Micronutrient deficiencies in Manitoba crops

Non-Peer Reviewe

Electrodynamics of quasi-two-dimensional BEDT-TTF charge transfer salts

We consider the millimeter-wave electrodynamics specific to quasi-two-dimensional conductors and superconductors based on the organic donor molecule BEDT-TTF. Using realistic physical parameters, we examine the current polarizations that result for different oscillating (GHz) electric and magnetic field polarizations. We show that, in general, it is possible to discriminate between effects (dissipation and dispersion) due to in-plane and interlayer ac currents. However, we also show that it is not possible to selectively probe any single component of the in-plane conductivity tensor, and that excitation of interlayer currents is strongly influenced by the sample geometry and the electromagnetic field polarization.Comment: 5 pages including 3 figures Minor correction to figure

Spectroscopic Temperature Determination of Degenerate Fermi Gases

We suggest a simple method for measuring the temperature of ultra-cold gases made of fermions. We show that by using a two-photon Raman probe, it is possible to obtain lineshapes which reveal properties of the degenerate sample, notably its temperature $T$. The proposed method could be used with identical fermions in different hyperfine states interacting via s-wave scattering or identical fermions in the same hyperfine state via p-wave scattering. We illustrate the applicability of the method in realistic conditions for $^6$Li prepared in two different hyperfine states. We find that temperatures down to 0.05 $T_{F}$ can be determined by this {\it in-situ} method.Comment: 7 pages, 4 figures, Revtex

Cyclotron effective masses in layered metals

Many layered metals such as quasi-two-dimensional organic molecular crystals show properties consistent with a Fermi liquid description at low temperatures. The effective masses extracted from the temperature dependence of the magnetic oscillations observed in these materials are in the range, m^*_c/m_e \sim 1-7, suggesting that these systems are strongly correlated. However, the ratio m^*_c/m_e contains both the renormalization due to the electron-electron interaction and the periodic potential of the lattice. We show that for any quasi-two-dimensional band structure, the cyclotron mass is proportional to the density of states at the Fermi energy. Due to Luttinger's theorem, this result is also valid in the presence of interactions. We then evaluate m_c for several model band structures for the \beta, \kappa, and \theta families of (BEDT-TTF)_2X, where BEDT-TTF is bis-(ethylenedithia-tetrathiafulvalene) and X is an anion. We find that for \kappa-(BEDT-TTF)_2X, the cyclotron mass of the \beta-orbit, m^{*\beta}_c, is close to 2 m^{*\alpha}_c, where m^{*\alpha}_c is the effective mass of the \alpha- orbit. This result is fairly insensitive to the band structure details. For a wide range of materials we compare values of the cyclotron mass deduced from band structure calculations to values deduced from measurements of magnetic oscillations and the specific heat coefficient.Comment: 12 pages, 3 eps figure

Haldane exclusion statistics and second virial coefficient

We show that Haldanes new definition of statistics, when generalised to infinite dimensional Hilbert spaces, is equal to the high temperature limit of the second virial coefficient. We thus show that this exclusion statistics parameter, g , of anyons is non-trivial and is completely determined by its exchange statistics parameter $\alpha$. We also compute g for quasiparticles in the Luttinger model and show that it is equal to $\alpha$.Comment: 11 pages, REVTEX 3.

Improving adherence to acute low back pain guideline recommendations with chiropractors and physiotherapists: the ALIGN cluster randomised controlled trial

Background Acute low back pain is a common condition, has high burden, and there are evidence-to-practice gaps in the chiropractic and physiotherapy setting for imaging and giving advice to stay active. The aim of this cluster randomised trial was to estimate the effects of a theory- and evidence-based implementation intervention to increase chiropractors’ and physiotherapists’ adherence to a guideline for acute low back pain compared with the comparator (passive dissemination of the guideline). In particular, the primary aim of the intervention was to reduce inappropriate imaging referral and improve patient low back pain outcomes, and to determine whether this intervention was cost-effective. Methods Physiotherapy and chiropractic practices in the state of Victoria, Australia, comprising at least one practising clinician who provided care to patients with acute low back pain, were invited to participate. Patients attending these practices were included if they had acute non-specific low back pain (duration less than 3 months), were 18 years of age or older, and were able to understand and read English. Practices were randomly assigned either to a tailored, multi-faceted intervention based on the guideline (interactive educational symposium plus academic detailing) or passive dissemination of the guideline (comparator). A statistician independent of the study team undertook stratified randomisation using computer-generated random numbers; four strata were defined by professional group and the rural or metropolitan location of the practice. Investigators not involved in intervention delivery were blinded to allocation. Primary outcomes were X-ray referral self-reported by clinicians using a checklist and patient low back pain-specific disability (at 3 months). Results A total of 104 practices (43 chiropractors, 85 physiotherapists; 755 patients) were assigned to the intervention and 106 practices (45 chiropractors, 97 physiotherapists; 603 patients) to the comparator; 449 patients were available for the patient-level primary outcome. There was no important difference in the odds of patients being referred for X-ray (adjusted (Adj) OR: 1.40; 95% CI 0.51, 3.87; Adj risk difference (RD): 0.01; 95% CI − 0.02, 0.04) or patient low back pain-specific disability (Adj mean difference: 0.37; 95% CI − 0.48, 1.21, scale 0–24). The intervention did lead to improvement for some key secondary outcomes, including giving advice to stay active (Adj OR: 1.96; 95% CI 1.20, 3.22; Adj RD: 0.10; 95% CI 0.01, 0.19) and intending to adhere to the guideline recommendations (e.g. intention to refer for X-ray: Adj OR: 0.27; 95% CI 0.17, 0.44; intention to give advice to stay active: Adj OR: 2.37; 95% CI 1.51, 3.74). Conclusions Intervention group clinicians were more likely to give advice to stay active and to intend to adhere to the guideline recommendations about X-ray referral. The intervention did not change the primary study outcomes, with no important differences in X-ray referral and patient disability between groups, implying that hypothesised reductions in health service utilisation and/or productivity gains are unlikely to offset the direct costs of the intervention. We report these results with the caveat that we enrolled less patients into the trial than our determined sample size. We cannot recommend this intervention as a cost-effective use of resources

Symmetrized mean-field description of magnetic instabilities in k-(BEDT-TTF)_2Cu[N(CN)]_2 Y salts

We present a novel and convenient mean-field method, and apply it to study the metallic/antiferromagnetic interface of k-(BEDT-TTF)_2Cu[N(CN)]_2 Y organic superconductors (BEDT_TTF is bis-ethylen-dithio-tetrathiafulvalene, Y=Cl, Br). The method, which fully exploits the crystal symmetry, allows one to obtain the mean-field solution of the 2D Hubbard model for very large lattices, up to 6x10^5 sites, yielding a reliable description of the phase boundary in a wide region of the parameter space. The metal/antiferromagnet transtion appears to be second order, except for a narrow region of the parameter space, where the transition is very sharp and possibly first order. The cohexistence of metallic and antiferromagnetic properties is only observed for the transient state in the case of smooth second order transitions. The relevance of the present resaults to the complex experimental behavior of centrosymmetric k-phase BEDT-TTF salts is discussed.Comment: 9 pages in PS format, 7 figures (included in PS), 1 tabl

Four-Wave mixing in degenerate Fermi gases: Beyond the undepleted pump approximation

We analyze the full nonlinear dynamics of the four-wave mixing between an incident beam of fermions and a fermionic density grating. We find that when the number of atoms in the beam is comparable to the number of atoms forming the grating, the dephasing of that grating, which normally leads to a decay of its amplitude, is suppressed. Instead, the density grating and the beam density exhibit large nonlinear coupled amplitude oscillations. In this case four-wave mixing can persist for much longer times compared to the case of negligible back-action. We also evaluate the efficiency of the four-wave mixing and show that it can be enhanced by producing an initial density grating with an amplitude that is less than the maximum value. These results indicate that efficient four-wave mixing in fermionic alkali gases should be experimentally observable.Comment: 9 pages, 8 figure

Entanglement between a qubit and the environment in the spin-boson model

The quantitative description of the quantum entanglement between a qubit and its environment is considered. Specifically, for the ground state of the spin-boson model, the entropy of entanglement of the spin is calculated as a function of $\alpha$, the strength of the ohmic coupling to the environment, and $\epsilon$, the level asymmetry. This is done by a numerical renormalization group treatment of the related anisotropic Kondo model. For $\epsilon=0$, the entanglement increases monotonically with $\alpha$, until it becomes maximal for $\alpha \lim 1^-$. For fixed $\epsilon>0$, the entanglement is a maximum as a function of $\alpha$ for a value, $\alpha = \alpha_M < 1$.Comment: 4 pages, 3 figures. Shortened version restricted to groundstate entanglemen

Saturation in heteronuclear photoassociation of 6Li7Li

We report heteronuclear photoassociation spectroscopy in a mixture of magneto-optically trapped 6Li and 7Li. Hyperfine resolved spectra of the vibrational level v=83 of the singlet state have been taken up to intensities of 1000 W/cm^2. Saturation of the photoassociation rate has been observed for two hyperfine transitions, which can be shown to be due to saturation of the rate coefficient near the unitarity limit. Saturation intensities on the order of 40 W/cm^2 can be determined.Comment: 5 pages, 3 figures, to appear in Phys. Rev. A (Rapid Communication