Flow Injection analysis with microdialysis probes enable minimally invasive and dynamic H₂O₂ measurements

This paper describes the optimization of a published flow injection analysis system coupled with microdialysis probes (MDP-FIA) for in-situ sampling and online measurements of hydrogen peroxide (H2O2). By modifying the commonly used Na2CO3 buffer by addition of EDTA and a changed order in reagent injection, interfering transition metals such as Fe(II) and Fe(III) are complexed and removed from the system without interfering with the chemiluminescent reaction of the used acridinium ester and H2O2. The system was then used to monitor changes in H2O2 concentration upon microwaving seawater and filtered seawater in the presence and absence of agar

Stable optical oxygen sensing materials based on click-coupling of fluorinated platinum(II) and palladium(II) porphyrins—A convenient way to eliminate dye migration and leaching

AbstractNucleophilic substitution of the labile para-fluorine atoms of 2,3,4,5,6-pentafluorophenyl groups enables a click-based covalent linkage of an oxygen indicator (platinum(II) or palladium(II) 5,10,15,20-meso-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin) to the sensor matrix. Copolymers of styrene and pentafluorostyrene are chosen as polymeric materials. Depending on the reaction conditions either soluble sensor materials or cross-linked microparticles are obtained. Additionally, we prepared Ormosil-based sensors with linked indicator, which showed very high sensitivity toward oxygen. The effect of covalent coupling on sensor characteristics, stability and photophysical properties is studied. It is demonstrated that leaching and migration of the dye are eliminated in the new materials but excellent photophysical properties of the indicators are preserved

Ciliary flows in corals ventilate target areas of high photosynthetic oxygen production

Most tropical corals live in symbiosis with Symbiodiniaceae algae whose photosynthetic production of oxygen (O2) may lead to excess O2 in the diffusive boundary layer (DBL) above the coral surface. When flow is low, cilia-induced mixing of the coral DBL is vital to remove excess O2 and prevent oxidative stress that may lead to coral bleaching and mortality. Here, we combined particle image velocimetry using O2-sensitive nanoparticles (sensPIV) with chlorophyll (Chla)-sensitive hyperspectral imaging to visualize the microscale distribution and dynamics of ciliary flows and O2 in the coral DBL in relation to the distribution of Symbiodiniaceae Chla in the tissue of the reef building coral, Porites lutea. Curiously, we found an inverse relation between O2 in the DBL and Chla in the underlying tissue, with patches of high O2 in the DBL above low Chla in the underlying tissue surrounding the polyp mouth areas and pockets of low O2 concentrations in the DBL above high Chla in the coenosarc tissue connecting neighboring polyps. The spatial segregation of Chla and O2 is related to ciliary-induced flows, causing a lateral redistribution of O2 in the DBL. In a 2D transport-reaction model of the coral DBL, we show that the enhanced O2 transport allocates parts of the O2 surplus to areas containing less chla, which minimizes oxidative stress. Cilary flows thus confer a spatially complex mass transfer in the coral DBL, which may play an important role in mitigating oxidative stress and bleaching in corals

Simultaneous visualization of flow fields and oxygen concentrations to unravel transport and metabolic processes in biological systems

From individual cells to whole organisms, O2 transport unfolds across micrometer- tomillimeter-length scales and can change within milliseconds in response to fluid flows and organismal behavior. The spatiotemporal complexity of these processes makes the accurate assessment ofO2 dynamics via currently availablemethods difficult or unreliable. Here, we present ‘‘sensPIV,’’ a method to simultaneously measure O2 concentrations and flow fields. By tracking O2-sensitive microparticles in flow using imaging technologies that allow for instantaneous referencing,we measuredO2 transport within (1) microfluidic devices, (2) sinking model aggregates, and (3) complex colony-forming corals. Through the use of sensPIV, we find that corals use ciliary movement to link zones of photosynthetic O2 production to zones of O2 consumption. SensPIV can potentially be extendable to study flow-organism interactions across many life-science and engineering applications

A study on African vernacular mosque: A lesson from tradition

Mosques as a symbol of Islamic cities have a significant place in Islamic Architecture and it prompts architects to create admirable, magnificent buildings. While several studies have done on features and prototypes in this field but mainly it leaded to exaggerate dominance of dome as inseparable component of mosques. Although dome construction is costly, it is not that much adaptable to different climates and even it is not a good culture indicator of different countries, still there is a strong insist on presence of dome in mosques everywhere. This paper aims to study African mosque example which deeply relied on vernacular architecture. Various styles of design in Mali as case study investigated in terms of material, design concept, to arrive at concrete results