scholarly journals Ion Selective Amperometric Biosensors for Environmental Analysis of Nitrate, Nitrite and Sulfate

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4326
Author(s):  
Niels Peter Revsbech ◽  
Michael Nielsen ◽  
Deby Fapyane
Keyword(s):  
Inorganic Ions ◽  
Natural Environments ◽  
Nitrogen Transformations ◽  
Redox Transformation ◽  
Whole Cells ◽  
Long Term Stability ◽  
High Degree ◽  
Insight Into ◽  
A Current

Inorganic ions that can be redox-transformed by living cells can be sensed by biosensors, where the redox transformation gives rise to a current in a measuring circuit. Such biosensors may be based on enzymes, or they may be based on application of whole cells. In this review focus will be on biosensors for the environmentally important ions NO3−, NO2−, and SO42−, and for comparison alternative sensor-based detection will also be mentioned. The developed biosensors are generally characterized by a high degree of specificity, but unfortunately also by relatively short lifetimes. There are several investigations where biosensor measurement of NO3− and NO2− have given new insight into the functioning of nitrogen transformations in man-made and natural environments such as sediments and biofilms, but the biosensors have not become routine tools. Future modifications resulting in better long-term stability may enable such general use.

Application of Mg-Al-LDH@MgFe2O4 Nanocomposite Supported on Gold Micron-Dendrites as an Efficient Electrocatalyst for Ethanol Oxidation

NANO ◽  
2020 ◽  
Vol 15 (03) ◽  
pp. 2050037
Author(s):  
Masoumeh Taei ◽  
Masoud Fouladgar ◽  
Foroozan Hasanpour ◽  
Fatemeh Hasheminasab
Keyword(s):  
Glassy Carbon ◽  
Current Density ◽  
Ethanol Oxidation ◽  
Carbon Electrode ◽  
Co Poisoning ◽  
Long Term Stability ◽  
Enhance Efficiency ◽  
A Current ◽  
Oxidation Of Ethanol

Mg-Al-LDH@MgFe2O4 nanocomposite was synthesized and was applied to enhance efficiency of gold micron-dendrites/glassy carbon electrode (Mg-Al-LDH@MgFe2O4/AuNDs/GCE) for oxidation of ethanol. Based on the results, Mg-Al-LDH@MgFe2O4/AuNDs showed a current density of 29.4[Formula: see text]mA cm[Formula: see text], which was 1.6 times higher than that on the surface of AuNDs/GCE. Also, long-term stability of the studied electrode showed that the nanocomposite improves CO-poisoning tolerance of the AuNDs. Accordingly, the Mg-Al-LDH@MgFe2O4/AuNDs catalyst exhibits an excellent potential for application in alkaline ethanol fuel cells.

Polyaniline/nano-in2O3 Composites Used as a Sensitive Material to NH3

2011 ◽  
Vol 239-242 ◽  
pp. 322-327 ◽  
Author(s):  
Ying Nan Xie ◽  
Zheng Hai Shi ◽  
Jian Lian Liu
Keyword(s):  
In Situ Polymerization ◽  
Average Diameter ◽  
Environmental Stability ◽  
Sensitive Material ◽  
Long Term Stability ◽  
Degree Of Crystallization ◽  
High Degree ◽  
Sulphosalicylic Acid

In presence of nano-In2O3 which were synthesised via a reverse microemulsion, Polyaniline/nano-In2O3 composites were prepared by in-situ polymerization of aniline in 5-sulphosalicylic acid(SSA) aqueous solution. They were characterized by means of TEM, XRD and FTIR.. TEM and XRD showed that the average diameter of In2O3 particles was 15nm with a narrow size distribution and with a high degree of crystallization. The FTIR suggested that the structure of PAn-SSA was not be changed by the mixture of In2O3. Sensitivity of the composites to 100~1000ppm NH3 were studied, the results reveal that polyaniline/nano-In2O3 composites have short response time and good reversibility, the gas sensitive of composites to NH3 under 300ppm increased linearly with the increasing concentration of NH3 and decreased with the increasing of In2O3 concentration. Long-term stability of polyaniline/nano-In2O3 composites were also investagated, it can be concluded that the organic-inorganic hybrid materials have better environmental stability.

scholarly journals Migration promotes plasmid stability under spatially heterogeneous positive selection

2018 ◽  
Vol 285 (1879) ◽  
pp. 20180324 ◽  
Author(s):  
Ellie Harrison ◽  
James P. J. Hall ◽  
Michael A. Brockhurst
Keyword(s):  
Positive Selection ◽  
Plasmid Stability ◽  
Mercury Resistance ◽  
Natural Environments ◽  
Compensatory Evolution ◽  
Long Term Stability ◽  
Compensatory Mutations ◽  
Selection For ◽  
The Stability

Bacteria–plasmid associations can be mutualistic or antagonistic depending on the strength of positive selection for plasmid-encoded genes, with contrasting outcomes for plasmid stability. In mutualistic environments, plasmids are swept to high frequency by positive selection, increasing the likelihood of compensatory evolution to ameliorate the plasmid cost, which promotes long-term stability. In antagonistic environments, plasmids are purged by negative selection, reducing the probability of compensatory evolution and driving their extinction. Here we show, using experimental evolution of Pseudomonas fluorescens and the mercury-resistance plasmid, pQBR103, that migration promotes plasmid stability in spatially heterogeneous selection environments. Specifically, migration from mutualistic environments, by increasing both the frequency of the plasmid and the supply of compensatory mutations, stabilized plasmids in antagonistic environments where, without migration, they approached extinction. These data suggest that spatially heterogeneous positive selection, which is common in natural environments, coupled with migration helps to explain the stability of plasmids and the ecologically important genes that they encode.

scholarly journals Study of lifetime of Platinum Modified Metal Oxides Electrodes

2020 ◽  
Vol 14 (4) ◽  
pp. 1479-1488
Author(s):  
Lemeyonouin Aliou Guillaume Pohan ◽  
Ollo Kambiré ◽  
Mohamed Berté ◽  
Lassiné Ouattara
Keyword(s):  
Metal Oxides ◽  
Platinum Metal ◽  
Porous Structures ◽  
Term Stability ◽  
Long Term Stability ◽  
Physical Measurements ◽  
Platinum Coating ◽  
The One ◽  
A Current

Pt, IrO2, RuO2, Pt-IrO2 and Pt-RuO2 electrodes have been shown to be effective in their application in various fields. However, it is necessary to study their long-term stability. So, our objective is to prepare them and study their lifetime using intensiostatic measurement. Then they were prepared at 400 °C on titanium plates used as a substrate. Physical measurements (scanning electron microscopy) of these anodes revealed that their surface are rough and porous structures. Lifetime study was carried out in H2SO4 9 N and under a current density of 410 mA /cm2. The long-term stability of Pt improved when coupled to IrO2 in contrast to RuO2. From this study, the performance of the electrode was found to increase in the order: RuO2 < Pt-RuO2 < Pt < Pt-IrO2 < IrO2. For RuO2 and IrO2 pure electrodes, the deactivation would be due to the dissolution of precursors deposited on the titanium. For the Pt pure electrode, deactivation would be due to the detachment of platinum coating. The deactivation of the Pt-IrO2 and Pt-RuO2 electrode would be due, on the one hand to the platinum detachment from IrO2 or RuO2 and on the other hand to the metal oxides (IrO2 or RuO2) dissolution.Keywords: Electrodes, platinum, metal oxides, lifetime.

scholarly journals Accuracy and Long-Term Stability Assessment of Inductive Conductivity Cell Measurements on Argo Floats

2020 ◽  
Vol 37 (12) ◽  
pp. 2209-2223
Author(s):  
Nikolay P. Nezlin ◽  
Mathieu Dever ◽  
Mark Halverson ◽  
Jean-Michel Leconte ◽  
Guillaume Maze ◽  
...  
Keyword(s):  
Statistical Tool ◽  
Argo Floats ◽  
Term Stability ◽  
Long Term Stability ◽  
Sensor Package ◽  
New Sensors ◽  
High Degree ◽  
The Western Pacific ◽  
Conductivity Cell

AbstractThis study demonstrates the long-term stability of salinity measurements from Argo floats equipped with inductive conductivity cells, which have extended float lifetimes as compared to electrode-type cells. New Argo float sensor payloads must meet the demands of the Argo governance committees before they are implemented globally. Currently, the use of CTDs with inductive cells designed and manufactured by RBR, Ltd., has been approved as a Global Argo Pilot. One requirement for new sensors is to demonstrate stable measurements over the lifetime of a float. To demonstrate this, data from four Argo floats in the western Pacific Ocean equipped with the RBRargo CTD sensor package are analyzed using the same Owens–Wong–Cabanes (OWC) method and reference datasets as the Argo delayed-mode quality control (DMQC) operators. When run with default settings against the standard DMQC Argo and CTD databases, the OWC analysis reveals no drift in any of the four RBRargo datasets and, in one case, an offset exceeding the Argo target salinity limits. Being a statistical tool, the OWC method cannot strictly determine whether deviations in salinity measurements with respect to a reference hydrographic product (e.g., climatologies) are caused by oceanographic variability or sensor problems. So, this study furthermore investigates anomalous salinity measurements observed when compared with a reference product and demonstrates that anomalous values tend to occur in regions with a high degree of variability and can be better explained by imperfect reference data rather than sensor drift. This study concludes that the RBR inductive cell is a viable option for salinity measurements as part of the Argo program.

Remarks on the stability of temporary cuts

1990 ◽  
Vol 27 (5) ◽  
pp. 687-692 ◽  
Author(s):  
S. Leroueil ◽  
P. La Rochelle ◽  
F. Tavenas ◽  
M. Roy
Keyword(s):  
Undrained Shear Strength ◽  
Short Term ◽  
Overconsolidation Ratio ◽  
Term Stability ◽  
Long Term Stability ◽  
Liquidity Index ◽  
The Stability ◽  
Insight Into ◽  
Undrained Shear

A re-analysis of the observations and data related to the stability of excavations in clays gives a new insight into the problem. It is shown that for clays with a liquidity index greater than 0.4, the short-term stability can be estimated on the basis of the undrained shear strength without applying any correction factor; it is also shown that the long-term stability is lower than the short-term stability by an amount that depends on the overconsolidation ratio of the clay. Finally, experience proving that pore-pressure equilibration is highly variable and difficult to predict, it is recommended to systematically instrument excavations with piezometers. Key words: clay, short-term stability, long-term stability, excavations, pore pressures, overconsolidation ratio.

An EHF resonant tunnel diode oscillator

1996 ◽  
Vol 74 (S1) ◽  
pp. 243-247
Author(s):  
M. Roschke ◽  
C. Chan ◽  
O. Berolo
Keyword(s):  
Quantum Wells ◽  
Mbe Growth ◽  
Resonant Tunnelling ◽  
Long Term Stability ◽  
Wafer Probing ◽  
Device Applications ◽  
Resonant Tunnel ◽  
High Degree ◽  
Tunnel Diode Oscillator

Resonant tunnelling diodes (RTDs) are emerging as some of the more promising electron devices in the field of communications. The rapid progress of molecular beam epitaxy (MBE) growth techniques during the last decade has resulted in RTDs that exhibit remarkable peak-to-valley ratios, opening the door to a variety of useful device applications. To study the applicability of low-power EHF oscillators for personal communications and global-positioning system applications, we fabricated RTDs using AlAs/GaAs/AlAs double- barrier quantum wells and a MESFET fabrication process. The dc and rf characteristics of the RTDs, which showed a high degree of bistability, were obtained by on-wafer probing using an HP8510 network analyzer with a cascade probe station. The devices were then used in a number of simple hybrid oscillator circuits on alumina substrates. Focusing on the oscillation frequency of 37 GHz, we report on the room-temperature short-, medium-, and long-term stability of the oscillators while monitoring thermal drift and dc bias control.

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