Efficient Refocussing of One Spin and Two Spin Interactions for NMR Quantum Computation

The use of spin echoes to refocus one spin interactions (chemical shifts) and two spin interactions (spin-spin couplings) plays a central role in both conventional NMR experiments and NMR quantum computation. Here we describe schemes for efficient refocussing of such interactions in both fully and partially coupled spin systems.Comment: 4 pages, RevTeX, including 4 LaTeX figure

Schemes for Parallel Quantum Computation Without Local Control of Qubits

Typical quantum computing schemes require transformations (gates) to be targeted at specific elements (qubits). In many physical systems, direct targeting is difficult to achieve; an alternative is to encode local gates into globally applied transformations. Here we demonstrate the minimum physical requirements for such an approach: a one-dimensional array composed of two alternating 'types' of two-state system. Each system need be sensitive only to the net state of its nearest neighbors, i.e. the number in state 1 minus the number in state 2. Additionally, we show that all such arrays can perform quite general parallel operations. A broad range of physical systems and interactions are suitable: we highlight two potential implementations.Comment: 12 pages + 3 figures. Several small corrections mad

The Impact of Stellar Migration on Disk Outskirts

Stellar migration, whether due to trapping by transient spirals (churning), or to scattering by non-axisymmetric perturbations, has been proposed to explain the presence of stars in outer disks. After a review of the basic theory, we present compelling, but not yet conclusive, evidence that churning has been important in the outer disks of galaxies with type II (down-bending) profiles, while scattering has produced the outer disks of type III (up-bending) galaxies. In contrast, field galaxies with type I (pure exponential) profiles appear to not have experienced substantial migration. We conclude by suggesting work that would improve our understanding of the origin of outer disks.Comment: Invited review, Book chapter in "Outskirts of Galaxies", Eds. J. H. Knapen, J. C. Lee and A. Gil de Paz, Astrophysics and Space Science Library, Springer, in press 39 pages, 15 figure

A-Site Strain and Displacement in Ba1-xCaxTiO3 and Ba1-xSrxTiO3 and the Consequences for the Curie Temperature

Classical computer simulations are performed on the whole solid solution range of Ba1–xCaxTiO3 (BCT) and Ba1–xSrxTiO3 (BST). The enthalpies and volumes of mixing are produced, and a full local structural analysis is performed. The simulations demonstrate that large degrees of disorder form in the BCT solid solution which leads to distortions in the TiO6 octahedra. Comparing the positions of Sr in BST and Ca in BCT, the position of the Sr cation is largely central within the dodecahedra while the position of the Ca is significantly off-center in many configurations. The relaxation is associated with a shift toward an eight coordinate site compared to a 12 coordinate cation. An empirical model is fitted for predicting the Curie Temperature of the solid solution based on the local structure which shows excellent agreement with experimental values

Quantum Logic Gates and Nuclear Magnetic Resonance Pulse Sequences

We demonstrate how NMR can in principle be used to implement all the elements required to build quantum computers, and briefly discuss the potential applications of insights from quantum logic to the development of novel pulse sequences with applications in more conventional NMR experiments.Comment: Sixteen pages, no figures. Submitted to Journal of Magnetic Resonance. Primarily pedagogical rather than a description of novel research result

A comparison of statistical machine learning methods in heartbeat detection and classification

In health care, patients with heart problems require quick responsiveness in a clinical setting or in the operating theatre. Towards that end, automated classification of heartbeats is vital as some heartbeat irregularities are time consuming to detect. Therefore, analysis of electro-cardiogram (ECG) signals is an active area of research. The methods proposed in the literature depend on the structure of a heartbeat cycle. In this paper, we use interval and amplitude based features together with a few samples from the ECG signal as a feature vector. We studied a variety of classification algorithms focused especially on a type of arrhythmia known as the ventricular ectopic fibrillation (VEB). We compare the performance of the classifiers against algorithms proposed in the literature and make recommendations regarding features, sampling rate, and choice of the classifier to apply in a real-time clinical setting. The extensive study is based on the MIT-BIH arrhythmia database. Our main contribution is the evaluation of existing classifiers over a range sampling rates, recommendation of a detection methodology to employ in a practical setting, and extend the notion of a mixture of experts to a larger class of algorithms

Acute effects of cannabinoids on addiction endophenotypes are moderated by genes encoding the CB1 receptor and FAAH enzyme

Understanding genetic factors that contribute to cannabis use disorder (CUD) is important, but to date, findings have been equivocal. Single‐nucleotide polymorphisms (SNPs) in the cannabinoid receptor 1 gene (CNR1; rs1049353 and rs806378) and fatty acid amide hydrolase (FAAH) gene (rs324420) have been implicated in CUD. Their relationship to addiction endophenotypes such as cannabis‐related state satiety, the salience of appetitive cues, and craving after acute cannabinoid administration has not been investigated. Forty‐eight cannabis users participated in a double‐blind, placebo‐controlled, four‐way crossover experiment where they were administered treatments in a randomized order via vaporization: placebo, Δ9‐tetrahydrocannabinol (THC) (8 mg), THC + cannabidiol (THC + CBD) (8 + 16 mg), and CBD (16 mg). Cannabis‐related state satiety, appetitive cue salience (cannabis and food), and cannabis craving were assessed each day. Participants were genotyped for rs1049353, rs806378, and rs324420. Results indicated that CNR1 rs1049353 GG carriers showed increased state satiety after THC/THC + CBD administration in comparison with placebo and reduced the salience of appetitive cues after THC in comparison with CBD administration; A carriers did not vary on either of these measures indicative of a vulnerability to CUD. CNR1 rs806378 CC carriers showed greater salience to appetitive cues in comparison with T carriers, but there was no evidence for changes in state satiety. FAAH rs324420 A carriers showed greater bias to appetitive cues after THC, in comparison with CC carriers. FAAH CC carriers showed reduced bias after THC in comparison with CBD. No SNPs modulated craving. These findings identify candidate neurocognitive mechanisms through which endocannabinoid system genetics may influence vulnerability to CUD

BIOSOLIDS USE FOR RECLAIMING FLUVIAL MINE TAILINGS

This study was conducted to determine the effect of biosolids and lime on reclamation of a heavily contaminated metal site. Within the Superfund area near Leadville, CO, biosolids and lime were amended (1998) to a 1 ha site at rates of 240 Mg per ha each. In 2006, soil samples were collected on a 10 m x 10 m grid to a depth of 30 cm across the site. Basic soil analysis included pH, EC, total C and N, inorganic and organic C, and NO3-N and NH4-N. A sequential fractionation for metal contaminants of concern (Cd, Cr, Fe, Pb, Mn, and Zn) identified associations with: 1) soluble/exchangeable; 2) specifically sorbed/weakly bound; 3) non-crystalline Fe/Mn oxides; 4) crystalline Fe/Mn oxides and organically complexed; 5) residual organic; and 6) residual inorganic phases. Sequential extraction data was cross correlated with basic soil analysis. Basic soil analysis were affected by both lime and biosolids applications. Cadmium was found primarily in mobile phases, Cu, Fe, Pb, and Mn in more resistant phases, and Zn distributed equally among all soil fractions. Metals were negatively correlated with basic soil analysis. The greatest mobile-phase metal concentrations were observed at the site’s south end. This may have been due to a lack of uniformly applied or incorporated biosolids, or not enough lime applied to raise soil pH and complex metals in more immobile phases. If mobile phases were present over the entire site prior to reclamation, then a positive phase shift has occurred towards more immobile metal phases following reclamation

Spin dynamics of wave packets evolving with the Dirac Hamiltonian in atoms with high Z

The motion of circular WP for one electron in central Coulomb field with high Z is calculated. The WP is defined in terms of solutions of the Dirac equation in order to take into account all possible relevant effects in particular the spin-orbit potential. A time scale is defined within which spin dynamics must be taken into account mainly in the atoms with high Z. Within this time scale there exists a mechanism of collapses and revivals of the spin already shown by the authors for harmonic oscillator potential and called the 'spin-orbit pendulum'. However this effect has not the exact periodicity of the simpler model, but the WP's spatial motion is nevertheless quite similar.Comment: 17 pages, 9 figures, LaTeX2e, uses IOP style files (included). Title changed, one reference adde