Initiator, effect

This arises because as the temperature in increased from ambient, the main initial effect is to loosen the hydrogen-bonded local stmcture that iitiribits reorientation. Flowever, at higher temperatures, the themial motion of the water molecules becomes so marked that cluster fomration becomes iitiiibited. 

In continuation of this series, Saini et al. [24] studied the initiation effect of a-PCPY on the polymerization of MMA [28] and MA [29]. The systems followed nonideal kinetics in both cases, which was explained in terms of... 

Meanwhile, it was found by Asai and colleagues [48] that tetraphenylphosphonium salts having such anions as Cl, Br , and Bp4 work as photoinitiators for radical polymerization. Based on the initiation effects of changing counteranions, they proposed that a one-electron transfer mechanism is reasonable in these initiation reactions. However, in the case of tetraphenylphosphonium tetrafluoroborate, it cannot be ruled out that direct homolysis of the p-phenyl bond gives the phenyl radical as the initiating species since BF4 is not an easily pho-tooxidizable anion [49]. Therefore, it was assumed that a similar photoexcitable moiety exists in both tetraphenyl phosphonium salts and triphenylphosphonium ylide, which can be written as the following resonance hybrid [17] (Scheme 21) ... 

Ethylacrylate (EA) and butylacrylate (BA) was grafted onto natural rubber using BPO as the initiator [25]. KPS and AIBN were ineffective in the production of the graft and the failure to form the graft is attributed to the initiator effect. ... 

Metals are most active when they first deposit on the catalyst. With time, they lose their initial effectiveness through continuous oxidation-reduction cycles. On average, about one third of the nickel on the equilibrium catalyst will have the activity to promote dehydrogenation reactions. 

Initial effective electrical resistance of tapes, as evidenced by the cathodic protection current demand, has been outstanding. There have been reports of increasing current demand with time which indicate a need for investigation. The current demand increase has been found, on occasion, to be due to poor construction practice, but not all tapes are affected in this way. 

Nicotine is the main psychoactive ingredient of tobacco and is responsible for the stimulant effects and abuse/ addiction that may result form tobacco use. Cigarette smoking rapidly (in about 3 sec ) delivers pulses of nicotine into the bloodstream. Its initial effects are caused by its activation of nicotinic acetylcholine (nACh) receptors. nACh receptors are ligand-gated ion-channels and pre- and postsynaptically located. Reinforcement depends on an intact mesolimbic dopamine system (VTA). nACh receptors on VTA dopamine neurons are normally activated by cholinergic innervation from the laterodorsal tegmental nucleus or the pedunculopontine nucleus. 

The known beneficial effects of retinoids on malignancies are assumed to relate to retinoid receptor-mediated antipromoting and anti-initiating effects. The latter appeals to be influenced by interference of several xenobiotics with different steps of the retinoid metabolism in the target cell. Of the carotenoids, (3-carotene is the most potent retinol precursor, yet being... 

Both the Pb disc test and the steel dent test are of particular significance to stab detonators. As a matter of illustration, the steel dent test (Ref 10) consists of firing a detonator in direct end-on contact with a steel block. The depth of the dent produced is a measure of output. The depth, or better, the volume of the dent correlates well with initiation effectiveness. The low-rate detonation, which crushes nearly as much sand as high-order detonation, makes no dent in a steel plate. It has been demonstrated that the depth of the dent is proportionate to the excess of pressure over the yield strength of the steel of the dent block, integrated over the volume of the detonation head. It has been found that a detonator of 0.190-inch diameter or larger, which produces a dent 0.010 of an inch deep in a mild steel block, will initiate a lead of Tetryl or RDX under favorable conditions. Specification requirements for detonators to be used in fuses are usually at least 0.015 to 0.020 inch in depth, and many produce dents up to 0.060 inch deep... 

Tolerance is characterized by reduced responsiveness to the initial effects of a drug after repeated exposure or reduced responsiveness to a related compound (i.e., cross-tolerance). Animal studies have not provided conclusive evidence of tolerance to the effects of the centrally active compounds in toluene or trichloroethane (Moser and Balster 1981 Moser et al. 1985). Observations in humans, on the other hand, have documented pronounced tolerance among subjects who chronically inhale substances with high concentrations of toluene (Glaser and Massengale 1962 Press and Done 1967) and butane (Evans and Raistrick 1987). Kono et al. (2001) showed that tolerance to the reinforcing effects of solvents is comparable to that conditioned by nicotine but less intense than that reported with alcohol or methamphetamine use. 

There are circumstances when a complex process may involve two competing (i.e., opposing) dynamic effects that have different time constants. One example is the increase in inlet temperature to a tubular catalytic reactor with exothermic kinetics. The initial effect is that the exit temperature will momentarily decrease as increased conversion near the entrance region depletes reactants at the distal, exit end. Given time, however, higher reaction rates lead to a higher exit temperature. 

The physicochemical data underline the striking influence of the dicyclopentadienyl unit on the properties of these silicone surfactants. In comparison to conventional products [7], the critical micelle formation concentration was lowered for up to two orders of magnitude whereas the minimum surface tension reached rose only slightly. The data collected indicate that the type of surfactant has been changed from the initial "effective" to a more "efficient" one. 

The formation of IBVE-aMeSt block polymers was further supported by results of film-casting experiments (12). These data also show that the starting quasiliving poly(IBVE) dication is sufficiently reactive to initiate effectively subsequent aMeSt polymerization. 

Over the subsequent decades, the database has continued to grow, and reviews of the available field data have been produced periodically [33-36]. In general, the initial effects that are observed in field studies with pyrethroids are consistent with predictions based on the laboratory data - those organisms that are observed to be among the most sensitive in the laboratory also tend to be among the most sensitive in the field. 

Several catastrophic fire incidents in the petroleum industry have been the result of the facility firewater pumps being directly affected by the initial effects of the incident. The cause of these impacts has been mainly due to the siting of the fire pumps in vulnerable locations without adequate protection measures from the probable incident and the unavailability or provision of other backup water sources. A single point failure analysis of firewater distribution systems is an effective analysis that can be performed to identify where design deficiencies may exist. For all high risk locations, fire water supplies should be available from several remotely located sources that are totally independent of each and utility systems which are required for support. 

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