Weighted observations

In some polysaccharides, the reducing terminal is linked, through a phosphoric diester linkage, to O-1 of a 2,3-di-6 -acylglycerol. This structural feature has been demonstrated for some capsular polysaccharides from E. coli and Neisseria species, - but is probably more common than that. Non-covalent linkage between the lipid part and the cell membrane may explain why extracellular polysaccharides often occur as capsules, and the high (apparent) molecular weight observed for these polysaccharides may be due to micelle formation in aqueous solution. 

The lowest molecular weight observed for all polymers prepared in this study was for copolymer 16, a copolymer prepared using 75 mole % cyclohexyl methyl and 25 mole % phenyl methyl silane. The low molecular weight observed for this copolymer may be due to the two bulky side groups of the monomers (phenyl and cyclohexyl) sterically interfering with propagation during the polymerization. 

Mitochondrial oligomycin-sensitive mg2+ATPase is thought to play a major role in oxidative phosphorylation (Boyer et al. 1977). It has been suggested that impairment of mitochondrial energy metabolism by chlordecone may contribute to the decreases in body weight observed following exposure to this chemical (Desaiah 1981). 

For entries 3-5 the increase in molecular weight observed can be assigned to the increase in the rate of insertion and the rate of termination remains practically the same. An increase of the rate of polymerisation with the steric bulk of the ligand is usually ascribed to the destabilisation of the alkene adduct while the energy of the transition state remains the same. As a chain transfer reaction presumably P-hydride elimination takes place or traces of water might be chain transfer agents. Chain transfer does occur, because a Schulz-Flory molecular weight distribution is found (PDI 2, see Table 12.2). Shorter chains are obtained with a polar ortho substituent (OMe, entry 2) and in methanol as the solvent, albeit that most palladium is inactive in the latter case. 

The EPA reference dose (RfD) of 0.6 mg/kg/day (IRIS 1998) is based on aNOAEL of 60 mg/kg/day for developmental effects (decreased fetal body weights) observed in rats at a dose of 120 mg/kg/day (Jones-Price et al. 1983a). 

Conformational equilibria still fast on the NMR timescale. From reference compounds (diastereomeric analogs, e.g., 4-/err-butyl or 3,5-cis-dimethyl substitution operating as a kind of conformational anchor), the NMR parameters of the purely equatorial and axial conformers (Pcq and Pax, respectively) can be determined. The equilibrium constant K [Eq. (3)] from these parameters and that of the population-weighted observed NMR parameter, P, can be estimated from the fast equilibrium [59CI(L)568] ... 

The intermediate-duration inhalation MRL was based on a NOAEL of 0.005 ppm administered to rats for 5 hours a day, 5 days a week for 3 weeks (Mobay Corporation 1984). At 0.3 ppm, decreased kidney weights were observed in both male and female rats, with decreased liver weights observed in females only. Hepatic and renal effects were not seen at an inhaled dose of 0.15 ppm and lower. Nasal lesions occurred in 80-90% of the animals exposed at the 0.3 ppm level, while only 50-70% of the animals were affected at the 0.15 ppm concentration. No significant lower respiratory tract alterations were noted at the 0.0175 ppm inhalation dose (NOAEL) however, at the same 0.0175 ppm dose, hemorrhage, inflammatory exudate, epithelial changes were observed in the nasal cavity. The 0.0175 ppm dose is also classified as an extra-thoracic respiratory tract LOAEL and is the toxicological end point that this intermediate-duration MRL is based upon. For the purposes of MRL derivation, the minimal LOAEL was placed at 0.0175 ppm and the NOAEL was placed at 0.005 ppm. Since there is no reported threshold for HDI immrmological hypersensitivity in hmnans, this MRL may not be protective for persons with hypersensitivities to HDI. Respiratory tract lesions in laboratory animals have been described in other studies (Dow Chemical 1964 E.l. Dupont de Nemours 1978 Haskell Laboratory 1961 Karol et al. 

The tin II product shows four peaks (from DSC data)-at 60, 85, 115 and 350 C. The tin IV product shows only two peaks at 85 and 370 C. The sodium ionomer shows peaks at 60, 95, 130 and beginning at 450 C. The pre-ionomer shows peaks at about 40, 90 and 430 C. In all cases, the highest transition appears to coincide with a loss in weight observed in the TGA and the lowest (approximately) corresponds to the softening temperature observed with the Fisher-Johns apparatus. It is believed that the lowest temperature corresponds to movement in the ethylene units and that the additional peaks may correspond to more complex movements involving the carboxylate moieties. 

Cleft palate, enlarged fontanelle and poly- and syndactyly (dog, mini-pig) were observed after administration of Aroclor 1254. The hyperpigmentation and low birth weights observed in monkeys when exposed to Aroclor 1254 prenatally is paralleled in humans under comparable conditions. 

The temperature was then increased to 200 C at a rate of 1 C per minute and maintained constant until elution was essentially complete. The absence of a data system interfaced to the LKB 9000P GC/MS precluded exhaustive structure elucidation. However, major components and compound types were identified by comparing mass spectra of the column effluents with standard API Project 44 mass spectra and by the m/z values observed in individual spectra in relation to the molecular weights observed in the group-type analyses. Semiquantitative analyses were calculated from the FID gas chromatograms obtained using the PE 3920 GC. 

If the specific heat of the metal is known, an approximate atomic weight can be determined. This can be done using the relationship between the specific heat of solid metallic objects and their atomic weights observed by Pierre Dulong and Alexis Petit in 1819 it is known as the Law of Dulong and Petit. 

Oral exposure to uranium compounds has caused body weight effects in animals, but these effects are not necessarily the result of systemic toxicity. The initial loss of body weight observed in animals exposed... 

The in vitro hydrolysis study, by means of potentiometry, weight loss, SEC and NMR, shows that the degradation mechanism involves simultaneous chain scissions and ester group hydrolysis. Indeed, ester hydrolysis was evidenced by the release of an acidic group as glyoxylic acid hydrate by NMR, or by the drop of pH and the loss of ethanol (weight loss and NMR). The decrease in molecular weight observed by SEC and the presence of small molecules by NMR prove that chain scissions occurred at the same time. 

---