Dissolved organic matter in seawater and the electric charge of immersed surfaces

Changes in the electrical charge that occur on the surfaces of test particles of quartz, germanium, and an anion-exchange resin when they are exposed to natural and artificial seawater have been studied by means of microelectrophoresis…

Absorption of an organic film at the platinum-seawater interface

Optical polarization analysis with an ellipsometer and microelectrophoretic and contact angle measurements all indicate that large changes in the properties of the platinum metal surface occurred on contact with Chesapeake Bay water from which particles and microorganisms had been removed. These changes were not observed with the same water from which organics had been removed by a photo-oxidation procedure...

The bio-physics of condensation of divalent cations into the bacterial wall has implications for growth of Gram-positive bacteria

Background: The anionic-polyelectrolyte nature of the wall of Gram-positive bacteria has long been suspected to be involved in homeostasis of essential cations and bacterial growth. A better understanding of the coupling between the biophysics and the biology of the wall is essential to understand some key features at play in ion-homeostasis in this living system. Methods: We consider the wall as a polyelectrolyte gel and balance the long-range electrostatic repulsion within this structure against the penalty entropy required to condense cations around wall polyelectrolytes. The resulting equations define how cations interact physically with the wall and the characteristic time required for a cation to leave the wall and enter into the bacterium to enable its usage for bacterial metabolism and growth. Results: The model was challenged against experimental data regarding growth of Gram-positive bacteria in the presence of varying concentration of divalent ions. The model explains qualitatively and quantitatively how divalent cations interact with the wall as well as how the biophysical properties of the wall impact on bacterial growth (in particular the initiation of bacterial growth). Conclusion: The interplay between polymer biophysics and the biology of Gram positive bacteria is defined for the first time as a new set of variables that contribute to the kinetics of bacterial growth. General significance: Providing an understanding of how bacteria capture essential metal cations in way that does not follow usual binding laws has implications when considering the control of such organisms and their ability to survive and grow in extreme environments

Evaluatie van het, in 1987 in het kader van het VREK-programma uitgevoerde onderzoek naar de cadmium-, lood-, kwik- en arseengehalten in vlees en organen van runderen, varkens, schapen, kalveren en pluimvee

De in 1987 in het kader van het LAC-signaleringsprograrruna VREK gevonden lood-, cadmium-, kwik- en arseengehalten zijn gepresenteerd en vergeleken met de resultaten van voorgaande jaren. Voorts zijn de gevonden gehalten getoetst aan de geldende aktiegrenzen en ontwerpnormen. In de verdelingen van de gevonden loodgehalten in vlees, levers en nieren van zowel runderen als varkens is in de loop van de jaren een verschuiving naar lagere waarden waarneembaar. De range waarbinnen de loodgehalten worden gevonden is echter nagenoeg konstant. De in 1987 gevonden loodgehalten in schapelevers liggen op een vergelijkbaar niveau als in 1986, maar op een beduidend lager niveau dan in de jaren daarvoor. Een mogelijke relatie tussen deze abrupte daling van de loodgehalten in schapelevers en de sterke toename van loodvrije benzine met een hiermee samenhangende vermeende daling in de atmosferische looddepositie zal nader worden onderzocht. In 1987 werden in kalfslevers meer lagere en in schapenieren daarentegen meer hogere cadmiumgehalten waargenomen. In 1987 werden in 1 monster varkensvlees en in 1 monster rundvlees de aktiegrens en de ontwerpnorm voor cadmium overschreden. Voorts werd in 2 monsters rundernier de voor cadmium geldende aktiegrens overschreden. In 1 monster van een rund werden in het vlees, de nier en de lever verhoogde arseengehalten waargenomen. Alleen de voor nieren geldende aktiegrens van arseen werd hierbij overschreden, terwijl de respectievelijke richtnormen niet werden overschreden

Analyseresultaten Zevenlanden-studie

In het kader van de Zevenlandenstudie, een epidemiologische studie naar de relatie tussen voeding en kanker, heeft het RIKILT de gemiddelde voedingspakketten van 16 cohorten onderzocht op het gehalte aan vitamines, spoorelementen en non-nutritieve stoffen als glucosinolaten en flavonoïden. In dit verslag worden de analytisch-chemische aspecten van dit onderzoek nader toegelicht, waarbij aandacht wordt besteed aan de gebruikte analysemethoden, de monstervoorbehandeling, de monsterbewaring en de kwaliteitsbewaking van de analyses

Electrode substrate innovation for electrochemical detection in microchip electrophoresis.

Microchip Electrophoresis (ME) represents the next generation of miniaturised electrophoretic devices and carry benefits such as significant improvement in analysis times, lower consumption of reagents and samples, flexibility, and procedural simplicity. The devices provide a separation method for complex sample matrices and an on-board detection method for the analytical determination of a target compound. The detection part of ME is increasingly leaning towards electrochemical methods, thus the selectivity and sensitivity of detection in ME is dependent upon the chosen working electrode composition in addition to operating conditions of the chip such as separation voltage. Given the current plethora of electrode materials that are available, there exists a possibility to creatively integrate electrodes into ME. This review will overview the application of several electrode materials, from the old through to the new. A particular recent focus has been the selectivity element of MEs overcome with the use of enzymes, carbon composites, and screen-printed technologies. This article is protected by copyright. All rights reserved

Atomic force microscopy studies of bioprocess engineering surfaces - imaging, interactions and mechanical properties mediating bacterial adhesion

The detrimental effect of bacterial biofilms on process engineering surfaces is well documented. Thus, interest in the early stages of bacterial biofilm formation; in particular bacterial adhesion and the production of anti-fouling coatings has grown exponentially as a field. During this time, Atomic force microscopy (AFM) has become an essential tool for the evaluation of bacterial adhesion. Due to its versatility AFM offers not only insight into the topographical landscape and mechanical properties of the engineering surfaces, but elucidates, through direct quantification the topographical and biomechnical properties of the foulants The aim of this paper is to collate the current research on bacterial adhesion, both theoretical and practical, and outline how AFM as a technique is uniquely equipped to provide further insight into the nanoscale world at the bioprocess engineering surface