Activation of U

Figure 1. Comparison of and series nuclide activities in some representative waters. The highest concentrations ate typically observed for The isotopes of Th and Ra are strongly depleted due to interaction with the host rock, while somewhat higher activities of U are generally maintained. Data from Krishnaswami et al. (1982) on the left, Tricca et al. (2001) in the center, and Luo et al. (2000) on the right.

The frequently observed difficulties in the activation of u,p-didehydropeptides, especially in the case of AAla, can be avoided by peptide construction using the corresponding (1-sub-stituted amino acids and subsequent p-elimination in the peptide)158-161 A further possibility is the phosphonate condensation, where the corresponding, modified phosphorylglycine esters can react with aldehydes to yield u,p-didehydropeptidesII5l l62 IM (Scheme 26). 

C HEMical wastes resulting from the activities of U.S. industry and other groups have been dumped into waste sites around the country for many years. Typically the wastes are put into steel drums, not labeled, carried to an authorized dump site, and placed into a pit, which when filled is usually covered with earth. In some waste sites the filled containers are deposited on the surface. Bulk chemicals have been dumped in a few. Wastes other than chemicals are often deposited at the same sites, and illegal dumping has occasionally occurred, so there are undoubtedly unidentified sites. 

Activities of U-series nuclides in MORBs have been determined by both nuclear particle counting and mass-spectrometric techniques. In this section, we highlight briefly the key... 

Fig. 8.1. (a) Aqueous equilibrium diagram of the U-O2-H2O system at 25°C and 100 kPa Total activity of U-bearing ions is 10 . (After Ostle and Ball (1973).) (b) Calculated molar concentration of soluble U species in pure water at 25°C plotted as function Eh and pH. (Diagram provided by A.M. Giblin, personal communication, 1977.)... 

Most of the atoms of Th that are produced from decay readily attach to particles and are removed from solution. In the surface ocean there are enough particles formed to create a deficiency in Th activity from that to be expected at secular equilibrium with At steady state, the depth-integrated deficiency of the activity concentrations of Th in the euphotic zone is equal to its flux from the surface ocean on particles. If one then knows the Th C ratio in the particles, the flux of particulate carbon can be calculated. An example of Th measurements in the surface waters of the subtropical Pacific (see Fig. 6.11) indicates that difference in Th activity from that expected at secular equilibrium (equal to the activity of U) is small but readily measurable. 

This is only one-twenty-second of the activity of U and each of its dau ters. This small contribution to the activity of naturd uranium will be disregarded in the remainder of this chapter. 

Similarly to the activity of U(IV) in nitrate solution, shown in Figure VI-2, that of Th" in chloride and nitrate solution can be described equally well with either the complexation model or the ion interaction approach cf. Appendix A reviews of [1952WAG/STO] and [2006NEC/ALT]). The application of the two models to thorium chloride and nitrate complexes is discussed in Sections VIII.2.2.1 and X.1.3.3, respectively. 

Figure 11.24 The consensus secondary stractuie of the hammerhead rihozyme The secondary stracture of the hammaerhead rihozyme consists of a 16-nucleotide enzyme strand and a 25-nucleotide substrate strand. Two base-paired regions (stems I and II) position the scissile bond, the third region (stem El), the hammerhead must contain enough base pairs to form a stable structure. The conserved bases (Ught, grayish) are required for catalytic activity and arrow indicates the cleavage site. The active site cytosine (C-17) is not conserved and can be replaced with A or U (A-17 works well but the activity of U-17 is reduced).

Table II.3 provides the specific activity of uranium for various levels of enrichment. These figures for uranium include the activity of U-234, which is concentrated during the enrichment process. 

Zurenko GE, Yagi BH, Schaadt, Allison jW, Kilbum JO, Glickman SE, Hutchinson, DK, Barbachyn MR, Brickner SJ. In vitro activities of U-100592 and U-100766. novel oxazolidi-none antibacterial agents. Antimicrob Agents Chemother 1996 40 839-845. 

Assuming secular equilibrium for the two decay chains, the activity of U is equal to that of its parent radionuclide, i.e., and is simply given by ... 

From this, individital monitoring worrldbe reqrrired if p 239, the activity of u, is greater than ... 

See Palmer, Wiley and Keast, Procurement and Training of Ground Combat Troops, pp. 489-492, for dates of the activation of U.S. Army divisions. 

Pb-214 and Bi-214 appear to be reliable indicators of the activity of U-238 in secular equilibrium, i.e. of natural origin. Comparison of Pb-214 and U-238 measurements by a-spectroscopy, and also of total a-emission with that estimated from Pb isotopes, suggests that, in practice, radon loss is not generally significant from the Dounreay materials considered here. This also avoids the need to rely on low-precision Pb-210 data. 

Various parts of Uncaria plants are conunraily used in the traditional medicine for the treatment of inflammatory diseases, fii a study, hydro-alcoholic extract (Et0H-H20) and an aqueous extract of bark of U. tomentosa have been analyzed for their antUnflaminatoiy activity [64]. The hydro-alcoholic extract exhibited higher activity in mouse paw edema model and suppressed NF-kB [64]. Phytochemical analysis of these extracts revealed that hydroalcoholic extract possesses higher oxindole alkaloid content than the aqueous extract. It is believed that the antiinflammatory activity of U. tomentosa is attributed to the synergistic effect from a combination of these compounds [64]. 

Immunomodulatory activity of U. tomentosa is also likely due to its ability to suppress TNF-alpha production. In an in vivo animal study, the mice were fed with the C-Med 100, a commercial extract of U. tomentosa which does not contain the high-molecular weight compounds such as tannins [59]. It was observed that there was an increment in the number of immune cells including B, T, and NK cells, granulocytes, and memory lymphocytes. The authors concluded that the prolonged survival of the mice was mainly due to the ability of U. tomentosa to decrease oxidative stress and to activate NF-kB that counteract apoptosis and increase DNA repair [79]. 

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