High-Performance Membrane Chromatography of Small Molecules

High-performance membrane chromatography (HPMC) proved to be a very efficient method for fast protein separations. Recently, it was shown to be applicable also for the isocratic chromatography of plasmid DNA conformations. However, no study about the separation of small molecules has been performed until now. In this work, we investigated the possibility of gradient and isocratic HPMC of small molecules with Convective Interaction Media disks of different chemistries and tried to explain the mechanism that enables their separation. We demonstrated that it is possible to achieve efficient separations of oligonucleotides and peptides in the ion-exchange mode as well as the separation of small hydrophobic molecules in the reversed-phase mode. It was shown that similar peak resolution can be provided in both gradient and isocratic modes.     

Rapid gas-chromatographic method for the determination of diacetyl in milk, fermented milk and butter

In this work, a simple and fast method for the determination of diacetyl by gas-chromatographic technique coupled with flame ionisation detector (GLC-FID) was developed. Diacetyl is the typical butter flavour, but it is also commonly present in others fermented dairy products. Recently, diacetyl determination has also attracted interest because it is one of the parameters on which lactic acid bacteria (L.A.B.) are characterized and valued. Only acetone and 2,3-pentanedione were used as chemicals. After centrifugation of acetone–milk mixture, supernatant was filtered and directly injected into gas-chromatographic apparatus, without a further purification procedure step.

This method was accurate and precise; diacetyl recovery on milk was 97% and the detection limit was 1 mg L⁻¹. Finally, by using this method, diacetyl was easily determined in fresh and high-temperature treated milk, commercial butter, yoghurt and also in a series of L.A.B. performance tests.     

Isolation of a hydroxytyrosol-rich extract from olive leaves (<Emphasis Type="Italic">Olea Europaea</Emphasis> L.) and evaluation of its antioxidant properties and bioactivity

In this research, a phenol extract of high hydroxytyrosol (OLPE) content was obtained from olive leaves (Olea europaea L.), and subsequently tested under different contexts. The method used to obtain the OLPE basically involved two steps: the use of strongly-acid aqueous steam, generated from 10% HCl (v/v) at 100°C, to directly hydrolyse the native complex phenols from integral olive leaves, and OLPE recovery by liquid–liquid extraction with ethyl acetate. Hydrolysis time was 1 h. Finally, the dried extract was dissolved in distilled water. The OLPE total phenols were determined by Folin–Ciocalteu’s method and by HPLC analysis. Hydroxytyrosol was about 92% of the total phenols present in OLPE, and the yield was about 0.2% on fresh leaves. OLPE showed antioxidant effects on different food lipids and did not inhibit lactic acid bacteria growth; however, it showed cytotoxicity on NIH/3T3 fibroblasts and human umbilical vein endothelial cells at concentrations higher than 0.32 mM (as hydroxytyrosol).     

Accidents in the construction industry in the Netherlands: An analysis of accident reports using Storybuilder

As part of an ongoing effort by the Ministry of Social Affairs and Employment of the Netherlands, a research project is being undertaken to construct a causal model for occupational risk. This model should provide quantitative insight into the causes and consequences of occupational accidents. One of the components of the model is a tool to systematically classify and analyse reports of past accidents. This tool ‘Storybuilder’ was described in earlier papers. In this paper, Storybuilder is used to analyse the causes of accidents reported in the database of the Dutch Labour Inspectorate involving people working in the construction industry. Conclusions are drawn on measures to reduce the accident probability. Some of these conclusions are contrary to common beliefs in the industry.     

Living with risk: a management question

Public authorities started to be really involved in risk management of hazardous materials some 30 years ago. Recent developments have led to fresh attention for this matter and many further developments are underway. The history of risk management and safety regulation is one of strongly variable interest, forgotten lessons and rude awakenings. The impetus exerted by accidents is short lived. Safety cases become documents to satisfy regulation rather than instruments to reduce risk. Deregulation, privatisation, and outsourcing pose new challenges to safety and risk management. Some of the unfortunate side effects have already become apparent. This invariably leads to the next disaster, which will have a striking resemblance to the previous one when abstracted from the immediate technological context. Lessons can be learned if we really want. The question remains: ‘Do we?’.     

Biochemical indicators of vitamin provision to Orenburg's schoolchildren and effectiveness of prophylactic vitamin administration]

The study of providing with vitamins of schoolchildren in Orenburg conducted in the spring of 1985-1986 has revealed decreased content of ascorbic acid in 92%, vitamin E in 62%, vitamin A in 39%, folic acid in 38%, vitamin B12 in 14% of the children, the incidence rate of vitamin deficiency among the children in the senior forms was higher as compared to that in the junior forms and in boys it was more frequent than in girls. Additional intake of multivitamin "Undevitum" by schoolchildren during 2-4 months led to a significant improvement of their providing with vitamins that was expressed in normal vitamin levels and elimination of cases of deep vitamin deficiency.     

Heterogeneity and physiological activity of bovine k-casein proteolysis products

Gel chromatography in columns with Sephadex G-50 and biogel P-2 was used to separate a number of fractions formed in k-casein of cow's milk after short-term treatment with swine trypsin. These fractions, similar to beta-casomorphin, are capable of reducing the respiration and heart rates in rabbits after intravenous injection in a dose of 100 micrograms/kg, that suggests their capacity for interaction with opiate receptors. Some fractions injected subcutaneously induce in starving animals an electroencephalographic picture of satiation, similar to that observed after cholecystokinin injections. Correlation of amino acid composition and physiologic activity has evidenced that cholecystokinin and opioid effects are caused by different peptides.     

Solving partial differential equations of gas–solid reactions by orthogonal collocation

In this work the solution of the coupled partial differential equations for noncatalytic gas–solid reactions has been considered by orthogonal collocation. First of all, by an integral transformation and then by applying the orthogonal collocation method, these partial differential equations are converted to the ordinary differential equations. Then the equations are solved and the conversion–time profiles are obtained. The solution of the equations for volume reaction model, grain model and grain model with product layer resistance, modified grain model, random pore model, nucleation model and reaction of two gas with one solid has been presented in this work. The orthogonal collocation is a rapid method for solving of these equations and shows a good accuracy with respect to other solution techniques in the literature.     

Calculation of multicomponent multiphase equilibria

An algorithm which gives very good first trial values for the computation of chemical equilibrium composition is proposed. It is based on writing the chemical reactions in “canonical form” and changing the independent component set until it is formed by the species present in greatest quantity at equilibrium. The advancement degrees ξ_r of the reactions are calculated considering the reactions to occur independently of any other. By applying a similar procedure to the series reactor method, a new powerful solution algorithm of the Rosenbrook's type is obtained. In the first method we linearize the equilibrium equations written making null the gradient of the free energy of the system with respect to the corresponding ξ_r whilst in the second one we make successive unidimensional searches solving the equations for ξ_r