Data acquisition phase

All two dimensional experiments use essentially the same data reduction process. Several years ago the data acquisition phase of 2D experiments was usually the shortest, with double transformation requiring up to several hours followed by, again, comparable plotting time. Off-line data processing was often used for faster processing, but this severely limited any widespread use of 2D methods. 

In a normal pulsed NMR experiment, the 90° excitation pulse is followed immediately by a data acquisition phase in which the FID is recorded and the data are stored in the computer. In experiments that use complex pulse sequences, such as DEPT, a preparation phase is included before data acquisition. During the preparation phase, the nuclear magnetization vectors are allowed to process, and information may be exchanged between magnetic nuclei. In other words, a given nucleus may become encoded with information about the spin state of another nucleus which may be nearby. 

There is a copy of DAR resident in memory for each GC-MS system. This is to assure quick response during the data acquisition phase. The remaining analysis and control programs are disc resident and are swapped in and out of memory, as needed, on a priority basis. Time spent in DAR is dead time for data collection. When... 

The Data Analysis Module concludes the last part of the inspection process. Once infield data acquisition phase is completed, in the office the Data Analysis Module allows the inspection team to review the checklists and, supported by the video, to fill missed information or to correct errors before drawing up the inspection report. 

A typical molecular dynamics simulation comprises an equflibration and a production phase. The former is necessary, as the name imphes, to ensure that the system is in equilibrium before data acquisition starts. It is useful to check the time evolution of several simulation parameters such as temperature (which is directly connected to the kinetic energy), potential energy, total energy, density (when periodic boundary conditions with constant pressure are apphed), and their root-mean-square deviations. Having these and other variables constant at the end of the equilibration phase is the prerequisite for the statistically meaningful sampling of data in the following production phase. 

Assuming that an equilibrium is now well established, the simulation may be restarted (not newly started) to begin with the sampling of structural and thermodynamic data. In our model case, data acquisition was performed for 3 ns (trajectory data plot not shown). For the production phase, also, the time evolution of the variables mentioned above should be monitored to detect stability problems or con-... 

Continuous Emissions Monitoring. A key aspect of the new CAAA is the requirement that plants prove their continued compHance to new emissions limits by installing continuous emissions monitoring systems (CEMs). The CAAA imposes new requirements for monitoring NO, SO2, and CO2 levels in a plant s exhaust gas stream. Affected plants typically must gather data from stack monitoring systems, gas analyzers, and the plant s data acquisition system and provide the data in a format approved by the EPA and state regulators. CEM systems must be in place by November 1993 for boilers affected by Phase I of the CAAA, and byjanuary 1995 for plants impacted by Phase II. 

The INEPT experiment can be modified to allow the antiphase magnetization to be precessed for a further time period so that it comes into phase before data acquisition. The pulse sequence for the refocused INEPT experiment (Pegg et al., 1981b) is shown in Fig. 2.13. Another delay, A. is introduced and 180° pulses applied at the center of this delay simultaneously to both the H and the C nuclei. Decoupling during data acquisition allows the carbons to be recorded as singlets. The value of Z), is adjusted to enable the desired type of carbon atoms to be recorded. Thus, with D, set at V4J, the CH carbons are recorded at VsJ, the CH2 carbons are recorded and at VeJ, all protonated carbons are recorded. With D3 at %J, the CH and CH ( carbons appear out of phase from the CH2 carbons. 

Phase-sensitive data acquisition NMR data are acquired in this manner so that peaks are recorded with pure absorption-mode or pure dispersionmode line shapes. 

Because an LSMBS is almost certain to involve more than one laboratory in the analytical phase, results obtained by multiple laboratories must be internally and externally consistent. For this reason, the use of a single method in all analyses, if possible, is advantageous. The method must conform to quality criteria and must be rugged, i.e., must be satisfactory for all analytes in all commodities, with instruments and data acquisition systems from various manufacturers. 

The electrochemical cell for the polarographic measurements had a four-electrode configuration equipped with a microsyringe, and was connected to a computer-assisted data-acquisition system [7]. On the other hand, the cyclic voltammetric measurements that are also assisted by a computer data-acquisition system were carried out using a gel electrode that contains the aqueous phase [8]. The cell structure was as follows ... 

Instrumentation requirements for SEC are somewhat simpler than those of other modes of HPLC, since mobile phase gradients are not used however, adequate computer support for data acquisition and processing is essential. Method development involves finding a suitable solvent for the sample and choosing a mixed bed column or, more often, a set of columns in series to match the pore size of the column(s) with the size distribution of the sample. 

Conventional utilization of solution-phase NMR data acquisition techniques on solid samples yields broad, featureless spectra (Fig. 1A). The broad nature of the signal is due primarily to dipolar interactions, which do not average out to zero in the solid state, and chemical shift anisotropy (CSA), which again occurs because our compound of interest is in the solid state. Before one describes the two principal reasons for the broad, featureless spectra, it is important to understand the main interactions that a nucleus with a magnetic moment experiences when situated within a magnetic field in the solid state. In addition, manifestations of these interactions in the solid state NMR spectrum need to be discussed. 

Pyrolysis-Gas Chromatography-Mass Spectrometry. In the experiments, about 2 mg of sample was pyrolyzed at 900°C in flowing helium using a Chemical Data System (CDS) Platinum Coil Pyrolysis Probe controlled by a CDS Model 122 Pyroprobe in normal mode. Products were separated on a 12 meter fused capillary column with a cross-linked poly (dimethylsilicone) stationary phase. The GC column was temperature programmed from -50 to 300°C. Individual compounds were identified with a Hewlett Packard (HP) Model 5995C low resolution quadruple GC/MS System. Data acquisition and reduction were performed on the HP 100 E-series computer running revision E RTE-6/VM software. 

Typical instrument set-ups for online sample preparation, for example, solid phase extraction and sample pre-concentration, require the control of a six-port valve with an additional special column and a second pump. Ideally, this system will be fully controlled by the data acquisition software (Figure 3.12 (A)). 

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