The impact of EPI voxel size on SNR and BOLD sensitivity in the anterior medio-temporal lobe: a comparative group study of deactivation of the Default Mode

Objectives  To quantify the gain in time-series SNR that can be achieved in the amygdala by reducing EPI voxel size, and to assess the extent to which this advantage is carried through to statistical significance in a group fMRI study, using a cognitive task to trigger task-independent deactivation of anterior medial temporal structures. Materials and methods  Two groups of seven subjects were posed number-series tasks to induce deactivation of the Default Mode network. This is known from PET work to include the amygdala, which lies in a region of high magnetic field gradient. In 3 T imaging, one group was studied with high resolution EPI with 6 μl voxels, the other with lower resolution EPI with 17 μl voxels. Field maps were acquired to allow field gradients in relevant ROIs to be assessed. Results  Time-series SNR was 45% higher in the amygdala in the high resolution EPI data than in the low resolution data. In activation results, whilst there was good agreement between other areas, the involvement of the amygdala could only be demonstrated in the high resolution data. Conclusion  We find that reduction in signal dephasing afforded by high resolution EPI is realized as a substantial increase in SNR and BOLD sensitivity in group fMRI data. This has allowed the first demonstration of the involvement of the amygdala in the Default Mode in fMRI.     

A study on skeletonization of complex petroglyph shapes

Multimedia Tools and Applications - In this paper, we present a study on skeletonization of real-world shape data. The data stem from the cultural heritage domain and represent contact tracings of...     

Expected position of the fatigue fracture plane by using the weighted mean principal Euler angles

The expected principal stress axes under multiaxial fatigue loading are determined by averaging the instantaneous Euler angles through suitable weight functions. Then, the fracture plane position is derived from such expected principal stress directions. Three weight functions based on stress parameters are discussed by comparing theoretical predictions with available test results related to six metallic materials under proportional and non-proportional loading. The fatigue fracture plane position under multiaxial loading may be established on the basis of the averaged direction of the maximum principal stress, with such a direction deduced by employing proper weight functions.     

Stroop theory, memory, and prefrontal cortical functioning: Reply to Cohen et al. (1997).

In this article, the authors respond to J. D. Cohen, K. O. Dunbar, D. M. Barch and T. S. Braver's (see record 1997-02838-005) comment on their target article (see record 1997-02838-004). The present article (a) takes issue with the characterization given by Cohen et al. of the authors' approach as a classical speed-of-processing account of Stroop effects, (b) discusses the value and relevance of other theoretical concepts, such as traditional accounts of working memory and parallel distributed processing (PDP) approaches to Stroop effects, (c) further examines the possibility that the differences the authors observed in Experiment 2 between normal participants' performance and that of participants with schizophrenia may have been due to distractor stimulus degradation, particularly for participants with schizophrenia, and (d) argues for the relevance of the prefrontal cortex, as well as other brain areas, in accounting for their results. The authors conclude with a final theoretical question. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

MOS Integrated Circuit Reliability

This paper presents information on the reliability of MOS integrated circuits based on p-channel enhancement-mode transistors, and describes their failure modes and mechanisms. The principal failure mechanisms were ion migration at the surface and oxide shorting. The results of experimental studies of the effects of variations in construction, processing, and levels of stress are presented, and are compared with other available information on MOS integrated circuit reliability. The failure rate for commercially available complex MOS arrays is on the order of 0.001 to 0.01 per 1000 h of operating life at 125°C for arrays containing approximately 600 p-channel transistors. This corresponds to a failure rate on the order of 5 × 10?6 to 5 × 10?5 per equivalent gate per 1000 h. The effects of device complexity, operating temperature, and other factors are discussed. A reliability prediction equation for MOS integrated circuits is derived from available information. An overall activation energy for functional failure mechanisms of approximately 5 kcal/mole (?0.2 eV/molecule) is considered applicable to typical MOS integrated circuits. Thus, the failure rate of MOS devices operated at 50°C ambient temperature can be predicted to be on the order of 10?6 to 10?5 per equivalent gate per 1000 h.     

Beitrag zur Abschätzung der Kriechriβeinleitung in fehlerbehafteten Bauteilen

Versuche zur Bestimmung des makroskopischen Kriechanrisses. Unterscheidung der Versagensarten: Riβspitzenschädigung –Ligamentschädigung. Auswertung betriebsbeanspruchter Guβstücke mit Herstellungsfehlern. Vergleich der Bauteilbefunde mit den Laborergebnissen mit Hilfe der fiktiv elastischen Spannungsintensität K_lid des Anfangsrisses und der Nennspannung σ_n im Fernfeld des Risses. Zusammenhang üblicher Kriechdaten (R_mt und A_u) mit der Spannungsintensität K_lid für Kriechriβeinleitung.     

Assessing heat-affected zone properties of pressure vessel weldments using simulation techniques

This paper describes simulation methods for mechanisms occurring in the coarse grain heat affected zone (HAZ) of thick-walled weldments. The simulation process is divided into overheating simulation and simulation of stress-relief heat treatment. Overheating simulation is mainly practised by inductive or conductive heating and produces an HAZ-representative microstructure. For the stress-relief heat treatment simulation, annealing tests and constant load creep tests at stress-relief temperatures are carried out.Classifications in order of crack sensitivity and service-suitability are proposed. The order of crack sensitivity is derived from the magnitude of deformability and creep resistance in constant load creep tests. The order of service-suitability is based on the results of notch-impact tests (ISO-V) and tensile tests subsequent to both simulation treatments. The techniques are demonstrated on an example of an ASTM A 508 CI 2 (22 NiMoCr 37) plate material.     

Improving the uniformity in combustion-synthesized titanium carbide

The effects of reactant dispersion and outgassing on the microstructure of combustion-synthesized TiC were investigated. Pressure filtration casting of Ti+C colloidal suspension was shown to be an effective reactant dispersion method to improve the homogeneity of the product. The relation between the nature of the outgassing atmosphere and the formation of titanium oxide and precombustion titanium carbide was investigated. The combination of the colloidal dispersion technique with outgassing was shown to provide TiC products with reduced defects and improved microstructure.