The development and evaluation of a diagnostic system of remediation for an auto-tutorial course in general college chemistry

Thesis (Ph. D.)--Michigan State University. Dept of Chemistry and Higher Education and Administration,Includes bibliographical references (pages 78-79

Near infrared reflectance spectroscopy for the determination of free gossypol in cottonseed meal

Gossypol is a toxic polyphenolic compound produced by the pigment glands of the cotton plant. The free gossypol content of cottonseed meal (CSM) is commonly determined by the American Oil Chemists’ Society (AOCS) wet chemistry method. The AOCS method, however, laboratory-intensive, time-consuming, and therefore, not practical for quick field analyses. To determine if the free gossypol content of CSM could be predicted by near infrared reflectance spectroscopy (NIRS), CSM samples were collected from all over the world. All CSM samples were ground and a portion of each analyzed for free gossypol by the AOCS procedure (reference data) and by NIRS (reflectance data). Both reflectance and reference data were combined in calibration. The coefficient of determination (r2) and standard error of prediction (SEP) were used to assess the calibration accuracy. The r2 was 0.728, and the SEP was 0.034 for the initial calibration that included samples from all over the world. However, the r2 and SEP improved to 0.921 and 0.014, respectively, if the calibration was made using CSM samples only from the United States. These results indicate that a general prediction equation can be developed to predict the free gossypol content of CSM by NIRS. From a practical standpoint, NIRS technology provides a method for quickly assessing whether a particular batch of CSM has a free gossypol content low enough to be suitable for use in poultry diets.This research was supported in part by grant 05-635GA from the Georgian Cotton Commission, Perry, G

Determination of phenprocoumon, an anticoagulant, in human plasma.

Abstract Phenprocoumon is extracted from acidified plasma, the organic phase evaporated, and part of the residue, in ethanol, is quantitatively applied to a thin-layer plate. After separation, the quantity of phenprocoumon is assayed by fluorescence densitometry in situ. Results are reproducible to about 2.5%. The lower limit of detection is 0.1 mg/liter, which makes the method fully applicable to human plasma, because therapeutic concentrations range from 1 to 3 mg/liter. Seven determinations can be made within 3 h. For toxicological purposes, a qualitative analysis can be done in a shorter time, because the phenprocoumon spots are visible under ultraviolet light at 254 nm.</jats:p

OBSERVATION OF DOUBLE-GAP-EDGE ANDREEV REFLECTION AT SI/NB INTERFACES BY POINT-CONTACT SPECTROSCOPY

Andreev reflection point-contact spectroscopy is performed on a bilayer consisting of 50-nm degenerately doped Si backed with Nb. Due to the short mean free path both injection into and transport across the Si layer are diffusive, in contrast to the ballistic conditions prevailing in clean metal layers. Nevertheless a large Andreev signal is observed in the point-contact characteristics, not reduced by elastic scattering in the Si layer or by interface scattering, but only limited by the transmission coefficient of the metal-semiconductor point contact. Two peaks in the Andreev reflection probability are visible, marking the values of the superconducting energy gap at the interface on the Nb and Si sides. This interpretation is supported by a method of solving the Bogolubov equations analytically using a simplified expression for the variation of the order parameter close to the interface. This observation enables a comparison with theoretical predictions of the gap discontinuity in the proximity effect. It is found that the widely used de Gennes model does not agree with the experimental data