Normalization of the measurement error in optical density

Factors that are affected the influence of the measurement error of the refractive index n in the flowing liquid (change in its optical density and temperature) are established. A during the using a differential flow type refractometer for measuring n flowing fliquid on the error in measuring the refractive index is additionally influenced by the scattering of radiation in the cell transducer and the wedge-shaped glass of the cell. New design of a differential refractometer for investigation of the optical density influence of the flowing liquid on the measurement error n is developped. New results confirming the influence of changes in the optical density of the flowing liquid on the measuring error of the refractive index n are recived. Compensation technique of the changes influence a optical density on the measurement error n is offered.

Download Full-text

Analysis of photographic emulsions for High-Voltage Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100148095 ◽

1993 ◽

Vol 51 ◽

pp. 452-453 ◽

Cited By ~ 1

Author(s):

James R. Kremer ◽

Paul S. Furcinitti ◽

Eileen O’Toole ◽

J. Richard McIntosh

Keyword(s):

Electron Microscope ◽

Optical Density ◽

High Voltage ◽

Noise Power ◽

Limited Information ◽

Modulation Transfer ◽

Transmission Microscopy ◽

High Voltage Electron Microscopy ◽

Voltage Range ◽

Voltage Electron

Characteristics of electron microscope film emulsions, such as the speed, the modulation transfer function, and the exposure dependence of the noise power spectrum, have been studied for electron energies (80-100keV) used in conventional transmission microscopy. However, limited information is available for electron energies in the intermediate to high voltage range, 300-1000keV. Furthermore, emulsion characteristics, such as optical density versus exposure, for new or improved emulsions are usually only quoted by film manufacturers for 80keV electrons. The need for further film emulsion studies at higher voltages becomes apparent when searching for a film to record low dose images of radiation sensitive biological specimens in the frozen hydrated state. Here, we report the optical density, speed and relative resolution of a few of the more popular electron microscope films after exposure to 1MeV electrons.Three electron microscope films, Kodak S0-163, Kodak 4489, and Agfa Scientia 23D56 were tested with a JEOLJEM-1000 electron microscope operating at an accelerating voltage of 1000keV.

Download Full-text

Benefits from Computerized Adaptive Testing as Seen in Simulation Studies

European Journal of Psychological Assessment ◽

10.1027//1015-5759.15.2.91 ◽

1999 ◽

Vol 15 (2) ◽

pp. 91-98 ◽

Cited By ~ 10

Author(s):

Lutz F. Hornke

Keyword(s):

Measurement Error ◽

Computerized Adaptive Testing ◽

Test Procedure ◽

Adaptive Testing ◽

Parameter Estimates ◽

Simulation Studies ◽

Computerized Adaptive Test ◽

Item Banks ◽

Item Parameters ◽

General Reliability

Summary: Item parameters for several hundreds of items were estimated based on empirical data from several thousands of subjects. The logistic one-parameter (1PL) and two-parameter (2PL) model estimates were evaluated. However, model fit showed that only a subset of items complied sufficiently, so that the remaining ones were assembled in well-fitting item banks. In several simulation studies 5000 simulated responses were generated in accordance with a computerized adaptive test procedure along with person parameters. A general reliability of .80 or a standard error of measurement of .44 was used as a stopping rule to end CAT testing. We also recorded how often each item was used by all simulees. Person-parameter estimates based on CAT correlated higher than .90 with true values simulated. For all 1PL fitting item banks most simulees used more than 20 items but less than 30 items to reach the pre-set level of measurement error. However, testing based on item banks that complied to the 2PL revealed that, on average, only 10 items were sufficient to end testing at the same measurement error level. Both clearly demonstrate the precision and economy of computerized adaptive testing. Empirical evaluations from everyday uses will show whether these trends will hold up in practice. If so, CAT will become possible and reasonable with some 150 well-calibrated 2PL items.

Download Full-text