An Experimental Approach to Assessing the Roles of Magnesium, Calcium, and Carbonate Ratios in Marine Carbonates

Marine biomineralization is a globally important biological and geochemical process. Understanding the mechanisms controlling the precipitation of calcium carbonate [CaCO3] within the calcifying fluid of marine organisms, such as corals, crustose coralline algae, and foraminifera, presents one of the most elusive, yet relevant areas of biomineralization research, due to the often-impenetrable ability to measure the process in situ. The precipitation of CaCO3 is assumed to be largely controlled by the saturation state [Ω] of the extracellular calcifying fluid. In this study, we mimicked the typical pH and Ω known for the calcifying fluid in corals, while varying the magnesium, calcium, and carbonate concentrations in six chemo-static growth experiments, thereby mimicking various dissolved inorganic carbon concentration mechanisms and ionic movement into the extracellular calcifying fluid. Reduced mineralization and varied CaCO3 morphologies highlight the inhibiting effect of magnesium regardless of pH and Ω and suggests the importance of strong magnesium removal or calcium concentration mechanisms. In respect to ocean acidification studies, this could allow an explanation for why specific marine calcifiers respond differently to lower saturation states.

Biochar as a Conducting Filler to Enhance Electrical Conduction Monitoring for Concrete Structures

Smart and resilient concrete structures will require building materials such as cements that sense flaws. One mechanism of crack detection in structures is monitoring their electrical conduction. Two mechanisms of charge in cement is ionic movement and moisture diffusion. Carbon rich electrically-conducting char is produced by pyrolyzing rice husks and can be used to enhance electrical conduction in cement. This paper studies the evolution of electrical properties in ordinary Portland cement added with up to 15 wt% rice husk-derived biochar. Resistance of cements decreased with increasing biochar addition while moisture loss and resistance both increase as curing time increases. Cement with 15 wt% biochar experiences the largest moisture loss and the most conducting. This suggest charge transport along percolation paths of biochar particles is dominant mechanism in these materials. Electron microscopy and energy dispersive spectroscopic studies reveal formation of Ettringite phase and good wetting/bonding at the interface of biochar particles and cement.

An Electrochemistry Study of Cryoelectrolysis in Frozen Physiological Saline

This is the first quantitative study on the fundamental physical and electrochemical processes that occur during cryoelectrolysis. Cryoelectrolysis is a new minimally invasive tissue ablation surgical technique that combines the processes of electrolysis and solid/liquid phase transformation (freezing). We measured the pH front propagation and the changes in resistance in a tissue simulant made of physiological saline gel with a pH dye as a function of the sample temperature in the high subzero range above the eutectic. Results demonstrate that effective electrolysis can occur in a high subzero freezing milieu and that the propagation of the pH front is only weakly dependent on temperature. These observations are consistent with a mechanism involving ionic movement through the concentrated saline solution channels between ice crystals at subfreezing temperatures above the eutectic. The Joule heating in these microchannel may cause local microscopic melting, the observed weak dependence of pH front propagation on temperature, and the large changes in resistance with time. In addition, we observed that the pH front propagation from the anode is more rapid than from the cathode. The explanation is the electro-osmotic flow from the cathode to the anode. The findings in this paper may be of fundamental value for designing future cryoelectrolytic ablation surgery protocols.

Cryoelectrolysis - electrolytic processes in a frozen physiological saline medium

Background: Cryoelectrolysis is a new minimally invasive tissue ablation surgical technique that combines the processes of electrolysis and solid/liquid phase transformation (freezing). Method: Performing a typical cryoelectrolytic ablation protocol in a tissue simulant made of physiological saline gel with a pH dye, we observed several new physical and electrochemical phenomena of relevance to tissue ablation. Results: We found that electrolysis can occur simultaneously with phase transformation, at high subzero freezing temperatures, above the eutectic temperature of the frozen salt solution. Another interesting finding is that electro-osmotic flows affect the process of cryoelectrolysis at the anode and cathode, in different ways. Discussion: The observations are consistent with a mechanism involving ionic movement through the concentrated saline solution channels between ice crystals, at subfreezing temperatures above the eutectic. The findings in this paper may become the scientific basis for designing future cryoelectrolytic ablation surgery protocols.

A Complex Variable Solution Based Analysis of Electric Displacement Saturation for a Cracked Piezoelectric Material

This paper presents an analysis of the effect of electric displacement saturation for a failing piezoelectric ceramic material based on a complex variable solution of a Mode III and a Mode I crack. This particular electric nonlinearity is caused by a reduction of the ionic movement in the material in the presence of high electric fields. Total and strain energy release rates are computed for varying far field stresses, electric displacements, and electric fields and compared for cases without and with full electric displacement saturation to further advance the understanding of failure initiation in piezoelectric ceramics.

Incorporation of a tricationic subphthalocyanine in an organic photovoltaic device

A new tricationic subphthalocyanine was synthesized and employed as light-harvesting and donor material in an ionic solid state organic photovoltaic cell. The incorporation of ionic dyes in organic photovoltaics aims to take advantage of ionic movement in order to enhance the charge transport properties of these materials. In this preliminary study, we report the results obtained in the fabrication of a partially solution-processed device with a cationic dye, where an effiency of 0.5% was reached.

Development of real-time radioisotope imaging systems for plant nutrient uptake studies

Ionic nutrition is essential for plant development. Many techniques have been developed to image and (or) measure ionic movement in plants. Nevertheless, most of them are destructive and limit the analysis. Here, we present the development of radioisotope imaging techniques that overcome such restrictions and allow for real-time imaging of ionic movement. The first system, called macroimaging, was developed to visualize and measure ion uptake and translocation between organs at a whole-plant scale. Such a device is fully compatible with illumination of the sample. We also modified fluorescent microscopes to set up various solutions for ion uptake analysis at the microscopic level. Both systems allow numerical analysis of images and possess a wide dynamic range of detection because they are based on radioactivity.

Ion Conductivity of Polymer Electrolytes Based on PEO Containing Li Salt and Additive Salt

Solid type polymer electrolyte is in progress of research and development in many ways to improve an ionic conductivity to attain 10-3 S/cm which is possibility of practical use of secondary lithium ion battery. There are two major methods of improving ionic conductivity; either lowering Tg of polymer or lowering the energy of ionic movement. In this work, the solid type polymer electrolyte (SPE) composites, which were composed of poly(ethylene oxide) (PEO), ethylene carbonate (EC) as a plasticizer, lithium salt, and 1-ethyl-3-methylimidazolium hexafluorophosphate (EMI-PF6) as a filler in order to improve the ion conductivity of the SPE, were prepared. The influence of EMI-PF6 contents on the ionic conductivity of the SPE composites was investigated in this work. As a result, the ionic conductivity of the SPE was enhanced by an increase in EMI-PF6 content, and showed the highest ionic conductivity at 40 wt.%. It was thought that there was a close correlation between the mobility of Li+ and EMI content in a SPE composite system.