Joint persistence

Fenner K, Scheringer M, Hungerbuhler K (2003) Joint persistence of transformation products in chemicals assessment case studies and uncertainty analysis. Risk Anal 23(l) 35-53... 

Pov is commonly calculated based on single-media half-fives that have been derived from degradation simulation studies such as those recommended in OECD 307 [23] and OECD 308 [24]. In these studies, disappearance of the chemical in question is followed as a function of time. The half-fives thus obtained therefore usually do not account for the formation of transformation products, which are likely to prolong exposure of the environment to chemicals that may still exhibit hazards similar to the parent compoimd. Joint persistence (JP) has therefore been suggested as a new indicator for overall persistence that reflects the prolonged exposure of the environment due to the formation of transformation products [4,5] (Eq. 2). Eor better distinction, the overall persistence of the parent compound alone will be termed primary persistence (PP) for the remainder of the chapter. 

Fig. 2 Primary (PP) and joint persistence (JP) for 16 pesticides, the surfactant nonylphe-nol polyethoxylate (NPnEO), and the solvent perchloroethylene sorted according to JP. The dashed line indicates the 60-day water half-life used as persistence criterion in the Stockholm Convention [25]. Reprinted with permission from [8], p 2447. (2007) American Chemical Society...

As discussed in this chapter, such modelhng studies are, however, currently still subject to considerable imcertainty. As analyzed in detail in [5], the largest uncertainty in the prediction of Joint Persistence and exposure concentrations stems from imcertainty in the prediction of degradation half-fives, which amounts to at least a factor of 5-10. Partition coefficients generally exhibit somewhat lower imcertainties and also tend to be less influential. Fractions of formation, although highly imcertain, are bounded between 0 and 1. As long as the focus is on major transformation products (>10%), the uncertainty in fractions of formation is therefore always below a factor of ten. 

The following three mechanisms of polymer chain flexibility are the best known in polymer physics freely jointed persistence, and rotational isomeric mechanisms [27]. The freely jointed mechanism corresponds to the simplest freely jointed model of a semiflexible polymer chain in which the chain is in the form of a sequence of hinged, long, rigid rods of length I and diameter d, with I d (Fig. 1.2a). In the persistence mechanism, the flexibility is due to gradual accumulation of the effect of small vibrations of valence angles, bonds, etc. A... 

Whenever possible, avoid exposure to infections. Contact the primary health care provider if minor cuts or abrasions fail to heal, persistent joint swelling or tenderness is noted, or fever, sore throat, upper respiratory infection, or other signs of infection occur. 

Durham, R.W. Oliver, B.G. J. Great Lakes Res. 1983, P, 160-168. Thomas, R.L. Veik. Intemat. Verein. Limnol. 1981, 21, 1666-1680. Literature Review of the Effects of Persistent Toxic Substances on Great Lakes Biota Fitchko, J., Ed. Report to the Great Lakes Science Advisory Board, International Joint Commission, Windsor, Ontario, 1986, 256p. Allan, R.J. Symp. Biol. Hung. 1989, 38, 217-243. 

Subchondral bone undergoes metabolic changes, including increased bone turnover, that appear to be precursors to tissue destruction. The normally contiguous bony surface becomes fissured. Persistent use of the joint eventually results in loss of cartilage, permitting bone-to-bone contact that ultimately promotes thickening and eburnation of exposed bone. Microfractures may appear in subchondral bone, and osteonecrosis may develop beneath the surface. 

Increased swelling or persistent pain in bones or joints... 

Nociceptors are bare or free nerve endings therefore, they do not adapt, or stop responding, to sustained or repeated stimulation. This is beneficial in that it keeps the individual aware of the damaging stimulus for as long as it persists. Nociceptors are widely distributed in the skin, dental pulp, periosteum, joints, meninges, and some internal organs. The three major classes of nociceptors are ... 

Joint stiffness typically is worse in the morning, usually exceeds 30 minutes, and may persist all day. 

Hypertension is defined by persistent elevation of arterial blood pressure (BP). The Seventh Report of the Joint National Committee on the Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) classifies adult BP as shown in Table 10-1. 

In order to determine the significance of the surface discontinuities and assess their persistence and connections at depth, useful information was obtained from a combined analysis of structural data (joints and faults of different scales, comparing the discontinuities recognized on the ground)... 

Buckley CD, Filer A, Haworth O, Parsonage G, Salmon M. Defining a role for fibroblasts in the persistence of chronic inflammatory joint disease. Ann Rheum Dis 2004 63 Suppl 11 92-5. 

Most patients with cystic acne respond to 1-2 mg/kg, given in two divided doses daily for 4-5 months. If severe cystic acne persists following this initial treatment, after a period of 2 months, a second course of therapy may be initiated. Common adverse effects resemble hypervitaminosis A and include dryness and itching of the skin and mucous membranes. Less common side effects are headache, corneal opacities, pseudotumor cerebri, inflammatory bowel disease, anorexia, alopecia, and muscle and joint pains. These effects are all reversible on discontinuance of therapy. Skeletal hyperostosis has been observed in patients receiving isotretinoin with premature closure of epiphyses noted in children... 

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