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Articoli di riviste sul tema "Oxygen microsensor"

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Autore: Grafiati

Pubblicato: 8 giugno 2024

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1

Lee, Chi-Yuan, Chia-Hung Chen, Sheng-Ming Chuang, Chin-Yuan Yang e Jia-Yu Hsu. "A Flexible 8-in-1 Microsensor Embedded in Proton Battery Stack for Real-Time Microscopic Measurements". Membranes 13, n. 6 (1 giugno 2023): 573. http://dx.doi.org/10.3390/membranes13060573.

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According to the latest literature, it is difficult to measure the multiple important physical parameters inside a proton battery stack accurately and simultaneously. The present bottleneck is external or single measurements, and the multiple important physical parameters (oxygen, clamping pressure, hydrogen, voltage, current, temperature, flow, and humidity) are interrelated, and have a significant impact on the performance, life, and safety of the proton battery stack. Therefore, this study used micro-electro-mechanical systems (MEMS) technology to develop a micro oxygen sensor and a micro clamping pressure sensor, which were integrated into the 6-in-1 microsensor developed by this research team. In order to improve the output and operability of microsensors, an incremental mask was redesigned to integrate the back end of the microsensor in combination with a flexible printed circuit. Consequently, a flexible 8-in-1 (oxygen, clamping pressure, hydrogen, voltage, current, temperature, flow, and humidity) microsensor was developed and embedded in a proton battery stack for real-time microscopic measurement. Multiple micro-electro-mechanical systems technologies were used many times in the process of developing the flexible 8-in-1 microsensor in this study, including physical vapor deposition (PVD), lithography, lift-off, and wet etching. The substrate was a 50 μm-thick polyimide (PI) film, characterized by good tensile strength, high temperature resistance, and chemical resistance. The microsensor electrode used Au as the main electrode and Ti as the adhesion layer.

2

Rathnayake, Rathnayake M. L. D., Shogo Sugahara, Hideaki Maki, Gen Kanaya, Yasushi Seike e Hisashi Satoh. "High spatial resolution analysis of the distribution of sulfate reduction and sulfide oxidation in hypoxic sediment in a eutrophic estuary". Water Science and Technology 75, n. 2 (23 novembre 2016): 418–26. http://dx.doi.org/10.2166/wst.2016.516.

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Bottom hypoxia and consequential hydrogen sulfide (H2S) release from sediment in eutrophic estuaries is a major global environmental issue. We investigated dissolved oxygen, pH and H2S concentration profiles with microsensors and by sectioning sediment cores followed by colorimetric analysis. The results of these analyses were then compared with the physicochemical properties of the bottom water and sediment samples to determine their relationships with H2S production in sediment. High organic matter and fine particle composition of the sediment reduced the oxidation-reduction potential, stimulating H2S production. Use of a microsensor enabled measurement of H2S concentration profiles with submillimetre resolution, whereas the conventional sediment-sectioning method gave H2S measurements with a spatial resolution of 10 mm. Furthermore, microsensor measurements revealed H2S consumption occurring at the sediment surface in both the microbial mat and the sediment anoxic layer, which were not observed with sectioning. This H2S consumption prevented H2S release into the overlying water. However, the microsensor measurements had the potential to underestimate H2S concentrations. We propose that a combination of several techniques to measure microbial activity and determine its relationships with physicochemical properties of the sediment is essential to understanding the sulfur cycle under hypoxic conditions in eutrophic sediments.

3

Ring, Andrej, Heiko Sorg, Andreas Weltin, Daniel J. Tilkorn, Jochen Kieninger, Gerald Urban e Jörg Hauser. "In-vivo monitoring of infection via implantable microsensors: a pilot study". Biomedical Engineering / Biomedizinische Technik 63, n. 4 (26 luglio 2018): 421–26. http://dx.doi.org/10.1515/bmt-2016-0250.

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Abstract The most common complication after implantation of foreign material is infection, leading to implant failure and severe patient discomfort. Smoldering-infections proceed inapparently and might not get verified by radiological diagnostics. Early identification of this type of infection might significantly reduce the rate of complications. Therefore, we manufactured a microsensor strip in a hybrid of thin-film and laminate technology in a wafer-level process. It comprises electrochemical, amperometric microsensors for glucose, oxygen and lactate as well as an integrated reference electrode. Microsensors have been implanted in the mouse dorsal skin fold chamber, which got inoculated with a human-pathogen bacterial strain. A selective signal could be measured for all parameters and time points. The infection led to measurable changes of the wound environment as given by a decrease of the oxygen- as well as the glucose-concentration while the lactate concentration increased markedly over time. The given results in this study are the first hints on a promising new tool and should therefore be interpreted as a proof of the principle to show the functionality of the microsensors in an in vivo setting. These microsensors could be used to monitor smoldering infections of implantable foreign materials reducing foreign implant associated complications.

4

Fang, Yuxin, Di Zhang, Qing Xia, Shouhai Hong, Yuan Xu e Yi Guo. "Fabrication of a Needle Microsensor and Its Applications in the Detection of Dissolved Oxygen". Journal of Sensors 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/408458.

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A novel needle microsensor measurement system was fabricated and applied to determine the concentration of dissolved oxygen. Platinum nanoparticles were employed to modify the surface of copper-core electrode in order to improve electrochemical response signal. The homemade electrode displayed efficient electrocatalytic reduction activity towards dissolved oxygen. The sensor responded linearly to dissolved oxygen in the range of 10 μM to 0.195 mM and had a remarkable sensitivity of 9.02 μA/mM. In addition, it showed an excellent reproducibility, stability, and selectivity. These results indicated that the needle microsensor when used, could yield good performance. Moreover, it is believed to be a potential tool for studying specific substances at a cellular level orin vivoin future.

5

Revsbech, Niels Peter. "An oxygen microsensor with a guard cathode". Limnology and Oceanography 34, n. 2 (marzo 1989): 474–78. http://dx.doi.org/10.4319/lo.1989.34.2.0474.

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6

Andersen, Knud, Thomas Kjær e Niels Peter Revsbech. "An oxygen insensitive microsensor for nitrous oxide". Sensors and Actuators B: Chemical 81, n. 1 (dicembre 2001): 42–48. http://dx.doi.org/10.1016/s0925-4005(01)00924-8.

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7

She, Didi, e Mark G. Allen. "A Self-Powered, Biodegradable Dissolved Oxygen Microsensor". Journal of Microelectromechanical Systems 29, n. 5 (ottobre 2020): 1074–78. http://dx.doi.org/10.1109/jmems.2020.3013208.

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8

Hong, Minyoung, Sarah S. Park, Yejin Ha, Jaegeun Lee, Kwangsik Yoo, Gil-Ja Jhon, Minah Suh e Youngmi Lee. "Heterogeneity of Skin Surface Oxygen Level of Wrist in Relation to Acupuncture Point". Evidence-Based Complementary and Alternative Medicine 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/106762.

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The distribution of partial oxygen pressure (pO2) is analyzed for the anterior aspect of the left wrist with an amperometric oxygen microsensor composed of a small planar Pt disk-sensing area (diameter = 25 μm). The pO2levels vary depending on the measurement location over the wrist skin, and they are systematically monitored in the analysis for both one-dimensional single line (along the wrist transverse crease) and two-dimensional square area of the wrist region. Relatively higher pO2values are observed at certain area in close proximity to the position of acupuncture points with statistical significance, indicating strong relationship between oxygen and acupuncture point. The used oxygen microsensor is sensitive enough to detect the pO2variation depending on the location. This study may provide information helpful to understand possible physiological roles of the acupuncture points.

9

Tan, Shuying, Tong Yu e Han-chang Shi. "Microsensor determination of multiple microbial processes in an oxygen-based membrane aerated biofilm". Water Science and Technology 69, n. 5 (14 dicembre 2013): 909–14. http://dx.doi.org/10.2166/wst.2013.730.

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Microsensor techniques were used to investigate in situ the simultaneous occurrence of sulfate reduction and nitrogen removal in a membrane aerated biofilm reactor. H2S, O2, pH, ORP, NH4+ and NO3− microsensors were fabricated and used to measure the profiles inside the membrane aerated biofilm. Production and consumption rates of H2S, O2, NH4+ and NO3− were estimated using corresponding concentration profiles. The results showed that in anoxic zone, located from the interface between biofilm and bulk liquid to about 550 μm below the interface, both sulfate reduction and denitrification occurred. Highest H2S production rates (around 0.27 mg L−1s−1) were found about 400 to 450 μm below the interface. Below the anoxic zone, an aerobic zone was present. High H2S oxidation activity occurred at around 550–700 μm below the interface. High oxygen consumption rates (0.34 mg L−1s−1) occurred at around 750–900 μm below the interface. Nitrification activity occurred at about 500–650 μm below the interface. Along the entire biofilm depth, pH changed slightly (within 0.2 unit). Near the interface of the aerobic and anoxic zone, there was a drastic redox potential change. These results demonstrated simultaneous sulfate reduction and nitrogen removal in a piece of membrane aerated biofilm.

10

Cronenberg, Carel, Bert van Groen, Dirk de Beer e Han van den Heuvel. "Oxygen-independent glucose microsensor based on glucose oxidase". Analytica Chimica Acta 242 (1991): 275–78. http://dx.doi.org/10.1016/0003-2670(91)87075-i.

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11

Urban, Sebastian, Vinayaganataraj Tamilselvi Sundaram, Jochen Kieninger, Gerald Urban e Andreas Weltin. "Microsensor Electrodes for 3D Inline Process Monitoring in Multiphase Microreactors". Sensors 20, n. 17 (28 agosto 2020): 4876. http://dx.doi.org/10.3390/s20174876.

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We present an electrochemical microsensor for the monitoring of hydrogen peroxide direct synthesis in a membrane microreactor environment by measuring the hydrogen peroxide and oxygen concentrations. In prior work, for the first time, we performed in situ measurements with electrochemical microsensors in a microreactor setup. However, the sensors used were only able to measure at the bottom of the microchannel. Therefore, only a limited assessment of the gas distribution and concentration change over the reaction channel dimensions was possible because the dissolved gases entered the reactor through a membrane at the top of the channel. In this work, we developed a new fabrication process to allow the sensor wires, with electrodes at the tip, to protrude from the sensor housing into the reactor channel. This enables measurements not only at the channel bottom, but also along the vertical axis within the channel, between the channel wall and membrane. The new sensor design was integrated into a multiphase microreactor and calibrated for oxygen and hydrogen peroxide measurements. The importance of measurements in three dimensions was demonstrated by the detection of strongly increased gas concentrations towards the membrane, in contrast to measurements at the channel bottom. These findings allow a better understanding of the analyte distribution and diffusion processes in the microreactor channel as the basis for process control of the synthesis reaction.

12

Revsbech, Niels Peter, Lars Peter Nielsen, Peter Bondo Christensen e Jan Sørensen. "Combined Oxygen and Nitrous Oxide Microsensor for Denitrification Studies". Applied and Environmental Microbiology 54, n. 9 (1988): 2245–49. http://dx.doi.org/10.1128/aem.54.9.2245-2249.1988.

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13

Griffiths, Jennifer. "O rats! An oxygen microsensor implanted in rat brains". Analytical Chemistry 81, n. 7 (aprile 2009): 2416. http://dx.doi.org/10.1021/ac900197z.

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14

Lee, Chi-Yuan, Chia-Hung Chen, Chin-Yuan Yang, John-Shong Cheong, Yun-Hsiu Chien e Yi-Chuan Lin. "Flexible 6-in-1 Microsensor for Real-Time Microscopic Monitoring of Proton Battery". Membranes 11, n. 8 (12 agosto 2021): 615. http://dx.doi.org/10.3390/membranes11080615.

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According to the comparison between a proton battery and a proton exchange membrane fuel cell (PEMFC), the PEMFC requires oxygen and hydrogen for generating electricity, so a hydrogen tank is required, leading to larger volume of PEMFC. The proton battery can store hydrogen in the carbon layer, combined with the oxygen in the air to form water to generate electricity; thus, the battery cost and the space for a hydrogen tank can be reduced a lot, and it is used more extensively. As the proton battery is a new research area, multiple important physical quantities inside the proton battery should be further understood and monitored so as to enhance the performance of battery. The proton battery has the potential for practical applications, as well as water electrolysis, proton storage and discharge functions, and it can be produced without expensive metals. Therefore, in this study, we use micro-electro-mechanical systems (MEMS) technology to develop a diagnostic tool for the proton battery based on the developed microhydrogen sensor, integrated with the voltage, current, temperature, humidity and flow microsensors developed by this laboratory to complete a flexible integrated 6-in-1 microsensor, which is embedded in the proton battery to measure internal important physical parameters simultaneously so that the reaction condition in the proton battery can be mastered more accurately. In addition, the interaction of physical quantities of the proton battery are discussed so as to enhance the proton battery’s performance.

15

Lee, Chi-Yuan, Chia-Hung Chen, Chin-Yuan Yang e Wan-Ting Chen. "An Internal Real-Time Microscopic Diagnosis of a Proton Battery Stack during Charging and Discharging". Materials 16, n. 9 (2 maggio 2023): 3507. http://dx.doi.org/10.3390/ma16093507.

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The proton battery has facilitated a new research direction for technologies related to fuel cells and energy storage. Our R&D team has developed a prototype of a proton battery stack, but there are still problems to be solved, such as leakage and unstable power generation. Moreover, it is unlikely that the multiple important physical parameters inside the proton battery stack can be measured accurately and simultaneously. At present, external or single measurements represent the bottleneck, yet the multiple important physical parameters (oxygen, hydrogen, voltage, current, temperature, flow, and humidity) are interrelated and have a significant impact on the performance, life, and safety of the proton battery stack. This research uses micro-electro-mechanical systems (MEMS) technology to develop a micro oxygen sensor and integrates the six-in-one microsensor that our R&D team previously developed in order to improve sensor output and facilitate overall operation by redesigning the incremental mask and having this co-operate with a flexible board for sensor back-end integration, completing the development of a flexible seven-in-one (oxygen, hydrogen, voltage, current, temperature, flow, and humidity) microsensor.

16

Yu, T., C. de la Rosa e R. Lu. "Microsensor measurement of oxygen concentration in biofilms: from one dimension to three dimensions". Water Science and Technology 49, n. 11-12 (1 giugno 2004): 353–58. http://dx.doi.org/10.2166/wst.2004.0878.

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In this study, we measured oxygen concentration in biofilms in one dimension in field conditions and in three dimensions in laboratory conditions by using a robust oxygen microsensor in combination with an automation and data acquisition system. The biofilms were on the discs of rotating biological contactors treating domestic wastewater. The results of this study provide experimental evidence on oxygen distribution in wastewater biofilms and on biofilm structure. (1) The three dimensional measurements of oxygen concentration in biofilms revealed “pockets” of oxygen in deep sections of biofilms. In these isolated "pockets," located 600-760 mm from the biofilm surface, dissolved oxygen concentration was as high as 1 mg/L. This depth of oxygen diffusion is deeper than what was determined based on one dimensional measurements. (2) The heterogeneity of oxygen distribution was related to the surface structure of biofilms. The structure of the biofilm surface affected the diffusion boundary layer over the surface and, in turn, the oxygen diffusion and distribution inside biofilms. (3) Oxygen concentration in biofilms changed generally from a high degree of heterogeneity near the biofilm surface to a low degree of heterogeneity in deep sections of biofilms, indicating a cell-clusters-like structure near the surface and a more compact base layer close to the substratum.

17

Santegoeds, Cecilia M., Timothy G. Ferdelman, Gerard Muyzer e Dirk de Beer. "Structural and Functional Dynamics of Sulfate-Reducing Populations in Bacterial Biofilms". Applied and Environmental Microbiology 64, n. 10 (1 ottobre 1998): 3731–39. http://dx.doi.org/10.1128/aem.64.10.3731-3739.1998.

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ABSTRACT We describe the combined application of microsensors and molecular techniques to investigate the development of sulfate reduction and of sulfate-reducing bacterial populations in an aerobic bacterial biofilm. Microsensor measurements for oxygen showed that anaerobic zones developed in the biofilm within 1 week and that oxygen was depleted in the top 200 to 400 μm during all stages of biofilm development. Sulfate reduction was first detected after 6 weeks of growth, although favorable conditions for growth of sulfate-reducing bacteria (SRB) were present from the first week. In situ hybridization with a 16S rRNA probe for SRB revealed that sulfate reducers were present in high numbers (approximately 108 SRB/ml) in all stages of development, both in the oxic and anoxic zones of the biofilm. Denaturing gradient gel electrophoresis (DGGE) showed that the genetic diversity of the microbial community increased during the development of the biofilm. Hybridization analysis of the DGGE profiles with taxon-specific oligonucleotide probes showed thatDesulfobulbus and Desulfovibrio were the main sulfate-reducing bacteria in all biofilm samples as well as in the bulk activated sludge. However, different Desulfobulbus andDesulfovibrio species were found in the 6th and 8th weeks of incubation, respectively, coinciding with the development of sulfate reduction. Our data indicate that not all SRB detected by molecular analysis were sulfidogenically active in the biofilm.

18

Liu, Xiaojun, Xiaoyu Chen, Yong Xu, Tongtong Chen e Xiangqun Zeng. "Effects of water on ionic liquid electrochemical microsensor for oxygen sensing". Sensors and Actuators B: Chemical 285 (aprile 2019): 350–57. http://dx.doi.org/10.1016/j.snb.2019.01.026.

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Hooijmans, C. M., C. Ras e K. Ch A. M. Luyben. "Determination of oxygen profiles in biocatalyst particles by means of a combined polarographic oxygen microsensor". Enzyme and Microbial Technology 12, n. 3 (marzo 1990): 178–83. http://dx.doi.org/10.1016/0141-0229(90)90035-o.

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Nielsen, Lars Peter, Peter Bondo Christensen, Niels Peter Revsbech e Jan Sørensen. "Denitrification and oxygen respiration in biofilms studied with a microsensor for nitrous oxide and oxygen". Microbial Ecology 19, n. 1 (gennaio 1990): 63–72. http://dx.doi.org/10.1007/bf02015054.

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Bachar, Ami, Enoma Omoregie, Rutger de Wit e Henk M. Jonkers. "Diversity and Function of Chloroflexus-Like Bacteria in a Hypersaline Microbial Mat: Phylogenetic Characterization and Impact on Aerobic Respiration". Applied and Environmental Microbiology 73, n. 12 (20 aprile 2007): 3975–83. http://dx.doi.org/10.1128/aem.02532-06.

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ABSTRACT We studied the diversity of Chloroflexus-like bacteria (CLB) in a hypersaline phototrophic microbial mat and assayed their near-infrared (NIR) light-dependent oxygen respiration rates. PCR with primers that were reported to specifically target the 16S rRNA gene from members of the phylum Chloroflexi resulted in the recovery of 49 sequences and 16 phylotypes (sequences of the same phylotype share more than 96% similarity), and 10 of the sequences (four phylotypes) appeared to be related to filamentous anoxygenic phototrophic members of the family Chloroflexaceae. Photopigment analysis revealed the presence of bacteriochlorophyll c (BChlc), BChld, and γ-carotene, pigments known to be produced by phototrophic CLB. Oxygen microsensor measurements for intact mats revealed a NIR (710 to 770 nm) light-dependent decrease in aerobic respiration, a phenomenon that we also observed in an axenic culture of Chloroflexus aurantiacus. The metabolic ability of phototrophic CLB to switch from anoxygenic photosynthesis under NIR illumination to aerobic respiration under non-NIR illumination was further used to estimate the contribution of these organisms to mat community respiration. Steady-state oxygen profiles under dark conditions and in the presence of visible (VIS) light (400 to 700 nm), NIR light (710 to 770 nm), and VIS light plus NIR light were compared. NIR light illumination led to a substantial increase in the oxygen concentration in the mat. The observed impact on oxygen dynamics shows that CLB play a significant role in the cycling of carbon in this hypersaline microbial mat ecosystem. This study further demonstrates that the method applied, a combination of microsensor techniques and VIS and NIR illumination, allows rapid establishment of the presence and significance of CLB in environmental samples.

22

Guimerà, Xavier, Ana Moya, Antonio David Dorado, Xavi Illa, Rosa Villa, David Gabriel, Xavier Gamisans e Gemma Gabriel. "A Minimally Invasive Microsensor Specially Designed for Simultaneous Dissolved Oxygen and pH Biofilm Profiling". Sensors 19, n. 21 (1 novembre 2019): 4747. http://dx.doi.org/10.3390/s19214747.

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A novel sensing device for simultaneous dissolved oxygen (DO) and pH monitoring specially designed for biofilm profiling is presented in this work. This device enabled the recording of instantaneous DO and pH dynamic profiles within biofilms, improving the tools available for the study and the characterization of biological systems. The microsensor consisted of two parallel arrays of microelectrodes. Microelectrodes used for DO sensing were bare gold electrodes, while microelectrodes used for pH sensing were platinum-based electrodes modified using electrodeposited iridium oxide. The device was fabricated with a polyimide (Kapton®) film of 127 µm as a substrate for minimizing the damage caused on the biofilm structure during its insertion. The electrodes were covered with a Nafion® layer to increase sensor stability and repeatability and to avoid electrode surface fouling. DO microelectrodes showed a linear response in the range 0–8 mg L−1, a detection limit of 0.05 mg L−1, and a sensitivity of 2.06 nA L mg−1. pH electrodes showed a linear super-Nernstian response (74.2 ± 0.7 mV/pH unit) in a wide pH range (pH 4−9). The multi-analyte sensor array was validated in a flat plate bioreactor where simultaneous and instantaneous pH and DO profiles within a sulfide oxidizing biofilm were recorded. The electrodes spatial resolution, the monitoring sensitivity, and the minimally invasive features exhibited by the proposed microsensor improved biofilm monitoring performance, enabling the quantification of mass transfer resistances and the assessment of biological activity.

23

Chaturvedi, P., B. A. Hauser, J. S. Foster, E. Karplus, L. H. Levine, J. L. Coutts, J. T. Richards, D. C. Vanegas e E. S. McLamore. "A multiplexing fiber optic microsensor system for monitoring spatially resolved oxygen patterns". Sensors and Actuators B: Chemical 196 (giugno 2014): 71–79. http://dx.doi.org/10.1016/j.snb.2014.01.094.

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Jung, Sung-Kwon, Waldemar Gorski, Craig A. Aspinwall, Lisa M. Kauri e Robert T. Kennedy. "Oxygen Microsensor and Its Application to Single Cells and Mouse Pancreatic Islets". Analytical Chemistry 71, n. 17 (settembre 1999): 3642–49. http://dx.doi.org/10.1021/ac990271w.

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Viebrock, Kevin, Dominik Rabl, Sven Meinen, Paul Wunder, Jan-Angelus Meyer, Lasse Jannis Frey, Detlev Rasch, Andreas Dietzel, Torsten Mayr e Rainer Krull. "Microsensor in Microbioreactors: Full Bioprocess Characterization in a Novel Capillary-Wave Microbioreactor". Biosensors 12, n. 7 (11 luglio 2022): 512. http://dx.doi.org/10.3390/bios12070512.

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Microbioreactors (MBRs) with a volume below 1 mL are promising alternatives to established cultivation platforms such as shake flasks, lab-scale bioreactors and microtiter plates. Their main advantages are simple automatization and parallelization and the saving of expensive media components and test substances. These advantages are particularly pronounced in small-scale MBRs with a volume below 10 µL. However, most described small-scale MBRs are lacking in process information from integrated sensors due to limited space and sensor technology. Therefore, a novel capillary-wave microbioreactor (cwMBR) with a volume of only 7 µL has the potential to close this gap, as it combines a small volume with integrated sensors for biomass, pH, dissolved oxygen (DO) and glucose concentration. In the cwMBR, pH and DO are measured by established luminescent optical sensors on the bottom of the cwMBR. The novel glucose sensor is based on a modified oxygen sensor, which measures the oxygen uptake of glucose oxidase (GOx) in the presence of glucose up to a concentration of 15 mM. Furthermore, absorbance measurement allows biomass determination. The optical sensors enabled the characterization of an Escherichia coli batch cultivation over 8 h in the cwMBR as proof of concept for further bioprocesses. Hence, the cwMBR with integrated optical sensors has the potential for a wide range of microscale bioprocesses, including cell-based assays, screening applications and process development.

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Schramm, Andreas, Cecilia M. Santegoeds, Helle K. Nielsen, Helle Ploug, Michael Wagner, Milan Pribyl, Jiri Wanner, Rudolf Amann e Dirk de Beer. "On the Occurrence of Anoxic Microniches, Denitrification, and Sulfate Reduction in Aerated Activated Sludge". Applied and Environmental Microbiology 65, n. 9 (1 settembre 1999): 4189–96. http://dx.doi.org/10.1128/aem.65.9.4189-4196.1999.

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ABSTRACT A combination of different methods was applied to investigate the occurrence of anaerobic processes in aerated activated sludge. Microsensor measurements (O2, NO2 −, NO3 −, and H2S) were performed on single sludge flocs to detect anoxic niches, nitrate reduction, or sulfate reduction on a microscale. Incubations of activated sludge with15NO3 − and35SO4 2− were used to determine denitrification and sulfate reduction rates on a batch scale. In four of six investigated sludges, no anoxic zones developed during aeration, and consequently denitrification rates were very low. However, in two sludges anoxia in flocs coincided with significant denitrification rates. Sulfate reduction could not be detected in any sludge in either the microsensor or the batch investigation, not even under short-term anoxic conditions. In contrast, the presence of sulfate-reducing bacteria was shown by fluorescence in situ hybridization with 16S rRNA-targeted oligonucleotide probes and by PCR-based detection of genes coding for the dissimilatory sulfite reductase. A possible explanation for the absence of anoxia even in most of the larger flocs might be that oxygen transport is not only diffusional but enhanced by advection, i.e., facilitated by flow through pores and channels. This possibility is suggested by the irregularity of some oxygen profiles and by confocal laser scanning microscopy of the three-dimensional floc structures, which showed that flocs from the two sludges in which anoxic zones were found were apparently denser than flocs from the other sludges.

27

Rolletschek, Hardy, Achim Stangelmayer e Ljudmilla Borisjuk. "Methodology and Significance of Microsensor-based Oxygen Mapping in Plant Seeds – an Overview". Sensors 9, n. 5 (27 aprile 2009): 3218–27. http://dx.doi.org/10.3390/s90503218.

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Hanna, Christine, Lydia Schonberg, Dirk de Beer e Angela Lawton. "OXYGEN MICROSENSOR STUDIES ON ZOOXANTHELLATE CLIONAID SPONGES FROM THE COSTA BRAVA, MEDITERRANEAN SEA1". Journal of Phycology 41, n. 4 (agosto 2005): 774–79. http://dx.doi.org/10.1111/j.0022-3646.2005.04226.x.

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van den Tempel, Tatjana, Jens K. Gundersen e Marianne S. Nielsen. "The microdistribution of oxygen in Danablu cheese measured by a microsensor during ripening". International Journal of Food Microbiology 75, n. 1-2 (maggio 2002): 157–61. http://dx.doi.org/10.1016/s0168-1605(01)00728-0.

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James, Garth A., Alice Ge Zhao, Marcia Usui, Robert A. Underwood, Hung Nguyen, Haluk Beyenal, Elinor deLancey Pulcini et al. "Microsensor and transcriptomic signatures of oxygen depletion in biofilms associated with chronic wounds". Wound Repair and Regeneration 24, n. 2 (16 febbraio 2016): 373–83. http://dx.doi.org/10.1111/wrr.12401.

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Lassen, Carsten, Leslie E. Bebout, Hans W. Paerl e Bo B. Jorgensen. "MICROSENSOR STUDIES OF OXYGEN AND LIGHT DISTRIBUTION IN THE GREEN MACROALGA CODIUM FRAGILE1". Journal of Phycology 30, n. 3 (giugno 1994): 381–86. http://dx.doi.org/10.1111/j.0022-3646.1994.00381.x.

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32

Grattieri, Matteo, Sofia Babanova, Carlo Santoro, Edoardo Guerrini, Stefano PM Trasatti, Pierangela Cristiani, Massimiliano Bestetti e Plamen Atanassov. "Enzymatic Oxygen Microsensor Based on Bilirubin Oxidase Applied to Microbial Fuel Cells Analysis". Electroanalysis 27, n. 2 (22 gennaio 2015): 327–35. http://dx.doi.org/10.1002/elan.201400543.

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33

Qin, Sun, Li Ma, Fernando Ferreira, Chelsea Brown, Manuel F. Navedo, Brian Reid e Min Zhao. "Diabetic Ocular Surface Has Defects in Oxygen Uptake Revealed by Optic Fiber Microsensor". Investigative Opthalmology & Visual Science 65, n. 3 (20 marzo 2024): 27. http://dx.doi.org/10.1167/iovs.65.3.27.

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34

Hooijmans, C. M., S. G. M. Geraats e K. Ch A. M. Luyben. "Use of an oxygen microsensor for the determination of intrinsic kinetic parameters of an immobilized oxygen reducing enzyme". Biotechnology and Bioengineering 35, n. 11 (maggio 1990): 1078–87. http://dx.doi.org/10.1002/bit.260351103.

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35

Park, Sarah S., Minyoung Hong, Cha-Kyong Song, Gil-Ja Jhon, Youngmi Lee e Minah Suh. "Real-Timein VivoSimultaneous Measurements of Nitric Oxide and Oxygen Using an Amperometric Dual Microsensor". Analytical Chemistry 82, n. 18 (15 settembre 2010): 7618–24. http://dx.doi.org/10.1021/ac1013496.

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36

Qin, Sun, Li Ma, Fernando Ferreira, Chelsea Brown, Brian Reid e Min Zhao. "Optic Fiber Microsensor Reveals Specific Spatiotemporal Oxygen Uptake Profiles at the Mammalian Ocular Surface". Biosensors 13, n. 2 (9 febbraio 2023): 245. http://dx.doi.org/10.3390/bios13020245.

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Abstract (sommario):

Oxygen (O2) uptake by cells and tissues is a critical indicator of metabolic demand, changes in microenvironment, and pathophysiology. O2 uptake from the atmosphere accounts for virtually all the O2 consumption in the avascular cornea; however, a detailed spatiotemporal profile of corneal O2 uptake (COU) remains undetermined. Here, we used a non-invasive self-referencing optical fiber O2 sensor—the scanning micro-optrode technique (SMOT)—to report the O2 partial pressure and flux variations at the ocular surface of rodents and non-human primates. In vivo spatial mapping in mice revealed a distinct COU, characterized by a centripetal gradient with a significantly higher O2 influx at the limbus and conjunctiva regions than at the center of the cornea. This regional COU profile was reproduced ex vivo in freshly enucleated eyes. The centripetal gradient was conserved across the following species analyzed: mice, rats, and rhesus monkeys. In vivo temporal mapping in mice showed a significant increase in the O2 flux in the limbus in the evening compared to other times. Altogether, the data unveiled a conserved centripetal COU profile, which may be associated with the limbal epithelial stem cells residing at the intersection of the limbus and conjunctiva. These physiological observations will serve as a useful baseline for comparative studies with contact lens wear, ocular disease, diabetes, etc. Moreover, the sensor may be applied to understand the responses of the cornea and other tissues to various insults, drugs, or changes in the environment.

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Park, Sarah S., Clarissa E. Tatum e Youngmi Lee. "Dual electrochemical microsensor for simultaneous measurements of nitric oxide and oxygen: Fabrication and characterization". Electrochemistry Communications 11, n. 10 (ottobre 2009): 2040–43. http://dx.doi.org/10.1016/j.elecom.2009.08.047.

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38

Klatt, J. M., A. Chennu, B. K. Arbic, B. A. Biddanda e G. J. Dick. "Possible link between Earth’s rotation rate and oxygenation". Nature Geoscience 14, n. 8 (agosto 2021): 564–70. http://dx.doi.org/10.1038/s41561-021-00784-3.

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Abstract (sommario):

AbstractThe biotic and abiotic controls on major shifts in atmospheric oxygen and the persistence of low-oxygen periods over a majority of Earth’s history remain under debate. Explanations of Earth’s stepwise pattern of oxygenation have mostly neglected the effect of changing diel illumination dynamics linked to daylength, which has increased through geological time due to Earth’s rotational deceleration caused by tidal friction. Here we used microsensor measurements and dynamic modelling of interfacial solute fluxes in cyanobacterial mats to investigate the effect of changing daylength on Precambrian benthic ecosystems. Simulated increases in daylength across Earth’s historical range boosted the diel benthic oxygen export, even when the gross photosynthetic production remained constant. This fundamental relationship between net productivity and daylength emerges from the interaction of diffusive mass transfer and diel illumination dynamics, and is amplified by metabolic regulation and microbial behaviour. We found that the resultant daylength-driven surplus organic carbon burial could have shaped the increase in atmospheric oxygen that occurred during the Great and Neoproterozoic Oxidation Events. Our suggested mechanism, which links the coinciding increases in daylength and atmospheric oxygen via enhanced net productivity, reveals a possible contribution of planetary mechanics to the evolution of Earth’s biology and geochemistry.

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Zilberstein, Judith, Avraham Bromberg, Anatol Frantz, Varda Rosenbach-Belkin, Amnon Kritzmann, Reuven Pfefermann, Yoram Salomon e Avigdor Scherz. "Light-dependent Oxygen Consumption in Bacteriochlorophyll-Serine-treated Melanoma Tumors: On-line Determination Using a Tissue-inserted Oxygen Microsensor". Photochemistry and Photobiology 65, n. 6 (giugno 1997): 1012–19. http://dx.doi.org/10.1111/j.1751-1097.1997.tb07962.x.

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40

Stief, Peter, Anna Behrendt, Gaute Lavik e Dirk De Beer. "Combined Gel Probe and Isotope Labeling Technique for Measuring Dissimilatory Nitrate Reduction to Ammonium in Sediments at Millimeter-Level Resolution". Applied and Environmental Microbiology 76, n. 18 (23 luglio 2010): 6239–47. http://dx.doi.org/10.1128/aem.01104-10.

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Abstract (sommario):

ABSTRACT Dissimilatory NO3 − reduction in sediments is often measured in bulk incubations that destroy in situ gradients of controlling factors such as sulfide and oxygen. Additionally, the use of unnaturally high NO3 − concentrations yields potential rather than actual activities of dissimilatory NO3 − reduction. We developed a technique to determine the vertical distribution of the net rates of dissimilatory nitrate reduction to ammonium (DNRA) with minimal physical disturbance in intact sediment cores at millimeter-level resolution. This allows DNRA activity to be directly linked to the microenvironmental conditions in the layer of NO3 − consumption. The water column of the sediment core is amended with 15NO3 − at the in situ 14NO3 − concentration. A gel probe is deployed in the sediment and is retrieved after complete diffusive equilibration between the gel and the sediment pore water. The gel is then sliced and the NH4 + dissolved in the gel slices is chemically converted by hypobromite to N2 in reaction vials. The isotopic composition of N2 is determined by mass spectrometry. We used the combined gel probe and isotopic labeling technique with freshwater and marine sediment cores and with sterile quartz sand with artificial gradients of 15NH4 +. The results were compared to the NH4 + microsensor profiles measured in freshwater sediment and quartz sand and to the N2O microsensor profiles measured in acetylene-amended sediments to trace denitrification.

41

Wittmann, Christiane, e Hardy Pfanz. "Bark and woody tissue photosynthesis: a means to avoid hypoxia or anoxia in developing stem tissues". Functional Plant Biology 41, n. 9 (2014): 940. http://dx.doi.org/10.1071/fp14046.

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Abstract (sommario):

In woody plants, oxygen transport and delivery via the xylem sap are well described, but the contribution of bark and woody tissue photosynthesis to oxygen delivery in stems is poorly understood. Here, we combined stem chlorophyll fluorescence measurements with microsensor quantifications of bark O2 levels and oxygen gas exchange measurements of isolated current-year stem tissues of beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.) to investigate how bark and woody tissue photosynthesis impairs the oxygen status of stems. Measurements were made before bud break, when the axial path of oxygen supply via the xylem sap is impeded. At that time, bark O2 levels showed O2 concentrations below the atmospheric concentration, indicating hypoxic conditions or O2 deficiency within the inner bark, but the values were always far away from anoxic. Under illumination bark and woody tissue photosynthesis rapidly increased internal oxygen concentrations compared with plants in the dark, and thereby counteracted against localised hypoxia. The highest photosynthetic activity and oxygen release rates were found in the outermost cortex tissues. By contrast, rates of woody tissue photosynthesis were considerably lower, due to the high light attenuation of the bark and cortex tissues, as well as resistances in radial oxygen diffusion. Therefore, our results confirm that bark and woody tissue photosynthesis not only play a role in plant carbon economy, but may also be important for preventing low oxygen-limitations of respiration in these dense and metabolically active tissues.

42

Marzioch, Julia, Friederike Kramer, Peter Dungel, Jochen Kieninger e Gerald A. Urban. "Pericellular Oxygen Monitoring during Low-Level Light Therapy in Cell Culture Using a Microsensor System". Proceedings 1, n. 4 (21 agosto 2017): 499. http://dx.doi.org/10.3390/proceedings1040499.

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43

Ferreira, Fernando, Guillaume Luxardi, Brian Reid, Li Ma, VijayKrishna Raghunathan e Min Zhao. "Real-time physiological measurements of oxygen using a non-invasive self-referencing optical fiber microsensor". Nature Protocols 15, n. 2 (10 gennaio 2020): 207–35. http://dx.doi.org/10.1038/s41596-019-0231-x.

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44

Berry, Adrian D., e Steven A. Sargent. "Real-time microsensor measurement of internal oxygen partial pressure in tomato fruit under hypoxic conditions". Postharvest Biology and Technology 52, n. 2 (maggio 2009): 240–42. http://dx.doi.org/10.1016/j.postharvbio.2009.01.007.

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45

Li, Tong, Björn Podola, Dirk de Beer e Michael Melkonian. "A method to determine photosynthetic activity from oxygen microsensor data in biofilms subjected to evaporation". Journal of Microbiological Methods 117 (ottobre 2015): 100–107. http://dx.doi.org/10.1016/j.mimet.2015.07.022.

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46

Christensen, P. B., N. P. Revsbech e K. Sand-Jensen. "Microsensor Analysis of Oxygen in the Rhizosphere of the Aquatic Macrophyte Littorella uniflora (L.) Ascherson". Plant Physiology 105, n. 3 (1 luglio 1994): 847–52. http://dx.doi.org/10.1104/pp.105.3.847.

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47

Revsbech, N. P., O. Pedersen, W. Reichardt e A. Briones. "Microsensor analysis of oxygen and pH in the rice rhizosphere under field and laboratory conditions". Biology and Fertility of Soils 29, n. 4 (3 agosto 1999): 379–85. http://dx.doi.org/10.1007/s003740050568.

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48

Revsbech, Niels Peter, Peter Bondo Christensen, Lars Peter Nielsen e Jan Sørensen. "Denitrification in a trickling filter biofilm studied by a microsensor for oxygen and nitrous oxide". Water Research 23, n. 7 (luglio 1989): 867–71. http://dx.doi.org/10.1016/0043-1354(89)90011-0.

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49

Dalsgaard, Tage, e Niels Peter Revsbech. "Regulating factors of denitrification in trickling filter biofilms as measured with the oxygen/nitrous oxide microsensor". FEMS Microbiology Letters 101, n. 3 (settembre 1992): 151–64. http://dx.doi.org/10.1111/j.1574-6968.1992.tb05771.x.

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50

Dalsgaard, Tage, e Niels Peter Revsbech. "Regulating factors of denitrification in trickling filter biofilms as measured with the oxygen/nitrous oxide microsensor". FEMS Microbiology Ecology 10, n. 3 (settembre 1992): 151–64. http://dx.doi.org/10.1111/j.1574-6941.1992.tb01651.x.

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