Frontal-Lobe Involvement in Spatial Memory: Evidence from PET,fMRI, and Lesion Studies

Many studies have identified the prefrontal cortex as the brain area that is critical for spatial memory, both in humans and in other primates. Other studies, however, have failed to establish this relation. Therefore, the aim of this paper was to review the literature regarding the role of the human prefrontal lobe in spatial memory. This was done by examining the evidence obtained from neuropsychological patients and from studies using brain-imaging techniques (PET and fMRI). Evidence supporting the notion that the prefrontal cortex is extensively involved in spatial working memory was found. The majority of these studies, however, suggests that frontal-lobe involvement is not related to the type of material that is being processed (e.g., spatial vs. nonspatial), but to process-specific functions, such as encoding and retrieval. Theoretically, these functions could be linked to the central executive within Baddeley's working-memory model, or to recent theories that emphasize the various processes that play a role in working memory. Also, methodological issues were discussed. Further research is needed to enhance our understanding of the precise interaction of domain-specific and general processes.     

Type D personality,but not Type A behavior pattern,is associated with coronary plaque vulnerability

Personality traits are associated with major adverse coronary events (MACE) in patients with coronary artery disease (CAD). However, the link between personality traits and intravascular morphology in CAD patients is poorly understood. This study investigated the relationship between personality traits, specifically Type A behavior pattern and Type D personality, and plaque vulnerability. After adjustment for demographic and clinical factors, multivariable regression analysis showed no association between Type A and optical coherence tomography indices. However, Type D personality was independently associated with lipid plaque, thin cap fibroatheroma (TCFA), and fibrous cap thickness. More specifically, negative affectivity of Type D was related to lipid plaque, TCFA and fibrous cap thickness, and social inhibition was associated with plaque rupture. Our results show that Type D personality was associated with plaque vulnerability, independent of clinical factors. Measurement of negative affectivity and social inhibition will increase our understanding of the progressive phase of the plaque vulnerability, which can contribute to the early identification of high risk patients and reduce the incidence of MACE.     

Static and dynamical ageing processes at room temperature in a Fe25Ni0.4C virgin martensite: effect of C redistribution at the nanoscale

The work-hardening behaviour of virgin martensitic steel has been investigated in a strictly un-aged state and after various ageing conditions. At room temperature (RT), the un-aged alloy shows astonishing tensile performances (ultimate tensile stress?=?1600?MPa/uniform elongation?=?15%) but unexpected serrations. These serrations can be suppressed by static ageing (at RT or higher) while maintaining the initial work-hardening rate (ageing at RT). Parallel investigations using atom probe tomography reveal that the distribution of carbon at the atomic scale evolves from purely homogeneous for virgin martensite to partly segregated at a very fine scale (5–10?nm) after static ageing. This particular mechanical behaviour can therefore be associated with a very local decrease in available carbon in solid solution due to redistribution and segregations on defects (nanotwins) that occurs rapidly, even after few days at RT.     

A thermodynamic model for nanocrystallization in bulk metallic glasses

The structural complexity of glass-forming alloys, which generally contain more than three components, can lead by partial crystallization during annealing to a dispersion of nanocrystals in an amorphous matrix, giving the material a very high mechanical strength. In the present study, the evolution of the driving force for crystallization is expressed as a function of the composition and the chemical potentials of the components. Application to Zr₆₀Al₁₀Cu₃₀ and Zr₆₀Al₁₀Cu₂₀Pd₁₀ bulk metallic glasses shows that the first crystallization step leads to a metastable equilibrium between nanocrystals of an intermetallic and a percolating amorphous phase. The effects of the number of components and of chemical bonding on the fraction crystallized is analysed and discussed.     

Influence of properties of layered silicate minerals on adsorbed DNA surface affinity,self-assembly and nanopatterning

We report on the specific interaction between DNA and some mica-family minerals and other layered silicate structures. The interaction depends on mineral surface's crystallography, chemistry and potential. These properties are responsible for a remarkable variety of adsorption mechanisms and can be used to modulate surface self-assembly and nanopatterning of DNA. The controlled deposition of DNA onto non-conductive mineral regions with atomically flat boundaries has very attractive applications in nano-biotechnology (for example, microelectronics, microarrays and sensors). In addition, the extreme affinity discovered for some mineral surfaces, together with their ability to organize the DNA molecules, could be an indication of their catalytic potential. It may also have had relevance in the prebiotic environment, with important implications for the earth and life sciences.     

Neutron and X-ray diffraction studies and cohesive interface model of the fatigue crack deformation behavior

The crack-tip deformation behavior during a single overload, fatigue test of ferritic stainless steel, and Ni-based HAYNES 230 superalloy is studied at different structural levels using (1) neutron-diffraction, from which both the elastic-lattice strain and volume-averaged total dislocation densities are obtained, (2) polychromatic X-ray microdiffraction to probe the geometrically necessary dislocations and boundaries distribution, and (3) an irreversible and hysteretic cohesive interface model which has been implemented into a finite element framework to simulate the stress/strain evolution near the fatigue crack tip. Neutron strain measurements and finite element simulations are in qualitative agreement on the macroscopic length scale. Large plastic deformation induced by the overload and the resulting compressive residual strains are observed in front of the crack tip after the overload, and are the principal reason for the fatigue-crack-growth retardation. Strong strain gradients surrounding the crack propagation result in the formation of a high density of geometrically necessary dislocations near the fractured surface and cause local lattice rotations on the submicron level.     

Characterization of PLZT ceramics modified by isovalent (Ba,Sr), donor (Nb) and acceptor (Zn) dopants for piezoelectric applications

This article describes the influence of microstructure on the dielectric and piezoelectric properties of isovalent- donor- and acceptor-modified lead lanthanum zirconium titanate (PLZT) ceramics. The ceramic compositions, with formula: [Pb_0.954La_0.016Ba_0.01Sr_0.02][Zr_0.525Ti_0.475]_{0.981?( m /2)}Nb_0.012Zn _m O₃ where m =?0, 0.2, 0.4, 0.6, 0.8 and 1.0 mol% Zn, were synthesized via a solid-state reaction method. X-ray diffraction studies are supported by tolerance factor and electronegativity difference measurements. Scanning electron microscopy studies reveal grain growth enhancement with increase of Zn concentration. As the Zn concentration increased from 0 to 0.8 mol%, the room-temperature dielectric constant increased while the Curie temperature decreased continuously. An increase in the Zn content had the most significant effect on the piezoelectric properties. The optimum piezoelectric properties were observed for 1 mol% Zn composition.     

Mechanically driven alloying forces in the fabrication of a Cr–Zr nanocomposite

A highly supersaturated nanocrystalline Cr–25?wt% Zr alloy has been prepared by mechanical alloying of elemental crystalline powders. High-purity powders of Cr and Zr were milled for up to 20?h. The development of the microstructure was investigated by X-ray diffraction (XRD) and scanning electron microscopy. XRD patterns confirmed complete alloying of the Zr and Cr. The contribution of grain boundaries, the chemical potential of a solute atom induced by dislocations, and the elastic strain energy arising from the different sizes of Cr and Zr atoms have been calculated. The alloy formation is discussed with respect to the thermodynamic conditions of the material. The role of internal strains and stored enthalpies by dislocations on solute atoms is the major mechanical driving force for alloying and this is critically assessed in this article.     

Small-angle X-ray scattering study on the fractal structure of solid products of bituminous coal at different carbonization temperatures

Carbonization is one of the main methods for comprehensive utilization of bituminous coal. Bituminous coal and its solid products from carbonization, namely char and coke, have complex pore structures, which can be characterized by fractals. We performed a study on the fractal structure of the solid products prepared from the bituminous coal of Shuiyu mine in Shanxi Province, China, at different carbonization temperatures (25°C～1000°C) by synchrotron radiation small-angle X-ray scattering (SAXS). The results show that the bituminous coal has a surface fractal structure during the whole carbonization process. The variation of fractal dimension with carbonization temperature illustrates the different stages of the carbonization process.