This paper presents a 27Al and 29Si MAS NMR study of K-feldspars and demonstrates that the spectra are sensitive to variations in the state of Al,Si order. For synthetically annealed samples, the results are in agreement with previous IR spectroscopy (Harris et al., 1989) and demonstrate that Al,Si rearrangement continues after the samples have become monoclinic as determined by powder XRD. NMR methods provide a significantly improved picture of the state of local Al,Si order in such samples. For triclinic samples, measures of the state of Al,Si order (M1 and M2 of 27Al spectra and M2 of 29Si spectra) correlate well with site occupancies determined by powder XRD, but for the monoclinic samples the NMR parameters continue to change whereas the XRD parameters do not. Interpretations based on the NMR results for the synthetically disordered samples are consistent with 1-step disordering, as observed by XRD. 27Al and 29Si MAS NMR is likely to be a useful tool for probing the state of local Al,Si order in a wide variety of natural samples.

Viséite is a poorly crystalline mineral which is difficult to study by X-ray diffraction pattern. NMR is a very useful technique to study such poorly crystalline minerals, and 31P, 27Al, and 29Si MAS NMR in conjunction with powder XRD results show that at least our Viséite sample is not a single phase with a structure analogous to that of analcime as previously reported. Rather, it is very disordered with a structure similar to that of crandallite and includes other phases including an undefined aluminophosphate, opal, and a framework aluminosilicate, probably a zeolite. The previously reported variations in the Si content of Viséite are probably due to variable amounts of opal and the framework aluminosilicate.

The effects of common cocklebur (Xanthium pensylvanicum Wallr.) on soybean [Glycine max (L.) Merr. ‘Wells′] development and seed yield were investigated at Urbana, Illinois, from 1974 through 1977. Increased densities of common cocklebur reduced soybean seed yield, total dry weight, and number of pods per plant. Under full-season competition, one common cocklebur/3 m of row reduced soybean seed yield by 3 to 12%. Soybean seed yield, total dry weight, and number of pods per plant increased as the length of time from soybean emergence to common cocklebur emergence increased. Common cocklebur emerging 4 weeks after soybean emergence reduced soybean seed yield by 7%. As duration of competition with common cocklebur increased, soybean seed yield, total dry weight, and number of pods per plant decreased. The reduction in soybean seed yield was less than 10% when common cocklebur was removed 6 weeks after soybean emergence. Effects of common cocklebur competition with soybeans in Illinois were similar to those observed in the southern United States.

Tom Dougherty has recently argued that non-consequentialists cannot accommodate our judgements about acceptable levels of risk-imposition. More specifically, he argues that the following two intuitively plausible claims are inconsistent: (i) that it is impermissible to provide small benefits to many people rather than saving the life of someone else, and (ii) that it is permissible to expose someone to a negligible risk of death in order to otherwise provide this person with a small benefit. Abandoning either principle has significant consequences: rejecting (i) requires rejecting an important argument against consequentialism and consequentialist approaches to beneficence; rejecting (ii) requires radically rethinking the way we live our lives, as we routinely expose individuals to negligible risks of death. This article shows that Dougherty's argument relies on a scope ambiguity involving permissibility. Once this ambiguity is resolved, Dougherty's argument fails.

John Broome argues that fairness requires that claims are satisfied in proportion to their strength. Broome holds that, when distributing indivisible goods, fairness requires the use of weighted lotteries as a surrogate to satisfy proportionally each candidate's claims. In this article, we present two arguments against Broome's account of fairness. First, we argue that it is almost impossible to calculate the weights of the lotteries in accordance with the requirements of fairness. Second, we argue that Broome rules out those methods whose use might provide some resolution to this problem. From these arguments, we conclude that, contra Broome, fairness does not require the proportional satisfaction of claims.

Stoichiometric CaAl2Si2O8 gels prepared by the Pechini process crystallize to triclinic anorthite via an intermediate, previously unknown pseudohexagonal phase. Hydrothermal treatment of this pseudohexagonal phase at 350 °C transforms it to hexagonal anorthite. These combined processes produce the hexagonal phase via a low-temperature, chemical route in contrast to the conventional high-temperature melting and crystallization method. Powder x-ray diffraction data and nuclear magnetic resonance (NMR) spectra of the hexagonal anorthite agree well with the published structure. They indicate a high degree of tetrahedral Si/Al ordering within the layers, but long-range disorder in the average structure due to (001) stacking faults present between the layers.

Phosphate glasses generally have lower glass-transition temperatures and greater thermal-expansion coefficients than silicate and borate glasses, and so are candidate materials for specialty glass-metal sealing applications. Phosphate glasses also have desirable optical properties (rare-earth stimulated-emission cross sections, low thermo-optical coefficients, ultraviolet transparency, etc.) and so are used as laser glasses. Recent developments of novel compositions for biomedical applications and as fast-ion conductors have also revived interest in the study of phosphate glass structures.

The structure/property relationships in simple phosphate glasses have not received nearly the attention paid to silicate and borate-based systems. This is partially due to the difficulty in preparing anhydrous compositions with more than 50-mol% P2O5. Ultraphosphate compositions (where the [O]/[P] ratio is less than 3) are highly reactive to ambient water. In addition because P2O5 sublimes at about 300°C, ultraphosphate glasses have not been studied to the extent that metaphosphate ([O]/[P] = 3) and polyphosphate ([O]/[P] > 3) compositions have.

27Al and 31P NMR spectroscopic data are presented for the tridymite polymorph of AlPO4 (AlPO4−1) through its structural phase transition at about 80 °C. The RT 27Al and 31P spectra of AlPO4−t both contain doublets of broad peaks, indicating two well-separated groups of sites in the RT structure with mean Al-O-P bond angles per tetrahedron of ∼ 147.8°and 153.1°(±1). With increasing temperature, the doublets remain the same up to about 74 °C, where the relative intensities of the two peaks start to change. The peak corresponding to smaller Al-O-P bond angles disappears, and above ∼88 °C the 27Al and 31P spectra contain single symmetrical peaks, corresponding to a mean Al-O-P bond angle of 153.4°. This bond angle increases gradually with increasing temperature to 153.7°at ∼150 °C and remains constant to about 500 °C. 27Al quadrupole echo experiments suggests that the 27Al nuclear quadrupole coupling constant (QCC) is small and decreases with increasing temperature. QCC remains nonzero in the high temperature phase of AlPO4−t, consistent with the previously proposed 3m local symmetry of Al in the high-temperature structure.

The local structure of barium-aluminofluorophosphate (Ba–Al–P–O–F) glasses was investigated using high resolution magic-angle sample spinning nuclear magnetic resonance (MASS-NMR) spectroscopy. The 27Al spectra show three different aluminum environments [Al(4), Al(5), and Al(6)] in these glasses. Changes were observed due to the addition of fluorine and nitrogen. 31P results indicate only one type of phosphorus environment which shifts with fluorine additions. The 19F spectra suggest that fluorine has both Ba and Al as nearest neighbors.