IR Imaging Study

An infrared (IR) imaging study was done by Dar et al. (1995), for the purpose of determining residual heat generation from reactive MAA/PMAA FRRPP system compared to its solution and nonreactive counterparts. For the FRRPP system, the 

This IR imaging study indicates the relatively hot FRRPP nanodomains, especially at the early stages ( 30 min) of reaction, as suspected in the proton NMR tests. The way the heat persistence compared between the FRRPP and solutions systems 

What is the effect of the reaction exotherm with this thermodynamic condition of phase separation above the LCST for the FRRPP process Here and at this point, the author will start to integrate concepts and experimental results into a cohesive and plausible picture. As shown in a ternary composition-temperature reaction trajectory plot (Fig. 2.1.11), when the polymer-rich domains are formed (Point B), its local temperature would increase due to the reaction exotherm. This places the reactive polymer-rich domains at Point B in the vertical temperature projection of Fig. 2.1.11 where diffusional fluxes drop to zero due to the approach of the system toward the spinodal curve at a higher temperature T2. Note that in Section 1.2, it was shown that all component mutual diffusion coefficients are zero at the spinodal. Then, the polymer-rich domains attain the binodal composition at C and at the higher temperature T2. If new chains are initiated and propagated at T2, then the reaction trajectory can go on, until a certain ceiling temperature is reached. 

The drop in the mutual diffusion coefficients of all the components would explain theoretically why even at such high temperatures the monomer and solvent would seem to be frozen in the system, as seen from NMR studies. This would have a profound effect on reactivity of the system, because it would also mean a reduction in conversion rate for the FRRPP system, which was indeed observed. One thing to note is that the explanation here applies to the point when the FRRPP system has already phase separated. Nanoscale domain formation at the early stages of FRRPP process requires a dilute regime explanation. 

Binodal at reactor fluid temperature, Tj Spinodal at a higher fluid temperature T2 Tj Binodal at a higher fluid temperature T2 Tj 

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In an early FT-IR imaging study, compositional differences between iliac crest biopsies from untreated osteoporotic patients and normal controls were examined... 

Figure 9.31 Sample preparation for FT-IR imaging studies of the diffusion of D2O into PAll.

There is substantial history regarding the application of conventional vibrational spectroscopy methods to study the intact surface of skin, the extracted stratum corneum and the ceramide-cholesterol-fatty acid mixtures that constitute the primary lipid components of the barrier. The complexity of the barrier and the multiple phases formed by the interactions of the barrier components have begun to reveal the role of each of these substances in barrier structure and stability. The use of bulk phase IR to monitor lipid phase behavior and protein secondary structures in the epidermis, as well as in stratum corneum models, is also well established 24-28 In addition, in vivo and ex vivo attenuated total reflectance (ATR) techniques have examined the outer layers of skin to probe hydration levels, drug delivery and percutaneous absorption at a macroscopic level.29-32 Both mid-IR and near-IR spectroscopy have been used to differentiate pathological skin samples.33,34 The above studies, and many others too numerous to mention, lend confidence to the fact that the extension to IR imaging will produce useful results. 

Permeation ofDMSO. To illustrate the power of IR imaging for studies of penetration enhancers through skin, the spatial distribution of a sample of DMSO-d6 that had been topically applied is depicted in Fig. 11.6. For these studies, solutions ofDMSO at 15 il cm-2 were applied to the stratum corneum surface of porcine skin and left for 3 h, after which the skin surface was wiped clean to... 

The resolution required varies by application however, most imaging applications require that targets be identifiable to the operator of the imaging system. This requirement has been studied in detail for IR imaging applications where it has been determined that approximately 12 resolved pixels across the characteristic dimension of the target are required for 50% identification [55], Therefore, identifying a handgun of size 18 cm would require a lateral resolution of 1.5cm. 

Within the context of muscle tissue, FT-IR and Raman imaging have each been applied more often to smooth muscle than to skeletal muscle. Both, FT-IR and Raman imaging of blood vessels were used to obtain chemical and spatial information about atherosclerosis [14—16]. Raman images of bronchial tissue containing not only cartilage and epithelium but also smooth muscle were reported [17]. Other FT-IR and Raman imaging studies on the esophagus, intestine and uterus concentrated rather on the epithelium than on smooth muscle, mainly because carcinomas arise in the epithehal tissues. 

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