The ventral premotor cortex (VPM) and resistance to interference.

The authors tested a patient suffering from a circumscribed lesion of the right frontal operculum (FO) in 3 experiments of visual attention involving spatial orienting, maintenance of task-relevant priorities, and control of interference from new and old task-irrelevant items. The authors found that spatial orienting and active maintenance of priorities were intact, but there were difficulties in controlling interference from new and old irrelevant items. These results suggest that the FO is necessary for the direct control of interference, but its lesion alone is not enough to disturb spatial orienting processes or active maintenance of task priorities. The authors discuss the results in light of a hybrid cognitive model of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Confidence level and feeling of knowing for episodic and semantic memory: an investigation of lorazepam effects on metamemory

The effects of lorazepam (0.026 or 0.038 mg/kg), a benzodiazepine, and of a placebo on metamemory, i.e. knowledge about one's own memory capabilities, were investigated in 36 healthy volunteers. Accuracy of confidence levels (CL) in the correctness of recalled answers and accuracy of feeling of knowing (FOK) the answers when recall fails were measured using a sentence memory task assessing episodic memory and a task consisting of general information questions and assessing semantic memory. Lorazepam impaired episodic memory. Unexpectedly, it also impaired performance in both the recall and recognition phases of the task assessing semantic memory, suggesting that it decreased the ability to distinguish between correct and incorrect information. In episodic memory, lorazepam 0.038 mg/kg-treated subjects exhibited an impaired CL accuracy, compared to placebo-treated subjects, and their FOK accuracy was at chance. In semantic memory, their overall CL and FOK accuracy was apparently spared. However, these subjects selectively overestimated their CL judgements for incorrect answers; moreover, secondary analyses showed that FOK accuracy for a subset of low-accuracy items was virtually nil. These results suggest that lorazepam impairs metamemory for both episodic and semantic memory.     

Subcortical dementia

Scanning tunneling microscopy was used to investigate the structure of the two-dimensional adsorbate formed by molecular self-assembly of the purine base, adenine, on the surfaces of the naturally occurring mineral molybdenite and the synthetic crystal highly oriented pyrolytic graphite. Although formed from adenine, which is achiral, the observed adsorbate surface structures were enantiomorphic on molybdenite. This phenomenon suggests a mechanism for the introduction of a localized chiral symmetry break by the spontaneous crystallization of these prebiotically available molecules on inorganic surfaces and may have some role in the origin of biomolecular optical asymmetry. The possibility that purine-pyrimidine arrays assembled on naturally occurring mineral surfaces might act as possible templates for biomolecular assembly is discussed.     

Design and implementation of a substrate integrated waveguide phase shifter

The design and implementation of a phase shifter based on the substrate integrated waveguide (SIW) technique operating at 10 GHz are presented. The proposed phase shifter consists of a SIW section with two inserted metallic posts. The phase shifting in this configuration is achieved by changing the diameter and the position of these posts. Numerical simulations have been carried out for different diameters and positions, which have shown good agreement with the theory. A parametric study was also conducted to assess the impact of errors made on the diameter and position of the two metallic posts. To prove the concept, prototypes were fabricated and measured. Experimental results agree well with simulations and SII was better than -14 dB, S21 better than -1.08 dB and the phase error was less than 1.5deg.     

The variation of valence and conduction band edges charge densities with lattice constant in GaP and InP

Valence and conduction band edge charge densities for direct band gap InP and indirect band gap semiconductors GaP are calculated for different values of the lattice constant. These variations affect the bonding properties of these semiconductors and the effect of interstitial impurities.