Feedback control optimisation of ESR experiments

Numerically optimised microwave pulses are used to increase excitation efficiency and modulation depth in electron spin resonance experiments performed on a spectrometer equipped with an arbitrary waveform generator. The optimisation procedure is sample-specific and reminiscent of the magnet shimming process used in the early days of nuclear magnetic resonance -- an objective function (for example, echo integral in a spin echo experiment) is defined and optimised numerically as a function of the pulse waveform vector using noise-resilient gradient-free methods. We found that the resulting shaped microwave pulses achieve higher excitation bandwidth and better echo modulation depth than the pulse shapes used as the initial guess. Although the method is theoretically less sophisticated than simulation based quantum optimal control techniques, it has the advantage of being free of the linear response approximation; rapid electron spin relaxation also means that the optimisation takes only a few seconds. This makes the procedure fast, convenient, and easy to use. An important application of this method is at the final stage of the implementation of theoretically designed pulse shapes: compensation of pulse distortions introduced by the instrument. The performance is illustrated using spin echo and out-of-phase electron spin echo envelope modulation experiments. Interface code between Bruker SpinJet arbitrary waveform generator and Matlab is included in versions 2.2 and later of the Spinach library

Enhancing engagement in evidence-based tobacco cessation treatment for smokers with mental illness: A pilot randomized trial.

ObjectiveTo evaluate the efficacy of a brief telephone-delivered Motivational Interviewing (MI)-based intervention to facilitate engagement in evidence-based cessation treatment for Veterans with mental illness referred to smoking cessation treatment.Methods86 military Veteran smokers with mental illness were recruited from a tobacco cessation consult clinic and randomized to receive either a MI-based treatment engagement intervention (TE; n = 48) or a non-MI assessment and information control (CON; n = 38) condition. Intervention was delivered during a single brief telephone contact. Primary engagement outcomes were 1) attending a treatment session within 30 days and 2) combination treatment (attending session plus using pharmacotherapy). Cessation outcomes included self-reported 24 h cessation attempts and 7 day point abstinence at 3 months post-intervention. Outcomes were assessed at 1 and 3 months post intervention.ResultsOutcome analyses included 85 participants (47 TE, 38 CON) using an intent-to-treat analytic approach. Participants were on average 49.5 (13.4) years old, 88% Male, 59% white, 18% African American and 14% Hispanic/Latino(a). Following intervention delivery TE and CON participants did not differ on likelihood of attending a treatment session during the subsequent 30 days (47% vs 45%, respectively). A significant difference was observed when classified as utilizing combination treatment, 40% of TE versus 18% of CON reported use of smoking cessation medication and behavioral counseling (p = 0.04). No statistical differences were observed for cessation outcomes, although more TE than CON participants reported 7 day point abstinence at 3 months post-intervention (30% vs 18%).ConclusionsThe present pilot study provides initial evidence for the feasibility, acceptability and efficacy of a telephone delivered TE intervention for enhancing engagement in combinationevidence evidence-based treatment in a sample of Veteran smokers with mental illness referred to smoking cessation treatment. Smokers with mental illness typically have greater difficulty stopping smoking than those without mental illness. Increased engagement in combination treatment thus has the potential to increase quit rates and ultimately reduce the burden of tobacco use for this population

A High Resolution Study of the Slowly Contracting, Starless Core L1544

We present interferometric observations of N2H+(1--0) in the starless, dense core L1544 in Taurus. Red-shifted self-absorption, indicative of inward motions, is found toward the center of an elongated core. The data are fit by a non-spherical model consisting of two isothermal, rotating, centrally condensed layers. Through a hybrid global-individual fit to the spectra, we map the variation of infall speed at scales ~1400AU and find values ~0.08 km/s around the core center. The inward motions are small in comparison to thermal, rotational, and gravitational speeds but are large enough to suggest that L1544 is very close to forming a star.Comment: 11 pages, 2 figures Accepted for publication in Astrophysical Journal Letter

Scaling issues in ensemble implementations of the Deutsch-Jozsa algorithm

We discuss the ensemble version of the Deutsch-Jozsa (DJ) algorithm which attempts to provide a "scalable" implementation on an expectation-value NMR quantum computer. We show that this ensemble implementation of the DJ algorithm is at best as efficient as the classical random algorithm. As soon as any attempt is made to classify all possible functions with certainty, the implementation requires an exponentially large number of molecules. The discrepancies arise out of the interpretation of mixed state density matrices.Comment: Minor changes, reference added, replaced with publised versio