Thesis (Ph. D.)--Institute of Paper Chemistry, 1949. / Includes bibliographical references (p. 56-58).

Not available / text

Studies of the temporal evolution of young stars and their associated properties rely upon the ability of astronomers to determine ages and masses of objects in different evolutionary states. The best method for determining the age and mass of a young stellar object is to place the object on the Hertzsprung-Russell (HR) diagram and to compare to theoretical evolutionary tracks. Accurate ages allow the investigation of the temporal evolution of properties associated with stellar youth (accretion rates, X-ray activity, circumstellar excess, etc...). One property intimately linked with stellar youth is the presence (or absence) of an optically thick primordial circumstellar disk. Objects in "young" star forming regions are more likely to show evidence for a disk than objects in "older" clusters. Within a single cluster, the picture is not as clear. There exist objects in very young clusters (~1 Myr) which show no evidence for circumstellar disks, and there exist objects in very old clusters (~10 Myr), which show evidence for robust disks, suggesting a variable other than stellar age is driving the evolution of the disks. To investigate whether these outliers are due to age spreads, initial conditions, or simply appear anomalous due to erroneous age determinations, we must determine better placements in the HR diagram by carefully transforming observable quantities (spectral type and apparent magnitude) into the quantities necessary for comparison evolutionary models (effective temperature and luminosity). In the Ophiuchus star forming region, I investigate whether or not objects with disks are younger than disk-less objects. I find no difference in the ages of the two populations, but the systematic and random uncertainties are large enough to mask all but the largest age differences. In the hope of better determining the physical parameters of young stellar objects, I embark on a spectral synthesis campaign to produce comparison synthetic spectra which account for the effects of magnetic fields. This requires the modification of the MOOG spectral synthesis program to handle the full Stokes vector treatment for polarized radiation through a magnetized medium. I create a grid of synthetic spectra covering ranges in effective temperature, surface gravity, and average magnetic field strength relevant for studies of young stellar objects, and develop a Chi-squared minimization routine to determine the best fit synthetic spectrum for a given observed spectrum at an arbitrary resolving power. This grid of synthetic spectra will be an invaluable complement to future near infrared, large band-pass, high-resolving power spectrographs (i.e. IGRINS). In addition to these observational and theoretical attempts to reduce systematic errors, I also helped to develop a suite of silicon and KRS-5 grisms for use in the FORCAST instrument, a mid infrared camera on the SOFIA telescope. These grisms will afford the imaging instrument a mid infrared spectroscopic capability at wavelengths normally inaccessible from the ground. I also report on my work to help write FG Widget, the quick-look reduction software package developed to support grism observations. / text

An infrared source with spatially and temporally variable radiance is designed. It can be used to simulate any other infrared source simultaneously in two wavelength bands. The theoretical analysis of the real and simulator source is performed to define the design parameters. A series of the concepts are evaluated for their potential as infrared sources. A three-dimensional heat transfer computer program is used to predict the thermal behavior of the prototype glassy carbon waffle target. Tests are performed on this target which show that its thermal and radiation properties are in agreement with its predicted behavior. Glassy carbon waffle source is a good infrared radiator which can be used repeatedly at high temperatures. Measurements are described which show that the uniformity in the surface temperature can be maintained even when a scanning laser beam is used to deposit the energy on the target surface. The target surface is described analytically as a low pass filter. Its time constant is shown to depend on the target material and the temperature distribution in the target.

Variable-temperature Fourier transform infrared (VT-FTIR) spectroscopy in conjunction with 2D correlation analysis was employed to study the unfolding of aspartate transcarbamylase (ATCase) and its individual subunits. The regulatory subunit (RSU) was uniformly labeled with 13C/15N and then reconstituted with the unlabeled catalytic subunit (CSU) to form the holoenzyme. The activity of the holoenzyme was shown to be unaffected by the isotopic labeling of the RSU. The VT-FTIR investigation of the isolated CSU and the CSU in the holoenzyme revealed that the CSU is more thermally stable when bound to the RSU (i.e., in the holoenzyme). The RSU also showed more thermal stability when bound to the CSU. The sequences of events leading to the unfolding of the isolated CSU and RSU and the CSU in the holoenzyme were deduced by 2D correlation analysis of the VT-FTIR spectra. The results for the isolated CSU demonstrated that beta-sheets unfold first, followed by a-helices and then turns, and finally aggregates form. The sequence of unfolding of the RSU showed an increase of turns followed by a loss of intramolecular beta sheets, then a loss of alpha-helices and the formation of aggregates. The CSU in the holoenzyme exhibited a slightly different unfolding pathway and was observed to unfold subsequent to the unfolding of the RSU, consistent with the two thermal transitions observed by differential scanning calorimetry.

Infrared spectra of microbial cells are highly specific, fingerprint-like signatures which can be used to differentiate microbial species and strains from each other. In this study, the potential applicability of Fourier transform infrared (FTIR) spectroscopy for the classification of yeast strains in terms of their biological taxonomy, their use in the production of wine, beer, and bread, and their sensitivity to killer yeast strains was investigated. Sample preparation, spectral data preprocessing methods and spectral classification techniques were also investigated. All yeast strains were grown on a single growth medium. The FTIR spectra were baseline corrected and the second derivative spectra were computed and employed in spectral analysis. The classification accuracy was improved when the principal component spectra (calculated from the second derivative spectra) were employed rather than the second derivative spectra or raw spectra alone. Artificial neural network (ANN) with 10 units in the input layer and 12 units in the hidden layer produced a robust prediction model for the identification of yeasts. Cluster analysis was employed for the classification of yeast strains in terms of their use in the production of wine, beer, and bread and in terms of their sensitivity to killer yeast strains. The optimum region for the classification in the former case was found to be between 1300 and 800 cm-1 in the infrared spectrum whereas the optimum region for the classification of yeast strains in terms of their sensitivity was between 900 and 800 cm-1 . The results of this work demonstrated that FTIR spectroscopy could be successfully employed for the classification and identification of yeast strains with minimal sample preparation.

Fourier transform near-infrared (FT-NIR) spectroscopy was investigated as a means of quantitative analysis of edible fats and oils. Initially, a method of simultaneously determining the cis and trans content, iodine value and saponification number of neat fats and oils using a heated transmission flow cell was developed. Two partial least squares (PLS) calibrations were devised, a process-specific calibration based on hydrogenated soybean oil and a more generalized calibration based on many oil types, the latter able to analyze oils from a variety of sources accurately and reproducibly. Methodology for the quantitative determination of the peroxide value (PV) of edible oils using a novel glass-vial sample handling system was subsequently developed, based on the stoichiometric reaction of triphenylphosphine with hydroperoxides to form triphenylphosphine oxide. The PV calibration was derived using PLS regression, and the results of a validation study demonstrated that PV could be quantitated accurately if a normalization routine was used to compensate for the inherent dimensional variability of the vials. The vial sample handling system was then used in the development of PLS IV calibrations for the process analysis of commercial oil samples, and these samples were also used to evaluate a global IV calibration devised by Bomem Inc. The discriminant features available through PLS were shown to enhance the accuracy of the IV predictions by facilitating the selection of the most appropriate calibrations based on the spectral characteristics of closely related oils. The predictions obtained using the global IV calibration provided clear evidence that a generalized calibration based on a large and varied selection of oils could provide a means of IV determination by FT-NIR spectroscopy. Subsequently, a generalized FT-NIR trans calibration was developed and shown to yield trans values that were in good agreement with those obtained by the AOCS mid-FTIR single-bounce hori

An industrial Fourier transform infrared (FTIR) milk analyser has been adapted for the proximate analysis of fresh or cooked meat and meat products. Stable freeze-dried samples of ground beef and bologna were prepared for the calibration of an FTIR spectrometer equipped with a 37-mum transmission cell maintained at a constant temperature of 65°C and were analysed for fat, protein, moisture, and ash by the official methods of analysis of the Association of Official Analytical Chemists (AOAC) prior to instrumental measurement. The requirement to prepare a "milk-like" emulsion of meat for FTIR analysis led to the development of two prototype high-pressure homogenizers specifically designed to produce analytical volumes of emulsions in which the largest residual colloids present in suspension would have dimensions smaller than 1 mum. Emulsified samples were examined by transmission electron microscopy and laser light scattering spectroscopy to determine the size distribution of fat globules and the dimensions of the residual insoluble fragments of protein. / "Milk-like" emulsions of meat passed three times through a high-pressure homogenizer operating at 20,000 psi (138 MPa) had an average fat globule diameter of less than 320 nm. Also, the use of high-pressure homogenization eliminated the need to filter out insoluble proteins from connective tissues prior to the infrared analysis, resulting in a more accurate determination of the protein content in the meat samples. The results of validation studies conducted with both fresh and freeze-dried samples demonstrated that it is possible to analyse meat samples simultaneously for fat, protein, carbohydrates and moisture with good accuracy in approximately 7½; minutes per sample employing existing FTIR instrumentation used for the routine analysis of milk and dairy products.

No description available.

A novel and rapid method was developed to monitor the autoxidation of edible oils by Fourier transform infrared (FTIR) spectroscopy with the use of disposable polymer infrared (PIR) cards having a microporous polytetrafluoroethylene (PTFE) sample substrate. Under conditions of mild heating (~58°C) and aeration, both model triacylglycerols (TAGS) and edible oils applied onto the PIR cards underwent rapidly accelerated oxidation. In order to compare the oxidative stability of samples on the PIR cards in terms of the time required to reach a peroxide value (PV) of 100 mequiv/kg oil, matching the end-point measured in the standard active oxygen method (AOM), an absorbance slope factor (ASF) was determined to relate changes in hydroperoxide (ROOH) absorbance (peak maximum found within the range of 3500--3200 cm-1 ) to PV. Similar ASF values were found for the four edible oils tested (safflower, canola, sunflower, and extra virgin olive oil), permitting determination of a pooled, universally applicable ASF value of 0.0526 mAbs/PV.