The cluster charge identification in the GEM detector for fusion plasma imaging by soft X-ray diagnostics.

The measurement system based on gas electron multiplier detector is developed for soft X-ray diagnostics of tokamak plasmas. The multi-channel setup is designed for estimation of the energy and the position distribution of an X-ray source. The focal measuring issue is the charge cluster identification by its value and position estimation. The fast and accurate mode of the serial data acquisition is applied for the dynamic plasma diagnostics. The charge clusters are counted in the space determined by 2D position, charge value, and time intervals. Radiation source characteristics are presented by histograms for a selected range of position, time intervals, and cluster charge values corresponding to the energy spectra.

Gaseous electron multiplier-based soft x-ray plasma diagnostics development: Preliminary tests at ASDEX Upgrade.

A Gaseous Electron Multiplier (GEM)-based detector is being developed for soft X-ray diagnostics on tokamaks. Its main goal is to facilitate transport studies of impurities like tungsten. Such studies are very relevant to ITER, where the excessive accumulation of impurities in the plasma core should be avoided. This contribution provides details of the preliminary tests at ASDEX Upgrade (AUG) with a focus on the most important aspects for detector operation in harsh radiation environment. It was shown that both spatially and spectrally resolved data could be collected, in a reasonable agreement with other AUG diagnostics. Contributions to the GEM signal include also hard X-rays, gammas, and neutrons. First simulations of the effect of high-energy photons have helped understanding these contributions.

[Assessment of blood flow velocity during cognitive stimulation in persons with suspected hydrocephalus]. / Badanie predkosci przeplywu krwi w czasie stymulacji poznawczej u osób z podejrzeniem wodoglowia.

The aim of this work is to evaluate middle cerebral arteries (MCA) blood flow velocity changes during performance of linguistic and visuospatial cognitive tasks. Two groups were investigated: eight patients with suspected hydrocephalus without perceptible cognitive disturbances, and eight healthy persons. Blood flow velocity in left and right MCA was recorded with transcranial Doppler sonography while the examined patients were performing three different tasks. The analysis of the results showed differences between the groups concerning both increase of blood flow velocity values and performance patterns. Compared to healthy individuals less increase in blood flow velocity during performance of all tasks and no difference in haemodynamic changes between both hemispheres during task performance were observed in patients with hydrocephalus. The results obtained suggest, that the pattern of functional lateralization in brain in patients with suspected hydrocephalus is probably changed.

[Dynamics of blood flow velocity in middle cerebral arteries in dyslexic persons]. / Dynamika przeplywu krwi w tetnicach srodkowych mózgu u osób z dysleksja.

The aim of our study was to investigate the blood flow in middle cerebral arteries during the different forms of cognitive activity in dyslectic persons. Two group of subjects were tested. The first group consisted of 10 students with school difficulties, diagnosed neuropsychologically as having a particular form of dyslexia, i.e. dysgraphy or dysorthography. 6 of them were right lateralized and 4--left lateralized. The second contained 10 students without such problems. 7 of them were right lateralized and 3--left lateralized. We used four kinds of cognitive tasks, during which the blood flow velocity in MCA in left and right hemisphere was measured with the Transcranial Doppler method. The analysis of the results showed differences between the groups of blood flow velocity levels, without a difference in performance profile. The dysgraphic persons had significantly higher blood flow velocity in the right hemisphere compared to the reference group. The results suggest particularly important role of right hemisphere in dyslexic persons, which is consistent with results obtained by other authors. The analysis of lateralization showed that this factor influences significantly the blood flow velocity level--the left lateralized persons showed lower rise of blood flow velocity than the right lateralized, regardless of the kind of task and measured hemisphere.

X-ray crystal spectrometer upgrade for ITER-like wall experiments at JET.

The high resolution X-Ray crystal spectrometer at the JET tokamak has been upgraded with the main goal of measuring the tungsten impurity concentration. This is important for understanding impurity accumulation in the plasma after installation of the JET ITER-like wall (main chamber: Be, divertor: W). This contribution provides details of the upgraded spectrometer with a focus on the aspects important for spectral analysis and plasma parameter calculation. In particular, we describe the determination of the spectrometer sensitivity: important for impurity concentration determination.

Cerebrospinal fluid pulse pressure waveform analysis in hydrocephalic children.

Analysis of cerebrospinal fluid pulse pressure was reported to be useful in the assessment of the cerebrospinal pressure-volume compensation. The method for the estimation of high-frequency centroid (HFC) was modified and used to verify the correlation between HFC and other compensatory parameters investigated by means of the lumbar infusion test in 94 hydrocephalic children. The results confirm that in hydrocephalus HFC is positively correlated to cerebrospinal elasticity coefficient, but inversely to mean CSF pressure and pulse wave amplitude. It was also demonstrated that HFC decreased dynamically during the infusion test.

Effect of dotarizine on CO2-dependent cerebrovascular reactivity.

Dotarizine is chemically related to calcium antagonist cinnarizine and flunarizine. The study presented investigates the influence of the drug on the diameter of cortical arteries and cerebral blood velocity measured in the MCA in two groups of anaesthetized cats. Changes of vessel diameter were measured indirectly using photographs of the cerebral cortex during experiments, and flow velocity was measured using transcranial Doppler sonography. Dotarizine was administrated by 20 minute intravenous infusion in a dose of 0.05 mg/kg/min. In the first group of animals the infusion was started during normoventilation, in the next group the infusion started during 30th minute of hyperventilation. The most conspicuous data were obtained in experiments conducted in hyperventilated animals where dotarizine abolished the vasoconstrictive effect of hyperventilation. The results suggest that dotarizine has a pronounced effect on basal as well as cortical arteries of the brain.

A computing system for the clinical and experimental investigation of cerebrovascular reactivity.

We present a computing system for the recording and on-line analysis of analogue signals derived from bedside cerebrovascular monitors in different pathophysiological conditions. These include arterial blood pressure and oxygen saturation, end-tidal carbon dioxide concentration, cerebral blood flow velocities using transcranial Doppler ultrasonography, and concentration changes in cerebral oxy- and deoxyhaemoglobin from near infrared spectroscopy. Configuration and analysis adopts arithmetic expressions of different signal processing functions, various statistical properties for each signal, frequency spectrum analysis using fast Fourier transformation, and correlation/cross-correlation. The software offers off-line analysis of non-invasive tests of cerebrovascular reactivity. Several examples of clinical assessment of cerebrovascular reactivity are presented, including cerebral haemodynamic stress tests which employ carbon dioxide, acetazolamide, the breath holding test, leg cuff inflation and deflation, and transient carotid artery compression. Application within the experimental setting with induced haemorrhagic hypotension can also be used.

Cerebrospinal compensation in hydrocephalic children.

One hundred and fifteen cases of hydrocephalus in children were analysed. Cerebrospinal compensatory reserve was assessed by a computerized, constant rate, lumbar infusion test. Head circumference and ventricular size were measured and a psychometric examination carried out. A classification of hydrocephalus based on resting cerebrospinal fluid pressure (CSFP) and resistance to cerebrospinal fluid outflow (RCSF) was introduced. Parameters of compensatory reserve were compared in atrophy (low CSFP, low RCSF), normal-pressure hydrocephalus (low CSFP, increased RCSF), non-communicating hydrocephalus (high CSFP, low RCSF) and acute hydrocephalus (high CSFP and increased RCSF). Significant differences were found between the factors describing compensatory ability in these groups. Sixty-two patients could be classified on the basis of resting CSFP and RCSF. Differentiation between the types of hydrocephalus was shown to be more accurate when all variables measured during the pressure-volume test were considered. The patterns of the time courses of CSFP during rate infusion tests in the different types of hydrocephalus are presented.