Thermosensitivity

In the 1990s hplc has become widely used in the flavor and fragrance industry to measure vanillin and other phenoHc compounds. Routine methods have been developed that are particularly adapted to thermosensitive products, such as vanillin and its derivative products, with elution gradient and uv detection at given wavelengths. Certain critical impurities can thus routinely be traced to very low (10 ppm) concentrations. 

Is the product thermosensitive The heat generated by the seal faces may cause polymerization. 

Chenite et al. reported on thermosensitive chitosan gels for encapsulating living cells and therapeutic proteins they are liquid below room temperature but form monolithic gels at body temperature [220-223]. 

Chun C, Lim HJ, Hong KY et al (2009) The use of injectable, thermosensitive poly (organophosphazene)-RGD conjugates for the enhancement of mesenchymal stem cell osteogenic differentiation. Biomaterials 30 6295-6308... 

It has been shown (Smith et al. 1978) that in enteric bacteria carrying thermosensitive plasmids coding for the utilization of citrate and for resistance to antibiotics, rates of transmission were negligible at 37°C but appreciable at 23°C—a temperature more closely approaching that which prevails in natural ecosystems. 

Smith HW, Z Parsell, P Green (1978) Thermosensitive antibiotic resistance plasmids in enterobacteria. J Gen Microbiol 109 37-47. 

The phase transition temperatures (lower critical solution temperature, LCST) of the pol5miers were obtained from the change in the transmittance of their aqueous solutions (Figure 1). The aqueous solution of the obtained pol5uner was prepared and its transmittance at 500 nm was monitored with increase in the ambient temperature. Both of poly-NIPA and poly-NEA showed a sudden decrease in the transmittance at 37.5 and 69.2 °C, respectively. The result shown in Figure 1 clearly suggests the thermosensitivity of the pol5mers, and the obtained LCST values are close to those reported for poly-NIPA (34.8 °C) [8] and poly-NEA (72 °C) [9]. 

By using thermosensitive poly-acrylamides, it is possible to prepare cubic Pt nanocrystals (with predominant (1 0 0) facets) and tetrahedral Pt nanocrystals (rich in (111) facets). These Pt nanocrystals can be supported on oxide (alumina) and used as a catalyst in structure-sensitive reaction, NO reduction by CH4. The results proved that morphologically controlled metal nanoparticles supported on adequate support give us a novel tool to connect the worlds of surface science with that of real catalysis. 

A singly black developing leuco dye was ultimately realized by the invention of 2 -anilino-6 -diethylamino-3 -methylfluoran (12).6 Fluoran 12 skillfully utilizes the steric hindrance of a methyl group at 3 -position to develop black color (see discussion below). Practically all black developing fluoran compounds marketed today are derivatives of 12, though each has an individual characteristic, especially for use in thermosensitive recording papers. 

In addition, dimer-type black developing fluoran compounds such as 2,2-bis(4-[6 -(/V-cyclohexyl-/V-methylamino)-3 -methylfluoran-2 -yl-amino]phenyl propane (59)60 are also proposed. Fluoran 59 has much lower solubility in organic solvents to improve image stability to plasticizer for use in thermosensitive recording label paper. 

Fluoran compounds have an optically active spiro-carbon atom. Consequently, some fluoran compounds, especially those having an alkylamino group of four or more carbon atoms at 3 -position, have been found to exhibit crystal modifications as determined by X-ray diffraction. Each crystal modification reveals different physical properties such as melting point, solubility, and affinity with acidic compounds, resulting in different characteristics regarding use for carbonless copying papers, thermosensitive recording papers, and the like. 

The thermosensitive recording paper itself is white like a plain sheet of paper. With the application of heat by means of a thermal pen or thermal head, the color-forming components in the thermosensitive layer are brought into reactive contact in the area delineated by the heat pattern... 

The color-forming mechanism is simple and direct, only requiring heat application, and the recording equipment is free from maintenance, highly reliable, and less expensive. Thermosensitive recording papers can be used... 

These dispersions thus obtained are mixed together, and after the introduction of other additives, coated (at about 5-10g/m2 as dry solid) on a substrate such as paper, synthetic paper, or plastic film, dried, and calendered to give thermosensitive recording paper. 

Coreactants have a substantial influence on whiteness, sensitivity, and image stability of thermosensitive recording paper. All of the coreactants used in thermosensitive recording papers are phenol derivatives, and representative examples are shown in Table 10. 

In addition to leuco dye and coreactant, many additives such as sensitizer, stabilizer, filler, lubricant, antipressure agent, etc. are used in the thermosensitive layer. 

Metallic soaps such as zinc stearate or calcium stearate are used as lubricant, which reduces the friction coefficient of the surface of the thermosensitive layer resulting in smooth running on recording machines. 

The smoothness of the surface of the thermosensitive layer has considerable influence on image intensity and image reproducibility. This is achieved by calendering of high line pressure. So, paraffin waxes are used as antipressure agent in order to prevent undesirable coloring on calendering. 

Table 3 Poly(AQV-Alkyl-Substituted Acrylamides) for the Study of Alkyl Group Effects on Thermosensitivity in Aqueous Swelling... 

Permeability control of solutes through thermosensitive hydrogel membranes may be thought of in terms of the degree of hydration and kinetics of... 

Figure 15 Mechanisms of drug release from thermosensitive monolithic devices.

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