Frame acquisition time

Variables which can generally be changed per scan include (with units) power (kVp), current ( xA), acquisition time (ms), views ( ), and frames per view ( ). Each has a direct effect on image quality and scan time and should be optimized for the specimen type to be acquired and desired resolution of the region of interest. 

Fig. 2 Positional detection and mean-square displacement (MSD). (a) The x, y-coordinates of a particle at a certain time point are derived from its diffraction limited spot by fitting a 2D-Gaussian function to its intensity profile. In this way, a positional accuracy far below the optical resolution is obtained, (b) The figure depicts a simplified scheme for the analysis of a trajectory and the corresponding plot of the time dependency of the MSD. The average of all steps within the trajectory for each time-lag At, with At = z, At = 2z,... (where z = acquisition time interval from frame to frame) gives a point in the plot of MSD = f(t). (c) The time dependence of the MSD allows the classification of several modes of motion by evaluating the best fit of the MSD plot to one of the four formulas. A linear plot indicates normal diffusion and can be described by = ADAt (D = diffusion coefficient). A quadratic dependence of on At indicates directed motion and can be fitted by = v2At2 + ADAt (v = mean velocity). An asymptotic behavior for larger At with = [1 - exp (—AA2DAt/)] indicates confined diffusion. Anomalous diffusion is indicated by a best fit with = ADAf and a < 1 (sub-diffusive)...

The fourth module is the control unit, consisting primarily of a state-of-the-art industry PC equipped with a suitable frame-grabber card for image frame acquisition, spectral and spatial real-time data evaluation and control of subsequent actuators or communication with process control systems. 

Fig. 1 Typical trajectories of a 0.5 im diameter, fluorescent polystyrene microsphere (represented by a sphere) embedded in a solution of glycerol 85% (A), Sterocoll FD 1% (B) and Sterocoll D 1% (C). The total acquisition time was 100 s, with an interval of 100 ms between consecutive frames...

LCTF Raman image of ratioed PuOz signal (469 cm 7442 cm" ), 15-mW laser power, 10X objective, 120-sec acquisition time (C) Raman spectrum of micrometer-sized Rocky Flats ash particle using the LCTF, step size 0.2 nm, 60 sec/frame (D) overlay of Pu x-ray image as a contour map on the Raman image. 

Fig. 6 — STEM imaging (200 kV Osiris STEM) combined with energy dispersive x-ray spectroscopy (EDX) of Pt-Pd catalytic nanoparticles. Unlike the high angle annular dark field (HAADF) image, EDX elemental mapping reveals the core shell structure of the nanoparticles. The high efficiency EDX system and high brightness electron source allows quickly obtaining elemental maps and statistically significant data within a realistic time frame. Total acquisition time was less than 12 minutes for (a) and less than 10 minutes for (b). The author would like to thank Dominique Delille (FEI company).

How much light goes into a sample for a single exposure in the two setups For this, an identical laser source and identical frame rates are assumed for both systems. In single beam scanning, the beam moves with finite speed over all regions of the sample. The total irradiation R of the sample is thus the product of the intensity of the laser beam I and the total acquisition time t for a frame. 

From the material presented here it appears that at the current stage the nucleonic techniques can provide very good spatial resolution (down to fractions of a millimetre) but at a cost of lengthy data acquisition times (hours or minutes at best). On the other hand the electrical tedmiques, such as ECT, can offer relatively fast imaging (currently up to 200 frames per second) but with much poorer spatial resolution, typically 5-10% of the bed diameter. 

Real time. A data-acquisition method in which the mass spectra are generated within the same time frame as the original experiment. 

Having developed estimates of benefits as well as costs, these values must be compared. Since costs and benefits are not necessarily experienced in the same time frames, the same financial analysis methods used by the firm to make its other capital investment decisions must be used to justify the LIMS acquisition. The LIMS which is desirable from the technical and operational viewpoint can then be shown to be a truly beneficial capital investment and not just another corporate overhead expense. 

The standard calorimetric reaction of tris(hydroxymethyl) aminomethane (THAM) neutralization with HC1 was used in several initial experiments to determine both precision and accuracy for the data acquisition and reduction process. Three to five minutes were allowed between acid additions, since this same time frame was used for all later suspension titrations in order to minimize the effects of slow surface reactions which occur during a titration (9,29,30). The amount of acid added in each experiment was varied to generate heat changes of 40-400 mj (typical heat changes observed in our adsorption studies with goethite suspensions). 

---