Search

The reorientational dynamics if toluene is neat liquid is investigated with the help of 13C nuclear magnetic relaxation technique. The temperature-dependent dipolar spin-lattice relaxation rates and cross-correlation rates between the dipolar and the chemical-shift anisotropy relaxation mechanisms are estimated in various 13C nuclei containing molecule over a temperature range of 253 to 318 K.

The reorientational motion of benzene is examined in the neat liquid and in a polystyrene/benzene solution, which was, investigated by NMR relaxation as well as MD simulation methods. It is concluded that the rotations about the C(sub 6) axis were much faster than about axis perpendicular to the C (sub 6) axis and this finding is in accordance to a previous MD study by Muller-Plathe.

The article discusses the microstructure formation in aluminum-silicon alloy which are directionally solidified in a rotating magnetic field. Accordingly, aluminum-silicon7Mg (AlSi7Mg) alloys are used in order to produce high stressed automotive components such as engine frames and cylinder heads in foundry industry. Various processes have been used in order to investigate the microstructure formation in AlSi7Mg0.3 and AlSi7Mg0.6 alloys during directional solidification.

Abstract: For the understanding of the formation of microstructures the initial transient, i.e. the very beginning of solidification, is of major relevance. At this stage a complex interaction between the velocity of the solidification front, the concentration pile-up and the temperature gradient takes place. In a Bridgman-Stockbarger furnace directional solidification experiments with binary AlCu 1.3wt.% were performed allowing solidification with a planar solid–liquid interface. The velocity and temperature profile were measured during the experiments, concentration profiles afterwards. In this paper we present experimental results. Parallel to the experimental work numerical simulations based on the model of Coriell et al. were performed and first results are compared to the experiments. [Copyright &y& Elsevier]

Presents a preoperative brain mapping using water activation positron emission tomography. Activation of Broca's area; Performance of a verb generation task in a right-handed patient with mild aphasia; Left frontal metastasis.

Abstract: The temperature and enthalpy of transformations of organic alloys from the ternary systems (D)camphor–neopentylglycol–succinonitrile (DC–NPG–SCN) were measured by means of differential scanning calorimetry (DSC). The phase diagram of this ternary system was assessed via the CALPHAD approach using Thermo-Calc based on the thermodynamic descriptions of the constituent binary systems published earlier and the thermodynamic and phase equilibrium data for the ternary alloys measured in the present work. Proper agreements between the experimental and the calculated data were achieved. Experiments and calculations show that the DC–NPG–SCN exhibits a nonvariant eutectic reaction with the eutectic point at 297.0K, 26.3mol%DC and 14.8mol%NPG. This eutectic reaction involves the ordered monoclinic crystals (OCs) of NPG and the orientationally disordered crystals (ODICs) of both, SCN (BCC_A2 phase) and DC (hexagonal phase). Unidirectional solidification experiments were performed with the nonvariant eutectic DC–NPG–SCN alloy in order to verify the phases involved in the solid–liquid equilibrium and the nature of eutectic growth. We find that in the eutectic alloy the eutectic growth is irregular: the extremely facetted monoclinic phase (NPG) grows as thin and long needle-like crystals that protrude far into the liquid and are then decorated with nonfacetted eutectic of BCC_A2 (SCN) and hexagonal (DC) lamellae, which mainly grow perpendicular to the growth direction of the monoclinic (NPG) needles. Few unidirectional solidification experiments were performed with dilute ternary alloys with composition close to the univariant eutectic reactions that extend from the constituent binary systems NPG–DC and SCN–DC, respectively. The destabilisation of planar eutectic interfaces due to constitutional supercooling were qualitatively monitored. [Copyright &y& Elsevier]

Abstract: The temperature and enthalpy of transformations of organic alloys from the ternary system 2-amino-2-methyl-1,3-propanediol–(D)camphor–neopentylglycol (AMPD–DC–NPG) were measured by means of differential scanning calorimetry (DSC). The phase diagram of this ternary system was assessed via the CALPHAD approach using Thermo-Calc based on the thermodynamic descriptions of the constituent binaries published earlier and on the thermodynamic and phase equilibrium data measured in the present work for ternary alloys. Good agreement between the experimental and calculated data was achieved. Experiments and calculations show that the AMPD–DC–NPG exhibits a nonvariant quasiperitectic reaction at 336.1K and composition AMPD-17.5mol% DC-42.56mol% NPG, with all solid phases being nonfaceted. Unidirectional solidification experiments were performed with three different alloys selected such that each exhibits a small amount of the primary BCC (AMPD solid solution), the FCC (NPG solid solution) and the hexagonal (DC solid solution) phase, respectively, in order to verify the nature of the phases involved in solid–liquid equilibria and the nature of coupled growth in this ternary system. We find that in all these cases once steady state growth is reached two solid phases grow at the solid–liquid interface with a rod-like coupled growth pattern: The hexagonal phase (DC solid solution) and the FCC phase (NPG solid solution). [Copyright &y& Elsevier]

Unlabelled: Working memory deficits are a cardinal feature of the pathophysiology of schizophrenia. Lesion studies and functional blood flow-dependent imaging methods with coarse temporal resolution, such as PET and functional MRI (fMRI), tend to paint a fairly static picture of the cortical regions involved. In contrast, functional transcranial Doppler sonography (fTCD) provides a high temporal resolution. Truly simultaneous fTCD-fMRI is not yet possible for technical reasons, but H(2)(15)O PET and fTCD can be used really simultaneously. However, this combination has not yet been used for cognitive activations in schizophrenia. We therefore investigated the extent to which there are both spatial (PET) and temporal changes (fTCD) in the activation patterns of schizophrenic patients., Methods: Eleven clinically stable chronic schizophrenic, right-handed patients and 10 healthy, right-handed control subjects, matched for age, sex, education, and intelligence quotient, participated in the study. We selected stable chronic schizophrenic patients who could perform a working memory task (N-back task) as well as healthy volunteers to exclude the possibility of imaged artifacts due to poor performance. All subjects were examined with a truly simultaneous fTCD-H(2)(15)O PET combination under cognitive activation., Results: Schizophrenic patients activate a significantly larger cortical volume for adequate task performance (P < 0.05), but with a significantly lower blood flow increase in this volume (P < 0.01), than do control subjects. Furthermore, they cannot significantly increase blood flow velocity during the time course of cognitive activation as control subjects do. There were only significant correlations between neuropsychologic performance and imaging parameters (fTCD changes, PET blood flow changes) in control subjects (all r >or= /0.65/; P < 0.05), but no significant correlations in schizophrenics (all r < /0.3/; P > 0.4)., Conclusion: We demonstrated that schizophrenic patients exhibit qualitative differences in the spatial and temporal resolution of cognitive processing. All facts could be interpreted as a sign of alternative, less efficient problem-solving strategies in schizophrenia that lead to the working memory deficits observed during the further course of this disease. Truly simultaneous fTCD-PET can be used in neuroscience to add fundamental new information on spatial and temporal cognitive activation behavior to understand the true physiologic nature of the disease-specific differences of mental illnesses that are seen as disorders of the mind arising in the brain.