An exercise in program design using SIMULA class invariants

The concept of an invariant assertion has been shown by Hoare to be central to the problem of proving correctness of data representation in a program. A consequent approach for program design is to establish the parts of an overall invariant which characterize the components of the design. In this way it is feasible to synthesize a verified program. There is a gulf between verification theory and practical reality in this area, but the SIMULA class concept is close to the data representation technique required for such an approach. Some of the benefits and problems of this approach to design have been explored by the development of a SIMULA program to simulate a bounded delay resource allocation strategy in a job scheduling environment.     

Chest wall thickness measurements and the dosimetric implications for male workers in the south Korean uranium industry

Using ultrasound techniques, the Human Monitoring Laboratory has measured chest wall thicknesses of a group of male workers at the Korea Atomic Energy Research Institute. A site-specific biometric equation has been developed for these workers, who are somewhat smaller than other workers reported in the literature. Chest wall thickness is an important modifier on lung counting efficiency. These data have been put into the perspective of the ICRP recommended dose limits for occupationally exposed workers: 100 mSv in a 5-year period with a maximum of 50 mSv in any one year. For measured chest wall thicknesses of 1.9 cm to 4.1 cm and a 30 min counting time, the achievable MDAs for natural uranium in the KAERI lung counter vary from 6.6 mg to 13.2 mg. These values are close to, or even exceed, the predicted amounts of natural uranium that will remain in the lung (absorption type M and S) after an intake equal to the Annual Limit on Intake corresponding to a committed dose of 20 mSv. This paper shows that the KAERI lung counter probably cannot detect an intake of Type S natural uranium in a worker with a chest wall thickness equal to the average value (2.7 cm) under routine counting conditions.     

Response of radiation protection dosemeters in mixed high-energy photon and electron radiation fields

The response of radiation protection dosemeters in terms of the phantom-related operational quantities Hp(10) and H'(10.0 degrees) was measured for personal and area monitoring systems in mixed high-energy electron and photon radiation fields with energies up to 7 MeV. Using mixed radiation fields composed of different fractions of charged particle and photon fluence, three conditions were produced at the point of measurement: charged particle equilibrium (CPE) (a), a lack (b) and an excess (c) of charged particles relative to the conditions of CPE. Personal and area dosemeters of different types were investigated under conditions (a)-(c). A large variability of the response of the different dosemeter types was observed. The results are presented and discussed.     

Strategies for Source-to-Source Constant Propagation

Data-flow optimizations are usually implemented on low-level intermediate representations. This is not appropriate for source-to-source optimizations, which reconstruct a source level program after transformation. In this paper we show how constant propagation, a well known data-flow optimization problem, can be implemented on abstract syntax trees in Stratego, a rewriting system extended with programmable rewriting strategies for the control over the application of rules and dynamic rewrite rules for the propagation of information.     

UV Laser Micromachining of Polymers for Microfluidic Applications

We have recently begun to explore the use of UV laser ablation micromachining to construct microfluidic devices in polymers. This technique can create microchannels rapidly and modify the resulting polymer surface in a single step. By ablating under different atmospheres, it is possible to alter both the surface chemistries and physical surface morphologies of the microchannels. We have employed electroosmotic flow measurements, chemical mapping, and optical microscopy to characterize the microfluidic devices. In addition, we have studied the parameters affecting the ablation, such as the laser wavelength, laser fluence, laser firing repetition rate, and the material being ablated.     

Role of protein kinase C (PKC) in agonist-induced mu-opioid receptor down-regulation: I. PKC translocation to the membrane of SH-SY5Y neuroblastoma cells is induced by mu-opioid agonists

Phosphorylation of specific amino acid residues is believed to be crucial for the agonist-induced regulation of several G protein-coupled receptors. This is especially true for the three types of opioid receptors (mu, delta, and kappa), which contain consensus sites for phosphorylation by numerous protein kinases. Protein kinase C (PKC) has been shown to catalyze the in vitro phosphorylation of mu- and delta-opioid receptors and to potentiate agonist-induced receptor desensitization. In this series of experiments, we continue our investigation of how opioid-activated PKC contributes to homologous receptor down-regulation and then expand our focus to include the exploration of the mechanism(s) by which mu-opioids produce PKC translocation in SH-SY5Y neuroblastoma cells. [D-Ala2,N-Me-Phe4,Gly-ol]enkephalin (DAMGO)-induced PKC translocation follows a time-dependent and biphasic pattern beginning 2 h after opioid addition, when a pronounced translocation of PKC to the plasma membrane occurs. When opioid exposure is lengthened to >12 h, both cytosolic and particulate PKC levels drop significantly below those of control-treated cells in a process we termed "reverse translocation." The opioid receptor antagonist naloxone, the PKC inhibitor chelerythrine, and the L-type calcium channel antagonist nimodipine attenuated opioid-mediated effects on PKC and mu-receptor down-regulation, suggesting that this is a process partially regulated by Ca2+-dependent PKC isoforms. However, chronic exposure to phorbol ester, which depletes the cells of diacylglycerol (DAG) and Ca2+-sensitive PKC isoforms, before DAMGO exposure, had no effect on opioid receptor down-regulation. In addition to expressing conventional (PKC-alpha) and novel (PKC-epsilon) isoforms, SH-SY5Y cells also contain a DAG- and Ca2+-independent, atypical PKC isozyme (PKC-zeta), which does not decrease in expression after prolonged DAMGO or phorbol ester treatment. This led us to investigate whether PKC-zeta is similarly sensitive to activation by mu-opioids. PKC-zeta translocates from the cytosol to the membrane with kinetics similar to those of PKC-alpha and epsilon in response to DAMGO but does not undergo reverse translocation after longer exposure times. Our evidence suggests that direct PKC activation by mu-opioid agonists is involved in the processes that result in mu-receptor down-regulation in human neuroblastoma cells and that conventional, novel, and atypical PKC isozymes are involved.     

On rf-magnetoresistance and flux flow resistivity of NbTi

The temperature and magnetic field dependences of the surface impedance of Nb50^wt/oTi were investigated with a TE₀₁₁-mode cavity operated at a frequency of 9.67 GHz. The results with the cavity cooled down in the earth's magnetic field show good agreement with the BCS-behaviour of the surface resistance in the Meissner state when a reduced gap, of 1.97, and a mean free path of 0.5 nm are assumed. Measurements in external magnetic fields up to 3 T were used to obtain the flux flow resistivity (FFR) of NbTi. The FFR obtained in this way shows a marked deviation from the phenomenological straight line behaviour , which has been found all low- and medium-K superconductors. This indicates that the high K of NbTi leads to reduced flux flow losses at lower magnetic fields in qualitative agreement with calculations by Hu and Thompson for gapless high-K superconductors. Investigations of the temperature dependence of the ffr resulted in a resistance minimum being deeper and occurring at higher temperatures than those which have been reported for all other materials investigated to date.     

Thin films of semiconductors and dielectrics produced by laser evaporation

Thin films of several III–V and II–VI compounds as well as of some dielectrics have been vacuum-deposited using a focused beam of a CO₂ or ruby laser to evaporate these materials. The crystallinity, morphology and the chemical composition of the produced thin films have been examined by various analytical methods. Films produced by the ruby laser were in most cases polycrystalline and stoichiometric, while films produced by the CO₂ laser were amorphous and non-stoichiometric. Different mechanisms of evaporation leading to the observed differences in characteristics of thin films are discussed.