CHARACTERISATION OF THE PTB THERMAL NEUTRON CALIBRATION FACILITY WITH THE BONNER SPHERE SPECTROMETER NEMUS.

The neutron field of the PTB Thermal Neutron Calibration Facility was characterised with the help of the Bonner sphere spectrometer of PTB, NEutron MUltisphere Spectrometer (NEMUS). For the analysis of the Bonner sphere data an analytical model of the neutron energy distribution was used. The unfolding of neutron spectra was performed via the method of Bayesian parameter estimation. Comparison of the results of thermal neutron fluence and thermal ambient dose equivalent with the results of the reference method of gold activation showed a very good agreement. For fast neutrons the results obtained with NEMUS will serve as reference values for this facility. The facility is ready for use as a thermal neutron reference field for calibrations of neutron measuring devices.

A Bayesian Approach for Measurements of Stray Neutrons at Proton Therapy Facilities: Quantifying Neutron Dose Uncertainty.

Bonner sphere measurements are typically analyzed using unfolding codes. It is well known that it is difficult to get reliable estimates of uncertainties for standard unfolding procedures. An alternative approach is to analyze the data using Bayesian parameter estimation. This method provides reliable estimates of the uncertainties of neutron spectra leading to rigorous estimates of uncertainties of the dose. We extend previous Bayesian approaches and apply the method to stray neutrons in proton therapy environments by introducing a new parameterized model which describes the main features of the expected neutron spectra. The parameterization is based on information that is available from measurements and detailed Monte Carlo simulations. The validity of this approach has been validated with results of an experiment using Bonner spheres carried out at the experimental hall of the OncoRay proton therapy facility in Dresden.

[Etiopathogenesis of type 2 diabetes mellitus]. / Etiopatogeneze diabetes mellitus 2. typu.

In the genesis and development of type 2 diabetes in the great majority of subjects the contemporary lifestyle characterized by inadequate physical activity and an excessive energy intake is of basic importance. The majority of abnormalities and defects revealed by laboratory tests is probably secondary and caused by the above mentioned factors. Contemporary views of the etiopathogenesis of the disease are demotivating for patients: if the cause of their disease were an inborn disorder at the level of transmission of a signal on membranes then probably nothing else can be done than to take prescribed drugs. If the mistake involves the lifestyle, the latter can be changed and the disease avoided. Any medicamentous treatment is associated with the risk of undesirable effects--the complication of hyperinsulinism in treatment with sulphonyl urea derivatives and insulin or lactate acidosis after treatment with biguanides. This risk is not influenced by early prevention: dietary restraint and adequate physical exercise. Diabetes type 2 and 1--despite the common sign of hyperglycaemia--are characterized by a fundamental difference: (not influenced by treatment) DM type 1 is characterized by enhanced catabolic processes, starvation at the cellular level. Type 2 is characterized by enhanced anabolic processes, excessive amounts of nutrients in cells. The authors submit recommendations which respect the secondary character of deviations for the development of DM 2 which can be detected by laboratory methods: The following are the basic etiopathogenetic mechanism for the development of DM 2: 1. Chronic excessive intake and inadequate output of energy a) increased nutrient supply to the liver with secondary increase of gluconeogenesis in the liver, b) chronic increased supply of glucose to peripheral tissues, in particular muscles and adipose tissue, inadequate physical exercise, with secondary restriction of nutrient supplies to these tissues. 2. Secondary affection of insulin secretion in the islets of Langerhans in the pancreas.

[Determination of serum lactic acid and the acid-base equilibrium in carbon monoxide poisoning]. / Význam vysetrení laktátémie a acidobazické rovnováhy pri otrave oxidem uhelnatým.

The authors present a description of severe accidental carbon monoxide poisoning. They stress the significance of the examination of lactic acid level at this poisoning. In case described the level of carbonyl haemoglobin could not be determined because of device trouble. Patient AA (16-year-old) was admitted in relatively very good condition, without clinical signs of severer affection. Considering the facts that gas-poisoning (over 24 hrs) was found through anamnesis, and simultaneous admission of patient's greatgrandmother in critical condition, the patient AA was treated also with oxygen of high concentration, monitored, kept in absolute rest. High lactate level (18.9 mmol/l) and the evidence of metabolic acidosis (pH 7.16, pO2 8.65, pCO2 2.06, sBE -22.1) made to suspect of severe poisoning. Despite intensive oxygenotherapy it came to severe left-side cardial failure associated with pulmonal edema, anuria, shock after 4 hours, managed successfully within 4 hours. Lactate level correlated very well with condition severity. Septum hypokinesis was demonstrated cardiografically and it disappeared within 6 days. However, symetric inversion of T wave in many leads (I, II, aVF, V 2-6) persisted for 24 days. The authors assume that routine examination of acid base balance and lactate level in addition to the determination of carbonyl haemoglobin level is very important for the consideration of the severity of carbon monoxide poisoning. Lactataemia determination is probably even more significant for the assumption of oxygen deficit and therefore for the total prognosis of the patient.

Ellipsometry with polarisation analysis at cryogenic temperatures inside a vacuum chamber.

In this paper we describe a new variant of null ellipsometry to determine thicknesses and optical properties of thin films on a substrate at cryogenic temperatures. In the PCSA arrangement of ellipsometry the polarizer and the compensator are placed before the substrate and the analyzer after it. Usually, in the null ellipsometry the polarizer and the analyzer are rotated to find the searched minimum in intensity. In our variant we rotate the polarizer and the compensator instead, both being placed in the incoming beam before the substrate. Therefore the polarisation analysis of the reflected beam can be realized by an analyzer at fixed orientation. We developed this method for investigations of thin cryogenic films inside a vacuum chamber where the analyzer and detector had to be placed inside the cold shield at a temperature of T ≈ 90 K close to the substrate. All other optical components were installed at the incoming beam line outside the vacuum chamber, including all components which need to be rotated during the measurements. Our null ellipsometry variant has been tested with condensed krypton films on a highly oriented pyrolytic graphite substrate (HOPG) at a temperature of T ≈ 25 K. We show that it is possible to determine the indices of refraction of condensed krypton and of the HOPG substrate as well as thickness of krypton films with reasonable accuracy.