changes and party organization. The parties' history and beliefs and the strength of the central leadership condition their ability or willingness to facilitate the emergence of meso-level elites. The institutional and electoral factors are facilitating factors that constitute additional motives for or against internal party decentralization

Party organisation in a multi-level system: Party organisational change in Spain and the UK

This article investigates the link between regionalization of the structure of government, regional elections and regionalism on the one hand, and the organization of state-wide political parties in Spain and the UK on the other. It particularly looks at two aspects of the relations between the central and regional levels of party organization: integration of the regional branches in central decision making and autonomy of the regional branches. It argues that the party factors are the most crucial elements explaining party change and that party leaders mediate between environmental changes and party organization. The parties' history and beliefs and the strength of the central leadership condition their ability or willingness to facilitate the emergence of meso-level elites. The institutional and electoral factors are facilitating factors that constitute additional motives for or against internal party decentralization.