Synchronisation

In order to prepare the system for 3D-CT, it is not enough to integrate a second detector array. Besides this special attention has to be paid to the computer hardware, the synchronisation between object movement and the data read out as well as to the collimator of the LINAC. The collimator has been built with 4 tungsten blocks which can be moved individually m order to shape different sht sizes for 2D-CT as well as different cone angles for 3D-CT or digital radiography. 

Block 3 a device for management and synchronisation. Serves for adjusting the parameters of the system, gain factor, input impedance, amplitude and the duration of the initial pulse, as well as ensures a database communication for the further processing by the computer. 

Even though the two parts of the manipulator are mechanically separated from each other the positioning of the manipulator is controlled by using one combined co-ordinate system. This is extremely vital since the tomographie reconstruction demands a synchronised movement with precise positioning when each projection is exposed. 

GenBank (NCBI, USA) EMBL Nucleotide Sequence Database (Europe) DDBJ (Japan) The three main nucleotide sequence databases, which are synchronised daiiy... 

Interaction tests should be made on all unprotected structures in the vicinity of a proposed cathodic protection installation, and should be repeated annually or at some other suitable interval to ensure that alterations in the layout of plant or in the electrical conditions are taken into account. It is most convenient if the tests on all unprotected pipes or cables are made at the same time, the potential measurements being synchronised with the regular switching on and off of the protection current. It may then be convenient to continue with further tests to confirm that any remedial measures applied to one installation do not adversely affect other installations. 

The synchronised oscillatory activity between the intrinsically linked thalamus and cortex. Under normal circumstances there is a level of activity which changes during the sleep-wake cycle increasing during periods of slow wave sleep. Excess synchrony occurs in conditions such as epilepsy. Thiazolidinedione... 

Figure 2.14 Relation between the EEG recorded from an epileptic focus on the surface of the cerebral cortex (EEG) and the activity of a single cortical neuron recorded extracellularly (e.c.) and intracellularly (i.c.) during an experimental epilepsy induced by topical application of penicillin. Note that the large EEG excursions correspond to the large (synchronised) depolarisations of the neuron, not to action potential discharges. (Adapted from Brain Res. 52 Ayala, GF et al. Genesis of Epileptic Interictal Spikes. New Knowledge of Cortical Feedback systems suggests a Neurophysiological Explanation of Brief Paroxysms, 1-17 (1973) with permission from Elsevier Science)...

As we relax in preparation for and pass into sleep, the active desynchronised awake EEG characterised by the low-amplitude (5-10 pV) high-frequency (10-30 Hz) beta waves becomes progressively more synchronised giving larger (20-30 pV) and slower (8-12 Hz) alpha waves, and then even slower (1-4 Hz) and bigger (30-150 pV) delta waves. This so-called slow-wave sleep is interrupted at intervals of some 1-2h by the break-up and desynchronisation of the EEG into an awake-like pattern. Since this is accompanied by rapid eye movements, even though sleep persists and can be deeper, the phase is known as rapid eye movement, REM or paradoxical, sleep. It is a time when dreaming occurs and when memory may be secured. 

These rhythms seem to be innately programmed although they can be adjusted. For instance, in a normal environment, the sleep-waking cycle of humans is obviously synchronised ( entrained ) with the (24-h) dark-light cycle whereas it assumes a period of around 25-27 h in a (time-free) environment where there are no diurnal cues. Interestingly, when humans are in a time-free environment, the change in the rhythm of... 

Figure 22.4 Idealised EEG-like patterns in sleep and waking. When we are awake and aroused the EEG is desynchronised (a). As we become drowsy and pass into sleep the EEG waves become more synchronised with 8-12 Hz alpha waves (b), sleep spindles then appear (c) before the EEG becomes even more synchronised with slow (about 1-2 Hz) high-voltage waves characteristic of deep slow-wave sleep (SWS). About every 90 min this pattern is disrupted and the EEG becomes more like that in arousal (d) except that the subject remains asleep. This phase of sleep is also characterised by rolling, rapid eye movements, the so-called REM sleep. SWS is consequently also known as non-REM sleep. These tracings have been drawn to show the main features of the different EEG phases of sleep and as such are much simpler than those that are actually recorded...

The more synchronised the activity of the cortical neurons, the greater the summation of currents and the larger and slower the EEG wave, as in the sleep pattern (Fig. 22.4). While there are some dissociations between EEG pattern and behavioural states, the EEG offers one way of determining experimentally the pathways (and neurotransmitters) that control arousal and sleep, and can be regarded as an important objective measurement of the cortical correlates of sleep and waking. 

Izard M.K. and Vandenbergh J.G. (1982a). Priming pheromones from oestrous cows increase synchronisation of estrous in dairy heifers after PGF-2a injection. J Reprod Fertil 66, 189-196. 

The construction of the optoelectronic interface can be based on a silicon photodiode since analytical and reference wavelengths are from the visible and the IR regions, respectively. The signals can be filtered out by optical filters (then two photodiodes are required) or one photodiode can be synchronised with modulation waves of the LEDs used. Finally, silica optical fibres can be used as light waveguides. The choice between single fibre or bundle is determined by the application of the sensor. 

There are also some important differences in the technology required to realise bistatic radar. In monostatic radar synchronisation between transmission and reception is done via a stable source, usually a local oscillator. In bistatic radar the separation of transmitter and receiver makes this much more difficult. An equivalent situation has to be achieved and this is done either via synchronised atomic clocks, a signal such as GPS or by reception of a reference signal received directly from the transmitter. The latter technique is typically used in PCL systems and we shall return to this later. 

Cibacron Blue C-R (Ciba) with a synchronised bifunctional aminofluorotriazine -sulphatoethylsulphone system. 

Under the relatively mild conditions of pad-batch fixation within 6 hours batching time, the heterobifunctional dye (Blue 221) behaved as if it were a monofunctional sulphatoethylsulphone dye and only the synchronised Cibacron C system showed truly bifunctional performance [78]. 

Fig. 8.3 Synchronised voltage-current data for polarisation curves.

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