Early time information

Although the eigenstate-to-eigenstate and autocorrelation function formulations of the spectrum, Ik(w), are mathematically equivalent, they focus attention on complementary features. The most readily interpretable features in the autocorrelation function picture are early-time features (initial decay rate, the times at which partial recurrences occur, the magnitudes of the earliest and largest partial recurrences) which primarily sample the potential surface at the highly localized and a priori known initial position of the wavepacket, I (O), before it has had time to explore the entire dynamically accessible region of the potential surface. This early time information is encoded in the broad envelope (low resolution) of the Ik(u>) spectrum (see Fig. 9.2). 

Since it was proposed in the early 1980s [6, 7], spin-relaxation has been extensively used to determine the surface-to-volume ratio of porous materials [8-10]. Pore structure has been probed by the effect on the diffusion coefficient [11, 12] and the diffusion propagator [13,14], Self-diffusion coefficient measurements as a function of diffusion time provide surface-to-volume ratio information for the early times, and tortuosity for the long times. Recent techniques of two-dimensional NMR of relaxation and diffusion [15-21] have proven particularly interesting for several applications. The development of portable NMR sensors (e.g., NMR logging devices [22] and NMR-MOUSE [23]) and novel concepts for ex situ NMR [24, 25] demonstrate the potential to extend the NMR technology to a broad application of field material testing. 

Essentially all biological catalysts in the modern world are themselves proteins, enzymes. However, in 1989 Sidney Altman and Thomas Cech received the Nobel prize in chemistry for showing that RNA itself could act as a catalyst for some biological reactions. This led to the idea that in an earlier time, as life was evolving, RNA may have been both the information molecule (a role usually played by the more stable DNA now) and the catalyst (the role that protein enzymes now play.) Since this idea indicates that in early times the synthesis of proteins was catalyzed by RNA, not by protein enzymes, the intriguing question is whether this is still true today. 

Other estimates of the amount and of the distribution of DM in the universe come from the study of large scale structures at more recent epochs in the cosmic evolution. The reason why cosmic structures contain a record of the DM distribution in the universe is due to the fact that the evolution of the parent density perturbations was dominated by their DM content from early times on (see Peacock in these Proceedings). Thus the study of galaxies and galaxy clusters - the largest gravitationally bound structures in the universe whose potential wells are dominated by DM - provide information on both the amount of DM and on its density distribution. 

Figure 24. Coincidence-imaging spectroscopy of dissociative multiphoton ionization processes in NO2 with 100-fs laser pulses at 375.3 nm, using angle-angle correlations. The polar plots show, at time delays of Ofs, 350 fs, 500 fs, 1 ps, and 10 ps, the angular correlation between the ejected electron and NO photofragment when the latter is ejected parallel to the laser field polarization vector. The intensity distributions change from a forward-backward asymmetric distribution at early times to a symmetric angular distribution at later times, yielding detailed information about the molecule as it dissociates. Taken with permission from Ref. [137]...

Fire ants are a major pest in sugarcane fields in the southern United States. There exists a controversy over the positive or negative role, that fire ants play in agroecosystems. Radiotracer studies of early times [202] although economical to carry out, cannot be used in croplands because of possible radioactive contamination of food. Studies involving Sm-labeled fire ants prevented food contamination problems and resulted in information on ant behaviour that was previously not available [203]. 

The preservation and maintenance of health has also been a subject of concern to humanity since early times. Archeological evidence from about 4000 bc shows that in city planning the inhabitants were well aware of the problems of health and sanitation and therefore were probably also aware of the treatment necessary to cure certain diseases. Written records from later times show they were well informed as to the operations used in... 

To provide meaningful toxicity data to discovery chemists during the early phase of lead identification the test systems must be robust and allow data to be delivered in a timely manner so that the information can be incorporated into the decision-makingprocess. At this early time in discovery, compound availability is usually limited, which means that the in vitro systems employed must have low compound requirements. Moreover, these test systems must be amenable to HTS formats, such as 96- or 384-well cell culture, and technically simple for rapid turnaround and successful integration with robotics platforms. 

Early time-resolved anisotropy experiments on PMAA used a combination of anthryl-based labels and probes [18,46,60,76] in an effort to fully characterize the conformational switch of the polyelectrolyte in aqueous solution. In their study of probes dispersed in and labels incorporated into PMAA, Treloar and coworkers [60,76] derived information from anisotropy experiments pertinent not only to the cluster size of the rotating units, but also to the structure of the hypercoil itself. 

To develop a kinetic mechanism for JP-10 oxidation, information about the initial decomposition pathway is needed. The initial JP-10 decomposition steps have been studied in a shock tube using a recently developed ultraviolet kinetic spectrograph [10]. Figure 10.11 shows the absorption cross-sections of JP-10 products at early times. At -5 and 15 fis, the JP-10 product spectra are nearly identical to 0.5x and 0.9x the cyclopentene products spectra, respectively. This allows one to suggest that JP-10 decomposes into cyclopentene at a very early stage and that the yield for this path approaches unity. At 50 fis, the JP-10 decomposition product absorption cross-section is nearly identical to that of twice the decomposition product spectra of cyclopentadiene. Both these observations are consistent with an initial decomposition pathway of JP-10 to cyclopentene and a Cs-compound. This Cs-compound has secondary decomposition products similar to cyclopentadiene (i.e., C5H5 and others). Using this technique, several... 

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