Effects of power line voltage variations on different types of400-W high-pressure sodium ballasts

This paper presents the results of laboratory tests to determine the effects of voltage sags, interruptions and fluctuations on high-pressure sodium (HPS) lamps and ballasts. The way these ballasted lamps react to sags and interruptions in the laboratory is then compared to a model of the real-world electrical environment created from data gathered during three recent North American power quality surveys. This work also shows how HPS immunity to voltage variations depends significantly on the ballast type and the lamp age     

A measles epidemic controlled by immunisation

AIM: In 1997, an immunisation campaign, using measles-mumps-rubella vaccine, was planned for children aged 2-10 years to prevent a measles epidemic predicted by mathematical modelling. The epidemic started before the campaign and is described here. METHOD: Measles hospitalisation, notification and laboratory data were combined. RESULTS: The epidemic started in April 1997 and was largely over by January 1998. No deaths were identified and only one hospitalisation was coded as measles encephalitis, compared to seven deaths and ten cases of measles encephalitis in the 1991 epidemic. For the 12 months from 1 March 1997 there were 2,169 (60 per 100,000) measles cases identified, 314 (9 per 100,000) of whom were hospitalised. Two-thirds of hospitalised cases were notified. The age-standardised measles incidence rates were 33, 34, and 174 per 100,000 for Europeans, Maori and Pacific people, respectively. The respective age-standardised hospitalisation rates were 4, 9 and 32 per 100,000. Measles incidence was highest for under one-year-olds (904 per 100,000) and low for 11-16 year-olds (27 per 100,000)--the cohort previously offered a second vaccine dose. Most cases were aged 10 years and under, and this group were the main drivers of virus transmission. CONCLUSIONS: The immunisation campaign prevented 90-95% of predicted cases. The campaign was appropriately targeted at children aged 10 years and under.     

Analysis on the surface adsorption of PEO/PPO/PEO triblock copolymers by radiolabelling and fluorescence techniques

We have examined the adsorption of poly(ethylene oxide)/ poly(propylene oxide)/poly(ethylene oxide) (PEO/PPO/PEO) triblock copolymers (Pluronics?) on dimethyldichlorosilane-treated glass (DDS-glass). The surface concentration of ¹²⁵I-labeled Pluronic F-68(76/30/76) reached a maximum of 0.3 μg/cm² when the bulk concentration in the adsorption solution was 3.0 mg/mL. Above 5.0 mg/ml, the surface Pluronic F-68 concentration started to decrease and reached 0.17 μg/cm² when the bulk concentration for adsorption was 10 mg/mL. The surface concentration of Pluronic F-108 (129/56/129), on the other hand, increased to 4.0 μg/cm² at the same bulk concentration. Fluroscence spectroscopic studies using pyrene suggested that the Pluronic F-68 molecules self-associated at the bulk concentration of 5.0 mg/mL and above. Because the aggregates are expected to expose the hydrophilic PEO segments to water, they may have lower affinity to DDS-glass. Aggregation of Pluronic F-68 also decreases the number of individual Pluronic molecules for adsorption. Pyrene fluorescence in Pluronic F-108 solution, however, suggests that Pluronic F-108 molecules do not form aggregates. It appears that the high surface concentrations of Pluronic F-108 may result from the preferential adsorption of individual molecules in multilayers. This explains the high effectiveness of Pluronic F-108 in preventing protein adsorption and platelet adhesion when adsorbed on to be hydrophobic surface. © 1994 John Wiley & Sons, Inc.     

Ibuprofen Release from Beads Coated with an Experimental Latex: Effect of Certain Variables

The objective of this study was to evaluate the effect of factors such as drug loading, particle size, plasticizer type, antiadherent type, and annealing method on the release of ibuprofen from controlled-release beads coated with an experimental latex. Further, the in vitro release kinetics and mechanism of drug transport across the polymeric membrane have been investigated. Ibuprofen-loaded beads were coated with the experimental latex using a fluidized-bed coating machine (Uniglatt). The drug release from these spherical membrane reservoir systems appeared to be diffusion controlled. Evaluation of the effect of osmotic pressure by using dissolution media of various osmolal concentrations indicated that it has no significant effect on the drug release. To further elucidate the mechanism of release from these polymeric membranes, the permeation of drug through free films was studied.     

Fault detection in analogue circuits using hybrid evolutionary algorithm and neural network

With the development of analog integrated circuits technology and due to the complexity, and various types of faults that occur in analog integrated circuits, fault detection is a new idea, has been studied in recent decades. In this paper a three amplifier state variable filter is used as circuit under test (CUT) and, a hybrid neural network is proposed for soft fault diagnosis of the CUT. Genetic algorithm (GA) has the powerful ability of searching the global optimal solution, and back propagation (BP) algorithm has the feature of rapid convergence on the local optima. The hybrid of two algorithm will improve the evolving speed of neural network. GA-BP scheme adopts GA to search the optimal combination of weights in the solution space, and then uses BP algorithm to obtain the accurate optimal solution quickly. Experiment results show that the proposed GA-BP scheme is more efficient and effective than BP algorithm.     

Risk analysis: Casing-while-Drilling (CwD) and modeling approach

In today's volatile economy and uncertain drilling environment, managers are encouraged to reduce well cost and time and have implemented Casing-while-Drilling (CwD) to improve operational excellence. Risk analysis is another valid tool that can be used to improve drilling operations. This paper discusses CwD as a new technology and how its benefits can be strengthened by including risk analysis as a complementary technique. A modeling approach is presented to demonstrate how risk analysis can be applied to CwD programs and to discuss the main concerns a well planner must address to achieve a successful drilling program. The integration of both CwD and risk analysis will add value to the overall excellence of the well operation. Very little work has been done on this integration, and the hope is that this approach will be a standard practice in the future.     

Personal identification using feature and score level fusion of palm- and fingerprints

The ever increasing demand of security has resulted in wide use of Biometric systems. Despite overcoming the traditional verification problems, the unimodal systems suffer from various challenges like intra class variation, noise in the sensor data etc, affecting the system performance. These problems are effectively handled by multimodal systems. In this paper, we present multimodal approach for palm- and fingerprints by feature level and score level fusions (sum and product rules). The proposed multi-modal systems are tested on a developed database consisting of 440 palm- and fingerprints each of 55 individuals. In feature level fusion, directional energy-based feature vectors of palm- and fingerprint identifiers are combined to form joint feature vector that is subsequently used to identify the individual using a distance classifier. In score level fusion, the matching scores of individual classifiers are fused by sum and product rules. Receiver operating characteristics curves are formed for unimodal and multimodal systems. Equal Error Rate (EER) of 0.538% for feature level fusion shows best performance compared to score level fusion of 0.6141 and 0.5482% of sum and product rules, respectively. Multimodal systems, however, significantly outperform unimodal palm- and fingerprints identifiers with EER of 2.822 and 2.553%, respectively.     

Photophysical Characterization of Insulin Denaturation and Aggregation at Hydrophobic Interfaces

The peak III/I ratio of pyrene monomer fluorescence was used to characterize surface-induced insulin denaturation and aggregation. An indicator of the hydrophobicity of pyrene's microenvironment, the IIM ratio can be used to study self-association of amphipathic molecules. In sodium lauryl sulfate (NaLS), the III/I ratio was 0.71 below the critical micelle concentration (CMC) and increased to 0.98 when the concentration was above the CMC. When insulin was placed in a polystyrene cuvet for 2 days at 37°C, the IWI ratio decreased from 0.84 to 0.78. The decrease in III/I ratio corresponds to surface-induced denaturation of insulin which exposed pyrene to a more polar environment. Increasing the duration of incubation for up to 12 days increased the III/I ratio to 1.06. Increased hydrophobicity of pyrene's environment correlates with the self-association of insulin. Once the aggregates reached a critical size, they began precipitating as was evident by an increase in the turbidity (absorbance at 600 nm) of solution. The results of this study support previous hypothesis that the aggregation and precipitation of insulin at hydrophobic interfaces is initiated by adsorption and surface-induced denaturation.     

Modulation of phosphatidylcholine biosynthesis by peroxisome proliferating fatty acid analogues

The modulation of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) biosynthesis by sulfur-substituted fatty acid analogues has been investigated in rats. We have compared the effects of two non-β-oxidizable fatty acid analogues, 3-thiadicarboxylic acid and tetradecylthioacetic acid, which induce proliferation of peroxisomes, with those of the analogue tetradecylthiopropionic acid, which is a weak peroxisome proliferator. Repeated administration of 3-thiadicarboxylic acid for seven days resulted in increased hepatic concentrations of both PC and PE, but the PC/PE ratio was decreased. PC synthesis was increased, as evidenced by increased incorporation of [³H]choline into PC and an increased activity of cytidinetriphosphate (CTP): phosphocholine cytidylyltransferase. This was accompanied by a reduction in the pool sizes of choline and phosphocholine. TheS-adenosylmethione/S-adenosylhomocysteine ratio (AdoMet/AdoHcy) was marginally affected, indicating no increase in the rate of methylation of PE to PC. Administration of tetradecylthioacetic acid also resulted in increased hepatic phospholipid levels, increased AdoMet/AdoHcy ratios and in slightly elevated activity of CTP:phosphocholine cytidylyltransferase. The most striking effect observed after tetradecylthiopropionic acid treatment was the development of fatty liver. The activity of CTP:phosphocholine cytidylyltransferase and the incorporation of [³H]choline into PC was reduced compared to 3-thiadicarboxylic acid treatment. Although the rate of methylation of PE seemed to be increased at an elevated AdoMet/AdoHcy ratio, this resulted in only minor changes in the hepatic PC and PE levels, and the PC/PE ratio remained unchanged. Furthermore, the hepatic levels of choline and phosphocholine were reduced in these rats. The activities of the two enzymes competing for choline in the liver, choline kinase and choline dehydrogenase were changed in opposite directions, with the activity of choline kinase increasing approximately 1.5-fold. In addition, it was found that the level of homocysteine was elevated in the liver of tetradecylthiopropionic acid-treated rats. The possibility is discussed that this reflects a reduced flux of choline through the oxidative pathway in the liver. In tetradecylthiopropionic acid-treated rats, there seemed to be a coordinated regulation of the two pathways for PC biosynthesis, with an increase in the methylation of PE to PC and a reduced synthesisvia the CDPcholine pathway. The increase in PC observed in rats treated with 3-thiadicarboxylic acid and tetradecylthioacetic acid suggests that increased PC synthesis is linked to peroxisome proliferation.     

Electrochemistry of chlorogenic acid: experimental and theoretical studies

Cyclic voltammetry, chronoamperometry and rotating disk electrode voltammetry as well as quantum chemical methods, are used for electrochemical study of chlorogenic acid, as an important biological molecule. The standard formal potential, diffusion coefficient, and heterogeneous electron transfer rate constant of chlorogenic acid in aqueous solution are investigated. Acidic dissociation constant of chlorogenic acid is also obtained. Quantum mechanical calculations on oxidation of chlorogenic acid in aqueous solution, using density functional theory are presented. The change of Gibbs free energy and entropy of oxidation of chlorogenic acid are calculated using thermochemistry calculations. The calculations in aqueous solution are carried out with the use of polarizable continuum solvation method. Theoretical standard electrode potential of chlorogenic acid is achieved to be 0.580 V versus standard calomel electrode (SCE) which is in agreement with the experimental value of 0.617 V obtained experimentally in this work. The difference is consistent with the values we previously reported for other quinone derivatives.