Manipulation of microenvironment with a built-in electrochemical actuator in proximity of a dissolved oxygen microsensor

Biochemical sensors for continuous monitoring require dependable periodic self diagnosis with acceptable simplicity to check its functionality during operation. An in-situ self-diagnostic technique for a dissolved oxygen microsensor is proposed in an effort to devise an intelligent microsensor system with an integrated electrochemical actuation electrode. With a built-in platinum microelectrode that surrounds the microsensor, two kinds of microenvironments, called the oxygen-saturated or oxygen-depleted phases, can be created by water electrolysis, depending on the polarity. The functionality of the microsensor can be checked during these microenvironment phases. The polarographic oxygen microsensor is fabricated on a flexible polyimide substrate (Kapton) and the feasibility of the proposed concept is demonstrated in a physiological solution. The sensor responds properly during the oxygen-generating and oxygen-depleting phases. The use of these microenvironments for in-situ self-calibration is discussed to achieve functional integration, as well as structural integration, of the microsensor system.     

Urban Field Guide Baltimore,Maryland

A changing economy and different lifestyles have altered the meaning of the forest in the Northeastern United States, prompting scientists to reconsider the spatial form, stewardship and function of the urban forest. Erika Svendsen, Victoria Marshall and Manolo F Ufer describe how social observation techniques and the employment of a novel, locally based, participatory hand-held monitoring system could aid the exposure of more positive socially orientated patterns of land use. Copyright © 2005 John Wiley & Sons, Ltd.     

Electrodeposited iridium oxide pH electrode for measurement of extracellular myocardial acidosis during acute ischemia

In the present paper, fabrication, characterization, and physiological applications of a solid-state pH electrode are described. The pH sensing layer was based on an anodic electrodeposited iridium oxide film (AEIROF). Sputtered platinum electrodes (1 mm diameter) fabricated on flexible Kapton films or platinum wires were used as planar or cylindrical supports. Each electrode site was coated with Nafion to attenuate the interference of anionic redox species and to protect the electrode surface during in vivo measurements. Performance of the AEIROF was evaluated, for the first time, as a pH electrode and proved to have a slightly super-Nernstian response with slope of -63.5 +/- 2.2 mV/pH unit for both wire and planar sputtered platinum electrodes. Linear pH responses were obtained in the pH range 2-10. The electrodes have a working lifetime of at least 1 month with accuracy of about 0.02 pH unit and fast response time. The electrodes showed very low sensitivities for different species, such as Na+, K+, Li+, NH4+, Ca2+, Mg2+, dissolved oxygen, lactate, ascorbate, and urate, which are important for physiological applications. The electrodes were applied in extracellular pH measurements during brief regional ischemia in a swine heart and no-flow ischemia in an isolated rabbit papillary muscle. A first report on extracellular pH, K+, and lactate simultaneous measurements during no-flow ischemia using the AEIROF pH electrode and the previously described K+ and lactate electrodes is presented as well.     

Incorporation of Eu(III) into hydrotalcite: a TRLFS and EXAFS study

The behavior of radionuclides in the environment (geo-, hydro-, and biosphere) is determined by interface reactions like adsorption, ion exchange, and incorporation processes. Presently, operational gross parameters for the distribution between solution and minerals are available. For predictive modeling of the radionuclide mobility in such systems, however, individual reactions and processes need to be localized, characterized, and quantified. A prerequisite for localization and clarification of the concerned processes is the use of modern advanced analytical and speciation methods, especially spectroscopy. In this study, Eu(III) was chosen as an analogue for trivalent actinides to identify the different species that occur by the Ln(III)/hydrotalcite interaction. Therefore, Eu(III) doped Mg-Al-Cl-hydrotalcite was synthesized and investigated by TRLFS, EXAFS, and XRD measurements. Two different Eu/hydrotalcite species were obtained. The minor part of the lanthanide is found to be inner-sphere sorbed onto the mineral surface, while the dominating Eu/hydrotalcite species consists of Eu(III) that is incorporated into the hydrotalcite lattice. Both Eu/hydrotalcite species have been characterized by their fluorescence emission spectra and lifetimes. Structural parameters of the incorporated Eu(III) species determined by EXAFS indicate a coordination number of 6.6 +/- 1.3 and distances of 2.41 +/- 0.02 A for the first Eu-OH shell.