Multiple-Perturbation Two-Dimensional Near-Infrared Correlation Study of Time-Dependent Water Absorption Behavior of Cellulose Affected by Pressure

2013 ◽  
Vol 67 (2) ◽  
pp. 163-170 ◽  
Author(s):  
Hideyuki Shinzawa ◽  
Kimie Awa ◽  
Isao Noda ◽  
Yukihiro Ozaki
Keyword(s):  
Water Absorption ◽  
Packing Density ◽  
Near Infrared ◽  
Correlation Method ◽  
Underlying Mechanism ◽  
Polymer Structure ◽  
Correlation Study ◽  
Time Dependent ◽  
Two Dimensional ◽  
Spectral Changes

Transient water absorption by cellulosic samples manufactured under varying pressure was monitored by near-infrared spectroscopy to explore the absorption behavior affected by the pressure. A substantial level of variation of the spectral features was induced by the water absorption and changes in the pressure. The detail of the spectral changes was analyzed with a multiple-perturbation, two-dimensional (2D) correlation method to determine the underlying mechanism. The 2D correlation spectra indicated that the compression of the cellulose increased the packing density of the samples, preventing the penetration of water. In addition, the compression substantially disintegrated its crystalline structure and eventually resulted in the development of inter- and intrachain hydrogen-bonded structures arising from an interaction between the water and cellulose. Consequently, the cellulose samples essentially underwent an evolutionary change in the polymer structure as well as in the packing density during the compression. This structural change, in turn, led to the seemingly complicated absorption trends, depending on the pressure.

The Effect of Chain Length on Mid-Infrared and Near-Infrared Spectra of Aliphatic 1-Alcohols

2017 ◽  
Vol 72 (2) ◽  
pp. 288-296 ◽  
Author(s):  
Michał Kwaśniewicz ◽  
Mirosław A. Czarnecki
Keyword(s):  
Correlation Analysis ◽  
Chain Length ◽  
Near Infrared ◽  
Hydrophobic Interactions ◽  
Principal Component ◽  
Butyl Alcohol ◽  
Two Dimensional ◽  
Data Set ◽  
Mid Infrared ◽  
Spectral Changes

Effect of the chain length on mid-infrared (MIR) and near-infrared (NIR) spectra of aliphatic 1-alcohols from methanol to 1-decanol was examined in detail. Of particular interest were the spectra-structure correlations in the NIR region and the correlation between MIR and NIR spectra of 1-alcohols. An application of two-dimensional correlation analysis (2D-COS) and chemometric methods provided comprehensive information on spectral changes in the data set. Principal component analysis (PCA) and cluster analysis evidenced that the spectra of methanol, ethanol, and 1-propanol are noticeably different from the spectra of higher 1-alcohols. The similarity between the spectra increases with an increase in the chain length. Hence, the most similar are the spectra of 1-nonanol and 1-decanol. Two-dimensional hetero-correlation analysis is very helpful for identification of the origin of bands and may guide selection of the best spectral ranges for the chemometric analysis. As shown, normalization of the spectra pronounces the intensity changes in various spectral regions and provides information not accessible from the raw data. The spectra of alcohols cannot be represented as a sum of the CH3, CH2, and OH group spectra since the OH group is involved in the hydrogen bonding. As a result, the spectral changes of this group are nonlinear and its spectral profile cannot be properly resolved. Finally, this work provides a lot of evidence that the degree of self-association of 1-alcohols decreases with the increase in chain length because of the growing meaning of the hydrophobic interactions. For butyl alcohol and higher 1-alcohols the hydrophobic interactions are more important than the OH OH interactions. Therefore, methanol, ethanol, and 1-propanol have unlimited miscibility with water, whereas 1-butanol and higher 1-alcohols have limited miscibility with water.

Two-Dimensional Attenuated Total Reflection Infrared and Near-Infrared Correlation Study of the Structure of Butyl Alcohol/Water Mixtures

2007 ◽  
Vol 61 (9) ◽  
pp. 928-934 ◽  
Author(s):  
Dagmara Wojtków ◽  
Mirosław A. Czarnecki
Keyword(s):  
Near Infrared ◽  
Correlation Study ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Effect Of Temperature ◽  
Two Dimensional ◽  
Experimental Conditions ◽  
Oh Groups ◽  
Alcohol Water ◽  
Anharmonicity Constants

The effect of temperature on attenuated total reflection infrared (ATR-IR) and near-infrared (NIR) transmission spectra of pure butan-1-ol, butan-2-ol, 2-methyl-propan-1-ol, 2-methyl-propan-2-ol, and mixtures with a small water content (XH2O ≤ 0.1) have been examined. The spectra were analyzed using a two-dimensional (2D) correlation approach. Two kinds of correlation analysis were performed: IR–IR and NIR–NIR homo-correlation and IR–NIR hetero-correlation. Our results reveal that the addition of small to moderate amounts of water does not destroy the structure of alcohol. The presence of water stabilizes the structure of alcohols and this effect is more evident for sec-butanol and tert-butanol. The ATR-IR spectra provide information on the most associated species, whereas absorption of the smaller associates and the free OH group is hardly seen. On the contrary, in the NIR spectra the absorption of the free OH groups dominates. The ability of resolution enhancement in the hetero-correlation asynchronous spectra is reduced as compared to that in the homo-correlation spectra. On the other hand, peaks may appear in the hetero-correlation synchronous spectra that are not observed in the homo-correlation contour plots. The positions of the synchronous peaks were used for evaluation of anharmonicity constants. These values for the free OH group do not depend on the experimental conditions. In contrast, the anharmonicity constants for the bonded OH groups determined from the spectra of pure alcohols may significantly differ from those obtained from diluted solutions.

Identification of Overlapped Near-Infrared Bands of Glucose Anomers Using Two-Dimensional Near-Infrared and Middle-Infrared Correlation Spectroscopy

2002 ◽  
Vol 56 (7) ◽  
pp. 897-901 ◽  
Author(s):  
Aminiel Awichi ◽  
Eric M. Tee ◽  
Giri Srikanthan ◽  
Wei Zhao
Keyword(s):  
Mixed Mode ◽  
Near Infrared ◽  
Spectroscopic Method ◽  
Nir Spectroscopy ◽  
Correlation Spectroscopy ◽  
Two Dimensional ◽  
Combination Band ◽  
Spectral Changes ◽  
Glucose Anomers ◽  
Middle Infrared

Near-infrared (NIR) spectroscopy is a useful tool in determining glucose in biological matrices. Because α-anomers and β-anomers of glucose are in equilibrium in the solution, the observed NIR bands may come from the overlapping of vibrational modes of the anomers. We have conducted NIR and mid-infrared (MIR) absorption spectra measurements to determine the nature of the observed NIR features by using two-dimensional (2D) NIR and MIR correlation spectroscopy. The 2D NIR correlation spectra and 2D synchronous NIR and MIR correlation heterospectra are constructed based on the spectral changes of individual anomers upon mutarotation. We have identified a new NIR feature at 4350 cm−1 for the α-anomers and two new NIR features at 4200 and 4250 for the β-anomers. The 4350-cm−1 band of the α-anomers could be assigned to the combination band of C–H stretch at 2945 cm−1 and a mixed mode of C–H bending and O–H bending at 1415 cm−1. The 4200/4250-cm−1 bands of the β-anomers might be tentatively assigned to the combination band of C–H stretching at 2870 cm−1 and a mixed mode of C–H bending and O–H bending at 1315/1370 cm−1. This finding provides the spectral information needed for implementation of a highly selective coherent two-dimensional vibrational spectroscopic method, the DOVE-Raman four wave mixing for selective identification of glucose anomers from aqueous solutions.

scholarly journals Integrable unsteady motion with an application to ocean eddies

1998 ◽  
Vol 5 (3) ◽  
pp. 145-151
Author(s):  
A. D. Kirwan, Jr. ◽  
B. L. Lipphardt, Jr.
Keyword(s):  
Potential Vorticity ◽  
Particle Motion ◽  
Gulf Stream ◽  
Incompressible Flows ◽  
Unsteady Motion ◽  
Ring System ◽  
Time Dependent ◽  
Two Dimensional ◽  
Ocean Eddies ◽  
Multilayered Systems

Abstract. Application of the Brown-Samelson theorem, which shows that particle motion is integrable in a class of vorticity-conserving, two-dimensional incompressible flows, is extended here to a class of explicit time dependent dynamically balanced flows in multilayered systems. Particle motion for nonsteady two-dimensional flows with discontinuities in the vorticity or potential vorticity fields (modon solutions) is shown to be integrable. An example of a two-layer modon solution constrained by observations of a Gulf Stream ring system is discussed.

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