Aging behavior

The time required to produce a 50% reduction in properties is selected as an arbitrary failure point. These times can be gathered and used to make a linear Arrhenius plot of log time versus the reciprocal of the absolute exposure temperature. An Arrhenius relationship is a rate equation followed by many chemical reactions. A linear Arrhenius plot is extrapolated from this equation to predict the temperature at which failure is to be expected at an arbitrary time that depends on the plastic s heat-aging behavior, which... 

Experimental design Groups of 12 male NMRI mouse pups were treated by gavage with 0, 50, or 290 mg/kg/day trichloroethylene in a 20% peanut oil emulsion. The pups were treated for 7 days begiiming at 10 days of age. The doses selected did not sedate the mice. At 17 and 60 days of age behavior was tested. The tests were performed between 8 am-12 pm. Locomotion, rearing, and total activity were measured in an automated device with high and low level infrared beams. 

Children Pain interviews may be conducted with children as young as 3 or 4 years of age however, communication may be limited by vocabulary.34 Terms familiar to children such as hurt, owie, or boo boo may be used to describe pain. The VAS is best used with children older than 7 years of age. Other scales based on numbers of objects (e.g., poker chips), increasing color intensity, or faces of pain may be helpful for children between 4 and 7 years of age. In children younger than 3 to 4 years of age, behavioral or physiologic measures, such as pulse or respiratory rate, may be more appropriate. Pain assessment in newborns and infants relies on behavioral observation for such clues as vocalizations (crying and fussing), facial expressions,... 

Hoffmann, M. Hofer, C. Schneller, T. Bottger, U. Waser, R. 2002. Preparation and aging behavior of chemical-solution-deposited (Pb(Mg1/3Nb2/3)03)i x-(PbTi03)x thin films without seeding layers. J. Am. Ceram. Soc. 85 1867-1869. 

Joyce CA, Paller KA, Mclsaac HK, Kutas M. (1998). Memory changes with normal aging behavioral and electrophysiological measures. Psychophysiology. 35(6) 669-78. 

Johnston, R. E. and Schmidt, T. (1979). Responses of hamsters to scent marks of different ages. Behavioral and Neural Biology 26,64-75. 

Figure 1. (a) A snapshot picture of a colloidal system obtained with confocal microscope, (b) Aging behavior observed in the mean square... 

Zero-Temperature Relaxation. This interpretation rationalizes the aging behavior found in exactly solvable entropy barrier models that relax to the ground state and show aging at zero temperature [190, 191]. At T = 0, the stimulated process is suppressed (microscopic reversibility, Eq. (8), does not hold), and Eq. (204) holds by replacing the free energy of a CRR by its energy, F = E. In these models a region corresponds to just a... 

Aging behavior observed in the mean square displacement, (Ax ), as a function of time for different ages. The colloidal system reorganizes slower as it becomes older, (c) y = (Ax )/3 (upper curve) and (Ax ) (lower curve) as a function of the age measured over a fixed time window At = 10 min. For a diffusive dynamics both curves should coincide, however these measurements show deviations from diffusive dynamics as well as intermittent behavior. Panels (a) and (b) from http // www.physics.emory.edu/ weeks/lab/aging.html and Panel (c) from Refill. 

The aging behavior of the porous zinc electrode in 6 M KOH in the presence of different electrolyte additives such as ZnO, LiOH, and KF has been studied using cyclic voltammetry by Shivkumar etal. [212]. The mechanism of the electrode reaction in all these electrolytes was investigated. 

The problems associated with the multifunctional curing agents for CTPB and the resultant aging behavior of the cured polymers have led to a practical solution for curing binders and propellants—i.e., using mixed aziridines or a mixture of an aziridine and an epoxide. Such mixtures, when appropriately balanced, usually provide satisfactory mechanical behavior and high temperature stability. In dual curing systems such as MAPO and BITA or MAPO and a suitable multifunctional epoxide,... 

Aziridine. Propellants cured with MAPO have excellent processing characteristics and satisfactory uniaxial tensile properties over a wide range of temperatures. However, the problems associated with the aging behavior of these propellants have led to the use of other types of curing systems which do not contain the P—N bond. These latter materials are di- and trifunctional aziridines, such as those shown in Table IV, and provide satisfactory propellants in which the uniaxial tensile properties can be tailored to a desired modulus. Such mixed aziridine-cured systems give satisfactory initial properties, reduce the postcure behavior, and improve the storage characteristics of CTPB propellants. 

Propellant Aging. Three structurally different chemicals and mixtures of these materials have been used to cure CTPB propellants. These are MAPO, other aziridines which do not contain the P—N bond, and epoxides. As stated in the discussion of curing agents, the aging behavior of CTPB propellants prepared with these materials is distinctly different, owing to the behavior of these compounds and their reaction products in the presence of ammonium perchlorate and at elevated temperatures. 

The aging behavior of a BITA-cured propellant is shown in Figure 12, and is distinctly different from that of MAPO-cured propellants. Here, the modulus increases upon exposure to elevated temperatures, and the propellant is said to postcure. This behavior is in agreement with the known reactions of BITA, which includes the formation of oxazolines. These oxazolines which are formed are far less reactive with carboxylic acids than the original aziridines and, hence, the curing reactions continue in the propellant, particularly at elevated temperatures. Epoxy-cured propellants also postcure, owing to the side reactions revealed in... 

Figures 1-4 illustrate the IFT behavior of four citrus oils against water as a function of time at different temperatures. All but one of the lemon oil 2 and orange oil 2 runs were made with triple distilled water. All lemon oil 1 and orange oil 1 runs were made with mono distilled water. Surface tension of the two water samples differed by 0.2 dynes/cm (mean of 6 runs). This difference is not believed to make a major contribution to the IFT aging behavior observed.

Figures 3 and 4 compare the interfacial aging behavior of lemon oil 2 and 1 respectively. As in the case of orange oil, aging behavior is a function of temperature and lemon oil used. At 45 and 50 C, the lemon oil 1/water interface aged to an IFT value too low to measure in 3 to 4 hrs. The lemon oil 2/water interface retained a finite value after 10 hrs. at 50 C. The rate of aging for both lemon oils decreases significantly as the temperature decreases,...

Figure 1. YIT aging behavior of the orange oil 2/triple distilled water interface ZS, 1.2 C O>O 50°C.

Figure 4. YIT aging behavior of the lemon oil 1/monodistilled water interface , O, 45 C , 5O C.

Figure 5. Effect of 30 C storage experiments on the YIT aging behavior of the orange oil 2/monodistilled water interface at 50 C , orange oil 2/monodistilled water interface stored at 30 C for 47 hrs. before temperature was raised to 50°C O, orange oil 2/monodistilled water interface stored at 30°C for 47 hrs. Orange oil 2 then transferred to fresh water and temperature raises to 50 C.

Figure 8. YIT aging behavior of the G/A supernatant phase/ orange oil 1 interface 1.2°C,O> , 50°C.

Figure 11. YIT aging behavior of the G/GA supernatant phase/ lemon oil 1 interface O> 40 C Q, 45°C.

Figure 13. YIT aging behavior of interfaces formed by the G/A complex coacervate phase with lemon oil 2 50°C ...

Marked variations in IFT aging behavior of replicate complex coacervate phase/citrus oil interfaces were observed occasionally. Figure 13 illustrates an example of this. Two IFT aging curves for the G/A complex coacervate phase/lemon oil 2 interface differ by 0.3 to 1.3 mJ/m2 throughout the 1.3-1.5 hour of aging needed for the IFT to reach a value too low to measure. A third run gave a value too low to measure immediately after the interface was formed. This type of behavior was encountered periodically, especially with complex coacervate phase/citrus oil interfaces at 40-45 C. Experimental technique probably caused most of these observations since it is difficult to place the Wilhelmy plate at complex coacervate phase/ citrus oil interfaces. However, the possibility that an IFT too low to measure immediately after formation of an interface is a characteristic feature of some complex coacervate phase/citrus oil interfaces at 40° and 34°C cannot be completely ruled out. 

Thermostable networks offer a very large diversity of thermal aging behaviors. Their design obeys the following rules ... 

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