EURADOS trial performance test for photon dosimetry

Within the framework of the EURADOS Action entitled Harmonisation and Dosimetric Quality Assurance in Individual Monitoring for External Radiation, trial performance tests for whole-body and extremity personal dosemeters were carried out. Photon, beta and neutron dosemeters were considered. This paper summarises the results of the whole-body photon dosemeter test. Twenty-six dosimetry services from all EU Member States and Switzerland participated. Twelve different radiation fields were used to simulate various workplace irradiation fields. Dose values from 0.4 mSv to 80 mSv were chosen. From 312 single results, 26 fell outside the limits of the trumpet curve and 32 were outside the range 1/1.5 to 1.5. Most outliers resulted from high energy R-F irradiations without electronic equilibrium. These fields are not routinely encountered by many of the participating dosimetry services. If the results for this field are excluded, most participating services satisfied the evaluation criteria.     

A thermoluminescence dosimetry system for personal monitoring in Ireland

In 1993 the decision was taken to replace film badges with thermoluminescence dosemeters (TLDs) as the main form of dosemeter for both whole-body and extremity monitoring at the Dosimetry Service of the Radiological Protection Institute of Ireland (RPII) in Dublin. A review of commercially available automatic TLD systems was carried out to identify the system which best met the RPII's requirements. This paper describes the dosimetry system used, and, in addition, discusses the problems encountered and how these were addressed.     

A Practical Implementation of Silicon Microchannel Coolers for High Power Chips

This paper describes a practical implementation of a single-phase Si microchannel cooler designed for cooling very high power chips such as microprocessors. Through the use of multiple heat exchanger zones and optimized cooler fin designs, a unit thermal resistance 10.5 C-mm² /W from the cooler surface to the inlet water was demonstrated with a fluid pressure drop of <35kPa. Further, cooling of a thermal test chip with a microchannel cooler bonded to it packaged in a single chip module was also demonstrated for a chip power density greater than 300W/cm². Coolers of this design should be able to cool chips with average power densities of 400W/cm² or more     

Autoxidation and effects of pro- and antioxidants in lyophilized red blood cell membranes

Oxygen uptake and effects of pro- and antioxidants have been compared at 80 C in lyophilized red blood cell (RBC) bilayer membranes (ghosts). In this dry and relatively immobile system, catalytic metals have pronounced effects. When ghosts are prepared in the usual manner, in phosphate buffer, hypotonic saline, or deionized water (DI), oxygen uptake is extremely slow and limited unless: (a) catalytic metal, e.g., cobaltous ion, is supplied in the absence of metal-complexing buffers and (b) residual phosphate buffer is removed by repeated deionized water or hypotonic saline washes. Ghosts adsorb d-α-tocopherol strongly from 1% alcohol emulsion in buffer in amounts far above normal RBC concentrations, whereas synthetic antioxidant uptake seldom exceeds the normal tocopherol level. Uptake and effectiveness of antioxidants introduced by either perfusion or in the vapor phase, and resistance of ghosts to autoxidation are discussed as they relate to protection of lyophilized membranes and freeze-dried foods.     

Electrical characteristics of thin Ni2Si,NiSi, and NiSi2 layers grown on silicon

We have determined the resistivity, carrier concentration, and Hall mobility as a function of thickness (700–3000 Å) of Ni₂Si, NiSi, and NiSi₂ layers formed by vacuum annealing at 270÷v300°C, ≈ 400°C, and ≈ 800°C, respectively, of nickel films vacuum-deposited on a silicon substrate (111 n-type and 100 p-type Si ρ ≈ 1KΩ). The layer thicknesses were measured by 2 MeV⁴He⁺ backscattering spectrometry. The silicide phase was confirmed by x-ray measurements. The electrical measurements were carried out using van der Pauw configuration. We found the electrical transport parameters to be independent of the film thickness within the experimental uncertainty. The Hall factors were assumed to be unity. The majority carriers are electrons in NiSi and holes in Ni₂Si and NiSi₂. The resistivity values are 24±2, 14±1, and 34±2 μΩcm, the electron concentrations are 9±3, 10 and 7±1, and ≈ 2 × 10²² cm^?3, and the Hall mobilities are 3±1, ≈ 4.5 and 6, and ≈ 9 cm²/Vs for Ni₂Si, NiSi (〈100〉 and 〈111〉), and NiSi₂, respectively. The systematic error in the measured values caused by currents in the high resistivity substrate is estimated to be less than 6% for the Hall coefficient. The results show that Ni₂Si, NiSi, and NiSi₂ layers formed by a thin film reaction are electrically metallic conductors, a result which concurs with those reported previously (1) for refractory metal silicides. The Hall mobility increases with the Si content in the silicide. The electron concentration is lowest for NiSi₂ leading to the highest resistivity for the epitaxial phase of NiSi₂.     

Modal Analysis of the Quasi-Optical Performance of Phase Gratings

This paper is concerned with the analysis of phase gratings as passive quasi-optical multiplexing devices. One important application of such components is in the local oscillator injection chain of heterodyne array receivers. Gaussian beam mode analysis can be applied as a powerful tool when modelling the optical performance of phase gratings in a real submillimeter system of finite throughput and bandwidth. In our experimental investigations we have concentrated on the Dammann Grating (DG) which is a binary optical component and thus straightforward to manufacture. A number of quartz gratings were fabricated and carefully tested to evaluate the practical limitations of such quasi-optical components. Because of its convenient refractive index quartz can be used to produce gratings with very low reflection losses. The results presented confirm DGs to be particularly suitable multiplexers for sparse arrays of finite bandwidth.     

The AutoPap system for primary screening in cervical cytology. Comparing the results of a prospective, intended-use study with routine manual practice

OBJECTIVE: To evaluate the effectiveness of the AutoPap System in detecting abnormal and normal cervical smears when used in a primary screening/quality control mode, as compared with currently established laboratory practices. STUDY DESIGN: Slides were obtained prospectively and were initially processed in the routine fashion with cytotechnologist screening followed by 10% random quality control rescreening. Slides were then processed on the AutoPap System and allocated into the following groups: (1) approximately 25% of the lowest-ranking slides were placed in the laboratory's archives as within normal limits; (2) the remaining approximately 75% of slides were subjected to manual screening. Approximately 15% of the highest-ranking slides in this group underwent quality control rescreening. For each slide needing manual screening, the cytotechnologist was supplied with a report giving the ranking score of that slide. All discrepant slides for either adequacy or diagnosis were subjected to a truth-determination process. The results obtained from the two arms of the protocol were then compared. RESULTS: The AutoPap System-assisted arm of the study was superior to the current practice arm for the identification of abnormal slides at the level of atypical squamous cells of undetermined significance and above (ASCUS+), low grade squamous intraepithelial lesion (LSIL) and higher LSIL+. AutoPap System-assisted practice was equivalent to current practice for the identification of unsatisfactory and satisfactory but limited by slides. All results showed statistical significance. In addition, AutoPap System-assisted practice in the study indicated improved specificity of diagnosis. CONCLUSION: AutoPap System-assisted practice shows superior sensitivity and specificity when compared to current practice. Its clinical use as a primary screening device should improve the overall practice of cervical cytology as well as provide potential enhancement in overall laboratory productivity.     

A Probabilistic Evaluation of the Least Squares Strain Tensor Derived from a Three-Dimensional Modular Strain Rosette Using the Monte-Carlo Technique

Abstract:  Strain gradients give rise to a number of problems in the field of embedded three-dimensional strain measurement. In order to avoid these problems a modular type three-dimensional strain rosette was embedded into known strain fields and the data from the individual gauges compared with theoretical predictions. Finally, the least squares strain tensor was predicted from experimental data analysed using the Monte-Carlo technique and the theoretical results forecast from finite element data taking into account the mechanical properties of the carrier, plug and prismatic bar. Some of the experimental results were found to correlate well with the theoretical values but some values in the least squares strain tensor, in particular under compression and torsional loading, departed considerably from the theoretical values. It was found that the effect of the measurement errors in the individual gauges combined with the matrix operations in the least squares strain tensor were responsible for biasing the resultant tensor data. However, the modular technique provided a solution to the problem of strain gradients.