On system rollback and totalized fields: An algebraic approach to system change

In system operations the term rollback is often used to imply that arbitrary changes can be reversed i.e. ‘rolled back’ from an erroneous state to a previously known acceptable state. We show that this assumption is flawed and discuss error-correction schemes based on absolute rather than relative change.Insight may be gained by relating change management to the theory of computation. To this end, we reformulate previously-defined ‘convergent change operators’ of Burgess into the language of groups and rings. We show that, in this form, the problem of rollback from a convergent operation becomes equivalent to that of ‘division by zero’ in computation. Hence, we discuss how recent work by Bergstra and Tucker on zero-totalized fields helps to clear up long-standing confusion about the options for ‘rollback’ in change management.     

Cushioning properties of convoluted foam

Convoluted polyurethane foam was tested for its cushioning ability in controlled drop tests using a cushion tester. The purpose of the tests was to relate the peak acceleration transmitted to the falling weight to key geometric features of the cushion, such as base thickness and area, along with finger height and spacing. It was found that the fingers had the effect of reducing the impact velocity in a predictable manner, allowing the convoluted cushion to be treated as a block design so that published cushion curves for the same material could be used to obtain the peak acceleration. In effect, convoluted foam behaves like a block cushion of the size of its own base in a drop from a reduced height, the reduction being several times the finger height. Copyright © 1999 John Wiley & Sons, Ltd.     

Dissolution and passivation of iron in acetonitrile and acetonitrile–water mixtures

The dissolution and passivation of iron in neutral acetonitrile–water mixtures have been studied under potentiodynamic and potentiostatic conditions. In “dry” acetonitrile (water content <0.02% or 200 ppm), passivation, due to an air-formed film, is maintained for a wide range of potentials up to 0.50 V, well above the corrosion potential E_corr≈−0.4 V. Transpassive dissolution at higher potentials is normally controlled by interfacial reactions rather than diffusion in the solution. Addition of a relatively small amount of water (0.5% or 0.28 M) to acetonitrile initiates active dissolution on iron surfaces damaged by previous transpassive dissolution. At a level of 2% water (1.1 M) active dissolution is initiated on undamaged surfaces and proceeds relatively slowly under control by interfacial reactions. Transpassive dissolution at similar potentials meanwhile becomes diffusion-controlled. As water content is increased further (e.g., to 6% or 3.3 M) the electrochemistry of iron becomes progressively similar to that in aqueous solutions, with both active dissolution and passivation being enhanced. Passivation is promoted by addition of hydrogen peroxide as a passivator, but the dynamic balance between the two processes can, as expected, be shifted to dissolution by increasing solution acidity. The similarities and differences in acetonitrile, water and their mixtures are discussed in terms of the relative reactivity and concentration of the two solvents. The profound effects of water on the kinetics of iron dissolution and passivation are attributed to the dominant reactivity associated with acidic hydrogen. Based on the potentiostatic and potentiodynamic features, the mechanism of phase change during dissolution is described in terms of a model of a shifting oxide film formed through two-dimensional nucleation and growth.     

Novel opportunities for marine hyperthermophiles in emerging biotechnology and engineering industries

Despite the increased interest in hyperthermophiles and the rate of discovery of new species, their potential within the biotechnology industry has not been fully realized to date. The physiological characterization and biochemical survival mechanisms of marine hyperthermophilic Bacteria and Archaea are currently under investigation. However, very little information on their application in bioprocess systems is available. Since only a fraction of the world's oceans has been explored, the potential for isolating novel strains of marine hyperthermophiles is significant and hence they represent an, as yet, untapped biotechnological resource. Although much research has focused on the extraction of thermoactive enzymes, whole cell applications have been relatively overlooked. Running bioprocess systems using marine hyperthermophiles poses an interesting set of objectives, such as high temperature bioreactor operation and corrosion reduction of materials, for bioreactor design and manipulation of their products. Here, we discuss the biotechnological potential of marine hyperthermophiles from a biochemical engineering perspective and their use in ‘green chemistry’ applications. Both the bioprocess intensification implications and problems associated with cultivating these microbes in industrially relevant bioreactor systems are discussed from both a microbiological and chemical engineering perspective. © 2000 Society of Chemical Industry     

Nutrient addition to enhance biological treatment of greywater.

This study compares the chemical oxygen demand (COD) removal and respiration rates of a microbial population treating real and synthetic greywaters dosed with nutrient supplements. The nutrient composition of the real and synthetic greywaters was analysed and the dosing regime for nitrogen, phosphorus and a range of trace metals planned accordingly. The doses consisted of eight single additives (macronutrients and trace metals) to the control greywater and six trace metal additions to C: N : P balanced greywater. The COD removal for the control real and synthetic greywater in lab-scale activated sludge systems (0.038 and 0.286 kg COD kg MLSS(-1) d(-1), respectively) confirmed nutrient limitation and the poor degree of greywater treatment. Nutrient dosing increased the COD removal rate and oxygen uptake rate in many cases. The greatest stimulation of microbial activity was observed with zinc additions to C: N: P balanced real greywater (1.291 kg COD kg MLSS(-1) d(-1) over 30 times the control). Inhibitory effects to various extents were rare and limited mainly to the additions of metals to synthetic greywater. The dominance of chemicals effects was observed on addition of some micronutrients; notably iron and aluminium, metals on which many coagulants for use in biotreatment of other wastewaters are based. The data indicate that the impact of understanding microbial processes and the nutrients required for wastewater treatment can only serve to optimise process efficiency for the proposed treatment of greywater.     

Intrauterine transmission of Borrelia burgdorferi in dogs

To determine whether intrauterine transmission of Borrelia burgdorferi could exist in dogs, 10 female Beagles were inoculated intradermally with approximately 1,000 B burgdorferi on day 1 of proestrus; inoculation was repeated every 2 weeks during the gestation period. Ten female control Beagles were similarly inoculated with phosphate-buffered saline solution. Prior to the start of the study, all females and 3 males used for breeding were seronegative for B burgdorferi on the basis of results of the indirect fluorescent antibody test and immunoblot (western analysis. Similarly, results of culture of blood for B burgdorferi were negative. All 20 of the females were bred naturally. Blood samples were collected weekly for serologic testing and culture. Blood samples were obtained from live pups on day 1 of life, then weekly until pups were 6 weeks old when they were euthanatized. Tissues were obtained for culture and testing by use of polymerase chain reaction (PCR). Of 10 spirochete-inoculated (SI) females, 8 became infected with B burgdorferi as evidenced by spirochete culture results and/or PCR-detected B burgdorferi DNA in the tissues of females or their pups. Of the 10 SI females, 8 delivered litters (3 to 7 pups) that had at least 1 neonatal or 6-week-old pup with B burgdorferi DNA-positive tissues (by PCR), and spirochetes were cultured from tissues from pups of 2 litters.(ABSTRACT TRUNCATED AT 250 WORDS)     

Subcellular biochemical changes during the development of the small intestine of pony foals

To examine the postnatal development of equine small intestine, biopsy specimens of jejunal mucosa from 8 ponies, between 6 and 28 weeks old, were subjected to analytical subcellular fractionation and assay of organelle marker enzymes. Fractionation revealed a reduction in the particulate brush border component of beta-galactosidase (lactase) activity between 6 and 28 weeks, and a corresponding increase in soluble activity, although the reduction in mean specific activity was not significant. There also was a decrease in the proportion of brush border to soluble aminopeptidase N activity, a relative loss of brush border gamma-glutamyltransferase activity, and a considerable decrease in the specific activity of alkaline phosphatase throughout the gradient fractions. In contrast, there were marked increases in activities of alpha-glucosidase (maltase) and sucrase in the older ponies, accompanied by considerable changes in the intracellular distribution of particulate alpha-glucosidase activity, which was predominantly associated with endoplasmic reticulum at 6 weeks, whereas the large increase in activity observed by 28 weeks was clearly associated with the brush border. The modal density of brush borders also increased with age, suggestive of an increase in the glycoprotein-to-lipid ratio of the microvillar membrane. In contrast to these brush border changes, there was relatively little alteration in the activities or density distributions of marker enzymes for endoplasmic reticulum, basolateral membranes, mitochondria, or lysosomes. These findings indicate that maturation of equine intestinal epithelium during the first few months of life results in major changes in the properties and enzyme composition of enterocyte brush borders.     

Water Renew systems: wastewater polishing using renewable energy crops.

Macronutrients concentrations were measured during the establishment year of short rotation coppice of Salix viminalis, Populus trichocarpa, Eucalyptus gunnii irrigated with secondary treated effluent. Twenty four plots of 12.25 m2 located in Cranfield, Bedfordshire, UK on heavy fine clay were drip-irrigated in order to maintain their soil moisture at field capacity. Soil water was sampled at 30 cm and 60 cm with soil water suction cup samplers fortnightly. Willow and eucalyptus received more than 900 mm of effluent corresponding to more than 290 kg-N/ha, 30 kg-P/ha and 220 kg-K/ha. Poplar and unplanted plots received less than 190 kg-N/ha, 17 kg-P/ha and 120 kg-K/ha. For soil water nitrogen concentrations as for potassium concentrations, there was an irrigation effect only on eucalyptus planted plots. On all plots, there was no significant effect of tree presence or species. There was no phosphorus measurable in soil water samples. Groundwater chemistry was unaffected by irrigation. Thus, intensive irrigation of short rotation coppice during the establishment year should not be considered as a major threat to groundwater quality. Willows and eucalyptus can absorb almost a third more effluent than poplar and unplanted plots without having any significant effect on soil water chemistry.     

The human A33 antigen is a transmembrane glycoprotein and a novel member of the immunoglobulin superfamily

The mAb A33 detects a membrane antigen that is expressed in normal human colonic and small bowel epithelium and > 95% of human colon cancers. It is absent from most other human tissues and tumor types. The murine A33 mAb has been shown to target colon cancer in clinical trials, and the therapeutic potential of a humanized antibody is currently being evaluated. Using detergent extracts of the human colon carcinoma cell lines LIM1215 and SW1222, in which the antigen is highly expressed, the molecule was purified, yielding a 43-kDa protein. The N-terminal sequence was determined and further internal peptide sequence obtained following enzymatic cleavage. Degenerate primers were used in PCRs to produce a probe to screen a LIM1215 cDNA library, yielding clones that enabled us to deduce the complete amino acid sequence of the A33 antigen and express the protein. The available data bases have been searched and reveal no overall sequence similarities with known proteins. Based on a hydrophilicity plot, the A33 protein has three distinct structural domains: an extracellular region of 213 amino acids (which, by sequence alignment of conserved residues, contains two putative immunoglobulin-like domains), a single hydrophobic transmembrane domain, and a highly polar intracellular tail containing four consecutive cysteine residues. These data indicate that the A33 antigen is a novel cell surface receptor or cell adhesion molecule in the immunoglobulin superfamily.