Lifetime definition

The OXVASC study showed that the annual incidence of stroke in the UK in the first few years of this century, including subarachnoid hemorrhage, was 2.3/1000 and the incidence of TIA was 0.5/1000 (Rothwell et al. 2005), with about a quarter of events occurring in those under the age of 65 and about a half in those above the age of 75 (Fig. 1.1). The incidence of cerebrovascular events in OXVASC was similar to that of acute coronary vascular events in the same population during the same period (Fig. 1.2), with a similar age distribution (Rothwell et al 2005). Incidence rates, however, measure first-ever-in-a-lifetime definite events only and exclude possible, recurrent and suspected events, so do not represent the true burden of a condition. This is especially true for TIA, where a significant proportion of cases referred to a TIA service have alternative, non-vascular... 

Definitive examples of intrinsic non-RRKM dynamics for molecules excited near their unimolecular tluesholds are rather limited. Calculations have shown that intrinsic non-RRKM dynamics becomes more pronounced at very high energies, where the RRKM lifetime becomes very short and dissociation begins to compete with IVR [119]. There is a need for establishing quantitative theories (i.e. not calculations) for identifying which molecules and energies lead to intrinsic non-RRKM dynamics. For example, at thenual... 

If we multiply the time elapsed per monomer added to a radical by the number of monomers in the average chain, then we obtain the time during which the radical exists. This is the definition of the radical lifetime. The number of monomers in a polymer chain is, of course, the degree of polymerization. Therefore we write... 

An important feature of pulse polarography is the sampling of the current at definite points in the lifetime of the mercury drop, and it is essential to... 

Sacrificial promoter definition, 9, 193 electrochemical promotion, 193 lifetime, 194,510... 

A free radical (often simply called a radical) may be defined as a species that contains one or more unpaired electrons. Note that this definition includes certain stable inorganic molecules such as NO and NO2, as well as many individual atoms, such as Na and Cl. As with carbocations and carbanions, simple alkyl radicals are very reactive. Their lifetimes are extremely short in solution, but they can be kept for relatively long periods frozen within the crystal lattices of other molecules. Many spectral measurements have been made on radicals trapped in this manner. Even under these conditions, the methyl radical decomposes with a half-life of 10-15 min in a methanol lattice at 77 K. Since the lifetime of a radical depends not only on its inherent stabihty, but also on the conditions under which it is generated, the terms persistent and stable are usually used for the different senses. A stable radical is inherently stable a persistent radical has a relatively long lifetime under the conditions at which it is generated, though it may not be very stable. 

Lifetime prevalence rates of psychiatric comorbidity co-existing with bipolar disorder are 42% to 50%.16 Comorbidities, especially substance abuse, make it difficult to establish a definitive diagnosis and complicate treatment. Comorbidities also place the patient at risk for a poorer outcome, high rates of suicidal-ity, and onset of depression.2 Psychiatric comorbidities include ... 

There are two types in acoustic cavitation. One is transient cavitation and the other is stable cavitation [14, 15]. There are two definitions in transient cavitation. One is that the lifetime of a bubble is relatively short such as one or a few acoustic cycles as a bubble is fragmented into daughter bubbles due to its shape instability. The other is that bubbles are active in light emission (sonoluminescence (SL)) or chemical reactions (sonochemical reactions). Accordingly, there are two definitions in stable cavitation. One is that bubbles are shape stable and have a long lifetime. The other is that bubbles are inactive in SL and chemical reactions. There exist... 

Kinetic vs. material chain. Kinetically, a chain reaction exists throughout the "life" of the radical, that is, from the initiation of a radical up to its termination by recombination or by disproportionation. The lifetime of a radical determines the so-called kinetic chain length Lp defined as the number of monomers consumed per initiating radical. Lp, by definition, can be calculated from the ratio between the propagation rate Rp to the initiation rate R, or, using steady-state hypothesis (Equation (1)), from the ratio between propagation rate to the termination rate Rt (Equation (3)). 

The performance of a lifetime detection system can be conveniently quantified by a figure-of-merit F, which is defined as the ratio of the SNR in a lifetime measurement and the SNR in an intensity measurement both carried out with the same number of photons. Based on this definition, F can be written as ... 

Pyridine ylide/LFP studies of 83-85 in pentane or isooctane afforded carbene lifetimes of 21-24 ns (k 4 to 5 x 107 s 1), similar to the lifetime of dimethylcarbene under these conditions. Unfortunately, these lifetimes are limited by reactions with the hydrocarbon solvents the lifetime of 83 is 1.5 times longer in cyclohexane-d12 than in cyclohexane. The observation that the lifetimes of 55-CI ( 1000 ns) and 55-F (—7000 ns) are considerably longer than those of 83 and 84 could reflect the superior stabilization provided by the halogen spectator substituents of 55, but this conclusion is tentative in the absence of definitive intramolecularly controlled lifetimes for 83-85. 

Given the above definition of a bond distance, we can analyze species lifetimes. The lifetime of all species is less than 12 fs above 2.6g/cc, which is roughly the period of an O-H bond vibration (ca. 10 fs). Hence, water does not contain any molecular states above 75 GPa and at 2000 K but instead forms a collection of short-lived transient states. The L simulations at 2.6g/cc (77 GPa) and 2000 K yield lifetimes nearly identical to that found in the S simulations (within 0.5 fs), which indicates that the amorphous states formed from the L simulations are closely related to the superionic bcc crystal states found in the S simulations. 

How long will it last An answer to this question is wanted by both suppliers and users, but it is usually a very difficult question to answer for polymer products. This is because the expected lifetime is often in tens of years, the service conditions may be complex and there is a scarcity of definitive data. 

Two of the fundamental hurdles in assessing the service life of a product are definition of the service conditions - uncertainty and variation - and establishing the time scales for expected lifetime. 

Definition of the plastic is fundamental to the prediction of the lifetime of a plastic component. 

The principal observation, which the laboratory scientist should not forget, was that most lifetime assessment of polymers is based on experience from service. Many of the respondents to the survey report examining parts taken from service at the end of life, or those that failed during warranty. Service experience is the principal source of information for the definition of insured lifetimes for polymer components in the construction industry. 

Table 15.1 Summary of key assumptions used in the definition of the case, and calculation of costs. Note that different capital charges have been used for industrial capital and distribution retail capital, respectively, reflecting different asset lifetimes (see text).

Fig. 1.6. Strategy for the choice of a fluorescent probe. Av, , and t are the Stokes shift, quantum yield and lifetime, respectively (see definitions in Chapter 3).

In this definition, each decay time is weighted by the corresponding fractional intensity. This average is called the intensity-averaged decay time (or lifetime). 

The definition used depends on the phenomenon under study. For instance, the intensity-averaged lifetime must be used for the calculation of an average colli-sional quenching constant, whereas in resonance energy transfer experiments, the amplitude-averaged decay time or lifetime must be used for the calculation of energy transfer efficiency (see Section 9.2.1). 

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