Static mode operation

A laboratory robot can operate unattended for 24 hours a day, releasing skilled technicians and scientists for more important and challenging work. Process workers can often be trained to bring the samples to the robot for analysis on a static mode operation. This provides valuable results with a fast timescale. 

The design and implementation of a portable fiber-optic cholinesterase biosensor for the detection and determination of pesticides carbaryl and dichlorvos was presented by Andreou81. The sensing bioactive material was a three-layer sandwich. The enzyme cholinesterase was immobilized on the outer layer, consisting of hydrophilic modified polyvinylidenefluoride membrane. The membrane was in contact with an intermediate sol-gel layer that incorporated bromocresol purple, deposited on an inner disk. The sensor operated in a static mode at room temperature and the rate of the inhibited reaction served as an analytical signal. This method was successfully applied to the direct analysis of natural water samples (detection and determination of these pesticides), without sample pretreatment, and since the biosensor setup is fully portable (in a small case), it is suitable for in-field use. 

Multi-collection mass spectrometers can analyze isotope ratios in a static mode to eliminate the errors from beam instability. However, the static multi-collection method depends on the extent to which the collectors (e.g., Faraday cups) are identical and to the extent to which the gain of each collector is stable. An alternative approach is to use the so-called dynamic multi-collector mode, to cancel out beam instability, detector bias, and performing a power-law mass fractionation correction. The following descriptions are modified from the Finnigan MAT 262 Operating manual (Finnigan, 1992). 

With the fundamental apparatus established, normal operation above 273 K proceeds in one of three static modes ... 

Sensitivity to First Monolayer Profiling Capability with Depth Possible Operation in Near Static Mode... 

Accelerated solvent extraction as implemented in commercial equipment is basically discrete in nature, so it is rarely coupled to other operations of the analytical process. In fact, only in two reported applications was the static mode coupled on-line to other operations such as chromatographic separation, preconcentration and detection. Both used custom extractors as the compact design of the commercial models precluded their adaptation. 

Static Mode in Liquids In liquids, the capillary force is not present allowing a more straightforward interpretation of the results. Furthermore, the contact area is as small as a single-atom contact. Special cantilevers have to be used for the operation in liquid. When reused, those cantilevers must be carefully cleaned and are best kept wet until employed again. 

A glucose sensor system consisting of an oxygen electrode and a glucose oxidase electrode was recently implanted into the vena cava of a dog (McKean and Gough, 1988). The sensors operated in the potentio-static mode and were connected to an implantable telemetry system. Both the enzyme stability and the power consumption allowed operation of the system for three months. 

The buffering action of a coating in this situation is determined by the relaxation modulus of the coating material. The relaxation modulus may be measured on a film cast from the material by carrying out tensile-stress relaxation measurements with a suitable apparatus such as a Rheovibron dynamic viscoelastometer operated in a static mode. Figure 13 (inset) displays such measurements for the four coating materials used on the fibers measured in Figure 12. The measurements were carried out at 23 °C at small tensile strains, where the materials exhibit linear viscoelastic behavior. 

Nitric oxide reduction by hydrocarbons over oxidized copper samples has been studied by multiplexed mass-spectrometry in an all quartz reactor operated in static mode. At 600°C the reaction proceeds exclusively via consumption of HC and NO. NO is not consumed in the presence of dioxygen but preoxidation of the copper sample is necessary to facilitate high conversion rates. Infrared spectra obtained in situ at 45- incidence angle verify the conversion and show that the bulk of the active catalyst consists of cuprous oxide. A combination of IR-and mass-spectroscopy has proven to be a successful way to identify additional products and intermediates in the gasphase. 

An Sl E system can be operated in one of two ways. In the dynamic extraction mode, the valve between the extraction cell and the restrictor remains open so that the sample is continually supplied with fresh supercritical fluid and the extracted material flows into the collection vessel where depressuriz-ation occurs. In the static extraction mode, the valve between the extraction cell and the restrictor is closed and the extraction cell is pressurized under static conditions. After a suitable period, (he exit valve is opened and the cell contents arc iransferred through the rcsiricior by a dynamic flow of fluid from the pump. The dynamic mode is more widciv used than the static mode. 

On thick mats, a typical rolling sequence consists of a vibrating roller for breaking down compaction, followed by a vibrating roller or a pneumatic roller for intermediate compaction and finishing with a static steel-wheel roller or vibrating roller operating in the static mode. 

Figure 4 Static isotope ratio mass spectrometer. The mass spectrometer depicted here, which is similar in many respects to that shown in Figure 1, is isolated from the pumping system during the analysis, by means of closing a valve, P (i.e., a static mode of operation).

Cantilever sensors can detect the following two physical parameters volume and/or mass of target molecules. Since all substances have volume and mass, we can measure almost any kind of substance by using cantilever sensors. To measure volume and mass of target molecules, there are basically two operation modes of cantilever sensors static mode and dynamic mode (Fig. 4.3.1). Details will be described in the following sections. 

FIGURE 43.1 Schematic illustrations of (a) static mode and (b) dynamic mode operations. It is important to note that the bending of a cantilever is caused by the adsorbate-induced surface stress in the case of static mode (the gravity effect is almost negligible). Reproduced from Ref. [10], vv/tfi permission from the Royai Society of Chemistry. 

A practical definition could finally also be derived from the capabilities of the instrumentation in use. For instance, SIMS, the most widespread MS technique, applied to surface and thin films can be operated in static mode (giving information from the first atomic layers of a nearly undamaged surface) or dynamic mode (depth profile of the layer). When the material to be analyzed is sputtered, this sputtering could be very slow, providing a practical limit (often in the micrometer range for SIMS) to the thickness range achievable in a reasonable amount of time. 

For example, has a dynamic rather than a static mode of operation been adopted so that failures resulting in a stuck SIS output state can be detected, e.g., by watchdog timer ... 

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