Thermometers for low temperature Magic Angle Spinning NMR.

The measurement of temperature in a Magic Angle Spinning NMR probe in the temperature range 85-300K is discussed. It is shown that the shift of the (119)Sn resonance of Sm(2)Sn(2)O(7) makes a good thermometer with shift being given by delta=223 - 9.54x10(4)/Tppm and a potential precision of better than 0.5K over the entire temperature range. The sensitivity is such (e.g. 4.2ppm/K at 150K) that small temperature gradients across the sample can readily be measured. Furthermore, since the spin-lattice relaxation time is very short, measurements can be made in approximately 1s enabling relatively rapid temperature changes to be followed. Values for the chemical shift of (207)Pb in Pb(NO(3))(2) down to approximately 85K are also presented. Although the (207)Pb shift variation is approximately linear near room temperature (we find a slope 0.725+/-0.002ppm/K over the range 293-153K), it clearly deviates from linearity below approximately 130K.

Effects of frequency and duration in telephone counselling for smoking cessation.

OBJECTIVE: This study evaluates alternative protocols in telephone counselling for smoking cessation. DESIGN: The American Cancer Society enrolled 6322 clients in a randomised trial comparing three counselling formats of varying duration and frequency of contact, with or without booster sessions, and mailed self help booklets without telephone counselling. SETTING AND PARTICIPANTS: Participants were drawn from callers to the American Cancer Society's National Cancer Information Center seeking assistance with smoking cessation who provided informed consent and were adult daily smokers, ready to make a quit attempt within two weeks, and from states not served by an evidence based proactive telephone counselling programme. OUTCOMES: Six-month cessation rates (30-day point prevalence) were measured in telephone interviews. RESULTS: There was a significant counselling effect. The overall cessation rates that were yielded by a brief protocol including booster sessions were equivalent to those obtained with the American Cancer Society's standard protocol with boosters. CONCLUSIONS: Based on these findings, the abbreviated protocol with five sessions and two boosters is considered to be an option for improving cost efficiency in the delivery of this service.

Multiple-quantum MAS NMR of quadrupolar nuclei. Do five-, seven- and nine-quantum experiments yield higher resolution than the three-quantum experiment?

The question of whether or not higher-order (five-, seven- and nine-quantum) multiple-quantum magic angle spinning (MQMAS) experiments yield isotropic NMR spectra of half-integer quadrupolar nuclei with higher resolution than the basic three-quantum MAS experiment is examined. The frequency dispersion is shown theoretically to be greatly increased in higher-order MQMAS spectra, but it is argued that whether or not this translates into an increase in resolution depends upon the ratio of the homogeneous to inhomogeneous contributions to the isotropic linewidth. Experimentally, it is demonstrated using three-, five- and seven-quantum 45Sc MAS NMR and three- and five-quantum 27Al MAS NMR of crystalline samples that higher-order MQMAS experiments can yield a real and useful increase in resolution but that, owing to the presence of inhomogeneous broadening in the isotropic spectra, this increase is less than the theoretically predicted value. A number of practical issues relating to resolution in MQMAS NMR are also pointed out.