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D
Voltammetry in which small potential pulses (constant height 10 to 100 mV, constant width 10 to 100 ms) are superimposed onto a linearly varying potential or onto a staircase potential ramp. The current is sampled just before the onset of the pulse (e.g. 10 to 20 ms) and for the same sampling time just before the end of the pulse. The difference between the two sampled currents is plotted versus the potential applied before the pulse. Thus, a differential pulse voltammogram is peak-shaped. Differential pulse polarography is differential pulse voltammetry in which a dropping mercury electrode is used as the working electrode. A pulse is applied before the mechani- cally enforced end of the drop and the current is sampled twice: just before the onset of the pulse and just before its end. The pulse width is usually 10 to 20 % of the drop life. The drop dislodgement is synchronized with current sampling, which is carried out as in DPV. The ratio of faradaic current to charging current is enhanced and the negative influence of charging current is partially eliminated in the same way as in normal pulse voltammetry (NPV). Moreover, subtraction of the charging current sampled before the application of the pulse further decreases its negative influence. Due to the more enhanced signal (faradaic current) to noise (charging current) ratio, the limit of detection is lower than with NPV. The sensitivity of DPV depends on the reversibility of the electrode reaction of the analyte. +
differentialpulsevoltammetry +
DifferentialRefractiveIndex +
differentialrefractiveindex +
Differential scanning calorimetry (DSC) is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature. Both the sample and reference are maintained at nearly the same temperature throughout the experiment. Generally, the temperature program for a DSC analysis is designed such that the sample holder temperature increases linearly as a function of time. The reference sample should have a well-defined heat capacity over the range of temperatures to be scanned. Additionally, the reference sample must be stable, of high purity, and must not experience much change across the temperature scan. Typically, reference standards have been metals such as indium, tin, bismuth, and lead, but other standards such as polyethylene and fatty acids have been proposed to study polymers and organic compounds, respectively. +
DifferentialScanningCalorimetry +
differentialscanningcalorimetry +
Differential Pulse Voltammetry in which small potential pulses are superimposed onto a staircase potential ramp. +
DifferentialStaircasePulseVoltammetry +
differentialstaircasepulsevoltammetry +
Differential thermal analysis (DTA) is a thermoanalytic technique that is similar to differential scanning calorimetry. In DTA, the material under study and an inert reference are made to undergo identical thermal cycles, (i.e., same cooling or heating programme) while recording any temperature difference between sample and reference.[1] This differential temperature is then plotted against time, or against temperature (DTA curve, or thermogram). Changes in the sample, either exothermic or endothermic, can be detected relative to the inert reference. Thus, a DTA curve provides data on the transformations that have occurred, such as glass transitions, crystallization, melting and sublimation. The area under a DTA peak is the enthalpy change and is not affected by the heat capacity of the sample. +
DifferentialThermalAnalysis +
differentialthermalanalysis +
DiffuseLayerPotential +
diffuselayerpotential +