Evaluating and assessing process hazard analyses

Process hazard analysis (PHA) is widely used across a spectrum of industries and facilities, but there are few metrics for the evaluation and assessment of PHAs. Most existing protocols address PHA solely in terms of regulatory compliance, but do not address the completeness or depth of the assessment, as most PHAs have been performed on a "performance basis" under the relevant regulations. It is possible to objectively assess PHAs, in order to determine adequacy of completion and degree of review, using both audit protocol and scoring approaches. Audit protocol approaches offer simplicity and ease of use, and when combined with specific scoring for adequacy allow for informed decisions about remedial action with respect to the PHA.     

Deposition of size-selected metal clusters generated by magnetron sputtering and gas condensation: a progress review

This paper presents a topical review of the production and deposition of size-selected metal clusters generated by magnetron sputtering and gas condensation. Clusters with up to 75,000 atoms can be obtained by controlling the gas pressure in the sputtering source, prior to size selection with a novel (time-of-flight) mass filter. The clusters are deposited on the model graphite substrate to study the cluster-surface interaction. Two regimes for cluster deposition have been identified at elevated impact energies: (i) 'pinning' (ca. 10 eV per atom) and (ii) implantation (ca. 100 eV per atom). Of particular importance is the pinning regime, since this allows the fabrication of monodispersed cluster arrays, which are stable against diffusion at room temperature (and above). The deposition of size-selected metal clusters represents a novel method of preparing surface nanostructures, with potential applications including model catalyst studies and the immobilization of biological molecules.     

Decoration of surfaces with size-selected clusters and molecular manipulation at room temperature: precision and uncertainty in organizing atoms

The deposition onto surfaces of clusters of atoms, prepared and size-selected in the gas phase, is, like atomic or molecular manipulation with the scanning tunnelling microscope, an appealing (but parallel) route to the creation of nanoscale surface features. Both of these seemingly orthogonal approaches allow, in principle, a selected number of atoms to be organized, and both are strongly affected by the lateral thermal diffusion of the constituent atoms, molecules or clusters over the surface. In this sense, the room-temperature (as opposed to cryogenic-temperature) regime can be regarded as a hostile environment for organizing atoms. In this paper we review recent achievements in size-selected cluster deposition and molecular manipulation at room temperature and thus address the fundamental question: with what precision can we organize atoms at room temperature?     

Liposome accumulation in ischaemic intestine following experimental mesenteric occlusion

Chromosome complements of murine thymic lymphomas induced by an alkylating agent N-methyl-N-nitrosourea (MNUA) were analyzed microscopically and karyotypically using the Q-banding technique. The chemical carcinogen was injected intraperitoneally into either neonatal or 7-week-old CFW/D mice. In addition, thymic lymphomas induced in 7-week-old AKR mice and thymic lymphomas developed spontaneously in this strain were also examined. All six lymphomas induced in neonatal CFW/D had hyperdiploid cell lines that accounted for 90% of the cells analyzed. Chromosome analysis of lymphomas induced in adult DFW/D mice showed that only out of nine lymphomas had predominantly hyperdiploid cell lines. The remaining five lymphomas had diploid modal chromosome number although they also carried a variant line characterized by 41 chromosomes. All eight lymphomas induced in adult AKR mice and six out of seven spontaneous AKR lymphomas showed predominantly diploid modal line. The remaining spontaneous lymphoma had a hyperdiploid stem line of 41 chromosomes. Microscopic and karyotypic analysis further identified trisomy 15 as the regular chromosome abnormality in the hyperdiploid cells in lymphomas of each group, whereas cells with diploid chromosome number had no detectable chromosome abnormality. Additional trisomies were also found, but their appearance was restricted to individual tumors. Thus, the incidence of trisomy 15 in lymphomas induced by MNUA in adult CFW/D and AKR mice, as well as in the spontaneous AKR lymphomas, is significantly lower than that in lymphomas induced in neonatal mice by the same carcinogen.     

Doses to fetal and maternal organs from intravenous 59FeCl3 or 57CoCl2

Doses from intravenous intakes of 59Fe or 57Co chloride during pregnancy were estimated. Near term fetal organ doses were derived via the MIRDOSE3 newborn phantom, with mean dose/cumulated activity (S) values rescaled for compatibility with near term fetus whole body S. A detailed in vivo biodistribution database provided indications of residence times in important maternal and fetal organs. 59Fe doses to the fetus whole body from early to late pregnancy were 7-11 mGy MBq(-1) (8.5-14.3 mSv MBq(-1)), similar to that to the mother. Doses to near term fetal spleen (59 mGy MBq(-1)), liver (36), and red marrow (9) were similar or higher than to the mother. 57Co doses to fetus whole body from early to late pregnancy were 0.7-3.3 mGy MBq(-1) (2.5-8.2 mSv MBq(-1)), similar or higher than to the mother. Doses to near term fetal small intestine (34 mGy MBq(-1)). liver (4.7) and red marrow (2.7) were similar or higher than to the mother.     

Phosphorylcholine-based polymer coatings for stent drug delivery

Phosphorylcholine-based polymers have been used commercially to improve the biocompatibility of coronary stents. In this study, one particular polymer is assessed for its suitability as a drug delivery vehicle. Membranes of the material are characterized in terms of water content and molecular weight cut-off, and the presence of hydrophilic and hydrophobic domains investigated by use of the hydrophobic probe pyrene. The in vitro loading and elution of a variety of drugs was assessed using stents coated with the polymer. The rate of a drug's release was shown not to be simply a function of its water solubility, but rather more closely related to the drug oil/water partition coefficient. This finding was explained in terms of the more hydrophobic drugs partitioning into, and interacting with, the hydrophobic domains of the polymer coating. The suitability of the coated stent as a drug delivery vehicle was assessed in vivo using a radiolabeled analog of one of the more rapidly eluting drugs, angiopeptin. Autoradiography showed that the drug was released locally to the wall of the stented artery, and could be detected up to 28 days after implantation.     

Electrokinetic injection for stacking neutral analytes in capillary and microchip electrophoresis

An on-column mechanism for electrokinetically injecting long sample plugs with simultaneous stacking of neutral analytes in capillary electrokinetic chromatography is presented. On-column stacking methods allow for the direct injection of long sample plugs into the capillary, with narrowing of the analyte peak width to allow for an increase in the detected signal. Low-pressure injections (approximately 50 mbar) are commonly used to introduce sample plugs containing neutral analytes. We demonstrate that injection can be accomplished by applying an electric field from the sample vial directly into the capillary, with neutral analytes injected by electroosmotic flow at up to 1 order of magnitude faster than the corresponding pressure injections. Since stacking occurs simultaneously with electrokinetic injection, stacking is initiated at the capillary inlet, resulting in an increased length of capillary remaining for separation. Reproducibility obtained for peak height and peak area with electroosmotic flow injection is comparable to that obtained with the pressure injection mode, while reproducibility of analysis time is markedly improved. Electrokinetic stacking of neutral analytes utilizing electroosmotic flow is demonstrated with discontinuous (high conductivity, high mobility) as well as continuous (equal conductivity, equal mobility) sample electrolytes. Injecting neutral analytes by electroosmotic flow affords a 10-fold or greater decrease in analysis times when capillaries of 50-microm i.d. or smaller are used. This stacking method should be exportable to dynamic pH junction stacking and electrokinetic chromatography with capillary arrays. Equations describing this electrokinetic injection mode are introduced and stacking of a neutral analyte on a microchip by electrokinetic injection using a simple cross-T channel configuration is demonstrated.     

Miniature heart cell force transducer system implemented in MEMS technology

A fully submersible force transducer system for use with isolated heart cells has been implemented using microelectromechanical systems (MEMS) technology. By using integrated circuit fabrication techniques to make mechanical as well as electrical components, the entire low-mass transducer is only a few cubic millimeters in size and is of higher fidelity (approximately 100 nN and 13.3 kHz in solution) than previously available. When chemically activated, demembranated single cells attached to the device contract and slightly deform a strain gauge whose signal is converted to an amplified electrical output. When integrated with a video microscope, the system is capable of optical determination of contractile protein striation periodicity and simultaneous measurement of heart cell forces in the 100-nN to 50-microN range. The average measured maximal force was Fmax = 5.77 +/- 2.38 microN. Normalizing for the cell's cross-sectional area, Fmax/area was 14.7 +/- 7.7 mN/mm2. Oscillatory stiffness data at frequencies up to 1 kHz has also been recorded from relaxed and contracted cells. This novel MEMS force transducer system permits higher fidelity measurements from cardiac myocytes than available from standard macro-sized transducers.     

Industry case studies in the use of immersive virtual assembly

In this paper, we report on two engineering case studies that have been conducted as part of a Virtual Assembly Technology Consortium. The objectives of the case studies were to determine if immersive virtual assembly capabilities allow industry assembly situations to be modelled and studied realistically, and to demonstrate the downstream value of the virtual assembly capabilities in areas such as ergonomics, assembly installation, process planning, installation, and serviceability. What is of special significance is that instead of modelling simplified problems or perceived representative situations, the case studies were constructed from actual assembly floor projects and situations encountered at industry member sites and with considerable participation from industry engineers and manufacturing shop floor personnel. Based on the success of the case studies, the consortium members inferred that virtual assembly methods are poised to move out of the realm of special projects and test scenarios to deployment in the actual design and manufacturing cycle. However, in order to be truly accepted in industry, there are still issues to be addressed in terms of ease of use, portability of the applications, and preparation of the models for the evaluations. Thus, the case studies added a new dimension to the exploration and understanding of how this new technology could be of practical value in industry.     

Numerical Optimization of an Active Voltage Controller for High-Power IGBT Converters

Feedback control of insulated gate bipolar transistors (IGBTs) in the active region can be used to regulate the device switching trajectory. This facilitates series connection of devices without the use of external snubber networks. Control must be achieved across the full active region of the IGBT and must balance a number of conflicting system goals including diode recovery. To date, the choice of control parameters has been a largely empirical process. This paper uses accurate device models and formalized optimization procedures to evaluate IGBT active voltage controllers. A detailed optimization for the control of IGBT turn-on is presented in this paper