Gas adsorption effects on surface conductivity of nonstoichiometric CuO

The aim of the present paper is to test the capability of nonstoichiometric CuO as a conductance sensor material. The surface conductivity changes in CuO were measured in the presence of various donor-acceptor couples. The influence of water and oxygen was investigated as well as NO2 and CO. NO2 had a very high sensitivity.Kinetic schemes of surface reactions are also reported and discussed. (C) 2003 Elsevier B.V. All rights reserved

A two electrode C–NiO Nafion amperometric sensor for NO2 detection

In this paper, the authors propose a new and simple Nafion-based NO2 amperometric sensor, a dedicated measurement system, and a measurement protocol. The system has a linear response to NO2 concentration, and a sensitivity up to 90 nA/ppm. Moreover, the developed sensors show a satisfactory repeatability and a low cross-sensitivity to common interfering gases such as CO and oxygen

Amperometric sensors based on Nafion Proton onductor: A comparison between two different structures

In this work the authors propose the development and the characterization of two NO2 amperometric detection systems, based on two different solid state electrochemical sensors. Both sensors have a Nickel Oxide counter electrode, a Graphite working electrode, and Nafion as protonic conductor. The first detection system exploits a two-electrode sensor that presents a satisfactory sensitivity to NO2, a very low cross-response to interfering gases (CO, O2), a short response time, and that requires simple front-end electronics. Nevertheless, the usage of this sensor is limited to the detection of low NO2 concentrations (below 10 ppm). A similar performance can be obtained by a system based on a three-electrode version of the sensor which can be used in a wider NO2 concentration range, but requires a more complex front end electronics

A Two Electrode C - NiO Nafion® Amperometric Sensor for NO2 Detection

In this paper the authors propose a new and simple Nafion® based amperometric sensor and a dedicated measurement system and measurement protocol. The system has a linear response to NO2 concentration and a sensitivity up to 90nA/ppm. Moreover, the developed sensor shows a satisfactory repeatability and a low cross-sensitivity to some common interfering gases (such as CO and oxygen)

A two electrode electrochemical amperometric sensor for NO2 detection

In this work a new and simple two electrode amperometric sensor for NO 2 detection is described. The sensor consists of a Nafion® proton exchange membrane (PEM), a Graphite working electrode, and a NiO counter electrode. The developed sensor presents a good sensitivity to NO2 and very small cross sensitivity to CO and O2. A dedicated measurement system was developed, and a measurement protocol was found, ensuring satisfactory performance also in terms of repeatability

The nitric oxide metabolism in the hypoxic, ischemic and reperfused human skeletal muscle cell: clinical and therapeutical observations

BACKGROUND: The biochemical and metabolic role played by nitric oxide (NO) in course of oxidative stress due to cell hypoxia, ischemia and reperfusion has a determinant relevance in the mitochondrial adaptive changes which antagonize the irreversible morpho-functional damage. In particular conditions, such as in prolonged ischemia and/or exogenous NO supplementation, this element is present in the radical form (NOO*) concurring to peroxidative cell injury. Aim of this study was to investigate these opposite NO aspects in hypoxic, ischemic and reperfused human skeletal muscle tissue. METHODS: Skeletal muscle samples were taken during elective knee orthopedic surgery in 10 consecutive patients. The biopsies were obtained before, after 5+/-1 min and 58+/-2 min from tourniquet application and then after 18+/-3 min following muscle reperfusion. The samples, immediately frozen in liquid nitrogen, were assayed for endocellular free NO following the gas-amperometric method described by Palmerini C. RESULTS: When compared with normoxic tissues, a significant decrease in free NO content was observed in hypoxic samples. After about 60 min of prolonged ischemia the NO levels show an evident increase, while the tissue reperfusion leads to a progressive restoration of physiological content in the cellular free nitric oxide. CONCLUSIONS: The obtained data in hypoxic muscle cell seem to underline the pivotal role played by NO in adapting the cytochrome c oxidase oxidative activity to lower O2 bio-availability. On the other hand the prolonged ischemia leads to a consistent NOO* generation triggered by oxyradical generation and Ca2+ intracellular over load. Even if the tissue reoxygenation restores the normal NO levels it is arguable that the pre-treatment of ischemic cell with antioxidants, Ca-antagonist and Dexamethasone supplementation could represent a crucial and specific therapeutic approach to critically ill patient