Variable-temperature diffuse reflectance

Fig. 5 A, diffuse reflectance IR spectra of SQ-33600 displaying the absorption band due to bound water of hydration after exposure to different relative humidity conditions of (a) initial sample containing 3.5% water, (b) 6%, (c) 15%, (d) 31%, (e) 43%, (f) 52%, (g) 70%, and (h) 84%. B, variable-temperature diffuse reflectance IR spectra of SQ-33600 initially containing 3.5% water.

Variable-Temperature Diffuse Reflectance Fourier Transform Infrared Spectroscopic Studies of Amine Desorption from a Siliceous Surface... 

Variable-temperature diffuse reflectance infrared Fourier transform spectroscopy was used in conjunction with pyridine desorption studies to assess the acidity of a siliceous surface. An amorphous, porous silica substrate was investigated. The results contribute to an understanding of the acidic strength and the distribution of acidic sites on this material. A hydrogen-bonding interaction was observed between pyridine and the surface. Isothermal rate constants and an activation energy for the desorption process are reported and can be used as direct measures of surface site acidity. 

Variable-temperature diffuse reflectance Fourier transform infrared spectroscopy provided qualitative and quantitative information concerning the acidity of surface sites on silica. Although the use of pyridine as a probe has been well known for many years, the ability of the technique to permit... 

See Silicon-aluminum interactions in biology Alzheimer s disease, role of aluminum, 606 Amine desorption, variable-temperature diffuse reflectance Fourier transform infrared (FTIR) spectroscopy from siliceous surface, 257-266 Amine-stabilized sol, manufacturing... 

Variable-Temperature Diffuse Reflectance Fourier Transform... 

K.G. Proctor and D.E. Leyden, Surface Acidity Characterization of Siliceous Materials by Variable Temperature Diffuse Reflectance FTIR, Chemically Modified Oxide Surfaces, Vol. 3, D.E. Leyden and W.T. Collins Eds., Gordon and Breach Science Publishers, New York, pp. 137-149, 1990. 

D.E. Leyden and K.G. Proctor, Variable-Temperature Diffuse Reflectance Fourier Transform Infrared Spectroscopic Studies of Amine Desorption from a Siliceous Surface, The Colloid Chemistry of Silica, ACS Advances in Chemistry Series No. 234, H. Bergna Ed., pp. 257-267, 1994. 

K. (2004) Solid-state thermochromism studied by variable-temperature diffuse reflectance spectroscopy. A new perspective on the chromism of sal-icylideneanilines. J. Rhys. Chem. B,... 

The utilization of IR spectroscopy is very important in the characterization of pseudopolymorphic systems, especially hydrates. It has been used to study the pseudopolymorphic systems SQ-33600 [36], mefloquine hydrochloride [37], ranitidine HC1 [38], carbovir [39], and paroxetine hydrochloride [40]. In the case of SQ-33600 [36], humidity-dependent changes in the crystal properties of the disodium salt of this new HMG-CoA reductase inhibitor were characterized by a combination of physical analytical techniques. Three crystalline solid hydrates were identified, each having a definite stability over a range of humidity. Diffuse reflectance IR spectra were acquired on SQ-33600 material exposed to different relative humidity (RH) conditions. A sharp absorption band at 3640 cm-1 was indicative of the OH stretching mode associated with either strongly bound or crystalline water (Fig. 5A). The sharpness of the band is evidence of a bound species even at the lowest levels of moisture content. The bound nature of this water contained in low-moisture samples was confirmed by variable-temperature (VT) diffuse reflectance studies. As shown in Fig. 5B, the 3640 cm-1 peak progressively decreased in intensity upon thermal... 

In this context, diffuse reflectance FTIR spectroscopy has been applied to analyze the influence of mixing variables (i.e. treatment concentration, time and temperature of mixing) on both the ultimate flller coating level and possible reaction between the treatment and flller surface [127]. 

The Life-365 software predicts the initiation period assuming ionic diffusion to be the dominant mechanism. This software differs from other diffusion models in that it accounts for the variability of the diffusion coefficient with age and with temperature. It also attempts to model the impact of various additives. For additives such as silica fume and fly ash it reduces the diffusion coefficient to reflect the lower permeability and for corrosion inhibitors it raises the chloride threshold required to initiate corrosion. To include the impact of sealers and membranes it reduces the rate of accumulation of the surface chloride concentration. The rate of accumulation and the maximum accumulation of surface chloride in this program are based on the type of structure, geographic location and exposure. ACI Committee 365 has also published a state-of-the-art report on service life prediction which is in the process of being updated (ACI 365.1R-00 (2000)). 

Here we consider the above-prepared radiation balance of a biplane system made from thin foils. Both planes (numbered 1 and 2) are lined up parallel to each other. The upper plane (2) on the upper side has reflectivity p2+, emissivity 2+ and absorption o +, and on the bottom reflectivity p2-, emis-sivity 2- and absorption 2- the transmissivity is T2. Analogous to this, the corresponding variables of the lower plane (1) are given by pu, Pi-, u, 1-, ai and Ti, where the subscript l-i- describes the characteristics of the upper layer and 1- those of the bottom of plane 1. The temperature of the upper foil is 2 and the temperature of the bottom foil is i. In the space above the second upper foil there is a diffuse black-body radiation of temperature 9 and in the space below the first foil a black-body radiation of temperature . ,. 

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