Chapter Sleep Spindles – As a Biomarker of Brain Function and Plasticity

Alternative & renewable energy sources & technolog

Sleep Spindles – As a Biomarker of Brain Function and Plasticity

Alternative & renewable energy sources & technolog

Long-term stability of transparent n/p ZnO homojunctions grown by rf-sputtering at room-temperature

ZnO-based n/p homojunctions were fabricated by sputtering from a single zinc nitride target at room temperature on metal or ITO-coated glass and Si substrates. A multi-target rf-sputtering system was used for the growth of all oxide films as multilayers in a single growth run without breaking the vacuum in the growth chamber. The nitrogen-containing films (less than 1.5 at.% of nitrogen) were n-type ZnO when deposited in oxygen-deficient Ar plasma (10% O2) and p-type ZnO when deposited in oxygen-rich Ar plasma (50% O2). The all-oxide homojunction ITO/n-ZnO/p-ZnO/ITO/glass was fabricated in a single deposition run and exhibited visible transparency in the range of 75–85%. The n/p ZnO homojunctions, having metallic contacts, formed on conventionally processed substrates showed a fairly unstable behavior concerning the current-voltage characteristics. However, the same homojunctions formed on Si3N4-patterned substrates and stored in atmosphere for a period of five months were stable exhibiting a turn-on voltage of around 1.5 V. The realization of a room temperature sputtered transparent and stable ZnO homojunction paves the way to the realization of all-oxide transparent optoelectronic devices

E-Government in the Arabian Gulf: A Vision toward Reality

This paper presents a review of e-government initiatives in the Arabian Gulf, where extensive efforts are being made to capitalize on the cyber technologies in order to enhance the government to citizen service. The described cases are from Kuwait, Bahrain, Saudi Arabia, Qatar, the United Arab Emirates and Oman,. While the efforts vary in size and intensity, what appears to be common is the top level support the e-government initiatives are receiving, which offers them visibility and hopefully warrants their eventual success

An intra-K-complex oscillation with independent and labile frequency and topography in NREM sleep

NREM sleep is characterized by K-complexes (KCs), over the negative phase of which we identified brief activity in the theta range. We recorded high resolution EEG of whole-night sleep from 7 healthy volunteers and visually identified 2nd and 3rd stage NREM spontaneous KCs. We identified 3 major categories: a) KCs without intra-KC-activity (iKCa), b) KCs with non-oscillatory iKCa, and c) KCs with oscillatory iKCa. The latter group of KCs with intra-KC-oscillation (iKCo), was clustered according to the duration of the iKCo. iKCa was observed in most KCs (1150/1522, 75%). iKCos with 2, 3 and 4 waves were observed in 52% (786/1522) of KCs in respective rates of 49% (386/786), 44% and 7%. Successive waves of iKCos showed on average a shift of their maximal amplitude in the anterio-posterior axis, while the average amplitude of the slow KC showed no spatial shift in time. The iKCo spatial shift was accompanied by transient increases in instantaneous frequency from the theta band towards the alpha band, followed by decreases to upper theta. The study shows that the KC is most often concurrently accompanied by an independent brief iKCo exhibiting topographical relocation of amplitude maxima with every consecutive peak and transient increases in frequency. The iKCo features are potentially reflecting arousing processes taking place during the KC

Spindle Power Is Not Affected after Spontaneous K-Complexes during Human NREM Sleep

<div><p>K-complexes and sleep spindles often grouped together characterize the second stage of NREM sleep and interest has been raised on a possible interaction of their underlying mechanisms. The reported inhibition of spindles power for about 15 seconds following evoked K-complexes has implications on their role in arousal. Our objective was to assess this inhibition following spontaneous K-complexes. We used time-frequency analysis of spontaneous K-complexes selected from whole-night EEG recordings of normal subjects. Our results show that spindles are most often observed at the positive phase following the peak of a spontaneous KC (70%). At latencies of 1–3 s following the peak of the K-complex, spindles almost disappear. Compared to long-term effects described for evoked KCs, sleep spindle power is not affected by spontaneous KCs for latencies of 5–15 s. Observation of the recurrence rate of sporadic spindles suggests that the reduction of power at 1–3 s most likely reflects a refractory period of spindles lasting for 1–2 s, rather than an effect of KCs. These results suggest that the mechanisms underlying spontaneous KCs do not affect spindle power as in the case of evoked KCs.</p> </div