A disturbance model for control/structure optimization with output feedback control

This paper deals with a technique for the integrated optimization of structure and control in the design of flexible systems. The current approach uses the concept of response to dynamic constraints to establish a concise variational methodology to total system optimization, and eliminates the need to specify rather arbitrary trade-offs between control energy and structural mass. Results give an explicit dependency between structural stiffness (hence mass), disturbance magnitude, available control energy, and deflection constraints. The current paper presents results for direct output feedback and dynamic filter compensation with optional positive real constraints on the filters. The key element of the design approach is to formulate a set of response constraints that bound the allowable deflections and a set of constraints that bound the allowable control energy. The results for model structures indicate the importance of the control-structure interaction in a light-weight structure and the trade-offs between controller complexity, energy and structural mass.     

Steep fronted surges applied to large AC motors-effect of surgecapacitor value and lead length

The line end coil of large AC motors is known to suffer increased inter-turn voltage stress under steep fronted surge conditions. Surge capacitors can be used to slow down the surge rise-time. The effects of capacitor value and lead length on the line end coil voltage are examined. The theoretical and measured waveforms for the line end coil of a 3.3 kV, 1 MW, four-pole induction motor are compared. The results show clearly that when the capacitor lead length approaches 1, even a relatively large capacitor value has little effect     

Measuring oxygen tension in the anterior chamber of rabbits

PURPOSE: Measuring the concentration of oxygen in the aqueous humor without penetrating the eye would provide a new dimension in understanding aqueous humor and corneal dynamics. In this study a preinvasive method was developed for determining the cameral oxygen concentration in anesthetized rabbits by measuring the excited-state lifetime of a phosphorescent dye. METHODS: A scanning ocular fluorometer was designed to excite phosphorescence with a brief flash of light and to measure the decay of luminescence for as long as 1000 microsec after excitation. The measurement window was scanned through the depth of the anterior chamber or fixed at the mid-anterior chamber. A depot of the phosphorescent dye Pd-uroporphyrin was injected into the vitreous of eight pigmented rabbits, and within a few days the dye was measurable in the anterior chamber. The excited-state lifetime of this dye is inversely correlated to oxygen concentration and was calibrated by measuring the lifetime of dye in cuvettes equilibrated with oxygen-nitrogen mixtures. Oxygen tensions were determined from lifetimes measured in the open eye, under a polymethylmethacrylate (PMMA) contact lens, under two oxygen-permeable contact lenses, and immediately after lid closure. RESULTS: Oxygen tension in the mid-anterior chamber before placing a PMMA contact lens was 23 +/- 3 mm Hg (mean +/- SD; n = 6). After 20 minutes of PMMA lens wear, oxygen tension decreased to 4 +/- 2 mm Hg. When the focal diamond was scanned through the anterior chamber, oxygen tension was 24 +/- 5 mm Hg near the corneal endothelium and decreased to 17 +/- 8 mm Hg near the crystalline lens. Under the PMMA contact lens this gradient reversed: Oxygen tensions near the endothelium and lens were 3 +/- 2 mm Hg and 6 +/- 2 mm Hg, respectively. Lid closure for 10 minutes or longer decreased the mid-anterior chamber oxygen tension from 21 +/- 2 mm Hg (n = 19 measurements from seven animals) to 10 +/- 3 mm Hg (n = 15 measurements from five animals). CONCLUSIONS: Measuring excited-state lifetime of phosphorescent dyes in the anterior chamber provides a useful method for determining oxygen concentration in vivo, without penetrating the eye. Cameral oxygen tension under PMMA contact lenses are significantly lower than in the uncovered eye. The profile of oxygen tension through the anterior chamber suggests that oxygen is supplied transcorneally to the aqueous humor.     

Video compression for the grand alliance: A historical perspective

This article outlines the evolution of the Grand Alliance (GA) highdefinition television (HDTV) standard from its divided beginnings among several systems to its final state as the proposed standard for HDTV transmission in the United Stales today. Earlier video compression standards are briefly described, and their influence on the first four all-digital HDTV proposals is demonstrated. The salient features of each proposed video compression system are high-lighted, and the more recent MPEG-2 compression standard is introduced. MPEG-2 was adopted as the basis for video compression by the GA, a group of the former HDTV competitiors. The formation of the GA is described, and the work of its Video Compression Specialists Group on evaluating modifications to MPEG-2 is reviewed.©1994 John Wiley & Sons Inc     

Preservation of mucosal and systemic adjuvant properties of ISCOMS in the absence of functional interleukin-4 or interferon-gamma

We have developed an efficient and rapid method to analyze transduction in human hematopoietic cells and to select them. We constructed two retroviral vectors using the recombinant humanized S65T green fluorescent protein (rHGFP) gene. Transduced cells appeared with specific green fluorescence on microscopy or fluorescence-activated cell sorting (FACS) analysis. The rHGFP gene was placed under the control of two different retroviral promotors (LTR) in the LGSN vector and in the SF-GFP vector. Amphotropic retroviruses were tested on NIH/3T3 fibroblasts or human hematopoietic (K562, TF-1) cell lines. Then CD34+ cells isolated from cord blood were infected three times after a 48-h prestimulation with IL-3, IL-6, SCF or with IL-3, IL-6, SCF, GM-CSF, Flt3-L and TPO. After 6 days of expansion, a similar number of total CD34(+)-derived cells, CD34+ cells and CFC was obtained in non-transduced and transduced cells, demonstrating the absence of toxicity of the GFP. A transduction up to 46% in total CD34(+)-derived cells and 21% of CD34+ cells was shown by FACS analysis. These results were confirmed by fluorescence of colonies in methyl-cellulose (up to 36% of CFU-GM and up to 25% of BFU-E). The FACS sorting of GFP cells led to 83-100% of GFP-positive colonies after 2 weeks of methyl-cellulose culture. Moreover, a mean gene transfer efficiency of 8% was also demonstrated in longterm culture initiating cells (LTC-IC). This rapid and efficient method represents a substantial improvement to monitor gene transfer and retroviral expression of various vectors in characterized human hematopoietic cells.     

A short history of gunpowder and the role of charcoal in its manufacture

Deflagrations caused by interactions of charcoal with potassium nitrate were discovered in 9th-century China. This led quickly to the development of primitive fuzes and ballistics. Roger Bacon, a 13th-century Franciscan monk experimented in England with gunpowder. The 18th-century saw the manufacture of charcoal by the cylinder method and the development of Waltham Abbey as the centre for gunpowder production which peaked to about 20 000 barrels per year at the time of the Battle of Waterloo. Methods of gunpowder manufacture changed little over the centuries until recent times. Whereas sulphur and nitre are reproducible ingredients, a mystery enshrined optimum specifications for gunpowder charcoal. Within recent years the application of modern analytical techniques has removed some of this mystery and anatomical features and physical properties have been characterized.     

In sight, in mind: retailer compliance with legislation on limiting retail tobacco displays

We investigated retailer compliance with point-of-sale display legislation, using a New Zealand region as a case study. An observational survey was conducted of nonspecialist tobacco retailers in the lower North Island of New Zealand during 2006. Compliance was assessed in relation to store type (dairies, convenience stores, supermarkets, and service stations) and by characteristics of the population of the census area unit in which the store was situated. These characteristics include the level of socioeconomic deprivation and proportions of Maori (indigenous New Zealanders), Pacific Islanders, and children aged less than 19 years. Out of the 288 stores surveyed, 185 (64%) had at least one breach of the point-of-sale regulations. The most common breaches were a failure to display a "Smoking Kills" sign, visibility of tobacco from outside the premises, and displaying tobacco less than 1 m from children's products. Compliance was significantly worse in dairies (small local general stores) and convenience stores. Stores situated in areas in the top quartile for the proportion of children were much more likely to have high levels of noncompliance (> or =3 breaches) and to display tobacco products close to children's products. This study is one of very few to systematically investigate retailer compliance with point-of-sale display regulations for tobacco products. The results suggest that the implementation of legislation to partly limit retail displays of tobacco products can be difficult. A ban on retail displays of tobacco products is likely to be a more effective and enforceable policy.     

A Review of the Effect of Diet on Cardiovascular Calcification

Cardiovascular (CV) calcification is known as sub-clinical atherosclerosis and is recognised as a predictor of CV events and mortality. As yet there is no treatment for CV calcification and conventional CV risk factors are not consistently correlated, leaving clinicians uncertain as to optimum management for these patients. For this reason, a review of studies investigating diet and serum levels of macro- and micronutrients was carried out. Although there were few human studies of macronutrients, nevertheless transfats and simple sugars should be avoided, while long chain ω-3 fats from oily fish may be protective. Among the micronutrients, an intake of 800 μg/day calcium was beneficial in those without renal disease or hyperparathyroidism, while inorganic phosphorus from food preservatives and colas may induce calcification. A high intake of magnesium (≥380 mg/day) and phylloquinone (500 μg/day) proved protective, as did a serum 25(OH)D concentration of ≥75 nmol/L. Although oxidative damage appears to be a cause of CV calcification, the antioxidant vitamins proved to be largely ineffective, while supplementation of α-tocopherol may induce calcification. Nevertheless other antioxidant compounds (epigallocatechin gallate from green tea and resveratrol from red wine) were protective. Finally, a homocysteine concentration >12 µmol/L was predictive of CV calcification, although a plasma folate concentration of >39.4 nmol/L could both lower homocysteine and protect against calcification. In terms of a dietary programme, these recommendations indicate avoiding sugar and the transfats and preservatives found in processed foods and drinks and adopting a diet high in oily fish and vegetables. The micronutrients magnesium and vitamin K may be worthy of further investigation as a treatment option for CV calcification.     

Isolation of Escherichia coli O86:K61 producing cyto-lethal distending toxin from wild birds of the finch family

The object of this study was to investigate the prevalence of Hepatitis C virus (HCV) by second-generation testing and to determine the effectiveness of risk factor-guided screening. We performed a prospective study of HCV exposure determined by second-generation enzyme-linked immunoadsorbent assay (ELISA) and confirmed by radioimmunoblot assay (RIBA). Risk factors (RF) were interpreted by univariate and multivariate analyses. Eight hundred eighty-six consecutive patients were tested for HCV over a 1-year period; 34 women tested positive for HCV and 32 were confirmed by RIBA (prevalence 3.6%). Forty-nine percent of women had at least one RF. Age, intravenous drug use, history of hepatitis strongly correlated with HCV (p <0.001). RF screening had a sensitivity of 81%. Twenty-one percent of women with HCV had no RF. The absence of any RF had a negative predictive value of 98.7%. RF screening is effective in identifying patients at low risk for HCV.     

Transient thermal characteristics of induction machine rotor cage

Thermal analysis of an induction machine cage rotor during stall conditions forms an important part of design calculations. The study of rotor circuit thermal behavior is also useful to identify causes of failure in large cage rotor induction machines. The authors present a three-dimensional finite-element-based electrical-thermal analysis of the bar and end-ring area of a large rotor to examine its thermal characteristics during a stall. Details of temperature variations at key locations in the bar and end ring are provided. The calculations are compared to experimental results, and the advantages and limitations of the solution technique for rotor analysis are discussed