David R. Wilson

A Comparison of Commercial and Military Computer Security Policies

Most discussions of computer security focus on control of disclosure. In Particular, the U.S. Department of Defense has developed a set of criteria for computer mechanisms to provide control of classified information. However, for that core of data processing concerned with business operation and control of assets, the primary security concern is data integrity. This paper presents a policy for data integrity based on commercial data processing practices, and compares the mechanisms needed for this policy with the mechanisms needed to enforce the lattice model for information security. We argue that a lattice model is not sufficient to characterize integrity policies, and that distinct mechanisms are needed to Control disclosure and to provide integrity.

The interaction of sucrose esters with β-lactoglobulin and β-casein from bovine milk

Abstract The interaction of three high hydrophilic-lipophilic balance (HLB), water soluble sucrose monoesters with β-lactoglobulin and β-casein from bovine milk was studied by fluorescence titration and equilibrium dialysis techniques. The β-lactoglobulin bound all forms of the sucrose ester investigated stoichiometrically with a single, comparatively high affinity site. In contrast, β-casein bound the emulsifier substoichiometrically, possibly by interaction with β-casein micelles. The interaction of lauryl and stearoyl sucrose esters with β-lactoglobulin was stronger than with β-casein. The affinity of binding increased with saturated fatty acid chain length for both proteins, with the stearoyl ester giving a dissociation constant of 2.3 μ.M with β-lactoglobulin. However, the interaction of the monounsaturated oleic sucrose ester with β-casein was marginally stronger than with β-lactoglobulin.

High concentrations of cellulosic ethanol achieved by fed batch semi simultaneous saccharification and fermentation of waste-paper

Highlights ► Batch addition of paper waste in SSSF results in up to 11.6% (v/v) ethanol. ► Low overall enzyme loadings (3.7 FPU/g substrate). ► High cumulative substrate loadings (65% w/v). ► High ethanol concentrations will improve distillation efficiencies.

Differences in the structure and dynamics of the adsorbed layers in protein-stabilized model foams and emulsions

Protein-stabilized food dispersions often contain a range of surface active species. Many of these are of low molecular weight and include lipids or food emulsifiers. Depletion measurements, fluorescence and fluorescence recovery after photobleaching (FRAP) studies have shown that competitive adsorption of these molecules at the interface causes breakdown of protein–protein interactions in the adsorbed layer. This results in partial displacement of adsorbed protein and the initiation of lateral diffusion in the remaining adsorbed fraction However, there are distinct differences between the structure of the adsorbed protein layers found at air/water and oil/water interfaces. This causes differences in behaviour of the adsorbed layer in response to competitive adsorption of low-molecular-weight surfactant. This paper contrasts the behaviour of adsorbed layers formed by the milk proteins, β-lactoglobulin and β-casein, adsorbed at the interfaces of air-suspended thin liquid films and the thin aqueous film between two oil droplets, as a function of increasing concentration of the non-ionic surfactant, Tween 20.

Characterization of cell wall components of wheat bran following hydrothermal pretreatment and fractionation.

BackgroundPretreatments are a prerequisite for enzymatic hydrolysis of biomass and production of ethanol. They are considered to open up the plant cell wall structure by altering, moving or solubilizing lignin and hydrolyzing a proportion of hemicellulosic moieties. However, there is little information concerning pretreatment-induced changes on wheat bran cell wall polymers and indeed on changes in cell wall phenolic esters in bran or other lignocellulosic biomass. Here, we evaluate polymeric changes (chemical and physical) as a result of selected hydrothermal pretreatment conditions on destarched wheat bran using controlled polymer extraction methods. Quantification of cell wall components together with soluble oligosaccharides, the insoluble residues and ease of extractability and fractionation of biomass residues were conducted.ResultsPretreatment solubilized selected arabinoxylans and associated cross-linking ferulic and diferulic acids with a concomitant increase in lignin and cellulosic glucose. The remaining insoluble arabinoxylans were more readily extractable in alkali and showed considerable depolymerization. The degree of arabinose substitution was less in xylans released by higher concentrations of alkali. The recalcitrant biomass which remained after pretreatment and alkali extraction contained mostly cellulosic glucose and Klason lignin. Pretreatment generated small but insignificant amounts of yeast-inhibiting compounds such as furfural and hydroxymethyl furfural.As such, simultaneous saccharification and fermentation of the hydrothermally pretreated bran resulted in increased ethanol yields compared to that of the control (97.5% compared to 63% theoretical).ConclusionHydrothermal pretreatment of destarched wheat bran resulted in degradation and depolymerization of the hemicellulosic arabinoxylans together with some breakdown of cellulosic glucose. This was accompanied by a significant reduction in the cross-linking phenolic acids such as ferulic and diferulic acids. The results suggest that hydrothermal pretreatment enhances enzymatic digestibility of the cellulose not only by depolymerization and solubilization of the hemicelluloses but by breakdown of interpolymeric phenolic cross-links between the remaining insoluble polymers. This allows easier access of hydrolytic enzymes by opening or loosening of the cell wall thus resulting in enhanced saccharification of cellulose and subsequent fermentation to ethanol. The reduction in cinnamic acids by selected breeding or biotechnological approaches could provide a useful basis for improved saccharification and fractionation of wheat bran polysaccharides.

Steam explosion of oilseed rape straw: Establishing key determinants of saccharification efficiency

Oilseed rape straw was steam exploded into hot water at a range of severities. The residues were fractionated into solid and liquid phases and chemically characterised. The effect of steam explosion on enzymatic hydrolysis of the water-insoluble fractions was investigated by studying initial cellulase binding and hydrolysis yields for different cellulase doses. Time-course data was modelled to establish rate-dependent differences in saccharification as a function of pretreatment severity and associated chemical composition. The study concluded: (1) the initial hydrolysis rate was limited by the amount of (pectic) uronic acid remaining in the substrate; (2) the proportion of rapidly hydrolysable carbohydrate was most closely and positively related to lignin abundance and (3) the final sugar yield most closely related to xylan removal from the substrate. Comparisons between milled and un-milled steam exploded straw highlighted the influence that physical structure has on hydrolysis rates and yields, particularly at low severities.

Weak acids: dissociation in complex buffering systems and partitioning into oils

A method is developed to predict pH changes in complex buffering systems resulting from the addition of weak acids. Such systems are often encountered in foods and microbiological growth media which contain proteins and proteinaceous digests. The ‘buffering capacity’ of the system is characterised by a strong acid titration curve, and the known dissociation constants of weak acids are used to predict pH changes resulting from the addition of either one or a mixture of weak acids to the system. Predictions by the method show close agreement with experimental data. The familiar Henderson–Hasselbalch equation describing the dissociation of weak acids is modified to account for partitioning of undissociated acid into an oil phase. The equation may be used in conjunction with the pH prediction method to calculate both the pH and the concentration of undissociated weak acid in the aqueous phase of an emulsion containing complex buffering species. The equations should find application wherever weak acids are used for microbiological control in complex systems such as foods and pharmaceutical preparations, for predicting pH changes resulting from microbial growth during the production of fermented food commodities (eg cheese and yoghurt) or during food spoilage, and in biotechnological processes ranging from industrial bioreactors to agricultural silage production. © 2000 Society of Chemical Industry

Simultaneous saccharification and fermentation of steam exploded duckweed: improvement of the ethanol yield by increasing yeast titre.

Highlights • Steam explosion of duckweed enhances SSF at low (2% w/v) substrate concentrations.• High substrate concentrations (20% w/v) result in much lower ethanol yields.• Ethanol yields can be considerably increased with higher yeast inoculum.• Or by preconditioning yeasts in steam explosion liquor containing inhibitors.• The extra/preconditioned yeast metabolise fermentation inhibitors.

Effect of steam explosion on waste copier paper alone and in a mixed lignocellulosic substrate on saccharification and fermentation.

Highlights • Steam explosion of copier paper reduces xylose and produces inhibitors.• Steam explosion at SF 3.6 and 3.9 increased initial rates of saccharification.• Steam explosion at moderate severities may reduce processing times.• Co-steam explosion of waste paper and wheat straw reduces inhibitor production.

Competitive effects in the adsorbed layer of oil-in-water emulsions stabilised by β-lactoglobulin–Tween 20 mixtures

Competitive adsorption has been investigated in oil-in-water emulsions stabilised using mixtures of the protein β-lactoglobulin and the surfactant Tween 20 and correlated with changes in the composition and physical properties of the adsorbed layer in oil–water–oil thin films. The emulsifying activity of a fixed concentration (3 mg ml–1) of β-lactoglobulin was studied as a function of increasing Tween 20 concentration by measurement of the specific surface area (SSA) of the emulsion. The SSA remained relatively constant up to a Tween 20 : β-lactoglobulin molar ratio (R) of 4. The SSA decreased sharply at higher R values. An increase in the level of incorporation of Tween 20 into the adsorbed layer of emulsions was also observed at R= 4. Thin films formed between oil droplets in the continuous phase of emulsions containing fluorescent-labelled β-lactoglobulin revealed that surface diffusion was observed in samples of composition R= 4 or greater. The difference between observations made here at the oil/water interface and previous studies at the air/water interfaces where transitions in composition and diffusion were observed at R= 1 appears to be explained by a shear-induced conformational change in the β-lactoglobulin that occurs during homogenisation.